Disclosure of Invention
The invention aims to solve the technical problems that the defects in the prior art are overcome, and the diaphragm of the reinforced low-resistance chlor-alkali electrolytic cell is provided, so that the diaphragm not only reduces the resistance of the diaphragm body and is beneficial to the rapid conduction of ions, but also reduces the adhesion force of the surface of the diaphragm to bubbles, improves the effective electrolytic area of the surface of the diaphragm, reduces the local polarization phenomenon, is suitable for running in a zero polar distance electrolytic cell under the novel high current density condition, can obviously reduce the cell voltage and reduce the energy consumption; the invention also provides a simple and feasible preparation method.
The reinforced low-resistance chlor-alkali electrolytic cell diaphragm comprises a base film, wherein both sides of the base film are provided with functional surface coatings, the base film consists of a perfluorosulfonic acid polymer layer and a perfluorocarboxylic acid polymer layer, a reinforcing material net is arranged in the perfluorosulfonic acid polymer layer, and a hollow tunnel is arranged in the perfluorosulfonic acid polymer layer; the functional surface coating is a porous rough structure formed by perfluorinated ionic polymer.
The thickness of the perfluorosulfonic acid polymer layer is 10-250 μm, preferably 70-150 μm; the exchange capacity of the perfluorosulfonic acid polymer is 0.6 to 1.5 mmol/g, preferably 0.8 to 1.2 mmol/g.
The thickness of the perfluorocarboxylic acid polymer layer is 1-20 μm, preferably 7-15 μm; the exchange capacity of the perfluorocarboxylic acid polymer is from 0.5 to 1.5 mmol/g, preferably from 0.8 to 1.2 mmol/g.
The perfluorinated sulfonic acid polymer layer contains criss-cross hollow tunnels; the distance between two adjacent main fibers in the reinforcing material net is 0.5-1.5mm, and the two adjacent main fibers contain 32-500 hollow tunnels; the diameter of the single tunnel is 1 to 50 μm, preferably 5 to 20 μm. The tunnel is in the shape of regular or irregular circle, ellipse, square, triangle and the like. The hollow tunnels can be arranged in a single way or can be formed by twisting a plurality of hollow tunnels to form a large channel.
The reinforced material net is an alkali-corrosion-resistant reinforced net, the material is preferably Polytetrafluoroethylene (PTFE) or polyethylene terephthalate (PET), the void ratio is 20-99%, the thickness is 40-200 μm, and the preferred thickness is 50-150 μm. Too low a void fraction, or too high a thickness, results in an increase in cell pressure.
The diameter of the hollow tunnel is 1-200 mu m, preferably 15-100 mu m, and the volume of the hollow tunnel accounts for 5-15%, preferably 5-12% of the volume of the perfluorosulfonic acid polymer layer.
The interior and the surface of the functional surface coating are in porous rough structures, and the thickness of the coating is 0.01-30 μm, preferably 1-10 μm.
The functional surface coating has a roughness Ra value within a range of 10 micrometers to 10 micrometers, and preferably within a range of 50 nanometers to 2 micrometers; the roughness Ra value in the range of 240 microns to 300 microns is between 300 nanometers and 10 microns, preferably between 1 micron and 5 microns.
The pores can be distributed on the surface of the coating or in the coating or can be concentrated in a designated area, the pores can be in a regular or irregular structure such as regular or irregular circles, ellipses, squares, rectangles and the like which are orderly or disorderly arranged, and the volume of the pores in the coating accounts for 5-95% of the volume of the coating, preferably 50-80%.
The perfluorinated ionic polymer is one or two of perfluorinated sulfonic acid polymer or perfluorinated phosphoric acid polymer, and is preferably perfluorinated sulfonic acid polymer.
The exchange capacity of the perfluorinated ion polymer is 0.5-1.5 mmol/g, preferably 0.8-1.1 mmol/g.
The functional surface coating has extremely low bubble adhesion in 0-300 g/L saline, and in a 0-300 g/L saline environment, the adhesion between bubbles with a volume of 3 microliters and the coating is 0-400 microliters, preferably 0-120 microliters.
The functional surface coating has a bubble contact angle of 4 microliter more than or equal to 125 degrees in 250g/L saline water environment at 25 ℃.
