High-wear-resistance and high-toughness polyurethane floor coating and preparation method thereof

Abstract

The invention relates to the technical field of coatings, and particularly discloses a high-wear-resistance and high-toughness polyurethane floor coating and a preparation method thereof. According to the technical key points, the high-wear-resistance and high-toughness polyurethane floor coating is prepared from the following components in parts by weight: 100 parts of cross-linked polyurethane matrix resin, 1 to 3 parts of nano ZnO (at) MCM-41 catalyst, 10 to 15 parts of core-shell microsphere powder filler, 5 to 10 parts of fiber filler, 15 to 20 parts of reactive diluent and 1 to 3 parts of photoinitiator, the cross-linked polyurethane matrix resin is composed of a disulfide bond-containing polyurethane prepolymer and an ultraviolet curing acrylate end group; the core-shell microsphere powder filler is prepared by taking a polyurethane-acrylate copolymer as a shell layer and diamond and silicon carbide composite particles as a core layer, and the particle size of the core-shell microsphere powder filler is 200-500nm. The polyurethane floor coating prepared in the invention has excellent performance, and the coating has high wear resistance and high toughness.

Description

Technical Field

[0001] This application relates to the field of coating technology, and more specifically, it relates to a high-wear-resistance and high-toughness polyurethane floor coating and a preparation method thereof. Background Art

[0002] Polyurethane floor coatings are widely used in industrial plants, underground garages, stadiums, hospitals and other places due to their excellent wear resistance, chemical corrosion resistance, impact resistance and decoration. However, with the continuous improvement of the requirements for floor performance in modern industry and high-end commercial scenarios, the limitations of traditional polyurethane coatings in extreme mechanical loads, high-frequency friction or long-term dynamic impact environments are gradually emerging, specifically manifested as the following problems:

[0003] 1. It is difficult to synergistically improve wear resistance and toughness: Traditional polyurethane coatings usually improve wear resistance by increasing the crosslinking density or adding hard fillers (such as quartz sand, silicon carbide), but this easily leads to an increase in the brittleness of the material and a decrease in toughness, and cracks or even peeling are likely to occur under frequent impacts or temperature changes. On the contrary, if the toughness is adjusted by plasticizers or flexible chain segments, the hardness and wear resistance of the coating may be sacrificed; 2. Insufficient weather resistance and chemical resistance: Some polyurethane coatings are prone to yellowing and powdering under ultraviolet irradiation or humid and hot environments, and their long-term tolerance to strong acids, strong alkalis or organic solvents is limited, which restricts their application in harsh scenarios such as chemical workshops and outdoors; 3. Problems of filler dispersion and interfacial bonding: In the prior art, although nano-fillers (such as nano-silica, carbon nanotubes) can improve wear resistance, their dispersion in the resin matrix is poor and they are prone to agglomeration, resulting in stress concentration inside the coating and instead reducing the mechanical properties; at the same time, the interfacial bonding strength between the filler and the polyurethane matrix is insufficient, easily causing interfacial peeling; 4. Environmental protection and construction process limitations: Solvent-based polyurethane coatings contain volatile organic compounds (VOCs) and do not conform to the trend of green environmental protection; while some solvent-free or water-based systems are environmentally friendly, but there are problems such as slow curing speed and poor leveling, which affect the construction efficiency and the apparent quality of the coating.

[0004] In response to the above problems, existing improvement schemes mostly focus on the optimization of a single performance. For example, Patent CN201410270768.0 improves the adhesion by introducing epoxy resin to modify polyurethane, but the improvement of toughness is limited; Patent JP201811123994.0 uses polyurea blending to enhance the impact resistance, but the wear resistance decreases. In addition, some technologies rely on complex processes (such as multi-step curing, high-temperature and high-pressure molding), with high costs and difficult to be applied on a large scale.

