JPH05170980A - Oxygen barrier resin composition and packaging material using the same - Google Patents

Abstract

(57) [Summary] [Objective] Saponified ethylene-vinyl acetate copolymer (hereinafter EVOH), which is an expensive resin with oxygen barrier properties.
It is intended to provide a resin composition and a packaging material that reduce the amount of the resin and exhibit excellent barrier properties. [Composition] An oxygen barrier resin composition comprising a polyolefin, EVOH and an oxidation catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition comprising a thermoplastic resin and having an excellent oxygen barrier property, a method for producing the resin composition and an oxygen barrier packaging material using the resin composition.

[0002]

2. Description of the Related Art Since thermoplastic resins can be molded by various methods such as melt extrusion molding, injection molding and blow molding, they are widely used in, for example, packaging films, sheets, bottles and containers. . However, particularly for packaging contents such as foods that dislike oxygen, saponified ethylene-vinyl acetate copolymer (hereinafter referred to as EVOH), which is an oxygen barrier property and is more expensive, is used. It was

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a resin composition and a packaging material which reduce the amount of a more expensive oxygen barrier resin and exhibit excellent barrier properties. The purpose is to provide.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in view of the above problems, and as a result, the above object of the present invention was to provide an oxygen barrier resin composition and a packaging material comprising polyolefin and EVOH and an oxidation catalyst. It was found that this can be achieved by providing.

The present invention will be described in detail below. Examples of the polyolefin used in the present invention include polyethylene such as low-density polyethylene, medium-density polyethylene, and high-density polyethylene, homo- or block-polymers or random copolymers of polypropylene, polybutene, ethylene-α-olefin (having 3 or more carbon atoms). ) Copolymers and the like can be mentioned. The content of the radical antioxidant in the polyolefin is preferably 500 ppm or less.

Further, EVOH having an ethylene content of 22 to 48 mol% and a saponification degree of 99 to 100 mol% is preferable in terms of the effect of oxygen barrier property.

In the present invention, polyolefin, EV
Nucleating agents or various additives in OH, such as compatibilizers, lubricants,
An antiblocking agent, a stabilizer, an antifogging agent, a colorant and the like may be contained. As the compatibilizing agent, a maleic anhydride graft-modified polyolefin or the like is used.

The oxidation catalyst used in the present invention is to promote the oxygen oxidation of polyolefin and EVOH, thereby reacting the oxygen which permeates and permeates polyolefin and EVOH with the polyolefin and EVOH to lower the oxygen permeability. As a result, polyolefin and EV
Any oxidation catalyst that can improve the oxygen barrier property of OH may be used. As such an oxidation catalyst, an oxidation catalyst composed of a transition metal compound or the like is suitable.

In the case of such a transition metal, it is considered that oxygen reacts with the polyolefin and EVOH to act as an oxidation catalyst during the transition of the metal ion from the oxidized state to the reduced state and from the reduced state to the oxidized state.

Such transition metals include Co and M
n, Fe, Cu, Ni, Ti, V, Cr and the like,
Of these, Co is preferable. As the compounds of these metals, salts of organic acids are used. Examples of such an organic acid include stearic acid, acetylacetonic acid, dimethyldithiocarbamic acid, linoleic acid, naphthenic acid, tall acid, oleic acid, resin acid and capric acid.

Further, as the oxidation catalyst of the present invention, A1, Mg, Ca and Zn compounds can also be used because they are hygienic, colorless and inexpensive. Further, the above-mentioned oxidation catalyst is preferably 100 ppm or more in terms of metal atomic weight in the polymer resin composition.

Further, the higher the concentration of such an oxidation catalyst, the more excellent the effect of the barrier property is, but if the content is too large, the rapid absorption of oxygen deteriorates the polyolefin and EVOH, Since it may be discolored when dispersed in another thermoplastic resin, it is preferably 2000 ppm or less with respect to the polymer resin composition.

The oxygen barrier resin composition of the present invention is formed by dispersing an oxidation catalyst in polyolefin and EVOH. Even if the polyolefin containing the oxidation catalyst and the EVOH exist in the form of islands without being mixed with each other, the oxygen barrier property is improved by the absorption of oxygen by the reaction with the oxidation catalyst. The mixing ratio of polyolefin and EVOH in such dispersion is 1: 100 to 100: 100.
Is preferred.

Next, the oxygen barrier resin composition comprising the polyolefin containing the oxidation catalyst and EVOH as described above is formed into a film by using various molding methods using heat.
It can be formed into sheets, containers, and other packaging materials.

For example, a film, a sheet, a pipe or the like is formed by melt extrusion molding, a container shape is formed by injection molding, and
By hollow molding, a hollow container such as a bottle can be molded. Hollow molding includes extrusion hollow molding in which a parison is molded by extrusion and then blown to perform molding, and injection hollow molding in which a preform is molded by injection molding and then blown to perform molding.

In the present invention, the sheet, packaging material, container, etc. obtained by the above molding may be a single layer,
It is more preferable to use it as a laminate with various other layers. That is, when EVOH is used in a single layer, the oxygen barrier property may be lowered due to the contents or moisture in the outside air. Therefore, a layer having a water vapor barrier property is laminated and used on the side where moisture exists.

