Preparation, application, chemical degradation and recycling method of recyclable sacrificial resin

Abstract

The invention relates to the technical field of 3D printing materials, in particular to a preparation, application, chemical degradation and recycling method of recyclable sacrificial resin, which comprises the following steps: synthesizing vanillin-based acrylate molecules; the preparation method comprises the following steps: adding polyamine and vanillin-based acrylate molecules into an organic solvent for reaction, and removing the organic solvent to obtain the degradable dynamic cross-linking agent; the preparation method comprises the following steps: fully mixing an acrylate monomer, a degradable dynamic cross-linking agent, a photoinitiator and a coloring agent, and carrying out photocuring to obtain the recyclable sacrificial resin. According to the present invention, the preparation, the application, the chemical degradation and the recycling method of the recyclable sacrificial resin are adopted, and the prepared recyclable sacrificial resin has characteristics of ultraviolet light curing, excellent mechanical property, cyclic processing, degradation and recycling.

Description

Technical Field

[0001] This invention relates to the field of 3D printing materials technology, and in particular to a method for preparing, applying, chemically degrading, and recycling a recyclable sacrificial resin. Background Technology

[0002] 3D printing is a forward-looking technology for manufacturing functional 3D structures. 3D printing based on specific wavelengths of light, especially digital light processing (DLP), can rapidly and accurately create complex objects. This technology projects light patterns layer by layer onto a digital model file, causing liquid resin (also known as ink) to solidify and build up layer by layer, effectively shortening printing time. However, traditional UV-cured resins are difficult to recycle after curing and are mostly synthesized from fossil fuels. Under the dual pressures of dwindling petroleum resources and environmental protection, developing bio-based UV-cured resins with reprocessability and sacrificial properties has become an important direction for sustainable development in this field.

[0003] While photopolymer 3D printing technology can produce intricate and complex objects with excellent mechanical properties faster and more accurately, it is prone to problems such as sagging or collapse of printed objects under unsupported conditions, especially for complex structures such as overhanging and cavity structures. Therefore, researchers have focused on chemically degradable sacrificial resins, attempting to improve the mechanical properties and complexity of printed objects by designing sacrificial support structures.

[0004] Currently, in the design of sacrificial resins based on chemical degradation, researchers have applied acid- or alkali-sensitive covalent bonds (such as imine bonds, acetal bonds, ester bonds, etc.) to the resin system, enabling the degradation of 3D printed support objects under relatively mild conditions. However, in existing technologies, acid and alkali treatments are typically used to degrade the polymer structure, resulting in irregular small molecules or oligomers that are difficult to separate and recycle, thus causing significant resource waste and organic pollution. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing, applying, chemically degrading, and recycling a recyclable sacrificial resin. The resulting recyclable sacrificial resin has ultraviolet curing properties, excellent mechanical properties, and the ability to be recycled and degraded.

[0006] To achieve the above objectives, the present invention provides a method for preparing a recyclable sacrificial resin, comprising the following steps: S1. Synthesis of vanillin-based acrylate molecules: Vanillin derivatives and acrylic acid derivatives are added to an organic solvent at a molar ratio of hydroxyl group in vanillin derivative to acid anhydride or acyl chloride in acrylic acid derivative of 1:(0.9-1.3), and reacted at 0-80℃ for 4-48h. After purification, vanillin-based acrylate molecules are obtained. S2. Synthesis of biodegradable dynamic crosslinking agent: Add polyamine and vanillin acrylate molecules from S1 to an organic solvent at a molar ratio of 1:(0.8-1.2) of amine groups to aldehyde groups of vanillin acrylate molecules, react at 20-80℃ for 4-24h, remove the organic solvent, and obtain the biodegradable dynamic crosslinking agent. S3. Preparation of sacrificial resin: The acrylate monomer, the biodegradable dynamic crosslinking agent of S2, the ultraviolet photoinitiator and the colorant are thoroughly mixed in a molar ratio of 100:(0.5-5):(1-4):(0-0.01) to obtain a recyclable sacrificial resin.

[0007] Preferably, the vanillin derivative in S1 includes one or more of vanillin, eugenol, isovanthanin, ethyl vanillin, o-vanillin, 2-hydroxy-5-methoxybenzaldehyde, 2-hydroxy-4-methoxybenzaldehyde, 3-methyl-4-hydroxybenzaldehyde, m-hydroxybenzaldehyde, 2,3-dihydroxybenzaldehyde, 2,4-dihydroxybenzaldehyde, 3,4-dihydroxybenzaldehyde, 3,5-dihydroxybenzaldehyde, 4-hydroxy-3,5-dimethylbenzaldehyde, 2,3,4-trihydroxybenzaldehyde, 2,4,5-trihydroxybenzaldehyde, 2,4,6-trihydroxybenzaldehyde, 2-hydroxy-5-nitrobenzaldehyde, 2-bromo-5-hydroxybenzaldehyde, 3-bromo-4-hydroxybenzaldehyde, 2-chloro-6-hydroxybenzaldehyde, 3-chloro-2-hydroxybenzaldehyde, and 3-chloro-4-hydroxybenzaldehyde; Acrylic acid derivatives include one or more of acrylic anhydride, methacrylic anhydride, acryloyl chloride, methacryloyl chloride, 3,3'-dimethylacryloyl chloride, and crotonyl chloride.

