Novel amino compounds and methods for producing the same, and epoxy resin curing agents, epoxy resin compositions, and epoxy resin cured products using the same.

Abstract

To provide a novel amino compound useful as an epoxy resin curing agent, a method for producing the same, etc., disclosed is an amino compound represented by formula (1) that has a quaternary carbon at the β-position of an amino group. [In formula (1): A represents any of (α) a hydrocarbon group having 2-30 carbon atoms that independently has at least one -O- bond attached to the carbon at the γ-position of an amino group and that may have substituents (the same applies hereinafter), (β) a hydrocarbon group having 2-30 carbon atoms that has at least one -O- bond attached to the carbon at the γ-position of an amino group, in a state of being attached to one of R1 to R4, and (γ) a hydrocarbon group having 2-30 carbon atoms that has at least one -O- bond attached to the carbon at the γ-position of an amino group, in a state of being attached to R1 or R2 and to R3 or R4; and R1 to R4 independently represent a hydrocarbon group having 1-10 carbon atoms (excluding group(s) attached to A).]

Description

Technical Field

[0001] The present invention provides an amino compound which is a novel compound and a method for producing the same, and also relates to a curing agent for epoxy resins, an epoxy resin composition, and a cured epoxy resin containing the novel amino compound.

Background Art

[0002] Conventionally, as curing agents for epoxy resins, for example, amino compounds such as diethylenetriamine, triethylenetetramine, polyoxypropylene diamine (registered trademark: Jeffamine), isophorone diamine (IPDA), metaxylylenediamine, 1,3-bis(aminomethyl)cyclohexane (1,3-BAC) have been widely used. These are industrially manufactured, and curing agents for epoxy resins containing amino compounds are sold. Also, reviews on the performance of various amines have been published (for example, see Non-Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, amino compounds having primary amino groups react quickly with epoxy resins and exhibit rapid curing properties. However, they have the disadvantage of a short time from compounding to gelation, limiting the working time after compounding. In particular, rapid curing is unsuitable for certain applications of epoxy resin compositions. For example, one method of manufacturing fiber-reinforced composites (hereinafter also called "FRP (Fiber Reinforced Plastics)") is the filament winding method. The filament winding method is a method of forming a molded product by coating the outer surface of a mandrel or the like with reinforcing fiber yarn impregnated with a matrix resin or its precursor. Thermosetting resin compositions such as epoxy resin compositions can be used as matrix resin precursors, but if the resin composition has a short pot life and is rapidly curing, a problem arises in that the thermosetting resin hardens before molding.

[0005] Therefore, the present invention has been made in view of the above-mentioned problems, and aims to provide a novel amino compound useful as a curing agent for epoxy resins, which was not previously known, a method for producing the same, and a curing agent for epoxy resins, an epoxy resin composition, and an epoxy resin cured product using the same. [Means for solving the problem]

[0006] The present inventors, after diligent research to solve the aforementioned problems, have discovered that by using an amino compound having a specific structure, it is possible to suppress the excessive rapid curing that is the aforementioned problem and improve workability by achieving a long pot life, thus completing the present invention. In other words, the contents of this disclosure are as follows.

[0007] [1] An amino compound represented by the following formula (1), having a quaternary carbon at the β-position of the amino group.

[0008] [ka]

[0009] In formula (1), A is any one of the following (α), (β), and (γ); (α) Alone, having at least one -O- bond bonded to the carbon at the γ-position of the amino group, and a hydrocarbon group having 2 to 30 carbon atoms which may have a substituent, (β) In a state of being bonded to any one of R 1 , R 2 , R 3 , and R 4 , having at least one -O- bond bonded to the carbon at the γ-position of the amino group, and a hydrocarbon group having 2 to 30 carbon atoms which may have a substituent, (γ) In a state of being bonded to R 1 or R 2 , and, R 3 or R 4 , having at least one -O- bond bonded to the carbon at the γ-position of the amino group, and a hydrocarbon group having 2 to 30 carbon atoms which may have a substituent, R 1 , R 2 , R 3 , and R 4 are each independently a hydrocarbon group having 1 to 10 carbon atoms which may have a substituent (however, excluding those bonded to A).

[0010] [2] A alone has a dioxane structure, or A has a dioxane structure in a state of being bonded to any one of R 1 , R 2 , R 3 , and R 4 , or A has a dioxane structure in a state of being bonded to R 1 or R 2 , and, R 3 or R 4 . The amino compound described in the above [1]. <A

[0011] <A [3] The amino compound described in the above [1] or [2], which is represented by the following formula (2) or formula (3).

[0012] [ka]

[0013] [4] A method for producing an amino compound, comprising the step of aminating a polyol compound represented by the following formula (1a) in the presence of a catalyst and ammonia to obtain an amino compound represented by the following formula (1) having a quaternary carbon at the β-position of the amino group.

