Electromagnetic brake friction material made from granules and process for its production

Abstract

The application relates to the technical field of friction materials, and discloses an electromagnetic brake friction material made of granular material and a preparation process thereof, aiming at the problems of difficult preparation or insufficient performance of existing electromagnetic brake friction plates, and the electromagnetic brake friction material comprises reinforcing materials, fillers, binders and complexing agents; the reinforcing materials comprise plasma modified aramid pulp, coupling modified composite mineral fibers, SiO2-coated four acicular zinc oxide whiskers and carbon fiber-aluminum silicon whiskers; the fillers comprise modified acicular wollastonite and organically modified precipitated barium sulfate; and the binders comprise boron-silicon synergistically modified phenolic resin and modified carboxyl nitrile rubber. The granular material is prepared through the improvement of raw materials and the adoption of a dense mixing and crushing process, the content of the binder can be greatly reduced, the mold loading efficiency can be improved, the mold thickness and the high-temperature thermal decay of the friction material are reduced, the cold pressing forming process can be saved, and the qualified rate of the finished friction material is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of friction materials, in particular to an electromagnetic brake friction material made of granular material and a preparation process thereof. BACKGROUND

[0002] The friction material is usually made of adhesive, reinforcing material and various fillers by mixing, molding and pressing, wherein the fillers are mostly fine-particle substances such as ore powder, metal oxide powder and organic friction powder. The specific surface area of the fine-particle fillers is large, resulting in a large wetting area of the fillers, thus increasing the required amount of adhesive, and too much adhesive can cause high-temperature degradation of the friction system of the friction material, greatly reducing the friction performance stability of the friction material. In addition, the electromagnetic brake friction plate has a hole in the center, so the flowability of the pressed material is required to be very high to facilitate smooth pressing, but the traditional powder material needs to be cold-pressed into a shape first and then hot-pressed, which is a complex process with low efficiency and also difficult to ensure the qualified rate of the finished friction material.

[0003] For example, the patent with publication number CN112852034 provides a kind of friction material, synthetic brake shoe and preparation method, including the following raw material components and volume fractions: binder 6~26 parts, rubber powder 10~40 parts, reinforcing fiber 5~30 parts, friction-enhancing filler 5~21 parts, friction-reducing filler 10~25 parts, other fillers 5~36 parts, the preparation method of the friction material includes the following steps: the prepared friction material is placed in a cold-pressing mold cavity, a cushion layer and a steel back are placed, the mold is removed after shaping, and then hot-pressed into a shape in a hot-pressing mold.

[0004] However, the existing technology has the following problems despite the optimization and improvement of the raw material formula of part of the friction material: first, the adhesive has insufficient heat resistance and is easily decomposed at high temperatures, resulting in degradation of the friction performance; second, the reinforcing material has poor dispersibility and is difficult to form a stable support structure, affecting the strength and wear resistance of the material; third, the filler has weak bonding force with the matrix and is prone to agglomeration, reducing the overall performance of the material; fourth, the mixing efficiency is low, the fiber dispersibility is poor, and the hot-pressing parameters are unreasonable in the preparation process, further affecting the quality stability of the product.

[0005] In summary, there are problems such as difficulty in pressing the filler, complex process, low efficiency, high adhesive content, etc. in the production and manufacturing of electromagnetic brake friction plates and other materials. SUMMARY

[0006] The present application aims to solve the problems of difficult preparation or insufficient performance of existing electromagnetic brake friction plates. By improving the raw materials and using a dense mixing and crushing process to make granular material, the adhesive content can be greatly reduced, the molding efficiency can be improved, the mold thickness can be reduced, the high-temperature thermal degradation of the friction material can be reduced, and the cold-pressing process can be omitted, thereby improving the qualified rate of the finished friction material.

[0007] The application is achieved by the following technical solutions:

[0008] The application provides an electromagnetic brake friction material made of granular materials, which comprises reinforcing materials, fillers, binders and complexing agents.

[0009] The reinforcing materials comprise plasma-modified aramid pulp, coupling-modified composite mineral fibers, SiO2-coated four-needle zinc oxide whiskers and carbon fiber-aluminum silicon whiskers.

[0010] The fillers comprise modified needle-shaped wollastonite and organically modified precipitated barium sulfate.

[0011] The binders comprise boron-silicon synergistically modified phenolic resin and modified carboxyl nitrile rubber.

