Silicone rubber soft magnet and preparation method thereof

Abstract

The invention relates to the technical field of soft magnetic materials, in particular to a silicone rubber soft magnet and a preparation method thereof. The silicone rubber soft magnet comprises the following raw materials in parts by weight: 30-150 parts of silicone rubber raw rubber, 60-95 parts of magnetic powder, 5-30 parts of white carbon black, 1-7 parts of a structured control agent, 0.1-3 parts of a coupling agent and 0.5-2 parts of a cross-linking agent, the raw silicone rubber comprises methyl vinyl silicone rubber with the vinyl content of 0.03%-0.08%; and the structured control agent comprises methyl silazane and vinyl silazane. The raw materials such as the raw silicone rubber, the magnetic powder and the white carbon black are utilized to cooperate under a specific proportion, and the silicone rubber soft magnet with high magnetism and excellent mechanical performance is obtained.

Description

Technical Field

[0001] The present application relates to the technical field of soft magnetic materials, and in particular to a silicone rubber soft magnet and a preparation method thereof. Background Art

[0002] Soft magnetic materials are a type of magnetic material with low coercive force and high magnetic permeability. Under the action of an external magnetic field, they are easy to magnetize and demagnetize, and are flexible and convenient to use. Soft magnetic composite materials that combine soft magnetic powders and polymer matrices have both excellent soft magnetic properties and good processing convenience, broadening the application range of soft magnetic materials. Traditional soft magnetic composite materials mostly use rubber or plastic as a polymer matrix, which has poor temperature resistance and weather resistance, resulting in a significant limitation on their application range. Compared with rubber or plastic, silicone rubber has excellent weather resistance, temperature resistance and biocompatibility, and the soft magnetic composite materials made from it can meet the application needs of more scenarios. However, it is difficult to balance the soft magnetic properties and mechanical properties of traditional silicone rubber soft magnets. Summary of the invention

[0003] Based on this, it is necessary to provide a silicone rubber soft magnet and a preparation method thereof to solve the problem that it is difficult to balance the soft magnetic properties and mechanical properties of traditional silicone rubber soft magnets.

[0004] The above-mentioned purpose of the present application is achieved through the following technical solutions:

[0005] In a first aspect of the present application, a silicone rubber soft magnet is provided, comprising the following raw materials in parts by weight:

[0006] ;

[0007] The silicone rubber raw rubber includes methyl vinyl silicone rubber with a vinyl content of 0.03% to 0.08%;

[0008] The structure control agents include methylsilazanes and vinylsilazanes.

[0009] In some embodiments, the weight ratio of the methylsilazane to the vinylsilazane is (30-180):1.

[0010] In some embodiments, the number average molecular weight of the methyl vinyl silicone rubber is 500,000 to 700,000.

[0011] In some embodiments, the magnetic powder includes at least one of permanent magnet ferrite and rare earth permanent magnet material; the permanent magnet ferrite includes at least one of strontium ferrite, barium ferrite and lead ferrite; the rare earth permanent magnet material includes at least one of samarium iron nitrogen permanent magnet material and neodymium iron boron permanent magnet material.

[0012] In some embodiments, the D50 particle size of the magnetic powder is 3 μm to 15 μm.

[0013] In some embodiments, the coupling agent includes at least one of KH-550, KH-560, KH-570, A171, and A174.

[0014] In some embodiments, the coupling agent includes KH-550, KH-560, and A171 in a molar ratio of (1-2):(1-2):(1-2).

[0015] In some embodiments, the white carbon black comprises fumed white carbon black, and the specific surface area of ​​the fumed white carbon black is 50 m 2 / g~450m 2 / g.

[0016] In some embodiments, the crosslinking agent includes hydrogen-containing silicone oil, and the hydrogen content of the hydrogen-containing silicone oil is 0.5% to 1%.

[0017] In some embodiments, the silicone rubber soft magnet further includes 0.1 to 2 parts of a catalyst.

[0018] In a second aspect of the present application, a method for preparing the above-mentioned silicone rubber soft magnet is provided, comprising the following steps:

[0019] Mixing silicone rubber raw rubber, a structural control agent and white carbon black to obtain a base rubber;

[0020] The base glue and the coupling agent are mixed, and then magnetic powder is added to obtain a magnetic material;

[0021] The magnetic material and the cross-linking agent are mixed, and cross-linking curing treatment and magnetization treatment are performed to obtain the silicone rubber soft magnet.

