BACKGROUND OF THE INVENTION
Field of the Invention
[0001] This invention relates to packaging materials for photosensitive materials.
Description of the Prior Art
[0002] Packaging bags capable of shielding completely from light are used for packaging
the articles or the materials which lose commercial values by exposing to light, such
as photosensitive materials. The packaging bags are necessary to have sufficient physical
strength, such as tensile strength, tear strength and impact puncture strength, according
to the size and weight of the materials to be packaged, as well as the above light-shielding
ability. Moreover, since the opening portion of the packaging bags are usually heat-sealed,
suitable heat sealing properties are necessary, and in order to prevent static electrification
due to the friction between the photosensitive materials and the packaging bag, antistatic
property is also necessary.
[0003] Heretofore, as the packaging materials used for such a packaging bag, there is a
laminated film composed of a high pressure branched low density polyethylene (LDPE)
resin film layer containing a light-shielding material, an aluminum foil layer and
a breached kraft paper layer laminated successively each through an LDPE resin extrusion
adhesive layer. In general, single layer films are difficult to satisfy the various
properties required as the packaging material for photographic photosensitive materials,
and only a thick light-shielding LDPE resin single layer film containing carbon black
was used for packaging light low photosensitivity photographic photosensitive materials
placed in protective pad papers and for packaging light photographic printing papers.
[0004] As the packaging material, particularly the light-shielding heat seal bag, for packaging
a roll of a photographic photosensitive material and sheets of a photosensitive material
having a weight of heavier than 1 kg, the inventor has already disclosed the laminated
film composed of a cross laminated film using uniaxially stretched high density polyethylene
(HDPE) resin films having a great physical strength and a LDPE resin film containing
at least either a light-shielding material or an antistatic agent (USP 4,147,291).
The inventor has also disclosed an inexpensive cross laminated film where heat sealing
properties and light-shielding ability are improved (USP 4,258,848).
[0005] Furthermore, the inventor has disclosed other packaging materials, composed of a
laminated film containing a light-shielding film layer composed of linear low density
polyethylene (L-LDPE) resin blended with carbon black, having a great physical strength,
being excellent in heat sealing properties, and being inexpensive (USP 4,701,359,
Japanese Patent KOKAI No. 18547/1987). As a packaging material using a metallized
film, the inventor has also disclosed a packaging material for photosensitive materials
composed of a metallized film layer and two L-LDPE resin polymer layers containing
more than 50 wt. % of L-LDPE resin laminated on both sides of the metallized film
layer. One or both of the L-LDPE resin polymer layers contains 0.3 to 30 wt. % of
a light-shielding material (USP 4,663,218).
[0006] However, the aforementioned conventional laminated film composed of the LDPE resin
film layer, the aluminum foil layer and the bleached kraft paper layer is thick and
stiff, and therefore, packaging workability is inferior. Physical strength, such as
tear strength, is small, and curling is great. Moreover, heat sealing properties are
inferior, and it is expensive. As a result, the packaging material was difficult to
secure light-shielding, moistureproofness and gas barrier because of the generation
of dust, puncture, tear or separation of heat sealed portion during packaging work
or transportation. In the case of the thick light-shielding LDPE resin single layer
film, physical strengh is small, and heat sealing properties are inferior. Therefore,
it is difficult to secure the quality of the photosensitive materials completely.
[0007] The packaging materials having a corss laminated film disclosed in USP 4,147,291
and USP 4,258,848 have a strong physical strength such as tear strength and tensile
strength, and they were put to practical use for packaging weight materials up to
recently. However, since an uniaxially stretched HDPE resin film is used as the heat
seal layer, they are stiff, and inferior in packaging workability and heat sealing
properties. Moreover, the physical strength and heat seal strength varies and curling
occurs due to the uneven thickness of an adhesive layer, the uneven draw ratio of
the uniaxially stretched HDPE resin films, or the like. Therefore, troubles occurred
in processing or packaging process, and occasionally, they were punctured, or the
heat sealed portion was separated during transportation. Moreover, the cross laminated
film where a longitudinally uniaxially stretched film was laminated to a laterally
uniaxially stretched film so that their orientation axes were crossed each other was
expensive, because two kinds of film molding machines were necessary.
[0008] Since the packaging materials having a light-shielding L-LDPE resin single layer
film disclosed in USP 4,701,359 or Japanese Patent KOKAI No. 18547/1987 are inexpensive
and excellent in heat sealing properties and physical strength such as tear strength
and impact puncture strength, they are excellent as the packaging material for photosensitive
materials. However, in the case of packaging a weight photosensitive material or a
photosensitive material having sharp edges, the light-shielding L-LDPE resin films
were occasionally elongated and made thin due to their low Young's modulus, though
they were not punctured nor torn. In this case, light-shielding and moistureproofness
cannot be secured sufficiently. In addition, in the case of using a L-LDPE resin having
a density of less than 0.925 g/cm³, slipping character was insufficient, and blocking
was liable to occur. In the packaging material disclosed in USP 4,663,218, physical
strength such as tear strength was improved. However, when a light-shielding material
was incorporated into one side of the L-LDPE resin polymer layer alone, curling was
great, and processibility was inferior. While, when the melting point of both L-LDPE
resin polymer layers were almost indentical with each other, the outside layer was
melted and broken, unless the heat sealer was modified. As a result, pinhole occurred,
and strength was decreased. Appearance was also inferior. Therfore, this packaging
material was put to practical use as a laminated film laminated with an aluminum vacuum
deposited nylon film or polyester film having a large Young's modulus and heat resistance.
However, the curling of the laminated film was great, and the aluminum vacuum deposited
nylon film and polyester film were expensive.
[0009] The inventor has also developed a coextruded multilayer inflation film comprising
an L-LDPE resin film layer and a polyolefin resin film layer, as a film improved in
physical strength such as impact puncture strength (Japanese Patent KOKAI No. 62-18548).
Such a coextruded multilayer inflation film is formed by using an inflation film molding
machine, such as shown in Figure 7. The inflation film molding machine is composed
of extruders 8 heating and kneading the resin, ring die 9 extruding the molten resin
from the slit (not indicated) into tube-shaped, blast tube 10 blowing compressed air,
air ring 11 cooling the molten resin extruded in tube-shaped, guide rollers 12 guiding
the tube-shaped resin film 13, guide plates 14 guiding the tube-shaped resin film
13 into flat, a pair of squeeze roll 15 (nip roll) nipping to attract the tube-shaped
resin film 13, and winder 16 winding the film. When the aforementioned coextruded
multilayer inflation film composed of an L-LDPE resin film layer and a polyolefin
resin film layer is molded by using the inflation film molding machine, L-LDPE resin
and HDPE resin having prescribed compositions respectively are melted and kneaded
by the extruders 8 and extruded from the circular slit of the ring die 9 so that the
L-LDPE resin film layer is disposed on the inside, i.e. the HDPE resin film layer
is disposed on the outside. At that time, compressed air is blown from the blast tube
10, and cooling air is blown from the air ring 11. The tube-shaped resin film 13 having
a prescribed diameter thus formed ascends with the guide of the guide rollers 12,
..., 12, and is led into flat by the guide plates 14. The film is made sheet shape
by passing the squeeze roll 15, and wound with the winder 16.
[0010] However, in the above inflation film molding process wherein the L-LDPE resin film
layer was disposed on the inside and the HDPE resin film layer was disposed on the
outside, there was a problem that the L-LDPE resin film layer was contacted with each
other to generate blocking at the time of winding it with the winder 16. Moreover,
fatty acid or fatty acid compound such as fatty acid amide, paraffin wax or metal
salt of fatty acid was added to the HDPE resin film layer in order to improve film
moldability or to render halogen compounds harmless, the additive was exposed out
of the HDPE resin film layer, and adhered to the guide rollers 12 resulting pressure
mark and abrasion of the film 13. The adhered additive was detached from the guide
rollers 12, adhered to the film in white lumps. When the film was wound, the white
lumps rendered film rupture as well as pressure mark to the film. On the other hand,
when the L-LDPE resin film layer was disposed on the outside and the HDPE resin film
was disposed on the inside, wrinkling and furrows occurred, and the yield of the film
decreased.
[0011] On the other hand, as the packaging bag for relatively heavy large photographic photosensitive
materials, double-sheet bags were used. Such a double-sheet bag was, for example,
composed of an outer sheet consisting of a Clupak paper, Duostress paper or unbleached
kraft paper coated with polyethylene resin by extrusion laminating and an inner sheet
consisting of an aluminum foil and two uniform polyethylene resin films containing
carbon black laminated on both sides of the aluminum foil. The kind of the packaged
product, instructions and the like were printed on the outer surface of the outer
sheet during the packaging process or another process. The double-sheet bag is excellent
in physical strength, and when the paper of the outer sheet contains a substance harmful
for photographic photosensitive materials, its affect can be shielded by the inner
sheet being in contact with the photographic photosensitive materials. However, the
double-sheet bags have problems in inferior workability and in expensive packaging
material cost. Therefore, various laminated films were developed for solving the inconvenience
in bag-making process to make the bag double. An example of the laminated film shown
in Figure 15 is composed of an aluminum foil layer 27, a bleached kraft paper layer
26 mainly composed of bleached kraft pulp and an LDPE resin film layer 28a blended
with a light-shielding material laminated on both sides of the aluminum foil layer
27 each through an adhesive layer 3. When a bag is made, the bleached kraft paper
layer 26 is disposed on the outside, i.e. the LDPE resin film layer 28a is disposed
on the inside. The physical strength of the laminated film is sufficient in the case
of light photographic photosensitive materials, but it is insufficient for packaging
heavy photographic photosensitive materials. Moreover, fibers occasionally adhered
to the packaged photographic photosensitive materials, and caused developing troubles.
