JP2012062378A - Coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition having good adhesiveness to a metal and an organic coating film coated on the metal.SOLUTION: The coating composition comprises: an acrylic resin (A) having a hydroxyl group and a carboxyl group; a nonyellowing polyisocyanate compound (B); and an isocyanate group-containing thiourethane-modified alkoxysilane (C). The coating composition contains 0.8-4.0 pts.mass of isocyanate group-containing thiourethane-modified alkoxysilane (C) based on 100 pts.mass of the acrylic resin (A).

Description

  The present invention relates to a coating composition, and more particularly to a coating composition suitable for coating plastics and pre-coated metal.

Conventionally, by applying a synthetic resin coating composition such as an acrylic urethane resin composition to the surface of various industrial products such as ceramic materials, steel, building materials, etc., and forming a coating film, For example, weather resistance and corrosion resistance are improved.
In recent years, rain streak contamination of buildings has been regarded as a problem in the suburbs of cities due to the increase of suspended solids such as exhaust gas. In particular, a coating film excellent in weather resistance has a long period until repair and repainting and is exposed to the atmosphere for a long period of time, so that it is required to have excellent contamination resistance.

As means for solving this problem, a technique has been developed in which an alkoxysilane compound such as tetraalkoxysilane or a partially hydrolyzed condensate thereof is blended in the coating composition as a contamination reducing component (Patent Documents 1 to 3). Etc.).
However, although the coating film formed from these conventional coating compositions is good in terms of stain resistance, the adhesion to the metal surface and the organic coating surface such as polyester applied to the metal is low, There was a problem of easy peeling.

JP-A-7-331136 JP-A-11-106684 JP 2001-329227 A

  This invention is made | formed in view of such a situation, and it aims at providing the coating composition which has favorable adhesiveness with respect to the organic coating film apply | coated to the metal and the metal.

  As a result of intensive studies to achieve the above object, the present inventor has, as a main ingredient, an acrylic resin having a hydroxyl group and a carboxyl group, and contains a predetermined amount of an isocyanate group-containing thiourethane-modified alkoxysilane compound as its curing agent. It is found that the obtained coating composition gives a coating film having good adhesion to the metal to be coated and an organic coating film such as a polyester coating film applied to the metal. The present invention has been completed.

That is, the present invention
1. (A) an acrylic resin having a hydroxyl group and a carboxyl group, (B) a non-yellowing polyisocyanate compound, and (C) an isocyanate group-containing thiourethane-modified alkoxysilane, And (A) 0.8 to 4.0 parts by mass of the coating composition, wherein 100 parts by mass of the acrylic resin is contained,
2. The coating composition of 1, wherein the (C) isocyanate group-containing thiourethane-modified alkoxysilane is obtained by reacting a mercapto group-containing alkoxysilane compound with a polyisocyanate compound,
3. The (C) isocyanate group-containing thiourethane-modified alkoxysilane is obtained by reacting a polyisocyanate compound with a partial hydrolysis condensate of a mercapto group-containing alkoxysilane compound and another alkoxysilane compound. Paint composition,
4). 2 or 3 coating compositions, wherein the mercapto group-containing alkoxysilane compound is at least one selected from 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropyltriethoxysilane;
5. The coating composition of 3, wherein the other alkoxysilane compound is a tetraalkylsilicate,
6). The coating composition according to any one of 3 to 5, wherein the polyisocyanate compound has 3 or more isocyanate groups,
7). Furthermore, (D) the coating composition according to any one of 1 to 6, comprising a partially hydrolyzed condensate of an alkoxysilane compound,
8). (E) The coating composition according to any one of 1 to 7 containing an organic solvent,
9. Provided is a coating composition according to any one of 1 to 8, which is used for plastic or precoated metal.

Since the coating composition of the present invention uses an isocyanate group-containing thiourethane-modified alkoxysilane as one component of the curing agent, the adhesion to a substrate having poor adhesion with a conventional coating such as a metal siding surface. An excellent coating film can be provided.
Furthermore, a coating film having excellent stain resistance can also be provided by blending a partially hydrolyzed condensate of an alkoxysilane compound with the coating composition.

