JP2008266541A - Epoxy resin hardener - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyoxyalkylene polyamine-based epoxy resin hardener which is excellent in flexibility, water resistance, and adhesiveness because of its sufficiently high reactivity even at a low temperature without using a hardening accelerator and, on the other hand, can give a non-colored hardened material. <P>SOLUTION: The epoxy resin hardener comprises polyoxyalkylene polyamine (A) and polyoxyalkylene polyamine (B), both having a specified chemical structure, the molar ratio of (A)/(B) being (97/3)-(60/40). The molar ratio of oxypropylene group/oxyethylene group in the oxyalkylene chain of the oxyalkylene polyamines (A) and (B) is (70/30)-(100/0). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a curing agent for epoxy resin having a sufficiently high reactivity, and in particular, for an epoxy resin that can obtain a cured product with little coloration because it can be reacted even at a low temperature without using a curing accelerator in combination. It relates to a curing agent.

Conventionally, epoxy resins obtained by using polyoxyalkylene polyamine as a curing agent are excellent in flexibility, water resistance, chemical resistance, etc., so a wide range of coating materials such as electrodeposition paints, adhesives, sealing materials, etc. It is used in the industrial field.
When polyoxyalkylene polyamine is used as a curing agent, the reactivity is generally low, so the epoxidation reaction temperature needs to be 100 ° C. or higher. (For example, Patent Documents 1 and 2). However, when it is made to react at 100 degreeC or more, there exists a problem that the obtained epoxy resin colors.

In order to sufficiently increase the reactivity even at a low temperature of 100 ° C. or lower, there is a method in which a curing accelerator such as 2,4,6-tris (dimethylaminomethyl) phenol and polyalkylene polyamine is used in combination with the curing agent (for example, patents). References 3, 4).
However, coloring problems still remain when a curing accelerator is used.
JP-A-10-120759 JP 2006-199863 A JP-A-62-215624 JP 2001-151862 A

Therefore, a polyoxyalkylene that does not use a curing accelerator and is sufficiently reactive even at low temperatures, so that it has excellent flexibility, water resistance, and adhesion, while being able to obtain a cured product without coloring. An object of the present invention is to provide a polyamine-based curing agent for epoxy resins.

As a result of studies to achieve the above-mentioned object, the present inventors have obtained an epoxy resin having excellent physical properties even at low temperatures without using a curing accelerator by using a polyoxyalkylene polyamine having a specific chemical structure. We have found that it can be obtained and have reached the present invention.
That is, the present invention comprises polyoxyalkylene triamine (A) represented by the following general formula (1) and polyoxyalkylene triamine (B) represented by the following general formula (2) as essential components, The molar ratio of / (B) is 97/3 to 60/40, and the molar ratio of oxypropylene group / oxyethylene group in the oxyalkylene chain of the polyoxyalkylenetriamine (A) and (B) is 70 / 30 to 100/0 epoxy resin curing agent (C); epoxy resin curing agent (C) and epoxy resin (D) thermosetting epoxy resin composition (E); and a coating film comprising this thermosetting epoxy resin composition.

[In the formulas (1) and (2), R ¹ and R ² each independently represents an alkylene group having 1 to 3 carbon atoms, and AO represents an oxyalkylene group. m, n, and k represent the average number of added moles of alkylene oxide, and are each 1 to 100. ]

  By using the epoxy resin curing agent of the present invention, it is possible to obtain an epoxy resin which is excellent in flexibility, water resistance and adhesion even at low temperatures and has no color.

  This invention is a hardening | curing agent for epoxy resins which has the polyoxyalkylene triamine (A) represented by the said General formula (1) and the polyoxyalkylene triamine (B) represented by the said General formula (2) as an essential component. . And said (A) / (B) molar ratio is 97 / 3-60 / 40, Furthermore, the oxypropylene group / oxyethylene group in the oxyalkylene chain in the molecule | numerator of polyoxyalkylene triamine (A) The molar ratio is 70/30 to 100/0. Similarly, the molar ratio of oxypropylene group / oxyethylene group in the oxyalkylene chain of the polyoxyalkylene triamine (B) is also 70/30 to 100/0.

