Low-temperature curable one-component epoxy composition containing resin-blocked urea curing agent

Abstract

The present disclosure provides latent curing accelerators, and compositions containing such latent curing accelerators with a substance to be cured (e.g., an epoxy resin). The latent cure accelerator comprises a urea compound and an encapsulant system having a polyphenol resin and / or at least one additional excipient. Methods of manufacture and use are further provided.

Description

Background Technology

[0001] Epoxy-based adhesives are used in a wide range of applications in the automotive, electronics, aerospace, and general industrial sectors. They are increasingly replacing conventional bonding systems such as brazing, welding, riveting, nailing, screwing, and bolting because they offer superior benefits. Some of these benefits include bonding similar and dissimilar substrates without damaging them, better stress distribution over a wide area, improved fatigue resistance, and resistance to noise and vibration.

[0002] Compositions containing epoxy resins and curing agents (hardeners) have been known for decades. Many curing agents are reactive with epoxy resins at room temperature and therefore need to be mixed just before use. Other curing agents, known as latent curing agents, are stable at ambient temperature when mixed with epoxy resins and only harden when heated to elevated temperatures. Some compounds also act as accelerators for latent curing agents such as dicyandiamide (DICY) or acid anhydrides, and achieve curing of epoxy resins at elevated temperatures. One-component epoxy-based adhesive systems are superior to two-component systems because they eliminate the mixing steps, the time required for application, and the cooling during storage and transportation associated with two-component systems.

[0003] US 4,866,133 describes the use of solid solutions of polymeric polyphenols and polyamines for curing epoxy resins. US Patent 4,689,390 describes the preparation of latent curing agents by reacting a diamine containing tertiary and primary or secondary amino groups with a polyepoxide compound and a phenolic resin or phenolic compound. US Patent Application 13 / 075403 describes a solution of a tertiary polyamine in a polyphenolic resin made from bisphenol A diglycidyl ether and a polyamino secondary amine as a latent epoxy curing agent. US Patent 7,910,667 describes a polyphenolic resin solution of a polyurea derivative of a tertiary polyamine that has been used as a latent epoxy curing agent. US Patent 9,546,243 describes polyphenolic resin solutions of certain classes of amines that have been used as the only latent epoxy curing agents besides DICY accelerators. Finally, US Patent 9,000,120 reports a thermally activated DICY accelerator composed of a tertiary amine and a phenolic varnish resin. Summary of the Invention

[0004] This invention relates to latent curing agents and accelerators for epoxy resins, including 100% solids epoxy compositions and water-based compositions, particularly for single-component 100% solids epoxy compositions. A "latent" curing agent is one that remains inactive in a formulated epoxy system under normal environmental conditions but readily reacts with the epoxy resin at elevated temperatures. An "accelerator" is one that accelerates the reaction between the epoxy resin and the curing agent. A "single-component" epoxy composition is typically a blend of epoxy resin, curing agent, and optionally an accelerator, as well as additives and fillers. "100% solids" means the epoxy composition is free of water or organic solvents. There is a need for latent epoxy curing agents or accelerators that exhibit prolonged storage stability at ambient temperatures and rapid curing at >100°C. Invention Overview

[0006] Therefore, this article provides epoxy curing agents and related compositions that allow for lower curing temperatures without compromising the latency of epoxy resin compositions.

[0007] We have discovered that epoxy curing agents with improved storage stability and low curing temperatures can be obtained through solutions containing encapsulating agent systems comprising urea compounds in combination with polyphenolic resins and / or one or more monomeric or polymeric compounds, any of which can be functionalized with structural moieties capable of interacting with tertiary amines (e.g., acidic substituents such as OH, COOH, SO3OH, PO(OH)3, and PO(OH)2). Non-functionalized compounds or polymers do not contain these functional groups and do not interact with tertiary amines.

[0008] In a first aspect, this disclosure relates to a latent curing accelerator composition [composition 1] comprising:

[0009] Encapsulating agent system, comprising:

[0010] Urea compounds,

[0011] Polyphenol resins, and

[0012] Additional excipients selected from functional and / or non-functional components.

[0013] In some embodiments, composition 1 is defined as follows:

[0014] 1.1 Composition 1, wherein the urea compound comprises the reaction product of an isocyanate and an alkylated polyalkylene polyamine.

[0015] 1.2 Composition 1 or 1.1, wherein the isocyanate is selected from aliphatic isocyanates, alicyclic isocyanates and aromatic isocyanates.

[0016] 1.3 Any of the foregoing compositions, wherein the isocyanate is selected from phenyl isocyanate, toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and polymeric diphenylmethane diisocyanate.

[0017] 1.4 Any of the foregoing compositions, wherein the alkylated polyalkylene polyamine has at least one primary or secondary amine and at least two tertiary amines of formula (A):

[0018]

[0019] Where R1, R2, R3, R4 and R5 are independently hydrogen, methyl or ethyl; m and n are independently integers from 1 to 6; and X is an integer from 1 to 10.

[0020] 1.5 The aforementioned composition, wherein R1 is hydrogen or methyl; R2 and R4 are methyl; and R3 and R5 are hydrogen or methyl.

[0021] 1.6 Any of the foregoing compositions, wherein the alkylated polyalkylene polyamine is N′-(3-dimethylaminopropyl)-N,N-dimethylpropyl-1,3-diamine ( 15) or poly-N-methyl-azacyclobutane.

[0022] 1.7 Composition 1, wherein the urea compound comprises the reaction product of a primary amine with a tertiary amine functional group and a urea (carbamide).

[0023] 1.8 The aforementioned composition, wherein the urea compound is 1,3-bis[3-(dimethylamino)propyl]urea (DABCONE1082).

[0024] 1.9 Any of the foregoing compositions, wherein the urea compound is present in an amount of about 5% to about 75% by weight based on the total weight of the composition.

[0025] 1.10 Any of the foregoing compositions, wherein the polyphenol resin is a phenolic resin of formula (B):

[0026]

[0027] Where R a R b R c and R d Each is independently hydrogen or branched or unbranched C1-C 17 Alkyl group, and n is an integer from 0 to 50.

[0028] 1.11 Any of the foregoing compositions, wherein the polyphenol resin comprises or is composed of phenolic varnish resin.

[0029] 1.12 Any of the foregoing compositions, wherein the polyphenol resin is a phenol-formaldehyde resin.

[0030] 1.13 Any of the foregoing compositions, wherein the polyphenol resin is Alnovol PN320.

[0031] 1.14 Any of the foregoing compositions, wherein the polyphenolic resin is present in an amount of about 5% to about 75% by weight based on the total weight of the composition.

[0032] 1.15 Any of the foregoing compositions, wherein the additional excipient is a functional compound comprising one or more of the following substances: (a) monomeric carboxylic acids, sulfonic acids, phosphonic acids, phosphoric acids or boric acids; (b) polyester resins; (c) acrylic resins; (d) polyether resins; (e) polybutadiene resins; and (f) polyamide resins.

[0033] 1.16 Any of the foregoing compositions, wherein the additional excipient is present in an amount of about 5% by weight to about 75% by weight based on the total weight of the composition.

[0034] 1.17 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of a functional compound present in an amount of about 5% to about 75% by weight based on the total weight of the composition.

[0035] 1.18 Any of the foregoing compositions, wherein the additional excipient is a monomeric carboxylic acid, sulfonic acid, phosphonic acid, phosphoric acid, or boric acid.

[0036] 1.19 Any of the aforementioned compositions, wherein the additional excipient comprises or is composed of a monomeric carboxylic acid.

[0037] 1.20 Any of the aforementioned compositions, wherein the additional excipient comprises or is composed of a monomeric sulfonic acid.

[0038] 1.21 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of a monomeric phosphonic acid.

[0039] 1.22 Any of the aforementioned compositions, wherein the additional excipient comprises or is composed of monomeric phosphoric acid.

[0040] 1.23 Any of the aforementioned compositions, wherein the additional excipient comprises or is composed of monomeric boric acid.

[0041] 1.24 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of a polyester resin.

[0042] 1.25 The aforementioned composition, wherein the polyester resin has a structure according to the following formula:

[0043]

[0044] Where R1 is a saturated or unsaturated alkyl or aryl group.

[0045] R2 is C 1-10 Alkyl or C 1-10 cycloalkyl, and

[0046] n is 0-20.

[0047] 1.26 Any of the foregoing compositions, wherein the polyester resin is a polycondensation product of polyols and polycarboxylic acids, such as a polycondensation product of various polyols and various polycarboxylic acids, such as a polycondensation product of dicarboxylic acid, diol (diol) and trifunctional alcohol or carboxylic acid.

[0048] 1.27 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of an acrylic resin.

[0049] 1.28 The aforementioned composition, wherein the acrylic resin has a structure according to the following formula:

[0050]

[0051] Where R1 is H or CH3; and

[0052] R2 is C 1-8 alkyl.

[0053] 1.29 Any of the foregoing compositions, wherein the acrylic resin is formed by free radical polymerization of acrylic monomers and vinyl monomers with unsaturated monomers containing hydroxyl or carboxyl groups.

