PEEK ultrafiltration membrane, hollow fiber ultrafiltration membrane, flat ultrafiltration membrane and preparation method thereof

Abstract

The invention discloses a PEEK ultrafiltration membrane, a hollow fiber ultrafiltration membrane, a flat ultrafiltration membrane and a preparation method thereof, and belongs to the technical field of filter membranes. Raw materials of a membrane casting solution of the PEEK ultrafiltration membrane comprise the following components: 10-25 parts by weight of PEEK-WC; 50-75 parts by weight of a solvent; 5-40 parts by weight of a pore forming agent; and 0-20 parts by weight of an additive. PEEK-WC with excellent oxidation resistance is applied to the ultrafiltration membrane, a specific membrane casting solution is prepared through reasonable formula design, the chemical resistance and permeability of the ultrafiltration membrane are improved, the hydrophilicity of the membrane is guaranteed, and the ultrafiltration membrane can be applied to wastewater which is difficult to treat and has high pollutant concentration, acidity and alkalinity and the like; by weaving the enhanced and improved hollow fiber ultrafiltration membrane, the mechanical property can be improved, and the service life can be prolonged; the surface of the PEEK flat ultrafiltration membrane is easy to clean, the PEEK flat ultrafiltration membrane can tolerate higher sludge concentration, attachment and accumulation of pollutants are reduced, and the anti-pollution capacity of a system is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of filtration membranes, and more specifically, relates to a PEEK ultrafiltration membrane, a hollow fiber ultrafiltration membrane, a flat ultrafiltration membrane and a preparation method thereof. Background Art

[0002] With the increasing importance of pharmaceuticals and personal care products, the pharmaceutical industry has played a major role in wastewater treatment and its treatment methods. Wastewater from pharmaceutical plants varies greatly and contains various solvents, reactants, products, by-products, etc., depending on the type of raw materials, products and manufacturing processes used. For the treatment of such wastewater, membrane filtration is a necessary step. Generally speaking, polyvinylidene fluoride (PVDF) and ceramic membranes are widely used in water treatment plants and wastewater treatment plants in Singapore and around the world, but each membrane has its own disadvantages. For example, PVDF membranes have relatively low tensile strength and low water flux, short life, and low tolerance to chemicals and solvents. Ceramic membranes have many useful properties, but their high capital cost is the biggest disadvantage that hinders their widespread application. Polytetrafluoroethylene (PTFE) is a popular and durable material with a wide operating temperature range and high resistance to damage by acids, bases, solvents and many chemicals. In existing wastewater treatment processes, membrane ultrafiltration is an essential step, and PVDF is the most commonly used membrane material. The main problems that occur with PVDF membranes are: 1) PVDF membranes have low resistance to chemicals (such as ethanol) and are prone to swelling or even damage. 2) PVDF membranes are very sensitive to cleaning agents (such as sodium hypochlorite). This is determined by the properties of PVDF polymers, and there is no way to improve it. 3) PVDF membranes are easily contaminated. PVDF itself is hydrophobic, and fouling agents can easily adhere to the membrane surface, blocking the pores and causing a decrease in productivity. For pharmaceutical wastewater treatment processes that contain solvents and other chemicals, the problems they face are even more serious.

[0003] Poly(etheretherketone) (PEEK) is a semi-crystalline and high-performance engineering polymer. PEEK is a good candidate for membrane formation due to its high mechanical strength, high thermal stability, and high solvent resistance. Currently, PEEK membranes are mainly formed by the thermally induced phase separation (TIPS) method using polyetherimide (PEI) as a diluent. Briefly, the PEEK / PEI blend is melted at high temperature to form a membrane, and the PEI is removed using n-methylpyrrolidone (NMP) solvent. The high temperature and solvent extraction process make the production of PEEK membranes on a commercial scale expensive and cumbersome. In recent years, interesting research has been conducted on the modification of PEEK, and the modified PEEK (i.e., PEEK-WC) is soluble in organic solvents used in the membrane industry. There have been some reports on the formation of PEEK-WC membranes. However, these membranes are not mechanically strong and may not last long in industrial processes. Summary of the invention

[0004] The purpose of the present invention is to provide a PEEK ultrafiltration membrane, a hollow fiber ultrafiltration membrane, a flat ultrafiltration membrane and a preparation method thereof in view of the above shortcomings. PEEK-WC is applied to the ultrafiltration membrane, and through reasonable formula design, its chemical resistance and permeability are improved, and the hydrophilicity of the membrane is ensured. It can be applied to difficult-to-treat wastewater with high pollutant concentration, acidity and alkalinity, etc.; the improved hollow fiber ultrafiltration membrane through weaving reinforcement can improve its mechanical properties and extend its service life.

[0005] To achieve the above object, the present invention is implemented by the following technical solutions:

[0006] In a first aspect, the present invention provides a PEEK membrane, wherein the raw materials of the casting solution of the PEEK ultrafiltration membrane include the following components:

[0007] PEEK-WC: 10-25 parts by weight; solvent: 50-75 parts by weight; pore-forming agent: 5-40 parts by weight; additives: 0-20 parts by weight.

