JPS59224343A - Multilayer structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer structure with low gas permeability and excellent heat sealability.

Films and containers for food packaging require materials with particularly low permeability to gases such as oxygen. Saponified ethylene-vinyl acetate copolymer is a material with extremely low gas permeability, but it can be used as a multilayer structure with olefin polymers such as polyethylene, which has excellent heat sealability, for food packaging materials, etc. used in

However, since olefin polymers and saponified ethylene-vinyl acetate copolymers have poor adhesion to each other, they can be bonded by interposing an adhesive layer or by surface-treating the olefin polymer layer. Although attempts have been made to improve sex,
These methods have the disadvantage that the manufacturing process is complicated and economical methods such as coextrusion cannot be used. In addition, in order to completely improve the adhesion of the olefin polymer layer, a method of completely graft copolymerizing an unsaturated carboxylic acid to an olefin polymer has been carried out (Japanese Patent Publication No. 36872/1983, etc.), but the adhesive strength is It is insufficient.

Furthermore, a method has been proposed in which a mixture of an olefin polymer and a rubber substance is reacted with unsaturated carboxylic acids (Japanese Patent Application Laid-open No. 159239/1983). In this case, since the rubber substance and the olefin polymer are not uniformly dispersed, the addition reaction of the unsaturated carboxylic acid cannot be carried out smoothly, resulting in uneven reaction and poor adhesion.

In recent years, with the diversification of food packaging methods, food packaging materials have to meet harsher usage and molding conditions than ever before, and the conventional methods described above are simply unable to meet these demands.

Therefore, the present inventors have conducted thorough research into materials that eliminate the drawbacks of conventional products and meet the strict demands of recent years, and have completed the present invention.

That is, the present invention comprises a layer (4) consisting of a saponified ethylene-vinyl acetate copolymer, a solid rubber and 0.05% by weight.
Olefinic polymer layer CB containing ~5% by weight (based on solid rubber) of a reaction product with α,β-unsaturated dicarboxylic acids)
The present invention relates to a multilayer structure formed by laminating layers.

To explain the components of the mass layer (A), the saponified ethylene-vinyl acetate copolymer in the present invention is a saponified product of a copolymer containing 10 to 60 mol of ethylene. Those having a saponification degree of vinyl acetate units of 70 molar or higher have sufficiently low gas permeability and are particularly suitable for use as food packaging materials.

Next, to explain the components of layer (I3), the solid rubber in the present invention refers to a rubber-like polymer that is solid at room temperature and is unvulcanized. It doesn't matter if it's synthetic rubber or natural rubber. Specific examples of solid rubber include polybutadiene rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, polyimbutylene, butyl rubber, and styrene-butadiene rubber. Among these, polyimbutylene and butyl rubber are particularly preferred since they have excellent compatibility with olefin polymers.

The α,β-unsaturated dicarboxylic acids/acids to be reacted with the solid rubber are typically α,β-unsaturated dicarboxylic acids and derivatives such as their anhydrides and esters, and specifically maleic acid, fumaric acid, etc. acid, itaconic acid, maleic anhydride,
Itaconic anhydride, maleic acid monomethyl ester, fumaric acid monomethyl ester, etc. are used, and among these, maleic anhydride is particularly preferred.

The amount of σ,β-unsaturated dicarboxylic acids to be reacted with the solid rubber is 0.05% by weight based on 100% by weight of the solid rubber.
~5 fold is. Saratra preferably 0.1 to 3% by weight
It is. When the weight exceeds 5 ts, in addition to addition reaction,
Decomposition and crosslinking reactions occur, resulting in poor mixing with the resulting reaction product olefin polymer, making it impossible to obtain a good composition and poor adhesion to layer ω. If the weight is less than 0.05, the purpose of improving adhesion to layer (A) cannot be achieved.