  The polyoxyalkylene triamine (A) represented by the general formula (1) has higher reactivity with the epoxy group of the polyglycidyl ether than the conventional polyoxyalkylene polyamine. Therefore, when polyoxyalkylene triamine (A) is used as an epoxy resin curing agent, a cured epoxy resin can be produced at a low temperature.

  However, since polyoxyalkylene triamine (A) is highly reactive, if (A) is cured alone as a curing agent for epoxy resin to form a coating film, the coating film will be cracked. Is difficult to use. This is because the reactivity between the primary amino group and the epoxy group is extremely high. Therefore, the polyoxyalkylene triamine (A) having two primary amino groups at the molecular ends locally has a high molecular weight. It is considered that the cohesive force of the portion was larger than that of the surrounding area, and the coating film was cracked.

  By using an appropriate amount of polyoxyalkylene triamine (B) in combination with the polyoxyalkylene triamine (A) of the present invention, cracks do not occur when it is formed into a coating film, which is useful when used as a curing agent for epoxy resins.

  However, when the molar ratio of the polyoxyalkylene triamine (A) to the polyoxyalkylene triamine (B) is 60/40 to 0/100, the reactivity of the polyoxyalkylene triamine (B) is low. It takes a long time to obtain and is not practical.

  Therefore, the molar ratio of polyoxyalkylene triamine (A) to polyoxyalkylene triamine (B) is 97/3 to 60/40, preferably 96/4 to 70/30, more preferably 95/5 to 75/25. It is. By setting the molar ratio of (A) / (B) to 97/3 to 60/40, an epoxy resin curing agent that provides a good coating film when reacted with an epoxy resin at a low temperature is obtained.

  In general formulas (1) and (2), AO represents an oxyalkylene group, and the oxyalkylene group of the present invention is an oxypropylene group or an oxyethylene group.

The molar ratio of oxypropylene group / oxyethylene group in the oxyalkylene chain of the polyoxyalkylene triamine (A) represented by the formula (1) is usually 70/30 to 100/0, preferably 90/10 to 100. / 0, more preferably 100/0 (oxypropylene group alone).
If the molar ratio of oxypropylene group / oxyethylene group is in the range of 0/100 to 70/30, it is not preferable because the water resistance deteriorates when reacted with an epoxy resin such as polyglycidyl ether to form a coating film.

The method for producing the polyoxyalkylene triamine (A) is not particularly limited. As described later, the polyoxyalkylene triamine (A) of the present invention is prepared by previously adding the raw material triamine (a) in the presence of an excessive amount of ketone. Then, heating and dehydration are carried out to convert the primary amino group into a ketimine group to block the ketimine, and this is subjected to an addition reaction using propylene oxide alone or propylene oxide and ethylene oxide in combination. Thereafter, an excess amount of water is added, the mixture is hydrolyzed with heating and stirring, and the resulting ketone and the excess amount of water are removed.
When propylene oxide and ethylene oxide are used in combination, the addition mode may be block addition, random addition, or a mixed system of block addition and random addition such as random addition of propylene oxide and ethylene oxide after propylene oxide addition.

M in Formula (1) is the average addition mole number of propylene oxide alone or the total of propylene oxide and ethylene oxide to the secondary amino group of the ketimine blocked triamine (a), and is usually 1 to 70, preferably 4 to 50.
If the average number of moles added is too high, the viscosity of the epoxy resin curing agent increases, which makes it difficult to handle at low temperatures.

Wherein ^{(1), R 1, R} 2 represents a straight-chain or branched alkylene group having 1 to 3 carbon atoms independently. Examples of the alkylene group having 1 to 3 carbon atoms include a methylene group, an ethylene group, and a propylene group. An ethylene group and a 1,3-propylene group are preferable. More preferably, it is an ethylene group.

