JP2000173573A - Separator for alkaline battery and manufacture of separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for an alkaline battery excellent in the electrolytic solution retaining property and internal pressure characteristic and offer a method to manufacture the separators. SOLUTION: A separator for an alkaline battery has polymerization layers of hydrophilic monomers and/or polymers at the outer surface of and inside a fiber sheet, wherein the polymerization amount (per unit volume) of the monomers and/or polymers near the outer surface of the sheet is no more than the corresponding value inside the sheet. The manufacturing method is such that the fiber sheet carrying the monomers and/or polymers is installed between a pair of electrodes positioned opposing (at least one of them carrying a dielectric substance at the opposing surface) in such a way that both electrodes (the dielectric substance, if applicable) are in contact with the outer surface, and electric discharge is generated in the voids in the sheet by impressing a voltage between the two electrodes, and thereby the monomers and/or polymers are polymerized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a separator for an alkaline battery and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a separator capable of holding an electrolytic solution has been arranged between these electrodes so that a positive electrode and a negative electrode of an alkaline battery can be separated from each other to prevent a short circuit, and that an electromotive reaction can be carried out smoothly. Have been.

[0003] Since the separator must not be attacked by an electrolytic solution such as potassium hydroxide, a separator made of polyolefin fiber having excellent alkali resistance can be suitably used. However, polyolefin-based fibers have a low affinity for the electrolytic solution, and thus have a drawback of poor retention of the electrolytic solution.

[0004] Therefore, as a means for solving such a drawback, a method of corona discharge treatment, a method of microwave discharge plasma treatment, a method of ultraviolet irradiation, and a method of electron beam irradiation are applied to a separator made of polyolefin fiber. A method of performing low-temperature plasma treatment or a method of irradiating radio waves has been proposed. However, in any of these methods, although the outer surface of the separator can be modified, the inside of the separator cannot be sufficiently modified, so that the distribution of the electrolytic solution varies. In other words, although the amount of the electrolyte was large near both surfaces of the separator, the amount of the electrolyte was small inside the separator, so that oxygen absorption during overcharge was poor, and only alkaline batteries with poor internal pressure characteristics could be manufactured. .

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an alkaline battery separator excellent in electrolyte solution retention and internal pressure characteristics, and a method for producing the same. With the goal.

[0006]

Means for Solving the Problems The separator for an alkaline battery of the present invention (hereinafter simply referred to as "separator") has a polymerized layer of a hydrophilic monomer and / or polymer on the outer surface and inside of a fiber sheet. And a hydrophilic monomer and / or in the vicinity of the outer surface of the fiber sheet.
Alternatively, the polymerization amount (per unit volume) of the polymer is equal to or less than the polymerization amount (per unit volume) of the hydrophilic monomer and / or polymer inside the fiber sheet. Since the polymer has a polymer layer of a hydrophilic monomer and / or polymer, the electrolyte has excellent retention properties. Since the polymerization amount of the hydrophilic monomer and / or polymer is large inside the separator, an alkaline battery having excellent internal pressure characteristics is provided. Can be manufactured.

[0007] In the method for producing a separator for an alkaline battery of the present invention, a pair of electrodes arranged so as to face each other (at least one of the electrodes carries a dielectric material on the opposing surface).
A fiber sheet carrying a hydrophilic monomer and / or polymer is arranged so that both of the electrodes (dielectric if a dielectric is carried) and the outer surface are in contact with each other, and a voltage is applied between the two electrodes. Is applied to generate a discharge in the internal space of the fiber sheet to polymerize the hydrophilic monomer and / or polymer. According to this method, the above separator can be easily manufactured.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a fiber sheet as a base of the separator of the present invention, for example, there are a woven fabric, a knitted fabric, a nonwoven fabric, and a composite thereof. In the present invention, a fiber sheet may be included, and a film, a porous film (for example, a perforated film, a film having a concavo-convex structure, or the like), or a composite integrally formed with a foam, etc. good. Among these, it is preferable that the fibers include a nonwoven fabric that can arrange fibers three-dimensionally and that has more excellent retention of the electrolyte. As the nonwoven fabric, for example, a dry nonwoven fabric (eg, a spunbonded nonwoven fabric, a meltblown nonwoven fabric, a needle-punched nonwoven fabric, a binder-bonded nonwoven fabric, a fiber-bonded nonwoven fabric, a hydroentangled nonwoven fabric), a wet nonwoven fabric, or a composite thereof can be used.

[0009] The fiber constituting the fiber sheet preferably contains a polyolefin-based fiber so as to have excellent alkali resistance, and more preferably comprises only a polyolefin-based fiber. Examples of the suitable polyolefin include, for example, ethylene resins (for example, low-density polyethylene, medium-density polyethylene, high-density polyethylene,
Linear low-density polyethylene, a copolymer of ethylene and methacrylic acid and / or acrylic acid, a copolymer of ethylene and vinyl alcohol, and a propylene-based resin (for example, polypropylene, propylene and one or more other types of A copolymer with a vinyl compound), a butene resin (for example, polybutene, a copolymer of butene with one or more other vinyl compounds), a methylpentene resin (polymethylpentene, methylpentene and one other type) Copolymers with the above vinyl compounds).

