A method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane

Abstract

This invention belongs to the field of membrane separation technology, specifically relating to a method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane. This invention adds a bio-based nano-reinforcing agent to an ultra-high molecular weight polyethylene matrix and utilizes a green compatibilizer to achieve its uniform dispersion. This improves the membrane's tensile strength and hydrophilicity while simultaneously forming a controllable microporous structure through a biaxial stretching process, achieving both high flux and high rejection rate. A composite support sleeve made of organic fibers and polylactic acid fibers is used, which, through simultaneous plasma activation and low-temperature solid-state welding, significantly enhances the interfacial bonding between the membrane layer and the sleeve, effectively solving the problem of easy peeling in traditional composite membranes and ensuring long-term structural stability. The entire process uses green raw materials, combined with low-energy plasma activation and programmed temperature-controlled welding processes, achieving excellent separation and anti-fouling performance while also possessing energy-saving and environmentally friendly characteristics, meeting the requirements of sustainable development.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, specifically relating to a method for preparing an enhanced modified ultra-high molecular weight polyethylene hollow fiber membrane. Background Technology

[0002] Currently, hollow fiber membrane technology still faces many bottlenecks: In terms of material systems, traditional membrane materials such as polyvinylidene fluoride, polysulfone, and polyethersulfone have inherent defects such as insufficient chemical resistance, limited mechanical strength, or easy aging and degradation; even when using high-performance substrates such as ultra-high molecular weight polyethylene, the lack of effective functional modification leads to poor anti-fouling performance and short service life of the membrane material. In terms of structural design, traditional composite membranes generally suffer from weak interfacial bonding. Due to the lack of effective interfacial activation treatment between the support and the separation layer, relying solely on physical winding and high-temperature melting bonding methods easily leads to membrane layer peeling and detachment, affecting the long-term stability of the module. In terms of manufacturing processes, existing methods generally suffer from high energy consumption and insufficient environmental friendliness. In particular, excessively high sintering temperatures can easily cause membrane structure deformation, and some processes still rely on toxic additives, which does not meet the requirements of green manufacturing.

[0003] With the increasing complexity of industrial wastewater composition and stricter environmental policies, developing a hollow fiber membrane preparation technology that combines excellent separation performance, strong interfacial bonding, and low-energy and environmentally friendly processes has become an urgent need to promote the high-end development of membrane technology. Summary of the Invention

[0004] The purpose of this invention is to address the existing problems by providing a method for preparing reinforced modified ultra-high molecular weight polyethylene hollow fiber membranes.

[0005] This invention is achieved through the following technical solution:

[0006] A method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane includes the following steps:

[0007] S1. Preparation of modified ultra-high molecular weight polyethylene masterbatch:

[0008] The premix of bio-based reinforcing agent and green compatibilizer is mixed evenly with ultra-high molecular weight polyethylene base material and green antioxidant at room temperature (500-600 rpm) and then fed into a twin-screw extruder for melt blending and granulation to obtain modified ultra-high molecular weight polyethylene masterbatch.

[0009] S2. Preparation and pretreatment of composite support sleeve:

[0010] Organic fibers and polylactic acid fibers are blended and woven at a mass ratio of (80~90):(10~20) to obtain a composite support sleeve, and then the sleeve is pretreated with low-temperature nitrogen plasma.

[0011] S3. Preparation of modified ultra-high molecular weight polyethylene porous membrane:

[0012] Porous membranes were prepared from modified ultra-high molecular weight polyethylene masterbatch using a biaxial stretching unit.

[0013] S4. Slitting and Surface Activation Treatment:

[0014] The porous membrane is fed into a precision slitting machine and cut into narrow strips with a width of 10~40mm;

[0015] The narrow strip surface (the bonding surface of the film narrow strip) was treated with plasma activation using the same parameters as in step S2. After treatment, the surface roughness of the narrow strip Ra = 0.3~0.8 μm.

[0016] S5, Precision winding and low-temperature solid-state welding:

[0017] The activated narrow strips are wrapped around the pretreated composite sleeve in a constant tension spiral winding manner, and then the wound semi-finished product is sent into a tunnel oven with a programmable temperature control system for processing.

[0018] Furthermore, the preparation method of the premix of bio-based enhancer and green compatibilizer mentioned in step S1 is as follows: the bio-based enhancer and green compatibilizer are premixed at 70~90℃ for 5~8min to obtain the premix.

[0019] Further, the mass ratio of the ultra-high molecular weight polyethylene substrate, bio-based reinforcing agent, green compatibilizer and green antioxidant in step S1 is (82~90):(2~4):(5~8):(0.2~0.5);

[0020] The ultra-high molecular weight polyethylene substrate has a weight-average molecular weight of 3-6 million and a density of 0.93-0.95 g / cm³. 3 ;

[0021] Green antioxidants are vitamin E (purity ≥ 98%) or tea polyphenols (purity ≥ 96%).

[0022] Furthermore, the preparation of the bio-based enhancer includes the following steps:

[0023] (1) Chitosan nanoparticles with a particle size of 80-150 nm were dispersed in a 2% acetic acid solution at a mass-volume ratio of 1 g:(100~120) mL. After ultrasonic dispersion, 0.5~0.8% glutaraldehyde by weight of chitosan was added to the dispersion. The mixture was stirred and reacted at a constant temperature of 50~55℃ for 2~3 h. After the reaction was completed, the mixture was washed 3~4 times with deionized water and then vacuum dried at 60~70℃ for 4~5 h to obtain cross-linked chitosan nanoparticles.

