An epoxy curing agent, its preparation method and application

Abstract

The present application relates to an epoxy curing agent and its preparation method and application, which is formed by the reaction of an anhydride with a ring (A), a diamine with long polyether chain (B) and an active diamine (C). The cyclic structure of the epoxy curing agent gives it high rigidity; the two amide groups are close to each other and located on the V-shaped dentiform structure, and the active hydrogen and nitrogen atoms on the two similar chains can react with the same epoxy resin molecule to form a new cross-linked cyclic structure, and the filler in the epoxy resin composition can be embedded in this new cyclic structure to improve its rigidity; the long polyether chain gives the epoxy curing agent high viscosity and toughness, and improves the impact strength of the cured product; the active diamine (C) improves the reaction rate of the epoxy curing agent, so that the epoxy resin composition has a short surface drying time.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to an epoxy curing agent, its preparation method, and its application. Background Technology

[0002] Polyamide-based epoxy curing agents typically use dimer acid-modified polyethylene polyamines as the basic skeleton. These have long carbon chains and high viscosity, resulting in cured products with high elasticity, adhesion, and water resistance. 650 epoxy curing agent is a common example. However, 650 epoxy curing agent cures slowly with bisphenol A type epoxy resin at room temperature. When crosslinking under heating conditions, the exothermic peak during curing is relatively flat, and the crosslinking density of the cured product is low. Although it has good flexibility, it often exhibits relatively low rigidity.

[0003] Existing techniques typically introduce tertiary amine accelerators into epoxy resins to accelerate curing; however, the improvement in rigidity is not significant. Furthermore, existing techniques also add rigid structural materials containing benzene rings and tertiary amine accelerators to epoxy resins to improve curing speed and rigidity; however, due to the limited physical addition of these substances, this method has limited ability to improve the rigidity of epoxy resin formulations. Summary of the Invention

[0004] This invention provides an epoxy curing agent, its preparation method, and its application to solve the problems of slow curing rate and difficulty in balancing rigidity and toughness in existing epoxy resins.

[0005] The technical solution provided by this invention is as follows: In a first aspect, the present invention provides an epoxy curing agent having the structure shown in general formula I:

[0006] General Formula I in: A is an aromatic or aliphatic ring that is substituted or unsubstituted by group B; R1NHCO- and R2NHCO- are ortho-substituents on A; group B is an electron-donating group; R1 is -C n H 2n -(CH3C m H 2m-1 O) x -NH 2-y (C p H 2p+1 ) y ; R2 is -C q H 2q -(NH-C r H 2r ) s -NH 2-z (Ct H 2t+1 ) z ; n, m, p, x, y; q, r, s, t, z are natural numbers.

[0007] In conjunction with the first aspect of the present invention, in some embodiments, n=0~3, m=1~3, p=1~3, x=2~16, y=0~2; q=1~3, r=1~3, s=1~4, t=1~3, z=0~2.

[0008] In conjunction with the first aspect of the present invention, in some embodiments, the epoxy curing agent has the following structural formula: the B group is a C1~C5 alkyl group.

[0009] Secondly, the present invention provides a method for preparing an epoxy curing agent, comprising the following steps: An anhydride A and diamine B undergo an addition reaction to produce intermediate C; The intermediate propylene and diaminebutane undergo a condensation reaction to obtain an epoxy curing agent; Wherein: the structural formula of acid anhydride A is ; The structural formula of intermediate C is ; The structural formula of diamine ethyl is NH2-C. n H 2n -(CH3C m H 2m-1 O) x -NH 2-y (C p H 2p+1 ) y ; The structural formula of diaminobutyric acid is NH2-C. q H 2q -(NH-C r H 2r ) s -NH 2-z (C t H 2t+1 ) z ; A is an aromatic or aliphatic ring that is substituted or unsubstituted by group B; R1NHCO- and R2NHCO- are ortho-substituents on A; group B is an electron-donating group; R1 is -C n H 2n -(CH3C m H 2m-1 O) x -NH 2-y (C p H 2p+1 ) y ; R2 is -C q H 2q -(NH-C r H 2r ) s -NH 2-z (C t H 2t+1 ) z ; n, m, p, x, y; q, r, s, t, z are natural numbers.

