Continuous dehydration method and method for producing polyarylene sulfide

A continuous dehydration method for a raw material mixture to be used in the production of polyarylene sulfide, which is carried out prior to the production of polyarylene sulfide, the method comprising:

• a supply step of continuously supplying a sulfur source and an organic polar solvent that constitute the raw material mixture to a continuous dehydration apparatus having one or more dehydration tanks;
• a dehydration step of continuously removing water from the raw material mixture;
• and
• an extraction step of continuously extracting the raw material mixture having a reduced water content from the continuous dehydration apparatus,
• the steps being carried out concurrently in parallel,
• wherein a temperature of the dehydration tank supplied with the sulfur source and the organic polar solvent in the continuous dehydration apparatus ranges from 110° C. to 270° C.;
• and
• a dehydration efficiency index determined according to the following Equation (1) is not less than 0.3:
• dehydration efficiency index=[Number of moles (mol) of the sulfur source in the raw material mixture having a reduced water content]/[Dehydration time (hr)×(Total internal volume (L) of the dehydration tanks)2/3] (1)
• where the dehydration time is a period of time until a moisture content per mole of the sulfur source in the raw material mixture having a reduced water content reaches not greater than 1.7 mol, including moisture consumed by the hydrolysis of the organic polar solvent.