Method for removing nylon in waste injection molding type bonded neodymium iron boron magnetic powder by using potassium permanganate chemical reaction method

Abstract

The invention discloses a method for recycling injection-molded bonded neodymium iron boron magnetic powder by removing organic matters in waste polyamide bonded neodymium iron boron magnetic powder through a potassium permanganate chemical reaction method, and relates to the technical field of material recycling. An adopted mixed solvent is composed of potassium permanganate, lauryl sodium sulfate, sodium hydroxide and deionized water, the concentration range of the potassium permanganate is 0.02-0.05 mol / L, the concentration range of the lauryl sodium sulfate is 0.01-0.03 mol / L, and the pH value of the solution is kept between 7 and 10 through the use amount of the sodium hydroxide. The method has the advantages that the pH value of the solution is adjusted through the potassium permanganate-sodium dodecyl sulfate (SDS) mixed solvent system and the alkaline medium, the solution formula and the treatment method which can effectively remove the polyamide binder in the waste injection molding type bonded neodymium iron boron magnetic powder and have small damage to the neodymium iron boron magnetic powder are provided, the recovery process is simple, operation is easy and convenient, and the method is suitable for industrial production. The safety is high, the cost is low, and the binder removal effect is remarkable.

Description

Technical Field

[0001] The invention discloses a method for removing nylon from waste injection-molded bonded NdFeB magnetic powder by using a potassium permanganate chemical reaction method, and belongs to the technical field of NdFeB material recovery. Background Art

[0002] With the rapid development and continuous progress of modern science and technology, rare earth permanent magnet materials have undergone significant iterative upgrades, from the initial samarium cobalt 1:5 type (first generation) and samarium cobalt 2:17 type (second generation) to the third generation with the best comprehensive performance - NdFeB permanent magnets. According to the differentiation of production and manufacturing technology, NdFeB permanent magnets can be subdivided into three categories: sintered NdFeB, bonded NdFeB and hot-pressed NdFeB. In the field of NdFeB recycling research, the current focus is mainly on the recycling of sintered NdFeB magnets. Compared with sintered magnets, bonded NdFeB exhibits excellent performance uniformity, simplified production process, lower cost, high-precision dimensional control, strong processing capabilities and the ability to meet precision manufacturing needs. These advantages are highly consistent with the development trend of contemporary electronic products towards miniaturization, lightweight and thinness. Therefore, it has been widely used in computers, electronic mobile devices, office automation equipment, new energy vehicles and various household appliances. However, with the scrapping of related products and the generation of scraps during processing, waste is inevitable, which not only leads to the waste of rare earth resources, but also causes pollution problems. In view of this, in order to promote the recycling of rare earth resources, strengthen environmental protection and reduce production costs, research on the field of bonded NdFeB recovery has far-reaching significance and value.

[0003] Bonded NdFeB magnets are mainly composed of NdFeB magnetic powder, binder and a series of additives (such as coupling agent, lubricant, antioxidant, etc.). Different molding processes use different binders. For example, molded bonded magnets often use epoxy resin and its curing agent, coupling agent, etc. mixed in a certain proportion to prepare the binder; calendaring bonded magnets generally use ethylene or nitrile rubber as a binder; and injection molded magnets tend to use thermoplastic polyamide (nylon) as a binder.

[0004] Given that different bonded NdFeB magnets use different types and contents of binders, as shown in Table 1, their recycling strategies are also completely different. A major challenge in the recycling of bonded magnets is how to effectively remove the difficult-to-degrade polymer binder while minimizing the damage to the magnetic powder. Currently, there have been preliminary studies on the recycling of molded bonded magnets (such as welding machine magnets using epoxy resin): Sun Shuo, Zhang Yu, Zhu Peihong and others from Beijing University of Technology used sodium hypochlorite and sodium hydroxide to react chemically with the cyano functional groups and epoxy groups in the cured epoxy resin at room temperature and pressure, respectively, to destroy the structure of the binder, thereby achieving effective stripping of organic matter from waste MQ bonded NdFeB magnetic powder. However, considering that the polyamide nylon binder used in injection-molded bonded magnets has a structure and properties that are completely different from those of epoxy resin and polyphenylene sulfide binders, and accounts for a large proportion, existing technical methods cannot decompose the nylon binder at room temperature and pressure, thereby achieving the recycling and reuse of NdFeB.