[0010] In conjunction with the second aspect of the present invention, in some embodiments, the equivalent ratio of acid anhydride A, diamine B, and diamine D is 2:(0.8~1.2):(0.8~1.2).

[0011] In conjunction with the second aspect of the invention, in some embodiments, the addition reaction and the condensation reaction are carried out in a first organic solvent; and / or, the reaction temperature of the addition reaction is 110±℃; and / or, the reaction temperature of the condensation reaction is 190±℃.

[0012] In conjunction with the second aspect of the invention, in some embodiments, both the addition reaction and the condensation reaction are carried out under catalyst-free conditions.

[0013] In conjunction with the second aspect of the present invention, in some embodiments, acid anhydride A is one or more of phthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and phthalic anhydride; and / or, diamine B is one or more of polyether diamines with a weight average molecular weight of 200 to 1000; and / or, diamine butyl is one or more of diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine.

[0014] Thirdly, the present invention provides an epoxy resin curing agent composition, wherein the curing agent is the above-mentioned epoxy curing agent.

[0015] Fourthly, the present invention provides the application of the above-described epoxy resin composition in epoxy coatings or structural adhesives for buildings.

[0016] Compared with the prior art, the present invention has at least the following advantages: The cyclic structure of the epoxy curing agent of the present invention imparts high rigidity to the epoxy curing agent; the two amide groups are close together and located on a V-shaped tooth structure, and the active hydrogen and nitrogen atoms on the two similar chains can react with the same epoxy molecule to form a new cyclic structure. The filler in the epoxy resin composition can be embedded in this new cyclic structure to improve its rigidity; the R1 chain is relatively long, which imparts high viscosity and toughness to the epoxy curing agent and improves the shear strength of the cured product; the R2 chain is relatively short and has high activity, which improves the reaction rate of the epoxy curing agent and makes the epoxy resin composition have a shorter surface drying time. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 The infrared spectrum of the epoxy curing agent provided in Example 2 of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] For simplicity, this invention only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated; similarly, any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0021] It should be noted that, in the description of this invention, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more. Relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0022] In the description of this invention, the terms "any embodiment / mode," "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment / mode or example, which are included in at least one embodiment / mode or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0023] The above description of the invention is not intended to describe every disclosed embodiment or implementation of the invention. Exemplary embodiments are described in more detail below. These embodiments can be used in various combinations. In each example, the listing is merely representative and should not be construed as exhaustive.

[0024] Epoxy curing agent: The epoxy curing agent provided by this invention has the structure shown in general formula I:

[0025] General Formula I in: A is an aromatic or aliphatic ring that is substituted or unsubstituted by group B; R1NHCO- and R2NHCO- are ortho-substituents on A; group B is an electron-donating group; R1 is -C n H 2n -(CH3C m H 2m-1 O) x -NH 2-y (C p H 2p+1 ) y ; R2 is -C q H 2q -(NH-C r H 2r ) s -NH 2-z (C t H 2t+1 ) z ; n, m, p, x, y; q, r, s, t, z are natural numbers.

[0026] The epoxy curing agent of this invention has a cyclic structure and a V-shaped toothed structure, and contains primary amine groups, secondary amine groups, amide groups, and a longer R1 chain and a shorter R2 chain. The cyclic structure imparts high rigidity to the epoxy curing agent; the two amide groups are close together and located on the V-shaped toothed structure, and the active hydrogen and nitrogen atoms on the two adjacent chains can react with the same epoxy molecule to form a new cyclic structure. The filler in the epoxy resin composition can be embedded in this new cyclic structure, improving its rigidity; the longer R1 chain imparts higher viscosity and toughness to the epoxy curing agent, increasing the shear strength of the cured product; the shorter R2 chain has higher activity, increasing the reaction rate of the epoxy curing agent, resulting in a shorter surface drying time for the epoxy resin composition.

