Rubber magnet with asymmetric magnetic field intensities on front and back sides and preparation method thereof

Abstract

The invention discloses a rubber magnet with asymmetric magnetic field intensities on front and back sides and a preparation method thereof. The rubber magnet comprises an anisotropic magnet layer and an isotropic magnet layer which are bonded together, the surface magnetic field intensity of the anisotropic magnet layer is more than 10 times that of the isotropic magnet layer, and N and S magnetic poles are alternately distributed on the surface of the anisotropic magnet layer. The anisotropic magnetic layer and the isotropic magnetic layer are bonded together at a high temperature and are magnetized by a special magnetic circuit, so that the composite rubber magnet with asymmetric magnetic field intensities on the front side and the back side is prepared. The strong magnetic field side can be used for directional adsorption, the weak magnetic field side can reduce interference to the environment, and the prepared composite rubber magnet has the characteristic of local magnetic field enhancement.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of rubber magnets, and particularly relates to a rubber magnet with asymmetric magnetic field intensity on the front and back surfaces. BACKGROUND

[0002] A rubber magnetic material is a kind of magnet with softness, elasticity and twistability, which is made of magnetic powder (such as ferrite, neodymium iron boron, etc.) and rubber matrix through extrusion molding, calendering molding, injection molding and other processes, and can be widely applied to the fields of refrigerators, kitchen cabinets, toys, stationery, advertising, etc. The rubber magnetic material can be divided into isotropic and anisotropic types according to the orientation degree of the magnetic powder: the easy magnetization direction (c-axis) of the anisotropic magnetic powder is oriented in the same direction (as shown in (a)), and after single or multi-pole magnetization, two kinds of magnetic circuits (as shown in (b) and (c)) can be formed, and the rubber magnet prepared therefrom has strong magnetic properties, but the strong magnetic field can cause electromagnetic interference to the surrounding electronic elements, and long-term contact can also have potential impact on human health; the c-axis of the isotropic magnetic powder is oriented in disorder (as shown in (a)), and after single or multi-pole magnetization, three kinds of magnetic circuits (as shown in (b), (c) and (d)) can be formed, and the rubber magnet prepared therefrom has low magnetic properties, and the weak magnetic characteristics make the adsorption force small, so it is safer to be applied to children's toys and stationery. Figure 1 Figure 1 Figure 1 Figure 2 Figure 2 Figure 2 Figure 2

[0003] However, in special application fields such as magnetic teaching aids and wearable devices, it is often necessary to use rubber magnetic materials with asymmetric magnetic field distribution, i.e., one side is strong in magnetism and the other side is weak in magnetism. If anisotropic rubber magnets are used, although high magnetic properties can be achieved on one side, the magnetism on the other side is also strong, which is difficult to meet the requirement of magnetic field distribution of "one strong and one weak"; and when isotropic rubber magnets are used, although the magnetic field distribution of "one strong and one weak" can be achieved according to the orientation of the magnetic powder, the magnetic properties of the strong magnetic side are not strong enough to meet the application requirement of strong adsorption. Figure 2 SUMMARY

[0004] Therefore, the present application provides a rubber magnet with asymmetric magnetic field intensity on the front and back surfaces and a preparation method thereof, so as to solve the problems in the background art. By high-temperature bonding of the anisotropic magnetic layer and the isotropic magnetic layer, there is an obvious gradient change from the strong magnetic field side to the weak magnetic field side of the composite rubber magnet, the strong magnetic field side can be used for directional adsorption, and the weak magnetic field side can reduce the interference to the environment, has the characteristics of local magnetic field enhancement, and meets the application requirement of strong adsorption.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme:​​​​​​​​

[0006] In a first aspect, the application discloses a rubber magnet with asymmetric magnetic field intensity on both sides, comprising an anisotropic magnet layer and an isotropic magnet layer which are bonded together; the surface magnetic field intensity of the anisotropic magnet layer is more than 10 times that of the isotropic magnet layer, and N and S magnetic poles are alternately distributed on the surfaces of the anisotropic magnet layer and the isotropic magnet layer.

[0007] As a further scheme of the application, the thickness of the anisotropic magnet layer is 0.8-1.5 mm, and the thickness of the isotropic magnet layer is 0.3-0.6 mm.

[0008] As a further scheme of the application, the anisotropic magnet layer and the isotropic magnet layer are both prepared from magnetic powder, thermoplastic material and rubber additives according to a mass ratio of (3-10):1:(0.1-0.3).

