A polymer membrane for lead-acid batteries

Abstract

The present invention discloses a polymer membrane for lead-acid batteries, comprising at least two film substrates, the film substrates comprising at least two of polyethylene terephthalate film, polypropylene film, nylon film, and composite polyimide / polytetrafluoroethylene film. The film substrates exhibit excellent strong acid corrosion resistance, high mechanical strength, wear resistance, and flame retardancy, thereby extending the service life of lead-acid batteries and increasing battery safety. The polymer membrane for lead-acid batteries includes an adhesive layer, wherein acid-responsive microcapsules therein rupture upon exposure to an acidic medium to release a crosslinking agent component, further enhancing the crosslinking density of the adhesive layer and optimizing the curing process, thereby improving the acid resistance and pressure resistance of the polymer membrane for lead-acid batteries, while also taking into account mechanical properties and environmental tolerance. The polymer membrane prepared by the present invention is suitable for modular lead-acid battery pole group sealing, thereby improving energy utilization.

Description

Technical Field

[0001] The present invention belongs to the technical field of power battery manufacturing, and in particular relates to a polymer membrane for lead-acid batteries. Background Art

[0002] Currently, lead-acid batteries mainly use hard polymer materials such as ABS as their shells. The advantage is that they are high-strength and can provide assembly pressure for the cluster. However, the shell is incompressible, making it inconvenient to insert the cluster into the shell, and the pressure shows a downward trend during use, resulting in degradation of lead-acid battery performance.

[0003] Conventional flexible polymer composite films are primarily composed of two to three or more layers of polypropylene, polyethylene terephthalate, and nylon. The inner layer of polypropylene provides resistance to electrolyte corrosion and heat-sealing adhesion. The outer layer is a polyester or nylon film, providing mechanical strength, wear resistance, and puncture resistance. The adhesive layer is a polyurethane or epoxy adhesive, ensuring interlayer bonding. During the lead-acid assembly process, these conventional flexible films can experience sulfuric acid or acid mist overflowing onto the outer layer, corroding it. Furthermore, sulfuric acid or acid mist can penetrate the adhesive layer, causing adhesive failure and delamination between the inner and outer layers. Furthermore, conventional curing processes typically utilize a single energy field mode, such as long-term heat curing or using only UV light to initiate surface curing. This can easily lead to premature hardening of the surface resin, hindering internal cross-linking and resulting in insufficient curing of the core layer. Both of these factors can reduce the peel strength between the composite film layers, limiting the long-term reliability of the packaging material under complex operating conditions.

[0004] To this end, the present invention provides a polymer film for lead-acid batteries to encapsulate the plates, so that they have the characteristics of lightweight, high energy density, high strength and acid resistance, and systematically balance the technical contradiction between rigid packaging and flexible deformation of lead-acid batteries. Summary of the Invention

[0005] The object of the present invention is to provide a strong acid-resistant and high-voltage-resistant polymer membrane for lead-acid batteries.

[0006] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are:

[0007] A polymer film for a lead-acid battery comprises at least two layers of film substrates. The compressive strength of the polymer film for the lead-acid battery is above 1500N.

[0008] Preferably, the polymer membrane for lead-acid batteries includes a three-layer, four-layer, five-layer, six-layer and seven-layer film substrate.

[0009] Preferably, the compressive strength is tested according to the national standard GB / T 21302-2007 for polymer membranes for lead-acid batteries.

[0010] Preferably, when the polymer membrane for lead-acid batteries is in contact with or immersed in 1.20-1.40 g / mL sulfuric acid for 6-8 days, the change rate of water vapor permeation is less than 10%.

[0011] Preferably, the tensile strength of the polymer film for lead-acid batteries is 80-200N / 15mm.

[0012] Preferably, the water vapor permeability of the polymer membrane for lead-acid batteries is 0.2-2.5 g / m 2 / 24h.

[0013] Preferably, the film substrate includes at least two of polyethylene terephthalate film, polypropylene film, nylon film and composite polyimide / polytetrafluoroethylene film.

