JP7748872B2 - Composite film, packaging bag, lid material, container with lid, and method for manufacturing composite film - Google Patents

Description

The present invention relates to a composite film, a packaging bag, a lid material, a container with a lid, and a method for manufacturing a composite film.

Traditionally, food-filled pouch products require the pouch to be opened before heating in a microwave oven in order to remove the water vapor generated inside the container.

In response to this, packaging sheets have been proposed that form steam release holes when heated in a microwave oven. For example, Patent Document 1 discloses a packaging sheet material for food to be cooked in a microwave oven, in which a base film and a sealant film are laminated together. The sealant film is a laminate of layers made of thermoplastic resins that have different melting points and are thermally adhesive to each other, so that heating during microwave cooking partially destroys the heat-sealed portions of the packaging sheet material where the sealant film is heat-sealed, forming release holes.

The packaging sheet material described in Patent Document 1 allows steam to pass through from unspecified locations in the heat-sealed portion. However, it has not been possible to allow steam to pass through from specific locations in the heat-sealed portion.

In contrast, microwave pouches are known that allow steam to be released from a desired location.

For example, Patent Document 2 proposes a laminate as a packaging material for pouches, in which a base layer, a heat-softening layer, and a heat-seal layer are laminated in that order. It also proposes making a half-cut on the heat-seal layer side of the laminate, so that when cooked in a microwave oven, steam can pass through the half-cut at the heat-sealed portion where the heat-sealed layers are thermally fused together.

Japanese Patent Application Publication No. 11-165771 Japanese Patent Application Laid-Open No. 2017-124859

However, the packaging material described in Patent Document 2 had an adhesive layer in addition to the heat-softening resin layer between the base layer and the heat-sealing layer. Specifically, in Patent Document 2, the heat-softening resin layer was only disposed in the half-cut area, and the heat-softening resin layer was embedded and scattered throughout the adhesive layer that was disposed over the entire surface.

For this reason, the packaging material described in Patent Document 2 not only complicates the manufacturing process for the laminate, but also increases costs.

The present invention was made in light of the above-mentioned background, and aims to provide a composite film that can achieve steam release performance equivalent to that of conventional films, even when only a single heat-softenable resin layer is disposed between the base layer and the heat-seal layer, and that, by providing half cuts in required locations, allows specific steam release locations to be identified when heating in a microwave oven or the like, and further, suppresses the occurrence of lamination lifting. The present invention also aims to provide a composite film, a packaging bag, a lid material, a lidded container, and a method for manufacturing the composite film, which can achieve steam release performance equivalent to that of conventional films, even when only a single heat-softenable resin layer is disposed between the base layer and the heat-seal layer, and that, by providing half cuts in required locations, allows specific steam release locations to be identified when heating in a microwave oven or the like, and further suppresses the occurrence of lamination lifting.

The inventors conducted extensive research to solve the above problems. They discovered that the above problems could be solved by using an adhesive composition with a specific configuration as a heat-softenable resin layer in a composite film used as a packaging material, and thus completed the present invention. Specifically, the present invention is as follows:

<<Aspect 1>>
A composite film in which at least a base layer, a heat-softenable adhesive resin layer, and a heat-sealable layer are laminated in this order,
The heat-softenable adhesive resin layer is composed of a heat-softenable adhesive resin having a crosslinked structure.
Composite film.
Aspect 2
2. The composite film according to claim 1, wherein the heat-softenable adhesive resin is formed from an adhesive composition containing 1 part by weight of a base resin and less than 0.2 parts by weight of a curing agent.
Aspect 3
2. The composite film according to claim 1, wherein the thermosoftenable adhesive resin is formed from an adhesive composition containing more than 0.125 parts by mass and less than 0.2 parts by mass of a curing agent per 1 part by mass of a base resin.
Aspect 4
A composite film according to Aspect 2 or 3, wherein the heat-softenable adhesive resin layer is a layer having a coating amount of the adhesive composition of less than 2.5 g/ ^m2 .
Aspect 5
Aspect 5. The composite film according to any one of Aspects 1 to 4, wherein the thermosoftenable adhesive resin is an ether-based resin.
Aspect 6
The lamination strength between the base layer and the heat seal layer at 25°C is 1.3 N/15 mm or more,
The lamination strength between the base layer and the heat seal layer at 70°C is 0.6 N/15 mm or less.
A composite film according to any one of aspects 1 to 5.
Aspect 7
Aspect 7. The composite film according to any one of Aspects 1 to 6, wherein the composite film has a half cut applied from the heat seal layer side and reaching the heat-softenable adhesive resin layer.
Aspect 8
A packaging bag formed from the composite film according to Aspect 7, comprising a seal portion formed by heat-sealing the heat-sealable layers to each other,
The half cut crosses the seal portion from the inside to the outside of the packaging bag.
Aspect 9
A packaging bag according to Aspect 8, which is suitable for use in a microwave oven.
Aspect 10
A lid material for sealing an upper end opening of a container body, formed from the composite film according to aspect 7,
The sealing is performed by heat-sealing the heat-seal layer to the container body so that the lid material covers the upper end opening, thereby forming an openable joint,
The half cut is arranged across the joint from the inside to the outside of the container body, a lid material.
Aspect 11
A lid material according to aspect 10, which is for use in a microwave oven.
Aspect 12
A container body;
A lid material formed from the composite film according to aspect 7 for sealing an upper end opening of the container body;
A container with an openable lid comprising:
The upper end opening of the container body has a flange,
the heat seal layer is heat sealed to the flange to form a releasable joint;
The half cut crosses the joint from the inside to the outside of the container body.
Openable container with lid.
Aspect 13
A container with a lid according to claim 12, which is suitable for use in a microwave oven.
Aspect 14
A method for producing the composite film according to aspect 7, comprising:
a half-cutting step of cutting the sheet including the heat-sealable layer by a rotary die cutter so as to penetrate the heat-sealable layer in a thickness direction;
a lamination step of laminating the base material layer and/or the heat-softenable adhesive resin layer on the sheet including the heat-sealable layer after the half-cut preparation step,
A method for manufacturing a composite film.

