WO2020141740A2 - Paint composition for primer coating - Google Patents

Abstract

The present invention relates to a paint composition for primer coating, the composition comprising a first urethane-modified polyester resin, a second urethane-modified polyester resin, an alkyd resin, a melamine resin, and an isocyanate resin.

Description

Medium coating composition

The present invention relates to a coating composition for intermediate use.

BACKGROUND OF THE INVENTION In order to protect the surface of an automobile body from external and external environments, it is common to perform electrodeposition coating, intermediate coating, base coating and clear coating. For example, after applying the electrodeposition coating to the vehicle body, the intermediate coating is applied and cured at 150° C. for 20 minutes. Subsequently, the base coat and the clear coat are continuously coated on the intermediate coating layer, followed by drying and curing. However, in recent years, the demand for more environmentally friendly and economical coating systems is increasing.

In this regard, Korean Patent Registration No. 484,060 (Patent Document 1) discloses a low temperature curing type water-soluble coating composition composed of a polyethylene oxide group-containing polyethylene glycol, a water-dispersible polyurethane polyol resin, and a water-blocking polyisocyanate resin. However, as in Patent Document 1, the conventional low-temperature curing type paint composition for automobiles has a limitation in application as a paint for a vehicle body because the mechanical properties of the prepared coating film are not sufficient.

Therefore, there is a need for research and development on the intermediate coating composition having excellent mechanical properties, such as appearance characteristics, adhesion, impact resistance, and chipping resistance, and curable at a low temperature of 140° C. or less.

Accordingly, the present invention is to provide a coating composition for intermediate use that is excellent in mechanical properties such as appearance properties, adhesion, impact resistance and chipping resistance of the prepared coating film, and can be cured at a low temperature of 140°C or less.

The present invention provides a coating composition for intermediate use, comprising a first urethane-modified polyester resin, a second urethane-modified polyester resin, an alkyd resin, a melamine resin, and an isocyanate resin.

The coating composition for intermediate use according to the present invention can be cured at a low temperature of 140° C. or less, and can produce a coating film having excellent mechanical properties such as appearance characteristics, adhesion, impact resistance, and chipping resistance, for painting automotive parts and body It is suitable as a paint.

The intermediate coating composition according to the present invention includes a first urethane-modified polyester resin, a second urethane-modified polyester resin, an alkyd resin, a melamine resin, and an isocyanate resin.

First urethane-modified polyester resin

The first urethane-modified polyester resin serves to improve the appearance characteristics, adhesion, impact resistance, and chipping resistance of the coating film prepared from the composition comprising the same.

The first urethane-modified polyester resin has a hydroxyl value (OHV) of 60 to 100 mgKOH/g, a solid content (NV) of 50 to 68% by weight relative to the total weight, and a viscosity at 25°C of 600 to 1,100 cps. Can be In another example, the first urethane-modified polyester resin has a hydroxyl value of 70 to 95 mgKOH/g, or 75 to 90 mgKOH/g, and the solid content is 55 to 65% by weight, or 58 to 62% by weight based on the total weight. And, the viscosity at 25 ℃ may be 630 to 1,070 cps, or 750 to 1,000 cps. When the hydroxyl value of the first urethane-modified polyester resin is within the above range, it has the effect of improving low temperature curing, adhesion and impact resistance, and when the solid content is within the above range, appearance characteristics, especially gloss, durability, elasticity and curing density When there is an improvement effect, and the viscosity at 25°C is within the above range, the solid content rises, thereby improving the SVR (Solid Volume Ratio) of the paint.

In addition, the first urethane-modified polyester resin may have an acid value (AV) of 1 to 10 mgKOH/g, and a weight average molecular weight (Mw) of 1,000 to 2,500 g/mol. As another example, the first urethane-modified polyester resin may have an acid value of 2 to 8 mgKOH/g, or 2.5 to 5 mgKOH/g, and a weight average molecular weight of 1,100 to 2,200 g/mol, or 1,200 to 2,000 g/mol have.

When the acid value of the first urethane-modified polyester resin is within the above range, appearance and adhesion are excellent, and when the weight average molecular weight is within the above range, appearance and gloss may be excellent.

The first urethane-modified polyester resin has a smaller hydroxyl value and lower viscosity at 25°C than the second urethane-modified polyester resin. For example, the hydroxyl value of the first urethane-modified polyester resin may be 0.4 to 0.8 times the hydroxyl value of the second urethane-modified polyester resin. As another example, the hydroxyl value of the first urethane-modified polyester resin may be 0.45 to 0.70 times, or 0.50 to 0.65 times the hydroxyl value of the second urethane modified polyester resin.

