BACKGROUND OF THE INVENTION
[0001] This invention relates to the shrink packaging of articles, particularly food articles
such as poultry, cheese, primal or subprimal meat cuts, fresh red meat and other processed
meat, fruits, vegetables, breads and food products. Shrink packaging refers to the
use of a packaging film manufactured in such a way that when it is exposed to a certain
amount of heat, it will contract, preferably in both directions, reducing its overall
surface area. When this type of film is wrapped around an object, sealed around its
edges and passed through a heated shrink tunnel where the package is exposed to an
elevated temperature, the film will react to the heat and contract around the object.
Depending on the respective application, the air trapped within the package may be
evacuated prior to final sealing, or small holes may be provided through the film
to allow air to escape during the heat shrinking process. This process results in
an attractive skin-tight package. Articles packaged using shrink packaging are numerous
and can include food articles, such as frozen pizzas, cheese, poultry, fresh red meat,
and processed meat products.
[0002] The shrink packaging of food articles such as poultry, cheese, fresh red meat, and
processed meat products requires tough, puncture resistant, yet flexible, film materials
suitable for use in fabricating individual heat-shrinkable packaging receptacles,
such as pouches and bags for packaging such food articles. Generally, the shrink packaging
method of food articles is predicated upon the heat-shrinking property of the receptacle
by placing a given food article or articles into an individual receptacle, evacuating
the receptacle to remove air so the receptacle collapses, heat sealing across the
receptacle's opening or mouth to close the receptacle and thereafter exposing the
receptacle to a heat source such as a flow of hot air, infrared radiation, hot water,
and the like, thereby causing the receptacle to shrink and come into intimate contact
with the contours of the food article or articles. The packaged article prepared by
this packaging method has an attractive appearance which adds to the commodity value
of the wrapped article, its contents are kept in a hygienic condition, and it allows
shoppers to examine the quality of the contents of the packaged article. Packaging
in this fashion also excludes air from the package to prolong shelf life.
[0003] This invention relates generally to packaging and specifically to hermetically heat
sealable, easy open, heat-shrinkable packaging for food products.
[0004] It is common practice package articles such as food products in thermoplastic films
or laminates to protect the product to be packaged from abuse and exterior contamination
and to provide a convenient and durable package for transportation and sale to the
end user. Shrink packaging of food products has become extensively used due to its
many advantageous properties,
e.g., strength, compactness, content security, purge resistance, the attractive appearance
of the packed article, etc., which add to the commodity value of the packaged article.
Shrink packaging refers to the use of a packaging film manufactured in such a way
that when it is exposed to a certain amount of heat, the film will contract in at
least one direction along its length or width, preferably in both directions, reducing
its overall surface area. When articles are packaged in this type of film, air in
the package is usually evacuated and the package is typically passed through a heated
shrink tunnel where the package is exposed to an elevated temperature which causes
the film to react to the heat and contract around the object. This process results
in an attractive skin-tight package. Articles packaged using shrink packaging are
numerous and can include food articles, such as frozen pizzas, cheese, poultry, fresh
red meat, and processed meat products as well as nonfood industrial articles such
as wooden blinds, CD's, etc.
[0005] Many food products, such as poultry, fresh red meat, cheeses, and processed meat
products, are packaged in individual, pre-manufactured bags of heat-shrinkable film.
Typically, individual bags or pouches for packaging food articles include one to three
sides heat sealed by the bag manufacturer leaving one side open to allow product insertion
and a final seal performed by the food processor. Such individual bags are typically
manufactured from shrink films by producing a seamless tube of heat-shrinkable film
having a desired diameter, heat sealing one end of a length of the tubular film and
cutting off the tube portion containing the sealed portion, thereby forming an individual
bag. The bag formed thereby, when it is laid flat, has a bottom edge formed by the
heat seal, an open mouth opposite the sealed bottom and two seamless side edges formed
by the fold produced when the tube is laid flat. Another method of forming bags from
a seamless tube comprises making two spaced-apart transverse seals across the tube
and cutting open the side of the tube. If flat sheets of film are used, bags are formed
therefrom by heat sealing three edges of two superimposed sheets of film or by end-folding
a flat sheet and sealing two sides. U.S. patents describing known heat shrinkable
bags include
U.S. Patent Nos. 6,511,688,
5,928,740, and
6,015,235.
U.S. Patent Application No. 10/371,950, in the name of Thomas Schell et al., filed
on February 20, 2003, entitled "HEAT-SHRINKABLE PACKAGING RECEPTACLE", discloses individual heat-shrinkable
bags formed from a sheet of film, preferably in a continuous process, wherein opposing
side edges of the sheet are sealed longitudinally to form a tube member, which is
then sealed and cut transversely to close an end of the tube member thereby forming
a backseamed bag.
[0006] The known bags for heat-shrink packaging include strong factory and final closing
seals to prevent the heat sealed seams from pulling apart during the heat shrinking
operation, or during the handling and transport of the packaged article. Although
the strong heat seals provide protection against unwanted seal failure, such seals
also make it difficult for the end user to open the package. Accordingly, there is
needed an improved heat-shrinkable packaging receptacle that includes seals of sufficient
seal strength to survive the heat shrinking process and handling and resist spontaneous
opening due to residual shrink forces, yet includes at least one heat seal that is
readily openable by application of force without requiring use of a knife or cutting
implement and without uncontrolled or random tearing or rupturing of the packaging
materials, e.g., away from the seal area, which may result in opening in undesired
location or in sudden destruction of the package and inadvertent contamination or
spillage of the contents of the package.
[0007] Typically, individual bags or pouches for packaging food articles include one to
three sides heat sealed by the bag manufacturer leaving one side open to allow product
insertion. Such individual bags are generally manufactured from shrink films by producing
a seamless tube of heat-shrinkable film having a desired diameter and heat sealing
one end of a length of the tubular film and cutting off the tube portion containing
the sealed portion, thereby forming a bag which, when it is laid flat, has a bottom
edge formed by the heat seal, an open mouth opposite the sealed bottom and two seamless
side edges formed by the fold produced when the tube is laid flat. Another method
of forming bags from a seamless tube comprises making two spaced-apart transverse
seals across the tube and cutting open the side of the tube. If flat sheets of film
are used, bags are formed therefrom by heat sealing three edges of two superimposed
sheets of film or by end-folding a flat sheet and sealing two sides.
[0008] Manufacturing bags from a seamless tube requires that the tube be extruded to a specified
width for the intended end use. Thus, fabricating small diameter tubes for small width
bags does not utilize the full capacity of the film manufacturing equipment and is
thus not economical. Seamless tube sizes are also limited by the manufacturing equipment
in how small the width can be made. The manufacture of individual bags by superimposing
two sheets and sealing about three edges requires costly machinery to handle the separate
sheets, properly align the sheets and provide seals around the several edges. Additionally,
having a third sealed edge (four sealed edges when closed) increases the risk of a
seal failure during the shrinking process. Folding a sheet of film and sealing two
sides creates a double thickness of film at the seals which undesirably protrude from
the side of the finished package.
[0009] EP0435498 discloses an oriented, heat-shrinkable, packaging film having a layer of polyamide
or polyester, and bags made therefrom.
[0010] US4,944,409 discloses an easy open package adapted to be heat sealed closed and peelably reopened
including a first package wall comprising an outer layer, an inner sealant layer and
a tie layer disposed between and peelably bonded to either the inner layer or the
outer layer and a second package wall joined about a portion of its perimeter to the
first package wall and comprising at least one layer, that layer being a sealant layer
having the same composition as the inner sealant layer of the first package wall and
disposed adjacent thereto, the sealant layers being heat sealable together to form
a bond having a bond strength greater than the bond between the tie layer and the
layer to which it is peelably bonded, that bond strength being predetermined by the
selection of the compositions of the adjacent layers.
[0011] Accordingly, although the known shrink bags meet many of the requirements for packaging
applications, a need still exists for an improved heat-shrinkable bag structure that
can be economically fabricated and sealed using standard bag sealing machinery at
the place of packaging.
SUMMARY OF THE INVENTION
[0012] In accordance with the present invention, there is provided an end-sealed packaging
receptacle according to claim 1.
[0013] The present invention also provides a method according to claim 43.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0014]
FIG. 1 illustrates a schematic view of an end-seal, shrink bag having a lap seal according
to the present invention, in a slightly open position from a lay-flat position.
FIG. 2 illustrates a transverse cross-sectional view of the bag illustrated in FIG.
1, taken through section 2-2 of FIG. 1.
FIG. 3 illustrates a schematic view of an end-seal, shrink bag having a butt-seal
according to the present invention, in a slightly open position from a lay-flat position.
FIG. 4 illustrates a transverse cross-sectional view of the bag illustrated in FIG.
3, taken through section 6-6 of FIG. 5.
FIG. 5 illustrates a preferred three-layer film structure for forming bags according
to the present invention.
FIG. 6 is a schematic representation of a preferred method of manufacturing films
for use with the present invention.
FIG. 7 illustrates a preferred seven-layer film structure for forming bags according
to the present invention.
FIG. 8 illustrates a schematic view of a film suitable for making a peelable sealed
heat shrink bag according to the present invention.
FIG. 9 illustrates a schematic view of a preferred embodiment of a heat-shrinkable
bag according to the present invention, in a substantially lay-flat position.
FIG. 10 illustrates a fragmentary cross-sectional view taken along lines A-A of FIG.
9 depicting an enlarged, not to scale, lap seal area of a preferred film for use in
fabricating the bag illustrated in FIGS. 9, 12 and 13.
FIG. 11 illustrates a fragmentary cross-sectional view taken along lines B-B of FIG.
9 depicting an enlarged, not to scale, end seal area of a preferred film.
FIG. 12 illustrates schematic view of another preferred embodiment of a heat-shrinkable
bag according to the present invention having a pull flap.
FIG. 13 illustrates a transverse cross-sectional view of the bag illustrated in FIG.
14, taken through section C-C of FIG. 14.
FIG. 14 illustrates a cross-sectional view taken along lines D-D of FIG. 13, depicting
an end seal.
FIG. 15 illustrates a bag which is outside the scope of the present invention having
a fin seal backseam.
FIG. 16 illustrates a cross-sectional view of the bag illustrated in FIG. 15, taken
through section E-E.
FIG. 17 illustrates an enlarged fragmentary cross-sectional view of the seal portion
of FIG. 16 detailing a preferred film structure.
FIG. 18 illustrates another bag embodiment according to the present invention having
a butt-seal backseam.
FIG. 19 illustrates a cross-sectional view of the bag illustrated in FIG. 18, taken
through section F-F.
FIG. 20 illustrates another bag according to the present invention having a peel strip.
FIG. 21 illustrates a cross-sectional view of the bag illustrated in FIG. 20, taken
along section G-G.
FIG. 22 is a schematic illustration of a preferred method of manufacturing films for
use with the present invention.
FIG. 23 is a schematic illustration of a preferred method of manufacturing bags according
to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] A preferred embodiment of the heat-shrinkable packaging receptacle of the present
invention is shown in FIGS. 1 and 2 generally as bag 10. The bag 10 is formed from
a sheet of heat-shrinkable film 11 having a first edge 12, a second edge 14, a top
surface 13 and a bottom surface 15. The bag 10 includes a first seal 16 bonding the
first and second edges 12 and 14 in an overlapping arrangement, or lap seal, from
the top of the bag to the bottom. A tube member 18 is formed, shown in FIGS. 1 and
2 in a partially lay-flat orientation, having a first bag wall 20, a second bag wall
22, a first bag edge 24, a second bag edge 26, an opening 28 and a bag end 30. In
other words, the first and second edges 12 and 14 are placed in an overlapping arrangement
and a seal, such as a heat seal, is provided between the top surface 13 of the first
edge 12 and bottom surface 15 of the second edge 14 such that the top surface 13 of
the first edge 12 is sealed in face-to-face contact with the bottom surface 15 of
the second edge. The bag 10 includes a second seal 32 provided through the first and
second bag walls 20 and 22 and extending laterally across the bag 10 from the first
bag edge 24 to the second bag edge 26, thereby closing the bag end 30 and defining
a product receiving chamber 34.
[0016] Although the first seal 16 is illustrated as being positioned between the first and
second tube edges 24 and 26 and running parallel thereto, one skilled in the art will
appreciate in view of the present disclosure that the position of the first seal 16,
when the bag 10 is in a lay-flat orientation, may be any desired position from first
edge 24 to second edge 26 of either first or second bag walls 20 and 22, as well as
being positioned at either of the first and second bag edges 24 and 26. The second
seal 32 is illustrated as being straight and extending perpendicular to the first
seal 16; however, the skilled artisan will appreciate that the second seal 32 may
take any shape, so long as the second seal 32 operates to close the bag end 30 and
thereby define a product receiving chamber 34. For example, common seal configurations
include straight, or linear, seals which usually extend perpendicular to the tube
edges 24 and 26 (the tube edges 24 and 26 generally extend parallel to each other),
and also include nonlinear or curved edges, e.g., such as those described in
U.S. Patent No. 5,149,943. Both linear and nonlinear seals may be made by any suitable sealing method known,
including hot bar and impulse sealing.
[0017] Another embodiment of the present invention is illustrated in FIGS. 3 and 4 generally
as bag 210. Bag 210 is formed from a sheet of heat-shrinkable film 210 having a first
edge 212, a second edges 214, an inner surface 213 and an outer surface 215. The bag
210 includes a first seal 216 comprising a butt-seal, that bonds the first and second
edges 212 and 214 in a longitudinally abutting relationship with or without directly
bonding surfaces of the first and second edges 212 and 214 together. The first seal
216 preferably includes a butt-seal tape 217, one side of which is sealed to the outer
surface 215 of the first edge 212 by seal 216a, while an opposing side of the tape
217 is sealed to the outer surface of the second edge by seal 216b, seals 216a and
216b being in regions adjacent to and along the first and second edges 212 and 214.
The first seal 216 defines a tube member 218, shown in FIGS 3 and 4 in a partially
lay-flat orientation, having a first bag wall 220, a second bag wall 222, a first
bag edge 224, a second bag edge 226, an opening 228 and a bag end 230. The bag 210
includes a second seal 232 provided through the first and second bag walls 220 and
222 extending laterally across the bag 210 from the first bag edge 224 to the second
bag edge 226, thereby closing the bag end 230 and defining a product receiving chamber
234.
[0018] The film used to fabricate the bags of the present invention may be multilayer or
monolayer flexible, heat-shrinkable film manufactured by any known process. For example,
in commercial poultry packaging operations, monolayer films made from polyethylene
and/or ethylene-vinyl acetate copolymers, and multilayer films containing polyethylene
and/or ethylene-vinyl acetate copolymers are used extensively. Likewise, in the packaging
of fresh red meat and processed meat products, multilayer heat-shrinkable films containing
polyethylene and/or ethylene-vinyl acetate copolymers in one or more layers of the
films are commonly employed. Preferred films may also provide a beneficial combination
of one or more or all of the below noted properties including high puncture resistance
(e.g. as measured by the ram and/or hot water puncture tests), high shrinkage values,
low haze, high gloss, and high seal strengths. The film and/or bags may also include
an indicia, such as they may be printed. For example, bags according to the invention
may preferably include an indicia indicating that the bag includes a bone-containing
product. It may be desirable for applications wherein the film is printed to corona
treat the film surface to improve ink adhesion. Since corona treated surfaces do not
normally heat seal as well as untreated surfaces, it may be desirable to corona treat
only those portions that will not form part of a heat seal or to limit the treated
area of the film to minimize adverse interaction with later sealed areas. For example,
a center portion of the film may be corona treated, while those portions along each
of the machine direction edges of the film are not. In this manner, those portions
along each machine direction edge, that are sealed together to form the first seals
16 as described above, are not corona treated and should not be adversely affected.
[0019] The film may have an unrestrained shrinkage of at least 20% in at least one direction
and preferably 35% or more in one or both the machine and transverse directions. Free
shrink is measured by cutting a square piece of film measuring 10 cm in each of the
machine and transverse directions. The film is immersed in water at 90 °C for five
seconds. After removal from the water the piece is measured and the difference from
the original dimension is multiplied by ten to obtain the percentage of shrink.
[0020] Although the films used in the bag according to the present invention can be monolayer
or multilayer films, the bags are preferably formed of a multilayer film having 2
or more layers; more preferably 3 to 9 layers; and still more preferably 3 to 5 to
7 layers. Since the inventive bags are primarily intended to hold food products after
evacuation and sealing, it is preferred to use a thermoplastic film which includes
an oxygen and/or moisture barrier layer. The terms "barrier" or "barrier layer" as
used herein means a layer of a multilayer film which acts as a physical barrier to
moisture or oxygen molecules. Advantageous for packaging of oxygen sensitive materials
such as fresh red meat, a barrier layer material in conjunction with the other film
layers will provide an oxygen gas transmission rate(O
2GTR) of less than 70 (preferably 45 or less, more preferably 15 or less ) cc per square
meter in 24 hours at one atmosphere at a temperature of 73°F (23°C) and 0% relative
humidity.
[0021] The bags 10 and 210 are preferably fabricated continuously from a continuous sheet
or roll stock. The roll stock is slit to a desired width and fed to the bag making
equipment, the machine direction edges of the film are brought together and sealed
longitudinally, either with a lap seal (bag 10) or butt-seal (bag 210) to form a continuous
single-seamed tube, or tube member. A transverse seal is made across the tube and
the section including the transverse seal is severed from the continuous tube to form
the individual bag.