[0005] Table 1 Common processes and binder components for bonded NdFeB magnets

[0006]

[0007]

[0008] At present, the research on the recovery of waste injection molded bonded NdFeB magnets at home and abroad is still in a state of scarcity. The binder of injection molded magnets is mainly composed of polyamide, and the existing research mainly focuses on the decomposition of polyamide fibers, and does not study whether it is suitable for the decomposition of the binder in waste injection molded bonded NdFeB magnetic powder, and whether it affects the main phase of NdFeB. For example, in the patent CN107056624 B, nylon 66 particles are subjected to alcoholysis reaction with alcohol and an acidic catalyst, and then an organic solvent is extracted and distilled to obtain a refined fraction of hexamethylenediamine. However, if the acidic catalyst used in this method is applied to the recovery of waste injection molded bonded NdFeB, it will corrode the NdFeB magnetic powder, thereby affecting the magnetic properties of the recovered powder. See also the patent CN 114874489A, which obtains a nylon solution by filtering after reacting polyamide crushed material with an ionic liquid, and then pouring the nylon solution into deionized water to precipitate nylon, and obtaining regenerated nylon powder after washing and drying. However, ionic liquids are composed of cations and highly electronegative anions, which are highly corrosive to NdFeB. In addition, the cost of ionic liquids is relatively high, which may become a potential obstacle to the large-scale industrialization of waste injection molded NdFeB magnet recycling projects.

[0009] In summary, there is an urgent need to develop an effective method for recycling injection molded bonded magnets, especially a recycling technology for polyamide bonded NdFeB magnets. Summary of the invention

[0010] The purpose of the present invention is to develop a solution formula and a treatment method which can effectively remove the polyamide binder in waste injection-molded bonded NdFeB magnetic powder and at the same time cause less damage to the NdFeB magnetic powder.

[0011] The invention provides a mixed solvent formula for removing nylon binder in waste injection-molded bonded NdFeB magnetic powder. The mixed solvent consists of potassium permanganate, sodium dodecyl sulfate, sodium hydroxide and deionized water, wherein the concentration range of potassium permanganate is 0.02-0.05 mol / L, the concentration range of sodium dodecyl sulfate is 0.01-0.03 mol / L, and the amount of sodium hydroxide is such that the pH value of the solution is maintained between 7 and 10.

[0012] The method for removing the polyamide binder from waste injection-molded bonded NdFeB magnetic powder to recover NdFeB magnetic powder provided by the present invention comprises the following steps:

[0013] (1) Crushing of waste magnets:

[0014] The bonded NdFeB magnet waste is put into a jaw crusher for crushing, and then sieved to obtain magnetic powder A with a particle size of less than 150 μm.

[0015] (2) Mixed solvent configuration:

[0016] Weigh a certain amount of potassium permanganate and sodium dodecyl sulfate (SDS) and add them to deionized water, and stir to promote dissolution to obtain a mixed solvent, in which the concentration range of potassium permanganate is 0.02-0.05 mol / L, and the concentration range of sodium dodecyl sulfate is: 0.01-0.03 mol / L. Then add an appropriate amount of NaOH to adjust the solution pH to 7-10.

[0017] (3) Binder decomposition:

[0018] Pour magnetic powder A into the mixed solvent with a solid-liquid ratio of 1g:1mL-1g:80mL, and introduce flowing argon atmosphere for protection. Stir at the same time, and keep the stirring paddle speed constant at 80-150r / min to avoid magnetic powder agglomeration or solution splashing. React under this condition for 2-4h.

[0019] (4) Separation of binder and magnetic powder:

[0020] After the reaction is completed, the reactants are centrifuged at 1500-2000 r / min for 2-3 times, each time for 5-10 min. The supernatant is discarded to obtain magnetic powder B.

[0021] (5) Recovering magnetic powder and cleaning:

[0022] Pour magnetic powder B and deionized water into a container at a mass volume ratio of 1g:20mL-1g:50mL, and clean with ultrasonic oscillation for 2-5 times, each time for 5-20min; then clean with ethanol ultrasonically for 2-5 times to remove the residual solvent to obtain magnetic powder C; the mass volume ratio of magnetic powder B and ethanol is 1g:20mL-1g:50mL;

[0023] (6) Magnetic powder drying:

[0024] The magnetic powder C is dried in a vacuum drying oven at an absolute vacuum degree of 0.01Pa-0.001Pa at room temperature to a constant weight, thereby obtaining the regenerated NdFeB magnetic powder D with the binder removed.

