Polyurethane acrylate oligomer, method for preparing the same, photo-curable material and use thereof

Abstract

The application discloses a kind of polyurethane acrylate oligomer and preparation method thereof, photocuring material and application, belong to high polymer material technical field.The preparation method of polyurethane acrylate oligomer of the application includes the following steps: S1: isocyanate, polyol and catalyst I are mixed, reaction I, and product I is obtained;S2: the product I, blocking agent and catalyst II are mixed, reaction II, product II, i.e., the polyurethane acrylate oligomer is obtained;Wherein, the catalyst I includes organic zirconium;The catalyst II includes organic bismuth.The two kinds of catalysts selected by the application are low in toxicity and environmentally friendly;The prepared photocuring material printing piece has high elastic modulus and high elongation at break, and has excellent performance, and the operation method is simple and easy to operate.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and particularly relates to a polyurethane acrylate oligomer, its preparation method, photocurable material, and applications. Background Technology

[0002] Photopolymer 3D printing technology has gained increasing recognition due to its ability to efficiently and precisely print complex three-dimensional structures. Polyurethane is a type of polymer whose main chain contains urethane characteristic units. Because of its excellent properties, this polymer material is widely used in various fields. Many have attempted to apply polyurethane to photopolymer 3D printing materials, but have not achieved satisfactory results.

[0003] Existing technology discloses a polyurethane photosensitive resin that is first photo-printed and then thermally cured, exhibiting good performance. However, this photosensitive resin consists of two components: they must be stored separately and mixed before use. After mixing the two components, their viscosity gradually increases, rendering them unusable after a few hours. This not only makes the process cumbersome but also easily leads to waste. Traditional photopolymer 3D printing sometimes requires tens to hundreds of hours. Furthermore, industrial-grade photopolymer 3D printers require adding 100-200 liters of photosensitive resin to the resin tank at once, to be used over several months. Therefore, the application of this short-lived two-component photosensitive resin is severely limited.

[0004] Existing technology also discloses a novel two-component, dual-curing resin material for 3D printing. In one embodiment, a curing agent component with end-capping protection is used. Under normal storage conditions, this curing agent component does not react with the photocuring component in the resin material, thereby improving the storage stability of the two-component resin material and reducing material waste. However, in practice, the applicant has found that two-component, dual-curing materials involve multiple components and multiple curing processes, making storage, transportation, and production processes more complex in practical applications, increasing product costs.

[0005] Therefore, developing a material with similar elastic properties, excellent mechanical properties, and simple operation has become a new trend. Summary of the Invention

[0006] In view of this, the present invention provides a polyurethane acrylate oligomer and its preparation method, a photocurable material and its application, the main purpose of which is to solve the technical problems of poor performance and inconvenience of use of photocurable materials.

[0007] On one hand, the present invention provides a method for preparing polyurethane acrylate oligomers, the method comprising the following steps:

[0008] S1: Isocyanate, polyol and catalyst I are mixed and reacted to yield product I;

[0009] S2: The product I, the capping agent and the catalyst II are mixed and reacted to obtain product II, namely the polyurethane acrylate oligomer;

[0010] Catalyst I comprises organozzirconium; catalyst II comprises organobismuth.

[0011] The inventors have discovered that in traditional methods for synthesizing polyurethane acrylate oligomers, large-chain polyether polyols are generally preferred to improve the elasticity of the photocured product, resulting in oligomers with higher viscosity. Furthermore, while the chain extension reaction between diisocyanate and polyol in the first step should theoretically produce long-chain polyurethane prepolymers with -NCO active groups at both ends, in actual preparation, the long-chain polyurethane prepolymers with -NCO active groups at both ends generated first react further with the remaining diol to produce prepolymers with even larger molecular weights. This further increases the viscosity of the polyurethane acrylate oligomers, making subsequent printing more difficult.

[0012] To solve the above-mentioned technical problems, the inventors have innovatively proposed to regulate the activity of the entire reaction process by controlling the different reaction degrees or activities of the first step chain extension reaction and the second step end-capping reaction, while selecting catalysts suitable for the reaction activities of different stages.

