A thioctic acid lignin-based DLP photocurable resin with both high stability and recyclability and its preparation method.

Abstract

This invention discloses a thioctic acid lignin-based DLP photocurable resin with both high stability and recyclability, and its preparation method. The resin comprises, by weight percentage: 16-80% thioctic acid polylactic acid oligomer, 0.5-7% thioctic acid lignin, 10-70% thioctic acid monofunctional diluent, and 0.5-7% photoinitiator, with the sum of the weight percentages of all components being 100%. This invention introduces thioctic acid lignin, utilizing its natural UV absorption capacity and rigid framework reinforcement, solving the problem of poor storage stability (less than one week) of traditional thioctic acid-based resins. It can be stored in a light-protected, sealed container for more than two years. The resin viscosity can be flexibly adjusted within the range of 10-2000 mPa·s to adapt to different DLP printing scenarios. After curing with 365-405 nm UV light, the tensile stress of the product reaches 30 MPa, and the fracture strain reaches 50%. The molding resin can be completely depolymerized and recycled in N,N-dimethylformamide at 150 °C without a catalyst. This invention achieves multiple objectives, including high stability, high precision, and recyclability, and can be widely applied in additive manufacturing fields such as rapid prototyping, precision parts, cultural and creative products, and medical devices.

Description

Technical Field

[0001] This invention relates to a lignin-based DLP photocurable resin with both high precision and recyclability, and particularly to a highly stable photocurable 3D printing resin containing lignin lipoic acid and its preparation method. Background Technology

[0002] Digital light processing 3D printing, as one of the mainstream technologies of photopolymer additive manufacturing, has been widely used in many fields such as rapid prototyping, customized medical devices, precision parts processing, and cultural and creative product production due to its advantages of fast forming speed, high printing accuracy, and excellent surface finish. The core of DLP printing is a liquid photopolymer resin system. Currently, commercial resins are still based on petroleum-based acrylates (CN121909247A, CN121895498A, CN121045890B, CN120209231B, CN121086150B). After polymerization initiated by ultraviolet light, they form a highly cross-linked thermosetting polymer network. The disadvantages of this type of polymer are also obvious. The molecular chains are connected by stable carbon-carbon covalent bonds, which makes it difficult to degrade, reprocess, and recycle. The large amount of printing waste generated causes a serious environmental burden and puts great pressure on our daily living environment. The raw materials rely on non-renewable petroleum resources, and various petroleum-based small molecule additives need to be added to improve the resin performance. These additives are prone to migration and loss, which leads to the degradation of material performance and further limits its application scenarios.

[0003] To address the issues of non-recyclability and high resource dependence of traditional DLP photopolymer resins, we introduced disulfide bonds into the polymer network. These dynamic covalent bonds construct a dynamic exchange network, endowing the resin with degradable, self-healing, and recyclable properties, effectively mitigating its environmental impact. Lipoic acid, a natural bio-based compound, contains a unique 1,2-dithiopentane structure, which can undergo ring-opening polymerization under UV light initiation. Introducing degradable dynamic disulfide bonds into the polymer backbone makes it an ideal raw material for obtaining recyclable and degradable photopolymer resins. A common problem with lipoic acid-based resins is their tendency to self-polymerize in the liquid state, typically limiting storage time to less than a week. Therefore, large amounts of polymerization inhibitors such as 2,6-di-tert-butyl-p-cresol (Nature 2024, 629, 1069–1074) or special modifications to improve their stability are often required (Science 2024, 385, 877–883). However, the former can only extend the stabilization time to 1-2 months, while also affecting the subsequent printing activity, while the latter is not only cumbersome to prepare but also significantly increases the cost, both of which restrict the promotion and application of thioctic acid derivatives in actual production.

