JPH06192616A - Water-dispersible coating resin composition - Google Patents

Abstract

PURPOSE:To obtain a compsn. which contains a water-dispersible polymer capable of forming a coating film excellent in performance characteristics as an undercoating film. CONSTITUTION:The compsn. contains a water-dispersible polymer which comprises 80-10wt.% acrylic resin which is a copolymer of a radical- polymerizable unsatd. monomer with a carboxylated radical-polymerizable unsatd. monomer and has an acid value of 15-200 and 20-90wt.% urethane resin which gives a film having a 100% modulus of 3-150kg/cm<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-dispersible coating resin composition for an undercoat which is applied on the floor bottom of an automobile or the like.

More specifically, the present invention is a water-dispersible coating resin composition for use as an undercoat for coating automobile steel sheets such as galvanized steel sheets and cationic electrodeposition steel sheets, and provides strong adhesion to adherends. The present invention relates to a water-dispersible coating resin composition having both properties and appropriate flexibility, capable of forming a coating that protects an automobile body from an impact caused by flying stones from a road surface during traveling and prevents rust due to chipping. Further, the present invention relates to a water-dispersible coating resin composition capable of forming a flexible and good-adhesive coating that also imparts vibration-proof and sound-proof effects to steel sheets.

[0003]

2. Description of the Related Art In recent years, the automobile industry has been confronted with global environmental problems, resource saving, and high performance, and is discharged during the recycling of solvents and structures discharged during the application of paints and the like. It is required to review the materials containing environmental pollutants. In particular, the problem of environmental pollution due to combustion of organic chlorine compounds has come to be highlighted.

Conventionally, a vinyl chloride plastisol composition has been widely used as an undercoating agent for the purpose of preventing rust and chipping resistance of the bottom surface of automobiles and the like. This is due to the development of a polyamide-based adhesion improver and a blocked isocyanate-based adhesion improver to improve the adhesion between galvanized steel sheets, cationic electrodeposition steel sheets and vinyl chloride plastisol. The property has improved dramatically.

However, in recent years, vinyl chloride resins used in automobiles have become a cause of environmental pollution because a large amount of chlorine gas is generated by incineration during the treatment of scrapped vehicles.

For this reason, dechlorination of undercoat agents has been promoted, and various alternative coating agents are being devised.

Among them, an aqueous coating agent which emits a small amount of solvent has been attracting attention, but this has a problem in adhesiveness to an adherend, water resistance, flexibility, etc. The development of coating agents is extremely difficult.

In order to solve these problems, the water-soluble resin, the water-dispersible resin, and the glass transition temperature (Tg) are -1.
There is a disclosure of a coating composition comprising an acrylic-modified butadiene-based polymer at 0 ° C. or lower and having good chipping resistance and high rust prevention (JP-A-4-142375).

There is also disclosed an aqueous coating composition comprising fine particles of a water-soluble resin and a core-shell structure having a different Tg (having a double structure consisting of a core having a high Tg and a shell having a low Tg). JP-A-59-136361).

Further, a water-dispersible alkyd resin mixed with an acrylic copolymer emulsion (Japanese Patent Publication No. 62-
No. 31748), there is proposed a method of improving the rust preventive property of a coating film by using a water-soluble or water-dispersible resin.

However, when a water-soluble resin or a water-dispersible resin is used, the viscosity of the coating composition becomes high, making it difficult to increase the concentration of the coating composition or locally curing the surface during the forced drying process of the coating film. However, there was a problem that the internal water content was poorly released, and therefore the coating film greatly contracted during drying, resulting in cracks and swelling.

Furthermore, when a water-soluble resin or a water-dispersible resin is used, the dryness of the coating film formed is poor, and when applied to line coating, it is necessary to slow the line speed in order to prevent swelling and cracking. There were problems such as deterioration in mass productivity.

Further, the water-soluble resin and the water-dispersible resin contain a large amount of hydrophilic functional groups, and the composition further contains a hydrophilic surfactant to prevent swelling and cracking as described above. Therefore, it is necessary to use a water-soluble auxiliary solvent such as a film forming agent or a film forming auxiliary agent. If these hydrophilic additives remain, they may impair the water-resistant adhesion of the dry coating film, which has the disadvantage of adversely affecting the physical properties of the coating film.

