Epoxy curing agent and use thereof

Abstract

An aqueous amine curing agent, a method of making such a curing agent, and a curable amine-epoxy composition. The curing agent comprises the reaction product of a first polyamine containing primary amine functionality, wherein the ratio of moles of polyamine / equivalents of polyepoxide is sufficient to provide an amine-terminated intermediate (a) comprising an adduct of about two moles of polyamine and one mole of polyepoxide, then reacting intermediate (a) with urea or formaldehyde to provide an amine-terminated intermediate (b), then reacting intermediate (b) with a second polyepoxide to provide an amine-terminated intermediate (c), terminating intermediate (c) with a monoepoxide composition comprising an aromatic glycidyl ether or an alkyl-substituted aromatic glycidyl ether or a combination of both to form a polyamine-polyepoxide adduct, and contacting the polyamine-polyepoxide adduct with a second polyamine having two or more active amine hydrogens.

Description

Technical Field

[0001] This invention relates to curing agents for epoxy resins suitable for use in aqueous applications, curable amine-epoxy compositions derived from such curing agents, and articles prepared from such compositions. The invention particularly relates to polyamine-epoxy adducts as curing agents. Background Technology

[0002] Due to increasingly stringent environmental regulations, particularly regarding the reduction of volatile organic compounds (VOCs), there is a driving force within the coatings industry to shift from traditional solvent-based systems to waterborne coatings. While waterborne polyepoxide coating systems are known, several drawbacks exist associated with these systems. For example, many aqueous systems exhibit poor moisture resistance in thin-film metallic coatings, leading to loss of adhesion and premature corrosion failure. Additionally, most systems have high amine hydrogen equivalent weight (AHEW), resulting in high dosage requirements. Several commercial waterborne epoxy coating compositions may have too short a working life, thus rendering the systems unusable in certain industrial applications.

[0003] U.S. Patent No. 9,550,912 describes a water-dilutable polyamine adduct formed by reacting a first polyamine with bisphenol diglycidyl ether and further formulating it with a second polyamine to form an aqueous curing agent solution with low dosage when curing epoxides.

[0004] U.S. Patent No. 6,245,835 describes an amino-epoxy adduct curing agent prepared by reacting a polyoxyalkylene diamine with a polyepoxide and a polyoxyalkylene diol diglycidyl ether, and emulsifying the reaction product in water.

[0005] U.S. Patent No. 5,508,324 describes an aqueous curing agent composition of a polyamine-epoxy adduct, wherein the polyamine-epoxy adduct is end-capped with an aromatic monoepoxide to improve compatibility between the resin and the curing agent.

[0006] U.S. Patent No. 5,246,984 describes the formation of a water-compatible polyamine adduct by reacting an amine-terminated adduct with a resin-compatible adduct. Both adducts are products of the reaction of polyamines with a mixture of monoepoxides and polyepoxides. The resulting mixture is further reacted with formaldehyde to reduce the primary amine content of the product.

[0007] U.S. Patent No. 5,032,629 describes the preparation of a water-compatible polyamine-epoxy adduct by reacting a poly(epoxy)monoamine or diamine with a polyepoxide to form an intermediate, followed by reacting the intermediate with an excess of polyamine.

[0008] U.S. Patent No. 4,608,405 describes a curing agent based on a polyamine adduct, which is formed by reacting a mixture of a diglycidyl ether of a polyether polyol and bisphenol A, wherein each primary amine in the resulting reaction product is further reacted with a monoepoxide or a monocarboxylic acid.

[0009] US Patent No. 4,246,148 discloses a polyamine-terminated difunctional epoxy adduct that is terminated with various monoepoxides or acrylonitrile.

[0010] US Patent No. 4,197,389 discloses a curing agent prepared by reacting at least one polyepoxide compound with at least one polyalkylene polyether polyol to form an adduct, followed by reacting the adduct with a polyamine. Summary of the Invention Invention Overview

[0012] This invention discloses an aqueous amine curing agent, a method for preparing such a curing agent, and a curable amine-epoxy composition. The curing agent (A) according to the invention comprises a reaction product of a first polyamine and a first polyepoxide, the first polyamine containing a primary amine functional group, and the first polyepoxide having an epoxide equivalent weight (EEW) of 130 to about 500, wherein the ratio of the number of moles of the polyamine to the number of EEW equivalents of the polyepoxide is sufficient to provide an amine-terminated intermediate (a), which comprises an adduct of about two moles of the polyamine and one mole of the polyepoxide. The intermediate (a) is then reacted with urea or formaldehyde to provide an amine-terminated intermediate (b), and then the intermediate is further reacted with urea or formaldehyde. (b) Reaction with a second polyepoxide to provide an amine-terminated intermediate (c), the second polyepoxide having an EEW of 200 to about 1000, the intermediate (c) being terminated with a monoepoxide composition to form a polyamine-polyepoxide adduct, the monoepoxide composition comprising an aromatic glycidyl ether or an alkyl-substituted aromatic glycidyl ether or a combination thereof, and contacting the polyamine-polyepoxide adduct with a second polyamine having two or more active amine hydrogens, wherein the second polyamine is different from the first polyamine.

[0013] The curing agent (A) of the present invention has an amine hydrogen equivalent weight of 80 to 400, or 100 to 300, or 100 to 250, or 100 to 200, and contains at least 40% by weight, or 50% by weight, or 60% by weight, or 65% by weight, or 70% by weight, or 80% by weight of a non-volatile organic compound.

[0014] In one aspect of the invention, the curing agent comprises a contact product of the following substances: a polyamine-polyepoxide adduct made of a first polyamine and a first polyepoxide, a second polyamine having two or more active amine hydrogens, different from the first polyamine, and water. The water solubility of the curing agent can be improved by acid-salting.

[0015] The curing agent can be used in an aqueous system to cure solid epoxy resin dispersions, liquid epoxy resins, or liquid epoxy resin emulsions. Therefore, another aspect of the invention is a curable amine-epoxy composition comprising a reaction product of a curing agent (A) and a polyepoxide resin composition (B), wherein the curing agent comprises a contact product of a polyamine-polyepoxide adduct made of a first polyamine and a first polyepoxide, and a second polyamine having two or more active amine hydrogens, different from the first polyamine, and the polyepoxide resin composition comprises at least one multifunctional epoxy resin having at least two epoxide groups per molecule.

[0016] Another aspect of the invention is a curable amine-epoxy composition comprising a curing agent and a reaction product of a polyepoxide resin composition, wherein the curing agent comprises a contact product of a polyamine-polyepoxide adduct made of a first polyamine and a first polyepoxide, a second polyamine having two or more active amine hydrogens, different from the first polyamine, and water, and the polyepoxide resin composition comprises at least one multifunctional epoxy resin having at least two epoxide groups per molecule.

[0017] Articles manufactured from the amine-epoxy compositions disclosed herein include, but are not limited to, adhesives, coatings, primers, sealants, curing compounds, building products, flooring products, or composite products. Furthermore, such coatings, primers, sealants, or curing compounds can be applied to metallic or cementitious substrates possessing excellent physical and chemical properties. Attached Figure Description

[0018] Figure 1 The results of differential performance tests for formulation 3, formulation 4, comparative formulation 5, and comparative formulation 6 of the present invention are shown. Invention Details

[0020] According to the present invention, the aqueous curing agent comprises a reaction product of a first polyamine and a first polyepoxide, the first polyamine containing a primary amine functional group, and the first polyepoxide having an epoxide equivalent weight (EEW) of 130 to about 500, wherein the ratio of the number of moles of the polyamine to the number of EEWs of the polyepoxide is sufficient to provide an amine-terminated intermediate (a), the intermediate (a) comprising an adduct of about two moles of the polyamine and one mole of the polyepoxide, and then the intermediate (a) is reacted with urea or formaldehyde to provide an amine-terminated intermediate (b), and then the intermediate is further reacted with urea or formaldehyde. The body (b) reacts with a second polyepoxide to provide an amine-terminated intermediate (c), the second polyepoxide having an EEW of 200 to about 1000, the intermediate (c) is terminated with a monoepoxide composition to form a polyamine-polyepoxide adduct, the monoepoxide composition comprising an aromatic glycidyl ether or an alkyl-substituted aromatic glycidyl ether or a combination thereof, and the polyamine-polyepoxide adduct is contacted with a second polyamine having two or more active amine hydrogens, wherein the second polyamine is different from the first polyamine.

