Lead-acid battery separator and lead-acid battery

Abstract

To provide a separator with high film strength and high seal strength by controlling the crystalline state of polyethylene in a separator for a lead-acid battery including polyethylene.SOLUTION: The separator for a lead-acid battery includes polyethylene. The crystalline orientation of a polyethylene (110) surface exceeds 0.780 in a wide-angle X-ray scattering analysis, in which X-rays are set to irradiate a film surface of the separator for a lead-acid battery from a direction normal to the film surface. Such a separator for a lead-acid battery and a lead-acid battery using the separator are provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a separator for a lead-acid battery and a lead-acid battery using the same. [Background technology]

[0002] Lead-acid batteries are widely used worldwide for in-vehicle applications (e.g., passenger cars, buses, trucks, motorcycles, and golf carts) and industrial applications (e.g., forklifts, farm machinery, railways, UPS, and communication equipment). In particular, in in-vehicle applications, lead-acid batteries are placed in locations where they are subjected to vibration (e.g., under the hood), so the separator, which is a component of lead-acid batteries, is required to have high film strength.

[0003] Porous membranes made of constituent materials such as polyethylene, silica particles, and oil are widely used as separators for lead-acid batteries. Increasing the membrane thickness can increase the membrane strength of the porous membrane, but this increases the separator's electrical resistance within the battery, leading to a decrease in the output of the lead-acid battery. Conversely, if the membrane strength per thickness is increased, the electrical resistance can be reduced by making the separator thinner. While it is believed that membrane strength can be changed by changing the ratio of the constituent materials, this significantly changes membrane properties other than strength, such as electrical resistance. Therefore, there is a need for a technology to improve membrane strength by methods other than changing the separator's constituent materials, their mixing ratio, and separator membrane thickness.

[0004] Furthermore, it is known that the electrode active material of lead-acid batteries deteriorates with the progress of charge-discharge cycles, making the active material particularly susceptible to softening and detachment from the positive electrode. A technique for preventing the detached active material from becoming conductive and causing a short circuit between the positive and negative electrodes has been reported (Patent Document 1). The ends of the pouch-shaped polyethylene separator can be bonded, for example, by a mechanical sealing method, which is excellent in production efficiency and manufacturing cost. If the seal strength is weak, the adhesive bond may peel off due to mechanical stress during assembly of the lead-acid battery, or due to volume changes in the negative or positive electrode during charge-discharge cycles of the lead-acid battery. This creates a site where the active material can enter and exit the pouch-shaped separator, leading to the formation of a short circuit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-229959 Summary of the Invention [Problem to be solved by the invention]

[0006] However, there have been no systematic reports on a technique for improving the membrane strength of a separator for a lead-acid battery containing polyethylene, or a technique for improving the seal strength of a sealed portion of a bag-shaped polyethylene separator, other than by changing the constituent materials, their mixing ratio, and membrane thickness.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a separator for a lead-acid battery containing polyethylene, in which the crystalline state of the polyethylene is controlled and the separator has high membrane strength and sealing strength. [Means for solving the problem]

[0008] The above problems are solved by the following technical means. <1> A separator for a lead-acid battery containing polyethylene, characterized in that the degree of crystal orientation of the polyethylene (110) plane exceeds 0.780 when analyzed by wide-angle X-ray scattering, in which X-rays are irradiated from the normal direction to the membrane surface of the separator for a lead-acid battery. <2> Item 2. The lead-acid battery separator according to item 1, wherein the lead-acid battery separator is a multilayer separator for lead-acid batteries in which two or more layers are stacked, and at least a part of the multilayer separator for lead-acid batteries has a sealed portion. <3> 3. The lead-acid battery separator according to item 1 or 2, wherein a crystallite size of the polyethylene is less than 35.5 nm when analyzed by wide-angle X-ray scattering, in which X-rays are irradiated from a normal direction to a membrane surface of the lead-acid battery separator. <4> 4. The lead-acid battery separator according to any one of items 1 to 3, wherein the lead-acid battery separator is a multilayer separator for lead-acid batteries in which two or more layers are laminated, and the multilayer separator for lead-acid batteries is formed by laminating two or more layers of the lead-acid battery separators with the MD direction aligned, and at least a part of the multilayer separator for lead-acid batteries has a sealed portion. <5> 5. The separator for a lead acid battery according to any one of items 1 to 4, wherein the degree of crystal orientation of the polyethylene (110) plane is 0.990 or less. <6> 6. The separator for a lead-acid battery according to any one of items 1 to 5, wherein the degree of crystal orientation of the polyethylene (110) plane is more than 0.780 and 0.840 or less. <7> 7. The separator for a lead-acid battery according to any one of items 1 to 6, wherein the separator for a lead-acid battery is in a pouch shape. <8> 8. The separator for a lead-acid battery according to any one of items 1 to 7, wherein the separator contains 10 to 40 parts by mass of the polyethylene per 100 parts by mass of the separator for a lead-acid battery. <9> 9. The separator for a lead-acid battery according to any one of items 1 to 8, comprising 40 to 70 parts by mass of inorganic particles per 100 parts by mass of the separator for a lead-acid battery. <10> 10. The separator for a lead-acid battery according to any one of items 1 to 9, wherein the thickness of the base portion of the separator for a lead-acid battery is 0.050 mm or more. <11> Item 10. The lead-acid battery separator according to item 9, wherein the inorganic particles are silica particles. <12> 12. The lead-acid battery separator according to any one of items 1 to 11, wherein the polyethylene comprises ultra-high molecular weight polyethylene. <13> 13. The separator for a lead acid battery according to any one of items 1 to 12, comprising 10 to 30 parts by mass of a plasticizer relative to 100 parts by mass of the separator for a lead acid battery. <14> Item 14. The separator for a lead-acid battery according to item 13, wherein the plasticizer is selected from the group consisting of petroleum oil, paraffin-based oil, and mineral oil. <15> 15. The lead-acid battery separator according to any one of items 1 to 14, wherein the lead-acid battery separator has ribs on at least one surface thereof. <16> 16. A lead-acid battery comprising a battery case, a lead oxide positive electrode, a lead negative electrode, and dilute sulfuric acid, wherein the lead-acid battery separator according to any one of items 1 to 15 is disposed between the lead oxide positive electrode and the lead negative electrode. <17> Item 8. A lead-acid battery comprising a battery case, a lead oxide positive electrode, a lead negative electrode, and dilute sulfuric acid, wherein the lead oxide positive electrode and / or the lead negative electrode are inserted into the pouch-shaped separator for a lead-acid battery according to Item 7. <18> A method for producing a separator for a lead-acid battery containing polyethylene, comprising: Two or more layers of lead-acid battery separators obtained by extrusion molding are stacked to form a multi-layer separator for lead-acid batteries; and A method for producing a separator for a lead-acid battery, comprising mechanically sealing at least a portion of the multi-layer separator for a lead-acid battery. <19> Item 19. The method for producing a separator for a lead-acid battery according to Item 18, wherein the multilayer separator for a lead-acid battery is formed by stacking two or more layers of the separator for a lead-acid battery with the MD direction of the separator aligned. <20> 20. A method for producing a separator for a lead-acid battery according to item 19, comprising a quenching process after the extrusion. <21> 21. The method for producing a lead-acid battery separator according to any one of items 18 to 20, wherein a degree of crystal orientation of the (110) plane of the polyethylene exceeds 0.780 in wide-angle X-ray scattering analysis in which X-rays are irradiated from a normal direction to a membrane surface of the lead-acid battery separator. [Effects of the Invention]

