Preparation method of polyurethane sound-absorbing spillplate

Abstract

The invention provides a preparation method of a polyurethane sound-absorbing spillplate. The preparation method comprises the following steps: mixing and molding cross-linking agent modified graphene, a wear-resistant agent, a processing aid, microspheres and polyurethane, and then carrying out irradiation treatment to obtain the polyurethane sound-absorbing spillplate. The invention solves the problem of poor performance of a polyurethane spillplate in the prior art, and belongs to the field of polyurethane spillplate materials.

Description

Technical Field

[0001] The invention relates to the field of polyurethane coal-blocking plate materials, and in particular to a method for preparing a polyurethane sound-absorbing coal-blocking plate. Background Art

[0002] With the advancement of coal mining technology, blasting coal dropping and general mining coal dropping have developed into comprehensive mechanized and even automated operations. The thin coal seam mining areas commonly contained in coal seams contain iron sulfide nodules, which are extremely hard and difficult to cut with the picks of the coal mining machine. Therefore, the blasting coal dropping process is widely used. Due to the high labor intensity and long time of the coal discharge process in the blasting coal dropping process, the use of scraper conveyors to discharge coal is currently the most common practice. The coal baffle plate, an important device installed on the pipe guard near the side chute of the scraper conveyor near the goaf, is used to resist the coal rushing towards the goaf during blasting coal dropping. It is the key to recovering floating coal into the scraper conveyor to avoid resource loss and realize automatic coal blocking behind the working face.

[0003] The current coal mining operation has extremely high requirements for coal retaining plates. Construction sites that use blasting coal dropping methods require that the coal retaining plates be able to withstand the instantaneous impact of blasting, have a certain impact strength, and are not prone to plastic deformation. At the same time, in the process of automated transportation, they can withstand long-term friction and wear, avoid frequent replacement, and improve production efficiency and safety. Therefore, the coal retaining plate needs to have good properties such as resistance to bending, wear resistance, impact resistance, hydrolysis resistance, acid and alkali corrosion resistance, and oil resistance to improve the reuse rate of the coal retaining plate. Polymer polyurethane materials are the main raw materials that can meet the above requirements and are easy to process and produce coal retaining plates. However, the polyurethane material has poor abrasion resistance, a significant decrease in mechanical properties under hydrolysis conditions, and strength still needs to be improved. It is necessary to effectively modify the polyurethane matrix to extend the long-term service capacity of the coal retaining plate. Therefore, the development of a high-strength, wear-resistant, cross-linked polyurethane sound-absorbing coal retaining plate is of great significance to the production and development of the coal mining industry. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for preparing a polyurethane sound-absorbing coal-blocking plate, so as to solve the problem of poor performance of the polyurethane coal-blocking plate in the prior art.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for preparing a polyurethane sound-absorbing coal-blocking board is provided, the method comprising: mixing and molding graphene modified by a cross-linking agent, a wear-resistant agent, a processing aid, microbeads and polyurethane, and then irradiating them to obtain the polyurethane sound-absorbing coal-blocking board.

[0006] Furthermore, the preparation method of the above-mentioned cross-linker-modified graphene is as follows: mixing a graphene dispersion with a cross-linker to obtain a mixed solution to be cross-linked; subjecting the above-mentioned mixed solution to be cross-linked to microwave irradiation functionalization treatment to obtain the above-mentioned cross-linker-modified graphene; preferably, the above-mentioned graphene dispersion is prepared according to the following method: mixing graphite powder, a dispersant and ultrapure water to obtain a graphite mixed suspension; and subjecting the above-mentioned graphite mixed suspension to liquid phase shear exfoliation to obtain the above-mentioned graphene dispersion.

[0007] Furthermore, the graphite is selected from any one or more of the following: microcrystalline graphite, thermally expandable graphite and highly oriented pyrolytic graphite.

[0008] Furthermore, the dispersant is selected from any one or more of the following: N-methylpyrrolidone, sodium dodecylbenzenesulfonate, sodium taurodeoxycholate, dimethylformamide, ethanol, o-dichlorobenzene or poloxamer.

[0009] Furthermore, the mass concentration of the graphite in the graphite mixed suspension is 1-10% and the mass ratio of the graphite to the dispersant is 100:(1-3). Furthermore, the instrument used for the liquid phase shear exfoliation is selected from any one or more of the following: a nano-bead mill, a pin sand mill, a turbine sand mill or a high-pressure homogenizer; preferably, the stirring treatment time is 30-60 min, the grinding speed is 800-2000 r / min, and the grinding time is 1-5 h; preferably, the graphene dispersion includes one or more graphene layers, the average number of graphene layers is 6-20 layers, and the mass concentration of the graphene in the graphene dispersion is 2-25%.

[0010] Furthermore, the cross-linking agent is selected from any one or more of the following: polyetherimide (M w =10 4 ~10 5 Da), polyaminopolyallylamine (M w =10 3 ~10 4 Da), polydopamine (M w =10 3 ~10 4 Da), polyurethane imide (M w =10 3 ~10 5 Da), trishydroxymethylaminomethane, cross-linked polystyrene-divinylbenzenesulfonic acid or γ-aminopropyltriethoxysilane; preferably, the concentration of the above-mentioned cross-linking agent is 0.15-2 mol / L; preferably, the molar ratio of the above-mentioned graphene dispersion and the above-mentioned cross-linking agent is (40-120):1.

[0011] Furthermore, the apparatus for carrying out the above microwave irradiation functionalization treatment is a microwave reactor, the reaction temperature is 90 to 160° C., and the reaction time is 5 to 35 min.

[0012] Furthermore, the water content of the graphene modified by the cross-linking agent is 0.1% to 5%; preferably, the water content of the graphene modified by the cross-linking agent is 0.08% to 4% by spray drying; preferably, the temperature of the spray drying is 130 to 160° C., and the liquid inlet speed of the graphene modified by the cross-linking agent is 5 to 18 mL / min.

[0013] Furthermore, the molecular weight of the polyurethane is 12,000 to 50,000.

