News Column

Researchers Submit Patent Application, "Sanitary Ware", for Approval

February 6, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Yagi, Shinichi (Fukuoka, JP); Hino, Takahiro (Fukuoka, JP); Ichiki, Tomoyasu (Fukuoka, JP); Amemori, Hiroaki (Fukuoka, JP); Takano, Satoshi (Fukuoka, JP); Tokudome, Hiromasa (Kanagawa, JP), filed on March 28, 2012, was made available online on January 23, 2014.

The patent's assignee is Toto Ltd.

News editors obtained the following quote from the background information supplied by the inventors: "Some sanitary wares are known for having a photocatalyst layer provided on the surface of the sanitary ware, for example, the surface of toilet bowls and such sanitary wares can suppress the deposition of contaminants thereon by a hydrophilicity developed upon exposure of the photocatalyst layer to ultraviolet light, and thus have an improved water-flushing function. Such treated sanitary wares can suppress the deposition of contaminants thereon by a hydrophilicity and, at the same time, can suppress bacterial growth by photocatalytic decomposition activity. By virtue of these properties, a cleaning burden can be highly alleviated.

"For such sanitary wares, JP H09(1997)-78665 (PTL 1) discloses toilet bowls that have on their surface a layer containing titanium oxide and silica and suppress the deposition of contaminants by a hydrophilicity developed by exposure to ultraviolet light. Further, JP H11(1999)-228865 (PTL 2) proposes the use of a titanium alkoxide and a silicon alkoxide from the viewpoint of enhancing the hardness of the photocatalyst layer. Furthermore, JP H10(1998)-114546 (PTL 3) discloses that the activity of the photocatalyst can be maintained for a long period of time by covering a titanium oxide layer with a zirconium alkoxide and firing the assembly.

"In the sanitary ware having the photocatalyst layer, it has become apparent that, since the sanitary ware is placed under a relatively wet environment, the photocatalyst layer is deteriorated by water. In particular, it has become apparent that ions dissolved in tap water seem to accelerate the deterioration. Accordingly, the photocatalyst layer provided on the surface of the sanitary ware should be resistant to water (this property will be hereinafter sometimes referred to as water resistance). In addition, while the photocatalyst layer may reduce the frequency of cleaning required, the photocatalyst layer is exposed to a sever condition such as scrubbing the surface with a brush in cleaning. Accordingly, a high level of abrasion resistance is required of the photocatalyst layer provided on the surface of the sanitary ware."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "The present inventors have now found that a photocatalyst layer on the surface of a glaze on a sanitary ware, which is good in water resistance and abrasion resistance while maintaining a good photocatalytic activity can be achieved with an oxide film constituting the photocatalyst layer obtained by co-firing a precursor of titanium oxide and a precursor of zirconium oxide. The present invention has been made based on such finding.

"Accordingly, an object of the present invention is to provide a sanitary ware with a photocatalyst layer provided thereon, the photocatalyst layer having a high level of water resistance and abrasion resistance while maintaining a good photocatalytic activity, and a process for producing the same.

"According to one aspect of the present invention, there is provided a sanitary ware comprising a glaze layer and a photocatalyst layer provided on the glaze layer, wherein the photocatalyst layer is an oxide film comprising a co-fired product of a precursor of titanium oxide and a precursor of zirconium oxide and contains 65 to 90% by mass of titanium oxide and 10 to 35% by mass of zirconium oxide.

"According to another aspect of the present invention, there is provided a process for producing the above sanitary ware, the process comprising at least applying a solution containing at least a precursor of titanium oxide and a precursor of zirconium oxide on a surface of the sanitary ware and then firing the coating to form a photocatalyst layer.

DESCRIPTION OF EMBODIMENTS

"Definition

"The term 'sanitary ware' as used herein means a ceramic ware product used in toilets and around lavatories, specifically toilet bowls, urinals, strainers for urinals, flush tanks for toilets or urinals, washbowls in washstands, or wash hand basins. The term 'ware' means, among ceramic wares, those that have a degree of body sintering that is somewhat water-absorptive and have a surface to which a glaze has been applied.