The preparation method of the diaphragm of the reinforced low-resistance chlor-alkali electrolytic cell comprises the following steps:
(1) compounding perfluorinated sulfonic acid resin and perfluorinated carboxylic acid resin into a perfluorinated ion exchange resin base membrane in a coextrusion casting mode; soaking the porous material compounded and woven by the reinforcing material and the protein fiber into the solvent subjected to ultrasonic treatment for treatment, taking out and drying the porous material, and compounding the porous material with the base membrane to form a precursor of the perfluorinated ion exchange membrane;
(2) carrying out overpressure treatment on the perfluorinated ion exchange membrane precursor prepared in the step (1), and then immersing the perfluorinated ion exchange membrane precursor into a mixed aqueous solution of a solvent and an alkali liquor for transformation to convert the perfluorinated ion exchange membrane precursor into a perfluorinated ion exchange membrane with an ion exchange function;
(3) adding the perfluorinated ionic polymer into a solvent for homogenization treatment to form a perfluorinated ionic polymer solution;
(4) adding a pore-forming agent into the perfluorinated ion polymer solution in the step (3), and performing ball milling to obtain a dispersion liquid;
(5) and (3) attaching the dispersion liquid obtained in the step (4) to the surface of a perfluorinated ion exchange membrane in a coating mode, and etching the surface to form a porous rough structure to obtain the reinforced low-resistance chlor-alkali electrolytic cell diaphragm.
In the step (1), the protein fiber is one or more of silk, wool, casein fiber, soybean protein fiber, peanut protein fiber or corn protein fiber.
In the step (1), the weaving mode is common knowledge of the technicians in the field; when the base film and the dried porous material are combined, the dried porous material may be pressed into the base film in parallel, but the present invention is not limited to this.
In the step (2), the overpressure treatment conditions are as follows: overpressure treatment is carried out at a temperature of 180 ℃ and 220 ℃ and a pressure of 80-120 tons and at a speed of 45 m/min by using an overpressure machine.
In the step (3), the solvent is prepared from ethanol and isopropanol according to the ratio of 1:1 by weight ratio.
In the step (4), the pore-forming agent is one or more of silicon oxide, aluminum oxide, zinc oxide, potassium carbonate, titanium oxide, silicon carbide, sodium carbonate, polytrimethylene terephthalate fiber, polyurethane fiber, polyvinylidene fluoride (PVDF) or polyethylene terephthalate fiber (PET).
In the step (5), the coating mode is one of spraying, brushing, rolling, transfer printing, dipping or spin coating.
In the step (5), the etching is one or a combination of several processes of alkaline hydrolysis, acid hydrolysis or hydrolysis.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the invention, the reinforcing material net and the composite base membrane are organically compounded, so that the mechanical support is added to the chlor-alkali perfluorinated ion exchange membrane, and the mechanical strength of the exchange membrane is ensured;
(2) the hollow tunnel reduces the resistance of the membrane body and is beneficial to the rapid conduction of ions;
(3) the functional surface coating is a porous rough structure formed by the perfluorinated ion polymer, so that the roughness of the surface of the exchange membrane is improved, the adhesion of the surface of the membrane to bubbles is reduced, the effective electrolysis area of the surface of the membrane is increased, and the local polarization phenomenon is reduced;
(4) the diaphragm of the reinforced low-resistance chlor-alkali electrolytic cell prepared by the invention has the functions of strong acid resistance and strong alkali resistance, is suitable for running in a zero polar distance electrolytic cell under the novel high current density condition, and can obviously reduce the cell voltage and the energy consumption;
(5) the preparation method of the reinforced low-resistance chlor-alkali electrolytic cell diaphragm is scientific and reasonable in design, simple and feasible and beneficial to industrial production.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to limit the practice of the invention.
Example 1
(1) The perfluorinated ion exchange resin base membrane is compounded by adopting perfluorinated sulfonic acid resin with IEC (International electrotechnical Commission) of 1.08mmol/g and perfluorinated carboxylic acid resin with IEC (International electrotechnical Commission) of 0.98mmol/g in a coextrusion casting mode, wherein the thickness of the perfluorinated sulfonic acid resin layer is 90 micrometers, and the thickness of the perfluorinated carboxylic acid resin layer is 7 micrometers. And then soaking the porous reinforcing material compounded and woven by polytetrafluoroethylene and silk into a trifluorotrichloroethane solvent subjected to ultrasonic treatment for 1.5 hours, wherein the thickness of the porous reinforcing material is 80 microns, the porosity is 85 percent, and the porous reinforcing material is taken out, dried and compounded with a perfluorinated ion exchange resin base membrane to form a perfluorinated ion exchange membrane precursor.
