High-temperature-resistant heat-conducting rubber magnetic material and preparation method thereof

Abstract

The invention relates to the technical field of rubber magnetic materials, and discloses a high-temperature-resistant heat-conducting rubber magnetic material and a preparation method thereof. The high-temperature-resistant heat-conducting rubber magnetic material comprises the following raw material components: magnetic powder, nitrile rubber, a vulcanizing agent, a heat-conducting filler, a vulcanization activator, a tackifier, a lubricant, an anti-aging agent and a coupling agent, wherein the vulcanizing agent is a phenolic resin vulcanizing agent. According to the preparation method disclosed by the invention, through the steps of mixing, tabletting and hot vulcanization and strictly controlling the preparation conditions of each step in the preparation process, the prepared high-temperature heat-conducting rubber magnetic material disclosed by the invention is smooth and flat in surface and has excellent magnetic property, mechanical property, heat-conducting property and high-temperature aging resistance, the residual magnetism (Br) reaches up to 2490-2550Gs, the tensile strength reaches up to 12.5-13.1 MPa, and the service life of the high-temperature heat-conducting rubber magnetic material is prolonged. The heat conductivity coefficient is 3.52-3.81 W / (m.K), and the use requirements of micromotors and the like under the working conditions of high rotating speed and high power can be met.

Description

Technical Field

[0001] This application relates to the field of rubber magnetic materials technology, and in particular to a high-temperature resistant and thermally conductive rubber magnetic material and its preparation method. Background Technology

[0002] Rubber magnetic materials are functional materials made from magnetic powder and rubber substrate through processes such as mixing, molding, and vulcanization. They combine the magnetic properties of rubber with its flexibility and are widely used in micro-motors, electronic devices, and medical equipment. Micro-motors generate a large amount of heat during high-speed rotation. If this heat cannot be dissipated in time, the internal temperature of the motor will rise, affecting the performance stability of the rubber magnetic material and even causing material aging and magnetic property decay, thus impacting the motor's lifespan and operational reliability.

[0003] In existing technologies, rubber magnetic materials used in micromotors typically use nitrile rubber as the base material, combined with magnetic powder and various additives. To achieve vulcanization, DCP (dicumyl peroxide) or BIBP (di-tert-butyl peroxide) are often chosen as vulcanizing agents. However, these two vulcanizing agents have short vulcanization half-lives, which can easily lead to excessive local cross-linking during vulcanization, resulting in an orange peel effect on the surface of the molded product, affecting its appearance and performance. Furthermore, the high-temperature resistance and thermal conductivity of existing rubber magnetic materials still need improvement, making it difficult to meet the requirements of high-speed, high-power operation of micromotors. Therefore, developing a rubber magnetic material with excellent high-temperature resistance and thermal conductivity, good molding quality, and stable magnetic properties is of significant practical importance. Summary of the Invention

[0004] To at least overcome one of the problems existing in the prior art, one objective of this invention is to provide a high-temperature resistant and thermally conductive rubber magnetic material. This material uses magnetic powder and nitrile rubber as a base combination, while introducing thermally conductive fillers to specifically address the poor thermal conductivity of traditional rubber magnetic materials. A phenolic resin vulcanizing agent is added to ensure the material's high-temperature resistance, resulting in a high-temperature resistant, thermally conductive, magnetic, and mechanically sound rubber magnetic material that meets the application requirements of high-speed, high-power applications such as micro-motors. A second objective of this invention is to provide a method for preparing the aforementioned high-temperature resistant and thermally conductive rubber magnetic material.

[0005] Therefore, the present invention adopts the following technical solution: The first aspect of the present invention provides a high-temperature resistant and thermally conductive rubber magnetic material, the raw material components of which include: magnetic powder, nitrile rubber, vulcanizing agent, thermally conductive filler, vulcanization activator, tackifier, lubricant, antioxidant and coupling agent, wherein the vulcanizing agent is a phenolic resin vulcanizing agent.

[0006] In the raw material components of the high-temperature resistant and thermally conductive rubber magnetic material of this application, magnetic powder provides the basic magnetic properties; nitrile rubber, as the matrix, provides good flexibility and oil resistance; phenolic resin vulcanizing agents ensure the high-temperature resistance of the rubber magnetic material and help avoid the orange peel phenomenon on the product surface caused by excessive local cross-linking; the addition of thermally conductive fillers establishes a heat conduction pathway and improves the overall thermal conductivity of the material; the introduction of vulcanization activators, tackifiers, lubricants, antioxidants, and coupling agents forms a complementary function, ensuring that the high-temperature resistant and thermally conductive rubber magnetic material of this application has good processability, interfacial bonding strength, and long-term durability. Through the specific combination of the above components, a balance is achieved in the high-temperature resistance, thermal conductivity, good processability, and magnetic properties of the rubber magnetic material, solving the problem that the improvement of one property may lead to the deterioration of other properties in the prior art.

[0007] Preferably, the magnetic powder is at least one of neodymium iron boron magnetic powder and ferrite magnetic powder, and its particle size is 1~5μm. More preferably, the magnetic powder is at least one of neodymium iron boron magnetic powder and ferrite magnetic powder, and its particle size is 3~5μm.

