| abstract |
A synthetic silicate of formula nSiO2, MxOy, mH2O where n is between 0.5 and 15, m is between 1 and 5 and MxOy is a metallic oxide or mixture of metallic oxides, is prepared by reacting a freshly prepared organosol of monomeric silicic acid with a metallic hydroxide so that the medium pH becomes immediately greater than 7, and subjecting the formed organic dispersion to evaporation and drying. The organosol is prepared by first forming a silica aquasol, e.g. by neutralizing completely or partially a mineral acid or lower aliphatic acid, e.g. formic, acetic, tartaric and glycollic acid, with an aqueous solution of sodium or potassium silicate. The aquasol is diluted with up to 2 volumes of a strongly polar organic liquid, e.g. acetone, isopropanol and mixtures thereof, adding a water soluble salt, e.g. NaCl preferably to saturation, and separating the organic layer. The metal hydroxide may be that of an alkaline earth metal, magnesium, aluminium, zinc, zirconium, nickel, magnanese, cobalt or lead. Aluminium, zinc and zirconium hydroxides are added in solution or suspension in an alkaline lye. The others may be used as freshly precipitated, or in dispersion in, e.g. the same organic solvent as is used for the organosol. The hydroxides of lead, nickel, manganese and cobalt may also be added in an alkaline lye. The dried product may be used as an opaquing filler in papers, resins and paints, as a reinforcing filler in rubber or as an ion-exchanger.ALSO:Synthetic silicates of formula n SiO2, MxOy, mH2O where n is between 0.5 and 15, m is between 1 and 5 and MxOy is a metallic oxide or mixture of metallic oxides, and characterized by the method of their preparation (see Division C1) are used as opacifying fillers for paper. |