[0004] Lignin, an abundant natural aromatic biopolymer found in agricultural and forestry waste, is a typical renewable biomass resource. Its molecular structure contains benzene rings and methoxy groups, which possess natural UV absorption capabilities, and its structure has been reported to enhance UV absorption efficiency (Advanced Materials 2021, 33, 2001588). The rigid polyphenol backbone can provide mechanical reinforcement to polymer networks, making it a high-quality candidate material to replace traditional petroleum-based small-molecule additives and modify DLP photopolymer resins. However, lignin itself contains a large number of hydrophilic groups, making it prone to aggregation when dispersed in resins. Furthermore, previous research on its polymerization inhibition has been limited to acrylate monomers, and there are no reports on its inhibitory effect on thioctic acid monomers. Summary of the Invention

[0005] Based on this, the present invention takes bio-based lipoic acid monomer as the core, and improves the stability and printing accuracy of DLP photopolymerization resin system by introducing lipoic acid lignin, so as to prepare a lipoic acid lignin-based DLP photocurable resin with both high stability and recyclability, and provides its preparation method to solve the problems of poor stability, limited performance and insufficient printing accuracy of lipoic acid-based 3D printing resins prepared by existing technologies.

[0006] This experiment provides a thioctic acid lignin-based DLP photocurable resin that combines high stability and recyclability, comprising thioctic acid polylactic acid with the following structure:

[0007] In the thioctic acid polylactic acid structure, n = 1~10.

[0008] Furthermore, the lignin-modified DLP photocurable resin, which possesses both antioxidant and recyclable properties, is synthesized using thioctic acid lignin monomers, the structure of which is as follows:

[0009] R1 can be independently represented as -OH or -OCH3. Furthermore, the lignin-modified DLP photocurable resin, which possesses both antioxidant and recyclable properties, has a thioctic acid monofunctional reactive diluent with the following monomer structure:

[0010] R2 can be independently represented as -C2H5O (ethanol), -C3H7O (n-propanol), -C4H9O (n-butanol), -C 10 H 21 Any one of the monohydric alcohols such as O (menthol).

[0011] Preferably, the thioctic acid lignin-modified DLP photocurable resin with both antioxidant and recyclable properties is characterized by the following synthesis process: (1) Preparation: The obtained thioctic ester monomers are compounded in pairs or in multiple combinations in a certain proportion, and a photoinitiator with a mass fraction of 0.5-7 wt% is added. At the same time, 0.5-7 wt% of thioctic lignin ester is added. After thorough mixing by a combination of vortex stirring and ultrasonic dispersion, a lignin-modified DLP photocurable resin with both antioxidant and recyclable properties is obtained.

[0012] (2) Printing: The lignin-modified DLP photocurable resin with both antioxidant and recyclable properties is added to the resin tank of the DLP 3D printer.

[0013] Preferably, the method for preparing lignin-modified DLP photocurable resin with both antioxidant and recyclable properties is characterized in that the photoinitiator in step (1) is one or a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 4-phenylbenzophenone, and isopropylthioxanthraquinone.

[0014] Preferably, the method for preparing lignin-modified DLP photocurable resin with both antioxidant and recyclable properties is characterized in that, in step (2), the light wavelength of the printer is 365-405 nm, the light intensity is 2-12 mW / cm², the bottom layer exposure time is 20-120 s, the exposure time of each layer is 10-80 s, and the layer thickness is 0.025-0.05 mm.

[0015] Preferably, the method for preparing the lignin-modified DLP photocurable resin with both antioxidant and recyclable properties is characterized in that the prepared resin can be dissolved in N,N-dimethylformamide without the action of a catalyst and can be completely depolymerized and recycled at 150 °C.

[0016] The lignin-modified DLP photocurable resin prepared by this invention has excellent storage stability and adjustable rheological properties, while the mechanical properties of the printed products are outstanding.

[0017] The resin can be stored for up to 2 years under light-proof and sealed conditions. During the storage period, there is no gelation or stratification, and the performance remains stable, which greatly improves the adaptability of storage and use in practical applications.

[0018] The viscosity of the resin system can be achieved to 10 mPa by adjusting the addition ratio of different monomers. s to 2000 mPa The wide range of adjustment of s allows for flexible adjustment of the formula ratio according to the molding requirements and precision requirements of different DLP printing scenarios, making it highly adaptable.

