JP3490878B2 - Paint composition for curtain coating and curtain coating method using this composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition capable of forming a good coating film without curtain breakage when curtain coating on a moving flat plate-like object, and curtain coating using this coating composition. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
As a method of coating a flat object to be coated, a roll coater coating method, a curtain coating method, a spray coating method, a dipping method,
The electrodeposition coating method and the like can be mentioned. Among them, the roll coater coating method is known as an excellent method for spreading a coating material on an object to be coated and forming a coating film having excellent smoothness. There is.

In the curtain coating method, the paint is dropped in the form of a thin film curtain on a moving flat object to be coated to form a paint film having a predetermined thickness on the object to be coated. In the curtain coating method, the bubbles in the paint film break and the curtain breaks before the thin curtain-shaped paint film reaches the object to be coated, or the curtain-shaped paint film is applied to the object to be coated. After reaching, many bubbles remained in the paint film as residual bubbles, and there was a problem that the coating surface state of the coating film after curing was deteriorated. The problem of the residual foam can be solved by using a large amount of a defoaming agent having a high defoaming property for the paint, for example, but this method usually tends to cause curtain breakage, At present, there is no known method for simultaneously solving the problems of curtain breakage and residual bubbles in the curtain coating method.

Therefore, the inventors of the present invention have earnestly studied in order to obtain a paint capable of simultaneously solving the problems of curtain breakage and residual bubbles and forming a paint film having a good paint surface appearance and paint performance. The invention was completed.

[0005]

Means for Solving the Problems That is, the present invention provides (A) a hydroxyl group-containing polyester having a number average molecular weight of 10,000 to 35,000 and a hydroxyl value of 1 to 150 mgKOH / g.
Le resin, and optionally, (B) crosslinking agent, resin solids per 100 parts by weight containing, (C) the hydroxyl group-containing Po
The difference in solubility parameter from the reester resin (A) is 2.
8 or less and a number average molecular weight of 3,000 to 50,
The present invention provides a coating composition for curtain coating, characterized in that it contains 0.2 to 3.0 parts by weight of a solid content of the acrylic resin type surface control agent of 000.

The present invention also provides a curtain coating method, which comprises coating the above coating composition on a flat object to be coated by a curtain coating method.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The coating composition of the present invention will be described in detail below.

[0008] hydroxyl-containing polyester resin (A) hydroxyl-containing polyester resin in the present invention the coating composition (A) has a number average molecular weight 10,000～35,00
0, preferably 15,000 to 25,000, hydroxyl value is 1 to 150 mgKOH / g, preferably 3 to 100 m
Mention may be made of one kind or a mixture of two or more kinds of polyester resin of gKOH / g.

In the present invention, the glass transition temperature (Tg)
Is measured by differential thermal analysis (DTA), and the number average molecular weight is measured by gel permeation chromatography (GPC) using a calibration curve of standard polystyrene.

In the hydroxyl group-containing polyester resin (A), when the number average molecular weight is less than 10,000, curtain breakage is apt to occur during curtain coating, while when the number average molecular weight exceeds 35,000, residual bubbles are left behind. It is easy to cause an abnormal coating surface such as armpits.

As the hydroxyl group-containing polyester resin (A) , oil-free polyester resin, oil-modified alkyd resin; modified products of these resins, for example, urethane-modified polyester resin, urethane-modified alkyd resin, epoxy-modified polyester resin, acrylic-modified polyester resin And so on.

The oil-free polyester resin comprises an esterified product of a polybasic acid component and a polyhydric alcohol component. As the polybasic acid component, for example, one or more selected from phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, succinic acid, fumaric acid, adipic acid, sebacic acid, maleic anhydride, etc. Dibasic acids and lower alkyl esterified products of these acids are mainly used, and if necessary, monobasic acids such as benzoic acid, crotonic acid, and pt-butylbenzoic acid, trimellitic anhydride, methylcyclohexene tricarboxylic acid. , A tribasic or higher polybasic acid such as pyromellitic dianhydride is used in combination. Examples of the polyhydric alcohol component include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol,
Dihydric alcohols such as neopentyl glycol, 3-methylpentanediol, 1,4-hexanediol, and 1,6-hexanediol are mainly used, and glycerin, trimethylolethane, trimethylolpropane, penta A trihydric or higher polyhydric alcohol such as erythritol can be used in combination. These polyhydric alcohols can be used alone or in admixture of two or more. The esterification or transesterification reaction of both components can be carried out by a method known per se. As the acid component, isophthalic acid, terephthalic acid,
And lower alkyl esterified products of these acids are particularly preferable.

