A bifunctional epoxy resin latent curing agent, its preparation method and application

Abstract

The present invention relates to the technical field of epoxy resin latent curing agents, and provides a novel bifunctional epoxy resin latent curing agent, a preparation method thereof, and an application thereof. Compared with traditional curing agents, the P-ILs@ZIF-8 epoxy resin curing agent prepared in the present invention has greatly improved low-temperature curability and storage stability at room temperature, and has a more excellent curing effect. Moreover, due to the introduction of phosphorus-containing ionic liquid into the curing agent, the modified epoxy resin will have certain flame retardancy and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of latent curing agents for epoxy resins, and particularly relates to a bifunctional latent curing agent for epoxy resins, a preparation method thereof, and an application thereof. Background Art

[0002] Traditional amine curing agents have problems such as high volatility, high toxicity, high melting point, poor compatibility with epoxy resins, poor material color, and being easily oxidized by air. Ionic liquids have excellent physical and chemical properties such as low melting point and moderate polarity. As a kind of curing agent, they can improve the compatibility, flame retardancy, wear self-healing property, and mechanical properties of epoxy resin materials, and extend the pot life of epoxy resin materials.

[0003] Ionic liquid curing agents are a new direction in the research of epoxy resin curing agents and have great application prospects. Ionic liquids with imidazolium cations are the most commonly used ionic liquid curing agents in epoxy systems. In 2003, Spychaj and Kowalczyk first reported an experiment on crosslinking epoxy resin with the ionic liquid curing agent 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]). In addition, imidazole lactates and imidazole acetates have been used as epoxy resin curing agents, and their storage period at room temperature is 10 days (Daniel Warren.et al.Process for Curing Epoxy Resins with a Salt of an Imidazole and Compositions Thereof[P].US 3356645-1967-12-05). At the same time, in order to endow epoxy resin materials with certain flame retardancy, Sonnier et al. used an ionic liquid containing phosphorus in both the cation and anion structures as a flame retardant for epoxy prepolymers and curing agents. The results showed that the phosphorus-containing ionic liquid could significantly reduce flammability without further adding a flame retardant (Onnier, R.;Dumazert, L.;Livi, S, et al.Flame retardancy of phosphorus-containing ionic liquid based epoxy networks[J].Polymer Degradation and Stability,2016,134:186-188.). However, existing ionic liquid curing agents usually have disadvantages such as low curing temperature, narrow curing temperature range, and the product being liquid, which is not conducive to storage and transportation. Ionic liquid curing agents also have a certain viscosity, which is not conducive to their mixing with epoxy resins and affects the curing effect. Summary of the Invention

[0004] The present invention aims to solve at least one of the above technical problems. On the basis of analyzing and comparing the structural characteristics and research status of the above-mentioned phosphorus-containing ionic liquids, it is proposed to encapsulate quaternary phosphonium ionic liquids into the pores of metal-organic framework materials (MOFs) to prepare P-ILs@MOFs composite materials, so as to reduce their reactivity, improve their storage stability, and endow them with certain latency and flame retardancy. And study the synthesis process conditions, structural properties of this type of composite material, and compound it with epoxy resin to form a one-component epoxy resin curing system, and study the curing performance of the epoxy resin curing system, in order to obtain a latent curing agent that cures under medium temperature conditions, has a long storage period at room temperature, and the cured product has excellent properties.

[0005] One aspect of the object of the present invention provides a preparation method of a bifunctional epoxy resin latent curing agent, comprising the following steps:

[0006] S1. Preparation of ZIF-8 material;

[0007] S2. Preparation of phosphorus-containing ionic liquid P-ILs: Dissolve quaternary phosphonium salt in water, and then carry out ion exchange through an alkaline ion exchange resin to obtain a phosphonium hydroxide solution; Take the phosphonium hydroxide solution and react with an organic acid in an equimolar amount and then dry to obtain the phosphorus-containing ionic liquid P-ILs;

[0008] S3. Add the obtained ZIF-8 material and P-ILs into a solvent, mix and stir at room temperature, and after drying, obtain the P-ILs@ZIF-8 epoxy resin curing agent.

