An improved method for the preparation of perfluorosulfonic acid ion exchange membranes by melt extrusion blow molding, the membranes prepared by the method and applications thereof

Abstract

This invention provides an improved method for preparing perfluorosulfonic acid ion exchange membranes by melt extrusion blow molding, as well as the films prepared by this method and their applications. The method includes the following steps: (1) mixing materials containing perfluorosulfonic acid fluorine resin, sulfonated graphene and additives in a mixer in proportion, extruding and granulating them using a vented twin-screw extruder, cooling and drying to obtain a masterbatch; the mass ratio of perfluorosulfonic acid fluorine resin, sulfonated graphene and 2,5-diamino-terephthalic acid is 100:10-20:1-3; (2) feeding the masterbatch obtained in step (1) into a single-screw extruder, melt extruding and blow molding it into a film through a blown film die head, and obtaining a perfluorosulfonic acid ion exchange membrane after cooling; (3) saponifying the perfluorosulfonic acid ion exchange membrane obtained in step (2) with NaOH methanol solution to obtain a sodium perfluorosulfonate type perfluorosulfonic acid hydrogen type ion exchange membrane; or reacting the perfluorosulfonic acid ion exchange membrane obtained in step (2) with HCl solution to obtain a perfluorosulfonic acid hydrogen type ion exchange membrane.

Description

Technical Field

[0001] This invention relates to the field of perfluorosulfonic acid ion exchange membrane preparation, and more specifically to an improved method for preparing perfluorosulfonic acid ion exchange membranes by melt extrusion blow molding, as well as the thin films prepared by this method and their applications. Background Technology

[0002] Perfluorosulfonic acid ion exchange membranes (PFSIEMs) are perfluoropolymers with a polytetrafluoroethylene (PTFE) backbone and alkylene ether structures with sulfonate groups at the ends as side chains. They possess excellent chemical and thermal stability, making them excellent ion exchange carriers. Therefore, PFSIEMs are widely used in chlor-alkali ion exchange membranes and fuel cell membranes. Perfluorosulfonic acid ion exchange resins and membranes also offer unparalleled advantages over other materials in various electrolytic preparation devices, electrodialysis, chemical catalysis, gas separation, gas drying, wastewater treatment, and seawater desalination.

[0003] Currently, perfluorosulfonic acid ion exchange membranes prepared by melt extrusion blow molding have high thickness precision and advantages such as uniform longitudinal and transverse strength, no need for edge trimming, flexible thickness and width variations, and high production efficiency. However, blow molding of perfluorosulfonic acid ion exchange membranes presents significant technical challenges because the properties of perfluorosulfonic acid resin itself do not meet the requirements for blow molding. For example, the presence of small amounts of volatiles adversely affects the blow-molded film, easily leading to numerous pinhole-like pores caused by volatiles; the resin is a shear-thinning non-Newtonian fluid, and its melt viscosity changes significantly with shear rate. During the blow molding process, the fluidity and viscoelasticity do not meet the requirements, easily causing film rupture and making film formation difficult. Summary of the Invention

[0004] In view of the problems existing in the background technology, the purpose of the present invention is to provide an improved method for preparing perfluorosulfonic acid ion exchange membranes by melt extrusion blow molding. By modifying the perfluorosulfonic acid fluorinated resin to meet the requirements of blow molding, a perfluorosulfonic acid ion exchange membrane with thinner and more uniform thickness, good dimensional stability and high mechanical strength is obtained. Furthermore, the conductivity of the ion membrane is improved after saponification or acidification treatment, which meets the requirements of practical use.

[0005] To achieve the above objectives, the present invention provides an improved method for preparing perfluorosulfonic acid ion exchange membranes by melt extrusion blow molding, comprising the following steps: (1) mixing materials containing perfluorosulfonic acid fluorinated resin, sulfonated graphene and additives in a mixer in proportion, extruding and granulating the mixture using a vented twin-screw extruder, cooling and drying the mixture to obtain a masterbatch; the mass ratio of perfluorosulfonic acid fluorinated resin, sulfonated graphene and 2,5-diamino-terephthalic acid is 100:10-20:1-3; (2) feeding the masterbatch obtained in step (1) into a single-screw extruder, melt extruding the mixture and blow molding it into a film using a blown film die head, and cooling the film to obtain a perfluorosulfonic acid ion exchange membrane; (3) saponifying the perfluorosulfonic acid ion exchange membrane obtained in step (2) with NaOH methanol solution to obtain a sodium perfluorosulfonate type perfluorosulfonic acid hydrogen type ion exchange membrane; or reacting the perfluorosulfonic acid ion exchange membrane obtained in step (2) with HCl solution to obtain a perfluorosulfonic acid hydrogen type ion exchange membrane.

