Titanium dioxide ceramic paint and methods of producing same

Titanium dioxide ceramic coating and preparation method thereof

The present invention relates to a titanium dioxide ceramic coating suitable for coating glass, metal, ceramic and plastic materials and a method of manufacturing the same.

The invention further relates to a paint coating which can be used to form a coating having superior hydrophilicity, photocatalytic activity and light transmittance, and a method for producing the same.

Various alkali metal silicates, phosphates, vermiculite sols and/or metal oxides are known as ceramic coatings, which have superior heat resistance and abrasion resistance compared to conventional organic coatings.

Conventional ceramic coatings have the same advantages of superior heat resistance and abrasion resistance. At present, attempts have been made to develop ceramic coatings with various new functions by using various metal oxides as main components.

Among various metal oxides, titanium dioxide is known to exhibit high hydrophilicity, similar to conventional ceramic materials such as cerium oxide. When the ceria ceramic coating is applied to the surface of the heat sink of the heat exchanger, the high hydrophilicity of the resulting coating helps to reduce the bridge phenomenon of the condensed water between the fins to prevent the water from scattering, and Improve heat exchange efficiency. Further, when the titanium dioxide ceramic coating is applied to the surface of a permeable member such as a glass article, the resulting hydrophilic ceramic coating prevents moisture from accumulating on the surface of the article to cause the surface to be tarnished and blurred.

Among various ceramic coatings, the titanium dioxide coating can form a coating film having excellent photocatalytic activity, and exhibits a relatively high oxidation activity upon irradiation with ultraviolet light. Therefore, it is known that when a titanium dioxide ceramic coating is applied on the surface of a metal, glass or ceramic article, the resulting ceramic coating is rust-proof, promotes decomposition of odor-producing substances, purification of water, corrosion prevention, anti-microbial treatment, and prevention. The decomposition of seaweed and the decomposition of substances that are not easily decomposed show better practicality. Accordingly, attempts have been made to provide a titanium dioxide coating that forms a titanium dioxide coating on the surface of an article, and a method of making the titanium dioxide coating.

Among the methods for forming a titanium dioxide coating layer, a sol-gel coating method is known in which a hydrolyzate of a titanium alkoxide is used as a main component of the coating. Similar to the sol-gel coating method, Japanese Patent Publication No. 4-83537 teaches the preparation of a titanium dioxide coating by adding a guanamine or ethylene glycol compound to titanium alkoxide. Further, Japanese Unexamined Patent Publication No. Hei 7-100,378 discloses a method of preparing a titania coating by adding an alcohol amine to a titanium alkoxide.

Further, Japanese Unexamined Patent Publication No. Hei No. 6-293,519 discloses a coating coating method in which a finely divided fine titanium oxide particle is treated with a dispersing agent by heat treatment at 100 ° C or higher than 100 ° C. The resulting dispersion is dispersed and coated, and another coating method in which a binder such as water glass, colloidal vermiculite or fluororesin is mixed with the crystalline titanium oxide particles, and the resulting mixture is applied.

Disadvantages of the sol-gel coating method are: (1) the acid used as the hydrolyzing agent and the amine or diol used as an additive are usually left in the resulting paint coating, and thus the resulting paint The coating is required to be baked at a high temperature to remove it, (2) the resulting titanium dioxide coating coating contains a large amount of combustible organic solvent, and (3) the starting material is expensive.

Further, in the above titanium oxide paint coating method, wherein the titanium dioxide crystal is grown at a temperature of 100 ° C or higher, the disadvantage is that: (1) the resulting coating has poor transparency and is therefore unsuitable for transparent articles, for example, The glass article, and (2) when applied to the heat sink of the heat exchanger, the titanium dioxide coating has low retention efficiency, and the coated heat sink produces a characteristic odor of the ceramic material.

Furthermore, the conventional titanium dioxide paint coating method using a resin as a binder of titanium dioxide particles has the following disadvantages: (1) although the resin contributes to an improvement in coating properties, adhesion and retention of the resulting coating, the resulting paint The durability of the coating is insufficient, because the resin is deteriorated by the photocatalytic action of titanium dioxide, and (2) the addition of the resin causes a decrease in the content of titanium dioxide. Therefore, the hydrophilicity and photocatalytic activity exhibited by the obtained paint coating layer are not good.

An object of the present invention is to provide a titanium dioxide ceramic coating having hydrophilicity, photocatalytic activity and light transmittance, which substantially contains no impurities harmful to the photocatalytic activity of titanium dioxide and organic substances such as alcohols, and can be formed. A ceramic paint coating that exhibits superior hydrophilicity and photocatalytic activity, light transmission and adhesion, and a method of making the same.

The above object can be achieved by the aqueous titanium dioxide ceramic coating of the present invention to form a paint coating having superior hydrophilicity, photocatalytic activity and light transmittance, comprising:

(A) at least one component selected from the group consisting of orthotitanic acid, titanium (IV) ions, and peroxotitanic acid, and

(B) Crystalline titania colloidal particles having an average particle size of 0.001 to 0.2 μm.

In the case of titanium, the weight ratio of the component (A) to the component (B) is from 1:0.1 to 1:200, and the ceramic coating is substantially free of impurity ions.

The above aqueous titanium dioxide ceramic coating can be produced by the method (1) of the present invention, which comprises subjecting the titanium salt aqueous solution to at least one of the following treatments:

(a) a dialysis treatment using a semipermeable membrane,

(b) an electrodialysis treatment using a semipermeable membrane, and

(c) an ion exchange treatment using an ion exchanger,

The impurity ions are removed from the aqueous titanium salt solution by hydrolyzing and converting at least a portion of the titanium salt to the orthotitanic acid and crystalline titanium dioxide particles.

In an embodiment of the method of the present invention, the aqueous titanium salt solution and the alkali metal hydroxide or ammonia (the amount thereof is less than 4) before performing at least one of (a), (b), and (c) Mohr, titanium present in the aqueous titanium salt solution per mole, and the resulting mixed aqueous solution is heated to a temperature of 50 ° C or higher but lower than 100 ° C.

Furthermore, the above aqueous titanium dioxide ceramic coating can be produced by the method (2) of the present invention, which comprises the following steps:

Mixing an aqueous solution of a titanium salt with an alkali metal hydroxide or ammonia to mix less than 4 moles of alkali metal hydroxide or ammonia per mole of titanium present in the titanium salt aqueous solution;

The obtained mixed aqueous solution is heated at a temperature of 50 ° C or higher but lower than 100 ° C to hydrolyze and convert at least a portion of the titanium salt into orthotitanic acid and crystalline titania colloidal particles;

Mixing the obtained aqueous solution containing titania-like colloidal particles with an alkali metal hydroxide or ammonia to cause precipitation formation;

Collecting the resulting precipitate from an aqueous solution;

The collected precipitate is dispersed in a dispersion medium containing an aqueous solution of a component selected from the group consisting of water, an aqueous peroxide solution, and a titanium salt.