  The molar ratio of oxypropylene group / oxyethylene group in the oxyalkylene chain of the polyoxyalkylene triamine (B) represented by the formula (2) is usually 70/30 to the same as in the case of the polyoxyalkylene triamine (A). 100/0, preferably 90/10 to 100/0, more preferably 100/0 (oxypropylene group alone).

N in the formula (2) is an average addition mole number of propylene oxide alone or a total of propylene oxide and ethylene oxide to the secondary amino group of the ketimine-blocked triamine (a), and is usually 1 to 70, preferably 4 to 50.
K is propylene oxide alone or the total number of added moles of propylene oxide and ethylene oxide to the primary amino group of the ketimine blocked triamine (a), and is usually 1 to 70, preferably 4 to 50. .
If the average number of added moles is too high, the viscosity of the curing agent for epoxy resin becomes very high, which makes it difficult to handle at low temperature, which is not preferable.

In formula (2), R ¹ and R ² are the same as those described in formula (1).

The total amine value of the curing agent for epoxy resins of the present invention is usually 30 to 600, preferably 50 to 500, and more preferably 65 to 400. If the total amine value is less than 30, the viscosity of the epoxy resin curing agent is too high, which makes it difficult to handle at low temperatures, which is not preferable. Moreover, since the flexibility (flexibility) of the coating film obtained will worsen when the total amine number exceeds 600, it is unpreferable.
The total amine value is the number of mg of potassium hydroxide equivalent to perchloric acid required to neutralize the amine in 1 g of the sample, and represents the content of amine contained in the sample. The total amine value is measured according to JIS K 7237 (1995).

The molar ratio between the polyoxyalkylene triamine (A) and (B) can be obtained by the following calculation formula by measuring the total amine value and the tertiary amine value of the curing agent for epoxy resin (C). .
(A) / (B) = [2T _a −3T ₃ ] / [3T ₃ −T _a ]
However, T ₃ = tertiary amine value and T _a = total amine value.
The tertiary amine value is the number of mg of potassium hydroxide equivalent to perchloric acid required to neutralize the tertiary amine in 1 g of the sample, and the content of the tertiary amine contained in the sample. Represents. The tertiary amine value (the tertiary amino group nitrogen content) is measured according to JIS K 7245 (2000).

The method for producing the polyoxyalkylene triamines (A) and (B) is not particularly limited, and examples thereof include a method for producing them through the following steps (i) to (iii) (for example, JP-A-63-079797). Publication).
(I) The starting triamine (a) contains two primary amino groups and one secondary amino group. By heating and dehydrating in the presence of a ketone compound, only the primary amino group is converted to a ketimine group.
(Ii) An oxyalkylene group is added to the secondary amino group by reacting with an alkylene oxide.
(Iii) By reacting with water, the protected ketimine group portion of the polyoxyalkylenetriamine compound is deprotected to form a primary amino group.

When producing only the polyoxyalkylene triamine (A), the above production process (i)
In Step 2, a large excess of the ketone compound is added to the two primary amino groups of the triamine so that all the two primary amino groups are protected, and then the steps (ii) and (iii) are performed. Just do it.

Moreover, a polyoxyalkylene triamine (B) can be manufactured with the following method.
In the production process (i) of the above polyoxyalkylene triamine, only one of the two primary amino groups of the starting triamine (a) is protected with a ketimine group by reducing the amount of the ketone compound used. The prepared compound is produced. This compound is reacted with an alkylene oxide. Thereafter, by reacting with water, the protected ketimine group portion of the polyoxyalkylene triamine compound is deprotected to produce polyoxyalkylene triamine (B).

In addition, in the production step (i) of the polyoxyalkylene triamine, the amount of the ketone compound is adjusted so that the polyoxyalkylene triamine (A) and the polyoxyalkylene triamine (B) are simultaneously mixed in an arbitrary ratio. It can be manufactured.
This method is more economical than the method of separately producing the polyoxyalkylene triamine (A) and the polyoxyalkylene triamine (B) and then mixing them at a predetermined ratio to produce the epoxy resin curing agent of the present invention. Is excellent.

