Treatment of waste paper to remove colour - by aging at normal press. and moderate temp. prior to bleaching and washing for reuse

摘要

Treatment of waste paper for re-use in paper manufacture with special reference to the removal of colouring matter and pigments comprises (a) stirring the waste paper with a warm solution of chemicals suitable for decolorising to form a low concentration fibre slurry (pulp). (b) transferring the pulp subsequently thickened by solvent withdrawal to an ageing tower in which it is retained hot under low pressure, and (c) subsequently washing out the colouring materials and pigments which have passed into solution from the aged pulp withdrawn from the tower. Process enables a recovered pulp to be obtained of improved degree of whiteness at increased yield. The effluent treatment required is less to that a reduction in plant coat is possible. The paper produced from the recovered pulp has a higher tear strength than that produced by the known technique.