KR101310616B1 - Automotive waterborne paint composition for many kinds of clearcoats - Google Patents

Abstract

The present invention relates to a water-soluble topcoat composition for automobiles that can be applied to a variety of clearcoat, and more particularly, based on the weight of the total coating composition, 5 to 40% by weight of the core / shell / shell microgel resin; 2 to 20 wt% polyurethane dispersion resin; 2 to 20 wt% polyester resin; 2 to 20% by weight of a hydrophilic imino group-containing melamine curing agent; 5-15 wt% of 2-ethylhexyl alcohol; 1 to 5% by weight of ethylene glycol monohexyl ether; 1 to 5% by weight of ethylene glycol monobutyl ether; 0.01 to 2 weight percent wetting agent; Antifoam 0.1 to 3 weight percent; 0.1 to 2 weight percent of catalyst; 0.1-3% by weight of ultraviolet absorbent; 0.1-5% by weight of flow control agent; 3 to 10 weight percent aluminum flake paste; 0.1 to 1 weight percent of a neutralizing agent; And 25 to 45% by weight of water. The water-soluble topcoat composition for automobiles according to the present invention can expand the applicable temperature / humidity range to the maximum possible, and can apply various clearcoats regardless of the clearcoat curing structure, and excellent coating appearance, gloss, adhesion, etc. Has physical properties.

Description

Water Soluble Top Coating Composition Applicable to Various Clear Coats {AUTOMOTIVE WATERBORNE PAINT COMPOSITION FOR MANY KINDS OF CLEARCOATS}

The present invention relates to a water-soluble topcoat composition for automobiles, and more particularly, to a water-soluble topcoat composition for automobiles that can be applied as a base coat of various kinds of clearcoats.

Recently, regulations on volatile organic compounds (VOC's) for global environmental protection have been tightened, and development of water-soluble paints to cope with this is being actively conducted. In particular, paints containing effect pigments (aluminum, mica, etc.) for automobile coatings, which have a large reduction effect among water-soluble paints, are rapidly replacing conventional organic solvent type paints, led by advanced automobile companies.

The difficulty of development in water-soluble paints for automobiles is that the drying of volatiles, which greatly affects the orientation of effect pigments, is sensitive to the temperature and relative humidity at the time of coating. This tendency causes the paint to slow down when the humidity is higher than the critical point or when the temperature is lower than the critical point, resulting in overall flow of the paint, staining of the effect pigments, humidity lower than the critical point, or temperature higher than the critical point. At this time, the drying of the paint is excessively fast, which causes dust coating, or the orientation of the effect pigment becomes poor, and thus the metallic effect cannot be sufficiently realized.

Therefore, the main technology of the development of water-soluble paints for automobiles aims to expand the applicationable temperature / humidity range to the maximum possible, and does not change sensitively according to the temperature / humidity change of the coating conditions to realize this. The resin is selected and the paint composition is designed.

On the other hand, core / shell-type acrylic resins using microgels as cores are manufactured by NAC (Non Aqueous Dispersion) as a means to reduce organic solvent discharge, and are applied in water systems or prepared by emulsion polymerization, in particular organic solvents. It is mainly applied to water-based metallic base coats because of its strong resistance to plasticity and plasticity. The biggest advantage of these resins is that they are not sensitive to changes in humidity during painting, so the temperature / humidity range is wide and the resistance to popping during baking is large. The need for a solvent is known to be the biggest disadvantage.

In addition, in order to increase the paintable temperature and humidity range of the water-soluble paint, the arrival NV (Non Volatile) during the solvent balance and the flash-off process (forced drying of the water contained in the water-soluble coating) must be optimized to prevent popping at low humidity. In particular, in order to solve the problem of high flow in the high humidity, the thixotropic properties of the paints should be optimized and designed. It is a factor that affects all stages such as ease of use, ease of filter and transportation in the coating machine, atomization in the coating machine, wetness of the body after arrival, formation of a good film and drying of the coating film. In order to optimize these thixotropic properties, in general, the flow control agent is generally used alone in the manufacture of the paint, but in this case, the viscosity optimization of all shear rates in the paint storage and transportation, painting and drying steps cannot be satisfied. have.

