JP7672191B2 - Latent curing agent composition and curable resin composition containing same - Google Patents

Description

The present invention relates to a latent curing agent composition and a curable resin composition containing the same.

Curable resins such as epoxy resins have excellent adhesion to various substrates, and the cured products obtained by curing with a curing agent have excellent heat resistance, chemical resistance, electrical properties, and mechanical properties, and are therefore highly valued for a wide range of applications, including paints, adhesives, and various molding materials.

Conventionally, the mainstream of curable resins such as epoxy resins have been two-component curing types, in which a curing agent or curing accelerator is added immediately before use. While these two-component curing type curable resins have the advantage of being able to cure at room temperature, they have problems such as the need to measure and mix immediately before use, and the fact that they can easily gel, making them difficult to use in automatic machines due to their short pot life. For this reason, there has been a demand for a one-component curing type epoxy resin composition that can solve these problems.

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 harden when heated.

Examples of latent curing agents proposed for epoxy resins include dicyandiamide, dibasic acid dihydrazides, boron trifluoride amine complex salts, guanamines, melamine, imidazoles, and modified amines.

As a method for increasing the stability of latent hardeners, for example, Patent Documents 1 and 2 propose a microencapsulated amine-based hardener that is excellent in both stability and hardening properties. However, because the amount of the active ingredient as a hardener is reduced, it is necessary to increase the amount added, which may cause an increase in viscosity.

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 that it is not sufficiently stable.

JP 2016-108429 A JP 2016-130287 A Patent No. 5475223

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.

As a result of intensive research to achieve the above object, the inventors discovered that by mixing a latent hardener with a specific organic acid under specific conditions, a latent hardener composition that is stable when mixed with a curable resin and also has excellent curability can be obtained, and thus arrived at the present invention.

That is, the present invention provides a latent curing agent composition obtained by mixing (A) at least one latent curing agent having a softening point of 70 to 130°C and (B) at least one 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).

The present invention also relates to a curable resin composition containing the latent curing agent composition and a curable resin.

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.

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 which is excellent in storage stability and curability.

The softening point of a latent hardener can be measured using a prism microscope. Specifically, about 0.01 g of a powder sample is placed on a heating block and heated at a rate of about 10-20°C per minute. As the sample approaches the softening point, the heating rate is gradually reduced, and the softening point is finally measured while heating at a rate of 2-3°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.

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

Examples of polyamine compounds having one or more active hydrogen atoms, which are 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, 1,2-diaminocyclohexane, and 1,4-diamino-3,6-diene. alicyclic polyamines such as 1,3-dimethylcyclohexane, 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, isophoronediamine, and norbornenediamine; m-xylylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, diethyltoluenediamine, 1 aromatic polyamines such as 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; polyether polyamines; guanamines such as benzoguanamine and acetoguanamine; 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-undecylimidazole, 2-heteroaryl imidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-undecylimidazole, 2-hexylimidazole, 2-hexyl-4-methyl ... Imidazoles such as butadecylimidazole, 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-diisopropyl ... 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-(3-aminopropyl)-N'-methylpiperidine, 4-(N,N-dimethylamino)benzylamine, 4-(N,N-diethyl ... N,N-(bisaminopropylamino)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-bisaminopropylbutyl Examples of such amines include 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, and bis[3-(N,N-dibutylaminopropyl)]amine.

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.

Examples of epoxy compounds that are component (a-2) include polyglycidyl ether compounds of mononuclear polyhydric phenol compounds such as hydroquinone, resorcinol, pyrocatechol, and phloroglucinol; dihydroxynaphthalene, biphenol, methylene bisphenol (bisphenol F), methylene bis(ortho-cresol), ethylidene bisphenol, isopropylidene bisphenol (bisphenol A), isopropylidene bis(ortho-cresol), tetrabromobisphenol 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, sulfonylbisphenol, oxybisphenol, phenol novolac, orthocresol novolac, ethylphenol novolac, butylphenol novolac, octylphenol novolac, resorcin novolac, terpene phenol, and other polynuclear polyhydric phenol compounds; polyglycyl ether compounds of ethylene glycol, propylene glycol, butylene glycol, hexanediol, polyglycol, thiodiglycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, bisphenol A-alkyl polyglycidyl ethers of polyhydric alcohols such as glycidyl ethers of ethylene oxide adducts; glycidyl esters of aliphatic, aromatic or alicyclic polybasic acids such as maleic acid, fumaric acid, itaconic acid, succinic acid, glutaric acid, suberic acid, adipic acid, azelaic acid, sebacic acid, dimer acid, trimer acid, 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; N,N-diglycidylaniline, bis(4-(N-methyl-N-glycidylamino)phenyl)methane, diglycidyl esters of glycidyl methacrylate, and the like; Examples of the epoxy compounds include those having a glycidylamino group such as di-orthotoluidine; epoxidized products of cyclic olefin compounds such as vinylcyclohexene diepoxide, dicyclopentadiene diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-6-methylcyclohexanecarboxylate, 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.

