Nonwoven fabric for lead acid storage battery and method for manufacturing same

Abstract

[Problem] One objective of the present invention is to provide a good nonwoven fabric, such as a pasting paper and a separator, which is positioned between electrode plates of a lead acid storage battery and with which a deterioration in the ability of the nonwoven fabric to follow the shape of the electrode plates, associated with charge and discharge cycles, is suppressed, the deterioration resulting from expansion and contraction of the electrode plates that occur due to charging and discharging of the lead acid storage battery, said nonwoven fabric such as a pasting paper and a separator does not contain pinholes, by using a surface modifier that produces little or no foam in a stirred liquid, when the surface modifier is used to modify the surface of a hydrophobic material that has cushioning properties, to impart hydrophilicity thereto. Another objective is to provide a method for manufacturing the nonwoven fabric. [Solution] Disclosed is a nonwoven fabric for a lead acid storage battery, the nonwoven fabric being composed of at least one kind of fiber selected from among glass fibers having a weight average fiber diameter of 4.0 µm or less, glass long fibers having a weight average fiber diameter of more than 4.0 µm, natural fibers, organic fibers having acid resistance, and thermally fusible organic fibers, the nonwoven fabric being characterized by additionally containing a material that has cushioning properties and is surface-modified using a surface modifier so as to have hydrophilicity, and by having no pinholes. Also disclosed is a method for manufacturing a nonwoven fabric for a lead acid storage battery, the nonwoven fabric being made through a papermaking process by mixing and stirring at least one kind of fiber selected from among glass fibers having a weight average fiber diameter of 4.0 µm or less, glass long fibers having a weight average fiber diameter of more than 4.0 µm, natural fibers, organic fibers having acid resistance, and thermally fusible organic fibers, and a material that is surface-modified using a surface modifier so as to have hydrophilicity. This method for manufacturing a nonwoven fabric for a lead acid storage battery is characterized in that: the surface modifier does not generate bubbles when mixed and stirred, and does not hold bubbles at the time of the papermaking; and no pinholes are generated in the nonwoven fabric.

Description

Nonwoven fabric for lead-acid batteries and method of manufacturing the same

[0001] The present invention relates to a nonwoven fabric for lead-acid batteries and a method for manufacturing the same, and more particularly to a nonwoven fabric for pasting paper, separators, etc., which has sufficient adaptability to the expansion and contraction of electrode plates caused by charge and discharge, and a method for manufacturing the same.

[0002] Lead-acid batteries contain multiple electrodes, with sheet-like separators interposed between the electrodes to prevent short circuits. Typical automotive lead-acid batteries use paste-type lead-acid batteries, which use pasting paper as a support to prevent lead paste from falling off during the manufacturing process and to facilitate assembly. These pasting papers and separators are typically made of nonwoven fabric and are manufactured by papermaking a suspended slurry solution. The dimensions (length and width) and thickness of these pasting papers and separators are adjusted as needed depending on the intended use.

[0003] Batteries function by transferring charge between the electrodes and the electrolyte, which is held in place by the separator. Battery performance improves with lower internal resistance and reduced electrolyte stratification. The battery's internal resistance is significantly affected by the ease of charge transfer within the electrolyte and the ease of charge transfer between the electrodes and the electrolyte. Charge transfer between the electrodes and the electrolyte occurs through an oxidation-reduction reaction between the electrodes and ions. Charge transfer between the electrodes and the electrolyte cannot occur without ions in contact with the electrodes. Therefore, it is important that the pasting paper and separator adhere closely to the electrodes. However, because the electrodes expand and contract with each charge and discharge, the pasting paper and separator are subjected to repeated external forces of compression and relaxation. Therefore, separators with poor resilience quickly undergo the so-called "sag phenomenon," resulting in a rapid decline in adhesion.

[0004] Due to the expansion and contraction of the electrodes during charging and discharging of lead-acid batteries, nonwoven fabrics such as pasting paper and separators located between the electrodes are repeatedly compressed and released. As a result, the ability of the nonwoven fabrics, such as the pasting paper and separators, to conform to the electrodes decreases as the charge and discharge cycles progress, and the nonwoven fabrics' ability to hold the electrodes down decreases. As the nonwoven fabric's ability to hold the electrodes down decreases, active material gradually falls off the electrodes, resulting in the end of the battery's life. In particular, in sealed lead-acid batteries, as the nonwoven fabric's ability to hold the electrodes down decreases, adhesion to the electrodes deteriorates, significantly increasing the battery's internal resistance. As a result, even if active material does not fall off, the battery's capacity may become insufficient, resulting in the end of its life.

[0005] Many improvements have been made to pasting paper and separators to enhance the adhesion between the separator and the electrode plate. For example, to improve the compression recovery of nonwoven fabrics such as pasting paper and separators, separators have been disclosed in which rubber particles are attached to fibers using an emulsion of rubber particles, resulting in an elastic body between the fibers at their intersections (see, for example, Patent Document 1). Furthermore, lead / sulfuric acid storage batteries have been disclosed that contain non-crosslinked natural or synthetic rubber to provide stability against antimony poisoning (see, for example, Patent Document 2). Furthermore, separators that suppress a decrease in compressive force after charging have been disclosed by blending silica powder and silica sol with glass fibers (see, for example, Patent Document 3).

[0006] In Patent Document 1, the presence of rubber particles of 10 μm or less between the fibers of a nonwoven fabric provides compression recovery to the nonwoven fabric. However, rubber materials are generally hydrophobic and have water-repellent properties. Therefore, hydrophobic properties are imparted between the fibers of the nonwoven fabric and / or on the fiber surfaces. This reduces the amount of electrolyte that the nonwoven fabric should retain, increasing the internal resistance of the battery, causing new problems such as reduced battery capacity and shortened battery life. Furthermore, the rubber particles are attached to the nonwoven fabric by immersing the nonwoven fabric in a rubber particle emulsion and then heating and drying it. There is no mention of using a crosslinking agent in the emulsion. Therefore, the resin is formed by drying and heating alone. Generally, rubber materials are believed to have strong rubber elasticity due to the crosslinking reaction that occurs when a crosslinking agent is used. However, simply immersing the nonwoven fabric in an emulsion and drying it alone is not sufficient to impart sufficient rubber elasticity to nonwoven fabrics such as pasting paper and separators.

[0007] In addition, in Patent Document 2, a separator containing a rubber material is produced by impregnating or coating a porous carrier material (a nonwoven fabric made of fibers) with non-crosslinked natural or synthetic rubber and drying it. However, although the rubber material is said to have strong rubber elasticity due to a crosslinking reaction caused by the use of a crosslinking agent, the fact that the rubber material is not crosslinked means that the porous carrier material (nonwoven fabric made of fibers) carrying the rubber material does not have sufficient rubber elasticity. Furthermore, with regard to stability against antimony poisoning, S is used as a substance that binds to antimony ions. ２－ It is known that antimony ions are chemically bonded to divalent sulfur, which is generally formed by vulcanization of rubber materials. However, in rubber materials that are not cross-linked by vulcanization or other methods, the antimony trapping effect is low.

[0008] Furthermore, Patent Document 3 discloses that a separator made of glass fibers mixed with silica powder and silica sol is immersed in a silica sol or alumina sol solution and dried, whereby the silica sol or alumina sol acts as a binder to improve the tensile strength of the separator, thereby increasing the ability to maintain compressive force. However, the separator is hard and loses flexibility, which reduces the separator's ability to conform to the electrode plates in their compressed and uncompressed states due to the expansion and contraction of the electrode plates. Furthermore, because the separator is hard and inflexible, it is not suitable for application of stress, such as bending, during battery assembly work, and there is a drawback in that the work method is limited to a specific method.

[0009] It is generally known that surfactants are used to modify the surface properties of water-repellent / hydrophobic materials when they are made into paper (see, for example, Patent Document 4). Patent Document 4 discloses a lead-acid battery separator containing glass fibers, a polyolefin resin, and an aluminum compound, with an average pore size of 10 μm or less, a glass fiber content of 87.0 mass% or more, and aluminum sulfate as the aluminum compound. The surfactant is added to address the issue of the separator's reduced hydrophilicity due to the incorporation of polyolefin resin. Furthermore, the polyolefin resin used is treated to be in an emulsion state, and since it is already dispersed in water, it does not entrap large amounts of air even when stirred, and therefore does not entrap large amounts of air bubbles in the stirred slurry. However, when a highly water-repellent material such as rubber particles that has not been treated to be hydrophilic is used, stirring using the surfactant described in Patent Document 4 or a commonly used surfactant causes the rubber particles floating in the water to entrap air (air bubbles), resulting in a highly foamy mixture. Therefore, if foamed material is used to make paper, a large number of pinholes (holes where air bubbles have escaped) will appear in the nonwoven fabric, making it impossible to make a nonwoven fabric suitable for use in lead-acid batteries.

