JP2021084950A - Curable composition, cured product and adhesive - Google Patents

Abstract

To provide a curable composition having particularly excellent adhesion to non-ferrous metal, and suitably used for structural adhesives, and a cured product thereof, and an adhesive.SOLUTION: A curable composition contains a phosphorus atom-containing epoxy resin (A) that has, as essential reaction raw materials, one or more of specific phosphorus atom-containing compounds, a flexible resin (B), and a curing agent or curing accelerator (C).SELECTED DRAWING: None

Description

The present invention relates to a curable composition having excellent adhesion to non-ferrous metals and suitable for adhesive use, a cured product thereof, and an adhesive.

Currently, thermosetting structural adhesives using epoxy resins are widely used in automobile bodies, railroad vehicles, ships, and the like. In addition to the liquid bisphenol type epoxy resin, urethane-modified epoxy resin, rubber-modified epoxy resin, blocked isocyanate resin, and the like are used for blending the adhesive in order to impart toughness, flexibility, and adhesive strength to the adhesive. On the other hand, in the automobile industry, the weight of the car body is being reduced in order to reduce fuel consumption, and replacement of the steel plate used so far with a lighter non-ferrous metal such as aluminum is being considered. As a material useful for adhesion to such non-ferrous metals, a phosphoric acid-modified epoxy resin obtained by modifying a bisphenol A type epoxy resin with phosphoric acid and urethane-modified is provided, but the content of phosphorus atoms is sufficiently increased. As a result, sufficient adhesive strength cannot be achieved, and improvement is required.

Japanese Unexamined Patent Publication No. 2018-16767

Therefore, the problem to be solved by the present invention is to provide a curable composition, a cured product thereof, and an adhesive which are particularly excellent in adhesion to non-ferrous metals and can be suitably used for structural adhesive applications. is there.

As a result of diligent studies to solve the above problems, the present inventors have found that the above problems can be solved by using an epoxy resin modified with a specific phosphorus atom-containing compound, and complete the present invention. It came to.

That is, the present invention has the following general formulas (1) to (4).

〔式中、Ｒは水素原子、アルキル基、アルコキシ基、アラルキル基又はアリール基であり、ｍ、ｎはそれぞれ０〜４の整数であり、ｌは０〜３の整数であり、ｍ’、ｎ’はそれぞれ０〜５の整数であり、複数あるＲは同一でも異なっていてもよい〕
で表されるリン原子含有化合物の１種以上を必須の反応原料とするリン原子含有エポキシ樹脂（Ａ）と、
柔軟性樹脂（Ｂ）と、
硬化剤又は硬化促進剤（Ｃ）と、を含有することを特徴とする硬化性組成物とその硬化物、並びに当該硬化性組成物からなる接着剤を提供するものである。

[In the formula, R is a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group or an aryl group, m and n are integers of 0 to 4, l is an integer of 0 to 3, and m'and n. 'Is an integer from 0 to 5, and multiple R's may be the same or different.]
A phosphorus atom-containing epoxy resin (A) containing one or more of the phosphorus atom-containing compounds represented by the above as essential reaction raw materials, and a phosphorus atom-containing epoxy resin (A).
Flexible resin (B) and
It provides a curable composition characterized by containing a curing agent or a curing accelerator (C), a cured product thereof, and an adhesive composed of the curable composition.

According to the present invention, a curable composition having good flexibility and toughness in a cured product, excellent adhesion to non-ferrous metals such as aluminum, and a curable composition suitable for use as a structural adhesive, a cured product thereof, and adhesion. The agent can be provided.

Hereinafter, the present invention will be described in detail.
The present invention has the following general formulas (1) to (4).

〔式中、Ｒは水素原子、アルキル基、アルコキシ基、アラルキル基又はアリール基であり、ｍ、ｎはそれぞれ０〜４の整数であり、ｌは０〜３の整数であり、ｍ’、ｎ’はそれぞれ０〜５の整数であり、複数あるＲは同一でも異なっていてもよい。〕
で表されるリン原子含有化合物の１種以上を必須の反応原料とするリン原子含有エポキシ樹脂（Ａ）と、
柔軟性樹脂（Ｂ）と、
硬化剤又は硬化促進剤（Ｃ）と、を含有することを特徴とする。

[In the formula, R is a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group or an aryl group, m and n are integers of 0 to 4, l is an integer of 0 to 3, and m'and n. 'Is an integer from 0 to 5, and a plurality of R's may be the same or different. ]
A phosphorus atom-containing epoxy resin (A) containing one or more of the phosphorus atom-containing compounds represented by
Flexible resin (B) and
It is characterized by containing a curing agent or a curing accelerator (C).

In the present invention, the phosphorus atom content in the composition can be easily adjusted by using the phosphorus atom-containing epoxy resin (A) modified from the epoxy resin by using a specific phosphorus atom-containing compound as an essential reaction raw material as described above. It can be enhanced, and as a result, the adhesion to non-ferrous metals can be improved. Further, by combining this phosphorus atom-containing epoxy resin (A) with another flexible resin (B), it becomes possible to obtain excellent toughness and the like required as a structural adhesive.

The phosphorus atom-containing compound is any compound represented by the general formulas (1) to (4). R in the general formulas (1) to (4) is a hydrogen atom or a monovalent substituent on the aromatic ring, and the monovalent substituent includes an alkyl group, an alkoxy group, an aralkyl group, and an aryl group. It is either. From the viewpoint of reactivity, R is preferably a hydrogen atom.

The alkyl group and the alkoxy group are preferably an alkyl group and an alkoxy group having 1 to 4 carbon atoms. Examples of the aralkyl group include a group in which a part of hydrogen atoms of an alkyl group having 1 to 4 carbon atoms is substituted with an aryl group such as a phenyl group, and examples of the aryl group include a phenyl group.

Examples of the phosphorus atom-containing compound include 9,10-dihydro-9-oxa-10-phosphineanthrene-10-oxide (trade name HCA manufactured by Sanko Chemical Co., Ltd.), 10- (2,5-dihydroxyphenyl) -10H. Examples thereof include -9-oxa-10-phosphaphenanthrene-10-oxide (trade name HCA-HQ manufactured by Sanko Co., Ltd.), diphenylphosphine oxide and the like.

