KR20040073184A - Method for forming multiple coating film in automobile - Google Patents

Abstract

PURPOSE: A method for forming multiple coating film in automobile is provided to prevent a popping phenomenon at final hardening, to shorten a time for a conventional hardening process and to ensure a good appearance. CONSTITUTION: The method for forming multiple coating film comprises coating a water soluble intermediate coat; coating a water soluble top coat; coating a thermosetting solvent type clear coat; and hardening by baking in one time. The water soluble intermediate coat comprises 20 to 60 wt.% of a water dispersible polyurethane resin, 1 to 20 wt.% of anhydrous dispersion, 1 to 15 wt.% of a crosslinkable amino resin and the balance of a pigment, an additive and water. The water soluble top coat comprises 20 to 60 wt.% of a water soluble polyurethane-acryl copolymer resin, 1 to 20 wt.% of anhydrous dispersion, 1 to 20 wt.% of a crosslinkable amino resin and the balance of a pigment, an additive and water. The clear coat is a one or two component or aqueous powder slurry.

Description

Method for forming multiple coating film in automobile}

The present invention relates to a method for forming a multilayer coating film of an automobile, and more particularly, by using a specific component in a middle paint and a top coat, it is possible to shorten the existing curing process without controlling the temperature / humidity of a special paint booth. The present invention relates to a method for forming a multilayer coating film of a low-VOC (volatile organic compound) type 3-coat 1-bake type vehicle capable of securing an appearance.

Recently, cars are recognized as a concept of use rather than a concept of ownership, and the number of automobile production is increasing every year. In particular, automotive paints can have a profound effect on not only the appearance completion but also the environmental protection aspects and the surge of automobile sales, which can represent huge economic benefits. Therefore, a high-functional form is required to further support economics and quality improvement. It is becoming.

Therefore, in addition to the policy of limiting the use of organic solvents and harmful heavy metals used in paints, automobile manufacturers save energy and shorten the process required for paint drying and curing. Is being demanded. Accordingly, the technological trend of global automotive paints is based on the development of water, and the development is under way to obtain visible effects such as energy saving, production equipment and operation cost reduction, and labor cost reduction.

In the current water-based automotive coating process, the water-soluble intermediate paint is first coated on the cured electrodeposition coating film, and then the water-soluble topcoat paint is applied after the curing process of 150 ° C. × 25 minutes, followed by hot air drying of 80 ° C. × 10 minutes. As a next step, a three-coat two-baking method is applied, in which a solvent-type one-component or two-component transparent paint is applied and completed through a curing process of 150 ° C. × 25 minutes.

In addition, as a technique for shortening the curing process in the above-described three-coat two-baking method, by proceeding to wet-on-wet from the intermediate paint to the coating of the transparent paint by eliminating the curing process of the intermediate paint Thus, a three-coat 1-baking coating process that undergoes one hardening process has been developed.

For example, Japanese Patent Application Laid-Open No. 8-290102 discloses a neutralization value generated by wet-on-wet by allowing the neutralizing value of the base resin of the water-soluble intermediate paint and the water-soluble topcoat to be coated in a wet-on-wet method to have a specific range. It is disclosed that the gloss and sensibility of a coating film surface can be maintained by preventing the interlayer reversal or mixing of the paint and the top coat. However, since various solvents are used in paint formulations, it is very difficult to control the interaction between layers only by the difference in the neutralization of the base resin, and even if no mixed layer is generated due to no interaction between layers, the coating is wet-on-wet on the middle paint. Since the top coat is soaked, there is a problem that the difference in final appearance according to the electrodeposition roughness appears as smoothness, image sharpness, and the like.

Moreover, study No. of coatings. 129 Oct. In 1997, the first coating material, which is a solvent type coating material using a water-soluble resin, was coated on the cured middle coating film to obtain a wetting property and a stable finish while being less affected by the booth humidity, and the water-soluble second coating material was coated with wet-on-wet. After the hot air drying about 80 ℃ × 5 minutes, a process of coating and curing the transparent paint is introduced. In the above process, since the first topcoat paint absorbs water immediately after arrival of the water-soluble topcoat, which is the second topcoat paint, the arrival viscosity increases rapidly even under high humidity coating conditions, so that a good brightness alignment and appearance can be obtained. However, since the process is a top coat concept introduced to improve the concealment problem because it is not well concealed to the bottom during pearl coating as a top coat, it is not a true three-coat 1-bak coating process according to process shortening. .

