| 摘要 |
A coating composition comprises a carrier and dispersed particles of white silicon carbide having a particle diameter of 100 to 1000 mm and a light reflectance of more than 80% as compared with magnesium oxide with less than a 20% variation over the entire visible spectrum. Elemental impurities in the particles which give rise to discolouration are counterbalanced with respect to each other so as to produce silicon carbide particles of a substantially white colour; the elements of the third and eighth columns of the Periodic Table according to Mendeleev being counterbalanced by the addition of at least one element of the fifth column and the elements of the fifth column being counterbalanced by the addition of at least one element of the third or eighth columns. The carrier may comprise a plasticizer, a solvent, a drying oil e.g. linseed, tung or fish oil, a resin e.g. alkyd, epoxy or polyurethane resins, a latex or an organic polymer or mixtures thereof. Driers, thinners, gelling agents, viscosity conditioners and tints may also be added.ALSO:White silicon carbide particles having a particle diameter of from 100 to 1000 m and a light reflectance of more than 80% as compared with magnesium oxide with less than a 20% variation over the entire visible spectrum, are produced by reacting in a reaction vessel a source of silicon consisting of quartz, sand, silicic acid, silica gel, colloidal silica, amorphous silica, elemental silicon, silicon dioxide or mixtures thereof with an excess of carbon at a temperature of from 1350 DEG to 1750 DEG C. in an atmosphere of hydrogen, carbon monoxide, argon or helium or mixtures thereof; the elemental impurities in the reaction vessel, silicon source, carbon or atmosphere which give rise to discoloration of the silicon carbide particles being counter balanced with respect to each other so as to produce silicon carbide particles of substantially white colour, the elements of the third and eighth columns of the Periodic Table according to Mendeleev being counterbalanced by the addition of at least one element of the fifth column and the elements of the fifth column being counterbalanced by the addition of at least one element of the third or eighth columns. The silicon carbide particles are dispersed in a carrier system comprising at least a plasticizer, a solvent, a drying oil, a resin, a latex, an organic polymer or mixtures thereof and used as a coating composition. |
