Magnetic thermoplastic resin composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of thermoplastic composite materials, and discloses a magnetic thermoplastic resin composite material as well as a preparation method and application thereof. Specifically, the invention discloses a magnetic thermoplastic resin master batch, which is prepared from the following raw material components in parts by weight: 80-150 parts of thermoplastic polymer; 50 to 100 parts of neodymium iron boron magnetic powder; 20-60 parts of samarium iron nitrogen magnetic powder; 0.5 to 2 parts of an interface modifier; 0.5 to 2 parts of a silane coupling agent; 0.1 to 1 part of an antioxidant; wherein the average particle size of the neodymium iron boron magnetic powder is 20-40 [mu] m; the average particle size of the samarium-iron-nitrogen magnetic powder is 1-10 [mu] m. A composite material prepared based on the magnetic thermoplastic resin master batch has excellent magnetic properties and mechanical properties, can be widely applied to preparation of magnetic induction related devices, and has excellent application prospects.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, and in particular to a magnetic thermoplastic resin composite material, its preparation method, and its application. Background Technology

[0002] Magnetic thermoplastic composites are a class of composite materials that use thermoplastic resins as the matrix and magnetic powders (such as iron, nickel, cobalt and their alloys or ferrites) as functional fillers. They combine the plasticity, lightweight and easy processing of thermoplastic resins with the magnetic permeability and magnetic induction intensity of magnetic fillers. They can not only be made into complex-shaped magnetic components through injection molding, extrusion and other processes, but the products also have functions such as electromagnetic shielding, beam absorption and sensing. They have great application prospects in the fields of electronics and electrical appliances (such as inductors and sensor housings), automotive industry and aerospace.

[0003] However, despite the enormous potential of magnetic thermoplastic composites, fully realizing their performance still faces significant challenges. For example, poor interfacial compatibility between magnetic powder and the thermoplastic resin substrate leads to weak bonding, making them prone to interfacial debonding under external forces. Furthermore, in electromagnetic fields, poor interfacial properties increase magnetic loss, affecting magnetic properties such as saturation magnetization and coercivity. In addition, the extremely high melt viscosity of thermoplastic resins (such as polypropylene (PP) and nylon (PA) at processing temperatures (typically reaching 500-5000 Pa·s) hinders the uniform dispersion of magnetic powder, especially ultrafine magnetic powders with extremely high specific surface area and surface energy, severely impacting the mechanical properties of the composite material.

[0004] Therefore, there is an urgent need to develop a magnetic thermoplastic composite material with high saturation magnetization and mechanical properties, as well as its preparation process. Summary of the Invention

[0005] The first objective of this invention is to provide a magnetic thermoplastic resin masterbatch.

[0006] The second objective of this invention is to provide a method for preparing magnetic thermoplastic resin masterbatch.

[0007] A third aspect of the present invention is to provide a magnetic thermoplastic resin composite material.

[0008] The fourth aspect of this invention is to provide a method for preparing a magnetic thermoplastic resin composite material.

[0009] The fifth aspect of this invention aims to provide the application of magnetic thermoplastic resin masterbatch or magnetic thermoplastic resin composite material in the preparation of magnetic induction materials.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a magnetic thermoplastic resin masterbatch, wherein the raw materials for preparation, by weight, comprise the following components: Thermoplastic polymer: 80~150 parts; Neodymium iron boron magnetic powder: 50~100 parts; Samarium iron nitrogen magnetic powder: 20~60 parts; Interface modifier: 0.5~2 parts; Silane coupling agent: 0.5~2 parts; Antioxidant: 0.1~1 part; The average particle size of the neodymium iron boron magnetic powder is 20~40μm; the average particle size of the samarium iron nitrogen magnetic powder is 1~10μm.

[0011] The magnetic thermoplastic resin masterbatch of the present invention has at least the following beneficial effects: This invention employs a compounding method of neodymium iron boron (NdFeB) magnetic powder and samarium iron nitride (SmFeN) magnetic powder to improve the magnetic properties of thermoplastic materials. NdFeB magnetic powder is a permanent magnet material with high saturation magnetization, primarily serving as the main source of strong magnetism. However, due to the extremely strong anisotropy of NdFeB magnetic powder and the very large intercrystalline interactions, cracks easily initiate and propagate at fragile interfaces under external forces, leading to brittle fracture in the composite material. This invention discovers that introducing another magnetic powder (such as SmFeN) with different shape, size, or surface properties helps to alter the stress field distribution within the composite material, thereby improving its mechanical properties.

[0012] In some embodiments of the present invention, the raw materials for preparation include the following components: Thermoplastic polymer: 90~120 parts; Neodymium iron boron magnetic powder: 50-80 parts; Samarium iron nitrogen magnetic powder: 25~60 parts; Interface modifier: 0.5~1.5 parts; Silane coupling agent: 0.5~1.5 parts; Antioxidant: 0.1~1 part.

