Particles, aqueous dispersion and film of titanium oxide, and preparation thereof

Abstract

An aqueous titanium oxide-dispersed sol comprising titanium oxide particles dispersed in water, said sol comprising chloride ions in an amount of 50 to 10,000 ppm by weight as the chlorine element. Titanium tetrachloride is hydrolyzed to form an aqueous titanium oxide-dispersed sol and the chloride ion concentration thereof is controlled. Another aqueous titanium oxide-dispersed sol comprising brookite-type titanium oxide particles dispersed in water, said titanium oxide particles having an average particle size of not more than 0.5 μm and a specific surface area of not less than 20 m2 / g. Addition of titanium tetrachloride to hot water at 75 to 100° C. followed by hydrolysis at 75° C. to the boiling point of the mixture.

Description

[0001] This is a divisional of application Ser. No. 10 / 753,567 filed Jan. 9, 2004, which is a divisional of application Ser. No. 09 / 758,202 filed Jan. 12, 2001, now U.S. Pat. No. 6,774,147, which is a divisional of application Ser. No. 08 / 921,343 filed Aug. 29, 1997, now U.S. Pat. No. 6,340,711, the disclosures of which are incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an aqueous titanium oxide-dispersed sol, a titanium oxide film formed on a substrate of a ceramic, a synthetic resin or the like from said sol, specific titanium oxide particles, and a process for preparing an aqueous titanium oxide-dispersed sol. The titanium oxide film of the present invention is transparent and is excellent in photocatalytic activity and adhesion to a substrate. [0004] 2. Description of the Related Art [0005] It is known that titanium dioxide (hereinafter simply referred to as “titanium oxide”) has three crystal...

AI Technical Summary

Benefits of technology

[0020] As the result of investigation into titanium oxide films formed from titanium oxide sols, the present inventors have found that chloride ions contained in a titanium oxide sol contribute to the transparency and adhesivity to the substrate of the titanium oxide film; a titanium oxide sol having a certain concentration of chloride ions provides a titanium oxide film having improved transparency and adhesivity; and the brookite-type titanium oxide with a large energy gap is particularly excellent in the photocatalytic activity.

Problems solved by technology

It was reported that formation of fine brookite-type titanium oxide particles in an liquid phase process was impossible.

As seen from the above, it was difficult to stably produce brookite-type titanium oxide in a liquid phase process.

Therefore, it was difficult to obtain fine brookite-type titanium oxide crystal particles.

As of the brookite-type titanium oxide, a pure material of brookite-type titanium oxide has not been obtained, and it was difficult to obtain fine particles of brookite-type titanium oxide having such a high specific surface area that they can be used as a photosemiconductor since the particles of brookite-type titanium oxide are prepared at such a high temperature that they are sintered.

However, the sols produced by the processes described before rarely provide a titanium oxide film having a high transparency and an illuminator having a brookite-type titanium oxide film as the photocatalyst has not been known.

In the conventional process of hydrolyzing titanium tetrachloride, it was difficult to obtain a titanium oxide sol having a very small particle size and an excellent crystallinity of the titanium oxide particles in the sol and providing a high transparency when formed into a film.

In the process of hydrolyzing titanium alkoxide, the particles of the obtained titanium oxide sol are excellent in powder characteristics including very fine particle size, but the sol includes alcohol, which involves a safety problem that explosion may be caused when the sol is heated to form a titanium film.

To prevent the explosion, a large scale apparatus for preventing the explosion is required and it is economically disadvantageous.

Further, titanium alkoxide is much more expensive than titanium tetrachloride.

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