JP2010111731A - Curing agent for epoxy resin, epoxy resin composition and cured product of epoxy resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a curing agent for an epoxy resin, capable of imparting high latency when mixed with an epoxy resin, and hardly damaging the electric characteristics of an obtained cured product of the epoxy resin, to provide an epoxy resin composition containing the curing agent for the epoxy resin and the epoxy resin, and to provide the cured product of the epoxy resin obtained therefrom. <P>SOLUTION: The curing agent for the epoxy resin is a reaction product of particles of a crosslinked polymer (A) containing a monovinyl monomer unit (a) having a carboxy group, with an imidazole compound (B), and is regulated so that the total content of a sodium ion, a calcium ion, a magnesium ion, a potassium ion, an aluminum ion and an iron ion in the curing agent for the epoxy resin may be ≤50 ppm. The epoxy resin composition thereof and the cured product of the epoxy resin are also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a curing agent for epoxy resin, an epoxy resin composition, and a cured epoxy resin.

Epoxy resin cured products have excellent adhesiveness, mechanical properties, thermal properties, and electrical properties, and are therefore widely used industrially in various applications such as paints, adhesives, and insulating materials for electrical and electronic applications. . Epoxy resin compositions used for these applications are largely divided into a one-component system and a two-component system.
The most commonly used epoxy resin composition is a two-component system. In the two-component epoxy resin composition, the epoxy resin-containing resin component and the curing agent-containing curing agent component are stored separately, and both are weighed and mixed to prepare an epoxy resin composition before use. In order to obtain a product, there is a problem that the quality is unstable, such as a measurement error or a variation in constituent components in each lot of the resin component and the curing agent component. In order to cope with such problems, various one-component epoxy resin compositions have been proposed. Among them, those using an imidazole compound are excellent in curability of epoxy resin compositions and are used in a wide range of applications because they give cured epoxy resins with high heat resistance.

Examples of a method for imparting latency to an imidazole compound include a reaction product of an imidazole compound and an aliphatic monocarboxylic acid such as acetic acid, an aliphatic hydroxymonocarboxylic acid such as lactic acid, or an aromatic hydroxymonocarboxylic acid such as salicylic acid. It is known to use things. However, it cannot be said that the reaction products of these organic carboxylic acids and imidazole compounds have sufficient potential when mixed with an epoxy resin.
In order to impart high potential, for example, a reaction product of a microgel containing a carboxylic acid group and a nitrogen-containing base such as an imidazole compound has been proposed. However, although the epoxy resin composition containing the reaction product as a curing agent has high potential, the microgel itself contains a large amount of ionic impurities, so that the epoxy resin cured product obtained is electrically There is a problem that the characteristics are impaired.
Japanese Patent Laid-Open No. 2-84426 JP-A-10-67819

  An object of the present invention is to provide a curing agent for an epoxy resin that can impart high potential when mixed with an epoxy resin and does not impair the electrical properties of the resulting cured epoxy resin, and the curing agent for the epoxy resin and the epoxy resin. It is providing the epoxy resin composition containing this, and the epoxy resin hardened | cured material obtained from it.

  The gist of the present invention is that a curing agent for an epoxy resin, which is a reaction product of particles of a crosslinked polymer (A) containing a monovinyl monomer unit (a) having a carboxyl group and an imidazole compound (B). The epoxy resin curing agent (hereinafter, “the total content of sodium ions, calcium ions, magnesium ions, potassium ions, aluminum ions and iron ions” contained in the epoxy resin curing agent is 50 ppm or less. This curing agent ”is referred to as the first invention.

Further, the gist of the present invention is that an epoxy resin having two or more epoxy groups in one molecule (hereinafter referred to as “the present epoxy resin”) and an epoxy resin composition (hereinafter referred to as “the curing agent”). The present invention is referred to as “the present epoxy resin composition”.
Furthermore, the gist of the present invention is a cured epoxy resin obtained by curing the epoxy resin composition (hereinafter referred to as “the cured epoxy resin”) as a third invention.

