Separating net and preparation method thereof

Abstract

The invention relates to a separation net and a preparation method thereof, the separation net is formed by blending the following components: 70-90% by mass of polypropylene, more than 0% and less than 10% by mass of polyethylene, 5-15% by mass of a toughening component, 0.2-2% by mass of an antibacterial agent, 0.2-2% by mass of a hydrophilic agent, and the balance of a lubricant and an antioxidant, and the sum of the contents of the components is 100% by mass. The separation net disclosed by the invention not only has excellent comprehensive mechanical properties including toughness, strength and dimensional stability, but also has excellent antibacterial property, pollution resistance and hydrophilicity. The separation net can effectively avoid the phenomena of rough surface, sharp corners, non-uniform wire diameter, non-uniform thickness and the like, the appearance quality is better, the thickness is convenient to regulate and control, the membrane (reverse osmosis membrane) is not easy to damage, the treatment efficiency of the membrane element is effectively improved, and the service life of the membrane element is effectively prolonged.

Description

Technical Field

[0001] The invention belongs to the field of reverse osmosis membranes, and relates to a separator and a preparation method thereof, in particular to a concentrated water separator for a rolled composite reverse osmosis membrane element and a preparation method thereof. Background Art

[0002] The rolled composite reverse osmosis membrane element is composed of a membrane sheet, a water production guide cloth and a concentrate screen rolled on a central tube. The concentrate screen is in direct contact with the concentrate and plays a role of rapid diversion by forming fluid channels between the membrane elements, thus becoming one of the key factors affecting the treatment efficiency of the membrane element. Currently, the commonly used concentrate screen is mainly made of polypropylene, but due to the strong hydrophobicity of polypropylene, it has poor resistance to adhesion to water pollutants, which can easily cause pollutant deposition, thereby leading to membrane pollution, reducing membrane element performance, and increasing system operation energy consumption.

[0003] In addition, as an important component of the rolled composite reverse osmosis membrane element, the concentrate screen usually needs to comprehensively consider factors such as fluid treatment efficiency, cost, and design, and combine and superimpose multiple layers of elements and screens, or design and develop special structural screens. This puts forward higher requirements on the thickness and performance of the screen: the screen has finer wires, better mechanical strength and toughness, and will not become soft and deformed due to reduced thickness, nor will it become unevenly hard due to increased thickness, which will affect the use effect and life of the membrane element.

[0004] At present, the main directions for optimizing the performance of concentrated water separators are: 1) grafting antimicrobial agents and anti-pollution agents on the surface of the separators, or using antimicrobial agents, antioxidants and polypropylene (PP) substrates for blending and modification to prepare antimicrobial, anti-pollution and corrosion-resistant functional separators; 2) changing the diameter or arrangement of the transverse and longitudinal mesh wires of the separators to increase the pressure resistance of the separators, thereby reducing energy consumption and reducing membrane damage; 3) changing the sheet structure or stacking method of the separators to expand the fluid channels between the membrane elements, increase the flux of the membrane assembly, reduce membrane damage, and achieve high water conservation.

[0005] Guizhou Material Industry Technology Research Institute disclosed a durable hydrophilic polypropylene mesh material and preparation method in patent document 1 (CN113549272A), in which magnesium sulfate whisker stiffness modification technology is combined with hydrophilic substance slow-release traction technology, and the self-polymerization ability of dopamine is used to pull hydrophilic agents such as natural amino acids to the surface of the material to form a uniform hydrophilic layer; and then the slow-release and confinement effects of slow-release agents such as EAA sodium salt are used to lock the hydrophilic substances, so that the mesh material has good appearance, stiffness, solvent resistance, and comprehensive mechanical properties, as well as permanent hydrophilicity and long-lasting anti-pollution properties.

[0006] In patent document 2 (CN111921379A), Times Vontron Technology Co., Ltd. disclosed a roll-type membrane element pressure-resistant concentrated water separator and its preparation method. The concentrated water separator is composed of a plurality of longitudinal mesh wires and transverse mesh wires arranged and woven in different directions. The longitudinal mesh wires and the transverse mesh wires are interwoven and connected to form nodes. The nodes are processed by hot melting, extrusion or fine grinding to form node characteristic planes. By setting the node characteristic plane, the stability and pressure resistance of the separator can be increased, and the damage of the separator to its adjacent membrane can be reduced.