[0009] According to the present invention, it is possible to increase the membrane strength of a polyethylene-containing separator for a lead-acid battery, and also to increase the seal strength of the seal portion of a bag-shaped polyethylene separator. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram illustrating sealing of a pouch-shaped separator for a lead-acid battery in one embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram for explaining a tensile test of a multi-layer separator for a lead-acid battery having a sealed portion and an unsealed portion. [Figure 3] FIG. 1 is a schematic diagram for explaining a tensile test of a lead-acid battery separator punched into a dogbone shape. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention (hereinafter abbreviated as "embodiments") will be described in detail. Note that the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

[0012] <Lead-acid battery separator> The lead-acid battery separator (hereinafter sometimes abbreviated as "separator") according to this embodiment contains polyethylene and is characterized in that, as determined by wide-angle X-ray scattering analysis in which X-rays are irradiated from the normal direction to the membrane surface of the lead-acid battery separator, the crystalline orientation of the polyethylene (110) plane exceeds 0.780. As long as the separator has a membrane surface, it may be a single-layer, multi-layer, laminated, flat membrane, or multi-layer membrane. Multiple separators according to this embodiment may be laminated, or a single separator according to this embodiment may be integrated with another separator, layer, or membrane. From the perspective of continuous mass production of long products and controlling the crystalline orientation or crystallite size of the polyethylene, the separator is preferably obtained by extrusion molding, for example, using a die. Note that, in this specification, the term "crystalline orientation" simply refers to the crystalline orientation of the polyethylene (110) plane.

[0013] The present invention will be broken down into smaller parts and explained in more detail below. In this specification, when describing the parts by mass of various components, the notation "A to B parts by mass" is used, which means A parts by mass or more and B parts by mass or less. In addition, in this specification, weight is expressed in g, which is interchangeable with mass (g).

[0014] <Polyethylene crystalline orientation> In the lead-acid battery separator according to the present embodiment, the crystalline orientation of the polyethylene (110) plane exceeds 0.780 as determined by wide-angle X-ray scattering analysis, in which X-rays are irradiated from the normal direction to the membrane surface of the polyethylene-containing lead-acid battery separator. In this specification, the crystalline orientation of the polyethylene (110) plane refers to the crystalline orientation obtained by wide-angle X-ray scattering analysis, which will be described later in the Examples section of this specification. Since increasing the crystalline orientation of the separator in the region exceeding 0.780 significantly improves membrane strength, the crystalline orientation is preferably greater than 0.780, more preferably 0.785 or greater, even more preferably 0.790 or greater, even more preferably 0.795 or greater, even more preferably 0.800 or greater, even more preferably 0.805 or greater, or even more preferably 0.810 or greater.

[0015] The significant improvement in membrane strength associated with a crystalline orientation degree exceeding 0.780 is believed to be due to the fact that the increased polyethylene crystalline orientation increases the intermolecular force between adjacent polymer chains, thereby increasing membrane strength. Furthermore, to obtain a separator with a high degree of crystalline orientation according to the present embodiment, it is preferable to reduce the extrusion speed during extrusion molding using a separator die. In this case, a separator with a higher degree of crystalline orientation can be obtained by incorporating a process for controlling the crystallite size to a smaller size using a rapid cooling process, as described below. A specific example of reducing the extrusion speed is to reduce the extrusion amount per unit time when a polyethylene-containing melt is extruded into a sheet form through a T-die, thereby reducing the line speed of the entire process up to product winding, which is preferable from the perspective of increasing the degree of crystalline orientation. Reducing the extrusion speed facilitates uniform crystal orientation of the polyethylene when the polyethylene-containing melt is extruded through the die. Therefore, the extrusion speed using a T-die is 950 kg / h or less, more preferably 900 kg / h or less, even more preferably 850 kg / h or less, even more preferably 820 kg / h or less, and particularly preferably 810 kg / h or less. From the viewpoint of increasing the production rate, the extrusion rate is preferably 100 kg / h or more, more preferably 300 kg / h or more, even more preferably 500 kg / h or more, still more preferably 600 kg / h or more, and particularly preferably 700 kg / h or more.

[0016] Furthermore, by reducing the line speed, the high-temperature residence time from the extrusion step to the drying step becomes longer, during which time the polyethylene crystal orientation becomes more uniform. In this case, by controlling the polyethylene crystallite size to a small size using the rapid cooling process described below, the degree of crystal orientation increases, and membrane strength can be significantly improved. From this perspective, the line speed is preferably 44 m / min or less, more preferably 43 m / min or less, even more preferably 42 m / min or less, still more preferably 41 m / min or less, even more preferably 40 m / min or less, particularly preferably 39 m / min or less, and most preferably 38 m / min or less. From the perspective of increasing the production rate, the line speed is preferably 10 m / min or more, more preferably 20 m / min or more, and even more preferably 30 m / min or more.