The aqueous titanium dioxide ceramic coating for forming a hydrophilic, photocatalytic and light permeable paint coating of the present invention contains at least one component of (A) orthotitanic acid, titanium (IV) ion and peroxotitanic acid. And (B) crystalline titanium dioxide colloidal particles having an average particle size of 0.001 to 0.2 μm (1 to 200 nm).

The orthotitanic acid used in the present invention exhibits high solubility in an aqueous acid solution and is substantially free of crystals, and thus can be distinguished from crystalline titanium oxide particles. Further, the titanium dioxide useful in the present invention includes meta-titanic acid, anatase titanium dioxide, and rutile titanium dioxide particles.

In the ceramic coating of the present invention, the orthotitanic acid may be added to an aqueous solution selected from the group consisting of at least one water-soluble titanium compound, for example, titanium tetrachloride, titanium sulfate, titanium oxychloride or titanium oxysulfate. At least one component of the composition: an alkali metal hydroxide, such as sodium hydroxide, and ammonium, is prepared by taking it into the temple. The obtained orthotitanic acid sulphate was collected by filtration and washed with water. The collected titanic acid can be used as a raw material for the ceramic coating of the present invention.

The peroxytitanic acid which can be used in the ceramic coating of the present invention can be prepared in the form of an aqueous solution which is prepared by adding an aqueous hydrogen peroxide solution to the aqueous solution of the orthotitanic acid prepared in the above step.

Also, titanium (IV) (Ti) which can be used in the ceramic coating of the present invention⁺⁺The ions can be prepared and provided by dissolving the titanium salt of the aqueous solution in water. In particular, the titanium (IV) ion can be stably present in an acidic aqueous solution having a pH of 3 or lower. The titanium (IV) ion is preferably present in the form of an organic or inorganic complex.

The titanium dioxide ceramic coating of the present invention must contain crystalline titanium dioxide particles, as well as orthotitanic acid, titanium (IV) ions and/or peroxotitanic acid. The crystalline form of the titanium dioxide particles is preferably anatase, followed by rutile.

The average particle size of the crystalline titanium oxide particles must be between 0.001 and 0.2 μm, preferably 0.002 to 0.1 μm, more preferably 0.002 to 0.07 μm. If the average particle size is less than 0.001 μm, the resulting titanium dioxide paint coating has poor hydrophilicity and photocatalytic activity. Further, if the average particle size is larger than 0.2 μm, the obtained titanium oxide paint coating layer is insufficient in hydrophilicity and light transmittance, and the adhesion to the surface of the substrate is also insufficient. When the average particle size is in the range of 0.002 to 0.1 μm, the resulting titanium dioxide ceramic paint coating can exhibit superior hydrophilicity.

In the titanium dioxide ceramic coating of the present invention, the weight of the component (A) composed of at least one component of orthotitanic acid, titanium (IV) ion and peroxotitanic acid is preferably from 0.001 to 0.2 μm, preferably from 0.001 to 0.2 μm. The weight ratio of the component (B) composed of the crystalline titanium oxide particles of 0.002 to 0.1 μm is in the range of 1:0.1 to 1:200. If the weight ratio is less than 1:200, that is, the content of the component (A) is too low and the content of the component (B) is too high, the hydrophilicity of the obtained paint coating and the adhesion to the surface of the substrate are exhibited. And opacity (transparency) are not ideal. Further, if the weight ratio is more than 1:0.1, that is, the content of the component (B) is too low, the resulting paint coating exhibits insufficient hydrophilicity and photocatalytic activity.

The titanium dioxide ceramic coating of the present invention can be prepared by mixing an aqueous solution of at least one component selected from the group consisting of orthotitanic acid, titanium (IV) ions and peroxotitanic acid with titanium dioxide particles or a sol containing titanium oxide particles; At least a portion of the titanium salt dissolved in water is hydrolyzed and converted to the orthotitanic acid and titanium dioxide particles, and optionally at least a portion of the orthotitanic acid is converted to peroxytitanic acid.

An aqueous solution of orthotitanic acid, titanium (IV) ion and peroxotitanic acid can be prepared by adding an aqueous alkaline earth metal solution to an aqueous solution of orthotitanate to form a precipitate of orthotitanic acid, and collecting the precipitate of orthotitanic acid. And collecting the collected orthotitanic acid precipitate in an aqueous dispersion medium containing an aqueous solution of water, a peroxide solution, and/or a titanium mismatch reagent.

The aqueous coating containing orthotitanic acid and titanium dioxide particles of the present invention can be prepared by the method of the present invention, wherein an aqueous solution of a titanium salt is subjected to a hydrolysis step to hydrolyze and convert a part of the titanium salt into orthotitanic acid and crystalline titanium oxide. The particles have an average particle size of 0.001 to 0.1 μm.

Further, the aqueous coating material containing peroxytitanic acid and titanium oxide particles of the present invention can be prepared by adding a peroxide such as hydrogen peroxide to an aqueous solution of orthotitanate before or after the hydrolysis step. Under such conditions, the content of peroxotitanic acid in the resulting aqueous coating can be adjusted to 0 to 100% by controlling the amount of peroxide to be added to the aqueous titanium salt solution. That is, when no peroxide is added, the resulting aqueous coating contains orthotitanic acid without peroxytitanic acid. Further, when the amount of the peroxide added is equal to or higher than the molar amount of the original titanic acid, the obtained aqueous coating material contains peroxotitanic acid and does not contain orthotitanic acid.

When the pH of the reaction system is low, such as 2 or lower, a portion of the orthotitanic acid is converted to titanium (IV) ions. In this case, in order to stabilize the obtained aqueous liquid, it is preferred to add a wrong reagent to the aqueous liquid to convert the titanium (IV) ion into a titanium (IV) complex to obtain a stable aqueous solution. coating.

The miscible reagent for forming the tetravalent titanium complex preferably comprises at least one component selected from the group consisting of lactic acid, oxalic acid, formic acid, and acetamidine. Further, gluconic acid, tartaric acid, acetic acid, malic acid, succinic acid, and EDTA (ethylenediaminetetraester acid) can also be used as a mismatching agent for titanium.

The titanium dioxide particles to be added to the aqueous solution of orthotitanic acid, titanium (4) ions and/or peroxotitanic acid may be in the form of solid particles or in the form of an aqueous sol. When the solid particles of titanium dichloride are added, the resulting mixture is preferably sufficiently stirred by, for example, a homomixer to uniformly disperse the titanium oxide particles to prevent the formation of agglomerated particles. A small amount of a dispersant such as a surfactant may also be added to the dispersion system to aid in the dispersion of the titanium dioxide particles.

In the method for producing an aqueous titanium dioxide ceramic coating, the titanium salt which can be used as a starting material is preferably named from titanium chloride, titanium sulfate, titanium oxysulfate and titanium oxychloride. Another water-soluble inorganic titanium salt and a water-soluble organic titanium salt, for example, titanium potassium oxalate and titanium citrate, can be used as the titanium salt in the method of the present invention.

The titanium salt aqueous solution can be prepared by dissolving a titanium salt in water or can be selected from commercially available diluted titanium salt aqueous solutions.