[0024] (2) Disperse cross-linked chitosan nanoparticles in deionized water at a ratio of 1g:(100~120)mL. After ultrasonic dispersion, adjust the pH to 4.5~6.0 with 1mol / L hydrochloric acid solution. Add amino-modified PEG (PEG-NH2, molecular weight 2000) and EDC / NHS condensing agent (EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide):NHS (N-hydroxysuccinimide) = 2:1, molar ratio). Stir the reaction at 60~65℃ and 300~400rpm for 3~4h. Centrifuge at 7000~8000rpm for 20~25min. Wash with deionized water until neutral. Vacuum dry at 60~70℃ for 6~7h to obtain cross-linked-polyethylene glycol-aminochitosan nanoparticles.

[0025] The mass ratio of the cross-linked chitosan nanoparticles, aminolated PEG, and EDC / NHS condensing agent is 20:10:3.

[0026] (3) Add cross-linked polyethylene glycol-amino chitosan nanoparticles to deionized water at a mass-to-volume ratio of 1:(100~120)mL. After stirring evenly, add 1mol / L NaOH to adjust the pH to 10. Then, stir at 30~35℃ for 30~40min. Add 3-chloro-2-hydroxypropyltrimethylammonium chloride (QAS, purity ≥97%, 5~8% of chitosan mass). Heat to 65~75℃ and stir at 350~450rpm for 3~4h. Neutralize with 1mol / L hydrochloric acid to pH=7. Wash with deionized water by centrifugation 3~4 times. The centrifugation speed is 8000~9000rpm and the centrifugation time is 15~20min each time. After centrifugation and washing, vacuum dry at 70~75℃ for 8~10h.

[0027] Furthermore, the preparation of the green compatibilizer includes the following steps:

[0028] 1) Use ultra-high molecular weight polyethylene (density 0.93~0.95 g / cm³) 3 GMA monomer (glycidyl methacrylate), dicumyl peroxide, tetraethyl orthosilicate (TEOS), acetic acid catalyst, and deionized water were stirred at 1000-1200 rpm for 5-7 minutes until a uniform premix was obtained.

[0029] The GMA monomer accounts for 4-6% of the mass of ultra-high molecular weight polyethylene, dicumyl peroxide accounts for 0.2-0.4% of the mass of ultra-high molecular weight polyethylene, ethyl orthosilicate accounts for 1-2% of the mass of ultra-high molecular weight polyethylene, acetic acid accounts for 5-6% of the mass of ethyl orthosilicate, and deionized water accounts for 10-15% of the mass of ethyl orthosilicate.

[0030] 2) Feed the above premixed material into a yellow screw extruder and set the temperature gradient: Zone 1 160℃, Zone 2 175℃, Zone 3 185℃, Zone 4 180~185℃, screw speed 400~500rpm, die head temperature 182~185℃. After extrusion and granulation, vacuum dry at 70~80℃ for 2~3 hours.

[0031] Furthermore, the process parameters of the twin-screw extruder mentioned in step S1 are: zone 1 temperature 160~165℃, zone 2 temperature 170~175℃, zone 3 temperature 178~183℃, zone 4 temperature 182~187℃, screw speed 250~300rpm, and die head temperature 180~185℃.

[0032] Further, the organic fiber mentioned in step S2 is selected from one of aramid, ultra-high molecular weight polyethylene fiber, and polyester fiber, wherein the tensile strength of aramid is ≥28cN / dtex, the tensile strength of ultra-high molecular weight polyethylene fiber is ≥35cN / dtex, the tensile strength of polyester fiber is ≥5cN / dtex, and the tensile strength of polylactic acid fiber is ≥3.0cN / dtex.

[0033] Sleeve dimensions: outer diameter 0.7~5.5mm, inner diameter 0.3~4.8mm, wall thickness uniformity error ≤3%.

[0034] Furthermore, in step S2, the plasma pretreatment process involves a processing power of 220-280W, a time of 30-40s, and a gas flow rate of 18-22sccm.

[0035] Furthermore, the process parameters for preparing porous membranes from modified ultra-high molecular weight polyethylene masterbatch using a biaxial stretching unit in step S3 are as follows: longitudinal stretching temperature is 95~105℃, stretching ratio is 2.5~3.0 times, transverse stretching temperature is 100~110℃, stretching ratio is 3.0~3.5 times, heat setting temperature is 115~120℃, and holding time is 15~20s.

[0036] Furthermore, the slitting speed during the slitting process described in step S4 is 25~40m / min, the longitudinal stretching amount is ≤2.0%, and the transverse shrinkage amount is ≤2.0%.

[0037] Furthermore, in step S5, the winding pitch is 0.95 to 1.05 times the width of the narrow strip, the winding tension is 6 to 10 N, and the number of winding layers is 2 to 4.

[0038] Furthermore, the processing in the tunnel oven described in step S5 is divided into three stages, specifically:

[0039] First stage (preheating): Increase the temperature from room temperature to 100-110℃ at a rate of 3-5℃ / min, and hold for 30 seconds;

[0040] Second stage (welding): Increase the temperature to 120-130℃ at a rate of 2-3℃ / min, and hold for 40-60 seconds;

[0041] The third stage (cooling): the temperature is controlled by a program of 2~5℃ / min to drop below 60℃, and then the product is taken out of the furnace and allowed to cool naturally to room temperature.

[0042] The present invention has the following advantages over the prior art:

[0043] 1. This invention provides a method for preparing a reinforced modified ultra-high molecular weight polyethylene (UHMWPE) hollow fiber membrane, significantly improving the comprehensive mechanical properties and structural stability of the hollow fiber membrane. By adding a bio-based nano-reinforcing agent and a green compatibilizer to the UHMWPE matrix in a synergistic manner, the bio-based reinforcing agent, as a rigid dispersed phase, forms covalent bonds with the green compatibilizer through epoxy groups, constructing a stable nano-reinforcing network within the UHMWPE matrix and improving the tensile strength of the membrane. A composite support sleeve, a blend of organic fibers and polylactic acid fibers, provides high-strength skeletal support for the membrane. Most notably, by simultaneously performing plasma activation treatment on the membrane layer and the sleeve, followed by precise low-temperature solid-state welding, the interfacial bonding force between the two is greatly enhanced, thus solving the problem of easy peeling of traditional composite membrane layers and ensuring the reliability of the membrane module during long-term operation.