[0021] In a preferred embodiment, excess of the first polyamine is removed from intermediate (a) by distillation to produce an amine-terminated adduct intermediate (ai), and then intermediate (ai) is reacted with urea or formaldehyde to form an amine-terminated intermediate (b).

[0022] In another preferred embodiment, the first polyamine has an amine hydrogen equivalent weight (AHEW) of about 12 to about 50.

[0023] In another preferred embodiment, intermediate (a) comprises an adduct of about two moles of polyamine and one mole of polyepoxide.

[0024] In another preferred embodiment, the amount of urea or formaldehyde reacting with intermediate (a) is about 0.5% to 8% by weight relative to the total weight of intermediate (a).

[0025] In another preferred embodiment, the amount of the second polyepoxide reacting with intermediate (b) is about 1% to 30% by weight relative to the total weight of intermediate (b).

[0026] In another preferred embodiment, the amount of the monoepoxide composition reacting with intermediate (c) is about 1% to 25% by weight relative to the total weight of intermediate (c).

[0027] In another preferred embodiment, the second polyamine has an amine hydrogen equivalent weight (AHEW) of about 12 to about 100.

[0028] In another preferred embodiment, the amount of the polyamine-polyepoxide adduct in the curing agent is 70% to 98% by weight relative to the total weight of the curing agent.

[0029] In another preferred embodiment, the amount of the second polyamine in the curing agent is about 2% to 30% by weight relative to the total weight of the curing agent.

[0030] In one embodiment, the aqueous curing agent comprises a contact product of the following substances: a polyamine-polyepoxide adduct made of a first polyamine and a first polyepoxide, and a second polyamine having two or more active amine hydrogens, different from the first polyamine, wherein the polyamine-polyepoxide adduct comprises a reaction product of the first polyamine and the first polyepoxide, the first polyamine containing a primary amine functional group, the first polyepoxide having an epoxide equivalent weight (EEW) in the range of 130 to about 2000, wherein the first polyamine may have an amine hydrogen equivalent weight (AHEW) in the range of about 12 to about 50, and the first polyepoxide has an epoxide equivalent weight (EEW) in the range of 130 to about 500. The ratio of the first polyamine to the first polyepoxide is greater than one mole of polyamine per mole of epoxide to produce an amine-terminated adduct intermediate (a), which comprises an adduct of about two moles of polyamine and one mole of polyepoxide. The intermediate (a) is further reacted with urea or formaldehyde by reacting about 0.5% to 8% of the total weight of the intermediate (a) to produce an amine-terminated intermediate (b). The intermediate (b) is further advanced by: [further process described in the original text]. An amount of about 1% to 30% by weight reacts with a polyepoxide having an epoxide equivalent weight (EEW) in the range of 200 to 1000 to produce an amine-terminated adduct intermediate (c). The intermediate (c) is then capped with a monoepoxide composition by reacting about 1% to 25% by weight of the total weight of the intermediate (c) to produce a polyamine-polyepoxide adduct (i), the monoepoxide composition comprising an aromatic glycidyl ether or an alkyl-substituted aromatic glycidyl ether or a combination of both. The polyamine-polyepoxide adduct (i) is further blended with a second polyamine (ii) having an AHEW of 12 to 100. The amount of adduct (i) in the curing agent is 70% to 98% by weight relative to the total weight of the curing agent, and the amount of the second polyamine (ii) in the curing agent is about 2% to 30% by weight relative to the total weight of the curing agent.

[0031] The term "contact product" is used herein to describe a composition in which components are contacted together in any order, in any manner, for any duration. For example, the components may be contacted by blending or mixing. Furthermore, contact of any components may occur in the presence or absence of any other components of the composition or formulation described herein. The incorporation of additional materials or components may be accomplished by any method known to those skilled in the art.

[0032] The first polyamine, which can be used to prepare the polyamine-polyepoxide adduct (i), and the second polyamine, which can be used to prepare the curing agent, (ii) each contain at least two nitrogen atoms per molecule and at least two, preferably at least three, active hydrogen atoms attached to the nitrogen atoms per molecule. Useful polyamines include aliphatic, polyether, aryliphatic, aromatic, alicyclic, and heterocyclic diamines and polyamines. Examples include polyalkylene polyamines, especially polyethylene polyamines (ethylenediamine, diethylenetriamine, triethylenetetramine, pentaethylenehexamine, and the like), 1,2-propanediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,3-pentanediamine, 1,6-hexanediamine, 3,3,5-trimethyl-1,6-hexanediamine, 2-methyl-1,5-pentanediamine, such as N-3-aminopropylethylenediamine (N3), N,N'-bis(3-aminopropyl)ethylenediamine (N4, which can be used as... 2655 (from Evonik Corporation), N,N,N'-tris(3-aminopropyl)ethylenediamine (N5), N-3-aminopropyldiethylenetriamine (N4); N-3-aminopropyl-[N'-3-[N-3-aminopropyl]aminopropyl]diethylenetriamine (N6); N,N'-bis(3-aminopropyl)diethylenetriamine (N5); N,N-bis(3-aminopropyl)diethylenetriamine (N5); N,N,N'-tris(3-aminopropyl)diethylenetriamine (N6); N,N',N'-tris(3-aminopropyl)diethylenetriamine (N6); N,N,N',N'-tetra(3-aminopropyl) Diethylenetriamine (N7); N,N-bis(3-aminopropyl)-[N'-3-[N-3-aminopropyl]aminopropyl]-[N'-3-aminopropyl]diethylenetriamine (N8); N-3-aminopropyl-[N'-3-[N-3-[N-3-aminopropyl]aminopropyl]-[N'-3-aminopropyl]diethylenetriamine (N7); polypropylene amines, such as propylenediamine, dipropylenetriamine, tripropylenetetramine, and aminopropylated propylenediamines, such as N,N,N'-tris(3-aminopropyl)-1,3-diaminopropane and analogs, araliphatic, such as m-phenylenediamine, polyetheramines or poly(epoxyalkyl)amines, including those containing... The name is purchased from Huntsman Corporation for diamines and triamines, for example D-230 D-400 D-2000 D-4000 T-403, EDR-148 EDR-192 C-346 ED-600 ED-900 ED-2001 and its analogues, or bis(3-aminopropyl)diethylene glycol ether (which can be used as...) 1922A (from Evonik Corporation) or combinations thereof; alicyclic polyamines, such as 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, isophorone diamine, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylmethane, 2,4'-diaminodicyclohexylmethane, hydrogenated o-toluenediamine, hydrogenated m-toluenediamine, hydrogenated m-phenylenediamine (commercially known as 1,3-BAC), mixtures of methylene-bridged poly(cyclohexyl aromatic)amines (also known as MBPCAA or MPCA), as described in U.S. Patent No. 5,280,091; aromatic amines, such as phenylenediamine, 4,4'-diaminodiphenylmethane, toluenediamine, bis(p-aminophenyl)methane and bis(p-aminophenyl)sulfone, heterocyclic amines, such as aminoethylpiperazine, and polyaminoamides. A mixture of the above-mentioned amines may also be used. The first polyamine is an amine different from the second polyamine.