[0017] Furthermore, from the viewpoint of increasing the elongation percentage (%) until breakage when a tensile force is applied to the separator, the crystalline orientation degree is preferably 0.990 or less, more preferably 0.950 or less, even more preferably 0.900 or less, even more preferably 0.880 or less, particularly preferably 0.850 or less, and most preferably 0.840 or less. In particular, when the separator is processed into a bag shape and a battery is assembled with electrodes inserted therein, it is preferable that the separator expands and contracts in accordance with the in-plane expansion and contraction of the electrodes during charging and discharging. From this viewpoint, a high elongation percentage is preferable. In order to obtain a good balance of high membrane strength, seal strength, and elongation percentage, the crystalline orientation degree is preferably 0.990 or less, more preferably 0.950 or less, even more preferably 0.900 or less, even more preferably 0.880 or less, particularly preferably 0.850 or less, and most preferably 0.840 or less.

[0018] <Sealing section> The lead-acid battery separator according to this embodiment is preferably a multilayer separator for lead-acid batteries in which two or more layers are stacked, and at least a portion of the multilayer separator preferably has a seal portion. The seal portion can be formed by applying mechanical compressive stress in the film thickness direction to two or more stacked separator layers to form a seal portion between the two layers. Since high sealing strength can be achieved by stacking separators with a high degree of crystalline orientation and applying mechanical compressive stress, it is preferable to form the seal portion in addition to mechanical compressive stress, and heating and / or ultrasonic waves may also be used. As an example of applying the mechanical compressive stress, a method in which two or more stacked separator layers are passed through the meshing portion of gears and an adhesive portion is formed between the two layers by the compressive stress caused by the meshing is preferred from the viewpoints of production efficiency and manufacturing costs.

[0019] From the viewpoint of facilitating entanglement of polyethylene molecular chains at the seal portion and improving seal strength when two or more separators with a high degree of crystal orientation are stacked and the mechanical compressive stress is applied to the laminate, the separator for a lead-acid battery according to the present embodiment has a crystal orientation degree of the polyethylene (110) plane of preferably more than 0.780, more preferably 0.785 or more, even more preferably 0.790 or more, even more preferably 0.795 or more, even more preferably 0.800 or more, even more preferably 0.805 or more, or even more preferably 0.810 or more, as determined by wide-angle X-ray scattering analysis in which X-rays are irradiated from the normal direction to the membrane surface of the separator.

[0020] From the viewpoint of increasing the sealing strength by stacking two or more separator layers with a high degree of crystal orientation with the crystal orientation of each layer aligned and applying the mechanical compressive stress to the laminate to increase the entanglement of polyethylene molecular chains in the sealing portion, it is preferable to produce the lead-acid battery separator according to this embodiment using an extrusion molding process, stack two or more separator layers with the MD direction aligned, and apply the mechanical compressive stress to the laminate to form the sealing portion. In this specification, the MD (machine direction) direction refers to the longitudinal direction of the separator when a long separator is obtained by extrusion molding, unless otherwise specified. For example, when a separator is produced by extrusion molding using a T-die, it refers to the extrusion direction. As an example of a pouch-shaped separator produced using this method, the separator for a lead-acid battery according to this embodiment is produced using an extrusion molding process, and a pouch-shaped separator (2) is produced by folding the separator (1) in half and passing the left and right ends between the gears to form a seal portion (3) as shown in Fig. 1, or a pouch-shaped separator (not shown) is produced by stacking two or more layers of separators with the MD direction of the separators aligned and passing two or three sides between the gears to form a seal portion. This results in a pouch-shaped separator for a lead-acid battery with high sealing strength.

[0021] <Polyethylene crystallite size> In the lead-acid battery separator according to the present embodiment, the crystallite size of the polyethylene is preferably less than 35.5 nm as determined by wide-angle X-ray scattering analysis, in which X-rays are irradiated from the normal direction to the membrane surface of the lead-acid battery separator. In this specification, the crystallite size of the polyethylene refers to the crystallite size obtained by wide-angle X-ray scattering analysis, which will be described later in the Examples section of this specification. In this specification, the term "crystallite size" simply refers to the crystallite size of the polyethylene (110) plane. From the viewpoint of reducing the crystallite size and increasing the degree of crystal orientation, the crystallite size is preferably less than 35.5 nm, more preferably 35.0 nm or less, even more preferably 34.5 nm or less, even more preferably 34.0 nm or less, and particularly preferably 33.5 nm or less. Increasing the degree of crystal orientation can increase membrane strength and seal strength. Although the method for obtaining a separator with a small crystallite size is not limited, as an example, in extrusion molding of a separator, immediately after a polyethylene-containing melt is extruded into a sheet form from a die, the sheet is preferably quenched by a quenching process using, for example, a pre-chilling roll to suppress crystallite growth. From the viewpoint of suppressing crystallite growth, it is preferable to quench the sheet temperature immediately after extrusion using the pre-chilling roll to 100°C or less, more preferably 90°C or less, even more preferably 80°C or less, particularly preferably 70°C or less, and most preferably 65°C or less. From this viewpoint, the temperature of the pre-chilling roll is preferably less than 55°C, more preferably 54°C or less, even more preferably 53°C or less, even more preferably 52°C or less, and most preferably 51°C or less. By reducing the crystallite size of the polyethylene through the quenching process, the crystal orientation of the polyethylene is more easily aligned during the high-temperature residence time from the extrusion step to the drying step, and a separator with a high degree of crystal orientation is obtained.

[0022] <Polyethylene> The lead-acid battery separator according to this embodiment is preferably a porous film containing polyethylene. From the viewpoint of improving the film strength or durability within the lead-acid battery, the polyethylene is preferably a high-molecular-weight polyethylene having a weight-average molecular weight of 600,000 or more. The polyethylene is more preferably ultra-high molecular weight polyethylene (UHMWPE), i.e., polyethylene having a weight-average molecular weight of 1,000,000 or more, particularly 4,000,000 or more, and most preferably 5,000,000 to 8,000,000. In this specification, ultra-high molecular weight polyethylene refers to polyethylene having a weight-average molecular weight of 1,000,000 or more.

[0023] The lead-acid battery separator according to this embodiment preferably contains 10 to 40 parts by mass of polyethylene per 100 parts by mass of the separator. From the viewpoint of increasing the membrane strength of the separator with polyethylene, the polyethylene content is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more per 100 parts by mass of the separator. Furthermore, from the viewpoint of reducing the blending ratio of hydrophobic polyethylene in the separator and reducing the electrical resistance of the separator inside the lead-acid battery, the separator preferably contains hydrophilic inorganic particles, and in this case, the polyethylene content is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, even more preferably 30 parts by mass or less, and most preferably 25 parts by mass or less per 100 parts by mass of the separator.

