阅读说明：本技术 低黄度指数复合质子交换膜及其制备方法 (Low-yellowness index composite proton exchange membrane and preparation method thereof ) 是由 李永哲 苏璇 刘婧 张栋梁 冯威 张永明 于 2019-10-25 设计创作，主要内容包括：本发明涉及质子交换膜技术领域,具体涉及一种低黄度指数复合质子交换膜及其制备方法。所述的低黄度指数复合质子交换膜,包括PVDF多孔膜中间层和中间层两侧的改性聚合物树脂层三层复合结构,PVDF多孔膜的膜孔里填充有改性聚合物树脂；复合质子交换膜由改性聚合物树脂涂布在PVDF多孔膜的上下表面,通过加湿干燥制得；所述改性聚合物树脂层是采用含过渡金属元素的添加剂对聚合物树脂进行改性制得。本发明的低黄度指数复合质子交换膜,结构致密、透气率低、黄度指数低,提高了质子交换膜的使用寿命,降低了质子交换膜的溶胀度,改善了质子交换膜的外观；本发明还提供其制备方法。(The invention relates to the technical field of proton exchange membranes, in particular to a low-yellowness index composite proton exchange membrane and a preparation method thereof. The composite proton exchange membrane with the low yellowness index comprises a three-layer composite structure of a middle layer of a PVDF porous membrane and modified polymer resin layers on two sides of the middle layer, wherein modified polymer resin is filled in membrane pores of the PVDF porous membrane; the composite proton exchange membrane is prepared by coating modified polymer resin on the upper surface and the lower surface of a PVDF porous membrane and humidifying and drying; the modified polymer resin layer is prepared by modifying polymer resin by adopting an additive containing a transition metal element. The low-yellowness index composite proton exchange membrane has a compact structure, low air permeability and low yellowness index, prolongs the service life of the proton exchange membrane, reduces the swelling degree of the proton exchange membrane, and improves the appearance of the proton exchange membrane; the invention also provides a preparation method of the composition.)

1. A low yellowness index composite proton exchange membrane is characterized in that: the composite structure comprises a PVDF porous membrane middle layer and modified polymer resin layers on two sides of the middle layer, wherein modified polymer resin is filled in membrane pores of the PVDF porous membrane; the composite proton exchange membrane is prepared by coating modified polymer resin on the upper surface and the lower surface of a PVDF porous membrane and humidifying and drying;

the modified polymer resin layer is prepared by modifying polymer resin by adopting an additive containing a transition metal element.

2. The low yellowness index composite proton exchange membrane according to claim 1 wherein: the polymer resin is perfluorosulfonic acid resin with equivalent weight range of 700-1400 g/mmol.

3. The low yellowness index composite proton exchange membrane according to claim 1 wherein: the PVDF porous membrane has a thickness of 10 to 25 μm and a pore diameter of 0.1 to 0.9. mu.m.

4. The low yellowness index composite proton exchange membrane according to claim 1 wherein: the thickness of the composite proton exchange membrane is 20-100 μm.

5. The low yellowness index composite proton exchange membrane according to claim 1 wherein: the additive containing transition metal element is one of transition metal simple substance, transition metal alloy, transition metal oxide and transition metal salt.

6. A method of preparing a low yellowness index composite proton exchange membrane according to claim 1, comprising the steps of:

(1) adding polymer resin into a solvent to prepare a polymer resin solution with the solid content of 15-18 wt%, and adding an additive containing a transition metal element into the polymer resin solution to uniformly disperse the additive in a perfluorinated sulfonic acid resin solution for complete reaction;

(2) firstly, uniformly coating a modified polymer resin on a base material, then placing a PVDF porous membrane on the modified polymer resin coating, then coating a layer of modified polymer resin on the PVDF porous membrane, and obtaining a wet membrane after leveling by a scraper;

(3) and (3) carrying out stage heating, humidifying and drying on the wet membrane to obtain the low-yellowness-index composite proton exchange membrane.

7. The method of preparing a low yellowness index composite proton exchange membrane according to claim 6, wherein: in the step (1), the solvent is a mixture of one or more of propanol, ethanol and acetonitrile and water.

8. The method of preparing a low yellowness index composite proton exchange membrane according to claim 6, wherein: in the step (1), the addition amount of the additive containing the transition metal element is 0.3-1% of the mass of the polymer resin.

9. The method of preparing a low yellowness index composite proton exchange membrane according to claim 6, wherein: the substrate in the step (2) is a glass plate.

10. The method of preparing a low yellowness index composite proton exchange membrane according to claim 6, wherein: the heating, humidifying and drying conditions in the step (3) are as follows: the first stage is as follows: drying at 50-70 deg.C and 50-80 RH% for 0.5-2 hr; and a second stage: drying at 80-100 deg.C and 50-99 RH% for 0.5-2 hr; and a third stage: drying at the temperature of 110 ℃ and 160 ℃ for 0.5-2h under the condition of no humidity.