[0006] Optionally, the additive is 2,5-diaminoterephthalic acid.

[0007] Optionally, the exhaust port of the exhaust-type twin-screw extruder in step (1) is connected to a vacuum pump, with a vacuum degree of 0.1-0.5MPa; the temperature of each section of the exhaust-type twin-screw extruder is 280-340℃, and the die head temperature is 290-310℃.

[0008] Optionally, the temperature of each section of the single screw extruder in step (2) is 260-330℃, and the temperature of the die head is 280-300℃.

[0009] Optionally, the vented twin-screw extruder of step (1) and the single-screw extruder of step (2) have a screw, barrel and die made of corrosion-resistant nickel-based alloy steel.

[0010] Optionally, the IEC value of the perfluorosulfonic acid ion-exchange membrane resin is 0.97-1.05.

[0011] Optionally, the sulfonated graphene has fewer than 10 layers, a radial dimension of 200 nm to 800 nm, a thickness of 6 to 500 nm, and an S element content of 0.5 to 18 wt%.

[0012] The present invention also provides a perfluorosulfonic acid ion exchange membrane prepared by the method described above.

[0013] The present invention also provides an application of the perfluorosulfonic acid ion exchange membrane as described above, wherein the perfluorosulfonic acid ion exchange membrane is used in fuel cells, lithium batteries, vanadium batteries, chlor-alkali electrolysis, gas separation and photocatalysis.

[0014] The beneficial effects of this invention are as follows:

[0015] 1. This paper describes a method that melts perfluorosulfonic acid fluororesin into a liquid state at high temperature without using solvents, thus solving the problems of human health damage and environmental pollution caused by solvent volatilization.

[0016] 2. By using sulfonated graphene and 2,5-diaminote-terephthalic acid to dope and modify perfluorosulfonic acid fluororesin, the perfluorosulfonic acid fluororesin can maintain stable fluidity during high-temperature processing, reduce non-Newtonian fluid properties, and its melt flow index (MFR) can be stably maintained between 1.6 and 2.6, possessing suitable melt strength. Thus, perfluorosulfonic acid ion exchange membranes can be successfully prepared using melt extrusion blow molding.

[0017] 3. The perfluorosulfonic acid ion exchange membrane prepared by melt extrusion blow molding of this invention has a membrane thickness of 15-20 μm, a thickness error range of 0.5 μm, an electrical conductivity of over 125 mS / cm at 25℃, a dimensional change rate of 0.5-1%, and a tensile strength of 35-40 MPa. Detailed Implementation

[0018] To make the above-mentioned objects, features and advantages of the invention more apparent and understandable, the specific embodiments of the invention are described in detail below.

[0019] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0020] The improved method for preparing perfluorosulfonic acid ion exchange membranes by melt extrusion blow molding according to the present invention includes the following steps: (1) mixing materials containing perfluorosulfonic acid fluorine type resin, sulfonated graphene and additives in a mixer in proportion, extruding and granulating them by a vented twin-screw extruder, cooling and drying to obtain masterbatch; the mass ratio of perfluorosulfonic acid fluorine type resin, sulfonated graphene and 2,5-diamino-terephthalic acid is 100:10-20:1-3; (2) feeding the masterbatch obtained in step (1) into a single-screw extruder, melt extruding and blow molding it into a film through a blown film die head, and obtaining perfluorosulfonic acid ion exchange membrane after cooling; (3) saponifying the perfluorosulfonic acid ion exchange membrane obtained in step (2) with NaOH methanol solution to obtain sodium perfluorosulfonate type perfluorosulfonic acid hydrogen type ion exchange membrane; or reacting the perfluorosulfonic acid ion exchange membrane obtained in step (2) with HCl solution to obtain perfluorosulfonic acid hydrogen type ion exchange membrane.

[0021] In the improved melt extrusion blow molding method for preparing perfluorosulfonic acid ion exchange membranes according to the present invention, the additive may be 2,5-diaminoterephthalic acid.