(2) And (2) performing overpressure treatment on the perfluorinated ion exchange membrane precursor prepared in the step (1) at the temperature of 180 ℃ and under the pressure of 120 tons and at the speed of 45 m/min by using an overpressure machine, and after the overpressure treatment, immersing the perfluorinated ion exchange membrane precursor into a mixed aqueous solution containing 18 wt% of dimethyl sulfoxide and 20 wt% of NaOH at the temperature of 85 ℃ for transformation for 80 minutes to obtain the perfluorinated ion exchange membrane with the ion exchange function. In the obtained ion exchange membrane, the distance between two adjacent main fibers in the reinforcing material net is 1.0 +/-0.2 mm, and the two adjacent main fibers contain 416 hollow tunnels; the diameter of the single tunnel is 2 +/-0.5 mu m.
(3) Preparing ethanol and isopropanol into a mixed solution according to the weight ratio of 1:1, adding perfluorinated sulfonic acid resin with the exchange capacity of 1.2mmol/g, and treating for 3 hours at 200 ℃ in a closed reaction kettle to obtain a uniform perfluorinated sulfonic acid solution with the mass fraction of 5%.
(4) Zinc oxide particles with the average particle size of 400 nanometers are mixed according to the mass ratio of 1: and 1, adding the mixture into the perfluorosulfonic acid solution obtained in the step 1, and carrying out ball milling for 36 hours to obtain a dispersion solution with the mass fraction of 28%.
(5) And (3) attaching the dispersion liquid obtained in the step (4) to the two side surfaces of the base membrane of the perfluoro ion exchange membrane for the chlor-alkali membrane with the thickness of 155 micrometers by adopting a spraying method, wherein the average thickness of the surface layer is 3.4 micrometers, and drying for 2 hours at 150 ℃.
(6) And (3) aging the film containing the coating obtained in the step (5) in a 20 wt% NaOH solution at 60 ℃ for 3 hours, and drying to obtain the enhanced low-resistance chlor-alkali electrolytic cell diaphragm.
Performance testing
In the functional surface coating, the volume of the pores accounts for 50% of the volume fraction of the coating.
The film surface was tested to have a roughness Ra value of 426 nm in the range of 10 microns by 10 microns and a roughness Ra value of 2.8 microns in the range of 240 microns by 300 microns.
The adhesion was measured in 250g/L NaCl solution with 3. mu.l air bubbles to be 46. mu.l.
Carrying out an electrolysis test on the prepared ion exchange membrane in an electrolytic cell by using a sodium chloride aqueous solution, supplying 300g/L of the sodium chloride aqueous solution to an anode chamber, supplying water to a cathode chamber, and ensuring that the concentration of sodium chloride discharged from the anode chamber is 200g/L and the concentration of sodium hydroxide discharged from the cathode chamber is 32%; the test temperature is 90 ℃, and the current density is 6kA/m2After 35 days of electrolysis experiments, the average cell pressure is 2.72V, and the average current efficiency is 99.6%.
The sheet resistance of the resulting film was measured to be 0.47. omega. cm by the standard SJ/T10171.5 method-2。
Example 2
(1) The perfluorinated ion exchange resin base membrane is compounded by adopting perfluorinated sulfonic acid resin with IEC (0.93 mmol/g) and perfluorinated carboxylic acid resin with IEC (0.95 mmol/g) in a coextrusion casting mode, wherein the thickness of the perfluorinated sulfonic acid resin layer is 100 micrometers, and the thickness of the perfluorinated carboxylic acid resin layer is 8 micrometers. And then soaking the porous reinforcing material compounded and woven by polytetrafluoroethylene and wool into a trifluorotrichloroethane solvent subjected to ultrasonic treatment for 3 hours, wherein the thickness of the porous reinforcing material is 70 micrometers, the porosity is 85 percent, and the porous reinforcing material is taken out, dried and compounded with a perfluorinated ion exchange resin base membrane to form a perfluorinated ion exchange membrane precursor.
(2) And (2) performing overpressure treatment on the perfluorinated ion exchange membrane precursor prepared in the step (1) at the temperature of 200 ℃ and under the pressure of 100 tons by using an overpressure machine at the speed of 45 m/min, and after the overpressure treatment, immersing the perfluorinated ion exchange membrane precursor into a mixed aqueous solution containing 15 wt% of dimethyl sulfoxide and 15 wt% of NaOH at the temperature of 80 ℃ for transformation for 80 minutes to obtain the perfluorinated ion exchange membrane with the ion exchange function. In the obtained ion exchange membrane, the distance between two adjacent main fibers in the reinforcing material net is 1.2 +/-0.2 mm, and the two adjacent main fibers contain 196 hollowed tunnels; the diameter of the single tunnel is 8 +/-1 mu m.
