JP4141447B2 - Colloidal silica-bonded polysiloxane-containing coating composition - Google Patents

Description

  The present invention relates to a coating composition capable of forming an antifouling layer having excellent stain resistance, hot water resistance and durability, and having a self-cleaning ability, and a method for preparing the same.

  A coating film using an organopolysiloxane-based inorganic resin as a binder is excellent in weather resistance, stain resistance, and the like, but easily cracks. In addition, a coating film using an organic-inorganic composite resin obtained by hydrolytic condensation reaction of organosilane or a partially hydrolyzed condensate thereof and a silyl group-containing compound as a binder is less susceptible to cracking, There was a problem that the weather resistance and solvent resistance were slightly inferior (see, for example, Patent Documents 1 and 2).

JP 2003-31497 A JP 2001-98221 A

  The present invention has been made against the background of such problems of the prior art. A polysiloxane obtained by hydrolytic condensation of a specific organosilane or a partially hydrolyzed condensate thereof as an inorganic resin and colloidal silica is provided. By using it as a binder, a coating composition that is less susceptible to cracking at low temperatures, is excellent in stain resistance, warm water resistance, durability, and can form an antifouling layer having a self-cleaning ability. The purpose is to provide.

That is, the present invention relates to an invention having the following configuration.
1. (A) General formula (1),
Si (OR ¹ ) _x (OR ² ) _(4-x)
Wherein, R ¹ and R ² is an organic group having 1 to 8 carbon atoms, x is an integer of 0-4. ]
100 parts by mass of a tetraalkoxysilane or a partially hydrolyzed condensate thereof represented by
(B) 10 to 500 parts by mass of colloidal silica (in terms of solid content);
To a silica-containing condensation product obtained by hydrolytic condensation of
(C) It contains a polysiloxane solution obtained by adding 250 to 700,000 parts by mass of water or an organic solvent as a diluent per 100 parts by mass of the tetraalkoxysilane or a partial hydrolysis condensate thereof. Paint composition.
2. A method for preparing a coating composition comprising the following steps:
(1) (a) General formula (1),
Si (OR ¹ ) _x (OR ² ) _(4-x)
Wherein, R ¹ and R ² is an organic group having 1 to 8 carbon atoms, x is an integer of 0-4. ]
100 parts by mass of a tetraalkoxysilane or a partially hydrolyzed condensate thereof represented by
(B) 10 to 500 parts by mass of colloidal silica (in terms of solid content);
Hydrolyzing and condensing to produce a silica-containing condensation product,
(2) To the silica-containing condensation product, 250 to 700,000 parts by weight of water or an organic solvent is added as a diluent per 100 parts by weight of the tetraalkoxysilane or a partially hydrolyzed condensate thereof. Preparing a polysiloxane solution,
(3) using the polysiloxane solution as a paint component;
A method for preparing a coating composition comprising:

Hereinafter, the present invention will be described in detail.
Each component of the coating composition of the present invention will be described.
First, each component used in order to manufacture the solution of polysiloxane used as the binder of the coating composition of this invention is demonstrated.

Regarding the component (a), the component (a) is represented by the general formula (1),
Si (OR ¹ ) _x (OR ² ) _(4-x)
Wherein, R ¹ and R ² is an organic group having 1 to 8 carbon atoms, x is an integer of 0-4. Or a partially hydrolyzed condensate thereof.
In the above formula, preferred examples of the organic group as R ¹ and R ² include an alkyl group, a cycloalkyl group, and an aryl group. R ¹ and R ² may be the same or different.
Here, the alkyl group may be linear or branched. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, pentyl group, hexyl group, Examples thereof include alkyl groups such as heptyl group and octyl group. Preferred alkyl groups are alkyl groups having 1 to 4 carbon atoms.

Preferred examples of the cycloalkyl group include a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and the like.
Examples of the aryl group include a phenyl group.
Specific examples of the tetraalkoxysilane represented by the above formula (1) include, for example, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, triethoxybutoxysilane, and the like.
These tetraalkoxysilanes can be used alone or as a mixture of two or more.

