Resin compositions, cured products, and articles

Abstract

The objective is to provide a resin composition that yields a cured product with excellent curability, adhesion, water resistance, and chemical resistance. [Solution] A resin composition is used that contains an acrylic polymer (A) having epoxy groups and a polythiol compound (B), characterized in that the molar ratio (t / e) of the thiol groups (t) of the polythiol compound (B) to the epoxy groups (e) of the acrylic polymer (A) is 0.3 to 5.

Description

Technical Field

[0001] The present invention relates to a resin composition, a cured product, and an article.

Background Art

[0002] Paint compositions used in automobiles, household electrical appliances, building materials, etc. are required to have various performances such as chemical resistance, abrasion resistance, and substrate adhesion. As a curing type that satisfies these required performances, an NCO-OH curing system that reacts an isocyanate group (NCO) and a hydroxyl group (OH) is generally widely used (see Patent Document 1).

[0003] This NCO-OH curing system has high versatility, but has problems with the influence of moisture in the air and the pot life after blending with an isocyanate curing agent. In addition, regulations have been made on the toxicity of free isocyanate in the curing agent, mainly in Europe.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a resin composition from which a cured product excellent in curability, adhesion, water resistance, and chemical resistance can be obtained.

Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the present inventors have found that a resin composition containing an acrylic polymer having an epoxy group and a polythiol compound in a specific ratio is excellent in curability and gives a cured product excellent in adhesion, water resistance, and chemical resistance, and have completed the invention.

[0007] In other words, the present invention relates to a resin composition containing an acrylic polymer (A) having epoxy groups and a polythiol compound (B), characterized in that the molar ratio (t / e) of the thiol groups (t) of the polythiol compound (B) to the epoxy groups (e) of the acrylic polymer (A) is 0.3 to 5. [Effects of the Invention]

[0008] The resin composition of the present invention yields a cured product with excellent curability, adhesion, water resistance, and chemical resistance, making it suitable for use as a paint or coating for various articles. [Modes for carrying out the invention]

[0009] The resin composition of the present invention is a resin composition containing an acrylic polymer (A) having epoxy groups and a polythiol compound (B), wherein the molar ratio (t / e) of the thiol groups (t) of the polythiol compound (B) to the epoxy groups (e) of the acrylic polymer (A) is 0.3 to 5.

[0010] The aforementioned acrylic polymer (A) has epoxy groups, but by using a monomer (a1) having epoxy groups as a monomer raw material, epoxy groups can be easily introduced into the acrylic polymer (A).

[0011] Examples of the epoxy group-containing monomer (a1) include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, (meth)allyl glycidyl ether, (meth)allyl methyl glycidyl ether, and 3,4-epoxycyclohexylmethyl (meth)acrylate, but glycidyl (meth)acrylate is preferred because it provides improved polymerizability and curability. These monomers (a1) can be used individually or in combination of two or more.

[0012] In this invention, "(meth)acrylic acid" refers to either or both methacrylic acid and acrylic acid, "(meth)acrylate" refers to either or both methacrylate and acrylate, "(meth)acrylamide" refers to either or both methacrylamide and acrylamide, and "(meth)acryloyl group" refers to either or both methacryloyl group and acryloyl group.

[0013] As the monomer raw material for the acrylic polymerization (A), other monomers other than the monomer (a1) having an epoxy group can be used.

[0014] The aforementioned other monomers are not particularly limited, but include, for example, vinyl monomers having an aromatic ring such as styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, and divinylbenzene;(Meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth) Acrylate, dodecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, Nt-butyl (meth)acrylamide, Nt-octyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, (meth)acrylonitrile, N,N-dimethyl Aminoethyl (meth)acrylate, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 2-methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxy-n-butyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-n-butyl (meth) Monofunctional unsaturated monomers such as acrylate, 3-hydroxy-n-butyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, glycerin 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 hydroxyl groups at the terminals;Ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate, bisphenol A-di( Examples include difunctional unsaturated monomers such as meth)acrylate, bisphenol A-EO modified di(meth)acrylate, and isocyanuric acid EO modified diacrylate; and trifunctional or more unsaturated monomers such as isocyanuric acid EO modified triacrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane EO modified tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hexa(meth)acrylate, and dipentaerythritol penta(meth)acrylate. Among these, it is preferable that the glass transition temperature of the polymer composed of these monomers is 0 to 100°C, as this further improves water resistance. These monomers can be used individually or in combination of two or more.