[0014]

As described above, in order to satisfy the rust prevention and the chipping resistance under the severe use conditions that generally require cold resistance, heat resistance, water resistance, salt resistance, etc., the conventional water-based coating agent is required. In that case, sufficient performance cannot be obtained and it has not been generalized.

In order to solve the above-mentioned problems, the present invention increases the flexibility of the coating by using a urethane resin and an acrylic resin which form a relatively flexible coating, and further improves the adhesiveness to the adherend. However, it is intended to improve chipping resistance and comprehensively improve the required performance as an undercoating agent.

[0016]

The present invention has been eagerly studied in order to solve such a problem, and as an undercoat resin composition for automobiles, the resin film strength is 3 Kg / cm ^{2 to} 150 Kg / cm at 100% modulus. A water-dispersible coating resin composition containing a urethane resin in the range of ² and a resin containing an acrylic resin copolymerized with an acid value in the range of 15 to ²⁰⁰ has excellent adhesiveness, chipping resistance, and They have found that they provide rust resistance and the like, and have completed the present invention.

That is, the physical properties of the resin film required as an undercoating agent for automobiles are appropriate flexibility, excellent anti-repulsion elasticity and strong adhesion to an adherend.

The urethane resin used in the present invention is preferably one whose resin film is relatively soft and has anti-repulsive elasticity, and is compounded with the acrylic resin used in the present invention to soften the film hardness of the acrylic resin. It is basically necessary to give elasticity.

The acrylic resin used in the present invention has an acid value of the resin component of 15 to 200. When the acid value is less than 15, the adhesion to the adherend is poor, and as the acid value increases, the adherence to the adherend becomes stronger, but the film becomes harder and the anti-repulsion elasticity tends to decrease. Have.

If the acid value of the resin component exceeds 200, the hydrophilicity becomes excessive and the synthetic property of emulsion polymerization deteriorates, which is not preferable.

According to the present invention, a urethane resin having a relatively soft and excellent anti-resilience property is blended with the acrylic resin of the present invention in a certain amount, so that water having proper flexibility and anti-resilience property can be firmly adhered to an adherend. A dispersible coating resin composition was found.

That is, the water-dispersible coating resin composition of the present invention comprises a resin component formed by copolymerization of a radical-polymerizable unsaturated monomer and a radical-polymerizable unsaturated monomer containing a carboxyl group. Acrylic resin [A] having an acid value in the range of 15 to 200, and resin film strength of 1
3% Kg / cm ^{2 to} 150 Kg / cm at 00% modulus
^The urethane resin [B] in the range of ² in solid content [A]:
[B] = A water-dispersible resin composition blended in a weight ratio of 80:20 to 10:90, further comprising a filler and various auxiliaries as usual, which is an undercoat agent for automobiles. As it has excellent chipping resistance, rust resistance after chipping, and adhesiveness, it also has good chipping resistance after a water resistance test.
Overall, we were able to bring out the performance superior to that of vinyl chloride plastisol undercoating agents.

The urethane resin used in the present invention has a resin film strength of 3 kg / cm ² at 100% modulus.
A commercially available product can be used as long as it is up to 150 Kg / cm ² .
For example Aizerakkusu S-1020 (100% ^{modulus, 6Kg / cm 2), S} -1040 (100% ^{modulus, 15Kg / cm 2), S} -2020 (100% ^{modulus, 20Kg / cm 2), S} -5050L (10
0% ^{modulus, 16Kg / cm 2), S} -1085C
(100% modulus, 15 Kg / cm ² ) (trade name, Hodogaya Chemical Co., Ltd.), Hydran HW-
111 (100% modulus, 32 Kg / cm ² ), H
W-301 (100% modulus, 15Kg / cm
² ), Bondik 1612 NSC (100% modulus, 15 Kg / cm ² ) (these product names, manufactured by Dainippon Ink and Chemicals, Inc.) and the like.