Hereinafter, the present invention will be described in more detail.
The coating composition according to the present invention includes (A) an acrylic resin having a hydroxyl group and a carboxyl group, (B) a non-yellowing polyisocyanate compound, and (C) an isocyanate group-containing thiourethane-modified alkoxysilane, and (C) an isocyanate. The group-containing thiourethane-modified alkoxysilane is contained in an amount of 0.8 to 4.0 parts by mass with respect to 100 parts by mass of (A) acrylic resin.

(A) Acrylic resin In the coating composition of this invention, what has a hydroxyl group and a carboxyl group is used as an acrylic resin which is a main ingredient.
The hydroxyl group and carboxyl group contents are not particularly limited, but considering that the adhesion of the resulting film to the substrate is further increased, the hydroxyl value is preferably 20 to 100 mgKOH / g, more preferably 30 to 70 mgKOH. / G is more preferable, and the carboxyl group is preferably 0.5 to 5 mgKOH / g, more preferably 1 to 4 mgKOH / g in terms of acid value.

Examples of the acrylic resin include those obtained by radical polymerization (copolymerization) of a hydroxyl group-containing acrylic monomer and a carboxyl group-containing acrylic monomer, or radical polymerization (homopolymerization) of a hydroxyl group and a carboxyl group-containing acrylic monomer. However, it is not limited to these.
Examples of the hydroxyl group-containing acrylic monomer include 2-hydroxyethyl (meth) acrylate (HEMA), 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4 -Hydroxybutyl (meth) acrylate, N-methylol acrylamide, ε-caprolactone-modified hydroxy (meth) acrylate, carbonate-modified methacrylate (manufactured by Daicel Chemical Industries, Ltd., HEMAC) and the like.
As the carboxyl group-containing acrylic monomer, for example, acrylic acid, methacrylic acid, or a terminal hydroxyl group of an acrylic monomer containing a hydroxyl group is reacted with an acid anhydride such as an aliphatic dicarboxylic acid such as succinic anhydride or glutaric anhydride. And the like.
These hydroxyl group-containing acrylic monomers and carboxyl group-containing acrylic monomers may be used alone, in combination of two or more, or in combination.

In the production of the acrylic resin of the present invention, other monomers copolymerizable with the above acrylic monomers having a hydroxyl group or a carboxyl group may be used.
Specific examples of other copolymerizable monomers include methyl (meth) acrylate, ethyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t -Butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isobornyl (meth) acrylate, lauryl (meth) acrylate, stearyl Alkyl group-containing (meth) acrylic monomers such as (meth) acrylate; Amide group-containing (meth) acrylic monomers such as (meth) acrylamide and ethyl (meth) acrylamide; Nitrile group-containing (meth) acrylic monomers such as acrylonitrile -Aromatic hydrocarbon vinyl monomers such as styrene, methylstyrene, chlorostyrene and vinyltoluene; α, β-ethylenically unsaturated carboxylic acids such as maleic acid, itaconic acid, crotonic acid, fumaric acid and citraconic acid; styrene Sulfonic acid-containing vinyl monomers such as sulfonic acid and vinyl sulfonic acid; Unsaturated bond-containing acid anhydrides such as maleic anhydride and itaconic anhydride; Chlorine-containing monomers such as vinyl chloride, vinylidene chloride and chloroprene; Hydroxyethyl vinyl ether and hydroxypropyl Hydroxyl-containing alkyl vinyl ethers such as vinyl ether and hydroxybutyl vinyl ether; alkylene glycol monoaryls such as ethylene glycol monoallyl ether, propylene glycol monoallyl ether and diethylene glycol monoallyl ether Ethers; α-olefins such as ethylene, propylene and isobutylene; vinyl acetates 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 Examples include allyl ethers such as allyl ether and butyl allyl ether, which may be used alone or in combination of two or more.
When a monomer having a hydroxyl group such as a hydroxyl group-containing alkyl vinyl ether is used, it can be copolymerized with a carboxyl group-containing acrylic monomer to obtain an acrylic resin having a hydroxyl group and a carboxyl group.