[0013] In the first step of this invention, diisocyanate and polyol are selected for chain extension reaction. Catalyst CAT1 (organic zirconium) with slightly lower catalytic activity for polymerization of NCO and OH is selected to avoid excessively vigorous reaction and excessively high proportion of ultra-high molecular weight products. Most of the products are the expected products and medium molecular weight products.

[0014] In the second step of this invention, the end-capping reaction of NCO polyurethane prepolymers at both ends is carried out using catalyst CAT2 (organic bismuth), which has good catalytic activity for end-capping reactions. Since a small amount of diisocyanate and polyol residues remain from the first step reaction, the catalyst CAT2 used in this step can continue to catalyze the reaction of the remaining diisocyanate and polyols, appropriately increasing the proportion of high molecular weight products without causing excessively high viscosity. Therefore, the catalytic activity of CAT2 for the polymerization reaction of NCO and OH in this step can be higher than that of CAT1.

[0015] Both catalysts used in this invention are low-toxicity, environmentally friendly catalysts.

[0016] Optionally, in step S2, when the actual content of isocyanate in product I reaches 0.95 to 1 times its theoretical value, a capping agent and catalyst II are added.

[0017] Optionally, the catalyst I is selected from zirconium isooctanoate and / or zirconium neodecanoate.

[0018] Optionally, the catalyst II is selected from at least one of bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, and bismuth naphthenate.

[0019] Optionally, the molar ratio of the isocyanate to the polyol in step S1 is 1.5 to 2.

[0020] Optionally, the molar ratio of the isocyanate to the polyol is selected from any value of 1.5, 1.6, 1.7, 1.8, 1.9, 2 or any range between two.

[0021] Optionally, the amount of catalyst I in step S1 is 0.01% to 0.1% of the total weight of the isocyanate and the polyol.

[0022] Optionally, the amount of catalyst I is any value or a range between any two of the total weight of the isocyanate and the polyol, which is 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%.

[0023] Optionally, the amount of catalyst II in step S2 is 0.01% to 0.05% of the total weight of the isocyanate and the polyol.

[0024] Optionally, the amount of catalyst II is any value or a range between any two of 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, and 0.05% of the total weight of the isocyanate and the polyol.

[0025] Optionally, the reaction temperature of reaction I is 60℃~80℃; the reaction temperature of reaction II is 70℃~90℃.

[0026] Optionally, the reaction temperature of reaction I is selected from any value of 60°C, 65°C, 70°C, 75°C, 80°C, or any range between two of them.

[0027] Optionally, the reaction time of reaction I is 1 to 3 hours.

[0028] Optionally, the reaction time of reaction I is selected from any value of 1, 1.5, 2, 2.5, 3 or a range between any two, in hours.

[0029] Optionally, the reaction temperature of reaction II is selected from any value of 70°C, 75°C, 80°C, 85°C, 90°C, or any range between two of them.

[0030] Optionally, the reaction time of reaction II is 1 to 3 hours.

[0031] Optionally, the reaction time of reaction II is selected from any value of 1, 1.5, 2, 2.5, 3 or a range between any two, in hours.

[0032] Optionally, the isocyanate is selected from at least one of diisocyanates, polyisocyanates, or derivatives thereof.

[0033] Optionally, the diisocyanate is selected from at least one of isophorone diisocyanate (IPDI), trimethylhexane diisocyanate (TMDI), toluene diisocyanate (TDI), xylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), 4,4-diphenylmethane diisocyanate (MDI), 4,4-dicyclohexylmethane diisocyanate (HMDI), and terephthalic diisocyanate (PPDI).

[0034] Optionally, the polyol is selected from polyether diols.

[0035] Optionally, the polyether diol is selected from at least one of polyethylene glycol diol, polypropylene glycol diol, polytetrahydrofuran ether diol, and polytrimethylene ether diol.

[0036] Optionally, the capping agent is selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

[0037] Optionally, a polymerization inhibitor is also added to reaction II.

[0038] Optionally, the polymerization inhibitor includes p-hydroxyanisole.

