Title of Invention
BARRIER FILM, LAMINATE, AND PACKAGING BAG
Technical Field
5 [0001] The present disclosure relates to a barrier film, a laminate, and a
packaging bag.
Background Art
[0002] Barrier films are widely used mainly as packaging materials for
foods, medical drugs, and the like which are subjected to heat sterilization
10 treatments such as a boiling treatment and a retort treatment. In
packaging these contents, emphasis has been placed particularly on
reducing oxygen permeability. As such a barrier film used for
packaging materials subjected to heat sterilization, a highly heat-resistant
polyethylene terephthalate film is generally used as a base material.
15 [0003] However, in recent years, with increased awareness about
environmental issues, there has been increasing interest in packaging
materials formed using a single material, so-called mono-material
packaging materials, in order to make packaging materials suitable for
recycling. Because olefinic films such as polypropylene are generally
20 used as a sealant layer in packaging materials, in order to produce monomaterial packaging materials using such a sealant layer, it is also required
to use polypropylene as a base material in barrier films. For example,
Patent Literature 1 and Patent Literature 2 below propose mono-material
packaging materials formed using polypropylene.
25 [0004] Polypropylene films are widely used for packaging materials and
the like because of their excellent transparency, mechanical strength, and
2
heat resistance. However, unlike polyethylene terephthalate and the
like, polypropylene does not have sufficient secondary workability such
as metal vapor deposition properties, adhesiveness to other resins, and
printability. Various methods have been proposed to solve these
5 problems. For example, Patent Literature 3 proposes a polypropylene
film formed from a blend of polypropylene and an ethylene-α-olefin
copolymer, and Patent Literature 4 proposes a polypropylene film having
a layer formed from a blend of polypropylene and an ethylene-α-olefin
copolymer, and a layer formed from a polypropylene resin.
10 Citation List
Patent Literature
[0005] [Patent Literature 1] Japanese Unexamined Patent Publication
No. 2020-40257
[Patent Literature 2] Japanese Unexamined Patent Publication
15 No. 2021-20391
[Patent Literature 3] Japanese Unexamined Patent Publication
No. S63-291929
[Patent Literature 4] Japanese Unexamined Patent Publication
No. S63-290743
20 Summary of Invention
Technical Problem
[0006] However, in the configuration of conventional barrier films and
laminates, not only can oxygen permeability not be suppressed to a low
level after a heat sterilization treatment, but also the adhesion strength
25 between films (interlaminar adhesion strength) after the heat sterilization
treatment is low. Therefore, with use in a pouch filled with contents,
3
there were problems of a low tear strength of a pouch, and a pouch being
susceptible to destruction by impact such as dropping.
[0007] The present disclosure has been made in view of the abovementioned circumstances, and an object thereof is to provide a barrier
5 film capable of suppressing oxygen permeability to a low level even after
a heat sterilization treatment, and capable of maintaining a sufficient
adhesion strength between films (interlaminar adhesion strength) even
after the heat sterilization treatment, and a laminate and a packaging bag
which are formed using the barrier film.
10 Solution to Problem
[0008] (First aspect)
The present disclosure provides a barrier film containing, in the
following order: a base material layer containing polypropylene; a vapor
deposition layer containing an inorganic oxide; and a gas barrier layer, in
15 which the above-mentioned base material layer has a multilayer structure
in which at least three layers, which are a first skin layer, a core layer, and
a second skin layer, are provided in this order, and in which when a
softening temperature of each of the layers of the above-mentioned base
material layer is measured by local thermal analysis (LTA), at least one
20 softening temperature of the above-mentioned first skin layer is 120°C or
higher, at least one softening temperature of the above-mentioned core
layer is 190°C or higher, and at least one softening temperature of the
above-mentioned second skin layer is 160°C or lower.
[0009] According to the above-mentioned barrier film, since the base
25 material layer has the first skin layer, the core layer, and the second skin
layer, each of which has a softening temperature within the above4
mentioned specific range, the adhesion strength between the base
material layer and each of the layers configuring the barrier film is
increased, which makes it possible to suppress oxygen permeability to a
low level even after a heat sterilization treatment, and to maintain a
5 sufficient adhesion strength between the films (interlaminar adhesion
strength) even after the heat sterilization treatment. Furthermore, when
a laminate is formed by laminating a sealant layer, or a sealant layer and
a second base material layer to the above-mentioned barrier film, the
adhesion strength between the barrier film and the sealant layer and/or
10 the second base material layer can be increased. Therefore, by using the
above-mentioned barrier film, it is possible to obtain a laminate capable
of suppressing oxygen permeability to a low level even after the heat
sterilization treatment, and capable of maintaining a sufficient adhesion
strength between the films (interlaminar adhesion strength) even after the
15 heat sterilization treatment, and a packaging bag formed using the
laminate.