[0010] JP-A-11-354092 Patent No. 3427845 JP-A-07-029560 Patent No. 6769306

[0011] The present invention aims to provide a method for producing good nonwoven fabrics such as pasting paper and separators that are free of pinholes, by suppressing the deterioration of electrode plate conformability of nonwoven fabrics such as pasting paper and separators located between electrode plates due to the expansion and contraction of electrode plates caused by the charge and discharge cycles of lead-acid batteries, and by using a surface modifier that generates little foam in the stirring liquid when modifying the surface of a hydrophobic material with cushioning properties to make it hydrophilic, which is caused by the expansion and contraction of electrode plates caused by the charge and discharge cycles of lead-acid batteries.

[0012] As a result of extensive research aimed at solving the above problems, the present invention has discovered a nonwoven fabric for lead-acid batteries having the following characteristics: (1) A nonwoven fabric for lead-acid batteries, comprising at least one of glass fibers having a weight-average fiber diameter of 4.0 μm or less, long glass fibers having a weight-average fiber diameter of more than 4.0 μm, natural fibers, acid-resistant organic fibers, and heat-fusible organic fibers, further comprising a cushioning material whose surface has been hydrophilically modified using a surface modifier, wherein the nonwoven fabric is free of pinholes. (2) The nonwoven fabric for lead-acid batteries according to (1), wherein the cushioning material is a powder of a vulcanized rubber material. (3) The nonwoven fabric for lead-acid batteries according to (2), wherein the content of the vulcanized rubber material powder is 3 wt % or more and 65 wt % or less. (4) The nonwoven fabric for lead-acid batteries according to (2) or (3), characterized in that the average particle diameter D50 of the powder of the vulcanized rubber material is 10 μm or more and 1000 μm or less. (5) The nonwoven fabric for lead-acid batteries according to any one of (2) to (4), characterized in that the average particle diameter D50 of the powder of the vulcanized rubber material is 50 μm or more and 500 μm or less. (6) The nonwoven fabric for lead-acid batteries according to any one of (2) to (5), characterized in that the powder of the vulcanized rubber material is an acid-resistant rubber material, and is one or more selected from natural rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile rubber, butyl rubber, and ethylene-propylene rubber. (7) The nonwoven fabric for lead-acid batteries according to any one of (2) to (6), characterized in that the powder of the vulcanized rubber material is ground tires and / or scrap tires. (8) The nonwoven fabric for a lead-acid battery according to any one of (2) to (7), further comprising an inorganic powder as a surface support for the powder of the vulcanized rubber material. (9) The nonwoven fabric for a lead-acid battery according to (8), characterized in that the inorganic powder is one or more acid-resistant powders selected from silica powder, silica sol, alumina sol, aluminum oxide powder, diatomaceous earth, and titanium oxide powder. (10) The nonwoven fabric for a lead-acid battery according to (8) or (9), characterized in that the blending ratio of the inorganic powder to the powder of the vulcanized rubber material is 90 wt % or less.(11) The nonwoven fabric for a lead-acid battery according to any one of (8) to (10), characterized in that the blending ratio of the inorganic powder is 75 wt% or less with respect to the powder of the vulcanized rubber material.

[0013] The present invention also provides a method for producing a nonwoven fabric for lead-acid batteries, characterized by the following characteristics: (12) A method for producing a nonwoven fabric for lead-acid batteries, the method being formed by mixing and stirring at least one of glass fibers having a weight-average fiber diameter of 4.0 μm or less, long glass fibers having a weight-average fiber diameter of more than 4.0 μm, natural fibers, acid-resistant organic fibers, and heat-fusible organic fibers, and a material whose surface has been hydrophilically modified using a surface modifier, wherein the surface modifier does not generate bubbles during the mixing and stirring and does not trap bubbles during the papermaking process, and wherein no pinholes are formed in the nonwoven fabric. (13) A method for producing a nonwoven fabric for lead-acid batteries as described in (12), the method being characterized in that the hydrophilically surface-modified material is obtained by hydrophilically modifying a powder of a vulcanized rubber material having cushioning properties using the surface modifier. (14) The method for producing a nonwoven fabric for a lead-acid battery according to (12) or (13) above, characterized in that the surface modifier is one or more selected from the group consisting of a silicone oil compound antifoaming agent, a silane coupling agent, and a cationic starch. (15) The method for producing a nonwoven fabric for a lead-acid battery according to any one of (12) to (14) above, characterized in that a polymer flocculant is further added after the mixing and stirring, and the papermaking is carried out.

[0014] Furthermore, the separator or pasting paper made of the nonwoven fabric for lead-acid batteries of the present invention, and the lead-acid battery using the same, have the following characteristics: (16) A separator or pasting paper characterized by being made of the nonwoven fabric for lead-acid batteries according to any one of (1) to (11) above. (17) A lead-acid battery characterized by using a separator or pasting paper made of the nonwoven fabric for lead-acid batteries according to any one of (1) to (11) above.

[0015] As described above, the nonwoven fabric for lead-acid batteries includes at least one fiber material selected from glass fibers having a weight-average fiber diameter of 4.0 μm or less, long glass fibers having a weight-average fiber diameter of more than 4.0 μm, natural fibers, acid-resistant organic fibers, and heat-fusible organic fibers. The surface of the nonwoven fabric is modified to be hydrophilic using a surface modifier that generates little foam in the agitated solution. This hydrophobic material with cushioning properties prevents the deterioration of the electrode-following ability of nonwoven fabrics, such as pasting paper and separators, located between the electrode plates during charge and discharge cycles due to expansion and contraction of the electrode plates during charge and discharge. This prevents pinholes and provides a method for manufacturing the same. Furthermore, the inclusion of a vulcanized rubber powder as the hydrophobic cushioning material in the nonwoven fabric for lead-acid batteries reduces self-discharge due to antimony ions and improves stability against antimony poisoning.

[0016] The nonwoven fabric for lead-acid batteries of the present invention is made by wet-sheeting using at least one type of fibrous material selected from glass fibers having a weight-average fiber diameter of 4.0 μm or less, long glass fibers having a weight-average fiber diameter of more than 4.0 μm, natural fibers, acid-resistant organic fibers, and heat-fusible organic fibers as the main raw material, and further adding a cushioning material whose surface has been hydrophilically modified using a surface modifier. The nonwoven fabric for lead-acid batteries of the present invention also preferably contains inorganic powder, a polymer flocculant, a paper strength enhancer, etc. In the present invention, the main raw material fibrous material preferably contains at least glass fibers having a weight-average fiber diameter of 4.0 μm or less and heat-fusible organic fibers, and further adding a cushioning material whose surface has been hydrophilically modified using a surface modifier. It is also preferable that the nonwoven fabric for lead-acid batteries of the present invention further contains inorganic powder.

[0017] As the glass fibers having a weight average fiber diameter of 4.0 μm or less and the long glass fibers having a weight average fiber diameter of more than 4.0 μm used in the nonwoven fabric for lead-acid batteries of the present invention, since the nonwoven fabric for lead-acid batteries of the present invention is used as a separator or pasting paper for lead-acid batteries, it is used in an electrolyte (aqueous sulfuric acid solution with a specific gravity of 1.3). Therefore, acid-resistant C-glass fibers are preferred, but any acid-resistant glass fibers may be used.

[0018] The glass fibers having a weight-average fiber diameter of 4.0 μm or less vary depending on the other materials combined, but from the viewpoint of stratification suppression, which is one of the functions expected of separators or pasting papers, as well as from the viewpoint of suppressing an increase in the internal resistance of batteries and suppressing a decrease in the charge acceptance of batteries, the weight-average fiber diameter is preferably 0.5 μm or more and 4.0 μm or less, and more preferably 3.0 μm or less. Furthermore, when further improvement in stratification suppression is required, such as when used in lead-acid batteries for idling stop-and-start systems (ISSs), the weight-average fiber diameter is even more preferably 2.0 μm or less. Furthermore, from the viewpoint of the basic physical properties (tensile strength, elongation) and liquid absorbency of separators or pasting papers, the weight-average fiber length is preferably 0.2 mm or more and 4.0 mm or less.

[0019] The long glass fibers having a weight-average fiber diameter of more than 4.0 μm are not particularly limited as long as they are generally used for separators for lead-acid batteries or pasting papers for lead-acid batteries. However, those having a weight-average fiber diameter of 6.0 μm or more and 30 μm or less and a cut length of 3.0 mm or more and 50 mm or less are preferred, and those having a weight-average fiber diameter of 6.0 μm or more and 15 μm or less and a cut length of 3.0 mm or more and 25 mm or less are more preferred.

[0020] The natural fibers used in the nonwoven fabric for a lead-acid battery of the present invention are preferably fibers made from natural pulp, which is a plant fiber (natural pulp fibers), PVA fibers, polylactic acid fibers, etc., more preferably fibers made from natural pulp (natural pulp fibers), and even more preferably fibers made only from natural pulp (100% pulp) (natural pulp fibers).

