Curing accelerator, epoxy resin material and preparation method thereof

Abstract

The invention relates to the technical field of epoxy resin materials, and discloses a curing accelerator, an epoxy resin material and a preparation method of the epoxy resin material. The preparation method comprises the following steps: preparing the following components in parts by weight: 100 parts of a polymer of 4, 4 '-(1-methylethylene) bisphenol and chloromethyl ethylene oxide, 50-80 parts of an aromatic polyamine curing agent, 8-12 parts of an imidazole adduct and 20-40 parts of 1-(3-aminopropyl)-3-methylimidazole brominated hydrobromate; the epoxy resin material comprises 100 parts of trifunctional epoxy resin, 100-180 parts of an anhydride curing agent and 2-7 parts of a curing accelerator. The epoxy resin material is prepared by taking the curing accelerator, an anhydride curing agent and trifunctional epoxy resin as raw materials, and the obtained epoxy resin material has good high temperature resistance and mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resin materials, and particularly to a curing accelerator, an epoxy resin material and a preparation method thereof. Background Art

[0002] The solvent-free epoxy resin material is an epoxy resin system that does not add volatile organic solvents during the preparation and use processes. It is composed of an epoxy resin and a curing agent, and forms a three-dimensional network structure through a chemical reaction. Because of its advantages such as environmental protection and high efficiency, it is widely used in the fields of coatings and composite materials. The existing solvent-free epoxy resin materials can withstand a certain temperature and pressure, but there is still a phenomenon of poor high-temperature resistance.

[0003] At present, there is a method to improve the high-temperature resistance of solvent-free epoxy resin materials by optimizing the curing system. Taking bisphenol A epoxy resin (E51) and methylhexahydrophthalic anhydride (MHHPA) as an example, at high temperatures, the acid anhydride MHHPA is prone to partial hydrolysis, thus generating dicarboxylic acid monomers. These dicarboxylic acid monomers will undergo ring-opening addition reactions with the epoxy groups on the epoxy resin E51 to produce secondary hydroxyl groups, and then the ring-opening addition reactions between carboxylic acids and epoxy groups will continuously occur until the reaction monomers are completely consumed. In this way, a cross-linked network structure with a relatively high molecular weight is formed. The tensile strength of the cured product formed by E51 and MHHPA can reach 32.11 MPa, the flexural strength can reach 92.83 MPa, and the shear strength can reach 11.03 MPa; in order to improve the high-temperature resistance, after the above-mentioned cured product is cured at 220 °C for 2 h, its tensile strength, flexural strength, and shear strength are respectively reduced by 19.84%, 24.59%, and 34.63% compared with the product before high-temperature curing. The decline in mechanical properties is due to the fact that at high temperatures, the epoxy resin will also undergo the cleavage of weak bonds on the α-carbon. The cleavage of these weak bonds will lead to the destruction of molecular chains, generating a large number of free radicals, and these free radicals will further initiate a chain reaction, resulting in the cleavage of more molecular chains, thus seriously affecting the mechanical properties of the epoxy resin. Therefore, how to optimize the curing system to obtain a solvent-free epoxy resin material with both excellent high-temperature resistance and mechanical properties is an urgent problem to be solved. Summary of the Invention

[0004] In view of this, the present invention provides a curing accelerator, an epoxy resin material and a preparation method thereof. The curing system is optimized with the curing accelerator of the present invention to solve the problem that it is difficult to effectively balance the high-temperature resistance and mechanical properties of the existing epoxy resin materials.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] On the one hand, the present invention provides a curing accelerator, comprising raw materials in the following parts by weight: 100 parts of a polymer of 4,4'-(1-methylethylidene) bisphenol and chloromethyl oxirane, 50 - 80 parts of an aromatic polyamine curing agent, 8 - 12 parts of an imidazole adduct, and 20 - 40 parts of 1-(3-aminopropyl)-3-methylimidazolium hydrobromide bromate.

[0007] Preferably, the polymer of 4,4'-(1-methylethylidene) bisphenol and chloromethyl oxirane is a bisphenol A epoxy resin with an epoxy equivalent of 150 - 550 g / eq.

[0008] Preferably, the aromatic polyamine curing agent includes one or more of m-phenylenediamine (m-PDA), 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl sulfone (DDS), m-xylylenediamine (MXDA), and diethyltoluenediamine (DETDA).

[0009] Preferably, the imidazole adduct includes one or more of the adducts of 2-methylimidazole (2MZ), 2-ethyl-4-methylimidazole (2E4MZ), 2-phenylimidazole (2PZ) with isocyanate, the adduct of 1-(2-aminoethyl)-2-methylimidazole with isocyanate, and 2-phenyl-4,5-dihydroxyimidazolium salt.

[0010] On the other hand, the present invention also provides an epoxy resin material, comprising 100 parts of a trifunctional epoxy resin, 100 - 180 parts of an acid anhydride curing agent, and 2 - 7 parts of the curing accelerator described in any one of the above.

[0011] Preferably, the trifunctional epoxy resin includes one or more of triglycidyl p-aminophenol, triglycidyl tris(2-hydroxyethyl) isocyanurate, diglycidyl 4,5-epoxyhexane-1,2-dicarboxylate, triphenolmethane triglycidyl ether, tris(epoxypropyl) isocyanurate, tris(2,3-epoxypropyl) isocyanurate, and a phenylboronic acid polymer based on the ring-opening polymerization of amino epoxy groups.

