Preparation method of photocurable bio-based resin containing dynamic imine bonds

Abstract

The invention relates to a preparation method of light-curable bio-based resin containing dynamic imine bonds, which specifically comprises the following steps: by taking acrylic epoxy unsaturated fatty acid vegetable oil AEVO as a monomer and methacrylate containing dynamic imine bonds as a cross-linking agent, blending, and curing by ultraviolet light to prepare the light-curable bio-based resin. The photocurable bio-based resin disclosed by the invention has the advantages of adjustable mechanical property, dynamic reversible self-repairing, chemical stability, controllable degradation recovery and 3D printing applicability, and can be widely applied to the fields of environment-friendly coatings, flexible electronic packaging, recyclable adhesives, functional 3D printing and the like, and an ultraviolet curing process has the advantages of high efficiency and energy conservation.

Description

Technical Field

[0001] This invention relates to a method for preparing a photocurable bio-based resin containing dynamic imine bonds, specifically belonging to the field of biomass material preparation technology. Background Technology

[0002] Traditional thermosetting resins (such as epoxy resins and unsaturated polyesters) are difficult to recycle and degrade due to their permanent cross-linked networks, resulting in resource waste and environmental pollution. To address this challenge, vitrimer-like polymers have emerged in recent years. By introducing dynamic covalent bonds (such as transesterification, disulfide bonds, and imine bonds) into the cross-linked network, these materials maintain excellent mechanical properties and stability while acquiring reprocessable and self-healing properties. Among these, imine bonds have attracted significant attention due to their ability to undergo exchange reactions without catalysts. However, the preparation of most dynamic network materials still relies on petrochemical raw materials, and the curing process typically requires high-temperature, long-duration heating, resulting in high energy consumption and incompatibility with high-efficiency, low-energy photopolymerization manufacturing technologies such as 3D printing.

[0003] In recent years, developing bio-based photocurable resins that can replace petroleum-based products has become an important direction for green chemistry and sustainable manufacturing. One UV-curable soybean oil-based composite resin (CN103980438B) improves the mechanical properties of a material by blending epoxidized soybean oil methacrylate with a hydroxyl-terminated polybutadiene-derived oligomer containing terminal double bonds and then photocuring. However, its toughening component is still a petrochemical-based raw material, and the network after curing is irreversible, meaning the material lacks reprocessing or chemical recycling properties. A fully bio-based photocurable material (CN113897082A) prepared from itaconic acid, acrylic acid, epoxy compounds, and a composite photoinitiator relies on petroleum-based acrylic acid as a key component. This not only makes it difficult to increase the bio-based content of the product but also introduces toxicity, process instability, and the risk of side reactions. Patent CN106928444B uses polyether polyol-modified epoxidized soybean oil as an active diluent and copolymerizes it with acrylate monomers to prepare an aqueous resin dispersion. Its curing depends on high-temperature crosslinking, resulting in slow curing speed and high energy consumption. A biimine-bonded vanillin-based epoxy resin and its preparation method (CN117285488A) produces a product with excellent mechanical properties and is biodegradable and recyclable, but it lacks photocurable properties, making rapid manufacturing impossible. Although previous research has made progress in bio-based photocurable systems, developing a novel material system that integrates rapid photocurable molding, excellent mechanical properties, dynamic reversibility, and complete bio-based origin to meet the multiple demands of advanced manufacturing technologies such as 3D printing for rapid material processing, adjustable properties, self-healing capabilities, and recyclability has become an important and urgent technical challenge in this field. Summary of the Invention

