阅读说明：本技术 一种全氟磺酸树脂分散液的提纯方法和离子交换膜 (Purification method of perfluorinated sulfonic acid resin dispersion liquid and ion exchange membrane ) 是由 王亚辉 张泽天 刘昊 李道喜 李蕴熙 刘一晨 周朝毅 李丹 杨望 于 2021-11-09 设计创作，主要内容包括：本发明公开了一种全氟磺酸树脂分散液的提纯方法和离子交换膜,全氟磺酸树脂分散液的提纯方法包括：a、将全氟磺酸树脂分散在溶剂中,所述溶剂包括第一溶剂和第二溶剂,得到全氟磺酸树脂分散液；b、向所述步骤a得到的全氟磺酸树脂分散液中加入萃取剂进行萃取,形成液液两相,得到的萃余相为提纯后的全氟磺酸树脂分散液,其中,所述萃取剂包括碳五烷烃、碳六烷烃、石油醚、碳七烷烃、碳八烷烃、全氟碳五烷烃或全氟碳六烷烃中的至少一种,所述萃取剂与第一溶剂不互溶且与第二溶剂互溶。本发明的全氟磺酸树脂分散液的提纯方法,能够提高全氟磺酸树脂产品纯度及批次稳定性,从而提高了全氟磺酸树脂制品的光学性能和稳定性。(The invention discloses a purification method of perfluorosulfonic acid resin dispersion and an ion exchange membrane, wherein the purification method of the perfluorosulfonic acid resin dispersion comprises the following steps: a. dispersing perfluorosulfonic acid resin in a solvent, wherein the solvent comprises a first solvent and a second solvent to obtain perfluorosulfonic acid resin dispersion liquid; b. and c, adding an extracting agent into the perfluorinated sulfonic acid resin dispersion liquid obtained in the step a for extraction to form a liquid-liquid two phase, wherein the obtained raffinate phase is the purified perfluorinated sulfonic acid resin dispersion liquid, the extracting agent comprises at least one of carbon pentaalkane, carbon hexaalkane, petroleum ether, carbon heptaalkane, carbon octaalkane, perfluorocarbon pentaalkane or perfluorocarbon hexaalkane, and the extracting agent is immiscible with the first solvent and miscible with the second solvent. The purification method of the perfluorosulfonic acid resin dispersion liquid can improve the purity and batch stability of the perfluorosulfonic acid resin product, thereby improving the optical performance and stability of the perfluorosulfonic acid resin product.)

1. A method for purifying a perfluorosulfonic acid resin dispersion liquid, comprising:

a. dispersing perfluorosulfonic acid resin in a solvent, wherein the solvent comprises a first solvent and a second solvent to obtain perfluorosulfonic acid resin dispersion liquid;

b. and c, adding an extracting agent into the perfluorinated sulfonic acid resin dispersion liquid obtained in the step a for extraction to form a liquid-liquid two phase, wherein the obtained raffinate phase is the purified perfluorinated sulfonic acid resin dispersion liquid, the extracting agent comprises at least one of carbon pentaalkane, carbon hexaalkane, petroleum ether, carbon heptaalkane, carbon octaalkane, perfluorocarbon pentaalkane or perfluorocarbon hexaalkane, and the extracting agent is immiscible with the first solvent and miscible with the second solvent.

2. The method for purifying a perfluorosulfonic acid resin dispersion according to claim 1, wherein in the step a, the first solvent is contained in an amount of 40 to 90% by mass and the second solvent is contained in an amount of 10 to 60% by mass.

3. The method for purifying a perfluorosulfonic acid resin dispersion according to claim 1 or 2, wherein in the step a, the first solvent comprises at least one of water, ethylene glycol, methanol, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, or N-methylpyrrolidone, and the second solvent comprises at least one of ethanol, N-propanol, isopropanol, tetrahydrofuran, or dichloromethane.

4. The method of purifying a perfluorosulfonic acid resin dispersion according to claim 1 or 2, wherein in the step a, the mass content of the perfluorosulfonic acid resin in the perfluorosulfonic acid resin dispersion is 0.1% to 50%.

5. The method for purifying a perfluorosulfonic acid resin dispersion according to claim 1 or 2, wherein in the step a, the temperature is controlled to be 20 to 270 ℃, the time is controlled to be 0.1 to 200 hours, and the pressure is controlled to be 0.1 to 20MPa during the process of dispersing the perfluorosulfonic acid resin in the solvent.

6. The method of claim 1, wherein the mass M of the extractant in the step b is the mass M of the perfluorosulfonic acid resin dispersion liquid_{Extracting agent}The mass M of the solvent in the perfluorosulfonic acid resin dispersion liquid obtained in the step a is not more than_Solvent(s)1.5 times of the total weight of the powder.

7. The method of claim 6, wherein in the step b, the concentration of the perfluorosulfonic acid resin dispersion is 0.2M_Solvent(s)≤M_{Extracting agent}≤1.5M_Solvent(s)。

8. The method for purifying a perfluorosulfonic acid resin dispersion according to claim 1, wherein in the step b, the extraction is at least two-stage extraction.

9. The method of purifying a perfluorosulfonic acid resin dispersion according to claim 1, wherein in step a, the perfluorosulfonic acid resin is at least one selected from the group consisting of a metal ion type perfluorosulfonic acid resin, an acid type perfluorosulfonic acid resin, an ammonium ion type perfluorosulfonic acid resin, a quaternary ammonium salt cation type perfluorosulfonic acid resin, an imidazole ion type perfluorosulfonic acid resin, and a waste containing perfluorosulfonic acid resin.

10. An ion exchange membrane obtained by using the perfluorosulfonic acid resin dispersion purified by the method according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of materials, and particularly relates to a method for purifying a perfluorinated sulfonic acid resin dispersion liquid, and particularly relates to an ion exchange membrane.