[0012] Preferably, in the reinforcing materials, the plasma-modified aramid pulp is aramid pulp with active groups introduced on the surface, the coupling-modified composite mineral fibers are composite mineral fibers with an organic coating layer formed on the surface by a titanate coupling agent, the SiO2-coated four-needle zinc oxide whiskers are four-needle zinc oxide whiskers coated with a SiO2 film on the surface, and the carbon fiber-aluminum silicon whisker is a composite of chopped carbon fibers and aluminum silicon whiskers forming an interwoven structure.

[0013] Preferably, in the fillers, the modified needle-shaped wollastonite is modified needle-shaped wollastonite with oil-wet and water-wet groups on the surface by being modified by sodium alkyl sulfonate and then by γ-aminopropyl triethoxysilane.

[0014] The organically modified precipitated barium sulfate is an inorganic core-organic shell structure composite with a phenolic resin prepolymer coated on the surface of the precipitated barium sulfate.

[0015] Preferably, in the binders, the boron-silicon synergistically modified phenolic resin is a complex containing a B-O-Si network structure, which is obtained by modifying phenolic resin with boron and then with silicon.

[0016] Preferably, in the binders, the modified carboxyl nitrile rubber is a modified rubber with polar groups in the molecular chain, which is obtained by grafting carboxyl groups on nitrile rubber and then chemically modifying the nitrile rubber with maleic anhydride.

[0017] Preferably, the reinforcing materials comprise 1-3 parts of plasma-modified aramid pulp, 1-3 parts of acrylic pulp, 10-15 parts of coupling-modified composite mineral fibers, 1-2 parts of SiO2-coated four-needle zinc oxide whiskers and 1-3 parts of carbon fiber-aluminum silicon whiskers in terms of mass fraction.

[0018] The filler comprises 10-15 parts of modified acicular wollastonite, 8-15 parts of organic modified precipitated barium sulfate, 5-10 parts of alumina, 8-12 parts of light calcium carbonate, 4-8 parts of flaky graphite, 1-3 parts of carbon black, and 5-8 parts of modified white carbon black.

[0019] The adhesive comprises 3-5 parts of boron-silicon synergistically modified phenolic resin and 10-15 parts of modified carboxyl nitrile rubber.

[0020] The compounding agent comprises 0.1-0.5 parts of vulcanizing agent, 0.3-1 part of accelerator, and 0.1-0.5 parts of stearic acid.

[0021] The application further provides a preparation process of the electromagnetic brake friction material made of the granular material.

[0022] S1: compounding: the raw materials are sequentially put into a compounding machine in the order of adhesive, reinforcing material, filler and compounding agent, and are compounded at 50-80 DEG C for 10-30 min to obtain a compounded mixture;

[0023] S2: crushing and sieving: the compounded mixture is crushed and sieved to obtain granular primary material with a desired particle size;

[0024] S3: hot pressing: the granular primary material is placed at 175±5 DEG C and hot pressed at 10-30 MPa for 60-80 s / mm;

[0025] S4: heat treatment: the material after hot pressing is placed in a heat treatment furnace for heat treatment, and is taken out after cooling;

[0026] S5: grinding: the granular material after heat treatment is ground to obtain the electromagnetic brake friction material made of the granular material.

[0027] Preferably, in step S2, the particle size of the granular material after sieving is controlled to be 1-2 mm.

[0028] Preferably, in step S3, before pressure maintaining, 3-5 times of exhaust is performed, and each exhaust process comprises pressing for 10 s and exhausting for 2 s.

[0029] Preferably, in step S4, the temperature condition of the heat treatment process comprises the following stages:

[0030] from room temperature to 120±5 DEG C at a rate of 0.8-1.2 h, and maintaining for 1-2 h;

[0031] then from 120±5 DEG C to 180±5 DEG C at a rate of 0.8-1.2 h, and maintaining for 1 h;

[0032] then from 180±5 DEG C to 220±5 DEG C at a rate of 0.8-1.2 h, and maintaining for 6-10 h;

[0033] Finally, the furnace is cooled to 50℃ or below, and the product is removed.

