KR20210108800A - Clear coat composition for refinishing automobiles - Google Patents

Abstract

The present invention relates to a clear coat composition for repairing a vehicle comprising: a first acrylic resin; a second acrylic resin; a third acrylic resin; and a polyester resin, wherein the first acrylic resin has a weight average molecular weight of 2,000-5,000 g/mol, and the second acrylic resin has a weight average molecular weight of 5,500-10,000 g/mol, and the third acrylic resin has a weight average molecular weight of 12,000 g/mol or more.

Description

Transparent paint 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.

Efforts to shorten working hours and reduce heat treatment costs are continuing in order to gain competitiveness in the automobile repair and painting industry due to the large size of automobile maintenance companies and the integration and closure of small companies. For this reason, the economic feasibility of paint and work is being emphasized more in the automobile repair painting system. In particular, in the era of high oil prices, there is a demand for paints that can be completed quickly while consuming less energy in the automobile repair field.

Automobile repair is a process that restores a wide range of damaged areas to their original form, ranging from small local vehicle damage to large 3-panel damage repair. Recently, with the advancement of the exterior of automobiles, there is a trend of increasing partial repair and local area repair.

The automobile repair process for repairing damaged parts is largely divided into a surface adjustment stage, an intermediate process stage, and a topcoat process stage. The top coating process step is typically a step of masking a portion that does not require topcoating, a step of applying a color paint to match the color, a step of applying a transparent paint to impart gloss and increasing durability, and a light to finish the exterior surface of the painting cleanly including betting and evaluation stages, etc. At this time, as the transparent paint used in the topcoating process step, a paint composition using various resins such as epoxy-based, urethane-based, sealant-based, and acrylic-based resins are used.

Specifically, Korean Patent Registration No. 1,826,058 (Patent Document 1) discloses an acrylic polyol resin synthesized using methyl methacrylate, isobornyl acrylate, butyl acrylate, hydroxyethyl methacrylate, and methacrylic acid; light stabilizer; UV 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 Document 1 has a limitation in that scratch resistance is insufficient.

Therefore, it is possible to form a coating film with excellent paintability, spreadability, pinhole resistance and hardness, and it is suitable for a transparent coating composition with a low content of volatile organic compounds (VOC), high solid content, and fast drying speed, which is excellent in economical efficiency. There is a need for R&D.

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

The present invention provides a transparent coating composition that can form a coating film with excellent paintability, spreadability, pinhole resistance and hardness, and has a low volatile organic solvent compound (VOC) content, high solid content, and fast drying speed, which is excellent in economical efficiency.

In order to achieve the above object, the present invention includes a first acrylic resin, a second acrylic resin, a third acrylic resin and a polyester resin,

The first acrylic resin has a weight average molecular weight of 2,000 to 5,000 g / mol,

The second acrylic resin has a weight average molecular weight of 5,500 to 10,000 g/mol,

The third acrylic resin has a weight average molecular weight of 12,000 g/mol or more, and provides a transparent paint composition for automobile repair.

The transparent paint composition for automobile repair according to the present invention includes three or more kinds of acrylic resins having different weight average molecular weights, and is economical due to high solids content and fast drying speed, and is environmentally friendly due to low VOC content. In addition, the coating film prepared from the transparent coating composition is excellent in paintability, spreadability, pinhole resistance and hardness.

Hereinafter, the present invention will be described in detail.

As used herein, "weight average molecular weight" is measured by a conventional method known in the art, for example, it can be measured by a GPC (gel permeation chromatograph) method. Furthermore, 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 method of titration.

In addition, in this specification, "(meth)acryl" means "acryl" and/or "methacrylic", and "(meth)acrylate" means "acrylate" and/or "methacrylate" .

The transparent paint composition for automobile repair according to the present invention includes a first acrylic resin, a second acrylic resin, a third acrylic resin, and a polyester resin. For example, the composition may include a main part including a first acrylic resin, a second acrylic resin, a third acrylic resin and a polyester resin, a solvent and an additive; and a curing agent unit; That is, the transparent coating composition may be a two-component coating composition including a main part and a curing agent part.

subject part

first acrylic resin

The first acrylic resin serves to improve the appearance characteristics, in particular, the gloss of the prepared coating film.

