Dual photo-thermal curing 3D printing polyurethane acrylate photosensitive resin and preparation method thereof

Abstract

The invention discloses dual photo-thermal curing 3D printing polyurethane acrylate photosensitive resin and a preparation method thereof, and belongs to the technical field of 3D printing manufacturing. The preparation method comprises the following steps: carrying out a reaction on dicyclomethane diisocyanate, 1, 5-pentanediol and a catalyst to prepare a polyurethane oligomer; then reacting with methyl ethyl ketoxime to prepare a polyurethane prepolymer sealed by isoacid radicals; finally, mixing and stirring with a cross-linking agent and zinc dimethacrylate to obtain a component A; methyl methacrylate, 1, 6-hexanediol dienoic acid ester and trimethylolpropane triacrylate are mixed and stirred, and a component B is prepared; the component A and the component B, the photoinitiator, the flatting agent and the polymerization inhibitor are mixed and stirred, and the coating is prepared. Through dual photo-thermal curing effects, an interpenetrating cross-linked network structure is formed, the toughness and impact resistance of a product are effectively improved while rapid curing is performed, the toughness and modulus are reduced, and the problem that low-modulus and high-elasticity products are difficult to prepare from existing DLP resin is solved.

Description

Technical Field

[0001] This invention relates to the field of 3D printing manufacturing technology, specifically to a dual photothermal curing 3D printing polyurethane acrylate photosensitive resin and its preparation method. Background Technology

[0002] Digital light processing (DLP) technology has been widely used in rapid prototyping and functional parts manufacturing due to its high precision and efficiency. DLP technology uses a surface light source to project liquid photosensitive resin, causing it to selectively cure under specific wavelengths of light, building up layer by layer. To meet printing efficiency requirements, DLP resin must be able to cure rapidly within an extremely short single-layer exposure time.

[0003] To achieve this rapid curing goal, existing DLP resin formulations typically rely on introducing a large number of highly functional (e.g., bifunctional, trifunctional, or even higher functionality) reactive monomers or oligomers. These monomers, under photoinitiation, can provide multiple reaction sites, rapidly forming a three-dimensional network structure, thus significantly increasing the curing speed. However, while this "multi-site, fast-reaction" mechanism leads to highly efficient molding, it also directly results in an extremely high crosslinking density in the resin system. This high crosslinking density makes the polymer network structure dense and rigid, severely restricting the mobility of molecular chain segments. Macroscopically, this manifests as an increase in Young's modulus and a significant decrease in elongation at break and toughness. Ultimately, the cured product often exhibits high brittleness and poor impact resistance, making it difficult to obtain molded parts with low modulus, high elasticity, and other rubber-like properties. This greatly limits the application of DLP technology in high-end fields such as flexible devices and elastomers.

[0004] Therefore, developing polymer materials with complex, synergistic network structures has become a cutting-edge research direction. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a dual photothermal curing 3D printing polyurethane acrylate photosensitive resin and its preparation method. This addresses the issues that existing DLP resins, in order to achieve rapid curing, typically contain a large number of high-functionality (e.g., bifunctional, trifunctional) monomers, resulting in high crosslinking density, which is detrimental to obtaining low modulus and high elasticity. Rapid reactions and multi-site reactions can quickly achieve high crosslinking density, but at this point, the chain network structure becomes denser, molecular chain movement is restricted, leading to brittle materials, decreased toughness (elongation at break) and impact resistance, and the inability to obtain highly elastic products.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A first aspect of the present invention provides a method for preparing a dual photothermal curing 3D printing polyurethane acrylate photosensitive resin, comprising the following steps: S1. First, react dicyclomethane diisocyanate, 1,5-pentanediol and catalyst to prepare polyurethane oligomers; S2. The polyurethane oligomer obtained in S1 is reacted with methyl ethyl ketone oxime to prepare an isobaric acid-blocked polyurethane prepolymer. S3. Mix and stir the isobaric acid-blocked polyurethane prepolymer obtained in S2, the crosslinking agent and zinc dimethacrylate to obtain component A polyurethane prepolymer; S4. Methyl methacrylate, 1,6-hexanediol diallylate and trimethylolpropane triacrylate are mixed and stirred to obtain component B acrylic resin prepolymer; S5. Mix and stir the polyurethane prepolymer of component A obtained in S3, the acrylic resin prepolymer of component B obtained in S4, the photoinitiator, the leveling agent and the polymerization inhibitor to obtain the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin.

