JPH01118577A - High-solid coating composition - Google Patents

Abstract

PURPOSE:To provide a coating composition which has a high solid content and excellent intercoat adhesion, weathering resistance, etc., by mixing a specified acrylpolyol with a liquid polyol and an alkoxy monomeric melamine resin at a specified weight ratio. CONSTITUTION:A high-solid coating composition is produced by mixing 15-60wt.% acrylpolyol (A) having a weight-average MW of 4,000-80,000 and a hydroxyl number of 60-200, wherein 10-90% of the hydroxyl groups originate in an adduct of an alpha,beta-ethylenically unsaturated monocarboxylic acid with an oxide compound of formula I or II (wherein R1, R2 and R3 are each H, methyl etc.) and/or in an adduct of glycidyl (meth)acrylate with a 2-4C monocarboxylic acid with 15-60wt.% normally liquid polyol (B) having a weight average MW of 400-4,000 and a hydroxyl number of 100-400 and 20-50wt.% alkoxy monomeric melamine resin (C).

Description

[Detailed description of the invention] L1 upper plate upper moon ±! The present invention relates to a high-solids coating composition with a low organic solvent content, and more particularly to a high-solids coating composition that exhibits excellent adhesion to living rooms during repeated coatings.

・ )" and ・ri" In recent years, there has been an increasing need for high solid content paints with low organic solvent content in order to prevent pollution and save resources. A coating composition using a polyol resin and a monomeric alkoxy melamine resin having
915), or a curing composition using a medium or high molecular weight polyol resin, a low molecular weight polyol with a high hydroxyl value that is liquid at room temperature, and a monomeric alkoxy melamine resin (Daicel Chemical Industry ■, polycaprolactone). catalogs, etc.) are introduced.

However, when these compositions are applied over and over again, there is a problem in that the adhesion to the living room is poor. The reason for this poor adhesion is largely due to the monomeric melamine resin and polyol having a high hydroxyl value that are used to achieve high solid content. Note that interlayer adhesion during repeated coating refers to the adhesion between layers when the same paint is applied and baked again after the paint has been painted and baked. This is an extremely important property.

First, the inventors of the present invention have significantly improved the adhesion of the living room during repainting without reducing the physical or chemical performance, weather resistance, smoothness, sharpness, etc. of the paint film. We conducted research on high-solids coating compositions that could improve the results. As a result, low molecular weight polyols that are liquid at room temperature can be converted into adducts of alkylene oxide with a small number of carbon atoms and α,β-ethylenically unsaturated monocarboxylic acid and/or adducts of glycidyl (meth)acrylate and monocarboxylic acid with a small number of carbon atoms. The present inventors have discovered that the above object can be achieved by using an acrylic polyol with a relatively high molecular weight containing a certain amount of hydroxyl groups derived from an adduct together with an alkoxy monomeric melamine resin, and have completed the present invention.

That is, the present invention provides (A) a weight average molecular weight of 4,000 to 80,000, a hydroxyl value of 60 to 200, and 10 to 90% of the hydroxyl groups;
is an α,β-ethylenically unsaturated monocarboxylic acid and the following (I
) or (II) formula % Formula % ( ) and/or an acrylic polyol which is a hydroxyl group based on an adduct of glycidyl methacrylate or glycidyl acrylate with a monocarboxylic acid having 2 to 4 carbon atoms. , (B) a polyol with a weight average molecular weight of 400 to less than 4000, a hydroxyl value of 100 to 400, and which is liquid at room temperature, and (C) an alkoxy monomeric melamine resin, the above (A) to (C) Based on the total weight of ingredients (
Component A) is 15 to 60% by weight, component (B) is 15 to 60% by weight.
It relates to a coating composition characterized in that component (C) is 20 to 50% by weight.

An adduct (hereinafter referred to as "carboxylic acid-
"Oxide adduct" for short. ) used in the production of
, β-ethylenically unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and the like. Also CI
) or (II), for example, 1,2-propylene oxide, 1,2-propylene oxide,
-butylene oxide, β-butylene oxide, cyclohexene oxide, etc.

2 carbon atoms used in the production of an adduct of glycidyl (meth)acrylate and a monocarboxylic acid having 2 to 4 carbon atoms (hereinafter abbreviated as rGMA-acid adduct), which is component (A) of the present invention. -4 monocarboxylic acids include acetic acid, propionic acid, and acetic acid.