The alkyd resin is obtained by reacting an oil fatty acid with a method known per se in addition to the acid component and alcohol component of the oil-free polyester resin, and examples of the oil fatty acid include coconut oil fatty acid and large oil fatty acid. Examples include soybean oil fatty acid, linseed oil fatty acid, safflower oil fatty acid, tall oil fatty acid, dehydrated castor oil fatty acid, tung oil fatty acid and the like. The oil length of the alkyd resin is preferably 30% or less, more preferably about 5 to 20%.

As the urethane-modified polyester resin,
The oil-free polyester resin, or a low molecular weight oil-free polyester resin obtained by reacting an acid component and an alcohol component used in the production of the oil-free polyester resin, is reacted with a polyisocyanate compound by a method known per se. Some of them are the ones. Further, the urethane-modified alkyd resin is obtained by reacting the alkyd resin, or a low molecular weight alkyd resin obtained by reacting each component used in the production of the alkyd resin, with a polyisocyanate compound by a method known per se. Things are included. Examples of the polyisocyanate compound that can be used when producing the urethane-modified polyester resin and the urethane-modified alkyd resin include hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate,
4,4'-methylenebis (cyclohexyl isocyanate), 2,4,6-triisocyanatotoluene and the like can be mentioned. As the urethane-modified resin, generally, those having a modification degree such that the amount of the polyisocyanate compound forming the urethane-modified resin is 30% by weight or less based on the urethane-modified resin can be preferably used.

As the epoxy-modified polyester resin,
Using a polyester resin produced from each component used in the production of the polyester resin, a reaction product of a carboxyl group of this resin and an epoxy group-containing resin, a hydroxyl group in the polyester resin and a hydroxyl group in the epoxy resin polyisocyanate A reaction product obtained by a reaction such as addition, condensation or grafting of a polyester resin and an epoxy resin, such as a product bonded via a compound, can be mentioned.
The degree of modification in such an epoxy-modified polyester resin is generally preferably such that the amount of the epoxy resin is 0.1 to 30% by weight based on the epoxy-modified polyester resin.

As the acrylic modified polyester resin,
Using a polyester resin produced from each component used in the production of the above polyester resin, a group having reactivity with these groups in the carboxyl group or hydroxyl group of the resin, for example, an acrylic resin containing a carboxyl group, a hydroxyl group or an epoxy group. And a reaction product obtained by graft-polymerizing (meth) acrylic acid or (meth) acrylic acid ester with a polyester resin using a peroxide-based polymerization initiator. The degree of modification in such an acrylic modified polyester resin is generally
The amount of the acrylic resin is preferably 0.1 to 50% by weight based on the acrylic modified polyester resin.

Among the polyester resins described above, the oil-free polyester resin is particularly suitable.

The hydroxyl group-containing polyester resin (A) is 1
It may be one kind of resin or a mixture of two or more kinds of resins. For example, the hydroxyl group-containing polyester resin (A) is a mixture of two kinds of polyester resins, and the difference in the number average molecular weight of each resin is 1,000 to
By using the composition of 10,000, it is possible to obtain a coating composition having a better balance of curtain coating suitability and coating film performance. Among them, it is a mixture of a polyester resin having a number average molecular weight of 12,000 to 18,000 and a polyester resin having a number average molecular weight of 15,000 to 25,000, and the difference in the number average molecular weight of each resin is 1,000. It is preferred to use a resin mixture in the range of to 5,000.

Cross-linking agent (B) The cross-linking agent (B) is added to the coating material as needed in order to cure the hydroxyl group-containing polyester resin (A).

Typical examples of the crosslinking agent (B) include, for example,
A melamine resin and a blocked polyisocyanate compound can be mentioned.

