Preparation method of non-isocyanate type light-cured resin

Abstract

The invention belongs to the technical field of 3D printing, and particularly relates to a preparation method of non-isocyanate type light-cured resin.The preparation method comprises the steps that cyclic carbonate and aliphatic primary amine react in nitrogen, and a polyurethane prepolymer is obtained through vacuum drying; the preparation method comprises the following steps: reacting a polyurethane prepolymer with a chain extender in the presence of dibutyltin dilaurate and nitrogen, and carrying out vacuum drying to obtain an intermediate product A; the preparation method comprises the following steps: reacting a methacrylate monomer with a curing agent in the presence of a catalyst a and nitrogen until an amine titration end point to obtain an intermediate product B; reacting A with B to obtain non-isocyanate type polyurethane acrylate C; and uniformly stirring the non-isocyanate type urethane acrylate C, a photoinitiator and a polymerization inhibitor to obtain liquid non-isocyanate type light-cured resin D. The preparation method comprises the following steps: uniformly stirring the non-isocyanate type urethane acrylate C, the photoinitiator and the polymerization inhibitor; a non-isocyanate synthesis system is adopted, toxicity and volatility of traditional isocyanate are avoided, and the production process is safer and more environmentally friendly; and multiple production requirements on mechanical reliability, curing efficiency and safety of the material in a 3D printing use scene are met.

Description

Technical Field

[0001] This invention belongs to the field of 3D printing technology, and particularly relates to a method for preparing a non-isocyanate type photocurable resin. Background Technology

[0002] Photopolymerization technology has become a mainstream technology in fields such as 3D printing resins due to its advantages such as high curing efficiency, low VOC emissions, and low energy consumption. Polyurethane acrylate oligomers, as the core matrix material of photopolymerization resins, combine the flexibility and abrasion resistance of polyurethane with the photopolymerization activity of acrylates, and are widely used in industrial anti-corrosion coatings, precision 3D printed parts, flexible electronic packaging materials, and other application scenarios.

[0003] Existing technologies for preparing polyurethane acrylate oligomers, such as those described in patent document KR1020240103819A, use isocyanate as the core raw material. A polyurethane prepolymer is generated through addition polymerization, and then acrylic acid double bonds are introduced to obtain the final product. This process is highly mature, and the resulting product exhibits high crosslinking density and excellent mechanical strength, thus maintaining a dominant market position for a considerable period.

[0004] However, isocyanates are highly toxic, volatile, and irritating, which can harm human health. Their production requires high-cost protective equipment and strict control, significantly increasing the labor costs for safety protection.

[0005] Developing cyanide-free, non-isocyanate-based polyurethane acrylate photocurable resins has become an industry upgrade direction. Existing solutions mostly use the ring-opening reaction of cyclic carbonates and amines to replace the addition reaction of isocyanates. However, the modification process of acrylic double bonds is complex, and there is a contradiction between photocuring activity and mechanical properties: either the photocuring rate is slow and the conversion rate of acrylic double bonds is low, which cannot meet the needs of rapid prototyping in 3D printing; or the mechanical properties (tensile strength, elongation at break) are significantly reduced, making it difficult to adapt to the application scenarios that require a balance between strength and toughness of the material. It is difficult to achieve both. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a non-isocyanate type photocurable resin, aiming to solve the technical problem that it is difficult to balance the photocuring activity and mechanical properties of non-isocyanate type photocurable resins.

