JP2015227040A - Coextrusion multilayer film for skin-pack lid material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coextrusion multilayer film for skin-pack lid materials which is excellent in pinhole resistance especially at low temperatures without using expensive resins such as ionomers, and furthermore has easy peelability and allows boiling sterilization.SOLUTION: A coextrusion multilayer film for skin-pack lid materials has, from outer layers, a ternary-copolymerized polyamide resin (3PA) layer, an adhesive resin (AD) layer, an ethylene-vinyl acetate copolymer saponified product (EVOH) layer, an adhesive resin (AD) layer, a linear low-density polyethylene (LLDPE) layer of a density of 0.910 or lower and/or an ethylene-vinyl copolymer resin (EVA) layer of a content of vinyl acetate of 8 mol% or higher and, as the innermost layer, a cohesion failure type easy peel layer. The thickness ratio of the ternary-copolymerization polyamide (3PA) layer is 40% or less of the total thickness; and the thickness ratio of the ethylene-vinyl acetate copolymer saponified product (EVOH) layer is 10% or less of the total thickness.

Description

  The present invention relates to a coextruded multilayer film which can be suitably used mainly as a lid for so-called skin pack packaging of foods such as ham, bacon, and processed fishery products.

Conventionally, PVC / PVDC / EVA film has been used as a skin pack film for sliced ham, bacon, processed fishery products, etc., but the processed fishery products with sharp bones are the contents. In addition, there is a problem that pinhole resistance is inferior particularly at low temperatures such as freezing, and there is still a trend of dechlorination of packaging materials.
For such problems, there is a film with a configuration in which Ny, EVOH, ionomer, and EVA are arranged. However, although the pinhole resistance is excellent, the Ny layer cannot be made too thick in terms of content adhesion. Therefore, there is a problem that pinhole resistance has to depend on an expensive ionomer layer. In addition, ionomers are weak against acetic acid, and there is a problem that they are difficult to use if the contents contain vinegar. (For example, Patent Document 1)
Further, Patent Document 2 includes a structure using polyamide as the outermost layer, EVOH as the middle layer, and a seal layer as the inner layer as a packaging that does not use an ionomer, has good adhesion to the contents, and does not have wrinkles. However, since it was produced by the biaxial stretching method, there was a problem that the shrinkage stress was strong and the contents were crushed.

Japanese Patent No. 3085626 JP 58-14743 A

  The present invention is intended to solve the above-mentioned problems of the prior art, and the problem of the present invention is that it does not use a large amount of expensive resins such as ionomers, and is excellent in pinhole resistance especially at low temperatures, and boil sterilization. It is also possible to provide a coextruded multilayer film for skin pack lid materials which has an easy peel property.

  The problem of the present invention is that the terpolymer polyamide resin (3PA) layer, adhesive resin (AD) layer, saponified ethylene-vinyl acetate copolymer (EVOH) layer, adhesive resin (AD) layer, density is 0 from the outer layer. .910 or less linear low density polyethylene (LLDPE) layer and / or ethylene-vinyl acetate copolymer resin (EVA) layer with vinyl acetate content of 8 mol% or more, cohesive failure type easy as innermost layer A coextruded multilayer film having a peel layer, wherein the thickness ratio of the terpolymer polyamide resin (3PA) layer is 40% or less of the total thickness, and the thickness ratio of the saponified ethylene-vinyl acetate copolymer (EVOH) layer Is achieved by 10% or less of the total thickness.

  According to the co-extruded multilayer film for skin pack lid material of the present invention, it does not use a large amount of expensive ionomer or the like, has excellent pinhole resistance particularly at low temperatures, has an easy peel property, and is boiled. It was possible to provide a coextruded multilayer film for skin packs that can be sterilized.

<Outermost layer: ternary copolymerized polyamide resin layer>
The outermost layer of the film of the present invention needs to be provided with a terpolymer polyamide resin in order to impart pinhole resistance, boil resistance and content adhesion.
The polyamide resin has a melting point and a decrease in crystallinity due to copolymerization, thereby increasing transparency, shrinkage, flexibility, and the like, and the suitability of the skin pack is improved by using the copolymerized polyamide resin.

Examples of the terpolymer polyamide resin include 6-66-610 nylon, 6-66-12 nylon, 6-66-612 nylon, and a mixture thereof. Among these, it is preferable to use 6-66-12 nylon.
6-66-12 nylon has higher heat shrinkability than binary copolymer polyamide resins such as 6-66 nylon and 6-12 nylon, and the content adhesion in the skin pack is good.
Further, the copolymerization ratio of 6 nylon of 6 nylon terpolymer polyamide resin is preferably 50% or more, and more preferably 70% in order to maintain physical properties suitable for skin pack such as stretchability and shrinkage of 6 nylon. The above is preferable.