[0007] The beneficial effects of this invention are as follows: This invention uses cyanate ester compounds as the main component of the polyurethane prepolymer in component A, and forms a high-temperature reversible isobaric acid-blocked polyurethane prepolymer through methyl ethyl ketone oxime, effectively ensuring the stability of the material. This allows for the formation of a precise network structure with the added crosslinking agent mocha during thermosetting. Zinc dimethacrylate is used as an ionic crosslinking point to increase the degree of crosslinking. A second crosslinking network structure with double reinforcement is formed through intermolecular urea bond covalent crosslinking and intermolecular chain ionic crosslinking. Three different acrylic monomers, respectively serving as hard-segment monomers, soft-segment monomers, and high-crosslinking-density monomers, are used as the main components of the acrylic resin prepolymer in component B. During photocuring, a heterogeneous but interconnected and mutually reinforcing complex network structure is formed through the monomer configuration, chain mobility, and steric hindrance among the three monomers, providing a basic framework structure for the subsequent thermosetting preparation of the second crosslinking network structure. The dual photothermal curing 3D printing polyurethane acrylate photosensitive resin obtained by this invention can be cured and prepared into products through a combination of photocuring 3D printing technology and thermosetting technology. The resulting product has a dense structure and excellent mechanical properties.

[0008] Furthermore, the molar ratio of the isocyanate group of dicyclomethane diisocyanate and the hydroxyl group of 1,5-pentanediol in S1 is (1.2-1.6):1; the catalyst is dibutylene dilaurate; the reaction temperature is 50-70℃, and the reaction time is 1-3 h.

[0009] Furthermore, the molar ratio of isocyanate groups of polyurethane oligomers to amino groups of methyl ethyl ketone oxime in S2 is (1-3):(0.8-1.2); the reaction temperature is 60-90℃ and the reaction time is 30-90 min.

[0010] Furthermore, in S3, the crosslinking agent is mocha, and the addition amount is 1%-10% of the mass of the isobaric acid-blocked polyurethane prepolymer; the addition amount of zinc dimethacrylate is 1%-10% of the mass of the isobaric acid-blocked polyurethane prepolymer; the mixing temperature is 30-50℃, the stirring speed is 300-700 rpm, and the stirring time is 1-5 h.

[0011] The beneficial effects of adopting the above-mentioned further technical solution are as follows: The present invention constructs a second crosslinking network structure using isobaric acid-blocked polyurethane prepolymer, mocha, and zinc dimethacrylate as the main raw materials. While forming a precise crosslinking network structure with the crosslinking agent mocha, the added zinc dimethacrylate serves as an ionic crosslinking point to increase the degree of crosslinking. Through intermolecular urea bond covalent crosslinking and intermolecular chain ionic crosslinking, a doubly reinforced second crosslinking network structure is formed, giving the final product superior mechanical properties and density.

[0012] Furthermore, the mass ratio of methyl methacrylate, 1,6-hexanediol diallylate, and trimethylolpropane triacrylate in S4 is (1-2):(1-2):(1-2); the mixing speed is 100-500 rpm, and the time is 1-5 h.

[0013] The beneficial effects of adopting the above-mentioned further technical solution are as follows: By selecting three different acrylic monomers as hard segment monomers, soft segment monomers and high crosslinking density monomers respectively, and by strictly controlling the ratio parameters between the three monomers, the monomer configuration, chain mobility and steric hindrance of the three monomers are mutually constrained, forming a heterogeneous but interconnected and mutually reinforcing complex network. During the photocuring process, a basic framework structure and constraint force are formed, which is beneficial to the formation of a second crosslinking network structure during the subsequent thermocuring process.

[0014] Furthermore, in S5, the mass ratio of component A (polyurethane prepolymer) to component B (acrylic resin prepolymer) is (80-100):(30-50); the amount of photoinitiator added is 1%-5% of the total prepolymer mass, the amount of leveling agent added is 0.5%-2% of the total prepolymer mass, the amount of defoamer added is 0.5%-2% of the total prepolymer mass, and the amount of polymerization inhibitor added is 1%-5%; the mixing speed is 400-800 rpm, and the time is 1-5 h.

[0015] The beneficial effects of adopting the above-mentioned further technical solution are as follows: By strictly controlling the distribution ratio of component A and component B, component B serves as both a provider of the first cross-linked network structure and a diluent added to the material system. It interpenetrates with the second cross-linked network structure formed by component A to form a dense and stable structure. This avoids the technical problems of material system performance imbalance and high system viscosity caused by improper design of the interpenetrating network cross-linked structure, which is not conducive to the DLP photopolymerization 3D printing molding process.

[0016] Preferably, the amount of photoinitiator added is 3% of the total prepolymer mass, the amount of leveling agent added is 1% of the total prepolymer mass, the amount of defoamer added is 1% of the total prepolymer mass, and the amount of polymerization inhibitor added is 3%; the mixing speed is 600 rpm and the time is 3 h.

