Environmentally friendly stripping agent for NdFeB materials and preparation method and use method thereof

Abstract

The present invention relates to the technical field of environmentally friendly materials. The present invention provides an environmentally friendly stripping agent for NdFeB materials, a preparation method thereof, and a use method thereof. The stripping agent contains 1-5 weight percent of ammonium carbonate, 5-10 weight percent of sodium dihydrogen phosphate or trisodium phosphate, 1-5 weight percent of sodium hydroxide, 10-15 weight percent of potassium citrate, 5-10 weight percent of aminotriethanol, 15-20 weight percent of hexamethylenetetramine or ethylenediamine, 40-50 weight percent of deionized water, and 0.1-1 weight percent of A chelating agent and a surface repair agent; wherein the surface repair agent is a composition comprising 0.1-1 weight percent nanoparticles and 0.1-0.5 weight percent rare earth element compounds; the nanoparticles and the rare earth element compounds are used to form a complex for repairing tiny surface defects; the rare earth element compounds include dysprosium compounds, and one or more of praseodymium compounds and / or samarium compounds; the nanoparticles include nano-neodymium oxide and nano-iron oxide, and the mass ratio of nano-neodymium oxide to nano-iron oxide is 1:1-2:3.

Description

Technical Field

[0001] The present invention relates to the technical field of fireproof materials, in particular to an environmentally friendly stripping agent for neodymium iron boron materials and a preparation method and a use method thereof. Background Art

[0002] With the widespread application of NdFeB rare earth permanent magnet materials in industries such as electronics, automobiles, and medical devices, the demand for their surface treatment technology is also increasing. In order to improve the corrosion resistance and aesthetics of NdFeB materials, they are usually electroplated, such as nickel plating, copper plating, zinc plating, zinc-nickel alloy plating, and chemical nickel plating. However, due to production process limitations and operational errors, defective products are often produced, requiring rework and deplating. Traditional deplating methods often use sodium cyanide as the main material. Although sodium cyanide has strong deplating ability, its highly toxic nature poses a great threat to operators and the environment. In addition, deplating solutions prepared with sodium cyanide will cause certain damage to the NdFeB substrate and its performance, resulting in a decrease in the qualified rate of deplated products.

[0003] In recent years, with the rise of environmental awareness and the emphasis on safe production, the development of a cyanide-free, environmentally friendly, and efficient stripping agent has become an urgent need within the industry. While existing cyanide-free stripping agents have addressed the toxicity of sodium cyanide to a certain extent, they still have shortcomings in terms of stripping efficiency, scope of application, and substrate protection. For example, some cyanide-free stripping agents can only strip specific coatings and are unable to simultaneously process multiple coatings, increasing production costs and operational complexity. Furthermore, some cyanide-free stripping agents exhibit slow stripping speeds when used at moderate temperatures, and their protective effects on the substrate are also unsatisfactory. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention provides an environmentally friendly stripping agent for NdFeB materials and a preparation method and a use method thereof, which solve the problems of the above-mentioned background technology.

[0005] According to a first aspect of the present invention, an environmentally friendly stripping agent for NdFeB materials is provided. Based on the total weight of the stripping agent, the stripping agent comprises, in percentage by weight:

[0006] 1-5 wt% of ammonium carbonate, 5-10 wt% of sodium dihydrogen phosphate or trisodium phosphate, 1-5 wt% of sodium hydroxide, 10-15 wt% of potassium citrate, 5-10 wt% of aminotriethanol, 15-20 wt% of hexamethylenetetramine or ethylenediamine, 40-50 wt% of deionized water, and 0.1-1 wt% of a chelating agent and a surface repair agent;

[0007] Wherein, the surface repair agent is a composition comprising 0.1-1 wt% of nanoparticles and 0.1-0.5 wt% of a rare earth element compound; the nanoparticles and the rare earth element compound are used to form a complex for repairing tiny surface defects;

[0008] The rare earth element compound includes one or more of a dysprosium compound, a praseodymium compound and / or a samarium compound;

[0009] The nanoparticles include nano-neodymium oxide and nano-iron oxide, and the mass ratio of the nano-neodymium oxide to the nano-iron oxide is 1:1-2:3.

