JP2007314634A - Coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating composition capable of forming a coating film having excellent anticorrosion property, initial drying property, sagging resistance, hot-water resistance, weather resistance, staining resistance, cracking resistance, etc. <P>SOLUTION: The coating composition is produced by compounding (I) 30-58 pts.mass of a partially hydrolyzed condensation liquid of an organosilane expressed by formula (1); R<SP>1</SP><SB>n</SB>Si(OR<SP>2</SP>)<SB>4-n</SB>(R<SP>1</SP>is a 1-8C organic group; R<SP>2</SP>is a 1-5C alkyl group; and n is 1 or 2), (II) 3-9 pts.mass of an organosilane condensation solid of an organosilane soluble in the partially hydrolyzed condensation liquid (I) and expressed by formula (1); R<SP>1</SP><SB>n</SB>Si(OR<SP>2</SP>)<SB>4-n</SB>(R<SP>1</SP>is a 1-8C organic group; R<SP>2</SP>is a 1-5C alkyl group; and n is 1 or 2), (III) 3-10 pts.mass of a phenoxy resin and (IV) 30-57 pts.mass of a compound having at least one epoxy group in the molecule. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a coating composition, and more particularly to a coating composition comprising an organopolysiloxane-based composition.

  In recent years, organopolysiloxane-based paints using organosilane and / or its partially hydrolyzed condensate as a binder form a coating film excellent in weather resistance and stain resistance, but are suitable for performance related to corrosion resistance. Absent. On the other hand, the phenoxy resin has excellent performance in anticorrosion, but its performance in terms of weather resistance is not sufficient, so that it is difficult to use it in the top coating field.

  In addition, organopolysiloxane-based inorganic coating films generally have high hardness and are prone to cracking, and in order to improve this, coatings using organic-inorganic composite resins as binders have also been developed. However, many organic solvents are blended, and the weather resistance and stain resistance of the resulting coating film are inferior to those of the organopolysiloxane inorganic coating. Thus, for example, in Patent Document 1, a paint that does not contain an organic solvent has been developed. However, since the paint contains an organometallic compound, there are concerns about air pollution and adverse effects on the human body. Further, since it does not contain a solid organosilane partial hydrolysis condensate, the initial drying property of the coating film is inferior, and the vertical surface coating has a drawback that it is easy to sag.

In addition, a paint using a water-based organic-inorganic composite resin as disclosed in Patent Document 2 has been developed. However, a water-based paint has a drawback of slow drying and curing speed, and is premised on outdoor coating. The current situation is not suitable for this.
Japanese Patent Publication No. 7-72250 JP 2000-110272 A

  The present invention has been made against the background of such problems of the prior art. By using a specific liquid organopolysiloxane inorganic resin, a specific solid organopolysiloxane inorganic resin, and a phenoxy resin, anticorrosion is achieved. It is intended to provide a coating composition that can be cured at room temperature, and can form a coating film excellent in initial drying property, drooping property, hot water resistance, weather resistance, stain resistance, crack resistance, etc. Objective.

As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved with the following configuration, and have reached the present invention. That is, the present invention includes the following component (I) Formula (1), R ¹ _n Si (OR ² ) _4-n [wherein R ¹ is an organic group having 1 to 8 carbon atoms, and R ² is , An alkyl group having 1 to 5 carbon atoms, and n is 1 or 2. A liquid partial hydrolysis condensate of organosilane represented by the formula: 30 to 58 parts by mass;
(II) Soluble in the above-mentioned (I) liquid partial hydrolysis-condensation product, and the formula (1), R ¹ _n Si (OR ² ) _4-n [wherein R ¹ has 1 to 8 carbon atoms. It is an organic group, R ² is an alkyl group having 1 to 5 carbon atoms, and n is 1 or 2. A solid organosilane condensate of 3 to 9 parts by mass of
(III) 3 to 10 parts by mass of a phenoxy resin,
(IV) A coating composition containing 30 to 57 parts by mass of a compound having at least one epoxy group in the molecule.

  According to the present invention, it is possible to provide a coating composition that is excellent in anticorrosion properties and can form a coating film excellent in initial drying property, sagging property, hot water resistance, weather resistance, stain resistance, crack resistance, and the like. became.