  The lower limit of the thickness of the ternary copolymerized polyamide resin (3PA) layer is preferably 5% or more, more preferably 8% or more of the total thickness. Further, the upper limit is preferably 40% or less, and more preferably 30% or less. By setting the lower limit to 5% or more, good pinhole resistance can be obtained, and by setting the upper limit to 40% or less, good content adhesion can be maintained.

<Intermediate layer: Saponified ethylene-vinyl acetate copolymer layer>
The intermediate layer is provided with an ethylene-vinyl acetate copolymer saponified product (EVOH) layer for the purpose of imparting oxygen barrier properties. The ethylene content of EVOH used in the EVOH layer is not particularly limited, but it is preferably 27 mol% or more and 47 mol% or less, and 32 mol% or more and 44 mol% or less from the viewpoint of film formation stability. More preferably. Further, EVOH has a saponification degree of 90% or more, preferably 95 mol% or more. By maintaining the ethylene content of EVOH and the saponification degree within the above ranges, the coextrudability of the film of the present invention and the strength of the film can be improved.

  The thickness of the EVOH layer is not particularly limited, but the lower limit is 3% or more of the total thickness, and the upper limit is 10% or less of the total thickness. A sufficient oxygen barrier property can be obtained by setting the lower limit of the thickness of the EVOH layer to 3%, and good content adhesion can be maintained by setting the upper limit to 10%.

<Intermediate layer: linear low density polyethylene layer, ethylene-vinyl acetate copolymer resin layer>
For the purpose of imparting flexibility and adhesiveness to the contents, the intermediate layer is a linear low density polyethylene (LLDPE) layer having a density of 0.910 or less, and / or ethylene having a vinyl acetate content of 8% or more. A vinyl acetate copolymer resin (EVA) layer is disposed.
By making the density of LLDPE 0.910 or less, more preferably 0.905 or less, and by making the vinyl acetate content of EVA 8% or more, more preferably 10% or more, good flexibility and Content adhesion can be obtained.

  The intermediate layer may be a linear low density polyethylene (LLDPE) having a density of 0.910 or less alone, or an ethylene-vinyl acetate copolymer resin (EVA) having a vinyl acetate content of 8% or more. Or they may be stacked.

<Adhesive resin layer>
In the film of the present invention, at least one adhesive resin (AD) layer may be disposed between the outermost layer (3PA layer) and the intermediate layer (EVOH layer) or between the innermost layer and the intermediate layer. it can.
Further, from the viewpoint of further increasing the interlayer adhesion strength, it is preferable to dispose the intermediate layer between the EVOH layer and the innermost layer, or between the outermost layer (3PA) and the intermediate layer (EVOH layer).

The adhesive resin used in the adhesive resin layer is not particularly limited as long as the outermost 3PA layer, the intermediate EVOH resin layer, and the innermost layer can be bonded with required strength. Preferred is a polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof.
Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid and the like. In addition, as the adhesive resin, an ester or anhydride of the unsaturated carboxylic acid can be used, and as derivatives, methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, butyl methacrylate, acetic acid. Vinyl, glycidyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, sodium acrylate, or the like can be used.

  As a commercially available adhesive resin, the Mitsui Chemicals make, brand name Admer is mentioned, for example, It can use suitably. Among them, the LLDPE type or EVA type can be preferably used.

<Innermost layer: Easy peel layer>
The cohesive failure type easy peel layer, which is the innermost layer, is based on the mass of the entire easy peel layer (100% by mass) and the resin composition (a) of 40% by mass to 80% by mass and 20% by mass shown below. % To 60% by mass of the resin composition (b).
Resin composition (a): linear low density polyethylene (LLDPE) having a Vicat softening point of 90 ° C. or lower, ethylene-vinyl acetate copolymer (EVA) having a melting point of 100 ° C. or lower, ethylene having a melting point of 100 ° C. or lower. -Acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA) having a melting point of 100 ° C or lower, ethylene-methacrylic acid copolymer (EMAA) having a melting point of 100 ° C or lower, ethylene having a melting point of 100 ° C or lower- Resin composition that is at least one selected from the group consisting of methyl methacrylate copolymer (EMMA), ethylene-methyl acrylate copolymer (EMA) having a melting point of 100 ° C. or less, and these ionomers Resin composition (b) : Resin composition whose main component is polypropylene (PP) or polybutylene (PB)

  The main component of the resin composition (a) is a linear low density polyethylene (LLDPE) having a Vicat softening point of 90 ° C. or lower, an ethylene-vinyl acetate copolymer (EVA) having a melting point of 100 ° C. or lower, and an ethylene having a melting point of 100 ° C. or lower. Acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA) having a melting point of 100 ° C. or lower, ethylene-methacrylic acid copolymer (EMAA) having a melting point of 100 ° C. or lower, ethylene-methacryl having a melting point of 100 ° C. or lower By forming a resin composition that is at least one selected from the group consisting of an acid methyl copolymer (EMMA), an ethylene-methyl acrylate copolymer (EMA) having a melting point of 100 ° C. or less, and these ionomers, Heat sealability can be obtained.

