CN-121988187-A - Polyethylene hollow fiber membrane and preparation method and application thereof

CN121988187ACN 121988187 ACN121988187 ACN 121988187ACN-121988187-A

Abstract

The invention relates to the technical field of membrane separation materials, and discloses a polyethylene hollow fiber membrane, a preparation method and application thereof, wherein the polyethylene hollow fiber composite membrane comprises a reinforcement body and a separation layer which is combined on the outer surface of the reinforcement body and contains ethylene copolymer, wherein the separation layer is partially embedded into the reinforcement body to form a composite interface; The water contact angle of the polyethylene hollow fiber composite membrane is not more than 75 degrees. The polyethylene hollow fiber composite membrane has good hydrophilicity and hydrophilic durability, and effectively avoids the defects of easy dropping of hydrophilic layers, poor stability, easy dissolution loss and the like existing in the prior art when the polyethylene hollow fiber membrane is directly coated or blended and modified by adopting a hydrophilic modifier.

Inventors

XI ZHENYU
ZHANG XINMIAO
LI SHAOHUA
GAO RONG
Liu Diequn
ZHANG CHENLIN
HUANG TING

Assignees

中国石油化工股份有限公司
中石化(北京)化工研究院有限公司

Dates

Publication Date: 20260508
Application Date: 20241108

Claims (12)

