Polymeric membrane for lead-acid storage battery

Abstract

The invention discloses a polymeric membrane for a lead-acid storage battery, which comprises at least two layers of membrane substrates, and the membrane substrates comprise at least two of a polyethylene glycol terephthalate membrane, a polypropylene membrane, a nylon membrane and a composite polyimide / polytetrafluoroethylene membrane. The lead-acid battery has excellent strong acid corrosion resistance, high mechanical strength, wear resistance and flame retardance, the service time of the lead-acid battery can be prolonged, and the safety of the battery is improved; the polymeric membrane for the lead-acid storage battery comprises a bonding layer, an acid response microcapsule in the bonding layer breaks when encountering an acid medium to release a cross-linking agent component, the cross-linking density of the bonding layer is further enhanced, meanwhile, a curing process is optimized, the acid resistance and pressure resistance of the polymeric membrane for the lead-acid storage battery are improved, and mechanical properties and environmental tolerance are both considered. The prepared polymeric membrane is suitable for sealing a modular lead-acid storage battery pole group, and the energy utilization rate is improved.

Description

Technical Field

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

[0002] Currently, lead-acid batteries mainly use hard polymer materials such as ABS as the outer shell. The advantage is high strength, which can provide assembly pressure for the battery cluster. However, the outer shell is not compressible, making it inconvenient to insert the battery cluster into the shell, and the pressure shows a downward trend during use, resulting in performance degradation of the lead-acid battery.

[0003] Ordinary flexible polymer composite films are mainly composed of more than 2 - 3 layers such as polypropylene, polyethylene terephthalate, and nylon. Polypropylene is used as the inner layer, playing a role in resisting electrolyte corrosion and heat-sealing adhesion; the outer layer is a polyester or nylon film, providing mechanical strength, abrasion resistance, and puncture resistance; the adhesive layer is a polyurethane or epoxy adhesive to ensure the bonding force between layers. During the assembly process of lead-acid batteries, sulfuric acid or acid mist overflows to the outer layer, corroding the outer layer, and sulfuric acid or acid mist penetrates into the adhesive layer, resulting in the failure of the adhesive layer and delamination between the inner and outer layers. At the same time, ordinary curing processes usually adopt a single energy field action mode, such as long-term heat curing or only using ultraviolet light to initiate surface curing, which easily causes premature hardening of the surface resin, hindering internal cross-linking and resulting in insufficient curing degree of the core layer. The above two points will both lead to a decrease in the interlayer peel strength of the composite film, restricting the long-term reliability of the packaging material under complex working conditions.

[0004] Therefore, the present invention provides a polymer film for lead-acid batteries, which encapsulates the electrode plate, making it have the characteristics of light weight, high energy density, high strength, and acid resistance, and systematically balances the technical contradiction between the rigid packaging and flexible deformation of lead-acid batteries. Summary of the Invention

[0005] The purpose of the present invention is to provide a polymer film for lead-acid batteries that is resistant to strong acids and high pressures.

[0006] The technical solution adopted by the present invention to achieve the above purpose is as follows: A polymer film for lead-acid batteries includes at least two layers of thin film substrates, and the pressure resistance of the polymer film for lead-acid batteries is above 1500N.

[0007] Preferably, the polymer film for lead-acid batteries includes three, four, five, six, and seven layers of thin film substrates.

[0008] Preferably, the pressure resistance is detected for the polymer film for lead-acid batteries in accordance with GB / T 21302 - 2007 of the national standard.

[0009] Preferably, the polymer film for lead-acid batteries is contacted or immersed in sulfuric acid with a density of 1.20 - 1.40 g / mL for 6 - 8 days, and the change rate of water vapor transmission rate is below 10%.

[0010] Preferably, the breaking force of the polymer film for lead-acid batteries is 80 - 200 N / 15 mm.

[0011] Preferably, the water vapor transmission rate of the polymer film for lead-acid batteries is 0.2 - 2.5 g / m 2 / 24 h.