[0044] 2. The preparation method of this invention successfully optimizes the membrane's separation performance, antifouling properties, and long-term stability. The biaxial stretching process endows the porous membrane with an ideal structure of uniform pore size and high porosity, achieving a good balance between high flux and high rejection rate. Furthermore, the introduction of bio-based enhancers significantly improves the hydrophilicity and active antibacterial properties of the membrane surface, making the membrane less susceptible to adsorption by pollutants during use, thereby delaying flux decay, enhancing antifouling ability and cleaning recovery efficiency, and extending service life.

[0045] 3. In terms of raw materials, this invention selects bio-based reinforcing agents, biodegradable polylactic acid fibers, and green additives such as vitamin E, reducing environmental impact. In terms of process, low-temperature plasma is used for surface activation, replacing traditional high-energy-consuming chemical treatments; and low-temperature solid-state welding is performed using a programmable temperature-controlled tunnel oven, avoiding energy waste and membrane structure damage caused by high-temperature sintering. This design allows the method to achieve high-performance products while also possessing energy-saving and environmental protection advantages, meeting the requirements of sustainable development. Detailed Implementation

[0046] To further explain the present invention, the following specific embodiments are described.

[0047] Unless otherwise specified, the raw materials used in this invention are all from commercially available conventional products.

[0048] Example 1

[0049] A method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane includes the following steps:

[0050] S1. Preparation of modified ultra-high molecular weight polyethylene masterbatch:

[0051] First, premix the bio-based enhancer and the green compatibilizer at 70°C for 5 minutes to obtain a premix.

[0052] Then the premix was mixed with ultra-high molecular weight polyethylene (weight average molecular weight 3 million, density 0.93 g / cm³). 3 The base material and vitamin E (purity ≥98%) are mixed evenly at 500 rpm at room temperature, and then fed into a twin-screw extruder for melt blending and granulation to obtain modified ultra-high molecular weight polyethylene masterbatch.

[0053] The mass ratio of the ultra-high molecular weight polyethylene substrate, bio-based reinforcing agent, green compatibilizer, and vitamin E is 82:2:5:0.2.

[0054] The process parameters of the twin-screw extruder are: zone 1 temperature 160℃, zone 2 temperature 170℃, zone 3 temperature 178℃, zone 4 temperature 182℃, screw speed 250rpm, and die head temperature 180℃.

[0055] The preparation of the bio-based enhancer includes the following steps:

[0056] (1) Chitosan nanoparticles with a particle size of 80 nm were dispersed in a 2% acetic acid solution at a mass-volume ratio of 1 g: 100 mL. After ultrasonic dispersion, 0.5% glutaraldehyde by weight of chitosan was added to the dispersion. The mixture was stirred and reacted at a constant temperature of 50 °C for 2 h. After the reaction was completed, the mixture was washed three times with deionized water and then vacuum dried at 60 °C for 4 h to obtain cross-linked chitosan nanoparticles.

[0057] (2) The cross-linked chitosan nanoparticles were dispersed in deionized water at a ratio of 1g:100mL. After being ultrasonically dispersed evenly, the pH was adjusted to 4.5 with 1mol / L hydrochloric acid solution. Amine-modified PEG (PEG-NH2, molecular weight 2000) and EDC / NHS condensing agent (EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide):NHS (N-hydroxysuccinimide) = 2:1, molar ratio) were added. The mixture was stirred at 60℃ and 300rpm for 3h. After centrifugation at 7000rpm for 20min, the mixture was washed with deionized water until neutral and then vacuum dried at 60~70℃ for 6h to obtain cross-linked polyethylene glycol-amino chitosan nanoparticles.

[0058] The mass ratio of the cross-linked chitosan nanoparticles, aminolated PEG, and EDC / NHS condensing agent is 20:10:3.

[0059] (3) Add cross-linked polyethylene glycol-amino chitosan nanoparticles to deionized water at a mass-volume ratio of 1:100mL. After stirring evenly, add 1mol / L NaOH to adjust the pH to 10. Then stir at 30℃ for 30min. Add 3-chloro-2-hydroxypropyltrimethylammonium chloride (QAS, purity ≥97%, 5% of chitosan mass). Heat to 65℃ and stir at 350rpm for 3h. Neutralize with 1mol / L hydrochloric acid to pH=7. Wash with deionized water by centrifugation 3 times. The centrifugation speed is 8000rpm and the centrifugation time is 15min each time. After centrifugation and washing, vacuum dry at 70℃ for 8h.

[0060] The preparation of the green compatibilizer includes the following steps:

[0061] 1) Use ultra-high molecular weight polyethylene (density 0.93 g / cm³) 3 GMA monomer (glycidyl methacrylate), dicumyl peroxide, tetraethyl orthosilicate (TEOS), acetic acid catalyst, and deionized water were stirred at 1000 rpm for 5 min until a uniform premix was obtained.

[0062] The GMA monomer accounts for 4% of the mass of ultra-high molecular weight polyethylene, dicumyl peroxide accounts for 0.2% of the mass of ultra-high molecular weight polyethylene, ethyl orthosilicate accounts for 1% of the mass of ultra-high molecular weight polyethylene, acetic acid accounts for 5% of the ethyl orthosilicate, and deionized water accounts for 10% of the ethyl orthosilicate.

[0063] 2) Feed the above premixed material into a yellow screw extruder and set the temperature gradient: Zone 1 160℃, Zone 2 175℃, Zone 3 185℃, Zone 4 180℃, screw speed 400rpm, die head temperature 182℃. After extrusion and granulation, vacuum dry at 70℃ for 2 hours.

