Cellulose-based modifier for forming neodymium-iron-boron magnet and preparation method of cellulose-based modifier

Abstract

The invention relates to the field of composite materials, in particular to a cellulose-based modifier for neodymium-iron-boron magnet forming and a preparation method thereof.The structural formula of the cellulose-based modifier is shown in the formula (I), R is H, imgabs0 # imgabs1 # n ranges from 2 to 300, m ranges from 1 to 2500, and when the cellulose-based modifier is applied to neodymium-iron-boron magnet forming, the cellulose-based modifier can be used for forming neodymium-iron-boron magnets. The green body density, the sintered blank density, the residual oxygen content and the residual carbon content of the neodymium-iron-boron magnet can meet the commercial application requirements, and the preparation method of the neodymium-iron-boron magnet is provided. # imgabs2 #

Description

Technical Field

[0001] The present invention relates to the field of composite materials, and specifically to a cellulose-based modifier for NdFeB magnet forming and its preparation method. Background Art

[0002] NdFeB magnets are an important rare-earth magnetic material, with many advantages such as high magnetic energy product and excellent heat resistance, and are widely used in various fields such as engines and electronic devices. It is mainly composed of three elements: neodymium (Nd), iron (Fe), and boron (B). In addition to these three main elements, a small amount of other elements such as heavy rare-earth elements like dysprosium (Dy) and terbium (Tb) are added to improve the coercivity of the magnet and enhance its demagnetization resistance; adding cobalt (Co) can improve the temperature characteristics of the magnet, enabling the magnet to maintain good magnetism at higher temperatures. The preparation process of NdFeB magnets includes melting, powder making, forming, and sintering. Among them, the particle size and shape of the powder in the powder-making process have a great impact on the final performance of the magnet. The prepared powder is put into a mold and oriented and pressed under the action of a magnetic field to form a green body. The green body density affects the finally prepared NdFeB magnet. The green body density is also affected by the number of times and pressure during the pressing process, as well as magnetic field orientation, powder strength, and particle shape. At the same time, there are some other problems in the forming process of NdFeB magnets, such as poor fluidity and easy cracking after forming, which limit the improvement of magnet performance. Therefore, it is necessary to develop a forming modifier to improve the forming performance and physical properties of NdFeB magnets.

[0003] NdFeB magnet forming modifiers play multiple key roles during the forming process. (1) Improving forming fluidity: Modifiers such as lubricants and dispersants can reduce the friction between powders, making the powders flow more easily and fill every corner of the mold, thus improving the forming efficiency; (2) Increasing bonding strength: Binders can enhance the bonding force between powder particles, which is crucial for the mechanical strength and magnetic properties of the final magnet. (3) Controlling the shrinkage rate: During the forming process, the magnet will undergo a certain amount of shrinkage. The modifier can help control this shrinkage and reduce defects in the final product. (4) Preventing powder agglomeration: Dispersants and surfactants can prevent powder particles from agglomerating during the forming process, ensuring the uniformity and consistency of the magnet. The roles of NdFeB magnet forming modifiers during the forming process are multi-faceted. They not only affect the final performance of the magnet but also affect production efficiency and cost. Selecting the appropriate modifier is crucial for producing high-quality and high-performance NdFeB magnets.

[0004] In response to the above technical problems, the inventor prepared a cellulose-based modifier during the research process. The modifier is efficient and durable Summary of the Invention

[0005] In view of this, the present invention uses common solvents to prepare a new type of convenient, concise, green and environmentally friendly molding modifier, and specifically discloses its preparation method, solving the problems of multiple types, multiple components, high cost, high toxicity, etc. of existing molding modifiers.

[0006] In the first aspect, the present invention provides a cellulose-based modifier for neodymium iron boron magnet molding, and the structural formula of the cellulose-based modifier is shown in formula (Ⅰ):

[0007]

[0008] Among them, R is H, n is 2 - 300, and m is 1 - 2500.

[0009] Preferably, n is 20 - 230, and m is 20 - 230.

[0010] In the second aspect, the present invention provides a preparation method of the cellulose-based modifier, including the following steps:

[0011] (1) Add an ester compound and 0.1% - 0.5% stannous octoate to a dried three-necked flask, and heat up to 40 - 50 °C;

[0012] (2) Dissolve a high molecular polymer that has been vacuum high-temperature dehydrated and has an equimolar amount with the ester compound in an organic solvent, and drop it into the system obtained in step (1) within 30 minutes;

[0013] (3) Keep the mixed solution obtained in step (2) warm for 2 - 12 h;

[0014] (4) Add ethyl cellulose to an organic solvent and heat and dissolve it in an oil bath at 60 - 90 °C;

[0015] (5) Drop the solution obtained in step (3) into the ethyl cellulose solution obtained in step (4);

[0016] (6) Keep the mixed solution obtained in step (5) warm for 2 - 12 h;

[0017] (7) Cool the mixed solution obtained in step (6) to room temperature;

[0018] (8) Add an organic solvent to the mixed solution obtained in step (7) to adjust the solid content to 20%.

