Separator for sealed lead storage battery

Abstract

The purpose of the present invention is to provide an optimal separator in which a gas absorption reaction point, which is one of the basic functions of a sealed lead-acid battery, cannot be sufficiently controlled in a conventional separator in which fiber distribution and fiber orientation are prescribed, and which is characterized in that: the gas permeability of the separator itself is controlled; as a result, the amount of adjustment of the electrolyte concentration (specific gravity) after tank formation of a sealed lead storage battery can be reduced, and abnormal heat generation of the battery in an actual battery use environment can be suppressed. The gas transmission rate in a wet state of the separator is 15 mm / min or less and / or the gas transmission rate in a wet state of the separator is 70% or less.

Description

Technical Field

[0001] The present invention relates to a separator for a sealed lead-acid battery. More specifically, it relates to a separator suitable for adjusting the specific gravity of the electrolyte during the tank formation of a sealed lead-acid battery. Background Art

[0002] Conventionally, a separator for a sealed lead-acid battery made of a wet-laid sheet is manufactured using an inclined or cylinder-type paper machine that performs forced dehydration under reduced pressure. When manufacturing a wet-laid sheet mainly composed of glass fibers using an inclined or cylinder-type paper machine, while dehydrating a papermaking raw material liquid obtained by dispersing glass fibers or the like in water from the lower surface side of a forming wire, the forming wire is moved, and thus glass fibers are accumulated on the upper surface of the forming wire to form a fiber layer. Therefore, relatively large fibers are concentrated on the back side (the side in contact with the forming wire) of the sheet, while relatively fine fibers are concentrated on the front side (the side opposite to the side in contact with the forming wire), and there is a problem that the fiber distribution in the thickness direction of the sheet becomes uneven. In addition, since relatively fine fibers are concentrated on the surface side of the sheet, there is also a problem that the surface smoothness of the sheet is very poor. In addition, on the glass fiber accumulation surface, that is, the surface on which the glass fiber layer is formed, while the forming wire is moved and the fiber is picked up, when one end of the fiber touches the forming wire surface, the fiber immediately becomes a shape stretched in the moving direction of the forming wire. Therefore, there is also a problem that the fibers are oriented more in the moving direction of the forming wire, that is, the length direction of the sheet, and the fiber orientation in the longitudinal and transverse directions of the sheet becomes uneven (a state where the fiber orientation has a direction). In particular, this problem becomes more significant when the papermaking speed is increased, so it also becomes one of the main reasons for the difficulty in increasing the papermaking speed.

[0003] Such problems can become major problems especially when the above-mentioned separator is used as a separator for a sealed lead-acid battery. First, if the fiber distribution in the thickness direction of the sheet is uneven, that is, a gradient is formed in the fiber distribution, the same tendency also appears in the density distribution in the thickness direction, and a difference is generated in the liquid absorption speed of the electrolyte on the front and back surfaces of the sheet. Therefore, the mobility of the electrolyte during charge and discharge becomes uneven, which is a cause of deviation in battery performance. In addition, if the surface smoothness of the sheet is poor, the adhesion to the electrode plate becomes poor, and the oxygen absorption reaction cannot be performed well, which is a cause of deterioration of battery performance. In addition, if the fiber orientation in the longitudinal and transverse directions of the sheet is uneven (a state where the fiber orientation has a direction), a difference is generated in the liquid absorption speed of the electrolyte in the longitudinal and transverse directions of the sheet. In addition, if the papermaking speed is not increased significantly, it is difficult to improve productivity, that is, it is difficult to reduce the manufacturing cost.

[0004] On the other hand, in the past battery manufacturing, plates that had completed the formation process were used for battery assembly. However, in recent years, it has become mainstream to assemble a battery using unformed plates before the formation process, inject electrolyte after assembling the battery, and perform power-on to form the unformed plates, which is called tank formation.

[0005] The mechanism of tank formation is the same as that of battery charging, but it requires more power than ordinary battery charging, so a large amount of oxygen is generated from the positive electrode inside the battery. The oxygen generated here is absorbed by the negative electrode to form water, but the unabsorbed oxygen is released outside the battery system. Therefore, corresponding to the amount of oxygen released outside the system, water is not generated, so the reduction of the electrolyte occurs.

[0006] Therefore, in tank formation, it is expected that there will be a certain degree of reduction of the electrolyte in such a way that the sulfuric acid concentration of the electrolyte after tank formation falls within a set range. However, on the other hand, if the gas absorption reaction during tank formation is overly promoted, the electrolyte concentration (specific gravity) after the end of tank formation is lower than the target concentration (specific gravity), which results in a decrease in battery capacity. Therefore, the gas absorption reaction occurs more frequently, and after the end of tank formation, it is necessary to adjust the electrolyte concentration (specific gravity), which requires extra power consumption and results in a higher energy cost, making it disadvantageous.

[0007] Furthermore, in the actual battery usage environment, the gas absorption reaction during charging is also an exothermic reaction. Therefore, if the gas absorption reaction occurs frequently, the temperature inside the battery rises. And during constant voltage charging, the current value also rises, which further causes the temperature inside the battery to rise and becomes the main cause of thermal runaway of the battery.

[0008] There is disclosed a separator for a sealed lead-acid battery mainly made of glass fiber, in which the fiber distribution of the separator is made uniform in the longitudinal and transverse directions (on the plane), so that the gas absorption reaction becomes uniform in the longitudinal and transverse directions of the electrode plate surface of the battery (for example, refer to Patent Document 1).

[0009] In addition, there is disclosed a separator for a sealed lead-acid battery mainly made of glass fiber, in which the two-dimensional fiber orientation on the plane of the separator is represented by the tensile strength ratio in the longitudinal and transverse directions (on the plane) of the separator, and further the three-dimensional fiber orientation of the separator is represented by the pressing force during electrolyte injection, so that the fiber orientation of the separator is numerically represented three-dimensionally, the planar fiber orientation is made uniform in the longitudinal and transverse directions (on the plane), and further the pressing force during electrolyte injection is increased, so that the fibers are also more oriented in the thickness direction (vertical direction) of the separator (for example, refer to Patent Document 2).

