Epoxy curing agent as well as preparation method and application thereof

Abstract

The invention relates to an epoxy hardener as well as a preparation method and application thereof. The epoxy hardener is prepared from ring-containing anhydride A, diamine B with a long polyether chain and active diamine D through reaction. The epoxy curing agent is endowed with relatively high rigidity by the annular structure of the epoxy curing agent; two amide groups are close to each other and are located on a V-shaped tooth-shaped structure, two close chains contain active hydrogen and nitrogen atoms which can react with the same epoxy resin molecule to form a new cross-linked ring structure, and a filler in the epoxy resin composition can be embedded into the new ring structure to improve the rigidity of the epoxy resin composition; the long polyether chain endows the epoxy curing agent with relatively high viscosity and toughness, and the impact strength of a cured product is improved; the active diaminobutyl improves the reaction rate of the epoxy curing agent, so that the epoxy resin composition has shorter surface drying time.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to an epoxy curing agent and a preparation method and application thereof. Background Art

[0002] Polyamide epoxy curing agents usually use dimer acid-modified polyethylene polyamine as the basic skeleton, with a long carbon chain and high viscosity, which can make the cured product have high elasticity, adhesion and water resistance. The common 650 epoxy curing agent is one of them. However, the 650 epoxy curing agent and bisphenol A epoxy resin cure slowly at room temperature. When cross-linked under heating conditions, the exothermic peak during the curing process is relatively gentle, and the cured product has a low cross-linking density. Although it has good flexibility, it often shows low rigidity.

[0003] The prior art usually introduces tertiary amine accelerators into epoxy resin to accelerate the curing speed, but the rigidity improvement is not significant. In addition, the prior art also adds rigid structural materials containing benzene rings and tertiary amine accelerators into epoxy resin to improve the curing speed and rigidity. However, due to the limited physical addition amount of these substances, the ability of this method to improve the rigidity of the epoxy resin formulation system is limited. Summary of the invention

[0004] The invention provides an epoxy curing agent and a preparation method and application thereof, so as to solve the problems in the prior art that the curing rate of epoxy resin is slow and it is difficult to balance rigidity and toughness.

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

[0006] Formula I in: A is an aromatic ring or an aliphatic ring substituted or unsubstituted by a B group; R1NHCO- and R2NHCO- are ortho substituents on A; and the B group 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 combination 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 a structural formula: the B group is a C1~C5 alkyl group.

[0009] In a second aspect, the present invention provides a method for preparing an epoxy curing agent, comprising the following steps: Allow anhydride A and diamine B to undergo addition reaction to generate intermediate C; The intermediate propane and diamine butane undergo condensation reaction to obtain an epoxy curing agent; Among them: The structural formula of anhydride A is ; The structural formula of intermediate C is ; The structural formula of diamine 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 diamine 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 ring or an aliphatic ring substituted or unsubstituted by a B group; R1NHCO- and R2NHCO- are ortho substituents on A; and the B group 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 B is 2: (0.8~1.2): (0.8~1.2).

[0011] In conjunction with the second aspect of the present 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±°C; and / or the reaction temperature of the condensation reaction is 190±°C.

[0012] In conjunction with the second aspect of the present invention, in some embodiments, both the addition reaction and the condensation reaction are carried out in the absence of a catalyst.

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

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

[0015] In a fourth aspect, the present invention provides use of the epoxy resin composition in epoxy coatings or building structural adhesives.

[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 gives the epoxy curing agent higher rigidity; the two amide groups are close to each other and are located on the V-shaped tooth structure, and the active hydrogen-containing nitrogen atoms on the two adjacent chains can react with the same epoxy molecule to form a new cyclic structure, and the filler in the epoxy resin composition can be embedded in the new cyclic structure to improve its rigidity; the R1 chain is relatively long, which gives the epoxy curing agent higher viscosity and toughness, and improves the shear strength of the cured product; the R2 chain is relatively short and has higher activity, which improves the reaction rate of the epoxy curing agent, so that the epoxy resin composition has a shorter surface drying time. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 This is the infrared spectrum of the epoxy curing agent provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] For simplicity, the present invention only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range; similarly, any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the endpoints of the range is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0021] It should be noted that, in the description of the present invention, unless otherwise specified, "above" and "below" are inclusive numbers, and the meaning of "multiple" in "one or more" is two or more. Relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0022] In the description of the present invention, the description with reference to the terms "any embodiment / method", "one embodiment / method", "some embodiments / methods", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments / methods or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments / methods or examples described in this specification and the features of the different embodiments / methods or examples, without contradiction.