[0012] Preferably, the thin film substrate includes at least two of polyethylene terephthalate film, polypropylene film, nylon film and composite polyimide / polytetrafluoroethylene film.

[0013] The composite polyimide / polytetrafluoroethylene film combines the superhydrophobicity and chemical resistance of polytetrafluoroethylene, can further resist the penetration of acidic media, and has excellent strong acid corrosion resistance; it combines the high strength of polyimide and the flexibility of polytetrafluoroethylene, and is suitable for flexible thin film substrates; in addition to having sulfuric acid corrosion resistance, it also has high mechanical strength, wear resistance, flame retardancy, can extend the service time of lead-acid batteries and increase the safety of the batteries.

[0014] Preferably, the polymer film for lead-acid batteries includes an adhesive layer.

[0015] Preferably, the adhesive layer includes a dynamic borate prepolymer.

[0016] Preferably, the dynamic borate prepolymer is obtained by reacting 1,4-benzenediboronic acid with diglycidyl ether of polyglycerol under the catalysis of p-toluenesulfonic acid.

[0017] Preferably, the adhesive layer includes acid-responsive microcapsules.

[0018] Preferably, the shell material of the acid-responsive microcapsules includes polymethyl methacrylate-co-acrylic acid.

[0019] Preferably, the core material of the acid-responsive microcapsules includes pentaerythritol triacrylate.

[0020] Preferably, the adhesive layer includes an epoxy-acrylate copolymer.

[0021] Preferably, the adhesive layer includes a dual-curing initiator.

[0022] Preferably, the dual-curing initiator includes ethyl 2,4,6-trimethylbenzoyl phenylphosphinate and dicumyl peroxide.

[0023] The acid-responsive microcapsules in the adhesive layer remain intact in neutral and alkaline environments, and rupture in the presence of an acidic medium to release the cross-linking agent component, further strengthening the cross-linking density of the adhesive layer and increasing acid resistance; the epoxy-acrylate copolymer provides ultraviolet-curing active groups, and cooperates with the dual-curing initiator to achieve the dual-curing mechanism of "rapid ultraviolet-curing shaping - deep thermal-curing cross-linking", which can not only fill the micro-pores on the surface of the substrate, but also dissipate external stress through the dynamic reversible characteristics, avoid interface cracking, and increase the compressive performance.

[0024] Preferably, the film substrates are compounded by light-thermal gradient cooperative curing.

[0025] Preferably, the light-thermal gradient cooperative curing includes ultraviolet curing and infrared curing.

[0026] The present invention also provides a method for preparing a polypropylene film, comprising: Preparation of the polypropylene film: Selecting block copolymerized polypropylene as the raw material, blending and plasticizing it with a nano-SiO2 masterbatch in a twin-screw extruder, and casting and molding to obtain the polypropylene film.

[0027] Preferably, the mass ratio of the block copolymerized polypropylene to the nano-SiO2 masterbatch is 4.5 - 45:0.5 - 5.

[0028] Preferably, the process temperature of the extruder is 220 - 240 °C.

[0029] Preferably, the screw speed is 250 - 350 rpm.

[0030] Preferably, the thickness of the polypropylene film is 650 - 750 μm.

[0031] The present invention also provides a method for preparing a polyethylene terephthalate film, comprising: Preparation of the polyethylene terephthalate film: Using polyethylene terephthalate chips, and forming them by a biaxial stretching process at 205 - 215 °C to obtain the polyethylene terephthalate film.

[0032] Preferably, the longitudinal and transverse stretching ratios are 4.5 - 5.5.

[0033] Preferably, the thickness of the polyethylene terephthalate film is 240 - 320 μm.

[0034] The present invention also provides a method for preparing a nylon film, comprising: Preparation of the nylon film: Using nylon 6 chips, and forming them by a biaxial stretching process at 245 - 255 °C to obtain the nylon film.

[0035] Preferably, the longitudinal and transverse stretching ratios are 4.5 - 5.5.

[0036] Preferably, the thickness of the nylon film is 50-70 μm.

