A process for the production of coated vitreous particles

In a modification of the invention claimed in the parent Specification, an aqueous dispersion of a resole in which is suspended an insoluble material (other than barium sulphate, the use of which is the subject of the parent Specification) of a particle size such that it forms a sol in water (1 millimicron to 1 micron) is used to coat vitreous particles, e.g. beads and fibres, and the coated particles are heated to thermoset the resole. The insoluble material may be added directly to the resole dispersion or formed by precipitation therein. Specified materials are barium, calcium and magnesium inorganic or organic salts which may be obtained by precipitation from the corresponding alkali used as catalyst in the preparation of the resole, and silica flour, ground glass, titania, alumina, magnesium oxide, wollastonite, zirconium silicate or oxide, chromium oxide and insoluble inert pigments which may all be reduced to the appropriate particle size and added directly.ALSO:Vitreous particles, e.g. beads or fibres, are coated with a composition which comprises an aqueous dispersion of a resole in which is suspended an insoluble material (other than barium sulphate the use of which is the subject of the parent Specification) of a particle size such that it forms a sol in water, and the coated particles are heated to thermoset the resole. The insoluble material may be added directly to the resole dispersion or formed by precipitation therein. Specified materials are barium, calcium and magnesium salts which may be obtained by precipitation from the corresponding alkali used as catalyst to prepare the resole, and silica flour, ground glass, titania, alumina, magnesium oxide, wollastonite, zirconium silicate or oxide, chromium oxide and insoluble inert pigments which may all be reduced to the appropriate particle size (1 millimicron to 1 micron) and added directly.ALSO:In a modification of the invention claimed in the parent Specification an aqueous dispersion of a resole in which is suspended an insoluble material (other than barium sulphate the use of which is the subject of the parent Specification) of a particle size such that it forms a sol in water (1 millimicron to 1 micron) is used to coat vitreous particles (e.g. beads and fibres) and the coated particles are heated to thermoset the resole. The insoluble material may be added directly to the resole dispersion or formed by precipitation therein. Specified materials are barium, calcium and magnesium inorgani