JPH0531866A - Multilayered stretched film and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a multilayered stretched film suitable as the raw laminating material of a packing film for food or the like and excellent not only in sequential biaxial stretching aptitude but also in transparency, mechanical strength, pinhole resistance, gas barrier properties, laminating aptitude, printability or the like. CONSTITUTION:In a multilayered stretched film wherein a polyamide resin layer (A) and a saponified ethylene/vinyl acetate copolymer resin layer (B) are laminated in the order of A-B-A-B-A, as the polyamide resin layer (A), a single layer of nylon MXD 6 obtained by the polycondensation of methaxylenediamine and adipic acid or a layer composed of a blend of nylon MXD 6 and other nylon is used.

Description

Detailed Description of the Invention

[0001]

The present invention relates to low density polyethylene, linear low density polyethylene, polypropylene, ethylene-
By laminating it with a resin or film such as vinyl acetate copolymer, ionomer, etc. by a method such as dry lamination or extrusion lamination, a film for bag packaging of food, sundries, etc., a retort container, a lid material for deep drawing packaging, etc. The present invention relates to a multilayer stretched film which is excellent in transparency, mechanical strength, pinhole resistance, gas barrier property, laminating suitability, printing suitability and the like used for a film and the like, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, with respect to packaging of foods and miscellaneous goods, each manufacturer has been moving to rationalize both production personnel and equipment in terms of production process.
For the purpose of automation, bag-filling and packaging machines such as pillow type packaging machines have been widely used. For such a packaging machine, a heat-sealable one such as OPP / PE is usually used. However, depending on the contents and distribution method, it is necessary that these films satisfy multiple functions such as mechanical strength and gas barrier property as properties required for these films. It is conceivable to disperse various functions in each layer so as to comprehensively have many functions.

For example, in the food industry, the quality is deteriorated due to various alterations such as loss of shape, color, taste and aroma due to temperature, moisture, oxygen, light rays, etc. and microorganisms such as bacteria and mold in the distribution process. Conventionally, a method of directly adding additives such as preservatives and antioxidants to foods has been used as a method of easily storing the product without degrading its quality until it enters the mouth of the consumer. However, in recent years, in the food processing industry, especially in the livestock meat processing and fish meat processing fields, restrictions on additives to foods have become strict, and the amount of additives used is decreasing or almost no longer used, so long-term storage of contents In order to secure the properties and freshness, it is necessary to develop a film in which the packaging material is provided with functionality such as oxygen gas barrier property. Further, in the transportation stage in the food distribution process, there is a problem that pinholes are generated depending on the transportation method, and a film having excellent pinhole resistance and mechanical strength is required.

From the above points, the structure of the film used must have a structure such as a mechanical strength imparting layer / barrier layer / sealant layer. For example, OPP / EVO.
H / PE, ONY / PVDC / EVA, etc. have been conventionally used. As a method for laminating these films,
Dry lamination and extrusion lamination are used.
However, these methods require laminating one by one, so that the more the number of layers increases and the more complicated the structure, the more manufacturing steps increase and the cost increases. Further, since the minimum thickness of each layer film is limited, it is impossible to manufacture a multilayer and ultrathin film.

As a biaxial stretching method for a film, a sequential biaxial stretching method by a tenter system and a simultaneous biaxial stretching method are known. Comparing these two methods, the sequential biaxial stretching method
The structure of the device is simple and the productivity is superior to the simultaneous biaxial stretching method. However, the conventionally used aliphatic polyamide resins represented by nylon 6 and nylon 6-6 are extremely difficult to transversely stretch because the intermolecular hydrogen bonds are oriented in the transverse stretching direction in the longitudinal stretching in successive biaxial stretching. Is. As a method for solving these problems, a method of blending a polyamide containing a metaxylylene group with an aliphatic polyamide is described in Japanese Patent Publication No. 51-29193. This publication describes a polyamide single-layer film, and the film obtained by this method has insufficient transparency and does not satisfy the requirements as a packaging film.

