Process for producing vinyl chloride resin

A process for producing a vinyl chloride polymer having an average particle diameter of 200-600 .mu.m by polymerizing a monomer having an ethylenic double bond and comprising vinyl chloride as an essential component in an aqueous medium by suspension polymerization in a polymerize vessel on the inner wall surface of which a coating of a polymer scale preventive agent has been previously formed, comprising the steps of previously applying a high-speed shearing force to a mixture comprising water, said monomer, a polymerization initiator, and (A) a dispersant comprising a partially saponified polyvinyl alcohol having an average degree of polymerization of 1,1500 to 2,500 and a degree of saponification of 70 to 99 mol % plus (B) a dispersant comprising a hydroxypropylmethylcellulose which has a methoxyl substitution degree of 15 to 35 wt. % and a hydroxypropoxyl substitution degree of 4 to 15 wt. % and the 2 wt. % aqueous solution of which has a viscosity of 5 to 4,000 cP at 20.degree. C. with the weight ratio (A)/(B) of the dispersant (A) to (B) being from 1/20 to 4/6 and the combined amount of the dispersant (A) and the dispersant (B) being 0.01 to 0.05 part by weight per 100 parts by weight of said monomer, and then subjecting the mixture to said suspension polymerization in said polymerization vessel under an agitation power of 50 to 200 kg.m/sec.ton.