[0025] This method uses an alkaline mixed solvent system consisting of potassium permanganate-sodium dodecyl sulfate and sodium hydroxide to decompose the polyamide binder at room temperature and pressure. The binder removal effect is significant, and the NdFeB magnetic powder is also well protected. The saturation magnetization (Ms), residual magnetization (Br), coercive force (Hcj) and other magnetic properties of the recovered magnetic powder can reach levels close to those of the original magnetic powder. Potassium permanganate oxidation of polyamide reaction formula:

[0026]

[0027] Reaction principle:

[0028] Potassium permanganate (KMnO4) attacks and breaks the amide bonds in the polyamide molecular chain under alkaline conditions, forming functional groups such as amine and carboxyl groups, which causes the polyamide to decompose and separate from the waste bonded magnetic powder, thus realizing the recovery of NdFeB magnetic powder.

[0029] The advantages of the present invention are:

[0030] 1. This method does not require extreme reaction conditions and can effectively remove the polyamide binder at room temperature and pressure. At the same time, room temperature and pressure also have little damage to NdFeB, which makes this method easy to implement and control in both laboratory and industrial production. Compared with traditional chemical or physical treatment methods, potassium permanganate oxidation has a lower risk of environmental pollution, and this method does not produce a large number of harmful by-products during the reaction process.

[0031] 2. Use sodium hydroxide to adjust the pH value to between 7 and 10. In an alkaline environment, the oxidizability of potassium permanganate will be reduced, and the reduction product will be K2MnO4, which will not produce MnO2 to interfere with the separation of magnetic powder and binder. At the same time, the reduced oxidizability will also weaken the destructive effect on NdFeB. When processing waste injection molded bonded NdFeB magnets, it has a strong selectivity for the amide bond of polyamide. This means that this method can accurately remove the target polymer with little impact on the magnet itself, thereby ensuring the performance and quality of the recovered magnetic powder.

[0032] 3. The sodium dodecyl sulfate (SDS) used in the present invention mainly exists as a surfactant and plays a dispersing and emulsifying role in the reaction system. It can help potassium permanganate to be better dispersed in the solution, increase its contact area with polyamide, and thus promote the oxidation reaction. At the same time, SDS may also inhibit the self-decomposition of potassium permanganate to a certain extent, thereby improving the reaction efficiency. And by using SDS to assist the decomposition of the binder, the amount of potassium permanganate can be reduced, further reducing the oxidative corrosion effect of the oxidant on the NdFeB magnetic powder.

[0033] 4. The magnetic properties of the recycled injection-molded magnetic powder obtained by the present invention are greatly improved. When the saturation magnetization and residual magnetization are significantly improved, the coercive force is also maintained at a high level (the coercive force recovery rate is more than 90%). At the same time, considering that the injection-molded bonded magnetic powder has better plasticity and toughness, it is easy to process and shape to obtain injection-molded bonded magnets and is not prone to cracking and breakage, it has a better production prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 : SEM image in Example 1.

[0035] Figure 2 : VSM diagram in Example 1. DETAILED DESCRIPTION

[0036] Example 1

[0037] The method for removing nylon binder from waste injection-molded bonded NdFeB magnetic powder and recovering NdFeB magnetic powder provided in this embodiment comprises the following steps:

[0038] (1) Crushing of waste magnets:

[0039] The bonded NdFeB magnet waste is put into a jaw crusher for crushing, and then sieved to obtain magnetic powder A with a particle size of less than 150 μm.

[0040] (2) Mixed solvent configuration:

[0041] Weigh 3.16g potassium permanganate and 3.456g sodium dodecyl sulfate (SDS) and add them to deionized water, stir to promote dissolution, and then obtain a mixed solvent, wherein the concentration of potassium permanganate is 0.05mol / L and the concentration of sodium dodecyl sulfate is 0.03mol / L. Then add an appropriate amount of NaOH to adjust the solution pH to 10.

[0042] (3) Binder decomposition:

[0043] Pour 10 g of magnetic powder A into 400 mL of mixed solvent with a solid-liquid ratio of 1 g:40 mL, introduce flowing argon atmosphere for protection, and stir at the same time. The stirring speed of the stirring paddle is constant at 150 r / min to avoid magnetic powder agglomeration or solution splashing. React under this condition for 3 h.

[0044] (4) Separation of binder and magnetic powder:

[0045] After the reaction is completed, the reactants are centrifuged at 2000 r / min for 2 times, each time for 10 min. The supernatant is discarded to obtain magnetic powder B.