[0014] [ka]

[0015] In equations (1) and (1a), A is one of the following (α), (β), and (γ); (α) A hydrocarbon group having 2 to 30 carbon atoms, which alone has at least one -O- bond attached to the carbon atom at the γ position of the amino group and may have substituents. (β)R 1 , R 2 , R 3 , and R 4 A hydrocarbon group having 2 to 30 carbon atoms, which is bonded to any one of the following, and has at least one -O- bond attached to the carbon atom at the γ position of the amino group, and which may have substituents. (γ)R 1 or R 2 , and R 3 or R 4 A hydrocarbon group having 2 to 30 carbon atoms, which, in a bonded state, has at least one -O- bond attached to the carbon atom at the γ position of the amino group, and which may have substituents. R 1 , R 2 , R 3 , and R 4 Each of these is independently a hydrocarbon group having 1 to 10 carbon atoms, which may have substituents (except those bonded to A).

[0016] [5] A, on its own, has a dioxane structure, or A is R 1, R 2 , R 3 , and R 4 In a state where it is bonded to any one of the following, it has a dioxane structure. A method for producing the amino compound described in [4] above.

[0017] [6] A step of aminating a polyol compound represented by the following formula (2a) in the presence of a catalyst and ammonia to obtain an amino compound represented by the following formula (2), or, A step of obtaining an amino compound represented by formula (3) by aminating a polyol compound represented by formula (3) in the presence of a catalyst and ammonia, A method for producing amino compounds containing [specific compound name].

[0018] [ka]

[0019] [7] A curing agent for epoxy resins, comprising any one of the amino compounds described in [1] to [3] above.

[0020] [8] An epoxy resin composition comprising the epoxy resin curing agent described in [7] above and an epoxy resin.

[0021] [9] A cured epoxy resin product obtained by curing the epoxy resin composition described in [8] above. [Effects of the Invention]

[0022] According to this disclosure, it is possible to provide novel amino compounds useful as curing agents for epoxy resins that have good coating appearance and drying properties, as well as long pot life, water spot resistance, and chemical resistance, and a method for producing the same, as well as a curing agent for epoxy resins, an epoxy resin composition, and an epoxy resin cured product using the same. [Modes for carrying out the invention]

[0023] The embodiments of this disclosure will be described below. The embodiments described below are illustrative examples for illustrating this disclosure, and this disclosure is not limited to these embodiments. Various modifications are possible without departing from the spirit of the disclosure.

[0024] [Amino compounds] The amino compound according to this embodiment is a compound having a quaternary carbon at the β position of the amino group and at least one -O- bond attached to the carbon at the γ position of the amino group (in other words, a site to which -O- is attached to the carbon at the γ position of the amino group), and is specifically represented by the following formula (1).

[0025] [ka]

[0026] In equation (1), A is one of the following (α), (β), and (γ). That is, A is (α) A hydrocarbon group having 2 to 30 carbon atoms, which alone has at least one -O- bond attached to the carbon atom at the γ position of the amino group and may have substituents, or (β)R 1 , R 2 , R 3 , and R 4 A hydrocarbon group having 2 to 30 carbon atoms, which is bonded to any one of the following, and has at least one -O- bond attached to the carbon atom at the γ position of the amino group, and may have substituents, or (γ)R 1 or R 2 , and R 3 or R 4 It is a hydrocarbon group having 2 to 30 carbon atoms that, while bonded to the γ-carbon of the amino group, has at least one -O- bond attached to the γ-carbon of the amino group, and may also have substituents. As shown above, A is a hydrocarbon group that contains an oxygen atom as a heteroatom.

[0027] Also, in equation (1), R 1 , R 2 , R 3 , and R 4Each of these is independently a hydrocarbon group having 1 to 10 carbon atoms, which may have substituents. However, R bonded to A is... 1 , R 2 , R 3 , and / or, R 4 As described in (β) and (γ) above, these form part of A and are therefore excluded from the definition here.

[0028] R 1 , R 2 , R 3 , and R 4 Examples of hydrocarbon groups having 1 to 30 carbon atoms include alkyl groups and alkoxy groups having 1 to 10 carbon atoms, such as methyl groups and ethyl groups; linear or branched propyl groups, butyl groups, pentyl groups, hexyl groups, heptyl groups, octyl groups, nonyl groups, and decyl groups; or cyclic cyclohexyl groups, cyclopentyl groups, phenyl groups, benzyl groups, and bicyclic hydrocarbon groups having a spirocycle skeleton. Also, A and R 1 , R 2 , R 3 , and R 4 Examples of substituents in this compound include hydroxyl groups and carbonyl groups.

[0029] More specifically, A alone has a dioxane structure, or R 1 , R 2 , R 3 , and R 4 It is preferable that the compound has a dioxane structure in a state of being bonded to any one of the following. In this case, more specifically, as the amino compound of formula (1) in this embodiment, 2,2'-(2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl)bis(2-methylpropane-1-amine) represented by the following formula (2), or 2-(5-(aminomethyl)-5-ethyl-1,3-dioxan-2-yl)-2-methylpropane-1-amine represented by the following formula (3), are more preferred examples.

