Curable composition and cured product thereof

Abstract

Provided is a curable composition characterized by containing an acrylic polymer (A) having a hydroxyl group, a polyisocyanate compound (B), and a quaternary ammonium salt (C) represented by general formula (1), the content of the quaternary ammonium salt (C) being 0.4-3 mass% with respect to the polymer (A). The curable composition can be used for a long time and has excellent curability, and a cured product having excellent solvent resistance and hot water resistance can be obtained. Therefore, the resin composition can be suitable for in-mold coating for molding and coating materials such as various coatings and plastics in the same mold for interior and exterior decoration of automobiles, automobile repair, plastics, films, industrial machinery, building materials, wood floors and the like. (In general formula (1), R1-R4 each independently represents an alkyl group having 1-18 carbon atoms, and R5 represents an alkyl group having 1-8 carbon atoms or a hydrogen atom)

Description

Technical Field

[0001] The present invention relates to a curable composition and a cured product thereof. Background Art

[0002] Conventionally, two-component urethane coatings comprising a combination of a hydroxyl group-containing resin and a polyisocyanate compound have been used for various applications, including automotive interior and exterior decoration, automotive repair, plastics, industrial machinery, and building materials.

[0003] For these coatings, balancing pot life and curability is a challenge. For example, a method for forming a cured coating film has been proposed, which involves applying a curable composition comprising a resin having a hydroxyl group, a polyisocyanate compound, and a quaternary ammonium carboxylate as a curing accelerator (see, for example, Patent Document 1).

[0004] However, coating films obtained from such curable compositions have a problem of insufficient hot water resistance. Therefore, there is a need for materials with long pot life and excellent coating properties such as hot water resistance.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 3867879 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] The problem to be solved by the present invention is to provide a curable composition that has a long pot life, excellent curability, and can produce a cured product having excellent solvent resistance and hot water resistance.

[0010] Means for solving problems

[0011] The present inventors have conducted intensive studies to solve the above-mentioned problems and have discovered that a curable composition containing an acrylic polymer having a hydroxyl group, a polyisocyanate compound, and a specific quaternary ammonium salt has a long pot life, excellent curability, and can produce a cured product with excellent solvent resistance and hot water resistance. This has led to the completion of the present invention.

[0012] That is, the present invention relates to the following curable composition, characterized in that it contains: an acrylic polymer (A) having a hydroxyl group, a polyisocyanate compound (B), and a quaternary ammonium salt (C) represented by the general formula (1), wherein the content of the quaternary ammonium salt (C) is 0.4 to 3% by mass relative to the polymer (A).

[0013] [Chemical Formula 1]

[0014]

[0015] (In general formula (1), R 1 ~R 4 Each independently represents an alkyl group having 1 to 18 carbon atoms, R 5 represents an alkyl group having 1 to 8 carbon atoms or a hydrogen atom.

[0016] Effects of the Invention

[0017] The curable composition of the present invention has a long pot life, excellent curability, and can produce a cured product with excellent solvent resistance and hot water resistance. Therefore, it is suitable for in-mold coating applications where various coatings, plastics, and other materials are molded and coated in the same mold for applications such as automotive interior and exterior decoration, automotive repair, plastics, films, industrial machinery, building materials, and wood flooring. DETAILED DESCRIPTION

[0018] The curable composition of the present invention contains an acrylic polymer (A) having a hydroxyl group, a polyisocyanate compound (B), and a quaternary ammonium salt (C) represented by the general formula (1), wherein the content of the quaternary ammonium salt (C) is 0.4 to 3% by mass relative to the polymer (A).

[0019] [Chemical Formula 2]

[0020]

[0021] (In general formula (1), R 1 ~R 4 Each independently represents an alkyl group having 1 to 18 carbon atoms, R 5 represents an alkyl group having 1 to 8 carbon atoms or a hydrogen atom.

[0022] The acrylic polymer (A) having a hydroxyl group has two or more hydroxyl groups and can be obtained, for example, by copolymerizing an acrylic monomer (a1) having a hydroxyl group and another monomer (a2).

[0023] Examples of the acrylic monomer (a1) having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxy-n-butyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-n-butyl (meth)acrylate, 3-hydroxy-n-butyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, N-(2-hydroxyethyl) (meth)acrylamide, glycerol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, and lactone-modified (meth)acrylates having a hydroxyl group at the terminal. These acrylic monomers (a1) having a hydroxyl group may be used alone or in combination of two or more.

