Abstract: A method of addition of polymerization initiator in the process of suspension polymerization or emulsion polymerization polymerizing a polymerizable monomer in aqueous medium, comprising introducing a low-temperature-active polymerization initiator taking part in the polymerization reaction to a piping system filled beforehand with water and successively adding said initiator in the piping system to polymerization system within 20 minutes using water.

Abstract: A process for the gas phase polymerization of vinyl chloride, which comprises homopolymerizing monomeric vinyl chloride or copolymerizing monomeric vinyl chloride with a monomer copolymerizable therewith in the gas phase at a polymerization temperature of 55.degree. C. to 65.degree. C. under such conditions that the ratio Pr of the polymerization pressure to the saturated vapor pressure at the polymerization temperature is in the range of 1>Pr>0.5, wherein a mixture comprising diisopropylperoxy dicarbonate and di-2-ethoxyethylperoxy dicarbonate at a weight ratio of from 3/2 to 85/15 is used as the initiator.

Abstract: A process for the gas phase homopolymerization of vinyl chloride or the gas phase copolymerization of vinyl chloride with a monomer copolymerizable therewith, wherein when the breeding ratio first exceeds 3.5 after initiation of the polymerization, the feed rate of a seed polymer is adjusted so that the breeding ratio is maintained at a level of from 3.5 to 5.5.

Abstract: The present invention relates to a process for manufacturing a petroleum resin wherein a fraction (component A) containing an aromatic hydrocarbon obtained by cracking of petroleum and a thermally polymerized oil (component B) obtained by previously thermal-polymerizing the component A are mixed and then the mixture of the components A and B is subjected to polymerization by employing a Friedel-Crafts catalyst. It is also directed to propose a petroleum resin of a superior quality having a softening point optionally in a range of 30.degree.-120.degree. C. and various bromine value in such a manner that a mixing ratio of the components A and B is properly adjusted.

Abstract: Disclosed is a process for polymerizing vinyl chloride, alone or in combination with a comonomer, in the vapor phase maintained at a pressure lower than the vapor pressure of the monomer at the polymerization temperature employed, and in the presence of the specified seed vinyl chloride polymer particles. The seed polymer particles used are prepared by polymerizing vinyl chloride, along or in combination with a comonomer, under bulk conditions, in the presence of 0.001% to 2% by weight, based on the weight of the monomer, of a cellulose ether soluble in the monomer.

Abstract: A process for preparing a polyvinylchloride composition by polymerizing vinyl chloride or vinyl chloride and a comonomer comprises polymerizing vinyl chloride or a mixture of vinyl chloride and a comonomer in the gaseous phase under a polymerization pressure which is less than the saturated vapor pressure of vinyl chloride at the polymerization temperature, in the presence of additives required for later formation of a molded product.

Abstract: A method of removing vinyl chloride monomer which remains in a polymer of vinyl chloride, which comprises irradiating the polymer of vinyl chloride with a high energy electromagnetic wave to excite the vinyl chloride monomer in said polymer to remove unreacted monomer.