Technical Field

The invention relates to the technical field of proton exchange membranes, in particular to a low-yellowness index composite proton exchange membrane and a preparation method thereof.

Background

Proton exchange membrane fuel cell technology relies on the development of two key materials, proton exchange membrane and electrocatalyst. The proton exchange membrane mainly plays the roles of electronic isolation of an anode and a cathode and isolation of reaction gas, and simultaneously provides the proton conduction function of the electrolyte. The proton exchange membrane is located at the middle position of the membrane electrode in the fuel cell, and is increasingly becoming a vital role in the research of the fuel cell.

The perfluorinated sulfonic acid proton exchange membrane is a proton exchange membrane which is most applied in the development of the proton exchange membrane fuel cell at present, and has excellent conductivity and a series of other advantages. Although the price is high, the comprehensive performance of the film is incomparable with other film materials at present. In addition to the Nafion membrane of dupont, similar products have been developed by companies such as Dow membrane of Dow Chemical company, usa, Aciplex membrane of Asahi Chemical company, japan, and Flemion membrane of Asahi Glass company.

The perfluorinated sulfonic acid proton exchange membrane is a solid polymer electrolyte, has excellent heat resistance, mechanical property, electrochemical property and chemical stability, and can be used under severe conditions of strong acid, strong base, strong oxidant medium and the like; however, perfluorosulfonic acid proton exchange membranes still have some disadvantages when used in fuel cells: high cost, low ion exchange capacity, low conductivity, low gas permeability, high methanol permeability, poor thermal stability, and the like.

Currently, commercially available Nafion membranes and Gore composite proton exchange membranes (Gore-Select membranes) are widely used, but these membranes have different appearance colors, gas permeability and lifetime. Therefore, modifying the existing proton exchange membrane to improve the comprehensive performance thereof becomes the key content of the extensive research of people.

The patent CN201910220927.9 discloses a proton exchange membrane and a preparation method thereof, wherein the proton exchange membrane consists of three layers of membranes, the middle layer comprises 3.125-16.25 wt% of transition metal sulfide, 6.25-62.5 wt% of vinyl polymer, 21.25-90.625 wt% of perfluorinated sulfonic acid, and the rest two layers comprise perfluorinated sulfonic acid and polyvinylidene fluoride copolymer; the coating is prepared by a layer-by-layer coating and drying method. The prepared proton exchange membrane has good heat resistance, greatly improved water retention capacity, long service life and high open circuit voltage of the battery.

Patent CN200510018912.2 discloses a method for preparing a composite proton exchange membrane from alkali metal ion type perfluorosulfonic acid resin, which comprises treating perfluorosulfonic acid resin solution with solution containing alkali metal ions to convert sulfonic acid functional group of the resin into M type with alkali metal ions, then compounding M type perfluorosulfonic acid resin into a porous polytetrafluoroethylene membrane, and performing vacuum drying treatment to form the porous polymer reinforced proton exchange membrane for fuel cells. The prepared membrane has good air tightness, high strength and proton conductivity, and has good application effect in proton exchange membrane fuel cells.

Patent CN200910231452.X discloses a perfluorosulfonic acid composite proton exchange membrane for fuel cells, which consists of perfluorosulfonic acid resin, M-type perfluorosulfonic acid resin and porous polymer reinforced material, wherein the M-type perfluorosulfonic acid resin is cerium or/and manganese metal ion type perfluorosulfonic acid resin formed by completely exchanging cerium or/and manganese ions with sulfonic acid groups or sulfonyl fluoride groups in the perfluorosulfonic acid resin. Cerium or/and manganese ions can be uniformly distributed in a membrane body, so that the thermal stability is high, the heat treatment temperature of the composite membrane is increased, the combination of a porous polymer reinforced material and perfluorinated sulfonic acid resin is facilitated, and the prepared composite proton exchange membrane has good mechanical strength and proton conductivity and is favorable for improving the performance of a fuel cell.

Although the above patent discloses cerium and/or manganese metal ion type perfluorosulfonic acid resin, manganese ions can be uniformly distributed in the membrane body, and the composite membrane has high thermal stability and increases the heat treatment temperature, while the thermal recombination temperature of the membrane is increased, the color of the membrane is changed, i.e. the yellowness index is increased, and the appearance of the membrane is affected.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a low-yellowness index composite proton exchange membrane which has a compact structure, low air permeability and low yellowness index, prolongs the service life of the proton exchange membrane, reduces the swelling degree of the proton exchange membrane and improves the appearance of the proton exchange membrane; the invention also provides a preparation method of the composition.