[0054] 1.30 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of a polyether resin.

[0055] 1.31 Any of the foregoing compositions, wherein the additional excipient is polyalkylene glycol.

[0056] 1.32 The aforementioned composition, wherein the polyalkylene glycol has a molecular weight between about 1,000D and about 100,000D.

[0057] 1.33 The aforementioned composition, wherein the polyalkylene glycol has a molecular weight between about 1,500D and about 35,000D.

[0058] 1.34 The aforementioned composition, wherein the polyalkylene glycol has a molecular weight between about 1,500D and about 10,000D.

[0059] 1.35 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of polybutadiene resin.

[0060] 1.36 The aforementioned composition, wherein the polybutadiene resin is carboxylated polybutadiene.

[0061] 1.37 The aforementioned composition, wherein the carboxylated polybutadiene has a polybutadiene backbone microstructure consisting of a combination of vinyl 1,2-linked, trans 1,4-linked and cis 1,4-linked bonds.

[0062] 1.38 Any of compositions 1.36-1.37, wherein the carboxylated polybutadiene has an average molecular weight between about 500D and about 10,000D.

[0063] 1.39 Any of compositions 1.36-1.38, wherein the carboxylated polybutadiene has a molecular weight between about 1,000D and about 7,000D.

[0064] 1.40 Any one of compositions 1.36-1.39, wherein the carboxylated polybutadiene has a molecular structure consisting of 70 to 90% cis double bonds, 10 to 30% trans double bonds and 0 to 3% vinyl double bonds.

[0065] 1.41 Any of compositions 1.36-1.40, wherein the carboxylated polybutadiene is a maleic anhydride adduct of cis-1,4-polybutadiene (e.g., low molecular weight cis-1,4-polybutadiene) which optionally has succinic anhydride side groups randomly distributed in the polymer chain.

[0066] 1.42 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of a polyamide resin.

[0067] 1.43 The aforementioned composition, wherein the polyamide resin is nylon (e.g., nylon-6, nylon 6-6, copolymers of nylon-6 and nylon 6-6, nylon-9, nylon-10, nylon-11, nylon-12, nylon 6-10), aromatic polyamide, elastomeric polyamide, and mixtures thereof.

[0068] 1.44 Any one of compositions 1.42-1.43, wherein the polyamide resin is an acid-functional thermoplastic polyamide.

[0069] 1.45 Any of the foregoing compositions, wherein the additional excipient is a nonfunctional component, which is a polymeric compound selected from acrylates, polybutadiene, polyamides, ketone-aldehyde condensates, polyimides, styrene-butadiene resins, olefin copolymers, and combinations thereof.

[0070] 1.46 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of a nonfunctional compound present in an amount of about 5% to about 75% by weight based on the total weight of the composition.

[0071] 1.47 Any of the foregoing compositions, wherein the composition has an onset temperature of about 135°C to about 142°C.

[0072] 1.48 Any of the foregoing compositions, wherein the composition has a viscosity of about 19,000 cP to about 21,000 cP.

[0073] 1.49 Any of the foregoing compositions, wherein the composition does not gel after 4 weeks under accelerated aging conditions (i.e., stored at 40°C for 4 weeks).

[0074] 1.50 Any of the foregoing compositions, wherein the composition has an overlap shear strength greater than 700 psi.

[0075] 1.51 Any of the foregoing compositions, wherein the additional excipient is an acrylic resin, and the composition has an overlap shear strength greater than 700 psi.

[0076] 1.52 Any of the foregoing compositions, wherein the composition has an adhesive strength, as determined by a T-peel test, between about 60 pli and 120 pli.

[0077] 1.53 Any of the foregoing compositions, wherein the additional excipient is an acrylic resin, and the composition has an adhesive strength, as determined by a T-peel test, between about 60 pli and 120 pli.

[0078] 1.54 Any of the foregoing compositions, wherein the composition is in liquid or solid powder form.

[0079] 1.55 Any of the foregoing compositions, wherein the composition is in the form of an aqueous solution.

[0080] 1.56 Any of the foregoing compositions, further comprising one or more of a wetting agent, a filler, a defoamer, and a rheology modifier.

[0081] 1.57 Any of the foregoing compositions, wherein the composition is a latent curing agent for epoxy resins (e.g., the only latent curing agent).

[0082] In a second aspect, this disclosure relates to a latent curing accelerator composition [composition 2], comprising:

[0083] Encapsulating agent system, comprising:

[0084] Urea compounds, and

[0085] Additional excipients selected from functional and / or non-functional components.

[0086] In some embodiments, composition 2 is defined as follows:

[0087] 2.1 Composition 2, wherein the urea compound comprises the reaction product of isocyanate and alkylated polyalkylene polyamine.

[0088] 2.2 Composition 2 or 2.1, wherein the isocyanate is selected from aliphatic isocyanates, alicyclic isocyanates and aromatic isocyanates.

[0089] 2.3 Any of the foregoing compositions, wherein the isocyanate is selected from phenyl isocyanate, toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and polymeric diphenylmethane diisocyanate.

[0090] 2.4 Any of the foregoing compositions, wherein the alkylated polyalkylene polyamine has at least one primary or secondary amine and at least two tertiary amines of formula (A):

[0091]

[0092] Where R1, R2, R3, R4 and R5 are independently hydrogen, methyl or ethyl; m and n are independently integers from 1 to 6; and X is an integer from 1 to 10.

[0093] 2.5 The aforementioned composition, wherein R1 is hydrogen or methyl; R2 and R4 are methyl; and R3 and R5 are hydrogen or methyl.

[0094] 2.6 Any of the foregoing compositions, wherein the alkylated polyalkylene polyamine is N′-(3-dimethylaminopropyl)-N,N-dimethylpropyl-1,3-diamine ( 15) or poly-N-methyl-azacyclobutane.

[0095] 2.7 Composition 2, wherein the urea compound comprises the reaction product of a primary amine with a tertiary amine functional group and a urea (carbamide).

[0096] 2.8 The aforementioned composition, wherein the urea compound is 1,3-bis[3-(dimethylamino)propyl]urea (DABCONE1082).

[0097] 2.9 Any of the foregoing compositions, wherein the urea compound is present in an amount of about 5% to about 75% by weight based on the total weight of the composition.

[0098] 2.10 Any of the foregoing compositions, wherein the additional excipient is a functional compound comprising one or more of the following substances: (a) monomeric carboxylic acids, sulfonic acids, phosphonic acids, phosphoric acids or boric acids; (b) polyester resins; (c) acrylic resins; (d) polyether resins; (e) polybutadiene resins; and (f) polyamide resins.

[0099] 2.11 Any of the foregoing compositions, wherein the additional excipient is present in an amount of about 5% to about 75% by weight based on the total weight of the composition.

[0100] 2.12 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of a functional compound present in an amount of about 5% to about 75% by weight based on the total weight of the composition.

[0101] 2.13 Any of the foregoing compositions, wherein the additional excipient is a monomeric carboxylic acid, sulfonic acid, phosphonic acid, phosphoric acid, or boric acid.

[0102] 2.14 Any of the aforementioned compositions, wherein the additional excipient comprises or is composed of a monomeric carboxylic acid.

[0103] 2.15 Any of the aforementioned compositions, wherein the additional excipient comprises or is composed of a monomeric sulfonic acid.

[0104] 2.16 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of a monomeric phosphonic acid.

[0105] 2.17 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of monomeric phosphoric acid.

[0106] 2.18 Any of the aforementioned compositions, wherein the additional excipient comprises or is composed of monomeric boric acid.

[0107] 2.19 Any of the aforementioned compositions, wherein the additional excipient comprises or is composed of a polyester resin.

[0108] 2.20 The aforementioned composition, wherein the polyester resin has a structure according to the following formula:

[0109]

[0110] Where R1 is a saturated or unsaturated alkyl or aryl group.

[0111] R2 is C 1-10 Alkyl or C 1-10 cycloalkyl, and

[0112] n is 0-20.

[0113] 2.21 Any of the foregoing compositions, wherein the polyester resin is a polycondensation product of polyols and polycarboxylic acids, such as a polycondensation product of various polyols and various polycarboxylic acids, such as a polycondensation product of dicarboxylic acid, diol (diol) and trifunctional alcohol or carboxylic acid.

[0114] 2.22 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of an acrylic resin.

[0115] 2.23 The aforementioned composition, wherein the acrylic resin has a structure according to the following formula:

[0116]

[0117] Where R1 is H or CH3; and

[0118] R2 is C 1-8 alkyl.

[0119] 2.24 Any of the foregoing compositions, wherein the acrylic resin is formed by free radical polymerization of acrylic monomers and vinyl monomers with unsaturated monomers containing hydroxyl or carboxyl groups.

[0120] 2.25 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of a polyether resin.

[0121] 2.26 Any of the foregoing compositions, wherein the additional excipient is polyalkylene glycol.

[0122] 2.27 The aforementioned composition, wherein the polyalkylene glycol has a molecular weight between about 1,000D and about 100,000D.