[0019] Printed products cured by 405 nm ultraviolet light have excellent mechanical properties, with a maximum tensile stress of 30 MPa and a maximum fracture strain of 50%, combining good strength and toughness to meet the actual mechanical requirements of various 3D printed products.

[0020] The core innovation of this invention lies in the organic combination of the recyclable characteristics of dynamic disulfide bonds and the multifunctional characteristics of lignin. Through precise monomer structure design and component matching, multiple goals are achieved for DLP photocurable resin: green recyclability, high printing precision, high performance stability, and easy recycling. At the same time, it solves several technical problems such as the high viscosity of thioctic acid resin and the non-recyclability of traditional resins. It has important application value and promotion prospects in the field of additive manufacturing materials.

[0021] This invention also protects the application of the aforementioned high-precision, high-stability recyclable 3D printing photosensitive resin in the plastics-related field. The resin can be widely used in rapid prototyping, precision parts processing, cultural and creative product manufacturing, customized consumables and other plastic product fields. It is especially suitable for DLP3D printing scenarios with high requirements for material precision, stability and environmental protection. It has a wide range of applications and great market potential. Attached Figure Description

[0022] Figure 1 A schematic diagram of a thioctic acid lignin-based DLP photocurable resin that combines high stability and recyclability. Figure 2 This is a schematic diagram of the photocured thioctic acid lignin-based DLP photocurable resin, which combines high stability and recyclability. Figure 3 Schematic diagram of the recyclable thioctic acid lignin-based DLP photocurable resin Preliminary preparations: Standardized instructions for synthesizing monomers i. Synthesis of lipoic acid and polylactic acid Wrap a 250 mL two-necked flask with tin foil to protect it from light. Add 5 g of dihydroxy-terminated polylactic acid (using n=7 structural units as an example, purchased from Hailuo Biotechnology), 30.0 g of lipoic acid, and 15.53 g of 4-dimethylaminopyridine to the flask. Add 200 mL of dichloromethane and stir magnetically for 10 minutes. After complete dissolution, transfer the mixture to an ice bath and add 20 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. After stirring and reacting for 24 hours, remove the flask and concentrate it to 40 mL of dichloromethane for dissolution. Extract the solution three times with 1-6 M hydrochloric acid and then three times with saturated sodium chloride. Finally, evaporate the solution to dryness to obtain lipoic acid polylactic acid.

[0023] ii. Synthesis of lipoic acid lignin Wrap a 250 mL two-necked flask with tin foil to protect it from light. Add 1.0 g of lignin, 1.388 g of thioctic acid, and 1.0 g of 4-dimethylaminopyridine to the flask. Add 40.0 mL of tetrahydrofuran. Stir for 10 minutes under magnetic stirring. After complete dissolution, transfer to an ice bath. Add 1.29 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. Stir and react for 24 hours. Remove the flask and concentrate by rotary evaporation. Dissolve the flask in 40 mL of dichloromethane. Extract the flask three times with 1-6 M hydrochloric acid and then three times with saturated sodium chloride. After extraction, evaporate to dryness to obtain thioctic acid lignin.

[0024] iii. Synthesis of lipoic acid monofunctional reactive diluent Taking menthol lipoic acid ester as an example, a three-necked flask was wrapped with aluminum foil to protect it from light. 6.3 g of menthol, 10 g of lipoic acid, and 100 mL of toluene were added to a 250 mL three-necked flask. The mixture was stirred magnetically at 140 °C until homogeneous. Then, 0.163 g of p-toluenesulfonic acid was added. The mixture was refluxed under a water separator and allowed to react for 6 hours. Afterward, the mixture was allowed to cool naturally to 80 °C, and then 0.2 g of triethylamine was added. After completely cooling to room temperature, the mixture was purified by column chromatography using alkaline alumina to obtain a yellow, oily menthol lipoic acid ester.

[0025] The grafting success was confirmed by infrared spectroscopy and proton nuclear magnetic resonance spectroscopy, and the grafting rate was measured to be over 95%.

