JP2002294066A - Resin composition and coating composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition allowing forming a coated film having an extremely excellent finish and extended in a working life and a coating composition containing the resin composition. SOLUTION: This resin composition is a urethane-curable resin composition and comprises (A) a compound having at least one hydroxyl group and one carboxyl group in one molecule and having <=2,000 of weight-average molecular weight in an amount of 0.01-10 pts.wt. and (B) an organometallic compound as a urethane curing catalyst in an amount of 0.01-10 pts.wt. based on 100 pts.wt. of the solid part of the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition capable of forming a coating film having excellent finishability and having an extended pot life, and a coating composition containing the same. The present invention relates to a coating composition suitable as a clear coating.

[0002]

2. Description of the Related Art Conventionally, repair of an automobile body,
Acrylic lacquer, acrylic urethane paint, acrylic melamine paint, etc. are used for painting and repairing industrial machinery, structures, furniture (including steel), etc., but dryness at normal temperature, finish, weather resistance, etc. As a result, acrylic urethane paints have become the mainstream as repair paints for automobile bodies. In particular, in the clear paint for repair in the two-coat finish, a coating film with high gloss, excellent drying properties and excellent polishing properties can be formed.
In addition, when wet-on-wet coating is performed, it is necessary that a colored base paint such as a metallic base paint has good return unevenness resistance and the like.

In a urethane curing mechanism such as the above-mentioned acrylic urethane paint, a curing catalyst such as an organometallic catalyst is added in order to promote curing from the viewpoint of drying properties. Slowing is effective and acids are conventionally used as retarding catalysts. For this reason, an acid group is usually introduced into the acrylic polyol using a carboxylic acid monomer as a copolymerization component of the acrylic polyol.

However, when an acid group is introduced using a carboxylic acid monomer as described above, a coating film formed by the coating composition containing the acrylic polyol and the polyisocyanate compound is cured at room temperature or under forced drying conditions. Not only the starting point is delayed, but also the curing is delayed, and the finish is improved, but the quick-drying property is reduced.

[0005] When a conventionally known acid catalyst is used, the curing start point is delayed and the finish is improved in the same manner as described above, but not only the curability is reduced, but also the coating performance as a low molecular component is reduced. Also had the problem of having an adverse effect.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a specific compound having a hydroxyl group and a carboxyl group is used as an acid serving as a negative catalyst of a urethane curing system. The present inventors have found that the finishing point is improved by delaying the curing starting point, and that the hydroxyl group in the molecule is cured by urethane and incorporated into the crosslink to maintain good coating film performance, thereby completing the present invention.

That is, the present invention relates to a urethane-curable resin composition comprising a compound having a weight-average molecular weight of 2000 or less having at least one hydroxyl group and one carboxyl group per molecule per 100 parts by weight of the resin solids. A resin composition containing 0.01 to 10 parts by weight of A) and 0.01 to 10 parts by weight of an organometallic compound (B) as a urethane curing catalyst, and a coating composition containing the same. Is what you do.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The compound (A) used in the present invention is a compound having at least one hydroxyl group and one carboxyl group in one molecule and having a weight average molecular weight of 2,000 or less. −
1) Or an oligomer (A-2) having at least one carboxyl group and hydroxyl group in one molecule can be used. If the weight-average molecular weight exceeds 2,000, the compatibility with the base resin is reduced, so that the finish is undesirably reduced.

The hydroxycarboxylic acid (A-1) is preferably a hydroxycarboxylic acid having 2 to 7 carbon atoms. When the number of carbon atoms is 8 or more, the solubility is remarkably reduced, which is not preferred. Further, hydroxycarboxylic acids having a carboxyl group and a hydroxyl group at both ends and having 4 or more carbon atoms between two functional groups are not preferable because a dehydration reaction easily occurs at room temperature to form a lactone. Examples of the hydroxycarboxylic acid include 2-hydroxy-
n-butyric acid, 2-hydroxyisobutyric acid, 2-hydroxy-
2-methylbutyric acid, 2-hydroxy-3-methylbutyric acid, leucic acid, glycolic acid, lactic acid, β-oxyacid, dimethylolbutanoic acid, glyceric acid, 3-hydroxybutyric acid,
Malic acid, citric acid, etc., and these are one kind,
Alternatively, two or more kinds can be used in combination. Among these, at least one selected from glycolic acid, 2-hydroxybutyric acid, 2-hydroxyisobutyric acid, 2-hydroxy-3-methylbutyric acid, and leucic acid is preferable, and 2-hydroxy-3-methylbutyric acid and glycolic acid are particularly preferable. Is particularly preferred because it has high reactivity with isocyanate groups and maintains coating film performance.