[0010] Optionally, the chelating agent is used to form a stable chelate with the metal ion.

[0011] Optionally, the surface repair agent is used to chemically react with the surface of the NdFeB material during the stripping process to repair tiny defects or damage on the surface.

[0012] Optionally, the surface repair agent can chemically react with the surface of the NdFeB material during the stripping process to repair tiny defects or damage on the surface and improve surface quality and performance.

[0013] Optionally, the chelating agent is selected from one or more of ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and hydroxyethylidenediphosphonic acid (HEDP).

[0014] Optionally, the particle size of the nanoparticles is between 1-100 nanometers.

[0015] Alternatively, nanoparticles can be evenly dispersed in the stripping agent and attached to the surface of NdFeB to fill tiny defects and improve the surface quality.

[0016] Optionally, the ratio of the mass of the dysprosium compound to the mass of the praseodymium compound and / or the samarium compound is 1:2-1:4;

[0017] The dysprosium compound includes one or both of dysprosium nitrate and dysprosium chloride;

[0018] The praseodymium compound includes one or both of praseodymium nitrate and praseodymium chloride;

[0019] The samarium compound includes one or more of samarium nitrate and samarium chloride.

[0020] Alternatively, praseodymium nitrate (Pr(NO3)3) and praseodymium chloride (PrCl3) can provide a repairing effect and have good solubility. Praseodymium compounds can form stable complexes with the neodymium element in neodymium iron boron, which helps to repair surface defects.

[0021] Optionally, dysprosium nitrate (Dy(NO3)3) and dysprosium chloride (DyCl3) can also provide a repair effect and help improve the corrosion resistance of the material. Dysprosium compounds can also synergize with the neodymium element in NdFeB, especially in improving magnetic properties.

[0022] Optionally, samarium nitrate (Sm(NO3)3) and samarium chloride (SmCl3) can form stable complexes with the neodymium element in NdFeB, which helps to repair surface defects, also provide a repair effect, and help improve the corrosion resistance of the material.

[0023] Compounds of praseodymium nitrate, praseodymium chloride, dysprosium nitrate, dysprosium chloride, samarium nitrate, and samarium chloride can chemically react with the neodymium element in the NdFeB material during the stripping process to form stable complexes. These complexes help repair minor surface defects and provide an additional protective layer. However, the concentration of neodymium in NdFeB is limited, and nano-neodymium oxide can enhance the complexation between the compounds and the neodymium element, thereby forming a thin film on the surface of the NdFeB material and filling the minor surface defects of the NdFeB material. Nano-iron oxide can be evenly dispersed in the stripping agent, adhere to the NdFeB surface, and fill the minor defects. The combination of compounds of praseodymium nitrate, praseodymium chloride, dysprosium nitrate, dysprosium chloride, samarium nitrate, and samarium chloride with nanoparticles enhances surface density and smoothness, reduces oxidation and corrosion, and improves surface quality.

[0024] Nano-neodymium oxide, due to its very small particle size (between 1 and 100 nanometers), has an extremely high specific surface area. This means that per unit mass, nano-neodymium oxide provides a larger surface contact area and better dispersibility, allowing it to form denser complexes with compounds and more stably fill tiny gaps. Furthermore, the amount of nano-neodymium oxide added in the present invention is slightly less than that of the compound, thereby reducing the risk of agglomeration between the neodymium oxide and the compound when not in use.

[0025] More importantly, as a permanent magnet material, NdFeB rare earth will affect its magnetic effect when its surface is slightly damaged. However, praseodymium and samarium can increase the remanence and maximum magnetic energy product of NdFeB materials, thereby enhancing its magnetic properties and reducing the damage to magnetic properties caused by stripping agents. Dysprosium can significantly improve the coercivity and thermal stability of NdFeB materials, especially under high temperature conditions. These compounds have high oxidation resistance and corrosion resistance, which can reduce oxidation and corrosion of NdFeB materials during the stripping process.

[0026] Optionally, the surface repair agent further comprises one of neodymium nitrate, neodymium chloride, ferric sulfate, ferric chloride, boric acid and borax.

