METHOD FOR PRODUCING GRANULAR POLYARYLENE SULFIDE, METHOD FOR INCREASING AVERAGE PARTICLE DIAMETER OF GRANULAR POLYARYLENE SULFIDE, METHOD FOR ENHANCING PARTICLE STRENGTH OF GRANULAR POLYARYLENE SULFIDE, AND GRANULAR POLYARYLENE SULFIDE

摘要

Provided are: a method for producing a granular polyarylene sulfide (PAS) that has increased average particle diameter and enhanced particle strength; a method for increasing the average particle diameter of a granular PAS; a method for enhancing the particle strength of a granular PAS; and a granular PAS. A method for producing a granular PAS according to the present invention comprises: a step 1 that is a preparation step for preparing a mixture that contains an organic amide solvent, a sulfur source, water, a dihaloaromatic compound and an alkali metal hydroxide; a step 2 that is a first-stage polymerization step wherein a polymerization reaction is started by heating the mixture, so that a prepolymer having a conversion rate of the dihaloaromatic compound of 50% or more is produced in the presence of less than the equimolar amount of an alkali metal hydroxide per one mole of the sulfur source; a step 3 that is a second-stage polymerization step wherein the polymerization reaction is continued in the presence of an equimolar amount or more of an alkali metal hydroxide per one mole of the sulfur source, thereby obtaining a reaction product mixture; and a step 4 that is a cooling step for cooling the reaction product mixture after the second-stage polymerization step. In this connection, the step 4 is carried out in the presence of at least one assistant such as a carboxylate salt.