  Hereinafter, the present invention will be described in detail.

  Each component of the coating composition of the present invention will be described.

[About component (I)]
Component (I) has the formula _{^{(1), R 1 n Si}} (OR 2) 4-n wherein, ^{R 1} is an organic group having 1 to 8 carbon atoms, ^{R 2} is C1-5 N is 1 or 2. ] The liquid partial hydrolysis-condensation product of the organosilane shown by this. In the above formula, examples of the organic group as R ¹ include an alkyl group, a cycloalkyl group, an aryl group, and a vinyl group. Here, the alkyl group may be linear or branched. Examples of such an alkyl group include a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, pentyl group, Examples thereof include alkyl groups such as hexyl group, heptyl group, octyl group and the like. Preferred alkyl groups are those 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. Each of the functional groups may optionally have a substituent. Examples of such a substituent include a halogen atom (for example, a chlorine atom, a bromine atom, and a fluorine atom), a (meth) acryloyl group, a mercapto group, and an alicyclic group. The alkyl group as R ² may be linear or branched. Examples of such an alkyl group include a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, and pentyl group. And preferred alkyl groups are those having 1 to 2 carbon atoms.

  Specific examples of the organosilane represented by the above formula (1) include, for example, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, and n-propyltrimethoxysilane. Ethoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3,3,3-tri Fluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, cyclohexyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercap Topropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane Methylphenyldimethoxysilane, dimethyldipropoxysilane, and the like are preferable, and methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, and dimethyldimethoxysilane are preferable.

  Component (I) is one of these organosilanes alone or two or more partially hydrolyzed condensates. The condensate has a polystyrene-reduced weight average molecular weight of, for example, 300 to 5000, preferably 500 to 4200. By using such a condensate, a coating film having good storage stability and good adhesion can be obtained. (I) As a manufacturing method of a component, the organosilane shown by Formula (1) is hydrolyzed and condensed in presence of water and a catalyst. The amount of water is suitably such that 30 to 90%, preferably 50 to 80% of the hydrolyzable groups initially present in the organosilane can undergo hydrolysis and condensation reactions.

  Examples of the catalyst include inorganic acids such as nitric acid and hydrochloric acid, and organic acids such as acetic acid, formic acid and propionic acid. The amount of the catalyst added is suitably such that the pH of the organosilane solution to which water has been added is, for example, 3-6. The hydrolysis condensation reaction can be carried out, for example, in the presence of water and a catalyst at a temperature of 40 to 80 ° C., preferably 45 to 70 ° C. with stirring for 2 to 10 hours. It is not limited. Next, the alcohol component generated by the reaction is removed by means such as heating and / or decompression to produce the component (I). In addition, (I) component is the organosilane and / or its partial hydrolysis-condensation product (I-1) whose n value is 1 in the above formula (1), and the organosilane and / or its n value is 2. A partial hydrolysis condensate obtained from a mixture having a mass ratio with the partial hydrolysis condensate (I-2) of 50:50 to 100: 0, preferably 60:40 to 95: 5 is stable during the reaction. It is desirable because a coating film with good crack resistance can be obtained.

  (I) A component contains 30-58 mass parts in a coating composition. When the amount is less than 30 parts by mass, the weather resistance is inferior. On the other hand, when the amount is more than 58 parts by mass, the alkali resistance is inferior.

  Specific examples of such condensates include commercially available SR2402 manufactured by Toray Dow Corning, DC3037, DC3074; KR-211, manufactured by Shin-Etsu Chemical Co., Ltd., KR-212, KR-213, KR-214. , KR-216, KR-218; TSR-145, TSR-160, TSR-165, YR-3187, etc. manufactured by Toshiba Silicone Corporation.

[About component (II)]
The component (II) can be dissolved in the liquid partial hydrolysis-condensation product of the organosilane of the component (I), the formula (1), R ¹ _n Si (OR ² ) _4-n [wherein R ¹ is an organic group having 1 to 8 carbon atoms, ^{R 2} is an alkyl group having 1 to 5 carbon atoms, n is 1 or 2. ] The solid hydrolysis condensate of organosilane shown by this.

