KR102238221B1 - Modified polytetrafluoroethylene, method for preparing the same, ion exchange membranes using the same and method for preparing ion exchange membranes using the same - Google Patents

Abstract

Through the present invention, it includes polytetrafluoroethylene modified to be hydrophilic by reacting a mixed solution for modification containing catechol and polyethyleneimine (PEI) with polytetrafluoroethylene; By applying a hydrocarbon-based polymer to the modified polytetrafluoroethylene, it is possible to provide an ion exchange membrane for a fuel cell that has excellent mechanical properties, improves dimensional stability, and prevents a decrease in ionic conductivity.

Description

Modified polytetrafluoroethylene, manufacturing method thereof, and manufacturing method of ion exchange membrane and ion exchange membrane using the same {MODIFIED POLYTETRAFLUOROETHYLENE, METHOD FOR PREPARING THE SAME, ION EXCHANGE MEMBRANES USING THE SAME AND METHOD FOR PREPARING ION EXCHANGE MEMBRANES USING THE SAME }

The present invention relates to a modified polytetrafluoroethylene and a method for producing the same, and more specifically, to a modified polytetrafluoroethylene that can be used for an ion exchange membrane for a fuel cell, and the production of an ion exchange membrane and an ion exchange membrane using the same It's about the method.

Many studies are being conducted to replace expensive polymer electrolyte membranes for perfluorine-based fuel cells. Among them, studies on hydrocarbon-based polymer electrolyte membranes are being conducted, but the hydrocarbon-based polymer electrolyte membrane has disadvantages of low mechanical strength, strong brittleness upon drying, and low dimensional stability due to expansion when wet. In order to solve this problem of the hydrocarbon-based polymer electrolyte membrane, various studies have been conducted to increase mechanical strength and increase dimensional stability. A typical method for improving dimensional stability is a method of impregnating a porous support with a polymer electrolyte. Porous PTFE is a representative support and has excellent chemical and mechanical strength due to carbon fluorine bonding. In fact, research has been conducted to impregnate a perfluorine-based polymer electrolyte into porous PTFE through an alcoholic solvent.

However, there is a problem with this method. First, due to the high hydrophobicity of PTFE, it is difficult to impregnate the hydrophilic hydrocarbon-based electrolyte polymer into the pores of PTFE. In addition, when a hydrocarbon-based polymer solvent is used as an alcohol solvent or an alcohol solvent is added to the polymer solution, precipitation of the electrolyte polymer may occur. During film formation or coating, the porous impregnation rate decreases due to the difference in boiling point between the solvents. The conductivity decreases. A solution to this problem is needed.

An object of the present invention is a modified polytetrafluoroethylene, which can improve mechanical strength and dimensional stability and prevent a decrease in ionic conductivity, for use in a fuel cell, an ion exchange membrane using the same, and an ion exchange membrane using the same. It is to provide a method of manufacturing an ion exchange membrane.

Modified polytetrafluoroethylene for one object of the present invention is modified by reacting a mixed solution for modification including catechol and polyethyleneimine (PEI) with polytetrafluoroethylene.

In one embodiment, the modified polytetrafluoroethylene may exhibit hydrophilicity.

Modified polytetrafluoroethylene production method for another object of the present invention comprises the steps of preparing a mixed solution for modification by mixing a solvent, catechol, and polyethyleneimine (PEI); And reacting the mixed solution for modification with polytetrafluoroethylene to modify the polytetrafluoroethylene.

In one embodiment, the modifying step may be performed for 6 to 50 hours.

In one embodiment, after the modifying step, the step of washing the modified polytetrafluoroethylene may be further included.

The ion exchange membrane for another object of the present invention comprises polytetrafluoroethylene modified by reacting with a modified mixed solution containing catechol and polyethyleneimine (PEI); It is formed by impregnating the modified polytetrafluoroethylene with a hydrocarbon-based polymer.

In one embodiment, the ion exchange membrane may have excellent mechanical strength.

In one embodiment, it may be used for hydrolysis, fuel cells, secondary cells, or redox cells.

The method for producing an ion exchange membrane for another object of the present invention is to mix polytetrafluoroethylene (PTFE) in a reforming mixed solution containing catechol and polyethyleneimine (PEI) to prepare the polytetrafluoroethylene. Modifying; And applying a hydrocarbon-based polymer electrolyte on the modified polytetrafluoroethylene.