[0039] Secondly, embodiments of the present invention provide a polyurethane acrylate oligomer, which is prepared by the above-described preparation method.

[0040] Thirdly, embodiments of the present invention provide a method for preparing a photocurable material, the method comprising: reacting a polyurethane acrylate oligomer, a reactive monomer, and a photoinitiator via reaction III to obtain the photocurable material; wherein the polyurethane acrylate oligomer comprises the aforementioned polyurethane acrylate oligomer.

[0041] Optionally, the reactive monomer is selected from at least one of N-vinylpyrrolidone, N-vinylcaprolactam, N-vinyloxazolidinone, N-vinylmethyloxazolidinone, acryloylmorpholine, isobornyl acrylate, isobornyl methacrylate, and dicyclopentenyl acrylate.

[0042] Optionally, the photoinitiator is selected from at least one of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 2,4,6-trimethylbenzoyl-bis(p-tolyl)phosphine oxide.

[0043] Fourthly, the present invention provides a photocurable material, which is prepared by the above-described preparation method.

[0044] Fifthly, the present invention provides an application of a photocurable material in 3D printing materials, wherein the photocurable material includes the aforementioned photocurable material.

[0045] Sixthly, the present invention provides a 3D printed article, wherein the material of the 3D printed article is the aforementioned photocurable material.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) Step 1: In the chain extension reaction stage of diisocyanate and polyol, this invention selects CAT1 (organozirconium), a catalyst with slightly lower catalytic activity for the polymerization reaction of NCO and OH, so as not to cause the reaction to be too violent and cause the proportion of ultra-high molecular weight products to be too high, with most of the expected products and medium molecular weight products being the main products.

[0048] Step 2: In the end-capping reaction stage where NCO polyurethane prepolymers are at both ends, catalyst CAT2 (organic bismuth) with good catalytic activity for end-capping reaction is selected. Since a small amount of diisocyanate and polyol will remain after the first step reaction, the catalyst CAT2 selected in this step can continue to catalyze the reaction of the remaining diisocyanate and polyol, appropriately increasing the proportion of high molecular weight products without causing excessive viscosity. Therefore, the catalytic activity of CAT2 for the polymerization reaction of NCO and OH in this step can be higher than that of CAT1.

[0049] (2) By adding catalysts with different activities in stages, this invention enables the preparation of oligomers using polyols with high molecular weight, but does not excessively increase the viscosity of the photocurable resin system, while ensuring that the photocurable product has excellent elastic properties.

[0050] (3) The two catalysts selected in this invention are low in toxicity and environmentally friendly; the prepared photocurable material has high elastic modulus and high elongation at break, and has excellent performance. Its operation method is simple and easy to operate. Detailed Implementation

[0051] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0053] This invention provides a specific method for preparing polyurethane acrylate oligomers, comprising:

[0054] S1: Isocyanate, polyol and catalyst I are mixed and reacted to yield product I;

[0055] S2: Product I, end-capping agent and catalyst II are mixed and reacted to obtain product II, i.e. polyurethane oligomer; wherein, catalyst I includes organozirconium; catalyst II includes organobismuth.

[0056] In the first step of this invention, diisocyanate and polyol are selected for chain extension reaction. Catalyst CAT1 (organic zirconium) with slightly lower catalytic activity for polymerization of NCO and OH is selected to avoid excessively vigorous reaction and excessively high proportion of ultra-high molecular weight products. Most of the products are the expected products and medium molecular weight products.

[0057] In the second step of this invention, the end-capping reaction of NCO polyurethane prepolymers at both ends is carried out using catalyst CAT2 (organic bismuth), which has good catalytic activity for end-capping reactions. Since a small amount of diisocyanate and polyol residues remain from the first step reaction, the catalyst CAT2 used in this step can continue to catalyze the reaction of the remaining diisocyanate and polyols, appropriately increasing the proportion of high molecular weight products without causing excessively high viscosity. Therefore, the catalytic activity of CAT2 for the polymerization reaction of NCO and OH in this step can be higher than that of CAT1.

[0058] Those skilled in the art can select suitable organozirconium catalysts from existing technologies according to actual needs.

