JP4710004B2 - Titanium oxide dispersion and method for producing the same - Google Patents

Description

  The present invention relates to a titanium oxide dispersion and a method for producing the same, and more particularly to a titanium oxide dispersion that is suitably used in the formation of a photocatalytic film and a functional oxide material.

  Titanium oxide is attracting attention as an electrode material for photocatalysts and dye-sensitized solar cells. In order to use for these uses, it is necessary to use as a film (titanium oxide film) coated on a substrate such as glass. Therefore, development of a method for forming a titanium oxide film on an arbitrary substrate has become an important technical problem. In order to make titanium oxide exhibit functions such as photocatalytic activity, the titanium oxide film mainly has particles having an anatase type crystal structure (this is referred to as “anatase type titanium oxide particles” in this specification). It is necessary that the titanium oxide film that is included is composed of “anatase-type titanium oxide film”).

  On the other hand, complex oxides containing titanium ions include a group of substances that exhibit electrical properties that are very useful for applications such as semiconductor properties and ferroelectricity. In order to exhibit this electrical property, it is necessary to calcinate these composite oxides at a temperature as low as possible in a short time. For this reason, a split acid solution of titanium oxide particles having high reactivity and sinterability and having a nano-level particle size that maintains a stable dispersion state in a solution is required as a precursor for production. ing.

  As a method of manufacturing a titanium oxide film having crystallinity by a chemical method, there is a method of forming an anatase-type titanium oxide film by applying a solution containing titanium ions to a substrate and then baking it. Generally, in order to obtain a titanium oxide film having crystallinity by applying a coating liquid to a substrate, baking at 400 ° C. or higher is required. That is, in the case of a chemical method in which a coating solution is applied and baked, it is difficult to form a crystalline titanium oxide film on a material such as an organic polymer that does not have heat resistance.

  As another method for manufacturing a titanium oxide film, there is a film forming method using a vapor deposition process in a vacuum such as a chemical vapor deposition method. According to this method, it is possible to form a film with highly controlled film thickness, crystallinity, etc., but there are restrictions on the material and size that can be formed, and other methods are required because a special vacuum device is required. As a result, the film forming cost becomes high.

Therefore, as a method for solving the above problems, a method for producing a titanium oxide film using an aqueous solution in which anatase-type titanium oxide particles are dispersed is disclosed in Patent Document 1 below. More specifically, in Patent Document 1 below, an anatase-type titanium oxide particle whose surface is modified with peroxy is formed by heat-treating an aqueous solution containing a titanium peroxy compound at 200 ° C. or lower. A technique is disclosed in which an anatase-type titanium oxide film is formed by stably dispersing in an aqueous solution and applying and drying an aqueous solution in which the anatase-type titanium oxide particles are dispersed on a substrate.
Japanese Patent Laid-Open No. 10-067516

  However, since the aqueous solution described in Patent Document 1 tends to aggregate and precipitate due to other cations present together, it must be purified using a large amount of distilled water in order to prepare a highly stable dispersion. There is a problem of not becoming. In addition, when used as a raw material for preparing a functional oxide material, it is necessary to mix and complex a solution in which anatase-type titanium oxide particles are dispersed with other materials. There is a problem that it is likely to occur. Furthermore, since hydrogen peroxide used in the production process has a high oxidation activity, if it remains in an aqueous solution in which fine titanium oxide particles are dispersed, there is a risk of foaming or a decrease in film formation due to secondary reactions.

  Therefore, an object of the present invention is to solve the above problems and provide an aqueous solution (titanium oxide dispersion) in which titanium oxide particles having higher stability are dispersed.

  As a result of extensive studies by the present inventors to achieve the above object, the titanium oxide particles are more stable in an aqueous solvent due to the interaction between the alcohol molecules and the solvent molecules by complexing the titanium oxide particles with the alcohol molecules. The present invention has been conceived.

