GB753832A - Improvements in the preparation of polyvinyl chloride - Google Patents

Abstract

Polyvinyl chloride suitable for plastisols and of average particle diameter in the latex state of from 0.45 to 1 micron, is made by polymerizing vinyl chloride in an aqueous medium in the presence of polyvinyl chloride seed particles of smaller diameter than those desired, a water-soluble peroxygen catalyst, and a dispersing agent selected from di-esters of sodium sulphosuccinic acid in which the esterifying groups each contain from 5 to 12 carbon atoms and tri-esters of sodium sulphotricarballylic acid in which the esterifying groups each contain from 5 to 12 carbon atoms, which is added to the reaction mixture after polymerization of the vinyl chloride has commenced, at a rate such that the coverage of dispersing agent on the surface of the growing polymer particles is maintained between 90 and 375 per cent of that quantity which would theoretically be required to cover the surface of the polymer particles with a closely packed mono-molecular layer, and when polymerization is complete or terminated, recovering the polyvinyl chloride, e.g. by spray-drying or coagulation. Two equations are given for calculating the weight of dispersing agent theoretically required to cover the polymer surface with a closely packed monomolecular layer. Specified dispersing agents are diamyl, dihexyl and dioctyl sodium sulphosuccinates, tri-(2-ethylbutyl) sodium sulphotricarballylate and di-(2-(p-tert.-butylphenoxy) ethyl) sodium sulphosuccinate. The water-soluble catalyst may be potassium persulphate. In examples plastisols are made by dispersing the polyvinyl chloride in dioctyl phthalate.