JPH02247264A - Thermosetting coating compound composition - Google Patents

Abstract

PURPOSE:To obtain a thermosetting coating compound composition suitable as a topcoating compound, forming a coating film having excellent acid resistance and scratching resistance, containing a hydroxyl group-containing resin, amino resin and a specific thermosetting resin. CONSTITUTION:The aimed thermosetting coating compound composition which comprises (A) 5-90wt.% hydroxyl group-containing resin selected from acrylic resin and polyester resin, (B) 5-50 pts.wt. amino resin and (C) 1-90 pts.wt. thermosetting resin [e.g. vinyl copolymer containing a compound shown by the formula (R1 is H or methyl)] having two or more carboxyl groups and two or more epoxy groups in one molecule and >=1,000 number-average molecular weight and provides coating film having excellent weather resistance, mechanical properties and appearance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thermosetting coating composition, more specifically, a thermosetting coating composition suitable for a top coating that can form a coating film with excellent acid resistance and scratch resistance. The present invention relates to coating compositions.

(Prior art and its problems) Conventionally, materials such as metals have been coated with paint films to impart rust prevention and cosmetic properties.

In recent years, damage caused by acid rain has become a serious social problem as air pollution increases and forests wither. There are problems such as etching of the paint film, whitening, staining, etc. on the paint film, and there is a strong demand for a paint film with good acid resistance.

Additionally, top coats, such as those applied to automobile exterior panels, are susceptible to scratches due to collisions with sand and dust while driving, or friction caused by cleaning brushes, etc. (one of the causes of deterioration in appearance). In particular, scratches are very noticeable in dark colored paint films such as black, navy blue, and brown, and there is a strong demand for improving the scratch resistance of top coat films.

Currently, paints containing hydroxyl group-containing resins and amino resins as binders are widely used as thermosetting top coat paints, but none that satisfy both acid resistance and scratch resistance have yet to be obtained.

(Means for Solving the Problems) The present inventors have made a leap forward in acid resistance and scratch resistance without impairing the weather resistance, solvent resistance, water resistance, mechanical properties, and appearance of the paint film. With the aim of achieving improved performance, we investigated the glass transition point, molecular weight, composition, etc. of hydroxyl group-containing resins and amino resin systems. As a result, although some effects were observed by changing these, it was still insufficient.

Therefore, as a result of intensive research on polymer blends, the present inventors found that by blending polymers that form crosslinking points by reaction between carboxyl groups and epoxy groups,
It is possible to obtain m1lI with significantly improved acid resistance and scratch resistance without impairing the performance or appearance of the coating film, and in addition to these properties, it is also possible to obtain a coating film with excellent water resistance and solvent resistance. This discovery led to the completion of the present invention.

That is, the present invention comprises the following components (A), CB) and (C
), 5 to 90 parts by weight of a hydroxyl group-containing resin (A) selected from acrylic resins and polyester resins, and 5 parts by weight of an amino resin (B).
~50 parts by weight, and a number average molecular weight of 1 having two or more carboxyl groups and two or more epoxy groups in one molecule.
The present invention provides a thermosetting coating composition characterized in that a resin composition containing 1 to 90 parts by weight of a curable resin (C) of 000 or more is used as a binder.

The binder in the coating composition of the present invention contains a hydroxyl group-containing resin (A), an amino resin (B), and a specific curable resin (C) as essential components.

The hydroxyl group-containing resin (A) in the present invention is a hydroxyl group-containing resin selected from Acnol resin and polyester resin, and may be one type or a mixture of two or more types of these resins.

Examples of this acrylic resin include copolymers of hydroxyl group-containing vinyl monomers and other vinyl monomers. As a hydroxyl group-containing vinyl monomer,
For example, C2-Cx4 hydroxyalkyl esters of acrylic acid or methacrylic acid such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxyethyl acrylate, etc., N-methylolacrylamide, N
-Methylolmethacrylamide, N-hydroxyethylacrylamide, N-hydroxyethylacrylamide, N,N-dihydroxyethylacrylamide, N,N
- Mono- or di-C1 of acrylic acid or methacrylic acid such as dihydroxyethyl methacrylamide, etc.
Examples include C1□hydroxyalkylamide. Examples of other vinyl monomers include methyl acrylate, ethyl acrylate, propyl acrylate, n-
Butyl acrylate, 1so-butyl acrylate, 3-pentyl acrylate, hexyl acrylate,
2-hebutyl acrylate, octyl acrylate, 2
-Octyl acrylate, nonyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-
C2-2 of acrylic acid such as ethyl butyl acrylate
4 alkyl ester, and methyl methacrylate, ethyl methacrylate, propyl acrylate, n-butyl methacrylate, 1so-butyl methacrylate,
Pentyl methacrylate, hexyl methacrylate, 2
- C1-2. Examples include alkyl esters and carboxyl group-containing vinyl monomers such as acrylic acid and methacrylic acid, as well as styrene, vinyltoluene, and glycidyl mequaacrylate.

