JPH04202502A - Production of vinyl chloride-based polymer powder - Google Patents

Abstract

PURPOSE:To obtain the title powder having excellent fluidity, hardly charging with electricity, suppressing reduction in bulk density by polymerizing a vinyl chloride-based monomer in an aqueous medium and after reaching a specific polymerization ratio, adding a small amount of polymethyl methacrylate having specific particle diameter to the polymerization system. CONSTITUTION:A vinyl-based monomer containing a vinyl chloride monomer is polymerized in an aqueous medium and after polymerization ratio reaches 70%, 0.001-1.0 pt.wt. based on 100 pts.wt. of the vinyl-based monomer of a polymethyl methacrylate having 0.03-0.5mum average particle diameter is added to the polymerization system to give the objective powder.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for producing a vinyl chloride polymer powder having good fluidity.

[Conventional technology]

Vinyl chloride polymers are vinyl chloride monomers or mixtures of vinyl monomers whose main component is vinyl chloride monomers.
! ! It is produced by polymerizing in an aqueous medium containing a clouding agent, a polymerization initiator, etc., and dehydrating and drying the resulting polymer. However, this polymer powder tends to be charged with static electricity during drying or transportation, resulting in decreased fluidity and formation of blocks, which can clog the inside of the dryer or the transportation pipe. Furthermore, since the bulk specific gravity of the charged polymer powder is significantly reduced, there is a problem in that, for example, when measuring by the volumetric method, a measurement error occurs between the actual weight and the charged polymer powder. These phenomena are caused by temperature,
It occurs significantly in winter when humidity is low. Various methods have been proposed to prevent static electricity, but by adding nonionic surfactants, anionic surfactants, or cationic surfactants to vinyl chloride polymer powder, it is possible to improve water retention on the surface of the polymer powder. A common method is to have However, the above method cannot sufficiently prevent a decrease in the bulk specific gravity or fluidity of the polymer powder, and may also impair the thermal stability of the product.

[Problem to be solved by the invention]

The present invention has been made in order to solve the above-mentioned problems, and it is possible to obtain a vinyl chloride polymer powder that is of high quality, is not easily charged, and does not have a decrease in bulk specific gravity or fluidity. The object of the present invention is to provide a method for producing a combined powder.

[Means to solve the problem]