[0010] The fiber diameter of the fibers constituting the fiber sheet is not particularly limited, but is suitably about 0.1 to 30 µm. Note that the smaller the fiber diameter, the smaller the internal voids formed inside the fiber sheet and the better the retention of the electrolytic solution. Therefore, the diameter is more preferably about 0.1 to 20 μm. When the cross-sectional shape of the fiber is non-circular, the diameter when the fiber cross-section is converted to a circular cross-section is regarded as the fiber diameter of the fiber.

[0011] The fibers constituting the fiber sheet may include those having various characteristics. For example, (1) a fiber having a non-circular fiber cross-sectional shape capable of improving the retention of an electrolytic solution with a larger surface area, and (2) when forming an electrode plate group, burr of the electrode plate penetrates through the separator. A tensile strength (measured by JIS L 1015 (chemical fiber staple test method)) of 5 g / d or more (preferably 7 g / d or more, more preferably 9 g / d) which can prevent short-circuiting between the electrode plates. d) or more, and (3) an adhesive fiber capable of improving tensile strength and softness. In the case where ultrafine fibers are generated from splittable fibers capable of generating ultrafine fibers having a fiber diameter of about 5 μm or less, undivided splittable fibers may be included.

Although the surface density of the fiber sheet is not particularly limited, it is preferably 30 to 100 g / m ² so that the capacity of the battery can be increased without insufficient tensile strength. , And more preferably 40 to 80 g / m ² . Further, the thickness is preferably about 0.1 to 0.3 mm. Further, the fiber sheet preferably has a porosity of 95% or less and an average pore diameter of 100 μm or less so as to be excellent in retention of the electrolytic solution. Preferably, it is 200 ml / cm ² · second. The average pore diameter can be measured by, for example, a Coulter porometer II (manufactured by Coulter), and the air permeability is determined according to JIS L 1096 (6.27.1).
A (Fragile method)).

[0013] The separator of the present invention has a polymerized layer of a hydrophilic monomer and / or polymer on the outer surface and inside of the above-mentioned fiber sheet. The “outer surface” means the surface of the fiber sheet that can come into contact with the virtual plane, and the “inside” means a portion other than the outer surface, in which fibers exist. Therefore, the polymerized layer is formed on the fiber surface constituting the outer surface and the fiber surface constituting the inside of the fiber sheet.

[0014] The monomer and / or polymer constituting the polymer layer is made of a hydrophilic material so that the separator can be made hydrophilic. For example, a monomer or polymer containing an oxygen-containing functional group such as a hydroxyl group, a carboxyl group, an ether group, a sulfonyl group, a phosphonyl group, a monomer or polymer containing a nitrogen-containing functional group such as an amino group, an imino group, or an acid amide group, or a sulfone It consists of a monomer or polymer containing a sulfur-containing functional group such as an acid group. More specifically, maleic acid compounds (eg, maleic anhydride, dimethyl maleate, etc.), itaconic acid compounds (eg, itaconic acid, dimethyl itaconate, etc.), acrylamide compounds (eg, acrylamide, 2-acrylamide-2- Methyl propane sulfonic acid, etc.), acrylic acid compounds (eg, acrylic acid, methyl acrylate, etc.), methacrylic acid compounds (eg, methacrylic acid, methyl methacrylate, 2-hydroxyethyl methacrylate, etc.), allyl compounds (eg, diallylamine, allyl) Alcohol, etc.) or polyol (for example, polyoxymethylene, polyethylene glycol, polypropylene glycol, etc.), polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyacrylic acid. De, polymethacrylic amide, polyethylene oxide, polyethylene imine, polyvinyl pyrrolidone, polystyrene sulfonate, a polymer consisting of polystyrene ammonium salt or the monomer, the polymer, such as may be used. Of these, polyols are preferred, and polyethylene glycol is particularly preferred.

[0015] The separator of the present invention has a polymerized layer of the hydrophilic monomer and / or polymer as described above. However, the polymerization amount of the hydrophilic monomer or polymer near the outer surface of the fiber sheet (per unit volume) ) Is equal to or less than the polymerization amount (per unit volume) of the hydrophilic monomer or polymer inside. Therefore, even in the inside of the separator because it is excellent in the retention of the electrolyte,
An alkaline battery using the separator of the present invention has excellent internal pressure characteristics. Furthermore, since a hydrophilic monomer or polymer is polymerized almost uniformly in the entire fiber sheet, and the air permeability is excellent, the generated gas is excellent in permeability. The “near the outer surface” refers to the outer surface and a part of the inner part continuous with the outer surface.

