阅读说明：本技术 汽车用水溶性涂料盒 (Water-soluble paint box for automobile ) 是由 李颂伊 曹洙英 金成晙 李本伊 于 2018-05-24 设计创作，主要内容包括：本发明涉及汽车用水溶性涂料盒,具体涉及一种耐崩裂性及外观优秀的汽车用水溶性涂料盒,包含：第一组合物,包含第一核/壳微凝胶树脂、第一二聚体改性聚酯树脂及二聚体/(甲基)丙烯酸改性聚氨酯树脂；以及第二组合物,包含第二核/壳微凝胶树脂、第二二聚体改性聚酯树脂及(甲基)丙烯酸-改性聚氨酯树脂。(The present invention relates to a water-soluble paint cartridge for an automobile, and more particularly, to a water-soluble paint cartridge for an automobile having excellent chipping resistance and appearance, comprising: a first composition comprising a first core/shell microgel resin, a first dimer-modified polyester resin, and a dimer/(meth) acrylic-modified polyurethane resin; and a second composition comprising a second core/shell microgel resin, a second dimer-modified polyester resin, and a (meth) acrylic-modified polyurethane resin.)

1. A water-soluble paint cartridge for an automobile, comprising:

a first composition comprising a first core/shell microgel resin, a first dimer-modified polyester resin, and a dimer/(meth) acrylic-modified polyurethane resin; and

a second composition comprising a second core/shell microgel resin, a second dimer-modified polyester resin, and a (meth) acrylic-modified polyurethane resin.

2. The water-soluble paint cartridge for automobiles according to claim 1, wherein the first core/shell microgel resin is obtained through polymerization of a composition containing an alkyl acrylate having an alkyl group with a carbon number of 1 to 8, and the content of the alkyl acrylate is 50 weight percent or more and 80 weight percent or less based on the total weight of solid components contained in the composition.

3. The water-soluble paint cartridge for automobiles according to claim 1, wherein the second core/shell microgel resin is obtained through polymerization of a composition comprising an alkyl acrylate having an alkyl group with a carbon number of 1 to 8, and the content of the alkyl acrylate is 50 weight percent or more and 80 weight percent or less based on the total weight of solid components contained in the composition.

4. The water-soluble paint cartridge for automobiles according to claim 1, characterized in that the first dimer-modified polyester resin is obtained by polymerization of a composition containing a dimer acid, and the content of the dimer acid is 10 to 40 weight percent based on the total weight of solid components contained in the composition.

5. The water-soluble paint cartridge for automobiles according to claim 1, characterized in that the second dimer-modified polyester resin is obtained by polymerization of a composition containing a dimer acid, and the content of the dimer acid is 5 to 25 weight percent based on the total weight of solid components contained in the composition.

6. The water-soluble paint cartridge for automobiles according to claim 1, wherein the dimer/(meth) acrylic modified urethane resin is obtained by reacting a reaction product of a polyol and an isocyanate, one or more dimer acids, and one or more (meth) acrylates.

7. The water-soluble paint cartridge for automobiles according to claim 6, wherein the dimer/(meth) acrylic acid-modified polyurethane resin is obtained by adding 1 to 50 weight percent of the dimer acid based on 100 weight percent of the polyurethane resin.

8. The water-soluble paint cartridge for automobiles according to claim 1, wherein the dimer/(meth) acrylic modified polyurethane resin has a solid content of 30 to 50% by weight, a number average molecular weight of 8000 to 100000, a glass transition temperature of-10 to 30 ℃, and an acid value of 15 to 35mgKOH/g, based on the total weight of the dimer/(meth) acrylic modified polyurethane resin.

9. The water-soluble paint cartridge for automobiles according to claim 1, wherein the first composition further comprises a first curing agent, a first solvent, a first co-solvent, a first acid catalyst and a first pigment.

10. The water-soluble paint kit for automobiles according to claim 9, wherein the first composition comprises 5 to 40 weight percent of the first core/shell microgel resin, 1 to 10 weight percent of the first dimer-modified polyester resin, 2 to 20 weight percent of the dimer/(meth) acrylic-modified urethane resin, 2 to 10 weight percent of the first curing agent, 5 to 30 weight percent of the first solvent, 3 to 15 weight percent of the first co-solvent, 0.1 to 2 weight percent of the first acid catalyst, and 1 to 30 weight percent of the first pigment.