[0022] In the improved melt extrusion blow molding method for preparing perfluorosulfonic acid ion exchange membranes according to the present invention, the exhaust port of the vented twin-screw extruder in step (1) can be connected to a vacuum pump, and the vacuum degree can be 0.1-0.5 MPa; the temperature of each section of the vented twin-screw extruder can be 280-340°C, and the die head temperature can be 290-310°C.

[0023] In the improved melt extrusion blow molding method for preparing perfluorosulfonic acid ion exchange membranes according to the present invention, the temperature of each section of the single screw extruder in step (2) can be 260-330°C, and the die head temperature can be 280-300°C.

[0024] In the improved melt extrusion blow molding method for preparing perfluorosulfonic acid ion exchange membranes according to the present invention, the vented twin-screw extruder in step (1) and the single-screw extruder in step (2) may have a screw, barrel and die made of corrosion-resistant nickel-based alloy steel.

[0025] In the improved melt extrusion blow molding method for preparing perfluorosulfonic acid ion exchange membranes according to the present invention, the IEC value of the perfluorosulfonic acid ion exchange membrane resin may be 0.97-1.05.

[0026] In the improved melt extrusion blow molding method for preparing perfluorosulfonic acid ion exchange membrane according to the present invention, the sulfonated graphene may have fewer than 10 layers, a radial dimension of 200 nm to 800 nm, a thickness of 6 to 500 nm, and an S element content of 0.5 to 18 wt%.

[0027] The present invention also provides a perfluorosulfonic acid ion exchange membrane prepared by the method described above.

[0028] The perfluorosulfonic acid ion exchange membrane according to the present invention is used in fuel cells, lithium batteries, vanadium batteries, chlor-alkali electrolysis, gas separation and photocatalysis.

[0029] Example 1

[0030] 10 kg of perfluorosulfonic acid fluorinated resin with a molecular weight of approximately 100,000, 2 kg of sulfonated graphene, and 0.3 kg of 2,5-diaminote-terephthalic acid were thoroughly mixed and fed into a vented twin-screw extruder with a screw diameter of 20 mm and an aspect ratio of 40 mm, made of corrosion-resistant nickel-based alloy steel. The mixture was melt-extruded and granulated, cooled, and dried to obtain masterbatch. The vented twin-screw extruder was connected to a vacuum pump with a vacuum degree of 0.1 MPa. The temperature of each section of the vented twin-screw extruder was 280-320°C, and the die head temperature was 290°C.

[0031] The masterbatch is added to a single-screw extruder made of corrosion-resistant nickel-based alloy steel, melt-extruded and blown into a film through a blown film die head, and the formed film is dried and rolled up to obtain a perfluorosulfonic acid ion membrane.

[0032] The membrane was saponified with NaOH methanol solution and reacted with HCl solution to obtain sodium perfluorosulfonate type and hydrogen perfluorosulfonate type ion exchange membranes, respectively.

[0033] Example 2

[0034] 10 kg of perfluorosulfonic acid fluorinated resin with a molecular weight of 300,000, 1 kg of sulfonated graphene, and 0.1 kg of 2,5-diaminote-terephthalic acid were thoroughly mixed and fed into a vented twin-screw extruder with a screw diameter of 20 mm and an aspect ratio of 40 mm, made of corrosion-resistant nickel-based alloy steel. The mixture was melt-extruded and granulated, cooled, and dried to obtain masterbatch. The vent of the vented twin-screw extruder was connected to a vacuum pump with a vacuum degree of 0.5 MPa. The temperature of each section of the vented twin-screw extruder was 295-340°C, and the die head temperature was 310°C.

[0035] The masterbatch is added to a single-screw extruder made of corrosion-resistant nickel-based alloy steel, melt-extruded, and blown into a film through a blown film die. The formed film is then dried and wound up to obtain a perfluorosulfonic acid ion-exchange membrane. The temperature of each section of the single-screw extruder is 280-330℃, and the die head temperature is 300℃.

[0036] The membrane was saponified with NaOH methanol solution and reacted with HCl solution to obtain sodium perfluorosulfonate type and hydrogen perfluorosulfonate type ion exchange membranes, respectively.

[0037] Example 3

[0038] 10 kg of perfluorosulfonic acid fluorinated resin with a molecular weight of approximately 134,180, 1.5 kg of sulfonated graphene, and 0.2 kg of 2,5-diaminote-terephthalic acid were thoroughly mixed and fed into a vented twin-screw extruder with a screw diameter of 20 mm and an aspect ratio of 40 mm, made of corrosion-resistant nickel-based alloy steel. The mixture was melt-extruded and granulated, cooled, and dried to obtain masterbatch. The vented twin-screw extruder was connected to a vacuum pump with a vacuum degree of 0.3 MPa. The temperature of each section of the vented twin-screw extruder was 292-328°C, and the die head temperature was 305°C.

