JP3133410B2 - Easy tear multilayer film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily tearable multilayer film. More specifically, the present invention relates to an easily tearable multilayer film which has excellent gas barrier properties and transparency and can be easily torn, and is suitable as a packaging material for foods.

[0002]

2. Description of the Related Art Conventionally, foods, especially meat and paste products, which have a high moisture content, are deteriorated and are cheap, are used as packaging materials for foods.
A resin film having excellent gas barrier properties and made of a material such as a polyamide resin or an ethylene-vinyl alcohol copolymer is used. Further, since these resin films have low water resistance, they are also supplemented with each other as a laminated film in which they are combined with a polyolefin resin layer having excellent water resistance. In order to package foods using these films, the foods are usually stored in a bag-like shape, the foods are housed inside, then sealed with heat seal and heat sterilized to obtain products.

[0003] The above-mentioned resin film is excellent in preventing deterioration of the contents because of its excellent gas barrier properties. However, since the tear strength of the film is high, the film is torn when the contents are taken out from the package. It is difficult to remove the contents. In particular, the tear strength of these films is further increased when they are hydrated. For example, when the package is subjected to a steam sterilization treatment, the tear strength of the film becomes extremely large, and it is more difficult to take out the contents, which is inconvenient for practical use.

[0004]

DISCLOSURE OF THE INVENTION The present invention has excellent gas barrier properties and transparency, and can be easily torn and opened at the time of opening, and is suitable as a packaging material for foods, especially foods which are easily deteriorated. It is intended to provide a tearable multilayer film.

[0005]

The inventors of the present invention have conducted various studies to solve the above-mentioned problems, and as a result, have found that a composition in which a polyamide resin or an ethylene-vinyl alcohol copolymer and a polyolefin resin are mixed at a specific ratio. Laminated film composed of a layer made of a material and a resin layer containing polyolefin as a main component has excellent gas barrier properties and transparency, can be easily torn, and is extremely useful as a packaging material for foods. The present invention has been achieved by confirming that it is suitable. That is, the gist of the present invention is that at least one layer composed of a mixture of a polyamide resin or an ethylene-vinyl alcohol copolymer (85 to 97% by weight) and a polyolefin resin (15 to 3% by weight) is mixed with polyolefin. An easily tearable multilayer film characterized by being laminated with at least one layer composed of a resin as a main component.

Hereinafter, the present invention will be described in detail. Examples of the polyamide resin used for the easily tearable multilayer film of the present invention include well-known polyamide resins based on nylon 6, such as nylon 6, nylon 6-6, and nylon 6-12. Examples of the ethylene-vinyl alcohol copolymer include an ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 60 mol%, preferably 27 to 47 mol%.

[0007] The above polyamide resin or the ethylene - The polyolefin resin to be mixed with the vinyl alcohol copolymer, medium density density 0.93 g / cm ³ or less of low density polyethylene, density 0.93～0.94Cm ³ polyethylene, density of 0.94 g / cm ³ or more high-density polyethylene, density polyethylene resin such as 0.93 g / cm ³ or less linear low density polyethylene; selected from polypropylene resin.

The mixing ratio of the polyolefin resin must be 3 to 15% by weight based on the total amount of the polyamide resin or the ethylene-vinyl alcohol copolymer and the polyolefin resin. The ratio of polyolefin resin is 3
If the amount is less than 15% by weight, sufficient tearability can not be imparted. If the amount is more than 15% by weight, practically sufficient gas barrier properties and transparency cannot be obtained. The polyamide resin or the ethylene-vinyl alcohol copolymer and the polyolefin resin may be mixed by a dry blending method or a melt blending method, but dry blending is usually employed.

The layer composed of a polyolefin-based resin to be laminated with a layer composed of a polyamide resin or a mixture of an ethylene-vinyl alcohol copolymer and the resin may be a low-density polyethylene, a medium-density polyethylene, a high-density polyethylene or a wire. Jo low density polyethylene, such as polyethylene, the outside of the polypropylene emissions, a copolymer of an olefin and another monomer as a main component known olefins such as ethylene
Len-vinyl acetate copolymer, ionomer resin, modified polyethylene resin, modified polypropylene resin, ethylene-
Examples include a layer composed of an ethyl acrylate copolymer, an ethylene-methyl methacrylate copolymer, an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid random copolymer, or a mixture thereof.

