06.05.12
U.S. 8,114,377 B2
E.I. du Pont de Nemours and Company has been granted a patent for a process for producing titanium dioxide pigment comprised of reacting titanium tetrahalide vapor, a rutile-forming agent and at least a stoichiometric amount of oxygen in a reactor to form a gaseous suspension comprised of titanium dioxide particles; 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; passing the gaseous suspension to a cooling conduit; introducing scouring, material particles, selected from the group consisting of calcined titanium dioxide and compressed titanium dioxide, and mixtures thereof, into the cooling conduit; wherein the scouring material particles have a diameter in the range of 0.25 mm to 12.7 mm and forming a cooled product having a solid and a vapor phase; separating the vapor phase from the cooled product to form a powder comprised of the titanium dioxide particles, chlorine-containing material comprising 500 to 3000 ppm of one or more oxychlorides, and the scouring material; and subjecting the powder to fluid energy milling in a fluid energy mill and substantially uniform heating at a temperature of approximately 200° C to 600° C, in the presence of moisture, the substantially uniform heating in the presence of moisture taking place in the fluid energy mill, to reduce the content of chlorine containing materials to an oxychlorides content of less than about 60 ppm; wherein the moisture present is in at least a stoichiometric amount with the oxychloride.
E.I. du Pont de Nemours and Company has been granted a patent for a process for producing titanium dioxide pigment comprised of reacting titanium tetrahalide vapor, a rutile-forming agent and at least a stoichiometric amount of oxygen in a reactor to form a gaseous suspension comprised of titanium dioxide particles; 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; passing the gaseous suspension to a cooling conduit; introducing scouring, material particles, selected from the group consisting of calcined titanium dioxide and compressed titanium dioxide, and mixtures thereof, into the cooling conduit; wherein the scouring material particles have a diameter in the range of 0.25 mm to 12.7 mm and forming a cooled product having a solid and a vapor phase; separating the vapor phase from the cooled product to form a powder comprised of the titanium dioxide particles, chlorine-containing material comprising 500 to 3000 ppm of one or more oxychlorides, and the scouring material; and subjecting the powder to fluid energy milling in a fluid energy mill and substantially uniform heating at a temperature of approximately 200° C to 600° C, in the presence of moisture, the substantially uniform heating in the presence of moisture taking place in the fluid energy mill, to reduce the content of chlorine containing materials to an oxychlorides content of less than about 60 ppm; wherein the moisture present is in at least a stoichiometric amount with the oxychloride.
