Isotropic rubber neodymium iron boron magnet and preparation method thereof

Abstract

The invention relates to an isotropic rubber neodymium-iron-boron magnet and a preparation method thereof. The isotropic rubber neodymium-iron-boron magnet is prepared from the following raw materials: isotropic neodymium-iron-boron magnetic powder, isotropic samarium-iron-nitrogen magnetic powder, a binder and an auxiliary material, the average particle size of the isotropic neodymium-iron-boron magnetic powder is 90 [mu] m-450 [mu] m; the average particle size of the isotropic samarium-iron-nitrogen magnetic powder is 1-5 [mu] m. The large-particle-size neodymium-iron-boron magnetic powder and the small-particle-size samarium-iron-nitrogen magnetic powder are selected, gaps among the large-particle-size neodymium-iron-boron magnetic powder are filled with the small-particle-size rare earth magnetic powder, the gaps among the formed materials are reduced, the adding proportion of the magnetic material is further increased, and therefore the magnetic performance is improved. The maximum magnetic energy product of the prepared isotropic rubber neodymium-iron-boron magnet is generally 4.2 MGOe or above, the surface magnetism is 790 Gs or above, meanwhile, the isotropic rubber neodymium-iron-boron magnet has excellent flexibility, and the requirements of different use scenes can be met.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic materials, and in particular to an isotropic rubber NdFeB magnet and a preparation method thereof. Background Art

[0002] Isotropic rubber NdFeB magnets are made of isotropic NdFeB magnetic powder, thermoplastic rubber and a small amount of processing aids through calendering, extrusion and other processes. The processing technology is simple and easy to form. It can be prepared into sheets, strips, rings and other complex shapes to meet different requirements. It can be widely used in micro motors, refrigerator door seals, toys, stationery, advertising and other industries. The prepared magnets have good rubber flexibility and better shock and drop resistance than traditional sintered or bonded (molded) NdFeB. However, the maximum magnetic energy product is generally lower than 9MGOe, and its application is limited.

[0003] Although isotropically bonded (molded) NdFeB has high magnetic properties and the maximum magnetic energy product can reach more than 10MGOe, it uses a small amount of epoxy resin as a binder and is prepared through a molding process. The prepared product does not have rubber flexibility. Traditional rubber NdFeB magnetic strips are usually made by heating and kneading isotropically bonded NdFeB powder with CPE, rubber and other polymer binders and auxiliary additives, and then calendering, extrusion, molding and other processes. It has good rubber flexibility and can be prepared into strips, rolls, sheets and various complex shapes. It is widely used in micro motors, refrigerators, disinfection cabinets, kitchen cabinets, toys, stationery, advertising, automation and other industries.

[0004] The magnetic properties of traditional rubber NdFeB are low, and the maximum magnetic energy product is lower than 9MGOe, generally 3-7MGOe, and the magnetic properties cannot meet the needs of high-end customers. In order to increase the maximum magnetic energy product, the traditional method is often to increase the powder filling amount in the formula, and the high powder filling amount has a great influence on the processing performance of rubber NdFeB, and the high powder filling amount will greatly reduce the flexibility of the rubber, affecting its use function.

[0005] In addition, since NdFeB materials are easy to oxidize, magnetic powder with small average particle size has large specific surface area, and the oxidation degree of magnetic powder is higher, which greatly reduces the magnetic properties of magnetic powder. Magnetic powder with small average particle size has natural risks. Therefore, the average particle size of bonded NdFeB powder on the market is generally tens to hundreds of microns. After the large-particle NdFeB powder is formed, there are a lot of gaps between the magnetic powder particles, resulting in a generally low magnetic energy product.

[0006] Therefore, in order to broaden the application field of rubber NdFeB and meet the requirements of more customers for magnetic properties, it is urgent to provide an isotropic NdFeB magnet with excellent magnetic properties and good flexibility and a preparation method thereof. Summary of the invention

[0007] In order to solve the above technical problems, the purpose of the present invention is to provide an isotropic rubber NdFeB magnet and a preparation method thereof. The isotropic rubber NdFeB magnet provided by the present invention has flexibility and high magnetic properties.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides an isotropic rubber NdFeB magnet, wherein the raw materials for preparing the isotropic rubber NdFeB magnet include mixed magnetic powder, a binder and auxiliary materials; the mixed magnetic powder includes isotropic NdFeB magnetic powder and isotropic SmFeN magnetic powder;

[0010] The average particle size of the isotropic NdFeB magnetic powder is 90 μm-450 μm; the average particle size of the isotropic SmFeN magnetic powder is 1 μm-5 μm.

