JP2022150018A - Coating composition, coated laminate and method for producing coated laminate - Google Patents

Abstract

To provide: a coating composition having excellent adhesion, hardness, water resistance and weatherability; a coated laminate; and a method for producing a coated laminate.SOLUTION: There is provided a coating composition which is a coating composition for coating a surface of a body to be coated 2. The coating composition comprises a first coating composition for forming a first coating layer 3 for covering a surface of a body to be coated and a second coating composition for forming a second coating layer 4 for covering a surface of the first coating layer. The first coating composition and the second composition are composed of predetermined compositions, respectively.SELECTED DRAWING: Figure 1

Description

The present invention relates to a coating composition, a coated laminate, and a method for producing a coated laminate.

BACKGROUND ART Conventionally, thermosetting resin compositions containing polyols and alkyl-etherified melamine resins have been used in the fields of vehicle paints and household appliance paints.

As such a thermosetting resin composition, for example, a thermosetting resin containing a resin (A) having a hydroxyl group, an alkyl etherified melamine resin (B), a Lewis acid catalyst (C), and a solvent (D) A composition has been proposed (see, for example, Patent Document 1).

International publication 2019/202964 pamphlet

On the other hand, coating films formed from such thermosetting resin compositions are required to have even higher adhesion, hardness, water resistance and weather resistance.

The present invention provides a coating composition excellent in adhesion, hardness, water resistance and weather resistance, a coated laminate, and a method for producing a coated laminate.

The present invention [1] is a coating composition for coating the surface of an object to be coated, comprising: a first coating composition for forming a first coating layer covering the surface of the object to be coated; and a second coating composition for forming a second coating layer covering the surface of the coating layer, wherein the first coating composition comprises the following (Ia) to (Id),
(Ia) a hydroxyl value of 20 mgKOH/g or more and 80 mgKOH/g or less;
A first hydroxyl group-containing resin having an acid value of 3 mgKOH/g or more and 50 mgKOH/g or less (excluding the first melamine resin (Ib))
(Ib) The average addition number of formaldehyde per 1 mol of melamine is 3 mol or more and 6 mol or less, and the first melamine resin modified with an alcohol having 1 or more and 6 or less carbon atoms (Ib) The electronegativity of Pauling is A Lewis acid catalyst (Id) pigment comprising a cation consisting of a metal of 1.31 or more and 2.02 or less and a counter anion that is a deprotonated form of nitric acid, and for the first melamine resin (Ib) The mass ratio of the first hydroxyl group-containing resin (Ia) (first hydroxyl group-containing resin (Ia)/first melamine resin (Ib)) is 60/40 or more and 95/5 or less,
The second coating composition includes the following (II-a) to (II-c),
(II-a) a second hydroxyl group-containing resin having a hydroxyl value of 70 mgKOH/g or more and 180 mgKOH/g or less (excluding the second melamine resin (II-b))
(II-b) The average addition number of formaldehyde per 1 mol of melamine is 3 mol or more and 6 mol or less, and the second melamine resin modified with an alcohol having 2 or more and 6 or less carbon atoms (II-c) The electronegativity of Pauling is A Lewis acid catalyst comprising a cation consisting of a metal of 1.31 or more and 2.02 or less and a counter anion that is a deprotonated form of nitric acid, and the second hydroxyl group-containing resin for the second melamine resin (II-b) The coating composition has a weight ratio of (II-a) (second hydroxyl group-containing resin (II-a)/second melamine resin (II-b)) of 60/40 or more and 95/5 or less.

In the present invention [2], the second coating composition further includes the coating composition according to [1] above, which further includes (II-d) below.
(II-d) A radical scavenger having a base dissociation constant pKb of 6 or more and 14 or less

The present invention [3] comprises an object to be coated, a first coating layer covering the surface of the object to be coated, and a second coating layer covering the surface of the first coating layer, wherein the first coating layer consists of a first coating composition, wherein the first coating composition comprises the following (Ia) to (Id),
(Ia) a hydroxyl value of 20 mgKOH/g or more and 80 mgKOH/g or less;
A first hydroxyl group-containing resin having an acid value of 3 mgKOH/g or more and 50 mgKOH/g or less (excluding the first melamine resin (Ib))
(Ib) The average addition number of formaldehyde per 1 mol of melamine is 3 mol or more and 6 mol or less, and the first melamine resin modified with an alcohol having 1 or more and 6 or less carbon atoms (Ib) The electronegativity of Pauling is A Lewis acid catalyst (Id) pigment comprising a cation consisting of a metal of 1.31 or more and 2.02 or less and a counter anion that is a deprotonated form of nitric acid, and for the first melamine resin (Ib) The mass ratio of the first hydroxyl group-containing resin (Ia) (first hydroxyl group-containing resin (Ia)/first melamine resin (Ib)) is 60/40 or more and 95/5 or less, and The second coating layer is composed of a second coating composition, and the second coating composition includes the following (II-a) to (II-c),
(II-a) a second hydroxyl group-containing resin having a hydroxyl value of 70 mgKOH/g or more and 180 mgKOH/g or less (excluding the second melamine resin (II-b))
(II-b) The average addition number of formaldehyde per 1 mol of melamine is 3 mol or more and 6 mol or less, and the second melamine resin modified with an alcohol having 2 or more and 6 or less carbon atoms (II-c) The electronegativity of Pauling is A Lewis acid catalyst comprising a cation consisting of a metal of 1.31 or more and 2.02 or less and a counter anion that is a deprotonated form of nitric acid, and the second hydroxyl group-containing resin for the second melamine resin (II-b) A coated laminate in which the mass ratio of (II-a) (second hydroxyl group-containing resin (II-a)/second melamine resin (II-b)) is 60/40 or more and 95/5 or less.

The present invention [4] includes the coated laminate according to the above [3], wherein the object to be coated is a resin.

The present invention [5] includes the coated laminate according to the above [4], wherein the resin is an acrylonitrile/styrene/butadiene copolymer resin.

The present invention [6] comprises a first step of applying a first coating composition to the surface of an object to be coated to form an uncured first coating layer, and after the first step, the uncured A second step of disposing an uncured second coating layer by applying a second coating composition to the surface of the first coating layer of the uncured first coating layer and the uncured second A third step of curing the coating layer at the same time, wherein the first coating composition includes the following (Ia) to (Id),
(Ia) a hydroxyl value of 20 mgKOH/g or more and 80 mgKOH/g or less;
A first hydroxyl group-containing resin having an acid value of 3 mgKOH/g or more and 50 mgKOH/g or less (excluding the first melamine resin (Ib))
(Ib) The average addition number of formaldehyde per 1 mol of melamine is 3 mol or more and 6 mol or less, and the first melamine resin modified with an alcohol having 1 or more and 6 or less carbon atoms (Ib) The electronegativity of Pauling is A Lewis acid catalyst (Id) pigment comprising a cation consisting of a metal of 1.31 or more and 2.02 or less and a counter anion that is a deprotonated form of nitric acid, and for the first melamine resin (Ib) The mass ratio of the first hydroxyl group-containing resin (Ia) (first hydroxyl group-containing resin (Ia)/first melamine resin (Ib)) is 60/40 or more and 95/5 or less,
The second coating composition includes the following (II-a) to (II-c),
(II-a) a second hydroxyl group-containing resin having a hydroxyl value of 70 mgKOH/g or more and 180 mgKOH/g or less (excluding the second melamine resin (II-b))
(II-b) The average addition number of formaldehyde per 1 mol of melamine is 3 mol or more and 6 mol or less, and the second melamine resin modified with an alcohol having 2 or more and 6 or less carbon atoms (II-c) The electronegativity of Pauling is A Lewis acid catalyst comprising a cation consisting of a metal of 1.31 or more and 2.02 or less and a counter anion that is a deprotonated form of nitric acid, and the second hydroxyl group-containing resin for the second melamine resin (II-b) A method for producing a coated laminate, wherein the mass ratio of (II-a) (second hydroxyl group-containing resin (II-a)/second melamine resin (II-b)) is 60/40 or more and 95/5 or less be.

The present invention [7] includes the method for producing a coated laminate according to the above [6], wherein the object to be coated is a resin.

The present invention [8] includes the method for producing a coated laminate according to the above [7], wherein the material of the resin film is an acrylonitrile/styrene/butadiene copolymer resin.

In the coating composition of the present invention, the first coating composition and the second coating composition each have a predetermined composition. Therefore, a coated laminate having excellent adhesion, hardness, water resistance and weather resistance can be produced.

In the coated laminate of the present invention, the first coating layer and the second coating layer are respectively composed of the first coating composition and the second coating composition having predetermined compositions. Therefore, it is excellent in adhesion, hardness, water resistance and weather resistance.

In the method for producing a coated laminate of the present invention, the uncured first coating layer and the uncured second coating layer are cured simultaneously. Therefore, it is excellent in production efficiency.