[0014] Furthermore, the wear-resistant agent is selected from any one or more of the following: polytetrafluoroethylene, ultra-high molecular weight polyurethane, molybdenum disulfide, polysiloxane, glass fiber, carbon fiber or aramid fiber.

[0015] Furthermore, the processing aid is selected from any one or more of the following: dibasic lead phosphite, methyl tin, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate or 2,6-di-tert-butyl-4-methylphenol.

[0016] Furthermore, the microbeads are organic microbeads or inorganic microbeads; the organic microbeads are selected from hybrid silicone microbeads; the inorganic microbeads are selected from any one or more of the following: 920DET40d25 microbeads, DU2201L microbeads or hollow glass microbeads.

[0017] Furthermore, the mass ratio of the cross-linking agent modified graphene to the wear-resistant agent is (3-10):1; the mass ratio of the wear-resistant agent to the polyurethane is (1-8):100; the mass ratio of the processing aid to the polyurethane is (1-9):1000; the mass ratio of the microbeads to the polyurethane is (1-7):100.

[0018] Furthermore, the mixed molding method is to place the mixed granules in a plate molding machine for compression molding; the upper and lower mold temperatures of the plate molding machine are 180-200°C, the pressure is 2-8MPa, the time is 10-16min, and the thickness of the molded plate is 8-20mm.

[0019] Furthermore, the radiation source of the above-mentioned irradiation is a high-energy electron beam or Co 60 Preferably, the irradiation dose is 30 to 100 kGy, the irradiation rate is 0.1 to 1.0 kGy / h, and the crosslinking density of the polyurethane sound-absorbing coal baffle after the irradiation is 120 to 500 mol / m 3 .

[0020] By applying the technical scheme of the present invention, polyurethane is mixed with graphene modified by a cross-linking agent, a wear-resistant agent, a processing aid and microbeads and then irradiated to prepare a polyurethane sound-absorbing coal-blocking plate which not only has high mechanical strength, but also has excellent properties such as wear resistance, antistatic and sound absorption, can prevent friction static electricity and reduce noise hazards, can greatly improve the service life of the coal-blocking plate on the scraper conveyor in complex environments, has broad application prospects, and is of great significance to the production and development of the coal mining industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0022] Figure 1 A schematic diagram showing a method for preparing the polyurethane sound-absorbing coal baffle of the present invention is shown. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0024] As mentioned in the background technology, current coal mining operations have put forward higher requirements on the performance of coal retaining plates, such as high impact strength, not easy to produce plastic deformation, friction and wear resistance, hydrolysis resistance, acid and alkali corrosion resistance, and oil resistance. Improving the above-mentioned properties of coal retaining plates can increase the reuse rate of coal retaining plates and increase their long-term service capacity, thereby effectively reducing the cost expenditure of coal mining operations in coal retaining plates, which is of great significance to the production and development of the coal mining industry. Based on the above problems, the inventor proposed a series of protection schemes of the present invention.

[0025] In a typical embodiment of the present invention, a method for preparing a polyurethane sound-absorbing coal-blocking board is provided, the preparation method comprising: mixing and molding graphene modified by a cross-linking agent, a wear-resistant agent, a processing aid, microbeads and polyurethane, and then irradiating the mixture to obtain the polyurethane sound-absorbing coal-blocking board (see Figure 1 ).

[0026] Graphene has a single-layer two-dimensional honeycomb lattice structure, has the advantages of high strength, good toughness, easy to load functional groups chemically, and able to absorb waves and reduce noise. The polyurethane coal-blocking board prepared by adding graphene has significantly improved performance. By modifying graphene with a cross-linking agent, the mechanical properties, mechanical strength, electrical conductivity, thermal conductivity, and chemical stability of graphene can be improved. The dispersibility of graphene can also be improved, so that it is evenly dispersed in the composite material, thereby improving the performance of the composite material. The cross-linking agent-modified graphene in the present invention improves the interfacial compatibility between the wear-resistant agent and the polyurethane during molding, and the increase in cross-linking density also suppresses the occurrence of mechanical relaxation. The use of cross-linking agent-modified graphene plays an important role in improving the performance of the polyurethane coal-blocking board.

[0027] There are various methods for preparing crosslinker-modified graphene, and the corresponding preparation method can be selected according to the type of crosslinking modification. In a preferred embodiment of the present invention, the preparation method of the above-mentioned crosslinker-modified graphene is as follows: a graphene dispersion is mixed with a crosslinker to obtain a mixed solution to be crosslinked; the above-mentioned mixed solution to be crosslinked is subjected to microwave irradiation functionalization treatment to obtain the above-mentioned crosslinker-modified graphene. Among them, microwave irradiation functionalization treatment is conducive to the formation of abundant functional group loading sites on the graphene flakes, inhibiting the slip between graphene flakes, and reducing the charge transfer barrier. In a preferred embodiment of the present invention, the instrument for the above-mentioned microwave irradiation functionalization treatment is a microwave reactor, the above-mentioned reaction temperature is 90-160°C, and the reaction time is 5-35min.

[0028] Graphene modified with different crosslinking agents has different properties, and the selection of crosslinking agent is crucial to improving the properties of graphene. The crosslinking agent is selected from any one or more of the following: polyetherimide (M w =10 4 ~10 5 Da), polyaminopolyallylamine (M w =10 3 ~10 4 Da), polydopamine (M w =10 3 ~10 4 Da), polyurethane imide (M w =10 3 ~10 5 Da), trishydroxymethylaminomethane, cross-linked polystyrene-divinylbenzenesulfonic acid or γ-aminopropyltriethoxysilane.

[0029] In a preferred embodiment of the present invention, the crosslinking agent is a mixture of polyetherimide and polyaminopolyallylamine, and the selection of the crosslinking agent has the beneficial effects of high thermal stability and chemical stability. In another preferred embodiment of the present invention, the crosslinking agent is polydopamine and polyurethaneimine, and the selection of this crosslinking agent has the beneficial effects of anti-oxidation and resistance to humid environments. In a third preferred embodiment of the present invention, the crosslinking agent is a mixture of polydopamine and trishydroxymethylaminomethane, and this crosslinking agent contributes to biological safety and mechanical properties.

