JP5179986B2 - Photocatalyst-containing coating composition - Google Patents

Description

  The present invention relates to a photocatalyst-containing coating composition. Specifically, the present invention relates to a photocatalyst-containing coating composition containing polyhydroxysiloxane having substantially no alkoxy group, an aqueous organic binder, and a photocatalyst.

  It is known that a coating film containing a photocatalyst is excellent in contamination resistance because a photochemical reaction is caused by irradiating light of a specific wavelength and the coating film surface is hydrophilized. However, the photocatalyst has the property of decomposing organic substances in addition to the property of hydrophilizing the coating film surface. For this reason, when a coating film is formed from a coating composition containing a normal organic resin and a photocatalyst, the coating film may collapse over time as the resin component is decomposed.

For this reason, it is common that a photocatalyst is coated with the inorganic material which does not contain an organic resin component as much as possible (for example, refer patent document 1). However, the coating film obtained by such coating has a problem of being easily broken. Furthermore, since it is necessary to bake at a high temperature in order to obtain a coating film, there are problems that it cannot be applied to a substrate having low heat resistance, and that it is difficult to increase the film thickness.
JP 2007-167718 A

  The present invention has been made in order to solve the above-described conventional problems. The object of the present invention is to have resistance to a decomposition reaction activated by a photocatalyst (hereinafter sometimes referred to as “decomposition resistance”) and possible. An object of the present invention is to provide a coating film having excellent flexibility and a photocatalyst-containing coating composition capable of forming the coating film.

  The photocatalyst-containing coating composition of the present invention comprises (A) a polyhydroxysiloxane solution substantially free of alkoxy groups, (B) an aqueous organic binder, and (C) a photocatalyst, and (A) an alkoxy group. The polyhydroxysiloxane concentration in the total solid content of the polyhydroxysiloxane solution substantially free and (B) the aqueous organic binder is 50 to 95% by mass.

  In a preferred embodiment, the (B) aqueous organic binder is an emulsion resin.

  In preferable embodiment, content of the said (C) photocatalyst is 20-90 mass parts with respect to 100 mass parts of total solid of a photocatalyst containing coating composition.

  According to another aspect of the present invention, a coating film is provided. The coating film is formed from the photocatalyst-containing coating composition.

  According to the present invention, a coating film excellent in decomposition resistance and flexibility, and a photocatalyst-containing coating composition capable of forming the coating film are provided.

[Photocatalyst-containing coating composition]
The photocatalyst-containing coating composition of the present invention comprises (A) a polyhydroxysiloxane solution substantially free of alkoxy groups, (B) an aqueous organic binder, and (C) a photocatalyst, and (A) an alkoxy group. The polyhydroxysiloxane concentration in the total solid content of the polyhydroxysiloxane substantially free and (B) the aqueous organic binder is 50 to 95% by mass.

  The solid content concentration (NV) of the photocatalyst-containing coating composition is preferably 1 to 10% by mass, more preferably 1 to 5% by mass, and still more preferably 1 to 3% by mass. If the solid content concentration is within the above-mentioned preferred range, there is an advantage that when the photocatalyst-containing coating composition is used for coating, there is little sagging and the like and the workability is excellent. In addition, the measuring method of solid content concentration is mentioned later.

  The viscosity at 20 ° C. of the photocatalyst-containing coating composition is preferably 2 to 20 mPa · s, more preferably 2 to 10 mPa · s, and further preferably 2 to 5 mPa · s. If the viscosity is within the above preferred range, it is easy to obtain a thin film of about 1 μm when the photocatalyst-containing coating composition is used for coating.

(A) Polyhydroxysiloxane solution substantially free of alkoxy groups Polyhydroxysiloxane solutions substantially free of alkoxy groups include polyhydroxysiloxanes substantially free of alkoxy groups (hereinafter referred to as “alkoxy groups”). Any suitable material including a solvent may be employed as long as it contains “a non-containing polyhydroxysiloxane”. In the present specification, the “polyhydroxysiloxane solution substantially free of alkoxy groups” is observed, for example, by a nuclear magnetic resonance analysis (H-NMR) or infrared spectroscopic analysis (IR). In other words, the polyhydroxysiloxane solution has no alkoxy group peak, or the peak intensity based on the alkoxy group is below the detection sensitivity.

（式中、ｎ１は１以上の数である。） The non-alkoxy group-containing polyhydroxysiloxane contained in the non-alkoxy group-containing polyhydroxysiloxane solution schematically includes a compound represented by the formula (1). Formula (1) shows a case where the alkoxy group-free polyhydroxysiloxane is a linear condensate having no branching or crosslinking.

(In the formula, n1 is a number of 1 or more.)

  The compound represented by the formula (1) is not usually a single compound, but typically a mixture of compounds having various structures in terms of the degree of condensation, the presence or absence of branching or crosslinking, and the like. Therefore, in the formula (1), n1 is an average value. n1 is 1 or more, 2-50 are preferable and 2-20 are more preferable. When n1 is 2 or more, since the number of hydroxysilyl groups increases, the hardness of the obtained coating film can be improved. Further, when n1 is 50 or less, the reactivity of the alkoxy group-free polyhydroxysiloxane solution can be relaxed, so that the handleability of the solution is good. The degree of condensation of the alkoxy group-free polyhydroxysiloxane can be determined using the molecular weight in terms of polystyrene by gel permeation chromatography (GPC).

  The alkoxy group-free polyhydroxysiloxane can preferably further comprise a polyhydroxysiloxane having an organic group. This polyhydroxysiloxane having an organic group is also substantially free of alkoxy groups. The polyhydroxysiloxane having an organic group has at least one Si—C bond. That is, it has a structure in which an organic group is bonded to a Si atom instead of a hydroxyl group. By including the compound, compatibility with the organic binder can be improved.

  In one embodiment, the organic group is preferably a substituted or unsubstituted linear or branched alkyl group having 1 to 21 carbon atoms, or an aromatic group having 6 to 21 carbon atoms, more preferably a substituted or unsubstituted group having 1 to 10 carbon atoms. An unsubstituted linear or branched alkyl group, a phenyl group, etc. are mentioned. When the organic group is an alkyl group having 4 or more carbon atoms, compatibility with an organic binder can be improved. The alkyl group preferably has a reactive group as a substituent. Examples of the reactive group include a mercapto group, an epoxy group, an amino group, and a vinyl group.

  Examples of the organic group having a reactive group as a substituent include vinyl, methacryloxypropyl, acryloxypropyl, glycidoxypropyl, (3,4-epoxycyclohexyl) ethyl, styryl, and N-2- (aminoethyl). Examples include aminopropyl, aminopropyl, N-phenylpropyl, mercaptopropyl, chloropropyl and the like. Preferred are vinyl, (meth) acryloxypropyl, glycidoxypropyl and aminopropyl.

  The content of the polyhydroxysiloxane having an organic group is preferably 1 to 50 parts by mass, more preferably 2 to 10 parts by mass with respect to 100 parts by mass of the compound represented by the formula (1). By using within this range, it is possible to obtain a coating film having a desired hardness, ensure sufficient compatibility with the organic binder, and suppress the rapid condensation reaction of polyhydroxysiloxane containing no alkoxy group. Can be obtained.

