Zero polar distance ion exchange membrane and preparation method thereof

Abstract

A zero polar distance ion exchange membrane. A polymer membrane is compositely prepared by a perfluorinated ion exchange resin and a reinforcing material, and the polymer membrane is converted into an ion exchange membrane. A non-electrode porous gas release layer is adhered to at least one side of the ion exchange membrane. The non-electrode porous gas release layer is formed by drying after adhering a dispersion liquid to an ion exchange membrane layer surface. The dispersion liquid is formed by dispersing perfluorinated sulphonic acid resin broken micro-particles in a sulphonic acid resin aqueous alcohol solution. The prepared zero polar distance ion exchange membrane is used in the chlor-alkali industry, stably and effectively treats an alkali metal chloride solution having a high impurity content, is able to better suited for operating in a zero polar distance electrolysis cell under high current density conditions, and has a very low surface resistance. Also provided is a preparation method for the zero polar distance ion exchange membrane. The preparation method has a simple and reasonable process, and facilitates industrial production.

Claims

1. A zero polar distance ion exchange membrane, wherein: the zero polar distance ion exchange membrane is a polymer membrane compositely prepared by perfluorinated ion exchange resin and a reinforcement material; the polymer membrane is converted to an ion exchange membrane, a non-electrode multi-porous gas release layer is attached to at least one side of the ion exchange membrane; the non-electrode multi-porous gas release layer is formed by drying after adhering a dispersion liquid to an ion exchange membrane surface; the dispersion liquid is formed by dispersing perfluorosulfonic acid resin broken micro-particles in a sulfonic acid resin water alcohol solution.

2. The zero polar distance ion exchange membrane, as recited in claim 1, wherein: the perfluorosulfonic acid resin broken micro-particles are formed by converting perfluorosulfonic acid resin in NaOH solution to sodium-type, and then grinding through a nano grinding machine, and finally obtaining the broken micro-particles with irregular polyhedron morphology.

3. The zero polar distance ion exchange membrane, as recited in claim 1, wherein: the reinforcement material is one of a mesh material, a fibrous material, a nonwoven fabric material and a porous membrane material which are made of any one of polytetrafluoroethylene (PTFE), polyperfluoroalkoxy resin (PFA), poly ethylene propylene (FEP), and ethylene-tetrafluoroethylene copolymer (ETFE).

4. The zero polar distance ion exchange membrane, as recited in claim 1, wherein: a surface hydrophilic contact angle of the ion exchange membrane attached with the non-electrode multi-porous gas release layer is smaller than 90, and a surface resistance of the ion exchange membrane is lower than 1.2 .Math.cm.sup.2.

5. The zero polar distance ion exchange membrane, as recited in claim 1, wherein: an ion exchange capability of the perfluorosulfonic acid resin broken micro-particles is in a range of 0.4-0.9 mmol/g; and a particle size of the perfluorosulfonic acid resin broken micro-particles is in a range of 0.05-20 m.

6. The zero polar distance ion exchange membrane, as recited in claim 5, wherein: in the dispersion liquid, a content of the perfluorosulfonic acid resin broken micro-particles by weight is 5-40%.

7. The zero polar distance ion exchange membrane, as recited in claim 1, wherein: in the sulfonic acid resin water alcohol solution, a content of the sulfonic acid resin by weight is 0.05-20%.

8. The zero polar distance ion exchange membrane, as recited in claim 5, wherein: a distribution quantity of the perfluorosulfonic acid resin broken micro-particles on the polymer membrane surface is 0.01-15 mg/cm.sup.2.

9. The zero polar distance ion exchange membrane, as recited in claim 4, wherein: the non-electrode multi-porous gas release layer is a non-continuous multi-porous layer, and has a porosity of 35-99%.