The composite film of the present invention, even in a configuration in which only one heat-softenable resin layer is disposed between the substrate layer and the heat-sealable layer, can be used to produce packaging bags such as pouches and openable containers that have vapor release performance equivalent to that of conventional products.

Furthermore, if no adhesive layer other than the heat-softenable adhesive resin layer is disposed between the base layer and the heat-sealable layer, the manufacturing process for the composite film can be simplified, contributing to reduced production capacity and production costs.

Furthermore, by providing half cuts where necessary, steam can be released from the intended location when heating in a microwave oven, etc.

Furthermore, the composite film of the present invention is a composite film that is suppressed from causing lamination lifting during storage and resulting poor appearance, and therefore packaging materials made from the composite film of the present invention can improve the storage properties of contents such as food.

1 is a cross-sectional view of a composite film according to one embodiment of the present invention. 1 is a diagram showing a packaging bag according to one embodiment of the present invention. 1 is a schematic diagram of a packaging bag according to an embodiment of the present invention when steam is released.

Composite film
The composite film of the present invention is a composite film in which at least a base material layer, a heat-softenable adhesive resin layer, and a heat-sealable layer are laminated in this order, and the heat-softenable adhesive resin layer is composed of a heat-softenable adhesive resin having a crosslinked structure.
Composite film.

<<Configuration of composite film>>
The structure of the composite film of the present invention will be described below with reference to the drawings. Figure 1 shows a cross-sectional view of one embodiment of the composite film of the present invention.

The composite film 10 according to one embodiment of the present invention shown in Figure 1 comprises a base layer 1, a heat-softenable adhesive resin layer 2 laminated on the inner side of the base layer 1, and a heat-seal layer 3 laminated on the inner side of the heat-softenable adhesive resin layer 2.

The composite film of the present invention essentially comprises a substrate layer, a heat-softenable adhesive resin layer, and a heat-seal layer, which are laminated in this order. In addition to the substrate layer, heat-softenable adhesive resin layer, and heat-seal layer, the present invention may also include optional layers, such as a barrier layer for imparting barrier properties, a reinforcing layer for reinforcing strength, or an adhesive layer for bonding layers together.

The composite film 10 shown in Figure 1 is an embodiment that includes only the essential components of the present invention: a base layer 1, a heat-softenable adhesive resin layer 2, and a heat-seal layer 3. However, other layers may be present, for example, between the base layer 1, the heat-softenable adhesive resin layer 2, and the heat-seal layer 3, or on the outside of the laminate that includes these layers.

The thickness of each layer constituting the composite film of the present invention can be determined appropriately depending on the intended use of the composite film.

<Base material layer>
The substrate layer is an essential constituent layer of the composite film of the present invention.

The composite film of the present invention has a substrate layer, a heat-softenable adhesive resin layer, and a heat-seal layer laminated in this order. Therefore, when a structure such as a packaging bag or package is formed, the substrate layer becomes the outer layer of the structure. Therefore, the substrate layer can serve as a protective layer when the innermost heat-seal layer is heat-sealed to form the structure. It can also serve as a printing layer for printing to indicate the contents, etc.

The material that makes up the base layer is not particularly limited, as long as it is a resin, particularly a resin that can be used as a protective layer and that can be printed on. Commonly used resins can be used, such as polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT), polyolefins such as polyethylene (PE), polypropylene (PP), and polystyrene (PS), polyamides (PA) such as nylon-6 and nylon-66, and polycarbonate (PC).

The resins constituting the substrate layer may be one type or a blend of two or more types, and additives may be added as needed to impart functionality, etc.