(3) Mixing ethanol and isopropanol according to the weight ratio of 1:1 to prepare a mixed solution, adding perfluorinated sulfonic acid resin with the exchange capacity of 0.9mmol/g, and treating for 3 hours at 220 ℃ in a closed reaction kettle to obtain a uniform perfluorinated sulfonic acid solution with the mass fraction of 5%.
(4) Zinc oxide particles with the average particle size of 400 nanometers are mixed according to the mass ratio of 2: and 1, adding the mixture into the perfluorosulfonic acid solution obtained in the step 1, and performing ball milling for 36 hours to obtain a dispersion solution with the mass fraction of 10%.
(5) And (3) attaching the dispersion liquid obtained in the step (4) to the two side surfaces of the base membrane of the perfluoro ion exchange membrane for the chlor-alkali membrane with the thickness of 155 micrometers by adopting a spraying method, wherein the average thickness of the surface layer is 3.2 micrometers, and drying for 2 hours at 150 ℃.
(6) And (3) aging the film containing the coating obtained in the step (5) in a 20 wt% NaOH solution at 60 ℃ for 3 hours, and drying to obtain the enhanced low-resistance chlor-alkali electrolytic cell diaphragm.
Performance testing
In the functional surface coating, the volume of the pores accounts for 40% of the volume fraction of the coating.
The film surface was tested to have a roughness Ra value of 396 nm in the range of 10 microns by 10 microns and a roughness Ra value of 2.6 microns in the range of 240 microns by 300 microns.
The adhesion was measured in 250g/L NaCl solution with 3. mu.l air bubbles to be 32. mu.l.
Carrying out an electrolysis test of a sodium chloride aqueous solution on the prepared ion exchange membrane in an electrolytic cell, supplying 300g/L of the sodium chloride aqueous solution to an anode chamber, supplying water to a cathode chamber, and ensuring that the concentration of sodium chloride discharged from the anode chamber is 200g/L and the concentration of sodium hydroxide discharged from the cathode chamber is 34%; the test temperature is 90 ℃, and the current density is 6kA/m2After 35 days of electrolysis experiments, the average cell pressure is 2.74V, and the average current efficiency is 99.3%.
The sheet resistance of the resulting film was measured to be 0.52. omega. cm by the standard SJ/T10171.5 method-2。
Example 3
(1) The perfluorinated ion exchange resin base membrane is compounded by adopting perfluorinated sulfonic acid resin with IEC (International electrotechnical Commission) of 1.3mmol/g and perfluorinated carboxylic acid resin with IEC (International electrotechnical Commission) of 1.22mmol/g in a coextrusion casting mode, wherein the thickness of the perfluorinated sulfonic acid resin layer is 250 micrometers, and the thickness of the perfluorinated carboxylic acid resin layer is 20 micrometers. And then soaking the porous reinforcing material compounded and woven by polytetrafluoroethylene and casein fibers into a trifluorotrichloroethane solvent subjected to ultrasonic treatment for 3 hours, wherein the thickness of the porous reinforcing material is 180 micrometers, the porosity is 85 percent, and the porous reinforcing material is taken out, dried and compounded with a perfluorinated ion exchange resin base membrane to form a perfluorinated ion exchange membrane precursor.
(2) And (2) performing overpressure treatment on the perfluorinated ion exchange membrane precursor prepared in the step (1) at the temperature of 190 ℃ and under the pressure of 100 tons by using an overpressure machine at the speed of 45 m/min, and after the overpressure treatment, immersing the perfluorinated ion exchange membrane precursor into a mixed aqueous solution containing 15 wt% of dimethyl sulfoxide and 15 wt% of NaOH at 80 ℃ for transformation for 80 minutes to obtain the perfluorinated ion exchange membrane with the ion exchange function. In the obtained ion exchange membrane, the distance between two adjacent main fibers in the reinforcing material net is 0.8 +/-0.1 mm, and the two adjacent main fibers contain 74 hollow tunnels; the diameter of the single tunnel is 11 +/-1 mu m.
(3) Preparing ethanol and isopropanol into a mixed solution according to the weight ratio of 1:1, adding perfluorinated sulfonic acid resin with the exchange capacity of 1.3mmol/g, and treating for 3 hours at 250 ℃ in a closed reaction kettle to obtain a uniform perfluorinated sulfonic acid solution with the mass fraction of 5%.
(4) Adding polyurethane fiber powder particles with the particle size of 1.2 microns into the perfluorosulfonic acid solution obtained in the step (1), and performing ball milling for 36 hours to obtain a dispersion solution with the mass fraction of 26%.
