JPH1140127A - Manufacture of battery separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a battery separator, which is capable of easily and safely introducing a functional group having hydrophilic property and ion exchange capacity. SOLUTION: Hydrolysis is applied to a polymer containing a monomer, having ester bonding as a polymerization component, thereby generating an acid group, and a battery separator consisting of nonwoven cloth has hydrophilic property and ion exchange functionality. This hydrolysis may be one of pre-fiber shaped of the polymer, post-fiber shaped, or fiber-shaped, and post-manufacture of nonwoven cloth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a separator for a battery, and more particularly to a method for manufacturing a separator for an alkaline secondary battery such as a nickel-cadmium battery, a nickel-zinc battery, and a nickel-hydrogen battery.

[0002]

2. Description of the Related Art At present, alkaline secondary batteries such as nickel-cadmium batteries, nickel-zinc batteries and nickel-hydrogen batteries have become widespread as driving power sources for not only small consumer devices but also large devices. Alkaline secondary batteries have characteristics such as high output, high energy density, long life, and high capacity, and are expected to be used in a wide range of industrial fields.

[0003] An alkaline secondary battery is composed of at least a positive electrode, a negative electrode, a battery separator, and an electrolytic solution.
A battery separator used in an alkaline secondary battery needs to have good affinity for an electrolytic solution (alkaline aqueous solution), and have excellent liquid absorption speed and liquid retention. Also,
It has alkali resistance and oxidation resistance that can withstand repeated charge and discharge for a long time, low internal resistance, and sufficient air permeability that does not hinder the transmission of gas and ions generated inside the battery. It is required to have performances such as a thin film, a uniform thickness, and excellent mechanical strength so as to cope with miniaturization of the battery.

As a battery separator satisfying the above characteristics, a nonwoven fabric is generally used. As fibers constituting the nonwoven fabric, polyester fibers, polyvinyl chloride fibers, polyvinyl alcohol fibers, polyacrylonitrile fibers,
Polyamide fibers, polyolefin fibers and the like are used. As the alkaline secondary battery, in the case of a nickel-cadmium battery which has been generally used in the past, a nonwoven fabric made of a polyamide fiber having an excellent affinity for an electrolytic solution has been often used.

[0005] In an alkaline secondary battery, when a charged battery is stored at a high temperature, a self-discharge phenomenon in which the capacity is reduced has become a problem. One possible cause is considered to be a reduction reaction of the positive electrode by a decomposition product of the battery separator. In particular, polyamide fibers have a drawback that they are easily hydrolyzed by an electrolytic solution, so that decomposition products are apt to be generated, and a self-discharge phenomenon is promoted. This phenomenon is more problematic in nickel-hydrogen batteries using a hydrogen storage alloy as the negative electrode.

[0006] For this reason, nonwoven fabrics containing polyolefin fibers as the main component, which are excellent in alkali resistance and oxidation resistance, have come to be predominantly used. However, polyolefin fibers have a low affinity for an electrolytic solution, so that it is necessary to perform a hydrophilic treatment such as a sulfonation treatment, a graft polymerization treatment of a hydrophilic monomer, a corona discharge treatment, and a surfactant immersion treatment.

[0007] Among the above-mentioned hydrophilization treatments, the sulfonation treatment and the graft polymerization treatment can introduce a functional group having an ion exchange ability such as a sulfonic acid group and a carboxylic acid group into the polyolefin fiber, and Is bonded to the fibers constituting the non-woven fabric, and thus has an advantage that hydrophilicity can be stably maintained for a long period of time.
It is considered that these functional groups capture impurities such as nitrogen compounds and polyvalent metal ions contained in the battery and improve battery characteristics. However, the sulfonation treatment
Since concentrated sulfuric acid is used, there are disadvantages that fibers are deteriorated, and that there are disadvantages such as poor working environment and high production cost. The graft polymerization treatment is a treatment in which a monomer and / or an oligomer having a carboxylic acid group is mainly bonded to a fiber constituting the nonwoven fabric. However, the monomer having a carboxylic acid group is highly irritating and deteriorates the working environment. There is. Further, in the graft polymerization treatment, there is a problem that a gel is easily generated, and it is difficult to obtain a uniform battery separator.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a battery separator which can easily and safely introduce a functional group having hydrophilicity and ion exchange ability.

[0009]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found the following invention.

