Preparation method of repairable solvent-resistant dynamic crosslinking epoxy resin material

Abstract

The invention discloses a preparation method of a repairable solvent-resistant dynamic cross-linked epoxy resin material, which successfully synthesizes a novel oily hydrazide molecule through molecular design, can realize solvent-free preparation of an amido urea-based dynamic polymer material, and has the advantages of easily available raw materials and simple preparation process. The dynamic cross-linked network is introduced into the epoxy resin, so that the epoxy resin can be endowed with dynamic characteristics, but the solvent resistance of the epoxy resin is reduced due to introduction of dynamic bonds. By adjusting the proportion of the curing agent, the blocked isocyanate and the epoxy monomer, the epoxy resin which not only has a high epoxy crosslinking structure, but also contains an amido urea-based dynamic crosslinking structure is prepared, and the problem of contradiction between good dynamic property and solvent resistance of the epoxy resin is solved. Remodeling and repairing of the resin can be achieved after the resin is crushed and then subjected to hot pressing, and in addition, the resin shows good tolerance to strong acid, strong alkali and strong polar solvents.

Description

Technical Field

[0001] The invention belongs to the technical field of epoxy resin materials, and particularly relates to a method for preparing a repairable, solvent-resistant, dynamically cross-linked epoxy resin material. Background Art

[0002] Dynamic bonds are a type of chemical bond that can undergo reversible breaking and reforming under specific circumstances, including dynamic covalent bonds and non-covalent bonds. Dynamic cross-linked polymers are a new type of polymer material that has emerged in recent years. They are called CANs in academia (some scholars also call them DCPNs), which combine the advantages of traditional thermosetting materials and thermoplastic materials. The polymer network of this type of material contains dynamic chemical bonds. At high temperatures, the dynamic bonds are activated and become thermoplastic. At low temperatures, the dynamic bonds are reformed and thus exhibit the characteristics of thermosetting resins. They have the advantages of self-repair, reprocessing, and configuration reshaping, which can extend the service life of the material and reduce environmental pollution. Among them, the amidourea bond can be regarded as a combination of urea and amide connected by N-N bonds, which is formed by the addition reaction of isocyanate and hydrazide. In recent years, there have been many studies on amidourea. For example, patents CN116003988A and CN109265636A both studied dynamic polymer materials based on amidourea. However, in the preparation process of these materials, they use a large amount of organic solvents, such as DMF and DMSO. This not only prolongs the material preparation cycle, but also poses a greater risk of environmental pollution.

[0003] Epoxy resins are a class of polymers with permanently cross-linked structures. They possess excellent mechanical properties, solvent resistance, and dimensional stability, making them widely used in the chemical, construction, aviation, and aerospace industries. However, their permanent cross-linking makes them difficult to repair and process. Once the material has failed, it cannot be reused, resulting in wasted resources and environmental pollution. Introducing dynamic cross-linking into epoxy resins could address these issues, but the presence of dynamic cross-linking also reduces the epoxy resin's solvent resistance.

[0004] In view of this, a solvent-free method for preparing a dynamically cross-linked epoxy resin material with good repair performance and solvent resistance is urgently needed in the industry. Summary of the Invention

[0005] The present invention synthesizes a novel oily hydrazide, using readily available and inexpensive raw materials and a simple production process that eliminates the need for complex separation and purification. The prepared oily hydrazide molecules, blocked isocyanate molecules, and epoxy monomers are mixed and cured in a specific proportion, achieving the solvent-free preparation of a repairable, solvent-resistant, dynamically cross-linked epoxy resin. The present invention is achieved through the following technical means:

[0006] The present invention first discloses a method for preparing a repairable solvent-resistant dynamically cross-linked epoxy resin material, comprising the following steps:

[0007] (1) 1 mol of a certain aldehyde acid ester is dissolved in 50-200 ml of anhydrous methanol, and then 0.5 mol of a diamine is added at room temperature and stirred for 12 hours. The reactant is then dried to remove water. After the water is removed, 1.5 mol of sodium borohydride is added in batches at 0°C, and the mixture is reacted at 70°C for 12 hours. The reactant is then quenched by adding water, and the pH value is adjusted to neutral. The mixture is then extracted with ethyl acetate, and the extract is then separated and rotary evaporated to obtain an oily diester product;

[0008] (2) Dissolve the oily diester in 50 ml of methanol, add hydrazine hydrate, react at room temperature for 12 h, and then obtain the oily dihydrazide by rotary evaporation;

[0009] (3) 1 mol of diisocyanate and 2 mol of blocking agent were reacted in 100 ml of anhydrous tetrahydrofuran at room temperature for 12 h, and then the solvent was removed at 60° C. to obtain blocked isocyanate;

[0010] (4) The oily dihydrazide, blocked isocyanate and epoxy resin monomer are mixed uniformly in proportion, and then the mixture is degassed under vacuum, injection molded and cured to obtain a repairable and solvent-resistant epoxy resin.

