A hydrophilic PA composite material and its preparation method

Abstract

This invention discloses a hydrophilic PA composite material and its preparation method, relating to the field of polyamide composite material modification and preparation technology. The hydrophilic PA composite material comprises the following raw materials in parts by weight: 60-70 parts modified polycaprolactam, 3-5 parts polyethylene glycol, 2-3 parts polyethylene oxide, 1-3 parts nano-calcium carbonate, 5-15 parts deionized water, 2-4 parts maleic anhydride-grafted polyethylene, 0.3-0.5 parts antioxidant 1010, 0.5-1 part zinc stearate, and 8-12 parts modified nano-silica. The raw material ratio of this hydrophilic PA composite material is scientific, containing multiple effective components such as modified polycaprolactam. Key raw materials undergo special modification treatments, such as pretreatment of nano-calcium carbonate with a silane coupling agent and three-stage modification of nano-silica, which improves material performance. The parameters for each step are clearly defined, and annealing treatment eliminates internal stress, ensuring stable product quality and combining good hydrophilicity with structural stability.

Description

Technical Field

[0001] This invention relates to the field of polyamide composite material modification and preparation technology, specifically to a hydrophilic PA composite material and its preparation method. Background Technology

[0002] Polycaprolactam, a commonly used polyamide material, possesses excellent mechanical strength, chemical resistance, and good processing flowability, making it widely used in textiles, electronics, and automotive industries. However, although pure polycaprolactam contains amide groups in its molecular structure, its overall hydrophilicity is relatively weak, and its surface contact angle is relatively large. This significantly limits its application in many scenarios where specific hydrophilic properties are required, such as moisture-wicking fabrics in the textile industry, hydrophilic catheters in the medical field, and heat dissipation substrates in the electronics industry.

[0003] To improve the hydrophilicity of polyamide materials, existing technologies often employ methods such as surface coating, grafting modification, and blending modification. While surface coating is simple to operate, the coating has poor adhesion to the substrate and is prone to peeling off during use, leading to a decrease in hydrophilicity. Grafting modification introduces hydrophilic groups into the polyamide molecular chain, resulting in a long-lasting modification effect. However, traditional grafting processes often suffer from harsh reaction conditions, difficulty in precisely controlling the grafting rate, and a tendency to degrade the material's mechanical properties. Blending modification achieves hydrophilicity modification by blending polyamide with hydrophilic components. This method is low-cost and easy to industrialize. However, conventional hydrophilic components have poor compatibility with the polyamide matrix, and uneven dispersion is common during blending. This not only fails to achieve the desired hydrophilic effect but may also damage the original mechanical and processing properties of the polyamide.

[0004] Furthermore, while the introduction of nanofillers can improve the mechanical and thermal properties of polyamide composites to some extent, nanoparticles, due to their large specific surface area and high surface energy, are prone to aggregation, resulting in poor dispersion in the polyamide matrix. This prevents them from fully utilizing the nano-effect and may even become internal defects, affecting the overall performance of the material. Simultaneously, some existing hydrophilic modification schemes do not adequately consider the stability of the material during long-term use, such as anti-aging properties and water-washing resistance. After repeated use or environmental aging, the modified material easily loses its hydrophilicity, further limiting its practical application range.

[0005] Therefore, developing a hydrophilic PA composite material that can achieve synergistic improvement in hydrophilicity, mechanical properties, and stability, and that has a simple preparation process and is easy to industrialize, has become a key issue that urgently needs to be addressed in the field of polyamide material modification. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a hydrophilic PA composite material and its preparation method, solving the problems of poor hydrophilicity, difficulty in achieving synergistic performance, and low processing adaptability of traditional PA composite materials.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A hydrophilic PA composite material comprising the following raw materials in parts by weight: 60-70 parts modified polycaprolactam, 3-5 parts polyethylene glycol, 2-3 parts polyethylene oxide, 1-3 parts nano-calcium carbonate, 5-15 parts deionized water, 2-4 parts maleic anhydride-grafted polyethylene, 0.3-0.5 parts antioxidant 1010, 0.5-1 part zinc stearate, and 8-12 parts modified nano-silica.

[0008] Furthermore, the nano-calcium carbonate has a particle size of 40-60 nm and is pretreated with 2% (w / w) of silane coupling agent KH-560. The pretreatment steps are as follows: 5 g of untreated nano-calcium carbonate is added to 30 mL of anhydrous ethanol and ultrasonically dispersed at 300 W for 15 min; then 0.1 g of silane coupling agent KH-560 is added dropwise, and the mixture is stirred at 50 °C and 300 r / min for 1 h; after centrifugation, the precipitate is dried at 60 °C for 4 h to obtain the nano-calcium carbonate. Pretreatment with silane coupling agent KH-560 can eliminate the hydroxyl groups on the surface of nano-calcium carbonate, enhance its interfacial bonding with the PA matrix, avoid agglomeration, and uniformly improve the tensile strength and impact toughness of the material without localized weak points.

[0009] Furthermore, the modified nano-silica is prepared using the following specific steps: A1. Take nano-silica, add anhydrous ethanol and deionized water, and ultrasonically disperse at 300W and 40℃ for 30min to form a uniform suspension; transfer the suspension to a three-necked flask, add silane coupling agent KH-550 and citric acid dropwise, and stir at 60℃ and 400r / min for 2h; after the reaction is completed, centrifuge the mixture, collect the precipitate, wash the precipitate three times with anhydrous ethanol, and dry the precipitate at 60℃ and -0.09MPa for 8h to obtain the first modified nano-silica; The amino group of silane coupling agent KH-550 undergoes a nucleophilic substitution reaction with the hydroxyl group on the surface of SiO2 to form a covalent graft. The carboxyl group of citrate forms a hydrogen bond with the residual hydroxyl group and imparts a negative charge site, thus simultaneously achieving organicification and electrostatic repulsion stabilization.

