A preparation process for flexible strong magnetic NdFeB magnets based on polymer silica gel

Abstract

A process for preparing a flexible, strong-magnetic NdFeB magnet based on a polymer silica gel comprises the following steps: adding a swelling agent to a first silica gel with a volume of V1, wherein the first silica gel expands to form a second silica gel in a solid state with a volume of V2, and the relationship V2≥4×V1 is satisfied; adding NdFeB powder to the second silica gel and stirring to form a third silica gel in a solid-liquid mixed state; granulating the third silica gel to form silica gel particles, wherein the third silica gel is heated to a first temperature twice during the granulation process, and the swelling agent is sequentially discharged at the first temperature; filling the silica gel particles into a mold and allowing the mold to cool to a second temperature T2, wherein a first pressing head vertically above the mold and a second pressing head with a guide pin at the punching end sequentially punch the silica gel particles, and the punched silica gel particles form a silica gel body; and the silica gel body is sequentially vulcanized and magnetized at the third temperature to form a silica gel magnet, wherein the mass of NdFeB in the silica gel magnet is 0 wt.% of the mass of the silica gel magnet.

Description

Technical Field

[0001] The present 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 widespread adoption of smartphones and the rapid development of wireless charging technology, wireless charging has become an indispensable charging method in modern life. However, in practice, most smartphones face a common problem when wirelessly charging: the battery cannot accurately align with the magnets inside the wireless charging pad, resulting in reduced charging efficiency. To solve this problem, a matching magnet is typically built into the phone, allowing it to automatically align with the magnets inside the wireless charging pad upon contact, thereby improving charging efficiency.

[0003] The above-mentioned magnets are usually made of a mixture of 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 create a key problem. The smaller the magnet, the smaller its magnetism will generally 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 require a high temperature and high pressure environment to soften the silicone and make it flow during the hot extrusion process. Since 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 a 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 colloidal silica is provided, wherein 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 volume of V2, and satisfying the relationship: V2 ≥ 4 × V1;

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

[0009] S30 granulates 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 sequentially discharged at the first temperature T1;

[0010] S40: The silicone particles are filled into the mold and allowed to cool to a second temperature T2. At the second temperature T2, a first pressing head vertically above the mold and a second pressing head with a guide pin at the pressing end sequentially press the silicone particles, and the pressed silicone particles form a silicone body.

[0011] S50 The silica gel is sequentially vulcanized at a third temperature T3 and magnetized in a magnetic field to form a silica gel magnet, wherein the mass of neodymium iron boron 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 viewed in the vertical direction is any one or a combination of circular, ring-shaped, rectangular, strip-shaped, trapezoidal, diamond-shaped, triangle, elliptical, arched 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 in the mold with a density of D1 at an extrusion force P1, and the density of the compacted silicone particles is D2, and the relationship D2 ≥ 2 × D1 is satisfied;

[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 pressure head is located directly above the first punching hole, the guide pin of the second pressure head is embedded in the first punching hole, and the second pressure 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] Wherein, if the silica gel density of the silica gel particles is D1, and 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] Here, 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 fed into a granulator, where the third silica gel flows and aggregates to form silica gel particles;

[0026] The silica gel particles are fed into a dryer, the dryer is evacuated, and when the internal pressure reaches 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 silicone particles through granulation and filling them into a mold, the silicone particles have good fluidity in the mold, reducing the time it takes to fill the entire mold. By stamping the silicone particles after cooling and allowing them to stand to a first temperature, the silicone body molding process no longer needs to be performed in a hot environment, reducing the heating step and improving production efficiency. By discharging the swelling agent from the silicone particles twice at a first temperature and vulcanizing the silicone particles to form a silicone body at a third temperature, the proportion of neodymium iron boron in the final silicone magnet is increased, thereby enhancing 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, a brief introduction will be given below to the drawings required for use in the implementation methods or the description of the prior art. 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 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 the state in which the punching machine according to 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 This is a schematic diagram of a state in which the third silicone rubber is pushed forward and the punch press punches the silicone rubber particles in the mold for the second time in one embodiment of the present application;

[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] Explanation 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] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0051] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. 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 commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are intended only to describe specific embodiments and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated 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, the method comprising the steps of:

[0054] S10 adds 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 in a solid state with a volume of V2, and the relationship: V2≥4×V1 is satisfied.

[0055] S20: adding NdFeB powder to the second silica gel and stirring. The NdFeB powder adheres 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 into 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 sequentially at the first temperature T1 .

