Composite having ion exchange function and preparation method and use thereof

Abstract

A preparation method of composite materials having ion exchange function is provided. The method comprises the following steps: adding a trace of strong protonic acid and/or Lewis acid as a catalyst into the material during compounding, to allow nitrile groups of at least one nitrile group-containing ion exchange resin and nitrile groups of functional monomers grafted on the porous fluoropolymer membrane to form a triazine ring crosslinked structure.

Claims

1. A method for preparing a composite material, wherein the method comprises the following steps: adding Lewis acid and/or strong protonic acid as a catalyst into the composite material during compounding, wherein the protonic acid is selected from H.sub.2SO.sub.4, CF.sub.3SO.sub.3H or H.sub.3PO.sub.4; the Lewis acid is selected from ZnCl.sub.2, FeCl.sub.3, AlCl.sub.3, organotin, organic antimony or organic tellurium; and reacting nitrile groups of at least one nitrile group-containing ion exchange resin with nitrile groups of functional monomers grafted on a porous fluoropolymer membrane to form a triazine ring crosslinked structure, wherein the composite material comprises one or more ion exchange resins having an ion exchange function and a porous fluoropolymer membrane, said one or more ion exchange resins having an ion exchange function is/are filled in micropores of said porous fluoropolymer membrane and covered on surfaces of said porous fluoropolymer membrane; the pore surfaces of said porous fluoropolymer membrane are modified by nitrile group-containing functional monomers through grafting; at least one of the ion exchange resins forming the composite material comprises nitrile groups, and the nitrile groups and that of the functional monomers grafted on the porous fluoropolymer membrane form a triazine ring crosslinked structure.

2. The method according to claim 1, wherein the Lewis acid or protonic acid is added in an amount of 0.1˜1 wt % of the resin.

3. The method according to claim 1, wherein the method comprises the following steps: (1) mixing a solution of a high-valence metal compound and an acidic crosslinking catalyst with a dispersion solution of the ion exchange resin, and then compounding the mixed solution with nitrile group-grafted porous fluoropolymer membrane with a micropore structure by performing pouring, tape casting, screen printing process, spraying, or impregnating process; (2) subjecting a wet membrane to heat treatment at 30˜300° C. to obtain a composite material forming a triazine ring crosslinked structure; wherein a solvent used in the processes of pouring, tape casting, screen printing, spraying, impregnating and other processes of the solution, is selected from one or more of a group consisting of dimethylformamide, dimethylacetamide, methylformamide, dimethylsulfoxide, N-methylpyrrolidone, hexamethylphosphoric acid amine, acetone, water, ethanol, methanol, propanol, isopropanol, ethylene glycol and/or glycerol; preparation is performed under the following conditions: concentration of the resin dispersion solution being 1˜80%, temperature of heat treatment being 30˜300° C., and time of heat treatment being 1˜600 minutes.

4. The method according to claim 3, wherein the preparation is performed under the following conditions: concentration of the resin dispersion solution being 5˜40%, temperature of heat treatment being 120˜250° C., and time of heat treatment being 5˜200 minutes.

5. The method according to claim 3, wherein said high-valence metal compound is added in an amount of 0.0001˜5 wt % of the resin.

6. The method according to claim 3, wherein said acidic crosslinking catalyst is a protic acid and/or Lewis acid, and is added in an amount of 0.1˜1 wt % of the resin.

7. The method according to claim 3, wherein said high-valence metal compound is added in an amount of 0.001˜1 wt % of the resin.

8. The method according to claim 1, wherein said nitrile group-containing functional monomer is one or more combinations selected from substances as defined in the following formula (I): ##STR00044## wherein e=1˜3; said ion exchange resin containing nitrile groups is one or more combinations of resins as defined in the following formula (II) and/or formula (III): ##STR00045## wherein e=1˜3; n=0 or 1; m=2˜5; x, y=an integer of 3˜15; ##STR00046## wherein a, b, c=an integer of 3˜15; a′, b′, and c′=an integer of 1˜3; and j=0˜3.

