Coating composition

Abstract

To provide a coating composition capable of inhibiting the coagulation of the main agent even when the solvent contains water.SOLUTION: A coating composition contains a hydroxy group-containing resin, an alkyl-etherified melamine resin, a microcapsule catalyst, and water. The microcapsule catalyst contains a core substance containing a catalyst, and a wall material encapsulating a catalyst. The catalyst has an SP value of 11 or less. The catalyst has an acidity of -3.0 or more and 5.0 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a coating composition. [Background technology]

[0002] 2. Description of the Related Art Conventionally, in the field of vehicle paints and home appliance paints, coating compositions containing a polyol and an alkyl etherified melamine resin have been used.

[0003] As such a coating composition, a coating composition containing a resin having a hydroxyl group, an alkyl-etherified melamine resin, a Lewis acid catalyst, and a solvent has been proposed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 202964 Brochure Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, from the viewpoint of environmental protection, it is being considered to use water as a part or the whole of the solvent instead of the organic solvent.

[0006] However, if the solvent contains water, there is a problem in that the base resin (a resin having a hydroxyl group) interacts with the metal catalyst and aggregates.

[0007] The present invention provides a coating composition capable of suppressing aggregation of the base component even when the solvent contains water. [Means for solving the problem]

[0008] The present invention [1] is a coating composition comprising a hydroxyl group-containing resin, an alkyl-etherified melamine resin, a microcapsule catalyst, and water, the microcapsule catalyst comprising a core material containing a catalyst and a wall material encapsulating the catalyst, the SP value of the catalyst being 11 or less, and the acidity of the catalyst being -3.0 or more and 5.0 or less.

[0009] The present invention [2] includes the coating composition according to the above [1], in which the catalyst is zinc dodecylbenzenesulfonate.

[0010] The present invention [3] includes the coating composition according to the above [1] or [2], wherein the wall material is polyurea.

[0011] The present invention [4] includes the coating composition according to the above [3], wherein the polyurea is a reaction product of a water-dispersible polyisocyanate with a polyamine and / or water.

[0012] The present invention [5] includes the coating composition according to the above [4], wherein the water-dispersible polyisocyanate is a reaction product of a polyisocyanate component and an active hydrogen group-containing compound that contains an ionic group. Effect of the Invention

[0013] The coating composition of the present invention contains a microencapsulated catalyst that contains a specific catalyst, and therefore, even if the solvent contains water, aggregation of the main component (hydroxyl group-containing resin) can be suppressed. [Brief description of the drawings]

[0014] [Figure 1] Figures 1A to 1C show one embodiment of a method for producing a laminate. Figure 1A shows a first step of preparing an object to be coated. Figure 1B shows a first step of forming a coating film on the surface (one surface in the thickness direction) of the object to be coated. Figure 1C shows a second step of curing the coating film at a predetermined temperature to form a cured layer as a cured product. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The coating composition contains a hydroxyl-containing resin, an alkyl-etherified melamine resin, a microcapsule catalyst, and water.

[0016] <Hydroxyl-containing resin> Examples of the hydroxyl-containing resin include hydroxyl-containing acrylic resin, hydroxyl-containing polyester resin, hydroxyl-containing polyurethane resin, and hydroxyl-containing epoxy resin. The hydroxyl-containing resin is preferably hydroxyl-containing acrylic resin.

[0017] [Hydroxyl-containing acrylic resin] The hydroxyl group-containing acrylic resin is, for example, a copolymer obtained by polymerizing a polymerization component containing an alkyl (meth)acrylate ester and a hydroxyl group-containing acrylic monomer.

[0018] Examples of (meth)acrylic acid alkyl esters include (meth)acrylic acid alkyl esters having an alkyl moiety with 1 to 12 carbon atoms. Examples of (meth)acrylic acid alkyl esters having an alkyl moiety with 1 to 12 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate. Note that (meth)acrylic acid means methacrylic acid and / or acrylic acid.

[0019] The (meth)acrylic acid alkyl esters can be used alone or in combination of two or more kinds.

[0020] Examples of hydroxyl group-containing acrylic monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate.

[0021] The hydroxyl group-containing acrylic monomers can be used alone or in combination of two or more kinds.

[0022] Furthermore, the polymerization components may contain, if necessary, a copolymerizable vinyl monomer that is copolymerizable with the (meth)acrylic acid alkyl ester and the hydroxyl group-containing acrylic monomer.

[0023] Examples of the copolymerizable vinyl monomer include carboxy group-containing vinyl monomers, amino group-containing vinyl monomers, glycidyl group-containing vinyl monomers, cyano group-containing vinyl monomers, sulfonic acid group-containing vinyl monomers and salts thereof, acetoacetoxy group-containing vinyl monomers, phosphoric acid group-containing compounds, amide group-containing vinyl monomers, aromatic vinyl monomers, N-substituted unsaturated carboxylic acid amides, heterocyclic vinyl compounds, vinylidene halide compounds, α-olefins, and dienes.

[0024] Examples of carboxy-group-containing vinyl monomers include (meth)acrylic acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, and crotonic acid.

[0025] 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.

[0026] An example of the glycidyl group-containing vinyl monomer is glycidyl (meth)acrylate.

[0027] An example of the cyano group-containing vinyl monomer is (meth)acrylonitrile.

[0028] Examples of the sulfonic acid group-containing vinyl monomer include allyl sulfonic acid and methallyl sulfonic acid. Examples of the salts include alkali metal salts (e.g., sodium salts and potassium salts) of the sulfonic acid group-containing vinyl monomer, such as ammonium salts. Specific examples include sodium allyl sulfonate, sodium methallyl sulfonate, and ammonium methallyl sulfonate.

[0029] An example of the acetoacetoxy group-containing vinyl monomer is acetoacetoxyethyl (meth)acrylate.

[0030] An example of the phosphate group-containing compound is 2-methacryloyloxyethyl acid phosphate.

[0031] An example of the amide group-containing vinyl monomer is (meth)acrylamide.

[0032] Examples of aromatic vinyl monomers include styrene, α-methylstyrene, and divinylbenzene.

[0033] An example of the N-substituted unsaturated carboxylic acid amide is N-methylol (meth)acrylamide.

[0034] An example of the heterocyclic vinyl compound is vinylpyrrolidone.

[0035] Examples of vinylidene halide compounds include vinylidene chloride and vinylidene fluoride.

[0036] Examples of the α-olefins include ethylene and propylene.

[0037] An example of the dienes is butadiene.

[0038] The copolymerizable vinyl monomers can be used alone or in combination of two or more kinds.

[0039] The hydroxyl-containing acrylic resin can be obtained by polymerizing (copolymerizing) polymerization components including an alkyl (meth)acrylate ester, a hydroxyl-containing acrylic monomer, and, if necessary, a copolymerizable vinyl monomer.

