JP6096536B2 - Photocatalyst composite particles and method for producing the same - Google Patents

Description

  The present invention relates to a photocatalyst composite particle and a method for producing the same.

  A photocatalyst typified by titanium oxide exhibits a strong organic substance decomposing force and a photoexcited superhydrophilic phenomenon when irradiated with light corresponding to an energy exceeding its band gap. That is, the holes and excited electrons generated when the photocatalyst absorbs light propagates to water and oxygen to generate radicals having strong oxidizing power and reducing power. The organic substance decomposing power for decomposing the organic substance is expressed by this radical. In addition, the photocatalyst that has received the light is excited to oxidize and separate oxygen in the crystal. As a result, a defect of an oxygen trace is formed in the photocatalyst, and a water molecule is adsorbed to the defect to develop a photoexcited superhydrophilic phenomenon.

  In outdoor use products using a photocatalyst, it is known that a self-cleaning function can be imparted by applying a photoexcited superhydrophilic phenomenon. However, it has been pointed out that when directly applied to an organic base material or the like, the organic base material itself is eroded by its organic substance decomposing power (for example, Patent Document 1).

  In Patent Document 1, at least one of crystalline titanium oxide having a crystallite diameter in the range of 1 to 10 nm or an optical semiconductor nanotube having a tube thickness in the range of 1 to 10 nm as an optical semiconductor crystal is provided. A photocatalyst film that exhibits a photoexcited superhydrophilization phenomenon while suppressing the decomposition of organic substances under sunlight irradiation by being contained on the main surface is disclosed.

  In addition, it is disclosed that by applying the quantum size effect expressed by reducing the crystallite and reducing the light absorption amount of the crystalline titanium oxide itself, the organic substance decomposing power of the crystalline titanium oxide can be suppressed (for example, Patent Document 2). In Patent Document 2, crystalline titanium oxide particles having a small crystallite diameter are obtained by photocorrosion (photodissolution) by irradiating strong ultraviolet rays to commercially available crystalline titanium oxide having a large crystallite diameter. It is disclosed that it can be obtained. The quantum size effect is a phenomenon in which the band gap energy increases as the particle size decreases.

JP 2009-208062 A JP 2012-5999 A

  However, in the case of the above-mentioned Patent Document 1, in order to produce a photocatalytic film, an amorphous titanium oxide film is used as a starting material, and treatment is performed at a temperature of 100 ° C. or less in the presence of moisture, so that a large amount of desired crystals are generated. For this purpose, a relatively long time of several tens of hours to several hundreds of hours is required. Therefore, the photocatalyst film of Patent Document 1 has a problem that it is difficult to produce it efficiently.

  Further, in the case of the above-mentioned Patent Document 2, it is necessary to irradiate light to a narrow region of the titanium oxide raw material to photodissolve the crystals contained in the titanium oxide raw material, so that there is a problem that the loss of the raw material is large (yield <30%). was there. Furthermore, since the obtained crystalline titanium oxide particles have a small particle size of about several nanometers, there is a problem that they are difficult to be combined with other materials due to aggregation or the like and are difficult to handle.

  Then, this invention aims at providing the photocatalyst composite particle which can express a photoexcited superhydrophilic phenomenon, suppressing organic substance decomposition power.

The photocatalyst composite particle according to the present invention is a photocatalyst composite particle comprising a base particle formed of an inorganic oxide and a coating layer having a crystal part fixed on the surface of the base particle and formed of the photocatalyst particle. the thickness of the layer Ri der than 13nm or less 0.5 nm, the weight obtained by particle size distribution analysis of the 4-hour sonication was allowed to dispersion for 6 hours at room temperature the photocatalyst composite particles 5g in addition to isopropanol 45g The converted particle size is characterized by being less than twice the average particle size obtained from 20 particles of 100,000 times images of the photocatalyst composite particles using a scanning electron microscope .

A method for producing a photocatalyst composite particle according to the present invention is a photocatalyst composite particle comprising: a mother particle formed of an inorganic oxide; and a coating layer having a crystal part fixed on the surface of the mother particle and formed of the photocatalyst particle. In the production method, the mother particles are formed by a sol-gel method, and an alcohol is added to an aqueous dispersion slurry of the mother particles to obtain a dispersion in which the mother particles are dispersed in the alcohol; and it but to form a coating layer of the photocatalyst particles on the surface of the base particles by hydrolysis by mixing a photocatalyst compound to the dispersion prepared by dispersing, and heat treating the coating layer at a temperature of 500 ° C. to 1200 ° C. It is characterized by providing.

  According to the present invention, since the crystal part has a particle size of about several nanometers, it exhibits a quantum size effect and has a larger band gap than a general bulk photocatalytic crystal, thereby suppressing the organic substance decomposing power. However, the photoexcited superhydrophilic phenomenon can be exhibited.