[0008] Neodymium iron boron magnetic powder has a high magnetic energy product, while ferrite magnetic powder has a lower cost and better corrosion resistance. Magnetic powder with a particle size of 1~5μm can be evenly dispersed in rubber magnetic materials, making it less prone to agglomeration, thereby obtaining stable magnetic properties and reducing wear on equipment during processing.

[0009] Preferably, the acrylonitrile content of the nitrile rubber is 28-40% by mass, and the Mooney viscosity ML(1+4) at 100°C is 40-70. More preferably, the acrylonitrile content of the nitrile rubber is 32-40% by mass, and the Mooney viscosity ML(1+4) at 100°C is 50-70. Even more preferably, the acrylonitrile content of the nitrile rubber is 35-40% by mass, and the Mooney viscosity ML(1+4) at 100°C is 55-70.

[0010] In the above technical solution, nitrile rubber helps the rubber magnetic material to have sufficient swelling resistance and structural stability in a high-temperature oily environment, while ensuring that the rubber compound still has suitable processing fluidity and mixing effect under a high proportion of magnetic powder filling, avoiding the situation that the material is easily deformed due to excessive fluidity during vulcanization.

[0011] Preferably, the phenolic resin vulcanizing agent comprises a mixture of thermoplastic phenolic resin and a curing agent in a weight ratio of (4~10):(1~3). More preferably, the phenolic resin vulcanizing agent comprises a mixture of thermoplastic phenolic resin and a curing agent in a weight ratio of (5.5~10):(1~3). Even more preferably, the phenolic resin vulcanizing agent comprises a mixture of thermoplastic phenolic resin and a curing agent in a weight ratio of (5.5~10):(1.8~3).

[0012] Preferably, the thermoplastic phenolic resin is selected from phenol-formaldehyde type thermoplastic phenolic resin or o-cresol-formaldehyde type thermoplastic phenolic resin. More preferably, the thermoplastic phenolic resin is selected from phenol-formaldehyde type thermoplastic phenolic resin.

[0013] Preferably, the curing agent is selected from at least one of hexamethylenetetramine, epoxy resin, amino resin, and aliphatic amine compounds. More preferably, the curing agent is selected from at least one of hexamethylenetetramine, epoxy resin, and amino resin. Even more preferably, the curing agent is selected from at least one of hexamethylenetetramine and epoxy resin.

[0014] Thermoplastic phenolic resins do not contain free hydroxymethyl groups in their molecular chains. The curing rate can be precisely controlled by adjusting the amount of curing agent, which promotes more uniform and complete cross-linking during curing and avoids the decline in mechanical properties caused by insufficient cross-linking. However, excessive curing agent can easily release volatile substances, leading to air bubbles within the material and affecting magnetic properties. This formulation can control curing agent costs while ensuring curing quality, making it suitable for large-scale industrial production. All curing agents used can undergo condensation reactions with the phenolic hydroxyl groups in the thermoplastic phenolic resin without producing side reaction impurities, thus ensuring the stability of the magnetic properties of the material after curing. Furthermore, they do not have adverse interactions with nitrile rubber or magnetic powder, avoiding performance interference.

[0015] Preferably, the thermally conductive filler is selected from at least one of boron nitride, alumina, and silicon carbide, and the particle size of the thermally conductive filler is 0.5~3μm. More preferably, the thermally conductive filler is selected from at least one of boron nitride, alumina, and silicon carbide, and the particle size of the thermally conductive filler is 1~3μm. Even more preferably, the thermally conductive filler is a mixture of boron nitride and alumina in a weight ratio of (2.5~4):(1~3), and the particle size of the thermally conductive filler is 1~3μm.

[0016] Boron nitride, alumina, and silicon carbide, all thermally conductive fillers, possess excellent thermal conductivity, which helps to construct good thermal conduction channels. At the microscopic level, boron nitride has a plate-like structure, while alumina has a spherical structure. A mixture of boron nitride and alumina in a weight ratio of (2.5~4):(1~3) facilitates the formation of a plate-spherical composite thermally conductive network, thereby reducing thermal resistance and further improving thermal conductivity. Controlling the particle size of the thermally conductive filler to 0.5~3μm, smaller than that of the magnetic powder, allows the filler to uniformly fill the gaps between the magnetic powder and the rubber, preventing the magnetic powder from being obstructed due to excessively large filler particle size.

[0017] Preferably, the sulfidation activator is selected from at least one of zinc oxide, magnesium oxide, and zinc carbonate. More preferably, the sulfidation activator is selected from at least one of zinc oxide and magnesium oxide. Even more preferably, the sulfidation activator is a mixture of zinc oxide and magnesium oxide in a weight ratio of (2~3):(1.2~2.5).

[0018] Preferably, the tackifier is selected from at least one of terpene resin, rosin resin, and modified lignin resin. More preferably, the tackifier is selected from at least one of terpene resin and rosin resin.

[0019] Preferably, the lubricant is selected from at least one of zinc stearate, calcium stearate, stearic acid, and polyethylene wax. More preferably, the lubricant is selected from at least one of zinc stearate, calcium stearate, and polyethylene wax.