[0046] (5) Recovering magnetic powder and cleaning:

[0047] Magnetic powder B and deionized water were poured into a container at a mass volume ratio of 1g:40mL, and ultrasonically cleaned for 3 times, each time for 10 minutes; then, ultrasonically cleaned with ethanol for 3 times to remove the residual solvent to obtain magnetic powder C; the mass volume ratio of magnetic powder B and ethanol was 1g:40mL;

[0048] (6) Magnetic powder drying:

[0049] The magnetic powder C was dried in a vacuum drying oven at an absolute vacuum degree of less than 0.01 Pa at room temperature to a constant weight, and the regenerated NdFeB magnetic powder D without the binder was obtained. The SEM test was performed on the magnetic powder D as shown in the attached figure. Figure 1 As shown in the figure, it can be seen that the surface of the recovered magnetic powder obtained after treatment is smooth and almost free of binder, indicating that the binder bonded between the magnetic powders is effectively dissolved. Then a VSM test was performed on it and the hysteresis loop under this embodiment was obtained as shown in the attached figure. Figure 2 shown.

[0050] The carbon and oxygen content comparison between the recycled bonded NdFeB magnetic powder obtained by this embodiment and the waste bonded NdFeB magnetic powder is shown in Table 2.

[0051] Table 2 Comparison of carbon and oxygen content between recycled bonded NdFeB magnetic powder and waste bonded NdFeB magnetic powder

[0052] Carbon content Oxygen content Waste bonded NdFeB magnetic powder 5.907087％ 0.607045％ Recycling bonded NdFeB magnetic powder 0.053216％ 0.104443％

[0053] The magnetic properties of the recycled bonded NdFeB magnetic powder obtained by this embodiment and the waste bonded NdFeB magnetic powder are compared as shown in Table 3.

[0054] Table 3 Comparison of magnetic properties between recycled bonded NdFeB magnetic powder and waste bonded NdFeB magnetic powder

[0055] Ms(emu / g) Mr(emu / g) Hcj(kOe) Waste bonded NdFeB magnetic powder 117.47 79.69 8.72 Recycling bonded NdFeB magnetic powder 127.33 86.76 8.49

[0056] Example 2

[0057] The method for removing nylon binder from waste injection-molded bonded NdFeB magnetic powder and recovering NdFeB magnetic powder provided in this embodiment comprises the following steps:

[0058] (1) Crushing of waste magnets:

[0059] The bonded NdFeB magnet waste is put into a jaw crusher for crushing, and then sieved to obtain magnetic powder A with a particle size of less than 150 μm.

[0060] (2) Mixed solvent configuration:

[0061] Weigh 1.106g potassium permanganate and 3.024g sodium dodecyl sulfate (SDS) into deionized water, stir to promote dissolution, and then obtain a mixed solvent, wherein the concentration of potassium permanganate is 0.02mol / L and the concentration of sodium dodecyl sulfate is 0.03mol / L. Then add an appropriate amount of NaOH to adjust the solution pH to 7.

[0062] (3) Binder decomposition:

[0063] Pour 10 g of magnetic powder A into 350 mL of mixed solvent with a solid-liquid ratio of 1 g:35 mL. Pass flowing argon atmosphere for protection while stirring. The stirring paddle speed is kept constant at 150 r / min to avoid magnetic powder agglomeration or solution splashing. React under this condition for 3 h.

[0064] (4) Separation of binder and magnetic powder:

[0065] After the reaction is completed, the reactants are centrifuged at 2000 r / min for 2 times, each time for 10 min. The supernatant is discarded to obtain magnetic powder B.

[0066] (5) Recovering magnetic powder and cleaning:

[0067] Magnetic powder B and deionized water were poured into a container at a mass volume ratio of 1g:50mL, and ultrasonically cleaned twice, each time for 10 minutes; then, ultrasonically cleaned three times with ethanol to remove the residual solvent to obtain magnetic powder C; the mass volume ratio of magnetic powder B and ethanol was 1g:50mL;

[0068] (6) Magnetic powder drying:

[0069] The magnetic powder C was dried in a vacuum drying oven at an absolute vacuum degree of less than 0.01 Pa at room temperature to a constant weight, thereby obtaining the regenerated NdFeB magnetic powder D with the binder removed.

[0070] The carbon and oxygen content comparison between the recycled bonded NdFeB magnetic powder obtained by this embodiment and the waste bonded NdFeB magnetic powder is shown in Table 4.

[0071] Table 4 Comparison of carbon and oxygen content between recycled bonded NdFeB magnetic powder and waste bonded NdFeB magnetic powder

[0072] Carbon content Oxygen content Waste bonded NdFeB magnetic powder 5.907087％ 0.607045％ Recycling bonded NdFeB magnetic powder 0.101066％ 0.579689％

[0073] Example 3

[0074] The method for removing nylon binder from waste injection-molded bonded NdFeB magnetic powder and recovering NdFeB magnetic powder provided in this embodiment comprises the following steps:

[0075] (1) Crushing of waste magnets:

[0076] The bonded NdFeB magnet waste is put into a jaw crusher for crushing, and then sieved to obtain magnetic powder A with a particle size of less than 150 μm.