The phosphorus atom-containing epoxy resin (A) used in the present invention can be easily obtained by reacting the phosphorus atom-containing compound with various epoxy resins, and is described in, for example, JP-A-2014-77075. Can be reacted by a known method. Specifically, the phosphorus atom-containing compound and the epoxy resin are used as tertiary amines such as benzyldimethylamine, quaternary ammonium salts such as tetramethylammonium chloride, triphenylphosphine, and tris (2,6-dimethoxy). Using various catalysts such as phosphines such as phenyl) phosphine, phosphonium salts such as ethyltriphenylphosphonium bromide, and imidazoles such as 2-methylimidazole and 2-ethyl-4-methylimidazole, the reaction temperature is 100 ° C. to 200 ° C. , More preferably, it can be carried out under stirring at 120 ° C. to 180 ° C. The reaction time can be determined by measuring the epoxy equivalent.

At this time, various bifunctional or higher functional phenol compounds other than the phosphorus atom-containing compound may be used in combination. Examples of the phenol compound that can be used in combination include bisphenol A, bisphenol S, bisphenol F, naphthalenediol, biphenol, phenol novolac resin, cresol novolac resin, glioxal tetraphenol resin, bisphenol A novolak resin, phenol aralkyl resin, naphthol aralkyl resin, and biphenol. Examples include aralkyl resin. Furthermore, 10- (1,4-dioxynaphthalene) -10H-9-oxa-10-phosphaphenanthrene-10-oxide (hereinafter referred to as HCA-NQ) and diphenylphosphinyl, which are phenols having a phosphorus atom. Hydroquinone (trade name PPQ manufactured by Hokuko Kagaku Kogyo Co., Ltd.), diphenylphosphenyl-1,4-dioxynaphthaline, 1,4-cyclooctylenephosphinyl-1,4-phenyldiol (manufactured by Nippon Kagaku Kogyo Co., Ltd.) Name CPHO-HQ), 1,5-cyclooctylenephosphinyl-1,4-phenyldiol (trade name CPHO-HQ manufactured by Nippon Kagaku Kogyo Co., Ltd.) and the like may be used in combination. Since the purpose of using the bifunctional or higher functional phenol compound is to adjust the phosphorus content, viscosity and epoxy equivalent of the obtained phosphorus atom-containing epoxy resin (A), it is preferable to adjust according to the purpose.

The epoxy resin to be reacted with the phosphorus atom-containing compound is not particularly limited, and various aliphatic diglycidyl ethers, alicyclic diglycidyl ethers, aromatic diglycidyl ethers and the like can be used.

Examples of the aliphatic diglycidyl ether include butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerin triglycidyl ether, and the like. Examples of the glycidyl ether include hydride bisphenol A diglycidyl ether and the like, and examples of the aromatic diglycidyl ether include bisphenol such as tetramethylbiphenol type epoxy resin, bisphenol A type epoxy resin and bisphenol F type epoxy resin. Examples include mold or biphenol type epoxy resin. Further, polyglycidyl ester compounds such as diglycidyl aniline, resorcinol diglycidyl ether, alkylphenol monoglycidyl ether, and neodecanoic acid glycidyl ester may be used.

The phosphorus atom-containing epoxy resin (A) obtained by the above reaction has a phosphorus atom content of 0 from the viewpoint of better adhesion to non-ferrous metals as the obtained curable composition. It is preferably in the range of .5 to 10% by mass, and particularly preferably in the range of 1.0 to 5.0% by mass. The phosphorus atom content is a value calculated from the raw material charging ratio.

The epoxy equivalent of the phosphorus atom-containing epoxy resin (A) in the present invention is preferably in the range of 100 to 1000 g / eq, particularly from 200 to 200, from the viewpoint of reactivity when prepared as a curable composition. It is preferably in the range of 700 g / eq.

The flexible resin (B) used in the present invention is a resin used to improve the toughness of a cured product, and its structure is not particularly limited. As a method for imparting flexibility to the resin, for example, a known method such as introduction of a rubber component or introduction of a polyoxyalkylene structure can be appropriately adopted.

Among them, from the viewpoint of availability of industrial raw materials, one or a combination of rubber-modified epoxy resin (B1), urethane-modified epoxy resin (B2), and blocked isocyanate resin (B3) should be used. Is preferable.

The rubber-modified epoxy resin (B1) is not particularly limited as long as it is an epoxy resin having two or more epoxy groups and a rubber skeleton. Examples of the rubber forming the skeleton include polybutadiene, acrylonitrile butadiene rubber (NBR), and carboxyl group-terminated NBR (CTBN). The rubber-modified epoxy resin (B1) can be used alone or in combination of two or more.

The rubber-modified epoxy resin (B1) is not particularly limited in its production. For example, it can be produced by reacting rubber and epoxy in a large amount of epoxy. The epoxy (for example, epoxy resin) used in producing the rubber-modified epoxy resin is not particularly limited, and conventionally known ones can be mentioned. Alternatively, a commercially available product may be used as it is.

The structure of the urethane-modified epoxy resin (B2) is not particularly limited as long as it is a resin having a urethane bond and two or more epoxy groups in the molecule. A urethane bond-containing compound having an isocyanate group obtained by reacting a polyol (b1) with a polyisocyanate (b2) and hydroxy It is preferably a resin obtained by reacting with a group-containing epoxy compound.

Examples of the polyol (b1) used in producing the urethane-modified epoxy resin (B2) include polyether polyols, polyester polyols, additives of hydroxycarboxylic acid and alkylene oxide, polybutadiene polyols, polyolefin polyols and the like. Be done. Above all, when a polyether polyol is used, a cured product having excellent adhesion, flexibility and the like can be obtained, which is preferable.

The molecular weight of the polyol (b1) is preferably 300 or more and 10000 or less, and more preferably 1000 or more and 5000 or less, as a number average molecular weight from the viewpoint of excellent balance between flexibility and curability.

In the present invention, the number average molecular weight (Mn) of the polyol is a calculated value from the hydroxyl value and the number of functional groups, and the other weight average molecular weight (Mw) is measured by gel permeation chromatography (GPC) under the following conditions. Value.

