Sphaerische Partikel auf der Basis von Metalloxiden, Verfahren zu deren Herstellung und deren Verwendung
Spherical particles of 5nm-10 mu m contain stannic oxide (SnO2) and optionally at least one further oxide of a main group 1-5 element and/or a transition metal (optionally containing organic groups). The surface of the particles is modified by organic groups, and the SnO2 content of the particles is 0.1-99.9 (preferably 10-90) wt.%. Also claimed are preparation methods of the particles, as follows: (1) forming one or more shells of metal oxide (or metal oxide mixtures) on spherical metal oxide particles, by partial or complete hydrolytic condensation of one or more compounds of M' (and/or their pre-condensates), optionally in presence of catalyst and/or solvent, by the action of water or moisture: (2) hydrolytic condensation of a mixture of tin compounds and at least one compound of M' (or a pre-condensate) as in (1); or (3) emulsifying an aqueous phase containing at least tin in the form of a precipitatable dissolved oxide (hydrate) or sol in an organic phase, using an emulsifier, pre cipitating SnO2 hydrate or other oxide (hydrate) in the water droplets (before, during or after emulsification) using a solution of ammonium, phosphonium or other onium compound or long-chain organic acid salt (already in the OH or H form or formed in situ) and removing the water by distillation. M' = silicon, boron, aluminium, phosphorus, tin, lead, transition metals, lanthanides and actinides USE - (I) are used as X-ray opaque fillers (claimed), particularly for dentistry. (I) are also useful in the preparation of bulk materials, coatings, films, fibres or optical, electro-optical or opto-electronic components; in chromatography or electrophoresis; as fillers, especially in polymers or polymerisable systems; or as carriers, e.g. for drugs. ADVANTAGE - (I) have a controllable particle size and surface nature. Especially when (I) are used as fillers the organic surface modification can be controlled to provide the required properties (e.g. modulus of elasticity, refractive index, impa c t strength, X-ray opacity, thermal expansion coefficient and permeability) in the obtained composite matrix. (I) can be used as fillers at high solids content and with reduced shrinkage. The surface modification provides improved dispersibility in organic media, and reduces agglomeration and sedimentation. The refractive index of (I) can be adjusted to that of the organic matrix. (I) can be prepared by simple, inexpensive and widely applicable methods. (I) show strong X-ray absorption and in some cases (depending on the nature of the outermost layer) may show bactericidal and fungicidal properties.
DE 1996-19643781 A: 19961029