[0022] The type of first seal 16 or 216 incorporated into the bags of the present invention
will need to be taken into account when selecting a suitable film. Generally, heat
seals are made by supplying sufficient heat and pressure between two polymeric film
layer surfaces for a sufficient amount of time to cause a fusion bond between the
polymeric film layers. Common methods of forming heat seals include hot bar sealing,
wherein adjacent polymeric layers are held in face-to-face contact by opposing bars
of which at least one is heated, and impulse sealing, wherein adjacent polymeric layers
are held in face-to-face contact by opposing bars of which at least one includes a
wire or ribbon through which electric current is passed for a very brief period of
time to cause sufficient heat to cause the film layers to fusion bond. Less area is
generally bonded with an impulse seal relative to a hot bar seal, thus the performance
of the film's sealing layer is more critical. However, an impulse seal is generally
more aesthetic since less area is used to form the bond. First seal 16, or lap seal,
requires that the top surface 13 and bottom surface 15 be capable of forming a suitable
heat seal therebetween. If a first seal 216, or butt-seal, is formed, then both the
top surface and bottom surfaces must be capable of forming a suitable heat seal. Likewise,
the butt-seal tape 217, must also be capable of forming a suitable heat seal with
the top surface or a suitable adhesive must be employed to adhere the tape 217 to
the top surface 13 or bottom surface 15, depending on whether the tape 217 is place
on the inside or outside of the bag 110.
[0023] A preferred multilayer barrier film structure for use with the present invention
is shown in FIG. 5 generally as 40. When an oxygen barrier layer 42 is needed, it
is usually provided as a separate layer of a multilayer film, most commonly as a core
layer sandwiched between an inner heat sealing layer 44 and an outer layer 46, though
additional layers may also be included, such as tie or adhesive layers as well as
layers to add or modify various properties of the desired film, e.g., heat sealability,
toughness, abrasion resistance, tear-resistance, heat shrinkability, delamination
resistance, stiffness, moisture resistance, optical properties, printability, etc.
Oxygen barrier materials which may be included in the films utilized for the inventive
bags include ethylene vinyl alcohol copolymers (EVOH), polyacrylonitriles, polyamides
and vinylidene chloride copolymers (PVDC). Preferred oxygen barrier polymers for use
with the present invention are vinylidene chloride copolymers or vinylidene chloride
with various comonomers such as vinyl chloride (VC-VDC copolymer) or methyl acrylate
(MA-VDC copolymer), as well as EVOH. A specifically preferred barrier layer comprises
about 85% vinylidene chloride-methyl acrylate comonomer and about 15% vinylidene chloride-vinyl
chloride comonomer, as for example described in
Schuetz et al. U.S. Pat. No. 4,798,751. Suitable and preferred EVOH copolymers are described in
U.S. Patent No. 5,759,648.
[0024] The inner heat sealing layer 44 is generally provided on a side of the barrier layer
42 that becomes the inner surface 38, or bottom surfaces 15 shown in Figs. 1-4, of
the bags 10 or 210. Other film layers may optionally be incorporated between the barrier
layer 42 and the inner heat sealing layer 44 as previously noted. Substantially linear
copolymers of ethylene and at least one alpha-olefin as well as copolymers of ethylene
and vinyl esters or alkyl acrylates, such as vinyl acetate, may be usefully employed
in one or more layers of the film, and may comprise monolayer and multilayer thermoplastic
films. Preferably, the inner heat sealing layer comprises a blend of at least one
ethylene-α-olefin copolymer (EAO), with ethylene vinyl acetate (EAO:EVA blend). Suitable
α-olefins include C
3 to C
10 alpha-olefins such as propene, butene-1, pentene-1, hexene-1, methylpentene-1, octene-1,
decene-1 and combinations thereof. The heat seal layer is optionally the thickest
layer of a multilayer film and may significantly contribute to the puncture resistance
of the film. Another desirable characteristic affected by this layer is the heat seal
temperature range. It is preferred that the temperature range for heat sealing the
film be as broad as possible. This allows greater variation in the operation of the
heat sealing equipment relative to a film having a very narrow range. For example,
it is desirable for a suitable film to heat seal over a broad temperature range providing
a heat sealing window of 62.2°C (80°F) or higher.
[0025] The outer layer 46 is provided on the side of the barrier layer opposite the heat
sealing layer 44 and acts as the outer surface 39. In the instance when a lap seal,
such as the first seal 32 of bag 10 is incorporated into a bag structure, the outer
layer 46 must be heat seal compatible with the inner heat sealing layer. Other polymer
layers may optionally be provided between the barrier layer and the outer layer as
previously discussed. The outer layer may comprise an ethylene-α-olefin copolymer
(EAO), ethylene vinyl acetate copolymer (EVA) or blends thereof. EAOs are copolymers
predominately comprising ethylene polymeric units copolymerized with less than 50
% by weight of one or more suitable α-olefins which include C
3 to C
10 alpha-olefins such as propene, butene-1, pentene-1, hexene-1, methylpentene-1, octene-1,
decene-1. Preferred alpha-olefins are hexene-1 and octene-1. Recent developments for
improving properties of a heat-shrinkable film include
U.S. Pat. No. 5,403,668, which discloses a multilayer heat-shrinkable oxygen barrier film wherein the film
outer layer is a four component blend of VLDPE, LLDPE, EVA and plastomer. LLDPE, or
linear low density polyethylene, is a class of ethylene-alpha olefin copolymers having
a density greater than 0.915 g/cm
3. VLDPE, also called ultra low density polyethylene (ULDPE), is a class of ethylene-alpha
olefin copolymers having a density less than 0.915 g/cm
3 and many commercial VLDPE resins are available having densities from 0.900 up to
0.915 g/cm
3. Plastomers are generally EAOs having densities below 0.900 g/cm
3.
U.S. Pat. No. 5,397,640 discloses a multilayer oxygen barrier film wherein at least one outer film layer
is a three component blend of VLDPE, EVA and a plastomer. Alternatively, the outer
layer may be formed of other thermoplastic materials as for example polyamide, styrenic
copolymers, e.g., styrenebutadiene copolymer, polypropylene, ethylene-propylene copolymer,
ionomer, or an alpha olefin polymer and in particular a member of the polyethylene
family such as linear low density polyethylene (LLDPE), very low density polyethylene
(VLDPE and ULDPE), high density polyethylene (HDPE), low density polyethylene (LDPE),
an ethylene vinyl ester copolymer or an ethylene alkyl acrylate copolymer or various
blends of two or more of these materials.
[0026] In general, the monolayer or multilayer films used in the heat-shrinkable bags of
the present invention can have any thickness desired, so long as the films have sufficient
thickness and composition to provide the desired properties for the particular packaging
operation in which the film is used, e.g., puncture-resistance, modulus, seal strength,
barrier, optics, etc. For efficiency and conservation of materials, it is desirable
to provide the necessary puncture-resistance and other properties using the minimum
film thicknesses. Preferably, the film has a total thickness from about 31.75 µm (1.25)
to about 203.2 µm (8.0 mils); more preferably from about 44.45 µm (1.75) to about
76.2 µm (3.0 mils).
[0027] Suitable films for use with the present invention are disclosed in
U.S. Patent No. 5,928,740. The '740 patent discloses a heat sealing layer comprising a blend of a first polymer
of ethylene and at least one α-olefin having a polymer melting point between 55 to
75 °C.; a second polymer of ethylene and at least one α-olefin having a polymer melting
point between 85 to 110 °C and a third thermoplastic polymer having a melting point
between 115 to 130 °C which is preferably selected from the group of ethylene homopolymers
such as HDPE and LDPE, and ethylene copolymers with at least one α-olefin; and optionally
and preferably a fourth polymer such as a copolymer of ethylene with an alkyl acrylate
or vinyl ester having a melting point between 80 to 105 °C, preferably 90 to 100 °C.
The '740 patent also discloses a preferred biaxially oriented, heat-shrinkable three-layer
barrier film embodiment for use with the present invention. The three-layer barrier
film embodiment comprises an inner heat sealing layer as described above in conjunction
with a barrier layer preferably comprising a polyvinylidene chloride (PVDC) or vinylidene
chloride methylacrylate copolymer (VDC-MA or MA-saran) or EVOH layer and an outer
layer formed of at least 50 wt. %, and preferably at least 70%, of a copolymer of
ethylene with at least one alpha-olefin or at least one vinyl ester or blends thereof.
Also, preferred EVAs will have between about 3% and about 18% vinyl acetate content.
[0028] Preferred films for use with the present invention are disclosed in
U.S. Patent Application Ser. No. 09/401,692 filed September 22, 1999. The '692 application discloses monolayer and multilayer films having at least one
layer comprising at least a three-polymer blend, optionally including a fourth polymer,
comprising: (a) a first polymer having a melting point of 80 to 98°C, preferably 80-92°C,
comprising a copolymer of ethylene and hexene-1; (b) a second polymer having a polymer
melting point of 115 to 128°C comprising ethylene and at least one α-olefin; and (c)
a third polymer having a melting point of 60 to 110°C comprising a copolymer of ethylene
with an alkyl acrylate or vinyl ester; and optionally (d) a fourth polymer having
a melting point of 80 to 110°C (preferably of 85 to 105°C), preferably selected from
the group of ethylene homopolymers such as HDPE and LDPE, and ethylene copolymers
with at least one α-olefin. The inventive blend finds utility as an inner heat sealing
layer in many multilayer embodiments. In a preferred three, four or five-layer embodiment,
an oxygen barrier layer of a vinylidene chloride copolymer, a polyamide or EVOH is
between a layer of the inventive blend and either a layer comprising at least 50%
by weight of an EAO or at least one vinyl ester or blends thereof, or another layer
comprising the inventive blend.
[0029] Additional preferred films for use with the present invention are disclosed in
U.S. Patent Application Ser. No. 09/611,192 filed July 6, 2000. The '192 application discloses multi-layer barrier embodiments formed of a flexible,
thermoplastic, biaxially stretched, heat-shrinkable film having at least one layer
comprising a blend of at least three copolymers comprising: 45 to 85 weight percent
of a first polymer having a melting point of from 55 to 98°C comprising at least one
copolymer of ethylene and at least one comonomer selected from the group of hexene-1
and octene-1; 5 to 35 weight percent of a second polymer having a melting point of
from 115 to 128°C comprising at least one copolymer of ethylene and at least one α-olefin;
and 10 to 50 weight percent of a third polymer having a melting point of from 60 to
110°C comprising at least one unmodified or anhydride-modified copolymer of ethylene
and a vinyl ester, acrylic acid, methacrylic acid, or an alkyl acrylate; where the
first and second polymers above have a combined weight percentage of at least 50 weight
percent based upon the total weight of the first, second and third polymers; and where
the bag film has a total energy absorption of at least 0.70 Joule and a shrinkage
value at 90°C of at least 50% in at least one of the machine and transverse directions.
A barrier layer formed of any suitable oxygen barrier material or blend of materials,
for example, ethylene-vinyl alcohol copolymer (EVOH) or copolymers of vinylidene chloride
(VDC) such as VDC-vinyl chloride (VDC-VC) or VDC-methylacrylate (VDC-MA) may be used.
Preferably the barrier layer comprises a blend of 85 wt.% VDC-MA and 15 wt.% VDC-VC.
The outer layer is preferably an EVA-VLDPE blend, and more preferably an EVA-VLDPE-plastomer
blend. The '192 application also discloses a film comprising a flexible, thermoplastic
film having at least one layer comprising a blend of at least two polymers comprising:
5 to 20 weight percent of (i) an ionomer polymer, e.g., an ethylene-methacrylate acid
copolymer whose acid groups have been neutralized partly or completely to forma salt,
preferably a zinc or sodium salt; 5 to 95 weight percent of (ii) a copolymer of ethylene
and at least one C
6 to C
8 α-olefin, having a melting point of from 55 to 95°C, and a M̅
w/M̅
n of from 1.5 to 3.5; 0 to 90 weight percent of (iii) a copolymer of ethylene and at
least one C
4 to C
8 α-olefin, having a melting point of from 100 to 125°C; and 0 to 90 weight percent
of (iv) a copolymer of propylene and at least one monomer selected from the group
of ethylene and butene-1, where the copolymer (iv) has a melting point of from 105
to 145°C; 0 to 90 weight percent of (v) a copolymer of ethylene and at least one monomer
selected from the group of hexene-1, octene-1 and decene-1, where the copolymer (v)
has a melting point of from 125 to 135°C; and polymers (ii), (iii), (iv), and (v)
have a combined weight percentage of at least 80 weight percent based upon the total
weight of polymers (i), (ii), (iii), (iv), and (v); and wherein the film has a total
energy absorption of at least 1.2 Joule. Optionally, the same blend may be used as
an inner heat sealing layer for a bag film.
[0030] Further preferred films for use with the present invention are described in
U.S. Pat. No. 5,302,402 to Dudenhoeffer et al.,
U.S. Pat. No. 6,171,627, Lustig et al. U.S. Pat. No. 4,863,769, and
U.S. Pat. No. 6,015,235 to Kraimer et al..
[0031] In a preferred embodiment of the present invention, the heat-shrinkable bag is formed
of a three-layer film. The three-layer film is preferably a biaxially oriented film
including a barrier layer disposed between an inner heat sealing layer and an outer
layer, as shown in FIG. 5. The inner heat sealing layer comprises a blend of about
37% of an ethylene-vinyl acetate (EVA) copolymer such as ESCORENE™ LD 701.ID available
from Exxon Chemical Co., Houston, Texas, USA; about 24% VLDPE resin such as SCLAIR™
10B available from Nova Chemicals, Ltd., Calgary, Alberta, Canada (0.77 dg/min Melt
Index and 0.911 g/cm
3 density); about 33% of a plastomer, such as EXACT™ 4053 available from Exxon Chemical
Co., Houston, Texas, USA; about 4% slip/processing aid, such as Spartech A27023 (slip/processing
aid in a VLDPE carrier resin); and about 2% of a processing stabilizer such as Spartech
A32434 (available from Spartech Polycom of Washington, Pennsylvania, U.S.A.). The
barrier layer comprises a blend of about 15% vinylidene chloride-vinyl chloride and
about 85% vinylidene chloride-methacrylate, such as further described in
U.S. Patent No. 4,798,751. The outer layer comprises a blend of about 40% of an ethylene-vinyl acetate (EVA)
copolymer such as ESCORENE™ LD 701.ID; about 33% of a plastomer, such as EXACT™ 4053;
about 25% of a VLDPE resin, such as SCLAIR™ 10B; and about 2% of a processing aid/slip
concentrate in a VLDPE carrier, such as Ampacet 501236, available from Ampacet Corporation,
Tarrytown, New York, USA. The inner layer, barrier layer and outer layer represent
about 57.7%, 17.7% and 25.1% respectively based on the total thickness of the three-layer
film.
[0032] In another preferred embodiment of the present invention, the heat-shrinkable bag
is formed of another three-layer biaxially oriented shrink film including a barrier
layer disposed between an inner heat sealing layer and an outer layer, as shown in
FIG. 5. The barrier layer preferably comprises a blend of about 15% vinylidene chloride-vinyl
chloride and about 85% vinylidene chloride-methacrylate such as further described
in
U.S. Patent No. 4,798,751. The barrier layer preferably comprises approximately 16.5% of the three-layer film's
thickness. The inner heat sealing layer preferably comprises about 57.1% of the film's
thickness and comprises a blend of about 35.1 wt. % of an ethylene-hexene-1 copolymer
such as EXACT™ 9519 ( 0.895 g/cm
3 and 2.2 dg/min Melt Index available from Exxon Chemical Co., Houston, Texas, USA);
about 36.5% of an ethylene-octene-1 copolymer such as ATTANE™ XU 61509.32 (a C
2C
8 (<10 wt. % C
8) VLDPE having a density of about 0.912 g/cm
3 and 0.5 dg/min Melt Index available from Dow Chemical Co., Midland, Michigan, USA);
about 26.5% of an ethylene-vinyl acetate (EVA) copolymer such as ESCORENE™ LD 701.ID
(an ethylene-vinyl acetate copolymer available from Exxon Chemical Co., Houston, Texas,
USA and reportedly having a density of 0.93 g/cm
3, a vinyl acetate content of 10.5 wt. %, a melt index of about 0.19 dg/min., and a
melting point of about 97 °C); about 3% of a slip/processing aid such as Spartech
A50050 (1.9% oleamide slip and an fluoroelastomer in a VLDPE carrier resin); and about
2% of a processing stabilizer such as Spartech A32434 (10% DHT4A in VLDPE carrier
resin available from Spartech Polycom of Washington, Pennsylvania, U.S.A.). The outer
layer preferably comprises about 26.4% of the film thickness and comprises about 35
wt. % of an ethylene-hexene-1 copolymer such as EXACT™ 9519; about 35 % of a ethylene-octene-1
copolymer such as ATTANE™ XU 61509.32; about 27% of a EVA copolymer such as ESCORENE™
LD 701.ID; and about 3% of a slip/processing aid such as Spartech A50050 (available
from Spartech Polycom of Washington, Pennsylvania, U.S.A.).
[0033] In another preferred embodiment, the film of the bag comprises a biaxially oriented
three-layer heat-shrinkable film having an inner heat sealing layer made of a blend
of about 17 wt. % ethylene-octene-1 copolymer such as ATTANE™ XU 61509.32; about 18
wt. % EVA such ESCORENE™ LD 701.ID; 58% of an ethylene-hexene-1 copolymer such as
EXACT™ 9110 (0.898 g/cm
3 density, 0.8 dg/min Melt Index and 89 °C melting point); about 2% of a processing
stabilizer such as Spartech A32434; and about 5% of a slip/processing aid such as
Spartech A50050. The outer layer is about 19 wt. % ethylene octene-1 copolymer such
as ATTANE™ XU 61509.32; 18% EVA (ESCORENE™ LD 701.ID); 60% of an ethylene-hexene-1
copolymer such as EXACT™ 9110; and 3% processing aid such as A50056. The barrier layer
is 85% vinylidene chloride-methyl acrylate and about 15% vinylidene chloride-vinyl
chloride. Preferably, the inner layer:barrier layer:outer layer thickness ratio is
about 62:9:29.
