Latent curing agent composition and curable resin composition containing same

Abstract

To provide a latent curing agent composition having excellent curability while having excellent stability in a mixed state with a curable resin, and to provide a curable resin composition having excellent storage stability and curability.SOLUTION: There is provided a latent curing agent composition which is obtained by mixing (A) at least one selected from latent curing agents having a softening point of 70 to 130°C and (B) at least one selected from organic acids having a melting point of 90 to 300°C at a temperature lower than the softening point of the component (A) and the melting point of the component (B). The latent curing agent as the component (A) may contain (a-1) a polyamine compound having one or more active hydrogens and (a-2) a modified amine obtained by reacting an epoxy compound.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a latent curing agent composition and a curable resin composition containing the same. [Background technology]

[0002] Epoxy resins and other curable resins have excellent adhesion to various substrates, and the cured products obtained by curing them with a curing agent have excellent heat resistance, chemical resistance, electrical properties, mechanical properties, etc., and therefore are highly valued for a wide range of applications, such as paints, adhesives, and various molding materials.

[0003] Conventionally, the mainstream of curable resins such as epoxy resins have been two-component curing types, in which a curing agent or a curing accelerator is added just before use. Although these two-component curing type curable resins have the advantage that they can be cured even at room temperature, they have problems in that they must be measured and mixed just before use, and they have a short pot life due to the risk of gelling easily, making them difficult to apply to automatic machines. Therefore, there has been a demand for a one-component curing type epoxy resin composition that can solve these problems.

[0004] In order to obtain a one-component curable resin composition that can solve the above problems, a so-called latent curing agent is required, which is a curing agent that does not react at room temperature but starts to react and cure when heated.

[0005] As latent curing agents for epoxy resins, for example, dicyandiamide, dibasic acid dihydrazide, boron trifluoride amine complex salts, guanamines, melamine, imidazoles, modified amines, and the like have been proposed.

[0006] As a method for improving the stability of a latent curing agent, for example, Patent Documents 1 and 2 propose a microencapsulated amine-based curing agent that is excellent in both stability and curability. However, since the amount of the active ingredient as a curing agent is reduced, it is necessary to increase the amount added, which may cause an increase in viscosity.

[0007] On the other hand, Patent Document 3 proposes using a latent curing agent, which is a modified polyamine, in combination with a polycarboxylic acid in a cyanate-epoxy composite resin, but this is a melt-mix of a modified amine and a polycarboxylic acid, and does not suggest a latent curing agent composition obtained by mixing them in a powder state. Furthermore, a curable resin composition using a latent curing agent composition obtained by melt-mixing has the disadvantage of being insufficiently stable. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2016-108429 A [Patent Document 2] JP 2016-130287 A [Patent Document 3] Patent No. 5475223 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a latent curing agent composition which has excellent stability when mixed with a curable resin and also has excellent curability. Another object of the present invention is to provide a curable resin composition having excellent storage stability and curability. [Means for solving the problem]

[0010] Means for Solving the Problems The present inventors conducted extensive research to achieve the above object and discovered that by mixing a latent curing agent with a specific organic acid under specific conditions, a latent curing agent composition which is stable in a mixed state with a curable resin and also has excellent curability can be obtained, thereby completing the present invention.

[0011] That is, the present invention provides a latent curing agent composition obtained by mixing (A) at least one selected from latent curing agents having a softening point of 70 to 130°C and (B) at least one selected from organic acids having a melting point of 90 to 300°C, at a temperature lower than the softening point of component (A) and the melting point of component (B).

[0012] The present invention also relates to a curable resin composition containing the latent curing agent composition and a curable resin. Effect of the Invention

[0013] The latent curing agent composition of the present invention has excellent stability when mixed with a curable resin such as an epoxy resin, and can satisfactorily cure the curable resin by heat, and therefore can be suitably used as a latent curing agent. Furthermore, the curable resin composition obtained by combining the latent curing agent composition of the present invention with a curable resin has excellent storage stability and curability, and therefore can be used in a wide range of applications, such as coatings or adhesives for various substrates, particularly in automotive applications. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The latent curing agent composition of the present invention will be described in detail below. The latent curing agent having a softening point of 70 to 130° C., which is the component (A) used in the present invention, is not particularly limited as long as it satisfies the conditions, and examples thereof include modified amines, etc. Among them, modified amines which are reaction products of (a-1) a polyamine compound having one or more active hydrogens and (a-2) an epoxy compound can be preferably used because they give a composition having excellent storage stability and curability.

[0015] The softening point of the latent hardener can be measured by a method using a prism microscope. Specifically, about 0.01 g of powder sample is placed on a heating block and heated at a rate of about 10 to 20°C per minute. When the sample approaches the softening point, the heating rate is gradually reduced, and the softening point is measured while heating at a rate of 2 to 3°C per minute. The softening point is the temperature at which small crystals completely turn into oil droplets and the corners of large crystals collapse or become partially liquid.

[0016] The modified amine may be a reaction product in which a part or all of the (a-2) epoxy compound is converted to an (a-3) isocyanate compound. The latent curing agent may contain the modified amine and (a-4) a phenol resin.

