JPH0735494B2 - Two-component urethane coating composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a two-component urethane coating composition, and more specifically, it can provide a coating appearance having excellent dispersion stability, high gloss and good transparency. The present invention also relates to a two-component urethane coating composition which is quick-drying, excellent in polishing property and workability, and extremely useful for automobile repair and the like.

2. Description of the Related Art 2 using a curing agent component composed of a compound having an isocyanate group and a film-forming resin component having a hydroxyl group
Since liquid urethane paint does not require baking, it is drawing attention in various fields such as automobile repair and woodworking.

It is desirable for such a coating to be quick-drying from the viewpoint of shortening the process, saving heat energy, and the like, and various measures have been made to impart quick-drying to the two-component urethane coating. None of these were satisfying.

For example, in the technology using an acrylic resin having a high molecular weight or a high glass transition temperature (Tg) as a resin component,
Since the sprayed solid content is low, the number of coatings increases, and the appearance is poor.Therefore, the technique of compounding cellulose type resins such as nitrocellulose and CAB has the same disadvantages as above, and there is a technique that uses a large amount of catalyst. However, there are many problems such as short pot life and poor appearance of the coating film, and the technique using an aromatic polyisocyanate has not been put into practical use in terms of weather resistance.

If two-component urethane paint is blended with suitable three-dimensionally cross-linked so-called gelled resin particles that are substantially insoluble in the solvent, it will be quick-drying due to the pigment filling effect as a plastic pigment and the hard resin effect due to the cross-linked resin. Expected to be obtained. Various studies have been made on such three-dimensionally crosslinked resin particles, but conventional ones increase the resin solid content in a coating using a solvent-type resin, and sagging, cissing or It has been developed for the purpose of controlling the rheology in order to make up for the drawbacks such as deterioration of weather resistance. The normal dry type two-component urethane paint has not been considered at all, and in fact, such three-dimensionally crosslinked resin particles are used. However, it was not possible to obtain a two-component urethane paint that was satisfactory in terms of workability, drying property, and finished appearance. In particular, when the conventional three-dimensional crosslinked resin particles are used, there is a problem in terms of dispersion stability, and it is not possible to obtain a coated surface having high gloss and good transparency and an excellent appearance of the coating film.

Problems to be Solved by the Invention Therefore, a two-component urethane coating composition, which can provide a coating surface with high gloss and good transparency and excellent appearance of the coating film,
It is an object of the present invention to obtain a coating composition which is particularly useful for automobile repair and the like, which is quick-drying, excellent in polishing property, workability, and excellent in dispersion stability.

Means for Solving the Problems According to the present invention, the above object is to provide a main agent component (A) consisting of a hydroxyl group-containing film forming resin, crosslinked resin fine particles and a solvent, and a curing agent component (B) consisting of a compound having an isocyanate group. 2), a crosslinked resin fine particle is a composite resin particle in which a polymer containing substantially no linear metal is graft-bonded to the three-dimensional resin particle, and the hydroxyl group-containing film-forming resin and the composite resin. The solid weight ratio of the particles is
99/1 to 40/60, the isocyanate group in the component (B) and the hydroxyl group in the component (A) (when the hydroxyl group of the above-mentioned hydroxyl group-containing film-forming resin and the above linear polymer include a hydroxyl group, And the equivalent ratio of the total amount of the hydroxyl groups and the hydroxyl groups of the film-forming resin) is 0.5 to 2.0.

The crosslinked resin particles used in the present invention are a novel type of composite three-dimensional resin particles in which a substantially linear polymer is bonded to the three-dimensional resin particles. As described in the specification of “Composite Three-Dimensional Resin Particles and Manufacturing Method Thereof” filed by the same applicant (application (2) dated April 18, 1986), the resin particles are polyester particles. Resin, epoxy resin, condensation resin such as amino resin and acrylic resin, polymer particles such as vinyl resin having a three-dimensional structure of diameter 0.01μ ~ 10μ, and in the manufacturing process, or It can be easily manufactured by carrying or introducing an addition-polymerizable unsaturated group on the surface or inside of the particles after production, and then addition-polymerizing an addition-polymerizable ethylene compound to form a linear polymer.

