Sulfite process for making pulp having a tactile softness from hardwood chips

摘要

Pulps having a tactile sense of softness which are made from hardwoods and processes for making such pulps. The process comprises the steps of: providing hardwood chips having specified sizes; introducing the chips into a digester; removing substantially all the free oxygen from the chips within the digester; providing a cooking liquor comprising from about 0.4% to about 3% ammonia and from about 9% to about 14% sulphur dioxide; completely submerging in cooking liquor all the chips within the digester; sulfonating the lignin within the chips at a temperature of less than about 110 DEG C.; rapidly increasing the temperature to an appropriate hydrolysis temperature; hydrolyzing the lignin sulfonation products at a temperature of from about 140 DEG to about 155 DEG C. at a pH from about 2 to about 3; and rapidly reducing the temperature of the system following the hydrolysis. Pulps made by this process were made into useful tissue paper webs having enhanced softness properties.