[0037] The present invention also provides a method for preparing a composite polyimide / polytetrafluoroethylene film, comprising: Under the condition of -4 to -6 °C, dissolve 4,4'-oxydianiline in N,N'-dimethylacetamide, add 3,3',4,4'-biphenyltetracarboxylic dianhydride, and react for 22-26 h to obtain polyamic acid; under room temperature conditions, react polyamic acid with triethylamine for 1-3 h, wash with acetone, and dry at 45-55 °C to obtain polyamic acid salt; dissolve the polyamic acid salt in deionized water, add PTFE emulsion, stir evenly, coat the film, dry at 75-85 °C for 7-9 h, and perform heat treatment at 395-405 °C for 1-3 h to obtain the composite polyimide / polytetrafluoroethylene film.

[0038] Preferably, the mass ratio of 4,4'-oxydianiline to N,N'-dimethylacetamide is 12.5-125:125-1250.

[0039] Preferably, the mass ratio of 3,3',4,4'-biphenyltetracarboxylic dianhydride to 4,4'-oxydianiline is 19.5-195:12.5-125.

[0040] Preferably, the mass ratio of polyamic acid to triethylamine is 12-120:5-50.

[0041] Preferably, the mass ratio of polyamic acid salt to deionized water is 5-50:45-450.

[0042] Preferably, the mass ratio of PTFE emulsion to polyamic acid salt is 2-20:5-50.

[0043] The present invention also provides a method for preparing acid-responsive microcapsules, comprising: Preparation of acid-responsive microcapsules: Disperse methyl methacrylate and acrylic acid in ethyl acetate, add azobisisobutyronitrile, stir evenly, and under nitrogen protection and at 65-75 °C, polymerize for 1-3 h to form a copolymer shell layer. Add pentaerythritol triacrylate and stir evenly to obtain a core / shell mixed solution; disperse Span 85 and Tween 20 in deionized water, stir evenly to obtain an emulsifier solution; under the stirring condition of 1500-2500 rpm, add the core / shell mixed solution to the emulsifier solution, continue stirring for 20-40 min, transfer to a well-ventilated environment, and under room temperature and the stirring condition of 200-400 rpm, evaporate the solvent for 5-7 h, centrifuge at 3500-4500 rpm for 5-15 min, wash, and dry at 35-45 °C for 1-3 h to obtain acid-responsive microcapsules.

[0044] Preferably, the mass ratio of methyl methacrylate to acrylic acid is 31.5 - 315:9 - 90.

[0045] Preferably, the mass ratio of methyl methacrylate to ethyl acetate is 31.5 - 315:94.5 - 945.

[0046] Preferably, the mass ratio of methyl methacrylate to azobisisobutyronitrile is 31.5 - 315:0.15 - 1.5.

[0047] Preferably, the mass ratio of pentaerythritol triacrylate to methyl methacrylate is 120 - 1200:31.5 - 315.

[0048] Preferably, the mass ratio of span 85 to deionized water is 1.75 - 17.5:1200 - 12000.

[0049] Preferably, the mass ratio of tween 20 to deionized water is 5.25 - 52.5:1200 - 12000.

[0050] Preferably, the particle size of the acid-responsive microcapsules is 10 - 30 μm.

[0051] The present invention also provides a preparation method of a pH-responsive adhesive, comprising: Preparation of the pH-responsive adhesive: uniformly mix 1,4-benzenediboronic acid with polyglycerol diglycidyl ether, add p-toluenesulfonic acid, and react at 115 - 125 °C for 1 - 3 h to obtain a dynamic borate prepolymer; uniformly mix ethyl 2,4,6-trimethylbenzoyl phenylphosphinate and dicumyl peroxide to obtain a dual-curing initiator; mix the dynamic borate prepolymer, acid-responsive microcapsules, epoxy-acrylate copolymer, and dual-curing initiator, and stir at 90 - 110 rpm for 1 - 3 h to obtain the pH-responsive adhesive.

[0052] Preferably, the mass ratio of 1,4-benzenediboronic acid to polyglycerol diglycidyl ether is 0.5 - 5:1 - 10.