  The alkoxy group-free polyhydroxysiloxane is typically in a solution as shown by a hydrolyzate of tetraalkoxysilane and / or its condensate described in JP-A-9-165450 and WO95 / 17349. In addition, no microdomains of 3 nm or more are formed. That is, it can be a uniform solution of polyhydroxysiloxane. The presence or absence of particulates or microdomains of 3 nm or more can be confirmed by observation with a transmission electron microscope (TEM), a laser light scattering measurement device, or a small-angle X-ray scattering device.

  The polyhydroxysiloxane concentration of the alkoxy group-free polyhydroxysiloxane solution is preferably 1 to 25% by mass, more preferably 1 to 20% by mass. If the solid content concentration is less than 1% by mass, the solid content concentration (NV) of the photocatalyst-containing coating composition may not be ensured. Moreover, when solid content concentration exceeds 25 mass%, manufacture may become difficult.

  In one embodiment, the pH of the alkoxy group-free polyhydroxysiloxane solution is preferably acidic, more preferably 2 to 5, further preferably 2.5 to 4.5, particularly preferably 3 to 4. is there. If it is such pH, the storage stability of the coating composition obtained can be improved when a cationic resin is used as an aqueous organic binder. In another embodiment, the pH of the alkoxy group-free polyhydroxysiloxane solution is preferably basic, more preferably 8 to 13, further preferably 8 to 12, particularly preferably 8 to 11. . If it is such pH, when an anionic resin is used as an aqueous organic binder, the storage stability of the obtained coating composition can be improved. In general, polyhydroxysiloxane becomes unstable in an environment where the pH is more than 5 and 7 or less, and phenomena such as precipitation and gelation are likely to occur.

  The alkoxy group-free polyhydroxysiloxane solution can be prepared by any suitable method. For example, by mixing an alkoxysilane compound, a hydrophilic organic solvent, water equal to or more than the equivalent (mole) of alkoxy groups of the alkoxysilane compound, and an acidic catalyst, an acidic solution of polyhydroxysiloxane containing no alkoxy group is obtained. (First preparation method). Moreover, the basic solution of an alkoxy group-free polyhydroxysiloxane can be obtained by adding an acidic solution of an alkoxy group-free polyhydroxysiloxane to a base (second preparation method). Further, by adding the alkoxysilane compound into water containing a basic catalyst or a mixed solvent of water and a hydrophilic organic solvent, a basic solution of polyhydroxysiloxane containing no alkoxy group can be obtained (third Preparation method).

A-1. First Preparation Method of Non-Alkoxy Group-Containing Polyhydroxysiloxane Solution In the first preparation method, an alkoxysilane compound, a hydrophilic organic solvent, water equal to or greater than the equivalent (mole) of alkoxy groups of the alkoxysilane compound, and By mixing an acidic catalyst, an acidic solution of an alkoxy group-free polyhydroxysiloxane can be obtained. The pH of the resulting acidic solution is usually 2-5, preferably 2.5-4.5, more preferably 3-4.

A-1-1. Alkoxysilane Compound The alkoxysilane compound contains tetraalkoxysilane and / or a condensate thereof. The tetraalkoxysilane and / or the condensate thereof is not usually a single compound, but typically a mixture of compounds having various structures in terms of the degree of condensation, the presence or absence of branching or crosslinking, and the like. For this reason, the tetraalkoxysilane and / or the condensate thereof are schematically represented by the formula (2). Formula (2) shows a case where the tetraalkoxysilane and / or its condensate has no branching or crosslinking.

  In Formula (2), n2 is an average value. n2 is 1 or more, preferably 1 to 50, and more preferably 1 to 20. The degree of condensation of the tetraalkoxysilane condensate can be determined by gel permeation chromatography (GPC).

In formula (2), each R ¹ is independently a substituted or unsubstituted linear or branched alkyl group, preferably a substituted or unsubstituted linear or branched group having 1 to 4 carbon atoms. It is an alkyl group, More preferably, it is a C1-C4 unsubstituted linear or branched alkyl group, More preferably, it is an unsubstituted C1-C2 alkyl group. When R ¹ is the above preferred alkyl group, the hydrolyzability is improved, so that polyhydroxysiloxane can be obtained efficiently.

Specific examples of R ¹ include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group. Of these, a methyl group, an ethyl group, a propyl group, an isopropyl group, and an n-butyl group are preferable, a methyl group and an ethyl group are more preferable, and a methyl group is more preferable.

  Therefore, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-iso-propoxysilane, tetra-n-butoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane or a condensate thereof Preferably used. Of these, tetramethoxysilane, tetraethoxysilane, and their condensates are preferable, and tetramethoxysilane and its condensates are more preferable. In the present invention, one type of tetraalkoxysilane and its condensate may be used, or two or more types may be used in combination.

  As the condensate of tetraalkoxysilane, those having 6 or more, more preferably 6 to 102, and still more preferably 12 to 42 alkoxy groups are used. This is because an appropriate number of hydroxysilyl groups can be obtained by hydrolysis, so that a coating film having high hardness can be obtained. As described above, since the condensate of tetraalkoxysilane can include those having various degrees of condensation, the number of the alkoxy groups is an average value thereof. The number of alkoxy groups contained in the condensate of tetraalkoxysilane can be determined from the degree of condensation.

When R ¹ has a substituent, the number of substituents contained in the tetraalkoxysilane or the condensate thereof is preferably half or less of the number of alkoxy groups. Any appropriate substituent can be used. Specific examples include halogen atoms such as chloro and bromo, alkoxy groups such as methoxy, ethoxy and butoxy, cyano groups and dimethylamino groups. When it has such a substituent, it is preferable that the sum total of carbon number of a substituted alkyl group is 1-6. The alkyl group may be substituted with a compound having an alkylene oxide unit. Examples of the type of alkylene oxide unit include ethylene oxide, propylene oxide, and tetramethylene oxide.

  The condensate of the tetraalkoxysilane can be prepared by hydrolytic condensation of any appropriate tetraalkoxysilane. Commercial products may also be used. Examples of the commercially available products include trade names “MKC silicate MS51”, “MKC silicate MS56”, “MKC silicate MS57”, “MKC silicate MS60” (all of which are condensates of tetramethoxysilane), Colcoat, manufactured by Mitsubishi Chemical Corporation. And trade names “Ethyl silicate 40” and “Ethyl silicate 48” (both are condensates of tetraethoxysilane). Examples of commercially available condensates of tetraalkoxysilanes containing different alkyl groups include, for example, trade names “MKC silicate MS56B15”, “MKC silicate MS56B30”, “MKC silicate MS58B15”, “MKC silicate MS58B15”, “ Examples thereof include “MKC silicate MS56I30”, “MKC silicate MS56F20”, manufactured by Colcoat Co., Ltd., and trade name “EMS-485”.

  When tetraalkoxysilane and its condensate are used in combination, the alkyl groups contained may be the same or different. Specific examples of the case where the alkyl groups contained are different include the case of containing a condensate of tetramethoxysilane and the monomer tetraethoxysilane. In addition, it is preferable that the compounding quantity of the monomer tetraalkoxysilane is 100 mass parts or less with respect to 100 mass parts of condensates of tetraalkoxysilane.

  The alkoxysilane compound may include an alkoxysilane having an organic group. The alkoxysilane having an organic group has at least one Si—C bond. Preferred is a trialkoxysilane having an organic group. This is because such an alkoxysilane compound is hydrolyzed to obtain an alkoxy group-free polyhydroxysiloxane containing the above-mentioned polyhydroxysiloxane having an organic group. The organic group is as described in the above section (A).