[0021] The acid-resistant organic fibers used in the nonwoven fabric for lead-acid batteries of the present invention are not particularly limited as long as they are generally used in nonwoven fabrics for lead-acid batteries, but preferred are those that are polyolefin-based resins or polyester-based resins as synthetic resin components, and preferably have a fineness of 0.06 to 4.0 dtex and a number-average fiber length of 1 to 25 mm, and more preferably are long fibers having a fineness of 0.5 dtex or more and a number-average fiber length of 3 mm or more.

[0022] The synthetic resin component of the heat-fusible organic fiber used in the nonwoven fabric for a lead-acid battery of the present invention is a synthetic resin such as a polyolefin resin such as polyethylene resin or polypropylene resin, a polystyrene resin, a polymethyl methacrylate resin, a polyacrylonitrile resin, a nylon resin, a polyester resin, or a polyfluoroethylene resin, and among these, the heat-melting component is a polyolefin resin such as polyethylene resin or polypropylene resin, or a heat-fusible polyester resin. In the present invention, polyolefin resins such as polyethylene resin or polypropylene resin, or polyester resins are preferably used from the viewpoint of improving the tensile strength (sheet strength).

[0023] As the heat-fusible organic fiber, in order to increase the number of heat-fusible organic fibers contained in the nonwoven fabric for lead-acid batteries, which is a measure to increase the tensile strength (sheet strength), heat-fusible organic fibers having a fineness of 2.5 dtex or less are preferred, heat-fusible organic fibers having a fineness of 1.6 dtex or less are more preferred, and heat-fusible organic fibers having a fineness of 1.5 dtex or less are even more preferred. Furthermore, if the fineness of the heat-fusible organic fiber is less than 0.4 dtex, the difference in specific gravity between the heat-fusible organic fiber and glass fiber or the like will affect the formation of the nonwoven fabric for lead-acid batteries, preventing the two from being mixed uniformly, resulting in large variations in the properties of the separator for lead-acid batteries or the pasting paper for lead-acid batteries made from the nonwoven fabric for lead-acid batteries, and resulting in the problem that a nonwoven fabric for lead-acid batteries of stable quality cannot be obtained. Therefore, the fineness of the heat-fusible organic fiber is preferably 0.4 dtex or more, more preferably 0.5 dtex or more, and even more preferably 0.6 dtex or more.

[0024] The heat-fusible organic fiber used in the nonwoven fabric for a lead-acid battery of the present invention preferably has a core-sheath structure. In this case, the core may be a commonly used resin such as a polyolefin resin (e.g., polyethylene resin, polypropylene resin) or a polyester resin, but an acid-resistant resin is preferred, and a polyester resin (e.g., polyethylene terephthalate) is preferred. The sheath is preferably a polyolefin resin (e.g., polyethylene resin, polypropylene resin) or a polyester resin, with crystalline polyolefin resins, crystalline or amorphous polyester resins (e.g., polyethylene terephthalate), and modified polyester resins (e.g., copolymerized polyethylene terephthalate) being more preferred.

[0025] The cushioning material used in the nonwoven fabric for lead-acid batteries of the present invention, which has been surface-modified to be hydrophilic using the surface modifier, is preferably a powder of a vulcanized rubber material. The rubber material is preferably acid-resistant, and natural rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile rubber, butyl rubber, and ethylene-propylene rubber are preferred. The powder of the vulcanized rubber material is preferably ground tires and / or scrap tires, as this contributes to a recycling-oriented society by using recycled materials.

[0026] Generally, the surface of the vulcanized rubber powder is hydrophobic and has water-repellent properties. Therefore, adding the vulcanized rubber powder directly to a nonwoven fabric for lead-acid batteries imparts hydrophobic properties to the spaces between the fibers and / or the fiber surface of the nonwoven fabric. This reduces the amount of electrolyte that the nonwoven fabric for lead-acid batteries should retain, increasing the internal resistance of the lead-acid battery, resulting in a decrease in battery capacity and a shortened battery life. Therefore, in the present invention, the surface of the vulcanized rubber powder is modified from hydrophobic to hydrophilic using the surface modifier, thereby enabling the production of nonwoven fabrics for lead-acid batteries, such as pasting paper and separators, that maintain wettability with the electrolyte. As a result, the increase in internal resistance and the decrease in battery capacity of lead-acid batteries manufactured using pasting paper and / or separators made from the nonwoven fabric for lead-acid batteries can be suppressed, thereby suppressing a shortened battery life.

[0027] In the present invention, the surface modifier used to modify the surface of the vulcanized rubber material powder from hydrophobic to hydrophilic is preferably a surface modifier that generates little foam in the stirring solution during the surface modification treatment. If the surface is modified using a general surfactant or the like, when the surface-modified vulcanized rubber material powder is mixed with the fiber material that constitutes the nonwoven fabric to form a slurry, a large number of bubbles will be contained in the slurry, and a large number of pinholes (bubble escape marks) will be generated in the nonwoven fabric produced. By using a surface modifier that generates little foam in the stirring solution during the surface modification treatment, good nonwoven fabrics such as pasting paper and separators that are free of pinholes can be obtained. Examples of surface modifiers that are preferably used in the present invention and that cause little foaming in the stirred solution when the surface modification treatment is carried out include cationic starch (e.g., Acedin HP-100 and HP-150 manufactured by Yamato Chemical Industry Co., Ltd.), silicone-based defoamers (e.g., FS Antifoam 93 manufactured by Dow Corning Toray Co., Ltd., KM-90 manufactured by Shin-Etsu Chemical Co., Ltd., KM-7750 manufactured by Shin-Etsu Chemical Co., Ltd., KM-7752 manufactured by Shin-Etsu Chemical Co., Ltd., and Dappo H-205N manufactured by San Nopco Ltd.), and the like.

[0028] In the present invention, the average particle diameter D50 of the vulcanized rubber material powder that has been surface-modified to be hydrophilic using the surface modifier is preferably 10 μm or more, and more preferably 50 μm or more. By using a rubber material powder with a large particle diameter (average particle diameter D50 of 10 μm or more), the nonwoven fabric is compressed during electrode plate expansion, reducing its thickness. However, once the nonwoven fabric has reduced to a certain thickness, the blended vulcanized (crosslinked) rubber material powder acts as a spacer to prevent the thickness reduction. Meanwhile, when the nonwoven fabric contracts due to electrode plate contraction, the rubber elasticity of the vulcanized (crosslinked) rubber material powder acts to restore the nonwoven fabric to its original state, allowing it to follow the electrode plate contraction more effectively than a nonwoven fabric that does not contain vulcanized (crosslinked) rubber material powder. In the present invention, the average particle diameter D50 of the vulcanized rubber material powder that has been surface-modified to be hydrophilic using the surface modifier is preferably 1000 μm or less, and more preferably 500 μm or less. If the particle size is too large, the powder of the vulcanized rubber material will not remain between the fibers that make up the nonwoven fabric, which will deteriorate the surface properties of the nonwoven fabric and increase the variation in thickness of the nonwoven fabric.

[0029] When forming a slurry using a hydrophobic material, a silane coupling agent can be used to obtain a raw material slurry that does not contain air bubbles. Alternatively, although the process becomes more complicated, the raw material slurry containing air bubbles can be washed away by rinsing with water, or if only a small amount of foam is generated, a general defoaming agent can be used to eliminate the bubbles in the raw material slurry, and the surface of the hydrophobic material can be modified to be hydrophilic before being mixed with other materials.

[0030] The inorganic powder used in the nonwoven fabric for lead-acid batteries of the present invention is preferably hydrophilic and acid-resistant, and examples thereof include particles or powders such as silica powder, silica sol, alumina sol, aluminum oxide powder, diatomaceous earth, and titanium oxide powder. Adding the inorganic powder to the raw material slurry for the nonwoven fabric for lead-acid batteries allows the inorganic powder to be supported on the surface of the powder of the vulcanized rubber material that has been surface-modified to be hydrophilic using the surface modifier, thereby further enhancing the hydrophilicity of the surface of the powder of the vulcanized rubber material. Supporting the inorganic powder on the surface of the powder of the vulcanized rubber material that has been surface-modified to be hydrophilic using the surface modifier increases the specific surface area of ​​the nonwoven fabric for lead-acid batteries, thereby suppressing dendrite growth in lead-acid batteries fabricated using pasting paper and / or separators made from the nonwoven fabric for lead-acid batteries, thereby extending the battery life of the lead-acid batteries. In the present invention, since the inorganic powder is supported on the surface of the powder of the vulcanized rubber material that has been surface-modified to be hydrophilic using the surface modifier, the particle size of the inorganic powder is preferably smaller than the particle size of the powder of the vulcanized rubber material to be supported. The average particle size of the inorganic powder is preferably 0.1 μm to 30 μm, more preferably 1 μm to 20 μm. Furthermore, a higher blend ratio of the powder of the vulcanized rubber material that has been surface-modified to be hydrophilic using the surface modifier will impart stronger conformability to the electrode plate relative to the nonwoven fabric. Therefore, it is necessary to further strengthen the hydrophilicity of the surface of the powder of the vulcanized rubber material. The blend ratio of the powder of the vulcanized rubber material that has been surface-modified to be hydrophilic using the surface modifier to the inorganic powder is preferably 1:0.9 or less, more preferably 1:0.7 or less.