  The component (II) is one kind of organosilane represented by the formula (1), or two or more kinds of hydrolysis condensates. The condensate has a polystyrene-reduced weight average molecular weight of, for example, 500 to 5000, preferably 800 to 4500. By using such a condensate, the drying property of the coating film becomes faster and the viscosity of the coating can be increased, so that sagging during coating is less likely to occur. As a method for producing the component (II), the organosilane represented by the formula (1) is hydrolyzed and condensed in the presence of water and a catalyst. The amount of water is suitably such that 100% of the hydrolyzable groups initially present in the organosilane can undergo hydrolysis and condensation reactions. Thus, hydrolyzable condensate of organosilane having a functional group of Si-OH can be obtained by using completely hydrolyzable water, and a condensate that is solid at room temperature can be usually obtained. .

  Examples of the catalyst include inorganic acids such as nitric acid and hydrochloric acid, and organic acids such as acetic acid, formic acid and propionic acid. The amount of the catalyst added is suitably such that the pH of the organosilane solution to which water has been added is, for example, 1 to 4. The hydrolysis condensation reaction can be carried out, for example, in the presence of water and a catalyst at a temperature of 40 to 80 ° C., preferably 45 to 70 ° C. with stirring for 2 to 10 hours. The method is not limited. Next, the reaction catalyst, excess water and the alcohol component generated by the reaction are removed by means such as heating and / or decompression to produce component (II). In addition, (II) component is the organosilane and / or its partial hydrolysis-condensation product (I-1) whose n value is 1 in the above formula (1), and the organosilane and / or its n value is 2. A partial hydrolysis condensate obtained from a mixture having a mass ratio with the partial hydrolysis condensate (I-2) of 40:60 to 100: 0, preferably 50:50 to 95: 5 is stable during the reaction. It is desirable because a coating film with good crack resistance can be obtained.

  (II) A component contains 3-9 mass parts in a coating composition. When the amount is less than 3 parts by mass, the sagging property is inferior. On the other hand, when the amount is more than 9 parts by mass, the coating stability is inferior.

  Specific examples of such condensates include commercially available products such as FR217, FR220, FR233, FR249, SH6018 manufactured by Toray Dow Corning.

[About component (III)]
The (III) component phenoxy resin is used to improve the anticorrosive properties of the coating film, and is mixed with the above (I) and (II) components after dissolving in the above (I) component and, if necessary, an organic solvent. It is to be blended.

  (III) A component contains 3-10 mass parts in a coating composition. If the amount of the component (III) is more than the above range, the viscosity of the coating is increased, which is not preferable. Moreover, when there are too few (III) components than the said range, since corrosion resistance worsens, it is unpreferable.

  Specifically, the component (III) includes PKHB, PKHC, PKHH, PKHJ, PKCP-67, PKCP-80, PKHM-30, PKHM-301 (manufactured by InChem), YP-50, YP-55, YP- 70 (manufactured by Toto Kasei) and the like.

[(IV) Component]
The component (IV) is a compound having at least one epoxy group in the molecule, and is added to improve the water resistance of the coating film and the adhesion to the substrate.

  The component (IV) contains 30 to 57 parts by mass in the coating composition. In addition, when there are too many (IV) components than the said range, since the weather resistance of a coating film will worsen, it is unpreferable. Moreover, when there are too few (IV) components than the said range, since the corrosion resistance of a coating film will worsen, it is unpreferable.

  Specifically, the component (IV) includes γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, and γ-glycidoxypropylmethyldimethoxysilane. Ethoxysilane, γ-glycidoxypropyltriisopropenyloxysilane, γ-glycidoxypropyltriiminooxysilane, β- (3,4-epoxycyclohexyl) ethylmethyldimethoxysilane, γ-isocyanatopropyltriisopropenyl Epoxy group-containing alkoxysilanes such as adducts of oxysilane and glycidol, alkyl glycidyl ethers such as butyl glycidyl ether, polyoxyethylene glycidyl ether, Cardura E (trade name, manufactured by Shell), butylphenyl glycidyl ether, and the like Typical examples include stealth, cycloepoxy compounds, Epicoats 815, 828, and 834 (trade names made by Yuka Shell Epoxy), hydrogenated epoxy resins YX-8000, YX-8034 (trade names made by Yuka Shell Epoxy), and the like. It is mentioned as a thing.