[0008] Preferably, the polyamine in S2 includes one or more of the following: ethylenediamine, propylenediamine, butyldiamine, pentanediamine, hexanediamine, poly(ethylene glycol)diamine, 2,2′-oxydiethylamine, 1,8-diamino-3,6-dioxaoctane, 4,4′-diaminodicyclohexylmethane, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 1,4-diaminenaphthalene, o-xylenediamine, 2-methyl-m-phenylenediamine, 2,2-dimethyl-1,3-propanediamine, 2,5-dimethyl-1,4-phenylenediamine, 2,3,5,6-tetramethyl-p-phenylenediamine, 2-nitro-1,4-phenylenediamine, 1,4-bis(3-aminopropoxy)butane, diethylenetriamine, tris(2-aminoethyl)amine, and N,N′-di(2-aminoethyl)-1,3-propanediamine.

[0009] Preferably, the organic solvents in S1 and S2 include one or more of dichloromethane, trichloromethane, tetrahydrofuran, ethyl acetate, acetone, toluene, xylene, chloroform, methanol, ethanol, isopropanol, n-butanol, diethyl ether, acetonitrile, N,N-dimethylformamide, and dimethyl sulfoxide.

[0010] Preferably, the acrylate monomers in S3 include one or more of methyl methacrylate, ethyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, 4-acryloylmorpholine, methyl acrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, and ethylene glycol dimethacrylate. The ultraviolet photoinitiator includes one or more of 2-hydroxy-2-methylphenylpropanone, Irgacure 819, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, benzoin dimethyl ether, and 1-hydroxycyclohexylphenyl ketone; The colorants include one or more of Sudan I, Sudan II, Sudan III, Sudan IV, Solvent Blue 35, Solvent Blue 59, and Transparent Blue 2N.

[0011] The present invention also provides a recyclable sacrificial resin, which is prepared by the above-described method for preparing a recyclable sacrificial resin.

[0012] The present invention also provides an application of recyclable sacrificial resin in 3D printing.

[0013] The present invention also provides a chemical degradation method for recyclable sacrificial resin, wherein a 3D printed part made of recyclable sacrificial resin is immersed in a degradation solution and treated at 40-90°C for 3-72 hours.

[0014] Preferably, the degradation solution is a mixture of organic solvent, deionized water, acid or alkali, with a pH of 1-11.

[0015] Preferably, the organic solvent includes one or more of methanol, ethanol, tetrahydrofuran, dichloromethane, chloroform, tetrahydrofuran, ethyl acetate, acetone, toluene, xylene, chloroform, isopropanol, n-butanol, diethyl ether, acetonitrile, N,N-dimethylformamide, and dimethyl sulfoxide. Acids include one or more of hydrochloric acid, sulfuric acid, acetic acid, and nitric acid; Alkali includes one or more of sodium hydroxide, potassium hydroxide, and magnesium hydroxide.

[0016] The present invention also provides a method for recycling and reusing recyclable sacrificial resin. The recyclable sacrificial resin is degraded by the above-mentioned chemical degradation method. After the degraded mixed solution is cooled to room temperature, thermoplastic resin is precipitated. After washing and drying, a white solid is obtained. The dried white solid is recycled for hot pressing molding.

[0017] Mechanism of the invention: This invention introduces a functional crosslinking agent containing degradable and dynamically crosslinked imine bonds into a functional resin precursor to obtain a recyclable sacrificial resin. This resin is then cured under ultraviolet light to form a thermosetting resin with a three-dimensional crosslinked network structure. Based on the dynamic crosslinking and acid degradation properties of the imine bonds, the resulting thermosetting resin possesses reprocessing and reuse capabilities as well as biodegradability. Therefore, this thermosetting resin can be used as a mold material for 3D printing, providing stable mechanical support and dimensional stability for the fabrication of complex three-dimensional 3D printed products such as hollow and suspended structures.

[0018] When used as a negative mold material for 3D printed products, the imine bonds at the cross-linking sites of the thermosetting resin degrade under acid catalysis, forming a linear thermoplastic resin that dissolves in an organic solvent to obtain a three-dimensional 3D printed product. This demolding process is mild and requires no additional mechanical force or high-temperature treatment, effectively avoiding structural damage caused by forced demolding. Simultaneously, the thermoplastic resin dissolved in the solvent can be concentrated and extracted for applications such as plastic product manufacturing and fiber composite preparation, achieving a green and closed-loop application throughout the material's entire lifecycle.