[0031] In the present invention, the blending amount of the cushioning material, which has been surface-modified to be hydrophilic using the surface modifier, in the nonwoven fabric for lead-acid batteries is preferably 3 wt% or more. If the blending amount is less than 3 wt%, the effects of the present invention cannot be obtained. Furthermore, the blending amount is preferably 65 wt% or less. If the blending amount exceeds 65 wt%, the tensile strength (sheet strength) of the nonwoven fabric becomes insufficient, and the shape retention of pasting paper or separators made of the nonwoven fabric for lead-acid batteries when immersed in an electrolyte (sulfuric acid) decreases. The blending amount of the fiber material as the main raw material (at least one selected from glass fibers having a weight-average fiber diameter of 4.0 μm or less, long glass fibers having a weight-average fiber diameter of more than 4.0 μm, natural fibers, acid-resistant organic fibers, and heat-fusible organic fibers) in the nonwoven fabric is preferably 35 wt% or more and 97 wt% or less.

[0032] The divalent bonded sulfur contained in the powder of vulcanized rubber material, which has been surface-modified to hydrophilicity using the surface modifier and is used in the nonwoven fabric for lead-acid batteries of the present invention, is known to chemically bond with antimony ions (see, for example, German Published Application No. 3111473). The surface of vulcanized rubber material is essentially hydrophobic, and unless the surface is modified to hydrophilicity, it will not come into contact with antimony ions present in the electrolyte. Therefore, the divalent bonded sulfur contained in the powder of vulcanized rubber material cannot chemically bond with antimony ions. In the present invention, by surface-modifying the hydrophobic surface of the powder of vulcanized rubber material to hydrophilicity using a surface modifier, the divalent bonded sulfur contained in the powder of vulcanized rubber material can easily come into contact with antimony ions present in the electrolyte. As a result, antimony ions can be captured in the powder of vulcanized rubber material, which has been surface-modified to hydrophilicity using the surface modifier, by chemical bonding.

[0033] In addition to lead-calcium alloys, lead-antimony alloys are known as grid alloys for the positive and negative electrodes of lead-acid batteries. Lead-antimony alloys are harder than lead-calcium alloys, making them easier to handle and facilitating the assembly of lead-acid batteries. However, lead-calcium alloys have been used to date because antimony ions leach into the electrolyte, resulting in self-discharge of the lead-acid battery due to ion migration between the positive and negative electrodes. However, by using pasting paper and / or separators made from the nonwoven fabric for lead-acid batteries of the present invention, the antimony ions in the electrolyte can be captured by the powder of the vulcanized rubber material, whose surface has been hydrophilically modified using the surface modifier contained in the nonwoven fabric for lead-acid batteries. This allows for the suppression of self-discharge caused by antimony ions, enabling the use of grids made of lead-antimony alloys. This, in turn, improves the productivity of lead-acid batteries.

[0034] The method for producing the nonwoven fabric for lead-acid batteries of the present invention involves adding a material whose surface has been hydrophilically modified using the surface modifier, preferably a powder of a vulcanized rubber material with cushioning properties, to a fiber material (at least one of glass fibers having a weight-average fiber diameter of 4.0 μm or less, long glass fibers having a weight-average fiber diameter of more than 4.0 μm, natural fibers, acid-resistant organic fibers, and heat-fusible organic fibers) that is the main raw material, and mixing and stirring to uniformly disperse the material to prepare a raw material slurry that is free of entrapped air bubbles, which is then paper-formed by a known method to produce the nonwoven fabric for lead-acid batteries of the present invention. In the present invention, the nonwoven fabric for the lead-acid battery of the present invention is produced by adding a hydrophilically surface-modified material, preferably a vulcanized rubber material powder with cushioning properties, to the main raw material fiber material (at least one of glass fiber having a weight average fiber diameter of 4.0 μm or less, long glass fiber having a weight average fiber diameter of more than 4.0 μm, natural fiber, acid-resistant organic fiber, and heat-fusible organic fiber) using the surface modifier, and then papermaking the nonwoven fabric for the lead-acid battery of the present invention. Therefore, it is preferable to add a polymer flocculant to the slurry before papermaking, and then flocculate the slurry before papermaking. As the polymer flocculant, cationic flocculants (e.g., Acryprimer GC3000MV manufactured by MT Aquapolymer Co., Ltd., and Clifix EC manufactured by Kurita Water Industries Ltd.) and nonionic flocculants (e.g., Cliflock PN manufactured by Kurita Water Industries Ltd.) are preferably used.

[0035] An example of a specific method for producing a nonwoven fabric for a lead-acid battery of the present invention is described below. First, 0.5 g of a vulcanized rubber material having an average particle diameter D50 of 10 μm or more (e.g., MicroDyne 78, manufactured by LeHigh Technologies, recycled tire rubber, average particle diameter D50: 90.8 μm) and 2 g of a surface modifier (e.g., cationic starch, such as Ace Dyn HP-100 or HP-150 manufactured by Daiwa Chemical Industry Co., Ltd.; an aqueous solution with a 10 wt% solids content) were added to 500 ml of water and stirred for 30 seconds with a mixer. Then, a predetermined amount of the main raw material fiber material (at least one of glass fiber having a weight average fiber diameter of 4.0 μm or less, long glass fiber having a weight average fiber diameter of more than 4.0 μm, natural fiber, acid-resistant organic fiber, and heat-fusible organic fiber) was added to the prepared rubber material dispersion and uniformly dispersed, producing a raw material slurry without entrapped air bubbles. An appropriate amount of a 0.2 wt % solution of a polymer flocculant (for example, Acryprimer GC3000MV, a cationic flocculant manufactured by MT Aquapolymer Co., Ltd.) was added to flocculate the slurry, and then the slurry was made into a paper sheet to obtain a nonwoven fabric for a lead acid battery according to the present invention.

[0036] In addition, 0.5 g of a vulcanized rubber material having an average particle size D50 of 10 μm or more (e.g., MicroDyne 78: tire recycled rubber manufactured by LeHigh Technologies, average particle size D50: 90.8 μm) and about 0.6 g to 4 g of a surface modifier (e.g., silicone-based antifoaming agent: FS Antifoam 93 manufactured by Toray Dow Corning Co., Ltd.; KM-90, KM-7750, KM-7752 manufactured by Shin-Etsu Chemical Co., Ltd.; Dappo H-205N manufactured by San Nopco Ltd.; etc.: an aqueous solution with a solids content of about 5 to 30 wt %) were added to 500 ml of water and stirred for a predetermined time. A predetermined amount of the main raw material fiber material (at least one of glass fiber having a weight average fiber diameter of 4.0 μm or less, long glass fiber having a weight average fiber diameter of more than 4.0 μm, natural fiber, acid-resistant organic fiber, and heat-fusible organic fiber) was added to the prepared rubber material dispersion and uniformly dispersed to prepare a raw material slurry without entrapped air bubbles. An appropriate amount of a 0.2 wt % solution of a polymer flocculant (e.g., Acryprimer GC3000MV, a cationic flocculant manufactured by MT Aquapolymer Co., Ltd.) was added to flocculate the slurry, and the nonwoven fabric for a lead-acid battery of the present invention was obtained by papermaking.

[0037] In the present invention, the hydrophobic vulcanized rubber powder can be mixed with a surface modifier to modify the surface condition of the vulcanized rubber powder to be hydrophilic. This can then be mixed with the fiber material that constitutes the nonwoven fabric to form a slurry, which can then be paper-formed to produce a nonwoven fabric for lead-acid batteries. The nonwoven fabric for lead-acid batteries thus produced maintains the elastic properties of the vulcanized rubber powder and can improve its ability to conform to the electrode plates during expansion and contraction of the electrode plates during charge and discharge reactions of the lead-acid battery. Furthermore, since the vulcanized rubber powder that has been surface-modified to be hydrophilic is mixed with the fiber material that constitutes the nonwoven fabric, the hydrophilic properties of the nonwoven fabric for lead-acid batteries are not impaired, the electrolyte necessary for the battery reaction can be retained, and an increase in the internal resistance of the lead-acid battery can be suppressed. Furthermore, if a common surfactant is used to modify the surface when mixing the hydrophobic vulcanized rubber powder with the fiber material that constitutes the nonwoven fabric to form a slurry, the slurry will contain a large number of air bubbles. As a result, a large number of pinholes (remains of bubbles) occur in the nonwoven fabric produced, making it unsuitable for use as pasting paper for lead-acid batteries, separators, etc. However, the surface modifier used in the present invention does not generate bubbles in the raw material slurry that would otherwise entrap air bubbles when mixed to form a slurry, and as a result, a good nonwoven fabric for lead-acid batteries can be obtained that is free of pinholes.

