U.S. patent application number 13/067966 was filed with the patent office on 2011-11-10 for food packaging film.
This patent application is currently assigned to SHIKOKU KAKOH CO., LTD.. Invention is credited to Ryo Matsuura, Masanori Mitani, Kazuhito Takebayashi.
Application Number | 20110271644 13/067966 |
Document ID | / |
Family ID | 40590592 |
Filed Date | 2011-11-10 |
United States Patent
Application |
20110271644 |
Kind Code |
A1 |
Mitani; Masanori ; et
al. |
November 10, 2011 |
Food packaging film
Abstract
In the present invention, there is provided a food packaging
film which is excellent in workability, processability,
productivity, gas barrier properties, low-temperature heat sealing
properties, safety and mechanical strengths, which can be used as
an alternative film to generally used cellophane/wax films, and can
be suitably used as a packaging film for melting cheese. The food
packaging film according to the present invention comprises at
least five layers of a heat seal layer/an adhesive layer/a gas
barrier layer/an adhesive layer/a heat seal layer, which heat seal
layer comprises an olefin-based resin and melts at not lower than
60.degree. C. and lower than 90.degree. C.
Inventors: |
Mitani; Masanori;
(Kagawa-ken, JP) ; Matsuura; Ryo; (Kagawa-ken,
JP) ; Takebayashi; Kazuhito; (Kagawa-ken,
JP) |
Assignee: |
SHIKOKU KAKOH CO., LTD.
Higashikagawa-shi
JP
|
Family ID: |
40590592 |
Appl. No.: |
13/067966 |
Filed: |
July 12, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12740151 |
Jul 29, 2010 |
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PCT/JP2007/001179 |
Oct 29, 2007 |
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13067966 |
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Current U.S.
Class: |
53/452 |
Current CPC
Class: |
Y10T 428/1341 20150115;
B32B 2307/31 20130101; Y10T 428/2826 20150115; B32B 27/32 20130101;
B65D 85/76 20130101; B32B 2250/05 20130101; B32B 2439/70 20130101;
B32B 2307/4026 20130101; B32B 27/306 20130101; B32B 7/12 20130101;
B32B 2307/306 20130101; B32B 27/365 20130101; B32B 27/34 20130101;
B32B 2307/72 20130101; B32B 2307/7242 20130101; B32B 27/30
20130101; B65D 65/40 20130101; B32B 27/36 20130101 |
Class at
Publication: |
53/452 |
International
Class: |
B65B 43/00 20060101
B65B043/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 18, 2006 |
JP |
2006-283226 |
Claims
1.-10. (canceled)
11. A method of making an air-tight food packaging comprising: (a)
forming a container of the food packaging film comprising at least
five layers of a heat seal layer/an adhesive layer/a gas barrier
layer/an adhesive layer/a heat seal layer, which heat seal layer
comprises an olefin-based resin and melts at not lower than
60.degree. C. and lower than 90.degree. C., in which the heat seal
layer comprises 40 to 100% by weight of polyethylene obtained by
polymerization in the presence of a metallocene catalyst, or the
heat seal layer comprises 40 to 95% by weight of the olefin-based
resin and 5 to 40% by weight of an anti-blocking agent and/or a
lubricant, (b) feeding a melted food having a temperature of not
lower than 60.degree. C. and less than 90.degree. C. into the
container, (c) folding the food packaging film, and (d)
heat-sealing at least part of a surface of one side and the surface
of an opposite side of the folded and overlapped food packaging
film by heat of the fed melted food having a temperature of not
lower than 60.degree. C. and less than 90.degree. C.
12. The method according to claim 11, wherein the heat seal layer
of the food packaging film comprises 40 to 75% by weight of
polyethylene having a density of less than 0.905 g/cm.sup.3 and
obtained by polymerization in the presence of a metallocene
catalyst, and 25 to 60% by weight of low-density polyethylene
having a density of not less than 0.905 g/cm.sup.3.
13. The method according to claim 11, wherein the polyethylene of
the food packaging film is obtained by polymerization in the
presence of a metallocene catalyst has a melting point of 60 to
70.degree. C.
14. The method according to claim 11, wherein the gas barrier layer
of the food packaging film comprises at least one polymer selected
from the group consisting of polyamide, ethylene-vinylalcohol
copolymer, polyethylene terephthalate, polyethylene naphthalate and
polycarbonate.
