METHOD FOR THE PREPARATION OF VINYL CHLORIDE RESINS BY SUSPENSION POLYMERIZATION

摘要

A suspension polymerization method for producing a polyvinyl chloride resin from monomers mainly comprising vinyl chloride monomers which are suspended in an aqueous polymerization medium comprising a suspending agent and a monomersoluble polymerization initiator consisting of an organic peroxide having a solubility in water of at least 0.2 weight percent at 20.degree.C. The method comprises coating, when empty, the inner surfaces of a polymerization reactor with an aqueous coating solution comprising, as a solute, an organic dye having at least one sulfonic acid or carboxylic acid group per molecule in the form of an alkali metal or ammonium salt and an alkali metal or ammonium salt of an organic sulfonic acid or carboxylic acid each of which has at least one pair of conjugated double bonds per molecule; drying the coating; and adding a water soluble thiocyanate to a polymerization mixture which is polymerized in the polymerization reactor. The method has the advantage of allowing the use of organic peroxide initiators with a relatively high degree of solubility in water, which produce thermally stable polyvinyl chloride resins, without polymer scale deposition on the reactor surfaces.