[0019] Therefore, the present invention employs the above-mentioned method for preparing, applying, chemically degrading, and recycling a recyclable sacrificial resin, which has the following beneficial effects: (1) The recyclable sacrificial resin provided by the present invention is prepared from renewable biomass vanillin derivatives, acrylic acid derivatives and diamines to obtain a biodegradable dynamic crosslinking agent containing functional groups of active free radical polymerization and dynamic imine bonds. It is blended with acrylate monomers and photoinitiators to form a functional resin precursor, which can be cured by ultraviolet light. The curing time is short, the energy consumption is low, and the cured product has excellent mechanical properties and high crosslinking density.

[0020] (2) The preparation method of the present invention is simple, the biodegradable functional monomer is easy to synthesize, the product yield is high, the raw materials are widely available and environmentally friendly, and meet the requirements of sustainable development.

[0021] (3) The sacrificial resin of the present invention can be recycled and reused. After being reprocessed by hot pressing and other methods, it can still maintain good mechanical properties and effectively improve resource utilization.

[0022] (4) The chemical degradation method provided by the present invention can achieve efficient and controllable degradation of 3D printed parts under mild temperature conditions by preparing a degradation solution with a specific pH. The solid mass loss can be monitored in real time during the degradation process. The degraded linear polymer can be recycled and reused, reducing resource waste and environmental pollution, and promoting the sustainable development and efficient recycling of polymers.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 These are comparative images of the morphology of the UV-cured films before and after hot pressing in Examples 1-3 of this invention. Figure 1 In the figure, 'a' represents the morphology of the sample before hot pressing of the UV-cured film. Figure 1 b in the figure is the morphology of the sample after hot pressing the UV-cured film; Figure 2 This is a comparative schematic diagram of the degradation rates of the UV-curable films in Examples 1-3 of the present invention; Figure 3 These are schematic diagrams showing the physical comparison of the degradation process of the UV-curable films in Examples 1-3 of this invention; Figure 4 This is a schematic diagram of the recycling-reforming process of the UV-cured films in Examples 1-3 of the present invention after degradation. Figure 4 (a) is a schematic diagram of the dried sample after degradation and recovery. Figure 4 (b) is a schematic diagram of the particles after the dried sample has been crushed. Figure 4 Image (c) is a schematic diagram of the actual object after the broken sample has been hot-pressed and reshaped; Figure 5 This is a structural sample image printed using digital light processing (DLP) technology according to Embodiment 5 of the present invention. Figure 5 Image (a) shows a sample diagram of the Expo logo structure. Figure 5 Image (b) shows a sample with a body-centered cubic (BCC) lattice structure. Figure 5 Image (c) shows a sample of the owl structure. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0026] This invention provides a method for preparing a recyclable sacrificial resin, comprising the following steps: S1. Synthesis of vanillin-based acrylate molecules: Vanillin derivatives and acrylic acid derivatives are added to an organic solvent at a molar ratio of hydroxyl groups in the vanillin derivative to anhydrides or acyl chlorides in the acrylic acid derivative of 1:(0.9-1.3). The mixture is reacted at 0-80℃ for 4-48h to introduce acrylate functional groups with free radical active polymerization into the vanillin molecule. After purification, vanillin-based acrylate molecules are obtained.

[0027] S2. Synthesis of biodegradable dynamic crosslinking agent: Add polyamine and vanillin acrylate monomers from S1 to an organic solvent at a molar ratio of 1:(0.8-1.2) of amine group to aldehyde group of vanillin acrylate molecule. React at 20-80℃ for 4-24h. Remove the organic solvent to obtain biodegradable functional monomer.

[0028] S3. Preparation of sacrificial resin: The acrylate monomer, the biodegradable dynamic crosslinking agent of S2, the ultraviolet photoinitiator and the colorant are thoroughly mixed in a molar ratio of 100:(0.5-5):(1-4):(0-0.01) to obtain a recyclable sacrificial resin.

[0029] This invention uses vanillin derivatives as starting materials to construct a biodegradable dynamic crosslinking agent containing both dynamic imine bonds and living free radical polymerization functional groups. The acrylate groups in this biodegradable dynamic crosslinking agent can participate in ultraviolet light-induced polymerization reactions to form a chemically crosslinked three-dimensional network structure. The dynamic imine bonds (-C=N-) act as functional sacrificial crosslinking points and can degrade under acidic conditions and appropriate temperatures, thereby degrading the three-dimensional crosslinked network into linear polymers, such as polymethyl methacrylate (PMMA). These polymers can be further concentrated and recycled for applications in plastic product manufacturing and composite material preparation.