[0017] Examples of the polyamine compound having one or more active hydrogen atoms, which is the component (a-1), include alkylene diamines such as ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,3-diaminobutane, 1,4-diaminobutane, and hexamethylenediamine; polyalkyl polyamines such as diethylenetriamine, triethylenetriamine, and tetraethylenepentamine; 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 1,3-diaminomethylcyclohexane, and 1,2-diaminocyclohexane. Alicyclic polyamines such as 1,4-diamino-3,6-diethylcyclohexane, 4,4'-diaminodicyclohexylmethane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 4,4'-diaminodicyclohexylpropane, bis(4-aminocyclohexyl)sulfone, 4,4'-diaminodicyclohexyl ether, 2,2'-dimethyl-4,4'-diaminodicyclohexylmethane, isophorone diamine, and norbornene diamine; m-xylylenediamine, diaminodi Aromatic polyamines such as phenylmethane, diaminodiphenyl sulfone, diethyltoluenediamine, 1-methyl-3,5-diethyl-2,4-diaminebenzene, 1-methyl-3,5-diethyl-2,6-diaminobenzene, 1,3,5-triethyl-2,6-diaminobenzene, 3,3'-diethyl-4,4'-diaminodiphenylmethane, 3,5,3',5'-tetramethyl-4,4'-diaminodiphenylmethane, etc.; polyether polyamines; guanamines such as benzoguanamine and acetoguanamine; 2-methylimide imidazoles such as 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 2-aminopropylimidazole; dihydrazides such as oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, and phthalic acid dihydrazide;N,N-dimethylaminoethylamine, N,N-diethylaminoethylamine, N,N-diisopropylaminoethylamine, N,N-diallylaminoethylamine, N,N-benzylmethylaminoethylamine, N,N-dibenzylaminoethylamine, N,N-cyclohexylmethylaminoethylamine, N,N-dicyclohexylaminoethylamine, N-(2-aminoethyl)pyrrolidine, N-(2-aminoethyl)piperidine, N-(2-aminoethyl)morpholine, N-(2-aminoethyl)piperazine, N-(2-aminoethyl)-N'-methylpiperazine, N,N-dimethylaminopropylamine, N,N-diethylaminopropylamine, N,N-diisopropylaminopropylamine, N,N-diallylaminopropylamine, N,N-benzylmethylaminopropylamine, N,N-dibenzylaminopropylamine, N,N-Cyclohexylmethylaminopropylamine, N,N-Dicyclohexylaminopropylamine, N-(3-aminopropyl)pyrrolidine, N-(3-aminopropyl)piperidine, N-(3-aminopropyl)morpholine, N-(3-aminopropyl)piperazine, N-(3-aminopropyl)-N'-methylpiperidine, 4-(N,N-Dimethylamino)benzylamine, 4-(N,N-Diethylamino)benzylamine, 4-(N,N-Diisopropylamino)benzylamine, N,N,-Dimethylisophoronediamine, N,N-Dimethylbisaminocyclohexane, N,N,N'-Trimethylethylenediamine, N'-Ethyl-N,N-Dimethylethylenediamine, N,N,N'-Trimethylethylenediamine, N'-Ethyl-N,N-Dimethylpropanediamine, N'-Ethyl-N,N-Dibenzylaminopropylamine;N,N-(bisaminopropyl)-N-methylamine, N,N-bisaminopropylethylamine, N,N-bisaminopropylpropylamine, N,N-bisaminopropylbutylamine, N,N-bisaminopropylpentylamine, N,N-bisaminopropylhexylamine, N,N-bisaminopropyl-2-ethylhexylamine, N,N-bisaminopropylcyclohexylamine, N,N-bisaminopropylbenzylamine, N,N-bisaminopropylallylamine, bis[3-(N,N-dimethylaminopropyl)]amine, bis[3-(N,N-diethylaminopropyl)]amine, bis[3-(N,N-diisopropylaminopropyl)]amine, bis[3-(N,N-dibutylaminopropyl)]amine, and the like.

[0018] In the present invention, it is particularly preferable to use a polyamine compound having two or more amino groups each having one or more active hydrogens, such as isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, or 1,2-diaminopropane, as component (a-1), since these compounds have excellent low-temperature curing properties.

[0019] Examples of the epoxy compound that is the component (a-2) include polyglycidyl ether compounds of mononuclear polyhydric phenol compounds such as hydroquinone, resorcin, pyrocatechol, and phloroglucinol; and polynuclear polyhydric phenol compounds such as dihydroxynaphthalene, biphenol, methylene bisphenol (bisphenol F), methylene bis(ortho-cresol), ethylidene bisphenol, isopropylidene bisphenol (bisphenol A), isopropylidene bis(ortho-cresol), tetrabromo bisphenol A, 1,3-bis(4-hydroxycumylbenzene), 1,4-bis(4-hydroxycumylbenzene), 1,1,3-tris(4-hydroxyphenyl)butane, 1,1,2,2-tetra(4-hydroxyphenyl)ethane, thiobisphenol, sulfonyl bisphenol, oxybisphenol, phenol novolac, orthocresol novolac, ethylphenol novolac, butylphenol novolac, octylphenol novolac, resorcin novolac, and terpene phenol. Polyglycidyl ether compounds of phenolic compounds; polyglycidyl ethers of polyhydric alcohols such as ethylene glycol, propylene glycol, butylene glycol, hexanediol, polyglycol, thiodiglycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, and bisphenol A-alkylene oxide adducts; maleic acid, fumaric acid, itaconic acid, succinic acid, glutaric acid, suberic acid, adipic acid, azelaic acid, sebacic acid, dimer acid, and trimer acid. glycidyl esters of aliphatic, aromatic or alicyclic polybasic acids, such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimesic acid, pyromellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and endomethylenetetrahydrophthalic acid, and homopolymers or copolymers of glycidyl methacrylate; epoxy compounds having a glycidylamino group, such as N,N-diglycidylaniline, bis(4-(N-methyl-N-glycidylamino)phenyl)methane, and diglycidyl orthotoluidine;Examples of the epoxy compounds include epoxidized cyclic olefin compounds such as vinylcyclohexene diepoxide, dicyclopentadiene diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-6-methylcyclohexane carboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate; epoxidized conjugated diene polymers such as epoxidized polybutadiene and epoxidized styrene-butadiene copolymers; and heterocyclic compounds such as triglycidyl isocyanurate. In the present invention, bisphenol A type epoxy resins and the like can be preferably used.