[0040] The polymerization method is not particularly limited, and any known polymerization method may be used.

[0041] In addition, a commercially available product may be used as the hydroxyl group-containing acrylic resin, such as NeoCryl XK-110 or NeoCryl XK-104 (both manufactured by DSM).

[0042] The hydroxyl-containing acrylic resin can also be diluted with a solvent to prepare a hydroxyl-containing acrylic resin solution. In the hydroxyl-containing acrylic resin solution, the solid content concentration of the hydroxyl-containing acrylic resin is, for example, 30% by mass or more, preferably 40% by mass or more, and 70% by mass or less, preferably 60% by mass or less.

[0043] The hydroxyl value of the hydroxyl-containing resin is, for example, 15 mgKOH / g or more, preferably 30 mgKOH / g or more, more preferably 60 mgKOH / g or more, and even more preferably 80 mgKOH / g or less, and for example, 150 mgKOH / g or less, preferably 100 mgKOH / g or less, more preferably 90 mgKOH / g or less.

[0044] The hydroxyl value of the hydroxyl-containing resin can be measured, for example, based on JIS K 0070-1992 (acetylation method).

[0045] The hydroxyl-containing resin has a polystyrene-equivalent weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) of, for example, 5,000 or more, preferably 8,000 or more, more preferably 10,000 or more, and for example, 200,000 or less, preferably 150,000 or less, more preferably 100,000 or less, and even more preferably 30,000 or less.

[0046] The hydroxyl group-containing resins can be used alone or in combination of two or more kinds.

[0047] The content of the hydroxyl-containing resin is, for example, 40 parts by mass or more, preferably 60 parts by mass or more, and for example, 90 parts by mass or less, preferably 80 parts by mass or less, per 100 parts by mass of the total amount of the hydroxyl-containing resin and the alkyl etherified melamine resin.

[0048] <Alkyl etherified melamine resin> The alkyl-etherified melamine resin can be obtained by modifying (alkyl-etherifying) at least a portion of the methylol groups of a melamine resin obtained from melamine and formaldehyde with an alcohol.

[0049] Formaldehyde can be prepared as an aqueous solution, or solid paraformaldehyde can be used as formaldehyde.

[0050] When formaldehyde is prepared as an aqueous solution, its concentration is, for example, 80% or more and, for example, 99% or less.

[0051] Examples of the alcohol include alcohols having 1 to 6 carbon atoms. Examples of the 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 the linear monohydric alcohols having 1 to 6 carbon atoms include methanol, ethanol, n-propanol, n-butanol, n-pentanol, and n-hexanol. Examples of the branched monohydric alcohols having 1 to 6 carbon atoms include isopropanol, isobutanol, sec-butanol, and tert-butanol.

[0052] The alcohol is preferably a linear monohydric alcohol having 1 to 6 carbon atoms. The alcohol is more preferably a linear monohydric alcohol having 1 to 4 carbon atoms. The alcohol is further preferably methanol, ethanol, and n-butanol. The alcohol is particularly preferably methanol.

[0053] The alcohols can be used alone or in combination of two or more kinds.

[0054] To obtain the alkyl etherified melamine resin, first, melamine and formaldehyde are subjected to a methylolation reaction to obtain the melamine resin.

[0055] To carry out a methylolation reaction between melamine and formaldehyde, melamine and formaldehyde are mixed together. Specifically, formaldehyde is mixed so that the average addition number of formaldehyde per 1 mole of melamine is 3 moles or more, preferably 4 moles or more and 6 moles or less.

[0056] The average number of additions may be, for example, 13 It can be calculated by C-NMR analysis.

[0057] When formaldehyde is added to all three amino groups of melamine, the number of moles of formaldehyde added is 6 moles.

[0058] In the methylolation reaction, an alcohol (to be subjected to alkyl etherification) is mixed in advance together with melamine and formaldehyde. The mixing ratio of the alcohol is, for example, 4 mol or more, preferably 6 mol or more, and, for example, 7 mol or less, per mol of melamine.

[0059] After the methylolation reaction, an acid catalyst is added, and at least a portion of the methylol groups of the melamine resin is modified with an alcohol (alkyl etherification).

[0060] The alcohol can be blended with an acid catalyst or can be pre-blended with the melamine and formaldehyde.

[0061] Examples of the acid catalyst include organic acids and inorganic acids. Examples of the organic acid include formic acid, oxalic acid, and paratoluenesulfonic acid. Examples of the inorganic acid include phosphoric acid, hydrochloric acid, sulfuric acid, and nitric acid. Examples of the acid catalyst include preferably organic acids. Examples of the acid catalyst include more preferably paratoluenesulfonic acid.

[0062] The acid catalysts can be used alone or in combination of two or more kinds.

[0063] The mixing ratio of the acid catalyst is appropriately set depending on the purpose and application.

[0064] As for reaction conditions, the reaction temperature is, for example, 60° C. or higher and, for example, 120° C. or lower, and the reaction time is, for example, 1 hour or higher and, for example, 12 hours or lower.

[0065] A neutralizing agent (eg, sodium hydroxide) is then added to neutralize the reaction product.

[0066] This gives an alkyl etherified melamine resin.

[0067] The alkyl-etherified melamine resin can also be diluted with a solvent (for example, isopropyl alcohol) to prepare an alkyl-etherified melamine resin solution.

[0068] In the alkyl-etherified melamine resin solution, the solids concentration of the alkyl-etherified melamine resin is, for example, 30 mass % or more, preferably 40 mass % or more, and for example, 80 mass % or less.

[0069] As such an alkyl-etherified melamine resin, a preferred example is a methyl-etherified melamine resin in which at least a portion of the methylol groups of a melamine resin is modified (alkyl-etherified) with methanol.

[0070] The polystyrene-equivalent 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 or more, more preferably 1300 or more, and for example, 10000 or less, preferably 6000 or less, more preferably 3000 or less, and even more preferably 2000 or less.

[0071] The alkyl etherified melamine resins can be used alone or in combination of two or more kinds.

[0072] The content of the alkyl etherified melamine resin is, for example, 10 parts by mass or more, preferably 20 parts by mass or more, and for example, 60 parts by mass or less, preferably 40 parts by mass or less, per 100 parts by mass of the total amount of the hydroxyl group-containing resin and the alkyl etherified melamine resin.

[0073] In addition, the mass ratio of the hydroxyl-containing resin to the alkyl-etherified melamine resin (hydroxyl-containing resin / alkyl-etherified melamine resin) is, for example, 1.00 or more, preferably 2.00 or more, more preferably 2.20 or more, and for example, 4.00 or less, preferably 3.00 or less, more preferably 2.50 or less.

[0074] <Microcapsule catalyst> The microcapsule catalyst comprises a core material containing a catalyst and a wall material encapsulating the catalyst.

