JPH06295715A - Nonwoven fabric for alkaline battery separator and manufacture thereof - Google Patents

Abstract

PURPOSE:To heighten strength of fiber itself and alkaline resistance, and obtain excellent water absorptivity by constituting nonwoven fabric of metallic ion added acrylic fiber having a specific fiber diameter and a ratio of a specific fiber length to a fiber diameter. CONSTITUTION:A battery for an alkaline battery separator is composed of metallic ion added acrylic fiber where at least one or more kinds of fibers are short fiber having a diameter of 3-l0mum and a ratio (L/D, an aspect ratio) of a fiber length L to a fiber diameter D is 1000-2000. When nonwoven fabric for this alkaline battery separator is manufactured, first of all, the metallic ion added acrylic fiber where at least one or more kinds of fibers are short fiber having a diameter of 3-10mum and a ratio (an aspect ratio) of a fiber length L to a fiber diameter D is 1000-2000, is dispersed in water, and is formed as slurry. Next, this slurry is combed in a wet system, and a web is formed. Next, after this web is entangled with/joined to each other by a water flow entangling method, the nonwoven fabric is manufactured by heat work.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-woven fabric for an alkaline battery separator, and particularly to a non-woven fabric for an alkaline battery separator which is excellent in both initial wettability and liquid retaining property of an electrolytic solution and has other properties. And a method for manufacturing the same.

[0002]

2. Description of the Related Art Alkaline batteries are widely used in electronic devices which are remarkably miniaturized and lightweight because they are excellent in charge / discharge characteristics and overcharge / overdischarge characteristics and can be repeatedly used with a long life. The characteristics of such an alkaline battery greatly depend on the characteristics of the battery separator.

The alkaline battery separator is generally required to have the following performance. (1) The positive electrode and the negative electrode can be physically separated. (2) It must have electrical insulation to prevent short circuits. (3) Must have electrolytic solution resistance. (4) It has electrochemical oxidation resistance. (5) It exhibits low electric resistance in a state of containing an electrolytic solution. (6) The electrolytic solution is easily wetted and the amount of the electrolytic solution retained is large. (7) It must have the strength and rigidity to withstand the battery assembly process. (8) Do not emit harmful substances for batteries. (9) Be breathable.

Therefore, conventionally, a polyamide fiber non-woven fabric, which is easily wetted by an electrolytic solution, has a large holding amount, and has a low electric resistance in the state of containing the electrolytic solution, has been used as a separator for alkaline batteries. In addition, a polyolefin fiber non-woven fabric is used as a separator for batteries that require durability at relatively high temperatures.

However, the alkaline battery separator made of the above-mentioned polyamide fiber nonwoven fabric has a drawback that nitrogen oxides are eluted from the fiber by repeated use and the life of the battery is shortened. Further, since the one made of the polyolefin fiber nonwoven fabric has a low water absorption, it is hard to be wet with the electrolytic solution, and the retained amount thereof is small.

Therefore, recently, in order to improve both the electrolytic solution resistance and the electrochemical oxidation resistance, and the wettability of the electrolytic solution and the retained amount thereof, for example, an alkaline battery separator disclosed in JP-A-3-257755. Is proposed. This separator is made of a non-woven fabric containing 35% or more of splittable conjugate fibers of polyolefin and ethylene vinyl alcohol copolymer.

[0007]

However, the separator made of a non-woven fabric containing the splittable conjugate fiber described above is insufficient in the air permeability of the non-woven fabric, the easiness of wetting of the electrolytic solution, the holding amount, and the like. Therefore, it is not possible to make the separator thin while also having the above-mentioned various performances, and in the alkaline battery using such a separator, high capacity, long life, high reliability, etc., required for recent cordless devices, etc. There is a problem that it is not possible to achieve a high degree of characteristics.

An object of the present invention is to provide a non-woven fabric for an alkaline battery separator, which has a low basis weight and also has the above-mentioned various properties, and is particularly excellent in both initial wettability and liquid retaining property of an electrolytic solution, and a method for producing the same. Especially.