[0015] The amount of monomer (a1) having the epoxy group used is preferably 20 to 70% by mass, and more preferably 25 to 60% by mass, of the monomer component that is the raw material for the acrylic polymer (A), in order to further improve the balance of the physical properties of the resulting cured product.

[0016] Furthermore, the epoxy equivalent of the acrylic polymer (A) is preferably 220 to 760 g / eq, and more preferably 250 to 600 g / eq, as this improves the balance of the physical properties of the resulting cured product.

[0017] Furthermore, the glass transition temperature of the acrylic polymer (A) is preferably 0 to 100°C, and more preferably 20 to 100°C, as this improves the water resistance of the resulting cured product.

[0018] In this invention, the glass transition temperature is defined as follows: FOX's formula: 1 / Tg = W1 / Tg1 + W2 / Tg2 + ... (Tg: glass transition temperature to be determined, W1: weight fraction of component 1, Tg1: glass transition temperature of the homopolymer of component 1) The values ​​were calculated according to the following. The glass transition temperatures of the homopolymers of each component shall be those listed in the "Adhesive Technology Handbook: 1997" published by Nikkan Kogyo Shimbun or the "Polymer Handbook: 2003" published by Wiley-Interscience.

[0019] Furthermore, the weight-average molecular weight of the acrylic polymer (A) is preferably 3,000 to 100,000, and more preferably 5,000 to 50,000, as this improves the balance of the physical properties of the resulting cured product. Here, the weight-average molecular weight is the value converted to polystyrene based on gel permeation chromatography (hereinafter abbreviated as "GPC") measurement.

[0020] The acrylic polymer (A) can be obtained using a monomer containing the monomer (a1) as a raw material and carried out by a known polymerization method, but solution radical polymerization is preferred because it is the simplest method.

[0021] The above-described solution radical polymerization method involves dissolving each monomer, which is the raw material, in a solvent and carrying out the polymerization reaction in the presence of a polymerization initiator. Examples of solvents that can be used in this process include hydrocarbon solvents such as toluene, xylene, cyclohexane, n-hexane, and octane; alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, isobutanol, and sec-butanol; ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and diethylene glycol dimethyl 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 individually or in combination of two or more.

[0022] Examples of the polymerization initiator include ketone peroxide compounds such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, and methylcyclohexanone peroxide; peroxyketal compounds such as 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-hexylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-octylperoxycyclohexyl)propane, and 2,2-bis(4,4-dicumylperoxycyclohexyl)propane; hydroperoxides such as cumene hydroperoxide and 2,5-dimethylhexane-2,5-dihydroperoxide; dialkyl peroxide compounds such as 1,3-bis(tert-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, diisopropylbenzene peroxide, and tert-butylcumyl peroxide; diacyl peroxide compounds such as decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, and 2,4-dichlorobenzoyl peroxide; peroxycarbonate compounds such as bis(tert-butylcyclohexyl) peroxydicarbonate; peroxyester compounds such as tert-butylperoxy-2-ethylhexanoate, tert-butylperoxybenzoate, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; and azo compounds such as 2,2'-azobisisobutyronitrile and 1,1'-azobis(cyclohexane-1-carbonitrile).

[0023] The polythiol compound (B) is a compound having two or more thiol groups in one molecule, and the thiol groups function as a curing agent by reacting with the epoxy groups of the acrylic polymer (A).

[0024] As the polythiol compound (B), there is no particular limitation as long as it can react with the acrylic polymer (A). For example, glycol di(3-mercaptopropionate), 4-t-butyl-1,2-benzenedithiol, 2-mercaptoethyl sulfide, 4,4'-thiodibenzene thiol, benzenedithiol, glycol dimercaptoacetate, glycol dimercaptopropionate ethylene bis(3-mercaptopropionate), 1,4-bis(3-mercaptobutyryloxy)butane and other bifunctional thiols; ethoxylated trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(3-mercaptopropionate), 4-mercaptomethyl-3,6-dithia-1,8-octanedithiol, trimethylolpropane tris(3-mercaptoacetate), 1,3,5-tris(2-(3-sulfanylbutanoyloxy)ethyl)-1,3,5-triazinane-2,4,6-trione and other trifunctional thiols; pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptoacetate), pentaerythritol tetrakis(3-mercaptobutyrate) and other tetrafunctional thiols; polymers such as polyethylene glycol dimercaptoacetate, polyethylene glycol di(3-mercaptopropionate) can also be mentioned. Among these, trifunctional or tetrafunctional thiols are preferred because they have excellent reactivity with epoxy groups and the curability is further improved. These polythiol compounds (B) can be used alone or in combination of two or more.