Photographic photosensitive materials are liable to deteriorate because of utilizing
oxidation-reduction reaction and containing a dye liable to degrade by pH, moisture,
heat or the like. Therefore, even in the case that it was necessary to use an oxidizing
or reducing substance for the surface of the packaging material to touch photographic
photosensitive materials, the oxidizing or reducing substance was restricted in the
kind and the blending amount. Moreover, unless the quality of the light-shielding
material was limited in the particle size, pH, the content of impurities and the like,
photographic troubles, such as fogging, spotting trouble and photosensitivity variation,
occurred.
SUMMARY OF THE INVENTION
[0012] An object of the invention is to provide a packaging material for photosensitive
materials excellent in physical strength, in little occurrence of blocking, curling
and lump generation, and particularly in heat sealing properties, in spite of single
layer film.
[0013] Another object of the invention is to provide a packaging material for photosensitive
materials having the safty in photographic properties and capable of securing the
quality of the photosensitive materials by using it as the inner surface layer, in
the case of a laminated film.
[0014] Another object of the invention is to provide a packaging material for photosensitive
materials excellent in the insertion of the photosensitive materials in the case of
making a tube-shaped bag, and capable of providing inexpensive moistureproof light-shielding
bag sesily.
[0015] Such objects have been achieved by a packaging material for photosensitive materials
which comprises a single layer polyolefin resin light-shielding film comprising 0.5
to 40 wt. % of polyethylene resin having a melt index of 0.6 to 15 g/10 minutes and
a density of 0.931 to 0.965 g/cm³, more than 40 wt. % of linear low density polyethylene
resin having a melt index of 0.6 to 10 g/10 minutes and a density of 0.919 to 0.930
g/cm³, 0.1 to 20 wt. % of carbon black, more than 0.01 wt. % of fatty acid compound
and 0.01 to 2 wt. % of antioxidant. In the above packaging material for photosensitive
materials, since the composition of the polyolefin resin light-shielding film is a
particular resin composition where a L-LDPE resin and a polyethylene resin having
particular characteristics respectively are combined, the polyethylene resin compensates
and further improves the defective properties of the L-LDPE resin with securing the
advantageous properties thereof. Moreover, it has been found that the resin composition
increases the haze of film and raises the light-shielding ability by more than 10
% That is, it has been found that, when more than 10 % of the blending amount of carbon
black is decreased, almost the same light-shielding ability can be secured.
[0016] Still another object of the invention is to provide a packaging material for photosensitive
materials which is a coextruded multilayer inflation film without the occurrence of
blocking between the inner layers, pressure mark, abrasion, puncture, wrinkling nor
furrowing.
[0017] Such an object has been achieved by a coextruded multilayer inflation film of which
the inner surface layer is a polyolefin resin film layer to which 0.5 to 70 wt. %
of polyethylene resin having a density of more than 0.936 g/cm³.
[0018] Still another object of the invention is to provide a packaging material for photographic
photosensitive materials having sufficient physical strength for packaging heavy photographic
photosensitive materials and little problem in developing trouble.
[0019] Another object of the invention is to provide a packaging material for photographic
photosensitive materials not affecting adversely the photographic photosensitive materials
packaged therein and being inexpensive.
[0020] Such objects have been achieved by a packaging material for photographic photosensitive
materials which comprises an aluminum vacuum metallized biaxially stretched thermoplastic
resin film layer, a long fiber paper layer, of which more than 50 % of the fibers
have a fiber length of longer than 3 mm, containing a paper reinforcing agent and
having a pH of 4 to 9 measured by cool water extracting method (JIS P-8133) laminated
on one side of the above thermoplastic resin film layer, and a polyolefin resin film
layer containing 0.1 to 15 wt. % of carbon black having a pH of 4 to 9 and a mean
particle size of 15 to 80 mµ and more than 5 wt. of an ethylene copolymer resin laminated
on the other side.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021]
Figures 1 to 3 are partially sectional views of preferred embodiment of the invention.
Figures 4 and 5 are partially sectional views of comparative packaging materials.
Figure 6 is a partially sectional view of a conventional packaging material.
Figure 7 is a schematic front view of an inflation molding machine.
Figure 8 is an enlarged sectional view of an inflation film of the invention at position
A of Figure 7, and Figure 9 is an enlarged sectional view of the inflation film at
position B of Figure 7.
Figures 10 to 13 are partially sectional views of preferred embodiment of the invention.
Figure 14 is a partially sectional view of a comparative packaging material.
Figure 15 is a partially sectional view of a conventional packaging material.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The polyethylene resin of the single layer polyolefin resin light-shielding film
has a melt index (HI, ASTM D-1238) of 0.6 to 15 g/10 minutes, preferably 1 to 5 g/10
minutes, and a density (ASTM D-1505) of 0.931 to 0.965 g/cm³, preferably 0.941 to
0.958 g/cm³. When the MI is less than 0.6 g/10 minutes, film moldability is inferior.
Moreover, molecular orientation is liable to occur greatly in longitudinal direction,
and a film having a good balance between the physical strength in longitudinal direction
and that in lateral direction is difficult to be produced. Lumps are liable to be
generated, and damage the photosensitive materials packaged. While, when the MI is
beyond 15 g/10 minutes, physical strength decreases. Young's modulus and tensile strength
are small, and film moldability is inferior. When the density is less than 0.931 g/cm³,
it is difficult to obtain a high Young's modulus polyolefin resin light-shielding
film excellent in antiblocking ability. While, when the density is beyond 0.965 g/cm³,
film moldability is inferior. Moreover, molecular orientation is liable to occur greatly
in longitudinal direction, and a film having a good balance between the physical strength
in longitudinal direction and that in lateral direction is difficult to be produced.
[0023] Lumps are liable to be generated to damage the photosensitive materials packaged,
and nevertheless, it is expensive. The polyethylene resin content of the light-shielding
film is 0.5 to 40 wt. %. When the content is less than 0.5 wt. %, the disadvantages
of L-LDPE resin such as low Young's modulus, low tensile strength, blocking problem
and insufficient slipping character cannot be compensated. Besides, film moldability
is inferior, and draw down occurs. Bubble stability is also insufficient. Even though
film is formed, bag-making ability of the film is inferior because of blocking and
deviated elongation due to insufficient tensile strength. While, when the content
is beyond 40 wt. %, tear strength is small. The balance between the tear strength
in longitudinal direction and that in lateral direction is inferior, and the bag made
of the packaging material of the invention is punctured. Various physical properties
and heat sealing properties becomes worse by blending carbon black, contrary to the
case of the present invention. Lumps are liable to be generated, and adversely affect
the photosensitive materials packaged, as well as the appearance of the packaging
material is inferior.
[0024] The L-LDPE resin of the single layer polyolefin resin light-shielding film has a
MI (ASTM D-1238) of 0.6 to 10 g/10 minutes and a density (ASTM D-1505) of 0.919 to
0.930 g/cm³. When the MI is less than 0.6, since the fluidity of the resin is insufficient,
film moldability is inferior. While, when the MI is beyond 10 g/10 minutes, physical
strength decreases. Tear strength and impact puncture strength are insufficient, and
blocking is liable to occur. When the density is less than 0.919 g/cm³, Young's modulus
and tensile strength are small. When blocking occurs, it is difficult to obtain a
film capable of achieving the object of the invention by a single layer film alone.
While, when the density is beyond 0.930 g/cm³, molecular orientation is liable to
occur in longitudinal direction, and the balance between the physical strength in
longitudinal direction and in lateral direction becomes worse. Particularly, anti-pinhole
ability is insufficient, and the film is difficult to be put to practical use as a
single layer film for heavy materials. The L-LDPE resin is called third polyethylene
resin, and it is a low cost high strength resin, having the advantages of both low,
medium density polyethylene resin and high density polyethylene resin, which meets
the requirements, i.e. resource conservation and energy conservation, of the times.
The L-LDPE resin is a copolymer of ethylene and α-olefin, and it has a linear structure
having short branches. The number of carbon atoms of the α-olefin is 3 to 13. Preferable
α-olefin has a number of carbon atoms of 4 to 10, and examples of the α-olefin are
butene-1, 4-methylpentene- 1, hexene-1 and heptene-1. The density is usually in the
range of 0.87 to 0.95 g/cm³. Most of the L-LDPE resin is synthetic by low pressure
method, and partly synthetic by modified high pressure method. Examples of commercial
L-LDPE resin are "G-Resin" and "TUFLIN" and "NUC-FLX" (UUC), "NUC Polyethylene-LL"
and "TUFTHENE" (Nippon Unicar) "Excelene V" (Sumitomo Chemical) "Idemitsu Polyethylene-L"
and "Moretec" (Idemitsu Petrochemical), "Dowlex" (Dow Chemical), "Suclear" (Dupont
de Nemour, Canada), "Marlex" (Phillips), "Neozex" and "Ultzex" (Mitsui Petrochemical
Industries), "Nisseki Linirex" (Nippon Petrochemicals), "Stamilex" (DSM), and the
like. The L-LDPE resin content of the light-shielding film is more than 40 wt. %,
preferably more than 70 wt. %. When the content is less than 40 wt. %, the effect
to increase the tear strength in longitudinal direction and that in lateral direction
is insufficient. Particularly, in the case of a thin single layer film, tear strength,
impact puncture strength, anti-pinhole ability and the like are insufficient as a
packaging material for photosensitive materials.
[0025] The carbon black used for the light-shielding film is blendable or dispersible in
the polyolefin resin. It blocks the transmission of visible and ultraviolet rays,
and impart light-shielding property to the polyolefin resin film. The carbon black
not only improves the tear strength, impact puncture strength and heat sealing properties
of the polyolefin resin film, but also functions to prevent the generation of lumps
caused by the oxidation of the resin, to prevent blocking, to adsorp harmful substances
such as oxidizing substance, reducing substance and metals. Carbon blacks are divided
into gas black, lamp blacks vegetable black and animal black according to their origin.