Further, as shown in the synthesis examples below, hydrophilicity is imparted by introducing an ionic group such as a carboxyl group into the side chain or terminal of the polyurethane resin polymer, and the polyurethane resin polymer is dispersed in water by self-emulsification. A self-emulsifying urethane resin synthesized by introducing a hydrophilic group such as ethylene oxide into a part of a polyol, which is a main raw material of polyurethane, to obtain a hydrophilic polyurethane resin and dispersing it in water can also be used. These urethane resins may be blended alone or as a mixture of two or more kinds.

The acrylic resin and urethane resin used in the present invention are mixed in a resin solid content of 80:20 to 10:90.
Good performance is obtained in (weight ratio). If the urethane resin weight ratio exceeds 90, the adhesion of the coating film to the adherend becomes insufficient. On the other hand, when it is less than 20, the desired flexibility and anti-repulsion elasticity cannot be obtained, and the product becomes brittle. In any case, the chipping resistance becomes extremely poor.

The acrylic resin used in the present invention can be synthesized by a known method, and two or more kinds of them can be mixed and used.

Further, in order to improve physical properties such as water resistance, a monomer having a plurality of radically polymerizable unsaturated groups in one molecule, or a radically polymerizable unsaturated monomer having mutually reactive functional groups is used. It may be used for intra-particle cross-linking during the polymerization process.

Further, by mixing and using the acrylic resin used in the present invention and a water-soluble or water-dispersible resin having a group capable of reacting with each other, a three-dimensional gel structure is formed between particles during baking and drying, resulting in water resistance, It is also possible to improve the drying property.

The main groups capable of reacting with each other which can be used in the present invention include an epoxy group and a carboxyl group, an epoxy group and an amino group, a blocked isocyanate group and a functional group having active hydrogen, a hydroxyl group or a carboxyl group. Examples include alkoxy melamine.

The radical-polymerizable unsaturated monomer and the unsaturated monomer having a carboxyl group constituting the acrylic resin used in the present invention have an acid value of 1 for the synthesized resin component.
There is no particular limitation as long as it is within the range of 5 to 200.

The radical-polymerizable unsaturated monomer is methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate,
Butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate,
Isodecyl acrylate, isodecyl methacrylate, lauryl acrylate, lauryl methacrylate, β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, acrylonitrile, methacrylonitrile, glycidyl methacrylate, and other acrylates, Methacrylate can be used, but is not limited to those listed here.

In addition, styrene, α-methylstyrene,
Vinyltoluene, vinyl acetate, etc. can also be used as a copolymerization component.

As the carboxyl group-containing radically polymerizable unsaturated monomer, acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid and the like can be used, but are not limited to those listed here. .

Both of the carboxyl group-containing radically polymerizable unsaturated monomers are one or two of these, respectively.
Mixtures of more than one can be used.

The method of synthesizing the acrylic resin according to the present invention by emulsion polymerization can be carried out by a method well known to those skilled in the art.

The acrylic resin according to the present invention has a temperature of 40 ° C to 8 ° C.
It is preferable to carry out emulsion polymerization at a low temperature of 0 ° C.

As the emulsifier that can be used in the emulsion polymerization of the acrylic resin, any of anionic, cationic and nonionic surfactants can be used. However, depending on the ionicity of the surfactant used in the polyurethane resin used in combination, I have to decide.

Further, in order to improve the water resistance of the coating film, it is possible to use a reactive emulsifier having an aryl group or a radically polymerizable unsaturated group.

As the reactive emulsifier, Latemur S-120 is used.
A, S-180A (trade name, manufactured by Kao Corporation), Aqualon HS-10, RN-20 (trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), Eleminol JS-2 (manufactured by Sanyo Kasei Co., Ltd.), etc. can give.

As the polymerization initiator, a common one such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, or a water-soluble azoamide compound can be used as a water-soluble substance, and a radical-polymerizable initiator is used. Examples of the polymerization initiator that is soluble in a saturated monomer include isobutyl peroxide, t-butyl peroxide, octanoyl peroxide, decanoyl peroxide,
Lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, azobiscyanovaleric acid and the like can be used, and these can also be synthesized by dissolving them in a monomer and dropping a previously emulsified monomer into water to carry out suspension polymerization.

