A body type polyurea 3D printing resin with hydrogen bond and hydroxyl group synergistically regulating interlayer reconstruction and a molding method

Abstract

The application discloses a preparation method of a high-dissipation boron-containing thermoplastic silicon elastomer with a wide temperature range, and the preparation of the material comprises the following raw materials: polyurea prepolymer 40-80 parts, liquid short-chain polyether amine 10-40 parts and photoinitiator TPO 0.1-5 parts. The multiple hydrogen bonds and side chain hydroxyl groups are introduced by chain extension of 1,3-diamino-2-propanol through adipic acid dihydrazide, and the wide-range adjustable mechanical properties are realized by synergistic control, the interlayer adhesion and isotropy are improved, the printed parts have recyclability, and the method is suitable for photocuring 3D printing forming of high-performance elastomer and plastic parts.

Description

Technical Field

[0001] This invention belongs to the field of photopolymer 3D printing materials and technology, specifically relating to a bulk polyurea 3D printing resin and molding method that uses hydrogen bonds and hydroxyl groups to synergistically regulate interlayer reconstruction. Background Technology

[0002] Photopolymer 3D printing technologies (such as SLA, DLP, and LCD) have broad application prospects in fields such as elastomers, engineering plastics, and functional materials due to their high molding precision, short manufacturing cycle, and ability to achieve integrated molding of complex structures. To overcome the limitations of single photopolymer resins in terms of mechanical properties, durability, and dimensional stability, the industry has widely introduced photothermal dual-curing technology.

[0003] Represented by the publicly disclosed polyurethane acrylate (PUA) dual-curing route, the first stage achieves initial shaping through UV-initiated free radical polymerization of acrylate double bonds; the second stage improves the final performance by thermally triggering the reaction of isocyanate with polyols or amines to form urethane / urea crosslinked networks or interpenetrating networks. However, existing technologies generally suffer from the following drawbacks in practical applications: (1) Significant interlayer interface defects and prominent anisotropy. Layer-by-layer photocuring creates physical interfaces between layers. Traditional thermocuring often involves secondary hardening within a confined network, making it difficult to achieve effective covalent bonding between layers. This results in significantly lower mechanical properties along the Z-axis compared to the XY-axis, making interlayer peeling fracture more likely. (2) Insufficient heat resistance. The main chain or side groups of the PUA system usually contain ester bonds (-COO-) or urethane bonds (-NHCOO-). Traditional photothermal curing polyurethanes are mostly linear structures. They rely on hydrogen bonds to drive the formation of physical crosslinking points, which are prone to creep at high temperatures. At the same time, the acrylate network and the polyurethane network are difficult to form an ideal interpenetrating network morphology, which easily forms a phase separation structure. The reliability of the parts is poor and it is difficult to meet the long-term service requirements of outdoor or harsh working conditions. (3) It is difficult to balance curing efficiency and shape retention. To reduce viscosity, reactive diluents are often introduced, resulting in low strength and poor creep resistance of the green sample after photocuring. Complex geometric structures are prone to collapse and deformation before heat treatment. (4) Thermosetting networks are not rearranged and are difficult to recycle and reuse. Conventional thermosetting forms irreversible cross-linked networks, making it difficult to reprocess and recycle materials.

[0004] To address the aforementioned issues, there is an urgent need for a photocurable 3D printing resin system that is designed collaboratively from the perspective of molecular structure and reaction process, can achieve molecular chain diffusion and covalent bond reconstruction at different interlayer interfaces in the post-processing stage, and possesses both durability and recyclability, so as to fundamentally solve the common industry pain points of anisotropy and poor weather resistance of 3D printed parts. Summary of the Invention

[0005] The purpose of this invention is to provide a polyurea 3D printing resin system based on the synergistic regulation of multiple hydrogen bonds and hydroxyl groups. Through time-decoupled photocuring shaping and thermal treatment reconstruction, covalent reconstruction and continuous network formation at the interlayer interfaces are achieved, thereby significantly reducing anisotropy and improving interlayer bonding. Simultaneously, the polyurea backbone and multiple hydrogen bond / micro-crosslinking structure enhance weather resistance, dimensional stability, and creep resistance, and achieve wide-range continuous tunability of mechanical properties and recyclability of 3D printed parts. Another objective of this invention is to provide a DLP 3D printing method for the above-mentioned resin system.