[0013] In some embodiments of the present invention, the thermoplastic polymer is selected from at least one of polypropylene, polyethylene, and polyamide.

[0014] Preferably, the polypropylene comprises homopolymer polypropylene, wherein the melt index (230°C / 2.16 kg) of the homopolymer polypropylene is 10~25 g / 10 min.

[0015] Preferably, the polyethylene comprises high-density polyethylene, wherein the density of the high-density polyethylene is 0.95~0.97 g / cm³.3 The melt index (190℃ / 2.16kg) is 10~25g / 10min.

[0016] In some embodiments of the present invention, the interface modifier is selected from at least one of polypropylene grafted maleic anhydride (PP-g-MAH), polyethylene grafted maleic anhydride (PE-g-MAH), polyolefin elastomer grafted maleic anhydride (POE-g-MAH), and styrene-ethylene-butene-styrene grafted maleic anhydride (SEBS-g-MAH).

[0017] When an interface modifier (such as PP-g-MAH) is heated, its anhydride groups can react with the functional groups of silane (such as amino groups) or residual groups on the particle surface, and at the same time physically encapsulate the magnetic powder to form a "core-shell" structure, thereby achieving preliminary encapsulation of the magnetic powder and helping to improve the wettability of the magnetic powder with thermoplastic materials.

[0018] The antioxidant is selected from at least one of hindered phenolic antioxidants and phosphite antioxidants.

[0019] In some embodiments of the present invention, the hindered phenolic antioxidant is selected from at least one of antioxidant 1010, antioxidant 1076, antioxidant 264, and antioxidant 2246.

[0020] In some embodiments of the present invention, the phosphite antioxidant is selected from at least one of antioxidant 168, antioxidant 626, antioxidant P-EPQ, and antioxidant 9228 (such as Doverphos S-9228).

[0021] In some embodiments of the present invention, the average particle size of the neodymium iron boron magnetic powder is 25~35μm.

[0022] In some embodiments of the present invention, the average particle size of the samarium iron nitrogen magnetic powder is 1-5 μm.

[0023] SmFeN magnetic powder exhibits excellent thermal stability (Curie temperature up to ~470°C), meaning it is less prone to demagnetization at high temperatures. The addition of SmFeN to the composite material of this invention provides a "thermally stable framework" for the entire magnetic system. When the composite material operates in environments with certain temperatures (such as during processing or device operation), SmFeN helps maintain the stability of the overall magnetic properties and compensates for the performance degradation of NdFeB magnetic powder at high temperatures.

[0024] This invention employs magnetic powders of varying sizes and properties. This graded filling helps reduce localized stress in the material, allowing stress to be more evenly distributed throughout the material rather than concentrated around a few large voids. Furthermore, it hinders crack propagation. When cracks encounter this dense and uneven particle arrangement during propagation, their paths deflect, branch, and detour, requiring more energy and thus improving the material's toughness and strength.

[0025] A second aspect of the present invention provides a method for preparing magnetic thermoplastic resin masterbatch as described in the first aspect, comprising the following steps: S1. Disperse the neodymium iron boron magnetic powder and samarium iron nitrogen magnetic powder in a first solvent, add a silane coupling agent, and react to obtain silanized magnetic powder. S2. The silanized magnetic powder is mixed with the interface modifier, and after heat treatment, an interface-modified magnetic powder is obtained. S3. Dissolve the thermoplastic polymer in a second solvent to obtain a dispersed liquid phase, then add the interface-modified magnetic powder and antioxidant, stir evenly, then add a pre-cooled third solvent, collect the precipitated solid phase, and after washing and drying, obtain the final product.

[0026] In some embodiments of the present invention, the first solvent and the third solvent are independently selected from either ethanol or acetone.

[0027] In some embodiments of the present invention, the temperature at which the third solvent is pre-cooled is 0~15°C.

[0028] In some embodiments of the present invention, the second solvent is selected from either decahydronaphthalene or xylene.

[0029] This invention discovers that liquid-phase dispersion (such as using decahydronaphthalene or xylene) can provide a low-viscosity, fully flowing environment for magnetic powders, effectively deagglomerates and achieve uniform dispersion. Subsequent rapid pre-cooling treatment can solidify and preserve this "primary dispersion" structure when forming the masterbatch, avoiding secondary sedimentation of the magnetic powders.

[0030] In some embodiments of the present invention, the mass-to-volume ratio of the thermoplastic polymer to the second solvent is 1:1.5 to 4. Preferably, the mass-to-volume ratio of the thermoplastic polymer to the second solvent is 1:1:2 to 3.5.

