KR102383359B1 - A clear coating composition, a method for preparing thereof, and a coating method using the same - Google Patents

Abstract

The present invention relates to a transparent coating composition having good coating workability, excellent swellability of the coating film, excellent appearance quality, and satisfactory coating film physical properties such as hardness, water resistance, and weather resistance. and a coating method using the same.

Description

Transparent paint composition, manufacturing method thereof, and coating method using the same

The present invention relates to a transparent coating composition having good coating workability, excellent swellability of the coating film, excellent appearance quality, and satisfactory coating film physical properties such as hardness, water resistance, and weather resistance. and a coating method using the same.

Conventionally, when painting an automobile bumper, multi-layer coating consisting of a primer coating layer, a base coating layer, and a transparent coating layer was performed. In particular, it was common to paint each layer with an oil-based paint.

However, as environmental problems such as emission regulation of volatile organic chemicals (VOC) have emerged, many attempts are being made to replace oil-based paints with water-soluble paints or high-solid paints.

However, when the transparent paint layer is formed with a water-soluble paint, there is a problem in painting workability, such as a remarkably lowering of the swellability of the paint film.

In addition, high-solid paint not only dries slowly during painting, but also significantly lowers the painting workability compared to the existing medium-solid paint. To make the paint high-solid, a resin with a high non-volatile component is used. When a resin with a low molecular weight is used, the reactivity of the resin is lowered, so compared to the medium-solid paint, the drying property is inferior and accordingly A phenomenon in which the coating film flows occurs and the appearance quality is deteriorated.

Accordingly, there is still a demand for the development of a transparent paint excellent in coating film slipping properties and appearance quality.

Korean Patent Publication No. 10-2016-0082637

The present invention has been devised to overcome the above problems of the prior art, and an object of the present invention is to provide a transparent coating composition having excellent coating film rise and appearance quality, and excellent coating film properties such as hardness, water resistance and weather resistance.

Another object of the present invention is to provide a method for preparing the transparent coating composition.

In addition, an object of the present invention is to provide a coating method using the transparent coating composition.

The object of the present invention is not limited to the object mentioned above. The object of the present invention will become clearer from the following description, and will be realized by means and combinations thereof described in the claims.

As a means for achieving the above object, the present invention provides a transparent coating composition having the following configuration, a manufacturing method thereof, and a coating method using the same.

The transparent coating composition according to the present invention comprises 55 wt% to 65 wt% of an acrylic resin containing hydroxyl groups, 5 wt% to 30 wt% of a polyester-based resin containing hydroxyl groups, and 10 wt% to 20 wt% of a solvent. 35 to 45 parts by weight of a curing agent based on 100 parts by weight of the main agent and the main agent.

In a preferred embodiment of the present invention, the acrylic resin may include 10% to 15% by weight of the first acrylic polyol resin and 45% to 55% by weight of the second acrylic polyol resin.

In a preferred embodiment of the present invention, the first acrylic polyol resin may have a solid content of 55 wt% to 65 wt%, and a hydroxyl value of 120 mgKOH/g to 160 mgKOH/g.

In a preferred embodiment of the present invention, the second acrylic polyol resin may have a solid content of 70 wt% to 80 wt%, and a hydroxyl value of 100 mgKOH/g to 140 mgKOH/g.

In a preferred embodiment of the present invention, the polyester-based resin may have a solid content of 60 wt% to 80 wt%, and a hydroxyl value of 100 mgKOH/g to 160 mgKOH/g.

In a preferred embodiment of the present invention, the solvent is toluene, xylene, dimethyl ketone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, ethyl propyl ketone, methyl isobutyl ketone, methyl aryl ketone, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, isopropyl, acetate, methylcellosolve acetate, cellosolve acetate, butylcellosolve acetate, carbitol acetate, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol and combinations thereof.

In a preferred embodiment of the present invention, the subject may further comprise 0.1% to 1% by weight of a surface conditioning agent, 1% to 10% by weight of a UV absorber, and 0.01% to 1% by weight of a curing accelerator. .

In a preferred embodiment of the present invention, the curing agent is selected from the group consisting of polyisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, and combinations thereof. can be selected.

In a preferred embodiment of the present invention, the curing agent may be one that maintains an equivalent ratio of the main hydroxyl group: isocyanate (NCO) = 1.0: 1.03 to 1.07.