[0026] Note: All the monomers mentioned above were synthesized by the applicant. Similar structures can also be synthesized using the above methods, and will not be described in detail here, as their preparation methods have been described in detail above. The monomers used in the following examples can all be prepared using the above methods, so their synthesis processes will not be described again. Detailed implementation method: The technical solution of the present invention will be further clearly and completely described below with reference to specific embodiments. It should be understood that the described embodiments are only used to better understand the principles and effects of the present invention, and are not intended to limit the present invention. Equivalent substitutions or improvements made by those skilled in the art without departing from the spirit and substance of the present invention should be considered to fall within the protection scope of the present invention.

[0027] Example 1 (1) Weigh 10 g of polylactic acid thioctic acid (polylactic acid structural unit n=7) according to 70% of the total resin mass; weigh 0.1429 g of lignin thioctic acid according to 1% of the total resin mass; weigh 3.5871 g of menthyl thioctic acid according to 27% of the total resin mass; and weigh 0.2857 g of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide according to 2% of the total resin mass. After mixing, stir at 40 ℃ for 1 h at a stirring speed of 1000 r / min, filter, remove bubbles under vacuum, let stand, and then cool to room temperature to obtain a highly stable and recyclable thioctic acid lignin-based DLP photocurable resin.

[0028] (2) The obtained resin is placed into the resin tank of the DLP type 3D printer. The light wavelength of the printer is 405nm, the light intensity is 6 mW / cm², the bottom layer exposure time is 60 s, the exposure time of each layer is 35 s, and the layer thickness is 0.025 mm.

[0029] Performance testing has verified that this resin formulation can be stored at room temperature for up to 2 years and maintains stability at 80 ℃ for more than 7 days, meeting the high-temperature accelerated aging test requirements in the "Standard for Photocurable Resins of 3D Printing Materials". Simultaneously, the resin has a critical exposure dose of 28 mJ / cm², a curing penetration depth of 0.1 mm, and a viscosity of 320 mPa. The resin formulation is adapted to the photopolymerization process, achieving a tensile strength of 37 MPa, an elongation at break of 41%, and a Shore hardness of 55 after curing, meeting the required mechanical properties. This resin formulation significantly improves high-temperature storage stability without sacrificing printing quality or mechanical properties, achieving synergistic optimization of storage performance and printing compatibility.

[0030] Comparative Example 1 (1) Weigh 10.0 g of polylactic acid thioctic acid (polylactic acid structural unit n=7) according to 70% of the total resin mass; weigh 0.1429 g of 2,6-di-tert-butyl-4-methylphenol (BHT) according to 1% of the total resin mass; weigh 3.5871 g of menthyl thioctic acid according to 27% of the total resin mass; and weigh 0.2857 g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (PTFE) according to 2% of the total resin mass. After mixing, stir at 40 °C for 1 h at a stirring speed of 1000 r / min, filter, remove bubbles under vacuum, let stand, and then cool to room temperature to obtain thioctic acid-based DLP photocurable resin containing the commercial polymerization inhibitor BHT.

[0031] (2) The obtained resin is placed into the resin tank of the DLP type 3D printer. The light wavelength of the printer is 405nm, the light intensity is 6 mW / cm², the bottom layer exposure time is 60 s, the exposure time of each layer is 35 s, and the layer thickness is 0.025 mm.

[0032] The resin can be stored at room temperature for up to one month, and in an 80°C oven for no more than seven days. Its viscosity is 240 mPa·s. After printing, the tensile strength is 25 MPa, the elongation at break is 33%, and the Shore hardness is 42. However, the short storage time does not meet the standards for photocurable resins used in 3D printing materials.

[0033] Comparative Example 2 (1) Weigh 10.0 g of polylactic acid thioctic acid (polylactic acid structural unit n=7) according to 70% of the total resin mass, weigh 4.0 g of menthyl thioctic acid according to 28% of the total resin mass, and weigh 0.2857 g of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide according to 2% of the total resin mass. After mixing, stir at 40 ℃ for 1 h at a stirring speed of 1000 r / min, filter, remove bubbles under vacuum, let stand, and then cool to room temperature to obtain a thioctic acid-based DLP photocurable resin without polymerization inhibitor.