"Photocatalyst Layer

"The sanitary ware according to the present invention has on its surface a photocatalyst layer formed of an oxide film that is a co-fired product of a precursor of titanium oxide and a precursor of zirconium oxide.

"In the present invention, titanium alkoxides and titanium chelates are suitable as the precursor of titanium oxide. The titanium alkoxide is represented by general formula: Ti(OR).sub.4 and is not particularly limited as long as photocatalytic titanium oxide is formed by hydrolysis. In the formula, a part of (OR) may be substituted by acetyl acetonate (C.sub.5H.sub.7O.sub.2) or ethyl acetoacetate (C.sub.6H.sub.9O.sub.3). In a preferred embodiment of the present invention, the titanium alkoxide is such that R moiety that is an organic group in the alkoxide (RO--) is a lower (preferably C.sub.1-6) alkyl group. Specific examples of preferred titanium alkoxides include tetraethoxytitanium, tetraisopropoxytitanium, tetra-n-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium, titanium diisopropoxybis(acetyl acetonate), titanium diisopropoxybis(ethyl acetoacetate), and mixtures thereof. For example, titanium tetraacetyl acetonate may be mentioned as the titanium chelate.

"Zirconium alkoxide and zirconium chelate are suitable as the precursor of zirconium oxide. The zirconium alkoxide is basically represented by general formula Zr(OR).sub.4 and is not particularly limited as long as zirconium oxide is formed by hydrolysis. In the formula, a part of (OR) may be substituted by acetyl acetonate (C.sub.5H.sub.7O.sub.2) or ethyl acetoacetate (C.sub.6H.sub.9O.sub.3). In a preferred embodiment of the present invention, the zirconium alkoxide is such that R moiety that is an organic group in the alkoxide (RO--) is a lower (preferably C.sub.2-6) alkyl group. Specific examples of preferred zirconium alkoxides include zirconium tetraethoxide, zirconium tetraisopropoxide, zirconium tetrabutoxide, zirconium tributoxy monoacetyl acetonate, zirconium dibutoxybis(ethyl acetoacetate), zirconium monobutoxy acetyl acetonate bis(ethyl acetoacetate), and mixtures thereof. For example, zirconium tetraacetyl acetonate may be mentioned as the zirconium chelate.

"In the present invention, an oxide film is a co-fired product of a precursor of titanium oxide and a precursor of zirconium oxide. The firing may be carried out under temperature and time conditions that are necessary for the conversion of the precursor of titanium oxide to photocatalytic titanium oxide and the conversion of precursor of zirconium oxide to zirconium oxide. The temperature and the time may be properly determined as long as titanium oxide having a good photocatalytic activity and a water-resistant and abrasion-resistant oxide film are obtained. For example, the firing may be carried out at a temperature of 700 to 800.degree. C. for 0.5 to 3 hr, preferably at a temperature of 725 to 775.degree. C. for about 1 to 2 hr.

"In the present invention, the photocatalyst layer formed of an oxide film that is a co-fired product of a precursor of titanium oxide and a precursor of zirconium oxide has a high level of water resistance and abrasion resistance. The reason for this has not been elucidated yet but is considered as follows. The following explanation is hypothetical, and the present invention is not bound thereby. It is believed that a Zr--O--Ti bond that is chemically and physically stronger than a Ti--O--Ti bond is formed by the deposition of zirconium oxide on the surface of photocatalytic, that is, crystalline, titanium oxide, and, further, a Zr--O--Si bond that is chemically and physically stronger than a Ti--O--Si bond is formed by the deposition of zirconium oxide at an interface between the photocatalyst layer and the glaze layer. It is considered that this bond is superior in water resistance and abrasion resistance to titanium oxide obtained by using as a starting compound a titanium alkoxide alone, or titanium oxide that contains a Ti--O--Si bond having a lower chemical stability than a Ti--O--Ti bond and is obtained by using as starting material titanium and a silicon alkoxide. The difference in bond is considered to be also reflected in a physical structure of an oxide film, that is, a photocatalyst layer. The difference is microscopically small and cannot be identified by various measurement or identification methods at the present time. The resultant oxide film, however, apparently has a high level of water resistance and abrasion resistance.

