Conc. titanium di:oxide suspension prodn. for use in paper mfr. - by filtering dechlorinated slurry of oxide from vapour phase oxidn. and mixing thixotropic filter cake with conc. suspension contg. dispersant

摘要

Prodn. of TiO2 suspension (I) with a high solids content comprises converting finely-divided TiO2, produced by vapour phase oxidn. of TiCl4, into a slurry contg. this TiO2 in the unflocculated state, with pH not over 4; dechlorinating and filtering the slurry; making the filter cake fluid with a dispersant (II); and milling. The novel features are that the slurry is subjected to pressure filtration without adding (II), giving a thixotropic filter cake (III); and (III) is incorporated by shear in a suspension (IV) contg. (II) and having a high solids content. Dechlorination is carried out before filtration so that the slurry contains no polyvalent anions or their precursors or the min. possible amt. of these, pref. max. 3x10power-3 mole/l. Dechlorination is carried out with H2O2 or NaHSO3 or H2O2 followed by NaHSO3. The slurry is filtered with a membrane filter press, pref. at 4-6 bar. The suspension is treated with ca. 0.1-5 (wt.)% (II) w.r.t. TiO2 in (III). USE/ADVANTAGE - (I) is esp. useful in paper mfr.. (I) contg. over 75% TiO2 can be produced economically without using dried, treated material and known problems in filtering the slurry are avoided. (I) is very stable and easy to transport and store and is suitable for direct use, without treating the TiO2 particles with inorganic cpds..