KR20070092627A - Photocatalyst dispersion - Google Patents

Abstract

A photocatalyst dispersion that can easily form on a neutral area a coating film showing high photocatalytic activity by the irradiation of visible rays is provided. As a dispersion containing a photocatalyst and an aqueous solvent, a photocatalyst dispersion contains ammonium phosphate in a ratio of less than 5 weight parts with respect to 100 weight parts of a photocatalyst, and does not contain a polymeric silicon compound or contains the polymeric silicon compound in a ratio of 7.5 weight parts or less with respect to 100 weight parts of the photocatalyst, wherein a weight ratio value of the polymeric silicon compound to the ammonium phosphate is 5 or less, and a pH of the dispersion is ranged from 5 to 9. The photocatalyst is a titanium oxide. The photocatalyst exhibits the photocatalytic activity to the light irradiation of a fluorescent lamp. The ammonium phosphate is monoammonium phosphate or/and diammonium phosphate.

Description

Photocatalyst Dispersion {PHOTOCATALYST DISPERSION}

The present invention relates to a photocatalyst dispersion useful for forming a coating film exhibiting photocatalytic activity.

When the semiconductor is irradiated with light, electrons having a strong reducing action and holes having a strong oxidation action are generated, and molecular species in contact with the semiconductor are decomposed by the redox action. This action is called a photocatalytic action, and by using this photocatalytic action, water and organic matter in the air can be decomposed and harmless. Therefore, a substance exhibiting a photocatalytic action, that is, a photocatalyst, has recently been widely used for various purposes, such as water treatment, deodorization, exhaust gas treatment, air purification, soil treatment, antibacterial and antifungal, antifouling and antifogging agents. it started.

As a substance which exhibits a photocatalytic action, that is, a photocatalyst, titanium oxide powder is the most common and practical use, for example.

By the way, when the photocatalyst such as titanium oxide powder is put into practical use, it is necessary to fix the photocatalyst such as titanium oxide powder to the substrate or the like. As one of the methods, the photocatalyst is dispersed in the liquid medium and applied to the substrate or the like in the state of the dispersion. There is a way.

Dispersions of photocatalysts are broadly classified as showing pH in acidic region, showing pH in neutral region, and showing pH in alkaline region, and are usually used differently according to the use. For example, when the corrosiveness to a base material or the danger to a human body becomes a problem, the dispersion which has a pH of neutral region rather than acidic or alkaline is considered to be preferable. However, in the neutral region, there is a drawback that the photocatalyst particles are difficult to disperse, and as a result, the dispersion stability is deteriorated, and there is a fear that a coating film cannot be stably formed.

Thus, in order to secure good dispersion stability in the dispersion having a pH in the neutral region, research has been conducted to include ammonium phosphate salt as a dispersion stabilizer.

Examples of the photocatalyst dispersion containing an ammonium phosphate salt include a photocatalyst, a polymerizable silicon compound, ammonium phosphate and a dispersion medium, and the content of ammonium phosphate is ammonium phosphate / polymerizable silicon compound in a weight ratio of 1/30 to 1/8. The coating material (USP6783845) which mix | blends the coating material (Unexamined-Japanese-Patent No. 2005-54139) in the range of and the oxide particle of the phosphate compound binder and an average particle diameter of 1-300 nm is proposed.

However, when an ammonium phosphate salt or a polymerizable silicon compound is excessively added to the photocatalyst dispersion, the photocatalytic activity tends to be lowered, and the dispersion disclosed in Japanese Unexamined Patent Publication No. 2005-54139 or USP6783845 also has insufficient photocatalytic activity. There was one case. Therefore, there has been a demand for a photocatalyst dispersion capable of forming a coating film exhibiting high photocatalytic activity while also ensuring dispersion stability in the neutral region.

Then, the subject of this invention is providing the photocatalyst dispersion which can form the coating film which shows high photocatalytic activity easily in a neutral area | region by irradiation of visible light.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to solve the said subject, as a result of containing an appropriate amount of ammonium phosphate salt as a dispersion stabilizer, it is possible to form a stable coating film even in a neutral region, and to include it as a conventional binder in many cases. Even when the silicon compound is not contained at all, or by containing it at a lower content (less amount for both the photocatalyst and the ammonium phosphate salt), the inventors have found that the above problems can be solved at once, and have completed the present invention. .

