JP6531664B2 - Coextruded multilayer film for retort and package for retort - Google Patents

Description

  The present invention particularly relates to a coextruded film and a deep drawn package which can be subjected to a high temperature sterilization treatment at 100 ° C. or higher.

Conventionally, a polyamide resin layer / adhesive resin is mainly used as a means for providing a deep drawn package having good pinhole resistance and suppressing curling of a flange portion (surface seal portion around the accommodation portion) after high-temperature sterilization. The bottom material (for example, patent document 1) of coextrusion film of layer / adhesion resin layer etc. / polypropylene resin layer is used.
In addition, a coextrusion film of polyamide resin layer / polyethylene resin layer / {heat seal layer or easy peel layer} is presented as a film for deep drawing base material where delamination (peeling) does not occur in retort (patent document 2).

Since a laminated film of polypropylene film / adhesive / polypropylene film is often used as a lid material for high temperature treatment, it is a film for deep-drawing bottom material which is resistant to high temperature treatment and is given easy peelability (easy openability). Polypropylene resin is used as the main component of the easy peel layer.
However, if the melting point of the easy peel layer polyropyrene resin is lower than 140 ° C., the lid and bottom material of the opening trigger portion of the package fuse at the time of high temperature sterilization, which causes a problem that opening becomes difficult. On the other hand, if the melting point of the easy peel layer polypropylene resin is 140 ° C. or higher, the heat seal temperature needs to be set to 160 ° C. or higher, under which condition the problem of the polypropylene in the lid outer layer welding to the seal hot plate occurs Resulting in.

  Moreover, in order to prevent the fusion of the opening trigger part, a method of applying a dedicated coating to the trigger part of the lid material sealing surface is used, but the number of processes increases and cost and delivery time are required, and the solvent of the coating is a film Have problems such as remaining in

Japanese Patent Application Laid-Open No. 10-76616 JP, 2014-128884, A

  The present invention has been made in view of the above-mentioned circumstances, and the object thereof is to combine an adherend mainly made of polypropylene resin with heat-sealed material to provide sufficient adhesion and easy peelability (easy openability), and It is an object of the present invention to provide a co-extruded multilayer film and a package which can prevent the fusion of the opening trigger even without a dedicated coating.

  As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be solved by adopting a specific configuration, and has completed the present invention.

  That is, the gist of the present invention is a coextruded multilayer film having an easy peel layer, an adhesive resin layer, and a polyamide resin layer in this order, wherein the easy peel layer is a propylene resin, a styrene elastomer, and an ethylene resin. The coextruded multilayer film for retort is characterized in that the adhesive resin layer is composed of a propylene-based resin and is adjacent to the easy peel layer.

  According to the coextruded multilayer film for retort of the present invention, the production process and the cost can be reduced since the anti-fusion coating is unnecessary. Moreover, since the opening trigger part after retort does not fuse and has good easy peelability, the opening work of the consumer becomes easy, and a highly convenient package for retort can be provided.

It is sectional drawing which shows the layer structural example of the coextruded multilayer film for retorts of this invention. It is a top view of an example of a deep draw package, and a deep draw package used for evaluation of an example. It is a side surface figure of the example of a shape of the deep draw package after high-temperature sterilization processing, and the deep draw package used for evaluation of an example.

Hereinafter, the present invention will be described in detail, but the present invention is not limited to the embodiments described below.
In the present specification, "constituted as a main component" means that other components are allowed to be included within the range that does not hinder the action and effect of the resin that constitutes each layer. Furthermore, this term does not limit the specific content rate, but it is 50% by mass or more and 100% by mass or less, preferably 70% by mass or more and 100% by mass or less, more preferably 85% by mass of the whole constituent components of each layer. It means that it occupies% or more and 100 mass% or less.

  The coextruded multilayer film for retort according to the present invention (hereinafter sometimes referred to as the film according to the present invention) is, as shown in FIG. 1 (a), the layer sequence of easy peel layer, adhesive resin layer and polyamide resin layer. Have in this order. When the package is produced, the easy peel layer is located on the side of the container, and the polyamide resin layer is located on the outside air side.

The film of the present invention can accommodate the contents together with the adherend and heat seal the periphery thereof to produce a package. The adherend is mainly composed of polypropylene resin, but the film of the present invention can also be used.
In the case of producing the package of the present invention, a configuration using the film of the present invention and an adherend film, a configuration using a lid and another base material using the film of the present, and other lids and the present Various configurations such as a configuration using a deep drawn bottom material using a film, and the like can be mentioned.