In addition, the conventional water-soluble topcoat is designed for a clear coat having a specific curing structure, and when applied to a clear coat having a different curing structure, the appearance of the water-soluble topcoat is different due to the difference in thermal flow characteristics such as curing behavior and drying rate and resin compatibility. There is a problem that becomes poor.

Many techniques have been proposed to overcome this problem. For example, Korean Patent Laid-Open Publication No. 2003-0057779 uses a reverse-phase core / shell structure microgel blended with an acrylic-urethane copolymer to expand the paintable temperature / humidity area and optimize the rheology of each coating step. One resin is presented. In addition, Korean Laid-Open Patent Publication No. 2003-0087449 discloses a paint that blends a polyacrylic water-dispersible resin and a reversed phase core / shell microgel resin and expands the coating temperature and humidity region by using two types of fluid thickeners.

Republic of Korea Patent Publication No. 2003-0057779 Republic of Korea Patent Publication No. 2003-0087449

In order to solve the problems of the prior art as described above, an object of the present invention is to provide a fluidity control agent and a co-solvent compounded as a main component of a microgel resin, a polyurethane resin, and a polyester resin made of a core / shell / shell structure It is to provide a water-soluble top coating composition for automobiles having an excellent appearance and mechanical properties while expanding the narrow coating temperature and humidity region by applying a specific content.

Another object of the present invention is to provide a water-soluble topcoat composition to which various kinds of transparent paints can be applied irrespective of the curing structure of the transparent paint applied on the topcoat.

In order to achieve the above object, the water-soluble topcoat composition for automobiles of the present invention, based on the weight of the total coating composition, 5 to 40% by weight of the core / shell / shell microgel resin; 2 to 20 wt% polyurethane dispersion resin; 2 to 20 wt% polyester resin; 2 to 20% by weight of a hydrophilic imino group-containing melamine curing agent; 5-15 wt% of 2-ethylhexyl alcohol; 1 to 5% by weight of ethylene glycol monohexyl ether; 1 to 5% by weight of ethylene glycol monobutyl ether; 0.01 to 2 weight percent wetting agent; Antifoam 0.1 to 3 weight percent; 0.1 to 2 weight percent of catalyst; 0.1-3% by weight of ultraviolet absorbent; 0.1-5% by weight of flow control agent; 3 to 10 weight percent aluminum flake paste; 0.1 to 1 weight percent of a neutralizing agent; And it is characterized in that it comprises 25 to 45% by weight of water.

The coating composition of the present invention can obtain the optimization of rheology in various coating steps, maximize the plasticity and maximize the paintable temperature / humidity area to the maximum possible, and is applied as a base coat to clearcoat hardened structure. Various clear coats can be applied irrespective of the quality and have excellent physical properties such as coating appearance, gloss, and adhesion.

Hereinafter, the components of the water-soluble coating composition for automobiles of the present invention will be described in more detail.

(1) core / shell / shell microgel resin

The core / shell / shell microgel resin used as a main component in the topcoat composition of the present invention is graft polymerized so that the core, which is the core, is crosslinked and stabilized around an encapsulation polymer called a shell (or mantle). .

The core / shell / shell microgel resin production method of the present invention is usually an emulsion method for transferring the particles obtained after the non-aqueous dispersion method to an aqueous system, but recently, a method obtained by an emulsion method in an aqueous system is also used. In the core / shell / shell microgel resin of the present invention, since the shell part has a carboxyl group partially or completely neutralized with an amine, the shell part not only contributes to stabilization of particles but also forms a loose network by mutual attraction with the shell of adjacent particles, thereby increasing viscosity. Cause. These mutual forces are reversible and are destroyed when high shear stress is applied and restored at low shear rates after arrival. Therefore, the paint containing the microgel of the present emissive has a plasticity property even at a low solids content, so that sagging can be solved while giving a good flop effect of the aluminum flakes when forming the coating film. In addition, since water has a lower solubility in air than organic solvents, when the thickness of the coating film is thin, it is possible to prevent the popping phenomenon of dissolved air, and the shell assists fusion of the polymer particles during the coating film formation. The microgel has a know-how of regulating rheology and is designed to give good coating performance by crosslinking the carboxyl group and the hydroxyl group of the shell portion with the melamine resin.