[0007] To achieve the above objectives, the present invention provides a method for preparing a non-isocyanate type photocurable resin, comprising the following synthesis steps:

[0008] Step 1: By weight, add 180-210 parts of cyclic carbonate and 80-110 parts of aliphatic primary amine to the reactor. Under nitrogen protection, heat to 50-90℃, stir at a uniform speed, and carry out polycondensation reaction for 4-48 hours. After post-treatment, polyurethane prepolymer can be obtained. Step 2: By weight, add 180-210 parts of polyurethane prepolymer and 80-110 parts of chain extender to the reactor, heat to 60-80℃, stir at a uniform speed, add 0.1-1 parts of dibutyltin dilaurate dropwise, and react for 3-5 hours under nitrogen protection; vacuum dry to obtain intermediate product A. Step 3: By weight, add 80-110 parts of methacrylate monomers and 80-110 parts of curing agent to the reactor. Under nitrogen protection, stir at 60-100℃, add 0.1-1 parts of catalyst a dropwise, and react for 2-6 hours. Monitor the reaction progress by amine titration until the mass fraction of amino NH2 in the system reaches 50.0%~50.2%, to obtain intermediate product B. Step 4: According to the weight, add 80-110 parts of intermediate product A and 180-210 parts of intermediate product B to the reaction vessel, heat to 50-70℃, stir at a uniform speed, and react for 9-11 hours to obtain non-isocyanate type polyurethane acrylate C. Step 5: By weight, take 80-110 parts of non-isocyanate polyurethane acrylate C, 0.8-1.2 parts of photoinitiator, and 0.1-1 parts of polymerization inhibitor. Stir at a constant temperature of 50-70℃ and a rotation speed of 400-500 r / min until homogeneous to obtain liquid non-isocyanate photocurable resin D.

[0009] Further, step one of the synthesis steps: By weight, add 180-210 parts of cyclic carbonate and 80-110 parts of trimethylhexanediamine to the reactor, heat to 50-90℃, stir at a uniform speed, add 0.1-5 parts of triethylamine catalyst, and carry out polycondensation reaction for 4-48 hours under nitrogen protection. Add diethyl ether as a stop agent, filter, wash, and vacuum dry to obtain polyurethane prepolymer.

[0010] Further, step one of the synthesis steps: By weight, add 180-210 parts of cyclic carbonate and 80-110 parts of bis(4-aminocycloethyl) ether to the reactor, heat to 50-90℃, stir at a uniform speed, add 0.1-5 parts of catalyst NaOH, and under nitrogen protection, carry out the polycondensation reaction for 4-48 hours. Add dilute hydrochloric acid as a stop agent, filter and wash, and vacuum dry to obtain polyurethane prepolymer.

[0011] Further, step one of the synthesis steps: By weight, add 180-210 parts of cyclic carbonate and 80-110 parts of isophorone diamine to the reactor. Under nitrogen protection, heat to 50-90℃ and stir at a uniform speed for 0.5-2 hours. Then, raise the temperature to 90-140℃ and carry out the polycondensation reaction for 4-48 hours. After vacuum drying, the polyurethane prepolymer can be obtained.

[0012] Further, the cyclic carbonate includes any one of ethylene carbonate, propylene carbonate, and 1,2-glycerol carbonate; the aliphatic primary amine includes any one of methylamine, ethylamine, propylamine, butylamine, pentamine, hexylamine, ethylenediamine, propylenediamine, butylamine, hexamethylenediamine, isophorone diamine, trimethylhexamethylenediamine, and bis(4-aminocycloethyl) ether.

[0013] Furthermore, the chain extender is any one of resorcinol dihydroxypropyl ether, hydroquinone dihydroxyethyl ether, bisphenol A dihydroxyethyl ether, and bisphenol A dihydroxypropyl ether.

[0014] Further, catalyst a in step three is titanium tetraisopropoxide; the methacrylate monomer in step three can be any one of 2-hydroxyethyl methacrylate, methyl methacrylate, n-butyl methacrylate or isobutyl methacrylate.

[0015] Furthermore, the curing agent in step three is any one of 4,4-diaminodiphenylmethane, 3,5-dimethylthiotoluenediamine, isobutyl 3,5-diamino-4-chlorobenzoate, or 1,4-bis-sec-butylaminobenzene.