[0009] As a further scheme of the application, the magnetic powder is neodymium-iron-boron magnetic powder or ferrite magnetic powder.

[0010] As a further scheme of the application, the thermoplastic material is at least one of TPU, TPE and TRO.

[0011] As a further scheme of the application, the rubber additives are composed of stearic acid, zinc oxide, accelerator M and plasticizer, and the mass ratio of the stearic acid, zinc oxide, accelerator M, plasticizer and thermoplastic material is (1-4):(1-4):(1-3):(0.5-5):100.

[0012] In a second aspect, the application discloses a preparation method of the rubber magnet with asymmetric magnetic field intensity on both sides, comprising the following steps:

[0013] (1) Anisotropic magnet layer preparation: anisotropic neodymium-iron-boron magnetic powder, thermoplastic material and rubber additives are mixed to obtain a mixed rubber; the mixed rubber is subjected to calendering and cooling solidification to obtain the anisotropic magnet layer; wherein the pressure of the calendering is 6-15 MPa, and the temperature is 140-180 DEG C.

[0014] (2) Isotropic magnet layer preparation: isotropic neodymium-iron-boron magnetic powder or isotropic ferrite powder, thermoplastic material and rubber additives are mixed to obtain a mixed rubber; the mixed rubber is subjected to calendering and cooling solidification to obtain the isotropic magnet layer; wherein the pressure of the calendering is 6-15 MPa, and the temperature is 140-180 DEG C.

[0015] (3) Composite: stack the anisotropic magnet layer and the isotropic magnet layer, composite under the condition of ≥2T magnetic field and 90-110℃, 3-6MPa, form the magnetic sheet M with the anisotropic magnet layer side orientation direction parallel to the magnetic sheet normal direction;

[0016] (4) Single-sided multi-pole magnetization: single-sided multi-pole magnetization is performed on the magnetic sheet M, current I1 is applied to the anisotropic magnet layer side, and current I2 is applied to the isotropic magnet layer side; wherein I1>I2, and the magnetization voltage is 1500-1800V.

[0017] In a third aspect, the application discloses a preparation method of the rubber magnet with asymmetric magnetic field strength on the front and back surfaces, and the method comprises the following steps:

[0018] (1) Anisotropic magnet layer preparation: anisotropic neodymium-iron-boron magnetic powder, thermoplastic material and rubber auxiliary agent are mixed to obtain a mixed rubber; the mixed rubber is formed by calendering under the condition of ≥2T magnetic field and is cooled and solidified, so that the anisotropic magnet layer with the orientation direction parallel to the magnetic sheet normal direction is obtained; wherein the pressure of the calendering is 6-15MPa, and the temperature is 140-180℃.

[0019] (2) Isotropic magnet layer preparation: isotropic neodymium-iron-boron magnetic powder or isotropic ferrite powder, thermoplastic material and rubber auxiliary agent are mixed to obtain a mixed rubber; the mixed rubber is formed by calendering and is cooled and solidified, so that the isotropic magnet layer is obtained; wherein the pressure of the calendering is 6-15MPa, and the temperature is 140-180℃.

[0020] (3) Composite: stack the anisotropic magnet layer and the isotropic magnet layer, composite under the condition of 90-110℃, 3-6MPa, form the composite magnetic sheet M;

[0021] (4) Single-sided multi-pole magnetization: single-sided multi-pole magnetization is performed on the composite magnetic sheet M: current I1 is applied to the anisotropic magnet layer side, and current I2 is applied to the isotropic magnet layer side; wherein I1>I2, and the magnetization voltage is 1500-1800V.

[0022] Further, I1≥3000A, and I2≤1000A.

[0023] In a fourth aspect, the application discloses an application of the rubber magnet with asymmetric magnetic field strength on the front and back surfaces in a magnetic teaching aid and a wearable device.

[0024] Compared with the prior art, the application has the following beneficial effects:

[0025] The rubber magnet with asymmetric magnetic field strength on both sides of the invention realizes the asymmetric distribution of the magnetic field strength by compounding the anisotropic magnet layer and the isotropic magnet layer, ensures that the anisotropic magnet layer obtains higher magnetization strength, while maintaining the low magnetic field characteristics of the isotropic magnet layer. The strong magnetic surface has significant adsorption force, and the weak magnetic surface effectively reduces the electromagnetic interference on the surrounding environment, meets the differentiated needs of the magnetic field directionality and strength in specific applications, and is particularly suitable for magnetic teaching aids, wearable devices and other scenes with high requirements for magnetic field control.