[0027] In the epoxy curing agent of the present invention, the amine and amide groups on the R1 and R2 chains have different activities and different reaction rates. The more active amine groups ensure that the epoxy resin composition has a shorter surface drying time, while the less active amide groups ensure that the epoxy resin composition continues to react after surface drying until the cured product can reach the designed strength.

[0028] In the epoxy curing agent of the present invention, the R1 chain has a longer chain length, a slower reaction rate, and a gentler curing exothermic peak. When used in conjunction with the R2 chain, it ensures that the epoxy curing agent has a suitable reaction rate and a moderate pot life, avoiding insufficient working time due to excessively rapid reaction.

[0029] The epoxy curing agent of the present invention has a high active hydrogen equivalent. Therefore, compared with traditional polyamide 650, the epoxy curing agent of the present invention can be effectively cured at room temperature and has a high curing crosslinking density.

[0030] All of the above factors enable the cured product using the epoxy curing agent of this invention to maintain excellent flexibility while having good rigidity and good impact resistance.

[0031] In some embodiments of the present invention, n=0~3, m=1~3, p=1~3, x=2~16, y=0~2; q=1~3, r=1~3, s=1~4, t=1~3, z=0~2.

[0032] In some embodiments of the present invention, the epoxy curing agent has the following structural formula: the B group is a C1-C5 alkyl group. These alkyl groups are electron-donating groups, which can improve the reactivity of the amine group; at the same time, alkyl groups with appropriate chain length can ensure the reactivity of the acid anhydride.

[0033] In some embodiments of the present invention, A is a substituted or unsubstituted benzene ring or a tetrahydrobenzene ring.

[0034] Preparation method: The method for preparing the epoxy curing agent provided by the present invention includes the following steps: An anhydride A and diamine B undergo an addition reaction to produce intermediate C; The intermediate propylene and diaminebutane undergo a condensation reaction to obtain an epoxy curing agent; Wherein: the structural formula of acid anhydride A is ; The structural formula of intermediate C is ; The structural formula of diamine ethyl is NH2-C. n H 2n -(CH3C m H 2m-1 O) x -NH 2-y (C p H 2p+1 ) y ; The structural formula of diaminobutyric acid is NH2-C. q H 2q -(NH-C r H 2r ) s -NH 2-z (C t H 2t+1 ) z ; A is an aromatic or aliphatic ring that is substituted or unsubstituted by group B; R1NHCO- and R2NHCO- are ortho-substituents on A; group B is an electron-donating group; R1 is -C n H 2n -(CH3C m H 2m-1 O) x -NH 2-y (C p H 2p+1 ) y ; R2 is -C q H 2q -(NH-C r H 2r ) s -NH 2-z (C t H 2t+1 ) z ; n, m, p, x, y; q, r, s, t, z are natural numbers.

[0035] In this preparation method, diamine ethyl containing a primary amine group first undergoes an addition reaction with an acid anhydride to generate a carboxyl-containing intermediate, propyl. Intermediate propyl then undergoes a condensation reaction with diamine butyl containing a primary amine group to generate an amide, thereby grafting two polyamine side chains onto acid anhydride methyl. This preparation method changes the uncertainty of raw material sources in traditional polyamide dimer acids, avoids interference from the complex components of plant-based raw materials, and directly uses phthalic anhydride-based raw materials to synthesize commercially available polyamide curing agents, expanding the types of polyamides and the channels for raw material sources. In addition, the production conditions of this preparation method are milder than those of traditional polyamide preparation methods, the phthalic anhydride acylation activity is higher than that of traditional dimer acids, the production operation is easier, and it not only has low energy consumption but is also more conducive to industrial production.

[0036] In some embodiments of the present invention, the equivalent ratio of acid anhydride A, diamine ethyl, and diamine butyl is 2:(0.8~1.2):(0.8~1.2). By controlling the ratio of these three components, the present invention improves the utilization rate of diamine ethyl and diamine butyl while reducing the generation of polymeric byproducts.