[0030] In addition, the concentration of the crosslinking agent and its molar ratio to the graphene dispersion may affect the crosslinking density, mechanical properties, thermal stability, electrical conductivity and dispersion stability of the material. Therefore, in order to better control the performance and processing characteristics of the composite material, it is necessary to accurately adjust the concentration and molar ratio of the crosslinking agent. In a preferred embodiment of the present invention, the concentration of the crosslinking agent is 0.15-2 mol / L; in another preferred embodiment of the present invention, the molar ratio of the graphene dispersion to the crosslinking agent is (40-120):1.

[0031] There are various methods for preparing the above-mentioned graphene dispersion. In a preferred embodiment of the present invention, the method for preparing the above-mentioned graphene dispersion is as follows: mixing graphite powder, a dispersant and ultrapure water to obtain a graphite mixed suspension; and subjecting the graphite mixed suspension to liquid phase shear exfoliation to obtain the above-mentioned graphene dispersion.

[0032] In a preferred embodiment of the present invention, the graphite is selected from any one or more of the following: microcrystalline graphite, thermal expansion graphite and highly oriented pyrolytic graphite, wherein microcrystalline graphite is a graphite with fine grains, good electrical conductivity and thermal conductivity, and is suitable for preparing high-performance graphite products; thermal expansion graphite is a graphite material with a high thermal expansion coefficient, which can expand at high temperature and is suitable for some special applications; highly oriented pyrolytic graphite is a graphite material with a highly oriented structure, which has excellent thermal conductivity and mechanical properties and is suitable for use under high temperature and high pressure conditions. Using graphite in a powder state to prepare a graphene dispersion may help to evenly distribute the graphite.

[0033] The role of the dispersant in the above preparation method is to promote the uniform dispersion of graphene sheets in the dispersion medium, prevent the restacking and aggregation of graphene sheets, and thus obtain a graphene dispersion with good dispersibility and stability. In a preferred embodiment of the present invention, the above dispersant is selected from any one or more of the following: N-methylpyrrolidone, sodium dodecylbenzenesulfonate, sodium taurodeoxycholate, dimethylformamide, ethanol, o-dichlorobenzene or poloxamer. These preferred dispersants are more effective in preventing the restacking and aggregation of graphene sheets than other dispersants in the prior art; the formed dispersion has a longer storage life, reduces precipitation and stratification; has the advantages of low toxicity and environmental friendliness.

[0034] It should be noted that the different mass concentrations and ratios of the above-mentioned graphite and the above-mentioned dispersant may affect the preparation of the graphene dispersion. Therefore, in a preferred embodiment of the present invention, the mass concentration of the above-mentioned graphite in the above-mentioned graphite mixed suspension is 1-10% and the mass ratio of the above-mentioned graphite to the above-mentioned dispersant is 100:(1-3). The graphene dispersion prepared according to the above ratio has the beneficial effects of achieving optimized dispersion and stability of graphene, while improving processing adaptability and application performance, and has cost-effectiveness and environmental friendliness.

[0035] In addition, the method of obtaining a graphene dispersion using liquid phase shear exfoliation technology is safer and more efficient, and the obtained graphene dispersion is also easier to surface modify. In a preferred embodiment of the present invention, the instrument used for the above-mentioned liquid phase shear exfoliation is selected from any one or more of the following: a nano bead mill, a pin sand mill, a turbine sand mill or a high-pressure homogenizer; preferably, the stirring treatment time is 30 to 60 minutes, the grinding speed is 800 to 2000 r / min, and the grinding time is 1 to 5 hours; the grinding time and speed determine the number and quantity of graphene dispersion layers. Preferably, the above-mentioned graphene dispersion includes one or more layers of graphene layers, the average number of layers of the above-mentioned graphene layers is 6 to 20 layers, and the mass concentration of the above-mentioned graphene in the above-mentioned graphene dispersion is 2 to 25%.

[0036] It should be noted that the cross-linking agent modified graphene needs to be dried before preparing the coal blocking plate to remove the moisture in the cross-linking agent modified graphene. The water content of the cross-linking agent modified graphene is 0.1% to 5%. In a preferred embodiment of the present invention, the drying process is carried out by spray drying, the temperature of the spray drying is 130 to 160°C, the liquid feeding speed of the cross-linking agent modified graphene is 5 to 18 mL / min, and the water content of the cross-linking agent modified graphene after drying is 0.08% to 4%.

[0037] The addition of anti-wear agents enhances the fluidity of the melt during mixed molding. The anti-wear agents are selected from any one or more of the following: polytetrafluoroethylene, ultra-high molecular weight polyurethane, molybdenum disulfide, polysiloxane, glass fiber, carbon fiber or aramid fiber. These preferred anti-wear agents have higher wear resistance and durability than other anti-wear agents in the prior art, extending the service life of the product; improving the fluidity of the melt, improving production efficiency and reducing energy consumption; providing better self-lubricating properties, reducing friction and wear during molding; maintaining performance under extreme temperature or chemical environment, improving product reliability; and enhancing the mechanical properties of the material, such as strength, rigidity and impact resistance.

[0038] The addition of processing aids has the effect of improving processing performance, increasing thermal stability, enhancing antioxidant properties and improving the overall performance of the material. The above-mentioned processing aids are selected from any one or more of the following: dibasic lead phosphite, methyl tin, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] or 2,6-di-tert-butyl-4-methylphenol. These preferred additives have the advantages of being able to maintain the stability and processability of the polymer in a wider temperature range than other additives in the prior art; being able to more effectively prevent thermal degradation of the material during high-temperature processing; providing more lasting protection against the degradation of material properties caused by oxidation; maintaining or improving the mechanical and electrical properties of the material by preventing degradation; and improving antioxidant and thermal stability.

[0039] The addition of microbeads can significantly improve the sound wave absorption capacity of the polyurethane coal baffle. The microbeads are organic microbeads or inorganic microbeads; the organic microbeads are selected from hybrid organic silicon microbeads; the inorganic microbeads are selected from any one or more of the following: 920DET40d25 microbeads, DU2201L microbeads or hollow glass microbeads. Compared with other types or specifications of microbeads in the prior art, these microbeads have the advantages of high sound wave absorption efficiency, light weight, durability, wide application range, chemical stability, thermal stability and environmental friendliness.

