JPS6179649A - Packaging material for radiation sterilization - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a packaging material for radiation sterilization that generates little odor during radiation sterilization.

More specifically, the present invention proposes a packaging material suitable for forming food packaging bags for radiation sterilization, packaging bags for medical materials, and the like.

[Conventional technology]

Currently, radiation irradiation is used as a method of sterilizing food packaging materials and medical product packaging materials, but this radiation irradiation causes changes in the physical properties of these materials to a greater or lesser extent. For example, when polypropylene is exposed to radiation, it decomposes and its tensile strength is drastically reduced. On the other hand, when polyvinyl chloride is exposed to radiation, it undergoes a dechlorination reaction, producing chlorine gas.

Polyethylene is a resin that is said to have relatively good radiation resistance, and is usually used for sterilization of packaging materials at 2 to 5 Mra.
Irradiation at a level of about 100 yen does not cause any change in the physical properties in practical terms, but the irradiation produces a sensually intense off-odor.

Ethylene-vinyl acetate copolymer also has radiation resistance, and although its physical properties do not change in practical terms when irradiated with radiation, irradiation generates a strong sensory odor.

Therefore, when packaging materials using these ethylene or ethylene-vinyl acetate copolymers are sterilized with radiation and filled with food products, the off-flavors may transfer to the food products and deteriorate their quality. On the other hand, even when medical materials are packaged and irradiated, a strange odor is generated, which can cause discomfort to workers at hospitals and other facilities, causing problems.

In order to elucidate the causative agent of this off-odor, the present inventor previously conducted an analysis of continuous substances generated from irradiated ethylene or ethylene-vinyl acetate copolymer. As a result, it was found that polyethylene mainly contains many volatile hydrocarbon compounds as well as carboxylic acids such as acetic acid, propionic acid, and valeric acid, and aldehydes such as butanal and pentanal. In particular, we found that acetic acid was produced in large amounts and was strongly involved in the odor produced during irradiation. In the case of polyethylene, this acetic acid and the like are presumed to be produced by an oxidation reaction with oxygen in the atmosphere.

On the other hand, in the case of ethylene-vinyl acetate copolymer, it is presumed that the vinyl acetate was cleaved by the energy of radiation. As described above, although the mechanism of acetic acid generation is different between ethylene and ethylene-vinyl acetate copolymer, oxides represented by acetic acid are generated in both cases, which causes off-odor.

The present inventor has proposed a method for reducing the generation of off-flavors in polyethylene or ethylene-vinyl acetate copolymers that have been previously irradiated with radiation, by removing the acetic acid, etc. generated, rather than preventing the generation of acetic acid, etc., which is the causative agent of the off-odor. We have invented a method to prevent the occurrence of strange odors. That is, it has been discovered that off-flavors can be removed by incorporating an inorganic hydroxide such as magnesium hydroxide or hydroxide into ethylene or ethylene-vinyl acetate copolymer.

However, packaging materials that can be heat-sealed by using a film in which inorganic hydroxide is kneaded into ethylene or ethylene-vinyl acetate copolymer are bonded to a film made of thermoplastic resin such as polyester or polyamide. In this case, the inorganic hydroxide mixed into the film comes into direct contact with the food, which is not necessarily hygienic. Also, in the case of medical packaging materials, since they come into direct contact with medical materials, inorganic hydroxides may fall off the film and contaminate the medical materials, which is not preferable. Furthermore, since it contains inorganic hydroxide, it has many drawbacks such as reduced heat sealing strength.

[Problems to be Solved by the Invention] On the other hand, this inorganic hydroxide can also be applied to a film made of a thermoplastic resin such as polyester or polyamide through an adhesive layer to a film made of a thermoplastic resin such as polyester or polyamide. A molding material in which an inorganic hydroxide such as magnesium hydroxide or calcium hydroxide is kneaded into any of the patent polymers characterized by vinyl acetate copolymer, polyethylene or ethylene-vinyl acetate copolymer. The molded film is laminated, and the film in which the inorganic hydroxide is kneaded is further molded with a blend polymer mainly composed of polyethylene or vinyl acetate copolymer. This is a packaging material for radiation sterilization in which films formed by molding materials are laminated.

An object of the present invention is to improve the drawbacks of the conventional packaging materials for radiation sterilization described above, and to provide an innovative packaging material for radiation sterilization that is hygienic and free from the problems of odor and physical property deterioration caused by radiation.