[0026] In addition, the invention adopts conventional rubber magnetic preparation process, combined with simple magnetic sheet stacking and magnetizing technology, not only reduces the production cost, but also improves the preparation efficiency, has good practicability and popularization value. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 For the orientation and magnetizing mode of the anisotropic magnetic powder in the background art, Fig. (a) is the orientation of the anisotropic magnetic powder, Fig. (b) is a single-pole magnetizing mode, and Fig. (c) is a multi-pole magnetizing mode schematic diagram;

[0028] Figure 2 For the orientation and magnetizing mode of the isotropic magnetic powder in the background art, Fig. (a) is the orientation of the anisotropic magnetic powder, Fig. (b) is a single-pole magnetizing mode, and Fig. (c) is a multi-pole magnetizing mode schematic diagram, and Fig. (d) is a multi-pole magnetizing mode schematic diagram;

[0029] Figure 3 For the magnetic circuit schematic diagram of the anisotropic magnet and the isotropic magnet in the composite rubber magnet of the invention;

[0030] Figure 4 For the magnetizing mode schematic diagram of the composite rubber magnet of the invention;

[0031] Figure 5 For the rubber magnetic structure schematic diagram of the embodiment (a) and the comparative example 1 (b), the comparative example 2 (c) of the invention. DETAILED DESCRIPTION

[0032] In order to facilitate the understanding of the invention, the invention will be described more fully below with specific embodiments. However, the invention can be realized 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 disclosure of the invention more thorough and comprehensive.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. The terms used in the specification of the invention herein are only for the purpose of describing the specific embodiments and are not intended to limit the invention.

[0034] Example 1

[0035] (1) Anisotropic magnet sheet preparation: 800g of anisotropic neodymium-iron-boron magnetic powder (RE x (Fe 1-a , M a ) 100-x-y B y , RE is a rare earth element, content x is 28.5wt.%-31.5wt.%; B is a boron element, content y is 0.9wt.%-1wt.%, M is at least one of Ga, Ti, Cu, Al and Co, the total amount a does not exceed 2wt.%, and the balance is Fe and unavoidable impurities) and 80g of TPE are mixed on an open mill, then 2g of stearic acid, 3g of zinc oxide, 2g of accelerator M, and 4g of plasticizer dioctyl phthalate are added in turn, and the mixing is continued until uniform, and the sheet is discharged to obtain a rubber compound. The rubber compound is calendered, the molding pressure is 15MPa, and the temperature is 160℃. After cooling and solidification, an anisotropic magnet sheet M1 with a thickness of 0.9mm is obtained.

[0036] (2) Isotropic magnet sheet preparation: 800g of isotropic neodymium-iron-boron magnetic powder (same composition as step (1)) and 80g of TPE are mixed, calendered, molded, and cooled and solidified to obtain an isotropic magnet sheet M2 with a thickness of 0.5mm. The rubber additives, the amount of the ingredients, and the hot-pressing molding process parameters are the same as in step (1).

[0037] (3) Compound: The magnet sheets M1 and M2 are stacked, the magnetic sheet is heated to 110℃, the adhesive TPE is softened and has a certain viscosity, and at the same time, a pressure of 5MPa is applied, the two rubber magnets are bonded to form a composite magnetic sheet M3; after 15min of temperature maintenance, a strong magnetic field of 2T is applied, and a composite magnetic sheet M3 is obtained, in which the orientation direction of the magnet sheet M1 is parallel to the normal direction of the magnetic sheet;

[0038] (4) Magnetization: The composite magnetic sheet M3 is single-sided multi-pole magnetized at a voltage of 1500V, a strong current of 3000A is applied to one side of the magnet sheet M1, and a weak current of 1000A is applied to one side of the M2 magnetic sheet, and a rubber magnet with asymmetric magnetic field strength on the opposite sides is obtained.

[0039] Example 2

[0040] (1) Anisotropic magnet sheet preparation: Take 800g of anisotropic neodymium-iron-boron magnetic powder (same composition as step (1) of Example 1) and 80g of TPE and perform open mill blending on an open mill. Then, add stearic acid 2g, zinc oxide 3g, accelerator M2 2g, and plasticizer dioctyl phthalate 4g in sequence, continue to mix uniformly, and sheet out to obtain a rubber compound. The rubber compound is calendered under a 2T magnetic field, with a forming pressure of 15MPa and a temperature of 160°C. After cooling and solidification, an anisotropic magnet sheet M1 with a thickness of 0.8mm is obtained.

