KR20200028662A - Clear paint composition - Google Patents

Abstract

The present invention relates to a transparent paint composition. The transparent paint composition of the present invention comprises: 25 to 35 parts by weight of an acrylic polyol resin; 40 to 50 parts by weight of two types of polyester polyol resins having different solid content; 0.1 to 1 part by weight of a curing accelerator; and 20 to 30 parts by weight of a solvent, thereby forming a coating film having excellent appearance and scratch resistance while maintaining excellent physical properties such as water resistance and weather resistance.

Description

Transparent paint composition {Clear paint composition}

The present invention relates to a transparent coating composition.

As automobiles are becoming more sophisticated, the level and demands of consumers are gradually increasing, and scratches, which are mentioned as customer complaints every year, are essential items that must be improved in order to improve and enhance the appearance. In order to prevent scratching of automotive exterior parts, a multi-layer coating of a primer-base-transparent coating composition is coated on a material such as ABS, PC + PBT using a scratch-resistant paint.

In addition, high-gloss exterior black painted parts are increasing to improve the quality of appearance. High-gloss specifications tend to generate a lot of scratches, especially scratches that occur in black colors have the disadvantage of being easily visible to the naked eye.

Thus, to improve the scratch resistance of the transparent paint, a method of increasing the hardness of the coating film to prevent scratching is known by using an acrylic resin having a high glass transition temperature (Tg), but such a method is vulnerable to the impact resistance of the coating film. there is a problem. In addition, a method of preventing scratches by increasing the hardness by mixing a reinforcing filler such as silica has also been developed, but these methods have limitations in realizing high gloss.

Accordingly, there is a continuing need for the development of a transparent coating that can form a coating film having excellent scratch resistance (especially, while exhibiting excellent scratch resistance even in a high gloss black color).

The present invention is to provide a transparent coating composition excellent in appearance and scratch resistance while maintaining excellent physical properties such as water resistance and weather resistance of the formed coating film.

In order to achieve the above object, the present invention is 25 to 35 parts by weight of acrylic polyol resin, 40 to 50 parts by weight of two types of polyester polyol resins having different solid content, 0.1 to 1 part by weight of curing accelerator, and 20 to 20 parts by weight of solvent. It provides a transparent coating composition comprising 30 parts by weight.

When the transparent coating composition of the present invention is used, it is possible to form a coating film excellent in appearance and scratch resistance while maintaining excellent physical properties such as water resistance and weather resistance. Therefore, even when used for black coating, while maintaining high gloss, it has excellent scratch resistance and can exhibit the effect of improving product quality.

Hereinafter, the present invention will be described in detail.

The transparent coating composition of the present invention includes 25 to 35 parts by weight of acrylic polyol resin, 40 to 50 parts by weight of two types of polyester polyol resins having different solid content, 0.1 to 1 part by weight of curing accelerator, and 20 to 30 parts by weight of solvent do.

Acrylic polyol resin

The transparent coating composition of the present invention contains an acrylic polyol resin as a main component. The acrylic polyol resin as described above may impart strength to a coating film formed using the transparent coating composition.

As the monomer of the acrylic polyol resin, an acrylic monomer having at least one hydroxy group may be used, but is not limited thereto, for example, 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (Meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylic Rate, ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, or mixtures thereof. The acrylic polyol resin formed using the monomer may be a resin formed of one of the monomers, or a blend or copolymer thereof.

In addition, the acrylic polyol resin has a solids content of 35 to 70% by weight, for example 40 to 65% by weight, 45 to 60% by weight, and another example is 50 to 55% by weight, and the weight average molecular weight is 8,000 to 14,000 g / mol, for example, 8,500 to 13,500 g / mol, another example may be 9,000 to 13,000 g / mol, or 10,000 to 12,000 g / mol. If the solid content and weight average molecular weight of the acrylic polyol resin is less than the above range, the appearance due to deterioration of the scalpability may be lowered, and if the solid content and weight average molecular weight of the acrylic polyol resin exceeds the above range, the smoothness of the coating film This can degrade.