[0011] It is known that the finer the magnetic powder particle size, the larger its specific surface area, and the easier it is for the prepared magnet to absorb oxygen and oxidize on the surface, especially when the particle size is less than 45μm. Therefore, the greater the proportion of fine particles in the magnetic powder, the lower the magnetic properties. The particle size of NdFeB magnetic powder is generally coarser, generally in the range of 90-450μm. After the larger NdFeB magnetic powder is mixed with rubber for calendering, the gap between the magnetic powder and the rubber is larger (such as the attached Figure 1 As shown in the figure, the density of the magnetic sheet produced is poor and the magnetic properties are also low.

[0012] The isotropic rubber NdFeB magnet provided by the present invention has NdFeB powder with high magnetic properties, and the maximum magnetic energy product (BH) max is about 16MGOe, but the magnetic powder particle size is generally large, about 90μm-450μm. The SmFeN powder has a finer particle size, and the average particle size is 1μm-5μm, but its magnetic properties are relatively low, and the maximum magnetic energy product (BH) max is about 10MGOe. The present invention selects large-particle-size NdFeB magnetic powder and small-particle-size SmFeN magnetic powder to cooperate with each other, and first performs particle size grading on the NdFeB magnetic powder, so that the magnetic strip has higher density and magnetic properties. Since the overall NdFeB magnetic powder particle size is relatively large, further, in the NdFeB magnetic powder after particle size grading, an appropriate amount of isotropic SmFeN magnetic powder with a finer particle size is filled, and the magnetic powder particle size is generally 2μm-6μm. The density and magnetic properties of the product are further improved.

[0013] By filling small-sized rare earth magnetic powder into large-sized NdFeB magnetic powder, the gap between the materials after molding can be reduced, and the addition ratio of magnetic material can be further increased, thereby improving the magnetic properties.

[0014] On the other hand, the present invention uses two different magnetic powders to mix and prepare isotropic rubber NdFeB magnets. Isotropic NdFeB magnetic powder has high magnetic properties and is one of the permanent magnets with the best magnetic properties at present, with high residual magnetic induction intensity, magnetic induction coercive force and maximum magnetic energy product. SmFeN magnetic powder has a higher Curie temperature and excellent oxidation resistance and corrosion resistance. Its maximum magnetic energy product is more than twice that of the mainstream rare earth bonded magnetic powder isotropic NdFeB. The use of these two magnetic powders in blending can improve the thermal stability and chemical stability of the magnet while maintaining high magnetic properties, reduce dependence on heavy rare earths, reduce costs, and improve the mechanical properties and molding freedom of the magnet. In addition, the particle size characteristics of SmFeN magnetic powder make the magnet show better mechanical properties, reduce wear on production molds, and reduce production costs. The magnet prepared by this blending method strikes a balance between magnetic properties and cost-effectiveness, and is suitable for application scenarios with special requirements for high temperature performance and corrosion resistance.