That is, this invention consists of the following structures.

(1) A dispersion containing a photocatalyst and an aqueous solvent, containing an ammonium phosphate salt in a proportion of less than 5 parts by weight with respect to 100 parts by weight of the photocatalyst, and containing no polymerizable silicon compound or 100 parts by weight of the photocatalyst. A photocatalyst dispersion, wherein the polymerizable silicon compound / ammonium phosphate salt (weight ratio) has a value of 5 or less and a pH of 5 to 9 while containing in a proportion of 7.5 parts by weight or less.

(2) The photocatalyst dispersion according to the above (1), wherein the photocatalyst is titanium oxide.

(3) The photocatalyst dispersion according to the above (1) or (2), wherein the photocatalyst exhibits photocatalytic activity with respect to light irradiation with a fluorescent lamp.

(4) The photocatalyst dispersion in any one of said (1)-(3) whose ammonium phosphate salt is either one or both of ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

According to the photocatalyst dispersion of this invention, the coating film which shows high photocatalytic activity by irradiation of visible light can be easily formed in a neutral region. That is, the photocatalyst dispersion of the present invention makes it easy to apply the photocatalyst to various materials such as, for example, fiber materials, building materials, automobile materials, etc., and to impart high photocatalytic activity to these materials. . Various materials imparted with photocatalytic activity by the photocatalytic dispersion of the present invention can decompose NOx in the atmosphere, decompose odorous substances (e.g., tobacco odors) in living spaces or work spaces, or bacteria (e.g., , Radiation bacteria), algae, fungi and the like can be suppressed.

Best Mode for Carrying Out the Invention

The photocatalyst dispersion of this invention contains a photocatalyst and an aqueous solvent.

The photocatalyst in this invention should just be a powder containing the component which shows photocatalytic activity, for example, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Co 1 type of metal element, such as Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, Ag, Au, Zn, Cd, Ga, In, Tl, Ge, Sn, Pb, Bi, La, Ce or And a powder containing two or more kinds of oxides, nitrides, sulfides, oxynitrides, oxysulfides, nitrides, acid fluorides, and oxyfluorides. Among these, titanium oxide is preferable as a photocatalyst in this invention. More specifically, there are anatase type and rutile type in titanium oxide, but anatase type titanium oxide is preferable in view of photocatalytic activity. In the case of anatase titanium oxide, the anatase ratio is preferably 40% or more, more preferably 60% or more, and still more preferably 80% or more. The anatase rate at this time can be calculated by measuring the diffraction spectrum by X-ray diffraction and obtaining the peak area of the strongest interference line (surface index 101) of titanium oxide in this spectrum.

The titanium oxide used as the photocatalyst is, for example, reacted with a titanium compound and a base, aged by adding ammonia to the product, and then subjected to solid-liquid separation, followed by calcining the solid content (hereinafter referred to as "titanium oxide preparation method May be referred to as "A". Hereinafter, although this titanium oxide preparation method A is described, the photocatalyst in this invention is not limited to what was obtained by this preparation method, of course.

In the titanium oxide preparation method A, for example, as a titanium compound, titanium trichloride [TiCl ₃ ], titanium tetrachloride [TiCl ₄ ], titanium sulfate [Ti (SO ₄ ) ₂ · mH ₂ O, 0 ≦ m ≦ 20] , Titanium oxysulfate [TiOSO ₄ · nH ₂ O, 0 ≦ n ≦ 20], titanium oxychloride [TiOCl ₂ ], and the like, and the base reacted with a titanium compound, for example, sodium hydroxide, potassium hydroxide, sodium carbonate, Potassium carbonate, ammonia, hydrazine, hydroxylamine, monoethanolamine, acyclic amine compounds, cyclic aliphatic amine compounds and the like can be used.

In the method for preparing titanium oxide, the reaction between the titanium compound and the base is at least pH 2, preferably at least pH 3, and is preferably performed at a pH of 7 or less, preferably at a pH of 5 or less. The reaction temperature of the titanium compound and the base is usually 90 ° C. or lower, preferably 70 ° C. or lower, and more preferably 55 ° C. or lower. In addition, reaction of a titanium compound and a base can also be performed in presence of hydrogen peroxide water.

