GB567774A - Improvements in or relating to processes of treating cellulosic raw material, and the improved cellulosic fibres resulting therefrom - Google Patents

Abstract

Cellulosic raw materials are impregnated with a wetting agent and then subjected to the action of chlorous acid, a chlorite, or chlorine dioxide. The treatment effects a bleaching of the materials and facilitates the subsequent removal of lignins, pentosans and other non-cellulosic constituents by alkali or other chemicals. The chlorite treatment itself effects at least a partial separation of the fibres and it may be continued until there is obtained a sufficiently purified white pulp not requiring further chemical treatment. Preferably, the material is impregnated with an acid or acid-reacting substance prior to treatment with a solution of a chlorite. The cellulosic material may be wood, flax, or other lignin-containing cellulosic raw material, or it may be raw cotton, cotton linters, or raw cotton waste. Wetting agents which may be used in the preliminary treatment are octyl phenols or their salts, complex condensation products of long chain aliphatic alcohols with phenols, water-soluble sulphonates of a condensation product of naphthalene and polymerized isobutylene, and tertiary alkylaryloxy alkylols. They may be added to the acidifying liquid. In an example, raw flax fibre is immersed in a dilute solution of acetic acid containing a wetting agent. The fibre is removed and excess liquid pressed out. The fibre is then immersed in a hot solution of sodium, calcium, or other metallic chlorite. It is removed from the liquid, washed, and then boiled in a solution of caustic soda. The fibre may then be bleached with hypochlorite solution. It may be employed in paper-making or may be used for spinning and weaving, or for conversion into cellulose derivatives and products such as plastics, films, filaments and the like. If desired, alternate treatments with chlorite and caustic soda solution may be performed on the raw material. If removal of lignin is not essential, the treatment with caustic soda or other reagent, subsequently to the chlorite treatment, may be omitted, since the fibre after the treatment with chlorite is in a bleached state suitable for paper-making or spinning. When chlorine dioxide is used, the cellulosic material may be wetted and then treated with a gaseous mixture of chlorine dioxide and hydrochloric acid or acetic acid vapour. Wood chips may be cooked under pressure in water containing a wetting agent and then after washing may be cooked in an open vessel containing sodium chlorite acidified with acetic acid. The chlorite treatment may be repeated. The pulp obtained may be cooked with a solution of caustic soda and finally bleached with hypochlorite.