  In addition, when a package having a mechanism for holding the film of the present invention and the adherend at the respective portions and opening the package without heat sealing a part of the corner of the package is prepared, the convenience for opening is enhanced. The part which is not heat-sealed in order to open said package body is called "the opening trigger part" in description of this invention.

Each layer will be described below.
<Easy peel layer>
The film of the present invention is an easy peel (hereinafter sometimes abbreviated as EP) having cohesive failure for the purpose of improving the openability of the films, and the package in which the lid member and the bottom material are sealed. Distribute. Here, having cohesive failure means peeling when cohesive failure occurs inside the easy peel layer when the package is opened, and the easy peel layer after the cohesive failure is the layer above and below it. Remain on both sides.

The easy peel layer of the film of the present invention is composed of a propylene-based resin, a styrene-based elastomer, and an ethylene-based resin.
By using a propylene-based resin as a main component of the easy peel layer, heat resistance can be imparted to the film. The lower limit of the mixing ratio of the propylene-based resin in the easy peel layer is preferably 50% by mass or more, more preferably 55% by mass or more, and still more preferably 60% by mass or more. 90 mass% or less is preferable, 85 mass% or less is more preferable, and 80 mass% or less is still more preferable. When the mixing ratio of the propylene-based resin is 50% by mass or more, the heat resistance against high temperature treatment and the like and the heat seal adhesion with the adherend mainly made of a polypropylene-based resin become good. Moreover, if the said mixing ratio is 90 mass% or less, easy peel property will become favorable.

The propylene-based resin may, for example, be a homopolypropylene, a random copolymer or a block copolymer of propylene and an α-olefin having 1 to 20 carbon atoms, and a homopolypropylene, a propylene-ethylene copolymer, or a mixture thereof preferable.
Among them, in order to prevent fusion of the opening trigger part at the time of high temperature sterilization, the melting point of the propylene-based resin is preferably 140 ° C. or more, more preferably 145 ° C. or more, and still more preferably 155 ° C. or more. The melting point can be measured according to JIS K 7121 method.

  The styrene-based elastomer to be mixed in the easy peel layer is a hydrogenated derivative of a vinyl aromatic hydrocarbon-conjugated diene block copolymer, and is represented by the general formula: a (b-a) n, (a-b) n, or One or more of hydrogenated derivatives of the block copolymer represented by a-b-c. However, in the formula, (a) is a polymer block of monovinyl-substituted aromatic hydrocarbon, (b) is a random copolymer block of monovinyl-substituted aromatic hydrocarbon and a conjugated diene or an elastomeric polymer block of conjugated diene, (C) is a block of a monovinyl-substituted aromatic hydrocarbon and a conjugated diene and is a tapered block in which monovinyl-substituted aromatic hydrocarbon is gradually increased, and n is an integer of 1 to 5.

As a vinyl aromatic hydrocarbon of the monomer which comprises said polymer block (a), (b) or (c), styrene, (alpha)-methylstyrene, (o-, m-, p-) methylstyrene And 1,3-dimethylstyrene, vinyl naphthalene, vinyl anthracene and the like, and among these, styrene or α-methylstyrene is preferable. As a conjugated diene monomer in said polymer block (b) or (c), butadiene and / or isoprene are preferable. When butadiene is used as a single conjugated diene monomer to form a polymer block (b) or (c), after the block copolymer is hydrogenated and the double bond is saturated In order to increase the compatibility with the propylene-based polymer, it is preferable to adopt polymerization conditions in which the 1,2-microstructure in the microstructure of polybutadiene is 50% by mass or more. The preferred proportion of 1,2-microstructure is 50% by weight to 90% by weight.
The proportion of the polymer block (a) in the hydrogenated block copolymer or the sum of the content of the polymer block (a) and the vinyl aromatic compound of the polymer block (c) is usually 3 to 30% by mass, preferably Is 5 to 20% by mass. When the sum of the proportion of the polymer block (a) or the content of the vinyl aromatic compound of the polymer block (a) and the polymer block (c) is less than 3% by mass, the mechanical strength of the resultant compositional foreign matter is It tends to be inferior. Also, when the proportion of the polymer block (a) or the sum of the content of the polymer block (a) and the vinyl aromatic compound of the polymer block (c) exceeds 30% by mass, the flexibility and transparency of the composition Tend to be inferior.

  The weight average molecular weight of the styrene-based elastomer (hydrogenated derivative of vinyl aromatic hydrocarbon-conjugated diene block copolymer) is usually 10 to 550,000, preferably 15 as a value in terms of polystyrene measured by gel permeation chromatography. It is preferably 500,000, more preferably 250,000. If the weight average molecular weight is less than 100,000, rubber elasticity and mechanical strength tend to be poor, and if it exceeds 550,000, the viscosity tends to be high and the molding processability tends to be poor.

