U.S. patent application number 10/467116 was filed with the patent office on 2004-04-22 for biodegradable bags for packing foods available in high speed production.
Invention is credited to Iwasaki, Yoshio, Kobayashi, Yukio, Mori, Hirotsugu.
Application Number | 20040076778 10/467116 |
Document ID | / |
Family ID | 18893264 |
Filed Date | 2004-04-22 |
United States Patent
Application |
20040076778 |
Kind Code |
A1 |
Mori, Hirotsugu ; et
al. |
April 22, 2004 |
Biodegradable bags for packing foods available in high speed
production
Abstract
It is an object of the present invention to provide a
biodegradable bag for packing a food capable of storing a food such
as a snack food which is required to have an oxygen barrier
property and a water vapor barrier property, which can be produced
at a high speed by a bag making and packaging machine, which can be
degraded by naturally occurring microorganisms in soil or water
finally to a non-hazardous degradation product, which can be
biorecycled, and which is not accumulated in nature. The present
invention is directed to a biodegradable bag for packing a food,
which comprises a laminated film obtainable by laminating in the
following order; a sealant layer comprising a biodegradable
polymer; a barrier layer having an oxygen barrier property and a
water vapor barrier property; and a barrier layer-supporting
substrate layer comprising a biodegradable polymer, said laminated
film being heat-sealed in order for the sealant layer to be
inside.
Inventors: |
Mori, Hirotsugu; (Kyoto,
JP) ; Iwasaki, Yoshio; (Shiga, JP) ;
Kobayashi, Yukio; (Tokyo, JP) |
Correspondence
Address: |
HOGAN & HARTSON L.L.P.
500 S. GRAND AVENUE
SUITE 1900
LOS ANGELES
CA
90071-2611
US
|
Family ID: |
18893264 |
Appl. No.: |
10/467116 |
Filed: |
December 8, 2003 |
PCT Filed: |
February 4, 2002 |
PCT NO: |
PCT/JP02/00858 |
Current U.S.
Class: |
428/35.2 |
Current CPC
Class: |
B65D 75/46 20130101;
Y02W 30/801 20150501; Y10T 428/1334 20150115; Y02W 30/80 20150501;
B32B 27/08 20130101; Y02W 90/13 20150501; Y02A 40/961 20180101;
Y10T 428/12431 20150115; Y02A 40/90 20180101; Y10T 428/1307
20150115; B65D 65/466 20130101; Y02W 90/10 20150501; B32B 27/00
20130101 |
Class at
Publication: |
428/035.2 |
International
Class: |
B65D 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 5, 2001 |
JP |
200128829 |
Claims
1. A biodegradable bag for packing a food, which comprises a
laminated film obtainable by laminating in the following order; a
sealant layer comprising a biodegradable polymer; a barrier layer
having an oxygen barrier property and a water vapor barrier
property; and a barrier layer-supporting substrate layer comprising
a biodegradable polymer, said laminated films being heat-sealed in
order for the sealant layer to be inside.
2. The biodegradable bag for packing a food according to claim 1,
wherein the sealant layer is a non-oriented film layer comprising a
biodegradable polymer with the melting point of 120.degree. C. or
below.
3. The biodegradable bag for packing a food according to claim 1 or
2, wherein the sealant layer is formed by laminating a
biodegradable polymer via an extrusion molding onto a barrier layer
supported by a barrier layer-supporting substrate layer.
4. The biodegradable bag for packing a food according to any of
claims 1 to 3, wherein the barrier layer is formed by means of a
vapor deposition of a ceramic and/or a metal.
5. The biodegradable bag for packing a food according to claim 4,
wherein the barrier layer is a single component vapor deposition
layer comprising at least one selected from the group consisting of
SiO.sub.x, Al.sub.2O.sub.3 and Al, or a dual component vapor
deposition layer comprising at least one combination of two
components selected from the group consisting of
SiO.sub.x/Al.sub.2O.sub.3, SiO.sub.x/ZnO, SiO.sub.x/CaO,
SiO.sub.x/B.sub.2O.sub.3 and CaO/Ca(OH).sub.2 and has a thickness
of 1500 angstrom or less.
6. The biodegradable bag for packing a food according to any of
claims 1 to 5, wherein the barrier layer-supporting substrate layer
comprises a biaxial oriented film of a biodegradable polymer.
7. The biodegradable bag for packing a food according to claim 6,
wherein the barrier layer-supporting substrate layer comprises a
biaxial oriented film of a biodegradable polymer with the melting
point of 150.degree. C. or higher.
8. The biodegradable bag for packing a food according to any of
claims 1 to 8, wherein the laminated film further comprises a paper
substrate layer made of a paper outside the barrier
layer-supporting substrate layer.
9. The biodegradable bag for packing a food according to claim 8,
wherein the barrier layer-supporting substrate layer is formed by
laminating a biodegradable polymer via an extrusion molding onto a
paper substrate layer.
10. The biodegradable bag for packing a food according to claim 8,
which is obtainable by extruding a biodegradable polymer onto the
paper substrate layer to effect a lamination whereby forming the
barrier layer-supporting substrate layer, followed by effecting a
vapor deposition of a ceramic and/or a metal onto the barrier
layer-supporting substrate layer to form the barrier layer,
followed by laminating the sealant layer via a biodegradable
adhesive onto the barrier layer.
11. The biodegradable bag for packing a food according to claim 8,
which is obtainable by laminating a biaxial oriented film of a
biodegradable polymer via a biodegradable adhesive onto the paper
substrate layer whereby forming the barrier layer-supporting
substrate layer, followed by effecting a vapor deposition of a
ceramic and/or a metal onto the barrier layer-supporting substrate
layer to form the barrier layer, followed by laminating the sealant
layer via a biodegradable adhesive onto the barrier layer.
12. The biodegradable bag for packing a food according to any of
claims 8 to 11, wherein the thickness of the sealant layer is 5 to
50 mm, the thickness of the barrier layer is 300 to 1500 angstrom,
the thickness of the barrier layer-supporting substrate layer is 5
to 20 mm and the thickness of the paper substrate layer converted
into a basis weight is 15 to 100 g/m.sup.2.
13. The biodegradable bag for packing a food according to any of
claims 8 to 12, which further comprises a printed layer comprising
a biodegradable ink outside the paper substrate layer.
14. The biodegradable bag for packing a food according to any of
claims 1 to 13, wherein the laminated film further comprises a
print-protecting layer comprising a biodegradable polymer between
the sealant layer and the barrier layer.
15. The biodegradable bag for packing a food according to claim 14,
which is obtainable by effecting a vapor deposition of a ceramic
onto the barrier layer-supporting substrate layer comprising a
biaxial oriented film of a biodegradable polymer to form the
barrier layer, followed by molding the print-protecting layer onto
the barrier layer, followed by forming a printed layer onto the
print-protecting layer, followed by laminating the sealant layer
via a biodegradable adhesive onto the printed layer.
