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CN-121975183-A - PTFE composite microporous film and preparation method thereof

CN121975183ACN 121975183 ACN121975183 ACN 121975183ACN-121975183-A

Abstract

The invention relates to the technical field of high polymer materials, in particular to a PTFE composite microporous film and a preparation method thereof, wherein the PTFE composite microporous film comprises a biaxially oriented polytetrafluoroethylene microporous film, a sulfonic group modified perfluoroalkyl vinyl ether copolymer, epoxy group modified polyaryletherketone and nanometer alumina particles; according to the invention, a protective system aiming at strong reducing substances in the strong alkaline waste liquid is constructed through the synergistic effect of the sulfonic acid group modified perfluoroalkyl vinyl ether copolymer anchoring layer, the epoxy group modified polyaryletherketone protective layer and the nano alumina particles, so that the PTFE defluorination degradation problem caused by the strong reducing substances is effectively solved.

Inventors

  • HUANG GUIJUN

Assignees

  • 佛山慧氟高分子材料有限公司

Dates

Publication Date
20260505
Application Date
20260407

Claims (7)

  1. 1. The PTFE composite microporous film is characterized by comprising, by weight, 80-92 parts of a biaxially oriented polytetrafluoroethylene microporous film, 3-8 parts of a sulfonic group modified perfluoroalkyl vinyl ether copolymer, 4-10 parts of epoxy group modified polyaryletherketone and 1-5 parts of nano alumina particles; the nanometer alumina particles are gamma crystal forms, the average particle diameter is 15-25nm, the specific surface area is 180-220m 2 /g, the purity is more than 99.5%, the nanometer alumina particles are pretreated before use, namely the nanometer alumina particles are placed in a muffle furnace, calcined for 4 hours in the air atmosphere at 400 ℃, cooled to room temperature in a dryer after calcination, and immediately transferred to a sealed container for storage.
  2. 2. The PTFE composite microporous membrane of claim 1, wherein the biaxially oriented polytetrafluoroethylene microporous membrane has an average pore size of 0.2-0.5 μm, a porosity of 70-85%, and a thickness of 50-100 μm.
  3. 3. The PTFE composite microporous membrane according to claim 1, wherein the method for preparing the sulfonic acid group modified perfluoroalkyl vinyl ether copolymer comprises the steps of: S11, adding perfluorohexane into a high-pressure reaction kettle protected by nitrogen, dissolving perfluoro-2- (2-fluorosulfonylethoxy) propyl vinyl ether monomer and perfluoropropyl vinyl ether comonomer into perfluorohexane, transferring into the reaction kettle, adding bis (4-tert-butylcyclohexyl) peroxydicarbonate into the reaction kettle, replacing nitrogen for three times after sealing, heating and stirring for reaction, pouring into anhydrous methanol for precipitation after cooling, filtering to obtain a crude product, dissolving in perfluorohexane/purifying for three times by methanol precipitation, and vacuum drying to obtain an intermediate A; S12, dissolving the intermediate A in a mixed solvent of perfluorohexane and tetrahydrofuran, dropwise adding a solution prepared from water, methanol and 25% sodium hydroxide under ice bath cooling, heating to continue the reaction, then pouring into 5% dilute hydrochloric acid for precipitation, filtering, washing with water until the filtrate is neutral and has the conductivity of less than 10 mu S/cm, and vacuum drying to obtain the sulfonic acid group modified perfluoroalkyl vinyl ether copolymer.
  4. 4. The PTFE composite microporous membrane according to claim 1, wherein the preparation method of the epoxy modified polyaryletherketone comprises the following steps: S21, adding 4,4 '-dihydroxybenzophenone, 4' -difluorobenzophenone, anhydrous potassium carbonate, N-methylpyrrolidone and toluene into a three-mouth bottle provided with a Dien-Stark water separator, heating to 145 ℃ under the protection of nitrogen, refluxing and dehydrating, heating to 165 ℃ for reaction, adding terephthalic acid, continuing to react, cooling to 80 ℃, pouring into deionized water for precipitation, filtering, washing with hot water until the conductivity of washing water is less than 10 mu S/cm, washing with 5% dilute hydrochloric acid to be neutral, and vacuum drying to obtain an intermediate B; S22, dissolving the intermediate B in N-methylpyrrolidone, adding epichlorohydrin and tetrabutylammonium bromide, dropwise adding 40% sodium hydroxide solution under ice bath cooling, heating, stirring for reaction, pouring into deionized water for precipitation after the reaction is finished, filtering, washing until no chloride ions exist, dissolving in tetrahydrofuran/precipitating with methanol for purification twice, and vacuum drying to obtain the epoxy modified polyaryletherketone.
  5. 5. The method for producing a PTFE composite microporous membrane according to any one of claims 1 to 4, comprising the steps of: S1, preparing a solution A, namely dissolving a sulfonic group modified perfluoroalkyl vinyl ether copolymer into a mixed solvent of perfluorohexane and isopropanol according to the mass fraction of 5%, and stirring for 8 hours at room temperature to obtain the solution A; S2, preparing a solution B, namely dissolving epoxy modified polyaryletherketone into a mixed solvent of N-methylpyrrolidone and tetrahydrofuran according to the mass fraction of 8%, stirring at 60 ℃ for 6 hours until the epoxy modified polyaryletherketone is completely dissolved, adding pretreated nano alumina particles, mechanically stirring for 2 hours, and performing ultrasonic dispersion for 30 minutes to obtain the solution B; S3, coating and fixing a hydrophilic anchoring layer, namely soaking and drying a biaxially oriented polytetrafluoroethylene microporous film with isopropanol, vertically immersing the film into the solution A, standing for 30 seconds, lifting the liquid level at a constant speed of 2-5 cm per second, placing the film in an 80 ℃ oven for drying for 30 minutes, drying at 120 ℃ for 1 hour to completely volatilize a solvent, placing the film in a flat press, isolating the film with polyimide films at the upper and lower parts, and hot-pressing the film at 280-290 ℃ and 3MPa for 8-10 minutes to obtain an intermediate composite film; S4, coating and crosslinking a chemical protection reinforcing layer, namely uniformly spraying the solution B onto the surface of the middle composite film, wherein the spraying distance is 15-20cm, the pressure is 0.2-0.3MPa, the total spraying is 3-5 times, the interval between each time is 1 minute, the solution B and the solution B are placed in an 80 ℃ oven for pre-drying for 1 hour, then the solution B is transferred into a vacuum hot press, and the solution B is subjected to heat treatment for 30 minutes under the vacuum degree of 180 ℃ and 1MPa pressure and minus 0.08MPa, and is slowly cooled to room temperature under vacuum, so that the PTFE composite microporous film is obtained.
  6. 6. The method for preparing a microporous PTFE composite film according to claim 5, wherein the volume ratio of perfluorohexane to isopropanol in the mixed solvent of perfluorohexane and isopropanol in step S1 is 7:3.
  7. 7. The method for preparing a microporous PTFE membrane according to claim 5, wherein the volume ratio of N-methylpyrrolidone to tetrahydrofuran in the mixed solvent of S2N-methylpyrrolidone and tetrahydrofuran is 6:4.