[0008] Furthermore, the raw materials of the casting solution are preferably: PEEK-WC: 13-18 parts by weight; solvent: 55-60 parts by weight; pore-forming agent: 10-30 parts by weight; additive: 5-10 parts by weight.

[0009] Furthermore, the pore-forming agent is any one of lithium chloride, calcium chloride, polyvinyl pyrrolidone or polyethylene glycol, preferably polyvinyl pyrrolidone or polyethylene glycol.

[0010] Furthermore, the additive is any one of methanol, ethanol, glycerol, butanol, titanium dioxide, silicon dioxide, copper oxide, zinc oxide, polyethylene glycol, polysorbate, and sodium dodecyl sulfate, preferably silicon dioxide or polyethylene glycol.

[0011] Furthermore, the solvent is dimethylacetamide or N-methylpyrrolidone.

[0012] In a second aspect, the present invention further provides a PEEK hollow fiber ultrafiltration membrane, which comprises a hollow braided tube and a resin layer coated on the surface of the hollow braided tube, wherein the resin layer is made of the casting liquid described in the first aspect.

[0013] Furthermore, the hollow braided tube is made of any one of polyethylene terephthalate, polyacrylic acid, and polytetrafluoroethylene, preferably polyethylene terephthalate.

[0014] In a third aspect, the present invention provides a method for preparing the PEEK hollow fiber ultrafiltration membrane according to the second aspect, comprising:

[0015] PEEK-WC, solvent, pore-forming agent and additive are mixed in proportion, stirred and dissolved to obtain a casting solution;

[0016] Spinning and extruding the casting solution and the hollow braided tube together to obtain primary membrane filaments;

[0017] The primary membrane filaments are passed through the air gap and then enter the coagulation bath for solidification;

[0018] The cured membrane fibers were collected to obtain a PEEK hollow fiber ultrafiltration membrane.

[0019] Furthermore, the PEEK-WC, solvent, pore-forming agent and additive are mixed at 50° C. to 80° C., stirred until the solid is completely dissolved, then cooled to room temperature, and stirred for at least 48 hours.

[0020] Furthermore, the method of spinning and extruding the casting solution and the hollow braided tube together to obtain primary membrane filaments comprises:

[0021] At room temperature, the casting liquid is pushed to the spinning head by a feed pump at a flow rate of 2 to 10 ml / min. The casting liquid is extruded together with the hollow braided tube entering from the center of the spinning head to complete the coating of the casting liquid on the outer surface of the hollow braided tube.

[0022] Furthermore, the primary membrane filaments enter a coagulation bath for solidification after passing through an air gap of 5 to 50 cm.

[0023] Furthermore, the coagulation bath is a water coagulation bath with a temperature of 25°C to 40°C.

[0024] Furthermore, the cured membrane filaments are collected by a reel at a collection speed of 2 to 10 m / min.

[0025] Specifically, the following steps are included:

[0026] (1) Preparation of casting solution:

[0027] PEEK-WC, solvent, pore-forming agent and additive are mixed in proportion, stirred continuously at 50°C to 80°C until all solids are completely dissolved, then cooled to room temperature, and stirred for at least 48 hours to obtain a casting solution;

[0028] (2) Resin layer coating:

[0029] At room temperature, the feed pump pushes the casting liquid to the spinning head at a flow rate of 2~10 ml / min. The casting liquid is extruded together with the hollow braided tube entering from the center of the spinning head to complete the coating of the casting liquid on the outer surface of the hollow braided tube. The braided tube with the casting liquid coating, that is, the primary membrane filaments, pass through an air gap of 5~50 cm and enter the water coagulation bath (25℃~40℃) for curing. The cured membrane filaments are collected by the reel at a speed of 2~10 m / min to obtain a braided reinforced PEEK hollow fiber ultrafiltration membrane.

[0030] In a fourth aspect, the present invention further provides a PEEK flat ultrafiltration membrane, wherein the flat ultrafiltration membrane is made of the casting liquid described in the first aspect.

[0031] In a fifth aspect, the present invention further provides a method for preparing the PEEK flat ultrafiltration membrane according to the fourth aspect, comprising:

[0032] PEEK-WC, solvent, pore-forming agent and additive are mixed in a set ratio, stirred and dissolved to obtain a casting solution;

[0033] The casting liquid is made into a wet film by a casting method or a scraping film method;

[0034] The wet membrane was dried and then peeled off to obtain a PEEK flat ultrafiltration membrane.