The above polymerization is carried out using a radical polymerization initiator in the presence of a suitable organic solvent.
Any organic solvent may be used as long as it does not adversely influence the reaction. For example, aliphatic or alicyclic hydrocarbons such as n-hexane, n-heptane, n-octane, cyclohexane and cyclopentane; toluene, Aromatic hydrocarbons such as xylene, ethylbenzene, low boiling aromatic naphtha, high boiling aromatic naphtha, etc .; ethyl acetate, n-butyl acetate, n-amyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol Monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether propionate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 3 Esters such as methoxybutyl acetate; methanol, ethanol, i-propanol, n-butanol, i-butanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, propylene glycol monomethyl ether, propylene glycol mono Alcohols such as n-propyl ether and diethylene glycol monobutyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl n-amyl ketone and cyclohexanone; dimethoxyethane, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol Dimethyl ether, diethylene glycol Ethers such as butyl ether; N- methylpyrrolidone, dimethylformamide, dimethylacetamide, ethylene carbonate, and the like. These may be used alone or in combination of two or more.

The radical polymerization initiator can be appropriately selected from known ones such as 2,2′-azobisisobutyronitrile, azobisisovaleronitrile, benzoyl peroxide, t-butyl peroxide, cumene hydro A peroxide etc. are mentioned. These may be used alone or in combination of two or more.
The reaction temperature is usually about 60 to 120 ° C. The reaction time is usually about 6 to 12 hours.

Although content of the acrylic resin in a composition is not specifically limited, 10-75 mass% is preferable as solid content in an acrylic resin solution, and 20-65 mass% is preferable.
The molecular weight of the acrylic resin used in the present invention is not particularly limited, but a number average molecular weight of 3,000 to 100,000 is preferable.
The number average molecular weight is a value measured by gel permeation chromatography (hereinafter abbreviated as GPC) by differential refractometer detection (polystyrene conversion value).

(B) Non-yellowing type polyisocyanate compound In the composition of this invention, a non-yellowing type polyisocyanate compound is used as one component of a hardening | curing agent from a viewpoint of improving the weather resistance etc. of the coating film obtained.
Non-yellowing isocyanates include tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), 2-methyl-pentane-1,5-diisocyanate, 3-methyl-pentane-1,5-diisocyanate, lysine diisocyanate, trioxyethylene diisocyanate, etc. Aliphatic diisocyanates such as: norbornane diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and allophanates, burettes thereof, Nurates and adducts (TMP adducts) of the above diisocyanates and trimethylolpropane And the like.

Each of the above polyisocyanate compounds may be used alone or in combination of two or more. However, in the present invention, it is preferable to use a trifunctional or higher polyisocyanate compound. It is preferable to use a polyisocyanate compound containing any of an allophanate body, a burette body, a nurate body, and a TMP adduct body.
Of these, HDI allophanate, burette, nurate and TMP adducts are preferred.

  The content of the non-yellowing polyisocyanate compound in the composition is not particularly limited, but is 5 to 20 parts by mass with respect to 100 parts by mass of (A) acrylic resin (the same applies hereinafter as the solid content). Preferably, 10-15 mass parts is more preferable.

  In addition, as long as it does not affect the weather resistance of the coating film, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane, if necessary, together with the non-yellowing polyisocyanate. Aromatic diisocyanates such as diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate; xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, tetramethylxylylene Aro-aliphatic diisocyanates such as range isocyanate, and allophanate, burette, nurate, and TMP adducts may be used in combination.

(C) Isocyanate group-containing thiourethane-modified alkoxysilane In the composition of the present invention, from the viewpoints of improving adhesion with the metal surface of the coating film obtained, reducing coloring, improving storage stability of the composition, etc. As a component of the agent, an isocyanate group-containing thiourethane-modified alkoxysilane is used.
The isocyanate group-containing thiourethane-modified alkoxysilane is not particularly limited, but in consideration of further improving the adhesion to the metal surface, etc., the polyisocyanate compound is reacted with the mercapto group-containing alkoxysilane compound. And a product obtained by reacting a polyisocyanate compound with a partially hydrolyzed condensate of a mercapto group-containing alkoxysilane compound and another alkoxysilane compound is preferred. The isocyanate group-containing thiourethane-modified alkoxysilane obtained in (1) is preferred.