FIG. 1 shows an embodiment of the method for producing a coated laminate of the present invention. FIG. 1A shows the step of preparing an object to be coated in the first step. FIG. 1B shows a step of placing an uncured first coating layer on the surface (one side in the thickness direction) of the object to be coated in the first step. FIG. 1C shows a second step of disposing an uncured second coating layer on the surface of the uncured first coating layer (on one side in the thickness direction). shows a third step of simultaneously curing the second coating layer of .

<Coating composition>
The coating composition of the present invention is used for coating the surface of the object 2 to be coated, although the details will be described later.

The coating composition comprises a first coating composition and a second coating composition. Specifically, the first coating composition and the second coating composition are compositions for forming the first coating layer 3 and the second coating layer 4, respectively. In other words, the mixture of the first coating composition and the second coating composition does not form the first coating layer 3 or the second coating layer 4 .

<First coating composition>
The first coating composition, which will be described later in detail, is a composition for forming the first coating layer covering the surface of the object 2 to be coated.

The first coating composition comprises (Ia) a first hydroxyl-containing resin, (Ib) a first melamine resin, (Ic) a Lewis acid catalyst, and (Id) a pigment.

<Resin containing first hydroxyl group>
The first hydroxyl group-containing resin is a resin having a predetermined acid value and a predetermined hydroxyl value. Examples of the first hydroxyl group-containing resin include hydroxyl group-containing acrylic resins, hydroxyl group-containing polyester resins, hydroxyl group-containing epoxy resins, and hydroxyl group-containing urethane resins, preferably hydroxyl group-containing acrylic resins. The first hydroxyl group-containing resin does not include the first melamine resin described later.

In the first hydroxyl-containing resin, the hydroxyl-containing acrylic resin is a polymerization product of the first polymerization component.

The first polymerized component is a monomer component. Specifically, the first polymerizable component is a polymerizable component (monomer component) capable of radical polymerization (vinyl polymerization).

The first polymerizable component contains a (meth)acrylic acid ester, an acidic group-containing vinyl monomer, a hydroxyl group-containing vinyl monomer, and, if necessary, a copolymerizable monomer copolymerizable therewith.

(Meth)acrylic acid esters include, for example, alkyl esters of (meth)acrylic acid having 1 to 12 carbon atoms. Examples of alkyl (meth)acrylic acid having 1 to 12 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate. Acrylate, t-butyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate acrylate, dodecyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, and benzyl (meth)acrylate, preferably C 1-8 alkyl esters of (meth)acrylic acid; More preferred are (meth)acrylic acid having 1 to 6 carbon atoms, and more preferred are methyl methacrylate and n-butyl acrylate. In addition, (meth)acrylic acid ester includes acrylic acid ester and/or methacrylic acid ester.

The (meth)acrylic acid esters may be used alone or in combination of two or more.

The acidic group-containing vinyl monomer is added to the first polymerization component from the viewpoint of dispersing the pigment (described later). Examples of acidic group-containing vinyl monomers include carboxyl group-containing vinyl monomers and sulfonic acid group-containing vinyl monomers.

Carboxyl group-containing vinyl monomers include monocarboxylic acids, dicarboxylic acids, and salts thereof. Examples of monocarboxylic acids include (meth)acrylic acid. Dicarboxylic acids include, for example, itaconic acid, maleic acid, fumaric acid, itaconic anhydride, maleic anhydride, and fumaric anhydride.

Sulfonic acid group-containing vinyl monomers include, for example, sulfonic acids and salts thereof. Sulfonic acids include, for example, allylsulfonic acid, methallylsulfonic acid, and acrylamido t-butylsulfonic acid. The sulfonic acid salts include, for example, alkali metal salts (eg, sodium salts, potassium salts) and ammonium salts of the above sulfonic acids. Specific examples include sodium allylsulfonate, sodium methallylsulfonate, and ammonium methallylsulfonate.

The acidic group-containing vinyl monomer preferably includes a carboxyl group-containing vinyl monomer, more preferably monocarboxylic acid, still more preferably (meth)acrylic acid, and most preferably methacrylic acid.

The acidic group-containing vinyl monomers can be used singly or in combination of two or more.

Examples of hydroxyl group-containing vinyl monomers include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate, preferably 2-hydroxyethyl (meth)acrylate. , and more preferably 2-hydroxyethyl methacrylate.

Examples of copolymerizable monomers include functional group-containing vinyl monomers (excluding acidic group-containing vinyl monomers and hydroxyl group-containing vinyl monomers; hereinafter the same), vinyl esters, aromatic vinyl monomers, and N-substituted unsaturated carboxylic acid amides. , heterocyclic vinyl compounds, vinylidene halide compounds, α-olefins, and dienes.

Functional group-containing vinyl monomers include, for example, amino group-containing vinyl monomers, cyano group-containing vinyl monomers, glycidyl group-containing vinyl monomers, and acetoacetoxy group-containing vinyl monomers.

Examples of amino group-containing vinyl monomers include 2-aminoethyl (meth)acrylate, 2-(N-methylamino)ethyl (meth)acrylate, and 2-(N,N-dimethyl(meth)acrylate). amino) ethyl.

Examples of cyano group-containing vinyl monomers include (meth)acrylonitrile.

Examples of glycidyl group-containing vinyl monomers include glycidyl (meth)acrylate.

Examples of acetoacetoxy group-containing vinyl monomers include acetoacetoxyethyl (meth)acrylate.

Examples of vinyl esters include vinyl acetate and vinyl propionate.

Aromatic vinyl monomers include, for example, styrene and α-methylstyrene.

Examples of N-substituted unsaturated carboxylic acid amides include N-methylol(meth)acrylamide.

Heterocyclic vinyl compounds include, for example, vinylpyrrolidone.

Vinylidene halide compounds include, for example, vinylidene chloride and vinylidene fluoride.

α-Olefins include, for example, ethylene and propylene.

Examples of dienes include butadiene.

Furthermore, a crosslinkable vinyl monomer can also be mentioned as a copolymerizable monomer.

Examples of crosslinkable vinyl monomers include compounds containing two or more vinyl groups. Examples of compounds containing two or more vinyl groups include methylenebis(meth)acrylamide, divinylbenzene, polyethylene glycol chain-containing di(meth)acrylate, trimethylolpropane tetraacrylate, pentaerythritol triacrylate, and pentaerythrol triacrylate. Stoll tetraacrylate can be mentioned.

The copolymerizable monomers can be used singly or in combination of two or more.

In the first polymerization component, the mixing ratio of the (meth)acrylic acid ester is, for example, 70 parts by mass or more, preferably 80 parts by mass or more, or, for example, 95 parts by mass with respect to 100 parts by mass of the first polymerization component. Below, preferably, it is 90 mass parts or less.

The mixing ratio of the acidic group-containing vinyl monomer is, for example, 0.1 part by mass or more, preferably 1 part by mass or more, and preferably 10 parts by mass or less, with respect to 100 parts by mass of the first polymerization component. is 5 parts by mass or less, more preferably 3 parts by mass or less.

If the mixing ratio of the acidic group-containing vinyl monomer is within the range described above, the acid value (described later) of the first hydroxyl group-containing resin can be adjusted to the predetermined range described later.

The blending ratio of the hydroxyl group-containing vinyl monomer is, for example, 3 parts by mass or more, preferably 10 parts by mass or more, and for example, 20 parts by mass or less, preferably 15 parts by mass, with respect to 100 parts by mass of the first polymerization component. It is not more than 12 parts by mass, more preferably not more than 12 parts by mass.

If the blending ratio of the hydroxyl group-containing vinyl monomer is within the range described above, the hydroxyl value (described later) of the first hydroxyl group-containing resin can be adjusted within a predetermined range described later.

Moreover, the blending ratio of the copolymerizable monomer is, for example, 0.1 parts by mass or more and, for example, 10 parts by mass or less with respect to 100 parts by mass of the first polymerizable component.

The first polymerization component preferably does not contain a copolymerizable monomer, and contains a (meth)acrylic acid ester, an acidic group-containing vinyl monomer, and a hydroxyl group-containing vinyl monomer. More preferably, the first polymerization component is It consists of a (meth)acrylic acid ester, an acidic group-containing vinyl monomer, and a hydroxyl group-containing vinyl monomer.

The hydroxyl group-containing acrylic resin is obtained by polymerizing the first polymerizable component.

A polymerization method is not particularly limited. The polymerization method includes, for example, bulk polymerization and solution polymerization, preferably solution polymerization.

When solution polymerization is employed as the polymerization method, the first polymerization component and, if necessary, a polymerization initiator are blended in a solvent and polymerized.

A well-known solvent is mentioned as a solvent. Solvents include, for example, alkyl esters (eg, butyl acetate) and alcohols (isobutanol).