  Specific examples of the alkoxysilane having an organic group include, for example, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, n-propyltrimethoxysilane, isobutyltrimethoxysilane, n-decyltrimethoxy. Silane, n-hexadecyltrimethoxysilane, 1,6-bis (trimethoxysilyl) hexane, γ-ureidopropyltriethoxysilane, γ-dibutylaminopropyltrimethoxysilane, nonafluorobutylethyltrimethoxysilane, γ-glycine Sidoxypropylmethyldimethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxy Run, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-anilinopropyltrimethoxysilane, cyclohexylmethyldimethoxysilane, vinyltrimethoxysilane, dimethyldimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl ) Propyl] ammonium chloride, γ- (meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyl Methyldimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, styryltrimethoxysilane, γ- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, It can be exemplified Le triethoxysilane.

  The amount of the alkoxysilane having an organic group is preferably 1 to 50 parts by mass, more preferably 2 to 10 parts by mass with respect to a total of 100 parts by mass of the tetraalkoxysilane and its condensate.

A-1-2. Hydrophilic organic solvent Any appropriate organic solvent can be used as long as it can dissolve the alkoxysilane compound to such an extent that the hydrolysis reaction proceeds. For example, alcohol, glycol, ether or ester of glycol, ketone and the like can be mentioned. Specifically, for example, methanol, ethanol, propanol, isopropyl alcohol, R ₂ —O— (CH ₂ CH (R ₃ ) O) _m —H (wherein R ₂ is an alkyl group having 1 to 4 carbon atoms. R ₃ is H or CH ₃ , m is an integer of 1 to 3), CH ₃ —O— (CH ₂ CH (R ₄ ) O) ₁ —CH ₃ (wherein R ₄ is H or CH ₃ and l is 1 or 2.), acetone, methyl ethyl ketone, diacetone alcohol, 3-methoxy-3-methyl-1-butanol and the like can be preferably used. As the hydrophilic organic solvent, only one kind may be used, or two or more kinds may be used in combination.

Solubility in water of the hydrophilic organic solvent as (20 ° C.) is preferably 5g / 100gH ₂ O or more, more preferably 20g / 100gH ₂ O or more, still more preferably 100g / 100gH ₂ O or more. By using a hydrophilic organic solvent having such solubility, a system containing the hydrophilic organic solvent, water, and an alkoxysilane compound that is not sufficiently soluble in water can be made uniform. As a result, the hydrolysis reaction of the alkoxysilane compound can proceed efficiently.

  The usage-amount of the said hydrophilic organic solvent should just be more than the quantity which can melt | dissolve an alkoxysilane compound. The amount of the mixture is, for example, 0.5 to 5 times, preferably 0.5 to 4 times, more preferably 1 to 4 times the mass of the alkoxysilane compound. When the mixing amount is in the preferred range, an acidic solution of an alkoxy group-free polyhydroxysiloxane that can be suitably used in the second preparation method described later is obtained.

A-1-3. Water Any appropriate water can be used as the water. For example, tap water, ion exchange water, and pure water are preferably used.

  The usage-amount of the said water is more than the equivalent (mol) of the alkoxy group which an alkoxysilane compound has. By using this amount of water, the hydrolysis reaction of the alkoxysilane compound can sufficiently proceed. As a result, a polyhydroxysiloxane solution having substantially no alkoxy group can be obtained. In addition, when using the mixed solvent of water and a hydrophilic organic solvent, the ratio of water shall be 50 mass% or more, and the usage-amount of the mixed solvent of water and a hydrophilic organic solvent is used, and the alkoxy group non-containing polyhydroxy obtained If the content of polyhydroxysiloxane containing no alkoxy group in the acidic solution of siloxane is an amount that can be 5 to 25% by mass, the amount of water used is inevitably equal to or greater than the equivalent (mol) of the alkoxy group of the alkoxysilane compound. Become.

  The amount of water used is preferably 20 times equivalent (mole) or less, more preferably 10 times equivalent (mole) or less of the alkoxy group of the alkoxysilane compound. By using the amount of water, precipitation of the alkoxysilane compound or the hydrolyzate thereof during the hydrolysis reaction can be prevented, and the storage stability of the resulting polyhydroxysiloxane can be improved.

A-1-4. Acid catalyst Any appropriate catalyst can be used as the acid catalyst as long as it is a proton acid or Lewis acid having a catalytic action on the hydrolysis reaction of the alkoxy group of the alkoxysilane compound. Specific examples include inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid; organic acids such as acetic acid and paratoluenesulfonic acid; metal alkoxides and chelate compounds such as titanium, aluminum and zirconium. This is because the catalytic action is moderate, so that the condensation of the produced polyhydroxysiloxane hardly proceeds. Among these, an aluminum catalyst is preferably used. Examples of the aluminum catalyst include aluminum trisacetylacetonate, aluminum monoacetylacetonate bis (ethylacetoacetate), and ethylacetoacetate aluminum diisopropylate.

  The amount of the acidic catalyst used may be at least an amount that exhibits a catalytic action for the hydrolysis reaction of the alkoxy group of the alkoxysilane compound. Specifically, the amount used is preferably 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the alkoxysilane compound.

A-1-5. Any suitable method can be adopted as the mixing method. Preferably, a method of adding water to a mixed solution in which an alkoxysilane compound, an acidic catalyst, and a hydrophilic organic solvent are mixed is used. By mixing in such a manner, white turbidity, formation of precipitates, or gelation of the obtained mixed solution can be prevented. Water is preferably added little by little, and more preferably added dropwise. In addition, when a precipitate etc. produce | generate as a by-product during mixing, what is necessary is just to remove by arbitrary appropriate methods, such as filtration, and to make it a state without turbidity visually.

  In the mixed liquid, polyhydroxysiloxane is generated because the hydrolysis reaction of the alkoxysilane compound proceeds. Examples of suitable conditions for the hydrolysis reaction include the following conditions. That is, the reaction temperature is preferably 10 to 100 ° C, more preferably 20 to 80 ° C, and still more preferably 40 to 60 ° C. The reaction time after completion of the addition of water is preferably 0.5 to 10 hours, more preferably 1 to 8 hours, and further preferably 2 to 6 hours. By performing the hydrolysis reaction under the conditions, the hydrolysis reaction can be sufficiently advanced to produce the desired polyhydroxysiloxane, and the condensation of the produced polyhydroxysiloxanes can be suppressed.

A-2. Second Preparation Method of Non-Alkoxy Group-Containing Polyhydroxysiloxane Solution In the second preparation method, the basicity of the non-alkoxy group-containing polyhydroxysiloxane is obtained by adding an acidic solution of non-alkoxy group-containing polyhydroxysiloxane to the base. A solution can be obtained. The pH of the resulting basic solution is usually 8-13, preferably 8-12, more preferably 8-11.

A-2-1. Acidic solution of non-alkoxy group-containing polyhydroxysiloxane Any appropriate solution can be adopted as the acidic solution of non-alkoxy group-containing polyhydroxysiloxane. For example, an acidic solution obtained by the first preparation method can be used. In this case, the acidic solution contains polyhydroxysiloxane, a hydrophilic organic solvent, water, a catalyst, and an alcohol generated by hydrolysis of an alkoxy group. In a preferred embodiment, alcohol or hydrophilic organic solvent is removed from the acidic solution prior to addition to the base. Any appropriate method can be adopted as these removal methods. Typically, the heating should be finished when the amount removed outside the system reaches a predetermined amount by heating to a temperature equal to or higher than the boiling points of the alcohol and the hydrophilic organic solvent to be removed. The removal may be performed under normal pressure or under reduced pressure.

