Method for producing epoxy resin

Abstract

To provide a method for producing an epoxy resin which can be stably emulsified while having a high molecular weight, and to provide a method for producing a cationic epoxy resin.SOLUTION: A method for producing an epoxy resin, comprising a preparation step of preparing a composition containing an epoxy resin having two glycidyl groups represented by the formula (1) and / or a polymer thereof, a temperature increase step of increasing the temperature of the composition from 110 °C to 145 °C in 65 minutes or less, and a polymerization step of polymerizing the composition in a temperature range of 145 °C or more and 180 °C or less. Wherein A is selected from a benzene ring, a naphthalene ring, an anthracene ring and formula (α).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing an epoxy resin, a method for producing a cationic epoxy resin, and a method for producing an emulsion. [Background technology]

[0002] Epoxy resins have traditionally been used as materials for adhesives, molding materials, paints, electronic components, and the like, because the cured products have excellent heat resistance. For example, Patent Document 1 discloses the use of an amine-modified epoxy resin having an amino group as the epoxy resin contained in a cationic electrodeposition coating composition. Patent Document 2 also discloses a manufacturing method for obtaining a high-molecular-weight epoxy resin. A common method for utilizing such epoxy resins is to obtain a coating by solvent coating or the like.

[0003] However, in recent years, the use of solvents has been avoided due to their impact on the environment and human body, and methods have been used in which resins are emulsified in water and used as emulsions to form coatings. For example, Patent Document 3 describes a method for blending paints in which epoxy resins are blended as emulsions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-2002 [Patent Document 2] Patent No. 3657720 [Patent Document 3] Patent Publication No. 2021-161306 Summary of the Invention [Problem to be solved by the invention]

[0005] Although high-molecular-weight epoxy resins have excellent heat resistance and insulating properties, they are difficult to emulsify stably, and therefore their use as emulsions is limited. Therefore, an object of the present invention is to provide a method for producing an epoxy resin that can be stably emulsified despite its high molecular weight, and a method for producing a cationic epoxy resin. Another object of the present invention is to provide a method for producing an emulsion using the cationic epoxy resin. [Means for solving the problem]

[0006] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by strictly specifying the temperature conditions in the polymerization of a resin containing an epoxy resin and controlling the reaction, and have arrived at the present invention. That is, the present invention includes the following. [1] A method for producing an epoxy resin, comprising: a preparation step of preparing a composition containing an epoxy resin having two glycidyl groups represented by formula (1) and / or a polymer thereof; a temperature-raising step of raising the temperature of the composition from 110°C to 145°C in 65 minutes or less; and a polymerization step of polymerizing the composition at a temperature in the range of 145°C to 180°C. [ka] [In formula (1), A is selected from a benzene ring, a naphthalene ring, an anthracene ring, and formula (α), and in formula (α), R 3 and R 4 are each independently selected from a single bond, an alkylene group, a phenylene group, and a cyclohexylene group; X 1 and Y 1 are each independently selected from a hydrogen atom and an alkyl group. 3 and R 4 is bonded to the carbon in formula (1). [2] The method for producing an epoxy resin according to [1], wherein the composition contains a dicarboxylic acid in which two carboxyl groups are bonded via at least one carbon atom. [3] The method for producing an epoxy resin according to [1] or [2], wherein the composition contains an epoxy resin represented by formula (2) or a polymer thereof. [ka] [In formula (2), R 1 represents an alkylene group having 3 to 10 carbon atoms which may have a substituent, a cyclohexylene group which may have a substituent, a phenylene group which may have a substituent, or -R a -R b -R c - and R a and R c is a cyclohexylene group or a phenylene group, and R b represents a methylene group which may have one or two substituents, and m and n are each independently an integer of 1 to 20. [4] A method for producing a cationic epoxy resin, comprising a step of reacting an epoxy resin produced by any one of [1] to [3] with an amine compound containing at least one active hydrogen capable of reacting with a glycidyl group at a temperature of 70°C or higher and 120°C or lower. [5] The method for producing a cationic epoxy resin according to [4], wherein the obtained cationic epoxy resin has a weight average molecular weight of 10,000 or more, an amine value of 30 mgKOH / g or less, and a viscosity of 15 to 45 Pa s at 40°C when the heating residue is 70%. [6] A method for producing an emulsion, comprising a step of emulsifying a cationic epoxy resin produced by the production method according to [4] or [5] using at least one organic acid selected from acetic acid, formic acid, lactic acid, and methanesulfonic acid. [Effects of the Invention]