[0020] Examples of the polyisocyanate compound that is the component (a-3) include aromatic diisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, phenylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, 1,5-naphthylene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, 3,3'-dimethyldiphenyl-4,4'-diisocyanate, dianisidine diisocyanate, and tetramethylxylylene diisocyanate; isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate; Examples of suitable isocyanate compounds include alicyclic diisocyanates such as tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4 and / or (2,4,4)-trimethylhexamethylene diisocyanate, lysine diisocyanate, and the like; isocyanurate trimerization products, biuret trimerization products, trimethylolpropane adducts, and the like, of the diisocyanates exemplified above; triphenylmethane triisocyanate, 1-methylbenzene-2,4,6-triisocyanate, dimethyltriphenylmethane tetraisocyanate, and the like. These isocyanate compounds may be used in a form modified by carbodiimide, isocyanurate, biuret, or the like, or in a form of blocked isocyanate blocked with various blocking agents. In the present invention, isophorone diisocyanate, tolylene diisocyanate, etc. can be preferably used.

[0021] When the modified amine is a reaction product of component (a-1) and component (a-2), the amount of each component used is preferably such that the epoxy group of component (a-2) is 0.1 to 2.0 equivalents, particularly 0.2 to 1.5 equivalents, relative to the amino group of component (a-1). When the (a-2) component is partially or entirely replaced with the (a-3) component for reaction, the epoxy groups of the (a-2) component and the isocyanate groups of the (a-3) component may be optionally substituted as long as the total of the epoxy groups of the (a-2) component and the isocyanate groups of the (a-3) component does not exceed 2.0 equivalents relative to the amino groups of the (a-1) component.

[0022] Examples of the phenolic resin that is the component (a-4) include polyhydric phenol compounds such as phenol novolak resin, cresol novolak resin, aromatic hydrocarbon formaldehyde resin-modified phenolic resin, dicyclopentadiene phenol addition type resin, phenol aralkyl resin (Xylok resin), naphthol aralkyl resin, trisphenylol methane resin, tetraphenylol ethane resin, naphthol novolak resin, naphthol-phenol co-condensed novolak resin, naphthol-cresol co-condensed novolak resin, biphenyl-modified phenolic resin (a polyhydric phenol compound in which phenol nuclei are linked by bismethylene groups), biphenyl-modified naphthol resin (a polyhydric naphthol compound in which phenol nuclei are linked by bismethylene groups), aminotriazine-modified phenolic resin (a compound having a phenol skeleton, a triazine ring, and a primary amino group in its molecular structure), and alkoxy group-containing aromatic ring-modified novolak resin (a polyhydric phenol compound in which phenol nuclei and alkoxy group-containing aromatic rings are linked by formaldehyde).

[0023] In the present invention, from the viewpoint of obtaining a well-balanced composition between storage stability and curability, it is preferable to use a phenolic resin having a number average molecular weight of 750 to 1,200 as the component (a-4).

[0024] The amount of the phenolic resin (a-4) used is preferably 10 to 100 parts by mass, and more preferably 20 to 60 parts by mass, per 100 parts by mass of the modified amine. If it is less than 10 parts by mass, sufficient curability cannot be obtained, and if it exceeds 100 parts by mass, the physical properties of the cured product decrease, which is not preferable.

[0025] In the present invention, among the modified amines, an adduct of isophoronediamine with a bisphenol A type epoxy resin, an adduct of 1,3-bisaminomethylcyclohexane with a bisphenol A type epoxy resin, an adduct of polyether polyamine with a bisphenol A type epoxy resin, and the like are preferred from the viewpoint of obtaining a latent curing agent having excellent stability and curability, and it is particularly preferred to use these modified amines in combination with a phenol novolac resin.

[0026] The average particle size (median size: D50) of the latent curing agent is preferably 3 to 10 μm, since a curable resin composition having excellent stability and curability can be obtained. The average particle size can be measured, for example, using LA-950V2 (manufactured by Horiba, Ltd.; laser diffraction / scattering type particle size distribution measuring device).