To copolymerize these monomers, 2. A conventionally known method is used, and it can be made into an organic solvent solution type or a non-aqueous dispersion type by a polymerization method, and either form can be used. Further, the acrylic resin has a number average molecular weight of 1000 to 50000, preferably 3000 to 3000.
A range of 0 is desirable.

In the present invention, the polyester resin that can be the hydroxyl group-containing resin (A) includes both oil-free polyester resin and alkyd resin, and includes phthalic acid and its acid anhydride, isophthalic acid, terephthalic acid, trimellitic acid, and Its acid anhydride, hexahydrophthalic acid and its acid anhydride, polybasic acid components such as succinic acid, adipic acid, pimelic acid, sebacic acid, brassic acid, ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, 1 .6-hexanediol, trimethylolpropane, glycerin, pentaerythritol, tricyclodecane dimetatool, and other polyol components are condensed and polymerized according to a conventional method.

In the above condensation polymerization reaction, the molecular weight may be adjusted by using, for example, benzoic acid, pt-butylbenzoic acid, etc. as an end-capping agent, or by further blending an oil or fat with the above acid component and polyol component. It also includes those obtained by oil modification using fatty acids such as coconut oil fatty acids, tall oil fatty acids, and castor oil fatty acids as part of the above-mentioned acid components. Further, it may be modified by chain extension with an aliphatic polyisocyanate such as 1,6-hexamethylene diisocyanate or ε-caprolactone.

The above polyester resin has a number average molecular weight of 800 to 50.
000, preferably in the range of 2000 to 20000.

Both the acrylic resin and the polyester resin, which are the hydroxyl group-containing resins (A), must have hydroxyl groups that serve as crosslinking reaction points, and the hydroxyl value of these resins is 20 to 150, preferably It is suitable that the acid value is in the range of 30 to 130, and the acid value is preferably 50 or less, preferably 5 to 3o.

The hydroxyl group-containing resin (A) may be any of the above acrylic resins and polyester resins, but acrylic resins are more preferred from the viewpoint of weather resistance.

In the present invention, the amino resin used as component (B) acts as a crosslinking agent, and is obtained by the reaction of an amino component such as melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, or dicyandiamide with an aldehyde. Examples include methylolated amino tit fats. As an aldehyde,
Examples include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. Furthermore, etherification of this methylolated amino resin with a suitable alcohol can also be used. Examples of alcohols used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol,
Examples include n-butyl alcohol, i-butyl alcohol, 2-ethylbutanol, 2-ethylhexanol, and the like. When using hexamethoxymethylmelamine or a melamine resin in which a portion of its methoxy groups are substituted with C1 or higher alcohol as the amino resin, it is preferable to add a commonly used curing catalyst such as para-toluenesulfonic acid.

The cured resin (C) used in the present invention may be any fat having a number average molecular weight of 1000 or more and having two or more carboxyl groups and two or more epoxy groups in one molecule. Examples include vinyl copolymers, polyesters, polyurethanes, polyethers, etc. Among them, vinyl copolymers are preferred from the viewpoint of storage stability.
I) (wherein R3 represents a hydrogen atom or a methyl group,
A copolymer containing the compound represented by ) as one of the monomer components is particularly preferred from the viewpoint of storage stability and curability.

When making a vinyl copolymer, 5-methacrylic acid and acrylic acid are generally used as carboxyl group-containing monomers to introduce carboxyl groups, but other
Maleic acid, iconic acid, crotonic acid, adducts of (meth)acrylic acid and ε-caprolactone, etc. can also be used.

In addition to the compound of formula (I), the epoxy group-containing monomers used for introducing epoxy groups into the vinyl copolymer include glycidyl acrylate, glycidyl methacrylate,
Allyl glycidyl ether etc. can be used. In addition, other monomer components other than the carboxyl group-containing monomer and the epoxy group-containing monomer that can be used to form the vinyl copolymer include 1, for example, methyl (meth)acrylate,
Alkyl (meth)acrylate having 1 to 18 carbon atoms such as ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl [meth)acrylate. ) Acrylate; hydroxyl group-containing unsaturated monomers such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and furyl alcohol; styrene, α-methylstyrene,
Vinyltoluene, vinyl acetate, (meth)acrylamide, (meth)acrylonitrile, N-methylol (meth)
Mention may be made of other copolymerizable monomers, such as acrylamide butyl ether.