[0005] Therefore, developing a polyurethane floor coating with high wear resistance, high toughness, excellent weather resistance and environmental protection, and achieving performance balance through an efficient preparation process has become an urgent technical problem to be solved in the current field of floor materials. Summary of the Invention

[0006] To solve the above technical problems, the present application provides a highly wear-resistant and highly tough polyurethane floor coating and a preparation method thereof.

[0007] In a first aspect, the present application provides a highly wear-resistant and highly tough polyurethane floor coating, adopting the following technical solutions:

[0008] A highly wear-resistant and highly tough polyurethane floor coating contains the following components in parts by weight: 100 parts of crosslinked polyurethane matrix resin, 1-3 parts of nano-ZnO@MCM-41 catalyst, 10-15 parts of core-shell microsphere powder filler, 5-10 parts of fiber filler, 15-20 parts of active diluent, and 1-3 parts of photoinitiator;

[0009] The crosslinked polyurethane matrix resin is composed of a disulfide-containing polyurethane prepolymer and an ultraviolet-curable acrylate end group;

[0010] The core-shell microsphere powder filler is prepared with a polyurethane-acrylate copolymer as the shell layer and diamond and silicon carbide composite particles as the core layer, and the particle size of the core-shell microsphere powder filler is 200-500 nm.

[0011] Further, in the crosslinked polyurethane matrix resin, the disulfide bond is introduced by the chain extender 2,2'-dithiobisethanol, and the disulfide bond accounts for 5%-10% of the molar content of the polyurethane main chain.

[0012] Specifically, the present application provides a preparation method of the crosslinked polyurethane matrix resin: mixing polycarbonate diol and isophorone diisocyanate to react to form a prepolymer, adding the chain extender 2,2'-dithiobisethanol and continuing the reaction, and finally terminating with hydroxyethyl acrylate to obtain it.

[0013] Further, in the core-shell microsphere powder filler, the mass ratio of diamond to silicon carbide is 1:(0.2-1), preferably 1:(0.2-0.5).

[0014] Further, the surface of the core layer formed by the diamond and silicon carbide composite particles is treated by grafting methacrylate groups through silane coupling agent modification.

[0015] Specifically, the present application provides a preparation method of the core-shell microsphere powder filler: mixing diamond and silicon carbide, after surface modification with a silane coupling agent, dispersing in deionized water, adding a polyurethane prepolymer and an emulsifier, pre-emulsifying and then dropping acrylate monomers and an initiator, forming a core-shell structure by emulsion polymerization method, and finally spray-drying to obtain the core-shell microsphere powder filler.

[0016] Further, the spray-drying conditions are: inlet temperature 150-170 °C, outlet temperature 70-90 °C, and the particle size distribution D90 of the obtained powder ≤ 200 nm.

[0017] Furthermore, in the nano-ZnO@MCM-41 catalyst, the loading amount of nano-ZnO is 10-25 wt%, preferably 15-20 wt%.

[0018] Furthermore, the nano-ZnO@MCM-41 catalyst of the present application can be purchased from the market, customized or self-made. The present application provides a preparation method of the nano-ZnO@MCM-41 catalyst. The specific steps are as follows: Cetyltrimethylammonium bromide and sodium metasilicate nonahydrate are completely dissolved in water according to a molar ratio of 1:5, and the pH is adjusted to 10.5 with dilute sulfuric acid to obtain a sol. Under stirring conditions, an aqueous zinc nitrate solution is added according to the ZnO loading amount of 10-25 wt%, and the pH is adjusted to 10.5. After continuous stirring for a period of time, a mixed solution is obtained. The reaction is carried out at 100-105 °C for 20 h. After the reactants are washed and dried, they are calcined at 550 °C for 6 h to obtain the nano-ZnO@MCM-41 catalyst.

[0019] Furthermore, the fiber filler is composed of aminated aramid nanofibers and short carbon fibers, and the weight percentage of aminated aramid nanofibers in the fiber filler is not less than 50 wt%.