15. The method according to claim 11, wherein the adhesive layer of
the food packaging film comprises an unsaturated carboxylic
acid-modified polyolefin.
16. The method according to claim 11, wherein the food is melted
cheese.
17. The method according to claim 11, wherein the food packaging
film is colored.
18. A method of packaging a product comprising the steps of: (a)
forming a container for a food product from a food packaging film
comprising at least five layers of a heat seal layer/an adhesive
layer/a gas barrier layer/an adhesive layer/a heat seal layer,
which heat seal layer comprises an olefin-based resin and melts at
not lower than 60.degree. C. and lower than 90.degree. C., in which
the heat seal layer comprises 40 to 100% by weight of polyethylene
obtained by polymerization in the presence of a metallocene
catalyst, or the heat seal layer comprises 40 to 95% by weight of
the olefin-based resin and 5 to 40% by weight of an anti-blocking
agent and/or a lubricant, (b) filing the container formed in step
(a) with a food product having a temperature of not lower than
60.degree. C. and lower than 90.degree. C., thereby causing the
heat seal layer or layers in contact with each other to fusion seal
from the heat of the food product thereby heat sealing the food
product in an air-tight container.
Description
[0001] This application is a divisional of application Ser. No.
12/740,151 filed Jul. 29, 2010, which in turn is the U.S. national
phase of International Application No. PCT/JP2007/001179, filed 29
Oct. 2007, the entire content of which is hereby incorporated by
reference in this application.
TECHNICAL FIELD
[0002] The present invention relates to a food packaging film. More
specifically, the present invention relates to a food packaging
film which is excellent in workability, processability,
productivity, gas barrier properties, low-temperature heat sealing
properties, safety and mechanical strengths, can be used as an
alternative film to generally used cellophane/wax films, and can be
suitably used as a packaging film for melting cheese.
BACKGROUND ART
[0003] When producing processed cheese, a cellophane/wax film which
is a sheet film and produced by coating the wax onto the surface of
cellophane (for example "Paraseal" (registered trademark)
manufactured by NIKKAN INDUSTRIES Co., Ltd.) is usually used, and
first, a block of processed cheese packaged with the cellophane/wax
film (about 1 to 10 kg weight) is produced. Concretely, the
cellophane/wax film is folded to a box-like shape and fixed to the
inside of a stainless cheese forming case, a prescribed amount of
melted cheese at 80 to 90.degree. C. are fed thereinto, the
cellophane/wax film is folded so as to remove air bubbles to
package the cheese, a stainless case cover is set thereon, and the
case is turned over. The inside and outside surfaces of film is
fusion-sealed by the wax which is melted by the heat and weight of
cheese so that the cheese is air-tightly packaged (for example,
refer to Patent Documents 1 and 2). A block of cheese after
refrigeration storage and solidified (block cheese) is taken out
from the stainless case, the block cheese is processed to a desired
shape, and finally, the cellophane/wax film package is removed
therefrom.
[0004] Although the above cellophane/wax film has an advantage that
the sealing can be made by the heat and weight of cheese, there are
problems that (1) the cellophane/wax film is poor in the mechanical
strength so that it is easy to break and foreign matters are got
inside thereof; (2) when the melted wax is leaked out from the
cellophane/wax film and adhered to the shaping case, it is
difficult to take out the block cheese from the shaping case to
deteriorate the workability; (3) although the melted wax is not
harmful, there is a possibility to remain the wax on the surface of
cheese and it is not preferable; and (4) by the relationship
between the used cellophane and wax, blue-color printing is
impossible so that it is difficult to find any scratches (usually,
in food packaging, blue-colored packaging materials are used for
preventing any foreign matters from getting inside.
[0005] As replacements of cellophane/wax film, there has been
proposed a film using a plastic film instead of cellophane so as to
enhance the mechanical strengths (for example, refer to Patent
Document 2). However, since this still uses wax for air-tightening,
the above problems (2) and (3) are still not overcome.
[0006] Further, there has been proposed a process for
air-tightening by using a film having heat seal property and heat
sealing thereof (for example, refer to Patent Document (3) and this
process is used for individually-packaging of sliced cheese.