[0035] Specifically, the following steps are included:

[0036] (1) Preparation of casting solution:

[0037] PEEK-WC, solvent, pore-forming agent and additive are mixed in proportion, stirred continuously at 50°C to 80°C until all solids are completely dissolved, then cooled to room temperature, and stirred for at least 48 hours to obtain a casting solution;

[0038] (2) Resin layer coating:

[0039] At room temperature, the casting liquid is poured onto the surface of a glass plate to cast into a film liquid with uniform thickness, or the casting liquid is evenly scraped onto a flat plate with a scraper, and then immersed in a 25-40° C. water coagulation bath for solidification after being exposed to air for a certain period of time; after the film is formed and automatically separated from the glass plate, it is immersed in deionized water for 48 hours, and then treated in a 50% glycerol solution for 48 hours, dried at room temperature, and stored to obtain the PEEK flat ultrafiltration membrane.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The PEEK ultrafiltration membrane of the present invention uses PEEK-WC as the basic raw material, and its anti-oxidation performance is better than that of materials such as polyamide. A specific casting solution is prepared through reasonable formula design, and on the basis of the above-mentioned performance, its chemical resistance and permeability are improved, and the hydrophilicity of the membrane is ensured;

[0042] The PEEK ultrafiltration membrane prepared by the present invention has good high temperature resistance, which can reach up to 300°C, and can be applied to some high temperature filtration occasions, such as the treatment of large boiler feed water and circulating cooling water, the treatment of printing and dyeing wastewater, etc., which can reduce the cost investment caused by the current reduction of water temperature, save engineering investment and operating costs; it has excellent structural stability characteristics, that is, the membrane pore structure can maintain a stable membrane pore size during long-term engineering applications, and can be used in occasions with high filtration accuracy requirements, purification and concentration of high value-added products, including fermentation, enzyme preparation industry, concentration, purification and clarification of pharmaceutical industry; concentration and separation of fruit juice; separation, concentration and clarification of soybeans, dairy products, sugar industry, wine, tea juice, vinegar, soy sauce, etc.; biological products, pharmaceutical products, traditional Chinese medicine products and food industry Separation, concentration and purification, etc.; it has excellent corrosion resistance, hydrolysis resistance, and high chemical stability. It can be widely used in sewage treatment and reuse in chemical enterprises, as well as the recovery of useful substances or solvents in sewage, such as electroplating wastewater treatment and the recovery of various metals in wastewater, purification and recovery of pigments, drugs, acids and alkalis in the petroleum and chemical industries, treatment and recovery of surface treatment wastewater in the electronics industry, and removal of harmful substances such as heavy metal ions; it has excellent high-irradiation resistance and antioxidant properties, and can be used in the emerging sewage treatment field of nuclear wastewater treatment, and can be used in the field of water treatment with strong oxidizing properties, such as the treatment of wastewater / drinking water containing strong oxidizing substances such as ozone and H2O2; it can widely replace PVDF and PTFE membranes in difficult-to-treat wastewater;

[0043] The PEEK hollow fiber ultrafiltration membrane of the present invention adds a hollow braided tube as a matrix on the basis of the PEEK ultrafiltration membrane, and the improved hollow fiber ultrafiltration membrane through braiding reinforcement can improve its mechanical properties and extend its service life; at the same time, due to the high corrosion resistance of the PEEK membrane, high concentrations of acid, alkali and oxidants can be used for cleaning and maintenance, thereby offsetting the disadvantages of the hollow membrane in operation and chemical cleaning compared with the flat membrane;

[0044] The PEEK flat ultrafiltration membrane of the present invention has the advantages of the PEEK ultrafiltration membrane and its surface is easy to clean, can tolerate higher sludge concentrations, reduces the adhesion and accumulation of pollutants, and improves the anti-pollution ability of the system; it is simple to operate, low in cost, and easy to achieve industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The scanning electron microscope image of the PEEK hollow fiber ultrafiltration membrane prepared in the example;

[0046] Figure 2 Schematic diagram of the preparation process of the PEEK hollow fiber ultrafiltration membrane described in the embodiment;

[0047] Figure 3The retention rate of the PEEK hollow fiber ultrafiltration membrane prepared in Example 1 for polyethylene oxides of different molecular weights;

[0048] Figure 4 The pore size distribution diagram of the PEEK hollow fiber ultrafiltration membrane prepared in Example 1;

[0049] Figure 5 This is a graph showing the chemical resistance test of the polymer described in the embodiment;

[0050] Figure 6 The performance of the PEEK hollow fiber ultrafiltration membrane prepared in each example is compared with the PEEK membrane described in the comparative example. DETAILED DESCRIPTION

[0051] The preferred embodiments of the present invention will be described in more detail below in conjunction with the accompanying drawings and specific examples.

[0052] The reagents used in the embodiments of the present invention are all commercially available from:

[0053] PEEK-WC: Zhejiang Palco New Materials Co., Ltd.;

[0054] Braided tube: BlueOcean Memtech Pte ltd., made of polyethylene terephthalate, outer diameter 1.6 mm;

[0055] Dimethylacetamide: TACT CHEMIE SEA Pte Ltd;

[0056] N-Methylpyrrolidone: TACT CHEMIE SEA Pte Ltd;

[0057] Polyvinylpyrrolidone: TACT CHEMIE SEA Pte Ltd;

[0058] Polyethylene glycol: TACT CHEMIE SEA Pte Ltd;

[0059] Glycerol: TACT CHEMIE SEA Pte Ltd;

[0060] Lithium chloride: Merck Pte Ltd;

[0061] Silica: Merck Pte Ltd.