The oligomer (A-2) includes, for example, the following polyester oligomers and acrylic oligomers each containing one or more hydroxyl groups and carboxyl groups in one molecule. These usually have a weight average molecular weight of 250 to 2,000 and an acid value of 50 to 500. The oligomer is suitable because it suppresses the initial yellowing of a coating film obtained when an ultraviolet absorber or a light stabilizer is blended in the coating material.

As the polyester oligomer, for example, ethylene glycol, butylene glycol, 1,6
-Hexanediol, 2-butyl-2-ethyl-1,3
Polyhydric alcohols such as propanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, trimethylolpropane, and pentaerythritol, and adipic acid, terephthalic acid, isophthalic acid, phthalic anhydride, succinic anhydride, and hexahydro Those obtained by a condensation reaction with a polyvalent carboxylic acid such as phthalic anhydride may be mentioned first. For example, it can be obtained by a ring-opening condensation reaction between a polyhydric alcohol and an acid anhydride, or can be obtained by reacting a polyhydric alcohol having three or more functional groups with a polycarboxylic acid under a compounding condition in which a carboxyl group is excessive. Conversely, it is also obtained by first synthesizing a hydroxyl-terminated polyester under the compounding condition of a polyhydric alcohol having an excess of hydroxyl groups, and then post-adding an acid anhydride such as phthalic anhydride, hexahydrophthalic anhydride, and succinic anhydride. be able to.

Further, the oligomer is formed by the addition reaction between the polyhydric alcohol and the acid anhydride as described above, and the ring-opening reaction of the acid anhydride occurs but the polyesterification reaction does not substantially occur. A half ester compound obtained by reacting under such conditions (for example, at a reaction temperature of 150 ° C. or lower) can also be used. The compounds have a low molecular weight and a narrow molecular weight distribution.

As the acrylic oligomer, conventionally known acrylic oligomers can be used without any particular limitation.

In the urethane-curable resin composition, the compound (A) is used based on 100 parts by weight of the resin solid content.
0.01 to 10 parts by weight, preferably 0.05 to 2 parts by weight is blended. Among them, hydroxycarboxylic acid (A-1)
Is preferably 0.01 to 5 parts by weight, preferably 0.05 to 2 parts by weight, based on 100 parts by weight of the resin solid content in the urethane-curable resin composition. If the amount is less than 0.01 part by weight, the effect of retarding the curing cannot be sufficiently obtained, while if it exceeds 5 parts by weight, the film properties such as water resistance and the curability are lowered. In the case of the oligomer (A-2), 0.1 to 10 parts by weight, preferably 0.5 to 2 parts by weight, is blended with respect to 100 parts by weight of the resin solid content in the urethane-curable resin composition. It is preferred that If the amount is less than 0.1 part by weight, a sufficient curing retardation effect cannot be obtained.
Exceeding the weight part is not preferred because it causes a decrease in coating film performance such as water resistance, a decrease in compatibility with the base resin and a decrease in curability.

The organometallic compound used as the urethane curing catalyst in the present invention includes, for example, tin octylate,
Dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate), dioctyltin diacetate, dibutyltin dilaurate, dibutyltin oxide, dibutyltin fatty acid salt, dioctyltin oxide, 2-ethylhexane Lead acid, zinc octylate, zinc naphthenate, zinc fatty acids, cobalt naphthenate, calcium octylate, copper naphthenate, tetra (2-ethylhexyl) titanate, etc., and these may be used alone or in combination of two or more. Can be used. Known urethane curing catalysts such as tertiary amines and phosphoric acid compounds can be used in combination with these, if necessary. The amount used is usually in the range of 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the resin solid content in the coating material.