Moreover, a commercial item can also be used as a solvent. Commercially available products include, for example, the Teasol series (aromatic hydrocarbons, manufactured by ENEOS Corporation).

Solvents can be used alone or in combination of two or more.

Examples of polymerization initiators include peroxide-based radical polymerization initiators (eg, t-butylperoxy-2-ethylhexanoate).

The mixing ratio of the polymerization initiator is appropriately set according to the purpose and application.

As polymerization conditions, the polymerization temperature is, for example, 70° C. or higher and, for example, 120° C. or lower. Moreover, the polymerization time is, for example, 1 hour or more and, for example, 12 hours or less.

Thereby, a hydroxyl group-containing acrylic resin is obtained.

The hydroxyl value of the first hydroxyl group-containing resin is 20 mgKOH/g or more, preferably 40 mgKOH/g or more, and 80 mgKOH/g or less, preferably 60 mgKOH/g or less.

When the hydroxyl value is equal to or higher than the lower limit, the crosslink density is improved, so that the first coating layer 3 having excellent water resistance can be obtained.

Further, when the hydroxyl value is equal to or less than the upper limit, an increase in curing shrinkage of the first coating layer 3 can be suppressed, so that the first coating layer 3 having excellent adhesion can be obtained.

Further, although details will be described later, preferably, the hydroxyl value of the first hydroxyl group-containing resin is set to be smaller than the hydroxyl value (described later) of the second hydroxyl group-containing resin.

The hydroxyl value can be determined, for example, according to JIS K 0070-1992 (acetylation method) (the same shall apply hereinafter).

The acid value of the first hydroxyl group-containing resin is 3 mgKOH/g or more, preferably 7 mgKOH/g or more, and 50 mgKOH/g or less, preferably 30 mgKOH/g or less, more preferably 20 mgKOH/g or less.

When the acid value is at least the lower limit, a first coating composition having excellent pigment dispersibility can be obtained.

Moreover, if the said acid value is below the said upper limit, the 1st coating layer 3 which is excellent in water resistance can be obtained.

The above acid value can be determined by, for example, JIS K 0070-1992 (potentiometric titration method) (the same shall apply hereinafter).

The polystyrene-equivalent weight average molecular weight (Mw) of the first hydroxyl group-containing resin measured by gel permeation chromatography (GPC) is, for example, 5000 or more, preferably 8000, more preferably 10000 or more. , 200,000 or less, preferably 100,000 or less, more preferably 80,000 or less, even more preferably 40,000 or less, particularly preferably 30,000 or less, most preferably 25,000 or less.

When the weight-average molecular weight is within the above range, the first coating layer 3 can be formed with excellent paintability, appearance, strength, hardness and wear resistance.

The glass transition temperature of the first hydroxyl group-containing resin is, for example, −30° C. or higher, preferably −20° C. or higher, more preferably 0° C. or higher, still more preferably 5° C. or higher, and for example, 80° C. or lower. The temperature is preferably 60° C. or lower, more preferably 50° C. or lower, and still more preferably 30° C. or lower.

If the glass transition temperature is within the above range, it is possible to form the first coating layer 3 having excellent paintability, hardness and water resistance.

The method for measuring the glass transition temperature will be described in detail in the examples below (the same applies hereinafter).

<First melamine resin>
The first melamine resin is an alkyl-etherified melamine resin obtained by modifying (alkyl-etherifying) with alcohol at least part of the methylol groups of the melamine resin obtained from melamine and formaldehyde.

Formaldehyde can be prepared as an aqueous solution. Moreover, solid paraformaldehyde can also be used as it is as formaldehyde.

When formaldehyde is prepared as an aqueous solution, its concentration is, for example, 80% or more and, for example, 99% or less.

In the first melamine resin, the alcohol is alcohol having 1 or more and 6 or less carbon atoms. On the other hand, when the alcohol is an alcohol having 7 or more carbon atoms, the alcohol does not volatilize during heat curing, resulting in a decrease in the curability of the first coating composition and a decrease in hardness and water resistance. Examples of alcohols having 1 to 6 carbon atoms include linear monohydric alcohols having 1 to 6 carbon atoms and branched monohydric alcohols having 1 to 6 carbon atoms. Linear monohydric alcohols having 1 to 6 carbon atoms include, for example, methanol, ethanol, n-propanol, n-butanol, n-pentanol, and n-hexanol. Examples of branched monohydric alcohols having 1 to 6 carbon atoms include isopropanol, isobutanol, sec-butanol, and tert-butanol.

The alcohol is preferably a linear monohydric alcohol having 1 to 6 carbon atoms, more preferably a linear monohydric alcohol having 1 to 4 carbon atoms, still more preferably methanol, ethanol, and , n-butanol, particularly preferably ethanol.

Alcohol can be used alone or in combination of two or more.

To obtain the first melamine resin, first, melamine and formaldehyde are subjected to a methylolation reaction to obtain a melamine resin.

Melamine and formaldehyde are blended for the methylolation reaction of melamine and formaldehyde. Specifically, formaldehyde is blended so that the average addition number of formaldehyde per 1 mol of melamine is 3 mol or more, preferably 4 mol or more and 6 mol or less.

When the average addition number is equal to or more than the lower limit, the crosslink density can be improved and the water resistance can be improved.

On the other hand, if the average number of additions is less than the lower limit, the water resistance is lowered.

The average number of additions can be calculated, for example, by ¹³ C-NMR analysis (the same shall apply hereinafter).

When formaldehyde is added to all three amino groups of melamine, the average number of formaldehyde additions is 6 mol.

In the above methylolation reaction, an alcohol is blended in advance together with melamine and formaldehyde. The blending ratio of alcohol is, for example, 4 mol or more, preferably 6 mol or more, and, for example, 8 mol or less with respect to 1 mol of melamine.

After the methylolation reaction, an acid catalyst is added to modify (alkyl etherify) at least a portion of the methylol groups of the melamine resin with alcohol.

Acid catalysts include, for example, organic acids and inorganic acids. Organic acids include, for example, formic acid, oxalic acid, and paratoluenesulfonic acid. Inorganic acids include, for example, phosphoric acid, hydrochloric acid, sulfuric acid, and nitric acid. Acid catalysts preferably include organic acids, more preferably para-toluenesulfonic acid.

Acid catalysts can be used alone or in combination of two or more.

The blending ratio of the acid catalyst is appropriately set according to the purpose and application.

As reaction conditions, the reaction temperature is, for example, 60° C. or higher and, for example, 120° C. or lower. Further, the reaction time is, for example, 1 hour or more and, for example, 12 hours or less.

A neutralizing agent (eg, sodium hydroxide) is then added to neutralize the reaction product.

Thereby, the first melamine resin is obtained. Such a first melamine resin is a melamine resin modified with an alcohol having 1 to 6 carbon atoms and having an average addition number of formaldehyde of 3 to 6 mol per 1 mol of melamine.

The polystyrene equivalent weight average molecular weight (Mw) of the first melamine resin measured by gel permeation chromatography (GPC) is, for example, 800 or more, preferably 1000, more preferably 1100 or more, and more preferably 1800 or more, and for example, 15000 or less, preferably 7000 or less, more preferably 5000 or less, still more preferably 2500 or less.

When the weight-average molecular weight is within the above range, the first coating layer 3 can be formed with excellent mechanical properties, smoothness, and appearance.

<Lewis acid catalyst>
A Lewis acid catalyst consists of a cation and a counter anion.

The cation is a cation of a metal having a Pauling electronegativity of 1.31 or more and 2.02 or less. Specifically, the Pauling electronegativity is 1.31 or more, preferably 1.50 or more, more preferably 1.60 or more, and 2.02 or less, preferably 1.80 or less.

If the electronegativity is at least the above lower limit, the first coating layer 3 having excellent water resistance, hardness, and weather resistance can be formed.

Moreover, when the electronegativity is equal to or less than the above upper limit, the water resistance, hardness, and weather resistance are excellent.

Examples of metals having a Pauling electronegativity of 1.31 or more and 2.02 or less include magnesium, manganese, aluminum, cobalt, nickel, tin, zinc, copper, and bismuth, preferably manganese, Aluminum, nickel, zinc, and more preferably aluminum.

The counter anion is the deprotonated form of nitric acid.

Specific examples of such Lewis acid catalysts include magnesium nitrate, manganese nitrate, aluminum nitrate, cobalt nitrate, nickel nitrate, tin nitrate, zinc nitrate, copper nitrate, and bismuth sulfate, preferably manganese nitrate, Aluminum nitrate, nickel nitrate, more preferably aluminum nitrate.

<Pigment>
Pigments include, for example, coloring pigments, luster pigments, and extender pigments.

Examples of coloring pigments include titanium oxide, zinc white, carbon black, cadmium red, molybdenum red, chrome yellow, chromium oxide, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, threne pigments, and perylene pigments.

Luster pigments include, for example, aluminum powder, aluminum paste, mica powder, and mica powder coated with titanium oxide.

