JPH1074503A - Separator for alkali storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for an alkali storage battery with excellent self-dischage property, a long life, high capacity and great discharge property. SOLUTION: Combined fibers in a split structure as hydrophilic and swelling polyolefinic fibers are given surface treatment by surface active agent mainly containing alkylphosphate to be a deposit amount of 0.5%. 60wt.% hydrophilic and swelling polyolefinic fibers in a split structure, 30wt.% polyolefinic fibers in a core sheath structure as binder and 10wt.% polyethylene based pulp fibers as non-hydrophilic and swilling polyolefinic fibers are mixed together, paper- formed by inclined wires to be a criterion basis weight of 50g/m<2> and dried by a yankee dryer to obtain a separator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator for an alkaline storage battery.

[0002]

2. Description of the Related Art The characteristics required of nickel-cadmium and nickel-metal hydride batteries have become different as their applications have expanded. For example,
Battery for disaster prevention lighting has improved trickle charging efficiency and longer life at high temperatures, higher energy density and faster charging characteristics for home appliances such as video, and more for power tools and radio control. This is an improvement in large current discharge characteristics. Since these characteristics have many contradictory factors, all the characteristics cannot be improved by one type of technology development, secondary battery manufacturers produce dedicated batteries according to their respective applications.

[0003] Improvement in trickle charge efficiency and long life at high temperatures are countermeasures by reducing self-discharge. The self-discharge refers to a phenomenon in which the capacity naturally drops when the battery is left unused. If the battery is recharged again, it will return to a normal state. However, if the user uses the battery that has not been used for a long time without charging, the power will be cut off in a much shorter time than expected.

[0004] The main cause of self-discharge was the polyamide-based separator used in storage batteries. The separator is decomposed by the electrolytic solution to generate impurities such as sulfite ions. This moves back and forth between the electrodes (this is called a shuttle effect), and self-discharge occurs due to repeated reduction of the active material of the positive electrode and oxidation of the active material of the negative electrode.

[0005] In particular, nickel-metal hydride batteries
When nitrogen is present, silver nitrate is generated by a chemical reaction during charge and discharge, which causes a shuttle effect. The initial nickel-metal hydride battery had a low capacity preservation ratio, which is an indicator of self-discharge, as 60% by weight or less when left at room temperature for one month. Therefore, a polyolefin having high alkali resistance and difficult to be decomposed by an electrolyte (for example, FT series manufactured by Japan Vilene Co., Ltd .: 0.23 mm in thickness, 300% in liquid retention, 50 m / 3 in liquid absorption speed)
0 min, electrical resistance of 0.9 mΩ / 100 cm ² / sheet, and properties such as alkali resistance of 2% or less).
However, polyolefins have slightly higher electrical resistance,
Since the liquid retention rate and the liquid absorption rate depend on the surfactant added, there are problems such as a decrease in surface activity due to charge and discharge of the battery.

One of the improvements is a blend of polyolefin (PO) and polyamide (PA). However, with respect to self-discharge at a high temperature, a polyamide nonwoven fabric is not preferable, and there is an adverse effect due to nitrogen oxide ions generated by decomposition. It is inevitable.

[0007] It has also been found that a substantial improvement can be achieved by treating a polypropylene nonwoven fabric with concentrated sulfuric acid or the like (called sulfonation treatment). However, this method uses a large amount of a dangerous gas such as sulfuric acid gas, and thus has problems in environmental problems, facility maintenance, and costs.

Further, the nonwoven fabric is exposed during high-frequency glow discharge to bond oxygen to the surface to change the hydrophilicity, so that the pure absorption rate is 40 mm in 2 minutes, and the liquid retention rate is twice its own weight, which is higher than that of polyamide. Some of them show characteristics, but the dispersion of hydrophilicity in the width direction is large, and as a result, the reliability of the battery is deteriorated.

Next, portable electronic devices are becoming smaller and lighter, and there is a strong demand for higher capacity (higher energy density). In short, increasing the capacity of a battery is how to fill a large amount of an active material having a high utilization rate. However, since the dimensions of the battery are determined by standards such as JIS and JEC, the volume efficiency (Wh / l) can be relatively easily improved by filling a large amount of the active material having a high utilization rate. However, if the amount of the active material alone is simply increased, the weight efficiency (Wh / kg) decreases.

