METHOD OF MAKING CHEMI-MECHANICAL PULP FROM HARDWOOD

摘要

A process for the manufacture of chemi-mechanical pulp from hardwood for wood-containing printing paper, especially wood-containing fine paper, is disclosed. The wood material in the form of chips is impregnated in one or two steps at a temperature below 80.degree.C with 15 to 40 kg NaOH and 0 to 30 kg Na2SO3 per ton pulp. Thereafter the chips are refined under pressure, so that the temperature of the chips prior to the refining does not exceed 80.degree.C for a time longer than ten seconds. The pulp is then bleached with peroxide, at which bleaching at least 15 kg NaOH per ton pulp is charged additionally, so that the total amount of NaOH charged is 30 to 80 kg per ton pulp. After the bleaching a second refining step is carried out. The process can be carried out with simple equipment and is characterized by reduced consumption of chemicals and electric energy without deteriorating the pulp quality.