[0012] Preferably, the acid anhydride curing agent includes one or more of methyl nadic anhydride, hexachlorendomethylene tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, tetrabromophthalic anhydride, glycerol phthalate anhydride, diphenyl ether tetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, hydrogenated methyl nadic anhydride, diphenyl sulfone-3,3',4,4'-tetracarboxylic dianhydride, methylcyclohexene tetracarboxylic dianhydride, and tung oil anhydride.

[0013] Preferably, the epoxy resin material further includes 1 - 10 parts of a non-trifunctional glycidylamine epoxy resin and / or 1 - 5 parts of a diluent and / or 0.2 - 0.6 parts of a coupling agent and / or 0.1 - 0.4 parts of a rheological agent.

[0014] Preferably, the non-trifunctional glycidylamine epoxy resin includes one or more of bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, resorcinol epoxy resin, 4,4'-diaminodiphenylmethane epoxy resin, bisphenol methane epoxy resin, and 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate.

[0015] Preferably, the diluent includes one or more of 1,4-butanediol diglycidyl ether, pentaerythritol diglycidyl ether, and tolyl glycidyl ether.

[0016] Preferably, the coupling agent includes one or more of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, and phenylaminomethylidene triethoxysilane.

[0017] Preferably, the rheological agent includes one or more of hydrogenated castor oil and polyethylene wax.

[0018] In addition, the present invention also provides a preparation method of the above epoxy resin material, comprising the following steps:

[0019] (1) Mix the raw materials to obtain a mixture;

[0020] (2) Subject the mixture to stepwise high-temperature curing to obtain the epoxy resin material.

[0021] Preferably, the temperature of the mixing is 40-60°C.

[0022] Preferably, the stepwise high-temperature curing includes a first curing stage and a second curing stage carried out in sequence. The first curing stage is carried out at 100-120°C for 1-2 h, and the second curing stage is carried out at 150-180°C for 1-2 h.

[0023] Preferably, the stepwise high-temperature curing includes a first curing stage, a second curing stage, and a third curing stage carried out in sequence. The first curing stage is carried out at 100-120°C for 1-2 h, the second curing stage is carried out at 150-180°C for 1-2 h, and the third curing stage is carried out at 220-240°C for 1-2 h.

[0024] The present invention provides a curing accelerator, an epoxy resin material, and a preparation method thereof. Compared with the prior art, the beneficial effects are as follows:

[0025] The curing accelerator of the present invention is prepared from a polymer of 4,4'-(1-methylethylidene)bisphenol and chloromethyl oxirane, an aromatic polyamine curing agent, an imidazole adduct, and 1-(3-aminopropyl)-3-methylimidazolium hydrobromide bromate. An epoxy resin material is prepared from the curing accelerator, an acid anhydride curing agent, and a trifunctional epoxy resin. The obtained epoxy resin material has both good high-temperature resistance and mechanical properties. The glass transition temperature of the epoxy resin material can reach 230 °C, the tensile strength reaches more than 25 MPa, the flexural strength reaches more than 125 MPa, and the shear strength reaches more than 6 MPa. Detailed implementation mode

[0026] The present invention will be described below through specific examples. Those skilled in the art can understand that the following specific examples are only for illustrative purposes and do not limit the scope of the present invention in any way. In addition, in the following examples, unless otherwise specified, the reagents and equipment used are commercially available. If the specific processing conditions and methods are not clearly described in the following examples, the conditions and methods known in the art can be used for processing.

[0027] In one aspect of the present invention, a curing accelerator is proposed, which comprises the following raw materials in parts by weight: 100 parts of a polymer of 4,4'-(1-methylethylidene)bisphenol and chloromethyl oxirane, 50-80 parts of an aromatic polyamine curing agent, 8-12 parts of an imidazole adduct, and 20-40 parts of 1-(3-aminopropyl)-3-methylimidazolium hydrobromide bromate.

[0028] In the present invention, the polymer of 4,4'-(1-methylethylidene)bisphenol and epichlorohydrin is used as a solvent or carrier, which can improve the dispersion uniformity of each raw material in the curing accelerator system and avoid phase separation. Moreover, the polymer of 4,4'-(1-methylethylidene)bisphenol and epichlorohydrin is a difunctional epoxy resin with good toughness. If high-rigidity resins such as trifunctional epoxy resin / tetrafunctional epoxy resin are used, the mechanical strength of the final epoxy resin material will be reduced. The aromatic polyamine curing agent is used as the main curing agent and directly participates in the cross-linking reaction of epoxy groups. The amino group of the polyamine undergoes a nucleophilic addition reaction with the epoxy group to generate ether bonds and hydroxyl groups, forming a cross-linked structure. The addition of the aromatic polyamine curing agent can reduce the curing temperature of the epoxy resin, shorten the reaction time, and improve the high-temperature resistance of the highest epoxy resin material. The imidazole adduct can accelerate the curing reaction of epoxy group - amino group. The nitrogen atom of imidazole has a lone pair of electrons, which can attack the epoxy group to form an oxygen anion intermediate, reducing the reaction activation energy and simultaneously releasing active hydrogen to promote the rapid cross-linking of amino group and epoxy group. 1-(3-aminopropyl)-3-methylimidazolium hydrobromide bromate has both the functions of a promoter and an auxiliary curing agent. The bromide ion acts as a nucleophile to catalyze the ring-opening of the epoxy group, accelerating the reaction. The amino group in the molecule can directly participate in the cross-linking of the epoxy group to form a denser network structure. When combined with the imidazole adduct, it further reduces the curing temperature and increases the curing degree.