In the present invention, the urethane-curable resin composition is mainly composed of a polyol and a polyisocyanate (which may be blocked), and the polyol contains at least two hydroxyl groups in one molecule. An acrylic resin, a polyester resin, a urethane resin, a silicone resin, a fluorine resin, and the like can be given. In ordinary temperature or forced drying applications, the urethane-curable resin composition usually contains a hydroxyl group-containing polymerizable unsaturated monomer (a).
And a copolymer (I) containing a monomer component composed of another polymerizable unsaturated monomer (b) copolymerizable therewith and a polyisocyanate compound (II) are preferably used. .

Examples of the above-mentioned hydroxyl-containing polymerizable unsaturated monomer (a) include 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2,3-dihydroxybutyl (meth) acrylate, and 4-hydroxybutyl. Monoesters of polyhydric alcohol and acrylic acid or methacrylic acid, such as (meth) acrylate and polyethylene glycol mono (meth) acrylate; ε-caprolactone is added to the monoester of polyhydric alcohol and acrylic acid or methacrylic acid. Ring-opening polymerized compounds such as "Placcel FA
-1 "," Placcel FA-2 "," Placcel FA-
3 "," Placcel FA-4 "," Placcel FA-
5 "," Placcel FM-1 "," Placcel FM-
2 "," Placcel FM-3 "," Placcel FM-
4 "and" Placcel FM-5 "(both of which are manufactured by Daicel Chemical Co., Ltd., trade names) and the like. These can be used alone or in combination of two or more.

In the present invention, "(meth) acrylate" means "acrylate or methacrylate". For example, the 2-hydroxyethyl (meth) acrylate as the component (a) means 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate.

Examples of other polymerizable unsaturated monomers (b) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl (meth). Acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl acrylate, n-octyl (meth) acrylate, cyclohexyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate, tridecyl (meth) A) C1-24 alkyl (meth) acrylates such as acrylate and stearyl (meth) acrylate; carboxyl group-containing polymerizable unsaturated monomers such as acrylic acid, methacrylic acid, maleic acid, and maleic anhydride; TA) acrylate, 3,
Epoxy group-containing polymerizable unsaturated monomers such as 4-epoxycyclohexylmethyl (meth) acrylate; N, N
-Dimethylaminoethyl (meth) acrylate, N, N
-Diethylaminoethyl (meth) acrylate, N, N
Aminoalkyl (meth) acrylates such as dimethylaminopropyl (meth) acrylate; acrylamide, methacrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethyl (Meth) acrylamide or a derivative thereof such as aminopropyl (meth) acrylamide, N-methylolacrylamide, N-methylolacrylamide methyl ether, N-methylolacrylamide butyl ether; acrylonitrile, methacrylonitrile, vinyl acetate, Beoba monomer (manufactured by Shell Chemical Company) Styrene, vinyltoluene, α-methylstyrene; 2- (2′-hydroxy-5 ′)
-Methacryloyloxyethylphenyl) -2H-benzotriazole, 4- (meth) acryloyloxy-
UV-absorbing or UV-stable polymerizable unsaturated monomers such as 1,2,2,6,6-pentamethylpiperidine. These compounds can be used alone or
More than one species can be used in combination.

The mixing ratio of each monomer constituting the copolymer (I) is such that the hydroxyl group-containing polymerizable unsaturated monomer (a) is 1 to 50% by weight, preferably 10 to 40% by weight based on all the constituent monomers. And the other monomer (b) is 50 to 99.
Suitably, it is in the range of 60% to 90% by weight. When the amount of the hydroxyl group-containing polymerizable unsaturated monomer (a) is less than 1% by weight, the curability of the obtained coating film is insufficient. On the other hand, when the amount exceeds 50% by weight, the finish of the coating film, resistance to uneven return, and polishing work. This is not preferred because the properties are significantly reduced.

In the present invention, a copolymerizable unsaturated monomer having a bridged alicyclic hydrocarbon group is used as the monomer (b) in view of the workability of polishing the coating film and the resistance to uneven return. It is desirable that it be contained in the monomer mixture constituting (I) in an amount of 1 to 50% by weight, preferably 15 to 30% by weight.

Examples of the polymerizable unsaturated monomer having a bridged alicyclic hydrocarbon group include isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, and adamantyl (meth) acrylate. Including isobornyl (meth) acrylate,
It is desirable that at least one selected from tricyclodecanyl (meth) acrylate is used.

