Multifunctional material having photocatalytic function

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a multifunctional material in which an action based on a photocatalytic function such as deodorization is added to a relatively low melting point base material that softens at a temperature at which a photocatalyst layer is formed by firing.

【0002】

[Previous technology]

Many proposals have been made for forming the photocatalyst layer on various substrates. As the method, a dry method such as sputtering or ion plating, a sol-gel method, an alkoxide method and a wet method are used. The wet method is often used because of its simplicity. For example, a photocatalyst layer is formed by applying titanium alkoxide on a glass substrate with Jinkaihei No. 5-7394, drying it, and then firing it at several 100 ° C. By irradiating the photocatalyst layer with ultraviolet rays, those that decompose organic substances in water can be mentioned.

【0003】

[Problems to be solved]

The alkoxide method proposed above is excellent in that a thin film can be formed at a relatively low temperature, and when a base material such as Pyrex glass or quartz glass that does not easily soften to about 500 ° C is used as a raw material. Is effective for. However, when a material having a low melting point such as soda glass is used as a base material, the base material has already started to soften at the temperature at which the thin film is formed, and the formed photocatalytic thin film is buried in the base material. Therefore, the light does not reach the photocatalyst layer and the photocatalyst function cannot be exhibited.

【0004】

[Means for solving problems]

The present invention has been made in view of the above problems, and the gist thereof is that the photocatalyst layer is an outside air in a multifunctional material having a photocatalyst function in which a photocatalyst layer mainly composed of a photocatalyst is held on the surface of a low melting point base material. A multifunctional material having a photocatalytic function, which is exposed so as to be in contact with the base material and is fixed to the base material via a layer having a melting point higher than that of the base material, and is a base material having a low melting point, for example, relatively inexpensive. The purpose is to form a photocatalyst layer on soda glass or the like that is easy to process with.

【0005】

It will be described in detail below. The low melting point base material refers to a base material having a softening point lower than the temperature at which the photocatalyst raw material is fired to form the photocatalyst layer. For example, when alkoxide is used, it is soda glass or the like which is a base material of 300 to 500 ° C or less.

【0006】

The photocatalytic layer mainly composed of a photocatalyst means that it may contain other metals such as copper, silver and zinc, and other oxide semiconductors having photocatalytic activity such as zinc oxide. Further, in the state where the photocatalyst layer is exposed so as to be in contact with the outside air, the photocatalyst particles must be exposed on the outermost layer of the base material in order to have both deodorant property and antibacterial property. However, in the case of an application in which only the deodorizing function is sufficient, the open pore portion when the photocatalyst layer is a porous layer is also included.

【0007】

The high melting point base material layer is a base material having a higher softening point than the low melting point base material. Generally, a base material having a high melting point has a high softening point, so it is decided to grasp the base material at a melting point that is easy to evaluate. What is required of the refractory base material layer, which is an intervening layer, is that, for example, in the case of forming a photocatalyst layer by the alkoxide method of titanium, it is difficult to soften at the crystallization temperature of highly active anatase-type titania. Further, when the photocatalyst layer is formed using sol or the like as a starting material, sufficient heat treatment is still required because the photocatalyst layer does not peel off, and it is necessary that the photocatalyst layer is not easily softened at the heat treatment temperature. In any case, it is necessary that the temperature does not easily soften even at a temperature exceeding 300 ° C, preferably 400 ° C or higher. For example, as a glass material, specifically, a glass that does not contain low melting point components such as lead and boron, and a glass that does not contain a large amount of alkali metal components such as sodium and potassium as much as soda glass can be basically applied. .. Further, the structure fixed to the low melting point base material simply means that it can be configured as an integral body of the multifunctional material, and does not need to be directly bonded.

