[0001] The present invention relates to an insulating paperboard, and more particularly
to an insulating paperboard containing bulky fibers.
[0002] Hot foods, particularly hot liquids, are commonly served and consumed in disposable
containers. These containers are made from a variety of materials including paperboard
and foamed polymeric sheet material. One of the least expensive sources of paperboard
material is cellulose fibers. Cellulose fibers are employed to produce excellent paperboards
for the production of hot cups, paper plates, and other food and beverage containers.
Conventional paperboard produced from cellulosic fibers, however, is relatively dense,
and therefore, transmits heat more readily than, for example, foamed polymeric sheet
material. Thus, hot liquids are typically served in double cups or in cups containing
multiple plies of conventional paperboard.
[0003] It is desirable to possess an insulating paperboard produced from cellulosic material
that has good insulating characteristics, that will allow the user to sense that food
in the container is warm or hot and at the same time will allow the consumer of the
food or beverage in the container to hold the container for a lengthy period of time
without the sensation of excessive temperature. It is further desirable to provide
an insulating paperboard that can be tailored to provide a variety of insulating characteristics
so that the temperature drop across the paperboard can be adjusted for a particular
end use.
[0004] US-A-6736933 discloses a multi-ply paperboard comprising at least one ply of conventional cellulose
fibers and from about 0.1 to about 6 weight percent of a water-borne binding agent;
and at least one ply of chemically intrafiber crosslinked cellulose high-bulk fibers
and from about 0.1 to about 6 percent of a water-borne binding agent.
[0005] US-A-5906894 discloses a multi-ply paperboard comprising at least one ply of conventional cellulose
fibers and from about 0.1 to about 6 weight percent of a water-borne binding agent;
and at least one ply containing up to 20% of chemically intra-fiber crosslinked cellulosic
high-bulk fibers and from about 0.1 to about 6 weight percent of a water-borne binding
agent.
[0006] This invention provides an insulating paperboard comprising at least one layer of
cellulose fibers, characterised in that at least some of the cellulose fibers in said
at least one layer are crosslinked cellulose fibers to provide bulky fibers and which
are present in an amount from 25% to 100% of said at least one layer, said paperboard
being sufficiently insulating to provide a hot water ΔT across said paperboard of
at least 0.7°C ± 2.3°C per 0.1 mm of calliper, said paperboard having a density of
less than 0.5 g/cc, and a basis weight of from 200 gsm to 500 gsm, and the caliper
of said board being greater than or equal to 0.5 mm.
[0007] By way of example the paperboard may have a basis weight of from 250 gsm to 400 gsm.
[0008] It is preferred that said paperboard has a hot water ΔT of 9°C ± 2.3°C at a caliper
of 0.6 mm and a hot water ΔT of 14°C ± 2.3°C at a caliper of 1.25 mm, said hot water
ΔT being a substantially linear progression relative to caliper in the temperature
range from below 9°C to above 14°C. In particular said linear progression may extend
from a ΔT of 9°C to a . ΔT of 14°C.
[0009] In any of the above arrangements said paperboard may be at least a two-ply board,
said at least one ply containing said crosslinked cellulose fibers.
[0010] The foregoing aspects and many of the attendant advantages of this invention will
become more readily appreciated as the same become better understood by reference
to the following detailed description, when taken in conjunction with the accompanying
drawings, wherein:
FIGURE 1 is a schematic cross-sectional view of a two-ply paperboard constructed in
accordance with the present invention;
FIGURE 2 is an isometric view of a hot cup made from the paperboard similar to that
shown in FIGURE 1 with a portion cut away; and
FIGURE 3 is an enlarged cross-sectional view of a portion of the paperboard used to
make the hot cup shown in FIGURE 2.