In the titanium oxide preparation method A, when the ammonia is added to the product obtained by the reaction of the titanium compound and the base for aging, the amount of ammonia to be added is the total amount of the added amount of the base used in the reaction. It is preferable to set so that the stoichiometric amount of the base required for converting a compound into titanium hydroxide will be exceeded. Specifically, 1.1 times or more is preferable based on the stoichiometric amount, More preferably, 1.5 times or more is preferable. In addition, since the upper limit at this time does not acquire an effect suitable for an amount even if there is too much base amount, it becomes economically disadvantageous, 20 times or less are preferable based on the said stoichiometric amount, More preferably, it is 10 times The following is good.

In the titanium oxide preparation method A, the temperature at the time of aging by adding ammonia is, for example, 0 ° C or higher, preferably 10 ° C or higher, 110 ° C or lower, preferably 80 ° C or lower, and more preferably 55 It is below C and the time to make it age can be performed by the method of holding for 1 minute-10 hours, Preferably it is 10 minutes-2 hours, stirring.

In the titanium oxide preparation method A, solid-liquid separation of the aged product can be performed by pressure filtration, reduced pressure filtration, centrifugation, decantation, or the like. Moreover, in solid-liquid separation, it is preferable to perform the operation of washing the obtained solid content together.

In the titanium oxide preparation method A, the firing of the solid-liquid separated solids or the solids subjected to any washing is usually performed at 300 ° C. or higher, preferably 350, using an apparatus such as an air flow firing furnace, a tunnel furnace, or a rotary furnace. It is more than 600 degreeC, 600 degrees C or less, Preferably it can carry out at temperature within the range of 500 degrees C or less, More preferably, 400 degrees C or less. What is necessary is just to determine baking time according to a baking temperature, a baking apparatus, etc., and it is not unique, but it is good to set it as 10 minutes-30 hours normally, Preferably it is 30 minutes-5 hours.

In the titanium oxide preparation method A, a compound showing solid acidity such as tungsten oxide, niobium oxide, iron oxide or nickel oxide, or a compound showing solid basicity such as lanthanum oxide or cerium oxide, is added to the titanium oxide obtained by firing, if necessary. Or a metal compound that absorbs visible light such as indium oxide, bismuth oxide, or the like.

It is preferable that the photocatalyst in this invention shows photocatalytic activity with respect to light irradiation by a fluorescent lamp. Specifically, photocatalysts that exhibit photocatalytic activity with respect to light irradiation having a wavelength of about 430 nm to about 830 nm are preferred. Specifically, after the powdered photocatalyst and acetaldehyde are put in a sealed container and sealed, light having a wavelength of about 430 nm to about 830 nm by a light source (for example, a 500 W xenon lamp) located about 15 cm away from the photocatalyst. When it was investigated, the average decomposition rate of acetaldehyde for 20 minutes (from the start of irradiation to 20 minutes later) is preferably 10 μmol / h or more, more preferably 20 μmol / h or more per 1 g of the photocatalyst.

The photocatalyst powder present in the photocatalyst dispersion of the present invention preferably has an average primary particle diameter of 500 nm or less, preferably 200 nm or less, more preferably 180 nm or less, and the average secondary particle diameter is usually It is good that it is 15 micrometers or less.

The content of the photocatalyst in the photocatalyst dispersion of the present invention may be appropriately set according to the use, and is not particularly limited. However, the lower limit is usually at least 0.1% by weight, preferably at least 1% by weight, and the upper limit is at most 30% by weight. Is set. Moreover, the mixing (especially initial stage mixing) mentioned later can be performed efficiently, so that content of a photocatalyst (namely, the quantity of the powder in a dispersion) increases.

In consideration of this, the content of the photocatalyst may be set so that the content of the photocatalyst is larger than the predetermined amount, and the desired content may be obtained by adding and diluting the solvent in a later step.

As the aqueous solvent in the present invention, water may be used as a main component, and an aqueous ammonium phosphate salt described later may be dissolved, for example, water; Aqueous media such as mixed solvents of alcohols such as ethanol, methanol, 2-propanol, butanol and water; Etc. can be mentioned. Among these, water is especially preferable.