[0010] A2. Take the first modified nano-silica and add it to deionized water. Disperse it by ultrasonication at 300W for 20 minutes. Transfer the dispersion to a four-necked flask, introduce nitrogen gas at a flow rate of 5L / min, add 2-acrylamide-2-methylpropanesulfonic acid and polyvinyl alcohol, dissolve at 45℃, then add ammonium persulfate. Maintain the reaction at 45℃ and 400r / min for 4 hours. After the reaction is completed, spray dry it at an inlet air temperature of 180℃ and an outlet air temperature of 80℃ to obtain the second modified nano-silica. At 45℃, ammonium persulfate thermally decomposes to generate sulfate free radicals, which abstract active hydrogen from 2-acrylamide-2-methylpropanesulfonic acid and polyvinyl alcohol, initiating free radical copolymerization and forming a hydrophilic network rich in sulfonic acid / hydroxyl groups on the SiO2 surface. Spray drying rapidly cures the coating and prevents solvent re-agglomeration.

[0011] A3. Take the second modified nano-silica, add deionized water, and ultrasonically disperse at 300W for 15 min; adjust the pH to 7.3-7.7 with 0.1mol / L sodium hydroxide solution, add silane-coated nano-zinc oxide, and stir at 70℃ and 400r / min for 2 h; centrifuge the system, collect the precipitate, and wash it with deionized water until the filtrate is neutral; dry the washed precipitate at 70℃ and -0.09MPa for 6 h to obtain modified nano-silica.

[0012] pH 7.3–7.7 to avoid dissolution of ZnO at its isoelectric point; the alkoxy groups of nano-zinc oxide coated with silane undergo dehydration condensation with the hydroxyl groups on the surface of the second nano-silica, which provides both UV shielding and increases surface roughness. The condensation reaction is terminated by washing with water until neutral and free alkali is removed.

[0013] Furthermore, the ratio of nano-silica, anhydrous ethanol, deionized water, silane coupling agent KH-550, and citric acid in A1 is 4-6g: 6-8mL: 18-22mL: 0.6-0.9g: 0.2-0.3g.

[0014] Furthermore, the ratio of deionized water, 2-acrylamide-2-methylpropanesulfonic acid, polyvinyl alcohol, and ammonium persulfate in A2 is 18-22 mL: 2.5-3.5 g: 1.0-2.0 g: 0.2-0.25 g.

[0015] Furthermore, the ratio of deionized water to silane-coated nano-zinc oxide in A3 is 18-22 mL: 1-1.5 g.

[0016] Furthermore, the modified polycaprolactam is prepared using the following specific steps: B1. Dry polycaprolactam chips at 80℃ and -0.09MPa for 4 hours; take sodium 2-acrylamide-2-methylpropanesulfonate and paraffin oil, knead at 60℃ and 300r / min for 30 minutes to obtain a paste; add the dried polycaprolactam chips to a twin-screw extruder, set the temperature as follows: zone 1 230℃, zone 2 240℃, zone 3 250℃, zone 4 220℃, screw speed 180r / min, after the polycaprolactam chips are completely melted, add the above paste and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, vacuum at -0.08MPa for 3-5 minutes, control the material residence time to 3-5 minutes; cool the extrudate in a 25℃ water cooling bath, blow dry the surface moisture at 60℃, and then cut it into particles with a particle size of 3-4mm to obtain the first modified polycaprolactam; Kneading ensures that sodium 2-acrylamide-2-methylpropanesulfonate is uniformly dispersed in the paraffin oil carrier; in the 230-250℃ melting section of the twin-screw extruder, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane is cracked to generate tert-butyloxy radicals, which abstract tert-hydrogen compounds from polycaprolactam. Subsequently, hydrophilic monomers are grafted onto the polycaprolactam backbone. The vacuum section at -0.08MPa removes low-molecular-weight volatiles and reduces subsequent bubbles.

[0017] B2. The first modified polycaprolactam was added to a torque rheometer and melted at 240℃ and 60r / min for 5min. Citric acid, triphenyl phosphite and silane-coated nano zinc oxide were added to it, and the mixture was melted and blended for another 10min, during which nitrogen gas was introduced at a flow rate of 5L / min. The melt was removed and placed in a flat vulcanizing machine and pressed into a sheet with a thickness of 2mm at 240℃ and 10MPa. The sheet was placed in an oven and annealed at 120℃ for 2h. After naturally cooling to room temperature, it was crushed into particles with a particle size of 2-3mm, washed once with anhydrous ethanol, and dried at 60℃ for 4h to obtain the second modified polycaprolactam. After melting at 240℃ in the torque rheometer, the carboxyl groups of citric acid and the amine end groups of the second-modified polycaprolactam form a salt, introducing hydrophilic sites; triphenyl phosphite captures the peroxy free radicals generated by high-temperature oxidation, protecting the molecular weight; the alkoxy groups of silane-coated nano-zinc oxide condense with the amino / carboxyl groups of the first-modified polycaprolactam, achieving chemical anchoring of inorganic particles; nitrogen gas isolates oxygen, and annealing at 120℃ promotes chain rearrangement, eliminates internal stress, and perfects crystallization.

