PLATELET SILICA, ITS PRODUCTION AND USES

1348002 Platelet silica gel W R GRACE & CO 6 July 1971 [6 July 1970] 31589/71 Heading C1A Microporous platelet silica gel particles are prepared by freezing an ammonium stabilized silicic acid solution and separating from the aqueous medium the so formed particles. The freezing and separation steps may be carried out (a) by freeze drying the ammonium stabilized silicic acid solution or (b) by freezing the solution and then thawing it before separating the silica particles formed, e.g. by filtration or centrifuging. In the case of (b) the pH of the solution should preferably be adjusted to about 8 to 9À5 with carbon dioxide or an acid just before the freezing step. The particles are about 0À1 to 5 microns thick and 1 to 100 microns long the ratio of length to thickness being generally between 5 : 1 to 50 : 1. The ammonium stabilized silicic acid solution may be formed by passing a solution of a soluble silicate through an ionexchange resin in the ammonium form.