[0011] Furthermore, the aldehyde ester in step (1) is selected from one or more of methyl 2-formaldehyde benzoate, methyl 3-formaldehyde benzoate, methyl p-formylbenzoate, and methyl 4-oxobutanoate.

[0012] Furthermore, the diamine in step (1) is selected from one or more of 1,3-phenylenediamine, isophorone diamine, polyetheramine 230, polyetheramine 400, polyetheramine 600, polyetheramine 900, polyetheramine 2000, 1,2-propylenediamine, and ethylenediamine.

[0013] Furthermore, the amount of hydrazine hydrate used in step (2) is 5 times the molar equivalent of the diester.

[0014] Furthermore, the diisocyanate in step (3) is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and tetramethyl-m-xylylene diisocyanate.

[0015] Furthermore, the blocking agent in step (3) is selected from one or more of methyl ethyl ketone oxime, phenol, caprolactam, imidazole, and pyrazole.

[0016] Furthermore, the epoxy resin monomer in step (4) is selected from one or more of bisphenol A diglycidyl ether, 1,4-bis(oxirane-2-ylmethoxy)benzene, and resorcinol diglycidyl ether.

[0017] Furthermore, in step (4), the oily dihydrazide, blocked isocyanate and epoxy resin monomer are mixed in a molar ratio of 2:1:4.

[0018] The present invention also discloses a repairable solvent-resistant dynamic cross-linked epoxy resin material prepared according to any of the above preparation methods.

[0019] The beneficial effects of the present invention are:

[0020] 1. Currently, dynamic polymers based on amidourea use a large amount of solvents, have a long preparation cycle, and pose the risk of environmental pollution. The present invention successfully synthesized a new type of oily hydrazide molecule through molecular design, which can realize the solvent-free preparation of dynamic polymer materials based on amidourea. The raw materials are easily available and the preparation process is simple.

[0021] 2. Introducing a dynamic cross-linking network into epoxy resin can give the epoxy resin dynamic properties, but the introduction of dynamic bonds reduces the solvent resistance of the epoxy resin. The present invention adjusts the ratio of curing agent, blocked isocyanate and epoxy monomer to prepare a dynamic cross-linked epoxy resin that has a high epoxy cross-linking structure and contains dynamic bond amidourea, thus solving the contradiction between the good dynamic properties and solvent resistance of epoxy resin. The resin can be reshaped and repaired by first crushing and then hot pressing, and the repair efficiency can reach 83.49%. In addition, the resin shows good tolerance to strong acids, strong bases and highly polar solvents. After soaking the resin in water for 7 days, it still retains 80.76% of its original strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the stress-strain diagram of the original resin;

[0023] Figure 2 is the stress-strain diagram after resin repair;

[0024] Figure 3 This is the stress-strain diagram of the resin after being immersed in water for 168 hours at room temperature;

[0025] Figure 4 It is the swelling ratio of the resin after being immersed in different solvents for 24 hours at room temperature;

[0026] Figure 5 Schematic diagram of resin restoration. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below with reference to specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0028] The experimental methods and detection methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0029] Example 1

[0030] (1) 1 mol of methyl 2-formylbenzoate was dissolved in 200 ml of anhydrous methanol, and then 0.5 mol of 1,3-phenylenediamine was added at room temperature and stirred for 12 h. The reactant was then dried to remove water. After the water removal was completed, 1.5 mol of sodium borohydride was added in batches at 0°C, and the mixture was reacted at 70°C for 12 h. The reactant was then quenched by adding water, and the pH value was adjusted to neutral. The product was extracted with ethyl acetate, and the ethyl acetate was then removed by rotary evaporation to obtain an oily diester product.

[0031] (2) The diester product obtained in step 1 was dissolved in 50 ml of methanol, and hydrazine hydrate (5 times the molar equivalent of the diester) was added and reacted at room temperature for 12 h, followed by rotary evaporation to obtain an oily dihydrazide;

[0032] (3) 1 mol of toluene diisocyanate and 2 mol of methyl ethyl ketone oxime were reacted in 100 ml of anhydrous tetrahydrofuran for 12 h, and then the solvent was removed at 60° C. to obtain a viscous blocked isocyanate;

[0033] (4) The oily dihydrazide in step 2, the blocked isocyanate in step 3, and bisphenol A diglycidyl ether are mixed uniformly at 120° C., wherein the molar ratio of the oily dihydrazide, the blocked isocyanate, and the bisphenol A diglycidyl ether is 2:1:4. The mixture is then degassed, injection-molded, and cured under vacuum to obtain a repairable solvent-resistant dynamic cross-linked epoxy resin.