[0017] Furthermore, the photoinitiator is TPO-L; the leveling agent is a modified polysiloxane leveling agent; the defoamer is a polyacrylate defoamer; and the polymerization inhibitor is MEHQ polymerization inhibitor.

[0018] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: By specifically selecting modified polysiloxane leveling agents and polyacrylate defoamers, the present invention can better control the rheological properties of the material system, the compatibility of each component and the interfacial contact, and form a synergistic effect with component A and component B, ensuring that the two cross-linked network structures can penetrate each other uniformly and effectively.

[0019] In a second aspect, the present invention provides a dual photothermal curing 3D printing polyurethane acrylate photosensitive resin, which is prepared by the above-described preparation method.

[0020] In a third aspect, the present invention provides a 3D printed product made using the above-mentioned dual photothermal curing 3D printing polyurethane acrylate photosensitive resin.

[0021] A fourth aspect of the present invention provides a method for preparing the above-mentioned 3D printed product, comprising the following steps: The 3D printed product is obtained by using the above-mentioned dual photothermal curing 3D printing polyurethane acrylate photosensitive resin as raw material in a photopolymerization printing equipment, followed by high-temperature curing.

[0022] The beneficial effects of the present invention are as follows: the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin prepared by the present invention has a fast curing speed during dual photothermal curing preparation, and the product maintains excellent mechanical properties. At the same time, it has rubber-like properties such as low modulus and high elasticity, which expands the application of DLP technology in high-end fields such as flexible devices and elastomers.

[0023] Furthermore, the parameters for 3D printing are: laser power density of 10-15 mW / cm². 2The single-layer exposure time is 5-7 seconds, and the printing layer thickness is 0.1-0.2 mm.

[0024] Furthermore, the high-temperature curing temperature is 100-130℃, and the time is 10-12 hours.

[0025] The present invention has the following beneficial effects: 1. The preparation process of the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin of this invention is simple and fast, suitable for industrial production and industrial application. Different performance requirements can be met by adjusting the raw material ratio, and it has broad application prospects.

[0026] 2. The dual photothermal curing 3D printing polyurethane acrylate photosensitive resin obtained in this invention forms a first cross-linked network structure through the interaction between the three different acrylic monomers in component B, which are mutually interpenetrating and reinforcing. This first cross-linked network structure is then synergistically prepared with a second cross-linked network structure, using polyurethane oligomers as the main material and methyl ethyl ketone oxime, mocha, and zinc dimethacrylate as auxiliary materials, through high-temperature curing. The two network structures, through uniform and effective interpenetration, form a stable three-dimensional structure, resulting in a product with excellent mechanical properties, structural stability, and density.

[0027] 3. The dual photothermal curing 3D printing polyurethane acrylate photosensitive resin prepared by this invention can combine the DLP photocuring 3D printing molding process with the high-temperature curing process to achieve rapid curing while improving the toughness and impact resistance of the cured product and reducing the toughness and modulus of the product. This solves the problem that existing DLP resins are difficult to prepare low-modulus, high-elasticity rubber-like products, expands the application of DLP technology in high-end fields such as flexible devices and elastomers, and has broad application prospects. Attached Figure Description

[0028] Figure 1 Stress-strain curves of the 3D printed products obtained in Example 1 and Comparative Examples 1-2 are shown. Figure 2 The cross-sectional SEM image of the 3D printed product obtained in Example 1; Figure 3 To obtain a cross-sectional SEM image of the 3D printed product for Comparative Example 1; Figure 4 SEM images of the cross-section of the 3D printed product were obtained for Comparative Example 2. Detailed Implementation

[0029] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0030] Example 1: A method for preparing a dual photothermal curing 3D printing polyurethane acrylate photosensitive resin includes the following steps: S1. Preparation of polyurethane oligomer PU Dicyclohexylmethane diisocyanate (HMDI) and dibutylene dilaurate (catalyst added at 1 wt% of HMDI) were added to a four-necked flask equipped with a mechanical stirrer, thermometer, constant pressure dropping funnel, and condenser. 1,5-pentanediol was added dropwise to the four-necked flask over 30 min using the constant pressure dropping funnel. The mixture was kept at 60 °C and stirred for 2 h to obtain polyurethane oligomer PU. The molar ratio of isocyanate groups in dicyclohexylmethane diisocyanate to hydroxyl groups in 1,5-pentanediol was 1.4:1.