[0034] The technical solution of the present application has the following beneficial effects:

[0035] (1) The boron-silicon synergistically modified phenolic resin and the modified carboxyl nitrile rubber synergistic system are used as the adhesive, the B-O-Si network structure is introduced into the molecular chain of the phenolic resin through the synergistic modification of boron and silicon, the decomposition temperature and the high-temperature residual carbon rate of the resin are improved, the carboxyl nitrile rubber grafted with maleic anhydride is combined, the interpenetrating network of rigid skeleton and flexible segment is constructed, the tensile strength and stability of the material are improved, the high-temperature recession is effectively inhibited, and the stability of the friction performance is ensured. In addition, the grafting modification of maleic anhydride makes the compatibility of the carboxyl nitrile rubber and the boron-silicon modified phenolic resin strong, and avoids the generation of abrasive dust due to interface peeling in the friction process.

[0036] (2) The traditional reinforcing material is prone to agglomeration in the matrix due to surface inertness, resulting in stress concentration points in the material and insufficient strength. In the present application, the aramid pulp is treated by air plasma to enhance the interfacial bonding strength, and the titanate coupling agent is used to improve the dispersion uniformity of the composite mineral fiber, and then the SiO2 coated four acicular zinc oxide whiskers and carbon fiber-aluminum silicon whiskers are used to form a three-dimensional reinforcing structure and a point-line interlaced structure, effectively solving the agglomeration problem and improving the impact strength.

[0037] (3) The modified acicular wollastonite and the composite system of barium sulfate with core-shell structure are used as fillers. The acicular wollastonite is modified by sodium alkyl sulfonate and γ-aminopropyl triethoxysilane, and the surface has both lipophilic and hydrophilic groups, which can simultaneously combine with rubber and inorganic fillers to improve the interfacial bonding strength. The inorganic core and organic shell of precipitated barium sulfate are modified, which can improve the compatibility with the matrix and enhance the flowability of the granular material, achieve better filling effect, and reduce the agglomeration problem during the reheat pressing process.

[0038] (4) In the present application, the raw materials are arranged in a specific order of adhesive, reinforcing material, filler and compounding agent. The adhesive and the reinforcing material form a preliminary matrix, the filler is added for uniform dispersion, and finally the compounding agent is added to ensure uniform vulcanization system. This can effectively improve the uniformity of the mixture, and the improved process is simple and operable, and has strong popularization. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below. In the embodiments, the specific conditions not specified are carried out according to the conventional conditions or the conditions recommended by the manufacturer; the instruments, devices or reagents, etc. not specified by the manufacturer are all conventional products that can be obtained by market purchase.

[0040] The application provides electromagnetic brake friction material made of granular material, which comprises the following raw material system (by mass fraction):

[0041] (1) reinforcing material: 1-3 parts of plasma modified aramid pulp, 1-3 parts of acrylic pulp, 10-15 parts of coupling modified composite mineral fiber, 1-2 parts of SiO2 coated four needle-shaped zinc oxide whisker, 1-3 parts of carbon fiber-aluminum silicon whisker.

[0042] Plasma modified aramid pulp: the aramid pulp is treated by air plasma to introduce active groups such as hydroxyl and carboxyl on the surface of the fiber, and the surface energy is increased from 40 mN / m to 65 mN / m, and the interfacial bonding force of the adhesive is increased by 30%.

[0043] Coupling modified composite mineral fiber: after the composite mineral fiber is dried by heating, 1-2 wt% of titanate coupling agent (NDZ-101) is added, and the fiber surface forms an organic coating layer by high-speed stirring in a high-speed mixer, and the dispersibility is significantly improved to form a uniform support network in the matrix.

[0044] SiO2 coated four needle-shaped zinc oxide whisker: a thin film of SiO2 with a thickness of 5-10 nm is coated on the surface of the four needle-shaped zinc oxide whisker by sol-gel method, which retains the three-dimensional reinforcing structure and improves the compatibility with the organic matrix, and solves the problem of agglomeration.

[0045] Carbon fiber-aluminum silicon whisker: 0.5-1 wt% of chopped carbon fiber with a length of 0.5-1 mm is introduced, and the carbon fiber is compounded with aluminum silicon whisker at a ratio of 1:2-5, and the point-line interlaced structure is built by taking advantage of the length-diameter ratio of the carbon fiber, and the dispersion uniformity of the reinforcing material in the matrix is improved by 40% by mechanical stirring and ultrasonic wave with a power of 500W.

[0046] (2) filler: 10-15 parts of modified needle-shaped wollastonite, 8-15 parts of organic modified barium sulfate, 5-10 parts of alumina, 8-12 parts of light calcium carbonate, 4-8 parts of flake graphite, 1-3 parts of carbon black, 5-8 parts of modified white carbon black.

