JPH01158079A - Thermosetting coating composition - Google Patents

Abstract

PURPOSE:To provide the title composition providing two coat.one bake type clear coating films maintaining weather and water resistances thereof and having excellent mar resistance, by comprising a specific acrylic copolymer, an alkyl etherified melamine resin, etc. CONSTITUTION:The objective composition comprises (A) 40-80wt.% of an acrylic copolymer obtained by copolymerizing (i) 10-50wt.% of a hydroxyl group-containing (meth)acrylic acid ester of formula I (R<1> is H or CH3; m is 3-5; n is 1-6), (ii) 0-40wt.% of a hydroxyl group-containing (meth)acrylic acid ester of formula II (R<2> is H or CH3; R<3> is 2-10C alkylene) and (iii) 30-80wt.% of a copolymerizable vinylic monomer, (B) 20-60wt.% of an alkyl etherified melamine resin and, as necessary, (C) 0-40wt.% of a blocked polyisocyanate.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to thermosetting coating compositions, and more specifically, to applications in fields where high cosmetic properties and performance are required, such as coatings on automobile bodies. The present invention relates to a clear coat paint that forms a coating film with excellent scratch resistance, gloss retention during outdoor exposure, and stain resistance.

[Conventional technology]

When painting automobile bodies, after electrocoating and intermediate coating, a pace coat paint containing coloring agents such as colored pigments and metallic pigments and a clear coat paint (top coat υ) are applied using a wet-on-wet method. Paint over and over,
So-called 2-coat 1 coating in which both paints are heated and cured at the same time.
A bake method is generally adopted.

In recent years, the durability of paint films has become a problem in the automobile industry, particularly the deterioration of the appearance of paint films due to scratches. The surface of the paint film, which is finished using a 2-coat, 1-base method using dark-colored pace coat paints such as black, navy blue, and red, and clear coat paints, is free from scratches caused by car wash brushes, sand particles flying up while driving, etc. is easily noticeable.

In particular, there is a strong desire both domestically and internationally to solve the problem of scratches caused by the car washing process of automatic car wash machines.

As a solution to this problem, it has been proposed to add scratch resistance by hard coating using UV or silicone paints, but it is difficult to find a coating film with a good balance of repairability and weather resistance. was difficult to form.

[Problems to be Solved by the Invention] The purpose of the present invention is to improve the weather resistance of an acrylamine thermosetting coating film in a two-coat/one-bake coating film.
To provide a clear coat paint that can maintain performance such as water resistance and form a coating film with excellent scratch resistance.

[Failure to solve the problem]

That is, the clear coat paint of the present invention is a clear coat used in a paint system in which a pace coat paint containing a coloring agent is applied, a clear coat paint is then overlaid, and then the clear coat paint is cured by heating to form a coating film. (a) general formula (I) (wherein R1 represents a hydrogen atom or a methyl group, and m is 3
-5, and n is an integer of 1-6. ) Hydroxyl group-containing (meth)acrylic acid ester A/
(b) General formula (If) (wherein, RZ is a hydrogen atom or a methyl group, and R3 is an alkylene group having 2 to 10 carbon atoms). ) acrylic acid ester/110 to 40% by weight, and (c) other vinyl monomers copolymerizable with these 3
0 to 80% by weight, the hydroxyl value obtained by copolymerizing is 60 to 160ηKOH
/f, an acrylic copolymer (A) having an acid value of 0 to 40'WKOH/f and a glass transition temperature of 150 to 40°C
40-80% by weight, alkyl etherified melamine resin (Bl 20-60% by weight, and optionally blocked polyisocyanate) (C) 0
It is characterized by containing ~40% by weight.

[Function] The acrylic copolymer used in the clear paint of the present invention (
In A), a hydroxyl group-containing compound represented by the general formula (I) (wherein R1 represents a hydrogen atom or a methyl yv group, m is an integer of 3 to 5, and 9n is an integer of 1 to 6) (Meth)acrylic acid ester IV
(a) is used as an essential component in terms of scratch resistance. Specific examples of hydroxyl group-containing (meth)acrylic acid ester A/(a) include 1 mole adduct of ε-caprolactone of 2-hydroxyethyl methacrylate, 2 mole adduct of 6-caprolactone of 2-hydroxyethyl methacrylate, and 2-hydroxyethyl methacrylate. Examples include adducts of 2-hydroxyethylv(meth)acrylate with organic lactones, such as a 1-mol adduct of ethyl p-acrylate with 1-caprolactone, and a 2-mol adduct of ε-caprolactone with 2-hydroxyethyl acrylate. Two or more of these may be used in combination.