10. A preparation method of a zero polar distance ion exchange membrane, comprising steps of: (1) through a screw extruder, in a co-extrusion manner, melting and casting perfluorinated ion exchange resin to a single layer membrane or a multi-layer composite membrane, and simultaneously, introducing a reinforcement material between two membrane forming rollers, pressing the reinforcement material into a membrane body under an action of a pressure between the rollers, and forming a polymer membrane; (2) immersing the polymer membrane in the step (1) to a mixed aqueous solution of dimethyl sulfoxide and NaOH, and converting the polymer membrane into an ion exchange membrane with ion exchange function; (3) dissolving perfluorosulfonic acid resin, putting the dissolved perfluorosulfonic acid resin into a water alcohol mixture, forming sulfonic acid resin water alcohol solution, adding perfluorosulfonic acid resin broken micro-particles, homogenizing in a ball mill, and forming a dispersion liquid; and (4) through surface coating, adhering the dispersion liquid to the ion exchange membrane surface obtained in the step (2), forming a discontinuous multi-porous gas release layer after drying, and obtaining a product.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0042] The present invention is further explained with accompanying embodiments in detail.

[0043] Concentrations in the examples are by mass unless otherwise specified.

[0044] A polymer membrane described in the examples is made of perfluorinated ion exchange resin with a structure as follows, wherein: a repetitive unit of sulfonic acid resin is

##STR00001##

[0045] a repetitive unit of carboxylic acid resin is

##STR00002##

[0046] a repetitive unit of sulfonic acid carboxylic acid polymer is

##STR00003##

Example 1

[0047] A preparation method of a zero polar distance ion exchange membrane comprises steps of:

[0048] (1) processing perfluorosulfonic acid resin with IEC=1.4 mmol/g, perfluorosulfonic acid carboxylic acid copolymer resin with IEC=1.0 mmol/g and perfluorocarboxylic acid resin with IEC=0.95 mmol/g, with a mass fraction ratio of 100:5:10 in a co-extrusion and cast manner, forming a composite membrane with a total thickness of 135 m; and simultaneously, introducing a PTFE (polytetrafluoroethylene) mesh fabric between two membrane forming rollers, the PTFE mesh fabric entering a membrane body through rolling compounding, and forming a polymer membrane;

[0049] (2) immersing the polymer membrane in the step (1) to a mixed aqueous solution of dimethyl sulfoxide with a weight percentage of 15 wt % and NaOH with a weight percentage of 20 wt % for 80 minutes at 85 C., and then converting the polymer membrane into an ion exchange membrane with ion exchange function;

[0050] (3) preparing a water alcohol mixture by mixing water and alcohol with a weight ratio of 1:1, dissolving perfluorosulfonic acid resin with IEC=0.9 mmol/g, putting the dissolved perfluorosulfonic acid resin into the water alcohol mixture, forming sulfonic acid resin solution with a concentration of 2 wt %, adding perfluorosulfonic acid resin broken micro-particles with IEC=0.78 mmol/g, an average particle size of 0.5 pm and irregular polyhedron morphology to the sulfonic acid resin solution, homogenizing in a ball mill, and forming a dispersion liquid with a content of 15 wt %; and

[0051] (4) through spraying, adhering the dispersion liquid to surfaces at two sides of the ion exchange membrane surface obtained in the step (2), and forming a discontinuous multi-porous gas release layer with a porosity of 86% after drying, wherein: a distribution quantity of the perfluorosulfonic acid resin broken micro-particles on the composite membrane surface is 4.6 mg/cm.sup.2, a hydrophilicity of the membrane is tested by a contact angle measuring instrument, and a contact angle is 77.

Performance Testing

[0052] An electrolytic test of the prepared ion exchange membrane about NaCl aqueous solution in an electrolysis cell is performed. 300 g/L NaCl aqueous solution is supplied to an anode chamber, water is supplied to a cathode chamber, it is ensured that a concentration of NaCl discharged from the anode chamber is 200 g/L, and a concentration of NaOH discharged from the cathode chamber is 32%; a test temperature is 90 C., a current density is 8 kA/m.sup.2; after 23 days of electrolysis experiments, the average cell voltage is 2.73 V and the average current efficiency is 99.1%.