  The mercapto group-containing alkoxysilane compound is not particularly limited, and examples thereof include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropyltriethoxysilane. It may be used alone or in combination of two or more.

Further, other alkoxysilane compounds that are partially hydrolyzed and condensed with this mercapto group-containing alkoxysilane compound are not particularly limited, and examples thereof include tetramethyl silicate (tetramethoxysilane), tetraethyl silicate (tetraethoxysilane), Tetra-n-propyl silicate (tetra n-propoxy silane), tetraisopropyl silicate (tetra i-propoxy silane), tetra-n-butyl silicate (tetra n-butoxy silane), tetraisobutyl silicate (tetra i-butoxy silane) ), Tetraalkyl silicates such as tetra-t-butyl silicate (tetra-t-butoxysilane); methyltrimethoxysilane, methyltriethoxysilane, octadecyltriethoxysilane, methyltri- alkyl trialkoxysilanes such as ec-octyloxysilane, methyltriisopropoxysilane, and methyltributoxysilane; aryltrialkoxysilanes such as phenyltrimethoxysilane and phenyltriethoxysilane; alkyltriaryloxysilanes such as methyltriphenoxysilane Glycidoxy trialkoxysilane such as 3-glycidoxypropyltrimethoxysilane and the like may be used, and these may be used alone or in combination of two or more.
Among these, considering that the adhesion of the obtained coating film to the metal surface and the like is further increased, tetraalkyl silicate is preferable, and tetraethyl silicate is particularly preferable.

As a method of partial hydrolysis, for example, a method of adding water to a mixture of a mercapto group-containing alkoxysilane compound and another alkoxysilane compound, causing partial hydrolysis and condensation is included.
In this case, the mixing ratio of the mercapto group-containing alkoxysilane compound and the other alkoxysilane compound is arbitrary, but is preferably 1/1 to 1/2 (molar ratio).
As these partial hydrolysis condensates, commercially available products may be used. For example, X41-1805 (Shin-Etsu Chemical Co., Ltd.), which is a partial hydrolysis condensate of 3-mercaptopropyltrimethoxysilane and tetraethyl silicate. Etc.) can be used.

  It does not specifically limit as a polyisocyanate compound made to react with the mercapto group containing alkoxysilane compound mentioned above, or the partial hydrolysis-condensation product of a mercapto group containing alkoxysilane compound and another alkoxysilane compound, The said (B) The aliphatic diisocyanate, alicyclic diisocyanate, aromatic diisocyanate, araliphatic diisocyanate, and their allophanate, burette, nurate, and TMP adducts, which are exemplified as the non-yellowing polyisocyanate compound, are used. In this case as well, in consideration of the weather resistance and the like of the resulting coating film, a non-yellowing polyisocyanate is preferable. , Nure DOO body, TMP adduct is more preferable, and isocyanurate of HDI is optimal.

  In the present invention, the content of the isocyanate group-containing thiourethane-modified alkoxysilane in the composition is 0.8 to 4.0 parts by mass with respect to 100 parts by mass of (A) acrylic resin. When the content is outside this range, the adhesion of the obtained coating film to the metal surface becomes insufficient.

(D) Partially hydrolyzed condensate of alkoxysilane compound In the composition of the present invention, a partially hydrolyzed condensate of alkoxysilane compound may be blended for the purpose of enhancing the stain resistance of the resulting coating film.
As the alkoxysilane compound, the same compounds as described in the above (C) can be used.
Commercially available products may be used as the partially hydrolyzed condensate of the alkoxysilane compound, for example, MKC silicate MS56S, MS56, MS51, manufactured by Mitsubishi Chemical Corporation, which is a partially hydrolyzed condensate of tetramethyl silicate. Colcoat ethyl silicate 40, ethyl silicate 48, methyl silicate 51, etc. can be used.
Although content of the partial hydrolysis-condensation product of the alkoxysilane compound in a composition is not specifically limited, 2-20 mass parts is preferable with respect to 100 mass parts of (A) acrylic resins, and 5-15 Part by mass is more preferable.

