JPH0761478A - Packaging material with oxygen barrier property - Google Patents

Abstract

PURPOSE:To impart a high oxygen barrier property for a long period of time from right after the processing while keeping a favorable processability by providing a thin film layer of an inorganic substance on a polyolefine resinlayer consisting of at least polyolefine and an oxidation catalyst. CONSTITUTION:A thin film layer 2 of an inorganic substance is provided on a polyolefine resinlayer 1 consisting of at least polyolefine and an oxidation catalyst. Preferably, for the oxidation catalyst, a metallic catalyst consisting of the compound of a transition metal, etc., is used, and the metals are Co, Mn, Fe, etc., and as the compounds of these metals, the salt of an organic acid is used. 10-1000ppm of the metal compound may be contained by the atomic density of a metal, based on a thermoplastic resin. As the inorganic substance of the thin film layer of an inorganic substance, either one of metals such as Al, Mg, Ca, etc., and their compounds and oxides of non-metallic inorganic substances is preferable. In the polyolefine resin layer, the polyolefine is oxidized by the reaction of an oxidation catalyst, and traps oxygen in the layer, and thus, an oxygen barrier property is developed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an oxygen barrier packaging material provided as a packaging material.

[0002]

2. Description of the Related Art Currently, packaging materials are mainly polymer materials, which can be easily processed into various shapes such as films, sheets, bottles and containers, and at the same time are lightweight and inexpensive to transport. What has been used is being used.

A high oxygen barrier property is required especially when the contents to be packaged are those that are easily deteriorated and deteriorated by oxidation such as foods. In order to meet such demands, conventional materials such as saponified ethylene-vinyl acetate copolymer (hereinafter referred to as EVOH), polyvinylidene chloride, or other polymeric materials or films on which aluminum or silicon oxide is deposited are used. Was offered to.

However, since the above-mentioned polymer material having an oxygen barrier property is expensive, its practical use is limited in terms of cost. Further, EVOH has a drawback that the oxygen barrier property is deteriorated by moisture absorption.

On the other hand, the above-mentioned vapor-deposited thin film has a drawback that the oxygen barrier property becomes unstable due to generation of pinholes and cracks.

The inventors of the present invention filed Japanese Patent Application Laid-Open No. 4-2133.
In Japanese Patent Laid-Open No. 46, a polyolefin resin composition using a polyolefin and an oxidation catalyst, which does not use an expensive oxygen barrier resin and which exhibits excellent oxygen barrier properties over time, is shown. However, in this polyolefin-based resin composition, the oxygen barrier property is exhibited over time, and therefore when the film is 100 μm or less, the oxygen barrier property immediately after film processing was not sufficient.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of such problems as described above.
An object of the present invention is to provide a packaging material that is inexpensive, has good processability, and has a high oxygen barrier property for a long period immediately after processing.

[0008]

In order to solve this problem, the present invention is an oxygen barrier packaging characterized by comprising an inorganic substance thin film layer on a polyolefin resin layer comprising at least a polyolefin and an oxidation catalyst. Provide the material.

The present invention will be described in detail below. The oxygen barrier packaging material of the present invention is used as a film, a sheet, etc. by laminating at least one thermoplastic resin layer on one side or both sides thereof and further laminating various films thereon.

The oxidation catalyst used in the present invention is preferably a metal catalyst composed of a transition metal compound or the like. In such a transition metal, it is considered that the metal ion catalyzes the reaction between oxygen and polyolefin in the process of transition from the oxidized state to the reduced state and from the reduced state to the oxidized state.

The transition metal is preferably Co,
Examples include metals such as Mn, Fe, Cu, Ni, Ti, V, and Cr. As compounds of these metals, salts of organic acids are used. Examples of such organic acid include stearic acid, naphthenic acid, linoleic acid, dimethyldithiocarbamic acid and the like, and organic metal complex salts having porphyrin, phthalocyanine, quinoline and the like as ligands are also preferably used. Besides, inorganic salts such as iron chloride, ammonium chloride and cobalt blue can also be used. Further, these metal compounds can be used alone or as a mixture of two or more kinds.

As the oxidation catalyst in the present invention, an aluminum compound can be used because it is hygienic, colorless and inexpensive.

These metal compounds may be contained in the thermoplastic resin in an atomic concentration of metal of 10 to 1000 ppm, and more preferably 50 to 500 ppm.

As the polyolefin in the present invention,
For example, homopolymers such as high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene, polybutene and polymethylpentene, and copolymers of two or more monomers selected from olefins such as ethylene, propylene, butene and methylpentene. Polymers may be mentioned.