[0007] The present invention provides a method for producing an epoxy resin that can be stably emulsified despite having a high molecular weight, a method for producing a cationic epoxy resin, and a method for producing an emulsion using the cationic epoxy resin. DETAILED DESCRIPTION OF THE INVENTION

[0008] Specific embodiments will be shown below to evaluate the present invention in detail. <Epoxy resin manufacturing method> The method for producing the epoxy resin (hereinafter sometimes simply referred to as "resin") according to this embodiment includes the steps of: preparing a raw material, a composition containing an epoxy resin having two glycidyl groups represented by formula (1) and / or a polymer thereof; a temperature-raising step of raising the temperature of the composition from 110°C to 145°C in 65 minutes or less; and a polymerization step of polymerizing the composition at a temperature in the range of 145°C to 180°C. [ka] In formula (1), A is selected from a benzene ring, a naphthalene ring, an anthracene ring, and formula (α), and in formula (α), R 3 and R 4 are each independently selected from a single bond, an alkylene group, a phenylene group, and a cyclohexylene group; X 1 and Y 1 are each independently selected from a hydrogen atom and an alkyl group. 3 and R 4 is bonded to the carbon in formula (1).

[0009] <Preparation process> In the preparation step, a composition containing an epoxy resin represented by the above formula (1) or a polymer thereof is prepared. The epoxy resin represented by the above formula (1) has two glycidyl groups per molecule. Its epoxy equivalent is not particularly limited, but is generally in the range of 170 to 500, preferably 170 to 400. In formula (α), R 3 and R 4 an alkylene group, X 1 and Y 1 The alkyl group is not particularly limited as long as it is linear or branched, but is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

[0010] The epoxy resin (1) can be obtained, for example, by reacting a polyol compound, an alkylene glycol having two or more carbon atoms in which two hydroxyl groups; one hydroxyl group and one hydroxyalkyl group, phenol group, or cyclohexanol group; one hydroxyalkyl group and one phenol group or cyclohexanol group; one phenol group and one cyclohexanol group; or two hydroxyalkyl groups (which may be the same or different) are bonded to the same carbon atom, a dihydric phenol, a bisphenol compound, or a dihydroxynaphthalene compound with an epihalohydrin (e.g., epichlorohydrin). Examples of the alkylene glycol include alkylene glycols in which two hydroxyl groups are bonded to the same carbon atom, such as 1,1-dihydroxyethane, 1,1-dihydroxypropane, and 2,2-dihydroxypropane; alkylene glycols in which one hydroxyl group and one hydroxyalkyl group are bonded to the same carbon atom, such as 2-hydroxypropanol and 2-hydroxybutanol; 2,2-(dihydroxymethyl)ethane, 2,2-(dihydroxyethyl)propane, 2,2-dimethyl-1,3-propanediol, and 2,2-dimethyl-1,3-propanediol. Alkylene glycols in which one or two hydroxyalkyl groups are bonded to the same carbon atom, such as 4-(1-hydroxyethyl)phenol, 3-(1-hydroxyethyl)phenol, and 4-(1-hydroxypropyl)phenol; alkylene glycols in which one hydroxyl group and one phenol group are bonded to the same carbon atom, such as 4-(1-hydroxyethyl)cyclohexanol and 2-(1-hydroxyethyl)cyclohexanol; 4-hydroxyphenyl-2-propanol, 4-hydroxyphenyl-2-propanol, and 4-hydroxyphenyl-2-propanol. alkylene glycols in which one hydroxyalkyl group and one phenol group are bonded to the same carbon atom, such as 2-(4-hydroxycyclohexyl)-1-propanol and 2,2-dimethyl-2-(4-hydroxycyclohexyl)-1-ethanol; alkylene glycols in which one hydroxyalkyl group and one cyclohexanol group are bonded to the same carbon atom, such as 2-(4-hydroxyphenyl)-2-(4-hydroxycyclohexyl)propane and 1-(4-hydroxyphenyl)-1-(4-hydroxycyclohexyl)propane; and the like. Examples of the dihydric phenol include catechol, resorcinol, and hydroquinone. Examples of the bisphenol compound include bisphenol A, bisphenol F, bisphenol E, bisphenol B, bisphenol S, bisphenol AP, and bisphenol BP. Examples of the dihydroxynaphthalene compound include 2,3-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 1,2-dihydroxynaphthalene, and 1,4-dihydroxynaphthalene.