[0034] A preferred seven-layer film for use in fabricating bags according to the present
invention is illustrated in FIG. 7 generally as film 60. The film 60 includes a first
or inner heat sealing layer 61 preferably comprising about 10% of the total mass of
the film 60. The inner heat sealing layer 61 preferably comprises a blend of about
94% EXACT™ 3139 (an ethylene-hexene copolymer having a reported Melt Index of 7.5
g/10 min and a density of 0.900 g/cm
3); about 4% Spartech A27023; and about 2% Spartech A32434. A second layer 62, adjacent
the first layer 61 preferably comprises about 42.2% of the total mass of the film
and comprises a blend of about 37% ESCORENE™ LD 701.ID; about 33% EXACT 4053; about
24% SCLAIR™ 10B; about 4% Spartech A27023; and about 2% Spartech A32434. The film
60 further includes first and second tie layers 63 and 65, each of which individually
preferably comprise about 5% of the total mass of the film 60 and further comprise
about 100% of VORIDIAN™ SP1330, an ethylene-methyl acrylate copolymer available form
Voridian, a division of Eastman Chemical Company, Kingsport, Tennessee, USA. The film
60 includes a barrier layer 64 between the first and second tie layers 63. The barrier
layer 64 preferably comprises about 17.7% of the total mass of the film and comprises
a blend of about 85% vinylidene chloride-methyl acrylate and about 15% vinylidene
chloride-vinyl chloride. Th film includes a third layer 66 that preferably comprises
about 15.1 % of the total mass of the film 60. The third layer 66 comprises a blend
of about 40% ESCORENE™ 701.ID; about 33% EXACT™ 4053; about 25% SCLAIR™ 10B; and about
2% Spartech A27339. The film 60 includes a fourth layer or outer layer 67 that preferably
comprises about 5% of the total mass of film 60 and comprises a blend of about 98%
EXACT™ 3139 and about 2% Spartech A27339. The total thickness of the film 60 is preferably
about 2 mils or greater.
[0035] Advantageously, it may be desirable to utilize high Melt Flow Index polymers in sealant
layer(s) of the film to aid in transversely sealing across the lap or butt seals.
High Melt Flow polymers, having a Melt Flow Index greater than about 5 dg/min. The
higher Melt Flow Index polymers fill gaps, such as gaps 9a (FIG. 2), and 9c (FIG.
4) that may form due to the dimensional difference encountered when the second seals
32, 132 or 232 are between the first and second bag walls in the area of the first
seals 16 and 216, more readily than lower Melt Flow Index polymers. For example, other,
high Melt Index polymers, such as EXACT™ 3040, which has a reported Melt Index of
16.5 g/10 min, could be used in the inner and outer layers 61 and 67 of film 60 to
replace the lower Melt Index ethylene-hexene copolymer.
[0036] The films selected to fabricate the inventive receptacles are preferably biaxially
oriented by the well-known trapped bubble or double bubble technique as for example
described in Pahlke
U.S. Pat. No. 3,456,044. In this technique an extruded primary tube leaving the tubular extrusion die is
cooled, collapsed and then preferably oriented by reheating and reinflating to form
a secondary bubble. The film is preferably biaxially oriented wherein transverse (TD)
orientation is accomplished by inflation to radially expand the heated film. Machine
direction (MD) orientation is preferably accomplished with the use of nip rolls rotating
at different speeds to pull or draw the film tube in the machine direction.
[0037] The stretch ratio in the biaxial orientation to form the bag material is preferably
sufficient to provide a film with total thickness of between about 1.5 and 3.5 mils.
The MD stretch ratio is typically 3:1-5:1 and the TD stretch ratio is also typically
3:1-5:1.
[0038] Referring now to FIG. 6, a double bubble or trapped bubble process is shown. The
polymer blends making up the several layers are coextruded by conveying separate melt
streams 311a, 311b, and 311c to the die 330. These polymer melts are joined together
and coextruded from annular die 330 as a relatively thick walled multilayered tube
332. The thick walled primary tube 332 leaving the extrusion die is cooled and collapsed
by nip rollers 331 and the collapsed primary tube 332 is conveyed by transport rollers
333a and 333b to a reheating zone where tube 332 is then reheated to below the melting
point of the layers being oriented and inflated with a trapped fluid, preferably gas,
most preferably air, to form a secondary bubble 334 and cooled. The secondary bubble
334 is formed by a fluid trapped between a first pair of nip rollers 336 at one end
of the bubble and a second pair of nip rollers 337 at the opposing end of the bubble.
The inflation which radially expands the film provides transverse direction (TD) orientation.
Orientation in the machine direction (MD) is accomplished by adjusting the relative
speed and/or size of nip rollers 336 and nip rollers 337 to stretch (draw) the film
in the machine direction. Rollers 337 also collapse the bubble forming an oriented
film 338 in a lay-flat condition which may be wound on a reel 339 or slit for further
processing close up.
[0039] The biaxial orientation preferably is sufficient to provide a multilayer film with
a total thickness of from about 31.75 µm to about 203.2 µm (1.25 to about 8.0 mils),
preferably 38.1 to 101.6 µm (1.5 to 4 mils) or more, preferably between 1.75 and 3.0
mils (44 to 76 µ), and more preferably about 63.5 µm (2.5 mils).
[0040] A preferred film and process for making film suitable for use in fabricating bags
according to the present invention is described in each of
U.S. Patent Applications No. 09/401,692 filed September 22, 1999 for "Puncture Resistant Polymeric Films, Blends and Process";
09/431,931 filed November 1, 1999 for "Puncture Resistant High Shrink Film, Blend and Process"; and
09/611,192 filed July 6, 2000 for "Ionomeric, Puncture Resistant Thermoplastic Patch Bag, Film, Blend and Process".
[0041] For a monolayer film, the process is similar but utilizes a single extruder (or multiple
extruders running the same polymeric formulation) to produce a primary tube, and biaxial
orientation is sufficient to provide a monolayer film preferably having a total thickness
of between 50.8 µm to 152.4 µm (2 to 6 mil) or higher, and more typically from about
88.9 µm to 114.3 µm (3.5 to 4.5 mils) and is generally in the same draw ratio range
as previously discussed, namely about 3:1 to 5:1 for both the MD and TD.
[0042] Although not essential, it is preferred to irradiate the film to broaden the heat
sealing range and/or enhance the toughness properties of the inner and outer layers
by irradiation induced cross-linking and/or scission. This is preferably accomplished
by irradiation with an electron beam at a dosage level of at least 2 megarads (MR)
and preferably in the range of 3-5 MR, although higher dosages may be utilized, such
as for thicker films. Irradiation may be provided on the primary tube or after biaxial
orientation. The latter, called post-irradiation, is preferred and described in
Lustig et al. U.S. Patent No. 4,737,391.
[0043] After orientation, the tubular film 338 is collapsed, slit open longitudinally, laid
flat and wound on a reel 339 for use as rollstock. One skilled in the art will appreciate
that the above method may be used to form the film, films may be made by conventional
single bubble, blown film processes, and oriented or nonoriented sheets may be made
by slot cast sheet extrusion processes with or without tentering to provide orientation.
One skilled in the art will further appreciate that the flatwidth of the collapsed
tube will determine the width of the sheet film that results therefrom. Thus, the
primary tube dimensions and subsequent processing may be selected to provide a maximum
flatwidth and film thickness for the desired application, thereby advantageously maximizing
the production capacity of the film making equipment.
[0044] Advantageously, a bag maker may produce bags of various lengths and widths from rolls
of film rollstock by adjusting the width of the sheet (by slitting or cutting rollstock
to a desired width) and the distances between the transverse end seal and bag mouth
for a particular bag or series of bags. This advantageously avoids the costly need
to produce specific widths of seamless tubes which are currently widely used by meat
packers. Also the present invention permits cost savings and manufacturing efficiencies
by permitting creation of numerous widths and lengths of bag from standard rollstock,
which was produced utilizing substantially 100% of the film producing equipment's
capacity. This reduces the need to carry larger inventories of a vast array of seamless
tube rollstock having different widths. The bag maker may simply slit film rollstock
to a desired width and form a continuous tube member by longitudinally sealing opposing
side edges as described for bags 10. and 210. Bags of adjustable lengths may be made
by transversely sealing and cutting through the tube member at a position spaced from
the transverse seal. The film may also be made into a continuous tube member rollstock
by longitudinally joining opposing side edges of a film as described above to form
a continuous tube member, collapsing the continuous tube member and winding the collapsed
continuous tube member on a reel. The continuous tube member rollstock may then be
provided to the food processor, who then forms the individual bags, such as bags 10,
and 210. Such continuous tube member rollstock may have a lay-flat width of up to
508 mm (20 inches), advantageously greater than 508 mm (20 inches), and more advantageously
greater than or equal to 558.8 mm (22 inches).
[0045] Preferably, bag making is a continuous process, wherein the film is directed to a
bag making assembly (not shown) where individual end-seal bags are made. As previously
stated, the rollstock may be slit to a desired width with the unused portion re-wound
for later use. Bags are produced by continuously bringing the opposing side edges
of the film together and forming a heat seal, such as a lap seal or fin seal to form
a continuous tube member, then making lateral, or transverse, heat seals across the
tube member width at spaced intervals to weld the first and second bag walls of the
tube member together. The tube member is severed preferably at the same time or during
the same step that it is transversely heat sealed to form a bag as shown in Figure
1 or 3. Typically as the transverse seal is made for one bag a transverse cut forming
the mouth of the adjacent bag is being made. This process forms a so called "end-seal"
bag which, when it is laid flat, has a bottom edge formed by the transverse heat seal,
an open mouth formed by the severed edge and two side edges formed by the fold produced
when the tube member is laid flat. The transverse heat seal should extend across the
entire tube member to ensure a hermetic closure. Each bag being formed from a length
of the tube member will necessarily be formed by at least two, usually parallel, spaced
apart, transverse cuts which cause a segment of the tube member to be made and one
transverse seal, usually adjacent one of these cuts, will define a bag bottom which
is located opposing the bag opening, which is formed by the distal cut. In typical
production the member tube is transversely sealed and an adjacent transverse cut made
as part of the same step and the seal and this proximate cut form a sealed end for
one bag while the same cut also forms the mouth opening for the adjacent bag, and
for that adjacent bag may be referred to as the distal cut. The spacing between the
lateral seal and the point of severance, which may vary, will determine the length
of the bags formed. The length of the bags can easily be varied by changing the distance
between cuts. The width of the bags can also be easily varied by changing the width
of the film by slitting the standard rollstock. In another embodiment of the invention,
cuts and seals may be made alternately and apart from each other to form dual attached
bags in saddle bag fashion.
[0046] The present invention advantageously provides for producing a heat-shrinkable bag
wherein the bag manufacturer may produce multiple bag sizes (different lengths and
widths) from a single film stock size, which advantageously maximizes film production
efficiency by eliminating the need to manufacture different widths of seamless tubes.
In other words, the present invention allows the bag manufacturer to produce one standard
width of sheet film stock, such as 2.18, 2.39, 2.49, 2.64, 2.84, 3.2, 4.11m (86, 94,
98, 104, 112, 126, 162 inch) or greater, depending on the capacity of the film producing
equipment. This standard sheet film stock may then be slit to a desired width, formed
into a bag as described herein, and the remaining portion of the sheet film stock
rewound for later use on another job. Prior art bags require the manufacturer thereof
to produce different seamless tube sizes for each size of bag produced, thereby reducing
production efficiency.
[0047] Unless otherwise noted, the following physical properties are used to describe the
invention, films and seals. These properties are measured by either the test procedures
described below or tests similar to the following methods.
Average Gauge: ASTM D-2103
Tensile Strength: ASTM D-882, method A
1% Secant Modulus: ASTM D-882, method A
Oxygen Gas Transmission Rate (O2GTR) : ASTM D-3985-81
Percent Elongation at Break: ASTM D-882, method A
Molecular Weight Distribution: Gel permeation chromatography
Gloss: ASTM D-2457, 45 Angle
Haze: ASTMD-1003-52
Melt Index: ASTM D-1238, Condition E (190°C) (except for propene-based (>50% C3 content) polymers tested at Condition L(230°C.))
Melting Point: ASTM D-3418, peak m.p. determined by DSC with a 10°C/min. heating rate.
Vicat Softening Point (Vsp): ASTM D-1525-82
Seal Strength: ASTM F88-94
[0048] All ASTM test methods noted herein are incorporated by reference into this disclosure.
[0049] Shrinkage Values: Shrinkage values are obtained by measuring unrestrained shrink of a 10 cm. square
sample immersed in water at 90°C (or the indicated temperature if different) for ten
seconds. Four test specimens are cut from a given sample of the film to be tested.
Specimens are cut into squares of 10 cm length (M.D.) by 10 cm. length (T.D.). Each
specimen is completely immersed for 10 seconds in a 90°C (or the indicated temperature
if different) water bath. The specimen is then removed from the bath and the distance
between the ends of the shrunken specimen is measured for both the M.D. and T.D. directions.
The difference in the measured distance for the shrunken specimen and each original
10 cm. side is multiplied by ten to obtain percent shrinkage in each direction. The
shrinkage of 4 specimens is averaged and the average M.D. and T.D. shrinkage values
reported. The term "heat shrinkable film at 90°C" means a film having an unrestrained
shrinkage value of at least 10% in at least one direction.
Tensile Seal Strength (Seal Strength) Test
[0050] Five identical samples of film are cut 1 inch (2.54 cm) wide and a suitable length
for the test equipment e.g. about 5 inches (77 cm) long with a 1 inch (2.54 cm) wide
seal portion centrally and transversely disposed. Opposing end portions of a film
sample are secured in opposing clamps in a universal tensile testing instrument. The
film is secured in a taut snug fit between the clamps without stretching prior to
beginning the test. The test is conducted at an ambient or room temperature (RT) (about
23 °C) test temperature. The instrument is activated to pull the film via the clamps
transverse to the seal at a uniform rate of 12.0 inches (30.48 cm) per minute until
failure of the film (breakage of film or seal, or delamination and loss of film integrity).
The test temperature noted and lbs. force at break are measured and recorded. The
test is repeated for four additional samples and the average grams at break reported.
Ram Puncture Test
[0051] The ram puncture test is used to determine the maximum puncture load or force, and
the maximum puncture stress of a flexible film when struck by a hemispherically or
spherically shaped striker. This test provides a quantitative measure of the puncture
resistance of thin plastic films. This test is further described in
U.S. Patent Application No. 09/401,692.
[0052] The following example is given to illustrate the invention and should not be construed
as limiting that which is described in the appended claims.
[0053] In the following example, the film composition was produced generally utilizing the
apparatus and method described in
U.S. Pat. No. 3,456,044 (Pahlke) which describes a coextrusion type of double bubble method and in further accordance
with the detailed description above. All layers were extruded as a primary tube which
was cooled upon exiting the die e.g. by spraying with tap water. This primary tube
was then reheated by radiant heaters(although other means known to those skilled in
the art, such as conduction or convection heating may be used) with further heating
to the draw (orientation) temperature for biaxial orientation accomplished by an air
cushion which was itself heated by transverse flow through a heated porous tube concentrically
positioned around the moving primary tube. Cooling was accomplished by means of a
concentric air ring. Draw point temperature, bubble heating and cooling rates and
orientation ratios were generally adjusted to maximize bubble stability and throughput
for the desired amount of stretching or orientation. All percentages are by weight
unless indicated otherwise.
EXAMPLE 1
[0054] A puncture-resistant bag according to the present invention, as generally illustrated
in Figs. 1 & 2, was produced from a film comprising a coextruded three-layer biaxially
oriented shrink film having (A) an inner heat sealing layer, (B) a barrier layer and
(C) an outer layer. The inner and outer layers being directly attached to opposing
sides of the barrier layer. The three layers included the following compositions:
(A) 33 wt. % EXACT™ 4053; 37% ESCORENE™ LD 701.ID; 24% SCLAIR™ 10B; 4% Spartech A27023;
and 2% Spartech A32434;
(B) a blend of about 85% vinylidene chloride-vinyl chloride copolymer and about 15%
vinylidene chloride-methacrylate copolymer; and
(C) 33 wt. % EXACT™ 4053; 25 % SCLAIR™ 10B; 40% ESCORENE™ LD 701.ID; and 2% Ampacet
501236.
[0055] One extruder was used for each layer. Each extruder was connected to an annular coextrusion
die from which heat plastified resins were coextruded forming a primary tube. The
resin mixture for each layer was fed from a hopper into an attached single screw extruder
where the mixture was heat plastified and extruded through a three-layer coextrusion
die into the primary tube. The extruder barrel temperature for the barrier layer (B)
was between about 250-300°F (121-149°C); for the inner layer (A) and for the outer
layer (C) were about 290-330°F(143-165°C). The coextrusion die temperature profile
was set from about 320 to 350°F (163 to 177°C). The extruded multilayer primary tube
was cooled by spraying with cold tap water 50-68 °F (about 10-20 °C).
[0056] A cooled primary tube of about 101.6 mm (4 inches) flatwidth was produced passing
through a pair of nip rollers. The cooled flattened primary tube was inflated, reheated,
biaxially stretched, and cooled again to produce a biaxially stretched and biaxially
oriented film which was slit open, laid flat to form a sheet having a width of approximately
406.4 mm (16 inches) and wound on a reel. The M.D. orientation ratio was about 5:1
and the T.D. orientation ratio was about 4:1 . The draw point or orientation temperature
was below the predominant melting point for each layer oriented and above that layer's
predominant glass transition point and is believed to be about 68-85 °C. The resultant
biaxially oriented film had an average gauge of about 63.5 µm (2.5 mil) and had an
excellent appearance.
[0057] The film was irradiated at a dosage level of about 5.0 MR. As previously noted, although
not essential, it is preferred to irradiate the entire film to broaden the heat sealing
range and/or enhance the toughness properties of the inner and outer layers by irradiation
induced cross-linking and/or scission. Irradiation may be done on the primary tube
or after biaxial orientation. The latter, called post-irradiation, is preferred and
described in Lustig et al.