However, it is also possible to chemically bond the linear polymer to the main body of the particle by allowing the polymer particles having a three-dimensional structure to retain an appropriate functional group and reacting it with a reactive derivative of another linear polymer. Therefore, both the main body of the particle and the linear polymer part can be made of any resin, and the manufacturing method thereof can be appropriately selected by those skilled in the polymer field.

However, in the present invention, what is important in terms of easiness of production and application in the field of coating materials in particular is a composite three-dimensional resin particle in which both the particle main body part and the linear polymer part are made of a polymer resin such as acrylic resin. .

The composite three-dimensional resin particles according to a particularly preferred embodiment can be advantageously produced by the following method. That is, a polyfunctional monomer containing two or more unsaturated groups having different copolymerizability,
Three-dimensional resin particles in which a polymerizable monomer containing a crosslinkable monomer that undergoes a polymerization reaction with one unsaturated group of the polyfunctional monomer is emulsion-polymerized to leave the other unsaturated group of the polyfunctional monomer. First, a polymerizable monomer that undergoes a polymerization reaction with the other unsaturated group described above and, if necessary, another polymerizable monomer are added and graft-polymerized to form a substantially linear polymer chain. Is a method of forming

An unsaturated group having different copolymerizability does not have selectivity for a partner monomer as represented by a mono-substituted ethylene or 1,1-di-substituted ethylene bond and a 1,2-di-substituted ethylene or poly-substituted ethylene bond. And those having selectivity, those having homopolymerization and those not having homopolymerization, or unsaturated bonds having different reactivity. In the present invention, such a copolymerizability is included in the molecule. A polyfunctional monomer having two or more unsaturated groups is advantageously used for the synthesis of composite three-dimensional resin particles. Particularly preferred polyfunctional monomers are allyl (meth) acrylate, an adduct of allyl glycidyl ether and (meth) acrylic acid, an adduct of monoallylamine or diallylamine and glycidyl (meth) acrylate or isocyanate having a (meth) acryloyl group, Addition product of allyl alcohol and isocyanate having (meth) acryloyl group, addition product of maleic acid or fumaric acid and glycidyl (meth) acrylate, addition product of maleic acid or fumaric acid monoester and glycidyl (meth) acrylate, and It is an adduct of a fatty acid having an unsaturated group and glycidyl (meth) acrylate.

Unsaturated groups contained in acryloyl and methacryloyl in these compounds have no selectivity for the partner monomer,
Reacts with any polymerizable monomer, but because the other allyl group or maleic acid type dipolymerization bond or double bond in unsaturated fatty acid reacts selectively with the polymerizable aromatic compound,
It is convenient to use the former for the synthesis of the particle body and the latter for the synthesis of the linear polymer.

Three-dimensional resin particles are first prepared by emulsion polymerization using the polyfunctional monomer and another compound having a α-β-ethylenically unsaturated bond, a part of which is a crosslinkable monomer. At this time, the crosslinkable monomer used is a compound having two or more radically polymerizable ethylenically unsaturated groups in the molecule, for example, a polymerizable unsaturated monocarboxylic acid ester of a polyhydric alcohol or a polybasic acid Unsaturated alcohol ester or mutually reactive functional group and one or more α, β
-A combination of compounds having an ethylenically unsaturated bond, such as (meth) acrylic acid and glycidyl (meth) acrylate; hydroxy (meth) acrylate and isocyanate alkyl (meth) acrylate (blocked); vinyltrialkoxysilane or ( A radically polymerizable silane coupling agent such as (meth) acryloxyalkyltrialkoxysilane is advantageously used. As the compound having another α, β-ethylenically unsaturated bond, any monomer used in the synthesis of an acrylic resin is used, but a maleic acid type double bond is left behind, so that a selective reaction therewith Polymerizable aromatic compounds exhibiting properties should be excluded.

Such monomers are roughly classified into the following groups.

(I) Carboxyl group-containing monomer such as acrylic acid,
Methacrylic acid, crotonic acid, itaconic acid, maleic acid,
Fumaric acid etc.

(II) Hydroxyl group-containing monomer such as 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, allyl alcohol, methallyl alcohol and the like.

(III) nitrogen-containing alkyl acrylates or methacrylates, such as dimethylamine noethyl acrylate,
Dimethylaminoethyl methacrylate, etc.