[0030] Preferably, the vanillin derivative in S1 includes one or more of vanillin, eugenol, isovanthanin, ethyl vanillin, o-vanillin, 2-hydroxy-5-methoxybenzaldehyde, 2-hydroxy-4-methoxybenzaldehyde, 3-methyl-4-hydroxybenzaldehyde, m-hydroxybenzaldehyde, 2,3-dihydroxybenzaldehyde, 2,4-dihydroxybenzaldehyde, 3,4-dihydroxybenzaldehyde, 3,5-dihydroxybenzaldehyde, 4-hydroxy-3,5-dimethylbenzaldehyde, 2,3,4-trihydroxybenzaldehyde, 2,4,5-trihydroxybenzaldehyde, 2,4,6-trihydroxybenzaldehyde, 2-hydroxy-5-nitrobenzaldehyde, 2-bromo-5-hydroxybenzaldehyde, 3-bromo-4-hydroxybenzaldehyde, 2-chloro-6-hydroxybenzaldehyde, 3-chloro-2-hydroxybenzaldehyde, and 3-chloro-4-hydroxybenzaldehyde; Acrylic acid derivatives include one or more of acrylic anhydride, methacrylic anhydride, acryloyl chloride, methacryloyl chloride, 3,3'-dimethylacryloyl chloride, and crotonyl chloride.

[0031] More preferably, the purification in S1 includes the following steps: extracting the reaction solution 2-4 times with saturated sodium bicarbonate aqueous solution, extracting 1-2 times with deionized water solution, extracting 2-4 times with saturated saline solution, and removing the organic solvent after drying the organic phase.

[0032] More preferably, vanillin acrylate molecules are vanillin methacrylate or vanillin acrylate.

[0033] In this invention, vanillin-based acrylate molecules possess acrylate functional groups with free radical polymerization activity. When a UV photoinitiator is present, they can participate in the polymerization reaction under UV photoinitiation conditions, thereby constructing a cross-linked network structure of the polymer.

[0034] In some specific embodiments of the present invention, the preparation method of vanillin methacrylate includes the following steps: dissolving vanillin and methacrylic anhydride in an organic solvent, then adding the catalyst 4-dimethylaminopyridine, reacting at a temperature of 40-80℃ for 12-48h, and obtaining the product after purification; wherein, the molar ratio of vanillin to methacrylic anhydride is 1:(1-1.2); and the amount of 4-dimethylaminopyridine used is 2%-4% of the total mass of vanillin.

[0035] In some specific embodiments of the present invention, the preparation method of vanillin acrylate includes the following steps: adding vanillin and acryloyl chloride to an organic solvent, then adding triethylamine as a catalyst, reacting at 0°C for 12-24 h, and purifying to obtain the product; wherein the molar ratio of vanillin to acryloyl chloride is 1:(1.0-1.2); and the molar ratio of vanillin to triethylamine is 1:(1.1-1.5).

[0036] Preferably, the polyamine in S2 includes one or more of the following: ethylenediamine, propylenediamine, butyldiamine, pentanediamine, hexanediamine, poly(ethylene glycol)diamine, 2,2′-oxydiethylamine, 1,8-diamino-3,6-dioxaoctane, 4,4′-diaminodicyclohexylmethane, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 1,4-diaminenaphthalene, o-xylenediamine, 2-methyl-m-phenylenediamine, 2,2-dimethyl-1,3-propanediamine, 2,5-dimethyl-1,4-phenylenediamine, 2,3,5,6-tetramethyl-p-phenylenediamine, 2-nitro-1,4-phenylenediamine, 1,4-bis(3-aminopropoxy)butane, diethylenetriamine, tris(2-aminoethyl)amine, and N,N′-di(2-aminoethyl)-1,3-propanediamine.

[0037] Preferably, the organic solvents in S1 and S2 include one or more of dichloromethane, trichloromethane, tetrahydrofuran, ethyl acetate, acetone, toluene, xylene, chloroform, methanol, ethanol, isopropanol, n-butanol, diethyl ether, acetonitrile, N,N-dimethylformamide, and dimethyl sulfoxide.

[0038] Preferably, the acrylate monomers in S3 include one or more of methyl methacrylate, ethyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, 4-acryloylmorpholine, methyl acrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, and ethylene glycol dimethacrylate.

[0039] In this invention, acrylate-based active radical polymer monomers serve as the main components of the resin, providing basic photocuring and mechanical properties. This not only ensures the system's good photocuring reactivity and molding performance, but also facilitates the embedding of degradable and dynamic imine bonds into the polymer crosslinking network backbone, thereby balancing material performance stability with controllable degradation of the crosslinking structure. Simultaneously, it provides a structural basis for subsequent degradation to form linear polymers.

[0040] The ultraviolet photoinitiator includes one or more of 2-hydroxy-2-methylphenylacetone, Irgacure 819, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, benzoin dimethyl ether, and 1-hydroxycyclohexylphenyl ketone.