[0031] In some embodiments of the present invention, the temperature of the heat treatment is 70~90°C.

[0032] In some embodiments of the present invention, the heat treatment time is 5 to 20 minutes.

[0033] In a third aspect, the present invention provides a magnetic thermoplastic resin composite material, which is prepared by melt blending the magnetic thermoplastic resin masterbatch, thermoplastic resin and polyolefin elastomer described in the first aspect.

[0034] In some embodiments of the present invention, the thermoplastic resin is selected from at least one of polypropylene resin, polyethylene resin, and polyamide resin.

[0035] In some embodiments of the present invention, the weight ratio of the magnetic thermoplastic resin masterbatch, thermoplastic resin and polyolefin elastomer is 1:0.5~2:0.1~0.5.

[0036] In some embodiments of the present invention, the weight ratio of the magnetic thermoplastic resin masterbatch, thermoplastic resin and polyolefin elastomer is 1:0.5~1.5:0.1~0.3.

[0037] A fourth aspect of the present invention provides a method for preparing the magnetic thermoplastic resin composite material described in the third aspect, comprising: mixing the magnetic thermoplastic resin masterbatch, thermoplastic resin and polyolefin elastomer, and preparing the composite material using a twin-screw extrusion process.

[0038] This invention employs a masterbatch method to prepare composite materials, which significantly reduces agglomerates and results in superior and more stable material properties (such as magnetic and mechanical properties). Secondly, in the masterbatch, the magnetic powders (especially easily oxidized samarium iron nitrogen and neodymium iron boron) are tightly coated with resin, maximizing the prevention of contact with air and avoiding oxidation. Simultaneously, the masterbatch's good flowability and particle morphology facilitate more uniform mixing with the matrix resin particles, ensuring smooth feeding and avoiding the "bridging" and uneven feeding problems commonly encountered in direct powder blending.

[0039] In some embodiments of the present invention, the twin-screw extrusion process parameters are set as follows: The temperature ranges for the first stage: 140~185℃, the second stage: 150~210℃, the third stage: 160~230℃, the fourth stage: 150~225℃, and the fifth stage: 150~215℃; the screw speed is 200~350 rpm.

[0040] In some embodiments of the present invention, the twin-screw extrusion process parameters are set as follows: The temperature ranges for the first stage: 140~170℃, the second stage: 150~185℃, the third stage: 160~200℃, the fourth stage: 150~185℃, and the fifth stage: 150~190℃; the screw speed is 200~350 rpm.

[0041] A fifth aspect of the invention provides the use of magnetic thermoplastic resin masterbatch as described in the first aspect or magnetic thermoplastic resin composite material as described in the second aspect in the preparation of magnetic induction materials.

[0042] The magnetic thermoplastic resin composite material, its preparation method, and its application of the present invention have at least the following beneficial effects: The process of this invention can effectively improve the problem of uneven dispersion of magnetic powder. The resulting magnetic thermoplastic resin composite material has a saturation magnetization of >21 emu / g, a remanence of >250 mT, and relatively low coercivity. In addition, it also has excellent mechanical properties, with high tensile strength (48~56 MPa) and elongation at break (303~311%), and moderate Shore hardness, which can meet the requirements of structural components and has good application prospects.

[0043] Other features and advantages of the present invention will be set forth in the following description. Detailed Implementation

[0044] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0045] The terms "preferred," "more preferably," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0046] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0047] In the description of this invention, the reference term "and / or" includes all and any combination of one or more of the associated listed items.

[0048] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0049] In an embodiment of the present invention, the homopolymer polypropylene is designated as HA840R, and its melt index (230°C / 2.16 kg) is 20 g / 10 min.

[0050] The grade of high-density polyethylene (HDPE) is HMA-016, and its density is 0.956 g / cm³. 3 The melt index (190℃ / 2.16kg) is 20 g / 10 min.

[0051] The neodymium iron boron magnetic powder (NdFeB) was purchased from Shanghai Naio Nanotechnology Co., Ltd., with a particle size of 500 mesh (approximately 25 μm).

[0052] Samarium iron nitrogen magnetic powder (SmFeN) was purchased from Qinghe County Benyu Metal Materials Co., Ltd., with product number BY-SmFeN and an average particle size of 1~3μm.

[0053] The polyolefin elastomer is designated as Dow 8150, with a heat distortion temperature of 70°C.

[0054] The brand name of PP-g-MAH is Jia Yi Rong. ® CMG9801.

[0055] The polypropylene resin granules were purchased from Qilu Petrochemical, and the grade is EPS30R.

[0056] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0057] Example 1: This embodiment provides a magnetic polypropylene resin composite material and its preparation method.