[0015] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0016] Preferably, based on the total mass of the raw materials for preparing the isotropic rubber NdFeB magnet as 100wt%, the mass fraction of the mixed magnetic powder is 94wt%-97wt%, for example, it can be 94wt%, 94.5wt%, 95wt%, 95.5wt%, 96wt%, 96.5wt% or 97wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, based on the total mass of the isotropic rubber NdFeB magnet as 100wt%, the mass fraction of the binder is 2.5wt%-10wt%, for example, it can be 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt% or 10wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0018] Preferably, based on the total mass of the isotropic rubber NdFeB magnet as 100wt%, the mass fraction of the auxiliary material is ≤2wt%, for example, it can be 2wt%, 1.8wt%, 1.6wt%, 1.4wt%, 1.2wt%, 1wt%, 0.8wt%, 0.6wt%, 0.5wt%, 0.4wt%, 0.3wt%, 0.2wt% or 0.1wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] Preferably, based on the total mass of the mixed magnetic powder as 100wt%, the mass fraction of the isotropic NdFeB magnetic powder is 94.5wt%-99wt%, for example, it can be 94.5wt%, 95wt%, 95.5wt%, 96wt%, 96.5wt%, 97wt%, 97.5wt%, 98wt%, 98.5wt% or 99wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] Preferably, based on the total mass of the mixed magnetic powder as 100wt%, the mass fraction of the isotropic samarium iron nitrogen magnetic powder is 1.0wt%-5.5wt%, for example, it can be 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% or 5.5wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] Preferably, based on the total mass of the raw materials for preparing the isotropic rubber NdFeB magnet as 100wt%, the mass fraction of the isotropic NdFeB magnetic powder is 88.8wt%-96wt%, for example, it can be 88.8wt%, 90.0wt%, 91wt%, 91.5wt%, 92wt%, 92.5wt%, 93wt%, 93.5wt%, 94wt%, 94.5wt%, 95wt%, 95.5wt% or 96wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0022] Preferably, based on the total mass of the isotropic rubber NdFeB magnet as 100wt%, the mass fraction of the isotropic SmFeN magnetic powder is 0.9wt%-5wt%, for example, it can be 0.9wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] The present invention further controls the mass fraction of isotropic NdFeB magnetic powder to be 88.8wt%-96wt%. When the content of the isotropic NdFeB magnetic powder is too much, there are too many large-diameter particles, forming more gaps, and the isotropic SmFeN magnetic powder with small particle size cannot completely fill the gaps, resulting in poor density and the inability to improve the magnetic properties, thereby reducing the maximum magnetic energy product of the isotropic rubber NdFeB magnet; and when the mass fraction of the isotropic NdFeB magnetic powder is too little, the addition ratio of high-performance NdFeB magnetic powder decreases, and the ratio of low-performance SmFeN powder is high, resulting in low magnetic properties.

[0024] Preferably, the maximum magnetic energy product of the isotropic NdFeB magnetic powder is 9MGOe-17MGOe, for example, it can be 9MGOe, 10MGOe, 11MGOe, 12MGOe, 13MGOe, 14MGOe, 15MGOe, 16MGOe or 17MGOe, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] The maximum magnetic energy product of the isotropic SmFeN magnetic powder is 3MGOe-10MGOe, for example, 3MGOe, 4MGOe, 5MGOe, 6MGOe, 7MGOe, 8MGOe, 9MGOe or 10MGOe, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] The present invention selects isotropic NdFeB magnetic powder with a maximum magnetic energy product of 9MGOe-17MGOe and isotropic SmFeN magnetic powder with a maximum magnetic energy product of 3MGOe-10MGOe as raw materials. When the (BH)max of the raw materials is larger, the magnetic properties of the obtained isotropic rubber NdFeB magnet are better. If the maximum magnetic energy product of the isotropic NdFeB magnetic powder raw material is less than 9MGOe, the maximum magnetic energy product of the prepared isotropic rubber NdFeB magnet cannot meet the use requirements.

[0027] In a second aspect, the present invention provides a method for preparing the isotropic rubber NdFeB magnet as described in the first aspect, the preparation method comprising the following steps:

[0028] Isotropic NdFeB magnetic powder, isotropic SmFeN magnetic powder, binder and auxiliary materials are mixed and kneaded according to the formula, and then sieved and rolled into sheets to obtain the isotropic rubber NdFeB magnet.

[0029] The preparation method of the present invention is simple. First, the NdFeB powder with a relatively coarse overall particle size is graded. The addition of the SmFeN powder with a finer particle size fills the gaps between the large particles of NdFeB powder, thereby improving its compactness and further improving the overall magnetic properties. In order to make the material mixing more uniform, the present invention adopts a secondary internal mixing process and a process of performing open mixing after internal mixing.

[0030] Preferably, the present invention does not limit the specific type of the adhesive, as long as it can achieve similar technical effects, for example, the adhesive includes rubber and / or thermoplastic material.