[0007] Shanghai Kaijin New Materials Technology Co., Ltd. disclosed a rolled reverse osmosis membrane element in patent document 3 (CN208660832U), which includes a central tube with a plurality of pure water diversion ports on the tube wall and a membrane assembly wound on the outside of the central tube, wherein the membrane assembly includes a reverse osmosis membrane bag whose opening is connected to the pure water diversion port and a multi-layer water inlet spacer layer superimposed on the membrane bag. The membrane element uses a multi-layer water inlet spacer instead of a traditional single-layer spacer, which can reduce the impact of high water pressure on the desalination layer of the reverse osmosis membrane, thereby improving the stability of the desalination layer, and further improving the water production performance and service life of the membrane element; it can also enlarge the water inlet flow channel of the membrane element, thereby improving the water production efficiency.

[0008] The important influence of brine separators on membrane element performance has led to their extensive research in the past 20 years, from the first stage (2001-2008) of hydraulic performance (such as mass transfer or pressure drop) research, to the second stage (2009-2015) of biological fouling research, and then to the third stage (2016-2020) of the design and development of new brine separators. Thanks to the progress of materials science and technology, some experimental research has been carried out on brine separators, mainly including: (1) improving surface properties by grafting or coating hydrophilic and antibacterial components on the surface of brine separators; (2) using high-precision 3D printing technology to manufacture brine separators with special configurations to optimize the separator configuration. Although these improvement technologies are relatively complete and have achieved good hydraulic performance and anti-fouling performance in the laboratory, there are still many problems in practical applications. For example, the operating stability of the coated components is poor; there is a risk of leakage of toxic substances; 3D printing technology is small in scale, high in cost, and low in efficiency; and the special configuration separators have poor universality.

[0009] Avner Ronen et al. reported in non-patent document 1 (Experimental characterization and numerical simulation of the anti-biofouling activity of nanosilver-modified feed spacers in membrane filtration, Journal of Membrane Science, 2015, 475: 320-329) that nanosilver was embedded into a polypropylene (PP) network using sonochemical deposition technology to prepare a nanosilver-modified feed spacer. The results of biological contamination experiments, CFD simulations, and confocal laser scanning microscopy (CLSM) observations showed that silver ions (Ag + ) concentration is high, corresponding to the high content of dead bacterial cells in these areas. However, since Ag has a weak chelating effect on PP and is easily leached in the concentrated water channel, the Ag-coated modified concentrated water screen will produce more serious colloid pollution after long-term operation.

[0010] Magdalena Jabońska et al. reported in non-patent document 2 (Assessment of anti-bacterialadhesion and anti-biofouling potential of plasma-mediated poly(sulfobetainemethacrylate) coatings of feed spacer, Desalination, 2020, 493: 114664) that the surface of the concentrated water screen was modified by combining atmospheric pressure plasma treatment and wet chemical coating of zwitterionic poly(sulfobetainemethacrylate) sulfobetaine (pSBMA). The short-term test results showed that the modified screen could achieve a 70% reduction in bacterial attachment and delay the production of extracellular polymeric substances (EPS), but its effect was not obvious in long-term biological contamination experiments.

[0011] Nurshaun Sreedhar et al. reported in non-patent document 3 (Mass transfer analysis of ultrafiltration using spacers based on triply periodic minimal surfaces: Effects of spacer design, directionality and voidage, Journal of Membrane Science, 2018, 561: 89-98) that several concentrate separators with complex triply periodic minimal surfaces (TPMS) geometries were designed and manufactured using additive manufacturing (AM) technology. In RO and UF biological contamination experiments, the channel permeation flux of the TPMS concentrate separators filled with TPMS increased by 15.5% and 38%, respectively, and the TOC content and bacterial cell count were reduced by more than 90% compared with commercial concentrate separators. It shows that the TPMS concentrate screen can not only improve the mass transfer and anti-fouling performance, but also avoid the increase of the inlet channel pressure (FCP) difference. However, since the thickness of the TPMS screen (2.3mm) is much larger than the thickness of the conventional concentrate screen (0.66-0.86mm), the total membrane area of ​​the rolled membrane element is greatly reduced, so its feasibility is low in practical applications. Summary of the invention

[0012] Problem that the invention aims to solve

[0013] In view of the problems of traditional polypropylene concentrated water separators such as poor hydrophilicity, easy deposition of pollutants and low mechanical strength, the purpose of the present invention is to provide a new concentrated water separator to give it hydrophilicity and antibacterial properties, and to solve the problems of membrane pollution caused by softening and deformation due to thickness changes, uneven surface and easy deposition of pollutants.