[0047] Modified needle-shaped wollastonite: first modified by sodium alkyl sulfonate, then modified by gamma-aminopropyl triethoxysilane, the specific treatment process is as follows: the wollastonite modified by surfactant is added into 1 wt% of KH550 and ethanol solution, and stirred at 60℃ to make the filler surface have both lipophilic and hydrophilic groups, and the bonding force of the organic matrix and inorganic filler is improved.

[0048] Organic modified precipitated barium sulfate: a layer of phenolic resin prepolymer is coated on the surface of barium sulfate by in-situ polymerization method to form an inorganic core-organic shell structure, the particle size is controlled in 5-10 mu m, the interfacial bonding strength of barium sulfate and the matrix is improved by 25%, and the flowability of the granular material is improved.

[0049] The present application designs a filler gradient distribution system combining rigidity and flexibility, the outer layer is 1000 mesh modified white carbon black to form a transition layer to improve the interfacial compatibility; the middle layer is 400 mesh precipitated barium sulfate to provide rigid support; and the inner layer is flaky graphite to form a lubricating layer to reduce the fluctuation of friction coefficient. Through this gradient distribution design, the bonding force of the filler and the matrix presents a gradient change, which not only ensures the overall strength, but also retains the toughness and lubricity of the friction material, and the wear rate is reduced by 20-30% compared with the traditional formula.

[0050] (3) Adhesive: including 3-5 parts of boron-silicon synergistically modified phenolic resin, 10-15 parts of modified carboxyl nitrile rubber.

[0051] Boron-silicon synergistically modified phenolic resin: first modified by boron, and then modified by silicon element again. Phenolic resin, boric acid (3-5wt%), and tetraethyl orthosilicate (2-4wt%) are mixed in dimethylbenzene solvent, and refluxed at 80 DEG C to form a network structure containing B-O-Si bond. The decomposition temperature of the modified resin is increased to above 550 DEG C, and the carbon residue rate at 1000 DEG C is increased to above 65%, which is increased by 10% compared with single boron modification.

[0052] Modified carboxyl nitrile rubber: the grafted carboxyl nitrile rubber is chemically modified by maleic anhydride, 0.5-1wt% of MAH and 0.1-0.3wt% of dicumyl peroxide (DCP) are added in the initial stage of mixing, and the rubber molecular chain is introduced into more polar groups by reacting at 120 DEG C. The compatibility of the modified rubber with the phenolic resin is increased by 20%, and the interfacial bonding strength is increased by 15%.

[0053] Through resin, rubber and nano filler, a three-dimensional interpenetrating network structure is constructed, boron-silicon modified phenolic resin forms a rigid skeleton to provide high temperature stability; maleic anhydride grafted carboxyl nitrile rubber forms a flexible segment to improve toughness; 1-2wt% of nano montmorillonite modified by octadecyl trimethyl ammonium chloride is added to further improve the heat resistance and mechanical properties through intercalation effect. After synergistic modification, the tensile strength retention rate of the adhesive system is increased from 70% to above 85% after aging at 250 DEG C for 100h.

[0054] (4) Compounding agent: including 0.1-0.5 parts of vulcanizing agent, 0.3-1 parts of accelerator, and 0.1-0.5 parts of stearic acid.

[0055] The preparation method of the electromagnetic brake friction material prepared from the granular material provided by the present application comprises the following steps:

[0056] S1 Compounding:

[0057] The raw materials of each component are weighed according to the proportion, and are put into the compounding machine in the order of adhesive, reinforcing material, filler and compounding agent for compounding. The compounding temperature is controlled at 50-80℃, the upper plunger pressure is 0.5-0.7MPa, the rotor speed is 30-50r / min, and the compounding time is 10-30min to obtain the compounding mixture.

[0058] The above feeding order can ensure that each component is fully mixed, and avoid the problem of uneven dispersion caused by the early addition of fillers.

[0059] S2 Crushing and sieving:

[0060] The compounded mixture is put into a crusher for crushing, and then sieved, and the particle size is strictly controlled at 1-2mm to obtain the granular material.

[0061] The particle size range can ensure that the granular material has good fluidity in the subsequent hot pressing process, while avoiding the problems of dust caused by too small particle size and uneven forming caused by too large particle size.