Furthermore, in the composition of the present invention, various additives such as a dehydrating agent, a matting agent, a pigment, an antioxidant, an ultraviolet absorber, a light stabilizer, a curing catalyst, etc. You may mix | blend 0.1-30 mass% in a composition.
Examples of the dehydrating agent include 2,2-dimethoxypropane, methyl orthoformate, ethyl orthoformate, methyl orthoacetate, and ethyl orthoacetate.
Examples of the matting agent include polyethylene wax.
Examples of the curing catalyst include organometallic compounds such as tin 2-ethylhexanoate, tin n-octylate, dibutyltin dilaurate, dibutyltin maleate, iron naphthenate, and lead octylate.

The composition of the present invention can be prepared by properly orienting the above components in any order, and an organic solvent may be used for the preparation.
Examples of the organic solvent include aromatic hydrocarbon solvents such as toluene and xylene; ester solvents such as ethyl acetate, n-butyl acetate and n-amyl acetate; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; cyclohexane, methylcyclohexane, Aliphatic hydrocarbon solvents such as ethylcyclohexane; Petroleum hydrocarbon solvents such as mineral spirits; Ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether Propionate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, glyco Ether ester solvent, and the like. These solvents may be used alone or in combination of two or more.
Although there is no restriction | limiting in particular in the usage-amount of a solvent, The quantity from which the total solid content in a composition will be about 10-70 mass% is preferable.
In addition, as an organic solvent, the residual solvent at the time of the acrylic resin manufacture mentioned above can also be used as it is.

Examples of the method of using the coating composition described above include a method in which the composition of the present invention is directly applied to the surface of a substrate and dried.
In this case, the coating method of the composition of the present invention is not particularly limited, and may be appropriately selected from known methods such as brush coating and roller coating. Moreover, what is necessary is just to make an application quantity, the thickness of a coating film, drying time, etc. suitable according to the material of a base material, the use of a coated article, etc.

The substrate to which the composition of the present invention is applied is arbitrary, but in particular, the conventional paint exhibits good adhesion even to a substrate made of a material having poor adhesion.
Examples of such a base material include a metal base material and a plastic base material.
As the metal substrate, cold rolled steel sheet, galvanized steel sheet, alloyed galvanized steel sheet, tin plated steel sheet, chrome plated steel sheet, aluminum plated steel sheet, lead plated steel sheet, nickel plated steel sheet, aluminum plate, magnesium alloy plate, titanium plate, Examples include stainless steel plates.
Examples of the plastic substrate include ABS resin, polycarbonate, acrylic resin, polystyrene, MS resin, polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, and triacetyl cellulose.

Hereinafter, although a synthesis example, an Example, and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the following Example. In addition, each physical property in an Example was measured with the following method. In the following, “part” means “part by mass”.
(1) Molecular weight device: High-speed GPC device manufactured by Tosoh Corporation HLC-8120GPC
Column: Two TSK-GEL SUPER H2000 connected column manufactured by Tosoh Corporation Column temperature: 40 ° C
Detector: Differential refractometer Eluent: THF
Column flow rate: 0.6 ml / min
(2) Viscosity equipment: Shibaura System Co., Ltd. Bismetron VG-A