[0022] This application has at least the following beneficial effects:

[0023] This application uses silicone rubber raw rubber and magnetic powder as the main raw materials, and uses methylsilazane and vinylsilazane as structural control agents, so that white carbon black can be grafted with vinyl, which not only weakens the structural effect caused by white carbon black, which is conducive to increasing the filling amount of magnetic powder, but also the vinyl on the white carbon black and the appropriate amount of vinyl on the methylvinyl silicone rubber undergo cross-linking reaction, thereby effectively improving the soft magnetic properties and mechanical strength of the silicone rubber soft magnet. At the same time, the coupling agent can increase the filling amount and dispersion uniformity of the magnetic powder, and make the silicone rubber soft magnet have good adhesion properties; the cross-linking agent can promote the cross-linking of silicone rubber to form a three-dimensional network polymer, thereby improving its mechanical properties, thermal stability and aging resistance. Therefore, this application uses raw materials such as silicone rubber raw rubber, magnetic powder and white carbon black to work together in a specific ratio to obtain a silicone rubber soft magnet with strong magnetism and excellent mechanical properties. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the present application, the present application is further described in detail below in conjunction with specific embodiments. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0026] In the present application, the meaning of "and / or" includes any and all combinations of one or more related listed items. "At least one" means more than one, such as one, two and more than two. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layer" means at least two layers, such as two layers, three layers, etc., unless otherwise clearly and specifically defined. In the description of the present application, "several" means at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0027] When a numerical range is disclosed in this application, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed in this application should be understood to include any and all subranges included therein.

[0028] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0029] In this application, "above" or "below" includes the number itself. For example, "1 below" includes 1.

[0030] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0031] In the present application, room temperature refers to indoor temperature, normal temperature or general temperature. Generally speaking, the range of room temperature can be any one of the following temperature intervals: 23°C ± 2°C, 25°C ± 5°C or 20°C ± 5°C.

[0032] In a first aspect, the present application provides a silicone rubber soft magnet to solve the problem that it is difficult to balance the soft magnetic properties and mechanical properties of traditional silicone rubber soft magnets.

[0033] In some embodiments, the silicone rubber soft magnet includes the following raw materials in parts by weight:

[0034] ;

[0035] Silicone rubber raw rubber includes methyl vinyl silicone rubber with a vinyl content of 0.03% to 0.08%;

[0036] Structure control agents include methylsilazanes and vinylsilazanes.

[0037] This application uses silicone rubber raw rubber and magnetic powder as the main raw materials, and uses methylsilazane and vinylsilazane as structural control agents, so that white carbon black can be grafted with vinyl, which not only weakens the structural effect caused by white carbon black, which is conducive to increasing the filling amount of magnetic powder, but also the vinyl on the white carbon black and the appropriate amount of vinyl on the methylvinyl silicone rubber undergo cross-linking reaction, thereby effectively improving the soft magnetic properties and mechanical strength of the silicone rubber soft magnet. At the same time, the coupling agent can increase the filling amount and dispersion uniformity of the magnetic powder, and make the silicone rubber soft magnet have good adhesion properties; the cross-linking agent can promote the cross-linking of silicone rubber to form a three-dimensional network polymer, thereby improving its mechanical properties, thermal stability and aging resistance. Therefore, this application uses raw materials such as silicone rubber raw rubber, magnetic powder and white carbon black to work together in a specific ratio to obtain a silicone rubber soft magnet with strong magnetism and excellent mechanical properties.

[0038] In the present application, in the silicone rubber soft magnet, the weight proportion of the silicone rubber raw rubber can be 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, 100 parts, 110 parts, 120 parts, 130 parts, 140 parts or 150 parts. Further, the weight proportion of the silicone rubber raw rubber can be 80 parts to 120 parts.

[0039] In the present application, the silicone rubber raw rubber includes methyl vinyl silicone rubber with a vinyl content of 0.03% to 0.08%. The vinyl content refers to the molar fraction of vinyl in methyl vinyl silicone rubber, which can be determined by referring to GB / T 36691-2018 Determination of Vinyl Content of Methyl Vinyl Silicone Rubber by Near Infrared Method. As an example, the vinyl content in methyl vinyl silicone rubber can be 0.03%, 0.04%, 0.05%, 0.06%, 0.07% or 0.08%. Furthermore, the vinyl content in methyl vinyl silicone rubber is 0.03% to 0.05%.