(1) One monomer having an ester bond is
A method for producing a battery separator in which a nonwoven fabric using a fiber containing a polymer contained as a polymerization component as a component is subjected to a hydrolysis treatment to generate an acid group.

(2) One monomer having an ester bond is
A method for producing a battery separator in which a fiber containing a polymer contained as a polymerization component as one component is subjected to hydrolysis treatment to generate an acid group, and then the nonwoven fabric is produced using the fiber.

(3) One monomer having an ester bond is
A method for producing a battery separator in which a polymer contained as a component is subjected to hydrolysis treatment to generate an acid group, and then a fiber containing the polymer as a component is formed, and then a nonwoven fabric is produced using the fiber. .

In the method for producing a battery separator according to the present invention, a polymer containing a monomer having an ester bond as one polymerization component is subjected to a hydrolysis treatment to generate an acid group, and the nonwoven fabric battery separator is hydrophilically treated. And ion exchange ability. Since this polymer constitutes the fibers of the nonwoven fabric, the acid groups are firmly bonded to the fibers. Therefore, unlike hydrophilicity developed by, for example, corona treatment or surfactant immersion treatment, long-term hydrophilicity and ion exchange ability can be stably exhibited.

Further, since the hydrolysis treatment can be performed under mild conditions, the fibers do not deteriorate. Also,
It does not deteriorate the working environment.

Further, a monomer having an ester bond is
When the polymer contained as a polymerization component is hydrolyzed, an acid group is uniformly generated in the polymer, and thus there is an advantage that almost no gel is generated.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The polymer according to the method for producing a battery separator of the present invention contains a monomer having an ester bond as one polymerization component. Examples of the monomer having an ester bond include (meth) acrylic acid ester, itaconic acid monoester, maleic acid monoester, and fumaric acid monoester. The polymer according to the method for producing a battery separator of the present invention may contain one or more of these monomers having an ester group.

The polymer according to the method for producing a battery separator of the present invention is used for adjusting the strength, alkali resistance, oxidation resistance, degree of swelling with an electrolytic solution, etc. of the polymer in addition to the monomer having an ester bond. Monomers such as ethylene, propylene, butene, butadiene, vinyl alcohol, vinyl acetate, styrene, and isoprene can be copolymerized with the above-mentioned monomers having an ester bond.
Further, it may have a crosslinking point.

In the method for producing a battery separator according to the present invention, an acid group is formed by hydrolyzing the ester bond of a polymer having a monomer having an ester bond as one polymerization component. As a method of hydrolyzing an ester group, "4th Edition Experimental Chemistry Course 22 Organic Synthesis IV-Acids, Amino Acids and Peptides" (edited by The Chemical Society of Japan, 19)
1992, published by Maruzen), "New Experimental Chemistry Course 14: Synthesis and Reaction of Organic Compounds II" (edited by The Chemical Society of Japan, 199)
(Published for 7 years, published by Maruzen) etc. can be used.

In the method for producing a battery separator according to the present invention, the step of hydrolyzing the ester bond of the polymer having a monomer having an ester bond as one polymerization component includes the steps of: It may be carried out either after the formation or after the formation of the nonwoven fabric.

As a specific method of hydrolysis relating to the method for producing a battery separator of the present invention, a method of treating an ester bond in an acid or alkali atmosphere can be mentioned. In acid hydrolysis, mineral acids (hydrochloric acid, oxalic acid, sulfuric acid),
Acetic acid, trifluoroacetic acid, formic acid, paratoluenesulfonic acid, Lewis acid, boron trichloride, boron tribromide and the like can be used. In the alkaline hydrolysis, sodium hydroxide, potassium hydroxide, barium hydroxide, sodium carbonate, triethylamine, imidazole, amidine and the like are used. Water is generally used as the medium, but when the hydrophilicity of the polymer is low, an alcohol such as methanol or ethanol may be added to water, or the alcohol itself may be used as the medium. This reaction is preferably performed at 15 to 90 ° C. In the method for producing a battery separator of the present invention, it is preferable to carry out hydrolysis mainly using potassium hydroxide contained in the electrolytic solution.

The acid groups generated by the hydrolysis have the ability to impart hydrophilicity to the nonwoven fabric and to trap impurities such as metal ions and nitrogen compounds. Therefore, a battery using the battery separator obtained by the method for producing a battery separator of the present invention can not only suppress the self-discharge phenomenon but also improve the battery characteristics. The ion exchange amount of the battery separator obtained by the method for producing a battery separator of the present invention is 0.1 to 2.5 meq / g.
Is preferred.