The viscosity of the first urethane-modified polyester resin at 25°C may be 0.3 to 0.9 times the viscosity of the second urethane-modified polyester resin at 25°C. As another example, the viscosity at 25°C of the first urethane-modified polyester resin may be 0.3 to 0.8 times, or 0.50 to 0.75 times the viscosity at 25°C of the second urethane-modified polyester resin.

In addition, the first urethane-modified polyester resin may be included in the composition in an amount of 15 to 30 parts by weight based on 1 to 10 parts by weight of the second urethane-modified polyester resin. As another example, the first urethane-modified polyester resin may be included in the composition in an amount of 15 to 28 parts by weight, or 18 to 25 parts by weight based on 1 to 10 parts by weight of the second urethane-modified polyester resin. When the content of the first urethane-modified polyester resin is within the above range, there is an effect of improving appearance characteristics, impact resistance, and chipping resistance.

Second urethane-modified polyester resin

The second urethane-modified polyester resin serves to control sagging of the composition containing the same.

The second urethane-modified polyester resin has a hydroxyl value (OHV) of 120 to 170 mgKOH/g, a solids content of 70 to 90% by weight relative to the total weight, and a viscosity at 25°C of 1,200 to 2,300 cps. . In another example, the second urethane-modified polyester resin has a hydroxyl value of 130 to 160 mgKOH/g, or 135 to 150 mgKOH/g, and the solid content is 75 to 85% by weight, or 78 to 82% by weight based on the total weight. And, the viscosity at 25 ℃ may be 1,230 to 2,270 cps, or 1,500 to 1,800 cps. When the hydroxyl value of the second urethane-modified polyester resin is within the above range, there is an effect of improving low temperature curing and crosslinking density, and when a solid content is within the above range, there is an effect of improving glossiness and curing reactivity, and a viscosity at 25°C. When within the above range, there is an effect of improving the SVR of the paint.

In addition, the second urethane-modified polyester resin may have an acid value (AV) of 1 to 10 mgKOH/g, and a weight average molecular weight (Mw) of 800 to 2,000 g/mol. As another example, the second urethane-modified polyester resin may have an acid value of 1 to 7 mgKOH/g, or 1 to 5 mgKOH/g, and a weight average molecular weight of 1,000 to 1,800 g/mol, or 1,100 to 1,500 g/mol. have. When the acid value of the second urethane-modified polyester resin is within the above range, there is an effect of improving crosslinking density and curing reactivity, and when the weight average molecular weight is within the above range, there is an effect of improving SVR of the paint.

Furthermore, the second urethane-modified polyester resin may be included in the composition in an amount of 1 to 10 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. As another example, the second urethane-modified polyester resin may be included in the composition in an amount of 2 to 8 parts by weight, or 4 to 7 parts by weight with respect to 15 to 30 parts by weight of the first urethane-modified polyester resin. When the content of the second urethane-modified polyester resin is within the above range, high gloss of the paint can be realized.

Alkyd resin

The alkyd resin serves to improve the appearance characteristics, adhesion, impact resistance and chipping resistance of the coating film prepared from the composition comprising the same.

The alkyd resin may have a hydroxyl value (OHV) of 150 to 250 mgKOH/g, a solid content of 40 to 65% by weight based on the total weight, and a viscosity at 25°C of 1,000 to 1,800. In another example, the alkyd resin has a hydroxyl value of 180 to 230 mgKOH/g, or 190 to 210 mgKOH/g, and the solid content is 50 to 60% by weight, or 51 to 58% by weight, at 25°C. The viscosity of may be 1,040 to 1,760 cps, or 1,200 to 1,500 cps. When the hydroxyl value of the alkyd resin is within the above range, there is an effect of improving appearance and hardness, and when the solid content is within the above range, high gloss can be realized, and when the viscosity at 25°C is within the above range, the effect of improving appearance and durability have.

In addition, the alkyd resin may have an acid value (AV) of 1 to 15 mgKOH/g, and a weight average molecular weight (Mw) of 1,500 to 3,500 g/mol. As another example, the alkyd resin may have an acid value of 3 to 12 mgKOH/g, or 4 to 10 mgKOH/g, and a weight average molecular weight of 2,000 to 3,200 g/mol, or 2,500 to 3,000 g/mol. When the acid value of the alkyd resin is within the above range, leveling of the coating is improved, and when the weight average molecular weight is within the above range, appearance and adhesion can be improved.

