JP7133139B2 - Laminate and bag composed of the laminate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laminate and a bag composed of the laminate.

BACKGROUND ART Conventionally, many bags made of plastic laminates filled and sealed with cooked or semi-cooked liquids, viscous substances, or mixtures of liquids and solids have been on the market. In the bag, the non-sealed portion where the laminated bodies are not joined constitutes the storage portion in which the contents are stored. Moreover, the sealing portion where the stacked bodies are joined together seals the accommodating portion. The contents are, for example, cooked foods such as curries, stews, and soups. The contents are heated by a microwave oven or the like while being accommodated in the bag.

By the way, when the contents contained in the sealed bag are heated using a microwave oven, the moisture contained in the contents evaporates with the heating, and the pressure in the container increases. If the pressure in the containing portion of the bag increases, the bag may burst, causing the contents to scatter and contaminate the inside of the microwave oven. In consideration of such problems, for example, Patent Literature 1 proposes to provide a mechanism for automatically communicating the storage portion with the outside when the pressure in the storage portion increases to release the steam in the storage portion to the outside. ing. In addition, in Patent Document 1, in order to provide the bag with resistance to heating, as a laminate constituting the bag, a stretched polyethylene terephthalate film, a silica-deposited stretched polyethylene terephthalate film, an alumina-deposited stretched polyethylene terephthalate film, a stretched nylon film, and a stretched polyethylene terephthalate film. It is proposed to use a polypropylene film, a polypropylene/ethylene-vinyl alcohol copolymer co-extruded co-stretched film, or a composite film in which two or more of these films are laminated.

JP 2015-120550 A

As a result of intensive studies by the inventors of the present invention, it has been found that there are cases where sufficient heat resistance cannot be achieved depending on the laminate constituting the conventional bag.

The present invention has been made in consideration of such points, and an object of the present invention is to provide a laminate having heat resistance.

The present invention provides a laminate comprising at least a first stretched plastic film, a second stretched plastic film, a third stretched plastic film and a sealant layer in this order, wherein the first stretched plastic film and the second stretched plastic film are provided. and the third stretched plastic film contain polyester or polyamide as a main component, and at least one of the first stretched plastic film, the second stretched plastic film, and the third stretched plastic film contains polyester. It is a laminate containing as a main component and at least one of the others containing a polyamide as a main component.

The laminate according to the present invention comprises a first adhesive layer positioned between the first stretched plastic film and the second stretched plastic film, and between the second stretched plastic film and the third stretched plastic film. a second adhesive layer positioned between said third stretched plastic film and said sealant layer; said first adhesive layer, said second adhesive layer and Each of the third adhesive layers may contain a cured product of a polyol and an isocyanate compound and have a thickness of 2 μm or more.

In the laminate according to the present invention, A1 is the product of the thickness and thermal conductivity of the first stretched plastic film, A2 is the product of the thickness and thermal conductivity of the second stretched plastic film, and A2 is the product of the thickness and thermal conductivity of the third stretched plastic film. Let A3 be the product of thickness and thermal conductivity, B1 be the product of thickness and thermal conductivity of the first adhesive layer, B2 be the product of thickness and thermal conductivity of the second adhesive layer, and B2 be the product of thickness and thermal conductivity of the second adhesive layer. When the product of the thickness of the adhesive layer and the thermal conductivity is B3, the following formula may hold.
A1+A2+A3<B1+B2+B3

In the laminate according to the present invention, the sealant layer may contain polypropylene.

In the laminate according to the present invention, the sealant layer may contain a propylene/ethylene block copolymer.

In the laminate according to the present invention, the first stretched plastic film and the third stretched plastic film may contain polyester as a main component, and the second stretched plastic film may contain polyamide as a main component. Alternatively, the first stretched plastic film and the second stretched plastic film may contain polyester as a main component, and the third stretched plastic film may contain polyamide as a main component. Alternatively, the second stretched plastic film and the third stretched plastic film contain polyester as a main component,
The first stretched plastic film may contain polyamide as a main component.

The present invention is a bag, comprising a laminate including an outer surface and an inner surface, and a seal portion for joining the inner surfaces of the laminate, wherein the laminate is arranged in a first order from the outer surface side to the inner surface side. At least a stretched plastic film, a second stretched plastic film, a third stretched plastic film, and a sealant layer are provided in this order, and the first stretched plastic film, the second stretched plastic film, and the third stretched plastic film are all made of polyester or containing polyamide as a main component, at least one of the first stretched plastic film, the second stretched plastic film and the third stretched plastic film containing polyester as a main component, and at least one of the others comprising A bag containing polyamide as a main component.

ADVANTAGE OF THE INVENTION According to this invention, the laminated body which has heat resistance can be provided.

It is a front view showing a bag in an embodiment of the invention. FIG. 2 is a cross-sectional view showing the bag shown in FIG. 1 as viewed along line III-III; FIG. 2 is a cross-sectional view showing an example of the layer structure of a laminate that constitutes a bag; FIG. 4 is a cross-sectional view showing an example of how heat is transferred from the inner surface side to the outer surface side of a laminate; 1 is a cross-sectional view showing an example of the layer structure of a stretched plastic film containing polyamide as a main component; FIG. It is a figure which shows an example of the measuring method of a puncture strength. FIG. 2 is a plan view showing a test piece for evaluating impact strength; FIG. 8 is a cross-sectional view of the test piece shown in FIG. 7; It is a figure which shows an example of the measuring method of impact strength. FIG. 2 is a diagram showing evaluation results of Examples 1 to 7 and Comparative Examples 1 and 2;

An embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. In addition, in the drawings attached to this specification, for convenience of illustration and easy understanding, the scale, the ratio of length and width, etc. are appropriately changed and exaggerated from those of the real thing.

In addition, the terms such as "parallel", "perpendicular", "same" and the like, length and angle values, etc. that specify shapes and geometric conditions and their degrees used in this specification are strictly It shall be interpreted to include the extent to which similar functions can be expected without being bound by the meaning.

FIG. 1 is a front view showing a bag 10 according to this embodiment. The bag 10 includes a containing portion 17 containing contents. Note that FIG. 1 shows the bag 10 before it is filled with contents. The bag 10 according to the present embodiment is configured so as to be suitable for use as a pouch for microwave ovens whose contents are heated by a microwave oven.

As shown in FIG. 1, the bag 10 according to the present embodiment includes a steam release mechanism 20 for releasing steam generated when the contents contained in the bag 10 are heated. The steam venting mechanism 20 allows the inside and outside of the bag 10 to communicate with each other to release the steam when the pressure of the steam exceeds a predetermined value, and suppresses the steam from escaping from places other than the steam venting mechanism 20. ,It is configured. The configuration of the bag 10 will be described below.

Bag In the present embodiment, the bag 10 is a gusseted bag that can stand on its own. The bag 10 includes an upper portion 11, a lower portion 12 and side portions 13 and has a generally rectangular profile in front view. The terms "upper", "lower" and "side", as well as terms such as "upper" and "lower" are based on the bag 10 standing on its own with the gussets down. It is merely a relative representation of the positions and directions of 10 and its components. The posture of the bag 10 during transportation and use is not limited by the names and terms used in this specification.

As shown in FIG. 1 , the bag 10 includes a surface film 14 forming the front surface, a back film 15 forming the back surface, and a lower film 16 forming the lower portion 12 . The lower film 16 is arranged between the surface film 14 and the back film 15 while being folded back at the folding portion 16f.

The terms "surface film", "back surface film", and "lower film" described above merely refer to sections of each film according to their positional relationship, and the method of providing the films when manufacturing the bag 10 is as follows: Do not be limited by the above terms. For example, the bag 10 may be manufactured using one film in which the surface film 14, the back film 15, and the bottom film 16 are continuously provided, or one film in which the surface film 14 and the bottom film 16 are continuously provided. It may be manufactured using a total of two films, a film and a backing film 15, or a total of three films, one fronting film 14, one backing film 15, and one bottom film 16. may be manufactured using

The inner surfaces of the surface film 14, the back film 15, and the lower film 16 are joined to each other by sealing portions. In the plan view of the bag 10 such as FIG. 1, the sealing portion is hatched.

As shown in FIG. 1 , the seal portion has an outer edge seal portion extending along the outer edge of the bag 10 and a steam release seal portion 20 a that constitutes the steam release mechanism 20 . The outer edge seal portion includes a lower seal portion 12 a extending over the lower portion 12 and a pair of side seal portions 13 a extending along the pair of side portions 13 . As shown in FIG. 1, the upper portion 11 of the bag 10 is an opening 11b before the bag 10 is filled with contents. After the contents are contained in the bag 10, the inner surface of the surface film 14 and the inner surface of the back film 15 are joined at the upper portion 11 to form an upper sealing portion and seal the bag 10. As shown in FIG.