9. The method according to claim 1, wherein said composite material further comprises one or more combinations of resins as defined in the following formula (IV) and/or formula (V) and/or formula (VI): ##STR00047## wherein x=3˜15; n=0˜2; p=2˜5; ion exchange capacity: 0.90˜1.60 mmol/g; ##STR00048## wherein c, d=an integer of 3˜15, and c′, an integer of 1˜3; ##STR00049## wherein f, g, h=an integer of 3˜15; f′, g′, h′=an integer of 1˜3; i=0˜3; M, M′=H, K, Na or NH.sub.4.

10. The method according to claim 9, wherein said resins as defined in the formulas (II), (III), (IV), (V) and (VI) have an ion exchange capacity of 0.80˜1.60 mmol/g and a number average molecular weight of 150,000˜450,000.

11. The method according to claim 1, wherein material of said porous fluoropolymer membrane is selected from porous polytetrafluoroethylene membrane, polytetrafluoroethylene-hexafluoropropylene membrane, porous polyvinylidene fluoride membrane (PVDF), porous polytrifluorochloroethylene membrane and porous polytetrafluoroethylene-ethylene (ETFE) membrane, which are uniaxial tensile membranes or biaxial tensile membranes; and said porous fluoropolymer membrane has a thickness of not greater than 100 μm, a porosity of 50˜97% and a pore size of 0.1˜10 μm.

12. The method according to claim 11, wherein the porous fluoropolymer membrane has a thickness of 5˜20 μm, a porosity of 60˜97%, and a pore size of 0.2˜5 μm.

13. The method according to claim 1, wherein said composite material further comprises a high-valence metal compound, part of acidic exchange groups of the ion exchange resin form physical bonding in between through the high-valence metal compound, and part of the high-valence metal compound is also a catalyst used for forming a triazine ring crosslinked structure.

14. The method according to claim 13, wherein the high-valence metal compound forming the physical bonding is one or more combinations selected from a group consisting of compounds of the following elements: W, Zr, Ir, Y, Mn, Ru, Ce, V, Zn, Ti, and La.

15. The method according to claim 13, wherein the high-valence metal compound is selected from of a group consisting of nitrates, sulfates, carbonates, phosphates, acetates of these metal elements in the highest valence state and intermediate valence state or double salts thereof; or one or more selected from a group consisting of cyclodextrins, crown ethers, acetylacetones, nitrogen-containing crown ethers and nitrogen-containing heterocyclic rings, EDTA, DMF, and DMSO complexes of these metal elements in the highest valence state and intermediate valence state; or selected from a group consisting of hydroxides of these metal elements in the highest valence state and intermediate valence state; or selected from a group consisting of oxides of these metal elements in the highest valence state and intermediate valence state which have a perovskite structure, including but not limited to compounds of Ce.sub.xTi.sub.(1-x)O.sub.2 (x=0.25˜0.4), Ca.sub.0.6La.sub.0.27TiO.sub.3, La.sub.(1-y)Ce.sub.yMnO.sub.3 (y=0.1˜0.4) and La.sub.0.7Ce.sub.0.15Ca.sub.0.15MnO.sub.3.

16. The method according to claim 13, wherein said high-valence metal compound is added in an amount of 0.0001˜5 wt % of the resin.

17. A composite material prepared by the method according to claim 1 and an ion exchange membrane comprising said composite material and a fuel cell comprising said ion exchange membrane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an ion exchange resin crosslinked and bonded with a porous membrane.

(2) FIG. 2 shows a schematic diagram illustrating chemical crosslinking.

(3) wherein “1” represents a perfluorinated ion exchange resin, “2” represents a porous membrane, “3” represents a molecule of perfluorinated ion exchange resin, and “4” represents chemical crosslinking.

(4) FIG. 3 shows a polarization curve of a single cell.

BEST MODES OF THE PRESENT INVENTION

(5) The present invention will be further illustrated in combination with embodiments, which are not used to limit the present invention.

Example 1

(6) A chqistex polytetrafluoroethylene membrane (Ningbo) with a thickness of 15 μm a porosity of 80% and a pore size of 1 μm was placed in a plasma generator and a plasma generated at a pressure of 1 Pa with Ar as working gas was grafted with the monomer

(7) ##STR00014##
(wherein e=1).

(8) The grafted polytetrafluoroethylene membrane was impregnated in an ethanol-water solution containing 25% perfluorosulfonic acid resin with a trace of triphenyltin and 1% cerium (III) nitrate, wherein the structural formula of the perfluorosulfonic acid resin is defined in formula (II).