Examples of such styrene-based elastomers (hydrogenated derivatives of vinyl aromatic hydrocarbon-conjugated diene block copolymer) include “Kraton G” (registered trademark) manufactured by Kraton Polymers, and “Septon” manufactured by Kuraray (registered trademark) Trademarks, "Hybler" (registered trademark), "TAFTEC" (registered trademark) manufactured by Asahi Kasei Corporation, "Dynalon" (registered trademark) manufactured by JSR Corporation, and styrene blocks and isobutylene blocks obtained by cationic polymerization manufactured by Kaneka Corporation. And “SIBSTAR” (registered trademark), etc.
Moreover, Mitsubishi Chemical "Zelas" (registered trademark) etc. are mentioned as a resin composition of a propylene-type resin and a styrene-type elastomer.

  The mixing ratio of the styrene-based elastomer in the easy peel layer is preferably 1% by mass or more and 15% by mass or less. The lower limit is more preferably 2% by mass or more, and still more preferably 3% by mass or more. The upper limit is more preferably 10% by mass or less and still more preferably 8% by mass or less. Adhesiveness to an adherend seal layer is easy to be expressed by 1 mass% or more, and fusion of an opening trigger part of a package by high temperature processing hardly occurs by 15 mass% or less.

The ethylene-based resin to be mixed in the easy peel layer is not particularly limited. For example, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), ethylene-vinyl acetate copolymer Ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethyl-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-based ionomer resin, or a mixture thereof can be used. Among them, LDPE, LLDPE, HDPE, or a mixture thereof is preferable from the viewpoint of easy peelability, and LLDPE, HDPE, or a mixture thereof is more preferable from the viewpoint of heat resistance to 95 ° C. boiling treatment, 121 ° C. retorting treatment, etc. . Furthermore, in the case of high retort treatment at 130 ° C., HDPE is particularly preferable, and it is effective for non-fusion of the opening trigger portion in high-temperature sterilization treatment.
When the above mixture is used as the ethylene-based resin, in view of heat resistance, the lower limit of the mixing ratio of HDPE to 100% by mass of the ethylene-based resin is preferably more than 50% by mass, and more preferably 55% by mass or more. The upper limit is not particularly limited, but may be 95% by mass or less.

  The mixing ratio of the ethylene-based resin in the easy peel layer is preferably 10% by mass or more and less than 50% by mass from the viewpoint of easy peelability and non-fusion property of the opening trigger part at high temperature treatment. As for a minimum, 15 mass% or more is more preferable, and 20 mass% or more is still more preferable. The upper limit is more preferably 40% by mass or less, still more preferably 35% by mass or less.

  The lower limit of the thickness of the easy peel layer is preferably 3 μm or more, more preferably 4 μm or more, and still more preferably 5 μm or more. 15 micrometers or less are preferable, 12 micrometers or less are more preferable, and 10 micrometers or less are still more preferable. When it is 3 μm or more, coextrusion film film forming property tends to be stable, and when it is 15 μm or less, generation of fuzzing (roughness of opening surface) at the time of package opening is suppressed and a good peeling appearance can be obtained.

  Fuzz occurs when cohesive failure does not occur well in the easy peel layer at the time of peeling. In the case where the thickness of the easy peel layer is increased or the mixing ratio is not appropriate, the cohesion of the layer becomes strong and it becomes difficult to be broken, and fuzzing tends to occur.

The peel strength (easy peel strength) between the film of the present invention and the adherend is preferably 2.0 N / 15 mm or more and 12.0 N / 15 mm or less. The lower limit is preferably 3.0 N / 15 mm or more, and more preferably 4.0 N / 15 mm or more. The upper limit is more preferably 10.0 N / 15 mm or less, and still more preferably 8.0 N / 15 mm or less.
If the peel strength is 2.0 N / 15 mm or more, the risk that the package will be broken from the heat-sealed part during high temperature sterilization is reduced, and if it is 12.0 N / 15 mm or less, the package The openability of the
In a package subjected to high-temperature sterilization treatment such as retort, a molded body composed of a homopolypropylene resin is often used as an adherend, but the film of the present invention and an adherend composed of a homopolypropylene resin The peel strength at 23 ° C. after being allowed to cool by heat sealing at 150 ° C. also includes the above-mentioned 2.0 N / 15 mm width or more and 12.0 N / 15 mm width or less as a preferable range.

  The peel strength is weaker than the interlayer strength of the film of the present invention, thereby causing cohesive failure in the easy peel layer of the film of the present invention when the seal portion between the film of the present invention and the adherend is peeled off. Can occur and peel off.