Measuring device; HLC-8220GPC manufactured by Tosoh Corporation
Column; TSK-GUARDCOLUMN SuperHZ-L manufactured by Tosoh Corporation
+ TSK-GEL SuperHZM-M x 4 manufactured by Tosoh Corporation
Detector; RI (Differential Refractometer)
Data processing; Multi-station GPC-8020modelII manufactured by Tosoh Corporation
Measurement conditions; column temperature 40 ° C
Solvent tetrahydrofuran
Flow velocity 0.35 ml / min Standard; Monodisperse polystyrene sample; 0.2 mass% tetrahydrofuran solution in terms of resin solid content filtered through a microfilter (100 μl)

Examples of the polyether polyol include an aliphatic polyether polyol and an aromatic ring-containing polyether polyol, and it is preferable to use an aliphatic polyether polyol from the viewpoint of flexibility. As the aliphatic polyether polyol, an alkylene oxide (hereinafter abbreviated as AO) having 2 to 12 carbon atoms of an aliphatic polyhydric alcohol having 2 to 20 carbon atoms and an aliphatic polyhydric alcohol having 2 to 20 carbon atoms is added. Things etc. can be mentioned.

Examples of the aliphatic polyhydric alcohol having 2 to 20 carbon atoms include linear or branched aliphatic dihydric alcohols having 2 to 12 carbon atoms [ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-dodecanediol, diethylene glycol, triethylene glycol and tetraethylene Linear alcohols such as glycols; 1,2-, 1,3- or 2,3-butanediol, 2-methyl-1,4-butanediol, neopentyl glycol, 2,2-diethyl-1,3-propane Diol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,6-hexanediol, 3-methyl-1,6-hexanediol, 2-methyl- 1,7-Heptanediol, 3-Methyl-1,7-Heptanediol, 4-Methyl-1,7-Heptanediol, 2-Methyl-1,8-octanediol, 3-Methyl-1,8-octanediol And branched alcohols such as 4-methyloctanediol]; alicyclic divalent alcohols having 6 to 20 carbon atoms [1,4-cyclohexanediol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanediol, 1 , 3-Cyclopentanediol, 1,4-Cycloheptandiol, 2,5-bis (hydroxymethyl) -1,4-dioxane, 2,7-norbornandiol, tetrahydrofuran dimethanol, 1,4-bis (hydroxyethoxy) ) Cyclohexane, 1,4-bis (hydroxymethyl) cyclohexane and 2,2-bis (4-hydroxycyclohexyl) propane, etc.]; Trivalent alcohols having 3 to 20 carbon atoms [aliphatic triol (glycerin, trimethylolpropane, etc.) ) Etc.]; 4-8 valent alcohols with 5 to 20 carbon atoms [aliphatic polyols (pentaerythritol, sorbitol, mannitol, sorbitan, diglycerin, dipentaerythritol, etc.); saccharides (sucrose, glucose, mannose, fructose, etc.) Methyl glucoside and its derivatives)]; and the like.

Examples of AOs having 2 to 12 carbon atoms include ethylene oxide (hereinafter abbreviated as EO), 1,2- or 1,3-propylene oxide (hereinafter abbreviated as PO), 1,2-, 2,3- or 1, Examples thereof include 3-butylene oxide, tetrahydrofuran, 3-methyltetrahydrofuran, α-olefin oxide, styrene oxide and epichlorohydrin (epicchlorohydrin and the like).

Specific examples of the aliphatic polyether polyol include polyoxyalkylene polyol [polyethylene glycol (hereinafter abbreviated as PEG), etc.], polyoxypropylene polyol [polypropylene glycol, etc.], polyoxyethylene / propylene polyol, and polytetramethylene ether. Glycol and the like can be mentioned.

Commercially available aliphatic polyether polyols include Sanniks PP-1000 [Mn = 1,000 poly (oxypropylene) diol, manufactured by Sanyo Kasei Kogyo Co., Ltd.] and Sanniks PP-2000 [Mn = 2,000]. Poly (oxypropylene) diol, manufactured by Sanyo Kasei Kogyo Co., Ltd.], Sanniks GP-1000 [Mn = 1,000 poly (oxypropylene) triol, manufactured by Sanyo Kasei Kogyo Co., Ltd.], Sanniks GP-3000 [Mn = 3,000 poly (oxypropylene) triol, manufactured by Sanyo Kasei Kogyo Co., Ltd.], Sanniks TP-400 [Mn = 400 poly (oxypropylene) triol, manufactured by Sanyo Kasei Kogyo Co., Ltd.], TEGOMER D3403 [Mn = 1,200 polyether polyol, manufactured by Ebony Degusa], PTMG1000 [Mn = 1,000 poly (oxytetramethylene) glycol, manufactured by Mitsubishi Chemical Co., Ltd.], PTMG2000 [Mn = 2,000 Poly (oxytetramethylene) glycol, manufactured by Mitsubishi Chemica Co., Ltd.], PTMG3000 [Mn = 3,000 poly (oxytetramethylene) glycol, manufactured by Mitsubishi Chemica Co., Ltd.], PTGL2000 [Mn = 2,000 modified poly (Oxytetramethylene) glycol, manufactured by Hodoya Chemical Industry Co., Ltd.] and PTGL3000 [Mn = 3,000 modified poly (oxytetramethylene) glycol, manufactured by Hodoya Chemical Industry Co., Ltd.] and the like.

Examples of the aromatic ring-containing polyether polyol include AOs of aromatic aliphatic dihydric alcohols having 8 to 20 carbon atoms [m- or p-xylylene glycol, bis (hydroxyethyl) benzene, bis (hydroxyethoxy) benzene, etc.]. Additives and AO additives of bisphenol compounds (bisphenol A, bisphenol B, bisphenol S and bisphenol F) and the like can be mentioned.

Specific examples of the aromatic polyether polyol include, for example, an ethylene oxide (hereinafter abbreviated as EO) adduct of bisphenol A [EO2 mol adduct of bisphenol A, EO4 mol adduct of bisphenol A, EO6 mol adduct of bisphenol A]. , EO 8 mol adduct of bisphenol A, EO 10 mol adduct of bisphenol A, EO 20 mol adduct of bisphenol A, etc.] and propylene oxide (hereinafter abbreviated as PO) adduct of bisphenol A [PO 2 mol adduct of bisphenol A, Examples thereof include polyols having a bisphenol skeleton such as bisphenol A PO3 mol adduct, bisphenol A PO5 mol adduct, etc., and EO or PO adducts of resorcin.