(9) ##STR00015##
(wherein e=1; n=1; m=2; x=13; y=11, number average molecular weight: 250,000).

(10) The wet membrane was then treated at 190° C. for 20 minutes to obtain a crosslinked composite membrane with a thickness of 16 μm.

Example 2

(11) A 15% mixed perfluorosulfonic acid resin solution comprises a resin A, the structure formula of which is

(12) ##STR00016##
(x=5; n=0; p=2; exchange capacity 1.35 mmol/g, number average molecular weight: 260,000) and resin B, the structure formula of which is

(13) ##STR00017##
(e=2, n=l, m=3, x=10, y=5, number-average molecular weight 230,000). Said mixed resin solution (the mass ratio of A to B is 5:1) a (n-)propanol-water mixed solution comprising a trace of triphenyltin and also 0.2% manganese (II) nitrate, was sprayed on a chqistex polytetrafluoroethylene membrane (Ningbo) with a thickness of 10 μm, a porosity of 85% and a pore size of 0.5 μm grafted with

(14) ##STR00018##
(wherein e=2) according to the graft method in Example 1.

(15) Then a sample of the wet membrane was dried in an oven at 2,000° C. for 60 seconds. In order to block the pores in the membrane completely, this step may be repeated for more than two times. Finally, the composite membrane was treated at 150° C. for 30 minutes to obtain a composite membrane with a thickness of 20 μm.

Example 3

(16) An isopropanol-(n-)propanol-water solution with a mass concentration of 10% was prepared by a perfluorosulfonic acid resin A comprising repeating units as shown in structure formula (IV)

(17) ##STR00019##
(x=4, n=0, p=4, exchange capacity: 1.25 mmol/g, number average molecular weight: 230,000) and a perfluorosulfonic acid resin B comprising repeating units as shown in structure formula (II)

(18) ##STR00020##
(e=3, n=l, m=4, x=7, y=9, number average molecular weight: 250,000)
(the mass ratio of A to B is 5:1). The isopropanol-(n-)propanol-water solution further comprised 5% La (III)-DMF complex and a trace of triphenyltin.

(19) A chqistex polytetrafluoroethylene membrane (Ningbo) with a thickness of 10 μm, a porosity of 90% and a pore size of 2˜3 μm which was grafted with

(20) ##STR00021##
(wherein e=3) according to the graft method in Example 1 was heated with the above-mentioned isopropanol-(n-)propanol-water solution at 240° C. for 10 minutes by following the screen printing method to obtain a membrane with a thickness of 11 μm.

Example 4

(21) A polyvinylidene fluoride membrane with a thickness of 30 μm, a porosity of 79% and a pore size of 5 μm which was grafted with both

(22) ##STR00022##
(wherein e=3)
and

(23) ##STR00023##
(wherein e=1)
(mass ratio of the two monomers is 1:1) (produced by Zhejiang (Torch) Xidoumen Membrane Industry Co., Ltd according to the same grafting method as depicted in Example 1) was impregnated in the DMF solution of 5% perfluorosulfonic acid resin which was further mixed with a trace of triphenyltin and 0.05% Ce-DMF complex, wherein the structural formula of repeating units of the perfluorosulfonic acid resin is

(24) ##STR00024##
(e=3, n=l, m=4, x=7, y=11, number average molecular weight: 250,000)

(25) Then a sample of the wet membrane was dried at 100° C. for 20 seconds in an oven and then treated at 190° C. for 20 minute to obtain a composite membrane with a thickness of 31 μm.

Example 5

(26) A chqistex polytetrafluoroethylene membrane (Ningbo) with a thickness of 50 μm, a porosity of 95% and a pore size of 0.5 μm which was grafted with both

(27) ##STR00025##
(wherein e=2)
and

(28) ##STR00026##
(wherein e=1) (mass ratio of the two monomers is 1:1) according to the grafting method in Example 1, was fixed by a tensioning device around the membrane.

