Preparation process of flexible strong magnetic neodymium-iron-boron magnet based on high-molecular colloidal silica

Abstract

A flexible strong magnetic neodymium-iron-boron magnet preparation process based on a polymer colloidal silica comprises the steps that a swelling agent is added into first silica gel with the volume of V1, solid second silica gel with the volume of V2 is formed after the first silica gel is expanded, and the relational expression that V2 is larger than or equal to 4 * V1 is met; adding neodymium iron boron powder into the second silica gel, and stirring to form third silica gel in a solid-liquid mixed state; performing granulation processing on third silica gel to form silica gel particles, heating the third silica gel twice to a first temperature during granulation processing, and discharging the swelling agent at the first temperature in sequence; the mold is filled with the silica gel particles, the silica gel particles stand and are cooled to a second temperature T2, a first pressing head above the mold in the vertical direction and a second pressing head with the punching end provided with a guide pin sequentially punch the silica gel particles, and the punched silica gel particles form a silica gel body; the silica gel body is sequentially vulcanized and magnetized at the third temperature to form a silica gel magnet, and in the silica gel magnet, the mass of neodymium iron boron is Qwt.% of the mass of the silica gel magnet.

Description

Technical Field

[0001] The invention relates to the field of magnetic materials, and in particular to a preparation process of a flexible strong magnetic NdFeB magnet based on polymer silica gel. Background Art

[0002] With the popularity of smartphones and the rapid development of wireless charging technology, wireless charging has become an indispensable charging method in modern life. However, in practical applications, most smartphones face a common problem when wirelessly charging: the battery cannot accurately align with the magnet inside the wireless charging stand, resulting in reduced charging efficiency. To solve this problem, it is usually necessary to build a matching magnet into the mobile phone so that it can automatically align with the magnet inside the wireless charging stand after contacting the wireless charging stand, thereby improving charging efficiency.

[0003] The above-mentioned magnets are usually mixed with silicone and magnetic materials (such as neodymium iron boron). Silicone acts as an adhesive and supporting material, while neodymium iron boron provides the required magnetic force. However, due to the size of the mobile phone battery and the thickness of the mobile phone, the size of the magnet must be kept within a small range, which will cause a key problem. The smaller the magnet, the smaller its magnetism will usually be, and the limitation of the magnet size may cause the problem of insufficient magnetic force. At present, in order to increase the magnetic force of the magnet, the density of the magnet is usually increased. The existing common molding process is usually to slice and hot-extrude solid silicone. Under this process, the solid silicone slices need a high temperature and high pressure environment to soften the silicone and make it flow during the hot extrusion process. Because this processing method is relatively complicated and it takes a certain amount of time to heat the solid silicone to soften it and flow in the mold and cool it after molding, the production efficiency is reduced, which limits the large-scale production of small objects such as silicone magnets.

[0004] Therefore, it is necessary to provide a flexible and strong magnetic NdFeB magnet preparation process based on polymer silica gel, which can improve production efficiency and increase the magnetic force of the magnet. Summary of the invention

[0005] The object of the present invention is to provide a process for preparing a flexible strong magnetic NdFeB magnet based on polymer silica gel, which can improve production efficiency and increase the magnetic force of the magnet.

[0006] According to one aspect of the present application, a process for preparing a flexible strong magnetic NdFeB magnet based on polymer silica gel is provided, characterized in that the process comprises the steps of:

[0007] S10: adding a swelling agent to a first silica gel having a volume of V1, and the first silica gel expands to form a second silica gel having a solid state and a volume of V2, and the relationship is satisfied: V2 ≥ 4 × V1;

[0008] S20: adding NdFeB powder to the second silica gel and stirring, wherein the NdFeB powder is bonded to the second silica gel, and after stirring, a third silica gel in a solid-liquid mixed state is formed;

[0009] S30: granulating the third silica gel into silica gel particles, wherein the third silica gel is heated twice to a first temperature T1 during the granulation process, and the swelling agent is discharged at the first temperature T1 in sequence;

[0010] S40 The silicone particles are filled into the mold and left to cool to a second temperature T2. At the second temperature T2, a first pressing head above the mold in a vertical direction and a second pressing head with a guide pin at a pressing end press the silicone particles in sequence, and the pressed silicone particles form a silicone body.

[0011] S50 The silica gel is successively vulcanized at a third temperature T3 and magnetized in a magnetic field to form a silica gel magnet, wherein the mass of NdFeB in the silica gel magnet is Qwt.% of the mass of the silica gel magnet.

[0012] More preferably, the shape of the silicone body formed after stamping when observed in the vertical direction is any one or a combination of circular, ring-shaped, rectangular, strip-shaped, trapezoidal, diamond-shaped, triangular, elliptical, arcuate or parallelogram.

[0013] More preferably, in step S40,

[0014] Vibration is used to shake off the silicone particles in the mold, and the compressor compacts the silicone particles with a density of D1 in the mold with an extrusion force P1, and the density of the compacted silicone particles is D2, and the relationship is satisfied: D2 ≥ 2 × D1;

[0015] If it is detected that the internal temperature of the mold is cooled to the second temperature T2, stamping is performed;

[0016] The first punching head punches the silica gel particles to form a first punching hole;

[0017] The mold is pushed forward in the horizontal direction. When the second pressing head is located directly above the first punching hole, the guide pin of the second pressing head is embedded in the first punching hole, and the second pressing head punches the silicone particles to form a second punching hole. The circular silicone body formed after punching separates from the mold along the edge of the second punching hole.

