Coating material, coated laminate, and method for manufacturing a coated laminate

Abstract

To provide a coating composition, a coating material, a coated laminate, and a method of manufacturing a coated laminate having excellent moisture resistance.SOLUTION: A coating composition for coating a surface of an object to be coated includes: a hydroxy group-containing resin; an alkyl-etherified melamine resin which has 3 mol or more and 6 mol or less of an average addition number of formaldehyde for 1 mol of melamine, and is modified by alcohol having carbon number 1 to 6; and Lewis acid catalyst, where the Lewis acid catalyst consists of cation consisting of a metal having Pauling electronegativity of 1.31 or more and 2.02 or less and a counter anion being a deprotonized body of protonic acid, and an SP value is 11 or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a coating composition, a coating material, a coated laminate, and a method for producing a coated laminate.

Background Art

[0002] Conventionally, in the fields of vehicle paints and home appliance paints, thermosetting resin compositions containing a polyol and an alkyl etherified melamine resin have been used.

[0003] [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0007] The present invention [1] is a coating composition for coating the surface of an object to be coated, and includes the following (A) to (C). (A) Hydroxyl group-containing resin (excluding alkyl ether-modified melamine resin (B)) (B) Alkyl etherified melamine resin modified with an alcohol having 1 to 6 carbon atoms, wherein the average number of formaldehyde added per 1 mole of melamine is between 3 moles and 6 moles. (C) A Lewis acid catalyst consisting of a cation made of a metal with a Pauling electronegativity of 1.31 to 2.02 and a counteranion which is a deprotonated protic acid, with an SP value of 11 or less.

[0008] The present invention [2] comprises the coating composition described in [1] above, wherein the protonic acid has an acid dissociation constant pKa of 1.0 or less.

[0009] The present invention [3] includes the coating composition described in [1] or [2] above, wherein the mass ratio of the hydroxyl group-containing resin (A) to the alkyl etherified melamine resin (B) (hydroxyl group-containing resin (A) / alkyl etherified melamine resin (B)) is 60 / 40 or more and 95 / 5 or less.

[0010] The present invention [4] is a coating material for coating the surface of an object to be coated, comprising a first coating material for forming a first coating layer covering the surface of the object to be coated, and a second coating material for forming a second coating layer covering the surface of the first coating layer, wherein the first coating material comprises a coating composition according to any one of [1] to [3] above and a pigment, the hydroxyl group-containing resin of the first coating material having a hydroxyl value of 20 mg KOH / g or more and 80 mg KOH / g or less, and an acid value of 3 mg KOH / g or more and 50 mg KOH / g or less, the second coating material comprises a coating composition according to any one of [1] to [3] above, the hydroxyl group-containing resin of the second coating material has a hydroxyl value of 55 mg KOH / g or more and 180 mg KOH / g or less, and the alkyl etherified melamine resin of the second coating material is modified with an alcohol having 2 to 6 carbon atoms.

[0011] The present invention [5] further comprises the coating material described in [4] above, wherein the second coating material further comprises a radical scavenger, the radical scavenger having a base dissociation constant pKb of 6 or more and 14 or less.

[0012] The present invention [6] includes a coated laminate comprising 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 is formed from the first coating material described in [4] above, and the second coating layer is formed from the second coating material described in [4] or [5] above.

[0013] The present invention [7] includes the coated laminate described in [6] above, wherein the object to be coated is a resin.

[0014] The present invention [8] includes the coated laminate described in [7] above, wherein the resin is an acrylonitrile-styrene-butadiene copolymer resin.

[0015] The present invention [9] includes a method for manufacturing a coated laminate, comprising: a first step of applying the first coating material described in [4] to the surface of an object to be coated to form an uncured first coating layer; a second step of applying the second coating material described in [4] or [5] to the surface of the uncured first coating layer after the first step to form an uncured second coating layer; and a third step of simultaneously curing the uncured first coating layer and the uncured second coating layer.

[0016] The present invention

[10] includes a method for manufacturing a coated laminate according to [9] above, wherein the object to be coated is a resin.

[0017] The present invention

[11] includes a method for producing a coated laminate as described in

[10] above, wherein the resin is an acrylonitrile-styrene-butadiene copolymer resin. [Effects of the Invention]

[0018] The coating composition of the present invention is a composition for coating the surface of an object to be coated, and comprises a hydroxyl group-containing resin, an alkyl etherified melamine resin, and a Lewis acid catalyst. The alkyl etherified melamine resin has an average number of formaldehyde additions per mole of melamine of 3 moles or more and 6 moles or less, and is modified with an alcohol having 1 to 6 carbon atoms. The Lewis acid catalyst consists of a cation made of a metal with a Pauling electronegativity of 1.31 or more and 2.02 or less, and a counteranion which is a deprotonated protic acid, and has an SP value of 11 or less. Therefore, a coating material can be prepared that has excellent moisture resistance, as well as excellent hardness, water resistance, and weather resistance.

[0019] The coating material of the present invention comprises a coating composition and includes a first coating material and a second coating material having a predetermined composition. Therefore, it is possible to manufacture a coated laminate that has excellent moisture resistance, as well as excellent hardness, water resistance, and weather resistance.

[0020] In the coated laminate of the present invention, the first coating layer and the second coating layer are each composed of a first coating material and a second coating material. Therefore, it has excellent moisture resistance, and further excellent adhesion, hardness, water resistance and weather resistance.

[0021] 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 has excellent production efficiency.

Brief Description of Drawings

[0022] [Figure 1] FIG. 1 shows an embodiment of a method for producing a coated laminate 1 of the present invention. FIG. 1A shows a step of preparing a coated object 2 in the first step. FIG. 1B shows a step of disposing an uncured first coating layer 3 on the surface (one side in the thickness direction) of the coated object 2 in the first step. FIG. 1C shows a second step of disposing an uncured second coating layer 4 on the surface (one side in the thickness direction) of the uncured first coating layer 3. FIG. 1D shows a third step of curing the uncured first coating layer 3 and the uncured second coating layer 4 simultaneously.

Embodiments for Carrying Out the Invention

[0023] <Coating Composition> The coating composition of the present invention, which will be described in detail later, is used for coating the surface of the coated object 2.

[0024] The coating composition contains a hydroxyl group-containing resin (A), an alkyl etherified melamine resin (B), and a Lewis acid catalyst (C).

[0025] [Hydroxyl Group-Containing Resin] Hydroxyl group-containing resins are resins having hydroxyl groups. Examples of hydroxyl group-containing resins include hydroxyl group-containing acrylic resins, hydroxyl group-containing polyester resins, hydroxyl group-containing epoxy resins, and hydroxyl group-containing urethane resins, with hydroxyl group-containing acrylic resins being preferred. Note that alkyl etherified melamine resins, which will be described later, are not included in the definition of hydroxyl group-containing resins.

[0026] In hydroxyl group-containing resins, the hydroxyl group-containing acrylic resin is a polymerization product of the polymerization component.

[0027] Polymerization components are monomer components. More specifically, polymerization components are polymerizable components (monomer components) that can undergo radical polymerization (vinyl polymerization).

[0028] The polymerization components include (meth)acrylic acid ester, hydroxyl group-containing vinyl monomer, optionally acid group-containing vinyl monomer, and optionally copolymerizable monomers that can copolymerize with these.

[0029] Examples of (meth)acrylic acid esters include alkyl esters of (meth)acrylic acid having 1 to 12 carbon atoms. Examples of alkyl esters of (meth)acrylic acid having 1 to 12 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)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, dodecyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, and benzyl (meth)acrylate. Preferably, alkyl esters of (meth)acrylic acid having 1 to 8 carbon atoms are used, more preferably, alkyl esters of (meth)acrylic acid having 1 to 6 carbon atoms are used, and even more preferably, methyl methacrylate and n-butyl acrylate are used. (Meth)acrylic acid esters include acrylic acid esters and / or methacrylic acid esters.