Extender pigments include, for example, talc, clay, kaolin, baryta, barium sulfate, barium carbonate, calcium carbonate, and alumina white.

As the pigment, a glittering pigment, more preferably an aluminum paste, is preferably used from the viewpoint of improving dispersibility by an acidic group-containing vinyl monomer (preferably a carboxyl group-containing vinyl monomer).

Pigments can be used alone or in combination of two or more.

<Preparation of first coating composition>
A first coating composition is obtained by mixing a first hydroxyl-containing resin, a first melamine resin, a Lewis acid catalyst, and a pigment.

Moreover, when a solvent is used in preparing the first hydroxyl group-containing resin and the first melamine resin, the solvent is contained in the first coating composition.

In addition, known additives can be added to the first coating composition, if necessary.

In the first coating composition, the mass ratio of the first hydroxyl group-containing resin (Ia) to the first melamine resin (Ib) (first hydroxyl group-containing resin (Ia) / first melamine resin (Ib )) is 60/40 or more, preferably 70/30 or more and for example 95/5 or less.

When the mass ratio is equal to or higher than the lower limit, it is possible to form the first coating layer 3 having excellent water resistance, hardness, and weather resistance.

If the mass ratio is equal to or less than the upper limit, the first coating layer 3 having excellent water resistance, hardness, and weather resistance can be formed.

The blending ratio of the first hydroxyl group-containing resin is, for example, with respect to 100 parts by mass of the total amount of the first hydroxyl group-containing resin, the first melamine resin, the Lewis acid catalyst, and the pigment (hereinafter referred to as the first component). 50 parts by mass or more, preferably 60 parts by mass or more, more preferably 70 parts by mass or more, and for example, 90 parts by mass or less, preferably 80 parts by mass or less.

The mixing ratio of the first melamine resin is, for example, 5 parts by mass or more, preferably 10 parts by mass or more, preferably 15 parts by mass or more, or, for example, 40 parts by mass with respect to 100 parts by mass of the first component. parts or less, preferably 30 parts by mass or less, more preferably 20 parts by mass or less.

The mixing ratio of the Lewis acid catalyst is, for example, 0.01 parts by mass or more, preferably 0.1 parts by mass or more, or, for example, 5 parts by mass with respect to the total amount of 100 parts by mass of the first hydroxyl group-containing resin and the first melamine resin. It is not more than 4 parts by mass, preferably not more than 4 parts by mass.

The mixing ratio of the Lewis acid catalyst is, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and for example, 10 parts by mass or less, preferably 100 parts by mass of the first component. , 5 parts by mass or less, more preferably 1 part by mass or less.

If the blending ratio of the Lewis acid catalyst is within the above range, it is possible to obtain a first coating composition that is excellent in storage stability and low-temperature curability.

The blending ratio of the pigment is, for example, 1 part by mass or more, preferably 2 parts by mass or more, more preferably 100 parts by mass in total of the first hydroxyl group-containing resin, the first melamine resin, and the Lewis acid catalyst. , 5 parts by mass or more, and, for example, 200 parts by mass or less, preferably 100 parts by mass or less, more preferably 50 parts by mass or less, still more preferably 30 parts by mass or less, particularly preferably 10 parts by mass or less be.

Further, the mixing ratio of the pigment is, for example, 0.5 parts by mass or more, preferably 3 parts by mass or more, and for example, 10 parts by mass or less, preferably 5 parts by mass, with respect to 100 parts by mass of the first component. It is below.

Although the details will be described later, the first coating layer 3 is obtained by applying the first coating composition to the surface (one side in the thickness direction) of the object to be coated 2 and curing it.

<Second coating composition>
The second coating composition is a composition for forming the second coating layer 4 covering the surface of the first coating layer 3, as will be described later in detail.

The second coating composition comprises (II-a) a second hydroxyl-containing resin, (II-b) a second melamine resin, (II-c) a Lewis acid catalyst, and optionally (II-d) a radical scavenging agents.

<Resin containing second hydroxyl group>
The second hydroxyl group-containing resin is a resin having a predetermined hydroxyl value. Specifically, the second hydroxyl group-containing resin has a hydroxyl value different from that of the first hydroxyl group-containing resin described above. Further, as will be described later, the second coating composition does not contain pigment when the second coating layer 4 is a clear layer, so dispersibility of the pigment is not required. Therefore, in such a case, the second hydroxyl group-containing resin does not require an acid value.

Examples of the second hydroxyl group-containing resin include the same resins as those exemplified for the first hydroxyl group-containing resin, preferably a hydroxyl group-containing acrylic resin. The second hydroxyl group-containing resin does not include a second melamine resin, which will be described later.

In the second hydroxyl-containing resin, the hydroxyl-containing acrylic resin is a polymerization product of the second polymerization component.

The second polymerized component is a monomer component. Specifically, the second polymerizable component is a polymerizable component (monomer component) capable of radical polymerization (vinyl polymerization).

The second polymerizable component contains a (meth)acrylic acid ester, a hydroxyl group-containing vinyl monomer, optionally an acidic group-containing vinyl monomer, and optionally a copolymerizable monomer copolymerizable therewith. As noted above, the second hydroxyl group-containing resin may not require an acid number. Therefore, the acidic group-containing vinyl monomer is an optional component.

The (meth)acrylic acid ester is the same as those exemplified for the first hydroxyl group-containing resin, preferably an alkyl ester of (meth)acrylic acid having 1 to 8 carbon atoms, more preferably a (meth)acrylic acid C 1-6 alkyl esters of acids, more preferably methyl methacrylate and n-butyl acrylate.

The hydroxyl group-containing vinyl monomer is the same as those exemplified for the first hydroxyl group-containing resin, preferably 2-hydroxyethyl (meth)acrylate, more preferably 2-hydroxyethyl methacrylate.

The acidic group-containing vinyl monomer is the same as those exemplified for the first hydroxyl group-containing resin, preferably a carboxyl group-containing vinyl monomer, more preferably monocarboxylic acid, still more preferably (meth)acrylic acid, especially Methacrylic acid is preferred.

The copolymerizable monomer is the same as those exemplified for the first hydroxyl group-containing resin.

In the second polymerization component, the mixing ratio of the (meth)acrylic acid ester is, for example, 60 parts by mass or more, preferably 70 parts by mass or more, or, for example, 95 parts by mass with respect to 100 parts by mass of the second polymerization component. Below, it is preferably 90 parts by mass or less, more preferably 80 parts by mass or less. The mixing ratio of the (meth)acrylic acid ester in the second polymerization component is preferably set smaller than the mixing ratio of the (meth)acrylic acid ester in the first polymerization component.

In addition, the blending ratio of the hydroxyl group-containing vinyl monomer is, for example, 12 parts by mass or more, preferably 20 parts by mass or more, more preferably 25 parts by mass or more with respect to 100 parts by mass of the second polymerization component. 40 parts by mass or less, preferably 30 parts by mass or less.

If the blending ratio of the hydroxyl group-containing vinyl monomer is within the range described above, the hydroxyl value (described later) of the second hydroxyl group-containing resin can be adjusted to a predetermined range described later.

Moreover, the mixing ratio of the hydroxyl group-containing vinyl monomer in the second polymerization component is preferably set to be higher than the mixing ratio of the hydroxyl group-containing vinyl monomer in the first polymerization component. Thereby, the hydroxyl value of the second hydroxyl-containing resin can be made larger than the hydroxyl value of the first hydroxyl-containing resin.

The mixing ratio of the acidic group-containing vinyl monomer is, for example, 0.1 parts by mass or more, and for example, 8 parts by mass or less, preferably 5 parts by mass or less, per 100 parts by mass of the second polymerization component. .

If the blending ratio of the acidic group-containing vinyl monomer is within the range described above, the acid value (described later) of the second hydroxyl group-containing resin can be adjusted within the predetermined range described later.

Also, the mixing ratio of the acidic group-containing vinyl monomer in the second polymerization component is preferably set smaller than the mixing ratio of the acidic group-containing vinyl monomer in the first polymerization component. Thereby, the acid value of the second hydroxyl group-containing resin can be made smaller than the acid value of the first hydroxyl group-containing resin.

Moreover, the blending ratio of the copolymerizable monomer is, for example, 0.1 parts by mass or more and, for example, 10 parts by mass or less with respect to 100 parts by mass of the second polymerizable component.

The second polymerization component preferably does not contain a copolymerizable monomer, and contains a (meth)acrylic acid ester, a hydroxyl group-containing vinyl monomer, and an acidic group-containing vinyl monomer. More preferably, the second polymerization component is It consists of a (meth)acrylic acid ester, a hydroxyl group-containing vinyl monomer, and an acidic group-containing vinyl monomer.

Then, the hydroxyl-containing acrylic resin is obtained by polymerizing the second polymerizable component.