[0053] Preferably, the mass ratio of p-toluenesulfonic acid to 1,4-benzenediboronic acid is 1.5 - 15 mg:0.5 - 5 g.

[0054] Preferably, the mass ratio of ethyl 2,4,6-trimethylbenzoyl phenylphosphinate to dicumyl peroxide is 1 - 10:2.25 - 22.5.

[0055] Preferably, the mass ratio of the dynamic borate prepolymer to the acid-responsive microcapsules is 15 - 150:6.75 - 67.5.

[0056] Preferably, the mass ratio of the dynamic borate prepolymer to the epoxy-acrylate copolymer is 15 - 150:25 - 250.

[0057] Preferably, the mass ratio of the dynamic borate prepolymer to the dual-curing initiator is 15 - 150:3.25 - 32.5.

[0058] The present invention also provides a method for preparing a polymer film for lead-acid batteries, comprising: Preparation of the polymer film for lead-acid batteries: corona-treat the surface of the first film substrate, then coat a pH-responsive adhesive to form a first adhesive layer, obtaining an inner-layer adhesive composite film; corona-treat the surface of the second film substrate, composite it with the inner-layer adhesive composite film, perform photo-thermal gradient synergistic curing, coat a pH-responsive adhesive to form a second adhesive layer, obtaining an intermediate-layer adhesive composite film; corona-treat the surface of the third film substrate, composite it with the intermediate-layer adhesive composite film, perform photo-thermal gradient synergistic curing; use a water-cooled roller for rapid cooling; after cooling, perform three-sided heat sealing to form a straight cut seal with a width of 4 mm, and spray a layer of polytetrafluoroethylene coating at the straight cut seal to obtain the polymer film for lead-acid batteries.

[0059] Preferably, the first film substrate comprises a polypropylene film.

[0060] Preferably, the second film substrate comprises one of a polyethylene terephthalate film and a nylon film.

[0061] Preferably, the third film substrate comprises a composite polyimide / polytetrafluoroethylene film.

[0062] Preferably, the thickness of the first adhesive layer is 10 - 30 μm.

[0063] Preferably, the thickness of the second adhesive layer is 10 - 30 μm.

[0064] Preferably, the photo-thermal gradient synergistic curing includes ultraviolet curing and infrared curing.

[0065] Preferably, the ultraviolet curing duration is 3 - 15 s.

[0066] Preferably, the infrared curing duration is 5 - 40 s.

[0067] Preferably, the rapid cooling rate is 14 - 16 °C / s.

[0068] Preferably, the hot knife temperature for three-sided heat sealing is 165 - 175 °C.

[0069] Preferably, the pressure for three-sided heat sealing is 0.6 - 0.8 MPa.

[0070] Preferably, the pressure holding time for three-sided heat sealing is 2 - 4 s.

[0071] The present invention also provides a polymer film for lead-acid batteries.

[0072] Preferably, the breaking strength of the polymer film for lead-acid batteries is 80-200 N / 15 mm.

[0073] More preferably, the longitudinal breaking strength of the polymer film for lead-acid batteries is 110-200 N / 15 mm.

[0074] More preferably, the transverse breaking strength of the polymer film for lead-acid batteries is 80-180 N / 15 mm.

[0075] Preferably, the water vapor transmission rate of the polymer film for lead-acid batteries is 0.2-2.5 g / m 2 / 24 h.

[0076] Preferably, the heat-resistant temperature of the polymer film for lead-acid batteries is above 65 °C and below 100 °C.

[0077] Preferably, the polymer film for lead-acid batteries is contacted or immersed in sulfuric acid with a density of 1.20-1.40 g / mL for 6-8 days, and the change rate of the water vapor transmission rate is below 10%.

[0078] Preferably, the pressure resistance of the polymer film for lead-acid batteries is above 1500 N and below 7000 N.