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

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

[0059] In step S10, the expander reacts in the first silica gel with a volume of V1, generating gas that expands the first silica gel to form a second silica gel with a volume of V2 (i.e., at least four times its original volume). The expanded second silica gel has improved plasticity and filling properties, facilitating processing in subsequent steps. Furthermore, the second silica gel exhibits superior physical properties and chemical stability to the first silica gel. In step S20, NdFeB powder, a magnetic material, is evenly dispersed into the solid second silica gel. Heating and stirring the mixture form a third silica gel, a solid-liquid mixture. NdFeB is a high-performance permanent magnet with a high magnetic energy product and coercive force, making it a key raw material for producing strong magnetic silica gel magnets. Stirring ensures thorough mixing of the NdFeB powder and silica gel, paving the way for the magnetization process in subsequent steps. In step S30, the uniformly mixed third silica gel is granulated to form silica gel granules 10. During the granulation process, the silica gel is heated twice to a first temperature T1 to expel the gas and volatiles generated by the expander, ensuring the purity and stability of the silica gel granules 10. Heating also promotes the cross-linking reaction of the silicone, improving its strength and heat resistance. The granulated silicone particles 10 are easy to store and transport, facilitating the filling and stamping steps in subsequent steps. In step S40, the silicone particles 10 are filled into the mold 30 and then left to cool to a second temperature T2, which imparts a certain degree of hardness and stability to the silicone particles 10. The second temperature T2 is within the normal temperature range, which means that the stamping process does not require heating the mold 30 or the silicone particles 10 within it. This eliminates the heating step in conventional hot-pressing slicing processes and facilitates large-scale production. During the stamping process, the silicone particles 10 are sequentially stamped using a first ram 21 vertically above the mold 30 and a second ram 22 with a guide pin 22A at the stamping end. The mold 30 transports the resulting silicone material toward the stamping press 20 via a pusher mechanism. The first ram 21 first creates a small internal notch in the silicone material, which can be square, circular, or other in shape. The extruded waste is discharged through a waste pipe below the silicone material. Then, the pushing mechanism continues to push the silicone material to the bottom of the second pressure head 22, and the central axis of the guide pin 22A coincides with the central axis of the inner hole. When the second pressure head 22 punches the silicone material, the guide pin 22A is first stuck in the inner hole, and as the second pressure head 22 continues to press down, the second pressure head 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 that uses heat and pressure to crosslink silicone molecular chains, forming a stable three-dimensional network structure, thereby improving the silicone's strength and heat resistance. The vulcanized silicone is then magnetized in a magnetic field, which orients the NdFeB powder within the silicone and generates magnetism. The magnetized silicone exhibits strong magnetic properties, and its magnetic strength and quality are directly proportional to the NdFeB powder content.

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

[0061] Among them, the first pressure head 21 and the second pressure head 22 of the punching machine can be cylindrical, square and irregular (special-shaped pressure head). The silicone material (compressed silicone particles 10) in the mold 30 can be formed into silicone bodies of various shapes by its movement in the mold 30 and the linkage of the first pressure head 21 and the second pressure head 22 to punch it. For example, if the first pressure head 21 is a cylinder with a diameter of R1, the second pressure head 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 pressure head 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 pressure head 22. At this time, the inner diameter of the circular silicone body is R1, and the outer diameter is R2. Similar to the above solution, if the first pressing head 21, the second pressing head 22, and the guide pin 22A are square, then after stamping, a square silicone body or a square ring silicone body will eventually be formed. The silicone magnets in this application can be used in various fields such as electronic products, the automotive industry, home appliances, and medical devices. Therefore, the shape and size of the silicone magnets can be adjusted according to different application scenarios, and the stamping 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 in the mold 30 with a density of D1 using an extrusion force P1. The density of the compacted silica gel particles 10 is D2, and the relationship D2≥2×D1 is satisfied.