[0020] Preferably, the antioxidant is selected from at least one of antioxidant 1010, antioxidant 4020, antioxidant MB, and antioxidant TNP. More preferably, the antioxidant is selected from at least one of antioxidant 1010, antioxidant 4020, and antioxidant TNP. Even more preferably, the antioxidant is selected from at least one of antioxidant 1010 and antioxidant TNP.

[0021] Preferably, the coupling agent is selected from at least one of silane coupling agents and titanate coupling agents. More preferably, the coupling agent is a mixture of silane coupling agent and titanate coupling agent in a weight ratio of (1~2):(1~1.8).

[0022] Preferably, the silane coupling agent is selected from at least one of KH550, KH560, KH570, and A171. More preferably, the silane coupling agent is selected from at least one of KH550, KH570, and A171.

[0023] Preferably, the titanate coupling agent is selected from at least one of NDZ-101, NDZ-201, and NDZ-301. More preferably, the titanate coupling agent is selected from at least one of NDZ-101 and NDZ-301.

[0024] The phenolic resin vulcanization system is effectively activated by a vulcanization activator, ensuring that the crosslinking reaction proceeds fully and efficiently. Tackifiers such as terpene resins enhance the adhesion between the magnetic powder and the rubber, reducing interfacial voids and making it easier to mold. Lubricants effectively reduce internal and external friction of the rubber compound, preventing sticking to rollers during processing, ensuring uniform mixing and smooth demolding, and improving production efficiency and product surface quality. Antioxidants slow down the aging rate of the material at high temperatures and during use, improving product durability and service life. Coupling agents build strong "molecular bridges" between the magnetic powder, thermally conductive filler, and rubber molecules, greatly improving their interfacial bonding force, thereby enhancing the material's mechanical strength, thermal conductivity, and thermal stability.

[0025] Preferably, in the raw materials of the high-temperature resistant and thermally conductive rubber magnetic material, the weight ratio of magnetic powder, nitrile rubber, vulcanizing agent, and thermally conductive filler is (85-92): (4-8): (0.05-0.1): (0.1-0.7).

[0026] Preferably, in the raw materials of the high-temperature resistant and thermally conductive rubber magnetic material, the weight ratio of magnetic powder, nitrile rubber, vulcanizing agent, thermally conductive filler, and vulcanization activator is (85-92): (4-8): (0.05-0.1): (0.1-0.7): (0.2-0.5).

[0027] Preferably, in the raw materials of the high-temperature resistant and thermally conductive rubber magnetic material, the weight ratio of magnetic powder, nitrile rubber, vulcanizing agent, thermally conductive filler, vulcanization activator, and tackifier is (85-92): (4-8): (0.05-0.1): (0.1-0.7): (0.2-0.5): (0.1-0.5).

[0028] Preferably, in the raw materials of the high-temperature resistant and thermally conductive rubber magnetic material, the weight ratio of magnetic powder, nitrile rubber, vulcanizing agent, thermally conductive filler, vulcanization activator, tackifier, and lubricant is (85-92): (4-8): (0.05-0.1): (0.1-0.7): (0.2-0.5): (0.1-0.5): (0.06-0.1).

[0029] Preferably, in the raw materials of the high-temperature resistant and thermally conductive rubber magnetic material, the weight ratio of magnetic powder, nitrile rubber, vulcanizing agent, thermally conductive filler, vulcanization activator, tackifier, lubricant, and antioxidant is (85-92): (4-8): (0.05-0.1): (0.1-0.7): (0.2-0.5): (0.1-0.5): (0.06-0.1): (0.2-0.9).

[0030] Preferably, in the raw materials of the high-temperature resistant and thermally conductive rubber magnetic material, the weight ratio of magnetic powder, nitrile rubber, vulcanizing agent, thermally conductive filler, vulcanization activator, tackifier, lubricant, antioxidant, and coupling agent is (85-92): (4-8): (0.05-0.1): (0.1-0.7): (0.2-0.5): (0.1-0.5): (0.06-0.1): (0.2-0.9): (0.08-0.2).

[0031] In the above technical solution, 85-92 parts by weight of magnetic powder effectively ensures that the high-temperature resistant and thermally conductive rubber magnetic material of this application possesses excellent magnetic properties, avoiding insufficient magnetic properties caused by excessive dosage; nitrile rubber provides flexibility to the rubber magnetic material, while avoiding a decrease in thermal conductivity caused by excessive proportion; the vulcanizing agent helps to accurately control the vulcanization crosslinking density, avoiding increased material brittleness due to excessive amount or performance degradation due to insufficient amount; the thermally conductive filler provides a better thermal conduction channel for the rubber magnetic material without affecting the dispersion of magnetic powder; sufficient vulcanization activator helps to effectively activate the vulcanizing agent and avoid vulcanization delay; in addition, the synergistic effect of antioxidants, coupling agents and other additives enables the rubber magnetic material of this application to simultaneously achieve high magnetic properties, high thermal conductivity, high heat resistance and excellent processability.

[0032] In the above technical solutions, since the magnetic powder and thermally conductive filler have small particle sizes and large specific surface areas, they will adsorb or coat the vulcanization activator, thereby affecting the vulcanization efficiency. Therefore, this application adjusts the weight fraction of the vulcanization activator to be higher than the weight fraction of the vulcanizing agent, so that even if some of the vulcanization activator is adsorbed or coated, there is enough vulcanization activator to help the vulcanization reaction of phenolic resin to proceed fully, thereby forming a complete and stable three-dimensional cross-linked network structure.