[0023] The above summary of the invention of the present invention is not intended to describe each disclosed embodiment or each implementation in the present invention. The following description more specifically illustrates exemplary embodiments. These embodiments can be used in various combinations. In each example, the enumeration is only used as a representative group and should not be interpreted as exhaustive.

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

[0025] Formula I in: A is an aromatic ring or an aliphatic ring substituted or unsubstituted by a B group; R1NHCO- and R2NHCO- are ortho substituents on A; and the B group 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 the present invention has a cyclic structure and a V-shaped tooth structure, and contains a primary amine group, a secondary amine group, an amide group, and a longer R1 chain and a shorter R2 chain. The cyclic structure gives the epoxy curing agent higher rigidity; the two amide groups are close to each other and are located on the V-shaped tooth structure, and the active hydrogen nitrogen atoms on the two adjacent chains can react with the same epoxy molecule to form a new cyclic structure, and the filler in the epoxy resin composition can be embedded in this new cyclic structure to improve its rigidity; the R1 chain is longer, which gives the epoxy curing agent higher viscosity and toughness, and improves the shear strength of the cured product; the R2 chain is shorter and more active, which improves the reaction rate of the epoxy curing agent, so that the epoxy resin composition has a shorter surface drying time.

[0027] In the epoxy curing agent of the present invention, the amine groups and amide groups on the R1 chain and the R2 chain have different activities and reaction rates. The amine groups with higher activity ensure that the epoxy resin composition has a shorter surface drying time, and the amide groups with lower activity ensure that the epoxy resin composition continues to react after the 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 relatively long chain length, a relatively slow reaction rate, and a gentle curing exothermic peak. When used in combination with the R2 chain, the epoxy curing agent has a suitable reaction rate and a moderate application period, thereby avoiding insufficient operating time due to an overly fast reaction.

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

[0030] The above factors ensure that the cured product using the epoxy curing agent of the present invention has 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 structural formula: the B group is a C1-C5 alkyl group. These alkyl groups are electron-donating groups, which can increase the reactivity of the amine group; at the same time, the alkyl group with a suitable 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 preparation method of the epoxy curing agent provided by the present invention comprises the following steps: Allow anhydride A and diamine B to undergo addition reaction to generate intermediate C; The intermediate propane and diamine butane undergo condensation reaction to obtain an epoxy curing agent; Among them: The structural formula of anhydride A is ; The structural formula of intermediate C is ; The structural formula of diamine 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 diamine 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 ring or an aliphatic ring substituted or unsubstituted by a B group; R1NHCO- and R2NHCO- are ortho substituents on A; and the B group 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 the preparation method, the diamine ethylene containing a primary amine group first undergoes an addition reaction with an acid anhydride to generate a carboxyl-containing intermediate propylene, and the intermediate propylene undergoes a condensation reaction with the diamine butyl containing a primary amine group to generate an amide, thereby grafting two polyamine side chains onto the acid anhydride ethylene. The preparation method changes the uncertainty of the source of raw materials for traditional polyamide dimer acid, avoids the interference of complex components of plant raw materials, directly uses phthalic anhydride raw materials to synthesize commercially available polyamide curing agents, and expands the types of polyamides and raw material source channels. In addition, the production conditions of the preparation method are milder than those of traditional polyamide preparation methods, the phthalic anhydride acylation activity is higher than that of traditional dimer acid, and the production operation is easier. Not only is the production energy consumption low, but it is also more conducive to industrial production.

[0036] In some embodiments of the present invention, the equivalent ratio of acid anhydride A, diamine B, and diamine B is 2: (0.8-1.2): (0.8-1.2). The present invention controls the ratio of the three, on the one hand, improves the utilization rate of diamine B and diamine B, and on the other hand, reduces the generation of high molecular by-products.