2. Structure of the present invention [Means for solving the problem] The packaging material for radiation sterilization of the present invention has a film containing an inorganic hydroxide on the adhesive layer provided on one side of the base film. It is characterized by having a film containing no inorganic hydroxide on the film. Here, the role of the inorganic hydroxide is to react with acetic acid etc. generated from the film by radiation irradiation to form calcium salts and magnesium salts, thereby preventing the generation of off-flavors.

In addition, by providing a film containing no inorganic hydroxide on top of the film containing inorganic hydroxide,
It can be used as a safe and hygienic packaging material for food, medical supplies, etc.

[For production]

The present invention will be explained in more detail below using the drawings.

FIG. 1 is a sectional view showing the structure of the packaging material for radiation sterilization according to the present invention. In the figure, 1 is a base film, 2 is an adhesive layer, 3 is a film containing inorganic hydroxide, and 4 is an inorganic hydroxide. This is a film that does not contain

In the above, the 10-base film is a film formed by molding a thermoplastic resin, such as stretched polyester or stretched polyamide.

Stretched polypropylene, ethylene-vinyl acetate copolymer,
Vinylidene coated polyester.

A laminated film such as aluminum-deposited polyester may be used, and these base films may be laminated together via an adhesive.

Next, in the present invention, the polyethylene used for films 3 and 4 is low-density polyethylene.

These include medium-density polyethylene, high-density polyethylene, linear polyethylene copolymers of ethylene and α-olefin having 3 to 10 carbon atoms, and linear low-density polyethylene.

In addition, the ethylene-vinyl acetate copolymer used in films 1, 3, and 4 has a vinyl acetate content of about 0.1 to 50% in polyethylene, and is especially used as a packaging film. The vinyl acetate content is about 3% to 15%.

It is also possible to blend ethylene-vinyl acetate copolymer with polyethylene for the positive ethylene or ethylene-vinyl acetate copolymer used in films 3 and 4, and polyethylene for the ethylene-vinyl acetate copolymer. It is. Furthermore, this polyethylene or ethylene-vinyl acetate copolymer contains butadiene, ethylene-vinyl acetate copolymer,
It is also possible to blend other thermoplastics such as propylene elastomers.

Next, in the present invention, magnesium hydroxide, calcium hydroxide, etc. can be applied as the inorganic hydroxide to be kneaded into the film in step 3. For example, in a film in which hydroxide is incorporated, acetic acid generated under pressure from ethylene or ethylene-vinyl acetate copolymer produces calcium salts according to the following reaction formula, which is fixed and causes no odor. Prevented.

Ca(OH)2+2CH,C0OH,(CHICo,
)2Ca+ 2H20These inorganic hydroxides are ethylene-
0.0011g for vinyl acetate copolymer! It is effective even if the amount is added at 30-40%. However, if more than 40% of total weight is added, the film forming properties of the ethylene-vinyl acetate copolymer will deteriorate. On the other hand, if the amount of Ω added is small, it will not be possible to react sufficiently with acetic acid etc. generated from the ethylene-vinyl acetate copolymer.

Acetic acid and the like generated from ethylene-vinyl acetate copolymer etc. increase linearly as the amount of radiation increases. Therefore, as the irradiation dose increases, the amount of inorganic hydroxide required also increases. However, since the dose normally irradiated for sterilization is 2 to 5 Mrad, in the case of hydroxide irradiation, about 0.05% to 1% by weight is sufficient.

However, when it is laminated with a film made of thermoplastic resin such as polyester via an adhesive layer.

This adhesive is applied using gravure coating, roll coating, etc., and organic solvents such as ethyl acetate may be used to improve coating performance, but there is a possibility that acids and other impurities may be mixed into this organic solvent. There is sex. This impurity may also react with calcium hydroxide and reduce its activity.

Furthermore, if an ethylene-vinyl acetate copolymer film mixed with calcium hydroxide or the like is left in the atmosphere, it tends to absorb impurities in the atmosphere and reduce its activity.

For this reason, in the case of a film in which calcium hydroxide or the like is kneaded into a thermoplastic resin film such as polyester through an adhesive layer, it is necessary to increase the amount of calcium hydroxide kneaded into the film. It is sufficient that the amount of calcium hydroxide mixed in is from 0.005% to 1% by weight before laminating the mats, but when laminating through an adhesive layer, the amount of calcium hydroxide mixed in is from 0.4% to 10M. It is necessary to increase the amount of kneading to the extent of 1. In this case, if this amount is added, it may cause changes in resin physical properties such as heat sealability, and the value may increase in potassium permanganate consumption in sanitary tests of polyethylene or ethylene-vinyl acetate copolymer. In some cases, this may not be desirable from an equity perspective.

