Degradable bio-based photosensitive resin, preparation method and application thereof

Abstract

This invention discloses a biodegradable bio-based photosensitive resin, its preparation method, and its applications. The invention uses polycaprolactone diol and castor oil as composite bio-based polyol components, which react with aliphatic or alicyclic diisocyanates under a catalyst to generate oligomers with terminal isocyanate groups. Then, an end-capping agent containing unsaturated double bonds is used to introduce photocurable acrylate groups into the molecular chain ends, yielding a bio-based polyurethane acrylate prepolymer. Finally, the prepolymer is mixed uniformly with an reactive diluent, a diamine chain extender, and a photoinitiator in a specific ratio to obtain the biodegradable bio-based photosensitive resin. This resin possesses suitable viscosity, high photoreactivity, and good interlayer bonding after curing, making it suitable for photopolymerization 3D printing processes. The printed products possess the necessary mechanical properties and can be controlled to degrade under alkaline conditions or in natural soil, making it applicable in fields such as environmentally friendly packaging, medical models, and medical devices.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, and relates to a biodegradable bio-based photosensitive resin, its preparation method and application. Background Technology

[0002] Photopolymer 3D printing technologies (such as Digital Light Processing (DLP)) have been widely applied in fields such as biomedical devices, soft robots, and personalized consumer products due to their personalized model customization and excellent printing accuracy and efficiency. The application potential of this technology largely depends on the comprehensive performance of its core material—photosensitive resin. Currently, most commercially available photosensitive resins capable of achieving high strength and high precision rely heavily on non-renewable resources such as petroleum-based acrylates as their main raw materials. The cross-linked network structure formed after photopolymerization of these resins is very stable, making it difficult for their products to be decomposed by microorganisms in natural environments (such as soil and water). Without special treatment after disposal, they will persist in the environment for a long time, causing cumulative ecological pressure, which clearly contradicts the current goals of green and circular development in manufacturing.

[0003] To reduce reliance on fossil resources and improve the environmental compatibility of materials, the development of bio-based photocurable resins based on renewable resources has become a research hotspot. Castor oil (CO), as a widely available natural polyol, possesses active hydroxyl groups and a long-chain fatty acid structure, making it an ideal raw material for preparing flexible polyurethane acrylates. However, resin materials constructed solely from castor oil (CO) often exhibit insufficient strength, modulus, and heat resistance after curing, making them unsuitable for structural components requiring high mechanical properties. Meanwhile, polycaprolactone diol (PCL), as a biodegradable polyester material, while possessing excellent biocompatibility and a controllable degradation cycle, lacks active groups that can participate in the photocuring reaction, preventing direct use in photocuring molding, and its products exhibit poor dimensional stability.

[0004] Therefore, the current technological dilemma lies in the fact that mature petroleum-based resins cannot simultaneously achieve both biodegradability and renewability; while existing bio-based or biodegradable resin solutions typically have significant shortcomings in key properties such as photocuring efficiency, product mechanical strength, and dimensional stability. Especially in processes like DLP, which have strict requirements on resin viscosity, reaction rate, and interlayer adhesion, achieving both high performance and biodegradability is a formidable task. Therefore, exploring and constructing a novel material system that organically combines the environmentally friendly properties of renewable resources with the functional design of biodegradable polymers from a molecular design perspective is of positive significance for advancing high-performance biodegradable photocurable 3D printing materials. Summary of the Invention

[0005] One object of the present invention is to provide a biodegradable bio-based photosensitive resin, comprising the following components in weight percentage:

[0006] Bio-based polyurethane acrylate prepolymer 40-70%;

[0007] Reactive diluent 26-50%;

[0008] Diamine chain extender 3-7%;

[0009] Photoinitiator 1-3%;

[0010] The simplified structural formula of the bio-based polyurethane acrylate prepolymer is as follows:

[0011] In the formula,

[0012] The simplified structure of R1 is: ;

[0013] n represents the number of segments of polycaprolactone, and the molecular weight of polycaprolactone segments is 500 to 2000.