In one embodiment, the modifying step may be performed for 6 to 50 hours.

In one embodiment, after the applying step, it may further include drying the ion exchange membrane.

The modified polytetrafluoroethylene of the present invention improves the hydrophilicity while maintaining the mechanical strength of the polytetrafluoroethylene by modifying the surface of the fiber structure of the existing polytetrafluoroethylene to hydrophilicity. It is possible to increase the compatibility of and increase the impregnation rate of the hydrocarbon-based electrolyte polymer. Through this, dimensional stability can be increased, and a decrease in ionic conductivity can be prevented. Therefore, since it is possible to manufacture an ion exchange membrane having excellent properties, it may be helpful in the development of a hydrogen fuel cell.

1 is a view showing the membranes of the present invention manufactured through Examples.
Figure 2 is a view showing the polytetrafluoroethylene modification of the present invention.
3 is a view showing the membranes of the present invention manufactured through Examples.
4 and 5 are views showing polytetrafluoroethylene according to an embodiment of the present invention.
6 and 7 are views showing analysis results of a membrane according to an embodiment of the present invention.

The terms used in the present application are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features or steps. It is to be understood that it does not preclude the possibility of addition or presence of, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein including technical or scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms as defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in the present application. Does not.

The modified polytetrafluoroethylene (PTFE, Polytetrafluoroethylene) of the present invention is modified by reacting polytetrafluoroethylene with a reforming mixed solution containing catechol and polyethyleneimine (PEI).

The polytetrafluoroethylene may have a porous structure and may include a fiber structure. For example, the polytetrafluoroethylene may be Teflon.

In one embodiment, the modified polytetrafluoroethylene may exhibit hydrophilicity.

The catechol is a type of phenol, and is a polyphenol compound, and the polyethyleneimine is a branched polymer compound that can be represented _{by -(CH 2} CH ₂ NH) _n.

The modified polytetrafluoroethylene of the present invention has excellent mechanical strength like unmodified polytetrafluoroethylene, but has improved hydrophilicity, thereby increasing compatibility with a hydrocarbon-based polymer electrolyte. The impregnation rate of the electrolyte polymer can be increased, and dimensional stability can be improved.

The modified polytetrafluoroethylene production method of the present invention comprises the steps of preparing a mixed solution for modification by mixing a solvent, catechol, and polyethyleneimine; And reacting the mixed solution for modification with polytetrafluoroethylene to modify the polytetrafluoroethylene.

In one embodiment, the modifying step may be performed for 6 to 50 hours.

In one embodiment, after the modifying step, the step of washing the modified polytetrafluoroethylene may be further included.

The washing step is not limited thereto, but may be washed using ethanol, deionized water, or the like.

The mixed solution for modification may contain catechol and polyethyleneimine. When polytetrafluoroethylene is mixed with the modified mixed solution, the surface of the fiber structure of the porous polytetrafluoroethylene is modified through a co-deposition reaction by the modified mixed solution. Can be.

In one embodiment, the surface of the fiber structure of the polytetrafluoroethylene may be modified through a co-deposition reaction of a modified mixed solution containing catechol and polyethyleneimine. In addition, the modified polytetrafluoroethylene of the present invention may be modified to be hydrophilic.

Since the surface of the fiber structure inside the polytetrafluoroethylene rather than the surface of the polytetrafluoroethylene is modified, the hydrophilicity inside the polytetrafluoroethylene increases, so that a hydrophilic solvent may penetrate into the polytetrafluoroethylene.

Through the modified polytetrafluoroethylene and the manufacturing method thereof of the present invention, it is possible to provide polytetrafluoroethylene having excellent mechanical strength and improved hydrophilicity. In addition, as the hydrophilicity is improved, the compatibility with the hydrocarbon-based polymer increases, so that the impregnation rate with the hydrocarbon-based electrolyte polymer can be increased, and a modified polytetrafluoroethylene having improved dimensional stability can be provided.

The ion exchange membranes of the present invention include polytetrafluoroethylene modified by reacting a modified mixed solution containing catechol and polyethyleneimine (PEI) with polytetrafluoroethylene; It is formed by impregnating a hydrocarbon-based polymer on the modified polytetrafluoroethylene.

In one embodiment, the ion exchange membrane may have excellent mechanical strength.

