JPH0531867A - Multilayered stretched film and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide the above multilayered stretched film suitable as the laminating raw 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 the multilayered stretched film wherein a polyamide resin layer (A) and a saponified ethylen/vinyl acetate copolymer resin layer (B) are laminated in the order of A-B-A-B-A, the polyamide resin layer (A) is composed of a blend of amorphous nylon and other nylon.

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 properties satisfy multiple functions such as mechanical strength and gas barrier property, and the film should have a laminated structure of several layers. 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 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 not used. 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, in the conventionally used aliphatic polyamide resins represented by nylon 6 and nylon 6-6, lateral stretching is extremely difficult because intermolecular hydrogen bonds are oriented in the lateral 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 is insufficient in transparency and does not satisfy the requirements as a packaging film.

A multilayer stretched film containing amorphous nylon as a polyamide layer is disclosed in JP-A-64-717.
As described in Japanese Patent Publication No. 49, the purpose of using amorphous nylon is only to improve the barrier property, and the stretching method is also the inflation method (tubular method). 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]

DISCLOSURE OF THE INVENTION In order to solve these drawbacks, the present invention has conducted intensive studies by the present inventors, and as a result, the polyamide layer was composed of a blend of amorphous nylon and other nylon. By using the layers, it was possible to obtain a multilayer stretched film having a good sequential biaxial stretchability and excellent pinhole resistance, transparency, gas barrier property, mechanical strength and the like, and a method for producing the same. The object of the present invention is to provide a multilayer stretched film which is excellent in successive biaxial stretching suitability, and also has excellent transparency, mechanical strength, pinhole resistance, gas barrier property, laminating suitability, printability, etc. To provide a method.

[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
The present invention relates to a multilayer stretched film characterized by using a layer made of a blend of amorphous nylon and other nylon, and a method for producing the same. 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 layer composed of a blend of amorphous nylon and other nylon. The amorphous nylon can be obtained by pressure melt polycondensation, decarboxylation condensation reaction and the like using a raw material such as dicarboxylic acid, diamine, lactam, diisocyanate. Examples of the dicarboxylic acid include adipic acid, suberic acid, azelaic acid, terephthalic acid and isophthalic acid. As the diamine, hexamethylenediamine, trimethylhexamethylenediamine, isophoronediamine, bis-p- (aminocyclohexyl) methane, bis-p- (aminocyclohexyl) propane and the like are used. Examples of lactams include caprolactam and laurolactam.
As the diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate and the like are used. Other nylons to be blended include nylon 6, nylon 12, nylon 11 and nylon 6-, which are produced by polycondensation reaction of ω-aminocarboxylic acid, polycondensation reaction of dibasic acid and didicarboxylic acid amine, and the like.
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 multi-layer stretched film of the present invention is not particularly limited, but when it is laminated with another film or resin for use in food packaging or the like, a thickness of about 10 to 30 μm is optimal.

Although the total thickness of the multilayer stretched film of the present invention is not particularly limited, a film having a thickness of about 10 to 30 μm is
It is optimal for use in applications such as food packaging by laminating with other films and resins. The multilayer stretched film of the present invention is A-
It has a laminated structure in which B-A-B-A are adjacent in this order. In addition,
An appropriate amount of a lubricant may be added to the PA resin layer (A) serving as the outer layer in order to improve mechanical suitability for a printing machine, a laminating machine, a packaging machine, and the like. In addition, PA resin layer (A) and E
A resin layer for adhesion (C) is laminated between the VOH resin layer (B) and A-C-B-A-B-B-A, A-C-B-C-A-C.
It is also possible to increase the adhesive strength between PA and EVOH by using a configuration such as -B-C-A. As the adhesive resin used, ethylene-vinyl acetate copolymer, or ethylene-
Propylene elastomer is chemically treated with monobasic unsaturated fatty acids such as acrylic acid and methacrylic acid, or anhydrides of dibasic unsaturated fatty acids such as maleic acid, fumaric acid and itaconic acid, that is, maleic anhydride. Examples thereof include acid-modified olefin resins obtained by binding.

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 the resin constituting each layer, PA SHERA PA342 manufactured by PA Mitsui DuPont Polychemical
6 (amorphous nylon) and Ube Industries
Blend with 1030B (6-Ny) EVOH Kuraray's Eval EP-F10
1 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 85 ° C Horizontal 100 ° C Stretching ratio Vertical 3.2 times Horizontal 3.4 times Heat setting temperature 190 ° C Line speed 100 M / min Table 1 shows the suitability for sequential biaxial stretching when the blending ratio of the PA layer is changed. It was

[0015]

[Table 1]

As shown in Comparative Examples 1 and 2, amorphous Ny, 6
Regarding -Ny alone, a good film could not be obtained because the film was broken or stretched unevenly during transverse stretching. On the other hand, the films of Examples 1 and 2 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 1 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. A film having these characteristics is used as an ONy film and a stretched EVOH film (Kuraray EVAL EF-
Even if an attempt is made by dry laminating with XL), there is a limit to the thickness of each film.
It is not possible to obtain m-thick films. One side of the film of Example 1 was corona treated, a pattern was printed, and a linear low density polyethylene (LLDP) having a thickness of 50 μm was further printed.
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,
A multilayer stretched film, wherein the polyamide resin layer (A) is a layer made of a blend of amorphous nylon and other nylon. 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.