[0077] (2) Mixed solvent configuration:

[0078] Weigh 3.95g potassium permanganate and 1.44g sodium dodecyl sulfate (SDS) into deionized water, stir to promote dissolution and obtain a mixed solvent, wherein the concentration of potassium permanganate is 0.05mol / L and the concentration of sodium dodecyl sulfate is 0.01mol / L. Then add an appropriate amount of NaOH to adjust the solution pH to 8.

[0079] (3) Binder decomposition:

[0080] Pour 10 g of magnetic powder A into 500 mL of mixed solvent with a solid-liquid ratio of 1 g:50 mL. Pass a flowing argon atmosphere for protection while stirring. The stirring paddle speed is kept constant at 150 r / min to avoid magnetic powder agglomeration or solution splashing. React under this condition for 3 h.

[0081] (4) Separation of binder and magnetic powder:

[0082] After the reaction is completed, the reactants are centrifuged at 1500 r / min for 2 times, each time for 10 min. The supernatant is discarded to obtain magnetic powder B.

[0083] (5) Recovering magnetic powder and cleaning:

[0084] Magnetic powder B and deionized water were poured into a container at a mass volume ratio of 1g:20mL, and ultrasonically cleaned twice, each time for 10 minutes; then, ultrasonically cleaned three times with ethanol to remove the residual solvent to obtain magnetic powder C; the mass volume ratio of magnetic powder B and ethanol was 1g:30mL;

[0085] (6) Magnetic powder drying:

[0086] The magnetic powder C is dried in a vacuum drying oven at an absolute vacuum degree of less than 0.01 Pa at room temperature to a constant weight, thereby obtaining the regenerated NdFeB magnetic powder D with the binder removed.

[0087] The carbon and oxygen content comparison between the recycled bonded NdFeB magnetic powder obtained by this embodiment and the waste bonded NdFeB magnetic powder is shown in Table 5.

[0088] Table 5 Comparison of carbon and oxygen content between recycled bonded NdFeB magnetic powder and waste bonded NdFeB magnetic powder

[0089] Carbon content Oxygen content Waste bonded NdFeB magnetic powder 5.907087％ 0.607045％ Recycling bonded NdFeB magnetic powder 0.083423％ 0.293659％

[0090] Example 4

[0091] The method for removing nylon binder from waste injection-molded bonded NdFeB magnetic powder and recovering NdFeB magnetic powder provided in this embodiment comprises the following steps:

[0092] (1) Crushing of waste magnets:

[0093] The bonded NdFeB magnet waste was put into a jaw crusher for crushing, and after sieving, magnetic powder A with a particle size of 150 μm was obtained.

[0094] (2) Mixed solvent configuration:

[0095] Weigh 0.948g potassium permanganate and 0.864g sodium dodecyl sulfate (SDS) into deionized water, stir to promote dissolution, and then obtain a mixed solvent, wherein the concentration of potassium permanganate is 0.02mol / L and the concentration of sodium dodecyl sulfate is 0.01mol / L. Then add an appropriate amount of NaOH to adjust the solution pH to 8.

[0096] (3) Binder decomposition:

[0097] Pour 5 g of magnetic powder A into 300 mL of mixed solvent with a solid-liquid ratio of 1 g:60 mL. Pass flowing argon atmosphere for protection while stirring. The stirring paddle speed is kept constant at 150 r / min to avoid magnetic powder agglomeration or solution splashing. React under this condition for 3 h.

[0098] (4) Separation of binder and magnetic powder:

[0099] After the reaction is completed, the reactants are centrifuged at 1500 r / min for 2 times, each time for 15 min. The supernatant is discarded to obtain magnetic powder B.

[0100] (5) Recovering magnetic powder and cleaning:

[0101] Magnetic powder B and deionized water were poured into a container at a mass volume ratio of 1g:30mL, and ultrasonically cleaned for 4 times, each time for 15 minutes; then, ultrasonically cleaned with ethanol for 2 times to remove the residual solvent to obtain magnetic powder C; the mass volume ratio of magnetic powder B and ethanol was 1g:25mL;

[0102] (6) Magnetic powder drying:

[0103] The magnetic powder C is dried in a vacuum drying oven at an absolute vacuum degree of less than 0.01 Pa at room temperature to a constant weight, thereby obtaining the regenerated NdFeB magnetic powder D with the binder removed.

[0104] The carbon and oxygen content comparison between the recycled bonded NdFeB magnetic powder obtained by this embodiment and the waste bonded NdFeB magnetic powder is shown in Table 6.