(5) And (3) attaching the dispersion liquid obtained in the step (4) to the two side surfaces of the base membrane of the perfluoro ion exchange membrane for the chlor-alkali membrane with the thickness of 505 micrometers by adopting a spraying method, wherein the average thickness of the surface layer is 4.2 micrometers, and drying for 2 hours at 150 ℃.
(6) And (3) aging the film containing the coating obtained in the step (5) in a 20 wt% NaOH solution at 80 ℃ for 2 hours, and drying to obtain the enhanced low-resistance chlor-alkali electrolytic cell diaphragm.
Performance testing
In the functional surface coating, the volume of the pores accounts for 48 percent of the volume fraction of the coating.
The film surface was tested to have a roughness Ra value of 1050 nm in the range of 10 microns by 10 microns and a roughness Ra value of 3.9 microns in the range of 240 microns by 300 microns.
The adhesion was determined to be 98. mu.N in 250g/L NaCl solution using 3. mu.L air bubbles.
Carrying out an electrolysis test on the prepared ion exchange membrane in an electrolytic cell by using a sodium chloride aqueous solution, supplying 300g/L of the sodium chloride aqueous solution to an anode chamber, supplying water to a cathode chamber, and ensuring that the concentration of sodium chloride discharged from the anode chamber is 200g/L and the concentration of sodium hydroxide discharged from the cathode chamber is 36%; the test temperature was 89 ℃ and the current density was 6kA/m2After 23 days of electrolysis experiments, the average cell pressure is 3.10V, and the average current efficiency is 99.9%.
The sheet resistance of the resulting film was 1.4. omega. cm as measured by the Standard SJ/T10171.5 method-2。
Comparative example 1
An ion exchange membrane was obtained by the same operation as in example 1 except that in step (1), only the porous reinforcing material woven with polytetrafluoroethylene was immersed in the trifluorotrichloroethane solvent which had been subjected to ultrasonic treatment for 3 hours, and an ion exchange membrane was obtained without a hollow tunnel.
An electrolytic test of a sodium chloride solution was carried out under the same conditions as in example 3, and after an electrolytic experiment for 35 days, the average cell pressure was 3.35V, the average current efficiency was 99.9%, and the sheet resistance was 1.6. omega. cm-2。
Example 4
(1) The perfluorinated ion exchange resin base membrane is compounded by adopting perfluorinated sulfonic acid resin with IEC (International electrotechnical Commission) of 1.1mmol/g and perfluorinated carboxylic acid resin with IEC (International electrotechnical Commission) of 1.05mmol/g in a coextrusion casting mode, wherein the thickness of the perfluorinated sulfonic acid resin layer is 130 micrometers, and the thickness of the perfluorinated carboxylic acid resin layer is 7 micrometers. And then soaking the porous reinforcing material compounded and woven by polytetrafluoroethylene and silk into a trifluorotrichloroethane solvent subjected to ultrasonic treatment for 3 hours, wherein the thickness of the porous reinforcing material is 80 microns, the porosity is 85 percent, and the porous reinforcing material is taken out, dried and compounded with a perfluorinated ion exchange resin base membrane to form a perfluorinated ion exchange membrane precursor.
(2) And (2) performing overpressure treatment on the perfluorinated ion exchange membrane precursor prepared in the step (1) at the temperature of 180 ℃ and under the pressure of 80 tons by using an overpressure machine at the speed of 45 m/min, and after the overpressure treatment, immersing the perfluorinated ion exchange membrane precursor into a mixed aqueous solution containing 15 wt% of dimethyl sulfoxide and 15 wt% of NaOH at the temperature of 80 ℃ for transformation for 80 minutes to obtain the perfluorinated ion exchange membrane with the ion exchange function. In the obtained ion exchange membrane, the distance between two adjacent main fibers in the reinforcing material net is 1.3 +/-0.2 mm, and the two adjacent main fibers contain 372 hollow tunnels; the diameter of the single tunnel is 3 +/-0.5 mu m.
(3) Preparing ethanol and isopropanol into a mixed solution according to the weight ratio of 1:1, adding perfluorinated sulfonic acid resin with the exchange capacity of 1.2mmol/g, and treating for 3 hours at 200 ℃ in a closed reaction kettle to obtain a uniform perfluorinated sulfonic acid solution with the mass fraction of 5%.
(4) Mixing calcium carbonate particles with the average particle size of 400 nanometers and PVDF powder with the average particle size of 500 nanometers according to the mass ratio of 1: and 1, adding the mixture into the perfluorosulfonic acid solution obtained in the step 1, and carrying out ball milling for 36 hours to obtain a dispersion solution with the mass fraction of 28%.