[0009] Preferably, the preparation method of the ZIF-8 material in step S1 includes:

[0010] S11. Add the organic ligand dimethylimidazole into a solvent, and dissolve it by ultrasonic to obtain an organic ligand solution; Add the metal salt zinc nitrate hexahydrate into a solvent to obtain a metal salt solution;

[0011] S12. Add the metal salt solution in step S1 into the organic ligand solution, stir at room temperature and then stand for a period of time, and after filtration, drying, and vacuum drying, obtain the ZIF-8 material.

[0012] Preferably, in step S11:

[0013] The molar concentration of the organic ligand solution is 0.5 - 2 mol / L;

[0014] The molar concentration of Zn(NO3)2·6H2O in the metal salt solution is 0.1 - 0.3 mol / L;

[0015] The solvent is one or more of water, N,N-dimethylformamide, methanol, toluene, dichloromethane, tetrahydrofuran, ethyl acetate.

[0016] Preferably, in step S12:

[0017] The temperature of the stirring is 10 - 45 °C, and the time is 0.5 - 2 h;

[0018] The time of the standing is 15 - 30 h.

[0019] Preferably, in step S2:

[0020] The quaternary phosphonium salt is one of tributylethylphosphonium bromide ([P 4442 Br), tetrabutylphosphonium bromide ([P 4444 Br), trihexylhexadecylphosphonium bromide ([P 66614 Br);

[0021] The organic acid is one of glycine (Gly), iminodiacetic acid (H2IDA), nitrilotriacetic acid (H3NTA).

[0022] Preferably, in step S2: The drying is first to remove a large amount of water by rotary evaporation, and then vacuum drying at 70 - 100 °C.

[0023] Preferably, in step S3:

[0024] The mass ratio of the phosphorus-containing ionic liquid P-ILs to the ZIF-8 material is 0.05 - 0.5;

[0025] The solvent is one or more of methanol, toluene, dichloromethane, and tetrahydrofuran;

[0026] The drying is vacuum drying at 70 - 100 °C after rotary evaporation.

[0027] Preferably, in steps S2 and S3: The temperature of the rotary evaporation is 50 - 80 °C.

[0028] Another aspect of the object of the present invention provides a bifunctional epoxy resin latent curing agent prepared according to the above preparation method.

[0029] Another aspect of the object of the present invention provides an application of the bifunctional epoxy resin latent curing agent in an epoxy resin curing system, mixing the above latent curing agent and epoxy resin evenly, and the mass ratio of the two is 0.05 - 0.5.

[0030] Preferably, the stirring speed of the mixing is 500 - 1200 r / min, and the time is 20 - 40 min.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] 1. The phosphorus-containing ionic liquid in the curing agent of the present invention is filled in the pores of the MOFs material and can be released under the action of heat. It is in powder form at room temperature. Transforming the ionic liquid curing agent from liquid state to powdery solid state not only facilitates storage and transportation, but also is easily mixed in epoxy resin. This epoxy resin latent curing agent has a long service life at room temperature and high storage stability. After being uniformly mixed with epoxy resin, it can be cured by heating. Moreover, compared with the curing agent of simple quaternary phosphorus ionic liquid, the curing temperature range becomes wider and it has a better curing effect.

[0033] 2. Compared with traditional curing agents, the P-ILs@ZIF-8 epoxy resin curing agent prepared in the present invention has greatly improved low-temperature curability and storage stability at room temperature, and has a more excellent curing effect. And because the phosphorus-containing ionic liquid is introduced into the curing agent, the modified epoxy resin will have certain flame retardancy and has good application prospects.

[0034] 3. The latent curing agent of the present invention can change the proportions of metal salts, ligands and ionic liquids, and adjust the curing temperature and rate of epoxy resin, that is, the latent curing agent of the present invention is applicable to various temperatures, has a wide application range and is simple to prepare. Description of the Drawings

[0035] Figure 1 It is the DSC curve obtained after the curing agents prepared in Examples 2, 4 - 6 are mixed and cured with epoxy resin, and the heating rate is 10 °C / min;

[0036] Figure 2 It is the DSC curve obtained after the curing agents prepared in Example 6 and Comparative Examples 1 - 2 are mixed and cured with epoxy resin, and the heating rate is 10 °C / min;