11. The water-soluble paint cartridge for automobiles according to claim 1, wherein the second composition further comprises a second curing agent, a second solvent, a second co-solvent, a second acid catalyst and a second pigment.

12. The water-soluble paint kit for automobiles according to claim 11, wherein the second composition comprises 5 to 40 weight percent of the second core/shell microgel resin, 1 to 10 weight percent of the second dimer-modified polyester resin, 2 to 20 weight percent of the (meth) acrylic acid-modified urethane resin, 2 to 10 weight percent of the second curing agent, 5 to 30 weight percent of the second solvent, 3 to 15 weight percent of the second co-solvent, 0.1 to 2 weight percent of the second acid catalyst, and 1 to 30 weight percent of the second pigment.

Technical Field

The present invention relates to a water-soluble paint cartridge for an automobile, and more particularly, to a water-soluble paint cartridge for an automobile having excellent chipping resistance and appearance.

Background

In recent years, the restriction of Volatile Organic Compounds (VOCs) for global environmental protection is being strengthened, and thus the development of water-soluble coatings is actively proceeding.

A three-Coat two-Bake (3Coat2Bake, 3C2B) automobile coating system, which is commonly used as an automobile coating system, is the most common automobile coating system, and comprises the steps of coating an electrophoretic paint on an automobile body, coating an intermediate Coat on the electrophoretic paint through an intermediate coating process, curing the electrophoretic paint at a temperature of 140-150 ℃ for 20-30 minutes, continuously coating a surface primer (top base Coat) and a surface varnish (top clear Coat) on the electrophoretic paint, and drying the electrophoretic paint at a temperature of 140-150 ℃ for 20-30 minutes.

Recently, however, automobile manufacturers have been more inclined toward environmentally friendly and economical coating systems, and thus have developed various coating systems. For example, in a coating method using a low-temperature-curing and High-solid water-soluble coating composition, the composition is cured at a low temperature to provide a High solid (High solid) and also to impart High impact resistance to a coating film, and the baking temperature is lowered to increase the solid content, thereby providing an effect of saving process costs and energy.

The water-soluble multi-layer coating method is a coating technique generally called "water-soluble three-Coat one-Bake (3Coat1Bake, 3C 1B)", and is economical because it can remove an essential intermediate Coat baking step (completely curing at a temperature of 140 to 150 ℃ for 20 to 30 minutes) in a three-Coat two-Bake coating system by making the intermediate Coat and the surface primer partially water-soluble to minimize the use of organic compounds, thereby realizing an environmentally friendly coating technique.

Thus, the three-coat one-bake coating omits a middle-coat baking process (complete curing at the temperature of 140-150 ℃ for 20-30 minutes), and only needs to be dried by hot air at the temperature of 50-80 ℃ for 2-3 minutes to coat the surface primer and the surface varnish, so that the three-coat one-bake coating has the advantage of not needing a large amount of operation cost and energy, and the research on the surface primer and the surface varnish is continued.

Disclosure of Invention

Technical problem

An object of the present invention is to provide a water-soluble paint cartridge for an automobile, which is applicable to a three-coat one-bake coating method, in which an uncured coating film and a primer film do not mix with each other and which has excellent smoothness and which can form a coating film having excellent water resistance, chipping resistance and appearance.

Technical scheme

In order to achieve the object, the present invention provides a water-soluble paint cartridge for an automobile, comprising: a first composition comprising a first core/shell microgel resin, a first dimer-modified polyester resin, and a dimer/(meth) acrylic-modified polyurethane resin; and a second composition comprising a second core/shell microgel resin, a second dimer-modified polyester resin, and a (meth) acrylic-modified polyurethane resin.

Effects of the invention

According to the present invention, by coating an automobile using an automobile water-soluble paint cartridge, energy consumption in the coating process can be reduced and CO can be reduced₂The coating film can be formed with excellent smoothness, water resistance, chipping resistance and appearance while saving coating equipment and maintenance cost and space of the coating line.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

The present invention will be described in further detail below.

The invention provides a water-soluble paint cartridge for an automobile.

The water-soluble paint cartridge of the present invention comprises a first composition and a second composition as described below in detail.