In order to achieve the above object, the method for producing a vinyl chloride polymer powder of the present invention involves polymerizing a vinyl monomer containing a vinyl chloride star mass in an aqueous medium, and achieving a polymerization rate of 70%.
After reaching 100 parts by weight of the vinyl monomer, 0.001 to 1.0 parts by weight of polymethyl methacrylate having an average particle size of 0.03 to 0.5 μm is added to the polymerization system. The vinyl monomer that is the raw material for the vinyl chloride polymer powder is vinyl chloride monomer alone, or 50% by weight or more of vinyl chloride monomer and other vinyl monomers that can be copolymerized with vinyl chloride monomer. It is a mixture with monomers. Examples of vinyl monomers copolymerizable with vinyl chloride monomers include vinyl esters such as vinyl acetate and vinyl propionate, methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate. Mention may be made of acrylic or methacrylic acid esters, olefins such as ethylene and propylene, vinyl ethers such as lauryl vinyl ether and isobutyl vinyl ether. Also, maleic anhydride,
Acrylonitrile, styrene, and vinylidene chloride can also be polymerized. These may be used singly or in combination. Specific products using polymethyl methacrylate as an additive include, for example, the MP series manufactured by Shinken Kagaku ■ and the micro gel manufactured by Nippon Paint ■, which have an average particle size of 0.0.
Use one with a length of 3 to 0.511 m. Those with an average particle size of less than 0.03 gm or more than 0.5a+n have poor dispersion in the polymerization system and have a low fluidity improving effect. It is desirable to add polymethyl methacrylate in an amount of 0.001 to 1.0 parts by weight per 100 parts by weight of the raw material vinyl monomer. If it is less than 0.001 part by weight, the fluidity of the obtained polymer powder will not be improved, and if it is added in excess of 1.0 part by weight, no further effect can be expected and it is uneconomical. Polymethyl methacrylate is added after the polymerization rate of the reaction system reaches 70%. If it is added at a polymerization rate of less than 70%, it is not preferable because it will adversely affect the formation of polymer particles. When adding polymethyl methacrylate to a polymerization system, it can be added in powder form or dispersed in water, but the preferred method is to disperse it in water and charge it into a pump1.
For dispersion, a dispersion aid used in the production of vinyl chloride polymers may be used in combination. Furthermore, during polymerization, dispersion aids and polymerization initiators that have been conventionally used in the production of vinyl chloride polymers can be used. Dispersing aids include, for example, water-soluble cellulose ethers such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose, water-soluble or oil-soluble partially saponified polyvinyl alcohols, acrylic acid polymers, gelatin, etc. Water-soluble polymers, sorbitan monolaurate, sorbitan triolate, sorbitan monostearate, glycerin tristearate and oil-soluble emulsifiers such as ethylene oxide-propylene oxide block copolymers, polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate and These include water-soluble emulsifiers such as lauric acid, calcium carbonate, calcium phosphate, and sodium dodecylbenzenesulfonate. These may be used singly or in combination. Examples of polymerization initiators include percarbonate compounds such as di-2-ethylhexyl peroxydicarbonate, diisopropyl peroxydicarbonate and jetoxyethyl peroxydicarbonate, t-butyl peroxybivalate, t-hexyl Peroxyvivalate, a-cumyl peroxyneodecanate and 2
．． 4.4-trimethylbenzene-2-peroxy-2-
Perester compounds such as neodecanate, acetylcyclohexylsulfonyl peroxide, 2.4.4
- peroxides such as trimethylbenzene-2-peroxyphenoxyacetate, 3.5.5-trimethylhexanoyl peroxide and lauroyl peroxide,
Azo compounds such as azohis-2,4-dimethylvaleronitrile and azobis(4-methoxy-2,4-dimethylvaleronitrile), as well as potassium persulfate, ammonium persulfate, hydrogen peroxide, cumene hydroperoxide, etc. One type or a combination of multiple types can be used. During polymerization, various polymerization conditions such as the method of charging the aqueous medium, vinyl monomer, dispersion aid, polymerization initiator, etc. to the polymerization vessel, charging ratio, and polymerization temperature may be set in the same manner as in the past. In the production method of the present invention, if necessary, a polymerization regulator, a chain transfer agent, a pH
Conditioner, gelling improver, antistatic agent, crosslinking agent, stabilizer,
It is also optional to add fillers, buffers, anti-scaling agents, etc. Furthermore, an antioxidant can be added to the polymerization system before the start of polymerization, during polymerization, or after the end of polymerization, for the purpose of suppressing the polymerization reaction and preventing deterioration of the produced polymer.