[0019] Preferably, the ester compound in step (1) is isophorone diisocyanate, toluene diisocyanate or hexamethylene diisocyanate.

[0020] Preferably, the polymer in step (2) is polyethylene glycol methyl ether, polyethylene glycol, polypropylene glycol, and polytetrahydrofuran ether diol.

[0021] Preferably, the organic solvent in steps (2), (4), and (8) is one or more of ethyl acetate, diethyl adipate, and propylene glycol methyl ether acetate.

[0022] In a third aspect, the present invention provides the use of the cellulose-based modifier described above in the preparation of shaped NdFeB magnets.

[0023] In a fourth aspect, the present invention provides a shaped NdFeB magnet, which is prepared by modifying an NdFeB magnet with the cellulose-based modifier described above.

[0024] The beneficial effects of the present invention are as follows: The present invention provides a cellulose-based modifier for shaping NdFeB magnets. When applied to the shaping of NdFeB magnets, the green density, sintered blank density, residual oxygen content, and residual carbon content of the NdFeB magnets can meet the requirements of commercial applications, and a preparation method thereof is provided. Detailed Embodiments

[0025] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0026] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0027] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0028] Without departing from the scope or spirit of the present invention, various modifications and variations can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are merely exemplary.

[0029] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to. Unless otherwise specified, the "parts" described in the present invention are calculated by weight.

[0030] The commercial two-component products in the following examples include antioxidant YSH-01 (Tianjin Yuesheng Magnetoelectric Technology Co., Ltd.) and lubricant YSH-06 (Tianjin Yuesheng Magnetoelectric Technology Co., Ltd.).

[0031] Example 1. Preparation method 1 of a cellulose-based molding modifier

[0032] It includes the following steps:

[0033] 22.232 g of isophorone diisocyanate (IPDI) and 0.12 g of stannous octoate are added to a dried three-necked flask, and the temperature is raised to 45 °C. Then, 50 g of mPEG (WM: 500) that has been vacuum dehydrated at high temperature is dissolved in a mixed solution of 150 mL of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate, and is added dropwise to the above system within 30 minutes, and kept warm for 5 hours.

[0034] 100 g of ethyl cellulose is added to a mixed solution of 500 mL of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate, heated and dissolved in an oil bath at 65 °C. Then, the above-synthesized IPDI-modified mPEG solution is added dropwise to the system. After keeping warm for 5 hours, it is cooled to room temperature, and a mixed solution of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate is added to adjust the solid content to 20% for standby.

[0035] Example 2. Preparation method 2 of a cellulose-based molding modifier

[0036] It includes the following steps:

[0037] 22.232 g of isophorone diisocyanate (IPDI) and 0.12 g of stannous octoate are added to a dried three-necked flask, and the temperature is raised to 45 °C. Then, 100 g of mPEG (WM: 1000) that has been vacuum dehydrated at high temperature is dissolved in a mixed solution of 250 mL of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate, and is added dropwise to the above system within 30 minutes, kept warm for 6 hours, and cooled to room temperature for standby.

[0038] Add 200 g of ethyl cellulose to 1000 mL of a mixed solution of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate, heat and dissolve it in an oil bath at 65 °C. Then, drop the above-synthesized IPDI-modified mPEG solution into the system. After keeping the temperature for 6 hours, cool it to room temperature, and add a mixed solution of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate to adjust the solid content to 20% for standby.

[0039] Example 3. Preparation method 3 of a cellulose-based molding modifier

[0040] It includes the following steps:

[0041] Add 11.116 g of isophorone diisocyanate (IPDI) and 0.1 g of stannous octoate to a dried three-necked flask, and raise the temperature to 45 °C. Then, dissolve 100 g of mPEG (WM: 2000) that has been dehydrated under vacuum at high temperature in 250 mL of a mixed solution of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate, and drop it into the above system within 30 min. Keep the temperature for 7 hours, and cool it to room temperature for standby.

[0042] Add 200 g of ethyl cellulose to 1000 mL of a mixed solution of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate, heat and dissolve it in an oil bath at 65 °C. Then, drop the above-synthesized IPDI-modified mPEG solution into the system. After keeping the temperature for 6 hours, cool it to room temperature, and add a mixed solution of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate to adjust the solid content to 20% for standby.