[0016] Furthermore, the photoinitiator in step five is any one or a combination of two of photoinitiator 184, photoinitiator TPO, photoinitiator 819, and photoinitiator 907.

[0017] Furthermore, the polymerization inhibitor in step five is any one of p-hydroxyanisole, hydroquinone, or 2,6-di-tert-butyl-p-cresol.

[0018] The above-described technical solutions of one or more of the methods for preparing a non-isocyanate type photocurable resin provided in the embodiments of the present invention have at least one of the following technical effects: 1. The non-isocyanate synthesis system avoids the toxicity and volatility of traditional isocyanates, making the production process safer and more environmentally friendly; the reaction conditions of each step are mild, mostly 60-150℃ and normal pressure, eliminating the need for high-temperature and high-pressure equipment and reducing the cost of industrial production. 2. By introducing cyclic carbonates and aliphatic primary amines as core raw materials, combined with catalysts, chain extenders, curing agents, and photoinitiators, the resin achieves a balance between photocuring rate and mechanical properties, meeting the requirements of rapid prototyping and interlayer fusion in 3D printing; after curing, the tensile strength is ≥30MPa and the elongation at break is ≥700%. 3. Compared with the existing technology of preparation process using non-isocyanate as the core raw material, the present invention has better flexibility and stronger resistance to damage, improved curing efficiency, lower cost, and is easier to industrialize and mass-produce, and can better meet the multiple production requirements of 3D printing application scenarios for material mechanical reliability, curing efficiency and safety. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The infrared absorption peak identification diagram provided in the embodiments of the present invention.

[0021] Figure 2 The infrared spectrum provided in Embodiment 1 of the present invention.

[0022] Figure 3 The infrared spectrum provided in Embodiment 2 of the present invention.

[0023] Figure 4 The infrared spectrum provided in Embodiment 3 of the present invention.

[0024] Figure 5 The infrared spectrum provided in Embodiment 4 of the present invention.

[0025] Figure 6 This is a schematic diagram of the structure of A1 provided in Embodiment 1 of the present invention.

[0026] Figure 7 This is a schematic diagram of the structure of C1 provided in Embodiment 1 of the present invention.

[0027] Figure 8 This is a schematic diagram of the structure of A2 provided in Embodiment 2 of the present invention.

[0028] Figure 9 This is a schematic diagram of the structure of C2 provided in Embodiment 2 of the present invention.

[0029] Figure 10 This is a schematic diagram of the structure of A3 provided in Embodiment 3 of the present invention.

[0030] Figure 11 This is a schematic diagram of the structure of C3 provided in Embodiment 3 of the present invention.

[0031] Figure 12 This is a schematic diagram of the structure of A4 provided in Embodiment 4 of the present invention.

[0032] Figure 13 This is a schematic diagram of the structure of C4 provided in Embodiment 4 of the present invention. Detailed Implementation

[0033] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to conventional techniques or conditions described in the literature in the art or according to the product manual.

[0034] The following examples use information on the main raw materials: Resorcinol dihydroxypropyl ether, INDSPEC Chemical Company, USA, molecular weight: 226.2, viscosity at 25°C: 20 Pa·s.

[0035] Hydroquinone dihydroxyethyl ether, Lane Chemical Company, product brand: Addolink 30 / 10, hydroxyl value: 560 mg KOH / g, melting point ≥104℃, moisture ≤0.1%.

[0036] Bisphenol A dihydroxyethyl ether, SEPPIC (France), product name: Dianol 220, hydroxyl value: 350 mg KOH / g, melting point approximately 110℃; Emulsifiers Corporation (Japan), product name: BA-2, hydroxyl value: 330-350 mg KOH / g.

[0037] Bisphenol A dihydroxypropyl ether, SEPPIC (France), product brands: Dianol 320 and Agodiol P2, with hydroxyl values ​​of 320 mg KOH / g and 325 mg KOH / g respectively; Emulsifiers Co., Ltd. (Japan), product brand: BA-P2, with hydroxyl values ​​of 310-325 KOH / g.