  By making the resin composition (b) a main component of polypropylene (PP) or polybutylene (PB), the cohesive failure can be imparted.

  The ratio of the resin composition (a) is 40% by mass to 80% by mass, more preferably 50% by mass to 70% by mass, and the ratio of the resin composition (b) is 20% by mass to 60% by mass, more preferably. By setting the content to 30% by mass or more and 50% by mass or less, good openability can be obtained.

  The thickness of the easy peel layer is not particularly limited as long as good heat sealability and openability can be obtained, but the lower limit is 3 μm or more, and the upper limit is 15 μm or less. By setting the lower limit value of the thickness of the easy peel layer to 3 μm, good openability can be obtained, and by setting the upper limit value to 15 μm, a good peeling state without stringing can be obtained.

<Other intermediate layers: ethylene-vinyl acetate copolymer layer, polyethylene layer>
In the intermediate layer, an ethylene-vinyl acetate copolymer (EVA) layer and a polyethylene (PE) layer can be provided as long as the content adhesion is not inhibited. The vinyl acetate content of EVA is not particularly limited, but is preferably 1.5 mol% or more and 20 mol% or less from the viewpoint of film-forming stability, and is 3 mol% or more and 15 mol% or less. More preferably it is.

  When the PE layer is disposed in the intermediate layer, the type of PE resin used in the PE layer is not particularly limited. For example, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), or a blend thereof can be used.

  The film of the present invention is an inorganic particle such as silica, talc, kaolin, calcium carbonate, or the like for the purpose of improving or adjusting various properties such as moldability and productivity within the range that does not significantly impair the effects of the present invention. Add additives such as pigments such as titanium and carbon black, flame retardants, weather resistance stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, nucleating agents, plasticizers, anti-aging agents, etc. it can.

<Layer structure>
The layer constitution of the film of the present invention is as follows: terpolymer polyamide resin (3PA) layer, adhesive resin (AD) layer, saponified ethylene-vinyl acetate copolymer (EVOH) layer, adhesive resin (AD) layer from the outer layer, A linear low density polyethylene (LLDPE) layer having a density of 0.910 or less and / or an ethylene-vinyl acetate copolymer resin (EVA) layer having a vinyl acetate content of 8 mol% or more, and cohesive failure as the innermost layer A co-extruded multilayer film having an easy peel layer of the type, wherein the thickness of the terpolymer copolymer polyamide resin (3PA) layer is 40% or less of the total thickness, and the saponified ethylene-vinyl acetate copolymer (EVOH) layer If the thickness is 10% or less of the total thickness, the layer structure of the other layers is not particularly limited.

  For example, a terpolymer polyamide resin (3PA) layer is (A), an EVOH layer is (B), a linear low density polyethylene (LLDPE) layer having a density of 0.910 or less (C), and vinyl acetate content When the ethylene-vinyl acetate copolymer resin layer of 8 mol% or more is represented as (D), PE or EVA layer as (E), adhesive resin layer as (F), and easy peel layer as (G), The following layer structure can be formed.

(1) A / B / F / C / G
(2) A / B / F / D / G
(3) A / B / F / C / D / G
(4) A / B / F / D / C / G
(5) A / F / B / F / C / G
(6) A / F / B / F / D / G
(7) A / F / B / F / C / D / G
(8) A / F / B / F / D / C / G
(9) A / B / F / E / C / G
(10) A / B / F / E / D / G
(11) A / B / F / E / C / D / G
(12) A / B / F / E / D / C / G
(13) A / F / B / E / F / C / G
(14) A / F / B / E / F / D / G
(15) A / F / B / E / F / C / D / G
(16) A / F / B / F / E / D / C / G
Among the above, a preferable layer structure is (5), (6), (7) or (8), and more preferably (7) or (8).

The coextruded film of the present invention can be produced using a known method. For example, an extrusion lamination method, a coextrusion inflation method, a coextrusion T die method, and the like can be used, and it is particularly preferable to use a coextrusion T die method.
In the above method, the film can be unstretched or stretched. However, in order to maintain the shape of the contents and wrap the film, the stretchability of the produced film and the contents adhesion are necessary. The non-stretching method is desirable.