[0041] (2) Isotropic magnet sheet preparation: Take 800g of isotropic neodymium-iron-boron magnetic powder (same composition as step (1) of Example 1) and 80g of TPE, and after mixing, calendering, and cooling and solidification, an isotropic magnet sheet M2 with a thickness of 0.3mm is obtained. The rubber additives, dosages, and hot-pressing process parameters are the same as in step (1).

[0042] (3) Compound: Heat the magnetic sheets to 100°C, so that the TPE in the magnetic sheets softens and has a certain viscosity, and at the same time, apply a pressure of 6MPa to make the two rubber magnets adhere to form a compound magnetic sheet M3;

[0043] (4) Single-sided multi-pole magnetization: The compound magnetic sheet M3 is single-sided multi-pole magnetized at a voltage of 1800V, with a strong current of 3000A applied to one side of the magnet sheet M1 and a weak current of 1000A applied to one side of the M2 magnetic sheet, obtaining a rubber magnet with asymmetric magnetic field strength on the front and back sides.

[0044] Example 3

[0045] (1) Anisotropic magnet sheet preparation: Take 800g of anisotropic neodymium-iron-boron magnetic powder (same composition as step (1) of Example 1) and 80g of TPE and perform open mill blending on an open mill. Then, add stearic acid 2g, zinc oxide 3g, accelerator M2 2g, and plasticizer dioctyl phthalate 4g in sequence, continue to mix uniformly, and sheet out to obtain a rubber compound. The rubber compound is calendered, and the hot-pressing pressure is 15MPa and the temperature is 160°C. After cooling and solidification, an anisotropic magnet sheet M1 with a thickness of 1.5mm is obtained.

[0046] (2) Isotropic magnet sheet preparation: Take 800g of isotropic neodymium-iron-boron magnetic powder (same composition as step (1) of Example 1) and 80g of TPE, and after mixing, calendering, and cooling and solidification, an isotropic magnet sheet M2 with a thickness of 0.6mm is obtained. The rubber additives, dosages, and hot-pressing process parameters are the same as in step (1).

[0047] (3) Compound: superimpose the magnet pieces M1 and M2, heat the magnetic pieces to 100°C, soften and make the adhesive TPE have certain viscosity, and at the same time, apply 3Mpa pressure to make the two pieces of rubber magnet adhere to form a compound magnetic piece M3; after 15 minutes of temperature preservation, apply a strong magnetic field of 2T to obtain the compound magnetic piece M3 with the orientation direction of the magnet piece M1 side parallel to the normal direction of the magnetic piece.

[0048] (4) Single-sided multi-pole magnetization: single-sided multi-pole magnetize the compound magnetic piece M3 with a voltage of 1600V, apply a strong current of 3500A to one side of the magnet piece M1, and apply a weak current of 1200A to one side of the M2 magnetic piece, to obtain a rubber magnet with asymmetric magnetic field strength on the front and back sides.

[0049] Example 4

[0050] (1) Anisotropic magnet piece preparation: take 800g of anisotropic neodymium-iron-boron magnetic powder (same composition as step (1) of Example 1) and 80g of TPE on an open mill for open mill blending, then add stearic acid 2g, zinc oxide 3g, accelerator M2g, plasticizer dioctyl phthalate 4g in turn, continue to mix uniformly, and then take out the sheet to obtain a rubber compound. The rubber compound is calendered and hot-pressed at a pressure of 15MPa and a temperature of 160°C. After cooling and solidification, an anisotropic magnet piece M1 with a thickness of 0.9mm is obtained.

[0051] (2) Isotropic magnet piece preparation: take 800g of isotropic neodymium-iron-boron magnetic powder (same composition as step (1) of Example 1) and 80g of TPE, and after mixing, calendering, and cooling and solidification, an isotropic magnet piece M2 with a thickness of 0.5mm is obtained. The amounts of rubber additives, feed, and hot-pressing process parameters are the same as step (1).