[0038] Tetraisopropoxide titanium, Sigma-Aldrich, USA, Product No.: 205273, Molecular Weight: 284.22, Purity: 97%.

[0039] 2-Hydroxyethyl Methacrylate, Mitsubishi, Japan, Product No.: 0699524, Hydroxyl Value: 160-170 mg KOH / g, Moisture ≤0.3%.

[0040] 1,4-Di-sec-butylaminobenzene, Dorf Ketal, product brand: Unilink 4100, hydroxyl value: 510 mg KOH / g, moisture ≤0.06%.

[0041] Isophorone diamine, Evonik Industries, Germany, product name: Vestamin IPD, purity ≥99.7%, moisture ≤0.2%, secondary / tertiary amine compound impurities <0.15%, color (APHA) ≤15.

[0042] If the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be obtained commercially.

[0043] Example 1 Step 1: According to the weight proportions, add 200g of propylene carbonate and 100g of isophorone diamine to the reaction vessel. Under nitrogen protection, heat to 80℃ and stir at a constant speed for 1 hour. Then heat to 100℃. The reaction endpoint is determined by detecting characteristic functional groups using Fourier transform infrared spectroscopy (FTIR). The table of characteristic functional groups is attached to the instruction manual. Figure 1 As shown; the FTIR (Full Time Infrared) spectroscopy results for the polycondensation reaction from start to finish (10 hours) are as per the attached instruction manual. Figure 2 As shown in the figure; prepolymer 1 can be obtained by vacuum drying, and the structure of prepolymer 1 is shown in the figure below:

[0044] Step 2: According to the weight proportions, add 200g of prepolymer 1 and 100g of chain extender (bisphenol A dihydroxyethyl ether) to the reactor. Raise the temperature to 70℃, stir at a uniform speed, and add 0.1g of dibutyltin dilaurate dropwise. Under nitrogen protection, react for 3 hours, then vacuum dry to remove moisture to obtain intermediate product A1. The structure of A1 is shown in the figure below and the instruction manual is attached. Figure 6 As shown:

[0045] Step 3: According to the weight proportions, add 100g of n-butyl methacrylate and 100g of curing agent (isobutyl 3,5-diamino-4-chlorobenzoate) to the reactor. Under nitrogen protection, stir at 90±10℃, and add 0.5g of catalyst a (titanium tetraisopropoxide) dropwise to the reactor. React for 4 hours, and titrate with amine value until the NH2 value is 50.1±0.1% to obtain intermediate product B1. The reaction equation is:

[0046] Step 4: According to parts by weight, add 100g of intermediate product A1 and 200g of intermediate product B1 to the reaction vessel, heat to 60℃, stir at a constant speed, and react for 10 hours to obtain non-isocyanate type polyurethane acrylate C1. The structure of C1 is shown in the figure below and the instruction manual is attached. Figure 7 As shown:

[0047] Step 5: According to the weight proportions, take 100g of non-isocyanate type polyurethane acrylate C1, 1g of photoinitiator TPO, and 0.2g of polymerization inhibitor (2,6-di-tert-butyl-p-cresol). Stir at a constant temperature of 60℃ and a rotation speed of 500r / min until homogeneous to obtain liquid non-isocyanate type photocurable resin D1.

[0048] Example 2 Step 1: According to the weight proportions, add 200g of 1,2-glycerol carbonate and 100g of isophorone diamine to the reactor, heat to 70±10℃, stir at a uniform speed, and react for 1 hour; raise the temperature to 100℃, and determine the reaction endpoint by detecting characteristic functional groups using Fourier Transform Infrared Spectroscopy (FTIR). The reaction lasts for 9 hours from the start to the endpoint. The FTIR results are shown in the attached instructions. Figure 3 As shown in the figure; prepolymer 2 can be obtained by vacuum drying, and the structure of prepolymer 2 is shown in the figure below:

