JPH10312786A - Separator for alkaline battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator excellent in alkali resistance and electrolyte holding property and improve the yield of its manufacture by applying the hydrophilic process to a nonwoven fabric applied with the split process of split fibers, the tangle process of fibers, and the fusion process of fusion fibers to a fiber web containing multiple split fibers capable of generating polyolefin extra-fine fibers, high-strength fibers, and fusion fibers at specific % respectively. SOLUTION: The hydrophilic process is applied to a nonwoven fabric applied with the split process of split fibers, the tangle process of fibers, and the fusion process of fusion fibers to a fiber web containing split fibers Al of 5-40 mass % capable of split-generating polyolefin extra-fine fibers A1 12 and ethylene-vinyl alcohol copolymer extra-fine fibers A2 11 by a physical action, split fibers B1 of 20-55 mass % capable of split-generating only polyolefin extra-fine fibers B1 12 by a physical action, high-strength fibers of 20-45 mass % having the single fiber strength of 5 g/d or above, and fusion fibers of 20-35 mass % having the resin component with the melting point lower than the melting point of the constituting resin components of the split fibers A1, B1 and the high-strength fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in order to prevent a short circuit by separating a positive electrode and a negative electrode of an alkaline battery, and to hold an electrolytic solution and smoothly carry out an electromotive reaction, a separator is provided between the positive electrode and the negative electrode. Is used.

[0003] Since the separator needs to retain an alkaline electrolyte for a long period of time and must not be attacked by the alkali itself, a separator made of a polyolefin fiber having excellent alkali resistance is preferable. However, the polyolefin fiber has poor hydrophilicity and poor electrolyte retention due to poor hydrophilicity, and burrs of the electrode penetrate the separator and short-circuit between the electrodes at the stage of manufacturing a battery (electrode group configuration). The disadvantage was that the yield was poor.

For this reason, surface treatments such as fluorine gas treatment and corona discharge treatment have been performed in order to improve the retention of the electrolytic solution, but the treatment is mainly on the surface of the separator and the inside of the separator is sufficiently filled. Since the electrolyte was not treated and the retention of the electrolytic solution inside the separator was poor, the oxygen absorption during overcharge was poor and the internal pressure characteristics were poor. On the other hand, as for the latter disadvantage of low yield, sufficient measures have not yet been taken.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and an alkaline battery separator which is excellent in alkali resistance and electrolytic solution retention ability and can produce batteries with good yield. To provide.

[0006]

Alkaline battery separator of the present invention solving the problem to means for the (hereinafter referred to simply as "separator") is divided by a physical action, polyolefin microfine fibers A ₁ and ethylene - vinyl alcohol copolymer Split fiber A capable of generating ultrafine fiber A2 is ₅ to 40 mass
%, Is divided by a physical action, a possible split fibers B generates only polyolefin microfine fibers _{B 1} 20～55Mas
s%, high strength fiber having a single fiber strength of 5 g / d or more
45 mass%, and a fused fiber having at least a resin component having a melting point lower than the melting points of the split fiber A constituent resin component, the split fiber B constituent resin component, and the high-strength fiber constituent resin component on the fiber surface. A nonwoven fabric formed by splitting the split fibers A and B, entanglement of the fibers, and fusion-bonding of the fusion-bonded fibers to a fiber web containing 20 to 35 mass% is made hydrophilic.