[0037] Figure 3 It is the DSC curve obtained after the curing agent prepared in Example 6 is mixed and cured with epoxy resin, and the heating rates are 10 °C / min, 15 °C / min, and 20 °C / min;

[0038] Figure 4 It is the XRD pattern of the curing agent prepared in Comparative Example 1 and the curing agent prepared in Example 2;

[0039] Figure 5 It is the BET pattern of the curing agent prepared in Comparative Example 1 and the curing agent prepared in Example 2. Detailed Embodiments

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] Example 1

[0042] This example provides a curing method for a phosphorus-containing epoxy resin curing agent and an epoxy resin, including the following steps:

[0043] (1) Weigh 11.9 g of zinc nitrate hexahydrate and 13.14 g of 2-methylimidazole, add them to anhydrous methanol respectively, mix them evenly by ultrasonic treatment, and after the reaction is completed, centrifuge, wash, and dry to obtain ZIF-8 material;

[0044] (2) Exchange the tributyl ethylphosphonium bromide solution through an alkaline ion exchange resin to obtain an aqueous solution of [P 4442 [OH], and calibrate the concentration of the alkaline solution; respectively take 10 mmol of the aqueous solution of [P 4442 [OH] and H2IDA (0.66 g), react them, evaporate a large amount of water by rotary evaporation at 60 °C, and place them in an oven at 80 °C for vacuum drying for 24 h to obtain [P 4442 2[IDA];

[0045] (3) Take 300 mg of ZIF-8 material and 30 mg of [P 4442 2[IDA], add them to anhydrous methanol, and stir at room temperature for 24 h. Then, perform rotary evaporation at 60 °C and vacuum drying at 80 °C to obtain [P 4442 2[IDA]@ZIF-8 epoxy resin curing agent;

[0046] (4) Stir and mix the obtained epoxy resin curing agent and the epoxy resin, with the mass ratio of the two being 1:3, the stirring speed being 900 r / min, and the stirring time being 30 min.

[0047] Example 2

[0048] This example provides a curing method for a phosphorus-containing epoxy resin curing agent and an epoxy resin, including the following steps:

[0049] (1) Weigh 11.9 g of zinc nitrate hexahydrate and 13.14 g of 2-methylimidazole, add them to anhydrous methanol respectively, mix them evenly by ultrasonic treatment, and after the reaction is completed, centrifuge, wash, and dry to obtain ZIF-8 material;

[0050] (2) Exchange the tributyl ethylphosphonium bromide solution through an alkaline ion exchange resin to obtain [P4442 [OH] aqueous solution, and standardize the concentration of the alkali solution; respectively take 10 mmol of [P 4442 [OH] aqueous solution and H2IDA (0.66 g) are reacted, and a large amount of water is removed by rotary evaporation at 60 °C, and then placed in an oven at 80 °C for vacuum drying for 24 h to obtain [P 4442 2[IDA];

[0051] (3) Take 300 mg of ZIF-8 material, [P 4442 2[IDA] 90 mg is added to anhydrous methanol, and the mixture is stirred at room temperature for 24 h. Subsequently, it is rotary evaporated at 60 °C and vacuum dried at 80 °C to obtain [P 4442 2[IDA]@ZIF-8 epoxy resin curing agent;

[0052] (4) The obtained epoxy resin curing agent and epoxy resin are stirred and mixed, and the mass ratio of the two is 1:3, the stirring speed is 900 r / min, and the stirring time is 30 min.

[0053] Example 3

[0054] This example provides a curing method for a phosphorus-containing epoxy resin curing agent and epoxy resin, including the following steps:

[0055] (1) Weigh 11.9 g of zinc nitrate hexahydrate and 13.14 g of 2-methylimidazole, add them to anhydrous methanol respectively, mix them uniformly by ultrasonic wave, and after the reaction, centrifuge, wash and dry to obtain ZIF-8 material;

[0056] (2) The tributylethylphosphonium bromide solution is exchanged through an alkaline ion exchange resin to obtain [P 4442 [OH] aqueous solution, and standardize the concentration of the alkali solution; respectively take 10 mmol of [P 4442 [OH] aqueous solution and H2IDA (0.66 g) are reacted, and a large amount of water is removed by rotary evaporation at 60 °C, and then placed in an oven at 80 °C for vacuum drying for 24 h to obtain [P 4442 2[IDA];

