JPH02263643A - Multilayer film - Google Patents

Abstract

PURPOSE:To facilitate release at the time of opening by laminating a seal layer wherein an ionomer and polypropylene are mixed in a specific ratio, an oxygen gas barrier layer and an outer layer resin using an adhesive layer if necessary. CONSTITUTION:A seal layer 5 wherein 60-90wt.% of an ionomer and 10-40wt.% of polypropylene are mixed, an outer layer resin 1, an oxygen gas barrier layer 3 and a polyamide resin layer 2 are laminated using an adhesive layer 4 if necessary. As the ionomer to be used, one wherein 50% or more of the carboxylic acid group of an ethylene/methacrylic acid copolymer whose acid content is 12% or more is formed into a crosslinking structure by sodium or zinc is used. As polypropylene, a hopopolymer or an ethylene/propylene copolymer is used. As the oxygen gas barrier layer 3, an ethylene/vinyl alcohol copolymer of a vinylidene chloride resin can be used. As the outer layer resin 1, a butadiene/styrene copolymer, a soft vinyl chloride resin and a polyamide resin are used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a packaging multilayer film that can be heat-sealed with an ethylene resin and can be easily peeled off when unsealed.

(Prior art) In the packaging of processed meat such as ham, sausage, bacon, roasted pork, processed seafood products such as kamaboko, and other foods, complete sealing is required mainly from the viewpoint of preservation, and low-density polyethylene, which has excellent sealing properties, Linear low-density polyethylene, ethylene-vinyl acetate copolymer, ionomer, etc. are widely used as general-purpose sealing layers, but on the other hand, it is required that the seal can be opened easily and the contents can be removed easily and cleanly. Research has been conducted on packaging materials that can be easily opened (hereinafter referred to as easy-open properties) by mixing different resins, causing the sealing surface to peel off, or by causing a part of the sealing layer to peel off due to cohesive failure. 1986-2
As seen in Publication No. 39238, the ionomer and ethylene-propylene copolymer have a cloudy feeling and the transparency is impaired, and in order to improve the transparency, the ethylene-propylene copolymer (2) has a low ethylene content. However, when the seal layer was cohesively destroyed when the package was opened, it remained in the form of fibers (hereinafter referred to as keba-dachi), and in severe cases, it became stringy, significantly impairing the aesthetics and reducing the product value. , I couldn't satisfy both transparency and kebadachi.

(Problems to be Solved by the Invention) The present invention is applicable to general-purpose seal layer resins such as low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, and ionomer as mating materials for heat sealing. The aim is to provide a material that has the contradictory properties of easy-opening properties, transparency in the sealing layer, and no blistering. Through repeated research on the above, the inventors discovered that the wrinkle phenomenon could be solved by using an ionomer with a high acid content and a high degree of metal crosslinking, leading to the completion of the present invention.

(Means for Solving the Problems) The present invention provides a sealing layer made of a mixture of 60 to 90% by weight of an ionomer and 10 to 40% by weight of polypropylene, an outer resin layer, an oxygen gas barrier layer, a polyamide resin layer, etc. It is a multilayer film that is laminated using an adhesive layer and is easily peeled off when the package is opened using an olefin resin as a mating sealing layer.

The ionomer used in the present invention is an ethylene-methacrylic acid copolymer with an acid content of 12% or more.
The melt flow at 190℃ is 0.5 to 5.0 g/1 with a crosslinked structure of more than % of sodium or zinc.
0 minutes (ASTM D-1238 and below) is used.

In order to suppress fluff, it is necessary for the ionomer to have a large cohesive force, and from a balance with processability, the melt flow should be 0.8 to 2.0 g/10 minutes, and the acid content should be 14 to 20%.
, metal crosslinking degree of 54 to 60%, and sodium crosslinking is preferable.

As the polypropylene, a homopolymer or an ethylene-propylene copolymer is used. When a homopolymer is used, the easy-opening property is good, but the transparency is slightly reduced, so it is preferable to use an ethylene-propylene copolymer.

A higher melt flow is advantageous for transparency, but increases selectivity with respect to the other resin and tends to cause fluff, so a melt flow of 1 to 2 g/10 minutes is preferred.

Furthermore, the mixing ratio of polypropylene is preferably 15 to 25% in terms of transparency and lintness.Since the sealing strength required varies somewhat depending on the type of partner resin, packaging form, and contents, the mixing ratio can be changed within this range for sealing. The intensity can be adjusted.

