PROCESS FOR PRODUCING TITANIUM DIOXIDE PARTICLES HAVING REDUCED CHLORIDES

• Main Authors: TAYLOR, STEPHEN WILLIAM, SUBRAMANIAN, NARAYANAN SANKARA, EATON, ALAN ROGER, GOROWARA, RAJEEV LOCHAN
• Format: Patent
• Language: English; French
• Published: 15.05.2008
• Subjects: ADHESIVES; CHEMISTRY; COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSESC01D OR C01F; DYES; INORGANIC CHEMISTRY; METALLURGY; MISCELLANEOUS APPLICATIONS OF MATERIALS; MISCELLANEOUS COMPOSITIONS; NATURAL RESINS; PAINTS; POLISHES; PREPARATION OF CARBON BLACK; TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS,TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES

This disclosure relates to process for producing titanium dioxide pigment having reduced chlorides, comprising: a) reacting titanium tetrahalide vapo r, 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 at least one point downstream of the point of contact of the titanium tetrahalide, the rutile f orming agent and the oxygen, and where at least 97% of the titanium tetrahal ide has been converted to titanium dioxide to provide a substantially unifor m encapsulation of pyrogenic Si.theta.2 on the titanium dioxide; c) passing the gaseous suspension to a cooling conduit; d) introducing scouring materia l, typically selected from the group of calcined titanium dioxide and compre ssed titanium dioxide, and mixtures thereof, into the cooling conduit; where in the particles of the scouring material have a diameter in the range of ab out 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 for m a powder comprising the titanium dioxide particles, and a content of chlor ine- containing material ranging from about 500 to about 3000 ppm of oxychlo ride, and the scouring material; and f) subjecting the powder to substantial ly uniform heating at a temperature of about 2000C to about 6000C, in the pr esence of moisture, to reduce the content of chlorine- containing material t o less than about 60 ppm oxychloride; wherein the moisture present is in at least a stoichiometric amount with the oxychloride.