[0014] This indicates the bond position in the molecule.

[0015] Furthermore, the active diluent is acrylomorpholine, hydroxyethyl methacrylate, isobornyl acrylate, isobornyl methacrylate, or N,N-dimethylacrylamide.

[0016] Furthermore, the diamine chain extender is 4,4-diaminodicyclohexylmethane, isophorone diamine, ethylenediamine, or hexamethylenediamine.

[0017] Furthermore, the photoinitiator is 2,4,6-trimethylbenzoyl diphenylphosphine oxide, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, or 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide.

[0018] Another object of the present invention is to provide a method for preparing the bio-based polyurethane acrylate prepolymer.

[0019] Step (1) Preparation of polyurethane oligomers with terminal isocyanate groups -NCO:

[0020] First, polycaprolactone diol (PCL) and castor oil (CO) are dehydrated at 100℃~110℃ and under a vacuum of less than -0.1MPa for 2~4 hours.

[0021] Then, the first step of chain extension reaction is carried out: under the protection of dry nitrogen or inert gas, the dehydrated polycaprolactone diol (PCL) is added dropwise to diisocyanate, with a molar ratio of PCL to diisocyanate of 1:(2-2.2); the addition process is carried out with uniform stirring, and the system temperature is raised to 70℃-75℃; the catalyst is added, and the reaction is stirred for 6-7 hours.

[0022] The second chain extension reaction is then carried out: while maintaining the temperature of the reaction system, castor oil CO is added dropwise to the system through an injection pump, and the reaction continues for 2-3 hours to obtain polyurethane oligomers with -NCO at the end; the molar ratio of polycaprolactone diol PCL to castor oil CO is 3:1.

[0023] Step (2) Preparation of bio-based polyurethane acrylate prepolymer:

[0024] The obtained polyurethane oligomers with -NCO terminal end were cooled to 50℃~55℃, a polymerization inhibitor was added, and the mixture was stirred evenly. The end-capping agent 2-(tert-butylamino)ethyl methacrylate t-BEMA was added dropwise to the system. After the addition was completed, the temperature was maintained and the reaction continued for 6~7h to obtain the bio-based polyurethane acrylate prepolymer. The molar ratio of t-BEMA to polycaprolactone diol PCL was (1~1.1):1.

[0025] Furthermore, the diisocyanate is isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), or dicyclohexylmethane diisocyanate (HMDI).

[0026] Furthermore, the catalyst is dibutyltin dilaurate, triethylamine, or bismuth isooctanoate, and the amount of catalyst added is 0.05 to 0.1 wt% of the total mass of the reaction system.

[0027] Furthermore, the polymerization inhibitor is hydroquinone or 2,6-di-tert-butyl-p-cresol, and the amount of polymerization inhibitor added is 0.05 to 0.1 wt% of the total mass of the total reaction system.

[0028] A third objective of this invention is to provide the application of this biodegradable bio-based photosensitive resin as a biodegradable 3D printing material. The 3D printing process includes printing using digital light processing (DLP), stereolithography (SLA), or liquid crystal display (LCD) printing equipment, followed by thermosetting after printing. The thermosetting temperature is 80–120°C, and the thermosetting time is 2–8 hours.

[0029] This invention proposes to introduce a composite bio-based structural unit of polycaprolactone and castor oil into a photosensitive resin system. A polyurethane acrylate prepolymer with photocurability, dynamic covalent bond structure and biodegradability is prepared by chemical synthesis. By uniformly mixing with reactive diluent, diamine chain extender and photoinitiator, a 3D printing photosensitive resin material with excellent comprehensive mechanical properties and biodegradability is obtained, which is suitable for high-precision DLP printing.

