Composite diaphragm material for electrolysis and preparation process thereof

Abstract

The invention discloses a composite diaphragm material for electrolysis and a preparation process thereof, and belongs to the technical field of diaphragm materials. The composite diaphragm material is formed by compounding a filter membrane A and a filter membrane B. The filter membrane A is prepared from the following raw materials in parts by weight: 12-18 parts of modified vinyl chloride-acrylonitrile copolymer, 65-70 parts of N, N-dimethylformamide, 15-20 parts of dimethyl sulfoxide and 1-2 parts of polyvinylpyrrolidone; the filter membrane B is prepared from the following raw materials in parts by weight: 10 to 15 parts of modified vinyl chloride-acrylonitrile copolymer, 4 to 6 parts of N, N-dimethylformamide, 60 to 65 parts of modified graphene oxide, 15 to 20 parts of dimethyl sulfoxide and 1 to 2 parts of polyvinylpyrrolidone. The prepared electrolytic diaphragm material has good water absorption and low surface resistance, and the production cost of metal nickel can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of diaphragm materials, and in particular to a composite diaphragm material for electrolysis and a preparation process thereof. Background Art

[0002] In the production practice of nickel electrowinning and electrorefining, electrode diaphragms play a vital role. They are mainly used to separate the cathode and anode in the electrolytic cell to form independent cathode and anode chambers. This requires them to have good chemical stability and sufficient mechanical strength. However, traditional diaphragm materials (such as natural fibers and synthetic fibers) have limitations in chemical stability and mechanical strength, making it difficult to meet the requirements of modern electrolysis technology. The diaphragms currently used are based on polyester filter cloth, which can withstand strong acid and strong alkali environments or in closed, high-pressure, high-temperature strong acid and alkali environments without corrosion. However, filter cloth is an insulating material, consumes a large amount of current during the electrolysis process, and has a high production cost. In addition, the hydrophobicity of polyester filter cloth is not conducive to the infiltration of electrolyte and the transmission of ions.

[0003] Chinese invention patent publication number CN116601334A discloses a substrate for an alkaline water electrolysis membrane and an alkaline water electrolysis membrane. The invention is an alkaline water electrolysis membrane substrate and an alkaline water electrolysis membrane comprising the substrate and a porous membrane of a polymer resin. The substrate is characterized in that it is composed of a non-woven fabric containing polyphenylene sulfide fibers having a profiled cross-section. The density of the substrate is 0.30 g / cm 3 Above and 0.80g / cm 3 Hereinafter, the tensile elongation in both the longitudinal and transverse directions is 10% or more and 35% or less, but the electrical resistance is relatively high. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a composite diaphragm material for electrolysis and a preparation process thereof.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A composite diaphragm material for electrolysis, composed of two filter membranes A and B. The filter membrane A comprises the following raw materials in parts by weight: 12-18 parts of modified vinyl chloride-acrylonitrile copolymer, 65-70 parts of N,N-dimethylformamide, 15-20 parts of dimethyl sulfoxide, and 1-2 parts of polyvinyl pyrrolidone;

[0007] The filter membrane B comprises the following raw materials in parts by weight: 10-15 parts of modified vinyl chloride-acrylonitrile copolymer, 4-6 parts of N,N-dimethylformamide, 60-65 parts of modified graphene oxide, 15-20 parts of dimethyl sulfoxide, and 1-2 parts of polyvinyl pyrrolidone;

[0008] The modified vinyl chloride-acrylonitrile copolymer is prepared by the following method:

[0009] S1: Polyethylene glycol monomethyl ether reacts with trimellitic anhydride to form a monoester compound; the reaction equation is as follows:

[0010]

[0011] S2: Monoester compound reacts with (4-vinylphenyl)methanol to form triester compound; the reaction equation is shown in FIG.

[0012]

[0013] The meaning is as follows:

[0014] S3: vinyl chloride, acrylonitrile and tri-fatty compound react to form a modified vinyl chloride-acrylonitrile copolymer. In this reaction, vinyl chloride, acrylonitrile and tri-fatty compound undergo polymerization to form a modified vinyl chloride-acrylonitrile copolymer.