[0027] The latent curing agent may be, for example, a commercially available product such as ADEKA HARDENER EH-3636S (manufactured by ADEKA CORPORATION; dicyandiamide type latent curing agent), ADEKA HARDENER EH-4351S (manufactured by ADEKA CORPORATION; dicyandiamide type latent curing agent), ADEKA HARDENER EH-5011S (manufactured by ADEKA CORPORATION; imidazole type latent curing agent), ADEKA HARDENER EH-5046S (manufactured by ADEKA CORPORATION; imidazole type latent curing agent), ADEKA HARDENER EH-4357S (manufactured by ADEKA CORPORATION; polyamine type latent curing agent), ADEKA HARDENER EH-5057P (manufactured by ADEKA CORPORATION; polyamine type latent curing agent), ADEKA HARDENER EH-5057PK (manufactured by ADEKA Corporation; polyamine-type latent hardener), Amicure PN-23 (manufactured by Ajinomoto Fine-Techno Co., Ltd.; amine adduct-based latent hardener), Amicure PN-40 (manufactured by Ajinomoto Fine-Techno Co., Ltd.; amine adduct-based latent hardener), Amicure VDH (manufactured by Ajinomoto Fine-Techno Co., Ltd.; hydrazide-based latent hardener), Fujicure FXR-1020 (manufactured by T&K TOKA Corporation; latent hardener), etc. can also be used. These can be used alone or in appropriate combination.

[0028] The organic acid having a melting point of 90 to 300°C, which is the component (B) used in the present invention, is not particularly limited as long as the melting point is within the above range, but aliphatic dicarboxylic acid compounds and aromatic carboxylic acid compounds can be preferably used because of their relatively high melting points. Examples of the organic acid that can be preferably used in the present invention include adipic acid, succinic acid, suberic acid, sebacic acid, oxalic acid, methyl adipic acid, glutaric acid, pimelic acid, azelaic acid, phthalic acid, terephthalic acid, isophthalic acid, thiodipropionic acid, maleic acid, fumaric acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, trimesic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and endomethylenetetrahydrophthalic acid. The melting points of organic acids are known, and can be determined, for example, by a method using a prism microscope, which is the above-mentioned method for measuring the softening point of the latent hardener.

[0029] Among these organic acids, it is preferable to use at least one selected from sebacic acid, adipic acid, glutaric acid, succinic acid, and malonic acid, since this can provide a latent curing agent composition that is more excellent in stability and curability.

[0030] In the latent curing agent composition of the present invention, the content of the latent curing agent as component (A) and the organic acid as component (B) is 1 to 50 parts by mass, and more preferably 3 to 30 parts by mass, of component (B) relative to 100 parts by mass of component (A). If the amount of component (B) is less than 1 part by mass, the effects of the present invention cannot be sufficiently obtained, and if it is more than 50 parts by mass, the curing speed may decrease.

[0031] The latent curing agent composition of the present invention is obtained by mixing the (A) component and the (B) component at a temperature that does not exceed either the softening point of the (A) component latent curing agent or the melting point of the (B) component organic acid, preferably 40° C. or lower. There is no particular lower limit to the mixing temperature, but from the viewpoint of workability, it is preferably 10° C. or higher. By not melt-mixing these components but keeping them in a state where the solids are mixed together, it is preferable because the stability is improved when used in a curable resin composition.

[0032] The curable resin composition of the present invention will be described in detail below.

[0033] The curable resin composition of the present invention contains the latent curing agent composition and a curable resin. The curable resin is not particularly limited as long as it is a resin capable of undergoing a curing reaction by heating or the like, and examples thereof include epoxy resins, urethane-modified epoxy resins, and block urethane resins.

[0034] Examples of the epoxy resin include the epoxy compounds exemplified as the component (a-2).

[0035] The urethane-modified epoxy resin is obtained by reacting an epoxy resin with a polyurethane. The epoxy resin used in the urethane-modified epoxy resin includes the epoxy compounds exemplified as the component (a-2). The polyurethane is obtained by reacting a polyhydroxy compound with a polyisocyanate compound.

[0036] Examples of the polyhydroxy compound used in the polyurethane include polyether polyol, polyester polyol, polycarbonate polyol, polyester amide polyol, acrylic polyol, and polyurethane polyol.

[0037] The polyether polyol is preferably an alkylene oxide adduct of a polyhydric alcohol, and the alkylene oxide preferably has 2 to 4 carbon atoms (molecular weight of about 100 to 5,500).

[0038] Examples of the polyhydric alcohol include aliphatic dihydric alcohols such as ethylene glycol, propylene glycol, 1,4-butylene glycol (tetramethylene glycol), and neopentane glycol; glycerin, trioxyisobutane, 1,2,3-butanetriol, 1,2,3-pentanetriol, 2-methyl-1,2,3-propanetriol, 2-methyl-2,3,4-butanetriol, 2-ethyl-1,2,3-butanetriol, 2,3,4-pentanetriol, 2,3,4-hexanetriol, and 4-propyl-3,4,5-heptanetriol. , 2,4-dimethyl-2,3,4-pentanetriol, pentamethylglycerin, pentaglycerin, 1,2,4-butanetriol, 1,2,4-pentanetriol, trimethylolpropane, etc.; tetrahydric alcohols such as erythritol, pentaerythritol, 1,2,3,4-pentanetetrol, 2,3,4,5-hexanetetrol, 1,2,3,5-pentanetetrol, 1,3,4,5-hexanetetrol, etc.; pentahydric alcohols such as adonite, arabitol, xylitol, etc.; hexahydric alcohols such as sorbitol, mannitol, idit, etc. Among these, dihydric to tetrahydric alcohols are preferred, and particularly propylene glycol, 1,4-butylene glycol, and glycerin are preferred.