When dehydrated titanium chloride is used as a starting material, dehydrated titanium chloride can be gradually dissolved in pure water while being prepared by ice cooling. Further, when titanium trichloride is used as a starting material, first, titanium (III) ions are oxidized to titanium (IV) ions with an oxidizing agent such as hydrogen peroxide, and then the obtained titanium tetrachloride is produced. The step of waterborne coatings.

The aqueous solution of titanium sulphate currently available on the market is a 30% aqueous solution. Therefore, commercially available aqueous solutions can also be used in the process of the present invention after appropriate dilution.

An aqueous solution of titanium oxysulfate or titanium oxychloride can be prepared by using, for example, an ion exchange membrane or an ion exchange resin, or by subjecting a hydrous titanium oxide solution to sulfuric acid or hydrochloric acid to an aqueous solution of titanium sulfate or titanium chloride. Removal of anions.

In the method (1) of the present invention, the titanium salt aqueous solution is subjected to a hydrolysis step of the titanium salt, comprising (1) at least one of the following treatments:

(a) Dialysis treatment using a semipermeable membrane,

(b) electrodialysis treatment using a semipermeable membrane, and

(c) ion exchange treatment using an ion exchanger, and optionally, prior to the foregoing treatment, (2) heat treatment, at a temperature of 50 ° C or higher but lower than 100 ° C, the titanium salt aqueous solution is subjected to Heat treatment, or (3) a combination of: (i) alkali treatment, mixing an alkali metal hydroxide or ammonia in an aqueous titanium salt solution in an amount of less than 4 moles per mole of titanium present in the titanium salt aqueous solution a metal hydroxide or ammonia, and (ii) heat treatment, heating the mixed aqueous solution at a temperature of 50 ° C or higher but lower than 100 ° C to hydrolyze at least a portion of the titanium salt And converted into orthotitanic acid and crystalline titanium dioxide colloidal particles having an average particle size of 0.001 to 0.2 μm. During the treatment of (a), (b) and/or (c), the impurity ions are removed from the aqueous titanium salt solution.

Treatments (2) and (3) selected as needed may help to hydrolyze the titanium salt prior to treatment (a), (b) and/or (c), and to improve (a), (b) and/or ( c) Impurity ion removal efficiency in the treatment.

Further, in the method (2) for producing an aqueous titanium dioxide ceramic coating of the present invention:

Mixing a titanium salt aqueous solution with an alkali metal hydride or ammonia in an amount of less than 4 moles of metal hydroxide or ammonia per mole of titanium present in the titanium salt aqueous solution; heating the resulting mixed aqueous solution to 50 °C or higher than 50 ° C but lower than 100 ° C to hydrolyze and convert at least a portion of the titanium salt into orthotitanic acid and crystalline titania colloidal particles;

The resulting aqueous solution containing the titania-containing colloidal particles is mixed with an alkali metal hydroxide or ammonia to form a precipitate, and then

The resulting precipitate is collected from the aqueous solution to provide a precipitate substantially free of impurity ions, and finally

The collected precipitate is dispersed in a dispersion medium consisting of one component selected from the group consisting of water, an aqueous peroxide solution, and a titanium mismatch reagent aqueous solution.

In the methods (1) and (2) of the present invention, the titanium salt aqueous solution to be subjected to the hydrolysis step preferably has a titanium concentration of from 0.1 to 10% by weight, more preferably from 0.5 to 4% by weight.

If the titanium concentration is less than 0.1% by weight, the resulting aqueous coating may not form a coating of a suitable thickness. Further, if the titanium concentration is more than 10% by weight, the obtained titanium salt aqueous solution may be gelled during the impurity removal treatment (a), (b) and/or (c) in the method (1).

In the method (1) of the present invention, the respective treatments (a), (b) and (c) are preferably carried out at a temperature of from 0 ° C to 80 ° C, more preferably from 10 to 50 ° C. During these treatments, at least a portion of the titanium salt in the aqueous titanium salt solution is hydrolyzed and converted to orthotitanic acid and crystalline titanium dioxide particles.

When the titanium salt is made of titanium tetrachloride (TiC1₄In the case of the composition, the hydrolysis of the titanium salt during the treatment of (a), (b) and/or (c) is carried out in accordance with the following reaction.

(1) TiCl₄+4H₂O TiO₂2H₂O+4HCl

(original titanic acid)

(2) TiCl₄+2H₂O TiO₂+4HCl

(crystalline titanium dioxide)

The by-products (i.e., HCl) of the reactions (1) and (2) are removed from the reaction mixture simultaneously with the impurity ions by the treatments of (a), (b) and/or (c).

In the process of the present invention, when the titanium salt is hydrolyzed during the treatment of (a), (b) and/or (c), the ratio of the obtained orthotitanic acid is relatively high. The resulting titanium dioxide particles have a very small particle size, so that the resulting paint coating exhibits better mechanical strength.

The titanium salt aqueous solution to be subjected to the method (1) of the present invention preferably contains at least one of titanium oxychloride and titanium oxysulfate.

In the method (1) of the present invention, the (a) treatment is a diffusion dialysis treatment using a semipermeable membrane and a diffusion medium composed of water, preferably pure water. The semipermeable membrane that can be used for (a) treatment can be selected from an anion exchange membrane and a membrane through which anions and cations can pass simultaneously, for example, reverse osmosis (RO) membrane, sputum (regenerated cellulose) membrane, and balloon membrane And rubber film. However, it is difficult for cation exchange membranes to remove impurity ions such as Cl.^-And SO₄^2-Ions, therefore, a semipermeable membrane composed only of a cation exchange membrane is less desirable in the present invention. However, a cation exchange membrane can be used with an anion exchange membrane to use a half permeable membrane.

The diffusion dialysis treatment (a) is preferably carried out for 1 hour or more, preferably, if possible, for 3 hours or more.

The degree of progress of diffusion dialysis can be determined by the pH or conductivity of the dialysis liquid. That is, the diffusion dialysis treatment (a) preferably continues until the pH of the dialysate is increased to 2 to 7, or until the conductivity of the dialysate silver is lowered to 1 mS/cm or less. However, the resulting aqueous paint may contain Cl of about 1 gram per liter or less.^-Ions to enhance the storage stability of orthotitanic acid and titanium dioxide particles.

The (b) treatment which can be used in the method (1) of the present invention is an electrodialysis treatment using a semipermeable membrane, preferably an anion exchange membrane. An advantage of the electrodialysis treatment compared to the diffusion dialysis treatment (a) is that the treatment can be completed in a relatively short period of time.

Electrodialysis using an anion exchange membrane is carried out in an electrodialysis flask having an anode plate and a cathode plate placed in parallel with each other, separated by an anion exchange membrane parallel to the anode plate and the cathode plate An anode chamber and a cathode chamber are formed. An aqueous titanium salt solution is placed in the anode chamber and water is contained in the cathode chamber.

The cathode plate is preferably a platinum plate, a platinum coated titanium plate or a DSE (insoluble cathode). The anode is preferably formed of a platinum plate coated with platinum or a stainless steel plate.