Among these, oil furnace carbon black having a mean particle size of less than 200
mµ, particularly less than 50 mµ is preferred in terms of light-shielding character,
cost, blendability and dispersibility. On the other hand, since acetylene black, Ketschen
carbon black and graphite have antistatic characteristics, they are also preferred,
though they are expensive. They may be blended with the oil furnace carbon black in
order to improve its character. Suitable pH of carbon black is at 5 to 9, and suitable
mean particle size is 10 to 200 mµ. The oil furnace carbon black having a pH 6 to
9 is preferred. By using the carbon black of such pH and particle size, a packaging
material having the following merits is obtained. That is, the occurrence of fogging
is rare, increase or decrease of photosensitivity rarely happens, light-shielding
ability is great, the lumps of carbon black and pinholes such as fish eyes hardly
occur, and the physical strength and heat sealing properties are improved. It is also
preferred to improve conductivity by adding metal fiber, carbon fiber, metal powder
or the like. The carbon black content of the light-shielding film is 0.1 to 20 wt.
%, preferably 0.5 to 12 wt. %, further preferably 1.5 to 7 wt. %. When the content
is less than 0.1 wt. %, the blending effect, such as to secure light-shielding and
to prevent static electrification, is insufficient. While, when the content is beyond
20 wt. %, the physical strength of the film, particularly tear strength and impact
puncture strength, decreases, and heat sealing properties are also inferior. Furthermore,
the photosensitive materials are contaminated by touching the surface of the film
or adhering carbon black released from the film to the photosensitive materials. The
blending amount of carbon black per an unit area of the light-shielding film is preferably
0.3 to 50 g/m². The blending method of carbon black into the resin may be carried
out by a known method such as the compound coloring method (colored pellets), the
liquid color method, the dry color method, the dye color granule method and the masterbatch
method, and the dye color granule method and the masterbatch method are preferred
in view of cost and the contamination of the working place.
[0026] The fatty acid compound used for the light-shielding film neutralizes the halide
and the like added as the polymerization catalyst of the polyolefin resin which are
harmful and adversely affected the photosensitive materials, and thereby makes them
harmless. The fatty acid compound improves the dispersibility of carbon black, antiblocking
properties, slipping character, and bag-making ability. It also prevents completely
the degradation of heat sealing properties by the gradual bleed out of the additives
in the polyethylene resin, together with the inhibition by more than 40 wt. % of the
L-LDPE resin blended in the resin composition of the invention. The fatty acid compound
suitable for the invention includes various saturated or unsaturated fatty acids such
as oleic acid, stearic acid, lauric acid, ricinoleic acid, naphthenic acid, octylic
acid, phthalic acid, adipic acid, sebacid acid, acetylricinoleic acid and maleic acid,
fatty acid amides, such as oleic acid amide, erucic acid amide stearic acid amide
and bisfatty acid amides, metal salts of fatty acids, such as magnesium stearate,
calcium stearate, zinc stearate, aluminum stearate, barium stearate, calcium laurate,
zinc octylate, and fatty acid esters, such as butyl oleate and bytyl stearate. Two
or more fatty acid compounds may be combined. The fatty acid compound content of the
light-shielding film is more than 0.01 wt. %, preferably 0.01 to 7 wt. %, more preferably
0.03 to 3.0 wt. %. When the content is less than 0.01 wt. %, the aforementioned effects
cannot be obtained. While, since too much content results various troubles, such as
the variation of ejection amount by the screw slip of extruder, bleed out problem
and degradation of heat sealing properties. When two or more fatty acid compounds
are used, the above content is the total amount of them.
[0027] The antioxidant used for the light-shielding film inhibits the generation of lumps
due to the oxidation of the resin during the film molding continued for a long period,
and thereby prevents the occurrence of pressure mark and abrasion due to the lumps,
when it is used as a light-shielding bag for packaging photographic photosensitive
materials. When a big lump generates, heat seal is incomplete, in addition to the
above problems. As a result, light-shielding, moistureproofness and gas barrier are
insufficient, and the quality of the photosensitive materials cannot be secured. By
combining the antioxidant with carbon black, oxidation inhibition effect is synergistically
exhibited. Suitable antioxidants are phenol antioxidants, sulfur-containing antioxidants,
phsphorus-containing antioxidants and the like. The phenol antioxidants include n-octadecyl-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate,
2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-p-cresol, 2,2′methylenebis(4-methyl-6-t-butylphenol),
4,4′-thiobis(3-methyl-6-t-butylphenol), 4,4′-butylidenebis (3-methyl-6-t-butylphenol),
stearyl-β-(3,5-di-4-butyl-4-hydroxyphenyl)propionate 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane,
1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene and tetrakis methylene-3(3′,5′-di-t-butyl-4′-hydroxyphenyl)
propionate methane. The sulfur-containing antioxidants include dilauryl-3,3′-thiodipropionate,
dimyristyl-3,3′-thiodipropionate, laurylstearylthiodipropionate, distearyl-3,3′-thiodipropionate
and ditridecyl-3,3′-thiodipropionate. The phosphorus-containing antioxidants include
trinonylphenylphosphite and triphenylphosphite. In addition, there are various antioxidants
disclosed in "Plastic Handbook", pp 794-799, Kogyo Chosa Kai, "Plastic Additives Data
List", pp 327-329, Kagaku Kogyo Sha and "Plastic Age Encyclopedia, Volume Advance",
pp 211-212, Plastic Age, 1986. Preferable antioxidants are phenol antioxidants, such
as 2,6-di-t-butyl-p-cresol (BHT), low volatile high molecular weight phenol antioxidant
("Irganox 1010", "Irganox 1076", trade names of Ciba-Geigy AG, "Topanol CA", trade
name of I.C.L., "Ionox 330" trade name of Shell), dilaurylthiodipropionate, distearylthiodipropionate
and dialkylphosphate. Two or more antioxidants may be combined. In some cases, oxidation
inhibition effect is improved by combining antioxidants. Such a combination includes
a combination of a phenol oxidant and a phosphorus-containing antioxidant and a combination
of a volatile antioxidant and a heat-resistant antioxidant. The antioxidant content
of the light-shielding film is 0.01 to 2 wt. %. The tolerance in the antioxidant content
greatly varies according to the kind of the photosensitive material.
[0028] In the case of the single layer polyolefin resin light-shielding film of the invention,
in general, antiblocking agent is not necessary. However, when the light-shielding
film contains more than 80 wt. % of L-LDPE resin having a density of 0.919 to 0.925
g/cm³ in order to improve tear strength, impact puncture strength, low temperature
physical strength and the like, the blending of an antioxidant is effective for preventing
blocking completely. Suitable antiblocking agents are silica, diatomaceous earth,
calcium silicate, aluminum silicate, talc, magnesium silicate, calcium carbonate,
higher fatty acid polyvinyl esters, n-octadecyl urea, dicarboxylic acid ester amides
and the like.
[0029] Various additives may be added to the single layer polyolefin resin light-shielding
film of the invention. Examples of the additives are described below.
(1) Plasticizer;
[0030] phthalic acid esters, glycol ester, fatty acid ester, phosphoric acid ester, etc.
(2) Stabilizer;
[0031] lead compounds, cadmium compounds, zinc compounds, alkaline earth metal compounds,
organic tin compounds, etc.
(3) Antistatic agent;
[0032] cationic surfactants, anionic surfactants, nonionic surfactans, ampholytic surfactans,
various carbon blacks, metal powder, graphite, etc.
(4) Flame retardant;
[0033] phosphoric acid esters phosphoric acid ester halides, halides, inorganic materials,
polyols containing phosphor, etc.
(5) Filler;
[0034] alumina, kaolin, clay, calcium carbonate, mica, talc, titanium dioxide, silica, etc.
(6) Reinforcing agent:
[0035] glass lobing, metallic fiber, glass fiber, glass milled fiber, carbon fiber, etc.
(7) Coloring agent;
[0036] inorganic pigments (Al, Fe₂O₃, TiO₂, ZnO, Cds, etc.), organic pigments, dyes, etc.
(8) Blowing agent;
[0037] inorganic blowing agents (ammonium carbonate, sodium hydrogen carbonate), organic
blowing agents (nitroso compounds, azo compounds), etc.
(9) Deterioration preventing agent;
[0038] ultraviolet absorber, antioxidant, metal deactivator, peroxide decomposing agent,
etc.
(10) Coupling agent;
[0039] silane compounds, titanium compounds, chromium compounds, aluminum compounds, etc.
[0040] Various thermoplastic resins may be added to the polyolefin resin light-shielding
film, such as various polyolefin resins including LDPE resin, MDPE resin, polypropylene
resin, propyleneethylene copolymer resin, EVA resin, EMA resin, EEA resin, EAA resin,
ionomer resin, ethylene-unsaturated carboxylic acid copolymer resins, various ethylene-alkyl
ester copolymer resins and various elastomers.
[0041] The single layer polyolefin resin light-shielding film exhibits a great effect in
the case of inflation film, and it is suitable as the package for a bulky and heavy
cylindrical photosensitive material having a diameter of more than 25 cm and a cylinder
length of more than 50 cm, called bulk roll. The light-shielding film is the most
effective in the flat bags and gusset bags formed from a cylindrical film molded by
inflation process of which the bottom is heat-sealed. On the other hand, both sides
of the inflation film may be slit to form sheet-shaped films, and laminated with other
flexible sheet(s). The laminated film may be used as a packaging material for silver
halide photographic photosensitive materials, because of imparting further excellent
properties by the lamination. Nevertheless, the most preferable uses are the packages
of the above bulk roll or a magnetic material of pancake, in a shape of a single layer
film. When the light-shielding film of the invention is used as a laminated film,
the light-shielding film is preferably used as the inner surface layer.
[0042] The packaging material of the invention may be used for packaging photosensitive
materials such as photographic photosensitive materials, foods, medicines or chemical
substances, and it is particularly suitable for packaging silver halide photographic
photosensitive materials, diazo photographic photosensitive materials, photofixing-type
thermosensitive photosensitive materials, photosensitive resin photosensitive materials,
ultraviolet curing-type photosensitive materials, transfer-type heat developing photosensitive
materials, direct positive type photographic photosensitive materials, self-developing
type photographic photosensitive materials, photosensitive materials for lithographic
printing and other photographic materials which is degraded by little amount of moisture,
light or gas.