[0018] More preferably, when the silica gel particles with a density of D2 after extrusion are at the second temperature T2, the magnetic induction intensity of the silica gel particles is recorded as M1, and when the silica gel particles are at the first temperature T1, the magnetic induction intensity of the silica gel particles is recorded as M2, and the relationship is satisfied: 0.7M1≤M2≤0.9M1;

[0019] If the silica gel density of the silica gel particles is D1, and when the silica gel particles are at the second temperature T2, the magnetic induction intensity of the silica gel particles is recorded as M3, then when the volumes of the silica gel particles are the same, the relationship is satisfied: M3≤0.5×M1.

[0020] More preferably, the relationship is satisfied:

[0021] 300kPa≤P1≤500kPa,

[0022] Among them, kPa is the pressure unit kilopascal.

[0023] More preferably, in step S30,

[0024] preheating the third silica gel and allowing it to stand after reaching the first temperature T1;

[0025] After the standing is completed, the third silica gel is sent to a granulator, and the third silica gel flows and agglomerates in the granulator to form silica gel particles;

[0026] The silica gel particles are sent into a dryer, the dryer is evacuated, and when the internal air pressure is an absolute pressure P2, the silica gel particles are heated to a first temperature T1 for drying;

[0027] After drying, the silica gel particles are filtered through an N-mesh standard sieve, and silica gel particles with a qualified particle size are injected into a mold.

[0028] More preferably, the relationship is satisfied:

[0029] P2≤10Pa,

[0030] Wherein, Pa is the pressure unit Pa.

[0031] More preferably, the relationship is satisfied:

[0032] 5≤N≤10.

[0033] More preferably, the relationship is satisfied:

[0034] 94.8≤Q≤95.2.

[0035] More preferably, the relationship is satisfied:

[0036] 80℃≤T1≤160℃,

[0037] 15℃≤T2≤30℃,

[0038] 150℃≤T3≤180℃.

[0039] The present invention has the following beneficial effects:

[0040] By forming silica gel particles through granulation and filling them into the mold, the fluidity of the silica gel particles in the mold is good, which reduces the time it takes for the silica gel particles to fill the entire mold. By stamping the silica gel particles after cooling and standing to the first temperature, the molding process of the silica gel body does not need to be carried out in a hot environment, reducing the heating steps and improving production efficiency. By discharging the swelling agent in the silica gel particles twice at the first temperature and vulcanizing the silica gel particles at the third temperature to form a silica gel body, the proportion of neodymium iron boron in the final silicone magnet is increased, thereby increasing the magnetic force of the silicone magnet. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 This is a flow chart of a process for preparing a flexible strong magnetic NdFeB magnet according to one embodiment of the present application;

[0043] Figure 2 This is a schematic diagram of the cross-sectional structure of the punching machine and the die in one embodiment of the present application;

[0044] Figure 3 This is a schematic diagram of a state in which the punching machine in one embodiment of the present application punches the silica gel particles in the mold for the first time;

[0045] Figure 4 This is a schematic diagram of a state in which the first punching head punches to form a first punching hole in one embodiment of the present application;

[0046] Figure 5 It is a schematic diagram of a state in which the third silicone rubber in one embodiment of the present application is pushed forward and the punch presses the silicone rubber particles in the mold for the second time;

[0047] Figure 6 This is a schematic diagram of a state in which the guide pin of the second pressing head is embedded in the first punching hole in one embodiment of the present application;

[0048] Figure 7 This is a schematic diagram of a state in which the second pressing head punches out a second punching hole on the silica gel particles and forms a silica gel body in one embodiment of the present application;

[0049] Description of the accompanying drawings: 10, silica gel particles; 20, punching machine; 21, first pressing head; 22, second pressing head; 22A, guide pin; 30, mold. DETAILED DESCRIPTION

[0050] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. 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.

[0051] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0052] 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. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0053] Please refer to Figure 1 - Figure 7 In one embodiment of the present application, a process for preparing a flexible strong magnetic NdFeB magnet based on a polymer silica gel is provided, and the method comprises the steps of:

[0054] S10: adding a swelling agent to the first silica gel with a volume of V1, and the first silica gel expands to form a second silica gel with a solid volume of V2, and the relationship is satisfied: V2≥4×V1.

[0055] S20: adding NdFeB powder to the second silica gel and stirring the mixture; the NdFeB powder is bonded to the second silica gel, and after stirring, a third silica gel in a solid-liquid mixed state is formed.

[0056] S30 granulates the third silica gel to form silica gel particles 10 . During the granulation process, the third silica gel is heated twice to the first temperature T1 , and the swelling agent is discharged at the first temperature T1 in sequence.

[0057] S40 The silicone particles 10 are filled into the mold 30 and left to cool to a second temperature T2. At the second temperature T2, a first pressing head 21 vertically above the mold 30 and a second pressing head 22 provided with a guide pin 22A at the punching end sequentially punch the silicone particles 10, and the punched silicone particles 10 form a silicone body.

