Electromagnetic shielding polyamide functional master batch and preparation method thereof

Abstract

The application discloses electromagnetic shielding polyamide functional master batch and a preparation method thereof, and raw material components are as follows: polyamide base material 50-70%; modified nano Fe3O4 20-40%; compatibility agent 3-8%; dispersing agent 1-5%; antioxidant 0.1-1%; the modified nano Fe3O4 is nano Fe3O4 modified by silane coupling agent and fatty acid, particle size is 20-80 nm, and a surface is grafted with a compatibility group containing amino or carboxyl. The electromagnetic shielding polyamide functional master batch is prepared through surface modification, high-speed mixing, melt blending, extrusion and granulation processes. The modified nano Fe3O4 is modified by silane coupling agent and fatty acid, has superparamagnetism and high conductivity, and is grafted with a polyamide compatibility group on a surface. Through optimization of component proportion and process parameters, the electromagnetic shielding polyamide functional master batch solves technical problems of poor compatibility, easy agglomeration and easy falling of nano Fe3O4 and polyamide base material.

Description

Technical Field

[0001] This invention relates to the field of textile materials technology, specifically to an electromagnetic shielding polyamide functional masterbatch and its preparation method. Background Technology

[0002] With the rapid development of electronics, electrical appliances, and communication technologies, electromagnetic radiation pollution has become an increasingly prominent problem, making electromagnetic shielding materials crucial for ensuring the normal operation of equipment and protecting human health. Polyamide (PA), as a high-performance engineering plastic, boasts advantages such as high strength, good heat resistance, and ease of processing and molding, and is widely used in electronic casings, automotive parts, and other fields. However, pure polyamide does not possess electromagnetic shielding properties and requires modification through the addition of functional fillers.

[0003] Nano Fe3O4 is an ideal electromagnetic shielding filler due to its superparamagnetism, high conductivity, and excellent electromagnetic loss capability. However, due to its strong surface polarity and large specific surface area, nano Fe3O4 presents the following technical challenges: (1) poor compatibility with non-polar or weakly polar polyamide substrates, resulting in weak interfacial bonding; (2) easy agglomeration, making it impossible to form an effective electromagnetic conduction network; (3) easy to detach from the substrate during processing and use, leading to a decrease in electromagnetic shielding performance and a decline in the mechanical properties of the product.

[0004] In existing technologies, nano-Fe3O4 is often modified using a single coupling agent, but the modification effect is limited, and it is still difficult to simultaneously achieve compatibility and dispersibility. Some solutions improve the agglomeration problem by increasing the amount of dispersant, but excessive dispersant will reduce the mechanical properties of the product. Therefore, developing an electromagnetic shielding polyamide functional masterbatch that can simultaneously solve the problems of compatibility, agglomeration, and shedding has important practical application value. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an electromagnetic shielding polyamide functional masterbatch and its preparation method. Through composite modification technology and formula optimization, the compatibility problem between nano Fe3O4 and polyamide is solved, the aggregation of nanoparticles is inhibited, the interfacial bonding force is enhanced, and the electromagnetic shielding performance and mechanical properties are synergistically improved.

[0006] This invention is implemented as follows: An electromagnetic shielding polyamide functional masterbatch, with the following raw material composition by weight percentage: Polyamide substrate 50-70%; Modified nano-Fe3O4 20-40%; Compatibilizer 3-8%; Dispersant 1-5%; Antioxidant 0.1-1%; The modified nano-Fe3O4 is a nano-Fe3O4 modified by a silane coupling agent and fatty acid, with a particle size of 20-80 nm, and the surface is grafted with compatible groups containing amino or carboxyl groups.

[0007] Furthermore, the polyamide substrate is selected from one or more blends of PA6, PA66, and PA12, and has a relative viscosity of 2.4-3.2.

[0008] Furthermore, the silane coupling agent is selected from one of KH550, KH560, and KH570, and the fatty acid is selected from one of stearic acid and palmitic acid. The amount of silane coupling agent is 1-5% of the mass of nano Fe3O4, and the amount of fatty acid is 0.5-3% of the mass of nano Fe3O4.

[0009] Furthermore, the compatibilizer is maleic anhydride-grafted polyolefin with a grafting rate of 0.5-2.0%, selected from maleic anhydride-grafted polyethylene and maleic anhydride-grafted polypropylene.