The side seal portion 13a, the steam release seal portion 20a and the upper seal portion are seal portions formed by joining the inner surface of the surface film 14 and the inner surface of the back film 15 together. On the other hand, the lower seal portion 12a is formed by joining the inner surface of the front film 14 and the inner surface of the lower film 16 together, and by joining the inner surface of the back film 15 and the inner surface of the lower film 16 together. including a configured seal.

As long as the opposing films can be joined together to seal the bag 10, the method for forming the seal portion is not particularly limited. For example, the inner surface of the film may be melted by heating and the inner surfaces may be welded to each other, that is, by heat sealing to form the sealed portion. Alternatively, the sealing portion may be formed by bonding the inner surfaces of the films facing each other using an adhesive or the like.

Steam Release Mechanism The configuration of the steam release mechanism 20 will be described below. FIG. 2 is a cross-sectional view showing the vapor release mechanism 20 of the bag 10 shown in FIG. 1 as viewed along line II-II.

The steam release seal portion 20a of the steam release mechanism 20 has a shape that is easily peeled off as the pressure of the housing portion 17 increases. For example, the steam release seal portion 20a has a shape protruding toward the inside of the bag 10 from the side seal portion 13a. As a result, the force applied to the steam release seal portion 20a when the pressure in the housing portion 17 increases can be made larger than the force applied to the side seal portion 13a. Further, the width of the steam release seal portion 20a is smaller than the width of the side seal portion 13a. 1 and 2, a non-sealed portion 20b is formed between the steam release seal portion 20a and the outer edge of the side portion 13. As shown in FIGS. Accordingly, communication between the housing portion 17 and the outside due to peeling of the seal portion can be more easily generated in the vapor release seal portion 20a than in the side seal portion 13a. Note that the structure and arrangement of the vapor release mechanism 20 are limited to the examples shown in FIGS. no.

Layer Structure of Front Film and Back Film Next, the layer structure of the front film 14 and the back film 15 will be described. FIG. 3 is a cross-sectional view showing an example of the layer structure of a laminate 30 that constitutes the surface film 14 and the back film 15. As shown in FIG.

As shown in FIG. 3, the laminate 30 includes a first stretched plastic film 40, a first adhesive layer 45, a second stretched plastic film 50, a second adhesive layer 55, a third stretched plastic film 60, and a third adhesive. At least an agent layer 65 and a sealant layer 70 are provided in this order. The first stretched plastic film 40 is positioned on the outer surface 30y side, and the sealant layer 70 is positioned on the inner surface 30x side opposite to the outer surface 30y. The inner surface 30x is a surface located on the housing portion 17 side.

Each layer of the laminate 30 will be described in detail below.

(stretched plastic film)
The first stretched plastic film 40, the second stretched plastic film 50 and the third stretched plastic film 60 are all plastic films stretched in a predetermined direction. Each of the stretched plastic films 40, 50, 60 may be a uniaxially stretched film stretched in one predetermined direction, or a biaxially stretched film stretched in two predetermined directions. The stretching direction of each stretched plastic film 40, 50, 60 is not particularly limited. For example, the stretched plastic films 40, 50, 60 may be stretched in the direction in which the side portion 13 extends, or may be stretched in the direction orthogonal to the direction in which the side portion 13 extends. The stretching directions of the stretched plastic films 40, 50, 60 may be the same or different. The stretch ratio of each stretched plastic film 40, 50, 60 is, for example, 1.05 times or more.

Each stretched plastic film 40, 50, 60 contains polyester or polyamide as a main component. In this embodiment, an example will be described in which the first stretched plastic film 40 and the third stretched plastic film 60 contain polyester as a main component, and the second stretched plastic film 50 contains polyamide as a main component. Other combinations are also possible. For example, the first stretched plastic film 40 and the second stretched plastic film 50 may contain polyester as a main component, and the third stretched plastic film 60 may contain polyamide as a main component. Alternatively, the second stretched plastic film 50 and the third stretched plastic film 60 may contain polyester as a main component, and the first stretched plastic film 40 may contain polyamide as a main component.

The characteristics of the stretched plastic film containing polyester as the main component and the characteristics of the stretched plastic film containing polyamide as the main component will be described below. In the following description, a stretched plastic film containing polyester as a main component is also referred to as a stretched polyester film. A stretched plastic film containing polyamide as a main component is also referred to as a stretched polyamide film.

[Stretched polyester film]
The stretched polyester film contains, for example, 51% by mass or more of polyester. Examples of polyester include polyethylene terephthalate (hereinafter also referred to as PET) and polybutylene terephthalate (hereinafter also referred to as PBT). In addition, 51% by mass or more of polyester in the stretched polyester film may be composed of one type of polyester, or may be composed of two or more types of polyester.

The thickness of the oriented polyester film is preferably 9 μm or more, more preferably 12 μm or more. Also, the thickness of the stretched polyester film is preferably 25 μm or less, more preferably 20 μm or less. By setting the thickness of the stretched polyester film to 9 μm or more, the stretched polyester film has sufficient strength. Further, by setting the thickness of the stretched polyester film to 25 μm or less, the stretched polyester film exhibits excellent moldability. Therefore, the process of manufacturing the bag 10 by processing the laminate 30 can be efficiently carried out.

The present embodiment aims to provide a laminate 30 having heat resistance. As one method for increasing the heat resistance of the laminate 30, it is conceivable to configure each layer of the laminate 30 using a material having a thermal conductivity equal to or higher than a predetermined value. For example, the thermal conductivity of the material constituting the stretched polyester film is preferably 0.05 W/m·K or more, more preferably 0.1 W/m·K or more. The thermal conductivity of PET is, for example, 0.14 W/m·K. Moreover, the thermal conductivity of PBT is higher than that of PET, and is, for example, 0.25 W/m·K.

The melting point of the oriented polyester film is preferably 200°C or higher, more preferably 220°C or higher. By setting the melting point of the stretched polyester film to 220° C. or higher, when the content contained in the bag 10 manufactured using the laminate 30 is heated, the stretched polyester film is not perforated or the stretched polyester film is heated. It is possible to suppress the formation of wrinkles on the

[Stretched polyamide film]
The stretched polyamide film contains, for example, 51% by mass or more of polyamide. Examples of polyamide systems include aliphatic polyamides or aromatic polyamides. Aliphatic polyamides include nylons such as nylon-6, nylon-6,6, and copolymers of nylon 6 and nylon 6,6, and aromatic polyamides include poly-meta-xylene adipamide ( MXD6) and the like. The puncture strength of the laminate 30 can be increased by providing the laminate with a stretched plastic film configured as a stretched polyamide film.

The thickness of the stretched polyamide film is preferably 12 μm or more, more preferably 15 μm or more. Also, the thickness of the stretched polyamide film is preferably 25 μm or less, more preferably 20 μm or less. The thermal conductivity of the stretched polyamide film is preferably 0.25 W/m·K or more, more preferably 0.3 W/m·K or more. The thermal conductivity of nylon is, for example, 0.35 W/m·K. The melting point of the stretched polyamide film is preferably 170°C or higher, more preferably 210°C or higher.

The stretched polyamide film may be composed of a single layer or multiple layers. If the oriented polyamide film comprises multiple layers, the oriented polyamide film is, for example, a coextruded film made by coextrusion. A second stretched plastic film 50 made of a stretched polyamide film produced by coextrusion comprises, for example, as shown in FIG. It includes two layers 52 and a third layer 53 of polyester such as PET. In addition, when the mass of the second layer 52 made of polyamide such as nylon is 51% or more of the mass of the entire stretched plastic film such as the second stretched plastic film 50, the stretched plastic film produced by co-extrusion is the main component. can be said to be a polyamide.

(First adhesive layer)
The first adhesive layer 45 contains an adhesive for bonding the first stretched plastic film 40 and the second stretched plastic film 50 by a dry lamination method. The adhesive constituting the first adhesive layer 45 is produced from an adhesive composition prepared by mixing a first composition containing a main agent and a solvent and a second composition containing a curing agent and a solvent. Specifically, the adhesive includes a cured product produced by reacting the main agent and solvent in the adhesive composition.