[0011] Referring to FIGURE 1, the substrate 10 for the insulating paperboard 12 of the present
invention is produced in a conventional manner from readily available fibers such
as cellulosic fibers. The paperboard of the present invention can be made in a single-ply,
a two-ply construction, or a multi-ply construction, as desired. While the paperboard
of the present invention may employ synthetic fibers as set forth above, it is most
preferred that paperboard comprise all or substantially all of the cellulosic fibers.
[0012] The distinguishing characteristic of the present invention is that at least one ply
14 of the paperboard, whether a single-ply or a multiple-ply structure, contains bulky
fibers. The bulky fibers increase the bulk density of the paperboard and thus the
insulating characteristics. As used herein, bulky fibers are kinked, twisted, curly,
cellulosic fibers. It is preferred, however, that the fibers be produced by intrafiber
crosslinking of the cellulosic fibers as described in more detail below.
[0013] Paperboard of the present invention may have a broad set of characteristics. For
example, its basis weight can range from 200 gsm to 500 gsm, more preferably, from
250 gsm to 400 gsm. Most preferably, the basis weight of the paperboard is equal to
or greater than 250 gsm. To achieve the insulating characteristics of the present
invention, it is preferred that the paperboard has a density of less than 0.5 g/cc,
more preferably, from 0.3 g/cc to 0.45 g/cc, and most preferably, from 0.35 g/cc to
0.40 g/cc.
[0014] When at least one ply of the paperboard contains bulky fibers in accordance with
the present invention, advantageous temperature drop characteristics can be achieved.
These temperature drop characteristics can be achieved by altering the amount of bulky
fiber introduced into the paperboard, by adjusting the basis weight of the paperboard,
by adjusting the caliper of the paperboard after it has been produced by running it,
for example, through nip rolls, and of course, by varying the number and thickness
of additional plies incorporated in the paperboard structure. It is preferred that
this paperboard have a caliper greater than or equal to 0.5 mm, a basis weight equal
to or greater than 250 gsm, and a density less than 0.5 g/cc. In a most preferred
form, the paperboard of the present invention exhibits a hot water ΔT of 10°C ± 2.3°C
at a caliper of 0.64 mm and a hot water ΔT of 14°C ± 2.3°C at a caliper of 1.25 mm.
The relationship of hot water ΔT to thickness is a linear one between the calipers
of 0.6 mm and 1.25 mm and continues to be linear with a reduction in the caliper below
0.6 mm or an increase above 1.25 mm. Stated another way, a paperboard constructed
in accordance with the present invention having a caliper of 0.3 mm or greater will
exhibit a hot water ΔT (as defined below) of 0.7°C ± 2.3°C per 0.1 mm of caliper,
and most preferably a hot water ΔT of 0.7°C ± 2.0°C.
[0015] The paperboard of the invention can be a single-ply product. When a single-ply product
is employed, the low density characteristics of the paperboard of the present invention
allow the manufacture of a thicker paperboard at a reasonable basis weight. To achieve
the same insulating characteristics with a normal paperboard, the normal paperboard
thickness would have to be doubled relative to that of the present invention. Using
the bulky fibers of the present invention, an insulating paperboard having the same
basis weight as a normal paperboard can be made. This effectively allows the manufacture
of insulating paperboard on existing paperboard machines with minor modifications
and minor losses in productivity. Moreover, a one-ply paperboard has the advantage
that the whole structure is at a low density. Furthermore, as will be described later,
the low density paperboard of the present invention is easily embossable.
[0016] Alternatively, the paperboard of the invention can be multi-ply product, and include
two, three, or more plies. Paperboard that includes more than a single-ply can be
made by combining the plies either before or after drying. It is preferred, however,
that a multi-ply paperboard be made by using multiple headboxes arranged sequentially
in a wet-forming process, or by a baffled headbox having the capacity of receiving
and then laying multiple pulp furnishes. The individual plies of a multi-ply product
can be the same or different.
[0017] The paperboard of the present invention can be formed using conventional papermaking
machines including, for example, Rotoformer, Fourdrinier, inclined wire Delta former,
and twin-wire forming machines.