[0062] S3 Hot pressing:

[0063] The 100T four-column hydraulic press is used for hot pressing, the granular material is uniformly put into the hot pressing mold and flattened, the pressing temperature is controlled at 175±5℃, the pressing pressure is 10-30MPa, the pressure holding time is 60-80s / mm, and the exhaust is performed 3-5 times before pressure holding at the pace and process of pressing for 10s and exhausting for 2s. The exhaust operation can effectively remove air in the granular material, prevent defects such as bubbles and pores in the finished product, and obtain the friction material semi-finished product after pressure holding.

[0064] S4 Heat treatment:

[0065] The friction material semi-finished product is put into a heat treatment furnace, and is heated from room temperature to 120±5℃ for 0.8-1.2h, and is kept at 120±5℃ for 1-2h; then heated from 120±5℃ to 180±5℃ for 0.8-1.2h, and kept at 180±5℃ for 1h; then heated from 180±5℃ to 220±5℃ for 0.8-1.2h, and kept at 220±5℃ for 6-10h; finally, the furnace is cooled to 50℃, and the product is taken out.

[0066] The stepwise heating and holding process can slowly release the internal stress of the material, further promote the crosslinking reaction, and improve the performance stability of the material.

[0067] S5 Grinding:

[0068] The heat-treated friction material is subjected to surface grinding treatment by a double-end surface abrasive belt grinder to remove surface oxide scale, burrs and flash, so as to ensure the surface flatness and dimensional accuracy of the friction material and meet the assembly requirements of the electromagnetic brake.

[0069] Example 1

[0070] This example mainly relates to preparation of the modified raw materials required in the electromagnetic brake friction material made of granular material of the application.

[0071] (1) Preparation of plasma-modified aramid pulp:

[0072] The aramid pulp is treated by air plasma, with a power of 300W and a time of 30s, to obtain plasma-modified aramid pulp.

[0073] (2) Preparation of coupling-modified composite mineral fiber:

[0074] The rock wool fiber, glass fiber and carbon fiber are mixed as a composite mineral fiber; the composite mineral fiber is dried at 80℃ for 2h, and 1.5% of titanium acid ester coupling agent by mass is added, which is treated in a high-speed mixer at 800rpm for 15min to obtain a coupling-modified composite mineral fiber.

[0075] (3) Preparation of SiO2-coated four-needle zinc oxide whisker:

[0076] The four-needle zinc oxide whisker is coated with a thin film of SiO2 with a thickness of about 7nm on the surface of the four-needle zinc oxide whisker by sol-gel method to obtain SiO2-coated four-needle zinc oxide whisker.

[0077] (4) Preparation of carbon fiber-aluminum silicon whisker:

[0078] The aluminum silicon whisker is added with chopped carbon fiber with a length of about 0.8mm at a mass ratio of 1:3, and ultrasonic dispersion is used with a power of 500W for 10min to obtain carbon fiber-aluminum silicon whisker.

[0079] (5) Preparation of modified acicular wollastonite:

[0080] First, the sodium alkyl sulfonate is treated, specifically: the acicular wollastonite is placed in a 2% mass concentration of dilute hydrochloric acid solution for 1.5h, filtered, washed with deionized water for 3 times, and placed in a 95℃ drying oven for 1.5h; then the acicular wollastonite is placed in deionized water, the solid-liquid ratio is controlled to be 20:100, and ultrasonic oscillation is performed for 45min to form a suspension; then a saturated sodium alkyl sulfonate aqueous solution is added under a 60℃ constant temperature water bath, the addition amount of the sodium alkyl sulfonate is 2% of the mass of the acicular wollastonite, a sodium hydroxide solution is added dropwise until the pH value of the reaction system is 7.2, ultrasonic oscillation reaction is performed for 2h, and then static placement is performed for 7min; filtration is performed, deionized water is used for washing for 5 times, and drying is performed at 80℃ for 2h.

[0081] Then, the γ-aminopropyl triethoxysilane modification treatment is performed, specifically: the acicular wollastonite treated by the sodium alkyl sulfonate is taken and added to a 1wt% KH550 and ethanol solution, and stirring reaction is performed at 60℃ for 2h to obtain modified acicular wollastonite.

[0082] (6) Preparation of organic modified precipitated barium sulfate:

[0083] The precipitated barium sulfate is taken, an in-situ polymerization method is adopted, a phenolic resin prepolymer coating layer is formed on the precipitated barium sulfate, and organic modified precipitated barium sulfate is obtained.