The reaction between the Pj1 type rubber and the α,β-unsaturated dicarbonate is carried out under heating, preferably in the presence of a peroxide. Is this reaction occurring in the extruder or in the Panbury mixer? Ji'J! , a method of melt-mixing and reacting in a non-molten culm such as in ffl, or aromatic hydrocarbons such as benzene, xylene, toluene, hexane, benzene,
There are no particular limitations on the method, such as heating and mixing in a solvent such as an aliphatic hydrocarbon such as octane.
It is preferable to carry out the process in an extruder because it is simple and inexpensive.

Examples of the 'f1 peroxides include benzoyl peroxide, lauryl peroxide, azobisisobutyronitrile, dicumyl peroxide, t-butyl hydroperoxide, α,α'-bis(t-butyl peroxide), Organic peroxides such as diingrovir) benzene, di-t-butyl peroxide, and 2,5-di(t-butylperoxy)hexyne are preferably used.

The olefin polymer to which the reaction product of solid rubber and α,β-unsaturated dicarboxylic acids is added is as follows:
For example, polyethylene, polypropylene, polybutene
1. Olefin homopolymers such as poly-4-methyl-pentene-1, ethylene, phlopylene, phtene-1.4-
Mutual copolymers of methyl-pentene-1, hexene-1, octene-1, etc., copolymers of ethylene and vinyl ester, unsaturated carboxylic acids, unsaturated carbon esters, etc. are used. Particularly preferred are polyethylene, polypropylene, and copolymers of ethylene and other α-olefins.

The mixing ratio of the reaction product of solid rubber and α,β-unsaturated dicarboxylic acids and olefin polymer in layer ω) is arbitrary, but the weight ratio is 10:90 to 50:5.
0 is preferred. More preferably 15:85-45:
It is 55. Solid rubber and α.

The ratio of reaction products with β-unsaturated dicarboxylic acids is 10
When it is less than 50, the adhesion of the olefin polymer to layer (2) is not improved, while when it is more than 50, the main components of the layer are solid rubber and α,β-unsaturated dicarboxylic acids. Although the reaction product improves the adhesion to layer (2), layer (2) becomes too flexible and does not form a so-called resin layer, making it unsuitable as a food packaging material.

g<72. The reaction product of the solid rubber and the α,β-unsaturated dicarboxylic acids and the olefin polymer constituting the composition may each be a single component or may be a mixture of two or more. In addition to these components, unmodified solid rubber, modified olefin polymer, etc. may be appropriately added and mixed.

Methods for manufacturing the multilayer structure of the present invention include coextrusion molding methods such as multilayer inflation method, multilayer T-die method, etc., in which a multilayer die is used and resins melted in an extruder are all joined at the tips of the dies to form a laminated structure. Multilayer blow molding method, injection molding method, etc. are applied. As for the structure of the multilayer structure in the present invention, in addition to the structure consisting of only two layers, layer (2) and layer (2), layers made of thermoplastic resin may be laminated as appropriate. Examples of thermoplastic resins include polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, polyvinyl alcohol, and the like, in addition to the above-mentioned olefin polymers.

When the multilayer structure of the present invention is used as a packaging material, various shapes can be used. For example, it may be in the form of a film, sheet, tube, hollow container, etc. Further, the thickness of each layer constituting the multilayer structure can be arbitrarily selected depending on the intended use.

The multilayer structure of the present invention comprises a layer made of a conventional olefin polymer graft-modified with an unsaturated dicarboxylic acid;
Alternatively, it is characterized by superior contact strength compared to those using a deposit made of a mixture of the graft modified product and an olefin polymer, and is particularly excellent in maintaining adhesive strength during deformation such as stretching.

The properties of the resin are made by reacting a mixture of olefin polymer and solid rubber with α,β-unsaturated carboxylic acids.
Alternatively, this cannot be achieved by mixing solid rubber with an olefin polymer modified with α,β-unsaturated carboxylic acids.

Due to these characteristics of the material constituting the layer (B) of the present invention, it can be suitably used for multilayer stretch blowing, which has been difficult to achieve with conventional multilayer structures.Of course, this multilayer structure can be It has sufficiently low permeability and excellent heat sealability.

Since the multilayer structure of the present invention has the above-described feature 4, it is useful as a packaging material for many fields such as foods, medicines, and cosmetics.