In the electrodialysis treatment (b), the current density of the applied current is preferably 0.01 to 10 A/dm.². If the current density is greater than 10A/dm²There is a problem that the colloidal particles stick to the semipermeable membrane. The anion exchange membrane which can be used for the treatment of (b) is preferably selected from the group consisting of strongly basic anion exchange membranes, which more preferably have high acid resistance.

In the method (1) of the present invention, the ion exchange treatment (c) is preferably carried out using an anion exchanger, more preferably an anion exchange resin. The anion exchanger may be selected from zeolites having anion exchange activity, alkaline muscovite, aqueous iron oxide, and aqueous zirconia.

In the ion exchange treatment (c), the contact of the aqueous solution of the titanium salt with the ion exchanger can be carried out by directly mixing an ion exchanger into the aqueous solution of the titanium salt or by allowing the aqueous solution of the titanium salt to be usually filled with the column of the ion exchanger. Achieved.

The degree of progress of ion exchange can be controlled by controlling the pH or conductivity of the resulting treatment liquid to a predetermined increase or a predetermined decrease.

During the treatment of (a), (b) and/or (c) above, at least a portion of the titanium salt in the titanium salt aqueous solution is hydrolyzed and converted into orthotitanic acid and titanium dioxide particles, and is present in the aqueous solution. Impurity ions are also removed. Therefore, the resulting aqueous coating is substantially free of impurity ions such as Cl^-And SO₄^2-Anion and Na⁺cation.

If the impurity ions are removed by conventional methods, for example, filtering the aqueous coating with a precision filter or ultrafiltration membrane, and then washing the filter with water to remove the orthotitanic acid, titanium (IV) ions and/or from the aqueous coating. The oxytitanic acid, together with the impurity ions, exhibits insufficient transparency (transmittance) and adhesion of the paint coating thus obtained.

In one embodiment of the method (1) of the present invention, prior to the treatment of (a), (b) and (c), a titanium salt such as titanium chloride, titanium sulfate, titanium oxysulfate or titanium oxychloride is contained. The aqueous solution is heated to a temperature of 50 ° C or higher but lower than 100 ° C, preferably 60 to 90 ° C to aid in the hydrolysis of the titanium salt. This heat treatment helps to increase the proportion of the resulting titanium dioxide particles and to control the resulting titanium dioxide particles to a desired size. That is, this heat treatment helps to achieve the desired level of photocatalytic activity exhibited by the resulting paint coating.

If the heating temperature is lower than 50 ° C, the titanium oxide particles having the desired particle size may be difficult to manufacture, and thus the photocatalytic activity of the resulting paint coating may not reach the desired level. Moreover, if the heating temperature is 100 ° C or more, the obtained aqueous coating material may contain a large amount of coarse titanium oxide particles, so that the storage stability may be low due to precipitation of the coarse titanium dioxide particles, and the obtained coating material The light transmission of the coating may be poor.

This heat treatment is preferably carried out for a period of from 3 to 240 minutes. If the heat treatment is carried out at a relatively low temperature, such as at 30 to 60 ° C, and the pH of the starting titanium salt aqueous solution is relatively high, such as 3 to 7, the heating time may be more than 240 minutes.

Preferably, the heat treatment utilizes a hot water type heat exchanger or a hot water bath while uniformly stirring to uniformly heat the entire titanium salt aqueous solution contained in the reactor. The use of an immersion heater to locally heat the aqueous titanium salt solution should be avoided. Moreover, in order to control the formation and growth of the titanium dioxide particles in the heat treatment, it is preferred to add a small amount of a nucleating agent to the titanium salt aqueous solution, which comprises titanium dioxide particles for forming titanium dioxide colloidal particles, or a dispersion liquid added with the nucleating agent. . After the heat treatment is completed, the obtained titanium oxide particle-containing liquid is cooled to a temperature of preferably 40 ° C or lower by water cooling, and then subjected to the above (a), (b) and/or (c) treatment. To further hydrolyze the remaining titanium salt, while an impurity such as Cl other than titanium, oxygen and/or hydrogen ions^-And SO₄^2-Ions, as well as impurity cations such as Na⁺The ions are also removed together.

In another embodiment of the method (1) of the present invention, an aqueous titanium salt solution is mixed with at least one of an alkali metal hydroxide or ammonia in an amount such that the amount of titanium present in the titanium salt aqueous solution per mole is lower than 4 moles, preferably 0.1 moles or more than 0.1 moles but less than 4 moles of alkali metal hydroxide or ammonia, heating the resulting mixed aqueous solution to 50 ° C or above 50 ° C but below 100 ° C The temperature is then treated as (a), (b) and/or (c).

More preferably, the total amount of salt metal hydroxide and/or ammonia is preferably 0.5 moles or more than 0.5 moles but less than 3 moles, per mole of titanium contained in the starting solution.

If the total amount of alkali metal hydroxide and/or ammonia is 4 moles or more, compared to the titanium present in the starting solution per mole, the resulting titanium dioxide particles are heat treated and (a) , (b) and / or (c) may not grow to the desired particle size during processing. Further, if the amount of the alkali metal hydroxide and/or ammonia is less than 0.1 mol, the heat treatment and the treatment of (a), (b) and/or (c) may result in the treatment of titanium per mole. Titanium dioxide particles grow too much.

The alkali metal hydroxide and/or ammonia is preferably added to the titanium salt aqueous solution at a concentration of 2 to 10% by weight in the case of diluting the aqueous solution.

Then, the solution in which the alkali metal and/or ammonia is mixed is subjected to the same heat treatment as described above. The titanium concentration of the mixed solution is preferably from 0.1 to 10% by weight, more preferably from 0.5 to 4% by weight. If the titanium concentration is less than 0.1% by weight, it may be difficult to obtain a paint coating having a thickness sufficient to exhibit the desired properties. Further, if the titanium concentration is higher than 10% by weight, the liquid obtained after the heat treatment may be gelled during the treatment of (a), (b) and/or (c).

The heat treatment of the aqueous solution of the titanium salt mixed with the alkali metal and/or ammonia is carried out under the same conditions as described above, that is, at a temperature of 50 ° C or higher but lower than 100 ° C.

After the heat treatment is completed, the hot liquid is allowed to cool to a temperature of preferably 40 ° C or lower, and then the treatments (a), (b) and/or (c) are carried out. During the mixing and heat treatment of the above alkali metal and/or ammonia and the treatment of (a), (b) or (c), at least a portion of the titanium salt is hydrolyzed and converted into orthotitanic acid and titanium dioxide particles. And during the treatment of (a), (b) and (c), the impurities are removed from the aqueous solution to obtain an aqueous ceramic coating containing titanium dioxide.

The combination of alkali metal and/or ammonia mixing treatment and heat treatment has the advantages of facilitating hydrolysis and conversion of titanium salt into orthotitanic acid and titanium dioxide particles, and the resulting coating coating exhibits better hydrophilicity, photocatalytic activity and Adhesive.