In polymerization, the polymerization method, polymerization conditions, type of solvent, and type of polymerization initiator are the same as those exemplified for the first hydroxyl group-containing resin.

Thereby, a hydroxyl group-containing acrylic resin is obtained.

The hydroxyl value of the second hydroxyl group-containing resin is 70 mgKOH/g or more, preferably 90 mgKOH/g or more, more preferably 110 mgKOH/g or more, and 180 mgKOH/g or less, preferably 140 mgKOH/g or less.

When the hydroxyl value is equal to or higher than the lower limit, the crosslink density is improved, so that the second coating layer 4 having excellent water resistance can be obtained.

Further, when the hydroxyl value is equal to or less than the upper limit, an increase in curing shrinkage of the first coating layer 3 can be suppressed, so that the second coating layer 4 having excellent adhesion can be obtained.

Further, although the details will be described later, preferably, the hydroxyl value of the second hydroxyl group-containing resin is set to be higher than the hydroxyl value of the first hydroxyl group-containing resin.

The acid value of the second hydroxyl group-containing resin is, for example, 0 mgKOH/g or more, preferably 0.5 mgKOH/g or more, more preferably 1 mgKOH/g or more, and for example, 50 mgKOH/g or less, preferably 30 mgKOH/g. g or less, more preferably 20 mgKOH/g, still more preferably 10 mgKOH/g or less, and particularly preferably 5 mgKOH/g or less.

If the acid value of the second hydroxyl group-containing resin is within the above range, a second coating composition having excellent compatibility and curability can be obtained.

Moreover, preferably, the acid value of the second hydroxyl group-containing resin is set to be smaller than the acid value of the first hydroxyl group-containing resin.

The polystyrene-equivalent weight average molecular weight (Mw) of the second hydroxyl group-containing resin measured by gel permeation chromatography (GPC) is, for example, 5000 or more, preferably 8000, more preferably 10000 or more. , 200,000 or less, preferably 100,000 or less, more preferably 80,000 or less, even more preferably 40,000 or less, and particularly preferably 25,000 or less.

If the weight average molecular weight is within the above range, the second coating layer 4 can be formed with excellent paintability, appearance, strength, hardness and wear resistance.

The glass transition temperature of the second hydroxyl group-containing resin is, for example, −30° C. or higher, preferably −20° C. or higher, more preferably 0° C. or higher, still more preferably 5° C. or higher, and for example, 80° C. or lower. The temperature is preferably 60° C. or lower, more preferably 30° C. or lower, and still more preferably 20° C. or lower.

If the glass transition temperature is within the above range, the second coating layer 4 having excellent paintability, hardness and water resistance can be formed.

<Second melamine resin>
The second melamine resin is an alkyl-etherified second melamine resin obtained by modifying (alkyl-etherifying) with alcohol at least part of the methylol groups of the melamine resin obtained from melamine and formaldehyde.

As formaldehyde, the same formaldehyde as exemplified in the first melamine resin can be used.

In the second melamine resin, the alcohol is an alcohol having 2 or more and 6 or less carbon atoms. On the other hand, when the alcohol is an alcohol having 7 or more carbon atoms, the alcohol does not volatilize during heat curing, resulting in a decrease in the curability of the second coating composition and a decrease in hardness and water resistance. Examples of alcohols having 2 to 6 carbon atoms include linear monohydric alcohols having 2 to 6 carbon atoms and branched monohydric alcohols having 2 to 6 carbon atoms. Linear monohydric alcohols having 2 to 6 carbon atoms include, for example, ethanol, n-propanol, n-butanol, n-pentanol, and n-hexanol. Examples of branched monohydric alcohols having 2 to 6 carbon atoms include isopropanol, isobutanol, sec-butanol, and tert-butanol.

The alcohol is preferably a linear monohydric alcohol having 2 to 6 carbon atoms, more preferably a linear monohydric alcohol having 2 to 4 carbon atoms, still more preferably ethanol, and n -butanol, particularly preferably n-butanol. In other words, it is particularly preferred that the alcohol in the second melamine resin is selected to have a higher number of carbon atoms than the alcohol in the first melamine resin. This improves the water resistance.

Alcohol can be used alone or in combination of two or more.

The second melamine resin can be obtained in the same manner as the first melamine resin described above.

In this method, the average addition number of formaldehyde to 1 mol of melamine is 3 mol or more, preferably 4 mol or more and 6 mol or less. This results in excellent water resistance, hardness, and weather resistance.

When the average addition number is equal to or higher than the lower limit, the crosslink density can be improved, and the second coating layer 4 having excellent water resistance, hardness, and weather resistance can be formed.

In this method, the blending ratio of alcohol, acid catalyst, and reaction conditions are the same as those exemplified for the first melamine resin.

Thereby, a second melamine resin is obtained. Such a second melamine resin is a melamine resin modified with an alcohol having 2 to 6 carbon atoms and having an average addition number of formaldehyde of 3 to 6 mol per 1 mol of melamine.

The polystyrene equivalent weight average molecular weight (Mw) of the second melamine resin measured by GPC is, for example, 800 or more, preferably 1000, more preferably 1100 or more, still more preferably 1800 or more. It is 15,000 or less, preferably 7,000 or less, more preferably 5,000 or less, and still more preferably 2,500 or less.

If the weight-average molecular weight is within the above range, the second coating layer 4 can be formed with excellent mechanical properties, smoothness, and appearance.

<Lewis acid catalyst>
Examples of Lewis acid catalysts include those exemplified for the first melamine resin and Lewis acid catalysts, preferably manganese nitrate, aluminum nitrate, nickel nitrate, zinc nitrate, and more preferably aluminum nitrate.

<Radical Scavenger>
The radical scavenger is used as a radical chain inhibitor that scavenges active radical species generated during the deterioration process of the second coating layer 4 .

Examples of radical scavengers include hindered piperidines. Moreover, a well-known polymerizable light stabilizer can also be used as a radical scavenger.

The base dissociation constant pKb of the radical scavenger is, for example, 6 or more, preferably 7.5 or more, more preferably 8.5 or more, and for example, 14 or less.

If the base dissociation constant pKb is within the above range, the acid-base reaction with the Lewis acid catalyst can be suppressed, and active radicals generated during the deterioration process of the second coating layer 4 within the range that does not impair the catalytic activity. Seeds can be captured.

Moreover, a commercial item can also be used as a radical scavenger. Specifically, Tinuvin 249 (pKb = 8.0), Tinuvin 152 (pKb = 7.0 and 9.4), Tinuvin 123 (pKb = 9.6) (manufactured by BASF), HOSTAVIN 3058LIQ (Clariant) manufactured by ADEKA) and ADEKA STAB LA-81 (manufactured by ADEKA).

<Preparation of second coating composition>
A second coating composition is obtained by mixing a second hydroxyl group-containing resin, a second melamine resin, a Lewis acid catalyst, and, if necessary, a radical scavenger.

Moreover, when a solvent is used in preparing the second hydroxyl group-containing resin and the second melamine resin, the second coating composition contains the solvent.

In addition, the second coating composition may optionally contain known additives (eg, ultraviolet absorbers).

As the ultraviolet absorber, those capable of suppressing coloration due to complex formation with the Lewis acid catalyst are preferably used. Examples of such UV absorbers include cyanoacrylate UV absorbers and triazine UV absorbers. Examples of cyanoacrylate ultraviolet absorbers include Uvinul 3030, Uvinul 3035, Uvinul 3039C (manufactured by BASF), and SEESORB 501 and SEESORB 502 (manufactured by Sipro Kasei). Triazine-based UV absorbers include, for example, Adekastab LA-46, Adekastab LA-F70 (manufactured by ADEKA), Tinvin 400, Tinvin 405, Tinvin 460, Tinvin 477, Tinvin 479 (manufactured by BASF), KEMISORB 102 (Kemipro Kasei (manufactured by Everlight Chemical), EVERSORB 40, EVERSORB 41FD, and EVERSORB 45 (manufactured by Everlight Chemical).

In the second coating composition, the mass ratio of the second hydroxyl group-containing resin (II-a) to the second melamine resin (II-b) (second hydroxyl group-containing resin (II-a)/second melamine resin (II-b )) is 60/40 or more, preferably 70/30 or more and for example 95/5 or less.

If the mass ratio is equal to or higher than the lower limit, the second coating layer 4 having excellent water resistance, hardness, and weather resistance can be formed.

If the mass ratio is equal to or less than the upper limit, it is possible to form the second coating layer 4 having excellent water resistance, hardness, and weather resistance.

In addition, the mixing ratio of the second hydroxyl group-containing resin is, with respect to 100 parts by mass of the total amount of the second hydroxyl group-containing resin, the second melamine resin, the Lewis acid catalyst, and the radical scavenger (hereinafter referred to as the second component), For example, it is 50 parts by mass or more, preferably 60 parts by mass or more, more preferably 70 parts by mass or more, and for example, 90 parts by mass or less, preferably 80 parts by mass or less.

