JPH11297293A - Separator for alkaline battery and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure high electrolyte retainability, improve the service life of a battery, and prevent interruption of work by cutting by realizing high strength by sulfonating nonwoven fabric, and forming easily sulfonating fiber of continuous fiber. SOLUTION: Fiber diameter of easily sulfonating fiber is desirably 0.3 to 10 μm, the easily sulfonating fiber is fiber not less than one selected from a group of polystyrene fiber, polyvinyl naphthalene fiber, polyeter sulfone fiber or polycarbonate fiber, the easily sulfonating fiber is syndiotactic polystyrene, at least 20 wt.% of polyolefine fiber is thermally fusible fiber having a fiber diameter not less than 8 μm and the thermally fusible fiber not less than 8 μm, is composite fiber of polypropylene and polyethylene. Therefore, nonuniformity of Metsuke unit (weight unit area) of a separator is reduced, and uniformity is improved to prevent the occurrence of failure by a battery short circuit by a pinhole. Gas permeability is secured, safety of a battery is improved, and the loss of balance of internal pressure between a positive electrode and a negative electrode is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a separator for an alkaline secondary battery.

[0002]

2. Description of the Related Art Conventionally, a separator has been used to prevent a short circuit between a positive electrode and a negative electrode of an alkaline battery, hold an electrolytic solution, and smoothly advance a charge / discharge reaction. In particular, in recent years, thinner separators have been demanded in order to further increase the capacity of batteries. For thin separators, nonwoven fabrics with less unevenness are required to further enhance electrolyte retention and to avoid pinholes.In addition, strength and gas permeability that are not inferior to conventional products are required. It has been.

[0003] Separators having a high affinity for an electrolytic solution and simultaneously introducing a thermally stable sulfonic acid group have already been known as a separator which has solved the above-mentioned problems such as the liquid retaining property of an electrolytic solution.

For example, JP-A-58-175256 discloses that
A separator in which a sulfonic acid group is introduced into a polyolefin-based structure is disclosed. However, this separator is concentrated sulfuric acid at a high temperature of 100 to 120 ° C. for 25 minutes to
Since the separator is obtained by long-term treatment of 1 hour, the sulfonation proceeds to the inside of the fiber, which causes a decrease in the strength of the fiber itself, and also causes a detachment phenomenon of the fiber surface. There was a problem that the amount of sulfonic acid groups did not increase. Particularly in the case of a thin separator, a decrease in strength due to the hydrophilic treatment was a serious problem.

As means for solving the above problems, Japanese Patent Application Laid-Open No. H10-78
No. 29 discloses a separator obtained by treating a polyolefin-based nonwoven fabric with a fluorine gas and a sulfurous acid gas. However, since this separator essentially imparts a large amount of hydrophilic groups to a polyolefin material having low chemical reactivity, the strength is significantly reduced, and handling of fluorine gas including waste gas treatment is complicated. There was a problem industrially.

Another solution is disclosed in Japanese Patent Application Laid-Open No. Hei 4-1749.
No. 64 discloses a separator in which a polyolefin resin and a polystyrene resin are mixed at the resin level into fibers and then sulfonated with concentrated sulfuric acid at a low temperature, but this separator has fibers that are not polyolefin single components,
Due to the mixed resin, not only the strength of the fiber after spinning becomes insufficient, but also the efficiency of sulfonation tends to decrease due to insufficient exposure of the polystyrene resin to the fiber surface.

Japanese Patent Application Laid-Open No. 8-273654 discloses a sulfonated separator obtained by mixing polystyrene in a split fiber. However, since polyethylene is used in a state in which polystyrene resin is previously mixed, the above-described separator is used. As in Japanese Patent Application Laid-Open No. 4-174964, polystyrene is easily buried, the sulfonation efficiency is insufficient, and the polystyrene is sulfonated with fuming sulfuric acid.
Like 75256, it was not a separator that had both strength and high electrolyte retention. Further, since the separator employs a wet papermaking method, the fiber length is 10 mm.
Since the fibers cut below were used, the strength of the nonwoven fabric was essentially insufficient.

