Patent GB-802953-A (GB)
Title: Method for increasing the bulk density and the degree of aggregation of extremely finely divided inorganic substances
IPC: C09C3/00
Filed: 1955-02-28
Abstract: The bulk density and degree of aggregation of finely-divided voluminous non-carbonaceous inorganic substances, especially pigmentary oxides, produced by vapour-phase reaction, which have a particle size of 5-300 millimicrons, is increased by wetting the substances with a liquid which has a maximum solubility for the substance of 1 part per 10,000 by weight, and thereafter drying the mixture.  The treatment may be effected under increased temperature and pressure.  Suitable liquids are hydrocarbons such as petroleum ether, chlorinated hydrocarbons, alcohols and water. According to examples: (1) silicon dioxide with an average particle size of 21 millimicrons was treated with water at 25 DEG  C. and the slurry so formed was dried.  The bulk density increased from 0.045 kg./l. to 0.21 kg./l. and the average size of the aggregate had increased from 2.25 to 6 times the original particle size.  The treated silica was employed as a filler in a rubber mix; the modulus at 300 per cent elongation was 3 times higher than that obtained with untreated silica whilst the tensile strength was substantially the same. Further examples relate to the treatment of silica with ethyl alcohol and water, with carbon tetrachloride and with petroleum ether.  (5) Alumina of average particle size of 11 millimicrons was stirred with petroleum ether at 25 DEG  C. and thereafter dried; the bulk density was increased from 0.07 to 0.38 kg./l. whilst the average aggregate size was increased up to 4.5 times the original particle size.  When compounded in a rubber mix, the modulus again was considerably increased.  (6) Titania of 13 millimicron particle size was treated with petroleum ether and the slurry dried and compounded in a rubber mix.  (7) Ferric oxide of an average particle size of 21 millimicrons and a degree of aggregation of 4 times the particle size was treated with petroleum ether and after drying the degree of aggregation had increased to 5.5 times the particle size, and the bulk density increased from 0.07 to 0.35 kg./l.  The iron oxide was then compounded in a rubber mix.  The treatment is preferably effected by adding the finely divided substance to the liquid whilst stirring vigorously and the slurry obtained is preferably spray-dried.ALSO:The bulk density and degree of aggregation of finely-divided voluminous non-carbonaceous inorganic substances, especially oxides, produced by vapour phase reaction, which have a particle size of 5-300 millimicrons, is increased by wetting the substances with a liquid which has a maximum solubility for the substance of 1 part per 10,000 by weight, and thereafter drying the mixture.  The treatment may be effected under increased temperature and pressure.  Suitable liquids are hydrocarbons such as petroleum ether, chlorinated hydrocarbons, alcohols and water. According to examples: (1) silicon dioxide with an average particle size of 21 millimicrons was treated with water at 25 DEG  C. and the slurry so formed was dried.  The bulk density increased from 0.045 kg./l. to 0.21 kg./l. and the average size of the aggregate had increased from 2.25 to 6 times the original particle size.  The treated silica was employed as a filler in a rubber mix; the modulus at 300 per cent elongation was 3 times higher than that obtained with untreated silica whilst the tensile strength was substantially the same.  Further examples relate to the treatment of silica with ethyl alcohol and water, with carbon tetrachloride and with petroleum ether.  (5) Alumina of average particle size of 11 millimicrons was stirred with petroleum ether at 25 DEG  C. and thereafter dried; the bulk density was increased from 0.07 to 0.38 kg./l. whilst the average aggregate size was increased up to 4.5 times the original particle size.  When compounded in a rubber mix the modulus again was considerably increased.  (6). Titania of 13 millimicrons particle size was treated with petroleum ether and the slurry dried and compounded in a rubber mix.  (7) Ferric oxide of an average particle size of 21 millimicrons and a degree of aggregation of 4 times the particle size was treated with petroleum ether and after drying the degree of aggregation had increased to 5.5 times the particle size and the bulk density increased from 0.07 to 0.35 kg./l. The iron oxide was then compounded in a rubber mix.  The treatment is preferably effected by adding the finely-divided substance to the liquid whilst stirring vigorously and the slurry obtained is preferably spray-dried.