Examples of adhesives include polyurethane and the like. Polyurethane is a cured product produced by reacting a polyol as a main agent with an isocyanate compound as a curing agent. Examples of polyurethanes include polyether polyurethanes, polyester polyurethanes, and the like. A polyether polyurethane is a cured product produced by reacting a polyether polyol as a main agent with an isocyanate compound as a curing agent. A polyester polyurethane is a cured product produced by reacting a polyester polyol as a main agent with an isocyanate compound as a curing agent.

Examples of isocyanate compounds include aromatic isocyanate compounds such as tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), and xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and the like. or adducts or polymers of the various isocyanate compounds described above can be used.

The material forming the first adhesive layer 45 preferably has a higher thermal conductivity than the materials forming the first stretched plastic film 40 , the second stretched plastic film 50 , the third stretched plastic film 60 and the sealant layer 70 . have. For example, the thermal conductivity of the material forming the first adhesive layer 45 is preferably 1.0 W/m·K or more, more preferably 3.0 W/m·K or more. The thermal conductivity of polyurethane is in the range of 3.0 W/m·K to 5.0 W/m·K, for example 5.0 W/m·K. Due to the high thermal conductivity of the material forming the first adhesive layer 45 , when the bag 10 manufactured using the laminate 30 is heated, the heat generated in the housing portion 17 is transferred to the inner surface 30 x of the laminate 30 . It becomes easy to diffuse the heat in the surface direction of the laminate 30 while the heat is transferred from the side to the outer surface 30y side. As a result, the heat dissipation of the laminate 30 can be enhanced, so that the temperature rise of the laminate 30 can be suppressed. As a result, it is possible to prevent the laminate 30 from being damaged by heat when the bag 10 is heated. That is, the heat resistance of the laminate 30 can be enhanced.

The thickness of the first adhesive layer 45 is preferably 2 μm or more, more preferably 3 μm or more. Also, the thickness of the first adhesive layer 45 is preferably 6 μm or less, more preferably 5 μm or less. By setting the thickness of the first adhesive layer 45 to 3 μm or more, heat diffusion in the surface direction of the laminate 30 is more likely to occur.

(Second adhesive layer)
The second adhesive layer 55 contains an adhesive for bonding the second stretched plastic film 50 and the third stretched plastic film 60 by dry lamination. An example of the adhesive for the second adhesive layer 55 is polyurethane or the like, as in the case of the first adhesive layer 45 . In addition to the configuration, materials, and characteristics described below, the configuration, materials, and characteristics of the second adhesive layer 55 may be the same as those of the first adhesive layer 45 .

As with the first adhesive layer 45, the material constituting the second adhesive layer 55 preferably includes the first stretched plastic film 40, the second stretched plastic film 50, the third stretched plastic film 60 and the sealant layer 70. It has a higher thermal conductivity than the material of which it is composed. For example, the thermal conductivity of the material forming the second adhesive layer 55 is preferably 1.0 W/m·K or more, more preferably 3.0 W/m·K or more.

The thickness of the second adhesive layer 55 is preferably 2 μm or more, more preferably 3 μm or more. Also, the thickness of the second adhesive layer 55 is preferably 6 μm or less, more preferably 5 μm or less.

(Third adhesive layer)
The third adhesive layer 65 contains an adhesive for bonding the third stretched plastic film 60 and the sealant layer 70 together. Examples of the adhesive for the third adhesive layer 65 include polyurethane, as in the case of the first adhesive layer 45 . In addition to the configuration, materials, and characteristics described below, the configuration, materials, and characteristics of the third adhesive layer 65 may be similar to those of the first adhesive layer 45 .

As with the first adhesive layer 45, the material constituting the second adhesive layer 55 preferably includes the first stretched plastic film 40, the second stretched plastic film 50, the third stretched plastic film 60 and the sealant layer 70. It has a higher thermal conductivity than the material of which it is composed. For example, the thermal conductivity of the material forming the third adhesive layer 65 is preferably 1.0 W/m·K or more, more preferably 3.0 W/m·K or more.

The thickness of the third adhesive layer 65 is preferably 2 μm or more, more preferably 3 μm or more. Also, the thickness of the third adhesive layer 65 is preferably 6 μm or less, more preferably 5 μm or less.

By the way, as mentioned above, aromatic isocyanate compounds and aliphatic isocyanate compounds exist as isocyanate compounds that constitute curing agents for adhesives. Among them, the aromatic isocyanate compound elutes components that cannot be used for food applications under high-temperature environments such as heat sterilization. By the way, the third adhesive layer 65 is in contact with the sealant layer 70 . Therefore, when the third adhesive layer 65 contains an aromatic isocyanate compound, the components eluted from the aromatic isocyanate compound will not adhere to the contents accommodated in the accommodation portion 17 in contact with the sealant layer 70. There is

In consideration of such problems, preferably, the adhesive constituting the third adhesive layer 65 is a cured product produced by reacting a polyol as a main agent and an aliphatic isocyanate compound as a curing agent. Use As a result, the third adhesive layer 65 can prevent components that cannot be used for food from adhering to the contents.

(Relational expression)
Next, the relational expressions established between the stretched plastic films 40, 50, 60 and the adhesive layers 45, 55, 65 will be described. In the laminated body 30, preferably, the following relational expression holds.
A1+A2+A3<B1+B2+B3
A1 is the product of the thickness of the first stretched plastic film 40 and the thermal conductivity.
A2 is the product of the thickness of the second stretched plastic film 50 and the thermal conductivity.
A3 is the product of the thickness of the third stretched plastic film 60 and the thermal conductivity.
B1 is the product of the thickness of the first adhesive layer 45 and the thermal conductivity.
B2 is the product of the thickness of the second adhesive layer 55 and the thermal conductivity.
B3 is the product of the thickness of the third adhesive layer 65 and the thermal conductivity.

The above relational expression means that the adhesive layers 45 , 55 , 65 have higher thermal conductivity in the plane direction of the laminate 30 than the stretched plastic films 40 , 50 , 60 . As a result, when the contents contained in the bag 10 are heated, it is possible to prevent the laminate 30 from being damaged by the heat. Examples of damage caused to the layered body 30 by the influence of heat include the formation of holes in the layered body 30 and the formation of wrinkles in the layered body 30 .

The reason why the damage caused by heat can be suppressed by satisfying the above relational expression will be considered. In addition, the reason for such action is not limited to the following considerations, and other considerations may also be adopted.

FIG. 5 is a diagram showing a state in which the contents 18 are attached to the inner surface 30x of the laminate 30 that constitutes the bag 10. As shown in FIG. The content 18 adheres to the inner surface 30x, for example, when the content 18 contained in the bag 10 is heated using a microwave oven, part of the content 18 jumps and reaches the inner surface 30x. obtain. When the content 18 adhering to the inner surface 30x is further heated, the temperature of the layered body 30 in contact with the content 18 also rises, and the layered body 30 may be perforated or wrinkled. can be considered.

Here, in the present embodiment, the laminate 30 is configured so that the above-described relational expression holds. The laminate 30 also comprises three or more stretched plastic films 40,50,60 and adhesive layers 45,55,65. Therefore, as shown in FIG. 5, while the heat generated in the content 18 is transferred from the inner surface 30x side of the laminate 30 to the outer surface 30y side, the heat is transferred particularly to the adhesive layers 45, 55, 65. It becomes easier to diffuse in the surface direction of the body 30 . As a result, heat can be easily released to the outside of the bag 10, so that temperature rise in the portion of the laminate 30 to which the contents 18 are attached can be suppressed. As a result, it is possible to prevent the laminated body 30 from being damaged by heat. That is, the heat resistance of the laminate 30 can be enhanced.

B1+B2+B3 is preferably 3.5 times or more, more preferably 4.0 times or more, still more preferably 4.5 times or more of A1+A2+A3.

(sealant layer)
Next, the sealant layer 70 will be described. As a material constituting the sealant layer 70, one or two or more resins selected from polyethylene such as low-density polyethylene, linear low-density polyethylene, and polypropylene can be used. The sealant layer 70 may be a single layer or multiple layers. Moreover, the sealant layer 70 preferably consists of an unstretched film. The term "unstretched" is a concept including not only films that are not stretched at all but also films that are slightly stretched due to the tension applied during film formation.

The bag 10 composed of the laminate 30 is subjected to sterilization treatment such as boiling treatment and retort treatment at a high temperature. Therefore, the sealant layer 70 used has heat resistance to withstand these high-temperature treatments.

The melting point of the material forming the sealant layer 70 is preferably 150° C. or higher, more preferably 160° C. or higher. By increasing the melting point of the sealant layer 70, the retort treatment of the bag 10 can be performed at a high temperature, thereby shortening the time required for the retort treatment. The melting point of the material forming the sealant layer 70 is lower than the melting point of the resin forming the stretched plastic films 40 , 50 , 60 .