A-2-2. Addition to Base Any appropriate base can be used as the base. A water-soluble base is preferable. Among them, monoamines such as ammonia, ethanolamine, diethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, N-methylethanolamine, triethanolamine, tetrabutylammonium hydroxide are preferable, and ammonia, More preferred are ethanolamine and diethanolamine, and even more preferred is ammonia.

  As a usage-amount of a base, 1-20 mol% of the hydroxysilyl group which an alkoxy-group-free polyhydroxysiloxane has is preferable, 1-10 mol% is more preferable, and 3-10 mol% is further more preferable. With such a use amount, a basic solution of polyhydroxysiloxane containing no alkoxy group can be obtained with the hydroxysilyl group remaining.

  The addition of the alkoxy group-free polyhydroxysiloxane to the base of the acidic solution is preferably performed little by little, and more preferably by dropwise addition. Thus, a basic solution can be prepared without substantially passing through pH 5-7 which will be in an unstable state by adding an acidic solution gradually to a base. In order to avoid the influence of heat of neutralization, the addition is preferably performed under cooling conditions. From the viewpoint of easy handling, the base is preferably in the form of an aqueous solution. The amount of the aqueous base solution is preferably such that the alkoxy group-free polyhydroxysiloxane content in the basic solution of the resulting alkoxy group-free polyhydroxysiloxane can be 5 to 25% by mass. Typically, it is about the same amount as the acidic solution of the non-alkoxy group-containing polyhydroxysiloxane to be added. If the content of the polyhydroxysiloxane containing no alkoxy group in the basic solution is less than 5% by mass, the viscosity may be low and it may not be used as a paint. When this content exceeds 25 mass%, it may be unable to manufacture by gelation.

A-3. Third Preparation Method of Alkoxy Group-Free Polyhydroxysiloxane Solution In the third preparation method, an alkoxysilane compound is added to water containing a basic catalyst or a mixed solvent of water and a hydrophilic organic solvent. A basic solution of an alkoxy group-free polyhydroxysiloxane can be obtained. The pH of the resulting basic solution is usually 8-13, preferably 8-12, more preferably 8-11. According to this method, since the polyhydroxysiloxane is not placed in an environment having a pH of 5 to 7, a basic solution of polyhydroxysiloxane can be stably prepared.

A-3-1. Alkoxysilane Compound As the alkoxysilane compound, the alkoxysilane compound described in the section A-1-1 can be used. The contents described in the section A-1-1 are also applied to the possibility of including an alkoxysilane having an organic group.

A-3-2. Basic catalyst As the basic catalyst, any appropriate water-soluble basic compound may be used. For example, inorganic hydroxides such as sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide; ammonia; monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, n-propylamine, isopropylamine, Amines such as diisopropylamine and n-butylamine; ethanolamines such as monoethanolamine, diethanolamine and triethanolamine; N, N-dimethylethanolamine, N, N-diethylethanolamine, N-methylethanolamine, N- Examples include amino alcohols such as methyldiethanolamine; other organic compounds having an amino group such as pyridine, polyvinylamine, and polyallylamine. The amines are preferably monoamines. Moreover, when using what has an amino group as a substituent as an alkoxysilane which has the said organic group, since these are basic compounds, they can function also as a basic catalyst. These basic catalysts may be used alone or in combination of two or more.

The hydrolysis reaction of the alkoxysilane compound is performed in a solvent containing a basic catalyst. At that time, the basic catalyst is used after being dissolved in water or a mixed solvent of water and a hydrophilic organic solvent, which will be described later. The amount of the basic catalyst used is determined by the degree of basicity (pK _b ) of the catalyst. Typically, the pH of the solvent before adding the alkoxysilane compound is within the range of 9-11. Adjusted.

A-3-3. Water or a mixed solvent of water and a hydrophilic organic solvent As the solvent used in the third preparation method, water or a mixed liquid of water and a hydrophilic organic solvent is used. When water is used as the solvent, there is an advantage that the hydrolysis reaction of the alkoxysilane compound is fast. On the other hand, when the alkoxysilane compound or the alkoxy group-free polyhydroxysiloxane has insufficient solubility in water, a mixed liquid of water and a hydrophilic organic solvent can be used as a solvent. As the hydrophilic organic solvent, those described in the above section A-1-2 can be used.

  Water is used for hydrolysis of the alkoxysilane compound. Therefore, the usage-amount of water needs to be more than the equivalent (mol) of the alkoxy group which an alkoxysilane compound has. When a mixed solvent of water and a hydrophilic organic solvent is used, the ratio of water is 50% by mass or more, and the amount of the mixed solvent of water and the hydrophilic organic solvent is set to the resulting alkoxy group-free polyhydroxysiloxane. If the content of the polyhydroxysiloxane containing no alkoxy group in the basic solution is an amount that can be 5 to 25% by mass, the amount of water used is inevitably equal to or greater than the equivalent (mol) of the alkoxy group of the alkoxysilane compound. .

A-3-4. Addition method The hydrolysis reaction of the alkoxysilane compound proceeds by adding the alkoxysilane compound to water containing a basic catalyst or a mixed solvent of water and a hydrophilic organic solvent. The addition time is preferably within 2 hours. As for the addition method, the whole amount may be added all at once, may be added continuously at a predetermined time, or may be added in small portions. When the alkoxy compound contains a condensate of tetraalkoxysilane, it is preferably added as a solution in which the alkoxysilane compound is dissolved in a hydrophilic organic solvent. This is because the hydrolysis reaction proceeds gently. In addition, when a precipitate etc. produce | generate as a by-product during mixing, like the said A-1-5 term, it should just remove by arbitrary appropriate methods, such as filtration, and make it a state without turbidity visually.

  As the reaction temperature and reaction time at the time of addition of the alkoxysilane compound, the contents described in the reaction temperature and reaction time in the above section A-1-5 are applied.

(B) Aqueous organic binder As the aqueous organic binder, any appropriate one can be adopted depending on the polyhydroxysiloxane containing no alkoxy group. For example, from the viewpoint of improving the storage stability of the coating composition, an anionic resin, a cationic resin, or a nonionic resin may be employed depending on the pH of the solution of non-alkoxy group-containing polyhydroxysiloxane. Specifically, when an acidic alkoxy group-free polyhydroxysiloxane solution is used, it is preferable to use a cationic resin or a nonionic resin. When using a basic alkoxy group-free polyhydroxysiloxane solution, it is preferable to use an anionic resin or a nonionic resin. The aqueous organic binder may or may not have a reaction point with the alkoxy group-free polyhydroxysiloxane (for example, alkoxysilyl group, hydroxysilyl group, hydroxy group). Moreover, a polymerizable double bond or an epoxy group may be included. By including the aqueous organic binder, the coating composition of the present invention can form a coating film having excellent flexibility with a sufficient film thickness. Furthermore, the VOC can be reduced.