[0014] Composite polyimide / PTFE films, combined with the super-hydrophobicity and chemical resistance of PTFE, can further resist the penetration of acidic media and have excellent resistance to strong acid corrosion. They have both the high strength of polyimide and the flexibility of PTFE, making them suitable for flexible film substrates. In addition to resistance to sulfuric acid corrosion, they also have high mechanical strength, wear resistance, and flame retardancy, extending the service life of lead-acid batteries and increasing battery safety.

[0015] Preferably, the polymer film for a lead-acid battery includes an adhesive layer.

[0016] Preferably, the adhesive layer comprises a dynamic borate prepolymer.

[0017] Preferably, the dynamic borate prepolymer is obtained by reacting 1,4-phenylenediboronic acid with polyglycerol diglycidyl ether under the catalysis of p-toluenesulfonic acid.

[0018] Preferably, the adhesive layer comprises acid-responsive microcapsules.

[0019] Preferably, the shell material of the acid-responsive microcapsules comprises polymethyl methacrylate-co-acrylic acid.

[0020] Preferably, the core material of the acid-responsive microcapsules comprises pentaerythritol triacrylate.

[0021] Preferably, the adhesive layer comprises an epoxy-acrylate copolymer.

[0022] Preferably, the adhesive layer comprises a dual cure initiator.

[0023] Preferably, the dual-cure initiator comprises ethyl 2,4,6-trimethylbenzoylphenylphosphonate and dicumyl peroxide.

[0024] The acid-responsive microcapsules in the adhesive layer remain intact in neutral and alkaline environments, and rupture when exposed to acidic media to release crosslinker components, further strengthening the crosslinking density of the adhesive layer and increasing acid resistance; the epoxy-acrylate copolymer provides UV-curing active groups, and cooperates with the dual-cure initiator to achieve a dual-curing mechanism of "photocuring rapid setting-thermal curing deep crosslinking", which can not only fill the micropores on the surface of the substrate, but also dissipate external stress through dynamic reversible characteristics, avoid interface cracking, and increase compressive resistance.

[0025] Preferably, the film substrates are composited by light-heat gradient synergistic curing.

[0026] Preferably, the light-heat gradient synergistic curing includes ultraviolet curing and infrared curing.

[0027] The present invention also provides a method for preparing a polypropylene film, comprising:

[0028] Preparation of polypropylene film: block copolymer polypropylene is selected as raw material, and it is blended, plasticized and cast with nano-SiO2 masterbatch in a twin-screw extruder to obtain polypropylene film.

[0029] Preferably, the mass ratio of block copolymer polypropylene to nano-SiO2 masterbatch is 4.5-45:0.5-5.

[0030] Preferably, the process temperature of the extruder is 220-240°C.

[0031] Preferably, the screw speed is 250-350 rpm.

[0032] Preferably, the polypropylene film has a thickness of 650-750 μm.

[0033] The present invention also provides a method for preparing a polyethylene terephthalate film, comprising:

[0034] Preparation of polyethylene terephthalate film: polyethylene terephthalate slices are used and formed by a biaxial stretching process at 205-215°C to obtain polyethylene terephthalate film.

[0035] Preferably, the stretch ratio between the longitudinal direction and the transverse direction is 4.5-5.5.

[0036] Preferably, the polyethylene terephthalate film has a thickness of 240-320 μm.

[0037] The present invention also provides a method for preparing a nylon film, comprising:

[0038] Preparation of nylon film: Nylon 6 chips are used and formed by a biaxial stretching process at 245-255°C to obtain nylon film.

[0039] Preferably, the stretch ratio between the longitudinal direction and the transverse direction is 4.5-5.5.

[0040] Preferably, the thickness of the nylon film is 50-70 μm.