When the film of the present invention and an adherend composed of a homopolypropylene resin are heat-sealed and a part of them is not heat-sealed but used as an opening trigger part, the opening trigger part is retorted even at 121 ° C. for 30 minutes It is desirable not to fuse. Furthermore, it is more desirable that the opening trigger portion does not fuse even when treated under high retort conditions of 130 ° C. and 30 minutes.
The size and shape of the opening trigger portion can be appropriately selected depending on the size, shape, thickness and the like of the package.
By the non-fusion of the opening trigger part, the film of the present invention and the adherend can be held separately to pull the package seal part open, and the convenience of use is enhanced.

<Adhesive resin layer>
The film of the present invention has an adhesive resin layer composed of a propylene-based resin adjacent to the easy peel layer. Moreover, in order to raise other interlayer strength, an adhesive resin layer can also be provided between those layers.

The propylene-based resin used for the adhesive resin layer preferably has a density of 890 kg / m ³ or more and a melting point of 130 ° C. or more in order to achieve sufficient interlayer adhesion even in high-temperature sterilization treatment.

  The lower limit of the thickness of the adhesive resin layer is preferably 5 μm or more, more preferably 8 μm or more, and still more preferably 10 μm or more from the viewpoint of obtaining sufficient interlayer strength. The upper limit is not particularly limited, but it is preferably 25 μm or less, more preferably 20 μm or less, and 15 μm or less, from the viewpoint of suppressing excessive production cost due to excessive total film thickness. It is further preferred that

<Polyamide resin layer>
The film of the present invention has at least one polyamide resin (hereinafter sometimes abbreviated as PA) layer for the purpose of imparting pinhole resistance. Moreover, when using the film of this invention for a deep-drawing bottom material, the deep-drawing formability of a film improves by arrangement | positioning of PA layer, and is preferable.

The polyamide resin is not particularly limited, but it is preferable to use 50 mol% or more of a lactam having 3 or more rings, polymerizable ω-amino acid, diamine and dicarboxylic acid.
When the polyamide resin is a copolymer, it is desirable that the content of the polyamide component is 80 mol% or more, preferably 85 mol% or more, and more preferably 90 mol% or more.
When the polyamide resin is a polymer blend, it is desirable that the polyamide component is contained at 70% by mass or more, preferably 75% by mass or more, and more preferably 80% by mass or more of the total mass of the polymer blend.

  Examples of the lactam having a three or more-membered ring include ε-caprolactam, ω-enantlactam, ω-laurolactam, α-pyrrolidone and the like.

  Examples of the polymerizable ω-amino acid include ω-aminocaproic acid, ω-aminoheptanoic acid, ω-aminononanoic acid, ω-aminound decanoic acid, ω-aminododecanoic acid and the like.

  As the diamine, for example, tetramethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine Aliphatic amines such as 2,4,4-trimethylhexamethylenediamine, 1,3 / 1,4-bis (aminomethyl) cyclohexane, isophorone diamine, piperazine, bis (4-aminocyclohexyl) methane, 2,2 Alicyclic diamines such as -bis- (4'-aminocyclohexyl) propane and aromatic diamines such as metaxylylene diamine and paraxylylene diamine.

  Examples of dicarboxylic acids include glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, nonanedioic acid, decanedioic acid, undecanedioic acid, aliphatic dicarboxylic acids such as dodecanedioic acid, and hexahydroterephthalic acid. Alicyclic carboxylic acids such as hexahydroisophthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid (1,2-body, 1,3-body, 1,4-body, 1,5-body, 1,6- Aromatic dicarboxylic acids such as body, 1, 7-body, 1, 8-body, 2,3-body, 2, 6-body, 2, 7-body) and metal-isophthalic sulfonic acid.

  In the polyamide resin layer, it is possible to use homopolymers or copolymers of the above three-membered ring lactam, polymerizable ω-amino acid, polyamide resin derived from diamine and dicarboxylic acid alone or as a mixture. Specifically, for example, 4 nylon, 6 nylon, 7 nylon, 11 nylon, 12 nylon, 46 nylon, 66 nylon, 66 nylon, 610 nylon, 611 nylon, 6 T nylon, 6 I nylon, MXD 6 nylon, 6-66. Nylon, 6-610 nylon, 6-611 nylon, 6-12 nylon, 6-612 nylon, 6-6T nylon, 6-6I nylon, 6-66-610 nylon, 6-66-12 nylon, 6-66- 612 nylon, 66-6T nylon, 66-6I nylon, 6T-6I nylon, 66-6T-6I nylon etc. are mentioned.