[0039] The masterbatch is added to a single-screw extruder made of corrosion-resistant nickel-based alloy steel, melt-extruded, and blown into a film through a blown film die. The formed film is then dried and wound up to obtain a perfluorosulfonic acid ion-exchange membrane. The temperature of each section of the single-screw extruder is 270-313℃, and the die head temperature is 295℃.

[0040] The membrane was saponified with NaOH methanol solution and reacted with HCl solution to obtain sodium perfluorosulfonate type and hydrogen perfluorosulfonate type ion exchange membranes, respectively.

[0041] Comparative Example 1

[0042] Except for the absence of sulfonated graphene and 2,5-diaminotetraphenylbenzenesulfonic acid, the rest was the same as in Example 3.

[0043] Comparative Example 2

[0044] Except for the absence of 2,5-diaminoterephthalic acid, it was the same as in Example 3.

[0045] Performance testing

[0046] The thickness, mechanical strength, and conductivity of the ion exchange membranes after saponification and acidification were tested for the examples and comparative examples, respectively. The specific data are shown in Table 1 below.

[0047] Table 1

[0048]

[0049] As can be seen from the examples and comparative data, the present invention modifies the perfluorosulfonic acid fluoride resin by using sulfonated graphene and 2,5-diaminote-terephthalic acid to meet the requirements of blow molding, resulting in a smooth, defect-free, thinner and more uniform thickness, good dimensional stability, and high mechanical strength perfluorosulfonic acid ion exchange membrane. Furthermore, the conductivity of the ion membrane is improved after saponification or acidification treatment, meeting the requirements for practical use.

[0050] The above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An improved method for preparing perfluorosulfonic acid ion exchange membranes by melt extrusion blow molding, characterized in that, Includes the following steps: (1) The materials containing perfluorosulfonic acid fluorinated resin, sulfonated graphene and 2,5-diaminote-phenylenedisulfonic acid are fully mixed in a mixer in proportion, extruded and granulated by a vented twin-screw extruder, cooled and dried to obtain masterbatch; the mass ratio of the perfluorosulfonic acid fluorinated resin, sulfonated graphene and 2,5-diaminote-phenylenedisulfonic acid is 100:10-20:1-3. (2) The masterbatch described in step (1) is fed into a single screw extruder, melt-extruded and blown into a film through a blown film die head, and then cooled to obtain a perfluorosulfonic acid ion membrane; (3) The perfluorosulfonic acid ion exchange membrane described in step (2) is saponified with NaOH methanol solution to obtain a sodium perfluorosulfonate type perfluorosulfonate hydrogen type ion exchange membrane; or the perfluorosulfonic acid ion exchange membrane described in step (2) is reacted with HCl solution to obtain a perfluorosulfonate hydrogen type ion exchange membrane.

2. The method as described in claim 1, characterized in that, The exhaust port of the exhaust-type twin-screw extruder in step (1) is connected to a vacuum pump, and the vacuum degree is 0.1-0.5MPa; the temperature of each section of the exhaust-type twin-screw extruder is 280-340℃, and the die head temperature is 290-310℃.

3. The method as described in claim 1, characterized in that, The temperature of each section of the single screw extruder in step (2) is 260-330℃, and the temperature of the die head is 280-300℃.

4. The method as described in claim 1, characterized in that, The vented twin-screw extruder of step (1) and the single-screw extruder of step (2) have screws, barrels and dies made of corrosion-resistant nickel-based alloy steel.

5. The method as described in claim 1, characterized in that, The sulfonated graphene has fewer than 10 layers, a radial dimension of 200 nm to 800 nm, a thickness of 6 to 500 nm, and a sulfur content of 0.5 to 18 wt%.

6. A perfluorosulfonic acid ion exchange membrane prepared by the method according to any one of claims 1-5.

7. The application of the perfluorosulfonic acid ion exchange membrane as described in claim 6, characterized in that, The perfluorosulfonic acid ion exchange membrane is used in fuel cells, lithium batteries, vanadium batteries, chlor-alkali electrolysis, gas separation, and photocatalysis.

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