Therefore, in the present invention, in order to solve the problems described above, extensive research has been conducted, using a specific non-aqueous dispersion in the intermediate coating and top coating, using the difference in the surface tension between layers between wet-on-wetting It prevents the reversal of phenomena and the phenomenon of mixed layer, prevents the top coat from being absorbed into the middle coat, and promotes the middle drying speed, thereby showing excellent performance in preventing popping during final curing. The present invention has been completed based on this finding.

Accordingly, it is an object of the present invention to provide a method for forming a multilayer coating film for automobiles that can shorten the existing curing process time and secure an excellent appearance without controlling the temperature / humidity of a special paint booth.

Another object of the present invention is to provide a method for forming a multilayer coating film for automobiles that can contribute to the reduction of environmental pollutants of low VOC (volatile organic compound) type.

In order to achieve the above and other objects, the multilayer coating film forming method of a vehicle according to the present invention is coated with a water-soluble middle paint on the surface to be coated, and then coated with a water-soluble top coat without baking, and then a thermosetting solvent-type transparent paint. Next, in the multilayer coating film formation method of the automobile by the 3-coat 1-baked coating film forming method to be baked at one time, the water-soluble intermediate paint is 20 to 60% by weight polyurethane water dispersion resin, non-aqueous dispersion 1 -20% by weight, 1-15% by weight of crosslinkable amino resin, and the rest include pigments, additives and water; The water-soluble topcoat comprises 20 to 60% by weight of a water-soluble polyurethane-acrylic copolymer resin, 1 to 20% by weight of a non-aqueous dispersion, 1 to 20% by weight of a crosslinkable amino resin, and the balance includes a pigment, an additive, and water; The transparent paint is characterized in that the solvent type 1 or 2 solutions, or an aqueous powder slurry (powder slurry).

Hereinafter, the present invention will be described in more detail.

As described above, the present invention provides a method for forming a multilayer coating film for automobiles that can secure an excellent appearance while shortening an existing curing process without controlling temperature / humidity of a special paint booth.

In the method of forming a coating film for automobiles according to the present invention, the curing process of the intermediate coating is omitted so that the coating process of the intermediate coating to the coating of the transparent coating is performed wet-on-wet through the coating process. It is a 3-coat 1-baking coating film formation process.

The water-soluble intermediate paint used in the present invention is (A) 20 to 60% by weight of the polyurethane water dispersion resin, (B) 1 to 20% by weight of the non-aqueous dispersion, (C) 1 to 15% by weight of the crosslinkable amino resin, and the rest Includes pigments, additives and water.

The polyurethane water dispersion resin (A) used in the water-soluble middle paint of the present invention is a non-yellowing aliphatic type, particularly preferably having a MFFT (minimum coating film formation temperature) of 0 to 30 ° C. and an average particle diameter of about 0.05 to 0.2 μm. The solid content is preferably 30 to 60% by weight. On the other hand, the content of the polyurethane water dispersion resin in the water-soluble intermediate paint is preferably 20 to 60% by weight, and when the content is less than 20% by weight, physical properties such as impact resistance, adhesion and water resistance are lowered, and 60% by weight. If it exceeds the content of the binder is too high to decrease the relative pigment content, there is a problem that the hiding power on the surface.

The non-aqueous dispersion (B) used in the water-soluble intermediate paint of the present invention includes a particle-crosslinked polyurethane resin, a polyurethane-acrylic copolymer resin, and an acrylic resin. Can be used.

At this time, the content of the non-aqueous dispersion in the water-soluble intermediate paint is preferably 1 to 20% by weight. When the content of the non-aqueous dispersion is out of the above range, the effect is hardly exhibited or a problem of storage performance may occur.