[0040] The vinyl content of methyl vinyl silicone rubber is within a suitable range, and can undergo cross-linking reaction with the vinyl provided by other raw materials to obtain good mechanical strength. If the vinyl content is too high, it is easy to cause the hardness of the soft magnet to be too high, and the tensile strength, tear strength, elongation at break and other properties to deteriorate.

[0041] In some embodiments, the number average molecular weight of the methyl vinyl silicone rubber is 500,000 to 700,000, for example, 500,000, 520,000, 540,000, 560,000, 580,000, 600,000, 620,000, 640,000, 660,000, 680,000 or 700,000. Further, the number average molecular weight of the methyl vinyl silicone rubber is 560,000 to 640,000.

[0042] If the number average molecular weight of methyl vinyl silicone rubber is too low, it will affect the mechanical properties of the soft magnet; if the molecular weight is too high, it will reduce the amount of magnetic powder added, making the soft magnetic properties worse. By controlling the number average molecular weight of methyl vinyl silicone rubber, the silicone rubber soft magnet can have both good mechanical properties and soft magnetic properties.

[0043] In the present application, in the silicone rubber soft magnet, the weight proportion of the magnetic powder can be 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts or 95 parts. Further, the weight proportion of the magnetic powder can be 80 parts to 90 parts.

[0044] In some embodiments, the magnetic powder includes at least one of permanent magnet ferrite and rare earth permanent magnet material; the permanent magnet ferrite includes at least one of strontium ferrite, barium ferrite and lead ferrite; the rare earth permanent magnet material includes at least one of samarium iron nitride (SmFeN) permanent magnet material and neodymium iron boron (NdFeB) permanent magnet material. Further, the magnetic powder is selected from rare earth permanent magnet material. Further, the magnetic powder is selected from neodymium iron boron permanent magnet material.

[0045] Permanent ferrite and rare earth permanent magnet materials have strong magnetic properties, which can make silicone rubber soft magnets obtain good soft magnetic properties. The magnetic properties of rare earth permanent magnet materials are higher than those of permanent ferrite, and the same soft magnetic properties can be obtained with less magnetic powder, which is beneficial to improve the mechanical properties of soft magnets. Among rare earth permanent magnet materials, neodymium iron boron (NdFeB) permanent magnet materials have the best magnetic properties, which is beneficial to further improve the magnetic and mechanical properties of soft magnets.

[0046] In some embodiments, the D50 particle size (i.e., median particle size) of the magnetic powder is 3 μm to 15 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm. Further, the D50 particle size of the magnetic powder is 8 μm to 10 μm.

[0047] If the D50 particle size of magnetic powder is too small, it is easy to oxidize during the preparation process, which reduces the magnetism. For rare earth permanent magnet materials, if the D50 particle size is smaller than the three-atom stacking diameter of SmFeN or NdFeB, it is easy to cause a sharp attenuation of its magnetism. If the D50 particle size of magnetic powder is too large, it will affect the mechanical properties of soft magnets. Therefore, the selection of magnetic powder of appropriate size is also conducive to making silicone rubber soft magnets have both good mechanical properties and soft magnetic properties.

[0048] In the present application, in the silicone rubber soft magnet, the weight proportion of white carbon black can be 5 parts, 8 parts, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, 28 parts or 30 parts. Further, the weight proportion of white carbon black can be 10 parts to 20 parts.

[0049] In some embodiments, the white carbon black comprises fumed white carbon black, and the specific surface area of ​​the fumed white carbon black is 50 m 2 / g~450m 2 / g, for example, 50m 2 / g、100m 2 / g, 150m 2 / g, 200m 2 / g, 250m 2 / g、300m 2 / g, 350m 2 / g, 400m 2 / g or 450m 2 / g. Furthermore, the specific surface area of ​​fumed silica is 150m 2 / g~300m 2 / g.

[0050] Fumed silica is an amorphous, flocculent nano-sized silica material produced by high-temperature gas phase reaction. It has high purity, small particle size, and large specific surface area, and can achieve better reinforcement effect. If the specific surface area of ​​fumed silica is too high, it is easy to cause a stronger structural effect, reducing the filling amount of magnetic powder. Therefore, the use of fumed silica with a suitable specific surface area can improve the reinforcement effect while increasing the amount of magnetic powder.

