Shin-etsu Chemical Co., Ltd.

Kazuhiko Kurimoto

Kinya Ogawa

Satoshi Kuwata

Hajime Kitamura

Shunichi Koyanagi

Shigenobu Tajima

Yoshihiro Shirota

Yoshitsugu Eguchi

Yoshitugu Eguchi

Kenichi Ito

Shigeru Arai

Yoshitaka Kiri

Koji Azuma

A novel process is proposed for the preparation of vinyl chloride based resins modified with a polymer latex, according to which the latex polymer is absorbed so completely and uniformly on the polyvinyl chloride resin that the effect of the modification of the resin properties is remarkably enhanced along with no adverse effects on the particle size distribution of the resin product and no effluence of the latex into the waste water discharged in the dehydration of the aqueous polymerizate slurry after completion of the polymerization. The process of the invention comprises introducing the modifier polymer latex into the polymerization mixture only when the monomer conversion is in the range from 30 to 95% and introducing an inorganic fine powder such as fume silica, bentonite and diatomaceous earth into the polymerization mixture at the same time as or before the introduction of the modifier polymer latex.

Process for the preparation of vinyl chloride-based resins

An improved method for the polymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride in an aqueous polymerization medium is proposed in which a water-insoluble polymerization initiator, being solid at room temperature as dispersed in the aqueous medium and having a particle size distribution of 50 .mu.m or finer, is added to the polymerization mixture which is maintained at a temperature where the half-life period of the initiator is 120 minutes or longer or, alternatively, over a duration equal to or shorter than one-tenth of the half-life period of the initiator at the temperature of the polymerization mixture. By this method the polymerization can be homogeneously proceeded to produce vinyl chloride polymers having a uniform particle size distribution, excellent heat stability and much less fish-eyes when fabricated into sheets.

Method for the preparation of vinyl chloride polymers

Vinyl chloride polymers or copolymers having a relatively low molecular weight or degree of polymerization are prepared by a method in which an organic compound containing a mercapto group and a hydroxy or carboxyl group in a molecule is used as the chain transfer agent. Due to their very high activity, these chain transfer agents are used in amounts that are smaller than conventionally required quantities. The quality of the polymer products is satisfactory with respect to heat stability, occurrence of fish-eyes, particle size distribution, plasticizer absorption and ease of removing residual monomer.

Method for preparing vinyl chloride polymers

A polymerization vessel equipped with a condenser is charged with vinyl chloride, a suspending agent or dispersing agent, and water. The mixture is subjected to a preparatory stirring in the absence of a catalyst. The polymerization catalyst is added thereto when bubbling caused by the preparatory stirring subsides and stable suspended oil drops form. Blockage of the condenser by polymer scale deposition is substantially reduced. The addition of an alkaline substance, an oxidizing substance or an azine dye further reduces polymer scale deposition. Preferably the operation of the condenser is initiated only after the conversion rate is higher than 5% or the average value per unit hour.

Method for suspension-polymerizing vinyl chloride

Vinyl chloride monomers or a monomeric mixture composed mainly of vinyl chloride is bulk-polymerized in a polymerization vessel. The inner walls and other surfaces of said vessel, coming into contact with the monomer or monomers, are coated with one or more specifically selected inorganic or organic compounds having a solubility greater than 0.5 g in 100 g of water at 25.degree. C and a boiling point higher than 60.degree. C. This bulk polymerization method serves to greatly reduce the deposition of polymer scale on the vessel walls and other surfaces. In addition the polymer scale deposited can be readily separated and removed by merely washing with water or gas under pressure. The present method provides high quality polymers.

Method for bulk polymerization of vinyl chloride

Unreacted monomer or monomers and any other volatile organic compounds contained in an aqueous dispersion of polymerizate are removed or separated by a method comprising circulating the aqueous polymerizate dispersion from the bottom of its container to the upper part of the container located over the surface of the dispersion via an exterior conduit. The pressure in the container is maintained at a level reduced to about the saturated vapor pressure of water at the temperature of the dispersion. This manner of separation of monomer from polymer serves to improve the working environment as well as the resulting polymer quality, and the monomer or monomers thus recoverd can be advantageously recycled.

Method for removing unreacted monomers from aqueous dispersions of

Vinyl chloride monomer is polymerized in aqueous medium under the influence of oil soluble polymerization initiators in the presence of alkali metal salts of higher fatty acid, higher alcohols and/or higher fatty acids, and hydroxides of alkali metals in certain amounts respectively, to produce vinyl chloride resin, stable for making resin/plasticizer pastes, mostly composed of particles having diameters lying between 0.1 and 2 microns. The resins are suitable for making resin/plasticizer pastes that have a low initial viscosity, little change in viscosities during storage, good thermal stability and excellent degassing property. Reduced deposition of polymer scales on the walls of the polymerization vessels was successful.

Method of preparing vinyl chloride resins

Vinyl chloride monomer, or a mixture thereof with a copolymerizable monomer or monomers, is bulkpolymerized so that the deposition of polymer scale on the inner walls of the polymerization vessel and other surfaces in contact with the monomer or monomers can be greatly reduced by coating them with phosphoric esters, polyphosphoric esters or their alkali metal salts before the polymerization is commenced. Clean-up operations following each polymerization run are much simplified.

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Ibaragi, Japan

Kazuhiko Kurimoto