As described above, since the separator of the present invention is mainly composed of polyolefin-based ultrafine fibers (A ₁ , A ₂ , B ₁ ), it has excellent alkali resistance. The separator of the present invention is an ethylene - contains ultrafine fibers, such as vinyl alcohol copolymer microfine fibers A _2, and since has been hydrophilized, near the surface of the separator can hold an electrolyte solution mainly by hydrophilic treatment, the separator internal ethylene - because it can hold the electrolyte solution by a hydrophilic vinyl alcohol copolymer microfine fibers a _2, is excellent in retention of electrolyte. As described above, since the electrolyte has excellent retention even inside the separator, it has excellent oxygen absorption during overcharge and excellent internal pressure characteristics. Furthermore, since the burr of the electrode plate can be prevented from penetrating the separator by containing the high-strength fiber, the battery can be manufactured with a high yield by using the separator of the present invention.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the nonwoven fabric constituting the separator of the present invention, in order to improve the retention of electrolyte solution (particularly inside the separator), to prevent short circuit due to dendrite, as can be thin is physically divided by the action, the polyolefin ultra-fine fibers a ₁ and ethylene - vinyl alcohol copolymer microfine fibers a ₂ and capable of generating a split fibers a, polyolefin microfine fibers a ₁ and ethylene - vinyl It is generating alcohol copolymer microfine fibers a _2.

The physical action includes, for example, a fluid flow such as a water flow, a needle, a calender, or a flat press. Among these, the fluid flow simultaneously performs the dividing process and the entangling process of the divided fiber A. It is a preferred physical action because it can be performed.

[0010] As the polyolefin ultra-fine fibers A ₁ which can be generated from the split fibers A, for example, polyethylene, polypropylene, polymethylpentene, ethylene - propylene copolymer, ethylene - butene - a resin component such as propylene copolymer 1 Contains more than kind. Among these, polypropylene ultrafine fiber A having excellent alkali resistance
_It preferably contains ₁ . Therefore, the split fiber A contains one or more of these polyolefin resin components. Linear density of the polyolefin ultra-fine fibers A ₁ is smaller, excellent retention of electrolyte, and since has excellent prevention of dendrites, but preferably not more than 45 [mu] g / m, has a certain degree of strength Like 1
It is preferably at least μg / m. A more preferred linear density is from 2.5 μg / m to 35 μg / m.

[0011] split fibers A is other than the polyolefin ultra-fine fibers A ₁ as described above of the present invention, ethylene - is capable of generating vinyl alcohol copolymer microfine fibers A _2. The ethylene - the presence of a vinyl alcohol copolymer microfine fibers A _2, to improve the retention of the electrolyte solution in the separator inside the present invention, have improved pressure properties. The ethylene - vinyl alcohol copolymer microfine fibers A ₂ is retention of the electrolyte solution,
The amount is preferably from 1 μg / m to 45 μg / m, more preferably from 2.5 μg / m to 35 μg / m, so that the dryout prevention property and the dendrite prevention property are excellent.

The split fiber A is composed of an ethylene-vinyl alcohol copolymer component and one or more polyolefin resin components. For example, as shown in FIGS. A multi-metal split fiber having a fiber cross section as shown can be used. Among these, the split fiber A having an orange fiber cross section, which is easily split even when a physical action is applied from any direction, can be suitably used. The split fiber A is a polyolefin extra fine fiber A
₁ and ethylene - may generate vinyl alcohol copolymer microfine fibers A ₂ other than the ultrafine fibers, but since the separator of the present invention are those of the alkaline battery, as excellent in alkali resistance, polyolefin ultrafine fibers A ₁ ethylene - preferably capable of generating only vinyl alcohol copolymer microfine fibers a _2.

The linear density of the split fiber A is not particularly limited as long as it can generate ultrafine fibers (A ₁ , A ₂ ) having the above linear density. The fiber length of the split fiber A may be 1 to 110 mm, but when the fiber web is formed by a wet method, the split fiber A having a length of 1 to 25 mm is used, and when the fiber web is formed by a dry method, , 25-
The split fiber A having a length of 110 mm is used. In the case where the fiber web is formed by a wet method, the thickness is more preferably 5 to 20 mm so that the fiber web can be easily entangled and a uniform and strong fabric web can be formed.

[0014] As the split fiber A is excellent in retention of electrolyte inside the separator, must contain more than 5 mass%, ethylene - vinyl alcohol copolymer microfine fibers A ₂ is compared with the polyolefin ultra-fine fibers A ₁ Therefore, the content is preferably 40% by mass or less. More preferably, it is 5 to 35 mass%, and most preferably, it is 10 to 30 mass%.