[0031] Preferably, the present invention does not limit the specific type of the binder, as long as it can achieve similar technical effects, for example, the binder includes any one of chloroprene rubber, ethylene propylene rubber, fluororubber, silicone rubber, nitrile rubber, chlorinated polyethylene (CPE), polyvinyl chloride (PVC), ethylene-vinyl acetate copolymer (EVA), thermoplastic elastomer (TPE) or thermoplastic polyolefin elastomer (TPO) or a combination of at least two, wherein typical but non-limiting combinations include a combination of chloroprene rubber and ethylene propylene rubber, a combination of fluororubber and silicone rubber, a combination of fluororubber and nitrile rubber, a combination of CPE and PVC, a combination of EVA and TPE, a combination of fluororubber, silicone rubber and nitrile rubber, and a combination of PVC, EVA, TPE and TPO.

[0032] Preferably, the present invention does not limit the specific types of auxiliary materials, as long as similar technical effects can be achieved. For example, the auxiliary materials include any one of vulcanizers, antioxidants or plasticizers, or a combination of at least two of them. Typical but non-limiting combinations include a combination of a vulcanizer and an antioxidant, a combination of an antioxidant and a plasticizer, a combination of a vulcanizer and a plasticizer, and a combination of a vulcanizer, an antioxidant and a plasticizer.

[0033] Preferably, the present invention does not limit the specific type of the vulcanizing agent, as long as it can achieve similar technical effects, for example, the vulcanizing agent includes any one of BIPB (di-tert-butyl peroxide isopropylbenzene), DCP (diisopropylbenzene peroxide), DCBP (2,4-dichloroperoxybenzoyl), BP (benzoyl peroxide) or sulfur, or a combination of at least two of them, wherein typical but non-limiting combinations include a combination of BIPB and DCP, a combination of DCBP and BP, a combination of BIPB, DCP and DCBP, and a combination of BIPB, DCBP, BP and sulfur.

[0034] Preferably, the present invention does not limit the specific type of antioxidant, as long as it can achieve similar technical effects. For example, the antioxidant includes any one of antioxidant RD, antioxidant 4010 or antioxidant TMQ, or a combination of at least two of them, wherein typical but non-limiting combinations include a combination of antioxidant RD and antioxidant 4010, a combination of antioxidant 4010 and antioxidant TMQ, a combination of antioxidant RD and antioxidant TMQ, and a combination of antioxidant RD, antioxidant 4010 and antioxidant TMQ.

[0035] Preferably, the present invention does not limit the specific type of plasticizer, as long as it can achieve similar technical effects, for example, the plasticizer includes DOP and / or soybean oil.

[0036] Preferably, the temperature of the banburying is 100°C-130°C, for example, it can be 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, the kneading time is 10 min-30 min, for example, 10 min, 15 min, 20 min, 25 min or 30 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0039] Taking the total mass of the raw materials for preparing the isotropic rubber NdFeB magnet as 100wt%, isotropic NdFeB magnetic powder with a mass fraction of 88.8wt%-96wt%, an average particle size of 90μm-450μm, and a maximum magnetic energy product of 9MGOe-17MGOe and isotropic SmFeN magnetic powder with a mass fraction of 0.9wt%-5wt%, an average particle size of 1μm-5μm, and a maximum magnetic energy product of 3MGOe-10MGOe are taken as mixed magnetic powders, a binder with a mass fraction of 2.5wt%-10wt% and auxiliary materials with a mass fraction of ≤2wt% are mixed and kneaded at 100℃-130℃ for 10min-30min, and after kneading, the material is poured out and sieved, and the sieved granular material is added to a preheated roller calender to be calendered into sheets to obtain the isotropic rubber NdFeB magnet.

[0040] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0041] Compared with the prior art, the present invention has at least the following beneficial effects:

[0042] (1) The isotropic rubber NdFeB magnet provided by the present invention, on the one hand, selects large-particle NdFeB magnetic powder and small-particle SmFeN magnetic powder, and fills small-particle rare earth magnetic powder in large-particle NdFeB magnetic powder to reduce the gap between the materials after molding, further increase the addition ratio of magnetic materials, reduce gaps, and thus improve magnetic properties. On the other hand, the present invention uses two different magnetic powders to mix and prepare isotropic rubber NdFeB magnets, which can improve the thermal stability and chemical stability of the magnet while maintaining high magnetic properties, reduce dependence on heavy rare earth, reduce costs, and improve the mechanical properties and molding freedom of the magnet.

