JPS6017415B2 - Manufacturing method of thermosetting resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a thermosetting resin, and more particularly, to a thermosetting resin useful as a binder for metal coating (particularly as a primer for metal materials such as iron plates, galvanized iron plates, and aluminum plates). Concerning a method for producing resin.

The method for painting the metal materials mentioned above is the so-called 2-coat, 2-bake method, in which the metal material is first subjected to a chemical conversion treatment, then a brimmer coating is applied as the first coating, and then a top coat is applied as the second coating. This method is common.

The so-called pre-coated metal coated in this way is used for many purposes such as building materials, and has a high degree of stiffness resistance.
Corrosion resistance, workability, water resistance, etc. are required. In particular, for the above primer coating, the adhesion with the base and top coat,
A primer paint that is excellent in processability, corrosion resistance, water resistance, chemical resistance, etc. must be used. Conventionally, primer paints meeting such required performance have been prepared using the structural formula: [where n is 0 or an integer from 1 to 14].

] Thermosetting type resins whose main component is a mixture of epoxy resin and amino resin or blocked isocyanate compound are often used.

However, although paints containing epoxy resins have excellent corrosion resistance and chemical resistance, they have the drawback of poor processability. On the other hand, in order to improve processability, for example, primers mainly composed of (1) high molecular weight epoxy resin, or (2) polyhydroxy polyether polyester made by increasing the molecular weight of relatively low molecular weight epoxy resin with dicarboxylic acid are used. paint is suggested.

However, although the high molecular weight epoxy resin (2) has excellent corrosion resistance and processability, it has poor solubility in solvents and compatibility with other paint raw materials. In addition, the polyhydroxypolyether polyester (2) is usually put into practical use in a mixed system with an amino resin or a blocked isocyanate compound, but especially when combined with a blocked isocyanate compound, the compatibility is insufficient. Therefore, it has the drawback of being unable to exhibit sufficient performance due to formulation restrictions.

Furthermore, in the above-mentioned polymerization, a reaction is carried out until the desired molecular weight is reached, but in this case, in addition to the addition reaction between glycidyl groups and carboxyl groups, hydroxyl groups contained in the epoxy resin or between glycidyl groups and carboxyl groups are added. Due to side reactions such as dehydration condensation reaction between the hydroxyl group generated by the addition reaction and the carboxyl group, highly branched polyhydroxy polyether polyester is generated, resulting in a resin that provides the desired processability. may not be obtained or may even gel during the reaction. Although these phenomena can be avoided by lowering the reaction temperature, the reaction time becomes longer and this method is impractical. By using catalysts such as tertiary amines, potassium hydroxide, sodium hydroxide, and quaternary ammonium salts, it is possible to increase the molecular weight at low temperatures and in a short time, but these catalysts remain in the resulting resin. , which has a negative effect on water resistance and chemical resistance. On the other hand, the structural formula, [wherein n has the same meaning as above.

] When starting from an epoxy resin represented by the above, the hydroxyl groups contained in the epoxy resin and the hydroxyl groups produced by the addition reaction of glycidyl groups and carboxyl groups are tertiary hydroxyl groups, so this is different from the above case. ,
A dehydration condensation reaction between hydroxyl groups and carboxyl groups is unlikely to occur, and polyhydroxypolyether polyester can be produced relatively stably.

However, since the hydroxyl groups contained in such polyhydroxyl polyether polyesters are tertiary hydroxyl groups, their reactivity with amino resins and blocked isocyanate compounds is extremely poor, making it difficult to obtain a sufficiently crosslinked coating film. competition at higher temperatures is required. The object of the present invention is to provide a heat-resistant resin which is useful as a binder for primer paints and satisfies the above-mentioned performance requirements. hardening resin,
It is an object of the present invention to provide a method that can be efficiently manufactured without causing the above-mentioned problems.