1. First composition

The first composition contained in the water-soluble paint kit of the present invention comprises a first core/shell microgel resin, a first dimer-modified polyester resin, and a dimer/(meth) acrylic-modified polyurethane resin.

The first core/shell microgel resin contained in the first composition is a component relating to overall physical properties, for example, appearance of a coating film, interlayer permeation resistance, leveling property, wettability, adhesion, water resistance, and the like.

The first core/shell microgel resin may be synthesized by polymerizing core-forming unsaturated monomers with shell-forming unsaturated monomers by conventional polymerization methods.

The unsaturated monomer forming the core may be one or more unsaturated monomers selected from the group consisting of acrylic acid, methacrylic acid, alkyl acrylates having an alkyl group of 1 to 8 carbon atoms, alkyl methacrylates having an alkyl group of 1 to 4 carbon atoms, aromatic vinyl compounds and vinyl cyanide compounds, hydroxyalkyl acrylates and hydroxyalkyl methacrylates having an alkyl group of 5 to 8 carbon atoms and containing one or more hydroxyl groups. For example, the unsaturated monomer may be selected from one or more of the group consisting of styrene, vinyl toluene, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, methyl methacrylate, acrylic acid, methacrylic acid, 2-ethylhexyl methacrylate, 1, 6-hexanediol diacrylate, and triallyl isocyanurate.

The unsaturated monomer forming the shell may be one or more unsaturated monomers selected from the group consisting of acrylic acid, methacrylic acid, alkyl acrylate having an alkyl group of 1 to 8 carbon atoms, alkyl methacrylate having an alkyl group of 1 to 4 carbon atoms, aromatic vinyl compounds, vinyl cyanide compounds, hydroxyalkyl acrylate and hydroxyalkyl methacrylate having an alkyl group of 5 to 8 carbon atoms and containing one or more hydroxyl groups. For example, the unsaturated monomer may be selected from at least one of the group consisting of acrylic acid, methacrylic acid, maleic acid, styrene, vinyl toluene, butyl acrylate, butyl methacrylate, ethyl acrylate, methyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, aryl methacrylate, 1, 6-hexanediol diacrylate.

The first core/shell microgel resin is obtained by polymerization of a composition for forming a first core/shell microgel resin, which includes alkyl acrylate having an alkyl group with a carbon number of 1 to 8, such as butyl acrylate, among a plurality of unsaturated monomers for forming the core and the shell as described above, and at this time, the content of the alkyl acrylate is 50 weight percent or more and 80 weight percent or less based on the total weight of solid components included in the composition for forming a first core/shell microgel resin. In the case of less than 50 weight percent, the appearance of the coating film becomes poor and the layer separation feeling of the coating film may be insufficient, and in the case of more than 80 weight percent, the appearance of the coating film becomes poor and chipping resistance, adhesion of the coating film may become poor.

As the first core/shell microgel resin, a first core/shell microgel resin having a solid content of 30 to 70% by weight, an acid value of 5 to 60mgKOH/g, a glass transition temperature of-15 to 20 ℃ and a particle size of 50 to 200nm, based on the total weight of the resin, may be used.

In the case where the solid content is less than 30 weight percent, based on the total weight of the first core/shell microgel resin, the drying of the coated film becomes slow and the appearance may be deteriorated, and in the case where it is more than 70 weight percent, the appearance may be deteriorated, the gloss may be decreased, and the adhesion may be decreased due to the rapid drying of the coated film.

In the case where the acid value of the first core/shell microgel resin is less than 5mgKOH/g, the dispersibility of the pigment and the storage stability of the coating may be reduced, in the case where the acid value is greater than 60mgKOH/g, the water resistance may be reduced, in the case where the glass transition temperature is less than-15 ℃, the hardness may be reduced, in the case where it is greater than 20 ℃, the adhesion may be reduced, in the case where it is smaller than 50nm, the solid content of the water-soluble paint cartridge may be reduced and sagging (sagging) may occur, and in the case where it is larger than 200nm, the appearance may be deteriorated.

Such first core/shell microgel resin may be included in an amount of 5 to 40 weight percent, preferably 10 to 35 weight percent, more preferably 20 to 30 weight percent, based on 100 weight percent of the first composition, but is not limited thereto.