[0033] A second aspect of the present invention provides a method for preparing a high-temperature resistant and thermally conductive rubber magnetic material according to the first aspect of the present invention, comprising the following steps: S1. Mixing: Mix the raw materials and knead them to obtain a compound. S2, tableting: The compounded rubber is tableted to obtain sheet rubber material; S3. Hot vulcanization: The sheet rubber compound is hot vulcanized and cooled to obtain the high-temperature resistant and thermally conductive rubber magnetic material.

[0034] Preferably, in step S1, the mixing temperature is 100~110℃ and the mixing time is 7~10min. More preferably, in step S1, the mixing temperature is 105~110℃ and the mixing time is 8~10min.

[0035] Preferably, in step S2, after the compounded rubber is unloaded, it needs to be naturally cooled to below 80°C before tableting. The temperature of the tableting rollers is 60~70°C, the roller gap is 4.8~7.0mm, the roller speed is 5~8rpm, and the number of tableting cycles is 2~3. More preferably, in step S2, after the compounded rubber is unloaded, it needs to be naturally cooled to below 80°C before tableting. The temperature of the tableting rollers is 65~70°C, the roller gap is 4.8~7.0mm, the roller speed is 6~8rpm, and the number of tableting cycles is 3.

[0036] In step S3, the temperature of the hot vulcanization is 140~160℃, and the time of the hot vulcanization is 10~20min. In a further step S3, the temperature of the hot vulcanization is 150~160℃, and the time of the hot vulcanization is 10~20min.

[0037] In this preparation method, the mixing in step S1 ensures that the components are evenly dispersed to obtain a compound; in step S2, the compound is pressed into a sheet to provide a uniform thickness basis for subsequent hot vulcanization; in step S3, the internal cross-linked network structure is effectively fixed by hot vulcanization and cooling, avoiding dimensional springback caused by high temperature.

[0038] In step S3, during the hot vulcanization process, the thermoplastic phenolic resin and the curing agent first undergo a cross-linking and curing reaction to form a phenolic resin network. Then, through the action of the vulcanization activator, it reacts with the allyl hydrogen atoms and cyano groups on the nitrile rubber molecular chain to form a strong covalent connection mainly composed of CC and COC bonds, forming a cross-linked network structure of resin-rubber co-crosslinking, which improves the high temperature resistance and mechanical strength of the rubber magnetic material.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects: 1) The raw material components of the high-temperature resistant and thermally conductive rubber magnetic material of this application include magnetic powder, nitrile rubber, vulcanizing agent, thermally conductive filler, vulcanization activator, tackifier, lubricant, antioxidant, and coupling agent. Among them, the vulcanizing agent is a phenolic resin vulcanizing agent. Through the reasonable proportion of each raw material component, especially the specific composition of the phenolic resin vulcanizing agent, thermally conductive filler, and vulcanization activator, the obtained high-temperature resistant and thermally conductive rubber magnetic material has good magnetic properties, mechanical properties, thermal conductivity, and high-temperature aging resistance. The remanence (Br) is as high as 2490~2550Gs, the tensile strength is 12.5~13.1MPa, and the thermal conductivity is 3.52~3.81W / (m·K). After heat aging at 100℃ for 72h, the remanence (Br)(Gs) retention rate is in the range of 97.2%~97.8%, which can meet the application requirements of high speed and high power conditions such as micro motors.

[0040] 2) In the preparation method of the high-temperature heat-conducting rubber magnetic material of this application, the high-temperature heat-conducting rubber magnetic material of this application is obtained by mixing, pressing and hot vulcanizing, and the preparation conditions of each step are strictly controlled in the preparation process, which effectively improves the heat resistance and overall stability of the rubber magnetic material. Detailed Implementation

[0041] The present invention will be further described in detail below through specific embodiments, comparative examples and tables, but is not limited to all the discussions and data.

[0042] The raw material components of the high-temperature resistant and thermally conductive rubber magnetic material include: ferrite magnetic powder (YXF-1 type barium ferrite magnetic powder, 2-4 μm particle size, purchased from Xiamen Yuxiang Magnetic Materials Technology Co., Ltd.); nitrile rubber (DN3350, 33% acrylonitrile content, Mooney viscosity ML (1+4) 100℃ 50, purchased from Ningbo Shunze Rubber Co., Ltd.); thermoplastic phenolic resin (PF-2123 type phenol-formaldehyde thermoplastic phenolic resin, purchased from Shanghai Shengquan High-Tech Electronic Materials Co., Ltd.); boron nitride (1.5 μm particle size, purchased from Shanghai Junyi Chemical Co., Ltd.); and alumina (2 μm particle size, purchased from Zibo Pengda Environmental Protection Technology Co., Ltd.); silane coupling agent KH550 (Hubei Xinlantian New Materials Co., Ltd.); and titanate coupling agent NDZ-101 (Anhui Taichang New Materials Technology Co., Ltd.).

[0043] It is particularly important to emphasize that, unless otherwise specified, the raw materials, reagents or devices used in this invention can be obtained from conventional commercial sources.

