Patent ID: 8157954

Claim:
A method to recover a base paper for gypsum board from a waste material of gypsum board comprising a gypsum core and the base paper for gypsum board adhering thereto, comprising the steps of: breaking the waste material of gypsum board, separating a gypsum component and a paper piece of the base paper for gypsum board from the broken waste material of gypsum board thereby forming a separated paper piece, and washing the separated paper piece with water in a rotary drum-type washing device so as to eliminate a gypsum component adhering to the separated paper piece from the separated paper piece, and further comprising a step of previously adding the separated paper piece into a portion of washing water before the separated paper piece is introduced to the rotary drum-type washing device, and after water washing, dewatering the separated paper piece wherein the step of dewatering the paper piece comprises squeezing and dewatering of the separated paper piece by one of a roller, a centrifugal machine, and a squeezing machine, wherein the rotary drum-type washing device comprises a separated paper piece inlet at one end of rotatably lying air and water through-flow drum and a separated paper piece outlet at the other end thereof and is capable of supplying washing water to a separated paper piece in the air and water through-flow drum.