Patent ID: 8268124
Filing Date: 2012-09-18
Classification: D21C

Abstract:
1. A pulp production process, comprising: a hydrophilicizing step of hydrophilicizing wood chips by immersing the wood chips into a dilute caustic soda aqueous solution at room temperature for 10 to 60 hours thereby obtaining hydrophilicized wood chips; a first washing step of removing alkali component from the hydrophilicized wood chips by adding water or warm water thereby obtaining first washed wood chips; an oxidizing step of selectively partially oxidizing lignin contained in the first washed wood chips by adding dilute nitric acid to the first washed wood chips at room temperature or while heating a mixture of the first washed wood chips and the dilute nitric acid; a second washing step of removing nitric acid from the wood chips obtained in said oxidizing step by adding water or warm water thereby obtaining second washed wood chips; a digesting step of digesting the second washed wood chips by adding another dilute caustic soda aqueous solution and heating a mixture of the second washed wood chips and the another dilute caustic soda aqueous solution thereby obtaining digested product; and a digested pulp/black liquor separating step of filtering the digested product and separating digested pulp and lignin-containing black liquor from the digested product thereby producing pulp.