[0044] Example of vulcanizing agent preparation: Preparation Example 1: The preparation method of a vulcanizing agent has the following steps: The vulcanizing agent is prepared by uniformly mixing 6g of PF-2123 type phenol-formaldehyde thermoplastic phenolic resin and 2g of hexamethylenetetramine.

[0045] Preparation Example 2: The preparation method of a vulcanizing agent has the following steps: The vulcanizing agent is prepared by uniformly mixing 8.5g of PF-2123 type phenol-formaldehyde thermoplastic phenolic resin and 1.5g of hexamethylenetetramine.

[0046] Preparation Example 3: The preparation method of a vulcanizing agent has the following steps: The vulcanizing agent is prepared by uniformly mixing 5g of PF-2123 type phenol-formaldehyde thermoplastic phenolic resin and 3g of hexamethylenetetramine.

[0047] Example of preparation of thermally conductive fillers: Preparation Example 4: The preparation method of a thermally conductive filler includes the following steps: The thermally conductive filler is prepared by uniformly mixing 2.5g of boron nitride and 1g of aluminum oxide.

[0048] Preparation Example 5: The preparation method of a thermally conductive filler includes the following steps: The thermally conductive filler was prepared by uniformly mixing 3g of boron nitride and 2.5g of aluminum oxide.

[0049] Preparation Example 6: The preparation method of a thermally conductive filler includes the following steps: The thermally conductive filler was prepared by mixing 4g of boron nitride and 1.5g of aluminum oxide evenly.

[0050] Example of preparation of vulcanization activator: Preparation Example 7: The preparation method of a vulcanization activator has the following steps: The sulfurization activator is prepared by mixing 2g of zinc oxide and 2.5g of magnesium oxide evenly.

[0051] Preparation Example 8: The preparation method of a vulcanization activator has the following steps: The sulfurization activator is prepared by mixing 2.5g of zinc oxide and 1.5g of magnesium oxide evenly.

[0052] Preparation Example 9: The preparation method of a vulcanization activator has the following steps: The sulfurization activator was prepared by mixing 3g of zinc oxide and 1.5g of magnesium oxide evenly.

[0053] Example of coupling agent preparation: Preparation Example 10: The preparation method of a coupling agent includes the following steps: The coupling agent was prepared by mixing 1.5g KH550 and 1.8g NDZ-101 evenly.

[0054] Comparative example of vulcanizing agent preparation: Preparation of Comparative Example 1: The preparation method of a vulcanizing agent has the following steps: The vulcanizing agent is prepared by uniformly mixing 3.5g of PF-2123 type phenol-formaldehyde thermoplastic phenolic resin and 3g of hexamethylenetetramine.

[0055] Comparative example of the preparation of thermally conductive fillers: Preparation of Comparative Example 2: The preparation method of a thermally conductive filler includes the following steps: The thermally conductive filler was prepared by mixing 3g of boron nitride and 4g of aluminum oxide evenly.

[0056] Examples of high-temperature resistant and thermally conductive rubber magnetic materials: A high-temperature resistant and thermally conductive rubber magnetic material is prepared by the following steps: S1. Mixing: Mix 85-92g magnetic powder, 4-8g nitrile rubber, 0.05-0.1g vulcanizing agent, 0.1-0.7g thermally conductive filler, 0.2-0.5g vulcanization activator, 0.1-0.5g tackifier, 0.06-0.1g lubricant, 0.2-0.9g antioxidant and 0.08-0.2g coupling agent, and mix at 100-110℃ for 7-10 minutes to obtain the compound. S2. Tableting: After the compounded rubber is discharged and naturally cooled to below 80℃, it is transferred to a tablet press. The roller temperature of the tablet press is adjusted to 60~70℃, the roller gap is 4.8~7.0mm, and the roller speed is 5~8rpm. The tableting is performed 2~3 times to obtain sheet rubber. S3. Hot vulcanization: Place the sheet rubber compound into a tunnel vulcanizing furnace and hot vulcanize it at a temperature of 140~160℃ for 10~20 minutes. Remove it and cool it to room temperature to obtain a high-temperature resistant and thermally conductive rubber magnetic material.