[0027] Alternatively, neodymium salts can chemically react with defects on the surface of NdFeB to fill tiny pores.

[0028] Optionally, the iron salt can react with the iron element on the surface of NdFeB to enhance the density of the surface.

[0029] Optionally, the boron compound can react with the boron element on the surface of NdFeB to repair minor surface damage.

[0030] Optionally, the pH value of the stripping agent is 10-15, and the pH value of the stripping agent is controlled by adjusting the amount of sodium hydroxide to optimize the stripping effect and protect the NdFeB substrate.

[0031] Optionally, the stripping agent further contains 0.5-2 wt % of an antioxidant, which can effectively prevent oxidation of the metal surface during the stripping process, thereby improving the stripping efficiency and the surface quality of the NdFeB substrate.

[0032] Optionally, the antioxidant is selected from one or more of ascorbic acid, sodium sulfite, and sodium metabisulfite.

[0033] In a second aspect, an embodiment of the present invention provides a method for preparing an environmentally friendly stripping agent for NdFeB materials, comprising the following steps:

[0034] S1: 40-50 wt % of deionized water, 15-20 wt % of hexamethylenetetramine or ethylenediamine, and 0.1-0.5 wt % of corrosion inhibitor W are mixed to form solution a;

[0035] S2: mixing the remaining deionized water with 1-5 wt % of ammonium carbonate, 5-10 wt % of sodium dihydrogen phosphate or trisodium phosphate, 1-5 wt % of sodium hydroxide, 10-15 wt % of potassium citrate, and 0.1-1 wt % of a chelating agent to form a solution b;

[0036] S3: Mixing solution a in S1 with solution b in S2 to form solution c;

[0037] S4: mixing the solution c in step S3 with 5-10 wt % of aminotriethanol, 0.5-2 wt % of an antioxidant and a surface repair agent to prepare the stripping agent.

[0038] In a third aspect, an embodiment of the present invention provides a method for using an environmentally friendly stripping agent on a NdFeB material, comprising the following steps:

[0039] (1) Soaking the NdFeB product that needs to be reworked and stripped in the stripping agent, and adjusting the stripping time according to the thickness of the coating, ranging from 5 to 180 minutes;

[0040] (2) After the stripping is completed, use ultrasonic cleaning to complete the stripping process;

[0041] (3) During the stripping process, the stripping agent is used at 70-100°C without damaging the NdFeB substrate and its performance.

[0042] Optionally, different immersion times can be used for different coatings, for example, for nickel coating, the immersion time is 10 minutes; for copper coating, the immersion time is 15 minutes; for zinc coating, the immersion time is 20 minutes; for zinc-nickel alloy coating, the immersion time is 25 minutes; for chemical nickel coating, the immersion time is 30 minutes.

[0043] Optionally, when the stripping agent is used under medium temperature conditions, the chelating agent forms a stable chelate with metal ions such as nickel, copper, and zinc, which significantly improves the stripping efficiency and reduces harmful byproducts generated during the stripping process.

[0044] Optionally, the antioxidant effectively prevents oxidation of the metal surface during the stripping process, thereby improving the stripping efficiency and the surface quality of the NdFeB substrate.

[0045] Optionally, during the stripping process, the components of the stripping agent work synergistically to significantly improve the stripping efficiency, shorten the stripping time, and do not damage the NdFeB substrate and its performance.

[0046] The present invention provides an environmentally friendly stripping agent for NdFeB materials. By incorporating nanoparticles and rare earth element compounds in specific proportions, it significantly improves stripping efficiency and surface quality while also enhancing the magnetic properties of NdFeB materials. Furthermore, the flexible and environmentally friendly formulation makes it suitable for a variety of applications, offering broad potential and significant competitive advantages. Through its unique formulation and component selection, it achieves rapid and efficient stripping of various coatings on NdFeB materials, including nickel, copper, zinc, zinc-nickel alloys, and electroless nickel.