The substrate layer is preferably made from a pre-formed film. The film that serves as the substrate layer may be a film formed from the above-mentioned resins, etc., and may be unstretched or uniaxially or biaxially stretched. Of these, a biaxially stretched film is preferred.

In addition, oxides such as silicon oxide and aluminum oxide may be vapor-deposited onto the film that serves as the substrate layer.

Furthermore, the film that serves as the substrate layer may be a single layer or a laminate consisting of multiple layers.

<Thermosoft adhesive resin layer>
The heat-softenable adhesive resin layer is an essential constituent layer of the composite film of the present invention, and is disposed between the substrate layer and the heat-sealable layer.

(Thermosoftening adhesive resin)
The thermosoftenable adhesive resin constituting the thermosoftenable adhesive resin layer of the present invention has a crosslinked structure. There are no particular limitations on the material for forming the thermosoftenable adhesive resin, as long as it can form a crosslinked structure, be softened by heat, and form a resin layer having adhesive properties .

The thermosoftenable adhesive composition that serves as the material for forming the thermosoftenable adhesive resin may be, for example, an adhesive composition containing a base agent and a curing agent.

{Main ingredient}
The main agent constituting the adhesive composition, which is the material for forming the thermosoftening adhesive resin, is not particularly limited, but is preferably liquid at room temperature from the viewpoint of facilitating dry lamination onto the substrate layer. Examples of the polyol include polycarbonate polyol, polycaprolactone polyol, polyester polyol, polyether polyol, polyolefin polyol, acrylic polyol, silicone polyol, castor oil-based polyol, and fluorine-based polyol. The main agent may be used alone or in combination of two or more types.

Among these, polyester polyols or polyether polyols are preferably used, and from the viewpoint of rapid curing, at least one polyol selected from the group consisting of polyester polyurethane polyols and polyether polyurethane polyols is more preferred.

In particular, polyether polyols capable of forming an ether-based resin layer are suitable, and the polyether polyol may be polyether polyurethane polyol.

{Hardening agent}
The curing agent constituting the adhesive composition, which is a material for forming the thermosoftenable adhesive resin, is not particularly limited, but is preferably a curing agent that is liquid at room temperature from the viewpoint of facilitating dry lamination onto the base layer. Examples of the curing agent include polyisocyanate.

Examples of polyisocyanates include aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 2,6-diisocyanatomethyl caproate; 1,3-cyclopentane diisocyanate; and 1,4 Alicyclic diisocyanates such as cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), methyl 2,4-cyclohexane diisocyanate, methyl 2,6-cyclohexane diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, and 1,3-bis(isocyanatomethyl)cyclohexane; m-phenylene diisocyanate, p-phenylene diisocyanate, and 4,4-diphenyl diisocyanate. aromatic diisocyanates such as 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate or 2,6-tolylene diisocyanate or a mixture thereof, 4,4'-toluidine diisocyanate, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate; aromatic aliphatic diisocyanates such as 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, tetramethylxylylene diisocyanate or a mixture thereof, and ω,ω'-diisocyanato-1,4-diethylbenzene; Examples of polyisocyanate monomers include aromatic or araliphatic organic triisocyanates such as triphenylmethane-4,4'4"-triisocyanate, 1,3,5-triisocyanatobenzene, and 2,4,6-triisocyanatotoluene, and organic tetraisocyanates such as araliphatic tetraisocyanates such as 4,4'-diphenyldimethylmethane-2,2'-5,5'-tetraisocyanate. Polyisocyanates may be derivatives or adducts obtained by reacting these monomers with other compounds, or derivatives such as dimers and trimers derived from these monomers.

{Composition ratio of base agent and curing agent}
The composition ratio of the main agent and curing agent contained in the adhesive composition, which is the material for forming the thermosoftenable adhesive resin, may be, for example, 1 part by mass of the main agent to less than 0.2 parts by mass of the curing agent.

When the composition ratio of the base agent to the curing agent in the adhesive composition is 0.2 mass parts of curing agent per 1 mass part of base agent, a heat-softenable adhesive resin layer with high lamination strength at 70°C is formed between the substrate layer and the heat seal layer. As a result, the resulting composite film has reduced vapor release performance.

On the other hand, if the composition ratio of the base agent to the curing agent in the adhesive composition is less than 0.01 parts by mass of curing agent per 1 part by mass of base agent, a heat-softenable adhesive resin layer is formed that has low adhesive strength between the base layer and the heat-sealable layer. As a result, the resulting composite film has weak lamination strength at room temperature and may experience lamination lifting.

The composition ratio of the main agent and curing agent contained in the adhesive composition, which is the material that forms the thermosoftenable adhesive resin, may be 0.15 parts by mass or less, 0.125 parts by mass or less, 0.10 parts by mass or less, 0.075 parts by mass or less, or 0.05 parts by mass or less of the curing agent per 1 part by mass of the main agent.