As a result of intensive research in order to achieve this objective, the present inventors made the above epoxy resin react with a dicarboxylic acid by reacting a specific epoxy resin, a dicarboxylic acid, and a secondary amine having a primary hydroxyl group. The desired thermosetting resin can be obtained by chain-extending the chain and adding the secondary amine to the end of the polymer, and then adding a partially protected polyisocyanate compound to the resulting product. , and the secondary amine exhibits a catalytic action and serves as a source for introducing primary hydroxyl groups into the polymer,
The present invention was completed based on the discovery that it is possible to react at low temperatures and in a short time and to improve the curability of polymers. That is, the gist of the present invention is the structural formula:
H3) 2,1CH2-, 1○1 or 1S1, and n
is 0 or an integer from 1 to 14.

], an epoxy resin component (a,) consisting of 50 to 10% by weight of an epoxy resin and 50 to 0% by weight of another epoxy resin, a dicarboxylic acid (a2), and at least 1
A product [A] obtained by reacting a secondary amine (a3) having primary hydroxyalkyl groups, a polyisocyanate compound (b,), and an isocyanate protecting group (Q). Number of isocyanate groups in (q)/(b2)
The number of primary hydroxyl groups contained in the product [A]/product [B] obtained by reacting so that the ratio of the number of active hydrogen groups is 5/1 to 5/4. The ratio of the number of free isocyanate groups contained in substance [B] is 10/1 to 1/
The present invention relates to a method for producing a thermosetting resin, which is characterized by reacting the resin in such a manner that the reaction becomes 1.

In the present invention, as the epoxy resin component (a,), an epoxy resin represented by the above structural formula may be used.
7'', ``YD-014'', ``YD-011'', ``YD-128'', Dainippon Ink & Chemicals Co., Ltd. under the trade name ``Epiclone 40501'', and these may be used alone or together. It is composed of a system in which 5% by weight or less of 5% by weight is substituted with other epoxy resin (for example, polyalkylene glycol diglycidyl ether, etc.).When the above substitution rate exceeds 5% by weight, the shaft resistance and water resistance deteriorate. , adhesiveness, chemical resistance, hardenability, etc. tend to decrease.In the present invention, the dicarboxylic acid (a2) is, for example, polymethylene dicarboxylic acid (adipic acid, azelaic acid, sebacic acid, etc.), aromatic acid, etc. Examples include dicarboxylic acids (phthalic anhydride, phthalic acid, isophthalic acid, terephthalic acid, etc.), dimer acids, polybutadiene dicarboxylic acids, polyester dicarboxylic acids, etc., and one or more of these can be used.

In particular, polymethylene dicarboxylic acid is preferred from the viewpoint of processability, solubility, and compatibility, and azelaic acid is most preferred. Further, trivalent carboxylic acids may be used in combination with the a2 component. In the present invention, the secondary amine (a
3) has the role of a catalyst that allows the reaction between component a and component a2, that is, the addition reaction of glycidyl groups and carboxyl groups, to proceed at low temperature and quickly. This is important in that it introduces a primary hydroxyl group to facilitate the crosslinking reaction during coating formation.

Further, since the nitrogen introduced into the resin skeleton effectively acts as a catalyst, the curing reaction is accelerated. Such second
Examples of the class amines include dialkanolamines (diethanolamine, dipropanolamine, dibutanolamine, etc.), alkylalkanolamines (ethylethylamine, etc.), and one or more of these may be used. .

Particularly preferred are dialkanolamines, among which jetanolamine is most suitable. The product according to the present invention [
A] is obtained by reacting the epoxy resin component (a,), dicarboxylic acid (a2), and secondary amiso (a3).

In this case, the reaction ratio of each component is usually [multi-equivalent of glycidyl group in (a,) - equivalent weight of carboxyl group in (a2)]/[total weight of (a.) ten (a2) ten (a3) (of〕
The value of is less than 7×10-42 equivalents/good, preferably 4×1
0-4 to 0.3 x 10-4 ta equivalent/unit, and [(a)
The ratio of TA equivalent of the carboxyl group in 10 (TA equivalent of the amino group in (a3))/[TA equivalent of the glycidyl group in (a,)] is 4/
It may be set within a range of 5 to 6/5, preferably 9/10 to 23/20.