[0030] The beneficial effects of this invention include: by employing a dual curing strategy of "first photocuring for shaping, then thermocuring for enhancement," the biodegradable ester bonds of polycaprolactone diol (PCL), the flexible bio-based crosslinking points and dynamic covalent bonds of castor oil CO, and the rigid polyurea network formed by diamine chain extension are integrated into one. The resulting material possesses excellent comprehensive mechanical properties (such as high tensile strength and high elongation at break), while the ester bonds in its main chain ensure a clear and controllable biodegradability under soil or alkaline hydrolysis conditions, effectively solving the problem of the non-degradability of traditional high-performance photocurable resins. Furthermore, using renewable castor oil CO and commercially available biodegradable PCL as the main backbone raw materials significantly reduces the product's dependence on non-renewable petroleum resources throughout its entire life cycle, meeting the development requirements of green chemistry and a circular economy. In addition to the above-mentioned characteristics, the optimized resin's rheological and photosensitive properties are suitable for precision 3D printing processes such as DLP, providing a feasible material solution for manufacturing complex end products. Attached Figure Description

[0031] Figure 1 These are schematic diagrams of infrared spectral analysis before and after end capping in Examples 1, 2, and 3;

[0032] Figure 2 Comparison charts of tensile property tests for Examples 1, 2, 3, 4, 5, and 6;

[0033] Figure 3 The following are degradation diagrams of alkaline aqueous solutions at room temperature for Examples 1, 2, and 3. Detailed Implementation

[0034] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0035] Example 1.

[0036] (1) Preparation of bio-based polyurethane acrylate prepolymer (IPDI-PUA):

[0037] Polycaprolactone diol (PCL) and castor oil (CO) were dehydrated at 105°C and -0.15 MPa vacuum for 3 hours. 54.24 g of isophorone diisocyanate (IPDI, Mn=222.29) was placed in a three-necked flask equipped with a mechanical stirrer. The system temperature was raised to 70°C. 120 g of dehydrated polycaprolactone diol (Mn=1000) was weighed and added dropwise to the reaction system at a rate of 60 ml / h using a syringe pump, while maintaining constant stirring. After the addition was complete, 0.12 g of dibutyltin dilaurate (DBTDL) was added, and the reaction was continued with stirring for 6 hours to complete the first step of the chain extension reaction. Maintaining the reaction system temperature at 70℃, 37.34g of dehydrated castor oil (Mn=933.44) was weighed and added dropwise to the reaction system. The reaction was continued for 2 hours to obtain a polyurethane oligomer with -NCO terminal (NCO-PCL-CO-NCO). Its infrared spectral analysis results are as follows: Figure 1 As shown in the (NCO-PCL-CO-NCO) spectrum, the important characteristic absorption peaks are marked. The reaction system was cooled to 50℃, and 0.2g of hydroquinone (MEHQ) was added and stirred until homogeneous. 23.72g of 2-(tert-butylamino)ethyl methacrylate (t-BEMA, Mn=185.26) was slowly and uniformly added dropwise to the system at a rate of 30ml / h using a syringe pump. After the addition was complete, the reaction was continued at 50℃ for 7h to obtain a bio-based polyurethane acrylate prepolymer (IPDI-PUA). By comparison... Figure 1 The changes in the characteristic peaks of the infrared spectrum of Example 1 and the characteristic peaks of (NCO-PCL-CO-NCO) show that while the -C=C- bond peak appears, the -NCO group peak almost disappears, confirming successful end-capping. The reaction process is as follows:

[0038]

[0039] (2) Preparation of biodegradable bio-based photosensitive resin:

[0040] The bio-based polyurethane acrylate prepolymer (IPDI-PUA) prepared above was weighed with acrylamide morpholine (ACMO), 4,4-diaminodicyclohexylmethane (PACM) and 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO) according to the amounts in Table 1, and then mixed evenly to obtain a photosensitive resin composition suitable for 3D printing.