[0024] Examples of the other monomers (a2) include: monomers having a carboxyl group, such as (meth)acrylic acid, crotonic acid, β-carboxyethyl (meth)acrylate, ω-carboxy-polycaprolactone mono(meth)acrylate, unsaturated monocarboxylic acids such as 2-(meth)acryloyloxyethyl succinate and 2-(meth)acryloyloxyethyl hexahydrophthalate; unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, or half esters of these unsaturated dicarboxylic acids; methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, and t-butyl (meth)acrylate. These monomers include 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, cyclohexyl (meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentyl (meth)acrylate, benzyl (meth)acrylate, acrylamide, N,N-dimethyl (meth)acrylamide, (meth)acrylonitrile, 3-(meth)acryloylpropyltrimethoxysilane, N,N-dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, 2-(meth)acryloyloxyethyl acid phosphate, styrene, α-methylstyrene, p-methylstyrene, and p-methoxystyrene. These monomers may be used alone or in combination of two or more.

[0025] In the present invention, “(meth)acrylic acid” refers to one or both of methacrylic acid and acrylic acid, “(meth)acrylate” refers to one or both of methacrylate and acrylate, and “(meth)acryloyl” refers to one or both of methacryloyl and acryloyl.

[0026] The acrylic polymer (A) can be produced by using the hydroxyl group-containing monomer (a1) and the other monomer (a2) as raw materials by a known polymerization method, but solution radical polymerization is the simplest and therefore preferred.

[0027] The solution radical polymerization method is a method in which the monomers serving as raw materials are dissolved in a solvent and a polymerization reaction is carried out in the presence of a polymerization initiator. Examples of solvents that can be used include hydrocarbon solvents such as toluene, xylene, cyclohexane, n-hexane, and octane; alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, isobutanol, sec-butanol, and ethylene glycol monomethyl ether; ester solvents such as methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, and amyl acetate; and ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. These solvents can be used alone or in combination of two or more.

[0028] Examples of polymerization initiators used in the production of the acrylic polymer (A) include azo compounds such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), and azobiscyanovaleric acid; organic peroxides such as t-butyl peroxypivalate, t-butyl peroxybenzoate, t-butyl peroxy-2-ethylhexanoate, di-t-butyl peroxide, cumene hydroperoxide, benzoyl peroxide, and t-butyl hydroperoxide; and inorganic peroxides such as hydrogen peroxide, ammonium persulfate, potassium persulfate, and sodium persulfate. These polymerization initiators may be used alone or in combination of two or more. The polymerization initiator is preferably used in an amount of 0.1 to 12% by mass based on the total amount of the monomers used as the raw materials for the polymer (A).

[0029] Furthermore, a chain transfer agent such as lauryl mercaptan, octyl mercaptan, 2-mercaptoethanol, octyl thioglycolate, 3-mercaptopropionic acid, or α-methylstyrene dimer may be used together with the above-mentioned polymerization initiator as needed.

[0030] From the viewpoint of further improving the balance between the usable time and curability, the acid value of the acrylic polymer (A) is preferably 0.1 to 15 mgKOH / g, more preferably 0.5 to 10 mgKOH / g, and even more preferably 1 to 8 mgKOH / g.

[0031] From the viewpoint of further improving the balance between the usable time and the curability, the hydroxyl value of the polymer (A) is preferably 10 to 200 mgKOH / g, more preferably 30 to 150 mgKOH / g, and even more preferably 40 to 130 mgKOH / g.

[0032] In addition, the acid value and hydroxyl value of the acrylic polymer in the present invention are values ​​measured in accordance with JIS test method K0070-1992.

[0033] The weight average molecular weight (Mw) of the acrylic polymer (A) is preferably 2000 to 50000, more preferably 4000 to 20000. The weight average molecular weight (Mw) is a value measured by gel permeation chromatography (hereinafter abbreviated as "GPC") and calculated in terms of polystyrene.

[0034] Examples of the polyisocyanate compound (B) include aromatic diisocyanate compounds such as tolylene diisocyanate, diphenylmethane diisocyanate, m-xylylene diisocyanate, and m-phenylenebis(dimethylmethylene) diisocyanate; and aliphatic or alicyclic diisocyanate compounds such as hexamethylene diisocyanate, lysine diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 2-methyl-1,3-diisocyanatocyclohexane, 2-methyl-1,5-diisocyanatocyclohexane, 4,4′-dicyclohexylmethane diisocyanate, and isophorone diisocyanate.