[0123] 2.28 The aforementioned composition, wherein the polyalkylene glycol has a molecular weight between about 1,500D and about 35,000D.

[0124] 2.29 The aforementioned composition, wherein the polyalkylene glycol has a molecular weight between about 1,500D and about 10,000D.

[0125] 2.30 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of polybutadiene resin.

[0126] 2.31 The aforementioned composition, wherein the polybutadiene resin is carboxylated polybutadiene.

[0127] 2.32 The aforementioned composition, wherein the carboxylated polybutadiene has a polybutadiene backbone microstructure consisting of a combination of vinyl 1,2-linked, trans 1,4-linked and cis 1,4-linked bonds.

[0128] 2.33 Any of compositions 2.31-2.32, wherein the carboxylated polybutadiene has an average molecular weight between about 500D and about 10,000D.

[0129] 2.34 Any of compositions 2.31-2.33, wherein the carboxylated polybutadiene has a molecular weight between about 1,000D and about 7,000D.

[0130] 2.35 Any one of compositions 2.31-2.34, wherein the carboxylated polybutadiene has a molecular structure consisting of 70 to 90% cis double bonds, 10 to 30% trans double bonds and 0 to 3% vinyl double bonds.

[0131] 2.36 Any of compositions 2.31-2.35, wherein the carboxylated polybutadiene is a maleic anhydride adduct of cis-1,4-polybutadiene (e.g., low molecular weight cis-1,4-polybutadiene), optionally having succinic anhydride side groups randomly distributed in the polymer chain.

[0132] 2.37 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of a polyamide resin.

[0133] 2.38 The aforementioned composition, wherein the polyamide resin is nylon (e.g., nylon-6, nylon 6-6, copolymers of nylon-6 and nylon 6-6, nylon-9, nylon-10, nylon-11, nylon-12, nylon 6-10), aromatic polyamide, elastomeric polyamide, and mixtures thereof.

[0134] 2.39 Any one of compositions 2.37-2.38, wherein the polyamide resin is an acid-functional thermoplastic polyamide.

[0135] 2.40 Any of the foregoing compositions, wherein the additional excipient is a nonfunctional component, which is a polymeric compound selected from acrylates, polybutadiene, polyamides, ketone-aldehyde condensates, polyimides, styrene-butadiene resins, olefin copolymers, and combinations thereof.

[0136] 2.41 Any of the foregoing compositions, wherein the additional excipient comprises or is composed of a nonfunctional compound present in an amount of about 5% to about 75% by weight based on the total weight of the composition.

[0137] 2.42 Any of the foregoing compositions, wherein the composition does not gel after 4 weeks under accelerated aging conditions (i.e., stored at 40°C for 4 weeks).

[0138] 2.43 Any of the foregoing compositions, wherein the composition is in liquid or solid powder form.

[0139] 2.44 Any of the foregoing compositions, wherein the composition is in the form of an aqueous solution.

[0140] 2.45 Any of the foregoing compositions, further comprising one or more of a wetting agent, a filler, a defoamer, and a rheology modifier.

[0141] 2.46 Any of the foregoing compositions, wherein the composition is a latent curing agent for epoxy resins (e.g., the only latent curing agent).

[0142] In a third aspect, this disclosure relates to a curable epoxy system [System 1] comprising:

[0143] Latent curing accelerator compositions (i.e., composition 1 and all subsequent items, or composition 2 and all subsequent items); and

[0144] Epoxy resin.

[0145] In some implementation schemes, System 1 is defined as follows:

[0146] 1.1 System 1, wherein the latent curing accelerator composition is according to any one of composition 1 and the following items.

[0147] 1.2 System 1, wherein the latent curing accelerator composition is according to any one of Composition 2 and the following items.

[0148] 1.3 Any of the aforementioned systems, wherein the epoxy resin is a glycidyl ether, a polyphenol, or an alicyclic epoxide (including a diepoxide of an alicyclic ester of a dicarboxylic acid).

[0149] 1.4 Any of the aforementioned systems, wherein the epoxy resin is a polymer according to the following formula:

[0150]

[0151] Where m is an integer and R is a divalent hydrocarbon group of a diphenol.

[0152] 1.5 Any of the aforementioned systems, wherein the system has an initial temperature of about 135°C to about 142°C.

[0153] 1.6 Any of the aforementioned systems, wherein the system has a viscosity of about 19,000 cP to about 21,000 cP.

[0154] 1.7 Any of the aforementioned systems, wherein the system does not gel after 4 weeks under accelerated aging conditions (i.e., stored at 40°C for 4 weeks).

[0155] 1.8 Any of the aforementioned systems, wherein the system provides an overlap shear of greater than 700 psi.

[0156] 1.9 Any of the foregoing systems, wherein the additional excipient in the latent accelerator composition is an acrylic resin, and the system provides an overlap shear of greater than 700 psi.

[0157] 1.10 Any of the aforementioned systems, wherein the system provides an adhesive strength, as determined by a T-peel test, between approximately 60 pli and 120 pli.

[0158] 1.11 Any of the foregoing systems, wherein the additional excipient in the latent accelerator composition is an acrylic resin, and the system provides an adhesive strength, as determined by a T-peel test, between approximately 60 pli and 120 pli.

[0159] 1.12 Any of the aforementioned systems, further comprising one or more of a wetting agent, a filler, a defoamer, and a rheology modifier.

[0160] 1.13 Any of the aforementioned systems, wherein the latent accelerator composition is a latent curing agent (e.g., a single latent curing agent) for epoxy resins.

[0161] 1.14 Any of the aforementioned systems, further comprising DICY.

[0162] In a fourth aspect, this disclosure relates to a method for curing a substance using a latent curing accelerator composition [Method 1].

[0163] The method includes the steps of combining the substance with the latent curing accelerator composition and heating the resulting mixture.

[0164] In some implementation schemes, method 1 is defined as follows:

[0165] 1.1 Method 1, wherein the substance is epoxy resin.

[0166] 1.2 Method 1 or 1.1, wherein the latent curing accelerator composition is according to Composition 1 and the following items.

[0167] 1.3 Method 1 or 1.1, wherein the latent curing accelerator composition is according to Composition 2 and thereafter.

[0168] 1.4 Any of the foregoing methods, wherein the mixture containing the substance and the latent curing accelerator is heated to a temperature of about 135°C to about 142°C.

[0169] 1.5 Any of the foregoing methods, wherein the latent curing accelerator composition is formed by blending the encapsulating agent system under a nitrogen atmosphere and heating it to a temperature of 120°C to 180°C.

[0170] 1.6 Any of the foregoing methods, wherein the composition is a latent curing agent for epoxy resin (e.g., the only latent curing agent).

[0171] 1.7 Any of the foregoing methods, wherein the composition is used as an accelerator for curing agents (such as DICY or acid anhydrides) of epoxy resins.

[0172] 1.8 Any of the foregoing methods, wherein the composition is used as a latent curing accelerator for structural adhesives and composites, electro-encapsulation and encapsulation, compositions for reinforcement and / or damping, in-situ cured pipes, impact-resistant adhesives, filament winding, transfer molding powders, prepregs using solid or liquid epoxy resins, sheet molding compounds, coatings on concrete, wood, metal, etc., resin transfer molding and / or EV battery pack adhesives.

[0173] This disclosure further provides a latent curing accelerator composition for use in methods of curing substances, such as in method 1 and any of the subsequent methods.

[0174] This disclosure further provides the use of the latent curing accelerator composition in the manufacture of a curable formulation comprising a substance and the latent curing accelerator composition, for example, in any of method 1 and thereafter.

[0175] Each aspect and embodiment of the invention disclosed herein is intended to be combined individually and in all possible combinations with all other disclosed aspects and embodiments of the invention. Invention Details

[0177] This disclosure provides a latent curing accelerator and a composition comprising such a latent curing accelerator and a substance to be cured (e.g., epoxy resin). Further methods for manufacturing and using are provided.

[0178] This invention relates to certain urea-(resin 1:resin 2) compound reaction product compositions and their use in cured epoxy resin compositions as curing agents or as accelerators for latent curing agents (such as dicyandiamide, thiols, or acid anhydrides).

[0179] In one embodiment, the latent curing agent and the latent curing agent accelerator are a composition which is the reaction product of (a) a urea compound and (b) a phenolic resin (resin 1), and combined with (c) another type of functional or non-functional monomeric compound or polymeric resin (resin 2).

[0180] In another embodiment, the latent curing agent and the latent curing agent accelerator are a composition which is the reaction product of the following substances: (a) a urea compound and (c) another type of functional or non-functional monomeric compound or polymeric resin (resin 2).

[0181] Urea compounds

[0182] The latent curing accelerator disclosed herein comprises an encapsulating agent system, which includes a urea compound as a major component.