[0014] Solutions for solving problems

[0015] In order to achieve the above objectives, the inventors of the present invention conducted intensive research and found that by blending polypropylene (PP for short), polyethylene (PE for short) with toughening components, antibacterial agents, and hydrophilic agents, a high-performance separator with antibacterial, anti-fouling, and hydrophilic properties can be provided.

[0016] By adding toughening components, it can work synergistically with PE to improve the compatibility with PP, and have a synergistic toughening and modification effect on PP. The toughening components can also inhibit the aggregation and crystallization of PE, and PE can play a role in refining the distribution particle size of the toughening components in PP; by adding antimicrobial agents in a blended manner, not only can the compatibility between the components used to form the separator be ensured and the dispersion uniformity be improved, but also the stability and high efficiency of the added antimicrobial agents can be guaranteed, so that the prepared separator can have a long-term antibacterial effect; by adding hydrophilic agents in a blended manner, the surface hydrophilicity of the separator can be improved, and the formation of a hydration layer that can play an anti-fouling role can be promoted, thereby reducing the adsorption / adhesion of pollutants, and the diversion effect of the separator for hydrophilic fluids can be improved, thereby improving the fluid treatment and cleaning effects.

[0017] One aspect of the present invention relates to a separator, wherein the separator is formed by blending the following components:

[0018] Polypropylene: 70-90% by mass

[0019] Polyethylene: more than 0% by mass and less than 10% by mass,

[0020] Toughening component: 5-15% by mass

[0021] Antibacterial agent: 0.2-2% by mass

[0022] Hydrophilic agent: 0.2-2% by mass

[0023] The balance of lubricants and antioxidants,

[0024] The sum of the contents of the above components is 100% by mass.

[0025] The separator described in the present invention, wherein the polypropylene is one or more of homopolymer polypropylene and copolymer polypropylene, preferably, the polyethylene is one or more of linear low-density high-pressure polyethylene, high-density polyethylene and ultra-high molecular weight polyethylene.

[0026] The separator described in the present invention, wherein the toughening component is one or more of ethylene propylene diene monomer (EPDM) elastomer, styrene-butadiene-styrene block copolymer (SEBS) elastomer, ethylene-octene copolymer (POE) elastomer and ethylene-vinyl acetate copolymer (EVA) elastomer, preferably, the antibacterial agent is one or more of cationic polymer antibacterial agents, inorganic silver ion antibacterial agents and organic-inorganic composite antibacterial agents, more preferably, the cationic polymer antibacterial agent is one or more of quaternary ammonium salt polymers, guanidine salt polymers, chitosan and its derivatives.

[0027] The separator described in the present invention, wherein the hydrophilic agent is one or more of amino acids, polysaccharides and polyether polyols, preferably, the amino acids are one or more of glycine, serine, threonine, cysteine, lysine, arginine, aspartic acid and glutamic acid, and the polysaccharides are one or more of chitin, pectin, chitosan and its derivatives, cellulose and its derivatives.

[0028] The separator described in the present invention, wherein the lubricant is one or more of paraffin, stearic acid and its salts, ethylenebisfatty acid amide and its modified products, preferably, the antioxidant is one or more of hindered phenol antioxidants, phosphite antioxidants, and flavonoid antioxidants.

[0029] Another aspect of the present invention relates to a method for preparing a separator, the method comprising blending the following components to form a mixture:

[0030] Polypropylene: 70-90% by mass

[0031] Polyethylene: more than 0% by mass and less than 10% by mass,

[0032] Toughening component: 5-15% by mass

[0033] Antibacterial agent: 0.2-2% by mass

[0034] Hydrophilic agent: 0.2-2% by mass

[0035] The balance of lubricants and antioxidants,

[0036] The sum of the contents of the above components is 100% by mass.

[0037] Effects of the Invention

[0038] The separator provided by the present invention not only has excellent comprehensive mechanical properties including toughness, strength and dimensional stability, but also has excellent antibacterial and hydrophilic properties, and can quickly kill bacterial microorganisms in contact with it to prevent biological contamination. In addition, pollutants are not easily deposited on the separator provided by the present invention, and the adhesion of dirt is reduced. The separator provided by the present invention promotes the flow of hydrophilic fluids and promotes the removal of dirt attached to its surface. The antibacterial agent and hydrophilic agent introduced into the separator of the present invention in a blended manner are evenly dispersed and can exist stably for a long time, thereby ensuring the long-term stability of the antibacterial effect and hydrophilicity.

