JP3144872B2 - Curable composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to curable compositions.
More specifically, the present invention relates to a curable composition useful as an overcoat used in, for example, architectural exteriors, automobiles, industrial machines, steel furniture, household appliances, plastics, and the like.

[0002]

2. Description of the Related Art As conventional thermosetting paints, there are known alkyd melamine resin paints, acrylic melamine resin paints, epoxy melamine resin paints and the like. In these, melamine was used as a crosslinking agent, and the odor problem was left unsolved.

As a paint capable of solving this problem, a paint comprising a polyol resin having a crosslinking type completely different from that of a conventional polyol resin and a melamine resin and a resin containing a hydrolyzable silyl group has been found. A patent application (Japanese Patent Laid-Open No. 1-141952) has already been filed. The coating film formed by this paint is excellent in weather resistance, chemical resistance, solvent resistance and the like.

[0004] However, the coating film of the paint comprising the polyol resin and the hydrolyzable silyl group-containing resin has a problem that the balance between the hardness and the impact resistance is balanced and the interlayer adhesion in two coats and two bake is low. .

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve these problems, and as a result, the acrylic resin having a hydroxyl group, the alkoxysilyl group-containing acrylic copolymer and the curing catalyst have been further blocked. It has been found that the incorporation of the isocyanate significantly improves the balance between the hardness and impact resistance of the coating film and the interlayer adhesion in two coats and two bake steps, and has completed the present invention.

That is, the present invention provides (A) an acrylic resin having a hydroxyl group, (B) a general formula (1):

[0007]

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Wherein R ¹ is an alkyl group having 1 to 10 carbon atoms, R ² is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms,
An alkoxysilyl group-containing acrylic copolymer containing a monovalent hydrocarbon group selected from the group consisting of an aryl group and an aralkyl group, a represents 0, 1 or 2), and (C) a curing catalyst And (D) a curable composition containing a block isocyanate as a main component.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The acrylic resin having a hydroxyl group as the component (A) used in the present invention (hereinafter, also referred to as the hydroxyl resin-containing acrylic resin (A) or simply as the component (A)) has hardness and solvent resistance immediately after baking. The main chain is substantially composed of an acrylic copolymer chain, so that the cured product has good weather resistance, chemical resistance, water resistance, and the like.

The acrylic resin (A) having a hydroxyl group can be obtained, for example, by mixing a hydroxyl-containing vinyl polymerizable compound with acrylic acid,
It can be obtained by copolymerization with methacrylic acid or a derivative thereof.

The hydroxyl group-containing vinyl polymerizable compound includes, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate,
2-hydroxyethyl vinyl ether, N-methylol (meth) acrylamide, Alonix 5700, 4-hydroxystyrene manufactured by Toagosei Chemical Industry Co., Ltd., HE-10, HE-20, HP- manufactured by Nippon Shokubai Chemical Industry Co., Ltd. 10 and HP-20 (both are acrylic acid ester oligomers having a hydroxyl group at the terminal), Blemmer P manufactured by NOF Corporation
P series (polypropylene glycol methacrylate), Blemmer PE series (polyethylene glycol monomethacrylate), Blemmer PEP series (polyethylene glycol polypropylene glycol methacrylate), Blemmer AP-400 (polypropylene glycol monoacrylate), Blemmer AE-35
0 (polyethylene glycol monoacrylate), Blemmer NKH-5050 (polypropylene glycol polytrimethylene monoacrylate) and Blemmer GLM
(Glycerol monomethacrylate), ε-caprolactone-modified hydroxyalkyl vinyl monomers obtained by reacting a hydroxyl group-containing vinyl compound with ε-caprolactone, and the like. Above all, by using an ε-caprolactone-modified hydroxyalkylvinyl-based monomer, the impact resistance and flexibility of the coating film can be improved.