[0010] However, in these patent documents, although it is disclosed that the gas permeation of the separator is made uniform to make the gas absorption reaction uniform on the electrode surface, and the oxygen generated in the positive electrode is quickly moved to the negative electrode to promote the gas absorption reaction, the control of the gas permeability itself is not shown at all.

[0011] Prior art documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent No. 4864457 Gazette

[0014] Patent Document 2: Japanese Patent No. 6606621 Gazette Summary of the invention

[0015] The present invention has been completed by focusing on the fact that the gas absorption reaction, which is one of the basic functions of a sealed lead-acid battery, cannot be sufficiently controlled in a separator having a conventionally specified fiber distribution and fiber orientation. The object is to provide an optimal separator. In order to control the gas permeability of the separator itself, first, an evaluation method for grasping the gas permeation performance in the wet state of the separator (the state where the space inside the separator is filled with water) is established. Furthermore, by using the established evaluation method, the electrolyte concentration (specific gravity) after the battery tank formation of the sealed lead-acid battery can be easily adjusted, and abnormal heating of the battery in the actual battery usage environment can be suppressed.

[0016] As a result of dedicated research to solve the above problems, the separator for a sealed lead-acid battery of the present invention is a separator for a sealed lead-acid battery having the following characteristics.

[0017] (1) A separator for a sealed lead-acid battery, characterized in that it is a non-woven fabric mainly composed of micro glass fibers, and the gas permeation speed in the wet state (Wet state) is 15 mm / min or less and / or the gas permeation rate is 70% or less.

[0018] (2) In the separator for a sealed lead-acid battery described in (1) above, it is characterized in that it is a non-woven fabric mainly composed of micro glass fibers, and the gas permeation speed in the wet state is 15 mm / min or less and the gas permeation rate is 70% or less.

[0019] (3) In the separator for a sealed lead-acid battery described in (1) or (2) above, it is characterized in that the number average fiber diameter of the micro glass fibers is 4.5 μm or less, and the separator for a sealed lead-acid battery is a mixture of two or more kinds of the micro glass fibers having different number average fiber diameters.

[0020] (4) In the separator for a sealed lead-acid battery according to any one of (1) to (3) above, it is characterized in that the water filtration resistance (SR: Schopper-Riegler) value of the separator is 20 or more.

[0021] (5) In the separator for a sealed lead-acid battery according to any one of (1) to (4) above, it is characterized in that the raw material concentration during the papermaking of the separator is 0.30% by weight or less.

[0022] (6) In the separator for a sealed lead-acid battery according to any one of (1) to (5) above, it is characterized in that the raw material flow rate during the papermaking of the separator is 10.0 m / min or more.

[0023] (7) In the separator for a sealed lead-acid battery according to any one of (1) to (6) above, it is characterized in that the blending amount of glass long fibers having a number average fiber diameter of 6 μm or more and a number average fiber length of 3 mm or more is 2% by weight or more.

[0024] (8) In the separator for a sealed lead-acid battery according to any one of (1) to (7) above, it is characterized in that the blending amount of organic fibers having a fineness of 0.5 dtex or more and a number average fiber length of 3 mm or more is 2% by weight or more.

[0025] (9) In the separator for a sealed lead-acid battery according to any one of (1) to (8) above, it is characterized in that the blending amount of inorganic powder is 5% by weight or more.

[0026] (10) In the separator for a sealed lead-acid battery according to any one of (1) to (9) above, it is characterized in that the blending amount of heat-meltable organic fibers is 5% by weight or more.

[0027] (11) A sealed lead-acid battery, characterized in that it uses the separator for a sealed lead-acid battery according to any one of (1) to (9) above.

[0028] As described above, a separator modulated in such a way that the gas permeation rate of the separator in the wet state becomes 15 mm / min or less and / or the gas permeability of the separator in the wet state becomes 70% or less can control (suppress) the gas permeability of the separator, so that it is possible to provide a separator that can easily adjust the electrolyte concentration (specific gravity) after the electrolytic tank formation of a sealed lead-acid battery and can suppress abnormal heating of the battery in the actual battery usage environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram showing an example of a gas supply jig used in a test for grasping gas permeation performance. Detailed implementation mode

[0030] In the present invention, it is necessary to compare and determine a state close to the state of use in an actual sealed lead-acid battery, that is, the gas permeability in a wet state (Wet state) where the separator is immersed in the electrolyte solution.

[0031] Conventionally, as an evaluation method for the gas permeability of a separator, a method is known in which a single separator is immersed in a volatile solvent in a lying state, a thin solvent layer is provided thereon, and then gas (air) is supplied from below the separator and forced to pass through the inside of the separator (for example, the bubble point method known as a method for measuring the maximum pore diameter).

[0032] However, in the actual battery use environment, the separator is arranged longitudinally (in the up-down direction) in alignment with the electrode plate and used in a state of being immersed in the electrolyte solution (sulfuric acid aqueous solution).

[0033] The gas movement in the battery is a phenomenon in which oxygen generated from the positive electrode moves to the negative electrode side in a state where the separator is pressed between the electrode plates. The separator is in a state of being filled with the electrolyte solution (sulfuric acid aqueous solution). Since oxygen is a gas, it cannot easily pass through the inside of the separator and advances along the rising path according to the characteristics of the gas.

[0034] In the evaluation method for grasping the gas permeability of the separator according to the present invention, about 10 separators are put into a polyethylene bag in an overlapping state, then the whole separator is made to contain water, and the separator is set in a press in a longitudinally (up-down direction) arranged manner. And, a test is carried out by supplying nitrogen gas in the lateral direction (the thickness direction of the separator) in a state of applying a pressure of 50 kPa, and the movement state of nitrogen gas in a state simulating the actual battery use environment is evaluated.

[0035] Here, considering the safety during measurement, a test is carried out by using the electrolyte solution (sulfuric acid aqueous solution) instead of water and using oxygen instead of nitrogen gas.

