Method of producing polyarylene sulfide

A method of polymerizing a dihalo aromatic compound and a sulfur source to produce polyarylene sulfide, the method comprising:

• preparing a mixture comprising an organic amide solvent, a sulfur source, a dihalo aromatic compound, and an alkali metal hydroxide in an amount that is less than an equimolar amount per 1 mol of the sulfur source, wherein a pH of a mixture is greater than 12.5 and at most 14;
• in a first-stage polymerization, initiating the polymerizing by heating the mixture to a temperature of 170° C. to 270° C. and producing a prepolymer until the pH of the mixture reaches a range of 10 to 11 and the conversion of the dihalo aromatic compound reaches 50% or greater to produce a polymerization mixture;
• in a second-stage polymerization, 1) adding from 0.01 to 0.6 mol of alkali metal hydroxide per 1 mol of the sulfur source to the polymerization mixture and continuing polymerization at a temperature of 245 to 290° C., and 2) adding a phase-separation agent at an amount of 0.01 to 20 mol per 1 kg of organic amide solvent to phase-separate the polymerization mixture into a concentrated polymer phase comprising dissolved polyarylene sulfide and a dilute polymer phase comprising organic amide solvent, wherein the polymerization reaction time of the second-stage polymerization is in the range of from 10 minutes to 72 hours;
• and recovering polyarylene sulfide from the concentrated polymer phase.