Queen's University at Kingston

M Catherine Depew

Jeffrey K Wan

Jeffrey K -s Wan

A method for bleaching unbleached softwood or hardwood pulps using hydrogen peroxide without added alkali for activation is described. The aqueous hydrogen peroxide solution contains an alkaline earth metal carbonate, preferably magnesium carbonate and can be used at elevated temperatures. Bleached hardwood or softwood mechanical pulps with high brightness, low yellowness (b*) and reduced reversion properties are produced.

Method for bleaching mechanical pulp with hydrogen peroxide and an alkaline earth metal carbonate

A method for reducing brightness reversion and yellowness (b*) of bleached mechanical wood pulps. The pulp is digested in an aqueous formaldehyde solution containing carbonate, preferably in an amount up to 30% by weight of pulp. Paper made from the digested pulp can be further improved by treating with a reversion inhibitor such as a polyethylene glycol bisthiol.

Method of reducing brightness reversion and yellowness (B*) of bleached

Novel substantially odor-free polymeric thiol-containing antioxidant compounds suitable for preventing light induced brightness reversion or yellowing of pulps and papers and polymeric materials are described. The novel compounds are based on a polymeric backbone having thiolactate or thioglycolate groups grafted onto the ends thereof and are soluble in water or alcohol.

Growing community of inventors

Kingston, Canada

M Catherine Depew