Cationically stabilized aqueons silica dispersions, method for manufacture and use thereof

A method for the production of cationically-stabilised silica in the form of an aqueous dispersion or powder (I), involves (a) mixing aminosilane(s) with an acid to form an acid aminosilane solution, (b) mixing silica (as a dispersion or powder) with the solution to form (I) and optionally (c) partly or completely removing the liquid components. An independent claim is included for cationically-stabilised silica as above (I), in which the silica particles are surface-modified with aminosilane. INORGANIC CHEMISTRY - Preferred Method: Stage (b) involves subjecting the solution to shear during and/or after the addition of silica. The acid aminosilane solution is an aqueous solution and the silica comprises pyrogenic, precipitated or colloidal silica, or core-shell particles with a silica shell and a metal oxide core. The aqueous silica dispersion contains 5-50 wt.% silica; this is mixed with the acid aminosilane solution in such proportions that the amount of aminosilane in the mixture is 0.1-60 wt.% based on silica. The acid aminosilane solution shows a pH of 2-6 and the acid used has at least one acid group with a pK a value of less than 6. The stabilised dispersion is treated with an organic binder and/or other additives. Preferred Product: Stabilised silica dispersion (I) with a silica content of 5-50 wt.%, a pH of 2-6, an electrical conductivity of less than 10 mS/cm, a viscosity of less than 1.5 Pa.s and an average particle size of not more than 800 nm, in which the surface modifier (aminosilane) is present in protonated form. The particles may also be surface-modified with other silane(s) without amino groups and the dispersion may also contain an organic binder and/or other additives; (I) is obtained by the above method. Es wird ein Verfahren zur Herstellung von kationisch stabilisiertem Silica beschrieben, bei dem Silica in Form einer wässrigen Dispersion oder eines Pulvers durch Mischen mit einer sauren Aminosilan-Lösung kationisch stabilisiert wird. Durch Entfernung des Lösungsmittels kann ein kationisch stabilisiertes Silicapulver erhalten werden. Die erhaltene kationisch stabilisierte Silicadispersion ist sehr lagerstabil. Eine Mischung mit organischen Bindemitteln wie PVA ist ohne signifikanten Viskositätsanstieg möglich. Die Dispersionen eignen sich insbesondere für Streichfarben für Druckmedien, wie Tintenstrahlpapier, aber auch zur Oberflächenbehandlung von Substraten, z.B. zur Hartbeschichtung von Kunststoffen, oder in Trennmitteln oder Schl