  That is, the titanium oxide dispersion according to the present invention is such that titanium oxide particles having at least one of a monohydric alcohol molecule, a dihydric or higher polyhydric alcohol molecule, and a sugar alcohol molecule on the surface are dispersed in the solution. One of the features. By having alcohol molecules on the surface of titanium oxide (compositing), a stable aqueous dispersion can be formed in a wide pH range, and various other oxide fine particles and their dispersions and precipitates can be generated. It becomes possible to mix uniformly. In particular, the adjustment of conventional particle dispersions often requires the pH of the solution to be adjusted to acidity or basicity, and if the pH of the solution deviates greatly, the substrate is corroded when a coating film or the like is formed. However, according to the present invention, it is possible to disperse the fine particles using the interaction between the alcohol molecules and the solvent while keeping the liquidity of the solution neutral. It becomes. In the present invention, “having alcohol molecules on the surface” means that Ti—O—C bonds are formed between the alcohol molecules and the titanium oxide particles.

  As the alcohol molecule complexed with the titanium oxide particles, either a monohydric alcohol molecule, a polyhydric alcohol molecule having a valence of 2 or more, or a sugar alcohol molecule can be used, but the reactivity such as hydrogen peroxide is high and unstable. In order to produce a more stable and safer titanium oxide dispersion without using a new substance, it is more desirable to combine a polyhydric alcohol having two or more valences with titanium oxide particles.

  By using this titanium oxide dispersion, it becomes possible to form a titanium oxide film on various materials such as metal, glass, and polymer films. Various photocatalysts, functional oxide materials, ultraviolet absorption films, etc. It can be applied to anything. In other words, application as a precursor material for producing composite oxide materials having various physical properties is expected.

  Further, in the method for producing a titanium oxide dispersion according to the present invention, a neutral or basic aqueous solution containing at least one of a monohydric alcohol, a dihydric or higher polyhydric alcohol, and a sugar alcohol is added to a titanium-containing compound. A step of heating to form a precipitate, a step of separating the formed precipitate from the aqueous solution, a step of washing the precipitate separated from the aqueous solution, a step of mixing and heating the washed precipitate and the acid solution Separating the precipitate from the acid solution, washing the precipitate separated from the acid solution, and dispersing the precipitate separated from the washed acid solution in an aqueous solution.

  Further, the method for producing a titanium oxide dispersion according to the present invention comprises adding a neutral or basic aqueous solution containing at least one of a tetrahydric or higher polyhydric alcohol and a sugar alcohol to a titanium-containing compound, followed by heating and precipitation. Forming the product, separating the formed precipitate from the aqueous solution, washing the precipitate separated from the aqueous solution, mixing and heating the washed precipitate and the acid solution, and from the acid solution A step of separating the precipitate, a step of washing the precipitate separated from the acid solution, and a step of dispersing the precipitate separated from the washed acid solution in an aqueous solution.

  A step of adding a neutral or basic aqueous solution containing at least one of a monohydric alcohol, a dihydric or higher polyhydric alcohol, and a sugar alcohol to the titanium-containing compound in the above production method to form a precipitate; It is desirable that at least one of the step of mixing and heating the washed precipitate and the acid solution is performed in a temperature range of 30 ° C. or higher and 120 ° C. or lower.

  A step of adding a neutral or basic aqueous solution containing at least one of a monohydric alcohol, a dihydric or higher polyhydric alcohol, and a sugar alcohol to the titanium-containing compound in the above production method to form a precipitate; It is also desirable that the step of mixing and heating the washed precipitate and the acid solution is performed within a range of 1 hour to 48 hours.

  Moreover, it is also desirable to use an acid aqueous solution having a pH of 4 or less in the step of mixing and heating the washed precipitate and the acid solution in the above production method.

As described above, the titanium oxide particle dispersion liquid of the present invention can maintain a stable dispersion state for a long period of time without almost sedimentation. An anatase-type titanium oxide film can be prepared by applying this dispersion solution to a substrate and drying at room temperature, and can be applied to a photocatalytic film. Moreover, this dispersion solution is stable in a wide pH range, and can maintain stability even when many metal ions coexist. Accordingly, various functional complex oxide thin films containing titanium ions and application as precursors for the production of sintered bodies are possible.