[0052] (3) Compound: superimpose the magnet pieces M1 and M2, heat the magnetic pieces to 100°C, soften and make the adhesive TPE have certain viscosity, and at the same time, apply 3Mpa pressure to make the two pieces of rubber magnet adhere to form a compound magnetic piece M3; after 15 minutes of temperature preservation, apply a strong magnetic field of 2T to obtain the compound magnetic piece M3 with the orientation direction of the magnet piece M1 side parallel to the normal direction of the magnetic piece.

[0053] (4) Single-sided multi-pole magnetization: single-sided multi-pole magnetize the compound magnetic piece M3 with a voltage of 1600V, apply a strong current of 3500A to one side of the magnet piece M1, and apply a weak current of 1200A to one side of the M2 magnetic piece, to obtain a rubber magnet with asymmetric magnetic field strength on the front and back sides.

[0054] Example 5

[0055] (1) Anisotropic magnet sheet preparation: 800 g of anisotropic neodymium-iron-boron magnetic powder (same composition as in step (1) of Example 1) and 80 g of TPE were mixed on an open mill, then 2 g of stearic acid, 3 g of zinc oxide, 2 g of accelerator M, and 4 g of plasticizer dioctyl phthalate were added in sequence, and the mixture was uniformly mixed and sheeted to obtain a rubber compound. The rubber compound was calendered, and the pressure was 15 MPa and the temperature was 160°C during hot pressing. After cooling and solidification, an anisotropic magnet sheet M1 with a thickness of 0.9 mm was obtained.

[0056] (2) Isotropic magnet sheet preparation: 800 g of isotropic ferrite magnetic powder (same composition as in step (1)) and 80 g of TPE were mixed and calendered, and after cooling and solidification, an isotropic magnet sheet M2 with a thickness of 0.5 mm was obtained. The rubber additives, the amounts of the materials, and the hot pressing process parameters were the same as in step (1).

[0057] (3) Compound: The magnet sheets M1 and M2 were stacked, and the magnetic sheets were heated to 110°C to soften the adhesive TPE and make it sticky, and at the same time, a pressure of 5 MPa was applied to make the two rubber magnets adhere to form a composite magnetic sheet M3. After 15 minutes of temperature maintenance, a strong magnetic field of 2T was applied to obtain a composite magnetic sheet M3 with the orientation direction of the magnet sheet M1 being parallel to the normal direction of the magnetic sheet.

[0058] (4) Magnetization: The composite magnetic sheet M3 was single-sidedly and multi-pole magnetized at a voltage of 1500V, and a strong current of 3000A was applied to one side of the magnet sheet M1, and a weak current of 1000A was applied to one side of the M2 magnetic sheet, to obtain a rubber magnet with asymmetric magnetic field strength on the opposite sides.

[0059] Comparative Example 1

[0060] 800 g of anisotropic neodymium-iron-boron magnetic powder (same composition as in step (1) of Example 1) and 80 g of TPE were mixed on an open mill, then 2 g of stearic acid, 3 g of zinc oxide, 2 g of accelerator M, and 4 g of plasticizer dioctyl phthalate were added in sequence, and the mixture was uniformly mixed and sheeted to obtain a rubber compound. The rubber compound was calendered, and the pressure was 15 MPa and the temperature was 160°C during hot pressing. After cooling and solidification, an anisotropic magnet sheet M1 with a thickness of 1.4 mm was obtained.

[0061] A strong magnetic field of 2T was applied to the magnetic sheet to obtain an anisotropic magnet sheet M1' with the orientation direction parallel to the normal direction of the magnetic sheet. The magnetic sheet M3 was single-sidedly and multi-pole magnetized at a voltage of 1500V and a current of 3000A, to obtain a rubber magnet with the same magnetic field strength on the opposite sides and strong magnetism.

[0062] Comparative Example 2

[0063] Take 800 g isotropic Nd-Fe-B magnetic powder (the same composition as step (1) of Example 1) and 80 g TPE on an open mill for open mill blending, then add stearic acid 2 g, zinc oxide 3 g, accelerator M 2 g, plasticizer dioctyl phthalate 4 g in turn, continue to mix uniformly, sheet out, get the rubber compound. The rubber compound is calendered and molded, the pressure is 15 MPa and the temperature is 160°C during hot pressing. After cooling and curing, an isotropic magnetic sheet M2' with a thickness of 1.4 mm is obtained.