A typical example of the ε-caprolactone-modified hydroxyalkyl vinyl monomer is, for example, a compound represented by the following general formula (2):

[0013]

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(Wherein, R ³ is H or CH ₃ , and n is an integer of 1 or more), and is manufactured by Daicel Chemical Industries, Ltd. with Placel FA-1 (R ³ = H, n =
1), Placcel FA-4 ( R 3 = H, n = 4), Placce
^{l FM-1 (R 3 =} CH 3, n = 1) and Placcel F
^{M-4 (R 3 = CH} 3, n = 4), T manufactured by UCC (Ltd.)
^{ONE M-100 (R 3 =} H, n = 2) and TONE
^{M-201 (R 3 = CH} 3, n = 1) , and the like.

These hydroxyl-containing vinyl polymerizable compounds may be used alone or in combination of two or more.

There are no particular restrictions on the derivatives of acrylic acid or methacrylic acid copolymerizable with the hydroxyl group-containing vinyl polymerizable compound. Specific examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate. ) Acrylate, 2-ethylhexyl (meth)
Acrylate, stearyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate, perfluorocyclohexyl (meth) acrylate, (meth) acrylonitrile, glycidyl (Meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, (meth) acrylamide, α-ethyl (meth) acrylamide, N-
Butoxymethyl (meth) acrylamide, N, N-dimethylacrylamide, N-methylacrylamide, acryloylmorpholine, N-methylol (meth) acrylamide, AS-6 and AN-6, macromonomers manufactured by Toa Gosei Chemical Industry Co., Ltd. , AA-6, AB-6 and A
K-5, containing a phosphoric ester group which is a condensation product of a hydroxyalkyl ester of an α, β-ethylenically unsaturated carboxylic acid such as a hydroxyalkyl ester of (meth) acrylic acid and a phosphoric acid or a phosphoric ester. Examples include vinyl compounds and (meth) acrylates containing urethane bonds or siloxane bonds.

The component (A) may contain a segment formed by a urethane bond or a siloxane bond in the main chain within a range not exceeding 50% (wt%, the same applies hereinafter). A segment derived from a monomer other than the acrylic acid derivative may be included. The monomer other than the (meth) acrylic acid derivative is not limited, and specific examples thereof include, for example, styrene, α-methylstyrene,
Aromatic hydrocarbon vinyl compounds such as chlorostyrene, styrene sulfonic acid, and vinyl toluene; maleic acid,
Unsaturated carboxylic acids such as fumaric acid and itaconic acid, salts thereof (alkali metal salts, ammonium salts, amine salts, etc.), their acid anhydrides (maleic anhydride, etc.), or those having 1 to 20 carbon atoms. Esters of unsaturated carboxylic acids such as diesters or halfesters with chain or branched alcohols; vinyl acetate, vinyl propionate,
Vinyl esters and allyl compounds such as diallyl phthalate; vinyl compounds containing amino groups such as vinyl pyridine and aminoethyl vinyl ether; itaconic acid diamide;
Amide group-containing vinyl compounds such as crotonamide, maleic acid diamide, fumaric acid diamide, N-vinylpyrrolidone; methyl vinyl ether, cyclohexyl vinyl ether, vinyl chloride, vinylidene chloride, chloroprene, propylene, butadiene, isoprene, fluoroolefin maleimide, N- And other vinyl compounds such as vinylimidazole and vinylsulfonic acid.

As a method for synthesizing the component (A), a solution polymerization method using an azo radical initiator such as azobisisobutyronitrile is preferable in terms of ease of synthesis.

In the solution polymerization method, n-
Dodecyl mercaptan, t-dodecyl mercaptan, n
The molecular weight can be adjusted using a chain transfer agent such as -butyl mercaptan. Also, the polymerization solvent used is
There is no particular limitation as long as it is a non-reactive solvent.

Further, an acrylic resin having a hydroxyl group (A)
May be a non-aqueous dispersion type in which polymer particles insoluble in a non-polar organic solvent such as heptane and pentane are dispersed.

