Heat-resistant modified single-component polyurea, preparation thereof and application of heat-resistant modified single-component polyurea in 3D printing

Abstract

The invention firstly provides application of modified single-component polyurea as a 3D printing hot bed coating. The modified single-component polyurea is used for the 3D printing hot bed coating for the first time, adhesion and fixation of a printed product at low temperature are achieved, energy consumption is reduced, and meanwhile the service life of the coating is prolonged. On the basis, the invention further provides the heat-resistant modified single-component polyurea. According to the heat-resistant modified single-component polyurea, on the basis of the modified single-component polyurea, a hollow zigzag composite filler independently researched and developed by the inventor is added; the hollow zigzag composite filler is a hollow zigzag structure Cu-MOF (at) PA (at) NiMoO4 which is formed by etching a Cu-MOF three-dimensional frame structure into a hollow structure by phytic acid and bridging NiMoO4 through phytic acid. The molar ratio of the Cu-MOF to the NiMoO4 to the phytic acid in the composite filler is (25 to 50): (5 to 10): 1. Compared with modified single-component polyurea, the heat-resistant modified single-component polyurea has the advantages that the heat resistance of a hot bed coating is remarkably improved, and release of harmful gas is effectively reduced based on good adsorption performance of the heat-resistant modified single-component polyurea.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and relates to a one-component polyurea, specifically to the preparation and application of a heat-resistant modified one-component polyurea coating for a 3D printing hot bed. Background Art

[0002] 3D printing technology, also known as additive manufacturing technology, is an advanced manufacturing technology that uses a digital model file as a basis, and uses filaments, liquids or powders as raw materials to directly construct complex geometric-shaped objects by layer-by-layer stacking. Compared with traditional subtractive manufacturing, 3D printing has outstanding advantages such as no need for molds, high design flexibility, short production cycle, and the ability to manufacture complex structures. In recent years, with the development of China's manufacturing industry towards intelligence, high efficiency and greenness, 3D printing technology, as a new generation of manufacturing technology, has received extensive attention and has become one of the important fields of global technological innovation. At present, the main processes of 3D printing include fused deposition modeling technology (FDM), stereolithography (SLA) and selective laser sintering technology (SLS). Among them, FDM has become the most widely used 3D printing process due to its low material cost, biodegradability, convenient equipment maintenance and low operating cost. FDM heats and melts thermoplastic materials, such as acrylonitrile-butadiene-styrene copolymer (ABS), polylactic acid (PLA), etc., to turn them into a fluid state, and precisely extrudes tiny molten particles using a nozzle. These particles quickly adhere to the surface of the printer hot bed after being ejected, cool and solidify, and finally build a three-dimensional solid model by layer-by-layer stacking.

[0003] Although the FDM technology has the above-mentioned remarkable advantages, the heating and melting steps bring a series of technical problems: (1) The high-temperature environment is not conducive to the stability of the printing platform coating. During the FDM printing process, the temperature of the molten material is usually 200-250°C, which causes the adjacent hot bed area to receive continuous thermal radiation, and has high requirements for the heat resistance of the coating. If the heat resistance of the coating is insufficient, long-term use will cause the coating to soften, degrade or peel off, affecting the printing quality and the coating life. (2) Toxic gases are released by consumables such as ABS under high-temperature conditions, which is not environmentally friendly. As is well known, the ABS material produces volatile organic compounds (VOCs), such as benzene, toluene, styrene, etc., under high-temperature conditions, which pose potential hazards to the health of operators and the working environment. How to reduce the release of harmful gases during the printing process has become a technical problem to be solved urgently. (3) The problem of insufficient adhesion of the hot bed. Existing FDM technologies usually adopt adhesion enhancement schemes such as PEI plates, glue, tapes, etc., which have problems of poor durability and rapid adhesion force attenuation, thus affecting the printing stability and success rate.

[0004] Polyurea is a high-performance elastomer formed by the rapid polymerization reaction of isocyanate (-NCO) and amino compounds (-NH2), including two-component polyurea and one-component polyurea. Among them, two-component polyurea needs to mix isocyanate prepolymer and amino resin (such as amine chain extender) on-site, relying on special spraying equipment, with a fast curing speed (in seconds), but the construction conditions are harsh; while one-component polyurea needs to pre-synthesize a stable system, without mixing, and the construction is convenient, but the technical difficulty is higher. At present, there are few reports on polyurea 3D printing technology, generally it is stereolithography 3D technology. Invention Patent 202111432462.7 discloses "Two-component polyurea material for 3D printing and method for 3D printing polyurea products". This invention patent realizes direct writing 3D printing, can print polyurea products with special complex structures, and the strength in the Z direction of the printed products can reach more than 85% of the XY plane, and products with different mechanical properties can be obtained. In this patent, two-component polyurea is used as the consumable for 3D printing, rather than the coating.

[0005] At present, there are no relevant reports on using one-component polyurea as a high-temperature resistant coating in FDM technology. Summary of the Invention

[0006] Aiming at the technical problems of insufficient coating stability, easy generation of harmful gases and insufficient adhesion caused by the heating and melting step in FDM technology in the prior art, this application first provides an application of a modified one-component polyurea as a 3D printing hot bed coating. This application first proposes to use modified one-component polyurea for 3D printing hot bed coating, realizing the adhesion and fixation of printed products at low temperature, while reducing energy consumption and extending the service life of the coating. On this basis, this application also provides a heat-resistant modified one-component polyurea. Based on the above-mentioned modified one-component polyurea, the hollow serrated composite filler independently developed by the inventor is added, which significantly improves the heat resistance of the hot bed coating, and based on its good adsorption performance, effectively reduces the release of harmful gases.

[0007] The technical solution of the present invention:

[0008] An application of a modified one-component polyurea as a 3D printing hot bed coating, the modified one-component polyurea is composed of the following components by weight percentage: 50-55 parts of polyisocyanate, 90-101 parts of modified polyester resin, 40-50 parts of solvent, 25-30 parts of latent curing agent, 0.4-0.6 parts of hydrolysis promoter, 0.2-0.3 parts of organotin catalyst, 0.75-1 part of hydroxyl-terminated polyether, and 0.5-0.75 parts of other additives. This application first proposes to use modified one-component polyurea for 3D printing hot bed coating, which can still maintain good adhesion at normal temperature or medium and low temperature, effectively reduce the warping and falling off of printed parts, improve the printing success rate, and save the consumable cost and energy consumption cost.