In the method (2) of the present invention, the titanium salt aqueous solution is subjected to a combination of the same alkali metal and/or ammonia mixed treatment and heat treatment as described above to hydrolyze and convert at least a portion of the titanium salt to a particle size of 0.001. Up to 0.2 μm of orthotitanic acid and titanium dioxide particles. Then, the obtained aqueous solution containing the orthotitanic acid and the oxidized particles is mixed with at least one of an alkali metal hydroxide or ammonia to form a precipitate. The precipitate was collected from the solution and washed with water as needed. The collected precipitate is dispersed in an aqueous dispersion medium comprising at least one component selected from the group consisting of water, an aqueous peroxide solution, and an aqueous solution of a mismatched reagent of titanium.

The precipitate obtained is substantially free of impurity ions by collecting the precipitate and optionally washing with water. Therefore, in the method (2) of the present invention, the above treatments (a), (b) and/or (c) may be omitted. The collection of the precipitate can be achieved by filtration or a centrifugal separator.

In the dispersion of the collected precipitate, the peroxide is preferably selected from the group consisting of hydrogen peroxide, sodium peroxide and barium peroxide. The peroxide compound reacts with at least a portion of the orthotitanic acid and titanium (IV) ions to form peroxytitanic acid. When hydrogen peroxide is used, hydrogen peroxide can be added before the precipitation is collected. Further, when sodium peroxide or barium peroxide is used, the resulting aqueous paint may be further subjected to the above treatments (a), (b) and/or (c) to remove sodium ions or barium ions from the aqueous paint.

The mismatching agent preferably contains at least one component selected from the group consisting of lactic acid, oxalic acid, formic acid, acetamidine, gluconic acid, tartaric acid, acetic acid, malic acid, succinic acid, and EDTA.

The aqueous titanium dioxide ceramic coating produced by the method (1) or (2) of the present invention contains a large amount of crystalline titanium oxide particles in addition to orthotitanic acid, titanium (IV) ions and/or peroxytitanic acid. Titanium dioxide particles typically have a crystalline form of anatase. However, depending on the conditions of the heat treatment, the titanium dioxide particles may include rutile crystal particles.

Further, the particle size of the titanium dioxide particles contained in the aqueous ceramic coating prepared by the method (1) or (2) of the present invention is 10^-aTo 4x10^-1Within the range of μm, and the average particle size is 0.001 to 0.2 μm, preferably 0.002 to 0.1 μm.

The method (1) or (2) or the prepared aqueous coating of the present invention may be mixed with photocatalytic titanium oxide particles or photocatalytic titanium colloidal particles or a sol.

Further, the aqueous titanium dioxide ceramic coating may optionally be mixed with a dyeing paint to impart a desired color to the resulting paint coating or to at least one component selected from the group consisting of: a basic ceramic material, for example, an abrasion resistant oxide. Nitride and carbide to improve the wear resistance of the paint coating, or mixed with fine metal particles, such as fine zinc or aluminum particles, to improve the corrosion resistance of the paint coating. That is, the composition of the aqueous coating can be adjusted in consideration of the properties required for the resulting paint coating.

The aqueous titanium dioxide ceramic coating of the present invention can be dried by applying the aqueous ceramic coating onto the surface of a substrate member, preferably at 100 to 700 ° C, more preferably 200 to 500 ° C. The dried lacquer layer is baked. Typically, the resulting baked paint coating contains anatase titanium dioxide crystals. However, when baked at a high temperature of 700 ° C or higher, at least a portion of the anatase crystals may be converted into rutile crystals. The conversion of the crystallization does not cause a decrease or loss of hydrophilicity of the paint coating.

When the aqueous titanium dioxide ceramic coating is applied to a substrate surface and dried, the resulting ceramic coating typically has a thickness of 0.05 to 1 μm. In the dried paint coating, the crystalline titanium dioxide particles are uniformly distributed, and the gelatinous or gelled orthotitanic acid or peroxytitanic acid fills the voids between the dispersed crystalline titanium dioxide particles. Even if the paint coating is dried only at a relatively low temperature of 100 to 200 ° C, the colloidal or gelled orthotitanic acid and / or peroxotitanic acid will be dehydrated and converted into hydrated titanium dioxide, the surface area of which increases and the water content High, or converted to titanium dioxide, the crystalline titanium dioxide particles are tightly bonded to adhere the paint coating to the surface of the substrate to enhance the hydrophilicity of the paint coating and to prevent or reduce the scattering of light on the surface of the particles. Further, the resulting paint coating does not contain a non-photocatalytic binder, and thus exhibits satisfactory photocatalytic activity, hydrophilicity, and light transmittance.

In the methods (1) and (2) for preparing an aqueous titanium dioxide ceramic coating of the present invention, titanium dioxide particles having superior hydrophilicity and photocatalytic activity are obtained by hydrolyzing a titanium salt in an aqueous medium under special conditions. And grow it to the desired optimal particle size. In the methods (1) and (2) of the present invention, when the titanium salt aqueous solution is mixed with the alkali metal hydroxide and/or ammonia and the mixing amount is titanium mixed in the initial titanium salt aqueous solution per mole is less than 4 Mohrs, preferably 0.1 moles or more than 0.1 moles but less than 4 moles of alkali metal hydroxide and/or ammonia, form nucleation particles of hydrated titanium dioxide.

If the titanium dioxide crystals excessively grow to form coarse particles, the basic ions are introduced into the coarse titanium dioxide crystals. The heat treatment helps prevent excessive growth of crystals, thereby preventing alkaline ions from being introduced into the crystals and improving the transparency and hydrophilicity of the resulting paint coating.

If the obtained aqueous titanium dioxide ceramic coating contains impurity ions, such as Cl^-, SO₄^2-And Na⁺The paint coating obtained by applying the aqueous coating to the surface of a substrate and drying the applied paint layer exhibits poor transparency and is a non-uniform white coating. Moreover, the resulting paint coating exhibits insufficient photocatalytic activity. Therefore, this aqueous coating is not suitable for coating on a transparent article such as a glass article.

In the method (1) of the present invention, the impurity ions are removed from the aqueous coating by special treatments such as (a), (b) and/or (c) , and at least a portion of the titanium salt is hydrolyzed and converted into the original Titanic acid and crystalline titanium dioxide particles. Further, in the method (2) of the present invention, the aqueous liquid containing the orthotitanic acid and the crystalline titanium oxide particles is mixed with an alkali metal hydroxide and/or ammonia to form a precipitate, and the resulting precipitate is collected and washed with water as needed. The collected precipitate substantially free of impurity ions is then dispersed in an aqueous dispersion medium consisting of water, an aqueous peroxide solution, and/or an aqueous solution reagent solution to provide a substantial Aqueous crystalline titanium dioxide ceramic coating containing impurity ions.

Since the aqueous titanium dioxide ceramic coating of the present invention contains substantially no impurity ions, the resulting paint coating has the following advantages: it exhibits superior transparency, adhesion, hydrophilicity, and photocatalytic activity.