[0011] The starting composition may include a dicarboxylic acid in which two carboxyl groups are linked through at least one carbon atom. The dicarboxylic acid is not particularly limited as long as it has two carboxyl groups in one molecule, and may contain a branched chain, a double bond, or a cyclic structure in its structure. Examples include succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dimer acids obtained by dimerizing vegetable oils and fats. Among these, dimer acids are preferred.

[0012] The raw material composition may contain an epoxy resin represented by formula (2) and / or a polymer thereof. [ka]

[0013] In equation (2), R 1 represents an alkylene group having 3 to 10 carbon atoms which may have a substituent, a cyclohexylene group which may have a substituent, a phenylene group which may have a substituent, or -R a -R b -R c -R a and R c is a cyclohexylene group or a phenylene group. b is a methylene group which may have 1 or 2 substituents, and m and n are each independently an integer of 1 to 20.

[0014] Here, examples of the substituent in the alkylene group, cyclohexylene group, phenylene group, and methylene group having 3 to 10 carbon atoms, which may have a substituent, include an alkyl group, a phenyl group, etc. Furthermore, these substituents may be substituted with another functional group (e.g., an alkyl group, a phenyl group, etc.). The alkyl group may be linear, branched, or cyclic. In addition, in this specification, "substituent" means the above-mentioned alkyl group, phenyl group, etc., unless otherwise specified.

[0015] R in the above formula (2) 1 may be, for example, a biscyclohexylene group represented by the following formula (3), a bisphenylene group represented by the following formula (4), or a phenylene group represented by the following formula (5). [ka]

[0016] In formula (3), X 2 and Y 2 are each independently a hydrogen atom, an alkyl group, or a phenyl group. 3 and Y 3 are each independently a hydrogen atom, an alkyl group, or a phenyl group. 4 and Y 4 are each independently a hydrogen atom, an alkyl group, a phenyl group, an alkoxyl group, or a hydroxyl group. X 2 , Y 2 , X 3 , Y 3 , X 4 and Y 4 The alkyl group as X is not particularly limited as long as it is linear or branched, but is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. 4 and Y 4 The alkoxyl group as the alkyl group is not particularly limited as long as it is linear or branched, but is preferably an alkoxyl group having 1 to 6 carbon atoms, more preferably an alkoxyl group having 1 to 3 carbon atoms.

[0017] As mentioned above, m and n in the above formula (2) may be any integer from 1 to 20, but are preferably any integer from 1 to 5, more preferably both m and n are any integer from 1 to 3, and particularly preferably both m and n are 1.

[0018] The raw material composition may contain other compounds as described above within the range that does not impair the effects of the present invention. Examples of other compounds include bisphenol compounds and dicarboxylic acid compounds other than those represented by formulas (1) and (2).

[0019] The other compounds, bisphenol compounds, are not particularly limited as long as they have two phenolic OH groups in one molecule, and examples thereof include bisphenol A, bisphenol B, bisphenol C, bisphenol D, bisphenol E, bisphenol F, bisphenol G, bisphenol H, bisphenol I ... Examples include phenol F, bisphenol E, bisphenol B, bisphenol S, bisphenol AP, bisphenol BP, etc. Among these, bisphenol A and bisphenol F are preferred.