[0009] Compared with the coatings used in the prior art that can achieve effective adhesion only at a temperature of at least 60 °C (when the temperature is too low, effective adhesion cannot be achieved, resulting in easy displacement of the sample during printing and printing failure), the modified one-component polyurea as a hot bed coating significantly reduces the adhesion temperature (35 °C), achieving an unexpected technical effect. Moreover, since the existing coatings must be at a relatively high temperature (not less than 60 °C) to achieve effective adhesion, it inevitably leads to poor coating durability and rapid adhesion force attenuation; while the coating described in this application, due to reducing the working temperature, fundamentally overcomes the technical defects of poor coating durability and rapid adhesion force attenuation, further reducing the use cost and the operational complexity brought by replacing the coating, and has broad application prospects.

[0010] Among them, the polyisocyanate is one or more of isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate. The modified polyester resin is one or more of polyethylene adipate, polypropylene adipate, polyhexanediol adipate, and poly(ethylene glycol adipate).

[0011] The latent curing agent is an imine-based latent curing agent, selected from one or more of methylcyclohexyl imine, p-tolyl imine, and isopropyl imine. The hydroxyl-terminated polyether is selected from any one or more of polytetrahydrofuran ether, polypropylene oxide ether, polyethylene oxide ether, and block copolymer ether. The organotin catalyst is any one or more of stannous octoate, dibutyltin dilaurate, isopropyl titanate, titanium citrate, and dibutyltin oxide. The hydrolysis promoter is one or more of ethanolamine, isopropanolamine, diethanolamine, ammonia water, tetramethylammonium hydroxide, borate ester, titanate ester, and other compounds with hydrolysis-promoting properties.

[0012] The other additives include defoamers and leveling agents; the defoamer is one or more of monoalkyl phosphate esters, trialkyl melamine, ethylene oxide, and polydimethylsiloxane; the leveling agent is an acrylate polymer or a modified polysiloxane, and is one or more of polydimethylsiloxane and alkyl-modified organosiloxane; the solvent is one or more of xylene, butyl acetate, and ethylene glycol monoethyl ether acetate.

[0013] The preparation method of the modified one-component polyurea is specifically as follows:

[0014] (1) Prepare a semi-prepolymer: Add the modified polyester resin to the reaction device, and dewater under reduced pressure with nitrogen at 90 °C - 110 °C for 1 - 2 h; cool down to 80 - 85 °C, add polyisocyanate and react at a constant temperature for 2 - 3 h to obtain a semi-prepolymer;

[0015] (2) Prepare one-component polyurea: Add the latent curing agent and other components to the above semi-prepolymer in step (2) to prepare the modified one-component polyurea.

[0016] A heat-resistant modified one-component polyurea, by weight percentage, consists of the components of the modified one-component polyurea in the aforementioned application and 15 - 20 parts of hollow serrated composite filler to improve the surface adhesion and heat resistance of the coating. The hollow serrated composite filler is a hollow serrated structure Cu-MOF@PA@NiMoO4 formed by etching the Cu-MOF three-dimensional framework structure with phytic acid into a hollow structure and bridging NiMoO4 through phytic acid; the molar ratio of Cu-MOF, NiMoO4, and phytic acid in the composite filler is (25 - 50):(5 - 10):1. Among them, the NiMoO4 is a nanoneedle structure, and the Cu-MOF is a three-dimensional framework structure obtained by self-assembly of Cu metal ions and ligands through coordination bonds; the ligand is 1,4-benzenedicarboxylic acid ligand, 2-aminoterephthalic acid, or 1,3,5-benzenetricarboxylic acid. The addition of the composite filler Cu-MOF@PA@NiMoO4 endows the coating with better thermal stability and heat resistance, and can maintain high structural integrity when contacting the extrusion port at 200 - 250 °C during the printing process, and is not easily softened or degraded, thereby prolonging the service life of the coating. Moreover, based on the nanoporous structure and good adsorption properties of the composite filler Cu-MOF@PA@NiMoO4, the coating can effectively capture and reduce VOCs released during the melting process of consumables such as ABS, further improving the safety of the printing environment.

[0017] The preparation method of the heat-resistant modified one-component polyurea as described above includes the following steps:

[0018] (1) Preparation of the hollow serrated composite filler: Disperse an appropriate amount of NiMoO4, Cu-MOF, and phytic acid (PA) evenly in water, and react at room temperature for 12 - 24 h under stirring conditions to obtain a suspension; after separation, washing, and drying treatments, the final product Cu-MOF@PA@NiMoO4, a light blue powder, is obtained, which is the novel hollow serrated composite filler. The drying conditions are vacuum drying, oven drying, or freeze drying. The vacuum drying is specifically: drying at 75 - 85 °C for 4 - 6 h; the oven drying is specifically: drying at 70 - 90 °C for 8 - 10 h; the freeze drying is specifically: drying at -50 to -60 °C for 10 - 12 h.

[0019] The preparation method uses Cu-MOF with a three-dimensional framework structure and NiMoO4 with a nanoneedle structure as precursors. By introducing phytic acid to etch Cu-MOF and bridge NiMoO4, a hollow serrated structure is further formed. Compared with the original Cu-MOF, the overall structure of the Cu-MOF@PA@NiMoO4 flame retardant has changed significantly - the regular polyhedron structure of Cu-MOF has been etched into a hollow structure, and a large number of needle-like nickel molybdates are loaded on the surface, so it is no longer smooth. The hollow serrated structure increases the surface area of the nanomaterials, provides more active sites, promotes the flame retardancy and smoke suppression effects, and thus further improves the flame retardancy and heat resistance performance.

[0020] (2) Prepare the semi-prepolymer: Add the modified polyester resin to the reaction device, and carry out nitrogen-decompression dehydration at 90 °C - 110 °C for 1 - 2 h; cool down to 80 - 85 °C, add polyisocyanate and react at a constant temperature for 2 - 3 h to obtain the semi-prepolymer;

[0021] (3) Prepare the one-component polyurea: Add the latent curing agent, the hollow serrated composite filler prepared in step (1) and other components to the above semi-prepolymer in step (2) to prepare a latent curing type one-component polyurea.