[0016] The separator of the present invention is excellent in hydrophilicity because a hydrophilic monomer or polymer is strongly polymerized even inside the separator. For example, the liquid absorption height (A) specified below before performing the boiling test specified below and the liquid absorption height (B) specified below after performing the boiling test specified below are: , B / A ≧ 0.5 (preferably B / A ≧ 0.6, more preferably B / A ≧ 0.
7, more preferably B / A ≧ 0.75), so that the hydrophilicity does not decrease even when charging and discharging are performed at a high temperature. (1) Liquid absorption height; Alkaline battery separator (width: 25
mm) from one end to 5 mm at a temperature of 20 ° C. ± 2.
Vertically immersed in an aqueous solution of potassium hydroxide having a specific gravity of 1.3 ° C., and after 30 minutes, the height of the aqueous solution of potassium hydroxide was measured, and this was taken as the liquid absorption height. (2) Boiling test; Boil the alkaline battery separator in pure water for 30 minutes, then dry

Further, an alkaline battery actually using the separator of the present invention was subjected to the following charge / discharge cycles for 600 cycles, and then the battery was disassembled, and the weight ratio of the positive electrode, the negative electrode and the electrolyte held by the separator was determined. By calculation, 15% or more (preferably 17%) of the total electrolyte
Is excellent in holding property. Charge / discharge, in which a cycle of charging at a charge rate of 1 C for 1.5 hours (150%) at a temperature of 20 ° C. and discharging at a discharge rate of 1 C until a final voltage of 0.8 V is achieved.

[0018] Since the separator of the present invention is excellent in the retention of the electrolytic solution inside the separator, an alkaline battery using the separator of the present invention can be charged and discharged as described above in 40 minutes.
Even after 0 cycles, the internal pressure is 2kgf / c
It has excellent internal pressure characteristics of not more than m ² (preferably not more than 1.5 kgf / cm ² ).

Further, since the separator of the present invention is excellent in the retention of the electrolytic solution, the above-described charge / discharge (temperature of 20 ° C.) is 6 times.
80% of the initial capacity, even after performing 00 cycles
The above capacity (preferably at least 85% of the initial capacity, more preferably at least 90% of the initial capacity) is maintained. At a temperature of 60 ° C., the same charge / discharge as described above was performed for 4 times.
70% of the initial capacity, even after performing 00 cycles
Or more (preferably at least 75% of the initial capacity, more preferably at least 80% of the initial capacity, most preferably at least 85%)
To maintain the capacity.

Since the separator of the present invention is excellent in electrolyte retention and internal pressure characteristics, for example, primary batteries such as alkaline manganese batteries, mercury batteries, silver oxide batteries, air batteries, etc.
It can be suitably used as a separator of a secondary battery such as a nickel-cadmium battery, a silver-zinc battery, a silver-cadmium battery, a nickel-zinc battery, and a nickel-hydrogen battery.

Next, a method for manufacturing the separator of the present invention will be described.

First, a fiber sheet carrying a hydrophilic monomer and / or a polymer (hereinafter, referred to as a “supported fiber sheet”) is placed between a pair of electrodes arranged so as to face each other. (If any), the outer surface is in contact with both. As described above, since both electrodes (the dielectric when a dielectric is supported) are in contact with the outer surface of the supported fiber sheet, it is possible to generate a discharge in the internal space of the supported fiber sheet. . In addition, at least one electrode carries a dielectric on the facing surface, and preferably both electrodes carry the dielectric on the facing surface, so that a stable discharge can be generated without spark discharge or the like. Can be.

[0023] The carrier fiber sheet is obtained, for example, by spraying or applying the monomer or polymer to the fiber sheet or dipping the fiber sheet in the monomer or polymer liquid when the monomer or polymer is a liquid. When the monomer or polymer is a solid, it is dissolved or suspended in a suitable solvent, and the solution is sprayed or applied to the fiber sheet, or only the solvent is removed after the fiber sheet is immersed in the solution. By doing so, a monomer or polymer can be obtained by being supported on a fiber sheet.

It is preferable to use a water-soluble monomer or polymer which is easy to handle in the production process, but in the present invention, it is preferable to use a highly hydrophobic polyolefin-based fiber as a fiber constituting the fiber sheet. Therefore, it may be difficult to uniformly support the monomer or polymer on such a fiber sheet. In such a case, if the discharge treatment is performed by a discharge treatment apparatus as described below and the pretreatment is performed, the inside of the fiber sheet can be uniformly and sufficiently treated, and a sufficient amount of the monomer or polymer can also be treated inside the fiber sheet. Can be supported. The discharge processing conditions may be the same as those described below or may be different.

The polymerized layer of the present invention is preferably made of a polymerized polyethylene glycol, and it has been experimentally confirmed that the polyethylene glycol preferably has a molecular weight of 200 to 2,000. If the molecular weight is less than 200 or exceeds 2,000, it is difficult to form a polymerized layer, and improvement in hydrophilicity cannot be expected much.
A more preferred molecular weight is from 250 to 2,000. In addition,
The molecular weight can be calculated from the number of hydroxyl groups per unit weight by measuring the amount of hydroxyl groups by the pyridine phthalic anhydride method.