[0043] Example 4. Preparation method 4 of a cellulose-based molding modifier

[0044] It includes the following steps:

[0045] Add 5.558 g of isophorone diisocyanate (IPDI) and 0.05 g of stannous octoate to a dried three-necked flask, and raise the temperature to 45 °C. Then, dissolve 125 g of mPEG (WM: 5000) that has been dehydrated under vacuum at high temperature in 250 mL of a mixed solution of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate, and drop it into the above system within 30 min. Keep the temperature for 7 hours, and cool it to room temperature for standby.

[0046] Add 225 g of ethyl cellulose to 1000 mL of a mixed solution of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate, heat and dissolve it in an oil bath at 65 °C. Then, drop the above-synthesized IPDI-modified mPEG solution into the system. After keeping the temperature for 6 hours, cool it to room temperature, and add a mixed solution of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate to adjust the solid content to 20% for standby.

[0047] Example 5. Preparation Method of a Cellulose-based Molding Modifier 5

[0048] The method comprises the following steps:

[0049] 5.558 g of isophorone diisocyanate (IPDI) and 0.05 g of stannous octoate are added into a dried three-necked flask, and the temperature is raised to 45 °C. Then, 250 g of mPEG (WM: 10000) that has been dehydrated under vacuum at high temperature is dissolved in a mixed solution of 500 mL of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate, and is added dropwise to the above system within 30 min. After keeping warm for 7 hours, it is cooled to room temperature for standby.

[0050] 550 g of ethyl cellulose is added into a mixed solution of 1500 mL of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate, and is heated and dissolved in an oil bath at 65 °C. Then, the above-synthesized IPDI-modified mPEG solution is added dropwise to the system. After keeping warm for 6 hours, it is cooled to room temperature, and ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate is added to adjust the solid content to 20% for standby.

[0051] Example 6. Preparation Method of a Cellulose-based Molding Modifier 6

[0052] The method comprises the following steps:

[0053] 5.558 g of isophorone diisocyanate (IPDI) and 0.05 g of stannous octoate are added into a dried three-necked flask, and the temperature is raised to 45 °C. Then, 500 g of mPEG (WM: 20000) that has been dehydrated under vacuum at high temperature is dissolved in a mixed solution of 1000 mL of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate, and is added dropwise to the above system within 30 min. After keeping warm for 7 hours, it is cooled to room temperature for standby.

[0054] 400 g of ethyl cellulose is added into a mixed solution of 1000 mL of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate, and is heated and dissolved in an oil bath at 65 °C. Then, the above-synthesized IPDI-modified mPEG solution is added dropwise to the system. After keeping warm for 6 hours, it is cooled to room temperature, and a mixed solution of ethyl acetate / diethyl adipate / propylene glycol methyl ether acetate is added to adjust the solid content to 20% for standby.

[0055] Example 7. Preparation of a Molded Neodymium-Iron-Boron Magnet

[0056] (1) The neodymium-iron-boron alloy material is crushed into powders with a size of 3 - 5 microns. To ensure good fluidity, uniformity, and integrity during the molding process, a cellulose-based molding modifier is added to the neodymium-iron-boron powder during mechanical crushing, and the addition amount of the modifier is 0.12% or 0.25% of the neodymium-iron-boron powder;

[0057] (2) In an inert atmosphere, the crushed neodymium-iron-boron powder is placed in a mold, and an external magnetic field and pressure are applied to orient the particles in the magnetic field direction. The applied pressures are 15, 20, 30, 40, or 50 MPa respectively.

[0058] (3) Study the green density, sintered blank density, residual oxygen content, and residual carbon content of neodymium-iron-boron magnets under different addition amounts and different pressures.

[0059] Table 1 Green density (g / cm3) of neodymium-iron-boron powder with 0.12% modifier addition under different pressure conditions

[0060]

[0061] The green density of neodymium-iron-boron powder with 0.12% modifier addition under different pressure conditions is shown in Table 1. It can be seen from Table 1 that the green density of neodymium-iron-boron powder with 0.12% modifier addition increases with the increase of pressure. Under the pressure condition of 40 MPa, the green density of neodymium-iron-boron powder has reached the same level as that of commercial two-component products, achieving good results.

[0062] Table 2 Green density (g / cm3) of neodymium-iron-boron powder with 0.25% modifier addition under different pressure conditions

[0063]

[0064] The green density of neodymium-iron-boron powder with 0.25% modifier addition under different pressure conditions is shown in Table 2. It can be seen that the green density of neodymium-iron-boron powder with 0.25% modifier addition increases with the increase of pressure. Under the pressure condition of 20 MPa, the green density of neodymium-iron-boron powder has reached the same level as that of commercial products, achieving good results.