[0006] To achieve the above objectives, the following technical solution is adopted: A bulk polyurea 3D printing resin and molding method for synergistic regulation of interlayer reconstruction by hydrogen bonding and hydroxyl groups, characterized in that the resin comprises the following components: (1) 40-80 parts of polyurea prepolymer A, wherein the main chain of the polyurea prepolymer contains multiple hydrogen bonds and the end is capped by a hindered urea structure, and is prepared by reacting alicyclic diisocyanate HMDI with long-chain polyether diamine D2000 and diamine small molecule B containing side chain hydroxyl groups, followed by chain extension by hydrazide-containing chain extender C, and then end capped by acrylate compound containing sterically hindered secondary amine group; (2) Mix polyurea prepolymer A and 10-40 parts of liquid short-chain polyetheramine C, add 0.1-5 parts of photoinitiator TPO, and mix thoroughly using a vacuum degassing mixer to obtain liquid photosensitive resin; In this process, the hindered urea structure in component A remains in a latent state during the photocuring stage; during the heat treatment stage, the hindered urea dissociates upon heating, releasing isocyanate groups, which undergo in-situ chain extension and cross-linking reactions with components B and C to form a three-dimensional polyurea cross-linked network that penetrates the interlayer interface.

[0007] The diamine molecule B containing side chain hydroxyl groups mentioned in step (1) is 1,3-diamino-2-propanol (DMPP).

[0008] The chain extender C containing an acylhydrazine group mentioned in step (1) is adipic acid dihydrazine (ADH).

[0009] The component C mentioned in step (2) is any one or a combination of triaminoT403 and diaminoD230.

[0010] The molar percentage of component B in step (1) is 5% to 40%, and the molar percentage of component C in step (2) is 10% to 60%. By adjusting the ratio of component B to component C, the tensile properties can be continuously adjusted over a wide range from elastomers to plastics.

[0011] The present invention discloses a bulk polyurea 3D printing resin and molding method for synergistic regulation of interlayer reconstruction by hydrogen bonding and hydroxyl groups, characterized by comprising the following steps: (1) The resin system is placed in a 3D printing device and exposed layer by layer to form the initial part, relying on the multiple hydrogen bond network to maintain the macroscopic shape retention of the initial part; (2) Place the initial molded part at 80°C. o C~160 o Heat treatment at C for 2-12 hours triggers the unblocking and rearrangement of the hindered urea, and the dynamic covalent bond exchange realizes a cross-layer body network, so that the tensile strength of the final part in the Z-axis direction is comparable to that in the XY-axis direction.

[0012] The present invention discloses a three-dimensional polyurea 3D printing resin and molding method for interlayer reconstruction synergistically regulated by hydrogen bonds and hydroxyl groups, characterized in that the 3D printed resin part has the ability to be repeatedly processed by hot pressing and solvent recovery.

[0013] Compared with the prior art, the beneficial effects of the present invention are: (1) Through hindered urea dissociation and in-situ chain extension during the heat treatment stage, interlayer covalent reconstruction is achieved, significantly improving the interlayer bonding strength and isotropy; (2) ADH introduces a high-density multiple hydrogen bond structure into the polyurea backbone, which significantly improves the strength and shape retention of the cured green body and suppresses deformation and collapse after printing; (3) The terminal amines of DMPP participate in chain extension, which can accelerate the photocuring reaction process. The side chain hydroxyl groups, as polar sites, induce micro-crosslinking and hydrogen bond aggregation, thereby improving dimensional stability, creep resistance and toughness. (4) The final solidified network backbone is mainly composed of urea bonds and three-dimensional networks, avoiding the risk of hydrolysis of ester / urethane bonds, and significantly improving hydrolysis resistance, weather resistance and creep resistance. (5) By adjusting the ratio of DMPP to short-chain amines, a wide range of continuously adjustable properties from high-resilience elastomers to high-strength plastics can be achieved; (6) The system has the potential for network reconstruction and reprocessing, and can realize hot pressing reshaping or solvent dissolution and recycling. Attached Figure Description