  Embodiments of the present invention will be described below.

  In the titanium oxide dispersion according to this embodiment, titanium oxide particles having at least one of a monohydric alcohol molecule, a dihydric or higher polyhydric alcohol molecule, or a sugar alcohol molecule on the surface are dispersed in a solution.

  The particles dispersed in the titanium oxide dispersion (hereinafter referred to as “the present dispersion”) are composed of crystalline titanium oxide or amorphous titanium oxide, a monohydric alcohol molecule, a divalent polyhydric or higher polyvalent. It is thought that the structure which consists of the part which consists of a monohydric alcohol molecule or a sugar alcohol molecule is compounded. In particular, it is considered that a stable dispersion state can be maintained without agglomeration in an aqueous solvent by interaction between alcohol molecules present on the particle surface and water molecules as a solvent. The particle size of the titanium oxide particles dispersed in this dispersion solution is 30 nm or less and is considered to have an anatase-type crystal structure or amorphous, and the titanium oxide particles are stable without almost any precipitation in water. scatter.

Next, a method for producing the titanium oxide dispersion will be described.
First, an aqueous solution containing at least one of a monohydric alcohol, a dihydric or higher polyhydric alcohol, or a sugar alcohol is added to and mixed with a titanium ion-containing compound (mixing step), and this mixed solution is placed in a sealed container and subjected to heat treatment. (Initial heat treatment step). This forms a precipitate containing titanium oxide particles in the aqueous solution.

Next, this solution is centrifuged or filtered to separate the precipitate (precipitation separation step). Then, the separated precipitate is dispersed in distilled water, and the precipitate is separated by centrifugation or filtration (precipitation washing step). This step cleans the precipitate and removes excess alcohol molecules from the precipitate.

Then, this precipitate is added to the acid solution and subjected to heat treatment (acid heat treatment) to obtain an aggregate of titanium oxide fine particles having alcohol molecules on the surface (aggregate production step).

  And the aggregate obtained by this is separated from an acid solution by centrifugation or filtration (aggregate separation step), then dispersed in an alcohol solution, and centrifuged or filtered (acid washing step) to settle. A solution in which titanium oxide particles are stably dispersed can be obtained (dispersing step).

As the “titanium-containing compound” used in this production method, titanium alkoxide such as titanium tetraisopropoxide, titanium tetrachloride, titanium sulfate and the like can be used. It is also possible to use a solution obtained by dissolving titanium hydroxide in an acid.

  Further, in the mixing step in this production method, a monohydric alcohol aqueous solution, a dihydric or higher polyhydric alcohol aqueous solution, or a sugar alcohol aqueous solution is mixed with a solution containing a titanium-containing compound. Obtainable. In this case, ethanol, isopropanol, propanol, butanol and the like can be used as the monohydric alcohol, and examples of the dihydric or higher polyhydric alcohol include ethylene glycol, propylene glycol, 1,4-butanediol, glycerin, pentaerythritol and the like. Can be used. As the sugar alcohol, erythritol, xylitol, D-mannitol, D-sorbitol and the like can be used.

  Further, the treatment temperature in the initial heat treatment step in this production method is not essential, but is preferably 30 ° C. or higher, and more preferably 40 ° C. or higher. For example, when the heat treatment temperature is 40 ° C., a precipitate in which titanium oxide particles and alcohol molecules are complexed (having alcohol molecules on the surface of the titanium oxide particles) can be obtained by treatment for 80 hours or more. When the temperature is lower than room temperature, a much longer time is required. Therefore, it is desirable that the temperature is 30 ° C. or higher as a practical range. The temperature for realizing a more practical range of reaction rate and crystallinity is more preferably 70 ° C. or higher. By increasing the heat treatment temperature, the time for producing a composite precipitate can be shortened, and the crystallinity of titanium oxide in the precipitate can be further increased.