  Examples of the epoxy resin (D) include glycidyl ether type epoxide (D1), glycidyl ester type epoxide (D2), glycidylamine type epoxide (D3), and alicyclic epoxide (D4).

Examples of the glycidyl ether type epoxide (D1) include glycidyl ether of dihydric phenol, glycidyl ether of polyhydric phenol, glycidyl ether of dihydric alcohol, and glycidyl ether of polyhydric alcohol.
Examples of the glycidyl ether of dihydric phenol include bisphenol F diglycidyl ether, bisphenol A diglycidyl ether, and bisphenol S diglycidyl ether.
Examples of the glycidyl ether of polyhydric phenol include dihydroxynaphthyl cresol triglycidyl ether, tris (hydroxyphenyl) methane triglycidyl ether and dinaphthyltriol triglycidyl ether, phenol novolac glycidyl ether, cresol novolac glycidyl ether and the like.
Examples of the glycidyl ether of dihydric alcohol include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tetramethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polyethylene glycol [weight average molecular weight (hereinafter, Mw): 150-4,000] diglycidyl ether and polypropylene glycol (Mw: 180-5,000) diglycidyl ether.
Examples of the glycidyl ether of polyhydric alcohol include trimethylolpropane triglycidyl ether, glycerin triglycidyl ether, pentaerythritol tetraglycidyl ether, sorbitol hexaglycidyl ether, and poly (degree of polymerization 2 to 5) glycerin polyglycidyl ether.

As the glycidyl ester type epoxide (D2), glycidyl ester of carboxylic acid, glycidyl ester type polyepoxide and the like are used.
Examples of the glycidyl ester of carboxylic acid include glycidyl methacrylate, diglycidyl phthalate, diglycidyl isophthalate, diglycidyl terephthalate, and triglycidyl trimellitic acid.

As the glycidylamine type epoxide (D3), glycidyl aromatic amine, glycidyl alicyclic amine, glycidyl heterocyclic amine and the like are used.
Examples of glycidyl aromatic amines include N, N-diglycidylaniline, N, N-diglycidyltoluidine, N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane, N, N, N ′, N′-tetraglycidyl. Examples include diaminodiphenyl sulfone and N, N, N ′, N′-tetraglycidyl diethyldiphenylmethane.
Examples of glycidyl alicyclic amines include bis (N, N-diglycidylaminocyclohexyl) methane (hydrogenated compound of N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane) and N, N, N ′, N ′. -Tetraglycidyl dimethylcyclohexylenediamine (hydrogenated compound of N, N, N ', N'-tetraglycidylxylylenediamine) and the like.
Examples of the glycidyl heterocyclic amine include trisglycidylmelamine and N-glycidyl-4-glycidyloxypyrrolidone.

  Alicyclic epoxides (D4) include vinylcyclohexene dioxide, limonene dioxide, dicyclopentadiene dioxide, bis (2,3-epoxycyclopentyl) ether, ethylene glycol bisepoxy dicyclopentyl ether and 3,4-epoxy- Examples include 6-methylcyclohexylmethyl-3 ′, 4′-epoxy-6′-methylcyclohexanecarboxylate.

  Among these epoxy resins, glycidyl ether type epoxides, glycidyl ester type epoxides and glycidyl amine type epoxides are preferable from the viewpoint of price and heat resistance, and glycidyl ether type epoxides and glycidyl ester type epoxides are more preferable. These epoxy resins may be used alone or in combination of two or more selected from these.