Specifically, the core / shell / shell microgel resin manufacturing method of the present invention

a) an unsaturated monomer mixture containing an acid-free or acid-containing unsaturated monomer having an acid value of 1 to 30 mgKOH / g, an emulsifier, a radical polymerization initiator and ionized water are reacted on a seed to form a core having a particle diameter of 25 to 250 nm. step;

b) containing a hydroxyl group containing an unsaturated monomer mixture, an emulsifier, a radical polymerization initiator and ionized water into the reaction product of step a), containing no hydroxyl group or an unsaturated monomer containing 0.01 to 80 mgKOH / g polyalkylene glycol Forming a one-step shell comprising an unsaturated monomer and an acid-free or acid containing unsaturated monomer having an acid value of 1 to 100 mgKOH / g; And

c) A hydroxyl group-containing unsaturated monomer and an acid value containing an unsaturated monomer mixture, an emulsifier, a radical polymerization initiator and ionized water into the reaction product of step b), wherein the hydroxyl group comprises an unsaturated monomer containing 1 to 80 mgKOH / g polyalkylene glycol. Forming a two-step shell comprising 40-200 mgKOH / g acid containing unsaturated monomer. Details of such a manufacturing method are specifically disclosed in the applicant's prior patent application No. 10-2010-0038183, and the contents of the patent application are incorporated herein.

The core / shell / shell microgel resin according to the present invention contains 20 to 60% solids, and has a glass transition temperature of -20 to -5 ° C, an acid value of 30 to 200 mgKOH / g, and a particle size of 50 to 150 nm. Appearance and leveling, wettability, adhesion, water resistance, etc. are enhanced, it is possible to implement a top coat with a coating temperature / humidity area. The microgel used in the aqueous basecoat is composed of polymer particles having a bilayer structure with a particle size of about 0.1 μm.

The core / shell / shell microgel resin according to the present invention may be used at 5 to 40% by weight based on the total weight of the coating composition. Within the above numerical range, the coating temperature and humidity region can be expanded, and the dispersibility of the polyester resin which is low in water solubility in paint can be improved to ensure excellent appearance quality. In particular, the wettability of the aluminum flakes can be improved to increase the flop effect, thereby contributing to the appearance improvement. If the amount of the coating in the paint is less than the above range, the coating film forming ability and dryness may be poor, resulting in a deterioration in appearance, and silver powder wettability may be lowered, thereby causing a coating defect in the form of a seed. In addition, there is a problem that the cold resistance chipping resistance, water resistance, etc. of the coating film slightly exceeds when the above range, and when the work in the high-humidity coating area, the coating flow and stains may occur.

(2) polyurethane dispersion resin

In the present invention, it is possible to obtain excellent interlayer penetration resistance, leveling resistance, and the like by using the polyurethane dispersion resin, and also to improve the proper wettability, adhesion, water resistance, impact resistance, cold resistance chipping resistance, etc. of the top coat. have.

As the polyurethane dispersion resin used in the present invention, a resin obtained by synthesizing dimethylol propionic acid and diisocyanate, polyester polyol, amine and the like under a water-soluble solvent process may be preferably used. In particular, a polyurethane dispersion resin having a solid content of 30 to 60%, a number average molecular weight of 8,000 to 30,000, an acid value of 15 to 35 mgKOH / g, and a particle size of 50 to 200 nm is preferable.