[0010] Furthermore, the dispersant is selected from one or more of calcium stearate, polyethylene wax, and polyethylene glycol, with a number average molecular weight of 1000-5000.

[0011] Furthermore, the antioxidant is a compound system, consisting of primary antioxidant 1010 and secondary antioxidant 168 in a mass ratio of 1:1 to 3:1.

[0012] Furthermore, the preparation method of the electromagnetic shielding polyamide functional masterbatch includes the following steps: (1) Preparation of modified nano Fe3O4: Nano Fe3O4 was dispersed in an ethanol aqueous solution, ultrasonically dispersed for 30-60 min, heated to 80-100℃, and silane coupling agent and fatty acid were added in sequence. The mixture was stirred for 2-4 h, filtered, washed, and vacuum dried to obtain modified nano Fe3O4. (2) Raw material mixing: Weigh the polyamide substrate, modified nano Fe3O4, compatibilizer, dispersant and antioxidant by weight percentage, add them to a high-speed mixer, mix at 80-100℃ for 15-30 min, and rotate at 800-1200 r / min to obtain the mixture; (3) Melt blending extrusion: Add the mixture to a twin-screw extruder, set the temperature of each section of the extruder to 220-260℃, and the screw speed to 150-250r / min. After melt blending, extrude and granulate to obtain primary masterbatch. (4) Post-processing: The initial masterbatch is vacuum dried at 80-100℃ for 8-12h to remove moisture and obtain electromagnetic shielding polyamide functional masterbatch.

[0013] Furthermore, in step (1), the volume fraction of ethanol in the aqueous ethanol solution is 60-80%, and the mass concentration of nano Fe3O4 in the aqueous ethanol solution is 5-10%.

[0014] Furthermore, in step (3), the temperature segments of the twin-screw extruder are set as follows: feeding section 220-230℃, compression section 230-245℃, melting section 245-260℃, and die head 240-250℃.

[0015] The present invention has the following advantages: (1) Improved compatibility: The surface of the modified nano-Fe3O4 is grafted with amino / carboxyl groups, which form hydrogen bonds with the amide bonds of polyamide. Combined with the interfacial bridging of the compatibilizer, the compatibility is significantly improved and the interfacial bonding is enhanced. (2) Agglomeration inhibition: The synergistic effect of ultrasonic dispersion and dispersant, combined with the strong shear force of twin-screw extruder, makes the modified nano Fe3O4 uniformly dispersed in the substrate, and the agglomerate particle size ≤50nm; (3) Prevention of shedding: The enhanced interfacial bonding force and uniform dispersion state make it difficult for nano Fe3O4 to detach during processing and use, and the electromagnetic shielding performance is stable. (4) Performance Synergy: The electromagnetic shielding effectiveness reaches 40dB, which meets the requirements of commercial shielding. At the same time, the mechanical properties are well retained, with tensile strength ≥60MPa and impact strength ≥5kJ / m². Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Figure 1 These are SEM images of electromagnetic shielding nylon fibers at different magnifications in embodiments of the present invention.

[0018] Figure 2 The stress-strain curves of electromagnetic shielding nylon fibers with different masterbatch contents are shown in the embodiments of the present invention. Figure 3 The stress-strain curves of electromagnetically shielded nylon yarns with different masterbatch contents are shown in the embodiments of the present invention. Figure 4 The electromagnetic shielding effectiveness curves of electromagnetic shielding nylon with different masterbatch contents are shown in the embodiments of the present invention. Figure 5 The TGA curves of electromagnetic shielding nylon and pure nylon with different masterbatch contents are shown in the embodiments of the present invention. Detailed Implementation

[0019] The following will be combined with the appendix Figure 1-5The technical solution of the present invention will be clearly and completely described in detail with specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0020] Example 1 Raw material composition (by weight): PA6 (relative viscosity 2.8) 60%, modified nano Fe3O4 (particle size 30-50nm) 30%, maleic anhydride grafted polyethylene (grafting rate 1.0%) 5%, calcium stearate 2%, antioxidant 1010 / 168 (mass ratio 2:1) 0.5%; Preparation of modified nano Fe3O4: Nano Fe3O4 was dispersed in 70% ethanol aqueous solution (8% by mass), ultrasonically dispersed for 40 min, heated to 90℃, 3% by mass of KH550 silane coupling agent of nano Fe3O4 was added, stirred for 1 h, 1% stearic acid was added, and the reaction continued for 2 h. After filtration and washing, it was vacuum dried at 100℃ for 6 h. Preparation process: (1) Raw material mixing: Weigh each raw material according to the proportion, add it to a high-speed mixer, and mix at 1000 r / min for 20 min at 90℃; (2) Melt extrusion: The temperature of the twin-screw extruder is set to 225℃ for the feeding section, 235℃ for the compression section, 250℃ for the melting section, 245℃ for the die head, and the screw speed is 200r / min for extrusion granulation; (3) Post-treatment: Vacuum drying at 85℃ for 10h to obtain functional masterbatch.