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

The type 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 At least one selected from the group consisting of ester, vinyl acetate, vinyl pyrrolidone, vinyl chloride, vinyl alcohol, acetoxystyrene, t-butylstyrene and vinyltoluene may be used.

As the (meth)acrylate monomer, for example, 2-hydroxypropyl methacrylate, propyl methacrylate, t-butylaminoethyl methacrylate, dicyclopentenyl oxyethyl methacrylate, acrylic acid dimer, hexane Diol 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, trimethyl from the group consisting of cyclohexyl methacrylate, methyl methacrylate, acrylic acid, t-butyl methacrylate, isobornyl methacrylate, methacrylonitrile, methacrylic acid, acrylamide, methacrylamide and cyclohexylvinylether One or more selected types may be used.

The first acrylic resin may be prepared using a radical polymerization method, and the weight average molecular weight may be adjusted according to an initiator and polymerization time.

In this case, the first acrylic resin may have a glass transition temperature (Tg) of 40 to 65 °C, or 50 to 63 °C. When the glass transition temperature of the first acrylic resin is within the above range, there is an effect of improving hardness. When the glass transition temperature of the first acrylic resin is out of the above range, hardness or sagging property may be reduced.

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, the solvent solubility of the resin and the image clarity of the coating film are improved.

The first acrylic resin may have a hydroxyl value (OHV) of 130 to 160 mgKOH/g, or 140 to 155 mgKOH/g. When the hydroxyl group of the first acrylic resin is within the above range, there is an effect that the sagging property is improved.

In addition, the first acrylic resin may have a weight average molecular weight (Mw) of 2,000 to 5,000 g/mol, 3,500 to 5,000 g/mol, or 4,000 to 5,000 g/mol. When the weight average molecular weight of the first acrylic resin is within the above range, there is a soft effect in chemical resistance and workability (spray feeling). When the weight average molecular weight of the first acrylic resin is out of the above range, paintability may decrease and curing time may be prolonged.

The first acrylic resin may have a solid content (NV) 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.

In addition, the first acrylic resin may be included in the composition in an amount of 0.5 to 20 parts by weight, or 1 to 15 parts by weight based on 40 to 70 parts by weight of the second acrylic resin. When the first acrylic resin is included within the content range, compatibility is good.

2nd acrylic resin

The second acrylic resin serves to secure 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 63 to 80 °C, or 65 to 78 °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. When the glass transition temperature of the second acrylic resin is out of the above range, the hardness and pinhole resistance of the coating film may be reduced.

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.

The second acrylic resin may have a hydroxyl value (OHV) of 95 to 125 mgKOH/g, or 100 to 120 mgKOH/g. When the hydroxyl group of the second acrylic resin is within the above range, the clarity of the coating film and the reactivity with the curing agent are improved.

In addition, the second acrylic resin may have a weight average molecular weight (Mw) of 5,500 to 10,000 g/mol, 5,800 to 9,000 g/mol, or 6,000 to 7,500 g/mol. When the weight average molecular weight of the second acrylic resin is within the above range, pinhole resistance, chemical resistance, abrasion resistance, and solvent resistance are improved. When the weight average molecular weight of the second acrylic resin is out of the above range, image clarity and smoothness may be deteriorated.

The second acrylic resin may have a solid content (NV) of 50 to 80% by weight, 55 to 75% by weight, or 60 to 67% 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 the urethane reactivity.

The second acrylic resin may be included in the composition in an amount of 40 to 70 parts by weight, or 40 to 60 parts by weight, based on 0.5 to 20 parts by weight of the first acrylic resin. When the second acrylic resin is included within the content range, there is an effect of controlling the drying rate and curing speed of the transparent paint.

3rd acrylic resin

The third acrylic resin lowers the hydroxyl value of the composition to reduce the amount of the curing agent used, thereby improving the economic feasibility of the composition and improving the solid content 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 30 to 60 °C, or 50 to 60 °C. When the glass transition temperature of the third acrylic resin is within the above range, there is an effect of improving the paintability and the softness of the coating film. When the glass transition temperature of the third acrylic resin is out of the above range, the paintability and image quality may be deteriorated.