Examples of the present invention will be described below, but the present invention is not limited thereto.
The following materials were used for each layer, and the layer configuration was described using abbreviations.
3PA: UBE Nylon 6-66-12 Ternary Copolymer Nylon made by Ube Industries PA: Novam 6Ny made by DSM Japan Engineering Plastics
2PA: DSM Japan Engineering Plastics Novamid 6-66 binary copolymer nylon Adhesive resin: Mitsui Chemicals Admer EVOH: Kuraray Eval (ethylene content 44 mol%)
Ionomer: High Milan EVA manufactured by Mitsui DuPont Chemical Co., Ltd .: Novatec EVA manufactured by Nippon Polyethylene (vinyl acetate content 15 mol%)
LL1: Japanese polyethylene kernel (density 0.903)
LL2: Japan Polyethylene Novatec LL (density 0.921)
Easy peel 1: Mixture of LLDPE (60%) with Vicat softening point 85 ° C and polybutene (40%) Easy peel 2: Mixture of EVA (55%) with melting point 97 ° C and random copolymer PP (45%) Easy peel 3: A mixture of EAA (55%) and random copolymer PP (45%) with a melting point of 99 ° C.

<Production of co-extruded multilayer film for skin pack lid>
Example 1:
Example 1 was obtained by obtaining a film having the following layer constitution by non-stretching of all layers coextrusion.
3 PA (15 μm) / Adhesive resin (10 μm) / EVOH (5 μm) / Adhesive resin (5 μm) / EVA (40 μm) / Easy peel 1 (5 μm)
Example 2:
Example 2 was obtained by obtaining a film having the following layer constitution by non-stretching of all layers coextrusion.
3 PA (20 μm) / Adhesive resin (5 μm) / EVOH (10 μm) / Adhesive resin (5 μm) / LL1 (65 μm) / Easy peel 2 (5 μm)
Example 3:
Example 3 was obtained by obtaining a film having the following layer constitution by non-stretching of all layers coextrusion.
3PA (20 μm) / Adhesive resin (5 μm) / EVOH (8 μsm) / Adhesive resin (5 μm) / LL1 (20 μm) / EVA (20 μm) / Easy peel 2 (3 μm)
Example 4:
A film having the following layer constitution was obtained by non-stretching by co-extrusion in all layers, and Example 4 was obtained.
3 PA (20 μm) / Adhesive resin (5 μm) / EVOH (8 μm) / Adhesive resin (5 μm) / LL2 (22 μm) / EVA (20 μm) / Easy peel 3 (5 μm)

Comparative Example 1:
A film having the following layer structure was obtained by non-stretching by coextrusion in all layers, and was designated as Comparative Example 1.
PA (15 μm) / Adhesive resin (10 μm) / EVOH (5 μm) / Adhesive resin (5 μm) / EVA (40 μm) / Easy peel 3 (5 μm)
Comparative Example 2:
A film having the following layer structure obtained by non-stretching of all layers coextrusion was obtained and used as Comparative Example 2.
2PA (20 μm) / Adhesive resin (5 μm) / EVOH (8 μm) / Adhesive resin (5 μm) / LL1 (20 μm) / EVA (20 μm) / Easy peel 2 (3 μm)
Comparative Example 3
A film having the following layer structure was obtained by coextrusion non-stretching in all layers, and was designated as Comparative Example 3.
3PA (20 μm) / Adhesive resin (5 μm) / EVOH (10 μm) / Adhesive resin (5 μm) / LL2 (67 μm) / Easy peel 2 (3 μm)
Comparative Example 4
A film having the following layer structure was obtained by non-stretching by coextrusion in all layers, and was designated as Comparative Example 4.
EVOH (20 μm) / adhesive resin (5 μm) / ionomer (10 μm) / EVA (35 μm) / easy peel 1 (5 μm)

<Production and evaluation of skin pack packaging sample>
Examples 1 to 4 and Comparative Examples 1 to 5 were used for the cover material, respectively, and EVOH (10 μm) / PA (20 μm) / adhesive resin (10 μm) / EVA (30 μm) to unstretched polypropylene (300 μm) for the bottom material. Using a sheet obtained by dry-laminating the coextruded film of), 100 g of sliced bacon was skin-packed using a skin pack packaging machine (Himan HI750 manufactured by Hipack) at a temperature of 140 ° C.
The following evaluation was performed on the skin-packed samples. The evaluation results are shown in Table 1.