The polymerization method for obtaining the copolymer (I) by polymerizing the above-mentioned monomer components is not particularly limited, and a polymerization method known per se, for example, a bulk polymerization method in the presence of a radical polymerization initiator. Among them, a solution polymerization method can be preferably used, such as a polymerization method, a solution polymerization method, a bulk-suspension two-stage polymerization method in which suspension polymerization is performed after bulk polymerization.

Examples of the radical polymerization initiator include ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide and methylcyclohexanone peroxide; and 1,1-bis (tert-butylperoxy). ) -3,
3,5-trimethylcyclohexane, 1,1-bis (te
rt-butylperoxy) cyclohexane, n-butyl-
4,4-bis (tert-butylperoxy) valerate,
2,2-bis (4,4-ditert-butylperoxycyclohexyl) propane, 2,2-bis (4,4-ditert
-Amyl peroxycyclohexyl) propane, 2,2
-Bis (4,4-ditert-hexylperoxycyclohexyl) propane, 2,2-bis (4,4-ditert-octylperoxycyclohexyl) propane, 2,2-
Peroxyketals such as bis (4,4-dicumylperoxycyclohexyl) propane; hydroperoxides such as cumene hydroperoxide and 2,5-dimethylhexane-2,5-dihydroperoxide;
1,3-bis (tert-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-2,5-di (tert
Dibutyl peroxides such as -butylperoxy) hexane, diisopropylbenzene peroxide and tert-butylcumyl peroxide; diacyl peroxides such as decanoyl peroxide, lauroyl peroxide, benzoyl peroxide and 2,4-dichlorobenzoyl peroxide Oxides; peroxycarbonates such as bis (tert-butylcyclohexyl) peroxydicarbonate; peroxyesters such as tert-butylperoxybenzoate and 2,5-dimethyl-2,5-di (benzoylperoxy) hexane And organic azo polymerization initiators such as 2,2'-azobisisobutyronitrile and 1,1-azobis (cyclohexane-1-carbonitrile).

As the polymerization method by the solution polymerization method,
For example, there can be mentioned a method in which the monomer mixture is dissolved or dispersed in an organic solvent, and the mixture is heated with stirring at a temperature of usually about 80 ° C. to 200 ° C. in the presence of the radical polymerization initiator. The reaction time is usually 1 to 24
Time is appropriate.

Examples of the organic solvent include hydrocarbon solvents such as heptane, toluene, xylene, octane and mineral spirit; esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate and diethylene glycol monobutyl ether acetate. Ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone and cyclohexanone; alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, sec-butanol and isobutanol; n-butyl ether, dioxane, ethylene glycol monomethyl Ethers, ethers such as ethylene glycol monoethyl ether and the like; Swazole 310, Swazole 1000, Swazole 1500 (or more, Both are manufactured by Cosmo Oil), SH
ELLSOL A (Shellsol A, manufactured by Shell Chemical Company)
And other aromatic petroleum solvents. These organic solvents can be used alone or in combination of two or more.

The copolymer (I) obtained as described above has a weight average molecular weight of 2,000 to 50,000, preferably 5,000 to 30,000. If the weight-average molecular weight is less than 2,000, the curability, reversion unevenness resistance and weather resistance of the resulting coating film are reduced. The copolymer (I) has a hydroxyl value of 1
0 to 240 mgKOH / g, preferably 50 to 160 m
Suitably, it is in the range of gKOH / g. When the hydroxyl value is less than 10 mgKOH / g, the curability, weather resistance, polishing workability, and the like of the obtained coating film are deteriorated.
If it exceeds gKOH / g, the compatibility of the varnish and the finish of the coating film are undesirably reduced. Further, the copolymer (I) preferably has a glass transition temperature in the range of 20 to 70 ° C.

The polyisocyanate compound (II) is used as a curing agent component, and can react with hydroxyl groups in the resin (I) to form a cured coating film.
As the polyisocyanate compound (II), for example,
Aliphatic diisocyanates such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4 (or 2,6) -diisocyanate;
Cycloaliphatic diisocyanates such as 4,4'-methylenebis (cyclohexyl isocyanate) and 1,3- (isocyanatomethyl) cyclohexane; aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate and diphenylmethane diisocyanate; lysine Organic polyisocyanate itself such as tri- or higher-valent polyisocyanate such as triisocyanate, or an adduct of each of these organic polyisocyanates with polyhydric alcohol, low molecular weight polyester resin or water, or as described above A cyclized polymer (for example, isocyanurate) of each organic diisocyanate, a biuret-type adduct, and the like can be given. Of these, isocyanurate of hexamethylene diisocyanate is preferred. These can be used alone or in combination of two or more.