[0018] When a single-ply paperboard is used in accordance with the present invention, it
is preferably homogeneous in composition. The single ply, however, may be stratified
with respect to composition and have one stratum enriched with bulky fibers and another
stratum enriched with non-bulky fibers. For example, one surface of the paperboard
may be enriched with bulky fibers to enhance that surface's bulk and the other surface
enriched with non-crosslinked fibers to provide a smooth, denser, less porous surface.
[0019] As stated, it is preferred and most economical to produce a paperboard that is homogeneous
in composition. The bulky fibers are uniformly intermixed with the regular cellulosic
fibers. For example, in the headbox furnish it is preferred that the bulky fibers
present in the insulating ply or layer be present in an amount from about 25% to about
100%, and more preferably from about 30% to about 70%. In a two-ply structure, for
example, the first ply may contain 100% non-bulky fibers while the second ply may
contain from 25% to 100% bulky fibers and preferably from 30% to 70% bulky fibers.
In a three-ply layer, for example, the bottom and top layers may comprise 100% of
non-bulky fibers while the middle layer contains from about 25% to about 100% and
preferably from about 30% to about 70% of bulky fibers.
[0020] When bulky fibers are used in paperboard in accordance with the present invention,
it has been found that the paperboard exiting the papermaking machine can be compressed
to varying degrees to adjust the temperature drop characteristics across the paperboard.
In accordance with the present invention, the paperboard once leaving the papermaking
machine may be compressed or reduced in caliper by up to 50 %, and more preferably,
from 15% to 25%. This adjustment in the caliper of the paperboard made in accordance
with the present invention allows the hot water ΔT to be varied as desired. This same
result can be achieved by lowering the basis weight of the paperboard.
[0021] In addition, the paperboard of the present invention can be embossed with a variety
of conventional embossing rollers to produce a paperboard that has a tactile sense
to the user quite different from that of the conventional paperboard. An embossed
surface not only provides a better gripping surface, but also provides an actual and
perceived reduction in the heat transfer from the surface of the paperboard to a person
touching the exterior of the paperboard. Flat embossed cauls may also be used to form
an embossed pattern on the paperboard. Any of a variety of embossed patterns can be
employed. However, when the paperboard is to be employed as a single-ply layer for
a hot cup, it is preferred that a fine pattern of indentations be embossed into the
cup so as in essence to provide a multiplicity of small surface indents that effectively
reduce the contact surface area for a person touching the surface of the paperboard.
This is especially effective when the paperboard is used in a hot cup or other container
that is held by a person for any period of time. The reduction in surface area reduces
the amount of heat transferred to the person's fingers and thus reduces the sensation
of excessive temperature. For example, the number of bumps and depressions in a one
centimeter square surface of paperboard might comprise a 6 by 6 array.
[0022] The paperboard of the present invention can be utilized to make a variety of structures,
particularly containers, in which it is desired to have insulating characteristics.
Referring to FIGURE 2, one of the most common of these containers is the ubiquitous
hot cup utilized for hot beverages such as coffee, tea, and the like. Other insulating
containers such as the ordinary paper plate can also incorporate the paperboard of
the present invention. Also, carry-out containers conventionally produced of paperboard
or of foam material can also employ the paperboard of the present invention. As shown
in FIGURES 2 and 3, a hot cup type container produced in accordance with the present
invention may comprise one or more plies 22 and 24, one of which, in this instance
24, contains bulky fibers. In this embodiment the bulky fibers are in the interior
ply 24. A liquid impervious backing 26 is preferably laminated to the interior ply.
The backing may comprise, for example, a variety of thermoplastic materials, such
as polyethylene. It is preferred that the paperboard used in the bottom of the cup
contain no bulky fibers.