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, the resin compatibility is improved and the image quality of the coated film is excellent.

The third acrylic resin may have a hydroxyl value (OHV) of 100 to 200 mgKOH/g, or 130 to 160 mgKOH/g. When the hydroxyl group of the third acrylic resin is within the above range, there is an effect of improving the sagging property.

In addition, the third acrylic resin may have a weight average molecular weight (Mw) of 12,000 g/mol or more, 12,000 to 15,000 g/mol, or 12,500 to 14,500 g/mol. When the weight average molecular weight of the third acrylic resin is within the above range, there is an effect of lowering the paint viscosity and improving the workability (spray feeling). When the weight average molecular weight of the third acrylic resin is out of the above range, workability (spray feeling) and gloss may be deteriorated.

The third acrylic resin may have a solid content (NV) of 60 to 90 wt%, or 60 to 70 wt%, 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 total volatile organic compounds (TVOC) as a high solid resin is lowered.

The third acrylic resin may be included in the composition in an amount of 1 to 15 parts by weight, or 5 to 10 parts by weight based on 0.5 to 20 parts by weight of the first acrylic resin. When the third acrylic resin is included within the content range, there is an advantageous effect in controlling the mixing ratio of the main agent and the curing agent.

The composition may include the first acrylic resin and the second acrylic resin in a weight ratio of 1: 2 to 30, or 1: 2.5 to 29. When the mixing weight ratio of the acrylic resins is within the above range, gloss and drying properties of the prepared coating film are improved.

The composition may include the first acrylic resin and the third acrylic resin in a weight ratio of 1: 0.1 to 5, or 1: 0.4 to 4. When the mixing weight ratio of the acrylic resins is within the above range, the spreadability of the prepared coating film is improved.

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 may be prepared by reacting a carboxylic acid with a polyol. In this case, the carboxylic acid is adipic acid (AA), isophthalic acid (IPA), trimmaletic anhydride (TMA), cycloaliphatic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, fumaric acid, maleic anhydride, It may be at least one 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 at least one 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 of the coating film and reducing the occurrence of popping. When the acid value of the polyester resin is out of the above range, hardness and gloss may be reduced.

In addition, the polyester resin may have a glass transition temperature (Tg) of -30 to -10 °C, or -25 to -15 °C. When the glass transition temperature of the polyester resin is within the above range, workability (spray feeling) is excellent, and there is an effect of imparting flexibility to the coating film. When the glass transition temperature of the polyester resin is out of the above range, workability (spray feeling) and image clarity may be deteriorated.

The polyester resin may have a hydroxyl value (OHV) of 100 to 180 mgKOH/g, or 110 to 150 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 the chemical resistance by the urethane reaction.

In addition, the polyester resin may have a weight average molecular weight (Mw) of 1,000 to 3,000 g/mol, 1,000 to 2,000 g/mol, or 1,300 to 1,900 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. When the weight average molecular weight of the polyester resin is out of the above range, smoothness and sagging properties of the paint may be deteriorated.

In addition, the polyester resin may have a solid content (NV) of 70 to 98% by weight, 75 to 90% by weight, or 75 to 85% 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 the content of total volatile organic compounds (TVOC) due to the high solid content.

The polyester resin may be included in the composition in an amount of 1 to 10 parts by weight, or 5 to 8.5 parts by weight based on 0.5 to 20 parts by weight of the first acrylic resin. When the polyester resin is included 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 serves to control the viscosity of the composition, improve dryness, and improve the appearance characteristics and spreadability of the prepared coating film. The solvent is not particularly limited as long as it is commonly used in the transparent coating composition.

Due to a large amount of solvent added to the coating composition, the solvent volatilizes into the atmosphere during the coating film formation process after coating. For this reason, the solvent included in the transparent coating composition according to the present invention may include an exempt solvent.

In this case, the t-VOC exemption solvents are substances designated by the Ministry of Environment as substances with low environmental impact among volatile organic compounds, particularly substances with low photochemical ozone creation potential (POCP) as substances exempt from content regulation. it means.