[0075] [catalyst] The catalyst consists of a cation and a counter anion.

[0076] The cation is a cation of a metal. Examples of the metal include magnesium, manganese, aluminum, cobalt, nickel, tin, zinc, copper, and bismuth. The metal is preferably zinc.

[0077] The counter anion is the deprotonated form of a protonic acid.

[0078] The protonic acid includes, for example, an inorganic acid and an organic acid.

[0079] Inorganic acids include, for example, hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid.

[0080] The organic acids include, for example, carboxylic acids and sulfonic acids.

[0081] Examples of the carboxylic acid include acetic acid, propionic acid, octanoic acid, and stearic acid. The carboxylic acid is preferably octanoic acid.

[0082] Examples of sulfonic acids include toluenesulfonic acid, benzenesulfonic acid, and dodecylbenzenesulfonic acid. A preferred example of the sulfonic acid is dodecylbenzenesulfonic acid.

[0083] Examples of such catalysts include zinc dodecylbenzenesulfonate, aluminum dodecylbenzenesulfonate, nickel dodecylbenzenesulfonate, and zinc octylate. Examples of the catalysts include preferably zinc dodecylbenzenesulfonate and zinc octylate. Examples of the catalysts include more preferably zinc dodecylbenzenesulfonate from the viewpoint of reactivity.

[0084] The catalyst has a Hildebrand solubility parameter value (SP value) of, for example, 11.0 or less, preferably 10.5 or less, more preferably 10 or less, and for example, 5 or more.

[0085] When the SP value is equal to or less than the upper limit, the polarity is low and the coating layer is hydrophobic, so that the coating layer has excellent moisture resistance.

[0086] The acidity of the catalyst is, from the viewpoint of suppressing aggregation of the hydroxyl-containing resin when the solvent contains water, for example, -3.0 or more, and preferably -2.0 or more, and from the viewpoint of promoting the curing reaction of the alkyl etherified melamine resin, for example, 5.0 or less, preferably 3.0 or less, more preferably 1.0 or less, and even more preferably -1.0 or less.

[0087] The acidity can be measured, for example, in accordance with "Chemical Handbook", 5th Revised Edition, Chemical Society of Japan, pp. II-332-333, ISBN 4-621-07341-9, 11.6 Equilibrium constants for non-aqueous systems, ibin, pp. 354-356.

[0088] The catalyst can also be prepared by reacting the above metal (the oxide of the above metal) with a protonic acid.

[0089] [Wall material] The wall material is not particularly limited, and examples thereof include amino resins (e.g., reaction products of urea and formaldehyde, reaction products of melamine and formaldehyde), acrylic resins (e.g., polymers mainly composed of (meth)acrylic acid ester), and polyurea (reaction products of water-dispersible polyisocyanate and polyamine and / or water). From the viewpoints of dispersibility and strength, polyurea is preferably used as the wall material. In the following description, the case where the wall material is polyurea will be described in detail.

[0090] Polyureas are reaction products of isocyanate compositions, including water-dispersible polyisocyanates, with polyamines and / or water.

[0091] The isocyanate composition includes a water-dispersible polyisocyanate.

[0092] The water-dispersible polyisocyanate is a reaction product of a polyisocyanate component and an active hydrogen group-containing component.

[0093] The polyisocyanate component includes a polyisocyanate.

[0094] Examples of the polyisocyanate include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and araliphatic polyisocyanates.

[0095] Examples of the aliphatic polyisocyanate include aliphatic diisocyanates. Examples of the aliphatic diisocyanate include 1,6-hexamethylene diisocyanate (1,6-HDI), 1,5-pentamethylene diisocyanate (1,5-PDI), tetramethylene diisocyanate, trimethylene diisocyanate, 1,2-, 2,3- or 1,3-butylene diisocyanate, and 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate. Examples of the aliphatic polyisocyanate include preferably 1,6-HDI and 1,5-PDI. Examples of the aliphatic polyisocyanate include more preferably 1,6-HDI.

[0096] Examples of alicyclic polyisocyanates include alicyclic diisocyanates. Examples of alicyclic diisocyanates include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), 4,4'-, 2,4'- or 2,2'-methylenebis(cyclohexyl isocyanate) or mixtures thereof (H 12 Examples of the alicyclic diisocyanate include 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or a mixture thereof (H6XDI), bis(isocyanatomethyl)norbornane (NBDI), 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, and methyl-2,6-cyclohexane diisocyanate. As the alicyclic diisocyanate, IPDI is preferably used.

[0097] Examples of aromatic polyisocyanates include aromatic diisocyanates. Examples of aromatic diisocyanates include 4,4'-, 2,4'- or 2,2'-diphenylmethane diisocyanate or mixtures thereof (MDI), 2,4- or 2,6-tolylene diisocyanate or mixtures thereof (TDI), o-tolidine diisocyanate, 1,5-naphthalene diisocyanate (NDI), m- or p-phenylene diisocyanate or mixtures thereof, 4,4'-diphenyl diisocyanate, and 4,4'-diphenyl ether diisocyanate.

[0098] Examples of the araliphatic polyisocyanate include araliphatic diisocyanates, such as xylylene diisocyanate (1,2-, 1,3-, or 1,4-xylylene diisocyanate or a mixture thereof) (XDI), 1,3-, or 1,4-tetramethyl xylylene diisocyanate or a mixture thereof (TMXDI), and ω,ω′-diisocyanato-1,4-diethylbenzene.

[0099] The polyisocyanate also includes derivatives of the polyisocyanate.

[0100] Examples of the polyisocyanate derivatives include isocyanurate derivatives, allophanate derivatives, polyol derivatives, biuret derivatives, urea derivatives, oxadiazinetrione derivatives, carbodiimide derivatives, uretdione derivatives, and uretonimine derivatives of the above-mentioned polyisocyanates. As the polyisocyanate derivatives, preferably, isocyanurate derivatives are used.

[0101] The polyisocyanate preferably includes an aliphatic polyisocyanate, a derivative of an aliphatic polyisocyanate (preferably an isocyanurate derivative of an aliphatic polyisocyanate), and an alicyclic polyisocyanate. The polyisocyanate more preferably includes an alicyclic polyisocyanate.

[0102] The active hydrogen group-containing component includes an active hydrogen group-containing compound that contains a hydrophilic group.

[0103] The active hydrogen group-containing compound containing a hydrophilic group is a compound that contains a hydrophilic group such as a nonionic group or an ionic group, and contains one or more active hydrogen groups such as an amino group or a hydroxyl group. Examples of the active hydrogen group-containing compound containing a hydrophilic group include an active hydrogen group-containing compound containing a nonionic group and an active hydrogen group-containing compound containing an ionic group.