[0051] In the present application, in the silicone rubber soft magnet, the weight proportion of the structure control agent can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts or 7 parts. Further, the weight proportion of the silicone rubber raw rubber can be 2 parts to 5 parts.

[0052] In the present application, methylsilazane refers to hexamethyldisilazane, which can react with the hydroxyl groups on the surface of silica to reduce the formation of hydrogen bonds between silica, thereby inhibiting the agglomeration of silica and improving the uniformity and processing performance of silicone rubber. Vinylsilazane refers to tetramethyldivinylsilazane, which can graft vinyl groups onto the surface of silica and participate in the cross-linking reaction of silicone rubber, thereby increasing the cross-linking density of silicone rubber and improving the mechanical properties, heat resistance and aging resistance of silicone rubber. The coordination between methylsilazane and vinylsilazane can effectively inhibit the structuring effect caused by silica and improve the mechanical properties and processing performance of silicone rubber soft magnets.

[0053] In some embodiments, the weight ratio of methylsilazane to vinylsilazane is (30-180):1, for example, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, 110:1, 120:1, 130:1, 140:1, 150:1, 160:1, 170:1 or 180:1. Further, the weight ratio of methylsilazane to vinylsilazane is (40-60):1.

[0054] By controlling the weight ratio between methylsilazane and vinylsilazane, the vinyl content in the structuring control agent can be controlled, thereby regulating the crosslinking density of the silicone rubber soft magnet, so that the silicone rubber soft magnet has excellent properties such as hardness, tensile strength, tear strength, and elongation at break.

[0055] In the present application, in the silicone rubber soft magnet, the weight proportion of the coupling agent can be 0.1 part, 0.2 part, 0.5 part, 0.8 part, 1 part, 1.2 parts, 1.5 parts, 1.8 parts, 2 parts, 2.2 parts, 2.5 parts, 2.8 parts or 3 parts. Further, the weight proportion of the coupling agent can be 0.2 parts to 1 part.

[0056] In some embodiments, the coupling agent includes at least one of KH-550 (γ-aminopropyltriethoxysilane), KH-560 (γ-(2,3-epoxypropyl)propyltrimethoxysilane), KH-570 (γ-methacryloxypropyltrimethoxysilane), A171 (vinyltrimethoxysilane) and A174 (γ-methacryloxypropyltrimethoxysilane).

[0057] The coupling bridging effect of the coupling agent can not only enhance the interaction between different raw materials, improve the uniformity of the dispersion of raw materials such as magnetic powder and white carbon black in the silicone rubber matrix, which is beneficial to increase the filling amount of magnetic powder, but also enhance the bonding strength between soft magnets and other materials, so that the soft magnets have certain bonding properties. Among them, KH-550 and KH-570 have a good bonding effect on substrates such as metals and plastics under thermal catalysis, which is beneficial to improve the self-adhesive properties of soft magnets; A171 and A174 contain vinyl in their molecular structure, which can be cross-linked with vinyl in raw materials such as silicone rubber, white carbon black and structural control agents to improve the mechanical strength of soft magnets.

[0058] In some embodiments, the coupling agent comprises KH-550, KH-560 and A171 in a molar ratio of (1-2): (1-2): (1-2). The molar ratio of KH-550, KH-560 and A171 may be 1:1:1, 1:1:2, 1:2:1, 1:2:2, 2:1:1, 2:1:2, 2:2:1 or 2:2:2. Further, the coupling agent comprises KH-550, KH-560 and A171 in a molar ratio of 1:1:2.

[0059] The synergistic combination of KH-550, KH-560 and A171 can effectively increase the amount of magnetic powder added and the uniformity of dispersion, making the soft magnet have excellent soft magnetic properties, while also ensuring good bonding strength between the soft magnet and a variety of substrates.

[0060] In the present application, in the silicone rubber soft magnet, the weight proportion of the crosslinking agent can be 0.5 parts, 0.8 parts, 1 parts, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts or 2 parts. Further, the weight proportion of the crosslinking agent can be 0.5 parts to 1 parts.

[0061] In some embodiments, the crosslinking agent includes hydrogen-containing silicone oil, and the hydrogen content of the hydrogen-containing silicone oil is 0.5% to 1%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%. Further, the hydrogen content of the hydrogen-containing silicone oil is 0.6% to 0.8%.