The polyurethane dispersion resin of the present invention may be used in an amount of 2 to 20% by weight based on the total weight of the coating composition, and may affect overall physical properties of the coating, such as adhesion improvement, drying property, and interlayer penetration prevention property. If the amount is less than the above range, the coating film forming ability and mechanical properties, etc. are poor, and if it exceeds the above range, the cold resistance chipping resistance, impact resistance, drying property, etc. of the coating film are somewhat poor.

(3) Polyester resin

The polyester resin used in the present invention contains 60 to 90% solids, preferably a number average molecular weight of 1,000 to 4,000, a glass transition temperature of -40 to -20 占 폚, and an acid value of 5 to 60 mgKOH / g.

The polyester resin of the present invention is used in 2 to 20% by weight based on the weight of the total coating composition, if the amount is less than the above range, physical properties such as interlayer adhesion deterioration and cold resistance chipping resistance may be lowered, in particular In the low-humidity coating conditions, the dry coating may reduce the appearance, and there is a concern that the appearance and the physical properties may be reduced when the transparent paint having various curing structures is applied. Moreover, when the said range is exceeded, there exists a problem that the water resistance and dryness of a coating film become poor.

(4) hydrophilic melamine resin (curing agent)

The imino group-containing hydrophilic melamine resin of the present invention is used for crosslinking reaction upon curing with the core / shell / shell microgel resin, polyurethane dispersion resin, polyester resin of the present invention, and the hydroxyl group and hydrophilic melamine of the above-mentioned resins. The methoxy group and imino group of resin crosslink reaction. The hydrophilic melamine resin of the present invention can be used directly or commercially available products according to known methods. Examples of the product applicable to the hydrophilic melamine resin of the present invention include Cymel-325, Cymel-327, Cymel-385, and Resimene HM-2608, Resimene 718, Resimene 717, and the like of INEOS.

In this invention, 2-20 weight% of imino group containing hydrophilic melamine resin is used. When the amount of the melamine resin according to the present invention is less than 2% by weight, uncrosslinked hydroxyl groups remain in the coating film, thereby degrading water resistance of the coating film and repainting adhesion of the coating film, and interlayer adhesion and deterioration in application of various clear coats. May occur. If it exceeds 20% by weight, the coating film tends to be broken due to self-polymerization of the unreacted hydrophilic melamine resin in the coating film, which may reduce the cold resistance chipping, impact resistance and bending resistance of the coating film, and also causes problems in heat storage. .

(5) fluidity regulator

The fluidity regulator of the present invention may be at least one of an alkali dissolving thickener or an inorganic thickener, and is preferably used in combination of two or more selected from the group consisting of alkali shellable acrylic emulsions, urethane thickeners, polyamide waxes and hectorite clays. do.

According to the present invention, the fluidity regulator is used in an amount of 0.1 to 5% by weight based on the weight of the entire coating composition. If the amount used is less than 0.1% by weight, it causes the high flow of the coating at high humidity. When the amount is more than 5% by weight, the viscosity of the paint is too high and the dispersibility of the pigment is poor, making it difficult to atomize the paint. May occur.

As the fluidity regulator of the present invention, a commercially available product can be used. Examples of commercially available products include Viscalex HV 30 of Ciba, AM-3, Nopall 642, AM-2, SN 660T, Nopall UT-666, Kusumoto Co. AQ-600, AQ-607, Benton AD and ED of Liax, Laponite RD and RDS from Rockwood, etc. are mentioned.

 (6) solvent

It can greatly contribute to volatilization of water, the main solvent according to the present invention, has a great influence on the prevention and popping of the coating film, and a coarse solvent is used to smooth the atomization of the paint during painting. In the present invention, a specific solvent mixture is applied to expand the application window of the coating temperature / humidity.

The co-solvent mixture applied in the present invention uses a mixture consisting of 5 to 15% by weight of 2-ethylhexyl alcohol, 1 to 5% by weight of ethylene glycol monohexyl ether and 1 to 5% by weight of ethylene glycol monobutyl ether. If the amount of use is less than the above range, when the painting work area is changed, the appearance deviation due to partial staining and dust and painting poorness such as Sagging or Seed may be severely generated.