[0037] In some embodiments of the present invention, the addition reaction and the condensation reaction are carried out in the first organic solvent; the reaction temperature of the addition reaction is 110±℃; the reaction temperature of the condensation reaction is 190±℃. The first organic solvent is preferably toluene. In the preparation method, the intermediate C can be stored for standby use, or diamine butane can be directly added to the original reaction solution containing the intermediate C to carry out the next condensation reaction. In order to save time and cost, the present invention directly adds diamine butane to the original reaction solution to carry out the condensation reaction. In an embodiment of the present invention, before adding diamine butane, the original reaction solution containing the intermediate C is filtered to filter out the by-products 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 the product cost and removal cost of the catalyst. The reason is that: the catalyst is difficult to completely remove, and the residual catalyst will slowly catalyze the side reaction 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 ring structure, which gives the epoxy catalyst high rigidity. In addition, these acid anhydrides have a V-shaped structure, and the epoxy curing agent formed after grafting has a V-shaped tooth structure. The V-shaped tooth structure makes the two amide groups of the epoxy curing agent closer, and the active hydrogen and nitrogen atoms on the two adjacent chains react with the same epoxy molecule to form a new ring structure. In the epoxy resin composition, the filler can be embedded in this new ring structure to improve the rigidity of the cured product.

[0039] In some embodiments of the present invention, the diamine 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, and 1000. These polyether diamines have ultra-long carbon chains, which give the epoxy curing agent high viscosity and can improve the shear strength of the epoxy curing agent; in addition, these polyether diamines have long chains, gentle curing exothermic peaks, and a certain applicable period, which brings convenience to process operation.

[0040] In some embodiments of the present invention, the diamine butane is one or more of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. These polyamines have short chain lengths, many amine groups, strong amine activity, and faster reaction speeds and heat release 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 invention provides an epoxy resin composition, comprising an epoxy resin and a curing agent, wherein the curing agent is the above-mentioned epoxy curing agent.

[0042] As described above, the epoxy curing agent of the present invention can shorten the surface drying time of the epoxy resin at room temperature, while ensuring that the epoxy resin composition can be completely cured at room temperature. The cured product also has high stiffness and toughness, greatly improving the bending modulus (rigidity) of the cured product, making it less likely to deform and collapse.

[0043] In some embodiments of the present invention, the epoxy resin composition includes epoxy resin, accelerator, epoxy curing agent, filler, diluent, and auxiliary agent; the filler is one or more of activated calcium carbonate, silicon powder, and mineral powder, and the filler content is 25wt%-70wt%; the diluent is one or more of benzyl alcohol, butanediol diglycidyl ether, dibenzyl ether, and glycerol glycidyl ether, and the diluent content is 1wt%-15wt%; the auxiliary agent is one or more of antioxidant, catalyst, brightener, plasticizer, flame retardant, heat stabilizer, and ultraviolet absorber, and the auxiliary agent content is 0.05wt%-1.50wt%. Preferably, the epoxy resin is bisphenol A type epoxy resin, accelerator, and benzyl dimethylamine. Further preferably, the weight ratio of epoxy resin, accelerator, and epoxy curing agent is 100:5:100.

[0044] application: The present invention provides application of the epoxy resin composition in epoxy coating or building structural adhesive.

[0045] The epoxy coating made from the epoxy resin composition of the present invention has a shorter surface drying time at room temperature, does not require heating during the construction process of the epoxy coating, and is suitable for a variety of scenarios; in addition, the epoxy coating has good toughness and rigidity, and the cured product has good impact resistance, thereby increasing the service life of the paint film and broadening the application range of the epoxy coating.

[0046] The construction process of the building structural adhesive made of the epoxy resin composition of the present invention does not require heating, and is very suitable for use in the construction field. The short room temperature surface drying time can shorten the construction period; in addition, the reaction of the building structural adhesive is still ongoing after the surface drying, which can improve the final strength of the building structural adhesive and ensure the quality of the project. The building structural adhesive has good toughness and rigidity, the cured product has good impact resistance, has good rigid support for the adherend, and reduces the occurrence of collapse and deformation problems.

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

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

[0049] Embodiment 1: ① Raw materials: 150 parts of phthalic anhydride, 460 parts of toluene, 230 parts of polyether diamine D230 (weight average molecular weight is 230), and 103 parts of diethylene triamine.