(5) And (3) attaching the dispersion liquid obtained in the step (4) to the two side surfaces of the base membrane of the perfluoro ion exchange membrane for the chlor-alkali membrane with the thickness of 240 microns by adopting a spraying method, wherein the average thickness of the surface layer is 4.4 microns, and drying for 2 hours at 150 ℃.
(6) And (3) aging the film containing the coating obtained in the step (5) in a 20 wt% NaOH solution at 60 ℃ for 3 hours, and drying to obtain the enhanced low-resistance chlor-alkali electrolytic cell diaphragm.
Performance testing
In the functional surface coating, the volume of the pores accounts for 50% of the volume fraction of the coating.
The film surface was tested to have a roughness Ra value of 520 nm in the range of 10 microns by 10 microns and a roughness Ra value of 3.5 microns in the range of 240 microns by 300 microns.
The adhesion was measured in 250g/L NaCl solution with 3. mu.l air bubbles to be 82. mu.l.
Subjecting the prepared ion exchange membrane to electrolysis test of sodium chloride aqueous solution in an electrolytic cell, and supplying 310g/L sodium chloride aqueous solution to anode chamber and water to cathode chamberThe concentration of sodium chloride discharged from the anode chamber is 204g/L, and the concentration of sodium hydroxide discharged from the cathode chamber is 36%; the test temperature was 89 ℃ and the current density was 6kA/m2After 23 days of electrolysis experiments, the average cell pressure is 2.76V, and the average current efficiency is 99.2%.
The sheet resistance of the resulting film was measured to be 0.56. omega. cm by the standard SJ/T10171.5 method-2。
Example 5
(1) The perfluorinated ion exchange resin base membrane is compounded by adopting perfluorinated sulfonic acid resin with IEC (International electrotechnical Commission) of 1.1mmol/g and perfluorinated carboxylic acid resin with IEC (International electrotechnical Commission) of 1.05mmol/g in a coextrusion casting mode, wherein the thickness of the perfluorinated sulfonic acid resin layer is 70 micrometers, and the thickness of the perfluorinated carboxylic acid resin layer is 15 micrometers. And then soaking the porous reinforcing material compounded and woven by polytetrafluoroethylene and soybean protein fibers into a trifluorotrichloroethane solvent subjected to ultrasonic treatment for 3 hours, wherein the thickness of the porous reinforcing material is 40 micrometers, the porosity is 85 percent, and the porous reinforcing material is taken out, dried and compounded with a perfluorinated ion exchange resin base membrane to form a perfluorinated ion exchange membrane precursor.
(2) And (2) performing overpressure treatment on the perfluorinated ion exchange membrane precursor prepared in the step (1) at 185 ℃ and 80 tons of pressure by using an overpressure machine at the speed of 45 m/min, and after the overpressure treatment, immersing the perfluorinated ion exchange membrane precursor into a mixed aqueous solution containing 15 wt% of dimethyl sulfoxide and 15 wt% of NaOH at 80 ℃ for transformation for 80 minutes to obtain the perfluorinated ion exchange membrane with the ion exchange function. In the obtained ion exchange membrane, the distance between two adjacent main fibers in the reinforcing material net is 0.7 +/-0.1 mm, and the two adjacent main fibers contain 158 hollow tunnels; the diameter of the single tunnel is 8 +/-1 mu m.
(3) Preparing ethanol and isopropanol into a mixed solution according to the weight ratio of 1:1, adding perfluorinated sulfonic acid resin with the exchange capacity of 1.3mmol/g, and treating for 3 hours at 230 ℃ in a closed reaction kettle to obtain a uniform perfluorinated sulfonic acid solution with the mass fraction of 15%.
(4) Sodium carbonate particles with the average particle size of 1 micron and silicon carbide particles with the average particle size of 500 nanometers are mixed according to the weight ratio of 7: and 3, adding the mixture into the perfluorosulfonic acid solution obtained in the step 1, and performing ball milling for 36 hours to obtain a dispersion solution with the mass fraction of 25%.
(5) And (3) attaching the dispersion liquid obtained in the step (4) to the two side surfaces of the base membrane of the perfluorinated ion exchange membrane for the chlor-alkali membrane with the thickness of 140 micrometers by adopting a spraying method, wherein the average thickness of the surface layer is 2.8 micrometers, and drying the surface layer for 2 hours at 150 ℃.
(6) And (3) aging the film containing the coating obtained in the step (5) in a 20 wt% NaOH solution at 60 ℃ for 3 hours, and drying to obtain the enhanced low-resistance chlor-alkali electrolytic cell diaphragm.