[0030] (Meth)acrylic acid esters can be used alone or in combination of two or more types.

[0031] Examples of hydroxyl group-containing vinyl monomers include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate, with 2-hydroxyethyl (meth)acrylate being preferred, and 2-hydroxyethyl methacrylate being more preferred.

[0032] Examples of vinyl monomers containing acidic groups include vinyl monomers containing carboxyl groups and vinyl monomers containing sulfonic acid groups.

[0033] Examples of carboxyl group-containing vinyl monomers include monocarboxylic acids, dicarboxylic acids, or salts thereof. Examples of monocarboxylic acids include (meth)acrylic acid. Examples of dicarboxylic acids include itaconic acid, maleic acid, fumaric acid, itaconic anhydride, maleic anhydride, and fumaric anhydride.

[0034] Examples of sulfonic acid group-containing vinyl monomers include sulfonic acid or salts thereof. Examples of sulfonic acid include allyl sulfonic acid, methallyl sulfonic acid, and acrylamide t-butyl sulfonic acid. Examples of sulfonic acid salts include alkali metal salts (e.g., sodium salts, potassium salts) and ammonium salts of the above sulfonic acid. Specifically, examples include sodium allyl sulfonate, sodium methallyl sulfonate, and ammonium methallyl sulfonate.

[0035] Examples of acidic group-containing vinyl monomers include carboxyl group-containing vinyl monomers, more preferably monocarboxylic acids, even more preferably (meth)acrylic acid, and particularly preferably methacrylic acid.

[0036] Acidic group-containing vinyl monomers can be used alone or in combination of two or more types.

[0037] Examples of copolymerizable monomers include functional group-containing vinyl monomers (excluding acid group-containing vinyl monomers and hydroxyl group-containing vinyl monomers; the same applies hereinafter), vinyl esters, aromatic vinyl monomers, N-substituted unsaturated carboxylic acid amides, heterocyclic vinyl compounds, vinylidene halides, α-olefins, and dienes.

[0038] Examples of functional group-containing vinyl monomers include amino group-containing vinyl monomers, cyano group-containing vinyl monomers, glycidyl group-containing vinyl monomers, and acetoacetoxy group-containing vinyl monomers.

[0039] Examples of amino group-containing vinyl monomers include 2-aminoethyl (meth)acrylate, 2-(N-methylamino)ethyl (meth)acrylate, and 2-(N,N-dimethylamino)ethyl (meth)acrylate.

[0040] Examples of cyano group-containing vinyl monomers include (meth)acrylonitrile.

[0041] Examples of vinyl monomers containing a glycidyl group include glycidyl (meth)acrylate.

[0042] Examples of vinyl monomers containing an acetoacetoxy group include acetoacetoxyethyl (meth)acrylate.

[0043] Examples of vinyl esters include vinyl acetate and vinyl propionate.

[0044] Examples of aromatic vinyl monomers include styrene and α-methylstyrene.

[0045] An example of an N-substituted unsaturated carboxylic acid amide is N-methylol(meth)acrylamide.

[0046] Examples of heterocyclic vinyl compounds include vinylpyrrolidone.

[0047] Examples of vinylidene halogen compounds include vinylidene chloride and vinylidene fluoride.

[0048] Examples of α-olefins include ethylene and propylene.

[0049] Examples of dienes include butadiene.

[0050] Furthermore, crosslinkable vinyl monomers can also be cited as copolymerizable monomers.

[0051] 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, trimethylolpropanetetraacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

[0052] Copolymerizable monomers can be used individually or in combination of two or more types.

[0053] Furthermore, hydroxyl group-containing acrylic resin is obtained by polymerizing the polymerization components.

[0054] The polymerization method is not particularly limited. Examples of polymerization methods include bulk polymerization and solution polymerization, with solution polymerization being preferred.

[0055] When solution polymerization is used as the polymerization method, the polymerization component and, if necessary, the polymerization initiator are mixed with the solvent, and polymerization is carried out.

[0056] Examples of solvents include well-known solvents. Examples of solvents include alkyl esters (e.g., butyl acetate) and alcohols (isobutanol).

[0057] Furthermore, commercially available solvents can also be used. Examples of commercially available solvents include the Solvesso series (aromatic hydrocarbons, manufactured by ExxonMobil Corporation).

[0058] Solvents can be used alone or in combination of two or more types.

[0059] Examples of polymerization initiators include peroxide-based radical polymerization initiators (e.g., t-butylperoxy-2-ethylhexanoate).

[0060] The proportion of polymerization initiators used is determined appropriately according to the purpose and application.

[0061] The polymerization conditions include a polymerization temperature of, for example, 70°C or higher, and for example, 120°C or lower. The polymerization time is, for example, 1 hour or more, and for example, 12 hours or less.

[0062] This yields a hydroxyl group-containing acrylic resin.

[0063] The weight-average molecular weight (Mw) of the hydroxyl group-containing resin, measured by gel permeation chromatography (GPC) and converted to polystyrene, is, for example, 5000 or more, preferably 8000, more preferably 10000 or more, and also, for example, 200000 or less, preferably 100000 or less, more preferably 80000 or less, even more preferably 40000 or less, particularly preferably 30000 or less, and most preferably 25000 or less.

[0064] If the above weight-average molecular weight is within the above range, a coating layer with excellent paintability, appearance, strength, hardness, and abrasion resistance can be formed.

[0065] The glass transition temperature of the hydroxyl group-containing resin is, for example, -30°C or higher, preferably -20°C or higher, more preferably 0°C or higher, even more preferably 5°C or higher, and also, for example, 80°C or lower, preferably 60°C or lower, more preferably 50°C or lower, and even more preferably 30°C or lower.

[0066] If the above glass transition temperature is within the above range, a coating layer with excellent paintability, hardness, and water resistance can be formed.

[0067] The method for measuring the glass transition temperature will be described in detail in the examples below (the same applies hereafter).

[0068] [Alkyl etherified melamine resin] Alkyl etherified melamine resin is obtained by modifying (alkylating) at least a portion of the methylol groups of melamine resin obtained from melamine and formaldehyde with alcohol.

[0069] Formaldehyde can be prepared as an aqueous solution. Alternatively, solid paraformaldehyde can be used directly.

[0070] When formaldehyde is prepared as an aqueous solution, its concentration is, for example, 80% by mass or more, and for example, 99% by mass or less.

[0071] In alkyl etherified melamine resins, the alcohol is an alcohol having 1 to 6 carbon atoms. On the other hand, if the alcohol has 7 or more carbon atoms, the alcohol does not volatilize during heat curing, reducing the curability of the coating composition and decreasing its 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. Examples of linear monohydric alcohols having 1 to 6 carbon atoms include 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.

[0072] Preferably, the alcohol is a linear monohydric alcohol having 1 to 6 carbon atoms, more preferably a linear monohydric alcohol having 1 to 4 carbon atoms, and even more preferably methanol, ethanol, and n-butanol.

[0073] Alcohol can be used alone or in combination of two or more types.

[0074] To obtain alkyl etherified melamine resin, first, melamine and formaldehyde are subjected to a methylolation reaction to obtain melamine resin.

[0075] To carry out the methylolation reaction between melamine and formaldehyde, melamine and formaldehyde are mixed together. Specifically, the amount of formaldehyde added per mole of melamine is 3 moles or more, preferably 4 moles or more, and 6 moles or less.

[0076] If the above average number of added crosslinks is above the above lower limit, the crosslink density can be improved, and water resistance can be improved.

[0077] On the other hand, if the average number of added particles is below the lower limit, the moisture resistance and water resistance will decrease.

[0078] The above average number of additions is, for example, 13 It can be calculated by analysis using 1C-NMR (the same applies below).