[0043] (2) The maximum magnetic energy product of the isotropic rubber NdFeB magnet prepared by the present invention is generally above 4.2 MGOe, and more preferably above 8.5 MGOe. The surface magnetism is above 790 Gs, and more preferably above 1300 Gs. It also has excellent flexibility and can meet the requirements of different usage scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a SEM image of a rubber NdFeB magnet made by mixing large-particle NdFeB magnetic powder with rubber and rolling it in the prior art;

[0045] Figure 2 This is a SEM image of the isotropic rubber NdFeB magnet prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0047] In the following examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the field; unless otherwise specified, the experimental methods and technical means used were conventional methods and means in the field.

[0048] Example 1

[0049] The present embodiment provides an isotropic rubber NdFeB magnet. With the total mass of the isotropic rubber NdFeB magnet being 100wt%, the raw materials for preparing the isotropic rubber NdFeB magnet include 94wt% of isotropic NdFeB magnetic powder, 90μm in average particle size, and 9MGOe in maximum magnetic energy product, 1wt% of isotropic SmFeN magnetic powder, 2μm in average particle size, and 9MGOe in maximum magnetic energy product (and 4.5wt% of nitrile rubber and 0.5wt% of DOP plasticizer;

[0050] The preparation method of the isotropic rubber NdFeB magnet provided in this embodiment comprises the following steps:

[0051] The raw materials are weighed according to the above formula and mixed and kneaded for 15 minutes at 150° C. After kneading, the materials are poured out and sieved. The sieved granular materials are added to a preheated roller calender and calendered into sheets to obtain the isotropic rubber NdFeB magnet.

[0052] The SEM image of the prepared isotropic rubber NdFeB magnet is shown in Figure 2As shown in the figure, it can be seen that the small-particle size SmFeN magnetic powder fills the gaps in the large-particle size NdFeB magnetic powder, thereby improving the density of the high magnetic material.

[0053] Example 2

[0054] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 1 only in that the mass fraction of the isotropic SmFeN magnetic powder is 2%, the mass fraction of the nitrile rubber is 3.8wt%, and the mass fraction of the DOP plasticizer is 0.2wt%; the preparation method remains unchanged.

[0055] Example 3

[0056] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 1 only in that the mass fraction of the isotropic SmFeN magnetic powder is 3%, the mass fraction of the nitrile rubber is 2.8wt%, and the mass fraction of the DOP plasticizer is 0.2wt%; the rest of the preparation method remains unchanged.

[0057] Example 4

[0058] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 1 only in that the isotropic NdFeB magnetic powder has an average particle size of 150 μm and a maximum magnetic energy product of 13 MGOe; the rest of the preparation method remains unchanged.

[0059] Example 5

[0060] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 4 only in that the mass fraction of the isotropic SmFeN magnetic powder is 2%, the mass fraction of the nitrile rubber is 3.8wt%, and the mass fraction of the auxiliary material is 0.2wt%; the rest of the preparation method remains unchanged.

[0061] Example 6

[0062] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 4 only in that the mass fraction of the isotropic SmFeN magnetic powder is 3%, the mass fraction of the nitrile rubber is 2.8wt%, and the mass fraction of the auxiliary material is 0.2wt%; the rest of the preparation method remains unchanged.

[0063] Example 7

[0064] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 6 only in that the average particle size of the isotropic NdFeB magnetic powder is 300 μm; the rest of the preparation method remains unchanged.

[0065] Example 8

[0066] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 4 only in that the maximum magnetic energy product of the isotropic NdFeB magnetic powder is 17 MGOe; the rest of the preparation method remains unchanged.

[0067] Example 9

[0068] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 8 only in that the mass fraction of the isotropic SmFeN magnetic powder is 2%, the mass fraction of the nitrile rubber is 3.8wt%, and the mass fraction of the auxiliary material is 0.2wt%; the rest of the preparation method remains unchanged.

[0069] Example 10

[0070] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 8 only in that the mass fraction of the isotropic SmFeN magnetic powder is 3%, the mass fraction of the nitrile rubber is 2.8wt%, and the mass fraction of the auxiliary material is 0.2wt%; the rest of the preparation method remains unchanged.

