JPS6034972B2 - Method for preventing plasticizer elution from soft vinyl chloride resin molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing plasticizer elution from soft vinyl chloride resin molded articles.

European vinyl chloride resin molded articles have the disadvantage that, while they are used for a long period of time, plasticizers and other additives gradually migrate to the surface of the molded article and ooze out.

As a way to solve this drawback, attempts have been made to treat the surface of the molded product with low-temperature plasma treatment. According to this method, a crosslinked layer is formed on the surface of the molded product, and this crosslinked layer has the effect of preventing plasticizer elution (migration). Be expected. However, this low-temperature plasma treatment cannot achieve the desired treatment effect with good reproducibility even if conditions such as gas pressure, gas flow rate, and applied power are kept constant. This was also observed when continuous low-temperature plasma treatment was performed, and the treatment effect was unreliable.

As a result of intensive research into this technical problem, the present inventors found that the effect of preventing plasticizer elution by low-temperature plasma treatment of soft vinyl chloride resin molded products depends on the temperature of the molded product to be treated and the input side for low-temperature plasma generation. The present invention was achieved by discovering that this is subtly influenced by the relationship with the electrode temperature. That is, in the present invention, a soft vinyl chloride resin molded article is placed in an internal electrode discharge type low-temperature plasma generator, and the temperature of the molded article (T,.

0) and the input side electrode temperature (LOO) are T,
=0~800 -・o≦T2≦・oo-allow. The present invention relates to a method for preventing plasticizer elution from soft vinyl chloride resin molded products, which is characterized by treating with low-temperature plasma of an inorganic gas of 10 torr or less while maintaining the temperature of the molded product. The advantage is that a crosslinked layer can be reliably formed, the effect of preventing plasticizer elution by this crosslinked layer is extremely remarkable, and this can be achieved with good reproducibility.

The method of the present invention will be explained in detail below. First, the soft vinyl chloride resin molded product to which the method of the present invention is carried out is a film or sheet-like product, a tube, This applies to both tubular bodies such as hoses and other irregularly shaped bodies, and there are no restrictions on the shape or type of molded articles.

Examples of copolymers mainly composed of vinyl chloride include vinyl chloride-vinyl acetate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, vinyl chloride-ethylene vinyl acetate copolymer, and vinyl chloride-vinyl acetate copolymer. Examples include acrylonitrile copolymer, vinyl-styrene chloride copolymer, vinyl-styrene chloride-ptadiene copolymer, vinyl chloride-vinylidene chloride copolymer, and graft copolymers mainly composed of polyvinyl chloride.

These vinyl chloride resins are not limited to one type, but may be used as a blend of two or more types, and other synthetic resins may be blended for the purpose of improving the mechanical strength etc. of the molded product. Examples of synthetic resins include ethylene-vinyl acetate copolymer, acrylonitrile-butadiene copolymer, styrene-acrylonitrile copolymer, methyl methacrylate-styrene-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, and ethylene-vinyl acetate copolymer. Examples include propylene elastomer, ethylene-propylene-lene elastomer, polyamide resin, caprolactam polymer, epoxy-modified polybutadiene, epoxy-modified polyol, and organopolysiloxane. Plasticizers are used to obtain soft vinyl chloride resin molded products, and these plasticizers include phthalate esters such as diethyl phthalate, di-2-ethylhexyl phthalate, and dinonyl phthalate;
Trimellitic acid esters such as trimethyl trimellitate and trioctyl trimellitate, aliphatic dibasic acid esters such as dioctyl adipate, disodecyl adipate, and dioctyl azelate, butyl oleate, methyl acetyl ricinoleate, chlorinated fatty acid methyl, etc. Examples of plasticizers include fatty acid esters, ethyl phthalyl ethylene glycolate, diethylene glycol dibenzoate, and tributyl acetyl citrate.

In addition, various additives are used as necessary, such as stabilizers, lubricants, fillers, pigments, dyes, ultraviolet absorbers, antioxidants, crosslinking agents, vulcanization accelerators, and various surfactants (cationic, anionic, nonionic). , amphoteric) may be appropriately blended.

The soft vinyl chloride resin molded article may be obtained by any conventional molding method for vinyl chloride resins, such as extrusion molding, injection molding, calendar molding, inflation molding, or compression molding. The molded product thus obtained is subjected to low-temperature plasma treatment, and in the method of the present invention, an internal electrode discharge type low-temperature plasma generator is used as the plasma generator, and the plasma treatment conditions are set such that the temperature of the molded product to be treated is T. , ℃, and the input side electrode temperature is T2℃.
In this case, T, = 0 to 80 pure'・female 2≦loo-total. is required to satisfy.

If this condition is not satisfied, it will be difficult to stably achieve the effect of preventing plasticizer melting with good reproducibility. An internal electrode discharge type low temperature plasma generator is a type in which an electrode is placed inside the generator in contact with an inorganic gas, and the low pressure inorganic gas introduced inside is turned into plasma near the electrode.
This acts on the surface of the molded article placed in the generator and achieves the desired treatment, namely the formation of a dense crosslinked layer on the surface of the molded article.