The molecular weight and hydroxyl value of the acrylic resin (A) having a hydroxyl group are not particularly limited, but the physical properties of a coating film formed from the curable composition of the present invention such as durability (hereinafter referred to as coating film physical properties). From the point that the number average molecular weight is 1,500 ~
It is preferably 40,000, more preferably 3,000 to 25,000. Further, it is necessary to have a hydroxyl group enough to crosslink sufficiently from the viewpoint of physical properties of the coating film such as strength and durability, and the hydroxyl value is preferably from 10 to 300 mgKOH / g, more preferably from 30 to 150 mgKOH / g. More preferably, there is.

The acrylic resin (A) having a hydroxyl group may be used alone or in combination of two or more.

The alkoxysilyl group-containing acrylic copolymer of the component (B) used in the present invention (hereinafter, also referred to as the alkoxysilyl group-containing acrylic copolymer (B) or simply the component (B)) has a general formula (I) 1):

[0024]

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A polymer having at least one, and preferably two or more, alkoxysilyl groups in one molecule. This alkoxysilyl group may be contained at the terminal of the main chain of the component (B), may be contained in a side chain, or may be contained in both.

When the number of alkoxysilyl groups in one molecule of the component (B) is less than 1, the solvent resistance of the coating film obtained from the composition of the present invention tends to decrease.

In the above formula, R ¹ is an alkyl group having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms. If the carbon number exceeds 10,
The reactivity of the alkoxysilyl group decreases, and the reactivity also decreases when R ¹ is other than an alkyl group, for example, a phenyl group or a benzyl group. Specific examples of R ¹ include, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and an isobutyl group.

In the above formula, R ² is a hydrogen atom or carbon atom 1
A monovalent hydrocarbon group selected from the group consisting of an alkyl group, an aryl group and an aralkyl group. Specific examples of the alkyl group as R ² include R
The same groups as ¹ are mentioned, and specific examples of the aryl group include, for example, a phenyl group, and specific examples of the aralkyl group include, for example, a benzyl group.

In the above formula, a represents 0, 1 or 2.

Specific examples of the alkoxysilyl group represented by the general formula (1) include, for example, groups derived from alkoxysilyl group-containing monomers described below.

The alkoxysilyl group-containing acrylic copolymer (B) is excellent in weather resistance, chemical resistance, water resistance, etc. of the cured product because the main chain is substantially composed of an acrylic copolymer chain. Further, since the alkoxysilyl group is bonded to the carbon atom, the cured product is excellent in water resistance, alkali resistance, acid resistance and the like.

The number average molecular weight of the alkoxysilyl group-containing acrylic copolymer (B) is preferably from 1,000 to 30,000, more preferably from 3,000 to 25,000, from the viewpoint of physical properties such as durability of a coating film obtained from the composition of the present invention. preferable.

The component (B) can be obtained, for example, by copolymerizing acrylic acid, methacrylic acid, a derivative thereof and the like with an alkoxysilyl group-containing monomer.

The derivatives of acrylic acid or methacrylic acid are not limited, and specific examples thereof include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. , Stearyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate, perfluorocyclohexyl (meth) acrylate, (meth) acrylonitrile, glycidyl ( (Meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, (meth) acrylamide, α-ethyl (meth) acrylamide, N-butoxy Chill (meth) acrylamide, N,
N-dimethylacrylamide, N-methylacrylamide, acryloylmorpholine, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, N-methylol (meth) acrylamide, Alonix M manufactured by Toa Gosei Chemical Industry Co., Ltd. −570
0, AS-6, AN-6, AA-6, AB-6 and AK-, which are macromonomers manufactured by Toa Gosei Chemical Industry Co., Ltd.
5. Placcel FA-1 manufactured by Daicel Chemical Industries, Ltd.
Placcel FA-4, Placcel FM-1 and Placc
el FM-4, a phosphate ester group which is a condensation product of a hydroxyalkyl ester of an α, β-ethylenically unsaturated carboxylic acid, such as a hydroxyalkyl ester of (meth) acrylic acid, and phosphoric acid or a phosphoric acid ester acid Vinyl compounds, (meth) acrylates containing urethane bonds or siloxane bonds, and the like.