[0058] 1. Magnetic thermoplastic resin composite material The magnetic polypropylene resin composite material in this example is prepared by melt blending magnetic masterbatch, polypropylene resin particles, and polyolefin elastomer. The raw materials for preparing the magnetic masterbatch include the following components by weight: Homopolymer polypropylene: 100 parts; Neodymium iron boron magnetic powder: 80 parts; Samarium iron nitrogen magnetic powder: 30 parts; PP-g-MAH: 1 part; Silane coupling agent KH-550: 1 part; Antioxidant 1010: 0.5 parts.

[0059] The weight ratio of the above magnetic masterbatch, polypropylene resin particles and polyolefin elastomer is 1:1:0.2.

[0060] 2. Preparation method of magnetic polypropylene resin composite material The specific preparation process of the magnetic polypropylene resin composite material in this example is as follows.

[0061] (1) Surface pretreatment of magnetic powder: Based on the above-mentioned weight proportions, neodymium iron boron magnetic powder (NdFeB) and samarium iron nitrogen magnetic powder (SmFeN) were ultrasonically dispersed in three volumes of anhydrous ethanol for 30 min to form a uniform magnetic powder suspension. Then, silane coupling agent KH-550 was added, and the mixture was stirred at 60℃ for 2 h to allow the silane to complete the hydrolysis-condensation reaction on the surface of the magnetic powder, forming an organic molecular layer. After the reaction was completed, the powder was filtered, washed, and vacuum dried to obtain silanized magnetic powder.

[0062] The silanized magnetic powder was mixed with PP-g-MAH and heat-treated at 80°C and 800 rpm for 10 min to obtain PP-g-MAH coated magnetic powder.

[0063] (2) Preparation of magnetic masterbatch: The preparation method of the magnetic masterbatch in this example includes the following steps: S1. Obtaining the dispersed liquid phase: According to the above weight proportions, add homopolymer polypropylene and three times the volume of decahydronaphthalene solvent to the reactor, and stir under oil bath conditions at 140℃ to obtain a homopolymer polypropylene resin solution. S2. Pre-dispersion treatment: The pre-treated PP-g-MAH coated magnetic powder is mixed with antioxidant 1010 and then added to the homopolymer polypropylene solution. The mixture is kept warm and stirred for 1 h to allow the magnetic powder to be fully impregnated and dispersed by the homopolymer polypropylene resin solution, thus obtaining a pre-dispersion mixture.

[0064] S3. Precipitation: Quickly pour the above pre-dispersed mixture into three times the volume of cold anhydrous ethanol (4°C) under high-speed stirring. After the precipitate has completely precipitated, filter, collect the solid phase, wash and vacuum dry to obtain magnetic masterbatch.

[0065] (3) Melt blending The magnetic masterbatch, polypropylene resin particles, and polyolefin elastomer obtained above were mixed in a weight ratio of 1:1:0.2 and melt-blended using a twin-screw extrusion process. The extrusion process employed a five-stage temperature control system, with the specific parameters set as follows: The temperature range is as follows: first stage: 165℃; second stage: 175℃; third stage: 190℃; fourth stage: 175℃; fifth stage: 180℃; screw speed: 300 rpm.

[0066] After extrusion, the material is cooled, stretched, and pelletized to obtain a magnetic polypropylene resin composite material.

[0067] Example 2: This embodiment provides a magnetic polypropylene resin composite material and its preparation method.

[0068] 1. Magnetic thermoplastic resin composite material The magnetic polypropylene resin composite material in this example is prepared by melt blending magnetic masterbatch, polypropylene resin particles, and polyolefin elastomer. The raw materials for preparing the magnetic masterbatch include the following components by weight: Homopolymer polypropylene: 100 parts; Neodymium iron boron magnetic powder: 55 parts; Samarium iron nitrogen magnetic powder: 55 parts; PP-g-MAH: 1 part; Silane coupling agent KH-550: 1 part; Antioxidant 1010: 0.5 parts.

[0069] The weight ratio of the above magnetic masterbatch, polypropylene resin particles and polyolefin elastomer is 1:1:0.2.

[0070] 2. Preparation method of magnetic polypropylene resin composite material The preparation process of the magnetic polypropylene resin composite material in this example is the same as in Example 1.

[0071] Example 3: This embodiment provides a magnetic polypropylene resin composite material and its preparation method.

[0072] 1. Magnetic thermoplastic resin composite material The magnetic polypropylene resin composite material in this example is prepared by melt blending magnetic masterbatch, polypropylene resin particles, and polyolefin elastomer. The raw materials for preparing the magnetic masterbatch include the following components by weight: Homopolymer polypropylene: 100 parts; Neodymium iron boron magnetic powder: 90 parts; Samarium iron nitrogen magnetic powder: 35 parts; PP-g-MAH: 1 part; Silane coupling agent KH-550: 1 part; Antioxidant 1010: 0.5 parts.