[0084] (7) Preparation of boron-silicon synergistically modified phenolic resin:

[0085] The phenolic resin, 4wt% boric acid and 3wt% tetraethyl orthosilicate are mixed in a xylene solvent, reflux reaction is performed at 80℃ for 3h, and a boron-silicon synergistically modified phenolic resin with a reticular structure containing B-O-Si bonds is formed.

[0086] (8) Preparation of modified carboxyl nitrile rubber:

[0087] The nitrile rubber grafted with carboxyl groups is taken, 0.8wt% MAH and 0.2wt% dicumyl peroxide are added in the initial stage of mixing, and reaction is performed at 120℃ for 15min to obtain modified carboxyl nitrile rubber.

[0088] (9) Preparation of modified white carbon black:

[0089] The white carbon black is placed in a drying oven and dried at 100℃ for 1.5h, then the white carbon black is put into a high-speed mixer, stirred at 95℃ for 55min, and the stirring speed is controlled at 800rpm; then Si69 is added, and the addition amount of Si69 is controlled to be 4% of the mass of the white carbon black, and stirring is continued for 40min; heating is performed to 130℃, and the temperature is maintained for 2h; and then the temperature is cooled to room temperature to obtain modified white carbon black.

[0090] Example 2

[0091] Step one: take 1 part of plasma modified aramid pulp, 2 parts of acrylic pulp, 15 parts of coupling modified composite mineral fiber, 1 part of SiO2coated four acicular zinc oxide whisker, 1.5 parts of carbon fiber-aluminum silicon whisker, 14 parts of modified acicular wollastonite, 10 parts of organic modified barium sulfate, 5 parts of aluminum oxide, 8 parts of light calcium carbonate, 5 parts of flake graphite, 1.2 parts of carbon black, 5 parts of boron-silicon synergistically modified phenolic resin, 3 parts of modified carboxyl nitrile rubber, 0.3 parts of vulcanizing agent, 0.3 parts of accelerator, 0.1 parts of stearic acid, all of which are from the raw materials prepared in example 1 or existing raw materials that can be directly purchased.

[0092] Step two: put the above raw materials into the internal mixer in the order of adhesive, reinforcing material, filler and compounding agent, set the mixing temperature to 60℃, the top bolt pressure to 0.6MPa, the rotor speed to 45r / min, and mix for 20min to obtain the mixed material.

[0093] Step three: crush the mixed material, then sieve to obtain granular material with a particle size of 1-2mm.

[0094] Step four: hot-press the granular material in a hot-pressing mold using a 100T four-column hydraulic press, control the pressing temperature at 175±5℃, the pressing pressure at 20MPa, and the pressure holding time at 70s / mm, and before pressure holding, press for 10s, exhaust for 2s, and repeat the process 4 times, then after pressure holding, obtain the semi-finished product of friction material.

[0095] Step five: place the semi-finished product of friction material in a heat treatment furnace, heat from room temperature to 120±5℃ for 1h, keep the temperature for 1.5h, then heat from 120±5℃ to 180±5℃ for 1h, keep the temperature for 1h, then heat from 180±5℃ to 220±5℃ for 1h, keep the temperature for 8h, finally cool down to below 50℃, and take out.

[0096] Step six: grind the heat-treated friction material by double-end-face abrasive belt grinding to remove the surface oxidation scale, burrs and flash, and obtain the electromagnetic brake friction material.

[0097] Example 3

[0098] The difference between this embodiment and embodiment 2 is that the raw materials include 2 parts of plasma modified aramid pulp, 2.5 parts of acrylic pulp, 10 parts of coupling modified composite mineral fiber, 1.2 parts of SiO2coated four acicular zinc oxide whisker, 3 parts of carbon fiber-aluminum silicon whisker, 12 parts of modified acicular wollastonite, 15 parts of organic modified precipitated barium sulfate, 8 parts of alumina, 12 parts of light calcium carbonate, 6 parts of flake graphite, 1.8 parts of carbon black, 6 parts of modified white carbon black, 4 parts of boron-silicon synergistically modified phenolic resin, 13 parts of modified carboxyl nitrile rubber, 0.4 parts of vulcanizing agent, 0.4 parts of accelerator, and 0.2 parts of stearic acid.

