Chemical paste prepn for papermaking - by caustic soda impregnation, mechanical treatment and heating in contact with oxygen and caustic soda

摘要

Chemical pastes for papermaking are prepd. from wood chips or similar ligno-cellulosic matls. by impregnation with an alkaline soln., mechanical treatment, then heat treatment in an oxygen based atmosphere in the presence of aq. alkaline soln., the essential alkali used in the first step being NaOH, and the mechanical treatment being such as to break down the fibres by partial rupture of the lignin based intermediate layers which join them together, in such a manner as to retain the organised structure of the wood chips. The mechanical treatment is effected by press. of rolls of relatively small dia. rotating in opposite directions to each other at equal tangential velocities such that the compression between the rools is exerted in a direction perpendicular to the direction of the fibres. The delignification treatment penetrates to the cores of the wood chips, improving the properties of the paste. Prodn. of polluting waste prods. is avoided.