[0057] Regarding step S1, in some specific embodiments, the magnetic powder can be at least one of neodymium iron boron magnetic powder and ferrite magnetic powder, and its particle size can be 1μm, 2μm, 3μm, or 5μm. The acrylonitrile content of the nitrile rubber can be 28%, 30%, 33%, 38%, or 40%, and the Mooney viscosity ML (1+4) at 100℃ can be 40, 50, 60, or 70. The vulcanizing agent is a phenolic resin vulcanizing agent, which can be a mixture of thermoplastic phenolic resin and curing agent in a weight ratio of 4:3, 5:2, 6:2, 8:2.1, or 10:1. The thermoplastic phenolic resin can be selected from phenol-formaldehyde type thermoplastic phenolic resin or o-cresol-formaldehyde type thermoplastic phenolic resin. The curing agent can be selected from at least one of hexamethylenetetramine, epoxy resin, amino resin, and aliphatic amine compounds. The thermally conductive filler may be selected from at least one of boron nitride, alumina, and silicon carbide, and the particle size of the thermally conductive filler may be 0.5 μm, 1 μm, 2 μm, or 3 μm. The thermally conductive filler is a mixture of boron nitride and alumina in a weight ratio of 2.5:3, 3:2, 3:1, or 4:1, and the particle size of the thermally conductive filler may be 0.5 μm, 1 μm, 2 μm, or 3 μm. The vulcanization activator may be selected from at least one of zinc oxide, magnesium oxide, and zinc carbonate, and the vulcanization activator may also be a mixture of zinc oxide and magnesium oxide in a weight ratio of 2:2.5, 2.3:2, 3:2, or 3:1.2. The tackifier may be selected from at least one of terpene resin, rosin resin, and modified lignin resin. The lubricant may be selected from at least one of zinc stearate, calcium stearate, stearic acid, and polyethylene wax. The antioxidant may be selected from at least one of antioxidant 1010, antioxidant 4020, antioxidant MB, and antioxidant TNP. The coupling agent may be selected from at least one of silane coupling agents and titanate coupling agents, and the coupling agent may be a mixture of silane coupling agent and titanate coupling agent in a weight ratio of 1:1.8, 1.5:1.6, or 2:1. The silane coupling agent may be selected from at least one of KH550, KH560, KH570, and A171. The titanate coupling agent may be selected from at least one of NDZ-101, NDZ-201, and NDZ-301.

[0058] Regarding step S1, in some specific embodiments, the amount of magnetic powder can be 85g, 88g, 90g, or 92g; the amount of nitrile rubber can be 4g, 5g, 6g, or 8g; the amount of vulcanizing agent can be 0.05g, 0.08g, or 0.1g; the amount of thermally conductive filler can be 0.1g, 0.3g, 0.5g, or 0.7g; the amount of vulcanization activator can be 0.2g, 0.3g, 0.4g, or 0.5g; and the amount of tackifier can be... The dosage can be 0.1g, 0.3g, 0.4g or 0.5g; the amount of lubricant can be 0.06g, 0.08g or 0.1g; the amount of antioxidant can be 0.2g, 0.4g, 0.7g or 0.9g; the amount of coupling agent can be 0.08g, 0.1g, 0.15g or 0.2g; the mixing temperature can be 100℃, 102℃, 105℃ or 110℃; and the mixing time can be 7min, 8min or 10min.

[0059] Regarding step S2, in some specific implementations, the roller temperature of the tablet press can be 60℃, 65℃ or 70℃, the roller speed can be 5rpm, 6rpm or 8rpm, the roller gap for the first tablet press is 6.0~7.0mm, the roller gap for the second tablet press is 5.0~5.2mm, and the roller gap for the third tablet press is 4.8~5.0mm, and tableting is performed three times.

[0060] Regarding step S3, in some specific implementations, the temperature of hot vulcanization can be 140°C, 150°C, or 160°C, and the time of hot vulcanization can be 10 min, 15 min, or 20 min. Example 1

[0061] A high-temperature resistant and thermally conductive rubber magnetic material is prepared by the following steps: S1. Mixing: Mix 90g magnetic powder, 5g nitrile rubber, 0.08g vulcanizing agent of Preparation Example 1, 0.3g thermally conductive filler of Preparation Example 4, 0.4g vulcanization activator of Preparation Example 7, 0.3g terpene resin, 0.08g calcium stearate, 0.5g antioxidant TNP and 0.1g coupling agent of Preparation Example 10, and mix at 105°C for 8 minutes to obtain the compound. S2. Tableting: After the compounded rubber is unloaded and naturally cooled to below 80℃, it is transferred to a tablet press. The roller temperature of the tablet press is adjusted to 65℃ and the roller speed is 6rpm. The roller gap for the first tableting is 6.5mm, the roller gap for the second tableting is 5.2mm, and the roller gap for the third tableting is 4.8~5.0mm. The tableting is performed three times to obtain sheet rubber. S3. Hot vulcanization: The sheet rubber compound is placed in a tunnel vulcanizing furnace and hot vulcanized at 150°C for 15 minutes. It is then removed and cooled to room temperature to obtain a high-temperature resistant and thermally conductive rubber magnetic material. Example 2

[0062] The preparation method and the amount of each raw material are the same as in Example 1, except that the vulcanizing agent in Example 2 is the same as that in Example 1. Example 3

[0063] The preparation method and the amount of each raw material are the same as in Example 1, except that the vulcanizing agent in Example 1 is the same as that in Example 3. Example 4

[0064] The preparation method and the amount of each raw material are the same as in Example 1, except that the thermally conductive filler in Example 4 is the same as that in Example 5. Example 5

[0065] The preparation method and the amount of each raw material are the same as in Example 1, except that the thermally conductive filler in Example 4 of Example 5 is the same as the thermally conductive filler in Example 6. Example 6

[0066] The preparation method and the amount of each raw material are the same as in Example 1, except that the vulcanization activator in Preparation Example 7 of Example 6 is the same as the vulcanization activator in Preparation Example 8. Example 7

[0067] The preparation method and the amount of each raw material are the same as in Example 1, except that the vulcanizing activator in Example 7 is the same as that in Example 9.