In the water-dispersible coating resin composition of the present invention, the additives that can be added in addition to the above-mentioned resins include fillers and other auxiliaries. Calcium carbonate is generally used as the filler, but kaolin, diatomaceous earth, talc and the like can also be used.

Other optional additives include thickeners. To apply the prepared coating liquid to a constant film thickness without dripping, a viscosity of about 10,000 cps and thixotropy are required. For these purposes, hydroxyethyl cellulose, carboxymethyl cellulose, water-soluble polysaccharides (trade name, Kelzan, manufactured by Sansho Co., Ltd.), polyacrylic acid salts, associative thickeners, etc. as an organic system, and anhydrous silica as an inorganic system. , Bentonite, synthetic mica, metal soap and the like can be used.

In addition, a surfactant, a polymer surfactant, a water-soluble polymer compound or the like can be used as the wetting and dispersing agent.

A film-forming agent and a film-forming auxiliary agent are used to adjust the surface of the dried coating film and prevent cracks and small cracks. For this, it is common to use alcohol, alcohol ethers or the like. In addition, an antifreezing agent for emulsion, an antiseptic / antifungal bactericide, and the like may be added.

When the water-dispersible coating resin composition of the present invention is applied to an adherend, the dry coating film has a thickness of 300 to 1000.
It may be applied so that the thickness becomes μm.

The undercoat agent for automobiles has been conventionally coated by a spray method, and the water-dispersible coating resin composition of the present invention is preferably coated by an airless spray coating machine.

The dry heating condition of the water-dispersible coating resin composition of the present invention applied to an adherend is at least 90 ° C.
After preheating for 10 minutes at 20 ~ 30 at 130 ~ 140 ℃
It is good to dry and heat for a minute.

[0048]

The water-dispersible coating resin composition for an automobile undercoat according to the present invention has an acid value of the resin component of 15 to 200 in order to improve flexibility after film formation and adhesion to an adherend.
In a weight ratio of urethane resin is 3Kg / cm ² ~150Kg / cm ² acrylic resin and the resin film strength at 100% modulus in the range of 80: 20 to 10: characterized in that by mixing in a range of 90 It is possible to easily and firmly adhere to a metal surface or a metal coated surface, particularly to a thick-film cationic electrodeposition steel plate surface which is difficult to adhere (where adhesive strength is not obtained), by heat-drying.

The undercoat agent for automobiles using the water-dispersible coating resin composition of the present invention is easy to handle as well as conventional vinyl chloride plastisol, has good storage stability, and is extremely stable even when stored for a long time. No increase in viscosity is observed. Furthermore, there is no coloration during processing or by heat treatment after coating, and even if the topcoat paint is applied thinly, the discoloration does not occur. Therefore, even when it is applied to an automobile manufacturing line or the like, the existing equipment such as coating equipment and heating / drying equipment can be replaced without any improvement.

[0050]

EXAMPLES The present invention will be explained below with reference to synthesis examples, examples and test examples, but the present invention is not limited to these. The test method in the test example will be described later. Central part and% are weight.

[Production of Acrylic Resin Emulsion] Synthesis Example 1 340.0 parts of ion-exchanged water, Solvalite S-80 (trade name, anionic surfactant, manufactured by Kyoeisha Chemical Co., Ltd.)
1.2 parts was weighed into a 1-liter four-necked flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser, and heated to 70 ° C to 72 ° C under a nitrogen stream. Next, 1/5 weight of the following monomer mixed solution and 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide] (trade name, VA-086, manufactured by Wako Pure Chemical Industries, Ltd.)
12 parts of a polymerization initiator aqueous solution prepared by dissolving 0.90 parts in 60 parts of ion-exchanged water was added, and initial polymerization was carried out at 70 ° C. for 1 hour. Then, the remaining monomer mixture and 48 parts of the polymerization initiator aqueous solution were dropped into the flask over 3 hours.
After the dropping was completed, the mixture was aged at the same temperature for 2 hours.

[0052] Methyl methacrylate 120.0 parts of ethyl methacrylate 30.0 parts N- butyl acrylate 170.0 parts of 2-ethylhexyl methacrylate 64.0 parts 2-hydroxyethyl methacrylate 5.0 parts methacrylic acid 16.0 parts Total 400 .0 copy

The acid value of the acrylic resin emulsion thus obtained was 13.4 (resin acid value, 26.1),
The solid content was 51.2%.

