GB570259A - Improvements in the pulping of fibrous cellulosic material - Google Patents

Abstract

Hemp, jute, seed flax straw and other bast fibre materials are subjected to the action of an acid aqueous solution of an inorganic chlorite, e.g. an acidified solution of sodium or calcium chlorite, in order to obtain a pulp suitable for the production of paper, e.g. bank-note paper, condenser tissue, carbon paper, electrical-insulating paper, or sand-paper. Bast fibre materials containing large amounts of shive or pith may be treated. The chlorite may be used in a concentration of 8-10 per cent based on the dry weight of the stock, and the pH value may be adjusted to 1.5-4.5 by the addition of acetic, hydrochloric, or other acid. The treatment may be carried out at elevated temperature. Prior to the treatment with chlorite, the cellulose material may be treated with caustic soda, sodium carbonate, chlorine, hypochlorite, or a mixture of caustic soda and sodium sulphide. In an example, hemp fibre is immersed in a warm solution of 20 per cent nitric acid for an hour. The liquid is decanted and the fibre is allowed to rest for several hours. It is then washed and boiled for an hour in dilute sodium carbonate solution. The material is washed and then treated for several hours with a hot acid solution of calcium chlorite. The treated material is washed and milled to form a pulp of good quality free from shives. In other examples, the hemp or flax straw is pretreated with water, sodium carbonate solution, caustic soda solution, a mixture of caustic soda and sodium sulphide, chlorine, or hypochlorite. The treatment with chlorite may be effected at boiling temperature. The acidity may be adjusted at intervals during the treatment by the addition of acid.