[0029] In some embodiments of the present invention, the curing accelerator includes the polymer of 4,4'-(1-methylethylidene)bisphenol and epichlorohydrin, and the polymer of 4,4'-(1-methylethylidene)bisphenol and epichlorohydrin is a bisphenol A epoxy resin with an epoxy equivalent of 150 - 550 g / eq. If its addition amount is too much, the overall heat resistance of the epoxy resin material will decrease.

[0030] In some embodiments of the present invention, the curing accelerator includes an aromatic polyamine curing agent, and the addition amount of the aromatic polyamine curing agent is 50 - 80 parts, specifically, it can be 50 parts, 60 parts, 70 parts, 80 parts, etc. The aromatic polyamine curing agent includes one or more of m-phenylenediamine (m-PDA), 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl sulfone (DDS), m-xylylenediamine (MXDA), diethyltoluenediamine (DETDA). If the addition amount of the aromatic polyamine curing agent is too much, the mixture will react too fast, resulting in the epoxy resin material not being able to achieve effective long-term storage at room temperature.

[0031] In some embodiments of the present invention, the curing accelerator includes an imidazole adduct, and the addition amount of the imidazole adduct is 8-12 parts, specifically, it can be 8 parts, 10 parts, 12 parts, etc. The imidazole adduct includes one or more of the adducts of 2-methylimidazole (2MZ), 2-ethyl-4-methylimidazole (2E4MZ), 2-phenylimidazole (2PZ) and isocyanate, the adduct of 1-(2-aminoethyl)-2-methylimidazole and isocyanate (such as PN-23 type latent accelerator), and 2-phenyl-4,5-dihydroxyimidazolium salt, and the isocyanate therein can be toluene diisocyanate. If the addition amount of the imidazole adduct is too much, it may over-catalyze the reaction of epoxy groups, resulting in too fast curing speed, concentrated heat release in the system, and easy to cause bubbles, cracks or deformation inside the epoxy resin material.

[0032] In some embodiments of the present invention, the curing accelerator includes 1-(3-aminopropyl)-3-methylimidazolium hydrobromide bromate, and the addition amount of 1-(3-aminopropyl)-3-methylimidazolium hydrobromide bromate is 20-40 parts, specifically, it can be 20 parts, 30 parts, 40 parts, etc. Excessive bromate may damage the curing network uniformity of the curing accelerator, increase the brittleness of the epoxy resin material, reduce the impact resistance or flexibility, and accelerate the aging of the material.

[0033] In some embodiments of the present invention, 1-(3-aminopropyl)-3-methylimidazolium hydrobromide bromate is prepared by alkylation reaction of 3-aminopropylimidazole and 3-bromopropanamine hydrobromide, and the reaction structural formula is as follows:

[0034]

[0035] Wherein the molar ratio of the 3-aminopropylimidazole to the 3-bromopropanamine hydrobromide is 1:1.1-1.25, specifically, it can be 1:1.1, 1:1.15, 1:1.2, 1:1.25, etc.

[0036] In some embodiments of the present invention, the preparation method of 1-(3-aminopropyl)-3-methylimidazolium hydrobromide bromate is as follows: under a protective atmosphere, 3-aminopropylimidazole, 3-bromopropanamine hydrobromide and an organic solvent are mixed, and then reflux reaction is carried out to obtain 1-(3-aminopropyl)-3-methylimidazolium hydrobromide bromate.

[0037] Among them, the protective atmosphere can be nitrogen, argon, etc.; the organic solvent can be absolute ethanol, acetonitrile (ACN), ethyl acetate (EAC), tetrahydrofuran (THF), etc.; the temperature of the reflux reaction is 75 - 95 °C, specifically it can be 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, etc., and the time of the reflux reaction is 20 - 25 h, specifically it can be 20 h, 22 h, 25 h, etc.; after the reflux reaction, the following steps are further included: cooling the reflux product to room temperature, and then filtering, washing, recrystallizing, and drying. There are no special limitations on filtration, washing, recrystallization, drying, etc., and conventional methods can be used.

[0038] In another aspect of the present invention, the present invention also provides an epoxy resin material, comprising 100 parts of trifunctional epoxy resin, 100 - 180 parts of acid anhydride curing agent, and 2 - 7 parts of the curing accelerator described in any one of the above.

[0039] The present invention uses a high-temperature-resistant trifunctional epoxy resin as the matrix resin. Without adding a solvent, due to the high viscosity of the epoxy resin, it is easy to mix unevenly or the molecular movement is restricted during the curing process, which may cause incomplete curing in some areas, forming internal defects and affecting the mechanical properties and durability of the material. Therefore, the present invention selects a low-viscosity, high-temperature-resistant acid anhydride curing agent for curing. On the one hand, it can reduce the viscosity of the epoxy resin, improve the mechanical strength of the material, and also maintain good construction performance, facilitating operations such as brushing and spraying. On the other hand, the acid anhydride curing agent has high latency, which means that there is a long time for processing and operation after mixing, which is beneficial to process control and product shaping, reducing the construction difficulties and quality instability problems caused by too fast curing speed, and effectively improving the reliability of product quality.