(29) A DMSO solution containing 30% perfluorosulfonic acid resin, 0.01% zinc nitrate and a trace of triphenyltin was sprayed on both sides of the polytetrafluoroethylene-ethylene membrane, wherein the structural formula of the perfluorosulfonic acid resin is shown in formula (III), with

(30) ##STR00027##
(a=9; b=6; c=3; a′=b′=c′=1; j=1, number average molecular weight: 250,000).

(31) Then a sample of the wet membrane was dried at 250° C. for 30 seconds in an oven. In order to block the pores in the membrane completely, this step may be repeated for more than two times. Finally, the composite membrane was treated at 200° C. for 20 minutes to obtain a composite membrane with a thickness of 50 μm.

Example 6

(32) A chqistex polytetrafluoroethylene porous membrane (Ningbo) with a thickness of 25 μm, a porosity of 70% and a pore size of 1 μm which was grafted with the two nitrile group-containing monomers that are the same as those in Example 5 (mass ratio of the two monomers is 2:1) according to the grafting method in Example 1 was fixed on a plate. And a (n-)propanol-water solution containing 20% perfluorosulfonic acid resin, 2% manganese (II) carbonate and a trace of triphenyltin was sprayed on a fixed polytrifluorochloroethylene porous membrane, wherein the structural formula of the perfluorosulfonic acid resin is shown in formula (III)

(33) ##STR00028##
(a=11; b=7; c=5; a′=b′=c′=1; j=1, number average molecular weight: 2,600,000). A sample of the wet membrane was dried at 1800° C. for 20 minutes in an oven, then the ion exchange resin contacting the polytetrafluoroethylene porous membrane was pressed into pores of the membrane through the hot pressing process to prepare a composite membrane.

Example 7

(34) A chqistex polytetrafluoroethylene membrane (Ningbo) with a thickness of 10 μm, a porosity of 80% and a pore size of 1 μm which was grafted with both

(35) ##STR00029##
(wherein e=3)
and

(36) ##STR00030##
(wherein e=1) (mass ratio of the two monomers is 1:3) according to the grafting method in Example 1 was fixed by a tensioning device around the membrane.

(37) A 30% mixed perfluorosulfonic acid resin was soaked in an NMP solution containing 5% cyclodextrin-vanadium and a trace of tetraphenylantimony; wherein the mixed perfluorosulfonic acid resin comprises resin A and resin B, the structural formula of the resin A is shown in formula (V)

(38) ##STR00031##
(c=7; d=5; c′=d′=1, number average molecular weight: 250,000) and the structural formula of the resin B is shown in formula (II),

(39) ##STR00032##
(e=2; n=1; m=3; x=9; y=10, number average molecular weight: 250,000) and the mass ratio of the resin A to resin B is 1:2 in the mixed resin solution. The mixed resin solution was tape-cast on the taut surface of the porous membrane, and the solvent was removed by gently heating with a blower. Then the other side of the porous membrane was coated with an ethanol-water solution of 14% perfluorosulfonic acid resin, wherein the structural formula of the perfluorosulfonic acid resin is shown in formula (IV)

(40) ##STR00033##
(x=4.5; n=0; p=4; exchange capacity: 1.20 mmol/g, number average molecular weight: 290,000).

(41) The ethanol-water solution was allowed to completely penetrate into the pores of the polytetrafluoroethylene membrane to reach the continuous resin layer at the first surface directly, and then a sample of the wet membrane was dried at 230° C. for 20 minutes in an oven to obtain a composite membrane.

Example 8

(42) The first surface of a chqistex polytetrafluoroethylene membrane (Ningbo) with a thickness of 80 μm, a porosity of 97% and a pore size of 4 μm which was grafted with

(43) ##STR00034##
(e=3) according to the grafting method in Example 1 was coated with a methanol-water solution containing 10% mixed perfluorosulfonic acid resin, 10% manganese sulfate and a trace of triphenyltin, wherein the mixed perfluorosulfonic acid resin comprises resin A with a structure formula as

(44) ##STR00035##
(a=9, b=7, c=5, a′=b′=c′=1, j=1, number average molecular weight: 230,000)
and resin B with a structural formula as

(45) ##STR00036##
(x=4.5; n=0; p=4; exchange capacity 1.20 mmol/g, number average molecular weight 290,000) and the mass ratio of the resin A to resin B is 1:1. Then the solvent was removed from the wetted polytetrafluoroethylene membrane by gently heating with a blower. In order to form a continuous layer of the ion exchange resin on the surface of the polytetrafluoroethylene membrane, this process were required to be repeated for more than two times. The membrane was then heated at 150° C. for 2 minutes to obtain a composite membrane.