The acrylic polyol resin may have a hydroxyl value of 110 to 150 mgKOH / g, for example, 115 to 135 mgKOH / g, 120 to 135 mgKOH / g, or 125 to 135 mgKOH / g. When the hydroxyl value of the acrylic polyol resin is less than 110 mgKOH / g, the dryness of the coating film may be lowered and the hardness may be lowered. When the hydroxyl value of the acrylic polyol resin is more than 150 mgKOH / g, the coating film is not sufficiently cured to thereby be water-resistant and scratch-resistant. Castle and weather resistance may deteriorate.

The glass transition temperature (Tg) of the acrylic polyol may be preferable in terms of physical properties and scratch resistance of the coating film on which it is formed to use 20 to 50 ° C, for example, 30 to 40 ° C. For example, when the glass transition temperature of the acrylic polyol is less than 20 ° C, scratch resistance may be deteriorated, and when the glass transition temperature exceeds 50 ° C, the pencil hardness of the coating film may be poor.

The acrylic polyol resin may be included in an amount of 25 to 35 parts by weight. When the acrylic polyol resin is included within the above range, the effect of improving the physical properties and scratch resistance of the coating film formed may be particularly excellent. For example, when the content is less than the content range, scratch resistance of the coating film formed by using the content may be poor, and when the content exceeds the content range, problems such as deterioration in gloss and workability of the coating film may be deteriorated.

Polyester polyol resin

The transparent coating composition of the present invention may include a polyester polyol resin as a main component. By using the polyester polyol resin as described above, the appearance of the coating film formed by using the transparent coating composition can be improved. In particular, the transparent coating composition of the present invention can improve the appearance and workability of the coating film formed by including two types of polyester polyol resins having different solid content.

More specifically, the two types of polyester polyol resin may include a first polyester polyol resin and a second polyester polyol resin.

The first polyester polyol resin has a solids content of more than 80% by weight and 100% by weight or less, for example, 85 to 100% by weight, 90 to 100% by weight, and another example is 95 to 100% by weight, 96 to 100% by weight , And the number average molecular weight may be 500 to 1,200 g / mol, for example, 530 to 1,175 g / mol, 600 to 1,000 g / mol, and 700 to 900 g / mol. When the solid content and the number average molecular weight of the first polyester polyol is less than the above range, it may be a smoothness of the coating film.

The first polyester polyol may have a hydroxyl value of 120 to 160 mgKOH / g, for example, 130 to 150 mgKOH / g, 135 to 145 mgKOH / g. When the hydroxyl value of the first polyester polyol is less than 120 mgKOH / g, the dryness may be lowered and the hardness of the coating film may be lowered, and when the hydroxyl value is more than 160 mgKOH / g, the coating film is not sufficiently cured and adhesion of the coating film Resistance to water, water, scratch resistance and weather resistance may deteriorate. The first polyester polyol resin has excellent self-recovery when forming a coating film, and thus it can greatly improve scratch resistance.

The second polyester polyol resin has a solid content of 20% by weight or more and 80% by weight or less, for example, 25 to 75% by weight, 30 to 65% by weight, 35 to 60% by weight, 40 to 55% by weight, 40 to 50% Weight percent, and having a weight average molecular weight of 2,500 to 8,000 g / mol, for example 2,850 to 7,500 g / mol, 3,000 to 7,000 g / mol, 4,000 to 6,000 g / mol, or 4,500 to 55,00 g / mol Can be When the solid content and the weight average molecular weight of the second polyester polyol are out of the above range, the smoothness, smoothness and appearance of the coating film may be deteriorated.

The second polyester polyol may have a hydroxyl value of 120 to 160 mgKOH / g, for example, 120 to 155 mgKOH / g, 125 to 150 mgKOH / g, 130 to 145 mgKOH / g. When the hydroxyl value of the second polyester polyol is less than 120 mgKOH / g, the dryness may be lowered and the hardness of the coating film may be lowered, and when the hydroxyl value is more than 160 mgKOH / g, the coating film is not sufficiently cured and adhesion of the coating film Resistance to water, water, scratch resistance and weather resistance can be degraded.

The second polyester polyol resin has an excellent appearance when forming a coating film, so that the coating film smoothness can be greatly improved by using it.

The first polyester polyol resin and the second polyester polyol resin may be used in a weight ratio of 1: 1.5 to 1: 4.5. When the ratio of the first polyester polyol resin and the second polyester polyol resin is less than 1: 1.5, appearance and smoothness may be deteriorated by using a relatively small amount of the second polyester polyol resin. When the ratio of the first polyester polyol resin and the second polyester polyol resin exceeds 1: 4.5, scratch resistance may be deteriorated by using a relatively small first polyester content.