[0059] Specifically, in step S2, when the actual content of isocyanate in product I reaches 0.95 to 1 times its theoretical value, a capping agent and catalyst II are added.

[0060] The present invention determines the timing of catalyst II addition based on the actual reaction effect, which can ensure that the polyurethane acrylate oligomer obtained after adding catalyst II under the above conditions has suitable viscosity and excellent mechanical properties.

[0061] Specifically, the catalyst I of the present invention is selected from zirconium isooctanoate and / or zirconium neodecanoate.

[0062] Preferably, the catalyst I of the present invention is zirconium isooctanoate.

[0063] Those skilled in the art can select suitable organobismuth catalysts from existing technologies according to actual needs.

[0064] Specifically, the catalyst II of the present invention is selected from at least one of bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, and bismuth naphthenate.

[0065] Preferably, the catalyst II of the present invention is selected from...

[0066] Specifically, in step S1 of the present invention, the molar ratio of isocyanate to polyol is 1.5 to 2:1.

[0067] Specifically, the molar ratio of isocyanate to polyol in this invention is selected from any value of 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 or any range between the two.

[0068] The ratio of isocyanate to polyol in this invention can be adjusted according to the molecular weight of the polymer product required in practice. Within the preferred range described above, the chain extension reaction effect is better.

[0069] Specifically, the amount of catalyst I used in step S1 of the present invention is 0.01% to 0.1% of the total weight of isocyanate and polyol.

[0070] Specifically, the amount of catalyst I used in this invention is any value or a range between any two of 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, and 0.1% of the total weight of isocyanate and polyol.

[0071] In this invention, the amount of catalyst I is determined by its catalytic activity and the control requirements for the intensity of the chain extension reaction. By using the above-mentioned proportions of this invention, most chain extension reactions can produce the expected product and the product with a medium molecular weight.

[0072] Those skilled in the art can adjust the proportion of catalyst I in the total amount of reactants according to the actual reaction conditions.

[0073] Specifically, the amount of catalyst II used in step S2 of the present invention is 0.01% to 0.05% of the total weight of isocyanate and polyol.

[0074] Specifically, the amount of catalyst II in this invention is any value among 0.01%, 0.02%, 0.03%, 0.04%, and 0.05% of the total weight of isocyanate and polyol, or any range between two values.

[0075] In this invention, the amount of catalyst II needs to be adjusted according to the end-capping reaction and the reaction of the remaining small amount of diisocyanate with polyol. At this time, the proportion of high molecular weight product can be appropriately increased, but it will not lead to excessively high viscosity.

[0076] Those skilled in the art can adjust the proportion of catalyst II in the total amount of reaction raw materials according to the actual reaction conditions.

[0077] By using the proportions of catalyst I and catalyst II provided in the embodiments of the present invention, the entire reaction process can be well controlled. This not only ensures appropriate product viscosity but also enables the synthesized polymer product to possess good mechanical properties, such as elastic modulus, elongation at break, and tensile strength.

[0078] Those skilled in the art can also select other suitable polymerization inhibitors according to actual needs.

[0079] Specifically, the reaction temperature of reaction I in this invention is 60℃~80℃; the reaction temperature of reaction II is 70℃~90℃.

[0080] Specifically, the reaction temperature of reaction I is selected from any value of 60℃, 65℃, 70℃, 75℃, 80℃ or any range between two of them.

[0081] Specifically, the reaction time of reaction I in this invention is 1 to 3 hours.

[0082] Specifically, the reaction temperature for reaction II can be any value from 70℃, 75℃, 80℃, 85℃, 90℃, or any range between two of these values.

[0083] Specifically, the reaction time of reaction I in this invention is 1 to 3 hours.

[0084] The present invention determines the preferred reaction I temperature and reaction II temperature based on the actual reaction effect. When the temperature is too high, the reaction will be accelerated, the raw materials will turn yellow, and the reaction process will be uncontrollable. When the temperature is too low, the reaction time will be longer. Therefore, within the above reaction temperature range, the overall reaction is controllable and the reaction effect is better.