[0039] Examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide (tetramethylene oxide), with propylene oxide and butylene oxide being particularly preferred.

[0040] Examples of the polyester polyol include conventionally known polyesters produced from polycarboxylic acids and polyhydric alcohols, and polyesters obtained from lactams.

[0041] Examples of the polycarboxylic acid include benzenetricarboxylic acid, adipic acid, succinic acid, suberic acid, sebacic acid, oxalic acid, methyladipic acid, glutaric acid, pimelic acid, azelaic acid, phthalic acid, terephthalic acid, isophthalic acid, thiodipropionic acid, maleic acid, fumaric acid, citraconic acid, and itaconic acid.

[0042] Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, bis(hydroxymethylchlorohexane), diethylene glycol, 2,2-dimethylpropylene glycol, 1,3,6-hexanetriol, trimethylolpropane, pentaerythritol, sorbitol, glycerin, and any polyhydric alcohol similar thereto. In addition to these, polyhydroxy compounds such as polytetramethylene glycol and polycaprolactone glycol can also be used.

[0043] Examples of the polycarbonate polyol include those obtained by a dephenolation reaction between a diol and diphenyl carbonate, a dealcoholization reaction between a diol and a dialkyl carbonate, and a deglycolization reaction between a diol and an alkylene carbonate.

[0044] Examples of the diol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, and 3,3-dimethylolheptane.

[0045] Examples of the polyisocyanate compound used in the polyurethane include propane-1,2-diisocyanate, 2,3-dimethylbutane-2,3-diisocyanate, 2-methylpentane-2,4-diisocyanate, octane-3,6-diisocyanate, 3,3-dinitropentane-1,5-diisocyanate, octane-1,6-diisocyanate, 1,6-hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate, lysine diisocyanate, and tolylene diisocyanate. isocyanate (TDI), xylylene diisocyanate, metatetramethyl xylylene diisocyanate, isophorone diisocyanate (3-isocyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate), 1,3- or 1,4-bis(isocyanatemethyl)cyclohexane, diphenylmethane-4,4'-diisocyanate (MDI), dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI), hydrogenated tolylene diisocyanate, and mixtures thereof. These polyisocyanate compounds may be trimerized isocyanurates. Among these polyisocyanate compounds, it is preferable to use at least one selected from the group consisting of 1,6-hexamethylene diisocyanate, tolylene diisocyanate, isophorone diisocyanate, and an isocyanurate of 1,6-hexamethylene diisocyanate, since a curable resin composition exhibiting strong adhesion to metal substrates can be obtained.

[0046] The production of polyurethane by reacting a polyhydroxy compound with a polyisocyanate compound can be carried out by a conventional method. The amounts of the polyhydroxy compound and the polyisocyanate compound used are such that the polyisocyanate compound is in excess relative to the polyhydroxy compound, specifically, such that the polyisocyanate compound has one or more isocyanate groups relative to one hydroxyl group of the polyhydroxy compound, preferably 1.2 to 5, and particularly preferably 1.5 to 2.5. By using such amounts, it is possible to obtain a polyurethane having an isocyanate content of 0.1 to 10% by mass. The isocyanate content of the obtained polyurethane is preferably 1 to 8% by mass.

[0047] The reaction temperature in producing polyurethane is usually 40 to 140° C., and preferably 60 to 130° C. In order to accelerate the reaction, it is also possible to use a known urethane polymerization catalyst, for example, an organometallic compound such as dioctyltin dilaurate, dibutyltin dilaurate, stannous octoate, stannous octoate, lead octoate, lead naphthenate, or zinc octoate, or a tertiary amine compound such as triethylenediamine or triethylamine.

[0048] The urethane-modified epoxy resin can be produced by reacting an epoxy resin with a polyurethane in a conventional manner. The amounts of epoxy resin and polyurethane used are preferably 50 / 50 to 90 / 10, more preferably 65 / 35 to 85 / 25, in terms of mass ratio (epoxy resin / polyurethane).

[0049] The reaction temperature in producing the urethane-modified epoxy resin is usually 40 to 140° C., preferably 60 to 130° C. When carrying out the modification reaction, it is also possible to use a known urethane polymerization catalyst in order to promote the reaction, for example, an organometallic compound such as dioctyltin dilaurate, dibutyltin dilaurate, stannous octoate, stannous octoate, lead octoate, lead naphthenate, or zinc octoate, or a tertiary amine compound such as triethylenediamine or triethylamine.

[0050] As the blocked urethane resin, a blocked urethane obtained by blocking, with a blocking agent, a polyurethane having an isocyanate (NCO) content of 0.1 to 10 mass% obtained by reacting a polyhydroxy compound with an excess amount of a polyisocyanate compound is preferably used.

[0051] Examples of the polyhydroxy compound include the compounds exemplified as polyhydroxy compounds used in urethane-modified epoxy resins. Among these polyhydroxy compounds, it is preferable to use one or more selected from a propylene oxide adduct of glycerin, a propylene oxide adduct of castor oil, and polyether polyols such as polytetramethylene glycol, because a cured product having excellent flexibility even at low temperatures can be obtained.

[0052] Examples of the polyisocyanate compound include the compounds exemplified as the polyisocyanate compounds used in the urethane-modified epoxy resin. Among these isocyanate compounds, it is preferable to use at least one selected from 1,6-hexamethylene diisocyanate, tolylene diisocyanate, and isophorone diisocyanate, since it is possible to obtain a curable resin composition that exhibits strong adhesion to metal substrates.