The polyester polyol resin is not limited thereto, for example, polyether polyurethane, polyester polyurethane, polycarbonate polyurethane, polyether ester polyurethane, polyether carbonate polyurethane, polycaprolactone polyurethane, hydrocarbon poly Urethanes, aliphatic polyurethanes, aromatic polyurethanes and mixtures thereof can be used.

The polyester polyol resin may be included in an amount of 40 to 50 parts by weight based on 25 to 35 parts by weight of the acrylic polyol resin. When the polyester polyol resin is included within the above range, the effect of improving the appearance characteristics of the coating film formed may be particularly excellent. For example, when the content is less than the content range, the effect of improving the appearance of the coating film formed using the effect is negligible, and when the content exceeds the content range, a problem that the hardness of the coating film is poor may occur.

The transparent coating composition of the present invention improves the appearance and resistance of the coating film by using the acrylic polyol resin and the polyester polyol resin, more specifically, the acrylic polyol resin and two kinds of polyester resins having different solid content as described above. Physical properties such as scratch resistance, hardness, and weather resistance can be greatly improved.

Curing accelerator

The transparent coating composition of the present invention can improve the curing performance of the coating composition by including a curing accelerator.

The curing accelerator is one commonly used in the art, but a known curing accelerator can be used, for example, dibutylbis [(1-oxododecyl) oxy] stanneine (Dibutylbis [(1-oxododecyl) oxy ] stannane, DBTDL, TL-100), tin compounds such as dibutyltin dilaurate, dibutyltin diacetate, diethyltin diacetate, dihexyltin diacetate, 2-methyl imidazole, 2-phenyl imide Imidazoles such as dazole, ethyl methyl imidazole, 2-ethyl imidazole, 1-benzyl 2-methylimidazole, 2-butyl imidazole, triphenyl phosphine, benzyl triphenylphosphonium chloride, butyl triphenylphos Quaternary ammoniums such as phonium chloride, tetraphenylphosphonium chloride, and the like, or mixtures thereof can be used. Preferably, dibutylbis [(1-oxododecyl) oxy] stannein, dibutyltin dilaurate or a mixture thereof can be used.

The curing accelerator may include the curing accelerator in an amount of 0.1 to 1 part by weight based on 25 to 35 parts by weight of the acrylic polyol resin. When the curing accelerator is included below the content range, the curability of the coating composition may be poor, and when it exceeds the content range, a problem in that storage properties of the coating composition may be deteriorated.

solvent

The present invention can be used as a solvent for maintaining the thickness of the coating film and improving the coating workability, a solvent commonly used in the transparent coating composition.

Examples of the solvent are not limited, for example, non-polar solvents such as n-heptane, toluene, xylene, petroleum compounds, and n-hexane; Ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, dibasic ester, 3-methoxy butyl acetate, amyl acetate, butyl glycol acetate, butyl cellosolve acetate, Polar solvents such as methyl ethyl ketone, methyl isobutyl ketone, acetone, diisobutyl ketone, isophorone and cyclohexanone; And it can be suitably selected and used according to the properties or volatility of the resin using at least one of these mixtures.

In one aspect, the solvent may be used at least one selected from the group consisting of an ester-based solvent, a hydrocarbon-based solvent and a glycol-based solvent.

The solvent may be 20 to 30 parts by weight based on 25 to 35 parts by weight of the acrylic polyol resin. If the content of the solvent is too high, the overall physical properties may be deteriorated, for example, problems such as deterioration in adhesion of the formed coating film and durability may be exhibited. If too little solvent is used, it is difficult to expect an effect due to the use of the solvent. .

The transparent coating composition of the present invention includes 25 to 35 parts by weight of the acrylic polyol resin disclosed above, 40 to 50 parts by weight of two types of polyester polyol resins having different solid content, 0.1 to 1 part by weight of the curing accelerator, and 20 to 30 parts by weight of the solvent. Included in the composition of wealth. If the composition deviates from the above composition, a problem that the effect of the transparent coating composition becomes poor appears.