[0085] In the above-mentioned reaction process of the present invention, multiple factors such as the molecular weight of diisocyanate and polyol, the reactivity and amount of catalyst I and catalyst II, the reaction temperature, and the timing of catalyst II addition will affect the effect of the entire reaction process. Multiple factors work together to synthesize polymer products with ideal conditions.

[0086] Specifically, the isocyanate of the present invention is selected from at least one of diisocyanates, polyisocyanates or their derivatives.

[0087] Specifically, the diisocyanate is selected from at least one of isophorone diisocyanate (IPDI), trimethylhexane diisocyanate (TMDI), toluene diisocyanate (TDI), xylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), 4,4-diphenylmethane diisocyanate (MDI), 4,4-dicyclohexylmethane diisocyanate (HMDI), and terephthalic diisocyanate (PPDI).

[0088] Preferably, the diisocyanate of the present invention is selected from isophorone diisocyanate (IPDI) and / or trimethylhexanediisocyanate (TMDI).

[0089] Specifically, the polyols in this invention are selected from polyether diols.

[0090] The polyether diol is selected from at least one of polyethylene glycol diol, polypropylene glycol diol, polytetrahydrofuran ether diol, and polytrimethylene ether diol.

[0091] Preferably, the polyol of the present invention is selected from polypropylene glycol diol.

[0092] Specifically, the capping agent of the present invention is selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

[0093] Specifically, a polymerization inhibitor is also added to reaction II of the present invention.

[0094] Specifically, the polymerization inhibitor is selected from p-hydroxyanisole.

[0095] In this invention, the amount of capping agent and polymerization inhibitor can be added according to the actual reaction of the raw materials.

[0096] In the following description, preferred embodiments and comparative embodiments are listed to better understand the present invention. These embodiments are for illustrative purposes only and are not intended to limit the invention.

[0097] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0098] Unless otherwise specified, this application uses conventional testing methods or testing methods recommended by the instrument.

[0099] The method for calculating the theoretical value of NCO in this invention:

[0100] Theoretical NCO value = (Molar amount of IPDI - Molar amount of PPG) × 2 × Molar mass of NCO / (Mass of IPDI + Mass of PPG) × 100%

[0101] Example 1 (Preparation of polyurethane acrylate oligomers using organozirconium + organobismuth catalysts)

[0102] Synthesis process: 444.6 g of isophorone diisocyanate and 12000 g of polypropylene glycol diol (molecular weight 12000) were added to separate 3 L reaction flasks. The temperature was slowly increased and controlled at 50-60 °C. 2.53 g of zirconium isooctanoate catalyst was added dropwise. After the addition was complete, the mixture was stirred at 80 °C for 1-3 h. When the NCO content in the product reached approximately 0.64%-0.67%, 1.26 g of organobismuth catalyst was added. Add 6.34g of polymerization inhibitor MEHQ (p-hydroxyanisole), then add 234.56g of hydroxyethyl acrylate dropwise. Control the temperature at 80℃ and stir the reaction for 3 hours. Infrared spectroscopy showed that the NCO groups in the reaction system had completely reacted.

[0103] Example 2 (Preparation of polyurethane acrylate oligomers using organozirconium + organobismuth catalysts)

[0104] Synthesis process: 444.6 g of isophorone diisocyanate and 12000 g of polypropylene glycol diol (molecular weight 12000) were added to separate 3 L reaction flasks. The temperature was slowly increased and controlled at 50-60 °C. 3.80 g of zirconium isooctanoate catalyst was added dropwise. After the addition was complete, the mixture was stirred at 80 °C for 1-3 h. When the NCO content in the product reached approximately 0.64%-0.67%, 1.26 g of organobismuth catalyst was added. Add 6.34g of polymerization inhibitor MEHQ (p-hydroxyanisole), then add 234.56g of hydroxyethyl acrylate dropwise. Control the temperature at 80℃ and stir the reaction for 3 hours. Infrared spectroscopy showed that the NCO groups in the reaction system had completely reacted.