The photocatalyst dispersion of this invention contains ammonium phosphate salt. By containing an ammonium phosphate salt functioning as a dispersion stabilizer, it is a dispersion having a pH in the neutral region and sufficiently maintains the dispersion stability of the photocatalyst powder, thereby making it possible to form a stable coating film. Further, for example, dispersion treatment may be performed with a wet medium mill for a certain time, so that a finer dispersion can be obtained, and a higher transparency photocatalyst film can be formed.

As said ammonium phosphate salt, either one or both of ammonium dihydrogen phosphate and diammonium hydrogen phosphate is mentioned preferably at the point which sufficient dispersion stability is easy to be obtained even in small quantities. In particular, ammonium dihydrogen phosphate is preferable.

It is important that content of the said ammonium phosphate salt is a ratio of less than 5 weight part with respect to 100 weight part of photocatalysts. As described above, the ammonium phosphate salt has the advantage of improving the dispersion stability of the photocatalyst powder in the dispersion, and this advantage is remarkable as the content of the ammonium phosphate salt is higher. However, on the other hand, when the content of ammonium phosphate is large (specifically, 8 parts by weight or more based on 100 parts by weight of the photocatalyst), the photocatalytic activity of the coating film obtained using the dispersion is lowered, or during storage (especially, high temperature (specific As a result, when stored for a long time in an atmosphere of about 40 ° C.), the viscosity of the dispersion may increase.

The photocatalyst dispersion of this invention does not contain a polymeric silicon compound, or contains it in the ratio of 7.5 weight part or less with respect to 100 weight part of photocatalysts. That is, even if it does not contain the polymerizable silicon compound which was often included as a binder at all, or contains it, it is made into content smaller than before like the said range.

Examples of the polymerizable silicon compound include alkoxysilanes, hydrolysis products of alkoxysilanes, partial condensates of alkoxysilanes, water glass, colloidal silica, and the like. 1 type of these polymeric silicone compounds may be sufficient, and 2 or more types may be sufficient as them.

When the photocatalyst dispersion of this invention contains a polymeric silicon compound, as mentioned above, the content is a ratio of 7.5 weight part or less with respect to 100 weight part of photocatalysts. Preferably, the content of the polymerizable silicon compound is less than 2 parts by weight based on 100 parts by weight of the photocatalyst, and more preferably 0 parts by weight, that is, no content is contained based on 100 parts by weight of the photocatalyst. Since there is a tendency for the photocatalytic activity of the photocatalyst coating film obtained that there are more content of a polymeric silicon compound, it is good that content of a polymeric silicon compound is as small as possible.

When the photocatalyst dispersion of this invention contains a polymeric silicon compound, it is preferable that the value of a polymeric silicon compound / ammonium phosphate salt (weight ratio) is 5 or less from a viewpoint of photocatalytic activity improvement.

The photocatalyst dispersion of this invention has a pH of 5-9. More preferably, pH is 6-8. Since the photocatalyst dispersion of the present invention has a pH in the neutral region in this way, there is an advantage that there is no corrosiveness to various substrates or a danger to the human body.

The photocatalyst dispersion of this invention can be made to contain various additives as needed in the range which does not lose the effect of this invention. As various additives, for example, amorphous silica, silicon oxide such as silica sol, amorphous alumina, oxide of aluminum such as alumina sol or hydroxide, aluminosilicate such as zeolite, kaolinite, magnesium oxide, calcium oxide, strontium oxide, oxide Oxides or hydroxides of alkaline earth metals such as barium, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, calcium phosphate, molecular, activated carbon, and Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, Ag, Au, Zn, Cd, Ga, In, Tl, Ge, Sn, Pb, Bi, Hydroxides of metal elements such as La and Ce, and amorphous oxides of these metal elements. 1 type of these additives may be sufficient and 2 or more types may be sufficient as them.

In order to obtain the photocatalyst dispersion of the present invention, for example, the photocatalyst, the ammonium phosphate salt, the aqueous solvent, a polymerizable silicon compound, and various additives may be mixed as necessary.

What is necessary is just to use the apparatus which can disperse | distribute photocatalyst powder in an aqueous solvent for the said mixing, For example, apparatuses, such as a medium stirring type disperser, an electric ball mill, and a vibration ball mill, can be employ | adopted. Among these, application of a medium stirred disperser is particularly recommended. In addition, as a dispersion medium in these apparatus, when a material is zirconia, alumina, or glass, for example, a diameter of 0.65 mm or less, preferably 0.5 mm or less, more preferably 0.3 mm or less, do.