U.S. Pat. No. 4,737,391. An advantage of post-irradiation is that a relatively thin film is treated instead
of the relatively thick primary tube, thereby reducing the power requirement for a
given treatment level.
[0058] The film was unwound and slit to a width of 330.2 mm (13 inches). The film was then
fed into the bag making equipment to form a tube member having a continuous longitudinally
extending lap seal. Bags according to the bag 10 depicted in FIG. 1 were formed by
sealing laterally across the tube member and simultaneously severing the sealed portion
from the continuous tube structure.
[0059] Various tests were performed on the film and/or resultant inventive bags. The film
thickness was determined to be an average 53.34 µm (2.1 mil). The lap seal was tested
to have a very strong average seal strength of about 8,000 to 10,000 grams. The bag
also had an average M.D. and T.D. heat shrinkability at 90 °C of 48 and 48, respectively.
The ram puncture results were likewise impressive. The puncture resistance of the
53.34 µm (2.1 mil) thick film was measured and had a maximum puncture force of 86
Newtons (N) and a total energy to failure of 0.9 Joules (J). This preferred bag has
very good heat shrink percentages which are highly desirable for packaging cuts of
fresh red meat and extremely good puncture resistance. Thus, an economical to produce
heat shrinkable bag having puncture resistance and strong seals has been made having
a unique combination of features and commercial advantages previously unknown.
[0060] Advantageously, the bags 10 may be fabricated of nearly any dimensions economically
since the bags 10 are not formed from a seamless tube that must be generated to the
desired width. The only limitation on size of fabricated bag is the size of a stock
sheet films having great enough widths to meet the specifications. Standard roll stock
films are available in widths in excess of 2.54 m (100 inches). The present invention
allows a bag manufacturer to fabricate any size bag from the same flat sheet of roll
stock, up to the dimensional limits of the roll stock. For example, if the roll stock
is 1.32 m (52 inches) in width, a tube member can be fabricated having a lay-flat
width of approximately 660.4 mm (26 inches), less the amount of overlap or abutment
in the first seal 16 used. If the manufacturer wishes to fabricate a bag having a
lay-flat width of 457.2 mm (18 inches), then the manufacturer slits the standard roll
stock to the appropriate width (approximately 914.4 mm (36) plus extra for the area
of the first seal 16). The unused portion slit form the standard roll stock is rewound
for use making bags of another dimension(s). In this manner, standard roll stock films
can be manufactured more economically because film manufacturing equipment may be
run at or near the upper limits of film width production and thereby use nearly all
the equipments capacity. Fabricating bags from seamless tubes requires that the film
making equipment be run at limited capacities to form the different smaller width
tubes. Additionally, the film making equipment requires costly set-up and breakdown
between jobs of differing dimensions that add significantly to the cost of manufacturing
the seamless tubes.
[0061] A preferred embodiment of the heat-shrinkable package of the present invention is
made from a sheet 410 of heat shrinkable film 411 having a first side edge 412a and
opposing, second side edge 412b connected by a third side edge 412c and a fourth side
edge 412d. First side edges 412a and second 412b are preferably parallel to each other
when film 411 is in a long flat planar state. Third side edge 412c and fourth side
412d are preferably parallel to each other when film 411 is in a lay flat planar state.
First and second side edges 412a, 412b are also preferably perpendicular to third
and fourth side edges 412c, 412d when film 411 is in a lay flat planar state. Film
411 has four corners at the intersections of the four sides with first corner 412ac
defined by the junction of first side edge 412a with third side edge 412c; second
corner 412b defined by the junction of first side edge 412a with third side edge 412c;
second comer 412bc defined by the junction of second side edge 412b with third side
edge 412c; third comer 412ad defined by the junction of first side edge 412a with
fourth side edge 412d; and fourth corner 412bd defined by the junction of second side
edge 412b with fourth side edge 412d. Film 411 has a top surface 413a circumscribed
by a perimeter 414 formed by sides 412a, 412c, 412b and 412d with an opposing bottom
surface 413b also circumscribed by said perimeter 414. FIG. 8 Depicts corner 412ad
of film 411 turned upward to reveal said bottom surface 413b.
[0062] Referring now to FIG. 9, a preferred embodiment of the present invention is depicted
generally as a bag 415 made from said film 411 of FIG. 8. The bag 415 is formed by
overlapping the first side edge 412a with the second side edge 412b and sealing preferably
by heat to produce a fusion bond lap seal 416 defined by parallel spaced apart dotted
lines 417a and 417b, and third side edge 412c and fourth side edge 412d. It should
be noted that while said lap seal 416 is depicted as a continuous elongated rectangle
extending from side 412c to side 412d, the invention further contemplates that the
seal shape may vary and could, for example, form a wavy line or zigzag shape or other
shapes as desired. Also, the width of the seal may be varied to be thicker or thinner
as desired. Also the seal may optionally be made by alternatives or additional means,
including, e.g., by applications of suitable flue or adhesive material known in the
art for sealing together films. It is further contemplated that said lap seal 416,
while depicted as a continuous lap seal 416 suitable for forming a hermetic package,
it is also contemplated that for some applications, e.g., for certain industrial or
non-perishable items, a noncontinuous seal having, e.g., the appearance of a dotted
or dashed line, may be employed. The intermittent seal embodiment permits air to escape
enclosure during packaging operations where it is not desired to either apply a vacuum,
or seal with a trapped bubble of air or other gas, or remove air by other means. Optionally,
the strength of the seal may be varied by one skilled in the art in view of the teachings
of the present application by selection of aforesaid parameters such as seal shape,
thickness, continuous or intermittent nature, material selection type of and known
parameter for varying the strength of different types of seals, e.g., by adjusting
dwell time or temperature for producing heat seals. Such variations and adjustments
may be made by those skilled in the art without undue experimentation.
[0063] Referring again to FIG. 9, lap seal 416 is preferably a heat seal forming a fusion
bond between top surface 413a and bottom surface 413b of film 411. The overlapped
sealed film 411 defines a tube member 418 in which top surface 413a of film 411 forms
an inner film surface 419 of said tube member 418. A second seal 420 extends laterally
across said tube member 418 adjacent the third side edge 412c of film 411 thereby
forming a closed bag end 421. A variety of seals may be used. Preferably second seal
420 will be a heat seal which fusion bonds the bag film inner surface 419 to itself.
The second seal 420 by closing bag end 421 both forms a first bag edge 422 and opposing
second bag edge 423, and the second seal extends across the tube member 418 from the
first bag edge 422 to the second bag edge 423. The second seal may also employ a variety
of shapes, thicknesses, structures, etc., as for the previously described lap seal
416. The lap seal does not need to be centered between edges 422 and 423 but preferably
is positioned anywhere therebetween.
[0064] Opposite the closed bag end 421 is a bag mount formed by lap sealed film under fourth
side edge 412d through which a product (not depicted) may be placed into a product
receiving chamber 425 defined by tube member 418, closed bag end 421 and bag mouth
424. The first bag edge 422 may extend from a first bag end comer 426 to a first bag
mouth point 427 and a second bag edge 423 may extend from a second bag end corner
428 to a second bag mouth point 429 such that bag 415 may be collapsed into a lay
flat condition having first bag edge 422 and opposing second bag edge 423. In a lay
flat condition or a state close to lay flat such as depicted in FIG. 9, bag end 421,
bag mouth 424 and connecting first bag edge 422 and second bag edge 423 defines a
first bag wall 430 and connected opposing bag wall 431. Tube member 418 has an inner
surface 419 and an outer surface 433. The first bag wall 430 has first bag wall first
side 430a proximate second side edge 412b and extending to second bag edge 423. The
first bag wall 430 also has an opposing first bag wall seamed side 430b proximate
first side edge 412a and extending to first bag edge 422.
[0065] Preferably, the second seal 420 is provided in a manner such that the first seal
416 is positioned within one of the first and second bag walls 430 and 431, thereby
forming a "backseam" of the bag. This provides one seamless bag wall and two seamless
bag edges that may include printed images applied to the film before forming bags
or after the bag is formed. Additionally, the second seal 420 may take any shape,
whether straight or curved, so long as the second seal 420 operates to close the end
421. At least one of the first seal 416 and second seal 420 comprises a peelable seal.
"Peelable seal" and like terminology is used herein to refer to a seal, and especially
heat seals, which are engineered to be readily peelable without uncontrolled or random
tearing or rupturing the packaging materials which may result in premature destruction
of the package and /or inadvertent contamination or spillage of the contents of the
package. An peelable seal is one that can be manually peeled apart to open the package
at the seal without resort to a knife or other implement to tear or rupture the package.
In the present invention, the peelable seal must have a seal strength sufficient to
prevent failure of the seal during the normal heat-shrinking process and further normal
handling and transport of the packaged article. The seal strength must also be low
enough to permit manual opening of the seal. Preferably seal parameters such as choice
of materials and sealing conditions will be used to adjust the seal strength to the
desired level for the particular package and application.
[0066] Many varieties of peelable seals are known in the art and are suitable for use with
the present invention. Peelable seals are generally made from thermoplastic films
having a peelable system designed therein. Suitable peelable films and/or peelable
systems are disclosed in
U.S. Patent Nos. 4,944,409 (Busche et al.);
4,875, 587 (Lulham et al.);
3,655,503 (Stanley et al.);
4,058,632 (Evans et al.);
4,252,846 (Romesberg et al.);
4,615,926 (Hsu et al.)
4,666,778 (Hwo);
4,784,885 (Carespodi);
4,882,229 (Hwo);
6,476,137 (Longo);
5,997,968 (Dries, et al.);
4,189,519 (Ticknor);
5,547,752 (Yanidis);
5,128,414 (Hwo);
5,023,121 (Pockat, et al.);
4,937,139 (Genske, et al.);
4,916,190 (Hwo); and
4,550,141 (Hoh) Preferred films for use in fabricating bags according to the invention may be selected
from multilayer, heat-shrinkable films capable of forming a peelable seal. Preferred
films may also provide a beneficial combination of one or more or all of the below
noted properties including high puncture resistance (
e.g., as measured by the ram and/or hot water puncture tests), high shrinkage values,
low haze, high gloss, high seal strengths and printability. Since the inventive bags
may advantageously be used to hold oxygen or moisture sensitive articles such as food
products after evacuation and sealing, it is preferred to use a thermoplastic film
which includes an oxygen and/or moisture barrier layer. The terms "barrier" or "barrier
layer" as used herein means a layer of a multilayer film which acts as a physical
barrier to moisture or oxygen molecules. Advantageous for packaging of oxygen sensitive
materials such as fresh red meat, a barrier layer material in conjunction with the
other film layers will provide an oxygen gas transmission rate(O
2GTR) of less than 70 (preferably 45 or less, more preferably 15 or less ) cc per square
meter in 24 hours at one atmosphere at a temperature of 73°F (23°C) and 0% relative
humidity. In an alternative embodiment, the gas permeability is controlled to allow
the escape of CO
2,
e.g., for packaging respiring foods such as cheese as described in
U.S. Patent No. 6,511,688. The film has an unrestrained shrinkage of at least 20% (preferably at least 35%)
at 90°C at least one and preferably both the machine (MD) and transverse (TD) directions.
Unrestrained (sometimes referred to as "free") shrink is measured by cutting a square
piece of film measuring 10 cm in each of the machine and transverse directions. The
film is immersed in water at 90°C for five seconds. After removal from the water the
piece is measured and the difference from the original dimensions are each multiplied
by ten to obtain the percentage of shrink in each respective direction.
[0067] Oxygen barrier materials which may be included in the films utilized for the inventive
bags include ethylene vinyl alcohol copolymers (EVOH), polyacrylonitriles, polyamides
and vinylidene chloride copolymers (PVDC). For some applications nylon may provide
useful oxygen barrier properties especially at low temperatures,
e.g., as used with frozen foods. Preferred oxygen barrier polymers for use with the present
invention are vinylidene chloride copolymers or vinylidene chloride with various comonomers
such as vinyl chloride (VC-VDC copolymer) or methyl acrylate (MA-VDC copolymer), as
well as EVOH. A specifically preferred barrier layer comprises about 85% vinylidene
chloride-methyl acrylate comonomer and about 15% vinylidene chloride-vinyl chloride
comonomer, as for example described in
Schuetz et al. U.S. Pat. No. 4,798,751. Suitable and preferred EVOH copolymers are described in
U.S. Patent No. 5,759,648..
[0068] A variety of peelable films and peelable sealing systems may be employed in the present
invention. In a preferred embodiment, a film comprising a coextrusion of at least
three layers (referred to as three layer peelable system to distinguish it from systems
using one or more contaminated seal layers described below) having an outer layer,
an inner heat seal layer and a tie layer disposed between the outer layer and the
inner heat seal layer is used. In this preferred three layer system embodiment, the
film layers are selected such that peeling occurs by breaking apart the tie layer
and/or a bond between the tie layer and at least one of the outer and inner layers.
Permanent, peelable, and fracturable bonds may be engineered into the coextrusion
process, e.g., by providing two adjacent first and second layers having materials
with a greater affinity for each other compared to the second layer and an adjacent
third layer where this establishes a relatively permanent bond between the layers,
when two materials have a lesser affinity for each other. This three layer structure
establishes a relatively permanent bond between the first and second layer which have
a greater affinity for one another than the second or third layers which have a lesser
affinity where the second layer is common to both the first and third layers as a
tie layer or connecting layer. Thus, the lesser affinity between the second and third
layers relative to the first and second layers produces a relatively peelable bond
between the second and third layers. Selection of the various materials determines
the nature of the bond, i.e., whether it is permanent, peelable, fracturable or combinations
thereof.
[0069] Suitable polymers for use in the outer, tie and inner heat sealable layers include
both poly-type material such as ethylene homopolymers and copolymers as well as ionomer
type material. Examples of suitable polymers include: ethylene vinyl acetate copolymer
(EVA, ethylene α-olefin copolymers, linear low density polyethylene, low density polyethylene,
very low density polyethylene (VLDPE), neutralized ethylene acid copolymer, plastomers,
ethylene acrylate copolymer, ethylene methyl acrylate copolymer and zinc or sodium
salts of partially or completely neutralized ethylene-methacrylate acid copolymers.
The inner heat seal layer beneficially uses heat sealable materials. The tie layer
is selected to have a relatively low peel strength when peelably bonded to one of
either the outer layer or inner heat seal layer. The tie layer is typically comprised
of a blend of about 5-30% polybutylene and another constituent, such as ethylene vinyl
acetate copolymer, ethylene copolymers with C
4 - C
8 alpha olefin, linear low density polyethylene, ionomers, neutralized ethylene acid
copolymer or unneutralized ethylene acid copolymer and mixtures thereof. The term
"polybutylene" as used herein includes having polymeric units derived from butene
-1 as the major (75% polymeric units) components and preferably at least 80% of its
polymeric units will be derived from butene -1. A preferred polybutylene is a random
copolymer of butene -1 with ethylene having a reported density of 0.908 g/cm
3 and a melt index of 1.0 g/10 min. and a melting point of 117.2°C (243°F), which is
commercially available from Basell Polyolefins Company, N.V., The Netherlands, under
the trade name PB 8640. In this preferred peelable embodiment, the heat seal formed
between the inner heat seal layer and another layer to which it is heat sealed, whether
part of another film or the same, should be permanent, i.e., should have a seal strength
greater than the peelable bond between the tie layer and one of its adjacent layers.
The preferred three layer coextruded peeling structure described above contemplates
optional additional layers to product a film of 4, 5, 6, 7, 8, 9, 10 or more layers.
It is further contemplated that one or more additional layers may be coextruded with
the described three layers or separately and that the multilayer film structure may
be formed not only by coextrusion, but also by other methods well known in the art
such as coating lamination, adhesive lamination or combinations thereof.
[0070] It is also contemplated that such one or more additional layers may be adjacent to
or between any of the described three layers. In one embodiment of the invention the
heat seal layer may be replaced by a permanent adhesive or glue that may or may not
be applied hot or in a melt state, liquid state or otherwise. However, it is preferred
to utilize a heat sealable layer.
[0071] It is also contemplated that a peelable seal using one or more so-called "contaminated"
surface layers may be utilized where peeling occurs at a seal layer interface 432
rather than at an interior layer of film 411. This type of peeling system suffers
from disadvantage associate with, e.g., controlling the diverging properties of providing
high seal strength with desirable low forms for peelings, as well as problems of sealing
under conditions which may adversely affect seal integrity, e.g., where an article
being packaged deposits particulates, starch, fat, grease or other components which
may lessen seal strength or hamper the ability to provide a seal of desired strength
such as a strong hermetic fusion bond, e.g., by heat sealing. Such sealing systems
are often referred to as two layer peeling systems, but may include 3, 4, 5, 6, 7,
8, 9, 10 or more layers in the film structure.
[0072] Preferred peelable sealing films and peelable seal systems are disclosed in
U.S. Patent No. 4,944,409 entitled "EASY OPEN PACKAGE".
[0073] A preferred multilayer, barrier film structure for use in fabricating bags according
to the present invention is illustrated in FIG. 10, which depicts an enlarged, end
view of the first seal 416 of FIG. 9 made from the sheet of heat-shrinkable film 411.
Layer thicknesses in FIG. 10 and other figures presented herein are not to scale,
but are dimensioned for ease of illustration. A preferred easy to peel heat shrinkable
film 411 is a five layer coextrusion and includes from inner surface 419 of the tube
member 419 (See FIG. 9) to an opposing outer surface 433.
- (a) an inner surface heat sealing layer 434 preferably comprising a blend of ethylene
vinyl acetate (EVA) and polyethylene;
- (b) a barrier layer 435 preferably comprising a vinylidene chloride copolymer (PVDC);
- (c) a core layer 436 preferably comprising a blend of EVA and polyethylene;
- (d) a tie layer 437 preferably comprising a blend of polyethylene and polybutylene;
and,
- (e) an outer surface heat sealing layer 438 preferably comprising polyethylene.