The polyamide resin is preferably a nylon-based resin from the viewpoint of imparting pinhole resistance to the film, and it is particularly preferable to use 6 nylon or 6-66 nylon.
In addition, two or more layers of the polyamide resin layer can be provided, and in that case, each layer may be formed of different types of nylon resins.

  The thickness of the polyamide resin layer is 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and the upper limit is 150 μm or less, preferably 120 μm or less, more preferably 100 μm or less. By setting the thickness to 10 μm or more, excellent pinhole resistance can be obtained, and by setting the thickness to 150 μm or less, the cuttability and deep drawability of the film can be maintained well.

<Propylene-based resin layer>
The film of the present invention may have a propylene-based resin layer on the side opposite to the adhesive resin layer side of the polyamide resin layer, that is, on the outside air side when producing the package as shown in FIG. it can.
By arranging the propylene-based resin layer on the outside air side of the package, it is effective to suppress curling of the flange portion after high-temperature sterilization (the seal portion around the housing portion in the package).
Examples of usable propylene-based resins include homopolypropylene, random copolymers or block copolymers with ethylene and the like. Homopolypropylene is preferred from the viewpoint of curl suppression and whitening prevention after high-temperature sterilization.

  The thickness of the propylene-based resin layer is 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and the upper limit is 150 μm or less, preferably 120 μm or less, more preferably 100 μm or less. By setting it as 10 micrometers or more, the curl of the flange part after high temperature sterilization can be suppressed, and the deep drawability of a film can be maintained favorable by setting it as 150 micrometers or less.

<Other layers>
The coextruded multilayer film of the present invention has an easy peel layer, an adhesive resin layer, and a polyamide resin layer in this order, and has another layer if it satisfies that the adhesive resin layer is adjacent to the easy peel layer. Can.

  For example, an ethylene-vinyl acetate copolymer saponified resin (hereinafter sometimes abbreviated as EVOH) layer between an adhesive resin layer and a polyamide resin layer, and / or MXD-6 nylon resin (hereinafter referred to as MXD) By arranging the layer (which may be abbreviated), the oxygen gas barrier property of the film can be improved.

  The lower limit of the thickness of the EVOH layer or MXD layer is preferably 5 μm or more, more preferably 7 μm or more, and still more preferably 10 μm or more. 50 micrometers or less are preferable, as for an upper limit, 40 micrometers or less are more preferable, and 30 micrometers or less are still more preferable. A good oxygen barrier property can be obtained by 5 μm or more, and a deep draw formability of the film is good by 50 μm or less.

<Whole film>
The film of the present invention can be produced by a known method such as coextrusion method, extrusion lamination method, dry lamination method and the like, and coextrusion method is preferable from the viewpoint of being able to concentrate the production steps.
In each layer of the film of the present invention, if necessary, an antifogging agent, an antistatic agent, a heat stabilizer, a nucleating agent, an antioxidant, a lubricant, an antiblocking agent, a mold release agent, an ultraviolet absorber, etc. It can add in the range which does not impair the objective of the present invention.

  70 micrometers or more are preferable, as for the lower limit of the total thickness of the film of this invention, 80 micrometers or more are more preferable, and 90 micrometers or more are still more preferable. The upper limit is preferably 300 μm or less, more preferably 250 μm or less, and still more preferably 200 μm or less. If it is 70 μm or more, good pinhole resistance can be obtained. If it is 300 μm or less, it is easy to obtain good easy openability (easy peelability), and in deep drawing, the molding heating time can be set relatively short, and deep drawing can be faithfully formed in the mold shape.

[Lid material]
The film of the present invention can be suitably used as a deep drawn bottom material, and an example of the configuration of a lid material to be an adherend in that case will be described below.
As a lid material of the package for retort, the laminated body of the outer layer which consists of a polypropylene resin film, the intermediate | middle layer which consists of a biaxially stretched polyamide resin film, and the inner layer which consists of a polypropylene resin film is mentioned. The outer layer is located on the outside air side of the package, and the inner layer is a layer located on the container side.
Below, the film of each layer is demonstrated.

<Outer layer: polypropylene resin film (PP film)>
The cover material is heated by contact from the outer layer at the time of heat sealing, and the melting point of the outer layer PP film is preferably 155 ° C. or more, more preferably 158 ° C. or more, 160 ° C. The above is more preferable. From that point of view, the use of homopolypropylene is preferred.

  The thickness of the outer layer PP film is preferably 20 μm or more. When it is 20 μm or more, it is effective for suppressing the curling of the flange portion of the package after the high temperature treatment, and when printing is performed, a good printing pitch can be maintained. The upper limit of the thickness of the PP film is not particularly limited, but is preferably 100 μm or less, more preferably 80 μm or less, and still more preferably 60 μm or less in order that the total film thickness becomes too thick and the heat sealability does not deteriorate.