[0079] Since the present invention adopts a structure in which at least two kinds of film substrates among polyethylene terephthalate film, polypropylene film, nylon film and composite polyimide / polytetrafluoroethylene film are compounded, and adopts a pH-responsive adhesive and optimizes the curing process, the following beneficial effects are obtained: the prepared polymer film has high barrier performance, excellent mechanical strength, strong acid and temperature resistance and good pressure resistance. Therefore, the present invention is a polymer film for lead-acid batteries with excellent performance. Description of the Drawings

[0080] Figure 1 It is a schematic structural diagram of the polymer film for lead-acid batteries. Detailed Embodiments

[0081] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0082] First, the concepts involved in this application will be described in conjunction with the accompanying drawings. It should be noted here that the following descriptions of each concept are only for making the content of this application easier to understand and do not represent a limitation on the protection scope of this application; at the same time, without conflict, the embodiments and features in the embodiments of this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0083] Embodiment 1: Preparation of polypropylene film: Block copolymer polypropylene was selected as the raw material and melt-blended and cast with a nano-SiO2 masterbatch in a twin-screw extruder to obtain a polypropylene film. The mass ratio of block copolymer polypropylene to nano-SiO2 masterbatch was 9:1, the process temperature of the extruder was 230 °C, the screw speed was 300 rpm, and the thickness of the polypropylene film was 700 μm.

[0084] Preparation of polyethylene terephthalate film: Polyethylene terephthalate chips were used and formed by a biaxial stretching process at 210 °C to obtain a polyethylene terephthalate film. The draw ratio in the longitudinal and transverse directions was 5, and the thickness of the polyethylene terephthalate film was 280 μm.

[0085] Preparation of composite polyimide / polytetrafluoroethylene film: At -5 °C, 4,4'-oxydianiline was dissolved in N,N'-dimethylacetamide, and 3,3',4,4'-biphenyltetracarboxylic dianhydride was added. After reacting for 24 h, polyamic acid was obtained; at room temperature, the polyamic acid was reacted with triethylamine for 2 h, washed with acetone, and dried at 50 °C to obtain polyamic acid salt; the polyamic acid salt was dissolved in deionized water, PTFE emulsion was added, stirred evenly, coated, dried at 80 °C for 8 h, and heat-treated at 400 °C for 2 h to obtain a composite polyimide / polytetrafluoroethylene film. The mass ratio of 4,4'-oxydianiline to N,N'-dimethylacetamide was 25:250, the mass ratio of 3,3',4,4'-biphenyltetracarboxylic dianhydride to 4,4'-oxydianiline was 39:25, the mass ratio of polyamic acid to triethylamine was 24:10, the mass ratio of polyamic acid salt to deionized water was 10:90, and the mass ratio of PTFE emulsion to polyamic acid salt was 4:10.

[0086] Preparation of acid-responsive microcapsules: Methyl methacrylate and acrylic acid were dispersed in ethyl acetate, and azobisisobutyronitrile was added. After stirring evenly, under nitrogen protection and at 70 °C, polymerization was carried out for 2 h to form a copolymer shell layer. Pentaerythritol triacrylate was added and stirred evenly to obtain a core / shell mixed solution; Span 85 and Tween 20 were dispersed in deionized water and stirred evenly to obtain an emulsifier solution; under the stirring condition of 2000 rpm, the core / shell mixed solution was added to the emulsifier solution, and stirring was continued for 30 min. Then it was transferred to a well-ventilated environment, and the solvent was volatilized for 6 h under the conditions of room temperature and 300 rpm stirring. Centrifugation was carried out for 10 min at 4000 rpm, and after washing, it was dried at 40 °C for 2 h to obtain acid-responsive microcapsules. The mass ratio of methyl methacrylate to acrylic acid was 63:18, the mass ratio of methyl methacrylate to ethyl acetate was 63:189, the mass ratio of methyl methacrylate to azobisisobutyronitrile was 63:0.3, the mass ratio of pentaerythritol triacrylate to methyl methacrylate was 240:63, the mass ratio of Span 85 to deionized water was 3.5:2400, and the mass ratio of Tween 20 to deionized water was 10.5:2400; the particle size of the acid-responsive microcapsules was 20 μm.