In addition, the mixing ratio of the second melamine resin is, for example, 5 parts by mass or more, preferably 10 parts by mass or more, preferably 15 parts by mass or more, or, for example, 40 parts by mass with respect to 100 parts by mass of the second component. parts or less, preferably 30 parts by mass or less, more preferably 20 parts by mass or less.

The blending ratio of the Lewis acid catalyst is, for example, 0.01 parts by mass or more, preferably 0.1 parts by mass or more, or, for example, 5 parts by mass with respect to the total amount of 100 parts by mass of the second hydroxyl group-containing resin and the second melamine resin. It is not more than 4 parts by mass, preferably not more than 4 parts by mass.

In addition, the blending ratio of the Lewis acid catalyst is, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and for example, 10 parts by mass or less, preferably with respect to 100 parts by mass of the second component. , 5 parts by mass or less, more preferably 1 part by mass or less.

If the blending ratio of the Lewis acid catalyst is within the above range, it is possible to obtain a second coating composition that is excellent in storage stability and low-temperature curability.

The blending ratio of the radical scavenger is, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and for example, 10 parts by mass or less, preferably 100 parts by mass of the second component. , 5 parts by mass or less, more preferably 1 part by mass or less.

Although the details will be described later, the second coating layer 4 is obtained by applying a second coating composition to the surface (one side in the thickness direction) of the first coating layer 3 and curing it.

<Method for producing coated laminate (method for using coating composition>
The coating composition is used for coating the surface of the object 2 to be coated. By coating the object 2 to be coated, a coated laminate is produced.

One embodiment of the method for producing a coated laminate of the present invention will be described with reference to FIG.

In FIG. 1, the vertical direction on the page is the vertical direction (thickness direction), the upper side on the page is the upper side (one side in the thickness direction), and the lower side on the page is the lower side (the other side in the thickness direction). Moreover, the left-right direction and the depth direction on the paper surface are plane directions orthogonal to the up-down direction. Specifically, it conforms to the directional arrows in each figure.

A method for producing a coated laminate 1 includes a first step of applying a first coating composition to the surface (one side in the thickness direction) of an object to be coated 2 to dispose an uncured first coating layer 3; After the first step, a second step of disposing an uncured second coating layer 4 by applying a second coating composition to the surface (one side in the thickness direction) of the uncured first coating layer 3; and a third step of simultaneously curing the uncured first coating layer 3 and the uncured second coating layer 4 .

In the first step, an uncured first coating layer 3 is placed on the surface (one side in the thickness direction) of the object 2 to be coated.

In the first step, as shown in FIG. 1A, first, an object 2 to be coated is prepared.

The object to be coated 2 is an object to be coated whose surface (one side in the thickness direction) is provided with various physical properties by the first coating layer 3 and the second coating layer 4 .

In FIG. 1A, the object 2 to be coated has a flat plate shape, but the shape of the object 2 to be coated is not particularly limited, and various shapes can be selected.

Examples of the object to be coated 2 include resin and metal.

Examples of resins include polyester resins, (meth)acrylic resins (including acrylic resins and/or methacrylic resins), polyolefin resins, polycarbonate resins, polyamide resins, polyimide resins, acrylonitrile-styrene-butadiene copolymer resins (ABS resins), Polystyrene resins, polyvinylidene chloride, styrene-acrylonitrile copolymer resins, and cellulose acetate. Polyester resins include, for example, polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. (Meth)acrylic resins include, for example, polymethyl methacrylate resin (PMMA). Polyolefin resins include, for example, polyethylene resins and polypropylene resins.

Metals include, for example, iron, aluminum, zinc, and stainless steel.

As the object 2 to be coated, preferably resin, more preferably acrylonitrile/styrene/butadiene copolymer resin (ABS resin) is used from the viewpoint of workability and lightness.

In particular, since the first coating layer 3 and the second coating layer 4 are respectively formed from a first coating composition comprising a first melamine resin and a second coating composition comprising a second melamine resin, low temperature (e.g., 60° C. or higher and 100° C. or lower). Therefore, even a resin with low heat resistance can be selected as the object to be coated 2 .

Next, in order to dispose the uncured first coating layer 3 on the surface (one side in the thickness direction) of the object 2 to be coated, as shown in FIG. , apply the first coating composition and, if necessary, dry if the first coating composition contains a solvent.

Thereby, the uncured first coating layer 3 can be arranged on the surface (one side in the thickness direction) of the object 2 to be coated. That is, the uncured first coating layer 3 can cover the surface (one side in the thickness direction) of the object 2 to be coated.

In the second step, the uncured second coating layer 4 is placed on the surface (one side in the thickness direction) of the uncured first coating layer 3 .

In order to dispose the uncured second coating layer 4 on the surface (one side in the thickness direction) of the uncured first coating layer 3, as shown in FIG. 1C, the surface of the uncured first coating layer 3 ( The second coating composition is applied to one side in the thickness direction), and dried if necessary when the first coating composition contains a solvent.

Thereby, the uncured second coating layer 4 can be arranged on the surface (one side in the thickness direction) of the uncured first coating layer 3 . That is, the surface (one side in the thickness direction) of the uncured first coating layer 3 can be covered with the uncured second coating layer 4 .

In the third step, the uncured first coating layer 3 and the uncured second coating layer 4 are cured simultaneously.

Specifically, as shown in FIG. 1D, the uncured first coating layer 3 and the uncured second coating layer 4 are heated, for example, at 60° C. or higher and 100° C. or lower, and the uncured first coating The layer 3 and the uncured second coating layer 4 are cured simultaneously.

Thereby, the coated laminate 1 is obtained. As shown in FIG. 1D, in the coated laminate 1, the surface (one side in the thickness direction) of the object 2 to be coated is covered with the first coating layer 3 (after curing), and the first coating layer 3 (after curing ) (one side in the thickness direction) is coated with the second coating layer 4 (after curing). That is, the coated laminate 1 includes the object to be coated 2, the first coating layer 3 covering the surface (one surface in the thickness direction) of the object 2 to be coated, and the surface (one surface in the thickness direction) of the first coating layer 3. and a second coating layer 4 to cover. Specifically, the coated laminate 1 includes an object to be coated 2, a first coating layer 3 directly disposed on the surface (one side in the thickness direction) of the object to be coated 2, and the surface of the first coating layer 3 (thickness and a second coating layer 4 directly disposed on one side).

The first coating layer 3 has a film shape. The first coating layer 3 is arranged on the entire bottom surface of the second coating layer 4 so as to be in contact with the bottom surface of the second coating layer 4 .

The first coating layer 3 is formed from the first coating composition as described above.

The first coating layer 3 is a pigment-containing paint layer and an undercoat layer.

The thickness of the first coating layer 3 is, for example, 5 μm or more and, for example, 40 μm or less.

The second coating layer 4 has a film shape. The second coating layer 4 is arranged on the entire upper surface of the first coating layer 3 so as to be in contact with the upper surface of the first coating layer 3 . The second coating layer 4 is the top layer of the coating laminate 1 .

The second coating layer 4 is formed from the second coating composition as described above.

The second coating layer 4 is a protective layer (topcoat layer), preferably a clear layer containing no pigment.

The thickness of the second coating layer 4 is, for example, 5 μm or more and, for example, 40 μm or less.

Also, the ratio of the thickness of the first coating layer 3 to the thickness of the second coating layer 4 (thickness of the first coating layer 3/thickness of the second coating layer 4) is, for example, 0.1 or more, preferably 0.1. 3 or more, and for example, 1.5 or less, preferably 1.0 or less.

<Effect>
In the coating composition, the first coating composition and the second coating composition each have a predetermined composition. Therefore, the coated laminate 1 having excellent adhesion, hardness, water resistance and weather resistance can be produced.

Specifically, in the coated laminate 1, the first coating layer 3 secures adhesion, while the second coating layer 4 secures hardness, water resistance, and weather resistance. As a result, the first coating layer 3 and the second coating layer 4 as a whole can ensure adhesion, hardness, water resistance, and weather resistance.

Specifically, the hydroxyl value of the first hydroxyl-containing resin in the first coating layer 3 (first coating composition) is the hydroxyl value of the second hydroxyl-containing resin in the second coating layer 4 (second coating composition). It is set relatively smaller than the value.

As a result, the first coating layer 3 having a low cross-linking density can ensure adhesion, while the second coating layer 4 having a high cross-linking density can ensure hardness, water resistance and weather resistance.

In the method for manufacturing the coated laminate 1, the uncured first coating layer 3 and the uncured second coating layer 4 are cured at the same time. Therefore, it is excellent in production efficiency.

In the coated laminate 1, the first coating layer 3 and the second coating layer 4 are respectively composed of a first coating composition and a second coating composition having predetermined compositions. Therefore, it is excellent in adhesion, hardness, water resistance and weather resistance.