Description

PTFE composite microporous film and preparation method thereof Technical Field The invention relates to the technical field of high polymer materials, in particular to a PTFE composite microporous film and a preparation method thereof. Background The Polytetrafluoroethylene (PTFE) microporous membrane has high porosity, controllable pore size distribution, excellent chemical stability, heat resistance and ageing resistance, and has important value in the fields of efficient filtration, special separation and the like. However, the inherent strong hydrophobicity of PTFE materials results in extremely poor wettability of its surface to aqueous media, severely impeding penetration and transport of liquids in the micropores, limiting its use in liquid separation, particularly in aqueous waste liquid treatment. In the prior art, hydrophilic modification is carried out on PTFE microporous membranes, hydrophilic polymers are grafted on the surfaces of PTFE microporous membranes mainly through surface physical coating or chemical surface grafting, for example, PTFE surfaces are activated by strong reducing agents such as sodium naphthalene complex and the like, active sites are introduced through partial defluorination reaction, and then functional monomers are grafted to obtain durable and stable hydrophilic surfaces. In the modification process, the concentration, the reaction time and the temperature of the sodium naphthalene are all in the strictly controlled range, and the reaction time is between a few seconds and a few minutes, so that the controllable directional activation of the PTFE surface is realized without damaging the matrix structure. However, when hydrophilically modified PTFE microporous membranes are used to treat strongly alkaline industrial waste streams containing trace amounts of unreacted and completely strongly reducing substances (e.g., sodium naphthalene complexes, organolithium reagents, etc.), completely different chemical environments are encountered. The strong reducing components in uncontrolled state, which are continuously present in the waste liquid, act as long-term aggressive media, which can cause a continuous chemical attack on the PTFE surface and the modified layer. It has been found that even a low concentration (e.g., 0.1 mol/L) sodium naphthalene solution, continuous contact at room temperature for a long period of time can initiate deep defluorination of the PTFE surface within several hours to several tens of hours, resulting in a sharp drop in the fluorine-carbon atomic ratio (F/C) from 2.0 to less than 0.5. The uncontrolled continuous exposure and the short-time controllable modification have essential differences in chemical reaction mechanism and material response, the continuous defluorination reaction can damage a hydrophilic modified layer grafted on the surface, so that the hydrophilicity is rapidly lost, the molecular main chain of a PTFE matrix can be directly attacked, the node-fiber network collapse of a microporous structure, the mechanical strength suddenly drops and the irreversible filtration function is invalid, and meanwhile, fluoride generated by the defluorination reaction is easy to combine with metal ions in waste liquid to form a precipitate, so that membrane pores are accelerated to be blocked. Disclosure of Invention (1) Technical problem to be solved The invention aims to provide a PTFE composite microporous film and a preparation method thereof, which are used for solving the problem that a PTFE matrix undergoes defluorination degradation reaction due to a strong reducing substance in a strong alkaline waste liquid. (2) Technical proposal In order to achieve the aim, in one aspect, the invention provides a PTFE composite microporous film, which comprises the following components, by weight, 80-92 parts of a biaxially oriented polytetrafluoroethylene microporous film, 3-8 parts of a sulfonic acid group modified perfluoroalkyl vinyl ether copolymer, 4-10 parts of epoxy group modified polyaryletherketone and 1-5 parts of nano alumina particles; the nanometer alumina particles are gamma crystal forms, the average particle diameter is 15-25nm, the specific surface area is 180-220m 2/g, the purity is more than 99.5%, the nanometer alumina particles are pretreated before use, namely the nanometer alumina particles are placed in a muffle furnace, calcined for 4 hours in the air atmosphere at 400 ℃, cooled to room temperature in a dryer after calcination, and immediately transferred to a sealed container for storage. Further, the average pore diameter of the biaxially oriented polytetrafluoroethylene microporous membrane is 0.2-0.5 mu m, the porosity is 70-85%, and the thickness is 50-100 mu m. Further, the preparation method of the sulfonic acid group modified perfluoroalkyl vinyl ether copolymer comprises the following steps: S11, adding perfluorohexane into a high-pressure reaction kettle protected by nitrogen, dissolving perfluoro-2- (2-fluorosulf