[0064] S2. Preparation and pretreatment of composite support sleeve:

[0065] A composite support sleeve is prepared by blending organic fibers and polylactic acid fibers at a mass ratio of 80:10 and weaving them together.

[0066] The organic fiber is ultra-high molecular weight polyethylene fiber (tensile strength ≥35cN / dtex); polylactic acid fiber has a tensile strength ≥3.0cN / dtex.

[0067] Sleeve dimensions: outer diameter 0.7mm, inner diameter 0.3mm, wall thickness uniformity error ≤3%;

[0068] The low-temperature nitrogen plasma pretreatment sleeve was used, with a processing power of 220W, a processing time of 30s, and a gas flow rate of 18sccm.

[0069] S3. Preparation of modified ultra-high molecular weight polyethylene porous membrane:

[0070] Porous membranes were prepared from modified ultra-high molecular weight polyethylene masterbatch using a biaxial stretching unit.

[0071] The process parameters are as follows: longitudinal stretching temperature is 95℃, stretching ratio is 2.5 times, transverse stretching temperature is 100℃, stretching ratio is 3.0 times, heat setting temperature is 115℃, and holding time is 15s.

[0072] S4. Slitting and Surface Activation Treatment:

[0073] The porous membrane is fed into a precision slitting machine and cut into narrow strips with a width of 10mm at a slitting speed of 25m / min. The longitudinal stretch is ≤2.0% and the transverse shrinkage is ≤2.0%.

[0074] The narrow strip surface (the surface to be bonded to the film strip) is treated with plasma activation using the same parameters as in step S2.

[0075] S5, Precision winding and low-temperature solid-state welding:

[0076] The activated narrow strip is wrapped around the pretreated composite sleeve in a constant tension spiral winding manner. The winding pitch is 0.95 times the width of the narrow strip, the winding tension is 6N, and the number of winding layers is 2.

[0077] The wrapped semi-finished product can be processed in a tunnel-type drying oven with a programmed temperature control system.

[0078] First stage (preheating): Increase the temperature from room temperature to 100℃ at a rate of 3℃ / min and hold for 30 seconds;

[0079] Second stage (welding): Increase to 120℃ at 2℃ / min and hold for 40s;

[0080] The third stage (cooling): The temperature is controlled to drop below 60°C at a rate of 2°C / min, and then the product is removed from the furnace and allowed to cool naturally to room temperature.

[0081] Example 2

[0082] A method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane includes the following steps:

[0083] S1. Preparation of modified ultra-high molecular weight polyethylene masterbatch:

[0084] First, the bio-based enhancer (particle size 140nm) and the green compatibilizer (grafting rate 1.1%) were premixed at 80℃ for 7min to obtain a premix.

[0085] Then the premix was mixed with ultra-high molecular weight polyethylene (weight average molecular weight 5 million, density 0.94 g / cm³). 3 After being mixed evenly at 550 rpm at room temperature, vitamin E (purity ≥98%) was fed into a twin-screw extruder for melt blending and granulation to obtain modified ultra-high molecular weight polyethylene masterbatch.

[0086] The mass ratio of the ultra-high molecular weight polyethylene substrate, bio-based reinforcing agent, green compatibilizer, and vitamin E is 86:3:6.5:0.35.

[0087] The process parameters of the twin-screw extruder are: zone 1 temperature 162℃, zone 2 temperature 172℃, zone 3 temperature 180℃, zone 4 temperature 185℃, screw speed 280rpm, and die head temperature 182℃.

[0088] The preparation of the bio-based enhancer includes the following steps:

[0089] (1) Chitosan nanoparticles with a particle size of 110 nm were dispersed in a 2% acetic acid solution at a mass-volume ratio of 1 g: 110 mL. After ultrasonic dispersion, 0.65% glutaraldehyde by weight of chitosan was added to the dispersion. The mixture was stirred at a constant temperature of 53 °C for 2.5 h. After the reaction was completed, the mixture was washed three times with deionized water and then vacuum dried at 65 °C for 4.5 h to obtain cross-linked chitosan nanoparticles.

[0090] (2) The cross-linked chitosan nanoparticles were dispersed in deionized water at a ratio of 1 g: 110 mL. After being ultrasonically dispersed evenly, the pH was adjusted to 5.0 with 1 mol / L hydrochloric acid solution. Amination-modified PEG (PEG-NH2, molecular weight 2000) and EDC / NHS condensing agent (EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide):NHS (N-hydroxysuccinimide) = 2:1, molar ratio) were added. The mixture was stirred at 63℃ and 350 rpm for 3.5 h. After centrifugation at 7500 rpm for 23 min, the mixture was washed with deionized water until neutral and then vacuum dried at 65℃ for 6.5 h to obtain cross-linked polyethylene glycol-amino chitosan nanoparticles.

[0091] The mass ratio of the cross-linked chitosan nanoparticles, aminolated PEG, and EDC / NHS condensing agent is 20:10:3.

[0092] (3) Add cross-linked polyethylene glycol-amino chitosan nanoparticles to deionized water at a mass-volume ratio of 1:110 mL. After stirring evenly, add 1 mol / L NaOH to adjust the pH to 10. Then, stir at 33℃ for 35 min. Add 3-chloro-2-hydroxypropyltrimethylammonium chloride (QAS, purity ≥97%, 6.5% of chitosan mass), heat to 70℃, and stir at 400 rpm for 3.5 h. Then, neutralize with 1 mol / L hydrochloric acid to pH=7. Wash with deionized water by centrifugation 3 times. The centrifugation speed is 8500 rpm and the centrifugation time is 18 min each time. After centrifugation and washing, vacuum dry at 73℃ for 9 h.