[0053] The production of polyurethane by reacting a polyhydroxy compound with a polyisocyanate compound can be carried out by a conventional method. The amounts of the polyhydroxy compound and the polyisocyanate compound used are such that the polyisocyanate compound is in excess relative to the polyhydroxy compound, specifically, such that the polyisocyanate compound has one or more isocyanate groups relative to one hydroxyl group of the polyhydroxy compound, preferably 1.2 to 5, and particularly preferably 1.5 to 2.5. By using such amounts, it is possible to obtain a polyurethane having an isocyanate content of 0.1 to 10% by mass. The isocyanate content of the obtained polyurethane is preferably 1 to 8% by mass.

[0054] The reaction temperature in producing polyurethane is usually 40 to 140° C., and preferably 60 to 130° C. In order to accelerate the reaction, it is also possible to use a known urethane polymerization catalyst, for example, an organometallic compound such as dioctyltin dilaurate, dibutyltin dilaurate, stannous octoate, stannous octoate, lead octoate, lead naphthenate, or zinc octoate, or a tertiary amine compound such as triethylenediamine or triethylamine.

[0055] Examples of the blocking agent include active methylene compounds such as malonic acid diesters (diethyl malonate, etc.), acetylacetone, and acetoacetate esters (ethyl acetoacetate, etc.); oxime compounds such as acetoxime, methyl ethyl ketoxime (MEK oxime), and methyl isobutyl ketoxime (MIBK oxime); monohydric alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, heptyl alcohol, hexyl alcohol, octyl alcohol, 2-ethylhexyl alcohol, isononyl alcohol, and stearyl alcohol, and isomers thereof; ethylene glycol monomethyl ether, ethylene glycol monoethyl Examples of blocking agents include glycol derivatives such as ether, ethyl diglycol, ethyl triglycol, ethylene glycol monobutyl ether, and butyl diglycol; amine compounds such as dicyclohexylamine; phenol, cresol, ethylphenol, n-propylphenol, isopropylphenol, butylphenol, tertiary butylphenol, octylphenol, nonylphenol, dodecylphenol, cyclohexylphenol, chlorophenol, bromophenol, resorcin, catechol, hydroquinone, bisphenol A, bisphenol S, bisphenol F, and naphthol; ε-caprolactone, ε-caprolactam, etc. Among these blocking agents, it is preferable to use one or more selected from dicyclohexylamine, diphenols, ε-caprolactone, and ε-caprolactam, since a curable resin composition having strong adhesiveness can be reliably obtained.

[0056] The blocking reaction for obtaining a blocked polyurethane from a polyurethane and a blocking agent can be carried out by a known reaction method. The amount of the blocking agent added is usually 1 to 2 equivalents, preferably 1.05 to 1.5 equivalents, based on the free isocyanate groups in the polyurethane.

[0057] The blocking reaction of polyurethane with a blocking agent is usually carried out by adding the blocking agent in the final reaction of polyurethane polymerization, but a blocked polyurethane can also be obtained by adding and reacting the blocking agent at any stage during polyurethane polymerization.

[0058] The blocking agent can be added at the end of a given polymerization, at the beginning of polymerization, or partly at the beginning of polymerization and the remainder at the end of polymerization, but is preferably added at the end of polymerization. In this case, the isocyanate % (here, isocyanate % can be measured according to JIS K 1603-1) may be used as a standard for the end of a given polymerization. The reaction temperature when the blocking agent is added is usually 50 to 150°C, preferably 60 to 120°C. The reaction time is usually about 1 to 7 hours. During the reaction, the above-mentioned known urethane polymerization catalyst can be added to promote the reaction. In addition, during the reaction, a plasticizer may be added in any amount.

[0059] As the blocked urethane, in addition to blocked urethane obtained by reacting polyurethane with a blocking agent, blocked isocyanate obtained by modifying a polyisocyanate compound (particularly an isocyanuric compound) with a blocking agent can also be used.

[0060] The amount of the latent curing agent composition used in the curable resin composition of the present invention can be appropriately selected depending on the application, but is preferably 5 to 70 parts by mass, and particularly preferably 10 to 60 parts by mass, relative to 100 parts by mass of the curable resin. When the amount of the latent curing agent composition used is either less than 5 parts by mass or more than 70 parts by mass, the performance of the obtained cured product may be impaired due to insufficient curing.

[0061] The curable resin composition of the present invention has excellent stability and curability by using the latent curing agent composition of the present invention described in detail, but the use of other curing agents is not completely excluded. The amount of the other curing agent used is not particularly limited, but is preferably within a range not exceeding 100 parts by mass relative to 100 parts by mass of the latent curing agent composition of the present invention.

[0062] The other curing agent is not particularly limited as long as it is a known curing agent, and examples thereof include phenolic resins, aliphatic amines, aromatic amines, acid anhydrides, polythiol compounds, etc. In particular, when the curable resin composition of the present invention is used in one liquid form, it is not preferable to use a curing agent other than the latent curing agent.