[0031] S2. Preparation of isobaric acid-blocked polyurethane prepolymer MPU At 75°C, methyl ethyl ketone oxime was slowly added dropwise to a three-necked flask containing the polyurethane oligomer PU obtained from S1 using a constant flow pump under an argon atmosphere. The mixture was stirred at 500 rpm for 1 hour, then cooled and discharged to obtain an isocyanate-blocked polyurethane prepolymer, which was then sealed and stored in the dark. The molar ratio of the amino groups in methyl ethyl ketone oxime to the isocyanate groups in polyurethane oligomer PU was 1:2.

[0032] Preparation of S3 and A component polyurethane prepolymer MPU-Zn Weigh the MPU obtained from S2, add 6 wt% of crosslinking agent Moca (MOCA) and 6 wt% of zinc dimethacrylate, stir at 40℃ and 500 rpm for 3 h, mix evenly, and obtain component A polyurethane prepolymer MPU-Zn.

[0033] Preparation of S4 and B component acrylic resin prepolymer MHT Methyl methacrylate (MMA), 1,6-hexanediol diacrylate (HDDA) and trimethylolpropane triacrylate (TMPTMA) were weighed and mixed in a mass ratio of 1:1:1 and stirred thoroughly at 300 rpm for 3 h to obtain component B acrylic resin prepolymer MHT.

[0034] S5. Preparation of Dual Photothermal Curing 3D Printing Polyurethane Acrylic Photosensitive Resin The polyurethane prepolymer MPU-Zn obtained from S3 and the acrylic resin prepolymer MHT obtained from S4 were mixed at a mass ratio of 100:30. At the same time, 3 wt% of the total prepolymer mass of photoinitiator TPO-L, 1 wt% of modified polysiloxane leveling agent (synde-121 modified silicone leveling agent, Zhuhai Xiande New Material Technology Co., Ltd.), 1 wt% of polyacrylate defoamer (polyacrylate defoamer CK-4007, Tianjin Gaotian New Material Technology Co., Ltd.), and 3 wt% of MEHQ polymerization inhibitor were added to the system. The mixture was stirred at 600 rpm for 3 h. After being mixed evenly, the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin MPU-Zn-MHT was obtained and stored in a light-proof and sealed container.

[0035] A method for preparing a 3D printed product includes the following steps: S6, 3D printing preparation Using a DLP photopolymerization 3D printing device, the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin obtained from S5 was imported into the device, and the printing parameters were selected as follows: laser power density 12 mW / cm². 2 With a single-layer exposure time of 6 s and a printing layer thickness of 0.15 mm, the three-dimensional structural sample is obtained by layering the layers one by one through bottom exposure.

[0036] S7, High Temperature Curing The resin on the surface of the sample printed by S7 photopolymerization was wiped clean, and then placed in a vacuum drying oven for high-temperature curing at 115°C for 11 hours. After high-temperature curing, the 3D printed product was obtained.

[0037] Example 2: A method for preparing a dual photothermal curing 3D printing polyurethane acrylate photosensitive resin includes the following steps: S1. Preparation of polyurethane oligomer PU Dicyclohexylmethane diisocyanate (HMDI) and dibutylene dilaurate (catalyst added at 1 wt% of HMDI) were added to a four-necked flask equipped with a mechanical stirrer, thermometer, constant pressure dropping funnel, and condenser. 1,5-pentanediol was added dropwise to the four-necked flask over 30 min using the constant pressure dropping funnel. The mixture was kept at a constant temperature of 60 °C and stirred for 2 h to obtain polyurethane oligomer PU. The molar ratio of isocyanate groups in dicyclohexylmethane diisocyanate to hydroxyl groups in 1,5-pentanediol was 1.2:1.

[0038] S2. Preparation of isobaric acid-blocked polyurethane prepolymer MPU At 75°C, methyl ethyl ketone oxime was slowly added dropwise to a three-necked flask containing the polyurethane oligomer PU obtained from S1 using a constant flow pump under an argon atmosphere. The mixture was stirred at 500 rpm for 1 hour, then cooled and discharged to obtain an isocyanate-blocked polyurethane prepolymer, which was then sealed and stored in the dark. The molar ratio of the amino groups in methyl ethyl ketone oxime to the isocyanate groups in polyurethane oligomer PU was 1:2.

[0039] Preparation of S3 and A component polyurethane prepolymer MPU-Zn Weigh the MPU obtained from S2, add 6 wt% of crosslinking agent Moca (MOCA) and 6 wt% of zinc dimethacrylate, stir at 40℃ and 500 rpm for 3 h, mix evenly, and obtain component A polyurethane prepolymer MPU-Zn.

[0040] Preparation of S4 and B component acrylic resin prepolymer MHT Methyl methacrylate (MMA), 1,6-hexanediol diacrylate (HDDA) and trimethylolpropane triacrylate (TMPTMA) were weighed and mixed in a mass ratio of 1:1.5:2. The mixture was stirred at 300 rpm for 3 h to obtain component B acrylic resin prepolymer MHT.