[0079] Furthermore, if formaldehyde is added to all three amino groups of melamine, the average number of formaldehyde molecules added is 6 moles.

[0080] Furthermore, in the methylolation reaction described above, alcohol is added beforehand along with melamine and formaldehyde. The proportion of alcohol added is, for example, 4 moles or more, preferably 6 moles or more, and for example, 8 moles or less, per mole of melamine.

[0081] After the methylolation reaction, an acid catalyst is added, and at least a portion of the methylol groups of the melamine resin are modified (alkyl etherified) with alcohol.

[0082] Examples of acid catalysts include organic acids and inorganic acids. Examples of organic acids include formic acid, oxalic acid, and p-toluenesulfonic acid. Examples of inorganic acids include phosphoric acid, hydrochloric acid, sulfuric acid, and nitric acid. Preferably, the acid catalyst is an organic acid, and more preferably, p-toluenesulfonic acid.

[0083] Acid catalysts can be used alone or in combination of two or more types.

[0084] The proportion of the acid catalyst is set appropriately according to the purpose and application.

[0085] The reaction conditions include a reaction temperature that is the reflux temperature of the alcohol, for example, 60°C or higher, and for example, 120°C or lower. The reaction time is for example, 1 hour or more, and for example, 12 hours or less.

[0086] Subsequently, a neutralizing agent (e.g., sodium hydroxide) is added to neutralize the reaction product.

[0087] This yields an alkyl etherified melamine resin. Such an alkyl etherified melamine resin has an average number of formaldehyde additions per mole of melamine of 3 moles or more and 6 moles or less, and is an alkyl etherified melamine resin modified with an alcohol having 1 to 6 carbon atoms.

[0088] The weight-average molecular weight (Mw) of the alkyl etherified melamine resin, measured by gel permeation chromatography (GPC), is, for example, 800 or more, preferably 1000, more preferably 1100 or more, even more preferably 1800 or more, and also, for example, 15000 or less, preferably 7000 or less, more preferably 5000 or less, even more preferably 2500 or less.

[0089] If the above weight-average molecular weight is within the above range, a coating layer with excellent mechanical properties, smoothness, and appearance can be formed.

[0090] <Lewis acid catalyst> Lewis acid catalysts consist of a cation and a counteranion.

[0091] The cation is a metal cation with a Pauling electronegativity of 1.31 or higher and 2.02 or lower. More specifically, the Pauling electronegativity is 1.31 or higher, preferably 1.50 or higher, more preferably 1.60 or higher, and 2.02 or lower, preferably 1.95 or lower.

[0092] If the electronegativity is above the lower limit mentioned above, a coating layer with excellent water resistance, hardness, and weather resistance can be formed.

[0093] Furthermore, if the electronegativity is below the above upper limit, a coating layer with excellent water resistance, hardness, and weather resistance can be formed.

[0094] Examples of metals with a Pauling electronegativity of 1.31 or higher and 2.02 or lower include magnesium, manganese, aluminum, cobalt, nickel, tin, zinc, copper, and bismuth, preferably aluminum, nickel, and zinc, and more preferably aluminum and nickel.

[0095] The counter anion is the deprotonated form of a protonate.

[0096] The acid dissociation constant pKa of the protonic acid is, for example, 5.0 or less, preferably 1.0 or less, more preferably -1.0 or less, and even more preferably -1.5 or less. Note that the above acid dissociation constant is the value when water is used as the solvent.

[0097] If the acid dissociation constant pKa of the protonic acid is below the above upper limit, a coating layer with excellent water resistance, hardness, and weather resistance can be formed.

[0098] Examples of protonic acids include inorganic acids and organic acids, with organic acids being preferred.

[0099] Examples of inorganic acids include hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid.

[0100] Examples of organic acids include carboxylic acids and sulfonic acids. Examples of carboxylic acids include acetic acid, propionic acid, octic acid, and stearic acid, with octic acid being preferred. Examples of sulfonic acids include toluenesulfonic acid, benzenesulfonic acid, and dodecylbenzenesulfonic acid, with dodecylbenzenesulfonic acid being preferred.

[0101] The Lewis acid catalyst has a Hildebrand solubility parameter value (SP value) of 11.0 or less, preferably 10.5 or less, and more preferably 10 or less.

[0102] If the SP value of the Lewis acid catalyst is below the above upper limit, it has low polarity and is hydrophobic, thus forming a coating layer with excellent moisture resistance.

[0103] Examples of such Lewis acid catalysts include aluminum dodecylbenzenesulfonate, nickel dodecylbenzenesulfonate, and zinc octoate, with aluminum dodecylbenzenesulfonate and nickel dodecylbenzenesulfonate being preferred.

[0104] <Preparation of coating composition> The coating composition is obtained by mixing a hydroxyl group-containing resin, an alkyl etherified melamine resin, and a Lewis acid catalyst.

[0105] Furthermore, when a solvent is used in the preparation of hydroxyl group-containing resins and alkyl etherified melamine resins, the coating composition will contain the solvent.

[0106] Furthermore, known additives may be incorporated into the coating composition as needed.

[0107] In the coating composition, the mass ratio of the hydroxyl group-containing resin (A) to the alkyl etherified melamine resin (B) (hydroxyl group-containing resin (A) / alkyl etherified melamine resin (B)) is, for example, 60 / 40 or more, preferably 70 / 30 or more, and for example, 95 / 5 or less.

[0108] If the above mass ratio is above the above lower limit, a coating layer with excellent water resistance, hardness, and weather resistance can be formed.

[0109] If the above mass ratio is below the above upper limit, a coating layer with excellent water resistance, hardness, and weather resistance can be formed.

[0110] 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, and for example, 5 parts by mass or less, preferably 4 parts by mass or less, and more preferably 2 parts by mass or less, based on 100 parts by mass of the total amount of the hydroxyl group-containing resin and alkyl etherified melamine resin.

[0111] If the blending ratio of the Lewis acid catalyst is within the above range, a coating composition with excellent storage stability and low-temperature curing properties can be obtained.

[0112] <Coating material> The coating material of the present invention, as will be described in more detail later, is used to coat the surface of the object to be coated 2.

[0113] The coating material comprises a first coating material and a second coating material. More specifically, the first coating material and the second coating material form a first coating layer 3 and a second coating layer 4, respectively. In other words, a mixture of the first coating material and the second coating material does not form the first coating layer 3 or the second coating layer 4.

[0114] <First coating material> The first coating material, as will be described in more detail later, is a coating material for forming a first coating layer 3 that covers the surface of the object to be coated 2.

[0115] The first coating material comprises the above-described coating composition and a pigment (Id).

[0116] In the following, the coating composition contained in the first coating material will be referred to as the first coating composition, and the hydroxyl group-containing resin (A), alkyl etherified melamine resin (B), and Lewis acid catalyst (C) in the first coating composition will be referred to as the first hydroxyl group-containing resin (Ia), the first alkyl etherified melamine resin (Ib), and the first Lewis acid catalyst (Ic), respectively.

[0117] Furthermore, detailed explanations of compositions similar to those described above will be omitted.

[0118] [Resin containing the first hydroxyl group] The first hydroxyl group-containing resin (Ia) has a predetermined acid value and a predetermined hydroxyl group value.

[0119] The first hydroxyl group-containing resin (Ia) preferably contains an acidic group-containing vinyl monomer as a polymerization component. Including an acidic group-containing vinyl monomer in the polymerization component improves the dispersibility of the pigment (described later).

[0120] In the first hydroxyl group-containing resin (Ia), the blending ratio of (meth)acrylic acid ester is, for example, 70 parts by mass or more, preferably 80 parts by mass or more, and for example, 95 parts by mass or less, preferably 90 parts by mass or less, per 100 parts by mass of the polymer component.

[0121] Furthermore, the proportion of the acidic group-containing vinyl monomer is, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and also, for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, per 100 parts by mass of the polymerized component.