[0023] Although available from other sources, nonbulky cellulosic fibers usable in the present
invention are derived primarily from wood pulp. Suitable wood pulp fibers for use
with the invention can be obtained from well-known chemical processes such as the
kraft and sulfite processes, with or without subsequent bleaching. Pulp fibers can
also be processed by thermomechanical, chemithermomechanical methods, or combinations
thereof. The preferred pulp fiber is produced by chemical methods. Groundwood fibers,
recycled or secondary wood pulp fibers, and bleached and unbleached wood pulp fibers
can be used. Softwoods and hardwoods can be used. Details of the selection of wood
pulp fibers are well known to those skilled in the art. These fibers are commercially
available from a number of companies, including Weyerhaeuser Company, the assignee
of the present invention. For example, suitable cellulose fibers produced from southern
pine that are usable with the present invention are available from Weyerhaeuser Company
under the designations CF416, NF405, PL416, FR516, and NB416.
[0024] In addition to fibrous materials, the paperboard of the invention may optionally
include a binding agent. Suitable binding agents are soluble in, dispersible in, or
form a suspension in water. Suitable binding agents include those agents commonly
used in the paper industry to impart wet and dry tensile and tearing strength to such
products. Suitable wet strength agents include cationic modified starch having nitrogen-containing
groups (e.g., amino groups), such as those available from National Starch and Chemical
Corp., Bridgewater, NJ; latex; wet strength resins, such as polyamide-epichlorohydrin
resin (e.g., KYMENE 557LX, Hercules, Inc., Wilmington, DE), and polyacrylamide resin
(see, e.g.,
U.S. Patent No. 3,556,932 and also the commercially available polyacrylamide marketed by American Cyanamid
Co., Stanford, CT, under the trade name PAREZ 631 NC); urea formaldehyde and melamine
formaldehyde resins; and polyethylenimine resins. A general discussion on wet strength
resins utilized in the paper field, and generally applicable in the present invention,
can be found in
TAPPI monograph series No. 29, "Wet Strength in Paper and Paperboard", Technical Association
of the Pulp and Paper Industry (New York, 1965).
[0025] Other suitable binding agents include starch, modified starch, polyvinyl alcohol,
polyvinyl acetate, polyethylene/acrylic acid copolymer, acrylic acid polymers, polyacrylate,
polyacrylamide, polyamine, guar gum, oxidized polyethylene, polyvinyl chloride, polyvinyl
chloride/acrylic acid copolymers, acrylonitrile/butadiene/styrene copolymers, and
polyacrylonitrile. Many of these will be formed into latex polymers for dispersion
or suspension in water.
[0026] The preferred bulky fibers for use in the invention are crosslinked cellulosic fibers.
Any one of a number of crosslinking agents and crosslinking catalysts, if necessary,
can be used to provide the crosslinked fibers to be included in the layer. The following
is a representative list of useful crosslinking agents and catalysts. Each of the
patents noted below is expressly incorporated herein by reference in its entirety.
[0027] Suitable urea-based crosslinking agents include substituted ureas, such as methylolated
ureas, methylolated cyclic ureas, methylolated lower alkyl cyclic ureas, methylolated
dihydroxy cyclic ureas, dihydroxy cyclic ureas, and lower alkyl substituted cyclic
ureas. Specific urea-based crosslinking agents include dimethyldihydroxy urea (DMDHU,
1,3-dimethyl-4,5-dihydroxy-2-imidazolidinone), dimethyloldihydroxyethylene urea (DMDHEU,
1,3-dihydroxymethyl-4,5-dihydroxy-2-imidazolidinone), dimethylol urea (DMU, bis[N-hydroxymethyl]urea),
dihydroxyethylene urea (DHEU, 4,5-dihydroxy-2-imidazolidinone), dimethylolethylene
urea (DMEU, 1,3-dihydroxymethyl-2-imidazolidinone), and dimethyldihydroxyethylene
urea (DMeDHEU or DDI, 4,5-dihydroxy-1,3-dimethyl-2-imidazolidinone).