[0093] The preparation of the green compatibilizer includes the following steps:

[0094] 1) Use ultra-high molecular weight polyethylene (density 0.94 g / cm³) 3 GMA monomer (glycidyl methacrylate), dicumyl peroxide, tetraethyl orthosilicate (TEOS), acetic acid catalyst, and deionized water were stirred at 1100 rpm for 6 min until a uniform premix was obtained.

[0095] The GMA monomer accounts for 5% of the mass of ultra-high molecular weight polyethylene, dicumyl peroxide accounts for 0.3% of the mass of ultra-high molecular weight polyethylene, ethyl orthosilicate accounts for 1.5% of the mass of ultra-high molecular weight polyethylene, acetic acid accounts for 5.5% of the mass of ethyl orthosilicate, and deionized water accounts for 13% of the mass of ethyl orthosilicate.

[0096] 2) Feed the above premixed material into a yellow screw extruder and set the temperature gradient: Zone 1 160℃, Zone 2 175℃, Zone 3 185℃, Zone 4 182℃, screw speed 450rpm, die head temperature 183℃. After extrusion and granulation, vacuum dry at 75℃ for 2.5h.

[0097] S2. Preparation and pretreatment of composite support sleeve:

[0098] A composite support sleeve is prepared by blending organic fibers and polylactic acid fibers at a mass ratio of 85:15 and weaving them together.

[0099] The organic fiber is ultra-high molecular weight polyethylene fiber (tensile strength ≥35cN / dtex); polylactic acid fiber has a tensile strength ≥3.0cN / dtex.

[0100] Sleeve dimensions: outer diameter 3mm, inner diameter 2.5mm, wall thickness uniformity error ≤3%;

[0101] The low-temperature nitrogen plasma pretreatment sleeve was used, with a processing power of 250W, a processing time of 35s, and a gas flow rate of 20sccm.

[0102] S3. Preparation of modified ultra-high molecular weight polyethylene porous membrane:

[0103] Porous membranes were prepared from modified ultra-high molecular weight polyethylene masterbatch using a biaxial stretching unit.

[0104] The process parameters are as follows: longitudinal stretching temperature is 100℃, stretching ratio is 2.8 times, transverse stretching temperature is 105℃, stretching ratio is 3.3 times, heat setting temperature is 118℃, and holding time is 17s.

[0105] S4. Slitting and Surface Activation Treatment:

[0106] The porous membrane is fed into a precision slitting machine and cut into narrow strips with a width of 30mm at a slitting speed of 30m / min. The longitudinal stretch is ≤2.0% and the transverse shrinkage is ≤2.0%.

[0107] The narrow strip surface (the surface to be bonded to the film narrow strip) is treated with plasma activation using the same parameters as in step S2.

[0108] S5, Precision winding and low-temperature solid-state welding:

[0109] The activated narrow strip is wrapped around the pretreated composite sleeve in a constant tension spiral winding manner. The winding pitch is 1 times the width of the narrow strip, the winding tension is 8N, and the number of winding layers is 3.

[0110] The wrapped semi-finished product can be processed in a tunnel-type drying oven with a programmed temperature control system.

[0111] First stage (preheating): Increase the temperature from room temperature to 105℃ at a rate of 4℃ / min and hold for 30 seconds;

[0112] Second stage (welding): Increase to 125℃ at 2.5℃ / min and hold for 50 seconds;

[0113] The third stage (cooling): The temperature is controlled to drop below 60℃ at a rate of 3.5℃ / min, and then the product is removed from the furnace and allowed to cool naturally to room temperature.

[0114] Example 3

[0115] A method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane includes the following steps:

[0116] S1. Preparation of modified ultra-high molecular weight polyethylene masterbatch:

[0117] First, the bio-based enhancer (particle size 180nm) and the green compatibilizer (grafting rate 1.3%) were premixed at 90℃ for 8min to obtain a premix.

[0118] Then the premix was mixed with ultra-high molecular weight polyethylene (weight average molecular weight 6 million, density 0.95 g / cm³).3 The base material and vitamin E (purity ≥98%) are mixed evenly at 600 rpm at room temperature, and then fed into a twin-screw extruder for melt blending and granulation to obtain modified ultra-high molecular weight polyethylene masterbatch.

[0119] The mass ratio of the ultra-high molecular weight polyethylene substrate, bio-based reinforcing agent, green compatibilizer, and vitamin E is 90:4:8:0.5.

[0120] The process parameters of the twin-screw extruder are: zone 1 temperature 165℃, zone 2 temperature 175℃, zone 3 temperature 183℃, zone 4 temperature 187℃, screw speed 300rpm, and die head temperature 185℃.

[0121] The preparation of the bio-based enhancer includes the following steps:

[0122] (1) Chitosan nanoparticles with a particle size of 150 nm were dispersed in a 2% acetic acid solution at a mass-volume ratio of 1 g: 120 mL. After ultrasonic dispersion, 0.8% glutaraldehyde by weight of chitosan was added to the dispersion. The mixture was stirred at a constant temperature of 55 °C for 3 h. After the reaction was completed, the mixture was washed 4 times with deionized water and then vacuum dried at 70 °C for 5 h to obtain cross-linked chitosan nanoparticles.

[0123] (2) The cross-linked chitosan nanoparticles were dispersed in deionized water at a ratio of 1g:120mL. After being ultrasonically dispersed evenly, the pH was adjusted to 6.0 with 1mol / L hydrochloric acid solution. Amination-modified PEG (PEG-NH2, molecular weight 2000) and EDC / NHS condensing agent (EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide):NHS (N-hydroxysuccinimide) = 2:1, molar ratio) were added. The mixture was stirred at 65℃ and 400rpm for 4h. After centrifugation at 8000rpm for 25min, the mixture was washed with deionized water until neutral and then vacuum dried at 70℃ for 7h to obtain cross-linked polyethylene glycol-amino chitosan nanoparticles.

[0124] The mass ratio of the cross-linked chitosan nanoparticles, aminolated PEG, and EDC / NHS condensing agent is 20:10:3.

