JPH11152448A - Coating composition for curtain coating and curtain coating method using the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating used for coating curtain, capable of simultaneously solving problems caused by the breakage of the curtain and by bubbles left in the curtain and capable of forming a coating film having a good coating appearance and a coating film performance. SOLUTION: The coating composition for coating curtain contains (A) a hydroxyl group-containing base resin having a number-average mol.wt. of 10,000-35,000 and a hydroxyl group value of 1-150 mgKOH/g, and, if necessary, (B) a cross-linking agent, and (C) an acrylic resin surface-adjusting agent having a number-average mol.wt. of 3,000-50,000 and a solubility parameter difference of <=2.8 between the surface-adjusting agent C and the hydroxyl group-containing base resign A in a solid content amount of 0.2-3.0 pts.wt. per 100 pts.wt. of the resin solid content. The method for coating curtain comprises applying the coating composition on a flat substrate to be coated by a curtain coating method.

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 a moving flat object to be coated, and a curtain coating using this coating composition. About the method.

[0002]

2. Description of the Related Art
Roll coating method, curtain coating method, spray coating method, dipping method,
The electrodeposition coating method and the like can be mentioned, and among these, the roll coater coating method is known as an excellent method for flowing a coating material on an object to be coated and forming a coating film having excellent smoothness. I have.

[0003] In the curtain coating method, a paint is formed into a thin film curtain shape and dropped on a moving flat plate-like workpiece to form a paint film having a predetermined thickness on the workpiece. In the curtain coating method, bubbles in the paint film break and break the curtain before the thin curtain-like paint film reaches the object to be coated, or the curtain-shaped paint film is applied to the object to be coated. There is a problem that many bubbles remain as residual bubbles in the paint film after reaching, deteriorating the coated surface state of the cured coating film. The problem of the residual foam can be solved, for example, by using a large amount of a defoaming agent having a high defoaming property with respect to the paint.However, in this method, the curtain usually tends to be easily cut, At present, there is no known method for simultaneously solving the problems caused by curtain breakage and residual bubbles in the curtain coating method.

The inventors of the present invention have conducted intensive studies to obtain a paint which can simultaneously solve the problems caused by curtain breaks and residual bubbles and can form a coating film having good coating surface appearance and coating film performance. The invention has been completed.

[0005]

That is, the present invention provides:
(A) a hydroxyl-containing base resin having a number average molecular weight of 10,000 to 35,000 and a hydroxyl value of 1 to 150 mgKOH / g;
And, if necessary, a difference in solubility parameter with (C) the hydroxyl group-containing base resin (A) is 2.8 or less per 100 parts by weight of a resin solid content containing (B) a crosslinking agent;
The present invention also provides a coating composition for curtain coating, comprising a solid content of an acrylic resin-based surface conditioner having a number average molecular weight of 3,000 to 50,000 in a solid content of 0.2 to 3.0 parts by weight. It is.

[0006] The present invention also provides a curtain coating method characterized by coating the above-mentioned coating composition on a flat object to be coated by a curtain coating method.

[0007]

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

Hydroxyl-containing base resin (A) Hydroxyl-containing base resin (A) in the coating composition of the present invention
Has a number average molecular weight of 10,000 to 35,000, preferably 15,000 to 25,000, and a hydroxyl value of 1 to 1.
50 mgKOH / g, preferably 3 to 100 mgKOH
/ G resin is not particularly limited,
As the resin type, for example, polyester resin, silicone polyester resin, acrylic resin, fluororesin, etc.
Species or mixtures of two or more can be mentioned.

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 standard polystyrene calibration curve.

When the number average molecular weight of the base resin (A) is less than 10,000, the curtain tends to be broken during curtain coating, while the number average molecular weight is less than 3%.
If it exceeds 5,000, a coating surface abnormality such as a side surface due to residual bubbles tends to occur.

As the base resin (A), polyester resins are preferable, and oil-free polyester resins and oil-modified alkyd resins; modified products of these resins, for example, urethane-modified polyester resins, urethane-modified alkyd resins, and epoxy-modified resins Examples thereof include a polyester resin and an acrylic-modified polyester resin.