[0024] ≪Inorganic particles≫ The lead-acid battery separator according to this embodiment preferably contains 40 to 70 parts by mass of inorganic particles per 100 parts by mass of the separator. From the viewpoint of increasing the hydrophilicity of the separator, the separator preferably contains 40 parts by mass or more of inorganic particles per 100 parts by mass of the separator, more preferably 45 parts by mass or more, and even more preferably 50 parts by mass or more. Furthermore, if the weight ratio of inorganic particles in the separator is high, the weight ratio of polyethylene becomes relatively low, and the binding strength between the inorganic particles and polyethylene becomes weak. Therefore, the separator preferably contains 70 parts by mass or less of inorganic particles per 100 parts by mass of the separator, more preferably 65 parts by mass or less.

[0025] Examples of inorganic particle materials include silica (amorphous silica, precipitated silica, gelled silica, fumed silica, etc.), alumina, sulfates (e.g., barium sulfate, calcium sulfate), titania (rutile type, anatase type), gibbsite, bayerite, boehmite, zirconia, magnesia, ceria, ithria, oxide-based ceramics such as iron oxide, nitride-based ceramics such as silicon nitride, titanium nitride, and boron nitride, silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, magnesium hydroxide, potassium titanate, talc, synthetic kaolinite, kaolin clay, kaolin (kaolinite, dickite, narcite), calcined kaolin, flybonite, stevensite, dickite, nacrite, halloysite, pyrophyllite, audinite, montmorillonite, beidellite, nontronite, and volkonscoite. , saponite, hectorite, fluorine hectorite, sauconite, swinholdite, vermiculite, fluorine vermiculite, berthelline, sericite, amesite, keryaite, fleiponite, prindriite, bentonite, zeolite, biotite, phlogopite, fluorine phlogopite, iron mica, eastonite, taeniolite, siderophyllite, tetraferriferric mica, lepidolite, fluorine tetrasilicic mica, polylithionite, muscovite, celadonite, ferro-ceradoite, ferro-aluminoceladonite, aluminoceladonite, Tobe mica, sodalite, klinite, kinoshi stone, viteite, anandite, pearlite, clinochlore, chamosite, pennantite, nimite, baylichrite, donbassite, cookesite, sudoite, hydrotalcite, calcium silicate, magnesium silicate, aluminum silicate, diatomaceous earth, and silica sand.

[0026] Among the above examples, the inorganic particles used in the lead-acid battery separator are preferably particles of silica, alumina, kaolin, titania, aluminum silicate, or barium sulfate, which have excellent acid resistance and oxidation resistance and are highly hydrophilic, more preferably silica particles, and even more preferably amorphous silica particles produced by a precipitation method.

[0027] The inorganic particles according to the present embodiment may be used singly or in combination of two or more kinds.

[0028] From the viewpoint of forming fine pores in the porous body, the average particle size of the inorganic particles is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 70 μm or less, even more preferably 50 μm or less, and still more preferably 25 μm or less. Furthermore, since fine powder of the particles tends to scatter during measurement or slurry preparation, from the viewpoint of workability, the average particle size of the inorganic particles is preferably 0.01 μm or more, more preferably 0.1 μm or more, even more preferably 0.3 μm or more, even more preferably 0.5 μm or more, even more preferably 1 μm or more, even more preferably 2 μm or more, even more preferably 5 μm or more, or even more preferably 8 μm or more.

[0029] The particle diameter d (μm) in this specification is the diameter of a particle observed when observing the cross section of a porous body with a scanning electron microscope (SEM). When the observed particles are not spherical, the particle diameter d is calculated by the following formula, where d1 (μm) is the maximum diameter of the particle confirmed by the observation, and d2 (μm) is the minimum diameter of the particle: d=(d1+d2) / 2 The average particle size in this specification is a value obtained by determining the particle diameter d of 50 particles randomly selected during the observation using the above-mentioned method, and then calculating the arithmetic mean value of the particle diameters of the 50 particles. For example, the average particle size of inorganic particles is a value obtained by determining the particle diameter d of 50 inorganic particles randomly selected from the porous body during the observation using the above-mentioned method, and then calculating the arithmetic mean value of the particle diameters of the 50 particles.

[0030] <Plasticizer> The lead-acid battery separator according to this embodiment preferably contains 10 to 30 parts by mass of a plasticizer relative to 100 parts by mass of the separator. The plasticizer is preferably oil, and may be petroleum, paraffin-based mineral oil, mineral oil, or any combination thereof.

[0031] Additives The separator of the present invention may include one or more performance-enhancing additives, such as surfactants, wetting agents, colorants, antistatic additives, antioxidants, and the like, and any combination thereof. The performance-enhancing additive may preferably be a surfactant. Some suitable surfactants are nonionic, while other suitable surfactants are anionic. The use of these specific suitable surfactants in combination with the separator of the present invention described herein can result in an improved separator that, when used in a lead-acid battery, can provide the battery with reduced water loss. Suitable surfactants include surfactants such as alkyl sulfates; alkylaryl sulfonates; alkylphenol-alkylene oxide adducts; soaps; alkyl-naphthalene sulfonates; one or more sulfosuccinates, such as anionic sulfosuccinates; dialkyl esters of sulfosuccinate salts; quaternary amines; block copolymers of ethylene oxide and propylene oxide; and mono- and di-alkyl phosphate ester salts. The additives can be non-ionic surfactants such as polyol fatty acid esters, polyethoxylate esters, polyethoxylated alcohols, alkyl polysaccharides such as alkyl polyglycosides and blends thereof, amine ethoxylates, sorbitan fatty acid ester ethoxylates, organosilicon based surfactants, ethylene vinyl acetate terpolymers, ethoxylated alkylaryl phosphate esters, and sucrose fatty acid esters.

[0032] <Manufacturing method for lead-acid battery separator> An example of a method for manufacturing a separator for a lead-acid battery according to the present embodiment will be described below. However, the method is not limited to a substrate obtained by the following manufacturing method as long as a separator with a high degree of crystal orientation can be obtained.