The input side electrode can be selected from various shapes such as a flat plate type, a net type, a coil type, and a comb type, but in the present invention, a temperature control means is provided to satisfy the above-mentioned temperature conditions. For this purpose, it is desirable to use an electrode that allows a heating medium to flow inside the electrode.

In addition, since the electrode is directly exposed to low-temperature plasma gas,
It is desirable to use a chemically stable material or to coat it with glass, enamel, or the like. To control the temperature of a processed molded product, for example, a temperature-controllable metal flat plate electrode is used as the ground side electrode, and the processed molded product is placed on top of this electrode, and the temperature of the processed molded product is controlled by the electrode temperature control. A method such as controlling the temperature of the product may be used.

Further, when a tube-shaped molded body is subjected to continuous low-temperature plasma treatment, it is convenient to flow a heat medium at a predetermined temperature into the tube. Generation of low-temperature plasma can be achieved by introducing an inorganic gas into the device, and applying a ratio of 13.58 to the electrodes, for example, 10 to 10.
A power of 700W may be applied.

Although the low-temperature plasma treatment time for a molded article varies depending on the applied voltage, generally a few seconds to several tens of minutes is sufficient. As the discharge frequency band for generating low-temperature plasma, in addition to the above-mentioned high frequency, low frequency, microwave, direct current, etc. can be used. Helium is an inorganic gas,
Examples include neon, argon, nitrogen, zincated nitrogen, nitrogen dioxide, oxygen, air, carbon monoxide, carbon dioxide, hydrogen, chlorine, as well as hydrogen chloride, sulfur dioxide gas, and hydrogen sulfide.
These gases may be used alone or in combination.

The gas pressure of these gases in the plasma generator is required to be such that the desired low-temperature plasma can be easily generated, that is, 10 Torr or less (preferably 0.01 Torr to 1 Torr). By subjecting the molded product to low-temperature plasma treatment in this way, the desired high-density crosslinked layer is generated on the surface of the molded product in an extremely short time, and this causes additives such as plasticizers to ooze out onto the surface of the molded product. A remarkable molded article is obtained in which the formation of a surface crosslinked layer (barrier layer) is completely suppressed, and the formed surface crosslinked layer (barrier layer) is highly flexible. - Next, examples of the present invention will be given.

Example 1 16,000 parts by weight of a blend consisting of 10 parts by weight of vinyl chloride resin (TK-1300, trade name manufactured by Shin-Etsu Chemical Co., Ltd.), parts by weight of DOP5, 1.5 parts by weight of calcium stearate, and 1.5 parts by weight of zinc stearate. The mixture was kneaded with a roll for 10 minutes, and then press-molded at 16500 to form a sheet with a thickness of 0.5.

One piece of this sheet (sample sheet) was placed on the flat metal ground electrode in an internal electrode discharge type low-temperature plasma generator, and the pressure was increased to 1.0 while carbon monoxide gas was passed through the device.
The temperature of both the input side electrode and the ground side electrode in the device was controlled by circulating a heating medium inside them, so that the sample sheet was kept at the same temperature as the ground side electrode. .

Low-temperature plasma was generated by applying a high frequency of 13.58 MHZ and 500 W to the input side electrode, and the sample sheet was subjected to low-temperature plasma treatment for 1 minute. The amount of plasticizer (DOP) extracted during n-hexane extraction was investigated using the test method shown below for each of the treated sheets in which the temperatures of the input side electrode and sample sheet were controlled to various values in the above process. The results shown in Table 1 were obtained. n
- Hexane extraction amount measurement method: Set a sheet at the bottom of a cylindrical extraction container of 100 [
of n-hexane and shaken for 2 hours in a 370 water bath, and the amount of plasticizer (DOP) extracted into the n-hexane was quantitatively analyzed by gas chromatography.

Table 1 Amount of plasticizer extracted (indication 26) Example 2 A sample sheet prepared in the same manner as in the previous example was prepared.

For each of the 1 women, the input side electrode temperature: 4
Controlled sample temperature at 0q0: Controlled at 40oo CO gas pressure: 0.5 Torr High frequency: 13.58M ratio, 300W Treatment time: Low temperature plasma treatment was performed in the same manner as in the previous example except that it was 2 minutes to reduce the amount of plasticizer extracted. It was measured.

For each of the other female sample sheets 1, the low-temperature plasma treatment was performed in the same manner as above, except that the temperature of the input electrode and the sample was not controlled at all, and the amount of plasticizer extracted was measured.

The results of each submission are shown in Table 2.
From these results, it is possible to achieve sufficient processing effects with good reproducibility by controlling the temperature of the input side electrode and sample, but if temperature control is not performed, the processing effects will vary widely and reproducibility will be poor. It turns out to be extremely bad.

Table 2 (Deer 1st Fleet Cicada)

Claims (1)

[Claims] 1. A soft vinyl chloride resin molded product is placed in an internal electrode discharge type low temperature plasma generator, and the temperature of the molded product (T_1°C
) and input side electrode temperature (T_2℃), respectively.
1=0~80 3/8T_1-10≦T_2≦100-5/8Plasticizer for soft vinyl chloride resin molded products, characterized by being treated with low-temperature plasma of inorganic gas of 10 torr or less while maintaining 10≦T_2≦100-5/8T_1 How to prevent elution.