[0022] Preferably, the NiMoO4 is prepared by a hydrothermal method, specifically: Dispersed sodium molybdate dihydrate and nickel nitrate hexahydrate in deionized water, and magnetically stirred until completely dissolved; then transferred to an autoclave for hydrothermal reaction. After the reaction is completed, it is cooled to room temperature, centrifuged, washed, and dried to obtain the product NiMoO4. Among them, the weight ratio of sodium molybdate dihydrate to nickel nitrate hexahydrate is 1:(1 - 4); the specific conditions of the hydrothermal reaction are 110 °C - 130 °C for 12 - 20 h, and the drying conditions are 60 - 80 °C for 6 - 8 h; the washing is carried out with deionized water.

[0023] The purpose of this step is to synthesize the transition metal oxide NiMoO4 with higher thermal stability by the hydrothermal method; the NiMoO4 is a nanoneedle structure with a relatively regular shape, and most of the sizes are 2 - 4 μm. Thus, the next assembly of nickel molybdate and Cu-MOF is realized, and further the improvement of the flame retardant effect of the flame retardant is achieved.

[0024] Preferably, the Cu-MOF is prepared by a solvothermal reaction. The specific method is as follows: Copper nitrate trihydrate is dispersed in a DMF solution and ultrasonically dispersed for 5-20 minutes to obtain a dispersion system A. Polyvinylpyrrolidone and an organic ligand are dispersed in a DMF solution to obtain a solution B. The dispersion system A and the solution B are mixed and transferred into an autoclave for solvothermal reaction. After centrifugation, washing, and drying, the product Cu-MOF is obtained. The weight ratio of the copper nitrate trihydrate, polyvinylpyrrolidone, and the organic ligand is (1-5):(1-3):1. The specific conditions of the solvothermal reaction are 80°C - 120°C, the reaction time is 12-24 hours, and the drying conditions are drying at 60-80°C for 8-10 hours. The mass concentration of the DMF solution is 500-1000 g / L; the washing is carried out with a DMF solution with a concentration of 500-1000 g / L. The organic ligand is 1,4-benzenedicarboxylic acid, 2-aminoterephthalic acid, or 1,3,5-benzenetricarboxylic acid.

[0025] The application of the heat-resistant modified one-component polyurea in 3D printing as described above, where the one-component polyurea is used as a coating for the heat bed bottom plate of a 3D printer. The specific application is as follows: The heat-resistant modified one-component polyurea is mixed with an appropriate amount of solvent to obtain a coating material, which is sprayed on the heat bed bottom plate of the 3D printer and cured to form a shape.

[0026] Advantages of the present invention:

[0027] (1) This application first provides an application of a modified one-component polyurea as a 3D printing heat bed coating. This application first proposes to use the modified one-component polyurea for the 3D printing heat bed coating, achieving the adhesion stability of the printed product at medium and low temperatures, producing unexpected technical effects, and at the same time reducing the energy consumption of the equipment.

[0028] (2) This application also provides a heat-resistant modified one-component polyurea. Based on the aforementioned modified one-component polyurea, the addition of a hollow serrated composite filler independently developed by the inventor significantly improves the heat resistance and stability of the heat bed coating. When in contact with an extrusion outlet at 200-250°C, it can maintain a high structural integrity, is not easily softened or degraded, thereby extending the service life of the coating.

[0029] (3) The heat-resistant modified one-component polyurea coating provided by the present invention not only improves the thermal stability and adhesion durability of the heat bed coating, but also effectively reduces the release of toxic gases during the printing process, achieving a significant improvement in technical effects. Description of the Drawings

[0030] Appendix Figure 1 XRD images of the products at each step during the preparation process of the novel hollow serrated structure material in Example 1.

[0031] Appendix Figure 2SEM and EDS images of the products at each step in the preparation process of the novel hollow serrated structure material in Example 1.

[0032] Attachment Figure 3 XPS images of the products at each step in the preparation process of the novel hollow serrated structure material in Example 1.

[0033] Attachment Figure 4 TG curve images of the modified one-component polyurea and heat-resistant polyurea prepared in Example 5.

[0034] Attachment Figure 5 Smoke release amount curves of the modified one-component polyurea and heat-resistant polyurea prepared in Example 5.

[0035] Attachment Figure 6 Carbon monoxide release rate curves of the modified one-component polyurea and heat-resistant polyurea prepared in Example 5. Detailed implementation manners

[0036] The present invention will be further described below in conjunction with examples. The raw materials used in the examples and comparative examples are described as follows, but are not limited to these materials:

[0037] The polyester resin is a carboxyl-terminated polyester with a hydroxyl value of 50 - 80 mg KOH / g, sourced from the market.

[0038] The isocyanate is isophorone diisocyanate and diphenylmethane diisocyanate with a molecular weight of 222 g / mol, sourced from the market.

[0039] The catalyst is dibutyltin dilaurate with a catalyst activity of 20 - 30%, sourced from the market.

[0040] The solvent is butyl acetate with a molecular weight of 130.19 g / mol, sourced from the market.

[0041] The hydrolysis promoter is an amine compound with a molecular weight of 100 - 200 g / mol, sourced from the market.

[0042] The latent curing agent is an imine-based latent curing agent, sourced from the market.

[0043] The leveling agent is a modified silane leveling agent with a molecular weight of 300 - 500 g / mol, sourced from the market.

[0044] The defoaming agent is a polysiloxane defoaming agent with a molecular weight of 500 - 1000 g / mol, sourced from the market.

[0045] Example 1: Preparation of a novel hollow serrated composite filler

[0046] (1) Preparation of NiMoO4: Sodium molybdate dihydrate and nickel nitrate hexahydrate were dispersed in deionized water and magnetically stirred until completely dissolved; then transferred to an autoclave for hydrothermal reaction. After the reaction was completed, it was cooled to room temperature, centrifuged, washed, and dried to obtain the product NiMoO4. The NiMoO4 has a nanoneedle-like structure, with a relatively regular shape, and most of the sizes are 2 - 4 μm. Among them, the weight ratio of sodium molybdate dihydrate to nickel nitrate hexahydrate is 1:1; the specific conditions of the hydrothermal reaction are reacting at 110 °C for 12 h, and the drying conditions are drying at 60 °C for 6 h; the washing is carried out with deionized water.