[0033] A preferred method for producing a lead-acid battery separator according to this embodiment is extrusion molding using a die, for example, from the viewpoints of continuous mass production of long products and controlling the degree of crystalline orientation or crystallite size of the polyethylene. One example includes the following steps: preparing polyethylene, such as ultra-high molecular weight polyethylene (hereinafter referred to as "UHMWPE"); preparing inorganic particles; preparing a plasticizer that is liquid at room temperature (25°C); mixing the UHMWPE, inorganic particles, plasticizer, and optional other additives to form a molten mixture at or above the melting point of the polyethylene; extruding the mixture through a die, such as a T-die, to form a sheet; quenching the sheet with a pre-chilling roll; optionally providing ribs on the sheet surface with a pattern roll; extracting the plasticizer from the sheet partially or completely using a solvent to form micropores in the separator; and drying the solvent. The separator with a microporous matrix obtained by the above method comprises UHMWPE, a plasticizer (if partially extracted), optional additives, and inorganic particles dispersed throughout the matrix.

[0034] Another example of a method for producing a lead-acid battery separator is a method for producing a lead-acid battery separator containing polyethylene, which comprises laminating two or more extrusion-molded lead-acid battery separator layers to form a multilayer lead-acid battery separator, and mechanically sealing at least a portion of the multilayer lead-acid battery separator. The lead-acid battery separator produced by this production method can have the degree of crystal orientation of the (110) plane of the polyethylene contained in the lead-acid battery separator, the crystallite size, and the like controlled within the numerical ranges described above.

[0035] From the viewpoint of obtaining a bag-shaped separator for lead-acid batteries having high sealing strength and puncture resistance, the multilayer separator for lead-acid batteries formed by extrusion molding is preferably a bag-shaped separator (2) in which a separator (1) is folded in half and the left and right ends are passed between gears (for example, between gears) to form a seal portion (3) as shown in FIG. 1; or a bag-shaped separator (not shown) in which two or more layers of lead-acid battery separators are stacked with the MD direction of the separators aligned, and two or three end sides are passed between gears (for example, between gears) to form a seal portion.

[0036] Another example of a method for producing a lead-acid battery separator may include the steps of preparing the UHMWPE described above, forming a molten mixture, quenching the sheet, providing ribs on the sheet surface, extracting the plasticizer, drying the solvent, and laminating two or more lead-acid battery separator layers with the MD direction aligned to form a multilayer lead-acid battery separator. From the viewpoint of suppressing the growth of polyethylene crystallites contained in the lead-acid battery separator, a quenching process is preferably carried out after extrusion molding, and more preferably, the sheet temperature immediately after extrusion is quenched to 100°C or less using a pre-cooling roll, and the temperature of the pre-cooling roll is even more preferably less than 55°C.

[0037] The rapid cooling process after extrusion makes it possible to control the crystallite size to be small, and by slowing down the extrusion speed during this process, it is possible to obtain a separator according to this embodiment with a high degree of crystal orientation.

[0038] <Physical properties of lead-acid battery separators> (Thickness) The thickness of the lead-acid battery separator according to this embodiment is not particularly limited. However, from the viewpoint of reducing electrical resistance within the battery, it is preferably 1.00 mm or less, more preferably 0.750 mm or less, even more preferably 0.500 mm or less, and even more preferably 0.300 mm or less. Furthermore, from the viewpoint of increasing membrane strength, the thickness of the separator is preferably 0.050 mm or more, more preferably 0.100 mm or more, and even more preferably 0.150 mm or more. Furthermore, when forming a seal portion of a two- or more-layer separator laminate, for example, through meshing between gears, the thickness of each layer is set to a predetermined value or more, and from the viewpoint of increasing the seal strength of the seal portion, the thickness of the separator is preferably 0.050 mm or more, more preferably 0.100 mm or more, and even more preferably 0.150 mm or more. In this specification, the thickness is determined by observing a cross-section of the separator with a scanning electron microscope (SEM) and measuring the thickness of five different regions in the observed region, and then calculating the arithmetic mean of the thicknesses of the five regions. In the case of a separator having ribs (protrusions) on the surface thereof, the thickness of the separator mentioned above means the thickness of the base portion (flat portion) excluding the ribs (protrusions).

[0039] (rib) When the lead-acid battery separator of this embodiment is produced by extrusion molding, ribs (convex shapes) can be formed in any shape on the separator surface after extrusion using a mechanical press, a calendar stack, a calendar roll, or a pattern roll. In some embodiments, the separator can have ribs on at least one surface. The ribs can be mounted opposite the positive electrode in a lead-acid battery to enhance the oxidation resistance of the separator. Furthermore, the height of the ribs (convex portions) is preferably 3 μm or more, since this can promote mixing of dilute sulfuric acid in the battery container and suppress stratification. Furthermore, from the viewpoint of reducing the volume of the lead-acid battery, the height of the ribs is preferably 3 mm or less, more preferably 2 mm or less. From the viewpoint of enhancing oxidation resistance, the ribs are preferably formed on at least one surface of the separator, and may be formed on both surfaces as necessary.

[0040] ≪Lead-acid battery≫ A lead-acid battery including the lead-acid battery separator according to the present embodiment is also an aspect of the present invention. The shape of the lead-acid battery separator can be determined so as to be compatible with each component of the lead-acid battery. One aspect of the lead-acid battery of the present invention is a lead-acid battery comprising a battery case, a lead oxide positive electrode, a lead negative electrode, and dilute sulfuric acid as an electrolyte, with the separator according to the present invention disposed between the positive electrode and the negative electrode. The positive electrode grid constituting the positive electrode may be lead or a lead alloy, and the positive electrode active material may be lead oxide, e.g., lead dioxide. The negative electrode grid constituting the negative electrode may be lead or a lead alloy, and the negative electrode active material may be lead, and the lead negative electrode itself may be, for example, in a spongy form. Furthermore, the active materials of these positive and negative electrodes may contain up to 50% by mass of other metal elements in their compositions. Furthermore, the dilute sulfuric acid is sulfuric acid with a specific gravity of 1.1 to 1.4, and may further contain additives such as aluminum ions or lithium ions. In this embodiment, the use of a separator with high membrane strength in a lead-acid battery can prevent the separator from breaking and causing a short circuit when subjected to strong vibrations or compressive stress from sharp electrode portions. Therefore, it is preferable to place a separator according to one embodiment of the present invention between the positive electrode and the negative electrode of a lead-acid battery. Furthermore, even in a lead-acid battery in which the separator for a lead-acid battery according to one embodiment of the present invention is placed between the positive electrode and the negative electrode in a state where it is stacked with another separator, the separator has high membrane strength, and if a seal portion is present, a strong seal strength can be obtained. Therefore, a lead-acid battery in which the separator for a lead-acid battery according to the present invention is placed between the positive electrode and the negative electrode in a state where it is stacked with another separator is also included in the lead-acid battery of the present invention. Furthermore, the separator for a lead-acid battery according to this embodiment may have a functional layer on the separator surface, for example, a carbon layer containing a binder resin may be applied to the separator.