[0015] In step S1, the mass ratio of the polyethylene glycol monomethyl ether to trimellitic anhydride is (3.5-3.8):1.

[0016] In step S2, the mass ratio of the monoester compound to (4-vinylphenyl)methanol is (3.3-3.5):1.

[0017] In step S3, the mass ratio of acrylonitrile, vinyl chloride and triglyceride is 5:6:(2-3).

[0018] The modified graphene is prepared by the following method:

[0019] N1: Graphene oxide reacts with glycine to generate carboxylated graphene; in this reaction, the epoxy groups on the surface of graphene oxide react with the amino groups of glycine to generate β-amino alcohol functional groups.

[0020] N2: Carboxylated graphene reacts with p-aminophenyltrimethoxysilane to generate amino-treated graphene; in this reaction, the hydroxyl groups on the surface of graphene oxide undergo a condensation reaction with the silyl methoxy groups of p-aminophenyltrimethoxysilane.

[0021] N3: Amination-modified graphene reacts with aniline to generate polyaniline graphene; in this reaction, the polyaniline structure is synthesized starting from the amino end of the grafted p-aminophenyltrimethoxysilane.

[0022] N4: Polyaniline graphene reacts with polyvinyl alcohol to generate modified graphene; in this reaction, the carboxyl groups in the polyaniline graphene react with the hydroxyl groups in the polyvinyl alcohol to undergo esterification.

[0023] In step N1, the mass ratio of the graphene oxide to glycine is 5:2.

[0024] In step N2, the mass ratio of the carboxylated graphene to p-aminophenyltrimethoxysilane is 3:1.

[0025] In step N3, the mass ratio of the amination-treated graphene to the aniline is 3:2.

[0026] In step N4, the mass ratio of the polyaniline graphene to the polyvinyl alcohol is 10:3.

[0027] A process for preparing a composite diaphragm material for electrolysis, characterized in that it comprises the following steps:

[0028] (1) Add the raw materials of filter membrane A and filter membrane B into two reaction tanks respectively, heat to 50-60°C, and stir to dissolve to form glue solution A and glue solution B;

[0029] (2) Dipping the polyester filter cloth into adhesive solution A and adhesive solution B respectively, extruding into membranes, soaking in a cold water pool, soaking in a hot water pool, and drying to obtain filter membranes A and B;

[0030] (3) Cut, align, and sew filter membranes A and B to obtain a composite diaphragm material.

[0031] Due to the adoption of the above technical solution, the beneficial effects of the present invention include:

[0032] (1) The modified vinyl chloride-acrylonitrile copolymer prepared by the present invention improves the hydrophilicity of the diaphragm and reduces the surface resistance of the diaphragm by introducing a hydrophilic ethylene glycol monomethyl ether chain segment and a benzene ring structure.

[0033] (2) The modified graphene prepared by the present invention improves its hydrophilicity and reduces the surface resistance by introducing polyvinyl alcohol segments and polyaniline structures, thereby reducing the production cost of metal nickel electrolysis. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0035] Example 1 Preparation of modified vinyl chloride-acrylonitrile copolymer

[0036] S1: Under nitrogen protection, 800 ml of anhydrous toluene, 100 g of trimellitic anhydride, 350 g of polyethylene glycol monomethyl ether (MPEG750) and 6 g of sodium propionate were added to a reactor, stirred and mixed, heated to 70°C, reacted for 6 h, cooled to room temperature, washed three times with deionized water (200 ml each time), and the organic phase was dried with 30 g of anhydrous magnesium sulfate, filtered, and distilled under reduced pressure at 70°C for 3 h to obtain a monoester compound;