[0065] Table 3 Sintered blank density (g / cm 3 ) of neodymium-iron-boron powder with 0.12% modifier addition under different pressure conditions

[0066]

[0067] The sintered blank density of neodymium-iron-boron powder with 0.12% modifier addition under different pressure conditions is shown in Table 3. It can be seen that the sintered blank density of neodymium-iron-boron powder with 0.12% modifier addition increases with the increase of pressure. Under the pressure condition of 20 MPa, the sintered blank density of neodymium-iron-boron powder has reached the same level as that of commercial products, achieving good results.

[0068] Table 4 Sintered blank density (g / cm 3 ) of neodymium-iron-boron powder with 0.25% modifier addition under different pressure conditions

[0069]

[0070] The densities of the sintered NdFeB powder compacts with a modifier addition of 0.25% under different pressure conditions are shown in Table 4. It can be seen that the density of the sintered NdFeB powder compacts with a modifier addition of 0.25% increases with the increase of pressure. Under the pressure condition of 15 MPa, the density of the sintered NdFeB powder compacts has been consistent with that of commercial products, achieving good results.

[0071] Table 5 Residual oxygen content (×1000 ppm) of NdFeB powder with a modifier addition of 0.25% under different pressure conditions

[0072]

[0073] When producing high-quality sintered NdFeB magnets, it is usually required that the oxygen content be as low as possible. The residual oxygen content of the NdFeB powder with a modifier addition of 0.25% under different pressure conditions is shown in Table 5. It can be seen that the designed and synthesized modifier is similar to or even lower than commercial products in terms of the residual oxygen content index, achieving good results in controlling the oxygen content.

[0074] Table 6 Residual carbon content (×1000 ppm) of NdFeB powder with a modifier addition of 0.25% under different pressure conditions

[0075] Pressure / MPa Commercial two-component product Example 2 Example 3 Example 4 15 0.09 0.078 0.0696 0.088 20 0.088 0.088 0.082 0.078 30 0.086 0.086 0.086 0.086 40 0.092 0.080 0.084 0.082

[0076] Excessive residual carbon content may have an adverse impact on the performance of the magnet, such as reducing the coercivity of the magnet. The residual carbon content of the NdFeB powder with a modifier addition of 0.25% under different pressure conditions is shown in Table 6. It can be seen that the designed and synthesized modifier is lower than commercial products in terms of the residual carbon content index, achieving good results in reducing the carbon content.

[0077] In summary, when the cellulose-based shaping modifier prepared in the present invention is applied to the shaping of NdFeB magnets, the green density, sintered compact density, residual oxygen content, and residual carbon content of the NdFeB magnets can already meet the requirements of commercial applications.

[0078] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

[0079] In addition, those skilled in the art can also make other changes within the spirit of the present invention. Of course, these changes made in accordance with the spirit of the present invention should all be included in the scope protected by the present invention.

Claims

1. A cellulose-based modifier for forming NdFeB magnets, characterized in that: The structural formula of the cellulose-based modifier is shown in formula (I): Where R is H, n is 2-300, and m is 1-2500.

2. The cellulose-based modifier according to claim 1, characterized in that n is 20-230, m is 20-230.

3. The method for preparing a cellulose-based modifier according to claim 1, characterized in that: The steps include: (1) adding an ester compound and 0.1%-0.5% stannous octoate into a dried three-necked flask and heating the flask to 40-50° C.; (2) dissolving a high molecular weight polymer that has been subjected to vacuum high temperature dehydration treatment in an organic solvent in an amount equal to the mole of the ester compound, and adding the high molecular weight polymer to the system obtained in step (1) dropwise within 30 minutes; (3) keeping the mixed solution obtained in step (2) warm for 2-12 hours; (4) adding ethyl cellulose to an organic solvent and heating in an oil bath at 60-90° C. to dissolve the ethyl cellulose; (5) adding dropwise the solution obtained in step (3) to the ethyl cellulose solution obtained in step (4); (6) keeping the mixed solution obtained in step (5) warm for 2-12 hours; (7) cooling the mixed solution obtained in step (6) to room temperature; (8) Add an organic solvent to the mixed solution obtained in step (7) to adjust the solid content to 20%.

4. The preparation method according to claim 3, characterized in that: The acid ester compound in step (1) is isophorone diisocyanate, toluene diisocyanate or hexamethylene diisocyanate.

5. The preparation method according to claim 3, characterized in that: The high molecular polymer described in step (2) is polyethylene glycol methyl ether, polyethylene glycol, polypropylene glycol and polytetramethylene glycol.

6. The preparation method according to claim 3, characterized in that: The organic solvent described in steps (2), (4) and (8) is one or more of ethyl acetate, diethyl adipate and propylene glycol methyl ether acetate.

7. Use of the cellulose-based modifier as claimed in claim 1 in the preparation of molded NdFeB magnets.

8. A molded NdFeB magnet, characterized in that: The molded NdFeB magnet is prepared by modifying the NdFeB magnet with the cellulose-based modifier as described in claim 1.

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