Shin-etsu Chemical Co., Ltd.

Yoshitaka Okuno

Tadashi Amano

Takashi Kobayashi

Hideshi Kurihara

Yasuhiro Takahashi

Toshio Shinohara

Genji Noguki

Junichi Watanabe

Toshihiko Nakano

Yoshihiko Hirai

Hitoshi Nakajima

Fumiaki Adachi

Norinobu Wada

Masatsugu Takano

Tohru Nishikawa

Yoshihrio Shirota

Tadaaki Kurokawa

The present invention provides a method of producing vinyl chloride polymers, including the steps of subjecting vinyl chloride monomer or a mixture of monomers containing vinyl chloride monomer to suspension polymerization reaction in an aqueous medium within a polymerization vessel equipped with a reflux condenser, and subsequently, after the completion of the polymerization reaction, recovering any unreacted monomer, wherein foam generated on the surface of the liquid phase inside the polymerization vessel is eliminated by discharging a high pressure water having a pressure of 20 kg/cm.sup.2 or more substantially linearly to the surface of the liquid phase. The high pressure water discharging is carried out at the polymerization step, particularly from the time when operation of the reflux condenser begins, and/or at the recovery step. A vinyl chloride polymer is thus obtained without the splashing of foam over the gaseous phase section of the polymerization vessel, regardless of whether the heat removal rate of the reflux condenser, or the recovery rate per unit time for the unreacted monomer are increased.

Method of removing foam during polymerization of vinyl chloride polymers

Novel 1,1,2,2-tetramethylpropylperoxy esters are provided. They are useful as a polymerization initiator in polymerizing vinyl chloride, vinylidene chloride and vinyl acetate monomers, with the advantage of completing polymerization within a short time.

1,1,2,2-tetramethylpropylperoxy esters and method for preparing vinyl

A polymerization apparatus comprising a cylindrical polymerization vessel having a straight cylindrical section, a cooling means for cooling the contents of the polymerization vessel, and paddle impellers, each fixed to a central shaft positioned along the center line of the vessel and spaced apart at predetermined positions, each impeller having impeller blades for agitating the contents inside the polymerization vessel as the shaft is rotated, wherein the polymerization vessel has an inner capacity of 100 m.sup.3 or more and has a ratio L/D (the length L of the cylindrical section to the inner diameter D of the vessel) of at least 1.5, wherein three or more of the paddle impellers are arranged on and along said shaft in the center of the vessel, and wherein polymerization/inhibitor charge openings are arranged at positions on the interior surface of the wall of the polymerization vessel in such a manner that one charge opening is provided per paddle impeller at a position on the vessel wall which corresponds to the position of a paddle impeller along the shaft.

Polymerization apparatus and a method for producing polymer using the

A vinyl chloride polymer is prepared through suspension polymerization of a vinyl chloride monomer in the presence of a polymerization initiator in a reactor. The reactor is charged with up to 4/5 of the overall monomer charge to initiate polymerization. Polymerization is carried out under a certain saturated vapor pressure of P1 kgf/cm.sup.2 at a preset polymerization temperature. When the internal pressure of the reactor declines to P2 kgf/cm.sup.2, the remainder of the overall monomer charge is continuously fed to the reactor so as to maintain the internal pressure within the range of (P1-.DELTA.P) wherein .DELTA.P=P1-P2 ranges from 0.1 to 2.0 kgf/cm.sup.2. A vinyl chloride polymer having a high degree of polymerization is efficiently produced while alleviating the load of heat removal.

Process for preparing vinyl chloride polymer under specified vapor

This process uses such a polymerization apparatus that the inner volume of the polymerization vessel is 100 m.sup.3 or more, the ratio L/D of the length L of the straight barrel to the inner diameter D is 1.5 or more, and the uppermost stirring impeller is arranged in the range of 150 to 300 cm downwardly from the upper end position of the straight barrel of the polymerization vessel in terms of the height of the center line of the vertical width of the blade, and is characterized in that after the liquid contents of the polymerization vessel are heated to a temperature near the polymerization temperature, noncondensable gases coming into the reflux condenser are evacuated under such conditions that the flow rate of the evacuation is 10 to 100 Nm.sup.3 /hour and the evacuation time is a period equal to 20% or more of the total polymerization time, and simultaneously with or after the start of the evacuation of the noncondensable gases, the cooling by the reflux condenser is started. According to the present invention, even if a long-term operation is carried out by using a large-sized polymerization vessel, since the quantity of heat dissipation by the reflux condenser can be kept stable, and scale can be prevented from being deposited on the polymerization vessel inner wall and the like.

Process of producing vinyl chloride type polymer

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

The time taken for a run of suspension polymerization of vinyl chloride monomer can be remarkably decreased without affecting the quality of the resin product when the temperature of the polymerization mixture under polymerization is increased continuously or step-wise during the period in which the conversion of the monomer to polymer is 10% or larger in such a manner that the average degree of polymerization of the polymer taken at an intermediate stage by sampling is always in the range from 90% to 110% of that of the finally obtained polyvinyl chloride resin product.

Method for suspension polymerization of vinyl chloride monomer

Unreacted residual monomer is removed from an aqueous slurry of a vinyl chloride polymerizate by a method, according to which the monomer-containing aqueous slurry continuously fed to a plate column from its top runs down by way of a cyclone-type mist separator and through a plurality of perforated plates, coming into counter-current contact with steam which is blown into the column from its bottom and ascends through the same perforated plates, to dissipate the monomer in the form of vapors, and the steam carrying the dissipated monomer vapors having entered the mist separator is subjected to mist separation and heat exchange with the slurry fed, and the resulting steam is discharged out of the column, followed by condensation to recover the monomer. The slurry having reached the bottom of the column is transferred to a flush tank where it is quenched to generate steam which is then blown into the column for recycling.

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Kamisu-machi, Japan

Yoshitaka Okuno