The above-mentioned alkoxysilyl group-containing monomer is not particularly limited except that it has a polymerizable double bond.

[0036]

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[0037]

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And (meth) acrylates having an alkoxysilyl group at the terminal via a urethane bond or a siloxane bond.

The proportion of the alkoxysilyl group-containing monomer in the component (B) is preferably from 5 to 90%, more preferably from 11 to 70%, in view of the curability of the composition and the durability of the coating film.

The component (B) may contain a segment formed by a urethane bond or a siloxane bond in the main chain within a range of not more than 50%, and may be a monomer other than the (meth) acrylic acid derivative. A derived segment may be included. The monomer other than the (meth) acrylic acid derivative is not limited, and specific examples thereof include aromatic hydrocarbons such as styrene, α-methylstyrene, chlorostyrene, styrenesulfonic acid, 4-hydroxystyrene, and vinyltoluene. -Based vinyl compounds; unsaturated carboxylic acids such as maleic acid, fumaric acid and itaconic acid;
Their salts (alkali metal salts, ammonium salts, amine salts, etc.), their acid anhydrides (maleic anhydride, etc.),
Esters of unsaturated carboxylic acids such as diesters or half esters thereof with linear or branched alcohols having 1 to 20 carbon atoms; vinyl acetate, vinyl propionate, vinyl esters such as diallyl phthalate and allyl compounds; vinyl pyridine, Amino group-containing vinyl compounds such as aminoethyl vinyl ether; amide group-containing vinyl compounds such as itaconic acid diamide, crotonamide, maleic acid diamide, fumaric acid diamide, N-vinylpyrrolidone; 2-hydroxyethyl vinyl ether, methyl vinyl ether, cyclohexyl Vinyl ether,
Other vinyl compounds such as vinyl chloride, vinylidene chloride, chloroprene, propylene, butadiene, isoprene, fluoroolefin maleimide, N-vinylimidazole, and vinylsulfonic acid.

The alkoxysilyl group-containing acrylic copolymer (B) is described in, for example, JP-A-54-36395 and JP-A-57-36109.
JP, No. 58-157810, etc., can be produced by a solution polymerization method using an azo radical initiator such as azobisisobutyronitrile from the viewpoint of ease of synthesis and the like. It is most preferred to manufacture.

In this case, if necessary, n-dodecylmercaptan, t-dodecylmercaptan, n-butylmercaptan, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane ,
γ-mercaptopropylmethyldiethoxysilane,

[0043]

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The molecular weight can be adjusted by using such a chain transfer agent. In particular, it is preferable to use a chain transfer agent having an alkoxysilyl group in the molecule, for example, γ-mercaptopropyltrimethoxysilane, because the alkoxysilyl group can be introduced into the terminal of the alkoxysilyl group-containing acrylic copolymer.

The polymerization solvent used in the solution polymerization method includes hydrocarbons (toluene, xylene, n-hexane, cyclohexane, etc.), acetates (ethyl acetate, butyl acetate, etc.), ethers (ethyl cellosolve, Butyl cellosolve, cellosolve acetate, etc.),
There is no particular limitation as long as it is a non-reactive solvent such as ketones (methyl ethyl ketone, ethyl acetoacetate, acetylacetone, methyl isobutyl ketone, acetone, etc.).

One of these alkoxysilyl group-containing acrylic copolymers (B) may be used alone, or two or more thereof may be used in combination.

There are no particular restrictions on the proportion of the components (A) and (B) used, but the weight ratio of component (A) / component (B) is 9%.
/ 1 to 1/9 are preferable, and 8/2 to 2/8 are more preferable. When the ratio of the component (A) / component (B) exceeds 9/1, the water resistance of the coating film obtained from the composition of the present invention tends to decrease. There is a tendency that the effect of blending the components cannot be sufficiently obtained.

