KR20200141175A - Clear coat composition for refinishing automobiles - Google Patents

Abstract

The present invention relates to an economical transparent paint composition for automobile repair due to fast drying speed and, more specifically, to a transparent paint composition for automobile repair, comprising: a first acrylic resin with a glass transition temperature of 70°C or more and less than 100°C; a second acrylic resin with a glass transition temperature of 100°C or more and 160°C or less; third and fourth acrylic resins with a glass transition temperature of 10°C or less; and a polyester resin, wherein a hydroxyl value of the third acrylic resin is lower than a hydroxyl value of the fourth acrylic resin.

Description

Transparent coating composition for automobile repair {CLEAR COAT COMPOSITION FOR REFINISHING AUTOMOBILES}

The present invention relates to a transparent coating composition for automobile repair capable of forming a coating film having excellent paintability, spreadability, pinhole resistance and hardness.

Due to the enlargement of automobile maintenance companies and the consolidation of small companies, efforts to shorten working hours and reduce heat treatment costs are continuing to become competitive in the automobile repair and painting industry. For this reason, the economic feasibility of paint and work in automobile repair and painting systems is more emphasized. In particular, in the era of high oil prices, there is a demand for paints that can quickly finish work while consuming less energy in the automotive repair field.

Car repair is a process of restoring a wide range of damaged areas from local vehicle damage areas to damage repairs of 3 panels to their original shape. Recently, partial repairs and local area repairs are increasing with the luxury of automobile exteriors.

The automobile repair process for repairing damaged parts is largely divided into a surface adjustment step, an intermediate step, and a top coat step. The top coat process step is typically a step of masking a portion where the top coat is not required, a step of applying a color paint to match colors, a step of applying a transparent paint to impart gloss and increase durability, and a light to cleanly finish the painted exterior surface. Includes betting and evaluation steps. At this time, the transparent paint used in the top coat process step is a paint composition using various resins such as epoxy-based, urethane-based, sealant-based, and acrylic-based.

Specifically, Korean Patent No. 1,826,058 (Patent Document 1) includes an acrylic polyol resin synthesized using methyl methacrylate, isobornyl acrylate, butyl acrylate, hydroxy ethyl methacrylate, and methacrylic acid; Light stabilizer; Ultraviolet absorbers; Silicone surfactants; Non-silicone surface active agents; Urethane reaction accelerator; And a stain-resistant transparent coating composition comprising an organic solvent is disclosed. However, the transparent coating composition of Patent Literature 1 has a limit in which scratch resistance is lowered.

Therefore, it is possible to form a coating film with excellent coating properties, spreadability, pinhole resistance, and hardness, and research and development for a transparent coating composition with excellent economical efficiency is possible due to the low content of volatile organic solvent compounds (VOC), high solid content, and fast drying speed. It is a necessary situation.

Korean Patent Registration No. 1,826,058 (published on June 30, 2014)

The present invention can form a coating film having excellent paintability, spreadability, pinhole resistance, and hardness, and has a low content of a volatile organic solvent compound (VOC), a high solid content, and a fast drying speed, thereby providing a transparent coating composition having excellent economy.

In order to achieve the above object, the present invention provides a first acrylic resin having a glass transition temperature of 70° C. or more and less than 100° C., a second acrylic resin having a glass transition temperature of 100° C. or more and 160° C. or less, and a glass transition temperature of 10° C. or less. It provides a transparent coating composition for automobile repair comprising a third and fourth acrylic resin and a polyester resin, wherein a hydroxyl value of the third acrylic resin is lower than that of the fourth acrylic resin.

The transparent paint composition for automobile repair according to the present invention is economical due to its high solid content and high drying speed, and is eco-friendly due to its low VOC content. In addition, the coating film prepared from the transparent coating composition has excellent paintability, spreadability, pinhole resistance and hardness.

Hereinafter, the present invention will be described in detail.

The "weight average molecular weight" as used herein is measured by a conventional method known in the art, and can be measured, for example, by a gel permeation chromatograph (GPC) method. Further, the "glass transition temperature" is measured by a conventional method known in the art, for example, it can be measured by differential scanning calorimetry (DSC). In addition, functional groups such as "acid value" and "hydroxyl value" may be measured by a method well known in the art, for example, may represent a value measured by a titration method.

The transparent paint composition for automobile repair according to the present invention comprises: a main part including a first acrylic resin, a second acrylic resin, a third acrylic resin, a fourth acrylic resin and a polyester resin, a solvent and an additive; And a hardener part; may include. That is, the transparent coating composition may be a two-component coating composition including a main part and a hardener part.

Subject part

1st acrylic resin

The first acrylic resin serves to improve the appearance characteristics, particularly gloss, of the produced coating film.

