JPH0543723A - Method for improving oxygen barrier property of polyolefin packaging material - Google Patents

Abstract

PURPOSE:To efficiently improve oxygen barrier properties of a polyolefin packaging material by exposing the polyolefin packaging material to radiation. CONSTITUTION:A packaging material, composed of a polyolefin such as PP and formed into a film, a sheet, a bottle, a container, etc., is exposed to radiation such as gamma-rays, preferably at >=10kGy radiation dose to improve the oxygen barrier properties of the polyolefin packaging material.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for improving the oxygen barrier property of a polyolefin packaging material.

[0002]

BACKGROUND OF THE INVENTION Polyolefins are thermoplastic and therefore
Since it can be molded by various methods such as melt extrusion molding, injection molding, and hollow molding, and is inexpensive, it is widely used for packaging films, sheets, bottles, containers, and the like. However, since such a polyolefin has a high oxygen permeability, it is used by being laminated with another resin having an oxygen barrier property and being more expensive, particularly for packaging, such as an ethylene-vinyl acetate copolymer, polyvinylidene chloride and the like. ..

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for improving the oxygen barrier property of the above-mentioned polyolefin packaging material by a simpler means.

[0004]

The present invention provides a method for improving the oxygen barrier property of a polyolefin packaging material, which is characterized in that the polyolefin packaging material is irradiated with radiation, and the radiation is γ-rays. To do.

The present invention will be described in detail below. In the present invention, a film, sheet, bottle, container or the like made of polyolefin may be molded and then subjected to radiation treatment to increase and promote the oxygen barrier property.

As the radiation for irradiating radiation, γ-rays using cobalt 60 as a radiation source are preferably used.
From the viewpoint of simplicity and safety of the device, an electron beam may be used,
It can also be used with α rays, β rays, and X rays.

It is desirable that the object to be irradiated is irradiated with γ-rays at a dose of 10 KGy or more. Such irradiation is applied to at least one surface of a film, sheet, bottle, container or the like composed of a single layer of polyolefin. Irradiation of such radiation can be performed by various known methods.

Polypropylene is preferably used as the polyolefin used in the present invention, and as other examples, low density polyethylene, medium density polyethylene,
Polyethylene such as high density polyethylene, polypentene,
Examples thereof include a copolymer of ethylene and propylene, a copolymer of ethylene and butene, and a copolymer of ethylene and pentene.

The polyolefin packaging material of the present invention is preferably made of a polyolefin that does not contain a radical inhibitor at all, without using a commercially available polyolefin containing a plurality of radical inhibitors as a raw material. This means that in a polyolefin containing a plurality of radical inhibitors, radical generation due to light or heat is unlikely to occur, and the polyolefin reacts with oxygen to make it difficult to develop an oxygen barrier property, so compared to a polyolefin containing no radical inhibitor at all, This is because it is necessary to irradiate radiation with larger energy.

[0010]

[Function] Polyolefin is apt to form radicals due to various factors such as light and heat during processing or storage,
Reacts with oxygen in the air to form peroxy radicals.
Further, this peroxy radical reacts with the polyolefin to generate hydroperoxide and a radical. 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.

The radiation irradiated in the present invention intentionally generates a large amount of the radicals accompanying the oxidation reaction of the polyolefin due to the energy, and reacts the oxygen that permeates and permeates the polyolefin with the polyolefin.
It is considered that the oxygen permeability is lowered, and as a result, the oxygen barrier property of the polyolefin is improved.

[0012]

【Example】

<Example 1> A polypropylene (melt index 0.5) containing no radical inhibitor was extruded at an extrusion temperature of 260 ° C to prepare a single-layer sheet sample having a sheet thickness of 500 µm. Sheet sample 1 was prepared by irradiating one surface with γ-rays at an irradiation dose of 20 KGy. Further, in the preparation of the sheet sample 1, a sheet sample 2 was prepared in the same manner except that the γ-ray irradiation dose was 100 KGy.

Further, in the preparation of the sheet sample 1, a comparative sheet sample 1 was prepared in the same manner except that the γ-ray irradiation was not performed.

Each of the obtained sheet samples 1 and 2 and comparative sheet sample 1 was charged with 10.0 g of each and 500 cc of air in an A4 size aluminum pouch and stored at 25 ° C., and the residual oxygen concentration in the pouch was changed with time. Table 1 shows the results of measurement.

[0015]

[Table 1]

Table 2 shows the cumulative oxygen absorption amount in the pouch.
Shown in.

[0017]

[Table 2]

As is clear from Tables 1 and 2, oxygen absorption capacity was confirmed in the sheet samples 1 and 2. The comparative sheet sample 1 does not absorb oxygen at all.

Next, sheet sample 2 and comparative sheet sample 1
Was allowed to stand at 25 ° C. and the oxygen permeability was measured over time. The measurement was performed with "Ox-TRAN100" (manufactured by Modern Control Co.) at 25 ° C. The results are shown in Table 3.

[0020]

[Table 3]

As is clear from Table 3, the sheet sample 2 irradiated with γ-ray has an oxygen barrier property.

Example 2 Polypropylene containing no radical inhibitor (melt index 0.5) was extruded at an extrusion temperature of 260 ° C. to prepare a single-layer sheet sample having a sheet thickness of 500 μm, and further extruded. The sheet sample 1 was prepared by irradiating one surface of the sheet sample with an electron beam at an acceleration voltage of 200 kV and an irradiation dose of 30 KGy. Moreover, in the above-mentioned sheet sample 1, the electron beam irradiation dose is 100 KG.
Sheet sample 2 was prepared in the same manner except that y was used.

Further, in the preparation of the sheet sample 1, a comparative sheet sample 1 was prepared in the same manner except that the electron beam irradiation was not performed.

Each of the obtained sheet samples 1 and 2 and comparative sheet sample 1 was filled with 10.0 g of each and 500 cc of air in an A4 size aluminum pouch and stored at 25 ° C., and the residual oxygen concentration in the pouch was changed with time. Table 4 shows the result of measurement.

[0025]

[Table 4]

The cumulative oxygen absorption amount in the pouch is shown in Table 5.
Shown in.

[0027]

[Table 5]

As is clear from Tables 4 and 5, oxygen absorption capacity was confirmed in the sheet samples 1 and 2. The comparative sheet sample 1 does not absorb oxygen at all.

Next, sheet sample 2 and comparative sheet sample 1
Was allowed to stand at 25 ° C. and the oxygen permeability was measured over time. The measurement was performed with "Ox-TRAN100" (manufactured by Modern Control Co.) at 25 ° C. The results are shown in Table 6.

[0030]

[Table 6]

As is clear from Table 6, the sheet sample 2 irradiated with the electron beam has an oxygen barrier property.

[0032]

By the improvement of the present invention described in detail above, it becomes possible to avoid using expensive other resins to be laminated and to form films, sheets, bottles, containers, etc. made of polyolefin. Since radiation treatment is performed later, the work process is simplified and the cost is greatly reduced.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomatsu Takeshi 1-5-1 Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. (72) Inventor Naoki Masuda 1-5-1 Taito, Taito-ku, Tokyo Toppan Imprint Co., Ltd.

Claims (2)

[Claims] 1. A method for improving the oxygen barrier property of a polyolefin packaging material, which comprises irradiating the polyolefin packaging material with radiation. 2. The method for improving the oxygen barrier property of a polyolefin packaging material according to claim 1, wherein the radiation is gamma rays.