FIG. 1A is a TEM image of particles according to Example and Comparative Example, FIG. 1A is Example 1-4-a, FIG. 1B is Example 1-4-b, FIG. 1C is Example 1-4-c, and FIG. This is Comparative Example 4-1-a. 2A is a SEM image of particles according to a comparative example, FIG. 2A is Comparative Example 1-0, FIG. 2B is Comparative Example 1-1, FIG. 2C is Comparative Example 1-2, FIG. 2D is Comparative Example 1-3, and FIG. Comparative Example 1-4 and FIG. 2F are Comparative Example 1-5. 3A is a SEM image of particles according to a comparative example, FIG. 3A is Comparative Example 2-0, FIG. 3B is Comparative Example 2-1, FIG. 3C is Comparative Example 2-2, FIG. 3D is Comparative Example 2-3, and FIG. Comparative Example 2-4 and FIG. 3F are Comparative Example 2-5, and FIG. 3G is Comparative Example 2-6. 4A is an SEM image of particles according to a comparative example, FIG. 4A is Comparative Example 3-0, FIG. 4B is Comparative Example 3-1, FIG. 4C is Comparative Example 3-2, FIG. 4D is Comparative Example 3-3, and FIG. This is Comparative Example 3-4. It is a SEM image of the particle concerning a comparative example, and Drawing 5A is comparative example 4-1, and Drawing 5B is comparative example 4-2.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(overall structure)
The article according to the present embodiment includes a base material and a photocatalytic film formed on the surface of the base material. Examples of the base material include acrylic resins such as polymethyl methacrylate, styrene resins such as polystyrene and ABS resins, olefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, 6-nylon and 6, Polyamide resins such as 6-nylon, polyvinyl chloride resins, polycarbonate resins, polyphenylene sulfide resins, polyphenylene ether resins, polyimide resins, cellulose resins such as cellulose acetate, polylactic acid, polyglycolic acid, polybutylene It can be formed with biodegradable resins such as succinate and polyvinyl alcohol. Further, the base material includes those having an organic coating film on the surface of a member made of a metal-based material, glass, a ceramic-based material, or other various inorganic or metal-based materials. Further, it may be a member made of a metal material, glass or ceramic material, or other various inorganic or metal materials.

  The photocatalyst film includes photocatalyst composite particles. The photocatalyst composite particles include base particles and a coating layer formed on the surface of the base particles.

  The mother particles preferably have a diameter of 10 nm to 2 μm. When the thickness is less than 10 nm, it is easy to form an aggregate, and the synthetic solution becomes viscous, making handling difficult. On the other hand, if it is 2 μm or more, it will be precipitated in the reaction solution, making it difficult to obtain a homogeneous synthesis.

  More preferably, the mother particles have a diameter of 20 nm or more and less than 200 nm. If it is in the said range, it can be used also for the optical use by which transparency is requested | required.

  The mother particle is formed of an inorganic oxide containing an inorganic substance, and is preferably formed of silica. The inorganic oxide is not limited to silica, and for example, titanium oxide, zirconia, barium oxide, iron oxide, cobalt oxide, chromium oxide, vanadium oxide, hafnium oxide, magnesium oxide, strontium oxide, and the like can be used. The mother particles are preferably formed by a sol-gel method.

  The coating layer has a crystal part formed of photocatalytic particles. The photocatalyst particles can be formed of, for example, titanium oxide or zinc oxide.

  The coating layer has a thickness of 0.5 nm to 13 nm. When the coating layer has a thickness of less than 0.5 nm, the mass of photocatalyst produced in the form of particles also has a size of less than 1 nm, there is not enough amorphous space to produce crystallites, and no crystallites are produced. Therefore, photocatalytic activity cannot be obtained.

  On the other hand, when the thickness of the coating layer exceeds 13 nm, the photocatalyst compound reacts outside the particle surface during synthesis, and there is a concern about the coalescence between the particles, and the generated crystallite is a general bulk photocatalytic crystal. The quantum size effect cannot be expected. Therefore, when the thickness exceeds 13 nm, the organic substance decomposition force cannot be suppressed. Further, when the thickness exceeds 13 nm, the photocatalytic compound reacts outside the particle surface at the time of synthesis and the particles are coalesced, so that dispersibility is deteriorated.

  The coating layer preferably has a thickness of 1 nm or more and less than 8 nm. If the thickness is within the above range, it is possible to synthesize photocatalyst composite particles without causing coalescence between particles, and since the photocatalyst particles fixed on the surface of the mother particles are extremely small, the generated crystal part is also small. As a result, the quantum size effect can be expressed more reliably.

  The photocatalyst composite particles preferably have a band gap of 3.3 eV or more and less than 3.7 eV. This is because when the band gap is less than 3.3 eV, the organic substance decomposing ability is equivalent to that of a commercially available photocatalytic crystal. Also. When the band gap is 3.7 eV or more, it is considered that almost no crystals exist in the photocatalyst particles and is almost amorphous, and not only the organic substance decomposition force but also the photoexcited superhydrophilic phenomenon is not exhibited.

  The photocatalyst composite particles preferably have a band gap of 3.40 eV or more and less than 3.65 eV. This is because if the band gap is within the above range, the photocatalyst particles can be expected to exhibit the photoexcited superhydrophilic phenomenon more reliably under sunlight while suppressing the organic substance decomposition force.

  The crystal part preferably contains one or more of anatase crystals, rutile crystals, and brookite crystals. The crystal part contains anatase crystals, and the crystallite diameter is more preferably 1 to 7 nm. If the crystallite diameter is within the above range, the quantum size effect can be obtained more reliably.

(Production method)
First, a method for producing photocatalyst composite particles will be described. The photocatalyst composite particles are produced by generating mother particles, dispersing the mother particles in a dispersion, and forming a coating layer on the surface of the mother particles. The case where silica is used as the inorganic oxide forming the mother particles and titanium oxide particles are used as the photocatalyst particles forming the coating layer will be described below.

  Silica particles as mother particles can be formed by a sol-gel method. That is, the mother particles can be produced by hydrolyzing, dehydrating and condensing, for example, silicon alkoxide as a compound containing an inorganic substance in a reaction solution composed of water, ammonia and alcohol.

  An alcohol solvent is used for the dispersion in which the mother particles obtained as described above are dispersed. As the alcohol solvent, intermediate alcohols having 4 to 10 carbon atoms such as butanol, pentanol, hexanol, heptanol, octanol, nonanol and decanol are preferably used.

  Preferably, the mother particles may be activated in the dispersion. The activation treatment is a treatment for accelerating proton elimination from the silanol group on the surface of the mother particle by the alkali acting on the surface of the mother particle. By performing this activation treatment, the adhesion between the mother particles and the coating layer can be improved. The activation treatment is performed by adding an alkaline aqueous solution to the dispersion. As the alkaline aqueous solution, an aqueous solution containing ammonia, an alkali metal hydroxide, an alkaline earth metal hydroxide, an alkali metal salt, an alkaline earth metal salt, or the like is used, and an aqueous ammonia solution is particularly preferable.