On the other hand, the composition ratio of the main agent to the curing agent contained in the adhesive composition may be 0.01 parts by mass or more, 0.025 parts by mass or more, 0.05 parts by mass or more, 0.075 parts by mass or more, 0.10 parts by mass or more, 0.125 parts by mass or more, or 0.15 parts by mass or more of the curing agent per 1 part by mass of the main agent.

Among these, when the composition ratio of the main agent to the curing agent contained in the adhesive composition, which is the material that forms the heat-softenable adhesive resin, is more than 0.125 parts by mass and less than 0.2 parts by mass of curing agent per 1 part by mass of main agent, and when the composite film of the present invention has a half cut made from the heat seal layer side that reaches the heat-softenable adhesive resin layer, leakage of the adhesive composition from the half cut can be prevented during the processing of the composite film.

{Other ingredients}
The adhesive composition that forms the thermosoftenable adhesive resin may optionally contain other components in addition to the base agent and curing agent, such as a solvent, a component for imparting functionality to the resulting thermosoftenable adhesive resin layer, or an additive.

(Laminate strength)
The composite film of the present invention has a laminate strength between the substrate layer and the heat seal layer at 25°C of 1.3 N/15 mm or more, and a laminate strength between the substrate layer and the heat seal layer at 70°C of less than 0.6 N/15 mm.

By having a lamination strength of 1.3 N/15 mm or more at 25°C between the substrate layer and the heat seal layer, structures formed from the composite film of the present invention have sufficient strength at around room temperature, and peeling (lamination lifting) does not occur between the substrate layer and the heat seal layer during storage and handling.

The laminate strength at 25°C between the substrate layer and the heat seal layer may be 1.5 N/15 mm or more, 1.8 N/15 mm or more, 2.0 N/15 mm or more, 2.4 N/15 mm or more, 2.8 N/15 mm or more, or 3.0 N/15 mm or more.

On the other hand, the laminate strength at 25°C between the base layer and the heat seal layer may be 6.0 N/15 mm or less, 5.0 N/15 mm or less, 4.5 N/15 mm or less, 4.0 N/15 mm or less, 3.5 N/15 mm or less, or 3.0 N/15 mm or less.

Furthermore, because the lamination strength between the base material layer and the heat seal layer at 70°C is less than 0.6 N/15 mm, when a structure formed from the composite film of the present invention is heated, spaces are more likely to form in the heat-softenable adhesive resin layer, and steam can be transported through these spaces, thereby achieving steam release performance equivalent to that of conventional films.

The laminate strength at 70°C between the substrate layer and the heat seal layer may be 0.5 N/15 mm or less, 0.4 N/15 mm or less, 0.3 N/15 mm or less, 0.2 N/15 mm or less, 0.1 N/15 mm or less, or 0.05 N/15 mm or less.

On the other hand, the laminate strength at 70°C between the base layer and the heat seal layer may be 0.01 N/15 mm or more, 0.05 N/15 mm or more, 0.1 N/15 mm or more, 0.2 N/15 mm or more, 0.3 N/15 mm or more, 0.4 N/15 mm or more, or 0.5 N/15 mm or more.

The composite film of the present invention has a laminate strength between the base layer and the heat seal layer at 25°C that is greater than the laminate strength at 70°C. Therefore, when the composite film of the present invention is heated in a microwave oven or the like, the laminate strength between the base layer and the heat seal layer decreases, making it easier to form spaces in the softenable resin layer. Steam can then migrate through the formed spaces.

<Heat seal layer>
The heat seal layer is an essential constituent layer of the composite film of the present invention.

The heat seal layer is the layer that is heat-sealed when forming structures such as packaging bags and packages. For this reason, the heat seal layer is positioned so that it is the innermost layer of the composite film.

The material that constitutes the heat seal layer is not particularly limited, as long as it is heat-sealable and can provide sufficient sealing strength to the molded structure. Known materials can be used, such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), polypropylene (PP), ethylene-propylene copolymer (EP), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ionomer resin, and ethylene-vinyl acetate copolymer (EVA).

For example, when forming a structure such as a packaging bag filled with contents, the heat seal layer constituting the composite film of the present invention becomes the layer that forms the space for filling the contents. Therefore, when it is desired to impart resistance to contents, it is preferable to use, for example, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), etc.

The heat-seal layer may be formed using a film preformed from the above materials, or may be formed by melting and extruding the material for forming the heat-seal layer onto the surface of a laminate comprising a base layer, a heat-softenable adhesive resin layer, and, if necessary, other layers, and then cooling and solidifying the material.

The resins constituting the heat seal layer may be one type or a blend of two or more types, and additives may be added to impart functionality, etc., as needed.

Furthermore, the heat seal layer may be a single layer or may be composed of multiple layers.

The heat seal layer constituting the composite film of the present invention may have easy-peel properties (easy-to-open properties) so that the joint can be easily opened during use. For example, if a heat seal layer has easy-peel properties, when a lid material is formed from the composite film of the present invention and heat-sealed to a container body to form a package, the lid material can be easily opened to remove the contents.