[0041] S5. Preparation of Dual Photothermal Curing 3D Printing Polyurethane Acrylic Photosensitive Resin The polyurethane prepolymer MPU-Zn obtained from S3 and the acrylic resin prepolymer MHT obtained from S4 were mixed at a mass ratio of 90:40. At the same time, 3 wt% of the total prepolymer mass of photoinitiator TPO-L, 1 wt% of modified polysiloxane leveling agent (synde-121 modified silicone leveling agent, Zhuhai Xiande New Material Technology Co., Ltd.), 1 wt% of polyacrylate defoamer (polyacrylate defoamer CK-4007, Tianjin Gaotian New Material Technology Co., Ltd.), and 3 wt% of MEHQ polymerization inhibitor were added to the system. The mixture was stirred at 600 rpm for 3 h. After being mixed evenly, the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin MPU-Zn-MHT was obtained and stored in a light-proof and sealed container.

[0042] A method for preparing a 3D printed product includes the following steps: S6, 3D printing preparation Using a DLP photopolymerization 3D printing device, the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin obtained from S5 was imported into the device, and the printing parameters were selected as follows: laser power density 12 mW / cm². 2 With a single-layer exposure time of 6 s and a printing layer thickness of 0.15 mm, the three-dimensional structural sample is obtained by layering the layers one by one through bottom exposure.

[0043] S7, High Temperature Curing The resin on the surface of the sample printed by S7 photopolymerization was wiped clean, and then placed in a vacuum drying oven for high-temperature curing at 115°C for 11 hours. After high-temperature curing, the 3D printed product was obtained.

[0044] Example 3: A method for preparing a dual photothermal curing 3D printing polyurethane acrylate photosensitive resin includes the following steps: S1. Preparation of polyurethane oligomer PU Dicyclohexylmethane diisocyanate (HMDI) and dibutylene dilaurate (catalyst added at 1 wt% of HMDI) were added to a four-necked flask equipped with a mechanical stirrer, thermometer, constant pressure dropping funnel, and condenser. 1,5-pentanediol was added dropwise to the four-necked flask over 30 min using the constant pressure dropping funnel. The mixture was kept at a constant temperature of 60 °C and stirred for 2 h to obtain polyurethane oligomer PU. The molar ratio of isocyanate groups in dicyclohexylmethane diisocyanate to hydroxyl groups in 1,5-pentanediol was 1.6:1.

[0045] S2. Preparation of isobaric acid-blocked polyurethane prepolymer MPU At 75°C, methyl ethyl ketone oxime was slowly added dropwise to a three-necked flask containing the polyurethane oligomer PU obtained from S1 using a constant flow pump under an argon atmosphere. The mixture was stirred at 500 rpm for 1 hour, then cooled and discharged to obtain an isocyanate-blocked polyurethane prepolymer, which was then sealed and stored in the dark. The molar ratio of the amino groups in methyl ethyl ketone oxime to the isocyanate groups in polyurethane oligomer PU was 1:2.

[0046] Preparation of S3 and A component polyurethane prepolymer MPU-Zn Weigh the MPU obtained from S2, add 6 wt% of crosslinking agent Moca (MOCA) and 6 wt% of zinc dimethacrylate, stir at 40℃ and 500 rpm for 3 h, mix evenly, and obtain component A polyurethane prepolymer MPU-Zn.

[0047] Preparation of S4 and B component acrylic resin prepolymer MHT Methyl methacrylate (MMA), 1,6-hexanediol diacrylate (HDDA) and trimethylolpropane triacrylate (TMPTMA) were weighed and mixed in a mass ratio of 2:1:1. The mixture was stirred at 300 rpm for 3 h to obtain component B acrylic resin prepolymer MHT.

[0048] S5. Preparation of Dual Photothermal Curing 3D Printing Polyurethane Acrylic Photosensitive Resin The polyurethane prepolymer MPU-Zn obtained from S3 and the acrylic resin prepolymer MHT obtained from S4 were mixed at a mass ratio of 80:50. At the same time, 3 wt% of the total prepolymer mass of photoinitiator TPO-L, 1 wt% of modified polysiloxane leveling agent (synde-121 modified silicone leveling agent, Zhuhai Xiande New Material Technology Co., Ltd.), 1 wt% of polyacrylate defoamer (polyacrylate defoamer CK-4007, Tianjin Gaotian New Material Technology Co., Ltd.), and 3 wt% of MEHQ polymerization inhibitor were added to the system. The mixture was stirred at 600 rpm for 3 h. After uniform mixing, the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin MPU-Zn-MHT was obtained and stored in a light-proof and sealed container.