  According to the present invention, a one-component epoxy resin composition having excellent latency, that is, storage stability and curability can be obtained, and the specific content of ions in the curing agent is 50 ppm or less. The cured resin has excellent electrical characteristics and is suitable for various uses such as a one-component adhesive, sealant, casting agent, laminating agent, and paint.

The crosslinked polymer (A) used in the present invention contains a monovinyl monomer unit (a) having a carboxyl group.
Examples of the monovinyl monomer (a ′) having a carboxyl group which is a raw material for constituting the monovinyl monomer unit (a) having a carboxyl group in the crosslinked polymer (A) include (meth) acrylic acid. 2-carboxyethyl (meth) acrylate, 2-methacryloyloxyethyl phthalate, 2-methacryloyloxyethyl hexahydrophthalate, maleic acid, monomethyl malate, monoethyl malate, fumaric acid, monomethyl fumarate, monoethyl fumarate, Itaconic acid, cinnamic acid, crotonic acid, 4-vinylphenylcyclohexanecarboxylic acid, 4-vinylphenylacetic acid and p-vinylbenzoic acid. These can be used alone or in combination of two or more.
Among these, (meth) acrylic acid, 2-methacryloyloxyethyl phthalate, and 2-methacryloyloxyethyl hexahydrophthalate are preferable from the viewpoint of polymerization stability.
In the present invention, “(meth) acrylate” and “(meth) acryloyl” represent “acrylate” or “methacrylate” and “acryloyl” or “methacryloyl”, respectively.

In the present invention, the crosslinked polymer (A) can contain other monovinyl monomer units (b) and crosslinking agent units (c) in addition to the monovinyl monomer units (a) having a carboxyl group. .
As content of the monomer unit (a) which has a carboxyl group in a crosslinked polymer (A), 5-80 mass% is preferable, 10-70 mass% is more preferable, 15-60 mass% is still more preferable. When the content of the monomer unit (a) having a carboxyl group is 5% by mass or more, the reaction point with the imidazole compound (B) which is a curing component increases, and the curability of the epoxy resin composition tends to be good. is there. In addition, when the content of the monomer unit (a) having a carboxyl group is 80% by mass or less, the stability when the particles of the crosslinked polymer (A) are synthesized tends to be good.

Examples of the other monovinyl monomer (b ′) which is a raw material for constituting the other monovinyl monomer unit (b) in the crosslinked polymer (A) include, for example, methyl (meth) acrylate, ethyl (meta ) Acrylate, 2-hydroxyethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and styrene. These can be used alone or in combination of two or more.
Among these, methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate are preferable from the viewpoint of polymerization stability.
The content of the other monovinyl monomer unit (b) in the crosslinked polymer (A) is preferably 0 to 80% by mass, more preferably 5 to 75% by mass, and more preferably 10 to 65% by mass from the viewpoint of polymerization stability. % Is more preferable.

Examples of the crosslinking agent (c ′) that is a raw material for constituting the crosslinking agent unit (c) in the crosslinked polymer (A) include poly (meth) acrylates of aliphatic, alicyclic or aromatic polyols, Examples include addition products of (meth) acrylic acid and polyglycidyl compounds, addition products of (meth) acrylic acid and glycidyl (meth) acrylate, alkenyl (meth) acrylate, dialkenylcyclohexane and dialkenylbenzene. These can be used alone or in combination of two or more.
Among the crosslinking agents (c ′), for example, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate, Polypropylene glycol di (meth) acrylate, 1,1,1-trimethylolpropane tri (meth) acrylate, diglycidyl ether di (meth) acrylate of bisphenol A, allyl (meth) acrylate, 1,6 hexanediol di (meth) Acrylate, 1,9 nonanediol di (meth) acrylate and divinylbenzene are preferred from the viewpoint of polymerization stability.
The content of the crosslinking agent unit (c) in the crosslinked polymer (A) is preferably 0.1 to 85% by mass, more preferably 1 to 75% by mass, and 3 to 65% by mass in terms of polymerization stability. Further preferred.