However, in this process, any extra film portion is necessary to
provide heat sealed portions, and when the heat sealing thereof is
not conducted under deaeration, air is remained between the cheese
and film so that this leads to getting moldy. Also, this operation
under deaeration is a major hurdle in the workability. Further, in
this process, since any extra film portion such as heat sealed
portions is required, there is a possibility that traces and
wrinkles caused by the extra film portion are formed on the surface
of cheese so that loss of cheese content and deterioration of
product value are caused. Therefore, it is difficult to apply this
process to packaging of cheese block.
[0007] Further, there is unknown a packaging film for block cheese
capable of air-tight packaging by fusion-sealing method of envelope
formation shape. [0008] Patent document 1: Japanese Utility Model
Application Laid-Open (KOKAI) No. 5-35786 [0009] Patent document 2:
Japanese Patent Application Laid-Open (KOKAI) No. 6-40485 [0010]
Patent document 3: Japanese Patent Application Laid-Open (KOKAI)
No. 10-750
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0011] The present invention has been made so as to overcome the
above problems, an object of the present invention is to provide a
food packaging film which can be heat-sealed by heat of fed melted
food having a temperature of not lower than 60.degree. C. and lower
than 90.degree. C. such as melted cheese without other heat-sealing
operation, which can be used as an alternative film to generally
used cellophane/wax films, and can be suitably used as a packaging
film for melting cheese, and which is excellent in workability,
processability, productivity, gas barrier properties,
low-temperature heat sealing properties, safety and mechanical
strengths. Especially, an object of the present invention is to
provide a food packaging film capable of solving a problem of poor
mechanical strengths which is a problem of conventional plastic
films for packaging block cheese (a part of broken piece of film is
remained on the surface when removing the film), a problem of
delamination of adhesive layer (by heat or oil of content), and a
problem that in case of using a colored resin added into the heat
seal layer instead of printing so as to preventing from remaining
broken film pieces, the coloring pigment is transferred and
attached to the content by heat of content, as well as capable of
remarkably reducing the cost to be increased by coating step and
printing step.
Means for Solving the Problem
[0012] As a result of present inventors' earnest study to solve the
above problems, it has been found that by a film comprising at
least five layers of a heat seal layer/an adhesive layer/a gas
barrier layer/an adhesive layer/a heat seal layer, which heat seal
layer comprises a specific resin, the above problems can be solved.
Thus, the present invention has been attained on the basis of the
above finding.
[0013] In an aspect of the present invention, there is provided a
food packaging film comprising at least five layers of a heat seal
layer/an adhesive layer/a gas barrier layer/an adhesive layer/a
heat seal layer, which heat seal layer comprises an olefin-based
resin and melts at not lower than 60.degree. C. and lower than
90.degree. C.
Effect of the Invention
[0014] Since the food packaging film according to the present
invention is excellent in workability, processability,
productivity, gas barrier properties, low-temperature heat sealing
properties, safety and mechanical strengths, it can be used as an
alternative film to generally used cellophane/wax films, and can be
suitably used as a packaging film for foods such as melting
cheese.
PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION
[0015] The present invention is described in more detail below. The
food packaging film according to the present invention comprises at
least five layers of a heat seal layer/an adhesive layer/a gas
barrier layer/an adhesive layer/a heat seal layer. By having the
above five layers structure in the film, various folding shapes and
air-tight sealing form can be practiced regardless of which sides
of film are selected because the heat seal layers are provided at
the both surfaces of film. At least other optional layer may be
inserted between the above optional contacting layers,
respectively.
[0016] As the above gas barrier layer, there is no limitation as
long as the layer has gas barrier property. As the resin
constituting the gas barrier layer, there are exemplified
polyamides (PA), ethylene-vinyl alcohol copolymer (EVOH),
polyethylene terephthalate (PET), polyethylene naphthalate (PEN),
polycarbonates (PC), or the like. Of these, polyamides (PA) and
ethylene-vinyl alcohol copolymer (EVOH) are preferred, especially
polyamides (PA, nylons) are preferred. As the polyamide, there are
exemplified nylons 4, 6, 7, 8, 11, 12, 66, 610, 611, 612, 6T, 6/66,
6/12, 6/6T, 6I/6T, MXD6, or the like.