[0010] In order to prevent this, the weight and volume of the constituent materials of the battery and the parts must be reduced rationally.
In a sealed nickel-cadmium storage battery, it is necessary to react and consume oxygen generated from the positive electrode during charging at the negative electrode during charging, and the separator is premised on porosity. In addition, since the ability to retain the electrolyte required during charging and discharging is also important, a polyamide nonwoven fabric (Japanese Vilene: known as the FT series, having a thickness of 0.2 mm, a liquid retention rate of 300%, a liquid absorption speed of 50 mm / 30 minutes, and an electrical resistance of 0 .5
mΩ · 100 cm ² / sheet, having physical properties such as alkali resistance of 15 to 20%).

In response to a demand for a higher energy density,
For thinning, there is a corresponding movement by reducing the fiber diameter. Currently used separators have a fiber diameter of 10 μm
Non-woven fabric of polypropylene (PP) fiber or polyamide (for example, nylon) fiber having a thickness of 0. The center is 15mm, but only 0. It is said that the battery capacity can be improved by about 15% even if the thickness is reduced by 05mm. However, the fiber density of the nonwoven fabric is increased in order to secure the strength as a separator while using fibers having a smaller diameter than before. At that time, maintaining the uniformity of the thickness and conductivity of the nonwoven fabric is the point of development. However, if the thickness is too thin, the liquid retention will deteriorate and the life will be shortened, or the life characteristics will be degraded due to minute short circuit due to so-called dendride. Careful consideration is required because of the Many improvements have been submitted but are still inadequate.

Further, electric tools and radio controlled toys are required to be rapidly charged together with a large current discharge characteristic in order to use as many times as possible within a unit time. In the case of a so-called Neumann-type sealed battery, a microporous thin film is preferable because a hole for gas permeation is required in the separator. But,
At present, there is no porous separator which is satisfactory in terms of cost, electrolyte retention ability, gas permeability and the like, and a cloth separator is used at present.

That is, in a system using an abundant amount of electrolyte,
Attention has been focused on film separators, which are less likely to cause a short circuit due to falling off of active material.
It is also required that the battery is easy to assemble and that the gas during charging does not accumulate in the battery when used in a secondary battery.

Further, in order to further improve the reliability of the battery, a microporous separator is preferable even in such a closed system. However, it is difficult to satisfy the cost and the ability to hold the electrolytic solution. Becomes

[0015] Separators are greatly involved in any of the demands of batteries such as miniaturization, weight reduction, long life, large output, high reliability, and low cost. It is not an exaggeration to encourage the expansion of the program.

[0016]

In recent years, separator materials for nickel-metal hydride batteries have shifted from polyamide-based materials to polypropylene-based materials. This is because the polypropylene system can improve self-discharge, which is one of the disadvantages of nickel-metal hydride batteries.

However, in order to use a polypropylene separator in a nickel-metal hydride battery, it is necessary to treat the fiber surface with a hydrophilic treatment. This is because polypropylene is water-repellent and does not hold an electrolytic solution. Usually, the fiber is modified by means of chemically adding a hydrophilic functional group such as a sulfone group to the surface of the fiber, so as to improve the absorbency and liquid retention of the electrolytic solution to the same level as the polyamide system.

However, technological development for improving battery characteristics must not sacrifice the long life and high reliability inherent in NiCd and nickel-metal hydride rechargeable batteries. No.

An object of the present invention is to provide a separator for an alkaline storage battery which has excellent self-discharge characteristics, can have a long life, and has excellent high capacity and large discharge characteristics.

[0020]

In order to achieve the above object, the invention of claim 1 comprises a hydrophilic and swellable polyolefin fiber and a non-hydrophilic polyolefin fiber. Further, the gist of the present invention is an alkaline storage battery separator containing 60% by weight or more of a polyolefin-based fiber having swellability.

To prevent self-discharge caused by the shuttle effect,
The purpose is to suppress the nitrogen content in the separator to “0”. Therefore, a polyolefin-based nonwoven fabric is used.
(Polyethylene) may be obtained by copolymerizing EVA (ethylene / vinyl alcohol) or vinyl acetate, but these are less stable in a strong alkali than the base material polyethylene.