  On the other hand, the upper limit of the treatment temperature in this step is not essential, but is preferably 120 ° C. or lower, and more preferably 100 ° C. or lower. When the temperature is higher than 120 ° C., there is a possibility that a decomposition reaction may occur when a polyhydric alcohol or a sugar alcohol molecule in the solution is used, and a by-product formation reaction may easily occur. Therefore, the range of the treatment temperature in the initial heat treatment step is 30 ° C. or more and 120 ° C. or less, more desirably 70 ° C. or more and 100 ° C. or less.

  The treatment time in the initial heat treatment step depends on the treatment temperature and the valence and concentration of the coexisting alcohol molecules, but is preferably in the range of 1 to 48 hours as a practical range. For example, when the heat treatment temperature is 95 ° C., of course, depending on the valence and concentration of the coexisting alcohol molecules, the precipitate of the complexed anatase-type titanium oxide particles and alcohol molecules in the heat treatment time of 24 hours. Can be obtained as

  Further, in the precipitation separation step and the precipitation washing step in the present production method, although not essential, the number of rotations is 3000 r. p. m. As described above, it is highly desirable to rotate for 10 minutes or more. This is because if the rotational speed is low, the recovery rate of the precipitate is lowered and the yield is deteriorated. The precipitation washing step is a step performed for washing the obtained precipitate and removing excess alcohol molecules. The number of times is not limited, but it is preferably repeated twice or more. The same applies to the aggregate separation step.

  The acid heat treatment in the present production method is intended to hydrolyze the bond between titanium oxide and alcohol molecules Ti—O—C present in the complexed product of titanium oxide particles and alcohol molecules. It is desirable to be performed in the state. The temperature range is the same as that in the initial heat treatment step. The heat treatment time is preferably 1 hour to 48 hours, more preferably 6 hours to 24 hours. If it is shorter than this, the effect of sufficient acid treatment cannot be obtained, and if it is longer than this, cleavage between the titanium oxide and the alcohol molecule proceeds and the molecular weight of the alcohol present on the titanium oxide surface decreases, or the acid This is because the stability of the titanium oxide dispersion finally obtained is reduced by the effect of adsorption of the anions contained in. The precipitate obtained in the previous precipitation washing step may be heat-treated with the acid solution without drying, or may be heat-treated by adding the acid solution after drying.

  The purpose of the acid washing step in this production method is to disperse the aggregate obtained in the above step in alcohol and dissolve excess acid in the alcohol. The alcohol used in this step is not essential, but ethanol, methanol, propanol, 1-butanol and the like can be suitably used, and alcohol having high hydrophilicity is more desirable in order to improve the acid washing efficiency. Further, in this step, centrifugation or filtration is performed to recover the precipitate dispersed in the alcohol. The conditions for the centrifugation are the same as in the precipitation separation step and the like. Furthermore, it is also useful to repeat the operation of collecting the collected precipitate again in alcohol and then collecting the precipitate by centrifugation or filtration twice or more in order to make the acid washing more complete. Further, a desirable acid solution range is pH 4 or less.

  Moreover, the dispersion | distribution process in this manufacturing method is performed by adding the obtained deposit to distilled water and stirring. As a stirring method, it is useful to use a stirrer, and a preferable range of the rotation speed and time of the stirrer is, for example, 500 rpm. p. m for 10 minutes. Thereby, the precipitate can be dispersed in distilled water. In this dispersion, almost no precipitate is confirmed even after standing for about 6 months, and the Tyndall phenomenon can be confirmed. On the other hand, in the conventional general unstable solution, precipitates are observed after standing for about one day, and when the acid is not sufficiently washed, the pH of this solution becomes about 3. May end up.