[0064] If it is detected that the internal temperature of the mold 30 has cooled to the second temperature T2, 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] After the silicone particles 10 are filled into the mold 30, they are shaken loose by vibration. This step ensures that the silicone particles 10 are evenly distributed within the mold 30, avoiding any accumulation or voids. A uniform particle distribution helps improve the density and physical properties of the silicone magnet and also helps reduce defects during the stamping process. Next, a compressor is used to apply a certain compressive force P1 to the silicone particles 10 within the mold 30 to compact the particles. This compaction process further eliminates interparticle gaps, improving the density and strength of the silicone magnet. By doubling the density, the mold 30 increases the space utilization within the mold 30 and enhances the magnetic properties of the silicone particles 10 within the same unit volume. The selection of the compressive force P1 should be determined based on the properties of the silicone and the design of the mold 30 to ensure the desired compaction effect without damaging the mold 30 or the silicone particles 10. After compaction, the mold 30 and silicone particles 10 are allowed to cool to a second temperature T2. This step allows the silicone particles 10 to stabilize within the mold 30 and reach a temperature suitable for stamping. The selection of the second temperature T2 must take into account the silicone's thermoplastic properties and the requirements of the stamping process to ensure smooth silicone deformation 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, stamping begins. First, the first punch 21 punches the silicone particles 10, forming the first punch hole. This step provides positioning and guidance for subsequent stamping. The mold 30 is then moved forward horizontally, positioning the second punch 22 directly above the first punch hole. At this point, the guide pin 22A of the second punch 22 engages in the first punch hole, providing positioning and guidance. The introduction of the guide pin 22A ensures accurate stamping by the second punch 22, avoiding issues such as dimensional inaccuracies or shape distortion in the silicone magnet due to positional deviations. Finally, the second punch 22 punches the silicone particles 10, forming the second punch hole. Simultaneously, the silicone object is released from the mold 30 along the edge of the second punch hole. This step completes the stamping process for 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. 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 particles 10 have a silica gel density of D1 and the silica gel particles 10 are at the second temperature T2, the magnetic induction intensity of the silica gel particles 10 is recorded as M3. 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 the NdFeB in the silica gel particles 10 comes from the specific arrangement of electrons inside it, which rotate around the atoms and generate a magnetic field. However, this electron arrangement is subject to temperature conditions. Under high temperature conditions, electrons will deviate from their original rotation trajectory, resulting in confusion of magnetic domains (i.e., areas where electrons are orderly arranged), thereby disrupting the local magnetic field. This confusion phenomenon will weaken the magnetism of the magnet and cause demagnetization. In addition, although the silica gel particles 10 in this 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 the 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 this application also makes good use of this characteristic of the influence of 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. This is because regardless of whether the silica gel particles 10 are compressed, the magnetism of the silica gel particles 10 is only the same as the amount of NdFeB they contain. The distribution of NdFeB within the silica gel particles 10 formed by the granulator is usually uniform, and the amount of NdFeB within each silica gel particle 10 is equivalent. This also means that if the density of the silica gel particle 10 is doubled by compressing it, then when compared with an uncompressed silica gel particle 10 of the same volume, the NdFeB content within it is approximately twice that of the latter, and the magnetic induction intensity it generates under the same distance and conditions is also nearly 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 silicone magnet quality 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 performance of the silicone magnet.

[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 the standing is completed, the third silica gel is sent to a granulator, where the third silica gel flows and aggregates to form silica gel particles 10 .

[0076] The silica gel particles 10 are fed into a dryer. When the dryer is evacuated and the internal pressure reaches 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 silica gel particles 10 with a qualified particle size are injected into the mold 30 .

[0078] Before entering the granulator, the third silica gel is preheated. This preheating softens the silica gel and reduces its viscosity, making it easier to flow and aggregate into granules within the granulator. After reaching a predetermined first temperature T1, the third silica gel is allowed to rest. This resting period ensures uniform temperature distribution across the silica gel, preventing local overheating or overcooling. It also allows time for the silica gel molecules to rearrange, facilitating the subsequent granulation process. After the resting period, the third silica gel is fed into the granulator. Granulators are typically equipped with a rotating drum. Within the granulator, the silica gel is dispersed by the centrifugal force of the drum. Through collision and aggregation, it forms silica gel particles 10 on the adsorption surface of the granulator. This process requires controlling the rotation speed of the third silica gel to ensure consistent particle size. The dryer removes moisture and volatile substances from the silica gel particles 10, enhancing their purity and stability. The silica gel particles 10 are dried by heating them to the first temperature T1 under a vacuum environment. The vacuum environment accelerates the evaporation and removal of moisture while preventing oxidation or decomposition of the silica gel at high temperatures. Drying effectively removes moisture and volatile substances from silica gel particles 10, improving the density and hardness of the silica gel while maintaining good magnetic and physical properties. The purpose of screening is to remove oversized and undersized particles to ensure that the particle size meets the requirements of mold 30. The design of mold 30 must take into account the fluidity and molding requirements of the silica gel to ensure the shape and dimensional 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 for 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 capabilities and cost factors in actual production, avoiding the equipment complexity and cost increase brought about by excessively high vacuum requirements.

[0082] More preferably, the relationship is satisfied:

[0083] 5≤N≤10.