  10-800 nm is preferable, as for the average primary particle diameter of the particle | grains of a crosslinked polymer (A), 30-700 nm is more preferable, and 40-200 nm is still more preferable. When the average primary particle diameter of the particles of the crosslinked polymer (A) is 10 nm or more, an increase in viscosity or poor dispersion of the epoxy resin composition tends to be suppressed. Moreover, the average primary particle diameter of the particles of the crosslinked polymer (A) tends to be good when the crosslinked polymer (A) having a high carboxyl group content is 800 nm or less.

As a method for producing the particles of the crosslinked polymer (A), known methods may be mentioned, but an emulsion polymerization method is preferred in that the imidazole compound (B) described later is reacted with the particles of the crosslinked polymer (A).
Examples of the surfactant when the particles of the crosslinked polymer (A) are produced by the emulsion polymerization method include various anionic, cationic and nonionic surfactants.

Anionic surfactants include, for example, carboxylates such as potassium oleate, sodium stearate, sodium myristate, sodium N-lauroyl sarcosine, dipotassium alkenyl succinate; sulfate esters such as sodium lauryl sulfate; dioctyl Sulfonates such as sodium sulfosuccinate, sodium dodecylbenzene sulfonate, sodium alkyldiphenyl ether disulfonate, ammonium lauryl sulfate, ammonium alkyl sulfosuccinate, ammonium alkenyl sulfosuccinate; and phosphate ester salts such as sodium polyoxyethylene alkyl ether phosphate Can be mentioned. These can be used alone or in combination of two or more.
Among these, ammonium lauryl sulfate and ammonium di-2-ethylhexylsulfosuccinate are used in view of the residual ion content in the particles of the crosslinked polymer (A) and the polymerization stability of the crosslinked polymer (A). preferable.

Examples of nonionic surfactants include oxyethylene-oxypropylene block polymers, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, sorbitan fatty acid esters, and polyoxyethylene fatty acids.
In the present invention, a reactive surfactant can be used as necessary in addition to the surfactant.

Examples of the reactive surfactant include ionic or nonionic surfactants having radical reactivity with an ethylenically unsaturated monomer.
Specific examples of the reactive surfactant include commercially available Adeka Soap SE-10N (anionic), Adeka Soap SE-20N (anionic), and Adeka Soap SR-10 (anionic) manufactured by ADEKA Corporation. ), Adekaria soap SR-20 (anionic), Adekaria soap NE-10 (nonionic), Adekaria soap NE-20 (nonionic), Adekaria soap NE-30 (nonionic), Adekaria soap NE-40 (nonionic), ADEKA rear soap ER-10 (nonionic), ADEKA rear soap ER-20 (nonionic), ADEKA rear soap ER-30 (nonionic), ADEKA rear soap ER-40 (nonionic) ), Adeka Soap SDX-730 (anionic), Adeka Soap SDX-731 (anionic), Ade Rear soap PP-70 (anionic) and Adequaria soap PP-710 (anionic), Eleminol JS-2 (anionic), Eleminol JS-20 (anionic) and Eleminol RS-30 manufactured by Sanyo Chemical Industries, Ltd. (Anionic), LATEMUL S-180A (anionic), LATEMUL S-180 (anionic) and LATEMUL PD-104 (anionic) manufactured by Kao Corporation, Aqualon BC- manufactured by Daiichi Kogyo Seiyaku Co., Ltd. 05 (anionic), Aqualon BC-10 (anionic), Aqualon BC-20 (anionic), Aqualon HS-05 (anionic), Aqualon HS-10 (anionic), Aqualon HS-20 (anionic) , Aqualon RN-10 (nonionic), Aqualon RN-20 (nonionic), Aqualon RN 30 (nonionic), Aqualon RN-50 (nonionic), Aqualon KH-05 (anionic), Aqualon KH-10 (anionic) and New Frontier S-510 (anionic) and manufactured by Toho Chemical Industry Co., Ltd. Phosphinol TX (anionic) (all the above are trade names). These can be used alone or in combination of two or more.