However, if the content of the first core/shell microgel resin in the first composition is less than 5% by weight, the coating film forming ability, drying property, mechanical properties, and the like may be deteriorated, and if it exceeds 40% by weight, the coating film may be deteriorated in wettability and leveling property, and thus the appearance of the coating film may be deteriorated, and the chipping resistance, impact resistance, and the like may be deteriorated.

The first dimer-modified polyester resin contained in the first composition is a component relating to physical properties such as leveling property, wettability, adhesion property, water resistance, impact resistance, and chipping resistance.

The first dimer-modified polyester resin is obtained by polymerization of a composition containing a dimer acid, and preferably, the content of the dimer acid is added in an amount of 10 to 40 weight percent based on the total weight of solid components contained in the composition, and if less than 10 weight percent, the improvement in chipping resistance is slight, and if more than 40 weight percent, the water resistance and compatibility may be decreased.

The first dimer-modified polyester resin may be synthesized by a conventional polymerization method. Specifically, it can be obtained by polycondensation of dicarboxylic acid and polyhydric alcohol. The dicarboxylic acid may be a dicarboxylic acid comprising a dimer acid, and the polyol may be a polyol comprising a reduced diol of the dimer acid. Preferably, it may be a polyester resin obtained by reacting both terminal hydroxyl groups of a product obtained by polycondensation reaction of 50 weight percent of a component containing a dicarboxylic acid of a dimer acid and 50 weight percent of a polyol component containing a reducing diol of the dimer acid with an acid anhydride. Among them, dimer acid (dimer acid) may be a dicarboxylic acid obtained by dimerizing unsaturated fatty acid (specifically, unsaturated fatty acid having 14 to 22 carbon atoms, such as stearic acid).

In the dimer-modified polyester resin, any one selected from the group consisting of succinic acid, adipic acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, tetrachlorophthalic acid, cyclohexanedicarboxylic acid, azelaic acid, 1, 10-decanedicarboxylic acid, and combinations thereof can be used as the dicarboxylic acid other than the dimer acid, and any one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, 1, 3-propanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 2-ethyl-1, 3-hexanediol, 1, 9-nonanediol, 1, 10-decanediol, propylene glycol, 1, 4-cyclohexanedimethanol, 1, 4-decanediol, and combinations thereof can be used as the polyol component other than the reducing diol of the dimer acid, Neopentyl glycol, 2-butyl-2-ethyl-1, 3-propanediol, 2-diethyl-1, 3-propanediol, 1, 4-cyclohexanedimethanol, 1, 3-cyclohexanedimethanol, hydrogenated bisphenol A, and combinations thereof.

The acid anhydride may be any one selected from the group consisting of 1, 3, 4-cyclopentanetricarboxylic anhydride, benzenetricarboxylic anhydride (1, 2, 3-benzenetricarboxylic anhydride, trimellitic anhydride (1, 2, 4-benzenetricarboxylic anhydride, etc.), naphthalenetricarboxylic anhydride (1, 2, 4-naphthalenetricarboxylic anhydride, 1, 4, 5-naphthalenetricarboxylic anhydride, 2, 3, 6-naphthalenetricarboxylic anhydride, 1, 2, 8-naphthalenetricarboxylic anhydride, etc.), 3, 4, 4 '-benzophenone tricarboxylic anhydride, 3, 4, 4' -biphenyl ether tricarboxylic anhydride, 3, 4, 4 '-biphenyl tricarboxylic anhydride, 2, 3, 2' -biphenyl tricarboxylic anhydride, 3, 4, 4 '-biphenyl methane tricarboxylic anhydride, 3, 4, 4' -biphenyl sulfone tricarboxylic anhydride, and a combination thereof.

For example, as the first dimer-modified polyester resin, a first dimer-modified polyester resin having a solid content of 60 to 90 weight percent, a number average molecular weight of 1000 to 4000(g/mol), and a glass transition temperature of-40 to-20 ℃ based on the total weight of the resin may be used.