[0053] Afterwards, based on standard SJ/T 10171.5, a surface resistance of the obtained membrane is tested to be 1.0 .Math.cm.sup.2; based on ASTM Standard D 1044-99, a wear loss of the obtained membrane is tested to be 2.6 mg.

Comparative Example 1

[0054] A same method as the example 1 is adopted to prepare the ion exchange membrane with ion exchange function; afterwards, a same method is adopted to prepare the dispersion liquid. Differences between the example 1 and the comparative example 1 are as follows. The perfluorosulfonic acid resin broken micro-particles in the dispersion liquid are replaced by zirconium oxide particles with an average particle size of 0.5 m, and then homogenized in the ball mill, and the dispersion liquid with a content of 15 wt % is formed. The same method is adopted to obtain the ion exchange membrane attached with the discontinuous multi-porous gas release layer at two sides thereof. The distribution quantity of the zirconium oxide particles on the composite membrane surface is also 4.6 mg/cm.sup.2, the porosity of the membrane is reduced to 73%; the hydrophilicity thereof is tested by the contact angle measuring instrument, and the contact angle is 126.

[0055] Under the same conditions as the example 1, the electrolytic test of NaCl aqueous solution is performed. After 23 days of electrolysis experiments, the average cell voltage is 2.98 V, the average current efficiency is 96.0%, the surface resistance is 2.3 .Math.cm.sup.2, and the wear loss is 7.4 mg.

Example 2

[0056] A same method as the example 1 is adopted to prepare an ion exchange membrane with ion exchange function. Afterwards, a water alcohol mixture is prepared by mixing water and alcohol with a weight ratio of 1:1, perfluorosulfonic acid resin with IEC=0.9 mmol/g is dissolved, the dissolved perfluorosulfonic acid resin is put into the water alcohol mixture, sulfonic acid resin solution with a concentration of 6 wt % is formed; and then perfluorosulfonic acid resin broken micro-particles with IEC=0.45 mmol/g, an average particle size of 0.05 m and irregular polyhedron morphology are added to the sulfonic acid resin solution and are homogenized in a ball mill, and a dispersion liquid with a content of 9 wt % is formed.

[0057] Through spraying, the dispersion liquid is adhered to surfaces at two sides of the above ion exchange membrane surface, and a discontinuous multi-porous gas release layer with a porosity of 91% is formed after drying, wherein: a distribution quantity of the perfluorosulfonic acid resin broken micro-particles on the composite membrane surface is 5.2 mg/cm.sup.2, a hydrophilicity of the membrane is tested by a contact angle measuring instrument, and a contact angle is 81.

[0058] An electrolytic test of the prepared ion exchange membrane about NaCl aqueous solution in an electrolysis cell described in Example 1 is performed; a current density is 10 KA/m.sup.2; after 17 days of electrolysis experiments, an average cell voltage is 2.79 V, and an average current efficiency is 99.0%.

[0059] Afterwards, based on standard SJ/T 10171.5, a surface resistance of the obtained membrane is tested to be 0.90 .Math.cm.sup.2; based on ASTM Standard D 1044-99, a wear loss of the obtained membrane is tested to be 3.1 mg.

Example 3

[0060] A same method as the example 1 is adopted to prepare an ion exchange membrane with ion exchange function. Afterwards, a water alcohol mixture is prepared by mixing water and propanol with a weight ratio of 1:1, perfluorosulfonic acid resin with IEC=0.9 mmol/g is dissolved, the dissolved perfluorosulfonic acid resin is put into the water alcohol mixture, sulfonic acid resin solution with a concentration of 1 wt % is formed; and then perfluorosulfonic acid resin broken micro-particles with IEC=0.75 mmol/g, an average particle size of 5 m and irregular polyhedron morphology are added to the sulfonic acid resin solution and are homogenized in a ball mill, and a dispersion liquid with a content of 4.6 wt % is formed.