[0040] Furthermore, although the high latency of the acid anhydride curing agent can enable the epoxy resin material to have a long service life, a long curing time and a high curing temperature are required for curing, which greatly reduces the production efficiency and cannot meet the requirements of large-scale production. The curing accelerator of the present invention can solve this problem. At room temperature, the mixture of trifunctional epoxy resin, acid anhydride curing agent and curing accelerator has a long storage time. When the temperature rises to the curing temperature, the curing accelerator can quickly react with the epoxy resin for curing. In this way, not only can the long-term storage of the epoxy resin material at room temperature be realized (the temperature resistance and mechanical properties basically do not change after being placed for six months), but also the curing time can be shortened and the production efficiency can be improved during use. Moreover, by adding the curing accelerator of the present invention, the mechanical properties of the epoxy resin material can be improved without affecting the temperature resistance.

[0041] Specifically, the reaction mechanism of trifunctional epoxy resin and anhydride curing agent is as follows: The anhydride first reacts with the opened epoxy group in the epoxy resin to form a monoester, and the carboxyl group in the monoester undergoes addition esterification with the epoxy group to form a diester. The anhydride group reacts with the epoxy group to form an ester bond (-COO-), and through secondary cross-linking with hydroxyl groups, a three-dimensional network is formed. The higher the cross-linking density, the more significantly the molecular chain movement is restricted, and the glass transition temperature (Tg) increases. In addition, after the epoxy resin reacts with the anhydride, the number of cross-linking points increases and the molecular chain rigidity enhances, thereby improving the mechanical properties.

[0042] Taking trifunctional epoxy resin 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester and anhydride curing agent methyltetrahydrophthalic anhydride as examples, the reaction equations involved are as follows:

[0043]

[0044] The reaction mechanism of trifunctional epoxy resin and curing accelerator is as follows: The curing effect of primary amines and secondary amines on epoxy resin is that the active hydrogen on the nitrogen atom opens the epoxy group, causing it to cross-link and cure, forming a highly cross-linked network and inhibiting the relaxation of molecular chains at high temperatures, thereby achieving high-temperature resistance performance. Taking 4,4'-diaminodiphenyl sulfone as an aromatic polyamine curing agent for the curing accelerator, the reaction equations involving trifunctional epoxy resin 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester and 4,4'-diaminodiphenyl sulfone are as follows:

[0045]

[0046] In some embodiments of the present invention, the epoxy resin material comprises an acid anhydride curing agent, and the addition amount of the acid anhydride curing agent is 100 - 180 parts, specifically it can be 100 parts, 120 parts, 140 parts, 160 parts, 180 parts, etc. The acid anhydride curing agent includes one or more of methyl nadic anhydride, hexachlorendomethylene tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, tetrabromophthalic anhydride, glycerol trimellitate, diphenyl ether tetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, hydrogenated methyl nadic anhydride, diphenyl sulfone - 3,3',4,4'-tetracarboxylic dianhydride, methylcyclohexene tetracarboxylic dianhydride, and tung oil anhydride. It should be noted that the compatibility of methyl hexahydrophthalic anhydride with trifunctional epoxy resin is poor. Specifically, methyl hexahydrophthalic anhydride is a fully hydrogenated six-membered ring (without double bonds), and its molecular polarity is significantly lower than that of methyltetrahydrophthalic anhydride, resulting in a large difference in solubility parameters with high-polarity trifunctional epoxy resin, and phase separation is likely to occur. Moreover, methyl hexahydrophthalic anhydride is a low-viscosity liquid at room temperature, but it may be difficult to disperse evenly in high-functional epoxy resin due to weak intermolecular forces. In addition, methyl hexahydrophthalic anhydride is prone to absorbing moisture to generate free acid, and the compatibility of free acid with epoxy resin is even worse, and it will interfere with the curing reaction, such as reducing the cross-linking efficiency. Therefore, the mechanical properties of the epoxy resin material obtained when using methyl hexahydrophthalic anhydride as the acid anhydride curing agent are poor.

[0047] In some embodiments of the present invention, the epoxy resin material comprises a curing accelerator, and the addition amount of the curing accelerator is 2 - 7 parts, specifically it can be 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, etc.

[0048] In some embodiments of the present invention, the trifunctional epoxy resin includes one or more of triglycidyl p-aminophenol, triglycidyl tris(2-hydroxyethyl) isocyanurate, 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester, triphenolmethane triglycidyl ether, tris(epoxypropyl) isocyanurate, tris(2,3-epoxypropyl) isocyanurate, and a phenylboronic acid polymer based on the ring-opening polymerization of amino epoxy groups; preferably, the trifunctional epoxy resin is selected from one or two of the above substances. If there are more than two, it will lead to a decrease in the high-temperature resistance and mechanical properties of the epoxy resin material.

[0049] In some embodiments of the present invention, the epoxy resin material further comprises 1 - 10 parts of non-trifunctional glycidylamine type epoxy resin and / or 1 - 5 parts of diluent and / or 0.2 - 0.6 parts of coupling agent and / or 0.1 - 0.4 parts of rheological agent.