[0025] In the resin composition of the present invention, when the molar ratio (t / e) of the thiol group (t) of the polythiol compound (B) to the epoxy group (e) of the acrylic polymer (A) is 0.3 to 5, a cured product excellent in various physical properties can be obtained. Since the physical properties of the cured product are further improved, the molar ratio (t / e) is more preferably 0.7 to 2.

[0026] The resin composition of the present invention may contain a catalyst to promote the reaction between the acrylic polymer (A) and the polythiol compound.

[0027] Examples of the catalysts include cyclic amidines such as 1,8-diazabicyclo[5.4.0]undeca-7-ene (DBU) and diazabicyclononene (DBN), heterocyclic aromatic amines such as pyridine, amines and ammonium salts such as 1,4-diazabicyclo[2.2.2]octane (DABCO), triethylmethylammonium 2-ethylhexanoate, and tetra-N-butylammonium hydroxide, and hydroxides such as sodium hydroxide. These catalysts can be used individually or in combination of two or more.

[0028] The catalyst content is preferably 0.01 to 5% by mass relative to the acrylic polymer (A), as this improves the various physical properties of the resulting cured product.

[0029] In addition to those mentioned above, the resin composition of the present invention may also contain other additives such as inorganic pigments, organic pigments, extender pigments, coloring pigments, high-brightness pigments, cellulose derivatives, waxes, surfactants, stabilizers, flow regulators, dyes, leveling agents, rheology control agents, ultraviolet absorbers, antioxidants, plasticizers, antistatic agents, defoaming agents, viscosity modifiers, light stabilizers, weather stabilizers, heat stabilizers, pigment dispersants, etc.

[0030] The resin composition of the present invention can be prepared by known methods, without any particular limitations. For example, it can be obtained by mixing a solution of the acrylic polymer (A), the polythiol compound (B), and, if necessary, a catalyst and other components.

[0031] Because the resin composition of the present invention has excellent curability, cured products such as cured coatings and molded products can be easily obtained.

[0032] Methods for obtaining cured products can be selected according to various applications. Examples include coating a substrate with a resin composition and then curing it at 25-150°C, or injecting a curable composition into a mold and then curing it at 60-150°C.

[0033] The method for coating the resin composition of the present invention varies depending on the article to be coated, but examples include gravure coaters, roll coaters, comma coaters, knife coaters, air knife coaters, curtain coaters, kiss coaters, shower coaters, wheeler coaters, spin coaters, dipping, screen printing, spraying, applicators, bar coaters, and brushes.

[0034] Furthermore, the resin composition of the present invention can be diluted with an organic solvent to adjust its viscosity to a level suitable for the above-described coating method. Examples of such organic solvents include aromatic hydrocarbon solvents such as toluene and xylene; alcohol solvents such as methanol, ethanol, isopropanol, t-butanol, 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 can be used individually or in combination of two or more.

[0035] The resin composition of the present invention can be suitably used as a paint because it can impart a cured coating film with excellent appearance and various coating film properties to the surface of various articles.

[0036] Articles having the cured product of the present invention include, for example, interior and exterior materials for various vehicles such as automobiles and railway cars; interior and exterior 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 ditches; 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 facsimile machines. [Examples]

[0037] The present invention will be described in more detail below with reference to specific examples. The epoxy equivalent and average molecular weight of the acrylic polymer were measured by the following method.

[0038] [Method for measuring epoxy equivalent] The epoxy equivalent was measured using the hydrochloric acid-pyridine method. 25 ml of hydrochloric acid-pyridine solution was added to the resin, heated at 130°C for 1 hour to dissolve, and then titrated with 0.1N potassium hydroxide alcohol solution using phenolphthalein as an indicator. The epoxy equivalent was calculated based on the amount of 0.1N potassium hydroxide alcohol solution consumed.