[0041] The biodegradable bio-based photosensitive resin composition obtained in Example 1 was placed in a photopolymerization 3D printer and cured layer by layer to obtain a three-dimensional product. After cleaning the surface of the three-dimensional product with ethanol to remove residual resin, it was transferred to a UV post-curing oven and cured on both sides for 2.5 min each. Then, it was transferred to a 100°C constant temperature oven for heat treatment for 6 h to obtain the final product. The tensile strength and elongation at break of the product were measured (by...). Figure 2 Data analysis of Example 1 in the example shows the results of tests such as differential scanning calorimetry, and the results are shown in Table 1.

[0042]

[0043] Table 1

[0044] Example 2.

[0045] (1) Preparation of bio-based polyurethane acrylate prepolymer (HDI-PUA):

[0046] Polycaprolactone diol (PCL) and castor oil (CO) were dehydrated at 100°C and -0.2 MPa vacuum for 4 hours. 88.80 g of hexamethylene diisocyanate (HDI, Mn=168.19) was placed in a three-necked flask equipped with a mechanical stirrer. The system temperature was raised to 72°C. 120 g of dehydrated PCL (Mn=500) was weighed and added dropwise to the reaction system at a rate of 50 ml / h using a syringe pump, while maintaining constant stirring. After the addition was complete, 0.33 g of triethylamine (TEA) was added, and the reaction was continued for 7 hours to complete the first step of chain extension. Maintaining the reaction temperature at 72°C, 74.68 g of dehydrated castor oil (CO) was weighed and added dropwise to the reaction system, and the reaction was continued for 3 hours to obtain a polyurethane oligomer with -NCO terminal (NCO-PCL-CO-NCO). Its infrared spectral analysis results are as follows: Figure 1 As shown in the (NCO-PCL-CO-NCO) spectrum, the important characteristic absorption peaks are marked. The reaction system was cooled to 52℃, and 0.33g of hydroquinone (MEHQ) was added and stirred until homogeneous. 48.91g of 2-(tert-butylamino)ethyl methacrylate (t-BEMA) was slowly and uniformly added to the system at a dropping rate of 30ml / h using a syringe pump. After the addition was complete, the reaction was continued at 52℃ for 6.5h to obtain the bio-based polyurethane acrylate prepolymer (HDI-PUA). By comparison... Figure 1 The changes in the characteristic peaks of the infrared spectrum of Example 2 and the characteristic peaks of (NCO-PCL-CO-NCO) show that while the -C=C- bond peak appears, the -NCO group peak almost disappears, confirming successful end-capping. The reaction process is as follows:

[0047]

[0048] (2) Preparation of biodegradable bio-based photosensitive resin:

[0049] The bio-based polyurethane acrylate prepolymer (HDI-PUA) prepared above was weighed with hydroxyethyl methacrylate (HEMA), isophorone diamine (IPDA) and 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide (TMO) according to the amounts in Table 2, and then mixed evenly to obtain a photosensitive resin composition suitable for 3D printing.

[0050] The biodegradable bio-based photosensitive resin composition obtained in Example 2 was placed in a photopolymerization 3D printer and cured layer by layer to obtain a three-dimensional product. After cleaning the surface of the three-dimensional product with ethanol to remove residual resin, it was transferred to a UV post-curing oven and cured on both sides for 2.5 min each. Then, it was transferred to an 80°C constant temperature oven for heat treatment for 8 h to obtain the final product. The tensile strength and elongation at break of the product were measured (by...). Figure 2 Data analysis of Example 2 shows the results of tests such as differential scanning calorimetry, and the results are shown in Table 2.

[0051]

[0052] Table 2

[0053] Example 3.