[0028] Suitable crosslinking agents include dialdehydes such as C
2-C
8 dialdehydes (e.g., glyoxal), C
2-C
8 dialdehyde acid analogs having at least one aldehyde group, and oligomers of these
aldehyde and dialdehyde acid analogs, as described in
U.S. Patent Nos. 4,822,453;
4,888,093;
4,889,595;
4,889,596;
4,889,597; and
4,898,642. Other suitable dialdehyde crosslinking agents include those described in
U.S. Patent Nos. 4,853,086;
4,900,324; and
5,843,061. Other suitable crosslinking agents include aldehyde and urea-based formaldehyde
addition products. See, for example,
U.S. Patent Nos. 3,224,926;
3,241,533;
3,932,209;
4,035,147;
3,756,913;
4,689,118;
4,822,453;
3,440,135;
4,935,022;
3,819,470; and
3,658,613. Suitable crosslinking agents may also include glyoxal adducts of ureas, for example,
U.S. Patent No. 4,968,774, and glyoxal/cyclic urea adducts as described in
U.S. Patent Nos. 4,285,690;
4,332,586;
4,396,391;
4,455,416; and
4,505,712.
[0029] Other suitable crosslinking agents include carboxylic acid crosslinking agents such
as polycarboxylic acids. Polycarboxylic acid crosslinking agents (e.g., citric acid,
propane tricarboxylic acid, and butane tetracarboxylic acid) and catalysts are described
in
U.S. Patent Nos. 3,526,048;
4,820,307;
4,936,865;
4,975,209; and
5,221,285. The use of C
2-C
9 polycarboxylic acids that contain at least three carboxyl groups (e.g., citric acid
and oxydisuccinic acid) as crosslinking agents is described in
U.S. Patent Nos. 5,137,537;
5,183,707;
5,190,563;
5,562,740; and
5,873,979.
[0030] Polymeric polycarboxylic acids are also suitable crosslinking agents. Suitable polymeric
polycarboxylic acid crosslinking agents are described in
U.S. Patent Nos. 4,391,878;
4,420,368;
4,431,481;
5,049,235;
5,160,789;
5,442,899;
5,698,074;
5,496,476;
5,496,477;
5,728,771;
5,705,475; and
5,981,739. Polyacrylic acid and related copolymers as crosslinking agents are described
U.S. Patent Nos. 5,549,791 and
5,998,511. Polymaleic acid crosslinking agents are described in
U.S. Patent No. 5,998,511 and
U.S. Application Serial No. 09/886,821.
[0031] Specific suitable polycarboxylic acid crosslinking agents include citric acid, tartaric
acid, malic acid, succinic acid, glutaric acid, citraconic acid, itaconic acid, tartrate
monosuccinic acid, maleic acid, polyacrylic acid, polymethacrylic acid, polymaleic
acid, polymethylvinylether-co-maleate copolymer, polymethylvinylether-co-itaconate
copolymer, copolymers of acrylic acid, and copolymers of maleic acid. Other suitable
crosslinking agents are described in
U.S. Patent Nos. 5,225,047;
5,366,591;
5,556,976; and
5,536,369.
[0032] Suitable crosslinking catalysts can include acidic salts, such as ammonium chloride,
ammonium sulfate, aluminum chloride, magnesium chloride, magnesium nitrate, and alkali
metal salts of phosphorous-containing acids. In one embodiment, the crosslinking catalyst
is sodium hypophosphite.
[0033] The crosslinking agent is applied to the cellulosic fibers as they are being produced
in an amount sufficient to effect intrafiber crosslinking. The amount applied to the
cellulosic fibers may be from about 1% to about 25% by weight based on the total weight
of fibers. In one embodiment, crosslinking agent in an amount from about 4% to about
6% by weight based on the total weight of fibers. Mixtures or blends of crosslinking
agents and catalysts can also be used.