[0018] B3. Take the second batch of modified polycaprolactam, add it to deionized water, place it in a three-necked flask, and stir at 80℃ and 300r / min for 2 hours to allow it to swell. Add polyvinyl alcohol and silane coupling agent KH-560 to the flask and continue stirring for 1 hour. After the process is complete, stop heating and allow it to cool naturally to 25℃. Add anhydrous ethanol dropwise at 0.5mL / min. After the process is complete, filter to separate the particles, rinse once with deionized water, and dry the particles at 60℃ for 4 hours to obtain modified polycaprolactam.

[0019] Swelling at 80℃ increases the interchain spacing of the second-modified polycaprolactam, and the hydroxyl groups of polyvinyl alcohol and the carbonyl groups of the second-modified polycaprolactam form a hydrogen-bonded interpenetrating network. The epoxy groups of the silane coupling agent KH-560 undergo ring-opening addition with the terminal amino groups of the second-modified polycaprolactam, and polyvinyl alcohol is grafted simultaneously to construct a continuous hydrophilic transition layer. The slow addition of anhydrous ethanol reduces the solvent polarity, induces controllable phase separation, and forms a micron-nano rough surface. The final particles are loose and porous, which enhances the dual effects of hydrophilicity and interface anchoring.

[0020] Furthermore, the silane-coated zinc oxide nanoparticles are prepared as follows: 5g of zinc oxide nanoparticles are dispersed in 50mL of anhydrous ethanol, sonicated at 300W for 15min, 0.25g of silane coupling agent KH-570 is added, refluxed at 70℃ for 2h, centrifuged, and dried at 80℃ for 4h to obtain silane-coated zinc oxide nanoparticles. Ultrasonic dispersion breaks up the agglomeration of zinc oxide nanoparticles, and reflux at 70℃ provides sufficient reaction time for the silane coupling agent KH-570, allowing it to fully coat the surface of the zinc oxide nanoparticles. This significantly improves the compatibility of zinc oxide nanoparticles with the organic phase, avoids agglomeration in the composite material, and retains its UV resistance and hydrophilic auxiliary effects. Furthermore, the ratio of polycaprolactam chips, sodium 2-acrylamide-2-methylpropanesulfonate, paraffin oil, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane in B1 is 72-78g: 2.5-3.5g: 0.5-0.6g: 0.15-0.25g.

[0021] Furthermore, the ratio of citric acid, triphenyl phosphite, and silane-coated nano zinc oxide in B2 is 0.2-0.3g: 0.05-0.07g: 0.8-1.2g.

[0022] Furthermore, the ratio of deionized water, polyvinyl alcohol, silane coupling agent KH-560, and anhydrous ethanol in B3 is 18-22 mL: 1.5-2.5 g: 0.2-0.3 g: 6-8 mL.

[0023] A method for preparing a hydrophilic PA composite material specifically includes the following steps: S1. Place the modified polycaprolactam, polyethylene glycol, and polyethylene oxide in a vacuum drying oven and dry them at 80℃ and -0.09MPa for 6 hours to remove moisture, prevent air bubbles from forming during subsequent extrusion, and ensure the material's density. Take nano-calcium carbonate and add it to deionized water, then ultrasonically disperse it at 300W for 20 minutes to form a uniform suspension for later use, avoiding agglomeration caused by direct addition of dry powder. S2. Add the dried modified polycaprolactam, maleic anhydride-grafted polyethylene, and antioxidant 1010 to a high-speed mixer and stir at 200 r / min for 10 min to obtain a premix. This reduces the difficulty of deep mixing in subsequent twin-screw extrusion and avoids the risk of oxidation caused by excessively low local concentrations of antioxidant. S3. Add the premix to a twin-screw extruder and set the extrusion temperatures as follows: Zone 1 220℃, Zone 2 230℃, Zone 3 240℃, Zone 4 235℃, and screw speed 200 r / min. At the second feed port of the extruder, slowly add the modified nano-silica and nano-calcium carbonate suspension and continue melt blending. At the third feed port, add polyethylene glycol, polyethylene oxide, and zinc stearate. Remove volatiles under vacuum at -0.08 MPa for 5-7 minutes, controlling the material residence time to 4-6 minutes. Segmented feeding avoids premature addition of the heat-sensitive component, polyethylene glycol, which could lead to degradation, ensuring maximum functionality of each component. S4. The extrudate is cooled and shaped in a 25℃ water-cooling bath, and the surface moisture is dried with hot air at 60℃. It is then cut into granules with a particle size of 3-4mm. The granules are placed in a flat vulcanizing machine and pressed into sheets with a thickness of 1-3mm at 230℃ and 15MPa for 5-8 minutes. The sheets are then allowed to cool naturally to room temperature. The sheets are then annealed in an 80℃ oven for 3 hours to obtain the hydrophilic PA composite material. Natural cooling reduces internal stress; annealing further eliminates internal stress, optimizes the crystal structure, improves the dimensional stability and mechanical properties of the material, and ensures the stable performance of the final product.

