PREPARATION OF SECONDARY PULP FROM WASTE PAPER STOCK, REMOVAL OF COLORANT FROM PREPARED PULP AND RECYCLED AND UTILIZED PAPER PRODUCT

摘要

PURPOSE: To efficiently remove a colorant from a waste pulp for producing a recycled and utilized paper without damaging fibers by reacting a pulp prepared from a waste paper material with an oxygen-containing gas under basic condition and reacting oxygen with coloring compounds present in the pulp. CONSTITUTION: A pulp prepared from a waste paper stock brought into contact with an oxygen-containing gas at a pH about =8 or a pH about =10 and one or more alkaline compounds comprising sodium hydroxide, sodium thiosulfate, sodium sulfate, sodium carbonate, sodium hyposulfite, ammonium hydroxide, etc., and a mixture thereof are added and oxygen is brought into contact with one or more coloring compounds present in the pulp such as dyes, pigments or printing inks or a mixture thereof so as to react therewith. The colorants are then removed in a method for removing the colorants from the pulp prepared from the waste paper stock. Thereby, a decolorized pulp suitable for the production of a recycled and utilized paper product is obtained.