Suspension polymerization of vinyl chloride with heating of reactor surfaces

In a process of suspension polymerization of vinyl chloride monomer or a monomer mixture mainly composed of vinyl chloride in an aqueous polymerization medium by introducing water, a suspending agent, a polymerization initiator and the monomer or monomer mixture into a polymerization reactor with accessory equipment to form a polymerization mixture and heating the polymerization mixture under agitation up to a polymerization temperature to start and conduct the polymerization reaction, an improvement which comprises:

• (a) heating at least a part of the surfaces of the polymerization reactor and the accessory equipment to the reactor coming into contact with the gaseous phase above the polymerization mixture in the polymerization reactor to an elevated temperature of 55.degree. C. or higher before the temperature of the polymerization mixture reaches 45.degree. C.;
• and
• (b) keeping at least a part of the surfaces of the polymerization reactor and the accessory equipment to the reactor coming into contact with the gaseous phase above the polymerization mixture in the polymerization reactor at an elevated temperature of 55.degree. C. or higher until a moment when conversion of the monomer or monomer mixture into polymer is at least 10% by weight;
• wherein the elevated temperature in steps (a) and (b) is higher by at least 2.degree. C. than the temperature of the polymerization mixture in the polymerization reactor.