[0062] Hydrogenated silicone oil can react with vinyl in silicone rubber to form Si-C bonds, thus achieving crosslinking and curing of silicone rubber. Compared with other crosslinking agents, the use of hydrogenated silicone oil as a crosslinking agent can significantly improve the thermal stability, high temperature resistance and aging resistance of silicone rubber soft magnets.

[0063] In this application, the hydrogen content in hydrogen-containing silicone oil generally refers to the molar fraction of Si-H bonds in the hydrogen-containing silicone oil. By controlling the hydrogen content of hydrogen-containing silicone oil, the crosslinking density of silicone rubber can be regulated, thereby improving the hardness, tensile strength, elongation at break, tear strength and other properties of silicone rubber soft magnets.

[0064] In some embodiments, the silicone rubber soft magnet includes the following raw materials in parts by weight:

[0065] .

[0066] In some embodiments, the silicone rubber soft magnet further includes 0.1 to 2 parts of a catalyst, for example, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8 or 2 parts. Further, the silicone rubber soft magnet further includes 0.1 to 1 part of a catalyst.

[0067] Adding an appropriate amount of catalyst can accelerate the hydrosilylation reaction of silicone rubber, reduce the occurrence of side reactions, improve production efficiency and reduce preparation costs.

[0068] In some embodiments, the catalyst in the silicone rubber soft magnet includes a platinum catalyst, for example, a Custer platinum catalyst can be used. The chemical name of the Custer platinum catalyst is divinyltetramethyldisiloxane platinum complex, which is a platinum catalyst with high activity, high selectivity and high catalytic efficiency, and can effectively promote the hydrosilylation reaction in the silicone rubber material. Among them, the platinum content in the Custer platinum catalyst is 100ppm~200000ppm. Further, the platinum content in the Custer platinum catalyst is 500ppm~1000ppm.

[0069] In a second aspect of the present application, a method for preparing the above-mentioned silicone rubber soft magnet is provided.

[0070] In some embodiments, the method for preparing a silicone rubber soft magnet comprises the following steps:

[0071] S1: mixing silicone rubber raw rubber, structure control agent and white carbon black to obtain base rubber;

[0072] S2: Mixing the base glue and the coupling agent, and then adding the magnetic powder to obtain the magnetic material;

[0073] S3: Mix the magnetic material and the cross-linking agent, perform cross-linking curing treatment and magnetization treatment, and obtain a silicone rubber soft magnet.

[0074] The present application utilizes a method of mixing silicone rubber raw rubber, a structural control agent and white carbon black to obtain a base rubber, and then first adding a coupling agent under vacuum conditions, which can prevent the coupling agent from decomposing under the action of water or oxygen and ensure the integrity of the active groups of the coupling agent. After the magnetic powder is added, the magnetic powder can be better coupled and bridged, thereby increasing the amount of magnetic powder added and the uniformity of dispersion, and then obtaining a silicone rubber soft magnet with stronger magnetic and mechanical properties and more stability after cross-linking, curing and magnetization.

[0075] The following is a detailed description of the preparation method of silicone rubber soft magnets in a step-by-step manner.

[0076] S1: Mix silicone rubber raw rubber, structure control agent and white carbon black to obtain base rubber.

[0077] In some embodiments, mixing silicone rubber raw rubber, a structuring control agent and white carbon black comprises the following steps: after the silicone rubber raw rubber and the structuring control agent are evenly mixed, white carbon black is added stepwise, and a first stirring treatment, a second stirring treatment and a third stirring treatment are performed to obtain a base rubber.

[0078] In some embodiments, the conditions of the first stirring treatment include: stirring at room temperature for 0.5 h to 1.5 h, wherein the temperature of the first stirring treatment may be 20° C. to 30° C., and the stirring time may be 0.5 h, 1 h or 1.5 h.

[0079] In some embodiments, the second stirring treatment conditions include: stirring at 160°C to 180°C for 0.5h to 1.5h. The temperature of the second stirring treatment may be 160°C, 165°C, 170°C, 175°C or 180°C, and the stirring time may be 0.5h, 1h or 1.5h.