[0058] S50 The silica gel is successively vulcanized at a third temperature T3 and magnetized in a magnetic field to form a silica gel magnet, wherein the mass of NdFeB in the silica gel magnet is Qwt.% of the mass of the silica gel magnet.

[0059] Among them, in step S10, the swelling agent reacts in the first silica gel with a volume of V1 to produce gas, so that the volume of the first silica gel expands, thereby forming a second silica gel with a volume of V2 (i.e., at least four times the original volume). The second silica gel obtained after expansion has better plasticity and filling properties, which is conducive to the processing of subsequent steps. In addition, the physical properties and chemical stability of the second silica gel are better than those of the first silica gel. In step S20, the magnetic material NdFeB powder is evenly dispersed in the solid second silica gel, and a third silica gel in a solid-liquid mixed state is formed by heating and stirring. NdFeB is a high-performance permanent magnetic material with a high magnetic energy product and coercive force, and is a key raw material for preparing strong magnetic silica gel magnets. By stirring, it is ensured that the NdFeB powder is fully mixed with the silica gel, laying the foundation for the magnetization process in the subsequent steps. In step S30, the evenly mixed third silica gel is granulated to form silica gel particles 10. During the granulation process, the silica gel is heated twice to the first temperature T1 to discharge the gas and volatiles generated by the swelling agent to ensure the purity and stability of the silica gel particles 10. At the same time, heating can also promote the cross-linking reaction of silica gel, improve its strength and heat resistance. The granulated silica gel particles 10 are easy to store and transport, and also provide convenience for filling and stamping in subsequent steps. In step S40, the silica gel particles 10 are filled into the mold 30, and cooled to the second temperature T2 by standing, so that the silica gel particles 10 have a certain hardness and stability, and the temperature range of the second temperature T2 is the normal temperature range, which also shows that the stamping process does not need to heat the mold 30 and the silica gel particles 10 in the mold 30, so that the heating step in the traditional hot pressing slicing process is omitted, which is more conducive to large-scale production. In the process of stamping the silica gel particles 10 in sequence using the first pressure head 21 above the mold 30 in the vertical direction and the second pressure head 22 with a guide pin 22A at the stamping end, the mold 30 transports the silica gel material formed after the silica gel particles 10 are pressed to the direction of the punch 20 through the push mechanism, and the first pressure head 21 first presses a smaller inner hole on the silica gel material, and the shape of the inner hole can be square, round or other shapes. The extruded waste is discharged through the waste pipe below the silica gel material. Then, the pushing mechanism continues to push the silicone material to the bottom of the second ram 22, and the central axis of the guide pin 22A coincides with the central axis of the inner hole. When the second ram 22 punches the silicone material, the guide pin 22A is first inserted into the inner hole, and as the second ram 22 continues to press down, the second ram 22 presses out a ring-shaped object with the inner hole on the silicone material, and the ring-shaped object is discharged along the discharge port below. During the stamping process, the guide pin 22A ensures the accuracy and consistency of the stamping to form a silicone body. This step is one of the key steps in preparing silicone magnets, which directly affects the dimensional accuracy and shape quality of the silicone magnets. In step S50, the stamped silicone body is vulcanized at a third temperature T3.Vulcanization is a chemical reaction process that causes cross-linking between silicone molecular chains through heating and pressurization to form a stable three-dimensional network structure, thereby improving the strength and heat resistance of silicone. The vulcanized silicone body is then magnetized in a magnetic field to orient the NdFeB powder in the silicone body and generate magnetism. The magnetized silicone body has strong magnetism, and its magnetic strength and quality are proportional to the content of NdFeB powder.

[0060] More preferably, the shape of the silicone body formed after stamping when observed in the vertical direction is any one or a combination of circular, ring-shaped, rectangular, strip-shaped, trapezoidal, diamond-shaped, triangular, elliptical, arcuate or parallelogram.

[0061] Among them, the first ram 21 and the second ram 22 of the punching machine can be a cylinder, a cube and an irregular body (special-shaped ram). The silicone material (compressed silicone particles 10) in the mold 30 can be formed into silicone bodies of various shapes by moving in the mold 30 and linking the first ram 21 and the second ram 22 to punch it. For example, if the first ram 21 is a cylinder with a diameter of R1, and the second ram 22 is a cylinder with a diameter of R2 and is provided with a cylindrical guide pin 22A with a diameter of R1, then after the first punching, a cylindrical inner hole with a diameter of R1 will be left on the silicone material. During the second punching, the cylindrical guide pin 22A with a diameter of R1 will first be embedded in the inner hole of the cylinder to achieve the positioning effect, and then as the second ram 22 continues to press down, the cylindrical part with a diameter of R2 punches the silicone material, and forms a circular silicone body after penetrating the silicone material, and the circular silicone body falls along the second ram 22. At this time, the inner diameter of the annular silicone body is R1, and the outer diameter is R2. Similar to the above scheme, if the first press head 21, the second press head 22 and the guide pin 22A are square bodies, a square silicone body or a square annular silicone body will eventually be formed after stamping. The silicone magnets in this application can be applied to various fields such as electronic products, the automotive industry, home appliances and medical devices, so the shape and size of the silicone magnets can be adjusted according to different application scenarios, and the punching machine in the preparation process can support the formation of these silicone magnets.