[0071] Embodiment 11

[0072] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 10 only in that the average particle size of the isotropic NdFeB magnetic powder is 300 μm; the rest of the preparation method remains unchanged.

[0073] Example 12

[0074] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 10 only in that the average particle size of the isotropic NdFeB magnetic powder is 420 μm; the rest of the preparation method remains unchanged.

[0075] Embodiment 13

[0076] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 12 only in that the mass fraction of the isotropic NdFeB magnetic powder is 93wt%, and the mass fraction of the isotropic SmFeN magnetic powder is 4wt%; the rest of the preparation method remains unchanged.

[0077] Embodiment 14

[0078] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 12 only in that the mass fraction of the isotropic NdFeB magnetic powder is 92wt%, and the mass fraction of the isotropic SmFeN magnetic powder is 5wt%; the rest of the preparation method remains unchanged.

[0079] Embodiment 15

[0080] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 1 only in that the mass fraction of the isotropic NdFeB magnetic powder is 85wt%, and the mass fraction of the isotropic SmFeN magnetic powder is 10wt%; the rest of the preparation method remains unchanged.

[0081] Example 16

[0082] This embodiment provides an isotropic rubber NdFeB magnet, which is different from Embodiment 1 only in that the maximum magnetic energy product of the isotropic NdFeB magnetic powder is 7 MGOe; the rest of the preparation method remains unchanged.

[0083] Comparative Example 1

[0084] This comparative example provides an isotropic rubber NdFeB magnet, which is different from Example 1 only in that no isotropic SmFeN magnetic powder is added, and the mass fraction of styrene-butadiene rubber is 5.5wt%; the rest of the preparation method remains unchanged.

[0085] Comparative Example 2

[0086] This comparative example provides an isotropic rubber NdFeB magnet, which is different from comparative example 1 only in that the mass fraction of the isotropic NdFeB magnetic powder is 95% and the mass fraction of the styrene-butadiene rubber is 4.5wt%; the rest of the preparation method remains unchanged.

[0087] Comparative Example 3

[0088] This comparative example provides an isotropic rubber NdFeB magnet, which is different from comparative example 1 only in that the maximum magnetic energy product of the isotropic NdFeB magnetic powder is 13 MGOe; the rest of the preparation method remains unchanged.

[0089] Comparative Example 4

[0090] This comparative example provides an isotropic rubber NdFeB magnet, which is different from comparative example 1 only in that the average particle size of the isotropic NdFeB magnetic powder is 150 μm and the maximum magnetic energy product is 13 MGOe; the rest of the preparation method remains unchanged.

[0091] Comparative Example 5

[0092] This comparative example provides an isotropic rubber NdFeB magnet, which is different from comparative example 4 only in that the mass fraction of the isotropic NdFeB magnetic powder is 95% and the mass fraction of the styrene-butadiene rubber is 4.5wt%; the rest of the preparation method remains unchanged.

[0093] Comparative Example 6

[0094] This comparative example provides an isotropic rubber NdFeB magnet, which is different from comparative example 5 only in that the average particle size of the isotropic NdFeB magnetic powder is 300 μm; the rest of the preparation method remains unchanged.

[0095] Comparative Example 7

[0096] This comparative example provides an isotropic rubber NdFeB magnet, which is different from comparative example 4 only in that the maximum magnetic energy product of the isotropic NdFeB magnetic powder is 17 MGOe; the rest of the preparation method remains unchanged.

[0097] Comparative Example 8

[0098] This comparative example provides an isotropic rubber NdFeB magnet, which is different from comparative example 6 only in that the maximum magnetic energy product of the isotropic NdFeB magnetic powder is 17 MGOe; the rest of the preparation method remains unchanged.

[0099] Comparative Example 9

[0100] This comparative example provides an isotropic rubber NdFeB magnet, which is different from comparative example 8 only in that the average particle size of the isotropic NdFeB magnetic powder is 420 μm; the rest of the preparation method remains unchanged.

[0101] The grades, average particle sizes and mass fractions of the two magnetic powders in the above-mentioned embodiments and comparative examples are detailed in Table 1.