[0041] The present invention also provides a method for preparing a composite polyimide / polytetrafluoroethylene film, comprising:

[0042] At -4-6°C, 4,4'-diphenyl ether diamine is dissolved in N,N'-dimethylacetamide, 3,3'4,4'-biphenyl dianhydride is added, and the reaction is carried out for 22-26 hours to obtain polyamic acid; at room temperature, the polyamic acid is reacted with triethylamine for 1-3 hours, and the reaction is carried out after washing with acetone and drying at 45-55°C to obtain polyamic acid salt; the polyamic acid salt is dissolved in deionized water, PTFE emulsion is added, and the mixture is stirred evenly. After coating, the mixture is dried at 75-85°C for 7-9 hours, and heat-treated at 395-405°C for 1-3 hours to obtain a composite polyimide / polytetrafluoroethylene film.

[0043] Preferably, the mass ratio of 4,4'-diphenyl ether diamine to N,N'-dimethylacetamide is 12.5-125:125-1250.

[0044] Preferably, the mass ratio of 3,3',4,4'-biphenyl dianhydride to 4,4'-diphenyl ether diamine is 19.5-195:12.5-125.

[0045] Preferably, the mass ratio of polyamic acid to triethylamine is 12-120:5-50.

[0046] Preferably, the mass ratio of polyamic acid salt to deionized water is 5-50:45-450.

[0047] Preferably, the mass ratio of PTFE emulsion to polyamic acid salt is 2-20:5-50.

[0048] The present invention also provides a method for preparing acid-responsive microcapsules, comprising:

[0049] Preparation of acid-responsive microcapsules: Methyl methacrylate and acrylic acid are dispersed in ethyl acetate, azobisisobutyronitrile is added, and the mixture is stirred evenly. Under nitrogen protection and at 65-75°C, polymerization is carried out for 1-3 hours to form a copolymer shell layer, and pentaerythritol triacrylate is added and stirred evenly to obtain a core material / shell material mixed solution; Span 85 and Tween 20 are dispersed in deionized water and stirred evenly to obtain an emulsifier solution; the core material / shell material mixed solution is added to the emulsifier solution under stirring conditions of 1500-2500 rpm, and stirring is continued for 20-40 minutes. The mixture is transferred to a well-ventilated environment, and the solvent is evaporated for 5-7 hours at room temperature and stirring conditions of 200-400 rpm. The mixture is centrifuged at 3500-4500 rpm for 5-15 minutes. After washing, the mixture is dried at 35-45°C for 1-3 hours to obtain acid-responsive microcapsules.

[0050] Preferably, the mass ratio of methyl methacrylate to acrylic acid is 31.5-315:9-90.

[0051] Preferably, the mass ratio of methyl methacrylate to ethyl acetate is 31.5-315:94.5-945.

[0052] Preferably, the mass ratio of methyl methacrylate to azobisisobutyronitrile is 31.5-315:0.15-1.5.

[0053] Preferably, the mass ratio of pentaerythritol triacrylate to methyl methacrylate is 120-1200:31.5-315.

[0054] Preferably, the mass ratio of Span 85 to deionized water is 1.75-17.5:1200-12000.

[0055] Preferably, the mass ratio of Tween 20 to deionized water is 5.25-52.5:1200-12000.

[0056] Preferably, the particle size of the acid-responsive microcapsules is 10-30 μm.

[0057] The present invention also provides a method for preparing a pH-responsive adhesive, comprising:

[0058] Preparation of pH-responsive adhesive: 1,4-phenylenediboric acid and polyglycerol diglycidyl ether are uniformly mixed, p-toluenesulfonic acid is added, and the mixture is reacted at 115-125°C for 1-3 hours to obtain a dynamic borate prepolymer; 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester and diisopropylbenzene peroxide are uniformly mixed to obtain a dual-cure initiator; the dynamic borate prepolymer, acid-responsive microcapsules, epoxy-acrylate copolymer, and dual-cure initiator are mixed, and the mixture is stirred at 90-110 rpm for 1-3 hours to obtain a pH-responsive adhesive.

[0059] Preferably, the mass ratio of 1,4-phenylenediboronic acid to polyglycerol diglycidyl ether is 0.5-5:1-10.