Examples of the polyester polyol include condensed polyester polyol, polylactone polyol, polycarbonate polyol, castor oil-based polyol and the like.

Examples of the condensed polyester polyol include a low molecular weight polyol having a molecular weight of less than 300 and a polyester polyol obtained by a polyvalent carboxylic acid having 2 to 10 carbon atoms or an ester-forming derivative thereof. Among the low molecular weight polyols, preferred are ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexane glycol, EO or PO low molar adduct of bisphenol A, and mixtures thereof. is there.

Examples of the polyvalent carboxylic acid having 2 to 10 carbon atoms or an ester-forming derivative thereof include an aliphatic dicarboxylic acid (succinic acid, adipic acid, azelaic acid, sebatic acid, fumaric acid, maleic acid, etc.) and an alicyclic dicarboxylic acid. Acids (such as dimer acid), aromatic dicarboxylic acids (such as terephthalic acid, isophthalic acid and phthalic acid), trivalent or higher polycarboxylic acids (such as trimellitic acid and pyromellitic acid), and anhydrides thereof (succinic anhydride). Acids, maleic anhydride, phthalic anhydride, trimellitic anhydride, etc.), their acid halides (dichloroide adipate, etc.), these low molecular weight alkyl esters (dimethyl succinate, dimethyl phthalate, etc.) and mixtures thereof. Can be mentioned.

Specific examples of the condensed polyester polyol include polyethylene adipatediol, polybutylene adipatediol, polyhexamethylene adipatediol, polyhexamethyleneisophthalatediol, polyneopentyl adipatediol, polyethylenepropylene adipatediol, polyethylenebutylene adipatediol, and polybutylene. Hexamethylene adipate diol, polydiethylene adipate diol, poly (polytetramethylene ether) adipate diol, poly (3-methylpentylene adipate) diol, polyethylene azelate diol, polyethylene sebacate diol, polybutylene azelate diol, polybutylene ceva Examples thereof include catediol and polyneopentyl terephthalate diol.

The polylactone polyol is, for example, a heavy addition of a lactone to a low molecular weight polyol having a molecular weight Mn of less than 300, and the lactone includes lactones having 4 to 12 carbon atoms (for example, γ-butyrolactone, γ-valerolactone and the like. Ε-Caprolactone) and the like. Specific examples of the polylactone polyol include polycaprolactone diol, polyvalerolactone diol, polycaprolactone triol and the like.

Examples of the polycarbonate polyol include the aliphatic polyhydric alcohol having 2 to 20 carbon atoms, a low molecular weight carbonate compound (for example, a dialkyl carbonate having 1 to 6 carbon atoms of an alkyl group, and an alkylene group having 2 to 6 carbon atoms. Examples thereof include a polycarbonate polyol produced by condensing an alkylene carbonate having an alkylene carbonate and a diaryl carbonate having an aryl group having 6 to 9 carbon atoms while undergoing a dealcohol reaction. Two or more kinds of aliphatic polyhydric alcohols and alkylene carbonates having 2 to 20 carbon atoms may be used in combination.

Examples of castor oil-based polyols include castor oil and polyols, modified castor oil modified with AO, and the like. Modified castor oil can be produced by transesterification of castor oil and polyol and / or addition of AO. Examples of castor oil-based polyols include castor oil, trimethylolpropane-modified castor oil, pentaerythritol-modified castor oil, and EO (4 to 30 mol) adducts of castor oil.

The polyisocyanate (b2) is an aromatic polyisocyanate having 2 to 3 or more isocyanate groups and having 6 to 20 carbon atoms (excluding carbon atoms in the isocyanate group, the same applies hereinafter), and having 2 carbon atoms. Examples include ~ 18 aliphatic polyisocyanates, alicyclic polyisocyanates having 4 to 15 carbon atoms, aromatic aliphatic polyisocyanates having 8 to 15 carbon atoms and their modified products, and two or more of them can be used alone or in combination. You may.

Aromatic polyisocyanates having 6 to 20 carbon atoms include 1,3- or 1,4-phenylenediocyanate, 2,4- or 2,6-tolylene diisocyanate (TDI), 4,4'-or 2, Examples thereof include 4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate, 4,4', 4 "-triphenylmethane triisocyanate, m- or p-isocyanatophenylsulfonyl isocyanate and crude MDI.

Aliphatic polyisocyanates having 2 to 18 carbon atoms include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate and 2-isocyanato. Ethyl-2,6-diisocyanatohexanoate and the like can be mentioned.

Examples of the alicyclic polyisocyanate having 4 to 15 carbon atoms include isophorone diisocyanate (IPDI), 4,4-dicyclohexylmethane diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), and bis (hydrogenated TDI). 2-Isocyanatoethyl) -4-cyclohexene-1,2-dicarboxylate and 2,5- or 2,6-norbornene diisocyanate and the like can be mentioned.

Examples of the aromatic aliphatic polyisocyanate having 8 to 15 carbon atoms include m- or p-xylene diisocyanate (XDI) and α, α, α', α'-tetramethylxylene diisocyanate (TMXDI).

Examples of the modified isocyanate include the above-mentioned modified polyisocyanate having a urethane group, a carbodiimide group, an alohanate group, a urea group, a biuret group, a uretdione group, a uretoimine group, an isocyanurate group or an oxazolidone group.

Among these, from the viewpoint of mechanical strength and adhesiveness of the obtained cured product, it is preferable to use an aliphatic polyisocyanate or an alicyclic polyisocyanate, and IPDI and hydrogenated MDI are particularly preferable.