  The coating layer formed on the surface of the mother particles is formed by precipitating the photocatalyst particles by hydrolysis, drying and baking treatment. Hydrolysis is performed by mixing a compound containing a photocatalyst with the dispersion. As a result, photocatalyst particles are deposited on the surface of the mother particles, and a coating layer is formed.

In the present embodiment, titanium alkoxide or a partial hydrolyzate thereof is used as the compound containing the photocatalyst. As titanium alkoxide, general formula Ti (OR) ₄ or Ti (R ′) n (OR) _4-n (wherein R and R ′ are alkyl groups or acyl groups, particularly alkyl groups having 1 to 5 carbon atoms, or An alkoxide of titanium represented by an acyl group having 2 to 6 carbon atoms, and n is an integer of 1 to 3.

  Examples of the partially hydrolyzed product of titanium alkoxide include a product obtained by partially hydrolyzing the alkoxy group of the titanium alkoxide represented by the above general formula. Hydrolysis, dehydration and condensation of titanium alkoxide or its hydrolyzate are carried out under the conditions used in the usual sol-gel method.

  Next, it is preferable to terminate the reaction by adding a reaction terminator to the hydrolyzing dispersion. As the reaction terminator, isopropyl alcohol and aqueous ammonia can be used.

  Subsequently, the obtained dispersion liquid is concentrated and dried to obtain mother particles on which a coating layer is formed. Concentration drying is performed using, for example, an evaporator.

  Finally, the mother particle on which the coating layer is formed is fired under a temperature condition of 500 ° C. to 1200 ° C. for 3 hours to 48 hours. Thus, composite particles can be obtained.

  Next, a method for producing a photocatalytic film will be described. A coating liquid in which the composite particles obtained as described above are dispersed in a dispersion liquid is generated. The coating liquid may contain functional particles such as a binder (film-forming component) and other inorganic fine particles represented by silica. The coating solution is applied onto a substrate by conventional methods such as dip coating, spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating. . Finally, the photocatalytic film can be obtained by drying.

(Function and effect)
The photocatalyst composite particle configured as described above includes a mother particle and a coating layer that is fixed to the surface of the mother particle and has a crystal part formed of the photocatalyst particle, and the thickness of the coating layer is 0.5 nm or more. 13 nm or less.

  Since the crystal part generated in the coating layer has a particle size of about several nanometers, it exhibits a quantum size effect and has a larger band gap than a general bulk photocatalytic crystal. Then, the coating layer shifts the wavelength range of the responding light to the short wavelength side, that is, blue shifts. Therefore, the photocatalyst composite particles can suppress the organic substance decomposing power because the wavelength range of light that can be absorbed under sunlight is greatly limited as compared with bulk photocatalytic crystals.

  That is, assuming that the amount of sunlight irradiated is constant, the photocatalyst composite particles are limited in the amount of radical generation and the amount of organic matter decomposition per unit time is suppressed compared to bulk photocatalyst crystals. Incidentally, the photocatalyst composite particles are limited in the amount of hydrophilic groups generated on the surface of the coating layer, so that the rate of superhydrophilization becomes slow, but the surface is not prevented from becoming superhydrophilic.

  Therefore, the photocatalyst composite particles can exhibit high weather resistance while maintaining super hydrophilicity even when they are combined with an organic binder or the like for outdoor use. In fact, a photocatalyst film obtained by compositing photocatalyst composite particles can exhibit a photoexcited superhydrophilic phenomenon while suppressing the decomposition of organic matter under sunlight.

  Since the photocatalyst composite particles have a coating layer thickness of 13 nm or less, the photocatalytic compound can be prevented from reacting outside the particle surface during synthesis, and good dispersibility can be obtained. can do.

  Furthermore, the photocatalyst composite particles can be dispersed in a water / alcohol solution by a relatively simple dispersion treatment such as ultrasonic treatment or bead mill treatment, and can be combined with various particles. Since the photocatalyst composite particles have small base particles and a thin coating layer, the photocatalyst composite particles can be applied to a transparent material by using a monodispersed liquid containing the photocatalyst composite particles.

  In the photocatalyst composite particles, a photocatalyst compound is mixed with a dispersion in which mother particles are dispersed, and a coating layer of the photocatalyst particles is formed on the surface of the mother particles by hydrolysis, and the coating layer is heated at a temperature of 500 ° C. to 1200 ° C. Since it can manufacture by doing, it can manufacture in a short time compared with the past. If the calcination temperature is less than 500 ° C., crystallization is difficult to proceed, and if the calcination temperature exceeds 1200 ° C., the mother particles are dissolved, so that spherical photocatalyst composite particles cannot be obtained. In addition, when the firing temperature exceeds 1200 ° C., the titanium oxide crystal is transferred to a rutile type that hardly exhibits a hydrophilization behavior, and when the mother particle is a silica particle, the mother particle body is dissolved. The particle shape may not be maintained.

  Since the photocatalyst composite particles are produced by reacting and stabilizing the photocatalyst compound that has been stabilized by activating the mother particles in the dispersion, a reaction time of less than one day and a yield of 80% or more can be obtained. Can be manufactured efficiently. Therefore, since the photocatalyst composite particles can uniformly fix the photocatalyst particles on the surface of the mother particles while maintaining the shape of the mother particles, the photocatalyst composite particles can be developed for applications utilizing the shape of the mother particles, and the photocatalytic characteristics can be stably obtained. .

(Example)
(Manufacture of photocatalyst composite particles)
Next, examples of the photocatalyst composite particles according to the present embodiment will be described. Photocatalyst composite particles were produced by the following procedure. First, a dispersion containing silica particles as mother particles was prepared. Three types of silica particles with particle sizes of 50 nm, 120 nm, and 1.0 μm were prepared. A dispersion containing mother particles of each particle size was produced as follows.