[0061] Through spraying, the dispersion liquid is adhered to surfaces at two sides of the above ion exchange membrane surface, and a discontinuous multi-porous gas release layer with a porosity of 94% is formed after drying, wherein: a distribution quantity of the perfluorosulfonic acid resin broken micro-particles on the composite membrane surface is 6.8 mg/cm.sup.2, a hydrophilicity of the membrane is tested by a contact angle measuring instrument, and a contact angle is 68.

[0062] An electrolytic test of the prepared ion exchange membrane about NaCl aqueous solution in an electrolysis cell described in Example 1 is performed; a current density is 12 KA/m.sup.2; after 23 days of electrolysis experiments, an average cell voltage is 2.83 V, and an average current efficiency is 99.0%.

[0063] Afterwards, based on standard SJ/T 10171.5, a surface resistance of the obtained membrane is tested to be 0.95 .Math.cm.sup.2; based on ASTM Standard D 1044-99, a wear loss of the obtained membrane is tested to be 2.1 mg.

[0064] Afterwards, 10 ppm organic matter n-chlorododecyl trimethyl ammonium chloride is added to the NaCl aqueous solution. Under the same conditions as the above description, after 40 days of electrolysis experiments, an average cell voltage is 2.85 V, and an average current efficiency is 99.0%.

Example 4

[0065] Differences between the example 4 and the example 3 are as follows. In the example 4, the prepared dispersion liquid is coated to one side of the ion exchange membrane with ion exchange function mentioned in the example 3 in a brush coating manner, and the side is installed to a cathode side of an electrolytic cell; after drying, a discontinuous multi-porous gas release layer with a porosity of 94% is formed; a distribution quantity of the perfluorosulfonic acid resin broken micro-particles on the composite membrane surface is 3.4 mg/cm.sup.2, a hydrophilicity of the membrane is tested by a contact angle measuring instrument, and a contact angle is 68.

[0066] An electrolytic test of the prepared ion exchange membrane about NaCl aqueous solution in an electrolysis cell described in Example 1 is performed; a current density is 12 KA/m.sup.2; after 23 days of electrolysis experiments, an average cell voltage is 2.85 V, and an average current efficiency is 98.6%.

[0067] Afterwards, based on standard SJ/T 10171.5, a surface resistance of the obtained membrane is tested to be 1.2 .Math.cm.sup.2; based on ASTM Standard D 1044-99, a wear loss of the obtained membrane is tested to be 2.1 mg.

Example 5

[0068] Differences between the example 5 and the example 3 are as follows. In the example 5, the prepared dispersion liquid is coated to one side of the ion exchange membrane with ion exchange function mentioned in the example 3 in a brush coating manner, and the side is installed to an anode side of an electrolytic cell; after drying, a discontinuous multi-porous gas release layer with a porosity of 94% is formed; a distribution quantity of the perfluorosulfonic acid resin broken micro-particles on the composite membrane surface is 3.4 mg/cm.sup.2, a hydrophilicity of the membrane is tested by a contact angle measuring instrument, and a contact angle is 68.

[0069] An electrolytic test of the prepared ion exchange membrane about NaCl aqueous solution in an electrolysis cell described in Example 1 is performed; a current density is 12 KA/m.sup.2; after 23 days of electrolysis experiments, an average cell voltage is 3.07 V, and an average current efficiency is 96.6%.

[0070] Afterwards, based on standard SJ/T 10171.5, a surface resistance of the obtained membrane is tested to be 2.7 .Math.cm.sup.2; based on ASTM Standard D 1044-99, a wear loss of the obtained membrane is tested to be 2.1 mg.