[0014] Figure 1 NMR spectrum of polyurea prepolymer molecular structure Figure 2 Tensile stress-strain curve of the photopolymer-printed sample. Figure 3 DSC curves showing accelerated photocuring reaction Figure 4 Schematic diagram of the hot pressing and solvent recovery process for printed parts. Figure 5 Scanning electron microscope image of heat treatment improving interlayer bonding. Figure 6 Compression-recovery curves of photopolymer 3D printed lattice parts Detailed Implementation Example 1 Step 1: Preparation of polyurea prepolymer A. Weigh 100 parts of D2000 and dissolve it in N,N-dimethylacetamide (DMAc). Under nitrogen protection, add HMDI and D2000 dropwise to the reactor at an NCO:NH2 equivalent ratio of (2.00–2.20):1. React at room temperature for 3 hours to obtain an isocyanate-terminated prepolymer. Add 10 parts of ADH for chain extension reaction for 8 hours. Heat to 60°C. o C. TBEMA was added and the end-capping reaction was carried out in equimolar amounts of residual NCO until the NCO peak disappeared as shown by FTIR, thus obtaining prepolymer A containing hindered urea structure and multiple hydrogen bond structure.

[0015] Step 2: Resin compounding. Take 60 parts of prepolymer A, add 25 parts of D230 and 1.5 parts of TPO, and mix and degas in a vacuum degassing mixer to obtain a liquid resin with a viscosity of about 1200 mPa·s.

[0016] Step 3: DLP Printing and Heat Treatment. A 405 nm DLP printer was used, with a layer thickness of 10 μm and a single-layer exposure time of 15 s to obtain the initial molded part; the initial molded part was then placed at 90°C. o After heat treatment at C for 5 hours, the final sample was obtained for testing.

[0017] Example 2 Step 1: Preparation of polyurea prepolymer A. Weigh 5 parts of DMPP and 95 parts of D2000 and dissolve them in N,N-dimethylacetamide (DMAc). Under nitrogen protection, add HMDI and D2000 to the reactor at an NCO:NH2 equivalent ratio of (2.00~2.20):1 and react at room temperature for 3 h to obtain an isocyanate-terminated prepolymer. Add 10 parts of ADH for chain extension reaction for 1 h. Heat to 60℃ and add TBEMA for end-capping reaction based on residual NCO until the NCO peak disappears on FTIR, obtaining prepolymer A containing hindered urea structure and multiple hydrogen bond structure.

[0018] Step 2: Resin compounding. Take 60 parts of prepolymer A, add 25 parts of D230 and 1.5 parts of TPO, and mix and degas in a vacuum degassing mixer to obtain a liquid resin with a viscosity of about 850 mPa·s.

[0019] Step 3: DLP printing and heat treatment. A 405 nm DLP printer with a layer thickness of 10 μm and a single-layer exposure time of 15 s was used to obtain the initial molded part. The initial molded part was then heat-treated at 100℃ for 3 h to obtain the final part for testing.

[0020] Example 3 Step 1: Preparation of polyurea prepolymer A. Weigh 15 parts of DMPP and 85 parts of D2000 and dissolve them in N,N-dimethylacetamide (DMAc). Under nitrogen protection, add HMDI and D2000 to the reactor at an NCO:NH2 equivalent ratio of (2.00~2.20):1 and react at room temperature for 3 h to obtain an isocyanate-terminated prepolymer. Add 10 parts of ADH for chain extension reaction for 1 h. Heat to 60℃ and add TBEMA for end-capping reaction based on residual NCO until the NCO peak disappears on FTIR, obtaining prepolymer A containing hindered urea structure and multiple hydrogen bond structure.