[0060] Preferably, the mass ratio of p-toluenesulfonic acid to 1,4-phenylenediboronic acid is 1.5-15 mg:0.5-5 g.

[0061] Preferably, the mass ratio of ethyl 2,4,6-trimethylbenzoylphenylphosphonate to dicumyl peroxide is 1-10:2.25-22.5.

[0062] Preferably, the mass ratio of the dynamic borate prepolymer to the acid-responsive microcapsules is 15-150:6.75-67.5.

[0063] Preferably, the mass ratio of the dynamic borate prepolymer to the epoxy-acrylate copolymer is 15-150:25-250.

[0064] Preferably, the mass ratio of the dynamic borate prepolymer to the dual-cure initiator is 15-150:3.25-32.5.

[0065] The present invention also provides a method for preparing a polymer film for a lead-acid battery, comprising:

[0066] Preparation of a polymer film for a lead-acid battery: corona-treating the surface of a first film substrate, coating it with a pH-responsive adhesive to form a first adhesive layer, and obtaining an inner adhesive composite film; corona-treating the surface of a second film substrate, compounding it with the inner adhesive composite film, and co-curing it through a light-heat gradient, coating it with a pH-responsive adhesive to form a second adhesive layer, and obtaining an intermediate adhesive composite film; corona-treating the surface of a third film substrate, compounding it with the intermediate adhesive composite film, and co-curing it through a light-heat gradient; rapidly cooling it using a water-cooled roller; and after cooling, heat-sealing it on three sides to form a straight-cut seal with a width of 4 mm, and spraying a layer of polytetrafluoroethylene coating on the straight-cut seal to obtain a polymer film for a lead-acid battery.

[0067] Preferably, the first film substrate comprises a polypropylene film.

[0068] Preferably, the second film substrate includes one of an ethylene terephthalate film and a nylon film.

[0069] Preferably, the third film substrate comprises a composite polyimide / polytetrafluoroethylene film.

[0070] Preferably, the thickness of the first adhesive layer is 10-30 μm.

[0071] Preferably, the thickness of the second adhesive layer is 10-30 μm.

[0072] Preferably, the light-heat gradient synergistic curing includes ultraviolet curing and infrared curing.

[0073] Preferably, the UV curing time is 3-15 seconds.

[0074] Preferably, the infrared light curing time is 5-40s.

[0075] Preferably, the rapid cooling rate is 14-16°C / s.

[0076] Preferably, the hot knife temperature for three-side heat sealing is 165-175°C.

[0077] Preferably, the heat sealing pressure on three sides is 0.6-0.8 MPa.

[0078] Preferably, the holding time for three-side heat sealing is 2-4s.

[0079] The present invention also provides a polymer film for a lead-acid battery.

[0080] Preferably, the tensile strength of the polymer film for lead-acid batteries is 80-200N / 15mm.

[0081] More preferably, the longitudinal tensile strength of the polymer film for lead-acid batteries is 110-200 N / 15 mm.

[0082] More preferably, the transverse tensile strength of the polymer film for lead-acid batteries is 80-180 N / 15 mm.

[0083] Preferably, the water vapor permeability of the polymer membrane for lead-acid batteries is 0.2-2.5 g / m 2 / 24h.

[0084] Preferably, the polymer film for lead-acid batteries has a heat-resistant temperature of above 65°C and below 100°C.

[0085] Preferably, when the polymer membrane for lead-acid batteries is in contact with or immersed in 1.20-1.40 g / mL sulfuric acid for 6-8 days, the change rate of water vapor permeation is less than 10%.

[0086] Preferably, the compressive strength of the polymer film for lead-acid batteries is greater than 1500N and less than 7000N.

