| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of manufacturing a vinyl chloride-based polymer excellent in moldability, more specifically a method of manufacturing a vinyl chloride polymer having low stickiness to a calender roll surface when molding a film or a sheet by calender molding, and excellent in fish eye, transparency and initial coloration of a molded body.SOLUTION: When a vinyl chloride-based monomer mainly containing a vinyl chloride monomer is suspension polymerized in an aqueous medium in a presence of a dispersant and an oil-soluble polymerization initiator, both the oil-soluble polymerization initiator (I) having the 10 hours half-life temperature of 30 to 40°C and the oil-soluble polymerization initiator (II) having the 10 hours half-life temperature of 41 to 60°C are used at a composition ratio of 1:10 to 1:1, and a first step polymerization is conducted at the polymerization temperature of 35 to 44°C till a polymerization conversion ratio of 5 to 20 mass%, then the temperature is increased, and a second step polymerization is conducted at the polymerization temperature of 55 to 80°C. The temperature increasing time is 1% to 20% of total polymerization time. |