Example 9

(46) A propanol-water solution containing 15% perfluorosulfonic acid resin as defined in structural formula (IV):

(47) ##STR00037##
(x=4, n=0, p=2, exchange capacity: 1.45 mmol/g; number average molecular weight: 270,000), 3% bipyridine-Ru complex and a trace of triphenyltin was sprayed onto a polytetrafluoroethylene membrane with a thickness of 10 μm, a porosity of 85% and a pore size of 0.5 μm which was grafted with

(48) ##STR00038##
(e=1) according to the grafting method in Example 1;

(49) Then a sample of the wet membrane was dried at 140° C. for 30 seconds in an oven. In order to block the pores in the membrane completely, this step may be repeated for more than two times. Finally, the composite membrane was treated at 1,500° C. for 30 minutes to obtain a membrane with a thickness of 20 μm.

(50) Further, a propanol-water solution of the resin comprising repeating units as shown in the structure formula (II):

(51) ##STR00039##
(e=1, n=l, m=4, x=7, y=13, number average molecular weight: 230,000) was sprayed onto the membrane obtained from the above with a thickness of 20 μm, then the membrane obtained above was composited with monolayer membrane by hot pressing to obtain a composite membrane of the present invention.

Example 10

(52) A propanol-water solution containing 15% perfluorosulfonic acid resin as defined in structural formula (IV):

(53) ##STR00040##
(x=4; n=0; p=2; exchange capacity: 1.45 mmol/g; number average molecular weight: 270,000) and a trace of triphenyltin was sprayed onto a polytetrafluoroethylene membrane with a thickness of 10 μm, a porosity of 85% and a pore size of 0.5 μm which was grafted with

(54) ##STR00041##
(e=1) according to the grafting method in Example 1.

(55) Then a sample of the wet membrane was dried at 140° C. for 30 seconds in an oven. In order to block the pores in the membrane completely, this step may be repeated for more than two times. Finally, the composite membrane was treated at 1,500° C. for 30 minutes to obtain a membrane with a thickness of 20 μm.

(56) Further, a propanol-water solution of the resin comprising repeating units as defined in structure formula (II)

(57) ##STR00042##
(e=1; n=1; m=4; x=7; y=13; number average molecular weight: 230000) was sprayed onto the membrane obtained from the above with a thickness of 20 μm. Then the membrane obtained above was composited with monolayer membrane by hot pressing to obtain a composite membrane of the present invention.

Example 11

(58) An isopropanol-propanol-water solution containing 15% perfluorosulfonic acid resin was prepared, wherein the structural formula of the perfluorosulfonic acid resin is shown in formula (IV):

(59) ##STR00043##
(x=4.6; n=0; p=4; exchange capacity: 1.18 mmol/g; number average molecular weight: 180,000).

(60) Then an ordinary composite ion membrane with a thickness of 20 μm was obtained by using a polytetrafluoroethylene membrane with a thickness of 20 μm, a porosity of 90% and a pore size of 2˜3 μm and the above isopropanol-propanol-water solution by following the screen printing method.

Example 12 Preparation and Characterization of Fuel Cell Membrane Electrode Assembly

(61) Preparation of Gas Diffusion Layer (GDL):

(62) Torry090 carbon paper was impregnated in a 25% PTFE emulsion for an appropriate period of time, followed by hydrophobic treatment The amount of the impregnated PTFE was determined by weighing method. Then the carbon paper impregnated with PTFE was placed in a muffle furnace and roasted at 340° C. so as to remove the surfactant in the PTFE emulsion impregnated in the carbon paper and also make the PTFE thermally melted and sintered and dispersed uniformly on the fibers of the carbon paper, and thereby to achieve a good hydrophobic effect. The mass fraction of PTFE in the roasted carbon paper was about 30%. A certain amount of carbon powder, PTFE, and an appropriate amount of isopropanol aqueous solution were mixed, oscillated with ultrasonic for 15 minutes, and then coated onto the carbon papers by adopting brush coating process, and the coated carbon papers were roasted at 340° C. for 30 minutes, respectively, to prepare a gas diffusion layer.