[0050] In some embodiments of the present invention, when it is necessary to enhance the toughness of the epoxy resin material, a non-trifunctional glycidylamine epoxy resin can be added. The addition amount of the non-trifunctional glycidylamine epoxy resin is 1-10 parts, specifically, it can be 1 part, 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, etc. The non-trifunctional glycidylamine epoxy resin includes one or more of bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, resorcinol epoxy resin, 4,4'-diaminodiphenylmethane epoxy resin, bisphenol methane epoxy resin, and 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate.

[0051] In some embodiments of the present invention, when it is necessary to reduce the viscosity of the epoxy resin material, a diluent can be added. The addition amount of the diluent is 1-5 parts, specifically, it can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, etc. The diluent includes one or more of 1,4-butanediol diglycidyl ether, pentaerythritol diglycidyl ether, and cresyl glycidyl ether.

[0052] In some embodiments of the present invention, when it is necessary to enhance the shear performance of the epoxy resin material, a coupling agent can be added. The addition amount of the coupling agent is 0.2-0.6 parts, specifically, it can be 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, etc. The coupling agent includes one or more of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, and phenylaminomethylenetriethoxysilane.

[0053] In some embodiments of the present invention, when it is necessary to enhance the stability and paintability of the epoxy resin material, a rheological agent can be added. The addition amount of the rheological agent is 0.1-0.4 parts, specifically, it can be 0.1 part, 0.2 parts, 0.3 parts, 0.4 parts, etc. The rheological agent includes one or more of hydrogenated castor oil and polyethylene wax.

[0054] It should be noted that in the above epoxy resin materials, the addition amounts of the acid anhydride curing agent, curing accelerator, non-trifunctional glycidylamine epoxy resin, diluent, coupling agent, and rheological agent are all defined based on the addition amount of 100 parts of the trifunctional epoxy resin.

[0055] In another aspect of the present invention, the present invention also provides a preparation method of the above epoxy resin material, including the following steps:

[0056] (1) Mix the raw materials to obtain a mixture;

[0057] (2) Subject the mixture to stepwise high-temperature curing to obtain an epoxy resin material.

[0058] In the present invention, first, the raw materials are mixed to obtain a mixture.

[0059] In some embodiments of the present invention, the temperature of the mixing is 40 - 60°C, specifically it can be 40°C, 45°C, 50°C, 55°C, 60°C, etc. If the mixing temperature is too high, it will cause the curing reaction of the mixing system to occur in advance; the mixing time is not specifically limited, and it is sufficient to mix until uniform.

[0060] In some embodiments of the present invention, the mixing of the raw materials is specifically as follows: first, a trifunctional epoxy resin, a non-trifunctional glycidylamine epoxy resin, a curing agent, and a curing accelerator are mixed, and then a diluent, a coupling agent, and a rheology modifier are added for mixing to obtain a mixture. Since the role of the curing accelerator is to accelerate the curing reaction at a certain temperature, in order to avoid the premature occurrence of the curing reaction after adding the curing accelerator, the mixing temperature needs to be below 60°C. In addition, since the diluent, the coupling agent, and the rheology modifier are all for modifying the entire system, they are added last.

[0061] In the present invention, after obtaining the mixture, subject the mixture to stepwise high-temperature curing to obtain an epoxy resin material.

[0062] In some embodiments of the present invention, the stepwise high-temperature curing includes a first curing stage and a second curing stage that are carried out in sequence. The first curing stage is to cure at 100 - 120°C for 1 - 2 h, and the second curing stage is to cure at 150 - 180°C for 1 - 2 h. Among them, the temperature of the first curing stage can specifically be 100°C, 110°C, 120°C, etc., and the time can specifically be 1 h, 1.5 h, 2 h, etc.; the temperature of the second curing stage can specifically be 150°C, 160°C, 170°C, 180°C, etc., and the time can specifically be 1 h, 1.5 h, 2 h, etc.

[0063] In some embodiments of the present invention, the stepwise high-temperature curing includes a first curing stage, a second curing stage, and a third curing stage that are carried out in sequence. Among them, the first curing stage and the second curing stage are the same as the above scheme and will not be elaborated here; the third curing stage is to cure at 220 - 240°C for 1 - 2 h, and the temperature of the third curing stage can specifically be 220°C, 230°C, 240°C, etc., and the time can specifically be 1 h, 1.5 h, 2 h, etc.

[0064] It should be noted that in the first curing stage, under the condition of a curing accelerator, the epoxy group starts to react preliminarily with the anhydride curing agent. The curing accelerator attacks the anhydride to generate carboxylate anions, triggering the ring-opening of the epoxy group, determining the preliminary cross-linking network, which can prevent the material from flowing and deforming, and providing a structural basis for subsequent curing; in the second curing stage, the cross-linking reaction further intensifies. The carboxylate anions continuously attack the epoxy group to generate ester bonds (-COO-) and hydroxyl groups (-OH). The hydroxyl groups further react with the anhydride to form a three-dimensional cross-linking structure, forming more chemical bonds, making the structure of the epoxy resin material more stable. At this time, it is the basic curing stage, and the reaction rate needs to be increased by heating and curing; in the third curing stage, the remaining unreacted active groups are completely cross-linked, and the unreacted epoxy groups, hydroxyl groups or amino groups continue to react at a higher temperature to eliminate the "reaction dead corners" and form a very stable chemical structure.

