TiO.sub.2 light scattering efficiency when incorporated in coatings

• US 5,650,002 A
• Filed: 11/13/1995
• Issued: 07/22/1997
• Est. Priority Date: 11/13/1995
• Status: Expired due to Term

• Current Assignee: The Chemours Company TT, LLC (The Chemours Company)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Bolt, John Davis
• Primary Examiner(s): Bonner, Melissa
• Application Number:
  US08/558,116
• Time in Patent Office: 617 Days
• Field of Search: 428/403, 428/404, 106/436, 106/438, 106/439, 106/441, 106/442, 106/443, 106/444, 106/449, 106/445
• US Class Current: 106/438
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01P 2002/88 by thermal analysis data, e.g. TGA, DTA, DSC
• CPC Class Codes: C01P 2004/01 depicted by an image
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2004/04 obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2004/10 extending in one dimension, e.g. needle-like
• CPC Class Codes: C01P 2004/62 Submicrometer sized, i.e. from 0.1-1 micrometer
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C01P 2004/82 two phases having the same anion, e.g. both oxidic phases
• CPC Class Codes: C01P 2006/10 Solid density
• CPC Class Codes: C01P 2006/12 Surface area
• CPC Class Codes: C01P 2006/19 Oil-absorption capacity, e.g. DBP values
• CPC Class Codes: C01P 2006/60 Optical properties, e.g. expressed in CIELAB-values
• CPC Class Codes: C08K 3/22 of metals
• CPC Class Codes: C08K 9/02 Ingredients treated with inorganic substances
• CPC Class Codes: C09C 1/0084 containing titanium dioxide
• CPC Class Codes: C09C 1/3661 Coating
• CPC Class Codes: C09D 7/62 modified by treatment with other compounds
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 428/2993 Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]

Abstract

A TiO₂ pigment particle having a surface coating of inorganic particles or mineral particles exhibiting improved light scattering efficiency of TiO₂ at a moderate to high pigment volume concentration (PVC) and a low oil absorption when incorporated in coatings applications is disclosed, and methods of accomplishing the same.

Claims

1. A TiO₂ pigment consisting essentially of TiO₂ particles having (a) substantially discrete inorganic particles having an average diameter size within the range of about 5 to about 100 nm dispersed on the surfaces of the TiO₂ particles in an amount of less than 20 wt. % based on total pigment weight, and (b) a top-coating comprising a hydrous oxide selected from the group consisting of silica, alumina, zirconia, and mixtures thereof.

3. The TiO₂ pigment of claim 1 or 2, wherein the inorganic particles are selected from the group consisting of oxides of silicon, titanium, zirconium, zinc, magnesium, aluminum, yttrium, antimony, cerium, and tin;

sulfates of barium and calcium;

sulfides of zinc;

carbonates of zinc, calcium, magnesium, lead, and mixed metals;

nitrides of aluminum;

phosphates of aluminum, calcium, magnesium, zinc, and cerium;

titanates of magnesium, calcium, and aluminum;

fluorides of magnesium and calcium;

silicates of zinc, zirconium, calcium, barium, magnesium, mixed alkaline earth metals and naturally occurring silicate minerals;

aluminosilicates of alkali and alkaline earth metals;

naturally occurring aluminosilicates;

aluminates of zinc, calcium, magnesium, and mixed alkaline earth metals;

hydroxides of aluminum;

diamond; and

mixtures or composites of the foregoing particles.

4. The TiO₂ pigment of claim 1 or 2, wherein the inorganic particles have an average diameter size within the range of 7 to 50 nm.

5. The TiO₂ pigment of claim 1 or 2, wherein the amount of inorganic particles is up to 15 wt. % and the amount of hydrous oxides is up to 16 wt. % based on total pigment weight.

6. The TiO₂ pigment of claim 1 or 2, wherein the amount of inorganic particles is up to 10 wt. % and the amount of hydrous oxides is up to 16 wt. % based on total pigment weight.

7. The TiO₂ pigment of claim 6, wherein the inorganic particles are selected from the group consisting of silica, alumina, calcium carbonate, and mixtures or composites thereof.