[0004] To address the above issues, this invention proposes a method for preparing a photocurable bio-based resin containing dynamic imine bonds. This method uses acrylic epoxy unsaturated fatty acid vegetable oil AEVO as a monomer and methacrylate containing dynamic imine bonds as a crosslinking agent. After blending, the mixture is cured under ultraviolet light to obtain a photocurable bio-based resin. The specific process is as follows: Step 1: Synthesize acrylic acid epoxy unsaturated fatty acid vegetable oil AEVO Epoxy unsaturated fatty acid vegetable oil, acrylic acid, tetrabutylammonium bromide and 4-methoxyphenol were mixed in proportion and reacted under nitrogen protection at 60℃-130℃ until the acid value dropped to 5mgKOH / g to obtain acrylic acid epoxy unsaturated fatty acid vegetable oil AEVO. The feed ratio of epoxy unsaturated fatty acid vegetable oil to acrylic acid is 100:10-50; the amount of tetrabutylammonium bromide is 0.5wt%-5wt% of the mass of epoxy unsaturated fatty acid vegetable oil; and the amount of 4-methoxyphenol is 0.05wt%-1wt% of the mass of epoxy unsaturated fatty acid vegetable oil. Step 2: Synthesis of methacrylates containing dynamic imine bonds Aromatic aldehydes and polyetheramine diamines were dissolved in an organic solvent at a molar ratio of 1.7-2.3:1 and reacted at 25-80°C. The organic solvent was removed by rotary evaporation to obtain the imine-containing intermediate IVAN. Intermediate IVAN was mixed with acrylic anhydride or methacrylic anhydride, and then 4-dimethylaminopyridine was added. The mixture was subjected to a condensation reaction at 40-80°C for 4-24 hours. The reaction product was then washed with 1M dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated sodium chloride solution, respectively. The organic phase was dried over anhydrous sulfate and concentrated under reduced pressure at 40°C to obtain methacrylate MIVAN containing dynamic imine bonds. The molar ratio of intermediate IVAN to acrylic anhydride or methacrylic anhydride was 1:2-2.4, and the amount of 4-dimethylaminopyridine was 1%-10% of the molar amount of intermediate IVAN. Step 3: Synthesize photocurable bio-based resin Acrylic epoxy unsaturated fatty acid vegetable oil AEVO and methacrylate MIVAN containing dynamic imine bonds are mixed at a mass ratio of 10-50:50-90 to obtain a resin mixture; 1wt%-5wt% of a photoinitiator is added to the resin mixture, and after stirring evenly, it is irradiated under 405nm ultraviolet light for 0.1-5 minutes to obtain a photocurable bio-based resin.

[0005] The epoxidized unsaturated fatty acid vegetable oil AEVO mentioned above is epoxidized soybean oil or epoxidized castor seed oil.

[0006] The photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide or phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0007] The aromatic aldehyde compounds mentioned are vanillin, 4-hydroxybenzaldehyde, or syringaldehyde.

[0008] The polyetheramine diamine is polyetheramine D230 or polyetheramine D400.

[0009] The organic solvent is dichloromethane, chloroform, toluene, or tetrahydrofuran.

[0010] The methacrylic anhydride compounds mentioned are methacrylic anhydrides.

[0011] The acrylic anhydride compounds mentioned are acrylic anhydrides.

[0012] The anhydrous sulfate mentioned is anhydrous magnesium sulfate or anhydrous sodium sulfate. The beneficial effects of this invention are:

[0013] 1. Adjustable mechanical properties By changing the ratio of methacrylate containing dynamic imine bonds and AEVO plant oil containing epoxy unsaturated fatty acids in acrylic acid, the tensile strength and elongation at break of photocurable bio-based resin materials can be controlled.

[0014] 2. Dynamic reversibility The imine bonds inside photocurable bio-based resin materials can undergo exchange reactions under thermal stimulation, exhibiting stress relaxation, self-healing (such as repairing surface scratches at 50°C), thermal welding (such as achieving cross-sectional reconstruction at 80°C), and shape memory functions.

[0015] 3. Chemical stability and controllable degradation.

[0016] Photocurable bio-based resin materials are stable in common organic solvents and weak acids, but can undergo amine exchange reactions in primary amine solutions, leading to network disintegration and enabling chemical recycling.