[0039] [Method for measuring average molecular weight] Measured using GPC. Measurement device: High-speed GPC device (HLC-8220GPC manufactured by Tosoh Corporation) Columns: The following columns manufactured by Tosoh Corporation were used, connected in series. "TSKgel G5000" (7.8mm I.D. x 30cm) x 1 "TSKgel G4000" (7.8mm I.D. x 30cm) x 1 "TSKgel G3000" (7.8mm I.D. x 30cm) x 1 "TSKgel G2000" (7.8mmI.D. x 30cm) x 1 Detector: RI (Differential Refractometer) Column temperature: 40℃ Eluent: Tetrahydrofuran (THF) Flow rate: 1.0mL / min Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 4 mg / mL) Standard samples: Calibration curves were prepared using the following monodisperse polystyrene.

[0040] (Monodisperse polystyrene) TSKgel Standard Polystyrene A-500, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene A-1000, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene A-2500, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene A-5000, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-1, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-2, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-4, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-20, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-40, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-80, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-128, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-288, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-550, manufactured by Tosoh Corporation.

[0041] (Synthesis Example 1: Synthesis of Acrylic Polymer (A-1)) In a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, 45 parts by mass of xylene were charged and the temperature was raised to 135°C under a nitrogen atmosphere. A mixture consisting of 15 parts by mass of styrene (hereinafter abbreviated as "St"), 29.8 parts by mass of methyl methacrylate (hereinafter abbreviated as "MMA"), 10.2 parts by mass of n-butyl methacrylate (hereinafter abbreviated as "n-BMA"), and 45 parts by mass of glycidyl methacrylate (hereinafter abbreviated as "GMA"), and a mixture consisting of 2 parts by mass of t-butyl peroxy-2-ethylhexanoate (hereinafter abbreviated as "PO"), 2 parts by mass of t-amyl peroxy-2-ethylhexanoate, 0.3 parts by mass of 1,1-bis(tert-butylperoxy)cyclohexane (hereinafter abbreviated as "PC"), and 21 parts by mass of xylene were added dropwise over 6 hours. After the dropwise addition was complete, the temperature was lowered to 125°C, 0.5 parts by mass of PC were added, and the polymerization reaction was carried out by holding for 6 hours. After cooling, the solution was diluted with xylene to obtain a solution of acrylic polymer (A-1) with a non-volatile content of 50% by mass. The weight-average molecular weight of acrylic polymer (A-1) was 6400, and the glass transition temperature (Tg) was 66°C.

[0042] (Synthesis Example 2: Synthesis of Acrylic Polymer (A-2)) In a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, 46.7 parts by mass of xylene were charged and the temperature was raised to 135°C under a nitrogen atmosphere. A mixture consisting of 20 parts by mass of St, 30 parts by mass of MMA, 21.5 parts by mass of n-BMA, 28.5 parts by mass of GMA, and 0.1 parts by mass of n-dodecyl mercaptan (hereinafter abbreviated as "L-SH"), and a mixture consisting of 3.7 parts by mass of PO, 0.3 parts by mass of di-t-butyl peroxide (hereinafter abbreviated as "P-D95"), and 19.3 parts by mass of xylene were added dropwise over 6 hours. After the dropwise addition was complete, the temperature was lowered to 125°C and a mixture consisting of 0.2 parts by mass of P-O and 0.67 parts by mass of xylene was added. The mixture was held for 6 hours to carry out the polymerization reaction. After cooling, the solution was diluted with xylene to obtain a solution of acrylic polymer (A-2) with a non-volatile content of 62.5% by mass. Acrylic polymer (A-2) was obtained. The weight-average molecular weight of this acrylic polymer (A-2) was 7200, and the glass transition temperature (Tg) was 65°C.

