Production of solution for forming titanium dioxide

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a method for producing a titanium oxide coating agent for forming a titanium oxide film on a substrate, and a titanium oxide film coating material produced by using the coating agent.

【0002】

[Conventional technology]

The titanium oxide film is formed by a coating method in which a titanium oxide powder slurry or an aqueous solution of titanium chloride or titanium sulfate is applied to a substrate and then fired, or a sol-gel method in which a sol prepared by hydrolysis of a metal alkoxide is applied to a substrate and then fired. , Sputtering method of sputtering an oxide target in a high vacuum to form a film on a substrate, CVD method of volatilizing an organic metal compound or halide and decomposing it in a heating furnace to form a film on the substrate, solid particles There is plasma firing which melts in plasma generated in the atmosphere and irradiates the surface of the substrate. Of these, the method of using a coating liquid as a method for forming the titanium oxide film is said to be simple and highly practical.

【0003】

Although the coating method using titanium oxide powder is simple, it is difficult to obtain a dense and good-adhesive film, and the formation of a titanium oxide film generally requires a high synthesis temperature, so that it has heat resistance to withstand the synthesis temperature. It is necessary to use the above-mentioned substrate, and there are restrictions on the types of substrates that can be applied. Further, an acid or an appropriate organic dispersant is generally used to obtain a dispersed liquid of the titanium oxide fine particles, and there is a drawback that a harmful halogen compound or the like is generated by firing. Further, the method of applying and firing an aqueous solution of titanium chloride, titanium sulfate or the like produces a harmful halogen compound, and the firing temperature also requires several hundred degrees or more.

【0004】

In addition, commercially available titanium oxide sol produced by the sol-gel method can be coated and impregnated, can be coated over a large area, and can be synthesized at low temperature, and has many industrial advantages. Since it had to be synthesized using a metal, the raw material was expensive, and the raw material was chemically unstable and was easily affected by temperature control and atmosphere, which made it difficult to handle. In addition, the sol-gel method contains acids and organic substances in the raw material sol, so heating at 400 ° C or higher is required to remove it by firing, which is not suitable for materials that are easily attacked by acids. There was a problem that it was easy to become.

【0005】

In addition, the sol-gel method is complicated and requires the use of an organic solvent, and acids, alkalis, or organic substances are added to the titanium oxide sol produced by the sol-gel method, which causes a problem of corrosion of the material to be coated. there were. In addition, a temperature of 400 ° C. or higher is required to decompose organic substances, and there are drawbacks such as the formation of harmful halides and nitrogen oxides during heating and firing.

【0006】

As described above, it is difficult to prepare a dense crystalline titania film at a low temperature by the conventional method, and it is necessary to decompose and eliminate organic substances, acids and the like by heat treatment in the sol-gel method which can be prepared at a relatively low temperature. This also causes the film to become more porous, and the heat treatment temperature had to be relatively high in order to produce a dense film. In addition, these auxiliaries have a drawback of producing harmful substances such as nitrogen oxides and organic gases by heat treatment.

【0007】

In contrast to these methods, it is known that when a titanium oxide film is formed from peroxotitanium hydrate, a film having good properties can be formed at a relatively low temperature. Peroxotitanium hydrate is produced in the form of solid precipitate by adding hydrogen peroxide solution directly to a solution of titanium tetrachloride, titanium sulfate, etc. to generate peroxotitanium hydrate ion, which is condensed to form a solid precipitate. Is known to be.

【0008】

In addition, peroxotitanium hydrate ions are generated as polynuclear ions containing two or more titanium atoms at a pH of 1 or higher, and gradually condense at room temperature to precipitate and precipitate. Therefore, it is difficult to use it as a coating agent for titanium oxide at a pH of 1 or more, and therefore, the types of substrates to which a strongly acidic coating agent having a pH of 1 or less can be applied are limited. In addition, there is also a problem that the contained halogen, sulfur and the like generate harmful substances such as hydrogen halide and sulfur oxide by heat treatment.

【0009】

Further, in order to prepare a high-purity titanium oxide film, hydrogen peroxide solution is directly added to or dissolved in titanium hydride or alkoxy titanium to dissolve it, and titanium hydrogen peroxide, that is, a substance considered to be peroxotitanium hydrate. Is proposed in Japanese Patent Application Laid-Open No. 62-252319. However, these titanium raw materials are not stable, and when a hydrogen peroxide solution is applied, a considerable exothermic reaction occurs, which has a drawback that adverse effects such as thermal decomposition of the raw materials and products occur. Therefore, when mass production is attempted, the peroxotitanic acid produced polymerizes and becomes extremely thickened due to insufficient cooling, and in extreme cases, the particles grow to the extent that they block the transmission of light. When used as a coating agent, it causes a decrease in film adhesion and density.