[0183] In a preferred embodiment of the invention, the urea compound (a) is a reaction product of an isocyanate and an alkylated polyalkylene polyamine, said alkylated polyalkylene polyamine having at least one primary or secondary amine and at least two tertiary amines of formula (A):

[0184]

[0185] Wherein R1, R2, R3, R4, and R5 independently represent hydrogen, methyl, or ethyl; m and n are independently integers from 1 to 6; and X is an integer from 1 to 10. In another preferred embodiment, R1 represents hydrogen or methyl; R2 and R4 represent methyl; and R3 and R5 represent hydrogen or methyl, i.e., methylated polyalkylene polyamines.

[0186] For other preferred embodiments of the foregoing aspects and embodiments, the R1-R5 substituents are selected individually or in any combination, provided that the amine molecule has one primary or secondary amine and at least two tertiary amines.

[0187] In other preferred embodiments of the foregoing aspects and implementation schemes, the integers m, n, and X are individually selected from the ranges specified above for each other or in any combination thereof, wherein some aspects of m and n are 2 or 3 and X is 1 to 7; m and n are 3 and X is 1; and m and n are 3 and X is 1 to 7.

[0188] Preferred isocyanates suitable for reaction with polyalkylene polyamines are any of aliphatic isocyanates, alicyclic isocyanates, and aromatic isocyanates (wherein the isocyanate functional group -NCO is directly bonded to the aromatic ring). Preferred isocyanates include phenyl isocyanates, toluene diisocyanates (TDI) (including 2,4-TDI, 2,6-TDI, and 2,4 / 2,6-TDI), and diphenylmethane diisocyanates (MDI) (including their polymethylene polyphenylene polyisocyanate polymer homologues, i.e., polymeric MDI).

[0189] The urea compounds of the present invention can be prepared by reactions known to chemists and reported in the literature, such as in Jerry March, Advanced Organic Chemistry, Wiley-Interscience, 4th edition, page 1299. In one embodiment, the isocyanate and polyamine are in a polyamine:isocyanate equivalent ratio of 1:1 for a polyamine having one primary or secondary amine and an isocyanate having one NCO group, 1:2 for a polyamine having a total of two primary and / or secondary amines and an isocyanate having one NCO group, and 2:1 for a polyamine having one primary or secondary amine and an isocyanate having two NCO groups; optionally, the reaction is carried out in a solvent such as toluene at elevated temperatures of 50-100°C, under an inert atmosphere, and at ambient pressure. Furthermore, the urea compounds are available from Sigma Aldrich, Evonik Industries AG, Huntsman, and AlChem.

[0190] In a preferred embodiment of the invention, the preferred polyalkylene polyamine for reaction with isocyanate comprises 3,3′-iminobis(N,N-dimethylpropylamine), also known as N′-(3-dimethylaminopropyl)-N,N-dimethylpropyl-1,3-diamine, and can be used as... The catalyst 15 was obtained from Evonik Industries AG and poly-N-methyl-azacyclobutane, the preparation and structure of which are taught in US2008-0194776-A1 (the disclosure of which is incorporated herein by reference). This embodiment is intended to be combined with all other disclosed aspects and embodiments of the invention.

[0191] In another preferred embodiment of the invention, the urea compound (a) is the reaction product of a primary amine with a tertiary amine functional group and a urea (carbamide). For example, 1,3-bis[3-(dimethylamino)propyl]urea (DABCO NE1082) is an example of this type of urea compound and is available from Evonik Corporation.

[0192] Polyphenol resins

[0193] In various embodiments, the encapsulating agent system of this disclosure further comprises a phenolic resin. The chemical structure of such a phenolic resin is represented by the following formula (B):

[0194]

[0195] Where R a R b R c and R d Each is independently hydrogen or branched or unbranched C1-C17 Alkyl group, and n is an integer from 0 to 50. In a preferred embodiment, R a R b R c and R d Each is independently hydrogen or branched or unbranched C1-C 10 Alkyl group, and n is an integer from 1 to 20. In these preferred embodiments, preferred alkyl groups include methyl, ethyl, n-propyl, isopropyl, and all isomers of butyl, pentyl, hexyl, octyl (including 2-ethylhexyl), decyl, and dodecyl. In another preferred embodiment of the phenolic resin, R a -R d Each is hydrogen. For other preferred embodiments of the aforementioned aspects and implementation schemes, R... a -R d Substituents may be selected individually or in any combination.

[0196] In a preferred embodiment of the invention, the phenolic resin is a phenolic varnish resin, a compound formed by the condensation of phenol with an aldehyde, particularly formaldehyde. Phenolic varnish resins are reaction products of monoaldehyde or dialdehyde (most commonly formaldehyde) with monophenols or polyphenolic materials. Preferred examples of monophenolic materials that can be used include phenol, cresol, p-tert-butylphenol, nonylphenol, octylphenol, and other alkyl and phenyl-substituted phenols. Preferred examples of polyphenolic materials include various diphenols, including bisphenol-A and bisphenol-F. Preferred aldehydes that can be used in phenolic varnish resins include formaldehyde, glyoxal, and higher aldehydes of up to about C4. Preferred phenolic varnish resins are typically complex mixtures with different hydroxyl functionalities.

[0197] Preferably, phenolic varnish resins can be prepared by reacting phenol or substituted phenol with aldehydes, especially formaldehyde, in the presence of acid or base. Preferred phenolic varnish resins are phenol-formaldehyde resins (e.g., Alnovol) with a weight-average molecular weight of 10,000 to 25,000. TM PN-320, available from Allnex GmbH.

[0198] Additional excipients

[0199] In various embodiments, the encapsulating agent system of this disclosure further includes additional excipients, which may be functional or nonfunctional monomeric compounds or polymeric compounds. Exemplary excipients are provided below. In various embodiments, the additional excipients may be present in an amount from about 5% by weight to about 75% by weight based on the total weight of the composition. If one or more additional excipients are present, this concentration may refer to the total amount of the additional excipients or a single additional excipient.

[0200] Functional compounds

[0201] The functional compounds according to this disclosure preferably include various chemical substances such as phenols, alkyl or aryl substituted carboxylic acids, sulfonic acids, phosphoric acids, phosphonic acids, and boric acids.

[0202] Preferred phenolic compounds that may be used contain at least one member selected from the group consisting of phenols or substituted phenols (substituents including alkyl, aryl ether, amino, or halogen atoms), such as p-tert-butylphenol, p-sec-butylphenol, o-tert-butylphenol, o-sec-butylphenol, p-tert-pentylphenol, p-tert-octylphenol, p-nonylphenol, p-cumylphenol, p-dodecylphenol, styrylphenol, 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, di-sec-butylphenol, 2,4-di-tert-pentylphenol, 2,4-dicumylphenol, o-cumyloctylphenol, α-naphthol, β-naphthol, bisphenol A, bisphenol F, bisphenol TMC, and mixtures thereof.

[0203] Preferred carboxylic acids that can be used contain at least one member selected from the group consisting of: acetic acid, propionic acid, hexanoic acid, 2-ethylhexanoic acid, decanoic acid, stearic acid, benzoic acid, salicylic acid, tall oil fatty acids (TOFA), dimer acids and mixtures thereof.

[0204] Various other acid-functionalized compounds may be used in the compositions disclosed herein. Non-limiting examples of such compounds include sulfonic acids, such as p-toluenesulfonic acid, methanesulfonic acid, dodecylbenzenesulfonic acid, trifluoromethanesulfonic acid, phosphonic acid, phosphoric acid, boric acid, etc.

[0205] Functional polymer compounds include a variety of chemical substances, such as polyesters, acrylic compounds, polyethers, polybutadiene, polyamides and combinations thereof.

[0206] As used herein, the term “functional” or “functionalized” refers to a compound or polymer that contains or has been modified to contain one or both of a carboxyl group and a hydroxyl group.

[0207] Polyester resin

[0208] Polyester resins are typically polycondensation products of polyols and polycarboxylic acids. According to this disclosure, polyester resins are preferably polycondensation products of polyols and polycarboxylic acids, and more preferably, polyester resins are polycondensation products of dicarboxylic acids, diols (diols), and trifunctional alcohols or carboxylic acids.

[0209] The chemical structure of this polyester resin is shown below:

[0210]

[0211] in:

[0212] R1 = saturated or unsaturated alkyl or aryl groups.

[0213] R2 = C 1-10 Alkyl or C1-10 cycloalkyl, and

[0214] n = 0-20.

[0215] Preferred examples of polycarboxylic acids, especially dicarboxylic acids, that can be used to prepare polyester resins include isophthalic acid, terephthalic acid, hexahydroterephthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4-oxybisbenzoic acid, 3,6-dichlorophthalic acid, tetrachlorophthalic acid, tetrahydrophthalic acid, hexahydroterephthalic acid, hexachlorobridgedmethylenetetrahydrophthalic acid, bridgedmethylenetetrahydrophthalic acid, phthalic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, cyclohexanedicarboxylic acid, maleic acid, fumaric acid, adipic acid, succinic acid, and trimellitic acid. These polycarboxylic acids can be used in their acid form or in their anhydride, acyl chloride, or low-carbon alkyl ester form. Mixtures of polycarboxylic acids can also be used. Furthermore, hydroxycarboxylic acids and lactones can be used. Preferred examples include hydroxypentanoic acid and ε-caprolactone. Monofunctional carboxylic acids can be used to close polymer chains.

