Use of sodium dithionite in the cellulose pulping process

摘要

Process for the manufacture of cellulose from material having lignocellulose, by decomposition with sulphite or decomposition with sulfate in the presence of a salt of the dithionic acid, characterized in that the salt of the dithionic acid is used in an amount in the range of 0.1 to 4.0% by weight in the case of the decomposition with sulphite and in an amount in the range of 1.0 to 2.0% by weight in the case of the decomposition with sulfate, referred in each case to the amount of material having dry lignocellulose in the oven and in which the salt of the dithionic acid is added to the sulfite decomposition, once the mixture of cooking liquor and material having lignocellulose to be decomposed by heating have reached a temperature in the range of 60 to 110 ° C and the mixture thus obtained is left at a temperature in the range of 100 to 110 ° C for 30 to 90 minutes (impregnation phase) and in which the decomposition with sulfate is added and the salt of the dithionic acid in the final phase of decomposition.