FIGS. 1 to 6 are schematic cross-sectional views of a discharge treatment apparatus that can be used in the present invention.

The discharge processing apparatus shown in FIG. 1 has a flat electrode 1a carrying a dielectric 2a and a flat electrode 1b carrying a dielectric 2b.
Are disposed so as to face each other.
The fiber sheet 5 is arranged such that both a and 2b are in contact with the outer surface of the fiber sheet 5. Since the dielectrics 2a and 2b carried on the flat electrodes 1a and 1b are larger than the surfaces on the opposite sides of the flat electrodes 1a and 1b, it is possible to prevent spark discharge easily occurring between the flat electrodes 1a and 1b. it can. One of the flat electrodes 1a is connected to an AC power supply 4 and the other flat electrode 1b is grounded so that an AC voltage can be applied between the flat electrodes 1a and 1b. In addition, contrary to FIG.
a may be grounded, and the other flat electrode 1b may be connected to an AC power supply.

The material constituting the flat electrodes 1a and 1b is not particularly limited, but has a specific resistance of 10 ³ Ω · cm.
Or less (preferably less 10 ⁰ Ω · cm) can be used a conductor of, for example, a metal (e.g., stainless steel, aluminum, tungsten, etc.), conductive metal oxides, carbon, or metal powder or carbon powder such as For example, conductive rubber obtained by compounding the above conductor and rubber can be used.

When the opposed surfaces of the flat electrodes 1a and 1b are curved from the periphery to the side walls, discharge occurs between the side walls of the flat electrodes 1a and 1b and the dielectrics 2a and 2b. Is less likely to occur, and damage to the dielectric can be suppressed, which is preferable.

[0030] Further, in such a discharge processing apparatus, since discharge is generated only in a portion sandwiched between the electrodes, discharge can be generated only in a desired portion.
For example, if a grid electrode is used as one of the electrodes, a discharge can be generated in a grid corresponding to the shape of the electrode. Therefore, since a portion having a high hydrophilicity and a portion having a low hydrophilicity can be formed, selective permeation of the generated gas can be promoted.

The dielectrics 2a and 2b in FIG. 1 cover the entire opposing surfaces of the plate-like electrodes 1a and 1b so as to stably generate a discharge without generating a spark discharge or the like. In addition, each of the flat electrodes 1a, 1b is controlled so that no spark discharge occurs between the flat electrodes 1a, 1b.
And protrudes from the opposing surfaces of the plate electrodes 1a and 1b.

The dielectrics 2a and 2b are preferably non-porous as a whole, but may partially include a porous portion. In particular, when a dielectric including a porous portion is used on the surface on the opposite side, a discharge is generated also in the porous portion of the dielectric, so that the discharge can be applied to the outer surface of the fiber sheet 5. If the porous portion is continuous in the thickness direction of the dielectric, spark discharge may occur in the porous portion. Therefore, it is preferable that the porous portion is not continuous in the thickness direction.

[0033] Materials constituting the dielectrics 2a and 2b include, for example, glass, ceramic (for example, alumina), rubber (for example, synthetic rubber such as silicone rubber, chloroprene rubber, butadiene rubber, and natural rubber).
Alternatively, a thermoplastic resin (for example, polytetrafluoroethylene, polyester, or the like) can be used. The thickness of the dielectric is not particularly limited,
It is preferably about 0.05 mm to 5 mm. If the thickness of the dielectric is less than 0.05 mm, the mechanical strength is reduced, and dielectric breakdown is likely to occur. If the thickness exceeds 5 mm, a high voltage is required for discharging.

The discharge processing apparatus shown in FIG. 2 has five small cylindrical electrodes 1a and 1 as electrodes carrying dielectrics 2a and 2b.
This is exactly the same as FIG. 1 except that two large cylindrical electrodes 1b are used. When the columnar electrode is used as described above, discharge can be continuously generated without damaging the fiber sheet.

The discharge processing apparatus of FIG. 3 is exactly the same as that of FIG. 1 except that a belt-shaped electrode 1a and one columnar electrode 1b are used as electrodes carrying dielectrics 2a and 2b. This discharge treatment device can also generate discharge continuously without damaging the fiber sheet.

The discharge processing apparatus of FIG. 4 is exactly the same as that of FIG. 1 except that five cylindrical electrodes 1a and a belt-like electrode 1b are used as electrodes carrying dielectrics 2a and 2b. This discharge treatment device can also generate discharge continuously without damaging the fiber sheet.

In the discharge treatment apparatus shown in FIG. 5, not only a dielectric (hereinafter referred to as "opposite dielectric") is carried on the surface on the opposite side of each flat electrode, but also a dielectric is provided on the side wall of each flat electrode. Except that a body (hereinafter, referred to as a “sidewall dielectric”) is supported, it is exactly the same as FIG. Since this discharge processing device carries the side wall dielectrics 3a and 3b, it is possible to prevent discharge between the side walls of the plate electrodes 1a and 1b and the opposing dielectrics 2a and 2b. The material forming the side wall dielectrics 3a and 3b is the opposite dielectric 2a,
It can be made of the same material as 2b. Further, the opposing dielectrics 2a, 2b and the sidewall dielectrics 3a, 3b need not be made of the same material, but may be made of different types of materials. Further, the opposing dielectrics 2a, 2b
And the side wall dielectrics 3a and 3b are separated from each other,
It may be in an integrated state.