[0043] (Synthesis Example 3: Synthesis of Acrylic Polymer (RA-1)) In a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, 30 parts by mass of xylene and 30 parts by mass of ethylbenzene were charged and heated to 135°C under a nitrogen atmosphere. A mixture consisting of 30 parts by mass of St, 28 parts by mass of MMA, 17 parts by mass of n-BA, and 25 parts by mass of 2-hydroxyethyl methacrylate (hereinafter abbreviated as "HEMA"), and a mixture consisting of 2 parts by mass of PO, 0.3 parts by mass of P-D95, 10 parts by mass of xylene, and 10 parts by mass of ethylbenzene were added dropwise over 6 hours. After the addition was complete, the mixture was maintained at 125°C for 6 hours to carry out the polymerization reaction. After cooling, the mixture was diluted with xylene to obtain a solution of acrylic polymer (RA-1) with a non-volatile content of 60% by mass. The weight-average molecular weight of this acrylic polymer (RA-1) was 4100, and the glass transition temperature Tg was 49°C.

[0044] Table 1 shows the monomer compositions of the acrylic polymers (A-1), (A-2), and (RA-1) obtained in the above synthesis examples 1 to 3.

[0045] [Table 1]

[0046] (Example 1: Preparation and evaluation of resin composition (1)) 200 parts by mass of a solution of the acrylic polymer (A-1) obtained in Synthesis Example 1, 12.5 parts by mass of pentaerythritol tetrakis(3-mercaptobutyrate), and 4.6 parts by mass of DBU (10% butanol solution) were mixed together. Xylene was then added to achieve a non-volatile content of 45% by mass, and the mixture was stirred until homogeneous to obtain resin composition (1). The molar ratio (t / e) was 0.3.

[0047] [Preparation of cured coating film (cured product) for evaluation] The resin compositions obtained above were applied to PP (polypropylene) substrates and ABS (acrylonitrile-butadiene-styrene copolymer) substrates using a bar coater. After that, they were set for 10 minutes, dried at 80°C for 30 minutes, and then left to stand at 23°C for 7 days to obtain an evaluation-grade cured coating film (film thickness: 18-22 μm) on the substrates.

[0048] [Evaluation of curing properties] The cured coating film (PP substrate) obtained above was peeled from the substrate, cut into 50mm x 50mm pieces, weighed, and then immersed in acetone at 25°C. After 24 hours, it was removed. The removed cured coating film was dried at 108°C for 1 hour and weighed again. The gel fraction was calculated from the mass of the cured coating film before and after acetone immersion according to the following formula, and the curability was evaluated according to the following criteria. Gel fraction (%) = (mass of cured coating after immersion) / (mass of cured coating before immersion) × 100 4: Gel fraction is 75% or higher 3: Gel fraction is 50% or more but less than 75% 2: Gel fraction is 25% or more but less than 50% 1: Gel fraction less than 25%

[0049] [Evaluation of adhesion] The cured coating film (ABS substrate) obtained for evaluation as described above was subjected to a grid test (1 mm, 100 squares, 4 directions) in accordance with JIS K 5600-5-6:1999, and its adhesion was evaluated according to the following criteria. Note that 5B is the best evaluation. 5B: No missing parts 4B: Damage is within 5% 3B: Missing area exceeds 5% but is within 15%. 2B: Missing area exceeds 15% but is within 35%. 1B: Missing area exceeds 35% but is within 65%. 0B: Missing portion exceeds 65.

[0050] [Evaluation of water resistance] The cured coating film (ABS substrate) obtained for evaluation as described above was immersed in 40°C water for 168 hours, and its appearance was visually inspected and evaluated according to the following criteria. In addition, the adhesion after water immersion was evaluated in the same manner as the adhesion evaluation described above. (Evaluation criteria for appearance) 4: No change due to immersion 3: Slightly bleached 2: Whitening (glossy) 1: Whitening (lack of gloss)

[0051] [Evaluation of chemical resistance] (Acid resistance test) The evaluation coating (ABS substrate) obtained above was placed horizontally, and 0.2 mL of 5% sulfuric acid aqueous solution was dropped onto it using a polydropper. The droplet on the coated surface was covered with a glass cup and sealed. After being left at 23°C for 7 days, the coated test piece was washed with water, air dried, and the gloss loss, blistering, cracking, wrinkling, softening, and discoloration of the coated surface were observed visually, and the chemical resistance was evaluated according to the following criteria. 4: No change in the coating. 3: The paint film has changed slightly. 2: The paint film has clearly changed. 1: The coating has changed significantly. (Alkali resistance test) The evaluation coating (ABS substrate) obtained above was placed horizontally, and 0.2 mL of 5% sodium hydroxide aqueous solution was dropped onto it using a polydropper. The droplet on the coated surface was covered with a glass cup and sealed. After being left at 23°C for 7 days, the coated test piece was washed with water, air dried, and the gloss loss, blistering, cracking, wrinkling, softening, and discoloration of the coated surface were observed visually, and the chemical resistance was evaluated according to the following criteria. 4: No change in the coating. 3: The paint film has changed slightly. 2: The paint film has clearly changed. 1: The coating has changed significantly.

