Formation of member having photocatalytic action

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a member having a function of decomposing harmful substances such as antibacterial property, antifouling property, deodorant property and NOx on the surface of a base material such as tile, glass, sanitary ware, decorative plywood, and toilet seat sheet.

【0002】

[Previous technology]

As a method of adding functions such as antibacterial property, antifouling property and deodorizing property to the surface of a base material, a method of forming a thin film of photocatalytic particles such as anatase-type titanium oxide on the surface of the base material has been conventionally proposed. As one of the methods, a method is known in which anatase-type titanium oxide is kneaded with a binder, and this is applied to the surface of a base material for heat treatment. As another method, a binder layer is formed on the surface of the plate-like member constituting the wall surface, floor surface or ceiling surface of the living space disclosed by the applicant in Japanese Patent Application Laid-Open No. 5-253544, and the binder layer is formed on the surface of the binder layer. A photocatalytic fine powder mainly composed of anatase-type titanium oxide is sprayed and adhered so that a part of the powder is exposed from the binder layer, and then heated in a range of 300 ° C or more and less than 900 ° C to melt the binder layer. , There is a method for manufacturing a plate-shaped member having a deodorizing function, which is characterized in that the binder layer is solidified by cooling.

【0003】

[Problems to be Solved by the Invention]

In the method of kneading anatase-type titanium oxide particles into a binder, applying the anatase-type titanium oxide particles to the surface of the substrate, and heat-treating the particles, the binder covers most of the active sites of the anatase-type titanium oxide particles, which is a photocatalyst, and thus deodorizes. The characteristics due to photocatalytic action such as, etc. were not sufficient. Further, in the method of JP-A-5-253544, the deodorizing property was good when the heat treatment was performed at 300 ° C or more and less than 900 ° C, but the good deodorizing property was not obtained at a low temperature of less than 300 ° C. Therefore, it has been difficult to add good photocatalytic activity such as excellent deodorizing properties to a base material such as plastic which does not have heat resistance. The reason is that in order to uniformly apply the photocatalyst particles to the substrate, it is necessary to monodisperse the photocatalyst fine particles in the suspension in the previous step, and for that purpose, an organic dispersant is added, and the dispersant is added. It is considered that the temperature is less than 300 ° C, it is not sufficiently decomposed and vaporized, and it remains so as to cover the active sites on the photocatalytic particles. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a member having good photocatalytic activity even in a low temperature heat treatment of less than 300 ° C.

【0004】

[Means for solving problems]

In the present invention, in order to solve the above problems, in a method for forming a member having a photocatalytic action, a binder layer is formed on the surface of a base material, and a photocatalytic layer is provided on the binder layer so that a part of the lower layer is embedded therein. After the formation, the photocatalyst particles were exposed to the outside air by irradiating with light containing 1.7 mW / cm2 or more of light having a wavelength of 390 nm or less to preferentially decompose and vaporize the surface treatment agent adhering to the photocatalyst surface.

【0005】

Further, in the method for forming a member having a photocatalytic action, after forming a layer mainly composed of photocatalytic particles and a thermosetting resin on the surface of a base material, light containing 1.7 mW / cm2 or more of light having a wavelength of 390 nm or less is irradiated. , The thermosetting resin on the photocatalyst particles was preferentially decomposed and vaporized to expose the photocatalyst particles to the outside air. Further, after forming a layer mainly composed of photocatalytic particles and a thermosetting resin on the surface of the base material via a thermosetting resin layer or a photocurable resin, light containing light having a wavelength of 390 nm or less is I.7 mW / cm2 or more. The thermosetting resin on the photocatalyst particles was preferentially decomposed and vaporized to expose the photocatalyst particles to the outside air.

【0006】

It will be described in detail below. Here, the material of the base material may be basically anything such as ceramics, ceramics, metals, glass, thermosetting resins, thermoplastic resins or composites thereof. The shape of the base material may be any shape, and even simple shapes such as spherical objects, cylindrical objects, cylindrical objects, tiles, wall materials, flooring materials, and other plate-like objects can be used as sanitary ware, wash basins, bathtubs, and sinks. , A complicated shape such as a toilet seat may be used. Further, the surface of the base material may be porous or dense.