[0065] In the present invention, before subjecting the mixture to stepwise high-temperature curing, the following steps are further included: degassing the mixture.

[0066] In some embodiments of the present invention, the degassing treatment is vacuum degassing. The temperature of the vacuum degassing is 40 - 60 °C, which is the same as the mixing temperature, and the vacuum degree of the vacuum degassing is ≤ -0.08 MPa.

[0067] Hereinafter, the technical solutions in the present invention will be clearly and completely described in conjunction with specific embodiments. The embodiments of this application are only for illustration. All other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present invention.

[0068] Example 1

[0069] This example provides a preparation method of an epoxy resin material, and the specific steps are as follows:

[0070] (1) Under nitrogen protection, 3-aminopropylimidazole and 3-bromopropylamine hydrobromide with a molar ratio of 1:1.14 are added to absolute ethanol, stirred until completely dissolved, heated to 75 °C and refluxed for 24 hours. After the reaction is completed, it is cooled to room temperature, filtered and rinsed three times with ethanol, and recrystallized with ethanol and dried to obtain 1-(3-aminopropyl)-3-methylimidazole hydrobromide bromate (AMH B);

[0071] (2) Mix 100 parts of the polymer of 4,4'-(1-methylethylidene)bisphenol (BPAF) and (chloromethyl)oxirane (MCBE), 65 parts of an aromatic polyamine curing agent, 8 parts of an imidazole adduct, and 20 parts of AMHB to obtain a curing accelerator; wherein the polymer of 4,4'-(1-methylethylidene)bisphenol and (chloromethyl)oxirane is a bisphenol A epoxy resin with an epoxy equivalent of 525 g / eq, the aromatic polyamine curing agent is 4,4'-diaminodiphenylsulfone, and the imidazole adduct is 2-ethyl-4-methylimidazole;

[0072] (3) Mix 100 parts of triglycidyl p-aminophenol (TGPAP), 80 parts of diglycidyl 4,5-epoxyhexane-1,2-dicarboxylate (TDE-85), 160 parts of methyl nadic anhydride (MNA), 20 parts of tetrabromophthalic anhydride (TBPA), and 10 parts of the curing accelerator at 60 °C for 20 min, then add 0.5 part of γ-glycidoxypropylsilane and 0.3 part of hydrogenated castor oil and stir for 20 min to obtain a mixture;

[0073] (4) Place the mixture in a vacuum box with a vacuum degree of -0.08 MPa and a temperature of 60 °C for degassing treatment, and then pour the degassed mixture into a mold for stepwise high-temperature curing (120 °C / 1 h → 180 °C / 2 h → 240 °C / 2 h) to obtain an epoxy resin material.

[0074] Example 2

[0075] This example is basically the same as Example 1, except for the change in the raw material composition and addition amount in step (3).

[0076] The raw material composition and addition amount in this example are as follows: 100 parts of triglycidyl p-aminophenol (TGPAP), 80 parts of diglycidyl 4,5-epoxyhexane-1,2-dicarboxylate (TDE-85), 160 parts of methyltetrahydrophthalic anhydride (MTHPA), 20 parts of tetrabromophthalic anhydride (TBPA), 10 parts of the curing accelerator, 0.5 part of γ-glycidoxypropylsilane, and 0.3 part of hydrogenated castor oil.

[0077] Example 3

[0078] This example is basically the same as Example 1, except for the change in the raw material composition and addition amount in step (3).

[0079] The raw material composition and addition amount in this example are as follows: 60 parts of triglycidyl tris(2-hydroxyethyl)isocyanurate (TGET), 2 parts of bisphenol A epoxy resin, 2 parts of dicyclopentadiene diepoxy resin, 100 parts of tung oil anhydride (TOA), and 4 parts of the curing accelerator.

[0080] Example 4

[0081] This example is basically the same as Example 1, except that: in step (3), there are changes in the raw material composition and addition amounts.

[0082] The raw material composition and addition amounts in this example are as follows: 100 parts of triglycidyl p-aminophenol (TGPAP), 6 parts of hydrogenated bisphenol A epoxy resin, 4 parts of dicyclopentadiene diepoxy resin, 100 parts of cyclopentanetetracarboxylic dianhydride (CPDA), and 4 parts of curing accelerator.

[0083] Example 5

[0084] This example is basically the same as Example 1, except that: in step (3), there are changes in the raw material composition and addition amounts.

[0085] The raw material composition and addition amounts in this example are as follows: 90 parts of tris(2,3-epoxypropyl)isocyanurate (TEPIC), 9 parts of 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate, 120 parts of methyltetrahydrophthalic anhydride (MTHPA), 2 parts of curing accelerator, and 4 parts of pentaerythritol diglycidyl ether.

[0086] Example 6

[0087] This example is basically the same as Example 1, except that: in step (3), there are changes in the raw material composition and addition amounts.

[0088] The raw material composition and addition amounts in this example are as follows: 90 parts of tris(2,3-epoxypropyl)isocyanurate (TEPIC), 9 parts of 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate, 120 parts of methyltetrahydrophthalic anhydride (MTHPA), 6 parts of curing accelerator, and 4 parts of pentaerythritol diglycidyl ether.