On the other hand, the non-aqueous dispersion is a state in which the particle crosslinked resin is dispersed in a water-soluble coagulant such as glycol ethers, glycol ether esters or alcohols, or a water-insoluble coagulant. It is preferable that the dispersion contains 40 to 95% by weight of a coarse solvent, and if the content of the co-solvent is less than 40% by weight, it is impossible to prepare a non-aqueous dispersion due to an increase in content. This is reduced and there is a problem that a large amount of the solvent is contained in the paint.

The solid content of the non-aqueous dispersion is preferably from 5 to 60% by weight, if the solid content is less than 5% by weight, there is a problem that a large amount of the solvent is contained in the paint, if it exceeds 60% by weight of the non-aqueous The preparation of the dispersion is impossible. In addition, the acid value of the non-aqueous dispersion is preferably 5 ~ 50mgKOH / g, when the acid value of the dispersion is out of the range is low compatibility with the water-soluble resin to form an opaque coating film to reduce the coating properties Cause.

As a crosslinkable amino resin (C) used as a crosslinking agent for the water-soluble middle paint of this invention, a metharolized amine resin obtained by reaction of an amino component, such as melamine, urea, benzo guanamine, and formaldehyde, or a metirol group in resin Some or all of the ethers are etherified with mono alcohols having 1 to 5 carbon atoms.

In this case, the content of the crosslinkable amino resin in the water-soluble intermediate paint is preferably 1 to 15% by weight, and when the content of the crosslinkable amino resin is less than 1% by weight, the crosslinking degree is low, and the coating film performance is lowered and exceeds 15% by weight. When the hardness increases, the impact resistance is lowered or the storage property of the paint is poor.

On the other hand, the water-soluble topcoat used in the present invention is 20 to 60% by weight of the (D) water-soluble polyurethane-acrylic copolymer resin, 1 to 20% by weight of the (E) non-aqueous dispersion, and 1 to 20% by weight of the (F) crosslinkable amino resin. %, And the remainder include pigments, additives and water.

Polyurethane-acrylic copolymer resin (D) used in the water-soluble topcoat of the present invention is a non-yellowing aliphatic system, having an MFFT of 5 to 20 ° C., an average particle diameter of about 0.05 to 0.5 μm, and a 30 to 60 wt% It is preferred to have a solids content.

The non-aqueous dispersion (E) and the crosslinkable amino resin (F) used in the water-soluble top coat of the present invention are as described above in the water-soluble middle paint.

At this time, the content of the non-aqueous dispersion in the water-soluble topcoat is preferably 1 to 20% by weight, and if the content of the non-aqueous dispersion is outside the above range, the effect is hardly exhibited or a problem of storage properties may occur.

In addition, the content of the crosslinkable amino resin in the water-soluble top coat is preferably 1 to 20% by weight. When the content of the crosslinkable amino resin is less than 1% by weight, the crosslinking degree is low, and the coating film performance is lowered, and it is more than 20% by weight. When the hardness increases, the impact resistance is lowered or the storage property of the paint is poor.

The transparent paint used in the present invention may be used without particular limitation as long as it is a transparent paint composition for automobiles known in the art, including a solvent type 1 or 2 solution, or an aqueous powder slurry.

In addition, the water-soluble intermediate and top coat used in the present invention may be mixed with other dendritic materials as necessary in addition to the components described above as long as they do not adversely affect the physical performance and properties of the paint, or other additives as desired. It can contain more.

Therefore, materials such as rheology modifiers such as bentonite clay, anti-gas generation agents, UV stabilizers, catalysts, fillers, and the like may be used in the water-soluble medium and top coats of the present invention. In addition, metal oxides such as titanium dioxide, silicate and iron oxide of various colors, and filling pigments such as carbon black, talc, china clay, carbonate, aluminum flakes and organic pigments of various colors, and binders may be used.