[0084] 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 a standard sieve is a unit used to measure particle size or sieve aperture size. It refers to the number of mesh holes in the sieve per one inch (25.4 mm) in length. 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, the size distribution of the silica gel particles 10 can be precisely controlled, ensuring that the particle size meets the requirements of the subsequent molding and magnetization processes. The size consistency of the silica gel particles 10 is crucial to the performance of the final product. Oversized particles can lead to uneven molding, affecting the shape and dimensional accuracy of the product; while undersized particles can increase molding difficulty and reduce production efficiency. Therefore, by controlling the mesh number N of the sieve, the appropriate size of the silica gel particles 10 can be ensured, thereby improving product quality. The appropriate mesh number N can also optimize the production process and reduce unnecessary waste and costs.

[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 ratio Q has a significant impact on the magnetic properties of the magnet. NdFeB, with its advantages of high remanence density, high coercivity, and high magnetic energy product, is an ideal choice for preparing strong magnetic silicone magnets. Therefore, the value of Q directly reflects the NdFeB content in the silicone magnet, which in turn affects the magnetic properties and application effects of the magnet. Within this range, a higher NdFeB content can ensure that the silicone magnet has excellent magnetic properties, such as high magnetic induction intensity and magnetic energy product, thus 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] Example 1:

[0094] The density of 5KG is 1.13-1.14g / cm 3 (i.e. an area of ​​approximately 4400cm 3 ) is added with about 20 kg of a swelling agent to expand 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 was added to 25 kg of the second silica gel and stirred. During the stirring process, the NdFeB powder was 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, a third silica gel is preheated in a container until the temperature inside the container reaches 80°C as monitored by a temperature sensor. Heating is then stopped and the container is allowed to stand. During the standing period, 48% of the swelling agent in the third silica gel is discharged. After the standing period, the fluidity of the third silica gel increases and the silica gel is conveyed to a granulator. The granulator is a drum granulator equipped with a tumbling drum and an adsorption surface. During the granulation process, the drum continuously rotates, causing the third silica gel in the drum to undergo centrifugal motion and adhere 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 converge at the discharge port at the bottom of the granulator.

[0098] The silica gel granules 10 in the granulator are poured into the dryer. After the dryer is sealed, a vacuum pump is used to evacuate the air inside the dryer to create a vacuum environment. When the pressure sensor detects that the internal pressure in the dryer is less than or equal to 10 Pa, the vacuum pump is controlled to stop exhausting air and the dryer is controlled to increase its temperature. When the temperature sensor detects that the internal temperature of the dryer reaches 80°C, the silica gel granules 10 are dried for a period of time. During the drying process, approximately 95.38% of the remaining swelling agent in each silica gel granule 10 is discharged on average. At this time, a total of 97.6% of the swelling agent in the third silica gel (i.e., 19.52 kg) is discharged in two steps.

[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 room temperature of 25°C, the mold 30 moves to a punching machine 20 equipped with a first punching head and a second punching head. The first punching head and the second punching 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 placed in a cross-linking agent in the vulcanization mold 30 and vulcanized at a temperature of 160°C. During the vulcanization process, the silica gel and the neodymium iron boron are chemically cross-linked. 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 approximately 94.8%.

[0100] In Comparative Example 1, a third silica gel was preheated in a container until the temperature inside the container reached 90°C as monitored by a temperature sensor. Heating was then stopped and the container was allowed to stand. During the standing period, 50% of the swelling agent in the third silica gel was discharged. After the standing period, the fluidity of the third silica gel increased and the silica gel was conveyed to a granulator. The granulator was a drum granulator equipped with a tumbling drum and an adsorption surface. During the granulation process, the drum continuously rotated, causing the third silica gel in the drum to undergo centrifugal motion and adhere to the adsorption surface. After a period of time, the third silica gel on the adsorption surface cooled and solidified into silica gel particles 10. The granulator was stopped, and the silica gel particles 10 on the adsorption surface fell and gathered at the discharge port at the bottom of the granulator.

[0101] The silica gel granules 10 in the granulator are poured into the dryer. After the dryer is sealed, a vacuum pump is used to evacuate the air inside the dryer to create a vacuum environment. When the pressure sensor detects that the internal pressure in the dryer is less than or equal to 10 Pa, the vacuum pump is controlled to stop exhausting air and the dryer is controlled to increase its temperature. When the temperature sensor detects that the internal temperature of the dryer reaches 90°C, the silica gel granules 10 are dried for a period of time. During the drying process, approximately 97.4% of the remaining swelling agent in each silica gel granule 10 is evenly discharged. At this time, a total of 98.7% of the swelling agent in the third silica gel (i.e., 19.74 kg) has been discharged in two times.

