Perfluorinated ternary resin copolymer containing bifunctional groups and preparation method thereof

Abstract

The invention provides a perfluorinated ternary resin copolymer containing bifunctional groups, which at least comprises a repeating unit A, a repeating unit B and a repeating unit C. The structural general formula of the repeating unit A is # imgabs0 #, and the structural general formula of the repeating unit B contains-SO2F or-SO3M; the structural general formula of the repeating unit C contains-COF or-COON. Therefore, the swelling property of the copolymer can be reduced, the tolerance of the resin copolymer to metal ions can be improved, and the chemical durability can be improved to better resist attack of free radicals, so that the prepared resin copolymer film can better adapt to the process requirements of preparing alkali from waste salt; when the material is applied to fuel cells (PEM hydrogen production), flow cells, electrolytic cells (carbon monoxide production from carbon dioxide, hypochlorous acid, hydrogen peroxide, TMA, TMAH and the like) and the like, the performance of the device is also improved (for example, the service life of a seawater direct electrolytic cell is greatly prolonged).

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and relates to a perfluoroternary resin copolymer, specifically to a perfluoroternary resin copolymer containing bifunctional groups and a preparation method thereof. Background Art

[0002] Ion-exchange membrane caustic soda is produced by electrolyzing brine using the ion-exchange membrane method to produce caustic soda (i.e., sodium hydroxide). The main principle is that a cation-exchange membrane is used, which has special selective permeability, allowing only cations to pass through while blocking anions and gases. Ion-exchange membrane caustic soda is a process commonly used in the world's chlor-alkali industry. The emergence and improvement of this method have brought revolutionary progress to the chlor-alkali industry. The ion-exchange membrane method process uses a selective ion-exchange membrane to separate the anode chamber and the cathode chamber, and can obtain a high-purity caustic soda solution. The ion-exchange membrane method is superior to the diaphragm method and the mercury method in terms of power consumption, construction cost, product quality, and environmental protection. It is recognized as the development direction of modern chlor-alkali, and is also an embodiment of the promotion and application of new materials in industry and the promotion of technological progress. Moreover, industries such as fuel cells (such as PEM hydrogen production), flow batteries, and electrolysis currently mainly use pure perfluorosulfonic acid resin membranes.

[0003] The perfluorinated ion-exchange membrane, as the core material of the chlor-alkali device, is usually composed of a perfluorosulfonic acid membrane, a perfluorocarboxylic acid membrane, and a polytetrafluoroethylene reinforcing mesh cloth, and hydrophilic coatings are attached to both sides of the membrane. The Chinese invention patent with the application number 2014102494082 discloses an ion-conducting membrane and a preparation method thereof, which is composed of a perfluorinated ion-exchange resin base membrane, a porous reinforcing material, and a perfluorosulfonic acid resin microparticle surface layer. The perfluorinated ion-exchange resin base membrane is composed of a resin layer mainly based on perfluorosulfonic acid resin and a resin layer mainly based on perfluorocarboxylic acid resin. The surface layer of this application has good compatibility and adhesiveness, so it can ensure good degassing effect during the entire service life of the ion-conducting membrane. It can be used in the chlor-alkali industry to stably and efficiently process alkali metal chloride solutions with a wide range of concentrations, and is suitable for operating in a zero-pole-distance electrolytic cell under new high-current density conditions, with very excellent product purity indicators. However, the above-mentioned ion-conducting membrane needs to set a perfluorosulfonic acid resin microparticle surface layer on the surface of the porous reinforcing material, and the structure and process are relatively complex, and there is still room for improvement in the metal ion tolerance and mechanical properties. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a perfluoroternary resin copolymer containing bifunctional groups, which can achieve higher performance adjustment and improve the mechanical strength and chemical stability of the membrane.

[0005] To achieve the above technical objectives, the present invention provides a perfluoroternary resin copolymer containing bifunctional groups, which at least comprises repeating unit A, repeating unit B and repeating unit C.

[0006] The general structural formula of the repeating unit A is

[0007] The general structural formula of the repeating unit B contains -SO2F or -SO3M, where M is H, Na, K or Li.

[0008] The general structural formula of the repeating unit C contains -COF or -COON, where N is H, Na, K or Li.

[0009] Optimally, the general structural formula of the repeating unit B is where m is 0 to 8 and n is 1 to 5.

[0010] Optimally, the general structural formula of the repeating unit C is where m is 0 to 8 and n is 1 to 5.