[0062] Example 1

[0063] This embodiment provides a PEEK hollow fiber ultrafiltration membrane, comprising a braided substrate and a resin layer coated on the surface of the braided substrate, wherein the raw materials of the resin layer include 67g of PEEK-WC, 292g of dimethylacetamide, 34.5g of polyvinyl pyrrolidone, and 12g of glycerol, and the braided substrate is a polyethylene terephthalate hollow braided tube; the preparation method thereof comprises the following steps:

[0064] (1) PEEK-WC, dimethylacetamide, polyvinyl pyrrolidone and glycerol were weighed according to the above weights and added to a mixing tank. The mixture was stirred continuously at 80° C. until completely dissolved. The mixture was then cooled to room temperature and stirred for 48 hours to obtain a homogeneous casting solution.

[0065] (2) If Figure 2 As shown, at room temperature, the feed pump pushes the casting liquid to the spinning head at a flow rate of 5 ml / min, and the casting liquid is extruded together with the braided tube entering from the center of the spinning head to complete the coating of the casting liquid on the outer surface of the braided tube to obtain the primary membrane filaments; the primary membrane filaments enter the room temperature water coagulation bath for solidification after a distance of 30 cm in the air section; the solidified membrane filaments are collected by the reel at a speed of 4.5 m / min. The prepared hollow fiber membrane filaments are moved to another water tank and soaked for 48 hours to completely complete the phase change and remove the solvent, pore-forming agent and additives remaining in the membrane filaments. The membrane filaments are soaked in an aqueous solution containing 50% glycerol for 48 hours and air-dried to obtain a hollow fiber ultrafiltration membrane.

[0066] Example 2

[0067] This embodiment provides a PEEK hollow fiber ultrafiltration membrane, comprising a braided substrate and a resin layer coated on the surface of the braided substrate, wherein the raw materials of the resin layer include 30g of PEEK-WC, 140g of dimethylacetamide, 20g of polyvinyl pyrrolidone, and 10g of glycerol, and the braided substrate is a polyethylene terephthalate hollow braided tube; the preparation method thereof comprises the following steps:

[0068] (1) PEEK-WC, dimethylacetamide, polyvinyl pyrrolidone and glycerol were weighed according to the above weights and added to a mixing tank. The mixture was stirred continuously at 80° C. until completely dissolved. The mixture was then cooled to room temperature and stirred for 48 hours to obtain a homogeneous casting solution.

[0069] (2) At room temperature, the feed pump pushes the casting liquid to the spinning head at a flow rate of 7 ml / min. The casting liquid is extruded together with the braided tube entering from the center of the spinning head to complete the coating of the casting liquid on the outer surface of the braided tube to obtain primary membrane filaments; the primary membrane filaments enter the room temperature water coagulation bath after a distance of 30 cm in the air section, and the collection speed is 5.5 m / min. The obtained hollow fiber membrane filaments are moved to another water tank and soaked for 48 hours to completely complete the phase change and remove the solvent, pore-forming agent and additives remaining in the membrane filaments. The membrane filaments are soaked in an aqueous solution containing 50% glycerol for 48 hours and air-dried to obtain a hollow fiber ultrafiltration membrane.

[0070] Example 3

[0071] This embodiment provides a PEEK hollow fiber ultrafiltration membrane, comprising a braided substrate and a resin layer coated on the surface of the braided substrate, wherein the raw materials of the resin layer include 33g of PEEK-WC, 100g of N-methylpyrrolidone, 60g of polyethylene glycol, and 5g of lithium chloride, and the braided substrate is a polyethylene terephthalate hollow braided tube; the preparation method thereof comprises the following steps:

[0072] (1) PEEK-WC, dimethylacetamide, polyvinyl pyrrolidone and glycerol were weighed according to the above weights and added to a mixing tank. The mixture was stirred continuously at 80° C. until completely dissolved. The mixture was then cooled to room temperature and stirred for 48 hours to obtain a homogeneous casting solution.

[0073] (2) At room temperature, the feed pump pushes the casting liquid to the spinning head at a flow rate of 5 ml / min. The casting liquid is extruded together with the braided tube entering from the center of the spinning head to complete the coating of the casting liquid on the outer surface of the braided tube to obtain primary membrane fibers; the primary membrane fibers enter the room temperature water coagulation bath after a distance of 30 cm in the air section, and the collection speed is 7 m / min. The obtained hollow fiber membrane fibers are moved to another water tank and soaked for 48 hours to completely complete the phase change and remove the solvent, pore-forming agent and additives remaining in the membrane fibers. The membrane fibers are soaked in an aqueous solution containing 50% glycerol for 48 hours and air-dried to obtain a hollow fiber ultrafiltration membrane.