[0038] Furthermore, by using an inorganic powder in addition to the fiber material and the powder of the vulcanized rubber material that has been surface-modified to be hydrophilic using the surface modifier, the nonwoven fabric for lead-acid batteries of the present invention can support the inorganic powder on the surface of the powder of the vulcanized rubber material, thereby further enhancing the hydrophilicity of the powder of the vulcanized rubber material that has been surface-modified to be hydrophilic using the surface modifier. Also, by supporting the inorganic powder on the surface of the powder of the vulcanized rubber material that has been surface-modified to be hydrophilic using the surface modifier, the specific surface area of ​​the nonwoven fabric for lead-acid batteries can be increased, and the effect of suppressing dendrite growth in the lead-acid battery can be added, thereby extending the battery life.

[0039] The nonwoven fabric for lead-acid batteries of the present invention is preferably used as pasting paper for lead-acid batteries or as a separator for lead-acid batteries. Pasting paper for lead-acid batteries made from the nonwoven fabric for lead-acid batteries of the present invention preferably has a thickness of 0.03 to 0.50 mm, more preferably 0.10 to 0.30 mm, and even more preferably 0.15 to 0.25 mm, when pressurized at 20 kPa. From the viewpoint of improving the electrical resistance and battery performance of the pasting paper, the thickness is desirably 0.03 mm or greater. Furthermore, since the spacing (electrode spacing) between the positive and negative electrodes in typical automotive lead-acid batteries is approximately 1.5 mm or less, if the pasting paper is too thick, it becomes difficult to use the separator. Therefore, the thickness must be kept to 0.50 mm or less. A separator for lead-acid batteries made from the nonwoven fabric for lead-acid batteries of the present invention preferably has a thickness of more than 0.50 mm, more preferably 0.60 mm or greater, when pressurized at 20 kPa. If the thickness is less than 0.50 mm, the total amount of electrolyte that the separator can hold decreases, which reduces the function of preventing stratification of the electrolyte and also reduces the absolute strength of the separator.

[0040] Next, an embodiment of a lead-acid battery using a separator for a lead-acid battery or pasting paper for a lead-acid battery made of the nonwoven fabric for a lead-acid battery of the present invention will be described, but the present invention is not limited to the following embodiment. The lead-acid battery may be either an open type or a sealed type (regulating valve type).

[0041] [Electrolyte] The electrolyte contains sulfuric acid in an aqueous solution. The electrolyte may be gelled as needed. The electrolyte may contain additives used in lead-acid batteries as needed. The specific gravity of the electrolyte at 20°C in a lead-acid battery in a fully charged state after formation is, for example, 1.10 g / cm ３ or more, and 1.35 g / cm ３ The following is the result.

[0042] [Positive Electrode Plate] Positive electrodes for lead-acid batteries are classified into paste type and clad type. Paste type positive electrodes include a positive electrode collector and a positive electrode material. The positive electrode material is held by the positive electrode collector. In the paste type positive electrode plate, the positive electrode material is the positive electrode plate excluding the positive electrode collector. The positive electrode collector may be formed in the same manner as the negative electrode collector, and can be formed by casting lead or a lead alloy or processing a lead or lead alloy sheet.

[0043] A clad positive electrode plate includes multiple porous tubes, a metal core inserted into each tube, a positive electrode material filled into the tube with the metal core inserted, and a connecting seat connecting the multiple tubes. In a clad positive electrode plate, the positive electrode material is the positive electrode plate excluding the tubes, the metal core, and the connecting seat.

[0044] As the lead alloy used for the positive electrode current collector, lead-calcium (Pb—Ca) alloys and lead-calcium-tin (Pb—Ca—Sn) alloys are preferred in terms of corrosion resistance and mechanical strength. Lead-antimony (Pb—Sb) alloys are also preferred because they are hard, easy to handle, and facilitate the assembly of lead-acid batteries. The positive electrode current collector may have lead alloy layers with different compositions, or multiple alloy layers. A lead-calcium (Pb—Ca) alloy or a lead-antimony (Pb—Sb) alloy is preferably used for the core metal. The positive electrode material contains a positive electrode active material (lead dioxide or lead sulfate) that develops capacity through an oxidation-reduction reaction. The positive electrode material may contain other additives as needed. In lead-acid battery separators or lead-acid battery pasting papers made from the nonwoven fabric of the present invention, it is also preferred to include antimony in the positive electrode active material in order to increase the corrosion resistance of the electrode plates during actual battery use and extend the battery life. Antimony is contained in the form of antimony oxide or the like, and its concentration in the positive electrode active material is preferably 0.01 wt % to 1 wt %, more preferably 0.02 wt % to 0.5 wt %, and even more preferably 0.05 wt % to 0.5 wt %. Instead of containing antimony in the positive electrode active material, antimony may be introduced by laminating a foil of a lead-antimony alloy on the positive electrode grid.

[0045] Unformed paste-type positive plates are obtained by filling a positive electrode current collector with positive electrode paste, aging it, and drying it, similar to the case of negative plates. The unformed positive plate is then formed. The positive electrode paste is prepared by kneading lead powder, additives, water, and sulfuric acid. Clad-type positive plates are formed by filling a tube with a core metal inserted with lead powder or lead powder slurry and connecting multiple tubes together.

[0046] [Negative Electrode Plate] The negative electrode plate of a lead-acid battery is composed of a negative electrode current collector and a negative electrode material. The negative electrode material is the negative electrode plate excluding the negative electrode current collector. The negative electrode current collector may be formed by casting lead or a lead alloy, or may be formed by processing a lead or lead alloy sheet. Examples of processing methods include expanding and punching. Using a negative electrode grid as the negative electrode current collector is preferable because it makes it easier to support the negative electrode material.

[0047] The lead alloy used for the negative electrode current collector may be any of a lead-antimony (Pb—Sb) alloy, a lead-calcium (Pb—Ca) alloy, and a lead-calcium-tin (Pb—Ca—Sn) alloy. These lead or lead alloys may further contain at least one additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc.

[0048] The negative electrode material contains a negative electrode active material (lead or lead sulfate) that develops capacity through an oxidation-reduction reaction, and may also contain a shrinkage inhibitor, lignin, a carbonaceous material such as carbon black, barium sulfate, etc., and may also contain other additives as needed. The negative electrode active material in a charged state is sponge lead, but an unformed negative electrode plate is usually made using lead powder.

[0049] The negative electrode plate can be formed by filling a negative electrode current collector with a negative electrode paste, aging and drying the paste to produce an unformed negative electrode plate, and then chemically forming the unformed negative electrode plate. The negative electrode paste can be produced by adding water and sulfuric acid to lead powder, an organic shrinkage inhibitor, and various additives as needed, and kneading the mixture. In the aging step, the unformed negative electrode plate is preferably aged at a temperature higher than room temperature and at a high humidity.

[0050] The formation can be carried out by immersing an electrode plate assembly including unformed negative plates in an electrolyte containing sulfuric acid in a battery jar of a lead-acid battery and then charging the electrode plate assembly. However, the formation can also be carried out before assembling the lead-acid battery or the electrode plate assembly. The formation produces spongy lead.

[0051] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. Nonwoven fabrics (separators or pasting papers) for lead-acid batteries in Examples 1 to 27 and Comparative Examples 1 to 8 were prepared using the following raw materials.

[0052] [Raw materials] (1) Glass fiber manufactured by Entech Asia Co., Ltd. Weight average fiber diameter 1.0 μm, fiber length 0.5 to 1.0 mm (2) Heat-fusible organic fiber manufactured by Unitika Ltd. Melty 4080, two-component core-sheath type (core: polyethylene terephthalate, sheath: copolymerized polyethylene terephthalate), fineness 1.5 dtex, number average fiber length 3 mm (3) Inorganic powder Silica (powder): manufactured by Evonik Industries AG BG-3, average particle diameter; 13 μm (4) Vulcanized rubber material (powder) A: manufactured by LeHigh Technologies MicroDyne 50-BU, average particle diameter D50; 58 μm B: manufactured by LeHigh Technologies MicroDyne 78-BU, average particle diameter D50; 91 μm C: MicroDyne 188-BU manufactured by LeHigh Technologies, average particle diameter D50: 122 μm D: MicroDyne 400-BU manufactured by LeHigh Technologies, average particle diameter D50: 466 μm The average particle diameter D50 of the vulcanized rubber material was measured using a laser diffraction particle size distribution measuring device "Mastersizer 3000" manufactured by Malvern Panalytical and a dispersion unit (Hydro MV), with the refractive index of the sample to be measured set to 1.525, the absorption coefficient set to 1.000, water used as a dispersant, and the rotation speed of the dispersion unit set to 1500 rpm.

