JPH05162254A - Multilayered stretched film - Google Patents

Abstract

PURPOSE:To provide an asymmetric multilayered stretched film having heat resistance, transparency, mechanical strength, barrier properties and heat sealability required as a laminating material for a packing film of food and the others or a solid industrial packing material and reduced in a curl phenomenon. CONSTITUTION:A multilayered stretched film is constituted of polyamide resin layer (A)/saponified ethylene/vinyl acetate copolymer resin layer (B)/polyamide resin layer (A')/adhesive resin layer (C)/seal layer (D) and characterized by that the sum of the thickness ratio of the polyamide resin layer (A) and that of the polyamide resin layer (A') is 50% or less and the thickness of the polyamide resin layer (A) does not exceed that of the polyamide resin layer (A').

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is excellent in transparency, mechanical strength, gas barrier property, etc., which can be widely used in the packaging field such as a lid material by laminating it with a polyester film or a stretched polypropylene film which is printed in a bag, a pillow package or the like. And a multi-layer stretched film.

[0002]

2. Description of the Related Art Packaging materials in the food field are required to have higher functionality due to the diversification of lifestyles due to the improvement of consumers' living standards and the trend toward gourmet foods. There is. For example, high oxygen gas barrier properties and water vapor barrier properties are required due to reduction of additives and changes in heat sterilization conditions, and packaging materials with excellent mechanical strength to prevent bag breakage during the distribution process due to the development of freezing and refrigerating distribution. Is required. Under such circumstances, it is essential for the packaging material to be able to satisfy multiple functions, and for this reason, the packaging material is made up of several layers to disperse various functions in each layer. Furthermore, in the case of thin packaging materials, the use of bags, pillow packaging, lid materials, etc., except for forming such as deep drawing, basically requires a packaging material with high mechanical strength, and stretched films are generally used. ..

On the other hand, dry lamination, extrusion lamination, coating, vapor deposition and the like are used as a method for producing a multi-layered packaging material including a stretched film. However, in these methods, the layer construction is complicated in order to impart many functions. As a result, the number of manufacturing processes has increased and there has been a problem inevitably increasing costs. Therefore, as a method for simplifying the process, multi-layer stretching for stretching a co-extruded film has been put into practical use. In multi-layer stretching, it does not occur when the layer structure is symmetrical, but with an asymmetric layer structure, the curl phenomenon occurs after stretching. Moreover, the degree of curling phenomenon is far greater than that of the conventional laminating method, which is a fatal problem during printing, laminating, bag making, and other processing.

[0004]

The present invention has been made as a result of various studies in order to solve the severe curl phenomenon that occurs in the conventional multi-layer drawing of an asymmetric layer structure. The purpose of the present invention is to obtain various layers. It enables multi-layer stretching of the structure and has many required functions such as heat resistance, transparency, mechanical strength,
It is to provide a multilayer stretched film having barrier properties, heat seal properties and the like.

[0005]

The present invention provides a polyamide resin layer (A) (A '), an ethylene-vinyl acetate copolymer saponified resin layer (B), an adhesive resin layer (C), a seal layer (D). ), And the stacking order is A-B-A'-C-
D, the total thickness ratio of the polyamide resin layer (A) and the polyamide resin layer (A ′) is 50% or less, and the thickness of the polyamide resin (A) does not exceed the thickness of (A ′). It is a multilayer stretched film.

The polyamide resins (A) and (A ') used in the present invention may be the same resin or different. As the polyamide resin, generally known 6 nylon, 6-6 nylon, 6-10 nylon, 6-12
Nylon, 11 nylon, 12 nylon, copolymers thereof, amorphous nylon, MXD6 nylon obtained by polycondensation of metaxylylenediamine and adipic acid, and blends thereof are used.

The ethylene-vinyl acetate copolymer saponified resin (hereinafter abbreviated as EVOH) (B) has an ethylene content of 2
5 to 75 mol%, and the degree of saponification with respect to vinyl acetate in the copolymer is 90% or more.

The adhesive resin (C) is polyethylene, polypropylene, a copolymer thereof, a copolymer with a different α-olefin, an ethylene-vinyl acetate copolymer, etc., and a base of acrylic acid, methacrylic acid, etc. An acid-modified olefin resin obtained by chemically bonding a unsaturated unsaturated fatty acid or an anhydride of a dibasic unsaturated fatty acid such as maleic acid, phthalic acid, or itaconic acid, that is, maleic anhydride is used.