[0021] Step 2: Resin compounding. Take 60 parts of prepolymer A, add 15 parts of T403 and 1.5 parts of TPO, and mix and degas in a vacuum degassing mixer to obtain a liquid resin with a viscosity of about 600 mPa·s.

[0022] Step 3: DLP Printing and Heat Treatment. A 405 nm DLP printer was used with a layer thickness of 10 μm and a single-layer exposure time of 15 s to obtain the initial molded part; the initial molded part was then placed at 120°C. o After heat treatment at C for 2 hours, the final part is obtained for testing.

[0023] Example 4 Step 1: Preparation of polyurea prepolymer A. Weigh 30 parts of DMPP and 70 parts of D2000 and dissolve them in N,N-dimethylacetamide (DMAc). Under nitrogen protection, add HMDI and D2000 to the reactor at an NCO:NH2 equivalent ratio of (2.00~2.20):1 and react at room temperature for 3 h to obtain an isocyanate-terminated prepolymer. Add 20 parts of ADH for chain extension reaction for 1 h. Heat to 60℃ and add TBEMA for end-capping reaction based on residual NCO until the NCO peak disappears on FTIR, obtaining prepolymer A containing hindered urea structure and multiple hydrogen bond structure.

[0024] Step 2: Resin compounding. Take 60 parts of prepolymer A, add 10 parts of T403, 10 parts of D230, and 1.5 parts of TPO, and mix and degas in a vacuum degassing mixer to obtain a liquid resin with a viscosity of approximately 520 mPa·s.

[0025] Step 3: DLP Printing and Heat Treatment. A 405 nm DLP printer was used with a layer thickness of 10 μm and a single-layer exposure time of 10 s to obtain the initial molded part; the initial molded part was then placed at 90°C. o After heat treatment at C for 8 hours, the final part was obtained for testing.

[0026] Example 5 Step 1: Preparation of polyurea prepolymer A. Weigh 50 parts of DMPP and 50 parts of D2000 and dissolve them in N,N-dimethylacetamide (DMAc). Under nitrogen protection, add HMDI and D2000 to the reactor at an NCO:NH2 equivalent ratio of (2.00~2.20):1 and react at room temperature for 3 h to obtain an isocyanate-terminated prepolymer. Add 15 parts of ADH for chain extension reaction for 1 h. Heat to 60℃ and add TBEMA for end-capping reaction based on residual NCO until the NCO peak disappears on FTIR, obtaining prepolymer A containing hindered urea structure and multiple hydrogen bond structure.

[0027] Step 2: Resin compounding. Take 60 parts of prepolymer A, add 20 parts of T403, 5 parts of D230 and 1 part of TPO, mix and degas in a vacuum degassing mixer to obtain a liquid resin with a viscosity of about 680 mPa·s.

[0028] Step 3: DLP Printing and Heat Treatment. A 405 nm DLP printer was used with a layer thickness of 10 μm and a single-layer exposure time of 8 s to obtain the initial molded part; the initial molded part was then placed at 90°C. o After heat treatment at C for 5 hours, the final part is obtained for testing.

[0029] Table 1 shows the mechanical properties of the sample specimens from the examples. The polyurea photocured printed specimens exhibit excellent performance, achieving a wide range of continuously tunable properties from high-resilience elastomers to plastics. Experimental results also demonstrate that this invention enhances the shape retention force of the cured green body by introducing multiple hydrogen bonds through ADH, induces micro-crosslinking and synergistic reconstruction through DMPP side chain hydroxyl groups, and combines hindered urea dissociation and in-situ chain extension during heat treatment to achieve the construction of a continuous interlayer network. This significantly improves the Z / XY strength ratio of the parts, bringing it close to isotropy, while also significantly improving dimensional stability and possessing reprocessing and recycling potential.

