Patent ID: 9315596
Filing Date: 2016-04-19
CPC Classification: C08F

Claim Text:
1. A method of preparing vinyl chloride polymer comprising: suspension-polymerizing vinyl chloride monomer in the presence of a protective colloid auxiliary, a polymerization initiator at a polymerization temperature, introducing additional vinyl chloride monomer (a) when the polymerization conversion rate reaches from 30 to 40%; and (b) when the polymerization conversion rate reaches from 60 to 70%, suspension-polymerizing the additional vinyl chloride monomer at the polymerization temperature, and adding one or more antioxidants selected from a group consisting of a phenol based antioxidant, an amine based antioxidant, a sulfur based antioxidant and a phosphate based antioxidant when the pressure of a reactor reaches 6.0 kg/cm wherein the additional vinyl chloride monomer is not introduced when the polymerization conversion rate is between 40 to 60%, wherein the amount of the additional vinyl chloride monomer added when the polymerization conversion rate reaches between 30 and 40% is from 15 to 25 weight part for 100 weight part of the total amount of the monomer; wherein the amount of the additional vinyl chloride monomer added when the polymerization conversion rates reaches between 60 to 70% is from 15 to 25 weight part for 100 weight part of the total amount of the monomer; wherein the protective colloid auxiliary is present in an amount of between 0.05 and 2.5 weight part for 100 weight part of the total amount of the monomer, and wherein the polymerization initiator is present in an amount of between 0.02 and 0.2 weight part for 100 weight part of the total amount of the monomer.