[0087] The present invention utilizes a composite structure of at least two film substrates selected from polyethylene terephthalate film, polypropylene film, nylon film, and composite polyimide / polytetrafluoroethylene film, employs a pH-responsive adhesive, and utilizes an optimized curing process. The resulting polymer film exhibits high barrier properties, excellent mechanical strength, strong acid and temperature resistance, and good pressure resistance. Therefore, the present invention provides a polymer film for lead-acid batteries with excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 Schematic diagram of the structure of polymer membrane for lead-acid batteries. DETAILED DESCRIPTION

[0089] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0090] The following first describes the concepts involved in this application with reference to the accompanying drawings. It should be noted that the following description of each concept is intended only to make the content of this application easier to understand and does not limit the scope of protection of this application. At the same time, the embodiments and features in the embodiments of this application can be combined with each other unless there is a conflict. The following detailed description of this application will be made with reference to the accompanying drawings and in conjunction with the embodiments.

[0091] Example 1:

[0092] Preparation of Polypropylene Film: Block copolymer polypropylene was used as the raw material and blended with nano-SiO2 masterbatch in a twin-screw extruder for plasticization and casting to produce polypropylene film. The mass ratio of block copolymer polypropylene to nano-SiO2 masterbatch was 9:1. The extruder temperature was 230°C, the screw speed was 300 rpm, and the thickness of the polypropylene film was 700 μm.

[0093] Preparation of polyethylene terephthalate film: Polyethylene terephthalate slices were biaxially stretched at 210°C to obtain polyethylene terephthalate film. The longitudinal to transverse stretch ratio was 5, and the polyethylene terephthalate film had a thickness of 280 μm.

[0094] Preparation of composite polyimide / polytetrafluoroethylene film: 4,4'-diphenyl ether diamine was dissolved in N,N'-dimethylacetamide at -5°C, 3,3'4,4'-biphenyl dianhydride was added, and the reaction was carried out for 24 hours to obtain polyamic acid; polyamic acid was reacted with triethylamine at room temperature for 2 hours, washed with acetone, and dried at 50°C to obtain polyamic acid salt; polyamic acid salt was dissolved in deionized water, PTFE emulsion was added, stirred evenly, and after coating, the film was dried at 80°C for 8 hours and heat-treated at 400°C for 2 hours to obtain a composite polyimide / polytetrafluoroethylene film. The mass ratio of 4,4'-diphenyl ether diamine to N,N'-dimethylacetamide is 25:250, the mass ratio of 3,3'4,4'-biphenyl dianhydride to 4,4'-diphenyl ether diamine is 39:25, the mass ratio of polyamic acid to triethylamine is 24:10, the mass ratio of polyamic acid salt to deionized water is 10:90, and the mass ratio of PTFE emulsion to polyamic acid salt is 4:10.

[0095] Preparation of acid-responsive microcapsules: Methyl methacrylate and acrylic acid are dispersed in ethyl acetate, azobisisobutyronitrile is added, and the mixture is stirred evenly. Under nitrogen protection and 70°C, the mixture is polymerized for 2 hours to form a copolymer shell layer. Pentaerythritol triacrylate is added and the mixture is stirred evenly to obtain a core material / shell material mixed solution. Span 85 and Tween 20 are dispersed in deionized water and stirred evenly to obtain an emulsifier solution. Under stirring conditions of 2000 rpm, the core material / shell material mixed solution is added to the emulsifier solution, and stirring is continued for 30 minutes. The mixture is transferred to a well-ventilated environment, and the solvent is evaporated for 6 hours at room temperature and stirring conditions of 300 rpm. The mixture is centrifuged at 4000 rpm for 10 minutes, washed, and dried at 40°C for 2 hours to obtain acid-responsive microcapsules. The mass ratio of methyl methacrylate to acrylic acid is 63:18, the mass ratio of methyl methacrylate to ethyl acetate is 63:189, the mass ratio of methyl methacrylate to azobisisobutyronitrile is 63:0.3, the mass ratio of pentaerythritol triacrylate to methyl methacrylate is 240:63, the mass ratio of Span 85 to deionized water is 3.5:2400, and the mass ratio of Tween 20 to deionized water is 10.5:2400; the particle size of the acid-responsive microcapsules is 20 μm.