(Preparation of a dispersion containing a base particle size of 50 nm)
As a dispersion containing an inorganic oxide, 100 g of Ube Nitto Kasei High Plessica AS (particle size 50 nm, CV value 27.6%, water-dispersed slurry solid content concentration 10 wt%) and 35 g of isopropanol are added, and the solid content concentration is 7.5 wt% or less. The solution was prepared at room temperature. And after concentrating until it became solid content concentration 15 wt% or more on condition of 80 degreeC and 30 mbar, the operation | work which made it dilute with isopropanol and made 7.5 wt% or less again was repeated 3 times. Then, it concentrates until it becomes solid content concentration 15wt% or more, After concentrating the solution of solid content concentration 7.5wt% or less which added 1-butanol in the liquid, it dilutes with 1-butanol and again 7.5wt The operation to make a solution of no more than% was repeated twice. Furthermore, by diluting with 1-butanol, a 10 wt% silica particle 1-butanol dispersion was prepared and used as liquid (1).

(Preparation of dispersion containing mother particles having a particle size of 120 nm)
Following the production of liquid (1), Ube Nitto Kasei High Plessica AS (particle size: 120 nm, CV value: 19.2%, water-dispersed slurry solid content concentration: 10 wt%) is prepared as a dispersion containing an inorganic oxide. (2).

(Preparation of dispersion containing mother particles having a particle diameter of 1.0 μm)
Add 10g Ube Nitto Kasei High Plessica FQ (particle size 1.0μm, CV value 3.5%) as an inorganic oxide to 90g of 1-butanol, and perform ultrasonic treatment at room temperature for 4 hours for 10wt% silica A particle 1-butanol dispersion was prepared as Liquid (3).

(Preparation of reaction terminator)
The reaction terminator was obtained by mixing 0.5% aqueous ammonia and isopropanol at a ratio of 2: 5.

(Sample adjustment)
Subsequently, Examples and Comparative Examples were produced using the liquids (1) to (3) obtained as described above and a reaction terminator. The production conditions of each example and comparative example are as follows.

(Example 1-1-a)
While stirring 20 g of liquid (1) with a magnetic stirrer in a 110 mL screw tube bottle, 0.5 g of 25% aqueous ammonia was added dropwise, and the mixture was stirred for 30 minutes while maintaining the liquid temperature at 20 ° C. Next, a titanium alkoxide mixed liquid of 0.25 g of titanium tetraisopoxide and 20 g of 1-butanol was added to the liquid at a rate of 4 g / min, and the mixture was further stirred for 30 minutes. And after adding 10g of reaction terminators and stirring for 15 minutes, it heated up to 60 degreeC, stirring was continued for 18 hours, maintaining 60 degreeC, and reaction was terminated. Further, this liquid was concentrated and dried using an evaporator under the conditions of 80 ° C. and 30 mbar to obtain particulate titanium oxide-coated silica particle powder. Further, firing was performed under the conditions of 300 ° C. for 2 hours (temperature increase time 30 minutes) and 500 ° C. for 24 hours (temperature increase time 30 minutes) to obtain photocatalyst composite particle powder.

(Example 1-1-b)
Photocatalyst composite, following Example 1-1-a, except that the firing temperature was 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 800 ° C. for 24 hours (including a temperature increase of 10 ° C./min). Particle powder was obtained.

(Example 1-2-a, b)
Photocatalyst composite particle powder was obtained in the same manner as in Examples 1-1-a and b except that a titanium alkoxide mixed solution of 0.5 g of titanium tetraisopoxide and 20 g of 1-butanol was used.

(Example 1-3-3-a, b)
Photocatalyst composite particle powder was obtained in the same manner as in Examples 1-1-a and b except that a titanium alkoxide mixed liquid of titanium tetraisopoxide 1.0 g and 1-butanol 20 g was used.

(Example 1-4-4-a, b)
Except for using a titanium alkoxide mixed solution of 1.5 g of titanium tetraisopoxide and 20 g of 1-butanol, a powder of photocatalyst composite particles was obtained in the same manner as in Examples 1-1-a and b.

(Example 1-4-4-c)
A titanium alkoxide mixed solution of 1.5 g of titanium tetraisopoxide and 20 g of 1-butanol is used, and the firing temperature is 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min), 1000 ° C. for 24 hours (including a temperature increase of 10 ° C./min). ) To obtain a powder of photocatalyst composite particles.

Example 2-1-a
Example (Except for using (Liquid 2) instead of (Liquid 1), 0.3 g of 25% ammonia water to be dropped, and using a titanium alkoxide mixed liquid of 0.2 g of titanium tetraisopoxide and 20 g of 1-butanol) In accordance with 1-1-a, powder of photocatalyst composite particles was obtained.

(Example 2-2a)
Photocatalyst composite particle powder was obtained in the same manner as in Example 2-1a except that a titanium alkoxide mixed solution of 0.4 g of titanium tetraisooxide and 20 g of 1-butanol was used.

(Example 2-3-3-a)
Except for using a titanium alkoxide mixed solution of 0.6 g of titanium tetraisopoxide and 20 g of 1-butanol, a powder of photocatalyst composite particles was obtained following Example 2-1-a.

(Example 2-4-a)
Except for using a titanium alkoxide mixed liquid of 0.8 g of titanium tetraisooxide and 20 g of 1-butanol, a powder of photocatalyst composite particles was obtained in the same manner as in Example 2-1-a.

(Example 2-4-b)
A titanium alkoxide mixed solution of 0.8 g of titanium tetraisopoxide and 20 g of 1-butanol is used, and the firing temperature is 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min), 800 ° C. for 24 hours (including a temperature increase of 10 ° C./min). ) To obtain a powder of photocatalyst composite particles.