Hydroxyl group-containing (meth)acrylic acid ester IV (a) is
It is incorporated in an amount of 10 to 50% by weight. If it is less than 10% by weight, the improvement in scratch resistance is insufficient, and if it exceeds 50% by weight, the hardness of the coating film will be low and the water resistance will also be reduced, which is not preferable.

(b) hydroxyl group-containing (meth)acrylic acid ester represented by the general formula (n) (wherein, RZ is a hydrogen atom or a methyl group, and R3 is an alkylene group having 2 to 10 carbon atoms); In combination with hydroxyl group-containing (meth)acrylic acid ester) v (a), the hydroxyl value of the acrylic copolymer (A) is 60 to
It is contained in an amount of 160 ■KOH/9. Specific examples of the hydroxyl group-containing (meth)acrylic acid ester A/(b) include 2-hydroxyethyl A/(meth)acrylate, 2-hydroxypropylv(meth)acrylate, 3
-Hydroxypropyl/L/(meth)acrylate, 4-
Examples include hydroxyalkyl/L/(meth)acrylates such as hydroxypetite/I/(meth)acrylate and 6-hydroxyhexylv(meth)acrylate, and two or more of these may be used in combination.

The other vinyl monomer (C) copolymerizable with these components (a) and (b) is used in an amount ranging from 30 to 80% by weight. That is, the glass transition temperature of the acrylic copolymer (4) to be produced is 150 to 40°C, and the acid value is 0 to 40ηKO, within a range that does not impair the scratch resistance, which is a feature of the present invention.
It is used so that H/f. Vinyl monomer (c)
Specific examples include styrene derivatives such as styrene, α-methyleneμ styrene, and vinyltoluene; acrylonitrile;
Polymerizable unsaturated nitrides such as methacrylonitrium 1vJL Vinyl esters such as vinyl acetate and vinyl propionate; N
-N-7μ koxy-substituted amides such as methoxymethylv(meth)acrylamide, N-butoxymethy/L/(meth)acrylamide; glycidi/I/(meth)acrylate, (meth)allyl glycidyl ether, metaglycidyl A/(meth) Epoxy group-containing monomers such as acrylic acid ester; basic monomers such as dimethyp-aminoethyl/L/(meth)acrylic acid, diethyl-aminoethyl/L/(meth)acrylic acid; (meth)acrylic μ acid, itaconic acid ,
Fumaric acid, crotonic acid, maleic acid, monomethyl itaconate, monobutyl itaconate, 2-μhoethyl liter/
Carboxyl group-containing vinyl esters such as (meth)acrylate; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, amino (meth)acrylate 〃, (meta)
Examples include cyclohexyl acrylate, phenyl (meth)acrylate, and benzyl (meth)acrylate.

The acrylic copolymer (A) consisting of these components can be obtained by any method such as solution polymerization, bulk polymerization, or emulsion polymerization, but solution polymerization is particularly used. It is preferable to do so.

In the case of solution polymerization, the mixture of monomers is copolymerized in the presence of an organic solvent and a polymerization initiator. The organic solvent may be a commonly used organic solvent such as isopropyl alcohol, n-butanol, toluene, or xylene, and the polymerization initiator may be a commonly used polymerization initiator such as azobisisobutyronitrile, benzoyl peroxide, or cumene hydroperoxide. A drug is sufficient. Furthermore, a chain transfer agent such as 2-mercapdroethano/L/, n-dodecylmercaptan, etc. may be used if necessary.

In the clear coat paint of the present invention, the acrylic copolymer thus obtained is contained in an amount of 40 to 80% by weight.If the content is less than 40% by weight, the scratch resistance cannot be improved. If it exceeds 80% by weight, the crosslinking density of the cured coating film will be low, resulting in insufficient water resistance and solvent resistance.

Furthermore, the acrylic copolymer (A) has a hydroxyl value of 6.
0 to 160 ■KOH/f, acid value 0 to 40 ■KOH/f
and a glass transition temperature of 150 to 4 aC. If the hydroxyl value is lower than the above range, the reaction force between the acrylic copolymer (A) and the alkyl etherified melamine resin will be insufficient, and a coating film with excellent scratch resistance will not be obtained. When the hydroxyl value exceeds the above range, water resistance,
Physical properties such as acid resistance become insufficient. Furthermore, if the acid value exceeds the above range, the cosmetic properties of the coating film will decrease. Further, if the glass transition temperature is less than 150°C, the hardness of the cured coating film will be insufficient, and if it exceeds 40°C, the scratch resistance will be insufficient.

The clear coat paint of the present invention contains the alkyl etherified melamine resin (B) in an amount of 20 to 603[[fi-]. If it is less than 20% by weight, the feature of improved scratch resistance of the present invention cannot be fully exhibited. Moreover, if it exceeds 60% by weight, the cured coating film becomes brittle and acid resistance also decreases, which is not preferable.