It is also possible to further add other additives to the polyethylene or ethylene-vinyl acetate copolymer kneaded with an inorganic hydroxide such as calcium hydroxide.

Therefore, in order to overcome the drawbacks of the film in which calcium hydroxide or the like is kneaded, an ethylene or ethylene-vinyl acetate copolymer film 7 or the like in which calcium hydroxide is not kneaded is further laminated on one side of this film. By laminating a film that does not contain calcium hydroxide, problems with heat sealability and hygiene can be overcome.

There are several methods of laminating a thermoplastic resin film such as polyester, a film made of polyethylene mixed with calcium hydroxide, etc., and a film made of polyethylene without kneaded, as listed below.

1. Coat a thermoplastic resin film such as polyester with a polyester polyol-based urethane adhesive using the extrusion method. A method of making a film that is coated with polyethylene or the like using an extrusion method without kneading calcium hydroxide etc. into the film. .

2. Coat a polyester polyol-based urethane adhesive as a primer on a thermoplastic resin film such as polyester, and then apply calcium hydroxide. A method of creating a laminated film by extrusion coating and co-extrusion extrusion method.

3. Co-extrusion of polyethylene with calcium hydroxide etc. and polyethylene without calcium hydroxide etc. is extruded using the inflation method to form a co-extruded film, which is combined with a thermoplastic resin film such as polyester and polyester polyol. This is a method of laminating layers using a dry lamination method using a urethane adhesive to create a laminated film.

This laminated film incorporating calcium hydroxide and the like is used as a packaging material for radiation sterilization.

There are several methods of radiation killing.

For example, there are γ-ray sterilization, electron beam sterilization, and X-ray sterilization using Co or 117('S) as a radiation source.

Gamma ray sterilization and electron beam sterilization methods are often used to sterilize food packaging materials, and two-gamma ray sterilization methods are commonly used to kill medical materials. When the box 1v film of the present invention is sterilized by radiation, the generation of off-odor due to radiation irradiation can be suppressed, and a film with good heat sealability and hygiene can be obtained.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A polyester film (thickness 12 μm) was roll-coated with a polyester polyol-based urethane adhesive, and 5% by weight of calcium hydroxide powder was added using a tandem extrusion extruder to make low-density polyethylene (Sumiyokusen L708 Sumitomo Chemical Co., Ltd.) Co., Ltd.) 20 μm, Extrusion Co., Ltd.) L, and low density polyethylene (Sumi Rikisen L708)
(manufactured by Sumitomo Chemical) 20μ is further laminated by extrusion coating.

This laminated film can be used to make small bags (20o) sealed on all four sides.
++ x 20cm) and sterilize it by irradiating with gamma rays at 25KGy. 500 g of sterile water was added to the sterilized bag in a sterile room and left for one week, after which a sensory test was conducted. In addition, the seal strength of this four-sided sealed pouch was measured.

Furthermore, a sanitary test was conducted in accordance with Ministry of Health and Welfare Notification No. 20, and potassium permanganate consumption was measured.

Comparative Example 1 A polyester film (thickness 12μ) was coated with a polyester polyol urethane adhesive for 197 m', and 5% by weight of calcium hydroxide powder was added using an extrusion extruder to produce low-density polyethylene (Sumiyokusen L7).
The bag was coated with 40μ of 08 Sumitomo Chemical Co., Ltd., and then prepared and sterilized in the same manner as in Example 1, and aseptically filled with sterile water.

This sample was subjected to a sensory test, as well as a seal strength measurement and a hygiene test.

Comparative Example 2 A polyester film (thickness 12μ) was roll-coated with a polyester polyol adhesive at 17/rn, and extrusion-coated with 40μ of low-density polyethylene (Sumiyokusen L708 Sumitomo Chemical ff) using an extrusion extruder. Sachets were similarly made, sterilized, and aseptically filled with sterile water.

This sample was subjected to a sensory test, as well as a seal strength measurement and a hygiene test.

Example 2 Co-extrusion In an inflation extruder, ethylene-vinyl acetate copolymer (EVACHI) D4020 (vinyl acetate content: 10% (manufactured by Sumitomo Chemical)) and ethylene-vinyl acetate copolymer (manufactured by Sumitomo Chemical) to which 2% by weight of magnesium hydroxide powder was added were prepared.
Evatate D4020) 30μ was extruded to form a coextruded film of 60μ.