The mixing may be performed in two or more stages. For example, in the first stage, an apparatus containing a dispersion medium having a relatively large diameter is used, and after the second stage, a apparatus in which a small diameter is sequentially used is performed. can do. By carrying out the mixing in multiple stages as described above, the photocatalyst powder can be efficiently dispersed in an aqueous solvent, whereby a dispersion in which the photocatalyst is uniformly dispersed is obtained.

The mixing is usually carried out at less than 40 ° C, preferably at 30 ° C or less, and usually at 10 ° C or more, preferably 20 ° C or more. If mixing is performed at a temperature outside the above range, there is a fear that the dispersibility is lowered.

When obtaining the photocatalyst dispersion of this invention, operation | movement, such as removal of coarse particle | grains, adjustment of a photocatalyst content (dilution etc.), pH adjustment, etc. can be performed further to the mixture obtained by the said mixing as needed. There is no restriction | limiting in particular as a specific method of these operations, What is necessary is just to employ | adopt a conventionally well-known method.

When storing the photocatalyst dispersion of the present invention, it is preferable to store it under the condition that light does not shine, for example, to store it in a dark room, or to store it in the light-shielding container which transmittance of an ultraviolet-ray and a visible light is 10% or less, respectively. It is preferable.

When forming a coating film using the photocatalyst dispersion of this invention, a dispersion is apply | coated by a conventionally well-known method, such as spin coat, dip coat, doctor blade, spray, or brush coating, for example, What is necessary is just to heat at the temperature which can remove an aqueous solvent.

The coating film formation by the photocatalyst dispersion of this invention can be performed with respect to all base materials, such as glass, a plastic, a metal, ceramics, and concrete, for example.

The coating film (namely, photocatalyst) formed by the photocatalyst dispersion of this invention is used as follows, for example. That is, the method of putting a photocatalyst and a to-be-processed object in the glass container which permeate | transmits visible light, and irradiating visible light with a wavelength of 430 nm or more to a photocatalyst using a light source, etc. are mentioned. What is necessary is just to select irradiation time suitably according to the light intensity of a light source, and the kind and quantity of a to-be-processed object. The light source to be used is not limited as long as it can irradiate visible light having a wavelength of 430 nm or more, and sun rays, fluorescent lamps, halogen lamps, black lights, xenon lamps, neon signs, LEDs, mercury lamps, or sodium lamps can be used. Can be.

EXAMPLE

Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to a following example.

In addition, the measurement of the average particle diameter and evaluation of a photocatalytic activity in an Example and a comparative example were performed with the following method.

<Measurement of Average Particle Diameter>

The average particle diameter (nm) of the sample was measured using the submicron particle size distribution measuring apparatus ("N4Puls" by a Coal company).

<Evaluation of Photocatalytic Activity (Acetaldehyde Resolution)>

The resulting photocatalyst dispersion was diluted with pure water so that the titanium oxide concentration was 10% by weight, and then added dropwise so as to have a solid content of 1.75 g / m 2 in a glass chalet container having an outer diameter of 70 mm, an inner diameter of 66 mm, a height of 14 mm, and a capacity of about 48 mL. The spread was spread evenly throughout the chalet. This was dried for 60 minutes with a 110 degreeC dryer, and the photocatalyst film | membrane (titanium oxide film) was formed, and the obtained chalet with a photocatalyst film was used as a measurement sample.

After putting the photocatalyst film-attached chalet as a measurement sample in a 1 liter gas bag, the gas bag was vacuumed, and a mixed gas of oxygen and nitrogen (oxygen: nitrogen = 1: 4 (volume ratio)) 600 mL was sealed. 1 vol% acetaldehyde was additionally charged in the gas bag so that the acetaldehyde was 200 ppm in volume concentration, and stabilized in a dark place for 1 hour. Then, light irradiation was started using a commercially available fluorescent lamp as a light source to decompose acetaldehyde. Was carried out. Light irradiation was performed by installing a chalet so that the illuminance of the film surface of a measurement sample might be 16000 lux. After starting light irradiation, the gas in a gas bag was sampled every 1.5 hours, and the residual density | concentration of acetaldehyde was measured by the gas chromatograph ("GC-14A by Shimadzu Corporation"). Then, with respect to the irradiation time, the concentration of acetaldehyde for each irradiation time was plotted on the logarithmic axis, and the slope of the obtained straight line was obtained as the first reaction rate constant, and the acetaldehyde resolution was evaluated by this value. The larger the primary reaction rate constant, the better the acetaldehyde resolution and the higher the photocatalytic activity.