[0020] Preferably, the diameter of the aminated aramid nanofibers is 10-30 nm, and the aspect ratio is greater than 100.

[0021] Preferably, the length of the short carbon fibers is 50-200 μm, and the surface is treated by oxidation.

[0022] Furthermore, the reactive diluent is selected from one or more of itaconic acid ester derivatives, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate.

[0023] Furthermore, the photoinitiator is selected from one or more of ethyl 2,4,6-trimethylbenzoyl phenylphosphinate, α,α'-dimethylbenzoyl ketal, 2-hydroxy-2-methyl-1-phenylpropanone, 2,4,6-trimethyldibenzoyl methane, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, anthraquinone, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, Michler's ketone, benzophenone, benzoin propyl ether, benzoin ethyl ether, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, methyl benzoylformate thioxanthone; diethyl thioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1-(4-(methylthio)phenyl)-2-morpholinopropan-1-one, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0024] In a second aspect, the present application provides a method for preparing a high-wear-resistant and high-toughness polyurethane floor coating, adopting the following technical solution:

[0025] A method for preparing a high-wear-resistant and high-toughness polyurethane floor coating includes coating formulation and two-step curing. The specific steps are as follows:

[0026] Coating formulation: Mix crosslinked polyurethane matrix resin, nano-ZnO@MCM-41 catalyst, core-shell microsphere powder filler, fiber filler, reactive diluent, and photoinitiator evenly to obtain the coating.

[0027] Two-step curing: After coating the coating on the substrate, first perform photocuring through a UV-LED light source, synchronously apply a pulsed magnetic field to induce the alignment of the filler, and then perform thermal curing at 60 °C for 30 min to complete the coating forming.

[0028] Furthermore, in the two-step curing process, the photocuring conditions are: wavelength 365 nm, intensity 500 mW / cm 2 , curing time 10 s; pulsed magnetic field intensity 0.5 T, frequency 10 Hz.

[0029] In summary, the present application has the following beneficial effects:

[0030] (1) In the present application, a polyurethane-acrylate copolymer is used as the shell layer to encapsulate nano-diamond / silicon carbide composite particles. The core-shell microsphere powder filler is prepared by emulsion polymerization, which simultaneously has the effects of: being evenly dispersed in the matrix, absorbing impact energy through elastic deformation when subjected to external forces, improving toughness (shell layer), and forming a self-reinforced wear-resistant layer (core layer) by exposing high-hardness nano-particles on the surface during the friction process.

[0031] (2) The crosslinked polyurethane matrix resin of this application uses a polyether-based polyurethane prepolymer with disulfide bonds, combined with a UV-curable acrylate end group, to form a "rigid-flexible-dynamic" network. The disulfide bonds break and recombine under stress, endowing the coating with self-healing ability. In addition, by adding nano-ZnO@MCM-41, that is, a supported nano-zinc oxide catalyst, it can reduce the activation energy during the recombination of disulfide bonds, improving the repair efficiency and repair effect.

[0032] (3) This application uses aramid nanofibers and short carbon fiber as composite fiber fillers to construct a three-dimensional interpenetrating network. Among them, the aramid nanofibers are combined with the polyurethane matrix through hydrogen bonds to inhibit crack propagation, and the short carbon fibers provide a macroscopic load transfer path to improve impact resistance.

[0033] (4) This application adopts a two-step curing method. The first step of curing uses UV curing, which can quickly form a surface crosslinked layer to lock the filler distribution. The second step of curing uses thermal curing, which can activate deep dynamic reconstruction, eliminate internal stress, and by applying a pulsed magnetic field, the magnetically modified silicon carbide particles are oriented along the friction force direction to form an ordered wear-resistant path. Detailed implementation mode

[0034] The following uses specific specific examples to illustrate the implementation mode of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific implementation modes, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application.