[0125] (3) Add cross-linked polyethylene glycol-amino chitosan nanoparticles to deionized water at a mass-volume ratio of 1:120 mL. After stirring evenly, add 1 mol / L NaOH to adjust the pH to 10. Then stir at 35°C for 40 min. Add 3-chloro-2-hydroxypropyltrimethylammonium chloride (QAS, purity ≥97%, 8% of chitosan mass), heat to 75°C, and stir at 450 rpm for 4 h. Then neutralize with 1 mol / L hydrochloric acid to pH=7. Wash with deionized water by centrifugation 4 times. The centrifugation speed is 9000 rpm and the centrifugation time is 20 min each time. After centrifugation and washing, vacuum dry at 75°C for 10 h.

[0126] The preparation of the green compatibilizer includes the following steps:

[0127] 1) Use ultra-high molecular weight polyethylene (density 0.95 g / cm³) 3 GMA monomer (glycidyl methacrylate), dicumyl peroxide, tetraethyl orthosilicate (TEOS), acetic acid catalyst, and deionized water were stirred at 1200 rpm for 7 min until a uniform premix was obtained.

[0128] The GMA monomer accounts for 6% of the mass of ultra-high molecular weight polyethylene, dicumyl peroxide accounts for 0.4% of the mass of ultra-high molecular weight polyethylene, ethyl orthosilicate accounts for 2% of the mass of ultra-high molecular weight polyethylene, acetic acid accounts for 6% of the mass of ethyl orthosilicate, and deionized water accounts for 15% of the mass of ethyl orthosilicate.

[0129] 2) Feed the above premixed material into a yellow screw extruder and set the temperature gradient: Zone 1 160℃, Zone 2 175℃, Zone 3 185℃, Zone 4 185℃, screw speed 500rpm, die head temperature 185℃. After extrusion and granulation, vacuum dry at 80℃ for 3 hours.

[0130] S2. Preparation and pretreatment of composite support sleeve:

[0131] A composite support sleeve is prepared by blending organic fibers and polylactic acid fibers at a mass ratio of 90:20 and weaving them together.

[0132] The organic fiber is ultra-high molecular weight polyethylene fiber (tensile strength ≥35cN / dtex); polylactic acid fiber has a tensile strength ≥3.0cN / dtex.

[0133] Sleeve dimensions: outer diameter 5.5mm, inner diameter 4.8mm, wall thickness uniformity error ≤3%;

[0134] The low-temperature nitrogen plasma pretreatment sleeve was used, with a processing power of 280W, a processing time of 40s, and a gas flow rate of 22sccm.

[0135] S3. Preparation of modified ultra-high molecular weight polyethylene porous membrane:

[0136] Porous membranes were prepared from modified ultra-high molecular weight polyethylene masterbatch using a biaxial stretching unit.

[0137] The process parameters are as follows: longitudinal stretching temperature is 105℃, stretching ratio is 3.0 times, transverse stretching temperature is 110℃, stretching ratio is 3.5 times, heat setting temperature is 120℃, and holding time is 20s.

[0138] S4. Slitting and Surface Activation Treatment:

[0139] The porous membrane is fed into a precision slitting machine and cut into narrow strips with a width of 40mm at a slitting speed of 40m / min. The longitudinal stretch is ≤2.0% and the transverse shrinkage is ≤2.0%.

[0140] The narrow strip surface (the surface to be bonded to the film strip) is treated with plasma activation using the same parameters as in step S2.

[0141] S5, Precision winding and low-temperature solid-state welding:

[0142] The activated narrow strip is wrapped around the pretreated composite sleeve in a constant tension spiral winding manner. The winding pitch is 1.05 times the width of the narrow strip, the winding tension is 10N, and the number of winding layers is 4.

[0143] The wrapped semi-finished product can be processed in a tunnel-type drying oven with a programmed temperature control system.

[0144] First stage (preheating): Increase the temperature from room temperature to 110℃ at a rate of 5℃ / min and hold for 30 seconds;

[0145] Second stage (welding): Increase to 130℃ at 3℃ / min and hold for 60s;

[0146] The third stage (cooling): The temperature is controlled at 5℃ / min to drop below 60℃, and then the product is removed from the furnace and allowed to cool naturally to room temperature.

[0147] Comparative Example 1

[0148] Compared with Example 2, Comparative Example 1 does not have a premixing process. In step S1, the ultra-high molecular weight polyethylene matrix, bio-based reinforcing agent, green compatibilizer and vitamin E are directly mixed in one step. The remaining steps are the same as in Example 2.

[0149] Comparative Example 2

[0150] Compared with Example 2, Comparative Example 2 uses unmodified raw chitosan nanoparticles instead of the bio-based enhancer prepared in this invention, while the remaining steps are the same as in Example 2.

[0151] Comparative Example 3

[0152] Compared with Example 2, Comparative Example 3 omits the bio-based enhancer and directly mixes the green compatibilizer with the ultra-high molecular weight matrix and vitamin E. The other steps are the same as in Example 2.

[0153] Comparative Example 4

[0154] Compared to Example 2, Comparative Example 4 uses conventional maleic anhydride-grafted polyethylene (CMG5804, Jia Yi Rong Fine-Blend). ® The green compatibilizer prepared in this invention can be substituted, and the other steps are the same as in Example 2.

[0155] Comparative Example 5

[0156] Compared with Example 2, Comparative Example 5 did not involve plasma treatment, but the remaining steps were the same as in Example 2.

[0157] Comparative Example 6

[0158] Compared with Example 2, Comparative Example 6 uses a single support sleeve, without polylactic acid fiber, and a pure ultra-high molecular weight polyethylene fiber braided sleeve, while the remaining steps are the same as in Example 2.