Specific examples of the curing catalyst (hereinafter, also referred to as the curing catalyst (C) or simply as the component (C)) as the component (C) used in the present invention include, for example, dibutyltin dilaurate, dibutyltin dimaleate, dioctyltin. Dilaurate, dioctyltin dimaleate, polymer of dioctyltin dimaleate, organic tin compounds such as tin octylate; phosphoric acid, monomethyl phosphate, monoethyl phosphate, monobutyl phosphate, monooctyl phosphate, monodecyl phosphate, dimethyl phosphate, Phosphoric acid or phosphoric acid ester such as diethyl phosphate, dibutyl phosphate, dioctyl phosphate, didecyl phosphate; propylene oxide, butylene oxide, cyclohexene oxide, glycidyl ester Acrylate, glycidol, acryl glycidyl ether, .gamma.-glycidoxypropyltrimethoxysilane, .gamma.-glycidoxypropyl triethoxysilane, .gamma.-glycidoxypropyl methyl dimethoxysilane,

[0049]

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Addition products of epoxy compounds such as Cardura E manufactured by Yuka Shell Epoxy Co., Ltd., Epikote 828 and Epikote 1001 manufactured by Yuka Shell Epoxy Co., and phosphoric acid and / or monoacid phosphate. Organic titanate compounds; organic aluminum compounds such as aluminum tris (ethylacetoacetate) and aluminum tris (acetylacetonate); tetrabutyl zirconate, tetrakis (acetylacetonato) zirconium, tetraisobutylzirconate, butoxytris (acetylacetate) Nart) organic zirconium compounds such as zirconium; maleic acid, adipic acid, azelaic acid, sebacic acid, itaconic acid, citric acid, succinic acid, phthalic acid, trimellitic acid, pyromellitic acid, these acid anhydrides, para-acids Acidic compounds such as toluene sulfonic acid; hexylamine, di-2-ethylhexylamine,
Amines such as N, N-dimethyldodecylamine and dodecylamine; mixtures or reactants of these amines with acidic phosphate esters; and alkaline compounds such as sodium hydroxide and potassium hydroxide.

Among these curing catalysts (C), organotin compounds, acidic phosphoric esters, mixtures or reactants of acidic phosphoric esters and amines, saturated or unsaturated polycarboxylic acids or their anhydrides, Silicon compounds, organic titanate compounds, organic aluminum compounds,
Organic zirconium compounds or mixtures thereof are preferred because of their high activity.

These curing catalysts (C) may be used alone or in combination of two or more.

The amount of the component (C) used is not particularly limited, but is usually 0.1 to 20 parts per 100 parts (parts by weight, hereinafter the same) of the resin solid content of the components (A) and (B). Preferably, 0.1 to 10 parts is more preferable. If the amount of the component (C) is less than 0.1 part, the curability tends to decrease,
If the amount exceeds 20 parts, the appearance of the coating film tends to decrease.

The block isocyanate which is the component (D) used in the present invention (hereinafter also simply referred to as the component (D))
The term “compound” refers to a compound having a group that is masked with a blocking agent and has a structure that is not reactive at room temperature. When the block isocyanate is heated to about 100 ° C. or higher, the blocking agent is dissociated, and the active hydrogen isocyanate group is regenerated. By blending the block isocyanate, the isocyanate group participates in the bond to impart toughness to the coating film, improve impact resistance, and increase the number of polar groups.
Improvements in physical properties such as improvement in interlayer adhesion at the time of baking the coat 2 are achieved. In addition, since the isocyanate is masked with the blocking agent, it does not adversely affect the pot life of the composition.

Further, it becomes possible to incorporate a blocked isocyanate in the base material,
In the case of a liquid paint or an enamel, a two-pack paint of a main agent and a curing catalyst can be used.

Examples of the isocyanate masked with the blocking agent include aliphatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, hydrogenated hexamethylene diisocyanate and hexamethylene diisocyanate, isophorone diisocyanate, and the like. And alicyclic isocyanates such as hydrogenated xylylene diisocyanate.