[0074] Example 4

[0075] This embodiment provides a PEEK hollow fiber ultrafiltration membrane, comprising a braided substrate and a resin layer coated on the surface of the braided substrate, wherein the raw materials of the resin layer include 45g of PEEK-WC, 100g of N-methylpyrrolidone, 62g of polyethylene glycol, and 5g of lithium chloride, and the braided substrate is a polyethylene terephthalate hollow braided tube; the preparation method thereof comprises the following steps:

[0076] (1) PEEK-WC, dimethylacetamide, polyvinyl pyrrolidone and glycerol were weighed according to the above weights and added to a mixing tank. The mixture was stirred continuously at 80° C. until completely dissolved. The mixture was then cooled to room temperature and stirred for 48 hours to obtain a homogeneous casting solution.

[0077] (2) At room temperature, the feed pump pushes the casting liquid to the spinning head at a flow rate of 6 ml / min. The casting liquid is extruded together with the braided tube entering from the center of the spinning head to complete the coating of the casting liquid on the outer surface of the braided tube to obtain primary membrane fibers; the primary membrane fibers enter the room temperature water coagulation bath after a distance of 30 cm in the air section, and the collection speed is 10 m / min. The obtained hollow fiber membrane fibers are moved to another water tank and soaked for 48 hours to completely complete the phase change and remove the solvent, pore-forming agent and additives remaining in the membrane fibers. The membrane fibers are soaked in an aqueous solution containing 50% glycerol for 48 hours and air-dried to obtain a hollow fiber ultrafiltration membrane.

[0078] Example 5

[0079] This embodiment provides a PEEK flat ultrafiltration membrane, wherein the raw materials of the casting solution of the flat ultrafiltration membrane include 40g of PEEK-WC, 180g of dimethylacetamide, 70g of polyvinyl pyrrolidone, and 15g of glycerol, and the preparation method thereof includes the following steps:

[0080] (1) PEEK-WC, dimethylacetamide, polyvinyl pyrrolidone and glycerol were weighed according to the above weights and added to a mixing tank. The mixture was stirred continuously at 80° C. until completely dissolved. The mixture was then cooled to room temperature and stirred for 48 hours to obtain a homogeneous casting solution.

[0081] (2) pouring the casting liquid onto the surface of a glass plate at room temperature to cast a film liquid with uniform thickness, or evenly scraping the casting liquid onto a flat plate with a scraper, exposing it to air for a certain period of time and then immersing it in a 25-40 °C water coagulation bath for solidification; after the film is formed and automatically separated from the glass plate, immersing it in deionized water for 48 hours, and then placing it in a 50% glycerol solution for 48 hours, drying it at room temperature, and storing it to obtain the PEEK flat ultrafiltration membrane.

[0082] Comparative Example 1

[0083] Existing technology reinforced PVDF hollow fiber membrane.

[0084] Comparative Example 2

[0085] This embodiment provides a PEEK hollow fiber membrane without a woven matrix. The composition ratio of the membrane casting liquid is the same as that of Example 3 and the membrane is prepared by spinning with an extrusion spinneret.

[0086] Performance Verification

[0087] 1. PEEK membrane morphology

[0088] The outer diameter of the PEEK hollow fiber ultrafiltration membrane prepared in the present application example is about 1.8-2.1 mm, and the fiber wall thickness is 0.4-0.5 mm. Figure 1As shown in the figure, it can be seen that the overall structure is good and the outer surface is porous.

[0089] Table 1: Comparison of the morphology of the PEEK membranes described in the examples and comparative examples

[0090] ;

[0091] As can be seen from the table, the outer diameter of the PEEK hollow fiber ultrafiltration membrane is between 2.1mm and 2.2mm, and the membrane wall thickness is between 0.5 and 0.6mm. By adjusting the formula, a pore size of 29-38nm can be obtained. The outer diameter of the PEEK hollow fiber ultrafiltration membrane is slightly smaller and the membrane wall thickness is slightly thinner, at 1.5mm and 0.3mm respectively. Based on a similar formula, the separation cortex of the membrane is also slightly dense, with a pore size of 18nm.

[0092] The present application conducted a pure water permeability (PWP) water filtration test on the PEEK hollow fiber ultrafiltration membrane prepared in the embodiment, and used the retention rate analysis of polyethylene oxide PEO with different molecular weights to characterize the pore structure. For PEO solution filtration, a total organic carbon (TOC) analyzer was used to analyze the concentration of feed and permeate. The retention rate (R) of different PEO can be calculated from the stock solution concentration (Cf) and the permeate concentration (Cp), and the calculation formula is as follows:

[0093] (1)

[0094] The Stokes diameter (ds) can be related to the molecular weight (M) using the following formula:

[0095] (2)

[0096] The retention rate is linearly related to the Stokes diameter of the measured PEO solute, and the formula is as follows:

[0097] (3)

[0098] Ignoring the interaction between PEO and membrane pores, the pore size d p The Stokes diameter d of the PEO solute s The same as the geometric mean variance σ p The ratio of the Stokes diameter of the PEO solute corresponding to the retention rate of 84.13% and 50% (d s,84.13 / d s,50 ). The pore size distribution of PEEK-WC membrane can be expressed as the following probability density function:

[0099] (4)

[0100] Where: is the average pore diameter.