The component (a) may be the partially hydrolyzed condensate of tetraalkoxysilane described above. The polystyrene-converted weight average molecular weight of the condensate is, for example, 300 to 5000, preferably 500 to 3000. By using a condensate having such a molecular weight, the storage stability is not deteriorated. A coating film with good adhesion can be obtained. Moreover, the partial hydrolysis-condensation product of tetraalkoxysilane is suitable to have one or more, preferably 3 to 30, —OH groups, —OR ¹ groups, or —OR ² groups bonded to silicon atoms. .
Specific examples of such condensates include commercially available products such as ethyl silicate 40 and ethyl silicate 56 (both manufactured by Colcoat).

Component (b) As the colloidal silica of component (b), silica particles dispersed in water or an organic solvent are preferably used. Colloidal silica usually has an average particle size of 5 to 100 nm, preferably 10 to 30 nm, in which substantially spherical silica particles are dispersed, and the silica particles have a thickness of 5 to 50 nm and a length of about 40 to 400 nm. There are a type in which chains are aggregated and dispersed in a solution, and a type in which silica particles having an average particle diameter of 5 to 50 nm are aggregated in a ring and dispersed in a solution. Also, different types can be mixed and used.
Silica particles in which approximately spherical silica particles are dispersed in water can be easily obtained as a commercial product. Such colloidal silica is, for example, SNOWTEX-20, SNOWTEX manufactured by Nissan Chemical Industries, Ltd. Preferred examples include -O, Snowtex-C, Snowtex-S, and Adelite AT-20, AT-20N, AT-20A, AT-300 manufactured by Asahi Denka Kogyo Co., Ltd.

  Colloidal silica in which almost spherical silica particles are dispersed in an organic solvent is, for example, lower alcohols such as methanol, ethanol, isopropanol, n-butanol, isobutanol; ethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monoacetate. Ethylene glycol derivatives such as ethyl ether; diethylene glycol derivatives such as diethylene glycol and diethylene glycol monobutyl ether; ketones such as acetone and methyl ethyl ketone; and silica particles dispersed in organic solvents such as toluene, xylene, ethyl acetate, and butyl acetate This organic solvent-dispersed colloidal silica can also be easily obtained as a commercial product. For example, Snowtex MA-ST-M, I manufactured by Nissan Chemical Industries, Ltd. A-ST, EG-ST, EG-ST-ZL can be preferably used.

The chain colloidal silica is dispersed in water or the above-mentioned organic solvent, and can be easily obtained as a commercial product. Specific examples thereof include, for example, Snowtex-UP manufactured by Nissan Chemical Industries, Ltd. SNOWTEX-OUP (above, water dispersion), SNOWTEX MA-ST-UP, IPA-ST-UP (above, organic solvent dispersion) and the like are preferable.
Examples of the commercially available cyclic colloidal silica include SNOWTEX-PS-SO, SNOWTEX-PS-M, SNOWTEX-PS-L, etc., manufactured by Nissan Chemical Industries, Ltd.

  (B) A component is used in order to improve the sclerosis | hardenability and stain resistance of a coating film, and the compounding quantity is 10-500 in conversion of solid content with respect to 100 mass parts of said (a) component, for example. Part by mass, preferably 20 to 300 parts by mass is appropriate. When the blending amount of the component (b) is less than the above range, the effect of improving the curability and stain resistance of the coating film is small. On the contrary, when the amount is too large, the mixing stability, the crack resistance of the coating film, etc. Tend to decrease.

The pH of the dispersion of colloidal silica (component (b)) is preferably 6 or less, and more preferably 3 to 5. When the pH of the colloidal silica dispersion is greater than 6, the storage stability of the resulting polysiloxane solution is insufficient, which is not preferable.
In the reaction between the component (a) and the component (b), if the component (b) is dispersed in water, the hydrolysis condensation reaction can be performed using the water in the component (b). . On the other hand, when the component (b) is dispersed in an organic solvent, the hydrolysis-condensation reaction can be performed by adding water in which the component (a) can be hydrolyzed by 50% or more. Moreover, it is preferable to add acetic acid, acids, such as hydrochloric acid, nitric acid, formic acid, or basic compounds, such as ammonia and an amine compound, as a catalyst for promoting reaction.
The hydrolysis or partial condensation reaction is usually performed at 40 to 80 ° C., preferably 45 to 65 ° C., for example, for 2 to 15 hours. In the presence of a catalyst, the reaction is performed at room temperature. Is also possible.

