Method of making titanium dioxide in the shape of columnar particles

Patent metadata

Field	Value
Publication number	US-8926713-B2
Application number	US-201213487370-A
Country	US
Kind code	B2
Filing date	Jun 4, 2012
Priority date	Mar 7, 2006
Publication date	Jan 6, 2015
Grant date	Jan 6, 2015

Abstract

Titanium dioxide which includes particles having a large major-axis length in a large proportion and comprises columnar particles having a satisfactory particle size distribution. A titanium compound, an alkali metal compound, and an oxyphosphorus compound are heated/fired in the presence of titanium dioxide nucleus crystals having an aspect ratio of 2 or higher to grow the titanium dioxide nucleus crystals. Subsequently, a titanium compound, an alkali metal compound, and an oxyphosphorus compound are further added and heated/fired in the presence of the grown titanium dioxide nucleus crystals. Thus, titanium dioxide is produced which comprises columnar particles having a weight-average major-axis length of 7.0-15.0 μm and in which particles having a major-axis length of 10 μm or longer account for 15 wt. % or more of all the particles.

First claim

The invention claimed is:

1. A process for producing titanium dioxide in the shape of columnar particles comprising the first step of heating and firing a titanium compound, an alkali metal compound and an oxyphosphorus compound in the presence of titanium dioxide nucleus crystals having an aspect ratio of 2 or higher, thereby growing titanium dioxide nucleus crystals; the second step of further adding a titanium compound, an alkali metal compound and an oxyphosphorus compound and heating and firing them in the presence of the grown titanium dioxide nucleus crystals; and the third step of forming an aqueous suspension, treating with an alkali and/or an acid to adjust pH of the suspension, heating the treated suspension, and removing soluble salts.

2. A process for producing titanium dioxide according to claim 1 , wherein at the first step, the titanium dioxide nucleus crystals are grown so that the ratio of weight-average major-axis length of the titanium dioxide nucleus crystals after growing to that of the titanium dioxide nucleus crystals reaches 3-7, and at the next second step, the titanium dioxide nucleus crystals are grown so that the ratio of weight-average major-axis length of the produced titanium dioxide to that of the titanium dioxide nucleus crystals reaches 2-5.

3. A process for producing titanium dioxide according to claim 1 , wherein the weight-average major-axis length of the titanium dioxide nucleus crystals used at the first step is 1-4 μm, and that of the titanium dioxide nucleus crystals used at the second step is 3-7 μm.

4. A process for producing titanium dioxide according to claim 1 , wherein the titanium dioxide nucleus crystals used at the first step are produced by heating and firing a titanium compound, an alkali metal compound and an oxyphosphorus compound.

5. A process for producing titanium dioxide according to claim 1 , wherein the step of growing titanium dioxide nucleus crystals by heating and firing a titanium compound, an alkali metal compound and an oxyphosphorus compound in the presence of titanium dioxide nucleus crystals having an aspect ratio of 2 or higher is repeated twice or more to grow titanium dioxide nucleus crystals.

6. A process for producing titanium dioxide according to claim 5 , wherein the titanium dioxide nucleus crystals are grown so that the ratio of weight-average major-axis length of the titanium dioxide nucleus crystals after growing to that of the titanium dioxide nucleus crystals used at each growing step reaches 1.2-7.

Assignees

• Isobe Kaoru
• Chiba Katsuichi
• Sakamoto Takanori
• Ishihara Sangyo Kaisha

Inventors

• Isobe Kaoru
• Chiba Katsuichi
• Sakamoto Takanori

Classifications

• C04B2235/3895

  Non-oxides with a defined oxygen content, e.g. SiOC, TiON · CPC title

• C04B35/62886

  by wet chemical techniques · CPC title

• C01G23/00

  Compounds of titanium {(preparation of Ti-compounds from ores or scraps C22B34/12)} · CPC title

• C04B2235/5409

  expressed by specific surface values · CPC title

• C01P2006/12

  Surface area · CPC title