Specific examples of the alkyl etherified melamine resin (B) include those obtained by alkyl etherification of aminotriazine with methylo-IV, fluorohexano-/I/, or alkanols having 1 to 6 carbon atoms; Specific examples include butyl etherified melamine resin, methyl etherified melamine resin, and butyl methyl mixed etherified melamine resin. A specific example of butyl etherified melamine resin is Kneepan 208E (Mitsui Toatsu Chemical @#)
, Super Beckamine (manufactured by Dainippon Ink Chemical Company), and Cyme N (manufactured by Mitsui Suyanamide Company) as a specific example of the methyl etherified melamine resin. Alkyl etherified melamine resin (the preferred amount of odor used is 30-50
Weight%.

Blocked polyisocyanate (0) may be added to the clear coat paint of the present invention for the purpose of further improving scratch resistance. Blocked polyisocyanates (0) include polyisocyanates such as isophorone diisocyanate, 1,6-hexamethylene diisocyanate, and tolylene diisocyanate, as well as phenol, ethyl acetoacetate, cyclohexanol, a-cablocktam, acetoxime, and diisobutylketone oxime. Examples include those blocked with etc. Blocked polyisocyanate (
The amount of 0) used is 0 to 40% by weight, but it is desirable to use it so that the total amount with the alkyl etherified melamine resin (B) is 20 to 60% by weight, preferably 130 to 50% by weight. Blocked polyisocyanate (C) is 4
If it exceeds 0% by weight, the cured coating film will be brittle, scorchability will be reduced, and scratch resistance will also be reduced.

In addition, the clear coat paint of the present invention may contain an external acid catalyst such as balatoluenesulfonic acid, dodazylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalene disulfonic acid, or amine neutralized products thereof. may be used as a catalyst for the alkyl etherified melamine resin (B).

The clear coat paint of the present invention containing the above C to (0) components is usually diluted with an organic diluting solvent to an appropriate viscosity before use. Examples of organic diluting solvents include xylene, which is an aromatic petroleum derivative, Trupetz+I Do (manufactured by Shell Chemical Company), and 2-heptanone (manufactured by Eastman Corporation), which is a ketone.

Examples of the resin system serving as the vehicle μ of the paste paint used with the clear coat paint of the present invention include thermosetting acrylic melamine resin systems and thermosetting alkyd melamine resin systems. For example, in the case of a base coat paint based on acrylic melamine resin, a film-forming acrylic resin with a functional group capable of reacting with an amino resin, a volatile organic liquid diluent, and a curing agent dissolved in the organic liquid diluent are used. A composition consisting of a certain amino resin may contain brightening agents such as aluminum paste, mica, and flaky iron oxide; organic pigments such as titanium oxide, carbon black, and quinacridone; and non-acrylic resins such as epoxy resins and cellulose resins. ; Auxiliary additives such as surface conditioners, ultraviolet absorbers, antioxidants, pigment antisettling agents, etc. are selected as necessary;
In addition, it is constituted by a numerical combination method.

[Example] Hereinafter, the present invention will be explained in detail based on an example. In addition, "part" means "part by weight."

40 parts of toluene and n-butano-A/
I prepared 10 copies. The contents of the reaction vessel were heated with stirring to raise the temperature to 100°C. Next, 101.5 parts of a solution consisting of 5 parts of styrene, 2 parts of methacrylic acid, 35 parts of methyl methacrylate, 46 parts of ethyl acrylate, 12 parts of 2-hydroxyethyl acrylate, and 1.5 parts of benzoyl peroxide were added dropwise over 4 hours. , 3 parts of a solution consisting of 0.6 parts of pencil peroxide and 20 parts of toluene.
It was dropped in 0 minutes. The reaction solution was further stirred and heated at 100° C. for 2 hours to increase the conversion rate to resin, and then 30 parts of toluene was added to terminate the reaction. The obtained acrylic copolymer solution (non-volatile content: 50 cm) is referred to as acrylic resin face (D). The weight average molecular weight of this acrylic copolymer was measured by gel permulation chromatography and was found to be 70,000.

Manufacturing example of base coat paint Place the amounts of each material shown in Table 1 in a stainless steel container.
After stirring thoroughly, adjust the viscosity with a mixed solvent for dilution.
Base coat paints B-1 and B-2 were manufactured.

Polymerization reactions were carried out using the following procedure for each of the seven mixtures having the monomer compositions shown in Table 1 and Table 2. Into a reaction vessel equipped with a stirrer, a temperature control device, and a condenser, 553 parts of Tsurupetz ÷100 (manufactured by Shell Chemical Company) were first charged, and heated while stirring to raise the temperature to 140°C. Next, 100 parts of each of the seven-mer mixtures listed in Table 2, 1 part of azobisisobutyronitrile, and 5 parts of t-butylperoxyisopropylcarbonate were added dropwise over 3 hours. Then 0.1 part of azobisisobutyronitrile was added four times at 30 minute intervals. 140
After further stirring and heating at ℃ for 2 hours to increase the conversion rate to resin, 3 parts of n-butano/L/15 was added to terminate the reaction.