[0021] Example 2 Raw material composition (by weight): PA66 (relative viscosity 3.0) 55%, modified nano Fe3O4 (particle size 20-40nm) 35%, maleic anhydride grafted polypropylene (grafting rate 1.5%) 6%, polyethylene wax (molecular weight 2000) 3%, antioxidant 1010 / 168 (mass ratio 1:1) 1%; Preparation of modified nano Fe3O4: Nano Fe3O4 was dispersed in a 65% ethanol aqueous solution (6% by mass), ultrasonically dispersed for 50 min, heated to 85℃, and 4% by mass of KH560 silane coupling agent of nano Fe3O4 was added. After stirring for 1.5 h, 2% palmitic acid was added, and the reaction was continued for 2.5 h. After filtration and washing, the mixture was vacuum dried at 95℃ for 8 h. Preparation process: (1) Raw material mixing: Weigh each raw material according to the proportion, add it to a high-speed mixer, and mix at 1100 r / min for 25 min at 95℃; (2) Melt extrusion: The temperature of the twin-screw extruder is set to 230℃ for the feeding section, 240℃ for the compression section, 255℃ for the melting section, 250℃ for the die head, and the screw speed is 220r / min for extrusion granulation; (3) Post-processing: Vacuum drying at 90℃ for 9 hours to obtain functional masterbatch.

[0022] Comparative Example Unmodified nano-Fe3O4 was used instead of modified nano-Fe3O4, and the composition of other raw materials and preparation process were the same as in Example 1.

[0023] Performance testing The performance of the functional masterbatches from Examples 1-2 and the comparative examples was tested using the following methods: Electromagnetic shielding effectiveness (EMI SE): Tested in the 8-12GHz frequency band using the coaxial transmission method; Dispersion: The dispersion state of nanoparticles in the substrate was observed by transmission electron microscopy (TEM); Shedding rate: The product was aged at 80℃ for 1000h, and the amount of nanoparticles shed from the surface was tested.

[0024] The test results are shown in the table below:

[0025] The test results show that the functional masterbatches of Examples 1-2 of the present invention have excellent electromagnetic shielding performance and dispersion stability, while the comparative examples, due to the use of unmodified nano Fe3O4, have obvious problems of agglomeration, poor compatibility and shedding, resulting in significant performance degradation.

[0026] Example 3: Preparation of magnetically shielding nylon with a masterbatch content of 2% 1. Raw material preparation: Weigh 2 kg of electromagnetic shielding functional nylon masterbatch prepared in Example 1 and 98 kg of pure nylon chips (relative viscosity 2.6, moisture content 0.03%, melting point 218℃).

[0027] 2. Raw material drying and mixing: The raw materials are directly mixed and then added to a vacuum dryer and dried at 90℃ and vacuum degree -0.09MPa for 5 hours. The moisture content of the mixed raw materials is 0.03%.

[0028] 3. Melt extrusion: Add the dried raw material to the screw extruder, set the temperature of zone 1 to 235℃, zone 2 to 250℃, zone 3 to 260℃, zone 4 to 265℃, and the die head to 260℃, the screw speed to 100r / min, and the melt pressure to 12MPa. Filter through a 250-mesh filter (the particle size of impurities after filtration is ≤8μm).

[0029] 4. Spinning and cooling: A stainless steel spinneret with a spinneret hole diameter of 0.15mm and 450 holes (Ra=0.02μm) is selected. The cooling air temperature is 23℃, the air velocity is 0.8m / s, the cooling distance is 100mm, and the relative humidity is 50% (humidity control accuracy ±3%).

[0030] 5. Oiling treatment: Use a non-ionic composite oil agent specifically for nylon (60% polyether ester, 30% fatty acid ester, 10% antistatic component, surface resistance 5×10). 7 Ω), oiling temperature 35℃, oiling rate 1.0%.