[0033] Preferred first polyamines that can be used to prepare the polyamine-polyepoxide adduct (i) of the present invention are polyethylene polyamines, namely ethylenediamine (EDA), diethylenetriamine (DETA), and especially triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA) and mixtures thereof, and aminopropylated ethylenediamines, such as N-3-aminopropylethylenediamine (N3), N,N'-bis(3-aminopropyl)ethylenediamine (N4, which can be used as... 2655 is derived from Evonik Corporation), N,N,N'-tris(3-aminopropyl)ethylenediamine (N5), N-3-aminopropyldiethylenetriamine (N4); N-3-aminopropyl-[N'-3-[N-3-aminopropyl]aminopropyl]diethylenetriamine (N6); N,N'-bis(3-aminopropyl)diethylenetriamine (N5); N,N-bis(3 N,N,N'-tris(3-aminopropyl)diethylenetriamine (N5); N,N,N'-tris(3-aminopropyl)diethylenetriamine (N6); N,N',N'-tris(3-aminopropyl)diethylenetriamine (N6); polypropylene amines, such as propylenediamine, dipropylenetriamine, tripropylenetetramine, and aminopropylated propylenediamines, such as N,N,N'-tris(3-aminopropyl)-1,3-diaminopropane and analogs.

[0034] The polyepoxides used to prepare polyamine-polyepoxide adducts (i) contain about two or more 1,2-epoxy groups per molecule. Examples include epoxides of polyunsaturated organic compounds, oligomers of epichlorohydrins, glycidyl derivatives of hydantoin and hydantoin derivatives, glycidyl ethers of polyols, glycidyl derivatives of triazines, and glycidyl ethers of diphenols. Epoxides of polyunsaturated organic compounds include divinylbenzene, cyclohexadiene, cyclooctadiene, dicyclopentadiene, cyclododecadiene, cyclododecanetriene, isoprene, 1,5-hexadiene, butadiene, polybutadiene, polyisoprene, and the like.

[0035] Useful polyepoxides are glycidyl ethers of polyols (including aliphatic or alicyclic alcohols), such as the glycidyl ethers of neopentyl glycol, ethylene glycol, propylene glycol and butanediol, trimethylolpropane, 2-ethyl-1,3-hexanediol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,6-hexanediol, 1,4-butanediol, 1,3-propanediol, 1,5-pentanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, glycerol, sorbitol, pentaerythritol and the like. Glycidyl ethers of polymeric polyols are also suitable, and include glycidyl ethers of the following substances: polyethylene glycol, polypropylene glycol, polybutane glycol, various copolymers of ethylene oxide, propylene oxide and butane oxide, polyvinyl alcohol, polyallyl alcohol and the like. The glycidyl derivatives include triglycidyl isocyanurate.

[0036] Useful polyepoxides also include glycidyl ethers of polyphenols, such as glycidyl ethers of diphenols, including resorcinol, hydroquinone, bis(4-hydroxy-3,5-difluorophenyl)-methane, 1,1-bis-(4-hydroxyphenyl)-ethane, 2,2-bis-(4-hydroxy-3-methylphenyl)-propane, 2,2-bis-(4-hydroxy-3,5-dichlorophenyl)-propane, 2,2-bis-(4-hydroxyphenyl)-propane (more commonly referred to as bisphenol A), and bis-(4-hydroxyphenyl)-methane (more commonly referred to as bisphenol F, which may contain varying amounts of the 2-hydroxyphenyl isomer) and the like. Upgraded diphenols having the following structures are also useful:

[0037]

[0038] Where m is a number between 0 and 10, and R1 is a divalent hydrocarbon group of a diphenol (such as those listed above). Materials according to this formula can be prepared by polymerizing a mixture of a diphenol and epichlorohydrin, or by upgrading a mixture of diglycidyl ethers of a diphenol. The material is invariably a mixture characterized by the average value of m, which is not necessarily an integer. Polymer-type materials having an average value of m between 0 and 7 are preferred.

[0039] Other polyepoxides that can be used in this invention include epoxy linear phenolic varnish resins, which are glycidyl ethers of linear phenolic varnish resins. Linear phenolic varnish resins are reaction products of monoaldehydes or dialdehydes (most commonly formaldehyde) with monophenols or polyphenolic materials. Examples of monophenolic materials that can be used include phenol, cresol, p-tert-butylphenol, nonylphenol, octylphenol, other alkyl and phenyl-substituted phenols and the like. Polyphenolic materials include various diphenols, including bisphenol A and the like. Aldehydes used in linear phenolic varnishes include formaldehyde, glyoxal, and higher aldehydes up to about C4. The linear phenolic varnishes are typically complex mixtures with different hydroxyl functionalities. For the purposes of this invention, a useful functionality range is from about 2 to about 4.

[0040] Other polyepoxides that can be used in this invention include epoxy resins prepared from epihaloalcohols and amines, wherein suitable amines may be diaminodiphenylmethane, aminophenol, phenylenediamine, aniline and the like, or combinations thereof; or resins prepared from epihaloalcohols and carboxylic acids, wherein suitable carboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, tetrahydro- and / or hexahydrophthalic acid, methylenetetrahydrophthalic acid, methylhexahydrophthalic acid and the like, and combinations thereof.

[0041] Preferred polyepoxides are diglycidyl ethers of bisphenol-A (DGEBA) and bisphenol-F, wherein m ranges from about 0 to about 7, and are epoxy linear phenolic varnishes derived from phenol and formaldehyde having an average functionality of about 2 to about 4. Most preferred are diglycidyl ethers of bisphenol-A and bisphenol-F.

[0042] The reaction product of intermediate (a) can be prepared over a wide range of reactant ratios. The amine must be used in sufficient excess (more than one mole of polyamine per epoxide) to minimize chain extension and substantially provide an amine-terminated adduct of two molecules of polyamine and one molecule of polyepoxide, avoiding unacceptably high viscosity in the final product. The reactant ratio can be 1.5 to 10 or more moles of polyamine per epoxide, preferably 2 to 6 per epoxide, ideally about 4 moles. Excess polyamine should be removed, preferably by vacuum distillation of volatile polyamine, to produce a separate adduct of two molecules of polyamine and one molecule of polyepoxide. Excess polyamine should be removed to the extent that intermediate (a) has a free polyamine content of <10% by weight, preferably <7% by weight, or <5% by weight, or <4% by weight.

[0043] The polyepoxide resin used for the adduct intermediate (a) is one of those types of polyepoxides taught above as suitable for preparing intermediate (a) but having an EEW of 130-500, preferably 180-500, and more preferably 180-300. It is preferred to use a type 1 solid epoxy resin to upgrade intermediate (a). Sufficient properties can be obtained if a liquid resin is used for upgrading; however, a high level of secondary adsorption is required to achieve the level of compatibility observed through adsorption with type 1 resins. High molecular weight (EEW ​​> 1000) resins can be used in this invention, but such materials may have an adverse effect on the viscosity of the final product.

[0044] Intermediate (a), preferably as a separate adduct, is further reacted with urea or formaldehyde by reacting about 0.5% to 8% by weight of the total weight of intermediate (a) to obtain amine-terminated intermediate (b). This reaction step reduces the primary amine content, increases the molecular weight, and also improves water compatibility and solubility. This approach is more advantageous for achieving high molecular weights than preparing intermediate (a) from the first polyamine with a high molecular weight polyepoxide, and also provides lower viscosity.

[0045] Intermediate (b) is further upgraded with a polyepoxide, preferably a type I solid epoxy resin, to produce intermediate (c). The polyepoxide resin used for adduct intermediate (a) is one of those types of polyepoxides taught above having an EEW of 200-1000, most preferably 400-1000. High molecular weight (EEW>2000) can be used in this invention, but such materials may have an adverse effect on the viscosity of the final product. The reactant ratio results in an excess of intermediate (b), i.e., the ratio of polyepoxide to intermediate (b) is about 1% to 30% by weight, or 0.0004 to 0.12 moles of epoxy resin per mole of intermediate (b). At low adsorption ratios (<1% by weight or <0.0004 moles), the final product does not have sufficient compatibility with the epoxy resin dispersion, and the coating exhibits a poor surface appearance. Higher adsorption ratios (>30% by weight or >0.12 moles) have an adverse effect on the viscosity of the final product.