【0010】

Further, a method for producing an aqueous solution considered to be peroxotitanium hydrate described as a titanyl ion hydrogen peroxide complex or titanic acid by adding a hydrogen peroxide solution to a hydroxide-containing titanium gel or sol is described in JP-A. It is described in Japanese Patent Application Laid-Open No. 63-35419 and Japanese Patent Application Laid-Open No. 1-224220. However, when hydrogen peroxide solution is added directly to titanium hydroxide, peroxolation and solution formation occur at the same time, which causes a large amount of heat generation and requires sufficient stirring and cooling. If it cannot be cooled sufficiently, there is a problem that thickening occurs, condensation occurs, the polymer grows as particles, and the polymer may become turbid.

【0011】

In addition, when preparing a gel or sol of titanium hydroxide-containing, a basic substance such as ammonia is added, but since the adsorption of titanium hydroxide is instantaneously generated, cations such as ammonium ions and chlorine ions which are impurities are used. It becomes easier to take in and adsorb the anions of. In particular, the presence of anionic impurities such as chlorine ions and sulfate ions promotes the condensation of peroxotitanium hydrate produced after the addition of the hydrogen peroxide solution, and a transparent aqueous solution may not be obtained. Further, it is difficult to completely remove impurities even if the hydrous titanium is washed with distilled water, which has been a big problem for stable production of peroxotitanium hydrate.

【0012】

Further, in JP-A-9-71418 and JP-A-10-67516, the present inventor obtained a coating agent in which anatase ultrafine particles were precipitated by heating peroxotitanium hydrate, whereby adhesion was obtained. Proposes that it is possible to form a good crystalline titanium film. With these methods, it is possible to form a crystalline titania film with better adhesion than conventional methods, but when the residual amount of cations such as ammonium ions is large, peroxotitanium hydration When an aqueous solution of an aqueous solution is heated to prepare an anatase sol, decomposition of the peroxo group is less likely to occur, the size of the particles becomes large, and the adhesion or density may be inferior when used as a coating agent. It was.

【0013】

[Problems to be Solved by the Invention]

The present invention improves the conventional problems and provides a new method for preparing an aqueous solution of peroxotitanium hydrate. That is, when an aqueous solution of peroxotitanium hydrate is prepared with hydrogen peroxide solution, the adhesion that occurs when it is used as a coating agent due to condensation due to thermal influence in the production process or excessive growth of particles, etc. An object of the present invention is to prevent a decrease in density, and an object of the present invention is to obtain a titanium oxide-forming solution capable of forming a titanium oxide coating film having good adhesion and a high density.

【0014】

[Means for solving problems]

In the present invention, in the method for producing a solution for forming a titanium oxide, a solution obtained by adding a basic substance after adding a hydrogen peroxide solution to a titanium-containing raw material aqueous solution to form a peroxotitanium complex is left or left. After forming a precipitate of a polymer of peroxotitanium hydrate by heating, at least the dissolved components other than water derived from the titanium-containing raw material aqueous solution are removed, and then a hydrogen peroxide solution is allowed to act to make a solution. This is a method for producing a solution for forming an oxide. Further, it is a method for producing the above-mentioned titanium oxide forming solution for removing dissolved components other than water derived from a basic substance added for hydrate formation. This is the method for producing the above-mentioned titanium oxide forming solution, in which the dissolved components are removed by washing with water or by an ion exchange reaction. Further, it is the above-mentioned method for producing a titanium-containing solution for forming a titanium oxide, in which a reaction between a precipitate of a polymer of peroxotitanium hydrate and a hydrogen peroxide solution is carried out at a temperature of 40 ° C. or lower.

【0015】

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention has found that in the process of producing a solution for forming a titanium oxide via peroxotitanium hydrate, a solution for forming a titanium oxide having excellent characteristics can be obtained by removing factors that promote condensation and the like. The present invention has been achieved. That is, condensation and the like are prevented by early separation of reaction products that promote condensation and the like in the reaction process, or impurities mixed in from the raw materials, and the exothermic reaction is not continuously carried out, but peroxidation. By separating the process of exothermic reaction by reaction with hydrogen water into a first exothermic reaction and a second exothermic reaction, the problem caused by the exothermic reaction is solved, and it is composed of the following steps.