The first acrylic resin is not particularly limited as long as it is commonly included in the transparent coating composition, and a product synthesized directly according to a known method may be used or a commercially available product may be used. In this case, the first acrylic resin may be prepared by polymerizing at least one of a vinyl monomer and a (meth)acrylate monomer.

The kind of the vinyl monomer is not particularly limited, but, for example, styrene, methylstyrene, dimethylstyrene, fluorostyrene, ethoxystyrene, methoxystyrene, phenylene vinyl ketone, vinyl t-butyl benzoate, vinyl cyclohexano Eight, vinyl acetate, vinyl pyrrolidone, vinyl chloride, vinyl alcohol, acetoxy styrene, t-butyl styrene and at least one selected from vinyl toluene may be used.

As the (meth)acrylate monomer, for example, 2-hydroxypropyl methacrylate, propyl methacrylate, t-butylaminoethyl methacrylate, dicyclopentenyl oxyethyl methacrylate, acrylic acid dimer, hexanediol Diacrylate, t-butyl acrylate, triisopropylsilyl acrylate, benzyl methacrylate, 2-hydroxyethyl methacrylate, trimethylolpropane triacrylate, tripropylene glycol diacrylate, ethyl methacrylate, Isobutyl methacrylate, hydroxyisopropyl methacrylate, isopropyl methacrylate, cyclohexyl methacrylate, triisopropyl silyl methacrylate, isobornyl acrylate, t-butylcyclohexyl methacrylate, trimethylcyclo Hexyl methacrylate, methyl methacrylate, acrylic acid, t-butyl methacrylate, isobornyl methacrylate, methacrylonitrile, methacrylic acid, acrylamide, methacrylamide, chlorostyrene, cyclohexyl vinyl ether More than one type can be used.

In this case, the first acrylic resin may have a glass transition temperature (Tg) of 70°C or more and less than 100°C, 70 to 90°C, or 80 to 90°C. When the glass transition temperature of the first acrylic resin is within the above range, there is an effect of improving the hardness.

In addition, the first acrylic resin may have an acid value (Av) of 3 to 15 mgKOH/g, or 3 to 10 mgKOH/g. When the acid value of the first acrylic resin is within the above range, solubility and clarity are improved.

In addition, the first acrylic resin may have a hydroxyl value (Ohv) of 130 to 160 mgKOH/g, or 140 to 150 mgKOH/g. When the hydroxyl group of the first acrylic resin is within the above range, the sagging property is improved.

In addition, the first acrylic resin may have a weight average molecular weight (Mw) of 1,500 to 3,500 g/mol, or 2,000 to 3,000 g/mol. When the weight average molecular weight of the first acrylic resin is within the above range, chemical resistance and a feeling of spraying (spraying) are soft.

In addition, the first acrylic resin may have a solid content of 60 to 90% by weight, 65 to 85% by weight, or 70 to 80% by weight based on the total weight of the resin. When the solid content of the first acrylic resin is within the above range, high solidification of the composition may be realized, and paintability may be excellent.

The first acrylic resin may be included in the composition in an amount of 5 to 20 parts by weight, or 8 to 15 parts by weight based on 10 to 30 parts by weight of the second acrylic resin in the main part. When the first acrylic resin is contained within the above content range, there is a good effect of compatibility.

2nd acrylic resin

The second acrylic resin serves to secure the dryness of the composition and improve the smoothness of the prepared coating film.

The second acrylic resin may be directly synthesized in the same manner as described for the first acrylic resin, or a commercially available product may be used.

In this case, the second acrylic resin may have a glass transition temperature (Tg) of 100°C or more and 160°C or less, 120 to 150°C, or 130 to 140°C. When the glass transition temperature of the second acrylic resin is within the above range, there is an effect of imparting hardness and improving drying properties of the coating film.

In addition, the second acrylic resin may have an acid value (Av) of 5 to 30 mgKOH/g, 7 to 20 mgKOH/g, or 8 to 15 mgKOH/g. When the acid value of the second acrylic resin is within the above range, mixing stability with other resins is increased and spreadability is excellent.

Further, the second acrylic resin may have a hydroxyl value (Ohv) of 95 to 125 mgKOH/g, or 100 to 115 mgKOH/g. When the hydroxyl group of the second acrylic resin is within the above range, clarity and reactivity are improved.

In addition, the second acrylic resin may have a weight average molecular weight (Mw) of 5,500 to 7,500 g/mol, or 6,000 to 7,000 g/mol. When the weight average molecular weight of the second acrylic resin is within the above range, there is an effect of improving pinhole resistance, chemical resistance, abrasion resistance, and solvent resistance.

