| 摘要 |
A process of bleaching defibered hardwood pulp with a peroxide-silicate composition to attain in a single bleaching step a brightness (General Electric) of 80+. The procedure requires a plurality of controlled conditions including bleaching time, temperature, pulp consistency, pH, sodium silicate and alkalinity concentrations, and particularly a peroxide solution concentration in actual contact with the pulp of between about 0.4 and 1.2 percent based on the weight of the aqueous bleach solution itself including any water in the pulp. The bleaching takes place at a consistency such that initially at least 3 percent by weight of peroxide based on the air dry pulp weight is present. Brightnesses well in excess of 80 are attained in a single bleaching step, and pre-treatment of pulp with barium chloride is effective in the attainment of such brightnesses at relatively low temperatures with reasonable peroxide consumptions.
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