【0007】

The type of binder may be a thermoplastic material such as inorganic glass, a thermoplastic resin, or a solder, or a thermosetting material such as a fluororesin, a siloxane resin, or a silicon resin. However, it is preferably a photocorrosion resistant material because it irradiates light including ultraviolet rays in a subsequent process. In addition, since the usefulness of the present application is particularly high when only heat treatment of 300 ° C or less is possible, a thermoplastic material can be softened at 300 ° C or less, and a thermosetting material can be cured at 300 ° C or less. It is preferably a material. Examples of the material satisfying these conditions include boric acid-based glassy, solder, acrylic resin and the like for thermoplastic materials, and fluororesin, siloxane resin, silicon resin and the like for thermosetting materials.

【0008】

As a method of applying these binder layers on the base material, when a thermoplastic material is used, there are a spray coating method, a roll coating method, a dip coating method and the like, and any of them can be used. Alternatively, other methods may be used. Further, the binder component does not necessarily have to match the binder composition at the time of completion of the member. For example, when the binder is made of inorganic glass, the coating material may be a suspension of an inorganic glassy composition such as granular, frit-like, lumpy, or powder, or a mixed solution of salts containing a constituent metal component. .. When the binder is a resin, a solution of the resin having the composition may be used, or other methods may be used.

【0009】

Before applying the photocatalyst particles on the binder layer, the applied binder layer may be dried to evaporate water or the like. The drying method at this time includes a method of leaving at room temperature, a method of heating together with the base material, and the like.

【0010】

Further, before the photocatalyst particles are applied onto the binder layer, the applied binder layer may be heat-treated at a temperature lower than the softening temperature of the base material, the binder layer changes to the binder composition at the time of completion of the member, and the temperature is softened. Good. According to this method, when the photocatalyst particles are formed on the binder layer, the binder layer becomes smoother in advance, so that even a small amount of the photocatalyst particles to be applied can exert a sufficient effect.

【0011】

When a thermosetting material is used, a method of mixing a binder with a curing agent and applying it to a base material is, for example, adding a diluent to a thermosetting resin and then adding a curing agent to obtain a mixed solution. This is done by applying it to the surface of the base material. It is desirable that the thickening viscosity is 105 poise or more and less than 1075 poise. By applying the photocatalyst particles after setting the viscosity value to 105poise or more, it is possible to bury the photocatalyst particles in a state where they are not completely buried in the binder layer, and by making it less than 1075poise, the photocatalyst particle layer This is because at least a part of the lowermost layer portion of the binder can be embedded in the lower layer of the binder.

【0012】

The photocatalytic layer is a layer having a photocatalytic action, and refers to a layer mainly composed of photocatalytic particles. Here, the photocatalytic particles are semiconductor particles having a band gap sufficient to exert a deodorizing function, an antibacterial function, and the like. There is a theory that photocatalytic particles have an antibacterial function when they are electrocuted when a voltage higher than a predetermined value is applied (Special Fair 4-2-9393), but in general, as with deodorant properties, active oxygen generated during light irradiation Is believed to be for. In order to generate active oxygen, it is necessary that the position of the conduction band of the semiconductor is above the hydrogen evolution potential when represented by the band model, and the upper end of the valence band is below the oxygen evolution potential. Semiconductors satisfying this condition include TiO2, SrTiO3, ZnO, SiC, GaP, CdS, CdSe, MoS3 and the like. In addition, since the position of the conduction band moves upward when atomized, there is a possibility that SnO2, Fe2O3, WO3, Bi2O3, etc. can also generate active oxygen if the particles are fine particles of about 1 to 10 nm. Of these, anatase-type titanium oxide is particularly preferable because fine particles that are chemically stable and have high activity can be obtained at low cost.

【0013】

The method of applying the photocatalyst particles to the surface of the binder layer is basically carried out by applying an appropriate treatment to the starting material on the binder layer. As a starting material, a sol suspension of a photocatalyst composition substance is desirable, but a suspension of fine particles having a photocatalyst composition can also be used. In any case, in order to obtain a uniform coating film, it is necessary to add a surface treatment agent such as a dispersant to prevent the photocatalyst composition in the suspension from aggregating. The coating on the binder layer includes a spray coating method, a roll coating method, a dip coating method and the like, any of which may be used, or any other method may be used.