[0017] When fill the melting cheese into the box-shaped film, the
film may become not elastic by softening due to steam generated
from the melting cheese (for example 50.degree. C.) so that the
film folds undesirably and the filling the cheese may be troubled.
Therefore, it is preferred to use a material which is not affected
by the steam generated from the filling food. Further, after
filling the melting cheese and the film is heated thereby at not
lower than 60.degree. C., if the film is sufficiently softened, it
is difficult to form fold lines and the film become a tunnel-like
shape structure. Namely, it is required for the film that during
filling the melting cheese, the film need to be elastic so as not
to fold thereby, when folding and packaging the melting cheese, the
film need to be softened so as to completely fusion-seal it. In
view of the above, of these polyamides, MXD6 is especially
preferred because of heat-resistance rigidity temperature is
suitable to the above range.
[0018] The thickness of gas barrier is usually 2 to 50 .mu.m,
preferably 4 to 30 .mu.m. When the thickness of gas barrier is less
than 2 .mu.m, the film is not elastic, in case of used for cheese
packaging, the film may be folded during feeding melting cheese so
that the melting cheese may not be filled. When the thickness of
gas barrier is more than 50 .mu.m, although the film is elastic,
the heat from the melting cheese may not be transferred when
heat-sealing by folding the film present in upper side of cheese so
that the heat sealing may not be completed. It is preferred that
the gas barrier layer comprises not less than 70% by weight of
resin having a density of not less than 0.9150. In this embodiment,
it can be prevented that low molecular compounds such as a pigment
and/or dye used in coloring the gas barrier layer exude onto the
film.
[0019] In the food packaging film according to the present
invention, the adhesive layer is required so as to adhere the above
gas barrier layer and heat seal layer. The adhesive layer
preferably comprises adhesive resin layer comprising a modified
polyolefin resin. The modified polyolefin resin is produced by
copolymerizing or graft polymerizing .alpha.,.beta.-unsaturated
carboxylic acid or derivatives thereof to a polyolefin resin which
comprises ethylene and/or propylene as the mainly component.
[0020] As the above polyolefin resin, there are exemplified
polyethylene, polypropylene, ethylene-propylene copolymer,
ethylene-butene-1 copolymer, ethylene-vinylacetate copolymer,
ethylene-acrylic acid copolymer, ethylene-ethylacrylic acid
copolymer, ethylene-sodium acrylate copolymer, or the like.
[0021] As the above copolymerized .alpha.,.beta.-unsaturated
carboxylic acid or derivatives thereof, there are exemplified
acrylic acid, methacrylic acid, sodium acrylate, zinc acrylate,
vinylacetate, glycidylmethacrylate, or the like. These are
contained in the molecular chain in a range of not more than 40 mol
%. As examples of copolymerized modified polyolefin resin,
ethylene-vinylacetate copolymer, ethylene-acrylic acid copolymer,
ethylene-ethylacrylic acid copolymer, ethylene-sodium acrylate
copolymer,
[0022] As the above grafted .alpha.,.beta.-unsaturated carboxylic
acid or derivatives thereof, there are exemplified acrylic acid,
methacrylic acid, ethacrylic acid, maleic acid, fumaric acid,
anhydrides thereof and esters thereof. Of these modifying
compounds, maleic anhydride is especially preferred. Further, the
graft percentage is selected from a range of 0.01 to 25% by weight,
preferably 0.05 to 1.5% by weight.
[0023] The graft polymerization is conducted by an ordinary method.
Usually, it is conducted by melt-mixing a polyolefin resin and
.alpha.,.beta.-unsaturated carboxylic acid or derivatives thereof
at a resin temperature of 150 to 300.degree. C. In the graft
polymerization, in order to conduct the reaction effectively, an
organic peroxide such as
.alpha.,.alpha.'-bis-t-butylperoxy-p-diisopropylbenzene is blended
thereinto at an amount of 0.001 to 0.05% by weight.