[0041] This invention introduces the aforementioned ultraviolet photoinitiator, enabling the resin system to efficiently initiate polymerization reactions under ultraviolet light, thereby improving the molding efficiency and curing quality of the material. It also facilitates the construction of a uniform and stable polymer network structure, enhancing the applicability and reliability of the material in the 3D printing process.

[0042] The colorants include one or more of Sudan I, Sudan II, Sudan III, Sudan IV, Solvent Blue 35, Solvent Blue 59, and Transparent Blue 2N.

[0043] By introducing one or more of the above-mentioned colorants, the present invention enables the resin system to have good visual characteristics, which is beneficial to improving the controllability and ease of operation of the photocuring molding process, while improving the overall molding quality and stability without affecting the curing performance of the material.

[0044] The present invention also provides a recyclable sacrificial resin, which is prepared by the above-described method for preparing a recyclable sacrificial resin.

[0045] The present invention also provides an application of recyclable sacrificial resin in 3D printing.

[0046] The present invention also provides a chemical degradation method for recyclable sacrificial resin, wherein a 3D printed part made of recyclable sacrificial resin is immersed in a degradation solution and treated at 40-90°C for 3-72 hours.

[0047] Preferably, the degradation solution is a mixture of organic solvent, deionized water, acid or alkali, with a pH of 1-11.

[0048] Preferably, the organic solvent includes one or more of methanol, ethanol, tetrahydrofuran, dichloromethane, chloroform, tetrahydrofuran, ethyl acetate, acetone, toluene, xylene, chloroform, isopropanol, n-butanol, diethyl ether, acetonitrile, N,N-dimethylformamide, and dimethyl sulfoxide. Acids include one or more of hydrochloric acid, sulfuric acid, acetic acid, and nitric acid; Alkali includes one or more of sodium hydroxide, potassium hydroxide, and magnesium hydroxide.

[0049] The present invention also provides a method for recycling and reusing recyclable sacrificial resin. The recyclable sacrificial resin is degraded by the above-mentioned chemical degradation method. After the degraded mixed solution is cooled to room temperature, thermoplastic resin is precipitated. After washing and drying, a white solid is obtained. The dried white solid is recycled for hot pressing molding.

[0050] During the degradation process, the vanillin functionalized monomers in the recyclable sacrificial resin molecular chain are completely degraded into linear polymers, dispersed in the degradation solution, and the linear polymers, i.e. thermoplastic resins, can be extracted from the degradation solution by precipitation or concentration, realizing the closed-loop recycling and reuse of materials; while the polyamine functionalized monomers are transformed into amine salts under acidic conditions and dissolved in the degradation solution, and the amine salts can be reused through subsequent neutralization and separation.

[0051] Example 1 This invention provides a recyclable sacrificial resin, the preparation method of which includes the following steps: S1. Synthesis of vanillin methacrylate: 10 g vanillin (0.066 mol), 11.14 g methacrylic anhydride (0.066 mol), 0.56 g catalyst 4-dimethylaminopyridine (DMAP, 0.005 mol) and 25 mL dichloromethane were added to a round-bottom flask. The round-bottom flask was placed in an oil bath at 60 °C and heated for 24 h. Then, it was extracted twice with 90 mL saturated sodium bicarbonate aqueous solution, once with 0.5 M sodium hydroxide aqueous solution, and twice with saturated saline solution. Anhydrous magnesium sulfate was added and dried for 30 min. The anhydrous magnesium sulfate was removed by filtration, and the dichloromethane was removed by rotary evaporation to obtain vanillin methacrylate.

[0052] S2. Synthesis of biodegradable dynamic crosslinking agent: Take 5g of vanillin methacrylate obtained in S1 and 1.7mL of 1,8-diamino-3,6-dioxane (at a molar ratio of aldehyde to amino of 1:1) and dissolve them in 30mL of dichloromethane. Stir the reaction at room temperature for 4h. Then extract twice with 0.5M sodium hydroxide aqueous solution, once with deionized water, and twice with saturated saline solution. Add anhydrous magnesium sulfate and dry for 30min. Filter to remove anhydrous magnesium sulfate and remove dichloromethane by rotary evaporation to obtain a biodegradable dynamic crosslinking agent containing imine bonds.

[0053] S3. Preparation of sacrificial resin: Take 0.26g of the biodegradable dynamic crosslinking agent obtained in S2, 10mL of methyl methacrylate solution and 0.294mL of 2-hydroxy-2-methylphenylacetone, stir evenly at room temperature, and maintain a nitrogen atmosphere in a glove box to obtain a recyclable sacrificial resin.

[0054] Example 2 The difference from Example 1 is that the amount of biodegradable dynamic crosslinking agent used in S3 is 0.52g, while the rest is the same as in Example 1.