Synthesis Example 2 375.0 parts of ion-exchanged water, Latemur S-180A 1
0.0 part was weighed in a 1-liter four-necked flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser, and heated to 55 ° C to 60 ° C under a nitrogen stream. Next, 1/3 weight of the following monomer mixed solution, 20.0 parts of a 5% aqueous solution of potassium persulfate, and 5.0% of a 5% aqueous solution of sodium metasulfite.
8 parts of an initiator aqueous solution mixed with 1 part was added and initial polymerization was carried out at 55 ° C. for 1 hour. Then, the remaining monomer mixed solution and 17 parts of the polymerization initiator aqueous solution were dropped into the flask over 3 hours. After the dropping was completed, the mixture was aged at the same temperature for 2 hours.

[0055] Methyl methacrylate 138.0 parts N- butyl acrylate 172.0 parts 40.0 parts Total 400.0 parts of 2-ethylhexyl acrylate 45.0 parts of 2-hydroxyethyl methacrylate 5.0 parts methacrylic acid

The acrylic resin emulsion thus obtained had an acid value of 32.7 (resin acid value, 65.2) and a solid content of 50.2%.

Synthetic Examples 3 to 10 Emulsion polymerization reactions were carried out in accordance with the synthetic method of Synthetic Example 1 at the monomer mixing ratios shown in Table 1 below to obtain respective acrylic resin emulsions.

[0058]

[Table 1]

[Production of Urethane Resin Emulsion] Synthesis Example 11 A four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a condenser was charged with 294 parts of polycarbonate diol (molecular weight 1958), and the pressure was reduced while stirring. The water was dehydrated by heating at 120 ° C below (-220 mmHg). The temperature inside the flask was lowered to 70 ° C, 600 parts of methyl ethyl ketone, 52 parts of diphenylmethane diisocyanate, and 0.06 part of dibutyltin dilaurate were charged under a nitrogen stream, and the mixture was reacted at 70 ° C to 75 ° C for 3 hours and 30 minutes.

Then, the internal temperature was lowered to 40 ° C., 7.8 parts of dimethylolpropionic acid was added, and the reaction was carried out at 70 ° C. to 75 ° C. for 4 hours. And polyoxyethylene polyoxypropylene block polymer (oxyethylene chain content 8%, propylene glycol molecular weight 3200) 7.
7 parts was added and reacted at the same temperature for 3 hours to obtain a highly viscous transparent resin liquid.

Furthermore, noniolite NS was added to the reaction solution.
-50 (trade name, nonionic surfactant, manufactured by Kyoeisha Chemical Co., Ltd.) was added, and the mixture was stirred at 70 ° C to 75 ° C for 30 minutes to obtain a transparent viscous solution. While lowering the temperature of the reaction solution to 55 ° C and stirring the mixture sufficiently, ion-exchanged water 34
0 part was gradually added to obtain a milky white dispersion liquid.

Finally, this was decompressed (-220 mmH
Methyl ethyl ketone was distilled off while stirring in g) at 55 ° C. for 4 hours. Thus, 598 g of a milky-white urethane resin emulsion having a solid content of 50% was obtained. The 100% modulus of the dry resin film of this product was 5.0 Kg / cm ² .

Synthesis Example 12 Using the same reaction apparatus as in Synthesis Example 11 above, a propylene oxide adduct of trimethylolpropane (average molecular weight 3000, acid value 5
300 parts of 6.1) are charged and 100 at 1 to 10 mmHg
After dehydration under reduced pressure at 120 ° C, the temperature was lowered to 40 ° C, 52.2 parts of tolylene diisocyanate was added, and the mixture was reacted at 80 ° C for 3 hours under a nitrogen stream to obtain a urethane prepolymer.

9 parts of dimethylolpropionic acid was reacted with this polymer under a nitrogen stream at 85 to 95 ° C. for 5 hours to obtain a carboxyl group-containing urethane prepolymer. This prepolymer was kept at 80 ° C., and Noniolite NS-50 (trade name, nonionic surfactant, manufactured by Kyoeisha Chemical Co., Ltd.) 1
The mixture was emulsified into 360 parts of ion-exchanged water containing 8 parts with a homomixer to obtain a milky white urethane resin emulsion having a solid content of about 50%. The 100% modulus of the dry film of this product was 4 Kg / cm ² .