For aluminum or copper articles requiring high hydrophilicity, for example, heat sink fin materials, the aqueous titania ceramic coating of the present invention can form a paint coating having superior photocatalytic activity on the article, and can The article has better antifouling, deodorizing, anti-corrosion, antibacterial and anti-algae activities. Further, the paint coating prevents the hydrophilicity from decreasing with time and prevents the odor generated by the growth of bacteria in the water droplets condensed on the surface of the object. Furthermore, since the paint coating formed by the aqueous titanium dioxide ceramic coating of the present invention has high transparency, the aqueous ceramic coating can be used for coating transparent articles such as glass articles, and thus is highly practical.

Instance

The following examples are used to further illustrate the invention.

Examples 1 to 4

In each of Examples 1 to 4, the aqueous coating was prepared by mixing a 10% aqueous sodium hydroxide solution with a 5% aqueous solution of titanium tetrachloride to form a precipitate, and collecting the precipitate composed of orthotitanic acid by filtration. The collected precipitate was washed with water, the precipitate was dispersed in water, and the obtained aqueous solution containing orthotitanic acid was mixed with the crystalline titanium oxide particles, and then, in Examples 1, 3 and 4, the obtained liquid was mixed with the wrong reagent. The mixing amount is as shown in Table 1, and in Example 2, it was mixed with an aqueous hydrogen peroxide solution in an amount sufficient to achieve the orthotitanic acid concentration shown in Table 1, and the mixed liquid was sufficiently stirred by a homomixer. . The above-mentioned crystalline titanium oxide particles can be obtained from the trademark of titanium dioxide P-25, which is manufactured by Nihon Aerosil KK. The above-mentioned mismatching reagent was composed of acetamidine acetone in Example 1, lactic acid in Example 3, and oxalic acid in Example 4.

Examples 5 and 6

In each of Examples 5 and 6, an aqueous coating was prepared as follows.

Mixing 10% aqueous solution of titanium tetrachloride with sodium hydroxide, mixing 1 mole of sodium hydroxide per mole of titanium in titanium tetrachloride aqueous solution, heating the mixed liquid at 90 ° C for 40 minutes, heating The liquid is mixed with a 5% aqueous solution of sodium hydroxide in an amount such that the resulting mixed liquid becomes neutral to form a precipitate, and the resulting precipitate containing orthotitanic acid and titanium dioxide is dispersed in water, and the obtained aqueous dispersion is mixed with The aqueous hydrogen peroxide solution was mixed in such a manner that the peroxytitanic acid concentration of the resulting mixed solution was as shown in Table 1, and the resulting mixed liquid was thoroughly stirred by a homomixer. An aqueous titanium dioxide ceramic coating is obtained.

As a result of the analysis, it was confirmed that the obtained aqueous coating material contained anatase crystal titanium oxide particles having an average particle size of 0.08 μm.

Examples 7 and 8

In each of Examples 7 and 8, an aqueous coating was prepared as follows.

A 10% aqueous solution of titanium tetrachloride is mixed with sodium hydroxide in an amount of 2 moles of sodium hydroxide per mole of titanium present in the aqueous solution of titanium tetrachloride, and the mixed liquid is heated at 75 ° C for 20 minutes. The heated liquid is mixed with a 5% aqueous sodium hydroxide solution in an amount such that the resulting mixed liquid becomes neutral to form a precipitate, and the resulting precipitate containing orthotitanic acid and titanium dioxide is dispersed in water, in Example 7. The obtained aqueous dispersion was mixed with gluconic acid having a concentration as shown in Table 1, and in Example 8, the obtained aqueous dispersion was mixed with an aqueous hydrogen peroxide solution in an amount such that the resulting mixed liquid was The peroxytitanic acid concentration was as shown in Table 1, and the resulting mixed liquid was thoroughly stirred with a homomixer. An aqueous titanium dioxide ceramic coating is obtained.

As a result of the analysis, it was confirmed that the obtained aqueous coating material contained anatase crystal titanium dioxide colloidal particles having an average particle size of 0.05 μm.

Example 9

An aqueous solution of titanium tetrachloride (20% by weight) was placed in a beaker and diluted with water. The diluted aqueous solution was heated at 80 ° C for 10 minutes and then cooled to 30 ° C with water.

The resulting liquid is subjected to diffusion dialysis using an anion exchange membrane at 27 ° C while flowing deionized water through the membrane to hydrolyze and convert a portion of the titanium tetrachloride into orthotitanic acid and crystalline titania particles, simultaneously Impurity ions are removed from the resulting aqueous coating.

Example 10

An aqueous solution of titanium tetrachloride (20% by weight) is placed in a beaker and diluted with water, and then mixed with a 10% by weight aqueous solution of sodium hydroxide in an amount of titanium present in the tetrachloride aqueous solution per mole. Mix 1 mole of hydrogenated sodium. The mixed liquid was heated at 55 ° C for 60 minutes and then cooled to 30 ° C with water. The heated liquid is subjected to diffusion dialysis using a celluloid film at 25 ° C while flowing deionized water through the film to hydrolyze and convert a portion of titanium tetrachloride present in the starting aqueous solution to titanium. The acid and crystalline titanium dioxide particles are simultaneously removed from the resulting aqueous coating.

The resulting titania-containing colloidal liquid was mixed with 0.5% by weight of lactic acid (mismatching reagent).

Example 11

A 20% by weight aqueous solution of titanium trichloride was placed in a beaker and diluted with water. The diluted solution was then mixed with 31% aqueous hydrogen peroxide until the purple titanium (III) ions in the aqueous solution were completely converted to colorless titanium (IV) ions. The obtained aqueous solution of titanium tetrachloride was mixed with 10% by weight of sodium hydroxide in an amount of 2 moles of sodium hydroxide per mole of titanium present in the aqueous solution. The mixed liquid was heated at 70 ° C for 30 minutes and then cooled to 30 ° C with water. The resulting liquid was subjected to diffusion dialysis treatment using a reverse osmosis (RO) membrane at 40 ° C while flowing deionized water through the membrane to prepare an aqueous titanium dioxide ceramic coating substantially free of impurity ions.

Example 12

A 20% by weight aqueous solution of titanium trichloride was placed in a beaker and diluted with water. The diluted solution was then mixed with 31% aqueous hydrogen peroxide until the purple titanium (III) ions in the aqueous solution were completely converted to colorless titanium (IV) ions. The obtained aqueous solution of titanium tetrachloride was mixed with 10% by weight of sodium hydroxide in an amount of 0.24 mol of sodium hydroxide per mole of titanium present in the aqueous solution. The mixed liquid was heated at 95 ° C for 5 minutes and then cooled to 30 ° C with water. The resulting liquid was subjected to diffusion dialysis treatment using anion exchange and a cation exchange membrane at 30 ° C while flowing deionized water through the membrane to prepare an aqueous titania-containing liquid substantially free of impurity ions. The titanium dioxide-containing aqueous liquid was mixed with 1.2% by weight of a mismatching reagent consisting of acetamidine.