(C) Component (a) To the silica-containing condensation product of component (a) and component (b) obtained as described above, (c) As a diluent, water or an organic solvent is added to form a polysiloxane solution. can get.
(C) As water used as a diluent, pure water, distilled water, ion exchange water, tap water, or the like can be used.
Examples of organic solvents include alcohols such as methanol, ethanol, propanol, and butanol; alcohol ethers such as ethylene glycol monoethyl ether and ethylene glycol monobutyl ether; and hydrophilic organic solvents such as ketones such as acetone and methyl ethyl ketone; It is possible to use a mixed organic solvent such as toluene, xylene, ethyl acetate, butyl acetate and other hydrophobic organic solvents for paints.

Component (c) is blended in an amount of 250 to 700,000 parts by weight, preferably 500 to 70000 parts by weight per 100 parts by weight of component (a). If the amount of component (c) is less than the above range, it is difficult to obtain a uniform coating film, whereas if it is too much, the stability of the resulting polysiloxane solution tends to be inferior.
Among organic solvents, water-soluble alcohols are particularly preferable in order to prevent the stability of the paint and lifting of the undercoat film. For example, lower alcohols such as methanol, ethanol, and propanol, particularly the general formula (2),
HO- (CHR ³ CH ₂ O) _n R ⁴
[Wherein, R ³ is CH ₃ or H, R ⁴ is an alkyl group having 1 to 8 carbon atoms, and n is 1 or 2. ]
It is preferable to contain the organic solvent shown by 1-5 mass% coating composition. Examples of the organic solvent of the general formula (2) include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and dipropylene glycol monomethyl. Preferred examples include ether and dipropylene glycol monoethyl ether.
These can be used alone or in combination.

About (d) component As needed, as (d) component, surfactant whose surface tension of 0.01 mass% concentration aqueous solution will be 40 dyn / cm (25 degreeC) or less can be used. Component (d) is preferably blended in the coating composition in an amount of 0.001 to 3% by mass in terms of solid content for the purpose of improving the appearance of the coating film of the polysiloxane solution obtained as described above. On the other hand, when the amount exceeds 3% by mass, the coating film appearance and the water resistance of the coating film tend to be inferior. If the surface tension of the aqueous solution having a concentration of component (d) of 0.01% by mass is larger than 40 dyn / cm, a uniform coating film cannot be obtained and the coating film appearance becomes uneven, which is not preferable.
(D) As the surfactant, for example, an anionic or nonionic surfactant can be used. Specific examples thereof include Neugen ET-143, ET-135 (Daiichi Kogyo Seiyaku Co., Ltd.), Perex NB-L (Kao Co., Ltd.), Florard FC4430 (Sumitomo 3M Co., Ltd.) Polyflow KL-600 (manufactured by Kyoei Chemical Co., Ltd.), Surflon S-111, S-141 (manufactured by Seimi Chemical Co., Ltd.) and the like are preferable, and a fluorosurfactant is particularly preferred.

In the polysiloxane solution thus obtained, the heating residue after drying at 150 ° C. for 30 minutes is usually 0.01 to 40% by mass. However, in order to obtain a uniform coating film, the polysiloxane solution For the reason of sufficient stability, the heating residue of the polysiloxane solution is desirably 0.1 to 10% by mass.
The coating composition of the present invention contains the above polysiloxane solution as a coating component.
The surface tension of the coating composition of the present invention is 50 dyn / cm (25 ° C.) or less, preferably 45 to 15 dyn / cm (25 ° C.), and uniform when it is greater than 50 dyn / cm (25 ° C.). Insufficient coating film performance cannot be achieved because the coating film cannot be formed smoothly.

The coating composition of the present invention contains a polysiloxane solution comprising the hydrolysis condensation reaction product of component (a) and component (b) described above and (c) a diluent. Accordingly, fillers, dyes, curing agents, and various additives such as curing accelerators, thickeners, pigment dispersants and the like may be blended in order to improve the coating film properties and coloring. .
As the filler, for example, various pigment extender pigments such as talc, barium carbonate, calcium carbonate, barium sulfate, bentonite, titanium oxide, carbon black, Bengala, and lithopone, and colored pigments can be used. The blending amount of the filler is 0 to 70% by mass, preferably 0 to 50% by mass in the solid content of the coating composition.

