The wet coagulation of PVA is usually carried out by any of the following procedures: (1) the method comprising extruding an aqueous PVA solution into an aqueous solution of a dehydrating salt such as sodium sulfate, (2) the method comprising extruding an aqueous PVA solution into an aqueous alkali solution such as caustic soda, (3) the method comprising extruding an aqueous PVA solution containin