(Half cut)
The composite film of the present invention may have a half cut that is made from the heat seal layer side and reaches the heat-softenable adhesive resin layer.

Here, a half cut refers to a cut that is formed in the thickness direction of the composite film but does not penetrate through the thickness direction of the composite film.

By providing half cuts in necessary locations, the composite film of the present invention allows steam to escape from the intended location when heated in a microwave oven or the like.

As described above, when a structure is formed from the composite film of the present invention, the heat seal layer is on the inside of the structure, i.e., it is the layer that comes into contact with the contents. Therefore, steam generated from the contents when heated penetrates the composite film in the thickness direction through the half cut.

At this time, if the half cut reaches the heat-softening adhesive resin layer, the steam generated from the contents will pass through the half cut and reach the heat-softening adhesive resin layer directly. As a result, the heat of the steam will directly heat the heat-softening adhesive resin layer, making it easier to soften than if it were indirectly heated.

Therefore, by providing half cuts in areas where steam needs to be released, the composite film of the present invention makes it possible to release steam from the intended location.

In the composite film 10 shown in Figure 1, the half cut C is made from the heat seal layer 3 side and reaches the surface of the heat-softenable adhesive resin layer 2.

The depth of the half cut may be up to the surface of the heat-softenable adhesive resin layer, or may extend to the interior of the heat-softenable adhesive resin layer, or may even penetrate the heat-softenable adhesive resin layer.

However, it is preferable that the half cut be deep enough not to reach the substrate layer, which is the outermost layer of the composite film. If the half cut reaches the substrate layer, the strength of the structure formed from the composite film may be reduced.

In particular, it is preferable that the half-cut be applied only to the heat-sealable layer. If the half-cut can be applied only to the heat-sealable layer, the effect of the half-cut can be enjoyed while the composite film has the highest strength.

The shape of the half cut may be either a continuous line or an intermittent line. There is no limit to the number of half cuts, as long as there is at least one. If multiple half cuts are provided, it is preferable that the half cuts be approximately parallel to each other.

Furthermore, the length of the half cut is not particularly limited. It may be long enough to be present only in areas where steam release is desired, or it may be evenly distributed throughout the entire composite film.

The method for forming the half cut is not particularly limited. For example, it may be created using a laser or the like after the composite film has been formed, or it may be created using a die cutter or the like from the heat seal layer side of a sheet containing a heat seal layer during the production of the composite film, and then laminated with other layers to form a composite film.

<Other demographics>
The composite film of the present invention may contain layers other than the substrate layer, the heat-softenable adhesive resin layer, and the heat-sealable layer as essential constituent layers.

The other layers are not particularly limited, and examples include a barrier layer to provide barrier properties, a reinforcing layer to increase strength, or an adhesive layer to bond layers together.

Barrier layers for imparting barrier properties include, for example, layers made of ethylene-vinyl alcohol copolymer (EVOH), nylon (NY), polyvinylidene chloride (PVDC), or polyacrylonitrile (PAN), which function to block gases such as oxygen and water vapor.

Examples of materials for the reinforcing layer to increase strength include paper, synthetic paper, and nonwoven fabric. These may be coated with an adhesive to provide adhesion to adjacent layers. It is also possible to provide a layer made of the material that makes up the base layer as a reinforcing layer, separate from the base layer.

Examples of adhesive layers used to bond layers together include layers made of ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), and ionomer.

The other layer may also be a layer made of adhesive used when dry laminating or hot melt laminating layers together.

The resins constituting the other layers may be one type or a blend of two or more types. Furthermore, additives may be added to impart functionality, etc., as needed.

<<Method for manufacturing composite film>>
The method for producing the composite film of the present invention is not particularly limited, and any known method can be used, such as dry lamination, hot melt lamination, extrusion lamination, and sandwich lamination.

For example, a laminate may be formed by adhering a film that will serve as the base layer and a film that will serve as the heat-sealable layer with an adhesive composition that will serve as the heat-softenable adhesive resin layer.

When this method is used, the coating amount of the adhesive composition for forming the thermosoftenable adhesive resin layer is not particularly limited, but may be, for example, 5.0 g/m2 or less, 4.5 g/ ^m2 or less, 4.0 g/m2 ^{or less} , 3.5 g/m2 or ^less , 3.0 g/m2 or ^less , 2.5 g/m2 ^or less, ^2.0 g/m2 or less, 1.5 g/m2 or ^less , or 1.0 g/ ^{m2 or} less, or may be 0.25 g/ ^m2 or more, 0.5 g/m2 or ^more , 0.75 g/ ^m2 or more, 1.0 g/m2 or ^more , or 1.5 g/m2 or ^more .

In particular, when the coating amount of the adhesive composition is less than 2.5 g/ ^m2 , if the composite film of the present invention has a half cut that is made from the heat seal layer side and reaches the heat-softenable adhesive resin layer, leakage of the adhesive composition from the half cut can be suppressed during the processing step of the composite film.