[0011] Another object of the present invention is to provide a preparation method of the above perfluoroternary resin copolymer containing bifunctional groups, which comprises the following steps:

[0012] (a) Mix tetrafluoroethylene with a first perfluorovinyl ether monomer and a second perfluorovinyl ether monomer to obtain a monomer mixture; the first perfluorovinyl ether monomer is a perfluorovinyl ether monomer containing -SO2F or -SO3M, and the second perfluorovinyl ether monomer is a perfluorovinyl ether monomer containing -COF or -COON;

[0013] (b) Carry out a free radical copolymerization reaction on the monomer mixture at a pressure of 1.0 to 3.0 MPa and a temperature of 60 to 90 °C to obtain a copolymer;

[0014] (c) Purify and dry the copolymer, and then form a film by melt extrusion or solution casting.

[0015] Optimally, in step (a), the mass percentages of the tetrafluoroethylene, the first perfluorovinyl ether monomer and the second perfluorovinyl ether monomer are 40 to 70%: 10 to 30%: 5 to 30%.

[0016] Optimally, in step (b), the free radical copolymerization reaction is initiated by an initiator in water containing a surfactant; the surfactant is sodium perfluorooctanoate, and its dosage is 0.1 to 0.4% of the total mass of the monomer mixture and water; the initiator is ammonium persulfate, and its dosage is 0.1 to 0.4% of the total mass of the monomer mixture and water; the reaction time is 1 to 4 h.

[0017] Preferably, in step (c), the purification is performed by washing the copolymer with water multiple times to remove unreacted monomers and by-products.

[0018] Further, in step (c), the drying is carried out at 80 - 200 °C for 2 - 24 h.

[0019] Furthermore, in step (c), the melt extrusion is to granulate the dried copolymer at a temperature of 200 - 300 °C, and then co-extrude with a multi-layer or single-layer extruder at a temperature of 150 - 300 °C to obtain a copolymer film.

[0020] Furthermore, in step (c), the solution casting is to disperse the dried copolymer in an organic solvent, and after casting, dry it at 60 - 220 °C to obtain a copolymer film; the solid content of the copolymer in the organic solvent is 5% - 50%, and the organic solvent is one or more selected from DMC, DMA, DMSO, methanol, ethanol, isopropanol, ethylene glycol, and n-propanol.

[0021] The perfluoroternary resin copolymer containing bifunctional groups of the present invention (i.e., the perfluoroternary resin copolymer containing both sulfonic acid groups and carboxylic acid groups) forms a structure containing at least repeating unit A, repeating unit B, and repeating unit C in the copolymer main chain, such that repeating unit B and repeating unit C have specific structures, which can reduce the swelling property of the copolymer, improve the tolerance of the resin copolymer to metal ions, and can also improve chemical durability to better resist the attack of free radicals, avoiding the disadvantages of blending perfluorosulfonic acid resin membranes and carboxylic acid resin membranes (the carboxylic acid resin in the blended membrane will reduce the proton conduction ability, and the swelling property of the sulfonic acid resin and the barrier property to OH - ions are not as good as those of the carboxylic acid membrane) to ensure the smoothness of the proton conduction channel and block OH-, so that the resin copolymer membrane made can better meet the requirements of the waste salt to alkali process, and also improve the performance of devices (such as greatly improving the life of a seawater direct electrolysis cell) when applied in fuel cells (PEM hydrogen production), flow batteries, electrolytic cells (carbon dioxide to carbon monoxide, hypochlorous acid, hydrogen peroxide, TMAH (tetramethylammonium hydroxide), etc.). Detailed Embodiments

[0022] The perfluoroternary resin copolymer containing bifunctional groups of the present invention at least comprises repeating unit A, repeating unit B, and repeating unit C, and the general structural formula of repeating unit A is The general structural formula of repeating unit B contains -SO2F or -SO3M, where M is H, Na, K, or Li; the general structural formula of repeating unit C contains -COF or -COON, where N is H, Na, K, or Li.