The exempt solvent may include, for example, dimethyl carbonate (DMC), para-chlorobenzotrifluoride (PCBTF, p-chlorobenzotrifluoride), and acetone. Specifically, dimethyl carbonate (DMC) can replace organic solvents such as toluene or xylene applied to conventional oil-based paints, is non-toxic, does not emit volatile organic compounds, and has high solubility.

In addition, the solvent may further include at least one selected from the group consisting of aromatics, acetates, alcohols, ketones, and propionates. For example, the solvent may include aromatic solvents such as toluene and xylene; 1-Methoxy-2-propyl acetate, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, dimethyl glutarate, dimethyl succinate, dimethyl adipate, propylene glycol methyl ether acetate (PMA), butyl carboxylate acetate-based solvents such as bitol acetate and butyl cellosolve acetate; alcohol solvents such as n-butanol, propanol, 1-methoxy-2-propanol, and 2-butoxyethanol; ketones such as acetone, methyl ethyl ketone, methyl butyl ketone and methyl isobutyl ketone; and propionate-based solvents such as ethylethoxypropionate; and the like. Moreover, as a commercial item of the said aromatic solvent, Cocosol #100, Cocosol #150, etc. are mentioned.

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 0.5 to 20 parts by weight of the first acrylic resin. When the solvent is included within the above range, there is an effect of improving workability and drying property by appropriately adjusting the viscosity of the composition.

additive

The transparent paint 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 conditioning agent, a pinhole inhibitor, a pot life delaying agent, and a reaction retarder. In this case, the additive is not particularly limited as long as it can be added to the coating composition in general.

The additive may be included in the composition in an amount of 1 to 5 parts by weight, or 1 to 4 parts by weight, based on 0.5 to 20 parts by weight of the first acrylic resin. When the additive is included within the 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 three kinds of acrylic resin, polyester resin, solvent and additives as described above; and a curing agent unit; That is, the transparent coating composition may be a two-component coating composition including a main part and a curing agent part.

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

hardener part

The curing agent part may include a curing agent and a curing agent part solvent.

In this case, the curing agent may be a polyisocyanate compound. In addition, the type of the curing agent is not particularly limited as long as it can form a urethane bond by reacting with the hydroxyl group of the main part. For example, the curing agent may include an aliphatic polyisocyanate compound without yellowing. Specifically, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexyl methane diisocyanate, tetramethyl xylene di 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 74 parts by weight, or 60 to 70 parts by weight based on 20 to 50 parts by weight of the curing agent solvent. 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 curing agent solvent serves to adjust the viscosity, dryness and hygroscopicity of the curing agent part. In this case, the curing agent solvent is not particularly limited as long as it can be used in the paint curing agent part, and the solvent disclosed in the solvent may be used.

In addition, the curing agent solvent may be included in the composition in an amount of 20 to 50 parts by weight, 25 to 45 parts by weight, or 30 to 40 parts by weight based on 50 to 80 parts by weight of the curing agent.

The main part and the curing agent part may be mixed in a weight ratio of 1 to 5:1, or 2 to 4:1 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 high solids content and fast drying speed, and is environmentally friendly due to low VOC content. In addition, the coating film prepared from the transparent coating composition is excellent in paintability, spreadability, pinhole resistance and hardness.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are only for helping the 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 16. Preparation of the main part of the transparent paint

A main part was prepared by mixing the components with the same content as in Tables 1 and 2. In this case, the additive includes 25 parts by weight of a curing accelerator, 4 parts by weight of a pinhole inhibitor, 4 parts by weight of a surface conditioner-1, 4 parts by weight of a surface conditioner-2, 1.5 parts by weight of a pot life delaying agent, and an ultraviolet absorber based on 100 parts by weight of the additive. 61.5 parts by weight was used.