[0074] The thicknesses of each layer, based on the total thickness of the film 411, may
be typically <50% inner surface heat sealing layer 434; <20% barrier layer 435; <28%
core layer 436; <15% tie layer 437; and <15% outer heat sealing layer 438. The first
seal 416 is made by longitudinally heat sealing the inner film surface 419 of film
411 to the outer film surface 433 along their respective lengths, such that inner
film surface 419 and outer film surface 433 overlap. In this manner, a fusion bond
is made between the inner surface heat sealing layer 434 and the outer surface heat
sealing layer 438. The peelable bond of the system is provided by the tie layer 437
and peeling occurs there, e.g., at the tie layer interface with the outer surface
heat sealing layer 438, and/or at the tie layer interface with core layer 436 and/or
between outer layer 438 and core layer 436. Thus, referring to FIGS. 9 and 10, the
peelable portion of the film is on the outside of the tube member 418, which is preferable.
This will insure that the first seal 416 is peelable, while the second seal 420 and
final closing seal (not shown) are strong fusion seals between the inner surface heat
sealing layer 434 of each bag wall 430 and 431.
[0075] Referring to FIG. 11, a fragmentary sectional view taken along lines B-B of FIG.
9 illustrates how a preferred embodiment of the invention works to create strong end
seals while permitting the lap seal to function as an easy to open peel seal. In FIG.
9, film 411 has an outer surface 433 with consecutive layers therefrom of outer surface
layer 438, tie layer 437, core layer 436, barrier layer 435, and inner surface heat
sealing layer 434. Referring to FIG. 9, the second seal 420 is provided across tube
member 418 to collapse its surface 419 upon itself. Referring again to FIG. 11, this
seal joins inner surface heat sealing layer 434 to itself with the peelable tie layer
437 being positioned distal from end seal interface 439. This preferred embodiment
of the invention depicted in FIGS. 9-11 combines (a) an end seal which mates like
materials with strong seal properties to each other keeping distal the easily peelable
tie layer 437 and (b) a lap seal having peelable tie layer 437 proximate the outer
surface heat sealing layer 438 and lap seal interface 432 , thereby providing an easily
peelable opening in bags or packages made using the described configuration.
[0076] The film 411 is designed to control the film failure when peeled manually. Due to
the composition of the peelable tie layer 437, its location proximate the lap seal
interface 432, and in the case of the preferred three layer peelable system, the thinness
and composition of the outer surface heat sealing layer 438; as the second side edge
412b is manually pulled across, up and away from the lap seal 416, a first rupture
or tear will begin. This tear will propagate from the heat seal at the edge 417b of
lap seal interface 432 through the outer heat sealing layer 438 thereof. If the peelable
bond is designed to occur at the tie layer 437, the continued application of opening
force causes: a delamination or breaking of the adhesive bond, along the tie layer
437/outer heat sealing layer 438 interface or along the tie layer 437/core layer 436
interface and/or causes fracture of the tie layer 437, or a combination thereof until
the tear reaches the opposite side edge 417a of the heat seal 416, where the tear
either propagates to edge 412a or back across the outer layer 438 and the bag is thereby
opened.
[0077] In general, the films used in the heat-shrinkable bags of the present invention can
have any thickness desired, so long as the films have sufficient thickness and composition
to provide the desired properties for the particular packaging operation in which
the film is used, e.g., peelable seal, puncture-resistance, modulus, seal strength,
barrier, optics, etc. For efficiency and conservation of materials, it is desirable
to provide the necessary puncture-resistance and other properties using the minimum
film thicknesses. Preferably, the film has a total thickness from about 31.75 µm (1.25)
to about 203.2 µm (8.0 mils); more preferably from about 44.45 µm (1.75) to about
76.2 µm (3.0 mils).
[0078] Another embodiment of the present invention is illustrated in FIGS. 12 and 13, generally
as bag 415a. Identical reference numerals have been used with respect to elements
of Bag 415a, which are also found in bag 415. Bag 415a further includes a pull flap
440. The pull flap 440 is formed by providing additional overlap by moving the first
and second sides edge 412a and 412b further apart and positioning the first lap seal
416 such that a portion of the first bag wall, first side 430a, that overlaps the
first bag wall second side 430b outside of the product receiving chamber 425 is not
sealed to the second side 430b. The pull flap 440 may be readily grasped by the end
user and pulled to easily open the package, without resort to a cutting instrument,
as is often required when opening packages without a peelable system. Although shown
as extending the entire length of the bag 415a, a skilled artisan will appreciate
that the pull flap 440 may be cut to a desired shape or that any other known device
known to aid initiation of peeling may be incorporated. The preferred film illustrated
in FIGS. 8, 10 and 11 described previously is also preferred for use with bag 415a.
[0079] The alternative embodiment illustrated in FIGS. 12 and 13 has reversed the location
of the bag mouth 424 and second seal 420 of FIG. 8 which is depicted in FIG. 12 as
bag mouth 424a and second seal 420a.
[0080] Referring to FIG. 14, an illustration of the second seal 420a in cross-section shows
first bag wall 430 sealed to second bag wall 431 from first bag edge 422 to second
bag edge 423 and across first lap seal 416 which is located between first side edge
412a and second side edge 412b. In the well known heat sealing process opposing sealing
bars or wires press together layers of film under elevated temperature and pressure
for a time sufficient to cause a fusion bond therebetween. These heat seal bars may
be rigid and/or flexible but generally are not supple or not as supple as the film
being sealed. As depicted in FIG.14, the second seal 420a has a seal interface 439a
which has two possible points proximate first side edge 412a and second side edge
412b where sealing pressure may be reduced during the sealing operation sealing pressure
may be reduced at second seal interface 439a at a point 441 below edge 412b, and also
at point 442 adjacent first edge 412a. It is also possible that a void may exist,
e.g., at point 442. In order to produce a desired strong seal particularly at points
441 and 442 as well as all along second seal interface 439a, sealing parameters such
as pressure, temperature, dwell time and heat sealing layer composition may be adjusted
as desired. In particular, it has been found that use of a high melt index polymer
component in the heat seal layer may be advantageous to fill potential voids. It may
also be advantageous to taper one or both edges 412a and 412b to increase contact
surfaces and/or pressure between the overlapping films particularly at points 441
and 442 and adjacent areas.
[0081] A bag which is not an embodiment of the present invention is illustrated in FIG.
15, generally as bag 415b. Again, like elements include like reference numerals. Bag
415b includes a first fin seal 516 joining the first and second sides 430a and 430b
of bag wall 430 such that the inner film surfaces 419 of each side are in a face-to-face
abutment, having a fin seal interface 517. One or both of the first and second side
edges 412a and 412b may extend outwardly beyond the first fin seal interface 517 such
that a pull flap (not shown) is provided. Bag 415a (FIG. 12) is preferred over bag
415b, since the plane of the first seal 416 is parallel to the plane of the shrink
forces encountered during the heat-shrinking process. The first fin seal 516 of bag
415b places the plane of the heat seal perpendicular to the shrink forces (as shown
by arrows Z' and Z" in FIG. 17), which increases the risk of seal failure (premature
peeling) during the heat-shrinking process. Additionally, since the inventive receptacles
are advantageously fabricated from a single sheet or web of film, then a fin seal
arrangement, such as first seal 516, requires that each seal of the receptacle be
a peelable seal. Also, the second seal 420 and final closing seal (not shown) are
also necessarily peelable since the first and second bag walls 430a and 430b are sealed
with the film in the same abutted relationship. For example, FIG. 17 depicts an enlarged
view of the first fin seal 516 shown in cross-section showing discrete layers of the
preferred film discussed above with bags 415 and 415a. Each wall 450 and 452 of the
seal 516 includes a three layer peelable system (the tie layer 437) equidistant from
and proximate to the sealed interface of sealant layer 438. Thus, it not only cannot
be predetermined in which wall 450 or 452 the peel failure will occur, but all seals
are easily peeled and the shrink force direction further reduces the ability to make
strong seals. For all these disadvantages this bag is outside the scope of the present
invention.
[0082] Another embodiment of the present invention is illustrated in FIGS. 18 and 19 generally
as bag 415c. Again, like elements include like reference numerals. Bag 415c includes
a first seal 616 comprising a butt-seal tape 641 comprising a butt-seal film 611 having
a first border 607, a second border 609, a sealing surface 615 and an exterior surface
614. The first seal 616 includes a first heat seal 618 longitudinally joining the
first side 430a of bag wall 430 to the first border 607 of the butt-seal tape 641,
and a second heat seal 619 longitudinally joining the second side 430b of bag wall
430 to the second border 609 of the butt-seal tape 641. Thus, first and second sides
430a and 430b are joined in an abutting edge-to-edge relationship thereby forming
bag wall 430 without a heat seal directly there between. Preferably, the butt-seal
film 611 comprises the same film as described in reference to bags 415, 415a and 415b
described above and illustrated in FIGS. 8-17, with the outer heat sealing layer 438
(FIG. 9) comprising the inner surface 615. Thus, bag 415c may be manufactured from
a film that does not include a peelable system therein, but includes a peelable seal
by means of the peelable system included in the butt-seal tape 641 used to form the
first seal 616. Conversely, the film 411 may preferably include a peelable system
while the butt-seal tape 641 does not, or both film 411 and butt-seal film 611 may
include a peelable system compatible with the other. The butt-seal film 611 is preferably
heat-shrinkable, but need not be. A pull flap 440 may be provided in the butt-seal
tape 641 to provide an area for the consumer to manually grasp and pull to easily
open the bag 415c. If the butt-seal tape 641 is sealed to the inner surface 419 of
the film 411, then a portion of the first or second sides 430a and 430b may extend
outwardly past the first or second heat seals 618 and 619 to provide a pull flap for
the consumer to grasp. The second seal 420 is preferably a permanent seal made between
the inner surfaces 419 of the first and second bag walls 430a and 430b.
[0083] Although depicted in FIG 18 as being sealed to the outer surfaces 415 of the first
and second sides 412 and 414, one skilled in the art will appreciate that the butt-seal
tape 641 that forms the first seal 616 may be placed on the inside of the bag 410c
(not shown), whereby the sealing surface 615 is heat sealed to inner surfaces 419
of the first and second sides 430a and 430b. In this instance, preferably at least
one of the first and second sides 430a and 430b include a portion that extends outwardly
beyond the heat seal to the butt-seal tape 641. Thus, the consumer is provided with
a pull flap to grasp.
[0084] A further embodiment of the present invention is illustrated in FIGS. 20 and 21 generally
as bag 415d. Like elements discussed above in connection with bags 415, 415a, 415b
and 415c have been given the same reference numerals in bag 415d. Bag 415d includes
a first seal 716 comprising a seal strip 741 comprising a strip film 711 having an
inside surface 714 and an outward surface 715. The seal strip 741 includes a first
margin 718 longitudinally heat sealed to the first side 430a by first heat seal 720,
such that the outward surface 715 is sealed in face-to-face contact with the inner
surface 419 of film 411. The seal strip 741 includes a second margin 719 longitudinally
heat sealed to the second side 430b by second heat seal 721, such that the inside
surface 714 is sealed in face-to-face contact with the outer surface 433 of the second
side 430b. A pull flap 440 may be provided by including a portion of the strip film
711 that extends outwardly beyond second heat seal 721 joining the second margin 719
and the second side 430b. Alternatively, the first side 430a could be provided with
a portion that extends outwardly beyond the second heat seal 420.
[0085] Preferably, the strip film 711 includes a peelable system and comprises the same
film as described in reference to bags 415, 415a and 415b described above and illustrated
in FIGS. 8-19, with the outer heat sealing layer 438 (FIGS. 10-11) comprising the
inside surface 714. In this manner, the heat seal 721 is peelable and the film 411
need not include a peelable system. Alternatively, the outer heat sealing layer 438
could comprise the outward surface 715, such that heat seal 720 is peelable. In this
case, the film 411 need not include a peelable system and the second seal 420 may
be made permanent. In a similar manner as described for bag 415c, the strip film 711
may not include a peelable system while the film 411 does include a peelable system,
or both film 411 and strip film 711 may include compatible peelable systems. The strip
film 711 is preferably heat-shrinkable, but need not be.
[0086] The bags according to the invention are preferably fabricated continuously from a
continuous sheet or roll stock as described in
U.S. Patent Application No. 10/371,950, in the name of Gregory Robert Pockat, et al.,
filed on February 20, 2003 entitled "HEAT-SHRINKABLE PACKAGING RECEPTACLE". The roll stock is slit to a desired
width and fed to bag making equipment, wherein the machine direction sides of the
film are brought together and sealed longitudinally, with a lap seal (bags 415 and
415a) to form a continuous single-seamed tube, or tube member. A transverse seal is
made across the tube member and the section including the transverse seal is severed
from the continuous tube to form the individual bag. Generally, heat seals are made
by supplying sufficient heat and pressure between two polymeric film layer surfaces
for a sufficient amount of time to cause a fusion bond between the polymeric film
layers. Common methods of forming heat seals include hot bar sealing, wherein adjacent
polymeric layers are held in face-to-face contact by opposing bars of which at least
one is heated, and impulse sealing, wherein adjacent polymeric layers are held in
face-to-face contact by opposing bars of which at least one includes a wire or ribbon
through which electric current is passed for a very brief period of time to cause
sufficient heat to cause the film layers to fusion bond. Less area is generally bonded
with an impulse seal relative to a hot bar seal, thus the performance of the film's
sealing layer is more critical. However, an impulse seal is generally more aesthetic
since less area is used to form the bond.
[0087] The films selected to fabricate the inventive receptacles are preferably biaxially
stretched or oriented by the well-known trapped bubble or double bubble technique
as for example described in
U.S. Patent Nos. 3,456,044 and
6,511,688. In this technique an extruded primary tube leaving the tubular extrusion die is
cooled, collapsed and then preferably oriented by reheating, reinflating to form a
secondary bubble and recooling. The film is preferably biaxially oriented wherein
transverse (TD) orientation is accomplished by inflation to radially expand the heated
film. Machine direction (MD) orientation is preferably accomplished with the use of
nip rolls rotating at different speeds to pull or draw the film tube in the machine
direction. The stretch ratio in the biaxial orientation to form the bag material is
preferably sufficient to provide a film with total thickness of between about 1 and
8 mils. The MD stretch ratio is typically 3:1-5:1 1 and the TD stretch ratio is also
typically 3:1-5:1.
[0088] Referring now to FIG. 22, a double bubble (also know as a trapped bubble) process
is shown. The polymer blends making up the several layers are coextruded by conveying
separate melt streams 611a, 611b, and 611c to the die 630. These polymer melts are
joined together and coextruded from annular die 630 as a relatively thick walled multilayered
tube 632. The thick walled primary tube 632 leaving the extrusion die is cooled and
collapsed by nip rollers 631 and the collapsed primary tube 632 is conveyed by transport
rollers 633a and 633b to a reheating zone where tube 632 is then reheated to below
the melting point of the layers being oriented and inflated with a trapped fluid,
preferably gas, most preferably air, to form a secondary bubble 634 and cooled. The
secondary bubble 634 is formed by a fluid trapped between a first pair of nip rollers
636 at one end of the bubble and a second pair of nip rollers 637 at the opposing
end of the bubble. The inflation which radially expands the film provides transverse
direction (TD) stretching and orientation. Orientation in the machine direction (MD)
is accomplished by adjusting the relative speed and/or size of nip rollers 636 and
nip rollers 637 to stretch (draw) the film in the machine direction.
[0089] The biaxial orientation preferably is sufficient to provide a multilayer film with
a total thickness less than 254 µm (10 mil) and typically from about 31.75 µm (1.25)
to 203.2 µm (8.0 mils) or more, preferably less than 127 µm (5 mil) and more preferably
between 1.75 and 3.0 mils (44.5 to 76 µ).
[0090] After orientation, the tubular film 238 is collapsed preferably to a flatwidth of
up to 2.03 m (80 inches), typically between about 127-762 mm (5-30 inches), slit open
longitudinally, laid flat and wound on a reel 239 for use as rollstock. One skilled
in the art will appreciate that while the above described method may be used to form
the film, films may be made by other conventional processes, including single bubble
blown film or slot cast sheet extrusion processes with subsequent stretching, e.g.,
by tentering to provide orientation. One skilled in the art will further appreciate
that the flatwidth of the collapsed tube will determine the width of the sheet film
that results therefrom. Thus, the primary tube dimensions and subsequent processing
may be selected to provide a maximum flatwidth and film thickness for the desired
application, thereby advantageously maximizing the production capacity of the film
making equipment.
[0091] Advantageously, a bag maker may produce bags of various lengths and widths from rolls
of film rollstock by adjusting the width of the sheet and the distances between the
transverse end seal and bag mouth for a particular bag or series of bags. This advantageously
avoids the costly need to produce specific widths of seamless tubes which are currently
widely used by meat packers and which do not include a peelable seal. Also the present
invention permits cost savings and manufacturing efficiencies by permitting creation
of numerous widths and lengths of bag from standard rollstock. The bag maker may simply
slit film rollstock to a desired width and form a continuous tube member by longitudinally
sealing opposing sides as described for bags 415, 415a and 415b. Bags of adjustable
lengths may be made by transversely sealing and cutting through the tube member at
a position spaced from the transverse seal.