(63) Preparation of Membrane Electrode Assembly (MEA):

(64) the amount of Pt loaded in the catalyst layer was 0.4 mg/cm.sup.2; a certain amount of 40% Pt/C (JM Company) electrocatalyst, deionized water and isopropanol were mixed, oscillated with ultrasonic wave for 15 minutes; after adding a certain amount of 5% resin solution of Example 12, ultrasonic oscillation was proceeded for another 15 minutes; after the solution turned ito an ink-like solution through ultrasonic processing, the mixed solution was sprayed onto the membrane of Example 2 uniformly to obtain a membrane electrode assembly (MEA).

(65) The prepared membrane electrode assembly and the leveled gas diffusion layer were combined to assemble a single cell, and galvanostatic polarization performance test was performed in a self-designed dual-channel low-power testing platform under test conditions as follows: effective active area of a single cell was 50 cm.sup.2; pressures of H.sub.2 and air were both 1.0 bar; H.sub.2 utilization rate was 70%; air utilization rate was 40%, relative humidity was 50%; and cell operating temperature was (95)° C. The polarization curve test was performed after the prepared electrode was activated, and the data was recorded at an interval of 1 minute after the respective measuring points were stabilized for 2 minutes so as to draw a polarization curve (FIG. 3).

Example 13

(66) This example is used to illustrate various performances of the composite membranes prepared in Examples 1-11.

(67) The performances of all membranes were characterized and the results are shown in Table 1. It can be seen from Table 1 that the electrical conductivity at 95° C., tensile strength, hydrogen permeation current, dimensional change rate, and other performances of the composite membrane of the present invention are all superior to those of an ordinary composite ion exchange membrane. The test conditions of the electrical conductivity value were as follows: T=95° C., under saturated humidity; and T=25° C., dried in a drier for two days; the method for testing the tensile strength was a GB standard method (GB/T20042.3-2009), and the method for testing the hydrogen permeation current was an electrochemical method (Electrochemical and Solid-State Letters, 10, 5, B101-B104, 2007).

(68) TABLE-US-00001 TABLE 1 Characteristics of various membranes Testing Condition Nos. and Method Results Electrical Membrane of Example 10 T = 95° C., under 0.0310/0.0119 Conductivity Membrane of Example 11 saturated humidity; or 0.0216/0.0041 (S/cm) Membrane of Example 1 T = 25° C., dried in 0.0286/0.0108 Membrane of Example 2 a drier for two days 0.0275/0.0131 Membrane of Example 3 0.0292/0.0113 Membrane of Example 4 0.0287/0.0118 Membrane of Example 5 0.0298/0.0119 Membrane of Example 6 0.0297/0.0113 Membrane of Example 7 0.0299/0.0111 Membrane of Example 8 0.0301/0.0132 Membrane of Example 9 0.0312/0.0119 Tensile Membrane of Example 10 GB standard 33 Strength Membrane of Example 11 method 30 (MPa) Membrane of Example 1 36 Membrane of Example 2 35 Membrane of Example 3 36 Membrane of Example 4 35 Membrane of Example 5 34 Membrane of Example 6 37 Membrane of Example 7 35 Membrane of Example 8 38 Membrane of Example 9 36 Hydrogen Membrane of Example 10 Electrochemical 2.1 Permeation Membrane of Example 11 method >4 Current Membrane of Example 1 0.12 (mA/cm.sup.2) Membrane of Example 2 0.12 Membrane of Example 3 0.09 Membrane of Example 4 0.10 Membrane of Example 5 0.11 Membrane of Example 6 0.11 Membrane of Example 7 0.09 Membrane of Example 8 0.08 Membrane of Example 9 0.09 Dimensional Membrane of Example 10 (GB/T20042.3- 2.5 Change Rate Membrane of Example 11 2009) 8.1 (%) Membrane of Example 1 0.6 Membrane of Example 2 1.1 Membrane of Example 3 0.6 Membrane of Example 4 1.0 Membrane of Example 5 1.1 Membrane of Example 6 1.6 Membrane of Example 7 1.1 Membrane of Example 8 1.2 Membrane of Example 9 1.4