The alkyd resin may be included in the composition in an amount of 5 to 20 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. As another example, the alkyd resin may be included in the composition in an amount of 8 to 15 parts by weight, or 10 to 13 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. When the content of the alkyd resin is within the above range, there is an effect of improving appearance characteristics and gloss.

Melamine resin

Melamine resin serves to cure the composition by reacting with the components in the composition containing it.

The melamine resin may include butoxy melamine resin and methylate melamine resin. For example, the intermediate coating composition may contain 5 to 20 parts by weight, or 10 to 15 parts by weight of butoxy melamine resin and 1 to 10 parts by weight, or 3 to 15 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. 8 parts by weight of methylate melamine resin. When the content of the butoxy melamine resin is within the above range, there is an effect of improving curing reactivity, and when the content of the methylate melamine resin is within the above range, there is an effect of improving appearance and storage stability.

In addition, the butoxy melamine resin has an acid value (AV) of 0.5 to 10 mgKOH/g, a solid content of 40 to 60% by weight based on the total weight, and a viscosity at 25°C of 55 to 110 cps. For example, the butoxy melamine resin has an acid value of 0.8 to 8 mgKOH/g, or 1 to 5 mgKOH/g, a solids content of 45 to 55% by weight, or 47 to 53% by weight, 25 The viscosity at °C can be between 65 and 100 cps, or between 75 and 95 cps. When the acid value of the butoxy melamine resin is within the above range, storage stability, impact resistance and chipping resistance are improved, and when the solid content is within the above range, there is an effect of improving low temperature curing reactivity, and the viscosity at 25°C is within the above range. In the case of tomorrow, there is an effect of improving the SVR of the paint.

Furthermore, the methylate melamine resin may have a density of 1.0 to 1.5 g/cm³, a solid content of 60 to 85% by weight relative to the total weight, and a viscosity at 25°C of 1,200 to 2,300 cps. For example, the methylate melamine resin has a density of 1.05 to 1.3 g/cm³, or 1.1 to 1.2 g/cm³, and a solids content of 65 to 82% by weight, or 70 to 80% by weight, 25 The viscosity at °C can be 1,250 to 2,250 cps, or 1,500 to 2,000 cps. When the density of the methylate melamine resin is within the above range, there is an effect of improving the crosslinking density of the paint, when the solid content is within the above range, there is an effect of improving the low temperature curing property, and when the viscosity at 25°C is within the above range, the SVR is improved It works.

The melamine resin may be included in the composition in an amount of 10 to 30 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. As another example, the melamine resin may be included in the composition in an amount of 13 to 23 parts by weight, or 15 to 20 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. When the content of the melamine resin is within the above range, there is an effect of improving the storage stability, impact resistance and chipping resistance of the paint.

Isocyanate resin

The isocyanate resin serves to cure the composition by crosslinking with other components in the composition containing the same. For example, the isocyanate group of the isocyanate resin reacts with hydroxyl groups of other components in the coating composition to form a urethane bond, thereby curing the coating composition.

The isocyanate resin may be used without particular limitation as long as it is a conventional isocyanate resin that can be used in the curing agent for paints. For example, hexamethylene diisocyanate (HMDI) having excellent yellowing resistance and weather resistance may be used as the isocyanate resin.

Meanwhile, the isocyanate resin may be diluted with an organic solvent. For example, the isocyanate resin may have a viscosity at 25°C of 1,500 to 3,500 cps, and a solid content of 70 to 80% by weight based on the total weight. For example, the isocyanate resin has a viscosity at 25°C of 2,000 to 3,300 cps, or 2,200 to 3,000 cps, and the solid content may be 72 to 78% by weight, or 74 to 76% by weight based on the total weight. When the viscosity of the isocyanate resin at 25°C is within the above range, there is an effect of improving leveling and wetting properties of the paint, and when the solid content is within the above range, impact resistance, chipping resistance and flexibility are improved. It works.

At this time, the organic solvent for diluting the isocyanate resin is not particularly limited as long as it is a common one used in the coating composition.

Furthermore, the isocyanate resin may be included in the composition in an amount of 1 to 8 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. For example, the isocyanate resin may be included in the composition in an amount of 2 to 8 parts by weight, or 1 to 4 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. When the content of the isocyanate resin is within the above range, there is an effect of improving the mechanical properties of the prepared coating film such as appearance, gloss, chipping resistance, and curing reaction.

solvent

The top coating composition may further include a solvent. At this time, the solvent serves to improve the workability by adjusting the viscosity of the composition.