[0092] Preferably, bag making is a continuous process; shown schematically in FIG. 23, wherein
the film is directed to a bag making assembly (not shown) where individual end-seal
bags are made. Film 411 is fed continuously from reel 639 and optionally slit to form
a desired width film 411a and an unused film 411b. Film 411a is fed to a bag making
assembly (not shown). Unused film 411b is rewound on reel 639b for later use, or may
be fed to another bag making assembly. The first and second sides 430a and 430b of
film 411a are brought together and sealed longitudinally, preferably in a first seal,
e.g., lap seal 416 having an additional overlap portion that will act as a pull flap,
to form a continuous backseamed tube member 418. The second seal 420 is provided transversely
across the tube member 418 at a desired location spaced from the opening 424. The
tube member 418 is then (or preferably simultaneously) severed to separate the portion
containing the second seal from the continuous tube, thereby forming bag 415. Typically
as the transverse seal is made for one bag a transverse cut forming the mouth of the
adjacent bag is being made. This process forms a so called "end-seal" bag which, when
it is laid flat, has a bottom edge formed by the transverse heat seal, an open mouth
formed by the severed edge and two side edges formed by the fold produced when the
tube member is laid flat. The transverse heat seal should extend across the entire
tube member to ensure a hermetic closure where such is desired. Each bag being formed
from a length of the tube member will necessarily be formed by at least two, usually
parallel, spaced apart, transverse cuts which cause a segment of the tube member to
be made and one transverse seal, usually adjacent one of these cuts, will define a
bag bottom which is located opposing the bag opening, which is formed by the distal
cut. The spacing between the lateral seal and the opening, which may vary, will determine
the length of the bags formed. The length of the bags can easily be varied by changing
the distance between transverse seals and cuts. The width of the bags can also be
easily varied by changing the width of the film by slitting the standard rollstock.
[0093] Unless otherwise noted, the following physical properties are used to describe the
invention, films and seals. These properties are measured by either the test procedures
described below or tests similar to the following methods.
Average Gauge: ASTM D-2103
Tensile Strength: ASTM D-882, method A
1% Secant Modulus: ASTM D-882, method A
Oxygen Gas Transmission Rate (O2GTR): ASTM D-3985-81
Percent Elongation at Break: ASTM D-882, method A
Molecular Weight Distribution: Gel permeation chromatography
Gloss: ASTM D-2457, 45° Angle
Haze: ASTM D-1003-52
Melt Index: ASTM D-1238, Condition E (190°C) (except for propene-based (>50% C3 content) polymers tested at Condition L(230°C.))
Melting Point: ASTM D-3418, peak m.p. determined by DSC with a 10°C/min. heating rate.
Vicat Softening Point (Vsp): ASTM D-1525-82
Seal Strength: ASTM F88-94 (Standard Test Methods for Seal Strength of Flexible Barrier
Materials)
[0094] Shrinkage Values: Shrinkage values are obtained by measuring unrestrained shrink of a 10 cm. square
sample immersed in water at 90°C (or the indicated temperature if different) for five
to ten seconds. Four test specimens are cut from a given sample of the film to be
tested. Specimens are cut into squares of 10 cm length (M.D.) by 10 cm. length (T.D.).
Each specimen is completely immersed for 5-10 seconds in a 90°C (or the indicated
temperature if different) water bath. The specimen is then removed from the bath and
the distance between the ends of the shrunken specimen is measured for both the M.D.
and T.D. directions. The difference in the measured distance for the shrunken specimen
and each original 10 cm. side is multiplied by ten to obtain percent shrinkage in
each direction. The shrinkage of 4 specimens is averaged and the average M.D. and
T.D. shrinkage values reported. The term "heat shrinkable film at 90°C" means a film
having an unrestrained shrinkage value of at least 10% in at least one direction.
Tensile Seal Strength (Seal Strength) Test
[0095] Five identical samples of film are cut 1 inch (2.54 cm) wide and a suitable length
for the test equipment e.g. about 5 inches (12.7 cm) long with a 1 inch (2.54 cm)
wide seal portion centrally and transversely disposed. Opposing end portions of a
film sample are secured in opposing clamps in a universal tensile testing instrument.
The film is secured in a taut snug fit between the clamps without stretching prior
to beginning the test. The test is conducted at an ambient or room temperature (RT)
(about 23 °C) test temperature. The instrument is activated to pull the film via the
clamps transverse to the seal at a uniform rate of 12.0 inches (30.48 cm) per minute
until failure of the film (breakage of film or seal, or delamination and loss of film
integrity). The test temperature noted and lbs. force at break are measured and recorded.
The test is repeated for four additional samples and the average grams at break reported.
Ram Puncture Test
[0096] The ram puncture test is used to determine the maximum puncture load or force, and
the maximum puncture stress of a flexible film when struck by a hemispherically or
spherically shaped striker. This test provides a quantitative measure of the puncture
resistance of thin plastic films. This test is further described in
U.S. Patent Application No. 09/401,692.
[0097] Following are examples and comparative examples given to illustrate the invention.
[0098] In all the following examples, unless otherwise indicated, the film compositions
were produced generally utilizing the apparatus and method described in
U.S. Patent Nos. 3,456,044 (Pahlke) and
6,511,688 (Edwards, et al.) which both describe a coextrusion type of double bubble method and in further accordance
with the detailed description above. In the following examples, all layers are extruded
(coextruded in the multilayer examples) as a primary tube which is then cooled upon
exiting the die e.g. by spraying with tap water. This primary tube is then reheated,
and stretched and cooled as taught in the above patents.
EXAMPLE 2
[0099] A heat-shrinkable bag according to the present invention, as generally illustrated
in FIGS. 10 & 11, is produced from a film comprising a coextruded five-layer biaxially
oriented shrink film having from inner surface to outer surface, (A) an inner heat
sealing layer, (B) a barrier layer (C) a core layer, (D) a tie layer and (E) an outer
heat sealing layer. The inner and outer layers being directly attached to opposing
sides of the barrier layer. The five layers included the following composition:
- (A) 37 wt. % VLDE; 24% EVA; 33 % plastomer (Exact 4053); 6% processing aids;
- (B) a blend of about 85% vinylidene chloride-vinyl chloride copolymer and about 15%
vinylidene chloride-methacrylate copolymer;
- (C) 100 wt. % EMA
- (D) 20 wt. % VLDPE; 33% plastomer (Exact 4053) and 20 wt. % polybutylene; and,
- (E) 40 wt. % VLDPE; 33% plastomer (Exact 4053); 25% EVA; 2% processing air.
[0100] One extruder was used for each layer. Each extruder was connected to an annular coextrusion
die from which heat plastified resins were coextruded forming a primary tube. The
resin mixture for each layer was fed from a hopper into an attached single screw extruder
where the mixture was heat plastified and extruded through a five-layer coextrusion
die into the primary tube under conditions similar to those disclosed in copending
U.S. Application No.
US 2004/0166262.
[0101] Although not essential, it is preferred to irradiate the entire film to broaden the
heat sealing range and/or enhance the toughness properties of the inner and outer
layers by irradiation induced cross-linking and/or scission. This is preferably done
by irradiation with an election beam at dosage level of at least about 2 megarads
(MR) and preferably in the range of 3-5 MR, although higher dosages may be employed
especially for thicker films or where the primary tube is irradiated. Irradiation
may be done on the primary tube or after biaxial orientation. The latter, called post-irradiation,
is preferred and described in
Lustig et al. U.S. Pat. No. 4,737,391. An advantage of post-irradiation is that a relatively thin film is treated instead
of the relatively thick primary tube, thereby reducing the power requirement for a
given treatment level.
[0102] The film is unwound and slit to a desired width. The film is then fed into the bag
making equipment to form a tube member having a continuous longitudinally extending
lap seal. Bags according to the bag 415a depicted in FIG. 12 may be formed by sealing
laterally across the tube member and simultaneously severing the sealed portion from
the continuous tube structure.
[0103] Various tests may be performed on the resultant inventive bags. The gauge thickness
will typically be a film thickness of less than 254 µm (10 mil), and preferably between
31.75 µm (1.25) to 127 µm (5.0 mil). The lap seal should typically have an average
seal strength of at least 2 kilograms per 25.4 mm (inch). The end seal will typically
have an average seal strength of at least 3 kilograms. The bag will also have an average
M.D. and T.D. heat shrinkability at 90 °C of at least 20%, and preferably at least
40% in both directions, respectively. This preferred bag will have very good heat
shrink percentages which are highly desirable for packaging cuts of fresh red meat
and also have extremely good puncture resistance, yet advantageously incorporate a
peelable seal heretofore not seen in individual food packaging bags. Thus an economical
to produce, heat shrinkable bag, having a peelable seal, puncture resistance and strong
end seals is provided having a unique combination of features and commercial advantages
previously unknown.
[0104] The present invention advantageously provides an individual heat-shrinkable bag having
an easily peelable seal. Thus, the receptacles or bags of the present invention may
be easily opened without resort to a knife or other cutting/opening instrument, which
allows food producers to offer a desirable, consumer-friendly package.
[0105] Another preferred embodiment of the present invention uses a 7-layer heat shrinkable
film to produce backseamed material. This 7-layer film has several advantages over
3 and 5 layer structures. Use of a polymeric having a high melt index greater than
2.0 dg/10 min, e.g., an ethylene α-olefin copolymer such as Exact 4053 in the sealant
layers helps seal through creases and wrinkles in the seal. This is important as the
overlapped area creates a crease in the seal.
[0106] Another advantage is use of a strong adhesive polymer, e.g., an ethylene methylacrylate
copolymer (EMA) such as Emact SP 1330 (which reportedly has: a density of 0.948 g/cm
3; melt index of 2.0 g/10min.; a melting point of 93°C; is at softening point of 49°C;
and a methylacrylate (MA) content of 22% as a PVDC tie layer to give improved adhesion.
This has been shown to give a superior bond strength. EMA gives bonds over 100g in
the finished film. A preferred 7-layer structure has a first heat seal layer comprising
an ethylene α-olefin copolymer (Exxon Exact 3139), a second peelable tie layer comprising
a polymeric blend having between 15 to 35% each of EVA (Exxon 701.ID); ethylene butene
-1 copolymer (Exxon Exact 4053); ethylene octene -1 copolymer (Nova VLDPE 10B) and
a third tie layer, e.g., comprising EMA (Voridian SP 1330); a fourth barrier layer,
e.g., as described above in Example 1; a fifth tie layer, e.g., comprising EMA; a
sixth intermediate layer comprising a blend of 20-45% each of EVA ethylene-butene
-1 copolymer and ethylene-octene -1 copolymer; and a seventh outer surface layer comprising
an ethylene α-olefin copolymer, e.g., Exxon Exact 3139.
[0107] The above film is preferably 50.8 µm (2 mils) thick overall and has a layer thickness
ratio for the first through seventh layers, respectively of 10:42:5:18:5:15:5.
[0108] The bags 415, 415a, 415b, 415c and 415d may be fabricated of nearly any dimensions
economically since the bags are not formed from a seamless tube that must be generated
to the desired width. The only limitation on size of fabricated bag is the size of
rollstock films. Standard roll stock films are available in widths in excess of 2.54
m (100 inches). The present invention allows a bag manufacturer to fabricate any size
bag from the same flat sheet of roll stock, up to the dimensional limits of the roll
stock. For example, if the roll stock is 1.32 m (52 inches) in width, a tube member
can be fabricated having a lay-flat width of approximately 660.4 mm (26 inches), taking
into account the amount of overlap, gap or abutment in the first seal 416, 516, 616
and 716 used. For example, if the manufacturer wishes to fabricate a lap seal or fin
seal bag having a lay-flat width of 457.2 mm (18 inches), then the manufacturer slits
the standard roll stock to the appropriate width (approximately 914.4 mm (36) plus
extra for the area of the first seal 416 or 516). The unused portion slit form the
standard roll stock is rewound for use making bags of another dimension(s). In this
manner, standard roll stock films can be manufactured more economically because film
manufacturing equipment may be run at or near the upper limits of film width production
and thereby use nearly all the equipments capacity. Fabricating bags from seamless
tubes requires that the film making equipment be run at limited capacities to form
the different smaller width tubes. Additionally, the film making equipment requires
costly set-up and breakdown between jobs of differing dimensions that add significantly
to the cost of manufacturing the seamless tubes.
[0109] An easily peelable heat shrinkable film has been described above with respect to
end sealed bags having seamless sides, it should be readily apparent in view of the
present disclosure that side seal heat shrinkable bags and pouches made from a plurality
of films may also be adapted to the present invention to provide easy to peel open
heat shrinkable receptacle. The present invention may be utilized with heat shrinkable
formed into a pouch as described in
U.S. Patent Nos. 6,015,235 (Kraimer, et al.) and
6,206,569 (Kraimer, et al.). .
1. An end-sealed packaging receptacle (10) formed from a sheet of a heat-shrinkable film
(11), said sheet of a heat-shrinkable film (11) having a first side (12), an opposing
second side (14), an inner surface (15) and an outer surface (13), said receptacle
(10) comprising:
a first seal (16) connecting said first side (12) to said second side (14) and defining
a tube member (18) having a first receptacle wall (20), a second receptacle wall (22),
opposing first and second receptacle edges (24,26), an end (30) and a second end (28)
opposite said first end (30);
a second seal (32) provided through said first and second receptacle walls (20,22),
said second seal (32) extending laterally across the width of both said first and
second receptacle walls (20,22) at a position proximate said end (30), whereby an
empty product receiving chamber (34) is defined by said first receptacle wall (20),
said second receptacle wall (22), said second seal (32) and said second end (28);
and,
characterised in that the receptacle is an severed and separated individual receptacle, the second end
which is an open mouthly (28), said first seal (16) comprises a peelable seal selected
from a lap seal, a seal strip or a butt-seal including a butt-seal tape, said second
seal (32) is nonpeelable, and said sheet of heat-shrinkable film (11) comprises a
biaxially stretched film having a shrinkage value of at least 20% shrink at 90°C in
at least one direction.
2. A receptacle (10) according to claim 1, wherein said first seal (16) comprises a butt-seal
including a butt-seal tape (217), said butt-seal tape (217) having a first border
and a second border, a first heat seal (216a) joining said first border to said first
side (212), and a second heat seal (216b) joining said second border to said second
side (214).
3. A receptacle (10) according to claim 2, wherein said butt-seal tape (217) includes
a pull flap (440).
4. A receptacle according to claim 2 or 3, wherein said first border is heat sealed to
the inner surface (15) of said first side (12) and said second border is heat sealed
to the inner surface (15) of said second side (14).
5. A receptacle (10) according to any of claims 2 to 4, wherein at least one of said
first and second sides (12,14) extends outwardly to form a pull flap (440).
6. A receptacle (10) according to any of claims 2 to 5, wherein said butt-seal tape (217)
comprises a butt-seal film including a peelable system.
7. A receptacle (10) according to any of claims 2 to 6, wherein said first and second
heat seals (216a,216b) are peelable.
8. A receptacle (10) according to claim 1, wherein said first seal (16) includes a seal
strip (741), said seal strip (741) comprising a strip film (711) having a first margin
(718), a second margin (719), an inside surface (714) and an outward surface (715);
a first heat seal (720) joining said outward surface(715) of said first margin (718)
to said inner surface (419) of said first side(430a); and a second heat seal (721)
joining said inside surface (714) of said strip film to said outer surface (433) of
said second side (430b).
9. A receptacle (10) according to claim 8, wherein said second heat seal (721) is a peelable
seal.
10. A receptacle (10) according to claim 8 or 9, wherein said first heat seal (720) is
a peelable seal.
11. A receptacle (10) according to any of claims 8 to 10, wherein said strip film (711)
comprises a peelable system.
12. A receptacle (10) according to any of claims 8 to 11, wherein said strip film (711)
includes a pull flap (440).
13. A receptacle (10) according to any preceding claim, wherein said sheet of heat-shrinkable
film (11) includes a peelable system.
14. A receptacle (10) according to claim 1, wherein said film (11) comprises a multilayer
barrier film.
15. A receptacle (10) according to claim 14, wherein said multilayer barrier film (411)
comprises:
(a) an inner heat sealing layer (434);
(b) a barrier layer (435);
(c) a core layer (436);
(d) a tie layer (437); and,
(e) an outer heat sealing layer (438).
16. A receptacle (10) according to claim 15, wherein said outer heat sealing layer (438)
forms the outer surface (13) of said receptacle (10).
17. A receptacle (10) according to claim 15 or 16, wherein said tie layer (437) is permanently
bonded to said core layer (436) and peelably bonded to said outer heat sealing layer
(438).
18. A receptacle (10) according to claim 15 or 16, wherein said tie layer (437) is permanently
bonded to said outer heat sealing layer (438) and peelably bonded to said core layer
(436).
19. A receptacle (10) according to any of claims 15 to 18, wherein said tie layer (437)
comprises a blend of polybutylene and at least one other constituent.
20. A receptacle (10) according to claim 19, wherein said at least one other constituent
comprises polyethylene.
21. A receptacle (10) according to any of claims 15 to 20, wherein said outer heat sealing
layer (438) comprises polyethylene.
22. A receptacle (10) according to any of claims 15 to 21, wherein said core layer (436)
comprises a blend of polyethylene and an ethylene-vinyl acetate copolymer.
23. A receptacle (10) according to any of claims 15 to 22, wherein said barrier layer
(435) is selected from the group consisting of vinylidene chloride copolymers, ethylene
vinyl alcohol copolymers, polyacrylonitriles and polyamides.
24. A receptacle (10) according to claim 23, wherein said barrier layer (435) comprises
a vinylidene chloride copolymer.
25. A receptacle (10) according to any of claims 15 to 24, wherein said inner heat sealing
layer (434) comprises a blend of polyethylene and ethylene-vinyl acetate copolymer.
26. A receptacle (10) according to any of claims 15 to 25, wherein said tie layer (437)
comprises a blend of polybutylene and at least one other constituent; said outer heat
sealing layer (438) comprises polyethylene; said core layer (436) comprises a blend
of polyethylene and an ethylene-vinyl acetate copolymer; said barrier layer (435)
comprises a vinylidene chloride copolymer; and said inner heat sealing layer (434)
comprises a blend of polyethylene and ethylene-vinyl acetate copolymer.
27. A receptacle (10) according to claim 26, wherein said at least one other constituent
comprises polyethylene and said barrier layer (435) comprises a blend of vinylidene
chloride-methyl acrylate copolymer and vinylidene chloride-vinyl chloride copolymer.