Among the above isocyanates, from the viewpoint of weather resistance, aliphatic isocyanates such as hexamethylene diisocyanate and alicyclic isocyanates such as isophorone diisocyanate are preferable, and from the viewpoint of impact resistance. And hexamethylene diisocyanate are preferred.

Specific examples of the isocyanate blocking agent include, for example, phenol, cresol, p-naphthol, thymol, p-nitrophenol, p-chlorophenol, xylenol, p-ethylphenol, o
Phenolic compounds such as -isopropylphenol, p-tert-butylphenol and p-tert-octylphenol, for example, methanol, ethanol, propanol, butanol, ethylene glycol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl carbitol, cyclohexanol, benzyl alcohol Alcohol compounds such as phenylcellosolve and furfuryl alcohol; oxime compounds such as formaldoxime, acetoaldoxime, methylethylketoxime and cyclohexanone oxime, such as dimethyl malonate, diethyl malonate, methyl acetoacetate, methyl acetoacetate and the like. Active methylene compounds such as butyl mercaptan, tert-dodecyl mercaptan, thiof Urea-based compounds such as urea, thiourea, and ethylene urea; carbamate-based compounds such as N-phenylcarbamate and 2-oxazolidone; and imine-based compounds such as ethyleneimine; Examples thereof include sulfite compounds such as sodium bisulfite and potassium bisulfite.

Preferred specific examples of the block isocyanate include hexamethylene diisocyanate obtained by blocking an isocyanate group with methyl ethyl ketoxime or the like. Commercially available products include Desmodur BL-3175, Desmodur BL-1100, DeathModule BL-1190, DeathModule BL-1265, DeathModule AP Stable manufactured by Sumitomo Bayer Urethane Co., Ltd.
Death Module AP-12 Stable, Death Module C
T Stable, Coronate manufactured by Nippon Polyurethane Co., Ltd.
HMDI block isocyanate such as 2507.

The amount of component (D) used is preferably 3 to 50 parts, more preferably 10 to 30 parts, per 100 parts of the resin solids of components (A) and (B). If the amount is less than 3 parts, the effect of improving impact resistance tends to be insufficient, and if it exceeds 50 parts, the curability tends to decrease.

The composition of the present invention may contain various other additives and fillers depending on the use and purpose.

For example, by adding an aminosilane compound, the adhesion to a metal substrate such as aluminum and stainless steel can be improved.

The aminosilane compound is not particularly limited as long as it has an amino group and a silicon group to which at least one hydrolyzable group is bonded in one molecule. Specific examples of the aminosilane-based compound include, for example,

[0064]

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A silane coupling agent containing an amino group, such as the above-mentioned silane coupling agent containing an amino group;

[0066]

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A reaction product with an epoxy group-containing silane coupling agent, such as the above-mentioned amino group-containing silane coupling agent, ethylene oxide, butylene oxide, epichlorohydrin, epoxidized soybean oil, and Yuka Shell Epoxy Co., Ltd. Epikote 828, Epikote 1001, Kyoeisha Yushi Kagaku Kogyo Co., Ltd. Epolite 4000, Epolite 40
E, ERL-4206, ERL-4221, E manufactured by Chisso Corporation
A reaction product with a compound having an epoxy group such as RL-4299 is exemplified.

The amount of the aminosilane-based compound to be added is from 0.2 to 100 parts by weight of the resin solids of the components (A) and (B).
10 parts is preferable, and 1 to 7 parts is more preferable. The amount
If it is less than 0.2 part, the effect of improving the adhesion becomes difficult to be exhibited, and 10
Exceeding the part lowers the weather resistance.

It is preferable to use a dehydrating agent or an alkyl alcohol in order to secure storage stability that does not cause a problem even if the prepared composition is used repeatedly over a long period of time. In particular, a remarkable effect can be seen when a dehydrating agent and an alkyl alcohol are used in combination.