In particular, the water-soluble intermediate and the top coat of the present invention may each contain 10 to 20% by weight of colored pigments. The coloring pigments may be used in combination of one or two or more coloring pigments for organic or inorganic paints. It is preferable that the viscosity of the said pigment is 30-150 second / Fordcup # 4/25 degreeC. In addition, the weight ratio of the pigment and the binder is preferably 1: 0.5 to 2, when the weight ratio is out of the range, the hiding power is lowered, or the water resistance and impact resistance physical properties are lowered.

On the other hand, the dispersion method of the pigment can be applied in a general high speed mixing, sand mill, ball mill or a combination of two or more using a resin for dispersing or a dispersant as known in the art.

The paint component of the present invention described above may be coated by a method such as spray, electrostatic spray, dipping, brush coating, etc., as is known in the art, but more preferably, electrostatic coating is preferable. In addition, it is possible to ensure a more excellent appearance by painting for multilayer coating of the vehicle through such means.

At this time, the dry coating thickness of the water-soluble middle paint and the dry coating thickness of the water-soluble topcoat are preferably 10 to 40 μm and 20 to 50 μm, respectively, and when the coating thickness is out of the range, the popping is caused by the transient film. The phenomenon occurs or sagging becomes poor. In addition, the dry coating thickness of the solvent-type transparent coating is 40 ~ 60㎛ good in terms of smoothness, gloss, image sharpness of the coating film.

As described above, according to the present invention, the intermediate coating and the top coating contain a non-aqueous dispersion, thereby preventing reversal or mixing between layers during wet-on-wet using the difference in surface tension between the layers. In addition to preventing the phenomenon of being absorbed into the intermediate coating film, it is possible to promote excellent performance in preventing the popping phenomenon during final curing by promoting the intermediate drying speed.

In addition, the non-aqueous dispersion resin used at this time is dispersed in a water-soluble or water-insoluble coagulant in the form of particle crosslinking, there is also a feature that improves the workability of the paint.

Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited to the following Examples.

Preparation Example 1

Preparation of Polyester Resin

In a reactor equipped with a stirrer, a thermometer, a condenser and a nitrogen injection tube, 303.70 g of 1,6-hexanediol, 156.23 g of neopentyl glycol, 146.14 g of adipic acid, 139.56 g of isophthalic acid, and 195.58 g of hexahydrophthalic anhydride were added. After the addition, the temperature was raised to 130 ° C, 0.95 g of dibutyltin dilaurate was added as a catalyst, and the temperature was raised to 180 ° C for reaction.

When the acid value of the resin (the reactant) was about 20 mgKOH / g, the temperature was raised to 220 ° C. and reacted until the acid value became 5 mgKOH / g or less. When the acid value was 5 mgKOH / g or less, nitrogen was blown to remove residual water and cooled. The acid value of the resin thus prepared was 3-5 mgKOH / g, the hydroxyl value was 50-60 mgKOH / g, and the weight average molecular weight was about 2,000.

Preparation Example 2

-Preparation of Polyurethane Water Dispersion Resin 1

Into a reactor equipped with a stirrer, a thermometer, a condenser, a metering pump, and a nitrogen injection tube, 800 g of the polyester obtained in Preparation Example 1 was placed, and 23.9 g of dimethyrol propionic acid and 0.4 g of dibutyltin dilaurate were added thereto. After that, the temperature was raised to 60 ° C. and 140 g of isophorone diisocyanate and 413.1 g of acetone were sequentially added and maintained for 8 hours. When the NCO content was determined to be 0, 14.3 g of triethylamine was added and maintained for 30 minutes. Dispersion was carried out by adding 546.4 g of deionized water for 30 minutes. When dispersion of the turbidity was completed, acetone was removed under reduced pressure to obtain a polyurethane water dispersion resin having a final solid content of 40% by weight and a particle size of 0.15 to 0.2 µm.