From the viewpoint of retort treatment, a material containing propylene as a main component can be used as the material constituting the sealant layer 70 . Here, the material "mainly composed of propylene" means a material having a propylene content of 90% by mass or more. Specific examples of materials containing propylene as a main component include polypropylenes such as propylene/ethylene block copolymers, propylene/ethylene random copolymers, and homopolypropylenes, and mixtures of polypropylene and polyethylene. can be done. Here, "propylene/ethylene block copolymer" means a material having a structural formula shown in formula (I) below. Further, the “propylene/ethylene random copolymer” means a material having the structural formula shown in formula (II) below. Further, "homopolypropylene" means a material having a structural formula shown in formula (III) below.

When a mixture of polypropylene and polyethylene is used as the propylene-based material, the material may have a sea-island structure. Here, the "sea-island structure" refers to a structure in which polyethylene is discontinuously dispersed within a region in which polypropylene is continuous.

When considered in terms of boiling treatment, examples of materials that may be used to form the sealant layer 70 include polyethylene, polypropylene, or combinations thereof. Examples of polyethylene include medium density polyethylene, linear low density polyethylene, or combinations thereof. For example, it is also possible to use the materials listed as the materials constituting the sealant layer 70 from the viewpoint of the retort treatment described above. The material forming the sealant layer 70 has a melting point of, for example, 100° C. or higher, more preferably 105° C. or higher, and even more preferably 110° C. or higher. When polyethylene is used as the material constituting the sealant layer 70, a melting point of 100° C. or higher can be achieved, for example, when polyethylene has a density of 0.920 g/cm ³ or higher. Specific examples of the sealant film for constituting the sealant layer 70 having a melting point of 100° C. or higher include TUX-HC manufactured by Mitsui Chemicals Tohcello, L6101 manufactured by Toyobo, and LS700C manufactured by Idemitsu Unitech. A specific example of the sealant film for constituting the sealant layer 70 having a melting point of 105° C. or higher is NB-1 manufactured by Tamapoly. Specific examples of the sealant film for constituting the sealant layer 70 having a melting point of 110° C. or higher include LS760C manufactured by Idemitsu Unitech and TUX-HZ manufactured by Mitsui Chemicals Tohcello.

Preferably, sealant layer 70 is a single layer film comprising a propylene-ethylene block copolymer. For example, the sealant film including the sealant layer 70 is a single-layer unstretched film whose main component is a propylene/ethylene block copolymer. By using the propylene/ethylene block copolymer, the impact resistance of the sealant film can be enhanced, thereby suppressing the breakage of the bag 10 due to the impact when dropped. In addition, the stab resistance of the laminate 30 can be enhanced.

Further, by using the propylene/ethylene block copolymer, the strength of the seal portion constituted by the sealant layer 70 (hereinafter also referred to as hot seal strength) at a high temperature, for example, 100° C. or higher is lower than that at a low temperature. , for example, the sealing strength at room temperature is extremely small. For example, the hot seal strength at 100° C. is one-third or less, preferably one-fourth or less of the seal strength at 25° C. (hereinafter also referred to as normal temperature seal strength). For example, the hot seal strength at 100° C. at a width of 15 mm is 30 N or less, preferably 25 N or less, more preferably 20 N or less, still more preferably 15 N or less. In addition, the normal temperature sealing strength at 25° C. at a width of 15 mm is 23 N or more, preferably 40 N or more, more preferably 50 N or more, and still more preferably 60 N or more. Since the hot seal strength is low, when the bag 10 is heated using a microwave oven, the steam release seal portion 20a is easily peeled off, and the steam in the containing portion 17 is easily released to the outside of the bag 10.例文帳に追加Therefore, it is possible to prevent the internal pressure of the accommodating portion 17 from becoming excessively high, thereby preventing damage to the laminate 30 during heating. Seal strength can be measured according to JIS Z1707 7.5. As a measuring instrument, for example, a tensile tester with thermostat RTC-1310A manufactured by Orientec Co., Ltd. can be used.

The propylene/ethylene block copolymer includes, for example, a sea component made of polypropylene and an island component made of an ethylene/propylene copolymer rubber component. The sea component can contribute to enhancing blocking resistance, heat resistance, rigidity, seal strength, etc. of the propylene/ethylene block copolymer. Also, the island component can contribute to increasing the impact resistance of the propylene/ethylene block copolymer. Therefore, by adjusting the ratio of the sea component and the island component, the mechanical properties of the sealant film 70 containing the propylene-ethylene block copolymer can be adjusted.

In the propylene/ethylene block copolymer, the mass ratio of the sea component made of polypropylene is higher than the mass ratio of the island component made of the ethylene/propylene copolymer rubber component. For example, in a propylene/ethylene block copolymer, the mass ratio of the sea component made of polypropylene is at least 51% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more.

The single-layer sealant film 70 may further contain a second thermoplastic resin in addition to the first thermoplastic resin made of a propylene-ethylene block copolymer. Examples of the second thermoplastic resin include α-olefin copolymers and polyethylene. The α-olefin copolymer is, for example, linear low density polyethylene. Examples of polyethylene include low density polyethylene, medium density polyethylene and high density polyethylene. The second thermoplastic resin can contribute to increasing the impact resistance of the sealant film 70 .

Low-density polyethylene is polyethylene having a density of 0.910 g/cm ³ or more and 0.925 g/cm ³ or less. Medium density polyethylene is polyethylene having a density of 0.926 g/cm ³ or more and 0.940 g/cm ³ or less. High-density polyethylene is polyethylene having a density of 0.941 g/cm ³ or more and 0.965 g/cm ³ or less. Low-density polyethylene is obtained by polymerizing ethylene at a high pressure of, for example, 1000 atmospheres or more and less than 2000 atmospheres. Medium-density polyethylene and high-density polyethylene are obtained by polymerizing ethylene at a medium or low pressure of 1 atmosphere or more and less than 1000 atmospheres, for example.

The medium-density polyethylene and the high-density polyethylene may partially contain a copolymer of ethylene and α-olefin. Also, even when ethylene is polymerized at medium or low pressure, medium or low density polyethylene can be produced if it contains a copolymer of ethylene and an α-olefin. Such polyethylene is referred to as the linear low density polyethylene mentioned above. Linear low-density polyethylene is obtained by copolymerizing an α-olefin into a linear polymer obtained by polymerizing ethylene at medium or low pressure to introduce short chain branches. Examples of α-olefins include 1-butene (C ₄ ), 1-hexene (C ₆ ), 4-methylpentene (C ₆ ), 1-octene (C ₈ ), and the like. The density of linear low-density polyethylene is, for example, 0.915 g/cm ³ or more and 0.945 g/cm ³ or less.

The α-olefin copolymer that constitutes the second thermoplastic resin of the propylene/ethylene block copolymer is not limited to the linear low-density polyethylene described above. An α-olefin copolymer means a material having a structural formula shown in formula (IV) below.

Ｒ_１、Ｒ_２はいずれも、Ｈ（水素原子）、又はＣＨ_３、Ｃ_２Ｈ_５などのアルキル基である。また、ｊ及びｋはいずれも、１以上の整数である。また、ｊはｋよりも大きい。すなわち、式（IV）に示すα－オレフィン共重合体においては、Ｒ_１を含む左側の構造がベースとなる。Ｒ_１は例えばＨであり、Ｒ_２は例えばＣ_２Ｈ_５である。

Both R ₁ and R ₂ are H (hydrogen atom) or alkyl groups such as CH ₃ and C ₂ H ₅ . Both j and k are integers of 1 or more. Also, j is greater than k. That is, in the α-olefin copolymer shown in formula (IV), the structure on the left containing R ₁ is the base. R ₁ is for example H and R ₂ is for example C ₂ H ₅ .

In the sealant film 70, the mass ratio of the first thermoplastic resin made of the propylene/ethylene block copolymer is higher than the mass ratio of the second thermoplastic resin containing at least the α-olefin copolymer or polyethylene. For example, in the single-layer sealant film 70, the mass ratio of the first thermoplastic resin made of a propylene/ethylene block copolymer is at least 51% by mass or more, preferably 60% by mass or more, and more preferably It is 70% by mass or more.

As described above, the second thermoplastic resin can contribute to increasing the impact resistance of sealant film 70 . Therefore, by adjusting the mass ratio of the second thermoplastic resin containing at least the α-olefin copolymer or polyethylene in the single-layer sealant film 70, the mechanical properties of the sealant film 70 can be adjusted.