Japanese Patent Application Laid-Open No. Hei 5-182654 discloses a separator in which a nonwoven fabric having a uniform and high fiber density is melt-blown and a nonwoven fabric having a low homogeneity and a high strength obtained by a dry card method are laminated and integrated. However, in a nonwoven fabric made of 100% melt-blown ultrafine fibers, it is difficult to release a by-product reactive gas having low air permeability,
The strength was also insufficient.

As described above, at present, no separator has been obtained which has good electrolyte retention properties, high nonwoven fabric uniformity, and high strength and high gas permeability.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and has as its object to provide an alkaline battery separator capable of simultaneously achieving the following four characteristics at a high level. It is assumed that. 1. Ensure high electrolyte retention and improve battery life. 2. By increasing the strength, workability during battery assembly can be improved, that is, work interruption due to cutting or the like can be avoided. 3. Improves the uniformity of the separator (reduces unevenness),
It is possible to avoid the occurrence of defects due to a battery short circuit due to a pinhole. 4. The required gas permeability of a certain level or more is ensured, and the safety of the battery is improved. At the same time, the internal pressure of the positive electrode and the negative electrode is prevented from being unbalanced, and the life of the battery is improved.

The inventors of the present invention focused on the functional sharing between polyolefin fibers and easily sulfonated fibers represented by polystyrene in order to obtain the above-mentioned alkaline battery separator. As a result, the polyolefin fibers had strength retention. It has been found that a good separator can be obtained by using a thick fiber for enhancing the function of the above and using a continuous fiber for improving the electrolyte retention, homogeneity and gas permeability as the easily sulfonated fiber.

Furthermore, by using ultrafine fibers as easily sulfonated fibers and adding continuous ultrafine fibers as olefin fibers in addition to the above-mentioned thick fibers, better homogeneity and gas permeability can be obtained. I found

Further, it has been found that when the non-woven fabric is sulfonated, the strength can be further improved by selectively sulfonating the surface of the easily sulfonated fiber.

In addition, it has been found that such a separator can be produced by alternately extruding olefin-based fibers and easily sulfonated fibers from adjacent orifices by a melt blow method and simultaneously blowing thick olefin-based short fibers. Was.

The present invention has been completed as a result of further study on the above findings.

[0016]

That is, the present invention relates to a separator for an alkaline battery comprising a nonwoven fabric obtained by mixing an easily sulfonated fiber and a polyolefin-based fiber, wherein the nonwoven fabric is sulfonated; An object of the present invention is to provide a separator for an alkaline battery, wherein the easily sulphonated fiber is a continuous fiber.

In a preferred embodiment of the alkaline battery separator of the present invention, the fiber diameter of the easily sulphonated fiber is:
0.3 to 10 μm.

In a preferred embodiment of the separator for an alkaline battery according to the present invention, the easily sulphonated fiber is at least one fiber selected from the group consisting of a polystyrene fiber, a polyvinyl naphthalene fiber, a polyethersulfone fiber and a polycarbonate fiber. Consists of

In a preferred embodiment of the separator for an alkaline battery according to the present invention, the easily sulfonated fiber is made of syndiotactic polystyrene.

In a preferred embodiment of the alkaline battery separator of the present invention, at least 20% by weight of the polyolefin-based fibers are heat-fusible fibers having a fiber diameter of 8 μm or more.

In a preferred embodiment of the separator for an alkaline battery of the present invention, the heat-sealing fiber having a fiber diameter of 8 μm or more is a composite fiber of polypropylene and polyethylene.

In a preferred embodiment of the separator for an alkaline battery according to the present invention, the easily sulphonated fiber in the nonwoven fabric is:
It is selectively sulfonated.