[0105] Table 6 Comparison of carbon and oxygen content between recycled bonded NdFeB magnetic powder and waste bonded NdFeB magnetic powder

[0106] Carbon content Oxygen content Waste bonded NdFeB magnetic powder 5.907087％ 0.607045％ Recycling bonded NdFeB magnetic powder 0.099641％ 0.508327％

[0107] Example 5

[0108] The method for removing nylon binder from waste injection-molded bonded NdFeB magnetic powder and recovering NdFeB magnetic powder provided in this embodiment comprises the following steps:

[0109] (1) Crushing of waste magnets:

[0110] The bonded NdFeB magnet waste is put into a jaw crusher for crushing, and then sieved to obtain magnetic powder A with a particle size of less than 150 μm.

[0111] (2) Mixed solvent configuration:

[0112] Weigh 3.16g potassium permanganate and 2.304g sodium dodecyl sulfate (SDS) into deionized water, stir to promote dissolution and obtain a mixed solvent, wherein the concentration of potassium permanganate is 0.05mol / L and the concentration of sodium dodecyl sulfate is 0.02mol / L. Then add an appropriate amount of NaOH to adjust the solution pH to 9.

[0113] (3) Binder decomposition:

[0114] Pour 5 g of magnetic powder A into 400 mL of mixed solvent with a solid-liquid ratio of 1 g:80 mL. Pass flowing argon atmosphere for protection while stirring. The stirring paddle speed is kept constant at 150 r / min to avoid magnetic powder agglomeration or solution splashing. React under this condition for 2 h.

[0115] (4) Separation of binder and magnetic powder:

[0116] After the reaction is completed, the reactants are centrifuged at 1000 r / min for 2 times, each time for 10 min. The supernatant is discarded to obtain magnetic powder B.

[0117] (5) Recovering magnetic powder and cleaning:

[0118] Magnetic powder B and deionized water were poured into a container at a mass volume ratio of 1g:25mL, and ultrasonically cleaned twice, each time for 10 minutes; then, ultrasonically cleaned twice with ethanol to remove the residual solvent to obtain magnetic powder C; the mass volume ratio of magnetic powder B and ethanol was 1g:20mL;

[0119] (6) Magnetic powder drying:

[0120] The magnetic powder C is dried in a vacuum drying oven at an absolute vacuum degree of less than 0.01 Pa at room temperature to a constant weight, thereby obtaining the regenerated NdFeB magnetic powder D with the binder removed.

[0121] The carbon and oxygen content of the recycled bonded NdFeB magnetic powder obtained by this embodiment and the waste bonded NdFeB magnetic powder are shown in Table 7.

[0122] Table 7 Comparison of carbon and oxygen content between recycled bonded NdFeB magnetic powder and waste bonded NdFeB magnetic powder

[0123] Carbon content Oxygen content Waste bonded NdFeB magnetic powder 5.907087％ 0.607045％ Recycling bonded NdFeB magnetic powder 0.064996％ 0.233543％

[0124] The magnetic properties of the recycled bonded NdFeB magnetic powder obtained by this embodiment and the waste bonded NdFeB magnetic powder are compared as shown in Table 8.

[0125] Table 8 Comparison of magnetic properties between recycled bonded NdFeB magnetic powder and waste bonded NdFeB magnetic powder

[0126] Ms(emu / g) Mr(emu / g) Hcj(kOe) Waste bonded NdFeB magnetic powder 117.47 79.69 8.72 Recycling bonded NdFeB magnetic powder 126.13 85.32 8.42

[0127] Example 6

[0128] The method for removing nylon binder from waste injection-molded bonded NdFeB magnetic powder and recovering NdFeB magnetic powder provided in this embodiment comprises the following steps:

[0129] (1) Crushing of waste magnets:

[0130] The bonded NdFeB magnet waste is put into a jaw crusher for crushing, and then sieved to obtain magnetic powder A with a particle size of less than 150 μm.

[0131] (2) Mixed solvent configuration:

[0132] Weigh 0.948g potassium permanganate and 1.728g sodium dodecyl sulfate (SDS) into deionized water, stir to promote dissolution and obtain a mixed solvent, wherein the concentration of potassium permanganate is 0.03mol / L and the concentration of sodium dodecyl sulfate is 0.03mol / L. Then add an appropriate amount of NaOH to adjust the solution pH to 8.

[0133] (3) Binder decomposition:

[0134] Pour 10 g of magnetic powder A into 200 mL of mixed solvent with a solid-liquid ratio of 1 g:20 mL. Pass flowing argon atmosphere for protection while stirring. The stirring paddle speed is kept constant at 150 r / min to avoid magnetic powder agglomeration or solution splashing. React under this condition for 3 h.