The amount of the epoxy resin curing agent (C) used is not particularly limited, but the total number of epoxy groups in the epoxy resin (D) and active hydrogens on the nitrogen atoms of the polyoxyalkylene triamines (A) and (B) The ratio to the number of moles is preferably 70/30 to 30/70. Incidentally, 1 mol of the primary amino group has two active hydrogens on the nitrogen atom.
When the molar ratio (A) / (B) is 100/0 to 70/30, cracks are generated in the coating film, which is not preferable.
If the molar ratio is 30/70 to 0/100, the low molecular weight compound derived from polyoxyalkylene triamine remains even after curing, so that when the coating is formed, the coating is easily peeled off, which is not preferable.
This molar ratio can be calculated from, for example, the measured value and the charged amount of the total amine value and tertiary amine value of the curing agent for epoxy resin (C), and the epoxy equivalent and charged amount of the epoxy resin (D).

  Although reaction temperature is not specifically limited, In order to color when it makes high temperature, the range of 0 to 100 degreeC is preferable.

  Further, the thermosetting epoxy resin composition (E) of the present invention includes the polyoxyalkylene triamine (A), polyoxyalkylene triamine (B), and epoxy resin (D) of the present invention as long as the properties are not impaired. ) As necessary, fillers, mold release agents, surface treatment agents, flame retardants, viscosity modifiers, plasticizers, antifungal agents, leveling agents, antifoaming agents, colorants, anticolorants, antioxidants , Stabilizers, coupling agents and the like may be blended.

The method for producing the thermosetting epoxy resin composition (E) of the present invention is not particularly limited as long as it can mix and disperse the materials used, and examples thereof include the following methods.
(I) Knead by hand with a stir bar, spatula, etc. in a suitable container such as a glass beaker, can, or plastic cup.
(Ii) Kneading with a double helical ribbon blade, a gate blade or the like.
(Iii) Kneading with a planetary mixer.
(Iv) Kneading with a bead mill.
(V) Kneading with three rolls.
(Vi) Kneading with an extruder-type kneading extruder.

  The thermosetting epoxy resin composition (E) of the present invention comprises a heavy-duty anti-corrosion paint, an anti-corrosion coating agent, a coating for flooring, an exterior paint, an automobile (electrodeposition) paint, a powder paint, a primer, Coating agents; structural adhesives, elastic adhesives, solvent-type reactive adhesives, adhesives, pressure-sensitive adhesives, etc .; sealing agents; concrete repair injections; laminates such as fiber reinforced laminates Matrix resin for casting; Casting insulation material, semiconductor sealant, interlayer insulation material, etching resist material, plating resist, solder resist, and other electronic materials; repair putty; other resin used for impregnation, injection, molding, etc. Etc. can be used.

  When the epoxy resin curing agent of the present invention is used, it is excellent in flexibility, water resistance and adhesion even at a low temperature, and on the other hand, a coating film without coloring can be obtained. In particular, it can be suitably used in a wide range of industrial fields such as coating materials including electrodeposition paints, adhesives, and sealing materials.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Production Example 1
A pressure-resistant reaction vessel equipped with a thermometer, stirrer, reflux condenser and nitrogen inlet was charged with 103 g (1.00 mol) of diethylenetriamine and 196 g (1.96 mol) of methyl isobutyl ketone, and the air in the reaction vessel was charged with nitrogen. After substituting with gas, it was heated at a reaction temperature of 115 ° C. for 5 hours to cause dehydration and ketimine reaction. It cooled to 60 degreeC after ketimine reaction.
To this was added 3.0 g of potassium hydroxide as an alkylene oxide addition catalyst, and after replacing with nitrogen gas, the vessel was sealed, heated to 100 ° C., and 319 g (5.5 mol) of propylene oxide was brought to a reaction temperature of 100 to 120 ° C. The solution was dropped and reacted.
After cooling to 60 ° C. after completion of the reaction, 20 g of Kyoward 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) and 10 g of water are added to the reaction product solution as an adsorbent to adsorb the added catalyst and remove the catalyst by filtration. did. Furthermore, 200 g of water was added to cause a hydrolysis reaction at 90 ° C. for 3 hours. Finally, excess water was distilled off while raising the temperature to 110 ° C. under normal pressure. When the temperature reached 110 ° C., the pressure was changed to reduced pressure. After reaching 2000 Pa, the solvent and ketone were distilled off for 1.5 hours. The epoxy resin curing agent (C-1) of the present invention was obtained.