Examples of the melamine resin include a methylolated amino resin obtained by the reaction of melamine and an aldehyde. Examples of the aldehyde used in the above reaction include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. Further, a resin obtained by etherifying the above methylolated amino resin with an appropriate alcohol can also be used as the melamine resin. Examples of alcohols used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethylbutanol,
2-ethylhexanol and the like can be mentioned.

The blocked polyisocyanate compound is a compound obtained by blocking free isocyanate groups of the polyisocyanate compound with a blocking agent.

Examples of the polyisocyanate compound before blocking are aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate; cycloaliphatic diisocyanates such as hydrogenated xylylene diisocyanate or isophorone diisocyanate; tolylene diisocyanate. Alternatively, an organic diisocyanate itself such as an aromatic diisocyanate such as 4,4′-diphenylmethane diisocyanate, or an adduct of each of these organic diisocyanates with a polyhydric alcohol, a low molecular weight polyester resin or water, or each of the above-mentioned organic compounds Examples thereof include cyclized polymers of diisocyanates, and isocyanate / biuret.

Examples of the blocking agent for blocking the isocyanate group include phenols such as phenol, cresol and xylenol; ε-caprolactam; δ-
Valerolactam, γ-butyrolactam, β-propiolactam and other lactams; methanol, ethanol, n-
Or i-propyl alcohol, n-, i- or t-butyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether,
Alcohols such as benzyl alcohol; formamidoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime and other oximes; dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone, etc. A blocking agent such as the active methylene-based compound can be preferably used.

By mixing the polyisocyanate compound and the blocking agent, the free isocyanate groups of the polyisocyanate compound can be easily blocked.

The crosslinking agent (B) may consist of one type of crosslinking agent or a mixture of two or more types of crosslinking agents. The blending amount of the crosslinking agent (B) is not particularly limited, but when blended, it is usually a hydroxyl group-containing polyester.
In the total solid content of 100 parts by weight of the resin (A) and the crosslinking agent (B), the range of 5 to 40 parts by weight is usually suitable.

Surface modifier (C) The surface modifier (C) is added for the purpose of defoaming the paint and paint film without breaking the curtain, and in order to satisfy these performances, in the present invention. Has a number average molecular weight of 3,000 to 50,000, preferably 7,000.
0 to 30,000 acrylic resin surface modifiers are used.

The surface conditioner (C) is a hydroxyl group-containing polyester.
Due to the relationship with the telluric resin (A), the difference in solubility parameter between the two is required to be 2.8 or less, preferably 0.1 to 2.6. You can select and use the one that meets the conditions. If the difference in the solubility parameter exceeds 2.8, curtain breakage is likely to occur during curtain coating. Surface conditioner (C) is 1
It can be used as a seed or as a mixture of two or more species. By using a mixture of two or more kinds as the surface conditioner (C), it becomes easy to balance curtain breakage and defoaming property, and it becomes easy to obtain a paint having good coating suitability and coating film appearance.

The blending amount of the surface conditioner (C) is 0.2 to 3.0 in terms of solid content based on 100 parts by weight of the total resin solid content [including the crosslinking agent (B)] in the coating composition. It is preferably in the range of 0.4 parts by weight, especially 0.4 to 2.0 parts by weight.
If the blending amount of the surface conditioner (C) is less than 0.2 parts by weight, the defoaming property is likely to deteriorate, and the resulting coating film has a crack caused by residual bubbles,
Coating defects such as cissing and dents are likely to occur, while when it exceeds 3.0 parts by weight, curtain breakage is likely to occur during curtain coating.

The coating composition of the present invention comprises a hydroxyl group-containing polyester.
In addition to the telluric resin (A), the surface conditioning agent (C) and the crosslinking agent (B) used as necessary, a solvent is usually contained,
If necessary, color pigments, curing catalysts, talc, clay, silica, mica, alumina and other extender pigments; strontium chromate, calcium chromate, zinc chromate, barium chromate, zinc phosphate and other rust preventive pigments, etc. It may be contained.