The composite proton exchange membrane with the low yellowness index comprises a three-layer composite structure of a middle layer of a PVDF porous membrane and modified polymer resin layers on two sides of the middle layer, wherein modified polymer resin is filled in membrane pores of the PVDF porous membrane; the composite proton exchange membrane is prepared by coating modified polymer resin on the upper surface and the lower surface of a PVDF porous membrane and humidifying and drying;

the modified polymer resin layer is prepared by modifying polymer resin by adopting an additive containing a transition metal element.

The polymer resin is perfluorosulfonic acid resin with equivalent weight range of 700-1400 g/mmol.

The PVDF porous membrane has a thickness of 10 to 25 μm and a pore diameter of 0.1 to 0.9. mu.m.

The modified polymer resin layers are uniformly coated on the upper and lower surfaces of the PVDF porous membrane.

The thickness of the composite proton exchange membrane is 20-100 μm.

The additive containing transition metal element is one of transition metal simple substance, transition metal alloy, transition metal oxide and transition metal salt. Preferably MnO ₂、Mn ₂O ₃、MnO、MnSO ₄、NiF ₂、NiSO ₄One kind of (1).

In the modified polymer resin, the sulfonated high molecular polymer and the additive can form a complex compound to prevent iron nickel ions and hydrogen peroxide from generating free radicals, so that the free radicals in the membrane are prevented from attacking the membrane, and the service life and the durability of the proton exchange membrane can be better improved.

The preparation method of the low-yellowness index composite proton exchange membrane comprises the following steps:

(1) adding polymer resin into a solvent to prepare a polymer resin solution with the solid content of 15-18 wt%, and adding an additive containing a transition metal element into the polymer resin solution to uniformly disperse the additive in a perfluorinated sulfonic acid resin solution for complete reaction;

(2) firstly, uniformly coating a modified polymer resin on a base material, then placing a PVDF porous membrane on the modified polymer resin coating, then coating a layer of modified polymer resin on the PVDF porous membrane, and obtaining a wet membrane after leveling by a scraper;

(3) and (3) carrying out stage heating, humidifying and drying on the wet membrane to obtain the low-yellowness-index composite proton exchange membrane.

In the step (1), the solvent is a mixture of one or more of propanol, ethanol and acetonitrile and water.

In the step (1), the addition amount of the additive containing the transition metal element is 0.3-1% of the mass of the polymer resin.

The substrate in the step (2) is a glass plate. The wet membrane is separated from the composite proton exchange membrane after being dried and is reused.

And (4) in the step (3), the temperature rise, humidification and drying are carried out by adopting an oven or a constant temperature and humidity test box with a humidification function. The stage heating, humidifying and drying is divided into three stages, the first two stages adopt humidifying and drying, and the third stage does not carry out humidifying.

The heating, humidifying and drying conditions in the step (3) are as follows: the first stage is as follows: drying at 50-70 deg.C and 50-80 RH% for 0.5-2 hr; and a second stage: drying at 80-100 deg.C and 50-99 RH% for 0.5-2 hr; and a third stage: drying at the temperature of 110 ℃ and 160 ℃ for 0.5-2h under the condition of no humidity.

When the wet film is dried and solidified, a unique stage heating, humidifying and drying process is adopted, humidity is respectively given during the first two stages of heating during drying gradient heating, the volatilization speed of the solvent is controlled, the dry cracking is prevented, and finally the aging temperature is increased for aging.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the invention, the polymer resin is modified by adopting the additive containing the transition metal element, and the polymer resin layer is modified by the transition metal ionic compound to form a complex compound, so that the free radicals in the membrane can be prevented from attacking the membrane, and the service life and the durability of the proton exchange membrane are further improved;

(2) the composite proton exchange membrane has a three-layer composite structure of a PVDF porous membrane middle layer and modified polymer resin layers on two sides of the middle layer, and the PVDF porous membrane has higher mechanical strength and has a reinforcing effect on the proton exchange membrane;

(3) the invention adopts a method of heating, humidifying and drying in stages to carry out heat treatment on the composite proton exchange membrane, can control the humidity in the drying process, further control the volatilization speed of the solvent in the modified polymer resin layer, prevent the modified polymer resin layer from cracking in the film forming process and greatly improve the yield.

Drawings

FIG. 1 is a schematic structural view of a low yellowness index composite proton exchange membrane according to the present invention;

1. a modified polymer resin; 2. a PVDF porous membrane; 3. PVDF porous membrane pores.

Detailed Description

The present invention is further illustrated by the following examples, but the scope of the present invention is not limited thereto, and modifications of the technical solutions of the present invention by those skilled in the art should be within the scope of the present invention.