[0030] [ka]

[0031] Furthermore, other examples of amino compounds represented by formula (1) include 3-amino-2,2-dimethylpropyl 3-amino-2,2-dimethylpropanoate represented by formula (4), 2,2'-(oxybis(methylene))bis(2-(aminomethyl)butan-1-ol) represented by formula (5-1), 2-((2,2-bis(aminomethyl)butoxy)methyl)-2-ethylpropane-1,3diol represented by formula (5-2), 2-(aminomethyl)-2-((2,2-bis(aminomethyl)butoxy)methyl)butan-1-ol) represented by formula (5-3), 2,2'-(oxybis(methylene))bis(2-ethylpropane-1,3-diamine) represented by formula (5-4), and 3,3'- represented by formula (6). Examples include oxybis(2,2-dimethylpropane-1-amine), 2-((3-amino-2,2-dimethylpropoxy)methyl)-2-ethylhexane-1-amine represented by formula (7) below, 2-((3-amino-2,2-dimethylpropoxy)methyl)-2-(aminomethyl)butan-1-ol represented by formula (8-1) below, 3-(2,2-bis(aminomethyl)butoxy)-2,2-dimethylpropane-1-ol represented by formula (8-2) below, and 2-((3-amino-2,2-dimethylpropoxy)methyl)-2-ethylpropane-1,3-diamine represented by formula (8-3) below.

[0032] [ka]

[0033] Furthermore, another example of an amino compound represented by formula (1) above is (3,12-diethyl-1,5,10,14-tetraoxadispiro[5.2.5 9 .2 6Examples of compounds represented by formula (10) include hexadecane-3,12-diyl) dimethanamine and compounds represented by the following formula (10). In formula (10), X represents a group selected from the group consisting of a linear alkyl group having 0 to 6 carbon atoms, a branched alkyl group having 3 to 6 carbon atoms, an aryl group, and a group having 6 to 20 carbon atoms. Examples of compounds represented by such formula (10) include (propane-2,2-diylbis(3-ethyl-1,5-dioxaspiro[5.5]undecane-9,3-diyl)) dimethanamine represented by the following formula (10-1) and ((9H-fluorene-9,9-diyl)bis(3-ethyl-1,5-dioxaspiro[5.5]undecane-9,3-diyl)) dimethanamine represented by the following formula (10-2).

[0034] [ka]

[0035] As described above, the compound represented by formula (2) (spirobisamine), the compound represented by formula (4), the compounds represented by formulas (5-1) to (5-4), the compound represented by formula (6), the compound represented by formula (7), and the compounds represented by formulas (8-1) to (8-3) are examples of amino compounds containing A in (α). Furthermore, the compound represented by formula (3) (dioxambisamine) is an example of an amino compound containing A in (β). In addition, the compound represented by formula (9), the compound represented by formula (10), the compound represented by formula (10-1), and the compound represented by formula (10-2) are examples of amino compounds containing A in (γ).

[0036] [Method for producing amino compounds] The amino compound represented by formula (1) can be obtained by amination of a polyol compound represented by formula (1a), for example, as shown below.

[0037] [ka]

[0038] In equations (1) and (1a), A is one of (α), (β), and (γ) as described above. That is, A is (α) A hydrocarbon group having 2 to 30 carbon atoms, which alone has at least one -O- bond attached to the carbon atom at the γ position of the amino group and may have substituents, or (β)R 1 , R 2 , R 3 , and R 4 A hydrocarbon group having 2 to 30 carbon atoms, which is bonded to any one of the following, and has at least one -O- bond attached to the carbon atom at the γ position of the amino group, and may have substituents, or (γ)R 1 or R 2 , and R 3 or R 4 It is a hydrocarbon group having 2 to 30 carbon atoms that, while bonded to the γ-carbon of the amino group, has at least one -O- bond attached to the γ-carbon of the amino group, and may also have substituents.

[0039] The amination reaction described here is not particularly limited, but it is preferable, for example, to react the starting polyol compound with ammonia in the presence of a reducing catalyst. Any catalyst commonly used in amination reactions can be used as the reducing catalyst. For example, noble metal catalysts such as platinum, palladium, ruthenium, and rhodium; or base metal catalysts such as nickel, cobalt, and iron catalysts can be used. These catalysts can be used as metals alone or supported on a carrier such as activated carbon, alumina, silica, titania, or zirconia. One catalyst can be used alone or in combination of two or more. Of these, it is even more preferable to use a ruthenium-supported catalyst from the viewpoint of increasing the yield of the amino compound.

[0040] The mass ratio of the polyol compound to the reduction catalyst is preferably 2 to 30, more preferably 5 to 20, and even more preferably 5 to 15. By setting the mass ratio of the polyol compound to the reduction catalyst within the above range, the yield and selectivity of the resulting amino compound tend to be increased.

[0041] The molar ratio of ammonia to the polyol compound is preferably 2 to 150, more preferably 5 to 100, and even more preferably 8 to 80. Setting the molar ratio above the lower limit tends to accelerate the reaction, while setting the molar ratio below the upper limit shortens the time required to remove the liquid ammonia, thereby improving production efficiency. Ammonia can also be used as a solvent, and can be in any form, such as liquid ammonia or aqueous ammonia.