  The aqueous organic binder can be in any suitable form. For example, forms such as emulsion, dispersion, water solubility and the like can be mentioned, and the form of emulsion is preferable. When the aqueous organic binder is an emulsion, the obtained coating film may be referred to as a portion (hereinafter referred to as “organic portion”) formed from an organic binder in an inorganic matrix formed from an alkoxy group-free polyhydroxysiloxane. ) Have a so-called sea-island structure dispersed. For this reason, even when the organic portion is decomposed by the photocatalyst, a porous and hard coating film (so-called honeycomb coating film) made of an inorganic matrix is formed, so that the coating film structure is in a practical state. Can be held in. When an emulsion is used as the aqueous organic binder, a dispersion or a water-soluble resin can be used in combination as long as the above-described sea-island structure is maintained. The sea-island structure can be confirmed by observing the cross section of the coating film with a transmission electron microscope.

  As the aqueous organic binder that is an emulsion, an acrylic emulsion resin is preferably used. This is because it is excellent in durability, gloss, cost, freedom of resin design, and the like. As the acrylic emulsion resin, for example, a copolymer of an acrylic monomer and another monomer copolymerizable with the acrylic monomer can be used.

  Examples of the acrylic monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and cyclohexyl (meth). Alkyl group-containing (meth) acrylic monomers such as acrylate; hydroxyl-containing (meth) acrylic monomers such as 2-hydroxyethyl (meth) acrylate; ethylenically unsaturated carboxylic acids such as (meth) acrylic acid; Amino group-containing (meth) acrylic monomers such as dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylate; Amide-containing (meth) acrylic monomers such as (meth) acrylamide and ethyl (meth) acrylamide Body: Containing nitrile groups such as acrylonitrile (meth) Acrylic monomers; glycidyl (meth) an epoxy group-containing (meth) acrylates such as may be exemplified acrylic monomers and the like. Only one type of the above monomers may be used, or two or more types may be used in combination.

  Other monomers copolymerizable with acrylic monomers include aromatic hydrocarbon vinyl monomers such as styrene, methylstyrene, chlorostyrene, vinyltoluene; maleic acid, itaconic acid, crotonic acid, fumaric acid Α, β-ethylenically unsaturated carboxylic acids such as acid and citraconic acid; sulfonic acid-containing vinyl monomers such as styrene sulfonic acid and vinyl sulfonic acid; acid anhydrides such as maleic anhydride and itaconic anhydride; vinyl chloride; Chlorine-containing monomers such as vinylidene chloride and chloroprene; hydroxyl-containing alkyl vinyl ethers such as hydroxyethyl vinyl ether and hydroxypropyl vinyl ether; alkylene glycol monoallyl ethers such as ethylene glycol monoallyl ether, propylene glycol monoallyl ether and diethylene glycol monoallyl ether Α-olefins such as ethylene, propylene and isobutylene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl pivalate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether and cyclohexyl vinyl ether; ethyl allyl ether And allyl ethers such as butyl allyl ether. Only one type of the above monomers may be used, or two or more types may be used in combination.

  The volume average particle diameter of the emulsion resin is typically 5 nm to 100 μm, preferably 10 nm to 10 μm, more preferably 20 nm to 1000 nm, and still more preferably 50 nm to 500 nm. The volume average particle diameter can be measured by a laser light scattering method or the like.

  The emulsion resin is prepared by any suitable preparation method. Typical preparation methods include emulsion polymerization and suspension polymerization. When preparing by emulsion polymerization, in addition to methods such as batch polymerization, monomer dropping polymerization, and emulsion monomer dropping polymerization, it is also possible to use a mini-emulsion polymerization method having an average particle size of 5 to 500 nm. Suspension polymerization is a method in which a monomer having a double bond is dispersed in water for polymerization. In general, first, a radically polymerizable monomer that is insoluble in a medium such as water is vigorously stirred to be dispersed and suspended to obtain droplets having a size of about 0.5 to 100 μm. An initiator soluble in the radical polymerizable monomer is added to this, and a polymerization reaction is caused in the droplets of the radical polymerizable monomer. Thereby, resin particles having a relatively large particle diameter of about 0.5 to 100 μm can be produced.

  Any appropriate emulsifier can be adopted as the emulsifier used in the polymerization. For example, anionic, cationic, nonionic, amphoteric, nonionic-cationic, nonionic-anionic ones can be used alone or in combination.

  Any appropriate polymerization initiator can be adopted as the polymerization initiator. For example, persulfates such as ammonium persulfate, redox initiators composed of a combination of hydrogen peroxide and sodium hydrogen sulfite, inorganic initiators such as ferrous salts and silver nitrate, disuccinic acid peroxide, diglutaric acid peroxide, etc. Examples thereof include organic initiators such as dibasic acid peroxide and azobisbutyronitrile. The usage-amount of a polymerization initiator is 0.01-5 mass parts normally with respect to 100 mass parts of monomers.

  Examples of the aqueous organic binder that is a dispersion include acrylic resins, polyester resins, urethane resins, silicone resins, and fluorine resins. These resins preferably have a water dispersibility-imparting group. Examples of the water dispersibility-imparting group include a cationic group such as an amino group; an anionic group such as a carboxyl group, a phosphoric acid group, and a sulfonic acid group; and a nonionic group such as a polyether group. Among the above resins, an acrylic resin is preferable. This is because it is excellent in durability, gloss, cost, freedom of resin design, and the like. As a preferable acrylic resin, for example, a copolymer of an acrylic monomer and another monomer copolymerizable with the acrylic monomer is used. The same explanation as above can be applied to these monomers.

  The volume average particle diameter of the dispersion resin is preferably 10 to 1000 nm, more preferably 20 to 500 nm, and still more preferably 50 to 200 nm.

  The dispersion resin is prepared by any appropriate preparation method. A typical preparation method includes post-emulsification. Post-emulsification can be carried out in any appropriate organic solvent when the water dispersibility-imparting group is a cationic group (for example, an amino group) and an anionic group (for example, a carboxyl group, a phosphoric acid group, or a sulfonic acid group). It can be carried out by adding water and a neutralizing agent to the resin polymerized by solution and mixing and stirring. When the water dispersibility-imparting group is a nonionic group (for example, a polyoxyethylene group), it can be performed by adding water to the resin and mixing and stirring. In post-emulsification, an emulsifier may be used in combination as necessary.

  Examples of the water-soluble aqueous organic binder include an acrylic resin, a cellulose resin, a urethane resin, which has a hydrophilic group (for example, an amide group, a polyoxyethylene group, etc.) and the resin itself is water-soluble. Urea resins, vinyl resins, polyether resins and polyamide compounds are preferred. In the resin having the water dispersibility-imparting group, the amount of water dispersibility-imparting groups (cationic group, anionic group and nonionic group) is increased. By summing up, water solubility can be imparted and used as a water-soluble resin.

  Specific examples of the water-soluble resin include polyvinyl alcohol, carboxymethyl cellulose, carboxymethyl cellulose sodium, polyacrylamide, and polyethylene oxide.

  The number average molecular weight (Mn) of the water-soluble resin is preferably 200 to 200,000. When the number average molecular weight (Mn) is less than 200, the solvent resistance, water resistance, and weather resistance of the coating film may decrease due to volatilization during heat curing, decrease in coating film hardness, and decrease in coating curability. is there. When the number average molecular weight (Mn) exceeds 200,000, the viscosity of the organic binder itself becomes high, and the content of the solvent in the diluted paint upon application may increase. In addition, in this specification, a number average molecular weight (Mn) is a number average molecular weight of polystyrene conversion measured by GPC (gel permeation chromatography).

