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

A TiO.sub.2 pigment consisting essentially of TiO.sub.2 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.

A process for preparing a TiO.sub.2 pigment, comprising the steps of:

• (a) mixing a slurry of TiO.sub.2 particles with a colloidal suspension of inorganic particles, wherein the TiO.sub.2 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 TiO.sub.2 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 TiO.sub.2 particles resulting from step (a).

A process for preparing a TiO.sub.2 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 TiO.sub.2 particles to form surface-coatings, and
• (b) mixing a slurry of the surface-coated TiO.sub.2 particles with a colloidal suspension of inorganic particles, wherein the TiO.sub.2 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 TiO.sub.2 particles in an amount of less than 20 wt. % based on total pigment weight.

A process for preparing a TiO.sub.2 pigment, comprising the steps of:

• (a) mixing a slurry of TiO.sub.2 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 TiO.sub.2 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 TiO.sub.2 particles resulting from step (a).

A process for preparing a TiO.sub.2 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 TiO.sub.2 particles to form surface-coatings, and
• (b) mixing a slurry of the surface-coated TiO.sub.2 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 TiO.sub.2 particles in an amount of less than 20 wt. % based on total pigment weight.

A process for preparing a TiO.sub.2 pigment slurry, comprising the steps of:

• (a) preparing finished TiO.sub.2 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 TiO.sub.2 particles with an aqueous mixture comprising a colloidal suspension of inorganic particles and dispersant, wherein the TiO.sub.2 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 TiO.sub.2 particles in an amount of less than 20 wt. % based on total pigment weight.