[0010] In the above-mentioned barrier film, when the softening
temperature of the above-mentioned first skin layer is measured by LTA,
at least one softening temperature of the first skin layer may be 120°C or
20 higher and 170°C or lower. In this case, the barrier film is capable of
suppressing oxygen permeability to a lower level even after the heat
sterilization treatment, and capable of maintaining a more sufficient
adhesion strength between the films even after the heat sterilization
treatment.
25 [0011] In the above-mentioned barrier film, when the softening
temperature of the above-mentioned second skin layer is measured by
5
LTA, at least one softening temperature of the second skin layer may be
120°C or higher and 160°C or lower. In this case, the barrier film is
capable of suppressing oxygen permeability to a lower level even after
the heat sterilization treatment, and capable of maintaining a more
5 sufficient adhesion strength between the films even after the heat
sterilization treatment.
[0012] In the above-mentioned barrier film, the above-mentioned first
skin layer and the above-mentioned second skin layer may contain a
copolymer of propylene and α-olefin. In this case, the barrier film is
10 capable of suppressing oxygen permeability to a lower level even after
the heat sterilization treatment, and capable of maintaining a more
sufficient adhesion strength between the films even after the heat
sterilization treatment.
[0013] In the above-mentioned barrier film, when the softening
15 temperature of each of the layers of the base material layer is measured
by LTA, at least one softening temperature of the above-mentioned core
layer may be higher than any of the softening temperatures of the abovementioned first skin layer and the above-mentioned second skin layer.
In this case, the barrier film is capable of suppressing oxygen
20 permeability to a lower level even after the heat sterilization treatment.
[0014] In the above-mentioned barrier film, when the softening
temperature of each of the layers of the above-mentioned base material
layer is measured by LTA, at least one softening temperature of the abovementioned first skin layer may be higher than any of the softening
25 temperatures of the above-mentioned second skin layer. In this case, the
barrier film is capable of suppressing oxygen permeability to a lower
6
level even after the heat sterilization treatment. Furthermore, when a
laminate is formed by laminating a sealant layer, or a sealant layer and a
second base material layer to the above-mentioned barrier film, the
adhesion strength between the barrier film and the sealant layer and/or
5 the second base material layer can be further increased.
[0015] In the above-mentioned barrier film, a thickness of each of the
above-mentioned first skin layer and the above-mentioned second skin
layer may be 2.0 μm or less. In this case, the barrier film is capable of
suppressing oxygen permeability to a lower level even after the heat
10 sterilization treatment, and capable of maintaining a more sufficient
adhesion strength between the films even after the heat sterilization
treatment.
[0016] In the above-mentioned barrier film, the above-mentioned vapor
deposition layer may contain at least one selected from the group
15 consisting of aluminum oxide and silicon oxide. In this case, the barrier
film is capable of suppressing oxygen permeability to a lower level even
after the heat sterilization treatment, and capable of maintaining a more
sufficient adhesion strength between the films even after the heat
sterilization treatment.
20 [0017] In the above-mentioned barrier film, the above-mentioned gas
barrier layer may contain a water-soluble polymer having a hydroxyl
group and at least one selected from the group consisting of a metal
alkoxide, a silane coupling agent, and a hydrolysate thereof. In this
case, the barrier film is capable of suppressing oxygen permeability to a
25 lower level even after the heat sterilization treatment, and capable of
7
maintaining a more sufficient adhesion strength between the films even
after the heat sterilization treatment.
[0018] In the above-mentioned barrier film, the above-mentioned vapor
deposition layer may be formed on a surface of the above-mentioned first
5 skin layer which is on an opposite side to the above-mentioned core layer.
Furthermore, in this case, the above-mentioned barrier film may further
have an anchor coat layer between the above-mentioned first skin layer
and the above-mentioned vapor deposition layer. The barrier film
having the above-mentioned configuration can further improve the
10 adhesion strength between the first skin layer and the vapor deposition
layer. Therefore, the above-mentioned barrier film is capable of
suppressing oxygen permeability to a lower level even after the heat
sterilization treatment, and capable of maintaining a more sufficient
adhesion strength between the films even after the heat sterilization
15 treatment.
[0019] The present disclosure further provides a laminate containing: the
above-mentioned barrier film of the present disclosure; and a sealant
layer, in which the above-mentioned sealant layer contains polyolefin.