  The solid content concentration (NV) of the aqueous organic binder is preferably 20 to 70% by mass, more preferably 25 to 60% by mass.

  A commercially available resin can be used as the aqueous organic binder. Examples of such commercially available products include Mitsui Chemicals Polyurethane, Inc., trade name “Takelac W-635”, EMS-PRIMD, Inc., trade name “PRIMD XL-552”, Bayer MaterialScience AG, Inc., trade name “Bihydrol XP2470”, ADEKA Product name "UN-420" etc. are mentioned.

  The content of the aqueous organic binder in the photocatalyst-containing coating composition is appropriately set as long as the polyhydroxysiloxane concentration in the total solid content of the alkoxy group-free polyhydroxysiloxane and the aqueous organic binder is 50 to 95% by mass. obtain. The polyhydroxysiloxane concentration is preferably 50 to 80% by mass, more preferably 50 to 70% by mass. If the polyhydroxysiloxane concentration exceeds 95% by mass, the flexibility of the resulting coating film may be reduced. Moreover, when the polyhydroxysiloxane concentration is less than 50% by mass, the degradation resistance may be reduced.

  The “polyhydroxysiloxane concentration in the total solid content of the alkoxy group-free polyhydroxysiloxane and the aqueous organic binder” means the mass ratio of the alkoxy group-free polyhydroxysiloxane to the total solid content. At this time, the alkoxy group-free polyhydroxysiloxane is treated as having the structure represented by the formula (1). The value of n1 in the formula (1) is determined from the value of n2 of the raw material alkoxysilane or the weight average molecular weight (polystyrene conversion) of the alkoxy group-free polyhydroxysiloxane obtained by GPC measurement. In addition, when the alkoxy group-free polyhydroxysiloxane includes a polyhydroxysiloxane having an organic group, the polyhydroxysiloxane component including the organic group is used.

(C) Photocatalyst Any appropriate photocatalyst can be used. By containing a photocatalyst, the photocatalyst-containing coating composition of the present invention can form a coating film excellent in stain resistance. In this specification, a photocatalyst means a substance that exhibits catalytic action when irradiated with light, and a catalyst that causes a photochemical reaction and decomposes organic substances when irradiated with light of a specific wavelength. Or substances that exhibit antifouling action (hydrophilization action), antibacterial or antifungal action, and the like.

  Examples of the photocatalyst include titanium oxide, zinc oxide, tin oxide, iron oxide, zirconium oxide, tungsten oxide, chromium oxide, molybdenum oxide, ruthenium oxide, germanium oxide, lead oxide, cadmium oxide, copper oxide, vanadium oxide, niobium oxide. And metal oxides such as tantalum oxide, manganese oxide, cobalt oxide, rhodium oxide, and rhenium oxide. Further, as a visible light responsive photocatalyst, an oxynitride compound (for example, see JP-A-2002-66333), an oxysulfide compound (for example, see JP-A-2002-233770), a nitride compound such as Ta3N5, d10 electrons Oxides containing metal ions in a state (see, for example, JP-A-2002-59008), nitrogen-doped titanium oxide (see, for example, JP-A-2002-29750, JP-A-2002-87818, JP-A-2002-154823) No. 2001-207082), sulfur-doped titanium oxide, oxygen-deficient titanium oxide (eg, see JP-A-2001-98219), and photocatalyst particles are treated with a halogenated platinum compound (eg, JP, 2002-239353, A), tungsten alkoxide It is treated with a de surface treated photocatalyst obtained by (see JP 2001-286755) and the like can be used. In this invention, a photocatalyst may be used independently and may use 2 or more types together.

  Among the photocatalysts, titanium oxide is preferable. This is because high catalytic activity can be exhibited by sunlight or illumination light used in daily life. Examples of the titanium oxide include rutile type titanium oxide, anatase type titanium oxide, and flukeite type titanium oxide, and preferably anatase type titanium oxide. This is because it is easy to obtain, inexpensive, stable in characteristics, harmless to the human body, and can exhibit excellent effects as a photocatalyst.

  Examples of commercially available titanium oxide fine particles include ST-01 and ST-21 manufactured by Ishihara Sangyo Co., Ltd., processed products ST-K01 and ST-K03, and water-dispersed STS. -01, STS-02, STS-21, Sakai Chemical Industry Co., Ltd. SSP-25, SSP-20, SSP-M, CSB, CSB-M, paint types LACT1-01, LACTI-03-A Titanium Co., Ltd. photocatalytic titanium oxide coating solutions TKS-201, TKS-202, TKC-301, TKC-302, TKC-303, TKC-304, TKC-305, TKC-351, TKC-352, photocatalyst Titanium oxide sols TKS-201, TKS-202, TKS-203, TKS-251, PTA, TO, TPX manufactured by Aritex Co., Ltd. , Tainokku AM-10 of Taki Chemical Co., include Tainokku A-6.

The above titanium oxide is a metal or metal oxide such as platinum, ruthenium, silver, ruthenium oxide, niobium, copper, tin, nickel oxide, silicon oxide, etc., attached or coated on its surface as a photocatalytic activity accelerator. It's okay. For example, as a fine particle of titanium oxide surface-treated with SiO ₂ , MPT-422 manufactured by Ishihara Sangyo Co., Ltd. can be mentioned.

  The form of the photocatalyst may be any of powder, dispersion, and sol. The photocatalyst sol and the photocatalyst dispersion are typically 0.01 to 80% by mass, preferably 0.1 to 50% by mass of primary particles and / or secondary particles in water and / or an organic solvent. It is dispersed as particles.

  The content of the photocatalyst in the photocatalyst-containing coating composition is preferably 20 to 90 parts by mass, more preferably 50 to 90 parts by mass with respect to 100 parts by mass of the total solid content of the photocatalyst-containing coating composition. By making it within this range, the degradation resistance and hydrophilicity of the coating film can be achieved at a high level. If it exceeds 90 parts by mass, the decomposition reaction of the organic matter is activated more than necessary, so that the degradation resistance of the coating film may be reduced. Moreover, since hydrophilicity of a coating film becomes inadequate as it is less than 20 mass parts, the stain resistance of a coating film may fall.

(D) Nonionic viscosity modifier The photocatalyst-containing composition of the present invention may further contain a nonionic viscosity modifier as necessary. Arbitrary appropriate things can be used as a nonionic viscosity modifier. By including a nonionic viscosity modifier, the photocatalyst-containing coating composition of the present invention can have an effect of being excellent in workability when applied. Specific examples of nonionic viscosity modifiers include, for example, urethane thickeners such as polyether polyol urethane prepolymers, cellulose thickeners such as hydroxyethyl cellulose and hydroxypropyl cellulose, montmorillonite, bentonite, and clay. Examples of layered compound thickeners include hydrophobically modified ethoxylate aminoplast thickeners. A thickener may be used independently and may use 2 or more types together.

  As the nonionic viscosity modifier, a commercially available one can be used. As a preferable commercial product, the product name “Adecanol UH-814N” (polyetherpolyol urethane polymer manufactured by ADEKA) as a urethane-based viscosity modifier, and the product name “HEC Daicel SP600N” (Daicel Chemical Industries, Ltd.) as a cellulose-based viscosity modifier. Hydroxyethyl cellulose), trade name “BENTONE HD” (made by Elementis Japan) as a layered compound based viscosity modifier, trade name “Optiflo H600VF” (produced by Rockwood Additives) as a hydrophobically modified ethoxylate aminoplast based viscosity modifier ) And the like.