In one embodiment, the ion exchange membrane may be used for water electrolysis, fuel cell, secondary cell, or redox flow battery. For example, the ion exchange membrane of the present invention may be used as an ion exchange membrane of a vanadium redox flow battery.

The method of manufacturing an ion exchange membrane of the present invention comprises the steps of modifying polytetrafluoroethylene (PTFE) using a modified mixed solution containing catechol and polyethyleneimine (PEI); And applying a hydrocarbon-based polymer electrolyte on the modified polytetrafluoroethylene.

In the modifying step, the surface of the fiber structure of the polytetrafluoroethylene forming a porous structure may be modified.

In one embodiment, the modifying step may be performed for 6 to 50 hours. For example, the modifying step may be performed for 8 to 48 hours.

After the applying step, it may further include the step of adjusting the ion exchange membrane thickness. For example, the thickness of the ion exchange membrane can be adjusted using a doctor blade.

In one embodiment, after the applying step, the step of drying the modified polytetrafluoroethylene may be further included. For example, the drying may include a first drying step and a second drying step.

For example, the first drying step may be performing the drying step for 10 to 30 hours at a temperature of 40 to 100 °C. In addition, the second drying step may be performing the drying step for 1 hour or more at a temperature of 100° C. or more in a vacuum atmosphere. For example, the first drying step and the second drying step may be continuously performed.

The hydrocarbon-based polymer is a sulfonated or unsulfonated poly ether ketone, a poly ether ketone ketone, a poly ether ether ketone ketone, and a poly ether ether. In ether ketone (poly ether ether ether keton), poly ether ketone-ether ketone ketone (poly ether keton-ether keton keton), poly arylene ether ketone (poly arylene ether ketone) or poly ether ether ketone (poly ether ether ketone) It may be one or more, for example, may be a sulfonated poly ether ether ketone (SPEEK, sulfated poly ether ether ketone) or a polyaryl ether ketone (Polyaryletherketone).

An ion exchange membrane having excellent mechanical strength and improved hydrophilicity can be provided through the ion exchange membrane and the method of manufacturing the ion exchange membrane of the present invention. In addition, it is possible to provide an ion exchange membrane capable of improving dimensional stability and preventing a decrease in ionic conductivity.

Hereinafter, embodiments of the present invention will be described in detail. However, the following examples are only some embodiments of the present invention, and the present invention should not be construed as being limited to the following examples.

Example 1. Porous polytetrafluoroethylene modification

First, porous polytetrafluoroethylene was soaked in ethanol for 30 minutes. In addition, a mixed solution for modification was prepared by dissolving 0.6 g of catechol and 0.15 g of polyethyleneimine in 500 ml of a tris-buffer solution (pH = 8.5, 10 mmol/L). Then, the porous polytetrafluoroethylene soaked in ethanol for 30 minutes was added to the prepared mixed solution for modification to obtain a mixture. Subsequently, the mixture was subjected to a co-deposition reaction at room temperature for 8 to 48 hours to modify the polytetrafluoroethylene in the mixture. After the reaction, the modified polytetrafluoroethylene was taken out and immersed in distilled water for about 24 hours to remove the remaining residues such as catechol and polyethyleneimine.

Example 2. Membrane Preparation 1

In order to impregnate the modified porous polytetrafluoroethylene prepared in Example 1 with a hydrocarbon-based polymer electrolyte, a modified polytetrafluoroethylene was laid on a glass plate, and a sulfonated polyether ether ketone (SPEEK, sulfated poly ether ether ketone) solution was poured to prepare a membrane. The sulfonated polyether ether ketone can be impregnated into the pores of the porous polytetrafluoroethylene through gravity and capillary action. Subsequently, the thickness of the membrane was adjusted using a doctor blade. Then, it was dried at 80° C. for 24 hours. Subsequently, it was further dried at 130° C. for 3 hours in a vacuum atmosphere to remove the residual solvent. Finally, a PTFE/SPEEK membrane that can be used as an ion exchange membrane was obtained.

Example 3. Membrane Preparation 2

Another example was carried out for the preparation of another membrane.

