Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1998-08-31
2002-06-18
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S158000, C502S236000, C502S242000, C106S287190
Reexamination Certificate
active
06407033
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to photocatalyst-carrying structures used for antifouling, cleaning water, deodorization, pasteurization, treatment of waste water, water decomposition, algae growth control and various chemical reactions and to coating material composites to produce the said photocatalyst-carrying structures. This invention relates to, in particular, to photocatalyst-carrying structures and photocatalyst coating materials, which can be used in the environment of high temperature and humidity and in the outdoor environment in which they should be alkali resistant.
BACKGROUND ART
Various types of carrier materials carrying a photocatalyst have been proposed. Examples are (A) light transmissible materials such as cellulose nitrate, glass, poly(vinyl chloride), plastics, nylon, methacrylic resins and polypropylene (Japanese Patent Laid-Open No. Sho 62-66861), (B) polypropylene fibers and ceramics (Japanese Patent Laid-Open No. Hei 2-68190) and (C) glass, ceramics, nylon, acrylic resin and polyester (Japanese Patent Laid-Open No. Hei 5-309267). However, it has been reported that, among the materials mentioned above, those comprising an organic substance used as its main component had a disadvantage of the decomposition or deterioration of the organic material when it carried a photocatalyst due to the catalytic reaction and that their durability was a problem (Fumiaki Ootani; Kobunshi Kako Vol. 42, No 5, page 18 (1993) and “Titanium Dioxide” by Manabu Kiyono, published by Gihodo, page 165).
In case that a carrier material is inorganic, such as glass or ceramic, the use of organic polymer resin as an adhesive for carrying a photocatalyst lowers the catalytic activity due to covering the surface of the photocatalyst particles by the resin. Besides, the resin is decomposed or deteriorated by the photocatalytic activity and the photocatalyst is exfoliated. The result is a problem in durability.
In case that a carrier material is an inorganic heat-resistant material, the following methods have been employed: spattering in which no organic materials are left at all (Japanese Patent Laid-Open No. Sho 60-044053), coating and baking of organic titanate (Japanese Patent Laid-Open No. Sho 60-118236) and spraying and baking of titania sol (Japanese Patent Laid-Open No. Hei 5-253544). These methods had problems of baking a substrate at a high temperature in order to produce and crystallize photocatalyst particles on the carrier and to adhere the photocatalyst with the carrier as well as difficulty in carrying the photocatalyst over a large area and very high production cost.
In order to carry a photocatalyst on glass fiber paper, a method to use a metal oxide sol as an adhesive has been proposed (Japanese Patent Laid-Open No. Hei 5-309267). Metal oxide sols, such as silica sol, have very weak bonding strength because it is based on the van der Waals force (Fine Ceramics, Vol. 1, page 216-223, 1980) and insufficient adhesiveness and alkali resistance. A baking process at a high temperature was required. The method was thus unable to apply for all carriers including general-purpose resins decomposed easily by heat.
In case that photocatalyst powder is carried on a metal oxide gel such as silica or clay mineral, it has been reported that the photocatalytic decomposition reaction of propione aldehyde gas is accelerated thanks to the effect of the carrier working as an adsorbent (Symposium “Recent Development in Photocatalytic Reaction”, previous manuscripts, by the Study of Photofunctional Materials, No.2-11, page 39, 1994). There have been no reports that photocatalyst-carrying structures excellent in adhesiveness and alkali resistance were obtained while maintaining high catalytic activity of a photocatalyst uniformly dispersed in a metal oxide gel.
There have been many attempts to adhere a photocatalyst directly on a carrier with a silica compound such as silica sol, colloidal silica, a hydrolysate of silicon alkoxide or polyorganosiloxane (Japanese Patent Laid-Open Nos. Hei 4-174679, Hei 6-296874 and Hei 7-171408). In each case, the surface of the photocatalyst layer was eroded and exfoliated when a photocatalyst-carrying structure was contacted with an aqueous solution of 5% by weight of sodium carbonate for 24 hours. It did not pass the alkali-resistance test defined in JIS K5400.
A method to fix a photocatalyst with fluororesin has been proposed (Japanese Patent Laid-Open No. Hei 6-315614). Its disadvantages are that fluororesin is expensive and that most surface of a catalyst particle should be covered with the fluororesin in order to adhere photocatalyst particles strongly on a carrier. As a result the catalytic activity becomes lower than that of powder. It has been tried that a photocatalyst was mixed with a non-decomposable binder such as fluororesin or polyorganosiloxane and adhered onto a substrate (EP-0633064). The products were unsatisfactory to solve practical problems of adhesiveness and alkali resistance.
Japanese Patent Laid-Open No. Hei 8-164334 has disclosed composites to produce a photocatalyst film, which consists of fine particles of titanium oxide of 1-500 nm, products of partially hydrolyzed silicon tetraalkoxide and a solvent. A photocatalyst film formed by using the said composite was exfoliated after being immersed in an aqueous solution of 5% by weight of sodium carbonate for 24 hours. The alkali resistance was thus unsatisfactory.
The following three themes should be solved to use a photocatalyst carried on a carrier outdoors or in the environment of high temperature and humidity:
1. A photocatalyst film adheres well with a carrier;
2. The photocatalytic activity of a photocatalyst film is not reduced due to a photocatalyst carried on a carrier; and
3. The carried photocatalyst film maintains bonding strength and is durable for a long time.
When a photocatalyst is used outdoors, alkali resistance is important, same as for paints and coating materials for outside walls. Particularly it is essential to resist aqueous alkaline solutions because it is impossible to avoid contacting with alkaline components seeping out from concrete, mortar or tile joints when used for outside walls and their surroundings. Therefore, an alkaline resistance test using an aqueous solution of 5% by weight of sodium carbonate is defined in JIS-K5400 of the Japan Industrial Standards for general paints. The present invention aims at providing structures carrying a photocatalyst which can be used for antifouling, cleaning water, deodorization, pasteurization, treatment of waste water, water decomposition, algae growth control and various chemical reactions and for solving the above-mentioned problems, and coating materials to produce the said structures.
DISCLOSURE OF THE INVENTION
In order to solve the problems mentioned above, composites of photocatalyst coating materials of this invention are (Composition 1) is a composite of photocatalyst coating materials which is characterized in containing a photocatalyst and a zirconium compound and/or tin compound for endowing alkali resistance.
As a more detailed composition of Composition 1, (Composition 2) is that the zirconium or tin compound is a zirconium or tin compound represented by Formula [I]
MO
x
L
y
Formula [I]
wherein M is zirconium or tin, x is 0, 1 or 2, L is a substituent selected from the group consisting of hydroxyl, nitrate, carbonate, ammonium, chlorine, carboxyl of 1 to 6 carbons, alkoxyl of 1 to 6 carbons, glycol of 1 to 6 carbons and substituents able to form a metal chelate compound by substituting the said alkoxy group, y is 0 or an integer of 1 to 4, and 2x+y=4, or a mixture thereof;
As a more detailed composition of Composition 1 or 2, (Composition 3) is that the zirconium or tin compound is a compound selected from the group consisting of zirconium or tin oxide, hydroxide, oxyhydroxide, oxycarbonate, alkoxides of 1 to 4 carbons and hydrolysates of the said alkoxides or a mixture thereof;
As a more detailed composition of one of Compositions 1
Kimura Nobuo
Yoshimoto Tetsuo
Bell Mark L.
Hailey Patricia L.
Nippon Soda Co. Ltd.
Schneller Marina V.
Venable
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