16. The biodegradable bag for packing a food according to claim 14
or 15, wherein the thickness of the sealant layer is 5 to 50 mm,
the thickness of the print-protecting layer is 0.02 to 0.2 mm, the
thickness of the barrier layer is 300 to 1500 angstrom, and the
thickness of the barrier layer-supporting substrate layer is 5 to
20 mm.
17. The biodegradable bag for packing a food according to any of
claims 1 to 16, which further comprises an adhesive layer
comprising a biodegradable adhesive between respective layers.
18. The biodegradable bag for packing a food according to any of
claims 1 to 17, which is used for packaging a snack food.
19. A method for packing a food, which comprises a back seal step.
in which a laminated film obtainable by laminating in the following
order; a sealant layer comprising a biodegradable polymer; a
barrier layer having an oxygen barrier property and a water vapor
barrier property; and a barrier layer-supporting substrate layer
comprising a biodegradable polymer is made tubular with the sealant
layer being inside to bring the both back sides into contact and
heat-sealed with each other, a food introducing step in which a
food is introduced to the inside of the tube of the laminated film,
and an end seal step in which the both ends of the tube of the
laminated film containing the food are heat-sealed.
Description
TECHNICAL FIELD
[0001] The present invention relates to a biodegradable bag for
packing a food, for example for a snack food such as a potato chips
especially which is required to have an oxygen barrier property and
a water vapor barrier property.
BACKGROUND ART
[0002] A conventional package material for a snack food frequently
has a 5-layer structure consisting of polypropylene resin
layer/polyethylene resin layer/metal aluminum vapor
deposition--biaxial oriented PET (polyethylene terephthalate)
layer/polyethylene layer/biaxial oriented polypropylene resin layer
in this order from the inside.
[0003] A polypropylene resin (PP) layer as the innermost layer
serves as a sealant layer. For such an innermost layer, a
polypropylene resin is selected since a low temperature heat seal
ability and a hot tack property immediately after the heat sealing.
The hot tack property is required because of a slightly pressurized
packaging process conducted while inflating a bag with air or
nitrogen for the purpose of preventing any damage on a snack food
as a content in the bag. The thickness of the polypropylene resin
layer as this innermost layer is frequently about 20 to 50
.mu.m.
[0004] A metal aluminum vapor deposition layer serves to shield an
external light and to prevent the permeation of oxygen and water
vapor. It has a thickness of 300 to 1500 angstrom and is formed
usually by a vapor deposition of a metal aluminum onto a biaxial
oriented PET film or a polypropylene resin.
[0005] A biaxial oriented PET layer consists of a biaxial oriented
polyethylene terephthalate (PET) film, which is a material onto
which a metal aluminum can be deposited most stably and frequently
has a thickness of about 12 .mu.m.
[0006] A polyethylene resin (PE) layer serves as an adhesive for
binding a biaxial oriented PET film with an outermost biaxial
oriented polypropylene (OPP) film or for binding an innermost
non-oriented polypropylene resin with a biaxial oriented PET film,
and has a thickness of about 15 .mu.m. The polyethylene resin layer
sometimes employs an ethylene-(meth)acrylic acid copolymer, and the
polyethylene resin layer is replaced sometimes with an
urethane-based adhesive or an organic solvent-free
monomer-containing adhesive.
[0007] A biaxial oriented polypropylene film as an outermost layer
is brought into a direct contact with a heat sealing device (seal
bar) at an elevated temperature, and serves to transmit the heat to
the innermost polypropylene resin layer. It has a thickness of 15
to 25 .mu.m.
[0008] A package material for a snack food having 4 to 5 layers as
described above has a total thickness of 40 to 117 .mu.m.
[0009] A method for fabricating a packaging material having the
above mentioned layer construction may frequently, when taking a
cost into consideration, involve a fabrication procedure in which a
PET film is subjected to a vapor deposition with a metal aluminum,
and then a PE (polyethylene) is extruded between the PET film vapor
deposition side and the non-oriented polypropylene film to effect a
lamination while extruding a PE between an OPP film and the PET
film (the opposite side of the vapor deposition side) whereby
effecting a lamination.
[0010] However, such a package structure poses an extreme
difficulty in recycling the materials because of the combination of
a diversity of materials such as polypropylene resins, PET resins,
polyethylene resins and the like. In addition, a polypropylene
resin forming an innermost layer adsorbs the flavors of a snack
food, resulting in a deteriorated taste. A further disadvantage is
that a total thickness as thick as about 40 to 120 .mu.m makes it
difficult to transmit a heat.
[0011] Recently, a demand of increasing the producibility leads to
a demand of a higher speed of a bag making and packaging machine.
In order to accomplish a high speed production, a heat seal should
be accomplished within a shorter seal time, resulting naturally in
a demand of a heat seal process at a high temperature within a
short time for giving a certain calorie. Thus, a high seal
temperature is required to give, within a shorter seal time, a
calorie given over conventional seal time, but conventional bag
material layer construction can not be sealed at a high temperature
because of a small difference in the melting point between the
outermost and the innermost layers.
[0012] On the other hand, such a plastic packaging material, which
has been employed for a long time, now poses an waste disposal
problem after being used. Generally, a plastic waste is collected
as a refuse, which is then incinerated or dumped in the ground.
[0013] When incinerated, a conventional plastic packaging material
consisting mainly of polyolefins gives a burning calorie as high as
4.2.times.10.sup.7 J/kg or more, which leads to a high possibility
of damaging a furnace, sometimes in combination with a possibility
of emitting dioxins depending on the incineration temperature when
containing chlorinated compounds, resulting in a controversy about
the incineration itself.
[0014] When dumped in the ground, a polyolefin such as a
polypropylene or polyethylene remains in the nature
semi-permanently, resulting in a cause of an environmental
pollution.
SUMMARY OF THE INVENTION
[0015] Under the circumstance described above, an object of the
invention is to provide a biodegradable bag for packing a food
capable of storing a food such as a snack food which is required to
have an oxygen barrier property and a water vapor barrier property,
which can be produced at a high speed by a bag making and packaging
machine, which can be degraded by naturally occurring
microorganisms in soil or water finally to a non-hazardous
degradation product, which can be biorecycled, and which is not
accumulated in nature.
[0016] Thus, the present invention is a biodegradable bag for
packing a food,. which comprises a laminated film obtainable by
laminating in the following order; a sealant layer comprising a
biodegradable polymer; a barrier layer having an oxygen barrier
property and a water vapor barrier property; and a barrier
layer-supporting substrate layer comprising a biodegradable
polymer, said laminated films being heat-sealed in order for the
sealant layer to be inside.
[0017] The sealant layer is preferably a non-oriented film
comprising biodegradable polymer with the melting point of
120.degree. C. or below, and is formed preferably by laminating a
biodegradable polymer via an extrusion molding onto a barrier layer
supported by a barrier layer-supporting substrate layer.