[0034] Example 2

[0035] (1) 1 mol of methyl paraformylbenzoate was dissolved in 200 ml of anhydrous methanol, and then 0.5 mol of polyetheramine was added at room temperature and stirred for 12 h. The reactant was then dried to remove water. After the water removal was completed, 1.5 mol of sodium borohydride was added in batches at 0°C, and the mixture was reacted at 70°C for 12 h. The reactant was then quenched by adding water, and the pH value was adjusted to neutral. The product was extracted with ethyl acetate, and the product was in the ethyl acetate layer. The ethyl acetate was then removed by rotary evaporation to obtain an oily diester product.

[0036] (2) The diester product obtained in step 1 was dissolved in 50 ml of methanol, and hydrazine hydrate (5 times the molar equivalent of the diester) was added and reacted at room temperature for 12 h, followed by rotary evaporation to obtain an oily dihydrazide;

[0037] (3) 1 mol of isophorone diisocyanate and 2 mol of methyl ethyl ketone oxime were reacted in 100 ml of anhydrous tetrahydrofuran for 12 h, and then the solvent was removed at 60° C. to obtain a viscous blocked isocyanate;

[0038] (4) The oily dihydrazide in step 2, the blocked isocyanate in step 3, and bisphenol A diglycidyl ether are mixed uniformly at 120° C., wherein the molar ratio of the oily dihydrazide, the blocked isocyanate, and the bisphenol A diglycidyl ether is 2:1:4. The mixture is then degassed, injection molded, and cured under vacuum to obtain a repairable solvent-resistant dynamic cross-linked epoxy resin.

[0039] Example 3

[0040] (1) 1 mol of methyl paraformylbenzoate was dissolved in 200 ml of anhydrous methanol, and then 0.5 mol of isophorone diamine was added at room temperature and stirred for 12 h. The reactant was then dried to remove water. After the water removal was completed, 1.5 mol of sodium borohydride was added in batches at 0°C, and the mixture was reacted at 70°C for 12 h. The reactant was then quenched by adding water, and the pH value was adjusted to neutral. The product was extracted with ethyl acetate, and the ethyl acetate was then removed by rotary evaporation to obtain an oily diester product.

[0041] (2) The diester product obtained in step 1 was dissolved in 50 ml of methanol, and hydrazine hydrate (5 times the molar equivalent of the diester) was added and reacted at room temperature for 12 h, followed by rotary evaporation to obtain an oily dihydrazide;

[0042] (3) 1 mol of diphenylmethane diisocyanate and 2 mol of methyl ethyl ketone oxime were reacted in 100 ml of anhydrous tetrahydrofuran for 12 h, and then the solvent was removed at 60° C. to obtain a viscous blocked isocyanate;

[0043] (4) The oily dihydrazide in step 2, the blocked isocyanate in step 3, and bisphenol A diglycidyl ether are mixed uniformly at 120° C., wherein the molar ratio of the oily dihydrazide, the blocked isocyanate, and the bisphenol A diglycidyl ether is 2:1:4. The mixture is then degassed, injection molded, and cured under vacuum to obtain a repairable solvent-resistant dynamic cross-linked epoxy resin.

[0044] Example 4

[0045] (1) 1 mol of methyl 4-oxobutyrate was dissolved in 200 ml of anhydrous methanol, and then 0.5 mol of isophorone diamine was added at room temperature and stirred for 12 h. The reactant was then dried to remove water. After the water removal was completed, 1.5 mol of sodium borohydride was added in batches at 0°C, and the mixture was reacted at 70°C for 12 h. The reactant was then quenched by adding water, and the pH value was adjusted to neutral. The product was extracted with ethyl acetate, and the ethyl acetate was then removed by rotary evaporation to obtain an oily diester product.

[0046] (2) The diester product obtained in step 1 was dissolved in 50 ml of methanol, and hydrazine hydrate (5 times the molar equivalent of the diester) was added and reacted at room temperature for 12 h, followed by rotary evaporation to obtain an oily dihydrazide;

[0047] (3) 1 mol of hexamethylene diisocyanate and 2 mol of methyl ethyl ketone oxime were reacted in 100 ml of anhydrous tetrahydrofuran for 12 h, and then the solvent was removed at 60° C. to obtain a viscous blocked isocyanate;

[0048] (4) The oily dihydrazide in step 2, the blocked isocyanate in step 3, and bisphenol A diglycidyl ether are mixed uniformly at 120° C., wherein the molar ratio of the oily dihydrazide, the blocked isocyanate, and the bisphenol A diglycidyl ether is 2:1:4. The mixture is then degassed, injection-molded, and cured under vacuum to obtain a repairable solvent-resistant dynamic cross-linked epoxy resin.