(Example 2-4-c)
A titanium alkoxide mixed solution of 0.8 g of titanium tetraisopoxide and 20 g of 1-butanol is used, and the firing temperature is 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min), 1000 ° C. for 24 hours (including a temperature increase of 10 ° C./min). ) To obtain a powder of photocatalyst composite particles.

(Example 2-5-a)
Except for using a titanium alkoxide mixed liquid of 2.0 g of titanium tetraisopoxide and 20 g of 1-butanol, a powder of photocatalyst composite particles was obtained in the same manner as in Example 2-1-a.

Example 3-1-b
Instead of (Liquid 1), (Liquid 3) is used, and 25% ammonia water to be dropped is 0.2 g. A titanium alkoxide mixed liquid of titanium tetraisopoxide 0.03 g and 1-butanol 20 g is used, and the firing temperature is 300. The powder of the photocatalyst composite particles was prepared in the same manner as in Example 1-1-a except that the temperature was 2 hours (including a temperature increase of 10 ° C./min) and 800 ° C. for 24 hours (including a temperature increase of 10 ° C./min). Obtained.

(Example 3-2-b)
Except for using a titanium alkoxide mixed liquid of 0.6 g of titanium tetraisopoxide and 20 g of 1-butanol, a powder of photocatalyst composite particles was obtained in the same manner as in Example 3-1-b.

(Example 3-3-3-b)
Except for using a titanium alkoxide mixed solution of titanium tetraisopoxide 0.12 g and 1-butanol 20 g, a powder of photocatalyst composite particles was obtained in the same manner as in Example 3-1-b.

(Comparative Example 1-0)
(Liquid 1) was concentrated and dried using an evaporator at 80 ° C. and 30 mbar to obtain a powder of silica particles.

(Comparative Example 1-0-a)
The comparative example 1-a was fired under the conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 500 ° C. for 24 hours (including a temperature increase of 10 ° C./min). Obtained.

(Comparative Example 1-0-b)
The comparative example 1-0 was fired under the conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 800 ° C. for 24 hours (including a temperature increase of 10 ° C./min). Obtained.

(Comparative Example 1-0-c)
The comparative example 1-0 was fired under the conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 1000 ° C. for 24 hours (including a temperature increase of 10 ° C./min). Obtained.

(Comparative Example 1-1)
A powder was obtained in the same manner as in Example 1-1-a except that the firing step was omitted.
(Comparative Example 1-2)
A powder was obtained in the same manner as in Example 1-2a except that the firing step was omitted.
(Comparative Example 1-3)
Except for omitting the firing step, a powder was obtained in the same manner as in Example 1-3-a.
(Comparative Example 1-4)
Except for omitting the firing step, a powder was obtained following Example 1-4-4-a.

(Comparative Example 1-5)
A powder was obtained in the same manner as in Example 1-1-a except that a titanium alkoxide mixed liquid of 4.0 g of titanium tetraisooxide and 20 g of 1-butanol was used and the firing step was omitted.

(Comparative Examples 1-5-a, b)
A powder was obtained in the same manner as in Examples 1-1-a and b except that a titanium alkoxide mixed solution of 4.0 g of titanium tetraisooxide and 20 g of 1-butanol was used.

(Comparative Example 2-0)
(Liquid 2) was concentrated and dried using an evaporator at 80 ° C. and 30 mbar to obtain silica particle powder.

(Comparative Example 2-0-a)
The comparative example 2-0 was fired under the conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 500 ° C. for 24 hours (including a temperature increase of 10 ° C./min) to obtain silica particle powder.

(Comparative Example 2-0-b)
Comparative Example 2-0 was fired under the conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 800 ° C. for 24 hours (including a temperature increase of 10 ° C./min) to obtain a powder of silica particles.

(Comparative Example 2-0-c)
The comparative example 2-0 was fired under the conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 1000 ° C. for 24 hours (including a temperature increase of 10 ° C./min) to obtain silica particle powder.

(Comparative Example 2-1)
Except for omitting the firing step, a powder was obtained following Example 2-1-a.
(Comparative Example 2-2)
A powder was obtained in the same manner as in Example 2-2a except that the firing step was omitted.
(Comparative Example 2-3)
A powder was obtained in the same manner as in Example 2-3-3-a except that the firing step was omitted.
(Comparative Example 2-4)
Except for omitting the firing step, a powder was obtained following Example 2-4-a.
(Comparative Example 2-5)
Except that the firing step was omitted, a powder was obtained according to Example 2-5-a.

(Comparative Example 2-6)
A powder was obtained in the same manner as in Example 2-1a except that a titanium alkoxide mixed solution of 20 g of titanium tetraisooxide and 20 g of 1-butanol was used and the firing step was omitted.

(Comparative Example 3-0)
(Liquid 3) was concentrated and dried using an evaporator at 80 ° C. and 30 mbar to obtain silica particle powder.

(Comparative Example 3-0-a)
The comparative example 3-0 was fired under the conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 500 ° C. for 24 hours (including a temperature increase of 10 ° C./min) to obtain silica particle powder.

(Comparative Example 3-0-b)
The comparative example 3-0 was fired under the conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 800 ° C. for 24 hours (including a temperature increase of 10 ° C./min) to obtain silica particle powder.

(Comparative Example 3-0-c)
The comparative example 3-0 was fired under the conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 1000 ° C. for 24 hours (including a temperature increase of 10 ° C./min) to obtain silica particle powder.

(Comparative Example 3-1)
Using (Liquid 3) instead of (Liquid 1), adding 25 g of 25% aqueous ammonia to 0.2 g, using a titanium alkoxide mixed liquid of 0.03 g of titanium tetraisopoxide and 20 g of 1-butanol, omitting the firing step. Except that, powder was obtained in the same manner as in Example 1-1-a.