[0053] [Surface Modification of Vulcanized Rubber Material (Powder)] 2 g of a surface modifier (cationic starch: Ace Din HP-100 manufactured by Yamato Chemical Industry Co., Ltd.) was dissolved in 500 ml of water. 0.5 g of vulcanized rubber material powder was added to the resulting solution, and the mixture was stirred with a mixer for 30 seconds to modify the surface of the vulcanized rubber material powder from hydrophobic to hydrophilic.

[0054] [Example 1] According to the formulation shown in Table 1, a powder of vulcanized rubber material (average particle size D50; 91 μm) surface-modified to hydrophilicity using glass fiber, heat-fusible organic fiber, and a surface modifier was placed in the container of a mixer (MV-152SP manufactured by Panasonic Corporation) so that the total weight was 10 g, and 1000 ml of water at pH 3.0 was added and stirred for 40 seconds to form a slurry. An appropriate amount of 0.2 wt% solution of polymer flocculant (Acryprimer GC3000MV: a cationic flocculant manufactured by MT Aquapolymer Co., Ltd.) was added, and the slurry was gently stirred for several seconds. Next, the slurry was placed in a small (250 mm x 200 mm) tapping machine (a homemade paper machine), and 9000 ml of dilution water at pH 3.0 was added, and the slurry was stirred, dispersed, and then dehydrated to form a paper. The wet paper thus produced was placed with several sheets of blotting paper on it, and a dedicated roller was rolled back and forth to absorb the moisture contained in the wet paper into the blotting paper. The wet paper was then dried in a box dryer at 130°C for 60 minutes, and further cured in a dryer at 160°C for 1 minute to obtain the nonwoven fabric for the lead-acid battery of Example 1.

[0055] [Examples 2 to 12] Nonwoven fabrics for lead-acid batteries of Examples 2 to 12 were obtained by the same operation as in Example 1, except that the compounding ratios of the glass fiber, the heat-fusible organic fiber, and the powder of the vulcanized rubber material that had been surface-modified to be hydrophilic using a surface modifier, and the average particle diameter D50 of the powder of the vulcanized rubber material that had been surface-modified to be hydrophilic using a surface modifier were changed according to the formulations shown in Table 1.

[0056] Example 13 A nonwoven fabric for a lead-acid battery of Example 13 was obtained by the same operation as in Example 1, except that glass fiber, heat-fusible organic fiber, inorganic powder (silica powder), and powder of a vulcanized rubber material (average particle diameter D50: 91 μm) that had been surface-modified to be hydrophilic using a surface modifier were used according to the formulation shown in Table 2.

[0057] [Examples 14 to 27] Nonwoven fabrics for lead-acid batteries of Examples 14 to 27 were obtained by the same operation as in Example 13, except that the compounding ratios of the glass fiber, the heat-fusible organic fiber, the inorganic powder (silica powder), and the powder of the vulcanized rubber material that had been surface-modified to be hydrophilic using a surface modifier, and the average particle diameter D50 of the powder of the vulcanized rubber material that had been surface-modified to be hydrophilic using a surface modifier, were changed according to the formulations shown in Table 2.

[0058] [Comparative Example 1] According to the formulation shown in Table 3, only the glass fiber was placed in the container of a mixer (MV-152SP manufactured by Panasonic Corporation) so that the total weight was 10 g, and 1000 ml of water at pH 3.0 was added and stirred for 40 seconds to form a slurry. Next, the slurry was placed in a small (250 mm x 200 mm) Tappy (a homemade paper machine), and 9000 ml of diluted water at pH 3.0 was added. The slurry was stirred and dispersed, and then dehydrated to form a paper. The formed wet paper was placed on several sheets of blotting paper and rolled back and forth over a dedicated roller to absorb the moisture contained in the wet paper into the blotting paper. The paper was then dried for 60 minutes in a box dryer at 130 ° C., and further cured for 1 minute in a dryer at 160 ° C. to obtain a nonwoven fabric for a lead-acid battery of Comparative Example 1.

[0059] [Comparative Examples 2 to 5] According to the formulations shown in Table 3, glass fiber and heat-fusible organic fiber were placed in the container of a mixer (MV-152SP manufactured by Panasonic Corporation) so that the total weight was 10 g, and 1000 ml of water at pH 3.0 was added and stirred for 40 seconds to form a slurry. Next, the slurry was placed in a small (250 mm x 200 mm) Tappy (a homemade paper machine), and 9000 ml of diluted water at pH 3.0 was added. The slurry was stirred and dispersed, and then dehydrated to form a paper sheet. The formed wet paper was placed on several sheets of blotting paper and rolled back and forth over a dedicated roller to absorb the moisture contained in the wet paper into the blotting paper. The wet paper was then dried for 60 minutes in a box dryer at 130 ° C. and further cured for 1 minute in a dryer at 160 ° C. to obtain nonwoven fabrics for lead-acid batteries in Comparative Examples 2 to 5.

[0060] [Comparative Examples 6 to 8] According to the formulations shown in Table 3, glass fiber, heat-fusible organic fiber, and inorganic powder (silica powder) were placed in the container of a mixer (MV-152SP manufactured by Panasonic Corporation) so that the total weight was 10 g, and 1000 ml of water at pH 3.0 was added and stirred for 40 seconds to form a slurry. An appropriate amount of 0.2 wt% solution of polymer flocculant (Acryprimer GC3000MV: a cationic flocculant manufactured by MT Aquapolymer Co., Ltd.) was added, and the slurry was gently stirred for several seconds. Next, the slurry was placed in a small (250 mm x 200 mm) tapping machine (a homemade paper machine), and 9000 ml of dilution water at pH 3.0 was added, and the slurry was stirred, dispersed, and then dehydrated to form a paper. The wet paper thus produced was placed with several sheets of blotting paper on it, and a dedicated roller was rolled back and forth to absorb the moisture contained in the wet paper into the blotting paper. The wet paper was then dried in a box dryer at 130°C for 60 minutes, and further cured in a dryer at 160°C for 1 minute to obtain nonwoven fabrics for lead-acid batteries of Comparative Examples 6 to 8.

[0061] [Test and Evaluation Methods] The above Examples and Comparative Examples were evaluated under the following conditions, and the results are summarized in Tables 1 to 3. (1) Basis weight (g / m ２ ) The nonwoven fabric for lead-acid batteries prepared was cut into a size of 250 mm x 200 mm to prepare a test piece. The weight (g) of the test piece was measured using a balance capable of measuring to two decimal places (0.01 g), and the measured value was multiplied by 20 and rounded to an integer. (2) Thickness (mm) when pressurized to 20 kPa The nonwoven fabric for lead-acid batteries prepared was cut into a size of 250 mm x 200 mm to prepare a test piece. The thickness (mm) was measured at any five points of the test piece using a dedicated thickness meter at 20 kPa, and the average value was rounded to two decimal places and presented. (3) Density (g / cm ３ Density (g / cm) was calculated using the following formula, rounded to the nearest three decimal places, and expressed as a percentage. ３ )=[Basic weight (g / m ２) )] ÷ [Thickness (mm) when pressurized to 20 kPa] ÷ 1000 (4) Tensile Strength (N / 25 mm) The prepared nonwoven fabric for lead-acid batteries was cut to a size of 25 mm wide x 160 mm long to prepare a test specimen. Using a tensile tester, the test specimen was clamped so that the chuck spacing was 100 mm and pulled at a rate of 25 mm / min. The strength at break was measured and expressed as the tensile strength (N / 25 mm), rounded to the nearest tenth. (5) Maximum Pore Diameter (μm) The maximum pore diameter (μm) was measured by the bubble point method and rounded to the nearest tenth. (6) Thickness Change Rate (%) (10 → 100) When Pressurized The prepared nonwoven fabric for lead-acid batteries was cut to a size of 100 mm x 100 mm to prepare a test specimen. Ten test pieces were stacked and set in a horizontal compression tester, and pressure was applied. First, the thickness of the test piece at a pressure of 10 kPa (initial thickness at a pressure of 10 kPa, mm) was measured, and then pressure was applied up to 100 kPa. During this time, the thickness (mm) of the test piece was measured every time the applied pressure increased by 10 kPa. This was calculated using the following formula and rounded to an integer to obtain the thickness change rate (%) under pressure (10 → 100). Thickness change rate (%) under pressure (10 → 100) = [thickness (mm) under pressure of 100 kPa] ÷ [initial thickness (mm) under pressure of 10 kPa] × 100 (7) Thickness change rate (%) under pressure (100 → 10) After measuring the thickness change rate (%) under pressure (10 → 100), the state in which a pressure of 100 kPa was applied was maintained for 3 minutes. Thereafter, the applied pressure was gradually released until the applied pressure reached 10 kPa, and the thickness of the test piece (thickness at 10 kPa pressure after release, mm) was measured. During this time, the thickness (mm) of the test piece was measured every time the applied pressure decreased by 10 kPa. This was calculated using the following formula and rounded to an integer to obtain the thickness change rate (%) upon pressure application (100 → 10). Thickness change rate (%) upon pressure application (100 → 10) = [thickness (mm) at 10 kPa pressure after release] ÷ [thickness (mm) at 100 kPa pressure] × 100