[0017] 4. Applicability of 3D printing Photocurable bio-based resins are suitable for photocurable 3D printing fields such as stereolithography (SLA) and digital light processing (DLP), and can manufacture complex three-dimensional structural materials with high precision. Attached Figure Description

[0018] Figure 1 : A schematic diagram of the synthetic route for the dynamic imine bond methacrylate crosslinking agent of this invention; Figure 2Comparison of Fourier transform infrared (FTIR) spectra of acrylic epoxidized soybean oil AESO and methacrylate MIVAN-D230 containing dynamic imine bonds prepared in Example 1 of this invention; Figure 3 Example 2 of this invention: Stress-strain curve of cured bio-based resin at AESO / MIVAN-D230=30 / 70; Figure 4 The stress relaxation curve of the photocurable bio-based resin material in Example 2 of this invention at 50°C; Figure 5 Example 2 of this invention: Thermal welding effect of photocurable bio-based resin material at 80°C; Figure 6 Example 2 of the present invention: Stress-strain curve of photocurable bio-based resin material after welding at 80°C; Figure 7 Photographs of the degradation products of the photocurable bio-based resin material in primary amine solution in Example 2 of this invention; Figure 8 Example 4 of this invention: A photo of a complex structural component formed by photocurable bio-based resin through photocuring 3D printing. Detailed Implementation

[0019] Example 1 Step 1: Synthesis of Acrylic Acid Epoxidized Soybean Oil AESO 10g of epoxidized soybean oil, 3g of acrylic acid, 0.05g of tetrabutylammonium bromide catalyst, and 0.03g of 4-methoxyphenol polymerization inhibitor were mixed in a specific ratio and reacted at 60℃ under nitrogen protection until the acid value was below 5 mg KOH / g, yielding a light yellow viscous liquid epoxidized soybean oil acrylic acid (AESO). Figure 2 AESO infrared spectral variations, AESO infrared spectrum in the 3300-3500 cm⁻¹ range -1 A -OH stretching vibration peak appears at 1630 cm⁻¹. -1 A C=C absorption vibration peak appears at 827 cm⁻¹. -1 The disappearance of the characteristic absorption peak of epoxy at the point of oxidation confirms the occurrence of the ring-opening esterification reaction.

[0020] Step 2: Synthesis of MIVAN-D230 methacrylate containing dynamic imine bonds 15g of vanillin and 11.3g of polyetheramine D230 were dissolved in 30 mL of chloroform and stirred at 25°C for 48 hours. The solvent was removed by rotary evaporation to obtain the imine-bonded intermediate IVAN-D230.

[0021] 15.2 g of the imine-bonded intermediate IVAN-D230, 11.3 g of methacrylic anhydride, and 0.1 g of the catalyst 4-dimethylaminopyridine were subjected to a condensation reaction at 60 °C for 15 hours. The product was washed with 1 M dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated sodium chloride solution, respectively. The organic phase was dried over anhydrous magnesium sulfate and concentrated under reduced pressure at 40 °C to obtain methacrylate MIVAN-D230 containing dynamic imine bonds.

[0022] See the synthetic route. Figure 1 The aromatic aldehyde group of vanillin undergoes an amination condensation reaction with the primary amine of polyetheramine D230 to generate the intermediate IVAN containing a dynamic imine bond. The phenolic hydroxyl group of intermediate IVAN-D230 undergoes an esterification reaction with methacrylic anhydride, introducing a methacrylate group under the catalysis of 4-dimethylaminopyridine, to obtain the methacrylate MIVAN-D230 containing a dynamic imine bond. The structure of MIVAN-230 is... Figure 2 FTIR verification at 1737 cm -1 An ester carbonyl group (-OC=O) appears at 1666 cm⁻¹. -1 Overlapping stretching vibration peaks of imine bonds (C=N) and methacrylate carbon-carbon double bonds (C=C).

[0023] Example 2 Preparation, performance testing and analysis of photocurable bio-based resins AESO and MIVAN-D230 were mixed at a mass ratio of 30 / 70 (AESO 2.1 g, MIVAN-D230 4.9 g), and 3 wt% of photoinitiator TPO (0.18 g) was added. The mixture was stirred until homogeneous resin was obtained.