[0009]

Means for Solving the Problems As a result of intensive research aimed at achieving the above object, the present inventors have invented a nonwoven fabric for alkaline batteries and a method for producing the same. That is,
The nonwoven fabric for alkaline battery separators of the present invention is at least one kind of short fibers having a fiber diameter of 3 to 10 μm, and has a ratio (L / D, aspect ratio) of the fiber length L to the fiber diameter D of 1.
It is composed of a non-woven fabric for an alkaline battery separator, which is made of a metal ion-added acrylic fiber of 000 to 2000.

In the method for producing a non-woven fabric for an alkaline battery separator according to the present invention, at least one or more kinds of short fibers having a fiber diameter of 3 to 10 μm and a ratio of the fiber length L to the fiber diameter D (L / D, aspect ratio). A metal ion-added acrylic fiber having a ratio of 1000 to 2000 is dispersed in water to form a slurry, the slurry is wet-paper-formed to form a web, and then the web is entangled by the hydroentangling method and then hot pressed. It is characterized by

The present invention will be described in detail below. In addition,
In the text, a non-woven fabric for an alkaline battery separator is simply referred to as a non-woven fabric. As the metal ion-added acrylic fiber in the present invention, all known fibers obtained by introducing a crosslink bond into an acrylic fiber, hydrolyzing it, and crosslinking or adding a monovalent metal ion with a divalent metal ion are used. (See, for example, Japanese Patent Laid-Open Nos. 2-84528 and 2-84532).

The raw acrylic fiber is an acrylonitrile polymer or copolymer fiber obtained from 40 to 100% by weight of acrylonitrile and 60 to 0% by weight of another vinyl monomer. Other vinyl monomers that may be copolymerized with acrylonitrile include, for example, methallyl sulfonic acid, P-styrene sulfonic acid, acrylic acid, methacrylic acid, and salts thereof, vinyl halides, vinylidene halides, acrylics. Examples thereof include acid ester, methacrylic acid ester, acrylamide, styrene and vinyl acetate.

The introduction of cross-linking into the raw material acrylic fiber can be carried out, for example, by heat-treating the fiber having a nitrile group with hydrazine, hydroxylamine or the like. The hydrolysis of the acrylic fiber in which the cross-linking has been introduced in this way can be carried out by heat treatment with an acid or a base, and the nitrile group can be converted into a carboxyl group or an amide group. Next, the cross-linking with metal ions is performed using Zn, Cu, Ca, Fe
And the like can be carried out by treating the fibers with a monovalent metal salt aqueous solution of Li, Na, K or the like.

The metal ion-added acrylic fiber used in the present invention preferably has a fiber diameter of 3 to 10 μm, preferably 4 to
It is more preferably 7 μm. A non-woven fabric using fibers in this range has easy control of pore diameter and air permeability.

The aspect ratio of the metal ion-added acrylic fiber used in the present invention is preferably 1000 to 2000. Fibers with an aspect ratio of more than 2,000 are difficult to disperse in water, so it is necessary to select an appropriate amount of dispersant and to use it in an appropriate amount. Also, once dispersed, it is re-aggregated to cause twisting, entanglement, and deception. The problem arises that it is easier to do. Also, the dispersion concentration must be lowered, resulting in poor productivity. Further, regarding the fiber length related to the aspect ratio, even if the fiber diameter is large, if the fiber length is more than 20 mm, the above-mentioned problems occur during wet papermaking of the web, and a web with good texture can be obtained. Can not.

A fiber having an aspect ratio of less than 1000 is easy to disperse, but it is easy to move due to water flow, so that it is difficult to bend and entangle the fiber, and it is difficult to obtain a nonwoven fabric having high strength. In addition, since the entire fibers move, the fibers are displaced from each other, which causes strain inside the nonwoven fabric, causing many wrinkles in the nonwoven fabric after jetting a water stream.

Since the hydroentangling method is one of the web processing methods, it is necessary to supply the web before processing. The web manufacturing method is a card method, a dry method such as an air-laid method,
A melt blow method, a spun bond method, a wet papermaking method and the like can be mentioned.

In the card method and the air laid method, fibers having a long fiber length can be used, but it is difficult to form a uniform web,
The non-woven fabric obtained by processing with a high-pressure columnar water flow also has a poor texture and a plaque pattern is observed when observed with transmitted light. When using the web obtained by the spunbond method, although the strength is high,
The formation is poor, the fibers are continuously connected, the free ends of the fibers are few, and a large amount of energy is required for three-dimensional entanglement. Further, according to this method, it is difficult to manufacture a web using fibers having a fiber diameter of 10 μm or less. Melt blow
The method can make fine fibers into a web, but has problems that the formation is poor, the production rate is slow, and the cost is high. As described above, since the webs produced by the above-mentioned four kinds of methods are not well formed, there is a problem that a high basis weight must be obtained in order to obtain a void diameter necessary for preventing a short circuit.

