Scale cleaning method in waste paper deinking process or paper making process

摘要

PROBLEM TO BE SOLVED: To sufficiently wash out and remove scale formed in the deinking of wastepaper and in papermaking by adopting an aqueous solution of a caustic alkali including hydroxycarboxylic acid or its salt as a washing liquid. SOLUTION: The method of this invention is to wash out and remove scale including 20-50 wt.% ash composition comprising e.g. 20-50 wt.% SiO2, 10-40 wt.% CaO and 20-50 wt.% Al2O3, formed in a process for the deinking of wastepaper in producing paper pulp, in a process for papermaking, or the like, by adopting an aqueous solution (showing =10 pH value) of a caustic alkali including at least one kind of hydroxycarboxylic acids selected from the group consisting of arabonic acid, glucaric acid, mucic acid, galactonic acid, heptonic acid and their salts (e.g. including 0.1-30 g/L sodium heptonate) as a washing fluid.