[0087] Preparation of pH-responsive adhesive: 1,4-benzenediboronic acid and polyglycerol diglycidyl ether were evenly mixed, and p-toluenesulfonic acid was added. The reaction was carried out at 120 °C for 2 h to obtain a dynamic borate prepolymer; 2,4,6-trimethylbenzoyl diphenylphosphine oxide and diisopropylbenzene peroxide were mixed evenly to obtain a dual-curing initiator; the dynamic borate prepolymer, acid-responsive microcapsules, epoxy-acrylate copolymer, and dual-curing initiator were mixed and stirred under vacuum at 100 rpm and 60 °C for 30 min to obtain a pH-responsive adhesive. The mass ratio of 1,4-benzenediboronic acid to polyglycerol diglycidyl ether was 1:2, the mass ratio of p-toluenesulfonic acid to 1,4-benzenediboronic acid was 3 mg:1 g, the mass ratio of 2,4,6-trimethylbenzoyl diphenylphosphine oxide to diisopropylbenzene peroxide was 2:4.5, the mass ratio of the dynamic borate prepolymer to the acid-responsive microcapsules was 30:13.5, the mass ratio of the dynamic borate prepolymer to the epoxy-acrylate copolymer was 30:50, and the mass ratio of the dynamic borate prepolymer to the dual-curing initiator was 30:6.5.

[0088] Preparation of the polymer film for lead-acid battery: The surface of the first film substrate is corona-treated and then coated with a pH-responsive adhesive to form a first adhesive layer, obtaining an inner adhesive composite film; the surface of the second film substrate is corona-treated and then laminated with the inner adhesive composite film, and through photo-thermal gradient synergistic curing, it is coated with a pH-responsive adhesive to form a second adhesive layer, obtaining an intermediate adhesive composite film; the surface of the third film substrate is corona-treated and then laminated with the intermediate adhesive composite film, and through photo-thermal gradient synergistic curing; rapid cooling is carried out using a water-cooled roller; after cooling, three-side heat sealing is performed to form a straight cut seal with a width of 4 mm, and a layer of polytetrafluoroethylene coating is sprayed at the straight cut seal to obtain the polymer film for 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 photo-thermal gradient synergistic curing includes ultraviolet curing and infrared curing. Infrared curing is carried out 35 s after ultraviolet curing for 10 s, and infrared curing is started within 0.3 s after the end of ultraviolet curing; in the three-side heat sealing, the temperature of the hot knife is 170 °C, the pressure is 0.7 MPa, and the pressure holding time is 3.0 s.

[0089] Example 2: Compared with Example 1, the only difference in this example lies in the preparation of the polymer film for lead-acid battery.

[0090] Preparation of nylon film: Nylon 6 chips are used and formed by a biaxial stretching process at 250 °C to obtain a nylon film. The draw ratios in the longitudinal and transverse directions are 5, and the thickness of the nylon film is 60 μm.

[0091] Preparation of the polymer film for lead-acid battery: The surface of the first film substrate is corona-treated and then coated with a pH-responsive adhesive to form a first adhesive layer, obtaining an inner adhesive composite film; the surface of the second film substrate is corona-treated and then laminated with the inner adhesive composite film, and through photo-thermal gradient synergistic curing, it is coated with a pH-responsive adhesive to form a second adhesive layer, obtaining an intermediate adhesive composite film; the surface of the third film substrate is corona-treated and then laminated with the intermediate adhesive composite film, and through photo-thermal gradient synergistic curing; rapid cooling is carried out using a water-cooled roller; after cooling, three-side heat sealing is performed to form a straight cut seal with a width of 4 mm, and a layer of polytetrafluoroethylene coating is sprayed at the straight cut seal to obtain the polymer film for 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; the photo-thermal gradient synergistic curing includes ultraviolet curing and infrared curing. Infrared curing is carried out 35 s after ultraviolet curing for 10 s, and infrared curing is started within 0.3 s after the end of ultraviolet curing; in the three-side heat sealing, the temperature of the hot knife is 170 °C, the pressure is 0.7 MPa, and the pressure holding time is 3.0 s.