[0039] The separator provided by the present invention can effectively avoid surface roughness, sharp corners, uneven wire diameter and uneven thickness, has better appearance quality, is easy to control thickness, and is not easy to damage the membrane (reverse osmosis membrane), effectively improving the processing efficiency and service life of the membrane element. DETAILED DESCRIPTION

[0040] Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments.

[0041] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0042] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0043] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0044] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0045] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0046] In this specification, when "normal temperature" or "room temperature" is used, the temperature may be 10-40°C.

[0047] The present invention relates to a separator, which is formed by blending the following components:

[0048] Polypropylene: 70-90% by mass

[0049] Polyethylene: more than 0% by mass and less than 10% by mass,

[0050] Toughening component: 5-15% by mass

[0051] Antibacterial agent: 0.2-2% by mass

[0052] Hydrophilic agent: 0.2-2% by mass

[0053] The balance of lubricants and antioxidants,

[0054] The sum of the contents of the above components is 100% by mass.

[0055] In the present invention, by adding toughening components, it can synergize with PE to improve the compatibility with PP, and have a synergistic toughening and modification effect on PP. The toughening components can also inhibit the aggregation and crystallization of PE, and PE can play a role in refining the distribution particle size of the toughening components in PP.

[0056] By adding antimicrobial agents in a blending manner, not only can the compatibility between the components used to form the separator be ensured and the dispersion uniformity be improved, but also the stability and high efficiency of the added antimicrobial agents can be guaranteed, so that the prepared separator can have a long-term antimicrobial effect.

[0057] By adding hydrophilic agents in a blended manner, the surface hydrophilicity of the separator can be improved, promoting the formation of a hydration layer that can play an anti-fouling role, thereby reducing the adsorption / adhesion of pollutants, and the separator can also improve the flow guidance effect of the hydrophilic fluid, thereby improving the fluid treatment and cleaning effects.

[0058] There is no particular limitation on the polypropylene, and the polypropylene commonly used in the art may be used. Preferably, the polypropylene is one or more of homopolypropylene and copolymer polypropylene.

[0059] The content of polypropylene is preferably 70 to 90% by mass, more preferably 75 to 85% by mass, based on the total mass of the separator.

[0060] There is no particular limitation on the polyethylene, and polyethylene commonly used in the art may be used. Preferably, the polyethylene is one or more of linear low-density high-pressure polyethylene, high-density polyethylene and ultra-high molecular weight polyethylene.

[0061] The content of polyethylene is preferably greater than 0% by mass and 10% by mass or less, and more preferably 5 to 10% by mass, based on the total mass of the separator.

[0062] Adding PE to PP can improve the low-temperature impact strength of PP while maintaining a certain strength. However, due to the limited compatibility between PE and PP, the interfacial adhesion between the two is weak, which reduces the mechanical properties of the material obtained by blending PE and PP. Adding toughening components can help improve the compatibility of the blended materials, thereby improving the comprehensive mechanical properties of the blended materials.

[0063] In the present invention, a toughening component compatible with both PE and PP is added by blending to modify PP together with PE, thereby reducing the content of PE in the blended material, reducing the adverse effects of PE on PP toughening and the modification cost, and significantly improving the comprehensive mechanical properties of the separator. Compared with a single PP separator, it has better toughness, strength and dimensional stability.

[0064] Preferably, the toughening component is one or more of ethylene propylene diene monomer (EPDM) elastomer, styrene-butadiene-styrene block copolymer (SEBS) elastomer, ethylene-octene copolymer (POE) elastomer and ethylene-vinyl acetate copolymer (EVA) elastomer. For example, the following brands of ethylene-octene copolymer elastomers can be cited: POE 8540, POE8999, POE 8201, etc.

[0065] The content of the toughening component is preferably 5 to 15% by mass, more preferably 10 to 15% by mass, based on the total mass of the separator.

[0066] The presence of defects such as rough surface and sharp corners on the screen will not only create resistance to fluid flow and affect fluid treatment efficiency, but also cause damage to membrane elements such as diaphragms, and easily lead to accumulation of pollutants, reducing the service life and effectiveness of membrane components.

[0067] The present invention adopts POE to improve the processing performance of PE / PP separators. The addition of POE can reduce the adverse effect of PE on PP toughening, improve the compatibility of the blended materials, increase the melt tension of the resin, improve the melt elasticity of polyolefins, and improve the flow stability of the blended materials, improve the melt fracture and uneven wire production of the blended materials during the extrusion molding process, avoid the defects of rough surface, sharp corners, uneven wire diameter and thickness of the separator, thereby effectively improving the processing efficiency and service life of the membrane assembly. The diaphragm of the present invention has better appearance quality, convenient thickness control, and is not easy to damage the diaphragm.