[0096] Preparation of pH-responsive adhesive: 1,4-phenylenediboronic acid and polyglycerol diglycidyl ether were uniformly mixed, p-toluenesulfonic acid was added, and the mixture was reacted at 120°C for 2 hours to obtain a dynamic borate prepolymer; 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester and diisopropylbenzene peroxide were uniformly mixed to obtain a dual-cure initiator; the dynamic borate prepolymer, acid-responsive microcapsules, epoxy-acrylate copolymer, and dual-cure initiator were mixed, and vacuum stirred at 100 rpm and 60°C for 30 minutes to obtain a pH-responsive adhesive. The mass ratio of 1,4-phenylenediboronic acid to polyglycerol diglycidyl ether is 1:2, the mass ratio of p-toluenesulfonic acid to 1,4-phenylenediboronic acid is 3 mg:1 g, the mass ratio of ethyl 2,4,6-trimethylbenzoylphenylphosphonate to diisopropylbenzene peroxide is 2:4.5, the mass ratio of dynamic borate prepolymer to acid-responsive microcapsules is 30:13.5, the mass ratio of dynamic borate prepolymer to epoxy-acrylate copolymer is 30:50, and the mass ratio of dynamic borate prepolymer to dual-cure initiator is 30:6.5.

[0097] Preparation of a polymer film for a lead-acid battery: corona-treating the surface of a first film substrate, coating it with a pH-responsive adhesive to form a first adhesive layer, and obtaining an inner adhesive composite film; corona-treating the surface of a second film substrate, compounding it with the inner adhesive composite film, and co-curing it through a light-heat gradient, coating it with a pH-responsive adhesive to form a second adhesive layer, and obtaining an intermediate adhesive composite film; corona-treating the surface of a third film substrate, compounding it with the intermediate adhesive composite film, and co-curing it through a light-heat gradient; rapidly cooling it using a water-cooled roller; and after cooling, heat-sealing it on three sides to form a straight-cut seal with a width of 4 mm, and spraying a layer of polytetrafluoroethylene coating on the straight-cut seal to obtain a polymer film for a lead-acid battery. The first film substrate is a polypropylene film, the second film substrate is a polyethylene terephthalate film, and the third film substrate is a composite polyimide / polytetrafluoroethylene film; the thickness of the first adhesive layer is 20 μm, and the thickness of the second adhesive layer is 20 μm; the light-heat gradient synergistic curing includes ultraviolet curing and infrared curing, ultraviolet curing for 10 seconds and infrared curing for 35 seconds, and infrared curing is started within 0.3 seconds after the end of ultraviolet curing; in the three-sided heat sealing, the hot knife temperature is 170°C, the pressure is 0.7 MPa, and the holding time is 3.0 seconds.

[0098] Example 2: Compared with Example 1, the only difference between this example and Example 1 is the preparation of the polymer membrane for lead-acid batteries.

[0099] Preparation of nylon film: Nylon 6 chips were biaxially stretched at 250°C to obtain a nylon film with a longitudinal to transverse stretch ratio of 5 and a thickness of 60 μm.

[0100] Preparation of a polymer film for a lead-acid battery: corona-treating the surface of a first film substrate, coating it with a pH-responsive adhesive to form a first adhesive layer, and obtaining an inner adhesive composite film; corona-treating the surface of a second film substrate, compounding it with the inner adhesive composite film, and co-curing it through a light-heat gradient, coating it with a pH-responsive adhesive to form a second adhesive layer, and obtaining an intermediate adhesive composite film; corona-treating the surface of a third film substrate, compounding it with the intermediate adhesive composite film, and co-curing it through a light-heat gradient; rapidly cooling it using a water-cooled roller; and after cooling, heat-sealing it on three sides to form a straight-cut seal with a width of 4 mm, and spraying a layer of polytetrafluoroethylene coating on the straight-cut seal to obtain a polymer film for a lead-acid battery. The first film substrate is a polypropylene film, the second film substrate is a nylon film, and the third film substrate is a composite polyimide / polytetrafluoroethylene film; the thickness of the first adhesive layer is 20 μm, and the thickness of the second adhesive layer is 20 μm; light-heat gradient synergistic curing includes ultraviolet curing and infrared curing, ultraviolet curing for 10 seconds and infrared curing for 35 seconds, and infrared curing is started within 0.3 seconds after the end of ultraviolet curing; in three-sided heat sealing, the hot knife temperature is 170°C, the pressure is 0.7 MPa, and the holding time is 3.0 seconds.