[0135] (4) Separation of binder and magnetic powder:

[0136] After the reaction is completed, the reactants are centrifuged at 2000 r / min for 2 times, each time for 10 min. The supernatant is discarded to obtain magnetic powder B.

[0137] (5) Recovering magnetic powder and cleaning:

[0138] Magnetic powder B and deionized water were poured into a container at a mass volume ratio of 1g:30mL, and ultrasonically cleaned for 3 times, each time for 15 minutes; then, ultrasonically cleaned with ethanol for 2 times to remove the residual solvent to obtain magnetic powder C; the mass volume ratio of magnetic powder B and ethanol was 1g:50mL;

[0139] (6) Magnetic powder drying:

[0140] The magnetic powder C is dried in a vacuum drying oven at an absolute vacuum degree of less than 0.01 Pa at room temperature to a constant weight, thereby obtaining the regenerated NdFeB magnetic powder D with the binder removed.

[0141] The carbon and oxygen content comparison between the recycled bonded NdFeB magnetic powder obtained by this embodiment and the waste bonded NdFeB magnetic powder is shown in Table 9.

[0142] Table 9 Comparison of carbon and oxygen content between recycled bonded NdFeB magnetic powder and waste bonded NdFeB magnetic powder

[0143] Carbon content Oxygen content Waste bonded NdFeB magnetic powder 5.907087％ 0.607045％ Recycling bonded NdFeB magnetic powder 0.403562％ 0.862514％

[0144] Example 7

[0145] The method for removing nylon binder from waste injection-molded bonded NdFeB magnetic powder and recovering NdFeB magnetic powder provided in this embodiment comprises the following steps:

[0146] (1) Crushing of waste magnets:

[0147] The bonded NdFeB magnet waste is put into a jaw crusher for crushing, and then sieved to obtain magnetic powder A with a particle size of less than 150 μm.

[0148] (2) Mixed solvent configuration:

[0149] Weigh 1.264g potassium permanganate and 0.576g sodium dodecyl sulfate (SDS) into deionized water, stir to promote dissolution, and then obtain a mixed solvent, wherein the concentration of potassium permanganate is 0.04mol / L and the concentration of sodium dodecyl sulfate is 0.01mol / L. Then add an appropriate amount of NaOH to adjust the solution pH to 7.

[0150] (3) Binder decomposition:

[0151] Pour 5 g of magnetic powder A into 200 mL of mixed solvent with a solid-liquid ratio of 1 g:40 mL. Pass flowing argon atmosphere for protection while stirring. The stirring paddle speed is kept constant at 150 r / min to avoid magnetic powder agglomeration or solution splashing. React under this condition for 3 h.

[0152] (4) Separation of binder and magnetic powder:

[0153] After the reaction is completed, the reactants are centrifuged at 2000 r / min for 2 times, each time for 10 min. The supernatant is discarded to obtain magnetic powder B.

[0154] (5) Recovering magnetic powder and cleaning:

[0155] Magnetic powder B and deionized water were poured into a container at a mass volume ratio of 1 g:20 mL, and ultrasonically cleaned for 5 times, each time for 10 min; then, ultrasonically cleaned with ethanol for 2 times to remove the residual solvent to obtain magnetic powder C; the mass volume ratio of magnetic powder B and ethanol was 1 g:20 mL;

[0156] (6) Magnetic powder drying:

[0157] The magnetic powder C is dried in a vacuum drying oven at an absolute vacuum degree of less than 0.01 Pa at room temperature to a constant weight, thereby obtaining the regenerated NdFeB magnetic powder D with the binder removed.

[0158] The carbon and oxygen content comparison of the recycled bonded NdFeB magnetic powder obtained by this embodiment and the waste bonded NdFeB magnetic powder is shown in Table 10.

[0159] Table 10 Comparison of carbon and oxygen content between recycled bonded NdFeB magnetic powder and waste bonded NdFeB magnetic powder

[0160] Carbon content Oxygen content Waste bonded NdFeB magnetic powder 5.907087％ 0.607045％ Recycling bonded NdFeB magnetic powder 0.095678％ 0.402658％

[0161] Example 8

[0162] The method for removing nylon binder from waste injection-molded bonded NdFeB magnetic powder and recovering NdFeB magnetic powder provided in this embodiment comprises the following steps:

[0163] (1) Crushing of waste magnets:

[0164] The bonded NdFeB magnet waste is put into a jaw crusher for crushing, and then sieved to obtain magnetic powder A with a particle size of less than 150 μm.