[0054] (1) Preparation of bio-based polyurethane acrylate prepolymer (HMDI-PUA):

[0055] Polycaprolactone diol (PCL) and castor oil (CO) were dehydrated at 110°C and -0.15 MPa vacuum for 2 hours. 33.06 g of dicyclohexylmethane diisocyanate (HMDI, Mn=262.35) was placed in a three-necked flask equipped with a mechanical stirrer. The system temperature was raised to 75°C. 120 g of dehydrated PCL (Mn=2000) was weighed and added dropwise to the reaction system at a rate of 50 ml / h using a syringe pump, while maintaining constant stirring. After the addition was complete, 0.15 g of bismuth isooctanoate (BiCAT) was added, and the reaction was continued for 6 hours to complete the first step of chain extension. Maintaining the reaction temperature at 75°C, 18.67 g of dehydrated castor oil (CO) was weighed and added dropwise to the reaction system, and the reaction was continued for 2 hours to obtain a polyurethane oligomer with -NCO terminal (NCO-PCL-CO-NCO). Its infrared spectral analysis results are as follows: Figure 1As shown in (NCO-PCL-CO-NCO), the important characteristic absorption peaks appearing in the spectrum have been marked. The reaction system was cooled to 55℃, and 0.15 g of 2,6-di-tert-butyl-p-cresol (BHT) was added and stirred until homogeneous. 11.67 g of 2-(tert-butylamino)ethyl methacrylate (t-BEMA) was slowly and uniformly added to the system at a dropping rate of 30 ml / h using a syringe pump. After the addition was complete, the reaction was continued at 55℃ for 6 h to obtain the bio-based polyurethane acrylate prepolymer (HMDI-PUA). By comparison... Figure 1 The changes in the characteristic peaks of the infrared spectrum of Example 3 and the characteristic peaks of (NCO-PCL-CO-NCO) show that while the -C=C- bond peak appears, the -NCO group peak almost disappears, confirming successful end-capping. The reaction process is as follows:

[0056]

[0057] (2) Preparation of biodegradable bio-based photosensitive resin

[0058] The HMDI-PUA prepared above was weighed with isobornyl acrylate (IBOA), ethylenediamine (EDA) and phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (819) according to the amounts in Table 3, and then mixed evenly to obtain a photosensitive resin composition suitable for 3D printing.

[0059] The biodegradable bio-based photosensitive resin composition obtained in Example 3 was placed in a photopolymerization 3D printer and cured layer by layer to obtain a three-dimensional product. After cleaning the surface of the three-dimensional product with ethanol to remove residual resin, it was transferred to a UV post-curing oven and cured on both sides for 2.5 min each. Then, it was transferred to a 110°C constant temperature oven for heat treatment for 6 h to obtain the final product. The tensile strength and elongation at break of the product were measured (by...). Figure 2 Data analysis of Example 3 shows the results of tests such as differential scanning calorimetry, and the results are shown in Table 3.

[0060]

[0061] Table 3

[0062] Example 4.

[0063] (1) Preparation of bio-based polyurethane acrylate prepolymer (IPDI-PUA):

[0064] The preparation method of the bio-based polyurethane acrylate prepolymer IPDI-PUA is the same as in Example 1.

[0065] (2) Preparation of biodegradable bio-based photosensitive resin

[0066] The IPDI-PUA prepared above was weighed with isobornyl methacrylate (IBOMA), hexamethylenediamine (HMD) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) according to the amounts in Table 4, and then mixed evenly to obtain a photosensitive resin composition suitable for 3D printing.

[0067] The biodegradable bio-based photosensitive resin composition obtained in Example 4 was placed in a photopolymerization 3D printer and cured layer by layer to obtain a three-dimensional product. After cleaning the surface of the three-dimensional product with ethanol to remove residual resin, it was transferred to a UV post-curing oven and cured on both sides for 2.5 min each. Then, it was transferred to a 120°C constant temperature oven for heat treatment for 2 h to obtain the final product. The tensile strength and elongation at break of the product were measured (by...). Figure 2 Data analysis of Example 4 shows the results of tests such as differential scanning calorimetry, and the results are shown in Table 4.

[0068]

[0069] Table 4

[0070] Example 5.

[0071] (1) Preparation of bio-based polyurethane acrylate prepolymer (IPDI-PUA):

[0072] The preparation method of the bio-based polyurethane acrylate prepolymer IPDI-PUA is the same as in Example 1.