[0101] Taking the membrane prepared in Example 1 as an example, the retention rate of PEO with molecular weights of 100K, 200K and 300K was measured in a filtration experimental device. The Stokes diameters of PEO with molecular weights of 100K, 200K and 300K were 17.98, 27.00 and 34.26nm, respectively. The pressure difference was 1 bar. The results are as follows: Figure 3 As shown, the retention rates are 29.87%, 62.72% and 82.69% respectively. Using formula (3), the Stokes diameter of PEO with a retention rate of 50% and 84.13% can be calculated, thereby obtaining the corresponding pore size and geometric mean variance. Finally, the spatial distribution can be obtained by plotting using formula (4), as shown in Figure 4 As shown in Figure 1, the separation layer of this group of membrane fibers contains pores with diameters ranging from 5nm to 70nm, and most of the pores are between 10nm and 50nm. Using formulas (2) and (3), it can also be calculated that the pore size with a retention rate of 90% is 38nm, and the corresponding molecular weight, that is, the molecular weight cut-off MWCO, is 350K. The PWP (PureWater Permeability, water flux) value of this membrane is 205 LMH / bar.

[0102] 2. Chemical resistance

[0103] First, the PEEK-WC polymer powder was immersed in different pure solvents such as acetone, ethanol, isopropanol, methanol and water for at least 3 weeks to test the stability of the PEEK-WC polymer. Figure 5 As shown, the PEEK-WC polymer powder did not dissolve significantly in the solvent used, and the turbidity of the solvent did not change, which indicated that the polymer was quite stable.

[0104] After the membrane is formed, the polymer becomes porous and its physical properties are different. The chemical resistance of the PEEK hollow fiber ultrafiltration membrane prepared in the example is tested in static and dynamic tests.

[0105] In the static test, the PEEK hollow fiber ultrafiltration membrane was immersed in each of the following solvents, namely acetone, ethanol, methanol, and isopropanol, which are common in industrial wastewater. After 4 weeks, the length changes of the fibers immersed in ethanol, isopropanol (IPA), and methanol were negligible, which means that the braided reinforced PEEK-WC hollow fiber membrane did not swell in ethanol, IPA, and methanol solvents and was damaged in acetone.

[0106] In the dynamic test, the PEEK hollow fiber ultrafiltration membrane was tested for filtration at a transmembrane pressure of 5 psi and a flow rate of 500 mL / min. Each test lasted for 3 weeks, and the retention rate of polyethylene (PEO) 100K was used to monitor possible changes in the membrane pore structure. Two groups of membrane samples were used simultaneously in the test. Sample #1 was used to filter synthetic solvent-containing wastewater, and sample #2 was used to filter acid, alkali and sodium hypochlorite solutions. The first test was the unbraided tube reinforced PEEK-WC membrane prepared in reference document 2. Membrane samples #1 and #2 were denser, and the retention rates of PEO100K before the dynamic filtration experiment were 87.9% and 91.6%, respectively. Table 2 summarizes the retention rates of PEO100K for these two groups of homogeneous membrane filaments after 3 weeks of continuous filtration experiments.

[0107] Table 2: Dynamic filtration retention rate of PEEK-WC membrane prepared in comparative example 2 (without braided tube reinforcement)

[0108] ;

[0109] If solvents or chemicals swell, dissolve or corrode PEEK-WC materials under dynamic conditions, they will affect the integrity of the hollow fiber membrane, resulting in changes in the pore structure, and the retention rate of PEO100K will be significantly reduced. As shown in Table 2, after 3 weeks of continuous filtration tests with 5000ppm IPA / water, ethanol / water and acetone / water, the retention rate of PEO100K by the homogeneous PEEK-WC membrane did not decrease. This shows that the synthetic water sample has no significant effect on the pore structure of the PEEK-WC hollow fiber membrane. It should be noted that the first sample #1 was subjected to the IPA / water filtration experiment, followed by the ethanol / water and acetone / water filtration experiments. After the IPA / water filtration experiment, the retention rate of the membrane sample for PEO100K needs to be tested, and the subsequent filtration experiments need to be carried out after cleaning. As a result, a small part of PEO100K will remain in the membrane pores and temporarily block the membrane pores, resulting in an increase in the retention rate after ethanol / water and acetone / water filtration. The same trend was also observed in the filtration experiments of HCl / water and NaOH / water carried out on sample #2. The retention rate of PEO100K of sample #2 after filtering NaClO / water of pH12 was 81.2%, indicating that some pores became larger or some defects were formed. NaClO not only oxidized the PEO100K remaining in the membrane pores, but also had an effect on the PEEK-WC material or pore structure, but the effect was not significant. In fact, poor chlorine resistance is a common feature of high molecular polymer membranes. Therefore, the performance of the PEEK-WC hollow fiber membrane prepared in comparative example 2 of the present application is reasonable and acceptable.