(Production Example-Photocatalytic Synthesis)

30 kg of ion-exchanged water was put into the reaction container provided with the pH electrode and the pH controller which is connected to the pH electrode, and has a mechanism which supplies 25 weight% ammonia water, and adjusts pH uniformly, and sets pH of a pH controller. Was set to 4. In this reaction vessel, when the pH of the liquid in the vessel becomes lower than the set value (4), ammonia water starts to be supplied, and is continuously supplied until the pH reaches the set value.

To the titanium oxysulfate aqueous solution prepared by dissolving 75 kg of titanium oxysulfate in 50 kg of ion-exchanged water, 30 kg of 35% hydrogen peroxide solution was added under cooling to obtain a mixed solution. This mixed solution was added to the above-mentioned reaction vessel containing ion-exchanged water at a rate of 530 mL / min while stirring at 42 rpm, and reacted with ammonia water supplied to the reaction vessel by a pH controller to obtain a product. At this time, the reaction temperature was in the range of 20 ° C to 30 ° C. After adding all the mixed solutions, the obtained product was kept for 1 hour while stirring, and then 25% by weight of ammonia water was supplied until the pH was 4 to obtain a slurry, and the obtained slurry was filtered and then washed with 300 kg of water. Solids (cakes) were obtained. The total amount of 25 wt% ammonia water supplied to the reaction vessel was 90 kg, which was twice the amount necessary to convert titanium oxysulfate to titanium hydroxide.

Next, 2.3 kg of the solids (cake) obtained above were divided into 12 sheets of 30 cmx40 cm stainless steel trays. 12 sheets of this tray were put into a box-type dryer (Ashihi Scientific Co., Ltd. "Super Tenp Oven HP-60", contents: 216 liters), the drying air was passed through at 40m3 / hour, and kept at 115 ° C for 5 hours. Then, it dried at 250 degreeC for 5 hours, and obtained the dry powder whose BET surface area is 18.0 m <2> / g. At this time, the maximum water vapor partial pressure in the dryer was 27.4 kPa. Subsequently, the obtained dried powder was calcined at 350 ° C. for 2 hours in an air atmosphere, and then cooled to room temperature to obtain titanium oxide powder as a photocatalyst.

(Example 1)

172.8 g of ammonium dihydrogen phosphate (manufactured by Wako Pure Chemical Industries, Limited Reagent) was dissolved in 10.74 kg of ion-exchanged water to prepare an aqueous solution of ammonium phosphate. 4.0 kg of the photocatalyst (titanium oxide powder) obtained by this ammonium phosphate aqueous solution and the manufacturing example were put into the medium-stirring disperser ("Dynomil KDL-PILOT A type" by Shinmal Enterprise Co., Ltd.), and the bead made from zirconia of diameter 0.3mm 4.2 Kg was used as a dispersion medium, the stirring speed was 8 m / sec at a circumferential speed, the processing liquid was circulated at a volume of 3 liters of circulating liquid, and mixed under conditions of a total processing time of 72 minutes. The average particle diameter of titanium oxide in the dispersion obtained here was 420 nm. Next, this dispersion was placed in a medium stirring disperser (Kotobuki Instruments, Inc. "Ultra Apex Mill"), and 13 kg of zirconia beads having a diameter of 0.05 mm were used as the dispersion medium, and the stirring speed was 8 m / s. It mixed for 94 minutes as a second (2000 rpm). The average particle diameter of titanium oxide in the dispersion obtained here was 183 nm. Further, 1 liter of the obtained dispersion was collected in a 1 liter original needle tube, and centrifuged at 1500 rpm for 30 minutes to remove granulated powder to obtain a photocatalyst dispersion having a solid content concentration of 16.7% by weight. This was diluted with ion-exchanged water to make solid content concentration 10 weight%.