<Interlayer: Biaxially Oriented Polyamide Resin Film (OPA Film)>
As the polyamide resin used for the OPA film, the exemplified resins can be used for the polyamide resin layer of the film of the present invention. The film draw ratio is not particularly limited as long as the draw effect appears, but the film flow direction is longitudinal. When the film width direction is horizontal, at a stretching temperature of 50 to 150 ° C., 2.5 times or more in length, 3.0 times or more in width, preferably 2.7 to 3.2 times in length, 3.3 to 4 in width. It is 0 times. The hot water shrinkage ratio of the OPA film at 95 ° C. for 5 minutes is 1.0 to 3.0% in length, 1.5 to 3.5% in width, preferably 1.5 to 2.5% in length, and 1.8 to It is 2.8%.
In addition, as the OPA film, a stretched film of a commercially available 6 nylon / MXD6 nylon / 6 nylon structure or a 6 nylon / EVOH / 6 nylon structure can also be suitably used.

  10-40 micrometers is preferable, as for the thickness of an OPA film, 12-30 micrometers is more preferable, and 15-25 micrometers is still more preferable. A good pinhole resistance is obtained by 10 μm, and a good cuttability of the film is obtained by 40 μm.

<Inner layer: polypropylene resin film (PP film)>
The lower limit of the melting point of the inner layer PP film is preferably 125 ° C. or more, more preferably 130 ° C. or more, and still more preferably 135 ° C. or more, because the lid layer inner layer does not fuse with the base material during high temperature sterilization. In addition, the upper limit of the melting point of the inner layer PP film is preferably 155 ° C. or less, more preferably 150 ° C. or less, and 145 ° C. or less, since the lid material inner layer is heat sealed without welding the lid material outer layer to the sealing heat plate. Is more preferred. From this point of view, use of a random copolymer of propylene and α-olefin is preferable.

  The thickness of the inner layer PP film is preferably 30 to 150 μm from the viewpoint of heat sealability, more preferably 35 to 120 μm, and still more preferably 40 to 100 μm.

<Overall lid material>
The total thickness of the lid is preferably 150 μm or less, more preferably 50 to 130 μm, and still more preferably 70 to 110 μm from the viewpoint of heat sealability. When it is 150 μm or less, the seal heating time can be set short, and the good heat sealability can provide sufficient packaging ability.

  The thickness ratio of the outer layer, the intermediate layer and the inner layer of the laminated film constituting the lid material is from the viewpoint of suppressing the curling of the flange when forming the deep-draw package, outer layer: intermediate layer: inner layer = 20-80: 10 50:10 to 100 are preferable, 25 to 60:10 to 40:30 to 80 are more preferable, and 30 to 50:15 to 30:40 to 70 are more preferable.

  The laminated film which comprises a lid material can provide a printing layer between an outer layer and an intermediate | middle layer. The printing layer is not limited to a layer representing a pattern, characters and the like, and may be a colorless and transparent layer consisting of only medium or resin (vehicle). In addition, it may be a layer consisting of a colorless and transparent layer consisting of only medium or resin (vehicle) and a layer representing a pattern or a character, etc., if necessary, such as antistatic, ultraviolet light absorption and ultraviolet light shielding. It may have a layer having a function.

  The formation of the printing layer can be carried out by a known method such as gravure printing, offset printing, screen printing, etc. However, quick-drying volatile-drying ink can be used, and high-speed printing can be performed with a web-type rotary printing press It is preferable to form by gravure from a viewpoint of etc. After forming the inner layer and the intermediate layer of the lid material, printing is performed, and then the film is laminated by a dry lamination method to provide a printed layer, and a bottom material having an excellent appearance is obtained.

  In each layer of the lid material, according to the present invention, an antifogging agent, an antistatic agent, a heat stabilizer, a nucleating agent, an antioxidant, a lubricant, an antiblocking agent, a mold release agent, an ultraviolet absorber, etc. It can be added in the range which does not impair the purpose of.

Hereinafter, although the example of the film of this invention is shown, this invention is not limited to this.
The film of the present invention can be used as a film of a bag, as a lid of a deep-draw package or as a bottom material, but in the following examples, an example of using the film of the present invention as a deep-drawn bottom Show.

A co-extruded multilayer film was produced using the resin raw material of the symbol shown below for each layer of the film of an Example and a comparative example.
The melting point of the resin is measured in accordance with the JIS K 7121 method.

