Treatment process for titanium dioxide pigments, novel titanium dioxide pigment and its use in paper manufacture

摘要

A novel titanium dioxide pigment consists of a titanium dioxide core covered successively with an aluminium phosphate layer, an alumina layer and a magnesium oxide layer. Pref. the pigment has a positive zeta potential at pH 7-8 and has the concn. (by wt.) 90-94.3% titanium dioxide, 2.5-4.5% aluminium phosphate, 3-4% alumina and 0.2-1.5 magnesium oxide. Also claimed are: (i) a process for surface treating a titanium dioxide pigment involving forming an aq. titanium dioxide pigment suspension, pptg. an aluminium phosphate layer on the pigment surface, pptg. an alumina layer on the pigment and then recovering the pigment from the suspension; and (ii) a process for surface treating a titanium dioxide pigment involving pptg. a magnesium oxide layer on the pigment after alumina pptn. and before pigment recovery.