Background

The perfluorosulfonic acid resin (PFSA) is a high-performance polyelectrolyte material, has excellent ion conductivity, thermochemical stability and oxidation resistance, and shows solvent resistance in a high crystalline state. At present, the perfluorinated sulfonic acid resin is applied to the fields of secondary batteries such as fuel batteries, flow batteries and lithium ion batteries, polyelectrolyte membranes for hydrogen production by water electrolysis, separation membranes, chlor-alkali industrial membranes, membrane reactors, organically synthesized green and environment-friendly catalysts, ionic polymer-metal composite materials (IPMC) and the like.

At present, the companies for producing the commercialized perfluorosulfonic acid resin mainly include kemu, 3M company in the united states, suwei company in belgium, asahi chemical company in japan, hydrogen energy in the east, juhua group, and sai saifu in the country, and the like. The product difference at home and abroad is not obvious by analyzing key technical indexes such as chemical structure, molecular weight distribution, EW value and the like, but is limited by the experience accumulation of the synthesis process, and the batch stability of the products at home still needs to be improved. The purity has an important influence on the batch stability and performance of the perfluorosulfonic acid resin product, and taking a perfluorosulfonic acid ion exchange membrane as an example, the electrochemical performance of the ion exchange membrane is unstable due to the existence of small-molecular acidic impurities, and the electrochemical performance can be obviously changed along with the loss of small-molecular acid and low-molecular-weight perfluorosulfonic acid resin. The existence of metal ion impurities can reduce the proton transmission capability, poison a catalytic system, and reduce the service life and the service performance of the fuel cell. Metal ion impurities represented by iron ions, organic micromolecule impurities, carbonyl groups generated by oxidation and tryptamine generated by decomposition of nitrogen-containing group substances can cause yellowing of perfluorosulfonic acid resin, and in severe cases, the resin is grayish brown.

In the related art, the post-process purification of the perfluorosulfonic acid resin preparation is mainly washing with water. The essence of water washing is a solid-liquid extraction technology, wherein small molecules and water-soluble substances with strong hydrophilicity in the resin are extracted by water, but the purification effect on small molecule impurities adsorbed or wrapped in the resin is limited, and particularly the small molecule impurities with strong adsorption effect and limited hydrophilicity are adsorbed by the resin. The presence of small molecular impurities can cause yellowing of the perfluorosulfonic acid resin product, and under heating conditions, the increase of carbonyl and tryptamine can cause further deepening of the color of the solid product. The color of part of the perfluorosulfonic acid resin solid can achieve the effect of bleaching through the treatment of hydrogen peroxide or nitric acid dispersion liquid, but the color of part of the perfluorosulfonic acid resin solid treated at high temperature cannot be bleached by nitric acid. In addition, the perfluorosulfonic acid resin has high unit price, good stability and great environmental hazard, and is very necessary to recycle waste perfluorosulfonic acid resin products. However, in the related art, the recovered perfluorosulfonic acid resin is mostly prepared by purifying solid products by using tubular chemicals with strong oxidizability, strong acidity and strong corrosivity, such as hydrogen peroxide and sulfuric acid, dissolving the purified solid products by using a solvent to obtain a recovered solution, and drying the recovered solution to obtain a recovered solid resin. The purification method can not completely remove organic impurities and nitrogen-containing group impurities in the resin, the obtained product can change color again after being heated at high temperature, and meanwhile, the strong oxidizing reagent can accelerate the deterioration of the perfluorosulfonic acid resin.

At present, aiming at the yellowing and discoloration phenomena of the perfluorinated sulfonic acid resin caused by non-metallic ions, the purpose of bleaching is realized by using strong oxidizing and strong corrosive reagents such as hydrogen peroxide, sulfuric acid, nitric acid and the like to destroy the chemical bonds of discoloration groups. Although this method may make the resin colorless and transparent after a certain period of time after the treatment, the resin solid turns yellow again macroscopically as time passes or the resin solid is accelerated to be produced from carbonyl and tryptamine at a high temperature. Such methods do not truly remove trace impurities from the resin and can cause damage to the perfluorosulfonic acid resin itself.

Therefore, it is highly desirable to develop a method capable of effectively removing impurities from perfluorosulfonic acid resin.

Disclosure of Invention

The present invention is based on the discovery and recognition by the inventors of the following facts and problems: in the related technology, the water-washing-based solid-liquid extraction can effectively remove inorganic salt, acid, alkali and other micromolecular water-soluble substances in the perfluorinated sulfonic acid resin, and can wash away most other impurities. However, residual trace impurities can be wrapped or adsorbed in the resin, and the resin solids are macroscopically yellowed by the generation of carbonyl or tryptamine species through slow oxidation at room temperature or rapid oxidation at high temperature, and the yellowness exists in the polymer dispersion of the resin solids and the resin. Commercial perfluorosulfonic acid resin products have very low levels of such impurities that are difficult to detect, but have a significant macroscopic color change and adversely affect product batch stability, optical properties and durability. Taking a Nafion117 ion exchange membrane as an example, treating the Nafion117 ion exchange membrane for 0.5 to 1 hour by using 3 percent hydrogen peroxide before use is considered to be a standard pretreatment process which needs to be implemented. The purpose of the operation is to use a strong oxidizing reagent to destroy carbonyl and tryptamine groups to obtain a colorless and transparent ion exchange membrane with good optical performance, and the light transmittance of the treated Nafion117 ion exchange membrane can reach 100%. However, the method does not really remove impurities in the resin matrix, the treated solid resin is discolored again after being subjected to high-temperature heat treatment for a period of time or after being slowly oxidized in the air for a long time, and part of the resin after the high-temperature heat treatment cannot be bleached, so that the resin is damaged.

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the embodiment of the invention provides a purification method of a perfluorosulfonic acid resin dispersion liquid, which can separate impurities which can generate carbonyl and tryptamine groups through oxidation in the perfluorosulfonic acid resin dispersion liquid, and improve the purity and batch stability of a perfluorosulfonic acid resin product, thereby improving the optical performance and stability of the perfluorosulfonic acid resin product.