A 49/rn' gravure coated polyether polyol urethane adhesive was applied to aluminum-deposited polyamide (thickness: 15 μm), and dry lamination was performed with the co-pressed film (60 μm) to obtain a laminated film. Using this laminated film, a pouch was made in the same manner as in Example 1, and the bag was sterilized and filled with sterile water. - This sample was subjected to sensory tests, seal strength measurements, and hygiene tests.

Comparative Example 3 Nytylene-vinyl acetate copolymer (Evacy) D4020 to which magnesium hydroxide powder was added in an amount of 2 wt. 2% by inflation extrusion 1. A film having a vinyl acetate content of 10 and Sumitomo Chemical 88 and 60 μm was formed. This film was made of aluminum-deposited polyamide (
They were dry laminated and laminated to a thickness of 15 μm. Using this laminated film, a pouch was made in the same manner as in Example 1, sterilized, and aseptically filled with sterile water.

We did a sensory test on this sample and found out! (Seal strength measurements and hygiene tests were conducted.

Comparative Example 4 Ethylene-vinyl acetate copolymer (Evacy) D4020 Vinyl acetate content 1 using an inflation extruder
0% Sumitomo Chemical! :A) A 60μ film was formed.

This film was dry laminated and laminated on polyamide (thickness 15 μm) coated with aluminum in the same manner as in Example 2. Using this laminated film, a pouch was made in the same manner as in Example 1), sterilized, and aseptically filled with sterile water.

This sample was subjected to a sensory test, as well as a seal strength measurement and a hygiene test.

Tab the measurement results of Example 1.2 and Comparative Examples 1 to 4.
Shown in le l.

Table l Measurement results 1) Amphiphilic test limit according to Ministry of Health and Welfare Notification No. 20; Potassium permanganate consumption fl 10 ppm Example 1 had good sensory tests, seal strength, and hygiene tests and had no problems, but Comparative Example 1
The decrease in seal strength exceeds the limit even in the Oshieishu test.

Comparative Example 2 had good seal strength and hygiene tests, but had a sensually unpleasant odor.

Furthermore, Example 2 was also subjected to a sensory test and seal strength.

The sanitary test was also good and there were no problems, but in Comparative Example 3, the seal strength decreased and exceeded the limit even in the sanitary test. Furthermore, Comparative Example 4 had a seal strength of 9. Hygiene test is good, but there is a strange odor.

〔Effect of the invention〕

Use the packaging material for radiation sterilization of the present invention! ≦, it is possible to form an innovative packaging bag for food, medical materials, etc. that is hygienic and free from problems of radiation-induced strange odor and deterioration of physical properties such as heat sealability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of the packaging material for radiation sterilization according to the present invention, in which 1 is a base film, 2 is an adhesive layer, 3 is a film containing inorganic hydroxide, and 4 is an inorganic hydroxide-containing film. It is an ugly film with . Patent amount A Negative Maru Fire Nippon Seal Notification 1] Street, E Gosai Meiyu Toshiro Patent Attorney Jumura S Chiten

Claims (1)

[Scope of Claims] 1) A film containing inorganic hydroxide is provided on an adhesive layer provided on one side of the base film, and a film containing no inorganic hydroxide is further provided on this film. A packaging material for radiation sterilization characterized by: (2) The base film is polyester, polyamide, polypropylene, ethylene-vinyl acetate copolymer, and the content of vinyl acetate in the polyethylene is 0.1 to 50% (hereinafter referred to as ethylene-vinyl acetate copolymer), etc. A packaging material for radiation sterilization according to claim (1), which is a film formed by molding a thermoplastic resin. (3) Claim (1) characterized in that the inorganic hydroxide is magnesium hydroxide, calcium hydroxide, etc.
Packaging materials for radiation sterilization described in . (4) The film containing inorganic hydroxide is mainly composed of polyethylene or ethylene-vinyl acetate copolymer (the content of vinyl acetate in polyethylene is 0.1% to 50%) or polyethylene or ethylene-vinyl acetate copolymer. A film made by molding a molding material in which 0.005% to 40% by weight of an inorganic hydroxide such as magnesium hydroxide or calcium hydroxide is kneaded into any of the blended polymers used as the material. A packaging material for radiation sterilization according to claim (1), characterized in that: (5) Molding a molding material in which the film containing no inorganic hydroxide is made of polyethylene, ethylene-vinyl acetate copolymer, or a blend polymer mainly composed of polyethylene or ethylene-vinyl acetate copolymer. A packaging material for radiation sterilization according to claim (1), which is a film made of. (6) The packaging material for radiation sterilization according to claim (1), wherein the adhesive layer is a polyester polyol-based urethane adhesive, a polyether polyol-based urethane adhesive, or the like.