【0016】

(1) Precipitation step of polymer of peroxotitanium hydrate A soluble titanium compound such as titanium tetrachloride is diluted with water and an appropriate amount of aqueous hydrogen peroxide solution is added to form a brown peroxo complex, and then a basic substance such as ammonia is added to add yellow peroxotitanium water. An aqueous solution of a Japanese product is prepared, and the aqueous solution is left at room temperature or heated to precipitate and precipitate a polymer of peroxotitanium hydrate. (2) Removal process of ionic substances and impurities The liquid containing the precipitate and precipitate of the polymer of peroxotitanium hydrate is washed, or treated by filtration and washing to remove ammonium ions and chlorine ions contained in the liquid, or impurities derived from the raw materials. .. (3) Step of forming peroxohydrate aqueous solution By adding hydrogen peroxide solution while cooling the peroxotitanium hydrate from which ionic substances and impurities have been removed by washing treatment to room temperature or below room temperature, a yellow transparent and semi-stable aqueous solution of peroxotitanium hydrate is prepared. To do. By producing by the above steps, a titanium oxide forming solution in which condensation is suppressed can be obtained.

【0017】

Examples of the soluble titanium compound used as a raw material in the method of the present invention include titanium tetrachloride, titanium sulfate, titanium nitrate, and alkoxytitanium. Further, the amount of hydrogen peroxide solution added to the aqueous solution of the soluble titanium compound needs to have a molar ratio of hydrogen peroxide / titanium of 1 or more, and if the amount is less than that, peroxolation is not completely completed. Moreover, since some of the added hydrogen peroxide solution decomposes without being involved in the reaction, it is preferable to add the hydrogen peroxide / titanium molar ratio in excess of 1.

【0018】

When hydrogen peroxide solution is added to a soluble titanium-containing solution, peroxolation occurs almost instantly, and when the pH is 3 or less, it is mainly dissolved as a cation, and when the pH is 3 or more, it is mainly an anion of peroxotitanium hydrate. Exists as. It is considered that this is because the higher the pH, the faster the condensation and the precipitation of the amorphous peroxotitanium hydrate polymer. Even when a basic substance is added, if the pH is low, the time for precipitating the polymer of peroxotitanium hydrate becomes long. Therefore, it is preferable to add the basic substance until the pH becomes 3 or more, and more preferably. It is better to adjust the pH to the neutral range.

【0019】

When a yellow precipitate is formed from the yellow transparent liquid of peroxotitanium hydrate produced by adding a basic substance, it may be left at room temperature, but the precipitation should be promoted by heating. Can be done. Precipitation becomes even faster with stirring. However, since anatase crystal particles may be generated when heated to 80 ° C. or higher, it is preferable to perform heating at a temperature of 80 ° C. or lower.

【0020】

In the step of removing ammonium ions and chlorine ions contained in the liquid or impurities derived from the raw material from the liquid containing the precipitate, a method such as decantation, filtration washing, centrifugation, or an ion exchange reaction, reverse osmosis A method of removing an ionic substance by applying a penetration method can be used.

【0021】

If the residual amount of impurities is large, the stability and properties of the finally obtained aqueous solution of peroxotitanium hydrate will be adversely affected, so sufficient treatment is desirable. In particular, anions such as chlorine ions are considered to promote the condensation of peroxotitanium hydrate, and if their removal is insufficient, they may not be completely transparent and may become turbid. On the other hand, even if cations such as ammonium ions remain, a yellow transparent aqueous solution containing peroxotitanium hydrate can be obtained by sufficiently removing the anions. Further, in the treatment of the precipitate, it is necessary to prevent the precipitate from being dried because it is dehydrated and solidified when the precipitate is dried, which adversely affects the subsequent solution step.

【0022】

Next, in the step of forming the peroxohydrate aqueous solution, when hydrogen peroxide solution is added to the liquid containing the washed precipitate precipitate, the amount of hydrogen peroxide solution added is 1 or more in the ratio of hydrogen peroxide / titanium. However, if it is less than that, it may not be possible to completely solubilize the solution. Further, if it is cooled to 40 ° C. or lower in advance, it is possible to prevent the liquid from being overheated due to the heat of reaction or the like, and it is possible to prevent the peroxotitanium hydrate in solution from being recondensed. When the liquid temperature during the reaction becomes 40 ° C or higher, the viscosity becomes very thick, so the liquid temperature needs to be 40 ° C or lower, and preferably cooled to 20 ° C or lower.