[0040] Polyurethanes with different molecular weights have differences in mechanical properties, dissolution and swelling, thermal stability and wear resistance. In a preferred embodiment of the present invention, the molecular weight of the polyurethane is 12,000 to 50,000. The polyurethane defined above is an ideal material for preparing coal retaining plates, and can significantly enhance the wear resistance, antistatic and impact resistance of the coal retaining plates.

[0041] The ratio of the above materials (graphene modified by the above cross-linking agent, the above wear-resistant agent, the above processing aid, the above micro-beads and the above polyurethane) for preparing the polyurethane coal-blocking board is closely related to the performance of the polyurethane coal-blocking board. In a preferred embodiment of the present invention, the mass ratio of the above cross-linking agent modified graphene to the above wear-resistant agent is (3-10):1; the mass ratio of the above wear-resistant agent to the above polyurethane is (1-8):100; the mass ratio of the above processing aid to the above polyurethane is (1-9):1000; the mass ratio of the above micro-beads to the above polyurethane is (1-7):100.

[0042] The above-mentioned mixed molding method can be selected according to needs. In a preferred embodiment of the present invention, a plate molding machine is selected for molding, and this molding method has the beneficial effects of high surface finish, good strength and rigidity. Preferably, the upper and lower mold temperatures of the plate molding machine are 180-200°C, the pressure is 2-8MPa, the time is 10-16min, and the thickness of the molded plate is 8-20mm.

[0043] The radiation source of the above irradiation is a high energy electron beam or Co 60 Preferably, the irradiation dose is 30 to 100 kGy, the irradiation rate is 0.1 to 1.0 kGy / h, and the crosslinking density of the polyurethane sound-absorbing coal baffle after the irradiation is 120 to 500 mol / m 3 After irradiation cross-linking, the cross-linking network in the system is dense, and the increase in chemical cross-linking structure and physical entanglement structure synergizes with graphene to provide better wear resistance.

[0044] The beneficial effects of the present invention will be further explained in detail below in conjunction with specific embodiments.

[0045] Example 1

[0046] A polyurethane sound-absorbing coal-blocking plate and a preparation method thereof, comprising the following steps:

[0047] S11. Preparation of graphene dispersion: Place graphite (microcrystalline graphite, 50 g) and dispersant (N-methylpyrrolidone / sodium dodecylbenzenesulfonate = 2:1) in 1 L of ultrapure water and stir evenly. The mass ratio of graphite to dispersant is 100:1. Liquid phase shear exfoliation technology (nano bead mill, stirring time of 30 min, grinding speed of 800 r / min, grinding time of 1.5 h) is used to prepare graphene dispersion. The average number of graphene layers obtained is 10, and the mass / volume concentration of graphene is 3%.

[0048] S12. Preparation of crosslinker-modified graphene: crosslinker (polyetherimide / polyaminopolyallylamine=1:3) was dissolved in ultrapure water, the molar ratio of graphene suspension to crosslinker solution (0.15 mol / L) was 60:1, placed in a microwave reactor to load the crosslinker (reaction temperature was 100°C, reaction time was 5 min), and after the reaction was completed, spray drying (temperature was 130°C, liquid feeding speed was 18 mL / min) was used to remove excess reactants to obtain crosslinker-modified graphene powder. The water content of the crosslinker-modified graphene before drying was 1%, and the water content of the crosslinker-modified graphene after drying was 0.08%.

[0049] S13. Preparation of high-performance coal-blocking plate: wear-resistant agent (polytetrafluoroethylene / ultra-high molecular weight polyurethane = 1:5), processing aid (dibasic lead phosphite / methyl tin = 2:1), microspheres (920DET40d25 microspheres), cross-linking agent-modified graphene, polyurethane pellets (molecular weight 15000) were mixed uniformly (the mass ratio of cross-linking agent-modified graphene to wear-resistant agent was 10:1, the mass ratio of wear-resistant agent to polyurethane was 1:100, the mass ratio of processing aid to polyurethane was 1:1000, and the mass ratio of microspheres to polyurethane was 1:100), and after mixed granulation, it was placed in a plate molding machine (upper and lower mold temperature was 180°C, pressure was 2MPa, time was 10min), the plate thickness was 10mm, and a radioactive source Co was used. 60 The plate was irradiated with an irradiation dose of 30 kGy and an irradiation rate of 1.0 kGy / h. The crosslinking density after irradiation was 120 mol / m 3 .

[0050] Example 2

[0051] A polyurethane sound-absorbing coal-blocking plate and a preparation method thereof, comprising the following steps:

[0052] S21. Preparation of graphene dispersion: Place graphite (thermal expansion graphite, 20 g) and dispersant (sodium taurodeoxycholate) in 1 L of ultrapure water and stir evenly. The mass ratio of graphite to dispersant is 100:1. Liquid phase shear exfoliation technology (nanobead mill, stirring time of 40 min, grinding speed of 1000 r / min, grinding time of 1.2 h) is used to prepare graphene dispersion. The average number of graphene layers obtained is 12, and the mass / volume concentration of graphene is 8%.

[0053] S22. Preparation of crosslinker-modified graphene: crosslinker (polydopamine / polyurethaneimine=1:4) was dissolved in ultrapure water, the molar ratio of graphene suspension to crosslinker solution (0.3 mol / L) was 40:1, placed in a microwave reactor to load the crosslinker (reaction temperature was 90°C, reaction time was 15 min), and after the reaction was completed, the excess reactants were removed by spray drying (inlet temperature was 140°C, liquid inlet speed was 15 mL / min), and the crosslinker-modified graphene powder was obtained. The water content of the crosslinker-modified graphene before drying was 3%, and the water content of the crosslinker-modified graphene after drying was 0.5%.