PA; 6 nylon PP; polypropylene resin EVOH; ethylene-vinyl acetate copolymer saponification (high heat resistance grade)
MXD; MXD-6 nylon ADPP; polypropylene adhesive resin (density 0.89 kg / m ³ , melting point 161 ° C.)

EP 1; composition of propylene-based resin (melting point 140 ° C.), styrenic elastomer, and linear low density polyethylene (melting point 120 ° C.), composition weight ratio 66: 4: 30
EP2: composition of propylene-based resin (melting point 140 ° C.), styrenic elastomer, and high density polyethylene (melting point 130 ° C.), composition weight ratio 66: 4: 30
EP 3; composition of propylene resin (melting point 140 ° C.) and high density polyethylene (melting point 130 ° C.), composition mass ratio 70:30
EP 4; composition of propylene-based resin (melting point 125 ° C.) and high density polyethylene (melting point 130 ° C.), composition mass ratio 70:30

The layer configuration of the coextruded multilayer film of each example is as follows. The numbers in parentheses are the layer thickness (μm).
Example 1 PA (100) / ADPP (10) / EP1 (10)
Example 2 PP (50) / PA (50) / ADPP (10) / EP1 (10)
Example 3 PA (100) / ADPP (10) / EP2 (10)
Example 4 PA (90) / EVOH (10) / ADPP (10) / EP2 (10)
Example 5 PA (90) / MXD (10) / ADPP (10) / EP2 (10)
Example 6 PP (50) / PA (50) / ADPP (10) / EP2 (10)
Comparative Example 1 PA (100) / ADPP (10) / EP3 (10)
Comparative Example 2 PA (100) / ADPP (10) / EP 4 (10)

<Evaluation method>
(1) Production of Deep Drawing Package The coextruded multilayer film produced in each example is used as a film for deep drawing base material, and the following lid material is used in a deep drawing packaging machine (FV6300 manufactured by Omori Machinery Co., Ltd.) The package as shown in FIG. 2 was produced by setting the seal width to 7 mm, the seal time to 2 seconds, and the seal temperatures to 140 ° C., 150 ° C. and 160 ° C., respectively.
In FIG. 2 and FIG. 3, the shaded area 5 is a deep-drawn portion including hamburger as the content 8, and the peripheral portion of the content is the heat seal portion 6 of the bottom material and the lid. The corner portion is the opening trigger portion 7 in which the lid material and the bottom material are not heat sealed. The long side of the package is 140 mm, the short side is 120 mm, and the opening trigger portion is 30 mm wide by 30 mm.

[Lid material]
The laminated film was produced by the dry lamination method using each film shown with the following abbreviations.
h-CPP; non-oriented homopolypropylene film (melting point 160 ° C, thickness 30 μm)
OPA; biaxially stretched nylon 6 film (melting point 220 ° C, thickness 15 μm)
OPET; biaxially stretched polyethylene terephthalate film (melting point 250 ° C, thickness 12 μm)
r-CPP; non-oriented random polypropylene film (melting point 140 ° C, thickness 40 μm)

<Lid 1> h-CPP // OPA // r-CPP
<Lid 2> OPA // r-CPP
<Cover 3> OPET // OPA // r-CPP

(2) Welding of Lid to Seal Hot Plate Using the coextruded multilayer film of each example and the lid, when heat sealing was performed at each temperature, it was observed whether the lid was welded to the seal hot plate. . The case without welding was evaluated as "○", and the case with welding was evaluated as "x".

(3) Easy peelability (EP)
Peeling strength at the time of heat sealing at each temperature using coextruded multilayer film of each example and lid material is conditions of autograph machine (MCT-2150 manufactured by A & D Co., Ltd.), peeling speed of 200 mm / min. It measured by.

(4) Curl height of flange The deep drawn package heat-sealed at 150 ° C using the coextruded multilayer film of each example and a lid material is retorted at 121 ° C for 30 minutes and allowed to cool, As shown in 2, when the bottom 4 of the package was placed on the upper side and the lid 5 was on the lower side, the height of the highest curled portion of the flange portion with respect to the horizontal surface 6 was measured.

(5) Fusion of the opening trigger part The deep drawn package heat-sealed at 150 ° C using the coextruded multilayer film of each example and a lid material is retorted at 121 ° C for 30 minutes, and the bottom material of the opening trigger part The presence or absence of fusion between the cover and the lid was observed. The case without fusion was evaluated as “○”, and the case with fusion was evaluated as “x”.
(6) Fusion of base material films Using two coextruded multilayer films of 10 cm square in each example, with easy peel layers facing each other, seal width 7 mm, seal time 2 seconds, seal temperature 150 ° C. The four sides around the film were heat sealed to produce a bag. The pouch was subjected to retort treatment at 121 ° C. for 30 minutes or 130 ° C. for 30 minutes, and the presence or absence of fusion between the films was observed. The case without fusion was evaluated as “○”, and the case with fusion was evaluated as “x”.