[0063] Examples of the phenol resins include polyhydric phenol compounds such as phenol novolac resin, cresol novolac resin, aromatic hydrocarbon formaldehyde resin-modified phenol resin, dicyclopentadiene phenol addition type resin, phenol aralkyl resin (Xylok resin), naphthol aralkyl resin, trisphenylol methane resin, tetraphenylol ethane resin, naphthol novolac resin, naphthol-phenol co-condensed novolac resin, naphthol-cresol co-condensed novolac resin, biphenyl-modified phenol resin (a polyhydric phenol compound in which phenol nuclei are linked by bismethylene groups), biphenyl-modified naphthol resin (a polyhydric naphthol compound in which phenol nuclei are linked by bismethylene groups), aminotriazine-modified phenol resin (a compound having a phenol skeleton, a triazine ring, and a primary amino group in its molecular structure), and alkoxy group-containing aromatic ring-modified novolac resin (a polyhydric phenol compound in which phenol nuclei and alkoxy group-containing aromatic rings are linked by formaldehyde).

[0064] Examples of the aliphatic amines include ethylenediamine, hexamethylenediamine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 4,4'-diaminodicyclohexylmethane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 4,4'-diaminodicyclohexylpropane, bis(4-aminocyclohexyl)sulfone, 4,4'-diaminodicyclohexylether, 2,2'-dimethyl-4,4'-diaminodicyclohexylmethane, isophoronediamine, norbornenediamine, and metaxylenediamine. Modified products of these amines may also be used. Methods for modifying amines include dehydration condensation with carboxylic acid, addition reaction with epoxy resin, addition reaction with isocyanate, Michael addition reaction, Mannich reaction, condensation reaction with urea, and condensation reaction with ketone. These can be used alone or in combination at any ratio.

[0065] Examples of the aromatic amines include diethyltoluenediamine, 1-methyl-3,5-diethyl-2,4-diaminebenzene, 1-methyl-3,5-diethyl-2,6-diaminobenzene, 1,3,5-triethyl-2,6-diaminobenzene, 3,3'-diethyl-4,4'-diaminodiphenylmethane, and 3,5,3',5'-tetramethyl-4,4'-diaminodiphenylmethane. Modified products of these amines may also be used. Methods for modifying amines include dehydration condensation with carboxylic acid, addition reaction with epoxy resin, addition reaction with isocyanate, Michael addition reaction, Mannich reaction, condensation reaction with urea, and condensation reaction with ketone. These can be used alone or in combination at any ratio.

[0066] Examples of the acid anhydrides include himic anhydride, phthalic anhydride, maleic anhydride, methyl himic anhydride, succinic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride-maleic anhydride adduct, benzophenonetetracarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, and hydrogenated methylnadic anhydride.

[0067] Examples of the polythiol compound include pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(thioglycolate), dipentaerythritol hexakis(3-mercaptopropionate), and dipentaerythritol. It is preferable to use hexakis(3-mercaptobutyrate), 1,3,4,6-tetrakis(2-mercaptoethyl)-1,3,4,6-tetraazaochydropentalene-2,5-dione, 1,3,5-tris(3-mercaptopropyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 4,8-, 4,7- or 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, or 1,3,4,6-tetrakis(2-mercaptoethyl)glycoluril, since they have an excellent balance between storage stability and curing properties. Commercially available products of these preferred thiol compounds include, for example, TS-G manufactured by Shikoku Chemical Industry Co., Ltd., DPMP and PEMP manufactured by SC Organic Chemical Co., Ltd., and PETG manufactured by Yodo Chemical Co., Ltd.

[0068] The curable resin composition of the present invention can use a curing catalyst. Examples of the curing catalyst include phosphines such as triphenylphosphine; phosphonium salts such as tetraphenylphosphonium bromide; imidazoles such as 2-methylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 1-cyanoethyl-2-methylimidazole, and imidazole silane (e.g., Shikoku Chemical Industry Co., Ltd.; 2MUSIZ); imidazole salts that are salts of the imidazoles with trimellitic acid, isocyanuric acid, boron, and the like; benzyl Examples of the curing catalyst include amines such as dimethylamine and 2,4,6-tris(dimethylaminomethyl)phenol, quaternary ammonium salts such as trimethylammonium chloride, ureas such as 3-(p-chlorophenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-phenyl-1,1-dimethylurea, isophorone diisocyanate-dimethylurea, and tolylene diisocyanate-dimethylurea, and complexes of boron trifluoride with amines, ether compounds, etc. These curing catalysts may be used alone or in combination of two or more. The content of the curing catalyst in the curable resin composition of the present invention is not particularly limited, and can be appropriately set depending on the application of the curable resin composition.

[0069] The curable resin composition of the present invention may contain, as necessary, radical or photopolymerization initiators; silane coupling agents; reactive or non-reactive diluents (plasticizers) such as monoglycidyl ethers, dioctyl phthalate, dibutyl phthalate, benzyl alcohol, and coal tar; glass fibers, carbon fibers, cellulose, silica sand, cement, kaolin, clay, aluminum hydroxide, bentonite, talc, silica, finely powdered silica, titanium dioxide, carbon black, graphite, iron oxide, bituminous substances, metal particles, and metal-coated resin particles. The composition may contain known additives such as fillers or pigments such as wax, beeswax, lanolin, spermaceti, montan wax, petroleum wax, fatty acid wax, fatty acid esters, fatty acid ethers, aromatic esters, and aromatic ethers; thickeners; thixotropic agents; antioxidants; light stabilizers; ultraviolet absorbing agents; flame retardants; antifoaming agents; rust inhibitors; colloidal silica, colloidal alumina, and the like, and further, adhesive resins such as xylene resins and petroleum resins can be used in combination.