[0057] (3) Take 300 mg of ZIF-8 material, [P 4442 2[IDA] 150 mg is added to anhydrous methanol, and the mixture is stirred at room temperature for 24 h. Subsequently, it is rotary evaporated at 60 °C and vacuum dried at 80 °C to obtain [P 4442 2[IDA]@ZIF-8 epoxy resin curing agent;

[0058] (4) The obtained epoxy resin curing agent and epoxy resin are stirred and mixed, and the mass ratio of the two is 1:3, the stirring speed is 900 r / min, and the stirring time is 30 min.

[0059] Example 4

[0060] This example provides a curing method for a phosphorus-containing epoxy resin curing agent and an epoxy resin, including the following steps:

[0061] (1) Weigh 11.9 g of zinc nitrate hexahydrate and 13.14 g of 2-methylimidazole, add them to anhydrous methanol respectively, mix them evenly by ultrasonic wave, and after the reaction ends, centrifuge, wash, and dry to obtain ZIF-8 material;

[0062] (2) Exchange the tributylethylphosphonium bromide solution through an alkaline ion exchange resin to obtain an aqueous solution of [P 4442 [OH], and calibrate the concentration of the alkaline solution; Take 10 mmol of the aqueous solution of [P 4442 [OH] and H2IDA (0.66 g) respectively, after reaction, rotary evaporate to remove a large amount of water at 60 °C, and place it in an 80 °C oven for vacuum drying for 24 h to obtain [P 4442 2[IDA];

[0063] (3) Take 300 mg of ZIF-8 material and 90 mg of [P 4442 2[IDA], add them to anhydrous methanol, and stir at room temperature for 24 h. Then rotary evaporate it at 60 °C and vacuum dry it at 80 °C to obtain [P 4442 2[IDA]@ZIF-8 epoxy resin curing agent;

[0064] (4) Stir and mix the obtained epoxy resin curing agent and the epoxy resin, the mass ratio of the two is 1:4, the stirring speed is 900 r / min, and the stirring time is 30 min.

[0065] Example 5

[0066] This example provides a curing method for a phosphorus-containing epoxy resin curing agent and an epoxy resin, including the following steps:

[0067] (1) Weigh 11.9 g of zinc nitrate hexahydrate and 13.14 g of 2-methylimidazole, add them to anhydrous methanol respectively, mix them evenly by ultrasonic wave, and after the reaction ends, centrifuge, wash, and dry to obtain ZIF-8 material;

[0068] (2) Exchange the tributylethylphosphonium bromide solution through an alkaline ion exchange resin to obtain an aqueous solution of [P 4442 [OH], and calibrate the concentration of the alkaline solution; Take 10 mmol of the aqueous solution of [P 4442 [OH] and H2IDA (0.66 g) respectively, after reaction, rotary evaporate to remove a large amount of water at 60 °C, and place it in an 80 °C oven for vacuum drying for 24 h to obtain [P 4442 2[IDA];

[0069] (3) Take 300 mg of ZIF-8 material, [P 4442 2[IDA] 90 mg and add them into anhydrous methanol. Stir the mixture at room temperature for 24 h. Then, carry out rotary evaporation at 60 °C and vacuum drying at 80 °C to obtain [P 4442 2[IDA]@ZIF-8 epoxy resin curing agent;

[0070] (4) Stir and mix the obtained epoxy resin curing agent with epoxy resin. The mass ratio of the two is 3:17, the stirring speed is 900 r / min, and the stirring time is 30 min.