[0068] Compared with the introduction of the antimicrobial agent and the hydrophilic agent by grafting, in the present invention, the antimicrobial agent and the hydrophilic agent are added by blending, thereby ensuring the uniform dispersion and long-term retention of the antimicrobial agent and the hydrophilic agent.

[0069] The addition of antibacterial agent and hydrophilic agent can form a uniform antibacterial hydrophilic layer on the surface of the prepared screen, improve the antibacterial and hydrophilic properties of the screen surface, can quickly kill bacteria and microorganisms in contact with the screen, prevent biological pollution; can also accelerate the flow of hydrophilic fluid, promote the removal of dirt on the surface of the membrane; can also adsorb water molecules to form a hydration layer, reduce the adhesion of dirt. The screen of the present invention has good antibacterial and anti-pollution properties, pollutants are not easy to deposit, and the fluid treatment efficiency is high.

[0070] Preferably, the antibacterial agent is one or more of a cationic polymer antibacterial agent, an inorganic silver ion antibacterial agent, and an organic-inorganic composite antibacterial agent.

[0071] The content of the antibacterial agent is preferably 0.2 to 2% by mass, more preferably 0.5 to 1.5% by mass, based on the total mass of the separator.

[0072] More preferably, the cationic polymer antibacterial agent is one or more of quaternary ammonium salt polymers, guanidine salt polymers, chitosan and derivatives thereof.

[0073] Preferably, the hydrophilic agent is one or more of amino acids, polysaccharides and polyether polyols, wherein the amino acids and polysaccharides may be natural or synthetic, preferably natural.

[0074] Preferably, the amino acid is one or more of glycine, serine, threonine, cysteine, lysine, arginine, aspartic acid and glutamic acid.

[0075] Examples of the polysaccharide include chitin, pectin, chitosan and derivatives thereof, and cellulose and derivatives thereof.

[0076] The content of the hydrophilic agent is preferably 0.2 to 2% by mass, more preferably 0.5 to 2% by mass, based on the total mass of the separator.

[0077] The cationic polymer antibacterial agent and natural hydrophilic agent used in the present invention are both non-toxic and harmless.

[0078] Preferably, lubricants and antioxidants are added, and there is no particular limitation on the type and content thereof, and lubricants and antioxidants commonly used in the art may be used.

[0079] Preferably, the lubricant is one or more of paraffin, stearic acid and its salts, ethylenebisfatty acid amide and its modified products.

[0080] The content of the lubricant is preferably 0.1 to 0.5 mass %, more preferably 0.2 to 0.5 mass %, based on the total mass of the separator.

[0081] Preferably, the antioxidant is one or more of hindered phenol antioxidants, phosphite antioxidants, and flavonoid antioxidants.

[0082] The content of the antioxidant is preferably 0.1 to 0.5% by mass, more preferably 0.2 to 0.5% by mass, based on the total mass of the separator.

[0083] Another aspect of the present invention relates to a method for preparing a separator, the method comprising blending the following components to form a mixture:

[0084] Polypropylene: 70-90% by mass

[0085] Polyethylene: more than 0% by mass and less than 10% by mass,

[0086] Toughening component: 5-15% by mass

[0087] Antibacterial agent: 0.2-2% by mass

[0088] Hydrophilic agent: 0.2-2% by mass

[0089] The balance of lubricants and antioxidants,

[0090] The sum of the contents of the above components is 100% by mass.

[0091] The description of each component is the same as the above description about the separator.

[0092] As a method for preparing the separator of the present invention, an exemplary embodiment is described as follows:

[0093] (1) placing the raw materials in a low-speed stirring pot and stirring for 5 to 10 minutes to obtain a uniform mixture; the raw materials are: polypropylene (PP): 70 to 90 mass%, polyethylene (PE): 0 to 10 mass%, POE: 5 to 15 mass%, antibacterial agent: 0.2 to 2 mass%, hydrophilic agent: 0.2 to 2 mass%, lubricant: 0.1 to 0.5 mass% and antioxidant: 0.1 to 0.5 mass%;

[0094] (2) The uniform mixture obtained in step (1) is fed into a feeding bin of a twin-screw extruder with a rotating head, and the feeding frequency is set to 100-500 kg / h, the extrusion temperature is 160-200°C, the main engine speed is 200-400 rpm, and the feeding frequency is 200-400 kg / h. After heating, melting, mixing, extrusion, rotating mold cooling and shaping, pulling, and winding, a high-performance antibacterial, anti-fouling, hydrophilic separator is obtained, and the thickness of the obtained separator is 10-80 mil.