Examples of the polyisocyanate compound that is 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, Alicyclic diisocyanates such as tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4 and/or (2,4,4)-trimethylhexamethylene diisocyanate, lysine diisocyanate, etc.; isocyanurate trimerization products, biuret trimerization products, trimethylolpropane adducts, etc. of the above-exemplified diisocyanates; triphenylmethane triisocyanate, 1-methylbenzene-2,4,6-triisocyanate, dimethyltriphenylmethane tetraisocyanate, etc. These isocyanate compounds may be used in a form modified by carbodiimide, isocyanurate, biuret, or the like, or in a form blocked by various blocking agents. In the present invention, isophorone diisocyanate, tolylene diisocyanate, etc. can be preferably used.

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 amount of 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 reaction is carried out by replacing a part or all of the (a-2) component with the (a-3) component, the epoxy groups of the (a-2) component and the isocyanate groups of the (a-3) component in total may be substituted at will within a range not exceeding 2.0 equivalents relative to the amino groups of the (a-1) component.

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

In the present invention, in order to obtain a product with an excellent balance between storage stability and curability, it is preferable to use a phenolic resin having a number average molecular weight of 750 to 1200 as component (a-4).

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 modified amine. If it is less than 10 parts by mass, sufficient curing properties will not be obtained, and if it exceeds 100 parts by mass, the physical properties of the cured product will decrease, which is not preferable.

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

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

The latent curing agent may be, for example, commercially available products 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), and ADEKA HARDENER EH-5057S. 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 combinations.

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.

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 provides a latent hardener composition that is more stable and has excellent hardening properties.

In the latent curing agent composition of the present invention, the content of the latent curing agent (A) and the organic acid (B) is 1 to 50 parts by mass, and more preferably 3 to 30 parts by mass, of component (B) per 100 parts by mass of component (A). If the amount of component (B) is less than 1 part by mass, the effect of the present invention will not be fully obtained, and if it is more than 50 parts by mass, the curing speed may decrease.

The latent curing agent composition of the present invention is a mixture of components (A) and (B) at a temperature that does not exceed either the softening point of the latent curing agent (A) or the melting point of the organic acid (B), preferably 40°C or lower. There is no particular lower limit to the mixing temperature, but from the viewpoint of workability, a temperature of 10°C or higher is preferable. By not melt-mixing these components but mixing the solids together, it is preferable because this provides good stability when used in a curable resin composition.

The curable resin composition of the present invention is described in detail below.

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 that can undergo a curing reaction by heating or the like, but examples thereof include epoxy resins, urethane-modified epoxy resins, and block urethane resins.

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

The urethane-modified epoxy resin is obtained by reacting an epoxy resin with a polyurethane. Examples of epoxy resins used in the urethane-modified epoxy resin include the epoxy compounds exemplified as component (a-2). Polyurethane is obtained by reacting a polyhydroxy compound with a polyisocyanate compound.

Examples of polyhydroxy compounds used in the polyurethane include polyether polyols, polyester polyols, polycarbonate polyols, polyesteramide polyols, acrylic polyols, polyurethane polyols, etc.

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).

Examples of the polyhydric alcohols 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. trihydric alcohols such as 2,4-dimethyl-2,3,4-pentanetriol, pentamethylglycerin, pentaglycerin, 1,2,4-butanetriol, 1,2,4-pentanetriol, and trimethylolpropane; tetrahydric alcohols such as erythritol, pentaerythritol, 1,2,3,4-pentanetetrol, 2,3,4,5-hexanetetrol, 1,2,3,5-pentanetetrol, and 1,3,4,5-hexanetetrol; pentahydric alcohols such as adonite, arabitol, and xylitol; and hexahydric alcohols such as sorbitol, mannitol, and idit. Among these, dihydric to tetrahydric alcohols are preferred, and in particular propylene glycol, 1,4-butylene glycol, and glycerin are preferred.