[0071] Example 6

[0072] This example provides a curing method for a phosphorus-containing epoxy resin curing agent and epoxy resin, including the following steps:

[0073] (1) Weigh 11.9 g of zinc nitrate hexahydrate and 13.14 g of 2-methylimidazole, add them into anhydrous methanol respectively. After ultrasonic homogenization, mix them. After the reaction ends, centrifuge, wash, and dry to obtain ZIF-8 material;

[0074] (2) Exchange the tributyl ethylphosphonium bromide solution through an alkaline ion exchange resin to obtain an aqueous solution of [P 4442 [OH], and calibrate the concentration of the alkaline solution; Take 10 mmol of the aqueous solution of [P 4442 [OH] and H2IDA (0.66 g) respectively. After reaction, rotary evaporate at 60 °C to remove a large amount of water, and place it in an oven at 80 °C for vacuum drying for 24 h to obtain [P 4442 2[IDA];

[0075] (3) Take 300 mg of ZIF-8 material, [P 4442 2[IDA] 90 mg and add them into anhydrous methanol. Stir the mixture at room temperature for 24 h. Then, carry out rotary evaporation at 60 °C and vacuum drying at 80 °C to obtain [P 4442 2[IDA]@ZIF-8 epoxy resin curing agent;

[0076] (4) Stir and mix the obtained epoxy resin curing agent with epoxy resin. The mass ratio of the two is 1:9, the stirring speed is 900 r / min, and the stirring time is 30 min.

[0077] Example 7

[0078] This example provides a curing method for a phosphorus-containing epoxy resin curing agent and epoxy resin, including the following steps:

[0079] (1) Weigh 11.9 g of zinc nitrate hexahydrate and 13.14 g of 2-methylimidazole, add them to anhydrous methanol respectively, mix them after ultrasonic homogenization, and after the reaction is completed, centrifuge, wash and dry to obtain ZIF-8 material;

[0080] (2) Exchange the tributylethylphosphonium bromide solution through an alkaline ion exchange resin to obtain an aqueous solution of [P 4442 [OH], and standardize the concentration of the alkali solution; Take 10 mmol of the aqueous solution of [P 4442 [OH] and Gly (0.75 g) respectively, after the reaction, rotary evaporate to remove a large amount of water at 60 °C, and place it in an oven at 80 °C for vacuum drying for 24 h to obtain [P 4442 [Gly];

[0081] (3) Take 300 mg of ZIF-8 material and 90 mg of [P 4442 [Gly], add them to anhydrous methanol, and stir at room temperature for 24 h. Then rotary evaporate it at 60 °C and vacuum dry it at 80 °C to obtain [P 4442 [Gly]@ZIF-8 epoxy resin curing agent;

[0082] (4) Stir and mix the obtained epoxy resin curing agent with epoxy resin, the mass ratio of the two is 1:9, the stirring speed is 900 r / min, and the stirring time is 30 min.

[0083] Example 8

[0084] This example provides a curing method for a phosphorus-containing epoxy resin curing agent and epoxy resin, including the following steps:

[0085] (1) Weigh 11.9 g of zinc nitrate hexahydrate and 13.14 g of 2-methylimidazole, add them to anhydrous methanol respectively, mix them after ultrasonic homogenization, and after the reaction is completed, centrifuge, wash and dry to obtain ZIF-8 material;

[0086] (2) Exchange the tributylethylphosphonium bromide solution through an alkaline ion exchange resin to obtain an aqueous solution of [P 4442 [OH], and standardize the concentration of the alkali solution; Take 10 mmol of the aqueous solution of [P 4442 [OH] and H3NTA (0.64 g) respectively, after the reaction, rotary evaporate to remove a large amount of water at 60 °C, and place it in an oven at 80 °C for vacuum drying for 24 h to obtain [P 4442 3[NTA];

[0087] (3) Take 300 mg of ZIF-8 material and 90 mg of [P 4442 3[NTA], add them to anhydrous methanol, and stir at room temperature for 24 h. Then rotary evaporate it at 60 °C and vacuum dry it at 80 °C to obtain [P4442 3[NTA]@ZIF-8 epoxy resin curing agent;

[0088] (4) Stir and mix the obtained epoxy resin curing agent with epoxy resin, with the mass ratio of the two being 1:9, the stirring speed being 900 r / min, and the stirring time being 30 min.