EXAMPLES
[0034] A variety of test methods are utilized in the following examples. Hot water ΔT is
determined in a simulated tester that models the heat transfer through a paper cup.
A box of plexiglass measuring 12.1 cm by 12.1 cm by 12.1 cm has a sample opening of
8.9 cm by 8.9 cm. The box is insulated with 2.54 cm thick polystyrene foam. A sample
of paperboard is laminated with a sheet of polyethylene using a hot air gun to adhere
the polyethylene to the surface of the paperboard. Alternatively, the polyethylene
may be extruded onto the surface of the board. Hot water at a temperature of 87.8°C
is poured into the box, a small stir bar inserted, and the polyethylene coated face
of the sample is placed into the apparatus. The box is then turned 90° to the horizontal
plane so that the water is in full contact with the sample and placed on a stir plate
to permit stirring during the measurement phase. Five thermocouple microprobes are
taped to the outside of the paperboard surface with conducting tape. A data logger
records the temperature of the inside water temperature and the outside surface temperature
from which the temperature drop (hot water ΔT) can be calculated. When the water temperature
reaches 82.2°C, an infrared pyrometer with a 0.93 emissivity is aimed at the outside
of the sample and the IR radiation measured. This IR gun is used to correlate the
thermocouple accuracy.
[0035] Durometer tests were conducted in accordance with ASTM method D2240-91. This ASTM
method is for rubber, cellular materials, elastomeric materials, thermoplastic materials,
and hard plastics.
EXAMPLE 1
[0036] A plurality of lab scale samples were produced on a pilot scale on a Delta Former,
an inclined wire twinhead former. Both single-ply and two-ply samples were produced.
The single-ply samples contained varying weight percentages of bulky fibers. In the
two-ply samples, varying levels of bulky fiber were used in the base (bottom) layer.
The nonbulky fiber was a cellulose softwood pine that was refined to 400 Canadian
standard freeness (CSF). The bulky fiber employed was a fiber crosslinked with malic
acid. The crosslinked cellulose fiber was crosslinked with a crosslinking agent. The
pH of the system was adjusted to 8 with caustic. 20 g/kg of cooked cationic potato
starch (Sta-Lok 400 available from Staley Manufacturing Company), 2 g/kg to 3 g/kg
of AKD (alkyl ketene dimer) for water repellency, 5 g/kg to 7.5 g/kg Kymene, and 0
g/kg to 20 g/kg of uncooked cationic potato starch were added to the machine chest.
See Table 1A below. Blends of crosslinked fiber and pine were lightly deflaked prior
to board formation. The paperboard made was sized with an ethylated starch (Staley
starch, Ethylx 2065) at the size press. Various samples were produced and are set
forth in Table 1B below.
Table 1A
Sample No. |
AKD Level
g/kg |
Kymene Level
g/kg |
Uncooked Starch
Level g/kg |
702P |
3 |
7.5 |
0 |
702R |
3 |
7.5 |
20 |
702S |
3 |
7.5 |
20 |
802D |
2 |
5 |
20 |
802E |
2 |
5 |
20 |
802G |
2 |
5 |
20 |
802H |
2 |
5 |
20 |
802I |
2 |
5 |
20 |
802J |
2 |
5 |
20 |
Table 1B
Sample No. |
Base Ply HBA% |
Nominal Base Ply Weight g/m2 |
Top Ply C-Pine % |
Nominal Top Ply Weight g/m2 |
Actual Board Weight g/m2 |
Actual Board Caliper mm |
Actual Board Density g/cc |
702P |
50% |
350 |
N/A |
0 |
379 |
1.20 |
0.32 |
702R |
50% |
350 |
N/A |
0 |
427 |
1.22 |
0.35 |
702S |
50% |
275 |
100% |
75 |
396 |
1.03 |
0.38 |
802D |
60% |
450 |
N/A |
0 |
439 |
1.22 |
0.361 |
802E |
60% |
350 |
100% |
75 |
437 |
1.16 |
0.378 |
802G |
50% |
325 |
100% |
75 |
405 |
0.95 |
0.427 |
802H |
50% |
275 |
100% |
75 |
313 |
0.73 |
0.428 |
8021 |
40% |
325 |
100% |
75 |
412 |
0.90 |
0.457 |
802J |
40% |
325 |
N/A |
0 |
436 |
0.99 |
0.439 |
EXAMPLE 2
[0037] The insulating characteristics of each of the samples produced in accordance with
Example 1 were measured using the hot water ΔT method described above. In addition,
samples of the paperboards 702P, 702R, and 702S were pressed to varying calipers on
a flat press. The caliper of the original boards as well as the pressed paperboards
were measured along with their corresponding temperature drops. Those results are
set forth in Table 2.
