JP2630958B2 - Γ-ray resistant vinyl chloride resin material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a gamma-ray-resistant vinyl chloride resin material, and in particular, a modified vinyl chloride resin material which does not easily discolor to gamma ray irradiation and has good transparency. It is about.

"Prior Art and Problems" Conventionally, sterilization with ethylene oxide gas or sterilization with γ-ray irradiation has been performed as a sterilization method for medical devices and the like. However, in the case of sterilization with ethylene oxide gas, there are disadvantages such as a problem of residual gas and poor workability. In the case of γ-ray sterilization, there is a disadvantage that the vinyl chloride resin product is discolored.

For this reason, polyethylene, polypropylene, etc., which are less discolored by γ-ray irradiation, may be used as a medical material, but still have the problem that the flexibility and transparency unlike vinyl chloride resin cannot be obtained. Thus, there is a need for a vinyl chloride-based resin material that is less discolored by γ-ray irradiation.

As a method for improving the γ-ray resistance of a vinyl chloride resin material, a method of adding various stabilizers (Japanese Patent Publication No. 57-3653, Sho 62
-10535), a polymer reaction product of a vinyl chloride resin and a dithiocarbamate (JP-A-50-63092), (Japanese Patent Application Laid-Open Nos. 55-34282 and 55-34283) have been disclosed, but addition of a stabilizer cannot be expected to sufficiently improve γ-ray resistance, and there are also problems such as elution. , With the above-mentioned polymer reaction products and vinyl chloride Has a problem that industrial production is difficult.
Also, compounds containing a benzene ring, such as styrene, are known to have good γ-ray resistance, but styrene and vinyl chloride do not copolymerize, and vinyl chloride resin and polystyrene have poor compatibility, and even when blended, Poor transparency and mechanical strength.

"Means for solving the problem" In view of such circumstances, the present inventors have repeated studies to improve the above-mentioned disadvantages, and as a result, a vinyl aromatic monomer, a methacrylate monomer, and a polymer An acrylic acid ester monomer having a glass transition temperature of 30 ° C. or lower, and a vinyl chloride resin obtained by previously impregnating a vinyl chloride resin with these and a crosslinkable monomer and then copolymerizing the same, and a plasticizer and a stabilizer. The present inventors have found that a material consisting of has excellent γ-ray resistance and transparency and completed the present invention.

Examples of the vinyl aromatic monomer used in the present invention include styrene (hereinafter, abbreviated as St), α-methylstyrene, chlorostyrene, and the like. Because St is good.

Examples of the methacrylate include methyl methacrylate (hereinafter abbreviated as MMA), ethyl methacrylate and the like, and MMA having good compatibility with the vinyl chloride resin is preferable.

As the acrylate having a glass transition temperature of the polymer of 30 ° C. or less, 2-ethylhexyl acrylate (EH
A), butyl acrylate (BA), methyl acrylate, and the like can be mentioned, but EHA and BA, which have a particularly low glass transition temperature and are often used industrially, are good.

Examples of the vinyl chloride resin used in the present invention include, in addition to vinyl chloride homopolymer, a vinyl chloride resin obtained by copolymerizing ethylene, propylene, and other olefins, and a vinyl chloride resin obtained by copolymerizing vinyl acetate, vinyl ether, and vinyl ester. Vinyl resins are also included.

In the present invention, the amount of the vinyl aromatic monomer used is preferably 20 to 70% by weight of the monomer mixture. If it is less than 20% by weight, the γ-ray resistance will not be improved, and if it exceeds 70% by weight, the transparency will be poor. In particular, γ-ray resistance is good at 25% by weight or more, and transparency is good at 50% by weight or less.

The amount of the methacrylate monomer used is preferably 5 to 30% by weight of the monomer mixture. If it is less than 5% by weight, the transparency is not improved, and if it exceeds 30% by weight, the grafting efficiency is deteriorated. In particular, the transparency is good at 10% by weight or more, and the graft efficiency is good at 20% by weight or less.

The amount of the acrylate monomer having a glass transition temperature of the polymer of 30 ° C. or lower is preferably 20 to 70% by weight of the monomer mixture. If it is less than 20%, the gamma ray resistance is not sufficiently improved, and
If the content is more than 10% by weight, the transparency deteriorates. In particular, γ-ray resistance is good at 40% by weight or more, and transparency is good at 60% by weight or less.

The amount of the monomer mixture is preferably 5 to 20 parts by weight based on 100 parts by weight of the vinyl chloride resin. If the amount is less than 5 parts by weight, the γ-ray resistance is not improved, and if it exceeds 20 parts by weight, the transparency deteriorates. In particular, γ-ray resistance is good at 10 parts by weight or more, and transparency is good at 15 parts by weight or less.

In the present invention, when a crosslinkable monomer is used in addition to the monomer mixture, the transparency of the obtained material is further improved.

Examples of the crosslinking monomer used in the present invention include polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, butylene glycol dimethacrylate, divinylbenzene, diallyl phthalate, diallyl maleate, bisphenol A-modified diacrylate, and bisphenol A-modified dimethacrylate. And so on,
From the viewpoint of heat stability and flexibility, bisphenol A-modified diacrylate (hereinafter abbreviated as BPADA), polyethylene glycol diacrylate, and butylene glycol dimethacrylate are preferred. The amount of the crosslinkable monomer is, vinyl chloride resin 10
0.01 to 5 parts by weight per 0 parts by weight is preferred. If the amount is less than 0.01 part by weight, the effect of crosslinking is not obtained. If the amount is more than 5 parts by weight, the processability is poor and the appearance of the molded article is poor. In particular, when the content is 0.02 parts by weight or more, the copolymer obtained from the monomer mixture and the vinyl chloride resin have good compatibility, and when the content is 2 parts by weight or less, the processability is good.