[0089] Example 9

[0090] This example provides a curing method for a phosphorus-containing epoxy resin curing agent and epoxy resin, including the following steps:

[0091] (1) Weigh 11.9 g of zinc nitrate hexahydrate and 13.14 g of 2-methylimidazole, add them to anhydrous methanol respectively, mix them uniformly by ultrasonic treatment, and after the reaction is completed, centrifuge, wash, and dry to obtain ZIF-8 material;

[0092] (2) Exchange the tributylethylphosphonium bromide solution through an alkaline ion exchange resin to obtain an aqueous solution of [P 4444 [OH], and calibrate the concentration of the alkaline solution; Take 10 mmol of the aqueous solution of [P 4444 [OH] and H2IDA (0.6 g), react them, evaporate a large amount of water by rotary evaporation at 60 °C, and place them in an oven at 80 °C for vacuum drying for 24 h to obtain [P 4444 2[IDA];

[0093] (3) Take 300 mg of ZIF-8 material and 90 mg of [P 4444 2[IDA], add them to anhydrous methanol, and stir at room temperature for 24 h. Then carry out rotary evaporation at 60 °C and vacuum drying at 80 °C to obtain [P 4444 2[IDA]@ZIF-8 epoxy resin curing agent;

[0094] (4) Stir and mix the obtained epoxy resin curing agent with epoxy resin, with the mass ratio of the two being 1:9, the stirring speed being 900 r / min, and the stirring time being 30 min.

[0095] Example 10

[0096] This example provides a curing method for a phosphorus-containing epoxy resin curing agent and epoxy resin, including the following steps:

[0097] (1) Weigh 11.9 g of zinc nitrate hexahydrate and 13.14 g of 2-methylimidazole, add them to anhydrous methanol respectively, mix them uniformly by ultrasonic treatment, and after the reaction is completed, centrifuge, wash, and dry to obtain ZIF-8 material;

[0098] (2) Exchange the tributylethylphosphonium bromide solution through an alkaline ion exchange resin to obtain an aqueous solution of [P 66614[OH] aqueous solution, and standardize the concentration of the alkali solution; separately take 10 mmol of [P 66614 [OH] aqueous solution and H2IDA (0.66 g) are reacted, and a large amount of water is removed by rotary evaporation at 60 °C, and then placed in an oven at 80 °C for vacuum drying for 24 h to obtain [P 66614 2[IDA];

[0099] (3) Take 300 mg of ZIF-8 material, and add 90 mg of [P 66614 2[IDA] to anhydrous methanol, and stir the mixture at room temperature for 24 h. Then it is rotary evaporated at 60 °C and vacuum dried at 80 °C to obtain [P 66614 2[IDA]@ZIF-8 epoxy resin curing agent;

[0100] (4) Stir and mix the obtained epoxy resin curing agent with epoxy resin, and the mass ratio of the two is 1:9, the stirring speed is 900 r / min, and the stirring time is 30 min.

[0101] Example 11

[0102] This example provides a curing method for a phosphorus-containing epoxy resin curing agent and epoxy resin, including the following steps:

[0103] (1) Weigh 11.9 g of zinc nitrate hexahydrate and 13.14 g of 2-methylimidazole, add them to anhydrous methanol respectively, mix them evenly by ultrasonic wave, and after the reaction, centrifuge, wash and dry to obtain ZIF-8 material;

[0104] (2) Exchange the tributylethylphosphonium bromide solution through an alkaline ion exchange resin to obtain [P 66614 [OH] aqueous solution, and standardize the concentration of the alkali solution; separately take 10 mmol of [P 66614 [OH] aqueous solution and H2IDA (0.66 g) are reacted, and a large amount of water is removed by rotary evaporation at 60 °C, and then placed in an oven at 80 °C for vacuum drying for 24 h to obtain [P 66614 2[IDA];

[0105] (3) Take 300 mg of ZIF-8 material, and add 90 mg of [P 66614 2[IDA] to anhydrous methanol, and stir the mixture at room temperature for 24 h. Then it is rotary evaporated at 60 °C and vacuum dried at 80 °C to obtain [P 66614 2[IDA]@ZIF-8 epoxy resin curing agent;

[0106] (4) Stir and mix the obtained epoxy resin curing agent with epoxy resin, and the mass ratio of the two is 1:9, the stirring speed is 900 r / min, and the stirring time is 30 min.