The ionomer is obtained by adding a small amount of a monomer having a carboxyl group such as acrylic acid in a side chain to an ethylene polymer to obtain a hydroxide such as Na, K, Mg, Zn, etc. And a structure in which most of the acid groups are neutralized by adding a lower fatty acid salt or the like. In addition, modified polyethylene resin and modified polypropylene resin have a small amount of maleic acid, maleic anhydride, acrylic acid, an unsaturated carboxylic acid such as acrylic anhydride, etc., graft-reacted to polyethylene or polypropylene to improve adhesiveness with other resins. It has been improved.

When a surfactant is added to the layer composed of the above-mentioned resin containing polyolefin as a main component, the effect of promoting easy tearing is exhibited. Examples of the surfactant include cationic surfactants such as quaternary ammonium salt type and imidazoline type, anionic surfactants such as alkyl sulfate type and alkyl phosphate type, sorbitan type and ether. And amphoteric surfactants such as betaine type and nonionic surfactants such as amine type. These surfactants are used in an amount of 100 ppm to 30,000 ppm, especially 500 ppm to 50 ppm, based on the resin.
It is preferable to mix about 00 ppm. The reason why the addition of the surfactant promotes the tearability of the resin layer is not clear, but it is thought to be based on the fact that the surfactant has poor miscibility with the resin.

A layer composed of a mixture of a polyamide resin or an ethylene-vinyl alcohol copolymer and a polyolefin resin (mixed resin layer), and a layer composed of a polyolefin-based resin (polyolefin resin layer) laminated thereon.
The thickness of the mixed resin layer is set to 5 to 100 μm from the viewpoint of gas barrier properties and strength, and the thickness of the polyolefin resin layer is set to 10 to 100 μm from the viewpoint of imparting water resistance.
It is preferred that In order to improve the adhesion between the mixed resin layer and the polyolefin resin layer, ^10-5 to 4 wt% of maleic acid, maleic anhydride, acrylic acid, acrylic anhydride, etc. It is preferable to interpose a modified polyethylene resin layer to which a saturated carboxylic acid is grafted, or to use the above-mentioned grafted modified polyethylene resin layer as a polyolefin resin layer.

The multilayer film of the present invention comprises at least one layer (mixed resin layer) composed of a polyamide resin or a mixture of an ethylene-vinyl alcohol copolymer and a polyolefin resin, and at least one layer composed of a resin mainly composed of polyolefin. This is a multilayer film obtained by laminating one layer (polyolefin resin layer), and can have an arbitrary multilayer structure depending on the application. When the multilayer film of the present invention is formed into a bag-like shape, a heat seal is often used. However, in order to perform the heat seal well, the innermost layer (heat-sealed) is used. (Layer) is preferably a polyolefin resin layer.

In order to produce the easily tearable multilayer film of the present invention, it is desirable to use a coextrusion molding method. Co-extrusion molding is a method in which a plurality of types of resins are melt-kneaded in separate extruders, the resin in the molten state is introduced into a die, and extruded in a stacked state in a die. In order to produce a multilayer film, a coextrusion inflation molding method is particularly suitable among coextrusion molding. Co-extrusion inflation
The drafting conditions are as follows: draft rate (take-off speed /
Extrusion speed) is 3 to 60, preferably about 5 to 50,
Up ratio (product diameter / die slit diameter) of 0.4 to 2, especially 0.
It is preferred to be about 7 to 1.6.

The film extruded by the above-mentioned method is brought into contact with a cooling roll or a mandrel at room temperature to about 40 ° C., or quenched by direct contact with water or another cooling medium, thereby providing transparency and flexibility. An easily tearable multi-layer film having excellent resistance is obtained. It should be noted that if a post-treatment such as a stretching treatment is performed, the tearability of the film is impaired. Therefore, it is desirable to produce the product as it is without performing the post-treatment.

[0016]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which, however, are not intended to limit the scope of the present invention.

Example 1 Resins A, B and C shown below were each melt-extruded by a separate extruder, supplied to one die, and melted and laminated in the order of A, B and C before the lip (die). Inner layer method), the blow-up ratio is 1.2, the thickness of A is 20 μm, and the thickness of B is 10 μm.
A multilayer film having a thickness of m and C of 50 μm was obtained. Table 1 shows the tearability, tear strength, heat seal strength, haze, and film formability of the multilayer film.