[0043] In the single layer polyolefin resin light-shielding film of the invention, since
a L-LDPE resin having particular properties is blended in the content of more than
40 wt. % the film is excellent in the balance between the physical strength in longitudinal
direction and that in lateral direction, in tear strength and in impact puncture strength.
The blending of less than 10 wt. % of carbon black improves tear strength and heat
sealing properties contrary to conventional packaging materials for photosensitive
materials using LDPE resin or HDPE resin wherein tear strength and heat sealing properties
are degraded by blending carbon black. Oxidation-inhibiting ability is also improved.
0.5 to 40 wt. % of the polyethylene resin having particular properties improves the
disadvantages of the above L-LDPE resin, i.e. low Young's modulus, blocking melt fracture
and crystallization rate, with securing the above advantages of the L-LDPE resin.
Since tensile strength is also improved compared to the L-LDPE resin alone, deviated
elongation of the film hardly occurs during molding process. Draw down, wrinkling
and furrowing hardly occur, and bubble stability through the inflation molding process
is excellent. Melt fracture hardly occurs, and the molded film is excellent in smoothness.
The above combination of the L-LDPE resin and the polyethylene resin increases, and
thereby, the amount of the light-shielding material can be saved by more than 10 %.
Since an antioxidant and a fatty acid compound are used, the dispersibility of carbon
black is improved. The generation of lumps by the oxidation of the polyolefin resin
light-shielding film is prevented by the synergistic effect of carbon black and an
antioxidant. The film moldability, the slipping character and antiblocking properties
are also improved. Moreover, the generation of white powder is prevented by blending
more than 40 wt. % of the L-LDPE resin. Carbon black powder is hardly generated, and
does not affect bag-making ability nor packaging properties.
[0044] The light-shielding film of the invention is provided with all of necessary properties
as a packaging material for photosensitive materials, in spite of a single layer film,
and blocking hardly occurs. The film is soft, and its physical strength is great.
The film is also excellent in film moldability and heat sealing properties. The inflation
film can be used for packaging a big heavy product such as bulk roll, as it is. Besides,
merely by cutting the inflation film in a prescribed length and heat-sealing the bottom,
a packaging bag excellent in moistureproofness and light-shielding ability can easily
be formed inexpensively. Since curling is little and heat sealing properties are excellent,
packaging workability is superior, resulting the decrease of cost due to the reduction
of packaging material cost and lavor saving.
[0045] The polyolefin resin film layer contains polyethylene resin having a density (ASTM
D-1505) of more than 0.936 g/cm³, preferably 0.941 to 0.970 g/cm³. When the density
is less than 0.936 g/cm³ it is difficult to obtain a high Young's modulus polyolefin
resin film excellent in antiblocking properties. Moreover, the MI (ASTM D-1238) of
the polyethylene resin is preferably more than 0.3 g/10 minutes, further preferably
0.5 to 10 g/10 minutes. When the MI is less than 0.3 g/10 minutes, film moldability
is inferior. Moreover, molecular orientation is liable to occur greatly in longitudinal
direction, and it is difficult to produce a film having a good balance between the
physical strength in longitudinal direction and that in lateral direction. Lumps are
liable to be generated, and damage the photosensitive materials to be packaged. The
polyethylene resin content of the polyolefin resin film layer is 0.5 to 70 wt. %,
preferably 2 to 40 wt. %, further preferably 5 to 30 wt. %. Wnen the content is less
than 0.5 wt. %, blocking occurs. While, when the content is beyond 70 wt. %, physical
strength decreases. The inner surface layer is too slippery, and wrinkling and furrowing
occur. The polyolefin resin film layer may contain other resins, such as L-LDPE resin
or LDPE resin.
[0046] In order to prevent blocking and static electrification, the polyolefin resin film
layer contains either or both of a light-shielding material and a fatty acid compound.
[0047] The light-shielding material is blendable or dispersible in the polyolefin resin
film layer and capable of shielding visible and ultraviolet light. Examples of the
light-shielding material are various carbon blacks, graphite, iron oxide, zinc white,
titanium dioxide, clay, aluminum powder, aluminum paste, calcium carbonate, mica,
barium sulfate, talc, cadmium pigments, red iron oxide, cobalt blue, copper-phthalocyanine
pigments, monoazo and polyazo pigments and aniline blacks. Various carbon black, aluminum
powder and aluminum paste from which volatile components are removed are preferred.
Carbon black is similar to described previously.
[0048] As the preferable light-shielding material, metal powder is in second place. Metal
powder is a light-reflective light-shielding material. It imparts a silver appearance,
and it is excellent in moistureproofness, light-shielding, antistatic property, thermal
shielding in the sunlight and gas barrier. As the metal powder, aluminum powder and
its paste are preferable. The paste of aluminum powder is produced by adding mineral
spirits and a small amount of a higher fatty acid such as stearic acid or oleic acid
to form a paste at the production of aluminum powder according to a known method such
as using a ball mill, a stamp mill or an atomizer. A polyolefin thermoplastic resin,
such as various polypropylene resins, various polyethylene resins, EVA resin, EEA
resin and EAA resin, is kneaded together with this aluminum paste while heating, and
volatile components mainly mineral spirits are removed by a vacuum pump. This product
is used as an aluminum paste compound resin or an aluminum paste masterbatch resin.
The aluminum paste masterbatch resin is preferable because it eliminates the noxious
smell and bad influences upon the photographic photosensitive materials. In order
to eliminate the noxious smell and bad influences upon the photographic photosensitive
materials, the content of mineral spirits should be less than 0.1 wt. %. When the
aluminum paste content of coextruded double layer film is made 2 wt. % by using a
masterbatch resin containing 40 wt. % of aluminum paste and 1.0 wt. % of the mineral
spirits, one part by weight of the masterbatch resin is blended with 19 parts by weight
of the main resin. Since a part of the mineral spirits evaporates during molding,
the final content of the mineral spirits is less than 0.05 wt. %. The aluminum powder
includes microflakes produced from aluminum foil which is crushed by a ball mill or
a stamp mill, in addition to usual aluminum powder manufactured by atomizaiton, dropping
on a rotary disc or evaporation from melted aluminum. Since aluminum powder is unstable,
it is stabilized by a known treatment, such as a surface treatment using a binder
or a higher fatty acid.
[0049] The light-shielding material content of the polyolefin resin film layer is 0.1 to
20 wt. %, preferably 0.5 to 12 wt. %, further preferably 1.5 to 7 wt. %. When the
content is less than 0.1 wt. %, the blending effect, such as to secure light-shielding
and to prevent static electrification, is insufficient. While, when the content is
beyond 20 wt. % the physical strength of the film, particularly tear strength and
impact puncture strength, decreases, and heat sealing properties are also inferior.
Furthermore, the photosensitive materials are contaminated by touching the surface
of the film or adhering the light-shielding material released from the film to the
photosensitive materials. The blending amount of the light-shielding material per
an unit area of the inflation film is preferably 0.5 to 50 g/m². The blending method
of the light-shielding material may be carried out by a known method, and the masterbatch
method is preferable in view of cost and the contamination of the working place. Two
or more light-shielding materials may be combined.
[0050] The fatty acid compound suitable for blending into the polyolefin resin film layer
may be selected from mentioned previously.
[0051] The coextruded multi layer inflation film of the invention is extruded so that the
polyolefin resin film layer is disposed on the inside.
[0052] In the coextruded multilayer inflation film, the layer extruded as the outer surface
layer is preferably an L-LDPE resin film layer. Preferable L-LDPE resins in view of
physical strength and heat seal strength are those having the number of carbon atoms
is 6 to 8, a MI (ASTM D-1238) of 0.8 to 30 g/10 minutes and a density (ASTM D-1505)
of 0.870 to 0.940 g/cm³, produced by liquid phase process or vapor phase process.
The L-LDPE resin content of the L-LDPE resin film layer is more than 30 wt. % preferably
50 to 95 wt. %. One or more other resins, such as LDPE resin, HDPE resin, ethylene
copolymer resin or polypropylene resin, may be blended into the L-LDPE resin film
layer. One or more of a light-shielding material, a fatty acid compound and an antiblocking
agent may be blended into the L-LDPE resin film layer in order to prevent blocking,
oxidation, molding and static electrification. The light-shielding material, the fatty
acid compound and the antiblocking agent may be similar to mentioned previously.
[0053] The polyolefin resin film layer and the L-LDPE resin film layer may contain various
additives selected from listed previously and lubricants including paraffin wax, fatty
acids, fatty acid amides, silicones, esters, higher alcohols, various thermoplastic
resins, deodorants, oxygen absorbers, absorber and rubbers.
[0054] One or more intermediate layers may be incorporated between the polyolefin resin
film layer and the L-LDPE resin film layer.
[0055] The coextruded multi layer inflation film may be formed by using a known inflation
film molding machine, such as a commercial machine.
[0056] The inflation film of the invention may be used for packaging photosensitive materials
such as photographic photosensitive materials, foods, medicines or chemical substances.
[0057] The package form may be conventional, and includes a single-sheet flat bag, a double-sheet
flat bag, a self-standing bag, a single-sheet gusset bag, a double-sheet gusset bag,
inner lining for a moisture proff box, inner lining for a light room-loading light-shielding
box, wrapping paper and a leader paper. The bag-making form may also be conventional,
and includes heat sealing, side welding (heat-cut sealing), impulse heat sealing,
supersonic sealing and high frequency sealing. The methods of using an adhesive may
also be utilized.
[0058] Since the coextruded multi layer inflation film of the invention is mold so that
the polyolefin resin film layer is disposed as the inner surface layer, when the tubular
film is wound by a winder, the polyolefin resin film layers touch each other to prevent
blocking. When the L-LDPE resin film layer is the outer surface layer, adhesion of
the additives to guide rollers and the like does not occur. Therefore, a coextruded
multilayer inflation film obtained is excellent in quality.
