| 摘要 |
PCT No. PCT/EP96/01274 Sec. 371 Date Nov. 6, 1997 Sec. 102(e) Date Nov. 6, 1997 PCT Filed Mar. 22, 1996 PCT Pub. No. WO96/30411 PCT Pub. Date Oct. 3, 1996The process for activating polysaccharides consists of contacting the polysaccharide with liquid ammonia at an initial pressure which is higher than atmospheric pressure and at a temperature of at least approximately 25 DEG C., the amount of liquid ammonia being sufficient at least for wetting the surface of the polysaccharide starting material which is then expanded. The volume available for the polysaccharide/liquid ammonia system is enlarged in the manner of an explosion by lowering the pressure by at least 5 bar. The process is particularly suitable for activating cellulose, guar gum, starch and chitin. The process enables cellulose to be modified in a novel manner. The activated polysaccharides display higher reactivity and improved elimination of reagents during acylation, alkylation, silylation, xanthogenation and carbomoylation with largely homogeneous reaction processes. |
