Towards Overcoming the Brightness Ceiling of Mechanical Pulps Prepared from Blue-Stained Lodgepole Pine Chips

摘要

A method to overcome the brightness ceiling of hydrosulfite (Y)-bleached TMP made from 25% blue-stained chips involves the addition of 0.2% of sodium borohydride to Y bleaching of the pulp. A high bleaching end pH (～10.0) in peroxide bleaching removes most to all of the blue stain in TMP made from the blue-stained chips. Under optimal peroxide bleaching conditions, TMP or CTMP made from 50 or 100% blue-stained chips was bleached to the same brightness as TMP or CTMP from the green chips.