8. The TiO₂ pigment of claim 7, wherein the pigment has an oil absorption of less than 35.

9. The TiO₂ pigment of claim 1 or 2, wherein the inorganic particles comprise silica particles in an amount up to 10 wt. % based on total pigment weight, and the hydrous oxides comprise up to 4 wt. % silica and up to 3 wt. % alumina based on total pigment weight.

10. The TiO₂ pigment of claim 9, wherein the pigment has an oil absorption of less than 25.

11. The TiO₂ pigment of claim 9, wherein the pigment has a light scattering coefficient greater than 0.31 m² /g at 25% pigment volume concentration and greater than 0.26 m² /g at 35% pigment volume concentration.

12. A TiO₂ pigment slurry comprising the TiO₂ pigment of claim 1 or 2, wherein the slurry has a TiO₂ pigment solids content above 50 wt. %.

2. A TiO₂ pigment consisting essentially of TiO₂ particles having (a) a surface-coating comprising a hydrous oxide selected from the group consisting of silica, alumina, zirconia, and mixtures thereof, and (b) substantially discrete inorganic particles having an average diameter size within the range of about 5 to about 100 nm which are dispersed on the surface of the hydrous oxide surface-coating in an amount of less than 20 wt. % based on total pigment weight.

13. A process for preparing a TiO₂ pigment, comprising the steps of:

(a) mixing a slurry of TiO₂ particles with a colloidal suspension of inorganic particles, wherein the TiO₂ particles and the colloidal particles are both above or below their respective isoelectric points such that substantially discrete inorganic particles having an average diameter size within the range of about 5 to about 100 nm are dispersed onto the surfaces of the TiO₂ particles in an amount of less than 20 wt. % based on total pigment weight; and

(b) precipitating a hydrous oxide selected from the group consisting of silica, alumina, zirconia, and mixtures thereof onto the TiO₂ particles resulting from step (a).

14. A process for preparing a TiO₂ pigment, comprising the steps of:

(a) precipitating a hydrous oxide selected from the group consisting of silica, alumina, zirconia, and mixtures thereof onto the surfaces of TiO₂ particles to form surface-coatings, and

(b) mixing a slurry of the surface-coated TiO₂ particles with a colloidal suspension of inorganic particles, wherein the TiO₂ particles and the colloidal particles are both above or below their respective isoelectric points such that substantially discrete inorganic particles having an average diameter size within the range of about to about 100 nm are dispersed onto the surface-coated TiO₂ particles in an amount of less than 20 wt. % based on total pigment weight.

15. A process for preparing a TiO₂ pigment, comprising the steps of:

(a) mixing a slurry of TiO₂ particles with reagents to form in-situ substantially discrete inorganic particles having an average diameter size within the range of about 5 to about 100 nm, wherein the inorganic particles are dispersed onto the surfaces of the TiO₂ particles in an amount of less than 20 wt. % based on total pigment weight; and

(b) precipitating a hydrous oxide selected from the group consisting of silica, alumina, zirconia, and mixtures thereof onto the TiO₂ particles resulting from step (a).

16. A process for preparing a TiO₂ pigment, comprising the steps of:

(a) precipitating a hydrous oxide selected from the group consisting of silica, alumina, zirconia, and mixtures thereof onto the surfaces of TiO₂ particles to form surface-coatings, and

(b) mixing a slurry of the surface-coated TiO₂ particles with reagents to form in-situ substantially discrete inorganic particles having an average diameter size within the range of about 5 to about 100 nm, wherein the inorganic particles are dispersed onto the surface-coated TiO₂ particles in an amount of less than 20 wt. % based on total pigment weight.

17. A process for preparing a TiO₂ pigment slurry, comprising the steps of:

(a) preparing finished TiO₂ particles having a surface-coating comprising a hydrous oxide selected from the group consisting of silica, alumina, zirconia, and mixtures thereof; and

(b) mixing the finished TiO₂ particles with an aqueous mixture comprising a colloidal suspension of inorganic particles and dispersant, wherein the TiO₂ particles and the colloidal particles are both above or below their respective isoelectric points, to form substantially discrete inorganic particles having an average diameter size within the range of about 5 to about 100 nm which are dispersed onto the surfaces of the TiO₂ particles in an amount of less than 20 wt. % based on total pigment weight.