The hydroxyl value and acid value of each of the obtained acrylic copolymers (P-1 to P-8) and the viscosity and nonvolatile content of the copolymer solution were as shown in Table 2.

Examples 1 to 3 and Comparative Examples 1 to 5 Using each of the acrylic copolymer solutions described above, eight types of clear coat paints were manufactured according to the paint formulations shown in Table 3.

*1) Butylated melamine resin manufactured by Mitsui Toatsu Chemical *2) Methylated melamine resin manufactured by Mikata Cyanamide *3) Surface conditioner manufactured by Monsanto *4) Blocked polyisocyanate manufactured by Takeda Pharmaceutical Company * *5) Ultraviolet absorber manufactured by Ciba Geigy *6) Antioxidant manufactured by Ciba Geigy *7) Total N mixing ratio of 2-heptanone and Sobetsona 100 *8) Measured at 20°C using Ford Cup & 4 did.

Formation of coating film and its evaluation Bonderite+144 dull steel plate (specially made by Japan Test Panel) was coated with automotive cationic electrodeposition paint and heated at 180°C.
Bake for 50 minutes. Next, an amino alkyd medium paint was applied, and after baking at 160°C for 30 minutes, the paint film was sanded and dried. On this coating film, the base coat paints listed in Table 1 and the clear coat paints listed in Table 3 were coated in combinations shown in Table 4 using a wet-on-wet method. This overcoating was performed as follows.

On the intermediate coating film! After applying the base coat paint to a dry film thickness of 20-30 μm and leaving it for 5 minutes,
A clear coat paint was applied to give a dry film thickness of 30 μm. The undried overcoated coating film was left at room temperature for 10 minutes and then baked in a hot air dryer at 140° C. for 25 minutes to form a coating film.

Table 4 shows the results of evaluating various film performances such as scratch resistance for each of the coating films thus obtained.

As is clear from the results, when the clear coat paint of the present invention is used, a coating film exhibiting excellent performance in terms of gloss, scratch resistance, hardness, gasoline resistance, hot water resistance, weather resistance, etc. is obtained. can get.

*1) 60° G: Suga Testing Machine ■Digital Angle Gloss Meter U
Measured using GV-4D.

*2) Using a friction fastness tester (manufactured by Ohtsuka Kagaku Seiki@),
Apply gauze to the area that will contact the painted surface, and apply a load of 1 to 9 to 10.
Perform a reciprocating friction test and visually judge the scar.

*3) Use Uni (specially made by Mitsubishi Pencil).

*4) Add 2 to regular gasoline (Nippon Oil special) at room temperature.
After soaking for 4 hours, visually evaluate the appearance.

*5) After 10 days of immersion in 50°C warm water I/C, the appearance was visually judged.

*6) After 1,000 hours of sunshine weather, the appearance was visually judged after a 240-hour humidity test at 50° C. and 98° RH.

〔Effect of the invention〕

The clear coat paint of the present invention forms a coating film with excellent scratch resistance, gloss, gasoline resistance, hot water resistance, weather resistance, etc., and is therefore extremely useful as an automobile body paint. .

Procedural amendment ( April 1988 Cow■

Claims (1)

[Scope of Claims] A clear coat paint used in a coating system in which a base coat paint containing a colorant is applied, a clear coat paint is overcoated, and then a paint film is obtained by heating and curing the paint. The coating paint has (a) General formula (I) ▲Mathematical formula, chemical formula, table, etc.▼(I) (In the formula, R^1 represents a hydrogen atom or a methyl group, and m is an integer from 3 to 5. (n is an integer of 1 to 6.) Hydroxyl group-containing (meth)acrylic acid ester 1 represented by
0 to 50% by weight, (b) General formula (II) ▲Mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, R^2 is a hydrogen atom or a methyl group, and R^3 has a carbon atom number of 2. 0 to 40% by weight of a hydroxyl group-containing (meth)acrylic ester represented by (10 to 10 alkylene groups), and (c) 30 to 40% by weight of another vinyl monomer copolymerizable with these.
80% by weight, the hydroxyl value obtained by copolymerizing is 60 to 160mgKO
B/g, an acrylic copolymer (A
) 40 to 80% by weight, alkyl etherified melamine resin (B) 20 to 60% by weight, and optionally blocked polyisocyanate (C) 0 to 4%.
A clear coat paint characterized by containing 0% by weight.