[0035] In addition, as the polyisocyanate compound (B), the following may be used: a prepolymer having an isocyanate group obtained by an addition reaction of the above-mentioned diisocyanate compound and a polyol; a compound having an isocyanurate ring obtained by cyclotrimerization of the above-mentioned diisocyanate compound; a polyisocyanate compound having a urea bond or a biuret bond obtained by reacting the above-mentioned diisocyanate compound with water; a homopolymer of an acrylic monomer having an isocyanate group, such as 2-isocyanatoethyl (meth)acrylate, 3-isopropenyl-α,α-dimethylbenzyl isocyanate, or (meth)acryloyl isocyanate; a copolymer having an isocyanate group obtained by copolymerizing the above-mentioned acrylic monomer having an isocyanate group with another acrylic monomer, a vinyl ester compound, a vinyl ether compound, an aromatic vinyl monomer, a fluoroolefin, or the like; and the like.

[0036] The polyisocyanate compound (B) may be used alone or in combination of two or more. From the viewpoint of further improving solvent resistance and hot water resistance, it is preferred that the polyisocyanate compound (B) contain a compound having three or more isocyanate groups in one molecule.

[0037] The quaternary ammonium salt (C) will be described below. The quaternary ammonium salt (C) serves as a curing catalyst and promotes the reaction between the hydroxyl groups of the polymer (A) and the isocyanate groups of the polyisocyanate compound (C).

[0038] The quaternary ammonium carbonate (C) is represented by the general formula (1), and examples thereof include tetramethylammonium octyl carbonate, methyltriethylammonium octyl carbonate, ethyltrimethylammonium octyl carbonate, propyltrimethylammonium hexyl carbonate, butyltrimethylammonium butyl carbonate, pentyltrimethylammonium propyl carbonate, hexyltrimethylammonium methyl carbonate, heptyltrimethylammonium methyl carbonate, octyltrimethylammonium methyl carbonate, nonyltrimethylammonium methyl carbonate, decyltrimethylammonium methyl carbonate, undecyltrimethylammonium methyl carbonate, dodecyltrimethylammonium methyl carbonate, tridecyltrimethylammonium methyl carbonate, tetradecyltrimethylammonium methyl carbonate, heptadecyltrimethylammonium methyl carbonate, hexadecyltrimethylammonium methyl carbonate, and heptadecyltrimethylammonium methyl carbonate. The quaternary ammonium carbonates (C) include monoalkyl carbonates such as trimethylammonium methyl carbonate, octadecyltrimethylammonium methyl carbonate, tributylmethylammonium methyl carbonate, trioctylmethylammonium methyl carbonate, tridodecylmethylammonium methyl carbonate, tetrabutylammonium methyl carbonate, tetrahexylammonium methyl carbonate, tetraoctylammonium methyl carbonate, and tetradodecylammonium methyl carbonate; and bicarbonates such as tetramethylammonium hydrogen carbonate, tetraethylammonium hydrogen carbonate, tetra-n-propylammonium hydrogen carbonate, tetra-n-butylammonium hydrogen carbonate, triethylmonomethylammonium hydrogen carbonate, tri-n-propylmonomethylammonium hydrogen carbonate, tri-n-butylmonomethylammonium hydrogen carbonate, and tri-n-butylmonoethylammonium hydrogen carbonate. Among these, monoalkyl carbonates are preferred, and monoalkyl carbonates having one or more methyl groups on the nitrogen atom are more preferred. It should be noted that these quaternary ammonium carbonates (C) may be used alone or in combination of two or more.

[0039] In the curable composition of the present invention, from the perspective of further improving the balance between solvent resistance and hot water resistance, the equivalent ratio (NCO / OH) of the isocyanate group (NCO) of the polyisocyanate compound (B) to the hydroxyl group (OH) of the polymer (A) is preferably 0.2 to 2, and more preferably 0.5 to 1.5.

[0040] The content of the quaternary ammonium carbonate (C) in the curable composition of the present invention is 0.4 to 3% by mass relative to the solid content of the acrylic polymer (A). From the perspective of further improving the balance between the pot life and the solvent resistance and hot water resistance, the content is preferably 0.5 to 2.0% by mass, and more preferably 0.5 to 1.5% by mass.