[0073] (2) Preparation of biodegradable bio-based photosensitive resin

[0074] The IPDI-PUA prepared above was weighed with N,N-dimethylacrylamide (DMAA), 4,4-diaminodicyclohexylmethane (PACM) and 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide (TMO) according to the amounts in Table 5, and then mixed evenly to obtain a photosensitive resin composition suitable for 3D printing.

[0075] The biodegradable bio-based photosensitive resin composition obtained in Example 5 was placed in a photopolymerization 3D printer and cured layer by layer to obtain a three-dimensional product. After cleaning the surface of the three-dimensional product with ethanol to remove residual resin, it was transferred to a UV post-curing oven and cured on both sides for 2.5 min each. Then, it was transferred to a 100°C constant temperature oven for heat treatment for 4 h to obtain the final product. The tensile strength and elongation at break of the product were measured (by...). Figure 2 Data analysis of Example 5 shows the results of tests such as differential scanning calorimetry, and the results are shown in Table 5.

[0076]

[0077] Table 5

[0078] Example 6 (Control Group).

[0079] (1) Preparation of bio-based polyurethane acrylate prepolymer (IPDI-PUA):

[0080] The preparation method of the bio-based polyurethane acrylate prepolymer IPDI-PUA is the same as in Example 1.

[0081] (2) Preparation of biodegradable bio-based photosensitive resin

[0082] The IPDI-PUA prepared above was weighed with acrylamide morpholine (ACMO) and 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO) according to the amounts in Table 6, and then mixed evenly to obtain a photosensitive resin composition suitable for 3D printing.

[0083] The biodegradable bio-based photosensitive resin composition obtained in Example 6 was placed in a photopolymerization 3D printer and cured layer by layer to obtain a three-dimensional product. After cleaning the surface of the three-dimensional product with ethanol to remove residual resin, it was transferred to a UV post-curing chamber and cured on both sides for 2.5 minutes to obtain the final product. The tensile strength and elongation at break of the product were measured (by...). Figure 2 Data analysis of Example 6 shows the results of tests such as differential scanning calorimetry, and the results are shown in Table 6.

[0084]

[0085] Table 6

[0086] The comparison results of Examples 1-6 show that although Example 6, without the addition of the diamine chain extender, can achieve preliminary material forming under pure photocuring conditions and possess certain functionalities, its tensile strength and elongation at break are significantly lower than the sample treated with both photocuring and thermal curing due to the lack of the key diamine structure for thermocuring. The above comparison demonstrates that the photocuring and thermal curing strategy is a key technical feature of this invention for achieving synergistic improvement in material processing and mechanical properties.

[0087] Degradation performance test: The cured resin standard samples obtained in Examples 1-6 were immersed in NaOH solution with pH=10 at room temperature, and the degradation was observed periodically. Figure 3 Digital photographic observation revealed that the samples all underwent significant degradation within 12 days, indicating that the resin of this invention has a certain degradation capacity under alkaline conditions.

[0088] In vitro cytotoxicity test: The cell compatibility of the resin-cured samples from Examples 1-6 was tested using the MTT assay according to GB / T16886.5-2017 standard. Using L929 mouse fibroblasts as a model, a material extract (extraction ratio 3 cm² / mL, 37℃ for 24 h) was prepared and co-cultured with the cells for 24 h. PBS extract was used as the negative control. The cell viability of groups 1-5 was >90% and showed no statistically significant difference compared to the negative control group, indicating that the resin material prepared in this invention has no significant cytotoxicity and good in vitro biocompatibility, meeting the basic requirements for non-cytotoxicity in the biological evaluation of medical devices.

[0089] The above are merely preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any simple substitutions or improvements made based on the above embodiments should be covered within the protection scope of the present invention.