[0055] Example 3 The difference from Example 1 is that the amount of biodegradable dynamic crosslinking agent used in S3 is 1.04g, while the rest is the same as in Example 1.

[0056] Example 4 The difference from Example 1 is that the ultraviolet photoinitiator in S3 is 0.529 mL of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and the rest is the same as in Example 1.

[0057] Example 5 The difference from Example 1 is that S3 is to take 0.011g of the biodegradable dynamic crosslinking agent prepared in S2 of Example 1, 10mL of 4-acryloylmorpholine solution, 0.11mL of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 0.0001g of Solvent Blue 35, stir evenly at room temperature, and maintain a nitrogen atmosphere in a glove box. The rest of the steps are the same as in Example 1 to obtain a recyclable sacrificial resin.

[0058] Comparative Example 1 The difference from Example 1 is that no biodegradable dynamic crosslinking agent was added. 10 mL of methacrylate solution and 0.294 mL of 2-hydroxy-2-methylphenylacetone were directly mixed and stirred at room temperature under a nitrogen atmosphere in a glove box to obtain a thermoplastic polyacrylate resin.

[0059] The recyclable sacrificial resins obtained in Examples 1-5 and the thermoplastic polyacrylate resin obtained in Comparative Example 1 were injected into a double-glass plate clamp using an injection molding method. The clamp had a gap thickness of 1 mm and was cured under an 80W UV curing lamp for 1 hour to obtain a UV-curable film. The glass transition temperature of the UV-curable film was then determined using a differential scanning calorimeter (DSC). Simultaneously, the mechanical properties of the UV-curable film were determined using a uniaxial tensile test, with the tensile strength measured at room temperature using a universal testing machine. The results are shown in Table 1.

[0060] Table 1 Glass transition temperature and tensile strength of different UV-curable films

[0061] As shown in Table 1, the biodegradable dynamic crosslinking agent introduced in Examples 1-5 of this invention can significantly improve the glass transition temperature and mechanical properties of the material at a lower crosslinking density, enabling the material to possess good structural stability and mechanical support during use, thereby meeting its application requirements as a recyclable sacrificial resin. In contrast, Comparative Example 1 exhibits a lower glass transition temperature and mechanical strength at a similar crosslinking density, indicating that the rigidity of the matrix resin has a significant impact on the performance of the crosslinking network. The above results demonstrate that the biodegradable dynamic crosslinking agent used in this invention can significantly improve the thermal and mechanical properties of sacrificial resins while maintaining their biodegradability.

[0062] Reprocessing experiment: The UV-curable films from Examples 1-4 were cut into small pieces and hot-pressed at 150℃ and 200MPa for 20 minutes. Their tensile strength was then tested, and the results are shown in Table 2. Figure 1 .

[0063] Table 2. Reprocessing properties of different UV-curable films

[0064] From Table 2 and Figure 1 It can be seen that in Example 1, the tensile strength after hot pressing remained at 1.6 GPa, which is close to the initial strength of 1.66 GPa before hot pressing, and the strength retention rate reached 96.4%; in Example 2, the tensile strength after hot pressing also remained at 1.6 GPa, and the strength retention rate was 93.0% compared to the initial strength of 1.72 GPa before hot pressing; in Example 3, the tensile strength after hot pressing remained at 0.8 GPa, and the strength retention rate was 45% compared to the initial modulus of 1.77 GPa before hot pressing, which reflects its recyclability and reprocessing performance. However, as the degree of crosslinking increased, the movement of chain segments was restricted, resulting in a large difference in tensile strength between the network before and after hot pressing; in Example 4, the tensile strength after hot pressing remained at 0.40 GPa, which was completely consistent with the initial strength before hot pressing, achieving complete retention of mechanical properties.

[0065] The tensile strength of the UV-curable film samples after hot pressing remained stable without significant attenuation. This demonstrates that the recyclable sacrificial resin of this invention retains high mechanical properties after repeated reprocessing, reflecting the material's excellent dynamic crosslinking function and reprocessing performance. During hot pressing, the dynamic crosslinking units of imine bonds within the material undergo reversible dynamic exchange reactions at high temperatures, resulting in reversible recombination of the polymer network topology and enabling the material to be reprocessed and reshaped.

[0066] Chemical recovery experiment: 60 mg of the UV-curable film fragments from Examples 1-3 were accurately weighed and placed in 20 mL of a pH=4 degradation solution (a mixture of hydrochloric acid, water, and N,N-dimethylformamide). Similarly, 60 mg of the UV-curable film fragments from Examples 4-5 were weighed and placed in 20 mL of a pH=4 degradation solution (a mixture of acetic acid and water). The samples were then immersed in a 90°C oven, and the time for complete dissolution (i.e., degradation time) was observed. The results are shown in Table 3 and... Figure 2-3 .