The amount of the polyisocyanate compound (II) used depends on the isocyanate group (NCO) contained therein.
With respect to the hydroxyl group (OH) in the resin (I),
It is appropriate that the equivalent ratio of O / OH is selected so as to be usually in the range of 0.2 to 2.0, preferably 0.5 to 1.5.

The resin composition of the present invention is a urethane-curable composition containing the above components (I) and (II). If necessary, an organic solvent, pigments, a non-aqueous resin,
A coating composition can be prepared by appropriately blending an ultraviolet absorber, a light stabilizer, a coating surface modifier, an antioxidant, a fluidity modifier, a wax, and the like.

The paint composition of the present invention obtained as described above is stored as a two-pack paint, mixed immediately before use, and provided for painting. The coating composition of the present invention is generally used as a forced-drying coating at room temperature or about 100 ° C. or lower.

The coating composition of the present invention can be swollen by a polar solvent such as for repairing automotive coatings and for repairing architectural exterior coatings.
When coating on easily soluble coatings, plastic materials with poor solvent resistance, or when applying wet-on-wet on uncured colored base coatings,
It is preferable to reduce or eliminate the use amount of the polar solvent in terms of preventing lifting of the lower layer coating film, preventing generation of solvent cracks in the plastic material, and preventing return unevenness of the colored base coating film. Examples of low-polar or non-polar solvents that are not polar solvents include hydrocarbon solvents, ether solvents, and aromatic petroleum solvents.

The coating composition of the present invention comprises iron, aluminum, brass, copper plate, stainless steel plate, tin plate, galvanized steel plate, alloyed zinc (Zn-Al, Zn-Ni, Zn-
Metals such as plated steel sheets, such as Fe); surface-treated metals obtained by subjecting these metal surfaces to a chemical conversion treatment such as a phosphate treatment or a chromate treatment; directly or on a material to be coated such as plastic, wood, concrete, or mortar A primer and / or a middle coat and / or a top coat is applied to a cured coating surface or an uncured coating surface of an object to be coated which is coated with a top coat coloring base, and a coating film having high gloss and excellent polishing finish is obtained. It can be formed and has excellent return unevenness resistance and the like, and can form a coating film having a very high finish.

The coating composition of the present invention may be a colored coating composition or a clear coating composition. By using a clear coating for multi-layer finishing, the effect of the present invention is maximized. Can be demonstrated.

When the coating composition of the present invention is used as a clear coating, a water-based or solvent-type liquid coloring base coating is usually applied to the surface to be coated which has been subjected to base adjustment, if necessary. In a state where the base coating film is uncured, a clear coating material is applied on the base coating film and dried to form a coating film. After applying the colored base coating, the base coating may be cured, and then a clear coating may be applied on the base coating and dried.

The coating thickness of the coating composition of the present invention is not particularly limited, but usually the cured coating thickness is 3 to 60.
μm, preferably about 5 to 50 μm.

[0037]

The coating film formed by a conventional coating composition containing an acrylic polyol and a polyisocyanate compound into which an acid group is introduced using a carboxylic acid monomer or a conventional acid catalyst is blended, Under normal temperature or forced drying conditions, not only the curing starting point is delayed but also the curing is delayed, and although the finishability is improved, the quick-drying property is reduced.However, in the present invention, the acid serving as a negative catalyst of the urethane curing system is used. As, by using a specific compound having a hydroxyl group and a carboxyl group, the coating film formed by a paint containing the same, at room temperature or forced drying conditions, not only improves the finish by delaying the curing start point, It has excellent quick-drying properties and is advantageous in terms of the pot life of the paint. Or is it is intended to maintain a good coating performance. Although the detailed reason is unknown, the compound having a hydroxyl group and a carboxyl group to be used is polyfunctional, and has a high coordination ability to a metal which is a curing catalyst by the hydroxyl group and the carboxyl group. It is possible to delay it, and then it is thought that if the coordination is lost, it will be hardened immediately and can keep quick drying.