The solvent is, for example, an aromatic hydrocarbon-based solvent such as toluene and xylene; Ketone solvents such as methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, and ethyl propyl ketone; Ester solvents such as methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate and ethyl ethoxypropionate; And alcohol-based solvents such as n-butanol, propanol and 1-methoxy-2-propanol; And the like. In addition, commercially available products of the aromatic hydrocarbon-based solvent include cocosol #100, cocosol #150, and the like.

The solvent may be included in the composition in an amount of 5 to 40 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. As another example, the solvent may be included in the composition in an amount of 8 to 35 parts by weight, or 10 to 30 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. When the solvent content in the composition is within the above range, there is an effect to improve the coating workability.

Pigment

The top coating composition may further include a pigment. At this time, the pigment serves to impart color to the prepared coating film.

In addition, the pigment is not particularly limited as long as it is a pigment commonly used in coating compositions, and for example, inorganic pigments, organic pigments, and the like can be used. For example, the pigment may include metal oxides such as titanium dioxide (TiO ₂ ), carbon black, zinc oxide, ultramarine, red iron oxide; Sulfides of lithopone, lead, cadmium, iron, cobalt, aluminum and hydrochloride or sulfates thereof; Azo pigments; And copper phthalocyanine pigments.

The pigment may be included in the composition in an amount of 5 to 30 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. As another example, the pigment may be included in the composition in an amount of 5 to 25 parts by weight, or 10 to 25 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. When the content of the pigment in the topcoat composition is within the above range, problems such as insufficient hiding power of the prepared film and stability of the composition and degradation of dispersibility of the pigment can be prevented.

additive

The intermediate coating composition may further include one or more additives selected from the group consisting of a flow prevention agent, a surface control agent, and a dispersing agent.

The additive may be included in the composition in an amount of 1 to 20 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. As another example, the additive may be included in the composition in an amount of 1 to 15 parts by weight, or 1 to 10 parts by weight based on 15 to 30 parts by weight of the first urethane-modified polyester resin. Flow inhibitors serve to control the flowability of the composition comprising them. In addition, the flow-preventing agent is not particularly limited as long as it is a surfactant or flow-controlling agent commonly used in coating compositions.

The surface modifier serves to control the smoothness of the coating film prepared by adjusting the surface tension after application of the coating composition, and can be used without particular limitation, as long as it is a common one that can be used in the coating composition. For example, the surface modifier may be a polyacrylate-based or silicone-based surface modifier.

The dispersant improves the dispersibility of various components in the composition and serves to increase the stability of the coating composition. In addition, the dispersant may be used without particular limitation as long as it is a conventional dispersant or dispersion stabilizer that can be used in the coating composition. Commercial products of the dispersant include BYPER's DISPERBYK-103, DISPERBYK-110, and DISPERBYK-161.

The intermediate coating composition may have a viscosity of 30 to 50 seconds based on the number 4 pod cup at 25°C. For example, the intermediate coating composition may have a viscosity of 30 to 45 seconds or 30 to 40 seconds based on the number 4 pod cup at 25°C. When the viscosity at 25°C of the intermediate coating composition is within the above range, atomization is possible when the coating is applied, and the workability is easy.

The coating composition for intermediate use according to the present invention as described above can be cured at a low temperature of 140° C. or less, and can produce a coating film excellent in mechanical properties such as appearance characteristics, adhesion, impact resistance, and chipping resistance, and automobile parts And it is suitable as a paint for car body painting.

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

In the present invention, functional groups such as'acid value' and'hydroxyl value' of the resin can be measured by methods well known in the art, and for example, may represent a value measured by a titration method.

In addition, the'weight average molecular weight' of the resin may be measured by a method well known in the art, for example, may represent a value measured by a method of gel permeation chromatograph (GPC).

In addition, the'glass transition temperature' of the resin may be measured by a method well known in the art, for example, may indicate a value measured by a differential scanning calorimetry (DSC) method.

Examples 1 to 8 and Comparative Examples 1 to 4. Preparation of intermediate coating composition

Intermediate coating of each component in the composition as described in Tables 1 and 2 to prepare a coating composition for the middle.