[0165] (2) Mixed solvent configuration:

[0166] Weigh 0.237g potassium permanganate and 0.288g sodium dodecyl sulfate (SDS) into deionized water, stir to promote dissolution, and then obtain a mixed solvent, wherein the concentration of potassium permanganate is 0.03mol / L and the concentration of sodium dodecyl sulfate is 0.02mol / L. Then add an appropriate amount of NaOH to adjust the solution pH to 8.

[0167] (3) Binder decomposition:

[0168] Pour 50 g of magnetic powder A into 50 mL of mixed solvent with a solid-liquid ratio of 1 g:1 mL. Pass flowing argon gas atmosphere for protection while stirring. The stirring paddle speed is kept constant at 150 r / min to avoid magnetic powder agglomeration or solution splashing. React under this condition for 3 h.

[0169] (4) Separation of binder and magnetic powder:

[0170] After the reaction is completed, the reactants are centrifuged at 2000 r / min for 2 times, each time for 10 min. The supernatant is discarded to obtain magnetic powder B.

[0171] (5) Recovering magnetic powder and cleaning:

[0172] Magnetic powder B and deionized water were poured into a container at a mass volume ratio of 1g:50mL, and ultrasonically cleaned for 3 times, each time for 15 minutes; then, ultrasonically cleaned with ethanol for 4 times to remove the residual solvent to obtain magnetic powder C; the mass volume ratio of magnetic powder B and ethanol was 1g:40mL;

[0173] (6) Magnetic powder drying:

[0174] The magnetic powder C is dried in a vacuum drying oven at an absolute vacuum degree of less than 0.01 Pa at room temperature to a constant weight, thereby obtaining the regenerated NdFeB magnetic powder D with the binder removed.

[0175] The carbon and oxygen content comparison of the recycled bonded NdFeB magnetic powder obtained by this embodiment and the waste bonded NdFeB magnetic powder is shown in Table 11.

[0176] Table 11 Comparison of carbon and oxygen content between recycled bonded NdFeB magnetic powder and waste bonded NdFeB magnetic powder

[0177] Carbon content Oxygen content Waste bonded NdFeB magnetic powder 5.907087％ 0.607045％ Recycling bonded NdFeB magnetic powder 1.925314％ 0.104443％

Claims

1. A method for removing nylon from waste injection-molded bonded NdFeB magnetic powder by potassium permanganate chemical reaction method, characterized in that: Provided is a mixed solvent for removing nylon binder from waste injection-molded bonded NdFeB magnetic powder. The mixed solvent consists of potassium permanganate, sodium dodecyl sulfate, sodium hydroxide and deionized water, wherein the concentration range of potassium permanganate is 0.02-0.05 mol / L, the concentration range of sodium dodecyl sulfate is 0.01-0.03 mol / L, and the amount of sodium hydroxide used is such that the pH value of the solution is maintained between 7 and 10.

2. The method according to claim 1, characterized in that The following steps are involved: (1) Crushing of waste magnets: Put the bonded NdFeB magnet waste into a jaw crusher for crushing, and then sieve to obtain magnetic powder A with a particle size of less than 150 μm; (2) Mixed solvent configuration: Weigh potassium permanganate and sodium dodecyl sulfate and add them to deionized water, and stir to promote dissolution to obtain a mixed solvent, wherein the concentration range of potassium permanganate is 0.02-0.05 mol / L, and the concentration range of sodium dodecyl sulfate is: 0.01-0.03 mol / L; then add NaOH to adjust the solution pH to 7-10; (3) Binder decomposition: Pour magnetic powder A into the mixed solvent with a solid-liquid ratio of 1g:1mL-1g:80mL, and introduce flowing argon atmosphere for protection while stirring. The stirring paddle speed is constant at 80-150r / min to avoid magnetic powder agglomeration or solution splashing. React under this condition for 2-4h; (4) Separation of binder and magnetic powder: After the reaction is completed, the reactants are centrifuged at a speed of 1500-2000 r / min for 2-3 times, each time for 5-10 minutes; the supernatant is discarded to obtain magnetic powder B; (5) Recovering magnetic powder and cleaning: Pour magnetic powder B and deionized water into a container at a mass volume ratio of 1g:20mL-1g:50mL, and clean with ultrasonic oscillation for 2-5 times, each time for 5-20 minutes; then clean with ethanol ultrasonically for 2-5 times to remove the residual solvent to obtain magnetic powder C; (6) Magnetic powder drying: The magnetic powder C is dried in a vacuum drying oven at an absolute vacuum degree of 0.01Pa-0.001Pa at room temperature to a constant weight, thereby obtaining the regenerated NdFeB magnetic powder D with the binder removed.

Images