[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 room temperature of 25°C, the mold 30 moves to a punching machine 20 provided with a first punching head and a second punching head. The first punching head and the second punching 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 placed in a cross-linking agent in the vulcanization mold 30 and vulcanized at a temperature of 170°C. During the vulcanization process, the silica gel and the neodymium iron boron are chemically cross-linked. 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, a third silica gel was preheated in a container until the temperature inside the container reached 100°C as monitored by a temperature sensor. Heating was then stopped and the container was allowed to stand. During the standing period, 52% of the swelling agent in the third silica gel was discharged. After the standing period, the fluidity of the third silica gel increased and the silica gel was conveyed to a granulator. The granulator was a drum granulator equipped with a tumbling drum and an adsorption surface. During the granulation process, the drum continuously rotated, causing the third silica gel in the drum to undergo centrifugal motion and adhere to the adsorption surface. After a period of time, the third silica gel on the adsorption surface cooled and solidified into silica gel particles 10. The granulator was stopped, and the silica gel particles 10 on the adsorption surface fell and gathered at the discharge port at the bottom of the granulator.

[0104] The silica gel granules 10 in the granulator are poured into the dryer. After the dryer is sealed, a vacuum pump is used to evacuate the air inside the dryer to create a vacuum environment. When the pressure sensor detects that the internal pressure in the dryer is less than or equal to 10 Pa, the vacuum pump is controlled to stop evacuating air and the dryer is controlled to increase its temperature. When the temperature sensor detects that the internal temperature of the dryer reaches 100°C, the silica gel granules 10 are dried for a period of time. During the drying process, approximately 99.38% of the remaining swelling agent in each silica gel granule 10 is discharged on average. At this time, a total of 99.7% of the swelling agent in the third silica gel (i.e., 19.94 kg) is discharged in two steps.

[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 room temperature of 25°C, the mold 30 moves to a punching machine 20 equipped with a first punching head and a second punching head. The first punching head and the second punching 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 placed in a cross-linking agent in the vulcanization mold 30 and vulcanized at a temperature of 180°C. During the vulcanization process, the silica gel and the neodymium iron boron are chemically cross-linked. 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 approximately 95.2%.

[0106] The performance of the silicone magnets obtained in 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 strength (Gs) was measured using a Lakeshore Model 425 Gaussmeter. The coercive force (Oe) was measured using a Brockhaus Model M-axis coercive force tester. The tensile strength (MPa) was measured using an Instron Model 5567 universal testing machine.

[0110] In this way, the silicone particles are formed by granulation and filled into the mold, making the silicone particles have good fluidity in the mold, reducing the time it takes for the silicone particles to fill the entire mold. By stamping the silicone particles after cooling and standing to the first temperature, the silicone body molding process 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 final silicone magnet is increased, thereby increasing the magnetic force of the silicone magnet.

[0111] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the scope of the present application, and all such modifications and improvements fall within the scope of protection of the present application.

Claims

1. A process for preparing a flexible strong magnetic NdFeB magnet based on polymer silica gel, 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 volume of V2, and satisfying the relationship: V2 ≥ 4 × V1; S20: adding NdFeB powder to the second silica gel and stirring; the NdFeB powder adheres to the second silica gel, and after stirring, a third silica gel in a solid-liquid mixed state is formed; S30 granulates 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 sequentially discharged at the first temperature T1; S40: The silicone particles are filled into the mold and allowed to cool to a second temperature T2. At the second temperature T2, a first pressing head located vertically above the mold and a second pressing head provided with a guide pin at the pressing end sequentially press the silicone particles, and the pressed silicone particles form a silicone body. The first pressing head presses the silicone particles to form a first punching hole. The mold is advanced 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. The second pressing head presses the silicone particles to form a second punching hole. The annular silicone body formed after the punching separates from the mold along the edge of the second punching hole. S50 The silica gel is sequentially vulcanized at a third temperature T3 and magnetized in a magnetic field to form a silica gel magnet, wherein the mass of neodymium iron boron in the silica gel magnet 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 silicone body formed after stamping when viewed in the vertical direction is any one of a circle, annulus, rectangle, strip, trapezoid, rhombus, triangle, ellipse, arch 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 in the mold with a density of D1 at an extrusion force P1, and the density of the compacted silicone particles is D2, and the relationship D2 ≥ 2 × D1 is satisfied; If it is detected that the internal temperature of the mold is cooled to the second temperature T2, stamping is performed; the annular silicone body is a circular silicone body.

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; Wherein, if the silica gel density of the silica gel particles is D1, and 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, Here, 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 fed into a granulator, where the third silica gel flows and aggregates to form silica gel particles; The silica gel particles are fed into a dryer, the dryer is evacuated, and when the internal pressure reaches 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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