Synthesis method of aliphatic long-carbon-chain epoxy resin curing agent

Abstract

The invention relates to a synthesis method of an aliphatic long-carbon-chain epoxy resin curing agent, so that other non-edible oil resources in the nature are used for modifying an amine curing agent, and the situation that most of amine modification raw materials are from edible oil such as soybean oil and palm oil is improved. Compared with a commercial curing agent, the toughness of a self-made epoxy resin system is greatly improved, the elongation at break is improved by 220%, the impact toughness is improved by 190%, the bending strength is reduced by 26.76%, and the bending modulus is reduced by 9.54%. The preparation method is characterized in that methyl oleate and ethylene glycol are used as raw materials to prepare long-carbon-chain diester through transesterification, and the long-carbon-chain diester and cysteamine hydrochloride are subjected to thiol-ene click reaction under the irradiation of an ultraviolet lamp by using 2, 2-dimethoxy-2-phenyl acetophenone as an initiator to synthesize the aliphatic long-carbon-chain epoxy resin curing agent. Therefore, the mechanical property of the epoxy resin is effectively improved.

Description

Technical Field

[0001] This invention belongs to the technical field of amine curing agent modification, specifically relating to a method for synthesizing an aliphatic long-chain epoxy resin curing agent. Background Technology

[0002] Epoxy resins are widely used in construction, transportation, aerospace, and energy fields due to their excellent physical and chemical properties. However, their high brittleness and poor toughness limit their further applications. Since the performance of epoxy resins largely depends on the curing agent used, curing agent modification has become a hot topic in epoxy resin research.

[0003] Common curing agents for epoxy resins include polyamines and acid anhydrides. However, existing short-chain amine curing agents are alkaline, easily soluble in water and fats, and their corrosiveness and skin penetration can harm human health. Therefore, researchers have attempted to modify amine curing agents by introducing natural, non-toxic bio-based materials. Zhao Huiping et al. prepared vegetable oil-based polyamine curing agents by starting with epoxidized triglycerides and sequentially converting ethylene oxide groups into diols, bromine, and azide groups, finally reducing them to amines. The results showed that this type of curing agent can effectively improve the toughness of epoxy resins. Biswas et al. used enzymes as catalysts and soybean azadiacarboxylic acid diethyl ester derivatives as raw materials to produce polyamines, which improved the toughness of epoxy resins. In addition, Zhang Xiaobo et al. introduced vegetable oils containing more rotating ether groups and flexible segments into amine curing agents and compared them with unmodified curing agents. The study showed that the modified curing agents had significantly improved flexibility, and their impact toughness was 10 times that of the unmodified ones.

[0004] Currently, most existing amine-modified raw materials are derived from edible oils such as soybean oil and palm oil. However, frequent use of edible oils can lead to competition with food supplies for humans. Therefore, our research group proposes utilizing other non-edible oil resources found in nature for the modification of amine curing agents. Research in this area is currently limited, and this study is expected to provide new ideas and methods for the modification of amine curing agents, expanding the application areas of epoxy resins. Summary of the Invention

[0005] The purpose of this invention is to provide a method for synthesizing an aliphatic long-chain epoxy resin curing agent, by introducing natural, non-toxic bio-based materials to modify the amine curing agent. This reduces the frequent use of edible oils, increases the utilization of other non-edible oil resources, and enables the curing agent to effectively improve the toughness of the epoxy resin.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] Step 1: Ethylene glycol and methyl oleate are placed in a three-necked flask at a mass ratio of 1:2.2 for transesterification reaction at 150-200 °C for 5-10 h.

[0008] Step 2: The deep eutectic solvent (DES) of catalyst B acid type is 5-10% of the mass of ethylene glycol. DES is prepared by melting choline chloride and oxalic acid in equal mass ratio at 30 °C.

[0009] Step 3: Dissolve the aliphatic diester, cysteine ​​hydrochloride, and 2,2-dimethoxy-2-phenylacetophenone in a mass ratio of 1:3:0.1 in a mixed solution of toluene, xylene, and tetrahydrofuran at 40-70 °C, and ensure dissolution by sonication;

[0010] Step 4: Place the mixed solution into a photoreactor and irradiate it with ultraviolet light for 12-24 hours.

[0011] Step 5: After removing the solvent by rotary evaporation, add 150 mL of saturated sodium carbonate solution to dissolve the remaining organic phase, and wash the solution with chloroform multiple times to ensure that the photoinitiator 2,2-dimethoxy-2-phenylacetophenone is completely removed.

[0012] Step 6: Add NaOH solution to adjust the pH of the solution to alkaline, wash the organic phase containing the product 6-10 times with saturated brine, dry the excess water with magnesium sulfate, remove other impurities by rotary evaporation again, and vacuum dry to obtain the final product, aliphatic long carbon chain epoxy resin curing agent.

[0013] The washing with chloroform solution is repeated 2 to 5 times.

[0014] The organic phase containing the product is washed with saturated brine at least five times.

[0015] The reaction temperature and time for ethylene glycol and methyl oleate are 150-200 °C for 5-10 h.