[0024] Furthermore, the annealing process employs a stepped heating method, increasing the temperature from room temperature to 80°C at a rate of 5°C / min, holding at that temperature for 3 hours, and then allowing it to cool naturally. This slow, stepped heating rate avoids thermal stress within the material caused by sudden temperature increases, preventing cracking or deformation. Holding at 80°C for 3 hours provides ample time for internal stress release and crystal structure optimization. Compared to direct heating at a constant temperature, this method more uniformly improves the internal structure of the material, ultimately enhancing the dimensional stability and mechanical property consistency of the composite material and avoiding localized performance differences.

[0025] This invention provides a hydrophilic PA composite material and its preparation method, which has the following beneficial effects: 1. Through a multi-step modification process, hydrophilic groups are first introduced into the modified polycaprolactam, and then the surface hydrophilic structure is optimized with citric acid, polyvinyl alcohol, etc. After multi-step treatment, the modified nano-silica not only becomes hydrophilic itself, but also synergistically constructs continuous hydrophilic channels with the matrix. The hydrophilic groups are deeply integrated into the molecular chain and the matrix, avoiding the problem of easy peeling of traditional surface coatings. Even after multiple washes or long-term use, it can still maintain a stable hydrophilic effect, which can meet the requirements of durable hydrophilicity for textile moisture-wicking fabrics, medical hydrophilic catheters, etc.

[0026] 2. After pretreatment with a silane coupling agent, the compatibility of nano-calcium carbonate with the matrix is ​​significantly improved. Its uniform dispersion provides excellent reinforcement, effectively enhancing the tensile strength and impact toughness of the material. Modified nano-silica forms a strong interfacial bond with the matrix, reducing internal defects. Precise temperature control during twin-screw extrusion, vacuum devolatilization, and subsequent stepped annealing effectively eliminate internal stress, preventing cracking and deformation, and ensuring stable performance under various operating environments. This makes it suitable for applications such as automotive interiors and electronic component housings.

[0027] 3. Although the preparation of key components involves multiple reactions, each parameter is clearly defined and controllable. The twin-screw extruder and flat vulcanizing machine used are conventional equipment, reducing equipment investment costs. The composite material preparation adopts a staged feeding process, first premixing modified polycaprolactam and maleic anhydride-grafted polyethylene, and then adding other components in stages. This ensures uniform dispersion of raw materials and avoids degradation of heat-sensitive components. The cooling, pelletizing, and annealing steps are clearly defined, allowing for continuous production. The weight range of raw materials is clearly defined, and the proportions can be adjusted according to requirements, resulting in high process flexibility.

[0028] 4. Antioxidant 1010 inhibits oxidative degradation of the material and slows down the decline in mechanical properties; maleic anhydride-grafted polyethylene not only improves compatibility but also enhances chemical corrosion resistance. Nitrogen protection during the preparation of modified polycaprolactam prevents oxidation, and the silane-coated nano-zinc oxide in modified nano-silica combines hydrophilicity and UV resistance. Annealing optimizes the internal crystal structure and reduces the impact of temperature changes on crystallinity. The material exhibits stable performance within a temperature range of -40℃ to 80℃ and can adapt to various complex operating environments, including outdoor and acid / alkali environments. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all 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.

[0030] Example 1: Preparation of hydrophilic PA composite material. The specific preparation steps are as follows: S1. Place the modified polycaprolactam, polyethylene glycol, and polyethylene oxide in a vacuum drying oven and dry them at 80℃ and -0.09MPa for 6 hours to remove moisture. Take 1 part of nano calcium carbonate and add 5 parts of deionized water, and ultrasonically disperse at 300W for 20 minutes to form a uniform suspension for later use. S2. Add 60 parts of dried modified polycaprolactam, 2 parts of maleic anhydride grafted polyethylene, and 0.3 parts of antioxidant 1010 to a high-speed mixer and stir at 200 r / min for 10 min to obtain a premix. S3. Add the premix to a twin-screw extruder and set the extrusion temperature as follows: Zone 1 220℃, Zone 2 230℃, Zone 3 240℃, Zone 4 235℃, and screw speed 200 r / min. Slowly add 8 parts of modified nano-silica and nano-calcium carbonate suspension to the second feed port of the extruder and continue melt blending. Add 3 parts of polyethylene glycol, 2 parts of polyethylene oxide, and 0.5 parts of zinc stearate to the third feed port. Remove volatiles under vacuum at -0.08 MPa for 5 minutes and control the material residence time to 4 minutes. S4. The extrudate is cooled and shaped in a 25°C water-cooling bath, and the surface moisture is dried with hot air at 60°C. It is then cut into granules with a particle size of 3 mm. The granules are placed in a flat vulcanizing machine and pressed into a sheet with a thickness of 1 mm at 230°C and 15 MPa for 5 min. The sheet is then allowed to cool naturally to room temperature. The sheet is then annealed in an 80°C oven for 3 h to obtain a hydrophilic PA composite material.

