Fine Particulate Titanium Dioxide, and Production Process and Use Thereof

Abstract

A high-purity ultrafine particulate titanium dioxide with a reduced fluctuation of the adsorbed water content which is a large mass fluctuation factor in a fine particulate powder body, is provided. The fine particulate titanium dioxide has a BET specific surface area of 10 to 200 m 2 /g, wherein when a powder of the titanium dioxide in an amount of 2 to 5 g is spread in a 10 cm-diameter glass-made Petri dish to a uniform thickness and left standing in an environment at 20° C. and a relative humidity of 80% for 5 hours, the rate of change of mass based on the mass before standing is from −5 mass % to 5 mass %. The process for producing the fine particulate titanium dioxide comprises a first step of high-temperature oxidizing a titanium tetrachloride-containing gas with use of an oxidative gas to produce a titanium dioxide powder, and a second step of contacting water vapor with the titanium dioxide powder while rolling the powder in a heating furnace, thereby effecting dechlorination and at the same time, increasing the adsorbed water.

1 . A fine particulate titanium dioxide having a BET specific surface area of 10 to 200 m 2 /g, wherein when a powder of the titanium dioxide in an amount of 2 to 5 g is spread in a 10 cm-diameter glass-made Petri dish to a uniform thickness and left standing in an environment at 20° C. and a relative humidity of 80% for 5 hours, the rate of change of mass based on the mass before standing is from −5 mass % to 5 mass %. 
     
     
         2 . The fine particulate titanium dioxide according to  claim 1 , wherein the 90% cumulative mass-particle size distribution diameter (hereinafter denoted as “D90”) is 2.2 μm or less. 
     
     
         3 . The fine particulate titanium dioxide according to  claim 1 , wherein the distribution constant n according to the Rosin-Rammler formula represented by the following formula (1) is from 1.7 to 3.5:
     R= 100exp(− bD   n )  (1)   
       wherein D is a particle diameter, R is a mass percentage of particles larger than D (particle diameter) based on the mass of all particles, and n is a distribution constant. 
     
     
         4 . A fine particulate titanium dioxide wherein, assuming that the BET specific surface area is α (m 2 /g) and the mass decrement when the powder is ignited in an electric furnace kept at 900° C. for 1 hour (hereinafter this decrement is called a loss on ignition) is X (mass %), the loss on ignition X is present in the range represented by formula (2):
   2.1×{α/(6×14)×18+(α−β)/(6×10 4 )×9}×100 ≧X≧ 0.25×{α/(6×10 4 )×18+(α−β)/(6×10 4 )×9}×100  (2)   
       herein β is a BET specific surface area (m 2 /g) after the powder is ignited in an electric furnace kept at 900° C. for 1 hour. 
     
     
         5 . A fine particulate titanium dioxide wherein, assuming that the BET specific surface area is α (m 2 /g) and the mass decrement when the powder is ignited in an electric furnace kept at 900° C. for 1 hour (hereinafter this decrement is called a loss on ignition) is X (mass %), the loss on ignition X is present in the range represented by formula (2′):
   1.3×{α/(6×10 4 )×18+(α−β)/(6×10 4 )×9}100 ≧X≧ 0.7×{α/(6×10 4 )×18+(α−β)/(6×10 4 )×9}×100  (2′)   
       wherein β is a BET specific surface area (m 2 /g) after the powder is ignited in an electric furnace kept at 900° C. for 1 hour. 
     
     
         6 . A fine particulate titanium dioxide wherein, assuming that the BET specific surface area is α (m 2 /g) and the mass decrement when the powder is ignited in an electric furnace kept at 900° C. for 1 hour (hereinafter this decrement is called “loss on ignition”) is X (mass %), the loss on ignition X is present in the range represented by formula (3):
   1.5×{α/(6×10 4 )×18+(α−β)/(6×10 4 )×9}×100 ≧X≧ 0.85×{α/(6×10 4 )×18+(α−β)/(6×10 4 )×9}×100  (3)   
       wherein β is a BET specific surface area (m 2 /g) after the powder is ignited in an electric furnace kept at 900° C. for 1 hour. 
     