[0054] S23. Preparation of high-performance coal-blocking plate: wear-resistant agent (ultra-high molecular weight polyurethane / molybdenum disulfide = 10:3), processing aid (dibasic lead phosphite / tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester = 5:1), microbeads (hybrid silicone microbeads), cross-linking agent-modified graphene, polyurethane pellets (molecular weight 12000) were uniformly mixed (the mass ratio of cross-linking agent-modified graphene to wear-resistant agent was 8:1, the mass ratio of wear-resistant agent to polyurethane was 8:1). The mass ratio of the raw materials is 3:100, the mass ratio of the processing aid to the polyurethane is 2:1000, and the mass ratio of the microspheres to the polyurethane is 3:100). After the mixed granules are formed, they are placed in a plate molding machine (the upper and lower mold temperatures are 185°C, the pressure is 4MPa, and the time is 12min). The plate thickness is 8mm. The plate is irradiated with a high-energy electron beam. The irradiation dose is 40kGy, the irradiation rate is 0.6kGy / h, and the crosslinking density after irradiation is 240mol / m 3 .

[0055] Example 3

[0056] A polyurethane sound-absorbing coal-blocking plate and a preparation method thereof, comprising the following steps:

[0057] S31. Preparation of graphene dispersion: Place graphite (highly oriented pyrolytic graphite, 10 g) and dispersant (dimethylformamide / ethanol = 5:1) in 1 L of ultrapure water and stir evenly. The mass ratio of graphite to dispersant is 100:1. Use liquid phase shear exfoliation technology (turbine sand mill, stirring time of 60 min, grinding speed of 800 r / min, grinding time of 5 h) to prepare graphene dispersion. The average number of graphene layers obtained is 20, and the mass / volume concentration of graphene is 2%.

[0058] S32. Preparation of crosslinker-modified graphene: crosslinker (polyetherimide / polyaminopolyallylamine=1:3) was dissolved in ultrapure water, the molar ratio of graphene suspension to crosslinker solution (2 mol / L) was 120:1, placed in a microwave reactor to load the crosslinker (reaction temperature was 90°C, reaction time was 25 min), and after the reaction was completed, the excess reactants were removed by spray drying (inlet temperature was 150°C, liquid inlet speed was 12 mL / min), and the crosslinker-modified graphene powder was obtained. The water content of the crosslinker-modified graphene before drying was 4%, and the water content of the crosslinker-modified graphene after drying was 2%.

[0059] S33. Preparation of high-performance coal-blocking plate: anti-wear agent (polydopamine / tris(hydroxymethyl)aminomethane = 10:1), processing aid (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] / 2,6-di-tert-butyl-4-methylphenol = 1:1), microbeads (DU2201L microbeads), graphene modified by cross-linking agent, and polyurethane pellets (molecular weight of 30,000) were uniformly mixed (the mass ratio of graphene modified by cross-linking agent to anti-wear agent was 6:1, and the mass ratio of anti-wear agent to graphene modified by cross-linking agent was 6:1). The mass ratio of the microspheres to the polyurethane is 5:100, the mass ratio of the processing aid to the polyurethane is 8:1000, and the mass ratio of the microspheres to the polyurethane is 5:100). After mixed granulation, the microspheres are placed in a plate molding machine (the upper and lower mold temperatures are 190°C, the pressure is 5MPa, and the time is 15min). The plate thickness is 15mm. The plate is irradiated with a high-energy electron beam. The irradiation dose is 70kGy, the irradiation rate is 0.4kGy / h, and the crosslinking density after irradiation is 360mol / m 3 .

[0060] Example 4

[0061] A polyurethane sound-absorbing coal-blocking plate and a preparation method thereof, comprising the following steps:

[0062] S41. Preparation of graphene dispersion: Place graphite (thermal expansion graphite, 20 g) and dispersant (ethanol / o-dichlorobenzene / poloxamer = 5:2:2) in 1 L of ultrapure water and stir evenly. The mass ratio of graphite to dispersant is 100:3. Use liquid phase shear exfoliation technology (nano bead mill, stirring time of 30 min, grinding speed of 2000 r / min, grinding time of 1 h) to prepare graphene dispersion. The average number of graphene layers obtained is 8, and the mass / volume concentration of graphene is 15%.

[0063] S42. Preparation of crosslinker-modified graphene: crosslinker (crosslinked polystyrene-divinylbenzene sulfonic acid / γ-amino 50 propyl triethoxysilane = 1:1) was dissolved in ultrapure water, the molar ratio of graphene suspension to crosslinker solution (1.5 mol / L) was 75:1, placed in a microwave reactor to load the crosslinker (reaction temperature was 160°C, reaction time was 35 min), and after the reaction was completed, the excess reactants were removed by spray drying (inlet temperature was 160°C, liquid inlet speed was 5 mL / min), and the crosslinker-modified graphene powder was obtained. The water content of the crosslinker-modified graphene before drying was 0.1%, and the water content of the crosslinker-modified graphene after drying was 0.08%.

[0064] S43. Preparation of high-performance coal-blocking plate: wear-resistant agent (ultra-high molecular weight polyurethane / glass fiber = 10:1), processing aid (dibasic lead phosphite / 2,6-di-tert-butyl-4-methylphenol = 5:1), microspheres (hollow glass microspheres), cross-linking agent-modified graphene, and polyurethane pellets (molecular weight 50,000) were uniformly mixed (the mass ratio of cross-linking agent-modified graphene to wear-resistant agent was 3:1, the mass ratio of wear-resistant agent to polyurethane was 8:100, the mass ratio of processing aid to polyurethane was 9:1000, and the mass ratio of microspheres to polyurethane was 7:100), and after mixed granulation, it was placed in a plate molding machine (upper and lower mold temperature was 200°C, pressure was 8 MPa, and time was 16 min). The plate thickness was 20 mm, and a radioactive source Co was used. 60 The plate was irradiated with an irradiation dose of 100 kGy and an irradiation rate of 0.1 kGy / h. The crosslinking density after irradiation was 500 mol / m 3 .