The method for manufacturing a composite film with half cuts is not particularly limited, but one example is to manufacture the composite film and then create the half cuts using a laser or the like.

Alternatively, half-cuts may be made during the production of the composite film, and the layer having the half-cut may be laminated with other layers to form a composite film. In this case, for example, a sheet including a heat-sealable layer may be cut using a rotary die cutter to penetrate the heat-sealable layer in the thickness direction (half-cut making process), and then a base layer and a heat-softenable adhesive resin layer may be laminated onto the sheet including the heat-sealable layer (lamination process), thereby producing a composite film.

<<Function of composite film>>
The function of the composite film of the present invention will be described below with reference to the drawings. Fig. 2 is a diagram showing a packaging bag according to one embodiment of the present invention. Fig. 3 is a schematic diagram of the packaging bag according to one embodiment of the present invention when steam is released.

There are no particular limitations on the structures formed using the composite film of the present invention. Because the composite film of the present invention has a heat-sealable layer as its innermost layer, various structures can be formed by heat-sealing the heat-sealable layers to each other, or by heat-sealing the heat-sealable layer to the flange portion of a flanged container body.

Figure 2 shows a packaging bag formed by heat-sealing the heat-sealed layers together. Figure 2 shows a packaging bag 100 in which the outer peripheries of the composite film 10 of the present invention having the half-cut C are heat-sealed together to form a sealed portion 4.

As shown in Figure 1, the composite film 10 is a laminate consisting of a base layer 1, a heat-softenable adhesive resin layer 2, and a heat-seal layer 3. As shown in Figure 2, each layer of the composite film 10 extends on an X-Y plane formed by the X and Y directions, and the Z direction (not shown) is the thickness direction of the composite film 10. In other words, Figure 2 is a top view of the packaging bag 100 as seen from the base layer 1 side.

In the composite film 10 constituting the packaging bag 100 shown in Figure 2, the half cuts C are provided in intermittent straight lines and are formed so as to cross the seal portion 4 of the packaging bag 100 from the inside to the outside of the packaging bag 100.

When such a packaging bag 100 is heated and steam is generated from the contents packed inside the packaging bag 100, the generated steam 5 is discharged to the outside of the packaging bag 100 from the location where the half cut C was made in the seal portion 4, as shown in Figure 2.

Here, we will explain using Figure 3 how steam 5 is discharged to the outside of the packaging bag 100 from the location where half-cut C was made in the sealed portion 4.

Figure 3 is a cross-sectional view of the composite film 10 in the Z direction (not shown). Figure 3 also shows the state in which the packaging bag 100 shown in Figure 2 is formed from the composite film 10 shown in Figure 1, and when the packaging bag 100 is heated and steam 5 is generated from the contents of the packaging bag 100, the heat-softenable adhesive resin layer 2 of the composite film 10 is softened by the steam 5.

The steam 5 generated inside the packaging bag 100 penetrates the composite film 10 in the thickness direction (Z direction) through the half cut C formed in the heat seal layer 3 of the composite film 10, and when it reaches the heat-softenable adhesive resin layer 2, it directly applies heat to the heat-softenable adhesive resin layer 2. This softens the heat-softenable adhesive resin layer 2 and makes it flexible.

The pressure inside the packaging bag 100 increases due to the pressure of the steam generated by the contents. As shown in Figure 3, the increase in internal pressure causes delamination between the softened heat-softenable adhesive resin layer 2 and the heat-sealable layer 3, and the heat-softenable adhesive resin layer 2 is lifted to the outside of the packaging bag 100 by the pressure of the steam 5, forming a space 6 in the delaminated area.

The steam 5 generated from the contents is then expelled from the inside to the outside of the packaging bag 100 through the space 6 that appears in the half-cut C area that crosses the seal portion 4, as shown in Figure 2.

<<Applications of composite film>>
The structure formed using the composite film of the present invention is not particularly limited.

For example, by heat-sealing the heat-sealable layers of the composite film of the present invention to one another, it is possible to form three-sided sealed bags, four-sided sealed bags, gusseted packaging bags, pillow packaging bags, Goebel-top-type bottomed containers, Tetra Classic (registered trademark), Brick Pack (registered trademark), tube containers, etc. Furthermore, a zipper can be provided on the heat-sealable layer to form a zippered packaging bag.

Alternatively, for example, a lid material can be formed from the composite film of the present invention and heat-sealed to the container body to create an openable package.

The following describes packaging bags and lid materials using the composite film of the present invention.

(packaging bag)
The packaging bag can be produced by heat-sealing the heat-sealable layers of the composite film of the present invention to each other to form a sealed portion.

At this time, half cuts may be made in the composite film, and the sealed portion where the heat-sealed layers are heat-fused together may be arranged so that the half cuts run across the packaging bag from the inside to the outside.