<Content adhesion>
The film was in close contact with the contents, there was almost no wrinkles, the contents were hardly crushed, and those in good condition were marked with ◯, those with wrinkles, or those with crushed contents.
<Pinhole resistance>
Put 20 skin pack products in a cardboard box, leave it at a temperature of 5 ° C for 24 hours, drop it from a height of 1.5m onto a concrete surface, and if there is no pinhole, ○ What was done was made into x.
<Boil resistance>
Boil the skin pack product in hot water at 90 ° C for 15 minutes. The skin pack product was good when the gloss reduction and the pack products were good without blocking, and the gloss reduction or the pack product was blocking. X.
<Easy peel strength>
Cut the seal part of the skin pack product into a strip with a width of 15 mm in the film flow direction, and peel off the cover and bottom material at a speed of 200 mm / min at a temperature of 25 ° C. using a tensile tester. (Gf / 15 mm width) was defined as easy peel strength.

In Examples 1 to 4, the adhesiveness of the contents was good, the aptitude as a film for skin pack was high, the pinhole resistance was good, and boil sterilization was possible.
On the other hand, Comparative Examples 1 and 2 had poor shrinkage due to the use of highly crystalline nylon for the outermost layer, and wrinkles remained on the skin pack product during packaging, and the appearance was poor.
In Comparative Example 3, since only high-density polyethylene was used between the EVOH layer and the easy peel layer, the film was hard, wrinkles remained, and the appearance was poor.
Comparative Example 4 had poor pinhole resistance, and the outer layers were blocked during boil sterilization.

  The film of the present invention does not use expensive resins such as ionomers, and can be suitably used as a skin pack lid material that has excellent pinhole resistance at low temperatures, has easy peel properties, and can be boil sterilized. .

Claims (7)

  Ternary copolymer polyamide resin (3PA) layer, adhesive resin (AD) layer, ethylene-vinyl acetate copolymer saponified product (EVOH) layer, adhesive resin (AD) layer, linear chain with a density of 0.910 or less from the outer layer Co-extrusion having a continuous low density polyethylene (LLDPE) layer and / or an ethylene-vinyl acetate copolymer resin (EVA) layer having a vinyl acetate content of 8% or more and a cohesive failure type easy peel layer as the innermost layer It is a multilayer film, the thickness ratio of the terpolymer polyamide resin (3PA) layer is 40% or less of the total thickness, and the thickness ratio of the saponified ethylene-vinyl acetate copolymer (EVOH) layer is 10% of the total thickness. A co-extruded multilayer film for skin pack lid material, characterized by:   The coextruded multilayer film for skin pack lid according to claim 1, wherein the terpolymer polyamide resin (3PA) is 6-66-12 nylon.   3. The coextruded multilayer film for skin pack lid according to claim 1, wherein a thickness of the ternary copolymerized polyamide resin (3PA) layer is 10% or more and 30% or less of the total thickness. The total thickness of the ternary copolymerized polyamide resin (3PA) layer and the saponified ethylene-vinyl acetate copolymer (EVOH) layer is 15% or more and 40% or less of the total thickness. A coextruded multilayer film for skin pack lid material according to any one of the above. The cohesive failure type easy peel layer is based on the mass of the entire easy peel layer (100% by mass) and the resin composition (a) of 40% by mass to 80% by mass and 20% by mass to 60% by mass shown below. The coextruded multilayer film for skin pack lids according to claim 1, wherein the coextruded multilayer film is composed of a resin composition (b) having a mass% or less.
Resin composition (a): linear low density polyethylene (LLDPE) having a Vicat softening point of 90 ° C. or lower, ethylene-vinyl acetate copolymer (EVA) having a melting point of 100 ° C. or lower, ethylene having a melting point of 100 ° C. or lower. -Acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA) having a melting point of 100 ° C or lower, ethylene-methacrylic acid copolymer (EMAA) having a melting point of 100 ° C or lower, ethylene having a melting point of 100 ° C or lower- Resin composition (b) which is at least one selected from the group consisting of methyl methacrylate copolymer (EMMA), ethylene-methyl acrylate copolymer (EMA) having a melting point of 100 ° C. or less, and these ionomers ): Resin composition whose main component is polypropylene (PP) or polybutylene (PB). The coextruded multilayer for skin pack lid according to any one of claims 1 to 5, wherein an easy peel strength of the easy peel layer at a temperature of 25 ° C is from 0.8 N / 15 mm width to 5.0 N / 15 mm width. the film.   The coextruded multilayer film for skin pack lid according to any one of claims 1 to 6, wherein the total thickness is 40 µm or more and 150 µm or less.