The purification method of the perfluorosulfonic acid resin dispersion liquid of the embodiment of the invention comprises the following steps:

a. dispersing perfluorosulfonic acid resin in a solvent, wherein the solvent comprises a first solvent and a second solvent to obtain perfluorosulfonic acid resin dispersion liquid;

b. and c, adding an extracting agent into the perfluorinated sulfonic acid resin dispersion liquid obtained in the step a for extraction to form a liquid-liquid two phase, wherein the obtained raffinate phase is the purified perfluorinated sulfonic acid resin dispersion liquid, the extracting agent comprises at least one of carbon pentaalkane, carbon hexaalkane, petroleum ether, carbon heptaalkane, carbon octaalkane, perfluorocarbon pentaalkane or perfluorocarbon hexaalkane, and the extracting agent is immiscible with the first solvent and miscible with the second solvent.

The method of the embodiment of the invention has the advantages and the technical effects that the method of the embodiment of the invention brings, 1, the extraction agent adopted in the method of the embodiment of the invention has low adsorption capacity with the perfluorosulfonic acid resin, is not easy to adsorb on the perfluorosulfonic acid resin to become new impurities, and is easy to desorb from the perfluorosulfonic acid resin; 2 in the method of the embodiment of the invention, the solvent used is wide in variety, except that concentrated sulfuric acid can use various perfluorinated sulfonic acid resin solvents; 3. in the method of the embodiment of the invention, the adopted extractant has the advantages of non-corrosiveness, low toxicity, low cost and the like, and the requirement on raw materials is not high, and industrial grade raw materials can be adopted, for example, industrial hexane and industrial heptane can be used as the extractant; 4. in the method of the embodiment of the invention, the extractant has better stability, the economy of the liquid-liquid extraction process is determined by the loss degree of the extractant, such as thermal decomposition or chemical reaction with the original component, and the like, and the lower alkane extractant adopted in the method of the embodiment of the invention does not have any chemical reaction with the effective component of the perfluorosulfonic acid resin and is not decomposed in the extraction process; 5. In the method of the embodiment of the invention, the dispersion liquid of the perfluorinated sulfonic acid resin is concentrated after extraction, and a small amount of the extractant enters the raffinate phase to change the interface action of the dispersion liquid and the hydrophobic material, thereby being beneficial to the preparation of the composite proton exchange membrane; 6. according to the method provided by the embodiment of the invention, the purity of the perfluorinated sulfonic acid resin obtained after extraction is improved, the batch stability of the resin product is effectively improved, and the adverse effects of carbon-containing impurities and nitrogen-containing impurities of the perfluorinated sulfonic acid resin on the durability in fuel cells and hydrogen production by water electrolysis can be reduced; 7. according to the method disclosed by the embodiment of the invention, the yellowness index of the perfluorinated sulfonic acid resin is obviously reduced after extraction, so that the optical performance of the resin is obviously improved, the resin solid is not discolored after high-temperature heat treatment, the oxidation resistance is obviously improved, the perfluorinated sulfonic acid resin is favorably applied to an anti-fogging coating, and the extracted and purified perfluorinated sulfonic acid resin disclosed by the embodiment of the invention can be coated on a transparent polymer or an inorganic non-metallic material to serve as an anti-fogging coating which is resistant to oxidation and is not discolored and applied to a display screen of intelligent human body wearing equipment, glasses, a medical protective mask and protective equipment on a biochemical battlefield; 8. in the method of the embodiment of the invention, the concentration of the perfluorosulfonic resin dispersion liquid is basically unchanged or concentrated after extraction is finished, the dispersion liquid can be directly used without treatment or continuously used after dilution, and trace or small amount of extractant lower alkane introduced in the purification process is easy to remove in the drying process.

In some embodiments, in step a, the mass content of the first solvent in the solvent is 40% to 90%, and the mass content of the second solvent in the solvent is 10% to 60%.

In some embodiments, in step a, the first solvent comprises at least one of water, ethylene glycol, methanol, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, or N-methylpyrrolidone, and the second solvent comprises at least one of ethanol, N-propanol, isopropanol, tetrahydrofuran, or dichloromethane.

In some embodiments, in the step a, the mass content of the perfluorosulfonic acid resin in the perfluorosulfonic acid resin dispersion liquid is 0.1% to 50%.

In some embodiments, in the step a, the temperature is controlled to be 20-270 ℃, the time is 0.1-200 h, and the pressure is 0.1-20MPa during the process of dispersing the perfluorosulfonic acid resin in the solvent.

In some embodiments, in step b, the mass M of the extractant_{Extracting agent}The mass M of the solvent in the perfluorosulfonic acid resin dispersion liquid obtained in the step a is not more than_Solvent(s)1.5 times of the total weight of the powder.

In some embodiments, in step b, 0.2M_Solvent(s)≤M_{Extracting agent}≤1.5M_Solvent(s)。

In some embodiments, in step b, the extraction is at least two-stage extraction.

In some embodiments, in step a, the perfluorosulfonic acid resin is selected from at least one of a metal ion type perfluorosulfonic acid resin, an acid type perfluorosulfonic acid resin, an ammonium ion type perfluorosulfonic acid resin, a quaternary ammonium salt cationic perfluorosulfonic acid resin, an imidazole ion type perfluorosulfonic acid resin, or a waste containing perfluorosulfonic acid resin.

The embodiment of the invention also provides an ion exchange membrane, which is prepared by adopting the perfluorinated sulfonic acid resin dispersion liquid obtained by purification by the method of the embodiment of the invention. The ion exchange membrane provided by the embodiment of the invention has the advantages that the impurity content is low, the yellowness index can reach 0, the transmittance reaches 100%, the haze is reduced to 0%, the performance is excellent, and after heat treatment, the yellowness index, the transmittance and the haze are not changed, and the performance is stable.

Drawings

FIG. 1 is a graph showing the particle size distribution of the resin dispersion before and after extraction in example 1.

FIG. 2 is a phase diagram of a three-component liquid system of n-hexane, ethanol and water in example 2.

FIG. 3 shows the results of the contact angle test of the dispersion of example 2 on expanded polytetrafluoroethylene.

FIG. 4 is a DSC temperature rise profile of dried ion-exchange membrane L-5 of example 7.