[0037] S2: Under nitrogen protection, 800 ml of toluene, 330 mol of the monoester compound, 100 g of (4-vinylphenyl) methanol, and 10 g of p-toluenesulfonic acid were added to a reactor, stirred and mixed, heated to 100 ° C, and reacted for 15 h. During this period, water produced by the reaction was removed by a water separator, cooled to room temperature, and the pH was adjusted to 7 with saturated sodium bicarbonate. The liquid was separated and washed three times with deionized water (200 ml each time). The organic phase was dried with 30 g of anhydrous magnesium sulfate, filtered, and distilled under reduced pressure at 70 ° C for 3 h to obtain a triester compound;

[0038] S3: 500 ml of DMF, 50 g of acrylonitrile, and 5 g of azobisisobutyronitrile were added to an autoclave, and the autoclave was evacuated to a vacuum degree of 640 mmHg using a vacuum pump. 60 g of vinyl chloride was added from a closed pipe by pressure difference, and stirred for 30 min. The temperature was raised to 45 ° C. and reacted at 0.8 MPa for 6 h. 150 ml of a DMF solution containing 20 g of a triglyceride was added, and the reaction was continued for 3 h. The product was cooled to room temperature, depressurized, and 800 ml of deionized water was added and stirred to precipitate the solid. The solid was filtered, washed three times with deionized water (200 ml each time), and dried in vacuo at 60 ° C for 24 h to obtain a modified vinyl chloride-acrylonitrile copolymer.

[0039] Example 2 Preparation of modified vinyl chloride-acrylonitrile copolymer

[0040] S1: Under nitrogen protection, 800 ml of anhydrous toluene, 100 g of trimellitic anhydride, 360 g of polyethylene glycol monomethyl ether (MPEG750) and 6 g of sodium propionate were added to a reactor, stirred and mixed, heated to 80°C, reacted for 5 h, cooled to room temperature, washed three times with deionized water (300 ml each time), and the organic phase was dried with 30 g of anhydrous magnesium sulfate, filtered, and distilled under reduced pressure at 70°C for 3 h to obtain a monoester compound;

[0041] S2: Under nitrogen protection, 800 ml of toluene, 340 g of the monoester compound, 100 g of (4-vinylphenyl) methanol, and 10 g of p-toluenesulfonic acid were added to a reactor, stirred and mixed, and the temperature was raised to 105 ° C. The reaction was carried out for 12 hours. During this period, the water produced by the reaction was removed by a water separator. The mixture was cooled to room temperature and the pH was adjusted to 7 with saturated sodium bicarbonate. The liquid was separated and washed three times with deionized water (200 ml each time). The organic phase was dried with 50 g of anhydrous magnesium sulfate, filtered, and distilled under reduced pressure at 70 ° C. for 3 hours to obtain a triester compound;

[0042] S3: 500 ml of DMF, 50 g of acrylonitrile, and 5 g of azobisisobutyronitrile were added to an autoclave, and the autoclave was evacuated to a vacuum degree of 640 mmHg using a vacuum pump. 60 g of vinyl chloride was added from a closed pipe by pressure difference, and stirred for 30 min. The temperature was raised to 50° C. and reacted at 0.8 MPa for 5 h. 150 ml of a DMF solution containing 25 g of a triglyceride was added, and the reaction was continued for 4 h. The product was cooled to room temperature, depressurized, and 800 ml of deionized water was added and stirred to precipitate the solid. The solid was filtered, washed three times with deionized water (200 ml each time), and dried in vacuo at 60° C. for 24 h to obtain a modified vinyl chloride-acrylonitrile copolymer.