  The titanium oxide dispersion obtained in this embodiment can use distilled water as a solvent, and an anatase-type titanium oxide thin film can be obtained simply by applying it to a substrate and drying it. In addition, it is safer without containing peroxide and the like, and since there is no instability of the solution due to decomposition of the peroxide, it can be stored stably for a long time. When the surface of the titanium oxide particle is dispersed in distilled water by surface modification with a functional group having a negative charge as in the prior art, the surface charge of the titanium oxide particle is reduced by adding other cations to the solution. Neutralized and easily agglomerated, but the surface of the titanium oxide particles obtained according to the present embodiment has a neutral alcohol molecule on the surface and realizes stable dispersion by interaction with the water molecule. Therefore, even if a cation such as another metal ion is added to the solution, a stable dispersion state can be maintained for a long time without causing aggregation. Therefore, it can be used as a precursor for producing a titanium ion-containing ceramic material by adding another metal ion-containing aqueous solution to the titanium oxide particle-dispersed solution and mixing it, followed by drying or coating the substrate, followed by heat treatment.

The following examples further illustrate the invention. However, the present invention is not limited in any way by the examples given here.
Example 1
D-mannitol (1.82 g, 0.01 mol), which is a hexavalent sugar alcohol, was dissolved in distilled water to make a total volume of 100 ml to prepare 100 ml of a 0.1 mol / l aqueous D-mannitol solution. Next, after 2.84 g (0.01 mol) of titanium tetraisopropoxide was weighed into a beaker, 100 ml of the previous 0.1 mol / l D-mannitol aqueous solution was added thereto and stirred well. This resulted in the formation of a white precipitate.

  The beaker was sealed and allowed to stand in an air constant temperature phase of 95 ° C. for 24 hours. In order to separate the precipitate obtained here, 3000 r. p. m. For 10 minutes. Next, the separated precipitate was dispersed in 100 ml of distilled water, and then centrifuged again. Further, the obtained precipitate was again dispersed in 100 ml of distilled water, followed by centrifugal separation to remove unreacted sugar alcohol and wash it. The obtained precipitate was dried at 75 ° C. for 12 hours to obtain a powder in which white titanium oxide and alcohol molecules were combined.

  In addition, it carried out similarly to the said method, changed D-mannitol aqueous solution density | concentration into each density | concentration of 0-0.5 mol / l, and obtained other powder by the same method.

  The obtained powder was measured with an X-ray diffractometer (MPX18 manufactured by Bruker AXS) using a copper target under measurement conditions of an acceleration voltage of 40 kV and a current of 200 mA. The result is shown in FIG. A diffraction peak due to anatase-type titanium oxide was observed up to a D-mannitol aqueous solution concentration of 0.02 mol / l. Moreover, it turned out that the half width of a diffraction peak increases as D-mannitol concentration increases, and the crystallite diameter of the obtained titanium oxide decreases. Moreover, when the D-mannitol solution density | concentration became 0.05 mol / l or more, it turned out that the obtained titanium oxide becomes amorphous. As described above, the concentration of the D-mannitol solution, which is a sugar alcohol, greatly affected the crystallinity of titanium oxide obtained by hydrolysis reaction of a titanium alkoxide with a sugar alcohol solution.

  The obtained powder was heat-treated at 1000 ° C. for 1 hour in an alumina crucible, and the ratio between the number of titanium atoms and the number of carbon atoms in the powder was calculated from the weight change before and after the heat treatment, and an aqueous D-mannitol solution was obtained. A graph plotted against concentration is shown in FIG. It was found that when the concentration of the aqueous D-mannitol solution was increased from 0.005 mol / l to 0.5 mol / l, the C / Ti (atomic ratio) of the obtained precipitate increased from 0.20 to 1.61. From this, it turned out that a composite_body | complex produces | generates between a titanium oxide and D-mannitol molecule | numerator by mixing a titanium alkoxide and D-mannitol aqueous solution and performing heat processing.