[0031] 6. Stretch setting: First-stage stretching temperature 65℃, stretching ratio 2.8 times; second-stage stretching temperature 85℃, stretching ratio 1.8 times; total stretching ratio 5.04 times; heat setting at 105℃ for 4 seconds.

[0032] 7. Winding and take-up: Winding speed 3500m / min, winding tension 8cN, winding density 0.6g / cm³.

[0033] Microstructure: SEM image of the electromagnetic shielding nylon fiber in Example 1 is shown below. Figure 1 As shown in the figure, the fiber diameter is 11.8±0.5μm, which is very small. The cross-section of the single filament is circular, and the surface is smooth without obvious defects. Fe3O4 nanoparticles are uniformly distributed on the fiber surface and inside, with slight local agglomeration (agglomeration particle size ≤50nm). The fiber porosity is 9.2%, and the pore diameter is 0.1-0.5μm.

[0034] Mechanical properties: Single filament fineness 0.35 dtex, breaking strength 3.9±0.2 cN / dtex, breaking elongation 45±2%, initial modulus 56 cN / dtex, spinning breakage rate 0.3 times / ton, unwinding breakage rate 0.15%, dry heat shrinkage rate 3.1%; Thermal stability: weight loss rate of 4.3% at 350℃, maximum weight loss rate temperature of 428℃, and thermal decomposition temperature of 385℃.

[0035] The magnetically shielding nylon with a masterbatch content of 2% prepared in Example 3 of this invention was compared with pure nylon for mechanical properties, electromagnetic shielding effectiveness, and thermal stability tests. Figure 2 Table 1 shows the stress-strain curves of pure nylon fiber and electromagnetically shielded nylon fiber, and the mechanical data of pure nylon fiber and electromagnetically shielded nylon fiber are shown in Table 1.

[0036] Table 1 Mechanical data of pure nylon and electromagnetically shielded nylon fiber

[0037] from Figure 2 As can be seen, under the same strain conditions, the stress of nylon fiber is significantly higher than that of electromagnetic shielding nylon fiber. This indicates that nylon fiber can withstand greater forces during stretching. Table 1 shows that the tensile strength of nylon fiber is better than that of electromagnetic shielding nylon fiber. The stress-strain curve of nylon fiber maintains an upward trend in the higher strain range, while the curve of electromagnetic shielding nylon tends to be stable at lower stress levels, indicating that nylon fiber has better ductility.

[0038] Figure 3 Table 1 shows the stress-strain curves of pure nylon and electromagnetically shielded nylon yarns, and Table 2 shows the mechanical data of pure nylon and electromagnetically shielded nylon yarns.

[0039] Table 2 Mechanical data of nylon and electromagnetic shielding nylon yarn

[0040] from Figure 3 It can be observed that under the same strain conditions, the stress of nylon yarn is significantly higher than that of electromagnetic shielding nylon yarn. This indicates that nylon yarn can withstand greater force during the stretching process. As shown in Table 2, the tensile strength of nylon yarn is better than that of electromagnetic shielding nylon yarn.

[0041] Figure 4 The electromagnetic shielding effectiveness curves are shown for pure nylon and electromagnetically shielding nylon. From... Figure 4As can be seen, in the low-frequency band (0~500MHz), the shielding effectiveness of nylon for electromagnetic shielding drops rapidly from nearly 100dB, exhibiting extremely strong initial shielding capability; while the shielding effectiveness of pure nylon remains consistently in the 0~10dB range, offering almost no shielding effect. In the mid-frequency band (500~2000MHz), the shielding effectiveness of nylon for electromagnetic shielding enters a fluctuating phase, showing a significant peak in the 1500~2000MHz range (the amplitude rebounds to over 30dB); ordinary nylon maintains an extremely low shielding level, offering no effective shielding capability. In the high-frequency band (2000~3000MHz), the shielding effectiveness of nylon for electromagnetic shielding decreases slightly after the peak, but overall still maintains a shielding effectiveness above 10dB, with minor fluctuations; ordinary nylon still shows no significant shielding effect. This indicates that nylon's shielding effectiveness is better than that of pure nylon.