In order to obtain the modified vinyl chloride resin of the present invention, it is necessary to uniformly impregnate the vinyl chloride resin with the monomer mixture, the crosslinkable monomer, and the polymerization initiator beforehand and then copolymerize the slurry. It is desirable to impregnate the vinyl chloride resin or the dried vinyl chloride resin with a monomer mixture, a crosslinkable monomer, and a polymerization initiator for 15 minutes or more, and industrially, for 15 minutes to 1 hour, and then copolymerize.

Examples of the polymerization initiator include peroxide initiators such as benzoyl peroxide, lauroyl peroxide, acetyl peroxide, diisopropyl peroxydicarbonate, and dioctyl peroxydicarbonate, and 2,2'-
Asobisisobutyronitrile, 2,2'-azobis-2,4-
Examples include an azo initiator such as dimethylvaleronitrile and a redox initiator.

When copolymerizing the monomer mixture or the crosslinkable monomer with the above monomer mixture, after polymerizing at 40 to 70 ° C. for 3 to 15 hours, 75 to 11
It is preferable to polymerize the residual monomer by heat treatment at 0 ° C. for 1 to 5 hours. Therefore, it is desirable to use a combination of a low-temperature active initiator and a high-temperature active initiator. Further, a chain transfer agent, a stabilizer, an ultraviolet absorber, an antioxidant and the like may be added together with the monomer mixture.

The modified vinyl chloride resin obtained as described above is converted into a gamma-resistant vinyl chloride resin material by adding a plasticizer and a stabilizer.

"Examples" Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Examples 1-8, Comparative Examples 1-4 Vinyl chloride resin 20 of polymer 1300 obtained by suspension polymerization method
In 00 g, the monomer mixture and bisphenol A shown in Table 1 were added.
After impregnated with 2 g of modified diacrylate, 0.2 parts by weight of dioctyl peroxydicarbonate as a polymerization initiator based on all monomers, and 0.2 parts by weight of lauryl peroxide based on all monomers were added for 30 minutes. 10 with stirrer
Polymerization was performed at 60 ° C. for 5 hours together with 5000 g of ion-exchanged water in an autoclave, followed by heat treatment at 80 ° C. for 3 hours to polymerize the remaining monomers.

55 parts by weight of dioctyl phthalate (hereinafter abbreviated as DOP), 100 parts by weight of the obtained modified vinyl chloride resin, epoxidized soybean oil (O-130-P, manufactured by Adeka Argus Chemical Co., Ltd.)
A composition containing 5 parts by weight, 0.2 parts by weight of zinc stearate, 0.2 parts by weight of calcium stearate, and 0.1 parts by weight of stearic acid was rolled at 150 ° C., and 2 cm thick and 10 cm × 10 cm.
Is manufactured by press molding, and irradiated with 2.5 Mrad of γ-ray, a color difference meter (Σ80 Color M) manufactured by Nippon Denshoku Industries Co., Ltd.
The degree of discoloration was examined by the change in b value before and after γ-ray irradiation using an easuring system). In addition, the transparency before γ-ray irradiation was also evaluated.

Comparative Example 5 A composition was obtained in the same manner using the vinyl chloride resin used in Examples 1 to 8 and Comparative Examples 1 to 4, a sample sheet was prepared, and the colorability and transparency were evaluated.

Example 9 The same operation as in Example 8 was performed except that 2 g of bisphenol A-modified diacrylate was not used, and evaluation was performed.

Examples 10 to 17 The same operation was performed as in Examples 1 to 8, except that EHA was used in place of BA. In this case, similar results were obtained.

As is clear from Table 1, it is found that the use of the modified vinyl chloride resin according to the present invention provides a material having good γ-ray resistance and good transparency.

[Actions and Effects] The reason why the present invention improves the γ-ray resistance is not clear, but it is because the benzene ring in the stellene stabilizes the radicals generated by γ-ray irradiation, and the acrylic acid such as EHA, BA, MMA, etc. It is considered that the ester and methacrylic acid ester increase the flexibility of the molded body, improve oxygen permeability, and stabilize oxygen by reacting with radicals. Further, it is considered that by further adding a crosslinkable monomer, the compatibility between the copolymer and the vinyl chloride resin is increased, and the transparency is further improved.

As described above, the material using the modified vinyl chloride resin according to the present invention is characterized by being stable to γ-ray irradiation and having good transparency.

Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location C08F 220: 10)

Claims (4)

(57) [Claims] (1) 100 to 100 parts by weight of a vinyl chloride resin, 20 to 70% by weight of a vinyl aromatic monomer and 5 of a methacrylic acid ester monomer
Modified vinyl chloride copolymerized by impregnating with 5 to 20 parts by weight of a monomer mixture consisting of 20 to 70% by weight of an acrylate monomer having a glass transition temperature of 30 ° C. or lower for the polymer A material for gamma irradiation sterilization consisting of resin, plasticizer and stabilizer. 2. The material for γ-ray irradiation sterilization according to claim 1, wherein styrene is used as the vinyl aromatic monomer. 3. The γ-ray irradiation sterilizing material according to claim 1, wherein methyl methacrylate is used as the methacrylic acid ester monomer. 4. The material for gamma irradiation sterilization according to any one of claims 1 to 3, wherein 2-ethylhexyl acrylate and / or butyl acrylate are used as the acrylate.