[0037] In some embodiments of the present invention, the addition reaction and condensation reaction are carried out in a first organic solvent; the reaction temperature of the addition reaction is 110±℃; and the reaction temperature of the condensation reaction is 190±℃. Toluene is preferably the first organic solvent. In this preparation method, intermediate C can be stored for later use, or diamine butyl can be directly added to the original reaction solution containing intermediate C to carry out the next condensation reaction. For the purpose of saving time and cost, the present invention directly adds diamine butyl to the original reaction solution to carry out the condensation reaction. In embodiments of the present invention, the original reaction solution containing intermediate C is filtered before adding diamine butyl to remove byproducts precipitated in the addition reaction. In some embodiments of the present invention, both the addition reaction and the condensation reaction are carried out under catalyst-free conditions, which can save on the product cost and removal cost of the catalyst. This is because the catalyst is difficult to completely remove, and the residual catalyst will slowly catalyze the side reactions of the epoxy curing agent after the reaction is completed, causing the product to deteriorate.

[0038] In some embodiments of the present invention, the acid anhydride A is one or more of phthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and phthalic anhydride; these acid anhydrides all have a cyclic structure, which imparts high rigidity to the epoxy catalyst. In addition, these acid anhydrides have a V-shaped structure, and the epoxy curing agent formed after grafting has a V-shaped toothed structure. The V-shaped toothed structure makes the two amide groups of the epoxy curing agent closer together, and the active hydrogen and nitrogen atoms on the two similar chains react with the same epoxy molecule to form a new cyclic structure. In the epoxy resin composition, the filler can be embedded in this new cyclic structure to improve the rigidity of the cured product.

[0039] In some embodiments of the present invention, diamine ethyl is one or more polyether diamines with a weight-average molecular weight of 200 to 1000; for example, polyether diamines with a weight-average molecular weight of 230, 400, or 1000. These polyether diamines have ultra-long carbon chains, which impart high viscosity to the epoxy curing agent and can improve the shear strength of the epoxy curing agent; in addition, these polyether diamines have relatively long chains, a flat curing exothermic peak, and a certain pot life, which brings convenience to the process operation.

[0040] In some embodiments of the present invention, diaminebutane is one or more of diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine. These polyamines have shorter chain lengths, more amine groups, and stronger amine activity, resulting in faster reaction and exothermic rates, thereby accelerating the room temperature curing speed of the epoxy resin composition and shortening the surface drying time of the epoxy resin composition.

[0041] Epoxy resin composition: The present invention provides an epoxy resin composition comprising an epoxy resin and a curing agent, wherein the curing agent is the aforementioned epoxy curing agent.

[0042] As described above, the epoxy curing agent of the present invention can shorten the surface drying time of epoxy resin at room temperature, while ensuring that the epoxy resin composition can be fully cured at room temperature. The cured product has high rigidity and toughness, which greatly improves the flexural modulus (rigidity) of the cured product, making it less prone to deformation and collapse.

[0043] In some embodiments of the present invention, the epoxy resin composition includes epoxy resin, accelerator, epoxy curing agent, filler, diluent, and additives; the filler is one or more selected from activated calcium carbonate, silica powder, and mineral powder, with a filler content of 25wt%-70wt%; the diluent is one or more selected from benzyl alcohol, butanediol diglycidyl ether, dibenzyl ether, and glycerol glycidyl ether, with a diluent content of 1wt%-15wt%; the additives are one or more selected from antioxidants, catalysts, whitening agents, plasticizers, flame retardants, heat stabilizers, and ultraviolet absorbers, with an additive content of 0.05wt%-1.50wt%. Preferably, the epoxy resin is bisphenol A type epoxy resin, and the accelerator is benzyl dimethylamine. More preferably, the weight ratio of epoxy resin, accelerator, and epoxy curing agent is 100:5:100.

[0044] application: This invention provides the application of the above-described epoxy resin composition in epoxy coatings or structural adhesives.

[0045] The epoxy resin composition of the present invention produces an epoxy coating with a short surface drying time at room temperature. The epoxy coating does not require heating during application and is suitable for various scenarios. In addition, the epoxy coating has good toughness and rigidity, and the cured product has good impact resistance, thereby improving the service life of the coating film and broadening the application range of epoxy coatings.