In addition, the second acrylic resin may have a solid content of 50 to 80% by weight, 55 to 75% by weight, or 60 to 70% by weight based on the total weight of the resin. When the solid content of the second acrylic resin is within the above range, there is an effect of improving urethane reactivity.

Further, the second acrylic resin may be included in the composition in an amount of 10 to 30 parts by weight, or 13 to 23 parts by weight based on 5 to 20 parts by weight of the first acrylic resin in the main part. When the second acrylic resin is contained within the above content range, there is an effect of controlling drying and curing speed of the transparent paint.

3rd acrylic resin

The third acrylic resin serves to improve the economy of the composition and improve the solid content of the composition by reducing the amount of hardener used by lowering the hydroxyl value of the composition.

The third acrylic resin may be directly synthesized in the same manner as described for the first acrylic resin, or a commercially available product may be used.

In this case, the third acrylic resin may have a glass transition temperature of 10°C or less, 1 to 10°C, or 3 to 8°C. When the glass transition temperature of the third acrylic resin is within the above range, there is an effect of improving paintability and softness of the coating film.

In addition, the third acrylic resin may have an acid value (Av) of 3 to 15 mgKOH/g, or 5 to 12 mgKOH/g. When the acid value of the third acrylic resin is within the above range, there is an effect of improving resin compatibility and excellent image image quality of the coated film.

Further, the third acrylic resin may have a hydroxyl value (Ohv) of less than 100 mgKOH/g, 50 to 80 mgKOH/g, or 65 to 75 mgKOH/g. When the hydroxyl group of the third acrylic resin is within the above range, there is an effect of improving sagging property.

In addition, the third acrylic resin may have a weight average molecular weight (Mw) of 2,000 to 3,000 g/mol, or 2,300 to 2,800 g/mol. When the weight average molecular weight of the third acrylic resin is within the above range, there is an effect of improving workability (spray feeling) by lowering the paint viscosity.

In addition, the third acrylic resin may have a solid content of 65 to 90% by weight, 70 to 85% by weight, or 75 to 83% by weight based on the total weight of the resin. When the solid content of the third acrylic resin is within the above range, there is an effect that the content of the total volatile organic compounds (TVOC) as the high solid content resin is lowered.

Further, the third acrylic resin may be included in the composition in an amount of 25 to 50 parts by weight, or 28 to 45 parts by weight based on 5 to 20 parts by weight of the first acrylic resin in the main part. When the third acrylic resin is included within the above content range, there is an advantageous effect in controlling the mixing ratio of the main material and the curing agent.

4th acrylic resin

The fourth acrylic resin serves to improve the appearance characteristics of the produced coating film, particularly the image sharpness.

The fourth acrylic resin may be directly synthesized in the same manner as described for the first acrylic resin, or a commercially available product may be used.

In this case, the fourth acrylic resin may have a glass transition temperature of 10°C or less, 1 to 10°C, or 5 to 10°C. When the glass transition temperature of the fourth acrylic resin is within the above range, the softness of the coating film is increased, thereby improving the rust resistance.

Further, the fourth acrylic resin may have a hydroxyl value (Ohv) of 120 to 160 mgKOH/g, 130 to 155 mgKOH/g, or 135 to 150 mgKOH/g. When the hydroxyl group of the fourth acrylic resin is within the above range, urethane reactivity is improved, so that a coating film having excellent pinhole resistance and chemical resistance can be prepared.

In addition, the fourth acrylic resin may have a weight average molecular weight (Mw) of 1,500 to 3,500 g/mol, or 2,300 to 3,000 g/mol. When the weight average molecular weight of the fourth acrylic resin is within the above range, not only excellent chemical resistance and abrasion resistance, but also surface stickiness of the coating film is minimized and spreadability is improved.

In addition, the fourth acrylic resin may have a solid content of 65 to 90% by weight, 70 to 85% by weight, or 75 to 83% by weight based on the total weight of the resin. When the solid content of the fourth acrylic resin is within the above range, there is an effect of highly solidifying the composition.

Further, the fourth acrylic resin may be included in the composition in an amount of 10 to 30 parts by weight, or 10 to 20 parts by weight with respect to the first acrylic resin in 5 to 20 parts by weight in the main part. When the fourth acrylic resin is included within the above range, the appearance is excellent and the gloss is increased.

The composition may include a first acrylic resin and a second acrylic resin in a weight ratio of 1: 0.7 to 2.2. When the mixing weight ratio of the acrylic resins is within the above range, there is an effect of improving the gloss and drying properties of the prepared coating film.

The composition may include a first acrylic resin and a third acrylic resin in a weight ratio of 1: 1.7 to 3.5. When the mixing weight ratio of the acrylic resins is within the above range, there is an effect of improving the spreadability of the prepared coating film.