PH of the obtained photocatalyst dispersion was 6.9, and acetaldehyde resolution was 0.66 (1 / h). Moreover, while the photocatalyst dispersion contains 4.3 weight part of ammonium phosphate salts with respect to 100 weight part of photocatalysts, it does not contain a polymeric silicon compound, and a polymeric silicon compound / ammonium phosphate salt (weight ratio) is zero.

In addition, the average particle diameter of titanium oxide in the obtained photocatalyst dispersion | distribution was 155 nm, and the viscosity of this photocatalyst dispersion was 3 mPa.s when measured at 25 degreeC with the BL type | mold viscosity meter. In addition, this average particle diameter and viscosity did not change even after 1 month, and the obtained photocatalyst dispersion was also excellent in storage stability.

(Example 2)

0.42 g of colloidal silica (Nissan Chemical Co., Ltd. "IPA-ST-ZL", solid content concentration 30 weight%) was added to 30 g of the photocatalyst dispersion of 16.7 weight% of solid content concentration obtained by carrying out similarly to Example 1 as a polymeric silicon compound. To obtain a photocatalyst dispersion, which was diluted with ion exchanged water to a solid content concentration of 10% by weight.

PH of the obtained photocatalyst dispersion was 6.9, and acetaldehyde resolution was 0.64 (1 / h). The photocatalyst dispersion contains 4.3 parts by weight of ammonium phosphate salt with respect to 100 parts by weight of photocatalyst and 2.5 parts by weight of polymerizable silicon compound with respect to 100 parts by weight of photocatalyst, and the polymerizable silicon compound / ammonium phosphate salt (Weight ratio) is 0.57.

(Example 3)

1.25 g of colloidal silica ("IPA-ST-ZL manufactured by Nissan Chemical, 30 weight% of solid content concentration") was added as a polymerizable silicon compound to 30 g of a photocatalyst dispersion having a solid content concentration of 16.7% by weight in the same manner as in Example 1. To obtain a photocatalyst dispersion, which was diluted with ion exchanged water to a solid content concentration of 10% by weight.

PH of the obtained photocatalyst dispersion was 6.9, and acetaldehyde resolution was 0.64 (1 / h). Moreover, the photocatalyst dispersion contains 4.3 weight part of ammonium phosphate salts with respect to 100 weight part of photocatalysts, and 7.5 weight part of polymerizable silicon compounds with respect to 100 weight part of photocatalysts, and is a polymeric silicon compound / ammonium phosphate salt (Weight ratio) is 1.74.

(Comparative Example 1)

157.5 g of 60% nitric acid (manufactured by Wako Pure Chemical Industries, Limited Reagent) was dissolved in 10.84 kg of ion-exchanged water to prepare an aqueous nitric acid solution. A photocatalyst dispersion was obtained in the same manner as in Example 1 except that this aqueous solution of nitric acid was used instead of the aqueous solution of ammonium phosphate (the amount of nitric acid in the dispersion was 0.026 by weight relative to titanium oxide).

PH of the obtained photocatalyst dispersion was 2.3 and acetaldehyde resolution was 0.62 (1 / h). The photocatalyst dispersion contains no ammonium phosphate salt and no polymerizable silicon compound, and the polymerizable silicon compound / ammonium phosphate salt (weight ratio) is zero.

The average particle diameter of titanium oxide in the obtained photocatalyst dispersion was 132.7 nm, and the viscosity of the photocatalyst dispersion was 3 mPa · s when measured at 25 ° C. with a BL-type viscometer.

(Comparative Example 2)

2.09 g of colloidal silica (Nissan Chemical Co., Ltd. "IPA-ST-ZL", solid content concentration 30 weight%) was added to 30 g of the photocatalyst dispersion of 16.7 weight% of solid content concentration obtained by carrying out similarly to Example 1 as a polymeric silicon compound. To obtain a photocatalyst dispersion, which was diluted with ion exchanged water to a solid content concentration of 10% by weight.

PH of the obtained photocatalyst dispersion was 6.9, and acetaldehyde resolution was 0.60 (1 / h). Moreover, the photocatalyst dispersion contains 4.3 weight part of ammonium phosphate salts with respect to 100 weight part of photocatalysts, and contains 12.5 weight part of polymerizable silicon compounds with respect to 100 weight part of photocatalysts, and the polymeric silicon compound / ammonium phosphate salt (Weight ratio) is 2.91.