[0031] Example 2: Preparation of hydrophilic PA composite material. The specific preparation steps are as follows: S1. Place the modified polycaprolactam, polyethylene glycol, and polyethylene oxide in a vacuum drying oven and dry them at 80℃ and -0.09MPa for 6 hours to remove moisture. Take 3 parts of nano calcium carbonate and add 15 parts of deionized water. Disperse the mixture by ultrasonication at 300W for 20 minutes to form a uniform suspension for later use. S2. Add 70 parts of dried modified polycaprolactam, 4 parts of maleic anhydride grafted polyethylene, and 0.5 parts of antioxidant 1010 to a high-speed mixer and stir at 200 r / min for 10 min to obtain a premix. S3. Add the premix to a twin-screw extruder and set the extrusion temperature as follows: Zone 1 220℃, Zone 2 230℃, Zone 3 240℃, Zone 4 235℃, and screw speed 200 r / min. Slowly add 12 parts of modified nano-silica and nano-calcium carbonate suspension to the second feed port of the extruder and continue melt blending. Add 5 parts of polyethylene glycol, 3 parts of polyethylene oxide, and 1 part of zinc stearate to the third feed port. Remove volatiles under vacuum at -0.08 MPa for 7 minutes and control the material residence time to 6 minutes. S4. The extrudate is cooled and shaped in a 25°C water-cooling bath, and the surface moisture is dried with hot air at 60°C. It is then cut into granules with a particle size of 4 mm. The granules are placed in a flat vulcanizing machine and pressed into a sheet with a thickness of 3 mm at 230°C and 15 MPa for 8 minutes. The sheet is then allowed to cool naturally to room temperature. The sheet is then annealed in an 80°C oven for 3 hours to obtain a hydrophilic PA composite material.

[0032] Example 3: Preparation of hydrophilic PA composite material. The specific preparation steps are as follows: S1. Place the modified polycaprolactam, polyethylene glycol, and polyethylene oxide in a vacuum drying oven and dry them at 80℃ and -0.09MPa for 6 hours to remove moisture. Take 2 parts of nano calcium carbonate and add 10 parts of deionized water, and ultrasonically disperse them at 300W for 20 minutes to form a uniform suspension for later use. S2. Add 65 parts of dried modified polycaprolactam, 3 parts of maleic anhydride grafted polyethylene, and 0.4 parts of antioxidant 1010 to a high-speed mixer and stir at 200 r / min for 10 min to obtain a premix. S3. Add the premix to a twin-screw extruder and set the extrusion temperature as follows: Zone 1 220℃, Zone 2 230℃, Zone 3 240℃, Zone 4 235℃, and screw speed 200 r / min. Slowly add 10 parts of modified nano-silica and nano-calcium carbonate suspension to the second feed port of the extruder and continue melt blending. Add 4 parts of polyethylene glycol, 2.5 parts of polyethylene oxide, and 0.7 parts of zinc stearate to the third feed port. Remove volatiles under vacuum at -0.08 MPa for 6 minutes and control the material residence time to 5 minutes. S4. The extrudate is cooled and shaped in a 25°C water-cooling bath, and the surface moisture is dried with hot air at 60°C. It is then cut into granules with a particle size of 3 mm. The granules are placed in a flat vulcanizing machine and pressed into a sheet with a thickness of 2 mm at 230°C and 15 MPa for 6 minutes. The sheet is then allowed to cool naturally to room temperature. The sheet is then annealed in an 80°C oven for 3 hours to obtain a hydrophilic PA composite material.

[0033] Example 4: Preparation of modified nano-silica. The specific preparation steps are as follows: A1. Take 4g of nano-silica, add 6mL of anhydrous ethanol and 18mL of deionized water, and sonicate at 300W and 40℃ for 30min to form a uniform suspension; transfer the suspension to a three-necked flask, add 0.6g of silane coupling agent KH-550 and 0.2g of citric acid, and stir at 60℃ and 400r / min for 2h; after the reaction is completed, centrifuge the mixture, collect the precipitate, wash the precipitate three times with anhydrous ethanol, and dry the precipitate at 60℃ and -0.09MPa for 8h to obtain the first modified nano-silica; A2. Take the first modified nano-silica and add 18 mL of deionized water. Disperse it by ultrasonication at 300 W for 20 min. Transfer the dispersion to a four-necked flask, introduce nitrogen gas at a flow rate of 5 L / min, add 2.5 g of 2-acrylamide-2-methylpropanesulfonic acid and 1.0 g of polyvinyl alcohol. After dissolving at 45 °C, add 0.2 g of ammonium persulfate. Stir the mixture at 45 °C and 400 r / min for 4 h. After the reaction is completed, spray dry it at an inlet air temperature of 180 °C and an outlet air temperature of 80 °C to obtain the second modified nano-silica. A3. Take the second modified nano-silica, add 18 mL of deionized water, and ultrasonically disperse at 300 W for 15 min; adjust the pH to 7.3 with 0.1 mol / L sodium hydroxide solution, add 1 g of silane-coated nano-zinc oxide, and stir at 70℃ and 400 r / min for 2 h; centrifuge the system, collect the precipitate, and wash it with deionized water until the filtrate is neutral; dry the washed precipitate at 70℃ and -0.09 MPa for 6 h to obtain modified nano-silica.