[0042] While not strictly necessary for the amination reaction, solvents commonly used in amination reactions can also be employed. Examples include benzene, toluene, xylene, nitromethane, nitrobenzene, carbon disulfide, acetonitrile, benzonitrile, hexane, cyclohexane, petroleum ether, diethyl ether, 1,4-dioxane, methyl acetate, tetrahydrofuran, acetone, methyl ethyl ketone, dichloroethane, dimethylformamide, dimethyl sulfoxide, dimethyl carbonate, and propylene carbonate. These solvents can be used individually or in combination of two or more.

[0043] Furthermore, the reaction temperature for the amination reaction is preferably 100 to 350°C, more preferably 150 to 300°C, and even more preferably 200 to 250°C. Setting the reaction temperature for the amination reaction above the lower limit improves reactivity, while setting the reaction temperature below the upper limit tends to reduce the amount of high-boiling compounds.

[0044] Furthermore, the initial hydrogen filling pressure for the amination reaction (excluding the self-pressure of liquid ammonia) is preferably 0 to 20 MPa, more preferably 0.1 to 10 MPa, and even more preferably 1 to 8 MPa. By setting the pressure of the amination reaction within the above range, the yield and selectivity of the resulting amino compounds tend to be increased.

[0045] Furthermore, the amination reaction can be carried out until the reaction is complete, but possible reaction times include, for example, 1 to 48 hours, 2 to 24 hours, or 4 to 10 hours.

[0046] More specifically, A in formulas (1) and (1a) has a dioxane structure on its own, or R 1 , R 2 , R 3 , and R 4 It is preferable that the compound has a dioxane structure in which it is bonded to any one of the following. In this case, more specifically, as a method for producing the amino compound of formula (1) in this embodiment, a more preferred example is a method of obtaining the amino compound of formula (2) by aminating 2,2'-(2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl)bis(2-methylpropan-1-ol) represented by the following formula (2a) in the presence of the appropriate catalyst and ammonia described above, or a method of obtaining the amino compound of formula (3) by aminating 2-(5-ethyl-5-(hydroxymethyl)-1,3-dioxan-2-yl)-2-methylpropan-1-ol represented by the following formula (3a).

[0047] [ka]

[0048] Other examples of polyol compounds represented by formula (1a) include 3-hydroxy-2,2-dimethylpropyl 3-hydroxy-2,2-dimethylpropanoate represented by formula (4a), 2,2'-(oxybis(methylene))bis(2-ethylpropane-1,3-diol) represented by formula (5a), 3,3'-oxybis(2,2-dimethylpropane-1-ol) represented by formula (6a), 2-ethyl-2-((3-hydroxy-2,2-dimethylpropoxy)methyl)hexane-1-ol represented by formula (7a), and 2-ethyl-2-((3-hydroxy-2,2-dimethylpropoxy)methyl)propane-1,3-diol represented by formula (8a).

[0049] [ka]

[0050] Furthermore, another example of the polyol compound represented by formula (1a) above is (3,12-diethyl-1,5,10,14-tetraoxadispiro[5.2.5 9 .2 6 Examples include hexadecane-3,12-diyl)dimethanol, a compound represented by the following formula (10a) (where X is the same as in formula (10) above), (propane-2,2-diylbis(3-ethyl-1,5-dioxaspiro[5.5]undecane-9,3-diyl))dimethanol represented by the following formula (10a-1), ((9H-fluorene-9,9-diyl)bis(3-ethyl-1,5-dioxaspiro[5.5]undecane-9,3-diyl))dimethanol represented by the following formula (10a-2), etc.

[0051] [ka]

[0052] By using the amino compounds described herein as curing agents for epoxy resins, it is possible to obtain epoxy resin compositions and epoxy resin cured products that have good coating appearance and drying properties, as described later, and that are particularly superior in terms of long pot life, water spot resistance, and chemical resistance compared to conventionally used amino compounds. Although the details of the mechanism of action are still unclear, it is presumed that in the amino compounds described herein, the quaternary carbon located at the β position of the amino group, or in addition, the A portion containing the -O- bond attached to the carbon at the γ position of the amino group, acts as steric hindrance, inhibiting the curing reaction of the epoxy resin, thereby achieving exceptionally superior properties, particularly in terms of long pot life. However, the mechanism of action is not limited to this.

[0053] [Hardener for epoxy resins] The amino compound represented by formula (1) can be suitably used as a curing agent for epoxy resins. When using the amino compound represented by formula (1) as a curing agent for epoxy resins, it is also possible to use other amine compounds that contribute to the curing of the epoxy resin in combination. In that case, it is preferable that the amount of the amino compound represented by formula (1) relative to the total amount of the amino compound represented by formula (1) and the other amine compounds is 20% by mass or more. Furthermore, in order to make better use of the characteristics of the curing agent for epoxy resins, it is more preferable that the amount of the amino compound represented by formula (1) relative to the total amount of the amino compound represented by formula (1) and the other amine compounds is 30% by mass or more, and even more preferable that it is 50% by mass or more. In addition, the curing agent for epoxy resins according to this disclosure using the amino compound represented by formula (1) may contain components that do not contribute to curing, such as solvents, in addition to the other amine compounds mentioned above, as long as the effects of the present invention are not impaired. Furthermore, when using the curing agent for epoxy resins according to this disclosure as an epoxy resin composition described later, it may of course be used in combination with other curing agents.