  The content of the nonionic viscosity modifier in the photocatalyst-containing coating composition is preferably 0.1 to 25 parts by mass, more preferably 0.3 to 100 parts by mass of the resin solid content of the aqueous organic binder. -15 parts by mass, more preferably 0.3-5 parts by mass. By setting the content within the above range, a viscosity suitable as a coating can be imparted to the coating composition.

(E) Other components The photocatalyst-containing coating composition may further contain any appropriate other components. Examples of other components include curing agents, matting agents, pigments, surface conditioners, antifoaming agents, plasticizers, film-forming aids, ultraviolet absorbers, light stabilizers (eg, HALS), and antioxidants. Can be mentioned.

  Any appropriate curing agent can be used. Specific examples include amino resins, blocked isocyanates, and epoxy resins. The content of the curing agent can be appropriately set according to the purpose. Content of a hardening | curing agent is 0.1-30 mass parts normally with respect to 100 mass parts of resin solid content in a photocatalyst containing coating composition.

(F) Manufacturing method A photocatalyst containing coating composition is manufactured by mixing said each component. Any suitable solvent may be further mixed as necessary. Any appropriate means such as a disper can be adopted as the mixing means.

[Coating]
In another aspect, the present invention provides a coating film. The coating film is formed from the photocatalyst-containing coating composition.

  The coating film of this invention is formed by apply | coating the said photocatalyst containing coating composition with respect to arbitrary appropriate to-be-coated objects. Any appropriate method can be adopted as a coating method. Examples thereof include a doctor blade method, a bar coater method, a spray method, and the like.

  You may heat-harden the coating film obtained by application | coating. By curing by heating, the physical properties and various performances of the coating film can be improved. The heating temperature can be appropriately set according to the type of the photocatalyst-containing coating composition. In general, the temperature is preferably set to 40 to 180 ° C. The heating time can be arbitrarily set according to the heating temperature.

  The coating film of the present invention is excellent in decomposition resistance and flexibility. Furthermore, for example, it is possible to increase the film thickness to 1 μm or more, and further to 5 μm or more. The mechanism by which such effects are achieved is not clear, but is presumed as follows. That is, the photocatalyst-containing coating composition of the present invention contains an alkoxy group-free polyhydroxysiloxane as an inorganic material. Since the polyhydroxysiloxane is excellent in compatibility with the aqueous organic binder, the coating film formed from the photocatalyst-containing coating composition of the present invention has a highly advanced inorganic matrix having excellent decomposition resistance and an organic matrix having excellent flexibility. It has a complicated structure. As a result, it is considered that a coating film having both decomposition resistance and flexibility can be formed. Furthermore, since the organic matrix contributes to the thickening of the film, it is considered that the thickening of the coating film is also possible. In addition, it can be judged by magnifying and observing the surface of a coating film with a microscope etc. whether it is excellent in flexibility. In a coating film having no flexibility, minute cracks exist on the surface. This is considered because the stress at the time of coating film formation cannot be relieved.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited by these Examples. Unless otherwise specified, parts and% in the examples are based on mass.

The measurement conditions for each measurement performed in the examples are shown below.
[Confirmation of presence or absence of alkoxy group]
IR analysis: A peak based on C—H stretching of the alkoxy group (in the case of Si—O—CH ₃ bond, around 2846 to 2849 cm ⁻¹ ) was observed.
When the peak or signal based on the alkoxy group was not observed, it was evaluated as “No”, and when it was observed, it was evaluated as “Yes”.

[Polyhydroxysiloxane concentration]
Using the average degree of condensation determined by GPC of the alkoxysilane used, the concentration of the active ingredient of polyhydroxysiloxane in the alkoxysilane, calculated from the amount charged, with a hydrolysis rate of 100% and a condensation reaction rate of 0% (Mass%).

[Solid content concentration (NV)]
After measuring the mass of the sample (about 1 g), the sample was dried in an oven at 140 ° C. for 10 minutes. Next, the mass of the dried sample was measured. The value obtained by dividing the weight of the sample after drying by the weight of the sample before drying and multiplying by 100 was taken as the solid content concentration (%).

[Flexibility]
The surface of the coating film was visually observed with a microscope, and a case where no crack was observed was accepted (◯), and a case where a crack was observed was regarded as unacceptable (x).

[Water contact angle]
After irradiating the coating film used in the flexibility evaluation with a black light (F15BB, manufactured by Toshiba Lighting & Technology Corp.) for 3 hours with light having an ultraviolet intensity of ² mW / cm ² , the water contact angle was measured using a contact angle meter CA manufactured by Kyowa Interface Science Co., Ltd. -Measured with type A.

[Observation of coating film structure]
The coating film obtained in Example or Comparative Example was cut out small, embedded with an epoxy resin, cut out in the cross-sectional direction with an ultramicrotome, and an ultra-thin section having a thickness of 80 nm was prepared as an observation sample. Using this sample, the transmission electron microscope “JEM-2000FXII” manufactured by JEOL Ltd. was used to observe the coating film structure at an accelerating voltage of 100 kV, and a microscopic structure in which a whitish domain (island) was present in the entire dark sea (the sea). When the layer separation structure was observed, it was assumed that there was a sea-island structure, and when it was not observed, it was evaluated that there was no sea-island structure.

[Degradation resistance]
About the coating film obtained by the Example or the comparative example, according to the conditions of JISK5600-7-7 cycle A, the super xenon acceleration | stimulation weather resistance test was implemented for 5000 hours with the radiation intensity of 180 W / m < ² >. Changes in the appearance of the coating film before and after the test were judged according to the following criteria.
○: No change, △: Slight change, ×: Significant change such as whitening

[Production Example 1]
In 1 L Kolben, 141 parts of methyl silicate 51 (MKC methyl silicate 51, manufactured by Mitsubishi Chemical Corporation; solid content 100%, molecular weight 576, content of O-CH ₃ unit 64.6% by mass), aluminum chelate D (aluminum monoacetylacetate) Nate bis (ethyl acetoacetate), solid content 76%), 6 parts by Kawaken Fine Chemical Co., Ltd.) and 341 parts Echinen F6 (manufactured by Nippon Alcohol Sales Co., Ltd.) were charged and heated to 40 ° C. with stirring. Ion exchange water 512 parts was dropped in 2 hours. The mixture was further heated and stirred at 40 ° C. for 2 hours and then cooled to obtain an acidic solution a-1 of polyhydroxysiloxane. The pH of the obtained solution was 3.4. Furthermore, Table 1 shows the polyhydroxysiloxane content, the SiO ₂ equivalent concentration and the total solid content concentration in the polyhydroxysiloxane in the obtained solution. When the obtained polyhydroxysiloxane solution was subjected to IR analysis, no peak based on alkoxy groups was observed. Note that the terms of SiO ₂ concentration in the polyhydroxy polysiloxane herein, refers to the concentration when converted polyhydroxy siloxane SiO 2 _(molecular weight = 60) (mass%).