[About component (V)]
The liquid thermoplastic organic polymer compound (V) is blended as necessary to impart adhesion and flexibility of the coating film and to improve crack resistance.

  The component (V) is a thermoplastic organic polymer compound that is liquid at room temperature, and is preferably compatible with the components (I) and (II). Examples of such thermoplastic organic polymer compounds include acrylic resins and polyester resins. In order to become liquid at room temperature, the weight average molecular weight of these resins is usually 1000 to 30000, preferably about 1500 to 15000, for example.

  (V) The usual compounding quantity of a component is 3-50 mass parts with respect to 100 mass parts of above-mentioned (I) and (II) components, Preferably, 10-30 mass parts is suitable. In addition, when there are too many (V) components than the said range, since the weather resistance of a coating film and corrosion resistance will worsen, it is unpreferable. Moreover, when there are too few (V) components than the said range, since the adhesiveness of a coating film and flexibility worsen, it is unpreferable.

[(VI) component]
Component (VI) is an organosilicon compound having an amino group and a hydrolyzable group directly bonded to a silicon atom in the molecule as a curing agent, and improves the initial drying property of the paint. As the hydrolyzable group, an alkoxysilane capable of hydrolytic condensation reaction is particularly suitable.

Specifically, the component (VI) is represented by the formula (2), (R ⁵ —NH—R ⁴ —) _n (R ⁶ ) _m Si (OR ³ ) _4-nm (where R ³ and R ⁶ is an alkyl group having 1 to 5 carbon atoms, R ⁴ is an alkylene group having 1 to 5 carbon atoms, R ⁵ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or 5 to 8 carbon atoms. An cycloalkyl group, an aryl group having 6 to 8 carbon atoms, or a substituted or unsubstituted amino group, n is 1 or 2, and m is 0 or 1. Containing alkoxysilanes can be used. The alkyl group as R ³ and R ⁶ may be linear or branched. Examples of the alkyl group as R ³ and R ⁶ include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, and t-butyl group. And alkyl groups such as a pentyl group are preferred. Preferred alkyl groups are those having 1 to 2 carbon atoms, for example. The alkylene group as R ⁴ may be linear or branched. Examples of such an alkylene group include a methylene group, an ethylene group, and a propylene group. Alkyl group of 1 to 5 carbon atoms as R ⁵ are the same as in the case of the ^{R 3} and ^{R 6.} Examples of the cycloalkyl group as R ⁵ include a cyclohexyl group and a cycloheptyl group. The aryl group as R ^5, for example, phenyl group. Further, examples of the amino group as R ^5, one or both of the hydrogen atoms in the amino group, for example, those substituted with alkyl groups of 1 to 5 carbon atoms may be mentioned as preferred.

  Examples of the amino group-containing alkoxysilane represented by the above formula (2) include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N- (β-aminoethyl) -γ-aminopropyltrimethoxy. Silane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldiethoxysilane, N-cyclohexyl-γ-aminopropyltrimethoxysilane N-cyclohexyl-γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) -aminopropyltrimethoxysilane, γ- (2-aminoethyl) -aminopropylmethyldimethoxysilane, γ-anilinopropyltrimethoxy A typical example is silane. (VI) The compounding quantity of a component is 0.3-10 mass% in a coating composition, Preferably, 0.5-5 mass% is suitable.

  The coating composition of the present invention comprises the component (I), the component (II), the component (III), the component (IV), and the component (V) and component (VI) blended as necessary. Furthermore, it is composed of a mixture of various additives such as a solvent, a filler, a curing accelerator, a dye, an ultraviolet absorber, a light stabilizer, a thickener, and a pigment dispersant as required.

  Examples of the solvent include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol, and monobutyl ether, as well as terpenes, low-boiling naphtha, toluene, xylene, dioxane, acetone, methyl ethyl ketone, ethyl acetate, and butyl acetate. The amount to be used is adjusted in accordance with the purpose of use.