[0047] (2) Preparation of Cu-MOF: Copper nitrate trihydrate was dispersed in a DMF solution and ultrasonically dispersed for 5 min to obtain dispersion system A. Polyvinylpyrrolidone and terephthalic acid were dispersed in a DMF solution to obtain solution B; dispersion system A and solution B were mixed and transferred to an autoclave for solvothermal reaction; after centrifugation, washing, and drying, the product Cu-MOF was obtained; the weight ratio of copper nitrate trihydrate, polyvinylpyrrolidone, and terephthalic acid is 3:2:1. The specific conditions of the solvothermal reaction are 80 °C, the reaction time is 12 h, and the drying conditions are drying at 60 °C for 8 h. The mass concentration of the DMF solution is 500 g / L; the washing is carried out with a DMF solution with a concentration of 500 g / L.

[0048] (3) Preparation of Cu-MOF@PA@NiMoO4: The NiMoO4 prepared in step (1), the Cu-MOF prepared in step (2), and phytic acid were dispersed in an aqueous deionized solution, ultrasonically dispersed evenly, and reacted at room temperature under magnetic stirring for 12 h to obtain a suspension; after centrifugation, washing, and freeze-drying, the product Cu-MOF@PA@NiMoO4 with a light blue powder morphology was obtained, which is the novel hollow serrated composite filler. Among them, the molar ratio of Cu-MOF, NiMoO4, and phytic acid is 25:5:1. The speed of the magnetic stirring is 500 rpm, the stirring time is 12 h, and the freeze-drying conditions are drying at -50 °C for 10 h. The washing is carried out with deionized water.

[0049] Example 2: Preparation of the novel hollow serrated composite filler

[0050] Differing from Example 1,

[0051] (1) Preparation of NiMoO4: The weight ratio of sodium molybdate dihydrate to nickel nitrate hexahydrate is 1:2; the specific conditions of the hydrothermal reaction are reacting at 120 °C for 16 h, and the drying conditions are drying at 70 °C for 7 h; the washing is carried out with deionized water.

[0052] (2) Preparation of Cu-MOF: The weight ratio of copper nitrate trihydrate, polyvinylpyrrolidone and 2-aminoterephthalic acid is 5:3:1. The specific conditions of the solvothermal reaction are 100 °C, the reaction time is 16 h, and the drying condition is drying at 70 °C for 9 h. The mass concentration of the DMF solution is 750 g / L; the washing is carried out with a DMF solution with a concentration of 750 g / L.

[0053] (3) Preparation of Cu-MOF@PA@NiMoO4: The molar ratio of the Cu-MOF, NiMoO4 and phytic acid is 40:7.5:1; the speed of the magnetic stirring is 750 rpm, the stirring time is 16 h, and the conditions of freeze-drying are drying at -55 °C for 11 h. The washing is carried out with deionized water.

[0054] Example 3: Preparation of a novel hollow serrated composite filler

[0055] Different from Example 1,

[0056] (1) Preparation of NiMoO4: Among them, the weight ratio of sodium molybdate dihydrate and nickel nitrate hexahydrate is 1:4; the specific conditions of the hydrothermal reaction are reacting at 130 °C for 20 h, and the drying condition is drying at 80 °C for 8 h; the washing is carried out with deionized water.

[0057] (2) Preparation of Cu-MOF: The weight ratio of copper nitrate trihydrate, polyvinylpyrrolidone and 1,3,5-benzenetricarboxylic acid is 1:1:1. The specific conditions of the solvothermal reaction are 120 °C, the reaction time is 24 h, and the drying condition is drying at 80 °C for 10 h. The mass concentration of the DMF solution is 1000 g / L; the washing is carried out with a DMF solution with a concentration of 1000 g / L.

[0058] (3) Preparation of Cu-MOF@PA@NiMoO4: The molar ratio of the Cu-MOF, NiMoO4 and phytic acid is 50:10:1; the mass concentration of the phytic acid solution is 850 g / L. The speed of the magnetic stirring is 1000 rpm, the stirring time is 24 h, and the conditions of freeze-drying are drying at -60 °C for 12 h. The washing is carried out with deionized water.

[0059] Example 4: Structural characterization of the hollow serrated composite filler prepared in Examples 1-3

[0060] The hollow serrated composite filler prepared in Examples 1-3 was characterized by XRD, SEM, EDS and XPS. Through XRD characterization, the crystal structure of the flame retardant can be determined, as Figure 1 shown. Through SEM and EDS analysis, the morphological changes and element distributions of the products in each step can be obtained, as Figure 2As shown. By performing XPS analysis on the hollow serrated supramolecular flame retardant, its surface composition and the valence states of elements can be obtained. For example, Figure 3 As shown. Taking Example 1 as an example, the detailed description is as follows:

[0061] (1) The crystal structure of the pre-prepared flame retardant was characterized by XRD. As Figure 1 shown in a, obvious characteristic peaks can be seen at 2θ = 13.6°, 22.7°, 26.7°, 29.6°, 33.1°, 36.2°, 45.3°, 47.3°, and 61.7°. The corresponding crystal planes are (110), (021), (-112), (220), (022), (-132), (204), and (530) (JCPDS 86 - 0361), indicating that the prepared NiMoO4 nanorods are of a monoclinic crystal structure of the α phase. As Figure 1 shown in b, Cu-MOF@PA@NiMoO4 has the same prominent peaks as before, indicating that NiMoO4 retains its crystallinity. In addition, new peaks appear at 2θ = 10.2°, 17.0°, 20.78°, and 24.7° for Cu-MOF@PA@NiMoO4, which are assigned to the (110), (021), (220), and (040) planes (CCDC number: 112954), proving the existence of Cu-MOF. In addition, some characteristic peaks of Cu-MOF and nickel molybdate disappear, possibly due to the etching and bridging of phytic acid.

[0062] (2) Figure 2 SEM images of the samples prepared in each step and the EDS elemental mapping of the final sample are shown. As can be seen from Figure 2 a, in step (1), nanoneedle-like NiMoO4 was successfully synthesized with a relatively regular shape and most of the sizes being 2 - 4 μm. As can be seen from Figure 2 b, after the solvothermal reaction, in step (2), cubic Cu-MOF with a size of about 5 μm was synthesized, and the surface of the cubic structure is relatively smooth. After introducing the reaction with phytic acid, Figure 2 c shows that the cubic structure of Cu-MOF is etched into a hollow structure, and at the same time, NiMoO4 nanoneedles aggregate onto the hollow structure, forming a hollow serrated structure with a rough surface. Figure 2 (d) shows that the elements present in the sample are C, P, O, Cu, Ni, and Mo, providing evidence for the successful synthesis of the hollow serrated supramolecular flame retardant.