  The amount of the surfactant used in the emulsion polymerization for obtaining the crosslinked polymer (A) can be appropriately determined depending on the surfactant to be used, the type and composition ratio of the monomer components, and the polymerization conditions. 0.1 parts by mass or more is preferable with respect to 100 parts by mass of the monomer component, and 0.5 parts by mass or more is more preferable. In addition, the amount of the surfactant used is preferably 30 parts by mass or less with respect to 100 parts by mass of the monomer component in terms of suppressing the residual amount of the surfactant in the obtained crosslinked polymer (A). Less than the mass part is more preferable.

As a polymerization initiator used at the time of emulsion polymerization at the time of obtaining a crosslinked polymer (A), either water-soluble or oil-soluble can be used.
Examples of the polymerization initiator include t-butyl hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide, isobutyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide. Oxide, t-butylcumyl peroxide, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 1,1-bis (t-butylperoxy) -3, 3, 5 -Trimethylcyclohexane, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, di-isobutyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl Organic peroxides such as ruperoxyisobutyrate; azobisisobutyronitrile, dimethylazodiisobutyrate, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2- Methylbutyronitrile), 2,2′-azobis (2-amidinopropane) dihydrochloride, 4,4′-azobis (4-cyanovaleric acid) and its ammonium salt, 2,2′-azobis {2- [ N- (2-carboxyethyl) amidino] propane}, 2,2′-azobis (2-methylpropionamidooxime) dihydrochloride, 2,2′-azobis (2-methylbutanamidooxime) dihydrochloride, 2,2 '-Azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] -propionamide}, 2,2'-azobis [2 Azo compounds such as -methyl-N- (2-hydroxyethyl) -propionamide]; persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate; hydrogen peroxide and various redox catalysts. These can be used alone or in combination of two or more.

When the above redox catalyst is used, examples of the oxidizing agent include ammonium persulfate, potassium persulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide and p-menthane hydroperoxide. Oxide can be used in combination. Moreover, as a reducing agent, sodium sulfite, acidic sodium sulfite, Rongalite, and ascorbic acid can be used together, for example.
Among the above polymerization initiators, ammonium persulfate, 4,4′-azobis (4-cyanovaleric acid) and 2,2′-azobis {2- [N- (2-Carboxyethyl) amidino] propane} is preferred.

  As for the usage-amount of the polymerization initiator used at the time of emulsion polymerization at the time of obtaining a crosslinked polymer (A), 0.01-5 mass parts is preferable with respect to 100 mass parts of ethylenically unsaturated monomers, 0.05 -3 mass parts is more preferable. When the polymerization initiator is 0.01 parts by mass or more, the polymerization reaction tends to proceed smoothly. When the polymerization initiator is 5 parts by mass or less, the retention of the particle shape of the crosslinked polymer (A) tends to be good.

The imidazole compound (B) used in the present invention is not particularly limited as long as it has an imidazole ring.
Specific examples of the imidazole compound (B) include imidazole, 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1-isobutyl. 2-methylimidazole, 2-phenyl-4-methylimidazole, 2-ethyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 2,4-diamino-6 (2′-methylimidazole (1 ′)) ethyl-s-triazine, 2,4-diamino- 6 (2'-undecyl imidazo (1 ′)) Ethyl-s-triazine, 2,4-diamino-6 (2′-ethyl, 4-methylimidazole (1 ′)) ethyl-s-triazine, 2-phenyl-3,5-dihydroxymethylimidazole 2-phenyl-4-hydroxymethyl-5-methylimidazole and 1-cyanoethyl-2-phenyl-3,5-dicyanoethoxymethylimidazole. These can be used alone or in combination of two or more.
Among these, 2-methylimidazole, 1,2-dimethylimidazole and 2-ethyl-4-methylimidazole having high water solubility are preferable.

  The amount of the imidazole compound (B) used is the number of moles of the monovinyl monomer unit (a) having a carboxyl group contained in the particles of the crosslinked polymer (A) from the viewpoint of storage stability of the epoxy resin composition. Equimolar number is preferable, and 0.8-0.9 mol is more preferable with respect to 1 mol of monovinyl monomer units (a) having a carboxyl group.