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

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

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.

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, or any polyhydric alcohol similar thereto. In addition to these, examples of the polyhydric alcohol include polyhydroxy compounds such as polytetramethylene glycol and polycaprolactone glycol.

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.

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.

Examples of polyisocyanate compounds 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, metatetramethylxylylene diisocyanate, isophorone diisocyanate (3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate), 1,3- or 1,4-bis(isocyanatomethyl)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 isocyanurates of 1,6-hexamethylene diisocyanate, since this produces a curable resin composition that exhibits strong adhesion to metal substrates.

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 per 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.

The reaction temperature when producing polyurethane is usually 40 to 140°C, preferably 60 to 130°C. It is also possible to use known urethane polymerization catalysts to accelerate the reaction, such as organometallic compounds such as dioctyltin dilaurate, dibutyltin dilaurate, stannous octoate, stannous octoate, lead octoate, lead naphthenate, and zinc octoate, and tertiary amine compounds such as triethylenediamine and triethylamine.

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).

The reaction temperature for producing urethane-modified epoxy resins 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 to promote the reaction, for example, organometallic compounds such as dioctyltin dilaurate, dibutyltin dilaurate, stannous octoate, stannous octoate, lead octoate, lead naphthenate, and zinc octoate, and tertiary amine compounds such as triethylenediamine and triethylamine.

As the block urethane resin, a block urethane obtained by blocking 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 with a blocking agent is preferably used.

The polyhydroxy compounds include, for example, 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 this ensures that a cured product with excellent flexibility can be obtained even at low temperatures.

The polyisocyanate compound may be, for example, the compound exemplified as the polyisocyanate compound 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 this produces a curable resin composition that exhibits strong adhesion to metal substrates.

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 per 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.

The reaction temperature when producing polyurethane is usually 40 to 140°C, preferably 60 to 130°C. It is also possible to use known urethane polymerization catalysts to accelerate the reaction, such as organometallic compounds such as dioctyltin dilaurate, dibutyltin dilaurate, stannous octoate, stannous octoate, lead octoate, lead naphthenate, and zinc octoate, and tertiary amine compounds such as triethylenediamine and triethylamine.

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, or 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, resorcinol, catechol, hydroquinone, bisphenol A, bisphenol S, bisphenol F, and naphthol; and ε-caprolactone and ε-caprolactam. 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 adhesive properties can be reliably obtained.

The blocking reaction to obtain a blocked polyurethane from polyurethane and a blocking agent can be carried out by a known reaction method. The amount of blocking agent added is usually 1 to 2 equivalents, preferably 1.05 to 1.5 equivalents, relative to the free isocyanate groups in the polyurethane.

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 it is also possible to obtain a blocked polyurethane by adding and reacting the blocking agent at any stage during polyurethane polymerization.

The blocking agent can be added at the end of a given polymerization, at the beginning of polymerization, or partially at the beginning of polymerization and the remainder at the end of polymerization. Preferably, the blocking agent is added at the end of polymerization. In this case, the isocyanate % (wherein the isocyanate % can be measured according to JIS K 1603-1) can be used as a guide 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. The reaction can be accelerated by adding the above-mentioned known urethane polymerization catalyst during the reaction. A plasticizer may also be added in any amount during the reaction.

The blocked urethane may be a blocked urethane obtained by reacting polyurethane with a blocking agent, or a blocked isocyanate obtained by modifying a polyisocyanate compound (particularly an isocyanuric compound) with a blocking agent.

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, per 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, there is a risk of impairing the performance of the resulting cured product due to poor curing.

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 it is preferably in a range not exceeding 100 parts by mass per 100 parts by mass of the latent curing agent composition of the present invention.

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 a latent curing agent.

