| 摘要 |
<p>1401629 Lead chromate pigment IMPERIAL CHEMICAL INDUSTRIES Ltd 15 Nov 1972 [30 Nov 1971 1 June 1972] 55496/71 and 25708/72 Heading C1A [Also in Division C4] Lead chromate pigment of improved heat stability is obtained by heating an aqueous suspension of the pigment at above 65‹ C. with a water-soluble metal salt and a water soluble silicate which react to precipitate a water-insoluble silicate. Suitable metal salts include aluminium or magnesium sulphate, zinc, calcium, barium or manganese chloride, and strontium nitrate. Sodium or potassium silicate may be used. The pigment may be coated simultaneously or subsequently with a further water-insoluble salt, e.g. by reaction of one of the foregoing metal salts with hydrofluoric, phosphoric, sulphuric, or fluosilicic acids or a water-soluble salt thereof. The treatment may precede or follow treatments to deposit a coating of silica or oxides of Al, Ce, Ti, Sn, Sb or Mn, or it may follow milling, or precede coating with fatty acids, rosins or metal salts thereof.</p> |