[Synthesis Example 1] Synthesis of acrylic resin In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet tube and dropping funnel, 2044 parts of toluene, 108 parts of xylene, 118.7 hydroxyl group-containing monomer (HEMA) Parts, methyl methacrylate (MMA) 782 parts, styrene 216 parts, n-butyl acrylate (n-BA) 311.3 parts, acrylic acid 4.3 parts, and reaction initiator (Perbutyl-O, manufactured by NOF Corporation) ) 7 parts were charged, the inside was replaced with nitrogen gas, and the mixture was heated to 95 ° C. In this, 363 parts of toluene, 182 parts of xylene, 203 parts of HEMA, 1332 parts of MMA, 365 parts of styrene, 527 parts of n-BA, 7.2 parts of acrylic acid, and a reaction initiator (Perbutyl-O, manufactured by NOF Corporation) While maintaining the reaction temperature at 110 ° C., 29 parts of the mixture was added dropwise over 4 hours to carry out the reaction. After completion of the dropping, 7 parts of a reaction initiator (perbutyl-O) and 468 parts of n-butyl acetate were further added dropwise over 2 hours, and the aging reaction was continued for 3 hours to obtain a solid content of 54% by mass and a viscosity of 8200 mP · s / 25. An acrylic resin solution having a hydroxyl value of 20.9 mgKOH / g, an acid value of 1.7 mgKOH / g, and a molecular weight (Mn) of 20580 was obtained.

[Synthesis Example 2] Production of isocyanate group-containing thiourethane-modified alkoxysilane A A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube was charged with 3-mercaptopropyltrimethoxysilane and tetraethyl silicate. 91 parts hydrolyzed condensate (X41-1805, manufactured by Shin-Etsu Chemical Co., Ltd.), 585 parts of HDI nurate (Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd.), 451 parts of xylene, and dibutyltin dilaurate (DBTDL) 0.10 parts of catalyst was added, the inside was replaced with nitrogen gas, and the reaction was performed at 80 ° C. for 6 hours to obtain an isocyanate group-containing thiourethane-modified alkoxysilane A having a solid content of 60% by mass and an NCO content of 10.6% by mass. It was.

[Synthesis Example 3] Production of isocyanate group-containing thiourethane-modified alkoxysilane B Part of 3-mercaptopropyltrimethoxysilane and tetraethylsilicate in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube Hydrolysis condensate (X41-1805, manufactured by Shin-Etsu Chemical Co., Ltd.) 91 parts, HDI burette body (Takenate D-165N, manufactured by Mitsui Chemicals Polyurethanes Co., Ltd.) 533 parts, xylene 505 parts, and DBTDL catalyst 0 0.09 part was added, the inside was replaced with nitrogen gas, and the reaction was performed at 80 ° C. for 6 hours to obtain an isocyanate group-containing thiourethane-modified alkoxysilane B having a solid content of 56 mass% and an NCO content of 10.6 mass%.

[Synthesis Example 4] Production of isocyanate group-containing thiourethane-modified alkoxysilane C In a reaction vessel equipped with a stirrer, thermometer, reflux condenser and nitrogen gas inlet tube, 62 parts of 3-mercaptopropyltrimethoxysilane and NDIrate of HDI 692 parts (Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd.), 503 parts of xylene, and 0.19 part of DBTDL catalyst were added, the inside was replaced with nitrogen gas, the reaction was carried out at 80 ° C. for 6 hours, and the solid content was 60 An isocyanate group-containing thiourethane-modified alkoxysilane C having a mass% and an NCO content of 10.6% by mass was obtained.

<Preparation of coating composition>
[Example 1]
100.0 parts by mass of acrylic resin obtained in Synthesis Example 1 (as solid content), 13.2 parts by mass of HDI nurate (Coronate-HX, manufactured by Nippon Polyurethane Industry Co., Ltd.) Stirring and stirring 9.7 parts by mass of isocyanate group-containing thiourethane-modified alkoxysilane A 0.8 part by mass (as solid content) and alkoxysilane compound partially hydrolyzed condensate (MKC-silicate MS56S, manufactured by Mitsubishi Chemical Corporation) The mixture was mixed to prepare a coating composition.

[Examples 2-6, Comparative Examples 1-4]
A coating composition was prepared in the same manner as in Example 1 except that the composition was changed to the composition shown in Table 1.