[0035] In addition, it should be understood that one or more method steps mentioned in this application do not exclude that there may be other method steps before and after the combined steps, or other method steps may be inserted between these clearly mentioned steps, unless otherwise stated. Moreover, unless otherwise stated, the numbers of each method step are only convenient tools for identifying each method step, rather than restricting the arrangement order of each method step or limiting the scope of implementation of this application. The change or adjustment of their relative relationship, without substantial change in technical content, should also be regarded as the scope of implementation of this application.

[0036] If the specific experimental conditions are not specified in the examples, they are usually in accordance with the conventional conditions in the art or in accordance with the conditions recommended by the reagent company; the materials, reagents, etc. used in the examples, unless otherwise specified, can be obtained through commercial channels.

[0037] Examples

[0038] Example 1

[0039] Preparation of crosslinked polyurethane matrix resin:

[0040] 50 g of polycarbonate diol (Mn = 1000) and 22 g of isophorone diisocyanate were mixed, 0.1 g of dibutyltin dilaurate catalyst was added, and the reaction was carried out at 75 °C for 2 h. Then 8 g of 2,2′-dithiobisethanol was added, and the reaction was continued at 70 °C for 3 h. After cooling to 40 °C, 10 g of 2-hydroxyethyl acrylate was added for end-capping. After reacting for 1 h, a crosslinked polyurethane matrix resin containing disulfide bonds was obtained.

[0041] Example 2

[0042] Preparation of nano-ZnO@MCM-41 catalyst:

[0043] Cetyltrimethylammonium bromide and sodium metasilicate nonahydrate were completely dissolved in water according to a molar ratio of 1:5, and the pH was adjusted to 10.5 with dilute sulfuric acid to obtain a sol. Under stirring conditions, an aqueous zinc nitrate solution was added according to a ZnO loading of 15 wt%, and the pH was adjusted to 10.5. After continuous stirring for a period of time, a mixed solution was obtained. The reaction was carried out at 100 °C for 20 h. After the reactants were washed and dried, they were calcined at 550 °C for 6 h to obtain the nano-ZnO@MCM-41 catalyst.

[0044] Example 3

[0045] Preparation of core-shell microsphere powder filler:

[0046] Nanodiamond (Element Six, average particle size 50 nm) and silicon carbide particles (Stanford Materials, average particle size 80 nm) were mixed according to a mass ratio of 3:1. The mixed particles were dispersed in ethanol, and the solid content was controlled to be 10%. Based on the mass of the mixed particles, 2 wt% of silane coupling agent KH-570 was added. The mixture was ultrasonically treated at 300 w for 0.5 h and refluxed at 80 °C for 4 h. After centrifugal separation and washing with ethanol three times, it was dried in vacuum at 60 °C to obtain composite core particles with methacrylate groups grafted on the surface.

[0047] Polytetrahydrofuran diol (Mn = 2000), isophorone diisocyanate, and dimethylolpropionic acid were reacted according to a molar ratio of 2:3:1 to prepare a polyurethane prepolymer with an NCO content of 6.5%.

[0048] Methyl methacrylate and butyl acrylate were mixed according to a mass ratio of 4:1, and vinyltriethoxysilane was added as a crosslinking agent at 1 wt% of the monomers to obtain a mixed solution of acrylate monomers.

[0049] Disperse 10 g of composite nuclear particles in 200 mL of water, add 50 g of polyurethane prepolymer and 1 g of sodium dodecyl sulfate emulsifier, and stir and pre-emulsify at 40 °C for 0.5 h; raise the temperature to 75 °C, add 30 g of acrylate monomer mixture and 0.5 g of sodium persulfate initiator, keep the temperature for reaction for 3 h, cool to room temperature, adjust the pH = 7.5, and filter to obtain a core-shell microsphere emulsion with a solid content of 35%; spray drying (inlet temperature 160 °C, outlet temperature 80 °C) to obtain a core-shell microsphere powder filler with a particle size of 50 - 200 nm.