Further, Japanese Patent Laid-Open No. 55-82650 discloses that
A polyamide film containing a metaxylylene group and an ethylene-vinyl acetate copolymer saponified resin film are laminated and stretched, and a film having a structure in which a heat-sealing resin is laminated is described. The vinyl acetate copolymer saponified resin layer is not always stretched. An inflation method is also known as one of the simultaneous biaxial stretching methods, but it is not suitable for stretching a film having a complicated structure as in the present invention.

[0007]

In order to solve these drawbacks, the present invention is based on the fact that the saponified ethylene-vinyl acetate copolymer resin is originally a resin excellent in gas barrier property.
Taking advantage of the fact that it is possible to further improve the gas barrier property by stretching, it is difficult to successively biaxially stretch in a single layer, but by using a polyamide containing a metaxylylene group as a polyamide layer, it is preliminarily laminated by coextrusion or the like. It has been found that the stretched product can be stretched. Its purpose is to provide a multilayer stretched film having excellent sequential biaxial stretching suitability, transparency, mechanical strength, pinhole resistance, gas barrier property, lamination suitability, printability, etc., and a method for producing the same. To provide.

[0008]

According to the present invention, a polyamide resin layer (A) and an ethylene-vinyl acetate copolymer saponified resin layer (B) are laminated in the order of A-B-A-B-A. In the multilayer stretched film, the polyamide resin layer (A) is
A multilayer stretched film characterized by using a single layer of nylon MXD6 obtained by polycondensation of metaxylylenediamine and adipic acid, or a layer comprising a blend of nylon MXD6 and other nylons, and a method for producing the same Is. That is, a polyamide resin layer is used as a mechanical strength imparting layer, an ethylene-vinyl acetate copolymer saponified resin layer is used as a gas barrier imparting layer, and a film having a laminated structure by a coextrusion method is sequentially biaxially stretched.

The polyamide (hereinafter abbreviated as PA) resin (A) used in the present invention is a single layer of nylon MXD6 obtained by polycondensation of metaxylylenediamine and adipic acid, or nylon MXD6 and other layers. It is a layer composed of a blend with nylon. Nylon MXD6 is produced by a polycondensation reaction of adipic acid with metaxylenediamine (MXDA) obtained by ammoxidating metaxylene and then reducing it. Other nylons to be blended include Nylon 6, Nylon 12, and Nylon 6, which are produced by polycondensation reaction of ω-aminocarboxylic acid, polycondensation reaction of dibasic acid and amine didicarboxylate, and the like.
Nylon 11, nylon 6-6, nylon 6-10, nylon 6-12, and copolymers or blends thereof are used.

The ethylene-vinyl acetate copolymer saponified resin (EVOH) layer (B) has a softening temperature (flow tester).
Method) is 150 ° C to 175 ° C and the ethylene content is 25
˜75 mol%, and the degree of saponification with respect to vinyl acetate in the copolymer is 90% or more.

The total thickness of the multilayer stretched film of the present invention is not particularly limited, but when it is laminated with another film or resin and used for food packaging or the like, a thickness of about 10 to 30 μm is optimal.

The multilayer stretched film of the present invention is ABA
A laminated structure in which the layers are adjacent to each other in the order of -BA An appropriate amount of a lubricant may be added to the PA resin layer (A) serving as the outer layer in order to improve the mechanical suitability for a printing machine, a laminating machine, a packaging machine and the like. In addition, by laminating the adhesive resin layer (C) between the PA resin layer (A) and the EVOH resin layer (B), A-
C-B-A-B-A, A-C-B-C-A-C-B-C
It is also possible to increase the adhesive strength between PA and EVOH by using a configuration such as -A. Examples of the adhesive resin used include ethylene-vinyl acetate copolymer or ethylene-propylene elastomer, a monobasic unsaturated fatty acid such as acrylic acid or methacrylic acid, or a dicarboxylic acid such as maleic acid, fumaric acid or itaconic acid. Examples thereof include acid-modified olefin resins obtained by chemically binding an anhydride of a basic unsaturated fatty acid, that is, maleic anhydride.

