JPH02269044A - Soft multilayer film - Google Patents

Abstract

PURPOSE:To enhance the preservability of content, fitteness and mechanical strength at low temp. by laminating a soft vinyl chloride resin as a soft main constitutional material, an oxygen barrier layer, a seal layer and a mechanical strength imparting layer, if necessary, through an adhesive layer. CONSTITUTION:A soft vinyl choride layer 1 as a soft main constitutional material, an oxygen barrier layer 2, a seal layer 4 and a mechanical strength imparting layer 3 are laminated, if necessary, through an adhesive layer 5. The mechanical strength imparting layer 3 is composed of polyurethane, a polyester elastomer, polybutene, an ionomer, an ethylene/acrylic acid copolymer or an ultralow density polyethylene. By this method, flexibility and mechanical strength can be obtained in a well-balanced state and, especially, thrust resistance and bending-resistant strength under environment of 10 deg.C or lower keeping food in cold storage can be enhanced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is used for vacuum packaging (hereinafter referred to as skin bank packaging) in which a film is heat-formed using a hot plate and then heat-sealed continuously without cooling the film. The present invention relates to a multilayer film for food packaging that is flexible and has excellent fit to contents.

(Prior art) Packaging has traditionally been done using plastic film, and the most convenient method is to fill a film that has been formed into a certain shape in advance, and then seal the contents on all sides with another film. It is being said.

When packaging foods such as processed meat and smoked seafood products, the above-mentioned method is used in a continuous machine, similar to deep crocodile/squeezing packaging. We use so-called vacuum packaging, which seals products in a vacuum to prevent them from being present.

At this time, in order to further improve the shelf life, it is more effective to use a barrier film that does not pass oxygen, which promotes food oxidation and bacterial growth.
Multilayer films using vinyl alcohol copolymers or vinylidene chloride resins have been considered and are widely used.

However, deep drawing vacuum packaging is simple and convenient for items with a fixed shape, but for items with irregular shapes or sliced items arranged in a staggered manner, the size of the molded product becomes larger than the contents. Therefore, during vacuum packaging, the formed film becomes wrinkled and wrinkles.Not only does it look bad, but it also causes cracks and pinholes. In addition, a film that has been cooled to near room temperature after molding has a poor fit to the contents, and moisture accumulates between the film and the contents, resulting in poor appearance and further deterioration of quality.

Therefore, instead of forming the film in advance, a method has been considered in which the film is heat-formed using a hot plate in a vacuum box and then heat-sealed continuously without cooling the film. Since it adheres closely to the contents, it has a good fit to the contents.

It is preferable that the film used be flexible, and the slack in the film caused by the difference between the size of the mold and the size of the contents can be absorbed by rubber-elastic molding, as shown in Japanese Utility Model Application Publication No. 140829/1983. Films made of a laminated layer of soft vinyl chloride resin, vinylidene chloride resin, and a sealing layer are widely used.

However, normally packaged foods are transported at temperatures below 10°C, and the soft vinyl chloride resin that is the main constituent material of the film becomes brittle at low temperatures, resulting in insufficient strength for the film as a whole, resulting in cracks and pinholes. occurs, and the shelf life of the contents is impaired.

In addition, in deep drawing packaging, 6-nylon and 6-6.6 nylon layers are introduced to increase the strength of the film, but it is too stiff for skin pack packaging, and the rubber elastic molding is small. As a result, a problem arose in that the fit was insufficient and the molded walnuts of the film remained wrinkled.

(Problems to be Solved by the Invention) In order to solve the above-mentioned problems, the present invention was completed through intensive research on the puncture resistance and layer resistance of various flexible resins at low temperatures. The purpose is to provide a multilayer film for skin backing that has excellent preservability of contents, is flexible, has good fitting properties, and has excellent mechanical strength at low temperatures.

(Means for Solving the Problems) The present invention includes a soft vinyl chloride resin layer as a soft main constituent material, an oxygen gas barrier layer, a sealing layer, and a mechanical strength imparting layer, which are laminated via an adhesive layer as necessary. It is a flexible multilayer film that is characterized by:

The soft vinyl chloride resin used in the present invention has an average polymerization degree of 7.
00 to 1800 vinyl chloride homopolymer, ethylene-vinyl chloride copolymer with ethylene content of 10% or less, or ethylene-vinyl acetate copolymer with ethylene-vinyl acetate content of 12% or less
Vinyl acetate-vinyl chloride graft copolymer (furthermore, a mixture of these with 40 to 70 parts by weight of a plasticizer added to 100 parts by weight of the base resin, or ethylene-vinyl acetate-chloride with a vinyl chloride ratio of 70 to 40%) Vinyl graft copolymers and urethane-vinyl chloride copolymers can be used.