1. A polyethylene hollow fiber composite membrane, which is characterized by comprising a reinforcement body and a separation layer containing ethylene copolymer combined on the outer surface of the reinforcement body, wherein the separation layer is partially embedded into the reinforcement body to form a composite interface; The ethylene copolymer is a copolymer of ethylene and a comonomer selected from the group consisting of formula 1 and/or formula 2; Wherein R 1 is C1-C16 alkyl, R 2 、R 3 、R 4 and R 5 are each independently H or C1-C16 alkyl, n is an integer from 0 to 16, and R4 and R5 are not both H; The water contact angle of the polyethylene hollow fiber composite membrane is not more than 75 degrees.
2. The polyethylene hollow fiber composite membrane according to claim 1, wherein the content of comonomer in the ethylene copolymer is 1-20wt%, preferably 5-10wt%; preferably, the weight average molecular weight of the ethylene copolymer is 50,000-500,000g/mol; preferably, the water contact angle of the polyethylene hollow fiber composite membrane is 55 ° -75 °, preferably 55 ° -65 °.
3. The polyethylene hollow fiber composite membrane according to claim 1 or 2, wherein the composite membrane has an average pore diameter of 0.05-0.5 μm; Preferably, the ratio of the average pore size to the peak pore size of the composite membrane is 0.8 to 1.2, preferably 0.85 to 1.15; preferably, the maximum pore diameter of the polyethylene hollow fiber composite membrane is 0.1-1 μm.
4. A polyethylene hollow fiber composite membrane according to any one of claims 1 to 3 wherein the reinforcement is selected from a woven fiber tube; Preferably, the fiber braided tube is selected from a fiber braided tube with a structure of crochet or braiding form by at least one of polyester fiber, nylon fiber, polypropylene fiber and polyethylene fiber; more preferably, the fiber woven tube is formed by weaving polyolefin fibers with a sheath-core structure, wherein the outer layer of the polyolefin fibers is polyethylene, and the inner core of the polyolefin fibers is polypropylene; preferably, the outer diameter of the fiber braided tube is 1-2mm, the wall thickness is 0.2-0.5mm, and the density is 20-40 meshes.
5. The polyethylene hollow fiber composite membrane according to any one of claims 1 to 4, wherein the polyethylene hollow fiber composite membrane has a breaking strength of 120 to 170MPa, a burst pressure of 0.4 to 0.7MPa, and a pure water flux of 550 to 850L/(m 2 -h) at 0.1 MPa.
6. A method of making a polyethylene hollow fiber composite membrane, the method comprising: (1) Mixing ethylene copolymer, pore-forming agent and diluent to obtain casting solution; (2) The method adopts a concentric circle composite spinning mode, so that the casting solution is combined on the outer surface of the tubular reinforcement body to form a separation layer partially embedded into the reinforcement body; (3) Sequentially washing, extracting and drying the nascent hollow fiber composite membrane obtained after spinning in the step (2) to obtain the polyethylene hollow fiber composite membrane; Wherein the extraction is ultrasonic extraction, and the extraction time is 3-9h; The ethylene copolymer is a copolymer of ethylene and a comonomer selected from the group consisting of formula 1 and/or formula 2; Wherein R 1 is C1-C16 alkyl, R 2 、R 3 、R 4 and R 5 are each independently H or C1-C16 alkyl, n is an integer from 0 to 16, and R4 and R5 are not both H; Wherein the content of comonomer in the ethylene copolymer is 1-20wt%.
7. The process according to claim 6, wherein the content of comonomer in the ethylene copolymer is from 5 to 10wt%; preferably, the weight average molecular weight of the ethylene copolymer is 50,000-500,000g/mol.
8. A method according to claim 6 or 7, wherein the porogen is selected from organic and/or inorganic porogens, preferably the organic porogen is selected from at least one of polyethylene oxide, polyethylene glycol and polyvinylpyrrolidone, preferably the inorganic porogen is selected from at least one of calcium chloride, magnesium chloride and sodium chloride; Preferably, the diluent is selected from at least one of white oil, kerosene, soybean oil and liquid paraffin; Preferably, in the film casting solution, the content of the ethylene copolymer is 12-35 wt%, the content of the pore-forming agent is 9-30 wt%, and the content of the diluent is 35-79 wt%.
9. The method according to any one of claims 6 to 8, wherein the method for producing the casting solution comprises: (a) Firstly mixing the ethylene copolymer and the pore-forming agent by adopting a ball mill, and secondly mixing the first mixed product and the diluent by adopting a colloid pump to obtain a film-forming suspension; (b) Introducing the film forming suspension into a double screw extruder, and shearing at high temperature to prepare homogeneous film casting solution; Preferably, the first mixing condition comprises the rotation speed of a ball mill of 100-600rpm and the ball milling time of 1-6 hours; Preferably, the second mixing condition comprises a colloid pump rotating speed of 1000-6000rpm and a treatment time of 10-60min; Preferably, the high temperature shear is at a temperature of 150-230 ℃.
10. The method according to any one of claims 6 to 9, wherein in step (2), the tubular reinforcement is a fiber-woven tube, preferably the fiber-woven tube is selected from the group consisting of a fiber-woven tube of a structure of crocheted or woven form of at least one of polyester fiber, nylon fiber, polypropylene fiber and polyethylene fiber, more preferably the fiber-woven tube has an outer diameter of 1 to 2mm, a wall thickness of 0.2 to 0.5mm, and a density of 25 to 30 mesh; Preferably, in the step (2), the concentric circle composite spinning mode comprises the steps of introducing a casting solution into a spinneret, compositing the casting solution with a reinforcement body through the spinneret, and then sequentially curing and forming through an air bath and a coagulating bath to form a nascent hollow fiber composite membrane; Preferably, the conditions of concentric circle composite spinning comprise that the contact distance between the casting solution and the reinforcement body at a spinneret is 0-8cm, the air bath height is 5-60cm, the spinning temperature is 150-210 ℃, and the spinning speed is 5-30m/min; preferably, the coagulation bath is carried out with water or a diluent, preferably the temperature of the coagulation bath is 20-70 ℃.
11. The method according to any one of claims 6 to 10, wherein the water washing conditions include a temperature of 25 to 50 ℃ for a period of 24 to 48 hours.
12. Use of a polyethylene hollow fiber composite membrane according to any one of claims 1 to 5, or obtained by a process according to any one of claims 6 to 11, in a membrane bioreactor and/or in an immersed ultrafiltration separation apparatus.