[0020] <Heating process> In this specification, the heating process is defined as a process in which a composition (raw material) at any temperature below 110°C is charged into a manufacturing vessel, and the composition is then heated by any method, with the starting point being the point at which the temperature inside the manufacturing vessel first reaches 110°C, and the ending point being the point at which the temperature inside the manufacturing vessel first reaches 145°C. In this embodiment, the time required from the start to the end of the temperature-raising step is 65 minutes or less, more preferably 35 minutes or less, and even more preferably 15 minutes or less. By carrying out the temperature increasing step within the above-mentioned time, an epoxy resin that has a high molecular weight and can be stably emulsified can be polymerized.

[0021] <Polymerization process> In this specification, the polymerization process refers to a process that starts at the end of the temperature-raising process and ends when the epoxy equivalent is measured at any time and confirmed to be ≥ 2150 g / eq. Furthermore, "polymerization" refers to this process, and "polymerization temperature" refers to the temperature controlled in this process. After reaching the end point, the polymerization process is stopped by rapidly cooling the mixture to 115°C or below. The epoxy equivalent indicates the weight of resin per epoxy group and can be measured using a method in accordance with JIS-K7236:2001.

[0022] The temperature inside the production vessel during the polymerization step is preferably maintained at 145° C. or higher and 180° C. or lower. More preferably, the temperature inside the production vessel during the polymerization step is 145° C. or higher and 165° C. or lower. Epoxy resin can be produced by carrying out the polymerization reaction at the above temperature. The polymerization time is not particularly limited, but is usually within the range of 10 minutes to 24 hours. The completion of the polymerization reaction is determined by the epoxy equivalent value as described above. It is desirable to install a thermometer on the side or bottom of the manufacturing vessel and use equipment that can constantly measure the temperature inside the manufacturing vessel. There are no regulations regarding the measurement method of the thermometer, but a thermocouple type is usually suitable.

[0023] In the polymerization step, a polymerization catalyst may be appropriately added. In this case, the type of polymerization catalyst is not particularly limited, but it is desirable to add a nitrogen-containing compound having a dissociation constant in water with a pKa value of 9 to 11 as the polymerization catalyst and carry out the polymerization reaction. Examples of polymerization catalysts that can be added during the polymerization step include ammonia, methylamine, diethylamine, triethylamine, dimethylbenzylamine, etc. These reaction catalysts may be used alone or in combination of two or more. There are no particular limitations on the amount of each catalyst added.

[0024] By applying such production conditions, high stability can be achieved during emulsification, even for epoxy resins in a state where the molecular weight has been increased by polymerization. In this specification, "high molecular weight" refers to a molecular weight that provides excellent heat resistance and insulating properties, and is, for example, a weight average molecular weight of 10,000 or more, as described below. Furthermore, while the viscosity of epoxy resins generally increases as their molecular weight increases, the epoxy resin of this embodiment has a low viscosity.

[0025] <Epoxy resin structure> The epoxy resin according to this embodiment contains the monomer structural unit contained in the raw material composition. nothing. Resins with this structure have excellent insulating properties and heat resistance. Heat resistance here refers to the temperature at which the resin begins to decompose, i.e., the temperature at which the weight loss of a sample measured by a thermogravimetric differential thermal analyzer (TG-DTA) reaches 5%, and is preferably 350°C or higher.

[0026] <Method for producing cationic epoxy resin> Another aspect of the present invention is a method for producing a cationic epoxy resin by cationically modifying the epoxy resin obtained above. That is, the epoxy resin can be obtained by reacting the obtained epoxy resin with an amine compound containing at least one active hydrogen capable of reacting with a glycidyl group, for example, at a reaction temperature in the range of 70° C. to 120° C. The reaction time is preferably 1 to 5 hours. In the production of cationic epoxy resins, the amount of amine compound added is preferably adjusted so that the amine value of the resulting cationic epoxy resin is in the range of 15 mgKOH / g to 30 mgKOH / g. Therefore, the amine value of the resulting cationic epoxy resin is preferably in the range of 15 mgKOH / g to 30 mgKOH / g, and more preferably in the range of 15 mgKOH / g to 20 mgKOH / g. When the amine value is within this range, better solution stability can be achieved. The amine value, i.e., the total amine value of the cationic epoxy resin, can be measured according to the potentiometric titration method of JIS K7237.