[0046] The intermediate (c) is then capped with a monoepoxide composition comprising an aromatic glycidyl ether and / or an alkyl-substituted aromatic glycidyl ether in a ratio of at least one mole of aromatic monoepoxide for each primary amine in the intermediate (c) to produce a polyamine-polyepoxide adduct (i).

[0047] Specific monoepoxide end-capping agents that can be used in this invention are aromatic and alkyl-substituted aromatic monoglycidyl ethers or styrene oxide. The aromatic monoglycidyl ethers include phenyl glycidyl ethers (PGE) and alkylphenyl glycidyl ethers containing C1 to C15 alkyl groups, such as tolyl glycidyl ether (CGE), tert-butylphenyl glycidyl ether, nonylphenyl glycidyl ether, and glycidyl ethers of cashew nut oil, which can be used as Cardolite, sold by Cardolite Corporation in Pennsylvania. TM NC513 is commercially available. Cardolite NC513 is a phenyl glycidyl ether containing a C15 alkyl group attached to an aromatic ring. Other monoglycidyl ethers, such as aliphatic glycidyl ethers including butyl glycidyl ether, can also be used in combination, provided that at least 65% of the aromatic monoglycidyl ethers are used.

[0048] The purpose of end-capping the adduct mixture is to reduce primary amines, improve system compatibility, and increase hydrophobicity and flexibility. It can also be used to extend the pot life. The level of the end-capping agent must be such that 1% to 25% by weight of the total weight of intermediate (c) reacts. Levels below this will result in coating formulations with a shorter than suitable pot life. The end-capping levels used in embodiments of the invention range from 3% to 25%, with a preferred level of 10% to 25%.

[0049] The adduct (i) is further blended with a second polyamine (ii) having an AHEW of from about 12 to about 100. The amount of the adduct (i) in the curing agent is from 70% to 98% by weight relative to the total weight of the curing agent, or from 50% to 90% by weight, or from 60% to 90% by weight relative to the total weight of the curing agent. The amount of the second polyamine (ii) in the curing agent is from about 2% to 30% by weight relative to the total weight of the curing agent, or from 4% to 30% by weight, or from 4% to 25% by weight, or from 4% to 20% by weight relative to the total weight of the curing agent.

[0050] Suitable second polyamines (ii) for preparing the curing agents of the present invention are taught above. Preferred types of second polyamines (ii) are polyetheramines or poly(epoxyalkylene)amines, for example... D-230 D-400 D-2000 D-4000 T-403, EDR-148 EDR-192 C-346 ED-600 ED-900 ED-2001 and analogues, bis(3-aminopropyl)diethylene glycol ether (can be used as...) 1922A (derived from Evonik Corporation) or combinations thereof; and alicyclic polyamines, such as 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, isophorone diamine, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylmethane, 2,4'-diaminodicyclohexylmethane, hydrogenated o-toluenediamine, hydrogenated m-toluenediamine, hydrogenated m-phenylenediamine (commercially known as 1,3-BAC), mixtures of methylene-bridged poly(cyclohexyl aromatic)amines (also known as MBPCAA or MPCA), and aryliphatic amines, such as m-phenylenediamine.

[0051] In some preferred embodiments, the second polyamine (ii) used to prepare the curing agent of the present invention is a polyetheramine. D-230 D-400 D-2000 T-403, bis(3-aminopropyl)diethylene glycol ether (can be used as...) 1922A (from Evonik Corporation); or alicyclic polyamines, such as 1,2-diamino-cyclohexane, isophorone diamine, 4,4'-diaminodicyclohexylmethane, hydrogenated m-phenylenediamine (commercially known as 1,3-BAC), mixtures of methylene-bridged poly(cyclohexyl aromatic)amines (also known as MBPCAA or MPCA), and aryliphatic amines, such as m-phenylenediamine.

[0052] Water can be added to the mixture of adduct (i) and the second polyamine (ii) to produce the curing agent of the present invention. The amount of water can range from 5% to 50% by weight, or 5% to 40% by weight, or 5% to 30% by weight, or 5% to 20% by weight, or 5% to 15% by weight of the curing agent. In a preferred embodiment, the aqueous curing agent is a clear aqueous solution in which no visible particles are present upon visual inspection.

[0053] Water solubility or dispersibility can be achieved by salting the polyamine-polyepoxide adduct (i) and the second polyamine (ii) with a volatile or non-volatile organic or inorganic acid. The degree of salt formation is selected to control many factors as needed, such as curing temperature, curing speed, pot life, and dispersibility. Typically, the amine groups are reacted with sufficient acid to obtain a salt formation from about 2% to about 40%, or about 2% to about 30%, or about 2% to about 25%, or about 2% to about 20%, or about 3% to about 20%, or about 2% to about 15%. The term "salinity" refers to the number of amine nitrogen equivalents reacting with the acid, expressed as a percentage of the total amine nitrogen equivalents in the system.

[0054] Suitable acids include volatile and nonvolatile acids, as well as organic and inorganic acids. Volatile acids will evaporate substantially completely at the drying and curing temperatures. The organic acids can be aliphatic, alicyclic, or heterocyclic, and can be saturated or unsaturated with up to 10 carbon atoms. Representative organic acids include acetic acid, formic acid, propionic acid, butyric acid, acrylic acid, methacrylic acid, cyclohexanoic acid, succinic acid, sebacic acid, and aminosulfonic acid. The organic acids will preferably be aliphatic monocarboxylic acids with up to 4 carbon atoms. Representative volatile inorganic acids include hydrochloric acid and hydrobromic acid. Preferred acids are acetic acid, formic acid, and propionic acid.

[0055] Another aspect of the present invention discloses a method for preparing an epoxy curing agent composition by means of the following process: (i) reacting a first polyamine and a first polyepoxide, the first polyamine containing a primary amine functional group, the first polyepoxide having an epoxide equivalent weight (EEW) in the range of 130 to about 500, wherein the ratio of the number of moles of polyamine to the number of equivalents of polyepoxide is sufficient to provide an amine-terminated intermediate (a), wherein the ratio of the first polyamine to the first polyepoxide is greater than one mole of polyamine per mole of epoxide; (ii) reacting the intermediate (a) with urea or formaldehyde to form an amine-terminated intermediate (b); (iii) The intermediate (b) is reacted with a second polyepoxide to form an amine-terminated intermediate (c), the second polyepoxide having an epoxide equivalent (EEW) in the range of 200 to 1000; (iv) the intermediate (c) is terminated with a monoepoxide composition to form a polyamine-polyepoxide adduct, the monoepoxide composition comprising an aromatic glycidyl ether or an alkyl-substituted aromatic glycidyl ether or a combination thereof; and (v) the polyamine-polyepoxide adduct is contacted with a second polyamine having two or more active amine hydrogens, wherein the second polyamine is different from the first polyamine.

[0056] In a preferred embodiment, the method for preparing the epoxy curing agent composition further includes step (ia), wherein excess of the first polyamine is removed from the intermediate (a) by distillation to produce an amine-terminated adduct intermediate (ai), and then the intermediate (ai) is reacted with urea or formaldehyde in step (ii) to form an amine-terminated intermediate (b).

[0057] In another preferred embodiment of the method, the first polyamine has an amine hydrogen equivalent weight (AHEW) of about 12 to about 50.

[0058] In another preferred embodiment of the method, the intermediate (a) comprises an adduct of about two moles of polyamine and one mole of polyepoxide.

[0059] In another preferred embodiment of the method, the amount of urea or formaldehyde reacting with intermediate (a) is about 0.5% to 8% by weight relative to the total weight of intermediate (a).

[0060] In another preferred embodiment of the method, the amount of the second polyepoxide reacting with intermediate (b) is about 1% to 30% by weight relative to the total weight of intermediate (b).

[0061] In another preferred embodiment of the method, the amount of the monoepoxide composition reacting with intermediate (c) is about 1% to 25% by weight relative to the total weight of intermediate (c).