[0102] Performance test: a. Test the maximum magnetic energy product (BH) max. b. Make a 50mm×50mm×3mm product and magnetize it in the thickness direction to test the surface magnetism. c. Winding The round bar was tested for flexibility. The test results are shown in Table 2.

[0103] Table 1

[0104]

[0105]

[0106] Table 2

[0107]

[0108]

[0109] Note: Flexibility OK means no cracking when wrapped around a Ф=6mm round bar. “○” represents the degree of cracking. The more “○” there are, the more serious the cracking is. Generally, the number of “○” ≤ 2 is required to be qualified.

[0110] The test results show that:

[0111] (1) It can be seen from Examples 1 to 16 that the present invention reduces the gap between the materials after molding by selecting large-particle NdFeB magnetic powder and small-particle SmFeN magnetic powder, and by filling the gaps between the large-particle NdFeB magnetic powder with small-particle rare earth magnetic powder, and further increases the addition ratio of magnetic materials, thereby improving the magnetic properties. The maximum magnetic energy product of the prepared isotropic rubber NdFeB magnet is generally above 4.2MGOe, and more preferably above 8.5MGOe, and the surface magnetism is above 790Gs, and more preferably above 1300Gs. At the same time, it has excellent flexibility and can meet the requirements of different usage scenarios.

[0112] (2) By comparing Examples 1 to 3, 4 to 6, 8 to 10, and 12 to 14, it can be seen that when the maximum magnetic energy product, average particle size and added content of the isotropic NdFeB magnetic powder are fixed, the mass percentage of the isotropic SmFeN magnetic powder is 3wt% and the added amount of SBR is only 2.8wt%, the maximum magnetic energy product and surface magnetism of the obtained isotropic rubber NdFeB magnet are greater.

[0113] (3) By comparing Examples 1, 4 and 8, Examples 2, 5 and 9, and Examples 3, 6 and 10, it can be seen that in the present invention, when the maximum magnetic energy product of the isotropic NdFeB magnetic powder is larger, the maximum magnetic energy product and surface magnetism of the obtained isotropic rubber NdFeB magnet are larger.

[0114] (4) By comparing Example 6 with Example 7, and by comparing Example 10 with Example 11, it can be seen that the effect obtained when the particle size of the isotropic NdFeB magnetic powder in the present invention is 150 μm is more excellent.

[0115] (5) By comparing Example 1 with Example 15, it can be seen that the maximum magnetic energy product and surface magnetism of the isotropic rubber NdFeB magnet obtained by further controlling the content of the isotropic NdFeB magnetic powder within the range of 88.8wt%-96wt% and the mass fraction of the isotropic SmFeN magnetic powder within the range of 0.9wt%-5wt%. When the content of the isotropic NdFeB magnetic powder is too little, its magnetic energy product decreases significantly.

[0116] (6) By comparing Example 1 with Example 16, it can be seen that the maximum magnetic energy product of the isotropic NdFeB magnetic powder is further controlled within the range of 9MGOe-17MGOe, and the maximum magnetic energy product of the isotropic rubber NdFeB magnet obtained is greater than the surface magnetism. When the maximum magnetic energy product of the isotropic NdFeB magnetic powder is low, the maximum magnetic energy product of the isotropic rubber NdFeB magnet cannot meet the use requirements.

[0117] (7) When only one isotropic NdFeB magnetic powder is used as the raw material for preparation in Comparative Examples 1 to 9, even if increasing the maximum magnetic energy product of the isotropic NdFeB magnetic powder raw material can improve the maximum magnetic energy product of the final magnet, the effect is still weak, and the effect is obviously inferior to the maximum magnetic energy product of the magnet obtained by blending large and small particles in the present invention.

[0118] (8) By comparing Example 1 with Comparative Example 1, Example 4 with Comparative Example 4, and Example 8 with Comparative Example 7, it can be seen that when small-particle isotropic SmFeN magnetic powder is not used to fill NdFeB magnetic powder, the performance of the prepared magnet is poor.

[0119] In summary, the present invention selects large-particle size NdFeB magnetic powder and small-particle size SmFeN magnetic powder, and fills the small-particle size rare earth magnetic powder in the gaps between the large-particle size NdFeB magnetic powder, thereby reducing the gap between the materials after molding, further increasing the addition ratio of the magnetic material, and thus improving the magnetic properties.