[0073] The weight ratio of the above magnetic masterbatch, polypropylene resin particles and polyolefin elastomer is 1:1:0.2.

[0074] 2. Preparation method of magnetic polypropylene resin composite material The preparation process of the magnetic polypropylene resin composite material in this example is the same as in Example 1.

[0075] Example 4: This embodiment provides a magnetic polyvinyl acid resin composite material and its preparation method.

[0076] 1. Magnetic thermoplastic resin composite material The magnetic polyvinyl acid resin composite material in this example is prepared by melt blending magnetic masterbatch, high-density polyethylene particles, and polyolefin elastomer. The raw materials for preparing the magnetic masterbatch include the following components by weight: High-density polyethylene: 100 parts; Neodymium iron boron magnetic powder: 80 parts; Samarium iron nitrogen magnetic powder: 30 parts; PE-g-MAH: 1 part; Silane coupling agent KH-550: 1 part; Antioxidant 1010: 0.5 parts.

[0077] The weight ratio of the above magnetic masterbatch, high-density polyethylene particles and polyolefin elastomer is 1:1:0.2.

[0078] 2. Preparation method of magnetic polyethylene resin composite material The specific preparation process of the magnetic polyethylene resin composite material in this example is as follows.

[0079] (1) Surface pretreatment of magnetic powder: Based on the above-mentioned weight proportions, neodymium iron boron magnetic powder (NdFeB) and samarium iron nitrogen magnetic powder (SmFeN) were ultrasonically dispersed in three volumes of anhydrous ethanol for 30 min to form a uniform magnetic powder suspension. Then, silane coupling agent KH-550 was added, and the mixture was stirred at 60℃ for 2 h to allow the silane to complete the hydrolysis-condensation reaction on the surface of the magnetic powder, forming an organic molecular layer. After the reaction was completed, the powder was filtered, washed, and vacuum dried to obtain silanized magnetic powder.

[0080] The silanized magnetic powder was mixed with PE-g-MAH and heat-treated at 80°C and 800 rpm for 10 min to obtain PE-g-MAH coated magnetic powder.

[0081] (2) Preparation of magnetic masterbatch: The preparation method of the magnetic masterbatch in this example includes the following steps: S1. Obtaining the dispersed liquid phase: According to the above weight proportions, add high-density polyethylene and three times the volume of xylene solvent to the reaction vessel, and stir under 120°C oil bath conditions to obtain a high-density polyethylene resin solution. S2. Pre-dispersion treatment: The pre-treated PE-g-MAH coated magnetic powder is mixed with antioxidant 1010 and added to the high-density polyethylene solution. The mixture is kept warm and stirred for 1 hour to allow the magnetic powder to be fully impregnated and dispersed by the high-density polyethylene resin solution, thus obtaining a pre-dispersion mixture.

[0082] S3. Precipitation: Quickly pour the above pre-dispersed mixture into three times the volume of cold anhydrous ethanol (4°C) under high-speed stirring. After the precipitate has completely precipitated, filter, collect the solid phase, wash and vacuum dry to obtain magnetic masterbatch.

[0083] (3) Melt blending The magnetic masterbatch, high-density polyethylene particles, and polyolefin elastomer obtained above were mixed in a weight ratio of 1:1:0.2 and melt-blended using a twin-screw extrusion process. The extrusion process employed a five-stage temperature control system, with the specific parameters set as follows: The temperature range is as follows: first stage: 145℃; second stage: 155℃; third stage: 170℃; fourth stage: 155℃; fifth stage: 160℃; screw speed: 300 rpm.

[0084] After extrusion, the material is cooled, stretched, and pelletized to obtain a magnetic polyvinyl acid resin composite material.

[0085] Comparative Example 1: This comparative example provides a polyacrylic acid resin material and its preparation method.

[0086] 1. Thermoplastic resin composite materials The raw materials for preparing the polyacrylic acid resin composite material in this example include the following components by weight: Homopolymer polypropylene: 100 parts; PP-g-MAH: 1 part; Silane coupling agent KH-550: 1 part; Antioxidant 1010: 0.5 parts; Polyolefin elastomer: 20 parts; Polypropylene resin granules: 100 parts.

[0087] 2. Preparation method of polyacrylic acid resin composite material The specific preparation process of the polyacrylic acid resin composite material in this example is as follows: According to the above-mentioned parts by weight, silane coupling agent KH-550, PP-g-MAH, homopolymer polypropylene, antioxidant 1010, polyolefin elastomer, and polypropylene resin particles are mixed, and then melt-blended using a twin-screw extrusion process. The extrusion process uses a five-stage temperature control, and the specific parameters are set as follows: The temperature range is as follows: first stage: 165℃; second stage: 175℃; third stage: 190℃; fourth stage: 175℃; fifth stage: 180℃; screw speed: 300 rpm.