The above 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, and the like Dibasic acids and lower alkyl esterified products of these acids are mainly used, and if necessary, monobasic acids such as benzoic acid, crotonic acid, pt-butylbenzoic acid, trimellitic anhydride, methylcyclohexenetricarboxylic acid And tribasic or higher polybasic acids such as pyromellitic anhydride. 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 if necessary, glycerin, trimethylolethane, trimethylolpropane, and pentane. A trihydric or higher polyhydric alcohol such as erythritol can be used in combination. These polyhydric alcohols can be used alone or in combination of two or more. The esterification or transesterification of both components can be carried out by a method known per se. As the acid component, isophthalic acid, terephthalic acid,
And lower alkyl esters of these acids are particularly preferred.

The alkyd resin is obtained by reacting an oil fatty acid by a method known per se in addition to the acid component and the alcohol component of the above-mentioned oil-free polyester resin. Soybean oil fatty acids, linseed oil fatty acids, safflower oil fatty acids, tall oil fatty acids, dehydrated castor oil fatty acids, kiri oil fatty acids and the like can be mentioned. The oil length of the alkyd resin is preferably 30% or less, particularly 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, reacts with a polyisocyanate compound by a method known per se. Examples include: Further, the urethane-modified alkyd resin, the alkyd resin, or a low molecular weight alkyd resin obtained by reacting each component used in the production of the alkyd resin was reacted with a polyisocyanate compound by a method known per se. Things are included. Examples of polyisocyanate compounds that can be used when producing urethane-modified polyester resin and 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. In general, as the urethane-modified resin, those having a modification degree in which 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 suitably used.

As the epoxy-modified polyester resin,
Using a polyester resin produced from each component used in the production of the above polyester resin, a reaction product of a carboxyl group of this resin and an epoxy group-containing resin, and a hydroxyl group in the polyester resin and a hydroxyl group in the epoxy resin are polyisocyanate. Reaction products such as addition, condensation, and grafting of a polyester resin and an epoxy resin, such as a product bonded via a compound, can be given.
In general, the degree of modification in such an epoxy-modified polyester resin is 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 polyester resin, a group having a reactivity with these groups to a carboxyl group or a hydroxyl group of the resin, such as an acrylic resin containing a carboxyl group, a hydroxyl group or an epoxy group. And a reaction product obtained by graft polymerization of (meth) acrylic acid or (meth) acrylic ester on a polyester resin using a peroxide-based polymerization initiator. The degree of modification in such an acrylic-modified polyester resin is generally
It is preferable that the amount of the acrylic resin is 0.1 to 50% by weight based on the acrylic-modified polyester resin.

Of the polyester resins described above, oil-free polyester resins are particularly preferred.

The base resin (A) may be a single resin or a mixture of two or more resins. For example, the base resin (A) is a mixture of two types of polyester resins, and the difference in the number average molecular weight of each resin is 1,000 to 10,000, so that the suitability for curtain coating can be improved. A coating composition having a better balance of coating film performance can be obtained. Above all,
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, wherein the difference in the number average molecular weight of each resin is 1,000 to 5, It is preferred to use a resin mixture in the range of 000.

Cross-linking agent (B) The cross-linking agent (B) is blended in the paint as needed to cure the base resin (A).

Representative examples of the crosslinking agent (B) include, for example,
Melamine resins and blocked polyisocyanate compounds can be mentioned.

Examples of the melamine resin include a methylolated amino resin obtained by reacting melamine with an aldehyde. Examples of the aldehyde used in the above reaction include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. Further, those 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.

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

Examples of the polyisocyanate compound before blocking include aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate; cycloaliphatic diisocyanates such as hydrogenated xylylene diisocyanate or isophorone diisocyanate; tolylene diisocyanate Or 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; Cyclic polymers among diisocyanates, and isocyanate / biuret compounds are also included.

Examples of the blocking agent for blocking the isocyanate group include phenols such as phenol, cresol and xylenol; ε-caprolactam;
Lactams such as valerolactam, γ-butyrolactam, β-propiolactam; 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; oximes such as formamidoxime, acetoaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime; dimethyl malonate, diethyl malonate, ethyl acetoacetate, ethyl acetoacetate, methyl acetoacetate, acetylacetone A blocking agent such as an active methylene type can be suitably used.

The free isocyanate groups of the polyisocyanate compound can be easily blocked by mixing the polyisocyanate compound with the blocking agent.