[0043] Example 3 Preparation of modified vinyl chloride-acrylonitrile copolymer

[0044] S1: Under nitrogen protection, 800 ml of anhydrous toluene, 100 g of trimellitic anhydride, 380 g of polyethylene glycol monomethyl ether (MPEG750) and 6 g of sodium propionate were added to a reactor, stirred and mixed, heated to 85°C, reacted for 4 h, cooled to room temperature, washed three times with deionized water (300 ml each time), and the organic phase was dried with 30 g of anhydrous magnesium sulfate, filtered, and distilled under reduced pressure at 70°C for 3 h to obtain a monoester compound;

[0045] S2: Under nitrogen protection, 800 ml of toluene, 350 g of the monoester compound, 100 g of (4-vinylphenyl) methanol, and 10 g of p-toluenesulfonic acid were added to a reactor, stirred and mixed, and the temperature was raised to 110° C. The reaction was carried out for 10 h, during which the water produced by the reaction was removed by a water separator. The mixture was cooled to room temperature, the pH was adjusted to 7 with saturated sodium bicarbonate, the liquid was separated, and the mixture was washed three times with deionized water (200 ml each time). The organic phase was dried with 30 g of anhydrous magnesium sulfate, filtered, and distilled under reduced pressure at 70° C. for 3 h to obtain a triester compound;

[0046] S3: 500 ml of DMF, 50 g of acrylonitrile, and 5 g of azobisisobutyronitrile were added to an autoclave, and the autoclave was evacuated to a vacuum degree of 640 mmHg using a vacuum pump. 60 g of vinyl chloride was added from a closed pipe by pressure difference, and stirred for 30 min. The temperature was raised to 55 ° C. and reacted at 0.8 MPa for 4 h. 150 ml of a DMF solution containing 30 g of a triglyceride was added, and the reaction was continued for 5 h. The product was cooled to room temperature, depressurized, and 800 ml of deionized water was added and stirred to precipitate the solid. The solid was filtered, washed three times with deionized water (200 ml each time), and dried in vacuo at 60 ° C for 24 h to obtain a modified vinyl chloride-acrylonitrile copolymer.

[0047] Example 4 Preparation of modified graphene

[0048] N1: 1000 ml of deionized water and 50 g of graphene oxide were added to a reactor and ultrasonically dispersed for 1 h. 10 g of NaOH and 20 g of glycine were added and stirred. The mixture was heated to 60°C and reacted for 8 h. The mixture was filtered and washed three times with deionized water (200 ml each time). The mixture was then dried under vacuum at 70°C for 24 h to obtain carboxylated graphene.

[0049] N2: 1000 ml of deionized water and 60 g of carboxylated graphene were added to a reactor and ultrasonically dispersed for 1 h; 20 g of p-aminophenyltrimethoxysilane was added, and then the pH was adjusted to 4 with acetic acid. The mixture was heated to 70°C and reacted for 4 h. The mixture was cooled to room temperature, filtered, washed with 200 ml of anhydrous ethanol and 200 ml of deionized water, and dried in vacuo at 80°C for 12 h to obtain amino-treated graphene;

[0050] N3: 800 ml of deionized water and 30 g of amino-modified graphene were placed in a reactor and ultrasonically dispersed for 1 h to prepare a dispersion; 200 ml of 1 M HCl solution and 20 g of aniline were mixed into an aniline salt solution, added to the reactor, cooled to 0°C, and 200 ml of an aqueous solution containing 62 g of ammonium persulfate was added dropwise for 1 h. The mixture was reacted for 12 h, filtered, washed with 200 ml of anhydrous ethanol and 200 ml of deionized water, and dried in vacuo at 80°C for 12 h to obtain polyaniline graphene;

[0051] N4: Add 350 ml of DMSO (dimethyl sulfoxide) and 10 g of polyaniline graphene to a reactor and ultrasonically disperse for 30 min. Then add 10 g of polyvinyl alcohol, 4 g of N,N'-dicyclohexylcarboximide and 1.5 g of 4-dimethylaminopyridine, stir and mix, heat to 50 ° C and react for 24 h, filter, wash three times with methanol (100 ml each time), and vacuum dry at 60 ° C for 12 h to obtain modified graphene.