[0062] In another preferred embodiment of the method, the second polyamine has an amine hydrogen equivalent weight (AHEW) of about 12 to about 100.

[0063] In another preferred embodiment of the method, the amount of the polyamine-polyepoxide adduct in the curing agent is 70% to 98% by weight relative to the total weight of the curing agent.

[0064] In another preferred embodiment of the method, the amount of the second polyamine in the curing agent is about 2% to 30% by weight relative to the total weight of the curing agent.

[0065] The polyamine-polyepoxide adduct (i) is prepared by a multi-step method, wherein intermediates (a) and (c), and the final capped intermediate (c), are prepared by an amine-epoxide adduction reaction, and can be carried out over a wide temperature range from about 40°C to 200°C, or 60°C to 150°C, or 60°C to 120°C. The reaction can be carried out undiluted or in the presence of a suitable solvent. The preferred solvent is a solvent suitable for formulations used in the final product application, such as those described below. Preferred solvents are glycol ethers described below, and the most preferred solvent is 1-methoxy-2-propanol. In the preparation of intermediate (a), excess first polyamine is removed by vacuum distillation so that the free first polyamine remains below 10% by weight relative to the weight of intermediate (a). The vacuum distillation can be carried out over a wide temperature range from 80°C to 300°C, or from 80°C to 260°C, or from 100°C to 260°C.

[0066] Intermediate (b) is prepared by reacting intermediate (a) with urea or formaldehyde to reduce the primary amine content and increase the molecular weight, thereby increasing the solubility of intermediate (b) in water and extending the pot life of the curing agent. This step can be carried out over a wide temperature range and under vacuum. For the urea reaction, the reaction can be carried out at temperatures between 80°C and 250°C, or between 80°C and 220°C, or between 80°C and 200°C, or between 80°C and 150°C. For the formaldehyde reaction, the reaction can be carried out at temperatures between 25°C and 150°C, or between 25°C and 130°C, or between 25°C and 110°C, or between 40°C and 150°C, or between 40°C and 110°C.

[0067] The water solubility or dispersibility of the curing agent can be further improved by salting with organic or inorganic salts. The amine groups of the curing agent react with sufficient acid to obtain about 2% to about 40%, or about 2% to about 30%, or about 2% to about 25%, or about 2% to about 20%, or about 3% to about 20%, or about 2% to about 15% of the total amine nitrogen equivalent in the system.

[0068] The curing agent can be manufactured in a water-soluble glycol ether, and the solid content can be adjusted to at least 40%, 50%, 60%, 65%, or 80% by weight of the total weight of the curing agent by adding water and additional glycol ether.

[0069] The curing agent of the present invention has an amine hydrogen equivalent weight of 80 to 400, or 90 to 300, or 100 to 300, or 100 to 250, or 100 to 200.

[0070] This disclosure also provides the use of the curing agent (A) as a hardener for epoxy resins. Therefore, another aspect of the invention is a curable amine-epoxy composition comprising the reaction product of a curing agent (A) and a polyepoxide resin composition (B), said polyepoxide resin composition (B) comprising at least one multifunctional polyepoxide resin having at least two epoxide groups per molecule. The polyepoxide resin composition may be liquid or solid, and preferably solid, and has a solid-based epoxide equivalent weight (EEW) of from about 150 to about 2000, preferably from about 170 to about 1000. Typically, the resin mixture will consist of two or more polyepoxide resins, such as those listed above suitable for preparing the polyamine-polyepoxide adduct.

[0071] The ratio of epoxy groups in the polyepoxide resin composition (B) to active amine hydrogens in the curing agent (A) can vary from about 0.5 to about 2, and will depend on the properties of the epoxy resin used, the application method, and the performance required to meet specific market demands. For example, in coating applications using certain amine-epoxide compositions, introducing more epoxy resin relative to the amount of the curing agent composition can result in an increased drying time for the coating, but with improved hardness and an improved appearance, such as as measured by gloss. The amine-epoxide compositions of the present invention generally have a stoichiometric ratio of epoxy groups in the epoxy composition to amine hydrogens in the curing agent composition ranging from about 2:1 to about 0.5:1. For example, such polyamine-compositions may have a stoichiometric ratio of epoxy to amine hydrogen of about 2.0:1 to about 0.5:1, or about 1.5:1 to about 0.5:1, or about 1.5:1 to about 0.7:1, or about 1.3:1 to about 0.7:1, or about 1.2:1 to about 0.7:1, or about 1.1:1 to about 0.7:1, or about 1.0:1 to about 0.7:1.

[0072] Depending on the application of the end use, it may be advantageous to reduce the viscosity of the polyepoxide resin composition by modifying it with a portion of a monofunctional epoxide. For example, the viscosity can be reduced to allow for higher pigment levels in the formulation or composition while still allowing for easy application, or to allow for the use of higher molecular weight epoxy resins. Therefore, for a polyepoxide resin composition comprising at least one polyfunctional epoxy resin, further inclusion of a monofunctional epoxide is within the scope of this invention. Examples of monoepoxides include, but are not limited to, styrene oxide, cyclohexane oxide, ethylene oxide, propylene oxide, butane oxide, and glycidyl ethers of phenol, cresol, tert-butylphenol, other alkylphenols, butanol, 2-ethylhexanol, C4 to C14 alcohols, and the like, or combinations thereof. The polyepoxide resin composition can be used as is, or it can be dissolved in a suitable solvent, or it can be used as an emulsion or dispersion already formed in water or a water / cosolvent blend. Those skilled in the art will recognize that, in the case of solid epoxy resins or extremely viscous liquid epoxy resins, solvents or water / cosolvent blends may be required.

[0073] Including one or more organic solvents in one or both components of the curable amine-epoxy composition is generally advantageous. The solvents are used, for example, to reduce the viscosity of individual or combined components, reduce the surface tension of the formulation, aid in component coalescence to optimize film formation, increase pot life, and improve the stability of one or both components. Particularly useful solvents are low molecular weight glycol ethers, such as ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monobutyl ether, and the like. Other useful solvents include aromatic solvents, such as xylene and blends of aromatic solvents, such as Aromatic 100; ketones, such as methyl ethyl ketone and methyl isobutyl ketone; esters, such as butyl acetate; and alcohols, such as isopropanol and butanol.

[0074] It is generally advantageous to include a plasticizer, such as benzyl alcohol, phenol, tert-butylphenol, nonylphenol, octylphenol, dodecylphenol, cashew phenol, and the like, in one or both of the components. The plasticizer lowers the glass transition temperature of the composition and thus allows the amine and epoxide to achieve a higher degree of reaction than otherwise possible. Accelerators for the epoxide / amine reaction can be used in the formulation. Useful accelerators are well known to those skilled in the art and include acids, such as salicylic acid, various phenols, various carboxylic acids, and various sulfonic acids, as well as tertiary amines, such as tris(dimethylaminomethyl)phenol.

[0075] The curable amine-epoxy composition may also include pigments and mixtures of pigments. The pigments may be ground into the epoxy resin, the curing agent, or both. They may also be incorporated using pigment grinding aids or pigment dispersants, which may be used in combination with the epoxy resin or the curing agent, or they may be used alone. The use of pigment dispersants is well known to those skilled in the art of coating formulation. The composition may also contain fillers and fibers, such as glass or carbon fiber.

[0076] Other additives may also be included in the curable amine-epoxy formulation. Such additives include defoamers, surfactants, slip agents and anti-scratch agents, rheological modifiers, flow aids, adhesion promoters, light stabilizers and heat stabilizers, corrosion inhibitors, biocides and the like.