(IV) Polymerizable amides such as acrylic acid amide and methacrylic acid amide.

(V) Polymerizable nitriles such as acrylonitrile and methacrylonitrile.

(VI) alkyl acrylate or methacrylate,
For example, methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate and the like.

(VII) Glycidyl (meth) acrylate.

(VIII) α-olefins such as ethylene and propylene.

(IX) Vinyl compounds such as vinyl acetate and vinyl propionate.

(X) Diene compounds such as butadiene and isoprene.

(XI) A compound obtained by reacting a compound having a functional group that chemically reacts with the above-mentioned monomer, for example, a reaction product monomer of a hydroxyl group-containing monomer (II) and an isocyanate compound, or a carboxyl group-containing monomer ( Monomers produced by reaction of I) with a glycidyl group-containing compound.

These monomers are used alone or in combination.

In emulsion polymerization, ordinary polymerization initiators and emulsifiers are used, and three-dimensional particles are prepared by a conventional method.
In the molecule as described in −129066 It is particularly preferable to use a resin having a group represented by (R is a C _{1 to} C ₆ alkylene or phenylene group and Y is —COO or SO ₃ ) as an emulsifier.

The reaction liquid containing the three-dimensional resin particles thus obtained is then added with a polymerizable aromatic compound, such as styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, etc., if necessary. Are added together with the graft polymerization to produce a substantially linear polymer chain.

Incidentally, in the step of forming a linear polymer chain, as a monomer optionally present together with the polymerizable aromatic compound, a group having an active hydrogen such as a hydroxyl group, a monomer having an amino group, etc .; a carboxyl group, a sulfonic acid group, Monomers having acidic groups such as phosphoric acid groups, basic groups such as amino groups and ammonium; various functional groups by using monomers having groups having atomic groups with high cohesive energy such as urea, urethane and acid amide Can be incorporated into a linear polymer.

Since the linear polymer chain is bonded to such a novel composite resin particle, the present inventors prevent the particles from approaching each other and help to uniformly disperse the particles in the system, and Has good compatibility and contributes to improving the appearance of the coating film,
It has been found that, when a pigment is present, it has a function of wrapping around and stabilizing it, which is useful for stabilizing dispersion, can provide a film-forming ability, and can give a coating film having excellent gloss, transparency, and excellent appearance. Moreover, since the resin particle main body is three-dimensionally cross-linked, it is found that it is an ideal resin particle to be added to a two-component urethane coating composition because it has excellent hard-drying effect as well as quick-drying and polishing properties in addition to the pigment filling effect. Was done.

In the present invention, the three-dimensional cross-linked composite resin particles are usually 1/99 to 60/40, preferably 5 by weight in solid content with the hydroxyl group-containing resin.
It is mixed in the ratio of / 95 to 30/70. This is because if the composite resin particles are less than 1% in terms of the resin solid content of the main component, the contribution to the drying property is too small and the quick drying property cannot be obtained.
If it exceeds, the leveling property is deteriorated and the appearance is deteriorated.

As described above, various functional groups can be supported on the linear polymer of the composite resin particles used in the present invention, but the present inventors include active hydrogen such as hydroxyl group and amino group. It has been found that by providing a group, an acidic group or a basic group, the reactivity of particles or the reactivity in the vicinity of particles can be improved and the drying property can be improved. That is, a hydroxyl group, an amino group and the like react with the isocyanate group of the curing agent, and the particles themselves react so that their immobilization, high molecular weight,
It directly contributes to the improvement of drying property by increasing the crosslink density,
Carboxyl groups, dialkylamino and the like promote the urethane reaction in the vicinity of the particles by a catalytic effect, and the resin around the particles reacts, and apparently crosslinks to improve the drying property.

Furthermore, a linear polymer having a group with high cohesive energy such as urea, urethane and acid amide, preferably 65
When a group having a cohesive energy of 00 cal / mol or more is present, the glass transition temperature (Tg) is increased and the initial drying property is improved, and hydrogen bonds between particles-particles and particles-binder are likely to occur. It was also found that is comparable to a weakly cross-linked structure, the particles and the binder are hard to move, the initial drying property is improved, and the scratch resistance and the polishing property are improved.