The number of carbon atoms in the oxide compound represented by formula (1) used in the production of the above-mentioned "carboxylic acid-oxide adduct" is 3.
For example, if ethylene oxide with a carbon number of 2 is used, excellent interlayer adhesion, which is a feature of the present invention, cannot be obtained. The reason for this is thought to be that all the hydroxyl groups in the "carboxylic acid-oxide adduct" are primary hydroxyl groups and there are no secondary hydroxyl groups. At least 70% of the hydroxyl groups in the "carboxylic acid-oxide adduct" obtained using an oxide compound become secondary hydroxyl groups, and these secondary hydroxyl groups greatly contribute to improving interlayer adhesion.

In addition, in the oxide compound of the present invention, the sum of the number of carbon atoms in R□ and R2 in formula (1) is within the range of 1 to 3, and R3 in formula (II) is a hydrogen atom or a methyl However, when the sum of the number of carbon atoms in R□ and R2 in formula (I) is 4 or more, or when R3 in formula (II) is a long-chain alkyl group of ethyl group or more, In the case of a base, the effect of improving interlayer adhesion is small. The reason for this is thought to be that the presence of long-chain hydrocarbon groups results in low polarity.

The above rGMA-acid adduct is produced by an addition reaction between glycidyl (meth)acrylate and a monocarboxylic acid having 2 to 4 carbon atoms. Here, when a monocarboxylic acid having 5 or more carbon atoms is used, the effect of improving interlayer adhesion becomes small.

The reason for this is also considered to be due to the low polarity of the hydrocarbon chain.

These “carboxylic acid-oxide adducts” or rGM
The method for producing "A-acid adduct" includes triethylamine,
Mixtures of α, β-ethylenically unsaturated carboxylic acids with certain oxide compounds, or glycidyl (meth) in the presence or absence of suitable catalysts such as dimethylaminoethanol, tetraethylammonium bromide, tetraisopropyl titanate, etc. It can be easily produced by keeping a mixture of acrylate and monocarboxylic acid at 130°C. At this time, the reaction can be carried out under pressure using an autoclave if necessary. The ``carboxylic acid-oxide adduct'' and rGMA-acid adduct'' produced in this way have hydroxyl groups, but at least 70% of these hydroxyl groups are secondary hydroxyl groups, and the remainder are primary hydroxyl groups. These two methods are used to improve the adhesion of the 0 interlayer material, which is the hydroxyl group of
hydroxyl group plays an important role.

(A) Component contains “carboxylic oxide adduct” and/or
or rGMA-acid adduct", it is appropriate to copolymerize these with other copolymerizable monomers, but other methods include α,
After copolymerizing β-ethylenically unsaturated carboxylic acid with a copolymerizable monomer, an oxide compound is added to the carboxyl group, or after copolymerizing glycidyl (meth)acrylate, a monocarboxylic acid is added to the epoxy group. A method of adding an acid can also be used.

In order to add a hydroxyl group to the acrylic polyol of component (A), the above-mentioned "carboxylic acid-oxide adduct" or rGMA
In addition to using "-acid adduct", it can also be provided by copolymerizing a hydroxyl group-containing monomer. Examples of usable hydroxyl group-containing monomers include 2-hydroxyethyl (
meth)acrylate, 3-hydroxypropyl(meth)
Acrylate; Monoether of polyether polyol such as polyethylene glycol, polypropylene glycol, polybutylene glycol, etc. and hydroxyl group-containing monomer such as 2-hydroxy(meth)acrylate; 2-hydroxyethyl(meth)acrylate, hydroxypropyl(
Examples include adducts of hydroxyl group-containing polymers such as meth)acrylates with lactones such as ε-caprolactone and β-methyl-δ-valerolactone. It is important that these hydroxyl groups are primary hydroxyl groups. As monomers that can be copolymerized with the above and above hydroxyl group-containing monomers to produce the acrylic polyol as component A), a wide range of monomers that are generally used in the synthesis of acrylic resins for paints can be used, such as ct-ts m Acrylic acid or methacrylic acid ester of alcohol, styrene,
Examples include acrylonitrile, acrylamide, methacrylamide, N-methylolacrylamide butyl ether, acrylic acid, methacrylic acid, and the like.

As a method for producing the acrylic polyol component (A), conventionally known methods can be used. That is, methods such as solution polymerization, aqueous suspension polymerization, emulsion polymerization, bulk polymerization, and non-aqueous dispersion polymerization using a dispersion stabilizer can be applied, and among them, solution polymerization is preferred.