The reaction between the polyol (b1) and the polyisocyanate (b2) is not particularly limited, and may be carried out by a normal urethanization reaction. For example, the reaction temperature is 40 to 140 ° C., preferably 60 to 130 ° C., and various urethane polymerization catalysts for accelerating the reaction, for example, metal catalysts [tin-based (trimethyltin laurate, trimethyltin hydroxyside, dimethyl). Tingilaurate, dibutyltin diacetate, dibutyltin dilaurate, stanas octoate, dibutyltin maleate, etc.), lead-based (lead oleate, lead 2-ethylhexanoate, lead naphthenate, lead octenoate, etc.), cobalt-based (lead oleate, lead 2-ethylhexanoate, lead octenoate, etc.) Cobalt naphthenate, etc.), bismuth-based {bismastris (2-ethylhexanoate, etc.} and mercury-based (phenylmercurypropionate, etc.), etc.], amine catalysts [triethylenediamine, tetramethylethylenediamine, tetramethylhexylene diamine, etc.] Diazabicycloalkenes {1,8-diazabicyclo [5.4.0] -7-undecene} etc .; Dialkylaminoalkylamines {dimethylaminoethylamine, dimethylaminopropylamine, diethylaminopropylamine, dibutylaminoethylamine, dimethylamino Octylamine and dipropylaminopropylamine, etc.] or heterocyclic aminoalkylamines [2- (1-aziridinyl) ethylamine and 4- (1-piperidinyl) -2-hexylamine, etc.] carbonates or organic acid salts ( (Glyate, etc.), etc .; N-methylmorpholin, N-ethylmorpholin, triethylamine, diethylethanolamine, dimethylethanolamine, etc.] and a mixture of two or more thereof can be mentioned.

The amount of the reaction catalyst used is preferably 1% by mass or less, more preferably 0.001 to 0.1% by mass, based on the total mass of the obtained raw materials.

The excess amount of isocyanate groups with respect to the hydroxyl groups in the polyol (b1) is in the range of 2.05 to 3.50 mol of isocyanate groups with respect to 1 mol of hydroxyl groups, so that the molecular weight of the product can be easily adjusted. It is preferable from the viewpoint of reducing unreacted polyisocyanate.

A urethane-modified epoxy resin (B2) can be obtained by reacting the urethane compound having an isocyanate group at the terminal obtained above with a hydroxy group-containing epoxy compound.

The hydroxy group-containing epoxy compound that can be used at this time is not particularly limited, and for example, the following general formula (5)

［式中Ｘはそれぞれ独立に下記一般式（５−１）〜（５−８）

[X in the formula is independently the following general formulas (5-1) to (5-8).

(In the formula, R ² is independently any of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and an alkoxy group having 1 to 4 carbon atoms, and R ³ is independently having 1 to 4 carbon atoms. Is any of the alkyl group and the alkoxy group having 1 to 4 carbon atoms, and n is the number of repetitions.)
It is a structural part represented by any of. ]
Among these, the compound represented by the above general formula (5-1) is mentioned from the viewpoint of easy availability of raw materials and good substrate adhesion when the obtained curable resin composition is used as an adhesive. ), (5-2), and (5-3) are preferable.

The epoxy group equivalent of the hydroxy group-containing epoxy compound is preferably in the range of 300 to 600 g / eq from the viewpoint of good handling of the curable composition containing the obtained urethane-modified epoxy resin.

The reaction between the hydroxy group-containing epoxy compound and the urethane compound having an isocyanate group obtained above can be carried out, for example, in the presence of a suitable reaction catalyst under temperature conditions of about 100 to 130 ° C. The mass ratio [urethane compound / epoxy compound] of the two is preferably in the range of 55/45 to 75/25 from the viewpoint of easily obtaining a composition having high toughness in the cured product.

The blocked isocyanate resin (B3) used in the present invention blocks polyurethane made of polyisocyanate (b2) with a blocking agent (b3) so as to form an excess isocyanate group with respect to the hydroxyl group in the polyol (b1). It is preferably a resin made of

As the polyol (b1) and the polyisocyanate (b2) in the blocked isocyanate resin (B3), any of the above can be used, and the same is true for the reaction. That is, in the above-mentioned, the isocyanate group of the obtained urethane compound was reacted with the hydroxy group in the epoxy compound to obtain a urethane-modified epoxy resin, but the blocked isocyanate resin (B3) blocks the isocyanate group of the urethane compound. It is blocked by (b3). As a curable composition, such a blocked isocyanate resin undergoes a cross-linking reaction with other resins by removing the blocking agent (b3) and forming an isocyanate group when performing a curing reaction, and is contained in the cured product. A flexible skeleton derived from polyol (b1) can be introduced.

When preparing a urethane compound for obtaining a blocked isocyanate resin (B3), it is preferable to set so that two or more isocyanate groups remain in one molecule, and a bullet form of polyisocyanate (b2), polyisocyanate (polyisocyanate) ( It is also preferable to use a modified product such as the isocyanurate compound of b2).

Examples of the blocking agent (b3) include lactams having 2 to 6 carbon atoms (ε-caprolactam, δ-valerolactam, γ-butyrolactam, etc.) and oximes having 1 to 15 carbon atoms [acetooximes, methylethylketooximes (MEK)). Oxime), methylisobutylketooxime (MIBK oxime) and cyclohexanone oxime, etc.], secondary amines with 2 to 15 carbon atoms [aliphatic amines (dimethylamine, diisopyramine, di-n-propylamine, diisobutylamine, etc.), Alicyclic amines with 4 to 15 carbon atoms (methylhexylamine, dicyclohexylamine, etc.), aromatic amines (aniline, diphenylamine, etc.)], phenols with 6 to 20 carbon atoms and alkylphenols [phenols, cresols, ethylphenols, etc. n-propylphenol, isopropylphenol, n-butylphenol, octylphenol, nonylphenol, xylenol, diisopropylphenol, di-t-butylphenol, etc.], a 5-membered ring compound having an imino group and a nitrogen-carbon double bond as a ring constituent unit. [Imidazole, 2-methylimidazole, pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole and 1,2,4-triazole, etc.], imine [ethyleneimine, polyethyleneimine, etc.], active oxime-containing compound [dimethylmalonate, etc.] , Diethyl malonate, diisopropyl malate, acetylacetone, methyl acetoacetate, ethyl acetoacetate, etc.], Blocking agents described in JP-A-2002-309217 and JP-A-2008-239890, and mixtures of two or more thereof. However, one type may be used alone or two or more types may be used in combination.