[0036] In addition, in order to be able to compare the maximum movement distance and time (speed) of nitrogen gas moving in the separator with good reproducibility for a variety of separators, the supply pressure and flow rate of nitrogen gas are set to 0.1 MPa and 0.025 L / min, respectively.

[0037] Specifically, the test method for grasping the gas permeability of the separator according to the present invention is carried out as follows, for example.

[0038] 1) Ten separators obtained by cutting the separator into 100×100 mm are overlapped in such a way that the flow direction (longitudinal direction: MD direction) of the separator is aligned to form a test piece.

[0039] 2) Measure the thickness when a pressure of 20 kPa (200 N) is applied to the test piece.

[0040] 3) Place the test piece and the gas supply fixture (refer to Figure 1 ) into a polyethylene bag, arrange the test piece and the gas supply fixture longitudinally (up and down direction) like an actual lead storage battery, and clamp them between the compression plates of a horizontal compressor.

[0041] The gas supply fixture is a box-shaped rigid rubber gas supply tool with dimensions of 100×105×16 mm. It is formed by integrating three rubber sheets (A side, middle side, B side) (NBR, hardness: 70°) with an adhesive, and a syringe for gas supply (pneumatic dust blower nozzle manufactured by Kinki Seisakusho, nozzle length: 100 mm, caliber: 1 mmφ, outer diameter: 1.5 mm) is inserted at the upper part of the middle side.

[0042] 4) Set the pressure applied to the specimen piece to 15 - 25 N, and using a funnel in the polyethylene bag, add water little by little until about 90% of the specimen piece is immersed, and let it stand for 30 minutes.

[0043] 5) Press the test piece to 50 kPa (500 N) and measure the thickness of the test piece.

[0044] 6) Let nitrogen gas with a pressure adjusted to 0.1 MPa and a gas flow rate adjusted to 0.025 L / min flow from the gas supply fixture to the test piece. Supply nitrogen gas from near the center of the gas supply fixture to near the center of the test piece, flow it horizontally (in the thickness direction of the separator), and finally, advance along the path rising upward to the test piece.

[0045] 7) Use a magnifying glass, etc., and carefully observe the bubbles (gas) leaking from the upper part of the test piece.

[0046] 8) After supplying the gas, observe the position (which sheet from the gas supply fixture) where the bubbles (gas) leak from the place farthest from the gas supply fixture in the test piece (which sheet of the separator from the gas supply fixture), and measure the time (seconds) until the leakage occurs from this position.

[0047] Here, in order to obtain data with good reproducibility, it is preferable to arrange the test piece so that the flow direction of the separator (longitudinal direction: MD direction) is in the longitudinal direction (up and down direction) and measure.

[0048] In addition, the number of separator sheets overlapping as the test piece can be increased or decreased considering the thickness of the separator. In this case, for the purpose of making the same comparison and judgment for various separators, it is best to convert it to 10 sheets for evaluation.

[0049] In addition, it is preferable to consider data fluctuations, repeat the test multiple times (e.g., 3 times), and use the average value for evaluation.

[0050] The gas permeation rate (mm / min) for grasping the gas permeation performance of the separator according to the present invention is obtained as described below, for example.

[0051] 1) Calculate the thickness of each separator based on the thickness of the test piece when pressurized to 50 kPa.

[0052] 2) Calculate the bubble (gas) generation distance (mm) based on the position where the bubble (gas) leaks out from the farthest point from the gas supply fixture in the test piece (which separator from the gas supply fixture).

[0053] For example, when the thickness of each separator at 50 kPa is a mm and the bubble (gas) leaks out from the b-th separator, it becomes a × b mm.

[0054] 3) Calculate the gas permeation rate (mm / min) based on the bubble (gas) generation distance (mm) and the time until leakage (seconds).

[0055] The gas permeation rate (mm / min) is an index for observing the speed at which oxygen generated in the positive electrode can move inside the separator under certain conditions. The larger the value, the easier it is for the oxygen generated in the positive electrode to reach the negative electrode.

[0056] In the separator for a sealed lead-acid battery of the present invention, the gas permeation rate (mm / min) is preferably 15 mm / min or less, more preferably 14 mm / min or less, and further preferably 13 mm / min or less.

[0057] Regarding the gas permeability (%) for grasping the gas permeation performance of the separator according to the present invention, if the thickness of the separator when pressurized to 20 kPa in the test is converted to 2.5 mm per sheet (25 mm for 10 sheets of separators) for evaluation, reproducible data can be obtained, and considering the reliability of the evaluation, it is preferable. By using the evaluation method for separators with a converted thickness, even for separators with various compositions, results with less data deviation and good reliability can be obtained, and they can be compared and judged uniformly.

[0058] The gas permeability (%) for grasping the gas permeation performance of the separator according to the present invention is obtained as described below.

[0059] 1) Calculate the thickness of the test piece when pressurized to 50 kPa (the thickness of the test piece at 50 kPa after 2.5 mm thickness correction, mm) when the thickness of the separator when pressurized to 20 kPa is set to 2.5 mm per sheet according to the following formula.

[0060] Thickness of the test piece (mm) when pressurized at 50 kPa after 2.5 mm thickness correction = [Thickness of the separator used in the test when pressurized to 20 kPa, converted to the thickness of the test piece at 2.5 mm per sheet, mm] × [Thickness of the test piece (mm) when pressurized to 50 kPa] ÷ [Thickness of the test piece (mm) when pressurized to 20 kPa]

[0061] 2) Calculate the gas permeability (%) according to the following formula.

[0062] Gas permeability (%) = [Bubble (gas) generation distance (mm)] ÷ [Thickness of the test piece (mm) when pressurized at 50 kPa after 2.5 mm thickness correction] × 100

[0063] The gas permeability (%) is an index for observing to what extent the oxygen generated in the positive electrode can move to the negative electrode under certain conditions. The larger the value, the easier it is to move to the negative electrode.

[0064] In the separator for a sealed lead-acid battery of the present invention, the gas permeability (%) is preferably 75% or less, more preferably 70% or less, and further preferably 60% or less.