If the half cut crosses the sealed portion from the inside to the outside of the packaging bag, a space can be formed in the half cut portion to allow steam to pass through when the packaging bag is heated. Steam generated inside the packaging bag can then be discharged to the outside of the packaging bag through this space.

This type of packaging bag is suitable for use in packaging that requires heating, and is extremely useful, for example, as a packaging bag for use in a microwave oven.

(lid material)
The composite film of the present invention can also be used as a lid for sealing the top opening of the container body.

The container body can be sealed by heat-sealing the heat-seal layer of the composite film to the container body so that the top opening of the container is covered with a lid made of the composite film of the present invention, forming an openable joint.

If the top opening of the container has a flange, a container with a lid can be formed by heat-sealing the heat-seal layer of the lid material made of the composite film of the present invention to the flange of the container body to form an openable joint.

If the heat seal layer has easy-peel properties (easy-to-open properties), the resulting sealed container will be a container with a lid that is easy to open.

Alternatively, a half cut may be made in the composite film and the half cut may be positioned across the joint where the flange of the container body and the heat seal layer are heat-sealed, from the inside to the outside of the container body.

If the half-cut crosses the joint from the inside to the outside of the container body, a space is formed in the half-cut portion for steam to pass through when the sealed container is heated. Steam generated inside the sealed container can then be discharged to the outside of the sealed container through this space.

Such a lidded container can be ideally used as a lidded container for heating, and is extremely useful, for example, as a lidded container for use in a microwave oven.

The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to these.

<Materials>
In the examples and comparative examples, the following materials were prepared as materials for constituting the layers.

(1) Base layer PET#12: biaxially stretched PET film (Toyobo Ester (registered trademark) E5100, Toyobo Co., Ltd., thickness: 12 μm)
OPP #20: Biaxially stretched PP film (Pylen (registered trademark) P2161, Toyobo Co., Ltd., thickness: 20 μm)
Ny#15: Nylon film (Bonyl (registered trademark) RX, Kohjin Film & Chemicals Co., Ltd., thickness: 15 μm)

(2) Heat-softening adhesive resin layer: TM-396 (base resin)/CAT-22B (hardener) (Toyo-Morton Co., Ltd.)
Eliter (registered trademark) XP-1586 (Unitika Ltd.)

(3) Heat seal layer CPP#20: Unstretched PP film (Pylen (registered trademark) P1128, Toyobo Co., Ltd., thickness: 20 μm)
CPP #30: Unstretched PP film (Pylen (registered trademark) P1128, Toyobo Co., Ltd., thickness: 30 μm)
E1901T#50: Laminated PP film (Diffarene (registered trademark) E1901T, DIC Corporation, thickness: 50 μm)

Examples 1 to 4, Comparative Examples 1 to 6, and Reference Example 1
<Production of composite film>
A laminate was prepared by bonding a film to serve as a base layer and a film to serve as a heat-sealable layer with an adhesive composition that forms a heat-softenable adhesive resin layer using the materials shown in Table 1 or 2. The coating amount of the adhesive composition was 3.0 g/ ^m2 for each layer.

The film that would become the heat seal layer in the laminate was cut to penetrate the heat seal layer in the thickness direction (half-cut production process), and then a base layer and a heat-softenable adhesive resin layer were laminated onto the sheet containing the heat seal layer to obtain a composite film with a half cut.

<Measurement of Laminate Strength>
The composite films obtained in Examples 1 to 4, Comparative Examples 1 to 6, and Reference Example 1 were cut to a width of 15 mm, and the interlaminar strength between the base layer and the heat-sealing layer was measured in an atmosphere of 25°C and an atmosphere of 70°C. The measurements were carried out by T-peel at a rate of 300 mm/min, and the average value was calculated over a range of displacement from 20 to 50 mm. The results are shown in Table 1 or Table 2. In the tables, "material failure" means that the laminate strength was too high, causing the material to break during peeling, making it impossible to measure.

<Preparation of pouches>
Pillow bags with inner dimensions of 130 mm x 135 mm were produced using the composite films produced in Examples 1 to 4, Comparative Examples 1 to 6, and Reference Example 1. A paper wiper (Kimwipe (registered trademark), manufactured by Nippon Paper Crecia) impregnated with 10 cc of water was enclosed inside the pillow bag. The half-cut was placed in the sealed portion of the pillow bag, traversing the sealed portion from the inside to the outside of the packaging bag. The pillow bags were produced using an impulse sealer with heating for 0.9 seconds and cooling for 2.0 seconds.

<Evaluation of steam permeability of pouch>
The prepared pouches were reheated in a microwave oven (700W) for 60 seconds. At this time, it was visually confirmed whether steam inside the pouch was released from the heat-sealed portion. Each pouch was reheated five times in the microwave and evaluated according to the following criteria. The results are shown in Table 1 or Table 2.
○: Steam was emitted in all five tests.
×: Steam was not discharged at least once.