FIG. 5 is a DSC temperature rise curve of dried ion-exchange membrane L-6 in comparative example 6.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

The purification method of the perfluorosulfonic acid resin dispersion liquid of the embodiment of the invention comprises the following steps:

a. dispersing perfluorosulfonic acid resin in a solvent, wherein the solvent comprises a first solvent and a second solvent to obtain perfluorosulfonic acid resin dispersion liquid;

b. and c, adding an extracting agent into the perfluorinated sulfonic acid resin dispersion liquid obtained in the step a for extraction, fully contacting the extracting agent with the perfluorinated sulfonic acid resin dispersion liquid in a stirring or ultrasonic or oscillation mode, standing to form a liquid-liquid two phase, wherein the obtained mixed system does not generate solids, the liquid system is divided into an upper phase and a lower phase, the upper phase is an extraction phase, the obtained clear and transparent lower phase is an raffinate phase, namely the purified perfluorinated sulfonic acid resin dispersion liquid, wherein the extracting agent comprises at least one of carbon pentaalkane, carbon hexaalkane, petroleum ether, carbon heptaalkane, carbon octaalkane, perfluorocarbon pentaalkane or perfluorocarbon hexaalkane, and the extracting agent is immiscible with the first solvent and miscible with the second solvent.

In the purification method of the perfluorosulfonic acid resin dispersion liquid of the embodiment of the invention, the adopted extractant and the perfluorosulfonic acid resin have low adsorption capacity, are not easy to adsorb on the perfluorosulfonic acid resin to become new impurities, and are easy to desorb from the perfluorosulfonic acid resin; in the method of the embodiment of the invention, the types of the adopted solvents are wide, except that concentrated sulfuric acid can use various perfluorinated sulfonic acid resin solvents; in the method of the embodiment of the invention, the adopted extractant has the advantages of non-corrosiveness, low toxicity, low cost and the like, and the requirement on the raw material is not high, and industrial grade raw materials can be adopted, for example, industrial hexane (the n-hexane content in the industrial hexane is 86%, and other carbon hexaalkanes comprise 2, 2-dimethylbutane, 2-methylpentane, 2, 3-dimethylbutane, 3-methylpentane and cyclohexane) can be used as the extractant; in the method of the embodiment of the invention, the extractant has better stability, the economy of the liquid-liquid extraction process is determined by the loss degree of the extractant, such as thermal decomposition or chemical reaction with the original component, and the like, and the lower alkane extractant adopted in the method of the embodiment of the invention does not have any chemical reaction with the effective component of the perfluorosulfonic acid resin and is not decomposed in the extraction process; in the method of the embodiment of the invention, the dispersion liquid of the perfluorinated sulfonic acid resin is concentrated after extraction, and a small amount of the extractant enters the raffinate phase to change the interface action of the dispersion liquid and the hydrophobic material, thereby being beneficial to the preparation of the composite proton exchange membrane; according to the method provided by the embodiment of the invention, the purity of the perfluorinated sulfonic acid resin obtained after extraction is improved, the batch stability of the resin product is effectively improved, and the adverse effects of carbon-containing impurities and nitrogen-containing impurities of the perfluorinated sulfonic acid resin on the durability in fuel cells and hydrogen production by water electrolysis can be reduced; according to the method provided by the embodiment of the invention, the yellowness index of the perfluorinated sulfonic acid resin is obviously reduced after extraction, the optical performance of the resin is obviously improved, the resin solid is not discolored after high-temperature heat treatment, the oxidation resistance is obviously improved, the perfluorinated sulfonic acid resin is favorably applied to an anti-fogging coating, the extracted and purified perfluorinated sulfonic acid resin provided by the embodiment of the invention can be coated on a transparent polymer or an inorganic non-metallic material to serve as an anti-fogging coating which is resistant to oxidation and is not discolored, and the perfluorinated sulfonic acid resin can be applied to a display screen of intelligent human body wearing equipment, glasses, a medical protective mask and protective equipment on a biochemical battlefield. In the method of the embodiment of the invention, the concentration of the perfluorosulfonic resin dispersion liquid is basically unchanged or concentrated after extraction is finished, the dispersion liquid can be directly used without treatment or continuously used after dilution, and trace or small amount of extractant lower alkane introduced in the purification process is easy to remove in the drying process.

In some embodiments, in step a, preferably, the mass content of the first solvent in the solvent is 40% to 90%, and the mass content of the second solvent is 10% to 60%. Further preferably, the first solvent includes at least one of water, ethylene glycol, methanol, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, or N-methylpyrrolidone, and the second solvent includes at least one of ethanol, N-propanol, isopropanol, tetrahydrofuran, or dichloromethane. In the method of the embodiment of the invention, the solvent is a mixed solvent consisting of a first solvent and a second solvent to disperse the perfluorosulfonic acid resin to form a resin dispersion liquid, and the resin dispersion liquid and the extractant lower alkane form a liquid-liquid two phase, and the purification of the perfluorosulfonic acid resin dispersion liquid is realized through extraction.

The perfluorosulfonic acid resin dispersion liquid only adopting the first solvent is almost immiscible with the extractant lower alkane, the distribution coefficient of small molecular impurities in the extractant is extremely low, and the composition of the perfluorosulfonic acid resin dispersion liquid phase and the extractant lower alkane phase material in the formed 2-phase system is basically unchanged. After the perfluorosulfonic acid resin dispersion liquid only containing the second solvent is mixed with the extractant lower alkane, the liquid phase in the system only has 1 phase, and the second solvent and the extractant lower alkane are mutually dissolved together. For the perfluorosulfonic acid resin dispersion liquid containing the first solvent and the second solvent, the number of phases of the liquid after mixing with the extractant lower alkane can be 1 or 2, and when the number of phases of the liquid is 1, the first solvent, the second solvent and the extractant are mixed together, so that the extraction operation cannot be carried out; when the phase number of the liquid is 2, according to the difference of the density, the liquid mainly comprising the first solvent is used as a lower phase, the liquid mainly comprising the extracting agent is used as an upper phase, the second solvent and the small molecular impurities are distributed in the upper phase and the lower phase, and the perfluorinated sulfonic acid resin is in the lower phase. In the method of the embodiment of the invention, the mixed solvent formed by combining the first solvent and the second solvent is adopted and mixed with the extractant to form liquid-liquid two phases, in the extraction process, the lower alkane extractant is used for extracting the second solvent and micromolecular impurities in the perfluorosulfonic acid resin dispersion liquid, and the perfluorosulfonic acid resin is kept in the lower phase mainly comprising the first solvent, and the extraction operation has the function of concentrating the resin dispersion liquid while removing the impurities and also changes the wettability of the resin dispersion liquid. In the application of the fuel cell, the expanded polytetrafluoroethylene is used as a support layer, so that the performance of the composite proton exchange membrane using the perfluorinated sulfonic acid resin as a proton transmission material can be obviously improved.

