JPH06248122A - Oxygen-barrier resin composition and its production - Google Patents

Abstract

PURPOSE:To obtain a resin compsn. which is reduced in the degradation of strengths without detriment to the oxygen-barrier properties by melt mixing a polyolefin resin with an oxidation catalyst to disperse it in the resin. CONSTITUTION:This resin compsn. is obtd. by melt mixing a polyolefin resin with an oxidation catalyst to disperse it in the resin. A conventional oxygen- barrier film for food packaging, etc., requires lamination with a more expensive resin, e.g. a saponified ethylene-vinyl acetate copolymer or a polyvinylidene chloride. A combination of a polyolefin resin with an oxidation catalyst, though exhibiting high oxygen-barrier properties without using an expensive oxygen- barrier resin, has the problem of degradation of strengths and is not suitable for a packaging material for long storage. The compsn. of this invention is reduced in the degradation of strengths without detriment to the oxygen-barrier properties.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a resin composition having an excellent oxygen barrier property and a method for producing the same.

[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 of contents such as foods that dislike oxygen, it is laminated with a more expensive resin having an oxygen barrier property, for example, saponified ethylene-vinyl acetate copolymer, polyvinylidene chloride or the like. It was actually used.

The present inventors have previously filed Japanese Patent Application Laid-Open No. 3-2133.
In Japanese Patent Laid-Open No. 46-46, a resin composition using a polyolefin and an oxidation catalyst, which does not use an expensive oxygen barrier resin and has an excellent oxygen barrier property, is shown. However, although the combination of the oxidation catalyst and the polyolefin alone shows a very high oxygen barrier property, the strength of the composition was deteriorated due to the too fast oxygen absorption reaction. Therefore, there is a problem as a packaging material particularly for long-term storage.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and its object is to retain the oxygen barrier function and to suppress the deterioration of strength. It is to provide a resin composition.

[0006]

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 is to provide a composition comprising a polyolefin having an oxygen absorbing function and an oxidation catalyst in the polyolefin. It has been found that this can be achieved by providing an oxygen-barrier resin composition that is dispersed and retains the overall strength.

As a method for producing the same, a composition comprising a polyolefin and an oxidation catalyst is melt-kneaded in advance and dispersed in the polyolefin.

The present invention will be described in more 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, homopolymer of polypropylene, block polymer or random copolymer, polybutene, ethylene-α olefin (number of carbon atoms). 3 or more) copolymers and the like. The antioxidant content in the polyolefin is preferably 500 ppm or less.

In the present invention, the above-mentioned polyolefin may contain a nucleating agent or various additives such as a compatibilizer, a lubricant, an anti-blocking agent, a stabilizer, an antifogging agent and a coloring agent. As the compatibilizing agent, a maleic anhydride graft-modified polyolefin or the like is used.

The oxidation catalyst used in the present invention means that oxygen which permeates and permeates the polyolefin is reacted with the polyolefin by promoting the oxygen oxidation of the polyolefin to lower the oxygen permeability, and as a result, the oxygen barrier of the polyolefin. As long as it can improve the property, an oxidation catalyst composed of a transition metal compound or the like is preferably used as such an oxidation catalyst.

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

Examples of such a transition metal include metals such as Co, Mn, Fe, Cu, Ni, Ti, V and Cr, and Co is preferably used.
As the compounds of these metals, salts of organic acids are used. Examples of such an organic acid include stearic acid,
Examples thereof include acetylacetonic acid, dimethyldithiocarbamic acid, linoleic acid, naphthenic acid, tallic acid, oleic acid, resin acid and capric acid.

Further, as the oxidation catalyst of the present invention, Al, Mg, Ca and Zn compounds can also be used because they are hygienic, colorless and inexpensive. The composition of the oxidation catalyst is 10 pp in terms of metal atomic weight.
It is desirable that the content be at least m.

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 polyolefin is deteriorated due to rapid oxygen absorption and discolored. From the viewpoint of fear, it is preferably used at 2000 ppm or less with respect to the entire oxygen barrier resin composition.