[0216] Polyols, particularly diols, can react with carboxylic acids or their analogues as described above to prepare polyester resins. Examples of polyols include aliphatic diols such as ethylene glycol, propylene-1,2-diol, propylene-1,3-diol, butane-1,2-diol, butane-1,4-diol, butane-1,3-diol, 2,2-dimethylpropane-1,3-diol (neopentyl glycol), hexane-2,5-diol, hexane-1,6-diol, 2,2-bis-(4-hydroxycyclohexyl)-propane (hydrogenated bisphenol-A), 1,4-dihydroxymethylcyclohexane, diethylene glycol, dipropylene glycol, 2,2-bis[4-(2-hydroxyethoxy)-phenyl]propane, hydroxypentanyl ester of neopentyl glycol, 4,8-bis-(hydroxymethyl)tricyclo[5,2,1,0]decane (=tricyclodecanedihydroxymethyl), and 2,3-butenediol.

[0217] Trifunctional or more functional alcohols or carboxylic acids can be used to obtain branched polyesters. Preferred examples of suitable trifunctional or more functional alcohols or carboxylic acids include, but are not limited to, glycerol, hexane, trimethylolethane, trimethylolpropane, pentaerythritol and sorbitol, trimellitic acid, trimellitic anhydride, pyromellitic acid and dimethylolpropionic acid (DMPA).

[0218] Polyesters can be prepared by commonly known polymerization methods, such as conventional esterification and / or transesterification, or by esterification and / or transesterification using a catalyst. Available catalysts include organotin compounds and organotitanium compounds. The polyester resins used in this invention can be hydroxyl- or carboxyl-functionalized. The conditions and COOH / OH ratio used to prepare the polyester resin can be selected such that a final product having an acid value or hydroxyl value within the intended numerical range is obtained. Polyester resins are classified as acid-functionalized when their hydroxyl value is lower than their acid value (AV). Resins are classified as hydroxyl-functionalized when their acid value is lower than their hydroxyl value. Hydroxyl-functionalized resins should have a hydroxyl value of about >1 to 200, and carboxyl-functionalized polyesters should have an acid value of about >1 to about 200. Polyester compounds can be liquids, solids, or solutions in organic solvents.

[0219] acrylic resins

[0220] Preferably, the acrylic polymers used in this invention can be prepared by free radical polymerization of acrylic monomers and vinyl monomers with unsaturated monomers having hydroxyl or carboxyl groups. Preferred acrylic resins include those having hydroxyl functionality with a hydroxyl value >1 to 200 and carboxyl functionality with an acid value >1 to 300. The preferred softening point of the acrylic polymer is approximately 50°C to 200°C.

[0221] Preferred functional monomers are selected from acrylic acid, methacrylic acid, crotonic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate. Other preferred acrylic monomers may be selected from esters of α,β-ene unsaturated carboxylic acids having 3 to 8 carbon atoms. Preferred acrylic monomers have the following formula:

[0222]

[0223] in:

[0224] R1 is H or methyl; and

[0225] R2 is C 1-8 alkyl.

[0226] Preferred acrylic monomers used in the compositions of this disclosure include: ethyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, and lauryl methacrylate.

[0227] In various embodiments, preferred acrylic polymers may optionally contain olefinic monounsaturated vinyl comonomers that are different from the functional monomers and acrylic monomers. Preferred examples of available olefinic monounsaturated vinyl comonomers are styrene, propylene, vinyltoluene, dimethylstyrene, α-methylstyrene, and vinyl acetate. The acrylic compound may be a liquid, a solid, or a solution in an organic solvent.

[0228] Preferably, the copolymer can be prepared in any known manner, preferably by free radical polymerization in bulk, solution, emulsion, or suspension. Preferably, the reaction is carried out in the presence of a free radical initiator, such as benzoyl peroxide, tert-butyl peroxide, decanoyl peroxide, or an azo compound such as azobisisobutyronitrile. Preferably, such an initiator is present in an amount from 0.1 to about 5% by weight of the total monomers.

[0229] In various embodiments, commercial examples of acrylic resins used in the compositions of this disclosure include ISOCRYL C-78 (sold by Estron Chemical Inc.), EPOMATT G-152 (sold by Estron Chemical Inc.), and JONCRYL 67 (sold by BASF).

[0230] polyether resin

[0231] Preferred polyether resins for use in the compositions of this disclosure are polyalkylene glycols. Preferably, the polyalkylene glycols may have a molecular weight of 1,000 to 100,000 Daltons, more preferably 1,500 to 35,000 Da, and particularly preferably 1,500 to 10,000 Da. Particularly preferred polyalkylene glycols are polyethylene glycol. Additionally, polypropylene glycol, polytetrahydrofuran, or polybutane glycol obtained from 2-ethylethylene oxide or 2,3-dimethylethylene oxide are also suitable. Other suitable polyethers are random or block copolymers of polyalkylene glycols obtained from ethylene oxide, propylene oxide, and butane oxide, such as polyethylene glycol-polypropylene glycol block copolymers. These block copolymers may be of type AB or type ABA.

[0232] Further preferred polyalkylene glycols also include those alkylated at one or both terminal OH groups. Suitable alkyl groups are branched or straight-chain C1-to-C1-2000. 22 -alkyl, preferably C1-C 18 -alkyl, such as methyl, ethyl, n-butyl, isobutyl, pentyl, hexyl, octyl, nonyl, decyl, dodecyl, tridecyl or octadecyl.

[0233] Preferred polyalkylene glycols also include those that are acid-terminated at one or both terminal OH groups. Phosphonic acid-terminated polyethers are such examples of preferred polyalkylene glycols. Another example of preferred polyalkylene glycols is a polyoxyethylene chain grafted onto a polycarboxylate backbone.

[0234] Methods for manufacturing the polyether copolymers according to this disclosure are well known in the art. This preparation is carried out by free radical polymerization, preferably in solution, in a non-aqueous organic solvent, or in a mixture of non-aqueous and aqueous solvents. Suitable methods of preparation are described, for example, in WO 2007 / 051743 and WO 2009 / 013202, the disclosures of which relating to methods of preparation are incorporated herein by reference in their entirety.

[0235] Polybutadiene resin

[0236] Preferred examples of polybutadiene-based polyol resins used in the compositions of the present invention include homopolymers, such as 1,2-polybutadiene polyols and 1,4-polybutadiene polyols; copolymers, such as poly(pentadiene-butadiene) polyols, poly(butadiene-styrene) polyols, and poly(butadiene-acrylonitrile) polyols; and hydrogenated polybutadiene-based polyols obtained by hydrogenation of these polyol resins. These polybutadiene-based polyol resins can be purchased, for example, as Poly bd R-15HT (hydroxyl value = 102.7 mg KOH / mg, Mw1200) and Poly bd R-45HT (hydroxyl value = 46.6 mg KOH / mg, Mw2800) from Idemitsu Kosan Co., Ltd.

[0237] Furthermore, considering the advantageous effects of this disclosure, the polybutadiene-based polyol resin preferably has a hydroxyl value of 40 to 330 mg KOH / g, more preferably 40 to 110 mg KOH / g. Additionally, the polybutadiene-based polyol resin preferably has a weight-average molecular weight (GPC) of 50 to 3,000, more preferably 800 to 1,500.

[0238] Other preferred polybutadiene resins suitable for the compositions of this disclosure include carboxylated polybutadiene, which can be in the form of a liquid polymer that is transparent at room temperature and has a polybutadiene backbone microstructure consisting of a combination of vinyl 1,2-linked, trans 1,4-linked, and cis 1,4-linked bonds. Vinyl 1,2-linking is preferably 30% by weight or less. Cis 1,4-linking is preferably 40% by weight or more. Less than 40% by weight of cis 1,4-linking may result in reduced adhesiveness of the resulting composition, and is therefore undesirable.

[0239] The carboxylated polybutadiene component can be obtained by reacting a carboxyl-introducing compound with liquid polybutadiene. The 1,3-butadiene constituting the liquid polybutadiene and the carboxyl-introducing compound are preferably used in proportions of 80 to 98% by mass (1,3-butadiene) and 2 to 20% by mass (the carboxyl-introducing compound).

[0240] The liquid polybutadiene used in this reaction preferably has a number average molecular weight of 500 to 10,000, more preferably 1,000 to 7,000. Ideally, the liquid polybutadiene has a broad molecular weight distribution. More preferably, the liquid polybutadiene has an iodine value of 30 to 500 g iodine / 100 g material, as determined according to DIN 53241. Preferably, the liquid polybutadiene has a molecular structure consisting of 70 to 90% cis double bonds, 10 to 30% trans double bonds, and 0 to 3% vinyl double bonds.