The present invention also provides a nonwoven fabric in which an olefin resin melt and an easily sulfonated resin melt are extruded and melt blown from an adjacent orifice, and at the same time, an olefin short fiber is blown into the extruded material to uniformly mix and integrate. Is provided with a sulfonation treatment of 0.01 to 15% by volume of SO ₃ gas at a temperature of 10 to 40 ° C. to produce a separator for an alkaline battery.

[0024]

DETAILED DESCRIPTION OF THE INVENTION The easily sulphonated fiber used in the present invention is not particularly limited as long as it is a fiber made of a material which is more easily sulphonated than a polyolefin fiber, and is, for example, a benzene ring. A polymer having an aromatic ring in the molecule. Further, specifically, polystyrene polystyrene-based polymers such as polystyrene, polymethylstyrene, and polyethylstyrene, polyvinyl naphthalene-based polymers, polyethersulfone-based polymers, and polycarbonate-based polymers are exemplified. Among them,
Polystyrene is most preferred, and syndiotactic polystyrene is particularly preferred because of its good heat resistance and strength.

The fiber diameter of the easily sulfonated fiber used in the present invention is preferably from 0.3 to 10 μm, more preferably from 1 to 8 μm. This is because the main purpose of the easily sulphonated fiber is to increase the sulphonation ratio, and it is preferable that the easily sulphonated fiber be an ultrafine fiber having a high relative surface area. At the same time,
Minimization increases uniformity and reduces the likelihood of pinholes. When the fiber diameter exceeds 10 μm, the contact area with the sulfonating agent decreases, and it becomes difficult to secure a high sulfonation rate.
If it is less than m, the inter-fiber voids of the separator will be reduced even if the polyolefin-based fibers described below are improved, and it will be difficult to ensure the gas permeability required for the alkaline secondary battery separator.

The easily sulphonated fiber used in the present invention is:
It must be a continuous fiber. The main purpose of the easily sulphonated fiber is to increase the sulfonation rate, but when the strength is extremely weak, it is difficult to secure the separator strength even if the improvement is performed with a polyolefin fiber described below. Becomes Since the easily sulphonated fiber does not melt below the melting point of the polyolefin fiber to be mixed, it is difficult to heat the easily sulphonated ultrafine fiber and maintain the strength by fusion. In addition, the continuous fiber is a fiber obtained by continuously extruding a raw material polymer by spinning, and refers to a fiber having a fiber length of at least 20 cm or more. Further, although it has been described above that the easily sulphonated fiber is difficult to be fused, it is possible to perform fusion at the intersection by entanglement of the fiber before solidification melt-spun from the spinning nozzle.

The method for producing the easily sulphonated fiber used in the present invention is preferably a melt blow method. Specifically, a method is used in which the molten raw material resin of the sulfonated fiber is extruded with a pressurized gas, stretched by suction, then solidified on a net made of metal or the like and simultaneously formed into a nonwoven fabric.

The polyolefin fibers used in the present invention are preferably polyethylene and polypropylene. This is because the alkali resistance is good.

It is preferable that at least 20% by weight of the polyolefin fiber used in the present invention is a heat-fusible fiber having a fiber type of 8 μm or more, more preferably 8 to 30 μm. Since ultra-sulfonated fibers are used as the easily sulphonated fibers, it is possible to increase the uniformity and reduce the possibility of pinhole generation to an extremely low level when the total amount of the polyolefin-based fibers is ultra-fine fibers. It is difficult to ensure a certain level of gas permeability.

The above-mentioned polyolefin fiber preferably has a fiber diameter of at least 1.2 times or more the ultra-sulfonated ultrafine fiber, more preferably 1.5 times or more. This is because it is necessary to ensure gas permeability.