Performance testing
In the functional surface coating, the volume of the pores accounts for 23 percent of the volume fraction of the coating.
The film surface was tested for roughness Ra values of 267 nm in the range of 10 microns by 10 microns and 2.3 microns in the range of 240 microns by 300 microns.
The adhesion was measured in 250g/L NaCl solution with 3. mu.l air bubbles to be 76. mu.l.
Carrying out an electrolysis test of a sodium chloride aqueous solution on the prepared ion exchange membrane in an electrolytic cell, supplying 305g/L of the sodium chloride aqueous solution to an anode chamber, supplying water to a cathode chamber, and ensuring that the concentration of sodium chloride discharged from the anode chamber is 208g/L and the concentration of sodium hydroxide discharged from the cathode chamber is 36%; the test temperature was 89 ℃ and the current density was 6kA/m2After 23 days of electrolysis experiments, the average cell pressure is 2.66V, and the average current efficiency is 100%.
The sheet resistance of the resulting film was measured to be 0.56. omega. cm by the standard SJ/T10171.5 method-2。
Example 6
(1) The perfluorinated ion exchange resin base membrane is compounded by adopting perfluorinated sulfonic acid resin with IEC (International electrotechnical Commission) of 1.08mmol/g and perfluorinated carboxylic acid resin with IEC (International electrotechnical Commission) of 0.98mmol/g in a coextrusion casting mode, wherein the thickness of the perfluorinated sulfonic acid resin layer is 75 micrometers, and the thickness of the perfluorinated carboxylic acid resin layer is 12 micrometers. And then soaking the porous reinforcing material compounded and woven by polytetrafluoroethylene and silk into a trifluorotrichloroethane solvent subjected to ultrasonic treatment for 1.5 hours, wherein the thickness of the porous reinforcing material is 42 microns, the porosity is 85%, and taking out the porous reinforcing material, drying the porous reinforcing material and compounding the porous reinforcing material with a perfluorinated ion exchange resin base membrane to form a perfluorinated ion exchange membrane precursor.
(2) And (2) performing overpressure treatment on the perfluorinated ion exchange membrane precursor prepared in the step (1) at the temperature of 180 ℃ and under the pressure of 120 tons and at the speed of 45 m/min by using an overpressure machine, and after the overpressure treatment, immersing the perfluorinated ion exchange membrane precursor into a mixed aqueous solution containing 18 wt% of dimethyl sulfoxide and 20 wt% of NaOH at the temperature of 85 ℃ for transformation for 80 minutes to obtain the perfluorinated ion exchange membrane with the ion exchange function. In the obtained ion exchange membrane, the distance between two adjacent main fibers in the reinforcing material net is 1.3 +/-0.2 mm, and the two adjacent main fibers contain 262 hollow tunnels; the diameter of the single tunnel is 5 +/-1 mu m.
(3) Mixing ethanol and isopropanol at a weight ratio of 1:1 to obtain a mixed solution, adding a perfluorinated phosphoric acid resin with an exchange capacity of 1.3mmol/g, and treating at 200 ℃ in a closed reaction kettle for 3 hours to obtain a uniform perfluorinated phosphoric acid solution with a mass fraction of 5%.
(4) Adding zinc oxide particles with the average particle size of 400 nanometers into the perfluorophosphoric acid solution obtained in the step (1), and performing ball milling for 36 hours to obtain a dispersion solution with the mass fraction of 28%.
(5) And (3) attaching the dispersion liquid obtained in the step (4) to the two side surfaces of the base membrane of the perfluoro ion exchange membrane for the chlor-alkali membrane with the thickness of 145 microns by adopting a spraying method, wherein the average thickness of the surface layer is 3.1 microns, and drying for 2 hours at 150 ℃.
(6) And (3) aging the film containing the coating obtained in the step (5) in a 20 wt% NaOH solution at 60 ℃ for 3 hours, and drying to obtain the enhanced low-resistance chlor-alkali electrolytic cell diaphragm.
Performance testing
In the functional surface coating, the volume of the pores accounts for 25 percent of the volume fraction of the coating.
The film surface was tested to have a roughness Ra value of 241 nm in the range of 10 microns by 10 microns and a roughness Ra value of 2.2 microns in the range of 240 microns by 300 microns.
The adhesion was measured in 250g/L NaCl solution with 3. mu.l air bubbles to be 72. mu.l.