Polyester resin

The polyester resin serves to increase the solid content of the composition and improve the appearance, smoothness, scratch resistance and slip properties of the prepared coating film.

The polyester resin may be directly synthesized according to a known method, or a commercially available product may be used. For example, the polyester resin can be prepared by reacting a carboxylic acid and a polyol. At this time, the carboxylic acid is adipic acid (AA), isophthalic acid (IPA), trimalic anhydride (TMA), alicyclic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, fumaric acid, maleic anhydride, It may be one or more selected from the group consisting of tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and derivatives thereof. In addition, the polyol is methoxypolyethylene glycol, 1,6-hexanediol (1,6-HD), neopentyl glycol (NPG), trimethylol propane (TMP), ethylene glycol, propylene glycol, diethylene glycol, butanediol 1 It may be one or more selected from the group consisting of, 4-hexanediol and 3-methylpentanediol.

In this case, the polyester resin may have an acid value (Av) of 5 to 15 mgKOH/g, or 8 to 13 mgKOH/g. When the acid value of the polyester resin is within the above range, rapid hardening by heat treatment is prevented, thereby preventing poor appearance and popping of the coating film.

In addition, the polyester resin may have a glass transition temperature (Tg) of -60 to -40°C, or -55 to -45°C. When the glass transition temperature of the polyester resin is within the above range, the coating spray feeling (spray feeling) is excellent, and there is an effect of imparting flexibility to the coating film.

Further, the polyester resin may have a hydroxyl value (Ohv) of 150 to 250 mgKOH/g, or 180 to 230 mgKOH/g. When the hydroxyl value of the polyester resin is within the above range, there is an effect of improving the spreadability of the coating film and improving chemical resistance by the urethane reaction.

In addition, the polyester resin may have a weight average molecular weight (Mw) of 1,500 to 3,500 g/mol, 2,000 to 3,000 g/mol, or 2,400 to 2,900 g/mol. When the weight average molecular weight of the polyester resin is within the above range, there is an effect of forming a smooth and soft (SOFT) coating film of the paint.

In addition, the polyester resin may have a solid content of 80 to 98% by weight, 85 to 95% by weight, or 88 to 93% by weight based on the total weight of the resin. When the solid content of the polyester resin is within the above range, there is an effect of reducing TVOC due to the high solid content.

Further, the polyester resin may be included in the composition in an amount of 1 to 10 parts by weight, or 1 to 5 parts by weight based on 5 to 20 parts by weight of the first acrylic resin in the main part. When the polyester resin is contained within the above content range, there is an effect of improving the appearance, scratch resistance, and smoothness of the coating film.

solvent

The transparent coating composition according to the present invention may further include a solvent. In this case, the solvent controls the viscosity of the composition, improves drying properties, and improves the appearance characteristics and spreadability of the prepared coating film. The solvent is not particularly limited as long as it is generally used in a transparent coating composition, but may include, for example, at least one selected from the group consisting of aromatic, acetate-based, alcohol-based, ketone-based, and propionate-based. Specifically, the solvent is an aromatic solvent such as toluene and xylene; 1-methoxy-2-propylacetate, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, dimethyl glutarate, dimethyl succinate, dimethyl adipate, propylene glycol methyl ether acetate, butyl carbitol acetate, etc. Acetate-based solvents; alcohol solvents such as n-butanol, propanol, and 1-methoxy-2-propanol; Ketone systems such as acetone, methyl ethyl ketone, methyl butyl ketone and methyl isobutyl ketone; And propionate solvents such as ethyl ethoxy propionate. Further, commercially available products of the aromatic solvent include cocosol #100, cocosol #150, and the like.

Further, the solvent may be included in the composition in an amount of 10 to 40 parts by weight, or 20 to 30 parts by weight based on 5 to 20 parts by weight of the first acrylic resin in the main part. When the solvent is contained within the above range, there is an effect of improving workability and drying properties by appropriately adjusting the viscosity of the composition.

additive

The transparent coating composition according to the present invention may further include at least one selected from the group consisting of a curing accelerator, an ultraviolet absorber, a surface modifier, a pinhole inhibitor, and a reaction retarder.

The curing accelerator serves to regulate the curing rate of the composition by accelerating the urethane reaction. At this time, the curing accelerator is not particularly limited as long as it is a urethane reaction accelerator commonly used. For example, the curing accelerator may include metal compounds such as dibutyl tin diacetate, dibutyl tin dilaurate, stern octate, and dibutyl tin mercaptide; Tertiary amines such as triethyldiamine, triethanolamine, 1,4-diazocyclooctane, dimethylethanolamine, ethylmorphine, dimethylaminoethylmorpholine, and dimethylcyclohexylamine; And alkali metal carboxylates or zinc-based complex compounds.