Ingredients (parts by weight) Example One 2 3 4 5 6 7 8 Article 1-1 Acrylic Resin 2 5 2.2 15 10 15 2 6.3 Part 1-2 acrylic resin - - - - - - - - Article 1-3 Acrylic Resin - - - - - - - - Article 2-1 Acrylic Resin 56 50 56 43.6 45.6 40.6 53.8 50.4 2-2 Acrylic resin - - - - - - - - Section 2-3 Acrylic Resin - - - - - - - - Article 3-1 Acrylic Resin 7.5 10 7.4 7 8 8 7.5 7.1 Article 3-2 Acrylic Resin - - - - - - - - Part 3-3 Acrylic Resin - - - - - - - - polyester resin-1 6.1 6.6 6 6 8 8 8.3 7.8 polyester resin-2 - - - - - - - - polyester resin-3 - - - - - - - - solvent 26 26 26 26 26 26 26 26 additive 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 gross weight 100 100 100 100 100 100 100 100

Ingredients (parts by weight) Example 9 10 11 12 13 14 15 16 Article 1-1 Acrylic Resin 4.6 3.1 8 2 - - 2.2 - Part 1-2 acrylic resin - - - - 2 - - - Article 1-3 Acrylic Resin - - - - - 2 - 2.2 Article 2-1 Acrylic Resin 53.3 52.7 12 50 - - - 56 2-2 Acrylic resin - - - - 56 - 56 - Section 2-3 Acrylic Resin - - - - - 56 - - Article 3-1 Acrylic Resin 6.9 7.7 30 11 - - - 7.4 Article 3-2 Acrylic Resin - - - - 7.5 - - - Part 3-3 Acrylic Resin - - - - - 7.5 7.4 - polyester resin-1 6.8 8.1 21.6 8.6 - - 6 - polyester resin-2 - - - - 6.1 - - 6 polyester resin-3 - - - - - 6.1 - - solvent 26 26 26 26 26 26 26 26 additive 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 gross weight 100 100 100 100 100 100 100 100

Comparative Examples 1 to 8. Preparation of the main part

A main part was prepared by mixing the components with the content shown in Table 3.

Ingredients (parts by weight) comparative example One 2 3 4 5 6 7 8 Article 1-1 Acrylic Resin - 58.2 9.5 2.2 - 2 2 - Article 1-4 Acrylic Resin - - - - 2 - - 2 Article 2-1 Acrylic Resin 56 - 56 56 56 - 56 - Article 2-4 Acrylic Resin - - - - - 56 - 56 Article 3-1 Acrylic Resin 9.5 7.4 - 13.4 7.5 7.5 - - Chapter 3-4 Acrylic resin - - - - - - 7.5 7.5 polyester resin-1 6.1 6 6.1 - 6.1 6.1 6.1 6.1 solvent 26 26 26 26 26 26 26 26 additive 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 gross weight 100 100 100 100 100 100 100 100

Hereinafter, the manufacturers and product names, or component names, etc. of each component used in Comparative Examples and Examples are shown in Table 4.

