Very finely divided silica micro-dispersions - obtd. by hydrolysis of tetra:alkoxy:silane(s) in dil. aq. ammonia soln. with distn. of ammonia and alcohol

摘要

Dispersions of microfine silica are claimed (I), with mean particle size (3-45 nm and solids content 0.5-25%. Also claimed is a process for the prodn. of (I) by hydrolysis of tetra-alkoxysilanes (II), opt. mixed with organo-alkoxysilanes (III) and possibly also in condensed form, in dil. aq. ammonia soln., with simultaneous and/or subsequent distn. of ammonia and the alcohol produced. Pref. (I) have mean particle size 4-15 (esp. 5-9) nm. Hydrolytic polycondensation is pref. carried out at 10-90 deg.C using silanes as above with OMe and/or OEt and/or OPr and/or O(iso-Pr) gps. and with up to 15 (pref. up to 10, esp. up to 5) wt.% of (II) replaced by (III). USE/ADVANTAGE - (I) are useful as fillers for plastics and rubber dispersions, stone reinforcing agents and additives in emulsions and dispersions which are microencapsulated by the thin layer or spray drying process (claimed). The invention provides a cost effective process (w.r.t. pyrogenic silica) for the prodn. of very finely divided silica microdispersions.