In the case where the solid content is less than 60 weight percent, water resistance may decrease, in the case where it is more than 90 weight percent, cratering of a coating film may be caused, in the case where it is less than 1000 number average molecular weight, chipping resistance and impact resistance may decrease, in the case where it is more than 4000 number average molecular weight, appearance may deteriorate, in the case where it is less than-40 ℃ glass transition temperature, hardness may decrease, and in the case where it is more than-20 ℃ impact resistance and chipping resistance may decrease, based on the total weight of the first dimer-modified polyester resin. Also, the first dimer-modified polyester resin may have an acid value of 5mgKOH/g to 40 mgKOH/g. In the case where the acid value of the dimer-modified polyester resin is less than 5mgKOH/g, the stability of the first composition may be deteriorated due to the decrease in water dispersibility, and in the case where it is more than 40mgKOH/g, the appearance of the coating film may be deteriorated and the water resistance may be decreased.

Such first dimer-modified polyester resin may be 1 to 10 weight percent, more specifically, 2 to 8 weight percent or 2 to 5 weight percent, based on 100 weight percent of the first composition, but is not limited thereto.

However, if the content of the first dimer-modified polyester resin in the first composition is less than 1% by weight, the appearance is deteriorated and there is a possibility that the adhesion and chipping resistance of the coating film are lowered, and if it exceeds 10% by weight, there is a possibility that the water resistance and hardness of the coating film are lowered.

The dimer/(meth) acrylic modified urethane resin contained in the first composition has an effect of affecting physical properties such as leveling property, wettability, adhesion property, water resistance, impact resistance, and chipping resistance.

The dimer/(meth) acrylic modified polyurethane resin can be obtained by a conventional polymerization method. Specifically, the dimer/(meth) modified polyurethane resin can be obtained by reacting a polyurethane prepolymer, which is a reaction product of a polyol and an isocyanate, with one or more dimer acids and one or more (meth) acrylates.

Specifically, the modified polyurethane resin may be prepared by including 60 to 80 weight percent of polyurethane prepolymer, 1 to 50 weight percent of dimer acid, and 20 to 40 weight percent of (meth) acrylate, based on 100 weight percent of the dimer/(meth) acrylic acid-modified polyurethane resin. In the case where the content of the polyurethane prepolymer is less than 60 weight percent, a large amount of impurities may be generated due to a decrease in compatibility, in the case where the content of the polyurethane prepolymer is more than 80 weight percent, hardness may be decreased, in the case where the content of dimer acid is less than 1 weight percent, chipping resistance may be decreased, in the case where the content of dimer acid is more than 50 weight percent, appearance may be deteriorated, in the case where the content of (meth) acrylate is less than 20 weight percent, hardness may be decreased, and in the case where the content of (meth) acrylate is more than 40 weight percent, a large amount of impurities may be generated and adhesion may be decreased.

For the dimer/(meth) acrylic acid-modified polyurethane resin, a dimer/(meth) acrylic acid-modified polyurethane resin having a solid content of 30 to 40% by weight, a number average molecular weight of 8000 to 100000, a glass transition temperature of-10 to 30 ℃ and an acid value of 15 to 35mgKOH/g can be used, based on the total weight of the dimer/(meth) acrylic acid-modified polyurethane resin.

When the solid content is less than 30% by weight, the coating film forming ability and chipping resistance may decrease, when the content is more than 40% by weight, the appearance may deteriorate due to drying delay, when the number average molecular weight is less than 8000, when the content is more than 100000, the appearance may deteriorate, when the glass transition temperature is less than-10 ℃, the hardness may decrease, when the glass transition temperature is more than 30 ℃, the adhesion may decrease, when the acid value is less than 15mgKOH/g, the appearance may deteriorate and the storage stability may decrease, and when the acid value is more than 35mgKOH/g, the water resistance may decrease.

Such a dimer/(meth) acrylic modified urethane resin may be contained in an amount of, for example, 2 to 20% by weight, more specifically, 3 to 18% by weight or 4 to 8% by weight, based on 100% by weight of the first composition, but is not limited thereto. When the content of the dimer/(meth) acrylic modified urethane resin in the first composition is less than 2% by weight, the coating film-forming ability and the mechanical properties such as chipping resistance and impact resistance may be deteriorated, and when it exceeds 20% by weight, the drying property of the coating film may be lowered to deteriorate the appearance.

The first composition of the present invention may further include one or more additives selected from the group consisting of a first curing agent, a first solvent, a first acid catalyst, a first pigment, a first co-solvent, a wetting agent, an ultraviolet absorber, a neutralizing agent, a tackifier, and a defoaming agent.