[0062] More preferably, in step S40,

[0063] The silica gel particles 10 in the mold 30 are shaken off by vibration, and the compressor compacts the silica gel particles 10 with a density of D1 in the mold 30 with an extrusion force P1, and the density of the compacted silica gel particles 10 is D2, and the relationship is satisfied: D2≥2×D1.

[0064] If it is detected that the internal temperature of the mold 30 is cooled to the second temperature T2, the punching is performed.

[0065] The first punching head 21 punches the silica gel particles 10 to form a first punching hole.

[0066] The mold 30 is pushed forward in the horizontal direction. When the second pressing head 22 is located directly above the first punching hole, the guide pin 22A of the second pressing head 22 is embedded in the first punching hole, and the second pressing head 22 punches the silicone particles 10 to form a second punching hole. The circular silicone body formed after punching separates from the mold 30 along the edge of the second punching hole.

[0067] Among them, after the silicone particles 10 are filled into the mold 30, the particles are shaken off by vibration. The purpose of this step is to ensure that the silicone particles 10 are evenly distributed in the mold 30 to avoid local accumulation or gaps. Uniform particle distribution helps to improve the density and physical properties of the silicone magnet, and also helps to reduce defects in the stamping process. Next, a compressor is used to apply a certain extrusion force P1 to the silicone particles 10 in the mold 30 to compact the particles. The compaction process can further eliminate the gaps between the particles, improve the density and strength of the silicone magnet, and after the density is compressed to twice the original, it not only increases the space utilization in the mold 30, but also makes the magnetism of the silicone particles 10 in the same unit volume stronger. The selection of the extrusion force P1 needs to be determined according to the characteristics of the silicone and the design of the mold 30 to ensure that the expected compaction effect can be achieved without causing damage to the mold 30 or the silicone particles 10. After compaction, the mold 30 and the silicone particles 10 need to be left to cool to the second temperature T2. The purpose of this step is to stabilize the silicone particles 10 in the mold 30 and reach a temperature suitable for stamping. The selection of the second temperature T2 needs to take into account the thermoplasticity of silicone and the requirements of the stamping process to ensure that the silicone can be deformed smoothly during the stamping process without cracking or other defects. During the stamping process, when the internal temperature of the mold 30 reaches the second temperature T2, the stamping begins. First, the first press head 21 stamps the silicone particles 10 to form a first stamping hole. This step provides positioning and guiding for subsequent stamping. Then, the mold 30 moves forward in the horizontal direction so that the second press head 22 is located directly above the first stamping hole. At this time, the guide pin 22A of the second press head 22 is embedded in the first stamping hole, which plays a role in positioning and guiding. The introduction of the guide pin 22A can ensure that the stamping process of the second press head 22 is accurate and avoids problems such as inaccurate size or shape distortion of the silicone magnet caused by position deviation. Finally, the second press head 22 stamps the silicone particles 10 to form a second stamping hole. At the same time, the silicone body is separated from the mold 30 along the edge of the second stamping hole. This step completes the stamping process of the silicone magnet.

[0068] More preferably, when the silica gel particles 10 with a density of D2 after extrusion are at the second temperature T2, the magnetic induction intensity of the silica gel particles 10 is recorded as M1, and when the silica gel particles 10 are at the first temperature T1, the magnetic induction intensity of the silica gel particles 10 is recorded as M2, and the relationship is satisfied: 0.7M1≤M2≤0.9M1. If the silica gel density of the silica gel particles 10 is D1, and the magnetic induction intensity of the silica gel particles 10 is recorded as M3 when the silica gel particles 10 are at the second temperature T2, then when the volumes of the silica gel particles 10 are the same, the relationship is satisfied: M3≤0.5×M1.

[0069] Among them, the magnetism of NdFeB in the silica gel particles 10 comes from the specific arrangement of its internal electrons, which rotate around atoms and generate magnetic fields. However, this electronic arrangement is limited by temperature conditions. In a high temperature environment, electrons will deviate from the original rotation trajectory, resulting in confusion of magnetic domains (i.e., regions where electrons are arranged in an orderly manner), thereby disrupting the local magnetic field. This disorder phenomenon will weaken the magnetism of the magnet and cause demagnetization. In addition, although the silica gel particles 10 in the present application have certain high temperature resistance, at the first temperature T1, the hardness and elastic modulus of the silica gel will still change, and may even cause the adhesion between the silica gel and NdFeB to weaken, further affecting the magnetic performance of the silica gel particles 10. Therefore, the magnetism of the silica gel particles 10 of the same density at room temperature (T2) and high temperature (T1) will be different, and the magnetism of the silica gel particles 10 at room temperature will be stronger. The cold pressing process used in the present application also makes good use of the characteristics of the influence of this temperature on magnetism, avoiding the influence of temperature on the silica gel particles 10 in the hot pressing process. When the temperature is the same, if the densities of two silica gel particles 10 of the same volume are D1 (before stamping) and D2 (after stamping), the magnetism of the silica gel particles 10 before stamping is weaker than that after stamping, and is related to the density before and after stamping, because whether the silica gel particles 10 are compressed or not, the magnetism of the silica gel particles 10 is only the same as the amount of NdFeB they contain, and the distribution of NdFeB in the silica gel particles 10 formed by the granulator is usually uniform, and the amount of NdFeB in each silica gel particle 10 is equivalent. This also shows that if the compression of the silica gel particle 10 makes its density twice as high as the original density, then when compared with a silica gel particle 10 of the same volume that has not been compressed, the NdFeB content inside it is approximately equal to twice that of the latter, and the magnetic induction intensity generated by it under the same distance and conditions is also close to twice that of the former.