Preparation Example 3

-Preparation of Polyurethane Water Dispersion Resin 2

Into a reactor equipped with a stirrer, a thermometer, a condenser, a metering pump, and a nitrogen inlet tube, 1000 g of the polyester obtained in Preparation Example 1 was placed therein, 24.2 g of dimethyrol propionic acid, 140 g of isophorone diisocyanate, and dibutyltin dilaur After inserting 0.4 g of rate, the temperature was raised to 60 ° C. and 291.1 g of acetone was added and maintained for 8 hours. When the NCO content was 0, 14.5 g of triethylamine was added and maintained for 30 minutes, followed by deionized water. Dispersion was carried out by adding 1621.8 g for 30 minutes. When dispersion of the turbidity was completed, acetone was removed under reduced pressure to obtain a polyurethane water dispersion resin having a final solid content of 40% by weight and a particle size of 0.15 to 0.2 µm.

Preparation Example 4

-Preparation of Non-Aqueous Dispersion-Polyurethane Type 1

900.0 g of 1,6-hexanediol adipate (hydroxy acid value: 56 mgKOH / g), 7.1 g of trimethol propane, 63.0 g of dimethrol propionic acid, acetone in a reactor equipped with a stirrer, a thermometer, a condenser, a metering pump and a nitrogen injection tube After 600 g was added, the temperature was raised to 60 ° C., and 550.0 g of isophorone diisocyanate and 0.760 g of dibutyltin dilaurate were added thereto, followed by reflux reaction. When the NCO content does not change as the reaction proceeds, it is cooled to 30 ° C., 49.9 g of triethylamine is added and maintained for 30 minutes, and 1690 g of water is injected over 10 minutes under high-speed stirring, and the water dispersion of the turbidity Upon complete progress, a mixture of 85.8 g of diethylenetriamine and 283.4 g of deionized water was then purchased.

At this time, the particle crosslinking reaction occurs, the exotherm of about 5 ~ 10 ℃ proceeds but kept as it was and slowly stirred for 2 hours. Then, the mixture was heated to 60 ° C. again to remove acetone present in the aqueous product to obtain a polyurethane water dispersion resin having a solid content of 35% by weight and a particle diameter of 0.05 to 0.1 μm.

Then, 500 g of the polyurethane water dispersion resin and 500 g of 2-ethylhexanol obtained above were added to a reactor equipped with a stirrer, a thermometer, a H-type separator, and a condenser inlet tube, and gradually heated up to 160 ° C. while stirring. Was removed. From this, a reddish brown non-aqueous dispersion having a final acid value of 16 mgKOH / g and a solid content of 35% by weight was obtained.

Preparation Example 5

-Preparation of Non-Aqueous Dispersion-Polyurethane Type 2

Polycarbonate diol (hydroxyl value: 56 mgKOH / g) in place of 1,6-hexanediol adipate was carried out in the same manner as in Preparation Example 4, the final acid value of 16 mgKOH / g, reddish brown with a solid content of 35% by weight A non-aqueous dispersion was obtained.

Preparation Example 6

-Preparation of Non-Aqueous Dispersion-Polyurethane Type 3

Except for using polycaprolactonediol (hydroxyl value: 56 mgKOH / g) instead of 1,6-hexanediol adipate was carried out in the same manner as in Preparation Example 4 red brown with a final acid value of 16mgKOH / g, 35% by weight solid content The non-aqueous dispersion of was obtained.

Preparation Example 7

-Preparation of Non-Aqueous Dispersion-Polyurethane Type 4

The same procedure as in Preparation Example 4 was repeated except that polytetramethylene ether glycol (hydroxyl value: 56 mgKOH / g) was used instead of 1,6-hexanediol adipate to have a final acid value of 16 mgKOH / g and a solid content of 35 wt%. A reddish brown non-aqueous dispersion was obtained.

Preparation Example 8

-Preparation of Non-Aqueous Dispersion-Polyurethane Type 5

Polypropylene glycol (hydroxyl value: 56 mgKOH / g) in place of 1,6-hexanediol adipate was carried out in the same manner as in Preparation Example 4, the final acid value of 16 mgKOH / g, reddish brown with a solid content of 35% by weight A non-aqueous dispersion was obtained.

Examples 1-5 and Comparative Example 1

A. Preparation of Water Soluble Middle Paint

The components and contents used in the preparation of the water-soluble intermediate paints of Examples 1 to 5 and Comparative Example 1, respectively, are shown in detail in Table 1 below.