Therefore, monostearic acid ester compounds and distearic acid ester compounds of polyhydric alcohols are
Composite fibers blended with PDE (low density PE) or (high density PE) have been proposed. In this method, an EO (ethylene oxide) component exudes to the PE surface in water or an electrolytic solution to make the fibers hydrophilic.

It is known that these polymers absorb water and expand in volume. In the present invention, a polyolefin fiber having hydrophilicity and swelling property (hereinafter referred to as hydrophilic / swelling PO fiber) is provided by the polymer. The EO component also absorbs and swells the liquid and retains the liquid at a level higher than the surface adsorption of the liquid.

In the present invention, the hydrophilic / swellable PO fibers are
It is desirable that the content be 0% by weight or more from the viewpoint of electrolyte solution retention.
Examples of the non-hydrophilic polyolefin-based fiber include polyolefin-based synthetic pulp, polypropylene-based single fiber, polyethylene-based single fiber, and polypropylene- and polyethylene-based composite fibers.

Therefore, the invention of claim 2 is characterized in that, in claim 1, the non-hydrophilic polyolefin-based fiber is selected from polyolefin-based synthetic pulp, polypropylene-based single fiber, polyethylene-based single fiber, polypropylene-based and polyethylene-based composite fiber. The gist is that at least one of the fibers is selected from the group consisting of:

The large current discharge characteristic can be countered by lowering the internal resistance during energization. The reason for using an alkaline solution for the electrolyte is that the resistance is low, but it is better that the resistance in the separator is low.

Therefore, it is preferable that the separator be as thin as possible and retain a large amount of electrolyte. The reason why the alkali-swellable PA nonwoven fabric has been used for many years is also the reason. The hydrophilic / swellable PO fiber contains a component which easily swells and, unlike other hydrophilic PO (polyolefin) fibers, exhibits a liquid absorbing property not less than the gap between the fibers.

Further, according to the invention of claim 3, in claim 1 or claim 2, the hydrophilic / swellable PO fiber comprises a hydrophilic / swellable polyolefin-based component and a lipophilic polypropylene-based component. A composite structure of a core and sheath in which a hydrophilic / swellable polyolefin component is arranged as a sheath, or a hydrophilic / swellable polyolefin component and a lipophilic polypropylene component alternate around a lipophilic polypropylene component as a core Is divided into petals.
The gist is that the component ratio is approximately 1: 1.

In the present invention, among the composite fibers, those having a core-sheath structure and those having a split structure are desirable as hydrophilic / swellable PO fibers. That is, the hydrophilic / swellable PO fiber is
Consisting of a swellable polyolefin-based component and a lipophilic polypropylene-based component, the component ratio of which is approximately 1: 1
It is suitable to use a core-sheath composite structure in which a hydrophilic / swellable polyolefin component is arranged as a sheath.

The reason why the composite fiber having the split structure is selected is as follows. As a measure for reducing the thickness of the separator for increasing the capacity of the battery, there is a method of reducing the basis weight or increasing the density. However, reducing the basis weight reduces the mechanical strength and the dendrite resistance, and lowers the reliability of the battery. Also, increasing the density lowers ion permeability, liquid retention, and liquid absorption.

Therefore, a method of reducing the basis weight without lowering the fiber density by using a fiber having a fiber diameter of less than 1 d can be considered. However, it is difficult to melt-spin only the component due to the properties of hydrophilic and swellable PO (polyolefin). Therefore, generally, a PO-based resin (mainly PP is used) suitable for spinning is used as a core, and Many fibers have a composite structure in which the components are sheathed. Therefore, these composite fibers have a thickness of 1 d.
It was difficult to make it less than.

In this case, it is possible to obtain a hydrophilic fiber of less than 1 d by arranging a PO resin for spinning, in particular, a lipophilic polypropylene resin and a hydrophilic / swellable PO resin in a petal shape, and making the component ratio approximately 1: 1. did it. This fiber has a P
O (especially lipophilic polypropylene), around which PO for spinning
(Especially lipophilic polypropylene) resin and hydrophilic / swellable PO
It is a splittable conjugate fiber in which resin is alternately arranged and divided into 5-33. If the number of divisions is less than 5, a sufficiently thin fiber cannot be obtained, and if it exceeds 33, spinnability deteriorates.

