GB671721A - Improvement in organo-silicon derivatives of cellulose - Google Patents

Abstract

A chemical product consisting essentially of a triorgano silyl derivative of cellulose in which there is an average of 0.25-2.0 triorgano silyl groups per glucose unit of the cellulose molecules is obtained. The triorgano silyl groups are of the formula (R2R1Si-) where R is an aryl radical and R1 is an aryl or alkyl radical, and each of the silicon atoms is attached through an oxygen atom to a cellulose carbon atom which before the substitution would normally carry a hydroxyl group. As aryl radical there may be used a phenyl, xenyl, tolyl, xylyl, or naphthyl group. The alkyl group may be methyl, ethyl, propyl, butyl, amyl, hexyl, octyl, dodecyl, or octadecyl. A partially esterified or etherified cellulose containing 1-2.75 ester or ether groups per glucose unit of the cellulose may be used in making the silicon derivative. Cellulose nitrate, acetate, or p-toluene sulphonate, or a cellulose methyl, ethyl, propyl, butyl, benzyl, allyl, hydroxy ethyl, triphenyl carbinyl or carboxy methyl ether, may be used. The cellulose ester or ether may be etherified with a triorgano silicon halide preferably in presence of a hydrogen halide acceptor such as pyridine, ammonia, piperidine, or other amino compound. The reaction may be effected at room temperature. Films may be obtained by casting a solution of the organo silicon cellulose derivative in an aromatic hydrocarbon or an ether on to a smooth surface, evaporating the solvent, and stripping the dried film. The films may be used for insulation of electrical equipment, and for packaging. The organo silicon cellulose derivatives may also be used for making articles by moulding or extrusion. Pigments, fillers, and finely-divided dielectric solids may be incorporated. In an example, methyl cellulose containing 1.7 methoxy groups per glucose unit is suspended in pyridine. A solution of triphenyl chloro silane in pyridine is added. Reaction proceeds at once and a clear viscous solution of the methyl cellulose silane reaction product is obtained. The solution is left for 2 days and then poured into dilute hydrochloric acid solution. The viscous mass is washed with water and then dissolved in benzene. The solution is cast to form a transparent film containing 1.3 triphenyl silyl groups per glucose unit of the cellulose. In other examples, ethyl cellulose containing 2.4 ethoxy radicals per glucose unit is reacted with diphenylethyl chloro silane, and cellulose acetate containing 2 acetyl groups per glucose unit is reacted with triphenyl chlorosilane.