[0054] [Epoxy resin composition] The epoxy resin composition according to this disclosure comprises an epoxy resin and a curing agent for epoxy resins using an amino compound represented by formula (1). The epoxy resin used in the epoxy resin composition according to this disclosure is not particularly limited as long as it is an epoxy resin having a glycidyl group that reacts with the active hydrogen derived from the amino group contained in the curing agent for epoxy resins according to this disclosure. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, or a mixture thereof can be suitably used as the main component. Furthermore, the epoxy resin composition according to this disclosure may appropriately use modifying components such as fillers and plasticizers, flow adjusting components such as reactive or non-reactive diluents and thixotropes, pigments, leveling agents, tackifiers, and additives such as anti-repellent agents, anti-sagging agents, spreading agents, defoaming agents, ultraviolet absorbers, and light stabilizers, depending on the application. In the epoxy resin composition according to this disclosure, the mixing ratio of the epoxy resin and the epoxy resin curing agent is preferably such that the ratio [ep / h] of the number of functional groups [ep] calculated from the epoxy equivalent of the epoxy resin to the number of functional groups [h] calculated from the active hydrogen equivalent of the epoxy resin is in the range of 0.90 to 1.10, and more preferably in the range of 0.95 to 1.05. The closer this mixing ratio is to equal amounts, the fewer residual functional groups remain, and an epoxy resin with excellent performance can be obtained.

[0055] [Cured epoxy resin] The epoxy resin composition according to this disclosure can be cured by known methods to obtain a cured epoxy resin product. The curing conditions can be appropriately selected depending on the application and are not particularly limited. For example, the epoxy resin composition according to this disclosure can be used at room temperature conditions of 15 to 30°C, or it can be heat-cured by heating to 30°C or higher. Furthermore, cured epoxy resin compositions according to this disclosure have the advantage of having good drying properties, water resistance, and an excellent appearance. [Examples]

[0056] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited in any way by these examples.

[0057] [Example 1] Synthesis of spirobisamine In a 100 mL SUS316 pressure vessel (shaking type), 4.1 g of spiroglycol (SPG) (reagent manufactured by Tokyo Chemical Industry Co., Ltd.), 8.8 g of liquid ammonia (manufactured by Mitsubishi Gas Chemical Company, Inc.), and 0.41 g of a 5% Ru / C catalyst (Type A, manufactured by N.E. Chemcat Co., Ltd.) were charged, and hydrogen gas was introduced until the pressure in the system reached 4.1 MPa. The catalyst used was prepared after being reduced at 250°C for 2 hours in a designated reduction apparatus. Subsequently, the contents of the vessel were heated to 230°C, and the vessel was shaken while maintaining this temperature to allow the amination reaction to proceed for 4.5 hours.

[0058] After the reaction was complete, the reaction product was purged with liquid ammonia, dissolved in 200 g of methanol, and the catalyst in the solution was removed by filtration. The reaction was then analyzed by GC (Shimadzu Corporation, model name "GC2010 PLUS", column: product name "HP-5ms", manufactured by Agilent Technologies, Inc., length 30 m x inner diameter 0.25 mm, film thickness 0.25 μm, conditions…carrier gas: He (constant pressure: 73.9 kPa), inlet temperature: 300 °C, detector: FID, detector temperature: 325 °C, column oven temperature: started at 80 °C, increased to 230 °C at 20 °C / min, increased to 240 °C at 1 °C / min, then increased to 325 °C at 20 °C / min, and held at 325 °C for 20 minutes). The reaction yield was calculated as the area percentage of the components detected by gas chromatography. As a result, the reaction yield of 2,2'-(2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl)bis(2-methylpropan-1-amine), represented by formula (2), was 97.6%.

[0059] [Example 2] Synthesis of spirobisamine (scale-up) In a 100 mL SUS316 pressure vessel (shaking type), 20.0 g of spiroglycol (reagent manufactured by Tokyo Chemical Industry Co., Ltd.), 10.1 g of liquid ammonia (manufactured by Mitsubishi Gas Chemical Company, Inc.), and 2.00 g of a 5% Ru / C catalyst (Type A, manufactured by N.E. Chemcat Co., Ltd.) were placed, and hydrogen gas was introduced until the pressure in the system reached 4.0 MPa. The catalyst used was prepared after being reduced at 250°C for 2 hours in a designated reduction apparatus. Subsequently, the contents of the vessel were heated to 228°C, and the vessel was shaken while maintaining this temperature to allow the amination reaction to proceed for 4.5 hours.