The battery separator obtained by the method for producing a battery separator according to the present invention contains fibers obtained by hydrolyzing a polymer containing the above-mentioned monomer having an ester bond as one polymerization component. In addition to the fiber,
Polyester, polyolefin, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyamide, recycled fiber, semi-synthetic fiber, natural fiber,
Composite fibers, split fibers and the like can be added.

The nonwoven fabric according to the battery separator manufacturing method of the present invention can be manufactured by a dry papermaking method such as a card method, an air lay method, a spun bond method, a melt blow method or a wet papermaking method. The nonwoven fabrics obtained by these methods can be appropriately laminated.

The nonwoven fabric may be three-dimensionally entangled with the fibers by a hydroentanglement process, a needle punching process, or the like.
Alternatively, the fibers can be partially or wholly fused by heat adhesion treatment or the like to improve the mechanical strength. In order to obtain a nonwoven fabric having an appropriate level of air permeability required for a battery separator, it is preferable to perform a hydroentanglement treatment.

The hydroentanglement treatment which can be used in the method for producing a battery separator of the present invention is a method in which a non-woven fabric is placed in a single layer or a multi-layer on a support, and a water stream is jetted from above the non-woven fabric to form fibers. This is a confounding process. This hydroentanglement treatment may be performed from only one side of the nonwoven fabric or from both sides.

The fiber used in the method for producing a battery separator of the present invention preferably has a fiber diameter of 0.5 to 50 μm. When the fiber diameter is smaller than 0.5 μm, the nonwoven fabric becomes too dense, and the air permeability decreases. On the other hand, when the fiber diameter exceeds 50 μm, the specific surface area of the nonwoven fabric decreases, and the liquid retention of the electrolyte decreases. Further, the fiber length is preferably 1 to 100 mm.
When manufacturing nonwoven fabric by wet papermaking method, 1 to 50 μm
Is preferred. If the fiber length exceeds 50 μm, the fibers are entangled when the fibers are dispersed in water, making it difficult to obtain a uniform nonwoven fabric.

There are no particular restrictions on the cross-sectional shape of the fibers according to the method for producing a battery separator of the present invention, and a circular, elliptical, triangular, star, T-shaped, U-shaped, Y-shaped, leaf-shaped or the like may be used. it can. Further, fibers having voids can also be used.

[0029]

Hereinafter, the present invention will be described in detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist.

Example 1 Production of a nonwoven fabric by a dry papermaking method Using an ethylene-ethyl acrylate copolymer (ethyl acrylate content: 25% by weight, melt index: 250 g / 10 minutes), a resin temperature of 250 was obtained from an extruder. The resin was extruded at ℃, stretched and thinned by high-speed air to form a yarn, and the yarn was randomly accumulated to form a sheet. This sheet is passed between an embossing roll and a smoothing roll, embossed at 150 ° C., and has a basis weight of 25.
g / m ² of a meltblown nonwoven fabric was obtained.

Hydroentanglement treatment Two sheets of the above nonwoven fabric are laminated and transported on a porous support which is a 100 mesh stainless steel wire at a speed of 20 mm.
It was conveyed at m / min and subjected to a water entanglement treatment with a columnar water flow using the nozzle head shown in Table 1. Under the same conditions, the hydroentanglement process was performed also from the back surface. After the hydroentanglement, drying was performed at 130 ° C. using a suction through dryer, and the basis weight was 50 g /
It was obtained m ² of non-woven fabric.

[0032]

[Table 1]

Hydrolysis treatment The non-woven fabric after the hydroentanglement treatment was treated with 100 parts by weight of potassium hydroxide, 400 parts by weight of ethanol and 500 parts by weight of ion-exchanged water.
It was immersed in a homogeneous solution consisting of parts by weight and maintained at 70 ° C. for 3 hours to carry out a hydrolysis treatment. Subsequently, the battery was washed with ion-exchanged water and dried with a suction drum dryer at 120 ° C. to obtain a battery separator I.

Comparative Example 1 Production of nonwoven fabric by dry papermaking method Polypropylene (melt index 300 g / 10
), The resin was extruded from the extruder at a resin temperature of 250 ° C., stretched and thinned by high-speed air to form a yarn, and the yarn was randomly accumulated to form a sheet. Pass this sheet between the embossing roll and the smoothing roll,
Embossing was performed at 0 ° C. to obtain a melt-blown nonwoven fabric having a basis weight of 25 g / m ² .