【0014】

It is preferable that the thickness of the photocatalyst layer embedded in the binder layer is 1/4 or more of the thickness of the photocatalyst layer in terms of the bond strength with the base material. Here, the thickness of the photocatalyst layer is determined by analyzing the component elements constituting the photocatalyst particles in the cross-sectional direction by EPMA or the like, and the amount of the component elements constituting the photocatalyst particles is substantially constant in the upper layer portion and the amount of the component elements constituting the photocatalyst particles. It consists of an embedded portion between the depth at which the amount of constituent elements beginning to decrease and the depth at which the amount of component elements constituting the binder begins to become constant.

【0015】

The surface treatment agent attached to the photocatalyst mainly consists of components added to disperse the sol of the starting material of the photocatalyst particles. Specific examples thereof include pentaerythrit, trimethylolpropane, triethanolamine, trimethylolamine, silicone resin, and alkylchlorosilane.

【0016】

Examples of the light source of light containing 1.7 mW / cm2 or more of light having a wavelength of 390 nm or less include BLB fluorescent lamps, ultraviolet lamps, germicidal lamps, xenon lamps, and mercury lamps. The reason why light having a wavelength of 390 nm or less must be contained at 1.7 mW / cm2 or more is that the dispersant component such as silicon resin has a certain degree of photocorrosion resistance and therefore does not decompose unless it has such an ultraviolet intensity. At this time, the shorter the ultraviolet wavelength, the faster the dispersant is decomposed, but depending on the type of binder, the binder may also be decomposed, which is harmful to the human body. From this, it is better to be 250 nm or more. In addition, the decomposition rate increases as the illuminance increases up to about 3 mW / cm2, but above that, increasing the illuminance does not contribute much to the improvement of the decomposition rate, so 3 mW / cm2 or less is sufficient.

【0017】

The above process is schematically shown in FIG. The photocatalyst layer 3 is formed on the base material 1 via the binder layer 2 by embedding a part of the lower layer in the binder layer 2. No. 4 is a layer made of a surface treatment agent or the like that inhibits photocatalytic activity. UV indicates light containing 1.7 mW / cm2 or more of light having a wavelength of 390 nm or less.

【0018】

Next, a layer in which a layer mainly composed of photocatalyst particles (5) and a thermosetting resin (6) is formed on the surface of the base material and similarly irradiated with ultraviolet rays to expose the photocatalyst layer will be described. (See Fig. 2) Also in this method, the photocatalyst particles are firmly fixed to the substrate by the thermosetting resin, and the surface of the photocatalyst particles is exposed to light containing 1.7 mW / cm2 or more of light having a wavelength of 390 nm or less. A photocatalytic reaction occurs in the light-irradiated portion, the surface treatment agent and the thermocurable resin in the direction of the light source are preferentially decomposed and vaporized, and the photocatalytic particles are exposed to the outside air, so that sufficient photocatalytic activity can be obtained. The method for forming a layer mainly composed of photocatalyst particles and a thermosetting resin is a mixed solution obtained by adding a thermosetting resin, a diluent and a curing agent in this order to, for example, a well-dispersed photocatalyst sol suspension. Is applied to the surface of the base material and heat-treated to form.

【0019】

Here, the sol in the photocatalytic sol suspension has a crystal diameter of 0.05 μm or less, more preferably 0.01 μm or less. This is because the smaller the crystal diameter, the higher the photocatalytic activity. Further, it is desirable that the sol in the photocatalytic sol suspension is as monodisperse as possible. This is because the better the dispersibility, the more uniform the coating film is possible.

【0020】

It is desirable that the thermosetting resin used here has light corrosion resistance against white light and ordinary fluorescent lamp level light. This is because it is more durable when used. In that sense, siloxane resin and fluororesin are particularly preferable.

【0021】

The diluent is added to reduce the viscosity of the mixed solution composed of the photocatalytic sol and the thermosetting resin and to facilitate the application of the mixed solution to the surface of the base material. Therefore, the diluent used here may be basically any solvent that can achieve this purpose. For example, water, ethanol, propanol and the like can be used.

【0022】

As a method of applying the mixed solution to the substrate, there are a spray coating method, a roll coating method, a dip coating method, a spin coating method and the like, any of which may be used, or any other method may be used. .. The heat treatment is generally limited to, but is not limited to, an electric furnace, a gas kiln, a vacuum furnace, a pressurizing furnace, or the like.