Production Example 2
The curing agent for epoxy resin of the present invention was the same except that the amount of methyl isobutyl ketone used in Production Example 1 was changed to 170 g (1.70 mol) and the amount of propylene oxide was changed to 435 g (7.5 mol). (C-2) was obtained.

Production Example 3
Except that the propylene oxide of Production Example 1 was replaced with a mixture of 255 g (4.4 mol) of propylene oxide and 48 g (1.1 mol) of ethylene oxide, the curing agent for epoxy resin (C- 3) was obtained.

Production Example 4
The input amount of diethylenetriamine in Production Example 1 was changed to 34.3 g (0.33 mol), the input amount of methyl isobutyl ketone was changed to 65.3 g (0.65 mol), and the input amount of propylene oxide was changed to 638 g (11 mol). Except for the above, the epoxy resin curing agent (C-4) of the present invention was obtained in the same manner.

Comparative production example 1
A curing agent for epoxy resin for comparison (C ′) except that the amount of methyl isobutyl ketone used in Production Example 1 was changed to 130 g (1.3 mol) and the amount of propylene oxide added was changed to 580 g (10 mol). -1) was obtained.

Comparative production example 2
A curing agent for epoxy resin for comparison (C) except that the propylene oxide of Production Example 1 was replaced with a mixture of 160 g (2.8 mol) of propylene oxide and 121 g (2.8 mol) of ethylene oxide. '-2) was obtained.

The total amine value and tertiary amine value of the resulting epoxy resin curing agents (C-1) to (C-4) and (C'-1) to (C'-2) were measured.
The composition ratio (molar ratio) of the polyoxyalkylene polyamines (A) and (B) of the respective curing agents for epoxy resins was obtained from the results of measurement of total amine value and tertiary amine value. The results are shown in Table 1.

<Measurement conditions for total amine value>
The total amine value was measured according to JIS K 7237 (1995).

<Measurement conditions of tertiary amine value (3rd amino group nitrogen content)>
The tertiary amine value (tertiary amino group nitrogen content) was measured according to JIS K 7245 (2000). The tertiary amine value is a value obtained by calculating the number of mg of potassium hydroxide equivalent to perchloric acid required to neutralize the tertiary amine in 1 gram of the sample.

Example 1
100 g of polyglycidyl ether (bisphenol A type epoxy resin, Epicoat 834, Mn = 470, manufactured by Japan Epoxy Resin Co., Ltd.) may be added to 45 g of the epoxy resin curing agent (C-1) obtained in Production Example 1 and blended. And the epoxy resin composition (E-1) of this invention was obtained.

Example 2
The epoxy resin composition (E-2) of the present invention was obtained in the same manner as in Example 1 except that the epoxy resin curing agent obtained in Production Example 2 was replaced with 60 g of (C-2).

Example 3
An epoxy resin composition (E-3) of the present invention was obtained in the same manner as in Example 1 except that the curing agent for epoxy resin obtained in Production Example 3 was replaced with 45 g of (C-3).

Example 4
The epoxy resin composition (E-4) of the present invention was obtained in the same manner as in Example 1, except that the epoxy resin curing agent obtained in Production Example 4 was replaced with 200 g of (C-4).

Comparative Example 1
An epoxy resin composition (E′-1) for comparison was obtained in the same manner as in Example 1 except that the epoxy resin curing agent obtained in Comparative Production Example 1 was replaced with 90 g of (C′-1). It was.

Comparative Example 2
An epoxy resin composition (E′-2) for comparison was obtained in the same manner as in Example 1 except that the epoxy resin curing agent obtained in Comparative Production Example 2 was replaced with 45 g of (C′-2). It was.