[0068] Comparative Example 1: The preparation method and the amount of each raw material are the same as in Example 1, except that the vulcanizing agent used in Comparative Example 1 is the same as that used in Comparative Example 1.

[0069] Comparative Example 2: The preparation method and the amount of each raw material are the same as in Example 1. The difference is that the vulcanizing agent in Preparation Example 1 of Comparative Example 2 is an equal amount of PF-2123 type phenol-formaldehyde type thermoplastic phenolic resin, that is, the vulcanizing agent does not contain curing agent.

[0070] Comparative Example 3: The preparation method and the amount of each raw material are the same as in Example 1, except that the thermally conductive filler in Comparative Example 4 is prepared using the thermally conductive filler prepared in Comparative Example 2.

[0071] Comparative Example 4: The preparation method and the amount of each raw material of a high-temperature resistant and thermally conductive rubber magnetic material are the same as in Example 1, except that the amount of vulcanizing activator in Preparation Example 7 of Comparative Example 4 is only 0.15g.

[0072] Material performance testing: The high-temperature resistant and thermally conductive rubber magnetic materials obtained in Examples 1-7 and Comparative Examples 1-4 were subjected to various performance tests, and the test methods are as follows: 1. Surface appearance: Use a microscope to magnify 20 times to observe the surface appearance of the material.

[0073] 2. Remanence (Br), coercivity (Hcb), and maximum energy product (BH)max: tested according to GB / T 3217-2013 standard.

[0074] 3. Hardness: Tested according to GB / T 531.1-2008 standard.

[0075] 4. Tensile strength: Tested in accordance with GB / T 528-2009 standard.

[0076] 5. Tear strength: Tested according to GB / T 529-2008 standard.

[0077] 6. Thermal conductivity: Tested in accordance with GB / T 10294-2008 standard.

[0078] 7. High temperature aging resistance: After being placed in a high temperature aging chamber at 100℃ for 72 hours, the remanence (Br) and tensile strength after aging are tested. The remanence (Br) retention rate and tensile strength retention rate are obtained by multiplying the test value after aging by the test value before aging by 100%.

[0079] The test properties of the high-temperature resistant and thermally conductive rubber magnetic materials of Examples 1-7 and Comparative Examples 1-4 are shown in Tables 1 and 2 below:

[0080]

[0081] The high-temperature resistant thermally conductive rubber magnetic materials in Examples 1-7 are prepared by rationally proportioning raw materials such as magnetic powder, nitrile rubber, phenolic resin vulcanizing agent, thermally conductive filler, vulcanization activator, and coupling agent. In particular, the specific components and proportions of phenolic resin vulcanizing agent, thermally conductive filler, and vulcanization activator result in a smooth and flat surface of the prepared high-temperature resistant thermally conductive rubber magnetic material, which has excellent magnetic properties, mechanical properties, thermal conductivity, and high-temperature aging resistance. The remanence (Br) is as high as 2490~2550Gs, the tensile strength is 12.5~13.1MPa, and the thermal conductivity is 3.52~3.81W / (m·K). After heat aging at 100℃ for 72h, the remanence (Br)(Gs) retention rate is in the range of 97.2%~97.8%, which can meet the application requirements of micro motors and other high-speed, high-power applications.

[0082] Compared with Example 1, Comparative Example 1 was prepared using the same method and in the same amount of raw materials. The difference was that the vulcanizing agent used in Comparative Example 1 was the same as that used in Example 1. The results showed that although the surface of the high-temperature resistant thermally conductive rubber magnetic material of Comparative Example 1 only showed slight orange peel, its magnetic properties, mechanical properties, thermal conductivity, and high-temperature aging resistance all decreased significantly. This may be because the amount of thermoplastic phenolic resin was insufficient while the amount of curing agent was excessive, which led to the decomposition of the curing agent during the vulcanization process, producing volatile substances and forming microbubbles, which destroyed the integrity of the cross-linked network. This reduced the uniformity of magnetic powder dispersion and the regularity of magnetic domain arrangement, and increased thermal resistance and weakened the stability of the mechanical structure. Therefore, its various performance levels decreased to varying degrees.

[0083] Compared with Example 1, Comparative Example 2 was prepared using the same method and with the same amount of raw materials. The difference was that the vulcanizing agent in Comparative Example 2 did not contain a curing agent, but was only thermoplastic phenolic resin. The results showed that the surface of the high-temperature resistant thermally conductive rubber magnetic material of Comparative Example 2 had obvious orange peel, and its performance was the worst among all samples. The remanence (Br) was only 2290 Gs, the tensile strength was 8.6 MPa, and the thermal conductivity was 2.45 W / (m·K). After aging at 100°C for 72 h, the remanence (Br) (Gs) retention rate was 88.3%. This may be because without a curing agent, the thermoplastic phenolic resin could not form an effective cross-linking network, and the cross-linking density of the nitrile rubber molecular chain was extremely low, resulting in uneven flowability of the rubber compound and the appearance of orange peel. At the same time, the magnetic powder and thermally conductive filler lacked stable structural support and were dispersed disorderly, resulting in broken thermal conductive pathways and weak mechanical strength. The aging performance of the material also decreased at high temperatures.