The above vinyl copolymer is obtained by blending the above carboxyl group-containing monomer, epoxy group-containing monomer, and other monomer components as necessary, and copolymerizing the mixture in the presence of a polymerization catalyst and preferably an organic solvent. . The polymerization temperature at this time is preferably 100°C or lower, more preferably 80°C or lower.

The number average molecular weight of the curable resin (C) used in the present invention can be used as long as it is 1000 or more, but 3000 to 10
It is preferably within the range of 0.000, and from 5000 to
It is more preferable that the number average molecular weight is within the range of 30,000.If the number average molecular weight is less than 1,000, there is a problem that storage stability is poor.

In addition, the number of carboxyl groups introduced into the curable resin (C) is 2 or more in one molecule to form a sufficient network, but it is particularly preferably within the range of 5 to 10. Furthermore, the number of epoxy groups introduced into the curable resin (C) is preferably in the range of 5 to 10, although two or more in one molecule will form a sufficient network.

In the present invention, hydroxyl group-containing resin (A
), amino (h (fat (, B)) and curable (sealing resin (C)) The blending ratio is 5 to 90 parts by weight of the hydroxyl group-containing resin based on 100 parts by weight of the total amount (resin solid content) of the three components. parts, preferably 30 to 60 parts by weight, amino resin 5 to 50 parts by weight,
Preferably 10 to 40 parts by weight, curable resin (C) 1 to 9
0 parts by weight, preferably 5 to 60 parts by weight, and more preferably 10 to 40 parts by weight.

If the amount of the hydroxyl group-containing resin (A) is less than 5 parts by weight, the adhesion to the base will decrease, while if it exceeds 90 ffi parts^
In this case, the resulting coating film has poor scratch resistance and acid resistance. If the blending ratio of the amino resin (B) is less than 5 parts by weight, the crosslinking density of the hydroxyl group-containing resin (A,) will be low and the water resistance and scratch resistance will be significantly impaired; if the blending ratio exceeds 50 parts by weight,
Problems arise such as poor mechanical properties and poor adhesion to the substrate. In addition, if the blending ratio of the curable resin (C) is less than 1 part by weight, the effect of auxiliary crosslinking is small, and the acid resistance and scratch resistance of the coating film cannot be improved. , problems such as poor adhesion to the substrate arise.

The thermosetting coating composition of the present invention contains, in addition to a binder containing the above-mentioned components (A), (B), and (C) as essential components, an organic solvent, a pigment, an ultraviolet absorber, and a coating surface conditioner, if necessary. , a curing catalyst, a pigment dispersant, and other additives.

Examples of the organic solvents include aromatic hydrocarbons such as xycene and toluene; esters such as ethyl acetate, propyl acetate, butyl acetate; ketones such as acetone and methyl ethyl ketone; ethylene glycol, cellosolve, butyl cellosolve, cellosolve acetate, etc. Examples include ether type.

These organic solvents can be used alone or in combination of two or more. Further, from the viewpoint of curability, those having a boiling point of about 150° C. or lower are preferable, but are not limited thereto.

Examples of pigments that may be contained in the composition of the present invention include organic pigments (for example, quinacridone-based pigments such as quinacridone-based pigments,
Azo pigments such as pigment red.

phthalocyanine blue, phthalocyanine green, etc.], inorganic pigments (e.g. titanium oxide, barium sulfate, calcium carbonate, baryta, clay, silica, etc.), carbon pigments (carbon black), scaly metallic powders (e.g. aluminum, mica, etc.) iron oxide, stainless steel, etc.), and anti-rust pigments (for example, red iron oxide, strontium chromate, etc.) can be used.

The composition of the present invention can be applied to metals (for example, steel plate 1 surface-treated steel plate, etc.)
It can be applied directly to the material to be coated, such as plastic, or to the coated surface of the material to be coated with a brimer or brimer/intermediate coat. When used as a top coat for automobile paint, it can be used as a top coat enamel paint such as 2-coat 1-bake, 2-coat 2-bake, and a solid color paint such as top coat clear paint: 1 coat 1-bake.

To exemplify the coating method of the composition of the present invention when used as an automobile top coat, for example, the coating composition of the present invention is coated for about 12 to 30 seconds (Ford Cup No. 4).
．． After adjusting the coating viscosity to 20℃), it is still! It can be carried out by painting (bell type, REA type, etc.), air spray painting, etc. to a dry film thickness of about 10 to 60 u, and the baking conditions are at a temperature of about 120 to about 180 ° C. Approximately 30 minutes is appropriate.