[0060] After the reaction was complete, the reaction product was purged with liquid ammonia, dissolved in 1000 g of methanol, and the catalyst in the solution was removed by filtration. The reaction was then analyzed by GC (Shimadzu Corporation, model name "GC2010 PLUS", column: product name "HP-5ms", Agilent Technologies, Inc., length 30 m x inner diameter 0.25 mm, film thickness 0.25 μm, conditions…carrier gas: He (constant pressure: 73.9 kPa), inlet temperature: 300 °C, detector: FID, detector temperature: 325 °C, column oven temperature: started at 80 °C, heated to 230 °C at 20 °C / min, heated to 240 °C at 1 °C / min, then heated to 325 °C at 20 °C / min, and held at 325 °C for 20 minutes). The reaction yield was calculated as the area percentage of the components detected by gas chromatography. As a result, the reaction yield of 2,2'-(2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl)bis(2-methylpropan-1-amine), represented by formula (2), was 88.1%.

[0061] [Example 3] Synthesis of dioxanbisamine In a 100 mL SUS316 pressure vessel (shaking type), 2.9 g of dioxane glycol, 8.9 g of liquid ammonia (manufactured by Mitsubishi Gas Chemical Company, Inc.), and 0.29 g of a 5% Ru / C catalyst (manufactured by N.E. Chemcat Co., Ltd., Type A) were placed, and hydrogen gas was introduced until the pressure in the system reached 4.8 MPa. The catalyst used was prepared after being reduced at 250°C for 2 hours in a designated reduction apparatus. Subsequently, the contents of the vessel were heated to 232°C, and the vessel was shaken while maintaining this temperature to allow the amination reaction to proceed for 4.5 hours.

[0062] After the reaction was complete, the reaction product was purged with liquid ammonia, dissolved in 150 g of methanol, and the catalyst in the solution was removed by filtration. The reaction was then analyzed by GC (Shimadzu Corporation, model name "GC2010 PLUS", column: product name "HP-5ms", Agilent Technologies, Inc., length 30 m x inner diameter 0.25 mm, film thickness 0.25 μm, conditions…carrier gas: He (constant pressure: 73.9 kPa), inlet temperature: 300 °C, detector: FID, detector temperature: 325 °C, column oven temperature: started at 80 °C, increased to 230 °C at 20 °C / min, increased to 240 °C at 1 °C / min, then increased to 325 °C at 20 °C / min, and held at 325 °C for 20 minutes). The reaction yield was calculated as the area percentage of the components detected by gas chromatography. As a result, the reaction yield of 2-(5-(aminomethyl)-5-ethyl-1,3-dioxan-2-yl)-2-methylpropan-1-amine, represented by formula (3), was 79.9%.

[0063] [Example 4] A curing agent composition for epoxy resin was prepared containing 48.2% by mass of the amino compound (spirobisamine) obtained in Example 1, 11.8% by mass of epoxy resin (bisphenol A diglycidyl ether jER828, manufactured by Mitsubishi Chemical Corporation), and 40% by mass of benzyl alcohol (manufactured by Kanto Chemical Co., Ltd.). Furthermore, 4.2 g of the above curing agent composition was mixed with 5.8 g of the main epoxy resin (bisphenol A diglycidyl ether jER828, manufactured by Mitsubishi Chemical Corporation) to prepare an epoxy resin composition. The active hydrogen equivalent (AHEW) of spirobisamine was calculated using the following formula (B), assuming a purity of 100% of the isolated compound (the same applies below), and was found to be 174. AHEW = (Molecular weight calculated from the identified chemical formula) ÷ (Number of active hydrogens [Number of functional groups of primary amine × 2 + Number of functional groups of secondary amine]) ... (B)

[0064] [Example 5] An epoxy resin curing agent composition was prepared containing 44.6% by mass of the amino compound (dioxanebisamine) obtained in Example 3, 15.4% by mass of epoxy resin (bisphenol A diglycidyl ether jER828, manufactured by Mitsubishi Chemical Corporation), and 40% by mass of benzyl alcohol (manufactured by Kanto Chemical Co., Ltd.). Furthermore, 4.8 g of the above curing agent composition was mixed with 5.2 g of the main epoxy resin (bisphenol A diglycidyl ether jER828, manufactured by Mitsubishi Chemical Corporation) to prepare an epoxy resin composition. The active hydrogen equivalent (AHEW) of dioxanebisamine was calculated from formula (B) above, assuming a purity of 100% for the isolated compound, and was found to be 135.

[0065] [Comparative Example 1] A curing agent composition for epoxy resin was prepared in the same manner as in Example 4, except that 39.4% by mass of 1,3-bis(aminomethyl)cyclohexane (1,3-BAC) (manufactured by Mitsubishi Gas Chemical Company, Inc.) and 20.6% by mass of an epoxy resin (bisphenol A diglycidyl ether jER828, manufactured by Mitsubishi Chemical Corporation) were used. Further, 3.5 g of the above curing agent composition was blended with 6.5 g of the main epoxy resin (bisphenol A diglycidyl ether jER828, manufactured by Mitsubishi Chemical Corporation) to prepare an epoxy resin composition. The active hydrogen equivalent (AHEW) of 1,3-BAC was 100.