[0050] ②Preparation method: Dissolve 230 parts of D230 polyether diamine in 200 parts (1 equivalent volume) of toluene, add to the reaction kettle, and slowly heat up; dissolve 150 parts of phthalic anhydride monomer in 260 parts (2 equivalent volumes) of toluene, drip the toluene solution of phthalic anhydride monomer into the kettle within 30-60 minutes, reflux at 110°C for 2 hours, and perform in-process control inspection (rotational viscometer to test the viscosity at 40°C). After the indicators are qualified, filter out the solid; add 103 parts of diethylenetriamine to the filtrate, slowly heat up and reflux, reflux at 190°C for 3-5 hours, maintain a vacuum of 0.9MPa after the reaction, remove toluene, water and a small amount of residual amine, until there is basically no reflux, perform in-process control inspection (perchloric acid method to test the amine value, rotational viscometer to test the viscosity at 40°C), filter and discharge the material after the indicators are qualified, and the epoxy curing agent is obtained.

[0051] ③ Epoxy curing agent technical indicators: Amine value: 235 mg KOH / g (perchloric acid method test); Viscosity: 20300 mPa·s, 40°C (rotor viscosity method); Active hydrogen equivalent: 203; Color: 3# (Gardner method).

[0052] ④Epoxy resin composition 1: Formula 1: 100 parts of E-51 bisphenol A 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 epoxy resin, 5 parts of DMP-30 accelerator, 100 parts of 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] Description: Normal temperature usability test (room temperature, thin coating 5mm).

[0055] The surface drying time of formula 1 is 15 hours and the Shore hardness is 46D after 24 hours. The surface drying time of formula 2 is 12 hours and the Shore hardness is 76D after 24 hours.

[0056] ⑤Epoxy resin composition 2: Formula 3: 100 parts of E-51 bisphenol A 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 epoxy resin, 5 parts of DMP-30 accelerator, 100 parts of 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] Description: Normal temperature usability test (room temperature, thin coating 5mm).

[0059] The surface drying time of formula 3 is 12 hours and the Shore hardness is 60D after 24 hours. The surface drying time of formula 4 is 9 hours and the Shore hardness is 79D after 24 hours.

[0060] Embodiment 2: ① Raw materials: 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, add to a reaction kettle, slowly heat up, dissolve 166 parts of methyltetrahydrophthalic anhydride in 290 parts (2 equivalent volumes) of toluene, drip the toluene solution of methyltetrahydrophthalic anhydride into the kettle for 30-60 minutes, reflux at 110°C for 2 hours, conduct in-process control inspection (use a rotary viscometer to test the viscosity at 40°C), and filter out the solid after the index is qualified; add 103 parts of diethylenetriamine to the filtrate, slowly heat up and reflux, reflux at 190°C for 3-5 hours, maintain a vacuum of 0.9MPa after the reaction, remove toluene, water and a small amount of residual amine, until there is basically no reflux, conduct in-process control inspection (use a perchloric acid method to test the amine value, and use a rotary viscometer to test the viscosity at 40°C), and filter out the material after the index is qualified to obtain the epoxy curing agent.

[0062] ③ Epoxy curing agent technical indicators: Amine value: 228 mg KOH / g (tested by perchloric acid method); Viscosity: 20800 mPa·s, 40°C (rotor viscosity method); Active hydrogen equivalent: 209; Color: 5# (Gardner method).

[0063] ④Epoxy resin composition three: Formula 5: 100 parts of E-51 bisphenol A 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 epoxy resin, 5 parts of benzyl dimethylamine accelerator, 100 parts of 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] Description: Normal temperature usability test (room temperature, thin coating 5mm).

[0066] The surface drying time of formula 5 is 15 hours and the Shore hardness is 49D after 24 hours. The surface drying time of formula 6 is 12 hours and the Shore hardness is 76D after 24 hours.

[0067] ⑤Epoxy resin composition 4: Formula 7: 100 parts of E-51 bisphenol A 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 epoxy resin, 5 parts of benzyl dimethylamine accelerator, 100 parts of 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] Description: Normal temperature usability test (room temperature, thin coating 5mm).

[0070] The surface drying time of formula 7 is 12 hours, and the Shore hardness is 61D after 24 hours. The surface drying time of formula 8 is 9 hours, and the Shore hardness is 82D after 24 hours.

[0071] The epoxy curing agent prepared in this example was tested by infrared spectroscopy. Figure 1 As shown, 3361cm -1 It is the absorption peak of amino N-H bond or amide N-H bond, 1609cm -1 It is the absorption peak of the formyl C=O double bond, 1460cm -1 It is the absorption peak of C—N bond, indicating that the target molecule of Example 2 was successfully constructed.