[0065] Regarding the gas absorption reaction inhibition effect for grasping the gas permeation performance of the separator according to the present invention, it is calculated as the ratio of the measured value of the gas permeability (%) and the measured value of the gas permeation rate (mm / min), and is expressed as a relative value when the ratio of the measured value of the separator of Comparative Example 1 as a conventional product is set to 1.0.

[0066] In the separator for a sealed lead-acid battery of the present invention, the gas absorption reaction inhibition effect is preferably 1.2 or more, more preferably 1.5 or more, and further preferably 1.8 or more.

[0067] The separator for a sealed lead-acid battery of the present invention is wet-laid with micro glass fibers as the main body. In addition to the micro glass fibers, it may also contain glass long fibers, non-melting organic fibers, melting organic fibers, inorganic powders, etc.

[0068] By blending single-filament organic fibers that do not have meltability, the compressive fracture strength (shearing force) of the non-woven fabric can be improved (for example, refer to Japanese Patent No. 4261821), and a better separator can be obtained.

[0069] In addition, a composite effect can also be expected through various combinations with materials that do not have meltability.

[0070] The micro glass fibers used in the separator for the sealed lead-acid battery of the present invention are preferably C glass fibers having acid resistance since they are used in an electrolytic solution (sulfuric acid aqueous solution with a specific gravity of 1.3), but are not limited thereto as long as they are glass fibers having acid resistance.

[0071] Regarding the fiber diameter of the micro glass fibers, although it also varies depending on the combined auxiliary materials, in one of the expected functions of the separator, there is suppression of delamination. From this perspective, the number average fiber diameter is preferably 4.5 μm or less, more preferably 4.0 μm or less. Furthermore, when it is necessary to further improve the suppression of delamination when used in a lead-acid battery of a face idle start-stop (idle Stop and start) system (ISS), the number average fiber diameter is further preferably 3.5 μm or less.

[0072] As the micro glass fibers, from the perspective of the physical strength of the separator, wool-like micro glass fibers are preferred.

[0073] In the separator for the sealed lead-acid battery of the present invention, in order to maintain the absolute strength and electrolyte retention function of the separator, the blending amount of the micro glass fibers is preferably 50% by weight or more.

[0074] In the separator for the sealed lead-acid battery of the present invention, it is also preferable to mix and use separators having different number average fiber diameters of the micro glass fibers. In this case, in such a way that the water filtration resistance (SR: Schopper-Riegler) value of the separator becomes 20 or more, it is preferable to combinatorially use the micro glass fibers having various number average fiber diameters. In addition, the value (average value) obtained by averaging the values of the number average fiber diameters of the micro glass fibers used in combination is preferably within the preferred range of the number average fiber diameter among the micro glass fibers.

[0075] In the separator for the sealed lead-acid battery of the present invention, in order to improve the gas permeability, it is also preferable to blend the glass long fibers. As the glass long fibers, there is no particular limitation as long as they are materials generally used in the separator for the sealed lead-acid battery, but it is preferable to use glass long fibers having a number average fiber diameter of 3 to 20 μm and a number average fiber length of 1 to 25 mm, and more preferably to use glass long fibers having a number average fiber diameter of 6 μm or more and a number average fiber length of 3 mm or more.

[0076] In the separator for the sealed lead-acid battery of the present invention, in order to improve the gas permeability, the glass long fibers are preferably blended in an amount of 2% by weight or more, more preferably 5% by weight or more.

[0077] When the blending amount is less than 2% by weight, the distribution of the fibers during papermaking becomes uneven, and the effect of sufficiently improving the gas permeability cannot be obtained.

[0078] In the separator for a sealed lead-acid battery of the present invention, in order to improve the gas permeability, it is also preferable to blend the non-melting organic fiber. As the non-melting organic fiber, there is no particular limitation as long as it is a material generally used in the separator for a sealed lead-acid battery. However, as the synthetic resin component, a polyester resin is preferable, and a material having a fineness of 0.06 to 4.0 dtex and a number average fiber length of 1 to 25 mm is preferably used, and a long fiber material having a fineness of 0.5 dtex or more and a number average fiber length of 3 mm or more is more preferably used.

[0079] In the separator for a sealed lead-acid battery of the present invention, in order to improve the gas permeability, the non-melting organic fiber is preferably blended in an amount of 2% by weight or more, and more preferably 5% by weight or more.

[0080] When the blending amount is less than 2% by weight, the distribution of the fibers during papermaking becomes uneven, and the effect of sufficiently improving the gas permeability cannot be obtained.

[0081] In the separator for a sealed lead-acid battery of the present invention, in order to maintain the tensile strength (sheet strength), the puncture strength, and the adhesiveness (peel strength) between the separators, it is also preferable to blend the melting organic fiber. As the melting organic fiber, there is no particular limitation as long as it is a material generally used in the separator for a sealed lead-acid battery. However, a material having a core-sheath structure is preferably used. In this case, the core portion may be a polyolefin resin such as polyethylene resin or polypropylene resin, or a resin generally used such as a polyester resin, but a resin having acid resistance is preferable, and a polyester resin is preferable. The sheath portion is preferably a polyolefin resin such as polyethylene resin or polypropylene resin, or a polyester resin, and more preferably a crystalline polyolefin resin, a crystalline or amorphous polyester resin.

[0082] As a measure for improving the tensile strength (sheet strength), in order to increase the number of the melting organic fibers contained in the separator, the fineness of the melting organic fiber is preferably 2.5 dtex or less, more preferably 1.6 dtex or less, and further preferably 1.5 dtex or less.

[0083] Regarding the number average fiber length of the melting organic fiber, 1 to 25 mm is preferably used.

[0084] In the separator for a sealed lead-acid battery of the present invention, in order to improve the mechanical strength, the melting organic fiber is preferably blended in an amount of 5% by weight or more.

[0085] In the separator for a sealed lead-acid battery of the present invention, in order to control the gas permeability, it is also preferable to blend the inorganic powder. By blending the inorganic powder, the powder remains between the micro glass fibers, and due to the filling effect, the average pore diameter of the entire separator is reduced. At the same time, it is considered that by aggregating a part of the powder during paper making, pores larger than the average can be locally formed, and gas is difficult to permeate in the thickness direction of the separator in the wet state, and the gas is not easily leaked outside the separator system.