[0066] [Comparative Example 2] A curing agent composition for epoxy resin was prepared in the same manner as in Example 4, except that 41.8% by mass of isophoronediamine (IPDA) (Vestamine IPD, manufactured by Evonik) and 18.2% by mass of an epoxy resin (bisphenol A diglycidyl ether jER828, manufactured by Mitsubishi Chemical Corporation) were used. Further, 3.6 g of the above curing agent composition was blended with 6.4 g of the main epoxy resin (bisphenol A diglycidyl ether jER828, manufactured by Mitsubishi Chemical Corporation) to prepare an epoxy resin composition. The active hydrogen equivalent (AHEW) of IPDA was 106.

[0067] [Characteristic Evaluation] <RCI Curing Rate> On a glass plate (25×348×2.0 mm, manufactured by Taiyu Kikai Co., Ltd.) as a substrate, the epoxy resin compositions obtained in Examples 4 and 5 and Comparative Examples 1 and 2 were applied using a 76-μm applicator under the conditions of 23°C and 50% R.H. to form a coating film. The glass plate with the coating film formed was set in a paint drying time measuring instrument (manufactured by Taiyu Kikai Co., Ltd.), and the time to reach each drying stage (tacky dry, semi-dry, fully dry) was measured based on the following criteria by observing the streak when the needle of the measuring instrument scratched the surface of the coating film. The shorter this time, the faster the curing rate (shorter pot life) of the epoxy resin composition. Tacky dry: The time when needle marks begin to remain on the glass plate Semi-dry (Dust Free): The time it takes for needle marks to emerge from within the paint film onto the surface. Complete drying (Dry through): The time it takes for needle marks to disappear from the paint film.

[0068] <Appearance of the coating film> On a zinc phosphate treated steel plate (Paltec Co., Ltd., SPCC-SD PB-N144, 0.8 × 70 × 150 mm) as a base material, the epoxy resin compositions obtained in Examples 4 and 5 and Comparative Examples 1 and 2 were applied using a 200 μm applicator under conditions of 23°C and 50% RH to form a coating film (thickness immediately after application: 200 μm). This coating film was stored under conditions of 23°C and 50% RH, and its appearance was visually observed after 1 day to evaluate its transparency and gloss according to the following criteria. Ex: Excellent, G: Good, F: Slightly Poor, P: Poor

[0069] <Paint film drying> The epoxy resin compositions obtained in Examples 4 and 5 and Comparative Examples 1 and 2 were applied to a substrate (zinc phosphate treated iron plate) in the same manner as described above for the appearance of the coating film, to form a coating film (thickness immediately after application: 200 μm). This coating film was stored under conditions of 23°C and 50% RH, and evaluated by touch after 1, 2, and 7 days according to the following criteria. Example: Excellent (Even when pressing the thumb with a force of approximately 50N, the coating does not become sticky, and no fingerprints are left behind.) G: Good (When pressing the thumb with a force of approximately 50N, the coating does not feel sticky, but fingerprints remain after touching it.) F: Acceptable (The coating becomes sticky when a thumb is pressed against it with a force of approximately 50N) P: Defective (The coating becomes sticky when a thumb is pressed against it with a force of approximately 5N)

[0070] <Pencil hardness> The epoxy resin compositions obtained in Examples 4 and 5 and Comparative Examples 1 and 2 were applied to a substrate (zinc phosphate treated iron plate) in the same manner as described above for the appearance of the coating film, to form a coating film (thickness immediately after application: 200 μm). This coating film was stored under conditions of 23°C and 50% RH, and after 7 days, the pencil hardness was measured in accordance with JIS K5600-5-4:1999.

[0071] <Waterproof spot resistance> In the same manner as described above for the appearance of the coating film, the epoxy resin compositions obtained in Examples 4 and 5 and Comparative Examples 1 and 2 were applied to the substrate (zinc phosphate treated iron plate) to form a coating film (thickness immediately after application: 200 μm). This coating film was stored at 23°C and 50% RH, and after 1, 2, and 7 days, 2 to 3 drops of pure water were dropped onto the surface of the coating film using a dropper, and the area was capped with a 50 mL screw-top bottle. After 24 hours, the water was wiped off, and the appearance was visually observed and evaluated according to the following criteria. Ex: No change, G: Slight change but good, F: Change present

[0072] <Chemical resistance> In the same manner as described above for the appearance of the coating, the epoxy resin compositions obtained in Examples 4 and 5 and Comparative Examples 1 and 2 were applied to the substrate (zinc phosphate treated iron plate) to form a coating (thickness immediately after application: 200 μm). After curing this coating at 23°C and 50% RH for 7 days, 2 to 3 drops of pure water or 5% saline solution were dropped onto the surface of the coating using a dropper, and the area was capped with a 50 mL screw-top bottle. After 1, 2, 3, and 4 weeks, the water or saline solution was wiped off, and the appearance was visually observed and evaluated according to the following criteria. Ex: No change G: The surface becomes rough. F: The surface is whitened, and slight rust spots are visible. P: The surface is rough, and rust spots are visible all over.