[0101] Test Example 1: Voltage resistance test of polymer membrane for lead-acid battery.

[0102] Test sample: polymer membrane for lead-acid battery prepared in each example.

[0103] Test method: According to the national standard GB / T 21302-2007, under the specified conditions, the test is carried out using a polymer membrane for lead-acid batteries.

[0104] The polymer membrane for lead-acid batteries prepared by the present invention adopts the dynamic interface bonding of pH-responsive adhesives, ultraviolet-infrared synergistic curing process and multi-layer composite structure design, so that the adhesive layer can adapt to the deformation of the substrate during the heat sealing process, reduce interface defects, and significantly improve the compressive strength of the polymer membrane for lead-acid batteries. Both can effectively withstand a pressure of more than 1500N. The compressive strength of Example 1 is 3540N, and the compressive strength of Example 2 is 2895N.

[0105] Test Example 2: Tensile strength test of polymer membrane for lead-acid batteries.

[0106] Test sample: polymer membrane for lead-acid battery prepared in each example.

[0107] Test method: Cut dumbbell-shaped specimens from polymer film of lead-acid batteries and use an electronic universal testing machine with a clamp spacing of 50 mm and a tensile speed of 50 mm / min. Record the maximum force when the specimen breaks and calculate the elongation at break.

[0108] The polymer film for lead-acid batteries prepared by the present invention combines the high strength of various film substrates with the high toughness of polypropylene. The longitudinal tensile strength of Example 1 is 158N / 15mm, and the transverse tensile strength is 132N / 15mm; the longitudinal tensile strength of Example 2 is 175N / 15mm, and the transverse tensile strength is 148N / 15mm, and the mechanical strength is excellent.

[0109] Test Example 3: Water vapor permeability test of polymer membranes for lead-acid batteries.

[0110] Test sample: polymer membrane for lead-acid battery prepared in each example.

[0111] Test method: Pour 30mL of deionized water into a moisture permeable cup with an inner diameter of 70mm. Seal the cup mouth of the sample, weigh the initial mass m0 of the polymer membrane for lead-acid batteries, and place it in a constant temperature and humidity chamber. After 24 hours, take it out and weigh the mass m1. The moisture permeable area is S. Calculate the water vapor transmission rate according to the formula WVT=(m1-m0) / (S×24h).

[0112] The polymer membrane for lead-acid batteries prepared by the present invention forms a high barrier structure through process optimization and material synergy. At the same time, the adhesive fills the interface micropores to further block the water vapor permeation path. The water vapor permeation rates of Example 1 and Example 2 are 1.48 g / m 2 / 24h and 1.62g / m 2 / 24h, water vapor transmission rate decreases.

[0113] Test Example 4: Acid resistance test of polymer membrane for lead-acid battery.

[0114] Test sample: polymer membrane for lead-acid battery prepared in each example.

[0115] Test method: Take the polymer film for lead-acid batteries, measure the initial water vapor transmission rate F0, cut it into 50mm×50mm after drying, and completely immerse it in 1.35g / mL sulfuric acid solution at 25℃. After soaking for 7 days, take it out, rinse it with deionized water 3 times, dry it at room temperature for 24 hours, and measure the final water vapor transmission rate F0. t , according to the formula ∆F=(F t -F0) / F0×100%, and calculate the change rate of water vapor transmission rate.