Experimental Example 1
Table 1 shows the results of evaluation methods (1) to (6) using the coextruded multilayer film of each example and the lid 1. In addition, "EP" in a table | surface means the peeling strength of an evaluation method (3), and the unit of a numerical value is (N / 15 mm). Moreover, "curl" means the largest curl height of the evaluation method (5), and the unit of a numerical value is (mm).

From Table 1, Examples 1-6 did not have welding to the sealing heat board of a lid material outer layer in sealing temperature 140 and 150 degreeC, and easy peel property was also favorable. Further, even when retort was performed, there was no fusion to the inner layer of the lid 1 and the curl was small.
In Example 2, the curl was particularly small by arranging the PP layer in the outermost layer.
In Examples 3 to 6, since high melting point polyethylene was used for the easy peel layer, the easy peel layers of the films did not fuse together even at 130 ° C. high retort conditions.

On the other hand, in Comparative Example 1, the easy peel layer does not contain a styrene-based elastomer, the peel strength is weak, the heat seal adhesion is insufficient, and the risk of the bag breakage at the seal portion of the package is concerned. Was the result.
In Comparative Example 2, although a styrene-based elastomer was not contained in the easy peel layer, a peel strength of 2.0 N / 15 mm or more was obtained by blending a propylene resin having a low melting point, but the melt at the opening trigger portion after retort Wearing occurred.

<Experimental Example 2>
The results of evaluation methods (1) to (5) using the coextruded multilayer film of Example 1 and lids 1 to 3 are shown in Table 2.
Moreover, the result of having performed evaluation method (1)-(5) is shown in Table 3 using the co-extruded multilayer film of Experimental example 6, and the lid materials 1-3.
Abbreviations in the table are the same as in Table 1.

  From Tables 2 and 3, since the lids 2 and 3 use OPA and OPET, which have a melting point higher than h-CPP of the outer layer of the lid 1, outer layer welding to the seal heat plate even at 160 ° C. seal Did not occur. Further, compared to the lid 1, the curl of the flange after retort is large, and the transportability of the product and the appearance product value tend to be lowered.

  According to the coextruded multi-layer film for retort of the present invention, since the anti-fusion coating is unnecessary, the coating manufacturing process becomes unnecessary, and the manufacturing cost can be reduced. In addition, while maintaining seal adhesion at the time of retort, since the fusion of the opening trigger part does not occur and it has good easy peelability, the consumer is not burdened with opening work, and the convenience is high. A package for retort can be provided.

DESCRIPTION OF SYMBOLS 1 easy peel layer 2 adhesive resin layer 3 polyamide resin layer 4 propylene-based resin layer 5 deep drawing part 6 heat seal part 7 opening trigger part 8 contents 9 lid material 10 horizontal surface 11 curl height

Claims (7)

  A coextruded multilayer film having an easy peel layer, an adhesive resin layer, and a polyamide resin layer in this order, wherein the easy peel layer is composed of a propylene resin, a styrene elastomer, and an ethylene resin, and the adhesive resin layer A coextruded multilayer film for retort, characterized in that it is composed of a propylene-based resin and is adjacent to an easy peel layer.   The melting point of the propylene-based resin of the easy peel layer is 140 ° C. or higher, and the ethylene-based resin of the easy peel layer contains 55% by mass or more of high density polyethylene resin with respect to 100% by mass of ethylene-based resin. Item 6. A coextruded multilayer film for retort according to Item 1.   It heat-seals at 150 degrees C with the adherend comprised with a polypropylene resin, and it is 23 N of peeling strengths after cooling at 2.0 N / 15 mm width or more and 12.0 N / 15 mm width or less. Coextruded multilayer film for retort.   Heat sealing is performed with an adherend made of polypropylene resin, a part of which is not heat sealed and used as an opening trigger portion, and the opening trigger portion is not fused even if retort processing is performed at 121 ° C. for 30 minutes. The coextruded multilayer film for retort as described in any of the above.   The coextruded multilayer film for retort according to any one of claims 1 to 4, wherein a propylene-based resin layer is provided on the side opposite to the adhesive resin layer side of the polyamide resin layer.   A lid material or a deep-drawn bottom material using the coextruded film for retort according to any one of claims 1 to 5.   A retort package comprising the lid material or deep-drawn bottom material according to claim 6, and a polypropylene-based resin adherend.

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