An imidazole derivative curing agent and a preparation method of a space rigidification material with low volatility and high stability

Abstract

The application relates to an imidazole derivative curing agent and a preparation method of a space rigidification material with low volatility and high stability, and belongs to the field of space unfolding material preparation. The method is as follows: after mixing a photocuring agent, an imidazole derivative curing agent, an acrylic ester resin and an epoxy resin, vacuumizing and removing bubbles, pouring into a standard dumbbell-shaped strip mold, and irradiating under ultraviolet light for 10-20 min, a flexible material with a first heavy network is prepared, and then pre-curing at 130-150 DEG C for 3-4 h and post-curing at 170-180 DEG C for 3-5 h, so that a rigid material is obtained. Through molecular synthesis scheme design, the imidazole derivative with high molecular weight is prepared, the reaction activity is reduced, the storage period is prolonged, and the problems of small molecule migration and vacuum degassing are solved. Due to the molecular scheme design, more imidazole groups are introduced on the molecular chain, the imidazole groups can be coordinated with metal ions to form ionic bonds, the reaction activity can be further reduced, the storage period can be prolonged, the molecular weight can be correspondingly increased, and the migration condition can be inhibited.

Description

Technical Field

[0001] This invention belongs to the field of space deployment material preparation, specifically relating to an imidazole derivative curing agent and a method for preparing a space rigidification material with low volatility and high stability. Background Technology

[0002] As spacecraft become larger and more complex, their structural mass increases significantly. However, the space constraints and load-bearing capacity of launch vehicles limit the design and launch of traditional spacecraft structures. To address this issue, dual-network structure construction technology has emerged. This technology first forms a primary network on the ground through the reaction of an initiator with monomers, giving the material initial flexibility. After the spacecraft enters orbit, a secondary network is triggered, causing the flexible material to gradually become rigid, ultimately achieving solidification and finalization in orbit.

[0003] Currently, the secondary curing process of this technology mainly relies on additive initiators. These initiators exist in a free state within the flexible matrix formed by the primary network. However, in the low-pressure environment of space, free initiators are prone to volatilization and migration (vacuum evaporation effect), causing them to escape from the material. More critically, the loss of initiators can severely interfere with or even interrupt the curing reaction, resulting in the final material failing to meet the preset performance indicators. This not only weakens the structural strength and durability of the material but may also jeopardize other critical functions, posing a significant risk to aerospace applications. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of small molecule migration and vacuum venting of the initiator before curing the second network in a dual-network system, as well as the short storage period after the first network is cured and before the second network is cured. The invention provides an imidazole derivative curing agent for the second network and a method for preparing a space-hardening material with low volatility and high stability.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing an imidazole derivative curing agent, the method comprising:

[0007] Step 1: Vacuum dry vinylimidazole before use, then add 3-mercapto-1,2-propanediol, vinylimidazole, and photoinitiator. -Hydroxyisobutyrobenzene (HMPP) and anhydrous dimethyl carbonate were placed in a round-bottom flask equipped with a rubber septum and an N2 gas injector. Before initializing the reaction, N2 was bubbled in the solution while stirring to remove oxygen. The reactor was irradiated with 365 nm ultraviolet light and emitted blue light until HMPP was completely decomposed. The reaction was continued for 30 min to ensure complete conversion. The reaction was then allowed to stand for 30 min. Dimethyl carbonate was removed by spin evaporation to obtain the reaction product -MPVI.

[0008] Step 2: Dissolve isophorone diisocyanate in dioxane to obtain solution A; dissolve polyethylene glycol-400 in dioxane to obtain solution B; dissolve the reaction product MPVI and isophorone diisocyanate in tetrahydrofuran to obtain solution C; under reflux condensation, nitrogen atmosphere, and 65-75°C, add solution B dropwise to solution A within 1 h, and react for 4 h; then under reflux condensation, nitrogen atmosphere, and 55-65°C, add solution C dropwise to the aforementioned mixture within 1 h, and react for 4 h to obtain a solution containing an imidazole derivative curing agent.

[0009] Further, in step one, the 3-mercapto-1,2-propanediol, vinylimidazole, and photoinitiator... The mass ratio of β-hydroxyisobutyrylbenzene is 8~12:8~10:0.05~0.10.