Also, the sealant layer 70 may further contain a thermoplastic elastomer. By using a thermoplastic elastomer, the impact resistance and puncture resistance of the sealant layer 70 can be further enhanced.

The thermoplastic elastomer is, for example, a hydrogenated styrene thermoplastic elastomer. The hydrogenated styrenic thermoplastic elastomer has a structure consisting of a polymer block A mainly composed of at least one vinyl aromatic compound and a polymer block B mainly composed of at least one hydrogenated conjugated diene compound. . The thermoplastic elastomer may also be an ethylene/α-olefin elastomer. Ethylene/α-olefin elastomers are low-crystalline or amorphous copolymer elastomers, and are random copolymers of 50 to 90% by mass of ethylene as a main component and α-olefin as a copolymerization monomer. be.

The content of the propylene/ethylene block copolymer in the sealant layer 70 is, for example, 80% by mass or more, preferably 90% by mass or more.

As a method for producing a propylene/ethylene block copolymer, there is a method of polymerizing raw materials such as propylene and ethylene using a catalyst. A Ziegler-Natta type catalyst, a metallocene catalyst, or the like can be used as the catalyst.

The thickness of the sealant layer 70 is preferably 30 μm or more, more preferably 40 μm or more. Also, the thickness of the sealant layer 70 is preferably 100 μm or less, more preferably 80 μm or less.

Preferred mechanical properties of a single-layer sealant film containing a propylene/ethylene block copolymer are described below.
The tensile elongation at 25° C. of the sealant film in the machine direction (MD) is preferably ≧600% and ≦1300%. Moreover, the product of the tensile elongation (%) of the sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably 35,000 or more and 80,000 or less. Also, the tensile elongation at 25° C. of the sealant film in the vertical direction (TD) is preferably 700% or more and 1400% or less. Moreover, the product of the tensile elongation (%) of the sealant film in the vertical direction (TD) and the thickness (μm) of the sealant film is preferably 40,000 or more and 85,000 or less.
The tensile modulus at 25° C. of the sealant film in the machine direction (MD) is preferably greater than or equal to 400 MPa and less than or equal to 1100 MPa. The product of the tensile modulus (MPa) of the sealant film and the thickness (μm) of the sealant film in the machine direction (MD) is preferably 30,000 or more and 55,000 or less. Also, the tensile modulus at 25° C. of the sealant film in the vertical direction (TD) is preferably 250 MPa or more and 900 MPa or less. The product of the tensile modulus (MPa) of the sealant film and the thickness (μm) of the sealant film in the vertical direction (TD) is preferably 20,000 or more and 45,000 or more.

Tensile modulus and tensile elongation can be measured according to JIS K7127. As a measuring instrument, a tensile tester RTC-1310A with a constant temperature bath manufactured by Orientec Co., Ltd. can be used. In the bag 10 shown in FIG. 1, the direction in which the upper portion 11 and the lower portion 12 extend is the direction in which the film constituting the bag 10, such as the sealant film, flows, and the direction in which the side portion 13 extends is the direction in which the sealant film or the like extends. , the vertical direction of the film forming the bag 10 . Although not shown, the bag 10 may be configured such that the direction in which the upper portion 11 and the lower portion 12 extend is the vertical direction of the film, and the direction in which the side portion 13 extends is the direction in which the film flows.

There are two main types of single-layer sealant films containing propylene-ethylene block copolymers.
The first type is ZK500, which will be described later, which has high tensile elongation and impact resistance. The first type of sealant film preferably also has the property of low hot seal strength. As a result, it is possible to prevent the internal pressure of the containing portion 17 from becoming excessive when the bag 10 is heated, and it is possible to prevent the laminate 30 from being damaged.
The second is a type having a high tensile modulus, such as ZK207, which will be described later. By using the second type of sealant film, the tearability of the bag 10 can be enhanced when the bag 10 is opened by the consumer by tearing the bag 10 along the first direction D1.

The product of the tensile elongation (%) of the first type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably 45000 or more, more preferably 50000 or more, 55000 or more, Or it may be 60000 or more. Also, the product of the tensile elongation (%) of the first type sealant film and the thickness (μm) of the sealant film in the vertical direction (TD) is preferably 53000 or more, more preferably 60000 or more. Since the sealant film has a high tensile elongation, it is possible to prevent the bag 10 from being broken due to an impact when dropped.
Also, the product of the tensile modulus (MPa) of the first type sealant film and the thickness (μm) of the sealant film in the machine direction (MD) is preferably 38000 or less, more preferably 35000 or less. Also, the product of the tensile modulus (MPa) of the first type sealant film and the thickness (μm) of the sealant film in the vertical direction (TD) is preferably 30,000 or less, more preferably 25,000 or less.

The product of the tensile modulus (MPa) of the second type sealant film and the thickness (μm) of the sealant film in the machine direction (MD) is preferably 35000 or more, more preferably 38000 or more, even more preferably 45,000 or more. In addition, the product of the tensile modulus (MPa) of the second type sealant film and the thickness (μm) of the sealant film in the vertical direction (TD) is preferably 25000 or more, more preferably 30000 or more, and further It is preferably 35,000 or more, and may be 38,000 or more. The high tensile modulus of the sealant film can enhance tearability when the bag 10 is opened.
Also, the product of the tensile elongation (%) of the second type sealant film in the machine direction (MD) and the thickness (μm) of the sealant film is preferably 55,000 or less, more preferably 50,000 or less. Also, the product of the tensile elongation (%) of the second type sealant film and the thickness (μm) of the sealant film in the vertical direction (TD) is preferably 60,000 or less, more preferably 55,000 or less.

(Other layers)
Laminate 30 may comprise further layers not shown in FIG. Examples of further layers are described below.

The laminate 30 may further include a printed layer. The printed layer is a layer provided in the laminate 30 to indicate product information and give an aesthetic appearance to the bag 10, and is printed on the first stretched plastic film 40, for example. The print layer expresses characters, numbers, symbols, graphics, patterns, and the like. Gravure printing ink and flexographic printing ink can be used as the material forming the printing layer. A specific example of the ink for gravure printing is FINART manufactured by DIC Graphics Corporation.

Moreover, the laminate 30 may further include a transparent gas barrier layer. The transparent gas barrier layer is formed on the surfaces of the stretched plastic films 40, 50, 60 and includes at least a transparent deposition layer made of a transparent inorganic material. Moreover, the transparent gas barrier layer may further include a transparent gas barrier coating film formed on the surface of the transparent deposition layer and having transparency.

The transparent deposition layer functions as a layer having a gas barrier function that prevents permeation of oxygen gas, water vapor, and the like. In addition, two or more layers of transparent vapor deposition layers may be provided. When there are two or more transparent deposition layers, they may have the same composition or may have different compositions. Examples of the method for forming the transparent deposition layer include physical vapor deposition methods (physical vapor deposition method, PVD method) such as vacuum deposition method, sputtering method, and ion plating method, plasma chemical vapor deposition method, thermal A chemical vapor deposition method (Chemical Vapor Deposition method, CVD method) such as a chemical vapor deposition method and a photochemical vapor deposition method can be used. Specifically, a vapor deposition layer can be formed on a film forming roller using a roller type vapor deposition film forming apparatus. Examples of the inorganic material forming the transparent deposition layer include aluminum oxide (aluminum oxide) and silicon oxide. The thickness of the transparent deposition layer is preferably 40 Å or more and 130 Å or less, more preferably 50 Å or more and 120 Å or less.

The transparent gas barrier coating film is a layer that functions as a layer that suppresses permeation of oxygen gas and water vapor. The transparent gas barrier coating film 37 has the general formula R ¹ _n M (OR ² ) _m (wherein R ¹ and R ² represent an organic group having 1 to 8 carbon atoms, and M represents a metal atom. , n represents an integer of 0 or more, m represents an integer of 1 or more, and n+m represents the valence of M.) and at least one or more alkoxides represented by the above polyvinyl alcohol- A transparent gas barrier composition that contains a sol-based resin and/or an ethylene-vinyl alcohol copolymer, and is polycondensed by the sol-gel method in the presence of a sol-gel catalyst, acid, water, and an organic solvent. can get.

Layer Structure of Lower Film Next, the layer structure of the lower film 16 will be described.

The layer structure of the lower film 16 is arbitrary as long as it has an inner surface that can be bonded to the inner surface of the front film 14 and the inner surface of the back film 15 . For example, the laminate 30 described above may be used as the lower film 16 in the same manner as the surface film 14 and the back film 15 . Alternatively, a film whose inner surface is composed of a sealant layer and whose composition is different from that of the laminate 30 may be used as the lower film 16 .