[0070] More preferably, the relationship is satisfied:

[0071] 300kPa≤P1≤500kPa, kPa is the pressure unit kilopascal.

[0072] Among them, the main function of the compressor to compact the silicone particles 10 with the extrusion force P1 is to ensure close contact between them and reduce gaps. This helps to improve the density and physical properties of the silicone magnet, such as strength and hardness. Through appropriate extrusion force, it can be ensured that the silicone particles 10 can be uniformly deformed during the stamping process, thereby producing silicone magnets with precise size and consistent shape. 300kPa as the lower limit ensures that the extrusion force is large enough to compact the silicone particles 10 and reduce gaps, while avoiding the degradation of the quality of the silicone magnet due to too little pressure. 500kPa as the upper limit limits the maximum value of the extrusion force, preventing the silicone particles 10 from breaking or the mold 30 from being damaged due to excessive pressure. It ensures the stability and safety of the manufacturing process. In actual production, in addition to the above-mentioned pressure range, it is also necessary to determine the specific extrusion force P1 value based on the formula of the silicone, the design of the mold 30 and the required silicone magnet performance.

[0073] More preferably, in step S30,

[0074] The third silica gel is preheated and allowed to stand after reaching the first temperature T1.

[0075] After standing, the third silica gel is sent to a granulator, where the third silica gel flows and agglomerates to form silica gel particles 10 .

[0076] The silica gel particles 10 are sent to a dryer. When the dryer is evacuated and the internal air pressure is an absolute pressure P2, the silica gel particles 10 are heated to a first temperature T1 for drying.

[0077] After drying, the silica gel particles 10 are filtered through an N-mesh standard sieve, and the silica gel particles 10 with a qualified particle size are injected into the mold 30 .

[0078] Before the third silica gel is fed into the granulator, it is first preheated. The purpose of preheating is to soften the silica gel and reduce its viscosity, so that it is easier to flow and cohere in the granulator to form particles. When the third silica gel reaches the predetermined first temperature T1, it is left to stand. The purpose of standing is to make the temperature of the silica gel evenly distributed, avoid local overheating or overcooling, and allow the silica gel molecules to have time to rearrange to a certain extent, which is beneficial to the subsequent granulation process. After the standing is completed, the third silica gel is fed into the granulator. The granulator is usually equipped with a rotating drum. In the granulator, the silica gel is dispersed by the centrifugal rotation of the rotating drum, and forms silica gel particles 10 on the adsorption surface of the granulator through mutual collision and cohesion. This process requires controlling the rotation speed of the third silica gel to ensure the size of the particles. The purpose of the dryer is to remove moisture and volatile substances in the silica gel particles 10 and improve the purity and stability of the silica gel. The silica gel particles 10 are heated to the first temperature T1 in a vacuum environment for drying. The vacuum environment helps to accelerate the evaporation and removal of moisture, while preventing the silica gel from oxidizing or decomposing at high temperatures. By drying, the moisture and volatile substances in the silica gel particles 10 are effectively removed, the density and hardness of the silica gel are improved, and good magnetic properties and physical properties are maintained. The purpose of screening is to remove oversized or undersized particles to ensure that the particle size meets the requirements of the mold 30, because the design of the mold 30 needs to take into account the fluidity and molding requirements of the silica gel to ensure the shape and size accuracy of the final product.

[0079] More preferably, the relationship is satisfied:

[0080] P2≤10Pa, Pa is the pressure unit Pa.

[0081] Among them, lowering the air pressure inside the dryer (i.e. increasing the vacuum degree) can lower the boiling point of water, thereby accelerating the evaporation of moisture and swelling agent in the silica gel particles 10. This is crucial to improving the purity of silica gel. In addition, heating the silica gel particles 10 in a vacuum environment can effectively prevent the silica gel from reacting with oxygen in the air at high temperatures, causing oxidation or decomposition. This helps to maintain the chemical stability and physical properties of the silica gel. The relationship "P2≤10Pa" sets the upper limit of the air pressure inside the dryer. This upper limit ensures that the vacuum environment is strong enough to accelerate the evaporation of moisture and prevent silica gel oxidation. At the same time, it also takes into account the equipment capacity and cost factors in actual production, avoiding the equipment complexity and cost increase caused by excessively high vacuum requirements.

[0082] More preferably, the relationship is satisfied:

[0083] 5≤N≤10.