[0089] Example 7

[0090] This example is basically the same as Example 1, except that: in step (3), there are changes in the raw material composition and addition amounts.

[0091] The raw material composition and addition amounts in this example are as follows: 90 parts of tris(2,3-epoxypropyl)isocyanurate (TEPIC), 9 parts of 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate, 120 parts of methyltetrahydrophthalic anhydride (MTHPA), 4 parts of curing accelerator, and 4 parts of pentaerythritol diglycidyl ether.

[0092] Example 8

[0093] This example is basically the same as Example 1, except that: in step (2), there are changes in the raw material composition and addition amounts of the curing accelerator.

[0094] 100 parts of a polymer of 4,4'-(1-methylethylidene)bisphenol (BPAF) and (chloromethyl)oxirane (MCBE), 75 parts of an aromatic polyamine curing agent, 8 parts of an imidazole adduct, and 25 parts of AMHB were mixed to obtain a curing accelerator. The polymer of 4,4'-(1-methylethylidene)bisphenol and (chloromethyl)oxirane was a bisphenol A epoxy resin with an epoxy equivalent of 525 g / eq, the aromatic polyamine curing agent was 4,4'-diaminodiphenyl sulfone, and the imidazole adduct was 2-ethyl-4-methyl.

[0095] Example 9

[0096] This example is basically the same as Example 1, except that: in step (3), there are changes in the raw material composition and addition amounts.

[0097] The raw material composition and addition amounts in this example are as follows: 100 parts of diglycidyl 4,5-epoxyhexane-1,2-dicarboxylate (TDE-85), 120 parts of methyl nadic anhydride (MNA), and 4 parts of a curing accelerator.

[0098] Comparative Example 1

[0099] This comparative example is basically the same as Example 1, except that: in step (3), no curing accelerator was added.

[0100] Comparative Example 2

[0101] This comparative example is basically the same as Example 1, except that: in step (3), there are changes in the raw material composition and addition amounts.

[0102] The raw material composition and addition amounts in this comparative example are as follows: 100 parts of triglycidyl p-aminophenol (TGPAP), 80 parts of diglycidyl 4,5-epoxyhexane-1,2-dicarboxylate (TDE-85), 160 parts of methylhexahydrophthalic anhydride (MHHPA), 20 parts of tetrabromophthalic anhydride (TBPA), 10 parts of a curing accelerator, 0.5 part of γ-glycidoxypropylsilane, and 0.3 part of hydrogenated castor oil.

[0103] Comparative Example 3

[0104] This comparative example is basically the same as Example 1, except that: in step (3), a commercially available curing accelerator was added. The manufacturer of this commercially available curing accelerator is Jinan Huifengda Chemical Co., Ltd., and the model is benzyldimethylamine (BDMA) ， CAS No.: 103-83-3.

[0105] Comparative Example 4

[0106] This comparative example is basically the same as Example 9, except that: in step (3), there are changes in the raw material composition and addition amounts.

[0107] In this embodiment, the compositions and addition amounts of the raw materials are as follows: 100 parts of diglycidyl 4,5-epoxyhexane-1,2-dicarboxylate (TDE-85), 40 parts of methyl nadic anhydride (MNA), and 1 part of a curing accelerator.

[0108] Comparative Example 5

[0109] This comparative example is basically the same as Example 9, and the only difference lies in: the change in the composition and addition amount of the raw materials in step (3).

[0110] In this embodiment, the compositions and addition amounts of the raw materials are as follows: 100 parts of diglycidyl 4,5-epoxyhexane-1,2-dicarboxylate (TDE-85), 200 parts of methyl nadic anhydride (MNA), and 1 part of a curing accelerator.

[0111] Comparative Example 6

[0112] This comparative example is basically the same as Example 1, and the only difference lies in: the change in the composition and addition amount of the raw materials in step (3).

[0113] In this embodiment, the compositions and addition amounts of the raw materials are as follows: 100 parts of triglycidyl p-aminophenol (TGPAP), 80 parts of diglycidyl 4,5-epoxyhexane-1,2-dicarboxylate (TDE-85), 10 parts of triphenolmethane triglycidyl ether (TPMGE), 172 parts of methyl nadic anhydride (MNA), 20 parts of tetrabromophthalic anhydride (TBPA), 10 parts of a curing accelerator, 0.5 part of γ-glycidoxypropylsilane, and 0.3 part of hydrogenated castor oil.

[0114] The compositions and addition amounts of the raw materials of the epoxy resin materials in Examples 1-9 and Comparative Examples 1-6 are summarized in Table 1.

[0115] Table 1

[0116]

[0117]

[0118]

[0119] The tensile strength, flexural strength, and shear strength of the epoxy resin materials in Examples 1-9 and Comparative Examples 1-6 were tested, and the results are shown in Table 2. Among them, the tensile strength test was carried out in accordance with GB / T 1040.2-2006, the flexural strength test was carried out in accordance with GB / T 9341-2008, and the shear strength test was carried out in accordance with GB / T 7124-2008.