[0041] The curable composition of the present invention contains the polymer (A), the polyisocyanate compound (B), and the quaternary ammonium carbonate (C), and other compounding agents may include inorganic pigments, organic pigments, extender pigments, coloring pigments, highlighter pigments, cellulose derivatives, waxes, surfactants, stabilizers, flow regulators, dyes, leveling agents, rheology control agents, ultraviolet absorbers, antioxidants, plasticizers, antistatic agents, defoamers, viscosity regulators, light stabilizers, weather stabilizers, heat stabilizers, and pigment dispersants.

[0042] Since the curable composition of the present invention has a long pot life and excellent curability, a cured product such as a cured coating film or a molded product can be easily obtained.

[0043] The method for obtaining the cured product can be selected according to various applications, and examples thereof include a method of applying the curable composition to a substrate and curing it at 25 to 150°C; a method of injecting the curable composition into a mold and curing it at 60 to 150°C, etc.

[0044] The method for applying the curable composition of the present invention varies depending on the article to be coated, and examples thereof include gravure coaters, roll coaters, comma coaters, knife coaters, air knife coaters, curtain coaters, kiss coaters, spray coaters, wheel coaters, spin coaters, dipping, screen printing, spraying, applicators, rod coaters, and brushes.

[0045] Furthermore, the curable composition of the present invention may be diluted with an organic solvent to adjust the viscosity to a viscosity suitable for the above-mentioned coating method. Examples of such organic solvents include: aromatic hydrocarbon solvents such as toluene and xylene; alcohol solvents such as methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, propylene glycol monomethyl ether, propylene glycol n-propyl ether, ethylene glycol monobutyl ether, and diacetone alcohol; ester solvents such as ethyl acetate, butyl acetate, isobutyl acetate, n-propyl acetate, propylene glycol monomethyl ether acetate, and ethyl 3-ethoxypropionate; and ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone. These solvents may be used alone or in combination of two or more.

[0046] The curable composition of the present invention can provide a cured coating film having excellent appearance and various coating properties on the surface of various articles, and therefore can be suitably used as a coating material.

[0047] Examples of articles having a cured coating film formed using the curable composition of the present invention include: interior and exterior finishing materials for various vehicles such as automobiles and railway vehicles; interior and exterior finishing materials for buildings such as industrial machinery, exterior walls, roofs, glass, decorative panels, and wooden floors; civil engineering components such as soundproof walls and drainage gutters; housings for home appliances such as televisions, refrigerators, washing machines, and air conditioners; housings for electronic devices such as personal computers, smartphones, mobile phones, digital cameras, and game consoles; and housings for office automation equipment such as printers and fax machines.

[0048] Example

[0049] The present invention will be described in more detail below with reference to specific examples. It should be noted that the acid value and hydroxyl value of the acrylic polymer are values ​​measured in accordance with JIS test method K 0070-1992, and the weight average molecular weight (Mw) is measured under the following GPC measurement conditions.

[0050] [GPC measurement conditions]

[0051] Measuring device: High-speed GPC device (Tosoh Corporation "HLC-8220GPC")

[0052] Column: The following columns manufactured by Tosoh Corporation were connected in series and used.

[0053] TSKgel G5000 (7.8mm I.D. x 30cm) x 1 piece

[0054] TSKgel G4000 (7.8mm I.D. x 30cm) x 1 piece

[0055] TSKgel G3000 (7.8mm I.D. x 30cm) x 1 piece

[0056] TSKgel G2000 (7.8mm I.D. x 30cm) x 1 piece

[0057] Detector: RI (differential refractometer)

[0058] Column temperature: 40°C

[0059] Eluent: tetrahydrofuran (THF)

[0060] Flow rate: 1.0 mL / min

[0061] Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 4 mg / mL)

[0062] Standard sample: The following monodisperse polystyrene was used to prepare a calibration curve.

[0063] (monodisperse polystyrene)