[0046] The epoxy resin composition of this invention, used to create a structural adhesive, requires no heating during application, making it ideal for the construction industry. Its short room temperature surface drying time shortens the construction cycle. Furthermore, the reaction continues after surface drying, enhancing the final strength of the adhesive and ensuring project quality. This structural adhesive exhibits good toughness and rigidity, and the cured product demonstrates excellent impact resistance, providing strong rigid support to the bonded surfaces and reducing the occurrence of collapse and deformation.

[0047] The technical solution of the present invention will be described in detail below through specific embodiments: Unless otherwise specified, all parts in the following examples are by weight.

[0048] The structural formula of diethylenetriamine used in the following examples is as follows: The structural formula of phthalic anhydride is: The structural formula of methyltetrahydrophthalic anhydride is: .

[0049] Example 1: ① Raw materials for production: Phthalic anhydride 150 parts, toluene 460 parts, polyether diamine D230 (weight average molecular weight of 230) 230 parts, diethylenetriamine 103 parts.

[0050] ②Preparation method: Dissolve 230 parts of D230 polyether diamine in 200 parts (1 equivalent volume) of toluene and add it to the reactor, then slowly heat. Dissolve 150 parts of phthalic anhydride monomer in 260 parts (2 equivalent volumes) of toluene, and add the toluene solution of phthalic anhydride monomer dropwise to the reactor over 30-60 minutes. Reflux at 110°C for 2 hours, and perform a control test (viscosity at 40°C using a rotational viscometer). After the test is passed, filter out the solids. Add 103 parts of diethylenetriamine to the filtrate, slowly heat and reflux at 190°C for 3-5 hours. After the reaction is complete, maintain a vacuum of 0.9 MPa to remove toluene, water, and residual trace amounts of amine until there is essentially no reflux. Perform a control test (amine value tested using the perchloric acid method, viscosity at 40°C tested using a rotational viscometer). After the test is passed, filter and discharge the material to obtain the epoxy curing agent.

[0051] ③ Technical specifications of epoxy curing agent: Amine value: 235 mg KOH / g (tested by perchloric acid method); Viscosity: 20300 mPa·s, 40℃ (rotor viscosity method); Active hydrogen equivalent: 203; Color: 3 (Gardnerfat).

[0052] ④ Epoxy resin composition one: Formula 1: 100 parts of E-51 bisphenol A type epoxy resin, 5 parts of DMP-30 accelerator, 100 parts of commercially available polyamide curing agent (650), and other fillers, diluents, and additives; Formula 2: 100 parts of E-51 bisphenol A type epoxy resin, 5 parts of DMP-30 accelerator, 100 parts of the epoxy curing agent prepared in this example, and other fillers, diluents, and additives; Curing process: Curing at room temperature for 3 days.

[0053] Table 1

[0054] Note: Room temperature usability test (room temperature, 5mm thin coating).

[0055] Formula 1 has a surface drying time of 15 hours and a Shore hardness of 46D after 24 hours. Formula 2 has a surface drying time of 12 hours and a Shore hardness of 76D after 24 hours.

[0056] ⑤ Epoxy resin composition two: Formula 3: 100 parts of E-51 bisphenol A type epoxy resin, 5 parts of DMP-30 accelerator, 100 parts of commercially available polyamide curing agent (115), and other fillers, diluents, and additives; Formula 4: 100 parts of E-51 bisphenol A type epoxy resin, 5 parts of DMP-30 accelerator, 100 parts of the epoxy curing agent prepared in this example, and other fillers, diluents, and additives; Curing process: Curing at room temperature for 3 days.

[0057] Table 2

[0058] Note: Room temperature usability test (room temperature, 5mm thin coating).

[0059] Formula 3 has a surface drying time of 12 hours and a Shore hardness of 60D after 24 hours. Formula 4 has a surface drying time of 9 hours and a Shore hardness of 79D after 24 hours.

[0060] Example 2: ① Raw materials for production: 166 parts of methyltetrahydrophthalic anhydride, 490 parts of toluene, 230 parts of D230 polyether diamine (weight average molecular weight 230), and 103 parts of diethylenetriamine.