ingredient note Article 1-1 Acrylic Resin NV: 75% by weight, Av: 6 mgKOH/g, Tg: 57°C, OHV: 148 mgKOH/g, Mw: 4,400 g/mol Part 1-2 acrylic resin NV: 75% by weight, Av: 10 mgKOH/g, Tg: 62° C., OHV: 154.6 mgKOH/g, Mw: 4,900 g/mol Article 1-3 Acrylic Resin NV: 75 wt%, Av: 4 mgKOH/g, Tg: 51°C, OHV: 140 mgKOH/g, Mw: 4,000 g/mol Article 1-4 Acrylic Resin NV: 75% by weight, Av: 5 mgKOH/g, Tg: 55° C., OHV: 145 mgKOH/g, Mw: 1,500 g/mol Article 2-1 Acrylic Resin NV: 64% by weight, Av: 10 mgKOH/g, Tg: 71.6° C., OHV: 113 mgKOH/g, Mw: 6,700 g/mol 2-2 Acrylic resin NV: 64% by weight, Av: 9 mgKOH/g, Tg: 65°C, OHV: 102 mgKOH/g, Mw: 6,100 g/mol Section 2-3 Acrylic Resin NV: 65 wt%, Av: 15 mgKOH/g, Tg: 77°C, OHV: 119 mgKOH/g, Mw: 7,300 g/mol Article 2-4 Acrylic Resin NV: 65 wt%, Av: 13 mgKOH/g, Tg: 70°C, OHV: 115 mgKOH/g, Mw: 5,350 g/mol Article 3-1 Acrylic Resin NV: 65% by weight, Av: 8 mgKOH/g, Tg: 55.8° C., OHV: 148 mgKOH/g, Mw: 13,500 g/mol Article 3-2 Acrylic Resin NV: 66 wt%, Av: 11 mgKOH/g, Tg: 50°C, OHV: 131 mgKOH/g, Mw: 12,500 g/mol Part 3-3 Acrylic Resin NV: 66 wt%, Av: 6 mgKOH/g, Tg: 60°C, OHV: 158 mgKOH/g, Mw: 14,300 g/mol Chapter 3-4 Acrylic resin NV: 65 wt%, Av: 9 mgKOH/g, Tg: 55°C, OHV: 145 mgKOH/g, Mw: 11,500 g/mol polyester resin-1 NV: 80% by weight, Av: 9 mgKOH/g, Tg: -23°C, OHV: 127 mgKOH/g, Mw: 1,640 g/mol polyester resin-2 NV: 82 wt%, Av: 11 mgKOH/g, Tg: -20°C, OHV: 118 mgKOH/g, Mw: 1,850 g/mol polyester resin-3 NV: 80% by weight, Av: 13 mgKOH/g, Tg: -16°C, OHV: 147 mgKOH/g, Mw: 1,400 g/mol solvent A mixture of 9.6 parts by weight of acetone, 28.9 parts by weight of dimethyl carbonate, 25.4 parts by weight of DOWANOL PMA, 33.9 parts by weight of butyl acetate, and 2.2 parts by weight of butyl cellosolve acetate based on 100 parts by weight of the solvent first
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My hardening accelerator 5% dbtdl in xylene pinhole inhibitor Manufacturer: BYK Chemie, Product name: BYK-072 Surface Conditioning Agent-1 Manufacturer: Allnex, product name: Additol VXL4930 Surface conditioner-2 Manufacturer: Cheongwoo CFC, Product name: VK-1300 time delay system Manufacturer: BRUNO BOCK CHEMISCHE FABRIK GMBH, product name: Thiocure 320 UV absorber Manufacturer: Everlight chemical industrial cor., Product name: Eversorb83

Reference example. Preparation of curing agent 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 (component name: hexamethylene di Isocyanate, NCO content: 21.8% by weight, viscosity: 3,000 mPa·s, solids: 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) to prepare a curing agent part.

Experimental Example 1. Characterization of the coating film

A transparent coating composition was prepared by mixing the main part prepared in Examples and Comparative Examples and the curing agent part of Reference Example in a weight ratio of 3:1. After that, a coating film having a dry thickness of 50 to 60 μm was formed by coating the transparent coating composition on the specimen twice by a wet-on-wet coating method, and then the physical properties of the coating film were measured in the following way. , the results are shown in Table 5 below.

(1) Workability (spray feeling)

With a SATA HVLP gun 1.4mm nozzle size, the discharge amount is 2 times, the air pressure is based on the 45cm X 45cm of the specimen 25cm apart based on 1.7bar, and when applied 5 times from top to bottom left and right reciprocating 5 times Based on this, workability (spray feeling) was evaluated. At this time, evaluation was made on the basis of a 5-point scale.

(2) Paintability

After coating the paint, drying it at 60° C. for 30 minutes, and then measuring the thickness of the coating film, the paintability was evaluated, and evaluation was performed on a 5-point scale.

(3) sagging

The thickness of the coating film was measured at the point where the paint started to flow when it was left in a vertical position after painting.

(4) curing conditions

After coating, the time for hardening of the coating film when dried at 60° C. was measured. At this time, the hardening time was measured as the time during which no marks were generated on the coating film when the coating film was strongly pressed by hand and twisted from side to side.

(5) pinhole resistance

After the paint was applied and dried at 60° C. for 30 minutes, the occurrence and degree of pinholes in the paint film were determined, and at this time, the relative evaluation was performed on a 5-point scale.