The polyolefins of the present invention are generally susceptible to oxidation and are commonly used with radical inhibitors. However, whether the radical inhibitor is not added to the polyolefin containing the oxidation catalyst in the present invention,
It may be 500 ppm or less. With such an amount of addition, the radical inhibitor cannot prevent the progress of oxidation of the polyolefin at all, and takes in oxygen, and therefore does not hinder the present invention. On the contrary, the ability of the oxygen barrier property can be controlled by adjusting the addition amount of the radical inhibitor.

As the inorganic substance of the inorganic substance thin film layer formed in the present invention, Al, Mg, Ca, Sn, Ti, Zn and Z are used.
It is preferable to be a metal such as r, an oxide thereof, or an oxide of a non-metal inorganic substance. As a method for forming the same, known methods such as vacuum vapor deposition, plasma vapor deposition, ion plating, and sputtering can be applied. The thickness of these inorganic material thin film layers may be 200 to 1500Å.

The polyolefin resin layer comprising the polyolefin and the oxidation catalyst in the present invention has thermal adhesiveness by itself, and is suitable as a packaging material.

Further, another thermoplastic resin is laminated to give a practical function. For example, in order to protect the inorganic material thin film layer from external and physical deterioration, a thermoplastic resin is laminated on the inorganic material thin film layer side. Further, for the purpose of improving the strength as a package, a thermoplastic resin is laminated on the polyolefin resin layer side composed of polyolefin and an oxidation catalyst. In this case, a method of first forming a laminate of the polyolefin resin layer and a thermoplastic resin and forming an inorganic substance thin film layer on the laminate, and forming the inorganic substance thin film layer on the polyolefin resin layer first In any of the above methods, a thermoplastic resin can be laminated by a well-known processing method.

[0019]

In the polyolefin-based resin layer containing the above-mentioned oxidation catalyst, the polyolefin is oxidized by the oxidation catalyst action to trap oxygen in the layer,
Oxygen barrier property is developed.

That is, the polyolefin according to the present invention easily forms radicals by light or heat during molding or storage in the presence of an oxidation catalyst, whereby polymer radicals are generated. This reacts with oxygen dissolved in the resin to form peroxy radicals. Further, this peroxy radical abstracts hydrogen from the polyolefin to form a polymer radical with hydroperoxide. It is considered that this hydroperoxide is decomposed into an alkoxy radical and a hydroxy radical and further reacts with the polyolefin to generate a radical. Oxygen can be trapped in the polyolefin resin layer by such a series of oxidation radical reactions.

It is considered that such a series of oxidation radical reactions start immediately in the presence of oxygen during molding of the polyolefin resin layer containing the oxidation catalyst, but the effect of trapping and barriering the oxygen at the initial stage of the reaction Is not enough. Therefore, the inorganic substance thin film layer in the present invention realizes the oxygen barrier property in the initial stage immediately after the formation of the oxygen barrier property packaging material of the present invention.

The inorganic thin film layer in the present invention suppresses the amount of oxygen passing through the polyolefin resin layer containing the oxidation catalyst. That is, the polyolefin resin layer containing the above-mentioned oxidation catalyst traps oxygen, which is about to pass through the inorganic material thin film layer due to pinholes or the like, in the layer, thereby exhibiting a high oxygen barrier property for a long period of time. .

[0023]

[Examples] Partial cross-sectional views of the oxygen-barrier packaging material or the oxygen-barrier laminated packaging material of the Examples, as shown in FIGS.
However, the present invention is not limited to the following examples.

<Example 1> As shown in FIG. 1, a polyolefin in which cobalt (II) stearate was used as an oxidation catalyst in polypropylene to which a radical inhibitor was not added and which had a cobalt atom concentration of 50 ppm. A film was formed so that the resin layer 1 had a thickness of 40 μm. Silicon oxide was formed as a thin film layer 2 of an inorganic substance on one surface of this film by a plasma deposition method to a thickness of 500 Å to obtain an oxygen barrier packaging material of the present invention.

<Example 2> After the polyolefin resin layer 1 in Example 1 was subjected to corona discharge treatment, aluminum was used as the inorganic material thin film layer 2 by vacuum deposition to form 500 parts of aluminum.
It was formed to a thickness of Å to obtain the oxygen barrier packaging material of the present invention.

<Comparative Example 1> In Example 1, a single-layer film having only the polyolefin resin layer 1 without the inorganic thin film layer 2 was prepared.

Comparative Example 2 A film was prepared in the same manner as in Example 1 except that the polypropylene resin layer was formed into a film of 40 μm without adding the oxidation catalyst.