[0077] This invention also relates to manufactured articles comprising the curable amine-epoxy compositions disclosed herein. The manufactured articles may comprise an amine-epoxy composition containing the reaction product of a curing agent and a polyepoxy resin composition. The epoxy composition may comprise at least one multifunctional epoxy resin. Optionally, depending on desired properties, various additives may be present in the compositions or formulations used to prepare the manufactured articles. These additives may include, but are not limited to, solvents (including water), accelerators, plasticizers, fillers, fibers (e.g., glass or carbon fibers), pigments, pigment dispersants, rheology modifiers, thixotropic agents, flow or leveling aids, surfactants, defoamers, biocides, slip agents and scratch-resistant agents, rheology modifiers, adhesion promoters, light stabilizers and heat stabilizers, corrosion inhibitors, and any combinations thereof.

[0078] The manufactured articles include, but are not limited to, adhesives, coatings, primers, sealants, curing compounds, building products, flooring products, and composite products. Additionally, such coatings, primers, sealants, or curing compounds can be applied to metallic or cementitious substrates. Specifically, the curable amine-epoxy compositions are used in metal coatings, particularly container coatings. Depending on the specific application, coatings based on these amine-epoxy compositions can be solvent-free or may contain diluents, such as water or organic solvents. The coatings may contain various types and levels of pigments used in paint and primer applications. For use in protective coatings applied to metal substrates, the curable amine-epoxy coating compositions comprise layers having a dry film thickness ranging from 10 to 200 μm, preferably 20 to 120 μm, more preferably 25 to 100 μm. Furthermore, for use in flooring or building products, depending on the type of product and the desired final performance, the coating composition comprises layers with a thickness ranging from 50 to 10,000 μm. Coating products that provide limited mechanical and chemical resistance comprise layers having a dry film thickness ranging from 50 to 500 μm, preferably 100 to 300 μm, while coating products that provide high mechanical and chemical resistance, such as self-leveling flooring, comprise layers having a thickness ranging from 800 to 10,000 μm, preferably 1,000 to 5,000 μm.

[0079] A wide variety of substrates are suitable for applying the coatings of the present invention, provided that the surface is properly prepared, as is known to those skilled in the art. Such substrates include, but are not limited to, concrete and various types of metals and alloys, such as steel and aluminum. The coatings of the present invention are suitable for painting or coating large metal objects or cement-based substrates, including ships, bridges, industrial plants and equipment, and floors.

[0080] The coatings of this invention can be applied by any number of techniques, including spraying, brushing, rolling, paint gloves, and similar means. For applying coatings of this disclosure with very high solids content or 100% solids, a multi-component spray application apparatus can be used, wherein the amine and epoxy components are mixed in the path leading to the spray gun, mixed within the spray gun itself, or mixed together as they leave the spray gun. Using this technique alleviates limitations regarding the pot life of the formulation, which typically decreases as both the amine reactivity and the solids content increase. Heated multi-component apparatus can be used to reduce the viscosity of the components, thereby improving ease of application. Detailed Implementation

[0081] The invention is further illustrated by the following examples, which should not be construed as limiting the scope of the invention. Various other aspects, embodiments, modifications, and equivalents thereof will be implied by those skilled in the art upon reading the description herein, without departing from the spirit of this disclosure or the scope of the appended claims.

[0082] Example

[0083] Example 1

[0084] The synthesis of curing agent (A) is carried out in the following 4 steps.

[0085] Step 1: Take 348g 2655 was placed into a 500 mL four-necked round-bottom flask equipped with a vacuum line, dropping funnel, nitrogen outlet, and stir bar. The contents were heated to 80°C with stirring. 115 g of diglycidyl ether bisphenol A epoxy resin (EEW ​​= 220-240), preheated at 80°C, was added to the flask over 2 hours. After the epoxy resin was added, the temperature was maintained at 80°C for another hour to ensure complete reaction. The flask was then heated to 200°C under vacuum to distill off excess free amine until the free amine content was <5% by weight, thus obtaining intermediate (c).

[0086] Step 2: Cool the reaction mixture obtained from Step 1 to 140°C, and add 3.9 g of urea to the flask over 30 minutes to react with intermediate (c). Continue the reaction for 4 hours to obtain intermediate (d).

[0087] Step 3: The reaction mixture obtained from Step 2 was cooled to 90°C, and 31.65 g (0.05 mol) of diglycidyl ether bisphenol A epoxy resin (EEW ​​= 450-500), 75% solids in xylene, was introduced into the reaction over a dropping funnel over 1 hour. The xylene was removed by vacuum distillation to obtain intermediate (e). The reaction product was capped with 15 g (0.03 mol) cashew oil glycidyl ether at 100°C for 1 hour to obtain intermediate (i). The reaction product was then blended with 10.62 g of isophorone diamine (IPDA) to obtain intermediate (ii).

[0088] Step 4: Add 111g of water to the reaction mixture in Step 3 to prepare curing agent (A), which has a solid content of 70%, an amine hydrogen equivalent weight (AHEW) of about 130, and a Gardner color of 6-8, and is a clear amber liquid.

[0089] Example 2

[0090] Example 2 used the same synthesis process as described in Example 1. Step 1: 292 g of triethylenetetramine (TETA) was used. Step 4: A 50% solid aqueous curing agent was prepared using 200 g of water and 45 g of 1-methoxy-2-propanol (PM), which had an AHEW of 175 based on the aqueous solution of the amine and a Gardner color of 6-8, and was a clear amber liquid.

[0091] Example 3

[0092] Example 3 used the same synthesis process as described in Example 1. Step 1: 292 g of triethylenetetramine (TETA) was used. Step 2: 3.9 g of urea was used. Step 3: 29.2 g of diglycidyl ether bisphenol A (EEW ​​= 450-500), 75% in 1-methoxy-2-propanol (PM), 9.7 g of NC513, and 9.7 g of IPDA were used. Step 4: A 70% solid aqueous curing agent was prepared using 101 g of water, having an AHEW = 125 based on the amine solution, and a Gardner color of 6-8, appearing as a clear amber liquid.

[0093] Example 4

[0094] Example 4 used the same synthesis process as described in Example 1. Step 1: 292 g of triethylenetetramine (TETA) was used. Step 3: 9.7 g of Jeffamine D230 was used. Step 4: An 80% solids aqueous curing agent was prepared using 59 g of water, having an AHEW of 105 (based on the aqueous amine) and a Gardner color of 6-8, and was a clear amber liquid.

[0095] Example 5

[0096] Example 5 employed the same synthesis process as described in Example 3, except that urea was not added to the reactor in step 2. In step 4, an aqueous curing agent with a 70% solids content was prepared using 100g of water, having an AHEW of 115 (based on the aqueous amine) and a Gardner color of 6-8. The finished curing agent was a translucent liquid.

[0097] Example 6

[0098] Example 6 uses the same synthesis process as described in Example 1. Step 2, using 3.9 g of formaldehyde. 146 g of water is added to a flask to prepare an aqueous curing agent with a 60% solids content, having an AHEW of 145 (based on the aqueous amine) and a Gardner color of 6-8, and is a clear amber liquid.

[0099] Example 7

[0100] Step 1: 300 g of diethylenetriamine (DETA) was placed into a 500 mL four-necked round-bottom flask equipped with a vacuum line, dropping funnel, nitrogen outlet, and stir bar. The contents were heated to 80 °C with stirring. 95 g of diglycidyl ether bisphenol A epoxy resin (EEW ​​= 184-190), preheated at 80 °C, was added to the flask over 2 hours. After the epoxy resin was added, the temperature was maintained at 80 °C for another 1 hour to ensure complete reaction. The flask was then heated to 180 °C under vacuum to distill off excess free amine until the free amine content was <4% by weight, thus obtaining intermediate (c).

[0101] Step 2: Cool the reaction mixture obtained from Step 1 to 130°C, and add 5 g of urea to the flask over 30 minutes to react with intermediate (c). Continue the reaction for 4 hours to obtain intermediate (d).