[0086] As the inorganic powder, there is no particular limitation as long as it is a material generally used in the separator for a sealed lead-acid battery, such as silica with excellent acid resistance and oxidation resistance.

[0087] In the separator for a sealed lead-acid battery of the present invention, in order to control the gas permeability, it is preferable to blend 5% by weight or more of the inorganic powder.

[0088] When the blending amount is less than 5% by weight, the distribution in the separator during papermaking becomes uneven, and the control effect of the gas permeability cannot be obtained sufficiently.

[0089] In addition, in this case, especially when increasing the blending amount, it is also preferable to use a dispersant or the like in combination to improve the dispersibility of the inorganic powder in the papermaking raw material liquid (slurry).

[0090] In the separator for a sealed lead-acid battery of the present invention, in order to improve the assemblability of the lead-acid battery, the tensile strength (sheet strength) of the separator preferably has a mechanical strength of 0.2 N / mm 2 or more, more preferably 0.3 N / mm 2 or more.

[0091] When the tensile strength (sheet strength) is lower than 0.2 N / mm 2 the assembling performance of the lead-acid battery and the basic physical properties during charge and discharge reactions deteriorate, and the battery life decreases.

[0092] In the separator for a sealed lead-acid battery of the present invention, in order to improve the assemblability of the lead-acid battery, the barb strength of the separator preferably has a mechanical strength of 2 N / mm or more, more preferably 4 N / mm or more, and further preferably 6 N / mm or more.

[0093] When the barb strength is lower than 2 N / mm, the assembling performance of the lead-acid battery and the basic physical properties during charge and discharge reactions deteriorate, and the battery life decreases.

[0094] Conventionally, a separator for a sealed lead-acid battery made of a wet-laid sheet material (non-woven fabric) mainly composed of glass fibers has been manufactured using an inclined papermaking machine or the like. Here, in the case of manufacturing a wet-laid sheet material (non-woven fabric) mainly composed of glass fibers using an inclined papermaking machine, while dewatering the papermaking raw material liquid obtained by dispersing glass fibers in water from the lower surface side of the forming wire, the forming wire is moved, so that glass fibers are accumulated on the upper surface of the forming wire to form a glass fiber layer. Therefore, relatively large fibers are concentrated on the back side (the side in contact with the forming wire) of the sheet, while relatively fine fibers are concentrated on the front side (the side opposite to the side in contact with the forming wire). There is a tendency that the fiber distribution in the thickness direction of the sheet becomes uneven. In addition, since relatively fine fibers are concentrated on the surface side of the sheet, there is also a problem that the surface smoothness of the sheet is very poor. In addition, on the glass fiber layer forming surface, which is the stacking surface of glass fibers, while the forming wire is moved and picked up, if one end of a fiber touches the forming wire surface, the fiber immediately becomes a shape stretched in the moving direction of the forming wire. Therefore, there is also a tendency that the fibers are more oriented in the moving direction of the forming wire, that is, the length direction of the sheet, and the fiber orientation in the longitudinal and transverse directions of the sheet becomes uneven (a state where the fiber orientation has directionality).

[0095] If the fiber distribution in the thickness direction of the sheet becomes uneven, that is, a gradient is formed in the fiber distribution, the same tendency also appears in the density distribution in the thickness direction, and a difference is generated in the gas permeability on the front and back surfaces of the sheet. In addition, if the surface smoothness of the sheet is poor, the adhesion to the electrode plate becomes poor, and the oxygen absorption reaction cannot be carried out well. In addition, if the fiber orientation in the longitudinal and transverse directions of the sheet is uneven (a state where the fiber orientation has directionality), a difference is generated in the gas permeability in the longitudinal and transverse directions of the sheet.

[0096] Therefore, in a separator for a sealed lead-acid battery made of a wet-laid sheet material (non-woven fabric) mainly composed of micro glass fibers, the papermaking conditions of the wet-laid sheet material (non-woven fabric) are adjusted so that the fiber distribution is uniform in the longitudinal and transverse directions and the thickness direction of the separator, the fiber orientation is uniform in the longitudinal and transverse directions and the thickness direction of the separator, and the angle of the fibers oriented in the thickness direction is relatively small with respect to the front and back surfaces, preferably 45° or less, which is required to control the gas permeability itself.

[0097] As the papermaking conditions for manufacturing the separator for a sealed lead-acid battery of the present invention, the raw material concentration during papermaking is preferably 0.30% by weight or less.

[0098] In addition, the raw material flow rate (spray) during papermaking is preferably 10 m / min or more.

[0099] When the raw material concentration during papermaking exceeds 0.30% by weight or the raw material flow rate is less than 10 m / min, the dispersion state of the papermaking raw materials (fibers, etc.) in the papermaking raw material liquid (pulp) becomes uneven. Furthermore, in the minute path of feeding the papermaking raw material liquid (pulp) to the forming wire, the papermaking raw materials start to settle, which causes raw material lumps due to the accumulation of papermaking raw materials (fibers, etc.) in the middle of the path. In addition, since the dispersion of the papermaking raw materials (fibers, etc.) is uneven, the fibers are unevenly deposited on the horizontal plane of the forming wire during papermaking, so a uniform fiber distribution cannot be achieved in the longitudinal and transverse directions of the partition plate.

[0100] Regarding the pH during papermaking, there is no particular limitation as long as the papermaking raw materials (fibers, etc.) in the papermaking raw material liquid (pulp) are evenly dispersed. However, from the perspective of dispersibility, it is preferably adjusted to 4 or less. In addition, when it is difficult to lower the pH, it is also preferably used in combination with surfactants, etc., to improve the dispersibility of the papermaking raw materials (fibers, etc.) in the papermaking raw material liquid (pulp).

[0101] The separator for a sealed lead-acid battery of the present invention is wet-laid with micro glass fibers as the main body. In order to control the gas permeation performance, the water filtration resistance (SR: Schopper-Riegler) value of the separator is preferably 20 or more. By forming a structure in which a large amount of micro glass fibers with a fine fiber diameter are blended, the average fine pore diameter of the separator becomes smaller, and the pressure required for gas permeation in the wet state becomes higher, so the gas movement speed (gas permeation speed) becomes slower.