Examples of the phenolic resins include polyhydric phenol compounds such as phenol novolac resin, cresol novolac resin, aromatic hydrocarbon formaldehyde resin modified phenolic resin, dicyclopentadiene phenol addition type resin, phenol aralkyl resin (Zylok 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 phenolic resin (a polyhydric phenol compound in which a phenol nucleus is linked by a bismethylene group), biphenyl modified naphthol resin (a polyhydric naphthol compound in which a phenol nucleus is linked by a bismethylene group), aminotriazine modified phenolic resin (a compound having a phenol skeleton, a triazine ring, and a primary amino group in the molecular structure), and alkoxy group-containing aromatic ring modified novolac resin (a polyhydric phenol compound in which a phenol nucleus and an alkoxy group-containing aromatic ring are linked by formaldehyde).

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 any combination.

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 acids, addition reaction with epoxy resins, addition reaction with isocyanates, Michael addition reaction, Mannich reaction, condensation reaction with urea, and condensation reaction with ketones. These can be used alone or in any combination at any ratio.

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.

Examples of the polythiol compounds 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 examples of these preferred thiol compounds include 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.

A curing catalyst can be used in the curable resin composition of the present invention. 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 (for example, 2MUSIZ, manufactured by Shikoku Chemical Industry Co., Ltd.), imidazole salts which are salts of the imidazoles with trimellitic acid, isocyanuric acid, boron, or the like, and 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 complex compounds of boron trifluoride with amines or ether compounds. 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.

The curable resin composition of the present invention may contain, as necessary, a radical or photopolymerization initiator; a silane coupling agent; a reactive or non-reactive diluent (plasticizer) such as monoglycidyl ethers, dioctyl phthalate, dibutyl phthalate, benzyl alcohol, or coal tar; glass fiber, carbon fiber, 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, or resin particles coated with metal. It may contain fillers or pigments such as wax, beeswax, lanolin, spermaceti, montan wax, petroleum wax, fatty acid wax, fatty acid esters, fatty acid ethers, aromatic esters, aromatic ethers, and other lubricants; thickeners; thixotropic agents; antioxidants; light stabilizers; ultraviolet absorbers; flame retardants; antifoaming agents; rust inhibitors; colloidal silica, colloidal alumina, and other known additives, and may also be used in combination with adhesive resins such as xylene resins and petroleum resins.

The curable resin composition of the present invention can be used for a wide range of applications, such as paints or adhesives for concrete, cement mortar, various metals, leather, glass, rubber, plastic, wood, cloth, paper, etc.; pressure sensitive adhesives, coating agents, fiber bundling agents, building materials, electronic components, etc. 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.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[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.
20 g of phenolic resin was added to 100 g of the modified amine obtained, and the solvent was removed for 1 hour at 180-190°C and 30-40 Torr, 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°C, and the average particle size (D50) was 4-7 μm.
5 g of sebacic acid pulverized by a jet mill was added to the obtained latent curing agent and mixed in a powder mixer to obtain a latent curing agent composition (EH-1) which is a light-dark color powder. The melting point of the sebacic acid used was 132 to 136°C.

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) that was a light-dark color powder.

[Example 2 and Comparative Example 2] (Production of Curable Resin Composition)
Adeka Resin QR-9466 (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 the mixture was 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.

<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.

<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 ×.

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.

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 (10)

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). The method for producing a latent curing agent composition according to claim 1, wherein the polyamine compound having one or more active hydrogens, which is component (a-1), is a polyamine compound having two or more amino groups each having one or more active hydrogens. The method for producing a latent hardener composition according to claim 1 or 2, wherein the average particle size of the latent hardener (A) is 3 to 10 μm. The method for producing a latent hardener composition according to any one of claims 1 to 3, wherein the organic acid (B) is a polycarboxylic acid having two or more carboxy groups. The method for producing a latent hardener composition according to any one of claims 1 to 4, wherein the organic acid component (B) is at least one selected from sebacic acid, adipic acid, glutaric acid, succinic acid, and malonic acid. A method for producing the latent curing agent composition according to any one of claims 1 to 5, in which the latent curing agent (A) and the organic acid (B) are mixed at a temperature below 40°C. 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. The method for producing a curable resin composition according to claim 7, wherein the curable resin is an epoxy resin. The method for producing a curable resin composition according to claim 7, wherein the curable resin is a block urethane resin. The method for producing the curable resin composition according to any one of claims 7 to 9, wherein the curable resin composition is an adhesive for automobile structure.