[0050] Example 4

[0051] Preparation of fiber filler:

[0052] Mix the aminated aramid nanofibers and chopped carbon fibers evenly according to the weight ratio of 1:1 to obtain the fiber filler. Among them, the average diameter of the aminated aramid nanofibers is 20 nm, the aspect ratio is 112, the average length of the chopped carbon fibers is 150 μm, and the surface is treated by nitric acid oxidation.

[0053] Example 5

[0054] Preparation of polyurethane floor coating:

[0055] Formulation:

[0056] 100 parts of crosslinked polyurethane matrix resin, prepared from Example 1;

[0057] 1 part of nano-ZnO@MCM-41 catalyst, prepared from Example 2;

[0058] 10 parts of core-shell microsphere powder filler, prepared from Example 3;

[0059] 5 parts of fiber filler, prepared from Example 4;

[0060] 18 parts of reactive diluent, dibutyl itaconate, VOC content less than 25 g / L;

[0061] 1 part of photoinitiator, photoinitiator TPO-L (ethyl 2,4,6-trimethylbenzoyl phenylphosphinate).

[0062] Mix the above raw material components evenly to obtain the coating. After coating the coating on the substrate, first carry out photocuring through a UV-LED light source (coating thickness 500 μm, wavelength 365 nm, intensity 500 mW / cm 2 、irradiation time 10 s), synchronously apply a pulsed magnetic field to induce the alignment of the filler (intensity 0.5 T, frequency 10 Hz, duration 5 s), and then carry out thermal curing at 60 °C for 30 min to complete the coating forming.

[0063] Example 6

[0064] Preparation of polyurethane floor coating:

[0065] Formulation:

[0066] 100 parts of crosslinked polyurethane matrix resin, prepared by Example 1;

[0067] 2 parts of nano-ZnO@MCM-41 catalyst, prepared by Example 2;

[0068] 12.5 parts of core-shell microsphere powder filler, prepared by Example 3;

[0069] 7.5 parts of fiber filler, prepared by Example 4;

[0070] 18 parts of reactive diluent, dibutyl itaconate, VOC content less than 25 g / L;

[0071] 1 part of photoinitiator, photoinitiator TPO-L (ethyl 2,4,6-trimethylbenzoyl phenylphosphinate).

[0072] Mix the above raw material components evenly to obtain the coating. After coating the coating on the substrate, first perform photocuring through a UV-LED light source (coating thickness 500 μm, wavelength 365 nm, intensity 500 mW / cm 2 , irradiation time 10 s), synchronously apply a pulsed magnetic field to induce the directional arrangement of the filler (intensity 0.5 T, frequency 10 Hz, duration 5 s), and then perform thermal curing at 60 °C for 30 min to complete the coating forming.

[0073] Example 7

[0074] Preparation of polyurethane floor coating:

[0075] Formulation:

[0076] 100 parts of crosslinked polyurethane matrix resin, prepared by Example 1;

[0077] 3 parts of nano-ZnO@MCM-41 catalyst, prepared by Example 2;

[0078] 15 parts of core-shell microsphere powder filler, prepared by Example 3;

[0079] 10 parts of fiber filler, prepared by Example 4;

[0080] 18 parts of reactive diluent, dibutyl itaconate, VOC content less than 25 g / L;

[0081] 1 part of photoinitiator, photoinitiator TPO-L (ethyl 2,4,6-trimethylbenzoyl phenylphosphinate).

[0082] Mix the above raw material components evenly to obtain a coating. After coating the coating on the substrate, first perform photocuring with a UV-LED light source (coating thickness 500 μm, wavelength 365 nm, intensity 500 mW / cm 2 , irradiation time 10 s), synchronously apply a pulsed magnetic field to induce the directional arrangement of the filler (intensity 0.5 T, frequency 10 Hz, lasting 5 s), and then perform thermal curing at 60 °C for 30 min to complete the coating formation.