The first curing agent functions as a crosslinking reaction when curing the first core/shell microgel resin, the first dimer-modified polyester resin, and the dimer/(meth) acrylic acid-modified polyurethane resin.

The first curing agent may be a melamine resin, and the hydroxyl groups of the plurality of resins may be crosslinked with the methoxy groups of the melamine resin, or the hydroxyl groups of the plurality of resins may be crosslinked with the methoxy groups and imino groups of the melamine resin. The melamine resin may be synthesized directly by a known method or may be a commercially available product such as Cymel-325, Cymel-327, Cymel-350, and Cymel-385 from Cytec, Resimene HM-2608, Resimene 718, and Resimene 717 from Enlish (INEOS).

The content of the first curing agent may be, for example, 2 to 10 weight percent, more specifically, 3 to 9 weight percent or 4 to 7 weight percent, based on 100 weight percent of the first composition, but is not limited thereto.

However, in the case where the content of the first curing agent in the first composition is less than 2% by weight, water resistance of the coating film may be deteriorated and adhesion of the coating film may be reduced due to the remaining of non-crosslinked hydroxyl groups in the coating film, and in the case where it is more than 10% by weight, the coating film tends to be broken due to self-polymerization of the unreacted curing agent remaining in the coating film, so chipping resistance, impact resistance and bending resistance of the coating film may be reduced, and there may also be caused a problem in thermal storage stability of a paint can.

As the first solvent that may be further included in the first composition, distilled water may be used, and may be 5 to 30 weight percent, more specifically, 8 to 27 weight percent or 10 to 25 weight percent, based on 100 weight percent of the first composition, but is not limited thereto. In the case where the content of water in the first composition is less than 5 weight percent, there may be a problem of appearance deterioration such as appearance of stains due to a decrease in rheology, and in the case where it is more than 30 weight percent, there may be a problem of sagging and reduction in masking property.

The first co-solvent affects the smoothness of the coating film, and imparts storage stability to the coating material, lowers the minimum coating film formation temperature, and contributes to solvent volatilization when used in coating work, and may be, for example, one or more selected from the group consisting of propylene glycol, N-methyl-2-pyrrolidone, N-propanol, isopropanol, N-butanol, propylene glycol monomethyl ether, butylene glycol, hexylene glycol, 2-ethylhexanol, and butyl carbitol (diethylene glycol monobutyl ether), and may be used in an amount of, for example, 3 to 15 wt% based on 100 wt% of the first composition. If, in the case of less than 3 weight percent, the appearance may be deteriorated, and in the case of more than 15 weight percent, the hardness may be decreased due to the delay of drying.

The thickener prevents the fluidity of the water-soluble paint cartridge and contributes to the painting workability and the coating film roughness, and may be, for example, one or more selected from the group consisting of alkali-soluble thickeners, acrylic thickeners, polyurethane thickeners, fused silica, cellulose thickeners, and bentonite thickeners, and may be used in an amount of, for example, 0.15 to 7.5 wt% based on 100 wt% of the first composition. If, at less than 0.15 weight percent, Sagging (Sagging) can occur, and at greater than 7.5 weight percent, the appearance can deteriorate.

The defoaming agent is used to suppress bubbles generated during all processes when the first composition is prepared, for example, after a coating operation and material arrival, or to rapidly remove bubbles, and may be, for example, one or more selected from the group consisting of fluorine-modified silicone defoaming agents, silicone emulsions, organic modified silicone defoaming agents, hydrophobic silica, and mineral oil, and may be used in an amount of 0.15 to 3 wt% based on 100 wt% of the first composition. In the case of less than 0.15 weight percent, the appearance may be deteriorated due to poor defoaming property, and in the case of more than 3 weight percent, the appearance may be deteriorated due to generation of craters (crating) in the coating film.