Among these, a monovalent phenol compound is preferable, and an alkyl group having 1 to 8 carbon atoms is particularly preferable, from the viewpoint that it does not easily affect the reaction when the cured product is obtained after the curable composition is prepared. It is preferably an alkylphenol having, and from the viewpoint of safety, it is most preferable to use pt-butylphenol.

The blocking reaction can be carried out by a known reaction method, and the amount of the blocking agent (b3) used is usually 1 to 2 equivalents, preferably 1.05 to 1.5 equivalents, relative to the free isocyanate group. is there.

The blocking reaction with the blocking agent (b3) usually takes the method of adding the blocking agent (b3) in the final reaction of the polymerization of the polyurethane, but the blocking agent (b3) is used at any stage of the polymerization of the polyurethane. Can also be added and reacted.

As a method of adding the blocking agent (b3), a method of adding at the end of a predetermined polymerization, adding at the beginning of polymerization, adding a part at the beginning of polymerization, and adding the rest at the end of polymerization is possible. However, it is preferably added at the end of polymerization. In this case, the isocyanate% may be used as a reference as a guideline at the end of the predetermined polymerization. The reaction temperature at the time of adding the blocking agent is usually 50 to 150 ° C, preferably 60 to 120 ° C. The reaction time is usually about 1 to 7 hours. At the time of the reaction, it is also possible to add the urethane polymerization catalyst to accelerate the reaction. In addition, an arbitrary amount of plasticizer may be added during the reaction.

The curable composition of the present invention is other than the phosphorus atom-containing epoxy resin (A), rubber-modified epoxy resin (B1), and urethane-modified epoxy resin (B2) from the viewpoint of ease of handling as an adhesive, curability, and the like. Other epoxy resins may be used in combination.

As the other epoxy resin that can be used here, when used as an adhesive, it is preferably an epoxy resin that is liquid at room temperature, for example, tetramethylbiphenol type epoxy resin, bisphenol A type epoxy resin, bisphenol F. Bisphenol type or biphenol type epoxy resin such as type epoxy resin; aliphatic polyol polyglycidyl such as butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, hexanediol diglycidyl ether, trimethylpropan triglycidyl ether, glycerin triglycidyl ether Ether; Ring structure-containing polyglycidyl compound such as diglycidyl aniline, resorcinol diglycidyl ether, hydride bisphenol A diglycidyl ether; Ring structure-containing monofunctional glycidyl compound such as alkylphenol monoglycidyl ether; Polyglycidyl ester such as neodecanoic acid glycidyl ester Examples include compounds. Of these, a bisphenol type or biphenol type epoxy resin is preferably used because a cured product having excellent flexibility and toughness can be obtained, and a bisphenol type epoxy resin is preferable from the viewpoint of industrial availability.

The epoxy equivalent of the bisphenol type or biphenol type epoxy resin is preferably in the range of 150 to 250 g / eq, and is more preferably in the range of 160 to 200 g / eq because it is particularly excellent in flexibility and toughness in a cured product. preferable.

In the curable composition of the present invention, it is preferable to adjust the phosphorus atom content to be 0.1 to 0.5% by mass with respect to the total mass of the resin components in the composition. Further, the usage ratio of the flexible resin (B) differs depending on the content of the flexible component. When urethane-modified epoxy resin (B2) and blocked isocyanate resin (B3) are used, the polyol component incorporated in these raw materials is in the range of 5 to 30% by mass with respect to the total mass of the resin components in the composition. It is preferable to adjust so as to be. Further, even when the rubber-modified epoxy resin (B1) is used, it is preferable to adjust it so that it is in the range of 3 to 30% by mass with respect to the total mass of the resin components in the composition.

In the present invention, the curable composition further contains a curing agent or a curing accelerator (C).

As the curing agent or curing accelerator (C), those generally used for curing epoxy resins can be widely used, for example, polyamine compounds, amide compounds, acid anhydrides, and phenolic hydroxyl group-containing resins. , Phosphorus compounds, imidazole compounds, imidazoline compounds, urea compounds, organic acid metal salts, Lewis acids, amine complex salts and the like.

The polyamine compound is, for example, trimethylenediamine, ethylenediamine, N, N, N', N'-tetramethylethylenediamine, pentamethyldiethylenetriamine, triethylenediamine, dipropylenediamine, N, N, N', N'-tetramethyl. Propylene diamine, tetramethylene diamine, pentan diamine, hexamethylene diamine, trimethyl hexamethylene diamine, N, N, N', N'-tetramethylhexamethylenediamine, N, N-dimethylcyclohexylamine, diethylenetriamine, triethylenetetramine, tetra Ethylenepentamine, dimethylaminopropylamine, diethylaminopropylamine, dibutylaminopropylamine, 1,4-diazabicyclo (2,2,2) octane (triethylenediamine), polyoxyethylenediamine, polyoxypropylenediamine, bis (2-dimethyl) Aminoethyl) Ether, dimethylaminoethoxyethoxyethanol, triethanolamine, dimethylaminohexanol and other aliphatic amine compounds;

Piperazine, piperazine, mentandiamine, isophoronediamine, methylmorpholin, ethylmorpholin, N, N', N "-tris (dimethylaminopropyl) hexahydro-s-triazine, 3,9-bis (3-aminopropyl) -2, 4,8,10-Tetraoxyspiro (5,5) undecane adduct, N-aminoethylpiperazine, trimethylaminoethylpiperazine, bis (4-aminocyclohexyl) methane, N, N'-dimethylpiperazine, 1,8-diazabicyclo -[5.4.0] -Alicyclic and heterocyclic amine compounds such as undecene (DBU);

Aromatic amines such as o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, benzylmethylamine, dimethylbenzylamine, m-xylenediamine, pyridine, picoline, α-methylbenzylmethylamine Compound;

Epoxy compound-added polyamines, Michael-added polyamines, Mannig-added polyamines, thiourea-added polyamines, ketone-blocking polyamines, dicyandiamides, guanidines, organic acid hydrazides, diaminomaleonitriles, amineimides, boron trifluoride-piperidin complexes, boron trifluoride-mono Examples thereof include modified amine compounds such as ethylamine complexes.

Examples of the amide compound include dicyandiamide and polyamide amine. The polyamide amines include, for example, aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid and azelaic acid, carboxylic acid compounds such as fatty acids and dimer acids, and aliphatic polyamines and polyoxyalkylenes. Examples thereof include those obtained by reacting a polyamine having a chain or the like.