As the oxygen gas barrier layer, ethylene-vinyl alcohol copolymer or vinylidene chloride resin can be used, the former being a saponified product of ethylene-vinyl acetate copolymer with an ethylene content of 32 to 47 mol%, and the latter It is a binary or multi-component copolymer of 60 to 97% by weight of vinylidene chloride and an unsaturated monomer such as vinyl chloride, alkyl acrylate, acrylic acid, or acrylonitrile.

As the outer layer resin, butadiene-styrene copolymer, copolymerized polyester, polypropylene, medium density polyethylene, linear low density polyethylene, soft vinyl chloride resin, polyamide resin, etc. are used, and the outer layer is made of ethylene-vinyl alcohol copolymer. You can also do that.

In order to further increase the mechanical strength, polyamide resins can be introduced, such as 6-nylon,
6-6+6 nylon, 6-12 nylon, or a mixture thereof is used, and in order to improve moldability, 30% by weight of non-grade polyamide, which is a copolymer of terephthalic acid, isophthalic acid, and hexamethylene diamine, is used. Can be mixed within.

As the adhesive layer, known adhesive layers can be used alone or in combination.

The film can be produced by a coextrusion method or a known lamination method, but the coextrusion method is preferred because it has a large number of layers and it is easy to introduce an easy oven layer.

(Example) A multilayer film having each layer structure shown in Table 1 was prepared by melt-extruding resin using 5 to 6 extruders by a coextrusion method.

The thickness of the obtained films was all 120μ, and the evaluation results of each film are shown in Table 1. Details of each evaluation are as follows.

1. Comparative evaluation was visually performed with a film having a similar structure in which a transparent ionomer was used as a sealing layer.

0 Transparency equivalent to that of a film using ionomer.

Δ Transparency decreases in comparison.

× It is cloudy and lacks transparency.

2. Sealing strength Heat sealing uses a bar-shaped sealer at a sealing temperature of 13
The test was performed at 0° C., a sealing pressure of 2 kg/cj, and a sealing time of 2 seconds, and the strength was measured using an autograph with a sample width of 15 and a peeling speed of 3005 m/win. (If the seal strength is less than 150g/15-, the sealing strength is weak, and there is a concern about sealing performance.)
If it is over 300g/15-, it feels too strong and the beer taste is bad).

3. A sample sealed under the same conditions as Kebadachi 2 was rated at 50.1 by autograph.
The condition of the peeled surface was examined by peeling at different speeds under five conditions: 00, 200, 300, and 500 cells/min.

O There are very fine burrs uniformly that do not spoil the aesthetic appearance.

× Large burrs and stringiness occur, significantly detracting from the aesthetics.

The resins used are as follows.

Butadiene-styrene copolymer: BS butadiene ratio 30% Melt flow 6g/10 minute density 1.01g
/cm' Acid-modified ethylene-vinyl acetate copolymer: AD Mitsubishi Yuka Preparation Modic E 300 H polyvinylidene chloride
: PVDC manufactured by Dow Chemical Company 5
ARAN 46B ethylene-vinyl alcohol copolymer: EVOH ■EVAL E manufactured by Kuraray Copolymer polyester: PETG manufactured by Eastman Kodak Co., Ltd. KODARPI! TG6763
Nylon 6: Ny-6 Made by Ube Industries ■ UBE Nylon 1030B Nylon 6-
6, 6: Ny-6-6,6 manufactured by Ube Industries ■ UBE nylon 5033B Soft vinyl chloride resin: PVC average degree of polymerization 1300P
VC100 parts by weight (dioctyl phthalate) 50 parts by weight ethylene-vinyl acetate copolymer: Ev^-25 manufactured by Mitsui Dupont Polychemicals Evaflex P25Q
5C (Effects of the Invention) According to the method of the present invention, a multilayer packaging film having an easy-open sealing layer with excellent formability, oxygen gas barrier properties, pinhole resistance, and sealing properties can be obtained, which solves the problems that have arisen in the past. Since it is possible to eliminate both the reduction in transparency and the smearing caused when opening the package, it is possible to obtain a packaging material that is easy to open and does not degrade the image of the contents.

[Brief explanation of drawings]

FIG. 1 is an example of a sectional view of the present invention. Patent Applicant: Sumitomo Bakelite Co., Ltd. Procedural Amendment (spontaneous) 1999 June 29th

Claims (2)

[Claims] (1) A sealing layer made of a mixture of 60 to 90% by weight of ionomer and 10 to 40% by weight of polypropylene, at least an oxygen gas barrier layer, and an outer resin layer are laminated using an adhesive layer as necessary. multilayer film. (2) Ionomer has an acid content of 12% or more and a degree of metal crosslinking of 5
The multilayer film according to claim 1, which has a content of 0% or more.