The crosslinking agent (B) may be composed of one kind of crosslinking agent, or may be a mixture of two or more kinds of crosslinking agents. The blending amount of the crosslinking agent (B) is not particularly limited, but when blended, usually, the total amount of the solid content of the base resin (A) and the crosslinking agent (B) is 100 parts by weight, A range of 5 to 40 parts by weight is preferred.

Surface conditioner (C) The surface conditioner (C) is compounded for the purpose of defoaming the paint and the paint film without breaking the curtain. Has a number average molecular weight of 3,000 to 50,000, preferably 7000
An acrylic resin-based surface conditioner of 0 to 30,000 is used.

The surface conditioner (C) must have a solubility parameter difference of 2.8 or less, preferably 0.1 to 2.6, in relation to the base resin (A). What is necessary is just to select and use, from the above surface conditioners, one that meets this condition. When the difference in the solubility parameter exceeds 2.8, curtain breakage tends to occur during curtain coating. The surface conditioner (C) can be used alone or as a mixture of two or more. By using a mixture of two or more kinds as the surface conditioner (C), the balance between the curtain breaking and the defoaming property can be easily obtained, and a paint having good coating suitability and good coating appearance can be easily obtained.

The compounding amount of the surface conditioner (C) is 0.2 to 3.0 in terms of the solid content based on 100 parts by weight of the total resin solids (including the crosslinking agent (B)) in the coating composition. It is preferably in the range of 0.4 to 2.0 parts by weight.
If the amount of the surface conditioner (C) is less than 0.2 parts by weight, the defoaming property tends to be poor, and the resulting coating film has residual foam,
Coating defects such as cissing and dents are liable to occur. On the other hand, if the content exceeds 3.0 parts by weight, curtain breakage tends to occur during curtain coating.

The coating composition of the present invention usually contains a solvent in addition to the base resin (A), the surface conditioner (C) and the optional crosslinking agent (B), and further contains an optional solvent. Color pigments, curing catalysts; extender pigments such as talc, clay, silica, mica, and alumina; and rust-preventive pigments such as strontium chromate, calcium chromate, zinc chromate, barium chromate, and zinc phosphate. Is also good.

The solvent to be incorporated in the above coating composition is used for improving the coating property and the like, and a solvent which can dissolve or disperse the above-mentioned base resin (A) and crosslinking agent (B) is used. Specifically, for example, toluene, xylene, hydrocarbon solvents such as high-boiling petroleum hydrocarbons, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ketone solvents such as isophorone, ethyl acetate,
Ester solvents such as butyl acetate, ethylene glycol monoethyl ether acetate and diethylene glycol monoethyl ether acetate; alcohol solvents such as methanol, ethanol and butanol; and ether alcohols such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and diethylene glycol monobutyl ether Examples thereof include a system solvent, water and the like, and these can be used alone or as a mixture of two or more.

Examples of the above-mentioned coloring pigments include coloring pigments usually used in the field of paints, for example, white pigments such as titanium white and zinc white; blue pigments such as cyanine blue and indaslen blue; Pigments;
Organic red pigments such as azo-based and quinacridone-based, red pigments such as bengalara; organic yellow pigments such as benzimidazolone-based, isoindolinone-based, isoindoline-based, and quinophthalone-based; yellow pigments such as titanium yellow and graphite; carbon Black pigments such as black, graphite, and pine smoke; glitter pigments such as aluminum powder, copper powder, nickel powder, mica powder coated with titanium oxide, mica powder coated with iron oxide, and glitter graphite; The compounding amount of the color pigment is not particularly limited and may be in a range in which good cosmetics can be exhibited, and is usually 1 to 120 parts by weight based on 100 parts by weight of all resin components [including a crosslinking agent]. Used in a range of parts.

The above-mentioned curing catalyst is blended as required in order to promote the curing reaction between the base resin (A) and the crosslinking agent (B), and is appropriately selected according to the type of the crosslinking agent (B). Can be selected and used.