[0041] The lead-acid battery of the present invention also includes a lead-acid battery in which the separator for a lead-acid battery according to one embodiment of the present invention is stacked with another separator, and the separators are bonded together using an organic component such as a resin or ultrasonic waves (which may also be heated) and then placed between the positive electrode and the negative electrode. The other separator is not limited to a specific one, but examples include (1) a nonwoven fabric containing inorganic fibers, (2) a nonwoven fabric containing organic fibers, (3) a separator containing inorganic fibers and inorganic particles, (4) a separator containing inorganic fibers, organic fibers, and inorganic particles, (5) a separator containing any of the above (1) to (4) and a resin binder, and (6) a polyethylene separator having micropores with an average pore diameter of 800 nm or less (which may contain inorganic particles). An example of the inorganic fibers of (1), (3), and (4) is glass fiber. The lead-acid battery of the present invention also includes cases where the above (1) to (5) are pasting papers that are protective films on the surfaces of the positive and / or negative electrodes of the lead-acid battery.

[0042] The lead-acid battery separator according to the present embodiment has high membrane strength, so that the membrane thickness can be reduced to reduce the electrical resistance. In this case, by combining it with the above-mentioned functional layer or other separators such as those in (1) to (6), it is possible to impart new functions while reducing the electrical resistance.

[0043] Furthermore, in this embodiment, the separator for a lead-acid battery may be used not only in the form of two overlapping layers, but also in a multi-layer form of three or more layers. Such a three-or-more-layer form includes at least the separator according to this embodiment as a specific single layer, and the remaining layers can be selected from any separator. By providing the separator according to this embodiment between the positive electrode and the negative electrode, a lead-acid battery with improved resistance to separator damage due to vibration or strong external force can be obtained. The separator for a lead-acid battery according to this embodiment can be used in both open-type lead-acid batteries and valve-regulated lead-acid batteries, but is preferably used in open-type lead-acid batteries, which do not necessarily require oxygen generated from the positive electrode during charging to be transferred to the negative electrode via the separator.

[0044] The lead-acid battery according to the present embodiment is a lead-acid battery including a battery case, a lead oxide positive electrode, a lead negative electrode, and dilute sulfuric acid, and the lead oxide positive electrode and / or the lead negative electrode are inserted into a pouch-shaped separator for a lead-acid battery having high sealing strength according to the present embodiment. By inserting the positive electrode and / or the negative electrode into the pouch-shaped separator for a lead-acid battery, peeling of the seal portion is suppressed, and short circuits due to falling off of the active material can be suppressed. [Example]

[0045] The present invention will be described in detail below based on examples, but these are described for the purpose of explanation and the scope of the present invention is not limited to the following examples.

[0046] <Preparing the separator for evaluation> The methods for preparing samples of the examples and comparative examples will be described in detail below.

[0047] (Experiment 1: Examples 1 to 3) A raw material composition was obtained by heating, melting, and mixing 10 parts by weight of ultra-high molecular weight polyethylene resin powder with a weight average molecular weight of 3 million as a polyolefin resin, 25 parts by weight of silica powder, 1 part by weight of surfactant, and 64 parts by weight of mineral oil as a plasticizer in a mixer. This raw material composition was extruded into a sheet using an extruder equipped with a T-die at a resin temperature of 220 ° C. and an extrusion rate of 800 kg / h (line speed: 37 m / min). Immediately thereafter, the sheet was brought into contact with the surface of a pre-cooling roll set at a surface temperature of 50 ° C. The sheet temperature was rapidly cooled from 220 ° C. to 60 ° C., and a predetermined groove for a main rib for abutting a pole plate was carved into one roll. The sheet was passed through a pair of forming rolls set at a surface temperature of 55 ° C. to obtain a film-like product in which a predetermined shape of a main rib for abutting a pole plate (protrusion) was integrally formed on one side of the flat sheet. Next, this film-like material was immersed in a solvent to extract and remove a portion of the mineral oil, and the solvent was dried to obtain a long separator for evaluation having a composition of 22 parts by weight of polyethylene resin, 56 parts by weight of silica, 2 parts by weight of surfactant, and 20 parts by weight of mineral oil. Three rectangular pieces measuring 130 mm wide x 260 mm long (the longitudinal direction of the rectangle was parallel to the MD direction) were cut out from two randomly selected regions of the long separator to serve as separators for evaluation. Various membrane types were evaluated for these three separators using the methods described below, and the results are shown in Table 1, Examples 1 to 3.

[0048] (Experiment 2: Comparative Examples 1-2) The evaluation separators were produced under the same process conditions as in Experiment 1, except for the extrusion speed, line speed, the presence or absence of a preliminary cooling roll, and the number of cut-out evaluation separators. In Comparative Examples 1 and 2, the line speed in the extrusion process was 45 m / min, and two rectangular pieces 130 mm wide x 260 mm long (the longitudinal direction and MD direction of the rectangle were parallel) were cut out from two randomly selected regions of the obtained long separator. Various membrane evaluations were performed on these evaluation separators using the methods described below, and the results are shown in Table 1 for Comparative Example 1 and Comparative Example 2.

[0049] The separators obtained in the above Example 1 and Experiment 2 were subjected to various measurements using the following methods.

[0050] <Thickness> The separator was cut to a width of 130 mm and a length of 260 mm, and the thickness of the separator was measured in five randomly selected regions using a film thickness meter. The arithmetic mean value of the thicknesses of the five regions is shown in Table 1. A superhard flat probe (bottom diameter: 4.3 mm) manufactured by Mitutoyo Corporation was used for the measurement, and the film thickness was measured with a load of 150 g applied to the probe. The unit of thickness is mm. The separators produced in Experiments 1 and 2 both had ribs (protrusions) of the same shape on one side of the separator, and the thickness was measured by measuring the thickness of the base (flat portion), avoiding the ribs (protrusions). The results are shown in Table 1.