[0027] The weight-average molecular weight of the cationic epoxy resin according to this embodiment is preferably from 10,000 to 30,000. The weight-average molecular weight value in this specification is a value measured by GPC (gel permeation chromatography) in accordance with JIS-K-7252-1 and converted from a calibration curve using polystyrene as a molecular weight standard substance.

[0028] The viscosity of the cationic epoxy resin is preferably in the range of 15 to 45 Pa·s when measured with an E-type viscometer at a heating residue of 70%. The viscosity measured with an E-type viscometer is measured according to a method in accordance with JIS K7117-2.

[0029] The following procedure is used to prepare a cationic epoxy resin sample for viscosity measurement. First, measure the resin's heating residue according to the test conditions for synthetic resin baking lacquers in JIS K5601-1-2. If the resulting heating residue exceeds 72%, adjust the heating residue to 70±2% by adding a solvent. The solvent used for adjustment must dissolve the resin, be non-reactive with epoxy or amino groups, and have a viscosity of 0.005 Pa·s or less at 40°C. Examples include butyl cellosolve, methyl isobutyl ketone, and propylene glycol methyl ether. If the resulting heating residue is below 68%, heat the sample for a desired time according to the test conditions for synthetic resin baking lacquers in JIS K5601-1-2, and adjust the heating residue to 70±2%. The sample prepared by these procedures is used for viscosity measurement.

[0030] <Amine compounds> Amine compounds are raw materials for introducing amino groups into epoxy resins. Therefore, amine compounds contain at least one active hydrogen capable of reacting with epoxy groups. The amine compound is not particularly limited as long as it can introduce amino groups. Examples include monomethylamine, dimethylamine, monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine, dibutylamine, monoethanolamine, diethanolamine, mono(2-hydroxypropyl)amine, di(2-hydroxypropyl)amine, monomethylaminoethanol, monoethylaminoethanol, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, tetraethylenepentamine, pentaethylenehexamine, diethylaminopropylamine, and diethylenetriamine. Among these, alkanolamines are preferred. Primary amines can also be ketiminated. These amine compounds may be used alone or in combination. When producing a cationic epoxy resin using two or more amine compounds, they may be added separately or simultaneously.

[0031] <Emulsion manufacturing method> Another aspect of the present invention is a method for producing an emulsion, including a step of emulsifying the cationic epoxy resin obtained above. The emulsion can be produced, for example, by adding a neutralizing acid to a mixture of a cationic epoxy resin and a curing agent (which may further contain a phenolic structure-containing resin), stirring, and then diluting with water. The neutralizing acid can be any organic acid, such as acetic acid, formic acid, lactic acid, or methanesulfonic acid. Among these, it is preferable to use a strong acid, such as methanesulfonic acid, which can produce a more stable emulsion with a low amine value. These acids can be used alone, or two or more types can be used together. When two or more types of acids are used, they can be added separately or simultaneously. Amino groups are cationized to impart water dispersibility. Cationization can be performed on all or some of the amino groups.

[0032] The amount of acid used for cationization is not particularly limited, but if it is too small, the amount of cations that impart water dispersibility will be small and an emulsion may not be formed, while if it is too large, the pH and electrical conductivity of the emulsion will increase, and the physical properties of the cured product formed from a composition containing the emulsion may deteriorate, so it is preferable to adjust the amount of acid appropriately. Preferably, it is desirable to adjust the electrical conductivity at the time of emulsification to less than 100 mS / m.

[0033] <Curing agent> The curing agent is not particularly limited as long as it can crosslink the cationic epoxy resin, and examples thereof include blocked isocyanate compounds, amine compounds, melamine, etc. Among these, blocked polyisocyanate compounds are preferred.

[0034] The blocked polyisocyanate compound is an addition reaction product of a polyisocyanate compound and a blocking agent, preferably an addition reaction product of a polyisocyanate compound and a blocking agent in approximately stoichiometric amounts. Examples of polyisocyanate compounds include tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, polymeric MDI (crude MDI), bis(isocyanatomethyl)cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, and isophorone diisocyanate. These compounds can be used alone or in combination of two or more.