The first acid catalyst is a catalyst for promoting a curing reaction of the acrylic emulsion and the polyester resin with the melamine resin to increase the compactness of the coating film, and a product obtained by polymerizing a sulfonic acid selected from the group consisting of p-toluenesulfonic acid (p-TSA), dinonylnaphthalene sulfonic acid (DNNSA), naphthalene disulfonic acid (DNNDSA), dodecylbenzene sulfonic acid, and fluorosulfonic acid with an amine or epoxy may be used. The first acid catalyst may be present in an amount of 0.1 to 2 weight percent, based on 100 weight percent of the first composition. In the case of less than 0.1 weight percent, the hardness of the coating film decreases, and in the case of more than 2 weight percent, the water resistance may decrease.

The first pigment that may be further contained in the first composition may use pigment components that are generally used in coatings for automobiles without limitation, and for example, an effect pigment that imparts a metallic effect to a coating film, a coloring pigment that imparts color and a masking effect by being used in combination with a coating film forming substance, or a combination thereof may be used. Examples of the effect pigment include an aqueous aluminum flake, an aluminum paste, a mica pigment, or a combination thereof. Examples of the coloring pigment include an inorganic pigment of an oxidation type, a polycyclic organic pigment containing Azo (Azo) or Vat pigment, an organic pigment of an anthraquinone type, or a mixture thereof.

The content of the first pigment may be 1 to 30 weight percent, more specifically, may be 3 to 27 weight percent or 5 to 25 weight percent, based on 100 weight percent of the first composition, but is not limited thereto. In the case where the content of the pigment in the first composition is less than 1 weight percent, the hiding power of the coating film may be problematic, and in the case where it is more than 30 weight percent, there may be problems in that the stability of the coating material is lowered and the dispersibility of the pigment is lowered.

The wetting agent, the ultraviolet absorber, and the neutralizer that may be contained in the first composition may be any known wetting agent, ultraviolet absorber, and neutralizer used in coating materials.

2. Second composition

The second composition contained in the water-soluble paint kit of the present invention comprises a second core/shell microgel resin, a second dimer-modified polyester resin and a (meth) acrylic-modified polyurethane resin.

The second core/shell microgel resin is the same as or different from the first core/shell microgel resin included in the first composition, and the second dimer-modified polyester resin is the same as or different from the first dimer-modified polyester resin included in the first composition. With respect to the second core/shell microgel resin and the second dimer-modified polyester resin, the foregoing description with respect to the first core/shell microgel resin and the first dimer-modified polyester resin, respectively, may be applied.

However, preferably, the second core/shell microgel resin is obtained through a polymerization reaction of a composition for forming the second core/shell microgel resin, which includes alkyl acrylate having an alkyl group with a carbon number of 1 to 8 among a plurality of unsaturated monomers for forming the core and the shell, for example, ethyl acrylate.

The second dimer-modified polyester resin is obtained by polymerization of a composition containing a dimer acid, and preferably, the content of the dimer acid may be added in an amount of 5 to 25% by weight, based on the total weight of solid components contained in the composition containing the dimer acid, and if less than 5% by weight, the effect of improving chipping resistance is slight, and if more than 25% by weight, water resistance and compatibility may be deteriorated.

The second composition may further include one or more additives selected from a second curing agent, a second solvent, a second acid catalyst, a second pigment and a second cosolvent, a wetting agent, an ultraviolet absorber, a neutralizer, a tackifier, and a defoaming agent.

The second curing agent, the second solvent, the second acid catalyst, the second pigment and the second co-solvent, the wetting agent, the ultraviolet absorber, the neutralizing agent, the tackifier and the defoaming agent, which are additives that may be further included in the second composition, may be the same as or different from the first curing agent, the first solvent, the first acid catalyst, the first pigment, the first co-solvent, the wetting agent, the ultraviolet absorber, the neutralizing agent, the tackifier and the defoaming agent, which are additives that may be further included in the first composition. The descriptions of the first curing agent, the first solvent, the first acid catalyst, the first pigment, the first cosolvent, the humectant, the ultraviolet absorber, the neutralizer, the tackifier, and the defoamer may be applied to the second curing agent, the second solvent, the second acid catalyst, the second pigment, the second cosolvent, the neutralizer, the tackifier, and the defoamer, respectively.

Next, the (meth) acrylic acid-modified urethane resin contained in the second composition will be described.

The (meth) acrylic acid-modified polyurethane resin has an effect on physical properties such as leveling property, wettability, adhesion property, water resistance, impact resistance, chipping resistance and the like.