In a preferred embodiment of the present invention, a CF (combination factor) value, which is an appearance evaluation index, may be 64 or more.

The method for producing a transparent coating composition according to the present invention contains 10 wt% to 15 wt% of the first acrylic polyol resin, 45 wt% to 55 wt% of the second acrylic polyol resin, and 5 wt% to 30 wt% of hydroxyl groups polyester resin, 10 wt% to 20 wt% of a solvent, 0.1 wt% to 1 wt% of a surface conditioner, 1 wt% to 10 wt% of a UV absorber, and 0.01 wt% to 1 wt% of a curing accelerator are mixed and adding 35 parts by weight to 45 parts by weight of a curing agent to the main agent based on 100 parts by weight of the main agent.

The coating method using the transparent coating composition according to the present invention comprises the steps of diluting the transparent coating composition so that the viscosity measured with a podcup #4 viscometer is 17 to 20 seconds, and the diluted transparent coating composition to a thickness of 28 μm to 38 μm. It includes the step of forming a coating film by coating and drying the coating film at 50° C. to 150° C. for 10 minutes to 2 hours.

Since the present invention includes the above configuration, according to this, the following effects can be obtained.

According to the present invention, it is possible to obtain a transparent coating composition having excellent coating film slipping properties and appearance quality, and excellent coating film physical properties such as hardness, water resistance and weather resistance.

In addition, since the transparent coating composition according to the present invention has a low content of volatile organic compounds (VOC), it is possible to prevent environmental pollution and has the effect of greatly improving the working environment of the painting.

The effects of the present invention are not limited to the above-mentioned effects. It should be understood that the effects of the present invention include all effects that can be inferred from the following description.

Hereinafter, the present invention will be described in detail through examples. The embodiments of the present invention may be modified in various forms as long as the gist of the present invention is not changed. However, the scope of the present invention is not limited to the following examples.

If it is determined that the subject matter of the present invention may be obscured, a description of known configurations and functions will be omitted. In the present specification, "comprising" means that other components may be further included unless otherwise specified.

As used herein, “volatile organic compounds” are also called VOCs (Volatile Organic Compounds), and are a generic term for liquid or gaseous organic compounds that are easily evaporated into the atmosphere due to their high vapor pressure. A substance that causes photochemical smog.

In addition, in the present specification, "hydroxyl value" is a parameter used for quantification of hydroxyl groups, and potassium hydroxide required to neutralize acetic acid generated when 1 g of a specific oil or fat containing a hydroxyl group is acetylated and then hydrolyzed. is the number of mg of

In addition, in the present specification, "slim-up" means that the paint is well applied to a substrate, etc., and has excellent adhesion to facilitate the formation of a paint film.

The transparent coating composition according to the present invention comprises 55 wt% to 65 wt% of an acrylic resin containing hydroxyl groups, 5 wt% to 30 wt% of a polyester-based resin containing hydroxyl groups, and 10 wt% to 20 wt% of a solvent. 35 to 45 parts by weight of a curing agent based on 100 parts by weight of the main agent and the main agent.

The present invention adjusts an appropriate content of an acrylic resin contributing to the oil-resistance and physical properties of the coating film and a polyester resin contributing to the appearance quality and physical properties of the coating film to provide excellent coating film rise and appearance quality, hardness, water resistance and Provided is a transparent coating composition excellent in coating film properties such as weather resistance.

Hereinafter, each configuration of the high-solid coating composition of the present invention will be described in detail.

Acrylic resin

The acrylic resin is a composition related to paint workability, appearance quality, and physical properties of the coating film, and includes 55 wt% to 70 wt%, specifically 55 wt% to 65 wt%, more specifically 63 wt% to the subject. It is preferable to be

If the content of the acrylic resin exceeds 70% by weight, the appearance quality may be deteriorated, and if it is less than 55% by weight, the slick property of the coating film may be deteriorated, thereby greatly reducing the painting workability.

The acrylic resin may include a first acrylic polyol resin and a second acrylic polyol resin.

The first acrylic polyol resin and the second acrylic polyol resin may be prepared by polymerizing an ethylenically unsaturated monomer, an acrylic monomer containing an acid group, a glycidyl ester, or a mixture thereof and an acrylic monomer containing a hydroxyl group.

Examples of the ethylenically unsaturated monomer include styrene, methyl (meth) acrylate, propyl (meth) acrylate, normal butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylic Late, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, lauryl (meth) acrylate, and the like can be used.