Description

Polyethylene hollow fiber membrane and preparation method and application thereof Technical Field The invention relates to the technical field of membrane separation materials, in particular to a polyethylene hollow fiber membrane and a preparation method and application thereof. Background The membrane separation technology has the advantages of high separation efficiency, low energy consumption, environmental friendliness and the like, has been developed into an important separation technology, and is widely used in the fields of municipal and industrial sewage treatment and recycling, drinking water purification, seawater desalination system pretreatment and the like. However, the most common hollow fiber membrane material in water treatment, polyvinylidene fluoride, is a fluoropolymer. Perfluoroalkyl and polyfluoroalkyl materials (per-and polyfluoroalkyl substances, PFAS) are potentially toxic due to their inability to degrade. The development of non-fluorine containing film materials has therefore become a hot spot in recent years. Polyethylene (PE) has good chemical stability and thermal stability, easily available raw materials, low price, no toxicity and no smell, and can replace the raw materials of the inlet fluorine-containing membrane. PE belongs to thermoplastic polymers, can form a homogeneous solution with certain solvents at high temperature, and can be prepared into PE hollow fiber membranes by a Thermal Induced Phase Separation (TIPS) method. However, the PE hollow fiber membrane prepared by the TIPS method has low surface energy and poor hydrophilicity, and the strength is difficult to meet the requirement of long-term use in the processes of membrane-bioreactor (MBR) and the like, and meanwhile, the surface is easy to pollute and the membrane wires are easy to damage in the running process, so that the service life is influenced, and the practical application of the PE hollow fiber membrane in the fields of ultrafiltration, MBR and the like is limited. For example, CN106268356a discloses a method for preparing ultra-high molecular weight polyethylene composite hollow fiber by thermally induced phase separation, after mixing ultra-high molecular weight polyethylene, polyvinylidene fluoride and diluent at high temperature by adopting a double screw extruder, metering by a gear pump, extruding by a hollow fiber spinneret, and performing cooling, winding, extraction, stretching and shaping procedures to prepare the ultra-high molecular weight polyethylene composite hollow fiber membrane. CN102068918a discloses a hydrophilic polyethylene hollow fiber membrane and a preparation method thereof, wherein a hydrophobic nascent polyethylene hollow fiber membrane is prepared in advance, then the nascent polyethylene hollow fiber membrane is soaked in a cellulose diacetate solution with a certain concentration, the cellulose diacetate solution is fully soaked in pores of membrane filaments, and a solvent of the cellulose diacetate solution is removed to obtain the hydrophilic polyethylene hollow fiber membrane. Although the method improves the hydrophilicity of the membrane, the cellulose diacetate on the surface of the membrane and in the pore canal has poor bonding performance with PE, is easy to fall off in the process of backwashing and long-term operation, has low strength, and cannot meet the requirement of long-term stable operation. Disclosure of Invention The invention aims to solve the problems of strong hydrophobicity, poor blending modification compatibility, poor modification effect and stability, complex modification process steps and the like of a polyethylene hollow fiber membrane in the prior art, and provides a polyethylene hollow fiber membrane and a preparation method and application thereof. The polyethylene hollow fiber membrane has the advantages of convenient modification process, high stability, good hydrophilicity and the like, and can be applied to process scenes such as a membrane-bioreactor (MBR) or immersed ultrafiltration. In order to achieve the above object, a first aspect of the present invention provides a polyethylene hollow fiber composite membrane, wherein the polyethylene hollow fiber composite membrane comprises a reinforcement and a separation layer containing an ethylene copolymer bonded to an outer surface of the reinforcement, wherein the separation layer is partially embedded inside the reinforcement to form a composite interface; The ethylene copolymer is a copolymer of ethylene and a comonomer selected from the group consisting of formula 1 and/or formula 2; Wherein R 1 is C1-C16 alkyl, R 2、R3、R4 and R 5 are each independently H or C1-C16 alkyl, n is an integer from 0 to 16, and R4 and R5 are not both H; The water contact angle of the polyethylene hollow fiber composite membrane is not more than 75 degrees. In a second aspect, the present invention provides a method for preparing a polyethylene hollow fiber composite membrane, wherein the method comprise