[0080] In some embodiments, the conditions of the third stirring treatment include: stirring at 160°C to 180°C and a vacuum condition of pressure ≤-0.08MPa for 1h to 3h. The temperature of the third stirring treatment may be 160°C, 165°C, 170°C, 175°C or 180°C, the vacuum degree may be -0.08MPa, -0.09MPa, -0.1MPa or -0.12MPa, and the stirring time may be 1h, 1.5h, 2h, 2.5h or 3h.

[0081] S2: Mix the base glue and the coupling agent, and then add the magnetic powder to obtain the magnetic material.

[0082] In some embodiments, the base glue and the coupling agent are mixed, and then the magnetic powder is added, comprising the following steps: stirring the base glue and the coupling agent under vacuum conditions with a pressure of ≤-0.08 MPa for 0.1 h to 1 h, and then adding the magnetic powder step by step at a temperature of ≤80°C and normal pressure, stirring for 0.1 h to 1 h to obtain a magnetic material.

[0083] Among them, the vacuum degree of the mixed base glue and coupling agent can be -0.08MPa, -0.09MPa, -0.1MPa or -0.12MPa, and the stirring time under vacuum conditions can be 0.1h, 0.2h, 0.4h, 0.6h, 0.8h or 1h; the temperature for adding magnetic powder can be 20℃, 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃, and the stirring time can be 0.1h, 0.2h, 0.4h, 0.6h, 0.8h or 1h.

[0084] S3: Mix the magnetic material and the cross-linking agent, perform cross-linking curing treatment and magnetization treatment, and obtain a silicone rubber soft magnet.

[0085] In some embodiments, before and / or after mixing the magnetic material and the cross-linking agent, a step of adding a platinum catalyst is also included.

[0086] In some embodiments, the cross-linking curing treatment comprises the following steps: heating and curing at 100°C to 150°C for 5min to 15min. The heating and curing method may be at least one of compression molding, extrusion molding and calendering molding, the heating and curing temperature may be 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, and the heating and curing time may be 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min or 15min.

[0087] In some embodiments, the magnetization treatment includes the following steps: magnetizing the cross-linked cured product for 1s to 10s using a magnetizer to obtain a silicone rubber soft magnet, wherein the magnetization voltage of the magnetizer can be 100V to 2000V, and the magnetization amount can be 150Gs to 3000Gs.

[0088] The following is further described in conjunction with specific embodiments and comparative examples. The raw materials involved in the following specific embodiments and comparative examples, unless otherwise specified, can all be commercially available, the instruments used, unless otherwise specified, can all be commercially available, and the processes involved, unless otherwise specified, are all routinely selected by those skilled in the art.

[0089] Example 1

[0090] The silicone rubber soft magnet of this embodiment includes the following raw materials in parts by weight: 100 parts of silicone rubber raw rubber, 85 parts of magnetic powder, 18 parts of white carbon black, 3 parts of structural control agent, 0.5 parts of coupling agent, 1 part of cross-linking agent and 0.1 parts of catalyst.

[0091] Among them, the composition and parameters of each raw material are as follows:

[0092] Silicone rubber: methyl vinyl silicone rubber, vinyl content is 0.03%, number average molecular weight is 600,000;

[0093] Magnetic powder: NdFeB magnetic powder, D50 particle size is 9.5μm;

[0094] White carbon black: Fumed white carbon black, with a specific surface area of ​​260m 2 / g;

[0095] Structuring control agent: methylsilazane and vinylsilazane, weight ratio 49:1;

[0096] Coupling agent: KH-550, KH-560 and A171, molar ratio of 1:1:2;

[0097] Cross-linking agent: hydrogen-containing silicone oil, hydrogen content is 0.7%;

[0098] Catalyst: Custer platinum catalyst, platinum content is 500ppm.

[0099] The silicone rubber soft magnet of this embodiment is prepared by the following method:

[0100] (1) The silicone rubber raw rubber and the structuring control agent are stirred evenly in a closed kneader, and white carbon black is added step by step to mix evenly. The mixture is stirred at room temperature for 1 hour, at 180°C for 1 hour, and at 180°C under vacuum to a pressure of ≤-0.08 MPa for 2 hours, and then cooled to obtain a base rubber.

[0101] (2) Place the base rubber and coupling agent in a closed kneader, evacuate to a pressure of ≤-0.08 MPa, and stir for 0.5 h. Then, add magnetic powder step by step at a temperature of 70°C and normal pressure, and stir for 0.5 h to obtain a magnetic material.