[0035] Blocking agents add to the isocyanate groups of polyisocyanate compounds to block them from reacting with other compounds. Blocked polyisocyanate compounds produced by blocking the isocyanate groups with a blocking agent are stable at room temperature. Examples of such blocking agents include lactam compounds such as ε-caprolactam and γ-butyrolactam; oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime; phenolic compounds such as phenol, para-t-butylphenol, and cresol; alcohols such as n-butanol and 2-ethylhexanol; and ether alcohol compounds such as ethylene glycol monobutyl ether and ethylene glycol monohexyl ether. These blocking agents can be used alone or in combination of two or more. In order to efficiently carry out the addition and dissociation reactions of the blocking agent and to efficiently obtain the intended addition reaction product, the hydroxyl groups in the cationic epoxy resin may be reacted with the isocyanate groups in the polyisocyanate compound in advance, and some or all of the other isocyanate groups in the polyisocyanate compound may be blocked with the blocking agent.

[0036] The emulsion may contain a phenolic resin. The phenolic resin is not particularly limited as long as it has a phenol group in the repeating structure. One type of phenolic resin may be used, or two or more types may be used in combination.

[0037] The emulsion may contain a curing catalyst. Examples of the curing catalyst include known catalysts such as tin catalysts, bismuth catalysts, titanium catalysts, zirconium catalysts, amine catalysts, carboxylate catalysts, and trialkylphosphine catalysts. These curing catalysts may be used alone or in combination of two or more.

[0038] <Application> The cationic epoxy resins or emulsions can be used in adhesives, eyeglasses, optical materials (e.g., imaging lenses), lining agents, inks, resists, liquid resists, printing plates, insulating varnishes, insulating sheets, laminates, printed circuit boards, sealants (e.g., for semiconductor devices, LED packages, liquid crystal injection ports, organic electroluminescent devices, optical elements, electrical insulation, electronic components, and separators), molding materials, putties, glass fiber impregnating agents, sealants, passivation films (e.g., for semiconductors and solar cells), interlayer insulating films, protective films, prism lens sheets (e.g., those used in backlights of liquid crystal displays), Fresnel lens sheets (e.g., those used in screens of projection televisions, etc.), lens portions of lens sheets such as lenticular lens sheets, or backlights using such sheets, optical lenses (e.g., microlenses), optical elements, optical connectors, optical waveguides, and casting agents for optical shaping. However, the uses of the cationic epoxy resins or emulsions are not limited to those mentioned above. [Example]

[0039] Examples of the present invention and comparative examples will be described below, but the present invention is not limited to the following examples.

[0040] <Production Example 1: Synthesis of epoxy resin> A manufacturing vessel equipped with a thermometer, reflux condenser, and stirrer was charged with 112.32 g of bisphenol A diepoxy resin (Table 1; A1), 72.75 g of propylene oxide-added diepoxy resin (Table 1; B1), 62.12 g of bisphenol A, 39.50 g of dimer acid, and 0.55 g of dimethylbenzylamine, and the raw materials were dissolved at 110°C. After dissolution, the temperature was raised to 145°C over a 15-minute period, after which cooling was initiated. After cooling began, the temperature was adjusted to a maximum of 160°C and stabilized at 155°C. The reaction was then continued at 155°C until the epoxy equivalent reached 2300 g / eq., and 37.84 g of methyl isobutyl ketone was added to terminate the reaction. Subsequently, 55.58 g of propylene glycol methyl ether and 18.53 g of butyl cellosolve were added to obtain the epoxy resin (Manufacturing Example 1).

[0041] <Production Examples 2 to 8> Epoxy resins of Production Examples 2 to 8 were synthesized using the raw materials having the structures shown in Table 1 and the formulations shown in Table 2 in the same manner as in Production Example 1.

[0042] [Table 1]

[0043] [Table 2]

[0044] <Production Examples 9 to 13 and Comparative Production Examples 1 to 3> Using the same raw materials as in Production Example 1, epoxy resins of Production Examples 9 to 13 and Comparative Production Examples 1 to 3 were synthesized under the temperature control method shown in Table 3.