As the acrylic monomer containing the acid group, for example, (meth)acrylic acid, fumaric acid, acrylic acid dimer, maleic acid, and the like may be used.

The glycidyl ester may be prepared by performing a glycidyl ester reaction between acrylic acid, methacrylic acid, or α-branched monocarboxylic acid and glycidol before, during, or after the polymerization reaction.

Examples of the hydroxyl group-containing acrylic monomer include hydroxylethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and hydroxyethyl to which epsilon-caprolactone is added. (meth)acrylates and the like can be used.

Preferably, the first acrylic polyol resin has a solid content of 55 wt% to 65 wt%, a hydroxyl value of 120 mgKOH/g to 160 mgKOH/g, and the second acrylic polyol resin has a solid content It is preferably 70 wt% to 80 wt%, and a hydroxyl value of 100 mgKOH/g to 140 mgKOH/g.

The acrylic resin is 10 wt% to 15 wt%, specifically 12 wt% to 15 wt% of the first acrylic polyol resin and 45 wt% to 55 wt%, specifically 48 wt% to 51 wt% of the second It may include an acrylic polyol resin.

When the content of the first acrylic polyol resin exceeds 15% by weight or the content of the second acrylic polyol resin is less than 45% by weight, the appearance quality may be deteriorated, and the content of the first acrylic polyol resin is less than 10% by weight Alternatively, when the content of the second acrylic polyol resin exceeds 55% by weight, the swellability of the coating film may be lowered, and thus the painting workability may be greatly deteriorated.

polyester profit

The polyester-based resin is a configuration related to the appearance quality and physical properties of the coating film, and it is included in the subject matter in an amount of 5 wt% to 30 wt%, specifically 10 wt% to 20 wt%, and more specifically 19 wt% desirable.

If the content of the polyester-based resin is less than 5% by weight, the appearance quality may be deteriorated, and if it exceeds 30% by weight, the hardness of the coating film may be deteriorated.

The polyester-based resin may be prepared by polymerizing a polyhydric alcohol and a polyhydric acid monomer.

Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,4-butylene glycol, trimethylolpropane, hydroxypivalyl hydroxypivalate, 1,6-hexanediol, neopentyl glycol. , methylpropanediol, cyclohexanedimethanol, hydrogenate bisphenol A, ethylene oxide addition bisphenol A, propylene oxide addition bisphenol A, ethylene oxide addition bisphenol F, propylene oxide addition bisphenol F, ethylene oxide addition bisphenol S and propylene oxide addition bisphenol S and the like can be used.

As the polyhydric acid monomer, phthalic anhydride, tetrahydrophthalic anhydride, isophthalic acid, terephthalic acid, adipic acid, azelaic acid, sebacic acid, cyclohexadiic acid, trimellitic anhydride, etc. may be used. there is.

The polyester-based resin is preferably a polyester polyol resin having a solid content of 60 wt% to 80 wt% and a hydroxyl value of 100 mgKOH/g to 160 mgKOH/g.

solvent

The solvent is preferably used in an amount of 10% to 20% by weight, specifically 15.4% by weight, and when the amount used is less than 10% by weight, the appearance quality may be deteriorated, and when it exceeds 20% by weight, flowability during painting, Coating workability may be deteriorated due to a reduction in the solid content of the coating composition.

The solvent may be an aromatic hydrocarbon-based solvent such as toluene or xylene; ketone solvents such as dimethyl ketone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, ethyl propyl ketone, methyl isobutyl ketone, and methyl aryl ketone; ester solvents such as methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, isopropyl, acetate, methylcellosolve acetate, cellosolve acetate, butylcellosolve acetate, and carbitol acetate; alcohol solvents such as n-propanol, isopropanol, n-butanol, isobutanol and tertiary butanol; and combinations thereof.

additive

The subject may further include 0.1 wt% to 1 wt% of a surface conditioning agent, 1 wt% to 10 wt% of a UV absorber, and 0.01 wt% to 1 wt% of a curing accelerator.

The surface conditioning agent is a component for improving the appearance quality by adjusting the surface tension of the coating film, and a surface conditioning agent such as polyacrylic or polysiloxane may be used.

If the content of the surface modifier is less than 0.1% by weight, the effect of improving the appearance quality may be insignificant, and if it exceeds 1% by weight, the repainting adhesion may be reduced.