In the wet papermaking method, the production speed is higher than that of the above method, and a plurality of fibers having different fineness and kinds can be mixed in an arbitrary ratio in the same apparatus. That is, even in the form of fiber,
A wide range of choices such as staple and pulp, and usable fiber diameters from so-called 7 μm or less ultrafine fibers to thick fibers can be obtained, and a web with a very good texture is obtained compared to other methods. It is a method to be done. Therefore, it is considered to be a web forming method which has a very wide range of applications and is easy to control the void diameter.

Next, a method for manufacturing the nonwoven fabric of the present invention will be described. First, a metal ion-added acrylic fiber having a fiber diameter and an aspect ratio within the range of the present invention is disintegrated with a pulper and dispersed in water under gentle agitation of an agitator to form a uniform slurry. To do. This slurry is a round net, a long wire,
Using a paper machine having at least one wire of an inclined type or the like, paper making is carried out to produce a web having a good texture so as to have a thickness of 400 μm or less.

Next, the web thus prepared is loaded on a porous support having a porosity of 40% or less and one opening size of 0.04 mm ² or less, and a high pressure is applied from above the web. Inject a columnar water stream to move the water stream and the web relatively,
The fibers are entangled three-dimensionally. As a method of moving the web and the water flow relatively, a method of rotating the conveyor type support or the drum type support is convenient. At this time, the transport speed of the support is determined by the applied energy applied to the web, but it can be used at a speed of 1 to 200 m / min or less.

When the porosity of the support is larger than 40%, the resulting nonwoven fabric has pores, which makes it difficult to adjust the void diameter. On the contrary, the smaller the porosity, the better the surface quality of the obtained non-woven fabric, but if the porosity is too small, the water required for the entanglement does not escape downward from the support and hits the support. Again, it bounces back to the web, and the water that bounces pushes up the web, causing a phenomenon of breaking the web, which is not preferable. Examples of such a porous support include a wire such as a plain weave, a twill weave, a metal such as stainless steel and bronze, or a material such as plastic such as reinforced polyester and polyamide.

Next, the non-woven fabric thus obtained has a temperature of 1
A non-woven fabric adjusted to an appropriate thickness can be produced by performing hot pressure processing such as thermal calender roll treatment under the conditions of a temperature of not more than 00 degrees and a linear pressure of not more than 500 kg / cm.

In the nonwoven fabric for an alkaline battery separator of the present invention, in order to secure sufficient air permeability, the maximum pore diameter is 70 μm or less, the average pore diameter is 25 μm or less, and the maximum pore diameter / average pore diameter is 3 or less. It is preferable. The thickness of the nonwoven fabric is preferably 180 μm or less so that it can be suitably used as an alkaline battery separator for cordless devices.

[0025]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.
In the examples, all parts and% are by weight.

Example 1 Obtained by introducing a cross-linking bond into an acrylic fiber, introducing a carboxyl group of 3.5 mmol / g and an amide group in the balance by a hydrolysis reaction, and then adding a monovalent sodium metal ion. 97 parts of a metal ion-added acrylic fiber having a fiber diameter of 5.4 μm and a fiber length of 6 mm (aspect ratio 1111), a fineness of 1 denier, and a fiber length of 3 mm, a hot water-soluble polyvinyl alcohol fiber (VPW103, manufactured by Kuraray Co., Ltd.).
3 parts by wet papermaking method on a cylinder paper machine, basis weight 50 g / m
^2. A web having a width of 50 cm was produced. This web 10
0 mesh stainless wire- (wire diameter 0.112mm
A plain weave using a monofilament of 34% open area ratio,
It was transported onto a porous support having one opening having a size of 0.023 mm ² ) and subjected to hydroentangling treatment with a high-pressure columnar water stream at a transport speed of 10 m / min. The nozzle bed uses 3 heads, the nozzle of the first head has a nozzle diameter of 120 μm, the nozzle spacing is 0.6 mm, the water pressure is 75 kgf / cm ^{2 in} two rows, and the nozzle of the second head has a nozzle diameter of 100 μm and the nozzle spacing is 0.3 m.
m, 1 row is 100 kgf / cm ² , the nozzle of the third head has a nozzle diameter of 100 μm, nozzle spacing is 0.3 mm, and 1 row is 125 mm.
It is kgf / cm ² . The entanglement was performed on one side first, and then on the back side under the same conditions. The non-woven fabric thus obtained is 8
Dry with 0 degree hot air dryer, then temperature 60 degree, linear pressure 4
A calendar roll treatment was performed at 15 kg / cm to form a nonwoven fabric having a thickness of about 130 μm, which was cut to obtain a separator. Various performance tests were conducted on this separator. The results are shown in Table 1.