[0016] The temperature of the mixed solution composed of toluene, xylene, and tetrahydrofuran is 40-70 ℃.

[0017] The catalyst B acid-type deep eutectic solvent (DES) is 5-10% of the mass of ethylene glycol.

[0018] The duration of ultraviolet light irradiation is 12-24 hours.

[0019] Beneficial effects

[0020] This invention provides a method for synthesizing an aliphatic long-chain epoxy resin curing agent, thereby proposing the use of other non-edible oil resources in nature for the modification of amine curing agents, improving the situation where most amine modification raw materials come from edible oils such as soybean oil and palm oil. Compared with commercial curing agents, the epoxy system using the self-made curing agent shows a significant improvement in toughness, with an increase in elongation at break of 220%, an increase in impact toughness of 190%, a decrease in flexural strength of 26.76%, and a decrease in flexural modulus of 9.54%. The innovation of this invention lies in the preparation of a long-chain diester through transesterification reaction using methyl oleate and ethylene glycol as raw materials, and the preparation of a long-chain aliphatic diamine curing agent by reacting the diester with cysteine ​​hydrochloride under ultraviolet light irradiation with 2,2-dimethoxy-2-phenylacetophenone as an initiator through a thiol-ene click reaction, thereby effectively improving the toughness of epoxy resin. Attached Figure Description

[0021] Figure 1 The reaction process and the molecular formulas of the products at each step. Detailed Implementation

[0023] To make the process and technical solution of this invention clearer, the process of this invention will be further described in detail below.

[0024] Example 1:

[0025] (1) Ethylene glycol and methyl oleate were placed in a three-necked flask at a molar ratio of 1:2.2 (methyl oleate was in excess by 20% to ensure complete reaction) for transesterification reaction at 150 °C for 5 h.

[0026] (2) The deep eutectic solvent (DES) of catalyst B acid type is 5% of the mass of ethylene glycol. DES is prepared by melting choline chloride and oxalic acid in an equal molar ratio at 30 °C.

[0027] (3) Dissolve the aliphatic diester, cysteine ​​hydrochloride, and 2,2-dimethoxy-2-phenylacetophenone in a molar ratio of 1:3:0.1 in a mixed solution of toluene, xylene, and tetrahydrofuran at 40 °C, and ensure dissolution by sonication;

[0028] (4) Place the mixed solution in a photoreactor and irradiate it with ultraviolet light for 12 h;

[0029] (5) After removing the solvent by rotary evaporation, add 150 mL of saturated sodium carbonate solution to dissolve the remaining organic phase, and wash the solution twice with chloroform to ensure that the photoinitiator 2,2-dimethoxy-2-phenylacetophenone is completely removed;

[0030] (6) Add NaOH solution to adjust the pH of the solution to alkaline, wash the organic phase containing the product 6 times with saturated saline, dry the excess water with magnesium sulfate, remove other impurities by rotary evaporation again, and vacuum dry to obtain the final product, aliphatic long carbon chain epoxy resin curing agent.

[0031] Example 2:

[0032] (1) Ethylene glycol and methyl oleate were placed in a three-necked flask at a molar ratio of 1:2.2 (methyl oleate was in excess by 20% to ensure complete reaction) for transesterification reaction at 180 °C for 7 h.

[0033] (2) The deep eutectic solvent (DES) of the acid type of catalyst B is 7% of the mass of ethylene glycol. DES is prepared by melting choline chloride and oxalic acid in an equal molar ratio at 30 °C.

[0034] (3) Dissolve the aliphatic diester, cysteine ​​hydrochloride, and 2,2-dimethoxy-2-phenylacetophenone in a molar ratio of 1:3:0.1 in a mixed solution of toluene, xylene, and tetrahydrofuran at 50 °C, and ensure dissolution by sonication;

[0035] (4) Place the mixed solution in a photoreactor and irradiate it with ultraviolet light for 16 h;

[0036] (5) After removing the solvent by rotary evaporation, add 150 mL of saturated sodium carbonate solution to dissolve the remaining organic phase, and wash the solution three times with chloroform to ensure that the photoinitiator 2,2-dimethoxy-2-phenylacetophenone is completely removed;

[0037] (6) Add NaOH solution to adjust the pH of the solution to alkaline, wash the organic phase containing the product 7 times with saturated brine, dry the excess water with magnesium sulfate, remove other impurities by rotary evaporation again, and vacuum dry to obtain the final product, aliphatic long carbon chain epoxy resin curing agent.

[0038] Example 3:

[0039] (1) Ethylene glycol and methyl oleate were placed in a three-necked flask at a molar ratio of 1:2.2 (methyl oleate was in excess by 20% to ensure complete reaction) for transesterification reaction at 190 °C for 9 h.

[0040] (2) The deep eutectic solvent (DES) of catalyst B acid type is 8% of the mass of ethylene glycol. DES is prepared by melting choline chloride and oxalic acid in an equal molar ratio at 30 °C.