(Comparative Example 3-2)
Using (Liquid 3) instead of (Liquid 1), adding 25 g of 25% ammonia water to 0.2 g, using a titanium alkoxide mixed liquid of 0.6 g of titanium tetraisopoxide and 20 g of 1-butanol, omitting the firing step. Except that, powder was obtained in the same manner as in Example 1-1-a.

(Comparative Example 3-3)
Using (Liquid 3) instead of (Liquid 1), adding 25 g of 25% ammonia water to 0.2 g, using a titanium alkoxide mixed liquid of 0.12 g of titanium tetraisopoxide and 20 g of 1-butanol, omitting the firing step. Except that, powder was obtained in the same manner as in Example 1-1-a.

(Comparative Example 3-4)
Using (Liquid 3) instead of (Liquid 1), adding 25 g of 25% aqueous ammonia to 0.2 g, using a titanium alkoxide mixed liquid of 2.0 g of titanium tetraisopoxide and 20 g of 1-butanol, omitting the firing step. Except that, powder was obtained in the same manner as in Example 1-1-a.

(Comparative Example 4-1)
In a 110 mL screw tube bottle, 20 g of 1-butanol and 0.5 g of 25% aqueous ammonia were stirred with a magnetic stirrer for 30 minutes while maintaining the liquid temperature at 20 ° C. Thereafter, a titanium alkoxide mixed solution of 1.5 g of titanium tetraisopoxide and 20 g of 1-butanol was slowly added to the solution over 5 minutes, and further stirred for 30 minutes. And after adding 10g of (Liquid 4) and stirring for 15 minutes, it heated up to 60 degreeC, stirring was continued for 18 hours, maintaining 60 degreeC, and reaction was terminated. Further, this liquid was concentrated and dried using an evaporator under conditions of 80 ° C. and 30 mbar to obtain a powder made of titanium oxide.

(Comparative Example 4-1-a)
The comparative example 4-1 was baked under conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 500 ° C. for 24 hours (including a temperature increase of 10 ° C./min) to obtain titanium oxide particle powder. .

(Comparative Example 4-1-b)
The comparative example 4-1 was fired under conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 800 ° C. for 24 hours (including a temperature increase of 10 ° C./min) to obtain titanium oxide particle powder. .

(Comparative Example 4-2)
A powder made of titanium oxide was obtained in the same manner as in Comparative Example 4-1, except that a titanium alkoxide mixed solution of 0.5 g of titanium tetraisopoxide and 1 g of 1-butanol was used.

(Comparative Example 4-2a)
The comparative example 4-2 was fired under the conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 500 ° C. for 24 hours (including a temperature increase of 10 ° C./min) to obtain titanium oxide particle powder. .

(Comparative Example 4-2b)
The comparative example 4-2 was fired under the conditions of 300 ° C. for 2 hours (including a temperature increase of 10 ° C./min) and 800 ° C. for 24 hours (including a temperature increase of 10 ° C./min) to obtain a powder of titanium oxide particles. .

(Comparative Example 5)
Titanium oxide powder ST-01 manufactured by Ishihara Sangyo was used.
(Comparative Example 6)
Ishihara Sangyo titanium oxide powder PT-501A was used.
(Comparative Example 7)
Titanium oxide powder TTO-51 made by Ishihara Sangyo was used.
(Comparative Example 8)
A titanium oxide aqueous dispersion PC-201 manufactured by Sumitomo Chemical was used.
(Comparative Example 9)
A titanium oxide aqueous dispersion STS-100 manufactured by Ishihara Sangyo was used.
(Comparative Example 10)
No particles.
Each characteristic was confirmed about the manufactured photocatalyst composite particle. Tables 1 to 4 show the characteristics of the manufactured Examples and Comparative Examples.

(Measurement of particle diameter and coating thickness)
The obtained powder was dispersed in water, the dispersion was dropped on a metal pedestal and dried, and then Pt for conduction was deposited by 50 mm using a metal evaporation machine (SC-701MCY) manufactured by Sanyu Electronics. Made a sample. SEM measurement was performed using a field emission type scanning electron microscope (JEM-6700F type, acceleration voltage 10 kV) manufactured by JEOL, and image analysis was performed with the company's image analysis software Smile view (ver. 2.2). The diameter was randomly determined for 20 particles from a 100,000-fold image, and the average value was taken as the particle size of the particles. Also, the thickness of the coating layer was obtained by subtracting the diameter of the mother particle from the diameter of the composite particle and dividing it by 2. This thickness is regarded as the size of the photocatalyst particles that grow in a dome shape.

When the particle size cannot be measured due to aggregation or the like, the amount of titanium tetraisopropoxide added per unit silica surface area (A [g / m ² ]), the calculated thickness of the coating layer (B [nm]), The following relational expression (Formula 1) was applied and calculated.

B = 3.7 × ln (A) +25.5 (Equation 1)

  The above (formula 1) is an approximate formula created from the values obtained in the examples. However, in the case of B ≧ 30, the term of the particle diameter (curvature R) of the silica particles is greatly involved, and the smaller the particle diameter of the silica particles, the higher the titanium oxide film thickness, the more the approximate expression is deviated. It cannot be applied.

When B ≦ 30, the silica particle weight (W [g]) in the reaction solution, the apparent specific gravity of the silica particles (2.0 [g / cm ³ ]), and the particle diameter of the silica particles (L [nm]) Thus, the total surface area (S [m ² ]) of the silica particles in the reaction solution was determined (Formula 2). In (Formula 2), [4/3 × π × (L / 2 × 10 ⁻⁹ ) ³ ] is the volume of one silica particle, and [4 × π × (L / 2 × 10 ⁻⁹ ) ² ] is silica. The surface area of one particle.

S = W ÷ [4/3 × π × (L / 2 × 10 ⁻⁹ ) ³ ] ÷ (2.0 × 10 ⁶ ) × [4 × π × (L / 2 × 10 ⁻⁹ ) ² ]
= 3 x W / L x 10 ³ (Formula 2)

  Further, the amount of titanium tetraisopropoxide (T [g]) used in the reaction was divided by S to calculate A (Formula 3).