[0031] The solvent to be incorporated into the coating composition, which is formulated for and improving coatability, the water
Those capable of dissolving or dispersing the acid group-containing polyester resin (A) and the cross-linking agent (B) can be used, and specific examples thereof include hydrocarbon solvents such as toluene, xylene, and high boiling point petroleum hydrocarbons, methyl ethyl ketone, Ketone solvents such as methyl isobutyl ketone, cyclohexanone, and isophorone, ester solvents such as ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate,
Examples thereof include alcohol solvents such as methanol, ethanol and butanol, ether alcohol solvents such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and diethylene glycol monobutyl ether, and water. These may be used alone or in combination of two or more. It can be mixed and used.

As the above-mentioned color pigment, a color pigment usually used in the paint field, for example, white pigments such as titanium white and zinc white; blue pigments such as cyanine blue and indanthrene blue; green pigments such as cyanine green and patina. Pigments;
Organic red pigments such as azo and quinacridone, red pigments such as red iron oxide, benzimidazolone, isoindolinone, isoindoline and quinophthalone organic yellow pigments, titanium yellow, yellow lead and other yellow pigments; carbon Black pigments such as black, graphite and pine smoke; aluminium powder, copper powder, nickel powder, titanium oxide-coated mica powder, iron oxide-coated mica powder and glittering pigments such as glittering graphite. The blending amount of the coloring pigment is not particularly limited as long as it can exhibit good cosmetic properties, and is usually 1 to 120 parts by weight with respect to 100 parts by weight of all resin components [including a crosslinking agent]. Used in part range.

The above-mentioned curing catalyst is added as necessary to accelerate the curing reaction between the hydroxyl group-containing polyester resin (A) and the crosslinking agent (B), and the crosslinking agent (B) It can be appropriately selected and used according to the type.

When the cross-linking agent (B) is a melamine resin, particularly a low-molecular weight methyl etherified or mixed etherified melamine resin of methyl ether and butyl ether, an acid catalyst such as a sulfonic acid compound is used as a curing catalyst. Alternatively, an amine neutralized product of a sulfonic acid compound is preferably used. Typical examples of the sulfonic acid compound include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, and the like. The amine in the amine-neutralized product of the sulfonic acid compound may be a primary amine, a secondary amine, or a tertiary amine. Among these, the amine neutralized product of p-toluenesulfonic acid and / or the amine neutralized product of dodecylbenzenesulfonic acid is preferable from the viewpoints of the stability of the coating material, the reaction accelerating effect, the physical properties of the resulting coating film, and the like.

When the crosslinking agent (B) is a blocked polyisocyanate compound, a curing catalyst that promotes dissociation of the blocking agent of the blocked polyisocyanate compound,
For example, tin octylate, dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate), dibutyltin dilaurate, dibutyltin oxide, dioctyltin oxide, lead 2-ethylhexanoate, etc. Organometallic catalysts and the like are preferably used.

The curtain coating method of the present invention will be described in detail below.

Curtain Coating Method of the Present Invention The subject to be curtain coated with the above-mentioned coating composition of the present invention is not particularly limited, but it is usually suitably applied to a moving plate-like subject.

Examples of the flat plate-like article to be coated are a metal plate, a cloth,
A plastic film etc. can be mentioned.

In the field of precoated steel sheets, a metal plate is generally used as a flat article to be coated.
A cold rolled steel plate, a zinc-based plated steel plate, an aluminum plate, a stainless steel plate, etc. can be mentioned. Examples of the zinc-based plated steel sheet include hot-dip galvanized steel sheet, electrogalvanized steel sheet, iron-zinc alloy-plated steel sheet, nickel-zinc alloy-plated steel sheet, and aluminum-zinc alloy-plated steel sheet (for example, "Galbarium" and "Galfan" product names). Plated steel sheet) and the like. The surface of these metal plates may be subjected to chemical conversion treatment such as phosphate treatment, composite oxide film treatment, or chromate treatment. Further, those coated with a primer coating on these metal plates can also be used as the article to be coated and are included in the above metal plates.

As a curtain coating machine for curtain coating the above-mentioned object, a slit type curtain coating machine for dropping the coating material from a slit into a curtain, and a coating film formed in a thin film on the surface of a rotating roll are scraped off. A roller curtain coating machine for dropping the paint in a curtain shape may be used.

