GB566766A - Improvements relating to the treatment of wood - Google Patents

Abstract

566,766. Treating wood. RUSSISHVILI, R. March 15, 1943, Nos. 4200 and 13622. [Class 145 (ii)] [Also in Group VIII] Wood is treated to remove most of the hemicelluloses by treatment with a heated solution of sodium hydroxide or carbonate, or both, or with a solution of sulphuric acid, is impregnated with a resinoid substance, and is subjected to 'pressure. A small part of the cellulose and the greater part of the lignin may be modified. The wood may be treated under pressure at 100‹ C. for 2 to 4 hours with an aqueous solution of sodium hydroxide and sodium sulphite or of sodium carbonate and sodium sulphite, or of sodium hydroxide, carbonate, and sulphite. The wood is then washed and dried, or first treated with hypochlorite solution containing 2 to 9 grains of active chlorine per litre and then washed and dried. Part of the modified lignin may be removed by a further treatment with a weak alkaline solution containing an oxidizing agent such as sodium peroxide or perborate. The wood may be first treated in the sodium hydroxide or carbonate solution, then in a slightly acid solution containing free chlorine, optionally in an alkaline hypochlorite solution and then in a weak alkaline solution which may contain oxidizing agents. Alternatively, the wood may be treated with aqueous sulphuric acid at from 7 to 25‹ C., then in the sodium hydroxide or carbonate solution, and then washed and dried. The acid treatment may, alternatively, be carried out in an aqueous sulphuric and nitric acid bath at 75-100‹ C. for 1 to 2.5 hours, and after washing the wood is treated with alkaline solutions containing sodium hydroxide or carbonate, or both, and optionally peroxides. Treatment with hypochlorite solutions may follow. The treated wood layers may be made into plywood by bonding with synthetic resins or other adhesives and before bonding, are impregnated with resins or adhesive emulsions. The plywood may comprise one or more layers of treated wood and one or more layers of untreated wood. Plywood itself may be treated according to the invention. Logs may first be treated with the alkaline solutions and cut into veneers before the further treatment. Treated wood panels may be pressed into desired shapes.