[0018] The barrier layer is formed preferably by means of a vapor
deposition of a ceramic and/or a metal, and is preferably a single
component vapor deposition layer comprising at least one selected
from the group consisting of SiO.sub.x, Al.sub.2O.sub.3 and Al, or
a dual component vapor deposition layer consisting of at least one
combination of two components selected from the group consisting of
SiO.sub.x/Al.sub.2O.sub.3, SiO.sub.x/ZnO, SiO.sub.x/CaO,
SiO.sub.x/B.sub.2O.sub.3 and CaO/Ca(OH).sub.2 and has a thickness
of 1500 angstrom or less.
[0019] The barrier layer-supporting substrate layer is formed
preferably by laminating a biodegradable polymer via an extrusion
molding onto a paper substrate layer, and preferably comprises a
biaxial oriented film of a biodegradable polymer, and more
preferably comprises a biaxial oriented film of a biodegradable
polymer with the melting point of 150.degree. C. or higher.
[0020] The biodegradable bag for packing a food of the present
invention preferably comprises a laminated film comprising a paper
substrate layer made of a paper outside the barrier
layer-supporting substrate layer. Such a biodegradable bag for
packing a food can be obtainable by extruding a biodegradable
polymer onto the paper substrate layer to effect a lamination
whereby forming the barrier layer-supporting substrate layer,
followed by effecting a vapor deposition of a ceramic and/or a
metal onto the barrier layer-supporting substrate layer to form the
barrier layer, followed by laminating the sealant layer via a
biodegradable adhesive onto the barrier layer. It is also possible
to produce such a biodegradable bag for packing a food by
laminating a biaxial oriented film of a biodegradable polymer via a
biodegradable adhesive onto the substrate layer whereby forming the
barrier layer-supporting substrate layer, followed by effecting a
vapor deposition of a ceramic and/or a metal onto the barrier
layer-supporting substrate layer to form the barrier layer,
followed by laminating the sealant layer via a biodegradable
adhesive onto the barrier layer.
[0021] The biodegradable bag for packing a food of the present
invention is preferable when the thickness of the sealant layer is
5 to 50 .mu.m, the thickness of the barrier layer is 300 to 1500
angstrom, the thickness of the barrier layer-supporting substrate
layer is 5 to 20 .mu.m and the thickness of the paper substrate
layer converted into a basis weight is 15 to 100 g/m.sup.2.
[0022] The biodegradable bag for packing a food of the present
invention preferably comprises a printed layer comprising a
biodegradable ink outside the substrate layer.
[0023] The biodegradable bag for packing a food of the present
invention preferably comprises a laminated film further comprising
a print-protecting layer comprising a biodegradable polymer between
the sealant layer and the barrier layer. Such a biodegradable bag
for packing a food can be obtainable by effecting a vapor
deposition of a ceramic onto the barrier layer-supporting substrate
layer comprising a biaxial oriented film of a biodegradable polymer
to form the barrier layer, followed by molding the print-protecting
layer onto the barrier layer, followed by forming a printed layer
onto the print-protecting layer, followed by laminating the sealant
layer via a biodegradable adhesive onto the printed layer. Such a
biodegradable bag for packing a food is preferable when the
thickness of the sealant layer is 5 to 50 .mu.m, the thickness of
the print-protecting layer is 0.02 to 0.2 .mu.m, the thickness of
the barrier layer is 300 to 1500 angstrom, and the thickness of the
barrier layer-supporting substrate layer is 5 to 20 .mu.m.
[0024] The biodegradable bag for packing a food of the present
invention which preferably further comprises an adhesive layer
comprising a biodegradable adhesive between respective layers.
[0025] The biodegradable bag for packing a food of the present
invention which is preferably used for packaging a snack food.
[0026] Also included in the present invention is a method for
packing a food comprising a back seal step in which a laminated
film in the following order; a sealant layer comprising a
biodegradable polymer; a barrier layer having an oxygen barrier
property and a water vapor barrier property ;and a barrier
layer-supporting substrate layer comprising a biodegradable polymer
is made tubular with the sealant layer being inside to bring the
both back sides into contact and heat-sealed with each other, a
food introducing step in which a food is introduced to the inside
of the tube of the laminated film, and an end seal step in which
the both ends of the tube of the laminated film containing the food
are heat-sealed.
BRIEF DESCRIPTION OF DRAWINGS
[0027] FIG. 1 shows the heat seal temperature property of the roll
for a snack food bag in Example 1 (product of the invention) and a
conventional roll film (conventional product).
[0028] FIG. 2 shows the heat seal temperature property of the roll
for a snack food bag in Example 2 (product of the invention).
[0029] FIG. 3 shows the laminate structure of a roll of a
biodegradable bag for packing a food according to the present
invention.
[0030] FIG. 4 shows a schematic view of a fin seal of a pillow
package.
[0031] FIG. 5 shows the heat seal temperature property of the roll
for a snack food bag in Example 6(product of the invention).
[0032] FIG. 6 shows the heat seal temperature property of the roll
for a snack food bag in Example 7(product of the invention) and a
conventional roll film (conventional product).
[0033] FIG. 7 shows the laminate structure of a roll of a
biodegradable bag for packing a food according to the present
invention.
[0034] In Figures, 1 is a sealant layer, 2 is an adhesive layer, 3
is a barrier layer, 4 is a barrier layer-supporting substrate
layer, 5 is a paper substrate layer, 6 is a printed layer, 7 is a
print-protecting layer, 8 is a back seal and 9 is an end seal.
DETAILED DISCLOSURE OF THE INVENTION
[0035] The present invention is detailed below.
[0036] A biodegradable bag for packing a food according to the
present invention which comprises a laminated film obtainable by
laminating in the following order; a sealant layer comprising a
biodegradable polymer; a barrier layer having an oxygen barrier
property and a water vapor barrier property and; a barrier
layer-supporting substrate layer consisting of a biodegradable
polymer.
[0037] The sealant layer comprises a biodegradable polymer.
[0038] The biodegradable polymer preferably has the melting point
of 120.degree. C. or below. The low melting point of 120.degree. C.
or below gives a compatibility with a high speed operation of the
the bag making and packaging machine. A temperature of 65.degree.
C. to 120.degree. C. is more preferable.
[0039] Such a biodegradable polymer may be any of
microorganism-derived polymers, naturally occurring polymers or
chemically synthesized polymers, and those employed preferably are
aliphatic polyester resins obtained by the polycondensation of
aliphatic diols and aliphatic dicarboxylic acids. When using an
aliphatic polyester resin, a polymer having a varying melting point
can be obtained by altering the combination of an aliphatic diol
and an aliphatic dicarboxylic acid employed.