Example 6

[0071] (1) processing perfluorosulfonic acid resin with IEC=1.2 mmol/g, and a blending resin forming by mixing perfluorosulfonic acid with IEC=1.3 mmol/g and perfluorocarboxylic acid with IEC=0.89mmol/g in a proportion of 1:1, with a mass fraction ratio of 100:9 in a co-extrusion and cast manner, forming a composite membrane with a total thickness of 120 m; and simultaneously, introducing a PFA non-woven fabric between two membrane forming rollers, the PFA non-woven fabric entering a membrane body through rolling compounding, and forming a polymer membrane;

[0072] (2) immersing the polymer membrane in the step (1) to a mixed aqueous solution of dimethyl sulfoxide with a weight percentage of 15 wt % and NaOH with a weight percentage of 20 wt % for 80 minutes at 85 C., and then converting the polymer membrane into an ion exchange membrane with ion exchange function;

[0073] (3) preparing a water alcohol mixture by mixing water and isopropanol with a weight ratio of 2:1, dissolving perfluorosulfonic acid resin with IEC=0.95 mmol/g, putting the dissolved perfluorosulfonic acid resin into the water alcohol mixture, forming sulfonic acid resin solution with a concentration of 0.05 wt %, adding perfluorosulfonic acid resin broken micro-particles with IEC=0.9 mmol/g, an average particle size of 10 um and irregular polyhedron morphology to the sulfonic acid resin solution, homogenizing in a ball mill, and forming a dispersion liquid with a content of 40 wt %; and

[0074] (4) through brush coating, adhering the dispersion liquid to surfaces at two sides of the ion exchange membrane surface obtained in the step (2), and forming a discontinuous multi-porous gas release layer with a porosity of 99% after drying, wherein: a distribution quantity of the perfluorosulfonic acid resin broken micro-particles on the composite membrane surface is 0.6 mg/cm.sup.2, a hydrophilicity of the membrane is tested by a contact angle measuring instrument, and a contact angle is 74.

[0075] An electrolytic test of the prepared ion exchange membrane about NaCl aqueous solution in an electrolysis cell described in Example 1 is performed; a current density is 8 KA/m.sup.2; after 43 days of electrolysis experiments, an average cell voltage is 2.71 V, and an average current efficiency is 99.2%.

[0076] Afterwards, based on standard SJ/T 10171.5, a surface resistance of the obtained membrane is tested to be 1.0 .Math.cm.sup.2; based on ASTM Standard D 1044-99, a wear loss of the obtained membrane is tested to be 2.9 mg.

Example 7

[0077] The substrate membrane prepared in the embodiment 6 is enhanced by adopting FEP multi-porous membrane to form a polymer membrane; and then is converted into an ion exchange membrane under same conversion conditions.

[0078] Afterwards, a water alcohol mixture is prepared by mixing water and ethanol with a weight ratio of 1:1.2, perfluorosulfonic acid resin with IEC=1.05 mmol/g is dissolved, the dissolved perfluorosulfonic acid resin is put into the water alcohol mixture, sulfonic acid resin solution with a concentration of 20 wt % is formed; and then perfluorosulfonic acid resin broken micro-particles with IEC =0.4 mmol/g, an average particle size of 20 pm and irregular polyhedron morphology are added to the sulfonic acid resin solution and are homogenized in a ball mill, and a dispersion liquid with a content of 5 wt % is formed.

[0079] Through spraying, the dispersion liquid is adhered to surfaces at two sides of the above ion exchange membrane surface, and a discontinuous multi-porous gas release layer with a porosity of 35% is formed after drying, wherein: a distribution quantity of the perfluorosulfonic acid resin broken micro-particles on the composite membrane surface is 15 mg/cm.sup.2, a hydrophilicity of the membrane is tested by a contact angle measuring instrument, and a contact angle is 83.

[0080] An electrolytic test of the prepared ion exchange membrane about NaCl aqueous solution in an electrolysis cell described in Example 1 is performed; a current density is 10 KA/m.sup.2; after 13 days of electrolysis experiments, an average cell voltage is 2.83 V, and an average current efficiency is 99.0%.

[0081] Afterwards, based on standard SJ/T 10171.5, a surface resistance of the obtained membrane is tested to be 1.2 .Math.cm.sup.2; based on ASTM Standard D 1044-99, a wear loss of the obtained membrane is tested to be 3.8 mg.