[0067] Table 3 Degradation time of different UV-curable films

[0068] From Table 3 and Figure 2-3 It can be seen that, under the same pH and temperature, the UV-cured samples with different formulations exhibited significant differences in controllable degradation: Example 1 achieved complete degradation within 2.5 hours, Example 4 within 2 hours, and Example 5 within 48 hours. The results indicate that this invention, through acid-triggered degradation of the functional crosslinking agent, gradually degrades the polymer's three-dimensional crosslinked network into a linear structure and eventually dissolves, thereby achieving controllable removal of the sacrificial resin. Examples 2 and 3 did not show complete degradation within 4 days. These two types of examples often correspond to higher crosslinking levels, reducing the rate at which acidic media penetrate the material's interior, resulting in the surface layer degrading first while the interior retains its network structure, macroscopically manifested as "partial degradation." Simultaneously, different formulations can achieve degradation rates ranging from rapid to slow, meeting the application requirements of different molding thicknesses, structural complexities, and demolding rates.

[0069] When the UV-curable film of the recyclable sacrificial resin in Example 1 is completely dissolved in the degradation solution, and the temperature of the mixed solution is lowered to room temperature, linear molecular chains precipitate out. After washing and drying, a white solid is obtained. The dried white solid can then be hot-pressed into shape, such as... Figure 4 As shown, the physical and chemical recycling of UV-cured films is achieved, and the recycled linear PMMA can be reused.

[0070] In Examples 4-5, the UV-curable films formed from the recyclable sacrificial resin were completely dissolved in the degradation solution. After the temperature of the mixed solution was lowered to room temperature, the linear polymer in the mixed solution was recovered by vacuum distillation. After washing and drying, a white solid was obtained. The dried white solid could be hot-pressed again to realize the degradation and closed-loop recycling of the sacrificial resin.

[0071] The recyclable sacrificial resin prepared in Example 5 was used to print a blue sample with a complete structure and clear details using a commercial DLP 3D printer. The sample was imported with a three-dimensional digital model (including the World Expo logo, a body-centered cubic lattice, and an owl model). Figure 5 As shown, the sacrificial resin of the present invention exhibits uniform shrinkage and stable cross-linking network formation during the curing process, enabling precise replication of the design details of the three-dimensional digital model. This effectively avoids problems such as collapse, deformation, and loss of details that are prone to occur in the printing of complex structures, and can meet the molding requirements of complex 3D printed products (such as precision parts, personalized structural parts, biomimetic models, etc.), especially suitable for complex configuration printing scenarios that require sacrificial support structures.

[0072] In addition to directly printing target structural components, the recyclable sacrificial resin of this invention can also be used to construct female mold structures that provide support, and to prepare complex hollow or suspended 3D parts. After obtaining the female mold structure through 3D printing, the prepolymer to be molded is injected into the female mold and cured to obtain a complex 3D part; subsequently, the entire 3D part is placed in an acidic degradation solution to trigger the degradation of the female mold material, ultimately obtaining the structurally complete target part. The above results demonstrate that the recyclable sacrificial resin of this invention can be used to prepare molded products with excellent mechanical properties and intricate complex structures through a combination of female mold printing and controlled degradation.

[0073] Therefore, this invention employs the above-mentioned method for preparing, applying, chemically degrading, and recycling a recyclable sacrificial resin. By introducing a biodegradable functional monomer containing dynamic imine bonds, a sacrificial resin that can be photocured, has good mechanical properties, and can achieve controllable chemical degradation and efficient physical recycling under mild conditions has been successfully prepared. This resin shows great application potential in the field of support for complex structure 3D printing and in sustainable material recycling.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a recyclable sacrificial resin, characterized in that: Includes the following steps: S1. Synthesis of vanillin-based acrylate molecules: Vanillin derivatives and acrylic acid derivatives are added to an organic solvent at a molar ratio of hydroxyl group in vanillin derivative to acid anhydride or acyl chloride in acrylic acid derivative of 1:(0.9-1.3), and reacted at 0-80℃ for 4-48h. After purification, vanillin-based acrylate molecules are obtained. S2. Synthesis of biodegradable dynamic crosslinking agent: Add polyamine and vanillin acrylate molecules from S1 to an organic solvent at a molar ratio of 1:(0.8-1.2) of amine groups to aldehyde groups of vanillin acrylate molecules, react at 20-80℃ for 4-24h, remove the organic solvent, and obtain the biodegradable dynamic crosslinking agent. S3. Preparation of sacrificial resin: The acrylate monomer, the biodegradable dynamic crosslinking agent of S2, the ultraviolet photoinitiator and the colorant are thoroughly mixed in a molar ratio of 100:(0.5-5):(1-4):(0-0.01) to obtain a recyclable sacrificial resin.

