Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
1997-05-15
2001-02-20
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C502S527120, C430S531000, C430S947000, C427S126100, C427S126300, C427S126500, C427S126600, C427S212000, C427S217000, C428S312200, C428S312600, C428S312800
Reexamination Certificate
active
06191062
ABSTRACT:
TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
The present invention relates to a photocatalytic functional material having many functions of antimicrobial, preventing smell or stainproof, or decomposition of harmful substances (NOx, and the like) based on the photocatalytic function. Particularly, it relates to a photocatalytic functional material which is prepared by the step of low temperature (about 300° C. or lower).
PRIOR ART
As a method for adding a function of antimicrobial property, stainproof property and deodorizing property, and the like, to the surface of a substrate, a method of forming a thin film of a photocatalyst such as an anatase type titanium oxide, and the like, on the surface of a substrate has heretofore been proposed. As one of the methods, there is a method of kneading anatase type titanium oxide particles with a binder and coating the resulting material to the surface of a substrate and subjecting to heat treatment. As the other method, there is a method disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 253544/1993 filed by the present applicant. This method is a method for producing a plate-shaped member (tile, and the like) which is to constitute a wall surface, floor surface or a ceiling surface of a residential space. In this method, a binder layer is formed on the surface of the plate-shaped member, a photocatalyst fine powder mainly comprising an anatase type titanium oxide is so sprayed on the surface of the binder layer as to expose a part of the powder from the binder layer and adhered thereto, and then, after melting the binder layer by heating within the range of 300° C. or higher and less than 900° C., the binder layer is solidified by cooling.
PROBLEMS TO BE SOLVED BY THE INVENTION
In the above-mentioned method wherein anatase type titanium oxide particles are kneaded with a binder and the material is sprayed to the surface of a substrate, and heat treatment is subjected, almost all the portion of active sites of the photocatalyst particles are covered by the binder so that characteristics by the photocatalyst function such as deodorizing property, and the like, are not sufficient.
Also, according to the method of Japanese Laid-Open Patent Publication (Kokai) No. 253544/1993, deodorizing property, and the like, are good if the material is subjected to heat treatment at 300° C. or higher to less than 900° C. However, by a low temperature heat treatment of less than 300° C., additives in the binder cannot sufficiently be removed so that good deodorizing property, and the like, cannot be obtained. Accordingly, it was difficult to add good photocatalytic functions such as excellent deodorizing characteristics, and the like, to a substrate such as a plastic having poor heat resistance.
Also, according to the method of Japanese Laid-Open Patent Publication (Kokai) No. 253544/1993, when the heat treatment temperature is less than 800° C., the photocatalyst layer forming the surface of a substrate becomes porous with a porosity of 40% or more. Further, it has a structure in which the photocatalyst particles are exposed to the outermost surface so that there is a tendency that the surface is easily peeled off.
The present invention has been accomplished in view of the above circumstances, and an object thereof is to provide a photocatalytic functional material in which a functional material having good photocatalytic activity can be prepared with a low temperature heat treatment, and the surface of the functional material has a high mechanical strength.
MEANS FOR SOLVING THE PROBLEM
In order to solve the above problems, the photocatalytic functional material of the present invention comprises a surface layer (a photocatalytic functional layer) containing a photocatalyst, an electron-trapping metal, and a photo-degradation-resistant matrix.
In the present invention, a mechanism of showing photo-catalytic functions such as deodorant, antimicrobial activities, and the like, whereas almost all the part of the photocatalyst (particles, and the like) in the photocatalyst functional layer are covered by the photodegradation resistant matrix (a thermosetting resin, and the like) can be supposed as mentioned below.
A photocatalytic reaction on the photocatalyst is considered to proceed as mentioned below. First of all, as the first step, the following reaction in which a photon decomposes to an electron and a positive pore occurs.
h&ngr;→h
+
+e
−
(1)
Next, the generated positive pore reacts with oxygen or water in air or in the layer to form an active oxygen species. The chemical formula in which it is reacted with water is shown below.
H
2
O →H
+
+OH
−
(2)
OH
−
+h
+
→OH· (3)
Here, the generated active oxygen species OH acts on a bad smell component or bacteria to show a deodorizing property or an antimicrobial property.
Provided that, the reaction of the formula (3) competes to the following reaction wherein the positive pore and an electron combine again to return to a photon as shown in the formula (4) below.
h
+
+e
−
→h&ngr; (4)
Subsequently, the case where the photocatalyst particles are exposed to air is considered. In this case, oxygen or water in air can directly react with a photocatalyst so that oxygen or water exists on the photocatalyst particles in addition to positive pores and electrons when the decomposition reaction of light represented by the formula (1) is caused. In this case, the formula (3) and the formula (4) become competition reaction so that active oxygen is formed by the formula (3) with a certain possibility (about 20% or so in the case of an anatase type titanium oxide). According to the action of the active oxygen, a photocatalytic reaction such as deodorization, antimicrobial property, and the like, is to be caused.
Next, the case where the photocatalytic particle is completely covered by a matrix in the state where no electron-trapping metal exist around the surroundings is considered. The photocatalyst is covered by a matrix so that oxygen or water in air cannot directly contact with the photocatalyst. Accordingly, for reacting oxygen or water with a positive pore according to the formula (3), it is necessary to diffuse the oxygen or water in air onto the photocatalyst, diffuse the positive pore to the outermost layer of a layer in which the oxygen or water exists, or cause both of the above diffusion. For this reason, an induction term is caused. On the other hand, an electron has already exist on the photocatalyst when the decomposition reaction of a photon occurs. Thus, before causing the above diffusion, that is, during the induction term, the reaction due to the formula (4) occurs, and thus, the active oxygen generating reaction due to the formula (3) seldom occurs.
From the above matter, when almost all part of the photocatalyst is covered by the matrix in the state that electron-trapping metals are not present at the surroundings, an active oxygen occurs with a certain possibility only at the portion where the photocatalyst is exposed. Thus, an amount of the formed active oxygen is little, whereby sufficient photocatalytic function such as deodorization, antimicrobial property, and the like, cannot be exhibited.
On the other hand, when electron-trapping metals (ion, particle, and the like) exist at the neighbor of the photocatalyst, even when the photocatalyst is completely covered by the matrix, electrons formed by the formula (1) are captured by these metals so that the recombination reaction of the formula (4) hardly occurs whereby positive pores remain for a long period of term without disappearance. Accordingly, even when the photocatalyst is covered by the binder and the active oxygen forming reaction of the formula (3) has an induced term by the reason as mentioned above, the positive pores become difficultly extinct by the formula (4) whereby the active oxygen formation of the formula (3) occurs after the induced term.
According to the above mechanism, since the
Chikuni Makoto
Hayakawa Makoto
Watanabe Toshiya
Jones Day Reavis & Pogue
Toto Ltd.
Wood Elizabeth D.
LandOfFree
Photocatalytic functional material and method for producing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Photocatalytic functional material and method for producing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photocatalytic functional material and method for producing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2580591