[0049] Step 2: According to the weight proportions, add 200g of prepolymer 2 and 100g of chain extender (hydroquinone dihydroxyethyl ether) to the reactor. Raise the temperature to 70℃, stir at a uniform speed, and add 0.1g of dibutyltin dilaurate dropwise. Under nitrogen protection, react for 4 hours, then vacuum dry to obtain intermediate product A2. The structure of A2 is shown in the figure below and the instruction manual is attached. Figure 8 As shown:

[0050] Step 3: According to the weight proportions, add 100g of isobutyl methacrylate and 100g of curing agent (1,4-bis-sec-butylaminobenzene) to the reactor. Under nitrogen protection, stir at 90℃, and add 0.5g of catalyst a (tetraisopropoxide titanium) dropwise to the reactor. React for 4 hours, and titrate to the reaction endpoint using amine value to obtain intermediate product B2. The reaction equation is:

[0051] Step 4: According to the weight proportions, add 100g of intermediate product A2 and 200g of intermediate product B2 to the reaction vessel, heat to 60℃, stir at a constant speed, and react for 10 hours to obtain non-isocyanate type polyurethane acrylate C2. The structure of C2 is shown in the figure below and the instruction manual is attached. Figure 9 As shown:

[0052] Step 5: According to the weight proportions, take 100g of non-isocyanate type polyurethane acrylate C2, 1g of photoinitiator TPO, and 0.2g of polymerization inhibitor (hydroquinone). Stir at a constant temperature of 60℃ and a rotation speed of 500r / min until homogeneous to obtain liquid non-isocyanate type photocurable resin D2.

[0053] Example 3 Step 1: According to the weight proportions, add 200g of propylene carbonate and 100g of bis(4-aminocycloethyl) ether to the reactor, heat to 60℃, and stir at a uniform speed; add 1g of NaOH catalyst, and under nitrogen protection, raise the temperature to 110±10℃. The reaction endpoint is determined by detecting characteristic functional groups using Fourier Transform Infrared Spectroscopy (FTIR). The polycondensation reaction lasts for 8 hours from the start to the endpoint. The FTIR results are shown in the attached instructions. Figure 4 As shown in the figure below; after adding a stop agent to bring the pH of the reaction system to 7±0.5 (the stop agent is 10% dilute hydrochloric acid), filter and vacuum dry to obtain prepolymer 3. The structure of prepolymer 3 is shown in the figure below:

[0054] Step 2: According to the weight proportions, add 200g of prepolymer 3 and 100g of chain extender (resorcinol dihydroxypropyl ether) to the reactor. Raise the temperature to 70℃, stir at a constant speed, and add 0.1g of dibutyltin dilaurate dropwise. Under nitrogen protection, react for 3 hours, then vacuum dry to obtain intermediate product A3. The structure of A3 is shown in the figure below and the instruction manual is attached. Figure 10 As shown:

[0055] Step 3: According to the weight proportions, add 100g of 2-hydroxyethyl methacrylate and 100g of curing agent (3,5-dimethylthiotoluene diamine) to the reactor. Under nitrogen protection, stir at 70±10℃, and add 0.5g of catalyst a (tetraisopropoxide titanium) dropwise to the reactor. React for 4 hours, and titrate with amine value until the NH2 value is 50.1±0.1% to obtain intermediate product B3. The reaction equation is:

[0056] Step 4: According to parts by weight, add 100g of intermediate product A3 and 200g of intermediate product B3 to the reaction vessel, heat to 60℃, stir at a constant speed, and react for 10 hours to obtain non-isocyanate type polyurethane acrylate C3. The structure of C3 is shown in the figure below and the instruction manual is attached. Figure 11 As shown:

[0057] Step 5: According to the weight proportions, take 100g of non-isocyanate type polyurethane acrylate C3, 1g of photoinitiator TPO, and 0.2g of polymerization inhibitor (p-hydroxyanisole). Stir at a constant temperature of 60℃ and a rotation speed of 500r / min until homogeneous to obtain liquid non-isocyanate type photocurable resin D3.