[0107] Comparative Example 1

[0108] This comparative example provides a curing method of ZIF-8 epoxy resin curing agent and epoxy resin, including the following steps:

[0109] (1) Weigh 11.9 g of zinc nitrate hexahydrate and 13.14 g of 2-methylimidazole, add them into anhydrous methanol respectively. After ultrasonic homogenization and mixing, centrifuge, wash and dry after the reaction to obtain ZIF-8 material;

[0110] (2) Take the ZIF-8 material and epoxy resin and stir and mix them. The mass ratio of the two is 1:9, the stirring speed is 900 r / min, and the stirring time is 30 min.

[0111] Comparative Example 2

[0112] This comparative example provides a curing method of [P 4442 2[IDA] epoxy resin curing agent and epoxy resin, including the following steps:

[0113] (1) Exchange the tributyl ethylphosphonium bromide solution through an alkaline ion exchange resin to obtain an aqueous solution of [P 4442 [OH], and calibrate the concentration of the alkaline solution; Take 10 mmol of the aqueous solution of [P 4442 [OH] and H2IDA (0.6 g) respectively. After reaction, rotate and evaporate a large amount of water at 60 °C, and place it in an 80 °C oven for vacuum drying for 24 h to obtain [P 4442 2[IDA];

[0114] (2) Stir and mix the obtained [P 4442 2[IDA] with epoxy resin. The mass ratio of the two is 1:9, the stirring speed is 900 r / min, and the stirring time is 30 min.

[0115] Figure 1 It is the DSC curve obtained after mixing and curing the curing agents prepared in Example 2 and Examples 4-6 with epoxy resin, and the heating rate is 10 °C / min. From Figure 1 it can be seen that the curing temperatures of the four curves are different. The reason is that the mass ratio of the curing agent and epoxy resin is different, and it also reflects that the curing effect is the best when the curing agent of the present invention accounts for 10% of the total mass of the curing agent and epoxy resin.

[0116] Figure 2 The DSC curves obtained after mixing and curing the curing agents prepared in Example 6 and Comparative Examples 1-2 with epoxy resin, and the heating rate is 10 °C / min. There are obvious differences in the curing temperatures of the three curves. Among them, the curing temperature of Comparative Example 1 is too high, and the curing temperature of Comparative Example 2 is relatively low.

[0117] Figure 3 The three DSC curves obtained after curing the curing agent prepared in Example 6 with epoxy resin, with the heating rates of the three curves being 10 °C / min, 15 °C / min, and 20 °C / min respectively. As the heating rate increases, the exothermic peak temperature of each DSC curve increases accordingly.

[0118] Figure 4 It is the XRD pattern of the curing agent prepared in Comparative Example 1 and the curing agent prepared in Example 2. The peak positions of the curing agent prepared in Example 2 are consistent with those of Comparative Example 1, indicating that the crystallinity of ZIF-8 is well maintained. Among them, after the curing agent prepared in Example 2 is doped with [P 4442 2[IDA], the peak intensity is slightly lower than that of Comparative Example 1, which may be because most of the pores of ZIF-8 are occupied by [P 4442 2[IDA].

[0119] Figure 5 It is the BET pattern of the curing agent prepared in Comparative Example 1 and the curing agent prepared in Example 2. The adsorption amount of the curing agent prepared in Example 2 has decreased significantly compared with that of the curing agent prepared in Comparative Example 1, indicating that [P 4442 2[IDA] has been successfully encapsulated into the pores of ZIF-8.

[0120] Table 1 compares the initial temperature (T i ), peak temperature (T p ), and termination temperature (T f ) in the DSC test of the mixtures prepared from the curing agents obtained in Examples 1-3 and epoxy resin, with a heating rate of 10 °C / min.

[0121] Table 1

[0122] Curing agent <![CDATA[T i / ℃]]> <![CDATA[T p / ℃]]> <![CDATA[T f / ℃]]> Example 1 99.68 131.81 147.01 Example 2 97.32 120.20 138.13 Example 3 91.12 118.64 136.62

[0123] As can be seen from Table 1, under the same external conditions such as temperature, humidity, and pressure, the larger the proportion of ionic liquid in the synthesized curing agent, the lower the reaction initial temperature T i . The curing temperatures of Examples 1 to 3 are different because the curing agents in the epoxy resin mixtures are different, that is, the ratios of ZIF-8 to [P 4442 2[IDA] are different, which also reflects that the phosphorus-containing curing agent of the present invention can flexibly adjust the curing temperature of epoxy resin.