[0092] Test Example 1: Pressure resistance test of the polymer film for lead-acid batteries.

[0093] Test sample: The polymer film for lead-acid batteries prepared in each example.

[0094] Test method: According to the national standard GB / T 21302-2007, under the specified conditions, the polymer film for lead-acid batteries was used for testing.

[0095] The polymer film for lead-acid batteries prepared by the present invention, through the dynamic interfacial bonding of the pH-responsive adhesive, the ultraviolet-infrared synergistic curing process, and the multi-layer composite structure design, enables the adhesive layer to adapt to the deformation of the substrate during the heat-sealing process, reduces interfacial defects, and significantly improves the pressure resistance strength of the polymer film for lead-acid batteries. All of them can effectively withstand a pressure of more than 1500 N. The pressure resistance strength of Example 1 is 3540 N, and the pressure resistance strength of Example 2 is 2895 N.

[0096] Test Example 2: Tensile breaking force test of the polymer film for lead-acid batteries.

[0097] Test sample: The polymer film for lead-acid batteries prepared in each example.

[0098] Test method: Cut dumbbell-shaped specimens from the polymer film for lead-acid batteries. Using an electronic universal testing machine, the distance between the clamps is 50 mm, and the tensile speed is 50 mm / min. Record the maximum force value when the specimen breaks, and calculate the elongation at break.

[0099] The polymer film for lead-acid batteries prepared by the present invention combines the high strength of various thin film substrates and the high toughness of polypropylene. The longitudinal tensile breaking force of Example 1 is 158 N / 15 mm, and the transverse tensile breaking force is 132 N / 15 mm; the longitudinal tensile breaking force of Example 2 is 175 N / 15 mm, and the transverse tensile breaking force is 148 N / 15 mm, with excellent mechanical strength.

[0100] Test Example 3: Water vapor transmission rate test of the polymer film for lead-acid batteries.

[0101] Test sample: The polymer film for lead-acid batteries prepared in each example.

[0102] Test method: Inject 30 mL of deionized water into a moisture permeation cup with an inner diameter of 70 mm. Seal the cup mouth with the specimen, weigh the initial mass m0 of the polymer film for lead-acid batteries, place it in a constant temperature and humidity chamber, take it out after 24 h and weigh the mass m1. The moisture permeation area is S. According to the formula WVT=(m1 - m0) / (S×24 h), calculate the water vapor transmission rate.

[0103] The polymer film 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 interfacial micropores, further blocking the water vapor penetration path. The water vapor transmission rates of Example 1 and Example 2 are 1.48 g / m 2 / 24 h and 1.62 g / m 2 / 24 h respectively, and the water vapor transmission rate decreases.

[0104] Test Example 4: Acid resistance test of the polymer film for lead-acid batteries.

[0105] Test samples: The polymer films for lead-acid batteries prepared in each example.

[0106] Test method: Take the polymer film for lead-acid batteries, measure the initial water vapor transmission F0. After drying, cut it into 50 mm × 50 mm, and completely immerse it in a sulfuric acid solution with a density of 1.35 g / mL at 25°C. After soaking for 7 days, take it out, rinse it 3 times with deionized water, dry it at room temperature for 24 h, and measure the final water vapor transmission rate F t According to the formula ∆F = (F t - F0) / F0×100%, calculate the change rate of the water vapor transmission rate.

[0107] The polymer film for lead-acid batteries prepared by the present invention remains intact in appearance after being soaked in sulfuric acid, without wrinkling, shrinking, delaminating or embrittling. The change rate of the water vapor transmission rate is less than 10%. The change rate of the water vapor transmission rate of Example 1 is 3.3%, and that of Example 2 is 4.7%. This shows that the dynamic 1,4-benzenediboronic acid ester bond in the pH-responsive adhesive remains stable in an acidic environment, and the acid-responsive microcapsules in the adhesive layer do not rupture, ensuring the interfacial bonding force between the adhesive layer and the substrate. At the same time, the role of the multi-layer film indicates that the inorganic layer can physically isolate the corrosive medium and enhance the acid resistance. Through material complementarity and process optimization, the composite film solves the durability problem of single materials in a strong acid environment and meets the long-term corrosion resistance requirements of lead-acid batteries.