With respect to the coating compositions prepared in the above Examples and Comparative Examples, the adhesion to each substrate and the rain streak-like contamination were measured and evaluated by the following methods. The results are shown in Table 2.
(1) Adhesiveness (1-1) Preparation of coating film The coating compositions prepared in the above Examples and Comparative Examples were applied to the surface of each substrate. After coating with a 12 bar coater, it was dried at 200 ° C. for 40 seconds to form a coating film.
(1-2) Standard Adhesion Test After the coating film is cured and formed on each substrate by the above method, the surface of the coating film is 5 × 5 based on the cross-cut test of JIS K 5600-5-6 (2007 edition). A cell was prepared on the cell, cellophane tape (CT-24 manufactured by Nichiban Co., Ltd.) was applied, and the tensile peeling state was confirmed upward. The squares that were not peeled off were recorded, and the evaluation criteria were as follows based on JIS.
○: Classification 0-2
Δ: Classification 3-4
×: Classification 5
(2) Rain streak contamination test After spray-coating each paint prepared in the above Examples and Comparative Examples on a 300 × 10 × 1 mm aluminum plate to a dry film thickness of 50 μm and drying and curing in a standard state for 3 days The inner angle was bent to 150 ° at a length of one third from above. The prepared specimens were placed outdoors in Kuki City, Saitama Prefecture, with the narrow area facing up to the south and the large area facing up. The rain streak after 3 months was evaluated according to the following criteria.
○: Rain stains are scarcely observed △: Rain stains are slightly observed ×: Rain stains are clearly recognized

As shown in Table 2, it can be seen that the coating formed from the coating composition prepared in each example is excellent in adhesion to various substrates.
On the other hand, since the coating composition prepared in Comparative Example 1 does not use the isocyanate group-containing thiourethane-modified alkoxysilane as one component of the curing agent, the obtained coating film has poor adhesion to the metal substrate. I understand that.
In addition, the coating film obtained from the coating composition prepared in Comparative Example 3 using a partially hydrolyzed condensate of mercapto group-containing alkoxysilane instead of the isocyanate group-containing thiourethane-modified alkoxysilane also has adhesion to the metal substrate. It turns out that it is inferior.
Furthermore, the coating film obtained from the coating composition prepared in Comparative Examples 2 and 4 in which the content of the isocyanate group-containing thiourethane-modified alkoxysilane is outside the range of 0.8 to 4.0 parts by mass with respect to the acrylic resin It can also be seen that the adhesion to the metal substrate is insufficient.
In addition, since the coating composition prepared in Example 6 does not contain a partially hydrolyzed condensate of alkoxysilane, the resulting coating film has insufficient stain resistance, but as in Example 2. It can be seen that sufficient contamination resistance is exhibited by adding a partially hydrolyzed condensate of alkoxysilane.

Claims (9)

(A) an acrylic resin having a hydroxyl group and a carboxyl group, (B) a non-yellowing polyisocyanate compound, and (C) an isocyanate group-containing thiourethane-modified alkoxysilane,
The coating composition, wherein the (C) isocyanate group-containing thiourethane-modified alkoxysilane is contained in an amount of 0.8 to 4.0 parts by mass with respect to 100 parts by mass of the (A) acrylic resin.   The coating composition according to claim 1, wherein (C) the isocyanate group-containing thiourethane-modified alkoxysilane is obtained by reacting a mercapto group-containing alkoxysilane compound with a polyisocyanate compound.   The (C) isocyanate group-containing thiourethane-modified alkoxysilane is obtained by reacting a polyisocyanate compound with a partial hydrolysis condensate of a mercapto group-containing alkoxysilane compound and another alkoxysilane compound. The coating composition according to 1.   The coating composition according to claim 2 or 3, wherein the mercapto group-containing alkoxysilane compound is at least one selected from 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropyltriethoxysilane. object.   4. The coating composition according to claim 3, wherein the other alkoxysilane compound is a tetraalkyl silicate.   The coating composition according to any one of claims 3 to 5, wherein the polyisocyanate compound has three or more isocyanate groups.   (D) The coating composition of any one of Claims 1-6 containing the partial hydrolysis-condensation product of an alkoxysilane compound.   (E) The coating composition of any one of Claims 1-7 containing an organic solvent.   The coating composition according to any one of claims 1 to 8, which is for plastics or precoated metal.