【0008】

[Example]

(Example 1) Before the titanium oxide coating was applied to the soda glass, the surface of the soda glass was coated with silica. Silica coating on the surface of 10 cm square soda glass was performed by the following method. First, tetraethoxysilane, 36% hydrochloric acid, pure water, and ethanol are mixed at a ratio of 6: 2: 6: 86 (weight ratio). At this time, it generates heat, so leave it for about 1 hour. This was flow coated on soda glass. Next, a coating solution is prepared. The coating solution is titanate tetraethoxydo and ethanol 1: It was prepared by further adding 36% hydrochloric acid to titanate tetraethoxydo in an amount of 10% by weight, which was mixed at 9 (weight ratio). The amount of 36% hydrochloric acid added here is preferably 1% by weight or more and 30% by weight or less, preferably 5% by weight or more and 20% by weight or less, based on titanate tetraethoxydo. By adding an appropriate amount of hydrochloric acid, it is possible to prevent cracks from forming during drying and firing in the subsequent process. That is, if the amount of hydrochloric acid is too small, crack prevention cannot be sufficiently achieved, and if the amount of hydrochloric acid is too large, the hydrolysis of titanate tetraethoxydo is accelerated by the increase in the amount of water contained in the hydrochloric acid reagent, and a homogeneous coating is applied. The membrane becomes difficult. The solution is then flow coated on the surface of the soda glass substrate in dry air. Here, dry air does not mean air that does not contain water at all, but refers to air that has less water than normal air. At this time, if the coating is performed in normal air without drying treatment, the hydrolysis of titanate tetraethoxydo is accelerated by the moisture in the air, and the amount of one coating film becomes too large, so that cracks occur during drying and firing in the subsequent process. Is easier to enter. In addition, it becomes difficult to control the amount of the coating film due to the accelerated hydrolysis. In order to prevent cracks, the amount of titanium oxide supported at one time is preferably 100 μg / cm2 or less. This time, the amount of titanium oxide supported at one time was 45 μg / cm2. After that, a titanium oxide film is formed by drying in dry air for 1 to 10 minutes. Titanium oxide can be obtained by the steps up to this point according to the principle shown below. Here, the starting material is titanate tetraethoxyde, which is a kind of titanium alkoxide (the same thing occurs in principle even if other titanium alkoxides are used). This titanate tetraethoxyde hydrolyzes with water in dry air mainly during flow coating to produce titanium hydroxide. Further, a dehydration condensation reaction occurs during drying, and amorphous titanium oxide is formed on the substrate. The titanium oxide particles produced at this time have high purity at about 3 to 150 nm. Therefore, this titanium oxide is characterized by sintering at a lower temperature than titanium oxide obtained by other manufacturing methods. There is a sign. The composite member obtained by the above method was further fired at 300 ° C to 500 ° C to obtain a multifunctional material. If necessary, the steps from the coating film of titanate tetraethoxydo to firing were repeated to apply a thick coat of titanium oxide.

【0009】

The deodorant property, abrasion resistance property, and antibacterial property of the sample thus obtained were evaluated. The results are shown in Table 1.

【0010】

[table 1]

<img file="JPH08108075A_D0001.tif" />【0011】

Regarding the deodorant characteristics, 30 when the sample was placed in a cylindrical container with a diameter of 26 cm and a height of 21 cm in which the initial concentration of methyl mercaptan was adjusted to 2 ppm, and a 4 W BLB fluorescent lamp was irradiated 8 cm away from the sample. It was evaluated by measuring the methyl mercaptan removal rate after minutes (R30 (L)) and the methyl mercaptan removal rate after 30 minutes when light was blocked (R30 (D)). The wear resistance characteristics were evaluated by performing sliding wear using a plastic eraser and comparing changes in appearance. The evaluation index at that time is shown below. : No change for 40 round trips : The titanium oxide film peels off due to scratches caused by sliding 10 times or more and less than 40 times. Δ: The titanium oxide film peels off due to scratches caused by sliding 5 times or more and less than 10 times. ×: Scratches occur after sliding less than 5 times, and the titanium oxide film peels off. For antibacterial properties, Escherichia coli Tested using W3110 strain). 0.15 ml (1 to 50000 CFU) of the bacterial solution was dropped on the outermost surface of the multifunctional material sterilized with 70% ethanol in advance, placed on a glass plate (100 × 100), and brought into close contact with the outermost surface of the base material to prepare a sample. After irradiating a white lamp (5200 lux) for 30 minutes, wipe the bacterial solution of the irradiated sample and the sample maintained under light-shielding conditions with sterile gauze and collect in 10 ml of physiological saline to determine the survival rate of the bacterial and evaluate it. And said. The evaluation index is shown below. +++: E. coli survival rate less than 10% ++: E. coli survival rate of 10% or more and less than 30% +: E. coli survival rate 30% or more and less than 70% -: E. coli survival rate of 70% or more [0012]