Workability seventy-one Sagging (㎛) curing conditions pinhole resistance Example One 5 5 45 24 hours 5 2 4 4 38 29 hours 4 3 4.5 4.5 39 27 hours 4.5 4 3.5 4 38 28 hours 4 5 4.5 5 42 25 hours 4.5 6 4 4 38 28 hours 3.5 7 4 4 40 26 hours 4 8 4.5 4.5 44 26 hours 5 9 4.5 4 40 26 hours 4 10 4 4.5 38 26 hours 4.5 11 3.5 3 37 28 hours 3.5 12 3 3.5 37 28 hours 3.5 13 4.5 4.5 40 27 hours 4 14 4.5 4 40 27 hours 4.5 15 4.5 4 4 26 hours 4.5 16 4 4.5 38 26 hours 4.5 comparative example One 3.5 2.5 36 28 hours 3 2 3 3.5 37 29 hours 2.5 3 2.5 3 37 29 hours 3.5 4 3 3.5 35 28 hours 3 5 3 2 37 31 hours 3 6 3 3 35 28 hours 2 7 2 2.5 37 28 hours 3 8 2 2 27 32 hours 2

As shown in Table 5, it was found that the coating films prepared from the compositions of Examples 1 to 16 had better physical properties than the coating films prepared from the compositions of Comparative Examples 1 to 8.

Specifically, compared to the coating film prepared from the compositions of Examples 1 to 16, Comparative Example 1 to which the first acrylic resin was not applied had lower paintability, and Comparative Example 2 to which the second acrylic resin was not applied had reduced pinhole resistance, In Comparative Example 3 to which the third acrylic resin was not applied, workability was lowered, and in Comparative Example 4 to which the polyester resin was not applied, it was found that the sagging property was lowered.

In addition, Comparative Example 5, in which the acrylic resin of No. 1-4 having a weight average molecular weight of less than 2,000 g/mol was applied, deteriorated paintability and took a long curing time, and Comparative Example 5 had a weight average molecular weight of less than 5,500 to 10,000 g/mol. In Comparative Example 6 to which 4 acrylic resin was applied, sagging properties and pinhole resistance were lowered, and in Comparative Example 7 to which acrylic resin 3-4 having a weight average molecular weight of less than 12,000 g/mol was applied, workability was lowered. In addition, in Comparative Example 8, in which the weight average molecular weight of all of the first to third acrylic resins was outside the preferred range, workability, staining property, sagging property, and pinhole resistance were all lowered, and the curing time was long.

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 Reference Example in a weight ratio of 3:1. Then, a base paint (manufacturer: KCC, product name: UT5901) is coated on the electrodeposition specimen (30 cm × 30 cm, width × length) to a dry thickness of 20 μm, and the transparent coating composition is applied on the base coating to a dry thickness of 60 μm. After coating, drying and curing, a transparent coating film was formed 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 6 below.

(1) Appearance of the 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. It was calculated by Equation 1 below. 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

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

Short wave and long wave values of the final coating film were measured using Wave Scan DOI (BYK Gardner), which is an automobile exterior measuring instrument.

(3) Seon Young-seong (DOI, Distinctness of Image )

The image quality (DOI) of the final coating film was measured using Wave Scan DOI (BYK Gardner), which is an automobile exterior measuring instrument.