[0058] Example 4 Step 1: According to the weight proportions, add 200g of propylene carbonate and 100g of trimethylhexanediamine to the reactor, heat to 60℃, and stir at a uniform speed; add 0.1g of triethylamine catalyst, and maintain a constant temperature of 60℃ under nitrogen protection. The reaction endpoint is determined by detecting characteristic functional groups using Fourier Transform Infrared Spectroscopy (FTIR). The polycondensation reaction lasts 12 hours from the start to the endpoint. The FTIR results are shown in the attached instructions. Figure 5 As shown in the figure below, the above mixture is slowly poured into the stopping agent diethyl ether, filtered, washed, and vacuum dried to obtain prepolymer 4. The structure of prepolymer 4 is shown in the figure below.

[0059] Step 2: According to the weight proportions, add 200g of prepolymer 4 and 100g of chain extender (bisphenol A dihydroxypropyl ether) to the reactor. Raise the temperature to 70℃, stir at a constant speed, and add 0.1g of dibutyltin dilaurate dropwise. Under nitrogen protection, react for 3 hours, then vacuum dry to obtain intermediate product A4. The structure of A4 is shown in the figure below and the instruction manual is attached. Figure 12 As shown:

[0060] Step 3: According to the weight proportions, add 100g of methyl methacrylate and 100g of curing agent (4,4-diaminodiphenylmethane) to the reactor. Under nitrogen protection, stir at 80℃, and add 0.5g of catalyst a (titanium tetraisopropoxide) dropwise to the reactor. React for 6 hours, and titrate with amine value until the NH2 value is 50.1±0.1% to obtain intermediate product B4. The reaction equation is:

[0061] Step 4: According to parts by weight, add 100g of intermediate product A4 and 200g of intermediate product B4 to the reaction vessel, heat to 60℃, stir at a constant speed, and react for 10 hours to obtain non-isocyanate type polyurethane acrylate C4. The structure of C4 is shown in the figure below and the instruction manual is attached. Figure 13 As shown:

[0062] Step 5: According to the weight proportions, take 100g of non-isocyanate polyurethane acrylate C4, 1g of photoinitiator TPO, and 0.2g of polymerization inhibitor (p-hydroxyanisole). Stir at a constant temperature of 60℃ and a rotation speed of 500r / min until homogeneous to obtain liquid non-isocyanate photocurable resin D4.

[0063] Comparative Example 1 A method for preparing a non-isocyanate type photocurable resin, comprising the following steps: Nitrogen gas was introduced into the reactor to purge air from the system, and the temperature was slowly raised to 150°C. 204.18 g of propylene carbonate and 0.02 g of cesium carbonate catalyst were then added and stirred until homogeneous. Next, 170.03 g of isophorone diamine was slowly added dropwise, and the reaction was maintained at this temperature for 5 hours to obtain a reaction intermediate. When the reaction system was cooled to 120°C, 284.3 g of glycidyl methacrylate containing 0.028 g of p-hydroxyanisole was slowly added dropwise, and the reaction was stirred at a constant temperature for 3 hours. Then, the mixture was distilled under reduced pressure for 1.5 hours to remove unreacted monomers, yielding a pale yellow polyurethane prepolymer.

[0064] Finally, the reaction system was cooled to 70°C, and 0.071 g of 2-isopropylthioxanthone and 0.08 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide were added. The mixture was stirred at high speed for 10 min under light-protected conditions, and then stirred at low speed for 10 min to obtain a non-isocyanate type photocurable resin.

[0065] Performance testing The properties of the liquid non-isocyanate type photocurable resins of Examples 1-4 and the non-isocyanate type photocurable resin obtained in Comparative Example 1 were characterized. The specific test items and test methods are as follows: (1) Uniaxial tensile properties test, refer to ASTM D412 "Tension test method for vulcanized rubber and thermoplastic elastomers".