The sealing layer resin (D) is low density polyethylene (LDPE), linear low density polyethylene (LLDP)
E), medium density polyethylene (MDPE), high density polyethylene (HDPE), polypropylene (PP) and other polyolefin resins and ethylene copolymers such as ethylene-vinyl acetate copolymer (EVA) and ethylene-methyl methacrylate copolymer Polymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EEA), ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MA)
H), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMMA), ionomer (ION) and other resins can be used.

The polyamide resin layer of the multilayer stretched film of the present invention is divided into two layers (A) and (A '), and the total thickness ratio of the two polyamide layers is 50% or less. When the total thickness ratio is 50% or more, the effect of improving the curl phenomenon cannot be sufficiently exhibited by changing the thickness ratio of the polyamide resin layers (A) and (A ′) described later. The smaller the total thickness ratio of the polyamide resin layer, the better the curl phenomenon.
It cannot be made too small from the viewpoint of imparting mechanical strength. Therefore, the total thickness ratio of the polyamide resin layers is preferably 10% or more.

From the viewpoint of imparting mechanical strength, it is not necessary to divide the polyamide resin layer into two layers, and the inventors of the present invention initially investigated the polyamide resin layer as one layer, but there is a limit to improvement in curling phenomenon. It was Therefore, it was revealed that when the polyamide resin layer is divided into two layers and the thickness ratio thereof is changed, the curl phenomenon of the multilayer stretched film is also greatly changed. As a result of further detailed examination, it was found that the curl phenomenon was significantly improved in a structure in which the thickness ratio of the outermost polyamide resin layer (A) did not exceed the thickness ratio of the inner polyamide resin layer (A ′).

A method for producing a multilayer stretched film will be described. First, a coextrusion method is desirable as a method for producing a raw film. A uniaxial stretching method and a biaxial stretching method are used in the subsequent stretching step. As the biaxial stretching method, a tubular method and a flat method, which are simultaneous biaxial stretching methods, and a sequential biaxial stretching method are used. After stretching, heat treatment may be performed depending on the application.

[0013]

【Example】

Example 1 A film (total thickness 450 μm) having a layer structure of polyamide resin 1 / ethylene-vinyl acetate copolymer saponified resin / polyamide resin 1 / adhesive resin / ionomer was prepared by a coextrusion method. When the thickness ratio of each layer was measured, it was 15/15/20/10/40 in the order of the above layer constitution.
(%)Met. The raw materials used for each layer are as follows. Polyamide resin 1: 6 Nylon (1030B made by Ube Industries) and amorphous nylon (PA3426 made by Mitsui Dupont Polychemical) Blend (blend ratio = 50: 5)
0) Ethylene-vinyl acetate copolymer saponified resin: (Eval EP-F101, manufactured by Kuraray) Adhesive resin: acid-modified linear low-density polyethylene (Admer NF-300, manufactured by Mitsui Petrochemical Co., Ltd.) Ionomer: (HIMIRAN 1652 Mitsui) The obtained raw film was sequentially stretched by a biaxial stretching method with a stretching ratio of length × width = 3 × 3 to form a multilayer stretched film having a total thickness of 50 μm. The curl phenomenon was evaluated by measuring the winding diameter of the film in a state where one end of a rectangular sample having a width of 20 mm and a length of 300 mm was fixed and hung down. In the case of biaxial stretching, samples were taken in both the longitudinal and transverse directions, and the average value was evaluated.

(Example 2) A film having a layer structure of polyamide resin 1 / ethylene-vinyl acetate copolymer saponified resin / polyamide resin 2 / adhesive resin / ethylene-vinyl acetate copolymer by coextrusion method (total) A thickness of 450 μm) was made. When the thickness ratio of each layer was measured, it was 15/15/20/10/40 (%) in the order of the above layer constitution. The raw materials used for each layer were as follows. Polyamide resin 1: 6 Nylon (1030B manufactured by Ube Industries) and amorphous nylon (PA3426 manufactured by Mitsui Dupont Polychemical) (blend ratio = 95:
5) Polyamide resin 2: 6-6,6 copolymer nylon (501
3B Ube Industries Co., Ltd.) Ethylene-vinyl acetate copolymer saponified resin: (Eval EP-F101 made by Kuraray) Adhesive resin: acid-modified linear low-density polyethylene (Admer NF-300 manufactured by Mitsui Petrochemical Industries) ethylene-acetic acid Vinyl copolymer: (Evatate D201
1 Sumitomo Chemical Co., Ltd.) The obtained raw film was sequentially stretched by a biaxial stretching method at a stretching ratio of length × width = 3 × 3 to form a multilayer stretched film having a total thickness of 50 μm. Evaluation of curl phenomenon (Example-1)
I went the same way.