[0047] The present invention adds ammonium carbonate and aminotriethanol as surfactants to effectively resist oxidation of the metal surface and improve stripping efficiency; sodium dihydrogen phosphate or trisodium phosphate and sodium hydroxide serve as corrosion inhibitors to stabilize the pH value of the stripping agent and prevent corrosion of the NdFeB substrate; potassium citrate and hexamethylenetetramine or ethylenediamine serve as complexing agents to form stable chelates with metal ions such as nickel, copper, and zinc, thereby enhancing the complexing effect of the stripping agent. These components work synergistically to not only significantly improve stripping efficiency and shorten stripping time, but also do not damage the NdFeB substrate and its performance, ensuring the high quality of the stripped product. In addition, the stripping agent reduces the generation of harmful byproducts, has good environmental performance and economic benefits.

[0048] The pH value of the stripping agent of the present invention is controlled between 10 and 15, ensuring efficient stripping while avoiding the corrosion risks associated with excessively high pH values. The addition of an antioxidant (such as ascorbic acid) helps prevent oxidation of the metal surface during the stripping process, improving stripping efficiency and the surface quality of the NdFeB substrate while also complying with environmental requirements.

[0049] While some rare earth element compounds and nanoparticles may be expensive, their significant performance improvements can offset this cost, especially in high-end applications such as high-performance magnet manufacturing and repair. Because the surface quality and magnetic properties of the material are effectively protected and improved after stripping, the scrap rate caused by surface defects is reduced, indirectly reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a flow chart of a method for preparing an environmentally friendly stripping agent for NdFeB materials according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] The embodiments of the present application provide an environmentally friendly stripping agent for NdFeB materials, and a preparation method and a use method thereof. DETAILED DESCRIPTION

[0053] Example 1: Basic formula

[0054] Ammonium carbonate: 3%

[0055] Sodium dihydrogen phosphate: 7%

[0056] Sodium hydroxide: 3%

[0057] Potassium citrate: 12%

[0058] Aminotriethanol: 7%

[0059] Hexamethylenetetramine: 18%

[0060] Deionized water: 45%

[0061] Chelating agent (EDTA): 0.5%

[0062] Surface repair agent (nano-neodymium oxide: nano-iron oxide = 1:1, dysprosium nitrate: praseodymium chloride = 1:2): 0.6% (0.3% nanoparticles + 0.3% rare earth element compound)

[0063] Antioxidant (ascorbic acid): 1%

[0064] Example 2: Increasing the content of nanoparticles

[0065] Changes: Nanoparticle content increased from 0.3% to 0.6%, rare earth element compounds remained unchanged.

[0066] Other ingredients remain unchanged

[0067] Example 3: Increasing the content of rare earth element compounds

[0068] Changes: Rare earth element compound content increased from 0.3% to 0.5%, while nanoparticles remained unchanged.

[0069] Other ingredients remain unchanged

[0070] Example 4: Adjusting the Ratio of Dysprosium to Praseodymium

[0071] Change: The ratio of dysprosium compound (dysprosium nitrate) to praseodymium compound (praseodymium chloride) was adjusted from 1:2 to 1:4.

[0072] Other ingredients remain unchanged

[0073] Comparative Example 1: No Nanoparticles

[0074] Variation: Nanoparticles removed, only rare earth element compounds (0.3%) retained.

[0075] Other ingredients remain unchanged

[0076] Comparative Example 2: No rare earth element compound

[0077] Variation: rare earth element compounds were removed, leaving only nanoparticles (0.3%).

[0078] Other ingredients remain unchanged

[0079] Experimental example:

[0080] According to the formulations in the various examples and comparative examples, different stripping agents were prepared.

[0081] During mixing, ensure that all ingredients are evenly dispersed and adjust the pH to 10-15 by gradually adding sodium hydroxide.

[0082] (1) Deplating experiment:

[0083] Prepare NdFeB samples of the same size and coating thickness.

[0084] Immerse the sample in the deplating agent, control the temperature within the range of 70-100°C, and record the deplating time.

[0085] Use ultrasonic cleaning to clean, observe and record the state of the sample surface.

[0086] The surface state after stripping was analyzed using electron microscopy and energy dispersive spectroscopy (EDS).