[0049] A method for preparing a 3D printed product includes the following steps: S6, 3D printing preparation Using a DLP photopolymerization 3D printing device, the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin obtained from S5 was imported into the device, and the printing parameters were selected as follows: laser power density 12 mW / cm². 2 With a single-layer exposure time of 6 s and a printing layer thickness of 0.15 mm, the three-dimensional structural sample is obtained by layering the layers one by one through bottom exposure.

[0050] S7, High Temperature Curing The resin on the surface of the sample printed by S7 photopolymerization was wiped clean, and then placed in a vacuum drying oven for high-temperature curing at 115°C for 11 hours. After high-temperature curing, the 3D printed product was obtained.

[0051] Comparative Example 1: A method for preparing a dual photothermal curing 3D printing polyurethane acrylate photosensitive resin includes the following steps: S1. Preparation of polyurethane oligomer PU Dicyclohexylmethane diisocyanate (HMDI) and dibutylene dilaurate (catalyst added at 1 wt% of HMDI) were added to a four-necked flask equipped with a mechanical stirrer, thermometer, constant pressure dropping funnel, and condenser. 1,5-pentanediol was added dropwise to the four-necked flask over 30 min using the constant pressure dropping funnel. The mixture was kept at 60 °C and stirred for 2 h to obtain polyurethane oligomer PU. The molar ratio of isocyanate groups in dicyclohexylmethane diisocyanate to hydroxyl groups in 1,5-pentanediol was 1.4:1.

[0052] S2. Preparation of isobaric acid-blocked polyurethane prepolymer MPU At 75°C, methyl ethyl ketone oxime was slowly added dropwise to a three-necked flask containing the polyurethane oligomer PU obtained from S1 using a constant flow pump under an argon atmosphere. The mixture was stirred at 500 rpm for 1 hour, then cooled and discharged to obtain an isocyanate-blocked polyurethane prepolymer, which was then sealed and stored in the dark. The molar ratio of the amino groups in methyl ethyl ketone oxime to the isocyanate groups in polyurethane oligomer PU was 1:2.

[0053] Preparation of S3 and A component polyurethane prepolymer MPU Weigh the MPU obtained from S2, add 6 wt% of crosslinking agent Moca (MOCA), stir at 40℃ and 500 rpm for 3 hours, mix evenly, and obtain component A polyurethane prepolymer MPU.

[0054] Preparation of S4 and B component acrylic resin prepolymer MHT Methyl methacrylate (MMA), 1,6-hexanediol diacrylate (HDDA) and trimethylolpropane triacrylate (TMPTMA) were weighed and mixed in a mass ratio of 1:1:1 and stirred thoroughly at 300 rpm for 3 h to obtain component B acrylic resin prepolymer MHT.

[0055] S5. Preparation of Dual Photothermal Curing 3D Printing Polyurethane Acrylic Photosensitive Resin The polyurethane prepolymer MPU (component A) obtained in S3 and the acrylic resin prepolymer MHT (component B) obtained in S4 were mixed at a mass ratio of 100:30. At the same time, 3 wt% of the total prepolymer mass of photoinitiator TPO-L, 1 wt% of modified polysiloxane leveling agent (synde-121 modified silicone leveling agent, Zhuhai Xiande New Material Technology Co., Ltd.), 1 wt% of polyacrylate defoamer (polyacrylate defoamer CK-4007, Tianjin Gaotian New Material Technology Co., Ltd.), and 3 wt% of MEHQ polymerization inhibitor were added to the system. The mixture was stirred at 600 rpm for 3 h. After uniform mixing, the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin MPU-MHT was obtained and stored in a light-proof and sealed container.

[0056] A method for preparing a 3D printed product includes the following steps: S6, 3D printing preparation Using a DLP photopolymerization 3D printing device, the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin obtained from S5 was imported into the device, and the printing parameters were selected as follows: laser power density 12 mW / cm². 2 With a single-layer exposure time of 6 s and a printing layer thickness of 0.15 mm, the three-dimensional structural sample is obtained by layering the layers one by one through bottom exposure.

[0057] S7, High Temperature Curing The resin on the surface of the sample printed by S7 photopolymerization was wiped clean, and then placed in a vacuum drying oven for high-temperature curing at 115°C for 11 hours. After high-temperature curing, the 3D printed product was obtained.