[0034] Example 5: Preparation of modified nano-silica. The specific preparation steps are as follows: A1. Take 6g of nano-silica, add 8mL of anhydrous ethanol and 22mL of deionized water, and sonicate at 300W and 40℃ for 30min to form a uniform suspension; transfer the suspension to a three-necked flask, add 0.9g of silane coupling agent KH-550 and 0.3g of citric acid, and stir at 60℃ and 400r / min for 2h; after the reaction is completed, centrifuge the mixture, collect the precipitate, wash the precipitate three times with anhydrous ethanol, and dry the precipitate at 60℃ and -0.09MPa for 8h to obtain the first modified nano-silica; A2. Take the first modified nano-silica and add 22 mL of deionized water. Disperse it by ultrasonication at 300 W for 20 min. Transfer the dispersion to a four-necked flask, introduce nitrogen gas at a flow rate of 5 L / min, add 3.5 g of 2-acrylamide-2-methylpropanesulfonic acid and 2.0 g of polyvinyl alcohol, dissolve at 45 °C, then add 0.25 g of ammonium persulfate. Maintain the reaction at 45 °C and 400 r / min with stirring for 4 h. After the reaction is completed, spray dry at an inlet air temperature of 180 °C and an outlet air temperature of 80 °C to obtain the second modified nano-silica. A3. Take the second modified nano-silica, add 22 mL of deionized water, and ultrasonically disperse at 300 W for 15 min; adjust the pH to 7.7 with 0.1 mol / L sodium hydroxide solution, add 1.5 g of silane-coated nano-zinc oxide, and stir at 70℃ and 400 r / min for 2 h; centrifuge the system, collect the precipitate, and wash it with deionized water until the filtrate is neutral; dry the washed precipitate at 70℃ and -0.09 MPa for 6 h to obtain modified nano-silica.

[0035] Example 6: Preparation of modified polycaprolactam. The specific preparation steps are as follows: B1. 72g of polycaprolactam chips were dried at 80℃ and -0.09MPa for 4h; 2.5g of sodium 2-acrylamide-2-methylpropanesulfonate and 0.5g of paraffin oil were kneaded at 60℃ and 300r / min for 30min to obtain a paste; the dried polycaprolactam chips were added to a twin-screw extruder, and the following temperatures were set: Zone 1 230℃, Zone 2 240℃, Zone 3 250℃, Zone 4 220℃, and screw speed 180r / min. After the polycaprolactam chips were completely melted, the above paste and 0.15g of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane were added, and the material was de-vaporized under vacuum at -0.08MPa for 3min, with the material residence time controlled at 3min; the extrudate was cooled in a 25℃ water cooling bath, the surface moisture was dried at 60℃, and then cut into granules with a particle size of 3mm to obtain the first modified polycaprolactam; B2. The first modified polycaprolactam was added to a torque rheometer and melted at 240℃ and 60r / min for 5min. 0.2g citric acid, 0.05g triphenyl phosphite, and 0.8g silane-coated nano zinc oxide were added, and the mixture was melted and blended for another 10min, during which nitrogen gas was introduced at a flow rate of 5L / min. The melt was removed and placed in a flat vulcanizing machine, pressed into a 2mm thick sheet at 240℃ and 10MPa. The sheet was placed in an oven and annealed at 120℃ for 2h, then naturally cooled to room temperature and pulverized into 2mm particles. The particles were washed once with anhydrous ethanol and dried at 60℃ for 4h to obtain the second modified polycaprolactam. B3. Take the second batch of modified polycaprolactam and add 18 mL of deionized water. Place the mixture in a three-necked flask and stir at 80°C and 300 rpm for 2 hours to allow it to swell. Add 1.5 g of polyvinyl alcohol and 0.2 g of silane coupling agent KH-560 to the flask and continue stirring for 1 hour. After the stirring is complete, stop heating and allow the mixture to cool naturally to 25°C. Add 6 mL of anhydrous ethanol dropwise at 0.5 mL / min. After the stirring is complete, filter to separate the particles, rinse once with deionized water, and dry the particles at 60°C for 4 hours to obtain modified polycaprolactam.

[0036] Example 7: Preparation of modified polycaprolactam. The specific preparation steps are as follows: B1. 78g of polycaprolactam chips were dried at 80℃ and -0.09MPa for 4h. 3.5g of sodium 2-acrylamide-2-methylpropanesulfonate and 0.6g of paraffin oil were kneaded at 60℃ and 300r / min for 30min to obtain a paste. The dried polycaprolactam chips were added to a twin-screw extruder with the following temperatures set: Zone 1 230℃, Zone 2 240℃, Zone 3 250℃, Zone 4 220℃, and screw speed 180r / min. After the polycaprolactam chips were completely melted, the above paste and 0.25g of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane were added. The mixture was vacuum-devoured at -0.08MPa for 5min, and the material residence time was controlled at 5min. The extrudate was cooled in a 25℃ water-cooling bath, dried at 60℃, and then cut into 4mm particles to obtain the first modified polycaprolactam. B2. The first modified polycaprolactam was added to a torque rheometer and melted at 240℃ and 60r / min for 5min. 0.3g citric acid, 0.07g triphenyl phosphite, and 1.2g silane-coated nano-zinc oxide were added, and the mixture was melted and blended for another 10min, during which nitrogen gas was introduced at a flow rate of 5L / min. The melt was removed and placed in a flat vulcanizing machine, pressed into a 2mm thick sheet at 240℃ and 10MPa. The sheet was placed in an oven and annealed at 120℃ for 2h, then naturally cooled to room temperature and pulverized into 3mm particles. The particles were washed once with anhydrous ethanol and dried at 60℃ for 4h to obtain the second modified polycaprolactam. B3. Take the second batch of modified polycaprolactam, add 22 mL of deionized water, place it in a three-necked flask, and stir at 80℃ and 300 r / min for 2 h to swell; add 2.5 g of polyvinyl alcohol and 0.3 g of silane coupling agent KH-560 to the flask, and continue stirring for 1 h; after the end, stop heating and let it cool naturally to 25℃; add 8 mL of anhydrous ethanol dropwise at 0.5 mL / min; after the end, filter to separate the particles, wash once with deionized water, and dry the particles at 60℃ for 4 h to obtain modified polycaprolactam.