Comparative Example 3
Epoxy resin composition for comparison in the same manner as in Example 1 except that 40 g of polyoxypropylene diamine (“Jephamine D-400”, Mn = 400, manufactured by Mitsuishi Texaco Chemical Co., Ltd.) was used instead of the epoxy resin curing agent. The thing (E'-3) was obtained.

After thermosetting the blended epoxy resin compositions (E-1) to (E-4) and (E′-1) to (E′-3), the following methods are used to achieve adhesion, flex resistance and Water resistance was evaluated.
The results are shown in Table 1.

<Adhesiveness by cross-cut tape method>
The compounded epoxy resin compositions (E-1) to (E-4) and (E′-1) to (E′-3) were applied to a thickness of 50 μm on a sufficiently washed steel plate, and the composition was at 60 ° C. It was cured by heating for 6 hours to obtain a coating film for evaluation tests.
Thereafter, an adhesion test was conducted in accordance with JIS K 5600-5-6 (1999) “Adhesiveness (cross-cut method)”.
As the determination of adhesion, out of 25 squares of 5 × 5, after the tape peeling operation, the number of squares that remained without being peeled without damaging the coating film was shown.

<Flexibility>
A cured coating film for an evaluation test is prepared in the same manner as in the adhesion test, and its flex resistance is in accordance with JIS K 5600-5-1 (1999) “Bend resistance (cylindrical mandrel method)”. went. The mandrel used was 2 mm.
The evaluation was determined according to JIS, ignoring the surface of the coating within 10 mm from the end of the test plate, visually inspecting the crack of the coating and peeling of the coating from the substrate, and making the following determination.
○: No cracking or peeling is observed ×: Cracking or peeling is observed

<Water resistance>
A cured coating film for an evaluation test was prepared in the same manner as in the adhesion test, and the water resistance was measured in accordance with JIS K 5600-6-2 (1999) “Liquid resistance (water immersion method)”. .
The test piece was immersed in warm water of 40 ± 1 ° C. for 240 hours. Thereafter, the test piece was taken out, and the state of the coating film when placed at room temperature for 24 hours was determined according to JIS K 5600-8-2 “bulging grade”.

  The coating films of Examples 1 to 4 in which the epoxy resin curing agent of the present invention was mixed with an epoxy resin and cured were incompatible with the conventional epoxy resin curing agent (Comparative Example 3) and (A) / (B) ratio. (Comparative Example 1) and high oxypropylene content (Comparative Example 3) Excellent adhesion, flex resistance, and water resistance compared to those obtained by blending and curing a curing agent in an epoxy resin. It turns out that a coating film can be obtained.

  When the epoxy resin curing agent of the present invention is used, it is excellent in flexibility, water resistance and adhesion even at a low temperature, and on the other hand, a coating film without coloring can be obtained. In particular, it can be suitably used in a wide range of industrial fields such as coating materials including electrodeposition paints, adhesives, and sealing materials.

Claims (4)

The polyoxyalkylene polyamine (A) represented by the following general formula (1) and the polyoxyalkylene polyamine (B) represented by the following general formula (2) are essential components, and the moles of (A) / (B) The ratio is 97/3 to 60/40, and the molar ratio of oxypropylene groups / oxyethylene groups in the oxyalkylene chains of the polyoxyalkylene polyamines (A) and (B) is 70/30 to 100/0. A curing agent for epoxy resin (C), which is characterized in that it exists.
[In the formulas (1) and (2), R ¹ and R ² each independently represents a linear or branched alkylene group having 1 to 3 carbon atoms. AO represents an oxyalkylene group. m, n, and k represent the average addition mole number of alkylene oxide, and are each independently a number of 1 to 70. ]   The curing agent for epoxy resins according to claim 1, wherein the total amine value is 30 to 600.   A thermosetting epoxy resin composition (E) comprising the epoxy resin curing agent (C) according to claim 1 or 2 and an epoxy resin (D). A coating film obtained by curing the thermosetting epoxy resin composition according to claim 3.