The weight average molecular weight of the acrylic polyol (A) component is 4.
If the molecular weight is less than 4,000, the mechanical properties and weather resistance of the coating film will deteriorate, and if it exceeds 80,000, the solid content concentration of the coating material may become low. , the appearance of the paint finish tends to deteriorate. The weight average molecular weight as used herein means a value measured by gel permeation chromatography using polystyrene as a standard substance and preparing a calibration curve.

In addition, the hydroxyl value of the acrylic polyol as component (A) is 60.
Must be between ~200. If the hydroxyl value is less than 60, the crosslinkability with the melamine resin of component (C) will be poor, resulting in poor solvent resistance and weather resistance.On the other hand, if it exceeds 200, the viscosity of the solution will increase, reducing the solid concentration of the paint, Adhesion during layering may deteriorate, and the appearance of the paint finish may deteriorate.

90 to 10%, preferably 80 to 20% of the hydroxyl groups in the polyol of component (A) are hydroxyl groups based on "carboxylic acid-oxide adduct" and rGMA-acid adduct, and the remainder has primary hydroxyl groups. It is important that the hydroxyl group is based on another hydroxyl group-containing monomer. If the proportion of hydroxyl groups based on the "carboxylic acid-oxide adduct" and rGMA-acid adduct exceeds 90% of the total hydroxyl groups, the reactivity with the melamine resin, which is component (C), will be poor and the coating film will deteriorate. solvent resistance,
On the contrary, if it is less than 10%, the effect of improving interlayer adhesion, which is a feature of the present invention, will not be exhibited.

In addition, in the component (A) of the present invention, for example, all of the hydroxyl groups are "carboxylic acid-oxide adduct" and rGMA.
-acrylic polyols based on ``acid adducts'' and other hydroxyl group-containing upper polymers in which all of the hydroxyl groups have primary hydroxyl groups.
is a mixture with an acrylic polyol based on
Also included are mixed polyols having hydroxyl groups in the range of 10 to 90% based on ``A-acid adduct''. Component (A), the acrylic polyol, is preferably a solution type obtained by solution polymerization, but in the case of a nonaqueous dispersion type, the dispersion stabilizer may be poly-12-hydroxystearic acid condensate, acrylic, or cellulose. Preferably, a non-aqueous dispersion type acrylic polyol is obtained by radically polymerizing a polymerizable unsaturated monomer using a polymeric dispersion stabilizer such as a polymeric dispersion stabilizer such as a melamine resin, a melamine resin, or an alkyd resin.

Component (B) of the present invention has a weight average molecular weight of 400 to 400.
less than 0, itself liquid at room temperature, and 100 to 4
It is a polyol having a hydroxyl value in the range of 0.00. Liquid at room temperature means that the viscosity at 20 to 30°C is about 1000 poise or less.

Examples of such polyols (B) include various polyester polyols, polyether polyols, polylactone polyols, acrylic polyols, and the like. Examples of polyether polyols include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polybutylene gellicol; adducts of ethylene oxide and propylene geloxide with bisphenol A, and the like. Examples of polyester polyols include polyesters made of adipic acid and 1,4-butanediol, and polyesters made of adipic acid, 1,6-hexanediol, and trimethylolpropane. As a polylactone polyol, ε- is synthesized using ethylene gelcol or trimethylolpropane as an initiator.
Examples include caprolactone-based polycaprolactone polyols. As the acrylic polyol, for example, n-
Examples include low molecular weight copolymers of butyl acrylate and 2-hydroxyethyl acrylate. The water and acid value of these liquid polyols must be between 100 and 400.

If it is less than 100, the crosslinkability with the melamine resin of component (C) is insufficient, resulting in poor weather resistance and solvent resistance. On the other hand, 40
If it exceeds 0, the adhesion of the paint to living rooms during repeated coatings and the wettability of the paint to the surface to be coated decreases, making it difficult to form a good painted surface. Moreover, the weight average molecular weight of these liquid polyols is 4
If it is less than 00, the resulting paint will have poor wettability and the mechanical properties of the paint film will be insufficient. On the other hand, 400
If it exceeds 0, the viscosity increases, making it difficult to achieve high solidity differentiation.

Component (C) is an alkoxy monomeric melamine.