[0024] The thickness of adhesive layer is usually not less than 2
.mu.m, preferably 3 to 20 .mu.m. When the thickness of adhesive
layer is less than 2 .mu.m, the adhesive property between the gas
barrier layer and adhesive layer is poor so that there is a
possibility that the heat seal layer is released from the gas
barrier layer when the heat seal layer is fused by the heat of
melted cheese. When the adhesive layer is too thick, the production
cost is increased while the adhesive property is no longer improved
more. Further, it is preferred that 70% by weight or more of the
resin constituting the adhesive layer comprises a resin having a
density of not less than 0.9150 g/cm.sup.3. In this embodiment, it
can be prevented that low molecular compounds such as a pigment
and/or dye used in coloring the gas barrier layer exude onto the
film surface through the adhesive layer.
[0025] The heat seal layer comprises an olefin-based resin whose
constituting material is not limited as long as it can be fused at
not lower than 60.degree. C. and lower than 90.degree. C.,
preferably 60 to 80.degree. C., more preferably 60 to 70.degree. C.
and can be used for food packaging. As the above material, there
are exemplified low density polyethylene (hereinafter may be
abbreviated as "LDPE"), polypropylene (PP) and polyethylene
obtained by polymerization in the presence of a metallocene
catalyst (hereinafter may be abbreviated as "M-LLDPE"). Further, in
case where a material having a melting point higher than the above
defined range as it is, the melting point may be adjusted to the
above defined range by blending the other resin thereinto to
depress the melting point.
[0026] The heat seal layer is fusion-sealed by the heat of food and
acts to air-tightly package the food. In addition, in case where
any layer other than the heat seal layer is colored, the heat seal
layer acts to prevent from migrating the coloring agent to the food
surface by the heat of food. Namely, by the presence of heat seal
layer, it is possible to use a colored film as the gas barrier
layer so that the printing step on the film surface so as to find
any film breaking is not required and then, it is possible to
reduce the post-processing and cost significantly.
[0027] In the above materials, M-LLDPE is preferred because it is
less sticky due to less content of low molecular weight components
and smell-less. It is more preferred that the heat seal layer
comprises 40 to 95% by weight of M-LLDPE. M-LLDPE is a linear
low-density polyethylene resin, namely copolymer of ethylene with
.alpha.-olefin having carbon number of 3 to 13 (ethylene content:
86 to 99.5 mol %), which M-LLDPE is obtained by gas-phase process,
liquid-phase process or solution process in the presence of
metallocene catalyst (single-site catalyst). As concrete examples
of .alpha.-olefin, there are mentioned propylene, butene-1,
hexene-1,4-methylpentene-1, octene-1, decene-1 and dodecene-1. The
melt index (MI) of M-LLDPE is usually 0.1 to 20 g/10 min
(230.degree. C.). M-LLDPE has a ratio (Mw/Mn) of weight average
molecular weigh (Mw) to number average molecular weight (Mn) is
usually 1.5 to 4.0, preferably 2 to 3.5 and a polymer having a
sharp molecular weight distribution and sharp composition
distribution is preferred.
[0028] The melting point of M-LLDPE is usually 60 to 70.degree. C.,
preferably 60 to 65.degree. C. When the melting point of M-LLDPE is
lower than 60.degree. C., there is a possibility that the film is
fusion-sealed during storage thereof in summer. When the melting
point of M-LLDPE is higher than 70.degree. C., it may be difficult
to fusion-seal thereof at 70 to 90.degree. C. As described above,
since M-LLDPE is a homogeneous polymer having the sharp molecular
weight distribution and sharp composition distribution and has the
less content of low molecular weight components, M-LLDPE has such a
property of rapid fusion-sealing at the fusion-sealing temperature
of the film according to the present invention.
[0029] The density of M-LLDPE is usually not less than 0.805
g/cm.sup.3 and less than 0.905 g/cm.sup.3, preferably 0.805 to
0.880 g/cm.sup.3. When the density of M-LLDPE is not less than
0.905 g/cm.sup.3, it may be difficult to fusion-seal at the
temperature of 70 to 90.degree. C. Although the density of M-LLDPE
of less than 0.805 g/cm.sup.3 is possible, such product may be
difficult to availability.
[0030] The melt flow rate (MFR) of M-LLDPE is usually 0.5 to 15.0
g/10 min, preferably 0.8 to 5.0 g/10 min. When the MFR is less than
0.5 g/10 min, the extruder tends to be overloaded and the resin
tends to be heated so that fish eye and gelation tend to occur.