[0040] The aliphatic dicarboxylic acid may for example be oxalic
acid, malonic acid, succinic acid, adipic acid, glutaric acid,
suberic acid, pimelic acid, sebacic acid, dodecane diacid compounds
and the like, while the aliphatic diol may for example be ethylene
glycol, diethylene glycol, triethylene glycol, propylene glycol,
dipropylene glycol, 1,4-butanediol, 1,4-cyclohexane dimethanol and
the like.
[0041] The aliphatic polyester resin is preferably a biodegradable
aliphatic polyester resin having the melting point of about
95.degree. C. obtained by using succinic acid and adipic acid as
dicarboxylic acids and 1,4-butanediol as an aliphatic diol, such as
a polybutylene succinate, polybutylene succinate adipate copolymer
and the like. Any of them are commercially available as a
biodegradable resin BIONOLLE (manufactured by SHOWA HIGHPOLYMER
CO., LTD.), and the production method is disclosed for example in
Japanese Kokai Publication Hei-4-189822 and Japanese Kokai
Publication Hei-5-70575.
[0042] Otherwise, the aliphatic polyester resin is preferably a
polyethylene succinate. This is commercially available as a
biodegradable resin Lunare SE (manufactured by NIPPON SHOKUBAI CO.,
LTD.).
[0043] The sealant layer consists preferably of a non-extended film
of a biodegradable polymer which was formed without any extension
process and is substantially non-oriented. Generally, the extension
of a plastic is conducted by stretching biaxial, i.e.,
longitudinally and widthwise at a temperature lower by 10 to
20.degree. C. than the melting point while undergoing a heat
fixation, and the resultant oriented film is imparted with the
pliability, transparency, oxygen barrier property which are
improved by about 3 times when compared with a non-oriented film,
and such physical characteristics can be maintained up to the
temperature of the heat fixation. Nevertheless, above this
temperature, the orientation imparted in the extension step is
disturbed, resulting in a shrinkage, which leads to a wrinkle at
the heat seal part during the heat seal step, as well as a
difficulty in accomplishing the heat seal step satisfactorily. A
non-oriented film gives no such problems.
[0044] When the sealant layer is a non-oriented film layer
comprising a biodegradable polymer, the sealant layer is formed
preferably by laminating the biodegradable polymer onto a barrier
layer-supporting substrate layer by means of an extrusion molding.
This extrusion molding needs no adhesive.
[0045] The biodegradable polymer employed in the sealant layer
preferably has hot tack and oil resistance, which may be imparted
by incorporating additives to the polymer.
[0046] The laminated films are heat-sealed in order for the sealant
layer to be inside, whereby being formed as a biodegradable bag for
packing a food according to the present invention.
[0047] When an aliphatic polyester resin is employed in the sealant
layer, the adsorption of the flavor of the content food can
advantageously be avoided.
[0048] The thickness of the sealant layer is preferably 5 to 50
.mu.m. A thickness less than 5 .mu.m leads to an uneven thickness
upon molding, resulting in difficulty in ensuring the thickness
sufficient for the seal. In addition, a high pressure upon sealing
causes a fluidity, which affects a sealing performance. On the
other hand, a thickness more than 50 .mu.m gives an increased
overall thickness, which leads to an increased weight, which is
problematic also in view of a container recycling law. Moreover, an
increased overall thickness allows a pin hole to be formed readily
upon sealing at the site of the crossing of the longitudinal and
widthwise seals.
[0049] The barrier layer has an oxygen barrier property and the
water vapor barrier property.
[0050] Such a barrier layer may be obtained for example by means of
a vapor deposition of a ceramic and/or a metal. The barrier layer
when providing a paper substrate layer outside the barrier
layer-supporting substrate layer as described below can be obtained
using a laminated film of a biodegradable polymer extruded on a
paper substrate layer or a biaxial oriented film of a biodegradable
polymer as a barrier layer-supporting substrate layer onto which a
ceramic and/or a metal is vapor-deposited.
[0051] The barrier layer is preferably a single component vapor
deposition layer comprising at least one selected from the group
consisting of SiO.sub.x, Al.sub.2O.sub.3 and Al, or a dual
component vapor deposition layer comprising at least one
combination of two components selected from the group consisting of
SiO.sub.x/Al.sub.2O.sub.3, SiO.sub.x/ZnO, SiO.sub.x/CaO,
SiO.sub.x/B.sub.2O.sub.3 and CaO/Ca (OH).sub.2.
[0052] Among those listed above, a metal aluminum (Al) is
preferably vapor-deposited for the purpose of ensuring a shield
from a light. When a paper substrate layer comprising a paper is
provided, the substrate layer serves to shield almost all light,
but a metal aluminum vapor deposition further ensures the light
shielding.
[0053] When a metal detector is employed preliminarily to identify
a contamination for example with a foreign body, then a single
component vapor deposition layer consisting of SiO.sub.x and
Al.sub.2O.sub.3, or a dual component vapor deposition layer
consisting of at least one combination of two components selected
from the group consisting of SiO.sub.x/Al.sub.2O.sub.3,
SiO.sub.x/ZnO, SiO.sub.x/CaO, SiO.sub.x/B.sub.2O.sub.3 and
CaO/Ca(OH).sub.2 is employed. The SiO.sub.x may for example be
SiO.sub.2, SiO.sub.1.8, SiO.sub.1.6 and the like. By means of a
vapor deposition of such a ceramic, a product which has not
conventionally been able to be subjected to a foreign body
detection due to the metal vapor deposition can be examined using a
metal detector.
[0054] When a ceramic has been vapor-deposited, a light shielding
performance may be inferior to that when a metal aluminum is
vapor-deposited, but a light shielding ability sufficient for
protecting the content from a quality deterioration can be obtained
by solid white printing over the entire surface as a background
upon printing which is effective in shielding an UV light and a
visible light.
[0055] The thickness of the barrier layer is preferably 1500
angstrom or less. A thickness more than 1500 angstrom affect a
biodegradation adversely. More preferably, the thickness is 300 to
1500 angstrom. A thickness less than 300 angstrom poses a
difficulty in accomplishing a uniform vapor deposition.
[0056] The barrier layer-supporting substrate layer comprises a
biodegradable polymer.
[0057] Such a biodegradable polymer is preferably one having a heat
resistance for the thermal hysteresis during a vapor deposition.
Such a biodegradable polymer may for example be on having a certain
heat resistance among aliphatic polyester resins which are
chemically synthesized biodegradable polymers.
[0058] The aliphatic polyester resin may for example be a lactic
acid-based polymer such as a homopolymer of a lactic acid,
copolymer of a lactic acid with other aliphatic hydroxycarboxylic
acid and the like.
[0059] The lactic acid may for example be L-lactic acid and
D-lactic acid, and the aliphatic hydroxycarboxylic acid may for
example be glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric
acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid,
5-hydroxyvaleric acid, 6-hydroxycaproic acid and the like.