(a) To prepare a mill base, first, deionized water, a resin for dispersing, a wetting agent, a dispersant, an antifoaming agent, TiO ₂ , a pigment and a black pigment are respectively mixed in the amounts shown in Table 1 below, followed by 2 hours using a sand mill. To disperse. At this time, the final particle size of the mill base is to be 5μ or less.

(b) the crosslinking agent, the wetting agent, the neutralizing agent, the cosolvent, the main resin, and the deionized water were respectively injected and stirred in the contents shown in Table 1 below, and then visually observed that there is no abnormality such as the occurrence of teeing. 25.51 g of the mill base prepared in a) was added thereto, and the mixture was stirred for 30 minutes, followed by adding a non-aqueous dispersion and a thickener (Comparative Example 1, the non-aqueous dispersion was not added). The intermediate coating was completed by adjusting with deionized water so as to (Ford Cup # 4).

A ingredient Usage Example 1 (g) Example 2 (g) Example 3 (g) Example 4 (g) Example 5 (g) Comparative Example 1 (g) Deionized Water 1 7.1 7.1 7.1 7.1 7.1 7.1 Efka-1502 Dispersion Resin 2.23 2.23 2.23 2.23 2.23 2.23 Efka-5044 Humectant 0.5 0.5 0.5 0.5 0.5 0.5 BYK-D190 Dispersant 1.0 1.0 1.0 1.0 1.0 1.0 (a) Tego Foamex830 Antifoam 0.3 0.3 0.3 0.3 0.3 0.3 CR97 TiO ₂ 7.1 7.1 7.1 7.1 7.1 7.1 BFM Pigment 7.1 7.1 7.1 7.1 7.1 7.1 Aerosil R972 Pigment 0.1 0.1 0.1 0.1 0.1 0.1 Bayferrox 303T Black pigment 0.08 0.08 0.08 0.08 0.08 0.08 Cymel 325 Crosslinking agent 3.5 3.5 3.5 3.5 3.5 3.5 Tego Wet 510 Humectant 1.0 1.0 1.0 1.0 1.0 1.0 angusAMP95 10% solution corrector 3.0 3.0 3.0 3.0 3.0 3.0 Butyl Cellosolve Solvent 2.0 2.0 2.0 2.0 2.0 2.0 Preparation Example 2 Main resin 38 Preparation Example 3 38 (b) NeoRez R989 ¹⁾ 38 UD220 ²⁾ 38 38 38 Deionized water 50.8 50.8 50.8 50.8 50.8 58.8 Preparation Example 4 Non-aqueous dispersion 8 - - - - - Preparation Example 5 - 8 - - - - Preparation Example 6 - - 8 - - - Preparation Example 7 - - - 8 - - Preparation Example 8 - - - - 8 - Viscalex HV 30 ³⁾ 10% solution Thickener 10.4 10.4 10.4 10.4 10.4 10.4

1) Avecia

2) Bond polymer Inc. product

3) Allied colloide

B. Preparation of Water-Soluble Topcoat

The components and contents used in the preparation of the water-soluble topcoats of Examples 1 to 5 and Comparative Example 1, respectively, are shown in detail in Table 2 below.

(a) The mill base is prepared by using a solvent, a wetting agent, a white pigment, and an antifoaming agent in the amounts shown in Table 2, respectively, and dispersing the mixture for 2 hours using a sand mill to have a final particle size of 5 μm or less.

(b) a crude solvent, a crosslinking agent, a main resin, and a neutralizing agent were added to each of the contents shown in Table 2 below, followed by stirring to visually observe the presence of teeing. Then, 41.84 g of the mill base prepared in (a) was added thereto. After stirring, a non-aqueous dispersion and a thickener (Comparative Example 1, non-aqueous dispersion was not added) were added and stirred for 30 minutes, and then adjusted using deionized water to give a final viscosity of 60 seconds (pod cup # 4). To finish the topcoat.