【0023】

A layer mainly composed of photocatalytic particles and a thermosetting resin may be formed on the surface of the base material via a thermosetting resin layer or a thermosetting resin layer (intermediate layer: 7). (See Figure 3) According to this method, even if the base material has irregularities or the like, a thermosetting resin layer or a photocurable resin layer arranged between the base material and the photocatalyst layer provides an extremely smooth surface before the photocatalyst layer is applied. Since it can be formed, the photocatalyst layer can be easily and uniformly formed. Further, since the thermosetting resin layer or the photocurable resin layer arranged between the base material and the photocatalyst layer can sufficiently bond with the base material, the photocatalyst particles and the photocatalyst are heat-cured even if the surface of the base material is uneven. Since the layer made of a sex resin can be formed thinly and the photocatalytic particles can be concentrated near the surface of the base material, the subsequent step of irradiating light containing light having a wavelength of 390 nm or less with 1.7 mW / cm2 or more is more effective. It can be done in a short time. In addition, since there is a layer composed of photocatalyst particles and a thermosetting resin on the upper surface, ultraviolet rays having sufficient strength to be decomposed and vaporized during the post-process and use are arranged in the middle of the thermosetting resin layer or photocurable. Since it does not reach the resin layer, the thermosetting resin in this part can be arbitrarily selected. For example, an inexpensive epoxy resin may be selected for cost reduction, or a colored resin may be used for designability.

【0024】

Here, the method for forming the thermosetting resin layer arranged between the base material and the photocatalyst layer is as follows, for example, a mixture obtained by adding a diluent to the thermosetting resin and then adding the curing agent is applied to the surface of the base material. It is applied and solidified by heat treatment or leaving to form. When the layer arranged in the middle of the photocatalyst layer is a photocurable resin layer, it is irradiated with light containing ultraviolet rays instead of heat treatment.

【0025】

Here, the diluent is added in order to reduce the viscosity of the mixed solution and facilitate the application of the mixed solution to the surface of the base material. Therefore, the diluent used here may be basically any solvent that can achieve this purpose. For example, water, ethanol, propanol and the like can be used.

【0026】

Further, as shown in FIGS. 4A and 4B, the gaps formed in the photocatalyst layer exposed on the surface of the base material by the above method are filled with particles smaller than the gaps (gap particles: 8). , It is desirable because the abrasion resistance can be further improved.

【0027】

Here, the particles smaller than the gaps are preferably made of an inorganic crystalline material, and more preferably have photocatalytic activity, so that titanium oxide, tin oxide, ferric oxide, zinc oxide, bismuth oxide, tungsten trioxide, etc. Oxide semiconductors such as strontium titanate are preferable. The size of the particles smaller than the gap should basically be smaller than the average value of the pore diameter or unevenness to be generated. The amount of particles smaller than the gap should be added to the extent that the surface porosity is less than 20%. This is because dirt is less likely to adhere.

【0028】

[Action]

By irradiating light containing 1.7 mW / cm2 or more of light with a wavelength of 390 nm or less, priority is given to the surface treatment agent or resin adhering to the light-irradiated surface of the photocatalytic particle surfaces that cannot be vaporized or decomposed by heat treatment below 300 ° C. As a result, the photocatalytic particles can be exposed to the outside air, and sufficient photocatalytic activity can be imparted to the member.

【0029】

[Example]

Example 1. On the surface of a 10 cm square alumina base material, 10% by weight of siloxane resin, a diluent, and a curing agent are applied to a titanium oxide sol (dispersed with an amine-based dispersant) having an average particle size of 0.01 μm. The mixed solution obtained by adding in order was applied and calcined at 150 ° C. to obtain a comparative sample. This sample was irradiated with various light sources for a predetermined time to obtain a sample. The deodorant property R30 (L) at the time of light irradiation was evaluated for the obtained sample. Here, the deodorant characteristic R30 (L) at the time of light irradiation is that the sample surface is placed at a distance of 8 cm from the light source (BLB fluorescent lamp 4W) in an 11 L glass container, and the methyl mercaptan gas is placed in a container so that the initial concentration is 3 ppm. It is the rate of change in concentration after injecting into the glass and irradiating with 30 spectra. The results are shown in Table 1. As a result, when the ultraviolet intensity was 1.69 mW / cm2 or more, the deodorant property exceeded 50%, and when the ultraviolet intensity was 2 mW / cm2 or more, the deodorant property R30 (L) exceeded 70%. Here, when the ultraviolet intensity was 1.69 mW / cm2 or more, good results were shown because a photocatalytic reaction occurred at the light-irradiated part on the surface of the photocatalytic particles, and the surface treatment agent and the thermosetting resin in the direction of the light source were preferentially decomposed. It is understood that the photocatalytic particles were vaporized and exposed to the outside air.