[0037] Comparative Example 1: A hydrophilic PA composite material was prepared. The specific preparation steps are as follows: The remaining steps remain unchanged, except that the modified nano-silica prepared in Example 4 used in Example 3 is replaced with unmodified nano-silica to prepare a hydrophilic PA composite material.

[0038] Comparative Example 2: A hydrophilic PA composite material was prepared. The specific preparation steps are as follows: The remaining steps remain the same, except that the modified polycaprolactam prepared in Example 7 used in Example 3 is replaced with unmodified polycaprolactam to prepare a hydrophilic PA composite material.

[0039] Comparative Example 3: A hydrophilic PA composite material was prepared. The specific preparation steps are as follows: The remaining steps remain unchanged, except that the modified nano-silica prepared in Example 4 used in Example 3 is replaced with unmodified nano-silica, and the modified polycaprolactam prepared in Example 7 is replaced with unmodified polycaprolactam, to prepare a hydrophilic PA composite material.

[0040] Performance testing Based on the performance test results, regarding the surface contact angle, Examples 1-3 have a contact angle of 41.6°. -55.3 Comparative Example 1, with its nano-silica replaced by unmodified nano-silica, and Comparative Example 2, with its polycaprolactam replaced by unmodified polycaprolactam, achieved 72.8% chromium content. 76.2 In comparison, 78.5% of the samples were replaced when both were replaced. This indicates that the synergistic use of modified nano-silica and modified polycaprolactam can significantly improve hydrophilicity; in terms of tensile strength, Examples 1-3 ranged from 78.6 to 85.9 MPa, while Comparative Examples 1-3 showed a significant decrease; the impact strength of Examples 1-3 ranged from 6.9 to 8.1 kJ / m. 2 Comparative Examples 1-3 have a concentration of 5.2-5.8 kJ / m³. 2 The heat distortion temperatures of Examples 1-3 were 79.5-86.7℃, and those of Comparative Examples 1-3 were 68.2-72.3℃, indicating that the modified component can enhance the mechanical and heat resistance properties of the material. Regarding water washability, the contact angles of Examples 1-3 after 5 washes were 48.2-62.1°. Comparative examples 1-3 ranged from 83.5% to 89.3%. It is evident that the modified components also improve the hydrophilic durability of the material.

[0041] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A hydrophilic PA composite material, characterized in that: It contains the following raw materials by weight: 60-70 parts modified polycaprolactam, 3-5 parts polyethylene glycol, 2-3 parts polyethylene oxide, 1-3 parts nano calcium carbonate, 5-15 parts deionized water, 2-4 parts maleic anhydride grafted polyethylene, 0.3-0.5 parts antioxidant 1010, 0.5-1 part zinc stearate, and 8-12 parts modified nano silica.

2. The hydrophilic PA composite material according to claim 1, characterized in that: The nano-calcium carbonate has a particle size of 40-60 nm and is pretreated with 2% by mass of silane coupling agent KH-560. The pretreatment steps are as follows: take 5g of untreated nano-calcium carbonate, add 30mL of anhydrous ethanol, and ultrasonically disperse at 300W for 15min. Then add 0.1g of silane coupling agent KH-560 dropwise, and stir at 50℃ and 300r / min for 1h; After centrifugation, the precipitate was dried at 60℃ for 4 hours to obtain the nano-calcium carbonate.

3. The hydrophilic PA composite material according to claim 1, characterized in that: The modified nano-silica is prepared using the following specific steps: A1. Take nano-silica, add anhydrous ethanol and deionized water, and ultrasonically disperse at 300W and 40℃ for 30min to form a uniform suspension; transfer the suspension to a three-necked flask, add silane coupling agent KH-550 and citric acid dropwise, and stir at 60℃ and 400r / min for 2h; after the reaction is completed, centrifuge the mixture, collect the precipitate, wash the precipitate three times with anhydrous ethanol, and dry the precipitate at 60℃ and -0.09MPa for 8h to obtain the first modified nano-silica; A2. Take the first modified nano-silica and add it to deionized water. Disperse it by ultrasonication at 300W for 20 minutes. Transfer the dispersion to a four-necked flask, introduce nitrogen gas at a flow rate of 5L / min, add 2-acrylamide-2-methylpropanesulfonic acid and polyvinyl alcohol, dissolve at 45℃, then add ammonium persulfate. Maintain the reaction at 45℃ and 400r / min for 4 hours. After the reaction is completed, spray dry it at an inlet air temperature of 180℃ and an outlet air temperature of 80℃ to obtain the second modified nano-silica. A3. Take the second modified nano-silica, add deionized water, and ultrasonically disperse at 300W for 15min; adjust the pH to 7.3-7.7 with 0.1mol / L sodium hydroxide solution, add silane-coated nano-zinc oxide, and stir at 70℃ and 400r / min for 2h; centrifuge the system, collect the precipitate, and wash with deionized water until the filtrate is neutral; The washed precipitate was dried at 70℃ and -0.09MPa for 6 hours to obtain modified nano-silica.

4. The hydrophilic PA composite material according to claim 3, characterized in that: The ratio of nano-silica, anhydrous ethanol, deionized water, silane coupling agent KH-550, and citric acid in A1 is 4-6g: 6-8mL: 18-22mL: 0.6-0.9g: 0.2-0.3g; The ratio of deionized water, 2-acrylamide-2-methylpropanesulfonic acid, polyvinyl alcohol, and ammonium persulfate in A2 is 18-22 mL: 2.5-3.5 g: 1.0-2.0 g: 0.2-0.25 g; The ratio of deionized water to silane-coated nano-zinc oxide in A3 is 18-22 mL: 1-1.5 g.