<Evaluation of pouch lamination>
Five pouches for each sample were prepared in the same manner as above and left to stand for one day in an atmosphere at 25°C. After leaving the pouches to stand, the presence or absence of lamination was visually confirmed and evaluated according to the following criteria. The results are shown in Table 1 or Table 2.
◯: No lamination was observed in any of the five pouches.
△: Lamination was observed in 1 to 3 pouches.
×: Lamination was observed in 4 to 5 pouches.

Examples 5 to 9 and Comparative Example 7
<Production of composite film>
A laminate was produced by bonding a film to serve as the base layer and a film to serve as the heat-sealable layer with an adhesive composition that forms a heat-softenable adhesive resin layer using the materials shown in Table 3. The coating amount of the adhesive composition was the amount shown in Table 3.

As in Example 1, a cut was made in the film that would become the heat seal layer in the laminate, penetrating the heat seal layer in the thickness direction (half-cut production process). Next, a base layer and a heat-softenable adhesive resin layer were laminated on the sheet containing the heat seal layer to obtain a composite film with a half cut.

<Measurement of Laminate Strength>
The interlaminar strength between the substrate layer and the heat seal layer was measured in the same manner as in Example 1. The results are shown in Table 3.

<Preparation of pouches>
In the same manner as in Example 1, a pillow bag having an inner dimension of 130 mm x 135 mm was prepared.

<Evaluation of steam permeability of pouch and evaluation of lamination separation of pouch>
The steam permeability of the pouch and the lamination separation of the pouch were evaluated in the same manner as in Example 1. The results are shown in Table 3.

<Evaluation of adhesive leakage from half cut>
In Examples 5 to 9 and Comparative Example 7, each raw roll of composite film was prepared in a 4000 m roll, and after aging, it was taken out and immediately rewound. During rewinding, it was checked whether any adhesive had leaked onto the roll or the like, and the results were evaluated according to the following criteria. The results are shown in Table 3.
○: No adhesive leakage was observed.
△: Slight leakage (does not affect processing)
×: Leakage of adhesive was observed.

REFERENCE SIGNS LIST 10 Composite film 1 Base material layer 2 Heat-softening adhesive resin layer 3 Heat-seal layer 4 Sealed portion 5 Steam 6 Space 100 Packaging bag C Half-cut

Claims (12)

A composite film in which at least a base layer, a heat-softenable adhesive resin layer, and a heat-sealable layer are laminated in this order,
the heat-softenable adhesive resin layer is made of a heat-softenable adhesive resin having a crosslinked structure,
The lamination strength between the base layer and the heat seal layer at 25°C is 1.3 N/15 mm or more,
The lamination strength between the base layer and the heat seal layer at 70°C is 0.6 N/15 mm or less, and
a half cut applied from the heat seal layer side and reaching the heat-softenable adhesive resin layer;
Composite film. The composite film according to claim 1, wherein the heat-softenable adhesive resin is formed from an adhesive composition containing less than 0.2 parts by mass of a curing agent per 1 part by mass of a base resin. The composite film according to claim 1, wherein the heat-softenable adhesive resin is formed from an adhesive composition containing more than 0.125 parts by mass and less than 0.2 parts by mass of a curing agent per 1 part by mass of a base resin. The composite film according to claim 2 or 3, wherein the heat-softenable adhesive resin layer is a layer in which the coating amount of the adhesive composition is less than 2.5 g/m ² . The composite film according to any one of claims 1 to 4, wherein the thermosoftenable adhesive resin is an ether-based resin. A packaging bag formed from the composite film according to any one of claims 1 to 5 , comprising a seal portion formed by heat-sealing the heat-sealing layers to each other,
The half cut crosses the seal portion from the inside to the outside of the packaging bag. The packaging bag according to claim 6 , which is suitable for use in a microwave oven. A lid material formed from the composite film according to any one of claims 1 to 5 for sealing an upper end opening of a container body,
The sealing is performed by heat-sealing the heat-seal layer to the container body so that the lid material covers the upper end opening, thereby forming an openable joint,
The half cut is arranged across the joint from the inside to the outside of the container body, a lid material. The lid material according to claim 8 , which is for use in a microwave oven. A container body;
A lid material formed from the composite film according to any one of claims 1 to 5 for sealing an upper end opening of the container body;
A container with an openable lid comprising:
The upper end opening of the container body has a flange,
the heat seal layer is heat sealed to the flange to form a releasable joint;
The half cut crosses the joint from the inside to the outside of the container body.
Openable container with lid. The container with lid according to claim 10 , which is suitable for use in a microwave oven. A method for producing the composite film according to any one of claims 1 to 5 ,
a half-cutting step of cutting the sheet including the heat-sealable layer by a rotary die cutter so as to penetrate the heat-sealable layer in a thickness direction;
a lamination step of laminating the base material layer and/or the heat-softenable adhesive resin layer on the sheet including the heat-sealable layer after the half-cut preparation step,
A method for manufacturing a composite film.