[0122] If the blending ratio of the acidic group-containing vinyl monomer is within the above-mentioned range, the acid value (described later) of the first hydroxyl group-containing resin (Ia) can be adjusted to a predetermined range described later.

[0123] Furthermore, the proportion of 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 or less, and more preferably 12 parts by mass or less, per 100 parts by mass of the polymerized component.

[0124] 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 (Ia) can be adjusted to a predetermined range described later.

[0125] Furthermore, the blending ratio of copolymerizable monomers 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, per 100 parts by mass of polymerized components.

[0126] In the first hydroxyl group-containing resin (Ia), the polymerization component preferably does not contain copolymerizable monomers and comprises (meth)acrylic acid ester, acid group-containing vinyl monomer, and hydroxyl group-containing vinyl monomer, and more preferably, in the first hydroxyl group-containing resin (Ia), the polymerization component consists of (meth)acrylic acid ester, acid group-containing vinyl monomer, and hydroxyl group-containing vinyl monomer.

[0127] The hydroxyl value of the first hydroxyl group-containing resin (Ia) is, for example, 20 mg KOH / g or more, preferably 40 mg KOH / g or more, and 80 mg KOH / g or less, preferably 60 mg KOH / g or less.

[0128] If the above hydroxyl value is above the above lower limit, the crosslinking density will improve, and a first coating layer with excellent water resistance can be obtained.

[0129] Furthermore, if the above hydroxyl value is below the above upper limit, the increase in curing shrinkage of the first coating layer can be suppressed, thereby obtaining a first coating layer with excellent adhesion.

[0130] Furthermore, as will be explained in more detail later, preferably, the hydroxyl value of the first hydroxyl group-containing resin (Ia) is set to be smaller than the hydroxyl value of the second hydroxyl group-containing resin (II-a) (described later).

[0131] The above hydroxyl value can be determined, for example, by JIS K 0070-1992 (acetylation method) (the same applies hereinafter).

[0132] The acid value of the primary hydroxyl group-containing resin (Ia) is, for example, 3 mg KOH / g or more, preferably 7 mg KOH / g or more, and 50 mg KOH / g or less, preferably 30 mg KOH / g or less, and more preferably 20 mg KOH / g or less.

[0133] If the above acid value is above the above lower limit, a first coating material with excellent pigment dispersibility can be obtained.

[0134] Furthermore, if the above acid value is below the above upper limit, a first coating layer 3 with excellent water resistance can be obtained.

[0135] The above acid value can be determined, for example, by JIS K 0070-1992 (potentiometric titration method) (the same applies hereinafter).

[0136] [Pigments] Examples of pigments (Id) include coloring pigments, luminescence pigments, and extender pigments.

[0137] Examples of coloring pigments include titanium dioxide, zinc oxide, carbon black, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, slene pigments, and perylene pigments.

[0138] Examples of luminous pigments include aluminum powder, aluminum paste, mica powder, and mica powder coated with titanium dioxide.

[0139] Examples of extender pigments include talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, and alumina white.

[0140] Preferably, as the pigment (Id), an acidic group-containing vinyl monomer (preferably a carboxyl group-containing vinyl monomer) is used, from the viewpoint of improving dispersibility, a lustrous pigment (Id), and more preferably, an aluminum paste, are used.

[0141] Pigments (Id) can be used alone or in combination of two or more types.

[0142] <Preparation of the first coating material> The first coating material is obtained by mixing the above-described coating composition (first coating composition) with a pigment (Id).

[0143] Furthermore, known additives may be incorporated into the first coating material as needed.

[0144] The blending ratio of the first hydroxyl group-containing resin (Ia) is, for example, 50 parts by mass or more, preferably 60 parts by mass or more, more preferably 70 parts by mass or more, and also, for example, 90 parts by mass or less, preferably 80 parts by mass or less, per 100 parts by mass of the first coating material.

[0145] The blending ratio of the first alkyl etherified melamine resin (Ib) is, for example, 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and also, for example, 40 parts by mass or less, preferably 30 parts by mass or less, more preferably 20 parts by mass or less, per 100 parts by mass of the first coating material.

[0146] The blending ratio of the first Lewis acid catalyst (Ic) is, for example, 0.01 parts by mass or more, preferably 0.1 parts by mass or more, and for example, 5 parts by mass or less, preferably 4 parts by mass or less, and more preferably 2 parts by mass or less, based on 100 parts by mass of the total amount of the first hydroxyl group-containing resin (Ia) and the first melamine resin.

[0147] The blending ratio of the first Lewis acid catalyst (Ic) 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 5 parts by mass or less, and more preferably 2 parts by mass or less, per 100 parts by mass of the first coating material.

[0148] If the blending ratio of the first Lewis acid catalyst (Ic) is within the above range, a first coating material with excellent storage stability and low-temperature curing properties can be obtained.

[0149] The proportion of pigment (Id) is, for example, 1 part by mass or more, preferably 2 parts by mass or more, more preferably 4 parts by mass or more, or, for example, 200 parts by mass or less, preferably 100 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 10 parts by mass or less, per 100 parts by mass of the first coating composition.

[0150] Furthermore, the blending ratio of the pigment (Id) 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 or less, per 100 parts by mass of the first coating material.

[0151] As will be explained in more detail later, the first coating layer 3 is obtained by applying the first coating material to the surface (one side in the thickness direction) of the object to be coated 2 and curing it.

[0152] <Second coating material> The second coating material, as will be explained in more detail later, is a coating material for forming the second coating layer 4 that covers the surface of the first coating layer 3.

[0153] The second coating material comprises the above-described coating composition and, if necessary, a radical scavenger (II-d).

[0154] In the following, the coating composition contained in the second coating material will be referred to as the second coating composition, and the hydroxyl group-containing resin (A), alkyl etherified melamine resin (B), and Lewis acid catalyst (C) in the second coating composition will be referred to as the second hydroxyl group-containing resin (II-a), the second alkyl etherified melamine resin (II-b), and the second Lewis acid catalyst (II-c), respectively.

[0155] Furthermore, detailed explanations of compositions similar to those described above will be omitted.

[0156] [Resin containing a second hydroxyl group] The second hydroxyl group-containing resin (II-a) is a resin having a predetermined hydroxyl value. Specifically, the second hydroxyl group-containing resin (II-a) has a different hydroxyl value than the first hydroxyl group-containing resin (Ia) described above. Furthermore, as will be described later, when the second coating layer becomes a clear layer, the second coating material does not contain pigment, and therefore pigment dispersibility is not required. For this reason, in such cases, the acid value of the second hydroxyl group-containing resin (II-a) is not required.

[0157] In the second hydroxyl group-containing resin (II-a), as described above, an acid value may not be required, therefore, the polymerization component may contain an acid group-containing vinyl monomer as needed.

[0158] In the second hydroxyl group-containing resin (II-a), the blending ratio of (meth)acrylic acid ester is, for example, 60 parts by mass or more, preferably 70 parts by mass or more, and for example, 95 parts by mass or less, preferably 90 parts by mass or less, more preferably 86 parts by mass or less, and even more preferably 80 parts by mass or less, per 100 parts by mass of the polymerization component. The blending ratio of (meth)acrylic acid ester in the polymerization component in the second hydroxyl group-containing resin (II-a) is preferably set to be smaller than the blending ratio of (meth)acrylic acid ester in the polymerization component in the first hydroxyl group-containing resin (Ia).

[0159] Furthermore, the proportion of 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, or, for example, 40 parts by mass or less, preferably 35 parts by mass or less, more preferably 30 parts by mass or less, per 100 parts by mass of the polymerized component.

[0160] If the blending ratio of hydroxyl group-containing vinyl monomer is within the above-mentioned range, the hydroxyl value (described later) of the second hydroxyl group-containing resin (II-a) can be adjusted to a predetermined range described later.