[0102] (3) Add a cross-linking agent and a catalyst to the magnetic material, stir for 0.1 h, and perform molding at 120°C for 10 min for cross-linking and curing. Then, use a magnetizer to magnetize for 3 s at a magnetizing voltage of 2000 V and a magnetizing amount of 2000 Gs to obtain a silicone rubber soft magnet.

[0103] Embodiment 2~6

[0104] Embodiments 2 to 6 are substantially the same as Embodiment 1, except that:

[0105] Example 2: The vinyl content of the methyl vinyl silicone rubber is 0.05%;

[0106] Example 3: The vinyl content of the methyl vinyl silicone rubber is 0.08%;

[0107] Example 4: methylsilazane and vinylsilazane, weight ratio is 30:1;

[0108] Example 5: methylsilazane and vinylsilazane, weight ratio is 180:1;

[0109] Example 6: A171 is used as coupling agent only;

[0110] Example 7: In step (2), the mixing of the base glue and the coupling agent is carried out under normal pressure without vacuuming.

[0111] Comparative Examples 1 to 6

[0112] Comparative Examples 1 to 6 are substantially the same as Example 1, except that:

[0113] Comparative Example 1: The vinyl content of the methyl vinyl silicone rubber is 0.5%;

[0114] Comparative Example 2: The structured control agent uses low-viscosity hydroxy silicone oil with a hydroxyl content of 8.5%;

[0115] Comparative Example 3: Only methylsilazane was added as the structure control agent;

[0116] Comparative Example 4: Only vinyl silazane was added as the structure control agent;

[0117] Comparative Example 5: No coupling agent was added.

[0118] Test Case

[0119] The following tests are performed on silicone rubber soft magnets:

[0120] (1) Shore hardness: Tested in accordance with GB / T 531.1-2008, where the unit HA represents Shore A hardness, which is applicable to softer materials.

[0121] (2) Tensile strength and tensile strength: Tested in accordance with GB / T 528-2009.

[0122] (3) Tear strength: Tested in accordance with GB / T 529-2008.

[0123] (4) Surface magnetic induction intensity: Tested using a handheld digital Gauss meter magnetic tester.

[0124] (5) Adhesion performance: The substrate is placed in a mold, and the silicone rubber composition is coated on the surface of the substrate. The substrate is pressurized and cured at 150°C for 3 min to form a 3 mm thick rubber layer. The rubber layer is then peeled off manually. The ratio of the remaining area of ​​the rubber layer to the adhesion area of ​​the entire rubber layer is the cohesive failure rate. The substrate includes a metal substrate and a plastic substrate with a size of 50 mm × 25 mm × 2 mm. The silicone rubber composition refers to a mixture of a magnetic material with a cross-linking agent and a catalyst added and stirred for 0.1 h. If the cohesive failure rate is ≥50%, it means that the adhesion performance is good and is recorded as OK. If the cohesive failure rate is <50%, it means that the adhesion performance is poor and is recorded as NG (not good).

[0125] The above test results are shown in Table 1.

[0126] Table 1. Performance test results of silicone rubber soft magnets

[0127]

[0128] It can be seen from Table 1 that the magnetic induction intensity on the surface of the silicone rubber soft magnets prepared in Examples 1 to 7 of the present application reaches 803Gs~926Gs, the Shore hardness reaches 61HA~72HA, the tensile strength reaches 3.2MPa~4.8MPa, the elongation at break reaches 226%~367%, the tear strength reaches 18KN / m~23KN / m, and has good adhesion to metal substrates and plastic substrates. This proves that the silicone rubber soft magnets provided in the present application have both excellent soft magnetic properties and good mechanical properties, and can meet the application requirements of high-performance soft magnetic materials.

[0129] It can be seen from Examples 1 to 3 that when the vinyl content of the methyl vinyl silicone rubber increases from 0.03% to 0.08%, the surface magnetic induction intensity gradually increases, and the Shore hardness, tensile strength and tear strength also gradually increase, but the elongation at break gradually decreases. The vinyl content of the methyl vinyl silicone rubber used in Comparative Example 1 increases to 0.5%, and the Shore hardness and surface magnetic induction intensity further increase, but the tensile strength, tear strength and elongation at break are greatly reduced, which proves that controlling the vinyl content of the methyl vinyl silicone rubber within a suitable range is conducive to improving the magnetic properties of the silicone rubber soft magnet while obtaining good mechanical properties.

