POLYVINYL CHLORIDE EXCELLING IN HEAT STABILITY AND ITS PRODUCTION

PROBLEM TO BE SOLVED: To obtain a polyvinyl chloride that has a specific molecular weight, and has very few number of branches in its polymer structure, and excellent heat stability by polymerizing vinyl chloride monomers by the use of a specific polymerization initiator. SOLUTION: This polyvinyl chloride, which has a number-average molecular weight of 5000 or more, preferably 1000 or more, and has the number of 0.3 branch, preferably 0.1 branch or less, in 1000 vinyl monomer units of the polyvinyl chloride, is obtained by polymerizing vinyl chloride monomers by the use of a polymerization initiator composed of organic aluminum compounds, such as n-butyl lithium, s-butyl lithium and t-butyl lithium, and organic aluminum compounds, such as methyl aluminoxane, at a mol ratio of (99:1) to (1:99), preferably (50:50) to (1:99), at 0 deg.C or higher polymerization temperature.