  Examples of the curing agent include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl)- γ-aminopropylmethyldimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldiethoxysilane, N-cyclohexyl-γ-aminopropyltrimethoxysilane, N-cyclohexyl-γ-aminopropyltriethoxy Having an amino group in the molecule such as silane, γ- (2-aminoethyl) -aminopropyltrimethoxysilane, γ- (2-aminoethyl) -aminopropylmethyldimethoxysilane, γ-anilinopropyltrimethoxysilane, Alkoxysilane capable of hydrolytic condensation reaction,

γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriisosilane Epoxy groups such as propenyloxysilane, γ-glycidoxypropyltriiminooxysilane, β- (3,4-epoxycyclohexyl) ethylmethyldimethoxysilane, and adducts of γ-isocyanatopropyltriisopropenyloxysilane and glycidol. The alkoxysilane etc. which can have a hydrolysis condensation reaction are mentioned.
Typical examples of the curing accelerator include organic tin compounds such as tin octylate, dibutyltin dilaurate, dibutyltin dimaleate, and tributyltin laurate, and amine compounds such as ethylenediamine, diethylenetriamine, piperidine, phenylenediamine, and triethylamine. In particular, organotin compounds are effective.

The coating composition of the present invention is applied to the surface of an object to be coated by a brush, spray, roll, dipping, or other coating means, and, for example, is baked at room temperature or a temperature of 300 ° C. or lower to form a cured coating film. It is possible.
As an object to be coated, it can be applied to various objects to be coated such as an inorganic ceramic substrate, various metal substrates such as stainless steel and aluminum, a glass substrate, a plastic substrate, and a paper substrate.

Hereinafter, the present invention will be described in more detail with reference to examples.
In the examples, “parts” and “%” are based on mass unless otherwise specified.

Reference example 1
A reactor equipped with a reflux condenser and a stirrer is charged with 200 parts of methanol, then (a) 100 parts of tetraethoxysilane, (b) isopropanol-dispersed colloidal silica (IPA, manufactured by Nissan Chemical Industries, Ltd.) -ST: Solid content 30%, pH 3.2) 230 parts were added and mixed, and then with stirring, a mixed solution of 250 parts of ion-exchanged water and 6 parts of 0.1N aqueous hydrochloric acid was added at 60 ° C. After reacting for 3 hours, 1200 parts of ion exchange water was added and cooled to room temperature to obtain a polysiloxane solution A (solid content 5%) having a surface tension of 25 dyn / cm.

Reference example 2
A reactor equipped with a reflux condenser and a stirrer is charged with 200 parts of methanol, then (a) 100 parts of tetramethoxysilane, (b) isopropanol-dispersed colloidal silica (manufactured by Nissan Chemical Industries, IPA) -ST; solid content 30%, pH 3.2) 100 parts were added and mixed, then with stirring, a mixture of 250 parts of ion-exchanged water and 6 parts of 0.1N aqueous hydrochloric acid was added, After reacting for a period of time, 750 parts of ion exchanged water was added and cooled to room temperature to obtain a polysiloxane solution B (solid content 5%) having a surface tension of 26 dyn / cm.

Reference example 3
A reactor equipped with a reflux condenser and a stirrer is charged with (a) 100 parts of tetraethoxysilane, and then (b) water-dispersed colloidal silica (manufactured by Nissan Chemical Industries, Snowtex-O; solid) After adding and mixing 150 parts (min 20%, pH 3.8), with stirring, a mixture of 250 parts of ion-exchanged water and 6 parts of 0.1N aqueous hydrochloric acid was added and reacted at 60 ° C. for 3 hours. Thereafter, 70 parts of propylene glycol monomethyl ether and 600 parts of ion exchange water were added and cooled to room temperature to obtain a polysiloxane solution C (solid content 5%) having a surface tension of 45 dyn / cm.

Reference example 4
A reactor equipped with a reflux condenser and a stirrer is charged with 200 parts of methanol, then (a) 100 parts of tetraethoxysilane and (b) water-dispersed colloidal silica (manufactured by Nissan Chemical Industries, Ltd., Snow After adding and mixing 500 parts of Tex-O; solid content 20%, pH 3.8), with stirring, a mixture of 250 parts of ion-exchanged water and 6 parts of 0.1N aqueous hydrochloric acid was added at 60 ° C. After reacting for 3 hours, 100 parts of dipropylene glycol monomethyl ether and 1700 parts of ion-exchanged water were added and cooled to room temperature to obtain a polysiloxane solution D (solid content 5%) having a surface tension of 40 dyn / cm.