[0087] The experimental data are shown in Table 1:

[0088] Table 1. Deplating experimental data of the deplating agents in Examples 1-4 and Comparative Examples 1-2

[0089]

[0090]

[0091] From this we can see that:

[0092] Chelating agent: Increasing the EDTA content can significantly improve the stripping efficiency and reduce the stripping time.

[0093] The role of nanoparticles: Increasing the content of nanoparticles can significantly improve the stripping efficiency (from 60 minutes to 55 minutes) and provide better surface repair effect, making the surface smoother and filling small defects.

[0094] Effect of rare earth element compounds: Increasing the content of rare earth element compounds can further improve surface quality and magnetic properties while reducing surface defects.

[0095] Adjustment of the ratio of dysprosium to praseodymium: Adjusting the ratio of dysprosium to praseodymium to 1:4 can make the surface very smooth and the minor defects are almost completely repaired.

[0096] Comparative experimental results: A control sample without nanoparticles or rare earth element compounds shows that these two ingredients are crucial for improving stripping efficiency, surface quality and magnetic properties.

[0097] (2) Magnetic performance test

[0098] Sample preparation: Use NdFeB samples of the same size and coating thickness.

[0099] Stripping treatment: stripping treatment was carried out according to the formulations in the examples and comparative examples, the temperature was controlled within the range of 70-100° C., and the stripping time was recorded.

[0100] Cleaning: Use ultrasonic cleaning to ensure that there is no residual stripping agent on the surface.

[0101] Magnetic properties test: The remanence (Br), coercive force (Hc) and maximum magnetic energy product (BHmax) of the stripped samples were measured using a vibrating sample magnetometer (VSM). The results are shown in Table 2:

[0102] Table 2. Magnetic performance experimental data of the stripping agents in Examples 1-4 and Comparative Examples 1-2

[0103]

[0104]

[0105] By comparing Example 2 with Example 1, it can be seen that increasing the nanoparticle content (from 0.3% to 0.6%) improves the remanence, coercive force and maximum magnetic energy product, indicating that nanoparticles help improve magnetic properties.

[0106] By comparing Example 3 with Example 1, it can be seen that increasing the rare earth element compound content (from 0.3% to 0.5%) further improves the remanence, coercive force and maximum magnetic energy product, indicating that the rare earth element compound has a significant improvement effect on the magnetic properties.

[0107] By comparing Example 4 with Example 1, it can be seen that when the ratio of dysprosium to praseodymium is adjusted to 1:4, the remanence, coercive force and maximum magnetic energy product are significantly improved, especially the coercive force is increased by about 15%, indicating that appropriately adjusting the ratio of rare earth elements can significantly optimize the magnetic properties.

[0108] By comparing Comparative Example 1 and Example 1, it can be seen that without the nanoparticles, the remanence, coercive force and maximum magnetic energy product are all reduced, indicating that nanoparticles are crucial for maintaining and improving magnetic properties.

[0109] By comparing Comparative Example 2 with Example 1, it can be seen that without the rare earth element compound, the remanence, coercive force and maximum magnetic energy product are significantly reduced, especially the coercive force is reduced by about 10%, indicating that the rare earth element compound is also important for improving the magnetic properties.

[0110] The effect of nanoparticles is shown in the following figure: increasing the nanoparticle content (from 0.3% to 0.6%) reduces the stripping time from 60 minutes to 55 minutes. This indicates that nanoparticles can significantly increase the reaction rate of the stripping agent, thereby shortening the stripping time and improving production efficiency.

[0111] Synergistic Effect of Nanoparticles and Rare Earth Compounds: In all examples containing nanoparticles and rare earth compounds, the surface of the NdFeB material after stripping was smoother, and minor defects were repaired or filled. Comparative samples without nanoparticles or rare earth compounds showed significant corrosion and more surface defects, further demonstrating the significant contribution of these two components to surface quality.