[0041] (3) Dissolve the aliphatic diester, cysteine ​​hydrochloride, and 2,2-dimethoxy-2-phenylacetophenone in a molar ratio of 1:3:0.1 in a mixed solution of toluene, xylene, and tetrahydrofuran at 60 °C, and ensure dissolution by sonication;

[0042] (4) Place the mixed solution in a photoreactor and irradiate it with ultraviolet light for 19 h;

[0043] (5) After removing the solvent by rotary evaporation, add 150 mL of saturated sodium carbonate solution to dissolve the remaining organic phase, and wash the solution 4 times with chloroform to ensure that the photoinitiator 2,2-dimethoxy-2-phenylacetophenone is completely removed;

[0044] (6) Add NaOH solution to adjust the pH of the solution to alkaline, wash the organic phase containing the product 8 times with saturated saline, dry the excess water with magnesium sulfate, remove other impurities by rotary evaporation again, and vacuum dry to obtain the final product, aliphatic long carbon chain epoxy resin curing agent.

[0045] Example 3:

[0046] (1) Ethylene glycol and methyl oleate were placed in a three-necked flask at a molar ratio of 1:2.2 (methyl oleate was in excess by 20% to ensure complete reaction) for transesterification reaction at 200 °C for 10 h.

[0047] (2) The deep eutectic solvent (DES) of catalyst B acid type is 10% of the mass of ethylene glycol. DES is prepared by melting choline chloride and oxalic acid in an equal molar ratio at 30 °C.

[0048] (3) Dissolve the aliphatic diester, cysteine ​​hydrochloride, and 2,2-dimethoxy-2-phenylacetophenone in a molar ratio of 1:3:0.1 in a mixed solution of toluene, xylene, and tetrahydrofuran at 70 °C, and ensure dissolution by sonication;

[0049] (4) Place the mixed solution in a photoreactor and irradiate it with ultraviolet light for 24 h;

[0050] (5) After removing the solvent by rotary evaporation, add 150 mL of saturated sodium carbonate solution to dissolve the remaining organic phase, and wash the solution 5 times with chloroform to ensure that the photoinitiator 2,2-dimethoxy-2-phenylacetophenone is completely removed;

[0051] (6) Add NaOH solution to adjust the pH of the solution to alkaline, wash the organic phase containing the product 9 times with saturated saline, dry the excess water with magnesium sulfate, remove other impurities by rotary evaporation again, and vacuum dry to obtain the final product, aliphatic long carbon chain epoxy resin curing agent.

Claims

1. A method for synthesizing an aliphatic long carbon chain epoxy resin curing agent, characterized by: The steps are as follows: Step 1, ethylene glycol and methyl oleate are placed in a three-necked flask in a mass ratio of 1:2.2 for ester exchange reaction at 150-200 ℃ for 5-10 h; Step 2, catalyst B acid type deep eutectic solvent (DES) is 5-10% of the mass of ethylene glycol, and the DES is prepared by melting equal mass ratio of choline chloride and oxalic acid at 30 ℃; Step 3, the aliphatic diester, cysteamine hydrochloride and 2, 2-dimethoxy-2-phenylacetophenone are dissolved in a 40-70 ℃ mixed solution composed of toluene, xylene and tetrahydrofuran in a mass ratio of 1:3:0.1, and ultrasonic is used to ensure dissolution; Step 4, the mixed solution is placed in a photoreactor and irradiated with ultraviolet light as the light source for 12-24 h; Step 5, after removing the solvent by rotary evaporation, 150 mL of saturated sodium carbonate solution is added to dissolve the remaining organic phase, and the solution is washed with chloroform multiple times to ensure that the photoinitiator 2, 2-dimethoxy-2-phenylacetophenone is completely removed; Step 6, NaOH solution is added to adjust the solution pH to alkaline, the organic phase containing the product is washed with saturated brine 6-10 times, dried with magnesium sulfate, and then rotary evaporated to remove other impurities, and vacuum dried to obtain the final product aliphatic long carbon chain epoxy resin curing agent.

2. The synthesis method of the aliphatic long carbon chain epoxy resin curing agent according to claim 1, characterized in that: The solution is washed with chloroform multiple times, which is 2-5 times.

3. The synthesis method of the aliphatic long carbon chain epoxy resin curing agent according to claim 1, characterized in that: The organic phase containing the product is washed with saturated brine multiple times, which is at least 5 times.

4. The synthesis method of an aliphatic long carbon chain epoxy resin curing agent according to claim 1, characterized in that: The reaction temperature and time of ethylene glycol and methyl oleate is 150-200 ℃ for 5-10 h.

5. The method for synthesizing an aliphatic long-chain epoxy resin curing agent according to claim 1 is characterized in that: The temperature of the mixed solution composed of toluene, xylene and tetrahydrofuran is 40-70 ℃.

6. The synthesis method of an aliphatic long carbon chain epoxy resin curing agent according to claim 1, characterized by: The catalyst B acid type deep eutectic solvent (DES) is 5-10% of the mass of ethylene glycol.

7. The method for synthesizing an aliphatic long-chain epoxy resin curing agent according to claim 1 is characterized in that: The ultraviolet light irradiation time is 12-24 h.

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