[0058] Comparative Example 2: A method for preparing a dual photothermal curing 3D printing polyurethane acrylate photosensitive resin includes the following steps: S1. Preparation of polyurethane oligomer PU Dicyclohexylmethane diisocyanate (HMDI) and dibutylene dilaurate (catalyst added at 1 wt% of HMDI) were added to a four-necked flask equipped with a mechanical stirrer, thermometer, constant pressure dropping funnel, and condenser. 1,5-pentanediol was added dropwise to the four-necked flask over 30 min using the constant pressure dropping funnel. The mixture was kept at 60 °C and stirred for 2 h to obtain polyurethane oligomer PU. The molar ratio of isocyanate groups in dicyclohexylmethane diisocyanate to hydroxyl groups in 1,5-pentanediol was 1.4:1.

[0059] S2. Preparation of isobaric acid-blocked polyurethane prepolymer MPU At 75°C, methyl ethyl ketone oxime was slowly added dropwise to a three-necked flask containing the polyurethane oligomer PU obtained from S1 using a constant flow pump under an argon atmosphere. The mixture was stirred at 500 rpm for 1 hour, then cooled and discharged to obtain an isocyanate-blocked polyurethane prepolymer, which was then sealed and stored in the dark. The molar ratio of the amino groups in methyl ethyl ketone oxime to the isocyanate groups in polyurethane oligomer PU was 1:2.

[0060] Preparation of S3 and A component polyurethane prepolymer MPU-Zn Weigh the MPU obtained from S2, add 6 wt% of crosslinking agent Moca (MOCA) and 6 wt% of zinc dimethacrylate, stir at 40℃ and 500 rpm for 3 h, mix evenly, and obtain component A polyurethane prepolymer MPU-Zn.

[0061] Preparation of S4 and B component acrylic resin prepolymer MMA Methyl methacrylate (MMA) was used as the prepolymer of acrylic resin in component B.

[0062] S5. Preparation of Dual Photothermal Curing 3D Printing Polyurethane Acrylic Photosensitive Resin The polyurethane prepolymer MPU-Zn obtained from S3 and the acrylic resin prepolymer MMA obtained from S4 were mixed at a mass ratio of 100:30. At the same time, 3 wt% of the total prepolymer mass of photoinitiator TPO-L, 1 wt% of modified polysiloxane leveling agent (synde-121 modified silicone leveling agent, Zhuhai Xiande New Material Technology Co., Ltd.), 1 wt% of polyacrylate defoamer (polyacrylate defoamer CK-4007, Tianjin Gaotian New Material Technology Co., Ltd.), and 3 wt% of MEHQ polymerization inhibitor were added to the system. The mixture was stirred at 600 rpm for 3 h. After uniform mixing, the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin MPU-Zn-MMA was obtained and stored in a light-proof and sealed container.

[0063] A method for preparing a 3D printed product includes the following steps: S6, 3D printing preparation Using a DLP photopolymerization 3D printing device, the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin obtained from S5 was imported into the device, and the printing parameters were selected as follows: laser power density 12 mW / cm². 2 With a single-layer exposure time of 6 s and a printing layer thickness of 0.15 mm, the three-dimensional structural sample is obtained by layering the layers one by one through bottom exposure.

[0064] S7, High Temperature Curing The resin on the surface of the sample printed by S7 photopolymerization was wiped clean, and then placed in a vacuum drying oven for high-temperature curing at 115°C for 11 hours. After high-temperature curing, the 3D printed product was obtained.

[0065] Experimental example: The mechanical properties and material cross-sections of the 3D printed products obtained in Example 1 and Comparative Examples 1-2 were characterized by SEM analysis. The experimental results are as follows: Figures 1-4 As shown in Table 1.

[0066] Table 1 Mechanical performance parameters

[0067] According to Table 1 and Figure 1 The mechanical property characterization results show that the 3D printed products prepared by the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin obtained in the embodiments of the present invention have significantly better tensile strength and nominal strain at break than those of Comparative Example 1 and Comparative Example 2.

[0068] according to Figures 2-4The SEM cross-sectional characterization results show that the 3D printed product obtained in Example 1 of this application has a flat and smooth cross-sectional structure with no obvious defects and good density; while the 3D printed products obtained in Comparative Example 1 and Comparative Example 2 have obvious concave / convex structures in their cross-sectional structures and have more defects, indicating that the products have poor density.

[0069] According to the performance comparison of Example 1 and Comparative Example 2, the present invention uses three acrylic monomers to construct the first network crosslinking structure. The three acrylic monomers are respectively used as hard segment monomers, soft segment monomers and high crosslinking density monomers. Through the monomer configuration, chain mobility and steric hindrance between the three monomers, a heterogeneous but interconnected and mutually reinforcing complex network structure is formed. This provides a constraint for the subsequent thermosetting to form the second crosslinking network structure and the columnar framework structure, thereby effectively improving the tensile strength and nominal strain at break of the final product and increasing the density of the final product.