When the above value exceeds 7×10-4 taeq/unit, sufficient processability tends to be insufficient. If the above ratio is less than 4/5, sufficient thermosetting properties cannot be obtained, and if it exceeds 6/5,
Unreacted dicarboxylic acids or secondary amines tend to remain and impair the water resistance and chemical resistance of the coating film. Total 2
, ~A3 components, first, after melting component a or dissolving it in a suitable non-reactive solvent, add components a2 and a3 to this, and if necessary, usually 80 to 200 q under N2 gas.
The reaction may be carried out for 1 to 1 hour at 0.

In this case, the secondary amine of the a3 component acts as an esterification catalyst for the reaction of the a, component and the a2 component.
It is preferable to carry out the reaction in the coexistence of the components. The product [B] in the present invention is a polyisocyanate compound (q) and an isocyanate protecting agent (b2) in which the ratio of the number of isocyanate groups in (q)/the number of active hydrogen groups in (b2) is 5/ 1
It can be obtained by reacting at a ratio of ~5/4.

This reaction is usually carried out without a solvent or in a non-reactive solvent at a temperature of room temperature to 150 qO, but after dissolving the q component in a non-reactive solvent and heating it to 50-100 qO, the b2 component or its appropriate non-reactive solvent is dissolved. It is preferable to react while dropping a solution with a reactive solvent from the viewpoint of quality of product [B] and reaction control. Examples of the above-mentioned polyisocyanate compound (q) include aliphatic or alicyclic diisocyanate compounds (hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, etc.), aromatic diisocyanate compounds (tri- Renzisocyanate, diphenylmethane-4,
(4'-diisocyanate, etc.), triisocyanate compounds, etc., and one or more of these may be used.

In particular, aliphatic or aliphatic diisocyanate compounds are preferred from the viewpoint of solubility, compatibility and processability of the thermosetting resin. The above isocyanate protecting agent (Q) comprises b,
The adduct formed by addition to the isocyanate group of the component must be stable at room temperature and dissociate when heated to 140 to 250 CO to regenerate the free isocyanate group. Such protective agents include, for example, lactam-based protective agents (gocaptractam, y
-butyrolactam, etc.), oxime protectants (methyl ethyl ketoxime, cyclohexanone oxime, etc.),
Examples include alcohol-based protective agents (methanol, ethanol, isobutyl alcohol, etc.), phenol-based protective agents (phenol, paratertiary butylphenol, cresol, etc.). The system of products [B] obtained by the reaction of the above-mentioned q component and a wide range of components usually includes a complete block in which all of the isocyanate groups are protected, and a part in which the isocyanate groups are partially protected and the remaining isocyanate groups are not protected. Blocked forms and unblocked forms in which all isocyanate groups remain unprotected coexist.

In this product [B], all the blocks function as a crosslinking agent when forming a thermosetting resin into a coating film. Among the partially blocked products, those having one free isocyanate group and one or more blocked isocyanate groups are called products [A].
and has a role as a crosslinking functional group during coating film formation, and those having two or more free isocyanate groups and one or more blocked isocyanate groups can extend the chain of the product [A]. It has the role of increasing the molecular weight and adding crosslinkable functional groups. The hexagonal block is chain-extended with the product [A] to increase its molecular weight and introduce a urethane bond into the primary mirror. In the method for producing a thermosetting resin according to the present invention, the desired thermosetting resin is obtained by reacting the product [A] with the product [B].

In this case, the reaction ratio is 10/1 to 1/1, preferably the number of primary hydroxyl groups contained in the product [A]/the number of free isocyanate groups contained in the product [B]. Set to be in the range of 5/1 to 5/4.