Water entanglement treatment Two sheets of the above nonwoven fabric are laminated and transported on a porous support made of a 100 mesh stainless steel wire at a speed of 20 mm.
It was conveyed at m / min and subjected to a water entanglement treatment with a columnar water flow using the nozzle head shown in Table 1. Under the same conditions, the hydroentanglement process was performed also from the back surface. After the hydroentanglement, drying was performed at 130 ° C. using a suction through dryer, and the basis weight was 50 g /
m ² of battery separator i was obtained.

Example 2 Fabrication of Fiber An ethylene-methyl methacrylate copolymer (methyl methacrylate content: 20% by weight, melt index: 20 g / 10 min) was used as a sheath component, and polypropylene was used as a core component (melt index: 27 g / m 2). 10 minutes)
And spinning at a spinning temperature of 200 to 240 ° C. and a take-up speed of 500 m / min by a composite spinning facility equipped with two single-screw extruders and a circular nozzle for composite fibers having a hole diameter of 0.4 mm. A composite fiber having a 50/50 cross-sectional area ratio between the core and the core and a single-fiber fineness of 3.0 denier was obtained. This fiber is drawn to obtain a fiber A having a fiber length of 5 mm and a fineness of 1.0 denier.
I got

Hydrolysis treatment 200 parts by weight of the fiber A was kept in a homogeneous solution consisting of 50 parts by weight of potassium hydroxide and 650 parts by weight of ethanol at 80 ° C. for 3 hours, washed with ion-exchanged water, and squeezed.
To obtain a solid acid group-containing fibers A ₁ 55% by weight.

[0038] and those impregnated with nonionic surfactant 1 wt% solution prepared above fibers A ₁ 98 parts by weight of the nonwoven fabric by a wet paper making method, hot water soluble polyvinyl alcohol fibers (VPW103; manufactured by Kuraray) 2 parts by weight A nonionic surfactant 1% by weight impregnated with a solution,
After putting into water and stirring for 3 minutes with a high-speed mixer to disintegrate the fibers, the mixture was gently stirred in a chest equipped with a reciprocating rotary stirrer (Agitator, manufactured by Shimazaki Seisakusho). Next, a 0.1% by weight aqueous solution of polyacrylamide (viscosity agent) was promptly added, followed by gentle stirring to prepare a uniform slurry. Using the slurry, a non-woven fabric having a width of 50 cm and a basis weight of 50 g / m ² was produced using a round-mesh paper machine.

Water entanglement treatment The above nonwoven fabric is conveyed on a porous support made of a 100-mesh stainless steel wire at a speed of 20 m / min, and subjected to a water entanglement treatment with a columnar water flow using a nozzle head shown in Table 1. went. Under the same conditions, the hydroentanglement process was performed also from the back surface. After the hydroentanglement, drying was performed at 130 ° C. using a suction through dryer to obtain a battery separator II.

Example 3 100 parts by weight of a hydrolyzed ethylene-ethyl acrylate copolymer (ethyl acrylate content 25% by weight, melt index 20 g / 10 minutes) was added to 1900 parts by weight of toluene. Next, a homogeneous solution composed of 20 parts by weight of potassium hydroxide and 180 parts by weight of ethanol was added, and the mixture was kept at 80 ° C. for 3 hours to perform a hydrolysis treatment. A reprecipitation treatment was performed twice using an aqueous solution consisting of 3500 parts by weight of methanol and 1500 parts by weight of ion-exchanged water, and dried to obtain a polymer a having a carboxylic acid group.

Production of Fiber The polymer a (melt index 27 g / 10 min) obtained by the above hydrolysis treatment was used as a sheath component, and polypropylene (melt index 27 g / 10 min) was used as a core component.
), A composite spinning machine equipped with two single-screw extruders and a circular nozzle for composite fibers having a hole diameter of 0.4 mm,
Spinning was performed under the conditions of a spinning temperature of 200 to 240 ° C and a take-up speed of 500 m / min to obtain a conjugate fiber having a cross-sectional area ratio of the sheath and the core of 50/50 and a single-fiber fineness of 3.0 denier. This fiber was drawn to obtain a fiber B having a carboxylic acid group having a fiber length of 5 mm and a fineness of 1.0 denier.