At a firing temperature of 300 ° C, the sliding test showed a good result of , but R30 (L) was 0%. It is considered that this is because the amorphous titanium oxide is not crystallized into anatase. At 400 ° C, where anatase can be confirmed by X-ray in a synthetic experiment, the sliding test also showed good results with , but R30 (L) also improved to about 60%. The antibacterial property was also +. In addition, the sliding test showed good results at 500 ° C as well, but R30 (L) also improved to about 60%. When the temperature was further increased, the soda glass of the base material was deformed at 550 ° C, and a multifunctional material could not be manufactured.

【0013】

(Example 2) Metal particles were supported in order to further improve the photocatalytic properties of the sample obtained in Example 1. The photocatalyst also undergoes a reduction reaction at the same time as the oxidation reaction. If the reduction reaction does not proceed, the electrons are not consumed, the particles are charged, and the oxidation reaction does not proceed. This seems to be the reason why R30 (L) remained at 60% in Example 1. To prevent this, metal particles may be supported on the titanium oxide particles to allow electrons to escape and prevent charging. The metal particles were supported by the following method. A solution of the metal salt was flow-coated on the photocatalyst, and a BLB fluorescent lamp 20 W was irradiated at a distance of 20 cm for 1 minute. As the metal salt solution, a 1 wt% ethanol solution of copper acetate was used in the case of supporting copper, and a 1 wt% ethanol / water = 1/1 mixed solution of silver nitrate was used in the case of silver. After irradiation, it was washed and dried. Here, the reason why the solution containing ethanol was used without using the metal salt aqueous solution is that the metal salt solution has good wettability with respect to the sample. The deodorant property, wear resistance property, and antibacterial property of the sample thus obtained were evaluated. The results are shown in Table 2. Only the sample obtained at a firing temperature of 500 ° C. was used.

【0014】

[Table 2]

<img file="JPH08108075A_D0002.tif" />【0015】

The sliding test showed good results with . In addition, R30 (L) improved dramatically to 98%. Antibacterial property was also +++.

【0016】

(Comparative Example) In Example 1, the same was applied except that the silica coating was not applied. That is, a 10 cm square soda glass was coated with titanium oxide. The results are shown in Table 3.

【0017】

[Table 3]

<img file="JPH08108075A_D0003.tif" />【0018】

As a result, the sliding test showed good results at 300 ° C, 400 ° C, and 500 ° C, but for R30 (L), the process from coating film to firing of titanate tetraethoxydo was repeated 10 times. Was also 0%. The antibacterial properties were all-. It is considered that the reason why R30 (L) is bad at 300 ° C is that titanium oxide has not yet crystallized from amorphous titanium oxide to anatase. On the other hand, at 400 ° C and 500 ° C, amorphous titanium oxide has already crystallized into anatase, and it cannot be explained that R30 (L) is bad for the above reasons. It is considered that this is because the titanium oxide film is buried in the glass because the soda glass of the base material is softened.

【0019】

[Effect of the invention]

Even if the base material has a relatively low melting point, a multifunctional material having deodorant and antibacterial properties can be produced by inserting a layer having a high melting point between the base material and the photocatalyst layer.