JP2721395B2 - Multilayer film for skin pack - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used for vacuum packaging (hereinafter referred to as skin pack) in which a film is heated with a hot plate and then adhered to the contents with compressed air, and at the same time heat sealed. The present invention relates to a multilayer film for food packaging, which is flexible and excellent in fitting property to contents, and can be subjected to a boil sterilization treatment in order to further enhance the preservability of the contents.

[Conventional technology]

2. Description of the Related Art Conventionally, packaging with a plastic film has been performed, and as a simplest method, a method in which contents are put into a film preliminarily formed into a predetermined shape, and the four sides are sealed so as to cover with another film is widely performed.

In the packaging of foods such as processed meats and seafood paste products, the above-mentioned method is performed using a continuous machine called deep drawing packaging, but in the case of foods, there is no air inside to improve the preservability of the contents. That is, so-called vacuum packaging for sealing in a vacuum state is performed. In this case, in order to further enhance the preservability, it is more effective to use a barrier film that does not allow oxygen to pass through, which promotes the oxidation and recent growth of food, and an ethylene-vinyl alcohol copolymer or vinylidene chloride-based material is used as an oxygen barrier layer A multilayer film using a resin is considered and widely used.

However, deep-draw vacuum packaging is simple and convenient when the shape of the contents is fixed, but when the irregular-shaped or sliced products are staggered, the size of the molded product is larger than the contents. As it becomes, when it is vacuum-packaged, it is formed and the film is excessively wrinkled and not only looks bad, but also
It causes cracks and pinholes. Further, the film cooled to near normal temperature after molding has poor fit to the contents, so that moisture accumulates between the film and the contents, resulting in poor appearance and further deterioration of quality.

Therefore, instead of pre-forming the film, heat-forming the film with a hot plate in a vacuum box, and then continuously heat-sealing the film without cooling it, a method is considered. As a result, the fit property to the contents became good.

As the film to be used, a flexible and easily stretchable film is preferred, and an ethylene-vinyl alcohol copolymer or a vinylidene chloride resin is used as an oxygen gas barrier layer for low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-α.
Various materials laminated with ethylene-based resins such as olefin copolymers and ionomers have been considered and used.

However, products packed with foods are generally transported and stored at a low temperature of 10 ° C or less, but multilayer films composed of the above resins have insufficient mechanical strength at low temperatures and often generate pinholes during the distribution process. , The preservability of the contents was impaired. In deep-drawing packaging, to increase the film strength, 6
-Nylon was introduced, but the film became stiffer and the softening temperature of the film increased, so that this film could not be used for skin pack packaging.

Further, the use of boil sterilization treatment to increase the preservability of the contents is increasing, but in the case of a film for a skin pack made of the above resin, the outer layers are heat-sealed or the film becomes cloudy and loses commercial value. As a result, the boil sterilization treatment could not be performed.

[Problems to be solved by the invention]

The present invention examines various types of nylon resin softened by copolymerization in order to impart mechanical strength without impairing the flexibility and fittability of the film, and examines the processability into a film, furthermore, cloudiness due to boil sterilization treatment, outer layer resin. The purpose of this study was to study the transparency and heat resistance of the product.
An object of the present invention is to provide a multilayer film for skin pack which has excellent mechanical strength and can be subjected to a boil sterilization treatment.

[Means for solving the problem]

The present invention relates to 6-6,6 or 6 having a 30-90% 6-nylon ratio.
A -12 copolymer nylon layer (2), an oxygen gas barrier layer (3), an outer resin layer (1), and a seal layer (4) are laminated via an adhesive layer (5) as necessary. 100
A multilayer film for a skin pack, which can be subjected to a boil sterilization treatment at a temperature of 5 ° C. for 5 to 60 minutes.

The copolymerized nylon used in the present invention is a 6-12 copolymerized nylon obtained by random condensation polymerization of ε-caprolactam and aminododecanoic acid or a low-molecular-weight condensation product of hexamethylenediamine and adipic acid is randomly mixed with ε-caprolactam. 6-6,6 copolymer nylon obtained by condensation polymerization and having a 6-nylon ratio of 30 to 90% is used. Flexibility, 6-
Those having a low nylon ratio are preferred because they are flexible and have a low melting point, but the melt viscosity is low and processing into a film becomes difficult. Therefore, those having a 6-nylon ratio of 50 to 85%, a melting point of 200 ° C or lower, and an average molecular weight of 20,000 or more are preferable. .