[0241] Preferred examples of compounds that introduce a carboxyl group include ethylene-based unsaturated dicarboxylic acid compounds, such as ethylene-based unsaturated dicarboxylic acids and their anhydrides or monoesters. Specific examples of such compounds include maleic acid, fumaric acid, itaconic acid, 3,6-tetrahydrophthalic acid, itaconic anhydride, 1,2-dimethylmaleic anhydride, monomethyl maleate, or monoethyl maleate. Among these substances, maleic anhydride is preferred due to its safety, economy, and reactivity (maleic polybutadiene is preferred).

[0242] The method for manufacturing polybutadiene / maleic anhydride adducts is known in the prior art.

[0243] Maleated liquid polybutadiene preferably has an acid value of 50 to 120 (mg KOH / g), more preferably 70 to 90 (mg KOH / g), as determined according to DIN ISO 3682. An acid value less than 50 (mg KOH / g) results in reduced adhesion of the resulting composition, while an acid value greater than 120 (mg KOH / g) results in increased viscosity, making the composition less processable. The maleic acid percentage of the maleated liquid polybutadiene is preferably 6 to 20%, more preferably 6 to 15%, and even more preferably 7 to 10%, but this needs to be considered in conjunction with viscosity.

[0244] The viscosity of maleic acid-modified liquid polybutadiene (at 20°C), as determined by DIN 53214, is preferably 3 to 16 Pa·s, more preferably 5 to 13 Pa·s, and even more preferably 6 to 9 Pa·s.

[0245] Furthermore, the maleic acid-modified liquid polybutadiene contains 30% or less of vinyl double bonds. Compared to liquid polybutadiene in which cis double bonds are present in a percentage below the lower limit specified above, liquid polybutadiene in which cis double bonds are present within the range specified above tends to have higher flexibility and a higher percentage of maleic acid (i.e., acid value) as described above. Therefore, the composition will possess endowed with high adhesive properties and sufficient polarity, making it possible to manufacture more flexible compositions and easily adjust the flexibility of the compositions disclosed herein. Furthermore, the resulting compositions have improved decorative properties.

[0246] The viscosity of liquid polybutadiene containing cis double bonds at a percentage below the lower limit specified above increases rapidly with increasing maleic acid percentage, while the viscosity of liquid polybutadiene containing cis double bonds within the range specified above shows only a slight increase. The low viscosity within the range specified above ensures high reactivity and improved processability. Furthermore, the resulting composition exhibits improved decorative properties.

[0247] Non-limiting examples of polybutadiene resins according to this disclosure are maleic anhydride adducts of cis-1,4-polybutadiene (e.g., low molecular weight cis-1,4-polybutadiene), optionally having succinic anhydride side groups randomly distributed in the polymer chain. Examples of such polybutadiene resins include POLYVEST OC 800S, POLYVEST OC 1200S, and POLYVEST MA-75, each of which is manufactured by Evonik Industries.

[0248] polyamide resin

[0249] Polyamides are typically condensation copolymers formed by the reaction of a dicarboxylic acid with a diamine or by ring-opening of a lactam. Various polyamides can be manufactured by adjusting the number of carbon atoms. The nomenclature used herein first specifies the number of carbon atoms in the diamine and then the number of carbon atoms in the diacid. Thus, polyamide-6,6 has six carbons from the diamine and six carbons from the diacid, while polyamide-6,12 would have six carbons from the diamine and twelve carbons from the diacid. Polyamide-6 is a homopolymer formed by ring-opening polymerization (i.e., ring-opening polymerization of caprolactam). Polyamides can also be nylon-9, nylon-12, nylon-11, nylon 4,6, nylon 6,10, or any polyamide listed herein.

[0250] Polyamide resins that can be used in the compositions disclosed herein include nylon-6, nylon 6-6, copolymers of nylon-6 and nylon 6-6, nylon-9, nylon-10, nylon-11, nylon-12, nylon 6-10, aromatic polyamides, elastomeric polyamides, and mixtures thereof.

[0251] The conditions and COOH / NH2 ratio used to prepare polyamide resins can be selected to obtain a final product with an acid value or amine value within the intended numerical range. Polyamide resins are classified as acid-functional when their amine value is lower than their acid value (AV). Resins are classified as amine-functional when their acid value is lower than their amine value. Evonik's Ancatherm 592 is an example of an acid-functional thermoplastic polyamide.

[0252] Nonfunctional polymer compounds

[0253] Nonfunctional polymeric compounds that can be used in the compositions disclosed herein include copolymers of polyimides, styrene-butadiene resins, and other olefins, and combinations thereof.

[0254] Preferred examples of nonfunctional resin compounds that can be used in combination with phenolic resins in this disclosure include compounds from Evonik’s POLYVEST liquid polybutadiene product line, thermoplastic acrylic resins and MBS polymers from Dow’s Paraaloid product line, nonfunctional polyamides from Evonik’s Vestamid product line, styrene-based block copolymers (SBCs) from Kraton made from butadiene, styrene and isoprene raw materials, and finally, ketone-aldehyde condensation resins, such as Evonik’s TEGO Variplus AP, can also be used in combination with polyphenols in this disclosure.

[0255] Curable epoxy resin

[0256] Each aspect and embodiment of the invention disclosed herein is intended to be combined individually and in all possible combinations with all other disclosed aspects and embodiments of the invention.

[0257] A solution of a urea compound in combination with the aforementioned phenolic resin and / or other resins is used as a curing agent for the epoxy resin. Epoxy resins available under the trade names DER 383 or DER 333 (available from Dow) and EPON 826 or EPON 828 (available from Hexion Specialty Chemicals) are suitable for use with the latent curing accelerator compositions disclosed herein.

[0258] Other epoxy resins may include, but are not limited to, bifunctional epoxides, such as bisphenol-A and bisphenol-F resins. As used herein, multifunctional epoxy resins are described as compounds containing two or more 1,2-epoxy groups per molecule. This type of epoxide compound is well known to those skilled in the art and is described in Y. Tanaka, “Synthesis and Characteristics of Epoxides,” CA May ed., Epoxy Resins Chemistry and Technology (Marcel Dekker, 1988), which is hereby cited and incorporated herein by reference.

[0259] A class of epoxy resins applicable to this disclosure include glycidyl ethers of polyphenols, including glycidyl ethers of diphenols. Exemplary examples include, but are not limited to, glycidyl ethers of the following substances: 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 (commercially known as bisphenol A), bis-(4-hydroxyphenyl)-methane (commercially known as bisphenol-F, and which may contain varying amounts of the 2-hydroxyphenyl isomer), etc., or any combination thereof. Additionally, higher diphenols with the following structures may also be used in this disclosure:

[0260]

[0261] Where m is an integer and R is a divalent hydrocarbon residue of a diphenol (such as those listed above).

[0262] The material according to this formula can be prepared by polymerizing a mixture of diphenol and epichlorohydrin or by advancing a mixture of diglycidyl ether of diphenol and diphenol. Although the value of m is an integer in any given molecule, the material is always a mixture and can be characterized by the average value of m, which is not necessarily an integer. In one aspect of this disclosure, polymeric materials with an average value of m between 0 and about 7 can be used. In other embodiments, the epoxy component can be a polyglycidylamine derived from one or more of 2,2'-methylenediphenylamine, m-xylenediphenylamine, hydantoin, and isocyanates.

[0263] The epoxy component can be a cycloaliphatic (alicyclic) epoxide. Examples of suitable alicyclic epoxides include diepoxides of alicyclic esters of dicarboxylic acids, such as bis(3,4-epoxycyclohexylmethyl) oxalate, bis(3,4-epoxycyclohexylmethyl) adipic acid, bis(3,4-epoxy-6-methylcyclohexylmethyl) adipic acid, vinylcyclohexene diepoxide; limonene diepoxide; bis(3,4-epoxycyclohexylmethyl) pimecrolate; dicyclopentadiene diepoxide; and other suitable alicyclic epoxides. Other suitable diepoxides of alicyclic esters of dicarboxylic acids are described, for example, in WO 2009 / 089145A1, which is hereby incorporated herein by reference.

[0264] Other alicyclic epoxides include 3,3-epoxycyclohexylmethyl esters of 3,4-epoxycyclohexanecarboxylic acid, such as 3,4-epoxycyclohexylmethyl ester; 3,3-epoxy-1-methylcyclohexanecarboxylic acid; 6-methyl-3,4-epoxycyclohexanecarboxylic acid; and 3,4-epoxy-2-methylcyclohexyl ester. Other suitable 3,4-epoxycyclohexanecarboxylic acid esters are described, for example, in U.S. Patent 2,890,194, which is incorporated herein by reference. In other embodiments, the epoxy component may comprise a polyol polyglycidyl ether derived from polyethylene glycol, polypropylene glycol, or polytetrahydrofuran, or combinations thereof.