(7) wetting agents

In the present invention, in order to provide leveling and wettability of the coating film, an organic-modified polysiloxane-based wetting agent or an acetylene alcohol type wetting agent is used. Commercially available products can be used as the humectant of the present invention. Commercially available products include BYK-345, BYK-348, Air Products' Surfynol-104BC, Ciba's EFKA 3522, and EFKA 3580 Tego's Wet 510. have.

According to the present invention, the humectant uses 0.01 to 2% by weight, based on the weight of the total coating composition. If the amount is less than the above range based on the total weight of the coating composition, the effect is reduced and can not exhibit the effects of suitable leveling and wettability, and when applied in excess of the above range may cause problems of poor water resistance and crater form on the surface.

(8) antifoam

Antifoaming agent is used to suppress bubbles generated during paint production and to suppress and eliminate phenomena such as pinholes or poppings caused during coating film formation. As the antifoaming agent, a commercially available product can be used. Examples of commercially available products include BYK-011, BYK-015, DF-21 from Air Product, agitan 281 from Munzing, and Foamster-324 from Sannovco.

According to the present invention, the antifoaming agent may be used in an amount of 0.1 to 3% by weight based on the weight of the entire coating composition. If the amount of the antifoaming agent is less than 0.1% by weight, there is no problem of defoaming effect, so bubbles are generated during paint production or coating film formation, so that the foaming agent is not easily turned off. have.

(9) catalyst

The catalyst is used so that the hydroxyl group between the core / shell / shell microgel resin, polyurethane dispersion resin, polyester resin and the methoxy group and imino group of the hydrophilic melamine resin can crosslink. Commercially available products can be used as the catalyst of the present invention. Examples of commercially available products include Nacure 2547, Nacure 3327, Nacure 3325, XP-221, Nacure 4167, and the like.

According to the present invention, the catalyst is used at 0.1 to 2% by weight based on the weight of the total coating composition. If the amount of the catalyst used is less than 0.1% by weight, the uncrosslinked hydroxyl group remains in the coating film, and in particular, the poor water resistance of the coating film and the recoating adhesion of the coating film may be reduced, and interlayer adhesion and deterioration may occur when various clear coats are applied. If it exceeds 2% by weight, the coating film tends to be broken due to self-polymerization of the unreacted hydrophilic melamine resin in the coating film, which may reduce the cold resistance chipping, impact resistance and bending resistance of the coating film, and also causes problems in heat storage. .

(10) UV absorbers

In the present invention, in order to improve the weather resistance of the final coating film, an ultraviolet absorber that prevents ultraviolet light that can reach the coating film is used. The UV absorber applied to the present invention is a method of obtaining a UV stabilizing effect by interfering with the starting step of forming free radicals in the photooxidation mechanism. It is a form using the principle. In the form, it is possible to give an effect of properly blocking ultraviolet rays as a benzotriazole system. Examples of these benzotriazole UV absorbers include Tinuvin 384 and Tinuvin 1130 from Ciba.

UV absorbers use a level of 0.1 to 3% by weight of the total coating composition. When less than the above range based on the weight of the total coating composition, the ultraviolet absorbing ability may also fall.

(11) aluminum flake paste

The aluminum flake paste used in the present invention is used alone or mixed with the aluminum flakes of Eckart, Silverline, Toyo aluminum in order to give a metallic effect to the coating film, the amount is 3 to 10% by weight based on the total weight of the coating composition desirable. If the amount is less than 3% by weight, it is difficult to impart a metallic effect to the metallic color coating film. If the amount is more than 10% by weight, the aluminum particles in the paint are increased, so that the smoothness of the coating film and the wettability of the silver powder are reduced. Coating defects may occur and may cause problems of deterioration of the coating appearance.