In addition, the ultraviolet absorber absorbs ultraviolet rays to prevent discoloration of the coating composition, and serves to prevent weather resistance of the coating film prepared from the composition. At this time, the ultraviolet absorber may be used without particular limitation as long as it is a conventional one that can be used in the coating composition, and examples thereof include benzotriazole-based, such as hydroxyphenyl benzotriazole. Further, commercially available products of the ultraviolet absorber include BASF's Tinuvin 384, and EVERLIGHT CHEMICAL's eversorb 83.

Furthermore, the surface modifier serves to improve the spreadability (leveling property) of the produced coating film. In addition, the surface modifier may be used without particular limitation as long as it is a conventional one that may be used in the coating composition, and examples thereof include a silicone-based surface modifier or a fluorine-based surface modifier. In addition, commercially available products of the silicone-based surface modifier include BYK-Chemical's BYK-077, BYK-300, BYK-330, BYK-358, BYK-361, BYK-375, BYK-380, BYK-385, etc., and Tego ( TEGO)'s Flow 425, Glide 435, and the like. Further, as a commercial product of the fluorine-based surface control agent, DIC (DaiNippon Ink & Chemicals)'s F-114, F-411, F-450, F-493, F-478, F-479, F-480SF, MCF-350SF, TF-1442, etc. are mentioned.

In addition, the pinhole inhibitor serves to prevent the occurrence of pinholes in the manufactured coating film. At this time, the pinhole inhibitor may be used without particular limitation as long as it is a conventional one that may be used in the coating composition, and for example, a polysiloxane-based compound may be mentioned. Further, commercially available products of the above pinhole inhibitors include Byk-051, Byk-052, Byk-054, Byk-057, Byk-063, Byk-065, Byk-072, Byk-085, Byk-088, and the like.

In addition, the reaction delay agent serves to delay pot life. At this time, the reaction retarding agent may be, for example, glycol dimercaptopropionate (GDMP, glycol-dimercaptopropionate).

The additive may be included in the composition in an amount of 1 to 20 parts by weight, or 3 to 10 parts by weight based on 5 to 20 parts by weight of the first acrylic resin in the main part. When the additive is included within the above content range, the physical properties of the transparent paint may be excellent.

The transparent coating composition according to the present invention includes a main part including four types of acrylic resins, polyester resins, solvents and additives as described above; And a hardener part; may include. That is, the transparent coating composition may be a two-component coating composition including a main part and a hardener part.

In this case, the main body may have a solid content of 50 to 60% by weight, or 54 to 59% by weight, based on the total weight of the main unit. When the solid content of the main part is within the above range, the TVOC is 430 μg/cm 2·hr or less, or 420 μg/cm 2·hr or less, which is an eco-friendly effect.

Hardener part

The hardener part may include a hardener and a hardener part solvent.

Furthermore, the curing agent may be a polyisocyanate compound. Further, the type of the curing agent is not particularly limited as long as it can react with the hydroxyl group of the main part to form a urethane bond. For example, the curing agent may include an aliphatic polyisocyanate compound without yellowing, and specifically, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethyl xylene diisocyanate Isocyanates or mixtures thereof.

In addition, the curing agent may be included in the composition in an amount of 50 to 80 parts by weight, 55 to 78 parts by weight, or 60 to 75 parts by weight based on 100 parts by weight of the curing agent part. When the content of the curing agent is within the above range, it is possible to improve the physical properties of the prepared coating film by forming a stable cured product.

The hardener part solvent serves to adjust the viscosity, dryness and hygroscopicity of the hardener part. At this time, the curing agent part solvent is not particularly limited as long as it can be used in the coating material curing agent part, and the solvent disclosed in the solvent may be used.

In addition, the curing agent part solvent may be included in the composition in an amount of 20 to 50 parts by weight, 22 to 45 parts by weight, or 25 to 40 parts by weight based on 100 parts by weight of the curing agent part.

The main part and the curing agent part may be mixed in a weight ratio of 1:1 to 5, and for another example, 1: 2 to 4 to prepare a transparent coating composition.

The transparent paint composition for automobile repair according to the present invention as described above is economical due to its high solid content and high drying speed, and is eco-friendly due to its low VOC content. In addition, the coating film prepared from the transparent coating composition has excellent paintability, spreadability, pinhole resistance and hardness.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are only intended to aid understanding of the present invention, and the scope of the present invention is not limited to these examples in any sense.

[Example]

Examples 1 to 9. Preparation of the main part

A main part was prepared by mixing the components of the same content as in Table 1.