[0061] ②Preparation method: Dissolve 230 parts of D230 polyether diamine in 200 parts (1 equivalent volume) of toluene and add it to a reaction vessel. Slowly raise the temperature. Dissolve 166 parts of methyltetrahydrophthalic anhydride in 290 parts (2 equivalent volumes) of toluene. Add the methyltetrahydrophthalic anhydride toluene solution dropwise to the vessel for 30-60 minutes. Reflux at 110°C for 2 hours. Perform a control test (viscosity at 40°C using a rotational viscometer). After the indicators are qualified, filter out the solids. Add 103 parts of diethylenetriamine to the filtrate and slowly raise the temperature to reflux. Reflux at 190°C for 3-5 hours. After the reaction is completed, maintain a vacuum of 0.9 MPa to remove toluene, water, and residual trace amounts of amine until there is basically no reflux. Perform a control test (amine value tested by perchloric acid method, viscosity at 40°C tested by a rotational viscometer). After the indicators are qualified, filter and discharge the material to obtain the epoxy curing agent.

[0062] ③ Technical specifications of epoxy curing agent: Amine value: 228 mg KOH / g (tested by perchloric acid method); Viscosity: 20800 mPa·s, 40℃ (rotor viscosity method); Active hydrogen equivalent: 209; Color: 5 (Gardnerfat).

[0063] ④ Epoxy resin composition three: Formula 5: 100 parts of E-51 bisphenol A type epoxy resin, 5 parts of benzyl dimethylamine accelerator, 100 parts of commercially available polyamide curing agent (650), and other fillers, diluents, and additives; Formula 6: 100 parts of E-51 bisphenol A type epoxy resin, 5 parts of benzyl dimethylamine accelerator, 100 parts of the epoxy curing agent prepared in this example, and other fillers, diluents, and additives; Curing process: Curing at room temperature for 3 days.

[0064] Table 3

[0065] Note: Room temperature usability test (room temperature, 5mm thin coating).

[0066] Formula 5 has a surface drying time of 15 hours and a Shore hardness of 49D after 24 hours. Formula 6 has a surface drying time of 12 hours and a Shore hardness of 76D after 24 hours.

[0067] ⑤ Epoxy Resin Composition Four: Formula 7: 100 parts of E-51 bisphenol A type epoxy resin, 5 parts of benzyl dimethylamine accelerator, 100 parts of commercially available polyamide curing agent (115), and other fillers, diluents, and additives; Formula 8: 100 parts of E-51 bisphenol A type epoxy resin, 5 parts of benzyl dimethylamine accelerator, 100 parts of the epoxy curing agent prepared in this example, and other fillers, diluents, and additives; Curing process: Curing at room temperature for 3 days.

[0068] Table 4

[0069] Note: Room temperature usability test (room temperature, 5mm thin coating).

[0070] Formula 7 has a surface drying time of 12 hours and a Shore hardness of 61D after 24 hours. Formula 8 has a surface drying time of 9 hours and a Shore hardness of 82D after 24 hours.

[0071] The epoxy curing agent prepared in this embodiment was subjected to infrared spectroscopy testing, such as... Figure 1 As shown, 3361cm -1 The absorption peak is for amino N-H bonds or amide N-H bonds, at 1609 cm⁻¹. -1 The absorption peak for the formyl C=O double bond is at 1460 cm⁻¹. -1 The absorption peak for the C-N bond indicates that the target molecule in Example 2 was successfully constructed.

[0072] Example 3: ① Raw materials for production: 166 parts of methyltetrahydrophthalic anhydride, 635 parts of toluene, 400 parts of D400 polyether diamine (weight average molecular weight of 400), and 103 parts of diethylenetriamine.