To impregnate the modified porous polytetrafluoroethylene prepared in Example 1 with a hydrocarbon-based polymer electrolyte, a modified polytetrafluoroethylene was laid on a glass plate, and a polyaryl ether ketone (PAEK-API, Polyaryletherketone) solution Was poured to prepare a membrane. Through gravity and capillary phenomena, polyaryl ether ketones can be impregnated into the pores of the porous polytetrafluoroethylene. Subsequently, the thickness of the membrane was adjusted using a doctor blade. Then, it was dried at 80° C. for 24 hours. Then, it was further dried at 130° C. for 3 hours in a vacuum atmosphere to remove the residual solvent. Finally, a PTFE/PAEK-API membrane that can be used as an ion exchange membrane was obtained.

1 is a view showing the membranes of the present invention manufactured through Examples. Specifically, FIG. 1 shows the top (a) and (c) and bottom (b) and ( d). In the case of (a) and (b) showing the unmodified membrane, it can be confirmed that the electrolyte polymer is formed or coated on the top (a), but in the case of the bottom (b), polytetrafluoroethylene is not modified. Therefore, it can be seen that the electrolyte solution did not penetrate into the pores of the polytetrafluoroethylene, and thus the film was not formed up to the bottom surface. On the other hand, (c) and (d) of FIG. 1 are modified polytetrafluoroethylene by reacting polytetrafluoroethylene for 48 hours using a mixed solution of tris buffer solution, catechol, and polyethyleneimine. It was prepared, showing an embodiment of the ion exchange membrane of the present invention prepared using the modified polytetrafluoroethylene and sulfonated polyether ether ketone, both the upper surface (c) and the lower surface (d) It can be confirmed that it was done.

Figure 2 is a view showing the polytetrafluoroethylene modification of the present invention. Specifically, FIG. 2 shows the simultaneous deposition reaction of catechol and polyethyleneimine by a chemical formula. In one embodiment, polytetrafluoroethylene is combined with catechol and polyethyleneimine used to prepare the modified polytetrafluoroethylene of the present invention. It can be seen to modify fluoroethylene. When catechol and polyethyleneimine are mixed, a Michael addition reaction and a Schiff base reaction are performed, so that the catechol and polyethyleneimine can be combined.

3 is a view showing the membranes of the present invention manufactured through Examples. Specifically, FIG. 3 is an upper surface (a) and (c) and a lower surface (b) of the PTFE/PAEK-API membranes prepared in Example 3 to compare the difference in the membrane according to the presence or absence of modification of polytetrafluoroethylene. And (d). In the case of (a) and (b) showing the unmodified membrane, the upper surface (a) appears to be formed, but in the case of the lower surface (b), it can be seen that the film is not formed. On the other hand, in (c) and (d) of FIG. 3, the modified polytetrafluoroethylene was prepared by reacting polytetrafluoroethylene for 48 hours using a mixed solution of a tris buffer solution, catechol, and polyethyleneimine. It was prepared, showing an embodiment of the ion exchange membrane of the present invention prepared using the modified polytetrafluoroethylene and polyaryl ether ketone, confirming that both the upper surface (c) and the lower surface (d) were formed. I can.

Accordingly, through FIGS. 1 and 3, it can be seen that uniform impregnation of the electrolyte solution is difficult without the hydrophilic modification of the porous polytetrafluoroethylene, and the polytetrafluoroethylene modified through the modification method of the present invention has hydrophilicity. Increasingly, since the solvent such as DMSO can easily penetrate into the porous interior of the polytetrafluoroethylene, it can be seen that the electrolyte polymer is penetrated and impregnated to uniformly form a film on both the upper, inner and lower surfaces.

Property evaluation

Modified polytetrafluoroethylene and ion exchange membranes prepared through the examples of the present invention were evaluated.

4 is a view showing polytetrafluoroethylene according to an embodiment of the present invention. Specifically, FIG. 4 shows a scanning electron microscope (SEM) image to confirm the degree of modification of polytetrafluoroethylene according to the modification time. FIGS. 4A and 4B show polytetrafluoroethylene before modification. Represents ethylene, Figure 4 (c) and (d) shows the polytetrafluoroethylene modified for 8 hours, Figure 4 (e) and (f) shows the polytetrafluoroethylene modified for 48 hours Show. Referring to Figure 4, it can be confirmed that the thickness of the fiber structure of the polytetrafluoroethylene becomes thicker as the time for modification by immersing polytetrafluoroethylene in a reforming mixed solution containing catechol and polyethyleneimine increases. I can.

