JPH0550565A - Easily tearable multilayered film - Google Patents

Abstract

PURPOSE:To ensure excellent gas barrier properties, transparency and tearable properties by laminating a layer composed of a easily polyamide resin or an ethylene/vinyl alcohol copolymer and a polyolefin resin and a layer composed of a resin based on polyolefin. CONSTITUTION:An easily tearable multilayered film is constituted by laminating at least two specific layers. That is, at least one layer is formed from a composition prepared by mixing 85-97wt.% of a polyamide resin or an ethylene/vinyl alcohol copolymer and 15-3wt.% of a polyolefin resin and at least the other one layer is formed from a resin based on polyolefin. Two layers are subjected to co-extrusion molding or laminate molding. By this method, the easy tearing multilayered film excellent in gas barrier properties and transparency, capable of being easily torn at the time of drying or hydration and suitable for a packing material of perishable foods is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an easily tearable multi-layer film. More specifically, the present invention relates to an easily tearable multi-layer film which has excellent gas barrier properties and transparency and can be easily torn, and which is suitable as a packaging material for foods.

[0002]

2. Description of the Related Art Conventionally, as a packaging material for foods, especially meats, pastes, etc., which have a high water content and are deteriorated and cheap,
A resin film having excellent gas barrier properties 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, it is also attempted to make up for these defects 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 film is usually formed into a bag, the foods are housed inside, sealed with a heat seal, and then heat-sterilized to obtain a product.

The above resin film is suitable for preventing the deterioration of the contents because it has excellent gas barrier properties, but since the film has a high tear strength, 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 contain water. For example, when the package is steam sterilized, the tear strength of the films becomes extremely large, making it more difficult to take out the contents, which is inconvenient for practical use.

[0004]

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 that are easily deteriorated. It is intended to provide a tearable multi-layer film.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, a composition obtained by mixing a polyamide resin or an ethylene-vinyl alcohol copolymer and a polyolefin resin in a specific ratio. A laminated film composed of a layer made of a material and a resin layer containing polyolefin as a main component is excellent in gas barrier property and transparency and can be easily torn, which 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 to provide at least one layer comprising a composition comprising a polyamide resin or an ethylene-vinyl alcohol copolymer 85 to 97% by weight and a polyolefin resin 15 to 3% by weight, and polyolefin. The easily tearable multi-layer film is characterized by being laminated with at least one layer made of a resin as a main component.

The present invention will be described in detail below. Examples of the polyamide resin used in 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 ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 60 mol%, preferably 27 to 47 mol%.

As the polyolefin resin mixed with the above polyamide resin or ethylene-vinyl alcohol copolymer, low density polyethylene having a density of 0.93 g / cm ³ or less,
Medium density polyethylene with a density of 0.93 to 0.94 g / cm ³ ,
High density polyethylene of 0.94g / cm ³ or more, density 0.93g / c
Polyethylene resin such as linear low density polyethylene of m ³ or less; polypropylene resin; or ethylene content of 90 mol%
The above-mentioned ethylene-vinyl acetate copolymer and the like can be mentioned.

The mixing ratio of the polyolefin resin needs to 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. If the proportion of the polyolefin resin is less than 3% by weight, sufficient tear strength is not imparted, and if it exceeds 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 usually a dry blending is adopted.

As the layer made of a resin containing polyolefin as a main component to be laminated with a layer made of a mixture of a polyamide resin or an ethylene-vinyl alcohol copolymer and a polyolefin resin, the above-mentioned low density polyethylene, medium density polyethylene and high density polyethylene can be used. Density polyethylene, polyethylene such as linear low density polyethylene, polypropylene, ethylene-
In addition to vinyl acetate copolymers and the like, well-known copolymers of olefins containing olefin as a main component with other monomers, such as ionomer resins, modified polyethylene resins, modified polypropylene resins, ethylene-ethyl acrylate copolymers. object,
Ethylene-methyl methacrylate copolymer, ethylene-
Examples of the layer include an acrylic acid copolymer, an ethylene-methacrylic acid random copolymer, or a mixture thereof.

The ionomer is an ethylene-based polymer obtained by copolymerizing a small amount of a monomer having a carboxyl group in its side chain, such as acrylic acid, with a hydroxide such as Na, K, Mg or Zn, or an alcohol. And a lower fatty acid salt are added to neutralize most of the acid groups. In addition, modified polyethylene resin and modified polypropylene resin have a small amount of maleic acid, maleic anhydride, acrylic acid, acrylic acid anhydride, and other unsaturated carboxylic acid graft-reacted with polyethylene or polypropylene to improve adhesion to other resins. It is an improvement.