Most of the divided fibers have a fan-shaped cross section, and when the paper layer is formed, the density becomes high due to the property that the direction in which the fiber surface is large is deposited horizontally. However, since the cross section is fan-shaped, a gap is formed at a portion corresponding to the sector, and sufficient liquid retention can be secured.

For splitting the split fibers, pulpers, beaters, refiners, homomixers, fiberizers, and the like used when pulp is defibrated and beaten are used.
When the split fibers are blended in an amount of 40% by weight or more, it is recognized that the fiber density increases even if the basis weight is reduced, and that the air permeability, which is an index of the dendrite resistance, is improved. It was recognized that the liquid properties did not decrease.

The invention according to claim 4 is the invention according to claims 1 to 3.
The hydrophilic / swellable PO fiber is treated with an alkali penetrant and has an adhesion amount of 0.01% to 1.0%.
The gist is that

That is, the higher the concentration of the alkali solution, the lower the permeability to the porous body, and therefore, the surface treatment with a surfactant as an alkali penetrant is performed.
However, many surfactants contain nitrogen. Therefore, a POE alkyl allyl ether type non-ion as an alkali penetrant, an alkali penetrant mainly containing alkyl sulfate or an alkali penetrant mainly containing alkyl phosphate is used.

Further, in order to minimize the influence of the alkali penetrant, the amount of the alkali penetrant to be applied should be 0.01% or less of the fiber weight.
1.0% is preferred. The nitrogen content in the entire separator can be reduced to less than 10 ppm by the above-mentioned amount of the alkali penetrant attached. Further, when the content is 0.1% to 0.5%, it is more preferable in terms of balance between the ability to retain the electrolyte and the ability to suppress self-discharge.

Therefore, the invention of claim 5 is based on claim 4, and the gist of the invention is that the alkali penetrant has a nitrogen content of 0.1% or less. These alkali penetrants include, for example, Neolate NA-20, Neolate N
A-30 and Sunmall BL600 (all are manufactured by Nichika Chemical Co., Ltd.).

The gist of the invention of claim 6 is that, in claim 4, the alkali penetrant is an alkyl phosphate or alkyl sulfate surfactant having good alkali resistance.

The invention of claim 8 is the first to seventh aspects of the present invention.
In any of the above, the basis weight of the separator is 20 g / m ² ~
Was 100 g / m ^2, bulk density of ^{0.2g / cm 3 ~0.5g / cm 3} , has as its gist the air permeability is 0.1 sec / 100Cc～20 sec / 100 cc.

[0041] If the basis weight A of the separator is in the range of ^{20g / m 2 ~100g / m 2} , the internal resistance of the separator, can take balance between strength. However, the basis weight of the separator is less than 20 g / m ^2, the internal resistance of the separator is reduced, but the large current characteristics are better, not preferred since the strength is reduced, the basis weight of the separator opposite the 100 g / m ^If it exceeds ² , the strength of the separator increases, but the internal resistance increases, which is not preferable.

The bulk density of the separator is 0.2 g / cm ^{3 to} 0.5 g / c.
When it is in the range of m ³ , the balance between the liquid retaining property of the electrolytic solution of the separator and the short circuit prevention property can be achieved. When the bulk density of the separator is less than 0.2 g / cm ³ , the liquid retention of the electrolytic solution is increased,
Since the short-circuit prevention property is deteriorated, it is not preferable,
If it exceeds 0.5 g / cm ³ , the liquid retention of the electrolytic solution will decrease,
Not preferred.

The air permeability of the separator is 0.1 sec / 100 cc to 20 sec.
If it is within the range of / 100cc, self-discharge of the separator is suppressed,
Balance with ion permeability can be achieved. If the air permeability of the separator is less than 0.1 sec / 100 cc, the ion permeability will be good, but the self-discharge suppression will deteriorate and the air permeability of the separator will decrease.
If it exceeds 20 seconds / 100cc, self-discharge suppression will be good,
It is not preferable because ion permeability deteriorates.

When the separator is multilayered, self-discharge suppression and short-circuit prevention are further improved. In order to obtain a stable and uniform layer, the basis weight per layer is preferably 10 g / m ² or more.