The (meth) acrylic-modified urethane resin may be a modified urethane resin obtained by reacting a polyol and a urethane prepolymer, which is a reaction product of isocyanate, with one or more (meth) acrylates. Specifically, the (meth) acrylic acid-modified urethane resin may be prepared to include 60 to 80 weight percent of the urethane prepolymer, and 20 to 40 weight percent of the (meth) acrylic acid ester, based on 100 weight percent of the urethane resin.

In the case where the polyurethane prepolymer is less than 60 weight percent, impact resistance may be reduced, in the case where it is more than 80 weight percent, chipping resistance may be reduced, and in the case where it is less than 20 weight percent, hardness may be reduced, and in the case where it is more than 40 weight percent, adhesion may be reduced.

In the preparation of the polyurethane prepolymer, the polyol may be selected from the group consisting of polyester polyol, polycarbonate polyol, polyether polyol and combinations thereof, the isocyanate may be selected from the group consisting of isophorone diisocyanate, 1, 6-hexamethylene diisocyanate, 4-diisocyanatocyclohexyl methane and combinations thereof, and the isocyanate may be selected from the group consisting of dimethylolpropionic acid, dimethylolbutyric acid and combinations thereof having a monofunctional carboxylic acid, and the (meth) acrylate may be selected from the group consisting of methyl methacrylate, butyl methacrylate, ethyl acrylate, n-butyl acrylate, aryl acrylate, 1, 6-hexanediol methacrylate and combinations thereof.

As the (meth) acrylic acid-modified polyurethane resin, a (meth) acrylic acid-modified polyurethane resin having a solid content of 30 to 60% by weight, a number average molecular weight of 8000 to 100000, an acid value of 15 to 35mgKOH/g, and a particle size of 50 to 200nm can be used, based on the total weight of the resin.

When the solid content is less than 30% by weight based on the total weight of the (meth) acrylic-modified urethane resin, the coating film forming ability and chipping resistance may be deteriorated, when it exceeds 60% by weight, the appearance may be deteriorated due to delayed drying, when the number average molecular weight is less than 8000, the appearance may be deteriorated when it exceeds 100000, the storage stability may be deteriorated when it is less than 15mgKOH/g, when it exceeds 35mgKOH/g, the water resistance may be deteriorated when it is less than 50nm, and when it exceeds 200nm, the coating solid content may be deteriorated.

For example, the amount of the (meth) acrylic-modified urethane resin contained in the second composition may be 2 to 20 weight percent, more specifically, 3 to 18 weight percent or 4 to 8 weight percent, based on 100 weight percent of the second composition, but is not limited thereto. When the content of the (meth) acrylic-modified urethane resin in the second composition is less than 2% by weight, the coating film-forming ability and the mechanical properties such as chipping resistance and impact resistance may be deteriorated, and when it exceeds 20% by weight, the drying property of the coating film may be lowered, thereby deteriorating the appearance.

3. Water-soluble paint box

The water-soluble paint kit of the present invention comprising the first composition and the second composition can be used in a painting method for automobiles which is generally used in an automobile painting line.

For example, the automobile coating method that can be used in the present invention is a three-coat one-bake coating method in which coating is performed on an electrophoretic surface using the first composition and the second composition as a first primer and a second primer on an automobile coating line, intermediate hot air drying is performed for 2 to 7 minutes at a temperature of 50 to 80 ℃ on the first primer and the second primer, and a clear coat is coated thereon and then cured by baking at one time. Wherein the second primer may further comprise effect pigments, as desired.

In the automobile coating method, the first composition is used as the first primer, and the second composition is used as the second primer, but the present invention is not limited thereto.

If the first composition and the second composition are used as the first primer or the second primer, it is possible to overcome the deterioration of the appearance of the coating film and to have excellent mechanical physical properties by minimizing the layer mixing (layer mixing) phenomenon between the first primer and the second primer or between the primer and the clear coat.

Such a first composition is contained in the first primer or the second primer in an amount of 50 to 100 weight percent based on the total weight of the first primer or the second primer, and if less than 50 weight percent, appearance may be deteriorated due to a mixed layer.

The second composition is contained in the first primer or the second primer in an amount of 50 to 100 weight percent based on the total weight of the first primer or the second primer, and if less than 50 weight percent, appearance may be deteriorated due to intermixing.