28. A receptacle (10) according to claim any of claims 15 to 27, wherein said inner heat
sealing layer (434) comprises from 0 to 50%, said barrier layer (435) comprises 0
to 20%; said core layer (436) comprises 0 to 28%; said tie layer (437) comprises 0
to 15%; and said outer heat sealing layer (438) comprises 0 to 15%, based on the total
thickness of said film (411).
29. A receptacle (10) according to any of claims 15 to 28, wherein said first seal (16)
comprises a lap seal and said inner heat sealing layer (434) forms the inside surface
(15) of the receptacle (10).
30. A receptacle (10) according to any of claims 1 or 14 to 29, wherein said first seal
(16) comprises a lap seal and said first side (12) includes an unsealed portion extending
outwardly beyond said first seal (16).
31. A receptacle (10) according to any of claims 1 or 14 to 30, wherein said first seal
(16) is a lap seal and has a seal strength of greater than 3 kilograms per 25.4mm
(per inch).
32. A receptacle (10) according to claim 31, wherein said first seal (16) has a seal strength
of greater than 6 kilograms per 25.4mm (per inch).
33. A receptacle (10) according to any of claims 1 to 30, wherein said first seal (16)
has a seal strength of less than 2 kilograms for a 25.4mm (one inch) strip.
34. A receptacle (10) according to claim 33, wherein said first seal (16) has a seal strength
of less than 2 kilograms for a 25.4mm (one inch) strip.
35. A receptacle (10) according to any preceding claim, wherein said sheet of heat-shrinkable
film (11) has a thickness from 31.75µm to 203.2µm (1.25 mil to 8.0 mil).
36. A receptacle (10) according to any preceding claim, wherein said sheet of heat-shrinkable
film (11) has a thickness from 44.45µm to 76.2µm(1.75 mil to 3.0 mil).
37. A receptacle (10) according to any preceding claim, wherein said shrinkage value is
in the machine direction.
38. A receptacle (10) according to any of claims 1 to 36, wherein said shrinkage value
is in the transverse direction.
39. A receptacle (10) according to any of claims 1 to 36, wherein said shrinkage value
is in both the machine direction and the transverse direction.
40. A receptacle (10) according to any preceding claim, wherein said second seal (32)
has a seal strength of greater than 3 kilograms per 25.4mm (per inch).
41. A receptacle (10) according to any preceding claim which is a bag, and wherein said
first and second receptacle walls (20,22) are first and second bag walls, and said
first and second receptacle edges (24,26) are first and second bag edges.
42. A receptacle (10) according to any preceding claim, wherein said first seal (16) connects
said first side (12) to said second side (14) along the lengths thereof and is continuous.
43. A method of forming an end-sealed, heat-shrinkable packaging receptacle (10) from
a flat sheet of film (11) comprising:
(a) providing a sheet of heat-shrinkable thermoplastic film (11) having a first side
(12) and an opposed second side (14);
(b) providing a first seal (16) between said first and second sides (12,14) to form
a tube member (18), said tube member (18) having a first receptacle wall (20), a second
receptacle wall (22), a bottom (30) at a first end of the receptacle and second end
(28) opposite the bottom; and,
(c) providing a second seal (32) through said first and second receptacle walls (20,
22), said second seal (32) extending laterally across said tube member (18) at a position
proximate said bottom (30);
characterised in that the receptacle is formed as an individual receptacle which is severed and separated
from the tube member, the second end of the receptacle is an open mouth, said first
seal (16) comprise a peelable seal selected from a lap seal, a seal strip or a butt-seal
including a butt-seal tape, said second seal (32) is nonpeelable, and said sheet of
heat-shrinkable film (11) comprises a biaxially stretched film having a shrinkage
value of at least 20% shrink at 90°C in at least one direction.
44. A method according to claim 43, wherein said sheet of heat-shrinkable thermoplastic
film (11) is slit to a desired width prior to bringing said first and second sides
(12,14) together.
45. A method according to claim 43 or 44, wherein said sheet of heat-shrinkable thermoplastic
film (11) comprises a continuous roll of film sheet and said method further includes
(d) providing a cut laterally through said tube member (18), said cut extending laterally
across at least the width of both said first and second receptacle walls (20,22) thereby
separating a portion of said tube member (18) including said second seal (32) from
said tube member (18).
46. A method according to any of claims 43 to 44, wherein said heat-shrinkable thermoplastic
film (11) is formed by coextruding a primary film tube, cooling the primary film tube,
collapsing the primary film tube, inflating the primary tube, reheating the inflated
primary film tube, biaxially stretching the primary film tube, cooling and recollapsing
the primary film tube, slitting the primary film tube longitudinally and laying open
the slit primary tube to produce a flat sheet of biaxially oriented film.
47. A method as claimed in any of claims 43 to 46, wherein said receptacle (10) is a bag
and wherein said first and second receptacle walls (20,22) are first and second bag
walls, and said first and second receptacle edges (24,26) are first and second bag
edges.
1. Endenverbundenes bzw. endenverschweißtes (endenversiegeltes) Verpakkungsbehältnis
(10) mit einer Lage einer wärmeschrumpfbaren Folie (Film) (11), wobei die wänneschrumpfhare
Folie (11) eine erste Seite (12), eine gegenüberliegende zweite Seite (14), eine innere
Oberfläche (15) und eine äußere Oberfläche (13) aufweist, wobei das Behältnis (10)
aufweist:
- eine erste Siegelung (16), welche die erste Seite (12) mit der zweiten Seite (14)
zur Bildung eines Schlauchkörpers (18) verbindet, wobei der Schlauchkörper (18) eine
erste Behältniswandung (20), eine zweite Behältniswandung (22), einander gegenüberliegende
erste und zweite Behältnisränder bzw. Behältnisflanken (24, 26), ein Ende (30) und
ein dem ersten Ende (30) gegenüberliegendes zweites Ende (28) aufweist;
- eine zweite Siegelung (32), welche durch die erste und zweite Behältniswandung (20,
22) gebildet bzw. bereitgestellt ist, wobei sich die zweite Siegelung (32) seitlich
bzw. quer über die Breite sowohl der ersten als auch der zweiten Behältniswandung
(20, 22) an einer Position in Nähe des Endes (30) erstreckt, so daß ein leerer Raum
(34) zur Produktaufnahme von der ersten Behältniswandung (20), der zweiten Behältniswandung
(22), der zweiten Siegelung (32) und dem zweiten Ende (28) abgegrenzt ist,
dadurch gekennzeichnet,
daß das Behältnis ein abgetrenntes und einzeln bzw. getrennt vorliegendes eigenständiges
Behältnis (Einzelbehältnis) ist, dessen zweites Ende eine Öffnung (28) ist, und daß
die erste Siegelung (16) eine abziehbare bzw. lösbare Siegelung aus der Gruppe von
überlappenden Siegelungen, Streifensiegelungen bzw. Siegelungsstreifen oder Stumpfsiegelungen
einschließlich eines Deckstreifens bzw. Stumpfsiegelungsstreifens umfaßt, die zweite
Siegelung (32) nicht abziehbar bzw. nicht lösbar ist und die Lage der wärmeschrumpfbaren
Folie (11) eine biaxial gestreckte Folie mit einem Schrumpfwert von mindestens 20
% Schrumpf bei 90 °C in mindestens eine Richtung umfaßt.
2. Behältnis (10) nach Anspruch 1, wobei die erste Siegelung (16) eine Stumpfsiegelung
einschließlich eines Deckstreifens (217) mit einer ersten und einer zweiten Grenze,
wobei der Deckstreifen (217) eine erste Wärmesiegelung (216a), welche die erste Grenze
mit der ersten Seite (212) verbindet, und eine zweite Wärmesiegelung (216b), welche
die zweite Grenze mit der zweiten Seite (214) verbindet, aufweist.
3. Behältnis (10) nach Anspruch 2, wobei der Deckstreifen (217) eine Zuglasche (440)
besitzt.
4. Behältnis nach Anspruch 2 oder 3, wobei die erste Grenze mit der inneren Oberfläche
(15) der ersten Seite (12) wärmeversiegelt ist und die zweite Grenze mit der inneren
Oberfläche (15) der zweiten Seite (14) wärmeversiegelt ist.
5. Behältnis (10) nach einem der Ansprüche 2 bis 4, wobei mindestens eine der ersten
und zweiten Seiten (12, 14) sich nach außen erstreckt, so daß eine Zuglasche (440)
gebildet ist.
6. Behältnis (10) nach einem der Ansprüche 2 bis 5, wobei der Deckstreifen (217) eine
Deckstreifenfolie mit einem abziehbaren bzw. lösbaren System umfaßt.
7. Behältnis (10) nach einem der Ansprüche 2 bis 6, wobei die erste und zweite Wärmesiegelung
(216a, 216b) abziehbar bzw. lösbar sind.
8. Behältnis (10) nach Anspruch 1, wobei die erste Siegelung (16) eine Streifensiegelung
(741) ist, wobei die Streifensiegelung (741) einen Folienstreifen (711) mit einem
ersten Rand (718), einem zweiten Rand (719), einer Innenfläche (714) und einer Außenfläche
(715) aufweist; eine erste Wärmesiegelung (720), welche die Außenfläche (715) des
ersten Randes (718) mit der inneren Oberfläche (419) der ersten Seite (430a) verbindet;
und eine zweite Wärmesiegelung (721), welche die Innenfläche (714) des Folienstreifens
mit der äußeren Oberfläche (433) der zweiten Seite (430b) verbindet, umfaßt.
9. Behältnis (10) nach Anspruch 8, wobei die zweite Wärmesiegelung (721) eine abziehbare
bzw. lösbare Siegelung ist.
10. Behältnis (10) nach Anspruch 8 oder 9, wobei die erste Wärmesiegelung (720) eine abziehbare
bzw. lösbare Siegelung ist.
11. Behältnis (10) nach einem der Ansprüche 8 bis 10, wobei der Folienstreifen (711) ein
abziehbares bzw. lösbares System aufweist.
12. Behältnis (10) nach einem der Ansprüche 8 bis 11, wobei der Folienstreifen (711) eine
Zuglasche (440) aufweist.
13. Behältnis (10) nach einem der vorangegangenen Ansprüche, wobei die Lage der wärmeschrumpfbaren
Folie (11) ein ablösbares System aufweist.
14. Behältnis (10) nach Anspruch 1, wobei die Folie (11) eine mehrschichtige Barrierefolie
umfaßt.
15. Behältnis (10) nach Anspruch 14, wobei die mehrschichtige Barrierefolie (411) aufweist:
(a) eine innere Wärmesiegelungsschicht (434);
(b) eine Barriereschicht (435);
(c) eine Kernschicht (436);
(d) eine Verbindungsschicht (437) und
(e) eine äußere Wärmesiegelungsschicht (438).
16. Behältnis (10) nach Anspruch 15, wobei die äußere Wärmesiegelungsschicht (438) die
äußere Oberfläche (13) des Behältnisses (10) bildet.
17. Behältnis (10) nach Anspruch 15 oder 16, wobei die Verbindungsschicht (437) dauerhaft
mit der Kernschicht (436) und abziehbar bzw. lösbar mit der äußeren Wärmesiegelungsschicht
(438) verbunden ist.
18. Behältnis (10) nach Anspruch 15 oder 16, wobei die Verbindungsschicht (437) dauerhaft
mit der äußeren Wärmesiegelungsschicht (438) und abziehbar bzw. lösbar mit der Kernschicht
(436) verbunden ist.
19. Behältnis (10) nach einem der Ansprüche 15 bis 18, wobei die Verbindungsschicht (437)
eine Mischung aus Polybutylen und mindestens einem anderen Bestandteil aufweist.
20. Behältnis (10) nach Anspruch 19, wobei der mindestens eine andere Bestandteil Polyethylen
aufweist.
21. Behältnis (10) nach einem der Ansprüche 15 bis 20, wobei die äußere Wärmesiegelungsschicht
(438) Polyethylen aufweist.
22. Behältnis (10) nach einem der Ansprüche 15 bis 21, wobei die Kernschicht (436) eine
Mischung aus Polyethylen und einem Ethylen/Vinylacetat-Copolymer aufweist.
23. Behältnis (10) nach einem der Ansprüche 15 bis 22, wobei die Barriereschicht (435)
ausgewählt ist aus der Gruppe von Vinylidenchlorid-Copolymeren, Ethylen/Vinylalkohol-Copolymeren,
Polyacrylnitrilen und Polyamiden.
24. Behältnis (10) nach Anspruch 23, wobei die Barriereschicht (435) ein Vinylidenchlorid-Copolymer
aufweist.
25. Behältnis (10) nach einem der Ansprüche 15 bis 24, wobei die innere Wärmesiegelungsschicht
(434) eine Mischung aus Polyethylen und Ethylen/Vinylacetat-Copolymer aufweist.
26. Behältnis (10) nach einem der Ansprüche 15 bis 25, wobei die Verbindungsschicht (437)
eine Mischung aus Polybutylen und mindestens einem weiteren Bestandteil aufweist;
die äußere Wärmesiegelungsschicht (438) Polyethylen umfaßt; die Kernschicht (436)
eine Mischung aus Polyethylen und einem Ethylen/Vinylacetat-Copolymer aufweist; die
Barriereschicht (435) ein Vinylidenchlorid-Copolymer aufweist; und die innere Wärmesiegelungsschicht
(434) eine Mischung aus Polyethylen und Ethylen/Vinylacetat-Copolymer aufweist.
27. Behältnis (10) nach Anspruch 26, wobei der mindestens eine andere Bestandteil Polyethylen
umfaßt und die Barriereschicht (435) eine Mischung von Vinylidenchlorid/Methylacrylat-Copolymer
und Vinylidenchlorid/ Vinylchlorid-Copolymer aufweist.
28. Behältnis (10) nach einem der Ansprüche 15 bis 27, wobei die innere Wärmesiegelungsschicht
(434) 0 bis 50 %; die Barriereschicht (435) 0 bis 20 %; die Kernschicht (436) 0 bis
28 %; die Verbindungsschicht (437) 0 bis 15 %; und die äußere Wärmesiegelungsschicht
(438) 0 bis 15 %, bezogen auf die Gesamtdicke der Folie (411), umfassen.
29. Behältnis (10) nach einem der Ansprüche 15 bis 28, wobei die erste Siegelung (16)
eine überlappende Siegelung umfaßt und die innere Wärmesiegelungsschicht (434) die
innere Oberfläche (15) des Behältnisses (10) bildet.
30. Behältnis (10) nach einem der Ansprüche 1 oder 14 bis 29, wobei die erste Siegelung
(16) eine überlappende Siegelung umfaßt und die erste Seite (12) einen nichtverschweißten
bzw. nichtversiegelten Abschnitt, welcher sich nach außen über die erste Siegelung
(16) erstreckt, aufweist.
31. Behältnis (10) nach einem der Ansprüche 1 oder 14 bis 30, wobei die erste Siegelung
(16) eine überlappende Siegelung ist und eine Siegelnahtstärke von mehr als 3 Kilogramm
pro 25,4 mm (pro Inch) aufweist.
32. Behältnis (10) nach Anspruch 31, wobei die erste Siegelung (16) eine Siegelnahtstärke
von mehr als 6 Kilogramm pro 25,4 mm (pro Inch) aufweist.
33. Behältnis (10) nach einem der Ansprüche 1 bis 30, wobei die erste Siegelung (16) eine
Siegelnahtstärke von weniger als 2 Kilogramm für einen 25,4 mm (ein Inch) langen Streifen
aufweist.
34. Behältnis (10) nach Anspruch 33, wobei die erste Siegelung (16) eine Siegelnahtstärke
von weniger als 2 Kilogramm für einen 25,4 mm (ein Inch) langen Streifen aufweist.
35. Behältnis (10) nach einem der vorangehenden Ansprüche, wobei die Lage der wärmeschrumpfbaren
Folie (11) eine Dicke von 31,75 µm bis 203,2 µm (1,25 mil bis 8,0 mil) aufweist.
36. Behältnis (10) nach einem der vorangehenden Ansprüche, wobei die Lage der wärmeschrumpfbaren
Folie (11) eine Dicke von 44,45 µm bis 76,2 µm (1,75 mil bis 3,0 mil) aufweist.
37. Behältnis (10) nach einem der vorangehenden Ansprüche, wobei sich der Schrumpfwert
auf die Maschinenrichtung bezieht.
38. Behältnis (10) nach einem der Ansprüche 1 bis 36, wobei sich der Schrumpfwert auf
die Querrichtung bezieht.
39. Behältnis (10) nach einem der Ansprüche 1 bis 36, wobei sich der Schrumpfwert sowohl
auf die Maschinenrichtung als auch auf die Querrichtung bezieht.
40. Behältnis (10) nach einem der vorangehenden Ansprüche, wobei die zweite Siegelung
(32) eine Siegelnahtstärke von mehr als 3 Kilogramm pro 25,4 mm (pro Inch) aufweist.
41. Behältnis (10) nach einem der vorangehenden Ansprüche, wobei das Behältnis (10) ein
Beutel ist, wobei die erste und zweite Behältniswandung (20, 22) die erste und zweite
Wandung des Beutels sind und der erste und zweite Behältnisrand (24, 26) der erste
und zweite Rand des Beutels sind.
42. Behältnis (10) nach einem der vorangehenden Ansprüche, wobei die erste Siegelung (16)
die erste Seite (12) mit der zweiten Seite (14) entlang ihrer Längen verbindet und
durchgängig ist.
