Patent GB-1092537-A (GB)
Title: Fused silica compositions
IPC: C04B24/20
Filed: 1964-10-02
Abstract: A composition comprises granular fused silica of silica content not less than 97% and thermal coefficient of expansion not greater than 6 x 10-7 cm./cm./ DEG C. suspended in colloidal silica aquasols having spherical silica particles of average particle size from 3 to 150 millimicrons and a SiO2/Na2O mole ratio of at least 60:1 in a ratio of fused silica to colloidal silica of from 10:0.5 to 10:60, and magnesium montmorillonite clay as a suspending agent. The composition may also contain as stabilizing agent water-soluble azo aromatic compounds; water-soluble compounds containing the quinoid grouping <FORM:1092537/C4-C5/1> or <FORM:1092537/C4-C5/2> wherein X is oxygen or sulphur atom or a radical of formula N-R or a salt thereof, where R is a hydrogen atom or an aliphatic and aromatic radical; or water soluble indigoid compounds containing the chromophore grouping <FORM:1092537/C4-C5/3> or <FORM:1092537/C4-C5/4> in a concentration of 0.01-1%.  The compositions may be used for producing heat resistant coatings on heat sensitive surfaces, e.g. surfaces contacted with molten metals which are subjected to erosion or fracture. The composition may be sprayed upon the surface, or applied by brushing, flow coating, dipping, the coated surface being simultaneously or subsequently heated to solidify the composition.ALSO:A composition comprises granular fused silica of silica content not less than 97% and thermal coefficient of expansion not greater than 6 x 10-7 cm./cm. DEG  C. suspended in colloidal silica aquasols having spherical silica particles of average particle size from 3 to 150 millimicrons and an SiO2/Na2O mole ratio of at least 60:1 in a ratio of fused silica to colloidal silica of from 10:0.5 to 10:60, and magnesium montmorillonite clay as a suspending agent. The composition may also contain water-soluble azo aromatic compounds; water-soluble compounds containing the quinoid grouping: <FORM:1092537/C1/1> or <FORM:1092537/C1/2> wherein X is oxygen or sulphur atom or a radical of formula N-R or a salt thereof, where R is a hydrogen atom or an aliphatic and aromatic radical; water-soluble indigoid compounds containing the chromophore grouping <FORM:1092537/C1/3> or <FORM:1092537/C1/4> The fused silica may be prepared by hammer-milling and grinding pure, fused silica glasses formed by reduction of pure silica sands by graphite electrodes in an electric arc furnace. The composition may have a solids content from 30 to 80%.  The azo aromatic compounds may be 4 - (2 - hydroxy - 1 - naphthylazo) - m - toluene sulphonic acid, and a list of azo dyes is given. Compounds containing quinoid groupings may be quinones such as p-quinone, p-quinone monoxime sodium salt, and anthraquinone dyes and thiazine dyes (listed).  The indigoid compounds may be indigo dyes (listed). The stabilizing compound concentration may be 0.01 to 1%. The fused silica can be added to the colloidal silica aquasol containing the stabilizing compound to which has been added magnesium montmorillonite clay with high shear mixing; or the fused silica and montmorillonite clay can be premixed in the dry state and added to the stabilizing compound-containing silica aquasol with high shear mixing; or each of the ingredients first suspended in aqueous medium and then mixed together with agitation.  The compositions may be used for producing heatresistant coatings on heat-sensitive surfaces, e.g. surfaces contacted with molten metals which are subjected to erosion or fracture such as the inner walls of moulds in casting metal ingots, say, of ferrous metals, the metal "stools" on which the moulds rest, troughs, shoots, ladles, conveying receptacles, furnaces.  The composition may be sprayed upon the surface, or applied by brushing, flow coating, dipping, the coated surface being simultaneously or subsequently heated to solidify the composition.ALSO:A composition comprises granular fused silica of silica content not less than 97% and thermal coefficient of expansion not greater than 6 x 10-7cm/cm/ DEG C suspended in colloidal silica aquasols having spherical silica particles of average particle size from 3 to 150 millimicrons and a SiO2/Na2O mole ratio of at least 60:1 in a ratio of fused silica to colloidal silica of from 10:05 to 10:60, and magnesium montmorillonite clay as a suspending agent.  The composition may also contain water-soluble azo aromatic compounds; water-soluble compounds containing the quinoid grouping: <FORM:1092537/B1-B2/1> or <FORM:1092537/B1-B2/2> wherein X is oxygen or sulphur atom or a radical of formula N-R or a salt thereof, where R is a hydrogen atom or an aliphatic and aromatic radical, water soluble indigoid compounds containing the chromophore grouping. <FORM:1092537/B1-B2/3> or <FORM:1092537/B1-B2/4> : The fused silica may be prepared by hammer-milling and grinding p  pure, fused silica glasses formed by reduction of pure silica sands by graphite electrodes, in an electric arc furnace.  The composition may have a solids content from 30 to 80%.  The azo aromatic compounds may be 4-(2-hydroxy-1-naphthylazo)-m-toluene sulphonic acid, and a list of azo dyes is given.  Compounds containing quinoid groupings may be quinones such as p-quinone, p-quinone monoxime sodium salt, and anthraquinone dyes and thiazine dyes (listed).  The indigoid compounds may be indigodyes (listed).  The stabilizing compound concentration may be 0.01% to 1%.  The fused silica can be added to the colloidal silica aquasol containing the stabilizing compound to which has been added magnesium montmorillonite clay with high shear mixing; or the fused silica and montmorillonite clay can be premixed in the dry state and added to the stabilizing compound-containing silica aquasol with high shear mixing; or each of the ingredients first suspended in aqueous medium and then mixed together with agitation.  The compositions may be used for producing heat resistant coatings on heat sensitive surfaces e.g. surfaces contacted with molten metals which are subjected to erosion or fracture such as the inner walls of moulds in casting metal ingots say of ferrous metals, the metal "stools" on which the moulds rest, troughs, chutes, ladles, conveying receptacles, furnaces. The composition may be sprayed upon the surface, or applied by brushing. flow coating, dipping, the coated surface being simultaneously or subsequently heated to solidify the composition.