[0120] Table 2

[0121]

[0122] As can be seen from Examples 1-9 in Table 2, the epoxy resin material prepared from a curing accelerator, an acid anhydride curing agent, and a trifunctional epoxy resin as raw materials of the present invention has both good high-temperature resistance and mechanical properties. By adding a curing accelerator, the temperature resistance and various mechanical properties of the epoxy resin material can be effectively improved. The glass transition temperature of the epoxy resin material of the present invention can reach 200 °C, the tensile strength reaches more than 25 MPa, the flexural strength reaches more than 125 MPa, and the shear strength reaches more than 6 MPa.

[0123] As can be seen from Example 1 and Comparative Examples 1-3, if no curing accelerator is added, a commercially available curing accelerator is added, or methylhexahydrophthalic anhydride is used as the acid anhydride curing agent, the various mechanical properties and the glass transition temperature of the prepared epoxy resin material will be significantly reduced.

[0124] As can be seen from Example 9 and Comparative Examples 4-5, when the addition amount of the acid anhydride curing agent is too small, the epoxy resin material cannot be cured under the same curing conditions, and when the addition amount of the acid anhydride curing agent is too large, the various mechanical properties and the glass transition temperature of the prepared epoxy resin material will be significantly reduced.

[0125] As can be seen from Example 1 and Comparative Example 6, at most two kinds of trifunctional epoxy resins can be added. If the number of types is too large, the various mechanical properties and the glass transition temperature of the epoxy resin material will be reduced.

[0126] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A curing accelerator, characterized in that, It comprises raw materials in the following parts by weight: 100 parts of a polymer of 4,4'-(1-methylethylidene)bisphenol and chloromethylepoxyethane, 50 - 80 parts of an aromatic polyamine curing agent, 8 - 12 parts of an imidazole adduct, and 20 - 40 parts of 1-(3-aminopropyl)-3-methylimidazolium hydrobromide bromate.

2. The curing accelerator according to claim 1, wherein, The polymer of 4,4'-(1-methylethylidene)bisphenol and chloromethylepoxyethane is a bisphenol A epoxy resin with an epoxy equivalent of 150 - 550 g / eq.

3. The curing accelerator according to claim 1 or 2, characterized in that, The aromatic polyamine curing agent includes one or more of m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, m-xylylenediamine, and diethyltoluenediamine; The imidazole adduct includes one or more of the adducts of 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenylimidazole with isocyanate, the adduct of 1-(2-aminoethyl)-2-methylimidazole with isocyanate, and 2-phenyl-4,5-dihydroxyimidazolium salt.

4. An epoxy resin material, characterized in that, It includes 100 parts of a trifunctional epoxy resin, 100 - 180 parts of an acid anhydride curing agent, and 2 - 7 parts of the curing accelerator according to any one of claims 1 - 3.

5. The epoxy resin material according to claim 4, characterized in that, The trifunctional epoxy resin includes one or more of triglycidyl p-aminophenol, triglycidyl tris(2-hydroxyethyl)isocyanurate, diglycidyl 4,5-epoxyhexane-1,2-dicarboxylate, triphenolmethane triglycidyl ether, tris(epoxypropyl)isocyanurate, tris(2,3-epoxypropyl)isocyanurate, and a phenylboronic acid polymer based on amino epoxy ring-opening polymerization; The acid anhydride curing agent includes one or more of methyl nadic anhydride, hexachlorendomethylene tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, tetrabromophthalic anhydride, glycerol trimellitate, diphenyl ether tetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, hydrogenated methyl nadic anhydride, diphenylsulfone-3,3',4,4'-tetracarboxylic dianhydride, methylcyclohexene tetracarboxylic dianhydride, and tung oil anhydride.

6. The epoxy resin material according to claim 4 or 5, characterized in that, It further includes 1 - 10 parts of a non-trifunctional glycidylamine epoxy resin and / or 1 - 5 parts of a diluent and / or 0.2 - 0.6 parts of a coupling agent and / or 0.1 - 0.4 parts of a rheological agent.

7. The epoxy resin material according to claim 6, characterized in that, The non-trifunctional glycidylamine epoxy resin includes one or more of bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, resorcinol epoxy resin, 4,4'-diaminodiphenylmethane epoxy resin, bisphenol methane epoxy resin, and 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate; The diluent includes one or more of 1,4-butanediol diglycidyl ether, pentaerythritol diglycidyl ether, and cresyl glycidyl ether; The coupling agent includes one or more of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, and phenylaminomethylenetriethoxysilane; The rheological agent includes one or more of hydrogenated castor oil and polyethylene wax.

8. A method for preparing the epoxy resin material according to any one of claims 4-7, characterized in that, It includes the following steps: (1) Mix the raw materials to obtain a mixture; (2) Subject the mixture to stepwise high-temperature curing to obtain an epoxy resin material.

9. The preparation method of the epoxy resin material according to claim 8, characterized in that, The temperature of the mixing is 40-60 °C.

10. The preparation method of the epoxy resin material according to claim 8 or 9, characterized in that, The stepwise high-temperature curing includes a first curing stage and a second curing stage carried out in sequence. The first curing stage is carried out at 100-120 °C for 1-2 h, and the second curing stage is carried out at 150-180 °C for 1-2 h; Or the stepwise high-temperature curing includes a first curing stage, a second curing stage and a third curing stage carried out in sequence. The first curing stage is carried out at 100-120 °C for 1-2 h, the second curing stage is carried out at 150-180 °C for 1-2 h, and the third curing stage is carried out at 220-240 °C for 1-2 h.

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