[0023] The structural general formula of the repeating unit B is In the formula, m is from 0 to 8, and n is from 1 to 5. The structural general formula of the repeating unit C is In the formula, m is from 0 to 8, and n is from 1 to 5. By forming a structure containing at least the repeating unit A, the repeating unit B, and the repeating unit C in the copolymer main chain, the repeating unit B and the repeating unit C have specific structures, which can reduce the swelling property of the copolymer, improve the tolerance of the resin copolymer to metal ions, and can also improve the chemical durability to better resist the attack of free radicals, avoiding the disadvantages of blending perfluorosulfonic acid resin membranes and carboxylic resin membranes (the carboxylic resin in the blended membrane will reduce the proton conduction ability, and the swelling property of the sulfonic acid resin and the barrier performance to OH - radicals are not as good as those of the carboxylic acid membrane) to ensure the smoothness of the proton conduction channel and block OH - , so that the resin copolymer membrane made can better meet the requirements of the waste salt to alkali process, and the performance of devices such as fuel cells (PEM hydrogen production), flow batteries, electrolytic cells (carbon dioxide to carbon monoxide, hypochlorous acid, hydrogen peroxide, TMAH (tetramethylammonium hydroxide), etc.) is also improved (such as greatly improving the life of a seawater direct electrolysis cell).

[0024] The preparation method of the above perfluoroternary resin copolymer containing bifunctional groups includes the following steps: mixing tetrafluoroethylene with a first perfluoro vinyl ether monomer and a second perfluoro vinyl ether monomer to obtain a monomer mixture; the first perfluoro vinyl ether monomer is a perfluoro vinyl ether monomer containing -SO2F or -SO3M, and the second perfluoro vinyl ether monomer is a perfluoro vinyl ether monomer containing -COF or -COON; (b) carrying out a free radical copolymerization reaction on the monomer mixture under a pressure of 1.0 to 3.0 MPa and a temperature of 60 to 90 °C to obtain a copolymer; (c) purifying and drying the copolymer, and then forming a film by melt extrusion or solution casting.

[0025] Among them, commercially available tetrafluoroethylene can be used, such as it can be purchased from Shandong Huaxia Shenzhou New Materials Co., Ltd. For the perfluoro vinyl ether monomer containing a sulfonic acid group, conventional ones can be used. For example, the method in Example 5 of the Chinese invention patent with the application number 201810798170.7 can be referred to for preparation for the following examples. When the structural general formula of the repeating unit C contains a carboxylic acid group, a perfluoro vinyl ether monomer containing a carboxylic acid group is usually selected and prepared by conventional existing methods (Hu Changming et al. reported that perfluorosulfonates can be converted into corresponding perfluorocarboxylic acids at room temperature and under light conditions. See "Synthesis Method of Perfluorocarboxylic Acids" in the 4th issue of "Organic Fluorine Industry" in 2020), and is used in the following examples.

[0026] In step (a), the mass ratio of the tetrafluoroethylene, the first perfluorovinyl ether monomer, and the second perfluorovinyl ether monomer is preferably 40-70%: 10-30%: 5-30%. In step (b), the free radical copolymerization reaction is initiated by an initiator in water containing a surfactant; the surfactant is sodium perfluorooctanoate, and its dosage is 0.1-0.4% of the total mass of the monomer mixture and water; the initiator is ammonium persulfate, and its dosage is 0.1-0.4% of the total mass of the monomer mixture and water; the reaction time is 1-4 h. In step (c), the purification is to wash the copolymer with water multiple times to remove unreacted monomers and by-products. The drying is carried out at 80-200 °C for 2-24 h. The melt extrusion is to granulate the dried copolymer at a temperature of 200-300 °C, and then co-extrude it with a multi-layer or single-layer extruder at a temperature of 150-300 °C to obtain a copolymer film. The solution casting is to disperse the dried copolymer in an organic solvent, and after casting, dry it at 60-220 °C to obtain a copolymer film; the solid content of the copolymer in the organic solvent is 5%-50%, and the organic solvent is one or more selected from DMC, DMA, DMSO, methanol, ethanol, isopropanol, ethylene glycol, and n-propanol.

[0027] The preferred embodiments of the present invention will be described in detail below.

[0028] Example 1

[0029] This example provides a perfluoroternary resin copolymer containing a bifunctional group and a preparation method thereof, which are specifically as follows:

[0030] (a) Mix tetrafluoroethylene (TFE, 100 g) with the first perfluorovinyl ether monomer (CF2=CF-O-CF2-CF2-SO3H, 30 g) and the second perfluorovinyl ether monomer ( m = 1, 10 g) to obtain a monomer mixture;

[0031] (b) Add the monomer mixture (take 40 g) to water (200 g) containing a surfactant (ammonium perfluorohexanoate, 0.2% of the total mass of the monomer mixture and water) and an initiator (ammonium persulfate, 0.2% of the total mass of the monomer mixture and water), and carry out a free radical copolymerization reaction at a pressure of 2.0 MPa and a temperature of 60 °C for 8 h to obtain a copolymer;

[0032] (c) Purify the copolymer (wash the copolymer 3 times with water to remove unreacted monomers and by-products), dry it (dry at 80 °C for 12 hours), then granulate the dried copolymer at a temperature of 200 °C, and then extrude it with a single-layer extruder at a temperature of 250 °C to obtain a copolymer film (control the thickness to be 200 μm).