(Example 2)
0.5 g of the composite powder of titanium oxide and D-mannitol obtained in Example 1 was dispersed in 100 ml of an aqueous nitric acid solution having a concentration of 0.1 mol / l to 1 mol / l and placed in a sealed container. It was allowed to stand for 24 hours in an air constant temperature phase of 95 ° C. By this operation, a white to milky yellow gel-like precipitate was obtained. In order to separate this precipitate from the aqueous acid solution, 3000 r. p. m. For 10 minutes. The supernatant was discarded and the resulting precipitate was dispersed in 50 ml of ethanol to wash the acid. In order to recover the precipitate from this dispersion, 3000 r. p. m. The mixture was centrifuged for 10 minutes and the collected precipitate was dispersed in ethanol. In order to recover the precipitate from this dispersion, 3000 r. p. m. The precipitate obtained by centrifuging for 10 minutes was dispersed in 200 ml of distilled water. p. m. And stirred for 5 minutes to obtain a dispersion.

  The obtained dispersion was allowed to stand for 1 week and the state of the solution was observed. Dispersion solutions obtained by heat treatment using 0.1 mol / l and 1 mol / l aqueous nitric acid solution were allowed to settle for 1 week. However, the dispersion obtained by heat treatment using a 0.5 mol / l nitric acid aqueous solution maintained a stable state with almost no precipitation for more than half a year. When the acid solution concentration is low, it is considered that the decomposition of the complex of titanium oxide and D-mannitol did not proceed sufficiently and the titanium oxide particles obtained after the acid treatment were not sufficiently dispersed. In addition, when the acid concentration is high, it is considered that stable dispersion could not be achieved due to a decrease in the number of alcohol molecules present on the surface of the titanium oxide particles obtained after the acid treatment or adsorption of anions contained in the acid. That is, the desirable concentration is in the range higher than 0.1 mol / l and lower than 1 mol / l, more desirably 0.2 mol / l to 0.8 mol / l, and further desirably 0.3 mol / l to 0 to 0. 0.7 mol / l or less.

  Titanium oxide and an alcohol molecule complex obtained by using a 0.1 mol / l D-mannitol aqueous solution in Example 1 and the complex were heated at 95 ° C. for 24 hours in a 0.5 mol / l nitric acid aqueous solution. FIG. 3 shows an X-ray diffraction pattern of the powder obtained by drying the obtained dispersion solution at 75 ° C. for 12 hours. The composite powder before heat treatment with nitric acid aqueous solution did not show a clear diffraction peak and was amorphous. However, the powder obtained by drying the dispersion obtained by acid treatment showed a diffraction peak derived from anatase type crystals. Thus, even if the complex of titanium oxide and alcohol molecules was amorphous, it was crystallized into anatase-type titanium oxide after heat treatment with an acid solution.

  In addition, the titanium oxide-alcohol molecule complex obtained using the 0.1 mol / l D-mannitol aqueous solution in Example 1 and the complex were heated at 95 ° C. for 24 hours in a 0.5 mol / l nitric acid aqueous solution. The carbon atom content ratio (weight ratio) derived from alcohol molecules contained in each of the powders obtained by drying the obtained dispersion solution at 75 ° C. for 12 hours was measured using a CHN element analyzer (manufactured by PerkinElmer). did. The carbon atom content in the composite powder was 11.69% (% by weight). The carbon atom content in the powder obtained by drying the dispersion was 2.28% (% by weight). From this result, it was found that the alcohol molecules were removed by the hydrolysis reaction by heating the complex of titanium oxide and alcohol molecules in an acid aqueous solution. In addition, it is considered that a stable dispersion solution of titanium oxide particles was generated because the bond due to alcohol molecules between the titanium oxide particles was broken by the acid treatment.