【Example】

The present invention will be explained in detail below. Examples 1 to 3 are examples to which the present invention is applied, and Comparative Examples 1 to 4 are examples to which the present invention is not applied. Example 1 A stainless steel polymerization vessel with an internal volume of 2000 R was charged with 98 [1 kg of deionized water, 382 g of partially saponified polyvinyl alcohol, and 143 g of water-soluble methylcellulose, and after deaerating the inside of the vessel, vinyl chloride monomer was added. 700k
6 Add di-2-ethylhexyl peroxydicarbonate 2 as a polymerization initiator while stirring inside the polymerization vessel.
At the same time as 80 g was fed by a high-pressure pump, the temperature began to rise to initiate polymerization, and once the temperature inside the polymerization vessel rose to 58°C, stirring was continued while maintaining that temperature. When the polymerization rate reached 85%, polymethyl methacrylate (manufactured by Nippon Paint ■, Microgel P-500210, 1 weight) with an average particle size of 0.05 gm was added to 100 parts by weight of the vinyl monomer mixture. The reaction is stopped when the internal pressure of the polymerization vessel reaches 5.5 kg/cm2G, and unreacted monomers are recovered, dehydrated and dried to form a vinyl chloride polymer. A combined powder was obtained. The state of scale adhesion was confirmed as follows. After collecting the unreacted monomers in the polymerization can, the polymer slurry was extracted from the can. The inside of the polymerization can was washed with water. After washing off the polymer loosely attached to the wall surface, the wall surface is dried by passing hot water through the jacket and the presence or absence of scale adhesion is confirmed.Example 2 Polymethyl methacrylate (Nippon Paint ■) with an average particle size of 0. Powder of a vinyl chloride polymer was obtained in the same manner as in Example 1, except for adding Microgel 5EP-1, manufactured by Microgel Co., Ltd. Made by Kenkagaku ■, acrylic ultrafine powder MP series MP-2
A vinyl chloride polymer powder was obtained in the same manner as in Example 1, except that 7011 was added when the polymerization rate reached 75%. Comparative Example 1 A vinyl chloride polymer powder was obtained in the same manner as in Example 1 except that polymethyl methacrylate was not added. Comparative Example 2 Polymethyl methacrylate with an average particle size of 1.5 am (manufactured by Shinken Kagaku ■, acrylic ultrafine powder UP series MP-14
A vinyl chloride polymer powder was obtained in the same manner as in Example 1 except that 001 was added. Comparative Example 3 Polymethyl methacrylate was added at a polymerization rate of 60%.
Powder of a vinyl chloride polymer was obtained in the same manner as in Example 1, except that the change was made at the time when %. Comparative Example 4 A vinyl chloride polymer powder was obtained in the same manner as in Example 1 except that 0.3 parts by weight of an amine surfactant was added instead of polymethyl methacrylate. The following tests were conducted on the vinyl chloride polymer powders obtained in Examples 1 to 3 and Comparative Examples 1 to 4 above.・Flowability test The obtained powder of each vinyl chloride polymer was heated at 0°C and 40% R.
After being left in an environment of H for a day and night, JIS K-672]
100 cc of the sample was placed in a specified funnel for measuring bulk specific gravity, and the falling time from the funnel was set at 1+1. In addition, each polymer powder was left to stand overnight in the same manner and was mixed for 5 minutes at 60 rpm using a Brabender planetary mixer to be charged, and then the falling time from the funnel was measured in the same manner as above. - Bulk specific gravity measurement test After each polymer powder was left in an environment of 0° C. and 40% RH for a day and night, the bulk specific gravity was measured according to the method specified in JIS K-6721. In addition, each polymer powder that had been left to stand day and night was charged by mixing at 60 rpm for 5 minutes using a Brabender planetary mixer, and then the bulk specific gravity was measured in the same manner as above.・Thermal stability test 100 parts by weight of vinyl chloride polymer and the following compound Zinc stearate 25 parts by weight Barium stearate 0.71ii 1 part Tribasic lead sulfate
05 parts by weight 300 parts by weight of dioctyl phthalate were added and kneaded for 5 minutes with rolls at 165°C, to form a sheet with a thickness of 1 m+n. This sheet is 195
Place it in an oven at ℃ and measure the time until it turns black.
Thermal stability was determined. Table 1 shows the test results of the fluidity test, bulk specific gravity measurement test, and thermal stability test. (Margins below) According to these test results, the vinyl chloride polymer powder obtained by the production method of the present invention has sufficient fluidity without deterioration in powder fluidity due to charging, and is environmentally friendly. It can be seen that the bulk specific gravity does not fluctuate due to changes and is stable. Basic required properties such as thermal stability are also well met. Furthermore, the effect of suppressing scale adhesion on the inner wall of the polymerization vessel during polymerization was also obtained.

【Effect of the invention】

As explained in detail above, according to the method for producing vinyl chloride polymer powder of the present invention, it is possible to produce vinyl chloride polymer powder that is difficult to be charged. The produced polymer powder has a suppressed decrease in bulk specific gravity and fluidity,
Furthermore, the quality required for a vinyl chloride polymer is ensured.

Claims (1)

[Claims] 1. Polymerize a vinyl monomer containing a vinyl chloride monomer in an aqueous medium, and after the polymerization rate reaches 70%, the average particle size is 0 with respect to 100 parts by weight of the vinyl monomer. .03～
0.5 μm polymethyl methacrylate 0.001-1
．． A method for producing a vinyl chloride polymer powder, which comprises adding 0 parts by weight to a polymerization system.