Shin-Etsu Chemical Co., Ltd.

Toshihiko Nakano

Tadashi Amano

Mikio Watanabe

Toshihide Shimizu

Susumu Ueno

Hajime Kitamura

Masahiro Usuki

Yoshitaka Okuno

There is provided a process of producing a vinyl chloride polymer wherein vinyl chloride monomer or a monomeric mixture containing vinyl chloride monomer is suspension polymerized in the presence of an oil-soluble polymerization initiator and a suspending agent in an aqueous medium in a polymerization vessel, said process comprising providing, as the oil-soluble polymerization initiator, a mixture of (A) t-butyl peroxyneoheptanoate with (B) a perester peroxide other than said t-butyl peroxyneoheptanoate, said perester peroxide being such that a 10-hour half-life period temperature of a benzene solution of said peroxide dissolved in an amount of 0.1 mole per 1 liter of benzene is 44 to 55.degree. C.; and completing the polymerization at a temperature higher than a preset temperature for the polymerization by from 10 to 20.degree. C. when or after the internal pressure of the polymerization vessel begin to drop at the terminal stage of the polymerization reaction. According to this process, it is possible to obtain a vinyl chloride polymer good in quality, particularly with low initial discoloration when processed into formed products, at a good yield in a short period of polymerization time.

Polymerization of vinyl chloride with t-butyl peroxyneoheptanoate and

The production process includes starting suspension polymerization of vinyl chloride-based monomer in a polymerization vessel in the presence of a particular combination of suspending agents; and, at the time when a polymerization conversion has reached 5 to 60%, further adding to the reaction mixture a partially saponified polyvinyl alcohol having an average polymerization degree of 1,500 to 4,000 and a saponification degree of 75 to 98 mole %, wherein a carboxylic acid ester of polyhydric alcohol is further added to at least one one selected from a content inside the polymerization vessel prior to the start of the polymerization, a content inside the polymerization vessel during the polymerization, and the resulting polymer. According to the process, there is obtained a vinyl chloride polymer having a large bulk specific gravity and a fast gelation rate, and from the polymer, a formed part small in both the number of fish eyes and the amount of residual monomer can be obtained.

Vinyl chloride polymerization with carboxylic acid ester of polyol and

A polymer scale preventive agent for use in polymerization of a monomer having an ethylenically unsaturated double bond, comprising an alkaline solution containing (A) a condensation product of (A-1) a hydroxynaphthalene compound and (A-2) an aldehyde compound, and (B) an inorganic colloid. This agent is used for forming a coating on the inner wall, etc. of a polymerization vessel. Such a vessel is effective in preventing polymer scale deposition, not only in the liquid-phase region but also in the vicinity of the interface between the gas and liquid phases in the vessel, and useful in producing a polymer that shows very few fish eyes and good whiteness when formed into sheets or the like.

Polymerization of ethylenic monomer with scale preventive agent

This process is a process of producing a vinyl chloride polymer by suspension polymerization of vinyl chloride or a mixture of vinyl monomers mainly made up of vinyl chloride in an aqueous medium in the presence of an oil-soluble polymerization initiator, wherein, as said oil-soluble polymerization initiator, (A) an organic peroxide such that a 10-hour half-life period temperature of a solution containing 0.1 mol of the organic peroxide per liter of benzene is 30.degree. to 50.degree. C. and the organic peroxide does not, in its structure, contain a benzene ring or an alkoxy group, and (B) 3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate are used in combination. The polymerization vessel used is preferably coated with a polymer scale preventive agent. According to the invention, in case where the amount of the polymerization initiator used is increased while using an existing polymerization apparatus, the deposition of polymer scale in the polymerization vessel is suppressed, the insufficient cooling capacity of the existing polymerization apparatus can be made up, and the polymerization time can be shortened to improve the productivity.

Process of producing vinyl chloride polymer using an organic peroxide in

A process for the production of a vinyl chloride polymer by suspension polymerization of vinyl chloride, optionally in the presence of other vinyl monomers, in an aqueous medium, in the presence of an oil-soluble polymerization initiator, which is a combination of (A) t-butyl peroxyneoheptanoate, and (B) a peresteric peroxide, such as t-butyl peroxyneodecanoate, other than the above component (A), in a polymerization vessel having at its inner wall surface, a polymer scale deposition preventative coating, which is formed by applying an alkaline coating liquid, of (a) at least one condensation product of a quinone compound and a condensate of a quinone compound with an amino group containing diphenyl compound, and (b) at least one of the substances, a water-soluble polymer compound, an inorganic colloid or an alkali metal silicate, followed by drying the above coating. According to this process, a vinyl chloride polymer can be produced having excellent properties, such as initial coloration, in a short polymerization time, while suppressing deposition of polymer scale in the polymerization vessel.

Process of producing vinyl chloride polymer

Polymer scale preventive agent containing a condensation product of a

A polymer scale preventive agent for use in polymerization of a monomer having an ethylenically unsaturated double bond, comprising an alkaline solution containing: (A) a condensation product of (A-1) a condensate of acetone with a hydroxybenzene compound having at least two hydroxyl groups, and (A-2) an aldehyde compound; (B) an inorganic colloid; and (C) a water-soluble polymeric compound. This agent is used for forming a coating on the inner wall, etc. of a polymerization vessel. Such a vessel is effective in preventing polymer scale deposition, not only on the areas in the liquid-phase region but also on the areas around the interface between the gas and liquid phases in the vessel, and useful in producing a polymer that shows very few fish eyes and good whiteness when formed into sheets or the like.

Process for polymerization with suppressed polymer scale formation

The method of the present invention lies in a method for forming a scale preventive coating for preventing polymer scale deposition generated on inner walls of a polymerization vessel during polymerization, wherein a coating liquid containing a scale preventive agent is sprayed from an upper portion in the closed polymerization vessel, suction of gas in the vessel is simultaneously performed from a bottom portion of the polymerization vessel, an excessive coating liquid is discharged, and a coating of the scale preventive agent is formed on inner walls of the polymerization vessel. According to this method, a coating of a scale preventive agent can be uniformly formed throughout the entire inner walls of a polymerization vessel even in the case of a closed and large polymerization vessel having a volume, for example, not less than 80 m.sup.3. Especially, it is extremely suitable for large scale industrial production because a coating can be effectively formed even on portions such as a valve at the bottom of the polymerization vessel. Further, operations (heating, spraying, suction) for coating formation can be allowed to proceed simultaneously, and discharge of an excessive coating liquid is simultaneously performed. Thus it also becomes possible to greatly reduce the time required for the coating formation operations.

Method for forming a scale preventive coating film on inner wall

A polymer scale preventive agent for use in polymerization of vinyl chloride monomer or a monomer mixture containing vinyl chloride monomer as a major component, comprising:

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Kamisu-machi, Japan

Toshihiko Nakano