Hardener

The transparent coating composition of the present invention may further include a curing agent. More specifically, it may be prepared in a form that can be used by mixing the curing agent portion immediately before using the transparent coating composition, or in a form that is already mixed.

The curing agent is preferably used, including an isocyanate-based curing agent. By using an isocyanate-based curing agent, a solid polyurethane coating film may be formed due to the combination of the isocyanate group in the curing agent and the hydroxyl group in the resin.

The curing agent, the molar ratio of the total hydroxyl group in the acrylic polyol resin and two types of polyester polyol resin and isocyanate group in the curing agent is 1: 1 to 1.5 (OH: NCO), for example, 1: 1.03 to 1.07 Content. For example, when using a hexamethylene diisocyanate trimer (HDI trimer) as the curing agent, 2 to 5: 1 based on the total weight of the acrylic polyol resin and two types of polyester polyol resin (resin: curing agent ), For example, may be included in a content that is a weight ratio of 2 to 3: 1.

Other additives

The transparent coating composition of the present invention may further include additives commonly used in transparent coating compositions, such as surface modifiers and ultraviolet absorbers, within the scope of not impairing the object of the present invention.

The surface modifier may be added to adjust the surface tension of the paint, but is not limited thereto, and for example, it may be used including at least one selected from the group consisting of polysiloxane-based compounds and non-silicone-based compounds.

The polysiloxane compound is not limited thereto, for example, polydimethylsiloxane, polyether-modified polydimethylsiloxane, polyether-modified methylpolysiloxane, polymethylalkylsiloxane, silicone oil, silicone-based surfactant, silicone-based synthetic lubricant, or mixtures thereof. Can be used.

The non-silicone-based compound is not limited thereto, for example, polyacrylate, lower alcohol, mineral oil, oleic acid, polypropylene glycol, glycerin higher fatty acid esters, and fluorine-containing surfactants can be used as a mixture thereof.

The ultraviolet absorber may be added to improve problems such as discoloration of the paint, swelling of the formed coating film, interlayer peeling, gloss loss, and the like, but is not limited thereto, known ultraviolet rays such as hydroxyphenyl benzotriazole Absorbents can be used.

The additives may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the transparent coating composition.

Hereinafter, examples and the like will be described in detail to help understanding of the present invention. However, the embodiments according to the present invention can be modified in many different forms, and the scope of the present invention should not be construed as being limited to the following examples. The embodiments of the present invention are provided to more fully explain the present invention to those having average knowledge in the field to which the present invention pertains.

Examples and comparative examples

[Preparation of transparent coating composition]

At 25 ° C, in a 1000 mL tin can or plastic container, the first polyester polyol resin, the second polyester polyol resin, and the acrylic polyol resin are added in the composition and content as shown in Tables 1 to 3 below, and using a stirrer. A homogeneous mixture was prepared by stirring at a speed of 700 rpm for 30 minutes. Thereafter, a UV absorber, a surface conditioner, a curing accelerator, and a solvent were added and stirred for 30 minutes to prepare a transparent coating composition. The solvent was added so that the composition had a viscosity of 24 to 30 sec.

Ingredient (g) Example One 2 3 4 5 6 7 1-1 polyester polyol 9 9 15 11 12 - - 2-1 polyester polyol 36 34 30 28 36 36 34 1-2 polyester polyol - - - - - 9 - 1-3 polyester polyol - - - - - - 9 2-2 polyester polyol - - - - - - 2-3 polyester polyol - - - - - - - Acrylic polyol resin 1-1 28 28 28 33 25 28 28 Acrylic polyol resin 1-2 - - - - - - - Acrylic polyol resin 1-3 - - - - - - - UV absorber 1.7 1.7 1.7 1.7 1.7 1.7 1.7 Curing accelerator 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Surface adjuster 0.2 0.2 0.2 0.2 0.2 0.2 0.2 solvent 24.95 26.95 24.95 25.95 24.95 24.95 26.95 Tot. 100 100 100 100 100 100 100