Thus, in the present invention, by using the novel composite three-dimensional resin particles, quick drying, polishing property,
It is possible to provide a two-component urethane coating composition which is excellent in workability and can give a coating surface having excellent gloss and transparency and a good coating appearance.

As the curing agent component, a compound having a normal isocyanate group, or a prepolymer thereof is conveniently used, and at this time, with an isocyanate group in the curing agent component,
The hydroxyl group in the main component resin (the total amount of the hydroxyl group in the hydroxyl group-containing resin and the hydroxyl group in the case where the linear polymer of the composite resin particles has the hydroxyl group) is practically 0.5-
It can be appropriately selected and used within the range of 2.0.

The hydroxyl group-containing film-forming resin, the solvent and the compound having an isocyanate group may be any materials usually used in urethane coatings, and both the main component and the curing agent may be used as ordinary two-component urethane type coatings. Any additives and auxiliaries used, such as UV absorbers, pigments, catalysts, solvents, etc., can be contained.

The coating composition of the present invention has a pot life suitable for air spray coating after mixing the curing base component (A) and the curing component (B) and adjusting the viscosity with a thinner or the like, and has excellent workability,
In addition, the drying property after coating is fast, the time until polishing is shortened, and a smooth, high-gloss and excellent-appearance coating film can be provided, which is particularly useful for automobile repair. It is expected to have a wide range of uses in various fields such as woodworking, heavy duty protection, and construction.

The present invention will be described below with reference to examples.

Reference Example 1 (Preparation Example of Hydroxyl Group-Containing Polymer) 100 parts of xylene was charged into a reactor equipped with a stirrer, a thermometer, a nitrogen inlet tube and a reflux condenser, and the mixture was placed in a nitrogen atmosphere at 1
The temperature is raised to 20 ° C., where 40 parts of styrene, 24 parts of n-butyl methacrylate, 16.9 parts of methyl methacrylate, 0.5 parts of methacrylic acid, 18.6 parts of 2-hydroxyethyl methacrylate and tert-butyl peroxyoctoate. The mixture consisting of 2.1 parts of 2.1 was added dropwise over 3 hours, and the reaction was continued by maintaining the same temperature for 3 hours after the completion of the addition. The nonvolatile content (NV) was 50% and the Gardner color was 1%.
Below, a polymer solution having an Mn of about 8,000, a Tg of 70 ° C., an OHV of 80 per solid, and an AV of 3.3 per solid was obtained. Hereinafter, this is abbreviated as acrylic resin A.

Reference Example 2 (Synthesis of Dispersion Stabilizer) In 2 Kolben equipped with a stirrer, nitrogen inlet tube, temperature control device, condenser, decanter, 134 parts of bishydroxyethyl taurine, 130 parts of neopentyl glycol, 236 parts of azelaic acid, anhydrous Charge 186 parts of phthalic acid and 27 parts of xylene and raise the temperature. Water generated by the reaction is removed by azeotropic distillation with xylene.

The temperature is brought to 190 ° C. over about 2 hours from the start of refluxing, stirring and dehydration are continued until the acid value corresponding to the carboxylic acid becomes 145, and then the temperature is cooled to 140 ° C. Then, the temperature of 140 ° C. is maintained, 314 parts of “CURJURA E10” (versatiic acid glycidyl ester manufactured by Shell Co.) is added dropwise over 30 minutes, and then stirring is continued for 2 hours to complete the reaction. The resulting polyester resin had an acid value of 59, a hydroxyl value of 90, and Mn1054.

Reference Example 3 (Synthesis of Dispersion Stabilizer) Using the same device as in Reference Example 2, sodium salt of taurine
Charge 73.5 parts, 100 parts of ethylene glycol, 200 parts of ethylene glycol monomethyl ether, and heat with stirring to raise the temperature to 120 ° C. After the contents reached a uniform dissolved state, Epicoat 1001 (Shell Chemical Co.,
A solution consisting of 470 parts of a diglycidyl ether type epoxy resin of bisphenol A, an epoxy equivalent of 470) and 400 parts of ethylene glycol monomethyl ether is added dropwise over 2 hours. After the dropping, stirring and heating are continued for 20 hours to complete the reaction. The reaction product is purified and dried to obtain 518 parts of modified epoxy resin. The acid value of this resin by KOH titration is 49.4, and the fluorescence X
The sulfur content by line analysis was 2.8%.