[0052] Example 5 Preparation of composite diaphragm material for electrolysis

[0053] (1) Weigh 120 g of modified vinyl chloride-acrylonitrile copolymer (prepared in Example 1), 650 g of N,N-dimethylformamide, 150 g of dimethyl sulfoxide, and 10 g of polyvinyl pyrrolidone, and add them sequentially into a reaction tank, heat to 50° C., and stir at 800 rpm for 30 min to prepare glue solution A;

[0054] 100 g of modified vinyl chloride-acrylonitrile copolymer (prepared in Example 1), 40 g of N,N-dimethylformamide, 600 g of modified graphene oxide (prepared in Example 4), 150 g of dimethyl sulfoxide, and 10 g of polyvinyl pyrrolidone were weighed and added to a reaction tank in sequence. The mixture was heated to 50° C. and stirred at 800 rpm for 30 min to prepare glue solution B.

[0055] (2) Glue solution A and glue solution B were injected into the laminating tank respectively, and the linked laminating machine was turned on. The polyester filter cloth was immersed into the glue tank through the guide rack at a speed of 1.5 m / min. After being rolled by the squeeze roller (pressure 20 MPa) to form a film, it was immersed in a 0°C cold water pool for 15 minutes, then immersed in a 60°C hot water pool for 15 minutes, and finally dried at 80°C for 5 hours to obtain filter membrane A and filter membrane B respectively;

[0056] (3) Cut filter membrane A and filter membrane B according to length × width = 1200 mm × 1140 mm, where the length 1200 mm is the side and the width 1140 mm is the bottom; align and sew with a sewing machine: 5 lines on the side, with a spacing of 1 mm; 6 lines on the bottom, with a spacing of 1 mm; fold the top at 60 mm and sew 2 lines, with a spacing of 1 mm; to obtain a composite diaphragm material.

[0057] Example 6 Preparation of composite diaphragm material for electrolysis

[0058] (1) Weigh 150 g of modified vinyl chloride-acrylonitrile copolymer (prepared in Example 2), 680 g of N,N-dimethylformamide, 180 g of dimethyl sulfoxide, and 15 g of polyvinyl pyrrolidone, and add them sequentially into a reaction tank, heat to 55°C, and stir at 800 rpm for 30 min to prepare glue solution A;

[0059] 120 g of modified vinyl chloride-acrylonitrile copolymer (prepared in Example 2), 50 g of N,N-dimethylformamide, 620 g of modified graphene oxide (prepared in Example 4), 180 g of dimethyl sulfoxide, and 15 g of polyvinyl pyrrolidone were weighed and added to a reaction tank in sequence. The mixture was heated to 55° C. and stirred at 800 rpm for 30 min to prepare glue solution B.

[0060] (2) Glue solution A and glue solution B were injected into the laminating tank respectively, and the linked laminating machine was turned on. The polyester filter cloth was immersed into the glue tank through the guide rack at a speed of 1.5 m / min. After being rolled by the squeeze roller (pressure 20 MPa) to form a film, it was immersed in a 0°C cold water pool for 15 minutes, then immersed in a 60°C hot water pool for 15 minutes, and finally dried at 80°C for 5 hours to obtain filter membrane A and filter membrane B respectively;

[0061] (3) Cut filter membrane A and filter membrane B according to length × width = 1200 mm × 1140 mm, where the length 1200 mm is the side and the width 1140 mm is the bottom; align and sew with a sewing machine: 5 lines on the side, with a spacing of 1 mm; 6 lines on the bottom, with a spacing of 1 mm; fold the top at 60 mm and sew 2 lines, with a spacing of 1 mm; to obtain a composite diaphragm material.

[0062] Example 7 Preparation of composite diaphragm material for electrolysis

[0063] (1) Weigh 180 g of modified vinyl chloride-acrylonitrile copolymer (prepared in Example 3), 700 g of N,N-dimethylformamide, 200 g of dimethyl sulfoxide, and 20 g of polyvinyl pyrrolidone, and add them sequentially into a reaction tank, heat to 60°C, and stir at 800 rpm for 30 min to prepare glue solution A;

[0064] 150 g of modified vinyl chloride-acrylonitrile copolymer (prepared in Example 3), 60 g of N,N-dimethylformamide, 650 g of modified graphene oxide (prepared in Example 4), 200 g of dimethyl sulfoxide, and 20 g of polyvinyl pyrrolidone were weighed and added to a reaction tank in sequence. The mixture was heated to 60° C. and stirred at 800 rpm for 30 min to prepare glue solution B.