Example 2 Fiber diameter 5.4 μm, fiber length 8 mm (aspect ratio 14
A separator was obtained in the same manner as in Example 1 except that the metal ion-added acrylic fiber of 81) was used. Various performance tests were conducted on this separator. The results are shown in Table 1.

Example 3 A separator was obtained in the same manner as in Example 1, except that a metal ion-added acrylic fiber having a fiber diameter of 5.4 μm and a fiber length of 10.5 mm (aspect ratio 1944) was used. Various performance tests were conducted on this separator. The results are shown in Table 1.

Example 4 Fiber diameter 3.1 μm, fiber length 6 mm (aspect ratio 19
A separator was obtained in the same manner as in Example 1 except that the metal ion-added acrylic fiber of 35) was used. Various performance tests were conducted on this separator. The results are shown in Table 1.

Example 5 Fiber diameter 6.9 μm, fiber length 12 mm (aspect ratio 17
A separator was obtained in the same manner as in Example 1 except that the metal ion-added acrylic fiber of 39) was used. Various performance tests were conducted on this separator. The results are shown in Table 1.

Example 6 Fiber diameter 9.8 μm, fiber length 15 mm (aspect ratio 15
A separator was obtained in the same manner as in Example 1 except that the metal ion-added acrylic fiber of 31) was used. Various performance tests were conducted on this separator. The results are shown in Table 1.

Example 7 As a metal ion-added acrylic fiber, a cross-linking bond was introduced into an acrylic fiber, and a hydrolysis reaction was carried out at 3.5 m mo.
A fiber diameter of 5.6 μm and a fiber length of 6 mm (aspect ratio of 11 is obtained by introducing 1 / g of a carboxyl group and an amide group into the balance, and then forming a crosslink with a divalent Zn metal ion.
A separator was obtained in the same manner as in Example 1 except that the metal ion-added acrylic fiber of 11) was used. Various performance tests were conducted on this separator. The results are shown in Table 1.

Comparative Example 1 Fiber diameter 5.4 μm, fiber length 5 mm (aspect ratio 92
Other than using the metal ion-added acrylic fiber of 5),
A separator was obtained in the same manner as in Example 1. Various performance tests were conducted on this separator. The results are shown in Table 2.

Comparative Example 2 Fiber diameter 5.4 μm, fiber length 12 mm (aspect ratio 2
A separator was obtained in the same manner as in Example 1, except that the metal ion-added acrylic fiber 222) was used. Various performance tests were conducted on this separator. The results are shown in Table 2.

Comparative Example 3 Fiber diameter 2.8 μm, fiber length 3 mm (aspect ratio 10
A separator was obtained in the same manner as in Example 1 except that the metal ion-added acrylic fiber of 87) was used. Various performance tests were conducted on this separator. The results are shown in Table 2.

Comparative Example 4 Fiber diameter 3.1 μm, fiber length 3 mm (aspect ratio 97
0) except that the metal ion-added acrylic fiber of 0) is used,
A separator was obtained in the same manner as in Example 1. Various performance tests were conducted on this separator. The results are shown in Table 2.

Comparative Example 5 A separator was obtained in the same manner as in Example 1 except that a metal ion-added acrylic fiber having a fiber diameter of 11.1 μm and a fiber length of 25 mm (aspect ratio: 2252) was used. Various performance tests were conducted on this separator. The results are shown in Table 2.