[0083] Performance test: According to GB / T 22374-2018, perform performance tests on the floor coatings prepared in Examples 5-7 respectively. The test results are shown in Table 1 below:

[0084] Table 1 Performance test results of the floor coatings in Examples 5-7

[0085]

[0086]

[0087] It can be seen from the test results in Table 1 that the polyurethane floor coating prepared in this application has excellent hardness, wear resistance and impact toughness, and its chemical resistance meets the standard requirements.

[0088] Comparative Example 1

[0089] Based on the preparation method of Example 3, change the core layer to prepare different core-shell microsphere powder fillers, and compare the toughening and wear-resistant effects of the core-shell microsphere powder fillers prepared with different particles as the core layer.

[0090] The specific operation method is as follows: The preparation method of the core-shell microsphere powder filler remains unchanged. Respectively use nanodiamond (average particle size 50 nm), silicon carbide particles (average particle size 80 nm), and nano-silica (average particle size 50 nm) to replace the nano-diamond / silicon carbide composite particles as the core layer to prepare the core-shell microsphere powder filler.

[0091] Taking Example 5 as a comparison, use different core-shell microsphere powder fillers to prepare polyurethane floor coatings for Comparative Example 1-1 (nanodiamond as the core layer), Comparative Example 1-2 (silicon carbide as the core layer), and Comparative Example 1-3 (nano-silica as the core layer), and respectively test the toughening and wear-resistant effects of several core-shell microsphere powder fillers on the floor coating. The results are shown in Table 2 below:

[0092] Table 2 Performance test results of the floor coatings prepared with different core layers

[0093]

[0094]

[0095] As can be seen from the test results in Table 2, the core-shell microsphere powder fillers prepared from different core layers have a great influence on the mechanical properties of floor coatings. For the polyurethane floor coatings prepared with nano-diamond, silicon carbide, and nano-silica as the core layers, their hardness and wear resistance gradually decrease, while the impact resistance shows a gradually increasing trend. The polyurethane floor coating prepared with nano-diamond / silicon carbide composite particles as the core layer has the best mechanical properties, and the hardness, wear resistance, and impact toughness are improved significantly.

[0096] Comparative Example 2

[0097] Comparative Example 2-1: On the basis of Example 5, nano-ZnO (average particle size 50 nm) was used to replace the nano-ZnO@MCM-41 catalyst to prepare a polyurethane floor coating.

[0098] Comparative Example 2-2: On the basis of the polyurethane floor coating formula in Example 5, the nano-ZnO@MCM-41 catalyst was not added.

[0099] The self-healing properties of the polyurethane floor coatings prepared in Comparative Example 2-1, Comparative Example 2-2, and Example 5 were compared.

[0100] Self-healing performance test method: Scratch manually with a scratch width of 20 μm, then heat the scratched coating at 65 °C for 10 min, measure the scratch width, and calculate the repair rate = (scratch width before heating and repair - scratch width after heating and repair) / scratch width before heating and repair × 100%. The test results are shown in Table 3 below:

[0101] Table 3 Self-healing performance test

[0102] Project Example 5 Comparative Example 2-1 Comparative Example 2-2 Scratch width before heating / μm 20.0 20.0 20.0 Scratch width after heating / μm 3.3 11.5 11.0 Repair rate / % 83.5 42.5 45

[0103] As can be seen from the test results in Table 3, the polyurethane floor coating prepared in this application has excellent self-healing properties. Moreover, from the test results of Example 5 and Comparative Example 2-1, it can be seen that the addition of the nano-ZnO@MCM-41 catalyst can significantly improve the self-healing efficiency and self-healing effect of the coating, which can verify the conjecture that the nano-ZnO@MCM-41 catalyst can reduce the activation energy of disulfide bond recombination.

