METHOD OF PREPARING SECONDARY FIBER IN PRODUCTION OF CELLULOSE-CONTAINING FIBROUS MATERIAL Russian patent published in 2007 - IPC D21C5/02 

FIELD: paper-and-pulp industry.

SUBSTANCE: invention is directed to preparing secondary fiber (waste paper) and can particularly be used in manufacture of paper and cardboard. Waste paper is subjected to pulping in presence of alkali and dispersant, namely phosphorus-containing acid sodium salt, while simultaneously adding polyamideamine-epichlorhydrin rubber in amount 0.8-1.5% of the weight of dry fiber. Phosphorus-containing acid sodium salt is, more particularly, sodium polyphosphate or sodium phosphate used in amount 0.1-0.2% of the weight of dry fiber. Preparation of secondary fiber is effected at pH 6.5-7.5.

EFFECT: increased destruction force in wet space and improved whiteness of material.

4 cl, 1 tbl, 5 ex