[0064] TSKgel Standard Polystyrene A-500 manufactured by Tosoh Corporation

[0065] TSKgel Standard Polystyrene A-1000 manufactured by Tosoh Corporation

[0066] TSKgel Standard Polystyrene A-2500 manufactured by Tosoh Corporation

[0067] TSKgel Standard Polystyrene A-5000 manufactured by Tosoh Corporation

[0068] TSKgel Standard Polystyrene F-1 manufactured by Tosoh Corporation

[0069] TSKgel Standard Polystyrene F-2 manufactured by Tosoh Corporation

[0070] TSKgel Standard Polystyrene F-4 manufactured by Tosoh Corporation

[0071] TSKgel Standard Polystyrene F-10 manufactured by Tosoh Corporation

[0072] TSKgel Standard Polystyrene F-20 manufactured by Tosoh Corporation

[0073] TSKgel Standard Polystyrene F-40 manufactured by Tosoh Corporation

[0074] TSKgel Standard Polystyrene F-80 manufactured by Tosoh Corporation

[0075] TSKgel Standard Polystyrene F-128 manufactured by Tosoh Corporation

[0076] TSKgel Standard Polystyrene F-288 manufactured by Tosoh Corporation

[0077] TSKgel Standard Polystyrene F-550 manufactured by Tosoh Corporation

[0078] (Synthesis Example 1: Synthesis of Acrylic Polymer (A-1) Having Hydroxyl Group)

[0079] In a flask equipped with a condenser, thermometer, dropping funnel, and stirrer, 397.0 parts by mass of butyl acetate was added, and the internal temperature was raised to 120°C. Next, a mixture of 200.0 parts by mass of styrene, 200.0 parts by mass of methyl methacrylate, 270.0 parts by mass of isobutyl methacrylate, 320.0 parts by mass of 2-hydroxyethyl methacrylate, 10.0 parts by mass of methacrylic acid, 150.0 parts by mass of n-butyl acetate, and 50.0 parts by mass of t-butyl peroxy-2-ethylhexanoate was added dropwise over 4 hours. A polymerization reaction was then carried out for 17 hours while maintaining the internal temperature at 120°C. Subsequently, additional butyl acetate was added to obtain a solution of a hydroxyl-containing acrylic polymer (A-1) containing 65% by mass of nonvolatile matter. The solution of this polymer had an acid value of 4.3 mgKOH / g, a hydroxyl value of 81.5 mg·KOH / g, and a weight-average molecular weight (Mw) of 10,000.

[0080] (Synthesis Example 2: Synthesis of Acrylic Polymer Having Hydroxyl Group (A-2))

[0081] A solution of a hydroxyl-containing acrylic polymer (A-2) was obtained in the same manner as in Synthesis Example 1, except that 100.0 parts by mass of t-butyl peroxy-2-ethylhexanoate was used. The nonvolatile content was 65% by mass. The solution had an acid value of 4.1 mgKOH / g, a hydroxyl value of 81.0 mg·KOH / g, and a weight-average molecular weight (Mw) of 7000.

[0082] (Synthesis Example 3: Synthesis of trioctylmethylammonium methyl carbonate)

[0083] 240.0 g of methanol, 194.4 parts by mass of trioctylamine, and 385.2 parts by mass of dimethyl carbonate were added to a sealed autoclave. The atmosphere in the autoclave was replaced with nitrogen, and the reaction was carried out at 140°C for 15 hours. After cooling, the methanol and unreacted dimethyl carbonate were removed using an evaporator to obtain trioctylmethylammonium methyl carbonate.

[0084] (Example 1: Preparation and Evaluation of Curable Composition (1))

[0085] 100.0 parts by mass of the solution of the hydroxyl group-containing acrylic polymer (A-1) obtained in Synthesis Example 1, 28.1 parts by mass of polyisocyanate (Sumidur N-3300 manufactured by Sumika Covestro Urethane Co., Ltd.), and 0.35 parts by mass of trioctylmethylammonium methyl carbonate were blended to obtain a curable resin composition (1).

[0086] (Examples 2 to 4: Preparation and Evaluation of Curable Compositions (2) to (5))

[0087] Except having changed the formulation as shown in Table 1, the same operation as in Example 1 was carried out to obtain curable compositions (2) to (5).

[0088] (Comparative Examples 1 to 4: Preparation and Evaluation of Curable Compositions (R1) to (R4))

[0089] Except having changed the formulation as shown in Table 2, it carried out similarly to Example 1, and obtained the curable composition (R1) - (R4).

[0090] [Preparation of coating]

[0091] A mixed solvent (xylene / butyl acetate / propylene glycol monomethyl ether acetate / ethyl 3-ethoxypropionate = 50 / 30 / 10 / 10 (mass ratio)) was added to the curable composition obtained above, and the viscosity was adjusted to about 10 seconds using an NK-2 Iwata viscosity cup (manufactured by Anest Iwata Corporation) to obtain a coating material.

[0092] [Evaluation of available time]

[0093] The initial viscosity (seconds) of the coating obtained above immediately after mixing and after storage at 23°C for 1 hour were measured using an NK-2 Iwata viscosity cup (manufactured by Anest Iwata Co., Ltd.). The usable life was evaluated according to the following criteria. The viscosity was measured at 23°C.