[0062] (8) Shrinkage Effect (%) In the present invention, the shrinkage effect (%) was used as an index to evaluate the ability to conform to the expansion of the electrode plate. The shrinkage effect (%) was calculated using the following formula: Shrinkage Effect (%) = [Thickness Change Rate (%) When Pressurized (10 → 100) in the Example] - [Thickness Change Rate (%) When Pressurized (10 → 100) in the Comparative Example]. The larger the negative (-) value of the shrinkage effect, the better the conformability (cushioning). On the other hand, a positive (+) value for the shrinkage effect indicates a smaller change in thickness when pressurized compared to the nonwoven fabric for lead-acid batteries in the comparative example, indicating that the nonwoven fabric is harder in the thickness direction and less susceptible to crushing. The comparative example used to compare the nonwoven fabrics for lead-acid batteries in Examples 1 to 12 was Comparative Example 4, which is a nonwoven fabric that does not contain vulcanized rubber particles and has been surface-modified to be hydrophilic using a surface modifier, and has a composition of glass fiber and heat-fusible organic fiber similar to that in Examples 1 to 12. The comparative example for comparison with the nonwoven fabrics for lead-acid batteries of Examples 13 to 15 was Comparative Example 6, which was a nonwoven fabric that did not contain vulcanized rubber particles and was surface-modified to be hydrophilic using a surface modifier, and had a blend of glass fiber, heat-fusible organic fiber, and inorganic powder (silica powder) similar to that of Examples 13 to 15. The comparative example for comparison with the nonwoven fabrics for lead-acid batteries of Examples 16 to 25 was Comparative Example 7, which was a nonwoven fabric that did not contain vulcanized rubber particles and was surface-modified to be hydrophilic using a surface modifier, and had a blend of glass fiber, heat-fusible organic fiber, and inorganic powder (silica powder) similar to that of Examples 16 to 25. The comparative example for comparison with the nonwoven fabrics for lead-acid batteries of Examples 26 to 27 was Comparative Example 8, which was a nonwoven fabric that did not contain vulcanized rubber particles and was surface-modified to be hydrophilic using a surface modifier, and had a blend of glass fiber, heat-fusible organic fiber, and inorganic powder (silica powder) similar to that of Examples 26 to 27. The shrinkage effect (%) of the nonwoven fabrics for lead acid batteries of Comparative Examples 2 to 8 was evaluated by comparing it with Comparative Example 1, which was a nonwoven fabric made only of glass fibers.

[0063] (9) Restoration Effect (%) In the present invention, restoration effect (%) was used as an index to evaluate the ability to follow the shrinkage of the electrode plate. The shrinkage effect (%) was calculated using the following formula: Restoration Effect (%) = [Thickness Change Rate (%) when Pressurized (100 → 10) in the Example] - [Thickness Change Rate (%) when Pressurized (100 → 10) in the Comparative Example]. A larger positive (+) value for restoration effect indicates better followability (cushioning). On the other hand, a negative (-) value for restoration effect indicates a smaller change in thickness due to a decrease in pressure than the nonwoven fabric for lead-acid batteries in the comparative example, indicating that the nonwoven fabric is less likely to return to its original shape in the thickness direction (low cushioning). The comparative example used to compare the nonwoven fabrics for lead-acid batteries in Examples 1 to 12 was Comparative Example 4, which is a nonwoven fabric that does not contain vulcanized rubber particles and has been surface-modified to be hydrophilic using a surface modifier, and has a composition of glass fiber and heat-fusible organic fiber similar to that in Examples 1 to 12. The comparative example for comparison with the nonwoven fabrics for lead-acid batteries of Examples 13 to 15 was Comparative Example 6, which was a nonwoven fabric that did not contain vulcanized rubber particles and was surface-modified to be hydrophilic using a surface modifier, and had a blend of glass fiber, heat-fusible organic fiber, and inorganic powder (silica powder) similar to that of Examples 13 to 15. The comparative example for comparison with the nonwoven fabrics for lead-acid batteries of Examples 16 to 25 was Comparative Example 7, which was a nonwoven fabric that did not contain vulcanized rubber particles and was surface-modified to be hydrophilic using a surface modifier, and had a blend of glass fiber, heat-fusible organic fiber, and inorganic powder (silica powder) similar to that of Examples 16 to 25. The comparative example for comparison with the nonwoven fabrics for lead-acid batteries of Examples 26 to 27 was Comparative Example 8, which was a nonwoven fabric that did not contain vulcanized rubber particles and was surface-modified to be hydrophilic using a surface modifier, and had a blend of glass fiber, heat-fusible organic fiber, and inorganic powder (silica powder) similar to that of Examples 26 to 27. The shrinkage effect (%) of the nonwoven fabrics for lead acid batteries of Comparative Examples 2 to 8 was evaluated by comparing it with Comparative Example 1, which was a nonwoven fabric made only of glass fibers.

[0064] (10) Overall Effect (%) In the present invention, the overall effect (%) was used as an index for comprehensively evaluating the ability to follow the expansion and contraction of the electrode plates. The overall effect (%) was calculated using the following formula: Overall Effect (%) = Restoration Effect (%) - Contraction Effect (%). A larger negative (-) value for the contraction effect indicates a greater effect on the compliance. On the other hand, a larger positive (+) value for the restoration effect indicates a greater effect on the compliance. Therefore, by using a calculation formula that subtracts the contraction effect value from the restoration effect value, an index for comprehensively evaluating the ability to follow the expansion and contraction of the electrode plates is obtained, which combines the contraction effect, which is an index for evaluating the ability to follow the expansion and contraction of the electrode plates, and the restoration effect, which is an index for evaluating the ability to follow the contraction of the electrode plates. In the present invention, a contraction effect of -5% or less or a restoration effect of 5% or more can be evaluated as having an effect on the ability to follow the expansion and contraction of the electrode plates, and is therefore preferable. A contraction effect of -5% or less and a restoration effect of 5% or more is more preferable because it can be evaluated as a higher effect related to the ability to follow the expansion and contraction of the electrode plate. A total effect of 15% or more is even more preferable because it can be evaluated as a further higher effect related to the ability to follow the expansion and contraction of the electrode plate.

[0065] The evaluation results of Examples 1 to 27 and Comparative Examples 1 to 8 are summarized in Tables 1 to 3.

[0066]

[0067]

[0068]

[0069] The results in Tables 1 to 3 reveal the following: Examples 1 to 12 are nonwoven fabrics for lead-acid batteries composed of glass fibers with a weight-average fiber diameter of 4.0 μm or less, heat-fusible organic fibers, and a powder of vulcanized rubber material whose surface has been hydrophilically modified using a surface modifier. The nonwoven fabrics for lead-acid batteries in Examples 1 to 12 were prepared by varying the blending amount of the powder of vulcanized rubber material whose surface has been hydrophilically modified using a surface modifier within a range of 4.5 wt % to 63.0 wt %, and the effects related to the ability to follow the expansion and contraction of the electrode plates were good, with a contraction effect of -5% or less, a restoration effect of 5% or more, and an overall effect of 15% or more. The nonwoven fabrics for lead-acid batteries in Examples 3-4 and 7-8 had the same blend amount (27.0 wt%) of powder of vulcanized rubber material that had been surface-modified to be hydrophilic using a surface modifier, and the average particle diameter D50 was varied within the range of 58 μm to 466 μm. However, with regard to the effect of compliance with expansion and contraction of the electrode plates, the contraction effect was -5% or less, the restoration effect was 5% or more, and the overall effect was 15% or more, so no significant difference was observed. In the nonwoven fabrics for lead-acid batteries of Examples 9 to 12, the amount of powder of vulcanized rubber material that has been surface-modified to be hydrophilic using a surface modifier was equal to or greater than the amount of glass fiber with a weight average fiber diameter of 4.0 μm or less, and the amount of heat-fusible organic fiber was varied in the range of 10 wt% to 30 wt%, but the effects related to the ability to follow the expansion and contraction of the electrode plate were such that the shrinkage effect was -5% or less, the restoration effect was 5% or more, and the overall effect was 15% or more, so no significant differences were observed. The powder of vulcanized rubber material that has been surface-modified to be hydrophilic using a surface modifier has a large average particle diameter D50 of 10 μm or more, and because the surface is modified to be hydrophilic, it is uniformly dispersed in the nonwoven fabric for lead-acid batteries of the present invention. Therefore, the powder of vulcanized rubber material that has been surface-modified to be hydrophilic using the surface modifier plays the role of a spacer, and at the same time, the powder of vulcanized rubber material that has been surface-modified to be hydrophilic using the surface modifier itself exhibits its own rubber elasticity, which provides high cushioning properties in the contracted (compressed) state of the nonwoven fabric for lead-acid batteries when the plates expand, and in the restored state of the nonwoven fabric for lead-acid batteries when the plates contract, and as a result, it is thought that the ability to follow the expansion and contraction of the plates is greatly improved.