[0038]

The present invention will be more specifically described below with reference to Production Examples, Examples and Comparative Examples. Unless otherwise specified, “parts” and “%” mean “parts by weight” and “% by weight”, respectively.

Production Example 1 of Acrylic Copolymer 60 parts of xylene and 10 parts of butyl acetate were charged into a four-necked flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet, and heated to 135 ° C. At the same temperature, a dropping monomer mixture having a composition comprising a monomer shown in Table 1 below and a polymerization initiator (t-butylperoxy-2-ethylhexanoate) was dropped over 4 hours, and after the dropping was completed. Then, the mixture was kept at 135 ° C. for about 1 hour, and then a mixed solution of 0.5 part of an additional catalyst (t-butylperoxy-2-ethylhexanoate) and 5 parts of xylene was added dropwise over 1 hour. After completion, the mixture was kept at 135 ° C. for about 2 hours to obtain a solid content of 60%.
Was obtained. The solid content and resin property value of the obtained acrylic copolymer solution are shown in Table 1 below.

Production Examples 2 to 4 In Production Example 1, a mixture of a monomer and a polymerization initiator,
Each acrylic copolymer solution was obtained in the same manner as in Production Example 1 except that the addition catalyst and the additional catalyst were used as shown in Table 1. The solid content and resin property values of each of the obtained acrylic copolymer solutions are shown in Table 1 below.

[0041]

[Table 1]

Production Example 5 of Oligomers A four-necked flask equipped with a stirrer, a thermometer, a condenser, a water separator, and a nitrogen gas inlet was charged with 65 parts of hexahydrophthalic anhydride, 10 parts of trimethylolpropane, and 25 parts of butyl-2-ethyl-1,3-propanediol were charged, the temperature was raised to 160 ° C., and the temperature was maintained at 160 ° C. for about 1 hour.
Next, 5 parts of xylene was added, and the temperature was further raised to 190 ° C.
The mixture was kept at 160 ° C. for about 2 hours while separating water to obtain a polyester oligomer having a solid content of 65%. The obtained oligomer had a weight average molecular weight of 1500 and an acid value of 125 mgK.
OH / g, hydroxyl value 30 mgKOH / g, glass transition temperature 19 ° C.

Production Example 6 70 parts of hexahydrophthalic anhydride and 30 parts of trimethylolpropane were charged into a four-necked flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet, and heated to 125 ° C. Then, after adding 25 parts of xylene, about 4 hours 125
The mixture was kept at ℃ to obtain an oligomer having a solid content of 65%. The obtained oligomer had a weight average molecular weight of 400 and an acid value of 254.
mgKOH / g, hydroxyl value 127 mgKOH / g, glass transition temperature 3 ° C.

Preparation of clear paint Examples 1 to 5 and Comparative Examples 1 to 5 Using the acrylic copolymer solution obtained in the above Production Examples 1 to 4, etc., the mixture was mixed according to the formulation shown in Table 2 below. To obtain clear paints. (Note 1) to (Note 4) in Table 2 have the following meanings, respectively.

(Note 1) "Death module N-330"
0 ": Sumitomo Bayer Urethane Co., Ltd., hexamethylene diisoisocyanate isocyanurate, NCO content 2
1.5%.

(Note 2) “Scat2L”: an organic tin catalyst (50% xylene solution of di-n-butyltin fatty acid salt and fatty acid zincs) manufactured by Sankyoki Gosei Co., Ltd. (Note 3) Calcium octylate: Nippon Chemical Sangyo Co., Ltd. (Note 4) 2-hydroxyisobutyric acid, 2-hydroxy-3
-Methylbutyric acid, glycolic acid: Both are manufactured by Tokyo Chemical Industry.

Each of the clear paints obtained in Examples 1 and 4 and Comparative Examples 1 and 3 was diluted with isobutyl acetate, and the viscosity was adjusted with a Ford cup # 4 for 14 seconds.
This viscosity-adjusted coating material is spray-coated on a tin plate, and the coating film is heated at 55 ° C. for 10 minutes and maintained at 55 ° C. 40 using a rigid pendulum type viscoelasticity meter (MODEL DDV-OPA III) manufactured by Orientec. The curing behavior was examined under the conditions of minutes, and the results are shown in Fig. 1. From this, the clear paint using Examples 1 and 4 has a longer curing start time than the clear paints using Comparative Examples 1 and 3. The curing behavior was slow and the curing speed was fast, suggesting an improvement in finishability.