[0038] The discharge processing apparatus of FIG.
It is exactly the same as FIG. 5 except that a belt-shaped thing is used as b. This discharge treatment device can prevent discharge between the side walls of each of the flat electrodes 1a and 1b and each of the opposed dielectrics 2a and 2b, and continuously generates discharge without damaging the fiber sheet. be able to.

In a state where the outer surface of the supporting fiber sheet is disposed between the pair of electrodes facing each other in such a manner that the outer surface of the supporting fiber sheet is in contact with both electrodes (dielectric material when a dielectric material is supported), An AC voltage is applied to generate a discharge in the internal voids of the fiber sheet to polymerize the hydrophilic monomer or polymer.

The state in which the outer surface of the supported fiber sheet is disposed between the pair of opposed electrodes so that the outer surface is in contact with both electrodes means that the electrode (dielectric if a dielectric is supported) and the fiber sheet Are brought into close contact with each other, and substantially no space is formed between the electrode (the dielectric if a dielectric is carried) and the outer surface of the fiber sheet. In such a state, discharge can be efficiently generated in the internal gap of the fiber sheet.

The AC voltage applied between the electrodes cannot be limited because it depends on the distance between the electrodes (including the dielectric) and the type of gas.
It is preferably at least 5 KVp, more preferably at least 0.5 KVp. The unit “KVp” indicates a voltage difference from the maximum value peak of the AC voltage to 0. On the other hand, the upper limit of the AC voltage is not particularly limited as long as the voltage does not cause damage to the fiber sheet.

The frequency of the AC voltage is 0.1 kHz to 100
KHz is preferred. If the frequency is less than 0.1 KHz, the discharge efficiency tends to decrease,
When z is exceeded, the dielectric sheet may be broken by being heated by dielectric heating.
KHz to 50KHz, more preferably 1KHz to 50K
Hz.

The waveform of the applied voltage may be, for example, a sine wave, a triangular wave, a rectangular wave, or a pulse wave. Among these, the pulse wave is preferable because it suppresses heat generation and spark discharge and hardly damages the fiber sheet. In particular,
When a discharge is generated while moving the fiber sheet using the discharge processing apparatus as shown in FIG. 5, a pulse wave having a fast rise (1 microsecond or less) is generated so that damage to the fiber sheet can be suppressed. It is suitable. Therefore, it is preferable to use an impulse power supply or a pulse power supply. Note that the rise time refers to a time from when the reference voltage reaches 90% of the first peak voltage. Also, the polarity of the applied voltage is not particularly limited, and a unipolar voltage or a bipolar voltage can be used, but the bipolar voltage is used because of high processing efficiency. Is preferred.

As shown in FIG. 1, FIG. 3, FIG. 5, and FIG. 6, when a discharge treatment is performed by sandwiching a fiber sheet between a pair of electrodes in a certain area, the discharge treatment can be performed uniformly, and the arc discharge can be performed. It is preferable that the output per 1 cm ² is 0.01 to 5 W so as not to cause the above. FIG.
As shown in FIG. 4 and FIG. 4, when performing a discharge treatment by sandwiching a fiber sheet linearly between a pair of electrodes, the output per 1 cm is preferably 0.1 to 9 W, and 0.1 to 6 W. Is more preferred. In the case where the discharge treatment is performed while the fiber sheet is sandwiched linearly and a plurality of electrodes are used, the above output means a value per electrode.

The application of such an AC voltage can be carried out at atmospheric pressure in the presence of oxygen (for example, in the presence of air), or at atmospheric pressure and in the absence of oxygen (for example, helium). , In the presence of an inert gas such as argon), but from the viewpoint of workability, the former is preferably carried out under atmospheric pressure and in the presence of oxygen. In addition, you may implement under reduced pressure. In the case where the process is performed in the absence of oxygen, for example, a unit capable of supplying an inert gas (eg, a pipe) or a unit capable of retaining the inert gas (eg, a chamber) is provided. Is preferred.

The application time of the AC voltage in the present invention, that is, the time during which the voltage is applied between the electrodes and the discharge is generated in the internal space of the fiber sheet is not particularly limited. When carried out below, it is preferably from 0.5 to 10 minutes, more preferably from 2 to 5 minutes.

As described above, the alternating voltage is applied between the electrodes to generate a discharge in the internal space of the fiber sheet, so that the electrode is brought into contact with the electrode of the fiber sheet (or a dielectric material if a dielectric material is carried). The outer surface tends to be less susceptible to discharge. However, since the area of the outer surface of the fiber sheet is very small in view of the total surface area of the fibers constituting the inside of the fiber sheet, the outer surface and the inside of the fiber sheet are substantially treated, and a polymerized layer of a monomer or a polymer is formed. It is thought to be formed. As described above, since the degree of electric discharge treatment is different between the outer surface and the inside of the fiber sheet, the polymerization amount of the monomer or polymer near the outer surface of the fiber sheet is equal to or less than the polymerization amount in the inside.