2. The method for preparing a recyclable sacrificial resin according to claim 1, characterized in that: The vanillin derivatives in S1 include one or more of the following: vanillin, eugenol, isovanthanin, ethyl vanillin, o-vanillin, 2-hydroxy-5-methoxybenzaldehyde, 2-hydroxy-4-methoxybenzaldehyde, 3-methyl-4-hydroxybenzaldehyde, m-hydroxybenzaldehyde, 2,3-dihydroxybenzaldehyde, 2,4-dihydroxybenzaldehyde, 3,4-dihydroxybenzaldehyde, 3,5-dihydroxybenzaldehyde, 4-hydroxy-3,5-dimethylbenzaldehyde, 2,3,4-trihydroxybenzaldehyde, 2,4,5-trihydroxybenzaldehyde, 2,4,6-trihydroxybenzaldehyde, 2-hydroxy-5-nitrobenzaldehyde, 2-bromo-5-hydroxybenzaldehyde, 3-bromo-4-hydroxybenzaldehyde, 2-chloro-6-hydroxybenzaldehyde, 3-chloro-2-hydroxybenzaldehyde, and 3-chloro-4-hydroxybenzaldehyde; Acrylic acid derivatives include one or more of acrylic anhydride, methacrylic anhydride, acryloyl chloride, methacryloyl chloride, 3,3'-dimethylacryloyl chloride, and crotonyl chloride.

3. The method for preparing a recyclable sacrificial resin according to claim 1, characterized in that: The polyamines in S2 include one or more of the following: ethylenediamine, propylenediamine, butyldiamine, pentanediamine, hexanediamine, poly(ethylene glycol)diamine, 2,2′-oxydiethylamine, 1,8-diamino-3,6-dioxaoctane, 4,4′-diaminodicyclohexylmethane, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 1,4-diaminenaphthalene, o-xylenediamine, 2-methyl-m-phenylenediamine, 2,2-dimethyl-1,3-propanediamine, 2,5-dimethyl-1,4-phenylenediamine, 2,3,5,6-tetramethyl-p-phenylenediamine, 2-nitro-1,4-phenylenediamine, 1,4-bis(3-aminopropoxy)butane, diethylenetriamine, tris(2-aminoethyl)amine, and N,N′-di(2-aminoethyl)-1,3-propanediamine.

4. The method for preparing a recyclable sacrificial resin according to claim 1, characterized in that: The organic solvents in S1 and S2 include one or more of the following: dichloromethane, trichloromethane, tetrahydrofuran, ethyl acetate, acetone, toluene, xylene, chloroform, methanol, ethanol, isopropanol, n-butanol, diethyl ether, acetonitrile, N,N-dimethylformamide, and dimethyl sulfoxide.

5. The method for preparing a recyclable sacrificial resin according to claim 1, characterized in that: S3 contains one or more of the following acrylate monomers: methyl methacrylate, ethyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, 4-acryloylmorpholine, methyl acrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, and ethylene glycol dimethacrylate. The ultraviolet photoinitiator includes one or more of 2-hydroxy-2-methylphenylpropanone, Irgacure 819, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, benzoin dimethyl ether, and 1-hydroxycyclohexylphenyl ketone; The colorants include one or more of Sudan I, Sudan II, Sudan III, Sudan IV, Solvent Blue 35, Solvent Blue 59, and Transparent Blue 2N.

6. A recyclable sacrificial resin, characterized in that: It is prepared by the method for preparing a recyclable sacrificial resin according to any one of claims 1-5.

7. The application of the recyclable sacrificial resin according to claim 6, characterized in that: Applications in 3D printing.

8. A chemical degradation method for a recyclable sacrificial resin as described in claim 6, characterized in that: 3D printed parts made of recyclable sacrificial resin are immersed in a degradation solution and treated at 40-90°C for 3-72 hours.

9. The chemical degradation method for a recyclable sacrificial resin according to claim 8, characterized in that: The degradation solution is a mixture of organic solvent, deionized water, acid or base, with a pH of 1-11; Organic solvents include one or more of methanol, ethanol, tetrahydrofuran, dichloromethane, chloroform, tetrahydrofuran, ethyl acetate, acetone, toluene, xylene, chloroform, isopropanol, n-butanol, diethyl ether, acetonitrile, N,N-dimethylformamide, and dimethyl sulfoxide; acids include one or more of hydrochloric acid, sulfuric acid, acetic acid, and nitric acid; and bases include one or more of sodium hydroxide, potassium hydroxide, and magnesium hydroxide.

10. A method for recycling and reusing sacrificial resin, characterized in that: The recyclable sacrificial resin is degraded by the chemical degradation method according to any one of claims 8-9. After the degraded mixed solution is cooled to room temperature, thermoplastic resin is precipitated. After washing and drying, a white solid is obtained. The dried white solid is recycled for hot pressing molding.

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