[0063] (3) Figure 3 a shows the full-scan spectrum of XPS. It can be seen that the elements present in the sample are C, P, O, Cu, Ni, and Mo. At the same time, these are also the constituent elements of the composite material. C 1s ( Figure 3b) Three independent peaks can be found, with binding energies of 284.80 (C═C / C - C), 286.17 (C - O), and 288.70 (O - C═O) eV respectively. Among them, the C═C / C - C signal corresponds to the benzene ring in the Cu - MOF framework, while C - O and O - C═O are mainly related to the carboxyl groups (COO - ) in the terephthalic acid molecule. The high - resolution spectrum of Cu 2p( Figure 3 c) shows two characteristic peaks at 933.6 and 953.6 eV, belonging to the spin - orbital states of Cu 2p 3 / 2 and Cu2p 1 / 2 respectively. At the same time, the characteristic peaks at 938.21, 944.19, 957.68, and 963.54 eV belong to their satellite peaks, which confirm that the Cu element is in the +2 valence state in this composite material. In addition, the characteristic peaks at 941.34 and 961.59 eV may be due to the chemical - environment change caused by P - O - Cu coordination. Regarding the O1s results( Figure 3 d), the two peaks near 530.17 and 531.78 eV can be assigned to M═O and C═O / P - O bonds, which come from MoO4 2- in NiMoO4, PO4 3- of phytic acid, and the carboxyl groups in the MOF ligand, further proving the successful synthesis of the Cu - MOF@PA@NiMoO4 composite material.

[0064] Example 5: Preparation of Modified One - Component Polyurea and Heat - Resistant Modified One - Component Polyurea

[0065] 1. Preparation of Modified One - Component Polyurea

[0066] The modified one - component polyurea is composed of the following components by weight percentage: 50 parts of polyisocyanate, 101 parts of modified polyester resin, 50 parts of solvent, 30 parts of latent curing agent, 0.6 part of hydrolysis accelerator, 0.3 part of organotin catalyst, 1 part of hydroxyl - terminated polyether, and 0.75 part of other additives.

[0067] Among them, the polyisocyanate is isophorone diisocyanate, the modified polyester resin is polyethylene adipate - glycol ester. The latent curing agent is methylcyclohexylamine, the hydroxyl - terminated polyether is polytetrahydrofuran ether, the organotin catalyst is dibutyltin dilaurate, and the hydrolysis accelerator is ethanolamine.

[0068] The other additives include defoamer and leveling agent. The defoamer is polydimethylsiloxane, the leveling agent is acrylate polymer, and the solvent is butyl acetate.

[0069] The preparation method of the modified one - component polyurea is specifically as follows:

[0070] (1) Preparation of semi-prepolymer: Add the modified polyester resin into the reaction device, and carry out vacuum dehydration for 2 h under the condition of nitrogen passing at 90 °C; after cooling to 85 °C, add polyisocyanate and react at a constant temperature for 2 h to obtain the semi-prepolymer;

[0071] (2) Preparation of modified one-component polyurea: Add a chain extender to the semi-prepolymer prepared in step (1), stir evenly for 15 min, then add the corresponding amounts of catalyst and hydrolysis promoter, and continue to react for about 40 min. After the temperature stabilizes at 85 °C, add the latent curing agent and stir for about 1 h before discharging to prepare the modified one-component polyurea.

[0072] 2. Preparation of heat-resistant modified one-component polyurea

[0073] The heat-resistant modified one-component polyurea is composed of the components of the modified one-component polyurea described in this example and 20 parts of hollow serrated composite filler by weight percentage.

[0074] The preparation method of the heat-resistant modified one-component polyurea includes the following steps:

[0075] (1) Preparation of semi-prepolymer: The same as the preparation of the modified one-component polyurea;

[0076] (2) Preparation of heat-resistant modified one-component polyurea: Add the latent curing agent, the hollow serrated composite filler prepared in Example 1 and other components to the semi-prepolymer prepared in step (1) to prepare the heat-resistant modified one-component polyurea.

[0077] Example 6: Preparation of modified one-component polyurea and heat-resistant modified one-component polyurea

[0078] 1. Preparation of modified one-component polyurea

[0079] The modified one-component polyurea is composed of the following components by weight percentage: 55 parts of polyisocyanate, 90 parts of modified polyester resin, 40 parts of solvent, 25 parts of latent curing agent, 0.4 part of hydrolysis promoter, 0.2 part of organotin catalyst, 0.75 part of hydroxyl-terminated polyether, and 0.5 part of other additives.

[0080] Among them, the polyisocyanate is hexamethylene diisocyanate, and the modified polyester resin is poly(propylene adipate). The latent curing agent is p-toluidine, the hydroxyl-terminated polyether is poly(propylene oxide) ether, the organotin catalyst is stannous octoate, and the hydrolysis promoter is isopropanolamine.

[0081] The other additives include a defoaming agent and a leveling agent. The defoaming agent is ethylene oxide, the leveling agent is modified polysiloxane, and the solvent is xylene.

[0082] The specific preparation method of the modified one-component polyurea is as follows:

[0083] (1) Preparation of semi-prepolymer: Add the modified polyester resin into the reaction device, and carry out vacuum dehydration for 1 h under the condition of nitrogen passing at 110 °C; after cooling to 80 °C, add polyisocyanate and react at a constant temperature for 2 h to obtain the semi-prepolymer;

[0084] (2) Preparation of modified one-component polyurea: Add a chain extender to the semi-prepolymer prepared in step (1), stir evenly for 15 min, then add the corresponding amount of catalyst and hydrolysis promoter, and continue to react for about 40 min. After the temperature stabilizes to 85 °C, add a latent curing agent and stir for about 1 h before discharging to prepare the modified one-component polyurea.

[0085] 2. Preparation of heat-resistant modified one-component polyurea

[0086] The heat-resistant modified one-component polyurea, by weight percentage, consists of the components of the modified one-component polyurea recorded in this example and 15 parts of hollow serrated composite filler.

[0087] The preparation method of the heat-resistant modified one-component polyurea includes the following steps:

[0088] (1) Preparation of semi-prepolymer: The same as the preparation of the modified one-component polyurea;

[0089] (2) Preparation of heat-resistant modified one-component polyurea: Add a latent curing agent, the hollow serrated composite filler prepared in Example 1 and other components to the semi-prepolymer prepared in step (1) to prepare the heat-resistant modified one-component polyurea.