5 is a view showing polytetrafluoroethylene according to an embodiment of the present invention. Specifically, FIG. 5 shows a water contact angle (water droplet image) in order to confirm the degree of modification of polytetrafluoroethylene according to the modification time, and FIGS. 5A and 5B are The previous polytetrafluoroethylene is shown, Figs. 5(c) and (d) show the polytetrafluoroethylene modified for 8 hours, and Figs. 5(e) and (f) show the polytetrafluoroethylene modified for 48 hours. Represents tetrafluoroethylene. Referring to FIG. 5, in the case of (a) and (b) of FIG. 5, the contact angle of water droplets is 139.81 °, and (c) and (d) of FIG. 5 are 62.1 ° of water droplets, and (e) of FIG. 5 And (f) it can be seen that the droplet form is completely spread to the water droplets. Therefore, it can be seen that as the modification time increases, the contact angle of water droplets decreases, and through this, as the modification time increases, the polytetrafluoroethylene is further modified, thereby further increasing the hydrophilicity.

As a result, it can be seen from FIGS. 4 and 5 that the degree of modification of the modified polytetrafluoroethylene of the present invention can be adjusted according to the modification time. In addition, it can be seen that the modified polytetrafluoroethylene of the present invention does not modify the surface of the polytetrafluoroethylene, but rather the surface of the fiber structure constituting the porous structure of the polytetrafluoroethylene. Since the surface of the fiber structure inside the polytetrafluoroethylene is modified rather than the surface of the polytetrafluoroethylene, the hydrophilicity increases, and the hydrophilic solvent may penetrate into the polytetrafluoroethylene.

6 and 7 are views showing analysis results of a membrane according to an embodiment of the present invention.

Specifically, FIG. 6 is a view showing measuring tensile strength of the ion exchange membranes prepared according to an embodiment of the present invention in order to determine whether the modified polytetrafluoroethylene is impregnated with a hydrocarbon-based polymer electrolyte. It can be seen from FIG. 6 that the modified polytetrafluoroethylene membranes (PTFE/SPEEK and PATFE/PAEK-API) have higher tensile strength and elongation than pure polymer electrolyte membranes (SPEEK and PAEK-API). have. Through this, it can be seen that the mechanical strength of the ion exchange membrane of the present invention is increased by using the modified porous polytetrafluoroethylene as a support.

Specifically, FIG. 7 shows the result of resistance analysis of the membrane with ionic conductivity in order to determine whether the modified polytetrafluoroethylene is impregnated with a hydrocarbon-based polymer electrolyte. In the case of using unmodified polytetrafluoroethylene, since only the upper surface of the membrane is partially formed, the ionic conductivity is significantly reduced than that of the pure polymer electrolyte membrane. On the other hand, the PTFE/SPEEK membrane using the modified polytetrafluoroethylene has only 10 to 15% reduction in cation conductivity than the pure polymer electrolyte membrane (SPEEK), as shown in FIG. It can be seen that the anion conductivity of the PTFE/PAEK-API membrane is reduced to less than 10% than that of the pure polymer electrolyte membrane (PAEK-API). Therefore, through the ion exchange membrane including the modified porous polytetrafluoroethylene of the present invention and a method for manufacturing the same, it is possible to prevent a decrease in ionic conductivity and excellent mechanical strength.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the present invention described in the following claims. You will understand that you can.

Claims (11)

delete delete delete delete delete delete delete delete Modifying polytetrafluoroethylene (PTFE) using a reforming mixed solution containing catechol and polyethyleneimine (PEI);
Applying a hydrocarbon-based polymer electrolyte on the modified polytetrafluoroethylene; And
Including the step of drying after the applying step,
The drying step includes a first drying step and a second drying step, wherein the first drying step and the second drying step are continuously performed,
The first drying step is performed at a temperature of 40 to 100° C. for 10 to 30 hours,
The second drying step is performed for 1 hour or more at a temperature of 100° C. or more in a vacuum atmosphere,
The modifying step is characterized in that it is carried out for 8 to 48 hours,
Method of manufacturing an ion exchange membrane.
The method of claim 9,
The ion exchange membrane is characterized in that it is used in water electrolysis, fuel cell, secondary cell or redox cell,
Ion Exchange Membrane Manufacturing Method. delete

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