When the MFR is more than 15.0 g/10 min, it may be difficult to
feed the resin into a mold uniformly so that such a problem that
the resin is not partially extruded may arise. As the commercial
product of M-LDDPE, there is exemplified "Carnel" (trade name)
manufactured by Japan Polyethylene Corporation.
[0031] As described above, LDPE and PP can be used for the heat
seal layer. In case of using LDPE and PP having a melting point of
90.degree. C. or higher, the melting point can be adjusted within
the above defined range by blending the other resin or blending the
same kind resin having lower melting point (for example, M-LLDPE)
so as to depress the melting point. Especially, it is preferred
that the heat seal layer comprises 40 to 75% by weight of M-LLDPE
having a density of less than 0.905 g/cm.sup.3 and 25 to 60% by
weight of LDPE having a density of not less than 0.905 g/cm.sup.3,
preferably not less than 0.915 g/cm.sup.3.
[0032] In the above embodiment (1), as the low-density polyethylene
having the density of not less than 0.905 g/cm.sup.3, there are
exemplified low density polyethylene (hereinafter may be
abbreviated as "LDPE") and/or linear low-density polyethylene
(hereinafter may be abbreviated as "LLDPE"). LLDPE is a copolymer
which comprises ethylene as the mainly component and
.alpha.-olefin, which has a density of 0.905 to 0.945 g/cm.sup.3,
and which is produced by various polymerization processes such as
gas-phase process, solution process and suspension polymerization
process using various catalysts such as Ziegler catalyst,
chromium-based catalyst and metallocene catalyst under low/medium
pressure or high pressure. As the above .alpha.-olefin, there are
exemplified propylene, butene-1, hexene-1,
octene-1,4-methylpentene-1, 4-methylhexene-1,4,4-dimethylpentene-1,
nonene-1, decene-1, undecene-1 and dodecene-1.
[0033] The melt index rate of the above LDPE and LLDPE according to
JIS K721 at 190.degree. C. under load of 2.16 kgf is usually 0.05
to 50 g/10 min, preferably 0.1 to 20 g/10 min.
[0034] Incidentally, as the concrete examples of the above, LLDPE
(commercial products), Unipole (by Union Carbide, Corporation),
Dowlex (by Dow Chemical Company), Screar (by DuPont Canada), Marlex
(by Philips), Neozex and Ultzex (by Mitsui Chemicals, Inc.),
Nisseki Linirex (by Nippon Oil Corporation) and Stamirex (by DSM)
are mentioned.
[0035] Further, by adding an anti-blocking agent and lubricant into
the resins such as M-LLDPE, LDPE and PP, the film producibility can
be enhanced while maintaining the melting point thereof within the
defined range. The amount of anti-blocking agent and lubricant
added is usually 5 to 40% by weight, preferably 10 to 30% by
weight. When the adding amount of anti-blocking agent and lubricant
is more than 40% by weight, the strength of film may be poor, it
may be difficult to fusion-seal and the anti-blocking agent and
lubricant tend to drop on the cheese surface from the film so that
it is not preferable. When the adding amount of anti-blocking agent
and lubricant is less than 5% by weight, blocking of film tends to
occur.
[0036] The anti-blocking agent and lubricant are not limited as
long as having high safety in order to use for a food packaging
film, and known organic fine particles and/or inorganic fine
particles can be used. As the anti-blocking agent comprising
organic fine particles, there are exemplified fine particles
comprising homopolymer or copolymer of polystyrene, polyethylene,
polyamides, polyesters, polyacrylates, polymethacrylates, epoxy
resins, polyvinyl acetate and polyvinyl chloride, which may have
any crosslinking agent. On the other hand, as the anti-blocking
agent comprising inorganic fine particles, there are exemplified
talc, kaolin, silica, calcium carbonate and glass powder. The
average particle size of the above anti-blocking agent is usually 1
to 10 .mu.m. Further, the inorganic fine particles may be used in a
composition form where they are previously blended to the resin
(master batch).
[0037] The thickness of heat seal layer is usually 5 to 50 .mu.m,
preferably 5 to 30 .mu.m. When the thickness of heat seal layer is
less than 5 .mu.m, there may be a possibility of insufficient heat
sealing strength at the heat sealing portion. There is no problem
when the thickness of heat seal layer is more than 50 .mu.m,
however, the thickness is too thick beyond necessity, it is a waste
of material and costly.