[0099] Example 4

[0100] The difference between this embodiment and embodiment 2 is that the raw materials include 2.5 parts of plasma modified aramid pulp, 1 part of acrylic pulp, 13 parts of coupling modified composite mineral fiber, 1.5 parts of SiO2coated four acicular zinc oxide whisker, 2 parts of carbon fiber-aluminum silicon whisker, 10 parts of modified acicular wollastonite, 8 parts of organic modified precipitated barium sulfate, 10 parts of alumina, 10 parts of light calcium carbonate, 8 parts of flake graphite, 2.5 parts of carbon black, 8 parts of modified white carbon black, 5 parts of boron-silicon synergistically modified phenolic resin, 12 parts of modified carboxyl nitrile rubber, 0.5 parts of vulcanizing agent, 0.5 parts of accelerator, and 0.3 parts of stearic acid.

[0101] Comparative Example 1

[0102] The difference between this comparative example and embodiment 2 is that the raw materials include 0.5 parts of plasma modified aramid pulp, 1 part of acrylic pulp, 3 parts of coupling modified composite mineral fiber, 0.5 parts of SiO2coated four acicular zinc oxide whisker, 0.5 parts of carbon fiber-aluminum silicon whisker, 5 parts of modified acicular wollastonite, 3.5 parts of organic modified precipitated barium sulfate, 10 parts of alumina, 10 parts of light calcium carbonate, 8 parts of flake graphite, 2.5 parts of carbon black, 8 parts of modified white carbon black, 1 part of boron-silicon synergistically modified phenolic resin, 5 parts of modified carboxyl nitrile rubber, 0.5 parts of vulcanizing agent, 0.5 parts of accelerator, and 0.3 parts of stearic acid.

[0103] Comparative Example 2

[0104] The difference between this comparative example and embodiment 2 is that the raw materials include 5 parts of plasma modified aramid pulp, 1 part of acrylic pulp, 18 parts of coupling modified composite mineral fiber, 3 parts of SiO2coated four acicular zinc oxide whisker, 5 parts of carbon fiber-aluminum silicon whisker, 18 parts of modified acicular wollastonite, 18 parts of organic modified precipitated barium sulfate, 10 parts of alumina, 10 parts of light calcium carbonate, 8 parts of flake graphite, 2.5 parts of carbon black, 8 parts of modified white carbon black, 8 parts of boron-silicon synergistically modified phenolic resin, 18 parts of modified carboxyl nitrile rubber, 0.5 parts of vulcanizing agent, 0.5 parts of accelerator, and 0.3 parts of stearic acid.

[0105] Comparative Example 3

[0106] The difference between this comparative example and Example 2 is that the untreated aramid pulp is used to replace the plasma modified aramid pulp, the untreated complex mineral fiber is used to replace the coupling modified complex mineral fiber, the untreated zinc oxide whisker is used to replace the SiO2-coated four-needle zinc oxide whisker, and the aluminum-silicon whisker is used to replace the carbon fiber-aluminum-silicon whisker.

[0107] Comparative Example 4

[0108] The difference between this comparative example and Example 2 is that the untreated acicular wollastonite is used to replace the modified acicular wollastonite, and the untreated precipitated barium sulfate is used to replace the organically modified precipitated barium sulfate.

[0109] Comparative Example 5

[0110] The difference between this comparative example and Example 2 is that the untreated phenolic resin is used to replace the boron-silicon synergistically modified phenolic resin, and the untreated nitrile rubber is used to replace the modified carboxyl nitrile rubber.

[0111] Test Example

[0112] Samples: Examples 2-4 and Comparative Examples 1-5

[0113] (1) The friction performance and wear of the above-mentioned friction material samples were determined according to the method of GB-T 5764-2023 “Automobile Clutch Facing”, and the results are shown in Table 1 below:

[0114] Table 1 Test results of friction performance of different friction material samples

[0115]

[0116] (2) The above-mentioned friction material samples were assembled into electromagnetic brakes, with the rated torque of the brake set to 1.5 N·m, and the static torque test of the assembled electromagnetic brake was carried out according to the method of GB / T 34114-2017 “General Technical Conditions for Electromagnetic Brakes for Electric Motors”. Each sample was tested twice, and the results are shown in Table 2 below:

[0117] Table 2 Static torque test results of different friction material samples

[0118]

[0119] Through the above experiment, according to the results of the sample material performance and use performance measured in Table 1 and Table 2, it can be found that the electromagnetic brake friction material proposed in the application can be prepared by using the granular material prepared by improving the raw materials and the synergistic effect between the components and adopting the dense mixing and crushing process, the wear rate of the friction material is obviously smaller under the condition of using a smaller amount of adhesive, the friction performance is good after high temperature or repeated use, and the preparation process of the electromagnetic brake friction material is simple and has strong popularization.

