| 摘要 |
An aqueous slurry of TiO2 pigment, containing metal impurities, is purified by treatment with an organic sequestering agent. The agent may be a diamine, preferably EDTA, amino acid, diacetic acid, imidazole, aryl sulphonic acid, or tartaric or oxalic acid; or their alkali metal or ammonium salts; examples are listed. 0.05-2% may be added to the slurry at pH 1-7.5. Addition may be effected during precipitation of hydrous oxides on to the TiO2 particles by adding, e.g. Ti(SO4)2, Al2(SO4)3, Na2SiO3, NaAlO3, TiCl4 or AlCl3, to the slurry at 30-70 DEG C., adjusting to pH 2-7.5 with NaOH, Na2CO3, HCl or H2SO4, and ageing at 70 DEG C. The pigment is then filtered, washed, dried at 110 DEG C. and milled in a fluid energy mill. The metal impurities, which are complexed into solution, may be Fe, Cu, Mn or Cr. |
