Strength of paper from mechanical or thermomechanical pulp

摘要

An additive comprising an anionic organic surface active agent is incorporated into mechanical or thermomechanical pulp at an elevated temperature and pressure. The additive causes dispersion of lignin and retards redeposition of lignin so that the bursting strength of the paper formed from the pulp is improved. The preferred additives are higher molecular weight anionic organic polyelectrolytes or polymers, particularly polymeric sulfonates. Further improvement in bursting strength is achieved by the wet end addition of a cationic organic polyelectrolyte or polymer, with or without starch. Lower molecular weight anionic organic detergents can also be used but should be rinsed from the pulp before forming paper.