The coating composition can be suitably used especially as a pre-coating paint (coating agent). Then, the coating composition and the coated laminate 1 obtained using the coating composition can be used for various industrial applications such as home electric appliance applications and vehicle applications, especially vehicle applications (for example, motorcycles Exterior), it can be suitably used.

Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited by the following examples. "Parts" and "%" are based on mass unless otherwise specified. In addition, specific numerical values such as the mixing ratio (content ratio), physical property values, and parameters used in the following description are the corresponding mixing ratios ( Content ratio), physical properties, parameters, etc. be able to.

1. Details of Components The trade names and abbreviations of the components used in each production example, each example, and each comparative example are described in detail.

MMA: methyl methacrylate n-BA: n-butyl acrylate HEMA: 2-hydroxyethyl methacrylate MAC: methacrylate PBO: t-butyl peroxy-2-ethylhexanoate, trade name "Perbutyl O", NOF T-SOL100 manufactured by Co., Ltd.: Aromatic hydrocarbon, Tinuvin123 manufactured by ENEOS Corporation: Radical scavenger, base dissociation constant pKb = 9.6, Tinuvin249 manufactured by BASF: Base dissociation constant pKb = 8.0, Tinuvin292 manufactured by BASF : Base dissociation constant pKb = 5.1, BASF Tinuvin144: base dissociation constant pKb = 5.5, BASF Tinuvin405: UV absorber, BASF Tinuvin384: UV absorber, BASF

2. Production of First Hydroxyl Group-Containing Resin or Second Hydroxyl Group-Containing Resin Production Example 1
51 g of T-SOL100 and 51 g of iso-butanol were charged into a four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet tube, and the temperature was raised to 100° C. while degassing with nitrogen. Then, a mixed solution of 50 g of MMA, 41.5 g of n-BA, 7.0 g of HEMA, 1.5 g of MAC, and 2.0 g of PBO was added dropwise over 4 hours, aged for 1 hour, and the first hydroxyl group-containing resin ( Ia1) was obtained. The solid content concentration was 50% by mass.

Production Example 2 to Production Example 9
A first hydroxyl group-containing resin was obtained in the same manner as in Production Example 1. However, the formulation was changed according to Table 1.

Production Example 10 to Production Example 13
A second hydroxyl group-containing resin was obtained in the same manner as in Production Example 1. However, the formulation was changed according to Table 2.

3. Production of first melamine resin or second melamine resin Production Example 14
126 g (1.0 mol) of melamine, 196 g (6.0 mol) of paraformaldehyde with a formalin concentration of 92% and 519 g of n-butanol were added to a four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet. (7.0 mol) was charged and the temperature was raised to the reflux temperature. The methylolation reaction was carried out at reflux temperature for 1 hour. 0.45 g (0.53 mmol) of a 20% aqueous solution of p-toluenesulfonic acid was added, and the alkylation reaction was carried out for 3 hours while dehydrating under reflux. The reaction product was then neutralized with 0.16 g (0.80 mmol) of 20% sodium hydroxide solution. Then, after distilling off the solvent under reduced pressure, the residue was diluted with n-butanol to a solid concentration of 60% by mass. Thus, a first melamine resin (I-b1) was obtained.

Production Example 15 to Production Example 19
A first melamine resin was obtained in the same manner as in Production Example 14. However, the formulation was changed according to Table 3.

Production Example 20 to Production Example 24
A second melamine resin was obtained in the same manner as in Production Example 14. However, the formulation was changed according to Table 4.

Further, as the first melamine resin (I-b5), trade name "Cymel 370" (manufactured by Daicel Ornex, solvent: iso-butanol, solid content concentration: 88%, average addition number of formaldehyde per 1 mol of melamine is 5 A melamine resin (methylated melamine resin) having a molecular weight of .8 mol and modified with methanol was prepared.

Further, as the second melamine resin (II-b3′), the product name is “Cymel 303” (manufactured by Daicel Ornex, solid content concentration: 98%, the average addition number of formaldehyde per 1 mol of melamine is 5.9 mol. , methanol-modified melamine resin (methylated melamine resin)).

4. Production of coated laminates Examples 1 to 24 and Comparative Examples 1 to 21

<Preparation of first coating composition>
A first coating composition was prepared by mixing a first hydroxyl group-containing resin, a first melamine resin, a Lewis acid catalyst, and a pigment according to the formulations shown in Tables 5 to 7. In Tables 5 to 7, the first hydroxyl group-containing resin, first melamine resin, Lewis acid catalyst, and pigment are solid content values.

<Preparation of second coating composition>
A second hydroxyl group-containing resin, a second melamine resin, a Lewis acid catalyst, a radical scavenger, and an ultraviolet absorber were mixed according to the formulations shown in Tables 5 to 7 to prepare a second coating composition. In Tables 5 to 7, the second hydroxyl group-containing resin, the second melamine resin, the Lewis acid catalyst, the radical scavenger, and the ultraviolet absorber are solid content values.

<Manufacture of coated laminate>
[First step]
ABS resin having a thickness of 2 mm was prepared as an object to be coated.

Next, the first coating composition was applied to one surface in the thickness direction of the object to be coated and dried at 25°C to form an uncured first coating layer.

[Second step]
The second coating composition was applied to one side in the thickness direction of the uncured first coating layer and dried at 25°C to form an uncured second coating layer.

[Third step]
The uncured first coating layer and the uncured second coating layer were heated at 70° C. for 20 minutes and cured simultaneously.

Thus, a coated laminate was obtained. In the coated laminate, the thickness of the first coating layer was 20 μm, and the thickness of the second coating layer was 20 μm.

5. Evaluation <acid value>
The acid value of the first hydroxyl group-containing resin and the second hydroxyl group-containing resin of each production example was measured based on JIS K 0070-1992 (potentiometric titration method). The results are shown in Tables 1 and 2.

<Hydroxyl value>
The hydroxyl value of the first hydroxyl group-containing resin and the second hydroxyl group-containing resin of each production example was measured based on JIS K 0070-1992 (acetylation method). The results are shown in Tables 1 and 2.

<Weight average molecular weight>
The weight average molecular weights of the first hydroxyl group-containing resin, the second hydroxyl group-containing resin, the first melamine resin, and the second melamine resin of each production example were measured according to the GPC method under the following measurement conditions. The results are shown in Tables 1-4.
Detector: differential refractometer (RI)
Column: TSKgel G7000 × 1, TSKgel G4000 × 2, TSKgel G2000 × 1 (all manufactured by Tosoh Corporation)
Mobile bed: Tetrahydrofuran (THF)
Column temperature: 25°C
Flow rate: 0.6 ml/min Sample concentration: 20 mg/ml (tetrahydrofuran solution)
Injection volume: 10 μl

The weight average molecular weight was calculated using a calibration curve prepared from monodisperse standard polystyrene.

<Glass transition temperature>
The first hydroxyl group-containing resin and the second hydroxyl group-containing resin of each production example were calculated by the FOX formula shown in the following formula (1).
₁ /Tg ₌ W1/Tg1 ₊ W2/Tg2+...+ _Wn / _Tgn ( ₁ )

In the above formula (1), Tg is the glass transition temperature (K) of the n kinds of first polymerized component or second polymerized component (monomer), and W ₁ , W ₂ , W _n is the mass fraction of each monomer. and W ₁ +W ₂ + . . . +W _n =1. Tg ₁ , Tg ₂ and _Tgn are glass transition temperatures (K) of homopolymers of respective monomers.

Further, the glass transition temperature of the homopolymer of the monomer can be the value described in the literature. 7 Introduction to Synthetic Resins for Paints", Kobunshi Publishing Association, pp. 168-169. The results are shown in Tables 1 and 2.

<Average addition number of formaldehyde>
For the first melamine resin and the second melamine resin of each production example, the average addition number of formaldehyde per 1 mol of melamine was measured by ¹³ C-NMR. The results are shown in Tables 3 and 4.

<Pigment Dispersibility>
Each of the first coating compositions was allowed to stand at 25°C for 24 hours. After that, the state of the first coating composition was visually observed. Pigment dispersibility was evaluated based on the following criteria. The results are shown in Tables 5-7.
[standard]
A: No sedimentation of the pigment was observed.
Good: Sedimentation of the pigment was observed, but the pigment could be redispersed by stirring.
x: Sedimentation of the pigment was observed, and the pigment was not dispersed even by stirring.

<Metal Corrosion>
A zinc phosphate-treated steel sheet was immersed in each of the first coating composition and the first coating composition maintained at 40° C. for 24 hours, and the condition of the zinc phosphate-treated steel sheet after taking out was visually observed. Metal corrosiveness was evaluated based on the following criteria. The results are shown in Tables 5-7.
[standard]
O: No coloration was observed on the steel plate.
x: Coloring due to rust was observed on the steel plate.