The oxygen barrier resin composition of the present invention is formed by dispersing a polyolefin containing an oxidation catalyst in the polyolefin. The combination of the polyolefin to be dispersed and the type of the polyolefin containing the oxidation catalyst is It doesn't matter. That is, the polyolefin containing the oxidation catalyst improves the oxygen barrier property by absorbing oxygen by the reaction with the oxidation catalyst even if it exists in the form of islands without being dissolved in the polyolefin to be dispersed. The mixing ratio of the polyolefin containing the oxidation catalyst and the polyolefin in such dispersion is 1:
It is 100 to 100: 100.

In the method for producing the oxygen barrier resin composition of the present invention, the oxidation catalyst and the polyolefin are melt-kneaded in advance using a biaxial kneader or the like. After that, the polyolefin composition containing the oxidation catalyst is dispersed in one of the polyolefins when the packaging material such as a film, a sheet and a container is processed.

That is, by pre-melting and kneading, the oxidation catalyst is better dispersed in the polyolefin and the oxygen absorption reaction of the polyolefin is improved.

In the present invention, an organic acid salt is used as the oxidation catalyst, and such an organic acid has been conventionally used as a lubricant or the like and has a function of lowering the viscosity of the polyolefin during processing. . That is, the dispersion in the polyolefin is improved by reducing the viscosity of the oxidation catalyst and the polyolefin composition. Further, in order to improve the dispersibility, a compatibilizing agent is added to the composition in an amount of 1: 100.
-40: 100 parts by weight may be contained.

The oxygen-barrier resin composition obtained by dispersing the polyolefin composition containing the oxidation catalyst in the polyolefin as described above is used for forming films, sheets, containers, etc. by various molding methods using heat. It can be molded into packaging materials and the like.

For example, a film, a sheet, a pipe or the like may be formed by melt extrusion molding, into a container shape by injection molding, or
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 molding 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.

As such a laminate, preferably,
The one in which another thermoplastic resin layer, for example, a thermoplastic resin layer containing no oxidation catalyst is formed on one side or both sides of the oxygen barrier resin composition layer is used.

Other thermoplastic resin layers used include:
Examples of the layer include polyester, polyolefin, polyamide, polyurethane, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polycarbonate and the like, or modified resins thereof.

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 as follows. 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 forming into a sheet or film,
It can be used as a bag material, a blister pack material, a container lid, and the like. Further, in the case of forming 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.

[0026]

As described above, in the oxygen barrier resin composition of the present invention, the polyolefin reacts with oxygen in the air in the presence of the oxidation catalyst to promote the oxygen absorption reaction of the polyolefin by the radical reaction. As a result, it is presumed that oxygen in the atmosphere is consumed and the oxygen barrier property is improved.

Here, although the combination of the oxidation catalyst and the polyolefin alone shows a very high oxygen barrier property, the strength of the polyolefin was deteriorated due to the too fast oxygen absorption reaction. By the constitution of the present invention, that is, by dispersing the polyolefin composition containing the oxidation catalyst in one of the polyolefins not containing the oxidation catalyst, strength deterioration of the entire oxygen barrier resin composition is prevented.

[0028]

EXAMPLES The present invention will be described in more detail with reference to the following examples.

<Example 1> Co (II) stearate 20
0 ppm and polypropylene J600 (Mitsui Petrochemical Co., Ltd .: MI = 0.5, no antioxidant) were mixed,
Extrusion molding was performed at an extrusion temperature of 220 ° C. using a twin-screw kneading extruder to obtain resin pellets. Next, a dispersion of polyethylene (Mitsui Petrochemical Co., Ltd .: trade name Mirason 14P) at a mixing ratio of 20:80 (weight ratio) was used to obtain 190
Extrusion molding was performed at an extrusion temperature of ° C to obtain a sheet having a thickness of 800 µm.

<Example 2> In the preparation of the sheet sample of Example 1, the mixing ratio of resin pellets made of Co (II) stearate and polypropylene to polyethylene was 10: 9.
A sheet was obtained in the same manner except that the weight ratio was 0.

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

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

Comparative Example 3 Polyethylene (manufactured by Mitsui Petrochemical Co., Ltd .: trade name Mirason 14P) was extruded at a temperature of 190 ° C.
Was extruded to obtain a sheet having a thickness of 800 μm.