[0105] Example 3 (Preparation of polyurethane acrylate oligomers using organozirconium + organobismuth catalysts)

[0106] Synthesis process: 444.6 g of isophorone diisocyanate and 12000 g of polypropylene glycol diol (molecular weight 12000) were added to separate 3 L reaction flasks. The temperature was slowly increased and controlled at 50-60 °C. 3.80 g of zirconium isooctanoate catalyst was added dropwise. After the addition was complete, the mixture was stirred at 80 °C for 1-3 h. When the NCO content in the product reached approximately 0.64%-0.67%, 3.80 g of organobismuth catalyst was added. Add 6.34g of polymerization inhibitor MEHQ (p-hydroxyanisole), then add 234.56g of hydroxyethyl acrylate dropwise. Control the temperature at 80℃ and stir the reaction for 3 hours. Infrared spectroscopy showed that the NCO groups in the reaction system had completely reacted.

[0107] Example 4 (Preparation of polyurethane acrylate oligomers using organozirconium + organobismuth catalysts)

[0108] Synthesis process: 666.9 g of isophorone diisocyanate and 12000 g of polypropylene glycol diol (molecular weight 6000) were added to separate 3 L reaction flasks. The temperature was slowly increased and controlled at 50-60 °C. 2.58 g of zirconium isooctanoate catalyst was added dropwise. After the addition was complete, the mixture was stirred at 80 °C for 1-3 h. When the NCO content in the product reached approximately 0.63%-0.66%, 1.26 g of organobismuth catalyst was added. Add 6.45g of polymerization inhibitor MEHQ (p-hydroxyanisole), then add 234.56g of hydroxyethyl acrylate dropwise, control the temperature at 80℃, and stir the reaction for 3 hours. Infrared spectroscopy showed that the NCO groups in the reaction system had completely reacted.

[0109] Comparative Example 1 (Preparation of polyurethane acrylate oligomers using organic bismuth catalysts)

[0110] Synthesis process: 444.6 g of isophorone diisocyanate and 12000 g of polypropylene glycol diol (molecular weight 12000) were added separately to 3 L reaction flasks. The temperature was slowly increased and controlled at 50-60℃. 3.80 g of [unspecified ingredient] was added dropwise. After the catalyst was added dropwise, the reaction was stirred at 80°C for 3 hours. Then, 6.34 g of polymerization inhibitor MEHQ was added, followed by dropwise addition of 234.56 g of hydroxyethyl acrylate. The temperature was maintained at 80°C, and the reaction was stirred for another 3 hours. Infrared spectroscopy confirmed that the NCO groups in the reaction system had completely reacted.

[0111] Comparative Example 2 (Preparation of polyurethane acrylate oligomers using organozirconium catalysts)

[0112] The synthesis process involved adding 444.6 g of isophorone diisocyanate and 12000 g of polypropylene glycol diol (molecular weight 12000) to separate 3 L reaction flasks. The temperature was slowly increased and controlled at 50–60 °C. 3.80 g of zirconium isooctanoate catalyst was added dropwise. After the addition was complete, the reaction was stirred at 80 °C for 3 hours. Then, 6.34 g of polymerization inhibitor MEHQ was added, followed by dropwise addition of 234.56 g of hydroxyethyl acrylate. The reaction was continued at 80 °C for 3 hours. Infrared spectroscopy confirmed that the NCO groups in the reaction system had completely reacted.

[0113] Comparative Example 3 (Preparation of polyurethane acrylate oligomers using organotin catalysts)

[0114] The difference between Comparative Example 3 and Comparative Example 2 is that 3.80g of organotin catalyst DBTDL (dibutyltin dilaurate) was used as the catalyst.

[0115] The following Comparative Examples 4-6 and Examples 5-8 use polyurethane acrylate oligomers to prepare photocurable resin materials.

[0116] Comparative Example 4 (Photocurable material prepared using oligomers from Comparative Example 1)

[0117] Photocurable resin materials were prepared by mixing and reacting photoinitiator TPO (diphenyl-(2,4,6-trimethylbenzoyl)phosphorus), antioxidant 1135, reactive monomer NVP (N-vinylpyrrolidone), LMA (lauryl methacrylate), and Black 30 (carbon black 30). The proportions of each component by weight are shown in Table 1, and the performance test data of the photocurable materials are shown in Table 2.