[0010] Further, in step two, in solutions A and B, the molar ratio of isophorone diisocyanate to polyethylene glycol-400 is 2:1; in solution C, the molar ratio of MPVI to isophorone diisocyanate is 2:1; and the molar ratio of polyethylene glycol-400 to MPVI is 1:2.

[0011] Furthermore, the method also includes a post-treatment scheme: the solution is added dropwise to a mixed solution of petroleum ether and ethyl acetate (V1:V2=3:1) for precipitation treatment, followed by vacuum filtration, and the yellow filter cake in the funnel is placed in a vacuum oven at 60°C and dried for 24 hours to obtain an imidazole derivative curing agent.

[0012] Furthermore, the method also includes step three: dissolving a certain amount of the reaction product PEG-MPVI from step two in methanol, dissolving an appropriate amount of zinc chloride in methanol, and then mixing the two together and stirring overnight; after the reaction is completed, performing a vacuum filtration operation, taking the filter cake from the funnel, and drying it in a vacuum oven at 60°C for 24 hours to obtain the metal coordination product PEG-MPVI-Zn.

[0013] A method for preparing a low-volatility, high-stability spatial rigid material containing an imidazole derivative curing agent prepared by the above-mentioned preparation method, the method comprising: a dual-network system: the first network uses acrylate resin, with a mass ratio of photocuring agent to acrylate resin of 2:100; the second network uses epoxy resin, with a mass ratio of imidazole derivative curing agent to epoxy resin of 5-20:100; the total amount of resin is 100%, and the mass percentage of epoxy resin is 50%~90%; after mixing the photocuring agent, imidazole derivative curing agent, acrylate resin and epoxy resin, vacuuming is performed to remove air bubbles, and the mixture is poured into a standard dumbbell-shaped template mold and irradiated with ultraviolet light for 10-20 minutes to prepare a flexible material of the first network; subsequently, it is pre-cured at 130-150℃ for 3-4 hours and then cured at 170-180℃ for 3-5 hours to obtain a rigid material.

[0014] Further, the photocuring agent is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0015] The advantages of this invention over the prior art are as follows:

[0016] 1. By designing molecular synthesis schemes, high molecular weight imidazole derivatives were prepared, which reduced reactivity, improved shelf life, and solved the problems of small molecule migration and vacuum venting.

[0017] 2. Due to the molecular design, more imidazole groups are introduced into the molecular chain, which can coordinate with metal ions to form ionic bonds, which can further reduce reactivity, increase shelf life, increase molecular weight, and inhibit migration; and can further improve the mechanical properties of the system. Attached Figure Description

[0018] Figure 1 A schematic diagram of a reaction equation for the synthetic route of imidazole derivative curing agents;

[0019] Figure 2 A schematic diagram of the two-equation reaction for the synthetic route of imidazole derivative curing agents;

[0020] Figure 3 The 1H NMR spectrum of the synthesized product MPVI and the reactants is shown in the figure.

[0021] Figure 4 The Fourier transform infrared (FTIR) data of the synthesized product MPVI and the reactants are shown in the figure.

[0022] Figure 5 The results of the 1H NMR spectrum of the synthesized product PEG-MPVI and the reactants are shown in the figure.

[0023] Figure 6 The Fourier transform infrared (FTIR) data of the synthesized product PEG-MPVI and the reactants are shown in the figure.

[0024] Figure 7 The molecular weight elution curve of the synthesized product PEG-MPVI is shown.

[0025] Figure 8 Fourier transform infrared (FTIR) data of the synthesized product PEG-MPVI and the product after metal coordination.

[0026] Figure 9 DSC diagrams of PEG-MPVI and PEG-MPVI-Zn epoxy resin systems;

[0027] Figure 10 This is a comparison chart of the elongation at break of the flexible material and the rigid material in Example 2;

[0028] Figure 11 This is a comparison chart of the moduli of the flexible and rigid materials in Example 2;

[0029] Figure 12 This is a comparison diagram of the strength of the flexible material and the rigid material in Example 2;

[0030] Figure 13 This is a comparison diagram of the glass transition temperatures of the flexible and rigid materials in Example 2. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0032] Example 1:

[0033] Step 1: As Figure 1 As shown in the synthetic route, vinylimidazole was first vacuum distilled before use. 10 g of 3-mercapto-1,2-propanediol, 8.7 g of vinylimidazole, 0.076 g of HMPP (photoinitiator), and 20 mL of anhydrous dimethyl carbonate were placed in a 150 mL round flask equipped with a rubber septum and an N2 gas injector. Before initializing the reaction, N2 was bubbled into the solution while stirring for 10 min to remove oxygen. The reactor was then irradiated with 365 nm ultraviolet light, emitting blue light, until HMPP was completely decomposed. The reaction was continued for 30 min to ensure complete conversion, followed by standing for 30 min. Dimethyl carbonate was then removed by spin evaporation to obtain the reaction product, MPVI.

[0034] The reaction product MPVI obtained in step one was characterized by: proton nuclear magnetic resonance (NMR) spectroscopy, such as... Figure 3 As shown, the peak at chemical shift 7.25 ppm corresponds to the solvent CDCl3. The figure shows that the absorption peaks of the carbon-carbon double bond (C=C) in the reactant vinylimidazole (VI) and the thiol group (-SH) in 3-mercapto-1,2-propanediol (MP) are not present in the spectrum of the synthesized product MPVI; Fourier transform infrared spectroscopy (FTIR) analysis reveals... Figure 4 As shown, 2550 cm -1 1650 cm -1 These are the absorption peaks of the thiol group (-SH) in the reactant 3-mercapto-1,2-propanediol (MP) and the carbon-carbon double bond (C=C) in the reactant vinylimidazole (VI), respectively. Both disappear in the spectrum of the synthesized product MPVI. Additionally, at 1500 cm⁻¹... -1 The absorption peaks are near the imidazole ring. Therefore, by comparing the NMR and IR spectra of the synthesized product and the reaction substrate, it can be seen that the synthesized product MPVI has been successfully prepared.

[0035] Step Two: As Figure 2 As shown in the synthetic route, 6 mmol of isophorone diisocyanate was dissolved in 60-80 mL of dioxane to obtain solution A; 3 mmol of polyethylene glycol-400 was dissolved in 10-20 mL of dioxane to obtain solution B; 6 mmol of MPVI, the product of step one, and 3 mmol of isophorone diisocyanate were dissolved in 25 mL of tetrahydrofuran to obtain solution C; under reflux condensation, nitrogen atmosphere, and 70 °C, solution B was added dropwise to solution A over 1 h, and the reaction was carried out for 4 h. Subsequently, under reflux condensation, nitrogen atmosphere, and 60 °C, solution C was added dropwise to the aforementioned mixture over 1 h, and the reaction was carried out for 4 h to obtain a solution containing PEG-MPVI. Post-treatment: The solution was added dropwise to a mixed solution of petroleum ether and ethyl acetate (V1:V2=3:1) for precipitation treatment, followed by vacuum filtration. The yellow filter cake in the funnel was collected and dried in a vacuum oven at 60 °C for 24 h to obtain the product PEG-MPVI.

[0036] The product PEG-MPVI obtained in step two was characterized by: proton nuclear magnetic resonance (NMR) spectroscopy, such as... Figure 5 As shown, the peak at chemical shift 7.25 ppm is that of the solvent CDCl3. The figure shows that the yellow shading indicates the hydroxyl absorption peak of the reactant polyethylene glycol (PEG), and the blue shading indicates the hydroxyl absorption peak of the reactant MPVI; neither of these peaks appears in the spectrum of the synthesized product PEG-MPVI. Fourier transform infrared spectroscopy (FTIR) analysis shows... Figure 6 As shown, 2243 cm -1The absorption peak is the absorption peak of the isocyanate group in the reactant isophorone diisocyanate (IPDI), at 3300 cm⁻¹ in PEG-MPVI. -1 1720 cm -1 The absorption peak is the absorption peak of the urethane bond formed by isocyanate and hydroxyl groups, and it is at 1500 cm⁻¹. -1 The absorption peak near the imidazole ring indicates that the synthesized product PEG-MPVI has been successfully prepared by comparing the NMR and IR spectra of the synthesized product and the reaction substrate. Gel chromatography analysis further confirms the presence of the absorption peak near the imidazole ring. Figure 7 As shown, the molecular weight of the synthesized product is Mn=53916g / mol, which meets the requirements for high molecular weight and can solve the problems of small molecule migration and vacuum gas extraction.