[0102] Step 3: The reaction mixture obtained from Step 2 was cooled to 90°C, and 45 g of diglycidyl ether bisphenol A epoxy resin (EEW ​​= 450-500), 75% solids in xylene, was introduced into the reaction via a dropping funnel over 1 hour. The xylene was removed by vacuum distillation to obtain intermediate (e). The reaction product was capped with 18 g of tolyl glycidyl ether (CGE) at 100°C for 1 hour to obtain intermediate (i). The reaction product was then reacted with 9 g of bis(3-aminopropyl)diethylene glycol ether (which can be used as...). 1922A (obtained from Evonik Corporation) was blended to obtain intermediate (ii). Then 4.5 g of acetic acid was added at 70 °C.

[0103] Step 4: Add 144.5 g of water to the reaction mixture obtained from Step 3 to prepare curing agent (A), which has a solids content of 60%, an amine hydrogen equivalent weight (AHEW) of about 170, and a Gardner color of 6-8, and is a clear amber liquid.

[0104] Example 8

[0105] The varnish formulation is prepared from a commercially available epoxy resin dispersion (part A) and a curing agent, water, and a co-solvent (part B). Detailed formulations of the varnish components are shown in Table 1. EPIKOTE TM 6520-WH-53A: 53% solids content, with an EEW of 1040 and a viscosity (Brookfield, 25°C.cP) of 1000-6000, is an aqueous dispersion derived from Hexion and Ancarez. TMAR555: 55% solids content, with an EEW of 1300 and a viscosity (Brookfield, 25°C.cP) of 200, is an aqueous dispersion obtained from Evonik Corporation. The embodiments of this invention use the curing agent obtained from Example 3, and the comparative examples use the curing agent obtained from Example 5 and a commercially available aqueous curing agent based on an epoxy-amine adduct.

[0106] Dipropylene n-butyl ether (DPnB) and 1-methoxy-2-propanol (PM) are used as cosolvents and are commercially available from DOW.

[0107] The test methods used in the embodiments include, but are not limited to, those shown in Table 2.

[0108] First, a wet film was prepared using a wet film coating machine and a blade coating method, achieving a wet film thickness of 100 μm. All panels were then placed in a constant-temperature laboratory at 23°C for 7 days. All clear film properties, such as the compatibility of the epoxy dispersion and the curing agent, the gloss of the finished film, and the film drying speed, were then tested, as shown in Table 2. The molar ratio of epoxide groups to amine groups was 1.3 / 1, and the epoxide groups exceeded the stoichiometry by 30% on a molar ratio basis. The data obtained in Table 3 indicate that the commercially available curing agents and the curing agents of Examples 3 and 5 provide good compatibility when cured with two commercial epoxy dispersions. Table 3 shows that formulations 1, 1, and 3 of the present invention, compared to formulations 2, 2, and 4 of the present invention, give different pencil hardnesses (2H), which is a result of the different epoxy dispersions. The adhesion test used was performed according to ASTM D3359, which involved pressing tape onto an X-cut film and then pulling the tape off to check how much coating was removed from the panel using a 0-5B rating system. A higher rating number indicates excellent performance, 5B indicates no coating was removed from the substrate, and 0 indicates that the coating was completely removed from the X-cut area beneath the tape. Regardless of the type of epoxy dispersion used in Table 1, the curing agents used in Examples 3 and 5 exhibited similar varnish properties to commercially available curing agents.

[0109] Table 1. Varnish Formulations

[0110]

[0111] Note: The molar ratio of epoxide to amine is 1.3 / 1.

[0112] Table 2. Test Methods

[0113]

[0114] Table 3. Varnish performance test after curing at 23°C for 7 days using the curing agents of Examples 3 and 5.

[0115]

[0116] Example 9

[0117] Differential performance test: Early clear coat film performance after curing for 7 days under high temperature and humidity (50℃ / 98% relative humidity)

[0118] Based on experience with traditional waterborne coatings, waterborne coatings exhibit poor film performance, poor moisture resistance, and poor corrosion resistance in the early stages compared to solvent-based epoxy coatings. To determine whether the curing agent of this invention produces good performance in the early stages when cured with an epoxy dispersion under high humidity, a specific test method was employed.

[0119] First, a wet film was prepared in the same manner as in Example 8. The varnish formulation was repeated as shown in Table 1. The wet film was applied by scraping, and then placed in an oven at 50°C for 30 minutes. Immediately afterwards, the film was transferred to a chamber with 50°C and 98% humidity, and then cured for 7 days. The film properties are summarized in Table 4.

[0120] Table 4. Differentiated properties of clear varnish cured for 7 days at 50°C and 98% humidity using the curing agent of Example 3.

[0121]

[0122] Adhesion rating: 5B - No film loss, excellent; 0B - Complete failure, poor.

[0123] Flexibility rating: 1mm, detection limit, excellent

[0124] Although the performance of the varnishes cured at room temperature in Table 3 did not show significant differences, the analysis of the coating results in Table 4 clearly demonstrates that the coating based on the curing agent of the present invention (Example 3), when cured at high humidity and high temperature, outperforms the commercially available water-based curing agent and the system of Example 5 in terms of early moisture resistance, exhibiting significantly improved adhesion, flexibility, and surface appearance. The coatings using the curing agent of the present invention show good compatibility with various commercially available resin dispersions, such as EPIKOTE. TM 6520-WH-53A or Ancarez TMAR555, as evidenced by its good adhesion and flexibility, however, showed very poor adhesion (0) and increased flexibility to 2 or 3 mm with the commercially available curing agent and Example 5. Surface appearance also showed similar results. The curing agent of the present invention maintained an acceptable surface appearance even after curing under high humidity testing, while the commercially available curing agent and Example 5 exhibited severe whitening. Both sets of data indirectly indicate that the curing agent of Example 3 had good moisture resistance at high temperatures in the early stages.

[0125] Example 10

[0126] To determine whether the curing agent of the present invention exhibits good performance in a complete formulation, a protective coating primer formulation was prepared as shown in Table 5 below. Detailed coating properties, such as touch-dry speed, pot life, impact resistance, gloss, adhesion, and salt spray resistance, are shown in Tables 6, 7, and 8.

[0127] Components A and B from Table 5 were thoroughly mixed at 23°C and allowed to stand for 15 minutes as the induction time before spraying. The viscosity of the resulting mixture of components A and B was approximately 60 Ku (KU method). The mixture was then sprayed onto a 7.6 × 15.2 cm Q plate for salt resistance testing and onto a 6.6 × 40 cm Q plate for other mechanical property testing. Film gloss was measured after 24 hours at 23°C, and other properties, such as adhesion, flexibility, and pencil hardness, were measured after 7 days of curing at 23°C.

[0128] Table 5. Formulation of metal protective coating primer using the curing agent of Example 3

[0129]

[0130] Note: Stoichiometry of epoxide / amine group = 1.3 / 1

[0131] The performance data of the curing agent were observed and described in this paper, using two commercially available epoxy dispersions for curing, as shown in Table 6. The curing agent of the present invention in Example 3 has competitive mechanical properties compared with commercially available water-based curing agents. Both curing agent / epoxy systems exhibit excellent impact resistance, good adhesion to Q-plates, good flexibility, and rapid hardening.

[0132] Pot life is a crucial parameter and challenge for waterborne epoxy coating systems, especially for waterborne container coatings. A short pot life can lead to low production efficiency, poor sag resistance, and poor adhesion when sprayed onto container substrates on-site. Viscosity stability, film gloss, and mechanical properties (flexibility / adhesion) are used to track the pot life of coating systems. This study investigated the pot life of two commercially available epoxy dispersions, Ancarez. TM AR555 and EPIKOTETM When used in 6520, the curing agents of Example 3 (Formulations 3 and 4 of the present invention) and commercially available curing agents exhibit viscosity stability and stable gloss over a long pot life. However, based on flexibility and adhesion tests, commercially available curing agents only provide a pot life of 2 hours, while the curing agent of the present invention provides a pot life of more than 5 hours.

[0133] Table 6. Performance of the metal protective coating primer using the curing agent of Example 3 after curing at 23°C for 7 days

[0134]

[0135] Adhesion rating: 5B - No film loss, excellent; 0B - Complete failure, poor.