【0023】

In the conventional method of adding hydrogen peroxide solution directly to titanium hydroxide or titanium oxide hydrate, a large amount of heat is generated because peroxoification and dissolution processes occur continuously, but peroxotitanium hydrate that has already been peroxoized. When the polymer is solubilized, the reaction proceeds relatively slowly without generating much heat, so that an aqueous solution of peroxotitanium hydrate having excellent quality can be obtained.

【0024】

In this solvation process, when heated to room temperature or higher, the solvated peroxotitanium hydrate is recondensed, so that the desired titanium oxide coating agent can be obtained by thickening the liquid, forming fine particles, and making it opaque. Since there may be no case, it is preferable to add the hydrogen peroxide solution after pre-cooling the precipitate-containing liquid, or to add the hydrogen peroxide solution under cooling.

【0025】

After being applied as a coating agent, the liquid for forming a titanium oxide of the present invention is an amorphous titanium oxide film in a heat treatment of less than 200 ° C, and a dense crystalline titanium oxide in a heat treatment of 200 ° C or more. A membrane can be made. These films have excellent acid resistance and can be used as various anticorrosion coatings.

【0026】

In addition, anatase sol liquid that has been heat-treated at 80 ° C or higher can form a crystalline titania film simply by applying it, so it is useful as a coating agent for materials that cannot be heat-treated. In such a method, it can be used for various purposes such as a protective film and a photocatalyst, and a material having a relatively high density and good adhesion can be obtained at a relatively low temperature.

【0027】

The titanium oxide coating agent of the present invention has a function of dispersing various fine particles, can be mixed with solid fine particles and dispersed by an ultrasonic wave, a ball mill, or the like, and the oxidation obtained by applying the fine particles and drying and firing. It is also possible to create a composite in which other substances are supported or dispersed in the titanium film. In addition, the substrate to be applied can be applied to any material such as ceramics, ceramics, metals, plastics, fibers, building materials, etc. that can withstand heat treatment according to the application, and can be applied to the inside of a porous body or powder. The titanium oxide coating agent produced in the present invention can be used for surface treatment of various materials such as protective coatings, photocatalytic films, ultraviolet blocking coatings, colored coating films, dielectric films, film-type sensors, and oxidation. It can be used in fields such as the production of titanium sol.

【0028】

[Example]

Hereinafter, the present invention will be described with reference to examples. Example 1 A brown transparent liquid was prepared by adding 20 ml of a 30% hydrogen peroxide solution to a solution obtained by diluting 5 ml of a 60% aqueous solution of titanium tetrachloride to 500 ml with distilled water, and adding ammonia water (1: 9) to this solution. Was added dropwise to adjust the pH to 7, and a transparent yellow solution was prepared. The obtained solution was left at 25 ° C for 24 hours to generate a yellow precipitate. After filtration and washing, the mixture was made into about 150 ml with distilled water, and 25 g each of a cation exchange resin and an anion exchange resin was added and left for 30 minutes to remove cation and anionic substances. As a cation exchange resin, Organo's Amberlite IR120B (Na)⁺Substitution type) was treated with 2N hydrochloric acid for 1 hour, washed, and H⁺ A substitution type resin is used, and the anion exchange resin is Organo's Amberlite IRA410 (Cl).^- Substitution type) was treated with 1N sodium hydroxide for 1 hour, then washed and OH.^- The replacement type was used.

【0029】

The obtained yellow precipitate was dried at 25 ° C, and the obtained powder was measured by an X-ray diffractometer (RAD-B manufactured by Rigaku Denki) using a copper target under the measurement conditions of an acceleration voltage of 30 kV and a current of 15 mA. The results are shown in Fig. 1. The obtained precipitate was in an amorphous state. In addition, a Fourier transform infrared absorption spectrum measuring device (FT / IR-5300 manufactured by JASCO Corporation) was used to form tablets by mixing powder obtained by drying at 25 ° C with potassium bromide powder. The measurement was performed by the permeation method, and the results are shown in Fig. 2. 900cm^-1Absorption was observed in the vicinity, and it was confirmed that a peroxo group was present.