The prepared ion exchange membrane is subjected to an electrolysis test of sodium chloride aqueous solution in an electrolytic cell, and 306g/L of the ion exchange membraneSupplying sodium chloride aqueous solution to an anode chamber, supplying water to a cathode chamber, and ensuring that the concentration of sodium chloride discharged from the anode chamber is 205g/L and the concentration of sodium hydroxide discharged from the cathode chamber is 36%; the test temperature was 89 ℃ and the current density was 6kA/m2After 35 days of electrolysis experiments, the average cell pressure is 2.64V, and the average current efficiency is 100%.
The sheet resistance of the resulting film was measured to be 0.56. omega. cm by the standard SJ/T10171.5 method-2。
Example 7
(1) The perfluorinated ion exchange resin base membrane is compounded by adopting perfluorinated sulfonic acid resin with IEC (International electrotechnical Commission) of 1.08mmol/g and perfluorinated carboxylic acid resin with IEC (International electrotechnical Commission) of 0.98mmol/g in a coextrusion casting mode, wherein the thickness of the perfluorinated sulfonic acid resin layer is 65 micrometers, and the thickness of the perfluorinated carboxylic acid resin layer is 18 micrometers. And then soaking the porous reinforcing material compounded and woven by polytetrafluoroethylene and silk into a trifluorotrichloroethane solvent subjected to ultrasonic treatment for 1.5 hours, wherein the thickness of the porous reinforcing material is 40 micrometers, the porosity is 85 percent, and the porous reinforcing material is taken out, dried and compounded with a perfluorinated ion exchange resin base membrane to form a perfluorinated ion exchange membrane precursor.
(2) And (2) performing overpressure treatment on the perfluorinated ion exchange membrane precursor prepared in the step (1) at the temperature of 180 ℃ and under the pressure of 120 tons and at the speed of 45 m/min by using an overpressure machine, and after the overpressure treatment, immersing the perfluorinated ion exchange membrane precursor into a mixed aqueous solution containing 18 wt% of dimethyl sulfoxide and 20 wt% of NaOH at the temperature of 85 ℃ for transformation for 80 minutes to obtain the perfluorinated ion exchange membrane with the ion exchange function. In the obtained ion exchange membrane, the distance between two adjacent main fibers in the reinforcing material net is 1.0 +/-0.1 mm, and the two adjacent main fibers contain 32 hollow tunnels; the diameter of the single tunnel is 28 +/-2 mu m.
(3) Preparing ethanol and isopropanol into a mixed solution according to the weight ratio of 1:1, adding perfluorinated sulfonic acid resin with the exchange capacity of 1.3mmol/g and perfluorinated phosphoric acid resin with the exchange capacity of 1.1mmol/g into the mixed solution, and treating the mixture for 2.5 hours at 220 ℃ in a closed reaction kettle to obtain a mixed solution of perfluorinated sulfonic acid and perfluorinated phosphoric acid with the mass fraction of 5%.
(4) Adding zinc oxide particles with the average particle size of 400 nanometers into the mixed solution of the perfluorosulfonic acid and the perfluorophosphoric acid in the step (1), and performing ball milling for 36 hours to obtain a dispersion solution with the mass fraction of 28%.
(5) And (3) attaching the dispersion liquid obtained in the step (4) to the two side surfaces of the base membrane of the perfluoro ion exchange membrane for the chlor-alkali membrane with the thickness of 138 microns by adopting a spraying method, wherein the average thickness of the surface layer is 2.7 microns, and drying for 2 hours at 150 ℃.
(6) And (3) aging the film containing the coating obtained in the step (5) in a 20 wt% NaOH solution at 60 ℃ for 3 hours, and drying to obtain the enhanced low-resistance chlor-alkali perfluorinated ion exchange membrane.
Performance testing
In the functional surface coating, the volume of the pores accounts for 30 percent of the volume fraction of the coating.
The film surface was tested to have a roughness Ra value of 128 nm in the range of 10 microns by 10 microns and a roughness Ra value of 2.1 microns in the range of 240 microns by 300 microns.
The adhesion was determined to be 89 μm in 250g/L NaCl solution using 3. mu.l air bubbles.
Carrying out an electrolysis test of a sodium chloride aqueous solution on the prepared ion exchange membrane in an electrolytic cell, supplying 306g/L of the sodium chloride aqueous solution to an anode chamber, supplying water to a cathode chamber, and ensuring that the concentration of sodium chloride discharged from the anode chamber is 205g/L and the concentration of sodium hydroxide discharged from the cathode chamber is 36%; the test temperature was 89 ℃ and the current density was 6kA/m2After 35 days of electrolysis experiments, the average cell pressure is 2.68V, and the average current efficiency is 100%.
The sheet resistance of the resulting film was measured to be 0.63. omega. cm by the standard SJ/T10171.5 method-2。