[0104] The above are only the preferred embodiments of the present invention, and do not impose any formal or substantial limitations on the present invention. It should be noted that for those of ordinary skill in the art, without departing from the method of the present invention, several improvements and supplements can still be made, and these improvements and supplements should also be regarded as within the protection scope of the present invention. For those skilled in the art, without departing from the spirit and scope of the present invention, any minor changes, modifications and equivalent variations made by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the substantial technology of the present invention still fall within the scope of the technical solutions of the present invention.

Claims

1. A high-wear-resistant and high-toughness polyurethane floor coating, comprising the following components in parts by weight: 100 parts of a crosslinked polyurethane matrix resin, 1-3 parts of a nano-ZnO@MCM-41 catalyst, 10-15 parts of a core-shell microsphere powder filler, 5-10 parts of a fiber filler, 15-20 parts of an active diluent, and 1-3 parts of a photoinitiator; The crosslinked polyurethane matrix resin is composed of a disulfide-containing polyurethane prepolymer and an ultraviolet-curable acrylate end group; The core-shell microsphere powder filler is prepared with a polyurethane-acrylate copolymer as the shell layer and diamond and silicon carbide composite particles as the core layer, and the particle size of the core-shell microsphere powder filler is 200-500 nm.

2. The polyurethane floor coating according to claim 1, wherein: In the crosslinked polyurethane matrix resin, the disulfide bond is introduced by a chain extender 2,2'-dithiobisethanol, and the disulfide bond accounts for 5-10% of the molar content of the polyurethane main chain.

3. The polyurethane floor coating according to claim 2, wherein: The preparation method of the crosslinked polyurethane matrix resin is: mixing polycarbonate diol and isophorone diisocyanate to react to form a prepolymer, adding a chain extender 2,2'-dithiobisethanol to continue the reaction, and finally end-capping with hydroxyethyl acrylate to obtain it.

4. The polyurethane floor coating according to claim 1, characterized in that: In the core-shell microsphere powder filler, the mass ratio of diamond to silicon carbide is 1:(0.2-1).

5. The polyurethane floor coating according to claim 4, characterized in that: The surface of the core layer formed by the diamond and silicon carbide composite particles is treated by grafting a methacrylate group through silane coupling agent modification.

6. The polyurethane floor coating according to claim 5, characterized in that: The preparation method of the core-shell microsphere powder filler is: mixing diamond and silicon carbide, subjecting them to surface modification with a silane coupling agent, dispersing them in deionized water, adding a polyurethane prepolymer and an emulsifier, pre-emulsifying, then dropping an acrylate monomer and an initiator, forming a core-shell structure by emulsion polymerization, and finally spray-drying to obtain the core-shell microsphere powder filler.

7. The polyurethane floor coating according to claim 1, characterized in that: In the nano-ZnO@MCM-41 catalyst, the loading amount of nano-ZnO is 10-25 wt%.

8. The polyurethane floor coating according to claim 1, characterized in that: The fiber filler is composed of amino-functionalized aramid nanofibers and short carbon fibers, and the weight proportion of amino-functionalized aramid nanofibers in the fiber filler is not less than 50 wt%.

9. A method for preparing the polyurethane floor coating according to any one of claims 1-8, characterized in that: It includes coating formulation and two-step curing, and the specific steps are as follows: Coating formulation: Mixing the crosslinked polyurethane matrix resin, nano-ZnO@MCM-41 catalyst, core-shell microsphere powder filler, fiber filler, active diluent and photoinitiator evenly to obtain a coating; Two-step curing: After coating the coating on a substrate, first perform photocuring with a UV-LED light source, synchronously apply a pulsed magnetic field to induce the alignment of the filler, and then perform thermal curing at 60 °C for 30 min to complete the coating forming.

10. The preparation method according to claim 9, characterized in that: In the two-step curing process, the conditions for photo-curing are: wavelength 365 nm, intensity 500 mW / cm 2 , and curing time 10 s; The pulsed magnetic field intensity is 0.5 T and the frequency is 10 Hz.

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