[0045] [Table 3]

[0046] <Production Example 14: Synthesis of cationic epoxy resin> 414.28 g of the epoxy resin (Production Example 1) and 9.11 g of diethanolamine were placed in a production vessel equipped with a thermometer, a reflux condenser, and a stirrer, and the mixture was reacted at 110°C for 5 hours to obtain a cationic epoxy resin (Production Example 14) with a heating residue of 70%.

[0047] <Production Examples 15 to 30 and Comparative Production Examples 4 to 6> In the same manner as in Production Example 14, cationic epoxy resins of Production Examples 15 to 30 and Comparative Production Examples 4 to 6 were obtained using the combinations of epoxy resins and amine compounds shown in Table 4. [Table 4]

[0048] <Weight average molecular weight measurement> The weight-average molecular weights of the epoxy resins produced in Production Examples 1 to 13 and Comparative Production Examples 1 to 3, and the cationic epoxy resins produced in Production Examples 14 to 30 and Comparative Production Examples 4 to 6 were measured using an HLC-8320GPC (manufactured by Tosoh Corporation). The measurements were carried out according to JIS K7252-1, using a TSKgel SuperAWM-H (manufactured by Tosoh Corporation) column, N,N-dimethylformamide (containing 100 mM lithium bromide / 50 mM phosphoric acid) as the eluent, and polystyrene as the molecular weight standard.

[0049] <Amine value measurement of cationic epoxy resin> The amine values ​​of the cationic epoxy resins produced in Production Examples 14 to 30 and Comparative Production Examples 4 to 6 were measured according to the potentiometric titration method of JIS K7237.

[0050] <Viscosity measurement of epoxy resin and cationic epoxy resin> Viscosity measurements were performed on the epoxy resins produced in Production Examples 1 to 13 and Comparative Production Examples 1 to 3, as well as the cationic epoxy resins produced in Production Examples 14 to 30 and Comparative Production Examples 4 to 6, using the following procedure to prepare samples. Measurements were performed using a TV-25 E-type viscometer (manufactured by Toki Sangyo Co., Ltd.) in accordance with JIS K7117-2, using a rotor with a diameter of 24 mm and a cone angle of 1°34'. Measurements were performed at a temperature of 40°C, a rotation speed of 0.5 rpm, and a measurement time of 2 minutes. The viscosity of the cationic epoxy resin samples was measured using the following procedure. First, the heating residue of the resin was measured in accordance with the test conditions for synthetic resin baking veneers in JIS K5601-1-2. If the heating residue exceeded 72%, a solvent was added to adjust the heating residue to 70±2%. The solvent used for this adjustment was butyl cellosolve. If the resulting heating residue was below 68%, the sample was heated for an arbitrary time under the test conditions for synthetic resin baking paints in JIS K5601-1-2, and adjusted to a heating residue of 70±2%. The sample prepared by these operations was used for viscosity measurement.

[0051] <Synthesis of blocked polyisocyanate curing agent> 77.1 g of methyl isobutyl ketone was added to 452.3 g of polymethylene polyphenyl polyisocyanate (Sumidur 44V20L, manufactured by Sumika Covestro Urethane Co., Ltd.), and the mixture was heated to 70°C, after which 470.7 g of butyl cellosolve was slowly added dropwise, and after completion of the dropwise addition, the mixture was heated to 90°C. The mixture was then allowed to react at 90°C for 12 hours to obtain a blocked polyisocyanate curing agent.

[0052] <Production Example 31: Preparation of emulsion> 423.46 g of the cationic epoxy resin of Production Example 14, 141.15 g of a blocked polyisocyanate curing agent, 6.7 g of a dioctyltin compound (Neostan U-820, manufactured by Nitto Kasei), and 4.20 g of methanesulfonic acid were mixed, and then 687.14 g of deionized water was slowly added thereto, followed by transfer emulsification to prepare an emulsion with a heating residue concentration of 33%.

[0053] <Production Examples 32 to 50 and Comparative Production Examples 7 to 9> In the same manner as in Production Example 31, emulsions of Production Examples 32 to 50 and Comparative Production Examples 7 to 9 were obtained using various cationic epoxy resins and organic acids shown in Table 5.

[0054] [Table 5]

[0055] <<Various evaluation tests>> In each evaluation, a score of 0 or above will be considered a pass.