The above reaction is usually carried out under 50 to 150 qo of N2 gas if necessary.
The reaction is carried out at a temperature of 100 ml until substantially no isocyanate groups are present. Further, in some cases, even if isocyanate groups remain, the reaction may be stopped by adding, for example, a monohydric alcohol when the molecular weight reaches a desired value. According to the method of the present invention having the above configuration, thermosetting resins useful as binders for metal coatings, especially primer coatings, can be efficiently produced at low temperatures and in a short time without gelation during the reaction. can be manufactured.

These thermosetting resins contain primary hydroxyl groups with excellent reactivity in their molecules, and are suitable for use in primers with the conventionally required excellent adhesion, processability, corrosion resistance, water resistance, and chemical resistance. Contributes to the provision of paint. When the thermosetting resin is made into a paint, it may be used alone as a thermosetting clear paint, or it is usually mixed with pigments, other fillers, additives (flow regulators, plasticizers, etc.), etc. Mix as appropriate and use. Furthermore, hardness, chemical resistance,
In order to further improve coating film performance such as water resistance, ordinary hardening agents (
block isocyanate compounds, amino resins, etc.) may be used in combination. Next, the present invention will be specifically explained by giving Examples, Comparative Examples, Reference Examples, and Test Examples. Example 1 Epoxy resin (product name: “Epoto YD-” manufactured by Toto Kasei Co., Ltd.
017'', epoxy equivalent 1960) was dissolved in 78.4 parts of xylol and 196 parts of celloacetate, 25.1 parts of azelaic acid and 13.3 parts of diethanolamine were added, and the mixture was heated under N2 gas. 14
The reaction was carried out for 4 and a half hours at 0 qo, and the acid value of the resin solid content was 1. When it reached the OH barrier, 314 parts of oxygen and 245 parts of methyl ethyl ketone were added, and it was cooled to give the product [
A-1] is obtained.

Separately, 224 parts of hexamethylene diisocyanate and 151 parts of caprolactam were added to 375 parts of celloacetate, and the mixture was reacted at 100°C for 3 hours.
62 ta equivalent of product [B-1] is obtained.

Next, 165.5 parts of product [A-1] was added to product [B-1].
] 7.5 parts and 26.3 parts of xylol were added and reacted for 3 hours at 100 qo under N2 gas. No absorption of isocyanate was observed in infrared absorption analysis, so 19.4 parts of methyl ethyl ketone was added and the mixture was cooled. Obtain a thermosetting resin solution. Example 2 392 parts of "Epotote YD-017" was added to 24 parts of xylol
After dissolving in 7 parts and 124 parts of celloacetate, 13.5 parts of sebacic acid and 6.7 parts of jetanolamine were added,
Reaction was carried out for 8 hours at 140 OO under N2 gas, and the acid value of the resin solid content was 2. When the shoes become OH female, they are cooled to obtain product [A-2].

Next, product [A-2] 29$ gourd Product of Example 1 [
B-1] 14 parts were added and reacted at 100° C. for 4 hours under N2 gas, and the isocyanate group disappeared, so 95 parts of methyl isobutyl ketone was added to obtain a thermosetting resin solution.

Example 3 Eboxy resin (trade name “Epoto YD-” manufactured by Toto Kasei Co., Ltd.)
After dissolving 475 parts of epoxy equivalent 950) in 95 parts of xylene and 119 parts of celloacetate, 39.2 parts of azelaic acid and 8.3 parts of jetanolamine were added, and the mixture was reacted at 145 qo for 6 hours to form a solid resin. When the acid value of 1.1 KOH reaches 9/2, xylol 2
0 parts and 130 parts of methyl ethyl ketone were added and cooled to obtain product [A-3].

Separately, Isoho.