【0030】

Next, after removing the ion exchange resin by filtration, make about 180 ml with distilled water, cool with ice water, add 20 ml of a 30% hydrogen peroxide solution, and continue cooling to make it transparent containing titanium after 1 hour. 200 ml of yellow liquid was obtained. Storage in the refrigerator at 7 ° C did not change after more than a month. The pH 5 days after preparation was 5.1. The powder obtained by drying this transparent yellow liquid at room temperature is also shown in FIG. 3 as a result of measurement by X-ray diffraction in the same manner. As a result of X-ray diffraction, no crystallinity peak was observed and it was amorphous. Similarly, Fig. 4 shows the results measured by Fourier transform infrared spectroscopy. 900cm^-1Absorption was observed in the vicinity, and it was confirmed that a large number of peroxo groups were present.

【0031】

Example 2 The yellow transparent liquid obtained in Example 1 was sealed in a glass container and heated at 100 ° C. for 5 hours to obtain a pale yellow translucent liquid. The pH of this liquid was 8.8. When the powder obtained by drying this liquid at room temperature was examined by X-ray diffraction in the same manner as in Example 1, crystalline anatase was produced, and the obtained liquid was anatase sol.

【0032】

Example 3 The liquid obtained in Example 1 was applied onto a slide glass and dried four times, and heat-treated at various temperatures to prepare a film having a thickness of about 1 μm. X-ray diffraction revealed that it was atypical below 200 ° C, but the presence of anatase was confirmed above 200 ° C. Further, the film dried or heat-treated at room temperature or higher did not peel off by the cellophane tape peeling test.

【0033】

In the cellophane tape peeling test, after scratching the formed film with a cutter knife at 1 mm intervals, the cellophane tape (manufactured by Nichiban) is adhered, and then the film is peeled off at a speed of 1 cm / sec in the direction perpendicular to the formed film. , The surface of the film and the surface of the cellophane tape were observed to check for peeling of the film.

【0034】

Example 4 A brown transparent liquid was prepared by adding 20 ml of a 30% hydrogen peroxide solution to a solution obtained by diluting 5 ml of a 60% aqueous solution of titanium tetrachloride to 500 ml with distilled water, and adding aqueous ammonia (1: 9) to this solution. The solution was added dropwise to adjust the pH to 7, and a transparent yellow solution was prepared and then heated at 50 ° C. for 2 hours to prepare a yellow precipitate. Then, the precipitated precipitate was filtered and washed. The liquid containing this yellow precipitate was made up to 130 ml, and 20 ml of a 30% hydrogen peroxide solution was added at 15 ° C. and left to stand to obtain 150 ml of a clear yellow liquid 12 hours later. The liquid temperature after adding the hydrogen peroxide solution rose to a maximum of 20 ° C. After a few days the pH was 5.0 and the viscosity of the liquid was 8 cp.

【0035】

Comparative example 1 Aqueous ammonia water (1: 9) was added dropwise to a solution obtained by diluting 5 ml of a 60% aqueous solution of titanium tetrachloride to 500 ml with distilled water to adjust the pH to 7, and white gel-like titanium hydroxide was precipitated and filtered and washed. The volume was adjusted to 130 ml with distilled water. Next, the liquid temperature was set to 15 ° C., 20 ml of a 30% hydrogen peroxide solution was added and left to stand, and after 12 hours, 150 ml of a yellow liquid containing titanium was obtained. During that time, the liquid temperature rose to a maximum of 41 ° C. The pH was 5.0 5 days after preparation. This liquid gelled into a jelly, and its viscosity was about 28000 cp, which made it difficult to use as a coating agent.

【0036】

[Effect of the invention]

If a solution for forming a titanium oxide is prepared by the production method according to the present invention, peroxoization and solvation, which have been simultaneously progressing in the conventional method, can be separated, and heating which becomes a problem especially when solvating is a problem. The condensation of peroxotitanium hydrate can be easily suppressed. As a result, an aqueous solution of peroxotitanium hydrate can be stably provided, and anatase sol produced by heating the aqueous solution of peroxotitanium hydrate can be stably supplied. Therefore, the effect on the industry is also great.

[Simple explanation of drawings]

[Figure 1]

FIG. 1 is a diagram for explaining the X-ray diffraction result of the precipitate obtained in the example.

[Figure 2]

FIG. 2 is a diagram illustrating a measurement result by Fourier transform infrared absorption spectrum measurement of the precipitate obtained in the example.

[Fig. 3]

FIG. 3 is a diagram for explaining the X-ray diffraction result of the transparent yellow liquid obtained in the examples.

[Fig. 4]

FIG. 4 is a diagram for explaining the measurement results of the transparent yellow liquid obtained in the examples by Fourier transform infrared absorption spectrum measurement.