(Actions and Effects of the Invention) The composition of the present invention contains, as a binder component, a curable resin (C) having both a carboxyl group and an epoxy group in one molecule, and the carboxyl group can be removed by heating. Because the epoxy groups react with each other to form a strong, dense, and highly hydrolyzed crosslinked structure, it can significantly improve acid resistance and scratch resistance, as well as provide excellent water and solvent resistance. It is thought that a coating film can be obtained. Also,
By keeping the blending amounts of binder components (A), (B), and (C) within a specific range, it was possible to avoid impairing the weather resistance, mechanical properties, and appearance of the paint film. It is something.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

In the following, "parts" and "%" mean "parts by weight" and "% by weight," respectively. 6 Production Example 1 30 parts of styrene and n- 40 parts of butyl methacrylate,
Monomers of 10 parts of 2-ethylhexyl acrylate, 18 parts of 2-hydroxyethyl acrylate, and 2 parts of acrylic acid were reacted to obtain a number average molecular weight of 6600 and a resin solid content of 5.
0%.

Gardner foam viscosity J hydroxyl group-containing acrylic resin solution (
A-1) was obtained.

Production Example 2 Monomers of 30 parts of styrene, 30 parts of n-butyl methacrylate, 15 parts of 2-ethylhexyl acrylate, and 25 parts of 2-hydroxyethyl acrylate were reacted in an organic solvent of 85 parts of quijirole and 15 parts of n-butanol. A hydroxyl group-containing acrylic resin solution (A-2) with a number average molecular weight of 5000, a resin solid content of 50%, and a Gardner foam viscosity of B.
I got it.

Production Example 3 0.29 mol of isophthalic acid, 0.23 mol of phthalic acid, 0.43 mol of hexahydrophthalic acid, 0.4 mol of trimethylolpropane, 06 mol of neopentyl glycol, and 1 mol of coconut oil fatty acid O were added to a reaction vessel. 200~230°
A coconut oil-modified polyester resin having an acid value of 8 and a hydroxyl value of 72 was obtained by C″c condensation polymerization.The polyester resin 100
Add 43 parts of xylene to 60 heavy black circles (A-3)
The viscosity was Y-(25°C, Gardner bubble viscosity)
Met.

Production Example 4 Acrylic acid 72 parts Compound 235 parts n-butyl methacrylate 693 parts Azobisdimethylvaleronitrile 30 parts 4 xylene 100 parts in a flask
The mixture of the above monomer and polymerization initiator was added dropwise over 3 hours to the mixture kept at 80°C, and after the addition was completed, the mixture was aged at 80°C for 2 hours to give a solid content of about 50% and Gardner. Curable resin solution (C-1) with viscosity P (25°C)
I got it. The number average molecular weight of the obtained resin was about 25,000. Additionally, this resin contains approximately 1.1 mol/epoxy group.
kg, and had about 1.0 mol/kg of carboxyl groups.

Production Example 5 Methacrylic acid 172 parts Compound 190 parts Methyl methacrylate 638 parts Azobisdimethylvaleronitrile 50 parts 1000 xylene in 4 flasks
The mixture of monomers and polymerization initiator was added dropwise over 3 hours to the mixture kept at 80°C, and after the addition was completed, the mixture was aged at 80°C for 2 hours to achieve a solid content of about 50% and a Gardner viscosity. A curable resin solution (C-2) of D (25°C) was obtained.

The number average molecular weight of the obtained resin was about 12,000.

Further, this resin had about 10 moles/kg of epoxy groups and about 2.0 moles/kg of carboxyl groups.

Example 1 100 parts (solid content: 50 parts) of the resin solution (A-1) obtained in Production Example 1, 33.3 parts of Knee Pan 20SE C Note 1)
20 parts by solid content), the resin solution obtained in Production Example 4 (C-1
) 60 parts (30 parts solids) and 1 part Raybow #3 (Note 2) was stirred, and then Swasol 1000
Add (Note 3) and paint viscosity 25 seconds () Eau de cup #
4/25°C) and used for the test.

(Note 1) Kneepan 20SE...manufactured by Mitsui Toatsu Chemical ■, butyl etherified melamine resin solution with solid content of approximately 60%, trade name.

(Note 2) Raybow #3: Silicone surface conditioner liquid with approximately 1% active ingredient, manufactured by Raybow Chemical ■, product name.

(Note 3) Swazol 1000: Cosmo Oil ■, petroleum-based aromatic solvent, trade name.