The ultraviolet absorber is a component for preventing discoloration and loss of gloss of the coating film, and may be selected from the group consisting of benzotriazole-based, benzylidenehydant-based, benzophenone-based, benzoguanine-based, and combinations thereof.

If the content of the ultraviolet absorber is less than 1% by weight, weather resistance may be lowered, and if it exceeds 10% by weight, the increase in the effect compared to the input amount is not large, which may cause a cost increase.

The curing accelerator is a component for improving the dryness of the coating film and shortening the curing time by accelerating the reaction of the acrylic resin and polyester resin with the curing agent, tetramethylbutanediamine, bicyclooctane, dibutyltin dilaurate, triethylamine, diethylenetriamine, triethyldiamine, zinc octoate, bismuth carboxylate, zirconium chelate, calcium octoate, and combinations thereof.

If the content of the curing accelerator is less than 0.01% by weight, the effect of improving drying properties and coating film properties may be insignificant, and if it exceeds 1.0% by weight, there is room for deterioration of appearance quality and shortening of pot life.

hardener

The subject includes an acrylic resin containing a hydroxyl group and a polyester resin containing a hydroxyl group. In order to form the main chemical coating film, a curing agent capable of bonding to the hydroxyl group is required.

The curing agent may be a polyisocyanate compound without yellowing phenomenon, for example, polyisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate and It may be selected from the group consisting of combinations thereof.

Accordingly, a strong polyurethane coating film may be formed by combining the hydroxyl group of the subject and the isocyanate of the curing agent.

The present invention uses 35 parts by weight to 45 parts by weight of the curing agent, specifically 40 parts by weight to 45 parts by weight, and more specifically 42 parts by weight based on 100 parts by weight of the main agent.

If the amount of the curing agent used is less than 35 parts by weight, the crosslinking force may decrease and the coating film properties such as weather resistance and scratch resistance may be deteriorated. Workability may be greatly reduced, and after curing, the coating film becomes too hard, and the physical properties of the coating film such as weather resistance may be deteriorated.

In addition, the curing agent preferably maintains an equivalent ratio of hydroxyl group: isocyanate (NCO) = 1.0: 1.03 to 1.07 so that the curing agent can effectively react with the hydroxyl group of the main agent. If the equivalence ratio is lower than the above range, a sufficient degree of crosslinking may not be formed, so that the physical properties of the coating film such as hardness and water resistance may be reduced.

Hereinafter, the present invention will be described in more detail through specific examples. However, these examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

The transparent coating compositions of Examples and Comparative Examples were prepared according to the composition of Table 1 below.

Specifically, the first acrylic polyol resin, the second acrylic polyol resin, and the polyester-based polyol resin are put in a container, mixed at low speed using a stirrer, and then a UV absorber, a surface conditioner, a curing accelerator and a solvent are added and stirred for 30 minutes. So I got the topic.

A transparent coating composition was obtained by adding 42 parts by weight of polyisocyanate (VPLS 2025, BAYER, hexamethylene diisocyanate trimer) to 100 parts by weight of the main agent as a curing agent.

(1st acrylic polyol Resin, second acrylic polyol profit, polyester polyol If the resin was manufactured and used separately, please add the manufacturing method)

Ingredients [wt%] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 1st acrylic
polyol resin ^{1 )} 12 15 58 5 15 25 2nd acrylic
polyol resin ^{2 )} 51 48 5 58 37 27 Polyester polyol resin ³⁾ 19 19 19 19 30 30 Surface conditioner ^{4 )} 0.6 0.6 0.6 0.6 0.6 0.6 UV absorber ^{5 )} 1.8 1.8 1.8 1.8 1.8 1.8 hardening accelerator ^{6 )} 0.2 0.2 0.2 0.2 0.2 0.2 solvent ^{7 )} 15.4 15.4 15.4 15.4 15.4 15.4 Sum 100 100 100 100 100 100 1) 1st acrylic polyol resin: solid content 55-65 wt%, hydroxyl value 120-160 mgKOH/g, self-synthesis
2) Second acrylic polyol resin: solid content 70-80 wt%, hydroxyl value 100-140 mgKOH/g, self-synthesis
3) Polyester polyol resin: solid content 60~80% by weight, hydroxyl value 100~160mgKOH/g, NUPLEX company, SETAL 82166
4) Surface conditioning agent: polysiloxane-based surface conditioning agent, BYK company, BYK-306
5) UV absorber: Benzotriazole UV absorber, BASF, TINUVIN 5151
6) Hardening accelerator: DBTDL
7) Solvent: DOW, PMA

The transparent coating compositions of Examples 1 and 2 and Comparative Examples 1 to 4 were coated to form a coating film.