Claims

1. A biodegradable bio-based photosensitive resin, characterized in that, It consists of the following components by mass percentage: Bio-based polyurethane acrylate prepolymer 40-70%; Reactive diluent 26-50%; Diamine chain extender 3-7%; Photoinitiator 1-3%; The simplified structural formula of the bio-based polyurethane acrylate prepolymer is as follows: In the formula, The simplified structure of R1 is: ; n represents the number of segments of polycaprolactone, and the molecular weight of polycaprolactone segments is 500 to 2000. This indicates the bond position in the molecule.

2. The biodegradable bio-based photosensitive resin as described in claim 1, characterized in that: The active diluent is acrylomorpholine, hydroxyethyl methacrylate, isobornyl acrylate, isobornyl methacrylate, or N,N-dimethylacrylamide.

3. The biodegradable bio-based photosensitive resin as described in claim 1, characterized in that: The diamine chain extender is 4,4-diaminodicyclohexylmethane, isophorone diamine, ethylenediamine, or hexamethylenediamine.

4. The biodegradable bio-based photosensitive resin as described in claim 1, characterized in that: The photoinitiator is 2,4,6-trimethylbenzoyl diphenylphosphine oxide, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, or 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide.

5. The method for preparing the bio-based polyurethane acrylate prepolymer of claim 1, characterized in that: Step (1) Preparation of polyurethane oligomers with terminal isocyanate groups -NCO: First, polycaprolactone diol (PCL) and castor oil (CO) are dehydrated at 100℃~110℃ and under a vacuum of less than -0.1MPa for 2~4 h. Then, the first step of chain extension reaction is carried out: under the protection of dry nitrogen or inert gas, the dehydrated polycaprolactone diol (PCL) is added dropwise to diisocyanate, with a molar ratio of PCL to diisocyanate of 1:(2-2.2); the addition process is carried out with uniform stirring, and the system temperature is raised to 70℃-75℃; the catalyst is added, and the reaction is stirred for 6-7 hours. The second chain extension reaction is then carried out: while maintaining the temperature of the reaction system, castor oil CO is added dropwise to the system through an injection pump, and the reaction continues for 2-3 hours to obtain polyurethane oligomers with -NCO at the end; the molar ratio of polycaprolactone diol PCL to castor oil CO is 3:

1. Step (2) Preparation of bio-based polyurethane acrylate prepolymer: The obtained polyurethane oligomer containing -NCO at the end was cooled to 50℃~55℃, a polymerization inhibitor was added, and the mixture was stirred evenly. The end-capping agent 2-(tert-butylamino)ethyl methacrylate t-BEMA was added dropwise to the system. After the addition was completed, the temperature was maintained and the reaction continued for 6~7 h to obtain a bio-based polyurethane acrylate prepolymer. The molar ratio of t-BEMA to polycaprolactone diol PCL was (1~1.1):

1.

6. The method for preparing the bio-based polyurethane acrylate prepolymer as described in claim 5, characterized in that: In step (1), the diisocyanate is isophorone diisocyanate IPDI, hexamethylene diisocyanate HDI, or dicyclohexylmethane diisocyanate HMDI.

7. The method for preparing the bio-based polyurethane acrylate prepolymer as described in claim 5, characterized in that: In step (1), the catalyst is dibutyltin dilaurate, triethylamine or bismuth isooctanoate, and the amount of catalyst added is 0.05 to 0.1 wt% of the total mass of the reaction system.

8. The method for preparing the bio-based polyurethane acrylate prepolymer as described in claim 5, characterized in that: In step (2), the polymerization inhibitor is hydroquinone or 2,6-di-tert-butyl-p-cresol, and the amount of polymerization inhibitor added is 0.05 to 0.1 wt% of the total mass of the total reaction system.

9. The application of the biodegradable bio-based photosensitive resin as described in claim 1 as a biodegradable 3D printing material.

10. The application of the biodegradable bio-based photosensitive resin as described in claim 9 as a biodegradable 3D printing material, characterized in that: The 3D printing process includes printing using digital light processing (DLP), stereolithography (SLA), or liquid crystal display (LCD) printing equipment. After printing, the product undergoes thermal curing treatment at a temperature of 80–120°C for 2–8 hours.

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