GB568335A - Improvements relating to the preparation of moulding products and mouldings from cellulosic materials and artificial resins - Google Patents

Abstract

Cellulosic material such as sawdust is subjected to a purification treatment comprising a combined alkali and oxidation treatment for several hours so as to remove rosin, lignin, and colouring matters, followed by washing and acidifying, and by bleaching with an agent having reducing properties, and the purified, washed, and dried cellulosic material is incorporated in an artificial resin which is in the form of a liquid. The composition may be dried and submitted to a partial curing and then ground to form a moulding powder. Articles may be obtained by moulding under heat and pressure. The sawdust may be dried in thin layers in a strong current of hot air at a temperature not exceeding 70 DEG C. until the humidity is reduced to 7.5 per cent or less. The dried sawdust may be treated with a solution of sodium peroxide and hydrogen peroxide. Ammonia may be added to the solution. The treatment may be carried out at temperatures up to 35 DEG C. for several hours. The treated sawdust is washed and the final wash water is slightly acid. The material may be bleached by treatment with an acidified solution of sodium formaldehyde sulphoxylate or with a solution of sodium hydrosulphite which may be buffered with pyrophosphate. The purified cellulosic material may be treated with a weak solution of formaldehyde. The dried material is mixed with the synthetic resin in any desired proportion and the weight of filler may exceed that of the resin. It may be mixed with a liquid partially-condensed ureaformaldehyde resin. Instead of sawdust, the cellulosic raw material may be straw or oat-husks.