[0024] The above resin was poured into a mold and irradiated under 405 nm ultraviolet light for 5 minutes. After complete curing, a transparent photocurable bio-based resin solid sheet was obtained.

[0025] The sheet was cut into dumbbell-shaped strips and its performance was tested. The results showed that: Adjustable mechanical properties: This photocurable bio-based resin material exhibits good mechanical properties (see...). Figure 3 The tensile strength reaches 5.32 MPa, and the elongation at break reaches 17.85%.

[0026] Dynamic performance: Stress relaxation tests were conducted at 50°C, demonstrating significant stress relaxation behavior (see...). Figure 4 The relaxation time is the time required for G(t) / G0 to decrease to 1 / e, and the sample relaxation time is only 198 seconds.

[0027] Welding performance: Dumbbell-shaped photocurable bio-based resin strips can be cut and rejoined after the cut surfaces are subjected to contact and pressure at 80°C for a period of time (see...). Figure 5 The sample undergoes a process from fracture to welding and is tensile, and can withstand certain mechanical loads (see...). Figure 6 The tensile strength reaches 3.61 MPa, and the elongation at break reaches 10.17%.

[0028] Example 3 Replace the acrylic epoxidized soybean oil with an equal mass of acrylic epoxidized linseed oil. The specific preparation of the acrylic epoxidized linseed oil is the same as in Example 1.

[0029] The reaction conditions of acrylic epoxy linseed oil with methacrylate containing dynamic imine bonds were the same as in Example 2. The resulting photocurable bio-based resin material also showed significant stress relaxation and self-healing ability, proving that the technical solution of the present invention has universality for acrylic epoxy unsaturated fatty acid vegetable oils.

[0030] Example 4 The vanillin was replaced with an equimolar amount of eugenol, and the preparation of the methacrylate MIVAN-eugenol containing dynamic imine bonds was the same as in Example 1.

[0031] The reaction conditions of acrylic epoxidized soybean oil with methacrylate MIVAN-eugenol containing dynamic imine bonds were the same as in Example 2. The resulting photocurable bio-based resin material also showed significant stress relaxation and self-healing ability, proving that the technical solution of the present invention has universality for aromatic aldehydes with different substituents.

[0032] Example 5 The polyetheramine D230 was replaced with an equimolar amount of polyetheramine D400, and the preparation of the methacrylate MIVAN-D400 containing dynamic imine bonds was the same as in Example 1.

[0033] The reaction conditions of epoxidized acrylic soybean oil with methacrylate containing dynamic imine bonds were the same as in Example 2. The resulting photocurable bio-based resin material also exhibited significant stress relaxation and self-healing capabilities, proving that the technical solution of the present invention has universality for polyetheramine diamines.

[0034] Example 6 Chemical recycling About 2g of the cured sample of the photocurable resin obtained in Example 2 was immersed in a tetrahydrofuran solution containing excess n-propylamine and left to stand at room temperature for 72 hours.

[0035] Observations revealed that the intact solid sample gradually fragmented into pieces, and eventually the network completely decrosslinked, confirming that the material can be chemically recycled through an amine exchange reaction (see process below). Figure 7(morphological changes from intact solid to fragmented disintegration).

[0036] Example 7 Applications of photocurable resins in 3D printing The photocurable resin prepared in Example 2 was poured into the feed tank of a DLP 3D printer. A three-dimensional lattice model was designed and sliced ​​using CAD software. The printer was set to an exposure time of 15 seconds per layer and a layer thickness of 0.05 mm for layer-by-layer printing.

[0037] After printing, the sample is cleaned with ethanol to obtain a three-dimensional lattice product with a complete structure and clear details (see...). Figure 8 3D printed products).