Examples 2 to 3 and Comparative Examples 1 to 3 The same procedure as in Example 1 was carried out except that the formulation of the mixture before viscosity was as shown in Table 1, and the paint viscosity was 25.
The temperature was adjusted to 25° C. () Ord Cup #4/25° C.) and used for the test.

The blending ratios of Examples and Comparative Examples in Table 1 are amounts (parts) converted to solid content or active ingredient amounts.

Notes in Table 1 are as follows.

(Note 4) Cymel 303...Made by Mitsui Suyanamide ■,
・Hexamethoxymethylolmelamine with a solid content of about 100%, trade name 6 (Note 5) Naicure 5225...manufactured by King Industries, USA, dodecylbenzenesulfone neutralized product with an active ingredient of about 25%, trade name.

(Coating Film Creation Conditions) Painting and cured coating films were created using the viscous paints of the Examples and Comparative Examples.

Epoxy-based cationic electrodeposition paint is electrodeposited on a 0.8 mm thick dull steel plate that has been subjected to zinc phosphate chemical conversion treatment to a dry film thickness of 20μ, and then an automotive interior coating is applied to the baked electrodeposition film. Surf Acer was painted and baked to a dry film thickness of approximately 20P, sanded with #400 sandpaper, drained and dried, and then degreased with petroleum benzine to provide a test material.

On this material, apply Magiclon Base Coat HM-22 (manufactured by Kansai Paint Co., Ltd., metallic paint, trade name) using an air spray gun F5 (Meiji Kikai Seisaku Seisaku, trade name) to a cured film thickness of approximately 15P. After leaving it at room temperature for about 3 minutes, the viscous paints of Examples 1 to 3 and Comparative Examples 1 to 3 were applied to a cured film thickness of about 4 minutes using the air spray gun F5.
After coating to a thickness of 0P, the coating was left at room temperature for about 10 minutes, then set at 0 order λ, and then heated and cured at 140° C. for 30 minutes in an electric hot air dryer.

Various tests were conducted on each of the baked coated plates obtained. The test results are shown in Table-1.

The tests in Table 1 were conducted according to the following test method.

Kusa 1'' Paint film appearance: The finished appearance of the paint film was evaluated based on the gloss and texture according to the following criteria.

0: Very good ■：Good condition ×: Bad 60° gloss: Specular reflectance was measured at 60°.

Pencil hardness: Pencil scratch value according to JIS K 5400 was displayed.

Acid resistance: Dip the test coated plate into a 40% sulfuric acid solution.
After being exposed to snow at 50°C for 5 hours, the painted surface was washed with water and evaluated using the following criteria.

0: No change at all O: There is no abnormality on the painted surface, but there is a slight step between the immersed and non-immersed areas. After immersion for 240 hours, the coated surface was washed with water and evaluated based on the following criteria.

O: No change at all ■ = Slight loss of gloss Solvent resistance: After wiping the painted surface 10 times with gauze impregnated with xylol.

Observe the painted surface and evaluate it using the following criteria. Ta.

0: There is almost no change ◎: There are noticeable scratches on the painted surface △: The painted surface has swelled and tends to whiten Scratch resistance: A car with a test coating plate attached to the roof is placed in a car wash. The condition of the painted surface of the coated plate was observed after the car was washed five times. The washing machine used was rPo 20 FWRCJ manufactured by Yasui Sangyo. The evaluation criteria are as follows.

0: Almost all scratches can be seen by visual observation. Crow, passed O: There are some scratches, but the The severity is extremely minor.

△: Scratches were noticeable by visual observation, and failed. The mixture was placed in a similar mesh container and extracted for 6 hours using a Waxley extractor using an acetone/methanol=1/1 solvent, and then the gel fraction was calculated using the following formula.

Claims (1)

[Claims] 1. Total amount of the following components (A), (B) and (C): 10
0 parts by weight, 5 to 90 parts by weight of a hydroxyl group-containing resin (A) selected from acrylic resins and polyester resins, 5 to 50 parts by weight of an amino resin (B), and 2 or more carboxyl groups and 2 parts by weight per molecule. 1. A thermosetting coating composition comprising, as a binder, a resin composition containing 1 to 90 parts by weight of a curable resin (C) having a number average molecular weight of 1000 or more and having at least three epoxy groups. 2.Claim 1, wherein the curable resin (C) is a vinyl copolymer.
Paint composition as described. 3. The vinyl copolymer is a compound represented by the following formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R_1 represents a hydrogen atom or a methyl group) as a monomer. The coating composition according to claim 2, which is a copolymer as a component.