Titanium-containing finely divided particulate material,...

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Reexamination Certificate

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C106S437000, C106S445000, C423S069000, C423S085000, C428S402000

Reexamination Certificate

active

06610135

ABSTRACT:

TECHNICAL FIELD
This invention relates to a titanium-containing finely divided particulate material having a minute particle diameter, an aqueous sol composition and coating liquid containing the titanium-containing material, a process for producing the titanium-containing material, a process for producing the coating liquid, and a shaped article having a film of the titanium-containing material.
The titanium-containing finely divided particulate material of the invention, and an aqueous sol composition and coating liquid containing the titanium-containing material are suitably used for the formation of a film on a substrate such as a ceramic or a synthetic resin. The thus-formed film exhibits excellent transparency, high photocatalytic activity, good adhesion to a substrate, and high ultraviolet rays absorption.
BACKGROUND ART
It is well known that titanium oxide is produced by hydrolysis of a titanium alkoxide or an aqueous solution of titanium tetrachloride, whereby a titanium oxide sol is produced.
Titanium oxide is known as exhibiting a photocatalytic activity. Recently, there have been proposed many techniques utilizing the photocatalytic activity. For example, a technique has been proposed wherein a titanium oxide sol is coated on the surface of a lighting appliance such as, for example, a glass tube of a fluorescent lamp or a cover thereof to form a film of titanium oxide. According to this technique, the titanium oxide film acts as a photocatalyst to decompose organic substances such as lampblack that adhere to the tube or cover, and thus, contaminants on the glass tube or cover are removed, and the glass or cover is prevented from contaminated.
In the case when a titanium oxide film formed on a substrate such as glass, plastic or other materials is utilized as a photocatalyst, it is required that the film has high transparency as well as high catalytic activity.
DISCLOSURE OF THE INVENTION
Therefore, a primary object of the present invention is to provide a titanium-containing finely divided particulate material which is capable of giving a film exhibiting an enhanced transparency while high catalytic activity is kept.
The inventors made extensive research into a process for producing titanium oxide by hydrolysis of titanium tetrachloride, and found that, by hydrolyzing titanium tetrachloride in an aqueous solution in the presence of a specific carboxylic acid, an aqueous coating liquid (i.e., a sol) of a titanium-containing finely divided particulate material having an average particle diameter of about 0.8 to 50 nm can be obtained, which has hitherto not been obtained; and that a film exhibiting excellent transparency which has hitherto not been obtained, while high catalytic activity is kept, can be formed from the sol. Based on these findings, the present invention has been completed.
In one aspect of the present invention, there is provided an amorphous titanium-containing finely divided particulate material, characterized in that said titanium-containing material has an average particle diameter in the range of 0.8 to 15 nm, and is prepared by hydrolyzing titanium tetrachloride in an aqueous solution in the presence of at least one carboxylic acid selected from oxalic acid, citric acid, tartaric acid, malic acid and succinic acid; and said titanium-containing material exhibits a light transmittance of at least 85% as measured at a wavelength of 450-700 nm for a thickness of 10 mm on an aqueous liquid containing the titanium-containing material in a concentration of 0.1 to 6.5 moles per liter as titanium.
In another aspect of the present invention, there is provided an aqueous sol composition or coating liquid of a titanium-containing finely divided particulate material, characterized by comprising the above-mentioned titanium-containing finely divided particulate material having an average particle diameter in the range of 0.8 to 15 nm, and further comprising at least one carboxylic acid selected from oxalic acid, citric acid, tartaric acid, malic acid and succinic acid; said titanium-containing material being contained in a finely dispersed form in a concentration of 0.1 to 6.5 moles as titanium per liter of the aqueous sol composition or coating liquid; and said coating liquid exhibiting a light transmittance of at least 85% as measured at a wavelength of 450 to 700 nm for a thickness of 10 mm.
In a further aspect of the present invention, there is provided a process for producing the above-mentioned titanium-containing finely divided particulate material or the above-mentioned titanium oxide-containing coating liquid, characterized in that titanium tetrachloride is hydrolyzed in an aqueous liquid in the presence of at least one carboxylic acid selected from oxalic acid, citric acid, tartaric acid, malic acid and succinic acid.
In a further aspect of the present invention, there is provided a shaped article comprising a shaped substrate and a film formed on a surface of the substrate; said film comprising the above-mentioned titanium-containing finely divided particulate material.


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