In some embodiments, in the step a, the mass content of the perfluorosulfonic acid resin in the perfluorosulfonic acid resin dispersion liquid is 0.1% to 50%. Preferably, the perfluorosulfonic acid resin is dispersed in the solvent at the temperature of 20-270 ℃ for 0.1-200 h and under the pressure of 0.1-20 MPa. Preferably, the perfluorinated sulfonic acid resin is at least one selected from metal ion type perfluorinated sulfonic acid resin, acid type perfluorinated sulfonic acid resin, ammonium ion type perfluorinated sulfonic acid resin, quaternary ammonium salt cationic perfluorinated sulfonic acid resin, imidazole ion type perfluorinated sulfonic acid resin or waste containing perfluorinated sulfonic acid resin. In the method of the embodiment of the present invention, the metal ion type perfluorosulfonic acid resin includes, but is not limited to: perfluorinated sulfonic acid resins such as alkali metal ions, iron ions, vanadium ions, titanium ions, cobalt ions, chromium ions, nickel ions, copper ions, aluminum ions, silver ions, zinc ions, calcium ions, magnesium ions, manganese ions, and tin ions; small molecule organic cationic perfluoro sulfonic acid resin such as quaternary ammonium salt cation, imidazolium cationic perfluoro sulfonic acid resin; the waste containing the perfluorinated sulfonic acid resin comprises a perfluorinated sulfonic acid resin ion exchange membrane, a membrane electrode assembly, a perfluorinated sulfonic acid resin catalyst, a supported perfluorinated sulfonic acid resin catalyst or an ionic polymer-metal composite material. The method of the embodiment of the present invention is not limited to the type of the perfluorosulfonic acid resin, and the method of the embodiment of the present invention can be used to purify the perfluorosulfonic acid resin. In the method of the embodiment of the invention, the prepared perfluorosulfonic acid resin can be used as a raw material, and waste materials containing the perfluorosulfonic acid resin can also be used as a raw material, so that the waste materials containing the perfluorosulfonic acid resin can be recycled, and the clean perfluorosulfonic acid resin can be obtained by recycling the waste materials containing the perfluorosulfonic acid resin, so that the cost of products such as an ion exchange membrane, a membrane electrode, an ionic polymer-metal composite (IPMC), a catalyst and the like can be reduced, and the performance stability of the products such as the ion exchange membrane, the membrane electrode, the IPMC, the catalyst and the like can be further improved by improving the purity.

In some embodiments, the amount of the extractant added in step b is not particularly limited as long as the amount of the extractant added satisfies the following conditions with respect to perfluoro-fluorideThe sulfonic acid resin dispersion liquid is mixed with a solvent to form a liquid-liquid two phase, and extraction can be realized. Preferably, the mass M of the extractant_{Extracting agent}The mass M of the solvent in the perfluorosulfonic acid resin dispersion liquid obtained in the step a is not more than_Solvent(s)1.5 times of that of (A), and more preferably 0.2M_Solvent(s)≤M_{Extracting agent}≤1.5M_Solvent(s). In the embodiment of the invention, the addition amount of the extracting agent is preferably selected, and the liquid obtained by mixing the solvent and the extracting agent in the resin dispersion liquid is 1 phase or emulsion due to the excessively high or excessively low addition amount of the extracting agent, so that the extraction cannot be carried out.

In some embodiments, in step b, the extraction is at least two-stage extraction. In the embodiment of the invention, multi-stage extraction is preferably carried out, and in practical application, multi-stage extraction can be carried out according to the impurity condition of the raw material perfluorosulfonic acid resin so as to obtain the high-purity perfluorosulfonic acid resin.

The embodiment of the invention also provides an ion exchange membrane, which is prepared by adopting the perfluorinated sulfonic acid resin dispersion liquid obtained by purification by the method of the embodiment of the invention. The ion exchange membrane provided by the embodiment of the invention has the advantages that the impurity content is low, the yellowness index can reach 0, the transmittance reaches 100%, the haze is reduced to 0%, the performance is excellent, and after heat treatment, the yellowness index, the transmittance and the haze are not changed, and the performance is stable.

The present invention will be described in detail below with reference to examples and the accompanying drawings.

In the examples of the present invention, yellowness index of resin solids and dispersions was measured: the yellowness index was characterized using an UltraScan VIS type spectrocolorimeter from HunterLab. The difference in yellowness index before and after extraction reflects the change in impurity content.

Determination of solid content of perfluorosulfonic acid resin: the solid content and volatile content were determined using a HX204 moisture meter from Mettler-Toritods. Test methods refer to the determination of the nonvolatile content of the adhesive in GBT 2793-1995.

Optical properties: the optical performance of the perfluorosulfonic acid resin film is measured by a Shanghai apparatus electronic light transmittance haze measuring instrument WGT-S, and the test is carried out according to GB/T2410-2008 standard. The higher the transmission, the lower the haze the better the optical properties and the fewer the impurities.

The particle size and the distribution of the perfluorosulfonic acid resin polymer dispersion sample were measured using a Malvern Zetasizer Nano type particle sizer with the following relevant experimental parameters: the refractive index and the viscosity of the sample are measured values, the measuring temperature is 25 ℃, each scanning is carried out for 13 times, and each scanning time is 10 s.