After dissolving 22 parts of celloacetate and heating to 80%, 11 parts of caprolactam was dissolved.
A solution of 3 parts of celloacetate and 113 parts of celloacetate was added dropwise over 1 hour to react. After the completion of dripping, continue for 3 hours at 8
The reaction was completed while keeping the temperature at 0.05 m, to obtain a product [B-2] having an isocyanate equivalent of 670 m. Next, 33.5 parts of product [B-2] and 71 parts of celloacetate were added to 5 parts of product [A-3] and reacted at 100°C for 3 hours. of the mixture and cooled to obtain a thermosetting resin solution.

Example 4 After dissolving 476 parts of epoxy resin (trade name "Epotote YD-011" manufactured by Toto Kasei Co., Ltd., epoxy equivalent weight 476) in xylol 112 and 141 parts of celloacetate, 86 parts of azelaic acid and 8.3 parts of jetanolamine were dissolved. of the solid resin was added and reacted at 140°C for 5 hours until the acid value of the solid resin was 1. When the dish has finished heating, it is cooled and 23 parts of xylene and 214 parts of cyclohexanone are added to obtain product [A-4].

Next, 1 $ part of the product [B-1] of Example 1 was added to 24 $ parts of product [A-4] and reacted at 100°C for 4 hours, and then 4 $ parts of isobutanol was added to heat cure the product. Obtain a synthetic resin solution.

Example 5 Epoxy resin (manufactured by Toto Kasei Co., Ltd., trade name rEpototo YD-
After dissolving 245 parts of 128 hepoxy equivalent (1 total) in 8 parts of xylene and 95 parts of celloacetate, 117 parts of azelaic acid and 6 parts of jetanolamine were added, and 145 parts of
000 for 6 hours and the resin solid content reached 2.1 KO.
Once cooled, 145 parts of xylene and 146 parts of methyl ethyl ketone were added to form the product [A].
-5] is obtained.

Next, 168 parts of product [A-5] and the product of Example 3 [
B-2〕8. When the two parts were mixed and reacted at 100 qo for 5 hours, the isocyanate group disappeared, so butyl acetate 17
．． 5 parts to obtain a thermosetting resin solution.

Example 6 After dissolving 295 parts of "Epototo YD-014" with 88 parts of xylene and 10 parts of celloacetate,
75 parts of dimer acid (carpoxyl equivalent: 289) and 5.2 parts of jetanolamine were added and reacted at 140°C for 8 hours, so that the acid value of the resin solid content was 2.5 parts. When the song OH Menota' is finished, it is cooled and 295 parts of carpitol acetate is added to obtain the product [A-6].

Next, 857 parts of product [A-6] and the product of Example 3 [
B-2] 3 parts were mixed and reacted at 100°C for 5 hours, and the isocyanate group disappeared, so 8 parts of inpropyl alcohol was added to obtain a thermosetting resin solution.

Example 7 Methyl glycidyl ether type epoxy resin (trade name: “Epicron 4050 H” manufactured by Dainippon Ink Chemical Industries, Ltd.)
After dissolving 48 parts of epoxy equivalent (950) in 96 parts of xylol and 120 parts of celloacetate, 3$ of azelaic acid
and 8.3 parts of jetanolamine, and
The mixture was reacted for 9 hours at 1000 yen, and when the acid value of the solid resin reached 2.1 KOH, the mixture was cooled to obtain product [A-7].

Next, 645 parts of product [A-7] and the product of Example 3 [
B-2] Mix 33 parts and 71 parts of celloacetate,
After reacting at qo for 3 hours, 76 parts of inpropyl alcohol was added and cooled to obtain a thermosetting resin solution.

Comparative example 1 "Etoport YD-017" 49 anchors and xylol 98
After dissolving the mixture in 1 part and 123 parts of celloacetate, 16 parts of azelaic acid was added and an attempt was made to react at 140 qC, but the reaction rate after 1 hour was about 20% and the reaction was discontinued.

Comparative Example 2 After dissolving 475 parts of "Etoport YD-014" in 214 parts of carbitol acetate, 39.9 parts of azelaic acid was dissolved. The mixture was tried to react at 180 oo, but gelation occurred after 4 hours.