[0088] After extrusion, the material is cooled, stretched, and pelletized to obtain a magnetic polypropylene resin composite material.

[0089] Comparative Example 2: This comparative example provides a magnetic polypropylene resin composite material and its preparation method.

[0090] 1. Magnetic thermoplastic resin composite material The magnetic polypropylene resin composite material in this example is prepared by melt blending magnetic masterbatch, polypropylene resin particles, and polyolefin elastomer. The raw materials for preparing the magnetic masterbatch include the following components by weight: Homopolymer polypropylene: 100 parts; Neodymium iron boron magnetic powder: 110 parts; PP-g-MAH: 1 part; Silane coupling agent KH-550: 1 part; Antioxidant 1010: 0.5 parts.

[0091] The weight ratio of the above magnetic masterbatch, polypropylene resin particles and polyolefin elastomer is 1:1:0.2.

[0092] 2. Preparation method of magnetic polypropylene resin composite material The specific preparation process of the magnetic polypropylene resin composite material in this example is as follows.

[0093] (1) Surface pretreatment of magnetic powder: According to the above-mentioned parts by weight, neodymium iron boron magnetic powder (NdFeB) was ultrasonically dispersed in anhydrous ethanol for 30 min to form a uniform magnetic powder suspension. Then, silane coupling agent KH-550 was added, and the mixture was stirred at 60℃ for 2 h to allow the silane to complete the hydrolysis-condensation reaction on the surface of the magnetic powder, forming an organic molecular layer. After the reaction was completed, the powder was filtered, washed, and vacuum dried to obtain silanized magnetic powder.

[0094] The silanized magnetic powder was mixed with PP-g-MAH and heat-treated at 80°C and 800 rpm for 10 min to obtain PP-g-MAH coated magnetic powder.

[0095] (2) Preparation of magnetic masterbatch: The preparation method of the magnetic masterbatch in this example is the same as in Example 1.

[0096] Comparative Example 3: This embodiment provides a magnetic polypropylene resin composite material and its preparation method.

[0097] 1. Magnetic thermoplastic resin composite material The magnetic polypropylene resin composite material in this example is prepared by melt blending magnetic masterbatch, polypropylene resin particles, and polyolefin elastomer. The raw materials for preparing the magnetic masterbatch include the following components by weight: Homopolymer polypropylene: 100 parts; Samarium iron nitrogen magnetic powder: 110 parts; PP-g-MAH: 1 part; Silane coupling agent KH-550: 1 part; Antioxidant 1010: 0.5 parts.

[0098] The weight ratio of the above magnetic masterbatch, polypropylene resin particles and polyolefin elastomer is 1:1:0.2.

[0099] 2. Preparation method of magnetic polypropylene resin composite material The specific preparation process of the magnetic polypropylene resin composite material in this example is as follows.

[0100] (1) Surface pretreatment of magnetic powder: According to the above-mentioned weight proportions, samarium iron nitrogen magnetic powder (SmFeN) was ultrasonically dispersed in anhydrous ethanol for 30 min to form a uniform magnetic powder suspension. Then, silane coupling agent KH-550 was added, and the mixture was stirred at 60℃ for 2 h to allow the silane to complete the hydrolysis-condensation reaction on the surface of the magnetic powder, forming an organic molecular layer. After the reaction was completed, the powder was filtered, washed, and vacuum dried to obtain silanized magnetic powder.

[0101] The silanized magnetic powder was mixed with PP-g-MAH and heat-treated at 80°C and 800 rpm for 10 min to obtain PP-g-MAH coated magnetic powder.

[0102] (2) Preparation of magnetic masterbatch: The preparation method of the magnetic masterbatch in this example is the same as in Example 1.

[0103] Comparative Example 4: This comparative example provides a magnetic polypropylene resin composite material and its preparation method.

[0104] 1. Magnetic thermoplastic resin composite material The magnetic polypropylene resin composite material in this example is prepared by melt blending magnetic masterbatch, polypropylene resin particles, and polyolefin elastomer. The raw materials for preparing the magnetic masterbatch include the following components by weight: Homopolymer polypropylene: 100 parts; Neodymium iron boron magnetic powder: 80 parts; Samarium iron nitrogen magnetic powder: 30 parts; PP-g-MAH: 1 part; Silane coupling agent KH-550: 1 part; Antioxidant 1010: 0.5 parts.

[0105] The weight ratio of the above magnetic masterbatch, polypropylene resin particles and polyolefin elastomer is 1:1:0.2.