[0060] The polylactic acid-based polymer may for example be "LACTY"
which is commercially available from SHIMADZU CORPORATION.
[0061] The barrier layer-supporting substrate layer, when providing
a paper substrate layer outside the barrier layer-supporting
substrate layer as described below, may for example be one formed
by laminating a biodegradable polymer onto the paper substrate
layer by means of an extrusion molding or one comprising a biaxial
oriented film of a biodegradable polymer.
[0062] When the barrier layer-supporting substrate layer is one
formed by laminating a biodegradable polymer onto the paper
substrate layer by means of an extrusion molding, such a
biodegradable polymer may for example be "LACTY" #9800 of an
extrusion lamination grade which is commercially available from
SHIMADZU CORPORATION.
[0063] When the barrier layer-supporting substrate layer is one
comprising a biaxial oriented film of a biodegradable polymer, such
a biodegradable polymer may for example be "LACTY" #9000 of a
crystalline grade which is commercially available from SHIMADZU
CORPORATION, "TERRAMAC" which is a biaxial oriented film comprising
a polylactic acid-based polymer and commercially available form
UNITIKA LTD., "Palgreen LC" which is a biaxial oriented film
consisting of a polylactic acid-based polymer and commercially
available form TOHCELLO CO., LTD.
[0064] When the barrier layer-supporting substrate layer is one
consisting of a film, the elasticity of the film itself is
increased and the film itself is imparted with an increased
resistance to the tension exerted upon winding and rewinding a roll
during a vapor deposition step since such a film is one formed by
orienting a biodegradable polymer biaxially.
[0065] When a non-oriented film comprising a polylactic acid-based
biodegradable polymer is subjected alone to a vapor deposition of a
ceramic and/or a metal, the film could undergo a shrinkage due to
the heat of the vapor deposition or the tension exerted upon
winding and rewinding the roll, resulting in a damage on a vapor
deposition layer once formed or a wrinkle which may lead to a
difficulty in accomplishing a uniform vapor deposition. On the
contrary, a barrier layer-supporting substrate layer which is one
comprising a biaxial oriented film of a biodegradable polymer
enables a uniform vapor deposition without deterioration or wrinkle
formation even in a vapor deposition environment involving a
complicatedly combined factors by which the vapor deposition is
affected adversely, such as heat, tension and the like.
[0066] A satisfactory vapor deposition can be ensured also by
further providing a paper substrate layer made of a paper outside
the barrier layer-supporting substrate layer of the laminated
film.
[0067] As a result of a stable vapor deposition, a stable barrier
layer is formed which is sufficient for obtaining desired oxygen
barrier property and water vapor barrier property.
[0068] More preferably, the barrier layer-supporting substrate
layer comprises a biaxial oriented film of a biodegradable polymer
with the melting point of 150.degree. C. or higher.
[0069] For example when the melting point of the innermost sealant
layer is 115.degree. C., the actual seal bar temperature should be
at least higher than 115.degree. C., such as 130 to 150.degree. C.
In addition, a higher speed packaging of foods should have a
shorter seal time, which requires a higher seal bar temperature,
which may be as high as about 200.degree. C.
[0070] Nevertheless, when the barrier layer-supporting substrate
layer employs a biodegradable polymer with the melting point of
150.degree. C. or higher and the sealant layer employs a
biodegradable polymer with the melting point of 120.degree. C. or
below, the difference of the melting point between the sealant
layer and the barrier layer-supporting substrate layer becomes
30.degree. C. or more, which enables a bag making by melting the
innermost sealant layer without undergoing any shrinkage of the
outermost barrier layer-supporting substrate layer even at a high
temperature of a high speed operation, resulting in the prevention
of any reduction in the commercial value. Also in an actual
packaging machine, the elongation of a packaging material itself
due to the tensility to the film can also be prevented, resulting
in the prevention of any skew seal or skew cut.
[0071] Also by means of providing a paper substrate layer
comprising a paper as an outermost layer of the laminated film
descryibed below, the heat shrinkage of a package bag can be
prevented.
[0072] The thickness of the barrier layer-supporting substrate
layer is preferably 5 to 20 .mu.m. A thickness less than 5 .mu.m
allows an effect of the vapor deposition heat on the tension upon
film sending and rewinding a roll to be evident, resulting in
difficulty in accomplishing a stable vapor deposition. On the other
hand, a thickness more than 20 .mu.m gives an increased overall
thickness, which leads to an increased overall weight, which is
problematic also in view of a container recycling law. Moreover, an
increased overall thickness allows a pin hole to be formed readily
at the site of the longitudinal seal.
[0073] A thickness of 3 to 15 .mu.m is more preferred.
[0074] The laminated film preferably furthermore has a paper
substrate layer comprising a paper outside the barrier
layer-supporting substrate layer.
[0075] Such a paper is not limited particularly and may be selected
as desired depending on an intended wrapping function or print
pattern, and may for example be a thin paper, high quality paper,
kraft paper, coat paper, cellulose-based unwoven fabric,
cellulose-based film and the like. Among those listed above, a thin
paper is preferred in view of the production cost and the
light-weight packaging.
[0076] The paper substrate layer serves to protect the barrier
layer-supporting substrate layer from the heat or tension exerted
during a vapor deposition, serves as a print substrate for
conducting a surface printing, and, due to its high heat
resistance, also serves to prevent the shrinkage of a packaging
material due to the heat exerted upon making a bag in an actual
packaging machine. Moreover, the paper substrate layer also has an
ability of promoting the hydrolysis of a biodegradable polymer such
as a polylactic acid in the barrier layer-supporting substrate
layer, since it has a water-retaining property.
[0077] The thickness of the paper substrate layer is not limited
particularly as long as it poses no friction against the film feed
upon making bags by a packaging machine, and is preferably 15 to
100 g/m.sup.2 when converted into a basis weight. A thickness less
than 15 g/m.sup.2 makes it difficult to ensure a stable quality due
to the difficulty in making papers themselves. On the other hand, a
paper substrate layer having a thickness more than 100 g/m.sup.2
serves as a heat insulant because of the difficulty in transmitting
the heat to melt the innermost sealant.
[0078] When the laminated film has a paper substrate layer
comprising a paper, a biodegradable bag for packing a food of the
present invention is preferably one obtainable by extruding a
biodegradable polymer onto the paper substrate layer to effect a
lamination whereby forming the barrier layer-supporting substrate
layer, followed by effecting a vapor deposition of a ceramic and/or
a metal onto the barrier layer-supporting substrate layer to form
the barrier layer, followed by laminating the sealant layer via a
biodegradable adhesive onto the barrier layer, or one obtainable by
laminating a biaxial oriented film of a biodegradable polymer via a
biodegradable adhesive onto the paper substrate layer whereby
forming the barrier layer-supporting substrate layer, followed by
effecting a vapor deposition of a ceramic and/or a metal onto the
barrier layer-supporting substrate layer to form the barrier layer,
followed by laminating the sealant layer via a biodegradable
adhesive onto the barrier layer. Such a laminate structure is shown
in FIG. 3. A biodegradable bag for packing a food thus obtained is
biodegradable.