Production of nonwoven fabric by wet papermaking method 98% by weight of the above fiber B was added to 1% by weight of a nonionic surfactant.
A solution impregnated with a solution and a solution obtained by impregnating 2 parts by weight of hot water-soluble polyvinyl alcohol fiber (VPW103; made by Kuraray) with a 1% by weight solution of a nonionic surfactant are put into water, and mixed with a high-speed mixer. After stirring for minutes for disintegrating the fibers, the fibers were gently stirred in a chest equipped with a reciprocating rotary stirrer (Agitator, manufactured by Shimazaki Seisakusho). Next, a 0.1% by weight aqueous solution of polyacrylamide (viscosity agent) was promptly added, followed by gentle stirring to prepare a uniform slurry. Using the slurry, a non-woven fabric having a width of 50 cm and a basis weight of 50 g / m ² was produced using a round-mesh paper machine.

Water entanglement treatment The above nonwoven fabric is conveyed on a porous support made of a 100-mesh stainless steel wire at a speed of 20 m / min, and subjected to a water entanglement treatment with a columnar water flow using a nozzle head shown in Table 1. went. Under the same conditions, the hydroentanglement process was performed also from the back surface. After the hydroentanglement, drying was performed at 130 ° C. using a suction through dryer to obtain a battery separator III.

Comparative Example 2 Production of a Nonwoven Fabric by a Wet Papermaking Method Splitting conjugate fiber having a fineness of 3 denier composed of polypropylene and an ethylene-vinyl alcohol copolymer, 0.2 denier (3.9 μm) after fiber division, and a fiber length of 10 mm 98
And a hot water-soluble polyvinyl alcohol fiber (VP)
W103; manufactured by Kuraray Co., Ltd.) 2 parts by weight impregnated with a 1% by weight solution of a nonionic surfactant were put into water, stirred for 3 minutes with a high-speed mixer to disintegrate the fibers, and then reciprocally rotated. The mixture was gently stirred in a chest equipped with a machine (Agitator, manufactured by Shimazaki Seisakusho). Next, a 0.1% by weight aqueous solution of polyacrylamide (viscosity agent) was promptly added, followed by gentle stirring to prepare a uniform slurry. Using the slurry, a non-woven fabric having a width of 50 cm and a basis weight of 50 g / m ² was produced using a round-mesh paper machine.

The above nonwoven fabric was transported on a porous support made of a 100-mesh stainless wire, and the speed was 20 m.
/ Min, and a water entanglement process was performed with a columnar water flow using the nozzle head of Table 1. Under the same conditions, the hydroentanglement process was performed also from the back surface. The nonwoven fabric after the hydroentanglement was dried at 130 ° C. using a suction drum dryer to obtain a battery separator ii.

Evaluation of Battery Separator The following characteristics were evaluated for battery separators I to III and i and ii, and the results are summarized in Table 2.

(1) Electrolyte absorption rate: A test piece of 2.5 × 18 cm was sampled from each battery separator, and was collected at 40 ± 5 ° C.
Preliminary drying is performed under the standard moisture content, and the test specimen is left in the test room at the standard temperature and humidity. Then, the test specimen is weighed at intervals of 1 hour or more. (A water equilibrium state). Next, the test pieces were hung down on a water tank containing a potassium hydroxide solution having a specific gravity of 1.3 at 20 ± 2 ° C., with the lower ends thereof aligned with a horizontal bar having a predetermined height, and the horizontal bars were lowered to lower each test piece. With the lower end of 5 mm immersed in the liquid, 30
After one minute, the height at which the potassium hydroxide solution rose by capillary action was measured.

(2) Electrolyte retention rate: A test piece having a size of 10 × 10 cm was sampled from each battery separator, and the weight when water equilibrium was established was defined as W (g). Next, the test piece was spread and immersed in the potassium hydroxide solution, allowed to stand for one hour or more, taken out of the solution, suspended at one corner of the test piece, and measured for weight W ₁ after 10 minutes. The electrolyte retention rate (%) was calculated from the following equation (1).

[0049]

## EQU1 ## Electrolyte retention rate (%) = [(W ₁ −W) / W] × 100

(3) Air permeability: Frazier air permeability (cc / cm ² / sec) was evaluated as an evaluation of the ease with which oxygen generated from the positive electrode side permeates through the battery separator to the negative electrode side.
c) was measured. Frazier air permeability is JIS-L-1
According to No. 096, the amount of air passing through the test piece was measured five times using a Frazier-type air permeability tester, and the average value was shown.