[0059] The aluminum vacuum metallized biaxially stretched thermoplastic resin film is a
biaxially stretched thermoplastic resin film processed with the vacuum deposition
method to form an aluminum vacuum deposition layer. The film improves tensile strength
and bursting strength of the packaging material, and it prevents the generation of
pinhole, bag rupture and thinning by the elongation of the packaging material, even
when a heavy product is placed. It also improves moistureproofness, gas barrier, antistatic
property and light-shielding. By stretching the thermoplastic resin film biaxially,
the stretched film has a high Young's modulus, and is excellent in moistureproofness
and gas barrier, in spite that it is thin. Since the stretched film has heat stability,
crazing hardly occurs at the time of forming the aluminum vacuum deposition layer.
The crazing of the aluminum vacuum deposition layer is also prevented by the increased
Young's modulus and the resistance to elongation. The resin suitable for the film
includes polyester resin, polyamide (nylon) resin, polyethylene resin, polystyrene
resin, polypropylene resin, polyvinyl chloride resin, polyvinylidene chloride resin,
vinylon resin, copolymer resins of the above resins and other resins, including binary,
ternary or more copolymers polymerized by random copolymerization or block copolymerization,
modified or crosslinked resins, and blend resins of the above resins and other resins.
Stretching may be carried out by a known biaxial drawing method such as simultaneously
biaxial drawing or successively biaxial stretching, and both of the draw ratios in
longitudinal direction (MD) and in lateral direction (CD) are 1.5 to 20 times, preferably
3 to 15 times, respectively. The drawing machine may be a known machine such as T
die film molding machine or inflation film molding machine. A preferable thickness
of the biaxially stretched thermoplastic resin film is 7 to 60 µm. When the thickness
is less than 7 µm, wrinkling and cut occur in the laminating process. While, when
the thickness is beyond 60 µm, the rigidity is too great. As a result, bag-making
ability and handling are inferior, and the film is expensive. The biaxially stretched
thermoplastic resin film may be a single layer film or a coextruded multi layer film.
[0060] Moreover, another resin, such as polyvnylidene chloride resin, silicone resin or
teflon resin, is coated or printed, or a metal membrane is provided on the stretched
film. The metal membrane may be provided by vacuum deposition, sputtering, ion plating,
electron beam deposition, or the like.
[0061] A preferable thickness of the aluminum vacuum deposition layer is 55 to 1,200 Å,
particularly 100 to 600 Å, in view of securing physical strength, light-shielding,
antistatic property, moistureproofness and gas barrier, cost and quality. When the
thickness is less than 55 Å, the static electrification generated around the aluminum
vacuum deposition layer cannot be decreased. It is difficult to secure moistureproofness,
gas barrier and light-shielding. While, when the thickness is beyond 1,200 Å, problems
occur in the degradation of the stretched film, the wrinkling due to shrinkage the
crazing of the vacuum deposition layer, caused by the heat of vacuum deposition, and
the decrease of physical strength of the packaging bag, though antistatic property,
moistureproofness, gas barrier and light-shielding are still secured.
[0062] A protection layer may be provided on the aluminum vacuum deposition layer, if necessary.
The usable resin for the protection layer includes acrylic resin, cellulose resins
such as cellulose acetate resin, urethane resin, epoxy resin, polyester resin, ionomer
resin, polyethylene resin, ethylene copolymer resin and polypropylene resin. Besides,
wax, gelatin, polyvinyl alcohol or the like is also usable. The thickness of the protection
layer is made extremely thin such as thinner than 50 µm, preferably thinner than 5
µm, in order to eliminate static electricity effectively. Such a protection layer
may be formed by a known extrusion coating, solution coating or spray coating.
[0063] More than 50 %, preferably more than 70 % of the fibers composing the long fiber
paper have a fiber length of longer than 3 mm, usually 3 mm to 7 mm. When the fiber
length is shorter than 3 mm, the generation of paper powder. and picking cannot be
prevented effectively. When the fibers having a fiber length of longer than 3 mm are
less than 50 % of total fibers, the generation of paper powder and picking cannot
be prevented effectively. The paper reinforcing agent is incoporated into the long
fiber paper in order to prevent the generation of paper powder and picking effectively.
The paper reinforcing agent usable for the invention includes cation-induced styrene-acrylic
copolymer, aminoamidepichlorohydrin condensate, carboxylmethglcellulose, various polyacrylamides
and copolymers thereof, carboxyl-modified polyacrylamide, polyethyleneimine, gum oleoresin,
sodium silicate, synthetic rubber latex, unacetylated PVA fiber, various starched
including modified starches, sulfomethylated resin, urea resin, alkylstyrene resin,
alkylketene dimer, gelatin, PVA, casein, methacylamide, polyamidaminepichlorohydrin,
sodium polyacrylate, carboxyl-modified polyvinyl alcohol, hydroxylethylcellulose and
the like. A suitable content of the paper reinforcing agnet is 0.05 to 8 wt. %, preferably
0.3 to 5 wt. %. A cool water-extracing pH (JIS P-8133) of the long fiber paper is
in the range of 4 to 9, preferably 5 to 9. When the cool water-extracting pH is less
than 4 or beyond 9, harmful substances for photographic photosensitive material are
produced. Long fiber neutral papers are particularly preferable. The contents of all
of harmful substances for photographic photosensitive materials should be less 1,000
ppm. The harmful substances are redioactive substances and the materials obtained
using a radioactive substance, such as the paper made using the river water, the pulp,
chip or waste paper exposed to the rain, after a nuclear test, mercury, alloys thereof,
mercury compounds and agents containing mercury, such as mercury, organic mercury
agents, broken fluoresent lamp and slime control agent used for paper-making, secondary
processed products of silicone, such as silicone oil and silicone grease, sulfur compounds,
such as Na₂S, H₂S and Na₂S₂O₃, lead compounds, such as PbS and PbSO₄, iron and iron
compound, such as iron powder, Fe₂O₃, FeO and FeCl₃, copper and copper compounds,
such as copper compounds, such as copper powder, CuO, CuSO₄ and CuCl₂, and aldehydes,
such as formaldehyde and acetaldehyde. Wnen the content of one of the above substances
is beyond 1,000 ppm, it adversely affect photographic photosensitive materials seriously.
The adverse affect of the substance can be decreased by neutralization, adsorption
or the like. In this case, the content of the above harmful substance may be beyond
1,000 ppm. For example, the adverse affect of iron, iron compounds and other metal
compounds can be removed by adding a chelating agent, and the adverse affect of formaldehyde
can be removed by adding urea, thiourea, a hydrazine compound, dicyandiamide or an
acid salt thereof, hydroxylamine or an acid salt thereof, such as hydroxylamine hydrochloride
or hydroxylamine sulfate, or formamide. The adverse affect of the harmful substances
can also be removed by selecting the equipments and materials so that the contamination
amounts are minimized, using clean water such as spring water, and forbidding the
use of the pulp, chip and waste paper exposed to rain. In order to reduce the generation
of paper powder, the surface of the long fiber paper is preferably processed by Yankee
calender or supercalender, and the surface strength is preferably more than 6. In
order to increase the surface strength of the paper, beating is necessary. The beating
is necessary to be carried out so that more than 50 % of the fibers have a fiber length
of longer than 3 mm. The long fiber paper may be a combination paper, and white or
colored.
[0064] The polyolefin resin film layer contains 0.1 to 15 wt. % of carbon black having a
pH of 4 to 9 and a mean particle size of 15 to 80 mµ The carbon black adsorbs harmful
substances for photographic photosensitive materials, when the long fiber paper is
contaminated, and it prevents the degradation of photographic properties, such as
fogging, the variation of photosensitivity and the decrease of concentration, when
a photographic photosensitive material is placed in the packaging material of the
invention for a long time, in addition to the light-shielding. When the pH of the
carbon black is less than 4 or beyond 9, the degradation of photographic properties,
such as fogging, the variation of photosensitivity and the decrease of concentration
occurs. When the mean particle size is less than 15 mµ, carbon black particles aggregate
to produce lumps and fish eye problem. While, when the mean particle size is beyond
80 µm, light-shielding ability decreases. Moreover, it is preferable that the free
sulfur content is less than 1,000 ppm, because the degradation of photographic properties,
such as fogging, the variation of photosensitivity and the decrease of concentration
occurs, when the content is beyond 1,000 ppm. The carbon black content is 0.1 to 15
wt. %. When the content is less than 0.1 wt. %, the effect of the carbon black, such
as to secure light-shielding, to prevent electrification, and to prevent oxidation,
is insufficient. While, when the content is beyond 15 wt. %, the physical strength
of the film, particularly tear strength and impact puncture strength, decreases, and
heat sealing properties are inferior. Furthermore, the surface strength decreases,
and dust is liable to be generated. The dust adheres to photographic photosensitive
materials, and causes developing trouble and contamination. The kind and preferable
carbon blacks are similar to described previously, other than mentioned above.
[0065] The polyolefin resin film layer contains more than 5 wt. % of an ethylene copolymer
resin. The ethylene copolymer resin improves heat sealing properties such as hot tack
properties, sealability with other materials, elapsed heat seal strength, heat seal
strength and heat seal tolerance, and the generation of pinhole at heat-sealed portion
is prevented. The dispersibility of carbon black is also improved. The ethylene copolymer
resin includes EVA resin, EEA resin, EMA resin, EAA resin and L-LDPE resin. L-LDPE
resin is preferable in view of improving physical strength, heat sealing properties
and the dispersibility of carbon black. The L-LDPE resin is similar to described previously
except that the preferable MI is 0.4 to 20 g/10 minutes and the preferable density
is 0.87 to 0.95 g/cm³. The content of the ethylene copolymer resin is more than 5
wt. %, preferably 15 to 95 wt. %. When the content is less than 5 wt. %, unless the
width of heat seal is increased, heat sealing properties, particularly elapsed heat
seal strength and sealability with other materials are inferior,and pinhole is liable
to be generated. Moreover, heat-sealed portion is liable to separate. When the ethylene
copolymer resin is L-LDPE, the suitable content is 5 to 99.9 wt. %, preferably 10
to 97 wt. %. The polyolefin resin film layer may be oriented or stretched.
