Dispersion stabilizer for suspension polymerization and method for producing vinyl resin

摘要

The present invention provides an easy-to-handle dispersion stabilizer for suspension polymerization that meets the following requirements: even if the amount of the dispersion stabilizer for suspension polymerization used for suspension polymerization of a vinyl compound is small, the resulting vinyl resin has high plasticizer absorptivity and is easy to work with; it is easy to remove residual monomer components from the resulting vinyl resin; and the resulting vinyl resin contains fewer coarse particles. The present invention relates to a dispersion stabilizer for suspension polymerization in the form of an aqueous liquid. This dispersion stabilizer contains, at a concentration of 20 mass % or more and 50 mass % or less, a PVA having a degree of saponification of 35 mol % or more and 65 mol % or less, a viscosity average degree of polymerization of 100 or more and 480 or less, a terminal aliphatic hydrocarbon group having 6 to 12 carbon atoms, and a block character of residual ester groups of 0.5 or more. In this dispersion stabilizer, the viscosity average degree of polymerization (P) of the PVA and the degree of modification (S) of the aliphatic hydrocarbon group satisfies 50≦S×P/1.880≦100.

主权项

1. A dispersion stabilizer for suspension polymerization in the form of an aqueous liquid, comprising:
a vinyl alcohol polymer (A) having a degree of saponification of 35 to less than 60 mol %, a viscosity average degree of polymerization (P) of 100 to 480, a terminal aliphatic hydrocarbon group having 6 to 12 carbon atoms, and a block character of residual ester groups of 0.5 to 2; and water, wherein the block character is determined by 13C-NMR spectroscopy, the viscosity average degree of polymerization (P) is calculated using the following Nakajima's equation,
[η]acetone, 30° C.=7.94×10−4·P0.62 the dispersion stabilizer is in the form of an aqueous liquid, the vinyl alcohol polymer (A) is present at a concentration of 20 to 50 mass % in said aqueous liquid, and wherein the relationship between the viscosity average degree of polymerization (P) of the vinyl alcohol polymer (A) and a degree of modification (S) of the aliphatic hydrocarbon group satisfies the following formula (1):
50≦S×P/1.880≦100  (1).