[0033] Example 2

[0034] This example provides a perfluoroternary resin copolymer containing bifunctional groups and its preparation method, which is basically the same as that in Example 1, except that: in step (a), tetrafluoroethylene (TFE, 100 g) is mixed with a first perfluoro vinyl ether monomer (CF2=CF-O-CF2-CF2-SO3H, 75 g) and a second perfluoro vinyl ether monomer ( m = 1, 75 g) to obtain a monomer mixture.

[0035] Example 3

[0036] This example provides a perfluoroternary resin copolymer containing bifunctional groups and its preparation method, which is basically the same as that in Example 1, except that: in step (a), tetrafluoroethylene (TFE, 100 g) is mixed with a first perfluoro vinyl ether monomer (CF2=CF-O-CF2-CF2-SO3H, 14.3 g) and a second perfluoro vinyl ether monomer ( m = 1, 7.1 g) to obtain a monomer mixture.

[0037] Example 4

[0038] This example provides a perfluoroternary resin copolymer containing bifunctional groups and its preparation method, which is basically the same as that in Example 1, except that: in step (a), tetrafluoroethylene (TFE, 100 g) is mixed with a first perfluoro vinyl ether monomer (CF2=CF-O-CF2-CF2-SO3H, 10 g) and a second perfluoro vinyl ether monomer ( m = 1, 10 g) to obtain a monomer mixture.

[0039] Example 5

[0040] This example provides a perfluoroternary resin copolymer containing bifunctional groups and its preparation method, which is basically the same as that in Example 1, except that: in step (a), tetrafluoroethylene (TFE, 100 g) is mixed with a first perfluoro vinyl ether monomer (CF2=CF-O-CF2-CF2-SO3H, 20 g) and a second perfluoro vinyl ether monomer ( m = 1, 10 g) to obtain a monomer mixture.

[0041] Example 6

[0042] This embodiment provides a perfluoroternary resin copolymer containing a bifunctional group and a preparation method thereof, which is basically the same as that in Embodiment 1, except that: in step (a), tetrafluoroethylene (TFE, 100 g) is mixed with a first perfluorovinyl ether monomer (CF2=CF-O-CF2-CF2-SO3H, 40 g) and a second perfluorovinyl ether monomer ( m = 1, 10 g) to obtain a monomer mixture.

[0043] Embodiment 7

[0044] This embodiment provides a perfluoroternary resin copolymer containing a bifunctional group and a preparation method thereof, which is basically the same as that in Embodiment 1, except that: in step (a),

[0045] tetrafluoroethylene (TFE, 100 g) is mixed with a first perfluorovinyl ether monomer (CF2=CF-O-CF2-CF2-SO3H, 50 g) and a second perfluorovinyl ether monomer ( m = 1, 10 g) to obtain a monomer mixture.

[0046] Comparative Example 1

[0047] This embodiment provides a perfluoroternary resin copolymer and a preparation method thereof, which is basically the same as that in Embodiment 1, except that: in step (a), the second perfluorovinyl ether monomer is not contained.

[0048] Comparative Example 2

[0049] This embodiment provides a preparation method of a polymer, which is basically the same as that in Embodiment 1, except that: steps (a) and (b) are not carried out, and in step (c), perfluorosulfonic acid resin (30 g) and perfluorocarboxylic acid resin (10) are directly mixed, granulated at a temperature of 200 °C, and then extruded with a single-layer extruder at a temperature of 250 °C to obtain a copolymer film.

[0050] The polymer films prepared in Embodiments 1-7 and Comparative Examples 1-2 were subjected to performance tests, and the results are listed in Table 1.

[0051] Table 1 Performance test table of the polymer films prepared in Embodiments 1-7 and Comparative Examples 1-2

[0052]

[0053] Note: The test method mainly refers to the actual use specification of ion membranes in Section 4.4 of <Modern Chlor-Alkali Handbook> 2020 edition and the national standard GBT-30297-2013.

[0054] Direct power consumption test CV (V) test basic conditions: current density 6 KA / m2 , at 80 - 90 °C, the brine solution at the anode inlet is 270 - 320 g / L NaCl, the concentration at the anode outlet is 210 g / L, and at the cathode caustic outlet, the NaOH concentration is 32 wt% (testing started after 2000 hours of stable operation).