Specifically, an oil-soluble primer was coated with a thickness of 8 μm to 12 μm on a polypropylene automobile bumper and left at room temperature for 5 minutes, then an oil-soluble base paint was coated with a thickness of 20 μm to 30 μm and left at room temperature for 5 minutes. .

Next, the transparent coating composition was diluted with a thinner thinner so that the viscosity measured with a podcup #4 viscometer was 17 to 20 seconds. The diluted transparent coating composition was coated on the base coating layer to a thickness of 28 μm to 38 μm, and the coating film was cured by drying in an oven at about 80° C. for about 30 minutes.

The appearance quality and physical properties of the coating film were measured as follows and evaluated according to the evaluation criteria of destruction, and the results are shown in Table 2.

<Evaluation criteria>

◎: Excellent ○: Good △: Normal ×: Poor

- Painting workability: The degree of atomization of the paint, the degree of smoothness, and the rise of the coating film were compared with the 30cm×40cm tin plate with IWATA 61 cases re-painting twice round-trip. If the atomization was good and the elasticity was 38㎛ or more, excellent, if the atomization was good and the elasticity was 33㎛~38㎛, good, if it was 28㎛~33㎛ or more, normal, and if it was less than 28㎛, it was evaluated as poor.

- Appearance quality (CF value): The degree of smoothness of the surface of the coating film was compared using a WAVE SCAN device.

-Adhesiveness: According to ASTM D3359 tape adhesion test method, the degree of peeling part was observed after the tape adhesion test among 100 1mm × 1mm scales. If there is no peeling at all, good, if there is no peeling on the side but some peeling on the grid line, good, if peeling less than 1/4 of one side, normal, if more than 1/4 of one side peeling off, it was evaluated as bad .

- Water resistance: After immersion of the finished coating film in a 40℃ thermostat for 10 days, adhesion test and appearance evaluation were performed. Excellent when there is no blister and no peeling at all, Good when there is no blister and some peeling on the grid line, Good when there is no blister and peeling less than 1/4 of one side Normal, if there is no blister or peeling off one side In the case of peeling of 1/4 or more, it was evaluated as defective.

- High-pressure car washability: The degree of peeling of the coating film was evaluated by spraying high-pressure water at a pressure of 70 kgf from a distance of 10 cm with a specified high-pressure car wash tester. Excellent when there is no blister and no peeling at all, Good when there is no blister and some peeling on the grid line, Good when there is no blister and peeling less than 1/4 of one side Normal, if there is no blister or peeling off one side In the case of peeling of 1/4 or more, it was evaluated as defective.

- Weather resistance: After exposure to 2,500 kJ of energy in a xenon weatherometer tester environment, the appearance quality, color difference, and adhesion of the coating were compared. If there is no abnormality in appearance and the color difference is 1.5 or less, it is excellent, if there is no abnormality in the appearance and the color difference is 2.0 or less, it is good, if there is some abnormality in the appearance and the color difference is 2.0 or less, normal, if there is an abnormality in the appearance and the color difference is 2.0 or more, it is evaluated as bad .

Item Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Painting workability ◎ ◎ △ ○ △ × Appearance (CF value) 72 64 53 62 55 48 adherence ◎ ◎ ◎ ◎ ◎ ◎ water resistance ◎ ◎ ◎ ◎ ◎ ◎ high pressure car wash ◎ ◎ ◎ ◎ ◎ ◎ weather resistance ◎ ◎ ◎ ◎ ◎ ◎

The coating films formed from the transparent coating compositions of Examples 1 and 2 received excellent evaluations in all items, and the CF value, which is an appearance evaluation index, was evaluated very well as 64 or higher.

On the other hand, in Comparative Example 1, it can be seen that the content of the first acrylic polyol resin exceeds 15% by weight and the content of the second acrylic polyol resin is less than 45% by weight, so the appearance quality is deteriorated and the painting workability is also poor.

In addition, in Comparative Example 2, since the content of the first acrylic polyol resin is less than 10% by weight and the content of the second acrylic polyol resin exceeds 55% by weight, the swellability of the coating film is lowered, so that the coating workability is improved compared to that of Example 1 It can be seen that Example 2 is not reached.