[0116] The polymer membrane for lead-acid batteries prepared by the present invention maintains an intact appearance after being soaked in sulfuric acid, without wrinkling, shrinkage, delamination or brittleness, and the water vapor permeability change rate is less than 10%. The water vapor permeability change rate of Example 1 is 3.3%, and the water vapor permeability change rate of Example 2 is 4.7%, indicating that the dynamic 1,4-phenylenediboronate bond in the pH-responsive adhesive remains stable in an acidic environment, and the acid-responsive microcapsules in the adhesive layer are not broken, thereby ensuring the interfacial bonding strength between the adhesive layer and the substrate. At the same time, the effect of the multiple membranes indicates that the inorganic layer can physically isolate the corrosive medium and enhance the acid resistance. The composite membrane solves the durability problem of a single material in a strong acid environment through material complementarity and process optimization, and meets the long-term corrosion resistance requirements of lead-acid batteries.

[0117] Test Example 5: Heat resistance test of polymer membrane for lead acid battery.

[0118] Test sample: polymer membrane for lead-acid battery prepared in each example.

[0119] Test method: Cut the polymer film for lead-acid batteries into 50mm×50mm pieces, place them in a drying oven, and heat them from room temperature at a rate of 5℃ / min. Observe the temperature at which the sample wrinkles or shrinks, and record it as the heat-resistance temperature.

[0120] The composite structure of the polymer membrane for lead-acid batteries prepared by the present invention has improved heat resistance and can effectively withstand temperatures above 65°C. The heat-resistant temperature of Example 1 is 80°C, and the heat-resistant temperature of Example 2 is 75°C.

[0121] The embodiments and / or implementation methods described above are only used to illustrate the preferred embodiments and / or implementation methods for realizing the technology of the present invention, and do not impose any form of limitation on the implementation methods of the technology of the present invention. Any person skilled in the art may make slight changes or modifications to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but they should still be regarded as technologies or embodiments that are essentially the same as the present invention.

[0122] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. The above is only the preferred implementation method of this application. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of this application, they can also make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the scope of protection of this application.

Claims

1. A polymer membrane for a lead-acid battery, comprising at least two layers of a film substrate and an adhesive layer, wherein the adhesive layer comprises a dynamic borate prepolymer and acid-responsive microcapsules, wherein the dynamic borate prepolymer is obtained by reacting 1,4-phenylenediboronic acid and polyglycerol diglycidyl ether under the catalysis of p-toluenesulfonic acid; the shell material of the acid-responsive microcapsules comprises polymethyl methacrylate-co-acrylic acid, and the core material of the acid-responsive microcapsules comprises pentaerythritol triacrylate. The polymer membrane for a lead-acid battery has a compressive strength of greater than 1500N.

2. A polymer membrane for a lead-acid battery according to claim 1, characterized in that: The polymer membrane for lead-acid batteries is immersed in 1.20-1.40 g / mL sulfuric acid for 6-8 days, and the change rate of water vapor transmission rate is less than 10%.

3. A polymer membrane for a lead-acid battery according to claim 1, characterized in that: The tensile strength of the polymer film for lead-acid batteries is 80-200N / 15mm.

4. The polymer membrane for lead-acid batteries according to claim 1, characterized in that: The water vapor permeability of the polymer film for lead-acid batteries is 0.2-2.5 g / m 2 / 24h.

5. The polymer membrane for lead-acid batteries according to claim 1, characterized in that: The film substrate includes at least two of polyethylene terephthalate film, polypropylene film, nylon film and composite polyimide / polytetrafluoroethylene film. The thickness of the polyethylene terephthalate film is 240-320 μm, the thickness of the polypropylene film is 650-750 μm, and the thickness of the nylon film is 50-70 μm.

6. The polymer membrane for lead-acid batteries according to claim 1, characterized in that: The adhesive layer includes an epoxy-acrylate copolymer.

7. The polymer membrane for lead-acid batteries according to claim 1, characterized in that: The adhesive layer includes a dual-cure initiator, and the dual-cure initiator includes ethyl 2,4,6-trimethylbenzoylphenylphosphonate and dicumyl peroxide.

8. The polymer membrane for lead-acid batteries according to claim 1, characterized in that: The film substrates are composited by light-heat gradient synergistic curing, and the light-heat gradient synergistic curing includes ultraviolet curing and infrared curing.

Images