(Parts by weight)	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7	Example 8
First urethane-modified polyester resin	20	28	20	19	20	31	20	22
Second urethane-modified polyester resin	5	5	8	5	5	4	11	6
Alkyd resin	11	11	11	15	11	11	11	3
Butoxy melamine resin	12	12	12	11	12	11	12	12
Methylate melamine resin	5	5	5	5	10	5	5	5
Isocyanate resin	3	3	3	3	3	3	3	3
solvent	23.6	17.6	20.6	22.6	20.6	20.6	20.6	26.6
Pigment	17	15	17	16	15	11	14	19
Flow inhibitor	2.7	2.7	2.7	2.7	2.7	2.7	2.7	2.7
Surface adjuster	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5
Dispersant	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2
Sum	100	100	100	100	100	100	100	100

(Parts by weight)	Comparative Example 1	Comparative Example 2	Comparative Example 3	Comparative Example 4
First urethane-modified polyester resin	-	20	20	22
Second urethane-modified polyester resin	6	-	5	6
Alkyd resin	12	11	-	12
Butoxy melamine resin	13	12	12	-
Methylate melamine resin	6	5	5	-
Isocyanate resin	3	3	3	3
solvent	36.6	28.6	33.6	31.6
Pigment	20	17	18	22
Flow inhibitor	2.7	2.7	2.7	2.7
Surface adjuster	0.5	0.5	0.5	0.5
Dispersant	0.2	0.2	0.2	0.2
Sum	100	100	100	100

Hereinafter, manufacturers and product names of the components used in Examples and Comparative Examples are shown in Table 3.

ingredient	Remark
First urethane-modified polyester resin	OHV: 80mgKOH/g, AV: 4mgKOH/g, Mw: 1,600g/mol, solid content: 60% by weight, viscosity at 25°C: 890cps
Second urethane-modified polyester resin	OHV: 140mgKOH/g, AV: 3mgKOH/g, Mw: 1,260g/mol, solid content: 80% by weight, viscosity at 25°C: 1,630cps
Alkyd resin	OHV: 198mgKOH/g, AV: 6mgKOH/g, Mw: 2,700g/mol, solid content: 54% by weight, viscosity at 25°C: 1,380cps
Butoxy melamine resin	AV: 3 mgKOH/g, solid content: 51 wt%, viscosity at 25°C: 83 cps
Methylate melamine resin	Density: 1.16 g/cm³, solids: 76% by weight, viscosity at 25° C.: 1,750 cps
Isocyanate resin	Solid content: 75% by weight, viscosity at 25°C: 2,700 cps
solvent	Aromatic hydrocarbon system (KOCOSOL #100, GS CALTEX)
Pigment	White pigment (TiO 2 , Titanium Dioxide)
Flow inhibitor	DISPERBYK-385N, BYK
Surface modifier	A-620-A2, ARKEMA
Dispersant	DISPERBYK-161, BYK

Test Example: Evaluation of properties of the prepared coating film

After coating the intermediate coating composition of Examples and Comparative Examples on the electrodeposition-coated specimens, they were dried at room temperature for 5 minutes and then cured at 140°C for 20 minutes to prepare a coating film having a thickness of 33 μm.

Thereafter, the dispersibility and storage stability of the coating composition for intermediate use, the appearance properties and physical properties of the final coating film were measured by the following methods, and the results are shown in Table 4.

(1) Dispersibility

After the intermediate coating composition was stirred at 1,500 rpm, the particle size of the coating composition was checked with a particle size meter to evaluate whether the composition was uniformly dispersed without lumps.

Specifically, when the average particle size was 3 µm or less, it was evaluated as excellent (◎), more than 3 µm and 5 µm or less, good (○), 5 µm or more and 7 µm or less, normal (△), and 7 µm or more, poor (×). Did.

(2) Storage stability

After the intermediate coating composition was stored at 50°C for 120 hours, the storage stability was evaluated by comparing the rate of viscosity increase with that before storage. At this time, when the rate of climb was 10% or less, it was evaluated as excellent (◎), more than 10% and less than 30%, good (○), more than 30% and less than 50%, normal (△), and more than 50%, poor (×). .

(3) Gloss

The 60° gloss of the final coating was measured.

(4) Adhesion

The final coating film was drawn with 100 squares (1 mm × 1 mm) in width and length, respectively, with a blade, the square was removed using a tape, and the number of remaining squares was measured to evaluate adhesion.

At this time, when 100 squares are 100% intact, excellent (◎), if the remaining squares are 70% or more and less than 100%, good (○), 50% or more and less than 70%, normal (△), 30% or more and less than 50% The case was evaluated as defective (×).