[0095] Example

[0096] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0097] Example 1

[0098] Prepare raw materials with the following composition:

[0099] 82% by mass of polypropylene PP T30S, 5% by mass of high-density polyethylene HD5502XA, 10% by mass of ethylene-octene copolymer elastomer POE 8540, 1% by mass of antibacterial agent, 1.5% by mass of hydrophilic agent, 0.3% by mass of lubricant, and 0.2% by mass of antioxidant.

[0100] The antibacterial agent is quaternized hyaluronic acid; the hydrophilic agent is glycine; the lubricant is stearic acid; and the antioxidant is hindered phenol antioxidant 1010.

[0101] Place all raw materials in a low-speed stirring pot and stir for 5 minutes to obtain a uniform mixture. Put the uniform mixture into the feeding bin of a twin-screw extruder with a rotating head, set the feeding frequency to 180kg / h, the extrusion temperature to 160℃, the main engine speed to 200rpm, and the feeding frequency to 300kg / h, and after heating, melting, mixing, extrusion, rotating mold cooling and shaping, pulling, and winding, a high-performance antibacterial, anti-fouling, hydrophilic separator with a thickness of 28mil is obtained.

[0102] Example 2

[0103] Prepare raw materials with the following composition:

[0104] 78% by mass of polypropylene PP EP300H, 7% by mass of high-density polyethylene HD5502XA, 12% by mass of ethylene-octene copolymer elastomer POE 8999, 0.8% by mass of antibacterial agent, 1.8% by mass of hydrophilic agent, 0.2% by mass of lubricant, and 0.2% by mass of antioxidant.

[0105] The antibacterial agent is polyhexamethylene biguanide hydrochloride; the hydrophilic agent is chitosan; the lubricant is paraffin; and the antioxidant is phosphite antioxidant 168.

[0106] Place all raw materials in a low-speed stirring pot and stir for 5 minutes to obtain a uniform mixture. Put the uniform mixture into the feeding bin of a twin-screw extruder with a rotating head, set the feeding frequency to 300kg / h, the extrusion temperature to 200℃, the main engine speed to 300rpm, and the feeding frequency to 300kg / h. After heating, melting, mixing, extrusion, rotating mold cooling and shaping, pulling, and winding, a high-performance antibacterial, anti-fouling, hydrophilic separator with a thickness of 34mil is obtained.

[0107] Example 3

[0108] Prepare raw materials with the following composition:

[0109] 80% by mass of polypropylene PP T30s, 6% by mass of high-density polyethylene HD5502XA, 11% by mass of ethylene-octene copolymer elastomer POE 8201, 1.2% by mass of antibacterial agent, 1.2% by mass of hydrophilic agent, 0.3% by mass of lubricant, and 0.3% by mass of antioxidant.

[0110] The antibacterial agent is chitosan; the hydrophilic agent is cellulose; the lubricant is stearate; and the antioxidant is a mixture of hindered phenol antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:1.

[0111] Place all raw materials in a low-speed stirring pot and stir for 5 minutes to obtain a uniform mixture. Put the uniform mixture into the feeding bin of a twin-screw extruder with a rotating head, set the feeding frequency to 400kg / h, the extrusion temperature to 180℃, the main engine speed to 400rpm, and the feeding frequency to 200kg / h, and after heating, melting, mixing, extrusion, rotating mold cooling and shaping, pulling, and winding, a high-performance antibacterial, anti-fouling, hydrophilic separator with a thickness of 46mil is obtained.

[0112] Performance Characterization and Test Results

[0113] (1) Mechanical properties

[0114] The mechanical properties of the samples prepared in Examples 1 to 3 and a single polypropylene spacer (grades T30S and EP300H) were tested under the following test conditions:

[0115] First, a vertical injection molding machine was used to prepare several standard mechanical splines with length, width and thickness of 80mm, 10mm and 4mm respectively, and the front and back 3 were discarded, leaving the test splines in the middle. Then, the tensile performance test was carried out according to GB / T 1040.2-2022, and the notched impact strength test was carried out according to GB / T 1043.2-2018. Eight splines were tested for each group of samples, and the maximum and minimum values ​​were discarded. The average value of the group of data was taken as the tensile strength, flexural strength, flexural modulus and notched impact strength of the group of samples. For the melt index, the injection molded splines were first crushed with a multi-functional crusher, and then the melt index was determined according to GB / T 3682.1-2018. Five splines were tested for each group of samples, and the maximum and minimum values ​​were discarded. The average value of the group of data was taken as the melt index of the group of samples.