[0136] Flexibility rating: 1mm, detection limit, excellent

[0137] Table 7. Differentiated Performance Tests: Performance of Fully Formulated Coatings Cured for 7 Days at High Temperature and High Humidity (50℃ / 98% Relative Humidity)

[0138]

[0139] Adhesion rating: 5B - No film loss, excellent; 0B - Complete failure, poor.

[0140] Flexibility rating: 1mm, detection limit, excellent

[0141] Because containers are semi-enclosed, water from the internal topcoat cannot be completely drained on the production line. Once the container is off the line, the doors are closed, and water evaporates into the overhead space, often causing the coating to fail in terms of corrosion and adhesion at an early stage. Therefore, the early performance of water-based coatings, such as early moisture resistance, is very important, and customers will benefit from this advantage.

[0142] Although the properties of the varnishes cured at room temperature in Table 6 did not show significant differences in adhesion and flexibility, Tables 7 and... Figure 1 The complete formulation results clearly demonstrate the superior coating performance using the curing agent of this invention, especially early moisture resistance, as exhibited by excellent hardness development, flexibility, and adhesion. All coatings were sprayed onto Q-plates. Compared to systems using commercially available water-based curing agents, the superior coating performance can be attributed to the rapid and complete curing of the coating and its greater hydrophobicity.

[0143] Salt spray resistance is a direct measure of the barrier properties of a coating. To investigate the overall performance of the curing agent of this invention used in waterborne interior container coatings (Waterborne Container Coating Standard: JTT 810-2011, Zinc-rich primer, dry film thickness 30 μm + interior epoxy topcoat, dry film thickness 40-50 μm), a zinc-rich primer starting formulation was developed, as shown in Table 8. The formulations in Table 5 were used for the said interior epoxy topcoat. The corrosion resistance test results are summarized in Table 9. The same zinc-rich primer formulation and similar layer thickness were used, and any performance differences were the result of the interior topcoat. Based on salt spray test data, the curing agent of Example 3 used in formulations 3 and 4 of this invention exhibited superior corrosion resistance compared to commercially available waterborne curing agents.

[0144] Table 8. Starting Formulation for Zinc-Rich Primer

[0145] 1 Tego Airex 901W (EVONIK) 0.18 2 1-Methoxy-2-propanol (PM) 4.94 3 Dipropylene n-butyl ether (DPnB) 2.28 4 Bentonite SD-2 1.35 5 Ancamide 2839 2.45 6 Zinc powder 65 7 sylosiv 3A molecular sieve 0.47 8 1-Methoxy-2-propanol (PM) 0.74 9 A380 flash rust agent 0.47 Total A 77.88 Components of Part B Ancarez AR555 (SER dispersion) 22.12 Total A+B 100

[0146] Table 9. Salt spray resistance test results based on ASTM D610-2008 and ASTM D714-2009

[0147]

[0148] Note: 5% NaCl aqueous solution, 35℃, grade 10, no bubbles on the film; grade 9, some sample bubbles on the film.

[0149] a. The salt spray test was manually stopped at 940 hours, and no membrane defects were found.

[0150] b. JTT 810-2011, China's standard for water-based container coatings.

Claims

1. An epoxy curing agent composition comprising a reaction product of a first polyamine and a first polyepoxide, the first polyamine containing a primary amine functional group, and the first polyepoxide having an epoxide equivalent weight of 130 to 500, wherein the ratio of the number of moles of the polyamine to the number of epoxide equivalents is sufficient to provide an amine-terminated intermediate a comprising an adduct of two moles of the polyamine and one mole of the polyepoxide, wherein intermediate a is then reacted with urea or formaldehyde to provide an amine-terminated intermediate b, wherein intermediate b is then reacted with a second polyepoxide to provide an amine-terminated intermediate c, the second polyepoxide having an epoxide equivalent weight of 200 to 1000, wherein intermediate c is terminated with a monoepoxide composition to form a polyamine-polyepoxide adduct, said monoepoxide composition comprising an aromatic glycidyl ether or an alkyl-substituted aromatic glycidyl ether or a combination thereof, and wherein said polyamine-polyepoxide adduct is mixed with a second polyamine having two or more active amine hydrogens, wherein said second polyamine is different from the first polyamine; The amount of the polyamine-polyepoxide adduct in the curing agent is 70% to 98% by weight relative to the total weight of the curing agent; and The amount of the second polyamine in the curing agent is 2% to 30% by weight relative to the total weight of the curing agent.

2. The composition according to claim 1, wherein excess of the first polyamine is removed from intermediate a by distillation to produce an amine-terminated adduct intermediate ai, and then intermediate ai is reacted with urea or formaldehyde to form an amine-terminated intermediate b.

3. The composition according to claim 1, wherein the first polyamine has an amine hydrogen equivalent weight of 12 to 50.

4. The composition according to claim 1, wherein intermediate a comprises an adduct of two moles of polyamine and one mole of polyepoxide.

5. The composition according to claim 1, wherein the amount of urea or formaldehyde reacting with intermediate a is from 0.5% to 8% by weight relative to the total weight of intermediate a.

6. The composition according to claim 1, wherein the amount of the second polyepoxide reacting with intermediate b is from 1% to 30% by weight relative to the total weight of intermediate b.

7. The composition according to claim 1, wherein the amount of the monoepoxide composition reacting with intermediate c is from 1% to 25% by weight relative to the total weight of intermediate c.

8. The composition according to claim 1, wherein the second polyamine has an amine hydrogen equivalent weight of 12 to 100.

9. A method for preparing an epoxy curing agent composition, the method comprising the following steps: i. Reacting a first polyamine with a first polyepoxide, the first polyamine containing a primary amine functional group, the first polyepoxide having an epoxide equivalent weight in the range of 130 to 500, wherein the ratio of the number of moles of polyamine to the number of equivalents of polyepoxide is sufficient to provide an amine-terminated intermediate a, wherein the ratio of the first polyamine to the first polyepoxide is greater than one mole of polyamine for every mole of epoxide. ii. React intermediate a with urea or formaldehyde to form amine-terminated intermediate b. iii. Reacting intermediate b with a second polyepoxide to form an amine-terminated intermediate c, the second polyepoxide having an epoxide equivalent weight in the range of 200 to 1000. iv. End-capping intermediate c with a monoepoxide composition to form a polyamine-polyepoxide adduct, said monoepoxide composition comprising an aromatic glycidyl ether or an alkyl-substituted aromatic glycidyl ether or a combination thereof, and v. Mixing the polyamine-polyepoxide adduct with a second polyamine having two or more active amine hydrogens, wherein the second polyamine is different from the first polyamine; The amount of the polyamine-polyepoxide adduct in the curing agent is 70% to 98% by weight relative to the total weight of the curing agent; and The amount of the second polyamine in the curing agent is 2% to 30% by weight relative to the total weight of the curing agent.

10. The method of claim 9, wherein the method further comprises step ia, wherein excess of the first polyamine is removed from intermediate a by distillation to produce an amine-terminated adduct intermediate ai, and then intermediate ai is reacted with urea or formaldehyde in step ii to form an amine-terminated intermediate b.

11. The method of claim 9, wherein the first polyamine has an amine hydrogen equivalent weight of 12 to 50.

12. The method of claim 9, wherein intermediate a comprises an adduct of two moles of polyamine and one mole of polyepoxide.

13. The method of claim 9, wherein the amount of urea or formaldehyde reacted in step ii is from 0.5% to 8% by weight relative to the total weight of intermediate a.

14. The method of claim 9, wherein the amount of the second polycyclic oxide reacted in step iii is from 1% to 30% by weight relative to the total weight of intermediate b.

15. The method of claim 9, wherein the amount of the monoepoxide composition reacted in step iv is from 1% to 25% by weight relative to the total weight of intermediate c.

16. The method of claim 9, wherein the second polyamine has an amine hydrogen equivalent weight of 12 to 100.

17. Use of the epoxy curing agent composition according to any one of claims 1-8 as a hardener for epoxy resins.

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