Plasticizers for soft vinyl chloride resin include phthalic acid, phosphoric acid,
Use known ingredients such as fatty acid, polyester, toric acid, pyromellitic acid, etc., and add other known ingredients such as stabilizers, lubricants, processing aids, secondary plasticizers and stabilizers, etc. be able to.

In order for the film to have good rubber elasticity, the proportion of the soft vinyl chloride resin is preferably 35% or more.

As a mechanical strength-enhancing layer, it has flexibility that does not prevent the elastic return of the film due to the rubber elasticity of the soft vinyl chloride resin, and it maintains strength against puncture, impact, and bending without becoming brittle even at low temperatures of 5°C or lower. Preferably, the following can be used:

Ester-based and ether-based polyurethanes are used, and thermoplastic polyurethanes having a Schitzer hardness of 55 degrees or less on the D scale are preferred.

The polyester elastomer is a block copolymer of a hard segment which is a condensation unit of terephthalic acid or isophthalic acid and a dihydric alcohol, and a soft segment which is a condensation unit of terephthalic acid or isophthalic acid and a dihydric alcohol having an ether bond. Preferably, a certain saturated polyester is used and has a melting point of 170° C. or less and a Shore hardness of 55 degrees or less on the D scale.

Polybutene-1 may be a homopolymer or a copolymer with ethylene, and preferably has a Vicat softening point of 70° C. or less and a Shore hardness of 55° or less on the D scale.

The ionomer used is one cross-linked with sodium or zinc with 9 to 15% methacrylic oxygen I, and preferably has a Vicat softening point of 75° C. or less and a Shore hardness of 63 degrees or less on the D scale.

Ethylene-acrylic acid copolymer has an acrylic acid content of 6 to 1
2% is used, and preferably has a Vicat softening point of 85° C. or less and a Shore hardness of 60 degrees or less on the D scale.

Ionomers and ethylene-acrylic acid copolymers have excellent sealing properties, so they can also serve as a sealing layer.

The ultra-low density polyethylene used has a density of 0.89 to 0.91, and has a Vicat softening point of 84°C or less and a Situ hardness of D.
Preferably, the angle is 40 degrees or less on the scale.

As the oxygen gas barrier layer, a vinylidene chloride resin or an ethylene-vinyl alcohol copolymer can be used. It is a binary or multi-component copolymer with monomers, and known plasticizers, stabilizers, etc. can be added as necessary.

The ethylene-vinyl alcohol copolymer used has an ethylene content of 32 to 47 mol% and a Young's modulus of 130 kgf/ms'' or less.

Ethylene resins for the sealing layer include low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-α olefin copolymer, ethylene-acrylic acid copolymer, ethylene-alkyl acrylate copolymer, Ionomer resin etc. can be used.

The adhesive layer is made of resin such as low-density polyethylene, linear low-density polyethylene, ethylene-α-olefin copolymer, ethylene-propylene copolymer, high-density polyethylene, ethylene-vinyl acetate copolymer, polypropylene, etc., and acrylic acid, Monobasic unsaturated fatty acids such as methacrylic acid or dibasic unsaturated fatty acids such as maleic acid, fumaric acid, itaconic acid, and those obtained by chemically combining these anhydrides, vinyl acetate content 15 % or more of ethylene-
Vinyl acetate copolymer, ethylene-maleic anhydride copolymer, and ethylene-methyl methacrylate-glycidyl acrylate terpolymer can be used alone or in combination of two or more.

The multilayer film of the present invention can be produced by a coextrusion method or a known dry lamination method, but since the number of layers is large, the coextrusion method is preferred because the production process is simple.

In addition, films produced by T-die coextrusion have anisotropy in physical properties in the longitudinal and transverse directions, so a known method can be used to
A film having shrinkage force and elastic return with a well-balanced length and width can also be obtained by axial stretching or uniaxial stretching in the transverse direction.

(Function) The film of the present invention is a skin pack packaging film mainly composed of a soft vinyl chloride resin that is flexible and has excellent rubber elasticity. Since it introduces a flexible mechanical strength-enhancing layer that does not alienate the skin, it has a good balance of flexibility and mechanical strength that could not be achieved by simply using strong resins such as polyamide, and is especially suitable for food products. Excellent puncture resistance and bending resistance when stored in a refrigerated environment at temperatures below 10°C.

(Example) 3 to 6 multilayer films with each layer configuration as shown in Table 1 were prepared.
The resin was melt-extruded using a stand-alone extruder and produced by a coextrusion method. The thickness of all the obtained multilayer films is 1
The evaluation results are shown in Table 1.

The resins used are as follows.