[0064] The magnetic sheet M3 is single-sided multipole magnetized by applying a voltage of 1500V, a strong current of 3000A on one side and a weak current of 1000A on the other side, obtaining a rubber magnet with slightly different magnetic field strengths on the front and back sides, but with weaker magnetism.

[0065] Comparative Example 3

[0066] Take 800 g anisotropic ferrite magnetic powder (the same composition as step (1) of Example 1) and 80 g TPE on an open mill for open mill blending, then add stearic acid 2 g, zinc oxide 3 g, accelerator M 2 g, plasticizer dioctyl phthalate 4 g in turn, continue to mix uniformly, sheet out, get the rubber compound. The rubber compound is calendered and molded, the pressure is 15 MPa and the temperature is 160°C during hot pressing. After cooling and curing, an anisotropic magnetic sheet M2' with a thickness of 1.4 mm is obtained.

[0067] The composite magnetic sheet M3 is single-sided multipole magnetized by applying a voltage of 1500V and a current of 3000A, obtaining a rubber magnet with the same magnetic field strength on the front and back sides, and slightly stronger magnetism.

[0068] Comparative Example 4

[0069] Take 800 g isotropic ferrite magnetic powder (the same composition as step (1) of Example 1) and 80 g TPE on an open mill for open mill blending, then add stearic acid 2 g, zinc oxide 3 g, accelerator M 2 g, plasticizer dioctyl phthalate 4 g in turn, continue to mix uniformly, sheet out, get the rubber compound. The rubber compound is calendered and molded, the pressure is 15 MPa and the temperature is 160°C during hot pressing. After cooling and curing, an isotropic magnetic sheet M2' with a thickness of 1.4 mm is obtained.

[0070] The magnetic sheet M3 is single-sided multipole magnetized by applying a voltage of 1500V, a strong current of 3000A on one side and a weak current of 1000A on the other side, obtaining a rubber magnet with slightly different magnetic field strengths on the front and back sides, but with very weak magnetism.

[0071] Anisotropic magnetic sheet M1 and isotropic magnetic sheet M2 were prepared according to the same raw materials and process parameters of Example 1, only the thickness of the finally obtained magnetic sheet was changed: M1' and M2' magnetic sheets with a thickness of 1.4 mm, as required in Example 1.

[0072] The adhesion and surface magnetism of the A and B sides of the magnetic sheets of Examples 1-5 and Comparative Examples 1-4 were compared, and the sample schematic diagram is shown in Figure 4 The test results are shown in Table 1. The same size rubber magnetic sheet was taken, a tension meter with an accuracy of ±1% was used to record the adhesion force (F), the sliding force of the magnetic sheet was measured by horizontally pulling the magnetic sheet, the constant loading speed was 5 mm / min, each magnetic sheet was repeatedly tested 3 times, and the average value was taken, and the results are shown in Table 1. At the same time, the magnetic field intensity of the surface of the magnetic sheet of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 was tested according to the requirements of GB / T 43264 Permanent Magnet Surface Magnetic Field Distribution Test Method, and the results are shown in Table 1.

[0073] Table 1

[0074]

[0075] From the data comparison in Table 1, it can be found that the uneven distribution of the magnetic field of the rubber magnet can be significantly changed by using the technology of the present application: the adhesion and surface magnetic field intensity of the A side of the magnetic sheet obtained by Examples 1-5 are larger, and the adhesion and surface magnetic field intensity of the B side are smaller; the adhesion of both sides of Comparative Example 1 is very strong, the adhesion of the A side of Comparative Example 2 is larger, and the adhesion of the B side is smaller, but compared with Examples 1, 2 and Comparative Example 1, the adhesion is still very small, and the adhesion of Comparative Examples 3 and 4 is smaller. The rubber magnetic material with asymmetric magnetic field distribution was prepared by using the technical solutions of Examples 1-5, forming a "strong and weak" magnetic field distribution.

[0076] Although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0077] Therefore, the above description is only a preferred embodiment of the present application, and is not intended to limit the scope of the present application; that is, any equivalent transformation made within the scope of the claims of the present application is within the protection scope of the claims of the present application.

Claims

1. A rubber magnet having an asymmetric magnetic field strength on both sides, characterized by, The magnetic sheet comprises an anisotropic magnetic layer and an isotropic magnetic layer bonded together; the surface magnetic field strength of the anisotropic magnetic layer is more than 10 times that of the isotropic magnetic layer, and the surface of the anisotropic magnetic layer alternately distributes multiple magnetic poles such as N and S.