Ingredients (parts by weight) Example One 2 3 4 5 6 7 8 9 1st acrylic resin-1 95 85 150 - - 150 95 - 150 2nd acrylic resin-1 150 180 130 - - 130 150 - 130 3rd acrylic resin-1 300 290 280 - - - - - 280 4th acrylic resin-1 135 160 100 - - - - - 100 1st acrylic resin-2 - - - 95 - - - 100 - 2nd acrylic resin-2 - - - 150 - - - 150 - 3rd acrylic resin-2 - - - 300 - 280 - - - 4th acrylic resin-2 - - - 135 - 100 - - - 1st acrylic resin-3 - - - - 100 - - - - 2nd acrylic resin-3 - - - - 150 - - - - 3rd acrylic resin-3 - - - - 310 - 300 310 - 4th acrylic resin-3 - - - - 120 - 135 120 - Polyester resin-1 30 15 50 - - 50 - - - Polyester resin-2 - - - 30 - - 30 - - Polyester resin-3 - - - - 30 - - 30 50 Solvent-1 125 120.5 125.5 125 140.5 125.5 125 140.5 125.5 Solvent-2 115 100 115 115 100 115 115 100 115 Solvent-3 5 5 5 5 5 5 5 5 5 Solvent-4 10 10 10 10 10 10 10 10 10 Hardening accelerator 15 15 15 15 15 15 15 15 15 Ultraviolet absorber 15 15 15 15 15 15 15 15 15 Surface Modifier-1 2 2 2 2 2 2 2 2 2 Surface Adjuster-2 2 1.5 1.5 2 1.5 1.5 2 1.5 1.5 Pinhole inhibitor One One One One One One One One One total 1000 1000 1000 1000 1000 1000 1000 1000 1000

Comparative Examples 1 to 4. Preparation of the main part

A main part was prepared by mixing the components of the contents shown in Table 2.

Ingredients (parts by weight) Comparative example One 2 3 4 1st acrylic resin-1 - 297.3 105 - 2nd acrylic resin-1 555 105 160 - 3rd acrylic resin-1 - - 300 - 4th acrylic resin-1 76- 260 145 - 1st acrylic resin-4 - - - 95 2nd acrylic resin-4 - - - 150 3rd acrylic resin-4 - - - 300 4th acrylic resin-4 - - - 135 Polyester resin-1 - 60 - - Polyester resin-4 80 - - 30 Solvent-1 85 102.3 125 125 Solvent-2 65.3 130 115 115 Solvent-3 6 10 5 5 Solvent-4 - - 10 10 Solvent-5 22.3 - - - Solvent-6 20 - - - Hardening accelerator 72 8 15 15 Ultraviolet absorber 15 21 15 15 Surface Modifier-1 -One 3 2 2 Surface Adjuster-2 1.8 2 2 2 Pinhole inhibitor 0.6 1.4 One One total 1000 1000 1000 1000

Hereinafter, the manufacturer and product names, or ingredient names of each component used in Comparative Examples and Examples are shown in Table 3.