Further, the above-mentioned polyolefin fiber is
P / PE composite fibers (core / sheath type or side-by-side type) are preferred. This is for improving the strength of the nonwoven fabric. By fusing the PE portions, the strength can be improved. Furthermore, ultrahigh molecular weight PE fibers can also be used effectively by taking advantage of their extremely high strength, and the strength can be improved by partially fusing.

Furthermore, from the viewpoint of improving the uniformity, it is important to uniformly mix the above-mentioned ultra-sulfonated ultrafine fibers with polyolefin fibers having a large fiber diameter. At the time of melt blow spinning, a method of blowing and integrating the above-mentioned thick polyolefin-based fiber which has been spun in advance by a method called coform is most preferable from the viewpoint of improving uniformity. At this time, the form of the fiber may be fiber length 1 to 1
It is preferably a short fiber having a length of 0 cm, more preferably a short fiber having a fiber length of 2 to 8 cm. Fiber length is 1cm
When the length is shorter, the reinforcing effect is insufficient, which is not desirable. When the length is longer than 10 cm, it is difficult to blow the fibers uniformly, which is not desirable. It is also preferable to crimp the short fibers from the viewpoint of improving the strength of the nonwoven fabric.

It is also effective to mix polyolefin-based ultrafine fibers in the polyolefin-based fibers. In particular, when spinning easily sulfonated ultrafine fibers by the melt blow method, when using a composite nozzle capable of spinning two kinds of thermoplastic resins, when polyolefin-based ultrafine fibers are spun simultaneously with easily sulfonated ultrafine fibers, The entanglement and fusion occur effectively in the two kinds of ultrafine fibers, which contributes to the improvement of the strength retention and the uniformity of the nonwoven fabric. However, as described above, in order to avoid a decrease in air permeability, it is desirable to mix the polyolefin-based ultrafine fibers in the range of 0 to 80% of the total polyolefin-based fibers, and particularly desirably 0.
〜60%. When the proportion of the easily sulphonated ultrafine fibers is high or the fiber diameter is low, the mixing ratio of the polyolefin-based ultrafine fibers is reduced so that the necessary minimum air permeability is obtained. It is necessary not to mix the fibers (mixing ratio 0%). The minimum necessary air permeability is a value of 9 cc / cm ² · s or more.

The mixing ratio (weight ratio) of the polyolefin fiber and the easily sulfonated fiber is preferably in the range of 1: 4 to 4: 1, and more preferably in the range of 1: 3 to 3: 1. If the proportion of either fiber is extremely small, it is difficult to balance the balance of functions, which is a feature of the present invention, which is not desirable.

By performing the sulfonation treatment on the nonwoven fabric having the characteristics described above under milder conditions than in the case of sulfonating a conventional nonwoven fabric containing a polyolefin as a main component, the separator of the present invention can be manufactured. It becomes possible.

The mild sulfonation conditions include, for example,
In the case of sulfonation treatment with sulfuric acid, treatment at 90 ° C. or less is desirable, and treatment at 70 ° C. or less is more desirable. Even in such a low-temperature treatment, the ultra-sulfonated ultrafine fibers used in the present invention can easily achieve an extremely high sulfonic acid group content without desorption of the sulfonated surface. Furthermore, under such mild sulfonation conditions, the sulfonation of the polyolefin fiber is insignificant, so that the strength of the polyolefin fiber decreases, and the sulfonated portion is desorbed.
There is no problem with conventional products.