Ingredient (g) Example 8 9 10 11 12 13 14 15 1-1 polyester polyol 10 9 9 10 - - 7.5 9 2-1 polyester polyol - - 34 35 - - 38 36 1-2 polyester polyol - - - - 9 - - - 1-3 polyester polyol - - - - - 9 - - 2-2 polyester polyol 35 - - - 36 - - - 2-3 polyester polyol - 36 - - - 34 - - Acrylic polyol resin 1-1 28 28 - - - - 26.5 28 Acrylic polyol resin 1-2 - - 28 - 28 - - - Acrylic polyol resin 1-3 - - - 28 - 28 - - UV absorber 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 Curing accelerator 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Surface adjuster 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 solvent 24.95 24.95 26.95 24.95 24.95 26.95 25.95 24.95 Tot. 100 100 100 100 100 100 100 100

Ingredient (g) Comparative example One 2 3 4 5 6 7 1-1 polyester polyol 9 6 11 10.8 7.2 16 - 2-1 polyester polyol 36 24 44 43.2 28.8 37 45 Acrylic polyol resin 28 42 15 33.6 22.4 15 28 UV absorber 1.7 1.7 2 2.04 1.36 2 1.7 Curing accelerator 1.5 0.15 0.15 0.18 0.12 One 0.15 Surface adjuster 0.2 0.1 0.2 0.24 0.16 One 0.2 solvent 23.6 26.05 27.65 9.94 39.96 28 24.95 Tot. 100 100 100 100 100 100 100

1-1 polyester polyol: solid content 96% by weight, hydroxyl value 140 mgKOH / g, number average molecular weight: 800 g / mol

1-2 polyester polyol: 100% by weight of solid content, 149 mgKOH / g hydroxyl value, number average molecular weight: 1,175 g / mol

1-3 polyester polyol: solid content 96% by weight, hydroxyl value 133 mgKOH / g, number average molecular weight: 530 g / mol

2-1 Polyester polyol: 45% by weight of solid content, 132 mgKOH / g hydroxyl value, and weight average molecular weight: 5,050 g / mol

2-2 polyester polyol: 40% by weight of solid content, 130 mgKOH / g hydroxyl value, and weight average molecular weight: 2,850 g / mol

2-3 polyester polyol: 50% by weight of solid content, 144 mgKOH / g hydroxyl value, weight average molecular weight: 7,500 g / mol

Acrylic polyol 1-1: solid content 52% by weight, hydroxyl value 130 mgKOH / g, Tg 35 ° C, weight average molecular weight: 11,000 g / mol

Acrylic polyol 1-2: solid content 50% by weight, hydroxyl value 120 mgKOH / g, Tg 31 ° C, weight average molecular weight: 8,500 g / mol

Acrylic polyol 1-3: 55% by weight of solid content, 138 mgKOH / g of hydroxyl value, 38 ° C of Tg, weight average molecular weight: 13,500g / mol

Surface modifier: Polysiloxane-based surface modifier (Polyetherpolysiloxane, Borchi Gol OL17, OMG BORCHERS GMBH)

UV absorber: (TINUVIN 5151, BASF AKTIENGESELLSCHAFT)

Hardening accelerator: (Dibutylbis [(1-oxododecyl) oxy] stannane, TL-100, SONGWON INDUSTRIAL company)

Solvent: XYLENE

Test example

After mixing the curing agent (HDI trimer) so that the weight ratio of the resin and the curing agent in the transparent coating composition prepared above is 2.5: 1, and using a diluent (0278 (JY), KCC) viscosity (Ford Cup # 4) 14 It was diluted to 16 sec. Painting was performed using the diluted composition.

First, after coating with a material such as ABS, PC + PBT, oil-soluble primer (RP2143 (H), KCC) to a thickness of 10 to 14 micrometers of the dried coating film, and dried at room temperature for 6-8 minutes. Thereafter, the coated film was coated with an oil-soluble black base coat (UT578 (A) -EB, KCC) to a thickness of 25 to 35 micrometers, and then dried at room temperature for 8-10 minutes. Thereafter, the diluted composition prepared above was coated on the formed coating film to have a thickness of 28 to 38 micrometers, and then cured for 30 minutes at 70 ° C hot air to form a final coating film.

[Painting workability]

A 30 x 40 cm tin plate was coated twice with 61 IWATA cases to evaluate the degree of atomization, smoothness, and paint repellency of the paint during painting.

[Exterior]

After coating the paint on the plastic material coated with the primer, dried for 8-10 minutes at 70 ° C., and then coated with the transparent paint prepared above, the degree of air bubbles, foreign matter, spots, grooves and smoothness on the surface Was evaluated.