[0090] Example 7: Preparation of modified one-component polyurea and heat-resistant modified one-component polyurea

[0091] 1. Preparation of modified one-component polyurea

[0092] Different from Example 1, the modified one-component polyurea, by weight percentage, consists of the following components: 53 parts of polyisocyanate, 95 parts of modified polyester resin, 45 parts of solvent, 28 parts of latent curing agent, 0.5 part of hydrolysis promoter, 0.25 part of organotin catalyst, 0.85 part of hydroxyl-terminated polyether, and 0.65 part of other additives.

[0093] Among them, the polyisocyanate is isophorone diisocyanate, and the modified polyester resin is poly(adipic acid-co-hexanediol). The latent curing agent is isopropyl imine, the hydroxyl-terminated polyether is polyethylene oxide ether, the organotin catalyst is dibutyltin oxide, and the hydrolysis promoter is diethanolamine.

[0094] The other additives include a defoaming agent and a leveling agent. The defoaming agent is polydimethylsiloxane, the leveling agent is an acrylate polymer, and the solvent is xylene.

[0095] The specific preparation method of the modified one-component polyurea is as follows:

[0096] (1) Preparation of semi-prepolymer: Add the modified polyester resin into the reaction device, and carry out vacuum dehydration for 1.5 h under the condition of nitrogen passing at 100 °C; after cooling to 85 °C, add polyisocyanate and react at a constant temperature for 3 h to obtain the semi-prepolymer;

[0097] (2) Preparation of modified one-component polyurea: Add a chain extender to the semi-prepolymer prepared in step (1), stir evenly for 15 min, then add the corresponding amounts of catalyst and hydrolysis promoter, and continue to react for about 40 min. After the temperature is stabilized at 85 °C, add the latent curing agent and stir for about 1 h and then discharge to prepare the modified one-component polyurea.

[0098] 2. Preparation of heat-resistant modified one-component polyurea

[0099] The heat-resistant modified one-component polyurea is composed of the components of the modified one-component polyurea recorded in this example and 18 parts of hollow serrated composite filler by weight percentage.

[0100] The preparation method of the heat-resistant modified one-component polyurea includes the following steps:

[0101] (1) Preparation of semi-prepolymer: The same as the preparation of the modified one-component polyurea;

[0102] (2) Preparation of heat-resistant modified one-component polyurea: Add the latent curing agent, the hollow serrated composite filler prepared in Example 1 and other components to the semi-prepolymer prepared in step (1) to prepare the heat-resistant modified one-component polyurea.

[0103] Example 8: Preparation of modified one-component polyurea and heat-resistant modified one-component polyurea

[0104] 1. Preparation of modified one-component polyurea

[0105] The modified one-component polyurea is composed of the following components by weight percentage: 50 parts of polyisocyanate, 101 parts of modified polyester resin, 50 parts of solvent, 30 parts of latent curing agent, 0.6 part of hydrolysis promoter, 0.3 part of organotin catalyst, 1 part of hydroxyl-terminated polyether, and 0.75 part of other additives.

[0106] Among them, the polyisocyanate is diphenylmethane diisocyanate, and the modified polyester resin is polyethylene adipate-diethylene glycol ester. The latent curing agent is methylcyclohexylamine, the hydroxyl-terminated polyether is polytetrahydrofuran ether, the organotin catalyst is dibutyltin dilaurate, and the hydrolysis promoter is ethanolamine.

[0107] The other additives include defoamer and leveling agent. The defoamer is ethylene oxide, the leveling agent is modified polysiloxane, and the solvent is butyl acetate.

[0108] The preparation method of the modified one-component polyurea is specifically as follows:

[0109] (1) Preparation of semi-prepolymer: Add the modified polyester resin into the reaction device, and carry out vacuum dehydration for 1 h under the condition of nitrogen passing at 100 °C; after cooling to 80 °C, add polyisocyanate and react at a constant temperature for 2 h to obtain the semi-prepolymer;

[0110] (2) Preparation of modified one-component polyurea: Add a chain extender to the semi-prepolymer prepared in step (1), stir evenly for 15 min, then add the corresponding amount of catalyst and hydrolysis promoter, and continue to react for about 40 min. After the temperature is stabilized at 85 °C, add a latent curing agent and stir for about 1 h and then discharge to prepare the modified one-component polyurea.

[0111] 2. Preparation of heat-resistant modified one-component polyurea

[0112] The heat-resistant modified one-component polyurea, by weight percentage, consists of the components of the modified one-component polyurea recorded in this example and 20 parts of hollow serrated composite filler.

[0113] The preparation method of the heat-resistant modified one-component polyurea includes the following steps:

[0114] (1) Preparation of semi-prepolymer: The same as the preparation of the modified one-component polyurea;

[0115] (2) Preparation of heat-resistant modified one-component polyurea: Add a latent curing agent, the hollow serrated composite filler prepared in Example 1 and other components to the semi-prepolymer prepared in step (1) to prepare the heat-resistant modified one-component polyurea.

[0116] Example 9: Application of modified one-component polyurea and heat-resistant modified one-component polyurea in 3D printing

[0117] Apply the modified one-component polyurea and heat-resistant modified one-component polyurea prepared in Examples 5-8 in 3D printing respectively. The specific operation is as follows: Mix the modified one-component polyurea or heat-resistant modified one-component polyurea with an appropriate amount of solvent to obtain a coating, spray it on the hot bed bottom plate of the 3D printer, and cure it to form. Among them, the spraying thickness is 60 μm. The performance test results such as the tensile strength, impact resistance, pencil hardness, adhesion, flexural resistance, salt spray resistance, adhesion between the coating and the 3D consumables when the hot bed is heated, and adhesion between the coating and the 3D consumables after the elastic steel plate is cooled and bent are shown in Table 1.

[0118] The detection methods are as follows:

[0119] (1) Tensile strength: Conduct according to GB / T 16777-2008 "Test Methods for Building Waterproof Coatings". Cut the cured coating film into standard specimens, use an electronic universal testing machine for testing, and record the tensile strength.

[0120] (2) Adhesion: Conducted in accordance with ASTM D4541-17 "Standard Test Method for Adhesion of Coatings". Using a PosiTest AT-A pull-off adhesion tester, under standard temperature and humidity conditions, fix the spindle to the coating surface with adhesive, and after curing, pull it off at a uniform speed until peeling, and record the adhesion strength between the coating and the steel plate.