[0118] Comparative Example 5 (Photocurable material prepared using oligomers from Comparative Example 2)

[0119] The difference between Comparative Example 5 and Comparative Example 4 lies in the component ratio, as shown in Table 1. The performance test data of the photocurable material are shown in Table 2.

[0120] Comparative Example 6 (Photocurable material prepared using oligomers from Comparative Example 3)

[0121] The difference between Comparative Example 6 and Comparative Example 4 lies in the component ratio, as shown in Table 1. The performance test data of the photocurable material are shown in Table 2.

[0122] Example 5 (Preparation of photocurable material using the oligomer from Example 1)

[0123] The differences between Example 5 and Comparative Example 4 are shown in Table 1 for component ratios, and Table 2 for performance test data of the photocurable material.

[0124] Example 6 (Preparation of photocurable material using oligomers from Example 2)

[0125] The differences between Example 6 and Comparative Example 4 are shown in Table 1 for component ratios, and Table 2 for performance test data of the photocurable material.

[0126] Example 7 (Preparation of photocurable material using the oligomer from Example 3)

[0127] The differences between Example 7 and Comparative Example 4 are shown in Table 1 for component ratios, and Table 2 for performance test data of the photocurable material.

[0128] Example 8 (Preparation of photocurable material using the oligomer from Example 4)

[0129] The differences between Example 8 and Comparative Example 4 are shown in Table 1 for component ratios, and Table 2 for performance test data of the photocurable material.

[0130] Using the liquid photocurable materials of Examples 5-8 and Comparative Examples 4-6, Die C dog bone-shaped tensile test specimens were printed according to ASTM D412 standard using LEAP technology. After post-treatment (immersing the printed part in an aqueous solution, with the addition of active amine additives to improve the degree of curing, drying after cleaning, and then performing a general exposure treatment to obtain a printed product with a higher degree of curing), the mechanical properties of the seven materials after curing were tested using an Instron 34TM-10 universal testing machine. The test results are shown in Table 2.

[0131] Table 1. Raw material ratios of photocurable materials in Comparative Examples 4-6 and Examples 5-8

[0132]

[0133]

[0134] Table 2. Performance testing of 3D printed parts prepared using the photocurable materials of Comparative Examples 4-6 and Examples 5-8

[0135]

[0136] As can be seen from the performance test results in Table 2:

[0137] The photocurable material in Comparative Example 4 used a single organic bismuth catalyst. This catalyst had high catalytic activity, resulting in extremely high viscosity, high elongation at break, and low elastic modulus of the polyurethane oligomer, which were significantly lower than those in other experimental examples.

[0138] In Comparative Example 5, a single organic zirconium catalyst was used in the photocurable material. This catalyst had lower catalytic activity than organic bismuth, resulting in lower viscosity, higher elastic modulus, and insufficient elongation at break of the polyurethane oligomer, which was significantly lower than in other experimental examples.

[0139] The use of a single organotin catalyst in the photocurable material of Comparative Example 6 resulted in polyurethane oligomers with moderate viscosity, moderate elastic modulus, and significantly insufficient elongation at break.

[0140] Examples 5 to 8 provided by the present invention use dual catalysts, that is, catalysts with different activities are used in the two reaction stages before and after the reaction, so that the viscosity of polyurethane oligomers is moderate and the elastic modulus, elongation at break and tensile strength are significantly improved.

[0141] The comparison of the above comparative examples and embodiments shows that the present invention designs a method for synthesizing polyurethane acrylate oligomers using two catalysts with different catalytic activities at different reaction stages. The resulting polyurethane acrylate oligomers exhibit good viscosity, elastic modulus, elongation at break, and tensile strength. When the polyurethane acrylate oligomers prepared by the method of the present invention are used to prepare photocurable materials, the 3D printed products show that the photocurable materials of the present invention also have good viscosity, elastic modulus, elongation at break, and tensile strength.