[0161] Furthermore, the proportion of hydroxyl group-containing vinyl monomer in the polymerization component of the second hydroxyl group-containing resin (II-a) is preferably set to be greater than the proportion of hydroxyl group-containing vinyl monomer in the polymerization component of the first hydroxyl group-containing resin (Ia). This makes it possible to make the hydroxyl value of the second hydroxyl group-containing resin (II-a) greater than that of the first hydroxyl group-containing resin (Ia).

[0162] Furthermore, the proportion 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 polymerized component.

[0163] If the blending ratio of the acidic group-containing vinyl monomer is within the range described above, the acid value (described later) of the dihydroxyl group-containing resin (II-a) can be adjusted to a predetermined range described later.

[0164] Furthermore, the proportion of acidic group-containing vinyl monomer in the polymerization component of the second hydroxyl group-containing resin (II-a) is preferably set to be smaller than the proportion of acidic group-containing vinyl monomer in the polymerization component of the first hydroxyl group-containing resin (Ia). This makes it possible to make the acid value of the second hydroxyl group-containing resin (II-a) smaller than that of the first hydroxyl group-containing resin (Ia).

[0165] Furthermore, the blending ratio of copolymerizable monomers is, for example, 0.1 parts by mass or more, and for example, 10 parts by mass or less, per 100 parts by mass of polymerized components.

[0166] In the second hydroxyl group-containing resin (II-a), the polymerization component preferably does not contain copolymerizable monomers and comprises (meth)acrylic acid ester, hydroxyl group-containing vinyl monomer, and acid group-containing vinyl monomer, and more preferably the polymerization component consists of (meth)acrylic acid ester, hydroxyl group-containing vinyl monomer, and acid group-containing vinyl monomer.

[0167] The hydroxyl value of the second hydroxyl group-containing resin (II-a) is, for example, 55 mgKOH / g or more, preferably 60 mgKOH / g or more, more preferably 90 mgKOH / g or more, even more preferably 110 mgKOH / g or more, and also, for example, 180 mgKOH / g or less, preferably 140 mgKOH / g or less.

[0168] If the above hydroxyl value is above the above lower limit, the crosslinking density will improve, and a second coating layer 4 with excellent water resistance can be obtained.

[0169] Furthermore, if the hydroxyl value is below the upper limit, the increase in curing shrinkage of the second coating layer 4 can be suppressed, thereby obtaining a second coating layer 4 with excellent adhesion.

[0170] Furthermore, as will be described in more detail later, preferably, the hydroxyl value of the second hydroxyl group-containing resin (II-a) is set to be greater than the hydroxyl value of the first hydroxyl group-containing resin (Ia).

[0171] The acid value of the second hydroxyl group-containing resin (II-a) is, for example, 0 mg KOH / g or more, preferably 0.5 mg KOH / g or more, more preferably 1 mg KOH / g or more, and for example, 50 mg KOH / g or less, preferably 30 mg KOH / g or less, more preferably 20 mg KOH / g, even more preferably 10 mg KOH / g or less, and particularly preferably 5 mg KOH / g or less.

[0172] If the acid value of the second hydroxyl group-containing resin (II-a) is within the above range, a second coating material with excellent compatibility and curability can be obtained.

[0173] Furthermore, preferably, the acid value of the second hydroxyl group-containing resin (II-a) is set to be lower than the acid value of the first hydroxyl group-containing resin (Ia).

[0174] [Second alkyl ether-modified melamine resin] In the second alkyl etherified melamine resin, the alcohol is an alcohol having 2 to 6 carbon atoms. 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. Examples of linear monohydric alcohols having 2 to 6 carbon atoms include 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.

[0175] Preferably, the alcohol is a linear monohydric alcohol having 2 to 6 carbon atoms, more preferably a linear monohydric alcohol having 2 to 4 carbon atoms, and even more preferably ethanol and n-butanol. In other words, preferably, the alcohol in the second melamine resin is selected to have more carbon atoms than the alcohol in the first melamine resin. This improves water resistance.

[0176] [Radical scavenger] Radical scavenger (II-d) is used as a radical chain inhibitor to capture active radical species generated during the degradation process of the second coating layer.

[0177] Examples of radical scavengers (II-d) include hindered piperidines. Alternatively, known polymerizable light stabilizers can be used as radical scavengers (II-d).

[0178] The base dissociation constant pKb of the radical scavenger (II-d) is, for example, 6 or more, preferably 7.5 or more, more preferably 8.5 or more, and also, for example, 14 or less.

[0179] If the base dissociation constant pKb is within the above range, acid-base reactions with the second Lewis acid catalyst can be suppressed, and active radical species generated during the degradation process of the second coating layer 4 can be captured within a range that does not impair catalytic activity.

[0180] Furthermore, commercially available radical scavengers (II-d) can also be used. Specifically, these include Tinuvin 249 (pKb=8.0), Tinuvin 152 (pKb=7.0 and 9.4), Tinuvin 123 (pKb=9.6) (all manufactured by BASF), HOSTAVIN 3058LIQ (manufactured by Clariant), and ADEKA LA-81.

[0181] <Preparation of the second coating material> The second coating material is obtained by mixing the above-described coating composition (second coating composition) with a radical scavenger (II-d) if necessary.

[0182] Furthermore, the second coating material may contain known additives (e.g., UV absorbers) as needed.

[0183] The ultraviolet absorber used is preferably one that can suppress discoloration caused by complex formation with the Lewis acid catalyst. Examples of such ultraviolet absorbers include cyanoacrylate-based ultraviolet absorbers and triazine-based ultraviolet absorbers. Examples of cyanoacrylate-based ultraviolet absorbers include Uvinul 3030, Uvinul 3035, Uvinul 3039C (manufactured by BASF), and SEESORB 501, SEESORB 502 (manufactured by Cipro Chemical Co., Ltd.). Examples of triazine-based UV absorbers include ADEKA LA-46, ADEKA LA-F70 (manufactured by ADEKA Corporation), Tinvin 400, Tinvin 405, Tinvin 460, Tinvin 477, Tinvin 479 (manufactured by BASF Corporation), KEMISORB 102 (manufactured by Chemipro Chemical Co., Ltd.), EVERSORB 40, EVERSORB 41FD, and EVERSORB 45 (manufactured by Everlight Chemical Corporation).

[0184] The blending ratio of the second hydroxyl group-containing resin (II-a) is, for example, 50 parts by mass or more, preferably 60 parts by mass or more, more preferably 70 parts by mass or more, and also, for example, 90 parts by mass or less, preferably 80 parts by mass or less, per 100 parts by mass of the second coating material.

[0185] Furthermore, the blending ratio of the second alkyl etherified melamine resin (II-b) is, for example, 5 parts by mass or more, preferably 10 parts by mass or more, preferably 15 parts by mass or more, and also, for example, 40 parts by mass or less, preferably 30 parts by mass or less, and more preferably 20 parts by mass or less, per 100 parts by mass of the second coating material.

[0186] The blending ratio of the second Lewis acid catalyst (II-c) is, for example, 0.01 parts by mass or more, preferably 0.1 parts by mass or more, and for example, 5 parts by mass or less, preferably 4 parts by mass or less, and more preferably 2 parts by mass or less, based on 100 parts by mass of the total amount of the second hydroxyl group-containing resin (II-a) and the second melamine resin.

[0187] Furthermore, the blending ratio of the second Lewis acid catalyst (II-c) 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 5 parts by mass or less, and more preferably 2 parts by mass or less, per 100 parts by mass of the second coating material.

[0188] If the blending ratio of the second Lewis acid catalyst (II-c) is within the above range, a second coating material with excellent storage stability and low-temperature curing properties can be obtained.

[0189] Furthermore, the blending ratio of the radical scavenger (II-d) 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 5 parts by mass or less, and more preferably 1 part by mass or less, per 100 parts by mass of the second coating material.

