Paper pulp mfr. by digestion with caustic soda and peroxide - avoiding pollution and giving results comparable with Kraft process

摘要

In the prodn. of paper pulp by delignification of lignocellulose material by first digesting with NaOH, then pulping and digesting again, and second digestion stage is carried out in the presence of an alkaline peroxide soln. contg. a stabiliser for the peroxide. Pref. H2O2 or an alkali-peroxide is used in an amt. of 0.5-10% in stage 2, whilst stage 1 is carried out with 0.1-10% NaOH w.r.t. the wt. of dry pulp. Alternatively, stage 2 is carried out with 0.1-1% peroxide and NaOH soln. contg. an aromatic nitrate, N-heterocyclic cpd. of the phenazine type or a cyclic ketone of the anthraquinone type is used in stage 1. The process avoids environmental pollution, esp. of the type associated with the Kraft process, and is efficient and simple. It can be carried out with relatively simple, existing plant and gives pulp with improved mechanical properties and good bleachability in better yields than the classical processes.