Comparative Example 3 475 parts of "Etoport YD-014" was mixed with 95 parts of xylol
After melting 11 parts of celloacetate and 11 parts of celloacetate, 39.2 parts of azelaic acid and 2.5 parts of penzyldimethylamine were added and reacted at 14,000 for 2 hours. Then, 8.3 parts of jetanolamine was added, and after further reaction for 2 hours, the mixture was cooled, and 20 parts of xylene and 13 parts of methyl ethyl ketone were added to obtain product [A-8].

Next, 645 parts of product [A-8] and the product of Example 3 [
B-2] 33.5 parts and 71 parts of celloacetate were mixed, and 1
After reacting for 3 hours at 0.00°C, 76 parts of inpropyl alcohol was added, and the mixture was cooled to obtain a thermosetting resin solution.
Reference Example 1 250 parts of the thermosetting resin solution of Example 1 is sufficiently mixed with 3 parts of rutile titanium oxide and 25 parts of strontium chromate using 3 rolls to prepare a paint for a primer.

Reference Example 2 1 part of isophorone diisocyanate blocked with caprolactam is added to 300 parts of the primer paint of Reference Example 1 to prepare a primer paint.

Reference Example 3 5 parts of caprolactam-blocked hexamethylene diisocyanate and 5 parts of methoxymethylated melamine are added to 310 parts of the primer paint of Reference Example 1 to prepare a primer paint.

Reference Examples 4 to 10 After thoroughly kneading 25 parts of each of the thermosetting resin solutions of Reference Examples 1 to 7, 3 parts of rutile titanium oxide and 25 parts of strontzyme chromate using three rolls, Add methoxymethylated melamine 1 to prepare paints for various primers.

Reference Example 11 (Comparative Paint) Thermosetting resin 25 of Comparative Example 3, 3 parts of rutile-type titanium oxide and 25 parts of strontium chromate were
Thoroughly knead using this roll.

5 parts of hexamethylene diisocyanate blocked with caprolactam and 5 parts of methoxymethylated melamine are added to the obtained kneaded product 31 to prepare a primer coating. Test Example 1 The various primer paints prepared in Reference Examples 1 to 11 were formed into films under the following conditions, and performance tests were conducted.

The results are shown in Table 1. ■ Material: Zinc phosphate treated galvanized iron plate ■ Primer coating conditions: 210qo x 49 sand ■ Primer film thickness: 8mm ■ Topcoat baking conditions: 210qo x 6 night sand ■ Topcoat film thickness: 15mm A commercially available coil coating paint was used.

Table 1 Note) In the table, ◎ is very excellent・ ○ is excellent・ △ is normal, and × is inferior.

Example 8 105.2 parts of "Etoport YD-014" was mixed with 46.2 parts of xylol. After dissolving in 58.7 parts of Celloacetate and celloacetate, epoxy resin which is diglycidyl ether of polypropylene glycol (trade name "Denacol EX" manufactured by Nagase Kasei Co., Ltd.) was added.
-920'', epoxy equivalent 180) 105.2 parts, azelaic acid 39.2 parts and jetanolamine 8.3
103.1 parts of xylene and 64.1 parts of methyl ethyl ketone were added and reacted for 7 hours at 14,520° C. When the acid value of the resin solid content was 9/1 of 1.1 KOH, 103.1 parts of xylene and 64.1 parts of methyl ethyl ketone were added and cooled to produce a Obtain item [A-9].

The proportions of the epoxy resin of the above-mentioned one-year formula and the other epoxy resins are 6% by weight of the former and 4% by weight of the latter. Next, 33.5 parts of the product [B-2] of Example 3 and 71 parts of celloacetate were added to 645 parts of the product [A-9], and the mixture was reacted at 100 qo for 3 hours. is added and cooled to obtain a thermosetting resin solution.