Method for Manufacturing Laminate Next, an example of a method for manufacturing the laminate 30 will be described.

First, the first stretched plastic film 40 and the second stretched plastic film 50 are prepared. Subsequently, the first stretched plastic film 40 and the second stretched plastic film 50 are laminated via the first adhesive layer 45 by a dry lamination method. After that, the laminate including the first stretched plastic film 40 and the second stretched plastic film 50 and the third stretched plastic film 60 are laminated via the second adhesive layer 55 by dry lamination. After that, the laminate including the first stretched plastic film 40, the second stretched plastic film 50 and the third stretched plastic film 60, and the sealant film for forming the sealant layer 70 are laminated via the third adhesive layer 65. Laminate. Thus, the laminate 30 including the first stretched plastic film 40, the second stretched plastic film 50, the third stretched plastic film 60 and the sealant layer 70 can be obtained.

The order in which the first stretched plastic film 40, the second stretched plastic film 50, the third stretched plastic film 60 and the sealant layer 70 are laminated by the dry lamination method is not limited to the order described above. For example, a first laminate including a first stretched plastic film 40 and a second stretched plastic film 50 and a second laminate including a third stretched plastic film 60 and a sealant layer 70 are laminated by a dry lamination method. You may manufacture the laminated body 30 by.

In the dry lamination method, first, an adhesive composition is applied to one of the two films to be laminated. Subsequently, the applied adhesive composition is dried to volatilize the solvent. The two films are then laminated via the dried adhesive composition. Subsequently, the two laminated films are aged in an environment of, for example, 20° C. or higher for 24 hours or longer in a wound state.

Method for Manufacturing Bag Next, a method for manufacturing the bag 10 using the laminate 30 described above will be described. First, the surface film 14 and the back film 15 each composed of the laminate 30 are prepared. In addition, the folded lower film 16 is inserted between the surface film 14 and the back film 15 . Subsequently, the inner surfaces of the films are heat-sealed to form seal portions such as the lower seal portion 12a and the side seal portions 13a. Also, the films bonded together by heat sealing are cut into a suitable shape to obtain the bag 10 shown in FIG. Subsequently, the content 18 is filled into the bag 10 through the opening 11b of the upper portion 11. As shown in FIG. Contents 18 are, for example, cooked foods containing water, such as curry, stew, and soup. In addition, the content 18 may include materials containing a large amount of oil, such as meat, fish, and seasonings such as miso. In addition to foods, other items that can be heated by boiling in hot water or the like can be accommodated in the bag 10 as contents. Thereafter, the upper portion 11 is heat-sealed to form an upper seal portion. Thus, the sealed bag 10 containing the content 18 can be obtained.

Method for Heating Content Next, an example of a method for heating the content 18 housed in the bag 10 will be described.

First, the bag 10 is placed inside the microwave oven with the lower portion 12 facing down and the bag 10 standing on its own. Next, heat the contents using a microwave oven. As a result, the temperature of the contents 18 rises, and along with this, the moisture contained in the contents 18 evaporates, and the pressure in the storage section 17 increases.

When the pressure of the containing portion 17 increases, the surface film 14 and the back film 15 bulge outward due to the force received from the containing portion 17 . Here, in this embodiment, the laminate 30 constituting the surface film 14 and the back film 15 includes three stretched plastic films 40 , 50 , 60 . Therefore, the rigidity of the laminate 30 is high, and as a result, the front film 14 and the back film 15 can be prevented from stretching when the front film 14 and the back film 15 receive force. As a result, the force generated due to the pressure generated in the housing portion 17 can be mainly used as the force for peeling off the steam releasing seal portion 20a, not as the force for stretching the surface film 14 and the back film 15. can. Therefore, the force applied to the steam release seal portion 20a can be increased. As a result, the steam release seal portion 20a is easily peeled off during heating, and the steam in the housing portion 17 can be released to the outside through the steam release mechanism 20. As shown in FIG.

Moreover, according to the present embodiment, as described above, the laminate 30 has heat resistance. Therefore, it is possible to prevent the layered body 30 from being perforated or wrinkled in the layered body 30 during heating.

Also according to this embodiment, the laminate 30 comprises at least three stretched plastic films 40, 50, 60, as described above. At least one of the three stretched plastic films 40, 50, 60 is a stretched polyamide film containing polyamide such as nylon as a main component. Therefore, the laminate 30 and the bag 10 constituted by the laminate 30 can be provided with piercing resistance. The puncture strength of the laminate 30 is preferably 15N or higher, more preferably 16N or higher, still more preferably 17N or higher, and particularly preferably 18N or higher.

Further, according to the present embodiment, as described above, the product of the tensile elongation (%) in the machine direction (MD) and the thickness (μm) of the sealant film constituting the sealant layer 70 of the laminate 30 is 45000. Thus, the product of tensile elongation (%) in the vertical direction and thickness (μm) is 53000 or more. Thereby, the impact strength of the laminate 30 can be increased. As a result, the impact resistance of the bag 10 made up of the laminate 30 can be enhanced. For example, it is possible to prevent the bag 10 from breaking due to impact when dropped. The impact strength of the laminate 30 is preferably 900 kJ/m or more, more preferably 1000 kJ/m or more, and further preferably 1100 kJ/m or more, 1200 kJ/m or more, or 1300 kJ/m or more. .

Various modifications can be made to the above-described embodiment. Modifications will be described below with reference to the drawings as necessary. In the following description and the drawings used in the following description, the same reference numerals as those used for the corresponding portions in the above-described embodiment are used for the portions that can be configured in the same manner as in the above-described embodiment, Duplicate explanations are omitted. Further, when it is clear that the effects obtained in the above-described embodiment can also be obtained in the modified example, the explanation thereof may be omitted.

(Modification of bag)
In the present embodiment described above, an example in which the bag 10 is a gusseted bag has been shown, but the specific configuration of the bag 10 is not particularly limited. For example, the bag 10 may be a so-called four-sided seal bag formed by joining the inner surfaces of the surface film 14 and the back film 15 of the laminate 30 at the upper portion 11, the lower portion 12 and the side portions 13.

Moreover, in the present embodiment described above, an example of heating the contents 18 housed in the bag 10 using a microwave oven has been shown, but the present invention is not limited to this. For example, the contents 18 housed in the bag 10 may be heated by boiling in hot water. In this case, the bag 10 does not have to be provided with the vapor release mechanism 20 described above.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the description of the Examples below as long as it does not exceed the gist thereof.

Examples 1 to 7 and Comparative Examples 1 and 2 were used to evaluate the puncture strength, impact strength and heat resistance of the laminate 30 of the present invention.

(Example 1)
Stretched PET films with a thickness of 12 μm were prepared as the first stretched plastic film 40 and the third stretched plastic film 60, respectively. As the second stretched plastic film 50, a stretched polyamide film containing polyamide as a main component and having a thickness of 15 μm was prepared. As the stretched polyamide film, as shown in FIG. 4 described above, a first layer 51 made of PET having a thickness of 2 μm, a second layer 52 made of nylon-6 having a thickness of 11 μm, and a third layer 53 made of PET having a thickness of 2 μm. A coextruded film (hereinafter also referred to as a stretched hybrid nylon film) prepared by coextrusion was used. As a film for forming the sealant layer 70, an unstretched polypropylene film ZK500 manufactured by Toray Advanced Film Co., Ltd. was prepared. ZK500 comprises the propylene-ethylene block copolymer and elastomer described above. The thickness of the sealant layer 70 was 60 μm.

ZK500 has a higher tensile elongation than common unstretched polypropylene films. Specifically, the tensile elongation of ZK500 in the machine direction (MD) is 1180% when the thickness is 50 μm and 1100% when the thickness is 60 μm. Also, the tensile elongation of ZK500 in the vertical direction (TD) is 1240% when the thickness is 50 μm and 1150% when the thickness is 60 μm. Therefore, the product of tensile elongation (%) and thickness (μm) of ZK500 in the machine direction is 59000 when the thickness is 50 μm and 66000 when the thickness is 60 μm. The product of tensile elongation (%) and thickness (μm) of ZK500 in the vertical direction is 62000 when the thickness is 50 μm and 69000 when the thickness is 60 μm.