Claims

1. A method for preparing a photocurable bio-based resin containing dynamic imine bonds, characterized in that: The preparation method described above uses acrylic epoxy unsaturated fatty acid vegetable oil AEVO as a monomer and methacrylate containing dynamic imine bonds as a crosslinking agent. After blending, the mixture is cured by ultraviolet light to obtain a photocurable bio-based resin. The specific process is as follows: Step 1: Synthesize acrylic acid epoxy unsaturated fatty acid vegetable oil AEVO Epoxy unsaturated fatty acid vegetable oil, acrylic acid, tetrabutylammonium bromide and 4-methoxyphenol were mixed in proportion and reacted under nitrogen protection at 60℃-130℃ until the acid value dropped to 5mgKOH / g to obtain acrylic acid epoxy unsaturated fatty acid vegetable oil AEVO. The feed ratio of epoxy unsaturated fatty acid vegetable oil to acrylic acid is 100:10-50; the amount of tetrabutylammonium bromide is 0.5wt%-5wt% of the mass of epoxy unsaturated fatty acid vegetable oil; and the amount of 4-methoxyphenol is 0.05wt%-1wt% of the mass of epoxy unsaturated fatty acid vegetable oil. Step 2: Synthesis of methacrylates containing dynamic imine bonds Aromatic aldehydes and polyetheramine diamines were dissolved in an organic solvent at a molar ratio of 1.7-2.3:1 and reacted at 25-80°C. The organic solvent was removed by rotary evaporation to obtain the imine-containing intermediate IVAN. Intermediate IVAN was mixed with acrylic anhydride or methacrylic anhydride, and then 4-dimethylaminopyridine was added. The mixture was subjected to a condensation reaction at 40-80°C for 4-24 hours. The reaction product was then washed with 1M dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated sodium chloride solution, respectively. The organic phase was dried over anhydrous sulfate and concentrated under reduced pressure at 40°C to obtain methacrylate MIVAN containing dynamic imine bonds. The molar ratio of intermediate IVAN to acrylic anhydride or methacrylic anhydride was 1:2-2.4, and the amount of 4-dimethylaminopyridine was 1%-10% of the molar amount of intermediate IVAN. Step 3: Synthesize photocurable bio-based resin Acrylic epoxy unsaturated fatty acid vegetable oil AEVO and methacrylate MIVAN containing dynamic imine bonds are mixed at a mass ratio of 10-50:50-90 to obtain a resin mixture; 1wt%-5wt% of a photoinitiator is added to the resin mixture, and after stirring evenly, it is irradiated under 405nm ultraviolet light for 0.1-5 minutes to obtain a photocurable bio-based resin.

2. The method for preparing a photocurable bio-based resin containing dynamic imine bonds according to claim 1, characterized in that: The epoxidized unsaturated fatty acid vegetable oil AEVO mentioned above is epoxidized soybean oil or epoxidized castor seed oil.

3. The method for preparing a photocurable bio-based resin containing dynamic imine bonds according to claim 1, characterized in that: The photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide or phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

4. The method for preparing a photocurable bio-based resin containing dynamic imine bonds according to claim 1, characterized in that: The aromatic aldehyde compounds mentioned are vanillin, 4-hydroxybenzaldehyde, or syringaldehyde.

5. The method for preparing a photocurable bio-based resin containing dynamic imine bonds according to claim 1, characterized in that: The polyetheramine diamine is polyetheramine D230 or polyetheramine D400.

6. The method for preparing a photocurable bio-based resin containing dynamic imine bonds according to claim 1, characterized in that: The organic solvent is dichloromethane, chloroform, toluene, or tetrahydrofuran.

7. The method for preparing a photocurable bio-based resin containing dynamic imine bonds according to claim 1, characterized in that: The methacrylic anhydride compounds mentioned are methacrylic anhydrides.

8. The method for preparing a photocurable bio-based resin containing dynamic imine bonds according to claim 1, characterized in that: The acrylic anhydride compounds mentioned are acrylic anhydrides.

9. The method for preparing a photocurable bio-based resin containing dynamic imine bonds according to claim 1, characterized in that: The anhydrous sulfate mentioned is anhydrous magnesium sulfate or anhydrous sodium sulfate.

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