[0034] (2) The obtained resin is placed into the resin tank of the DLP type 3D printer. The light wavelength of the printer is 405nm, the light intensity is 6 mW / cm², the bottom layer exposure time is 60 s, the exposure time of each layer is 30 s, and the layer thickness is 0.025 mm.

[0035] The resin has a shelf life of only 48 hours at room temperature and only 30 minutes in an 80°C oven, with a viscosity of 460 mPa·s. After printing, the tensile strength is 27 MPa, the elongation at break is 43%, and the Shore hardness is 43. The short shelf life does not meet the standards for photocurable resins used in 3D printing materials.

[0036] Comparative Example 3 (1) Weigh 10.0 g of polylactic acid thioctic acid (polylactic acid structural unit n=20) according to 70% of the total resin mass, weigh 0.1429 g of lignin thioctic acid according to 1% of the total resin mass, weigh 3.5871 g of menthyl thioctic acid according to 27% of the total resin mass, and weigh 0.2857 g of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide according to 2% of the total resin mass. After mixing, stir at 40 ℃ for 1 h at a stirring speed of 1000 r / min, filter, remove bubbles under vacuum, let stand, and then cool to room temperature to obtain high viscosity lignin-based DLP photocurable resin.

[0037] (2) The obtained resin is placed into the resin tank of the DLP type 3D printer. The light wavelength of the printer is 405nm, the light intensity is 6 mW / cm², the bottom layer exposure time is 60 s, the exposure time of each layer is 35 s, and the layer thickness is 0.025 mm.

[0038] The resin was too viscous, and its storage time at room temperature was only 10 days. Even after storing it in an 80°C oven, the storage time did not exceed 7 days, and the viscosity remained at 3600 mPa·s. After printing, the tensile strength was 48 MPa, the elongation at break was 6%, and the Shore hardness was 65. The excessive viscosity and short storage time did not meet the standards for photocurable resins used in 3D printing materials.

[0039] Example 2 (1) Weigh 10.0 g of polylactic acid thioctic acid (polylactic acid structural unit n=4) according to 50% of the total resin mass; weigh 0.2 g of lignin thioctic acid according to 1% of the total resin mass; weigh 9.4 g of ethanol thioctic acid according to 47% of the total resin mass; and weigh 0.4 g of isopropylthioxanthraquinone photoinitiator according to 2% of the total resin mass. After mixing, stir at 40 ℃ for 1 h at a stirring speed of 1000 r / min, filter, remove bubbles under vacuum, let stand, and then cool to room temperature to obtain a highly stable and recyclable thioctic acid lignin-based DLP photocurable resin.

[0040] (2) The obtained resin is placed into the resin tank of the DLP type 3D printer. The light wavelength of the printer is 405nm, the light intensity is 6 mW / cm², the bottom layer exposure time is 60 s, the exposure time of each layer is 35 s, and the layer thickness is 0.025 mm.

[0041] Performance testing verified that this resin formulation can be stored at room temperature for up to one year. Testing showed that the resin could be stored in an 80°C oven for over 7 days, with a viscosity of 180 mPa·s. After printing, the tensile strength was 26 MPa, the elongation at break was 32%, and the Shore hardness was 41, meeting the standards for photocurable resins used in 3D printing materials. The comprehensive performance test results indicate that the tensile strength, elongation at break, Shore hardness, and other mechanical properties of the resin at this formulation meet the requirements of practical applications.

[0042] Comparative Example 4 (1) Weigh 10.0 g of polylactic acid thioctic acid (polylactic acid structural unit n=4) according to 90% of the total resin mass; weigh 0.1111 g of lignin thioctic acid according to 1% of the total resin mass; weigh 0.7778 g of ethanol thioctic acid according to 7% of the total resin mass; and weigh 0.2222 g of isopropylthioxanthrone photoinitiator according to 2% of the total resin mass. After mixing, stir at 40 ℃ for 1 h at a stirring speed of 1000 r / min, filter, remove bubbles under vacuum, let stand, and then cool to room temperature to obtain thioctic acid lignin-based DLP photocurable resin.