<Adhesion>
In accordance with JIS K5400 8.5.2: 1990, the coated laminate of each example and comparative example was cut vertically and horizontally with a 1 mm width using a knife to reach the object to be coated. . Next, an adhesive tape was adhered to the surface, and the state of the coating film was visually observed after the adhesive tape was instantly peeled off. Adhesion was evaluated based on the following criteria. The results are shown in Tables 5-7.
[standard]
◯: No peeling or chipping of the coating film was observed.
x: Peeling and chipping of the coating film were observed over the entire surface.

<Water resistance>
The coated laminate of each example and comparative example was immersed in hot water maintained at 40° C. for 8 hours, and the state after taking out was visually observed. Water resistance was evaluated based on the following criteria. The results are shown in Tables 5-7.
[standard]
A: Abnormalities such as whitening were not observed.
O: Whitening was slightly observed, but disappeared within 12 hours.
x: Remarkably whitened, whitening did not disappear.

<Pencil hardness>
In accordance with JIS K 5600-5-4, the coated laminate of each example and comparative example was applied with a pencil lead at an angle of about 45 °, and the lead was pressed forward against the coated surface of the test plate as strongly as not to break. It was moved about 10 mm at a uniform speed. The hardness symbol of the hardest pencil that did not scratch the coating film was taken as the pencil hardness. The results are shown in Tables 5-7.

<Gloss>
The 60 degree gloss of the coated test piece was measured according to JIS K 5600-4-7. Gloss was evaluated based on the following criteria. The results are shown in Tables 5-7.
[standard]
Good: The 60 degree gloss value was 90 or more.
x: The 60 degree gloss value was less than 90.

<Weather resistance>
According to JIS D 0205, the coated laminate of each example and comparative example was tested for 500 hours at a black panel temperature of 63 ± 3 ° C., and the change in color difference (ΔE) from the coated test piece at 0 hours of the test was measured. . Weather resistance was evaluated based on the following criteria. The results are shown in Tables 5-7.
[standard]
◎: 0 ≤ ΔE ≤ 1.5
○: 1.5 < ΔE ≤ 3.0
×: 3.0 < ΔE

1 coated laminate 2 object to be coated 3 first coating layer 4 second coating layer

Claims (8)

A coating composition for coating the surface of an object to be coated,
a first coating composition for forming a first coating layer covering the surface of the object to be coated;
and a second coating composition for forming a second coating layer covering the surface of the first coating layer,
The first coating composition includes the following (Ia) to (Id),
(Ia) a hydroxyl value of 20 mgKOH/g or more and 80 mgKOH/g or less;
A first hydroxyl group-containing resin having an acid value of 3 mgKOH/g or more and 50 mgKOH/g or less (excluding the first melamine resin (Ib))
(Ib) The average addition number of formaldehyde per 1 mol of melamine is 3 mol or more and 6 mol or less, and the first melamine resin modified with an alcohol having 1 or more and 6 or less carbon atoms (Ib) The electronegativity of Pauling is A Lewis acid catalyst (Id) pigment comprising a cation consisting of a metal of 1.31 or more and 2.02 or less and a counter anion that is a deprotonated form of nitric acid, and for the first melamine resin (Ib) The mass ratio of the first hydroxyl group-containing resin (Ia) (first hydroxyl group-containing resin (Ia)/first melamine resin (Ib)) is 60/40 or more and 95/5 or less,
The second coating composition includes the following (II-a) to (II-c),
(II-a) a second hydroxyl group-containing resin having a hydroxyl value of 70 mgKOH/g or more and 180 mgKOH/g or less (excluding the second melamine resin (II-b))
(II-b) The average addition number of formaldehyde per 1 mol of melamine is 3 mol or more and 6 mol or less, and the second melamine resin modified with an alcohol having 2 or more and 6 or less carbon atoms (II-c) The electronegativity of Pauling is A Lewis acid catalyst comprising a cation consisting of a metal of 1.31 or more and 2.02 or less and a counter anion that is a deprotonated form of nitric acid, and the second hydroxyl group-containing resin for the second melamine resin (II-b) A coating composition in which the mass ratio of (II-a) (second hydroxyl-containing resin (II-a)/second melamine resin (II-b)) is 60/40 or more and 95/5 or less. The coating composition according to claim 1, wherein the second coating composition further comprises (II-d) below.
(II-d) A radical scavenger having a base dissociation constant pKb of 6 or more and 14 or less An object to be coated, a first coating layer covering the surface of the object to be coated, and a second coating layer covering the surface of the first coating layer,
The first coating layer comprises a first coating composition,
The first coating composition includes the following (Ia) to (Id),
(Ia) a hydroxyl value of 20 mgKOH/g or more and 80 mgKOH/g or less;
A first hydroxyl group-containing resin having an acid value of 3 mgKOH/g or more and 50 mgKOH/g or less (excluding the first melamine resin (Ib))
(Ib) The average addition number of formaldehyde per 1 mol of melamine is 3 mol or more and 6 mol or less, and the first melamine resin modified with an alcohol having 1 or more and 6 or less carbon atoms (Ib) The electronegativity of Pauling is A Lewis acid catalyst (Id) pigment comprising a cation consisting of a metal of 1.31 or more and 2.02 or less and a counter anion that is a deprotonated form of nitric acid, and for the first melamine resin (Ib) The mass ratio of the first hydroxyl group-containing resin (Ia) (first hydroxyl group-containing resin (Ia)/first melamine resin (Ib)) is 60/40 or more and 95/5 or less,
the second coating layer comprises a second coating composition;
The second coating composition includes the following (II-a) to (II-c),
(II-a) a second hydroxyl group-containing resin having a hydroxyl value of 70 mgKOH/g or more and 180 mgKOH/g or less (excluding the second melamine resin (II-b))
(II-b) The average addition number of formaldehyde per 1 mol of melamine is 3 mol or more and 6 mol or less, and the second melamine resin modified with an alcohol having 2 or more and 6 or less carbon atoms (II-c) The electronegativity of Pauling is A Lewis acid catalyst comprising a cation comprising a metal of 1.31 or more and 2.02 or less and a counter anion that is a deprotonated form of nitric acid, and the second hydroxyl group-containing resin for the second melamine resin (II-b) A coated laminate in which the mass ratio of (II-a) (second hydroxyl group-containing resin (II-a)/second melamine resin (II-b)) is 60/40 or more and 95/5 or less. The coated laminate according to claim 3, wherein the object to be coated is a resin. 5. The coated laminate according to claim 4, wherein the resin is an acrylonitrile-styrene-butadiene copolymer resin. A first step of disposing an uncured first coating layer by applying a first coating composition to the surface of an object to be coated;
a second step of disposing an uncured second coating layer after the first step by applying a second coating composition to the surface of the uncured first coating layer;
a third step of simultaneously curing the uncured first coating layer and the uncured second coating layer;
The first coating composition includes the following (Ia) to (Id),
(Ia) a hydroxyl value of 20 mgKOH/g or more and 80 mgKOH/g or less;
A first hydroxyl group-containing resin having an acid value of 3 mgKOH/g or more and 50 mgKOH/g or less (excluding the first melamine resin (Ib))
(Ib) The average addition number of formaldehyde per 1 mol of melamine is 3 mol or more and 6 mol or less, and the first melamine resin modified with an alcohol having 1 or more and 6 or less carbon atoms (Ib) The electronegativity of Pauling is A Lewis acid catalyst (Id) pigment comprising a cation consisting of a metal of 1.31 or more and 2.02 or less and a counter anion that is a deprotonated form of nitric acid, and for the first melamine resin (Ib) The mass ratio of the first hydroxyl group-containing resin (Ia) (first hydroxyl group-containing resin (Ia)/first melamine resin (Ib)) is 60/40 or more and 95/5 or less,
The second coating composition includes the following (II-a) to (II-c),
(II-a) a second hydroxyl group-containing resin having a hydroxyl value of 70 mgKOH/g or more and 180 mgKOH/g or less (excluding the second melamine resin (II-b))
(II-b) The average addition number of formaldehyde per 1 mol of melamine is 3 mol or more and 6 mol or less, and the electronegativity of the second melamine resin (II-c) Pauling modified with an alcohol having 2 or more and 6 or less carbon atoms is A Lewis acid catalyst comprising a cation comprising a metal of 1.31 or more and 2.02 or less and a counter anion that is a deprotonated form of nitric acid, and the second hydroxyl group-containing resin for the second melamine resin (II-b) A method for producing a coated laminate, wherein the mass ratio of (II-a) (second hydroxyl group-containing resin (II-a)/second melamine resin (II-b)) is 60/40 or more and 95/5 or less. The method for producing a coated laminate according to claim 6, wherein the object to be coated is a resin. 8. The method for producing a coated laminate according to claim 7, wherein the material of the resin film is an acrylonitrile/styrene/butadiene copolymer resin.

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