     
         7 . A fine particulate titanium dioxide wherein, assuming that the BET specific surface area is α (m 2 /g) and the mass decrement when the powder is ignited in an electric furnace kept at 900° C. for 1 hour (hereinafter this decrement is called “loss on ignition”) is X (mass %), the loss on ignition X is present in the range represented by formula (3′):
   1.15×{α/(6×10 4 )×18+(α−β)/(6×10 4 )×9}×100 ≧X≧ 0.85×{α/(6×10 4 )×18+(α−β)/(6×10 4 )×9}×100  (3′)   
       wherein β is a BET specific surface area (m 2 /g) after the powder is ignited in an electric furnace kept at 900° C. for 1 hour. 
     
     
         8 . The fine particulate titanium dioxide according to  claim 1 , wherein the Fe, Al and S contents each is 10 ppm by mass or less. 
     
     
         9 . The fine particulate titanium dioxide according to  claim 1 , wherein the content of Cl in the powder body is 50 mass % or less of the loss on ignition. 
     
     
         10 . A process for producing a fine particulate titanium dioxide, comprising a first step of high-temperature oxidizing a titanium tetrachloride-containing gas with use of an oxidative gas to produce a titanium dioxide powder, and a second step of contacting water vapor with the titanium dioxide powder while rolling the powder in a heating furnace, thereby effecting dechlorination and at the same time, increasing the adsorbed water. 
     
     
         11 . The process for producing a fine particulate titanium dioxide according to  claim 10 , wherein the oxidative gas is water vapor. 
     
     
         12 . The process for producing a fine particulate titanium dioxide according to  claim 11 , wherein the amount of water vapor contacted is from 2 to 30 mol per mol of the titanium tetrachloride gas. 
     
     
         13 . The process for producing a fine particulate titanium dioxide according to  claim 10 , wherein the titanium tetrachloride-containing gas and the oxidative gas supplied to the reaction tube each is preheated at a temperature of 600° C. to less than 1,100° C. 
     
     
         14 . The process for producing a fine particulate titanium dioxide according to  claim 10 , wherein in the second step, the water vapor and the powder body are counter-currently contacted by introducing the water vapor into the heating furnace at a ratio of 1 to 60 mass % based on the titanium dioxide powder. 
     
     
         15 . The process for producing a fine particulate titanium dioxide according to  claim 10 , wherein in the second step, the water vapor and the powder body are counter-currently contacted by introducing the water vapor into the heating furnace to occupy a ratio of 1 to 50 mass % based on the titanium dioxide powder. 
     
     
         16 . The process for producing a fine particulate titanium dioxide according to  claim 10 , wherein in the second step, the titanium dioxide is heated at 150 to 500° C. 
     
     
         17 . The process for producing a fine particulate titanium dioxide according to  claim 10 , wherein in the second step, the residence time of the powder in the heating furnace is from 0.5 hours to less than 3 hours. 
     
     
         18 . A process for producing a fine particulate titanium dioxide, comprising spraying water droplets having a liquid droplet diameter of 5 to 500 μm at the time of packing the powder in a resin bag, and closing and then storing the bag. 
     
     
         19 . A fine particulate titanium dioxide produced by the process described in  claim 10 . 
     
     
         20 . A perovskite compound using the fine particulate titanium dioxide described in  claim 1  as a part of the raw materials. 
     
     
         21 . A dielectric raw material comprising the titanium dioxide powder described in  claim 1 . 
     
     
         22 . A slurry comprising the titanium dioxide powder described in  claim 1 . 
     
     
         23 . A composition comprising the titanium dioxide powder described in  claim 1 . 
     
     
         24 . A photocatalyst material comprising the titanium dioxide powder described in  claim 1 . 
     
     
         25 . A cosmetic material comprising the titanium dioxide powder described in  claim 1 . 
     
     
         26 . A solar cell material comprising the titanium dioxide powder described in  claim 1 . 
     
     
         27 . An additive for silicone rubber, comprising the titanium dioxide powder described in  claim 1 .