The ninth aspect of the present invention is the first to eighth aspects.
In any of the above, the compressive strength in the thickness direction is 3kg / cm
The gist is that it is ² cm or more. That is, if heat treatment is performed at 135 ° C. to 145 ° C. after papermaking, the strength further increases, and particularly, the compressive strength in the thickness direction increases, so that a very strong winding tension (2 kg / cm or more) is produced when manufacturing a cylindrical storage battery. Therefore, the thickness of the separator is not crushed, and a sufficient electrolytic solution can be held. In addition, when the electrode swells and the volume increases during use of the battery, the separator is compressed to push the electrolyte out of the separator. However, this compression-resistant product has an effect that the electrolyte performance is high even in this case.

(Manufacturing method) The nonwoven fabric used as the separator of the present invention is formed by a wet papermaking method in order to suppress the variation in the weight per unit area in the flow direction and the width direction. Although a PO-based fiber generally has a specific gravity of 1 or less, a short net or an inclined wire is preferable.

The wet paper web is dried using a tunnel type hot air dryer or a drum type contact dryer (Yankee dryer). However, in the tunnel type hot air dryer, the web is liable to be thermally contracted as a whole and become porous. In addition, it is necessary to adjust the paper thickness with a heat calender.

[0048]

Embodiments of the present invention will be described below. The raw materials used in Examples 1 to 8 have the mixing ratios shown in Table 1, and also show the mixing ratios of Comparative Examples 1 to 3.

[0049]

[Table 1] In the table, A to H represent specific product names, and are as follows.

A: Core-sheath type hydrophilic / swellable PO fiber (1.2d × 5 mm) B: Core-sheath type hydrophilic / swellable PO fiber (2d × 5 mm) C: Core-sheath type hydrophilic / swellable PO fiber (2d) D: PZ (Daiwabo Co., Ltd. 0.5d × 3mm) E: EDC chop (Chisso Corporation, 2d × 5mm) F: EA chop (Chisso Corporation, 2d × 5mm) G: SWP (Mitsui) Petrochemical Co., Ltd.) H: SWP (Mitsui Petrochemical Co., Ltd.) In each of the above Examples and Comparative Examples, among the above-mentioned raw materials, conjugate fibers having a split structure were obtained by splitting with a beater.
In addition, among the samples of Examples and Comparative Examples, hydrophilic / swelling type P
The O fiber is a surfactant (Neolate NA-20, manufactured by Nika Chemical Co., Ltd.) containing alkyl phosphate as a main component.
The amount of adhesion is 0. The surface treatment was performed to 5%. And
Each of the above samples was blended at a blending ratio shown in Table 1, and paper was formed using a slanted wire as a paper machine so as to have a basis weight of 50 g / m ² , and dried with a Yankee dryer to obtain a separator.

Next, the strength, the electrolyte retaining property, the short-circuit material shielding property, and the self-discharge preventing property were measured by the following measuring methods. 1) Strength test The tensile strength F of a sample piece (15 mm x 250 mm) was measured with a Shopper tension tester set at an interval of 180 mm.

The evaluation was as follows: F <1 kg, × 1 kg ≦ F <2 kg, △ 2 kg ≦ F <4 kg, and 4 kg ≦ F. 2) Retention of electrolyte solution Each sample piece (50 mm x 50 mm) was weighed, and the value at this time was A
g. After being immersed in a 30% KOH solution at room temperature (20 to 20 ° C.) for 30 minutes, it is pulled up and drained for 30 minutes.
After removing the appropriate weight, weigh again. The value at this time is defined as Bg.
The liquid holding amount Q is calculated by the following equation.

Q = (BA) / A In the evaluation, Q <1 was evaluated as ×, 1 ≦ Q <2 as Δ, 2 ≦ Q <4 as Δ, and 4 ≦ Q as ◎. 3) Short-circuit substance shielding property A sample piece (50 mm x 50 mm) was measured for air permeability S sec / 100 ml by a Gurley air permeability test.

The evaluation was 0. 1> S as x, 0. 1 ≦ S <1
△, 1 ≦ S <20, Δ, and 20 ≦ S, ◎. 4) Self-Discharge Prevention Property The total nitrogen content Tppm of 50 g of a sample piece was measured by the Kjeldahl method.