  As the filler, for example, various extender pigments for paints such as talc, barium carbonate, calcium carbonate, barium carbonate, bentonite, titanium oxide, carbon black, bengara, 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.

  Typical examples of the curing accelerator include amine compounds such as ethylenediamine, diethylenetriamine, piperidine, phenylenediamine, and triethylamine, and tin compounds.

  The coating composition of the present invention can form a cured coating film by coating the surface of an object to be coated with a brush, spray, roll, dipping or other coating means, and baking at room temperature or a temperature of 300 ° C. or lower. Is possible. In addition, as a to-be-coated object, it can be used for various to-be-coated objects, such as an inorganic ceramic base material, various metal substrates, such as iron, 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.

<Synthesis of component (I)>
(Synthesis Example 1)
In a reactor equipped with a reflux condenser and a stirrer, 75 parts of methyltrimethoxysilane and 25 parts of dimethyldimethoxysilane were added and mixed. 05 parts were added and a partial hydrolysis-condensation reaction was carried out at 70 ° C. for 5 hours. After completion of the reaction, the solvent was removed under reduced pressure [133 × 10 ² Pa (100 Torr)] to obtain a liquid organopolysiloxane (A) having a weight average molecular weight of 2500 and a viscosity of 2.0 Ps / 20 ° C.

<Synthesis of component (II)>
(Synthesis Example 2)
To a reactor equipped with a reflux condenser and a stirrer, 20 parts of dimethyldimethoxysilane and 80 parts of phenyltrimethoxysilane were added and mixed, and then 20 parts of ion-exchanged water and 0.5 part of 1N hydrochloric acid were added, A partial hydrolysis condensation reaction was carried out at 55 ° C. for 7 hours. After completion of the reaction, the solvent was removed under reduced pressure [133 × 10 ² Pa (100 Torr)] to obtain a solid organopolysiloxane (B) having a weight average molecular weight of 3000.

(Examples 1-4 and Comparative Examples 1-2)
Each component was mixed in the ratio shown in the following Table 1, and heated and stirred at 60 ° C. for 3 hours to prepare a uniformly dissolved organopolysiloxane solution, and each paint was prepared.

  The obtained coating compositions of Examples 1 to 4 and Comparative Examples 1 and 2 were tested for storage stability and initial drying property by the following methods, and the results are shown in Table 1, respectively.

  In addition, a coated plate was prepared as shown below, and coating film appearance, corrosion resistance, hot water resistance, stain resistance, alkali resistance, weather resistance, and crack resistance were tested, and the results are shown in Table 1. Indicated.

<Storage stability test>
Each coating composition prepared as described above was stored at 50 ° C. for one month, and then the viscosity change and appearance of the coating composition were visually examined.

<Evaluation criteria>
○ ・ ・ ・ No change △ ・ ・ ・ Thickening × ・ ・ ・ Gelification, generation of precipitate

<Initial drying>
Each coating composition was applied to a glass plate with a 6 mil applicator and dried at room temperature, and the touch drying time and semi-curing time were determined according to the JIS K5400 drying time test method.

<Film performance test>
The coating composition shown in Table 1 was spray-coated on a steel plate degreased with xylene so as to have a dry film thickness of about 80 μm, dried at 20 ° C. for 10 days, and used as a test plate. Each test was done about the obtained coating film. The test method and evaluation criteria were as follows.

<Appearance of coating film>
The appearance of the coating film formed on the coated plate was visually judged.

<Evaluation criteria>
○ ・ ・ ・ No cracks in the coating film △ ・ ・ ・ Minor cracking or turbidity or irregularity × ・ ・ ・ Significant cracking, turbidity or irregularity

<Anti-corrosion>
After performing a salt spray test for 150 hours in accordance with JIS K5400.99.1, the coating state was visually determined.

<Evaluation criteria>
◎ ・ ・ ・ No change ○ ・ ・ ・ Slight reduction in gloss △ ・ ・ ・ Slight change in gloss, whitening, etc. × ・ ・ ・ Large change in gloss, whitening, etc.