[0042] Figure 5 This is a TGA diagram of pure nylon and electromagnetic shielding nylon. From... Figure 5 As can be seen, the weight changes of both materials are small before the temperature reaches approximately 350°C, indicating good thermal stability within this temperature range. When the temperature exceeds 350°C, the weight changes of both electromagnetic shielding nylon and regular nylon increase, but the weight change of electromagnetic shielding nylon is smaller. This suggests that electromagnetic shielding nylon has better thermal stability than regular nylon.

[0043] In summary, this invention utilizes composite modification technology to surface-modify nano-Fe3O4, combined with an optimized formulation system and preparation process, successfully solving the technical challenges of poor compatibility, easy agglomeration, and easy detachment between nanoparticles and polyamide substrates. The prepared electromagnetic shielding polyamide functional masterbatch possesses both excellent electromagnetic shielding performance and mechanical properties. The processing technology is simple and the cost is controllable, making it widely applicable in the preparation of electromagnetic shielding products in fields such as electronics, automobiles, and aerospace, and possessing significant industrialization value.

[0044] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An electromagnetic shielding polyamide functional masterbatch, characterized in that: The raw material composition, by weight percentage, is as follows: Polyamide substrate 50-70%; Modified nano-Fe3O4 20-40%; Compatibilizer 3-8%; Dispersant 1-5%; Antioxidant 0.1-1%; The modified nano-Fe3O4 is a nano-Fe3O4 modified by a silane coupling agent and fatty acid, with a particle size of 20-80 nm, and the surface is grafted with compatible groups containing amino or carboxyl groups.

2. The electromagnetic shielding polyamide functional masterbatch according to claim 1, characterized in that: The polyamide substrate is selected from one or more blends of PA6, PA66, and PA12, with a relative viscosity of 2.4-3.

2.

3. The electromagnetic shielding polyamide functional masterbatch according to claim 1, characterized in that: The silane coupling agent is selected from one of KH550, KH560, and KH570, and the fatty acid is selected from one of stearic acid and palmitic acid. The amount of silane coupling agent is 1-5% of the mass of nano Fe3O4, and the amount of fatty acid is 0.5-3% of the mass of nano Fe3O4.

4. The electromagnetic shielding polyamide functional masterbatch according to claim 1, characterized in that: The compatibilizer is maleic anhydride-grafted polyolefin with a grafting rate of 0.5-2.0%, selected from maleic anhydride-grafted polyethylene and maleic anhydride-grafted polypropylene.

5. The electromagnetic shielding polyamide functional masterbatch according to claim 1, characterized in that: The dispersant is selected from one or more of calcium stearate, polyethylene wax, and polyethylene glycol, with a number average molecular weight of 1000-5000.

6. The electromagnetic shielding polyamide functional masterbatch according to claim 1, characterized in that: The antioxidant is a compound system, consisting of primary antioxidant 1010 and secondary antioxidant 168 in a mass ratio of 1:1 to 3:

1.

7. A method for preparing an electromagnetic shielding polyamide functional masterbatch as described in any one of claims 1-6, characterized in that: Includes the following steps: (1) Preparation of modified nano Fe3O4: Nano Fe3O4 was dispersed in an ethanol aqueous solution, ultrasonically dispersed for 30-60 min, heated to 80-100℃, and silane coupling agent and fatty acid were added in sequence. The mixture was stirred for 2-4 h, filtered, washed, and vacuum dried to obtain modified nano Fe3O4. (2) Raw material mixing: Weigh the polyamide substrate, modified nano Fe3O4, compatibilizer, dispersant and antioxidant by weight percentage, add them to a high-speed mixer, mix at 80-100℃ for 15-30 min, and rotate at 800-1200 r / min to obtain the mixture; (3) Melt blending extrusion: Add the mixture to a twin-screw extruder, set the temperature of each section of the extruder to 220-260℃, and the screw speed to 150-250r / min. After melt blending, extrude and granulate to obtain primary masterbatch. (4) Post-processing: The initial masterbatch is vacuum dried at 80-100℃ for 8-12h to remove moisture and obtain electromagnetic shielding polyamide functional masterbatch.

8. The preparation method according to claim 7, characterized in that: In step (1), the volume fraction of ethanol in the aqueous ethanol solution is 60-80%, and the mass concentration of nano Fe3O4 in the aqueous ethanol solution is 5-10%.

9. The preparation method according to claim 7, characterized in that: In step (3), the temperature segments of the twin-screw extruder are set as follows: feeding section 220-230℃, compression section 230-245℃, melting section 245-260℃, and die head 240-250℃.

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