The present curing agent is obtained by reacting the imidazole compound (B) with a carboxyl group present in the particles of the crosslinked polymer (A).
Moreover, this hardening | curing agent contains the monovinyl monomer unit (a) which has a carboxyl group, and contains sodium ion, calcium ion, magnesium ion, potassium ion, aluminum ion, and iron ion in the particle | grains of a crosslinked polymer (A). The total content is 50 ppm or less.
By setting the total content of sodium ions, calcium ions, magnesium ions, potassium ions, aluminum ions and iron ions in the hardener to 50 ppm or less, it is possible to improve the electrical properties of the cured epoxy resin described later. it can.

  As a method of adjusting the total content of sodium ion, calcium ion, magnesium ion, potassium ion, aluminum ion and iron ion in the present curing agent to 50 ppm or less, for example, as an auxiliary material such as an emulsifier and initiator used for polymerization, This can be achieved by using a substance that does not contain sodium ion, calcium ion, magnesium ion, potassium ion, aluminum ion and iron ion.

As a method of reacting the imidazole compound (B) with the carboxyl group present in the particles of the crosslinked polymer (A), for example, the particles of the crosslinked polymer (A) and the imidazole compound (B) are contacted at 10 to 60 ° C. Can be achieved.
As a specific example of the method of reacting the imidazole compound (B) with the carboxyl group present in the particles of the crosslinked polymer (A), the latex obtained by producing the crosslinked polymer (A) by an emulsion polymerization method, A method of adding the imidazole compound (B) while stirring at room temperature can be mentioned.
In addition, in the said method, the method of adding the imidazole compound (B) in the state of the solution previously diluted with solvents, such as water or isopropyl alcohol, is preferable.

In the present invention, the particles of the present curing agent obtained by reacting the particles of the crosslinked polymer (A) with the imidazole compound (B) can be recovered by a known method.
Specific examples of the powder recovery method of the particles of the curing agent include salting out or acid precipitation, freeze drying, and spray drying, but spray drying is preferable from the viewpoint of dispersibility in epoxy resin. preferable.

  This hardening | curing agent can be used as a hardening accelerator of an epoxy resin. When this curing agent is used as a curing accelerator, a phenolic curing agent such as a phenol novolak resin or a cresol novolak resin, an amine curing agent, an acid anhydride curing agent, or the like can be added as a curing agent. In this case, the amount of the curing agent is preferably the same as the stoichiometric amount of the epoxy group in the epoxy resin.

This epoxy resin has two or more epoxy groups in one molecule.
The molecular structure and molecular weight of the epoxy resin are not particularly limited, and specific examples of the epoxy resin include various epoxy resins such as dicyclopentadiene type, cresol novolac type, phenol novolac type, bisphenol type, and biphenyl type. . These can be used alone or in combination of two or more.

The present epoxy resin composition is obtained by blending the present epoxy resin and the present curing agent.
0.1-50 mass parts is preferable with respect to 100 mass parts of this epoxy resin, as for the compounding quantity of this hardener to this epoxy resin, 0.2-40 mass parts is more preferable, and 0.3-35 mass parts is. Particularly preferred. It exists in the tendency which can fully harden this epoxy resin with the compounding quantity of this hardening | curing agent 0.1 mass part or more. Further, when the content is 50 parts by mass or less, the curing agent tends to be easily dispersed in the epoxy resin composition, and a significant increase in viscosity of the epoxy resin composition tends to be suppressed.
Examples of the method of blending the epoxy resin and the curing agent include a three roll mill, a bead mill, a ball mill, and a planetary mixer.

The cured epoxy resin is obtained by curing the epoxy resin composition.
Examples of curing conditions for the epoxy resin composition include a method of heat curing at 80 to 150 ° C. for 1 to 12 hours.

  The present invention will be specifically described below with reference to examples. Moreover, the following evaluation was implemented about the crosslinkable polymer, the epoxy resin composition, and the epoxy resin hardened | cured material. In the following, “part” and “%” represent “part by mass” and “% by mass”, respectively, unless otherwise specified.