[0066] The above flexible sheet layers may be laminated according to a known method such
as a heat sealing (hot bar sealing, impulse heat sealing, supersonic welding, etc.)
or a method using an adhesive (wet laminating, dry laminating, hot melt laminating,
extrusion laminating, etc.).
[0067] The adhesive is selected by considering both layers to be joined, and includes thermoplastic
resin melt adhesives including a polyolefin adhesive, hot melt type gum adhesives
and solution type adhesives. The polyolefin adhesives include a homopolymer and a
copolymer of an olefin such as various polyethylenes, polypropylenes, polybutenes
and ethylenepropylene copolymers and L-LDPE, a copolymer of an olefin and another
monomer such as ethylene-vinyl acetate copolymer, ethylene-acrylate ester copolymer,
various ionomers ("SURLYN" Dupont, "HIMIRAN" Mitsui Polychemicals Co., Ltd., etc.)
and a graft copolymer. The solution type adhesives are divided into adheisves for
wet lamination and adhesives for dry lamination. The adhesives for wet lamination
are emulsion-type or latex-type. Examples of the emulsion-type adhesives are polyvinyl
acetate emulsion, the emulsion of vinyl acetate-ethylene copolymer, the emulsion of
vinyl acetate-acrylate ester copolymer, the emulsion of vinyl acetate-maleate ester
copolymer, the emulsion of acrylic copolymer and the emulsion of ethylene-acrylic
acid copolymer. Examples of the latex-type adhesives are natural rubber latex, styrene-butadiene
rubber latex, acrylonitrile-butadiene rubber latex and chloroprene rubber latex.
An example of the adhesives for dry lamination is polyurethane adhesive. Adhesives
for hot melt lamination containing paraffin wax, microcrystalline wax, ethylene-vinyl
acetate copolymer and ethylene-ehtylacrylate copolymer, pressure-sensitive adhesives
and temperature-sensitive adhesives may also be employed. The melting point of the
adhesive employed is preferably more than 5°C below the melting point of the flexible
sheet in order to laminate without adverse influences upon the flexible sheet by a
thermal melting adhesion.
[0068] The thickness of the adhesive layer formed by extrusion laminating using a thermoplastic
resin is usually 6 to 50 µm, preferably 10 to 20 µm. However, the thickness is determined
based upon cost, rate of application, thickness of the total layers, and etc., and
accordingly, the thickness is not limited to the above range.
[0069] The adhesive strength of the adhesive layer may be improved by coating an anchor
coating agent, physical surface treatment, chemical agent treatment, or etc.
[0070] Anchor coating agent is a generic name of adhesive promoter and cross-linking agent
used in the field of laminating, and it is also called primer. Representative examples
of the anchor coating agent are as follows:
Organic titanate anchor coating agent
[0071] Tetrapropyl titanate or tetraisobutyl titanate is used as the principal constituent,
and tetrastearyl titanate is added as a hydrolysis-adjusting agent.
Polyethyleneimine anchor coating agent
[0072] A relatively high polymer of ethyleneimineCH₂-CH₂-NH
n is used. This agent is particularly preferable because its handling is easy and its
pot life is long.
Polyisocyanate anchor coating agent
[0073] One-component type; Polymer having isocyanate group alone
Two-component type; Combination of a polymer having isocyanate group and a polyester
having OH group
[0074] A chemical reaction such as a crosslinking reaction occurs in both types, and an
adhesive effect appears. Pot life is short, and this coating agent is expensive.
Polyester and urethane anchor coating agent
[0075] Saturated polyester resin or urethane resin is dissolved in a solvent such as ethyl
acetate or toluene.
Polyolefin anchor coating agent
Polybutadiene anchor coating agent
[0076] The anchor coat layer is preferably made extremely thin. The coating method may be
gravure roll coating, kiss roll coating, curtain coating, bar coating, reverse roll.
coating, direct roll coating, air knife coating or the like.
[0077] Representative examples of the physical surface treatment are described below. Two
or more kinds of the physical surface treatment may be combined, or the physical surface
treatment may be combined with the coating of an anchor coating agent.
Flame treatment ..... Running cost is high, and there is the danger of fire.
Plasma treatment .... Argon gas is converted into plasma, and joining surface is treated
with the plasma. The treating strength is several times as much as corona discharge
treatment, but the equipment cost for plasma treatment is several tenths higher than
corona discharge treatment.
Corona discharge treatment ... Treatable materials are various polymer films and sheets,
aluminum foil, aluminum vacuum metallized film, etc. This inexpensive treatment is
widely utilized, and the treated effect is large.
Sandblasting treatment ... Sand such as silica sand is blasted at a high pressure
to the joining surface, and the surface is made rough.
[0078] Representative examples other treatments are as follows:
Chemical agent treatment ... Treated with a dichromate solution or etc.
Ozone treatment ..... Treated in a box filled with ozone. gas. Even though the resin
temperature of extrusion laminating is lowered, the adhesive strength is still improved.
Preheat treatment ... The flexible sheet to be conducted with extrusion laminating
preheated with a heat drum, hot air or etc.
Ultraviolet irradiation
High-frequency heating
Dielectric heating
Mirrowave heating, etc.
[0079] The photographic photosensitive materials suitable for the above packaging material
are similar to enumerated previously. The package form and bag-making form may be
similar to mentioned in the case of the coextruded multilayer inflation film.
[0080] In the above packaging material for photographic photosensitive materials, the release
of fibers and the picking of paper do not occur from the long fiber paper, and they
do not adhere to photographic photosensitive materials as a foreign material. The
long fiber paper improves the Young's modulus, heat resistance and drawing ability
by writing tools. The aluminum vacuum metallized biaxially stretched thermoplastic
resin film layer imparts antistatic property, moistureproofness, gas barrier and light-shielding,
and prevents the penetration of harmful substances. The polyolefin resin film layer
secures sealing and the carbon black contained therein does not affect the photogdraphic
photosensitive materials adversely. The packaging bag formed of the packaging material
may be a single sheet bag, and is excellent in bag-making ability and packaging workability.
[0081] Representative embodiments of the packaging material comprising a single layer polyolefin
resin light-shielding film are illustrated in Figures 1 to 3.
[0082] The packaging material of Figure 1 is composed of a single layer of a polyolefin
resin light-shielding film 1a containing carbon black.
[0083] The packaging material of Figure 2 is composed of three layers consisting of a polyolefin
resin light-shielding film 1a containing carbon black, and a flexible sheet layer
4 laminated thereto through an adhesive layer 3.
[0084] The packaging material of Figure 3 is composed of three layers consisting of two
polyolefin resin light-shielding film layers 1a, 1a laminated to each other through
an adhesive layer 3.
[0085] Figure 4 indicates a comparative packaging material I composed of a single layer
of a HDPE resin light-shielding film 5a.
[0086] Figure 5 indicates a comparative packaging material II composed of a single layer
of a L-LDPE resin light-shielding film 6a.
[0087] Figure 6 indicates a conventional packaging material I composed of a single layer
of a LDPE resin light-shielding film 7a.
[0088] Subsequently, representative embodiments of the packaging material comprising an
aluminum vacuum metallized biaxially stretched thermoplastic resin film layer, a long
fiber layer and a polyolefin resin film layer are illustrated in Figures 10 to 13.
[0089] The packaging material of Figure 10 is composed of an aluminum vacuum metallized
biaxially stretched thermoplastic resin film layer 21 consisting of a biaxially stretched
thermoplastic resin film layer 19 and an aluminum vacuum deposition layer 20, a long
fiber paper layer 22 laminated on the aluminum vacuum deposition layer 20 as the outer
layer, and a light-shielding polyolefin resin film layer 23a on the biaxially stretched
thermoplastic resin film layer 19 as the inner layer, each through an adhesive layer
3.
[0090] The packaging material of Figure 11 is similar to the packaging material of Figure
10, except that the light-shielding polyolefin resin film layer 23a is replaced by
a coextruded multilayer film layer 25a consisting of a light-shielding thermoplastic
resin film layer 24a and a light-shielding polyolefin resin film layer 23a.
[0091] The packaging material of Figure 12 is similar to the packaging material of Figure
11, except that the aluminum vacuum metallized biaxially stretched thermoplastic resin
film layer 21 is turned inside out.
[0092] The packaging material of Figure 13 is similar to the packaging material of Figure,
10, except that the light-shielding polyolefin resin film layer 23a is directly laminated
by the extrusion laminating method.
[0093] Figure 14 indicates a comparative pckaging material VI similar to the packaging material
of Figure 11, except that the long fiber paper layer 22 is replaced by a conventional
bleached kraft paper layer 26.
EXAMPLES
[0094] Examples I, II and III are the examples of the packaging material comprising a single
layer polyolefin resin light-shielding film.
[0095] The packaging material of Example I was a single layer inflation film 70 µm in thickness
composed of 1.0 wt. % of HDPE resin having a MI of 1.1 g/10 minutes and a density
of 0.954 g/cm³, 95.85 wt. % of L-LDPE resin of a copolymer of ethylene and octene-1
having a MI of 4 g/10 minutes and a density of 0.925 g/cm³, 3 wt. % of oil furnace
carbon black ("#44B", mean particle size 21 mµ, pH 7.7, Mitsubishi Chemical Industries
Ltd.), 0.03 wt. % of oleic acid amide, 0.07 wt. % of calcium stearate and 0.05 wt.
% of antioxidant.
[0096] The packaging material of Example II was a single inflation layer film 70 um in thickness
composed of 10 wt. % of HDPE resin having a MI os 1.1 g/10 minutes and a density of
0.954 g/cm³, 86.85 wt. % of L-LDPE resin of a copolymer of ethylene and octene-1 having
a MI of 2.0 g/10 minutes and a density of 0.920 g/cm³, 3 wt. % of carbon black, 0.03
wt. % of oleic acid amide, 0.07 wt. % of calcium stearate and 0.05 wt. % of antioxidant.