[0066] a. The above-mentioned liquid non-isocyanate type photocurable resin and polyurethane acrylate containing photosensitive monomers were cured using a metal halide lamp as the curing light source. Test strips conforming to ASTM D412 standard were poured into a transparent cavity mold. The above-mentioned test strips were placed in water at 95±5℃ for 11±1 hours, and then transferred to an oven at 95±5℃ for 5±0.5 hours. b. Place the above-mentioned specimen into a universal testing machine for testing.

[0067] (2) Curing activity test a. Take 0.5g of the liquid non-isocyanate type photocurable resin of Examples 1-4 above and the polyurethane acrylate containing photosensitive monomer of Comparative Example 1 respectively, and place them on a glass slide to form a film with a thickness of 80μm. b. Using a 405nm ultraviolet light source with a light intensity of 15mw / cm², gently touch the resin surface with a clean probe every 10ms and record the shortest time in which the probe does not stick to the resin and the sample shape remains unchanged. This is the curing time.

[0068] The test results are shown in Table 1.

[0069]

[0070] Table 1 Table 1 shows the performance test results of the samples obtained after curing the liquid non-isocyanate type photocurable resin prepared in Examples 1-4 and the polyurethane acrylate containing photosensitive monomer prepared in Comparative Example 1 under the same conditions and methods.

[0071] Referring to the test results of Examples 1-4 and Comparative Example 1, Examples 1-4 used a non-isocyanate system to prepare prepolymers, combined with chain extenders such as resorcinol dihydroxypropyl ether, and then combined with curing agents such as methacrylates and 3,5-dimethylthiotoluene diamine, while using TPO photoinitiator, which enabled the material to achieve a tensile strength of 30-50 MPa, an elongation at break of 700-1000%, and a curing time of only 40-70 ms.

[0072] Compared with existing technologies that use isocyanate as the core raw material, the production process is safer. Compared with the preparation process of Comparative Example 1 that does not use isocyanate as the core raw material, Examples 1-4 have better flexibility and stronger resistance to damage. The curing efficiency is more than 50% higher than that of Comparative Example 1. The cost is lower and it is easier to mass-produce in industrial applications. The overall performance is better than that of Comparative Example 1, and it can better meet the multiple requirements of mechanical reliability, curing efficiency and safety of materials in 3D printing application scenarios.

[0073] 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, and improvements 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 non-isocyanate type photocurable resin, characterized in that, The synthesis steps include the following: Step 1: By weight, add 180-210 parts of cyclic carbonate and 80-110 parts of aliphatic primary amine to the reactor. Under nitrogen protection, heat to 50-90℃, stir at a uniform speed, and carry out polycondensation reaction for 4-48 hours. After post-treatment, polyurethane prepolymer can be obtained. Step 2: By weight, add 180-210 parts of polyurethane prepolymer and 80-110 parts of chain extender to the reactor, heat to 60-80℃, stir at a uniform speed, add 0.1-1 parts of dibutyltin dilaurate dropwise, and react for 3-5 hours under nitrogen protection; vacuum dry to obtain intermediate product A. Step 3: By weight, add 80-110 parts of methacrylate monomers and 80-110 parts of curing agent to the reactor. Under nitrogen protection, stir at 60-100℃, add 0.1-1 parts of catalyst a dropwise, and react for 2-6 hours. Monitor the reaction progress by amine titration until the mass fraction of amino NH2 in the system reaches 50.0%~50.2%, to obtain intermediate product B. Step 4: According to the weight, add 80-110 parts of intermediate product A and 180-210 parts of intermediate product B to the reaction vessel, heat to 50-70℃, stir at a uniform speed, and react for 9-11 hours to obtain non-isocyanate type polyurethane acrylate C. Step 5: By weight, take 80-110 parts of non-isocyanate polyurethane acrylate C, 0.8-1.2 parts of photoinitiator, and 0.1-1 parts of polymerization inhibitor. Stir at a constant temperature of 50-70℃ and a rotation speed of 400-500 r / min until homogeneous to obtain liquid non-isocyanate photocurable resin D.