[0073] The evaluation results for each of the above properties are summarized in Table 1. As is clear from Table 1, the epoxy resin composition of the example was found to be significantly superior in long pot life, water spot resistance, and chemical resistance compared to the epoxy resin composition of the comparative example using a conventional epoxy resin curing agent. Furthermore, since the amino compounds of this disclosure other than those of the example also have a quaternary carbon at the β position of the amino group and an A portion containing an -O- bond attached to the carbon at the γ position of the amino group, it is presumed that they can achieve equivalent effects through a mechanism similar to that of the example.

[0074] [Table 1]

[0075] As described above, the amino compounds and methods for producing the same according to this disclosure, as well as the epoxy resin curing agents, epoxy resin compositions, and epoxy resin cured products using the same, have good coating film appearance and drying properties, and exhibit particularly superior long pot life, water spot resistance, and chemical resistance compared to conventional products. Therefore, they can be widely and effectively used in various applications where these properties are required. This application is based on Japanese Patent Application No. 2021-091643, filed on May 31, 2021, and its contents are incorporated herein by reference.

Claims

1. An amino compound represented by the following formula (1), having a quaternary carbon at the β-position of the amino group. 【Chemistry 1】 (In formula (1), A is one of the following (α), (β), and (γ); (α) A hydrocarbon group having 2 to 30 carbon atoms, which alone has at least one -O- bond attached to the carbon atom at the γ position of an amino group, and which may have substituents selected from hydroxyl groups and carbonyl groups. (β)R １ , R ２ , R ３ , and R ４ A hydrocarbon group having 2 to 30 carbon atoms, having at least one -O- bond attached to the carbon atom at the γ position of the amino group, and which may have substituents selected from hydroxyl groups and carbonyl groups, (γ)R １ or R ２ , and R ３ or R ４ A hydrocarbon group having 2 to 30 carbon atoms, which, in a bonded state, has at least one -O- bond attached to the carbon atom at the γ position of the amino group, and may have substituents selected from hydroxyl groups and carbonyl groups. R １ , R ２ , R ３ , and R ４ is each independently a hydrocarbon group having 1 to 10 carbon atoms which may have a substituent selected from a hydroxyl group and a carbonyl group (however, excluding those bonded to A).

2. A, on its own, has a dioxane structure, or A is R １ , R ２ , R ３ , and R ４ In a state of being bonded to any one of the following, it has a dioxane structure, or A is R １ or R ２ , and R ３ or R ４ In a bonded state, it has a dioxane structure, The amino compound according to claim 1.

3. The amino compound according to claim 1 or 2, represented by the following formula (2) or formula (3). 【Chemistry 2】

4. A method for producing an amino compound, comprising the step of aminating a polyol compound represented by the following formula (1a) in the presence of a catalyst and ammonia to obtain an amino compound represented by the following formula (1) having a quaternary carbon at the β-position of the amino group. 【Transformation 3】 (In equations (1) and (1a), A is one of the following (α), (β), and (γ); (α) A hydrocarbon group having 2 to 30 carbon atoms, which alone has at least one -O- bond attached to the carbon atom at the γ position of an amino group, and which may have substituents selected from hydroxyl groups and carbonyl groups. (β)R １ , R ２ , R ３ , and R ４ A hydrocarbon group having 2 to 30 carbon atoms, having at least one -O- bond attached to the carbon atom at the γ position of the amino group, and which may have substituents selected from hydroxyl groups and carbonyl groups, (γ)R １ or R ２ , and R ３ or R ４ A hydrocarbon group having 2 to 30 carbon atoms, which, in a bonded state, has at least one -O- bond attached to the carbon atom at the γ position of the amino group, and may have substituents selected from hydroxyl groups and carbonyl groups. R １ , R ２ , R ３ , and R ４ Each of these is a hydrocarbon group having 1 to 10 carbon atoms, which may independently have substituents selected from hydroxyl groups and carbonyl groups (except those bonded to A).

5. A, on its own, has a dioxane structure, or A is R １ , R ２ , R ３ , and R ４ In a state of being bonded to any one of the following, it has a dioxane structure, or A is R １ or R ２ , and R ３ or R ４ In a bonded state, it has a dioxane structure, A method for producing an amino compound according to claim 4.

6. A step of aminating a polyol compound represented by the following formula (2a) in the presence of a catalyst and ammonia to obtain an amino compound represented by the following formula (2), or, A step of obtaining an amino compound represented by formula (3) below by aminating a polyol compound represented by formula (3) below in the presence of a catalyst and ammonia, A method for producing amino compounds containing [specific compound name]. 【Chemistry 4】

7. A curing agent for epoxy resins comprising the amino compound described in any one of claims 1 to 3.

8. An epoxy resin composition comprising the epoxy resin curing agent described in claim 7 and an epoxy resin.

9. An epoxy resin cured product obtained by curing the epoxy resin composition according to claim 8.

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