Example 13

A 30% by weight aqueous solution of titanium sulphate was placed in a beaker and diluted with water. The diluted solution was heated at 65 ° C for 90 minutes and then cooled to 30 ° C with water.

The heated aqueous liquid is subjected to an electrodialysis treatment in an electrodialysis bottle having an anode chamber including an anode composed of a platinum plated titanium plate, and a cathode chamber including A cathode composed of a platinum plated platinum plate, the anode chamber and the cathode chamber are supported by an anion exchange membrane (trademark: Selemion AMV, manufactured by Asahi Garasu KK). The anode plate, the anion exchange membrane and the cathode plate are arranged in this order and are parallel to each other, and the anode chamber is filled with a heat-treated titanium oxide-containing aqueous liquid, and the anode chamber is filled with water. Electrodialysis treatment at a temperature of 45 ° C, current density of 1 to 5 A / dm²Execute.

A titanium dioxide ceramic coating substantially free of impurity ions is obtained.

Example 14

A 30% by weight aqueous solution of titanium sulphate was placed in a beaker and diluted with water. The diluted titanium hydride solution is mixed with 2% by weight of sodium hydroxide in an amount of 1 mole of sodium hydroxide per mole of titanium present in the aqueous solution of titanium sulfate, and heated to 90 ° C for 5 minutes. It was then cooled to 30 ° C with water.

The heat-treated aqueous liquid was subjected to an anion exchange membrane (available from Asahi Garasu K.K. under the trademark Selemian AMW) and a cation exchange membrane (available under the trademark Selemion CMW from Asahi Garasu K.K.) in an electrodialysis flask. Obtained by electrodialysis treatment, the electrodialysis bottle is divided into three chambers by the anion exchange membrane and the cation exchange membrane, that is, an anode chamber containing an anode and facing the anion exchange membrane, the anode is plated a titanium plate having platinum, a cathode chamber containing a cathode and facing a cation exchange membrane, the cathode system being composed of a platinum plated titanium plate, and a central chamber formed between the anion exchange membrane and the cation exchange membrane . The anode plate, the anion exchange membrane, the cation exchange membrane, and the cathode plate are arranged in this order and are parallel to each other. The anode and cathode compartments are filled with water and the central compartment is filled with a heat treated aqueous titanium dioxide containing liquid.

Electrodialysis treatment at a temperature of 30 ° C, current density of 0.2 to 0.6 A / dm²Execute.

An aqueous titanium dioxide ceramic coating substantially free of impurity ions is obtained.

Example 15

An 8 wt% aqueous solution of titanium oxysulfate was placed in a beaker and diluted with water, then heated at 60 ° C for 180 minutes and cooled to 30 ° C with water.

The heat-treated aqueous liquid was passed through an anion exchange resin head (available from Diaion SA under the trademark Mitsubishi Kaseikogyo KK) and an anode sub-exchange resin head (available from Diaion SK under the trademark Mitsubishi Kaseikogyo KK) at 30 °C. Column.

An aqueous titanium dioxide ceramic coating substantially free of impurity ions is obtained.

Example 16

A 15% by weight aqueous solution of titanium oxysulfate was placed in a beaker and diluted with water, then heated at 80 ° C for 8 minutes and cooled to 30 ° C with water.

The heat-treated aqueous liquid was passed through a column packed with an anion exchange resin head (available from Diaion SA under the trademark Mitsubishi Kaseikogyo KK) at 50 °C.

An aqueous titanium dioxide ceramic coating substantially free of impurity ions is obtained.

Example 17

A 10% by weight aqueous solution of titanium oxychloride was placed in a beaker and diluted with water, then heated at 85 ° C for 10 minutes, and cooled to 30 ° C with water.

The heat-treated aqueous liquid was passed through a column packed with an ion exchange resin as in Example 16 at 40 °C.

An aqueous titanium dioxide ceramic coating substantially free of impurity ions is obtained.

Example 18

A 20% by weight aqueous solution of titanium tetrachloride was placed in a beaker and diluted with water. The diluted solution was subjected to diffusion dialysis treatment using an anion exchange membrane (trademark: Selemion DMV, Asahi Garasu KK) at room temperature (20 to 30 ° C) while passing deionized water through the membrane until it was in an aqueous liquid. The acid concentration was reduced to 0.1N sodium hydroxide (NaOH) standard solution and bromophenol blue indicator before the dialysis.

An aqueous titanium dioxide ceramic coating substantially free of impurity ions is obtained.

Example 19

A 30% by weight aqueous solution of titanium sulphate was placed in a beaker and diluted with water.

The diluted solution is subjected to a diffusion dialysis treatment using an anion exchange membrane (trademark: Selemion DMV) while passing deionized water through the membrane, and the dialysis system is cooled to 1 to 10 ° C until the acid concentration of the aqueous liquid is lowered. Until the original acid concentration before dialysis is 1/10 or lower. The acid concentration was determined as in Example 18.

An aqueous titanium dioxide ceramic coating substantially free of impurity ions is obtained.

Example 20

A 20% by weight aqueous solution of titanium tetrachloride was placed in a beaker and diluted with water while stirring the aqueous solution, and the aqueous solution was mixed with an anion exchange resin head (trademark: Diaion SA, manufactured by Mitsubishi Kaseikogyo) at 20 to 30 ° C until The acid concentration in the aqueous solution is reduced to 1/10 or less of the original acid concentration before the ion exchange resin treatment. The acid concentration was determined as in Example 18.

An aqueous titanium dioxide ceramic coating substantially free of impurity ions is obtained.

Comparative Examples 1 to 3

In each of Comparative Examples 1 to 3, an aqueous titanium dioxide ceramic coating was prepared by mixing a 5% by weight aqueous solution of titanium tetrachloride with 10% by weight of sodium hydroxide to form a precipitate, collecting the precipitate and washing with water. The obtained orthotitanic acid precipitate is dispersed in water, and the obtained aqueous solution of orthotitanic acid is mixed with titanium dioxide particles, and then mixed with an aqueous hydrogen peroxide solution in an amount such that the obtained solution contains peroxotitanic acid as shown in Table 1. At the concentration, the resulting mixture was thoroughly stirred. In Comparative Example 1, the mixed titanium oxide particles were rutile-type titanium oxide varnish particles having an average particle size of 0.5 μm. In Comparative Example 2, the mixed titanium oxide particles were examples of titanium dioxide paint (anatase or rutile). (Trademark: P-25, manufactured by Nihon Aerosil KK), in Comparative Example 3, the mixed titanium dioxide particles are anatase-type titanium dioxide colloidal particles having an average particle size of 0.01 μm and being in the form of an aqueous colloidal solution. It was prepared by heating an 8% by weight aqueous solution of titanium oxychloride at 75 ° C for 20 minutes to subject the heated solution to diffusion dialysis using an ion exchange membrane.

Comparative example 4

A 17% by weight aqueous solution of titanium tetrachloride was placed in a beaker, diluted with water, heated at 100 ° C for 15 minutes, and cooled to room temperature.