In the present invention, the alkoxy monomeric melamine has an average of three methylol groups etherified with a monohydric alcohol having 1 to 5 carbon atoms, such as methanol, n-butanol, imbutanol, etc., per triazine nucleus. or more, and the average degree of condensation is 2 or less, preferably 1.1-1.8
It means a low molecular weight melamine in which the proportion of mononuclear bodies is 50% by weight or more. These melamines are commercially available products such as Cymel 303, Cymel 325, Cymel 327, Cymel 350, Cymel 370 [all manufactured by Mitsui Toatsu Chemical Co., Ltd.], Nikaratsuku MS17, and Nikaratsuku MS15 [all manufactured by Sansho Chemical Co., Ltd.]. Ko, Regimin 7
41 Methyl etherified melamine such as [manufactured by Sunmont Co., Ltd.], Sumimaru M-55 [manufactured by Sumitomo Chemical Co., Ltd.], Cymel 2
02, Sinul 235. Cymel 238. Cymel 25
4. Cymel 272, Cymel 1130 [all manufactured by Mitsui Toatsu Chemical Co., Ltd.], Nikaratsuku MX-485, = force 5-/
') MX-487 [All manufactured by Sansho Chemical Co., Ltd.]
, methyl ether/butyl ether mixed etherified melamine such as Resimin 755 (manufactured by Monsanto).

The composition of the present invention has the above-mentioned components (A) to (C) as main components, and the composition ratio of these components is 15 to 60% based on the total weight of components (A) to (C). % by weight, preferably 20 to 40% by weight, component (B) 15 to 60% by weight, preferably 30 to 50% by weight, and component (C) 20 to 50% by weight, preferably 25 to 40% by weight. %. If component (A) is less than 15% by weight, the mechanical properties of the coating film will be insufficient, while if it is more than 60% by weight, the solid content concentration of the paint will decrease, so both are undesirable. Component (B) is less than 15% by weight,
If the solid content concentration of the coating material decreases, and on the other hand exceeds 60% by weight, the mechanical properties, chemical resistance, solvent resistance, etc. of the coating film will become insufficient, which is not preferable. (C) component is 20% by weight
When the amount is less than 50% by weight, the solid content concentration of the paint decreases, the crosslinking property of the coating film becomes low, and the solvent resistance and weather resistance are inferior. On the other hand, when it exceeds 50% by weight, the mechanical properties and chemical resistance of the coating film decrease , which is particularly unfavorable because it lowers acid resistance.

The coating composition of the present invention is suitably obtained by dissolving or dispersing the components (A) to (C) above in an organic solvent. The organic solvent is preferably one that can dissolve or disperse components (A) to (C), and specifically includes hydrocarbons such as hexane, heptane, octane, xylene, and toluene, ethyl acetate, butyl acetate, and amyl acetate. , esters such as ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, hexyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, nickelene glycol diethyl ether, diethylene glycol monobutyl ether, etc. Ethers, alcohols such as methyl alcohol, ethanol, isopropanol, butanol, amyl alcohol, 2-ethylhexyl alcohol, cyclohexanol, ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, and products manufactured by Cosmo Oil. Aromatic petroleum solvents such as Swazol 310, Swazol 1000, and Sufzol 1500 can be preferably used.

The coating composition of the present invention can be used either as a clear coating or as an enamel coating containing a suitable pigment. Pigments that can be used include inorganic pigments such as titanium oxide and carbon black, organic pigments such as quinacridone, azo, and copper phthalocyanine, metallic powders such as aluminum powder, copper powder, and mica powder, clay, Examples include extender pigments such as talc.

The coating composition of the present invention may further contain a coating surface conditioner, fluidity conditioner, ultraviolet absorber, light stabilizer, curing catalyst, etc., as required.

The coating composition of the present invention is a thermosetting coating, which is preferably applied by air spraying, airless spraying, electrostatic spraying, etc., and can be cured under normal baking conditions. Further, the appropriate coating film thickness is about 20 to 50 IL in terms of cured film thickness.

idanjiriki 1 The coating composition of the present invention has a high solids content, has good interlayer adhesion during repeated coatings, and has good weather resistance, solvent resistance, chemical resistance, water resistance, etc. It is a coating composition with excellent practical properties.

Examples and comparative examples are given below to further clarify the present invention. Note that unless otherwise specified, "parts" and "%" mean "parts by weight" and "% by weight," respectively.

[Preparation of 1F Sample (A) Production Example of Component Production Example 1 (Production of Polyol Solution A) In a normal acrylic resin reaction tank equipped with a stirrer, thermometer, reflux condenser, etc., 50 parts of pheasant roll and 15 parts of n-butanol were added.
A portion of the mixture was charged and heated, and while maintaining the temperature at 125° C., the following 7-mer mixture was added over a period of 3 hours.