Further, the above Examples 1 to 5 and Comparative Examples 1 to 4
The solid content of each clear paint obtained in the above was adjusted with a mixed solvent having a composition of xylene / butyl acetate / Shellsol A (Note 5) = 60/20/20 (weight ratio), and the pot life of each was evaluated. . The viscosity of each clear paint is adjusted to about 14 seconds (Ford cup # 4, 25 ° C) with the above mixed solvent, spray-coated on a tin plate to a dry film thickness of about 40 µm, and dried at 60 ° C for 30 minutes. Thus, each test coated plate was obtained. The finish was evaluated according to the following test method. The results are also shown in Table 2. (Note 5) Shellsol A: trade name, aromatic petroleum solvent manufactured by Shell Chemical Company.

(Test Method) Pot life (pot life): Each clear paint was solid content 3
0%, 2 hours after mixing the acrylic copolymer solution and the polyisocyanate compound, 4 hours after, and 6 hours after mixing.
The viscosity (sec / 1 hour) of each clear coating at 2 ° C. was measured with an Iwatani cup. The clear paint of the example is
Even after 6 hours, there was not much thickening.

Finishing property: The glossiness of the surface of each test coated plate was visually evaluated (out of 5 points). Furthermore, "Wave-Sc" manufactured by BYK, which is an apparatus for optically scanning the light / dark pattern of light on the coating film surface and analyzing the contrast (intensity) of reflected light.
“an” means a long wavelength value measured in a wavelength region of 600 to 1000 μm.
And a short wavelength value measured in a wavelength range of 100 to 600 μm or less was obtained, and each was evaluated as a parameter of the finished skin. These are the variances of the measured light intensity. The higher the value, the more impaired the smoothness.

[0051]

[Table 2]

[Brief description of the drawings]

FIG. 1 shows the curing behavior of a coating film with each clear paint obtained in Example 1 of the present invention and Comparative Examples 1 and 3.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C09D 175/04 C09D 175/04 // (C08L 75/04 C08L 67:04 67:04) F-term (reference) 4J002 CF182 CK051 EG006 EG046 FD156 GH01 4J034 DA01 DB03 DC38 DC39 DC50 DF01 DF24 DP03 DP18 HA07 HC03 HC12 HC17 HC22 HC46 HC52 HC61 HC64 HC71 QA02 QA05 RA07 4J038 DG111 DG181 DG191 DG261 KA04 KA06 PC02 P02P

Claims (8)

[Claims] In a urethane-curable resin composition, a compound (A) having a weight average molecular weight of 2000 or less having at least one hydroxyl group and a carboxyl group in one molecule per 100 parts by weight of the resin solid content is used. A resin composition comprising 0.01 to 10 parts by weight and 0.01 to 10 parts by weight of an organometallic compound (B) as a urethane curing catalyst. 2. The resin composition according to claim 1, wherein the compound (A) is a hydroxycarboxylic acid having 2 to 7 carbon atoms. 3. The method of claim 1, wherein the hydroxycarboxylic acid is glycolic acid,
The resin composition according to claim 2, wherein the resin composition is at least one selected from 2-hydroxybutyric acid, 2-hydroxyisobutyric acid, 2-hydroxy-3-methylbutyric acid, and leucic acid. 4. The compound (A) has at least one compound per molecule.
The resin composition according to claim 1, which is an oligomer having two carboxyl groups and hydroxyl groups. 5. The resin composition according to claim 4, wherein the oligomer is formed by an addition reaction between a polyhydric alcohol and an acid anhydride. 6. The urethane-curable resin composition comprises a monomer component comprising (a) a hydroxyl group-containing polymerizable unsaturated monomer and (b) another polymerizable unsaturated monomer copolymerizable with the (a) monomer. As a component, having a weight average molecular weight of 2,000 to 50,000 and a hydroxyl value of 10 to 240.
The resin composition according to claim 1, which comprises a copolymer (I) having a mg KOH / g and a polyisocyanate compound (II). 7. The resin composition according to claim 6, wherein (b) a monomer mixture comprising isobornyl (meth) acrylate and tricyclodecanyl (meth) acrylate in the monomer mixture constituting the copolymer (I). . 8. A coating composition containing the resin composition according to claim 1.