The above-mentioned method is a method in which a discharge is caused to act on a supported fiber sheet. After a discharge is caused to act on a fiber sheet which does not carry a hydrophilic monomer or polymer by the same method as described above, the hydrophilic sheet is subjected to a discharge. Even when the fiber sheet is brought into contact with the monomer or the polymer, the polymerization amount (per unit volume) of the hydrophilic monomer and / or the polymer in the vicinity of the outer surface of the fiber sheet becomes smaller than the polymerization amount of the hydrophilic monomer and / or the polymer inside the fiber sheet. The same amount or less (per unit volume) of separator can be manufactured.

Hereinafter, Examples of the separator of the present invention will be described, but the present invention is not limited to the following Examples.

[0050]

(Example 1) As a fiber sheet, a dividable fiber composed of polypropylene and high-density polyethylene was wet-processed as a fiber sheet, and then entangled with a water flow, and at the same time, the dividable fiber was made of ultrafine polypropylene fiber (fiber diameter: 3.6 μm). , Approximately triangular cross section) and high-density polyethylene ultrafine fibers (fiber diameter: 3.
Nonwoven fabric (porosity: 5 μm, substantially triangular cross section)
70%, average pore diameter: 7 μm, thickness: 0.2 mm, areal density: 60 g / m ² ). The air permeability when three nonwoven fabrics were laminated was 5.56 ml / cm ² · sec.

As a discharge treatment device, a non-porous polytetrafluoroethylene sheet (size: 180 mm × 350) is used as opposed dielectrics 2a and 2b as shown in FIG.
mm, thickness: 0.1 mm), and a plate-like electrode 1a, 1b made of a stainless steel plate (150 mm x 300 mm) was provided so as to face each other. In addition, one flat electrode 1a was connected to the sine wave power supply 4, and the other flat electrode 1b was grounded.

Next, the opposing dielectrics 2a, 2b of this discharge device
In between, a laminated body of three nonwoven fabrics is arranged so that both opposing dielectrics 2a and 2b and both outer surfaces of the laminated body are in contact with each other, and the plate-shaped electrode 1a is placed under atmospheric pressure and in the presence of air. , 1
By applying a sine wave AC voltage (AC voltage: 10 KVp, frequency: 20 KHz, output: 800 W) for 3 minutes between b, discharge was generated in the internal voids of the laminate, and the laminate was subjected to a hydrophilic treatment.

Next, the laminate subjected to the hydrophilic treatment was immersed in an 8% aqueous solution of polyethylene glycol (molecular weight: 1000). Next, the laminate was pulled up, squeezed so that a three-fold amount of polyethylene glycol aqueous solution adhered to the weight of the laminate before immersion, and then dried at 60 ° C. And
After the laminate having polyethylene glycol adhered thereto was subjected to electric discharge under the same conditions as in the above-mentioned hydrophilization treatment, the laminate was cooled to 6
Washed twice with warm water of 0 ° C. for 30 minutes and dried. When this laminate was separated into nonwoven fabrics and weighed, the weight of the nonwoven fabric existing at the center increased by 5 g / m ² , while the weight of the nonwoven fabric existing on both surfaces increased by 4 g / m ^2. 0.7 g / m ^2, indicating that more polyethylene glycol was polymerized inside than near the surface.

(Example 2) As a fiber sheet, a dividable fiber composed of polypropylene and high-density polyethylene was wet-processed and then entangled by a water flow, and at the same time, the dividable fiber was made of ultrafine polypropylene fiber (fiber diameter: 3.6 μm, High-density polyethylene ultrafine fiber (fiber diameter: 3.5)
μm, approximately triangular cross section) (porosity: 8)
0%, average pore size: 9 μm, air permeability 15.3 ml / cm ²
・ Second, thickness: 0.3 mm, area density: 75 g / m ² ).

Next, the same discharge treatment device as that of the first embodiment is used, and is disposed between the opposed dielectrics 2a and 2b of the discharge device such that both outer surfaces of the nonwoven fabric are in contact with the opposed dielectrics 2a and 2b. Then, under atmospheric pressure and in the presence of air, a sine wave AC voltage (AC voltage: 3 KV) is applied between the plate electrodes 1a and 1b.
(p, frequency: 12.5 KHz, output: 800 W) was applied for 3 minutes to generate a discharge in the internal voids of the nonwoven fabric, and the nonwoven fabric was hydrophilized.

Next, the nonwoven fabric subjected to the hydrophilic treatment was used in Example 1.
In exactly the same manner as described above, the separator of the present invention was produced by immersion in an aqueous solution of polyethylene glycol, adjustment of the amount of the aqueous solution of polyethylene glycol, drying, discharge treatment, washing and drying. This separator had an 8% increase in weight (amount of polyethylene glycol).