Hereinafter, the effects of the present invention will be explained in detail with reference to Examples and Comparative Examples.

Example 1 Polyisobutylene [viscosity average molecular weight 140,000. Product name Vistanex 1401 100 parts by weight and 0.00 parts by weight of maleic anhydride.
25 parts by weight and organic peroxide [2,5 dimethyl, 2,
5-di(tert-butylperoxy)hexyne-3)
Add 10.02 parts by weight and add 20 parts by weight in a Banbury mixer.
A reaction product was obtained by kneading at 0°C for 15 minutes. 20 parts by weight of the reaction product and 80 parts by weight of linear low density polyethylene (copolymer of ethylene and butene-1, density 0.928, melt index 2) were mixed to form an olefin polymer mixture. Obtained.

Using a blown film molding machine, the olefin polymer mixture and saponified ethylene-vinyl acetate copolymer (trade name: EVAL ED-F, manufactured by Kuraray Co., Ltd.) were supplied to a multilayer die, and the die temperature was 230°C. They were merged in front of the die lip and laminated to form a two-layer inflation film. - When t, the thickness of the laminated film (laminated structure) is olefin polymer mixture/? ! 70
μ/ethylene-vinyl acetate copolymer saponified material layer had a thickness of 30 μ.

A test piece with a width of 25 mm was prepared from the above laminated film, and the adhesive strength was defined as the interlayer peel strength when it was pulled at an angle of 180 degrees and a take-up speed of 50 feed/min using a Tensilon method tensile tester. The results are shown in Table 1. Table 1 also shows the peel strength (adhesive strength) measured after the test piece was stretched 4.5 times in advance.

Examples 2 to 3 Ethylene-propylene rubber (trade name, EP-02F, manufactured by Japan Synthetic Rubber Co., Ltd.) was used in place of the polyimbutylene in Example 1.
(Example 2), polybutadiene rubber (trade name: BR-'
02. (manufactured by Japan Synthetic Rubber Co., Ltd.) (Example 3), a multilayer structure was obtained in the same manner as in Example 1. The results are shown in Table 1.

Examples 4-8. Comparative Examples 1 to 2 A multilayer structure was obtained in the same manner as in Example 1 except that the amount of maleic anhydride, the type of olefin polymer, and the amount of mixture with the olefin polymer were changed. The results are shown in Table 1.

Comparative Example 3 In place of the polyisobutylene of Example 1, the linear low-density polyethylene of Example 1 was used. The results are shown in Table 1.

(1) Same olefin polymer as Example 1 (2
) Japan Petroleum Chemical System Product Name Nippon Polypro F-150H, MFI = 7 (3)
Nippon Petrochemical System product name: Nippon Oil & Chemical Industry Co., Ltd. Product name: Nippon Oil & Chemical Industry Co., Ltd.
d=0.948201-

Claims (1)

[Scope of Claims] (1) A layer (2) consisting of a saponified ethylene-vinyl acetate copolymer, solid rubber and 0.05% to 5% by weight (based on solid rubber) of α,β-unsaturation. A multilayer structure formed by laminating an olefin polymer layer (B) containing a reaction product with dicarboxylic acids. (2) The solid rubber is selected from the group consisting of polyimbutylene, butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, polyphtadiene rubber, and styrene-propylene rubber. The multilayer structure according to item 1. (3) The mixing ratio (weight ratio) of the reaction product of the solid rubber and α,β-unsaturated carboxylic acids and the olefin polymer is 10:90 to 50: 50. (4) The olefin polymer is polyethylene,
Polypropylene, polybutene-1, poly-4-methylpentene-1, ethylene, propylene, butene-1,
selected from the group consisting of mutual copolymers of 2s or more of 4-methylpentene, hexene-1 or octene-1, or copolymers of ethylene and vinyl esters, unsaturated carboxylic acids or unsaturated carboxylic acid esters A multilayer structure according to claim 1, which is a multilayer structure. (5) The multilayer structure according to claim 4, wherein the α,β-unsaturated dicarboxylic acid is maleic anhydride.