Titanium dioxide pigment having improved light stability
View Patent ↗In various embodiments, methods and compositions are provided comprising titanium dioxide and silica spacers having improved light stability for use in paper, plastic and paints.
1. A process for preparing coated titanium dioxide pigment having improved light stability, comprising:
combining a titanium dioxide base, a phosphate compound and a water soluble silicon compound in an aqueous slurry so as to form a coated titanium dioxide pigment comprising a base titanium dioxide particle coated with a phosphate compound and substantially spherical shaped silica spacer particles having an average particle size range between about 5 to about 50 nanometers, wherein the substantially spherical shaped spacer particles weigh between about 7 to about 20 weight % based on the weight of the titanium dioxide.
2. A process according to claim 1 , further comprising combining the coated titanium dioxide pigment with alum.
3. A process according to claim 1 , wherein an aluminum compound is added to the slurry of coated titanium dioxide pigment to form an alumina coating.
4. A process for preparing titanium dioxide pigment having improved light stability comprising the steps of:
(a) preparing an aqueous slurry of base titanium dioxide particles;
(b) adding a surface coating agent and a silicon compound to the slurry under conditions so as to form substantially spherical shaped silica spacer particles on the base titanium dioxide particles, wherein substantially spherical shaped silica spacer particles have an average particle size range between about 5 to about 50 nanometers; and
(c) adding a retention aid to the slurry to form the titanium dioxide pigment having improved light stability; wherein said retention aid is polyaluminum chloride, polyamide, epichlorohydrin, polyethyleneimine, polyacrylamide; cationic formaldehyde, melamine formaldehyde resins, cationic starch, chitosan or a combination thereof.
5. A process according to claim 4 , wherein the base titanium dioxide particles are anatase or rutile titanium dioxide.
6. A process according to claim 4 , wherein the surface coating agent is a phosphate compound.
7. A process according to claim 6 , wherein the phosphate compound is selected from a group consisting of tetrapotassium pyrophosphate, sodium polyphosphate, tetrasodium pyrophosphate, sodium tripolyphosphate, potassium tripolyphosphate, sodium hexametaphosphate, phosphoric acid or a combination thereof.
8. A process according to claim 1 , wherein the water soluble silicon compound is a water soluble alkali metal silicate.
9. A process according to claim 8 , wherein the water soluble alkali metal silicate is sodium silicate.