Reference Example 5
In a reactor equipped with a reflux condenser and a stirrer, 100 parts of methanol was added, and then 100 parts of (a) tetraethoxysilane was added and mixed, and then 36 parts of ion-exchanged water and 0. After adding 2.5 parts of a 1N hydrochloric acid aqueous solution and reacting at 60 ° C. for 3 hours, adding 450 parts of ion-exchanged water, cooling to room temperature, and a polysiloxane solution E (solid solid with a surface tension of 30 dyn / cm) Min. 5.2%).

Reference Example 6
50 parts of methanol was put into a reactor equipped with a reflux condenser and a stirrer, and then (b) water-dispersed colloidal silica (manufactured by Nissan Chemical Industries, Snowtex-O; solid content 20%, pH 3. 8) After adding 50 parts and mixing, with stirring, 100 parts of ion-exchanged water was added and stirred at room temperature for 3 hours to obtain a silica dispersion F having a surface tension of 70 dyn / cm (solid content 5%).

Reference Example 7
A reactor equipped with a reflux condenser and a stirrer was charged with 78 parts of ion-exchanged water, and then (b) water-dispersed colloidal silica (manufactured by Nissan Chemical Industries, Snowtex-O; solid content 20%, pH 3.8) 20 parts were added and mixed, and then, with stirring, (a) 2 parts of tetraethoxysilane was added and stirred at room temperature for 3 hours to obtain a silica mixed solution G having a surface tension of 37 dyn / cm (solid content of 4. 7%).

The surface tension and the heating residue were measured as follows.
<Method for measuring surface tension>
The surface tension was measured at 25 ° C. using a surface tension meter (CBUP-A5 type) manufactured by Kyowa Interface Science Co., Ltd.
<Measurement method of heating residue>
The heating residue is precisely weighed about 3 grams of sample in an aluminum cup, weighed after drying for 30 minutes using a 150 ° C. oven, calculated from the mass of the residue relative to the original weight, and the heating residue ( %).
The coating film performance evaluation of the obtained polysiloxane solution and coating composition was performed as follows.

<Performance evaluation test>
(i) Storage stability test of polysiloxane solution Polysiloxane solutions A to E, silica dispersion solution F, and silica mixed solution G obtained in Reference Examples 1 to 7 were each sealed in a container sealed in a 50 ° C incubator for 4 weeks. It was allowed to stand and examined for changes in appearance and viscosity. As a result, the polysiloxane solutions A to D and the silica dispersion solution F were not changed, but the polysiloxane solution E not subjected to the condensation reaction with the component (b) was thickened. Further, insoluble matter was partially generated in the silica mixed solution G obtained by simply mixing the components (a) and (b).

(ii) Preparation of test plate for evaluating coating film performance of paint composition A gypsum slag perlite plate (thickness 12 mm) was used as a material, and a polyisocyanate prepolymer solution sealer “V-Selan # 100 sealer” (Dainippon Paint) Co., Ltd., butyl acetate: xylene = 100% diluted with a solvent of 1: 1) was spray-coated so that the coating amount was 90 to 100 g / m ² (wet mass). This was dried at 100 ° C. for 5 minutes. Next, an acrylic silicone resin-based paint “V-Selan # 500 Enamel” (Dainippon Paint Co., Ltd., diluted 40% with a solvent of butyl acetate: xylene = 1: 1) as a base paint is applied in an amount of 80 to 90 g / m. Spray painting was performed so that ² (wet mass) was obtained. This was dried at 120 ° C. for 15 minutes.
Next, a surfactant, a diluent, and the like were added to each of the prepared solutions, and the top coating composition shown in Table 1 was spray-coated so that the coating amount was 70 to 80 g / m ² (wet mass). . After drying this at 120 ° C. for 15 minutes, it was dried at room temperature for 3 days, and each performance evaluation test of hardness, warm water resistance, stain resistance, weather resistance and frost damage resistance of the obtained coating film was carried out. Is shown in Table 1.
In addition, the test method and evaluation criteria of each performance evaluation test were performed based on the following.