[0073] ②Preparation method: Dissolve 400 parts of D400 polyether diamine in 345 parts (1 equivalent volume) of toluene and add it to the reactor, then slowly heat. Dissolve 166 parts of methyltetrahydrophthalic anhydride in 290 parts (2 equivalent volumes) of toluene, and add the methyltetrahydrophthalic anhydride toluene solution to the reactor dropwise over 30-60 minutes. Then reflux at 110°C for 2 hours. Perform a control test (viscosity at 40°C using a rotational viscometer). If the indicators are qualified, filter out the solids. Add 103 parts of diethylenetriamine to the filtrate, slowly heat and reflux at 190°C for 3-5 hours. After the reaction is complete, maintain a vacuum of 0.9 MPa to remove toluene, water, and residual trace amounts of amine until there is basically no reflux. Perform a control test (amine value tested by perchloric acid method, viscosity at 40°C tested by a rotational viscometer). If the indicators are qualified, filter and discharge the material to obtain the epoxy curing agent.

[0074] ③ Technical specifications of epoxy curing agent: Amine value: 218 mg KOH / g (tested by perchloric acid method); Viscosity: 27600 mPa·s, 40℃ (rotor viscosity method); Active hydrogen equivalent: 239; Color: 6 (Gardnerfat).

[0075] ④ Epoxy resin composition five: Formula 9: 100 parts of E-51 bisphenol A type epoxy resin, 5 parts of DMP-30 accelerator, 100 parts of commercially available polyamide curing agent (650), and other fillers, diluents, and additives; Formula 10: 100 parts of E-51 bisphenol A type epoxy resin, 5 parts of DMP-30 accelerator, 100 parts of epoxy curing agent prepared in this embodiment, and other fillers, diluents, and additives; Curing process: Curing at room temperature for 3 days.

[0076] Table 5

[0077] Note: Room temperature usability test (room temperature, 5mm thin coating).

[0078] Formula 9 has a surface drying time of 12 hours and a Shore hardness of 66D after 24 hours. Formula 10 has a surface drying time of 6 hours and a Shore hardness of 79D after 24 hours.

[0079] ⑤ Epoxy resin composition six: Formula 11: 100 parts of E-51 bisphenol A type epoxy resin, 5 parts of benzyl dimethylamine accelerator, 100 parts of commercially available polyamide curing agent (115), and other fillers, diluents, and additives; Formula 12: 100 parts of E-51 bisphenol A type epoxy resin, 5 parts of benzyl dimethylamine accelerator, 100 parts of the epoxy curing agent prepared in this example, and other fillers, diluents, and additives; Curing process: Curing at room temperature for 3 days.

[0080] Table 6

[0081] Note: Room temperature usability test (room temperature, 5mm thin coating).

[0082] Formula 11 has a surface drying time of 24 hours and a Shore hardness of 59D after 24 hours. Formula 12 has a surface drying time of 12 hours and a Shore hardness of 80D after 24 hours.

[0083] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing an epoxy curing agent, characterized in that, Includes the following steps: An anhydride A and diamine B undergo an addition reaction to produce intermediate C; The intermediate propylene and diaminebutane undergo a condensation reaction to obtain an epoxy curing agent; The equivalent ratio of acid anhydride A, diamine B, and diamine D is 2:(0.8~1.2):(0.8~1.2). The acid anhydride A is one or more of phthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and phthalic anhydride; The diamine ethyl is one or more polyether diamines with a weight average molecular weight of 200-1000; The diaminebutane is one or more of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine; The epoxy curing agent has the structure shown in general formula I: General Formula I in: A is a group derived from the reaction of the acid anhydride A; R1NHCO- and R2NHCO- are ortho substituents on A; R1 is -C n H 2n -(CH3C m H 2m-1 O) x -NH 2-y (C p H 2p+1 ) y ; R2 is the group formed after the diaminobutyric acid removes an amino group from a primary amine; n=0~3, m=1~3, p=1~3, x=2~16, y=0~2.

2. The method for preparing the epoxy curing agent according to claim 1, characterized in that: The addition reaction and the condensation reaction are carried out in a first organic solvent; and / or, The reaction temperature for the addition reaction is 110°C; and / or, The reaction temperature for the condensation reaction is 190°C.

3. The method for preparing the epoxy curing agent according to claim 2, characterized in that: Both the addition reaction and the condensation reaction were carried out under catalyst-free conditions.

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