The above-mentioned laminate may further have a second base material
20 layer on a surface on an opposite side to the above-mentioned sealant
layer of the above-mentioned barrier film, in which the above-mentioned
second base material layer may contain polyolefin. Since the abovementioned laminate is formed using the above-mentioned barrier film of
the present disclosure, oxygen permeability can be suppressed to a low
25 level even after the heat sterilization treatment, and a sufficient adhesion
strength can be maintained between the films even after the heat
8
sterilization treatment. Furthermore, the above-mentioned laminate is
useful as a mono-material packaging material.
[0020] The present disclosure still further provides a packaging bag
formed by making the above-mentioned laminate of the present
5 disclosure into a pouch shape. Since the above-mentioned packaging
bag is formed using the above-mentioned laminate of the present
disclosure, oxygen permeability can be suppressed to a low level even
after the heat sterilization treatment, and a sufficient adhesion strength
can be maintained between the films even after the heat sterilization
10 treatment. Furthermore, the above-mentioned packaging bag is useful
as a mono-material packaging material.
[0021] (Second aspect)
The present disclosure provides a barrier film containing, in the
following order: a base material layer containing polypropylene; a vapor
15 deposition layer containing an inorganic oxide; and a gas barrier layer, in
which the above-mentioned base material layer has two layers, which are
a skin layer and a core layer, in order from the vapor deposition layer, and
in which, when a softening temperature of each of the layers of the abovementioned base material layer is measured by local thermal analysis
20 (LTA), at least one softening temperature of the above-mentioned skin
layer is 115°C or higher and 170°C or lower, and at least one softening
temperature of the above-mentioned core layer is 190°C or higher.
[0022] According to the above-mentioned barrier film, since the abovementioned base material layer has the above-mentioned skin layer and
25 the above-mentioned core layer, each of which has a softening
temperature within the above-mentioned specific range, the adhesion
9
strength between the films is increased, which makes it possible to
suppress oxygen permeability to a low level even after a heat sterilization
treatment, and to maintain a sufficient adhesion strength between the
films even after the heat sterilization treatment. Therefore, by using the
5 above-mentioned barrier film, it is possible to obtain a laminate capable
of suppressing oxygen permeability to a low level even after the heat
sterilization treatment, and capable of maintaining a sufficient adhesion
strength between the films even after the heat sterilization treatment, and
a packaging bag formed using the laminate.
10 [0023] The above-mentioned barrier film, the above-mentioned skin
layer may contain a copolymer of propylene and α-olefin. In this case,
the barrier film is capable of suppressing oxygen permeability to a lower
level even after the heat sterilization treatment, and capable of
maintaining a more sufficient adhesion strength between the films even
15 after the heat sterilization treatment.
[0024] In the above-mentioned barrier film, the above-mentioned skin
layer may contain an ethylene-1-butene-propylene random copolymer.
In this case, the barrier film is capable of suppressing oxygen
permeability to a lower level even after the heat sterilization treatment.
20 [0025] In the above-mentioned barrier, a thickness of the abovementioned skin layer may be 0.2 μm or more and 2.0 μm or less. In this
case, the barrier film is capable of suppressing oxygen permeability to a
lower level even after the heat sterilization treatment, and capable of
maintaining a more sufficient adhesion strength between the films even
25 after the heat sterilization treatment.
10
[0026] In the above-mentioned barrier film, a ratio of a thickness of the
above-mentioned skin layer to a thickness of the above-mentioned core
layer may be 1/100 to 1/5. In this case, the barrier film is capable of
suppressing oxygen permeability to a lower level even after the heat
5 sterilization treatment, and capable of maintaining a more sufficient
adhesion strength between the films even after the heat sterilization
treatment.
[0027] In the above-mentioned barrier film, the above-mentioned vapor
deposition layer may contain at least one selected from the group
10 consisting of aluminum oxide and silicon oxide. In this case, the barrier
film is capable of suppressing oxygen permeability to a lower level even
after the heat sterilization treatment, and capable of maintaining a more
sufficient adhesion strength between the films even after the heat
sterilization treatment.
15 [0028] In the above-mentioned barrier film, the above-mentioned gas
barrier layer may be formed from a coating liquid containing at least one
silicon compound selected from Si(OR1
)4 and R2Si(OR3
)3 (where OR1
and OR3
are each independently a hydrolyzable group, and R2
is an
organic functional group) or a hydrolysate thereof, and containing a
20 water-soluble polymer having a hydroxyl group. In this case, the barrier
film is capable of suppressing oxygen permeability to a lower level even
after the heat sterilization treatment, and capable of maintaining a more
sufficient adhesion strength between the films even after the heat
sterilization treatment.