(5) Hardness

The hardness of the intermediate coating film was measured by the pencil hardness method. Specifically, 3B, 2B, B, HB, F, H, 2H, and 3H were used to measure the maximum hardness without damaging the intermediate coating film (3B, 2B, B, HB, F, H, 2H) , 3H: thirteen ⇔ excellent).

(6) Impact resistance

When the weight of 500 g was dropped on the final coating film while changing the drop height of the weight from 20 cm to 50 cm, the final coating film was observed to measure the maximum drop height at which the cracks and peeling phenomenon did not occur in the final coating film, and the impact resistance was evaluated.

Specifically, when the maximum drop height was 40 cm or more, excellent (◎), 30 cm or more and less than 40 cm were evaluated as good (○), 20 cm or more and less than 30 cm were evaluated as normal (△), and 20 cm or less was poor (×).

(7) Chipping resistance

After leaving the final coating film at -20°C for 3 hours, 50 g of chipping stone was pushed out at a pressure of 4 bar to strike the surface of the final coating film. At this time, when the damage area of the final coating film was 1 mm or less, it was evaluated as excellent (◎), good (○) if more than 1 mm and less than 2 mm, normal (△) if more than 2 mm and less than 3 mm, and poor (×) when more than 3 mm.

Item

Example 1

Example 2

Example 3

Example 4

Example 5

Example 6

Example 7

Example 8

Comparative Example 1

Comparative Example 2

Comparative Example 3

Comparative Example 4

25℃ Pod Cup #4 reference composition viscosity (sec)

34

35

34

36

34

39

38

39

44

43

43

45

Dispersibility

◎

◎

○

○

◎

△

△

○

X

○

X

△

Storage stability

◎

◎

◎

◎

○

◎

○

○

○

X

X

○

Polish(%)

92

88

89

88

86

84

82

82

74

68

69

73

Adhesion

◎

◎

◎

◎

○

◎

◎

△

△

△

○

X

Hardness

H

F

F

HB

HB

HB

HB

HB

B

B

2B

2B

Impact resistance

◎

◎

◎

◎

○

◎

◎

○

X

○

△

X

Chipping resistance

◎

○

◎

◎

◎

△

○

◎

X

○

X

X

As shown in Table 4, the coating composition for intermediates of Examples 1 to 8 has excellent dispersibility and storage stability of the coating, and the coating film prepared therefrom has gloss, adhesion, hardness, impact resistance, chipping resistance, etc. It was found that the durability was excellent.

Claims (7)

1. A coating composition for intermediate use, comprising a first urethane-modified polyester resin, a second urethane-modified polyester resin, an alkyd resin, a melamine resin, and an isocyanate resin.
2. The method according to claim 1,

   The first urethane-modified polyester resin has a hydroxyl value of 60 to 100 mgKOH/g, an acid value of 1 to 10 mgKOH/g, a viscosity at 25°C of 600 to 1,100 cps, and a weight average molecular weight of 1,000 to 2,500 g. /mol, a coating composition for intermediate use.
3. The method according to claim 1,

   The second urethane-modified polyester resin has a hydroxyl value of 120 to 170 mgKOH/g, an acid value of 1 to 10 mgKOH/g, a viscosity at 25°C of 1,200 to 2,300 cps, and a weight average molecular weight of 800 to 2,000 g /mol, a coating composition for intermediate use.
4. The method according to claim 1,

   The alkyd resin has a hydroxyl value of 150 to 250 mgKOH/g, an acid value of 1 to 15 mgKOH/g, a viscosity at 25°C of 1,000 to 1,800 cps, and a weight average molecular weight of 1,500 to 3,500 g/mol. For coating composition.
5. The method according to claim 1,

   The melamine resin comprises a butoxy melamine resin and a methylate melamine resin, the intermediate coating composition.
6. The method according to claim 1,

   The isocyanate resin has a viscosity at 25°C of 1,500 to 3,500 cps, and a solids content of 70 to 80% by weight based on the total weight.
7. The method according to claim 1,

   The intermediate coating composition includes 15 to 30 parts by weight of the first urethane-modified polyester resin, 1 to 10 parts by weight of the second urethane-modified polyester resin, 5 to 20 alkyd resins, 10 to 30 parts by weight melamine resin, and 1 to 8 parts. A coating composition for intermediate use, comprising parts by weight of an isocyanate resin.