ZK500 also has a lower tensile modulus than common unstretched polypropylene films. Specifically, the tensile modulus of ZK500 in the machine direction (MD) is 640 MPa for a thickness of 50 μm and 550 MPa for a thickness of 60 μm. Also, the tensile modulus of ZK500 in the vertical direction (TD) is 480 MPa when the thickness is 50 μm and 400 MPa when the thickness is 60 μm. Therefore, the product of the tensile modulus (MPa) and the thickness (μm) of ZK500 in the machine direction is 32000 for a thickness of 50 μm and 33000 for a thickness of 60 μm. Also, the product of the tensile modulus (MPa) and thickness (μm) of ZK500 in the vertical direction is 24000 when the thickness is 50 μm and 35000 when the thickness is 60 μm.

Subsequently, the first stretched plastic film 40, the second stretched plastic film 50, the third stretched plastic film 60, and the sealant layer 70 were laminated by dry lamination to produce the laminate 30. FIG. As the first adhesive layer 45, the second adhesive layer 55, and the third adhesive layer 65, a two-liquid type polyurethane adhesive (main agent: RU-40, curing agent: H-4) manufactured by Rock Paint Co., Ltd. was used. RU-40 as the main agent is a polyester polyol. The thickness of the first adhesive layer 45, the second adhesive layer 55 and the third adhesive layer 65 was 3.5 μm.

[Evaluation of puncture resistance]
Subsequently, the puncture strength of the laminate 30 was measured according to JIS Z1707 7.4. As a measuring instrument, a Tensilon universal material testing machine RTC-1310 manufactured by A&D was used. Specifically, as shown in FIG. 6, a semicircular needle 90 having a diameter of 1.0 mm and a tip shape radius of 0.5 mm is applied to the test piece of the laminated body 30 in a fixed state from the outer surface 30y side. was pierced at a speed of 50 mm/min (50 mm per minute), and the maximum value of stress until the needle 90 penetrated the laminate 30 was measured. The maximum value of stress was measured for five or more test pieces, and the average value was defined as the puncture strength of the laminate 30 . The environment during the measurement was a temperature of 23° C. and a relative humidity of 50%. As a result, the puncture strength was 17.6N.

[Evaluation of impact resistance]
Subsequently, the two laminates 30 were stacked and heated at 190° C. for 1 second to heat-seal the inner surfaces 30x of the laminates 30 . Next, the two heat-sealed laminates 30 were cut into a width of 15 mm to prepare a test piece 100 . 7 is a plan view showing the test piece 100, and FIG. 8 is a cross-sectional view of the test piece 100 of FIG. The test piece 100 has a width W3 of 15 mm and a length W4 of 50 mm. A seal portion is not formed. Subsequently, as shown in FIG. 9, the unsealed portion of one laminate 30 and the unsealed portion of the other laminate 30 are placed in opposite directions in a direction perpendicular to the surface direction of the seal portion 101 . , that is, to form a T-shape, the end of the unsealed portion of one laminate 30 and the end of the unsealed portion of the other laminate 30 are attached to jigs 102, respectively. , 103. At this time, the distance T between the jigs 102 and 103 in the direction orthogonal to the surface direction of the seal portion 101 was set to 40 mm. Subsequently, when one jig 102 is hit with a hammer 104 from the surface of the first stretched plastic film 40 side of one laminate 30 to separate one laminate 30 and the other laminate 30 The impact strength of was measured. As a measuring device, a digital impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd. was used for evaluation. A 2J hammer was used for applying impact to the test piece 100 . As a result, the impact strength was 1016 kJ/m.

[Evaluation of heat resistance]
Subsequently, a bag 10 was produced using the laminate 30, and the heat resistance of the bag 10 was evaluated. Specifically, first, the bag 10 shown in FIG. 1 was produced using the laminate 30 . The bag 10 had a height S1 of 145 mm and a width S2 of 150 mm. Further, the height S3 of the folded back lower film 16, that is, the height from the lower end of the bag 10 to the folded portion 16f was 43 mm. In the following description, the bag 10 having a height S1 of 145 mm, a width S2 of 150 mm, and a height S3 of 43 mm is also referred to as an M size bag 10 . Subsequently, the inside of the bag 10 was filled with 100 g of content containing a large amount of oil such as meat and miso, and the upper portion 11 was heat-sealed to form an upper sealed portion.

After that, the bag 10 containing the contents was heated for 2 minutes using a microwave oven with an output of 500 W, and it was confirmed whether or not the laminate 30 constituting the bag 10 was damaged. The test was performed on ten bags 10 . As a result, it was confirmed that 8 out of 10 bags 10 had no damage such as holes in the laminate 30 or formation of wrinkles in the laminate 30 .

(Example 2)
Except that a stretched PET film with a thickness of 12 μm was used as the first stretched plastic film 40 and the second stretched plastic film 50, and a stretched hybrid nylon film with a thickness of 15 μm was used as the third stretched plastic film 60. A laminate 30 was produced in the same manner as in Example 1.

Subsequently, in the same manner as in Example 1, the puncture strength and impact strength of the laminate 30 were measured. As a result, the puncture strength was 17.6 N and the impact strength was 1124 kJ/m.

Subsequently, a bag 10 was produced using the laminate 30 in the same manner as in Example 1, and the heat resistance of the bag 10 was evaluated. The size of the bag 10 was M size, as in the case of the first embodiment. As a result, it was confirmed that 8 out of 10 bags 10 had no damage such as holes in the laminate 30 or formation of wrinkles in the laminate 30 .

(Example 3)
Except that a stretched PET film with a thickness of 12 μm was used as the second stretched plastic film 50 and the third stretched plastic film 60, and a stretched hybrid nylon film with a thickness of 15 μm was used as the first stretched plastic film 40. A laminate 30 was produced in the same manner as in Example 1.

Subsequently, in the same manner as in Example 1, the puncture strength and impact strength of the laminate 30 were measured. As a result, the puncture strength was 17.8 N and the impact strength was 973 kJ/m.

Subsequently, a bag 10 was produced using the laminate 30 in the same manner as in Example 1, and the heat resistance of the bag 10 was evaluated. The size of the bag 10 was M size, as in the case of the first embodiment. As a result, it was confirmed that 9 out of 10 bags 10 had no damage such as holes in the laminate 30 or formation of wrinkles in the laminate 30 .

(Example 4)
A laminate 30 was produced in the same manner as in Example 1, except that a single-layer stretched nylon film having a thickness of 15 μm was used as the second stretched plastic film 50 .

Subsequently, in the same manner as in Example 1, the puncture strength and impact strength of the laminate 30 were measured. As a result, the puncture strength was 18.3 N and the impact strength was 1345 kJ/m.

Subsequently, a bag 10 was produced using the laminate 30 in the same manner as in Example 1, and the heat resistance of the bag 10 was evaluated. The size of the bag 10 was M size, as in the case of the first embodiment. As a result, it was confirmed that 8 out of 10 bags 10 had no damage such as holes in the laminate 30 or formation of wrinkles in the laminate 30 .

(Example 5)
A laminate 30 was produced in the same manner as in Example 1, except that an unstretched polypropylene film ZK207 manufactured by Toray Advanced Film Co., Ltd. was used as the sealant film for forming the sealant layer 70 . The unstretched polypropylene film ZK207 had a thickness of 70 μm.

ZK207 has a higher tensile modulus than ZK500. Specifically, the tensile modulus of ZK207 in the machine direction (MD) is 780 MPa for a thickness of 50 μm and 680 MPa for a thickness of 60 μm. Also, the tensile modulus of ZK207 in the vertical direction (TD) is 630 MPa when the thickness is 50 μm and 560 MPa when the thickness is 60 μm. Therefore, the product of the tensile modulus (MPa) and the thickness (μm) of ZK207 in the machine direction is 39000 for a thickness of 50 μm and 40800 for a thickness of 60 μm. The product of the tensile modulus (MPa) and thickness (μm) of ZK207 in the vertical direction is 31500 when the thickness is 50 μm and 33600 when the thickness is 60 μm. By using ZK207, tearability of the laminate 30 and the bag 10 including the laminate 30 can be enhanced.

ZK207 also has a lower tensile elongation than ZK500. Specifically, the tensile elongation of ZK207 in the machine direction (MD) is 790% when the thickness is 50 μm and 730% when the thickness is 60 μm. Also, the tensile elongation of ZK207 in the vertical direction (TD) is 1020% when the thickness is 50 μm, and 870% when the thickness is 60 μm. Therefore, the product of tensile elongation (%) and thickness (μm) of ZK207 in the machine direction is 39500 for a thickness of 50 μm and 43800 for a thickness of 60 μm. The product of tensile elongation (%) and thickness (μm) of ZK207 in the vertical direction is 51000 when the thickness is 50 μm and 52200 when the thickness is 60 μm.