2. The method for preparing a non-isocyanate type photocurable resin according to claim 1, characterized in that, Step one of the synthesis steps: By weight, add 180-210 parts of cyclic carbonate and 80-110 parts of trimethylhexanediamine to the reactor, heat to 50-90℃, stir at a uniform speed, add 0.1-5 parts of triethylamine catalyst, and carry out polycondensation reaction for 4-48 hours under nitrogen protection. Add diethyl ether as a stop agent, filter, wash, and vacuum dry to obtain polyurethane prepolymer.

3. The method for preparing a non-isocyanate type photocurable resin according to claim 2, characterized in that, Step one of the synthesis steps: By weight, add 180-210 parts of cyclic carbonate and 80-110 parts of bis(4-aminocycloethyl) ether to the reactor, heat to 50-90℃, stir at a uniform speed, add 0.1-5 parts of catalyst NaOH, and under nitrogen protection, carry out the polycondensation reaction for 4-48 hours. Add dilute hydrochloric acid as a stop agent, filter and wash, and vacuum dry to obtain polyurethane prepolymer.

4. The method for preparing a non-isocyanate type photocurable resin according to claim 1, characterized in that, Step one of the synthesis steps: By weight, add 180-210 parts of cyclic carbonate and 80-110 parts of isophorone diamine to the reactor. Under nitrogen protection, heat to 50-90℃ and stir at a uniform speed for 0.5-2 hours. Then, raise the temperature to 90-140℃ and carry out the polycondensation reaction for 4-48 hours. After vacuum drying, the polyurethane prepolymer can be obtained.

5. A method for preparing a non-isocyanate type photocurable resin according to any one of claims 1-4, characterized in that: The cyclic carbonate includes any one of ethylene carbonate, propylene carbonate, and 1,2-glycerol carbonate; the aliphatic primary amine includes any one of methylamine, ethylamine, propylamine, butylamine, pentamine, hexylamine, ethylenediamine, propylenediamine, butylamine, hexamethylenediamine, isophorone diamine, trimethylhexamethylenediamine, and bis(4-aminocycloethyl) ether.

6. A method for preparing a non-isocyanate type photocurable resin according to any one of claims 1-4, characterized in that: The chain extender is any one of resorcinol dihydroxypropyl ether, hydroquinone dihydroxyethyl ether, bisphenol A dihydroxyethyl ether, and bisphenol A dihydroxypropyl ether.

7. A method for preparing a non-isocyanate type photocurable resin according to any one of claims 1-4, characterized in that: The catalyst a in step three is titanium tetraisopropoxide; the methacrylate monomer in step three can be any one of 2-hydroxyethyl methacrylate, methyl methacrylate, n-butyl methacrylate or isobutyl methacrylate.

8. A method for preparing a non-isocyanate type photocurable resin according to any one of claims 1-4, characterized in that: The curing agent used in step three is any one of 4,4-diaminodiphenylmethane, 3,5-dimethylthiotoluenediamine, isobutyl 3,5-diamino-4-chlorobenzoate, or 1,4-bis-sec-butylaminobenzene.

9. A method for preparing a non-isocyanate type photocurable resin according to any one of claims 1-4, characterized in that: The photoinitiator mentioned in step five is any one or a combination of two of photoinitiator 184, photoinitiator TPO, photoinitiator 819, and photoinitiator 907.

10. A method for preparing a non-isocyanate type photocurable resin according to any one of claims 1-4, characterized in that: The polymerization inhibitor mentioned in step five is any one of p-hydroxyanisole, hydroquinone, or 2,6-di-tert-butyl-p-cresol.

Images