5. The hydrophilic PA composite material according to claim 1, characterized in that: The modified polycaprolactam is prepared using the following specific steps: B1. Dry polycaprolactam chips at 80℃ and -0.09MPa for 4 hours; take sodium 2-acrylamide-2-methylpropanesulfonate and paraffin oil, knead at 60℃ and 300r / min for 30 minutes to obtain a paste; add the dried polycaprolactam chips to a twin-screw extruder, set the temperature as follows: zone 1 230℃, zone 2 240℃, zone 3 250℃, zone 4 220℃, screw speed 180r / min, after the polycaprolactam chips are completely melted, add the above paste and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, vacuum at -0.08MPa for 3-5 minutes, control the material residence time to 3-5 minutes; cool the extrudate in a 25℃ water cooling bath, blow dry the surface moisture at 60℃, and then cut it into particles with a particle size of 3-4mm to obtain the first modified polycaprolactam; B2. Add the first modified polycaprolactam to a torque rheometer and melt it at 240℃ and 60r / min for 5min. Citric acid, triphenyl phosphite, and silane-coated nano-zinc oxide were added to the mixture, and the mixture was melt-blended for 10 minutes, during which nitrogen gas was introduced at a flow rate of 5 L / min. The melt was removed and placed in a flat vulcanizing machine, and pressed into a sheet with a thickness of 2 mm at 240 °C and 10 MPa. The sheet was placed in an oven and annealed at 120 °C for 2 hours. After naturally cooling to room temperature, it was crushed into particles with a particle size of 2-3 mm, washed once with anhydrous ethanol, and dried at 60 °C for 4 hours to obtain the second modified polycaprolactam. B3. Take the second batch of modified polycaprolactam, add it to deionized water, place it in a three-necked flask, and stir at 80℃ and 300r / min for 2 hours to allow it to swell. Add polyvinyl alcohol and silane coupling agent KH-560 to the flask and continue stirring for 1 hour. After the process is complete, stop heating and allow it to cool naturally to 25℃. Add anhydrous ethanol dropwise at 0.5mL / min. After the process is complete, filter to separate the particles, rinse once with deionized water, and dry the particles at 60℃ for 4 hours to obtain modified polycaprolactam.

6. The hydrophilic PA composite material according to claim 5, characterized in that: The silane-coated nano zinc oxide is prepared as follows: 5g of nano zinc oxide is dispersed in 50mL of anhydrous ethanol, sonicated at 300W for 15min, 0.25g of silane coupling agent KH-570 is added, refluxed and stirred at 70℃ for 2h, centrifuged, and dried at 80℃ for 4h to obtain silane-coated nano zinc oxide.

7. The hydrophilic PA composite material according to claim 5, characterized in that: The ratio of polycaprolactam chips, sodium 2-acrylamide-2-methylpropanesulfonate, paraffin oil, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane in B1 is 72-78g: 2.5-3.5g: 0.5-0.6g: 0.15-0.25g. The ratio of citric acid, triphenyl phosphite, and silane-coated nano-zinc oxide in B2 is 0.2-0.3g: 0.05-0.07g: 0.8-1.2g. The ratio of deionized water, polyvinyl alcohol, silane coupling agent KH-560, and anhydrous ethanol in B3 is 18-22 mL: 1.5-2.5 g: 0.2-0.3 g: 6-8 mL.

8. A method for preparing a hydrophilic PA composite material, characterized in that: Specifically, it includes the following steps: S1. Place the modified polycaprolactam, polyethylene glycol, and polyethylene oxide in a vacuum drying oven and dry them at 80℃ and -0.09MPa for 6 hours to remove moisture. Take nano-calcium carbonate, add it to deionized water, and ultrasonically disperse it at 300W for 20 minutes to form a uniform suspension for later use. S2. Add the dried modified polycaprolactam, maleic anhydride-grafted polyethylene, and antioxidant 1010 to a high-speed mixer and stir at 200 r / min for 10 min to obtain a premix. S3. Add the premix to a twin-screw extruder and set the extrusion temperature as follows: Zone 1 220℃, Zone 2 230℃, Zone 3 240℃, Zone 4 235℃, and screw speed 200 r / min. Slowly add the modified nano-silica and nano-calcium carbonate suspension to the second feed port of the extruder and continue melt blending. Add polyethylene glycol, polyethylene oxide, and zinc stearate to the third feed port and remove volatiles under vacuum at -0.08 MPa for 5-7 minutes, controlling the material residence time to 4-6 minutes. S4. The extrudate is cooled and shaped in a 25℃ water-cooling bath, and the surface moisture is dried with hot air at 60℃. It is then cut into granules with a particle size of 3-4mm. The granules are placed in a flat vulcanizing machine and pressed into thin sheets with a thickness of 1-3mm at 230℃ and 15MPa for 5-8 minutes. The sheets are then allowed to cool naturally to room temperature. The thin sheets are then annealed in an 80℃ oven for 3 hours to obtain the hydrophilic PA composite material.

9. The method for preparing a hydrophilic PA composite material according to claim 8, characterized in that: The annealing process employs a stepped heating method, raising the temperature from room temperature to 80°C at a rate of 5°C / min, holding it at that temperature for 3 hours, and then allowing it to cool naturally.

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