[0055] Test conditions for chlorine purity (%) in the case of metal Ni contamination: The test conditions are the same as those for the direct power consumption test. The only difference is that the ion-exchange membrane is pre-soaked in a nickel solution, a single-element standard solution of nickel standard solution, Ni ion standard sample GNM-SNI-002-2013, nickel 100 μg / ml for 1 minute.

[0056] Test conditions for chlorine purity (%) in the case of Si / Al impurity contamination: The test conditions are the same as those for the direct power consumption test. The difference is that Al powder and SiO2 are added to the anode brine solution, with Al and SiO2 being 1 ppm and 30 ppm respectively, and the current density is increased to 8 kA / m 2 .

[0057] Test conditions for linear swelling: From 50% RH, 23 °C (73 °F) to immersion in water at 100 °C (212 °F).

[0058] As described above, it is only the preferred specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. A perfluoroternary resin copolymer containing bifunctional groups, which at least comprises repeating unit A, repeating unit B and repeating unit C, and is characterized in that: The structural general formula of the repeating unit A is In the structural general formula of the repeating unit B, it contains -SO2F or -SO3M, where M is H, Na, K or Li; In the structural general formula of the repeating unit C, it contains -COF or -COON, where N is H, Na, K or Li.

2. The perfluoroternary resin copolymer containing bifunctional groups according to claim 1, wherein: The structural general formula of the repeating unit B is wherein, m is 0 to 8, and n is 1 to 5.

3. The perfluoroternary resin copolymer containing a bifunctional group according to claim 1, characterized in that: The structural general formula of the repeating unit C is In the formula, m is 0 to 8 and n is 1 to 5.

4. The preparation method of the perfluoroternary resin copolymer containing a bifunctional group according to any one of claims 1 to 3, characterized in that, It includes the following steps: (a) Mix tetrafluoroethylene with a first perfluorovinyl ether monomer and a second perfluorovinyl ether monomer to obtain a monomer mixture; the first perfluorovinyl ether monomer is a perfluorovinyl ether monomer containing -SO2F or -SO3M, and the second perfluorovinyl ether monomer is a perfluorovinyl ether monomer containing -COF or -COON; (b) Carry out a radical copolymerization reaction on the monomer mixture at a pressure of 1.0 - 3.0 MPa and a temperature of 60 - 90 °C to obtain a copolymer; (c) Purify and dry the copolymer, and then form a film by melt extrusion or solution casting.

5. The preparation method of the perfluoroternary resin copolymer containing bifunctional groups according to claim 4, characterized in that: In step (a), the mass percentages of the tetrafluoroethylene, the first perfluorovinyl ether monomer and the second perfluorovinyl ether monomer are 40 - 70%: 10 - 30%: 5 - 30%.

6. The preparation method of the perfluoroternary resin copolymer containing bifunctional groups according to claim 4, characterized in that: In step (b), the radical copolymerization reaction is initiated by an initiator in water containing a surfactant; the surfactant is sodium perfluorooctanoate, and its dosage is 0.1 - 0.4% of the total mass of the monomer mixture and water; the initiator is ammonium persulfate, and its dosage is 0.1 - 0.4% of the total mass of the monomer mixture and water; the reaction time is 1 - 4 h.

7. The preparation method of the perfluoroternary resin copolymer containing bifunctional groups according to claim 4, characterized in that: In step (c), the purification is to wash the copolymer with water multiple times to remove unreacted monomers and by-products.

8. The preparation method of the perfluoroternary resin copolymer containing bifunctional groups according to claim 7, characterized in that: In step (c), the drying is carried out at 80 - 200 °C for 2 - 24 h.

9. The preparation method of the perfluoroternary resin copolymer containing a bifunctional group according to claim 8, characterized in that: In step (c), the melt extrusion is to granulate the dried copolymer at a temperature of 200 - 300 °C, and then co-extrude with a multi-layer or single-layer extruder at a temperature of 150 - 300 °C to obtain a copolymer film.

10. The preparation method of the perfluoroternary resin copolymer containing bifunctional groups according to claim 8, characterized in that: In step (c), the solution casting is to disperse the dried copolymer in an organic solvent, and obtain a copolymer film after drying at 60 - 220 °C after casting; the solid content of the copolymer in the organic solvent is 5% - 50%, and the organic solvent is one or more selected from DMC, DMA, DMSO, methanol, ethanol, isopropanol, ethylene glycol and n-propanol.

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