[0070] The curable resin composition of the present invention can be used in a wide range of applications, such as paints or adhesives for concrete, cement mortar, various metals, leather, glass, rubber, plastics, wood, cloth, paper, etc.; pressure-sensitive adhesives, coating agents, fiber bundling agents, building materials, and electronic components. In particular, a curable resin composition using a block urethane resin as the curable resin can be suitably used as an adhesive for automobile structures. EXAMPLES

[0071] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0072] [Example 1] (Preparation of latent curing agent composition) A flask was charged with 352 g of isophoronediamine, and 580 g of ADEKA RESIN EP-4100E (trade name of ADEKA CORPORATION; bisphenol A type epoxy resin, epoxy equivalent: 190) [epoxy equivalent of ADEKA RESIN EP-4100E per mole of isophoronediamine: 1.47] was charged in portions at 80 to 120°C and reacted to obtain a modified amine. 20g of phenolic resin was added to 100g of the modified amine obtained, and the solvent was removed at 180-190℃ and 30-40 Torr for 1 hour, and then the mixture was pulverized in a jet mill to obtain a latent curing agent. The softening point of the obtained latent curing agent was 90-100℃, and the average particle size (D50) was 4-7μm. 5 g of sebacic acid pulverized by a jet mill was added to the obtained latent hardener, and mixed in a powder mixer to obtain a latent hardener composition (EH-1) which is a light-dark powder. The melting point of the sebacic acid used was 132 to 136°C.

[0073] Comparative Example 1 (Synthesis of Latent Curing Agent Composition) 20 g of phenol resin and sebacic acid were added to 100 g of the modified amine obtained in the same manner as in Example 1, and the solvent was removed at 180 to 190°C and 30 to 40 Torr for 1 hour. The mixture was then pulverized using a jet mill to obtain a latent curing agent composition (HEH-2) in the form of a light-dark powder.

[0074] [Example 2 and Comparative Example 2] (Production of Curable Resin Composition) Adeka Resin QR-9466 (made by ADEKA CORPORATION; block urethane resin), mineral spirits, and the latent curing agent composition obtained in Example 1 or Comparative Example 1 were blended in the ratio (parts by mass) shown in Table 1, and stirred, mixed, and dispersed to obtain the curable resin compositions of Example 2 and Comparative Example 2, respectively. Tests were carried out using the obtained curable resin compositions by the following methods. The results are shown in Table 1.

[0075] <Viscosity> The viscosity of the curable resin composition immediately after preparation and after standing at 40° C. for 1 day and 2 days was measured using an E-type rotational viscometer.

[0076] <Curability> The curable resin composition was heated at 100° C. for 10 minutes, and the presence or absence of curing was confirmed by visual inspection. Cured cases were indicated by ◯, and not cured cases by ×.

[0077] [Table 1]

[0078] As is clear from the examples, the curable resin composition of Example 2, which uses the latent curing agent composition of the present invention obtained from a specific latent curing agent and a specific organic acid, is excellent in stability and curability. In contrast, the curable resin composition of Comparative Example 2, which uses the latent curing agent composition obtained by melt-mixing a latent curing agent and an organic acid, is inferior in stability.

[0079] The latent curing agent composition of the present invention can provide a curable resin composition having excellent stability by being combined with a curable resin, particularly a block urethane resin, and the curable resin composition can be suitably used as an automotive material.

Claims

1. A method for producing a latent curing agent composition, comprising mixing (A) a powdered latent curing agent containing (a-1) a modified amine which is a reaction product of a polyamine compound having one or more active hydrogens and (a-2) an epoxy compound, and (a-4) a phenol resin, the powdered latent curing agent having a softening point of 70 to 130°C and an average particle size (median size: D50) of 3 to 10 μm, and (B) a powdered organic acid having a melting point of 90 to 300°C, at a temperature lower than the softening point of component (A) and the melting point of component (B).

2. The method for producing a latent curing agent composition according to claim 1, wherein the polyamine compound having one or more active hydrogens as component (a-1) is a polyamine compound having two or more amino groups each having one or more active hydrogens.

3. 3. The method for producing a latent curing agent composition according to claim 1, wherein the average particle size of the latent curing agent, component (A), is 3 to 10 μm.

4. The method for producing a latent curing agent composition according to any one of claims 1 to 3, wherein the organic acid which is component (B) is a polycarboxylic acid having two or more carboxy groups.

5. The method for producing a latent curing agent composition according to any one of claims 1 to 4, wherein the organic acid (B) is at least one selected from the group consisting of sebacic acid, adipic acid, glutaric acid, succinic acid and malonic acid.

6. 6. The method for producing the latent curing agent composition according to claim 1, wherein the latent curing agent as component (A) and the organic acid as component (B) are mixed at a temperature of less than 40°C.

7. A method for producing a curable resin composition, comprising producing a latent curing agent composition by the method for producing a latent curing agent composition according to any one of claims 1 to 6, and mixing the resulting latent curing agent composition with at least one curable resin.

8. The method for producing a curable resin composition according to claim 7, wherein the curable resin is an epoxy resin.

9. The method for producing a curable resin composition according to claim 7, wherein the curable resin is a block urethane resin.

10. The method for producing a curable resin composition according to any one of claims 7 to 9, wherein the curable resin composition is an adhesive for automobile structure.

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