[0121] (3) Pencil hardness: Conducted in accordance with GB / T 6739-2006 "Determination of Film Hardness of Paints and Varnishes by the Pencil Method". Use standard pencils with different hardnesses to draw lines on the film surface at a 45° angle, and record the highest hardness pencil grade that will not leave scratches.

[0122] (4) Impact resistance: Refer to the method of GB / T 1732-2020 "Determination of Impact Resistance of Films of Paints and Varnishes". Use a falling weight impact tester to freely drop a weight at a specified height, and observe whether there are cracks or peeling on the film.

[0123] (5) Flexibility: Conducted in accordance with GB / T 6742-2007 "Determination of Flexibility of Films of Paints and Varnishes". Bend the coated sample on a round bar with a specified diameter, and observe whether the coating film cracks or peels off.

[0124] (6) Resistance to artificial aging: Conducted in accordance with the method of GB / T 1865-2009 "Artificial Weathering of Paints and Varnishes - Xenon-Arc Lamp". Place the sample in a xenon lamp aging chamber, set the aging cycle and irradiation intensity, and observe the changes in the coating film color, adhesion, cracking, etc. after aging to evaluate the weather resistance.

[0125] (7) Adhesion between the coating and 3D consumables during hot bed heating: Coat the modified polyurea on the surface of the 3D printing hot bed, print standard squares on the hot bed using PLA or other consumables under the set temperature conditions, and after printing is completed, use a thrust meter to measure the maximum thrust value required to peel off the printed part to evaluate the adhesion.

[0126] (8) Adhesion between the coating and 3D consumables after the elastic steel plate is cooled and bent: Cool the elastic steel plate sprayed with polyurea to room temperature and then perform manual bending treatment, and then print the 3D consumables on the bent surface, measure the adhesion performance through a thrust meter, and observe whether there are phenomena such as warping and peeling.

[0127] Table 1 Performance Characterization of Coatings Prepared with the Modified Polyurea and Heat-Resistant Polyurea Described in Examples 5-8

[0128]

[0129] Note: 1. Coating-consumable adhesion I: Adhesion between the coating and 3D consumables during hot bed heating (35°C);

[0130] 2. Coating - Consumable - Adhesion II: Adhesion between the coating and 3D consumables after the elastic steel plate is cooled and bent (20 °C).

[0131] As can be seen from the results in Table 1, the tensile strength of the modified polyurea prepared in Examples 5 - 8 is 20.23 - 24.74 MPa, while that of the heat - resistant polyurea is 18.88 - 23.25 MPa; the adhesion of the modified polyurea is 7.5 - 9.2 MPa, while that of the heat - resistant polyurea is 8.0 - 9.8 MPa; the pencil hardness of the modified polyurea is 3 - 5H, while that of the heat - resistant polyurea is 4 - 6H; the impact resistance of the modified polyurea is 52 - 58 Kg, while that of the heat - resistant polyurea is 55 - 60 Kg; the flexural resistance of the modified polyurea is 3 - 5 mm, while that of the heat - resistant polyurea is also 3 - 5 mm; the resistance to artificial aging of the modified polyurea is 350 - 400 h, while that of the heat - resistant polyurea is also 350 - 500 h. This shows that for the heat - resistant polyurea after adding hollow serrated composite fillers, although its tensile strength is lower than that of the modified polyurea, its flexural resistance is the same as that of the modified polyurea, but other performance indicators including adhesion have been improved.

[0132] In addition, the adhesion I (i.e., the adhesion at 35 °C when the hot bed is heated) between the modified polyurea coating prepared in Examples 5 - 8 and 3D consumables is 15 - 25 N, while the adhesion I between the heat - resistant polyurea coating and 3D consumables is 17 - 30 N. This shows that both the modified polyurea coating and the heat - resistant polyurea coating can achieve effective adhesion at low temperature (35 °C). Compared with the coatings used in the prior art that can achieve effective adhesion only at least at 60 °C, an unexpected technical effect is achieved. At the same time, the adhesion II (the adhesion at 20 °C after the elastic steel plate is cooled and bent) between the modified polyurea coating and 3D consumables is 6 - 9 N, while the adhesion II between the heat - resistant polyurea coating and 3D consumables is 7 - 10 N. This shows that the modified polyurea coating and the heat - resistant polyurea coating not only achieve effective adhesion at low temperature, reduce energy consumption and extend the service life, but also can achieve rapid desorption of the printed sample after the elastic steel plate cools down, having significant practical application value.

[0133] In summary, both the modified polyurea coating and the heat - resistant polyurea coating can, on the one hand, provide high - strength bonding force and good impact resistance under low - temperature conditions, effectively absorb the micro - vibrations between the print head and the material, and prevent the printed parts from shifting or detaching due to stress during the layer - by - layer stacking process; on the other hand, the adhesion force rapidly decreases after cooling, thus realizing the rapid desorption of the printed sample. Therefore, both the modified polyurea coating and the heat - resistant polyurea coating reduce the energy consumption of the equipment and have good application prospects as hot - bed coatings in 3D printing.

[0134] Example 10: Testing the thermal stability and flue gas release amount of the modified polyurea and heat - resistant polyurea prepared in Examples 5 - 8

[0135] The thermal stability and flue gas release amount of the modified one-component polyurea and heat-resistant modified one-component polyurea prepared in Examples 5-8 were tested, and the results were consistent. Taking Example 5 as an example, the details are as follows:

[0136] As Figure 4 shown, the residual rate of the modified one-component polyurea material after combustion in an air atmosphere is only 0.49%, indicating that it is easily decomposed under high-temperature conditions, has poor thermal stability, and releases a large amount of toxic gases and smoke during the decomposition process, presenting an obvious fire hazard. For the heat-resistant modified one-component polyurea with the introduction of Cu-MOF@PA@NiMoO4 composite filler, its residual rate is significantly increased to 17.47%, an increase of 16.98 percentage points compared with the pure polyurea material, indicating that this composite filler can effectively improve the thermal stability and heat resistance of the polyurea coating under high-temperature printing conditions.

[0137] As Figure 5 shown, the total smoke production of the modified one-component polyurea is as high as 4.53 m 2 , indicating that the combustion of the modified one-component polyurea releases a large amount of smoke. For the heat-resistant modified one-component polyurea with the introduction of Cu-MOF@PA@NiMoO4 composite filler, the total smoke production is 2.51 m 2 , a decrease of 44.59% compared with the pure polyurea. This shows that the addition of the Cu-MOF@PA@NiMoO4 composite filler significantly inhibits the heat release and smoke release of the polyurea material.