(1) Average primary particle diameter Using a CHDF2000 type particle size distribution meter manufactured by MATEC USA, a sample obtained by diluting a latex obtained by the production of a crosslinked polymer to a concentration of 3% with distilled water was used. The primary particle size was measured. The measurement conditions were the following standard conditions recommended by MATEC.
(Standard conditions)
Using a dedicated particle separation capillary cartridge and carrier liquid, diluted latex sample 0 with a concentration of 3% with neutral liquidity, flow rate 1.4 ml / min, pressure 28 MPa and temperature 35 ° C. .1 ml was used for the measurement. As the standard particle size substance, monodispersed polystyrene having a particle size of 12 points selected from 30 to 800 nm and having a known particle size manufactured by DUKE, USA was used.

(2) Residual metal ion amount As a sample pretreatment, 0.25 g of a curing agent, which is a reaction product of the crosslinked polymer (A) particles and the imidazole compound (B), is placed in 10 ml of nitric acid and subjected to microwave (wet decomposition). The sample was decomposed and diluted to 50 ml with distilled water to prepare a test solution. The obtained test solution was measured for the amount of residual metal ions in the curing agent using an ICP emission analyzer (IRIS Intrepid II XSP manufactured by Thermo). Note that the calibration curve was prepared using four residual metal ion known amount samples of 0 ppm, 0.1 ppm, 1 ppm and 10 ppm. The measurement wavelengths of each metal ion are 589.5 nm for sodium ion measurement, 766.4 nm for potassium ion measurement, 184.0 nm for calcium ion measurement, 279.5 nm for magnesium ion measurement, and aluminum ion measurement. In this example, 396.1 nm and 259.9 nm were used for measuring iron ions.

(3) Amine value The amine value of the powder particles of the curing agent was measured by an indicator titration method according to JIS K7237.

(4) Storage stability Using a B-type viscometer, the change in the viscosity of the epoxy resin composition at 40 ° C. was observed over time, measured until the viscosity became twice the initial viscosity, and storage stability was measured using the number of days as an index. Sex was compared.

(5) Water Absorption Rate A sheet-like molded body of a cured epoxy resin having a thickness of 3 mm was cut into a width of 50 mm and a length of 50 mm to obtain a test piece, and the water absorption rate was measured based on JIS K6911.

(6) Relative permittivity and dielectric loss tangent A sheet-like molded body of a cured epoxy resin having a thickness of 3 mm was cut into a width of 30 mm and a length of 30 mm to produce a test piece. Then, the dielectric constant and dielectric loss tangent of the cured epoxy resin were measured under the following conditions.
Measuring apparatus: RF impedance / material analyzer HP4291B (manufactured by Agilent Technologies)
Measurement frequency: 1MHz and 1GHz
Measurement temperature: 23 ° C
Measurement humidity: 60%

[Production Example 1]
A 5-neck flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, monomer addition port and thermometer was charged with 533 parts of deionized water and 4.7 parts of ammonium di-2-ethylhexylsulfosuccinate as a surfactant, The temperature was raised to 70 ° C.
Next, 15 parts of methacrylic acid as the monovinyl monomer (a ′) having a carboxyl group, 65 parts of methyl methacrylate as the other monovinyl monomer (b ′), and 10 parts of ethylene glycol dimethacrylate as the crosslinking agent (c ′) A monomer mixture composed of 10 parts of trimethylolpropane trimethacrylate was prepared, 1/10 amount of the monomer mixture was weighed and charged into a flask, and 0.17 part of ammonium persulfate was added as an initiator for polymerization. Started.
After holding for 1 hour from the start of polymerization, the remaining monomer mixture was dropped into the flask over 2 hours, and then kept for 1 hour to obtain a latex of a crosslinked polymer (A-1). The obtained latex had a solid content of 14.2% and an average primary particle size of 120 nm.

Next, 154 parts of a 10% strength 2-ethyl-4 methylimidazole aqueous solution was added to the latex and mixed well to obtain a latex of a curing agent (I).
Then, using a spray dryer (L-8 type manufactured by Okawara Chemical Industries Co., Ltd.), the curing agent (I) was used under the conditions of a drying gas inlet temperature of 140 ° C., an outlet temperature of 70 ° C., and an atomizer speed of 25,000 rpm. The latex was sprayed to obtain a hardener (I) powder. The amine value of the powder of the obtained curing agent (I) was 56.0. Table 1 shows the evaluation results of the amount of metal ions in the powder of the curing agent (A).