[0051] <Wide-angle X-ray scattering measurement> (Measurement method) Wide-angle X-ray scattering measurements were performed using a NANOPIX (Rigaku Corporation) using the transmission method. A portion of the separator cut to a width of 130 mm and a length of 260 mm was used for the measurements. CuKα X-rays with a wavelength of 0.154 nm were irradiated from the normal direction to the film surface of the base of the separator, and X-ray scattering was detected. A point collimation optical system was used, and measurements were performed under the following slit diameters: 1st slit: φ = 0.55 mm, 2nd slit: open, guard slit: φ = 0.35 mm. Furthermore, a two-dimensional semiconductor detector, HyPix-6000, was used as the detector. Wide-angle X-ray scattering measurements were performed in a vacuum environment with an exposure time of 10 minutes per sample and a camera length of 86 mm.

[0052] (Polyethylene (110) plane crystal orientation analysis method) For the X-ray scattering pattern obtained using the 2D detector, the 12 o'clock direction was defined as the azimuth angle φ = 0°, and the azimuth angle clockwise on the detector plane was defined as 0° ≦ φ < 360°. Here, the 12 o'clock direction corresponds to the MD direction of the separator. Next, the 2D X-ray scattering pattern was subjected to detector background correction and empty cell scattering correction. The integrated intensity I(φ) in the range 20.8° < 2θ < 22.4°, where the polyethylene (110) plane diffraction peak exists, was then plotted against the azimuth angle φ. Here, 2θ is the scattering angle. In I(φ), single peaks centered at φ = 0° and 180° were observed when the molecular chain c-axis was aligned perpendicular to the 12 o'clock direction of the film plane. A baseline was drawn connecting 80° < φ < 280° for the single peak centered at φ = 180°, and a Gaussian function was fitted to determine the full width at half maximum (FWHM) of the peak. Using this FWHM, the degree of crystal orientation f was calculated according to the following formula 1. The degree of crystal orientation of the polyethylene (110) plane means the degree to which the polyethylene (110) plane is oriented in the MD direction of the separator, and a larger value of f means that the polyethylene (110) plane is more oriented in the MD direction of the separator. f=1-FWHM / 180 Equation 1 f: Crystal orientation degree FWHM: Full width at half maximum (°) of the Gaussian function obtained from the fitting results

[0053] (Polyethylene (110) crystallite size analysis method) In the X-ray scattering pattern obtained using the 2D detector, scattering intensities at the same distance from the center correspond to the same scattering angle when the center is the position where the X-rays irradiated the sample traveled straight through the sample, passed through the sample, and reached the 2D detector. Therefore, a 1D scattering intensity profile versus scattering angle 2θ can be obtained by calculating the average intensity at each scattering angle (circular averaging) for the measured X-ray scattering pattern. The obtained 1D scattering profile was separated into four peaks: the (110) diffraction peak of orthorhombic polyethylene, the (200) diffraction peak of orthorhombic polyethylene, a peak derived from amorphous polyethylene, and a peak derived from amorphous silicon, in the range from 2θ = 10° to 2θ = 30°. The (110) diffraction peak and (200) diffraction peak of polyethylene were fitted with a Voigt function, and the peaks derived from amorphous polyethylene and Si were fitted with a Gaussian function. The position of the amorphous peak of polyethylene was fixed at 2θ = 19.6°, with a full width at half maximum of 6.3°. Peak separation was performed without fixing the peak position and full width at half maximum of the polyethylene crystalline peak and the peak derived from amorphous silicon. The crystallite size was calculated from the full width at half maximum of the (110) plane diffraction peak calculated by peak separation according to the Scherrer equation (Equation 2 below). The crystallite size obtained by this analysis refers to the thickness of the crystal in the direction perpendicular to the polyethylene (110) plane of the separator. D(110)=Kλ / (βcosθ) Equation 2 Explanation of symbols in formula 2 D(110): Crystallite size (nm) K: 0.9 (constant) λ: wavelength of incident X-rays (nm) β:(β1 2 -β2 2 ) 0.5 β1: Full width at half maximum (°) of the (hkl) peak calculated as a result of peak separation β2: FWHM of incident beam (°) θ: Bragg angle

[0054] <Puncture strength> A portion of the separator cut to a width of 130 mm and a length of 260 mm was sandwiched and fixed between two flat plates each having an opening of 11 mm in diameter in the center (the openings of the upper and lower plates were fixed so as to overlap), and a cylindrical metal pin (the tip of the pin was flat and had a diameter of 1.93 mm) was pierced from the normal direction to the membrane surface of the separator (piercing speed: 300 mm / min), and the peak strength (N) at this time was measured. Note that the pin pierced the base portion (flat portion) as explained in the thickness measurement method above.

[0055] <Seal strength> Two 80mm x 30mm test pieces were cut from the separator (130mm wide x 260mm long) with the short edges aligned along the machine direction. The two test pieces (Figure 2a) were then stacked together to form a laminated separator 4 (laminate) (the machine direction of the two upper and lower test pieces was aligned). One of the short edges of the laminate was then passed through a pair of gears, and a seal (3) was formed between the two layers parallel to the machine direction due to the compressive stress between the gears (Figure 2b). The other short edge was then expanded from the stacked state to a single layer, yielding a 150mm x 30mm test piece for seal strength measurement (Figure 2c). The total length of the side (5) in Figure 2c is 150mm. The test piece was fixed to a tensile tester with a chuck distance of 80 mm and a chuck width of 30 mm so as not to slacken in the tensile direction, and a tensile test was carried out at a tensile speed of 300 mm / min in an environment of 24°C to measure the peak strength (N). Note that this peak strength corresponds to the peak strength at which the seal portion peels off.

[0056] <Growth rate> As shown in Figure 3, a separator for evaluation was punched into a dogbone shape using a Thomson blade from the separator cut to a width of 130 mm and a length of 260 mm. A tensile test was performed in the longitudinal direction of the dogbone using a Tensilon at a chuck distance of 80 mm (each of the longitudinal ends of the dogbone was fixed at 17.5 mm), a tensile speed of 300 mm / min, and an environment of 24°C. The elongation (%) was then calculated using Equation 3. Note that the elongation to break in Equation 3 was measured from the time the tensile strength was detected after the start of measurement until the test sample broke and the tensile strength could no longer be detected. (Equation 3) Elongation (%) = (elongation to break (mm) / 50) × 100

[0057] <Results of Examples and Comparative Examples> The results of the Examples and Comparative Examples shown in Table 1 will be explained below.