[0037] Step 3: Dissolve a certain amount of the reaction product PEG-MPVI from Step 2 in 20 mL of methanol, and dissolve an equivalent amount of zinc chloride in 20 mL of methanol. Then mix the two together and stir overnight. After the reaction is complete, perform a vacuum filtration operation, take the filter cake from the funnel, and dry it in a vacuum oven at 60℃ for 24 h to obtain the metal coordination product PEG-MPVI-Zn.

[0038] The metal coordination product PEG-MPVI-Zn synthesized in step three was characterized by Fourier transform infrared spectroscopy (FTIR), as shown in the following tests. Figure 8 As shown, after PEG-MPVI coordinates with zinc chloride, some characteristic peaks in the infrared spectrum change. The C=N bond on the imidazole ring undergoes a red shift after coordination, and a new absorption peak (N→Zn) appears. This is confirmed by non-isothermal DSC testing. Figure 9 As shown, when the product PEG-MPVI and zinc chloride coordinate to form the metal complex PEG-MPVI-Zn, the peak curing temperature increases by 51°C under the same equivalent in the epoxy resin system. This indicates that after coordination, the activity of the curing agent is further inhibited, and the shelf life is thus extended.

[0039] Example 2:

[0040] Step 1: First, the vinylimidazole is vacuum distilled before use. 10 g of 3-mercapto-1,2-propanediol, 8.7 g of vinylimidazole, 0.076 g of HMPP (photoinitiator), and 20 mL of anhydrous dimethyl carbonate are placed in a 150 mL round bottle equipped with a rubber septum and an N2 gas syringe. Before initializing the reaction, N2 is bubbled into the solution while stirring for 10 min to remove oxygen. Then, the reactor is irradiated with 365 nm ultraviolet light, emitting blue light, until the HMPP is completely decomposed. The reaction continues for 30 min to ensure complete conversion, followed by standing for 30 min. Dimethyl carbonate is then removed by spin evaporation to obtain the reaction product, MPVI.

[0041] Step Two: As Figure 2 As shown in the synthetic route, 6 mmol of isophorone diisocyanate was dissolved in 60-80 mL of dioxane to obtain solution A; 3 mmol of polyethylene glycol-400 was dissolved in 10-20 mL of dioxane to obtain solution B; 6 mmol of MPVI, the product of step one, and 3 mmol of isophorone diisocyanate were dissolved in 25 mL of tetrahydrofuran to obtain solution C; under reflux condensation, nitrogen atmosphere, and 70 °C, solution B was added dropwise to solution A over 1 h, and the reaction was carried out for 4 h. Subsequently, under reflux condensation, nitrogen atmosphere, and 60 °C, solution C was added dropwise to the aforementioned mixture over 1 h, and the reaction was carried out for 4 h to obtain a solution containing PEG-MPVI. Post-treatment: The solution was added dropwise to a mixed solution of petroleum ether and ethyl acetate (V1:V2=3:1) for precipitation treatment, followed by vacuum filtration. The yellow filter cake in the funnel was collected and dried in a vacuum oven at 60 °C for 24 h to obtain the product PEG-MPVI.

[0042] Sample preparation: Weigh 1.2 g of PEG-MPVI product, then add 6 g of epoxy resin, stir thoroughly and sonicate for 30 min, then place in an oven and heat at 60℃ for 5 min; then weigh 9 g of difunctional acrylate resin and 0.5 g of pentafunctional acrylate resin, add 0.22 g of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone, sonicate for 10 min to dissolve the photoinitiator in the acrylate resin, mix the prepared acrylate resin and epoxy resin in a 3:7 ratio, vacuum degas for 30 min, pour into a silicone mold, and expose to 365 nm ultraviolet light at an intensity of 50 mW / cm². 2 After irradiation for 10 minutes, a flexible material with a first network was obtained. The material was then cured at 130°C for 3 hours and at 170°C for 3 hours to obtain a rigid material with a second network.