(Comparative Example 1) A nonwoven fabric (having no hydrophilic treatment) formed in the same manner as in Example 2 was immersed in a polyethylene glycol aqueous solution, the amount of the polyethylene glycol aqueous solution attached was adjusted, and After drying, a nonwoven fabric to which polyethylene glycol was attached was manufactured. Next, the nonwoven fabric to which the polyethylene glycol is adhered is subjected to a discharge treatment by a conventional glow discharge device (pressure: 1 torr, frequency: 13.56 MHz, output per unit area: 0.1.
5 W / cm ² ) for 1 minute. Next, the discharge-treated nonwoven fabric was washed twice with warm water at 60 ° C. for 30 minutes and dried to produce a separator. This separator had an 8% increase in weight (amount of polyethylene glycol).

(Comparative Example 2) A nonwoven fabric adhered to polyethylene glycol and produced exactly in the same manner as in Example 2 (no discharge treatment was performed after polyethylene glycol was adhered) was used as a separator. This separator had an 8% increase in weight (amount of polyethylene glycol).

(Comparative Example 3) A nonwoven fabric subjected to only the hydrophilization treatment in the same manner as in Example 2 (no adhesion of polyethylene glycol and no discharge treatment after adhesion of polyethylene glycol) was used as a separator.

(Battery Life Test at Room Temperature) The separators of Example 2 and Comparative Examples 1 to 3 were used as separators, nickel hydroxide was charged into a foamed nickel support as a positive electrode, and a hydrogen storage alloy (mesh metal MmNi) was used as a negative electrode. ₅ type)
Was filled in a foamed nickel support, and 5 g of a 7.2N potassium hydroxide / 1N lithium hydroxide aqueous solution was used as an electrolytic solution to form a cylindrical paste-paste sealed nickel-metal hydride battery (battery capacity: 1750 mA).
h) was prepared. The separator of Example 2 had good absorbability of the electrolytic solution and was excellent in workability during battery production.

Next, the battery was charged in a constant temperature bath at 20 ° C. at a charging rate of 1 C for 1.5 hours (150%), and a final voltage of 0.1% was applied.
The battery was activated (initial stage) by performing five cycles of charging and discharging with one cycle of discharging at a discharge rate of 1 C until reaching 8 volts (initial stage). Next, the same charge / discharge as described above was performed for 600 cycles in a thermostat at 20 ° C. The result of calculating the ratio of the capacity to the initial capacity at that time was as shown in Table 1. Thus, the separator of the present invention was excellent in capacity retention.

[0062]

【table 1】

(Battery Life Test at High Temperature) 400 cycles of charge / discharge were performed in exactly the same manner as the above (battery life test at room temperature) except that the test was carried out in a constant temperature bath at 60 ° C. The result of calculating the ratio of the capacity to the initial capacity at that time was as shown in Table 1. Thus, the separator of the present invention was excellent in capacity retention even at high temperatures.

(Retention of Electrolyte Solution) After performing the above (battery life test at room temperature), the battery was disassembled, immediately separated into a positive electrode, a negative electrode and a separator, and the weight of each was measured. Next, each was dried to remove water, and then the weight was measured. The total of the weight reduction was regarded as the total electrolyte weight, and the percentage of the electrolyte held in the separator was calculated. The results were as shown in Table 1. Thus, it was found that the separator of the present invention was excellent in the retention of the electrolytic solution.

(Absorbing height before and after boiling) Example 2 and Comparative Example 1
Of the separator (width: 25 mm) from one end to 5 mm is vertically immersed in an aqueous potassium hydroxide solution having a specific gravity of 1.3 maintained at a temperature of 20 ° C. ± 2 ° C. The rising height of the aqueous solution was measured and defined as the liquid absorption height (liquid absorption height before boiling).

Further, the separators of Example 2 and Comparative Examples 1 to 3 were boiled in pure water for 30 minutes and dried, and then the height of the aqueous potassium hydroxide solution was measured in the same manner as described above.
This was taken as the liquid absorption height (liquid absorption height after boiling). These results were as shown in Table 1. Thus, it has been found that the separator of the present invention can produce a long-life battery in which the hydrophilicity does not decrease even at a high temperature.

(Measurement of Battery Internal Pressure) After connecting the internal pressure sensor to the cylindrical paste-paste sealed nickel-metal hydride battery manufactured in the same manner as in the above (Battery life test at room temperature), the above-mentioned (Battery life test at room temperature) After 400 cycles of charge / discharge were carried out in the same manner as described above, the maximum value of the battery internal pressure at the time of overcharge was measured. The results were as shown in Table 1. Thus, the separator of the present invention had excellent internal pressure characteristics.

(Serial Change of Separators) The separators of Example 2 and Comparative Examples 1 to 3 were left in a room at a temperature of 20 ° C. and a humidity of 65% for 60 days. Thereafter, the height of the aqueous potassium hydroxide solution was measured in the same manner as described above (absorbing height before and after boiling). The results were as shown in Table 1. Thus, it was found that the separator of the present invention was stable in quality without deterioration over time.