When the crosslinking agent (B) is a melamine resin, especially a low molecular weight melamine resin of methyl etherification or a mixed etherification of methyl ether and butyl ether, an acid catalyst such as a sulfonic acid compound is used as a curing catalyst. Alternatively, amine neutralized sulfonic acid compounds are preferably used. Representative examples of the sulfonic acid compound include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and dinonylnaphthalenedisulfonic acid. The amine in the amine-neutralized sulfonic acid compound may be any of a primary amine, a secondary amine and a tertiary amine. Among them, an amine neutralized product of p-toluenesulfonic acid and / or an amine neutralized product of dodecylbenzenesulfonic acid are preferable from the viewpoint of the stability of the coating material, the effect of accelerating the reaction, and the properties of the obtained coating film.

When the crosslinking agent (B) is a blocked polyisocyanate compound, a curing catalyst for promoting the 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. Are preferably used.

Hereinafter, the curtain coating method of the present invention will be described in detail.

Curtain coating method of the present invention The object to be curtain-coated with the coating composition of the present invention is not particularly limited, but is usually suitably applied to a moving flat plate-shaped object.

[0038] As the above-mentioned flat object to be coated, a metal plate, cloth,
Plastic films and the like can be mentioned.

In the field of precoated steel sheet, a metal plate is generally used as a flat object to be coated.
Examples thereof include cold-rolled steel sheets, galvanized steel sheets, aluminum sheets, and stainless steel sheets. Examples of the galvanized steel sheet include hot-dip galvanized steel sheet, electro-galvanized steel sheet, iron-zinc alloy-plated steel sheet, nickel-zinc alloy-plated steel sheet, and aluminum-zinc alloy-plated steel sheet (for example, trade names such as “Galvalume” and “Galphan”). Plated steel sheet). These metal plates may be those whose surfaces have been subjected to a chemical conversion treatment such as a phosphate treatment, a composite oxide film treatment, and a chromate treatment. In addition, those obtained by forming a primer coating film on these metal plates can also be used as objects to be coated, and are included in the above metal plates.

As the curtain coating machine for applying the curtain coating to the object to be coated, a slit type curtain coating machine for dropping the coating material from the slit into a curtain shape, and a coating film formed as a thin film on the surface of a rotating roll are scraped off. And a roller curtain coating machine for dropping paint in a curtain shape.

For curtain coating, the coating composition of the present invention generally has a viscosity of 60 to 150 seconds, preferably 80 to 1 second.
20 seconds (Ford Cup # 4, measured at 25 ° C)
The viscosity is adjusted to be within the range described above. The thickness of the coating film formed on the substrate is not particularly limited, but is usually 10 to 30 μm, preferably 15 to 25 μm, in dry film thickness.
Suitably, it is in the range of μm. After coating, the paint film applied on the object can be cured by baking. The baking conditions may be appropriately set in accordance with the curing conditions of the coating composition.
The baking is performed at 50 ° C. for a baking time of 20 seconds to 30 minutes.

[0042]

The present invention will be described below in detail with reference to examples. Hereinafter, both “parts” and “%” are based on weight.

Examples 1 to 11 and Comparative Examples 1 to 8 Coatings were made according to the composition shown in Table 1 below to obtain respective top coatings. On a 0.5 mm thick electrogalvanized steel sheet subjected to chromate treatment, KP Color 8620 primer (polyester primer for pre-coated steel sheet) manufactured by Kansai Paint Co., Ltd. is applied to a dry film thickness of about 4 μm. Then, it was baked for 30 seconds so that the maximum temperature of the material reached 220 ° C. to obtain a primer-coated steel sheet.

Each of the top coats obtained as described above was applied to cyclohexanone / swazol 1500 (Cosmo Oil Co., Ltd.).
(Aromatic petroleum solvent) = 60/40 (weight ratio), adjust the paint viscosity with a Ford cup # 4 to about 100 seconds (paint temperature 25 ° C), and use a slit mold in a 25 ° C room. Using a curtain coating machine [BURKLE slit curtain coater], the film was circulated for 5 minutes under the condition of a slit width of 0.8 mm, and then curtain-coated on the primer-coated steel sheet so as to have a dry coating thickness of about 18 μm. ,
Then, the resultant was baked for 45 seconds in a hot-air dryer so that the maximum temperature of the material reached 220 ° C. to obtain each overcoated steel sheet. Various tests were performed on the obtained coated steel sheet. The test results are shown in Table 4 below.