[0065] (2) Glue solution A and glue solution B were injected into the laminating tank respectively, and the linked laminating machine was turned on. The polyester filter cloth was immersed into the glue tank through the guide rack at a speed of 1.5 m / min. After being rolled by the squeeze roller (pressure 20 MPa) to form a film, it was immersed in a 0°C cold water pool for 15 minutes, then immersed in a 60°C hot water pool for 15 minutes, and finally dried at 80°C for 5 hours to obtain filter membrane A and filter membrane B respectively;

[0066] (3) Cut filter membrane A and filter membrane B according to length × width = 1200 mm × 1140 mm, where the length 1200 mm is the side and the width 1140 mm is the bottom; align and sew with a sewing machine: 5 lines on the side, with a spacing of 1 mm; 6 lines on the bottom, with a spacing of 1 mm; fold the top at 60 mm and sew 2 lines, with a spacing of 1 mm; to obtain a composite diaphragm material.

[0067] Comparative Example 1

[0068] The raw material composition and preparation process of the composite diaphragm material for electrolysis are basically the same as those in Example 6, except that the modified vinyl chloride-acrylonitrile copolymer (prepared in Example 2) used in glue A and glue B is replaced by a modified vinyl chloride-acrylonitrile copolymer of equal mass prepared by the following method:

[0069] The preparation method of the modified vinyl chloride-acrylonitrile copolymer is basically the same as that of Example 2, except that the (4-vinylphenyl)methanol in step S2 is replaced by an equal mass of 3-butene-1-ol.

[0070] Comparative Example 2

[0071] The raw material composition and preparation process of the composite diaphragm material for electrolysis are basically the same as those in Example 6, except that the modified vinyl chloride-acrylonitrile copolymer (prepared in Example 2) used in glue A and glue B is replaced by an equal mass of modified vinyl chloride-acrylonitrile copolymer prepared by the following method:

[0072] The preparation method of the modified vinyl chloride-acrylonitrile copolymer is basically the same as that of Example 2, except that the polyethylene glycol monomethyl ether (MPEG750) in step S1 is replaced by polyethylene glycol monomethyl ether (MPEG1500) of equal mass.

[0073] Comparative Example 3

[0074] The raw material composition and preparation process of the composite diaphragm material for electrolysis are basically the same as those in Example 6, except that the modified vinyl chloride-acrylonitrile copolymer (prepared in Example 2) used in glue A and glue B is replaced by an equal mass of modified vinyl chloride-acrylonitrile copolymer prepared by the following method:

[0075] The preparation method of the modified vinyl chloride-acrylonitrile copolymer is basically the same as that of Example 2, except that the polyethylene glycol monomethyl ether (MPEG750) in step S1 is replaced by polyethylene glycol monomethyl ether (MPEG350) of equal mass.

[0076] Comparative Example 4

[0077] The raw material composition and preparation process of the composite diaphragm material for electrolysis are basically the same as those in Example 6, except that the modified graphene (prepared in Example 4) is replaced by an equal mass of polyaniline graphene (prepared in step N3 of Example 4).

[0078] Comparative Example 5

[0079] The raw material composition and preparation process of the composite diaphragm material for electrolysis are substantially the same as those of Example 6, except that the modified graphene (prepared in Example 4) is replaced with an equal mass of modified graphene prepared by the following method:

[0080] N1: 1000 ml of deionized water and 50 g of graphene oxide were added to a reactor and ultrasonically dispersed for 1 h. 10 g of NaOH and 20 g of glycine were added and stirred. The mixture was heated to 60°C and reacted for 8 h. The mixture was filtered and washed three times with deionized water (200 ml each time). The mixture was then dried under vacuum at 70°C for 24 h to obtain carboxylated graphene.