The contact angle of a perfluorosulfonic acid resin dispersion liquid sample is measured by adopting a Baiohlin Theta Lite optical contact angle measuring instrument, the wettability of the dispersion liquid in expanded polytetrafluoroethylene with the thickness of 6 mu m of Japan Dajin is measured, and relevant test parameters are as follows: the dropping volume was 4. mu.L, and the dropping rate was 1.5. mu.L/s.

Thermal properties of perfluorosulfonic acid resin solids: the DSC performance curve of the perfluorosulfonic acid resin solid was tested using a differential scanning calorimeter (model number DSC 3) of Mettler-Toridol. The heating rate is 10 ℃/min, the heating temperature range is determined according to the properties of the sample, and the sample is prevented from generating decomposition phenomenon.

Nafion117 ion exchange membranes were purchased from kemu corporation; perfluorosulfonic acid resin A (hereinafter referred to as resin A) is a commercial product; the content of n-hexane in industrial hexane is 86%, and other hexaalkanes include 2, 2-dimethylbutane, 2-methylpentane, 2, 3-dimethylbutane, 3-methylpentane and cyclohexane; the industrial heptane contains n-heptane, iso-heptane and cycloheptane as main components and small amount of C₈H₁₈And C₆H₁₄(ii) a Petroleum ether is a light petroleum product, is a mixture of hydrocarbons with low relative molecular mass, and mainly comprises carbon pentaalkane and carbon hexaalkane; other medicines are analytically pure.

EXAMPLE 1 Industrial Hexane purification of Perfluorosulfonic acid resin

Performing ion exchange on a Nafion117 ion exchange membrane in 1 mol/L sodium chloride dispersion liquid, heating and stirring at 60 ℃ for 1h, washing and soaking with deionized water to remove redundant sodium ions to obtain a sodium Nafion117 ion exchange membrane J_{Original source}。

Dissolving and dispersing a sodium Nafion117 ion exchange membrane in a mixed solvent composed of dimethyl sulfoxide and tetrahydrofuran, wherein the mass content of the dimethyl sulfoxide in the mixed solvent is 80%, the mass content of the tetrahydrofuran is 20%, dissolving for 6 h at 180 ℃ under the protection of nitrogen, and obtaining a uniform and transparent Nafion117 polymer dispersion liquid J (hereinafter referred to as dispersion liquid J), wherein the mass content of perfluorosulfonic acid resin in the dispersion liquid J is 5.21%, and the yellowness index is 0.57.

Mixing 50 g of the dispersion liquid J with 75 g of industrial hexane for extraction operation, stirring for 1h, performing ultrasonic treatment for 1h, finally oscillating for 1h, standing to form liquid-liquid two phases, and separating to obtain a lower extraction raffinate phase perfluorosulfonic acid resin dispersion liquid J-1.

The above extraction procedure was repeated to treat the dispersion J-1 in accordance with the method for treating the dispersion J, to obtain a dispersion J-2.

The mass content of the perfluorinated sulfonic acid resin in the dispersion liquid J-1 is 5.19%, and the yellowness index is 0.25; the mass content of the perfluorosulfonic acid resin in the dispersion J-2 is 5.22%, and the yellowness index is 0.

The particle size distributions of the dispersion J, the dispersion J-1 and the dispersion J-2 in this example are shown in FIG. 1, and it can be seen that the particle size distributions of the resin dispersion before and after the extraction were not changed.

EXAMPLE 2 purification of Perfluorosulfonic acid resin with n-hexane

Ion exchange is carried out on a Nafion117 ion exchange membrane in 1 mol/L sulfuric acid dispersion liquid, heating and stirring are carried out for 1h at the temperature of 60 ℃, and deionized water is used for washing and soaking to remove redundant hydrogen ions to obtain an acid Nafion117 ion exchange membrane K_{Original source}。

Dissolving and dispersing an acid Nafion117 ion exchange membrane in a mixed solvent consisting of water and ethanol, wherein the mass content of the water in the mixed solvent is 50%, the mass content of the ethanol is 50%, and dissolving for 6 h at 180 ℃ under the protection of nitrogen to obtain a uniform and transparent Nafion117 polymer dispersion liquid K (hereinafter referred to as dispersion liquid K), wherein the mass content of perfluorinated sulfonic acid resin in the dispersion liquid K is 10.08%, and the yellowness index is 0.42.

Mixing 50 g of dispersion liquid K and 50 g of n-hexane for extraction operation, stirring for 1h, performing ultrasonic treatment for 1h, finally oscillating for 1h, standing to form liquid-liquid two phases, and separating the liquid to obtain a lower extraction raffinate phase perfluorosulfonic acid resin dispersion liquid K-1.

And (3) repeating the extraction operation, mixing 20 g of the dispersion solution K-1 with 15 g of n-hexane for extraction operation, stirring for 1h, performing ultrasonic treatment for 1h, finally oscillating for 1h, standing to form a liquid-liquid two phase, and separating to obtain a lower extraction raffinate phase perfluorosulfonic acid resin dispersion solution K-2.

The mass content of the perfluorinated sulfonic acid resin in the dispersion liquid K-1 is 15.78%, and the yellowness index is 0.04; the mass content of the perfluorosulfonic acid resin in the dispersion K-2 is 18.52%, and the yellowness index is 0.

In this example, a three-phase diagram of water-n-hexane-ethanol related to the solvent and the extractant adopted is shown in fig. 2, and fig. 2 is a three-component liquid system phase diagram of n-hexane-ethanol-water at 10.0 ℃ and under an atmospheric pressure of 101.90 kPa, where the data are mass percentage, and n-hexane and ethanol, ethanol and water are miscible with each other at any ratio, and n-hexane and water are almost immiscible. Within the curve BDC, i.e. the cap-shaped zone, the three component systems are partially miscible to form two conjugated three component dispersions with a phase number of 2. Outside the cap-shaped region, the three-component systems were completely miscible with each other, and the number of phases was 1 (phase diagram of n-hexane-ethanol-water three-component system [ J ]. Shanghai college of academic, 2016,36(6): 74-177). In this example, the mixed solvent and the extractant form two conjugated three-component dispersions, thereby achieving the operation of extraction and impurity removal.