43. Verfahren zur Herstellung eines endenverschweißten bzw. endenverbundenen (endenversiegelten),
wärmeschrumpfbaren Verpackungsbehältnisses (10) aus einer ebenen Lage einer Folie
(11), umfassend:
(a) Bereitstellung einer Lage einer wärmeschrumpfbaren thermoplastischen Folie (11)
mit einer ersten Seite (12) und einer gegenüberliegenden zweiten Seite (14);
(b) Bereitstellung einer ersten Siegelung (16) zwischen der ersten und der zweiten
Seite (12, 14) zur Bildung eines Schlauchkörpers (18), wobei der Schlauchkörper (18)
eine erste Behältniswandung (20), eine zweite Behältniswandung (22), einen Boden (30)
an einem ersten Ende des Behältnisses und ein dem Boden gegenüberliegendes zweites
Ende (28) aufweist; und
(c) Bereitstellung einer zweiten Siegelung (32) durch die erste und zweite Behältniswandung
(20, 22), wobei sich die zweite Siegelung (32) seitlich bzw. quer über den Schlauchkörper
(18) an einer Position in Nähe des Bodens (30) erstreckt;
dadurch gekennzeichnet,
daß das Behältnis als ein eigenständiges Behältnis (Einzelbehältnis) ausgebildet ist,
welches abgetrennt und getrennt von dem Schlauchkörper vorliegt und dessen zweites
Ende eine Öffnung ist, und daß die erste Siegelung (16) eine abziehbare bzw. lösbare
Siegelung aus der Gruppe von überlappenden Siegelungen, Streifensiegelungen bzw. Siegelstreifen
und Stumpfsiegelungen einschließlich eines Deckstreifens bzw. Stumpfsiegelungsstreifens
umfaßt, die zweite Siegelung (32) nicht abziehbar bzw. nicht lösbar ist und die Lage
der wärmeschrumpfbaren Folie (11) eine biaxial gestreckte Folie mit einem Schrumpfwert
von mindestens 20 % Schrumpf bei 90 °C in mindestens eine Richtung umfaßt.
44. Verfahren nach Anspruch 43, wobei die Lage der wärmeschrumpfbaren thermoplastischen
Folie (11) vor Zusammenbringen der ersten und der zweiten Seite (12, 14) auf die gewünschte
Breite geschnitten wird.
45. Verfahren nach Anspruch 43 oder 44, wobei die Lage der wärmeschrumpfbaren thermoplastischen
Folie (11) eine kontinuierliche Rolle der Folienlage umfaßt und das Verfahren weiterhin
(d) eine Bereitstellung eines Schnitts seitlich bzw. quer durch den Schlauchkörper
(18) umfaßt, wobei sich der Schnitt seitlich bzw. quer über mindestens die Breite
sowohl der ersten als auch der zweiten Behältniswandung (20, 22) erstreckt und so
einen Teil bzw. Abschnitt des Schlauchkörpers (18) einschließlich der zweiten Siegelung
(32) von dem Schlauchkörper (18) abtrennt.
46. Verfahren nach einem der Ansprüche 43 oder 44, wobei die wärmeschrumpfbare thermoplastische
Folie (11) durch Coextrudierung eines Primärfolienschlauches, Abkühlen des Primärfolienschlauches,
Kollabieren des Primärfolienschlauches, Aufblasen des Primärfolienschlauches, erneutes
Erhitzen des aufgeblasenen Primärfolienschlauches, biaxiales Strecken des Primärfolienschlauches,
Abkühlen und erneutes Kollabieren des Primärfolienschlauches, längsseitiges Aufschneiden
des Primärfolienschlauches und Ausbreiten des aufgeschnittenen Primärfolienschlauches
zur Herstellung einer ebenen bzw. flachen Lage einer biaxial ausgerichteten Folie
hergestellt wird.
47. Verfahren nach einem der Ansprüche 43 bis 46, wobei das Behältnis (10) ein Beutel
ist und wobei die erste und zweite Behältniswandung (20, 22) die erste und zweite
Wandung des Beutels bilden und der erste und zweite Rand des Behältnisses (24, 26)
den ersten und zweiten Rand des Beutels bilden.
1. Réceptacle d'emballage à extrémité scellée (10) formé à partir d'une feuille d'un
film thermorétractable (11), ladite feuille de film thermorétractable (11) ayant un
premier côté (12), un second côté opposé (14), une surface interne (15), une surface
externe (13), ledit réceptacle (10) comprenant :
un premier scellement (16) reliant ledit premier côté (12) audit second côté (14)
et définissant un élément tubulaire (18) ayant une première paroi de réceptacle (20),
une deuxième paroi de réceptacle (22), des premier et deuxième bords de réceptacles
opposés (24, 26), une extrémité (30) et une seconde extrémité (28) opposée à ladite
première extrémité (30) ;
un deuxième scellement (32) réalisé sur lesdites première et deuxième parois de réceptacle
(20, 22), ledit deuxième scellement (32) s'étendant latéralement sur la largeur desdites
première et deuxième parois de réceptacle (20, 22) sur une position proximale de ladite
extrémité (30), une chambre vide recevant un produit (34) étant définie par ladite
première paroi de réceptacle (20), ladite deuxième paroi de réceptacle (22), ledit
deuxième scellement (32) et ladite seconde extrémité (28) ; et
caractérisé en ce que le réceptacle est un réceptacle individuel tranché et séparé, la seconde extrémité
duquel est une ouverture à "gueule ouverte" (28), ledit premier scellement (16) comprend
un scellement pelable choisi parmi un scellement par recouvrement, une bande de scellement
ou un scellement en bout comprenant une bande de scellement en bout, ledit deuxième
scellement (32) étant non pelable, et ladite feuille de film thermorétractable (11)
comprenant un film étiré biaxialement ayant une valeur de rétraction d'au moins 20
% de retrait à 90 °C dans au moins une direction.
2. Réceptacle (10) selon la revendication 1, dans lequel ledit premier scellement (16)
comprend un scellement en bout comprenant une bande de scellement en bout (217), ladite
bande de scellement en bout (217) ayant une première bordure et une deuxième bordure,
un premier scellement thermique (216a) joignant ladite première bordure audit premier
côté (212) et un deuxième scellement thermique (216b) joignant ladite deuxième bordure
audit deuxième côté (214).
3. Réceptacle (10) selon la revendication 2, dans lequel ladite bande de scellement en
bout (217) comprend un rabat de traction (440).
4. Réceptacle selon la revendication 2 ou 3, dans lequel ladite première bordure est
thermoscellée sur la surface interne (15) dudit premier côté (12) et ladite deuxième
bordure est thermoscellée sur la surface interne (15) dudit second côté (14).
5. Réceptacle (10) selon l'une quelconque des revendications 2 à 4, dans lequel au moins
l'un desdits premier et second côtés (12, 14) s'étend vers l'extérieur pour former
un rabat de traction (440).
6. Réceptacle (10) selon l'une quelconque des revendications 2 à 5, dans lequel ladite
bande de scellement en bout (217) comprend un film de scellement en bout comprenant
un système pelable.
7. Réceptacle (10) selon l'une quelconque des revendications 2 à 6, dans lequel lesdits
premier et deuxième scellements (216a, 216b) sont pelables.
8. Réceptacle (10) selon la revendication 1, dans lequel ledit premier scellement (16)
comprend une bande de scellement (741), ladite bande de scellement (741) comprenant
un film pelliculable (711) ayant une première marge (718), une deuxième marge (719),
une surface interne (714) et une surface externe (715) ; un premier scellement thermique
(720) joignant ladite surface externe (715) de ladite première marge (718) à ladite
surface interne (419) dudit premier côté (430a) ; et un deuxième scellement thermique
(721) joignant ladite surface interne (714) dudit film pelliculable à ladite surface
externe (433) dudit second côté (430b).
9. Réceptacle (10) selon la revendication 8, dans lequel ledit deuxième scellement thermique
(721) est un scellement pelable.
10. Réceptacle (10) selon la revendication 8 ou 9, dans lequel ledit premier scellement
thermique (720) est un scellement pelable.
11. Réceptacle (10) selon l'une quelconque des revendications 8 à 10, dans lequel ledit
film pelliculable (711) comprend un système pelable.
12. Réceptacle (10) selon l'une quelconque des revendications 8 à 11, dans lequel ledit
film pelable (711) comprend un rabat de traction (440).
13. Réceptacle (10) selon l'une quelconque des revendications précédentes, dans lequel
ladite feuille de film thermorétractable (11) comprend un système pelable.
14. Réceptacle (10) selon la revendication 1, dans lequel ledit film (11) comprend un
film barrière multicouche.
15. Réceptacle (10) selon la revendication 14, dans lequel ledit film barrière multicouche
(411) comprend :
(a) une couche thermoscellable intérieure (434) ;
(b) une couche barrière (435) ;
(c) une couche centrale (436) ;
(d) une couche de liaison (437) ; et
(e) une couche de thermoscellable extérieure (438).
16. Réceptacle (10) selon la revendication 15, dans lequel ladite couche thermoscellable
(438) extérieure forme la surface externe (13) dudit réceptacle (10).
17. Réceptacle (10) selon la revendication 15 ou 16, dans lequel ladite couche de liaison
(437) est liée de façon permanente à ladite couche centrale (436) et liée de façon
pelable à ladite couche thermoscellable extérieure (438).
18. Réceptacle (10) selon la revendication 15 ou 16, dans lequel ladite couche de liaison
(437) est liée de façon permanente à ladite couche thermoscellable extérieure (438)
et est liée de façon pelable à ladite couche centrale (436).
19. Réceptacle (10) selon l'une quelconque des revendications 15 à 18, dans lequel ladite
couche de liaison (437) comprend un mélange de polybutylène et d'au moins un autre
constituant.
20. Réceptacle (10) selon la revendication 19, dans lequel au moins ledit autre composant
comprend du polyéthylène.
21. Réceptacle (10) selon l'une quelconque des revendications 15 à 20, dans lequel ladite
couche thermoscellable extérieure (438) comprend du polyéthylène.
22. Réceptacle (10) selon l'une quelconque des revendications 15 à 21, dans lequel ladite
couche centrale (436) comprend un mélange de polyéthylène et d'un copolymère éthylène
- acétate de vinyle.
23. Réceptacle (10) selon l'une quelconque des revendications 15 à 22, dans lequel ladite
couche barrière (435) est choisie dans le groupe comprenant des copolymères de chlorure
de vinylidène, des copolymères d'alcool éthylène-vinyle, des polyacrylonitriles et
des polyamides.
24. Réceptacle (10) selon la revendication 23, dans lequel ladite couche barrière (435)
comprend un copolymère de chlorure de vinylidène.
25. Réceptacle (10) selon l'une quelconque des revendications 15 à 24, dans lequel ladite
couche thermoscellable intérieure (434) comprend un mélange de polyéthylène et d'un
copolymère d'éthylène - acétate de vinyle.
26. Réceptacle (10) selon l'une des revendications 15 à 25, dans lequel ladite couche
de liaison (437) comprend un mélange de polybutylène et d'au moins un autre constituant
; ladite couche thermoscellable extérieure (438) comprenant du polyéthylène ; ladite
couche centrale (436) comprenant un mélange de polyéthylène et d'un copolymère d'éthylène
- acétate de vinyle ; ladite couche barrière (435) comprenant un copolymère de chlorure
de vinylidène ; et ladite couche thermoscellable intérieure (434) comprenant un mélange
de polyéthylène et de copolymère d'éthylène - acétate de vinyle.
27. Réceptacle (10) selon l'une des revendications 26, dans lequel au moins ledit autre
constituant comprend du polyéthylène et ladite couche barrière (435) comprend un mélange
de copolymère de chlorure de vinylidène - méthylacrylate et un copolymère de chlorure
de vinylidène - chlorure de vinyle.
28. Réceptacle (10) selon l'une quelconque des revendications 15 à 27, dans lequel ladite
couche thermoscellable intérieure (434) comprend de 0 à 50 %, ladite couche barrière
(435) comprend de 0 à 20 % ; ladite couche centrale (436) comprend de 0 à 28 % ; ladite
couche de liaison (437) comprend de 0 à 15 % et ladite couche thermoscellable extérieure
(438) comprend de 0 à 15 % sur la base de l'épaisseur totale dudit film (411).
29. Réceptacle (10) selon l'une quelconque des revendications 15 à 28, dans lequel ledit
premier scellement (16) comprend un scellement par recouvrement et ladite première
couche thermoscellable intérieure (434) forme la surface interne (15) du réceptacle
(10).
30. Réceptacle (10) selon l'une quelconque des revendications 1 ou 14 à 29, dans lequel
ledit premier scellement (16) comprend un scellement par recouvrement et ledit premier
côté (12) comprend une partie non scellée s'étendant vers l'extérieur au-delà dudit
premier scellement (16).
31. Réceptacle (10) selon l'une quelconque des revendications 1 ou 14 à 30, dans lequel
ledit premier scellement (16) est un scellement par recouvrement et a une résistance
de scellement supérieure à 3 kg par 25,4 mm (par pouce).
32. Réceptacle selon la revendication 31, dans lequel ledit premier scellement (16) a
une résistance de scellement supérieure à 6 kg par 25,4 mm (par pouce).
33. Réceptacle (10) selon l'une quelconque des revendications 1 à 30, dans lequel ledit
premier scellement (16) a une résistance de scellement inférieure à 2 kg par bande
de 25,4 mm (par pouce).
34. Réceptacle (10) selon la revendication 33, dans lequel ledit premier scellement (16)
a une résistance de scellement inférieure à 2 kg par bande de 25,4 mm (par pouce).
35. Réceptacle (10) selon l'une quelconque des revendications précédentes, dans lequel
ladite feuille de film thermorétractable (11) a une épaisseur de 31,75 µm à 203,2
µm (1,25 à 8,0 millièmes de pouce).
36. Réceptacle (10) selon l'une quelconque des revendications précédentes, dans lequel
ladite feuille de film thermorétractable (11) a une épaisseur de 44,45 µm à 76,2 µm
(1,75 à 3,0 millièmes de pouce).
37. Réceptacle (10) selon l'une quelconque des revendications précédentes, dans lequel
ladite valeur de retrait est dans le sens de la machine.
38. Réceptacle (10) selon l'une quelconque des revendications 1 à 36, dans lequel ladite
valeur de retrait est dans le sans transversal.
39. Réceptacle (10) selon l'une quelconque des revendications 1 à 36, dans lequel ladite
valeur de retrait est à la fois dans le sens de la machine et dans le sens transversal.
40. Réceptacle (10) selon l'une quelconque des revendications précédentes, dans lequel
ledit deuxième scellement (32) a une résistance de scellement supérieure à 3 kg par
25,4 mm (par pouce).
41. Réceptacle (10) selon l'une quelconque des revendications précédentes, qui est un
sac, et dans lequel lesdites première et deuxième parois du réceptacle (20, 22) sont
les première et deuxième parois du sac et lesdits premier et deuxième bords du réceptacle
(24, 26) sont les premier et deuxième bords du sac.
42. Réceptacle (10) selon l'une quelconque des revendications précédentes, dans lequel
ledit premier scellement (16) relie ledit premier côté (12) audit second côté (14)
le long des longueurs de celui-ci et est continu.
43. Procédé de formation d'un réceptacle d'emballage à extrémité scellée, thermorétractable
(10) selon la revendication 1 à partir d'une feuille plane ou d'un film (11) comprenant
(a) la mise à disposition d'une feuille de film thermorétractable thermoplastique
(11) ayant un premier côté (12) et un second côté opposé (14) ;
(b) la réalisation d'un premier scellement (16) entre lesdits premier et second côtés
(12, 14) pour former un élément tubulaire (18), ledit élément tubulaire (18) ayant
une première paroi de réceptacle (20), une deuxième paroi de réceptacle (22), un fond
(30) au niveau d'une première extrémité du réceptacle et une seconde extrémité (28)
opposée au fond (30); et
(c) la réalisation d'un deuxième scellement (32) au travers desdites première et deuxième
parois de réceptacle (20, 22), ledit deuxième scellement (32) s'étendant latéralement
sur ledit élément tubulaire (18) et sur une partie proximale dudit fond (30) ;
caractérisé en ce que le réceptacle est formé de manière à ce qu'il soit un réceptacle individuel tranché
et séparé de l'élément tubulaire, la seconde extrémité étant une ouverture à "gueule
ouverte", ledit premier scellement (16) comprend un scellement pelable choisi parmi
un scellement par recouvrement, une bande de scellement ou un scellement en bout comprenant
une bande de scellement en bout, ledit deuxième scellement (32) étant non pelable,
et ladite feuille de film thermorétractable (11) comprenant un film étiré biaxialement
ayant une valeur de rétraction d'au moins 20 % de retrait à 90 °C dans au moins une
direction.
44. Procédé selon la revendication 43, dans lequel ladite feuille de film thermoplastique
thermorétractable (11) est fendue jusqu'à une largeur souhaitée avant de joindre lesdits
premier et second côtés (12, 14) l'un à l'autre.
45. Procédé selon la revendication 43 ou 44, dans lequel ladite feuille de film thermorétractable
thermoplastique (11) comprend un rouleau continu de film et ledit procédé comprend
en outre (d) la réalisation d'une coupe latérale dans ledit élément tubulaire (18),
ladite coupe s'étendant latéralement sur au moins la largeur desdites première et
deuxième parois de réceptacle (20, 22), séparant ainsi une partie dudit élément tubulaire
(18) comprenant ledit deuxième scellement (32) dudit élément tubulaire (18).
46. Procédé selon l'une quelconque des revendications 43 à 44, dans lequel ledit film
thermorétractable thermoplastique (11) est formé par co-extrusion d'un tube de film
primaire, refroidissement du tube de film primaire, affaissement du tube de film primaire,
gonflement du tube de film primaire, réchauffement du tube de film primaire gonflé,
étirement biaxial du tube de film primaire, refroidissement et nouvel affaissement
du tube de film primaire, incision du tube de film primaire longitudinalement et ouverture
du tube primaire fendu pour produire une feuille plane de film orientée biaxialement.
47. Procédé selon l'une quelconque des revendications 43 à 46, dans lequel ledit réceptacle
(10) est un sac et dans lequel lesdites première et deuxième parois du réceptacle
(20, 22) sont les première et deuxième parois du sac et lesdits premier et deuxième
bords du réceptacle (24, 26) sont les premier et deuxième bords du sac.