[0084] Among them, the mesh number N of the sieve determines the maximum size of the silica gel particles 10 that can pass through the sieve. The mesh number of the standard sieve is a unit used to measure the particle size or the size of the sieve aperture, which refers to the number of mesh holes in the sieve in a length of one inch (25.4 mm). It is used to describe the density of the sieve and the maximum size of the particles that can pass through the sieve. By selecting the appropriate mesh number of the sieve, the size distribution of the silica gel particles 10 can be accurately controlled to ensure that the particle size meets the requirements of the subsequent molding and magnetization process. The size consistency of the silica gel particles 10 is crucial to the performance of the final product. Too large particles may cause uneven molding and affect the shape and dimensional accuracy of the product; while too small particles may increase the difficulty of molding and reduce production efficiency. Therefore, by controlling the mesh number N of the sieve, the size of the silica gel particles 10 can be ensured to be moderate, thereby improving the quality of the product. The appropriate mesh number N of the sieve can also optimize the production process and reduce unnecessary waste and cost.

[0085] More preferably, the relationship is satisfied:

[0086] 94.8≤Q≤95.2.

[0087] Among them, in silicone magnets, NdFeB is the main magnetic material, and its mass proportion Q has an important influence on the magnetic properties of the magnet. NdFeB is an ideal choice for preparing strong magnetic silicone magnets with its advantages of high remanence density, high coercive force and high magnetic energy product. Therefore, the value of Q directly reflects the content of NdFeB in silicone magnets, which in turn affects the magnetic properties and application effects of the magnet. Within this range, a higher content of NdFeB can ensure that the silicone magnet has excellent magnetic properties, such as higher magnetic induction intensity and magnetic energy product, thereby meeting the needs of various application scenarios.

[0088] More preferably, the relationship is satisfied:

[0089] 80℃≤T1≤160℃,

[0090] 15℃≤T2≤30℃,

[0091] 150℃≤T3≤180℃.

[0092] According to the steps S10-S50, Example 1, Example 2 and Comparative Example 1 related to the ferromagnetic silicone magnet are provided.

[0093] Embodiment 1:

[0094] The density of 5KG is 1.13-1.14g / cm 3 (i.e. the area is approximately 4400cm 3 ) is added with about 20 kg of a swelling agent, which expands the volume of the first silica gel to about 17600 cm 3, and form a 25KG solid second silica gel.

[0095] About 100 kg of NdFeB powder is added to 25 kg of the second silica gel and stirred. During the stirring process, the NdFeB powder is fully bonded to the surface of the second silica gel to form about 125 kg of a third silica gel in a solid-liquid mixed state.

[0096] Among them, NdFeB powder is prepared by melting neodymium, iron, boron and other elements into an alloy and then rapidly cooling it to form very fine grains during the solidification process, and finally crushing the grains.

[0097] In Example 2, the third silica gel is preheated in a container until the temperature in the container is 80°C as monitored by a temperature sensor, and then the heating is stopped and the container is allowed to stand. During the standing time, 48% of the swelling agent in the third silica gel is discharged. After the standing time, the fluidity of the third silica gel is enhanced and the silica gel is transported to a granulator. The granulator is a drum granulator, which is provided with a rolling drum and an adsorption surface. During the granulation process, the drum rotates continuously, and the third silica gel in the drum performs centrifugal motion and adheres to the adsorption surface. After a period of time, the third silica gel on the adsorption surface cools and solidifies into silica gel particles 10. The rotation of the granulator is stopped, and the silica gel particles 10 on the adsorption surface fall and gather at the discharge port at the bottom of the granulator.

[0098] Pour the silica gel particles 10 in the granulator into the dryer, and after closing the dryer, use a vacuum pump to extract the air in the dryer to create a vacuum environment. When the air pressure sensor detects that the internal air pressure in the dryer is less than or equal to 10Pa, control the vacuum pump to stop exhausting, and control the dryer to heat up, and start drying the silica gel particles 10 for a period of time when the temperature sensor detects that the internal temperature of the dryer is 80°C. During the drying process, about 95.38% of the remaining bulking agent in each silica gel particle 10 is discharged on average. At this time, a total of 97.6% of the bulking agent (i.e., 19.52KG) in the third silica gel is discharged twice.

[0099] After drying, the silica gel particles 10 are sieved with a 5-mesh standard sieve, and the silica gel particles 10 of qualified size are injected into the mold 30. After the silica gel particles 10 in the mold 30 are compacted and the temperature of the silica gel particles 10 reaches the room temperature of 25°C, the mold 30 moves to the punching machine 20 provided with a first punch head and a second punch head. The first punch head and the second punch head punch the compacted silica gel particles 10 in turn and form a silica gel body with an outer diameter of 500mm and an inner diameter of 350mm. The silica gel body is vulcanized at a temperature of 160°C by placing a cross-linking agent in the vulcanization mold 30. During the vulcanization process, the silica gel is chemically cross-linked with the NdFeB. After the vulcanization is completed, the silica gel body is demolded and placed in a magnetizer. After the magnetizer is powered on, the silica gel body is pulse magnetized, and finally a silica gel magnet is formed. At this time, the mass proportion of NdFeB in the silicone magnet is about 94.8%.

[0100] Comparative Example 1, preheat the third silica gel in a container until the temperature in the container is 90°C as monitored by the temperature sensor, then stop heating and let stand. During the standing time, 50% of the swelling agent in the third silica gel is discharged. After the standing, the fluidity of the third silica gel is enhanced and it is transported to a granulator. The granulator is a drum granulator, which is provided with a rolling drum and an adsorption surface. During the granulation process, the drum rotates continuously, and the third silica gel in the drum performs centrifugal motion and adheres to the adsorption surface. After a period of time, the third silica gel on the adsorption surface cools and solidifies into silica gel particles 10. Stop the rotation of the granulator, and the silica gel particles 10 on the adsorption surface fall and gather at the discharge port at the bottom of the granulator.