In the dispersion liquid K, the dispersion liquid K-1, and the dispersion liquid K-2 obtained in this example, the mass content of the perfluorosulfonic acid resin gradually increases because, after the extraction operation, the mass of the solvent ethanol entering the upper phase extraction phase is higher than the mass of the extractant n-hexane entering the lower phase raffinate phase (i.e., the dispersion liquid), and thus, the mass content of the perfluorosulfonic acid resin in the dispersion liquid after the extraction is improved.

In this example, the introduction of n-hexane exerted the function of a surfactant, and as shown in fig. 3, the difference in contact angle between different dispersions and expanded polytetrafluoroethylene indicates that the introduction of n-hexane improved the wettability of the resin dispersion and expanded polytetrafluoroethylene.

EXAMPLE 3 purification of perfluorosulfonic acid resin with n-hexane

Dissolving and dispersing the resin A in a mixed solvent consisting of water and ethanol at room temperature, wherein the mass content of the water in the mixed solvent is 40%, and the mass content of the ethanol is 60%, so as to obtain a uniform and transparent perfluorosulfonic acid resin dispersion liquid L. The dispersion liquid L contained 9.89% by mass of a perfluorosulfonic acid resin and had a yellowness of 0.96.

The structural formula of the repeating unit of the resin A in this example is:

mixing 50 g of dispersion liquid L and 30 g of n-hexane for extraction operation, stirring for 1h, performing ultrasonic treatment for 1h, finally oscillating for 1h, standing to form liquid-liquid two phases, and separating to obtain lower extraction raffinate phase perfluorosulfonic acid resin dispersion liquid L-1. The mass content of the perfluorosulfonic acid resin in the L-1 dispersion liquid was 10.35%, and the yellowness was 0.

Example 4 purification of perfluorosulfonic acid resin with Petroleum Ether

The same purification procedure as for the perfluorosulfonic acid resin of example 3 was followed, except that the extractant used was petroleum ether. And separating to obtain lower extraction raffinate phase perfluorosulfonic acid resin dispersion liquid L-2. The mass content of the perfluorosulfonic acid resin in the L-2 dispersion liquid was 10.84%, and the yellowness was 0.

EXAMPLE 5 Perfluoroalkane purification of Perfluorosulfonic acid resin

The method is the same as the method for purifying the perfluorosulfonic acid resin in the example 3, except that the adopted extracting agent is a mixed solvent of perfluoron-pentane and perfluoron-hexane, and the mass ratio of the two solvents is 1: 1. And separating to obtain lower extraction raffinate phase perfluorosulfonic acid resin dispersion liquid L-3. The mass content of the perfluorosulfonic acid resin in the L-3 dispersion liquid was 10.22%, and the yellowness was 0.

EXAMPLE 6 Industrial Heptane purification of Perfluorosulfonic acid resin

The same procedure as for the purification of perfluorosulfonic acid resin of example 3 was followed, except that the extractant used was industrial heptane. And separating to obtain lower extraction raffinate phase perfluorosulfonic acid resin dispersion liquid L-4. The mass content of the perfluorosulfonic acid resin in the L-4 dispersion was 10.41%, and the yellowness was 0.

Example 7 preparation of ion exchange membranes

The dispersion J-2 obtained in example 1, the dispersion K-2 obtained in example 2 and the dispersion L-1 obtained in example 3 were poured into an ultra-flat petri dish and vacuum-dried at 60 ℃ to obtain an ion-exchange membrane having a thickness of 100. + -.1. mu.m.

Casting the dispersion J-2 in a culture dish to obtain an ion exchange membrane J-3, casting the dispersion K-2 in the culture dish to obtain an ion exchange membrane K-3, and casting the dispersion L-1 in the culture dish to obtain an ion exchange membrane L-5.

Through tests, the yellowness index of the ion exchange membranes J-3, K-3 and L-5 is 0, the transmittance is 100%, and the haze is 0%.

The ion exchange membranes J-3, K-3 and L-5 prepared in the embodiment are treated at the high temperature of 150 ℃ for 30min, and the yellowness index, the transmittance and the haze of the ion exchange membranes J-3, K-3 and L-5 are not changed.

FIG. 4 is a DSC temperature rise profile of dried ion exchange membrane L-5. As can be seen from the figure, the glass transition temperature of the ion exchange membrane prepared from the resin dispersion after the purification treatment was 60.48 ℃, and the cold crystallization temperature thereof was 101.76 ℃. A weaker cold crystallization peak is formed after the cold crystallization peak, only a tiny signal disturbance peak appears at 250 ℃ after the test is finished, the baseline is straight, and the phenomenon of impurity decomposition is shown, so that the ion exchange membrane L-5 is high in purity and basically free of impurities.

Comparative example 1

Ion exchange Membrane J of Nafion117 in sodium form before unpurified treatment in example 1_{Original source}The test was conducted and the yellowness index was 1.21, transmittance was 99.37%, and haze was 0.11%.

Comparative example 2

Ion exchange membrane K of acid Nafion117 in example 2 before unpurified treatment_{Original source}The yellowness index of the test was 1.10, the transmittance was 99.42%, and the haze was 0.09%.

Comparative example 3

Acid Nafion117 ion exchange membrane K before unpurified treatment in example 2 was treated with 3% hydrogen peroxide at 60 deg.C_{Original source}Treating for 30min, and then treating for 30min at 60 ℃ by using deionized water to remove residual hydrogen peroxide. Vacuum drying at 60 ℃ for 2 h to obtain the dried acid Nafion117 ion exchange membrane HS (hereinafter referred to as membrane HS). The film HS had a yellowness index of 0 and a transmittance of 100%,the haze was 0%.

The film HS obtained in comparative example 3 was treated at a high temperature of 150 ℃ for 30min, and had a yellowness index of 0.08, a transmittance of 99.89% and a haze of 0.06%.