In curtain coating, the coating composition of the present invention usually has a viscosity of 60 to 150 seconds, preferably 80 to 1
20 seconds (Ford Cup # 4, measured at 25 ° C)
Viscosity is adjusted to the range of and painted. The coating film thickness formed on the article to be coated is not particularly limited, but is usually a dry coating film thickness of 10 to 30 μm, preferably 15 to 25.
A range of μm is suitable. After coating, the paint film applied on the article can be hardened by baking. The baking conditions may be appropriately set according to the curing conditions of the coating composition, and usually the maximum temperature reached by the material is 80 to 2
The baking is performed at 50 ° C. for a baking time of 20 seconds to 30 minutes.

[0042]

EXAMPLES The present invention will be specifically described below with reference to examples. Hereinafter, "parts" and "%" are based on weight.

Examples 1 to 11 and Comparative Examples 1 to 8 Each of the topcoat paints was obtained by applying the composition as shown in Table 1 below. On a chromate-treated 0.5 mm thick electrogalvanized steel sheet, Kansai Paint Co., Ltd. KP Color 8620 primer (polyester primer for pre-coated steel sheet) was applied to a dry film thickness of about 4 μm. Then, it was baked for 30 seconds so that the maximum temperature reached by the material was 220 ° C. to obtain a primer-coated steel sheet.

Each of the topcoat paints obtained as described above was applied to Cyclohexanone / Swasol 1500 (Cosmo Oil Co., Ltd.).
Manufactured by Aromatic Petroleum Solvent) = 60/40 (weight ratio), the paint viscosity was adjusted to about 100 seconds (paint temperature 25 ° C) with Ford Cup # 4 and slit type in a room at 25 ° C. Using a curtain coating machine [BURKLLE slit curtain coater] for 5 minutes under the condition of a slit width of 0.8 mm, and then curtain coating on the above primer-coated steel sheet so that the dry coating film thickness becomes about 18 μm. ,
Then, each top-coated steel sheet was obtained by baking for 45 seconds with a hot air dryer so that the maximum temperature reached by the material was 220 ° C. Various tests were conducted on the obtained coated steel sheet. The test results are shown in Table 4 below.

Further, the number of times the falling paint curtain causes curtain breakage while each topcoat paint was circulated in the slit type curtain coater under the conditions of a slit width of 0.8 mm for 5 minutes, was measured visually as follows. The curtain was evaluated according to the standard. The evaluation results are shown in Table 4 below.

◯: No curtain breakage was observed. Δ: Curtain breakage was observed 1 to 10 times within 5 minutes of paint circulation. ×: 11 or more curtain breaks were observed within 5 minutes of paint circulation.

The amounts of the polyester resin, melamine resin and blocked polyisocyanate compound in Table 1 are indicated by the weight of the solid content, and the amount of the curing catalyst is the amount of the active ingredient excluding the solvent (Nacure 5225 is a sulfonic acid compound-amine. The weight of the Japanese equivalents and the amount of formate TK-1 are organic tin. Further, the amount of the surface conditioner is shown by the solid content. When the top coat paints of Examples and Comparative Examples were made into paints, white titanium, which was a white pigment, was dispersed.

[0048]

[Table 1]

(Note) in Table 1 has the following meanings.

The base resins shown in (* 1) to (* 7) in Table 1 are all polyester resins manufactured by Arakawa Chemical Co., Ltd., and these polyester resins have the property values shown in Table 2 below. .

[0051]

[Table 2]

(* 8) Cymel 303: Mitsui Cytec Co., Ltd., low molecular weight methyl etherified melamine resin, hexakis (methoxymethyl) melamine content of 60% by weight or more. (* 9) Super Beckamine J-820-60: n-butyl etherified melamine resin manufactured by Dainippon Ink and Chemicals, Inc. (* 10) Desmodur BL-3175: Blocked polyisocyanate compound manufactured by Sumitomo Bayer Urethane Co., Ltd.

(* 11) Naicure 5225: A solution of dodecylbenzenesulfonic acid in amine neutralized product, manufactured by King Industries, USA (neutralization equivalent: about 1.0). (* 12) Formate TK-1: Takeda Yakuhin Kagaku Kogyo KK, organotin compound catalyst.