[0190] As will be explained in more detail later, the second coating layer 4 is obtained by applying the second coating material to the surface (one side in the thickness direction) of the first coating layer 3 and curing it.

[0191] <Manufacturing method for coated laminates (method of using coating materials)> The coating material is used to coat the surface of the object to be coated 2. By coating the object to be coated 2, a coated laminate 1 is manufactured.

[0192] Referring to Figure 1, one embodiment of the method for manufacturing the coated laminate 1 of the present invention will be described.

[0193] In Figure 1, the vertical direction of the paper is the vertical direction (thickness direction), with the top of the paper being the top (one side in the thickness direction) and the bottom of the paper being the bottom (the other side in the thickness direction). The horizontal and depth directions of the paper are plane directions perpendicular to the vertical direction. Specifically, these correspond to the directional arrows in each figure.

[0194] The method for manufacturing the coated laminate 1 comprises a first step of applying a first coating material to the surface (one side in the thickness direction) of the object to be coated 2 to form an uncured first coating layer 3; a second step of applying a second coating material to the surface (one side in the thickness direction) of the uncured first coating layer 3 after the first step to form an uncured second coating layer 4; and a third step of simultaneously curing the uncured first coating layer 3 and the uncured second coating layer 4.

[0195] In the first step, an uncured first coating layer 3 is placed on the surface (one side in the thickness direction) of the object to be coated 2.

[0196] In the first step, as shown in Figure 1A, the object to be painted 2 is first prepared.

[0197] The object to be coated 2 is an object to be coated in which various physical properties are imparted to its surface (one side in the thickness direction) by the first coating layer 3 and the second coating layer 4.

[0198] In Figure 1A, the object to be painted 2 has a flat plate shape, but the shape of the object to be painted 2 is not particularly limited, and various shapes can be selected.

[0199] Examples of the object to be coated 2 include resin and metal.

[0200] Examples of resins include polystyrene resin, (meth)acrylic resin (including acrylic resin and / or methacrylic resin), polyolefin resin, polycarbonate resin, polyamide resin, polyimide resin, acrylonitrile-styrene-butadiene copolymer resin (ABS resin), polystyrene resin, polyvinylidene chloride, styrene-acrylonitrile copolymer resin, and cellulose acetate. Examples of polystyrene resins include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of (meth)acrylic resins include polymethyl methacrylate resin (PMMA). Examples of polyolefin resins include polyethylene resin and polypropylene resin.

[0201] Examples of metals include iron, aluminum, zinc, and stainless steel.

[0202] Preferably, the object to be coated 2 is a resin, more preferably an acrylonitrile-styrene-butadiene copolymer resin (ABS resin), from the viewpoint of processability and light weight.

[0203] In particular, since the first coating layer 3 and the second coating layer 4 are formed from a first coating material containing a first alkyl etherified melamine resin (Ib) and a second coating material containing a second alkyl etherified melamine resin (II-b), respectively, they can be cured at low temperatures (for example, between 60°C and 100°C). Therefore, even resins with low heat resistance can be selected as the substrate 2.

[0204] Next, in order to place the uncured first coating layer 3 on the surface (one side in the thickness direction) of the object to be coated 2, as shown in Figure 1B, the first coating material is applied to the surface (one side in the thickness direction) of the object to be coated 2, and if the first coating material contains a solvent, it is dried as necessary.

[0205] This allows an uncured first coating layer 3 to be placed on the surface (one side in the thickness direction) of the object to be coated 2. In other words, the surface (one side in the thickness direction) of the object to be coated 2 can be covered with the uncured first coating layer 3.

[0206] In the second step, an uncured second coating layer 4 is placed on the surface (one side in the thickness direction) of the uncured first coating layer 3.

[0207] To place 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 Figure 1C, the second coating material is applied to the surface (one side in the thickness direction) of the uncured first coating layer 3, and if the second coating material contains a solvent, it is dried as necessary.

[0208] This allows the uncured second coating layer 4 to be placed on the surface (one side in the thickness direction) of the uncured first coating layer 3. In other words, 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.

[0209] In the third step, the uncured first coating layer 3 and the uncured second coating layer 4 are cured simultaneously.

[0210] Specifically, as shown in Figure 1D, the uncured first coating layer 3 and the uncured second coating layer 4 are heated, for example, at a temperature of 60°C or higher and 100°C or lower, to cure the uncured first coating layer 3 and the uncured second coating layer 4 simultaneously.

[0211] This results in a coated laminate 1. As shown in Figure 1D, in the coated laminate 1, the surface (one side in the thickness direction) of the object to be coated 2 is covered by a first coating layer 3 (after curing), and the surface (one side in the thickness direction) of the first coating layer 3 (after curing) is covered by a second coating layer 4 (after curing). In other words, the coated laminate 1 comprises an object to be coated 2, a first coating layer 3 that covers the surface (one side in the thickness direction) of the object to be coated 2, and a second coating layer 4 that covers the surface (one side in the thickness direction) of the first coating layer 3. Specifically, the coated laminate 1 comprises an object to be coated 2, a first coating layer 3 that is directly placed on the surface (one side in the thickness direction) of the object to be coated 2, and a second coating layer 4 that is directly placed on the surface (one side in the thickness direction) of the first coating layer 3.

[0212] The first coating layer 3 has a film shape. The first coating layer 3 is arranged to cover the entire upper surface of the object to be coated 2 so as to be in contact with the upper surface of the object to be coated 2.

[0213] As described above, the first coating layer 3 is formed from the first coating material.

[0214] The first coating layer 3 is a paint layer containing pigment, and also serves as a primer layer.

[0215] The thickness of the first coating layer 3 is, for example, 5 μm or more, and for example, 40 μm or less.

[0216] The second coating layer 4 has a film shape. The second coating layer 4 is positioned over 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 uppermost layer of the coated laminate 1.

[0217] The second coating layer 4 is formed from the second coating material, as described above.

[0218] The second coating layer 4 is a protective layer (top coat layer), and is preferably a clear layer that does not contain pigment.

[0219] The thickness of the second coating layer 4 is, for example, 5 μm or more, and for example, 40 μm or less.

[0220] Furthermore, 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 0.3 or more, and for example, 1.5 or less, preferably 1.0 or less.

[0221] <Effects and Effects> The coating composition is a coating composition for the surface of an object to be coated, and contains a hydroxyl group-containing resin, an alkyl etherified melamine resin, and a Lewis acid catalyst. The alkyl etherified melamine resin has an average number of formaldehyde additions per mole of melamine of 3 moles or more and is modified with an alcohol having 1 to 6 carbon atoms. The Lewis acid catalyst consists of a cation made of a metal with a Pauling electronegativity of 1.31 or more and a counteranion which is a deprotonated protic acid, and has an SP value of 11 or less. Therefore, a coating material with excellent moisture resistance, as well as excellent hardness, water resistance, and weather resistance can be prepared. In particular, if the average number of formaldehyde additions per mole of melamine is 3 moles or more, the crosslinking density can be improved, and water resistance can be improved. Furthermore, if the SP value of the Lewis acid catalyst is 11 or less, it has low polarity and is hydrophobic, so a coating layer with excellent moisture resistance can be formed.

[0222] Furthermore, if the acid dissociation constant pKa of the protonic acid is 1.0 or less, a coating layer with excellent water resistance, hardness, and weather resistance can be formed.

[0223] The coating material comprises a coating composition and includes a first coating material and a second coating material having a predetermined composition. Therefore, it is possible to manufacture a coated laminate that has excellent moisture resistance, as well as excellent hardness, water resistance, and weather resistance.

[0224] Furthermore, the coated laminate 1 is formed from a first coating material and a second coating material, and the first coating material and the second coating material each contain a coating composition. Therefore, it has excellent moisture resistance, as well as excellent hardness, water resistance, and weather resistance.