[0056] <Insulation test> The resulting emulsion was applied to a cold-rolled steel plate (150 mm (length) × 70 mm (width) × 0.8 mm (thickness)) to a dry film thickness of 20 μm, and then cured by heating at 180°C for 20 minutes to obtain a coated plate for evaluation. Using this coated plate for evaluation, the voltage until breakdown was measured in a short-term test specified in JIS C2110. (Evaluation criteria) ◎: 3.0kV or more ○: 2.0 kV or more and less than 3.0 kV △: 1.5kV or more and less than 2kV ×: Less than 1.5 kV

[0057] <Heat resistance test> The resulting emulsion was dried and then measured for the 5% weight loss temperature using a differential thermal and thermogravimetric simultaneous analyzer (TG / DTA7300, Hitachi High-Tech Science Corporation) while the sample temperature was raised at a rate of 10°C / min. Alumina was used as the measurement reference, and the measurement was carried out under a nitrogen gas flow. (Evaluation criteria) ◎: 350℃ or higher 〇: 300℃ or higher but less than 350℃ △: 250℃ or higher but less than 300℃ ×: Less than 250℃

[0058] <Emulsion stability test> The emulsions thus produced were left to stand in a thermostatic chamber at 25°C for 3 months, and their stability was evaluated. (Evaluation criteria) ◎: No settling ○: Returns to original state by shaking △: Does not return to its original state even after shaking ×: Completely phase separated

[0059] The test results are shown in Tables 6 to 8. The results clearly show that the production method of the present invention can produce cationic epoxy resins with a molecular weight of 10,000 or more and a viscosity of 15 to 45 Pa s, and that cationic epoxy resins with these physical properties have excellent stability as emulsions, as well as excellent insulating properties and heat resistance.

[0060] [Table 6]

[0061] [Table 7]

[0062] Table 8

Claims

1. A method for producing an epoxy resin, comprising: a preparation step of preparing a composition containing an epoxy resin having two glycidyl groups represented by formula (1) and / or a polymer thereof; a temperature-raising step of raising the temperature of the composition from 110°C to 145°C over a period of 65 minutes or less; and a polymerization step of polymerizing the composition at a temperature in the range of 145°C or higher and 180°C or lower. 【Chemistry 1】 [In formula (1), A is selected from a benzene ring, a naphthalene ring, an anthracene ring, and formula (α), and in formula (α), R ３ and R ４ are each independently selected from a single bond, an alkylene group, a phenylene group, and a cyclohexylene group; X １ and Y １ are each independently selected from a hydrogen atom and an alkyl group. ３ and R ４ is bonded to the carbon in formula (1).

2. 2. The method for producing an epoxy resin according to claim 1, wherein the composition comprises a dicarboxylic acid in which two carboxyl groups are bonded via at least one carbon atom.

3. The method for producing an epoxy resin according to claim 1, wherein the composition contains an epoxy resin represented by formula (2) or a polymer thereof. 【Chemistry 2】 [In formula (2), R １ represents an alkylene group having 3 to 10 carbon atoms which may have a substituent, a cyclohexylene group which may have a substituent, a phenylene group which may have a substituent, or -R ａ -R ｂ -R ｃ - and R ａ and R ｃ is a cyclohexylene group or a phenylene group, and R ｂ represents a methylene group which may have one or two substituents, and m and n are each independently an integer of 1 to 20.

4. A method for producing a cationic epoxy resin, comprising a step of reacting the epoxy resin produced by the method according to any one of claims 1 to 3 with an amine compound containing at least one active hydrogen capable of reacting with a glycidyl group at a temperature of 70°C or higher and 120°C or lower.

5. The obtained cationic epoxy resin has a weight average molecular weight of 10,000 or more, an amine value of 30 mgKOH / g or less, and a viscosity of 15 to 45 Pa·s at 40°C with a heating residue of 70%.

5. The method for producing a cationic epoxy resin according to claim 4, wherein

6. A method for producing an emulsion, comprising a step of emulsifying the cationic epoxy resin produced by the method according to claim 4 with at least one organic acid selected from the group consisting of acetic acid, formic acid, lactic acid, and methanesulfonic acid.

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