[0110] The dynamic filtration experiment of the braided tube reinforced PEEK-WC hollow fiber ultrafiltration membrane used similar conditions as the homogeneous membrane. For comparison, the commercial reinforced PVDF hollow fiber membrane used in PET engineering projects was also tested in parallel. The test results are listed in Table 3. Obviously, the newly developed PEEK-WC hollow fiber ultrafiltration membrane is superior to PVDF hollow fiber in terms of PWP value and retention rate of PEO solute.

[0111] Table 3: Stability test of braided reinforced PEEK-WC hollow fiber membrane

[0112] ;

[0113] *New PVDF samples replace the damaged samples and continue the subsequent tests

[0114] Before the filtration experiment, the retention rate of PEO300K by the braided tube reinforced PEEK-WC hollow fiber ultrafiltration membrane was determined to be 80.8%, while the retention rate of PEO300K by the commercial reinforced PVDF membrane was 78.3%. In order to more reasonably compare the structure and performance of the two groups of membrane fibers, the retention rate of PEO300K was used in the filtration experiment to reflect the possible changes in the pore structure. From the retention rate of PEO300K, the pore structure of the reinforced PEEK-WC ultrafiltration membrane was stable after filtration tests on synthetic organic wastewater such as IPA / water, ethanol / water and acetone / water, and the acidity and alkalinity changes did not affect the structure of the membrane. In the NaClO / water filtration experiment, the concentration of NaClO was increased to 5000ppm, and the reinforced PEEK-WC membrane showed good resistance. In contrast, commercial enhanced PVDF membranes are very sensitive to IPA and ethanol in synthetic wastewater. 5000ppm of solvent has caused changes in the pore structure of the PVDF membrane, so the retention rate of PEO300K is greatly reduced. After the ethanol / water filtration experiment, a new PVDF membrane was replaced to continue the acetone / water test, and acetone / water also caused changes in the pore structure of the membrane. Enhanced PEEK-WC and PVDF hollow fiber membranes are relatively stable at different pH levels, but after NaClO / water filtration, the retention rate of PVDF membrane for PEO300K decreased by 36%, while enhanced PEEK-WC was not affected. These experimental results clearly prove that PEEK-WC is significantly superior to PVDF in terms of solvent resistance, acid and alkali resistance, and oxidant resistance.

[0115] 3. Hydrophilic properties

[0116] PEEK-WC polymer is not hydrophobic, but its hydrophilicity is average, close to polysulfone and polyethersulfone, as measured by water contact angle. In order to enhance the hydrophilicity of PEEK-WC membrane, chemical modification of membrane, blending with hydrophilic polymer and addition of hydrophilic nanoparticles were also tried. The water contact angles of PEEK-WC membranes (Examples 1, 2 and 5) using polyvinyl pyrrolidone as pore-forming agent were 70°, 73° and 65°, the water contact angle of PEEK-WC membranes (Example 3) using lithium chloride as additive was 75°, and the water contact angle of PEEK-WC membranes (Example 4) using silica as additive was 59°. Polyvinyl pyrrolidone has the function of pore-forming and improving hydrophilicity, but it is soluble in water and easily oxidized by oxidants such as NaClO, so the hydrophilic modification of membranes by polyvinyl pyrrolidone is only effective in the early stage of membrane use. As it is dissolved in water or oxidized by an oxidant, the amount of polyvinyl pyrrolidone in the membrane will gradually decrease until it disappears completely, and the hydrophilicity of the membrane will return to the level of the membrane material itself. Silicon dioxide is a hydrophilic inorganic substance that is insoluble in water and has excellent chemical stability. Adding a small amount of silicon dioxide to the PEEK-WC membrane helps to significantly improve the hydrophilicity of the membrane, and the stability of silicon dioxide is much higher than that of polyvinyl pyrrolidone, making it a better hydrophilic modified material than the latter. The hydrophilic characterization results of the membranes prepared in each embodiment and comparative example are shown in Table 4.

[0117] Table 4: Water contact angles of films prepared in various examples and comparative examples

[0118] ;

[0119] The hydrophilicity of PEEK-WC membrane can also be improved by reaction with PEI. For example, a small amount of PEI is added in the process of dissolving PEEK-WC to prepare the casting solution. PEI will react with PEEK-WC. After the casting solution is coated on the surface of the braided tube to obtain the enhanced PEEK-WC hollow fiber membrane, the water contact angle is 61°. The reaction of PEI and PEEK-WC will increase the viscosity of the casting solution, so the reaction time and temperature in the whole process need to be strictly controlled.