[0043] (2) The obtained resin is placed into the resin tank of the DLP type 3D printer. The light wavelength of the printer is 405nm, the light intensity is 6 mW / cm², the bottom layer exposure time is 60 s, the exposure time of each layer is 35 s, and the layer thickness is 0.025 mm.

[0044] Performance testing verified that this resin formulation can be stored at room temperature for up to one year. Tests also showed that storing the resin in an 80°C oven for over 7 days resulted in a viscosity of 608 mPa·s. However, due to the excessively low diluent content, the cured resin was too brittle to be molded.

[0045] Comparative Example 5 (1) Weigh 1.0 g of polylactic acid thioctic acid (polylactic acid structural unit n=4) according to a ratio of 5% of the total resin mass; weigh 0.2 g of lignin thioctic acid according to a ratio of 1% of the total resin mass; weigh 18.4 g of ethanol thioctic acid according to a ratio of 92% of the total resin mass; and weigh 0.4 g of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide according to a ratio of 2% of the total resin mass. After mixing, stir at 40 ℃ for 1 h at a stirring speed of 1000 r / min, filter, remove bubbles under vacuum, let stand, and then cool to room temperature to obtain high-flowability lignin-based DLP photocurable resin.

[0046] (2) The obtained resin is placed into the resin tank of the DLP type 3D printer. The light wavelength of the printer is 405nm, the light intensity is 6 mW / cm², the bottom layer exposure time is 60 s, the exposure time of each layer is 35 s, and the layer thickness is 0.025 mm.

[0047] Tests showed that the resin, when stored in an 80°C oven for more than 7 days, maintained a viscosity of 103 mPa·s. After printing, the tensile strength was 0.8 MPa, the elongation at break was 16%, and the Shore hardness was 32. These results indicate that the hardness and tensile strength are too low and do not meet the standards for photocurable resins used in 3D printing materials.

[0048] Example 3 (1) Weigh 10.0 g of polylactic acid thioctic acid (polylactic acid structural unit n=4) according to 40% of the total resin mass; weigh 1.25 g of lignin thioctic acid according to 5% of the total resin mass; weigh 13 g of butanol thioctic acid according to 52% of the total resin mass; and weigh 0.75 g of 4-phenylbenzophenone photoinitiator according to 3% of the total resin mass. After mixing, stir at 40 ℃ for 1 h at a stirring speed of 1000 r / min, filter, remove bubbles under vacuum, let stand, and then cool to room temperature to obtain a highly stable and recyclable thioctic acid lignin-based DLP photocurable resin.

[0049] (2) The obtained resin is placed into the resin tank of the DLP type 3D printer. The light wavelength of the printer is 405nm, the light intensity is 6 mW / cm², the bottom layer exposure time is 60 s, the exposure time of each layer is 35 s, and the layer thickness is 0.025 mm.

[0050] Performance testing has verified that this resin formulation can be stored at room temperature for up to 2 years. Testing also showed that storing the resin in an 80℃ oven for over 7 days resulted in a viscosity of 780 mPa·s. After printing, the tensile strength was 36 MPa, the elongation at break was 22%, and the Shore hardness was 44, meeting the standards for photocurable resins used in 3D printing materials.

[0051] Comparative Example 6 (1) Weigh 10.0 g of polylactic acid thioctic acid (polylactic acid structural unit n=4) according to 40% of the total resin mass; weigh 2.5 g of thioctic lignin according to 10% of the total resin mass; weigh 12 g of butanol thiocate according to 47% of the total resin mass; and weigh 0.75 g of 4-phenylbenzophenone photoinitiator according to 3% of the total resin mass. After mixing, stir at 40 ℃ for 1 h at a stirring speed of 1000 r / min, filter, remove bubbles under vacuum, let stand, and then cool to room temperature to obtain thioctic acid-based DLP photocurable resin containing a large amount of thioctic lignin.