As a method for producing a film, a method of melt-extruding from a laminating die by a coextrusion method using a plurality of extruders and then cooling and solidifying is most suitable. As a stretching method, a sequential biaxial stretching method by a tenter system is used, and the stretching temperature is preferably 50 ° C. to 200 ° C. and the stretching ratio is 2 to 6 times. Further, after the stretching, heat setting is performed at a temperature higher by 5 ° C. or more than the stretching temperature. Alternatively, the heat-shrinkable film can be obtained without heat setting.

[0014]

[Example] PA / EVOH / PA / EVOH / PA was melt extruded from a multi-layer coextrusion die by the T-die extrusion method.
A film (thickness 170 μm) having the layer structure of was prepared. The thickness ratio of each layer was 25/10/30/10/25%. As a raw material for each layer constituent resin, PA MX Mitsubishi 6007 manufactured by Mitsubishi Gas Chemical Co., Inc.
(Nylon MXD6) and Ube Industries 1030B (6-N
Blend with y) EVOH Eval EP-F101 manufactured by Kuraray was used. The obtained multilayer film was applied to a tenter type sequential biaxial stretching production apparatus and stretched under the following conditions to prepare a film having a thickness of 15 μm. Stretching temperature Vertical 95 ° C Horizontal 110 ° C Stretching ratio Vertical 3.3 times Horizontal 3.3 times Heat setting temperature 190 ° C Line speed 100M / min Table 1 shows the sequential biaxial stretching suitability when the blending ratio of the PA layer is changed. It was

[0015]

[Table 1]

As shown in Comparative Example 1, with 6-Ny alone, a good film could not be obtained because the film was broken or stretched during transverse stretching. On the other hand, the films of Examples 1 to 3 according to the present invention could be stretched without any particular problem, and good films were obtained. The physical properties of the film of Example 2 are shown in Table 2.

[0017]

[Table 2]

As shown in Table 2, Example 2 according to the present invention
The mechanical strength and transparency of this film are almost the same as those of the stretched nylon (ONy) film (15 μm) on the market. Moreover, the oxygen gas barrier property is very excellent. Films that combine these characteristics are ONy film and stretched EVOH film (Kuraray EVAL EF).
-XL) even when trying to obtain by dry lamination
Since the thickness of each film is limited, it is
It is not possible to obtain a film with a thickness of μm. Example 2
One side of the film is corona treated, a pattern is printed, and 50 μm thick linear low density polyethylene (LLDP
E) The film was laminated with a urethane adhesive by a dry laminating method to prepare a film having a thickness of 65 μm.
There were no particular problems such as mechanical suitability in each step of corona treatment, printing and dry lamination. With this film,
A bag of appropriate size was prepared by a three-side seal bag making machine or a horizontal pillow packaging machine, and the appearance, bag breaking strength, etc. were tested, but there was no particular problem.

[0019]

INDUSTRIAL APPLICABILITY The multilayer stretched film according to the present invention has excellent suitability for successive biaxial stretching, and also has excellent transparency, mechanical strength, pinhole resistance, gas barrier property, laminate suitability, printability, and the like. Therefore, it is suitable as a raw material for laminating foods and other packaging films.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display area B29L 7:00 4F 9:00 4F

Claims (2)

[Claims] 1. A polyamide resin layer (A) and a saponified ethylene-vinyl acetate copolymer resin layer (B) are ABA.
-In the multilayer stretched film laminated | stacked in order of BA,
The polyamide resin layer (A) is a nylon MXD6 obtained by polycondensation of metaxylylenediamine and adipic acid.
Or a layer composed of a blend of nylon MXD6 and other nylon is used. 2. The method for producing a multilayer stretched film according to claim 1, wherein the stretching temperature is 50 to 200 ° C. and the stretching ratio is 2 to 6 times, and the biaxial stretching is successively performed.