[0065] Example 5

[0066] A polyurethane sound-absorbing coal-blocking plate and a preparation method thereof, comprising the following steps:

[0067] S51. Preparation of graphene dispersion: Place graphite (thermal expansion graphite, 30 g) and dispersant (ethanol / 2,6-di-tert-butyl-4-methylphenol = 3:2) in 1 L of ultrapure water and stir evenly. The mass ratio of graphite to dispersant is 100:1. Use liquid phase shear exfoliation technology (nano bead mill, stirring time of 50 min, grinding speed of 1500 r / min, grinding time of 1.5 h) to prepare graphene dispersion. The average number of graphene layers obtained is 6, and the mass / volume concentration of graphene is 25%.

[0068] S52. Preparation of crosslinker-modified graphene: crosslinker (polydopamine / tris(hydroxymethyl)aminomethane=5:1) was dissolved in ultrapure water, the molar ratio of graphene suspension to crosslinker solution (2.0 mol / L) was 75:1, placed in a microwave reactor to load the crosslinker (reaction temperature was 150°C, reaction time was 30 min), after the reaction was completed, spray drying (inlet temperature was 150°C, liquid inlet speed was 6 mL / min) was used to remove excess reactants, and crosslinker-modified graphene powder was obtained. The water content of crosslinker-modified graphene before drying was 5%, and the water content of crosslinker-modified graphene after drying was 4%.

[0069] S53. Preparation of high-performance coal-blocking plate: wear-resistant agent (ultra-high molecular weight polyurethane / glass fiber = 10:1), processing aid (dibasic lead phosphite / 2,6-di-tert-butyl-4-methylphenol = 5:1), microspheres (hollow glass microspheres), cross-linking agent-modified graphene, and polyurethane pellets (molecular weight 50000) are uniformly mixed (the mass ratio of cross-linking agent-modified graphene to wear-resistant agent is 3:1, the mass ratio of wear-resistant agent to polyurethane is 8:100, the mass ratio of processing aid to polyurethane is 9:1000, and the mass ratio of microspheres to polyurethane is 7:100), and after mixed granulation, the mixed granules are placed in a plate molding machine (upper and lower mold temperatures are 190°C, pressure is 5MPa, and time is 15min). The plate thickness is 8mm, and the plate is irradiated with a high-energy electron beam. The irradiation rate is 1.0kGy / h, the irradiation dose is 100kGy, and the cross-linking density after irradiation is 120mol / m 3 .

[0070] Example 6

[0071] The polyurethane sound-absorbing coal baffle was prepared by basically adopting the method of Example 1. The difference is that in this example, no dispersant was used to prepare the graphene dispersion, but the graphite was directly subjected to liquid phase shear exfoliation in ultrapure water.

[0072] Example 7

[0073] The polyurethane sound-absorbing coal-blocking plate was prepared by basically adopting the method of Example 2. The difference is that the cross-linking agent-modified graphene used in this example did not use the microwave-assisted method to load the cross-linking agent.

[0074] Comparative Example 1

[0075] The polyurethane sound-absorbing coal-blocking board was prepared by basically adopting the method of Example 1. The difference is that no microbeads were added in this example.

[0076] Comparative Example 2

[0077] The polyurethane sound-absorbing coal-blocking plate was prepared by the same method as in Example 2. The difference was that in this example, no radiation cross-linking was performed after compression molding.

[0078] Comparative Example 3

[0079] The polyurethane sound-absorbing coal baffle was prepared by basically adopting the method of Example 3. The difference was that in this example, no wear-resistant agent was added in the molding stage after mixing and granulation.

[0080] Comparative Example 4

[0081] The polyurethane sound-absorbing coal-blocking plate was prepared by basically adopting the method of Example 4. The difference is that the graphene used in this example was not modified by a cross-linking agent.

[0082] Comparative Example 5

[0083] The polyurethane sound-absorbing coal baffle was prepared by basically adopting the method of Example 5. The difference is that no processing aid was added in this example.

[0084] Structural characterization and performance testing:

[0085] Tensile properties test :The obtained polyurethane coal retaining plate was cut to obtain tensile specimens, and the tensile properties of the plate were tested using a universal tensile machine (model 4403, sensor 100N) of Instron, USA, according to the ASTM D638-2003 plastic tensile properties test standard of the American Society for Testing and Materials. At least 3 parallel test samples were guaranteed for each group, and the results were averaged.

[0086] Impact resistance test The obtained polyurethane coal retaining plate was cut to obtain standard samples, and the impact resistance of the plate was tested using a simple beam impact tester (model 9050) of the British Instron Instrument Group according to the ASTM D4812-19 plastic impact resistance test standard of the American Society for Testing and Materials. At least 3 parallel test samples were guaranteed for each group, and the results were averaged.

[0087] Tribological performance test The wear resistance test of the samples is based on ASTM G132-96, and the test instrument is HSR-2M high-speed reciprocating friction and wear tester. GCR15 bearing steel balls with a diameter of 5mm are selected as the corresponding material. The steel ball loading load is 20N, the reciprocating frequency is 16.67Hz, the reciprocating length is 5mm, and the friction time is 1000min, reaching 1×10 6 The tribological properties were studied at room temperature after reciprocating friction cycles. The wear volume (M, mg) was measured using a high-precision electronic balance, and the friction coefficient (ε) was calculated using the following formula (1):

[0088]

[0089] Where M1 (mg) is the wear amount of the standard sample, and M2 (mg) is the wear amount of the tested sample.

[0090] The instrument's electronic probe measures wear volume (V, mm 3 ), and use the following formula (2) to calculate the wear rate (K, mm 3 N m -1 ):

[0091]

[0092] Where F(N) is the load during the friction test, and x(m) is the total sliding distance of 30 min. To ensure the accuracy of the experimental data, each sample was tested three times.

[0093] Antistatic performance test : Use 4339A / B type high insulation resistance meter to test the volume resistivity of each sample. Clamp both ends of the sample with copper clips and test according to GB / T1410-2006.

[0094] Sound absorption performance test : The sound absorption coefficient of the sample is tested using a two-channel acoustic impedance tube. The sample thickness is 5mm and the diameter is 30mm. The sound wave frequency range is 100-5000Hz. The test is carried out in accordance with GB / T 18696.1-2004.