[0049] Test Example 1

[0050] Tensile Properties Testing of Repairable and Solvent-Resistant Dynamically Cross-Linked Epoxy Resins

[0051] The tensile properties of the materials were tested using an Instron 5567 universal material testing machine. The repairable solvent-resistant dynamic cross-linked epoxy resin prepared in the example was cut into dumbbell-shaped specimens, and the hot press repaired epoxy resin was cut into dumbbell-shaped specimens and the dumbbell-shaped specimens soaked in water at room temperature for 168 hours were tested at 50 mm min. -1 The sample was uniaxially stretched at room temperature (approximately 1 mm (T) x 2 mm (W) x 15 mm (L)) at a stretching rate of 100 nm and a stress-strain curve was recorded. At least 3 samples were tested in parallel in each group.

[0052] The prepared repairable solvent-resistant epoxy resin ( Figure 1 ), mechanical properties of epoxy resin materials repaired by hot pressing after damage ( Figure 2 ) and mechanical properties of epoxy resin immersed in water for 168 hours at room temperature ( Figure 3 The figure shows that the original tensile strength and Young's modulus of the material were 74.27 MPa and 1.71 GPa, respectively. After hot-press repair, the tensile strength and Young's modulus of the material were 62.01 MPa and 2.17 GPa, respectively; the material's strength repair efficiency was 83.49%. After immersion in water for 168 hours, the tensile strength and Young's modulus of the specimen were 59.98 MPa and 1.71 GPa, respectively, representing 80.76% of the original strength and 100% of the original modulus. Figure 4is the swelling rate of the resin in different solvents, where HCl and NaOH represent 1 mol / L hydrochloric acid and sodium hydroxide aqueous solutions, ACE, EtOH, DMF, and DMSO represent pure solvents of acetone, anhydrous ethanol, dimethylformamide, and dimethyl sulfoxide, respectively. The swelling rate is the ratio of the mass of the material after solvent swelling to the mass of the material before solvent swelling; Figure 5 It illustrates the reprocessing and repair process after the resin is crushed.

[0053] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a repairable, solvent-resistant, dynamically cross-linked epoxy resin material, comprising: (1) 1 mol of a certain aldehyde acid ester is dissolved in 50-200 ml of anhydrous methanol, and then 0.5 mol of a diamine is added at room temperature and stirred for 12 hours. The reactant is then dried to remove water. After the water is removed, 1.5 mol of sodium borohydride is added in batches at 0°C, and the mixture is reacted at 70°C for 12 hours. The reactant is then quenched by adding water, and the pH value is adjusted to neutral. The mixture is then extracted with ethyl acetate, and the extract is then separated and rotary evaporated to obtain an oily diester product; (2) Dissolve the oily diester in 50 ml of methanol, add hydrazine hydrate, react at room temperature for 12 h, and then obtain the oily dihydrazide by rotary evaporation; (3) 1 mol of diisocyanate and 2 mol of blocking agent were reacted in 100 ml of anhydrous tetrahydrofuran at room temperature for 12 h, and then the solvent was removed at 60° C. to obtain blocked isocyanate; (4) The oily dihydrazide, blocked isocyanate and epoxy resin monomer are mixed uniformly in proportion, and then the mixture is degassed under vacuum, injection molded and cured to obtain a repairable and solvent-resistant epoxy resin.

2. The preparation method according to claim 1, wherein: The aldehyde ester in step (1) is selected from one or more of methyl 2-formaldehyde benzoate, methyl 3-formaldehyde benzoate, methyl p-formylbenzoate, and methyl 4-oxobutanoate.

3. The preparation method according to claim 1, wherein: The diamine in step (1) is selected from one or more of 1,3-phenylenediamine, isophorone diamine, polyetheramine 230, polyetheramine 400, polyetheramine 600, polyetheramine 900, polyetheramine 2000, 1,2-propylenediamine, and ethylenediamine.

4. The preparation method according to claim 1, wherein: The amount of hydrazine hydrate used in step (2) is 5 times the molar equivalent of the diester.

5. The preparation method according to claim 1, wherein: The diisocyanate in step (3) is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and tetramethyl-m-xylylene diisocyanate.

6. The preparation method according to claim 1, wherein: The blocking agent in step (3) is selected from one or more of methyl ethyl ketone oxime, phenol, caprolactam, imidazole, and pyrazole.

7. The preparation method according to claim 1, wherein: The epoxy resin monomer in step (4) is selected from one or more of bisphenol A diglycidyl ether, 1,4-bis(oxirane-2-ylmethoxy)benzene, and resorcinol diglycidyl ether.

8. The preparation method according to claim 1, wherein: In step (4), the oily dihydrazide, blocked isocyanate and epoxy resin monomer are mixed in a molar ratio of 2:1:

4.

9. A repairable, solvent-resistant, dynamically cross-linked epoxy resin material prepared according to the preparation method according to any one of claims 1 to 8.

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