[0079] The biodegradable adhesive may for example be one obtained
by dissolving an aliphatic polyester resin or a biodegradable
polymer such as a polylactic acid-based polymer as main ingredients
in a solvent such as toluene, methyl ethyl ketone, chloroform and
the like.
[0080] A biodegradable bag for packing a food according to the
present invention may further comprise a printed layer comprising a
biodegradable ink on the surface of the substrate layer side. By
using as a biodegradable printing ink, the biodegradablity is not
affected adversely.
[0081] The biodegradable ink is not limited particularly, and may
for example be a regenerated vegetable oil ink, soybean oil ink and
the like. The soybean oil ink is obtained by replacing all or a
part of a petroleum-based solvent and a drying oil in a
conventional ink with a soybean oil, and is advantageous since it
allows the ink to be readily separated from the paper and to be
degraded in a soil. The soybean oil ink may be available
commercially for example from TOYO INK MFG. CO., LTD. or TOPPAN
PRINTING CO., LTD..
[0082] When the barrier layer is formed by means of a transparent
vapor deposition using a ceramic and the like, then a
print-protecting layer consisting of a biodegradable polymer is
further provided between the sealant layer and the barrier layer of
the laminated film to conduct the printing whereby forming a
printed layer on the print-protecting layer, thus accomplishing a
reverse printing. When the barrier layer of a vapor-deposited
ceramic is printed directly, the barrier layer may undergo a
microcracking upon printing, which may lead to a reduced barrier
performance.
[0083] The biodegradable polymer may for example be a polyvinyl
alcohol.
[0084] Such a polyvinyl alcohol may for example be any of those
which are commercially available such as POVAL manufactured by
KURARAY CO., LTD., GOHSENOL manufactured by NIPPON SYNTHETIC
CHEMICAL INDUSTRY CO., LTD., Dolon Va. manufactured by AICELLO
CHEMICAL CO., LTD. and the like.
[0085] The thickness of the print-protecting layer is preferably
0.02 to 0.2 .mu.m. A thickness less than 0.02 .mu.m may lead to a
deterioration of a vapor deposition layer due to a friction, or may
affect the close contact with the printing adversely. On the other
hand, a thickness more than 0.2 .mu.m may lead to a poor ink
contact or drying, which is disadvantageous in an actual
production.
[0086] Nevertheless, it is possible to print directly on a barrier
layer if the barrier layer is formed by a dual component vapor
deposition and the printing is conducted under the condition
involving a tension as low as about 2% or less elongation.
[0087] The ink employed in the printing is preferably a
biodegradable ink similar to those described above.
[0088] When the laminated film has a print-protecting layer, a
biodegradable bag for packing a food according to the present
invention is obtainable preferably by effecting a vapor deposition
of a ceramic onto the barrier layer-supporting substrate layer
comprising a biaxial oriented film of a biodegradable polymer to
form the barrier layer, followed by molding the print-protecting
layer onto the barrier layer, followed by forming a printed layer
onto the print-protecting layer, followed by laminating the sealant
layer via a biodegradable adhesive onto the printed layer. Such a
laminate structure is shown in FIG. 7.
[0089] A biodegradable bag for packing a food according to the
present invention may further comprise an adhesive layer comprising
a biodegradable adhesive between respective layers. By providing
the biodegradable adhesive between the respective layers, the
adhesiveness between the respective layers can further be enhanced
without affecting the biodegradability adversely.
[0090] As described above, the present invention allows a high
function bag for packing a food to be obtained which is
biodegradable, give no burden on a global environment, has an
oxygen barrier property and a water vapor barrier property, and can
withstand a high temperature sealing upon making bags at a high
speed.
[0091] While the applications of a biodegradable bag for packing a
food according to the present invention is not limited
particularly, it is employed preferably for packaging a food which
is required to have an oxygen barrier property and a water vapor
barrier property, especially a snack food.
[0092] The adsorption of the flavors of a snack food can be
prevented especially when using a polyester-based resin in the
internal surface layer which is brought into contact with the snack
food in the bag.
[0093] While the method for packing a food with a biodegradable bag
for packing a food according to the present invention is not
limited particularly, it is preferably be a method comprising a
back seal step in which the laminated film is made tubular with the
sealant layer being inside to bring the both back sides into
contact and heat-sealed with each other, a food introducing step in
which a food is introduced to the inside of the tube of the
laminated film, and an end seal step in which the both ends of the
tube of the laminated film containing the food are sealed (sealing
as shown in FIG. 4).
[0094] The method described above is also one of the aspects of the
present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0095] The invention is further described in the following
examples, which are not intended to restrict the invention.
(EXAMPLE 1)
[0096] A 15 .mu.m aliphatic polyester resin polybutylene succinate
(BIONOLLE #1001m, manufactured by SHOWA HIGHPOLYMER CO., LTD.) was
dry-laminated using a biodegradable adhesive (mixture of several
aliphatic polyester resins dissolved in methyl ethyl ketone) onto a
thin paper with a basis weight of 20 g/m.sup.2 (about 20 .mu.m in
thickness) which had been laminated with a 10 .mu.m biodegradable
polylactic acid LACTY grade #9800 commercially available from
SHIMADZU CORPORATION by means of a melt extrusion and which had
then been vapor-deposited with Al.sub.2O.sub.3 on its polylactic
acid side, whereby obtaining a film roll for a snack food bag.
[0097] The resultant film roll and a conventional film roll
comprising OPP (18 .mu.m)/PE (13 .mu.m)/PET (12 .mu.m)/Al vapor
deposition (500 angstrom)/PE (13 .mu.m)/CPP (20 .mu.m) were
examined for the heat seal temperature property, O.sub.2
permeability and H.sub.2O permeability, which were then compared.
The results are shown in FIG. 1 and Table 1.
[0098] The measurement of the O.sub.2 permeability and H.sub.2O
permeability were conducted under the conditions described
below.
[0099] O.sub.2 permeability: OX-TRAN2/20MH, manufactured by MOCON
,INC.; 23.degree. C., Dry
[0100] H.sub.2O permeability: PERMATRAN W3/31MG, manufactured by
MOCON ,INC.; 37.degree. C., 90%RH
1 TABLE 1 Evaluation item O.sub.2 permeability (ml/m.sup.2
.multidot. D .multidot. H.sub.2O permeability Atm) (g/m.sup.2
.multidot. D) Film roll Product of the invention 1.6 1.8
Conventional product 1.7 1.5
[0101] Subsequently, each of these rolls was subjected to an actual
machine test using an actual snack food packaging machine (APEX
packaging machine, manufactured by ISHIDA CO.,LTD.). The results
are shown in Table 2.