Further, sulfonation treatment with SO ₃ gas is also effective. The treatment temperature is preferably in the range of 10 to 40 ° C, more preferably in the range of 15 to 30 ° C. The simplest method is to use γ-type sulfuric anhydride diluted with nitrogen for SO ₃ gas. However, γ-type sulfuric anhydride has a freezing point of 1%.
Since the temperature is 6 ° C., it is difficult to gasify at a stable concentration even if dilution with nitrogen gas or the like is performed at a temperature lower than 10 ° C., which is not desirable. On the other hand, if the temperature is higher than 40 ° C., the reactivity is too high, and the strength of the polyolefin fiber is greatly reduced. In addition, the concentration of SO ₃ gas in the total gas is also an important control item.
_{3 The} gas concentration is desirably in the range of 0.01 to 15% by volume, and more desirably in the range of 0.05 to 10% by volume. If the concentration exceeds 10% by volume, the strength of the polyolefin-based fiber is greatly reduced, which is not desirable. When the concentration is less than 0.01% by volume, the reactivity of the easily sulphonated fiber is extremely high. Therefore, if the reaction time is lengthened, it is possible to produce the separator, but this is not desirable from the viewpoint of production cost.

As a method for judging the mild sulfonation conditions, a separator made of 100% polyolefin fiber having a fiber diameter equivalent to that used in the separator of the present invention is used, and the strength of the separator before sulfonation is used. It is desirable to carry out under the condition that the strength is maintained at 75% or more after sulfonation, more preferably at least 85%. The above value is defined as a polyolefin strength retention (%), and will be described in more detail in Examples below.
Under such conditions, the easily sulphonated ultrafine fibers are sufficiently sulfonated, but the sulfonation of the polyolefin-based fibers is very small and sufficient strength can be maintained. Conversely, when the separator is prepared under strong sulfonation conditions where the polyolefin strength retention rate is less than 75%, the sulfonation of the polyolefin fiber progresses too much, and the primary purpose of maintaining the strength is mainly. It is not desirable because it cannot be achieved.

Although fuming sulfuric acid heated to 100 ° C. or higher has been used in the production of a conventional polyolefin-based sulfonic acid group-containing separator, it is difficult to use it in the present invention because the reactivity is too high. However, it can be used if the temperature is controlled to a low temperature of 10 to 40 ° C., and at the same time, after a treatment within several seconds, a washing step is promptly introduced and a special control such as stopping the reaction is carried out.

The degree of sulfonation of the entire nonwoven fabric is a measure of the liquid retention of the separator. Therefore, it is desirable to control the treatment time and the like so that the sulfur content of the surface layer, which is an index of the degree of sulfonation, is in the range of 0.5 to 20 element%.
More preferably, it is in the range of 2 to 15 element%. When the sulfur content of the fiber surface layer is lower than 0.5 element%, the retention of the electrolyte is not sufficient, which is not desirable. When the sulfur content is higher than 20 element%, the reaction time is too long, and it is estimated that excessive sulfonation is progressing, and peeling of the surface layer and extreme decrease in strength occur, which is not desirable.

The present invention can be used most effectively for a thin separator having a thickness of 70 to 140 μm. A separator having a thickness of 70 μm or less is not desirable because of insufficient liquid retention. In addition, the present invention is a highly excellent separator having high electrolyte retention, high strength, good uniformity, gas permeability of a certain level or more, and sulfonic acid groups with high heat resistance. In a battery for applications such as "medical use, emergency power supply, and electric vehicle" which require high reliability, the separator can be effectively used even in a separator having a thickness of 140 to 220 [mu] m.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to embodiments. The physical properties shown in the examples were measured by the following methods.

A. The sulfur content was measured by X-ray photoelectron spectroscopy, abbreviated as ESCA or XPC. Specifically, Shimadzu Corporation ESCA750 type was used for the measurement, and ESCAPAC760 type was used for the analysis. The content of elements including carbon was measured and expressed as elemental% of sulfur contained.

B. Air permeability The value measured by a Frazier-type tester according to the air permeability A method described in JIS L 1096 was defined as the air permeability in the present invention.

C. Separator Thickness The thickness of the separator was measured under a load of 300 kPa. Specifically, a micrometer (Mitutoyo M1102-) having a measuring force of 10 N and a measuring surface of 6 mmΦ.
25 type).