ingredient Remark 1st acrylic resin-1 NV: 75% by weight, Av: 6mgKOH/g, Tg: 85°C, OHV: 145mgKOH/g, Mw: 2,500g/mol 1st acrylic resin-2 NV: 72% by weight, Av: 3mgKOH/g, Tg: 81°C, OHV: 140mgKOH/g, Mw: 2,000g/mol 1st acrylic resin-3 NV: 74% by weight, Av: 10mgKOH/g, Tg: 90°C, OHV: 150mgKOH/g Mw: 3,000g/mol 1st acrylic resin-4 NV: 65% by weight, Av: 24mgKOH/g, Tg: 105°C, OHV: 125mgKOH/g Mw: 4,000g/mol 2nd acrylic resin-1 NV: 64% by weight, Av: 11mgKOH/g, Tg: 135°C, Ohv: 107mgKOH/g, Mw: 6,400g/mol 2nd acrylic resin-2 NV: 65% by weight, Av: 8 mgKOH/g, Tg: 130°C, Ohv: 100 mgKOH/g, Mw: 6,000 g/mol 2nd acrylic resin-3 NV: 66% by weight, Av: 15mgKOH/g, Tg: 139°C, Ohv: 115mgKOH/g, Mw: 7,000g/mol 2nd acrylic resin-4 NV: 65% by weight, Av: 3mgKOH/g, Tg: 95°C, Ohv: 90mgKOH/g, Mw: 5,000g/mol 3rd acrylic resin-1 NV: 75% by weight, Av: 8mgKOH/g, Tg: 5°C, Ohv: 70mgKOH/g, Mw: 2,550g/mol 3rd acrylic resin-2 NV: 80% by weight, Av: 5mgKOH/g, Tg: 3°C, Ohv: 65mgKOH/g, Mw: 2,300g/mol 3rd acrylic resin-3 NV: 83% by weight, Av: 12mgKOH/g, Tg: 8°C, Ohv: 75mgKOH/g, Mw: 2,800g/mol 3rd acrylic resin-4 NV: 60% by weight, Av: 0mgKOH/g, Tg: -1°C, Ohv: 46mgKOH/g, Mw: 1,800g/mol 4th acrylic resin-1 NV: 77% by weight, Tg: 7°C, Ohv: 142mgKOH/g, Mw: 2,600 g/mol 4th acrylic resin-2 NV: 81% by weight, Tg: 5°C, Ohv: 135mgKOH/g, Mw: 2,300 g/mol 4th acrylic resin-3 NV: 80% by weight, Tg: 10°C, Ohv: 150mgKOH/g, Mw: 3,000 g/mol 4th acrylic resin-4 NV: 60% by weight, Tg: -7°C, Ohv: 165mgKOH/g, Mw: 3,700 g/mol Polyester resin-1 NV: 90% by weight, Ohv: 200mgKOH/g, Tg: -50°C Av: 10mgKOH/g, MW: 2,600g/mol Polyester resin-2 NV: 92% by weight, Ohv: 180mgKOH/g, Tg: -55°C Av: 8mgKOH/g MW: 2,400g/mol Polyester resin-3 NV: 88% by weight, Ohv: 230mgKOH/g, Tg: -45°C Av: 13mgKOH/g MW: 2,900g/mol Polyester resin-4 NV: 60% by weight, Ohv: 138mgKOH/g, Tg: -66°C, Av: 1mgKOH/g MW: 1,000g/mol Solvent-1 Butyl acetate Solvent-2 Propylene glycol methyl ether acetate Solvent-3 Butyl carbitol acetate Solvent-4 Acetone Solvent-5 Xylene Solvent-6 Methyl ethyl ketone (MEK) Hardening accelerator 5% dibutyltinbis[(1-oxododecyl)oxy]stannan solution (solvent: xylene) Ultraviolet absorber Manufacturer: EVERLIGHT CHEMICAL, Product name: eversorb 83 Surface Modifier-1 Manufacturer: BYK-Chemical, Product Name: BYK-358 Surface Adjuster-2 Manufacturer: TEGO, Product Name: Flow 425 Pinhole inhibitor Manufacturer: BYK-Chemical, Product Name: BYK-072

Reference example. Preparation of hardener part

46 parts by weight of polyisocyanate compound-1 (ingredient name: hexamethylene diisocyanate, NCO content: 20.9% by weight, viscosity: 375 mPa·s, solid content: 90% by weight), 22 parts by weight of polyisocyanate compound-2 (ingredient name: hexamethylene di Isocyanate, NCO content: 21.8% by weight, viscosity: 3,000 mPa·s, solid content: 100% by weight, Mw: 2,149 g/mol), 1.5 parts by weight of triethyl ortho-formate (boiling point: 146° C., Mw: 148.23 g /mol), and 30.5 parts by weight of butyl acetate (specific gravity: 0.881, flash point: 24°C, melting point: 78°C) were mixed to prepare a curing agent part.

Experimental Example 1. Evaluation of properties of coating film

A transparent coating composition was prepared by mixing the main part prepared in Examples 1 to 9 and Comparative Examples 1 to 4 and the curing agent part of the reference example at a weight ratio of 3:1. Thereafter, the transparent coating composition was coated twice with a wet-on-wet coating method on the specimen to form a coating film having a dry thickness of 50 to 60 µm, and then the physical properties of the coating film were measured in the following manner. And the results are shown in Table 4 below.

(1) Total volatile organic compounds (TVOC) emission

For example, put a specimen with a coating film of 10 cm × 10 cm (width × length) in a chamber at 25°C and 50% relative humidity (RH), and install a thermal desorption device (ATD-400, Markers, UK) and an adsorption tube (Tenax TA). After measuring the amount of volatile organic compounds released, it was calculated using the calculation formula. At this time, the formula for calculating the content of Article 3 of the National Institute of Environmental Sciences Notice No. 2005-11 was applied.

(2) spray feeling

SATA HVLP gun 1.4mm nozzle standard, discharge volume 2 turns, air pressure based on 1.7bar of air pressure, 25cm apart from the specimen 45cm x 45cm (width x length) and applied 5 times from top to bottom left and right, the repulsive force of the sprayed paint and the amount of paint discharged, the coating film The spray feeling was evaluated based on the amount of paint arriving at.

(3) Painted voice

After coating the paint, it was dried at 60° C. for 30 minutes, and then the coating film thickness was measured to impart paintability.