[0225] In detail, in the coated laminate 1, adhesion is ensured, particularly by the first coating layer 3, while hardness, water resistance, and weather resistance are ensured, particularly by the second coating layer 4. As a result, adhesion, hardness, water resistance, and weather resistance can be ensured for the first coating layer 3 and the second coating layer 4 as a whole.

[0226] Specifically, the hydroxyl value of the first hydroxyl group-containing resin in the first coating layer 3 (first coating material) is set to be relatively lower than the hydroxyl value of the second hydroxyl group-containing resin in the second coating layer 4 (second coating material).

[0227] This allows the first coating layer 3, with its low crosslinking density, to ensure adhesion, while the second coating layer 4, with its high crosslinking density, ensures hardness, water resistance, and weather resistance.

[0228] In the manufacturing method of the coated laminate 1, the uncured first coating layer 3 and the uncured second coating layer 4 are cured simultaneously. Therefore, it offers excellent production efficiency.

[0229] The coating composition can be suitably used, in particular, as a pre-coat paint (coating agent). The coating composition and the coated laminate 1 obtained using the coating composition can be used in various industrial applications such as home appliances or vehicles, and can be suitably used, in particular, in vehicle applications (for example, the exterior of motorcycles).

[0230] <Variation> In the embodiment described above, the coated laminate 1 consists of a workpiece 2 and two coating layers.

[0231] However, the coated laminate 1 may consist of the object to be coated 2 and a single coating layer. In that case, the composition of the coating material, the hydroxyl value and acid value of the hydroxyl resin, and the number of carbon atoms of the alcohol used in the alkyl etherified melamine resin can be appropriately selected according to the properties of the coating layer. [Examples]

[0232] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Unless otherwise specified, "parts" and "%" are based on mass. Furthermore, specific numerical values ​​such as blending ratios (content), physical properties, and parameters used in the following description may be replaced with the corresponding upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to" or "greater than") of the blending ratios (content), physical properties, and parameters described in the "Modes for Carrying Out the Invention" above.

[0233] 1. Details of the ingredients The product names and abbreviations of the components used in each manufacturing example, each embodiment, and each comparative example are described in detail below.

[0234] MMA: Methyl methacrylate n-BA: n-butyl acrylate HEMA: 2-hydroxyethyl methacrylate MAC: Methacrylic acid PBO: t-butylperoxy-2-ethylhexanoate, trade name "Perbutyl O", manufactured by NOF Corporation. Solvesso 100: Aromatic hydrocarbon, manufactured by ExxonMobil Corporation. Tinuvin123: Radical scavenger, base dissociation constant pKb=9.6, manufactured by BASF. Tinuvin249: Radical scavenger, base dissociation constant pKb=8.0, manufactured by BASF. Tinuvin 405: UV absorber, manufactured by BASF. Tinuvin384: UV absorber, manufactured by BASF.

[0235] 2. Production of hydroxyl group-containing resins Manufacturing Example 1 51 g of Solvesso 100 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 mixture was heated to 100°C while degassing with nitrogen. Next, a 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, and the mixture was allowed to mature for 1 hour to obtain a primary hydroxyl group-containing resin (I-a1). The solid content concentration was 50% by mass.

[0236] Manufacturing Examples 2-5 A resin containing the first hydroxyl group was obtained using the same method as in Manufacturing Example 1. However, the formulation was modified according to Table 1.

[0237] Manufacturing Examples 6-8 A resin containing a second hydroxyl group was obtained using the same method as in Manufacturing Example 1. However, the formulation was modified according to Table 2.

[0238] 3. Production of alkyl etherified melamine resin Manufacturing Example 9 In a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, 126 g (1.0 mol) of melamine, 196 g (6.0 mol) of paraformaldehyde with a formalin concentration of 92%, and 519 g (7.0 mol) of n-butanol were charged and the mixture was heated to 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 under reflux for 3 hours while dehydrating. Subsequently, the reaction product was neutralized with 0.16 g (0.80 mmol) of a 20% sodium hydroxide solution. Then, after removing the solvent under reduced pressure, the mixture was diluted with n-butanol to a solid content concentration of 60% by mass. This yielded the first alkyl etherified melamine resin (I-b1).

[0239] Manufacturing Examples 10-14 A first alkyl ether-modified melamine resin was obtained using the same method as in Manufacturing Example 9. However, the formulation was modified according to Table 3.

[0240] Manufacturing Examples 15-19 A melamine resin with a second alkyl ether was obtained using the same method as in Manufacturing Example 9. However, the formulation was modified according to Table 4.

[0241] Furthermore, as the first alkyl ether-modified melamine resin (I-b5), we prepared the trade name "Cymel 370" (manufactured by Daicel Ornex, solvent: iso-butanol, solids content: 88%, average number of formaldehyde added per 1 mol of melamine is 5.8 mol, and it is a methanol-modified melamine resin (methylated melamine resin)).

[0242] 4. Manufacturing of painted laminates Examples 1 to 23, and Comparative Examples 1 to 7

[0243] <Preparation of the first coating material> The first coating material was prepared by mixing the first hydroxyl group-containing resin, the first alkyl etherified melamine resin, the first Lewis acid catalyst shown in Table 5, and the pigment according to the formulations described in Tables 7 to 9. In Tables 7 to 9, the values ​​for the first hydroxyl group-containing resin, the first alkyl etherified melamine resin, the first Lewis acid catalyst, and the pigment are solid content values.

[0244] <Preparation of the second coating material> A second coating material was prepared by mixing a second hydroxyl group-containing resin, a second alkyl etherified melamine resin, a second Lewis acid catalyst shown in Table 6, a radical scavenger, and an ultraviolet absorber according to the formulations described in Tables 7 to 9. In Tables 7 to 9, the values ​​for the second hydroxyl group-containing resin, second alkyl etherified melamine resin, second Lewis acid catalyst, radical scavenger, and ultraviolet absorber are solid content values.

[0245] <Manufacturing of coated laminates> [1st step] A 2mm thick ABS resin was prepared as the object to be painted.

[0246] Next, the first coating material was applied to one side in the thickness direction of the object to be coated, and dried at 25°C to form an uncured first coating layer.

[0247] [Second process] The second coating material was applied to one side in the thickness direction of the uncured first coating layer, and the uncured second coating layer was formed by drying it at 25°C.

[0248] [3rd step] The uncured first coating layer and the uncured second coating layer were heated at 70°C for 20 minutes to cure them simultaneously.

[0249] This resulted in the acquisition of a coated laminate. 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.

[0250] 5. Rating <Acid value> The acid value of the primary hydroxyl group-containing resin and the secondary hydroxyl group-containing resin of each production example was measured according to JIS K 0070-1992 (potentiometric titration method). The results are shown in Tables 1 and 2.

[0251] <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 according to JIS K 0070-1992 (acetylation method). The results are shown in Tables 1 and 2.

[0252] <Weight average molecular weight> For each production example, the weight-average molecular weight of the primary hydroxyl group-containing resin, secondary hydroxyl group-containing resin, primary alkyl etherified melamine resin, and secondary alkyl etherified melamine resin was measured using the GPC method under the following measurement conditions. The results are shown in Tables 1 to 4. Detector: Differential refractometer (RI) Columns: TSKgel G7000 x 1, TSKgel G4000 x 2, TSKgel G2000 x 1 (all manufactured by Tosoh Corporation) Mobile layer: Tetrahydrofuran (THF) Column temperature: 25℃ Flow rate: 0.6ml / min Sample concentration: 20 mg / mL (tetrahydrofuran solution) Injection volume: 10μl

[0253] The weight-average molecular weight was calculated using a calibration curve created from monodisperse standard polystyrene.