[0142] In the process of synthesizing polyurethane oligomers from diisocyanate and polyol, this invention designs two catalysts with different activities instead of one catalyst used in traditional synthesis methods. The catalyst with lower catalytic activity is used in the early chain extension reaction, while the catalyst with higher catalytic activity is used in the later chain extension reaction. The timing of adding the second catalyst can also be adjusted according to the product viscosity and performance requirements. The polyurethane oligomers and photocurable materials synthesized using this technical approach have significant technical effects.

[0143] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing polyurethane acrylate oligomers, characterized in that, The method includes the following steps: S1: Isocyanate, polyol and catalyst I are mixed and reacted to yield product I; S2: The product I, the capping agent and the catalyst II are mixed and reacted to obtain product II, namely the polyurethane acrylate oligomer; Catalyst I comprises organozzirconium; catalyst II comprises organobismuth.

2. The method for preparing a polyurethane acrylate oligomer according to claim 1, characterized in that, In step S2, when the actual content of isocyanate in product I reaches 0.95 to 1 times its theoretical value, a capping agent and catalyst II are added.

3. The method for preparing a polyurethane acrylate oligomer according to claim 1, characterized in that, The catalyst I is selected from zirconium isooctanoate and / or zirconium neodecanoate; Catalyst II is selected from at least one of bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, and bismuth naphthenate; The amount of catalyst I used in step S1 is 0.01 wt% to 0.1 wt% of the total weight of the isocyanate and the polyol. The amount of catalyst II used in step S2 is 0.01 wt% to 0.05 wt% of the total weight of the isocyanate and the polyol. The molar ratio of the isocyanate to the polyol in step S1 is 1.5 to 2. The reaction temperature of reaction I is 60℃~80℃; The reaction temperature for reaction II is 70℃~90℃.

4. The method for preparing a polyurethane acrylate oligomer according to claim 1, characterized in that, The isocyanate is selected from at least one of polyisocyanates or their derivatives.

5. The method for preparing a polyurethane acrylate oligomer according to claim 1, characterized in that, The isocyanate is a diisocyanate; The diisocyanate is selected from at least one of isophorone diisocyanate (IPDI), trimethylhexane diisocyanate (TMDI), toluene diisocyanate (TDI), xylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), 4,4-diphenylmethane diisocyanate (MDI), 4,4-dicyclohexylmethane diisocyanate (HMDI), and terephthalic diisocyanate (PPDI). The polyol is selected from at least one of polyethylene glycol diol, polytetrahydrofuran ether diol, and polytrimethylene ether diol; The capping agent is selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. A polymerization inhibitor is added to reaction II; The polymerization inhibitor includes p-hydroxyanisole.

6. The method for preparing a polyurethane acrylate oligomer according to claim 1, characterized in that, The polyol is polypropylene glycol diol.

7. A polyurethane acrylate oligomer, characterized in that, The polyurethane acrylate oligomer is prepared by the preparation method according to any one of claims 1 to 6.

8. A method for preparing a photocurable material, characterized in that, The method includes: mixing polyurethane acrylate oligomers, reactive monomers, and photoinitiators, reacting in reaction III to obtain the photocurable material; wherein the polyurethane acrylate oligomers include the polyurethane acrylate oligomers of claim 7.

9. The method for preparing a photocurable material according to claim 8, characterized in that, The reactive monomer is selected from at least one of N-vinylpyrrolidone, N-vinylcaprolactam, N-vinyloxazolidinone, N-vinylmethyloxazolidinone, acrylmorpholine, isobornyl acrylate, isobornyl methacrylate, and dicyclopentenyl acrylate. The photoinitiator is selected from at least one of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 2,4,6-trimethylbenzoyl-bis(p-tolyl)phosphine oxide.

10. A photocurable material, characterized in that, The photocurable material is prepared by the preparation method described in claim 9.

11. The application of a photocurable material in 3D printing materials, characterized in that, The photocurable material includes the photocurable material according to claim 10.

12. A 3D printed product, characterized in that, The material of the 3D printed product is the photocurable material as described in claim 10.

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