[0104] Examples of the active hydrogen group-containing compound containing a nonionic group include active hydrogen compounds containing a polyoxyethylene group.

[0105] The polyoxyethylene group-containing active hydrogen compound is a compound that contains a polyoxyethylene group in the main chain or side chain and has one or more active hydrogen groups. A preferred example of the active hydrogen group is a hydroxyl group.

[0106] Examples of active hydrogen compounds containing a polyoxyethylene group in the main chain include polyoxyethylene glycol (e.g., number average molecular weight of 200 or more, preferably 300 or more and 6000 or less, preferably 3000 or less) and one-end-capped polyoxyethylene glycol.

[0107] An example of a one-end-blocked polyoxyethylene glycol is an alkoxyethylene glycol (monoalkoxypolyethylene glycol) one end of which is blocked with an alkyl group.

[0108] In the monoalkoxypolyethylene glycol, the number of carbon atoms in the alkyl group for capping one end is, for example, 1 or more, and for example, 20 or less, preferably 10 or less, more preferably 8 or less, even more preferably 4 or less, and particularly preferably 2 or less. That is, a preferred example of the alkyl group for capping one end is a methyl group.

[0109] Specific examples of such monoalkoxypolyethylene glycols having one end blocked with an alkyl group include methoxypolyethylene glycol and ethoxypolyethylene glycol, and preferably methoxypolyethylene glycol.

[0110] The number average molecular weight (polystyrene equivalent molecular weight measured by GPC) of the one-end-blocked polyoxyethylene glycol is, for example, 200 or more, preferably 300 or more, and for example, 6000 or less, preferably 3000 or less.

[0111] Examples of active hydrogen compounds containing polyoxyethylene groups in the side chain include polyols containing polyoxyethylene side chains.

[0112] The polyoxyethylene side chain-containing polyol is an organic compound that contains a polyoxyethylene group in the side chain and has two or more (preferably two) hydroxyl groups at the main chain terminals, and can be synthesized as follows.

[0113] That is, first, a diisocyanate (preferably HDI) and the one-end-blocked polyoxyethylene glycol are subjected to a urethane reaction in such a ratio that the isocyanate groups of the diisocyanate are in excess relative to the hydroxyl groups of the one-end-blocked polyoxyethylene glycol, and if necessary, unreacted diisocyanate is removed to obtain a polyoxyethylene chain-containing monoisocyanate.

[0114] As the diisocyanate, preferably, the above-mentioned alicyclic diisocyanates are used.

[0115] The reaction conditions may be known conditions and are appropriately set depending on the purpose and application.

[0116] Next, the obtained polyoxyethylene chain-containing monoisocyanate and dialkanolamine (for example, diethanolamine, etc.) are subjected to a urea-forming reaction in such a ratio that the amount of the isocyanate group of the polyoxyethylene group-containing monoisocyanate is approximately equal to the amount of the secondary amino group of the dialkanolamine.

[0117] This gives a polyol containing a polyoxyethylene side chain (preferably a diol containing a polyoxyethylene side chain).

[0118] The number average molecular weight (polystyrene equivalent molecular weight measured by GPC) of the polyoxyethylene side chain-containing polyol is, for example, 200 or more, preferably 300 or more, and for example, 6000 or less, preferably 3000 or less.

[0119] In the active hydrogen group-containing compound containing a nonionic group, the number average molecular weight of the nonionic group, specifically, the polyoxyethylene group, is, for example, 600 or more and 6,000 or less.

[0120] As the active hydrogen group-containing compound containing a nonionic group, preferably, a polyol containing a polyoxyethylene side chain is used.

[0121] The active hydrogen group-containing compound containing an ionic group is, for example, an organic compound having both an anionic group such as carboxylic acid or a cationic group such as a quaternary amine and two or more active hydrogen groups such as hydroxyl groups or amino groups, and preferably an organic compound having both an anionic group and two or more hydroxyl groups, and more preferably an organic compound having both a carboxylic acid and two hydroxyl groups (an active hydrogen group-containing compound containing a carboxy group (for example, a carboxy group-containing polyol, etc.)).

[0122] Examples of the carboxyl group-containing polyol include polyhydroxyalkanoic acids (dihydroxyalkanoic acids) such as 2,2-dimethylolacetic acid, 2,2-dimethylollactic acid, 2,2-dimethylolpropionic acid (also known as dimethylolpropionic acid), 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, and 2,2-dimethylolvaleric acid. A preferred example of the carboxyl group-containing polyol is 2,2-dimethylolpropionic acid.

[0123] As the active hydrogen group-containing compound containing a hydrophilic group, from the viewpoint of reactivity, preferably, an active hydrogen group-containing compound containing an ionic group is used. That is, preferably, the water-dispersible polyisocyanate is a reaction product of a polyisocyanate component and an active hydrogen group-containing compound containing an ionic group.

[0124] The active hydrogen group-containing compound containing a hydrophilic group can be used alone or in combination of two or more kinds.

[0125] The active hydrogen group-containing component optionally includes a low molecular weight polyol and a macropolyol.

[0126] The low molecular weight polyol is a compound having a molecular weight of 50 or more, preferably 70 or more, and 650 or less, preferably 600 or less.

[0127] Examples of low molecular weight polyols include short chain diols having 2 to 6 carbon atoms. Examples of short chain diols having 2 to 6 carbon atoms include alkane diols having 2 to 6 carbon atoms (alkylene glycols having 2 to 6 carbon atoms), ether diols having 2 to 6 carbon atoms, and alkene diols having 2 to 6 carbon atoms.

[0128] Examples of alkanediols having 2 to 6 carbon atoms include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, and 1,3- or 1,4-cyclohexanediol.

[0129] Examples of the ether diol having 2 to 6 carbon atoms include diethylene glycol, triethylene glycol, and dipropylene glycol.

[0130] An example of the alkenediol having 2 to 6 carbon atoms is 1,4-dihydroxy-2-butene.

[0131] The low molecular weight polyols can be used alone or in combination of two or more kinds.

[0132] A macropolyol is a compound having a molecular weight of 650 or more, preferably 700 or more, and 3000 or less, preferably 2000 or less.

[0133] Examples of the macro polyol include polyether polyol, polyester polyol, polycarbonate polyol, polyurethane polyol, epoxy polyol, vegetable oil polyol, polyolefin polyol, acrylic polyol, and vinyl monomer modified polyol. The macro polyol is preferably polycarbonate polyol.

[0134] Polycarbonate polyols can be obtained by reacting dihydric alcohols with carbonate esters.

[0135] Examples of dihydric alcohols include 2-methyl-1,3-propanediol and 1,6-hexanediol.

[0136] Examples of carbonate esters include dimethyl carbonate and diethyl carbonate.