[0138] In addition, according to Figure 6 the CO release curve shown, it can be clearly seen that the overall CO release of the heat-resistant modified one-component polyurea with the introduction of Cu-MOF@PA@NiMoO4 composite filler is much lower than that of the pure modified one-component polyurea. During the combustion process, the Cu, Ni, and Mo elements in the Cu-MOF@PA@NiMoO4 composite filler can form their respective corresponding oxides NiO, CuO, and MoO3. It is these oxides dispersed in the flame-retardant polyurea composite material that exert their catalytic effects to promote the formation of a carbon layer in the continuous combustion of the polymer matrix, thereby effectively blocking the generation and transfer of heat. While blocking the upper heat, it is also beneficial to prevent the continued combustion of the lower matrix, and the formation of a dense carbon layer will naturally result in a reduction in the heat release amount. Secondly, the Cu-MOF@PA@NiMoO4 composite filler will decompose into mixed metal oxides, CO2, and H2O during combustion, and a large amount of heat will be absorbed during this process, thereby reducing the temperature of the polymer surface and matrix. The released H2O will also play a positive role in reducing the heat.

[0139] In summary, (1) The present application innovatively uses the modified one-component polyurea as a 3D printing hot bed coating, achieving limited adhesion at low temperature - rapid desorption after cooling, and achieving unexpected effects. (2) Compared with the modified one-component polyurea, the heat-resistant modified one-component polyurea provided in the present application has significantly improved heat resistance and stability of the hot bed coating. During the printing process, when the heat-resistant coating contacts the extrusion port at 200 - 250 °C, it can maintain high structural integrity, is not easily softened or degraded, thereby extending the service life of the coating. At the same time, it avoids the release of toxic gases and fumes that may be generated under high-temperature conditions during the printing process, achieving a significant improvement in technical effects.

Claims

1. Application of a modified one-component polyurea as a 3D printing hot bed coating, characterized in that: The modified one-component polyurea is composed of the following components by weight percentage: 50-55 parts of polyisocyanate, 90-101 parts of modified polyester resin, 40-50 parts of solvent, 25-30 parts of latent curing agent, 0.4-0.6 parts of hydrolysis promoter, 0.2-0.3 parts of organotin catalyst, 0.75-1 part of hydroxyl-terminated polyether, and 0.5-0.75 parts of other additives.

2. The application according to claim 1, characterized in that: The polyisocyanate is one or more of isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate; the modified polyester resin is one or more of polyethylene adipate, polypropylene adipate, polyhexylene adipate, and poly(diethylene glycol) adipate.

3. The application according to claim 2, characterized in that: The latent curing agent is an imine-based latent curing agent, selected from one or more of methylcyclohexylimine, p-toluenesimine, and isopropylimine; the hydroxyl-terminated polyether is selected from any one or more of polytetrahydrofuran ether, polypropylene oxide ether, polyethylene oxide ether, and block copolymer ether.

4. The application according to claim 2 or 3, characterized in that: The organotin catalyst is any one or more of stannous octoate, dibutyltin dilaurate, isopropyl titanate, titanium citrate, and dibutyltin oxide; the hydrolysis promoter is one or more of ethanolamine, isopropanolamine, diethanolamine, ammonia water, tetramethylammonium hydroxide, borate ester, titanate ester, and other compounds with hydrolysis-promoting properties.

5. The application according to claim 4, wherein: The other additives include a defoaming agent and a leveling agent; the defoaming agent is one or more of monoalkyl phosphate ester, trialkyl melamine, ethylene oxide, and polydimethylsiloxane; the leveling agent is one or more of acrylate polymer, modified polysiloxane, polydimethylsiloxane, and alkyl-modified organosiloxane; the solvent is one or more of xylene, butyl acetate, and ethylene glycol monoethyl ether acetate.

6. A heat-resistant modified one-component polyurea, characterized in that: By weight percentage, it is composed of the components of the modified one-component polyurea in any one of claims 1-5 and 15-20 parts of hollow serrated composite filler; the hollow serrated composite filler is a hollow serrated structure Cu-MOF@PA@NiMoO4 formed by etching the Cu-MOF three-dimensional framework structure with phytic acid into a hollow structure and bridging NiMoO4 through phytic acid; wherein, the molar ratio of Cu-MOF, NiMoO4, and phytic acid in the flame retardant is (25-50):(5-10):

1.

7. The heat-resistant modified one-component polyurea according to claim 6, wherein: The NiMoO4 is a nanoneedle structure, and the Cu-MOF is a three-dimensional framework structure obtained by self-assembly of Cu metal ions and ligands through coordination bonds; the ligand is 1,4-benzenedicarboxylic acid ligand, 2-aminoterephthalic acid, or 1,3,5-benzenetricarboxylic acid.

8. The preparation method of the heat-resistant modified one-component polyurea according to claim 6 or 7, characterized in that: It includes the following steps: (1) Preparation of the hollow serrated composite filler: Uniformly disperse an appropriate amount of NiMoO4, Cu-MOF, and phytic acid in water, and react at room temperature for 12-24 h under stirring conditions to obtain a suspension; After separation, washing, and drying treatments, the final product Cu-MOF@PA@NiMoO4 in the form of a light blue powder, i.e., the novel hollow serrated composite filler, is obtained. (2) Preparation of semi-prepolymer: Add the modified polyester resin into the reaction device, and dewater under reduced pressure by passing nitrogen at 90 °C - 110 °C for 1 - 2 h; cool down to 80 - 85 °C, add polyisocyanate and react at a constant temperature for 2 - 3 h to obtain the semi-prepolymer; (3) Preparation of one-component polyurea: Add a latent curing agent, the hollow serrated composite filler prepared in step (1) and other components to the above semi-prepolymer in step (2) to prepare a heat-resistant modified one-component polyurea.

9. Use of the heat-resistant modified one-component polyurea according to claim 6 or 7 in 3D printing, characterized in that: The one-component polyurea is used as a coating for the hot bed bottom plate of a 3D printer.

10. Use of the heat-resistant modified one-component polyurea according to claim 9 in 3D printing, characterized in that: The specific application is as follows: Mix the one-component polyurea with an appropriate amount of solvent to obtain a coating material, spray it on the hot bed bottom plate of the 3D printer, and cure and form to obtain the coating.

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