[0159] Comparative Example 7

[0160] Compared with Example 2, Comparative Example 7 does not involve staged temperature control, but directly sintersing at 130°C for 60 seconds, without the preheating-welding-cooling step-by-step process, and the remaining steps are the same as in Example 2.

[0161] Performance testing

[0162] (1) Mechanical property testing

[0163] Tensile strength: GB / T 1040.3-2006, test speed 50mm / min;

[0164] Interlayer peel strength: GB / T 2792-2014, peel angle 180°, speed 100mm / min.

[0165] The experimental results are shown in Table 1.

[0166] (2) Separation performance test

[0167] Pure water flux: Stable flux value was tested at 25℃ and 0.1MPa;

[0168] Retention rate: 200nm polystyrene microspheres were used at a concentration of 100mg / L;

[0169] Contact angle: Static water contact angle test;

[0170] Antibacterial rate: Based on GB / T 31402-2023 standard (Escherichia coli).

[0171] The experimental results are shown in Tables 1 and 2.

[0172] Table 1 Comparison of Mechanical Properties

[0173]

[0174] Table 2. Comparison of Separation Performance

[0175]

[0176] As can be seen from Tables 1 and 2 above, the comprehensive performance of the reinforced modified polyethylene hollow fiber membrane prepared by the method of the example is significantly better than that of the comparative example. Compared with Example 2, Comparative Example 1 did not premix, and its tensile strength and interlaminar peel strength decreased significantly. Its flux and rejection rate were also lower than those of Example 2, and its contact angle increased. This indicates that premixing is a key pre-step to ensure that the bio-based reinforcing agent and the green compatibilizer fully interact and achieve nanoscale uniform dispersion. Uneven dispersion will lead to stress concentration, irregular pore structure and insufficient exposure of hydrophilic groups, resulting in poor overall membrane performance.

[0177] Compared with Example 2, Comparative Example 2 used unmodified chitosan, which had a large contact angle, extremely low antibacterial rate, and significantly reduced tensile strength. This is because the original nanoparticles, which were not modified by PEG grafting and quaternization, had extremely poor hydrophilicity and antibacterial properties, and had weak binding with the matrix, resulting in limited reinforcing effect.

[0178] Compared to Example 2, Comparative Example 3, lacking a bio-based reinforcing agent, exhibited a tensile strength reduced to 29.8 MPa, a contact angle as high as 78.9°, an antibacterial rate of 0, and a relatively low retention rate. This indicates that the bio-based reinforcing agent prepared by the method of this invention can enhance mechanical properties while also providing hydrophilic, antifouling, and antibacterial effects.

[0179] Compared with Example 2, Comparative Example 4 used traditional maleic anhydride-grafted polyethylene instead of the green compatibilizer prepared in this invention, and its performance was significantly inferior to that of Example 2. This shows that the green compatibilizer of this invention can establish a stronger and more stable interface between the bio-based reinforcing agent and the ultra-high molecular weight polyethylene matrix, thereby achieving better mechanical properties and more stable separation performance.

[0180] Compared with Example 2, Comparative Example 5, without plasma treatment, showed a sharp decrease in interlayer peel strength to 7.2 N / cm, while tensile strength and elongation at break were less affected. The separation performance was very close to that of Example 2, indicating that plasma treatment can improve interfacial bonding while having little effect on the microstructure and chemical composition of the separation layer itself.

[0181] Compared with Example 2, Comparative Example 6 used a single sleeve, and the interlayer peel strength (9.5 N / cm) was much lower than that of Example 2 (16.8 N / cm). The separation performance was similar to that of Example 2. This indicates that the introduction of polylactic acid fibers produced better chemical bonding or mechanical interlocking with the plasma-activated surface, thereby significantly enhancing the interfacial bonding force.

[0182] Compared with Example 2, Comparative Example 7, which was directly sintered at high temperature, showed significantly worse mechanical properties, with reduced throughput and increased contact angle. This is because the staged low-temperature solid-state welding process avoided internal stress, structural deformation, or interface damage caused by sudden temperature rises and falls, thus obtaining a more stable and robust composite structure. Direct high-temperature sintering, on the other hand, caused irreversible damage to the material structure.

[0183] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane, characterized in that, Includes the following steps: S1. After the premix of bio-based reinforcing agent and green compatibilizer is mixed evenly with ultra-high molecular weight polyethylene substrate and green antioxidant at room temperature, it is fed into a twin-screw extruder for melt blending and granulation to obtain modified ultra-high molecular weight polyethylene masterbatch. S2. Organic fibers and polylactic acid fibers are blended and woven to obtain a composite support sleeve, and then the sleeve is pretreated with low-temperature nitrogen plasma. S3. Prepare porous membranes from modified ultra-high molecular weight polyethylene masterbatch using a biaxial stretching unit; S4. Feed the porous membrane into a precision slitting machine and cut it into narrow strips with a width of 10~40mm; The narrow strip surface is activated using plasma with the same parameters as in step S2; S5. Wrap the activated narrow strips onto the pretreated composite sleeve using a constant tension spiral winding method, and then send the wound semi-finished product into a tunnel oven with a programmable temperature control system for processing.

2. The method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane according to claim 1, characterized in that, The preparation method of the premix of bio-based enhancer and green compatibilizer mentioned in step S1 is as follows: the bio-based enhancer and green compatibilizer are premixed at 70~90℃ for 5~8min to obtain the premix.

3. The method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane according to claim 1, characterized in that, The mass ratio of the ultra-high molecular weight polyethylene substrate, bio-based reinforcing agent, green compatibilizer and green antioxidant mentioned in step S1 is (82~90):(2~4):(5~8):(0.2~0.5); The ultra-high molecular weight polyethylene substrate has a weight-average molecular weight of 3-6 million and a density of 0.93-0.95 g / cm³. 3 ; Green antioxidants include vitamin E or tea polyphenols; When mixing at room temperature, the rotation speed should be controlled at 500~600 rpm.