[0265] Resins 1 and 2 are reacted with the urea compound under nitrogen at an elevated temperature of 120 to 180°C. Sufficient resin is reacted to block substantially all tertiary amine functional groups in the urea composition. Generally, approximately 25% to 100% by weight of the resin, based on the urea compound, is added to the urea composition and reacted with it. If insufficient phenolic resin 1 is added, the resulting product is viscous and agglomerated. If too much is added, the activation temperature for curing the epoxy resin becomes too high. After a 1-hour reaction time, the hot solution is poured onto a Teflon block or aluminum sheet and allowed to cool to room temperature. The resin can be added to the reactor either pure or dissolved in some type of polar solvent such as methanol, as described above. In the latter case, the resulting reaction mixture is refluxed for 2 hours to form a clear solution. The mixture is then cooled to room temperature, and the solvent is removed by evaporation. The resulting product is further dried under vacuum.

[0266] Once collected from the reactor, the final curing agent formulation is ground into a fine powder using methods such as spray drying, ceramic bead milling, jet milling, and coffee grinding. The particle size of the powder can range from 1 micrometer to 100 micrometers. The powder is then incorporated into the epoxy resin and mixed using a high-speed mixer, a Cowles blade mixer, or a planetary mixer. Optional additives, such as wetting agents, fillers, defoamers, and rheology modifiers, can be added if desired.

[0267] In one aspect of the invention, the urea-(resin 1:resin 2) compound reaction product can be used as an epoxy curing agent in one-component and two-component epoxy compositions, such as adhesives and composites, decorative and protective coatings (including powder coatings, coatings on concrete, wood, metal, etc.), filament winding, printed circuit boards, electroplating and encapsulation, in-situ cured pipes, impact-resistant adhesives, transfer molding powders, prepregs using solid or liquid epoxy resins, sheet molding compounds, resin transfer molding, EV battery pack adhesives, and similar epoxy resin applications. Typically, 0.5 to 10 parts by weight (pbw) of the urea-(resin 1:resin 2) compound reaction product is used per 100 pbw of epoxy resin in the epoxy composition, preferably 2 to 6 pbw.

[0268] In another aspect of the invention, the urea-(resin 1:resin 2) compound reaction product can also be used as an accelerator for curing agents (such as dicyandiamide, thiols, and acid anhydrides such as acetic anhydride) in one-component and two-component epoxy compositions, such as adhesives and composites, decorative and protective coatings (including powder coatings, coatings on concrete, wood, metal, etc.), filament winding, printed circuit boards, electroplating and encapsulation, in-situ cured pipes, impact-resistant adhesives, transfer molding powders, prepregs using solid or liquid epoxy resins, sheet molding compounds, resin transfer molding, EV battery pack adhesives, and similar epoxy resin applications. Typically, 0.5 to 10 parts by weight (pbw) of curing agent, preferably 2 to 6 pbw, are used per 100 pbw of epoxy resin in the epoxy composition, and 0.5 to 10 parts by weight (pbw) of urea-(resin 1:resin 2) compound reaction product, preferably 2 to 6 pbw, are used per 100 pbw of epoxy resin in the epoxy composition as an accelerator.

[0269] The reaction product of a urea-(resin 1:resin 2) compound is combined with an epoxy resin as a curing agent or as an accelerator together with the curing agent, said epoxy resin being a polyepoxide compound containing more than one 1,2-epoxy group per molecule. Such epoxides are well known in the field of epoxy resins and are described in Y. Tanaka, “Synthesis and Characteristics of Epoxides”, CA May ed., Epoxy Resins Chemistry and Technology (Marcel Dekker, 1988). Examples include those epoxides disclosed in U.S. Patent 5,599,855 (columns 5 / 6 to 6 / 20), which is incorporated herein by reference. Preferred polyepoxides are diglycidyl ethers of bisphenol A, higher diglycidyl ethers of bisphenol A, diglycidyl ethers of bisphenol F, and epoxy phenolic varnish resins. Both liquid and solid epoxy resins are suitable for use in one-component epoxy compositions. Powder coating compositions may contain solid epoxy resins, urea compounds, and dicyandiamide.

[0270] In one aspect of the invention, the one-component epoxy resin composition comprises a reaction product of such a urea-(resin 1:resin 2) compound as a curing agent and a contact product of epoxy resin. In another aspect of the invention, the one-component epoxy resin composition comprises a contact product of dicyandiamide, thiol, or acid anhydride as a latent curing agent, a reaction product of such a urea-(resin 1:resin 2) compound as an accelerator for said curing agent, and epoxy resin.

[0271] In another aspect of the invention, a one-component 100% solid epoxy composition comprising a urea-(resin 1:resin 2) compound reaction product, a latent curing agent (such as dicyandiamide, thiol or acid anhydride), and an epoxy resin provides low-temperature curing and storage stability, i.e., a longer latency period.

[0272] In another aspect of the invention, a one-component water-based epoxy composition comprising a urea-(resin 1:resin 2) compound reaction product, a latent curing agent (such as dicyandiamide, thiol, or anhydride), and an epoxy resin provides low-temperature curing and storage stability, i.e., a longer latency period.

[0273] In another aspect of the invention, a one-component 100% solid epoxy composition comprising a urea-(resin 1:resin 2) compound reaction product as a latent curing agent, optionally an accelerator, and an epoxy resin provides low-temperature curing and storage stability, i.e., a longer latency period.

[0274] In another aspect of the invention, a one-component water-based epoxy composition comprising a urea-(resin 1:resin 2) compound reaction product as a latent curing agent, optionally an accelerator, and an epoxy resin provides low-temperature curing and storage stability, i.e., a longer latency period.

[0275] It has been found that the urea-(resin 1:resin 2) compound reaction product of the present invention cures epoxy resin compositions at low temperatures and can be used as the sole curing agent in a single-component epoxy resin composition or as an accelerator for latent curing agents (such as dicyandiamide (DICY), thiols or acid anhydrides).

[0276] Epoxy compositions containing urea-(resin 1:resin 2) compound reaction products as the sole curing agent or accelerator can provide long pot life, low activation temperature, good glass transition temperature, or a combination of these properties.

[0277] The term "contact product" is used herein to describe a composition in which the components are contacted together in any order, in any manner, and 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 described herein. In addition, when the components are contacted together, two or more of the components may react to form other components.

[0278] Epoxy compositions containing urea-(resin 1:resin 2) compound reaction products and epoxy resins can be formulated with a variety of ingredients known to those skilled in the art of coating formulation, including solvents, fillers, pigments, pigment dispersants, rheology modifiers, thixotropic agents, flow and leveling aids, and defoamers.

[0279] Although a one-component epoxy composition containing 1 to 90% by weight of organic solvent, or an epoxy composition containing 100% by weight of solids, or a water-based (i.e., aqueous) epoxy composition containing 20 to 80% by weight of solids may be used, the epoxy composition is preferably 100% by weight of solids.

[0280] The epoxy compositions of the present invention can be applied as coatings using a variety of techniques, including spraying, brushing, rolling, paint mitts, etc. As is well understood in the art, many substrates are suitable for application of the coatings of the present invention with appropriate surface pretreatment. Such substrates include, but are not limited to, many types of metals, particularly steel and aluminum, as well as concrete.

[0281] The one-component epoxy composition of the present invention can be cured at elevated temperatures from about 80°C to about 240°C, wherein a curing temperature of 120°C to 160°C is preferred. The two-component epoxy composition of the present invention can be cured at temperatures from about 80°C to about 240°C, wherein a curing temperature of 80°C to 160°C is preferred. Detailed Implementation

[0282] Example

[0283] Example 1

[0284] 208 g of N′-(3-dimethylaminopropyl)-N,N-dimethyl-prop-1,3-diamine was loaded into a 1-liter four-necked glass container equipped with a mechanical stirrer, thermocouple, electrically heated jacket, feeding funnel, reflux condenser, and nitrogen purging. The container was heated to 60-70°C under nitrogen. Once the temperature stabilized, 127 g of toluene diisocyanate monomer was slowly metered in over 45-60 minutes via the feeding funnel. After the addition was complete, the mixture was maintained at 60-80°C for 1 hour. The temperature was then increased to 150°C, and 82.5 g of Isocryl C-78 acrylic resin and 82.5 g of Alnovol PN320 phenolic resin were added over 60-90 minutes. Once the addition was complete, the mixture was maintained at 150°C with stirring for another 1 hour. The product was then discharged from the reactor at this temperature and allowed to cool to ambient temperature before grinding.

[0285] Example 2

[0286] 208 g of N′-(3-dimethylaminopropyl)-N,N-dimethyl-prop-1,3-diamine was loaded into a 1-liter four-necked glass container equipped with a mechanical stirrer, thermocouple, electrically heated jacket, feeding funnel, reflux condenser, and nitrogen purging. The container was heated to 60-70°C under nitrogen. Once the temperature stabilized, 127 g of toluene diisocyanate monomer was slowly metered in over 45-60 minutes via the feeding funnel. After the addition was complete, the mixture was maintained at 60-80°C for 1 hour. The temperature was then increased to 150°C, and 82.5 g of Epomatt G-152 acrylic resin and 82.5 g of Alnovol PN320 phenolic resin were added over 60-90 minutes. Once the addition was complete, the mixture was maintained at 150°C with stirring for another 1 hour. The product was then discharged from the reactor at this temperature and allowed to cool to ambient temperature before grinding.