(Comparative Example 3)

5.57g of colloidal silica (Nissan Chemical Co., Ltd. "IPA-ST-ZL", solid content concentration 30 weight%) is added to 20 g of photocatalyst dispersion of 16.7 weight% of solid content concentration obtained by carrying out similarly to Example 1 as a polymeric silicon compound. To obtain a photocatalyst dispersion, which was diluted with ion exchanged water to a solid content concentration of 10% by weight.

PH of the obtained photocatalyst dispersion was 6.9, and acetaldehyde resolution was 0.54 (1 / h). Moreover, the photocatalyst dispersion contains 4.3 weight part of ammonium phosphate salts with respect to 100 weight part of photocatalysts, and contains 50 weight part of polymerizable silicon compounds with respect to 100 weight part of photocatalysts, and the polymeric silicon compound / ammonium phosphate salt (Weight ratio) is 11.62.

(Comparative Example 4)

A photocatalyst dispersion having a solid content concentration of 21.0 wt% and a pH of 6.9 was obtained in the same manner as in Example 1 except that the amount of ammonium dihydrogen phosphate was doubled (diluted with ion-exchanged water to make the solid content concentration 10 wt%). Did not do it).

Since this photocatalyst dispersion gelled when left at room temperature, the acetaldehyde resolution could not be measured. Moreover, the photocatalyst dispersion contains ammonium phosphate salt 8.6 weight part with respect to 100 weight part of photocatalysts, and does not contain a polymeric silicon compound, and polymerizable silicon compound / ammonium phosphate salt (weight ratio) is zero.

As mentioned above, the following was understood from the result of an Example and a comparative example. That is, since Example 1 is a photocatalyst dispersion which does not contain a polymeric silicon compound, and Example 2 and Example 3 are a photocatalyst dispersion which contains a polymeric silicon compound within the range prescribed | regulated by this invention, either It was found that a coating film having high photocatalytic activity can be formed. In more detail, when comparing Example 1 with Example 2 or Example 3, since Example 1 which does not contain a polymeric silicon compound has high acetaldehyde resolution, in order to obtain a coating film with a high photocatalytic activity, it is possible to obtain a polymeric silicon film. It was found that the fewer the compounds, the better.

On the contrary, in Comparative Example 1, the photocatalyst particles were sufficiently dispersed by setting the pH to an acidic region. However, since the acidic acid was concerned, corrosiveness to the substrate, danger to human body, etc. were concerned, and the photocatalytic activity of the photocatalyst dispersion according to the present invention. Fell slightly. In addition, since the comparative example 2 and the comparative example 3 are the photocatalyst dispersions which contain a polymeric silicon compound more than the range prescribed | regulated by this invention, the photocatalytic activity of the coating film formed in all was inferior to the Example.

In addition, since the comparative example 4 is a photocatalyst dispersion which contains the ammonium phosphate salt beyond the range prescribed | regulated by this invention, a viscosity rise occurred and it gelled at room temperature.

The photocatalyst dispersion of the present invention makes it easy to form photocatalysts in various materials such as, for example, fiber materials, building materials, automobile materials, etc., and makes it possible to impart high photocatalytic activity to these materials. Various materials imparted with photocatalytic activity by the photocatalytic dispersion of the present invention can decompose NOx in the atmosphere, decompose odorous substances (e.g., tobacco odors) in living spaces or work spaces, or bacteria (e.g., , Radioactive bacteria), algae, fungi and the like can be suppressed.

Claims (4)

As a dispersion containing a photocatalyst and an aqueous solvent, it contains ammonium phosphate salt in the ratio of less than 5 weight part with respect to 100 weight part of photocatalysts, and also contains no polymeric silicon compound or 7.5 weight part with respect to 100 weight part of photocatalysts While containing in the following ratios, the value of polymeric silicon compound / ammonium phosphate salt (weight ratio) is 5 or less, and pH is 5-9, The photocatalyst dispersion characterized by the above-mentioned. The method of claim 1, A photocatalyst dispersion wherein the photocatalyst is titanium oxide. The method according to claim 1 or 2, The photocatalyst dispersion which photocatalyst shows photocatalytic activity with respect to light irradiation by a fluorescent lamp. The method according to claim 1 or 2, The photocatalyst dispersion whose ammonium phosphate salt is either one or both of ammonium dihydrogen phosphate and diammonium hydrogen phosphate.