[0102] In the separator for a sealed lead-acid battery of the present invention, it is preferable to blend 2% by weight or more of glass long fibers with a number average fiber diameter of 6 μm or more and a number average fiber length of 3 mm or more and / or organic fibers with a fineness of 0.5 dtex or more and a number average fiber length of 3 mm or more. Long fibers with a number average fiber length of 3 mm or more tend to be oriented in a direction perpendicular to the thickness direction of the separator. Therefore, when gas permeates in the wet state, it is easy to move along the long fibers, so the gas movement speed (gas permeation speed) becomes faster. On the other hand, the gas is easily released to the outside of the separator system, and the gas permeation distance (gas permeation rate) becomes smaller.

[0103] In the separator for a sealed lead-acid battery of the present invention, it is preferable to blend 5% by weight or more of inorganic powder. The inorganic powder is finer than the micro glass fibers, so the inorganic powder enters between the fibers of the micro glass fibers, which has the effect of reducing the fine pore diameter of the separator. Therefore, the pressure required for gas permeation in the wet state becomes higher, and the gas permeation distance (gas permeation rate) becomes smaller.

[0104] Next, an embodiment of the sealed lead-acid battery using the separator for the sealed lead-acid battery of the present invention will be described, but the sealed lead-acid battery of the present invention is not limited to the following embodiments.

[0105] [Electrolyte]

[0106] The electrolyte contains sulfuric acid in an aqueous solution. The electrolyte can be gelled as needed. The electrolyte can contain additives used in the sealed lead-acid battery as needed.

[0107] The specific gravity of the electrolyte in the sealed lead-acid battery after formation and in the fully charged state at 20 °C is, for example, 1.10 g / cm 3 or more and 1.35 g / cm 3 or less.

[0108] [Positive electrode plate]

[0109] The positive electrode plate of the sealed lead-acid battery is a paste type.

[0110] The paste-type positive electrode plate includes a positive electrode current collector and a positive electrode material. The positive electrode material is held by the positive electrode current collector. In the paste-type positive electrode plate, the positive electrode material is the material obtained by removing the positive electrode current collector from the positive electrode plate. The positive electrode current collector can be formed in the same manner as the negative electrode current collector, and can be formed by casting lead or a lead alloy, or processing a lead or lead alloy sheet.

[0111] As the lead alloy used in the positive electrode current collector, from the viewpoints of corrosion resistance and mechanical strength, a Pb-Ca-based alloy or a Pb-Ca-Sn-based alloy is preferred. The positive electrode current collector may also have lead alloy layers with different compositions, and there may be multiple alloy layers.

[0112] The positive electrode material contains a positive electrode active material (lead dioxide or lead sulfate) that exhibits capacitance through a redox reaction. The positive electrode material may also contain other additives as needed.

[0113] Based on the case of the negative electrode plate, a positive electrode paste is filled into the positive electrode current collector, matured, and dried to obtain an unformed paste-type positive electrode plate. Thereafter, the unformed positive electrode plate is formed. The positive electrode paste is prepared by mixing lead powder, additives, water, and sulfuric acid.

[0114] [Negative electrode plate]

[0115] The negative electrode plate of a lead-acid battery is composed of a negative electrode current collector and a negative electrode electrode material. The negative electrode electrode material is the material obtained by removing the negative electrode current collector from the negative electrode plate. The negative electrode current collector can be formed by casting lead (Pb) or a lead alloy, or can be formed by processing a lead or lead alloy sheet. As the processing method, for example, expansion processing and blanking (punching) processing can be cited. When using a negative electrode grid as the negative electrode current collector, it is preferable because it is easy to carry the negative electrode electrode material.

[0116] The lead alloy used in the negative electrode current collector can be any one of Pb-Sb series alloys, Pb-Ca series alloys, and Pb-Ca-Sn series alloys. These leads or lead alloys can further contain at least one selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. as an additive element.

[0117] The negative electrode electrode material contains a negative electrode active material (lead or lead sulfate) that exhibits capacitance through a redox reaction, and can also contain a shrinkage inhibitor, a carbonaceous material such as lignin and carbon black, barium sulfate, etc. According to needs, other additives can also be contained.

[0118] The negative electrode active material in the charged state is spongy lead, and lead powder is usually used to make an unformed negative electrode plate.

[0119] An unformed negative electrode plate is made by filling the negative electrode current collector with a negative electrode paste, maturing it, and drying it. After that, a negative electrode plate can be formed by forming the unformed negative electrode plate. A negative electrode paste can be made by adding water and sulfuric acid to lead powder, an organic shrinkage inhibitor, and various additives as needed and mixing them evenly. In the maturing process, it is preferable to mature the unformed negative electrode plate at a temperature higher than room temperature and high humidity.

[0120] Forming can be performed by charging the electrode plate group including the unformed negative electrode plate while it is immersed in an electrolyte containing sulfuric acid in the battery case of the lead-acid battery. However, forming can also be performed before assembling the lead-acid battery or the electrode plate group. Through forming, spongy lead is generated.

[0121] Examples

[0122] Hereinafter, examples and comparative examples will be given to more specifically illustrate the present invention, but the present invention is not limited to the following examples as long as it does not exceed its gist.

[0123] Using the following raw materials, separators for sealed lead-acid batteries of Examples 1 to 15 and Comparative Examples 1 to 4 were made.