[0095] Table 1. Test results of mechanical properties, tribological properties and antistatic properties of high-performance polyurethane coal retaining plate

[0096]

[0097]

[0098] Experimental results: Table 1 compares the test results of mechanical properties, tribological properties and antistatic properties of the polyurethane coal retaining plate obtained in the embodiment and the comparative example.

[0099] The role of microbeads is to increase the porosity of the material through its porous or hollow structure, so that sound waves are scattered and absorbed more when propagating inside the material, thereby effectively reducing noise and significantly improving the sound absorption performance of the polyurethane coal-blocking board. In addition, the addition of microbeads can increase the hardness of the material, reduce its brittle fracture, reduce its volume resistivity, and improve its wear resistance and scratch resistance. Comparing the experimental results of Example 1 (adding microbeads) and Comparative Example 1 (no microbeads added), the addition of microbeads significantly increases the sound absorption coefficient of the coal-blocking board, further enhancing the noise reduction properties of the coal-blocking board, which corresponds to the sound absorption properties of the microbeads.

[0100] Irradiation can promote the establishment of a cross-linked network, thereby affecting the mechanical properties of the polyurethane matrix material, increasing the interaction between the internal reinforcement phase and the matrix in the matrix material, and further affecting the wear resistance and even the anti-noise performance. Comparing the experimental results of Example 2 (irradiation cross-linking) and Comparative Example 2 (no irradiation cross-linking), the irradiation cross-linked polyurethane coal-blocking board has better performance in tensile strength, impact strength, wear resistance, volume resistivity and sound absorption coefficient than the coal-blocking board that has not been irradiated and cross-linked.

[0101] The main function of the anti-wear agent is to increase the wear resistance of the coal-blocking plate, which is specifically manifested in low friction coefficient and low wear rate. Secondly, the addition of anti-wear agent is also beneficial to improve the tensile strength, impact strength and sound absorption coefficient of the coal-blocking plate, and is beneficial to reduce the volume resistivity of the coal-blocking plate to enhance the antistatic properties of the coal-blocking plate. Comparing the experimental results of Comparative Example 3 (without adding anti-wear agent) and Example 3 (adding anti-wear agent), the friction coefficient and wear rate of the coal-blocking plate with the addition of anti-wear agent in Example 3 are lower. The friction coefficient of Comparative Example 3 is large and the wear rate is high, mainly because no anti-wear agent is added during compression molding, resulting in poor processing flowability, and a large number of defects on the surface of the molded coal-blocking plate, which is easy to wear.

[0102] Cross-linker-modified graphene has a significant improvement effect on the compatibility between the matrix and the filler, bringing a series of performance improvements to the polyurethane coal barrier board: not only does it enhance the mechanical strength and thermal stability, it may also optimize the sound absorption and antistatic properties of the material, while improving the flame retardancy and impact resistance, improving the processing performance, and enhancing the chemical corrosion resistance and environmental stability, thereby enabling the coal barrier board to exhibit better overall performance in industrial applications.

[0103] Comparing the experimental results of Example 4 (graphene modified with a cross-linker) and Comparative Example 4 (graphene used was not modified with a cross-linker), the tensile strength, impact strength and sound absorption coefficient of the coal keep out plate prepared in Example 4 are all higher than those in Comparative Example 4, while the friction coefficient, wear rate and volume resistivity are all lower than those in Comparative Example 4, indicating that the use of graphene modified with a cross-linker to prepare the coal keep out plate is helpful to improve the mechanical strength, wear resistance, noise reduction and antistatic properties of the coal keep out plate.

[0104] The role of processing aids is to improve processing performance, improve thermal stability, enhance antioxidant properties and enhance the overall performance of materials. The experimental results of Example 5 (using processing aids) and Comparative Example 5 (not using processing aids) show that the coal retaining plate with added processing aids in Example 5 is better than Comparative Example 5 in terms of tensile strength, impact strength, noise reduction, wear resistance and antistatic properties. The role of the dispersant is to inhibit the accumulation and precipitation of the graphene suspension. Poor dispersion will cause the graphene to be unable to bear tensile stress and have poor impact resistance and even wear resistance, antistatic and sound absorption effects. Comparing the experimental results of Example 1 (containing dispersant) and Example 6 (without dispersant), the results show that the coal retaining plate of Example 1 is significantly better than the coal retaining plate of Example 6 in tensile strength and impact strength, and the friction coefficient and wear rate of the coal retaining plate of Example 1 are lower, the sound absorption coefficient is higher, and the performance is better than the coal retaining plate of Example 6. The experimental conclusion corresponds to the role of the dispersant.

[0105] The effects of microwave-assisted cross-linking include: 1) providing functional sites to fully improve the compatibility of graphene in the matrix material, thereby improving the tensile strength and impact strength of the polyurethane coal-blocking board; 2) releasing the conductive properties of graphene and reducing the volume resistivity; 3) after cross-linking, graphene acts as a reinforcing phase material in the polyurethane coal-blocking board, so that the functional groups can interact with other additives to synergistically improve the wear resistance and quiet performance. According to the experimental results of Example 2 (obtaining cross-linker-modified graphene using microwave-assisted method) and Example 7 (obtaining cross-linker-modified graphene without microwave-assisted method), the tensile strength, impact strength and sound absorption coefficient of the coal-blocking board of Example 2 are significantly better than those of the coal-blocking board of Example 7, and the wear resistance is good, and the friction coefficient and wear rate are lower.

[0106] In summary, the coal retaining plates (Examples 1 to 7) prepared by the scheme of the present invention all exhibit extremely high tensile strength (59.6 to 98.9 MPa) and impact strength (85.7 to 197.1 MPa), and have extremely high mechanical strength. Examples 1 to 7 have relatively low friction coefficients (0.01 to 0.15) and wear rates (1.13×10 -5 ~7.72×10 -5 mm 3 N m -1 ), which significantly improves the resistance of the polyurethane coal baffle surface to friction erosion under cyclic friction.

[0107] It is also significant that Examples 1 to 7 have relatively low volume resistivity (0.95×10 6 ~4.06×10 7 Ω·cm), showing excellent antistatic ability, which is very suitable for the antistatic needs of the coal retaining plate under high cycle friction during coal transportation.