As such a laminate, one or both surfaces of the oxygen-barrier resin composition layer comprising the above-mentioned oxidation catalyst-containing polyolefin and EVOH is another thermoplastic resin layer, for example, an oxidation catalyst-free thermoplastic resin layer. Those formed with are preferable.

Other thermoplastic resin layers used include:
Examples of the layer include polyester, polyolefin, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, or a modified resin thereof having a high water vapor barrier property.

As a method for laminating these layers, each method such as lamination using an adhesive, coextrusion molding, coextrusion hollow molding or coinjection hollow molding is used.

The oxygen barrier resin composition of the present invention can be used in various applications such as the following. For example, it can be used as a material for a container for storage of a substance that is easily modified by oxygen, such as food.

When formed into a sheet or film,
It can be used as a bag material, a blister pack material, a container lid, and the like. Further, when formed into a pipe shape, a container can be obtained by closely adhering the openings at both ends with a metal lid or the like. For injection molded containers and bottles,
It can be used as it is as a container.

[0022]

[Function] Polyolefin and EVOH react with oxygen in the atmosphere in the presence of an oxidation catalyst to promote an oxygen absorption reaction by a radical reaction, resulting in consumption of oxygen in the atmosphere and improvement in oxygen barrier properties. It is supposed to be.

Among them, EVOH has an initial oxygen barrier property, but the promotion of the oxygen absorption reaction by this oxidation catalyst was slow. Therefore, in the constitution of the present invention, by adding a polyolefin having a great effect of promoting the oxygen absorption reaction by the oxidation catalyst, the initial oxygen barrier property and the excellent oxygen barrier property over time are realized.

[0024]

The present invention will be described more specifically with reference to the following examples.

<Example 1> Co (II) stearate 20
0ppm and polypropylene (Mitsui Petrochemical Co., Ltd.,
"B240" MI = 0.5, no antioxidant) and EV
Mixing ratio of OH (Kuraray Co., Ltd., "Eval F101" ethylene content 32 mol%, degree of saponification 99% or more) 2
Extrusion molding was carried out at an extrusion temperature of 210 ° C. at a weight ratio of 0:80 to obtain a film having a thickness of 50 μm. Using a urethane adhesive on both sides of the created film, thickness 50 μm
The unstretched polypropylene film of was laminated to prepare a laminated film.

Example 2 A laminated film was prepared in the same manner as in Example 1 except that the mixing ratio of polypropylene and EVOH was 5:95 (weight ratio).

Comparative Example 1 A laminated film was prepared in the same manner as in Example 1 except that Co (II) stearate was not included in Example 1.

Comparative Example 2 A laminated film was prepared in the same manner as in Example 2 except that Co (II) stearate was not included in Example 2.

Comparative Example 3 Co (II) stearate 20
0ppm and EVOH (Kuraray Co., Ltd., "Eval F1
01 ”ethylene content 32 mol%, saponification degree 99% or more) was extruded at an extrusion temperature of 210 ° C. to a thickness of 50
A μm film was made. Using the above film, a laminated film was prepared in the same manner as in Example 1.

Examples 1 and 2 and Comparative Examples 1, 2, and 3
The oxygen transmission rate (O ₂ -T
The measurement results of R) are shown in Table 1. The measurement is "Mokon Ox-T
RAN10 / 50A "(made by Modern Control),
It was carried out under the conditions of 25 ° C and 100% -RH.

[0031]

[Table 1]

As is clear from Table 1, the oxygen barrier film of the present invention has a very low oxygen permeability and has an extremely excellent oxygen barrier property.

<Example 3> In the production of the multilayer film in Example 1, the oxidation catalyst was changed to cobalt stearate, aluminum stearate, zinc stearate,
Magnesium stearate, cobalt linoleate, and cobalt naphthenate were used as shown in Table 2.

The results of evaluating the laminated film containing the oxidation catalyst and the laminated film of Comparative Example 1 not containing the oxidation catalyst in the same manner as in Example 1 are shown in Table 2.

[0035]

[Table 2]

As is clear from Table 2, the oxygen barrier property can be obtained even when each oxidation catalyst is used.

[0037]

As described in detail above, according to the present invention, the use of more expensive oxygen barrier resin is reduced,
Further, it is possible to provide a thermoplastic resin composition and an oxygen barrier packaging material that exhibit excellent oxygen barrier properties.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keiko Nakamura 1-5-1 Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. (72) Inventor Hiroshi Umeyama 1-5-1 Taito, Taito-ku, Tokyo Toppan In Printing Co., Ltd. (72) Inventor Takeo Kato 1-5-1, Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. (72) Inventor Shunichi Kato 1-1-5, Taito, Taito-ku, Tokyo Toppan Printing Within the corporation

Claims (2)

[Claims] 1. An oxygen barrier resin composition comprising a polyolefin, a saponified product of an ethylene-vinyl acetate copolymer and an oxidation catalyst. 2. An oxygen barrier packaging material comprising the oxygen barrier resin composition according to claim 1.