Reference Example 4 (Synthesis of Dispersion Stabilizer) 140 parts of ethylene glycol monomethyl ether and 140 parts of xylene were put into 1 Kolben equipped with a stirrer, a temperature controller, a dropping funnel, a nitrogen introducing tube, and a condenser for cooling, and 12
The temperature was raised to 0 ° C. Separately prepared methyl methacrylate 74
Part, 2-ethylhexyl acrylate 70 parts, 2-hydroxyethyl methacrylate 24 parts, methacrylic acid 12 parts 5 parts azobisisobutyronitrile dissolved in a monomer mixture liquid and ethylene glycol monomethyl ether 150 parts N A solution in which 20 parts of-(3sulfopropyl) -N-methacryloyloxyethyl-N, N-dimethyl-ammonium betaine was dissolved was separately added dropwise to Kolben over 3 hours. 30 minutes after the completion of dropping, t-butylperoxy-2-
A solution prepared by dissolving 0.4 parts of ethyl hexanoate in 8 parts of ethylene glycol monomethyl ether was added, and the reaction was terminated by aging at the same temperature for 1 hour. The solvent was removed to obtain a non-volatile 92% zwitterionic group-containing acrylic resin.

Reference Example 5 (Synthesis of Monomer Having Unsaturated Group Having Different Copolymerizability) Monocolene maleate 430 in 1 Kolben equipped with a stirrer, nitrogen inlet tube, temperature controller, condenser for cooling
And 1.6 parts of hydroquinone were added and the temperature was raised to 150 ° C. Then add 373 parts of glycidyl methacrylate in 20 minutes,
It was kept at the same temperature for 60 minutes. The reaction was terminated after confirming that the acid value was 3 KOHmg / g or less.

Reference Example 6 (Synthesis of Polymerizable Monomer) Using the same apparatus as in Reference Example 5, phenyl isocyanate 27
0.4 parts and 0.9 parts of hydroquinone methyl ether were put into Kolben and the temperature was raised to 60 ° C. Then, 286 parts of 2-hydroxyethyl methacrylate was added dropwise over 30 minutes, and at the same temperature 60
Hold for a minute. The reaction was terminated by confirming that there was no absorption of isocyanate groups by IR (infrared spectrophotometer).

Reference Example 7 (Synthesis of Polymerizable Monomer) Using the same apparatus as in Reference Example 5, 2-ethylhexylamine 26
0 part and 1.0 part of hydroquinone methyl ether were put into Kolben and heated to 60 ° C. Then, 310 parts of isocyanate ethyl methacrylate was added dropwise over 30 minutes, and the mixture was kept at the same temperature for 90 minutes. The reaction was terminated by confirming that there was no absorption of isocyanate by IR (infrared spectrophotometer).

Reference Example 8 (Synthesis of Composite Three-Dimensional Resin Particles) 330 parts of deionized water was put into one Kolben equipped with a stirrer, a temperature controller, a dropping funnel, a nitrogen introducing pipe, and a condenser for cooling, and the temperature was raised to 80 ° C. . Then, 12 parts of the amphoteric ion group-containing polyester resin obtained in Reference Example 2, 1.2 parts of dimethylethanolamine, and 104 parts of deionized water were made into an aqueous solution of a dispersion stabilizer, and 66 parts of methyl methacrylate were stirred with a disper. Then, a mixed solution of 60 parts of n-butyl acrylate, 14 parts of allyl methacrylate and 40 parts of ethylene glycol dimethacrylate was gradually added to prepare an emulsion. Separately, an aqueous solution containing 2 parts of azobiscyanovaleric acid, 1.3 parts of dimethylethanolamine and 40 parts of deionized water was prepared.

The aqueous solution thus prepared was added dropwise over 80 minutes, and the emulsion was added over 60 minutes from 10 minutes after the start of the addition of the aqueous solution. After standing at the same temperature for 30 minutes, a mixed solution of 12 parts of styrene, 4 parts of n-butyl methacrylate, 4 parts of methyl methacrylate and 0.8 parts of azobiscyanovaleric acid, 0.6 parts of dimethylethanolamine, and 20 parts of deionized water. Was added dropwise over 20 minutes and then aged for 1 hour to complete the reaction. Water was removed from the obtained emulsion using a spray dryer to obtain composite three-dimensional resin particles. Hereinafter, this is abbreviated as gelled particles a.