Specific examples of the dehydrating agent include, for example, methyl orthoformate, ethyl orthoformate, methyl orthoacetate, ethyl orthoacetate, methyltrimethoxysilane, γ
-Hydrolysable ester compounds such as methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, methyl silicate and ethyl silicate. Further, specific examples of the alkyl alcohol include low molecular weight alcohols such as methanol and ethanol.

The dehydrating agent and the alkyl alcohol may be added to the alkoxysilyl group-containing acrylic copolymer (B) before the polymerization, after the polymerization, or during the polymerization. The amount of the dehydrating agent or alkyl alcohol used is not particularly limited, but is preferably 0.5 to 20 parts, more preferably 2 to 10 parts based on 100 parts of the resin solids of the components (A) and (B).

Further, additives that can be added to the curable composition of the present invention include diluents, pigments (including extenders), ultraviolet absorbers, light stabilizers, anti-settling agents, leveling agents and the like; Fibrous materials such as cellulose and cellulose acetate butyrate; and resins such as epoxy resin, melamine resin, vinyl chloride resin, chlorinated polypropylene, chlorinated rubber, and polyvinyl butyral.

After applying the composition of the present invention to an object to be coated by various coating methods as described above, by curing, a coating film excellent in balance between strength and impact resistance, adhesion and durability is obtained. Can be formed. Examples of the coating method include conventional methods such as immersion, spraying, and brushing, and curing conditions are usually 60 to 250 ° C, preferably 80 to 200 ° C, and 1 to 60 minutes. In particular, when the composition of the present invention is applied by two coats and two bake, a coating film having excellent interlayer adhesion can be formed.

Next, the curable composition of the present invention will be described in more detail with reference to Examples.

Synthesis Example 1 [Synthesis of Acrylic Resin (A) Having Hydroxy Group]
A reaction vessel equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube and a dropping funnel was charged with 31.3 parts of butyl acetate and 9.5 parts of xylene, and heated to 110 ° C while introducing nitrogen gas. (A) was dropped at a constant speed over 5 hours by a dropping funnel.

Mixture (a) 18.0 parts of xylene 37 parts of styrene 24 parts of n-butyl acrylate Placcel FM-4 39 parts (reacted product of 2-hydroxyethyl methacrylate and ε-caprolactone manufactured by Daicel Chemical Industries, Ltd.) 1.8 parts of 2,2'-azobisisobutyronitrile After the completion of the dropwise addition of the mixture (a), 0.2 parts of 2,2'-azobisisobutyronitrile and 3.8 parts of toluene were added dropwise over 1 hour. After completion of the dropwise addition, the mixture was reacted at 110 ° C. for 2 hours and cooled, and xylene was added to the resin solution to adjust the solid concentration to 60%. The hydroxyl value (mgKOH / g solid content) of the component (A) obtained by the above reaction was 37, and the number average molecular weight was 10,000.

Synthesis Example 2 [Synthesis of Acrylic Copolymer Containing Alkoxysilyl Group (B)] In a reaction vessel similar to that of Synthesis Example 1, 45.9 parts of xylene was charged, and the temperature was raised to 110 ° C. while introducing nitrogen gas. Later
The mixture (b) having the following composition was dropped at a constant speed over 5 hours using a dropping funnel.

Mixture (b) Styrene 12.8 parts Methyl methacrylate 45.7 parts Acrylamide 1.5 parts γ-methacryloxypropyltrimethoxysilane 40.0 parts Xylene 13.5 parts 2,2′-azobisisobutyronitrile 1.0 part Drop of mixture (b) After completion, 0.5 part of 2,2'-azobisisobutyronitrile and 5 parts of toluene were dropped at a constant speed over 1 hour. After dropping, the mixture was aged at 110 ° C for 2 hours, cooled, and xylene was added to the resin solution to reduce the solids concentration to 60%.
Was adjusted. The number average molecular weight of the component (B) obtained by the above reaction was 15,000.

