Abstract: Silylated silica is prepared by silylating silica with an organosiloxane composed of A units of the formula (I) (R13SiO1/2)??(I) and B units of the formulae (IIa-c) (R12SiO2/2), and/or??(IIa) (R1SiO3/2), and/or??(IIb) (SiO4/2)??(IIc), optionally having 1 or 2 attached groups —X on Si atoms, where X is OR, R being hydrogen or a monovalent alkyl radical having 1-4 carbon atoms, halogen, or acetoxy, R1 is a saturated or unsaturated, monovalent, optionally halogenated C1-18 hydrocarbon radical the groups ?SiX or ?SiX2 optionally present in a number C, wherein A, B, and C satisfy the relationships: 1?B?100 or 750<B<10 000, B?A+C, and, when A+C=0, 10?B?100 or 750<B<10 000. The silylated silica has a particularly homogenous coating of silylating agent.

Abstract: Organosilicon compounds containing SiC-bonded biuret groups are prepared by (I) adding a silane containing 1 or 2 silicon atoms per molecule and an SiC-bonded organic radical having at least one basic ##STR1## group and at least one SiOC-bonded aliphatic radical per molecule to a monoisocyanate or a diisocycanate at a temperature up to 125.degree. C. and (II) maintaining the temperature at 110.degree. C. to 125.degree. C. for at least two minutes. In an alternate procedure the silane and mono- or diisocyanate may be heated to a temperature in the range of from 110.degree. C. up to 200.degree. C. for at least two minutes, after or while adding additional monoisocyanate or diisocyanate.The resultant silicon compounds are used in the preparation of polyurethanes and as additives to lacquers.