A = T ÷ S (Equation 3)

  A transmission electron microscope (TEM) image of the photocatalyst composite particles according to Example 1-4-ac is shown in FIG. Moreover, the scanning electron microscope (SEM: Scanning Electron Microscope) image about the particle | grains concerning the comparative example obtained for reference is shown in FIGS.

(Crystal system measurement)
The obtained powder was subjected to XRD measurement using an X-ray diffractometer (X'Pert PRO) manufactured by PANalytical to identify the crystal system.

(Band gap measurement)
The obtained powder was packed in a quartz cell for measurement, and a diffuse reflection spectrum was measured using a JEOL ultraviolet-visible spectrophotometer (V-670) in which an integrating sphere (ISN-723) manufactured by JEOL was set. . For the baseline, the attached Spectralon (standard white plate for integrating sphere) was used, and dark correction was performed by blocking light transmission to the detection unit with a metal plate. The measurement conditions were: measurement mode:% T (transmission), response: medium, band width: 5.0 nm, scanning speed: 400 nm / min, measurement wavelength of 300 to 800 nm, and data capture interval: 1 nm. In addition, band gap analysis is performed with the company's band gap analysis software (VWBG-773) from the obtained data, and those identified as anatase type are identified as rutile type using direct transition calculation. For, band gap was calculated using indirect transition calculation.

(Crystallite diameter measurement)
Each powder dispersed in isopropanol is placed on a carbon mesh-supported molybdenum mesh as a sample, and a magnification of 4,000,000 using a field emission transmission electron microscope (JEM-2012F type, acceleration voltage 200 kV) manufactured by JEOL. Image measurement was carried out under the conditions of double and photographic range 50 nm × 65 nm, and the crystallite diameter was measured directly from the photograph.

(Synthetic solution)
The synthetic solution obtained by synthesizing the particles was measured with a viscomate viscometer (VM-1G) manufactured by Yamaichi Electric Industry Co., Ltd., and when the measured value was less than 50 cP, the viscosity was low, and when the measured value was 50 cP or more and less than 100 cP, the viscosity was A case where the measured value was 100 cP or more and less than 1000 cP was defined as a high viscosity Δ.

(Yield calculation)
The weight (yield) of the powder finally obtained after synthesis is divided by the sum of the solid content of the silica particles, which are the mother particles used in the synthesis, and the amount of titanium oxide produced from the titanium alkoxide. Yield. The case where the yield exceeded 80% was rated as ◎, the case where the yield exceeded 50% and 80% or less was indicated as ◯, the case where the yield exceeded 30% and less than 50% was indicated as △, and the case where the yield could not be taken out as powder.

  At this time, the solid content of the silica particle dispersion was collected by weighing about 1 g in an aluminum cup and weighed, then dried on a hot plate set at 150 ° C. for 1 hour and allowed to stand at room temperature for 10 minutes. It was calculated by measuring the weight of the food. In addition, the synthesized powder of each particle was taken out and further dried in an oven at 80 ° C. for 3 days to obtain the weight.

(Dispersibility check)
In a 110 mL screw tube bottle, 5 g of the obtained powder of each particle was dissolved in 45 g of isopropanol, and sonicated for 4 hours at room temperature using an AZONE ultrasonic processor.

  Then, the bottom of the screw tube bottle is observed, and whether or not a large lump is visually observed and the sedimentation of the particles when left for 6 hours is confirmed. The case where the sedimentation of the particles is observed is indicated by Δ. In addition, for highly dispersible particles in which particle sedimentation cannot be visually recognized, the dispersion particle size is measured using a light scattering meter (ELS-Z) manufactured by Otsuka Electronics Co., Ltd., and the weight-converted particle size obtained by particle size distribution analysis. Was the dispersed particle size. The case where the value obtained at this time was less than twice the particle size measured by SEM was evaluated as ◎, and the case where it was 2 times or more was evaluated as ◯.

(Manufacture of photocatalytic film)
Then, the evaluation film | membrane for evaluating photocatalyst performance was manufactured in the following procedures. First, 10 g of ethyl cellosolve and 5.07 g of titanium tetraisopropoxide (manufactured by Nippon Soda Co., Ltd.) were placed in a 50 mL glass container and stirred for 10 minutes with a magnetic stirrer while maintaining the temperature at 30 ° C. A mixed liquid of 0.31 g of distilled water, 0.85 g of 60% nitric acid and 3.91 g of ethyl cellosolve was added dropwise thereto, and the mixture was hydrolyzed for 4 hours while maintaining the liquid temperature at 30 ° C. The solid content concentration of the liquid containing the titania hydrolyzate (hereinafter referred to as “hydrolysis condensation liquid”) was 7.1% in terms of TiO ₂ . By using this hydrolysis-condensation liquid, an amorphous titanium oxide film can be formed. The amorphous titanium oxide film does not exhibit photocatalytic performance with this component alone, and the initial water contact angle can be set higher than that of the silica film. Therefore, the amorphous titanium oxide film can more easily evaluate the photocatalytic performance (hydrophilization behavior, organic matter decomposing ability) of the composite particles.

Next, 5 g of ethyl cellosolve, 3 g of the above-mentioned hydrolysis-condensation liquid, and 2 g of 10 wt% isopropanol dispersion of particles obtained using the items for confirming dispersibility were stirred and mixed in this order while keeping the liquid temperature at 20 ° C. Combined. Thereafter, using a spin coater made by Sanyu Electronics, a 3 mm-thick float glass plate of 5 cm was spin-coated at a rotation speed of 2000 rpm in a 20 ° C. environment for 1.5 minutes. Furthermore, it was dried in an oven at 120 ° C. for 2 minutes to obtain a photocatalytic function evaluation film. This evaluation film is covered with photocatalyst composite particles to be evaluated. Therefore, the evaluation film can be evaluated as a simple titanium oxide film because the surface is formed of titanium oxide particles that are coating layers of the photocatalyst composite particles to be evaluated.
The following characteristics of the obtained evaluation film were confirmed. Each characteristic is shown to Tables 1-4.