[0254] <Glass transition temperature> For each manufacturing example, the first hydroxyl group-containing resin and the second hydroxyl group-containing resin were calculated using the FOX formula shown in formula (1) below. 1 / Tg = W1 / Tg1 + W2 / Tg2 + ... + W n / Tg n (1)

[0255] In the above formula (1), Tg is the glass transition temperature (K) of n types of first or second polymerization components (monomers), where W1, W2, W n This represents the mass fraction of each monomer, where W1 + W2 + ... + W n = 1. Also, Tg1, Tg2, Tg n This is the glass transition temperature (K) of the homopolymer of each monomer.

[0256] Furthermore, the glass transition temperatures of monomer homopolymers can be obtained using values ​​found in the literature, such as those listed in Mitsubishi Rayon Co., Ltd.'s acrylic ester catalog (1997 edition) and in "New Polymer Library 7: Introduction to Synthetic Resins for Coatings" by Kyozo Kitaoka, published by Polymer Publishing Association, pp. 168-169. The results are shown in Tables 1 and 2.

[0257] <Average number of formaldehyde particles added> For the first alkyl etherified melamine resin and the second alkyl etherified melamine resin of each production example, the average number of formaldehyde additions per mole of melamine was determined as follows: 13 The results were measured by 13C-NMR. The results are shown in Tables 3 and 4.

[0258] <Pigment dispersibility> Each of the first coating materials for each example and comparative example was left to stand at 25°C for 24 hours. Afterward, the state of the first coating material was visually observed. Pigment dispersibility was evaluated based on the following criteria. The results are shown in Tables 7 to 9. [standard] ◎: No pigment sedimentation was observed. ○: Pigment sedimentation was observed, but the pigment could be redispersed by stirring. ×: Pigment sedimentation was observed, and the pigment did not disperse even after stirring.

[0259] <Corrosive to metals> In each example and comparative example, zinc phosphate treated steel sheets were immersed for 24 hours in the first and second coating materials, respectively, which were maintained at 40°C. The condition of the zinc phosphate treated steel sheets after removal was visually observed. Metal corrosion resistance was evaluated based on the following criteria. The results are shown in Tables 7 to 9. [standard] ○: No discoloration was observed on the steel plate. ×: Discoloration caused by rust was observed on the steel plate.

[0260] <Adhesion> In accordance with JIS K5400 8.5.2:1990, a knife was used to make a grid pattern of 1 mm wide vertical and horizontal cuts into the coated laminates of each example and comparative example, reaching the substrate. Then, adhesive tape was applied to the surface and the condition of the coating film was visually observed after it was instantly peeled off. Adhesion was evaluated based on the following criteria. The results are shown in Tables 7 to 9. [standard] ○: No peeling or chipping of the coating was observed. ×: Peeling and chipping of the coating were observed throughout the entire surface.

[0261] <Water resistance> The painted laminates of each example and each comparative example were immersed in warm water maintained at 40°C for 8 hours, and the state after taking them out was visually observed. The water resistance was evaluated based on the following criteria. The results are shown in Tables 7 to 9. [Criteria] ◎: No abnormalities such as whitening were observed. 〇: A slight whitening was observed, but the whitening disappeared within 12 hours. △: A slight whitening was observed, but the whitening disappeared within 24 hours. ×:显著白化,且白化未消失。

[0262] <Pencil hardness> In accordance with JIS K 5600-5-4, the tip of a pencil was applied to the painted laminates of each example and each comparative example at an angle of approximately 45°, and while pressing strongly against the test paint surface so that the tip would not break, it was moved forward at a uniform speed of approximately 10 mm. The hardness mark of the hardest pencil for which no scratches occurred on the paint film was taken as the pencil hardness. The results are shown in Tables 7 to 9. [Criteria] 〇: B or higher ×: 2B or lower

[0263] <Water resistance> The painted laminates of each example and each comparative example were placed under conditions of 50°C and 85% RH for 100 hours, then placed at 25°C for 2 hours, and the state of the paint film was visually observed. The water resistance was evaluated based on the following criteria. The results are shown in Tables 7 to 9. [Criteria] 〇: There is no peeling or chipping of the paint film at all. △: There is some peeling or chipping of the paint film. ×: There is peeling and chipping of the paint film over the entire surface.

[0264] <Weather resistance> In accordance with JIS D 0205, the painted laminate of each example and each 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 painted test piece at 0 hours of the test was measured. The weather resistance was evaluated based on the following criteria. The results are shown in Tables 7 to 9. [Criteria] ◎: 0 ≦ ΔE ≦ 1.5 〇: 1.5 < ΔE ≦ 3.0 ×: 3.0 < ΔE

[0265] [Table 1]

[0266] [Table 2]

[0267] [Table 3]

[0268] [Table 4]

[0269] [Table 5]

[0270] [Table 6]<​​​​​​​​​​​​​​​​​​​​ [Table 9] [Explanation of symbols]

[0274] 1. Painted laminate 2 Object to be painted 3. First coating layer 4. Second coating layer

Claims

1. A coating material for coating the surface of an object to be painted, A first coating material for forming a first coating layer that covers the surface of the object to be coated, The device comprises a second coating material for forming a second coating layer that covers the surface of the first coating layer, The first coating material includes a coating composition comprising the following (A) to (C): The second coating material comprises a coating composition including the following (A) to (C), A coating material wherein the hydroxyl value of the hydroxyl group-containing resin in the first coating material is smaller than the hydroxyl value of the hydroxyl group-containing resin in the second coating material. (A) Hydroxyl group-containing resin (excluding alkyl ether-modified melamine resin (B)) (B) Alkyl etherified melamine resin modified with an alcohol having 1 to 6 carbon atoms, wherein the average number of formaldehyde added per 1 mol of melamine is 3 mol or more and 6 mol or less. (C) A Lewis acid catalyst consisting of a cation made of a metal with a Pauling electronegativity of 1.31 or higher and 2.02 or lower, and a counteranion which is a deprotonated protic acid, with an SP value of 11 or less.

2. The coating material according to claim 1, wherein the proton acid has an acid dissociation constant pKa of 1.0 or less.

3. The coating material according to claim 1, wherein the mass ratio of the hydroxyl group-containing resin (A) to the alkyl etherified melamine resin (B) (hydroxyl group-containing resin (A) / alkyl etherified melamine resin (B)) is 60 / 40 or more and 95 / 5 or less.

4. The first coating material further comprises a pigment, The hydroxyl group-containing resin of the first coating material has a hydroxyl value of 20 mg KOH / g or more and 80 mg KOH / g or less, and an acid value of 3 mg KOH / g or more and 50 mg KOH / g or less. The hydroxyl group-containing resin of the second coating material has a hydroxyl value of 55 mg KOH / g or more and 180 mg KOH / g or less. The coating material according to claim 1, wherein the alkyl etherified melamine resin of the second coating material is modified with an alcohol having 2 to 6 carbon atoms.

5. The second coating material further comprises a radical scavenger, The coating material according to claim 1, wherein the radical scavenger has a base dissociation constant pKb of 6 or more and 14 or less.

6. The device 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. The first coating layer is formed from the first coating material described in claim 1, The second coating layer is formed from the second coating material described in claim 1, in a coated laminate.

7. The coated laminate according to claim 6, wherein the object to be coated is a resin.

8. The coated laminate according to claim 7, wherein the resin is an acrylonitrile-styrene-butadiene copolymer resin.

9. A first step involves applying the first coating material described in claim 1 to the surface of the object to be coated, thereby forming an uncured first coating layer. A second step is to apply the second coating material described in claim 1 to the surface of the uncured first coating layer after the first step, thereby forming an uncured second coating layer. A method for manufacturing a coated laminate, comprising a third step of simultaneously curing the uncured first coating layer and the uncured second coating layer.

10. The method for manufacturing a coated laminate according to claim 9, wherein the object to be coated is a resin.

11. The method for producing a coated laminate according to claim 10, wherein the resin is an acrylonitrile-styrene-butadiene copolymer resin.

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