[0130] It can be seen from Examples 1, 4 and 5 that when the structured control agent uses methylsilazane and vinylsilazane and the weight ratio of the two is controlled within the range of (30-180):1, the silicone rubber soft magnets all show the advantages of high magnetism and high mechanical strength. Comparative Example 2 uses low-viscosity hydroxyl silicone oil, and the magnetism of the silicone rubber soft magnet is significantly deteriorated; Comparative Example 3 only adds methylsilazane, and Comparative Example 4 only adds vinylsilazane, and the mechanical properties of the silicone rubber soft magnets are not good.

[0131] Compared with Example 1, the coupling agent of Example 6 only uses A171, and the adhesion performance of the silicone rubber soft magnet to plastic is poor. In Comparative Example 5, no coupling agent is added, and the tear strength, elongation at break and surface magnetic induction intensity of the silicone rubber soft magnet are significantly deteriorated, and the adhesion performance to metals and plastics is poor, indicating that the coupling agent using a combination of KH-550, KH-560 and A171 is beneficial to improving the magnetic properties, mechanical properties and self-adhesion properties of the silicone rubber soft magnet.

[0132] Compared with Example 1, Example 7 does not perform vacuum treatment when mixing the base glue and the coupling agent. The coupling agent is easily hydrolyzed under normal pressure, which is not conducive to the uniform dispersion and coupling bridging of the magnetic powder. As a result, the magnetic induction intensity on the surface of the silicone rubber soft magnet decreases significantly.

[0133] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0134] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of protection of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the attached claims.

Claims

1. A silicone rubber soft magnet, characterized in that: The invention comprises the following raw materials in parts by weight: ； The silicone rubber raw rubber includes methyl vinyl silicone rubber with a vinyl content of 0.03% to 0.08%; The structure control agents include methylsilazanes and vinylsilazanes.

2. The silicone rubber soft magnet according to claim 1, characterized in that: The weight ratio of the methylsilazane to the vinylsilazane is (30-180):

1.

3. The silicone rubber soft magnet according to claim 1, characterized in that: The number average molecular weight of the methyl vinyl silicone rubber is 500,000 to 700,000.

4. The silicone rubber soft magnet according to any one of claims 1 to 3, characterized in that: The magnetic powder satisfies at least one of the following conditions: (1) The magnetic powder includes at least one of permanent magnet ferrite and rare earth permanent magnet material; the permanent magnet ferrite includes at least one of strontium ferrite, barium ferrite and lead ferrite; the rare earth permanent magnet material includes at least one of samarium iron nitrogen permanent magnet material and neodymium iron boron permanent magnet material; (2) The D50 particle size of the magnetic powder is 3 μm to 15 μm.

5. The silicone rubber soft magnet according to any one of claims 1 to 3, characterized in that: The coupling agent includes at least one of KH-550, KH-560, KH-570, A171 and A174.

6. The silicone rubber soft magnet according to claim 5, characterized in that: The coupling agent includes KH-550, KH-560 and A171 in a molar ratio of (1-2): (1-2): (1-2).

7. The silicone rubber soft magnet according to any one of claims 1 to 3, characterized in that: The white carbon black comprises fumed white carbon black, and the specific surface area of ​​the fumed white carbon black is 50 m 2 / g~450m 2 / g.

8. The silicone rubber soft magnet according to any one of claims 1 to 3, characterized in that: The cross-linking agent includes hydrogen-containing silicone oil, and the hydrogen content of the hydrogen-containing silicone oil is 0.5% to 1%.

9. The silicone rubber soft magnet according to any one of claims 1 to 3, characterized in that: The silicone rubber soft magnet also includes 0.1 to 2 parts of a catalyst.

10. A method for preparing a silicone rubber soft magnet according to any one of claims 1 to 9, characterized in that: The following steps are involved: Mixing silicone rubber raw rubber, a structural control agent and white carbon black to obtain a base rubber; The base glue and the coupling agent are mixed, and then magnetic powder is added to obtain a magnetic material; The magnetic material and the cross-linking agent are mixed, and cross-linking curing treatment and magnetization treatment are performed to obtain the silicone rubber soft magnet.

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