[0116] The results are shown in Table 1 below.

[0117] Table 1

[0118]

[0119] (2) Antibacterial properties

[0120] The antibacterial properties of the samples prepared in Examples 1 to 3 and a single polypropylene separator (brands T30S and EP300H) were tested under the following test conditions:

[0121] First, each sample and a single polypropylene screen (brand T30S and EP300H) were cut into 15×35 mm in size and placed under a 40W ultraviolet lamp (wavelength 253.7nm) for 30 min for sterilization; then, an appropriate amount of Gram-negative Escherichia coli (E. coli) or Gram-positive Staphylococcus aureus (Staphylococcus aureus) was introduced into 30 mL LB culture medium by standard serial dilution method. aureus, S.aureus), and cultured at 37°C for 24 hours for later use; the sterilized screen sample was placed in the above bacterial solution, and kept at 37°C for 1 hour, then the screen was taken out, and the surface of the screen was rinsed with 15mL ultrapure water to peel off the bacteria on the surface of the screen, the water used to rinse the screen was collected and diluted 1000 times, and it was evenly applied to the surface of the pre-made LB solid culture medium, and after culturing at 37°C for 24 hours, the number of colonies N1 was counted; the number of colonies N2 obtained by culturing the bacterial solution without the screen was used as the control group, and the antibacterial efficiency A of each screen can be calculated by the following formula:

[0122]

[0123] The results are shown in Table 2 below.

[0124] Table 2

[0125]

[0126] (3) Hydrophilic properties

[0127] The hydrophilic properties of the samples prepared in Examples 1 to 3 and a single polypropylene spacer (grades T30S and EP300H) were tested under the following test conditions:

[0128] (a) The contact angle of the sample surface was measured using a Shanghai Zhongchen JC2000D contact angle meter.

[0129] First, a thin sample with a length and width of 80 mm was prepared using a vertical injection molding machine, and the sample was fixed flatly on a glass slide with double-sided tape. Then, 1 μL of deionized water was added to the sample surface using a sampling needle. After the droplet was in contact with the sample surface for 10 seconds, the contact angle at this time was recorded. At least 5 different locations on each sample surface were selected for contact angle measurement, and the average value was taken as the contact angle of the sample.

[0130] (b) The surface roughness of the sample was analyzed using a German Bruker Dimension ICON atomic force microscope (Atomic Force Microscope, AFM). Similarly, the prepared thin sample was first fixed on a glass slide with double-sided tape for testing. Under room temperature conditions, the scanning range was set to 10×10μm, and the AFM test was performed. At least 5 different locations on each sample surface were selected for surface roughness analysis, and the average value was taken as the surface roughness of the sample.

[0131] The results are shown in Table 3 below.

[0132] Table 3

[0133] sample Water drop contact angle (°) Roughness(nm) T30S 102.6 45.8 EP300H 103.4 46.2 Example 1 47.3 21.3 Example 2 49.6 22.7 Example 3 46.2 20.5

[0134] (4) Anti-pollution performance

[0135] Using bovine serum albumin (BSA) as a pollutant model, each sample prepared in Examples 1 to 3 and a single polypropylene spacer (grade T30S and EP300H) were installed in a membrane module, and the water flux retention rate of each membrane module after 168 hours of operation and the water flux recovery rate after cleaning the pollutants were compared. The water flux retention rate and the water flux recovery rate were obtained as follows:

[0136] (a) The feed solution (deionized water) was run for 0.5 h, and the permeation flux J0 of the membrane assembly was measured; (b) the pollutant solution (deionized water + 200 mg / L BSA) was continuously run for 168 h, and the permeation flux J1 of the membrane assembly after contamination was measured; (c) deionized water was run for 1 h to fully flush the membrane assembly, and the permeation flux J2 of the flushed membrane assembly to the feed solution (deionized water) was measured after the flux stabilized.

[0137] The anti-pollution parameter calculation method is as follows:

[0138] Water flux retention rate:

[0139] Water flux recovery rate:

[0140] The results are shown in Table 4 below.