D. The strength of the separator was measured using a sample having a width of 5 cm and a length of 15 cm in accordance with JISL 1068 (test method for tensile strength of woven fabric) with a gripping interval of 10 cm and a pulling speed of 30.
cm / min, the tensile strength in the machine direction (MD) was measured using a Tensilon RTM-100 tester.

Example 1 Polypropylene and syndiotactic polystyrene were extruded alternately from adjacent orifices at a temperature of 295 ° C. Single hole discharge amount: polypropylene = 0.3 g / mi
n. , Syndiotactic polystyrene = 0.5 g / m
in. And Furthermore, it is made to draw and thin by a 300 ° C. air flow at 0.8 kg / cm ² , and at the same time, a composite fiber of polypropylene / polyethylene (Chisso Corporation, ES fiber, fiber diameter 16 μm, length 50 mm) is blown, and three kinds of fibers are obtained. A uniformly mixed nonwoven fabric was prepared. Hot pressing was performed at 100 ° C. to a thickness of 120 μm. FIG. 1 shows a schematic view of the nonwoven fabric making apparatus. The above sample was cut into a size of 10 cm in width × 60 cm in length, and 10% by volume of SO ₃ gas was used.
This was carried out by a treatment with a nitrogen gas at room temperature (25 ° C.) for 30 seconds. After the treatment, the reaction tank was replaced with a large amount of nitrogen gas to stop the sulfonation reaction. The SO ₃ gas used was obtained by evaporating Nisso Sulfan manufactured by Nippon Soda Co., Ltd. with nitrogen gas. The processing equipment used is shown in FIG.

Using the prepared separator, a capacity of 2500
A Ni / hydrogen secondary battery of mAh was prepared, charge and discharge were repeated at 0.4 C, and the discharge capacity retention ratio was measured. The discharge capacity is 100 discharge capacity in the initial cycle after one or two preliminary charge / discharge cycles for activating the hydrogen storage alloy.
%, And the maintenance rate of the discharge capacity when the charge / discharge cycle was repeated was measured. An aqueous solution of potassium hydroxide was used as the electrolyte. The number of cycles when the discharge capacity retention ratio decreased to 50% was evaluated as the life of the battery.

Table 1 summarizes the results of the life evaluation based on the separator preparation conditions, physical properties, and the discharge capacity retention ratio.

Further, in order to confirm the strength of the sulfonation conditions, a nonwoven fabric having the same fiber diameter as that of Example 1 was prepared using only polyolefin fibers without using syndiotactic polystyrene. The tensile strength was measured (T0). Further, after performing a sulfonation treatment under the same sulfonation conditions as in Example 1, the tensile strength was measured (T1). Here, (T1 / T0) * 10
The value obtained at 0 (%) was defined as the polyolefin strength retention (%), and was used as a measure of strength measurement under sulfonation conditions. As a result, the polyolefin strength retention in Example 1 was a high value of 95%, and it was confirmed that the sulfonation rate of the polyolefin fiber was small and that the polystyrene microfine fiber was selectively sulfonated. Hereinafter, in each of the examples, the nonwoven fabric using the corresponding polyolefin-based fiber was used to measure the polyolefin strength retention in each of the examples.

Examples 2 to ₃ Separators were prepared and evaluated in the same manner as in Example 1 except that the mixing ratio of the fibers used, the fiber diameter, and the sulfonation time with SO ₃ gas were changed. . Table 1 summarizes the results of the life evaluation based on the separator preparation conditions, physical properties, and the discharge capacity retention ratio.

Examples 4-5 Examples 1-5 except that the sulfonation treatment was carried out with sulfuric acid.
A separator was prepared and evaluated in the same manner as in Example 2. Table 1 summarizes the results of the life evaluation based on the separator preparation conditions, physical properties, and the discharge capacity retention ratio.

Comparative Example 1 A nonwoven fabric of 100% polyolefin containing no sulfonated fiber was treated with fuming sulfuric acid containing 15% by weight of SO ₃ at 110 ° C., and the same measurement as in Example 1 was performed.
Insufficient values were found in both the sulfur content and the strength of the surface layer.
The results are summarized in Table 2.