  When the nitric acid aqueous solution concentration is 0.5 mol / l, when the heat treatment time at 95 ° C. is treated for each time from 6 hours to 24 hours, the finally obtained dispersion solution is stable and has one month. Even when allowed to stand at room temperature, almost no precipitation / aggregation occurred. However, when the heat treatment time was 1 hour or less and 48 hours or more, aggregation occurred upon standing at room temperature for 1 week, and formation of precipitates was observed. Therefore, it is necessary to determine an appropriate acid solution concentration, treatment time, and treatment temperature for each alcohol molecule and acid solution complexed with titanium oxide particles.

  Dispersion obtained after heat treatment of titanium oxide and alcohol molecule complex obtained in Example 1 using a 0.1 mol / l aqueous D-mannitol solution at 95 ° C. for 24 hours in a 0.5 mol / l nitric acid aqueous solution. The form of the titanium oxide particles contained in the powder obtained by drying the solution at 75 ° C. for 12 hours was observed with an electrolytic emission scanning electron microscope (manufactured by JEOL Ltd.) under the conditions of an acceleration voltage of 5 kV and an emission current of 12 μA. The image is shown in FIG. It can be seen that particles having an average particle diameter of 8.4 nm were obtained.

(Example 3)
After preparing a complex of titanium oxide and alcohol molecules by the method shown in Example 1 for each of 0.01 mol / l, 0.05 mol / l, 0.1 mol / l, and 0.5 mol / l D-mannitol aqueous solution. In Example 2, a 0.5 mol / l nitric acid aqueous solution was used and heat treatment was performed at 95 ° C. for 24 hours to obtain an anatase-type titanium oxide particle-dispersed aqueous solution. The form of the titanium oxide particles contained in the powder obtained by drying this dispersion solution at 75 ° C. for 12 hours was measured under the conditions of an accelerating voltage of 5 kV and an emission current of 12 μA using an electrolytic emission scanning electron microscope (JSM- manufactured by JEOL). The particle size was determined by observation. FIG. 5 shows a graph plotting the relationship between the D-mannitol aqueous solution concentration and the particle size of the obtained anatase-type titanium oxide particles. As the D-mannitol concentration increased from 0.01 mol / l to 0.5 mol / l, the particle size decreased from 16.4 nm to 6.9 nm. From the above, it was found that when the concentration of the aqueous D-mannitol solution was increased, the particle size of the titanium oxide particles in the finally obtained titanium oxide particle split acid solution was reduced.

Example 4
Titanium oxide-alcohol under the same conditions except that 0.1 mol / l D-sorbitol, which is a hexavalent sugar alcohol, was used instead of the D-mannitol aqueous solution, which is the hexavalent sugar alcohol used in Example 1. A molecular complex powder was prepared. Then, this powder was heat-treated with a 0.5 mol / l and 1 mol / l nitric acid aqueous solution at 95 ° C. for 24 hours by the method shown in Example 2 to prepare a titanium oxide particle dispersion solution. When a 0.5 mol / l nitric acid aqueous solution was used, the obtained dispersion solution had low stability and sedimentation was observed after standing for 1 day. Even if the dispersion obtained using a 1 mol / l nitric acid aqueous solution was allowed to stand at room temperature for 1 month, almost no precipitation was observed.

(Example 5)
Preparation of titanium oxide-alcohol molecular complex powder under the same conditions except that 0.1 mol / l of erythritol, which is a tetravalent sugar alcohol, was used instead of the D-mannitol aqueous solution of the hexavalent sugar alcohol used in Example 1. Went. Then, this powder was heat-treated with a 0.5 mol / l nitric acid aqueous solution at 95 ° C. for 24 hours by the method shown in Example 2 to prepare a titanium oxide particle dispersion solution. From the X-ray diffraction measurement of the powder obtained by drying the obtained dispersion solution at 75 ° C. for 24 hours, it was found that anatase-type titanium oxide was obtained. In addition, no precipitation was observed even when the obtained dispersion was allowed to stand at room temperature for 1 month.