In Comparative Examples 3 and 4, since the content of the acrylic resin is less than 55% by weight, it can be seen that the coating workability is very poor due to the deterioration of the coating film, and in particular, in the case of Comparative Example 4, the first acrylic polyol resin Since the content of the acrylic polyol resin exceeds 15% by weight and the content of the second acrylic polyol resin is less than 45% by weight, it can be seen that the painting workability is further deteriorated.

As the experimental examples and examples of the present invention have been described in detail above, the scope of the present invention is not limited to the above-described experimental examples and examples, and the basic concept of the present invention defined in the following claims. Various modifications and improved forms used by those skilled in the art are also included in the scope of the present invention.

Claims (14)

a main agent comprising 55 wt% to 65 wt% of an acrylic resin containing hydroxyl groups, 19 wt% to 30 wt% of a polyester-based resin containing hydroxyl groups, and 10 wt% to 20 wt% of a solvent; and
35 parts by weight to 45 parts by weight of a curing agent based on 100 parts by weight of the main agent,
The acrylic resin is
10% to 15% by weight of the first acrylic polyol resin; and
48% to 51% by weight of the second acrylic polyol resin; contains,
The first acrylic polyol resin has a solid content of 55 wt% to 65 wt%, and a hydroxyl value of 120 mgKOH/g to 160 mgKOH/g,
The second acrylic polyol resin has a solid content of 70 wt% to 80 wt%, and a hydroxyl value of 100 mgKOH/g to 140 mgKOH/g,
The polyester-based resin has a solid content of 60 wt% to 80 wt%, and a hydroxyl value of 100 mgKOH/g to 160 mgKOH/g.
delete delete delete delete According to claim 1,
The solvent is toluene, xylene, dimethyl ketone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, ethyl propyl ketone, methyl isobutyl ketone, methyl aryl ketone, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, selected from the group consisting of isopropyl, acetate, methylcellosolve acetate, cellosolve acetate, butylcellosolve acetate, carbitol acetate, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, and combinations thereof transparent paint composition.
According to claim 1,
the subject is
0.1 wt% to 1 wt% of a surface conditioning agent;
1% to 10% by weight of an ultraviolet absorber; and
A transparent coating composition further comprising 0.01 wt% to 1 wt% of a curing accelerator.
According to claim 1,
The curing agent is a transparent coating composition selected from the group consisting of polyisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, and combinations thereof.
According to claim 1,
The curing agent is a hydroxyl group of the main agent: isocyanate (NCO) = 1.0: a transparent coating composition that maintains an equivalent ratio of 1.03 to 1.07.
The method of claim 1,
A transparent coating composition having a CF (combination factor) value of 64 or more, which is an appearance evaluation index.
55 wt% to 65 wt% of an acrylic resin containing a hydroxyl group, 19 wt% to 30 wt% of a polyester resin containing a hydroxyl group, 10 wt% to 20 wt% of a solvent, 0.1 wt% to 1 wt% preparing a main agent by mixing a surface conditioning agent, 1 wt% to 10 wt% of a UV absorber, and 0.01 wt% to 1 wt% of a curing accelerator; and
and adding 35 to 45 parts by weight of a curing agent to the main agent based on 100 parts by weight of the main agent,
The acrylic resin is
10% to 15% by weight of the first acrylic polyol resin; and
48% to 51% by weight of the second acrylic polyol resin,
includes,
The first acrylic polyol resin has a solid content of 55 wt% to 65 wt%, and a hydroxyl value of 120 mgKOH/g to 160 mgKOH/g,
The second acrylic polyol resin has a solid content of 70 wt% to 80 wt%, and a hydroxyl value of 100 mgKOH/g to 140 mgKOH/g,
The polyester-based resin has a solid content of 60 wt% to 80 wt%, and a hydroxyl value of 100 mgKOH/g to 160 mgKOH/g.
delete delete A step of diluting the transparent coating composition according to claim 1 so that the viscosity measured with a podcup #4 viscometer is 17 to 20 seconds;
forming a coating film by coating the diluted transparent coating composition to a thickness of 28 μm to 38 μm; and
A coating method using a transparent coating composition comprising the step of drying the coating film at 50° C. to 150° C. for 10 minutes to 2 hours.