Styrene 20 parts n-butyl methacrylate 29.5 n-butyl acrylate 20 2-hydroxyethyl acrylate 13.5
HPA (Note 1. Postscript) 15 Acrylic acid 2 α,α'-Azobisisobutyronitrile 2 After the addition of the above monomer mixture, the mixture was kept at 125°C for an additional hour, and then 7-butyl peroctoate 1 A mixture of 1 part and 10 parts of Kijirole was added over a period of 1 hour. After the addition was completed, stirring was continued while maintaining the temperature at 125° C. for another 2 hours, and then the mixture was cooled.

Pheasant roll was added to this to obtain an acrylic polyol solution A containing 50% solid molecules of 1jf. The weight average molecular weight Mw of acrylic polyol A is 19500, and the hydroxyl value is 13.
0. The fraction of hydroxyl groups derived from the "carboxylic acid-oxide adduct" and rGMA-acid adduct (hereinafter referred to as "OH group fraction from the adduct") in the total hydroxyl value is 0.
It was 50.

Production Examples 2 to 15 (Production of Acrylic Polyol Solution B-0) Acrylic polyol solutions B to 0 were produced in the same manner as Production Example 1 except that the monomer mixture was as shown in Table 1. did. All solid content concentrations are 49.
The content ranged from 0 to 51.0% by weight. Table 1 shows the compositions of the acrylic polyol solutions A to 0, their weight average molecular weights Qw, hydroxyl values, and "OH group fractions from adducts."

Notes in Table 1 are as follows.

(Note 1) HPA: 1/1 mole adduct of acrylic acid and 1,2-propylene oxide.

(Note 2) HPMA: 1/1 mole adduct of methacrylic acid and 1,2-propylene oxide.

(Note 3) HBA: 1/1 mole adduct of acrylic acid and 1,2-butylene oxide.

(Note 4) CHO-MAC...1/1 mole adduct of cyclohexene oxide and methacrylic acid.

(Note 5) GMA-PAC...1/1 molar adduct of glycidyl methacrylate and propionic acid.

(Note 8) AOE-MAC...1/1 mole adduct of AOEX24 (mixture of α-olefin epoxides having 12 and 13 carbon atoms, product of Daicel Chemical Industries, Ltd.) and methacrylic acid.

(Note 7) GMA-INA: 1/1 mono-C adduct of glycidyl methacrylate and isononanoic acid.

Top coating compositions having the compositions shown in Tables 2 and 3 were prepared using the above-mentioned component (A). Pigment dispersion was carried out using a batch type sand mill using component (A) in each paint formulation as a dispersing resin. All blending amounts in Tables 2 and 3 indicate the solid content or the amount of active ingredient.

Component (B) in Examples and Comparative Examples in Tables 2 and 3 is Plaxel 308: ε-caprolactone trifunctional polycaprolactone polyol with a viscosity of about 15 at 25°C.
Boies, weight average molecular weight is approximately 1280, hydroxyl value is 19
No. 8, liquid polyol (Daicel Chemical Industry ■ product) Oligodene: A bifunctional polyol made by adding 6 moles of ethylene oxide to 1 mole of bisphenol A, the viscosity at 25°C is about 30 voids, and the weight average molecular weight is about 710.
, the hydroxyl value is 230. (manufactured by Nippon Soda ■) K-FLEx 188 is a dichlorohexanedimetatool-based bifunctional polyester polyol with a viscosity of about 100 voids at 25°C, a weight average molecular weight of about 610, and a hydroxyl value of 230. (Product from King, USA) Polyester polyol A: 0.8 mol of adivic acid and 1
．． Polyester polyol A was synthesized by reacting with 1.0 mol of 6-hexanediol in a conventional manner until the acid value reached 4. The viscosity of this product at 25° C. was about 35 voids, the weight average molecular weight was 1500, and the hydroxyl value was 110.

Polyester polyol B: Polyester polyol B was synthesized by reacting 0.6 mol of adivic acid, 0.5 mol of trimethylolpropane, and 0.5 mol of 1.6-hexanediol in a conventional manner until the acid value reached 1. This product had a viscosity of about 150 voids at 25°C, a weight average molecular weight of about 1550, and a hydroxyl value of 390.