[0070] Based on the performance comparison between Example 1 and Comparative Example 1, it can be seen that the present invention uses methyl ethyl ketone oxime to form a high-temperature reversible isocyanate-blocked polyurethane prepolymer, effectively ensuring the stability of the material. During the thermosetting process, a deblocking reaction occurs at a certain temperature, releasing a large number of isocyanate groups. Zinc dimethacrylate serves as an ionic crosslinking point, synergistically interacting with the crosslinking agent mocha to form a tightly linked network structure again, achieving the preparation of a doubly reinforced second network crosslinking structure. In contrast, Comparative Example 2 lacks zinc dimethacrylate as an ionic crosslinking point, resulting in a lower degree of crosslinking in the crosslinked network structure during thermosetting. It cannot form a doubly reinforced second network crosslinking structure through the synergistic effect of intermolecular urea bond covalent crosslinking and intermolecular chain ionic crosslinking, leading to a decrease in tensile strength and nominal strain at break, and a reduction in density.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a dual photothermal curing 3D printing polyurethane acrylate photosensitive resin, characterized in that, Includes the following steps: S1. First, react dicyclomethane diisocyanate, 1,5-pentanediol and catalyst to prepare polyurethane oligomers; S2. The polyurethane oligomer obtained in S1 is reacted with methyl ethyl ketone oxime to prepare an isobaric acid-blocked polyurethane prepolymer. S3. Mix and stir the isobaric acid-blocked polyurethane prepolymer obtained in S2, the crosslinking agent and zinc dimethacrylate to obtain component A polyurethane prepolymer; S4. Methyl methacrylate, 1,6-hexanediol diallylate and trimethylolpropane triacrylate are mixed and stirred to obtain component B acrylic resin prepolymer; S5. Mix and stir the polyurethane prepolymer of component A obtained in S3, the acrylic resin prepolymer of component B obtained in S4, the photoinitiator, the leveling agent and the polymerization inhibitor to obtain the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin.

2. The preparation method of the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin according to claim 1, characterized in that, The molar ratio of the isocyanate group of dicyclomethane diisocyanate and the hydroxyl group of 1,5-pentanediol in S1 is (1.2-1.6):1; the catalyst is dibutylene dilaurate; the reaction temperature is 50-70℃ and the reaction time is 1-3 h.

3. The preparation method of the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin according to claim 1, characterized in that, The molar ratio of isocyanate groups of the polyurethane oligomer and amino groups of methyl ethyl ketone oxime in S2 is (1-3):(0.8-1.2); the reaction temperature is 60-90℃ and the reaction time is 30-90 min.

4. The preparation method of the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin according to claim 1, characterized in that, In S3, the crosslinking agent is mocha, and the addition amount is 1%-10% of the mass of the isobaric acid-blocked polyurethane prepolymer; the addition amount of zinc dimethacrylate is 1%-10% of the mass of the isobaric acid-blocked polyurethane prepolymer; the mixing temperature is 30-50℃, the stirring speed is 300-700 rpm, and the stirring time is 1-5 h.

5. The method for preparing the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin according to claim 1, characterized in that, The mass ratio of methyl methacrylate, 1,6-hexanediol diallylate, and trimethylolpropane triacrylate in S4 is (1-2):(1-2):(1-2); the mixing speed is 100-500 rpm, and the time is 1-5 h.

6. The preparation method of the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin according to claim 1, characterized in that, The mass ratio of component A (polyurethane prepolymer) to component B (acrylic resin prepolymer) in S5 is (80-100):(30-50); the amount of photoinitiator added is 1%-5% of the total prepolymer mass, the amount of leveling agent added is 0.5%-2% of the total prepolymer mass, the amount of defoamer added is 0.5%-2% of the total prepolymer mass, and the amount of polymerization inhibitor added is 1%-5%; the mixing speed is 400-800 rpm, and the time is 1-5 h.

7. A dual photothermal curing 3D printing polyurethane acrylate photosensitive resin, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. A 3D printed product, characterized in that, It is prepared using the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin as described in claim 7.

9. The method for preparing the 3D printed product according to claim 8, characterized in that, Includes the following steps: The 3D printed product is obtained by using a photopolymerization printing device with the dual photothermal curing 3D printing polyurethane acrylate photosensitive resin as described in claim 7 as the raw material for 3D printing, followed by high-temperature curing.

10. The method for preparing a 3D printed product according to claim 9, characterized in that, The parameters for the 3D printing process are: laser power density of 10-15 mW / cm². 2 The single-layer exposure time is 5-7 seconds, and the printing layer thickness is 0.1-0.2 mm. The high-temperature curing temperature is 100-130℃, and the time is 10-12 h.

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