[0052] (2) The obtained resin is placed into the resin tank of the DLP type 3D printer. The light wavelength of the printer is 405nm, the light intensity is 6 mW / cm², the bottom layer exposure time is 60 s, the exposure time of each layer is 35 s, and the layer thickness is 0.025 mm.

[0053] Performance testing has verified that this resin formulation can be stored at room temperature for up to 2 years. Testing also showed that storing the resin in an 80℃ oven for over 7 days resulted in a viscosity of 980 mPa·s. However, due to its excessively high thioctic acid lignin content, it acts as a polymerization inhibitor and cannot be cured into shape.

Claims

1. A thioctic acid lignin-based DLP photocurable resin with both high stability and recyclability, characterized in that, It includes the following components by weight percentage: 16-80% polylactic acid thioctic acid, 0.5-7% lignin thioctic acid, 10-70% monofunctional diluent thioctic acid, and 0.5-7% photoinitiator, with the sum of the weight percentages of each component being 100%.

2. The thioctic acid lignin-based DLP photocurable resin with both high stability and recyclability according to claim 1, characterized in that, The structure of polylactic acid lipoic acid is as follows: In the thioctic acid polylactic acid structure, n = 1 to 10.

3. The thioctic acid lignin-based DLP photocurable resin with both high stability and recyclability according to claim 1, characterized in that, The structure of lipoic acid lignin monomer is as follows: R1 can be independently represented as -OH or -OCH3.

4. The thioctic acid lignin-based DLP photocurable resin with both high stability and recyclability according to claim 1, characterized in that, The structure of the lipoic acid monofunctional reactive diluent is as follows: R2 can be independently represented as -C2H5O (ethanol), -C3H7O (n-propanol), -C4H9O (n-butanol), -C 10 H 21 Any one of the monohydric alcohols such as O (menthol).

5. The thioctic acid lignin-based DLP photocurable resin with both high stability and recyclability according to claim 1, characterized in that, The photoinitiator is one or a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 4-phenylbenzophenone, and isopropylthioxanthraphenone.

6. A method for preparing claim 1 5. The method for obtaining a thioctic acid lignin-based DLP photocurable resin with both high stability and recyclability as described in any one of the claims, characterized in that: The polylactic acid thioctic acid, thioctic acid monofunctional diluent, thioctic acid lignin, and photoinitiator are poured into a container and mixed. The mixture is stirred at 40–50 °C for 1–6 h at a stirring speed of 1000–2000 r / min. After filtration, vacuum degassing, and standing, the mixture is cooled to room temperature to obtain a photocurable resin slurry.

7. According to claim 1 The thioctic acid lignin-based DLP photocurable resin with both high stability and recyclability as described in any one of the following six claims is characterized in that... The prepared thioctic acid-based DLP resin was stored in the dark for 2 days. Three years later, it still maintains good fluidity, with a viscosity range of 100–2000 mPa·s.

8. According to claim 1 The thioctic acid lignin-based DLP photocurable resin with both high stability and recyclability as described in any one of the following six claims is characterized in that... The DLP photopolymerization printing conditions are: light wavelength of 365 nm. 405 nm, illumination intensity 2 12 mW / cm², bottom layer exposure time is 20 120 s, with an exposure time of 10 seconds per layer. 80 s, layer thickness 0.025 0.05 mm.

9. According to claim 1 The thioctic acid lignin-based DLP photocurable resin with both high stability and recyclability as described in any one of the following six claims is characterized in that... The prepared resin, after photocuring, can be used in N,N Dimethylformamide was completely depolymerized and recovered into monomers at 150°C without the action of a catalyst.

10. The thioctic acid lignin-based DLP photocurable resin with both high stability and recyclability as described in claim 1, or as described in claim 1. Application of thioctic acid lignin-based DLP photocurable resins prepared by any of the preparation methods described in 5 in additive manufacturing related fields.

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