[0102] "APEX packaging machine" manufactured by ISHIDA is disclosed
in U.S. Pat. No. 5,347,795.
2 TABLE 2 Evaluation item Seal bar set temperature Packaging speed
(.degree. C.) (BMP) Film roll Product of the invention 140 140
Conventional product 170 80
[0103] As evident from FIG. 1, the heat seal temperature curve of
the inventive film began to rise at about 120.degree. C., and
allowed the heat seal step to be accomplished at a temperature
lower by 20 to 30.degree. C. when compared with a conventional
film. As a result, the packaging speed was increased as shown in
Table 2, enabling a 1.7-fold faster packaging process when compared
with the conventional film. Thus, the conventional film could pack
only 80 bags per minute, but the inventive film could pack 140 bags
per minute. Also since the use of a paper in the outermost layer
resulted in no seal bar-induced heat deterioration or shrinkage of
the packaging material upon sealing at a high temperature, a
further higher speed operation will be possible.
[0104] Especially in the case of the machine for packing a snack
food among the food to be packed, as shown in FIG. 4, a snack food
packaging film is made tubular with a 15 .mu.m BIONOLLE #1001 film
(manufactured by SHOWA HIGHPOLYMER CO., LTD.) (a sealant layer
consisting of a biodegradable polymer having a melting point of
120.degree. C. or less) being inside and the meeting edges are
heat-sealed in a back-to-back manner (back seal). Then, a snack
food is charged into the inside of the tubular snack food bag.
Subsequently, the both ends of the tubular snack food bag are
heat-sealed (end seals). As a result, the snack food is packed in
the snack food bag.
[0105] The package material thus obtained was buried in a soil (in
ISHIDA CO., LTD. SIGA PLANT, RITTO CITY, SHIGA PREFECTURE) at a
depth of about 10 cm to evaluate the biodegradability, and the
results indicated that a half was degraded at the time of about 3
months, and the original shape was lost at the time of 12
months.
(EXAMPLE 2)
[0106] A 15 .mu.m aliphatic polyester resin polybutylene succinate
(BIONOLLE #1001m, manufactured by SHOWA HIGHPOLYMER CO., LTD.,
melting point: 114.degree. C.) was laminated using a biodegradable
adhesive employed in EXAMPLE 1 with a thin paper with a basis
weight of 20 g/m.sup.2 (about 20 .mu.m in thickness) which had been
laminated using a biodegradable adhesive employed in EXAMPLE 1 with
a biaxial oriented (20 .mu.m in thickness) LACTY #9000 (melting
point of 150 to 170.degree. C.) from SHIMADZU CORPORATION with its
biaxial oriented film side being subjected to a vapor deposition
with SiO.sub.1.8, whereby obtaining a film roll for a snack food
bag.
[0107] The resultant film roll was examined for the heat seal
temperature property, O.sub.2 permeability and H.sub.2O
permeability. The results are shown in FIG. 2 and Table 3.
3 TABLE 3 Evaluation item O.sub.2 permeability (ml/m.sup.2
.multidot. D .multidot. H.sub.2O permeability Atm) (g/m.sup.2
.multidot. D) Film roll Product of the invention 1.8 2.0
[0108] The heat seal temperature property shown in FIG. 2 appeared
as a curve which was almost identical to that of the heat seal
temperature property of EXAMPLE 1 shown in FIG. 1, since the
package material structure was identical to that of EXAMPLE 1 and
the total thickness and the sealant layer were completely similar.
Accordingly, the packaging speed of the actual packaging machine is
assumed to be similar to the speed in EXAMPLE 1.
(EXAMPLE 3)
[0109] The surface of the paper of the roll film of the present
invention obtained in EXAMPLE 1 was printed with a soybean ink
manufactured by TOYO INK MFG. CO., LTD. which is a biodegradable
ink.
[0110] A piece of this roll film was buried in the soil to be
subjected to the biodegradability test similarly to EXAMPLE 1, and
the results indicated a satisfactory biodegradability.
(EXAMPLE 4)
[0111] A 15 .mu.m aliphatic polyester resin polybutylene succinate
(BIONOLLE #1001m, manufactured by SHOWA HIGHPOLYMER CO., LTD.,
melting point: 114.degree. C.) was laminated using a biodegradable
adhesive employed in EXAMPLE 1 with a thin paper with a basis
weight of 20 g/m.sup.2 (about 20 .mu.m in thickness) which had been
laminated using a biodegradable adhesive employed in EXAMPLE 1 with
a polylactic acid-derived biaxial oriented TERRAMAC (15 .mu.m in
thickness, melting point: 170.degree. C.) from UNITIKA LTD. with
its biaxial oriented film side being subjected to a vapor
deposition with Al.sub.2O.sub.3, and then the paper surface was
printed with the biodegradable ink similar to that in EXAMPLE 3,
whereby obtaining a film roll for a snack food bag.
[0112] The film roll was examined for the heat seal temperature
property, O.sub.2 permeability and H.sub.2O permeability, and the
results are favorably compared with those in EXAMPLES 1 and 2. A
piece of this roll film was buried in the soil to be subjected to
the biodegradability test similarly to EXAMPLE 1, and the results
indicated a satisfactory biodegradability.
(EXAMPLE 5)
[0113] An inventive roll film obtained in EXAMPLE 1 and a
conventional roll film were subjected to a test in which a snack
food (potato chips) immediately after production was filled and
packaged. The packaging machine employed was "APEX packaging
machine" manufactured by ISHIDA CO.,LTD., and an N.sub.2 purge was
also performed.
[0114] The package bags thus obtained were placed in a thermostat
chamber to perform a 40.degree. C. 1-month storage test, after
which an organoleptic evaluation was conducted by 10 panelists. The
results are shown in Table 4. Each figure in the table is the mean
of 10 panelists.
4 TABLE 4 Evaluation item Flavor on unsealing Taste/Flavor Film
roll Product of the invention 4.6 4.8 Conventional product 3.5
4.3
[0115] Note-1) The results were judged on a 0 to 5 scale, with the
score immediately after the production being 5.0 and the palatable
limit being 3.0, and the samples having 3.0 or higher scores were
judged to be valuable commercially. Note-2) The flavor at the
instance of breaking the bag was regarded as an Flavor on
unsealing, while the taste and the flavor when eating with relish
the potato chips was regarded as a Taste/Flavor.
[0116] As evident from Table 4, the inventive sample exhibited
excellent Flavor on unsealing as well as taste and flavor upon
eating with relish, when compared with the conventional sample.
These findings are due to a polyester-based sealant undergoing less
flavor adsorption being used as the innermost layer of the
inventive laminate.