Table 2 shows characteristic values of the urethane resin emulsion obtained in the above synthesis example and the commercially available urethane resin emulsion used in this test.

[0066]

[Table 2]

[Production of Water-Dispersible Coating Resin Composition] Example 1 Each emulsion resin, filler, and other additive components were charged in a kneader stirrer according to the formulation shown in Table 3 below, and kneaded at room temperature for 30 minutes, Then, the mixture was degassed under reduced pressure at room temperature to prepare a water-dispersible coating resin composition.

Next, the water-dispersible coating resin composition obtained above was treated with an airless spray coating machine at 150 m.
It was coated on a cationic electrodeposition steel sheet having a size of m × 75 mm and a thickness of 8 mm so that the dry film thickness was about 500 μm.

Further, the coated plate is kept at room temperature (25
C.) and then heated and dried at 90.degree. C. for 10 minutes and further at 130.degree. C. for 30 minutes by a blower dryer to prepare a test plate.

Examples 2 to 12 and Comparative Examples 1 to 8 Table 3 (Examples 1 to 12) and Table 4 (Comparative Examples 1 to 1) shown below.
A test plate was prepared by the above method according to the formulation of 8), and the results of the performance evaluation described below are also shown in Table 3 and Table 4.

[Evaluation Items]

Dryability: The dry film thickness on the cationic electrodeposition steel sheet is
Gradient coating is performed so as to have a thickness of 100 to 1200 μm, and the coating film is dried by air blowing at 90 ° C. for 10 minutes and further at 130 ° C. for 30 minutes.
Those having a film thickness of 500 μm and having no swelling or cracks are indicated by a circle, and any of them is indicated by a cross.

Adhesiveness: The coating film heated and dried under the above conditions is peeled off with a nail, and it is confirmed whether it is cohesive failure or interface failure. Cohesive failure is indicated by cf and interface failure is indicated by af.

Chipping resistance: A test piece heated and dried under the above conditions was dipped within 2 to 3 hours after drying, and as chipping resistance, dipped in warm water of 40 ° C. for 10 days, and after 10 minutes at 1.0 mm intervals. A test piece that has been cross-cut and dried at room temperature for 2 hours is evaluated by the nut dropping method (M-4 nut weight measurement).

Gravel resistance: A test piece heated and dried under the above conditions was exposed to room temperature (20 ° C.) within 2 to 3 hours after drying.
At 20 ° C., air pressure of 4.0 kg / cm ² , 500 g of No. 6 crushed stone, 5 times of damage caused by flying stones, then 7
Perform a salt spray test for 2 hours to check for rust. This is shown by the inspection of rust generation in the central portion 50 mm × 120 mm of the test piece.

Storage stability: The presence or absence of gelation at the beginning of the water-dispersible coating resin composition and after storage at 35 ° C. for 10 days is checked. Those not gelled are indicated by a circle, and those gelled are indicated by a cross.

[0077]

[Table 3]

[0078]

[Table 4]

[0079]

The coating film formed using the water-dispersible coating resin composition according to the present invention is excellent in performance as an undercoating agent.

Claims (3)

[Claims] 1. A water-dispersible coating resin composition containing a water-dispersible polymer, wherein the water-dispersible polymer contains an acrylic resin [A] and a urethane resin [B],
The weight ratio [A]: [B] is 80:20 to 10:90, and the water-dispersible coating resin composition is characterized. 2. The acrylic resin [A] is such that the radical-polymerizable unsaturated monomer and the radical-polymerizable unsaturated monomer containing a carboxyl group have an acid value of 15 to 200 (as an acid value of the resin component). The water-dispersible coating resin composition according to claim 1, wherein the water-dispersible coating resin composition is copolymerized within the range. 3. A urethane resin (B) is water-dispersible coating resin composition according to claim 1, characterized in that it comprises a film strength in the range of 3Kg / cm ² ~150Kg / cm ² at 100% modulus.