O Soft vinyl chloride resin: PVC average degree of polymerization 1300 Vinyl chloride homopolymer lO cap 1 part Plasticizer 1 part polyester with a molecular weight of 1800 1 part Epoxidized linseed oil 5 parts by weight Polyurethane: PU ester system Situa hardness (Roscale) 50 Degree density 1.19g/cm' 100% tensile stress 100kg
f/cii polyester elastomer: TPE density 1.15g/cd Sitza hardness (Roscale) 40 degrees, melting point 163°C Polybutene: PB Density 0.90g/cj Sitza hardness (Roscale) 4
0 degree Vicat Softening point 59°C Melting point 71°C Ionomer: IONO tacrylic acid content 10% Sodium crosslinked type Density 0.94g/cj
Melting point: 96°C Vicat softening point: 74°C Situ hardness (Roscale): 62° Ethylene-acrylic acid copolymer: EAA acrylic acid oxygen content % Density: 0.94 g/cd Vicat softening point: 80°C
Shea hardness (roscale) 58 degrees Ultra low density polyethylene: VLDPE density 0.90 g/d
Vicat softening point 70°C Situa hardness (Roscale) 32
Polyethylene-vinyl acetate copolymer (vinyl acetate content 25%)
): EVA-25Mitsui Dupont Polychemical ■Evaflex P 2505
C Ethylene-vinyl acetate copolymer (vinyl acetate content 17%)
): EVA-17 manufactured by Mitsui Dupont Polychemical ■ Evaflex V527-4 Vinylidene chloride resin 1: PVDC-1 Vinylidene chloride 78 parts by weight Copolymer of 22 parts by weight of vinyl chloride Density 1.65 g/cj Melting point 140° CO chloride Vinylidene resin■ Vinylidene chloride 92 parts by weight: PVDC-n Acrylic acid Copolymer of 8 parts Density: 1, 70 g Nod Melting point: 155°C Ethylene-vinyl alcohol co-11c: EVOH Ethylene content: 144 mol% Melting point: 164°C Young Rate 110kgf/■ 閤! 0 acid-modified ethylene-vinyl acetate copolymer: Ad manufactured by Mitsubishi Yuka■ Modic E 300 HO direct image low density polyethylene: LL [JP! ! Density 0.93g/d
Melting point 122 degrees Bikaft softening point 110 degrees Celsius hardness (D scale) 55
Degree O6-6.6 Nylon: 6-6.6Ny Made by Ube Industries ■
UBE nylon 5033B evaluation methods are as follows.

1. Suitability for skin pack FV-630081 made by Omori Machinery Co., Ltd. as a sealer and mold 180×135mm, depth 12m, four corners are I
To install the OR shape, skin pack the films of Examples and Comparative Examples as lid materials under the conditions of sealing temperature 130°C, sealing time 1 second, and vacuum time 4.0 seconds, and wrinkles remain for 1 second, vacuum The films of Examples and Comparative Examples were skin-packed as lid materials for a time of 4.0 seconds, and it was examined whether wrinkles remained.

The bottom material is 120μ hard vinyl chloride sheet and 30μ ethylene-vinyl acetate copolymer with 10% vinyl acetate content.
The contents are dry laminated with a thickness of 2
Three slices of sliced ham with a diameter of 100 m were arranged in a staggered manner.

No wrinkles remain on O-back products.

Some Δ-packed products retain wrinkles, while others do not.

Wrinkles appear on X-back products.

2. Fit property A skin pack was applied in the same manner as in ①, and the adhesion of the contents to the unevenness was examined.

O The film adheres neatly to the unevenness of the contents.

×Air or liquid has accumulated in the recesses of the contents.

Or the convex part is crushed.

3. Using a puncture strength autograph, use a puncture needle with a sail of 5R at the tip of 20
The load when breaking through the film at a speed of 0 n+m/min was measured.

The measurement was performed after the sample was left in an atmosphere at 5° C. for 5 minutes.

4. Flexural Strength (Gelbo Test) Using a Gelpo Flex Tester No. 902 manufactured by Rigaku Kogyo Co., Ltd., torsional expansion and contraction at 440° C. was applied 300 times, and the number of pinholes generated was counted.

Incidentally, the torsional expansion and contraction was performed in an atmosphere at 5°C.

(Effects of the invention) The film obtained according to the invention has oxygen gas barrier properties,
It has excellent sealing properties, flexibility, and fit, and is particularly resistant to pinholes at low temperatures, so packaged products have a good appearance and have excellent storage stability, and pinholes occur even during transportation and storage at low temperatures. It is suitable as a skin pack packaging film.

[Brief explanation of drawings]

FIG. 1 shows implementation JI of the present invention! FIG.

Claims (2)

[Claims] (1) A soft multilayer characterized by being formed by laminating a soft vinyl chloride resin layer as a soft main constituent material, a basic gas barrier layer, a sealing layer, and a mechanical strength imparting layer via an adhesive layer as necessary. film. (2) The mechanical strength-imparting layer is polyurethane, polyester elastomer, polybutene, ionomer, or ethylene ray.
The flexible multilayer film according to claim 1, which is an acrylic acid copolymer or an ultra-low density polyethylene.