As the outer resin layer, a soft vinyl chloride-based resin and a linear low-density polyethylene can be used as a flexible material having heat resistance that is not fused by boil sterilization treatment and has good transparency. The soft vinyl chloride resin is a vinyl chloride homopolymer having an average degree of polymerization of 700 to 1800, an ethylene-vinyl chloride copolymer having an ethylene content of 10% or less, or an ethylene-vinyl acetate having an ethylene-vinyl acetate copolymer content of 12% or less. A vinyl chloride graft copolymer, or a mixture obtained by adding 40 to 70 parts by weight of a solubilizing agent to 100 parts by weight of the base resin can be used. As the solvating agent for the soft vinyl chloride resin, use known ones such as phthalic acid type, phosphoric acid type, fatty acid type, polyester type, trimellitic acid type, pyromellitic acid type, and other stabilizers, lubricants, processing aids. A known material such as a secondary solubilizer and stabilizer can be added.

The linear low density polyethylene is obtained by copolymerizing ethylene with hexene or octene, and preferably has a density of 0.935 g / cm ³ or less, a melting point of 120 ° C. or more, and a softening point of 110 ° C. or more.

As the oxygen gas barrier layer, a vinylidene chloride-based resin or an ethylene-vinyl alcohol copolymer can be used.The vinylidene chloride-based resin has 60 to 97 parts by weight of vinylidene chloride and vinyl chloride, alkyl acrylate, acrylic acid,
It is a binary or multi-component copolymer with an unsaturated monomer such as acrylonitrile, and may contain a known solubilizer, stabilizer and the like as necessary.

An ethylene-vinyl alcohol copolymer having an ethylene content of 32 to 47 mol% and a Young's modulus of 150 kgf / mm ² or less is used.

Ethylene resin as the sealing layer is low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer, ethylene-
An acrylic acid copolymer, an ethylene-alkyl acrylate copolymer, an ionomer resin, etc. can be used, but an ethylene-vinyl acetate copolymer having a vinyl acetate content of 15 to 20%, which is flexible and has excellent low-temperature sealability, is often used. .

Examples of the adhesive layer include resins such as low-density polyethylene, linear low-density polyethylene, ethylene-α-olefin copolymer, ethylene-propylene copolymer, high-density polyethylene, ethylene-vinyl acetate copolymer, polypropylene, and acrylic acid, methacrylic acid. Monobasic unsaturated fatty acids such as acids or dibasic unsaturated fatty acids such as malenic acid, fumaric acid, itaconic acid, and those obtained by chemically combining these anhydrides, and a vinyl acetate content of 15% or more Ethylene
A vinyl acetate copolymer, an ethylene-maleic anhydride copolymer, an ethylene-methyl methacrylate-glycidyl acrylate terpolymer, and a copolymerized polyester resin can be used alone or as a blend of two or more.

Known methods such as a coextrusion method and a dry lamination method are used for the production of the multilayer film of the present invention, but it is preferable to use a coextrusion method in which the production process is simple because of the large number of layers.

[Action]

In order to obtain good fit properties in skin pack packaging, the film needs to have flexibility, but flexible materials that have been used for skin pack packaging have poor mechanical strength and often cause pinholes.

In the present invention, the strength is increased without impairing the flexibility of the film by using copolymerized nylon which is softened by copolymerization of 6-6, 6 or 6-12, and has a low melting point and a low softening point. It can be an excellent film. In addition, it has a heat resistance that does not fuse in hot water of 85 ° C to 98 ° C, and obtains a film that can be subjected to boil sterilization treatment by using a soft vinyl chloride resin excellent in transparency and a linear low-density polyethylene as an outer layer. be able to. At this time, if a soft vinyl chloride resin is used, there is no problem with heat resistance, but since the moisture permeability is large, if the treatment is performed at a high temperature for a long time, the inner barrier layer, nylon layer, adhesive layer can be passed through the outer soft vinyl chloride resin layer. It is preferable to limit the processing conditions to 85 ° C. for 30 minutes, 90 ° C. for 15 minutes, 95 ° C. for 10 minutes, and 98 ° C. for 5 minutes, since water infiltrates into the inside and causes cloudiness from the inside. On the other hand, when a linear low-density polyethylene is used, it is slightly inferior in flexibility and transparency, but since the moisture permeability as the outer layer resin is small, more severe boil treatment conditions (100 ° C. for 30 minutes or the like) can be performed.

Furthermore, in the case of skin pack packaging in which only the lid material is molded, the lid material is made of a soft vinyl chloride resin, and the bottom material is made of a linear low-density polyethylene. It is also possible to make a package that allows processing conditions.

In addition, the film of the present invention can be favorably used for skin pack packaging without boil processing.