[0101] The silica gel particles 10 in the granulator are poured into the dryer. After the dryer is closed, the air in the dryer is extracted by a vacuum pump to create a vacuum environment. When the air pressure sensor detects that the internal air pressure in the dryer is less than or equal to 10Pa, the vacuum pump is controlled to stop extracting air, and the temperature of the dryer is controlled to rise. When the temperature sensor detects that the internal temperature of the dryer is 90°C, the silica gel particles 10 are dried for a period of time. During the drying process, about 97.4% of the remaining bulking agent in each silica gel particle 10 is discharged on average. At this time, 98.7% of the bulking agent (i.e. 19.74KG) in the third silica gel is discharged twice.

[0102] After drying, the silica gel particles 10 are sieved with a 5-mesh standard sieve, and the silica gel particles 10 of qualified size are injected into the mold 30. After the silica gel particles 10 in the mold 30 are compacted and the temperature of the silica gel particles 10 reaches the room temperature of 25°C, the mold 30 moves to the punching machine 20 provided with a first punch head and a second punch head. The first punch head and the second punch head punch the compacted silica gel particles 10 in turn and form a silica gel body with an outer diameter of 500mm and an inner diameter of 350mm. The silica gel body is vulcanized at a temperature of 170°C by placing a cross-linking agent in the vulcanization mold 30. During the vulcanization process, the silica gel is chemically cross-linked with the neodymium iron boron. After the vulcanization is completed, the silica gel body is demolded and placed in a magnetizer. After the magnetizer is powered on, the silica gel body is pulse magnetized, and finally a silica gel magnet is formed. At this time, the mass proportion of neodymium iron boron in the silicone magnet is about 95%.

[0103] In comparative example 2, the third silica gel is preheated in a container until the temperature in the container is 100° C. as monitored by a temperature sensor, and then the heating is stopped and the container is allowed to stand. During the standing time, 52% of the swelling agent in the third silica gel is discharged. After the standing time, the fluidity of the third silica gel is enhanced and the silica gel is transported to a granulator. The granulator is a drum granulator, which is provided with a tumbling drum and an adsorption surface. During the granulation process, the drum rotates continuously, and the third silica gel in the drum performs centrifugal motion and adheres to the adsorption surface. After a period of time, the third silica gel on the adsorption surface cools and solidifies into silica gel particles 10. The granulator is stopped, and the silica gel particles 10 on the adsorption surface fall and gather at the discharge port at the bottom of the granulator.

[0104] Pour the silica gel particles 10 in the granulator into the dryer, and after closing the dryer, use a vacuum pump to extract the air in the dryer to create a vacuum environment. When the air pressure sensor detects that the internal air pressure in the dryer is less than or equal to 10Pa, control the vacuum pump to stop pumping, and control the dryer to heat up, and start drying the silica gel particles 10 for a period of time when the temperature sensor detects that the internal temperature of the dryer is 100°C. During the drying process, about 99.38% of the swelling agent remaining in each silica gel particle 10 is discharged on average. At this time, a total of 99.7% of the swelling agent (i.e., 19.94KG) in the third silica gel is discharged twice.

[0105] After drying, the silica gel particles 10 are sieved with a 5-mesh standard sieve, and the silica gel particles 10 of qualified size are injected into the mold 30. After the silica gel particles 10 in the mold 30 are compacted and the temperature of the silica gel particles 10 reaches the room temperature of 25°C, the mold 30 moves to the punching machine 20 provided with a first punch head and a second punch head. The first punch head and the second punch head punch the compacted silica gel particles 10 in turn and form a silica gel body with an outer diameter of 500mm and an inner diameter of 350mm. The silica gel body is vulcanized at a temperature of 180°C by placing a cross-linking agent in the vulcanization mold 30. During the vulcanization process, the silica gel is chemically cross-linked with the NdFeB. After the vulcanization is completed, the silica gel body is demolded and placed in a magnetizer. After the magnetizer is powered on, the silica gel body is pulse magnetized, and finally a silica gel magnet is formed. At this time, the mass proportion of NdFeB in the silicone magnet is about 95.2%.

[0106] The performance of the silica gel magnets obtained in the above-mentioned Example 2, Comparative Example 1 and Comparative Example 2 was tested, and the test data are shown in Table 1.

[0107] Example 2 Comparative Example 1 Comparative Example 2 Magnetic field strength (Gs) 1213 1242 1266 Coercivity(Oe) 807 817 833 Tensile strength(MPa) 3.98 3.87 3.69

[0108] Table 1

[0109] The magnetic field intensity (Gs) was measured by a 425-model Gaussmeter from Lakeshore, Inc. The coercive force (Oe) was measured by an M-axis coercive force tester from Brockhaus, Inc. The tensile strength (MPa) was measured by a 5567-model universal material testing machine from Instron, Inc.