[0141] Table 4

[0142] sample Water flux retention rate (%) Water flux recovery rate (%) T30S 48.8 55.1 EP300H 47.6 52.3 Example 1 96.5 94.4 Example 2 98.2 95.2 Example 3 97.8 94.7

[0143] From the above test results, it can be seen that the separator samples prepared in Examples 1 to 3 have high strength, good toughness, smooth surface, and overall performance (including antibacterial properties, hydrophilicity, and anti-pollution properties) are significantly better than single polypropylene separators.

[0144] In addition, the separator provided by the present invention has uniform mesh thickness, regular node shapes, no breakpoints or sharp corners, and can meet the basic requirements of commercial separators.

[0145] It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto.

[0146] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A separator, the separator being formed by blending the following components: Polypropylene: 70-90% by mass Polyethylene: more than 0% by mass and less than 10% by mass, Toughening component: 5-15% by mass Antibacterial agent: 0.2-2% by mass Hydrophilic agent: 0.2-2% by mass The balance of lubricants and antioxidants, The sum of the contents of the above components is 100% by mass.

2. The separator according to claim 1, wherein the polypropylene is one or more of homopolypropylene and copolymer polypropylene, and preferably, the polyethylene is one or more of linear low-density high-pressure polyethylene, high-density polyethylene and ultra-high molecular weight polyethylene.

3. The separator according to claim 1 or 2, wherein the toughening component is one or more of ethylene propylene diene monomer (EPDM) elastomer, styrene-butadiene-styrene block copolymer (SEBS) elastomer, ethylene-octene copolymer (POE) elastomer and ethylene-vinyl acetate copolymer (EVA) elastomer, preferably, the antibacterial agent is one or more of a cationic polymer antibacterial agent, an inorganic silver ion antibacterial agent and an organic-inorganic composite antibacterial agent, more preferably, the cationic polymer antibacterial agent is one or more of a quaternary ammonium salt polymer, a guanidine salt polymer, chitosan and its derivatives.

4. The separator according to claim 1 or 2, wherein the hydrophilic agent is one or more of amino acids, polysaccharides and polyether polyols, preferably, the amino acids are one or more of glycine, serine, threonine, cysteine, lysine, arginine, aspartic acid and glutamic acid, and the polysaccharides are one or more of chitin, pectin, chitosan and its derivatives, cellulose and its derivatives.

5. The separator according to claim 1 or 2, wherein the lubricant is one or more of paraffin, stearic acid and its salts, ethylenebisfatty acid amide and its modified products, and preferably, the antioxidant is one or more of hindered phenol antioxidants, phosphite antioxidants, and flavonoid antioxidants.

6. A method for preparing a screen, the method comprising blending the following components to form a mixture: Polypropylene: 70-90% by mass Polyethylene: more than 0% by mass and less than 10% by mass, Toughening component: 5-15% by mass Antibacterial agent: 0.2-2% by mass Hydrophilic agent: 0.2-2% by mass The balance of lubricants and antioxidants, The sum of the contents of the above components is 100% by mass.

7. The method according to claim 6, wherein the polypropylene is one or more of homopolypropylene and copolymer polypropylene, and preferably, the polyethylene is one or more of linear low-density high-pressure polyethylene, high-density polyethylene and ultra-high molecular weight polyethylene.

8. The method according to claim 6 or 7, wherein the toughening component is one or more of ethylene propylene diene monomer (EPDM) elastomer, styrene-butadiene-styrene block copolymer (SEBS) elastomer, ethylene-octene copolymer (POE) elastomer and ethylene-vinyl acetate copolymer (EVA) elastomer, preferably, the antibacterial agent is one or more of a cationic polymer antibacterial agent, an inorganic silver ion antibacterial agent and an organic-inorganic composite antibacterial agent, more preferably, the cationic polymer antibacterial agent is one or more of a quaternary ammonium salt polymer, a guanidine salt polymer, chitosan and its derivatives.

9. The method according to claim 6 or 7, wherein the hydrophilic agent is one or more of amino acids, polysaccharides and polyether polyols, preferably, the amino acids are one or more of glycine, serine, threonine, cysteine, lysine, arginine, aspartic acid and glutamic acid, and the polysaccharides are one or more of chitin, pectin, chitosan and its derivatives, cellulose and its derivatives.

10. The method according to claim 6 or 7, wherein the lubricant is one or more of paraffin, stearic acid and its salts, ethylenebisfatty acid amide and its modified products, and preferably, the antioxidant is one or more of hindered phenol antioxidants, phosphite antioxidants, and flavonoid antioxidants.

Images