<Heat resistant water>
The coated plate was immersed in hot water at 80 ° C. for 3 hours, and the appearance of the coating film was visually determined.

<Evaluation criteria>
○ ・ ・ ・ No change △ ・ ・ ・ Slight changes such as gloss reduction and whitening × ・ ・ ・ Large changes such as gloss reduction and whitening

<Contamination resistance>
24 hours after the red and black magic inks were applied to the surface of the coating film, it was wiped off with a cloth wetted with n-butanol, and visually judged.

<Evaluation criteria>
◎ ・ ・ ・ Repels magic ink ○ ・ ・ ・ Complete removal △ ・ ・ ・ Slightly contaminated × ・ ・ ・ Contaminated

<Alkali resistance>
Each coated plate was immersed in a saturated slaked lime alkali aqueous solution at 40 ° C. for 10 days, and then the surface of the coating film was visually evaluated.

<Evaluation criteria>
○ ・ ・ ・ No change △ ・ ・ ・ Slightly cloudy coating surface × ・ ・ ・ Remarkably cloudy coating surface

<Weather resistance>
Sunshine Weather-Ohmeter 3000 hours <Evaluation criteria>
○ ... No change in coating film appearance, gloss retention of 95% or more △ ... There is a slight change in coating film appearance, gloss retention of 80-94%
× ・ ・ ・ Appearance change is remarkable, gloss retention is less than 80%

<Crack resistance>
Measured according to ASTM-C666A method (80 cycles)
<Evaluation criteria>
◎ ・ ・ ・ No cracks in coating film ○ ・ ・ ・ Generation of very slight cracks △ ・ ・ ・ Crack generation or partial peeling of coating film × ・ ・ ・ Significant crack generation, coating film peeling

Note 1) Liquid organopolysiloxane (trade name, manufactured by Toray Dow Corning)
Note 2) Solid organopolysiloxane (trade name, manufactured by Dow Corning Toray)
Note 3) Phenoxy resin (trade name, manufactured by InChem)
Note 4) Phenoxy resin (trade name, manufactured by Tohto Kasei Co., Ltd.)
Note 5) Hydrogenated epoxy resin (trade name made by Yuka Shell Epoxy)
Note 6) Acrylic resin (trade name, manufactured by Mitsubishi Rayon Co., Ltd.) * Liquid thermoplastic resin

  As is clear from Table 1, Examples 1 to 4, which are the coating compositions of the present invention, were excellent in corrosion resistance and weather resistance, stain resistance and crack resistance. In Comparative Example 1 having a small amount of component (IV), the corrosion resistance, hot water resistance and alkali resistance were inferior. Further, in Comparative Example 2 in which the amount of (III) phenoxy resin was large, the hot water resistance, stain resistance, and weather resistance were inferior.

  As described above, the coating composition of the present invention can form a coating film excellent in corrosion resistance, hot water resistance, weather resistance, stain resistance, crack resistance and the like.

Claims (3)

(I) Formula (1), R ¹ _n Si (OR ² ) _4-n [wherein R ¹ is an organic group having 1 to 8 carbon atoms, and R ² is an alkyl group having 1 to 5 carbon atoms. And n is 1 or 2. A liquid partial hydrolysis condensate of organosilane represented by the formula: 30 to 58 parts by mass;
(II) Soluble in the above-mentioned (I) liquid partial hydrolysis-condensation product and the formula (1), R ¹ _n Si (OR ² ) _4-n [wherein R ¹ has 1 to 8 carbon atoms. It is an organic group, R ² is an alkyl group having 1 to 5 carbon atoms, and n is 1 or 2. A solid organosilane condensate of 3 to 9 parts by mass,
(III) 3 to 10 parts by mass of a phenoxy resin,
(IV) A coating composition comprising 30 to 57 parts by mass of a compound having at least one epoxy group in the molecule.   The paint composition according to claim 1, further comprising (V) a liquid thermoplastic organic polymer compound in addition to the components (I), (II), (III), and (IV). object. The organosilicon compound having (VI) an amino group and a hydrolyzable group directly bonded to a silicon atom as a curing agent is used in an amount of 0.3 to 10% by mass in the coating composition. Or the coating composition of 2.