Table 1 shows the results of time-dependent measurement of oxygen permeability at 25 ° C. and 95% -RH for Examples 1 and 2 and Comparative Examples 1 and 2. The measurement was performed with an oxygen permeability measuring device “MOCON OX-TRAN 10 / 50A” (manufactured by Modern Control Co.).

[0029]

[Table 1]

As is clear from Table 1, the oxygen barrier packaging materials of the present invention of Examples 1 and 2 have extremely high oxygen barrier properties.

<Example 3> In the preparation of the oxygen barrier packaging material in Example 1, aluminum stearate, zinc stearate, magnesium stearate, cobalt linoleate, and cobalt naphthenate were used instead of the oxidation catalyst of cobalt stearate. And the oxygen barrier packaging material of the present invention was obtained. Table 2 shows the results of evaluation performed in the same manner as in Example 1.

[0032]

[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.

<Embodiment 4> As shown in FIG. 2, in order to protect the inorganic material thin film layer 2 from external physical deterioration, the inorganic material thin film layer 2 in Embodiment 1 is protected by a dry lamination method. Biaxially oriented polyester film 1 of layer 3
2 μm was laminated to obtain an oxygen barrier packaging material of the present invention.

Example 5 An unstretched polyethylene film of 30 μm was used as the protective layer 3 in Example 4. In this way, when an unstretched thermoplastic resin film is used, both sides of the polyolefin resin layer 1 and the protective layer 3 can have thermal adhesiveness.

<Example 6> As shown in FIG. 3, a support layer 4 was provided for the purpose of increasing the strength of the entire packaging material. In this embodiment, the polypropylene resin layer 40 μm is formed by the melt coextrusion method.
As the support layer 4 and the polyolefin resin layer 1
A laminated film having a thickness of 0 μm was prepared. Silicon oxide was formed on this laminated film as the inorganic material thin film layer 2 by a plasma deposition method to a thickness of 500 μm to obtain an oxygen barrier packaging material of the present invention.

<Example 7> For the same purpose as in Example 6, except that in this example, ethylene / vinyl acetate copolymer excellent in low-temperature fusion property was formed on the polyolefin resin layer 1 containing the oxidation catalyst in Example 1. A polymer resin film 40 μm was provided as the support layer 4 by using the dry lamination method to obtain the oxygen barrier packaging material of the present invention.

<Embodiment 8> As shown in FIG.
The oxygen barrier packaging material of the present invention was obtained by laminating a biaxially stretched polypropylene film 12 μm as the protective layer 3 and an unstretched polypropylene film 30 μm as the support layer 4 on the above oxygen barrier packaging material using a dry lamination method. In the case of the present embodiment, since the resin used is a single polypropylene resin, it can be melted and recycled, and the proportion of the inorganic material layer 2 contained is very small and does not hinder this.

<Embodiment 9> In FIG. 4, when it is feared that the oxidation catalyst and other additives contained in the polyolefin resin layer 1 are transferred to the contents, the inorganic substance thin film layer 2 is used as the inner side of the packaging material. Shut off. A heat-adhesive non-stretched polyethylene film 40 μm is used for the protective layer 3, and a printed biaxially stretched polyester film 12 μm is laminated on the support layer 4 by a dry lamination method to obtain the oxygen barrier packaging material of the present invention. Obtained.

The oxygen permeability of Examples 4, 5, 6, 7, 8, and 9 was evaluated in the same manner as in Example 1, and it was found that all of them exhibited high oxygen barrier properties. The results are shown in Table 3.
It was shown to.

[0042]

[Table 3]

[0043]

Industrial Applicability According to the present invention, a packaging material having a high oxygen barrier property can be provided by a polyolefin resin which is inexpensive and has good workability. Further, by laminating another thermoplastic resin, various practical functions can be imparted without impairing the high oxygen barrier property.

[0044]

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of an embodiment of the oxygen barrier packaging material of the present invention.

FIG. 2 is a partial cross-sectional view of an embodiment of the oxygen barrier packaging material of the present invention.

FIG. 3 is a partial cross-sectional view of an embodiment of the oxygen barrier packaging material of the present invention.

FIG. 4 is a partial cross-sectional view of an embodiment of the oxygen barrier packaging material of the present invention.

[Explanation of symbols]

 1 ... Polyolefin resin layer 2 ... Inorganic substance thin film layer 3 ... Protective layer 4 ... Support layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiko Nakamura 1-5-1 Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. (72) Inventor Mamoru Sekiguchi 1-5-1 Taito, Taito-ku, Tokyo Toppan Imprint Co., Ltd.

Claims (1)

[Claims] 1. An oxygen barrier packaging material, comprising an inorganic thin film layer provided on a polyolefin resin layer comprising at least a polyolefin and an oxidation catalyst.