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

A layer made of a mixture of a polyamide resin or an ethylene-vinyl alcohol copolymer and a polyolefin resin (mixed resin layer), and a layer made of a resin containing polyolefin as a main component to be laminated thereon (polyolefin resin layer)
As the layer structure with, the thickness of the mixed resin layer is 5 to 100 μm from the viewpoint of gas barrier property and strength, and the thickness of the polyolefin resin layer is 10 to 100 μm from the viewpoint of imparting water resistance.
Is preferred. In addition, in order to improve the adhesiveness between the mixed resin layer and the polyolefin resin layer, polyethylene (10 ⁻⁵ to 4 wt% of maleic acid, maleic anhydride, acrylic acid, acrylic acid anhydride, etc.) is added to the polyethylene between both layers. It is preferable to interpose a modified polyethylene resin layer grafted with a saturated carboxylic acid or to use the above grafted modified polyethylene resin layer as the polyolefin resin layer.

The multilayer film of the present invention comprises at least one layer (mixed resin layer) made of a mixture of a polyamide resin or an ethylene-vinyl alcohol copolymer and a polyolefin resin, and at least a resin having polyolefin as a main component. It is a multi-layer film formed by laminating one layer (polyolefin resin layer), and may have an arbitrary multi-layer structure depending on the application. Further, when the multilayer film of the present invention is formed into a bag shape, it often depends on a heat seal, but in order to perform a good heat seal, the innermost layer (heat seal) is used. It is preferable that the layer) is a polyolefin resin layer.

In order to produce the easily tearable multi-layer film of the present invention, it is preferable to use a coextrusion method. Coextrusion molding is a method in which a plurality of types of resins are melt-kneaded by separate extruders, the resin in the molten state is introduced into a die, and the resin is extruded in a laminated and laminated state in the die. Among the coextrusion molding methods, the coextrusion inflation molding method is particularly suitable for producing a multilayer film. Coextrusion inflation-
Draft ratio (take-off speed /
(Extrusion speed) 3 to 60, preferably about 5 to 50, the blow
Up ratio (product diameter / die slit diameter) 0.4 to 2, especially 0.
It is preferably about 7 to 1.6.

The film extruded by the above method is brought into contact with a cooling roll or a mandrel at room temperature to about 40 ° C., or is brought into direct contact with water or another cooling medium to be rapidly cooled to obtain transparency and flexibility. An easily tearable multi-layer film having excellent properties can be obtained. It should be noted that the post-treatment such as the stretching treatment impairs the easy tearability of the film, so that it is desirable to use the product as it is without performing the post-treatment.

[0016]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded.

Example 1 Resin A, resin B, and resin C shown below were melt-extruded by separate extruders, fed to one die, and melt-laminated in the order of A, B, and C before the lip (die. Inner lamination method), the blow-up ratio is 1.2, A thickness is 20μm, B thickness is 10μ
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-forming property of the above-mentioned multilayer film.

Resin A: 100 parts by weight of nylon 6 (Novamid
1022CK2, a product of Mitsubishi Kasei) and 5 parts by weight of low density polyethylene [melt index (MI): 2, density: 0.927] are dry blended. 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 for the film in the dry state and the water-containing state. The V notch was inserted and observed.
The tear strength is measured according to JIS Z1702,
The heat seal strength was measured according to JIS K1526, and the haze was measured according to JIS K7105.

Example 2 Resin A, Resin B, Resin C, Resin D and Resin E shown below
Melt-extruded by separate extruders, fed to one die and melt-laminated in the order of A, B, C, D and E before the lip
(In-die laminating method) to obtain a multilayer film having a blow-up ratio of 1.4, a thickness of A and E of 30 μm, a thickness of B and D of 10 μm, and a thickness of C of 40 μm. Table 1 shows the tearability, tear strength, heat seal strength, haze and film-forming property of the above-mentioned 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: 100 parts by weight of Nylon 6 (Novamid 1020) 10 parts by weight Part of low density polyethylene (MI: 2.5, density: 0.920) dry blended.

Example 3 Resin A, Resin B, Resin C, Resin D and Resin E shown below
Melt-extruded by separate extruders, fed to one die and melt-laminated in the order of A, B, C, D and E before the lip
(In-die laminating method), set the blow-up ratio to 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. A multi-layer film of
Table 1 shows the tearability, tear strength, heat seal strength, haze and film-forming property of the above-mentioned 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) dry blended with 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 In Example 1, resin N (mixture of nylon 6 and low density polyethylene) was used instead of resin A, and nylon 6 was used in the same manner as in example 1 except that resin B and resin C were used.
Was 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-forming property of this multilayer film.

Comparative Example 2 In Example 2, resin A (a mixture of nylon 6 and low density polyethylene) was used instead of resin C, except that nylon 6 was used. ,
The resin D and the 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-forming property of this multilayer film.

Comparative Example 3 In Example 3, the ethylene-vinyl alcohol-containing resin B was used.
Without using a copolymer, and using only nylon 6 instead of resin C (a mixture of nylon 6 and low density polyethylene),
In the same manner as in Example 3 except for the above, 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-forming property 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 it is dried but also when it contains water. It is extremely suitable as a packaging material for foods.

Front page continuation (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // B29C 47/04 7717-4F B65D 65/40 A 9028-3E

Claims (2)

[Claims] 1. 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. An easily tearable multi-layer film, which is formed by laminating at least one layer of the resin. 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 polyolefin as a main component. An easily tearable multi-layer film formed by laminating and molding at least one layer of a resin by a coextrusion molding method.