(4) Spreadability

After drying in the same manner as in item (3), the spreadability of the coating film was measured based on the OP value and the DOI value using the WAVESCAN DOI as a measuring device.

(5) sagging

After coating, the thickness of the coating film was measured at the point where the paint began to flow when left vertically.

(6) Curing conditions

After coating the paint, the time for the coating film to harden upon drying at 60°C was measured. At this time, the time to be hardened was measured for the time when the coating film was hardly pressed and twisted left and right, and no marks were generated on the coating film.

(7) Pinhole resistance

After coating the paint, it was dried at 60° C. for 30 minutes, and then the occurrence and degree of pinholes in the coating film were checked.

As shown in Table 4, it was found that the coating films prepared from the compositions of Examples 1 to 9 were superior to the coating films prepared from the compositions of Comparative Examples 1 to 4 in physical properties.

Experimental Example 2.

A transparent coating composition was prepared by mixing the main part prepared in Examples and Comparative Examples and the curing agent part of the reference example at a weight ratio of 3:1. Thereafter, a base paint (manufacturer: KCC, product name: UT5901) was coated to a dry thickness of 20 μm on the electrodeposited specimen (30cm×30cm, width×length), and the transparent coating composition was coated on the base coating film to a dry thickness of 60㎛. Painted, dried, and cured to form a transparent coating film to obtain a final coating film. Thereafter, the physical properties of the final coating film were measured in the following manner, and the results are shown in Table 5 below.

(1) hardness

The hardness of the final coating film was measured by measuring the number of reciprocations of the pendulum using a Pendulum Hardness Tester.

(2) Appearance of coating film

The gloss (LU), image sharpness (SH), and smoothness (OP) of the final coating were measured using Wave Scan DOI (BYK Gardner), a vehicle exterior measuring instrument, and the overall appearance evaluation value (CF) was calculated using the measured physical properties. It was calculated by the following Equation 1. At this time, it was determined that the higher the CF, the better the appearance characteristics of the coating film.

[Equation 1]

CF = LU×0.15 + SH×0.35 + OP×0.5

(3) SW (Short Wave) and LW (Long Wave)

The short wave and long wave values of the final coating film were measured using a Wave Scan DOI (BYK Gardner), which is an automobile appearance measuring device.

(4) Young-Sung Sun (DOI, Distinctness of Image )

Using a Wave Scan DOI (BYK Gardner), which is an automobile appearance measuring instrument, the image sharpness (DOI) of the final coating was measured.

As shown in Table 5, the coating film prepared from the compositions of Examples 1 to 9 has better hardness than the coating film prepared from the composition of Comparative Examples 2 to 4, and CF, LU, and the coating film prepared from the composition of Comparative Example 1 It was found that smoothness such as SH and DOI was excellent.

Claims (7)

Including a first acrylic resin having a glass transition temperature of 70°C to less than 100°C, a second acrylic resin having a glass transition temperature of 100°C to 160°C, and a third and fourth acrylic resin and polyester resin having a glass transition temperature of 10°C or less and,
A transparent coating composition for automobile repair, wherein the hydroxyl value of the third acrylic resin is lower than that of the fourth acrylic resin. The method according to claim 1,
The first acrylic resin has an acid value of 3 to 15 mgKOH/g, a hydroxyl value of 130 to 160 mgKOH/g, and a weight average molecular weight of 1,500 to 3,500 g/mol, a transparent paint composition for automobile repair. The method according to claim 1,
The second acrylic resin has an acid value of 5 to 30 mgKOH/g, a hydroxyl value of 95 to 125 mgKOH/g, and a weight average molecular weight of 5,500 to 7,500 g/mol, a transparent paint composition for automobile repair. The method according to claim 1,
The third acrylic resin has an acid value of 3 to 15 mgKOH/g, a hydroxyl value of less than 100 mgKOH/g, and a weight average molecular weight of 2,000 to 3,000 g/mol, a transparent paint composition for automobile repair. The method according to claim 1,
The fourth acrylic resin has a hydroxyl value of 120 to 160 mgKOH/g, and a weight average molecular weight of 1,500 to 3,500 g/mol, a transparent paint composition for automobile repair. The method according to claim 1,
The polyester resin has an acid value of 5 to 15 mgKOH/g, a glass transition temperature of -60 to -40°C, and a hydroxyl value of 150 to 250 mgKOH/g, a transparent paint composition for automobile repair. The method according to claim 1,
The transparent paint composition is 5 to 20 parts by weight of the first acrylic resin, 10 to 30 parts by weight of the second acrylic resin, 25 to 50 parts by weight of the third acrylic resin, 10 to 30 parts by weight of the fourth acrylic resin and 1 to A transparent coating composition for automobile repair comprising 10 parts by weight of a polyester resin.