[0052] (Examples 2-4: Preparation and evaluation of resin compositions (2)-(4)) Resin compositions (2) to (4) with a non-volatile content of 45% by mass were prepared by the same procedure as in Example 1, except that the formulation of acrylic polymer (A-1) and pentaerythritol tetrakis (3-mercaptobutyrate) was changed so that the molar ratio (t / e) was as shown in Table 2, and various physical properties were evaluated.

[0053] (Example 5: Preparation and evaluation of resin composition (5)) 200 parts by mass of a solution of the acrylic polymer (A-2) obtained in Synthesis Example 2, 9.7 parts by mass of pentaerythritol tetrakis(3-mercaptobutyrate), and 3.6 parts by mass of DBU (10% butanol solution) were mixed together. Xylene was then added to bring the non-volatile content to 45% by mass, and the mixture was stirred until homogeneous to obtain resin composition (5). The molar ratio (t / e) was 0.3.

[0054] (Examples 6-8: Preparation and evaluation of resin compositions (6)-(8)) Resin compositions (6) to (8) with a non-volatile content of 45% by mass were prepared by the same procedure as in Example 5, except that the blending ratio of the acrylic polymer (A-2) and the polythiol compound (B-1) was changed as shown in Table 3, and various physical properties were evaluated.

[0055] (Comparative Example 1: Preparation and Evaluation of Resin Composition (R1)) To 200 parts by mass of a solution of acrylic polymer (A-1), xylene was added to achieve a non-volatile content of 45% by mass. The mixture was then stirred until homogeneous to obtain resin composition (R1). The molar ratio (t / e) was 0.

[0056] (Comparative Example 2: Preparation and Evaluation of Resin Composition (R2)) To 200 parts by mass of a solution of acrylic polymer (A-2), xylene was added to achieve a non-volatile content of 45% by mass. The mixture was then stirred until homogeneous to obtain resin composition (R2). The molar ratio (t / e) was 0.

[0057] (Comparative Example 3: Preparation and Evaluation of Resin Composition (R3)) 200 parts by mass of a solution of the acrylic polymer (RA-1) obtained in Synthesis Example 3, 32.2 parts by mass of pentaerythritol tetrakis(3-mercaptobutyrate), and 3.6 parts by mass of DBU (10% butanol solution) were mixed together. Xylene was then added to achieve a non-volatile content of 45% by mass, and the mixture was stirred until homogeneous to obtain resin composition (R3). The molar ratio (t / e) was 0.3.

[0058] The evaluation results of the resin compositions (1) to (8) obtained in Examples 1 to 8 above are shown in Tables 2 and 3.

[0059] [Table 2]

[0060] [Table 3]

[0061] Table 4 shows the evaluation results of the resin compositions (R1) to (R3) obtained in Comparative Examples 1 to 3 above.

[0062] [Table 4]

[0063] The resin compositions of the present invention described in Examples 1 to 8 were confirmed to yield cured products with excellent curability, adhesion, water resistance, and chemical resistance.

[0064] On the other hand, Comparative Examples 1 and 2, which do not contain the polythiol compound (B), were found to have poor curability, and the adhesion and water resistance of the coating film were insufficient.

[0065] Comparative Example 3 is an example using an acrylic polymer (A) that does not have epoxy groups, but it was found to have poor curability, and the adhesion, water resistance, and chemical resistance of the coating film were insufficient.

Claims

1. A resin composition comprising an acrylic polymer (A) having epoxy groups and a polythiol compound (B), characterized in that the molar ratio (t / e) of the thiol groups (t) of the polythiol compound (B) to the epoxy groups (e) of the acrylic polymer (A) is 0.3 to 5.

2. The resin composition according to claim 1, wherein the epoxy equivalent of the acrylic polymer (A) is 220 to 760 g / eq.

3. A cured product of the resin composition according to claim 1 or 2.

4. An article having the cured product described in claim 3.

Images