The acid anhydrides include, for example, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydro. Examples include phthalic anhydride.

Examples of the phenolic hydroxyl group-containing resin include phenol novolac resin, cresol novolac resin, aromatic hydrocarbon formaldehyde resin-modified phenol resin, dicyclopentadienephenol-added resin, phenol aralkyl resin (Zyroc resin), and naphthol aralkyl resin. Trimethylol methane resin, tetraphenylol ethane resin, naphthol novolac resin, naphthol-phenol co-condensed novolak resin, naphthol-cresol co-condensed novolak resin, biphenyl-modified phenol resin (polyphenol compound in which phenol nuclei are linked by bismethylene groups) , Biphenyl-modified naphthol resin (polyhydric naphthol compound in which phenol nuclei are linked by bismethylene group), aminotriazine-modified phenol resin (polyvalent phenol compound in which phenol nuclei are linked by melamine, benzoguanamine, etc.) and alkoxy group-containing aromatic ring modification Examples thereof include polyhydric phenol compounds such as novolak resin (polyhydric phenol compound in which a phenol nucleus and an alkoxy group-containing aromatic ring are linked with formaldehyde).

The phosphorus compound is, for example, an alkylphosphine such as ethylphosphine or butylphosphine, a first phosphine such as phenylphosphine; a dialkylphosphine such as dimethylphosphine or dipropylphosphine; a second phosphine such as diphenylphosphine or methylethylphosphine; , Triethylphosphine, third phosphine such as triphenylphosphine and the like.

The imidazole compounds include, for example, imidazole, 1-methylimidazole, 2-methylimidazole, 3-methylimidazole, 4-methylimidazole, 5-methylimidazole, 1-ethyl imidazole, 2-ethyl imidazole, 3-ethyl imidazole, 4 -Ethyl imidazole, 5-ethyl imidazole, 1-n-propyl imidazole, 2-n-propyl imidazole, 1-isopropyl imidazole, 2-isopropyl imidazole, 1-n-butyl imidazole, 2-n-butyl imidazole, 1-isobutyl Imidazole, 2-isobutylimidazole, 2-undecyl-1H-imidazole, 2-heptadecyl-1H-imidazole, 1,2-dimethylimidazole, 1,3-dimethylimidazole, 2,4-dimethylimidazole, 2-ethyl-4- Methylimidazole, 1-phenylimidazole, 2-phenyl-1H-imidazole, 4-methyl-2-phenyl-1H-imidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl- 2-Phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 2-phenylimidazole Isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 1-cyanoethyl-2-phenyl-4, Examples thereof include 5-di (2-cyanoethoxy) methylimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 1-benzyl-2-phenylimidazole hydrochloride and the like.

Examples of the imidazoline compound include 2-methylimidazoline and 2-phenylimidazoline.

The urea compound includes, for example, p-chlorophenyl-N, N-dimethylurea, 3-phenyl-1,1-dimethylurea, 3- (3,4-dichlorophenyl) -N, N-dimethylurea, N- (3). -Chloro-4-methylphenyl) -N', N'-dimethylurea and the like can be mentioned.

In the present invention, when a curing agent having a functional group capable of reacting with an epoxy group is used, the amount of the curing agent or curing accelerator (C) blended with the curing agent is 1 mol of the epoxy group in the composition. It is preferable to blend in a ratio of the functional group in the range of 0.5 to 1.1 mol. When a curing accelerator is used, it is preferably blended in a proportion of 0.5 to 10 parts by mass with respect to a total of 100 parts by mass of the epoxy resin in the composition.

In addition, the curable composition of the present invention includes organic solvents, ultraviolet absorbers, antioxidants, silicon-based additives, fluorine-based additives, flame retardants, plasticizers, silane coupling agents, organic beads, inorganic fine particles, and the like. It may contain an inorganic filler, a rheology control agent, a defoaming agent, an antifogging agent, a coloring agent and the like. Any amount of these various components may be added depending on the desired performance.

The curable composition of the present invention is prepared by uniformly mixing the various optional components using a pot mill, a ball mill, a bead mill, a roll mill, a homogenizer, a super mill, a homodisper, a universal mixer, a Banbury mixer, a kneader, or the like. can do.

The use of the curable composition of the present invention is not particularly limited, and it can be used in various applications such as paints, coating agents, molding materials, insulating materials, sealing agents, sealing agents, and fiber binding agents. Above all, it can be suitably used as an adhesive for structural members in the fields of automobiles, trains, civil engineering and construction, electronics, aircraft, and the space industry by taking advantage of its excellent flexibility and toughness in cured products. Even when the adhesive of the present invention is used for adhering different materials such as between metal and non-metal, high adhesiveness can be maintained without being affected by changes in the temperature environment, and peeling or the like occurs. hard. Further, the adhesive of the present invention can be used not only for structural members but also as an adhesive for general office work, medical use, carbon fiber, electronic material, etc., and as an adhesive for electronic material, for example, build-up Adhesives for multilayer substrates such as substrates, adhesives for joining optical components, adhesives for bonding optical disks, adhesives for mounting printed wiring boards, die bonding adhesives, adhesives for semiconductors such as underfill, underfill for BGA reinforcement Examples thereof include a fill, an anisotropic conductive film, and an adhesive for mounting such as an anisotropic conductive paste.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Synthesis example 1
Under a nitrogen atmosphere, HCA [9,10-dihydro-9-oxa-10-phosphineanthrene-10-oxide, Mw: 216) manufactured by Sanko Co., Ltd., 161 parts by mass, bisphenol A type liquid epoxy resin manufactured by DIC Corporation EPICLON 850 839 parts by mass of −S (epoxy equivalent: 188 g / eq) and 0.5 parts by mass of triphenylphosphine (TPP) as a catalyst were added, the temperature was raised to 150 ° C., and the reaction was carried out at the same temperature for 3 hours. A resin (A-1) was obtained. The epoxy equivalent of the obtained (A-1) was 270 g / eq.

Synthesis Examples 2-6
Phosphorus atom-containing epoxy resins (A-2) to (A-6) were obtained from the compounding compositions in Table 1 in the same manner as in Synthesis Example 1.