(4) Tensile strength: When wound around an electrode plate, the strength required for winding while pulling in the flow direction, and the longitudinal (paper flow direction) tensile strength (kg / 2 cm width).
Tensile strength was measured according to JIS-P-8113. Each battery separator was cut into a width of 2 cm and a length of 20 cm, and the load at the time of breaking was measured 10 times using a Tensilon measuring instrument (Horizon Tech; HTM-100). It measured and showed the average value.

(5) Battery self-discharge characteristics: A foamed nickel electrode as a positive electrode, a hydrogen storage alloy as a negative electrode, a potassium hydroxide solution having a specific gravity of 1.3 as an electrolyte, and battery separators I to III and i as separators , Ii were used to produce nickel-hydrogen batteries. One of these batteries
After the battery was charged at a constant current of 120% at C, the battery was discharged at a constant current of 1 C until the battery voltage reached 1.0 V, and the initial discharge capacity V ₁ was measured. Next, when charging at 120% constant current at 1 C, 6
After being left in a thermostat at 0 ° C. for 3 days, the battery was discharged at a constant current of 1 C, the discharge capacity V ₂ was measured, and the capacity storage rate (%) was obtained from the following equation (2).

[0053]

[Equation 2] Capacity storage rate (%) = (V ₂ / V ₁ ) × 100

(6) Ion exchange amount: 1 g of a test piece was collected from each battery separator and added to a 1N HCl solution.
After impregnation at 0 ° C. for 1 hour, the pH is adjusted to 6 to 7 with ion exchanged water.
Washed several times until Next, the test piece was dried for 2 hours with a blow dryer at 90 ° C., and cooled to room temperature.
₂ was measured to 0.01 mg. After the test piece after the weight measurement was impregnated with about 110 g of a 0.01 N KOH solution at 70 ° C. for 1 hour, the test piece was taken out, and the solution was cooled to room temperature. Approximately 100 g of the cooled solution was weighed to 0.01 g (S ₁ ), and the pH was measured at 0.02 g by using a pH meter (manufactured by Horiba Ltd.)
Neutralization titration was performed with N HCl solution. The blank solution was titrated in the same manner, and the potassium ion exchange amount was calculated from the following equation (3).

[0055]

(Equation 3)

[0056]

[Table 2]

The battery separators I to III obtained by the method for producing a battery separator of the present invention can be prepared without using a highly irritating harmful compound having an acid group in a molecule such as acrylic acid, and without using sulfone. A carboxylic acid group having hydrophilicity and ion exchange ability could be easily introduced without deteriorating the fiber as in the case of the chemical conversion treatment.

The battery separator I obtained by the method for producing a battery separator according to the present invention exhibits higher liquid absorption, liquid retention and potassium ion exchange compared to the battery separator i of the comparative example. The self-discharge phenomenon of the battery was suppressed. Further, the battery separators II to III obtained by the method for producing a battery separator of the present invention,
Compared to the battery separator ii of the comparative example, high liquid absorption,
It exhibited liquid retention and potassium ion exchange amount, and was able to suppress the self-discharge phenomenon of the battery.

[0059]

As described above, according to the method for producing a battery separator of the present invention, an acid group is generated by hydrolysis of an ester group, so that a good working environment can be obtained.
The nonwoven fabric can easily have hydrophilicity and ion exchange ability. The battery separator manufactured by the method for manufacturing a battery separator according to the present invention has an excellent effect that a self-discharge phenomenon can be suppressed efficiently and a battery exhibiting good battery characteristics can be provided.

Claims (3)

[Claims] 1. A method for producing a battery separator in which a non-woven fabric using a fiber containing a polymer containing a monomer having an ester bond as one polymer component as a component is subjected to hydrolysis treatment to generate an acid group. 2. A battery for producing a non-woven fabric by using a fiber comprising a polymer containing a monomer having an ester bond as one polymerization component as a component to generate an acid group by subjecting the fiber to hydrolysis treatment. Manufacturing method of separators for automobiles. 3. A polymer containing a monomer having an ester bond as one component is subjected to a hydrolysis treatment to generate an acid group, and then a fiber containing the polymer as one component is formed. A method for producing a battery separator for producing a nonwoven fabric using the same.