Examples 1 to 6 and Comparative Examples 1 to 2 In a 350 ml glass bottle, 102.8 g of the solution containing the component (A) obtained in Synthesis Example 1 and titanium oxide (CR90 manufactured by Ishihara Sangyo Co., Ltd.) 72
g, methanol 11g, methyl orthoacetate 11g, xylene
26 g and 70 ml of glass beads were dispersed for 2 hours with a paint shaker.

Next, 77.2 g of the solution containing the component (B) obtained in Synthesis Example 2 was added to the mixture, and dispersed similarly for 30 minutes to obtain a white enamel having a solid content of 60%.

To 30 g of the above white enamel, 0.5 g, 1.1 g and 2.2 g of block isocyanate were added, 0.05 g of dioctyltin maleate was added to each, and Epicoat 828 manufactured by Yuka Ciel Epoxy Co., Ltd. and γ-aminopropyl were added. After adding 0.22 g of an equivalent reaction product with triethoxysilane and stirring, the mixture was diluted with a thinner to a spray viscosity and spray-coated on a degreased aluminum plate (A1050P, plate thickness 0.8 mm). 30 minutes at 150 ° C or 30 minutes at 150 ° C
After baking for minutes, a coated plate having a thickness of about 30 μm was prepared.

The hardness and impact resistance of the obtained coating film were evaluated. Table 1 shows the results.

Next, the film was applied and baked on the baked coating film under the same conditions to prepare a coating film of two coats and two bake layers, and the interlayer adhesion was examined by the following method. Table 1 shows the results. Table 2 shows the results of evaluating the storage stability when 2.2 g of block isocyanate was added to 30 g of the above white enamel by the change in viscosity in a closed system at 50 ° C.

The viscosity change rate is a value obtained by dividing the value measured at 23 ° C. by a B-type viscometer by the initial viscosity after storage at 50 ° C.

(Adhesion between layers) A total of 100 squares were cut at intervals of 1 mm in length and 1 mm in width, and a peel test was carried out with a cellophane tape.

[0086]

[Table 1]

[0087]

[Table 2]

[0088]

By using the curable composition of the present invention, it is possible to form a coating film excellent in hardness, impact resistance and balance between them. Further, when a coating film is formed by two coatings and two baking, a coating film having excellent interlayer adhesion is obtained.

Claims (5)

(57) [Claims] (A) an acrylic resin having a hydroxyl group,
(B) General formula (1): (Wherein, R ¹ is an alkyl group having 1 to 10 carbon atoms, R ² is a hydrogen atom or a monovalent hydrocarbon group selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an aryl group and an aralkyl group, a represents 0, 1 or 2), an alkoxysilyl group-containing acrylic copolymer containing a group represented by the formula (C):
A curable composition mainly comprising a curing catalyst and (D) a block isocyanate. 2. The acrylic resin as the component (A) has a hydroxyl value of 10 to 300 mgKOH / g and a number average molecular weight of 1,500 to 1,500.
The curable composition according to claim 1, wherein the amount is 40,000. 3. The method according to claim 1, wherein the alkoxysilyl group-containing acrylic copolymer as the component (B) contains 5-90% by weight of an alkoxysilyl group-containing monomer unit having a polymerizable double bond and an alkoxysilyl group in a molecule. The curable composition according to claim 1, which is a united product. 4. The curing catalyst of the component (C) is an organotin compound, an acidic phosphoric acid ester, a mixture or a reaction product of an acidic phosphoric acid ester and an amine, a saturated or unsaturated polycarboxylic acid, a saturated or unsaturated compound. Acid anhydrides of polycarboxylic acids, reactive silicon compounds, organic titanate compounds,
The curable composition according to claim 1, which is an organic aluminum compound, an organic zirconium compound, or a mixture thereof. 5. The curable composition according to claim 1, wherein the block isocyanate of the component (D) is hexamethylene diisocyanate block isocyanate.