[0030] Table 1 Mechanical Properties and Sample Hardness The three-dimensional polyurea photothermal dual-curing 3D printing resin system and molding method provided by this invention, through the synergistic regulation of multiple hydrogen bonds and hydroxyl groups and the interlayer covalent reconstruction mechanism in the heat treatment stage, can significantly improve the shape retention, interlayer bonding and isotropy of the cured green body while maintaining the high precision and high efficiency of DLP printing. It also achieves comprehensive performance advantages such as weather resistance, wide-range adjustable mechanical properties and recyclability, and is suitable for photocuring 3D printing of high-performance elastomers and plastic parts.

Claims

1. A three-dimensional polyurea 3D printing resin and molding method for synergistic regulation of interlayer reconstruction by hydrogen bonding and hydroxyl groups, characterized in that, The resin comprises the following components: (1) 40-80 parts of polyurea prepolymer A, wherein the main chain of the polyurea prepolymer contains multiple hydrogen bonds and the end is capped by a hindered urea structure, and is prepared by reacting alicyclic diisocyanate HMDI with long-chain polyether diamine D2000 and diamine small molecule B containing side chain hydroxyl groups, followed by chain extension by hydrazide-containing chain extender C, and then end capped by acrylate compound containing sterically hindered secondary amine group; (2) Mix polyurea prepolymer A and 10-40 parts of liquid short-chain polyetheramine C, add 0.1-5 parts of photoinitiator TPO, and mix thoroughly using a vacuum degassing mixer to obtain liquid photosensitive resin; In this process, the hindered urea structure in component A remains in a latent state during the photocuring stage. During the heat treatment stage, the hindered urea dissociates upon heating, releasing isocyanate groups, which then undergo in-situ chain extension and cross-linking reactions with components B and C to form a three-dimensional polyurea cross-linked network that penetrates the interlayer interface.

2. The three-dimensional polyurea 3D printing resin and molding method for synergistic regulation of interlayer reconstruction by hydrogen bonding and hydroxyl groups according to claim 1, characterized in that... The diamine molecule B containing a side-chain hydroxyl group is 1,3-diamino-2-propanol (DMPP).

3. The three-dimensional polyurea 3D printing resin and molding method for synergistic regulation of interlayer reconstruction by hydrogen bonding and hydroxyl groups according to claim 1, characterized in that... The chain extender containing an acylhydrazide group is adipic acid dihydrazide (ADH).

4. The three-dimensional polyurea 3D printing resin and molding method for synergistic regulation of interlayer reconstruction by hydrogen bonding and hydroxyl groups according to claim 1, characterized in that... The component C is any one or a combination of triaminoT403 and diaminoD230.

5. The three-dimensional polyurea 3D printing resin and molding method for synergistic regulation of interlayer reconstruction by hydrogen bonding and hydroxyl groups according to claim 1, characterized in that... The molar percentage of component B is 5% to 40%, and the molar percentage of component C is 10% to 60%. By adjusting the ratio of component B to component C, the tensile properties can be continuously adjusted over a wide range from elastomers to plastics.

6. The three-dimensional polyurea 3D printing resin and molding method for synergistic regulation of interlayer reconstruction by hydrogen bonding and hydroxyl groups according to claim 1, characterized in that, Includes the following steps: (1) The resin system is placed in a 3D printing device and exposed layer by layer to form the initial part, relying on the multiple hydrogen bond network to maintain the macroscopic shape retention of the initial part; (2) Place the initial molded part at 80°C. o C~160 o Heat treatment at C for 2-12 hours triggers the unblocking and rearrangement of the hindered urea, and dynamic covalent bond exchange realizes a cross-layer body network, so that the tensile strength of the final part in the Z-axis direction is comparable to that in the XY-axis direction.

7. The three-dimensional polyurea 3D printing resin and molding method for synergistic regulation of interlayer reconstruction by hydrogen bonding and hydroxyl groups according to claim 1, characterized in that, The 3D printed resin parts described herein have the ability to be repeatedly processed by hot pressing and to recover solvents.

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