Comparative example 4

The same procedure as in example 7 was conducted except that the resin dispersion used was dispersion J obtained in example 1, to obtain an ion exchange membrane J-4 having a thickness of 100. + -.1. mu.m.

The ion-exchange membrane J-4 prepared in comparative example 4 had a yellowness index of 4.52, a transmittance of 98.21%, and a haze of 0.51%. The ion exchange membrane J-4 is treated at the high temperature of 150 ℃ for 30min, the yellowness index is 7.75, the transmittance is 97.96%, and the haze is 0.67%.

Comparative example 5

The same procedure as in example 7 was conducted except that the resin dispersion used was the dispersion K obtained in example 2, to obtain an ion exchange membrane K-4 having a thickness of 100. + -. 1 μm.

The ion-exchange membrane K-4 prepared in comparative example 5 had a yellowness index of 7.63, a transmittance of 97.86%, and a haze of 0.71%. The ion exchange membrane J-4 is treated at the high temperature of 150 ℃ for 30min, the yellowness index is 9.87, the transmittance is 97.33%, and the haze is 0.95%.

Comparative example 6

The same procedure as in example 7 was conducted except that the resin dispersion used was the dispersion L obtained in example 3, to obtain an ion exchange membrane L-6 having a thickness of 100. + -.1. mu.m.

The ion-exchange membrane L-6 prepared in comparative example 6 had a yellowness index of 8.09, a transmittance of 98.33%, and a haze of 0.54%. The ion exchange membrane L-6 is treated at the high temperature of 150 ℃ for 30min, the yellowness index is 10.02, the transmittance is 97.54%, and the haze is 0.88%.

FIG. 5 is a DSC temperature rise profile of dried ion exchange membrane L-6. As can be seen from FIG. 5, the ion exchange membrane prepared from the resin dispersion without purification also showed a glass transition signal and a weak cold crystallization signal. But a clear thermal signal appeared after the cold crystallization peak, which is a thermal signal resulting from the decomposition of impurities, indicating the presence of impurities in the ion-exchange membrane L-6.

Comparative example 7

Dissolving and dispersing the perfluorinated sulfonic acid resin A in a mixed solvent composed of dimethyl sulfoxide, N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide and water in a mass ratio of 1:1 respectively to obtain 4 resin dispersions, wherein the mass content of the perfluorinated sulfonic acid resin in the dispersion is shown in Table 1. Adding n-hexane into the 4 kinds of dispersion liquid, wherein the mass ratio of the n-hexane to the solvent in the dispersion liquid is 1:1, stirring and mixing for 1h, standing to form liquid-liquid two phases, and separating to obtain a lower phase extraction raffinate phase resin dispersion liquid.

As shown in table 1, the mass content of the perfluorosulfonic acid resin in the 4 dispersions prepared in this comparative example before and after mixing with n-hexane was changed by less than 0.1%, the yellowness index was not changed, and impurities or other substances were not effectively extracted by n-hexane.

TABLE 1

Solvent(s)	Resin concentration before extraction	Resin concentration after extraction	Yellowness index before extraction	Yellowness index after extraction
					Dimethyl sulfoxide	7.1%	7.14%	1.21	1.20
N, N dimethyl acetamide	7.5%	7.55%	0.76	0.76
					N-methyl pyrrolidone	7.2%	7.18%	1.31	1.32
Dimethyl sulfoxide and water (1: 1)	6.8%	6.87%	0.98	0.98

Comparative example 8

Dissolving and dispersing the resin A in ethanol, n-propanol, isopropanol and a mixture of the components in a mass ratio of 3: 1 of isopropanol and dichlorohexane to obtain 4 kinds of resin dispersion. Adding n-hexane into the obtained 4 kinds of dispersion liquid, wherein the mass ratio of the n-hexane to the solvent in the dispersion liquid is 1:1, stirring and mixing for 1h, standing, and enabling the liquid not to be layered, wherein the phase number of the liquid is 1.

As can be seen from the above examples and comparative examples, the ion exchange membranes J-3 and K-3 obtained in example 7 were the same as the sodium Nafion117 ion exchange membranes J in comparative examples 1 and 2_{Original source}And acid Nafion117 ion exchange membrane K_{Original source}Compared with the prior art, in example 7, due to the adoption of the purification method, the impurity content is obviously reduced, the yellowness indexes reach 0, the transmittance reaches 100%, the haze is reduced to 0%, and the optical performance and the yellowness indexes are not changed after heat treatment, so that the performance is stable. In comparative example 3, the acid Nafion117 ion exchange membrane in example 2 was treated with hydrogen peroxideK_{Original source}And (3) performing purification treatment, wherein the yellowness index can reach 0, the transmittance reaches 100% and the haze is reduced to 0% after the hydrogen peroxide treatment, but the yellowness index is increased, the transmittance is reduced, the haze is increased and the performance is unstable after the high-temperature heat treatment, which shows that the impurities in the ion exchange membrane prepared by the purification of the comparative example 3 are not effectively removed.

Ion exchange membranes J-4, K-4 and L-6 were prepared using the dispersion J, the dispersion K and the dispersion L without extraction treatment in comparative examples 4, 5 and 6, the yellowness index was increased to 4.52, 7.63 and 8.09, the transmittance was decreased to 98.21%, 97.86% and 98.33%, and the haze was increased to 0.67%, 0.71% and 0.54%, respectively, as compared with the ion exchange membranes J-3, K-3 and L-5 prepared in example 7, and the performance was further deteriorated after the high-temperature heat treatment, indicating that the ion exchange membranes J-4, K-4 and L-6 prepared in comparative examples 4, 5 and 6 had a higher content of impurities. The ion exchange membranes J-3, K-3 and L-5 in the embodiment 7 effectively reduce the impurity content after extraction operation, and after heat treatment, the performance is stable, the yellowness index can reach 0, the transmittance reaches 100%, the haze is reduced to 0%, and the performance is excellent.

In the present disclosure, the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" and the like mean that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.