"In the present invention, the photocatalyst layer contains 65 to 90% by mass of titanium oxide and 10 to 35% by mass of zirconium oxide. The content of titanium oxide is preferably 67.5 to 85% by mass, more preferably 70 to 80% by mass. The content of zirconium oxide is preferably 15 to 32.5% by mass, more preferably 20 to 30% by mass.

"Sanitary Ware

"Body of Sanitary Ware

"The ware body of the sanitary ware according to the present invention is not particularly limited and may be a conventional sanitary ware body. A glaze layer may be provided as an intermediate layer under the glaze layer having the surface texture of the outermost layer.

"Production Process of Sanitary Ware Body

"The sanitary ware body according to the present invention is preferably produced by the following method. Specifically, at the outset, a ware body is prepared by casting, utilizing a water absorptive mold, of a sanitary ware body slurry prepared from raw materials such as quartz sand, feldspar, and clay into a proper shape. Thereafter, the glaze material is coated by a properly selected commonly used method such as spray coating, dip coating, spin coating, or roll coating onto the dried cast body surface. The cast body with a precursor layer of the surface glaze layer formed thereon is then fired. The firing temperature is preferably a temperature of 1,000 to 1,300.degree. C. at which the ware body is sintered and the glaze is softened.

"Glaze

"The composition of the glaze for the formation of the glaze layer in the sanitary ware according to the present invention is not particularly limited as long as the above surface texture can be realized. In the present invention, the glaze material may be generally defined as a mixture of naturally occurring mineral particles such as quartz sands, feldspars, and limestones. Examples of pigments include cobalt compounds and iron compounds, and examples of opacifiers include zirconium silicate and tin oxide. Amorphous glazes refer to glazes obtained by melting a glaze material formed of a mixture of the naturally occurring mineral particles and the like at an elevated temperature and rapidly cooling the melt for vitrification, and, for example, frit glazes are suitable for use.

"In a preferred embodiment of the present invention, the preferable glaze has a composition comprising, for example, 10 to 30% by weight of feldspar, 15 to 40% by weight of quartz sand, 10 to 25% by weight of calcium carbonate, not more than 10% by weight of each of corundum, talc, dolomite, and zinc flower, and not more than 15% by weight in total of an opacifier and a pigment.

"Production Process

"The sanitary ware according to the present invention can be produced by applying, preferably coating, a solution containing titanium alkoxide and zirconium alkoxide, that is, a coating liquid, on a sanitary ware having a glaze layer and free from a photocatlyst layer and then firing the coating.

"In addition to titanium alkoxide and zirconium alkoxide, other ingredients may be added to the coating liquid. Examples thereof include surfactants such as leveling agents that are added from the viewpoint of enhancing evenness of the photocatalyst layer.

"Solvents for the coating liquid are not particularly limited as long as titanium alkoxide and zirconium alkoxide are dissolved. Examples of such solvents include alcohols such as ethanol, isopropanol, and n-butanol; cellosolves such as methyl cellosolve and butyl cellosolve; aromatic hydrocarbons such as toluene and xylene; and esters such as ethyl acetate and butyl acetate.

"Preferred methods for the application of the coating liquid on the sanitary ware having a glaze layer and free from a photocatlyst layer include commonly extensively used methods, for example, brush coating, roller coating, spray coating, roll coater coating, flow coater coating, dip coating, flow coating, and screen printing. After coating of the coating liquid on the sanitary ware, firing is carried out. The firing temperature and time may be in the above respective ranges."

For additional information on this patent application, see: Yagi, Shinichi; Hino, Takahiro; Ichiki, Tomoyasu; Amemori, Hiroaki; Takano, Satoshi; Tokudome, Hiromasa. Sanitary Ware. Filed March 28, 2012 and posted January 23, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=2722&p=55&f=G&l=50&d=PG01&S1=20140116.PD.&OS=PD/20140116&RS=PD/20140116

Keywords for this news article include: Quartz, Titanium, Toto Ltd, Light Metals, Photocatalyst, Nanotechnology, Photocatalytic, Silicon Dioxide, Emerging Technologies.

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Source: Politics & Government Week


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