[0108] Examples 1 to 7 have relatively high sound absorption coefficients (0.31 to 0.68), showing good sound absorption and noise reduction performance, and have unique advantages in dealing with high noise environments using coal baffles.

[0109] From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects: the present invention adopts liquid phase shear exfoliation technology to exfoliate graphite to obtain a graphene dispersion, and obtains functionalized graphene powder modified with a crosslinker by a microwave-assisted crosslinking method, and the polyurethane is mixed with the crosslinker-modified graphene, wear-resistant agent, processing aid and microbeads and then irradiated. The prepared polyurethane sound-absorbing coal baffle not only has high mechanical strength, but also has excellent wear resistance and antistatic properties, which can greatly improve the service life of the coal baffle on the scraper conveyor under complex environment, prevent friction static electricity and noise hazards, and has broad application prospects.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a polyurethane sound-absorbing coal-blocking plate, characterized in that: The preparation method comprises: The cross-linking agent-modified graphene, a wear-resistant agent, a processing aid, microbeads and polyurethane are mixed and molded, and then irradiated to obtain the polyurethane sound-absorbing coal-blocking board.

2. The preparation method according to claim 1, characterized in that: The preparation method of the cross-linking agent modified graphene is as follows: Mixing the graphene dispersion with the cross-linking agent to obtain a mixed solution to be cross-linked; Performing microwave irradiation functionalization treatment on the mixed solution to be cross-linked to obtain the graphene modified by the cross-linking agent; Preferably, the graphene dispersion is prepared by the following method: mixing graphite powder, a dispersant and ultrapure water to obtain a graphite mixed suspension; The graphite mixed suspension is subjected to liquid phase shear exfoliation to obtain the graphene dispersion.

3. The preparation method according to claim 2, characterized in that: The graphite is selected from any one or more of the following: microcrystalline graphite, thermally expanded graphite and highly oriented pyrolytic graphite.

4. The preparation method according to claim 2, characterized in that: The dispersant is selected from any one or more of the following: N-methylpyrrolidone, sodium dodecylbenzene sulfonate, sodium taurodeoxycholate, dimethylformamide, ethanol, o-dichlorobenzene or poloxamer.

5. The preparation method according to claim 2, characterized in that: The mass concentration of the graphite in the graphite mixed suspension is 1-10% and the mass ratio of the graphite to the dispersant is 100:(1-3).

6. The preparation method according to claim 2, characterized in that: The instrument used for the liquid phase shear stripping is selected from any one or more of the following: a nano-bead mill, a pin-type sand mill, a turbine sand mill or a high-pressure homogenizer; Preferably, the stirring treatment time is 30 to 60 minutes, the grinding speed is 800 to 2000 r / min, and the grinding time is 1 to 5 hours; Preferably, the graphene dispersion comprises one or more graphene layers, the average number of graphene layers is 6 to 20, and the mass concentration of the graphene in the graphene dispersion is 2 to 25%.

7. The preparation method according to claim 2, characterized in that: The crosslinking agent is selected from any one or more of the following: polyetherimide M w =10 4 ~10 5 Da, polyamino polyallylamine M w =10 3 ~10 4 Da, polydopamine M w =10 3 ~10 4 Da, polyurethane imine M w =10 3 ~10 5 Da, tris(hydroxymethyl)aminomethane, cross-linked polystyrene-divinylbenzenesulfonic acid or γ-aminopropyltriethoxysilane; Preferably, the concentration of the cross-linking agent is 0.15 to 2 mol / L; Preferably, the molar ratio of the graphene dispersion to the cross-linking agent is (40-120):

1.

8. The preparation method according to claim 2, characterized in that: The instrument for carrying out the microwave irradiation functionalization treatment is a microwave reactor, the reaction temperature is 90-160° C., and the reaction time is 5-35 minutes.

9. The preparation method according to claim 2, characterized in that: The water content of the cross-linking agent modified graphene is 0.1% to 5%; Preferably, the water content of the cross-linking agent-modified graphene is 0.08% to 4% by spray drying; Preferably, the spray drying temperature is 130-160° C., and the liquid inflow rate of the cross-linking agent-modified graphene is 5-18 mL / min.

10. The preparation method according to claim 1, characterized in that: The molecular weight of the polyurethane is 12,000 to 50,000.

11. The preparation method according to claim 1, characterized in that: The wear-resistant agent is selected from any one or more of the following: polytetrafluoroethylene, ultra-high molecular weight polyurethane, molybdenum disulfide, polysiloxane, glass fiber, carbon fiber or aramid fiber.

12. The preparation method according to claim 1, characterized in that: The processing aid is selected from any one or more of the following: dibasic lead phosphite, methyl tin, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate or 2,6-di-tert-butyl-4-methylphenol.

13. The preparation method according to claim 1, characterized in that: The microbeads are organic microbeads or inorganic microbeads; the organic microbeads are selected from hybrid silicone microbeads; the inorganic microbeads are selected from any one or more of the following: 920DET40d25 microbeads, DU2201L microbeads or hollow glass microbeads.

14. The preparation method according to claim 1, characterized in that: The mass ratio of the cross-linking agent modified graphene to the wear-resistant agent is (3-10):1; the mass ratio of the wear-resistant agent to the polyurethane is (1-8):100; the mass ratio of the processing aid to the polyurethane is (1-9):1000; and the mass ratio of the microbeads to the polyurethane is (1-7):

100.

15. The preparation method according to claim 1, characterized in that: The mixed molding method is to mix and granulate and then place the mixture in a plate molding machine for compression molding; Preferably, the temperature of the upper and lower molds of the plate molding machine is 180-200° C., the pressure is 2-8 MPa, the time is 10-16 min, and the thickness of the molded plate is 8-20 mm.

16. The preparation method according to claim 1 or 15, characterized in that: The irradiation source is a high energy electron beam or Co 60 ; Preferably, the irradiation dose is 30-100 kGy, the irradiation rate is 0.1-1.0 kGy / h, and the crosslinking density of the polyurethane sound-absorbing coal baffle after irradiation is 120-500 mol / m 3 .

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