〔Example〕

The multilayer film having each layer configuration as shown in Table 1
The resin was melt-extruded using six extruders and prepared by a co-extrusion method. All the obtained multilayer films have a thickness of 120
μ and the evaluation results are shown in Table 1. The resins used are as follows.

Soft vinyl chloride resin: PVC Average polymerization degree 1300 100 parts by weight of vinyl chloride homopolymer 100 parts by weight Solubilizer 50 parts by weight polyester of 1800 molecular weight 5 parts by weight of epoxidized linseed oil Vinylidene chloride resin: 92% by weight of PVDC vinylidene chloride Acrylic acid copolymer of 8 parts by weight Density 1.70 g / cm ³ Melting point 155 ° C ・ Ethylene-vinyl alcohol copolymer: EVOH Ethylene content 44 mol% Melting point 164 ° C Young's modulus 150kgf / mm ²・ Acid-modified ethylene-vinyl acetate copolymer Polymer: AD Modic E300H manufactured by Mitsubishi Yuka Co., Ltd.-Linear low density polyethylene: LLDPE Density 0.93 g / cm ³ Melting point 122 ° C Vicat softening point 110 ° C Shore hardness (D scale) 55 degrees ・ 6-12 copolymer nylon : 6-12Ny 12 component ratio 20% Melting point 200 ° C Average molecular weight 20,000 ・ 6-6,6 Nylon copolymer: 6-6,6Ny 6,6 component ratio 15% Melting point 195 ° C Average molecular weight 30,000 ・ 6-Nylon: 6- Ny UBE nylon manufactured by Ube Industries, Ltd. 1030B ・ Ethylene-vinyl acetate copolymer (vinyl acetate content 17%): EVA-17 Evaflex V527-4 manufactured by DuPont Mitsui Polychemicals Co., Ltd. ・ Ionomer: ION Himilan 1705 manufactured by DuPont Mitsui Polychemicals Co., Ltd. ・ Propylene- α-Olefin copolymer: TUF Mitsui Petrochemical Co., Ltd. Toughmer YR106L Each evaluation method is as follows.

1. Fitability Using a skin pack machine manufactured by Furukawa Seisakusho, skin pack was performed using the same film lid and bottom at the sealing temperature of 120 ° C and the film heating time of 20 seconds. Contents are thickness
Three sliced hams having a diameter of 2 mm and a diameter of 100 mm were staggered and used, and the fit to the contents was examined.

○ The film adheres neatly along the irregularities of the contents.

× Air or juice is accumulated in the concave portion of the content or the convex portion is crushed.

2.Puncture strength 200m with 0.5R tip piercing needle using autograph
The load when breaking through the film at a speed of m / min was measured.
The measurement was performed after the sample was left in an atmosphere at 5 ° C. for 5 minutes.

3. Flexural strength (Gelbotest) Using a No. 902 Gelboflex tester manufactured by Rigaku Kogyo Co., Ltd., 300 times of twisting expansion and contraction at 440 ° C. was performed 300 times, and the number of generated pores was counted.

 The torsion expansion and contraction was performed in a 5 ° C. atmosphere.

4. Suitability of boil The pack product prepared in 1 was subjected to boil sterilization treatment in a hot water bath, and the fusion of the film surface and the cloudiness of the film were examined. The treatment was performed at three conditions: 85 ° C. for 30 minutes, 95 ° C. for 15 minutes, and 98 ° C. for 15 minutes.

○ Good appearance without fusing or white turbidity.

C: Fusing or clouding occurs and the commercial value is lost.

[Effects of the Invention] The film obtained according to the present invention is excellent in oxygen gas barrier properties, sealing properties, flexibility, and fit properties, and has particularly strong pinhole resistance at low temperatures, and also has the drawback of conventional boil processing. Since fusion and cloudiness are eliminated, it is suitable as a skin pack packaging film for boil sterilization treatment.

[Brief description of the drawings]

FIG. 1 is a sectional view of a multilayer film showing an embodiment of the present invention.

Claims (2)

(57) [Claims] 1. A nylon layer of 6-6,6 or 6-12 copolymer having a 6-nylon ratio of 30 to 90%, an oxygen gas barrier layer, an outer resin layer, and a seal layer are laminated via an adhesive layer if necessary. A multi-layer film for skin packs, which can be subjected to a boil sterilization treatment within a condition range of 80 to 100 ° C. and 5 to 60 minutes. 2. The multilayer film for a skin pack according to claim 1, wherein the outer resin layer is a soft vinyl chloride resin or a linear low density polyethylene.