[0038] The thickness of food packaging film according to the
present invention is usually 40 to 120 .mu.m, preferably 60 to 100
.mu.m. When the film thickness is less than 40 .mu.m, the film is
not elastic, in case of used for cheese packaging, the film may be
folded during feeding melting cheese so that the melting cheese may
not be filled. When the film thickness is more than 120 .mu.m,
although the film is elastic, the heat from the melting cheese may
not be transferred when heat-sealing by folding the film present in
upper side of cheese so that the heat sealing may not be
completed.
[0039] Next, the process for producing the feed packaging film
according to the present invention is explained. The feed packaging
film according to the present invention is preferably produced by
coextrusion inflation method to obtain a cylindrical shape laminate
film. As the inflation method, there may be employed a known method
(water-cooling method) comprising drawing a film formed by
extrusion from a cyclic dye to downward of dye, cooling thereof by
blowing cooling air to the film, thereafter further quenching
thereof with water and winding thereof. Usually, such method
comprises using an equipment comprising an airing equipment to blow
cooling air to the film placed at downward of cyclic dye, and guide
plates and a winding roll placed at downward of the airing
equipment sequentially; coextruding plural kinds of material resins
from the cyclic dye so as not to stretch the film substantially;
cooling the film by passing through the airing equipment; quenching
the film with water; feeding the quenched cylindrical shape film to
the winding roll through the guide plates to fold thereof; and
winding thereof as a laminate film.
[0040] The food packaging film according to the present invention
can air-tightly heat seal by the heat of fed melting food. Namely,
a food melted at 80 to 90.degree. C. is fed into the food packaging
film according to the present invention whose shape is adjusted to
box-like shape and the film is closed so that the film surfaces are
fusion-sealed by the heat of food and the film packages the food
air-tightly. The food packaging film according to the present
invention can be preferably used for packaging a food which is
melting state (liquid) at 80 to 90.degree. C. when packaging and is
solid at ordinary temperature such as another of cheese, chocolate,
pudding, jam, marmalade, jelly, and agar-agar. Further, the food
packaging film can be used for air-tightly packaging a processed
food. For example, a processes food heated at 80 to 90.degree. C.
is fed into the food packaging film according to the present
invention whose shape is adjusted to box-like shape and the film is
closed so that the film surfaces are fusion-sealed by the heat of
food and the film packages the food air-tightly. As the processed
foods, there are exemplified in addition to liquid foods including
solids such as stew, curries, and miso soups and prepared meats
such as steak, hamburger steak, sausages, and hams, Chinese daily
dishes, the Japanese food daily dishes, the European food daily
dishes, rice, rice gruels, and rice cakes, etc. Further, the film
according to the present invention is preferably used for air-tight
packaging of beverage goods as long as processed by the heating
sterilization and the extraction at the temperature of 80 to
90.degree. C., such as water, natural water, ion water, health
drink, various healthy drinks, various soups, various juices,
milks, green tea, teas, coffees, cocoas, and other various soft
drinks. Therefore, these embodiments are also within the scope of
the present invention.
EXAMPLES
[0041] The present invention is described in more detail below by
way of the examples. However, the examples are only illustrative
and therefore the present invention is not limited to these
examples. In the following Examples and Comparative Examples, all
"parts" and "percents (%)" are by weight unless otherwise noted.
The materials used in each Example and Comparative Example are
shown in the following.
Resin for the Gas Barrier Layer:
[0042] (A-1) 6 Nylon ("NOVAMID 1010" manufactured by Mitsubishi
Engineering-Plastics Corporation).
Resin for the Adhesive Layer:
[0043] (B-1) Adhesive polyethylene ("Modic-AP M552" manufactured by
Mitsubishi Chemical Corporation).
Resin for the Heat Seal Layer:
[0044] (C-1) polyethylene (M-LLDPE, density: 0.880 g/m.sup.3,
Mw/Mn=2.3, "Carnel" manufactured by Japan Polyethylene
Corporation).
[0045] (C-2) Crystalline olefin-ethylene/butylene-crystalline
olefin block copolymer (CBEC, density: 0.880 g/m.sup.3, "DYNARON
6200P" manufactured by JSR corporation).
