Subpigmentary titanium dioxide with improved photostability
First Claim
1. A process for preparing metal ion-doped subpigmentary titanium dioxide particles having improved photostability wherein the metal ion-dopant is homogeneously intracrystalline-distributed internally in the subpigmentary titanium dioxide particles, said process comprising the steps of:
- (a) providing a suspension of subpigmentary titanium dioxide;
(b) introducing a first portion of a metal ion-dopant into the suspension;
(c) maturing the suspension for a first period of time;
(d) introducing the remainder of the metal ion-dopant into the suspension;
(e) maturing said suspension for a second period of time;
(f) recovering subpigmentary titanium dioxide from said suspension;
thereby producing metal ion-doped subpigmentary titanium dioxide particles with the dopant distributed intracrystallinely throughout the particles.
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Abstract
Subpigmentary titanium dioxide with decreased photoactivity is produced if known ions for increasing photostability in titanium dioxide pigments are not deposited on the surface of the subpigmentary particles, but instead are included intracrystallinely in the pigment particle (i.e., doped). In a preferred process for preparation of doped subpigmentary titanium dioxide particles, an acid solution containing the dopant is added in two stages to a suspension of subpigmentary titanium dioxide.
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Citations
16 Claims
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1. A process for preparing metal ion-doped subpigmentary titanium dioxide particles having improved photostability wherein the metal ion-dopant is homogeneously intracrystalline-distributed internally in the subpigmentary titanium dioxide particles, said process comprising the steps of:
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(a) providing a suspension of subpigmentary titanium dioxide; (b) introducing a first portion of a metal ion-dopant into the suspension; (c) maturing the suspension for a first period of time; (d) introducing the remainder of the metal ion-dopant into the suspension; (e) maturing said suspension for a second period of time; (f) recovering subpigmentary titanium dioxide from said suspension; thereby producing metal ion-doped subpigmentary titanium dioxide particles with the dopant distributed intracrystallinely throughout the particles. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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- 11. Subpigmentary titanium dioxide particles, wherein said particles comprise a crystalline lattice with a metal ion-dopant for improving photostability distributed intracrystallinely throughout said lattice.
Specification