Subsequently, in the same manner as in Example 1, the puncture strength and impact strength of the laminate 30 were measured. As a result, the puncture strength was 17.2 N and the impact strength was 901 kJ/m.

Subsequently, a bag 10 was produced using the laminate 30 in the same manner as in Example 1, and the heat resistance of the bag 10 was evaluated. The size of the bag 10 was M size, as in the case of the first embodiment. As a result, it was confirmed that 7 of the 10 bags 10 did not suffer damage such as holes in the laminate 30 or formation of wrinkles in the laminate 30 .

(Example 6)
A laminate 30 was produced in the same manner as in Example 2, except that an unstretched polypropylene film ZK207 manufactured by Toray Advanced Film Co., Ltd. was used as the sealant film for forming the sealant layer 70 . The unstretched polypropylene film ZK207 had a thickness of 70 μm.

Subsequently, in the same manner as in Example 1, the puncture strength and impact strength of the laminate 30 were measured. As a result, the puncture strength was 17.1 N and the impact strength was 1008 kJ/m.

Subsequently, a bag 10 was produced using the laminate 30 in the same manner as in Example 1, and the heat resistance of the bag 10 was evaluated. The size of the bag 10 was M size, as in the case of the first embodiment. As a result, it was confirmed that 5 out of 10 bags 10 had no damage such as holes in the laminate 30 or formation of wrinkles in the laminate 30 .

(Example 7)
A laminate 30 was produced in the same manner as in Example 3, except that an unstretched polypropylene film ZK207 manufactured by Toray Advanced Film Co., Ltd. was used as the sealant film for forming the sealant layer 70 . The unstretched polypropylene film ZK207 had a thickness of 70 µm.

Subsequently, in the same manner as in Example 1, the puncture strength and impact strength of the laminate 30 were measured. As a result, the puncture strength was 17.4 N and the impact strength was 913 kJ/m.

Subsequently, a bag 10 was produced using the laminate 30 in the same manner as in Example 1, and the heat resistance of the bag 10 was evaluated. The size of the bag 10 was M size, as in the case of the first embodiment. As a result, it was confirmed that 7 of the 10 bags 10 did not suffer damage such as holes in the laminate 30 or formation of wrinkles in the laminate 30 .

(Comparative example 1)
A laminate was produced by laminating two stretched plastic films and a sealant layer by a dry lamination method. Of the two stretched plastic films, a stretched PET film with a thickness of 12 μm was used as the first stretched plastic film located on the outer surface side of the laminate. As the second stretched plastic film positioned closer to the sealant layer than the first stretched plastic film, a stretched hybrid nylon film having a thickness of 15 μm was used. As the film for constituting the sealant layer, as in Example 1, an unstretched polypropylene film ZK500 manufactured by Toray Advanced Film Co., Ltd. was used. The thickness of the sealant layer was 60 μm. As the two adhesives for laminating the two stretched plastic films and the sealant layer, as in Example 1, a two-liquid type polyurethane adhesive manufactured by Rock Paint Co., Ltd. (main agent: RU-40, Curing agent: H-4) was used. The thickness of the adhesive layer made of adhesive was 3.5 μm. The layer structure of the laminate in Comparative Example 1 can be expressed in order from the outer surface side to the inner surface side as follows.
Stretched PET film/adhesive layer/stretched hybrid nylon film/adhesive layer/sealant layer "/" indicates a boundary between layers.

Subsequently, the puncture strength and impact strength of the laminate were measured in the same manner as in Example 1. As a result, the puncture strength was 15.2 N and the impact strength was 1207 kJ/m.

Subsequently, a bag 10 was produced using the laminate 30 in the same manner as in Example 1, and the heat resistance of the bag 10 was evaluated. The size of the bag 10 was M size, as in the case of the first embodiment. As a result, no holes were found in the laminated bodies 30 of 2 of the 10 bags 10 , but holes were found in the laminated bodies 30 of 8 of the 10 bags 10 .

(Comparative example 2)
A stretched hybrid nylon film having a thickness of 15 μm is used as the first stretched plastic film located on the outer surface side of the laminate, and a second stretched plastic film located closer to the sealant layer than the first stretched plastic film has a thickness of A laminate 30 was produced in the same manner as in Comparative Example 1, except that a stretched PET film having a thickness of 12 μm was used.

Subsequently, the puncture strength and impact strength of the laminate were measured in the same manner as in Example 1. As a result, the puncture strength was 15.4 N and the impact strength was 1096 kJ/m.

Subsequently, a bag 10 was produced using the laminate 30 in the same manner as in Example 1, and the heat resistance of the bag 10 was evaluated. The size of the bag 10 was M size, as in the case of the first embodiment. As a result, no holes were found in the laminate 30 in 3 of the 10 bags 10, but holes were found in the laminate 30 in 7 of the 10 bags 10.

The layer structures and evaluation results of the laminates of Examples 1 to 7 and Comparative Examples 1 and 2 are collectively shown in FIG. In FIG. 10, in the column of "Layer Configuration", the constituent elements of the laminate are listed in order from the outer layer. As can be seen from the comparison between Examples 1 to 7 and Comparative Examples 1 and 2, the heat resistance of the laminate 30 can be increased by including three stretched plastic films laminated by dry lamination. rice field. Further, as can be seen from the evaluation results of Examples 1 to 7, by using a stretched polyamide film containing polyamide as a main component as at least one stretched plastic film out of the three stretched plastic films, the puncture of the laminate 30 was reduced. A strength of 17 N or higher was achieved. In addition, in Examples 1 to 4 using ZK500 as a sealant film for forming the sealant layer 70, compared to Examples 5 to 7 using ZK207, a laminate having excellent impact resistance and heat resistance and was able to get a bag.

10 bag 11 upper part 12 lower part 12a lower seal part 13 side part 13a side seal part 14 surface film 15 back film 16 lower film 17 storage part 18 contents 20 steam release mechanism 20a steam release seal part 30 laminate 40 first stretched plastic Film 45 First adhesive layer 50 Second stretched plastic film 55 Second adhesive layer 60 Third stretched plastic film 65 Third adhesive layer 70 Sealant layer

Claims (9)

A laminate,
At least a first stretched plastic film, a first adhesive layer, a second stretched plastic film, a second adhesive layer, a third stretched plastic film, a third adhesive layer and a sealant layer in this order,
Each of the first stretched plastic film, the second stretched plastic film, and the third stretched plastic film contains polyester or polyamide as a main component,
At least one of the first stretched plastic film, the second stretched plastic film, and the third stretched plastic film contains polyester as a main component, and at least one of the others contains polyamide as a main component,
Each of the first adhesive layer, the second adhesive layer, and the third adhesive layer contains a cured product of a polyol and an isocyanate compound and has a thickness of 2 μm or more,
A1 is the product of the thickness and thermal conductivity of the first stretched plastic film, A2 is the product of the thickness and thermal conductivity of the second stretched plastic film, and A2 is the product of the thickness and thermal conductivity of the third stretched plastic film. is A3, the product of the thickness and thermal conductivity of the first adhesive layer is B1, the product of the thickness and thermal conductivity of the second adhesive layer is B2, the thickness of the third adhesive layer and the heat If the product of conductivity is B3, B1 + B2 + B3 is 3.5 times or more of A1 + A2 + A3,
laminate. 2. The laminate of Claim 1, wherein the sealant layer comprises polypropylene. 3. The laminate of claim 2, wherein the sealant layer comprises a propylene-ethylene block copolymer. The first stretched plastic film and the third stretched plastic film contain polyester as a main component,
The laminate according to any one of claims 1 to 3, wherein the second stretched plastic film contains polyamide as a main component. The first stretched plastic film and the second stretched plastic film contain polyester as a main component,
The laminate according to any one of claims 1 to 3, wherein the third stretched plastic film contains polyamide as a main component. The second stretched plastic film and the third stretched plastic film contain polyester as a main component,
The laminate according to any one of claims 1 to 3, wherein the first stretched plastic film contains polyamide as a main component. The laminate according to any one of claims 1 to 6, which is for a microwave oven. is a bag,
The first stretched plastic film, the first adhesive layer, the second stretched plastic film, the second adhesive layer, the third stretched plastic film, the third adhesive layer and the The laminate according to any one of claims 1 to 7, comprising at least a sealant layer in this order;
and a sealing portion that joins inner surfaces of the laminate. 9. The bag of claim 8, comprising a steam release mechanism.

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