[0070] Examples 13 to 27 are nonwoven fabrics for lead-acid batteries composed of glass fibers with a weight-average fiber diameter of 4.0 μm or less, heat-fusible organic fibers, a powder of vulcanized rubber material whose surface has been hydrophilically modified using a surface modifier, and an inorganic powder (silica powder). The nonwoven fabrics for lead-acid batteries in Examples 13 to 15 had a 50:50 blend ratio of the powder of vulcanized rubber material whose surface has been hydrophilically modified using a surface modifier to the inorganic powder (silica powder). The blending amount of the inorganic powder (silica powder) was varied between 10.0 wt% and 14.3 wt%, and the blending amount of the heat-fusible organic fibers was varied between 5.0 wt% and 20.0 wt%. However, the effects of the nonwoven fabrics on the ability to follow the expansion and contraction of the electrode plates were not significantly different, with a shrinkage effect of -5% or less, a restoration effect of 5% or more, and a total effect of 15% or more.

[0071] In the nonwoven fabrics for lead-acid batteries of Examples 16 to 25, the blending ratio of the powder of vulcanized rubber material that has been surface-modified to be hydrophilic using a surface modifier to the inorganic powder (silica powder) was varied in the range of 10:90 to 75:25, the blending amount of the inorganic powder (silica powder) was varied in the range of 11.3 wt% to 40.5 wt%, the average particle diameter D50 of the powder of vulcanized rubber material that has been surface-modified to be hydrophilic using a surface modifier was varied in the range of 58 μm to 466 μm, and the blending amount of the heat-fusible organic fiber was varied in the range of 5.0 wt% to 30.0 wt%, and the effect related to the followability to the expansion and contraction of the electrode plate was good, with a shrinkage effect of -5% or less, a restoration effect of 5% or more, and an overall effect of 15% or more.

[0072] The nonwoven fabrics for lead-acid batteries in Examples 26 and 27 had a 50:50 blend ratio of vulcanized rubber powder that had been surface-modified to be hydrophilic using a surface modifier and inorganic powder (silica powder), with the blending amount of inorganic powder (silica powder) varying within the range of 31.5 wt% to 33.3 wt%, and the blending amount of heat-fusible organic fiber varying within the range of 5.0 wt% to 10.0 wt%. The effects of the fabrics on their ability to follow the expansion and contraction of the electrode plates were good, with a shrinkage effect of -5% or less, a restoration effect of 5% or more, and an overall effect of 15% or more.

[0073] Generally, when silica powder is blended, the silica powder aggregates with itself due to the effect of the flocculant, forming large clumps that are trapped between glass fibers or organic fibers to form a nonwoven fabric. As a result, the resulting nonwoven fabric has poor cushioning and is hard. The shrinkage, restoration, and overall effects of the nonwoven fabrics for lead-acid batteries of Comparative Examples 6 to 8 are lower than those of the nonwoven fabrics for lead-acid batteries of Comparative Examples 2 to 5, which do not contain silica powder. This suggests that the ability to follow the expansion and contraction of the electrode plates is reduced. On the other hand, when silica powder is used in combination with a powder of vulcanized rubber material that has been hydrophilically surface-modified using a surface modifier, the particle size of the powder of vulcanized rubber material that has been hydrophilically surface-modified using a surface modifier is larger than the particle size of the silica powder. Therefore, during the aggregation of the powders by the flocculant, the silica powder is supported on the surface of the powder of vulcanized rubber material that has been hydrophilically surface-modified using a surface modifier with a larger particle size, which is thought to suppress the hardening effect of the nonwoven fabric. Therefore, the rubber elasticity of the powder of vulcanized rubber material whose surface has been modified to be hydrophilic using a surface modifier is not impaired, and as a result, it is believed that the effect of being able to follow the expansion and contraction of the electrode plate has been maintained in a good state.

[0074] The nonwoven fabric for lead-acid batteries of the present invention can suppress the deterioration of the plate conformity of the pasting paper and separator located between the plates due to expansion and contraction of the plates caused by charging and discharging the lead-acid battery. Furthermore, by using a surface modifier that generates little foaming during stirring, it is possible to produce good pasting paper and separators that are free of pinholes. Furthermore, by including a powder of a vulcanized rubber material in the nonwoven fabric, it is possible to suppress self-discharge caused by antimony ions, thereby improving the productivity of lead-acid batteries.

Claims

1. A nonwoven fabric for lead-acid batteries, comprising at least one of glass fibers having a weight-average fiber diameter of 4.0 μm or less, long glass fibers having a weight-average fiber diameter of more than 4.0 μm, natural fibers, acid-resistant organic fibers, and heat-fusible organic fibers, and further comprising a cushioning material whose surface has been modified to be hydrophilic using a surface modifier, wherein the nonwoven fabric is free of pinholes.

2. The nonwoven fabric for a lead-acid battery according to claim 1, wherein the cushioning material is a powder of a vulcanized rubber material.

3. The nonwoven fabric for a lead-acid battery according to claim 2, wherein the content of the vulcanized rubber powder is 3 wt % or more and 65 wt % or less.

4. The nonwoven fabric for a lead-acid battery according to claim 2, wherein the average particle diameter D50 of the vulcanized rubber material powder is 10 μm or more and 1000 μm or less.

5. The nonwoven fabric for a lead-acid battery according to claim 2, wherein the average particle diameter D50 of the powder of the vulcanized rubber material is 50 μm or more and 500 μm or less.

6. The nonwoven fabric for a lead-acid battery according to claim 2, wherein the vulcanized rubber powder is made of an acid-resistant rubber material, and is at least one selected from the group consisting of natural rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile rubber, butyl rubber, and ethylene-propylene rubber.

7. The nonwoven fabric for a lead-acid battery according to claim 2, wherein the vulcanized rubber powder is a crushed product of tires and / or scrap tires.

8. The nonwoven fabric for a lead-acid battery according to claim 2, wherein inorganic powder is further used as a surface carrier for the vulcanized rubber material powder.

9. The nonwoven fabric for a lead-acid battery according to claim 8, wherein the inorganic powder is one or more acid-resistant materials selected from the group consisting of silica powder, silica sol, alumina sol, aluminum oxide powder, diatomaceous earth, and titanium oxide powder.

10. The nonwoven fabric for a lead-acid battery according to claim 8, wherein the blending ratio of the inorganic powder to the powder of the vulcanized rubber material is 90 wt % or less.

11. The nonwoven fabric for a lead-acid battery according to claim 8, characterized in that the blending ratio of the inorganic powder to the powder of the vulcanized rubber material is 75 wt % or less.

12. A method for producing a nonwoven fabric for a lead-acid battery, which is produced by mixing and stirring at least one of glass fibers with a weight average fiber diameter of 4.0 μm or less, long glass fibers with a weight average fiber diameter of more than 4.0 μm, natural fibers, acid-resistant organic fibers, and heat-fusible organic fibers, and a material whose surface has been modified to be hydrophilic using a surface modifier, wherein the surface modifier is a surface modifier that does not generate bubbles when mixed and stirred, and does not trap bubbles when the material is made into a sheet, and wherein no pinholes are produced in the nonwoven fabric.

13. A method for producing a nonwoven fabric for a lead-acid battery as set forth in claim 12, characterized in that the hydrophilically surface-modified material is a powder of a vulcanized rubber material having cushioning properties, which has been surface-modified to be hydrophilic using the surface modifier.

14. The method for producing a nonwoven fabric for a lead-acid battery according to claim 12, wherein the surface modifier is one or more selected from the group consisting of a silicone oil compound antifoaming agent, a silane coupling agent, and cationic starch.

15. The method for producing a nonwoven fabric for a lead-acid battery according to claim 12, characterized in that a polymer flocculant is further added after the mixing and stirring, and then the papermaking is carried out.

16. A separator for a lead-acid battery or pasting paper for a lead-acid battery, characterized in that it is made of the nonwoven fabric for a lead-acid battery according to any one of claims 1 to 11.

17. A lead-acid battery, characterized in that it uses a separator or pasting paper for a lead-acid battery made of the nonwoven fabric for a lead-acid battery according to any one of claims 1 to 11.

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