[0108] Test Example 5: Heat resistance test of the polymer film for lead-acid batteries.

[0109] Test samples: The polymer films for lead-acid batteries prepared in each example.

[0110] Test method: Cut the polymer film for lead-acid batteries into 50 mm × 50 mm, put it into a drying oven, heat it from room temperature at a rate of 5°C / min, observe the temperature at which the sample wrinkles and shrinks, and record it as the heat resistance temperature.

[0111] The composite structure in the polymer film for lead-acid batteries prepared by the present invention improves the heat resistance, and can effectively withstand temperatures above 65°C. The heat resistance temperature of Example 1 is 80°C, and that of Example 2 is 75°C.

[0112] The above-described embodiments and / or implementation manners are merely used to illustrate the preferred embodiments and / or implementation manners for implementing the technology of the present invention, and do not impose any formal restrictions on the implementation manners of the technology of the present invention. Any person skilled in the art, without departing from the scope of the technical means disclosed in the content of the present invention, may make some modifications or changes to other equivalent embodiments, but should still be regarded as the same technology or embodiment as the present invention in essence.

[0113] In this article, specific examples are used to elaborate on the principles and implementation manners of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application. The above is only the preferred implementation manner of the present application. It should be noted that due to the limitation of literal expression and objectively existing infinite specific structures, for those of ordinary skill in the art, without departing from the principle of the present application, several improvements, refinements or changes can also be made, or the above technical features can be combined in an appropriate manner; these improvements, refinements, changes or combinations, or directly applying the concept and technical solution of the invention to other occasions without improvement, should all be regarded as the protection scope of the present application.

Claims

1. A polymer film for lead-acid batteries, comprising at least two layers of thin film substrates, and the pressure resistance of the polymer film for lead-acid batteries is above 1500 N.

2. The polymer film for lead-acid batteries according to claim 1, characterized in that, The polymer film for lead-acid batteries is immersed in sulfuric acid with a density of 1.20 - 1.40 g / mL for 6 - 8 days, and the change rate of water vapor transmission rate is below 10%.

3. The polymer film for lead-acid batteries according to claim 1, wherein The breaking force of the polymer film for lead-acid batteries is 80 - 200 N / 15 mm.

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

5. A polymer film for lead-acid batteries according to claim 1, characterized in that, The thin film substrates include at least two of polyethylene terephthalate film, polypropylene film, nylon film and composite polyimide / polytetrafluoroethylene film.

6. The polymer film for lead-acid batteries according to claim 1, characterized in that The polymer film for lead-acid batteries includes an adhesive layer, the adhesive layer includes a dynamic borate prepolymer, and the dynamic borate prepolymer is obtained by reacting 1,4-benzenediboronic acid with polyglycerol diglycidyl ether under the catalysis of p-toluenesulfonic acid.

7. The polymer film for lead-acid batteries according to claim 6, characterized in that, The adhesive layer includes acid-responsive microcapsules, the shell material of the acid-responsive microcapsules includes polymethyl methacrylate-co-acrylic acid, and the core material of the acid-responsive microcapsules includes pentaerythritol triacrylate.

8. The polymer film for lead-acid batteries according to claim 6, wherein The adhesive layer includes an epoxy-acrylate copolymer.

9. The polymer film for lead-acid batteries according to claim 6, wherein, The adhesive layer includes a dual-curing initiator, and the dual-curing initiator includes ethyl 2,4,6-trimethylbenzoyl phenylphosphinate and diisopropylbenzene peroxide.

10. A polymer film for lead-acid batteries according to claim 1, characterized in that, The thin film substrates are compounded by photo-thermal gradient synergistic curing, and the photo-thermal gradient synergistic curing includes ultraviolet curing and infrared curing.

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