(12) neutralizer

According to the present invention, a neutralizing agent of amines is used for storage stability and pH control of the final paint composed of the resin and the additive, and the pH of the paint is controlled by measuring about 7.5 to 9.0. At this time, the amount of the neutralizing agent is preferably 0.1 to 1% by weight, and when the amount of the neutralizing agent is less than 0.1% by weight, the pH of the paint decreases, thereby affecting the storage stability, causing pigmentation and re-agglomeration, and 1 weight. If it exceeds%, the paint is alkalized, and there is a problem in that the alkali resistance of the coating film is significantly lowered. On the other hand, amines applicable as the neutralizing agent include ammonia, triethylamine, dimethylethanolamine, methylethanolamine, Angus AMP-95, and the like.

(13) Other Pigments

According to the present invention, the pigment and the extender pigment, which are components necessary for preparing the water-soluble coating composition, may be further included in an amount of 1 to 5% by weight, and a desired effect may be achieved within the above range. The colored pigment and the extender pigment may be appropriately selected and used from those known in the art.

The following Examples and Comparative Examples will be described in more detail, but the scope of the present invention is not limited thereto.

Example  And Comparative example

While mixing in the order shown in Table 1, the final viscosity was adjusted to 60 seconds with Pod Cup # 4 to prepare a water-soluble coating composition for automobiles. Each of the automotive water-soluble topcoat compositions prepared as described above was bell coated to have a dry coating of 10 to 15 microns on the middle (coating condition: 80 ° C relative humidity 80%, 25 ° C relative humidity 70%, 28 ° C relative humidity 60%). After blowing hot air at 80 ℃ for 3 minutes, the remaining water in the paint is evaporated to coat the top transparent paint and cured at 140-150 ℃ for 20-30 minutes in a general oven to form a final coating film. And physical properties were measured respectively, and the results are shown in Table 2 below.

Furtherance Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Laponite rd 0.2 0.2 0.2 0.2 Distilled water 11.8 11.8 11.8 11.8 Core / shell / shell microgel resin 19.0 19.0 19.0 19.0 Antifoam 1.5 1.5 1.5 1.5 Solvents 1 9.5 9.5 4.5 9.5 Solvents 2 1.5 1.5 1.5 Solvents 3 1.0 1.0 5.5 1.0 Normal Butyl Alcohol 1.0 Normal propyl alcohol 1.0 Polyurethane dispersion resin 6.5 12.5 6.5 6.5 Polyester resin 6.0 6.0 6.0 Melamine curing agent 6.5 6.5 6.5 6.5 catalyst 1.0 1.0 1.0 1.0 Wetting agent 1.5 1.5 1.5 1.5 Ultraviolet absorber 0.2 0.2 0.2 0.2 Extender pigment 3.0 3.0 3.0 3.0 Pigmentation Pigment 0.1 0.1 0.1 0.1 Urethane thickener 0.7 0.7 0.7 Alkali dissolving thickener 1.5 1.5 1.5 1.5 Aluminum flake paste 5.0 5.0 5.0 5.0 corrector 4.5 3.5 4.3 4.5 Distilled water 19.0 20.0 19.2 19.7 system 100.0 100.0 100.0 100.0

(Unit: wt%)

Components used in the Examples and Comparative Examples are each carried out using the following components, except as specifically illustrated.

Core / Shell / Shell Microgel Resin: Solid content 25%, Acid value 40-50mgKOH / g, Glass transition temperature -15 ~ -10 ℃, Particle size 60-100nm (KCC)

Polyurethane dispersion resin: solid content 35%, number average molecular weight 20,000, acid value 18-23 mgKOH / g, glass transition temperature -20--15 ° C, particle size 50-80 nm (KCC)

Polyester resin: Solid content 70%, Acid value 45-52 mgKOH / g, Number average molecular weight 1,500, Glass transition temperature -25--20 degreeC, Hydroxide value molecular weight 1,500 (KCC)

Melamine curing agent: melamine resin containing imino group (Cymel 327, Cytec)