25 [0029] The above-mentioned barrier film may further have an anchor
coat layer between the above-mentioned skin layer and the above11
mentioned vapor deposition layer. The barrier film having the abovementioned configuration can further improve the adhesion strength
between the skin layer and the vapor deposition layer. Therefore, the
above-mentioned barrier film is capable of suppressing oxygen
5 permeability to a lower level even after the heat sterilization treatment,
and capable of maintaining a more sufficient adhesion strength between
the films even after the heat sterilization treatment.

claims:
1 A barrier film comprising, in the following order:
a base material layer containing polypropylene;
a vapor deposition layer containing an inorganic oxide; and
5 a gas barrier layer,
wherein the base material layer has a multilayer structure in which
at least three layers, which are a first skin layer, a core layer, and a second
skin layer, are provided in this order, and
when a softening temperature of each of the layers of the base
10 material layer is measured by local thermal analysis (LTA), at least one
softening temperature of the first skin layer is 120°C or higher, at least
one softening temperature of the core layer is 190°C or higher, and at least
one softening temperature of the second skin layer is 160°C or lower.
2 The barrier film according to claim 1, wherein, when the
15 softening temperature of the first skin layer is measured by LTA, at least
one softening temperature of the first skin layer is 120°C or higher and
170°C or lower.
3 The barrier film according to claim 1, wherein, when the
softening temperature of the second skin layer is measured by LTA, at
20 least one softening temperature of the second skin layer is 120°C or
higher and 160°C or lower.
4 The barrier film according to claim 1, wherein the first
skin layer and the second skin layer contain a copolymer of propylene
and α-olefin.
25 5 The barrier film according to claim 1, wherein, when the
softening temperature of each of the layers of the base material layer is measured by LTA, at least one softening temperature of the core layer is
higher than any of the softening temperatures of the first skin layer and
the second skin layer.
6 The barrier film according to claim 1, wherein, when the
5 softening temperature of each of the layers of the base material layer is
measured by LTA, at least one softening temperature of the first skin layer
is higher than any of the softening temperatures of the second skin layer.
7 The barrier film according to claim 1, wherein a thickness
of each of the first skin layer and the second skin layer is 2.0 μm or less.
10 8 The barrier film according to claim 1, wherein the vapor
deposition layer contains at least one selected from the group consisting
of aluminum oxide and silicon oxide.
9 The barrier film according to claim 1, wherein the gas
barrier layer contains a water-soluble polymer having a hydroxyl group
15 and at least one selected from the group consisting of a metal alkoxide, a
silane coupling agent, and a hydrolysate thereof.
10 The barrier film according to claim 1, wherein the vapor
deposition layer is formed on a surface of the first skin layer which is on
an opposite side to the core layer.
20 11 The barrier film according to claim 10, further comprising
an anchor coat layer between the first skin layer and the vapor deposition
layer.
12 A barrier film comprising, in the following order:
a base material layer containing polypropylene;
25 a vapor deposition layer containing an inorganic oxide; and
a gas barrier layer,
62
wherein the base material layer has two layers, which are a skin
layer and a core layer, in order from the vapor deposition layer, and
when a softening temperature of each of the layers of the base
material layer is measured by local thermal analysis (LTA), at least one
5 softening temperature of the skin layer is 115°C or higher and 170°C or
lower, and at least one softening temperature of the core layer is 190°C
or higher.
13 The barrier film according to claim 12, wherein the skin
layer contains a copolymer of propylene and α-olefin.
10 14 The barrier film according to claim 12, wherein the skin
layer contains an ethylene-1-butene-propylene random copolymer.
15 The barrier film according to claim 12, wherein a
thickness of the skin layer is 0.2 μm or more and 2.0 μm or less.
16 The barrier film according to claim 12, wherein a ratio of
15 a thickness of the skin layer to a thickness of the core layer is 1/100 to
1/5.
17 The barrier film according to claim 12, wherein the vapor
deposition layer contains at least one selected from the group consisting
of aluminum oxide and silicon oxide.
20 18 The barrier film according to claim 12, wherein the gas
barrier layer is formed from a coating liquid containing at least one silicon
compound selected from Si(OR1
)4 and R2Si(OR3
)3 (where OR1
and OR3
are each independently a hydrolyzable group, and R2
is an organic
functional group) or a hydrolysate thereof, and containing a water-soluble
25 polymer having a hydroxyl group.
63
19 The barrier film according to claim 12, further comprising
an anchor coat layer between the skin layer and the vapor deposition
layer.
20 A laminate comprising:
5 the barrier film according to any one of claims 1 to 19; and
a sealant layer,
wherein the sealant layer contains polyolefin.
21 The laminate according to claim 20, further comprising:
a second base material layer on a surface on an opposite side to
10 the sealant layer of the barrier film,
wherein the second base material layer contains polyolefin.
22 A packaging bag formed by making the laminate
according to claim 20 into a pouch shape.