[0106] The neodymium iron boron magnetic powder has a particle size of 100 mesh (approximately 150 μm, grade XND-New Nord 2654); the samarium iron nitrogen magnetic powder has a particle size of 100 mesh (approximately 150 μm, purchased from XND-New Nord, grade 3060).

[0107] 2. Preparation method of magnetic polypropylene resin composite material The preparation process of the magnetic polypropylene resin composite material in this example is the same as in Example 1.

[0108] Comparative Example 5: This comparative example provides a magnetic polypropylene resin composite material and its preparation method.

[0109] 1. Magnetic polypropylene resin composite material The raw materials for preparing the magnetic polypropylene resin composite material in this example include the following components by weight: Homopolymer polypropylene: 100 parts; Neodymium iron boron magnetic powder: 80 parts; Samarium iron nitrogen magnetic powder: 30 parts; PP-g-MAH: 1 part; Silane coupling agent KH-550: 1 part; Antioxidant 1010: 0.5 parts; Polyolefin elastomer: 20 parts; Polypropylene resin granules: 210 parts.

[0110] 2. Preparation method of magnetic polypropylene resin composite material The preparation method of the magnetic polypropylene resin composite material in this example is as follows: According to the above-mentioned weight proportions, neodymium iron boron magnetic powder (NdFeB), samarium iron nitrogen magnetic powder (SmFeN), silane coupling agent KH-550, PP-g-MAH, homopolymer polypropylene, antioxidant 1010, polyolefin elastomer, and polypropylene resin particles are mixed, and then melt-blended using a twin-screw extrusion process. The extrusion process employs a five-stage temperature control, with specific parameter settings as follows: The temperature range is as follows: first stage: 165℃; second stage: 175℃; third stage: 190℃; fourth stage: 175℃; fifth stage: 180℃; screw speed: 300 rpm.

[0111] After extrusion, the material is cooled, stretched, and pelletized to obtain a magnetic polypropylene resin composite material.

[0112] Example of detection: This test example examines the magnetic and mechanical properties of the magnetic polypropylene resin composite materials prepared in Examples 1-4 and Comparative Examples 1-5. The specific test methods are as follows: (1) Magnetic properties test: Using a vibrating sample magnetometer (VSM), the saturation magnetization Ms, remanence Br, coercivity Hcb and intrinsic coercivity Hcj were measured according to the hysteresis loop test method.

[0113] (2) Tensile strength and elongation at break tests: in accordance with GB / T1040.3 The test was conducted according to the 2006 standard "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". The test specimen was 25 mm wide, 100 mm long, and 0.5 mm thick, with a tensile rate of 50 mm / min.

[0114] (3) Shore hardness test: according to GB / T2411 The 2008 standard test used a type D hardness tester.

[0115] The test results are shown in Table 1.

[0116] Table 1:

[0117] According to the above performance test results, the magnetic polyplastic resin composite material prepared using the formulation and process of this invention has excellent magnetic properties, with a saturation magnetization of >21 emu / g and a remanence of >250 mT. It also exhibits relatively low coercivity, which helps to improve the magnetic response speed, reduce losses, and minimize defects such as deformation, warping, or performance instability caused by stress release during processing (e.g., injection molding, extrusion) and subsequent use. Furthermore, the magnetic polypropylene resin composite material of this invention also possesses excellent mechanical properties, with high tensile strength (48~56 MPa) and elongation at break (303~311%), combining strength and toughness. Simultaneously, its Shore hardness (82~91) is moderate, meeting the requirements for structural components.

[0118] Compared to Example 1, Comparative Example 1 did not add magnetic powder, and the results showed that its tensile strength was 37 MPa, its elongation at break was 328%, and its Shore hardness was 81.

[0119] Compared to Example 1, Comparative Example 2 only added NdFeB magnetic powder. The results showed that the saturation magnetization was similar (21.89 emu / g), the remanence was slightly higher (270 mT), but the coercivity and intrinsic coercivity were significantly reduced to 121 kA / m and 130 kA / m, respectively. At the same time, the tensile strength decreased to 42 MPa and the elongation at break decreased to 274%, which is presumably related to the poor interfacial bonding between the single NdFeB magnetic powder and the polypropylene matrix.

[0120] Compared to Example 1, Comparative Example 3 only added samarium iron nitrogen magnetic powder. The results showed that its saturation magnetization (21.64 emu / g) was comparable to that of Example 1, but the remanence decreased to 205 mT, while the coercivity and intrinsic coercivity increased (208 kA / m and 225 kA / m, respectively). The tensile strength decreased to 45 MPa, and the elongation at break decreased to 287%. This is attributed to the fact that samarium iron nitrogen itself has low remanence but high coercivity, and the single particle type leads to uneven dispersion and weak interfacial bonding, thus affecting the mechanical properties.