[0081] N2: 350 ml of DMSO and 10 g of carboxylated graphene were added to a reactor and ultrasonically dispersed for 30 min. 10 g of polyvinyl alcohol, 4 g of N,N'-dicyclohexylcarboximide, and 1.5 g of 4-dimethylaminopyridine were added and stirred to mix. The mixture was heated to 50°C and reacted for 24 h. The mixture was filtered and washed three times with methanol (100 ml each time). The mixture was then dried under vacuum at 60°C for 12 h to obtain modified graphene.

[0082] The graphene oxide used in the examples and comparative examples of the present application is model SE243EW with a solid content of 42 wt%, produced by Changzhou Sixth Element Materials Technology Co., Ltd.; the polyvinyl pyrrolidone is PVP K30; the polyester filter cloth is model T6220-5×5 (warp density: 62 roots / inch, weft density: 20 roots / inch, warp yarn 21s / 5, weft yarn 21s / 5; square meter weight 500g); the polyvinyl alcohol is model PVA17-99; and the sewing thread used for sewing by a sewing machine is a 221-s 5-ply twisted polyester yarn.

[0083] The membrane materials prepared in Examples 5-7 and Comparative Examples 1-5 were tested for water absorption and surface resistance. The test results are shown in Table 1.

[0084] The water absorption test is conducted in accordance with GB / T 21655.1-2008: Cut membrane A and membrane B into 10 cm × 10 cm specimens respectively, accurately weigh the total mass m of the two specimens, place both specimens simultaneously in 100 ml of 23°C deionized water, soak for 5 minutes, remove them, and hang them vertically until the specimens stop dripping. Weigh the total mass m0 of the two specimens and calculate the water absorption: (m0-m) / m×100%. Repeat three times and take the average value.

[0085] The surface resistance test was conducted in accordance with SJ / T 10171.5-1991: Membrane A and Membrane B were cut into 40 mm × 60 mm specimens and immersed in a 40 wt % sodium hydroxide solution at 23°C for 4 h. The 40 wt % sodium hydroxide solution was injected into a resistance test tank. An insert was inserted into the resistance test tank, and the resistance value R1 of the solution was measured. The specimens of Membrane A and Membrane B were aligned and clamped in the insert, which was then inserted into the resistance test tank. The total resistance value R2 of the specimen and solution was measured, and the membrane surface resistance R = (R2 - R1) S (S is the membrane area).

[0086] Table 1 Performance test data

[0087]

[0088]

[0089] It can be seen from the data of Examples 5, 6 and 7 in Table 1 that the electrolytic diaphragm material prepared by the present invention has good water absorption and low surface resistance.

[0090] The composite diaphragm material for electrolysis prepared by the present invention has good water absorption and low surface resistance. The reasons are: the modified vinyl chloride-acrylonitrile copolymer prepared by the present invention contains polyethylene glycol segments, whose hydrophilicity can reduce the interfacial tension between the electrolyte and the diaphragm, promoting rapid penetration of the electrolyte into the pores; the benzene ring structure in the modified vinyl chloride-acrylonitrile copolymer can form a continuous electron channel with graphene through π-π stacking, reducing the energy barrier for electron migration across the interface and achieving the purpose of reducing surface resistance; the cross-linked structure of the modified vinyl chloride-acrylonitrile copolymer can form a uniform coating on the surface of the polyester filter cloth, improving the mechanical stability and chemical inertness of the diaphragm and extending the life of the diaphragm. The modified vinyl chloride-acrylonitrile copolymer used in Comparative Example 2 has a longer polyethylene glycol segment, which increases the surface resistance due to steric hindrance; the modified vinyl chloride-acrylonitrile copolymer used in Comparative Example 3 has a shorter polyethylene glycol segment and poorer hydrophilicity.