[0124] Table 2

[0125] Curing agent <![CDATA[T i / ℃]]> <![CDATA[T p / ℃]]> <![CDATA[T f / ℃]]> Example 6 98.64 134.43 170.43 Comparative Example 1 271.52 302.14 321.78 Comparative Example 2 90.64 117.96 125.43

[0126] As can be seen from Table 2, under the same external conditions such as temperature, humidity, and pressure, [P 4442The reaction initiation temperature T of the curing agent i is relatively low, indicating high curing reaction activity at low temperatures, resulting in poor storage stability; while the reaction initiation temperature T of the porous material ZIF-8 curing agent i is too high and it is difficult to apply in actual production. However, due to the slow-release effect of the material of the curing agent of the present invention, its reaction initiation temperature T i has been increased to a certain extent compared with the 4442 curing agent, and its curing temperature range is greatly broadened, indicating its wide application range.

[0127] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a bifunctional epoxy resin latent curing agent, characterized in that, It includes the following steps: S1. Preparation of ZIF-8 material; S2. Preparation of phosphorus-containing ionic liquid P-ILs: Dissolve quaternary phosphonium salt in water, and then perform ion exchange with basic ion exchange resin to obtain phosphonium hydroxide solution; Take the phosphonium hydroxide solution and organic acid for equimolar reaction and then dry to obtain phosphorus-containing ionic liquid P-ILs; The quaternary phosphonium salt is one of tributylethylphosphonium bromide and tetrabutylphosphonium bromide, and the organic acid is one of glycine, iminodiacetic acid, and nitrilotriacetic acid; S3. Add the obtained ZIF-8 material and P-ILs into a solvent, and the mass ratio of P-ILs to ZIF-8 material is 0.05-0.5; Mix and stir at room temperature, and after drying, obtain P-ILs@ZIF-8 epoxy resin curing agent in powder state at normal temperature.

2. The preparation method of a bifunctional epoxy resin latent curing agent according to claim 1, characterized in that, The preparation method of ZIF-8 material in step S1 includes: S11. Add organic ligand dimethylimidazole into a solvent and dissolve it by ultrasonic to obtain organic ligand solution; Add metal salt zinc nitrate hexahydrate into a solvent to obtain metal salt solution; S12. Add the metal salt solution in step S1 into the organic ligand solution, stir and then stand for a period of time, filter, dry, and vacuum dry to obtain ZIF-8 material.

3. The preparation method of a bifunctional epoxy resin latent curing agent according to claim 2, characterized in that, In step S11: The molar concentration of the organic ligand solution is 0.5-2 mol / L; The molar concentration of Zn(NO3)2·6H2O in the metal salt solution is 0.1-0.3 mol / L; The solvent is one or more of water, N,N-dimethylformamide, methanol, toluene, dichloromethane, tetrahydrofuran, and ethyl acetate.

4. The preparation method of a bifunctional epoxy resin latent curing agent according to claim 1, characterized in that, In step S12: The temperature of the stirring is 10-45 °C and the time is 0.5-2 h; The standing time is 15-30 h.

5. The preparation method of a bifunctional epoxy resin latent curing agent according to claim 1, characterized in that, In step S2: The drying is to first remove a large amount of water by rotary evaporation and then vacuum dry at 70-100 °C.

6. The preparation method of a bifunctional epoxy resin latent curing agent according to claim 1, characterized in that, In step S3: The solvent is one or more of methanol, toluene, dichloromethane, and tetrahydrofuran; The drying is vacuum drying at 70-100 °C after rotary evaporation.

7. A bifunctional epoxy resin latent curing agent, characterized in that, Prepared by the preparation method according to any one of claims 1-6.

8. An epoxy resin curing system, characterized in that, Mix the bifunctional epoxy resin latent curing agent according to claim 7 with epoxy resin evenly, and the mass ratio of the two is 0.05-0.

5.

9. The epoxy resin curing system according to claim 8, characterized in that, The stirring speed of the mixing is 500-1200 r / min and the time is 20-40 min.

Images