[0120] On the other hand, the present invention uses two different magnetic powders to mix and prepare isotropic rubber NdFeB magnets. Isotropic NdFeB magnetic powder has high magnetic properties and is one of the permanent magnets with the best magnetic properties at present, with high residual magnetic induction intensity, magnetic induction coercive force and maximum magnetic energy product. SmFeN magnetic powder has a higher Curie temperature and excellent oxidation resistance and corrosion resistance. Its maximum magnetic energy product is more than twice that of the mainstream rare earth bonded magnetic powder isotropic NdFeB. The use of these two magnetic powders in blending can improve the thermal stability and chemical stability of the magnet while maintaining high magnetic properties, reduce dependence on heavy rare earths, reduce costs, and improve the mechanical properties and molding freedom of the magnet. In addition, the particle size characteristics of SmFeN magnetic powder make the magnet show better mechanical properties, reduce wear on production molds, and reduce production costs. The magnet prepared by this blending method strikes a balance between magnetic properties and cost-effectiveness, and is suitable for application scenarios with special requirements for high temperature performance and corrosion resistance.

[0121] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. An isotropic rubber NdFeB magnet, characterized in that: The raw materials for preparing the isotropic rubber NdFeB magnet include mixed magnetic powder, binder and auxiliary materials; the mixed magnetic powder includes isotropic NdFeB magnetic powder and isotropic SmFeN magnetic powder; The average particle size of the isotropic NdFeB magnetic powder is 90 μm-450 μm; the average particle size of the isotropic SmFeN magnetic powder is 1 μm-5 μm.

2. The isotropic rubber NdFeB magnet according to claim 1, characterized in that: Taking the total mass of the raw materials for preparing the isotropic rubber NdFeB magnet as 100wt%, the mass fraction of the mixed magnetic powder is 94wt%-97wt%, the mass fraction of the binder is 2.5wt%-10wt%, and the mass fraction of the auxiliary material is ≤2wt%; Preferably, based on the total mass of the mixed magnetic powder being 100wt%, the mass fraction of the isotropic NdFeB magnetic powder is 94.5wt%-99wt%, and the mass fraction of the isotropic SmFeN magnetic powder is 1.0wt%-5.5wt%; Preferably, based on the total mass of the raw materials for preparing the isotropic rubber NdFeB magnet as 100wt%, the mass fraction of the isotropic NdFeB magnetic powder is 88.8wt%-96wt%, and the mass fraction of the isotropic SmFeN magnetic powder is 0.9wt%-5wt%; Preferably, the maximum magnetic energy product of the isotropic NdFeB magnetic powder is 9MGOe-17MGOe, and the maximum magnetic energy product of the isotropic SmFeN magnetic powder is 3MGOe-10MGOe.

3. A method for preparing an isotropic rubber NdFeB magnet as claimed in claim 1 or 2, characterized in that: The preparation method comprises the following steps: Isotropic NdFeB magnetic powder, isotropic SmFeN magnetic powder, binder and auxiliary materials are mixed and kneaded according to the formula, and then sieved and rolled into sheets to obtain the isotropic rubber NdFeB magnet.

4. The preparation method according to claim 3, characterized in that: The adhesive includes rubber and / or thermoplastic material.

5. The preparation method according to claim 3 or 4, characterized in that: The adhesive includes any one of chloroprene rubber, ethylene propylene rubber, fluororubber, silicone rubber, nitrile rubber, CPE, PVC, EVA, TPE or TPO, or a combination of at least two thereof.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The auxiliary material includes any one of a vulcanizing agent, an antioxidant or a plasticizer, or a combination of at least two of them.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The vulcanizing agent includes any one of BIPB, DCP, DCBP, BP or sulfur, or a combination of at least two of them.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The antioxidant includes any one of antioxidant RD, antioxidant 4010 or antioxidant TMQ, or a combination of at least two of them.

9. The preparation method according to any one of claims 3 to 8, characterized in that: The plasticizer includes DOP and / or soybean oil.

10. The preparation method according to any one of claims 3 to 9, characterized in that: The temperature of the banburying is 100°C-130°C; Preferably, the kneading time is 10 min-30 min.

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