Comparative Example 6 Example 1 was repeated except that an acrylic fiber having a fiber diameter of 3.5 μm and a fiber length of 6.0 mm (aspect ratio 1714) obtained by copolymerizing 91 parts of acrylonitrile and 9 parts of methyl acrylate was used. A separator was obtained in the same manner as in. Various performance tests were conducted on this separator. The results are shown in Table 2.

Comparative Example 7 Various performance tests were conducted on a nylon dry-type nonwoven fabric (melt spinning type) separator. The results are shown in Table 2.

[0040]

[Table 1]

[0041]

[Table 2]

The performance test methods in Examples and Comparative Examples are as follows. As the evaluation of the strength of the non-woven fabric,
When winding on the electrode plate, since it is wound while pulling, the longitudinal (flow direction) tensile strength (kg / 2 cm width) was measured. Tensile strength was measured according to JIS-8113 by cutting the separator into a width of 2 cm and a length of 20 cm, and using a tensilon measuring machine (manufactured by Orientec, HTM-100), measuring the load at break 10 times with a full scale of 10 kg. The average value was shown.

The Frazier air permeability (cc / cm ² / sec) was measured as an evaluation of the ease with which oxygen generated from the positive electrode side permeates the negative electrode side through the nonwoven fabric. The Frazier air permeability was measured according to JIS-L-1096 using a Frazier type air permeability tester to measure the amount of air passing through the test piece to 5
The measurement was performed once and the average value was shown.

Further, as the evaluation of the permeability of oxygen generated from the positive electrode side to the negative electrode side and whether or not the nonwoven fabric is short-circuited,
The pore diameter (μm) was measured. Pore diameter is ASTM-F-
The maximum pore diameter and the average pore diameter were determined by the bubble point method and the mean flow method described in 316.

To evaluate the ease of impregnation of the non-woven fabric with the electrolytic solution (initial wettability), the electrolytic solution absorption rate (cm after 30 minutes) was measured. The electrolyte absorption rate was set to 4 by taking three 2.5 cm x 20 cm test pieces from the length direction of each sample.
After pre-drying at 0 ± 5 ° C to make it less than the official moisture content, leave the sample in the standard greenhouse condition test room, and then weigh the sample at intervals of 1 hour or more, and the mass before and after that. It is assumed that the difference is within 0.1% of the subsequent mass (this state is called a water equilibrium state). Next, the test piece was placed on a horizontal tank of a predetermined height on a water tank containing a caustic potash (KOH) solution having a specific gravity of 1.3 (20 ° C) at 20 ± 2 ° C, and each sample was placed on this horizontal bar at its lower end. Align each other and fix with a pin to hang down each sample, and lower the horizontal bar so that the lower end of each test piece was immersed in the liquid for 5 cm, and after 30 minutes, the height at which the KOH solution rose due to the capillary phenomenon was measured. It was measured.

The evaluation of the liquid retaining property of the non-woven fabric is as follows.
The electrolytic solution retention rate (%) was measured. The electrolytic solution retention rate is obtained by collecting three test pieces each having a size of 10 cm × 10 cm from each sample and measuring the weight W (mg) when the water equilibrium state is established. Then, the test piece is spread and immersed in the KOH solution, left for 1 hour or more, taken out of the solution, and one corner of the test piece is clipped and hung down, and after 10 minutes, the weight W
₁ (mg) was measured, and the initial electrolytic solution retention rate (%) was calculated by the following formula 1.

[0047]

[Formula 1] Electrolytic solution retention rate (%) = (W ₁ −W) / W × 100

For the evaluation of the alkali resistance of the nonwoven fabric, the weight loss rate (%) after the alkali treatment was measured. The weight loss rate after alkali treatment corresponds to the electrolytic solution after measuring three weights W (mg) at the time of water equilibrium by collecting three test pieces of 10 cm × 10 cm from each sample. %
It is immersed in a KOH solution having a concentration and stored in an atmosphere of 80 ± 2 ° C. for 7 days. After that, the sample taken out was washed with water and dried until it reached the neutralization point, and the weight W ₂ (mg) at the time of reaching the water equilibrium state again was measured, and the weight loss rate (%) after the alkali treatment was calculated by the following formula 2. It was

[0049]

[Number 2] weight loss rate after alkali treatment (%) = (W-W 2)
/ W x 100

As shown in Examples 1 to 7 in Table 1, the non-woven fabric for an alkaline battery separator of the present invention has a strong tensile strength in the flow direction due to the strong entanglement of fibers, and is also excellent in alkali resistance. It also has various properties required as a separator, and is particularly excellent in wettability of electrolyte and liquid retention.