[0091] The modified graphene prepared by the present invention is a graphene oxide with polyvinyl alcohol segments and a polyaniline structure introduced into it. This improves the dispersion of graphene in the adhesive and prevents increased surface resistance due to agglomeration. The polyvinyl alcohol segments contain a large number of hydroxyl groups, which provide strong hydrophilicity and can form hydrogen bonds with the ethylene glycol monomethyl ether segments in the modified vinyl chloride-acrylonitrile copolymer, helping to form a stable structure and improving the mechanical stability of the diaphragm. The π-conjugated system of the polyaniline structure forms a π-π stack with the graphene, which can reduce the interfacial charge transfer impedance and achieve efficient carrier migration.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. However, any equivalent changes, modifications and evolutions made by ordinary technicians in this field without departing from the scope of the technical solution of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A composite membrane material for electrolysis, composed of two filter membranes A and B, characterized in that: The filter membrane A comprises the following raw materials in parts by weight: 12-18 parts of modified vinyl chloride-acrylonitrile copolymer, 65-70 parts of N,N-dimethylformamide, 15-20 parts of dimethyl sulfoxide, and 1-2 parts of polyvinyl pyrrolidone; The filter membrane B comprises the following raw materials in parts by weight: 10-15 parts of modified vinyl chloride-acrylonitrile copolymer, 4-6 parts of N,N-dimethylformamide, 60-65 parts of modified graphene oxide, 15-20 parts of dimethyl sulfoxide, and 1-2 parts of polyvinyl pyrrolidone; The modified vinyl chloride-acrylonitrile copolymer is prepared by the following method: S1: Polyethylene glycol monomethyl ether reacts with trimellitic anhydride to form a monoester compound; S2: The monoester compound reacts with (4-vinylphenyl)methanol to form a triester compound; S3: Vinyl chloride, acrylonitrile and triglyceride react to form modified vinyl chloride-acrylonitrile copolymer.

2. The composite diaphragm material for electrolysis according to claim 1, characterized in that: In step S1, the mass ratio of the polyethylene glycol monomethyl ether to trimellitic anhydride is (3.5-3.8):

1.

3. The composite diaphragm material for electrolysis according to claim 1, characterized in that: In step S2, the mass ratio of the monoester compound to (4-vinylphenyl)methanol is (3.3-3.5):

1.

4. The composite diaphragm material for electrolysis according to claim 1, characterized in that: In step S3, the mass ratio of acrylonitrile, vinyl chloride and triglyceride is 5:6:(2-3).

5. The composite diaphragm material for electrolysis according to claim 1, characterized in that: The modified graphene is prepared by the following method: N1: Graphene oxide reacts with glycine to produce carboxylated graphene; N2: Carboxylated graphene reacts with p-aminophenyltrimethoxysilane to form amino-treated graphene; N3: amination-modified graphene reacts with aniline to produce polyaniline graphene; N4: Polyaniline graphene reacts with polyvinyl alcohol to produce modified graphene.

6. The composite diaphragm material for electrolysis according to claim 5, characterized in that: In step N1, the mass ratio of the graphene oxide to glycine is 5:

2.

7. The composite diaphragm material for electrolysis according to claim 5, characterized in that: In step N2, the mass ratio of the carboxylated graphene to p-aminophenyltrimethoxysilane is 3:

1.

8. The composite diaphragm material for electrolysis according to claim 5, characterized in that: In step N3, the mass ratio of the amination-treated graphene to the aniline is 3:

2.

9. The composite diaphragm material for electrolysis according to claim 5, characterized in that: In step N4, the mass ratio of the polyaniline graphene to the polyvinyl alcohol is 10:

3.

10. A process for preparing the composite diaphragm material for electrolysis according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) Add the raw materials of filter membrane A and filter membrane B into two reaction tanks respectively, heat to 50-60°C, and stir to dissolve to form glue solution A and glue solution B; (2) Dipping the polyester filter cloth into adhesive solution A and adhesive solution B respectively, extruding into membranes, soaking in a cold water pool, soaking in a hot water pool, and drying to obtain filter membranes A and B; (3) Cut, align, and sew filter membranes A and B to obtain a composite diaphragm material.

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