[0120] The preferred embodiments of the application are described above, but the application is not limited to the above, and various modifications and changes can be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. An electromagnetic brake friction material made from a granular material, characterized in that, The reinforcing material comprises 1-3 parts of plasma modified aramid pulp, 1-3 parts of acrylic pulp, 10-15 parts of coupling modified composite mineral fiber, 1-2 parts of SiO2 coated four acicular zinc oxide whisker, and 1-3 parts of carbon fiber-aluminum silicon whisker. The filler comprises 10-15 parts of modified acicular wollastonite, 8-15 parts of organic modified precipitated barium sulfate, 5-10 parts of aluminum oxide, 8-12 parts of light calcium carbonate, 4-8 parts of flake graphite, 1-3 parts of carbon black, and 5-8 parts of modified white carbon black; the adhesive comprises 3-5 parts of boron-silicon synergistically modified phenolic resin and 10-15 parts of modified carboxyl nitrile rubber. The modified acicular wollastonite is prepared by modifying acicular wollastonite with sodium alkyl sulfonate and then with γ-aminopropyl triethoxysilane to form modified acicular wollastonite with both lipophilic and hydrophilic groups on the surface. The organic modified precipitated barium sulfate is an inorganic core-organic shell structure composite in which a phenolic resin prepolymer is coated on the surface of the precipitated barium sulfate. The modified white carbon black is prepared by drying white carbon black in a drying box at 100℃ for 1.5h, then stirring the white carbon black in a high-speed mixer at 95℃ for 55min at a speed of 800rpm, adding Si69 in an amount of 4% of the mass of the white carbon black, and then stirring for 40min, heating to 130℃, and maintaining the temperature for 2h, and cooling to room temperature. The boron-silicon synergistically modified phenolic resin is prepared by modifying phenolic resin with boron and then with silicon. The modified carboxyl nitrile rubber is prepared by grafting carboxyl groups on nitrile rubber and then chemically modifying the nitrile rubber with maleic anhydride. The plasma modified aramid pulp is aramid pulp with active groups on the surface, the coupling modified composite mineral fiber is composite mineral fiber with an organic coating layer on the surface formed by a titanate coupling agent, the SiO2 coated four acicular zinc oxide whisker is four acicular zinc oxide whisker coated with a SiO2 film, and the carbon fiber-aluminum silicon whisker is a composite of chopped carbon fiber and aluminum silicon whisker with an interwoven structure.

2. The electromagnetic brake friction material made from granules according to claim 1, characterized in that, The compounding agent comprises 0.1-0.5 parts of vulcanizing agent, 0.3-1 part of accelerator, and 0.1-0.5 parts of stearic acid.

3. The electromagnetic brake friction material made from granules of claim 1, wherein, The method comprises the following steps:

4. A process for the production of electromagnetic brake friction material made from granules according to any one of claims 1 to 3, characterized in that, S1: mixing: sequentially adding the raw materials of the adhesive, the reinforcing material, the filler, and the compounding agent into a mixer, mixing at 50-80℃ for 10-30min, and obtaining mixed material; S2: crushing and sieving: crushing and sieving the mixed material to obtain granular primary material with a desired particle size; S3: hot pressing: placing the granular primary material in a hot press at 175±5℃ under a pressure of 10-30MPa for 60-80s / mm; S4: heat treatment: placing the hot-pressed material in a heat treatment furnace for heat treatment, and then taking out the material after cooling; and ​ S5 grinding: grinding the granular material after heat treatment to obtain electromagnetic brake friction material made of granular material.

5. The process for the preparation of electromagnetic brake friction material made of granules according to claim 4, characterized in that, In step S2, the particle size is controlled to be 1-2 mm after sieving.

6. The process for making electromagnetic brake friction material from granules according to claim 4, wherein, In step S3, 3-5 times of exhaust are performed before hot pressing, and each exhaust process includes pressing for 10 s and exhausting for 2 s.

7. The process for making electromagnetic brake friction material from granules according to claim 4, wherein, In step S4, the temperature conditions of the heat treatment process include the following stages: from room temperature to 120±5℃ for 0.8-1.2h, and holding for 1-2h; then from 120±5℃ to 180±5℃ for 0.8-1.2h, and holding for 1h; then from 180±5℃ to 220±5℃ for 0.8-1.2h, and holding for 6-10h; finally, cooling to 50℃ or below in the furnace, and taking out.

Images