Comparative Example 4 Co (II) stearate 20
0 ppm and polypropylene J600 (Mitsui Petrochemical Co., Ltd .: MI = 0.5, no antioxidant) were mixed,
Extrusion was performed at an extrusion temperature of 190 ° C. to obtain a sheet having a thickness of 800 μm.

The above Examples 1 and 2 and Comparative Examples 1 and 2,
Table 1 shows the measurement results of the oxygen transmission rate with time for each of the sheets obtained in 3 and 4. Measurement is Mokon Ox-TRAN10
/ 50A (manufactured by Modern Control Co.) at 25 ° C.

[0036]

[Table 1]

As is clear from Table 1, the oxygen barrier sheets of the present invention of Examples 1 and 2 and Comparative Example 4 have an oxygen permeability which decreases with time, and have an extremely excellent oxygen barrier property. is doing.

Example 3 In the production of the oxygen barrier sheet in Example 1, the oxidation catalyst was changed to cobalt stearate, and aluminum stearate, zinc stearate, magnesium stearate, cobalt linoleate, and cobalt naphthenate were displayed. Table 2 shows the results of evaluating the sheet sample of Comparative Example 1 shown below, which was used as shown in Example 2 and did not contain the following sheet samples A, B, C, D, E and the oxidation catalyst, in the same manner as in Example 1.

[0039]

[Table 2]

In Table 2, A is aluminum stearate, B is zinc stearate, C is magnesium stearate, D is cobalt linoleate, and E is cobalt naphthenate.

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

Examples 1, 2 and Comparative Examples 1, 2, 3,
The elongation at break of the sheet sample obtained in No. 4 was measured. The measurement was performed with a tensile tester. (Test piece: 100
mm x 10 mm, between clippers: 20 mm, load: 40 kg
f, crosshead speed: 200 mm / min) The results are shown in Table 3.

[0043]

[Table 3]

As is clear from Table 3, the oxygen barrier sheets of the present invention obtained in Examples 1 and 2 suppress the decrease in elongation at break with time.

Example 4 In the production of the oxygen barrier sheet in Example 1, this was extruded into a film having a thickness of 40 μm. Using urethane adhesive,
A film obtained by sequentially laminating a K-coated (vinylidene chloride-coated) stretched PET film having a thickness of 12 μm, the oxygen barrier film of the present invention, a PET film having a thickness of 12 μm, and an unstretched PP film having a thickness of 30 μm is dried. It was created by laminating.

Example 5 In the production of the oxygen barrier sheet in Example 2, this was extruded into a film having a thickness of 40 μm. Using urethane adhesive,
A film obtained by sequentially laminating a K-coated (vinylidene chloride-coated) stretched PET film having a thickness of 12 μm, the oxygen barrier film of the present invention, a PET film having a thickness of 12 μm, and an unstretched PP film having a thickness of 30 μm is dried. It was created by laminating.

Comparative Example 5 A laminated film was prepared in the same manner as in Example 3 except that Co (II) stearate was not added.

Table 4 shows the measurement results of the oxygen transmission rate over time for each of the laminated films obtained in Examples 4 and 5 and Comparative Example 5 above. Measurement is Mokon Ox-TRAN10 / 50A
(Manufactured by Modern Control) at 25 ° C.

[0049]

[Table 4]

As is clear from Table 4, the oxygen barrier laminate films of Examples 4 and 5 of the present invention have a very low oxygen permeability and have an extremely excellent oxygen barrier property.

[0051]

As described in detail above, according to the present invention, saponified ethylene-vinyl acetate copolymer, polyvinylidene chloride, etc., which are expensive, can be used without using any other oxygen barrier resin or in a small amount. It is possible to provide a thermoplastic resin composition having excellent oxygen barrier properties and a method for producing the same.

 ─────────────────────────────────────────────────── ─── Continuation of 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 Imprint Co., Ltd.

Claims (2)

[Claims] 1. An oxygen barrier resin composition in which a composition comprising a polyolefin and an oxidation catalyst is dispersed in the polyolefin. 2. A method for producing an oxygen-barrier resin composition, characterized in that a composition comprising a polyolefin and an oxidation catalyst is melt-kneaded in advance and dispersed in the polyolefin.