[Production Example 2]
To 1 L Kolben, 9.6 parts of 25% aqueous ammonia was added, and diluted by adding 838.4 parts of ion-exchanged water. While cooling with water at 25 ° C. and stirring, 152 parts of tetramethoxysilane (solid content: 100%, molecular weight: 152, O—CH ₃ unit content: 81.6% by mass) was added dropwise over 2 minutes and 30 seconds. The liquid temperature rose to 38 ° C. After dropping, the mixture was stirred for 1 hour while cooling, and then filtered with a filter paper to obtain a basic solution a-2 of polyhydroxysiloxane. The pH of the obtained solution was 9.4. Furthermore, Table 1 shows the polyhydroxysiloxane content, the concentration of polyhydroxysiloxane in terms of SiO ₂ and the total solid content in the obtained solution. When the obtained polyhydroxysiloxane solution was subjected to IR analysis, no peak based on alkoxy groups was observed.

[Production Example 3]
In 100 mL Kolben, 75.1 parts of ion-exchanged water and 1.2 parts of 25% aqueous ammonia were charged and stirred. To the obtained solution, 13.7 parts of tetramethoxysilane was added dropwise in about 3 minutes. After stirring for 1 hour, a mixed solution of 0.67 part of vinyltrimethoxysilane (solid content 100%, molecular weight 148, O-CH ₃ unit content 62.8% by mass) and 0.67 part of methanol was added dropwise. After dropping, the mixture was further stirred for 1.5 hours, and the resulting solution was filtered with a filter paper (No. 2 qualitative filter paper manufactured by Advantech Toyo Co., Ltd.) to obtain a colorless transparent polyhydroxysiloxane basic solution a-3. Furthermore, Table 1 shows the polyhydroxysiloxane content, the concentration of polyhydroxysiloxane in terms of SiO ₂ and the total solid content in the obtained solution. When the obtained polyhydroxysiloxane solution was subjected to IR analysis, no peak based on alkoxy groups was observed.

[Production Example 4]
141 liters of methyl silicate 51 (MKC methyl silicate 51, manufactured by Mitsubishi Chemical Corporation), 6 parts of aluminum chelate D (aluminum monoacetylacetonate bis (ethyl acetoacetate), Kawaken Fine Chemicals) 6 parts, 1 Equinene F6 (Japan) 831.8 parts) (alcohol sales company) was charged and heated to 40 ° C. with stirring. 21.2 parts of ion-exchanged water was added dropwise over 10 minutes. The mixture was further heated and stirred at 40 ° C. for 2 hours and then cooled to obtain a polyhydroxysiloxane solution a-4. Furthermore, Table 1 shows the polyhydroxysiloxane content, the concentration of polyhydroxysiloxane in terms of SiO ₂ and the total solid content in the obtained solution. When the obtained polyhydroxysiloxane solution was subjected to IR analysis, peaks based on alkoxy groups were observed.

[Water-based organic binder]
The following were used as the aqueous organic binder.
b-1: Polyurethane dispersion (W-635 manufactured by Mitsui Chemicals, solid content concentration: 36%)
b-2: Ammonia neutralized acrylic emulsion (solid content concentration 50%, particle size 180 nm, pH: 9)
b-3: Water-soluble urethane resin (UNE-420 manufactured by ADEKA, solid content concentration 30%, pH: 7)

[photocatalyst]
The following were used as photocatalysts.
c-1: Titanium oxide sol (manufactured by Taki Chemical Co., Ltd., Tynock AM-10, TiO ₂ concentration 15%, crystallite size 10 nm, pH: 4)
c-2: Titanium oxide sol (manufactured by Taki Chemical Co., Ltd., Tynock A-6, TiO ₂ concentration 6%, crystallite size 10 nm, pH: 10)
c-3: Titanium oxide sol surface-treated with SiO ₂ (manufactured by Ishihara Sangyo Co., Ltd., MPT-422, sol concentration 20%, crystallite size 30 nm, pH: 7.5)

[Examples 1-7]
A polyhydroxysiloxane solution, an aqueous organic binder, and a photocatalyst shown in Table 2 were mixed at a blending ratio shown in Table 2 to prepare a coating composition. The obtained paint was diluted with water so that the solid content concentration was 2%. On the other hand, Aude Power 600 clear paint made by Nippon Paint was applied to an aluminum plate with a 6 mil doctor blade and dried at 100 ° C. for 10 minutes. The diluted paint was applied to this plate by spraying so that the dry film thickness was 2 μm, and dried at room temperature for 24 hours to obtain a coating film. After visually evaluating the surface of the obtained coating film and evaluating the flexibility, the water contact angle was measured, and the presence or absence of a sea-island structure was further observed. Moreover, the decomposition resistance of the coating film was evaluated. The results are shown in Table 2. In addition, the unit of the mixture ratio of a component-c component in Table 2 is a mass part.

[Comparative Examples 1-3]
A polyhydroxysiloxane solution, an aqueous organic binder, and a photocatalyst shown in Table 3 were mixed at a blending ratio shown in Table 3 to prepare a coating composition. The following procedures are the same as in the examples to form a coating film. After visualizing the surface of the obtained coating film and evaluating the flexibility, the water contact angle is measured, and the presence or absence of a sea-island structure. Was observed. The results are shown in Table 3. In addition, the unit of the mixture ratio of a component-c component in Table 3 is a mass part.

[Evaluation]
As is apparent from Tables 2 and 3, the coating films obtained from the coating compositions of the examples of the present invention simultaneously satisfy very good hydrophilicity and very good appearance. In other words, the coating film obtained from the coating composition of the present invention has excellent decomposition resistance and excellent flexibility. On the other hand, in the coating composition of Comparative Example 1 having a low polyhydroxysiloxane content, the contact angle measurement coating film was whitened after irradiation with black light, and the water contact angle could not be measured. In the coating composition of Comparative Example 2 that did not contain an aqueous organic binder, cracks occurred in the coating film applied to the aluminum plate. In the coating composition of Comparative Example 3 using polyhydroxysiloxane having an alkoxy group, cracks occurred in the coating film for contact angle measurement after the black light irradiation, and the water contact angle could not be measured. The coating composition of Example 7 having a low photocatalyst content had a large water contact angle and insufficient hydrophilicity compared to Examples 1-6. In addition, Examples 3 and 4 using an emulsion resin as an aqueous organic binder are superior in decomposition resistance of the coating film compared to Examples 1, 2, 5 and 6 using a dispersion or a water-soluble resin. It was. This is considered to be because the coating film structure has a so-called sea-island structure in which a portion formed from an organic binder is dispersed in an inorganic matrix formed from polyhydroxysiloxane.

  The photocatalyst-containing coating composition of the present invention can be suitably used in the field of coatings and the like.

Claims (4)

(A) a polyhydroxysiloxane solution substantially free of alkoxy groups;
(B) an aqueous organic binder;
(C) a photocatalyst,
(A) The polyhydroxysiloxane concentration in the total solid content of the polyhydroxysiloxane solution substantially free of alkoxy groups and (B) the aqueous organic binder is 50 to 95% by mass,
A photocatalyst-containing coating composition.   The photocatalyst-containing coating composition according to claim 1, wherein the (B) aqueous organic binder is an emulsion resin.   The photocatalyst-containing coating composition according to claim 1 or 2, wherein the content of the (C) photocatalyst is 20 to 90 parts by mass with respect to 100 parts by mass of the total solid content of the photocatalyst-containing coating composition.   The coating film formed from the photocatalyst containing coating composition in any one of Claims 1-3.