<Appearance of coating film> The appearance of the coating film before the test was visually evaluated as follows.
○… Good (transparent film)
×… Bad (cloudy film)

<Hot water resistance>
The appearance of the coating film after the coating plate produced as described above was immersed in warm water at 80 ° C. for 3 hours was visually determined as follows during immersion and after drying the coating film.
◎ ... No change during soaking and after drying of coating film ○ Slight whitening during soaking, but no change after drying of coating film △ ... Severe whitening during soaking ×: Slightly whitening during soaking, large changes in gloss, whitening, etc. after drying the coating

<Contamination resistance>
24 hours after drawing with red and black magic inks on the coated plate, it was wiped off with a cloth moistened with n-butanol, and its decontamination property was visually judged as follows.
◎… Complete removal ○… Very slight contamination △… Slight contamination ×… Significant contamination

<Weather resistance>
The weather resistance was determined as follows using a sunshine weather-ometer for 3000 hours.
○: No change in coating film appearance, gloss retention of 95% or more Δ: Minor change in coating film appearance, gloss retention of less than 80-95% ×: Significant change in coating film appearance, gloss retention of 80 %Less than

<Frost resistance>
The frost damage resistance of 40 cycles was measured by ASTM-C666A method, and visually judged as follows.
○: No cracks occurred in the coating film △: Very slight cracks occurred ×: Cracking or partial peeling of the coating film

1) Anionic surfactant “Perex NB-L” (manufactured by Kao Corporation)
35% by mass of active ingredient, surface tension 38 dyn / cm (25 ° C., 0.01% by mass aqueous solution)

As is clear from Table 1, Examples 1 to 4 using the coating composition containing the polysiloxane solution of the present invention had excellent coating performance.
On the other hand, in the paint using the polysiloxane solution E not subjected to the condensation reaction with the component (b) of Comparative Example 1, the stain resistance, weather resistance and frost damage resistance were poor. In the paint using the silica dispersion solution F not subjected to the condensation reaction with the component (a) in Comparative Example 2, the coating film appearance, hot water resistance, weather resistance and frost damage resistance were very poor. Moreover, in the coating material using the silica mixed solution G in which the components (a) and (b) in Comparative Example 3 were simply mixed, the coating film appearance, warm water resistance, and stain resistance were very poor.

Claims (5)

(A) General formula (1),
Si (OR ¹ ) _x (OR ² ) _(4-x)
Wherein, R ¹ and R ² is an organic group having 1 to 8 carbon atoms, x is an integer of 0-4. ]
100 parts by mass of a tetraalkoxysilane or a partially hydrolyzed condensate thereof represented by
(B) 10 to 500 parts by mass of colloidal silica (in terms of solid content),
To a silica-containing condensation product obtained by hydrolytic condensation of
(C) As a diluent, water is obtained by adding 250 to 700,000 parts by mass per 100 parts by mass of the tetraalkoxysilane or a partial hydrolysis condensate thereof ,
A coating composition comprising a polysiloxane solution and having a surface tension of 50 dyn / cm (25 ° C.) or less . Further, as the component (d), a surfactant having a surface tension of an aqueous solution having a concentration of 0.01% by weight of 40 dyn / cm (25 ° C.) or less is 0.001 to 3% by weight (solid content conversion) in the coating composition. The coating composition of Claim 1 contained. The coating composition according to claim 1 or 2 , wherein a heating residue of the polysiloxane solution at 150 ° C for 30 minutes is 0.1 to 10% by mass. A method for preparing a coating composition comprising the following steps:
(1) (a) General formula (1),
Si (OR ¹ ) _x (OR ² ) _(4-x)
Wherein, R ¹ and R ² is an organic group having 1 to 8 carbon atoms, x is an integer of 0-4. ]
100 parts by mass of a tetraalkoxysilane or a partially hydrolyzed condensate thereof represented by
(B) 10 to 500 parts by mass of colloidal silica (in terms of solid content);
Hydrolyzing and condensing to produce a silica-containing condensation product,
(2) To 100 parts by mass of the tetraalkoxysilane or its partial hydrolysis condensate, (c) as a diluent, 250 to 700,000 parts by mass of water is added to the silica-containing condensation product, Preparing a siloxane solution;
(3) using the polysiloxane solution as a paint component;
A method for preparing a coating composition having a surface tension of 50 dyn / cm (25 ° C.) or less . The preparation method according to claim 4, wherein the colloidal silica is used as a dispersion, and the pH of the solution is 6 or less.