[0137] The active hydrogen group-containing component preferably does not include a low molecular weight polyol and a macro polyol, and is composed of an active hydrogen group-containing compound containing a hydrophilic group, or does not include a low molecular weight polyol, and is composed of an active hydrogen group-containing compound containing a hydrophilic group and a macro polyol.

[0138] When the active hydrogen group-containing component is composed of an active hydrogen group-containing compound containing a hydrophilic group, the active hydrogen group-containing compound containing a hydrophilic group preferably comprises an active hydrogen group-containing compound containing a nonionic group, and more preferably comprises an active hydrogen group-containing compound containing a nonionic group.

[0139] In addition, when the active hydrogen group-containing component is composed of an active hydrogen group-containing compound containing a hydrophilic group and a macropolyol, the active hydrogen group-containing compound containing a hydrophilic group preferably includes an active hydrogen group-containing compound containing an ionic group, and more preferably consists of an active hydrogen group-containing compound containing an ionic group.

[0140] In addition, when the active hydrogen group-containing component is composed of an active hydrogen group-containing compound containing a hydrophilic group and a macro polyol, the content of the active hydrogen group-containing compound containing a hydrophilic group is, for example, 1 mass% or more, preferably 5 mass% or more, and, for example, 20 mass% or less, preferably 10 mass% or less, based on the active hydrogen group-containing component. In addition, the content of the macro polyol is, for example, 80 mass% or more, preferably 90 mass% or more, and, for example, 99 mass% or less, preferably 95 mass% or less, based on the active hydrogen group-containing component.

[0141] More preferably, the active hydrogen group-containing component does not contain a low molecular weight polyol, and is composed of an active hydrogen group-containing compound containing a hydrophilic group and a macropolyol.

[0142] To produce the water-dispersible polyisocyanate, a polyisocyanate component and an active hydrogen group-containing component are mixed in an equivalent ratio (isocyanate group / active hydrogen group) of the isocyanate group in the polyisocyanate component to the active hydrogen group (hydroxyl group) in the active hydrogen group-containing component that exceeds 1, preferably in a ratio of 1.1 or more and 10 or less, and then reacted (polymerized).

[0143] The polymerization method includes bulk polymerization and solution polymerization, and is preferably solution polymerization.

[0144] In the solution polymerization, for example, a polyisocyanate component and an active hydrogen group-containing component are mixed in an organic solvent (solvent) under a nitrogen atmosphere and reacted. As reaction conditions, the reaction temperature is, for example, 20° C. or higher and, for example, 80° C. or lower. The reaction time is, for example, 1 hour or higher and, for example, 20 hours or lower.

[0145] Examples of the organic solvent include those which are inactive to isocyanate groups and highly hydrophilic, such as acetone, methyl ethyl ketone, butyl acetate, tetrahydrofuran, and acetonitrile.

[0146] Furthermore, for example, when an anionic group is contained as the hydrophilic group, it is preferable to neutralize the hydrophilic group by adding a neutralizing agent (for example, triethylamine) to form a salt of the anionic group.

[0147] In the polymerization, if necessary, for example, a reaction catalyst (for example, dioctyltin dilaurate) may be added. In addition, unreacted polyisocyanate components can be removed by a known method such as distillation or extraction.

[0148] This gives a water-dispersible polyisocyanate.

[0149] The isocyanate group concentration of the water-dispersible polyisocyanate is, for example, 0.1 mass % or more, preferably 1.0 mass % or more, for example, 22 mass % or less, preferably 15 mass % or less.

[0150] The isocyanate composition preferably includes another isocyanate-terminated prepolymer.

[0151] Other isocyanate-terminated prepolymers are reaction products of other polyisocyanate components with other macropolyols.

[0152] The other polyisocyanate component may be the polyisocyanate exemplified in the polyisocyanate of the water-dispersible polyisocyanate. The other polyisocyanate component may preferably be an alicyclic polyisocyanate. The other polyisocyanate component may more preferably be IPDI.

[0153] As the other macropolyol, the macropolyol exemplified in the macropolyol of the water-dispersible polyisocyanate may be mentioned. As the other macropolyol, preferably, polycarbonate polyol may be mentioned.

[0154] The other isocyanate-terminated prepolymer can be obtained by reacting (polymerizing) the other polyisocyanate component with the other macropolyol.

[0155] The reaction method (equivalent ratio in polymerization (isocyanate group / active hydrogen group), reaction temperature and reaction time) are the same as those for the above water-dispersed polyisocyanate.

[0156] This gives another isocyanate-terminated prepolymer.

[0157] When the isocyanate composition contains another isocyanate-terminated prepolymer, the content of the other isocyanate-terminated prepolymer is, for example, 30% by mass or more, preferably 45% by mass or more, and for example, 70% by mass or less, preferably 60% by mass or less, relative to the isocyanate composition. The content of the water-dispersed polyisocyanate is, for example, 30% by mass or more, preferably 40% by mass or more, and for example, 70% by mass or less, preferably 55% by mass or less, relative to the isocyanate composition.

[0158] The isocyanate composition is then reacted with a polyamine by a method described below to obtain a polyurea.

[0159] [Method of manufacturing microcapsule catalyst] The method for producing the microcapsule catalyst is not particularly limited, and examples thereof include an interfacial polymerization method, an in-situ polymerization method, a coacervation method, a submerged drying method, a spray drying method, a melt dispersion cooling method, an orifice method, an air suspension coating method, and an inorganic wall microencapsulation method. The method for producing the microcapsule catalyst is preferably an interfacial polymerization method.

[0160] In the interfacial polymerization method, a catalyst is first dispersed in a dispersion medium.

[0161] The dispersion medium is a known organic solvent, such as ethyl acetate, toluene, and hexanol.

[0162] The isocyanate composition is then formulated.

[0163] Next, water is added, and the mixture is emulsified and dispersed using, for example, a homogenizer.

[0164] Next, the polyamine is blended.

[0165] Examples of polyamines include aromatic polyamines, aromatic aliphatic polyamines, alicyclic polyamines, aliphatic polyamines, amino alcohols, polyoxyethylene group-containing polyamines, alkoxysilyl compounds having a primary amino group, alkoxysilyl compounds having both a primary amino group and a secondary amino group, and hydrazine.Preferably, hydrazine is used as the polyamine.

[0166] Then, the polyisocyanate and the polyamine and / or water (a small amount of water in the system) react at the interface between the dispersion medium and the water to produce an aqueous dispersion of microcapsules encapsulating the catalyst.

[0167] In the above reaction, the reaction temperature is, for example, 5° C. or more, preferably 10° C. or more, and for example, 50° C. or less, preferably 30° C. or less. The reaction time is, for example, 30 minutes or more, preferably 60 minutes or more, and for example, 300 minutes or less, preferably 180 minutes or less. The equivalent ratio of the isocyanate groups of the polyisocyanate to the amino groups of the polyamine (isocyanate groups / amino groups) is, for example, 0.7 or more, preferably 0.9 or more, and for example, 1.1 or less.

