Treated titanium dioxide pigment with high magnesium oxide addition, process of making thereof and use thereof in paper manufacture

Abstract

Process for the surface treatment of a titanium dioxide pigment, characterized in that it comprises the following steps: an aqueous suspension of titanium dioxide pigments is formed, in a first step, a layer of alumina phosphate is precipitated on the surface of the pigment, in a second step, a layer of alumina is precipitated over the first layer of alumina phosphate, and in a third step, a layer of magnesium oxide and alumina is precipitated on the layer of alumina. Also included are titanium dioxide pigments made by the disclosed process and method using said pigments in paper manufacturing.

1 - 9 . (canceled) 
     
     
         10 . A titanium dioxide pigment comprising:
 a titanium dioxide core coated successively with layers of alumina phosphate, alumina and magnesium oxide, wherein the pigment comprises from about 80% to 90% by weight of titanium dioxide and from about 6% to 10% by weight of analyzed alumina, and has a BET surface area greater than 15 m 2 /g.   
     
     
         11 . The titanium dioxide pigment of  claim 10 , wherein said pigment comprises more than 0.01% MgO. 
     
     
         12 . The titanium dioxide pigment of  claim 10 , wherein the pigment comprises from about 84% to 88% by weight of titanium dioxide and from about 7% to 9% by weight of alumina, and has a BET surface greater than 15 m 2 /g and less than or equal to 40 m2/g. 
     
     
         13 . The titanium dioxide pigment of  claim 10 , wherein said pigment further comprises from 1 to 4% by weight P 2 O 5 . 
     
     
         14 . The titanium dioxide pigment of  claim 10 , wherein said layer of alumina is a layer that was formed by a multi-stage alumina surface treatment. 
     
     
         15 . The titanium dioxide pigment of  claim 13 , wherein said multi-stage alumina surface treatment utilized at least two different alumina sources. 
     
     
         16 . The titanium dioxide pigment of  claim 10 , wherein said pigment has a water-soluble pH of from 6.0 to 8.0. 
     
     
         17 . A titanium dioxide pigment comprising:
 a titanium dioxide core coated successively with a first layer of alumina phosphate, a second layer of alumina, and a third layer that was formed by the precipitation of magnesium oxide with alumina on said second layer of alumina, wherein the pigment comprises from 81% to 88% by weight of titanium dioxide, from 2% to 3% by weight P 2 O 5 , from 7% to 9% by weight of analyzed alumina, and from 0.1% to 2.90% MgO, and has a BET surface area from 15 m 2 /g to 40 m 2 /g.   
     
     
         18 . The titanium dioxide pigment of  claim 17 , wherein said pigment has a BET surface area from 20 m 2 /g to 40 m 2 /g. 
     
     
         19 . The titanium dioxide pigment of  claim 17 , wherein said layer of alumina is a layer that was formed by a multi-stage alumina surface treatment. 
     
     
         20 . The titanium dioxide pigment of  claim 19 , wherein said multi-stage alumina surface treatment utilized at least two different alumina sources. 
     
     
         21 . The titanium dioxide pigment of  claim 17 , wherein said pigment has a water-soluble pH of from 6.0 to 8.0. 
     
     
         22 . A titanium dioxide pigment comprising:
 a titanium dioxide core coated successively with a first layer of alumina phosphate, a second layer of alumina, and a third layer that was formed by the precipitation of magnesium oxide with alumina, wherein the pigment comprises from 81% to 88% by weight of titanium dioxide, from 2% to 3% by weight P 2 O 5 , from 7% to 9% by weight of analyzed alumina, and from about 0.1% to about 1.75% MgO, and has a BET surface area from 15 m 2 /g to 35 m 2 /g.   
     
     
         23 . The titanium dioxide pigment of  claim 22 , wherein said pigment has a BET surface area from 22 m 2 /g to 35 m 2 /g. 
     
     
         24 . The titanium dioxide pigment of  claim 22 , wherein said layer of alumina is a layer that was formed by a multi-stage alumina surface treatment. 
     
     
         25 . The titanium dioxide pigment of  claim 24 , wherein said multi-stage alumina surface treatment utilized at least two different alumina sources. 
     
     
         26 . The titanium dioxide pigment of  claim 22 , wherein said pigment has a water-soluble pH of from 6.0 to 8.0. 
     
     
         27 . The titanium dioxide pigment of  claim 22 , wherein the pigment comprises from 84% to 88% by weight of titanium dioxide, from 2% to 3% by weight P 2 O 5 , from 7% to 9% by weight of analyzed alumina, and from about 0.1% to about 1.75% MgO, and has a BET surface area from 18 m 2 /g to 33 m 2 /g. 
     
     
         28 . The titanium dioxide pigment of  claim 22 , wherein said pigment has a BET surface area from 18 m 2 /g to 24 m 2 /g. 
     
     
         29 . The titanium dioxide pigment of  claim 22 , wherein said pigment has a BET surface area from 28 m 2 /g to 33 m 2 /g.