[0043] Characterization testing involves performing mechanical property tests on the prepared specimens, such as... Figure 10 , 11 As shown in Figures 12 and 13, the tensile modulus, strength, and elongation at break of the flexible material in the first network are 1.59 MPa, 0.65 MPa, and 45%, respectively; while the tensile modulus, strength, and elongation at break of the rigid material in the second network are 1855 MPa, 44 MPa, and 5.8%, respectively. Furthermore, the glass transition temperature of the flexible material in the first network increases from -1.08℃ to 84℃ of the rigid material in the second network. Therefore, it can be concluded that the material successfully completes the transition from the flexible state of the first network to the rigid state of the second network.

Claims

1. A method for preparing an imidazole curing agent, characterized in that: The method is as follows: Step 1: Vacuum dry vinylimidazole before use, then add 3-mercapto-1,2-propanediol, vinylimidazole, and photoinitiator. -Hydroxyisobutyrophenyl (HMPP) and anhydrous dimethyl carbonate were placed in a round-bottom flask equipped with a rubber septum and an N2 gas injector. Before initializing the reaction, N2 was bubbled in the solution while stirring to remove oxygen. The reactor was subjected to 365 nm ultraviolet irradiation and emitted blue light until HMPP was completely decomposed. The reaction was continued for 30 min to ensure complete conversion. The reaction was then allowed to stand for 30 min. Dimethyl carbonate was removed by spin evaporation to obtain the reaction product -MPVI. Step 2: Dissolve isophorone diisocyanate in dioxane to obtain solution A; dissolve polyethylene glycol-400 in dioxane to obtain solution B; dissolve the reaction product MPVI and isophorone diisocyanate in tetrahydrofuran to obtain solution C; under reflux condensation, nitrogen atmosphere, and 65-75℃, add solution B dropwise to solution A within 1 h and react for 4 h; then under reflux condensation, nitrogen atmosphere, and 55-65℃, add solution C dropwise to the aforementioned mixture within 1 h and react for 4 h to obtain a solution containing imidazole curing agent; add the solution dropwise to a mixed solution of petroleum ether and ethyl acetate (volume ratio of petroleum ether to ethyl acetate 3:1) for precipitation treatment, followed by vacuum filtration, and take the yellow filter cake from the funnel, which is then placed in a vacuum oven at 60℃ and dried for 24 h to obtain the imidazole curing agent PEG-MPVI.

2. The method for preparing an imidazole curing agent according to claim 1, characterized in that: In step one, the 3-mercapto-1,2-propanediol, vinylimidazole, and photoinitiator... The mass ratio of β-hydroxyisobutyrylbenzene is 8~12:8~10:0.05~0.

10.

3. The method for preparing an imidazole curing agent according to claim 1, characterized in that: In step two, in solutions A and B, the molar ratio of isophorone diisocyanate to polyethylene glycol-400 is 2:1; in solution C, the molar ratio of MPVI to isophorone diisocyanate is 2:1; and the molar ratio of polyethylene glycol-400 to MPVI is 1:

2.

4. A method for preparing an imidazole curing agent according to any one of claims 1 to 3, characterized in that: The method further includes step three: dissolving a certain amount of the reaction product PEG-MPVI from step two in methanol, dissolving an appropriate amount of zinc chloride in methanol, and then mixing the two together and stirring overnight; after the reaction is completed, performing a vacuum filtration operation, taking the filter cake from the funnel, and drying it in a vacuum oven at 60°C for 24 hours to obtain the metal coordination product PEG-MPVI-Zn.

5. A method for preparing a low-volatility, high-stability space-hardening material containing an imidazole curing agent prepared by any one of claims 1 to 4, characterized in that: The method is as follows: a dual-network system: the first network uses acrylate resin, with a mass ratio of UV curing agent to acrylate resin of 2:100; the second network uses epoxy resin, with a mass ratio of imidazole curing agent to epoxy resin of 5~20:100; the total amount of resin is 100%, and the mass percentage of epoxy resin is 50%~90%. After mixing the UV curing agent, imidazole curing agent, acrylate resin, and epoxy resin, vacuum is applied to remove air bubbles. The mixture is then poured into a mold and irradiated with ultraviolet light for 10~20 minutes to prepare the flexible material of the first network. Subsequently, it is pre-cured at 130~150℃ for 3~4 hours and then cured at 170~180℃ for 3~5 hours to obtain a rigid material.

6. The method for preparing a low-volatility, high-stability space stiffener material according to claim 5, characterized in that: The photocuring agent is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

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