[0168] The solids concentration of the microcapsule solution is, for example, 1 mass % or more, preferably 3 mass % or more, and for example, 15 mass % or less, preferably 10 mass % or less.

[0169] The volume average particle diameter of the microcapsules is, for example, 1.0 μm or more, preferably 2.0 μm or more, and for example, for example, 20.0 μm or less, preferably 10.0 μm or less, more preferably 8.0 μm or less, even more preferably 4.0 μm or less, and particularly preferably 3.0 μm or less.

[0170] The method for measuring the volume average particle size will be described in detail in the Examples described later.

[0171] The catalyst content in the microcapsule catalyst is, per 100 parts by mass of the total amount of the hydroxyl group-containing resin and the alkyl etherified melamine resin, for example, 1 part by mass or more, preferably 5 parts by mass or more, and for example, 25 parts by mass or less, preferably 15 parts by mass or less, and more preferably 8 parts by mass or less.

[0172] <Water> Water is the dispersion medium in the coating composition.

[0173] The water content is, for example, 50 mass % or more, preferably 55 mass % or more, more preferably 60 mass % or more, and for example, 80 mass % or less, relative to the coating composition.

[0174] The coating composition also contains an organic solvent, specifically, an organic solvent used in producing the hydroxyl group-containing resin and the alkyl-etherified melamine resin.

[0175] The content of the organic solvent with respect to the coating composition is, for example, 20 mass % or less, or preferably 15 mass % or less, from the viewpoint of environmental protection.

[0176] The coating composition has a solids concentration of, for example, 10 mass % or more, and for example, 50 mass % or less, preferably 40 mass % or less.

[0177] <Preparation of Coating Composition> The coating composition is prepared by mixing a hydroxyl-containing resin, an alkyl-etherified melamine resin, a microcapsule catalyst, and water. The water used in producing the microcapsule catalyst can be used as is, or water can be newly added when the hydroxyl-containing resin, the alkyl-etherified melamine resin, and the microcapsule catalyst are mixed.

[0178] In the above preparation, additives can be further blended in an appropriate ratio, that is, the coating composition can also contain additives.

[0179] Examples of the additives include pigments, dyes, leveling agents, stability improvers, foam inhibitors, weather resistance improvers, popping inhibitors, antioxidants, dispersants, wetting agents, thixotropic agents, and ultraviolet absorbing agents.

[0180] The additives can be used alone or in combination of two or more kinds.

[0181] This prepares the coating composition.

[0182] <Method of manufacturing laminate> With reference to FIG. 1, one embodiment of a method for producing a laminate (a method for using a coating composition) will be described.

[0183] In Fig. 1, the up-down direction of the paper is the up-down direction (thickness direction), the upper side of the paper is the upper side (one side in the thickness direction), and the lower side of the paper is the lower side (the other side in the thickness direction). The left-right direction and the depth direction of the paper are surface directions perpendicular to the up-down direction. Specifically, they follow the directional arrows in each figure.

[0184] The method for producing a laminate comprises a first step of forming a coating film 3 on the surface of an object to be coated 2, and a second step of curing the coating film 3 at a predetermined temperature to form a cured layer 4. In this method, the laminate 1 is produced and the cured layer 4 is also produced as a cured product.

[0185] [1st step] In the first step, a coating film 3 is formed on the surface (one surface in the thickness direction) of an object 2 to be coated.

[0186] In the first step, as shown in FIG. 1A, first, an object to be coated 2 is prepared.

[0187] The object 2 is an object to be coated, the surface (one surface in the thickness direction) of which is imparted with various physical properties by the hardened layer 4.

[0188] In FIG. 1A, the object to be coated 2 has a flat plate shape, but the shape of the object to be coated 2 is not particularly limited, and various shapes can be selected.

[0189] From the viewpoint of industrial availability, the object 2 to be coated is preferably made of resin or metal.

[0190] Examples of the resin include polyester 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 the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of the (meth)acrylic resin include polymethyl methacrylate resin (PMMA). Examples of the polyolefin resin include polyethylene resin and polypropylene resin.

[0191] Examples of metals include iron, aluminum, zinc, stainless steel, and alloys thereof.

[0192] Next, as shown in FIG. 1B, a coating composition is applied to the surface (one surface in the thickness direction) of the body 2 to be coated, and dried as necessary.

[0193] Examples of the coating method include spray coating, dip coating, roll coating, gravure coating, spin coating, bar coater, and doctor blade methods. The coating method is preferably the bar coater method.

[0194] As a result, a coating film 3 is formed on the surface (one surface in the thickness direction) of the body 2 to be coated.

[0195] [Second process] In the second step, as shown in FIG. 1C, the coating film 3 is cured at a predetermined temperature to form a cured layer 4.

[0196] Specifically, the coating film 3 is cured at, for example, 40°C or higher, preferably 60°C or higher, and, for example, 100°C or lower.

[0197] The curing time (heating time) is, for example, 15 minutes or more, preferably 20 minutes or more, and for example, 120 minutes or less, preferably 60 minutes or less.

[0198] As a result, the catalyst is released from the wall material of the microcapsule catalyst. Then, in the presence of the catalyst, the hydroxyl-containing resin reacts with the alkyl-etherified melamine resin, curing the coating film 3 to form a cured layer 4 as a cured product.

[0199] The thickness of the cured layer 4 is, for example, 1 μm or more, preferably 3 μm or more, and for example, 50 μm or less, preferably 20 μm or less, more preferably 16 μm or less.

[0200] In this manner, the laminate 1 is produced which includes the body 2 to be coated and the cured layer 4 in that order in the thickness direction.

[0201] <Action and effect> The coating composition contains a microencapsulated catalyst that contains a specific catalyst, and therefore, even when the solvent contains water, aggregation of the hydroxyl-containing resin can be suppressed.

[0202] Specifically, it is contemplated that the solvent in an environmentally friendly coating composition may be partially or entirely replaced by water instead of an organic solvent.

[0203] However, when the solvent contains water, from the viewpoint of compatibility, there is a problem in that the resin having a hydroxyl group interacts with the metal-based catalyst and the additive containing a metal (metal-based additive) among the additives that are blended as necessary, resulting in aggregation.

[0204] On the other hand, in the coating composition, the catalyst is encapsulated, which can suppress aggregation of the hydroxyl group-containing resin from the viewpoint of compatibility. EXAMPLES

[0205] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Note that "parts" and "%" are based on mass unless otherwise specified. In addition, the specific numerical values ​​of the blending ratio (content ratio), physical property values, parameters, etc. used in the following description can be replaced with the upper limit value (numerical value defined as "less than or equal to" or "less than") or lower limit value (numerical value defined as "more than or equal to" or "exceeding") of the corresponding blending ratio (content ratio), physical property values, parameters, etc. described in the above "Form for carrying out the invention".