- Dry 20J epoxy cationic electrodeposition paint on a dull steel plate with a thickness of 0.8+am that has been subjected to zinc biphosphate chemical conversion treatment.
Electrodeposited it in the shape of L, baked it at 170℃ for 20 minutes, then sanded it with #400 sandpaper, wiped it with petroleum benzine to degrease it, and then applied an inner coating for automobiles to a dry coating of about 25 tiles. air spray painted,
After baking at 140° C. for 30 minutes, it was wet-sanded with #400 sandpaper, drained and dried, and then degreased with petroleum benzine to obtain a test material.

Next, each of the coating compositions in Tables 2 and 3, Examples and Comparative Examples was applied onto this material with a mixed solvent of Kijirol/cellosolve acetate/n-butanol = 40150/lo to a viscosity of 29 to 31 seconds. (Ford Cup #4/20°C) was heated using a Wider W71 (air spray gun manufactured by Iwata Painting Machinery Co., Ltd.) to give a cured coating film thickness of 28 to 32 l. After spraying and setting at room temperature for 10 minutes, heat in an electric hot air baking oven at 140°C.
Bake hardening was carried out at "C" for 30 minutes.

The results of the performance tests on this cured coating are shown in Tables 4 and 5.

The tests in Tables 4 and 5 were conducted according to the following method.

(Note 10): Paint film appearance The finished appearance of the paint film was evaluated based on gloss and texture.

@: Very good (noted): Impact resistance Tested using a DuPont impact tester with a firing pin tip radius of 1/2 inch and a falling bell weight of 500 g. Indicates the maximum height without cracks on the painted surface (5c+o increments).

(Note 12): Water resistance The test piece is immersed in a constant temperature water bath at 40°C for 240 hours. After taking it out, make sure there are no abnormalities such as glossy pique or blistering on the paint film.
And so.

(Note 13): Gasoline resistance After immersing the coated plate in Nisseki Silver gasoline at 20°C for 8 hours, it was pulled out and changes in the coated surface were observed and evaluated. discoloration,
Those with no blisters, shiny pockets, or swelling were rated as 0.

(Note 14): Spot 5 cc of acid-resistant 10% sulfuric acid Q on the painted surface and
After being left at 5% RH for 48 hours, it was washed with water and the coated surface was observed.

Those with no abnormality were rated O.

(Note 15): After being tested for 600 hours using a #climate sunshine weather meter, the coated plate was washed with water and evaluated as follows based on the gloss retention rate (%) of 600 gloss.

@281% or more 0275-80% 4270-74% (Note 16) Two-layer adhesion A method coated plate was further spray-painted with the same paint to a dry film thickness of 30 ml, and allowed to set at room temperature for 10 minutes. rear,
Bake for 30 minutes at 140'O in an electric hot air baking oven.

On the baking coated plate, 11 parallel score lines reaching the substrate were drawn at 1 mm intervals vertically and horizontally with a cutter knife to create goblin marks, and then a peeling test was performed using cellophane tape.

019 If all the squares of lOOke are not peeled off and remain
Those with 0 or more squares remaining were evaluated as O, and those with less than 0 squares were evaluated as ×.

(Note 17) The same process as in (Note 17) except that the two-layer adhesion method B coated plate was further baked at 160°C for 30 minutes, then spray-painted with the same paint and baked at 120°C for 30 minutes. This is a test method.

Method B is a more severe interlayer adhesion test method than Method A.

Claims (1)

Scope of Claims: (A) a weight average molecular weight of 4,000 to 80,000, a hydroxyl value of 60 to 200, and 10 to 90% of the hydroxyl groups;
is an α,β-ethylenically unsaturated monocarboxylic acid and the following formula (I) or (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (II) Formula Among them, R_1 and R_2 represent a hydrogen atom, a methyl group, an ethyl group, or a propyl group. However, the sum of the numbers of carbon atoms in R_1 and R_2 is within the range of 1 to 3. Moreover, R_3 represents a hydrogen atom or a methyl group. an acrylic polyol having a hydroxyl group based on an adduct with an oxide compound represented by and/or an adduct of glycidyl methacrylate or glycidyl acrylate with a monocarboxylic acid having 2 to 4 carbon atoms; (B) a weight average molecular weight of 400 to less than 4000; , a polyol having a hydroxyl value of 100 to 400 and liquid at room temperature, and (C) an alkoxy monomeric melamine resin, based on the total weight of the components (A) to (C) (
Component A) is 15 to 60% by weight, component (B) is 15 to 60% by weight.
A coating composition characterized in that component (C) is 20 to 50% by weight.