[0058] [Table 1]

[0059] The results of Experiment 1 (Examples 1, 2, and 3) and Experiment 2 (Comparative Examples 1 and 2) show that in the region where the crystalline orientation exceeds 0.780, the puncture strength improves significantly as the crystalline orientation improves. Furthermore, in the region where the crystalline orientation exceeds 0.780, the seal strength improves as the crystalline orientation improves. This is thought to be because, when separators with a high crystalline orientation are stacked and a mechanical compressive stress is applied to the laminate to form a seal, the polyethylene molecular chains with a high crystalline orientation between the layers become more easily entangled at the seal (interlayer adhesive surface), thereby improving the seal strength. As a result, when the separator is sealed and made into, for example, a bag-shaped separator is obtained that has high adhesive strength at the edges, is less likely to peel at the edges, and is highly durable. From the viewpoint of increasing the film strength and / or seal strength, it is preferable that the degree of crystal orientation is greater than 0.780, more preferably 0.785 or more, even more preferably 0.790 or more, even more preferably 0.795 or more, even more preferably 0.800 or more, even more preferably 0.805 or more, or even more preferably 0.810 or more.

[0060] It is also clear that the degree of crystal orientation increases as the crystallite size of the polyethylene-containing polyethylene decreases to a range of less than 35.5 nm. From this, from the viewpoint of reducing the crystallite size and increasing the degree of crystal orientation, the crystallite size is preferably less than 35.5 nm, more preferably 35.0 nm or less, even more preferably 34.5 nm or less, still more preferably 34.0 nm or less, and particularly preferably 33.5 nm or less.

[0061] On the other hand, with regard to the elongation percentage when a separator is subjected to a tensile test, the lower the degree of crystal orientation, the higher the elongation percentage. Therefore, from the viewpoint of achieving a good balance of high membrane strength, high seal strength, and high elongation percentage, the degree of crystal orientation is preferably 0.990 or less, more preferably 0.950 or less, even more preferably 0.900 or less, still more preferably 0.880 or less, particularly preferably 0.850 or less, and most preferably 0.840 or less. [Industrial Applicability]

[0062] The separator for a lead-acid battery according to the present invention can be used as a separator for a lead-acid battery that requires high membrane strength and / or high sealing strength, and a lead-acid battery using a separator having these properties can be provided. [Explanation of symbols]

[0063] 1 Separator 2. Bag-shaped separator 3 Seal part 4. Laminated separator 5 Sides x Tensile test direction

Claims

1. A separator for a lead-acid battery comprising polyethylene, wherein, when analyzed by wide-angle X-ray scattering analysis in which X-rays are irradiated from a direction normal to a membrane surface of the separator for a lead-acid battery, the degree of crystal orientation of the polyethylene (110) plane exceeds 0.780, and the crystallite size of the polyethylene is less than 35.5 nm.

2. 2. The lead-acid battery separator according to claim 1, wherein the lead-acid battery separator is a multilayer separator for lead-acid batteries in which two or more layers are stacked, and at least a part of the multilayer separator for lead-acid batteries has a sealed portion.

3. 3. The lead-acid battery separator according to claim 1, wherein the lead-acid battery separator is a multilayer separator for lead-acid batteries in which two or more layers are laminated, and the multilayer separator for lead-acid batteries is formed by laminating two or more layers of the lead-acid battery separators with the MD direction aligned, and at least a part of the multilayer separator for lead-acid batteries has a sealed portion.

4. The separator for a lead acid battery according to any one of claims 1 to 3, wherein the degree of crystal orientation of the polyethylene (110) plane is 0.990 or less.

5. The separator for a lead acid battery according to any one of claims 1 to 4, wherein the degree of crystal orientation of the polyethylene (110) plane is greater than 0.780 and not greater than 0.

840.

6. The lead acid battery separator according to any one of claims 1 to 5, wherein the lead acid battery separator is bag-shaped.

7. The separator for a lead acid battery according to any one of claims 1 to 6, wherein the polyethylene is contained in an amount of 10 to 40 parts by mass per 100 parts by mass of the separator for a lead acid battery.

8. The separator for a lead acid battery according to any one of claims 1 to 7, comprising 40 to 70 parts by mass of inorganic particles per 100 parts by mass of the separator for a lead acid battery.

9. The separator for a lead acid battery according to any one of claims 1 to 8, wherein the thickness of the base portion of the separator for a lead acid battery is 0.050 mm or more.

10. 9. The separator for a lead acid battery according to claim 8, wherein the inorganic particles are silica particles.

11. The lead acid battery separator according to any one of claims 1 to 10, wherein the polyethylene comprises ultra-high molecular weight polyethylene.

12. The separator for a lead acid battery according to any one of claims 1 to 11, comprising 10 to 30 parts by mass of a plasticizer per 100 parts by mass of the separator for a lead acid battery.

13. 13. The lead acid battery separator according to claim 12, wherein the plasticizer is selected from the group consisting of petroleum oils, paraffin-based oils, and mineral oils.

14. The separator for a lead acid battery according to any one of claims 1 to 13, wherein a rib is provided on at least one surface of the separator for a lead acid battery.

15. A lead-acid battery comprising a battery case, a lead oxide positive electrode, a lead negative electrode, and dilute sulfuric acid, wherein the lead oxide positive electrode and the lead negative electrode are separated by the lead-acid battery separator according to any one of claims 1 to 14.

16. A lead-acid battery comprising a battery case, a lead oxide positive electrode, a lead negative electrode, and dilute sulfuric acid, wherein the lead oxide positive electrode and / or the lead negative electrode are inserted into the bag-shaped separator for a lead-acid battery according to claim 6.

17. A method for producing a separator for a lead-acid battery containing polyethylene, comprising: In the extrusion molding of a lead-acid battery separator, a quenching process is included in which a sheet temperature immediately after extrusion is quenched to 100°C or less by a pre-cooling roll, Two or more layers of the lead-acid battery separator obtained by the extrusion molding are stacked to form a multi-layer separator for a lead-acid battery; and A method for producing a separator for a lead-acid battery, comprising mechanically sealing at least a portion of the multi-layer separator for a lead-acid battery.

18. 18. The method for manufacturing a separator for a lead acid battery according to claim 17, wherein the multilayer separator for a lead acid battery is formed by stacking two or more layers of the separator for a lead acid battery with their MD directions aligned.

19. 19. The method for producing a lead-acid battery separator according to claim 17 or 18, wherein a degree of crystal orientation of the (110) plane of the polyethylene exceeds 0.780 in wide-angle X-ray scattering analysis in which X-rays are irradiated from a normal direction to a membrane surface of the lead-acid battery separator.

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