[0097] The packaging material of Example III was a single layer inflation film 70 µm in
thickness composed of 15 wt. % of HDPE resin having a MI of 2.0 g/10 minutes and a
density of 0.935 g/cm³, 81.85 wt. % of L-LDPE resin of a copolymer of ethylene and
4-methylpentene-1 having a MI of 2.1 g/10 minutes and a density of 0.920 g/cm³, 3
wt. % of carbon black, 0.03 wt. % of oleic acid amide, 0.07 wt. % of calcium stearate
and 0.05 wt. % of antioxidant.
[0098] Comparative packaging material I was a single layer inflation film 70 µm in thickness
composed of 97 wt. % of HDPE resin of Example II having a MI of 1.1 g/10 minutes and
a density of 0.954 g/cm³, and 3 wt. % of carbon black.
[0099] Comparative packaging material II was a single layer inflation film 70 µm in thickness
composed of 97 wt. % of L-LDPE resin of Example II of a copolymer of ethylene and
butene-1 having a MI of 1.0 g/10 minutes and a density of 0.890 g/cm³, and 3 wt. %
of carbon black.
[0100] Conventional packaging material was a single layer inflation film 70 µm in thickness
composed of 97 wt. % of LDPE resin having a MI of 2.4 g/10 minutes and a density of
0.923 g/cm³, and 3 wt. % of carbon back.
[0101] Various properties of the above films were measured, and the results are tabulated
in Table 1.
Table 1
|
Unit |
Invention |
Comparative |
Conventional |
|
|
I |
II |
III |
I |
II |
I |
Layer Composition |
- |
Fig. 1 |
Fig. 1 |
Fig. 1 |
Fig.4 |
Fig. 5 |
Fig. 6 |
Polyethylene Resin |
- |
HDPE |
HDPE |
HDPE |
HDPE |
- |
LDPE |
" MI |
g/10 min. |
1.1 |
1.1 |
2.0 |
1.1 |
- |
2.4 |
" Density |
g/cm³ |
0.954 |
0.954 |
0.935 |
0.954 |
- |
0.923 |
" Content |
wt. % |
1 |
10 |
15 |
97 |
- |
97 |
L-LDPE Resin |
- |
L-LDPE |
L-LDPE |
L-LDPE |
- |
L-LDPE |
- |
" MI |
g/10 min. |
4 |
2.0 |
2.1 |
- |
1 |
- |
" Density |
g/cm³ |
0.925 |
0.920 |
0.920 |
- |
0.890 |
- |
" Content |
wt. % |
95.87 |
86.85 |
81.85 |
- |
97 |
- |
Tear Strength (MD) |
g |
1600 |
1275 |
1126 |
60 |
- |
186 |
" (CD) |
g |
" |
1518 |
1243 |
120 |
1600 |
453 |
Impact Puncture Strength |
kg cm |
30 |
25 |
35 |
7 |
" |
10 |
Antiblocking Property |
- |
A |
A |
A |
A |
30 |
C |
Heat Sealing Properties |
- |
A |
A |
A |
D |
A |
C |
Film Moldability |
- |
B |
B |
B |
D-E |
D-E |
B |
[0102] Evaluations in Table 1 were carried out as follows:
A very excellent
B excellent
C practical
D having a problem
E impractical
Testing methods are as follows:
Melt Index: ASTM D-1238
Density: ASTM D-1505
Tear Strength: JIS P-8116
Impact Puncture Strength: JIS P-8134
Antiblocking Property:
[0103] Each inflation film was molded under the conditions of the following film moldability,
and wound. The film was cut in a size of 100 mm x 100 mm by a razor, and the antiblocking
property was judged through opening of the cut portion.
Heat Sealing Properties:
[0104] Judged by hot tack properties, sealability with other materials, heat seal strength,
elapsed heat seal strength and temperature tolerance of heat sealing collectively.
Film Moldability:
[0105] Judged by bubble stability, the occurrence of draw down, the occurrence of wrinkling
and furrowing and the variation of film thickness collectively, when each inflation
film 70 µm in thickness was molded using a ring die 100 mm in diameter having a lip
clearance of 1 mm in a blow-up ratio of 1.76.
[0106] The coextruded multilayer inflation film of the invention was formed by using the
inflation film molding machine shown in Figure 7. The resin composition composing
the polyolefin resin film layer 17 was put into one of the extruders 8, and the resin
composition composing the L-LDPE resin film layer 18 was put into the other extruder
8. They were melted by heating. Subsequently, the resin composition of the pololefin
resin film layer 17 was extruded from the inside slit of the ring die 9, and the resin
composition of the L-LDPE resin film layer 18 was extruded from the outside slit of
the ring die 9. Compressed air was blown from the blast tube 10, and cooling air was
blown from the air ring 11. Thus, a tube-shaped resin film 13 was molded so that the
polyolefin resin film layer 17 was disposed on the inside and the L-LDPE resin film
layer 18 was disposed on the outside, as shown in Figure 8. The tube-shaped resin
film 13 asended with the guide of the guide rollers 12,···, 12, and was led into flat
by the guide plates 14. The film was deflated into sheet shap by passing the squeeze
roll 15, and wound with the winder 16. In the above film-forming process, since the
L-LDPE resin film layer 18 was contacted with the guide rollers 12,···, 12, the guide
plates 14 and the squeeze roll 15, the additives of the film did not adhere to them.
Since the inflation film was wound in the state that the polyolefin resin film layers
17 were contacted with each other, as shown in Figure 9, blocking did not occur between
the inner surface layers.
[0107] By the above process, the following packaging materials were produced.
The packaging material of Example IV:
[0108] The inner surface layer was a polyolefin resin film layer 35 µm in thickness composed
of 20 wt. % of HDPE resin having a MI of 1.1 g/10 minutes and a density of 0.954 g/cm³,
76.9 wt. % of L-LDPE resin of a copolymer of ethylene and 4-methylpentene-1 having
a MI of 2.0 g/10 minutes and a density of 0.920 g/cm³, 3 wt. % of oil furnace carbon
black and 0.1 wt. % of oleic acid amide.
[0109] The outer surface layer was an L-LDPE resin film layer 35 µm in thickness composed
of 96.75 wt. % of L-LDPE resin of a copolymer of ethylene and 4-methylpentene-1 having
a MI of 2.1 g/10 minutes and a density of 0.920 g/cm³, 3 wt. % of oil furnace carbon
black, 0.05 wt. % of oleic acid amide and 0.2 wt. % of synthetic silica as an antiblocking
agent.
The packaging material of Example V:
[0110] The inner surface layer was a polyolefin resin film layer 35 µm in thickness composed
of 2 wt. % of HDPE resin having a MI of 1.1 g/10 minutes and a density of 0.954 g/cm³,
93 wt. % of L-LDPE resin of a copolymer of ethylene and octene-1 having a MS of 2.0
g/10 minutes and a density of 0.920 g/cm³, 3 wt. % of oil furnace carbon black 2 wt.
% of calcium stearate and 0.1 wt. % of oleic acid amide, and the rest was the same
as Example IV.
Comparative packaging material III:
[0111] The inner surface layer was an L-LDPE resin film layer 35 µm in thickness composed
of 97 wt. % of L-LDPE resin of a copolymer of ethylene and octene-1 having a MI of
2.0 g/10 minutes and a density of 0.920 g/cm³ and 3 wt. % of oil furnace carbon black.
[0112] The outer furface layer was an L-LDPE resin film layer 35 µm in thickness composed
of 96.75 wt. % of L-LDPE resin of a copolymer of ethylene and 4methylpentene-1 having
a MI of 2.1 g/10 minutes and a density of 0.920 g/cm³, 3 wt. % of oil furnace carbon
black, 0.05 wt. % of oleic acid amide and 0.2 wt. % of synthetic silica.
Comparative packaging material IV:
[0113] The inner surface layer was a HDPE resin film layer 25 µm in thickness composed of
95 wt. % of HDPE resin having a MI of 0.4 g/10 minutes and a density of 0.964 g/cm³,
3 wt. % of oil furnace carbon black and 2 wt. % of calcium stearate.
[0114] The outer surface layer was an L-LDPE resin film layer 45 µm in thickness composed
of 96.95 wt. % of L-LDPE resin of a copolymer of ethylene and 4methylpentene-1 having
a MI of 2.1 g/10 minutes and a density of 0.920 g/cm³, 3 wt. % of oil furnace carbon
black, 0.05 wt. % of oleic acid amide and 0.2 wt. % of synthetic silica as antiblocking
agent.
Comparative packaging material V:
[0115] Having the same layer composition as Example V, except that the inner surface layer
and the outer surface layer were turned inside out.
Conventional packaging material II:
[0116] A single layer inflation film 70 µm in thickness composed of 96.95 wt. % of LDPE
resin having a MI of 2.4 g/10 minutes and a density of 0.923 g/cm³, 3 wt. % of oil
furnace carbon black and 0.05 wt. % of oleic acid amide.
[0117] Various properties of the above films were measured, and the results are tabulated
in Table 2.
