Hoechst Celanese Corporation

Leonard L Diaddario, Jr

Mark A Schroeder

A process is disclosed for maximizing the brightness of wood pulps which have been treated with anionic bleaching agents wherein the brightness is enhanced by the use of selected quaternary ammonium compounds.

Quaternary compounds as brightness enhancers

An aqueous sulfuric acid anolyte solution is circulated through the anode compartment of an electrolytic cell, and an aqueous NaHSO.sub.3 catholyte solution is circulated through its cathode compartment, while maintaining an anolyte and catholyte temperature range of 20.degree.-25.degree. C., a catholyte pH range of 4.6 to 5.8, and a reduction potential of -1.25 to -1.50 V versus Ag.degree./AgCl, to produce an aqueous solution of Na.sub.2 S.sub.2 O.sub.4. Optimum pH is maintained by small additions of an alkali to the catholyte solution for electrolysis and solution stability.

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Portsmouth, VA, United States of America

Leonard L Diaddario, Jr