[0121] Compared to Example 1, Comparative Example 4 used magnetic powder of the same size, and the results showed that its elongation at break decreased to 266%. This may be due to the uniform particle size distribution, which reduces dispersion efficiency and interfacial bonding force, resulting in a decrease in mechanical properties.

[0122] Compared to Example 1, Comparative Example 5 was prepared by direct melt mixing. The results showed that its magnetic and mechanical properties were significantly reduced, such as saturation magnetization reduced to 15.03 emu / g, remanence reduced to 182 mT, tensile strength reduced to 40 MPa, and elongation at break reduced to 254%. It is speculated that this is because direct mixing makes it difficult to uniformly disperse the magnetic powder.

[0123] In summary, this invention provides a magnetic thermoplastic resin composite material and its preparation method. The process of this invention can effectively improve the problem of uneven dispersion of magnetic powder. The obtained magnetic polypropylene resin composite material has a saturation magnetization of >21 emu / g, a remanence of >250 mT, and relatively low coercivity. In addition, it also has excellent mechanical properties, with high tensile strength (48~56 MPa) and elongation at break (303~311%), and moderate Shore hardness, which can meet the requirements of structural components and has good application prospects.

[0124] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A magnetic thermoplastic resin masterbatch, characterized in that, The raw materials for preparation comprise the following components in parts by weight: Thermoplastic polymer: 80~150 parts; Neodymium iron boron magnetic powder: 50~100 parts; Samarium iron nitrogen magnetic powder: 20~60 parts; Interface modifier: 0.5~2 parts; Silane coupling agent: 0.5~2 parts; Antioxidant: 0.1~1 part; The average particle size of the neodymium iron boron magnetic powder is 20~40μm; the average particle size of the samarium iron nitrogen magnetic powder is 1~10μm.

2. The magnetic thermoplastic resin masterbatch according to claim 1, characterized in that, The thermoplastic polymer is selected from at least one of polypropylene, polyethylene, and polyamide; And / or, the interface modifier is selected from at least one of polypropylene grafted with maleic anhydride, polyethylene grafted with maleic anhydride, polyolefin elastomer grafted with maleic anhydride, and styrene-ethylene-butene-styrene grafted with maleic anhydride.

3. The method for preparing magnetic thermoplastic resin masterbatch as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Disperse the neodymium iron boron magnetic powder and samarium iron nitrogen magnetic powder in a first solvent, add a silane coupling agent, and react to obtain silanized magnetic powder. S2. The silanized magnetic powder is mixed with the interface modifier, and after heat treatment, an interface-modified magnetic powder is obtained. S3. Dissolve the thermoplastic polymer in a second solvent to obtain a dispersed liquid phase, then add the interface-modified magnetic powder and antioxidant, stir evenly, and then add it to a pre-cooled third solvent. Collect the precipitated solid phase, wash and dry it to obtain the final product.

4. The preparation method according to claim 3, characterized in that, The first solvent and the third solvent are independently selected from either ethanol or acetone; And / or, the pre-cooling temperature of the third solvent is 0~15℃; And / or, the second solvent is selected from either decahydronaphthalene or xylene.

5. The preparation method according to claim 3 or 4, characterized in that, The heat treatment temperature is 70~90℃; And / or, the heat treatment time is 5~20 min.

6. A magnetic thermoplastic resin composite material, characterized in that, It is prepared by melt blending the magnetic thermoplastic resin masterbatch, thermoplastic resin, and polyolefin elastomer as described in claim 1 or 2.

7. The magnetic thermoplastic resin composite material according to claim 6, characterized in that, The thermoplastic resin is selected from at least one of polypropylene resin, polyethylene resin, and polyamide resin; And / or, the weight ratio of the magnetic thermoplastic resin masterbatch, thermoplastic resin and polyolefin elastomer is 1:0.5~2:0.1~0.

5.

8. A method for preparing a magnetic thermoplastic resin composite material as described in claim 6 or 7, characterized in that, include: The magnetic thermoplastic resin masterbatch, thermoplastic resin, and polyolefin elastomer are mixed and prepared using a twin-screw extrusion process.

9. The preparation method according to claim 8, characterized in that, The twin-screw extrusion process parameters are set as follows: The temperature ranges for the first stage: 140~185℃, the second stage: 150~210℃, the third stage: 160~230℃, the fourth stage: 150~225℃, and the fifth stage: 150~215℃; the screw speed is 200~350 rpm.

10. The use of the magnetic thermoplastic resin masterbatch as described in any one of claims 1 to 2 or the magnetic thermoplastic resin composite material as described in any one of claims 6 to 7 in the preparation of magnetic induction materials.

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