(Measurement of hydrophilization behavior)
For the hydrophilization behavior, the above evaluation film was sufficiently hydrophobized (water contact angle> 40 °) in a dark place using a stainless steel sealed container for light shielding, and then irradiated with ultraviolet rays of various wavelengths. And the change with time of the contact angle with respect to distilled water was traced with a contact angle meter (G-1-1000) manufactured by Elma Sales. Those having a contact angle of 30 ° or less after irradiation with ultraviolet rays of various wavelengths for 10 hours were considered to have photoresponsiveness at that wavelength. At this time, the case where the photoresponsiveness was observed at 310 nm or more and less than 350 nm was evaluated as ◎, the case where it was 350 nm or more and less than 365 nm was evaluated as ○, the case where 365 nm or less was less than 380 nm was evaluated as Δ, and the case where 380 nm or more was measured as ×.

At this time, a xenon light source (MAX-302) manufactured by Asahi Spectroscopic Co., Ltd. was used as the light source, and light having a predetermined wavelength with a half-value width of 15 nm or less was extracted by interposing a bandpass filter. Table 5 shows the light source used, its irradiation wavelength region, and the illuminance of light. Each illuminance was set so that the number of photons of various dominant wavelengths was substantially the same (3.7 × 10 ¹⁵ quanta / cm ² / s, ² mW / cm ² at 365 nm).

(Decomposition measurement of organic matter)
In accordance with the wet decomposition method defined in JIS R 1703-2, an organic matter decomposition index was determined by a methylene blue decomposition test. The organic substance decomposition index obtained at that time was evaluated as ◎ when the organic compound was less than 1, ◯ when it was 1 or more and less than 3, and Δ when it was 3 or more and less than 5, and x when it was 5 or more.

(Comprehensive evaluation)
Of the evaluations given in each evaluation, the lowest score was taken as the overall evaluation score for each powder. In each example, it was confirmed that the overall evaluation was で to Δ.

  Comparative Examples 1-0, 1-0-a to c, 2-0, 2-0-a to c, 3-0, and 3-0-a to c are all photocatalysts because they do not have a coating layer. Since the activity could not be obtained, the evaluation of “hydrophilization behavior” was x.

  Since all of Comparative Examples 1-1 to 5-1, 2-1 to 6, and 3-1 to 4 omit the firing treatment, the titanium oxide particles forming the coating layer are amorphous. Therefore, since the photocatalytic activity could not be obtained, the evaluation of “hydrophilization behavior” was x.

  In Comparative Examples 1-5, 1-5-a, b, 2-6, and 3-4, since the thickness of the coating layer exceeds 13 nm, the particles are aggregated. Evaluation became x.

  Since Comparative Examples 4-1, 4-2, 4-1-a, b, 4-2-a, b are not provided with mother particles, the dispersibility is deteriorated. Was evaluated as x.

Since Comparative Examples 5, 6, 8, and 9 are commercially available titanium oxides, all have high organic matter decomposing power, the evaluation of “hydrophilization behavior” is x or Δ, and the evaluation of “organic decomposing power” is x. became.
Since Comparative Example 10 was evaluated in the absence of particles, the photocatalytic activity was naturally not obtained, so the evaluation of “hydrophilization behavior” was x.

(Modification)
The present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the gist of the present invention.

Claims (8)

Mother particles formed of an inorganic oxide;
In the photocatalyst composite particle comprising a coating layer having a crystal part fixed to the surface of the mother particle and formed of the photocatalyst particle,
The thickness of the coating layer is Ri der than 13nm or less 0.5 nm,
The weight-converted particle diameter obtained by the particle size distribution analysis of a dispersion obtained by adding 5 g of the photocatalyst composite particles to 45 g of isopropanol, sonicating at room temperature for 4 hours, and allowing to stand for 6 hours is a scanning electron microscope of the photocatalyst composite particles. The photocatalyst composite particles, wherein the average particle diameter is less than twice the average particle diameter obtained from 20 particles of 100,000 times of the image using   The photocatalyst composite particle according to claim 1, wherein the band gap is 3.3 eV or more and less than 3.7 eV.   The photocatalyst composite particle according to claim 1 or 2, wherein the crystal part includes an anatase crystal and has a crystallite diameter of 1 to 7 nm.   The photocatalyst composite particle according to any one of claims 1 to 3, wherein the base particle has a particle size of 10 nm or more and 2 µm or less.   A dispersion liquid in which the photocatalyst composite particles according to any one of claims 1 to 4 are dispersed.   An article having a photocatalyst film containing the photocatalyst composite particles according to any one of claims 1 to 4 on the surface of a substrate. Mother particles formed of an inorganic oxide;
In the method for producing photocatalyst composite particles, comprising a coating layer having a crystal part fixed on the surface of the mother particles and formed of photocatalyst particles,
The mother particles are formed by a sol-gel method, and an alcohol is added to an aqueous dispersion slurry of the mother particles to obtain a dispersion in which the mother particles are dispersed in the alcohol;
And said base particles to form a coating layer of the photocatalyst particles on the surface of the base particles by hydrolysis by mixing a photocatalyst compound to the dispersion obtained by dispersing,
Heat-treating the said coating layer at the temperature of 500 to 1200 degreeC, The manufacturing method of the photocatalyst composite particle characterized by the above-mentioned. Before forming the coating layer of the photocatalyst particles on the surface of the mother particles, it further comprises adding an alkaline aqueous solution to the dispersion in which the mother particles are dispersed to subject the mother particles to an activation treatment. The method for producing photocatalyst composite particles according to claim 7.

Images