[Adhesiveness]

According to the ASTM D3359 tape adhesion test method, the degree of the peeled portion after the tape adhesion test among 100 1 mm x 1 mm scales was observed.

[Water resistance]

After the coating film specimen prepared above was immersed in a constant temperature bath at 40 ° C for 10 days, adhesion test and appearance evaluation were performed.

[Scratch resistance]

Using the AMTEC KISTLER car wash tester, the coated film specimen prepared above was mounted on a test bench and set at a moving speed of 5 m / min to reciprocate 10 times.

Gloss retention (%) = Gloss after evaluation / Gloss before evaluation * 100 (%)

[Weatherability]

After exposing the coated film specimen prepared above with an energy of 2500 kJ in an Xenon weatherometer tester environment, the appearance, color difference, and adhesion of the coated film were evaluated.

[Hardness]

Using a standard pencil (pencil hardness 2B to HB) on the test piece, apply force and draw about 5 cm in a straight line, and then check the surface condition of the coating film.

The evaluation results are shown in Tables 3 and 4 below.

Property evaluation Example One 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Paintability ◎ ◎ ○ ◎ ◎ ◎ ○ ○ ○ ◎ ◎ ○ ○ △ ◎ Exterior ◎ ◎ ○ ◎ ◎ ◎ ○ ○ ○ ◎ ◎ ○ ○ △ ○ Adhesion ◎ ◎ ◎ ◎ ◎ ○ ○ ◎ ○ ◎ ○ ○ ◎ ◎ ◎ Water resistance ◎ ◎ ◎ ◎ ◎ ○ ○ ◎ ○ ◎ ○ ○ ◎ ◎ ◎ Scratch resistance ○ ◎ ◎ ◎ ◎ ○ ○ ◎ ○ ○ ○ ○ ○ ○ △ Weatherability ◎ ◎ ◎ ◎ ◎ ◎ ○ ◎ ○ ◎ ○ ○ ◎ ◎ ◎ Hardness ◎ ◎ ◎ ◎ ◎ ◎ ○ ○ ◎ ○ ○ ○ ○ ○ ○ Evaluation: ◎ -excellent, ○ -good, △ -normal, X-poor

Property evaluation Comparative example One 2 3 4 5 6 7 Paintability △ X X X X ○ ○ Exterior △ △ △ X X ○ X Adhesion ◎ ◎ ◎ ◎ ◎ ◎ ◎ Water resistance ◎ ◎ ◎ ○ ○ ◎ ○ Scratch resistance X X X X X ◎ X Weatherability ◎ ◎ ○ ◎ ◎ △ ◎ Hardness ○ ○ ○ ○ ○ ○ ○ Evaluation: ◎ -excellent, ○ -good, △ -normal, X-poor

As can be seen in Tables 4 and 5, the coating film prepared using the transparent coating composition of the present invention was excellent in physical properties such as coating workability, appearance, adhesion, water resistance, scratch resistance, weather resistance.

Claims (4)

25 to 35 parts by weight of an acrylic polyol resin;
40 to 50 parts by weight of two types of polyester polyol resins having different solid content;
Curing accelerator 0.1 to 1 part by weight; And
Solvent 20 to 30 parts by weight; containing a transparent coating composition. The method according to claim 1,
The acrylic polyol resin has a solids content of 35 to 70% by weight, a weight average molecular weight of 8,000 to 14,000 g / mol, a hydroxyl value of 110 to 150 mgKOH / g, and a glass transition temperature (Tg) of 20 to 50 ° C. Transparent paint composition. The method according to claim 1,
The two types of polyester polyol resin include a first polyester polyol resin and a second polyester polyol resin,
The first polyester polyol resin has a solids content of more than 80% by weight and 100% by weight or less, a number average molecular weight of 500 to 1,200 g / mol, and a hydroxyl value of 120 to 160 mgKOH / g,
The second polyester polyol resin has a solid content of 20 wt% or more and 80 wt% or less, a weight average molecular weight of 2,500 to 8,000 g / mol, and a hydroxyl value of 120 to 160 mgKOH / g. The method according to claim 1,
The weight ratio of the first polyester polyol resin and the second polyester polyol resin is 1: 1.5 to 1: 4.5 transparent coating composition.