[0110] In this way, the silicone particles are formed by granulation and filled into the mold, so that the silicone particles have good fluidity in the mold, reducing the time for the silicone particles to fill the entire mold. By stamping the silicone particles after cooling and standing to the first temperature, the molding process of the silicone body does not need to be carried out in a hot environment, reducing the heating steps and improving production efficiency. By discharging the swelling agent in the silicone particles twice at the first temperature and vulcanizing the silicone particles to form a silicone body at the third temperature, the proportion of neodymium iron boron in the silicone magnet finally formed is increased, thereby increasing the magnetic force of the silicone magnet.

[0111] The above-mentioned 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 the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A process for preparing a flexible strong magnetic NdFeB magnet based on polymer colloidal silica, characterized in that: The process comprises the steps of: S10: adding a swelling agent to a first silica gel having a volume of V1, and the first silica gel expands to form a second silica gel having a solid state and a volume of V2, and the relationship is satisfied: V2 ≥ 4 × V1; S20: adding NdFeB powder to the second silica gel and stirring, wherein the NdFeB powder is bonded to the second silica gel, and after stirring, a third silica gel in a solid-liquid mixed state is formed; S30: granulating the third silica gel into silica gel particles, wherein the third silica gel is heated twice to a first temperature T1 during the granulation process, and the swelling agent is discharged at the first temperature T1 in sequence; S40 The silicone particles are filled into the mold and left to cool to a second temperature T2. At the second temperature T2, a first pressing head above the mold in a vertical direction and a second pressing head with a guide pin at a pressing end press the silicone particles in sequence, and the pressed silicone particles form a silicone body. S50 The silica gel is successively vulcanized at a third temperature T3 and magnetized in a magnetic field to form a silica gel magnet, in which the mass of NdFeB is Qwt.% of the mass of the silica gel magnet.

2. The process for preparing a flexible strong magnetic NdFeB magnet based on polymer colloidal silica according to claim 1, characterized in that: The shape of the silica gel body formed after stamping when viewed in the vertical direction is any one of a circle, ring, rectangle, strip, trapezoid, rhombus, triangle, ellipse, arcuate or parallelogram or a combination of multiple thereof.

3. The process for preparing a flexible strong magnetic NdFeB magnet based on polymer colloidal silica according to claim 1, characterized in that: In the step S40, Vibration is used to shake off the silicone particles in the mold, and the compressor compacts the silicone particles with a density of D1 in the mold with an extrusion force P1, and the density of the compacted silicone particles is D2, and the relationship is satisfied: D2 ≥ 2 × D1; If it is detected that the internal temperature of the mold is cooled to the second temperature T2, stamping is performed; The first punching head punches the silica gel particles to form a first punching hole; The mold is pushed forward in the horizontal direction. When the second pressing head is located directly above the first punching hole, the guide pin of the second pressing head is embedded in the first punching hole, and the second pressing head punches the silicone particles to form a second punching hole. The circular silicone body formed after punching separates from the mold along the edge of the second punching hole.

4. The process for preparing a flexible strong magnetic NdFeB magnet based on polymer colloidal silica according to claim 3, characterized in that: When the silica gel particles with a density of D2 after extrusion are at the second temperature T2, the magnetic induction intensity of the silica gel particles is recorded as M1, and when the silica gel particles are at the first temperature T1, the magnetic induction intensity of the silica gel particles is recorded as M2, and the relationship is satisfied: 0.7M1≤M2≤0.9M1; If the silica gel density of the silica gel particles is D1, and when the silica gel particles are at the second temperature T2, the magnetic induction intensity of the silica gel particles is recorded as M3, then when the volumes of the silica gel particles are the same, the relationship is satisfied: M3≤0.5×M1.

5. The process for preparing a flexible strong magnetic NdFeB magnet based on polymer colloidal silica according to claim 4, characterized in that: Satisfies the relationship: 300kPa≤P1≤500kPa, Among them, kPa is the pressure unit kilopascal.

6. The process for preparing a flexible strong magnetic NdFeB magnet based on polymer colloidal silica according to claim 1, characterized in that: In the step S30, preheating the third silica gel and allowing it to stand after reaching the first temperature T1; After the standing is completed, the third silica gel is sent to a granulator, and the third silica gel flows and agglomerates in the granulator to form silica gel particles; The silica gel particles are sent into a dryer, the dryer is evacuated, and when the internal air pressure is an absolute pressure P2, the silica gel particles are heated to a first temperature T1 for drying; After drying, the silica gel particles are filtered through an N-mesh standard sieve, and silica gel particles with a qualified particle size are injected into a mold.

7. The process for preparing a flexible strong magnetic NdFeB magnet based on polymer colloidal silica according to claim 6, characterized in that: Satisfies the relationship: P2≤10Pa, Wherein, Pa is the pressure unit Pa.

8. The process for preparing a flexible strong magnetic NdFeB magnet based on polymer colloidal silica according to claim 7, characterized in that: The relationship is satisfied: 5≤N≤10.

9. The process for preparing a flexible strong magnetic NdFeB magnet based on polymer colloidal silica according to claim 1, characterized in that: The relationship is satisfied: 94.8≤Q≤95.

2.

10. The process for preparing a flexible strong magnetic NdFeB magnet based on polymer colloidal silica according to claim 1, characterized in that: Satisfies the relationship: 80℃≤T1≤160℃， 15℃≤T2≤30℃， 150℃≤T3≤180℃。

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