While circulating each of the top coatings in the slit type curtain coating machine under the condition of a slit width of 0.8 mm for 5 minutes, the number of times the falling paint curtain causes the curtain to break was visually measured. Evaluation of curtain break was performed according to the standard. The evaluation results are shown in Table 4 below.

：: No curtain break is observed. Δ: 1 to 10 curtain breaks are observed in 5 minutes of paint circulation. ×: 11 or more curtain breaks are observed in 5 minutes of paint circulation.

In Table 1, the amounts of the polyester resin, melamine resin and blocked polyisocyanate compound 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 (Nailure 5225 is the sulfonic acid compound-amine The amount of the hydrate and the amount of the formate TK-1 were the amount of the organic tin). Further, the amount of the surface conditioner was indicated by the solid content. In addition, at the time of making the top coats of Examples and Comparative Examples into a paint, titanium white as a white pigment was dispersed.

[0048]

[Table 1]

(Note) in Table 1 has the following meanings, respectively.

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

[0051]

[Table 2]

(* 8) Cymel 303: manufactured by Mitsui Cytec Co., Ltd., having a low molecular weight methyl etherified melamine resin and a content of hexakis (methoxymethyl) melamine 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: a blocked polyisocyanate compound manufactured by Sumitomo Bayer Urethane Co., Ltd.

(* 11) Nailure 5225: A solution of an amine neutralized dodecylbenzenesulfonic acid (manufactured by King Industries, USA) (neutralization equivalent: about 1.0). (* 12) Formate TK-1: an organic tin compound catalyst manufactured by Takeda Pharmaceutical Co., Ltd.

Table 3 below shows properties and resin types of the surface conditioners shown in (* 13) to (* 18) in Table 1. (* 1
3), (* 14), (* 16) and (* 17) are all surface conditioners manufactured by Kusumoto Kasei Kogyo Co., Ltd.
5) and (* 18) are both surface conditioners 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 performed according to the following test method.

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

：: No irregularities on the painted surface such as repelling, dents and fogging are observed. Δ: Any of repelling, dents and fogging is observed on the painted surface. X: Repelling, dents and fogging on the painted surface. Is remarkably observed, or a continuous coating film is not formed due to curtain breakage.

[0060] Pencil hardness: JIS
A pencil scratch test specified in K-5400 8.4.2 (1990) was performed, and evaluation by scratches was performed.

Adhesion: JIS K-5400 8.5.
2 (1990) According to the crosscut-tape method, 11 parallel vertical and horizontal straight lines are drawn at 1 mm intervals on the surface of the coating film of the test plate so as to reach the substrate with a cutter knife, and the distance is 1 mm. 100 × 1 mm squares were created. A cellophane adhesive tape was adhered to the surface, and the degree of peeling of the squares when the tape was abruptly peeled was observed and evaluated according to the following criteria.

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

Impact resistance: JIS K5400 8.3.
2 (1990) According to the DuPont impact test,
00g, weight drop distance 50cm, tip diameter 1/2
Performed under inch conditions. When there was no damage on the coating film, it was indicated as good (O).

[0064]

The coating composition of the present invention does not cause curtain breakage during curtain coating, has good defoaming properties, and is capable of coating the cured film such as cissing, dents and clouding 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.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // (C09D 167/02 161: 28)

Claims (5)

[Claims] (A) a number average molecular weight of 10,000 to 3
5,000, a hydroxyl group-containing base resin having a hydroxyl value of 1 to 150 mg KOH / g, and, if necessary, (B) a crosslinking agent, per 100 parts by weight of a resin solid content. (C) The hydroxyl group-containing base resin (A ) And a number average molecular weight of 3.0 or less.
A coating composition for curtain coating, comprising from 0.2 to 3.0 parts by weight of an acrylic resin surface conditioner having a solid content of from 0.00 to 50,000. 2. The coating composition according to claim 1, wherein the hydroxyl-containing base resin (A) is a hydroxyl-containing polyester resin. 3. The hydroxyl group-containing base 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 10,000. Paint composition. 4. 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-containing base resin (A) is 60 per 100 parts by weight of the resin component. The coating composition according to any one of claims 1 to 3, wherein the amount of the crosslinking agent (B) is 10 to 40 parts by weight. 5. A curtain coating method comprising coating the coating composition according to claim 1 on a flat object to be coated by a curtain coating method.