[0046] (C-3) Ethylene-.alpha.-olefin copolymer (density: 0.870
g/m.sup.3, "TAFMER P0480" manufactured by Mitsui Chemicals,
Inc.).
[0047] (C-4) Low-density polyethylene (LDPE, density: 0.918
g/m.sup.3, "NOVATEC LD LF240" manufactured by Japan Polyethylene
Corporation).
[0048] (C-5) Polypropylene (density: 0.900 g/m.sup.3, "NOVATEC PP
FG3D" manufactured by Japan Polypropylene Corporation).
[0049] (C-6) Anti-blocking agent (average particle size: 3 .mu.m,
8% zeolite masterbatch "LX-ABI" manufactured by Japan Polyethylene
Corporation).
[0050] (C-7) Anti-blocking agent (2% erucamide masterbatch "NOVATEC
PE-AF" manufactured by Japan Polyethylene Corporation).
[0051] The evaluations of food packaging film were conducted by the
following methods.
(1) Evaluation of Heat Sealing:
[0052] After heat sealing of five layers laminated film obtained in
each Example and Comparative Example at the temperature of 55 to
75.degree. C., under pressure of 1.45 kg/cm.sup.3 for 30 seconds,
the seal strength thereof was measured according to the method of
JIS A 1707. When the seal strength is not less than 3N/15 mm width,
the heat sealing is completed.
Examples 1 to 12
[0053] The above (A-1) as the resin for gas barrier layer, the
above (B-1) as resin for the adhesive layer and the resins shown in
Tables 1 and 2 as resin (anti-blocking agent) as the heat sealing
layer were used respectively, and using a five kinds five layers
inflation molding machine (die diameter: 250 mm.phi.), die lip: 2
mm and die temperature: 240.degree. C.), a five layer tubular
laminate film comprising heat seal layer (outside)/adhesive
layer/gas barrier layer/adhesive layer/heat seal layer (inside) was
produced. As the thicknesses of heat seal layers, the thickness of
outside seal layer was 20 .mu.m and the thickness of inside seal
layer was 28 .mu.m, the thickness of each adhesive layer was 4 mm,
the thickness of gas barrier layer was 24 .mu.m, the total
thickness of film was 80 .mu.m and folding diameter was 350 mm. To
the obtained food packaging film, heat sealing properties at
various temperatures were evaluated. The results are shown in
Tables 1 and 2.
TABLE-US-00001 TABLE 1 Composition of heat seal Examples layer (%
by weight) 1 2 3 4 5 6 M-LLDPE C-1 95 75 70 65 60 40 CBEC C-2 -- --
-- -- -- -- Ethylene-.alpha.-olefin C-3 -- -- -- -- -- -- copolymer
LDPE C-4 5 25 30 35 40 60 PP C-5 -- -- -- -- -- -- Anti-blocking
agent C-6 10 10 10 10 10 10 C-7 2 2 2 2 2 2 Heat sealing 55.degree.
C. X X X X X X evaluation at 60.degree. C. .largecircle.
.largecircle. X X X X respective heat seal 65.degree. C.
.largecircle. .largecircle. .largecircle. .largecircle. X X
temperatures 70.degree. C. .largecircle. .largecircle.
.largecircle. .largecircle. X X 75.degree. C. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. X
80.degree. C. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.: Heat
sealed X: Non-heat sealed
TABLE-US-00002 TABLE 2 Composition of heat seal Examples layer (%
by weight) 7 8 9 10 11 12 M-LLDPE C-1 85 80 85 80 80 80 CBEC C-2 --
-- 15 20 -- -- Ethylene-.alpha.-olefin C-3 -- -- -- -- 15 20
copolymer LDPE C-4 -- -- -- -- -- -- PP C-5 15 20 -- -- -- --
Anti-blocking agent C-6 10 10 10 10 10 10 C-7 2 2 2 2 2 2 Heat
sealing 55.degree. C. X X X X X X evaluation at 60.degree. C. X X X
X X X respective heat seal 65.degree. C. .largecircle. X
.largecircle. X X X temperatures 70.degree. C. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. 75.degree. C. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. 80.degree.
C. .largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle.: Heat sealed X: Non-heat
sealed
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