[0072] Embodiment 3: ① Raw materials: 166 parts of methyltetrahydrophthalic anhydride, 635 parts of toluene, 400 parts of D400 polyether diamine (weight average molecular weight is 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 to the reaction kettle, and slowly heat up; dissolve 166 parts of methyltetrahydrophthalic anhydride in 290 parts (2 equivalent volumes) of toluene, drip the toluene solution of methyltetrahydrophthalic anhydride into the kettle within 30 to 60 minutes, and then reflux at 110°C for 2 hours, and perform in-process control inspection (rotational viscometer to test the viscosity at 40°C). After the indicators are qualified, filter out the solid; add 103 parts of diethylenetriamine to the filtrate, slowly heat up and reflux, reflux at 190°C for 3 to 5 hours, maintain a vacuum of 0.9MPa after the reaction, remove toluene, water and a small amount of residual amine, until there is basically no reflux, perform in-process control inspection (perchloric acid method to test the amine value, rotational viscometer to test the viscosity at 40°C), filter and discharge the material after the indicators are qualified, and the epoxy curing agent is obtained.

[0074] ③ Epoxy curing agent technical indicators: Amine value: 218 mg KOH / g (perchloric acid method test); Viscosity: 27600 mPa·s, 40°C (rotor viscosity method); Active hydrogen equivalent: 239; Color: 6# (Gardner method).

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

[0076] Table 5

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

[0078] The surface drying time of formula 9 is 12 hours and the Shore hardness is 66D after 24 hours. The surface drying time of formula 10 is 6 hours and the Shore hardness is 79D after 24 hours.

[0079] ⑤Epoxy resin composition VI: Formula 11: 100 parts of E-51 bisphenol A 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 epoxy resin, 5 parts of benzyl dimethylamine accelerator, 100 parts of 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] Description: Normal temperature usability test (room temperature, thin coating 5mm).

[0082] The surface drying time of formula 11 is 24 hours, and the Shore hardness is 59D after 24 hours. The surface drying time of formula 12 is 12 hours, and the Shore hardness is 80D after 24 hours.

[0083] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be 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 present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An epoxy curing agent, characterized in that It has the structure shown in general formula I: Formula I in: A is an aromatic ring or an aliphatic ring substituted or unsubstituted by a B group; R1NHCO- and R2NHCO- are ortho substituents on A; and the B group 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.

2. The epoxy curing agent according to claim 1, characterized in that: 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.

3. The epoxy curing agent according to claim 1, characterized in that: The structural formula of the epoxy curing agent is: the B group is a C1~C5 alkyl group.

4. A method for preparing an epoxy curing agent, characterized in that: The steps include: Allow anhydride A and diamine B to undergo addition reaction to generate intermediate C; The intermediate propane and diamine butane undergo condensation reaction to obtain an epoxy curing agent; Among them: The structural formula of anhydride A is ; The structural formula of intermediate C is ; The structural formula of diamine 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 diamine 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 ring or an aliphatic ring substituted or unsubstituted by a B group; R1NHCO- and R2NHCO- are ortho substituents on A; and the B group 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.

5. The method for preparing the epoxy curing agent according to claim 4, characterized in that: The equivalent ratio of acid anhydride A, diamine B and diamine B is 2: (0.8~1.2): (0.8~1.2).

6. The method for preparing the epoxy curing agent according to claim 4, characterized in that: 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±°C; and / or, The reaction temperature of the condensation reaction is 190±°C.

7. The method for preparing the epoxy curing agent according to claim 6, characterized in that: The addition reaction and the condensation reaction are both carried out in the absence of a catalyst.

8. The method for preparing the epoxy curing agent according to claim 6, characterized in that: The acid anhydride A is one or more of phthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and phthalic anhydride; and / or, The diamine is one or more polyether diamines having a weight average molecular weight of 200 to 1000; and / or, The diamine butane is one or more of diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

9. An epoxy resin composition, characterized in that The invention comprises an epoxy resin and a curing agent, wherein the curing agent is the epoxy curing agent according to any one of claims 1 to 3.

10. Use of the epoxy resin composition according to claim 9 in epoxy coatings or building structural adhesives.

Images