Solvent 1: 2-ethylhexyl alcohol

Solvent 2: Ethylene glycol monohexyl ether

Solvent 3: ethylene glycol monobutyl ether

Wetting agent: acetylene alcohol type wetting agent (Surfynol 104BC, Air Product)

Antifoam: Inorganic antifoam containing oil (agitan 281, Munzing)

Catalyst: Dodecylbenzene sulfonic acid type acid catalyst (XP-221, King Industries)

Extender pigments: barium sulfate-based inorganic pigments (KCC)

Pigmented Pigments: Commonly used organic-inorganic pigments (KCC)

UV absorbers: benzotriazole-based structures (Tinuvin 384, Ciba)

Rheology modifiers: alkali-soluble thickeners (AM-3, San Nopco),

 Urethane Thickener (AM-2, San Nopco)

Neutralizing agent: 10% solution of DMEA dimethylethanolamine

division Example Comparative Example 1 Comparative Example 2 Comparative Example 3
Painting condition Temperature
(℃) 28 25 20 28 20 20 20 20 20 20 20 20 Relative Humidity (%)
60
70
80
60
75
80
80
80
80
80
80
80 Storage stability ○ ○ ○ ○ ○ ○ × × × ○ ○ ○ Painting workability ◎ ◎ ◎ ○ ○ ○ ○ ○ ○ ○ ○ ○ Coating appearance ◎ ◎ ◎ × ○ △ △ △ △ × △ △ Polish ◎ ◎ ◎ ○ ○ ○ ○ ○ ○ ○ ○ ○ Overbaking Repaintability ◎ ◎ ◎ △ △ △ ○ ○ ○ ○ ○ ○ Impact resistance ◎ ◎ ◎ △ △ △ ○ ○ ○ ○ ○ ○ Water resistance ◎ ◎ ◎ ○ ○ ○ ○ ○ ○ ○ ○ ○ Chilsung Castle ◎ ◎ ○ △ △ × × △ △ △ × × Chipping resistance ◎ ◎ ◎ △ △ △ ○ ○ ○ ○ ○ ○ Evaluation: ◎ Excellent ○ Good △ Normal × Bad

Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 normal course
Transparent paint
Kinds Acrylic / Melamine Curing Type Acid / Epoxy Curing Type Acrylic Urethane 2K Curing Type Acrylic / Melamine Curing Type Acid / Epoxy Curing Type Acrylic Urethane 2K Curing Type Acrylic / Melamine Curing Type Acid / Epoxy Curing Type Acrylic Urethane 2K Curing Type Acrylic / Melamine Curing Type Acid / Epoxy Curing Type Acrylic Urethane 2K Curing Type Coating appearance ◎ ◎ ◎ ○ ○ ○ △ △ ○ △ △ ○ Polish ◎ ◎ ◎ ○ ○ ○ ○ ○ ○ ○ ○ ○ With Overbaking Repaint ◎ ◎ ◎ △ △ × ○ ○ ○ ○ ○ ○ Impact resistance ◎ ◎ ◎ △ △ ○ ○ ○ ○ ○ ○ ○ Water resistance ◎ ◎ ◎ ○ ○ ○ ○ ○ ○ ○ ○ ○ Chipping resistance ◎ ◎ ◎ △ △ ○ ○ ○ ○ ○ ○ ○ Evaluation: ◎ Excellent ○ Good △ Normal × Bad

Storage stability: After leaving for 5 days at 45 ℃, within 15% of the viscosity change when measuring viscosity at room temperature, and free from dust, foreign matter, hard mass in paint container

· Painting workability: Good spraying condition when discharging paint, and good wettability.

· Appearance of film: The final CF value is measured by applying Wave Scan DOI (BYK Gardner), an automobile appearance measuring instrument. The measurement results are indicated as: ◎ excellent (CF 65 or more), ○ good (CF 60 to 65), △ normal (CF 55 to 60), × poor (less than CF 55).