[0287] Example 3

[0288] 208 g of N′-(3-dimethylaminopropyl)-N,N-dimethyl-prop-1,3-diamine was loaded into a 1-liter four-necked glass container equipped with a mechanical stirrer, thermocouple, electrically heated jacket, feeding funnel, reflux condenser, and nitrogen purging. The container was heated to 60-70°C under nitrogen. Once the temperature stabilized, 127 g of toluene diisocyanate monomer was slowly metered in over 45-60 minutes via the feeding funnel. After the addition was complete, the mixture was maintained at 60-80°C for 1 hour. The temperature was then increased to 150°C, and 33 g of Joncryl 67 acrylic resin and 132 g of Alnovol PN320 phenolic resin were added over 60-90 minutes. Once the addition was complete, the mixture was maintained at 150°C with stirring for another 1 hour. The product was then discharged from the reactor at this temperature and allowed to cool to ambient temperature before grinding.

[0289] Example 4

[0290] A mixture of 220.3 g of N'-(3-dimethylaminopropyl)-N,N-dimethyl-prop-1,3-diamine and 50 g of toluene was loaded into a 1-liter four-necked glass vessel equipped with an air-driven mechanical stirrer, thermocouples, a heating jacket with a water circulation bath, and nitrogen purging. The vessel was heated to 60–70 °C under nitrogen. Once the temperature stabilized, 104.9 g of toluene diisocyanate was metered into the 50 g of toluene over 45–60 minutes. After the addition was complete, the mixture was held at 70 °C for 1 hour. The temperature was lowered to 40 °C, and the crude liquid product from the reactor was placed on a rotary evaporator to remove all toluene. Temperature and vacuum were applied slowly to prevent bubbling. The final conditions for distillation were 10–20 mmHg and 80 °C for 15 minutes. The stripping product was then placed in a three-necked flask equipped with a mechanical stirrer, thermocouples, an electrically heated jacket, and nitrogen purging. Stabilize the container at 140-160°C and add 174.8 g of phenolic resin over 30-60 minutes. Maintain the mixture at 160°C with stilling for another hour. Discard the product from the reactor at this temperature and allow it to cool to ambient temperature before grinding.

[0291] Example 5 - Differential Scanning Calorimetry (DSC) of Resin-Blocked Urea Curing Agent

[0292] Curing profiles of the reaction products of Examples 1-4 as epoxy curing agents were screened using differential scanning calorimetry (DSC). The epoxy formulation contained polyglycidyl ether (Epon 828) of bisphenol A resin, 2 phr (parts by weight / 100 parts by weight of resin) of Examples 1-4 as an accelerator, 6 phr of dicyandiamide as a curing agent, and 2% by weight of fumed silica. The resulting mixture was thoroughly blended for 2 minutes using a high-speed mixer. Immediately after preparation, the mixture was analyzed by DSC (TAinstruments QA20) to determine the initial curing temperature, heat of reaction (ΔH), and glass transition temperature (Tg). DSC was run according to standard methods using the software included in the DSC. DSC analysis was performed on approximately 10 to 15 mg of material samples using a ramp heating rate of 10 °C / min. The obtained data are shown in Table 1 below.

[0293] Table 1

[0294]

[0295] Example 6: Latency of resin-blocked urea curing agent

[0296] The latency of Examples 1-4 as DICY accelerators was studied at 40°C, using an epoxy formulation comprising bisphenol A resin polyglycidyl ether (Epon 828), 2 phr of the accelerator, 6 phr of dicyandiamide as a curing agent, and 2 wt% fumed silica. Using 0.5 mL of sample, the latency of viscosity change during aging at 40°C was monitored at 25°C using a Brookfield cone-plate viscometer (model HADVII+CP) with a #52 rotor. Storage stability was determined by visually observing the gelation time. Fresh epoxy samples were thoroughly mixed for 2 minutes using a high-speed mixer, cooled to 25°C, and the initial viscosity was measured using a Brookfield cone-plate viscometer. Samples were stored in a 40°C oven, cooled to 25°C, and viscosity changes were measured over time. The resulting data are shown in Table 2.

[0297] Table 2

[0298]

[0299] Example 7: Adhesive Properties

[0300] The adhesive properties of resin-sealed urea curing agents were measured using lap shear and T-peel techniques. Lap shear measurements were performed on an Instron Model 1125 instrument according to ASTM method D1876, repeated at least five times. The test material was applied to a 1” x 0.4” x 0.32” cold-rolled steel sheet (ACT Cold Roll Steel 01X04X032 B952 P60 DIW: unpolished). The material was applied to the 1 / 2” end of the specimen with 10 mil glass beads (based on 1% by weight of the formulation). Another specimen was placed on top, overlapping the 1 / 2” section of the other specimen. The plate with the test material was cured at 130°C to 160°C for 15–30 minutes, then cooled to room temperature before measurement.

[0301] T-peel measurements were performed on an Instron Model 1125 instrument according to ASTM method D1876 for lap shear, repeated at least five times. The test material was applied to a 1” x 4” x 0.32” cold-rolled steel sheet (ACT Cold Roll Steel 01X04X032B952 P60 DIW: unpolished), which was pre-bent at a right angle 7 / 8” from the end, leaving a 3 1 / 8” x 1” surface. The material was applied with 10 mil glass beads (based on 1% by weight of the formulation). The test material was cured at 130°C to 160°C for 15–30 minutes, then cooled to room temperature before measurement. The results of the lap shear and T-peel measurements are shown in Table 3 below:

[0302] Table 3

[0303]

[0304] Although the invention has been described with reference to certain aspects and embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for its elements without departing from the scope of the invention. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of the invention without departing from its essential scope. Therefore, the invention is not intended to be limited to the specific aspects or embodiments disclosed as the best mode of carrying out the invention, but rather the invention will include all embodiments falling within the scope of the appended claims, including the use of aspects or embodiments of the invention individually or in combination with each other.

Claims

1. A latent curing accelerator composition comprising: Encapsulating agent system, the encapsulating agent system comprising: Urea compounds, Polyphenol resins, and Additional excipients selected from functional and / or non-functional components.

2. The composition according to claim 1, wherein the polyphenol resin is a phenolic varnish resin.

3. The composition according to claim 2, wherein the phenolic varnish resin is a phenol-formaldehyde resin.

4. A latent curing accelerator composition comprising: Encapsulating agent system, the encapsulating agent system comprising: Urea compounds, and Additional excipients selected from functional and / or non-functional components.

5. The composition according to any one of the preceding claims, wherein the urea compound comprises the reaction product of an isocyanate and an alkylated polyalkylene polyamine.

6. The composition according to any one of the preceding claims, wherein the isocyanate is selected from aliphatic isocyanates, alicyclic isocyanates and aromatic isocyanates.

7. The composition according to claim 6, wherein the isocyanate is selected from phenyl isocyanate, toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and polymeric diphenylmethane diisocyanate.

8. The composition according to any one of claims 5-7, wherein the alkylated polyalkylene polyamine has at least one primary or secondary amine and at least two tertiary amines of formula (A): Where R1, R2, R3, R4 and R5 are independently hydrogen, methyl or ethyl; m and n are independently integers from 1 to 6; and X is an integer from 1 to 10.

9. The composition according to claim 8, wherein R1 is hydrogen or methyl; R2 and R4 are methyl; and R3 and R5 are hydrogen or methyl.

10. The composition according to any one of the preceding claims, wherein the additional excipient is a functional polymer compound.

11. The composition according to any one of the preceding claims, wherein the additional excipient is selected from polyamide resins, polybutadiene resins, polyester resins, polyether resins, and acrylic resins.

12. The composition according to any one of the preceding claims, wherein the additional excipient is an acrylic resin.

13. The composition according to any one of the preceding claims, wherein the composition is combined with an epoxy resin to form a curable epoxy system, wherein the curable epoxy system does not gel after 4 weeks under accelerated aging conditions (i.e., 4 weeks of storage at 40°C).

14. The composition according to any one of the preceding claims, wherein the composition is combined with an epoxy resin to form a curable epoxy system, wherein the curable epoxy system provides an overlap shear of greater than 700 psi.

15. A method for curing a substance using a latent curing accelerator composition according to any one of the preceding claims, the method comprising the steps of combining the substance with the latent curing accelerator composition and heating the resulting mixture.

16. The method of claim 15, wherein the substance is an epoxy resin.

17. The method according to claim 15 or 16, wherein the composition is a latent curing agent for epoxy resins (e.g., a single latent curing agent), or wherein the composition is used as a curing agent for epoxy resins such as DICY or an anhydride accelerator.

18. The method according to any one of claims 15-17, wherein the composition is used as a latent curing accelerator for structural adhesives and composites, electro-encapsulation and encapsulation, compositions for reinforcement and / or damping, in-situ cured pipes, impact-resistant adhesives, filament winding, transfer molding powders, prepregs using solid or liquid epoxy resins, sheet molding compounds, coatings on concrete, wood, metal, etc., resin transfer molding and / or EV battery pack adhesives.

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