Table 2
Experimental
Board 0702H
Sample |
Pressure
kg/cm2 |
Board
Caliper
(mm) |
Hot Water
ΔT°C |
0702P |
0 |
1.21 |
14 |
0702P |
57 |
0.98 |
13 |
0702P |
85 |
0.92 |
13 |
0702P |
114 |
0.81 |
12 |
0702P |
171 |
0.73 |
12 |
0702R |
0 |
1.17 |
13 |
0702R |
57 |
0.77 |
11 |
0702R |
85 |
0.70 |
10 |
0702R |
114 |
0.67 |
11 |
0702R |
171 |
0.64 |
10 |
07025 |
0 |
1.06 |
14 |
0702S |
85 |
0.80 |
12 |
0702S |
114 |
0.77 |
11 |
0702S |
171 |
0.69 |
10 |
0802D |
0 |
1.22 |
25 |
0802E |
0 |
1.16 |
14 |
0802G |
0 |
0.95 |
11 |
0802H |
0 |
0.73 |
10 |
0802I |
0 |
0.90 |
9 |
0802J |
0 |
0.99 |
11 |
EXAMPLE 3
[0038] Samples of paperboards 802E, 802G, and 802I were tested for hardness and embossability
using the Durometer testing method set forth above. In addition, a standard hot cup
paperboard sheet containing no bulky fiber was also tested. The results of the durometer
testing are set forth in Table 3 below.
Table 3
|
Durometer ID |
Board ID |
% HBA |
Type A: PTC
Model 306L |
Type D: Shore
#62126 |
802E |
60% |
81 |
34 |
802G |
50% |
88 |
40 |
802I |
40% |
90 |
44 |
Standard Paperboard |
0% |
96 |
60 |
[0039] The reduced hardness of the paperboard made in accordance with the present invention
clearly indicates that the paperboard is more easily embossable than standard paperboard
with no bulky fiber.
EXAMPLE 4
[0040] Three samples of the paperboards 802E, 802G, and 802I were subjected to pressure
in a press, and thereafter, the caliper was measured and the percent caliper change
calculated. Each of the boards was compared with a standard hot cup paperboard containing
no bulky fiber. The results are shown in Table 4.
Table 4
kg/cm2 |
0 |
90 |
226 |
316 |
|
Board ID |
caliper, mm |
% HBA |
802E |
1.10 |
0.82 |
0.58 |
0.54 |
60% |
802G |
1.07 |
0.81 |
0.57 |
0.52 |
50% |
8021 |
0.91 |
0.77 |
0.64 |
0.61 |
40% |
Standard Board |
0.45 |
0.45 |
0.44 |
0.40 |
0% |
Board ID |
caliper change |
% HBA |
802E |
0% |
25% |
48% |
51% |
60% |
802G |
0% |
25% |
47% |
51% |
50% |
802I |
0% |
16% |
29% |
33% |
40% |
Standard Board |
0% |
0% |
3% |
11% |
0% |
[0041] The compressibility, and thus embossability, of paperboard made in accordance with
the present invention is clearly superior to that of standard paperboard.