(4) hardness

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

item CF LU SH OP SW LW DOI Hardness
(number) line
city
Yes One 84.84 75.4 84.8 87.7 6.1 0.6 95.7 62 2 72.755 75.9 72.2 72.2 18.3 2.1 93.7 55 3 77.425 68.1 77.6 80.1 15.3 1.6 94.5 56 4 73.75 76.8 72.8 73.5 16.8 2.5 95.1 57 5 79.94 70.2 78.6 83.8 8.4 0.8 95.2 60 6 74.16 80.5 70.1 75.1 16 2.4 92.7 56 7 77.665 73.2 78.1 78.7 12.9 1.1 94.7 59 8 79.175 68.7 79.2 82.3 7.6 0.9 93.6 60 9 75.35 72.3 75.3 76.3 14.3 1.3 94.3 56 10 77.03 71.1 76.9 78.9 11.5 1.6 93.7 58 11 68.035 68.8 70.9 65.8 19.6 2.7 93.3 47 12 68.555 68.2 70.5 67.3 22.8 2.8 92.8 50 13 76.465 69.8 78.7 76.9 10.4 1.4 93.9 55 14 77.25 70.1 77.1 79.5 14.9 1.1 93.3 54 15 75.095 68.8 77.5 75.3 12.1 1.4 95.1 55 16 73.445 78.2 75.9 70.3 15.6 1.6 95.2 57 rain
school
Yes One 65.555 44.2 70.5 68.5 22.7 2.9 92.7 48 2 60.845 61.1 68.8 55.2 20 3.4 87.7 53 3 64.365 63.7 65.6 63.7 36 4.4 84.5 40 4 54.34 45.5 54.9 56.6 23.4 2.2 88.3 50 5 66.58 60.6 66.4 68.5 22 3.1 85 45 6 62.18 60.7 68.5 58.2 23 2.7 72.7 50 7 65.135 47.1 68.2 68.4 20 2.3 90 53 8 50.305 41.6 50.9 52.5 24.5 4.9 81.5 38

As shown in Table 6, it was found that the coating films prepared from the compositions of Examples 1 to 16 had better physical properties than the coating films prepared from the compositions of Comparative Examples 1 to 8.

Specifically, in Comparative Example 1 to which the first acrylic resin was not applied, the gloss was lowered compared to the coating films prepared from the compositions of Examples 1 to 16, and in Comparative Example 2 to which the second acrylic resin was not applied, smoothness was lowered, and the third In Comparative Example 3 to which an acrylic resin was not applied, sharpness and hardness were lowered, and in Comparative Example 4 to which a polyester resin was not applied, it could be seen that the overall appearance of the gloss lamp was lowered.

In addition, in Comparative Example 5 to which the acrylic resin 1-4 having a weight average molecular weight of less than 2,000 g/mol was applied, the hardness was lowered compared to the coating film prepared from the compositions of Examples 1 to 16, and the weight average molecular weight was 5,500 to 10,000 g/mol In Comparative Example 6 to which the 2-4 acrylic resin out of mol was applied, the smoothness was lowered, and in Comparative Example 7 to which the 3-4 acrylic resin having a weight average molecular weight of less than 12,000 g/mol was applied, it was found that the gloss was lowered. In addition, it was found that in Comparative Example 8, in which the weight average molecular weight of all of the first to third acrylic resins was out of the preferred range, appearance such as gloss, image sharpness, smoothness, and hardness were generally lowered.

Claims (6)

a first acrylic resin, a second acrylic resin, a third acrylic resin, and a polyester resin;
The first acrylic resin has a weight average molecular weight of 2,000 to 5,000 g / mol,
The second acrylic resin has a weight average molecular weight of 5,500 to 10,000 g/mol,
The third acrylic resin has a weight average molecular weight of 12,000 g/mol or more, a transparent paint composition for automobile repair. The method according to claim 1,
The first acrylic resin has a glass transition temperature of 40 to 65 °C, an acid value of 3 to 15 mgKOH/g, and a hydroxyl value of 130 to 160 mgKOH/g, a transparent paint composition for automobile repair. The method according to claim 1,
The second acrylic resin has a glass transition temperature of 63 to 80 °C, an acid value of 5 to 30 mgKOH/g, and a hydroxyl value of 95 to 125 mgKOH/g, a transparent paint composition for automobile repair. The method according to claim 1,
The third acrylic resin has a glass transition temperature of 30 to 60 °C, an acid value of 3 to 15 mgKOH/g, and a hydroxyl value of 100 to 200 mgKOH/g, 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 -30 to -10 °C, and a hydroxyl value of 100 to 180 mgKOH/g, a transparent paint composition for automobile repair. The method according to claim 1,
The transparent coating composition comprises 0.5 to 20 parts by weight of the first acrylic resin, 40 to 70 parts by weight of the second acrylic resin, 1 to 15 parts by weight of the third acrylic resin, and 1 to 10 parts by weight of the polyester resin. Transparent paint composition.