The abbreviations in Table 1 indicate the following compounds.
Emulsifier 1: Ammonium di-2-ethylhexyl sulfosuccinate 1118S-70: Polyoxyethylene alkyl ether (trade name; Emulgen 1118S-70, manufactured by Kao Corporation)
1150S-60: Polyoxyethylene alkyl ether (trade name; Emulgen 1150S-60, manufactured by Kao Corporation)
SR-10: Adeka Soap SR-10 (trade name) manufactured by ADEKA Corporation)
DBSNa: sodium dodecylbenzenesulfonate MAA: methacrylic acid monomer 1: 2-methacryloyloxyethyl hexahydrophthalate MMA: methyl methacrylate BA: butyl acrylate EGDMA: ethylene glycol dimethacrylate TMPTMA: trimethylolpropane trimethacrylate

[Production Examples 2 to 5]
The raw material composition of the crosslinked polymer was set to the composition shown in Table 1. Otherwise in the same manner as in Production Example 1, latexes of the crosslinked polymers (A-2) to (A-4) and (A′-5) and curing agents (b) to (e) were obtained. Table 1 shows the evaluation results of the crosslinked polymers (A-2) to (A-4) and (A′-5) and the curing agents (b) to (e).

[Example 1]
The powder of the curing agent (I) and bisphenol A type epoxy resin (Japan Epoxy Resin Co., Ltd., trade name: Epicoat 828) were blended in the amounts shown in Table 2, and the planetary ball mill was used for 8 hours at 150 rpm. An epoxy resin composition (A) was obtained by mixing under conditions. Table 2 shows the evaluation results of the storage stability of this epoxy resin composition (A).
In addition, the compounding quantity of the powder of hardening | curing agent (I) was mix | blended so that it might become 2.5 mass parts as imidazole with respect to 100 mass parts of epoxy resins.

  Subsequently, the epoxy resin composition (a) obtained above was kneaded at 2,000 rpm for 5 minutes using a vacuum defoaming kneader. Thereafter, the kneaded product of the epoxy resin composition (A) is poured into a glass cell in which the end between the two glass plates is sealed, and is first cured at 100 ° C. for 3 hours and then at 150 ° C. for 3 hours, A sheet-like molded body (α) of a cured epoxy resin having a thickness of 3 mm was produced. Using the obtained sheet-like molded body (α), the water absorption, relative dielectric constant and dielectric loss tangent were measured. The evaluation results are shown in Table 2.

[Examples 2 to 4 and Comparative Examples 1 and 2]
Instead of the curing agent (ii), the curing agents (b) to (e) or 2-ethyl-4-methylimidazole shown in Table 2 were used in the amounts shown in Table 2. Other than that was carried out similarly to Example 1, and produced the epoxy resin composition (ii)-(ka) and the epoxy resin hardened | cured sheet-like molded object ((beta))-(ζ). Using the obtained sheet-like molded bodies (β) to (ζ), the water absorption rate, the relative dielectric constant, and the dielectric loss tangent were measured. The evaluation results are shown in Table 2.

  As is apparent from Table 2, since the curing agent for epoxy resin is excellent in storage stability and the amount of residual metal ions is small, the cured product of epoxy resin is excellent in electrical characteristics.

Claims (4)

  A curing agent for an epoxy resin, which is a reaction product of particles of a crosslinked polymer (A) containing a monovinyl monomer unit (a) having a carboxyl group and an imidazole compound (B), the epoxy resin curing The hardening | curing agent for epoxy resins whose total content of a sodium ion, a calcium ion, a magnesium ion, a potassium ion, an aluminum ion, and an iron ion contained in an agent is 50 ppm or less.   The hardening | curing agent for epoxy resins of Claim 1 in which a crosslinked polymer (A) contains 5-80 mass% of monovinyl monomer units (a) which have a carboxyl group.   An epoxy resin composition comprising an epoxy resin having two or more epoxy groups in one molecule and the epoxy resin curing agent according to claim 1.   A cured epoxy resin obtained by curing the epoxy resin composition according to claim 3.