[0124] [Formulation of raw materials]

[0125] (1) Micro glass fiber

[0126] A: ENTEK Asia Co., Ltd. with a number average fiber diameter of 0.6 μm

[0127] B: ENTEK Asia Co., Ltd. with a number average fiber diameter of 0.8 μm

[0128] C: ENTEK Asia Co., Ltd. with a number average fiber diameter of 1.0 μm

[0129] D: ENTEK Asia Co., Ltd. with a number average fiber diameter of 1.2 μm

[0130] E: ENTEK Asia Co., Ltd. with a number average fiber diameter of 2.0 μm

[0131] F: ENTEK Asia Co., Ltd. with a number average fiber diameter of 3.0 μm

[0132] G: ENTEK Asia Co., Ltd. with a number average fiber diameter of 4.0 μm

[0133] (2) Glass long fiber

[0134] ECS03T - 790DE manufactured by Nippon Electric Glass Co., Ltd., number average fiber diameter 6 μm, number average fiber length 3 mm

[0135] (3) Non - heat - fusible organic fiber

[0136] EP053 manufactured by Kuraray Co., Ltd., polyethylene terephthalate, fineness 0.53 dtex, number average fiber length 3 mm

[0137] (4) Heat - fusible organic fiber

[0138] Melty 4080 manufactured by Unitika Ltd., two - component core - sheath type (core: polyethylene terephthalate, sheath: copolyethylene terephthalate), fineness 1.5 dtex, number average fiber length 3 mm

[0139] (5) Inorganic powder

[0140] Silica (powder): BG - 3 manufactured by Evonik Industries AG

[0141] [Manufacture of separator]

[0142] According to the formulations and papermaking conditions shown in Tables 1 - 2, through the following process, separators for sealed lead - acid batteries of Examples 1 - 15 and Comparative Examples 1 - 4 were manufactured.

[0143] Dissociate and disperse a raw material mainly composed of micro glass fibers combined in such a way that the water filtration resistance (SR: Schopper - Riegler) value of the separator becomes 20 or more, using dissociation water of a predetermined pH. After dilution to a predetermined raw material concentration, it is flowed into an inclined papermaking machine set at a predetermined papermaking angle at a predetermined raw material flow rate to produce a separator.

[0144] [Test and evaluation methods]

[0145] For the above - mentioned examples and comparative examples, evaluation was carried out under the following conditions, and the results are shown collectively in Tables 1 - 2.

[0146] (1) Water filtration resistance (SR: Schopper - Riegler) value

[0147] Take 2.00 g of the produced AGM separator as a test sample for measurement. Put the sample into a stirrer (MV - 152SP manufactured by Panasonic Corporation), add 800 ml of water and stir for 90 seconds. Transfer all of the stirred sample to a glass graduated cylinder, take 1000 ml, and then measure the SR value according to the method described in JIS P - 8121 2012: Pulp - Water drainage degree test method - Part 1: Schopper - Riegler method.

[0148] (2) Apparent density (g / cm 3 )

[0149] Cut the produced AGM separator into pieces of 100 mm × 100 mm size as test pieces, and measure according to the method described in Item 7.2.3 of the Battery Industry Association Standard SBA S 0406 - 2017 Edition for AGM separators for lead - acid batteries, and calculate by the following formula.

[0150] Apparent density (g / cm 3 ) = [weight (g / m 2 )] ÷ [thickness (mm)] ÷ 1000

[0151] (3) Gas permeability (%)

[0152] Measure according to the method for measuring the gas permeability (%) for grasping the gas permeation performance of the separator according to the present invention, and calculate by the following formula.

[0153] Gas permeability (%) = [bubble (gas) generation distance (mm)] ÷ [test piece thickness (mm) at 50 kPa pressure after 2.5 mm thickness correction] × 100

[0154] (4) Gas permeation rate (mm / min)

[0155] The measurement method of the gas permeation rate (mm / min) for grasping the gas permeation performance of the partition according to the present invention is used for measurement, and the calculation is performed by the following formula.

[0156] Gas permeation rate (mm / min) = [Bubble (gas) generation distance (mm)] ÷ [Time until leakage (seconds)] × 60

[0157] (5) Gas absorption reaction inhibition effect (relative value)

[0158] Based on the measured value of the gas permeability (%) and the measured value of the gas permeation rate (mm / min), the calculation is performed by the following formula. The gas absorption reaction inhibition effect is expressed as a comparison with the partition of Comparative Example 1 (conventional product), that is, it is expressed as a ratio (relative value) when the measured value of Comparative Example 1 (conventional product) is set to 1.0.

[0159] Gas absorption reaction inhibition effect = [Measured value of gas permeability of Comparative Example 1 (%)] ÷ [Measured value of gas permeability of the sample (%)] × [Measured value of gas permeation rate of Comparative Example 1 (mm / min)] ÷ [Measured value of gas permeation rate of the sample (mm / min)]

[0160] The evaluation results of Examples 1 to 15 and Comparative Examples 1 to 4 are collectively shown in Tables 1 to 2.

[0161] [Table 1]

[0162]

[0163] [Table 2]

[0164]

[0165] The separator as in Example 1 is prepared from a raw material formulated in such a way that the water filtration resistance (SR: Schopper-Riegler) value is 39 and the number average fiber diameter (average value) of the micro glass fibers is 0.8 μm. The raw material concentration during sheet forming is set to 0.24 wt% (≤0.30 wt%), and the raw material flow rate (spraying) is set to 20 m / min (≥10 m / min). Thus, a separator with a gas permeability of 47% and a gas permeation rate of 9.8 mm / min in the wet state can be produced. Compared with the separator of Comparative Example 1 (conventional product) with a gas permeability of 77% and a gas permeation rate of 15.7 mm / min in the wet state (raw material concentration during sheet forming: 0.41 wt%, raw material flow rate (spraying): 5 m / min), the gas permeability is significantly suppressed, and the inhibitory effect on the gas absorption reaction is 2.6 times. As a result, during electrolytic cell formation, the energy consumption can be reduced by suppressing the gas absorption reaction. Furthermore, since the reduction in the electrolyte concentration (specific gravity) is small, after the electrolytic cell formation is completed, adjustment of the electrolyte concentration (specific gravity) is not required. In addition, the gas absorption reaction during battery charging can be suppressed, resulting in suppression of the temperature rise inside the battery and improvement of battery safety (suppression of battery thermal runaway).