Table 3 below shows the properties, resin species, etc. of the surface modifiers (* 13) to (* 18) in Table 1. (* 1
3), (* 14), (* 16) and (* 17) are all surface conditioning agents manufactured by Kusumoto Kasei Kogyo Co., Ltd.
5) and (* 18) are both surface modifiers manufactured by Kyoeisha Chemical Co., Ltd.

[0055]

[Table 3]

[0056]

[Table 4]

In Table 4, the coating film performance test of the coated steel sheet was carried out according to the following test method.

Appearance of coating film: The appearance of the coating film was visually observed and evaluated according to the following criteria.

◯: No abnormalities in the coating surface such as cissing, dents and cloudiness were observed on the coating surface Δ: Any of cissing, dents and cloudiness was slightly observed on the coating surface ×: cissing, dents and cloudiness on the coating surface Either is noticeable, or the continuous coating film is not formed due to curtain breakage.

Pencil hardness: JIS for the coating film on the test plate
The pencil scratch test defined in K-5400 8.4.2 (1990) was performed to evaluate the scratches.

Adhesion: JIS K-5400 8.5.
2 (1990) According to the cross-tape method, 1 mm was drawn by drawing 11 parallel straight lines at 1 mm intervals so that the coating film surface of the test plate reached the substrate with a cutter knife. 100 squares of × 1 mm were created. A cellophane adhesive tape was brought into close contact with the surface, and the degree of peeling of the squares when the tape was rapidly peeled off was observed and evaluated according to the following criteria.

◯: No peeling of the coating film was observed Δ: The coating film was slightly peeled off, but 90 or more squares remained ×: The coating film was considerably peeled off, and the number of remaining squares was less than 90 .

Impact resistance: JIS K5400 8.3.
2 (1990) According to DuPont impact test, falling weight weight 5
00g, weight drop distance 50cm, tip diameter of wick 1/2
It went under the condition of inch. When the coating film was not damaged, it was indicated as good (◯).

[0064]

EFFECTS OF THE INVENTION The coating composition of the present invention does not cause curtain breakage during curtain coating, has good defoaming properties, and is applied to a coating film after curing such as cissing, dents, and cloudiness due to residual bubbles. A coating film without film defects can be formed. Further, a coating film having excellent coating film performance can be formed from the coating composition of the present invention.

Continuation of front page (51) Int.Cl. ⁷ identification code FI // (C09D 167/02 C09D 161: 28 161: 28) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09D 1/00 -10/00 C09D 101/00-210/10 B05D 1/00-7/26

Claims (5)

(57) [Claims] 1. (A) Number average molecular weight 10,000 to 3
(C) the hydroxyl group-containing polyester resin (A) per 100 parts by weight of a resin solid content containing 5,000, a hydroxyl group-containing polyester resin having a hydroxyl value of 1 to 150 mgKOH / g, and, if necessary, (B) a crosslinking agent. 0.2 to 3.0 parts by weight in terms of solid content of an acrylic resin-based surface modifier having a solubility parameter difference of 2.8 or less with) and a number average molecular weight of 3,000 to 50,000. A coating composition for curtain coating, comprising: 2. A contract wherein the hydroxyl group-containing base resin (A) is a mixture of two types of polyester resins, and the difference in the number average molecular weight of the respective resins is 1,000 to 10,000.
The coating composition according to claim 1 . 3. The crosslinking agent (B) is at least one crosslinking agent selected from a melamine resin and a blocked polyisocyanate compound, and the amount of the hydroxyl group-containing base resin (A) is 60 parts by weight in 100 parts by weight of the resin component. 90 parts by weight, the amount of the crosslinking agent (B) is 10 to 40 parts by weight claim
The coating composition according to 1 or 2 . 4. The acrylic resin surface conditioner (C) is 2
The mixture according to any one of claims 1 to 3, which is a mixture of two or more kinds.
The listed coating composition. 5. A curtain coating method, which comprises coating the coating composition according to claim 1 on a flat article to be coated by a curtain coating method.