[0120] In addition, the performance of the reinforced PEEK-WC hollow fiber ultrafiltration membrane has been greatly improved. Figure 6As shown, the homogeneous PEEK-WC membrane (Comparative Example 2) is relatively dense, with a retention rate of 90% for PEO100K and a retention rate of 100% for PEO300K. By adjusting the formula, enhanced PEEK-WC hollow fiber membranes with different pore structures can be achieved. For example, after reducing the content of PEEK-WC material in the casting solution from 16.5% to 15%, the PWP of the enhanced PEEK-WC hollow fiber ultrafiltration membrane increased from 205 to 890 LMH / bar while maintaining the retention rate for PEO300K. The hydrophilicity of the membrane using silica additives (Example 4) is greatly improved, and the PWP reaches 819 LMH / bar. The new sample after optimizing the spinning conditions on the basis of Example 4 can reach a PWP level of 1104 LMH / bar, which not only has a much higher water flux than the commercial enhanced PVDF membrane (Comparative Example 1: 508 LMH / bar) but also maintains a high retention rate of PEO300K.

[0121] 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. Without departing from the scope and technical principles of the described embodiments, many modifications and changes are obvious to those of ordinary skill in the art, and these modifications and changes should also be regarded as the scope of protection of the present invention.

Claims

1. A PEEK ultrafiltration membrane, characterized in that: The raw materials of the casting solution of the PEEK ultrafiltration membrane include the following components: PEEK-WC: 10-25 parts by weight; solvent: 50-75 parts by weight; pore-forming agent: 5-40 parts by weight; additives: 0-20 parts by weight.

2. The PEEK ultrafiltration membrane according to claim 1, characterized in that The raw materials of the casting solution include the following components: PEEK-WC: 13-18 parts by weight; solvent: 55-60 parts by weight; pore-forming agent: 10-30 parts by weight; additives: 5-10 parts by weight.

3. The PEEK ultrafiltration membrane according to claim 1 or 2, characterized in that: The pore-forming agent is any one of lithium chloride, calcium chloride, polyvinyl pyrrolidone or polyethylene glycol.

4. The PEEK ultrafiltration membrane according to claim 1 or 2, characterized in that: The additive is any one of methanol, ethanol, glycerol, butanol, titanium dioxide, silicon dioxide, copper oxide, zinc oxide, polyethylene glycol, polysorbate, and sodium dodecyl sulfate.

5. A PEEK hollow fiber ultrafiltration membrane, characterized in that: The hollow fiber ultrafiltration membrane comprises a hollow braided tube and a resin layer coated on the surface of the hollow braided tube, and the resin layer is made of the casting solution according to any one of claims 1 to 4.

6. The PEEK hollow fiber ultrafiltration membrane according to claim 5, characterized in that: The hollow braided tube is made of any one of polyethylene terephthalate, polyacrylic acid and polytetrafluoroethylene.

7. A method for preparing the PEEK hollow fiber ultrafiltration membrane according to claim 5, characterized in that: include: PEEK-WC, solvent, pore-forming agent and additive are mixed in a set ratio, stirred and dissolved to obtain a casting solution; Spinning and extruding the casting solution and the hollow braided tube together to obtain primary membrane filaments; The primary membrane filaments are passed through the air gap and then enter the coagulation bath for solidification; The cured membrane fibers were collected to obtain a PEEK hollow fiber ultrafiltration membrane.

8. The method for preparing a PEEK hollow fiber ultrafiltration membrane according to claim 7, characterized in that: The method of spinning and extruding the casting solution and the hollow braided tube together to obtain primary membrane filaments comprises: At room temperature, the casting liquid is pushed to the spinning head by a feed pump at a flow rate of 2 to 10 ml / min. The casting liquid is extruded together with the hollow braided tube entering from the center of the spinning head to complete the coating of the casting liquid on the outer surface of the hollow braided tube.

9. The method for preparing a PEEK hollow fiber ultrafiltration membrane according to claim 7, characterized in that: The primary membrane filaments pass through an air gap of 5 to 50 cm and then enter a coagulation bath for solidification; And / or, the coagulation bath is a water coagulation bath with a temperature of 25°C to 40°C.

10. The method for preparing a PEEK hollow fiber ultrafiltration membrane according to claim 7, characterized in that: The cured membrane filaments are collected by a reel at a collection speed of 2 to 10 m / min.

11. A PEEK flat ultrafiltration membrane, characterized in that: The flat ultrafiltration membrane is made of the casting solution according to any one of claims 1 to 4.

12. A method for preparing the PEEK flat ultrafiltration membrane according to claim 11, characterized in that: include: PEEK-WC, solvent, pore-forming agent and additive are mixed in a set ratio, stirred and dissolved to obtain a casting solution; The casting liquid is made into a wet film by a casting method or a scraping film method; The wet membrane was dried and then peeled off to obtain a PEEK flat ultrafiltration membrane.

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