METHOD OF NEUTRALIZING ACIDITY OF PAPER Russian patent published in 2004 - IPC

FIELD: paper-and-pulp industry.

SUBSTANCE: invention concerns treatment of paper used, for example, for books, documents, and other cellulose-based paper produce, as well as for restoring paper produce, in particular restoring and treating used paper. Acidity of paper is neutralized by treating it with solvent in subcritical state containing 7-33% alcoholic solution of active substance, in particular alkali-earth metal alkoxide or alkoxicarbonate, solvent further including chladone and carbon dioxide at weight ratio (11-27):1, whereas weight ratio of alcoholic solution to solvent is 1:(12-20). Treatment is carried out first holding paper in sealed container containing solvent with above-indicated alcoholic solution at pressure 3.5-4.5 MPa and temperature 10-20^оС for at least 5 min, after which carbon dioxide is introduced into container at a rate of 0.6-2.6 MPa/min to achieve pressure 5.2-7.0 MPa and then pressure slowly (0.05-0.1 MPa/min) drops during at least 1 h to atmospheric value. According to invention, paper, prior to be treated with alcoholic solution of active substance, is purged with pure carbon dioxide at 10-20^оС and pressure 5.0-6.0 MPa for at least 1 h.

EFFECT: achieved high alkali reserve level without presence of powder on paper surface.

5 cl, 1 dwg, 1 tbl