Comparative Example 2 A non-woven fabric of 100% polyolefin containing no easily sulfonated fiber was treated under the same mild sulfonation conditions as in Example 1. As a result, although only the surface layer was sulfonated, the sulfur content of the surface layer was low, the liquid retention was not sufficient, and the function as a separator was insufficient. The results are summarized in Table 2.

Comparative Example 3 Using a polypropylene and syndiotactic polystyrene, spinning was carried out by the same melt-blowing method as in Example 1, but without blowing composite fibers, a non-woven fabric was prepared and then heated at 120 ° C. A non-woven fabric having a thickness of 120 μm was obtained by pressing. This non-woven fabric was subjected to a sulfonation treatment under the same sulfonation conditions as in Example 1 to prepare a separator, and the separator was evaluated. The balance of the internal pressure was lost, and the life was extremely shortened. The results are summarized in Table 2.

[0056]

[Table 1]

[0057]

[Table 2]

[0058]

As described above, the present invention simultaneously achieves the following four characteristics required for a separator for an alkaline battery at a high level at the same time. Bring properties. 1: Ensure high electrolyte retention and improve battery life. 2: Improvement of workability at the time of assembling the battery due to the high strength, that is, no work interruption due to cutting or the like. 3: Improve the uniformity of the separator (reduce unevenness) and eliminate the occurrence of defects due to battery short-circuit due to pinholes. 4: Ensuring required gas permeability of a certain level or more, improving the safety of the battery and improving the cycle life of the battery. Further, in addition to the above four points, it has a characteristic that it has a sulfonic acid group that is thermally stable for a long period of time.
Furthermore, the present invention is particularly effective in producing a separator having a small thickness, and thus contributes to an increase in battery capacity.

[Brief description of the drawings]

FIG. 1 is a schematic view of a nonwoven fabric manufacturing apparatus.

FIG. 2 is a schematic view of a sulfonation treatment apparatus using SO ₃ gas.

Claims (8)

[Claims] 1. An alkaline battery separator comprising a nonwoven fabric obtained by mixing a sulfonated fiber and a polyolefin fiber, wherein the nonwoven fabric is sulfonated, and the sulfonated fiber is a continuous fiber. A separator for an alkaline battery. 2. The fiber of the easily sulfonated fiber having a fiber diameter of 0.1.
The alkaline battery separator according to claim 1, wherein the thickness is 3 to 10 m. 3. The fiber according to claim 1, wherein the easily sulfonated fiber is at least one fiber selected from the group consisting of a polystyrene fiber, a polyvinyl naphthalene fiber, a polyethersulfone fiber, and a polycarbonate fiber. 3. The separator for an alkaline battery according to 2. 4. The alkaline battery separator according to claim 1, wherein the easily sulphonated fiber is composed of syndiotactic polystyrene. 5. The alkaline battery separator according to claim 1, wherein at least 20% by weight of the polyolefin-based fiber is a heat-fusible fiber having a fiber diameter of 8 μm or more. 6. The alkaline battery separator according to claim 5, wherein the heat-fused fiber having a fiber diameter of 8 μm or more is a composite fiber of polypropylene and polyethylene. 7. The fiber according to claim 1, wherein the easily sulfonated fibers in the nonwoven fabric are selectively sulfonated.
The alkaline battery separator according to claim 6. 8. A nonwoven fabric which is extruded and melt blown from an adjacent orifice with an olefin-based resin melt and an easily sulfonated resin melt and simultaneously blows olefin-based short fibers into the extruded material to uniformly mix and integrate the nonwoven fabric at a temperature of 1 ° C.
A method for producing a separator for an alkaline battery, comprising performing sulfonation treatment with 0.01 to 15% by volume of SO ₃ gas at 0 to 40 ° C.