[0112] Improved remanence, coercivity, and maximum magnetic energy product: The remanence (Br), coercivity (Hc), and maximum magnetic energy product (BHmax) of all examples were improved to varying degrees. In particular, when the ratio of dysprosium to praseodymium was adjusted to 1:4, the coercivity increased by approximately 15%, and the maximum magnetic energy product reached 450 kJ / m 3 The magnetic properties of the comparative samples without nanoparticles or rare earth element compounds decreased significantly, especially the coercivity, which decreased by 10%-15%, indicating that these components are crucial for maintaining and improving the magnetic properties.

[0113] By adjusting the content of nanoparticles, rare earth element compounds, and the ratio of dysprosium to praseodymium, the stripper formulation can be flexibly optimized to meet specific performance requirements in different application scenarios. This stripper is suitable for applications requiring efficient stripping, high-quality surface finishes, and good magnetic property retention, such as the rework of high-performance NdFeB magnets.

[0114] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0115] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. An environmentally friendly stripping agent for NdFeB materials, characterized in that: Based on the total weight of the stripping agent, the stripping agent contains, by weight percentage: 1-5 wt% ammonium carbonate, 5-10 wt% sodium dihydrogen phosphate or trisodium phosphate, 1-5 wt% sodium hydroxide, 10-15 wt% potassium citrate, 5-10 wt% aminotriethanol, 15-20 wt% hexamethylenetetramine or ethylenediamine, 40-50 wt% deionized water, and 0.1-1 wt% of a chelating agent and a surface repair agent; and 0.5-2 wt% of an antioxidant. Wherein, the surface repair agent is a composition comprising 0.1-1 wt% of nanoparticles and 0.1-0.5 wt% of a rare earth element compound; the nanoparticles and the rare earth element compound are used to form a complex for repairing tiny surface defects; The rare earth element compound includes one or more of a dysprosium compound, a praseodymium compound and / or a samarium compound; The nanoparticles include nano-neodymium oxide and nano-iron oxide, and the mass ratio of the nano-neodymium oxide to the nano-iron oxide is 1:1-2:3; Wherein, the chelating agent is selected from one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and hydroxyethylidene diphosphonic acid; The particle size of the nanoparticles is between 1 and 100 nanometers; The ratio of the mass of the dysprosium compound to the mass of the praseodymium compound and / or the samarium compound is 1:2-1:4; The dysprosium compound includes one or both of dysprosium nitrate and dysprosium chloride; The praseodymium compound includes one or both of praseodymium nitrate and praseodymium chloride; The samarium compound includes one or more of samarium nitrate and samarium chloride.

2. The environmentally friendly stripping agent for NdFeB materials according to claim 1, characterized in that: The surface repair agent further comprises one of neodymium nitrate, neodymium chloride, ferric sulfate, ferric chloride, boric acid and borax.

3. The environmentally friendly stripping agent for NdFeB materials according to claim 1, characterized in that: The pH value of the stripping agent is 10.

4. The environmentally friendly stripping agent for NdFeB materials according to claim 1, characterized in that: The antioxidant is selected from one or more of ascorbic acid, sodium sulfite and sodium metabisulfite.

5. A method for preparing an environmentally friendly stripping agent for NdFeB materials according to any one of claims 1 to 4, characterized in that: The following steps are involved: Mixing 40-50 wt % of deionized water with 15-20 wt % of hexamethylenetetramine or ethylenediamine to form a solution a; The remaining deionized water is mixed with 1-5 wt % of ammonium carbonate, 5-10 wt % of sodium dihydrogen phosphate or trisodium phosphate, 1-5 wt % of sodium hydroxide, 10-15 wt % of potassium citrate, and 0.1-1 wt % of a chelating agent to form a solution b; Mixing the solution a with the solution b to form a solution c; The solution c is mixed with 5-10 wt % of aminotriethanol, 0.5-2 wt % of an antioxidant and a surface repair agent to prepare the stripping agent.

6. A method for using the stripping agent according to any one of claims 1 to 4, characterized in that: The following steps are involved: Soak the NdFeB product that needs to be reworked and stripped in the stripping agent, and adjust the stripping time according to the thickness of the coating, ranging from 5 to 180 minutes; After the stripping is completed, use ultrasonic cleaning to complete the stripping process; During the stripping process, the stripping agent is used at 70-100° C. without damaging the NdFeB substrate and its performance.

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