The resins in Table 1 are as follows.
HCA-HQ: HCA-HQ manufactured by Sanko Co., Ltd. [10- (2,5-dihydroxyphenyl) -9,10-dihydro 9-oxa-10-phosphaphenanthrene-10-oxide, Mw: 324]
830-S: EPICLON 830-S [Bisphenol F type epoxy resin manufactured by DIC Corporation, epoxy equivalent: 169 g / eq]
EX-717: Polyoxypropylene-added bisphenol A type epoxy resin manufactured by Nagase Chemitex Co., Ltd., epoxy equivalent: 310 g / eq)

Synthesis example 7
Under a nitrogen atmosphere, a polyether polyol (Actcol ED-28 Mn: 4000 functional groups: 2), which is a polyoxyethylene (PE) -polyoxypropylene (PP) copolymer manufactured by Mitsui Chemicals & SKC Polyurethane (MCNS), 834 parts by mass, 96 parts by mass of isophorone diisocyanate (IPDI) was mixed, 0.1 part by mass of Neostan U-820 (dioctyl tin manufactured by Nitto Kasei Co., Ltd.) was added as a catalyst, and the mixture was reacted at 80 ° C. for 5 hours, and then as a blocking agent. 70 parts by mass of paracatalyst butylphenol (PTBP) was added and reacted at 90 ° C. for 5 hours to obtain a blocked isocyanate resin (B3-1).

Synthesis example 8
A blocked isocyanate resin (B3-2) was obtained from the compounding composition shown in Table 2 with the same formulation as in Synthesis Example 7.

Synthesis example 9
Under a nitrogen atmosphere, 224 parts by mass of ED-28 and 26 parts by mass of IPDI were mixed, 0.03 parts by mass of Neostan U-820 was added as a catalyst, and the mixture was reacted at 80 ° C. for 5 hours, and then EPICLON 850-S 750 parts by mass was added. The mixture was charged and reacted at 90 ° C. for 5 hours to obtain a urethane-modified epoxy resin (B2-1).

Synthesis example 10
A urethane-modified epoxy resin (B2-2) was obtained from the compounding composition shown in Table 2 with the same formulation as in Synthesis Example 9.

The resins in Table 2 are as follows.
T-3000: PP polyol manufactured by MCNS (Mn: 3000, number of functional groups: 3)
TDI: MCNS tolylene diisocyanate T-80

Example 1
20 parts by mass of phosphorus atom-containing epoxy resin (A-1) synthesized in Synthesis Example 1, 25 parts by mass of blocked isocyanate resin (B3-1) synthesized in Synthesis Example 7, EPICLON 850-S 55 parts by mass, manufactured by DIC Co., Ltd. Rubber-modified epoxy resin EPICLON TSR-6019 9 parts by mass, dicyandiamide (DICY) 5 parts by mass as a curing agent, 3,4-dichlorophenyl-N, N-dimethylurea (DCMU) 1 part by mass as a curing accelerator, calcium carbonate as a filler (CaCO ₃ ) was mixed by 20 parts by mass to obtain a curable composition (1). Regarding this curable composition (1), the adhesiveness between the steel plate SPCC-SD (JIS G3141) and the aluminum plate (A5052P) was evaluated for the cured product cured at 170 ° C. for 30 minutes.

<Tensile shear test>
The tensile shear strength was measured using AUTOGRAPH AG-XPlus 100 kN manufactured by Shimadzu Corporation under the condition of 25 ° C. by the JIS K6859 (adhesive creep rupture test) method.

<T-shaped peeling test>
The peel strength was measured using AUTOGRAPH AG-IS 1kN manufactured by Shimadzu Corporation under the condition of 25 ° C. by the JIS K6854-3 (adhesive peeling adhesive strength test) method.

Example 2-6
The same evaluation was carried out for the curable compositions (2) to (6) which were blended in the same manner as in Example 1 with the formulas shown in Table 3 instead of the formulas of Example 1. The evaluation results are summarized in Table 3.

Comparative Example 1
A urethane-modified chelated epoxy resin (A') was synthesized in the same manner as in Production Example 1 described in JP-A-2008-239890. Similar evaluations were carried out for the curable compositions (11) to (14) prepared with the formulation shown in Table 4 in place of the curable composition (1) of Example 1. The evaluation results are summarized in Table 4.

Claims (10)

The following general formulas (1) to (4)

[In the formula, R is a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group or an aryl group, m and n are integers of 0 to 4, l is an integer of 0 to 3, and m'and n. 'Is an integer from 0 to 5, and a plurality of R's may be the same or different. ]
A phosphorus atom-containing epoxy resin (A) containing one or more of the phosphorus atom-containing compounds represented by
Flexible resin (B) and
A curable composition comprising a curing agent or a curing accelerator (C). The phosphorus atom-containing epoxy resin (A) is one or more of the phosphorus atom-containing compounds represented by the general formulas (1) to (4), and an aliphatic diglycidyl ether, an alicyclic diglycidyl ether, or an alicyclic diglycidyl ether. The curable composition according to claim 1, which is a reaction product with aromatic diglycidyl ether. The curable composition according to claim 1 or 2, wherein the phosphorus atom content of the phosphorus atom-containing epoxy resin (A) is in the range of 1.0 to 5.0% by mass. Claims 1 to 3 wherein the flexible resin (B) is one or more resins selected from the group consisting of a rubber-modified epoxy resin (B1), a urethane-modified epoxy resin (B2), and a blocked isocyanate resin (B3). The curable composition according to any one of the above. The blocked isocyanate resin (B3) is formed by blocking polyurethane made of polyisocyanate (b2) with a blocking agent (b3) so as to form an excess isocyanate group with respect to the hydroxyl groups in the polyol (b1). The curable composition according to claim 4, which is a resin. The curable composition according to claim 5, wherein the blocking agent (b3) is a monovalent phenol compound. The curable composition according to claim 5 or 6, wherein the polyol (b1) is a polyether polyol or a polyester polyol. The curable composition according to any one of claims 5 to 7, wherein the polyisocyanate (b2) is a diisocyanate. A cured product of the curable composition according to any one of claims 1 to 8. An adhesive comprising the curable composition according to any one of claims 1 to 8.