2. The rubber magnet according to claim 1, wherein The thickness of the anisotropic magnetic layer is 0.8-1.5 mm, and the thickness of the isotropic magnetic layer is 0.3-0.6 mm.

3. The rubber magnet according to claim 1, wherein the magnetic field intensity asymmetry is 0.1 or more. The anisotropic magnetic layer and the isotropic magnetic layer are both prepared from magnetic powder, thermoplastic material and rubber additive according to a mass ratio of (3-10):1:(0.1-0.3).

4. The rubber magnet according to claim 3, wherein the thickness of the magnet is 0.5 to 2.0 mm. The magnetic powder is neodymium iron boron magnetic powder or ferrite magnetic powder.

5. The rubber magnet according to claim 3, wherein the thickness of the magnet is 0.5 to 2.0 mm. The thermoplastic material is at least one of TPU, TPE and TRO.

6. The rubber magnet according to claim 3, wherein the thickness of the magnet is 0.5 to 2.0 mm. The rubber additive is composed of stearic acid, zinc oxide, accelerator M and plasticizer; the mass ratio of the stearic acid, zinc oxide, accelerator M, plasticizer and thermoplastic material is (1-4):(1-4):(1-3):(0.5-5):

100.

7. A method of producing a rubber magnet having a magnetic field strength asymmetry in both the front and back surfaces as claimed in any one of claims 1 to 6, characterized by, The method comprises the following steps: (1) Anisotropic magnetic layer preparation: anisotropic neodymium iron boron magnetic powder, thermoplastic material and rubber additive are mixed to obtain a mixed rubber; the mixed rubber is subjected to calender molding and cooling solidification to obtain the anisotropic magnetic layer; the pressure of the calender molding is 6-15 MPa, and the temperature is 140-180℃. (2) Isotropic magnetic layer preparation: isotropic neodymium iron boron magnetic powder or isotropic ferrite powder, thermoplastic material and rubber additive are mixed to obtain a mixed rubber; the mixed rubber is subjected to calender molding and cooling solidification to obtain the isotropic magnetic layer; the pressure of the calender molding is 6-15 MPa, and the temperature is 140-180℃. (3) Compound: the anisotropic magnetic layer and the isotropic magnetic layer are stacked and compounded under the conditions of a magnetic field of ≥2T, 90-110℃ and 3-6 MPa to form a magnetic sheet M with the anisotropic magnetic layer side orientation direction parallel to the normal direction of the magnetic sheet; (4) Single-sided multi-pole magnetization: the magnetic sheet M is subjected to single-sided multi-pole magnetization, an electric current I1 is applied to the anisotropic magnetic layer side, and an electric current I2 is applied to the isotropic magnetic layer side, wherein I1>I2, and the magnetization voltage is 1500-1800V.

8. A method of producing the composite gradient magnetic field rubber magnet according to any one of claims 1 to 6, characterized by, The method comprises the following steps: (1) Anisotropic magnetic layer preparation: anisotropic neodymium iron boron magnetic powder, thermoplastic material and rubber additive are mixed to obtain a mixed rubber; the mixed rubber is subjected to calender molding and cooling solidification to obtain the anisotropic magnetic layer; the pressure of the calender molding is 6-15 MPa, and the temperature is 140-180℃. (2) Isotropic magnetic layer preparation: isotropic neodymium iron boron magnetic powder or isotropic ferrite powder, thermoplastic material and rubber additive are mixed to obtain a mixed rubber; the mixed rubber is subjected to calender molding and cooling solidification to obtain the isotropic magnetic layer; the pressure of the calender molding is 6-15 MPa, and the temperature is 140-180℃. (3) Compound: the anisotropic magnetic layer and the isotropic magnetic layer are stacked and compounded under the conditions of 90-110℃ and 3-6 MPa to form a compound magnetic sheet M; (4) Single-sided multi-pole magnetization: the composite magnetic sheet M is subjected to single-sided multi-pole magnetization, a current I1 is applied to the anisotropic magnet layer side, and a current I2 is applied to the isotropic magnet layer side; wherein I1>I2, and the magnetization voltage is 1500-1800V.

9. The production method according to claim 7 or 8, characterized by, I1≥3000A, I2≤1000A.

10. The application of the rubber magnet with asymmetric magnetic field strength on both sides as claimed in any one of claims 1-8 in magnetic teaching aids and wearable devices.

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