As shown in Examples 1 to 3 of Table 1, in the nonwoven fabric of the present invention, the tensile strength becomes stronger as the aspect ratio becomes larger as long as the fiber diameter is within the range of the present invention.

As shown in Examples 1 and 7 of Table 1,
The effect of the electrolyte solution wettability and liquid retention of the nonwoven fabric made of the metal ion-added acrylic fiber is almost the same when the monovalent metal ion is added and when the divalent metal ion is crosslinked. Further, the tensile strength and the like are almost the same when the monovalent metal ion is added and when the divalent metal ion is crosslinked.

As shown in Comparative Examples 1 to 2 and 4 to 5 in Table 2, even if the fiber diameter is within the range of the present invention, if the aspect ratio is smaller than 1000, it is difficult to entangle the fibers. , The tensile strength of the non-woven fabric becomes very weak. Further, when the aspect ratio exceeds 2000, the web made by the paper machine before the entanglement has many undisaggregated portions and binding of the fibers, which causes insufficient entanglement, and the tensile strength of the nonwoven fabric after the entanglement. The strength also becomes weak. Further, since the texture and surface quality are inferior, the maximum pore diameter cannot be controlled.

As shown in Comparative Example 3 in Table 2, even if the aspect ratio is within the range of the present invention, if the fiber diameter is smaller than 3 μm, the strength of the fiber itself is weak and the entanglement between the fibers is also unsatisfactory. It becomes sufficient, and the tensile strength of the nonwoven fabric becomes weak.

As shown in Comparative Example 6 in Table 2, in the case of a non-woven fabric made of an acrylic fiber in which a crosslinking bond is introduced into an acrylic fiber, which is hydrolyzed and is not crosslinked or added with a metal ion,
The initial wettability and liquid retention of the electrolytic solution are almost the same as those of the nylon dry-type nonwoven fabric, which is considerably inferior to the nonwoven fabric made of the metal ion-added acrylic fiber.

As shown in Comparative Example 7 of Table 2, the melt-spun type dry nonwoven fabric made of nylon has poor texture,
The basis weight must be increased, the air permeability and alkali resistance are remarkably inferior, and the wettability and liquid retention of the electrolytic solution are considerably inferior to the nonwoven fabric of the present invention.

[0057]

Since the nonwoven fabric of the present invention comprises the metal ion-added acrylic fiber, the fiber itself has high strength and alkali resistance and is also excellent in water absorption. Therefore, the electrolytic solution resistance and the electrochemical oxidation resistance are high, and the electrolytic solution is easily wetted and the retained amount is large. Furthermore, since the nonwoven fabric of the present invention produced from this fiber has a low basis weight and a uniform pore diameter, it is possible to obtain the same air permeability as the conventional one with a pore diameter smaller than the conventional one. Therefore, the thickness of the non-woven fabric can be further reduced and the weight can be reduced. As a result, according to the present invention, a non-woven fabric having various performances required for an alkaline battery separator, particularly excellent in initial wettability and electrolyte retention.
Further, it becomes possible to provide a method for producing the same, and it can be suitably used for an alkaline battery of a cordless device which requires high characteristics such as high capacity, long life and high reliability.

Claims (2)

[Claims] 1. At least one type of fiber having a diameter of 3 to 1
A short fiber of 0 μm and a ratio of the fiber length L to the fiber diameter D (L /
D, aspect ratio) is a non-woven fabric for an alkaline battery separator made of a metal ion-added acrylic fiber of 1000 to 2000. 2. The method for producing a non-woven fabric for an alkaline battery separator according to claim 1, wherein at least one or more types of short fibers having a fiber diameter of 3 to 10 μm and a ratio of the fiber length L to the fiber diameter D ( L / D, aspect ratio) 1000 to 20
A metal ion-added acrylic fiber of No. 00 is dispersed in water to form a slurry, the slurry is wet-paper-formed to form a web, and then the web is entangled by a hydroentangling method and then hot pressed. A method for manufacturing a nonwoven fabric for an alkaline battery separator.