[0206] <Ingredient details> The trade names and abbreviations of the components used in each Production Example, each Example, each Preparation Example, and each Comparative Example will be described in detail. NeoCryl XK-110: Acrylic resin solution containing hydroxyl groups, solid content concentration 46.5% by mass, weight average molecular weight 20,000, hydroxyl value 84 mgKOH / g, manufactured by DSM NeoCryl XK-104: Acrylic resin solution containing hydroxyl groups, solid content concentration 53% by mass, weight average molecular weight 120,000, hydroxyl value 40 mgKOH / g, manufactured by DSM Zinc octylate: SP value 9.2, acidity 4.9, manufactured by Nacalai Tesque Aluminum nitrate nonahydrate: SP value 15.4, acidity -1.3, Wako Pure Chemical Industries, Ltd. ETERNACOLL UH-100: Polycarbonate polyol, manufactured by Ube Industries, Ltd. DHD-1000: An active hydrogen compound containing a polyoxyethylene group in the side chain, obtained by reacting MPEG-1000 (methoxypolyethylene glycol) with HDI, removing the unreacted HDI, and then reacting with diethanolamine. Takenate WD-726 (water-dispersible polyisocyanate obtained using an active hydrogen group-containing compound containing a nonionic group, isocyanate group concentration 10.1% by mass, solid content concentration 80% by mass, manufactured by Mitsui Chemicals, Inc.) Duranate TKA-100: Reaction product of isocyanurate derivative of HDI and MPEG-1000 (methoxypolyethylene glycol) (isocyanate group concentration 21.8% by mass, solid content concentration 100% by mass, manufactured by Asahi Kasei Corporation)

[0207] <Preparation of methyl etherified melamine resin solution> Preparation Example 1 126g of melamine, 163.2g of paraformaldehyde with a formalin concentration of 92% and 192.2g of methanol were charged into a four-neck flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet tube, and the temperature was raised to the reflux temperature. A methylolation reaction was carried out at the reflux temperature for 1 hour. Next, 0.180g of a 50% aqueous solution of paratoluenesulfonic acid was added, and a methyl etherification reaction was carried out under reflux for 3 hours. Thereafter, the reaction product was neutralized with 0.160g of a 20% sodium hydroxide solution, and then ethanol and water were distilled off under reduced pressure, followed by dilution with isopropyl alcohol to a solid concentration of 72.4% by mass to obtain a methyl etherified melamine resin solution. The weight average molecular weight of the methyl etherified melamine resin was 1400.

[0208] <Preparation of zinc dodecylbenzenesulfonate> Manufacturing Example 1 100 parts by mass of 99.5% ethanol and 1 part by weight of zinc oxide were added to a four-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, and 8.02 parts by mass of dodecylbenzenesulfonic acid (manufactured by TCI) were added while stirring at 70°C, and the mixture was stirred until it became transparent. After the reaction, unreacted components and 99.5% ethanol were removed by distillation at 100°C under reduced pressure. This resulted in zinc dodecylbenzenesulfonate (SP value: 9.4, acidity -1.8).

[0209] <Production of other isocyanate-terminated prepolymers> Manufacturing Example 2 In a four-neck flask (1 L), 207.7 parts by mass of ETERNACOLL UH-100, 92.3 parts by mass of isophorone diisocyanate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 200 parts by mass of butyl acetate, and 0.02 parts by mass of dioctyltin dilaurate (Neostan U-810, manufactured by Nitto Kasei Kogyo Co., Ltd.) were dissolved by stirring at room temperature (25° C.), and then reacted at 75° C. This produced another isocyanate group-terminated prepolymer (isocyanate group concentration 3.5% by mass).

[0210] <Production of Water-Dispersible Polyisocyanate> Production Example 3 In a four-neck flask (1 L), 310.8 parts by mass of DHD-1000, 89.2 parts by mass of hexamethylene diisocyanate (manufactured by Tosoh Corporation), 100 parts by mass of butyl acetate, and 0.02 parts by mass of dioctyltin dilaurate (Neostan U-810, manufactured by Nitto Kasei Kogyo Co., Ltd.) were dissolved by stirring at room temperature (25° C.) and then reacted at 75° C. This produced a water-dispersible polyisocyanate (isocyanate group concentration 5.6% by mass).

[0211] Production Example 4 In a four-neck flask (1 L), 19.1 parts by mass of dimethylolpropionic acid (Tokyo Chemical Industry Co., Ltd.), 242.5 parts by mass of ETERNACOLL UH-100, 138.4 parts by mass of isophorone diisocyanate (Fujifilm Wako Pure Chemical Industries, Ltd.), 100 parts by mass of butyl acetate, and 0.02 parts by mass of dioctyltin dilaurate (Neostan U-810, Nitto Chemical Industry Co., Ltd.) were dissolved by stirring at room temperature (25° C.) and then reacted at 75° C. This produced a water-dispersible polyisocyanate (isocyanate group concentration 5.0% by mass).

[0212] <Production of Microcapsule Catalyst Aqueous Dispersion> Production Example 5 (embodiment using water-dispersible polyisocyanate obtained by using an active hydrogen group-containing compound having a nonionic group) After uniformly mixing 1.6 parts by mass of zinc dodecylbenzenesulfonate and 4.36 parts by mass of butyl acetate of Production Example 1, an isocyanate composition containing 1.8 parts by mass of Takenate WD-726 and 1.4 parts by mass of Duranate TKA-100 was added and stirred uniformly. Next, 86.8 parts by mass of distilled water was added and emulsified and dispersed with a homogenizer.

[0213] Next, 3.6 parts by mass of a 10% aqueous hydrazine solution was added with stirring at 10° C., and after stirring for 2 hours, the temperature was raised to 20° C. to react the isocyanate composition with hydrazine for 2 hours.

[0214] This resulted in the production of a microcapsule catalyst aqueous dispersion. The solid content of the microcapsule catalyst aqueous dispersion was 4.8% by mass. The volume average particle size of the microcapsules was 7.09 μm.

[0215] Production Example 6 (embodiment using water-dispersible polyisocyanate obtained by using an active hydrogen group-containing compound having a nonionic group) After uniformly mixing 1.2 parts by mass of zinc octylate (manufactured by Nacalai Tesque) and 2.4 parts by mass of butyl acetate, an isocyanate composition containing 4.0 parts by mass of Takenate WD-726 was added and uniformly stirred. Next, 89.5 parts by mass of distilled water was added and emulsified and dispersed with a homogenizer.

[0216] Next, 2.9 parts by mass of a 10% aqueous hydrazine solution was added with stirring at 10° C., and the isocyanate composition and hydrazine were reacted for 2 hours.