(Example 6)
A titanium oxide-alcohol molecular complex powder was prepared under the same conditions except that 0.1 mol / l of xylitol, which is a pentavalent sugar alcohol, was used instead of the D-mannitol aqueous solution used in Example 1. Then, this powder was heat-treated with a 0.5 mol / l nitric acid aqueous solution at 95 ° C. for 24 hours by the method shown in Example 2 to prepare a titanium oxide particle dispersion solution. From the X-ray diffraction measurement of the powder obtained by drying the obtained dispersion solution at 75 ° C. for 24 hours, it was found that anatase-type titanium oxide was obtained. In addition, no precipitation was observed even when the obtained dispersion was allowed to stand at room temperature for 1 month.

  In Example 1, a titanium oxide-alcohol molecular complex powder was prepared under the same conditions except that a 0.1 mol / l aqueous solution of hexavalent sugar alcohol D-mannitol was used. Then, this powder was heat-treated with a 0.5 mol / l nitric acid aqueous solution at 95 ° C. for 24 hours by the method shown in Example 2 to prepare a titanium oxide particle dispersion solution. A glass substrate (50 mm × 25 mm × 1 mm) was immersed in this dispersion, slowly pulled up (1 cm / min) and dried at 95 ° C. to form a titanium oxide thin film on the glass substrate. The film thickness of the obtained film was about 100 nm. Further, as a result of X-ray diffraction measurement, it had an anatase type crystal structure.

X-ray diffraction pattern of titanium oxide-D-mannitol composite powder Dependence of carbon atom content in titanium oxide-D-mannitol complex composite powder on D-mannitol aqueous solution concentration X-ray diffraction pattern of titanium oxide-D-mannitol composite powder before and after heat treatment in nitric acid aqueous solution (95 ° C., 24 hours) Field emission scanning electron micrograph of titanium oxide particles present in titanium oxide particle dispersion Dependence of Titanium Oxide Particle Size in Titanium Oxide Dispersion Solution on D-Mannitol Solution Concentration

Claims (7)

A step of adding a neutral or basic aqueous solution containing a tetrahydric or higher sugar alcohol to a titanium-containing compound and heating to form a precipitate;
Separating the formed precipitate from the aqueous solution;
Washing the precipitate separated from the aqueous solution;
Mixing and heating the washed precipitate and acid solution;
Separating the precipitate from the acid solution;
Washing the precipitate separated from the acid solution;
Dispersing the precipitate separated from the washed acid solution in an aqueous solution. The step of adding a neutral or basic aqueous solution containing a tetrahydric or higher sugar alcohol to the titanium-containing compound and heating to form a precipitate is performed in a temperature range of 30 ° C. to 120 ° C. The method for producing a titanium oxide dispersion according to claim 1 . The method for producing a titanium oxide dispersion according to claim 1 , wherein the step of mixing and heating the washed precipitate and the acid solution is performed in a temperature range of 30 ° C to 120 ° C. The step of adding a neutral or basic aqueous solution containing a tetrahydric or higher sugar alcohol to the titanium-containing compound and heating to form a precipitate is performed in a range of 1 hour to 48 hours. The method for producing a titanium oxide dispersion according to claim 1 . The method for producing a titanium oxide dispersion according to claim 1 , wherein the step of mixing and heating the washed precipitate and the acid solution is performed within a range of 1 hour to 48 hours.   The method for producing a dispersion solution of titanium oxide according to claim 1, wherein the step of mixing and heating the washed precipitate and the acid solution uses an acid aqueous solution having a pH of 4 or less.   A step of adding a neutral or basic aqueous solution containing a tetrahydric or higher sugar alcohol to a titanium-containing compound and heating to form a precipitate;
Separating the formed precipitate from the aqueous solution;
Washing the precipitate separated from the aqueous solution;
Mixing and heating the washed precipitate and acid solution;
Separating the precipitate from the acid solution;
Washing the precipitate separated from the acid solution;
A titanium oxide dispersion in which titanium oxide particles having sugar alcohol molecules on the surface are dispersed in a solution, which is produced by dispersing the precipitate separated from the washed acid solution in an aqueous solution.