[0084] Compared with Example 1, Comparative Example 3 was prepared using the same method and in the same amount of raw materials. The difference was that the thermally conductive filler used in Comparative Example 3 was the same as that used in Comparative Example 2. The results showed that although the surface of the high-temperature resistant thermally conductive rubber magnetic material of Comparative Example 3 was smooth and flat, its thermal conductivity, mechanical properties and high-temperature aging resistance were all lower than those of the Example. This may be because excessive alumina destroyed the composite thermally conductive network of lamellar boron nitride and spherical alumina. The spherical alumina occupied the continuous arrangement space of lamellar boron nitride, which led to an increase in thermal resistance. At the same time, the compatibility between the excessive alumina and the nitrile rubber matrix decreased, forming local stress concentration, which weakened the mechanical strength and the interface stability at high temperature. Therefore, its performance was not as good as that of the thermally conductive filler used in this application.

[0085] Compared with Example 1, Comparative Example 4 was prepared using the same method and with the same amount of raw materials. The difference was that the amount of vulcanization activator in Comparative Example 4 was only 0.15g. The results showed that the surface of the high-temperature resistant thermally conductive rubber magnetic material of Comparative Example 4 was smooth and flat, but its magnetic properties, mechanical properties, thermal conductivity, and high-temperature aging resistance all decreased to varying degrees. This may be because the high specific surface area of ​​the magnetic powder and thermally conductive filler adsorbed and coated the vulcanization activator, resulting in insufficient vulcanization activator to effectively participate in the vulcanization reaction. The vulcanization crosslinking reaction between phenolic resin and nitrile rubber was incomplete, and the crosslinking network density was low, which could not effectively fix the position of the magnetic powder and thermally conductive filler. This made it easier for interface peeling and magnetic domain disorder to occur at high temperatures. At the same time, the stability of the mechanical structure and thermal conductivity pathway decreased, so its various performance levels decreased to varying degrees.

[0086] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A high-temperature resistant and thermally conductive rubber magnetic material, characterized in that, Its raw material components include: magnetic powder, nitrile rubber, vulcanizing agent, thermally conductive filler, vulcanization activator, tackifier, lubricant, antioxidant and coupling agent, wherein the vulcanizing agent is a phenolic resin vulcanizing agent.

2. The high-temperature resistant and thermally conductive rubber magnetic material according to claim 1, characterized in that, The magnetic powder is at least one of neodymium iron boron magnetic powder and ferrite magnetic powder, and its particle size is 1~5μm.

3. The high-temperature resistant and thermally conductive rubber magnetic material according to claim 1, characterized in that, The acrylonitrile content of the nitrile rubber is 28-40%, and the Mooney viscosity ML (1+4) at 100℃ is 40-70.

4. The high-temperature resistant and thermally conductive rubber magnetic material according to claim 1, characterized in that, The phenolic resin vulcanizing agent comprises a mixture of thermoplastic phenolic resin and curing agent in a weight ratio of (4~10):(1~3).

5. The high-temperature resistant and thermally conductive rubber magnetic material according to claim 4, characterized in that, The curing agent is selected from at least one of hexamethylenetetramine, epoxy resin, amino resin, and aliphatic amine compounds.

6. The high-temperature resistant and thermally conductive rubber magnetic material according to claim 1, characterized in that, The thermally conductive filler is selected from at least one of boron nitride, alumina, and silicon carbide, and the particle size of the thermally conductive filler is 0.5~3μm.

7. The high-temperature resistant and thermally conductive rubber magnetic material according to claim 1, characterized in that, The sulfidation activator is selected from at least one of zinc oxide, magnesium oxide, and zinc carbonate; And / or, the tackifier is selected from at least one of terpene resin, rosin resin, and modified lignin resin; And / or, the lubricant is selected from at least one of zinc stearate, calcium stearate, stearic acid, and polyethylene wax; And / or, the antioxidant is selected from at least one of antioxidant 1010, antioxidant 4020, antioxidant MB, and antioxidant TNP; And / or, the coupling agent is selected from at least one of silane coupling agents and titanate coupling agents.

8. The high-temperature resistant and thermally conductive rubber magnetic material according to any one of claims 1 to 7, characterized in that, Its raw materials include the following components in parts by weight: 85-92 parts of magnetic powder; 4-8 parts of nitrile rubber; Vulcanizing agent 0.05-0.1 parts; 0.1 to 0.7 parts of thermally conductive filler; 0.2–0.5 parts of vulcanization activator; 0.1 to 0.5 parts of tackifier; Lubricant 0.06-0.1 parts; Antioxidant 0.2–0.9 parts; Coupling agent 0.08-0.2 parts.

9. A method for preparing a high-temperature resistant and thermally conductive rubber magnetic material as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Mixing: Mix the raw materials and knead them to obtain a compound. S2, tableting: The compounded rubber is tableted to obtain sheet rubber material; S3. Hot vulcanization: The sheet rubber compound is hot vulcanized and cooled to obtain the high-temperature resistant and thermally conductive rubber magnetic material.

10. The method for preparing the high-temperature resistant and thermally conductive rubber magnetic material according to claim 9, characterized in that, In step S1, the mixing temperature is 100~110℃, and the mixing time is 7~10min; In step S3, the temperature of the hot vulcanization is 140~160℃, and the time of the hot vulcanization is 10~20min.

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