【0030】

[table 1]

<img file="JPH08131842A_D0001.tif" />【0031】

Example 2. A solution of a siloxane resin with a diluent and a curing agent added to the surface of a 10 cm square alumina base material is applied, dried at room temperature for about 6 hours, and then titanium oxide sol with an average particle size of 0.01 μm (with an amine-based dispersant). A mixed solution obtained by adding 10% by weight of a siloxane resin, a diluent, and a curing agent in this order was applied to the dispersion-treated product) and calcined at 150 ° C. to obtain a comparative sample. This sample was irradiated with various light sources for a predetermined time to obtain a sample. The deodorant property R30 (L) at the time of light irradiation was evaluated for the obtained sample. The results are shown in Table 2. As a result, when the ultraviolet intensity was 1.69 mW / cm2 or more, the deodorant characteristic exceeded 60%, and when the ultraviolet intensity was 2 mW / cm2 or more, the deodorant characteristic R30 (L) exceeded 80%. Here, when the ultraviolet intensity was 1.69 mW / cm2 or more, good results were shown because a photocatalytic reaction occurred at the light-irradiated part of the photocatalyst particle surface, which caused the light-irradiated surface of the photocatalyst particle surface that could not be vaporized or decomposed by heat treatment. It is understood that the surface treatment agent adhering to the surface treatment agent can be preferentially decomposed and vaporized, and as a result, the photocatalytic particles are exposed to the outside air.

【0032】

[Table 2]

<img file="JPH08131842A_D0002.tif" />【0033】

Example 3. A solution of a siloxane resin supplemented with a diluent and a curing agent is applied to the surface of an alumina base material of 3.10 cm square, dried at room temperature for about 6 hours, and then titanium oxide sol (with an amine-based dispersant) having an average particle size of 0.01 μm. A mixed solution obtained by adding 10% by weight of a siloxane resin, a diluent, and a curing agent in this order was applied to the dispersion-treated product) and fired at 150 ° C. The particle gap on the surface of the member at this stage was about 0.1 to 0.2 μm on average. After that, after irradiating light with an ultraviolet intensity of 2 mW / cm2 (ultraviolet lamp) for 3 days and confirming that R30 (L) exceeds 80%, tin oxide sol with an average particle size of 0.0035 μm was applied to titanium oxide. A sample was obtained by applying 70% by weight on the surface and drying at 110 ° C. In this sample as well, R30 (L) showed a good result of 81%. In addition, when a sliding test using a plastic eraser was performed, the sample to which tin oxide was not added was scratched and the titanium oxide was peeled off after sliding less than 5 times, but the sample to which tin oxide was added was 10 times or more. There was no change even when sliding. From the above, it was confirmed that the wear resistance is improved by filling the gap formed on the surface of the member with tin oxide particles smaller than the gap.

【0034】

[Effect of the invention]

As described above, according to the present invention, it is possible to provide a member having good photocatalytic activity even when a layer having a photocatalytic action treated at a low temperature of less than 300 ° C. is formed.

[Simple explanation of drawings]

[Figure 1]

The figure which shows the Example of this invention.

[Figure 2]

The figure which shows the Example of this invention.

[Fig. 3]

The figure which shows the other embodiment of this invention.

[Fig. 4]

The figure which shows the other embodiment of this invention.

[Explanation of symbols]

1 ... base material, 2 ... binder layer, 3 ... photocatalytic layer, 4 ... photocatalytic activity inhibitory membrane, 5 ... photocatalytic particles, 6 ... thermosetting resin, 7 ... Intermediate layer, 8 ... interstitial particles