The particle size of these particles in an emulsion state was 150 nm.

Reference Examples 9 to 13 (Synthesis of Composite Three-Dimensional Resin Particles) The composite stabilizer was prepared in the same manner except that the dispersion stabilizer and the polymerizable monomer of Reference Example 8 were changed as shown in Table 1. Resin particles were obtained. Hereinafter, these are abbreviated as gelled particles b to f.

The particle sizes of these are shown in Table 1.

Reference Example 14 (Synthesis of three-dimensional resin particles) Using the same apparatus as in Reference Example 8, 330 parts of deionized water was charged and the temperature was raised to 80 ° C. Then azobiscyanovaleric acid 2
Parts, 1.3 parts of dimethylethanolamine, and 40 parts of deionized water were added dropwise over 80 minutes.

Further, 10 minutes after the start of dropping of the aqueous solution, 40 parts of the dispersion stabilizer obtained in Reference Example 4, 1.2 parts of dimethylethanolamine, 104 parts of deionized water, 95 parts of methyl methacrylate, 75 parts of n-butyl acrylate, 75 parts of ethylene glycol. Dimethacrylate
An emulsion of 30 parts was added dropwise over 60 minutes.

After the dropping of the aqueous solution was completed, the temperature was maintained at the same temperature for 90 minutes to complete the reaction, and an emulsion having a particle diameter of 160 nm was obtained. Water is removed from this emulsion using a spray dryer,
Three-dimensional resin particles were obtained. Hereinafter, this is abbreviated as gelled particles g.

Reference Example 15 (Synthesis of three-dimensional resin particles) The amount of methyl methacrylate shown in Reference Example 14 was 60 parts, the amount of n-butyl acrylate was 60 parts, and the amount of ethylene glycol dimethacrylate was 80 parts. Reference example 14 except for changes
Three-dimensionalized resin particles were obtained in the same manner as in. Hereinafter, this is abbreviated as gelled particles h.

Examples 1 to 8 and Comparative Examples 1 to 3 The acrylic resin A obtained in Reference Example 1, the gelled particles a to h obtained in Reference Examples 8 to 15 and the mixed solvent I shown below are shown in Table-
Mix in the mixing ratio as shown in 3 to make it a paint,
Further, the curing agent components shown in the same table were blended and the spray viscosity was adjusted with the following mixed solvent I to obtain coating materials of Examples 1 to 8 and Comparative Examples 1 to 3.

The above paint was applied on a mild steel plate having a thickness of 0.8 mm so as to have a film thickness of about 50 to 60 μm, and allowed to dry under conditions of a temperature of 20 ° C. and a humidity of 75%, and was subjected to each test. Table of the results
3 shows.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Kashihara 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Co., Ltd. (72) Inventor Tadafumi Miyazono 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Incorporated (56) References JP 62-246970 (JP, A) JP 62-292864 (JP, A)

Claims (4)

[Claims] 1. A main agent component (A) consisting of a hydroxyl group-containing film forming resin, crosslinked resin fine particles and a solvent, and a curing agent component (B) consisting of a compound having an isocyanate group.
A composite resin particle consisting of a liquid, in which crosslinked resin particles are graft-bonded to a three-dimensional resin particle with a polymer that does not substantially contain a linear metal, and a hydroxyl group-containing film-forming resin and a solid resin particle The weight-to-weight ratio is 99 / 1-40 / 60,
The isocyanate group in the component (B) and the hydroxyl group in the component (A) (when the hydroxyl group of the above-mentioned hydroxyl group-containing film forming resin and the above linear polymer include a hydroxyl group, the hydroxyl group and the film forming resin A two-component urethane coating composition having an equivalent ratio of 0.5 to 2.0 to the total amount of hydroxyl groups). 2. The composition according to claim 1, wherein the linear metal-free polymer contains a group having active hydrogen. 3. The composition according to claim 1, wherein the linear metal-free polymer contains an acid group or a basic group. 4. The composition according to claim 1, wherein the linear metal-free polymer has a group having an atomic group having a cohesive energy of 6500 cal / mol or more.