Comparative Example 4 92.7 parts of Epoto YD-128J was mixed with 8 parts of xylol.
After dissolving in 7.8 parts and 93.7 parts of celloacetate, epoxy resin which is diglycidyl ether of neobentyl alcohol (trade name "Denacol EX21" manufactured by Nagase Kasei Co., Ltd.) was dissolved.
1'', 113.4 parts of epoxy equivalent (140 parts), 117 parts of azelaic acid and 6 parts of jetanolamine were added,
Reacted at 40℃ for 6 hours, and the acid value of the resin solid content was 2.1KO.
Cool at the end of the H side/xylol 143.
Ikaribe and 144.0 parts of methyl ethyl ketone are added to obtain product [A-10].

The proportions of the epoxy resin of the above general formula and other epoxy resins are 45% by weight of the former and 55% by weight of the latter. Next, product [A-10] 1 Isobe and product [B-2] 8. When the two parts were mixed and reacted at 100°C for 5 hours, the isocyanate group disappeared, so 19.1 parts of butyl acetate was added to obtain a thermosetting resin solution.

Reference Example 12 Using 250 parts of the thermosetting resin solution of Example 8, a paint for a primer is prepared in the same manner as in Reference Examples 4 to 10.

Reference Example 13 (Comparative Paint) Using 250 parts of the thermosetting resin solution of Comparative Example 4, a paint for a primer is prepared in the same manner as in Reference Examples 4 to 10.

Test Example 2 The various primer paints prepared in Reference Examples 12 and 13 were coated in the same manner as in Test Example 1, and performance tests were conducted.

The results are shown in Table 2. Table 2

Claims (1)

[Claims] 1 Structural formula, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, -R is -H or -CH_3, -A- is ▲ Numerical formulas, chemical formulas, tables, etc. ▼ -CH_2- , -O- or -S-, and n are 0 or an integer of 1-14. ] An epoxy resin component (a_1) consisting of 50 to 100% by weight of an epoxy resin represented by the formula and 50 to 0% by weight of another epoxy resin, a dicarboxylic acid (a_2), and a second component having at least one primary hydroxyalkyl group. The product [A] obtained by reacting the class amine (a_3), the polyisocyanate compound (b_1), and the isocyanate protecting agent (b_2) in the ratio of the number of isocyanate groups in (b_1)/(b_2) The ratio of the number of active hydrogen groups is 5/1 to 5
/4 The number of primary hydroxyl groups contained in the product [A]/The number of free isocyanate groups contained in the product [B] A method for producing a thermosetting resin, characterized in that the reaction is carried out so that the ratio of 2 Epoxy resin component (a_1) and dicarboxylic acid (a_
2) and the secondary amine (a_3) are simultaneously reacted. 3 Epoxy resin component (a_1) and dicarboxylic acid (a_
In the reaction ratio between 2) and the secondary amine (a_3),
[g equivalent of glycidyl group in (a_1) - g equivalent of carboxyl group in (a_2)]/[(a_1)+(a_2)
+ (a_3) total weight (g)] is 7 x 10^-^4g
equivalent/g or less, and [g equivalent of carboxyl group of (a_2) + g equivalent of amino group of (a_3)]/[(a_1
The method according to item 1 or 2 above, wherein the ratio of g equivalent of glycidyl group in ) is set to 4/5 to 6/5. 4. The method according to any one of the above items 1 to 3, wherein the dicarboxylic acid (a_2) is polymethylene dicarboxylic acid. 5. The method according to any one of the above items 1 to 3, wherein the dicarboxylic acid (a_2) is azelaic acid. 6. The method according to any one of the above items 1 to 5, wherein the secondary amine (a_3) is diethanolamine. 7. The method according to any one of the above items 1 to 6, wherein the polyisocyanate compound (b_1) is isophorone diisocyanate. 8. The method according to any one of items 1 to 6 above, wherein the polyisocyanate compound (b_1) is hexamethylene diisocyanate. 9. The method according to any one of the above items 1 to 8, wherein the isocyanate protecting agent (b_2) is ε-caprolactam.