Gloss: 60 degree gloss 90 or more.

Overbaking repaint adhesion: After final film curing at 150 ° C for 20 minutes, overbaking at 150 ° C for 60 minutes, then repainting and curing topcoat and clearcoat paints, and then conduct adhesion test (1mm After making 100 crosscuts, remove them using Scotch tape and judge them good if there are no problems.

Impact resistance: There should be no crack or peeling on the coating film when dropped from 30cm or more using a 500g weight.

Water resistance: Adhesion test and discoloration evaluation after 10 days deposition of finished coating film in 40 ℃ thermostat

· Flowability: There should be no paint flow or gloss decrease when observed after curing the electrodeposited and intermediate coated specimens vertically and coating the top coat under each condition.

Cold resistance chipping: After leaving at -20 ℃ X3 hours, use 50g chipping stone to push 50g chipping stone at 4 bar pressure to hit the surface of coating film. Excellent judgment, when there are 10 or less damages of 1 to 2 mm or less, good judgment.

As shown in Table 2, the water-soluble topcoat according to the embodiment of the present invention is expanded compared to the conventional topcoat paint to exhibit a good appearance, workability and flowability when working even in low or high humidity conditions It was found that the paintable temperature and humidity range was expanded, and the mechanical properties such as adhesion, water resistance, and cold resistance chipping resistance were excellent. In addition, as shown in Table 3, the coating material of the embodiment of the present invention can obtain a final coating film excellent in appearance and coating properties even after the subsequent coating of various clear coats.

In the case of Comparative Example 1, a problem in the resin composition in the low-humidity conditions due to the resin composition problems, problems in the physical properties of the adhesion, impact properties, Comparative Example 2, the paint storage stability is lowered due to a decrease in compatibility with the resin in the solvent composition, In low humidity conditions, the appearance was reduced. In the case of Comparative Example 3, it is determined that the appearance decrease due to the change in temperature and humidity due to the deterioration of the effect of the thickener.

Claims (6)

5 to 40% by weight of core / shell / shell microgel resin, based on the weight of the total coating composition; 2 to 20 wt% polyurethane dispersion resin; 2 to 20 wt% polyester resin; 2 to 20% by weight of a hydrophilic imino group-containing melamine curing agent; 5-15 wt% of 2-ethylhexyl alcohol; 1 to 5% by weight of ethylene glycol monohexyl ether; 1 to 5% by weight of ethylene glycol monobutyl ether; 0.01 to 2 weight percent wetting agent; Antifoam 0.1 to 3 weight percent; 0.1 to 2 weight percent of catalyst; 0.1-3% by weight of ultraviolet absorbent; 0.1-5% by weight of flow control agent; 3 to 10 weight percent aluminum flake paste; 0.1 to 1 weight percent of a neutralizing agent; And 25 to 45% by weight of water. The method of claim 1,
The flow control agent is a water-soluble top coat composition for automobiles, characterized in that the combination of two or more selected from the group consisting of alkali shellable acrylic emulsion, urethane thickener, polyamide wax and hectorite clay. The method of claim 1,
The core / shell / shell microgel resin has a solid content of 20 to 60%, a glass transition temperature of -20 to -5 ° C, an acid value of 30 to 200 mgKOH / g, and a particle size of 50 to 150 nm. Paint composition. The method of claim 1,
The polyurethane dispersion resin has a solid content of 30 to 60%, a number average molecular weight of 8,000 to 30,000, an acid value of 15 to 35 mgKOH / g, and a particle size of 50 to 200 nm. The method of claim 1,
The polyester resin has a solid content of 60 to 90%, a number average molecular weight of 1,000 to 4,000, a glass transition temperature of -40 to -20 ℃, an acid value of 5 to 60 mgKOH / g, characterized in that the water-soluble top coating composition for automobiles. The method of claim 1,
A water-soluble top coat composition for automobiles, further comprising 1 to 5% by weight of colored pigments and extender pigments.