[0217] This resulted in the production of a microcapsule catalyst aqueous dispersion. The solid content of the microcapsule catalyst aqueous dispersion was 4.6% by mass. The volume average particle size of the microcapsules was 3.5 μm.

[0218] Production Example 7 (An embodiment using a water-dispersible polyisocyanate obtained by using an active hydrogen compound containing a polyoxyethylene group in the side chain, and another isocyanate-terminated prepolymer) After uniformly mixing 2.3 parts by mass of zinc dodecylbenzenesulfonate and 4.7 parts by mass of butyl acetate from Production Example 1, an isocyanate composition containing 1.7 parts by mass of another isocyanate-terminated prepolymer from Production Example 2 and 1.2 parts by mass of a water-dispersible polyisocyanate from Production Example 3 was added and stirred uniformly. Next, 89.3 parts by mass of distilled water was added and emulsified and dispersed with a homogenizer.

[0219] Next, 0.8 parts by mass of a 10% aqueous hydrazine solution was added with stirring at 10° C., and after stirring for 2 hours, the temperature was raised to 20° C. to react the isocyanate composition with hydrazine for 2 hours.

[0220] This resulted in the production of a microcapsule catalyst aqueous dispersion. The solid content of the microcapsule catalyst aqueous dispersion was 4.4% by mass. The volume average particle size of the microcapsules was 3.4 μm.

[0221] Production Example 8 (Water-dispersible polyisocyanate obtained by using an active hydrogen group-containing compound containing an ionic group, and an embodiment using another isocyanate group-terminated prepolymer) After uniformly mixing 2.0 parts by mass of zinc dodecylbenzenesulfonate of Production Example 1, 2.0 parts by mass of toluene, and 0.9 parts by mass of hexanol, an isocyanate composition containing 2.5 parts by mass of another isocyanate group-terminated prepolymer of Production Example 2 and 2.5 parts by mass of water-dispersed polyisocyanate of Production Example 4 was added and uniformly stirred. Then, 0.05 parts by mass of triethylamine (neutralizer) was added and stirred. Next, 89.2 parts by mass of distilled water was added, and the mixture was emulsified and dispersed with a homogenizer.

[0222] Next, 0.9 parts by mass of a 10% aqueous hydrazine solution was added with stirring at 10° C., and after stirring for 2 hours, the mixture was heated to 20° C. and the isocyanate composition and hydrazine were reacted for 2 hours.

[0223] This resulted in the production of a microcapsule catalyst aqueous dispersion. The solid content of the microcapsule catalyst aqueous dispersion was 5.1% by mass. The volume average particle size of the microcapsules was 2.3 μm.

[0224] Production Example 9 In a 1000 mL flask, 90 parts by mass of zinc dodecylbenzenesulfonate was added to 10 parts by mass of toluene, and the mixture was stirred at room temperature (25° C.) to dissolve, and then stirred to prepare a 10% zinc dodecylbenzenesulfonate solution.

[0225] <Preparation of Coating Composition> Examples 1 to 7 and Comparative Examples 1 to 3 A hydroxyl group-containing resin, an alkyl-etherified melamine resin, a microcapsule catalyst, and water were mixed according to the formulation shown in Table 1. In this way, a coating composition was prepared.

[0226] <Evaluation> [Isocyanate group concentration (unit: mass%)] The isocyanate group concentration was measured by the n-dibutylamine method in accordance with JIS K 1603-1.

[0227] <Volume average particle size (unit: μm)> For the microcapsule particles of each production example, 1 g of sample and 10 g of distilled water were placed in a 30 ml glass sample bottle and stirred for 5 minutes with a magnetic stirrer, after which particle size analysis measurements were performed using a particle size analyzer Microtrac HRA (manufactured by Nikkiso Co., Ltd.).

[0228] [Laminate manufacturing] (1st step) A steel plate (150 mm x 70 mm x 0.8 mm thick) was prepared as the object to be coated.

[0229] [Second process] The coating composition of each Example and Comparative Example was applied to the surface (one side in the thickness direction) of the substrate using a bar coater and dried at 80° C. for 30 minutes to form a coating film.

[0230] [3rd step] The coating film was heated at 80° C. for 30 minutes to be cured, thereby forming a coating layer (thickness: 15 μm), thereby producing a laminate.

[0231] [Appearance of coating composition] The coating compositions of each Example and Comparative Example were visually observed. The appearance was evaluated based on the following criteria. The results are shown in Table 1. {standard} ◯: No aggregates or precipitates were observed. △: Aggregates and / or precipitates were observed in some areas, but were no longer observed upon stirring. ×: Aggregates and / or precipitates were clearly observed.

[0232] [Coating appearance] The coating films of each Example and Comparative Example were visually observed. The appearance of the coating films was evaluated based on the following criteria. The results are shown in Table 1. {standard} ◯: No bumps were observed on the coating. △: Blemishes were observed in some parts of the coating film. ×: A large number of lumps were observed on the coating film.

[0233] [Cure property (gel fraction measurement)] The laminates of each Example and Comparative Example were immersed in acetone refluxed in a Soxhlet fat extractor for 4 hours. The acetone was then dried by heating. The masses of the coated laminates were measured before and after immersion in acetone, and the gel fraction was calculated using the following formula (1). If the gel fraction is high, it is understood that the methyl etherified melamine resin is sufficiently cured (crosslinked) when the coating film formed from the aqueous resin composition is cured, and therefore the curing property is excellent. Note that in Comparative Example 3, coagulation occurred in the aqueous resin composition when aluminum nitrate nonahydrate was added, so that the measurement was not possible. G = 100 × (m2 / m1) (1) G: Gel fraction (%) m1: Mass of the test piece before immersion in acetone (mg) m2: Mass of residue after immersion in acetone (mg)

[0234] [Table 1] [Explanation of symbols]

[0235] 1. Laminate 2 Object to be painted 3. Coating 4 Hardened layer

Claims

1. A hydroxyl group-containing resin; an alkyl etherified melamine resin; A microcapsule catalyst; and water, The microcapsule catalyst includes a core material containing a catalyst and a wall material encapsulating the catalyst, The catalyst has an SP value of 11 or less, The coating composition, wherein the acidity of the catalyst is -3.0 or more and 5.0 or less.

2. 10. The coating composition of claim 1, wherein the catalyst is zinc dodecylbenzenesulfonate.

3. The coating composition of claim 1 , wherein the wall material is a polyurea.

4. 4. The coating composition of claim 3, wherein the polyurea is a reaction product of a water-dispersible polyisocyanate with a polyamine and / or water.

5. 5. The coating composition according to claim 4, wherein the water-dispersible polyisocyanate is a reaction product of a polyisocyanate component and an active hydrogen group-containing compound that contains an ionic group.

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