[0094] A: It has fluidity after 1 hour, and the viscosity is less than 2 times of the initial viscosity

[0095] B: Fluidity is maintained after 1 hour, but the viscosity is more than 2 times and less than 3 times the initial viscosity.

[0096] C: Fluidity is maintained after 1 hour, but the viscosity is more than 3 times the initial viscosity

[0097] D: No mobility after 1 hour

[0098] [Preparation of cured coating film]

[0099] The coating obtained above was spray-coated onto substrates (ABS and PP). After standing for 10 minutes, the coating was dried at 80°C for 30 minutes and then allowed to stand at 23°C for 2 hours to form a cured coating film on the substrate. The film thickness was 30 μm.

[0100] [Evaluation of curability]

[0101] The cured coating film (PP substrate) obtained above was peeled from the substrate, cut into 50 mm x 50 mm pieces, weighed, and immersed in acetone for 24 hours before removal. The removed cured coating film was dried at 100°C for 60 minutes and weighed again. The gel fraction was calculated using the following formula based on the mass of the cured coating film before and after immersion in acetone, and curability was evaluated according to the following criteria.

[0102] Gel fraction (%) = (mass of cured coating after immersion) / (mass of cured coating before immersion) × 100

[0103] A: Gel fraction is more than 90%

[0104] B: Gel fraction is 80% or more and less than 90%

[0105] C: Gel fraction is 70% or more and less than 80%

[0106] D: Gel fraction is less than 70%

[0107] [Evaluation of solvent resistance]

[0108] One drop of xylene was added to the cured coating film (ABS substrate) obtained above using a 2 mL polyethylene pipette and allowed to stand at 23°C for 1 minute. The xylene was then wiped off with a soft cloth, and the coating film appearance was evaluated according to the following criteria.

[0109] A: No trace left

[0110] B: There are traces left on part of the coating film

[0111] C: There are traces of residue on the entire coating film

[0112] D: The coating dissolves and the substrate is exposed

[0113] [Hot water resistance test]

[0114] The cured coating film (ABS substrate) obtained above was cured for 7 days at 23° C. Then, it was immersed in water (tap water) heated to 50° C. for 240 hours, and its appearance was visually inspected. Hot water resistance was evaluated according to the following criteria.

[0115] A: No change

[0116] B: The coating is slightly whitened

[0117] C: Severe whitening of the coating

[0118] Tables 1 and 2 show the formulations and evaluation results of the curable compositions (1) to (5) and (R1) to (R4) obtained above.

[0119] [Table 1]

[0120]

[0121] [Table 2]

[0122]

[0123] The evaluation results of Examples 1 to 4 confirmed that the curable composition of the present invention has a long pot life, excellent curability, and excellent solvent resistance and hot water resistance.

[0124] On the other hand, in Comparative Example 1, the amount of the quaternary ammonium salt (C) relative to the hydroxyl group-containing acrylic polymer (A) was less than 0.4 mass %, which is the lower limit of the present invention. Therefore, insufficient curability, solvent resistance, and hot water resistance were confirmed.

[0125] Comparative Example 2 is an example in which the amount of the quaternary ammonium salt (C) relative to the hydroxyl group-containing acrylic polymer (A) exceeds the upper limit of the present invention, ie, 3% by mass. Insufficient pot life and hot water resistance were confirmed.

[0126] Comparative Examples 3 and 4 are examples in which quaternary ammonium acetate was used instead of the quaternary ammonium salt (C) which is an essential component of the present invention, and it was confirmed that the hot water resistance was insufficient.

Claims

1. A curable composition, characterized in that It contains: an acrylic polymer A having a hydroxyl group, a polyisocyanate compound B, and a quaternary ammonium salt C represented by the general formula (1), wherein the content of the quaternary ammonium salt C is 0.4% to 3% by mass relative to the polymer A. In the general formula (1), R 1 ~R 4 Each independently represents an alkyl group having 1 to 18 carbon atoms, R 5 It represents an alkyl group having 1 to 8 carbon atoms or a hydrogen atom.

2. The curable composition according to claim 1, wherein The polyisocyanate compound B includes a compound having three or more isocyanate groups in one molecule.

3. The curable composition according to claim 1, wherein The quaternary ammonium salt C is a quaternary ammonium monoalkyl carbonate. 4 . A cured product comprising the curable composition according to claim 1 .

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