[0166] For the separators as in Examples 2 to 7, which are prepared from a raw material formulated by combining micro glass fibers in such a way that the water filtration resistance (SR: Schopper-Riegler) value is 20 or more, with the raw material concentration during sheet forming set to ≤0.30 wt% and the raw material flow rate (spraying) set to ≥10 m / min, they also have gas permeation performance in the wet state equivalent to that of the separator of Example 1 with a water filtration resistance (SR: Schopper-Riegler) value of 39 (gas permeability: 55 - 75%, gas permeation rate: 13.3 - 15.0 mm / min). In addition, compared with the separator of Comparative Example 1 (conventional product), the inhibitory effect on the gas absorption reaction is 1.2 - 1.7 times.

[0167] The separator as in Example 8 is prepared from a raw material formulated in such a way that the water filtration resistance (SR: Schopper-Riegler) value is 21 and the number average fiber diameter (average value) of the micro glass fibers is 2.0 μm. The raw material concentration during sheet forming is set to 0.22 wt% (≤0.30 wt%), and the raw material flow rate (spraying) is set to 32 m / min (≥10 m / min). Thus, a separator with a gas permeability of 54% and a gas permeation rate of 12.2 mm / min in the wet state can be produced. Compared with the separator of Comparative Example 1 (conventional product), the inhibitory effect on the gas absorption reaction is 1.8 times.

[0168] As in the separators of Examples 9 to 12, using a raw material that contains, in addition to micro glass fibers, glass long fibers with a number average fiber diameter of 6 μm and a number average fiber length of 3 mm, or non-melting organic fibers (made of polyethylene terephthalate) with a fineness of 0.53 dtex and a number average fiber length of 3 mm, setting the raw material concentration during sheet formation to 0.30 wt% or less, and setting the raw material flow rate (spraying) to 10 m / min or more, the separators thus produced also have gas permeability in the wet state equivalent to that of the separator of Example 1 using such fine fibers as the filter water resistance (SR: Schopper - Riegler) value is 39 (gas permeability is 36 - 44%, gas permeation rate is 7.7 - 12.8 mm / min). In addition, compared with the separator of Comparative Example 1 (conventional product), the inhibitory effect on the gas absorption reaction is 2.2 - 4.2 times.

[0169] As in the separators of Examples 13 to 15, using a raw material that contains, in addition to micro glass fibers, melting organic fibers with a fineness of 1.5 dtex and a number average fiber length of 3 mm, and silica (powder), setting the raw material concentration during sheet formation to 0.30 wt% or less, and setting the raw material flow rate (spraying) to 10 m / min or more, the separators thus produced also have good gas permeability in the wet state (gas permeability is 25 - 38%, gas permeation rate is 7.6 - 17.0 mm / min). In addition, compared with the separator of Comparative Example 1 (conventional product), the inhibitory effect on the gas absorption reaction is 1.9 - 6.4 times.

[0170] As in the separators of Comparative Examples 1 to 4, even when using a raw material prepared by combining micro glass fibers with a filter water resistance (SR: Schopper - Riegler) value of 20 or more, but in the separators produced by setting the raw material concentration during sheet formation to exceed 0.30 wt% and setting the raw material flow rate (spraying) to less than 10 m / min, as the gas permeability in the wet state, the gas permeability is 77 - 92%, the gas permeation rate is 15.� - 27.4, and the inhibitory effect on the gas absorption reaction is lower than that of the separator of Comparative Example 1 (conventional product).

[0171] The separator for a sealed lead - acid battery of the present invention can suppress the gas absorption reaction during cell formation, so it can reduce the energy consumption during cell formation. In addition, it can reduce the reduction of the electrolyte concentration (specific gravity), so the electrolyte concentration (specific gravity) adjustment is not required after cell formation. Furthermore, it can suppress the gas absorption reaction during battery charging, so it can suppress the temperature rise inside the battery and contribute to improving the safety such as suppressing thermal runaway of the battery.

[0172] Industrial applicability

[0173] The separator for a sealed lead-acid battery of the present invention can control (suppress) the gas permeability of the separator, so it can reduce the adjustment amount of the electrolyte concentration (specific gravity) after the battery case formation of the sealed lead-acid battery, and can suppress the abnormal heating of the battery in the actual battery usage environment.

Claims

1. A separator for a sealed lead-acid battery, characterized in that the separator for the sealed lead-acid battery is a non-woven fabric mainly composed of micro glass fibers, and the gas permeation rate in the wet state is 15 mm / min or less and / or the gas permeability is 70% or less.

2. The separator for the sealed lead-acid battery according to claim 1, characterized in that the separator for the sealed lead-acid battery is a non-woven fabric mainly composed of micro glass fibers, and the gas permeation rate in the wet state is 15 mm / min or less and the gas permeability is 70% or less.

3. The separator for the sealed lead-acid battery according to claim 1 or 2, characterized in that the number average fiber diameter of the micro glass fibers is 4.5 μm or less, and the separator for the sealed lead-acid battery is made by mixing two or more kinds of the micro glass fibers having different number average fiber diameters.

4. The separator for the sealed lead-acid battery according to claim 1 or 2, characterized in that the water filtration resistance (SR) value of the separator is 20 or more.

5. The separator for the sealed lead-acid battery according to claim 1 or 2, characterized in that the raw material concentration during the formation of the separator is 0.30% by weight or less.

6. The separator for the sealed lead-acid battery according to claim 1 or 2, characterized in that the raw material flow rate during the formation of the separator is 10.0 m / min or more.

7. The separator for the sealed lead-acid battery according to claim 4, characterized in that the blending amount of glass long fibers with a number average fiber diameter of 6 μm or more and a number average fiber length of 3 mm or more is 2% by weight or more.

8. The separator for the sealed lead-acid battery according to claim 4, characterized in that the blending amount of organic fibers with a fineness of 0.5 dtex or more and a number average fiber length of 3 mm or more is 2% by weight or more.

9. The separator for the sealed lead-acid battery according to claim 4, characterized in that the blending amount of inorganic powder is 5% by weight or more.

10. The separator for the sealed lead-acid battery according to claim 4, characterized in that the blending amount of heat-melting organic fibers is 5% by weight or more.

11. A sealed lead-acid battery, characterized in that the separator for the sealed lead-acid battery according to claim 1 or 2 is used.

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