(Example 3) A nonwoven fabric subjected to a hydrophilic treatment in the same manner as in Example 2 was treated with 8% polyethylene glycol (molecular weight: 300
0) A separator was manufactured in exactly the same manner as in Example 2 except that the separator was immersed in an aqueous solution. This separator had a weight increase of 0.5% (amount of polyethylene glycol).

(Example 4) A nonwoven fabric subjected to a hydrophilic treatment in the same manner as in Example 2 was treated with 8% polyethylene glycol (molecular weight: 30).
0) A separator was manufactured in exactly the same manner as in Example 2 except that the separator was immersed in an aqueous solution. This separator had a 3% increase in weight (amount of polyethylene glycol).

(Example 5) A nonwoven fabric subjected to hydrophilic treatment in the same manner as in Example 2 was treated with 8% polyethylene glycol (molecular weight: 20).
0) A separator was manufactured in exactly the same manner as in Example 2 except that the separator was immersed in an aqueous solution. This separator had a 0.2% increase in weight (amount of polyethylene glycol).

(Example 6) A nonwoven fabric subjected to hydrophilic treatment in the same manner as in Example 2 was treated with 8% polyethylene glycol (molecular weight: 10
0) A separator was manufactured in exactly the same manner as in Example 2 except that the separator was immersed in an aqueous solution. This separator had a weight increase of 0.05% (amount of polyethylene glycol).

From Examples 2 to 6, it was found that when polyethylene glycol having a molecular weight of about 200 to 2,000 was used, the polymerization amount was large and the hydrophilicity was excellent. In Examples 2 to 6, an aqueous solution having a concentration of 8% was used, but the same tendency was observed when the concentration was within a range of about 1 to 20%.

[0074]

The separator for an alkaline battery according to the present invention is excellent in retention of electrolyte and internal pressure characteristics. Also,
ADVANTAGE OF THE INVENTION According to the manufacturing method of the separator for alkaline batteries of this invention, the separator which is excellent in the retention property and internal pressure characteristic of electrolyte solution can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a discharge treatment device that can be used in the present invention.

FIG. 2 is a schematic cross-sectional view of another electric discharge processing apparatus that can be used in the present invention.

FIG. 3 is a schematic cross-sectional view of still another discharge treatment apparatus that can be used in the present invention.

FIG. 4 is a schematic cross-sectional view of still another discharge treatment apparatus that can be used in the present invention.

FIG. 5 is a schematic cross-sectional view of still another electric discharge processing apparatus that can be used in the present invention.

FIG. 6 is a schematic cross-sectional view of still another electric discharge processing apparatus that can be used in the present invention.

[Explanation of symbols]

 1a, 1b Electrodes 2a, 2b Opposing dielectric 3a, 3b Sidewall dielectric 4 AC power supply 5 Fiber sheet

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4J005 AA04 BB01 4J011 UA06 VA01 VA05 VA10 WA10 5H021 AA06 BB15 BB19 CC02 CC05 EE04 EE34 HH00 HH01 HH07 HH10 5H024 AA02 AA03 AA04 AA11 AA14 BB11 CB18 BB11 CB11 CCB AA01 BB10 BB15 BB17 BB19 CC08 CC10 EE06 HH00 HH01

Claims (5)

[Claims] Claims 1. An alkaline battery separator having a polymerized layer of a hydrophilic monomer and / or polymer on the outer surface and inside of a fiber sheet, wherein the hydrophilic monomer and / or polymer is located near the outer surface of the fiber sheet. Wherein the polymerization amount (per unit volume) is equal to or less than the polymerization amount (per unit volume) of the hydrophilic monomer and / or polymer inside the fiber sheet. 2. The alkaline battery separator according to claim 1, wherein the hydrophilic polymer is polyethylene glycol. 3. A fiber sheet carrying a hydrophilic monomer and / or polymer between a pair of electrodes arranged so as to face each other (at least one electrode carrying a dielectric on the facing surface), An electrode (dielectric if a dielectric is carried) is arranged so that both the outer surface and the electrode are in contact with each other, and a voltage is applied between the two electrodes to generate a discharge in the internal gap of the fiber sheet. The hydrophilic monomer and / or
Alternatively, a method for producing an alkaline battery separator, comprising polymerizing a polymer. 4. The hydrophilic polymer has a molecular weight of 200 to 20.
The method for producing a separator for an alkaline battery according to claim 3, wherein the polyethylene glycol is polyethylene glycol. A fiber sheet before supporting a hydrophilic monomer and / or polymer is placed between a pair of electrodes (at least one electrode having a dielectric material on the opposing surface) arranged so as to face each other. Then, both of the electrodes (dielectric if a dielectric is carried) are arranged so that the outer surface is in contact with the electrodes, and a voltage is applied between the two electrodes to generate a discharge in the internal gap of the fiber sheet. The method for producing a separator for an alkaline battery according to claim 3, wherein the fiber sheet is pre-treated.