4. The method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane according to claim 1, characterized in that, The preparation of the bio-based enhancer in step S1 includes the following steps: (1) Chitosan nanoparticles with a particle size of 80-150 nm were dispersed in a 2% acetic acid solution at a mass-volume ratio of 1 g:(100~120) mL. After ultrasonic dispersion, 0.5~0.8% glutaraldehyde by weight of chitosan was added to the dispersion. The mixture was stirred and reacted at a constant temperature of 50~55℃ for 2~3 h. After the reaction was completed, the mixture was washed 3~4 times with deionized water and then vacuum dried at 60~70℃ for 4~5 h to obtain cross-linked chitosan nanoparticles. (2) Disperse cross-linked chitosan nanoparticles in deionized water at a ratio of 1g:(100~120)mL. After ultrasonic dispersion, adjust the pH to 4.5~6.0 with 1mol / L hydrochloric acid solution. Add amino-modified PEG and EDC / NHS condensing agent. Stir at 60~65℃ and 300~400rpm for 3~4h. Centrifuge at 7000~8000rpm for 20~25min. Wash with deionized water until neutral. Vacuum dry at 60~70℃ for 6~7h to obtain cross-linked-polyethylene glycol-amino chitosan nanoparticles. The mass ratio of the cross-linked chitosan nanoparticles, aminolated PEG, and EDC / NHS condensing agent is 20:10:

3. (3) Add cross-linked polyethylene glycol-amino chitosan nanoparticles to deionized water at a mass-to-volume ratio of 1:(100~120)mL. After stirring evenly, add 1mol / L NaOH to adjust the pH to 10. Then, stir at 30~35℃ for 30~40min. Add 3-chloro-2-hydroxypropyltrimethylammonium chloride, raise the temperature to 65~75℃, and stir at 350~450rpm for 3~4h. Then, neutralize with 1mol / L hydrochloric acid to pH=7. Centrifuge and wash 3~4 times with deionized water. The centrifugation speed is 8000~9000rpm and the centrifugation time is 15~20min each time. After centrifugation and washing, vacuum dry at 70~75℃ for 8~10h.

5. The method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane according to claim 1, characterized in that, The preparation of the green compatibilizer includes the following steps: 1) Stir ultra-high molecular weight polyethylene, GMA monomer, dicumyl peroxide, tetraethyl orthosilicate, acetic acid catalyst, and deionized water at 1000~1200 rpm for 5~7 min until uniform to obtain a premix. The GMA monomer accounts for 4-6% of the mass of ultra-high molecular weight polyethylene, dicumyl peroxide accounts for 0.2-0.4% of the mass of ultra-high molecular weight polyethylene, ethyl orthosilicate accounts for 1-2% of the mass of ultra-high molecular weight polyethylene, acetic acid accounts for 5-6% of the mass of ethyl orthosilicate, and deionized water accounts for 10-15% of the mass of ethyl orthosilicate. 2) Feed the above premixed material into a yellow screw extruder and set the temperature gradient: Zone 1 160℃, Zone 2 175℃, Zone 3 185℃, Zone 4 180~185℃, screw speed 400~500rpm, die head temperature 182~185℃. After extrusion and granulation, vacuum dry at 70~80℃ for 2~3 hours.

6. The method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane according to claim 1, characterized in that, The process parameters of the twin-screw extruder mentioned in step S1 are: zone 1 temperature 160~165℃, zone 2 temperature 170~175℃, zone 3 temperature 178~183℃, zone 4 temperature 182~187℃, screw speed 250~300rpm, and die head temperature 180~185℃.

7. The method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane according to claim 1, characterized in that, The mass ratio of organic fiber to polylactic acid fiber in step S2 is (80~90):(10~20); The organic fiber is selected from one of aramid, ultra-high molecular weight polyethylene fiber, and polyester fiber. The tensile strength of aramid is ≥28cN / dtex, the tensile strength of ultra-high molecular weight polyethylene fiber is ≥35cN / dtex, the tensile strength of polyester fiber is ≥5cN / dtex, and the tensile strength of polylactic acid fiber is ≥3.0cN / dtex. Sleeve dimensions: outer diameter 0.7~5.5mm, inner diameter 0.3~4.8mm, wall thickness uniformity error ≤3%; The plasma pretreatment process involves a processing power of 220-280W, a time of 30-40s, and a gas flow rate of 18-22sccm.

8. The method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane according to claim 1, characterized in that, The process parameters for preparing porous membranes from modified ultra-high molecular weight polyethylene masterbatch using a biaxial stretching unit in step S3 are as follows: longitudinal stretching temperature is 95~105℃, stretching ratio is 2.5~3.0 times, transverse stretching temperature is 100~110℃, stretching ratio is 3.0~3.5 times, heat setting temperature is 115~120℃, and holding time is 15~20s.

9. The method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane according to claim 1, characterized in that, The slitting speed described in step S4 is 25~40m / min, the longitudinal stretching amount is ≤2.0%, and the transverse shrinkage amount is ≤2.0%.

10. The method for preparing a reinforced modified ultra-high molecular weight polyethylene hollow fiber membrane according to claim 1, characterized in that, In step S5, the winding pitch is 0.95 to 1.05 times the width of the narrow strip, the winding tension is 6 to 10 N, and the number of winding layers is 2 to 4. The processing in the tunnel oven is divided into three stages, specifically: First stage: Increase the temperature from room temperature to 100-110℃ at a rate of 3-5℃ / min, and hold for 30 seconds; Second stage: Increase to 120-130℃ at a rate of 2-3℃ / min, and hold for 40-60 seconds; The third stage: the temperature is controlled by a program of 2~5℃ / min to drop below 60℃, and then the product is taken out of the furnace and allowed to cool naturally to room temperature.

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