E.i. Dupont De Nemours and Company

Alan Roger Eaton

Narayanan Sankara Subramanian

Stephen William Taylor

Russell Bertrum Diemer, Jr

George Alan Schurr

David A Zimmerman

Eric Lee Brantley

Rajeev Lochan Gorowara

Stephen Claude De La Veaux

This disclosure relates to process for producing titanium dioxide pigment having reduced chlorides, comprising: a) reacting titanium tetrahalide vapor, rutile-forming agent and at least a stoichiometric amount of oxygen in a reactor to form a gaseous suspension comprising titanium dioxide particles; b) introducing silicon tetrachloride into the reactor at least one point downstream of the point of contact of the titanium tetrahalide, the rutile forming agent and the oxygen, and where at least 97% of the titanium tetrahalide has been converted to titanium dioxide to provide a substantially uniform encapsulation of pyrogenic SiOon the titanium dioxide; c) passing the gaseous suspension to a cooling conduit; d) introducing scouring material, typically selected from the group of calcined titanium dioxide and compressed titanium dioxide, and mixtures thereof, into the cooling conduit; wherein the particles of the scouring material have a diameter in the range of about 0.25 mm to about 12.7 mm and forming a cooled product having a solid and a vapor phase; e) separating the vapor phase from the cooled product to form a powder comprising the titanium dioxide particles, and a content of chlorine-containing material ranging from about 500 to about 3000 ppm of oxychloride, and the scouring material; and f) subjecting the powder to substantially uniform heating at a temperature of about 200&#xb0; C. to about 600&#xb0; C., in the presence of moisture, to reduce the content of chlorine-containing material to less than about 60 ppm oxychloride; wherein the moisture present is in at least a stoichiometric amount with the oxychloride.

Process for producing titanium dioxide particles having reduced chlorides

This invention relates to a supersonic center-feed nozzle system within the feed-inlet tube of a fluid-energy mill used for grinding particulate material such as titanium dioxide. Particularly, in the feed-inlet tube of the present invention, particulate material is introduced into the supersonic feed jet of primary grinding fluid in almost a perpendicular fashion, with the supersonic nozzle installed in the center of the particulate material core, imparting momentum to the particulate material. The momentum entrains the particulate into the main grinding chamber of the feed-inlet tube. In the main grinding chamber of the feed-inlet tube, a secondary stream of grinding fluid, introduced annularly, constricts the primary jet's divergent flow, enabling a higher turbulent mixing of the grinding fluids and the particulate material.

Center-feed nozzle in a contained cylindrical feed-inlet tube for improved fluid-energy mill grinding efficiency

This disclosure relates to process for producing titanium dioxide (TiO) pigments, comprising the following steps: a) oxidizing a mixture of titanium tetrahalide and a rutile forming agent, such as aluminum halide, present in the vapor phase and in the presence of a nucleant to form a gaseous suspension comprising titanium dioxide particles; b) passing the gaseous suspension to a cooling conduit; c) introducing scouring material into the cooling conduit; wherein the particles of the scouring material have a diameter in the range of about 0.25 mm to about 12.7 mm; d) separating the vapor phase to form a powder comprising the titanium dioxide particles and the scouring material; and e) simultaneously subjecting the powder to substantially uniform heating at a temperature of about 300&#xb0; C. to about 600&#xb0; C. and reducing the size of the titanium dioxide particles and the particles of the scouring material in the powder to a mean particle size of about 50 nm to about 1000 nm, whereby the titanium dioxide pigment has a chloride content of less than about 500 ppm. The so treated powder may have a residual free chlorine content of less than about 1 ppm.

Titanium dioxide finishing process

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Hendersonville, TN, United States of America

Alan Roger Eaton