A method for the production of surface by means of a helicoidal guide pulled out rearwards oxide particles

摘要

1349089 Coated oxide particles LAPORTE INDUSTRIES Ltd 13 July 1972 [13 July 1971] 32907/71 Headings C1N and C1A Pigmentary oxide particles are surface coated with oxycompounds by precipitation under hydrothermal pressure conditions at a temperature of at least 140‹ C., preferably not above 275‹ C. The oxycompound may contain Be, Mg, Ca, Ba, B, Al, Si, Sn, Pb, Sb, Bi, Ti, Zr, Hf, Nb, Ta, Mn, Zn, or Ce. Hydrous oxides may be precipitated by hydrolysis of TiCl 4 , SnCl 4 , ZnCl 2 , Ca acetate, Al 2 (SO 4 ) 3 or titanyl Al sulphate. Oxysalts may be precipitated from two or more compounds, e.g. a borate; Zn silicate from ZnSO 4 and Na silicate; Ti phosphate from TiCl 4 and Na 3 PO 4 ; or Sn and Al may be precipitated together from SnCl 4 and Al 2 (SO 4 ) 3 . Several layers may be deposited, e.g. TiO 2 may first be precipitated from titanyl Al sulphate with NaOH and the Al may then be precipitated under pressure; alternatively, a first coating may be precipitated under pressure and a second coating precipitated by adjusting the pH. Some surface reaction may occur, e.g. to produce Ca titanate on TiO 2 . The process may be carried out in a stirred, rocking, or rotating autoclave. Pressure may be augmented by introducing air or N 2 . Further reagents may be introduced through pressure locks. After precipitation, the pigment may be subjected to a hydrothermal pressure treatment at a temperature of at least 50‹ C., as described in Specification 1,336,292. The pressure in the autoclave may be used to convey the pigment to the next treatment stage. The exemplified pigment is TiO 2 ; others mentioned are Cr and Fe oxides.