B ingredient Usage Examples 1-5 (g) Comparative Example 1 (g) 2-ethyl hexanol Solvent 2.50 2.50 Wet 510 Humectant 0.45 0.45 (a) CR97 White Pigment 38.22 38.22 Foamast324 Antifoam 0.67 0.67 DPM Solvent 3.00 3.00 Hexyl cellosolve Solvent 4.00 4.00 CYMEL325 Crosslinking agent 2.00 2.00 AC2509 ¹⁾ Main resin 43.00 43.00 (b) 10% AMP corrector 3.40 3.40 Preparation Example 4 Non-aqueous dispersion 8.00 - 2% laponite RD Thickener 10.00 10.00 33% HV30 Thickener 2.00 2.00 Deionized water 30.00 38.00

1) Product of ALBERDINGK: Acrylic-urethane resin

C. Multi-Layer Coating

After coating the water-soluble intermediate paint obtained in the above A on the specimen coated with the cationic electrodeposition paint (KCC product: ED-6000) on the CR steel plate, and coating the water-soluble topcoat obtained in the above-mentioned B, hot-air drying for 80 ° C./5 minutes. After coating the solvent type two-component transparent paint (KCC product: Cleansense) and curing for 150 ℃ / 20 minutes to prepare a multilayer coating film, the physical properties of the results are shown in Table 3 below.

At this time, the coating process using an automatic coating machine at a temperature of 70% relative humidity and 25 ℃, the middle coating paints 10 to 40㎛, the top coat 20 to 50㎛, and the transparent paint 40 to 60㎛ respectively Was performed.

division Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Remarks Appearance (Gloss and Clearness) Great Great Good Good Good Bad Visual observation Workability Great Great Good Great Great usually Chilsung Castle Paint stability Great Great Great Great Great Good Viscosity change after storage at 45 ℃ / 5 days, measured by Pod Cup # 4, within ± 20% Popping Great Great Good Great Great Bad Comparison Vertical QMS Data ¹⁾ Gloss 51 48 42 47 54 44 45 ^。 DOI 60 59 53 58 62 51 Image sharpness Orange peel 49 47 40 46 47 38 Orange peel

1) QMS (quality measurement system): perceptrom company

DOI (Image Sharpness): Higher value indicates better condition.

As can be seen in Table 3, when the coating according to the method of the present invention, not only excellent appearance and excellent stability of the coating, but also prevented popping phenomenon during curing.

As described above, according to the present invention, a low-VOC (volatile organic compound) type 3-coat 1-baking can shorten the existing curing process and secure the existing appearance without controlling the temperature and humidity of the special coating booth. A type coating film forming method is provided. The method according to the present invention can make a great contribution not only to saving energy by shortening the coating process but also to improving productivity and reducing environmental pollutants.

Claims (5)

In the method of forming a 3-coat 1-baked coating film which is coated with a water-soluble intermediate paint on the surface to be coated, and then coated with a water-soluble top coat without any baking process, and then coated with a thermosetting solvent-type transparent paint, followed by baking at once. In the multilayer film forming method of automobiles by The water-soluble intermediate paint comprises 20 to 60% by weight of polyurethane water dispersion resin, 1 to 20% by weight of non-aqueous dispersion, 1 to 15% by weight of crosslinkable amino resin, and the balance includes pigments, additives and water; The water-soluble topcoat comprises 20 to 60% by weight of a water-soluble polyurethane-acrylic copolymer resin, 1 to 20% by weight of a non-aqueous dispersion, 1 to 20% by weight of a crosslinkable amino resin, and the balance includes a pigment, an additive, and water; The transparent coating is a solvent type 1 or 2 liquid, or an aqueous powder slurry (powder slurry), characterized in that the vehicle multilayer coating film forming method. The method of claim 1 wherein the non-aqueous dispersion comprises particle crosslinked polyurethane resin, polyurethane-acrylic copolymer resin, acrylic resin, or mixtures thereof. The method of claim 1, wherein the non-aqueous dispersion comprises 40 to 95% by weight of a water-soluble coagulant or a water-insoluble coagulant. The method of claim 1, wherein the non-aqueous dispersion contains 5 to 60% by weight of solids. The method according to claim 1, wherein the acid value of the non-aqueous dispersion is 5 to 50 mgKOH / g.