The evaluation was 0. 1> T is ◎, 0. 1 ≦ T <1
Was evaluated as ○, and 10 ≦ T was evaluated as ×. Table 2 shows the results. In each of the examples, it was confirmed that they were excellent in strength, electrolyte solution retaining property, short-circuit substance shielding property, and self-discharge prevention property (self-discharge property).

[0056]

[Table 2]

[0057]

As described above in detail, according to the present invention, the self-discharge characteristics are excellent, the life is prolonged, the electrolytic solution retention property is excellent, and the short-circuit substance blocking property is excellent. An alkaline storage battery separator having excellent discharge characteristics can be obtained.

In particular, automobile manufacturers are working to make emission-free vehicles mandatory in the US in California in 2003, but they are the closest to practical use of emission-free vehicles. It is suitable as a separator.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 11, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0050

[Correction method] Change

[Correction contents]

A: Core-sheath type hydrophilic / swellable PO fiber (1.2 d × 5 mm) B: Split type hydrophilic / swellable PO fiber (2 d × 5 mm) C: Core-sheath type hydrophilic / swellable PO fiber (2d × 5mm) D: PZ (Daiwabo Co., Ltd. 0.5d × 3mm) E: EDC chop (Chisso Corporation, 2d × 5mm) F: EA chop (Chisso Corporation, 2d × 5mm) G: SWP (Mitsui Oil) Chemical Co., Ltd.) H: SWP (Mitsui Petrochemical Co., Ltd.) In each of the above Examples and Comparative Examples, among the above-mentioned raw materials, conjugate fibers having a split structure were obtained by splitting with a beater.
In addition, among the samples of Examples and Comparative Examples, hydrophilic / swelling type P
The O fiber is a surfactant (Neolate NA-20, manufactured by Nika Chemical Co., Ltd.) containing alkyl phosphate as a main component.
The amount of adhesion is 0. The surface treatment was performed to 5%. And
Each of the above samples was blended at a blending ratio shown in Table 1, and paper was formed using a slanted wire as a paper machine so as to have a basis weight of 50 g / m ² , and dried with a Yankee dryer to obtain a separator.

Claims (9)

[Claims] 1. A polyolefin fiber having hydrophilicity and swellability and a non-hydrophilic polyolefin fiber, wherein the polyolefin fiber having hydrophilicity and swellability is contained in an amount of 60% by weight or more. Separator for alkaline storage batteries. 2. The non-hydrophilic polyolefin fiber is a polyolefin synthetic pulp, a polypropylene single fiber,
The alkaline storage battery separator according to claim 1, wherein at least one selected from a polyethylene-based single fiber, a polypropylene-based fiber, and a polyethylene-based composite fiber is selected. 3. The polyolefin fiber having hydrophilicity and swelling property comprises a hydrophilic / swelling polyolefin-based component and a lipophilic polypropylene-based component, and its structure is sheathed by the hydrophilic / swellable polyolefin-based component. A composite structure of a core-sheath arranged as described above, or a divided structure in which a hydrophilic polyolefin component and a lipophilic polypropylene component are alternately arranged in a petal shape around a lipophilic polypropylene component as a core. 3. The alkaline storage battery separator according to claim 1, wherein the ratio is approximately 1: 1. 4. A polyolefin fiber having hydrophilicity and swelling property is treated with an alkali penetrant and has an adhesion amount of 0.01%.
The alkaline storage battery separator according to any one of claims 1 to 3, wherein the content is from 1.0 to 1.0%. 5. The alkali penetrant has a nitrogen content of 0.1%.
The alkaline storage battery separator according to claim 4, wherein: 6. The separator for an alkaline storage battery according to claim 4, wherein the alkali penetrant is an alkyl phosphate or alkyl sulfate-based surfactant having good alkali resistance. 7. The number of divisions of the polyolefin fiber having hydrophilicity and swelling property of the divided structure is 5 to 33.
4. The separator for an alkaline storage battery according to claim 1. The basis weight of 8. The separator is a ^{20g / m 2 ~100g / m 2} , bulk density 0. 2g / cm ³ ~0. 5 g / cm ³ and air permeability is 0. The alkaline storage battery separator according to any one of claims 1 to 7, wherein the rate is 1 second / 100 cc to 20 seconds / 100 cc. 9. The alkaline storage battery separator according to claim 1, which has a compressive strength in a thickness direction of 3 kg / cm ² · cm or more.