(Example 3) A film having a layer constitution of polyamide resin 1 / ethylene-vinyl acetate copolymer saponified resin / polyamide resin 2 / adhesive resin / ethylene-vinyl acetate copolymer by coextrusion method (total) Thickness 270 μm). When the thickness ratio of each layer was measured, it was 5/15/15/10/55 (%) in the order of the above layer constitution. The raw materials used for each layer were as follows. Polyamide resin 1: 6-nylon (1030B manufactured by Ube Industries) and MXD6 nylon (6001 manufactured by Mitsubishi Gas Chemical Co., Inc.) (blend ratio = 80:20) Polyamide resin 2: 6-12 nylon (7024B manufactured by Ube Industries) Ethylene- Saponified vinyl acetate copolymer resin: (Eval EP-E105, manufactured by Kuraray) Adhesive resin: Acid-modified ethylene-vinyl acetate copolymer (Modic E-300H, manufactured by Mitsubishi Petrochemical) Ionomer: (HIMIRAN 1652, manufactured by Mitsui Deyupon Polychemical) The obtained raw film was sequentially stretched by a biaxial stretching method at a stretching ratio of length × width = 3 × 3 to form a multilayer stretched film having a total thickness of 30 μm. The curl phenomenon was evaluated in the same manner as in Example-1.

Comparative Example 1 A film (total thickness 450 μm) having a layer structure of polyamide resin / ethylene-vinyl acetate copolymer saponified resin / adhesive resin / ethylene-vinyl acetate copolymer was prepared by a coextrusion method. It was The thickness ratio of each layer was 35/15/10/40 (%). The obtained raw film is sequentially biaxially stretched at a stretching ratio of length × width = 3 ×
Stretching was performed at 3 to produce a multilayer stretched film having a total thickness of 50 μm. The curl phenomenon was evaluated in the same manner as in Example-1.

Comparative Example 2 A film having a layer structure of polyamide resin 1 / ethylene-vinyl acetate copolymer saponified resin / polyamide resin 2 / adhesive resin / ethylene-vinyl acetate copolymer (total) A thickness of 450 μm) was made. When the thickness ratio of each layer was measured, it was 25/15/30/10/20 (%) in the order of the above layer constitution. The raw materials used for each layer were the same as in Example-1. The obtained raw film is sequentially biaxially stretched, and the stretching ratio is length × width =
Stretching was performed at 3 × 3 to produce a multilayer stretched film having a total thickness of 50 μm. The curl phenomenon was evaluated in the same manner as in Example-1.

Comparative Example 3 A film having a layer structure of polyamide resin 1 / ethylene-vinyl acetate copolymer saponified resin / polyamide resin 2 / adhesive resin / ethylene-vinyl acetate copolymer (total) Thickness 270 μm). When the thickness ratio of each layer was measured, it was 15/15/10/10/50 (%) in the order of the above layer constitution. The raw materials used for each layer were the same as in Example-2. Table 1 shows the evaluation results of the curl phenomenon with respect to the multilayer stretched films of Examples 1-3 and Comparative Examples 1-3.

[0019] In each of the comparative examples, the winding diameter is small and the curl phenomenon is strong, while in the examples, the winding diameter is large and the curl phenomenon is significantly improved.

[0020]

EFFECTS OF THE INVENTION The multilayer stretched film according to the present invention has a small curling phenomenon even if it is asymmetrical, and can be processed without problems such as printing, laminating and bag making. It is used for laminating packaging films in a wide range of fields such as the food packaging field and industrial product packaging field. ， In addition, it can be used as a packaging material for business as it is plain.

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Claims (1)

[Claims] 1. A polyamide resin layer (A) (A '), an ethylene-vinyl acetate copolymer saponified resin layer (B), an adhesive resin layer (C) and a seal layer (D), which are laminated. The order is A-B-A'-C-D, the total thickness ratio of the polyamide resin layer (A) and the polyamide resin layer (A ') is 50% or less, and the thickness of the polyamide resin layer (A) is ( A multilayer stretched film, characterized in that it does not exceed the thickness of A ').