Resin A: 100 parts by weight of nylon 6 (Novamid
1022CK2 (Mitsubishi Kasei Co., Ltd. product) dry blended with 5 parts by weight of low density polyethylene [Melt index (MI): 2, density: 0.927]. Resin B: Modified polyethylene resin (MI: 0.9, density: 0.92) Resin C: Linear low-density polyethylene (MI: 0.8, density: 0.924) The tearability in Table 1 is determined by the film in the dry state and the water-containing state. A V-notch was inserted and the torn state was observed.
The tear strength is measured according to JISZ1702,
The heat seal strength was measured according to JIS K1526, and the haze was measured according to JIS K7105.

Example 2 Resins A, B, C, D and E shown below
Are melt extruded in separate extruders, fed to one die, and laminated in the order of A, B, C, D and E before the lip.
(In-die lamination method) A multilayer film having a blow-up ratio of 1.4, A and E thicknesses of 30 μm each, B and D thicknesses of 10 μm each, and C thickness of 40 μm was obtained. Table 1 shows the tearability, tear strength, heat seal strength, haze, and film formability of the multilayer film. Resin A and Resin E: Polypropylene (MI: 6, density: 0.89) Resin B and Resin D: Modified polypropylene resin (MI: 10, density: 0.89) Resin C: 10 parts by weight of 100 parts by weight of nylon 6 (Novamid 1020) Dry-blended low-density polyethylene (MI: 2.5, density: 0.920).

Example 3 Resins A, B, C, D and E shown below
Are melt extruded in separate extruders, fed to one die, and laminated in the order of A, B, C, D and E before the lip.
(Lamination method in die), the blow-up ratio is 1.0, the thickness of A is 18 μm, the thickness of B is 12 μm, the thickness of C is 20 μm, the thickness of D is 10 μm, and the thickness of E is 20 μm. Was obtained.
Table 1 shows the tearability, tear strength, heat seal strength, haze, and film formability of the multilayer film.

Resin A: Modified polyethylene resin (MI: 1.8, density: 0.91) Resin B: Ethylene-vinyl alcohol copolymer (MI: 3.2, ethylene content: 32 mol%) Resin C: 100 parts by weight of nylon 6 (Novamid 1020) obtained by dry blending 10 parts by weight of low density polyethylene (MI: 0.8, density: 0.924). Resin D: Modified polyethylene resin (MI: 0.9, density: 0.92) Resin E: Linear low-density polyethylene (MI: 0.8, density: 0.924)

Comparative Example 1 Resin B and resin C were prepared in the same manner as in Example 1 except that only nylon 6 was used instead of resin A (a mixture of nylon 6 and low-density polyethylene).
And a film was formed to obtain a multilayer film. Table 1 shows the tearability, tear strength, heat seal strength, haze, and film formability of this multilayer film.

Comparative Example 2 Resin A and resin B were prepared in the same manner as in Example 2 except that only nylon 6 was used instead of resin C (a mixture of nylon 6 and low density polyethylene). ,
It was melt-laminated with resin D and resin E and formed into a film to obtain a multilayer film. Table 1 shows the tearability, tear strength, heat seal strength, haze, and film formability of this multilayer film.

Comparative Example 3 In Example 3, an ethylene-vinyl alcohol resin B was used.
Using no nylon 6 instead of resin C (a mixture of nylon 6 and low density polyethylene)
Otherwise, in exactly the same manner as in Example 3, resin A, resin D and resin E were melt-laminated and formed into a film to obtain a multilayer film. Table 1 shows the tearability, tear strength, heat seal strength, haze, and film formability of this multilayer film.

[0025]

[Table 1]

[0026]

As shown in Examples and Comparative Examples, the multilayer film of the present invention has excellent gas barrier properties and transparency, and can be easily torn not only when dry but also when wet. It is extremely suitable as a packaging material for foods.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C08L 23/08 C08L 23/08 (56) References JP-A-1-225550 (JP, A) JP-A-63-135245 (JP) JP-A-61-220839 (JP, A) JP-A-62-152848 (JP, A) JP-A-4-19137 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B32B 1/00-35/00

Claims (2)

(57) [Claims] At least one layer comprising a composition obtained by mixing 85 to 97% by weight of a polyamide resin or an ethylene-vinyl alcohol copolymer with 15 to 3% by weight of a polyolefin resin, and a polyolefin as a main component. Na and at least one layer made of resin is laminated is, excellent moisture
Easy-tear resistant multilayer film that have a Akirasei. 2. At least one layer comprising a composition obtained by mixing 85 to 97% by weight of a polyamide resin or an ethylene-vinyl alcohol copolymer and 15 to 3% by weight of a polyolefin resin, and a polyolefin as a main component. Ri Na laminated molded by at least one layer comprising the resin coextrusion, easy splitting multilayer film that have a good transparency.