Table 2
|
Unit |
Invention |
Comparative |
Conventional |
|
|
IV |
V |
III |
IV |
V |
II |
Inner Surface Layer |
|
|
|
|
|
|
|
HDPE Resin Content |
wt. % |
20 |
2 |
- |
95 |
- |
- |
Polyolefin Resin |
- |
C6 MI 2.1 g/10 min. L-LDPE Resin |
C8 MI 2.0 g/10 min. L-LDPE Resin |
C8 MI 2.0 g/10 min. L-LDPE Resin |
- |
C6 MI 2.1 g/10 min. L-LDPE Resin |
- |
" Content |
wt. % |
76.9 |
- |
97 |
- |
96.95 |
- |
CB Content |
" |
3 |
3 |
3 |
3 |
3 |
- |
Fatty Acid Comp. Content |
" |
Oleic Amide 0.1 |
Ca Stearate 2 |
- |
Ca Stearate 2 |
Oleic Amide 0.1 |
- |
Outer Surface Layer |
|
|
|
|
|
|
|
L-LDPE Content |
" |
C6 MI 2.1 g/10 min. 96.75 |
C6 MI 2.1 g/10 min. 96.75 |
C6 MI 2.1 g/10 min. 96.75 |
C6 MI 2.1 g/10 min. 96.75 |
(HDPE) (95) |
(LDPE) (96.95) |
CB Content |
" |
3 |
3 |
3 |
3 |
3 |
3 |
Fatty Acid Comp. Content |
" |
Oleic Amide 0.05 |
Oleic Amide 0.05 |
Oleic Amide 0.05 |
Oleic Amide 0.05 |
Ca Stearate 2 |
Oleic Amide 0.05 |
Antiblocking Agent Content |
" |
Silica 0.2 |
Silica 0.2 |
Silica 0.2 |
- |
- |
- |
Properties |
|
|
|
|
|
|
|
Antiblocking Property |
- |
A |
A |
E |
E |
E |
C |
Film Moldability |
- |
B |
B |
C |
C |
C |
B |
White Powder Generation |
- |
B |
B |
B |
E |
E |
B |
Physical Strength |
- |
A |
B |
B |
B |
B |
E |
Wrinkling Furrowing |
- |
A |
A |
C |
C |
C |
B |
Bag-Making Ability |
- |
A |
A |
B |
A |
A |
D |
[0118] The meaning of the indications A through E in the table are the same as Table 1.
Antiblocking Property:
[0119] Each wound inflation film was cut in a size of 330 mm (lay-flat width) x 220 mm by
a razor, and the antiblocking property was judged through opening of the cut portion.
Film Moldability:
[0120] Judged by motor load (electric current value), bubble stability, the position of
frosting line, fish eye, lumps, wrinkling and the uniformity in film thickness collectively.
White Powder Generation:
[0121] Judged by the degree of the white powder and agglomerates thereof adhered to the
guide rollers, guide plates and squeeze roll and wound film by visual observation,
when each inflation film was molded using a die having a clearance of 1 mm at a blow-up
ratio of 2.1.
Physical Strength:
[0122] Judged by tear strength (JIS P-8116), impact puncture strength, bursting strength
(JIS P-8112) and heat seal strength collectively.
Wrinkling, Furrowing:
[0123] Judged by the generation degree of wrinkling and furrowing of each film by visual
observation, when each film was molded using a die having a clearance of 1 mm at a
blow-up ratio of 2.1.
Bag-Making Ability:
[0124] Judged by the difference of melting points between the inner surface layer and the
outer surface layer, low temperature heat sealing properties, heat seal strength,
hot tack properties, sealability with other materials, elapsed heat seal strength,
curling, the generation of pinhole, bag rupture during transportation of products,
collectively.
[0125] Examples VI and VII are the examples of the packaging material comprising an aluminum
vacuum metallized biaxially stretched thermoplastic resin film layer, a long fiber
paper layer and a polyolefin resin film layer.
[0126] The packaging material of Example VI corresponds to illustrated in Figure 11.
[0127] The long fiber paper layer 22 consisted of a bleached kraft paper composed of the
fibers having a fiber length of about 4 mm, containing 2.5 wt. % of polyacrylamide
resin ("Polystlon", Arakawa Rinsan Kagaku K.K.) as paper reinforcing agent and each
less than 500 ppm of harmful substances for photographic photosensitive materials,
and having a cool water extracting pH of 4.8, a surface strength of 9, an areal weight
of 35 g/m², and a glossy face by Yankee calender, made by using aluminum sulfate as
a fixer.
[0128] The biaxially stretched thermoplastic resin film 19 of the aluminum vacuum metallized
biaxially stretched thermoplastic resin film layer 21 was a biaxially stretched nylon
resin film 15 µm in thickness. The thickness of the aluminum vacuum deposition layer
20 was 400 Å.
[0129] The light-shielding polyolefin resin film layer 23a of the coextruded multilayer
film layer 25a was composed of 91.75 wt. % of ethylene-4-methylpentenel-1 copolymer
resin, 5 wt. % of LDPE resin, 3 wt. % of oil furnace carbon black having a pH of 8.0,
a mean particle size of 21 mµ and a free sulfur content of 450 ppm and 0.2 wt. % of
antioxidant, 0.05 wt. % of oleic acid amide, having a thickness of 40 µm.
[0130] The light-shielding thermoplastic resin film layer 24a was composed of 71.75 wt.
% of ethylene-4-methylpentenel-1 copolymer resin, 20 wt. % of HDPE resin having a
density of 0.954 g/cm³, 5 wt. % of LDPE resin, 3 wt. % of the same oil furnace carbon
black as the light-shielding polyolefin resin film layer 23a, 0.2 wt. % of antioxidant
and 0.05 wt. % of oleic acid amide having a thickness of 40 µm.
[0131] The adhesive layers 3 were LDPE resin extrusion laminating adhesive layers 13 µm
in thickness.
[0132] The laminations of laminated film was carried out in the same process using a tandem
laminator.
[0133] The packaging material of Example VII corresponds to illustrated in Figure 11.
[0134] The long fiber paper layer 22 consisted of an unbleached kraft neutral paper composed
of the fibers having a fiber length of about 3.5 mm, containing 0.2 wt. % of alkylketene
dimer ("Aquapel", Dick Hercules) and 0. 5 wt. % of modified starch as paper reinforcing
agent and each less than 1,000 ppm of harmful substances for photographic photosensitive
materials, and having a cool water extracting pH of 6.8, a surface strength of 8,
and an areal weight of 50 g/m², made by using aluminum sulfate as a fixer.
[0135] The other layers were the same as Example VI.
[0136] Comparative packaging material VI corresponds to illustrated in Figure 14.
[0137] The beached kraft paper layer 26 consisted of a semibleached kraft paper composed
of the fibers having a fiber length of 2.5 mm, containing 2.0 wt. % of melamine-formaldehyde
resin as paper reinforcing agent and 1870 ppm of formaldehyde adversely affecting
photographic photosensitive materials, and having a cool water extracting pH of 4.3,
a surface strength of 6 and an areal weight of 50 g/m², made by using aluminum sulfate
as a fixer.
[0138] The other layers were the same as Example VI.
[0139] Conventional packaging material III corresponds to illustrated in Figure 15.
[0140] The bleached kraft paper layer 26 consisted of a bleached kraft paper composed of
the fibers having a fiber length of 2.5 mm, having a cool water extracting pH of 4.5,
a surface strength of 5 and an areal weight of 30 g/m² made by using aluminum sulfate
as a fixer.
[0141] The metal foil layer 27 was aluminum foil 7 µm in thickness.
[0142] The thermoplastic resin film layer 28a was a LDPE resin film 80µm in thickness containing
3 wt. % of the same carbon black as Example VI.
[0143] The adhesive layers 3 were LDPE resin extrusion laminating adhesive layers 40 µm
in thickness.
[0144] The laminated film was formed by laminating through twice extrusion laminating processes
successively.
[0145] Various properties of the above films were measured, and the results are tabulated
in Table 3.
Table 3
|
Invention |
Comparative |
Conventional |
|
I |
II |
I |
I |
Layer Composition |
Fig. 11 |
Fig. 11 |
Fig. 14 |
Fig. 15 |
Light-Shielding after Dropping Test |
B |
B |
B |
E |
Hot Tack Properties |
A |
A |
A |
E |
Sealability with Other Materials |
A |
A |
A |
E |
Elapsed Heat Seal Strength |
A |
A |
A |
D |
Bag Rupture Strength |
A |
A |
A |
E |
Paper Powder Generation |
B |
B |
D |
D |
Surface Strength |
9 |
8 |
6 |
5 |
Photographic Properties |
B |
B |
E |
B |
Tear Strength (MD) (g) |
1120 |
1075 |
957 |
286 |
" (CD) (g) |
1230 |
1186 |
1051 |
384 |
[0146] The meaning of the indications A through E in the table are the same as Table 1.
[0147] In the following tests, the packaging bag used was a single-sheet gusset bag, and
4 rolls of color printing paper of 8.9 cm in width x 180 m in length were placed in
a corrugated board box in two layers through a corrugated board pad.
Light-Shielding after Dropping Test:
[0148] After the dropping test of JIS Z-0202 level I, each packaging bag was exposed to
80,000 luxes light for 1 hour. The color printing paper was developed, and the light-shielding
was judged.
Hot Tack Properties (Hot-Seal Ability):
[0149] Two sheets of each exemplified film having 15 mm in width were heat-sealed at 170°C,
and just after, the open ends were pulled by the weight of 45 g at the releasing angle
of 22.5 degree. This character was estimated by the released length (cm).
Sealability with Other Materials:
[0150] Each exemplified film was cut in a width of 15 mm, and the cigarette end after smoking
was smeared on the heat seal face by using a finger. Thereafter, two sheets of the
films were superposed, and heat-sealed at each optinal temperature at a sealing pressure
of 1 kg/m² for one second. This character was estimated by the load necessary for
releasing the sealed portion at 180 degrees.
Elapsed Heat Seal Strength:
[0151] Two sheets of each exemplied film having a width of 15 mm were heat sealed at each
optimal temperature at a sealing pressure of 1 kg/m² for one second. This character
was estimated by the load necessary for releasing the sealed portion at 180 degrees
after one month from the heat seal.
Bag Rupture Strength:
[0152] Judged by the bag rupture state after the dropping test of JIS Z-0202 level I.
Paper Powder Generation:
[0153] Judged by the amount of paper powder after the shaking test of JIS Z-0232 level I.
Surface Strength:
[0154] Measured by the wax method of JIS P-8129, and it is expressed in wax number.
Photographic Properties:
[0155] According to a contact test with the uppermost layer.
Teat Strength:
[0156] According to JIS P-8116.