(EXAMPLE 6)
[0117] A 15 .mu.m aliphatic polyester resin polybutylene succinate
(BIONOLLE #1001m, manufactured by SHOWA HIGHPOLYMER CO., LTD.) was
dry-laminated using a biodegradable adhesive (mixture of several
aliphatic polyester resins dissolved in methyl ethyl ketone) onto a
15 .mu.m polylactic acid-derived biaxial oriented form (TERRAMAC
hard type, manufactured by UNITIKA LTD.) which had been subjected
to a vapor deposition with Al.sub.2O.sub.3 to the thickness of 500
angstrom and then painted with a 4 weight % solution of a polyvinyl
alcohol (PVA205, manufactured by KURARAY CO., LTD.) in
water:alcohol (1:1) to the solid thickness of 0.1 .mu.m and then
further printed with a soybean oil ink by TOYO INK MFG. CO., LTD
which was a biodegradable ink, whereby obtaining a film roll for a
snack food bag.
[0118] The resultant film roll and a conventional film roll
comprising OPP (18 .mu.m)/PE (13 .mu.m)/PET (12 .mu.m)/Al vapor
deposition (500 angstrom)/PE (13 .mu.m)/PP (20 .mu.m) were examined
for the heat seal temperature property, O.sub.2 permeability and
H.sub.2O permeability, which were then compared. The results are
shown in FIG. 5 and Table 5.
5 TABLE 5 Evaluation item O.sub.2 permeability (ml/m.sup.2
.multidot. D .multidot. H.sub.2O permeability Atm) (g/m.sup.2
.multidot. D) Film roll Product of the invention 2.0 2.2
Conventional product 1.7 1.5
[0119] Subsequently, each of these rolls was subjected to an actual
machine test using an actual snack food packaging machine (APEX
packaging machine, manufactured by ISHIDA CO.,LTD.). The results
are shown in Table 6.
6 TABLE 6 Evaluation item Seal bar set temperature Packaging speed
(.degree. C.) (BMP) Film roll Product of the invention 140 140
Conventional product 170 80
[0120] As evident from FIG. 5, the heat seal temperature curve of
the inventive film began to rise at about 100.degree. C., and
allowed the heat seal step to be accomplished at a temperature
lower by 30 to 40.degree. C. when compared with a conventional
film. As a result, the packaging speed was increased as shown in
Table 6, enabling a 1.7-fold faster packaging process when compared
with the conventional film. Thus, the conventional film could pack
only 80 bags per minute, but the inventive film could pack 140 bags
per minute. An attempt was also made to set the seal bar
temperature at 180.degree. C. and the packaging speed was increased
to 160 cycles to conduct the packaging. As a result, the inventive
sample in this EXAMPLE underwent a shrinkage on the surface brought
into contact with a seal bar and was not successful in exhibiting a
satisfactory performance, but the inventive sample in EXAMPLE 1
exhibited a satisfactory performance. Such findings may be due to
the paper substrate layer on the surface.
[0121] The package material thus obtained was buried in a soil (in
ISHIDA CO., LTD. SIGA PLANT, RITTO CITY, SHIGA PREFECTURE) at a
depth of about 10 cm to evaluate the biodegradability, and the
results indicated that a half was degraded at the time of about 6
months, and the original shape was lost at the time of 12
months.
(EXAMPLE 7)
[0122] A 20 .mu.m in thickenss biaxial oriented film consisting of
a polylactic acid which is a biodegradable polymer (TERRAMAC hard
type, manufactured by UNITIKA LTD.) was subjected to a vapor
deposition with SiO.sub.1.8 to the thickness of 800 angstrom, and
the vapor deposition side was extrusion-laminated with an aliphatic
polyester resin polybutylene succinate (BIONOLLE #1001m,
manufactured by SHOWA HIGHPOLYMER CO., LTD.) to the thickness of 10
.mu.m, whereby obtaining a film roll for a snack food bag having a
total thickness of about 35 .mu.m.
[0123] The resultant film roll was examined for the heat seal
temperature property, O.sub.2 permeability and H.sub.2O
permeability. The results are shown in FIG. 6 and Table 7.
7 TABLE 7 Evaluation item O.sub.2 permeability (ml/m.sup.2
.multidot. D .multidot. H.sub.2O permeability Atm) (g/m.sup.2
.multidot. D) Film roll Product of the invention 1.8 2.0
(EXAMPLE 8)
[0124] An inventive roll film obtained in EXAMPLE 6 and a
conventional roll film were subjected to a test in which a snack
food (potato chips) immediately after production was filled and
packaged. The packaging machine employed was "APEX packaging
machine" manufactured by ISHIDA CO.,LTD., and an N.sub.2 purge was
also performed.
[0125] The package bags thus obtained were placed in a thermostat
chamber to perform a 40.degree. C .1-month storage test, after
which an organoleptic evaluation was conducted by 10 panelists. The
results are shown in Table 8. Each figure in the table is the mean
of 10 panelists.
8 TABLE 8 Evaluation item Flavor on unsealing Taste/Flavor Film
roll Product of the invention 4.6 4.8 Conventional product 3.5
4.3
[0126] Note-1) The results were judged as one of 5 degrees, with
the score immediately after the production being 5.0 and the
palatable limit being 3.0, and the samples having 3.0 or higher
scores were judged to be valuable commercially. Note-2) The flavor
at the instance of breaking the bag was regarded as an Flavor on
unsealing, while the taste and the flavor when eating the potato
chips was regarded as a Taste/Flavor.
[0127] As evident from Table 8, the inventive sample exhibited
excellent Flavor on unsealing as well as taste and flavor upon
eating, when compared with the conventional sample. These findings
are due to a polyester-based sealant undergoing less flavor
adsorption being used as the innermost layer of the inventive
laminate.
[0128] Industrial Applicability
[0129] According to the present invention, an automatic bag making
using a packaging machine can be conducted at a higher speed, and a
biodegradable bag for packing a food capable of being degraded
spontaneously when buried in a soil and like after disposal can be
obtained. Thus, by altering the structure of bag materials, while
imparting the bag with a barrier function, from a conventional
composite structure consisting of different resins which are
difficult to be recycled as materials and which pose problems upon
disposal such as OPP (or PET)/vapor deposition layer/polyolefin and
the like to a novel structure such as a biodegradable polymer
sealant layer/biodegradable adhesive layer/ceramic or metal vapor
deposition layer/biodegradable polymer barrier layer-supporting
substrate layer/paper/biodegradable ink-bearing printing layer, or
a biodegradable polymer sealant layer/(biodegradable adhesive
layer)/biodegradable polymer-derived biodegradable ink-bearing
printing layer/biodegradable polymer print-protecting layer/oxygen
or water vapor barrier layer/biodegradable polymer-derived biaxial
oriented barrier layer-supporting substrate layer, a biodegradable
food package bag can be obtained. Furthermore, a biodegradable bag
for packing a food according to the present invention can reduce
burning calories upon an incineration disposal after use when
compared with a conventional package material structure employing
polyolefin resins generating high burning calories as major
constituents, whereby preventing any damage of the incineration
furnace.
* * * * *