The heat-treated aqueous liquid was subjected to diffusion dialysis treatment using a cellophane film.

Comparative Example 5

A 30% by weight aqueous solution of titanium sulphate was placed in a beaker and diluted with water. Then, the diluted aqueous solution is mixed with a 10% by weight aqueous sodium hydroxide solution in an amount of 4.5 parts of sodium hydroxide per mole of titanium present in the aqueous solution while stirring and cooling the solution with water, and then Heat at 70 ° C for 15 minutes. After cooling, the obtained aqueous solution was subjected to the same diffusion dialysis as in Comparative Example 4.

Comparative Example 6

A 5% by weight aqueous solution of titanium oxychloride was placed in a beaker, heated at 40 ° C for 30 minutes and cooled to room temperature. The heat-treated aqueous solution was subjected to the same electrodialysis treatment as in Examples 13 to 15, using an ion exchange membrane.

test

The aqueous titanium dioxide ceramic coatings of the examples and comparative examples were subjected to the following analysis and measurement.

(1) Concentration of titanium dioxide in waterborne coatings

A 20 ml sample of the aqueous coating was placed in a beaker and dried in an oven at 80 ° C to evaporate the moisture of the sample, followed by heating at 500 ° C for 2 hours to provide a solid titanium dioxide. The concentration of titanium dioxide in the sample was measured from the original weight of the sample and the weight of the solid titanium dioxide.

When the sample contains orthotitanic acid, titanium (IV) ions, and/or peroxotitanic acid, the total amount measured in the following manner is converted into the weight of titanium dioxide, and the weight of the solid titanium dioxide is subtracted from the converted weight. The result of the subtraction is the actual weight of the titanium dioxide particles present in the aqueous coating.

(2) The concentration of peroxotitanic acid in waterborne coatings

A sample of the aqueous coating was diluted with water and filtered through a 5C filter paper. The resulting filtrate was mixed with hydrochloric acid to acidify the filtrate. The absorption of the acidified filtrate at a wavelength of 430 nm was measured using a spectrophotometer. The concentration of peroxotitanic acid present in the sample was determined from the obtained absorption value.

(3) Total concentration of orthotitanic acid and titanium (IV) ions in waterborne coatings

A sample of the aqueous coating was filtered through a 5C filter paper, and the resulting filtrate was acidified with hydrochloric acid and mixed with hydrogen peroxide to convert the orthotitanic acid and titanium (IV) ions into peroxotitanic acid. The resulting modified filtrate was measured for absorption at a wavelength of 430 nm by the method described above. The total concentration of orthotitanic acid and titanium (IV) ions in the sample is determined from the measurement results.

When the sample contains peroxytitanic acid, the concentration of peroxotitanic acid in the sample is determined by the method described in the above (2), and the previously determined orthotitanic acid and/or titanium (IV) ions and The total concentration of peroxotitanic acid is subtracted from the concentration of peroxytitanic acid obtained.

(4) Test of paint coating

Each aqueous paint was applied to a glass plate of 75 mm x 75 mm surface area or an aluminum plate (JIS A1200) to form a paint layer having a thickness of about 0.5 μm. The paint layer was dried at a temperature of 100 ° C and dried at a temperature of 280 ° C to form a dry paint coating. The obtained specimens with a dry paint coating were subjected to the following tests to test their hydrophilicity, corrosion resistance, transparency, adhesion, and photocatalytic activity.

(a) Hydrophilicity of the paint coating

In the dried paint coating of each specimen, 5 ml of pure water was dropped dropwise, and the contact angle of the formed water droplets was measured with a FACE contact angle measuring device (CA-P type, Kynwa Kaimenkagaku KK).

Immediately after the drying step and after 5 treatment cycles, the above measurements were taken on the coating of the specimen, each treatment cycle consisting of immersing the specimen in running water for 8 hours at room temperature and then dip at 80 ° C. The water sample was dried for 16 hours. The hydrophilicity of the paint coating is evaluated as follows:

Hydrophilic series contact angle

4 Less than l0 degrees

3 10 degrees or greater than 10 degrees but less than 20 degrees

2 20 degrees or more than 20 degrees but less than 30 degrees

1 30 degrees or more than 30 degrees

(b) Corrosion resistance of paint coating

Each aqueous paint was applied to the surface of an aluminum plate, and the resulting specimen was subjected to a salt water spray test for 200 hours according to Japanese Industrial Standards (JlS) Z 2371. The ratio of the total area of the corroded portion of the paint coating to the total area of the paint coating is measured and evaluated as follows.

Corrosion resistance grade Total area of corrosion

3 Less than 5%

2 More than 5% but less than 25%

1 25% or more than 25%

(c) Transparency of paint coating

Each of the baked paints formed on the glass plate was visually observed, and the results observed were evaluated as follows.

Transparency progression

4 The paint coating is free of stains and discoloration and is uniformly transparent.

3 The paint coating is slightly discolored and is evenly transparent

2 Paint coating has some discoloration

1 The paint coating has some stains and is opaque

(d) Viscosity of paint coating

A layer of adhesive is adhered to the surface of the paint coating to be tested and stripped from the surface. Observe whether the coating of the coating is removed from the coating.

(e) Photocatalytic activity of paint coating

A paint coating is formed on a surface area of 25 mm X 75 mm of a glass plate. A test oil containing tristearic acid was applied to the surface of the paint coating, and ultraviolet light was irradiated onto the test oil for 72 hours from a 15 watt ultraviolet lamp. The amount of the decomposed test oil (mg/m 2 ) was determined from the difference in weight between the original test oil layer and the decomposed test oil layer.

Table 1 shows the test results of Examples 1 to a and Comparative Examples 1 to 3.

Table 2 shows the test results of Examples 9 to 17 and Comparative Examples 4 to 6.

Table 3 shows the test results of Examples 18 to 20.<img file="TW445285B_D0001.tif" /><img file="TW445285B_D0002.tif" /><img file="TW445285B_D0003.tif" /><img file="TW445285B_D0004.tif" />

Tables 1 to 3 clearly show that the aqueous titanium dioxide ceramic coatings of Examples 1 to 20 of the present invention can form a paint coating having superior hydrophilicity, corrosion resistance, adhesion, transparency, and photocatalytic activity. However, the above properties of the aqueous paints of Comparative Examples 1 to 6 were not good.

As evident from Examples 1 to 20, the aqueous titanium dioxide ceramic coating of the present invention can be used to form a paint coating having excellent transparency, corrosion resistance, adhesion, and superior hydrophilicity and photocatalytic activity.

Further, the method for producing an aqueous titanium dioxide ceramic coating of the present invention is industrially advantageous, and is superior to conventional methods such as a sol-gel method in that starting materials and chemicals are inexpensive and the resulting water-based paint is obtained. It is expected to show better safety and stability. Therefore, the aqueous titanium dioxide ceramic coating produced by the methods (1) and (2) of the present invention can be effectively used for rust prevention, decomposition of materials for odor generation, antimicrobial treatment, corrosion prevention, purification of water and air, and the like. Therefore, it has a high degree of industrial availability.