[0015] The separator of the present invention divides the physical action, polyolefin microfine fibers B ₁ generated only polyolefin microfine fibers B ₁ from which can be generated split fibers B
Contains. The presence of the polyolefin ultra-fine fibers B _1, can more prevent a short circuit due to dendrite, also can reduce the thickness of the separator. This physical action is similar to the splitting of split fiber A, and for the same reason,
Preferably, it is a fluid stream. The physical action of the split fiber B may be the same as the physical action for splitting the split fiber A, or may be different from the physical action for splitting the split fiber A. Above, it is preferable that they are the same.

[0016] The split fibers as polyolefin microfine fibers B ₁ which can be generated from B, split fibers may if the same resin component as polyolefin microfine fibers A ₁ which can be generated from A, same reason polypropylene microfine fibers B ₁ in Preferably. In particular, the split fiber B composed of a polyethylene component and a polypropylene component, particularly a high-density polyethylene component and a polypropylene component, can be easily spun and produced, and further, the polyethylene microfine fiber _B1-1 and the polypropylene microfine fiber B _1-2 , these ultrafine fibers (B _1-1 ,
Since the degree of hydrophilicity in the same conditions B _1-2) are different, by slightly different retention distribution of the electrolyte,
This is a suitable combination because even if gas is generated in the sealed secondary battery, it can be quickly transmitted to the other electrode, and there is no danger of bursting due to an increase in internal pressure.

The linear density of the split fibers B polyolefin microfine fibers B ₁ generated from the smaller, better retention of the electrolytic solution, moreover excellent for use in prevention of dendrites, and even less 45 [mu] g / m It is preferably at least 1 μg / m so as to have a certain strength. A more preferable linear density is 2.5 μg / m to 35 μg / m.
m.

The split fiber B is composed of two or more kinds of polyolefin resin components. For example, the split fiber shown in FIGS. 1 to 4 has an orange cross section, and the split fiber shown in FIG. 5 has a multi-bimetal type. Split fibers can be used. Among these, the split fiber B having an orange fiber cross section, which is easily split even when a physical action is applied from any direction, can be suitably used. Incidentally, the split fibers B, as excellent alkali resistance, generates only polyolefin microfine fibers B _1.

The linear density of the split fibers B may be any capable of generating ultrafine fibers B ₁ having the linear density, it is not particularly limited. The fiber length of the split fiber B is 1 to 1
It is sufficient if it is 10 mm, but if the fiber web is formed by a wet method, a split fiber B having a length of 1 to 25 mm is used, and if it is formed by a dry method, 25 to 110 mm
A long split fiber B is used. In the case where the fiber web is formed by a wet method, the thickness is more preferably 5 to 20 mm so that the fiber web can be easily entangled and a uniform and strong fabric web can be formed.

The split fiber B needs to contain 5 mass% or more so that the short circuit due to dendrite can be further prevented and the thickness of the separator can be reduced. From the relation with other fibers, the split fiber B has a content of 55 mass% or less. Preferably it is. It is more preferably 5 to 40 mass%, and most preferably 10 to 30 mass%.

The separator of the present invention contains at least one kind of high-strength fiber having a single fiber strength of 5 g / d or more so that burrs of the electrode plate do not penetrate the separator and short-circuit each other when the battery is manufactured. In. Single fiber strength is 5g / d
If it is less than 10 g, there is no short-circuit preventing effect. More preferably, high-strength fibers of 7 g / d or more are used. The single fiber strength refers to a value measured according to JIS L 1015 (chemical fiber staple test method).

[0022] As excellent the high strength fibers are also alkali resistance, the same polyolefin resin component and the polyolefin ultra-fine fibers A ₁ which can be generated from the split fibers A described above, preferably contains at least the fiber surface. Among these, it is preferable to use a polypropylene component or an ultrahigh molecular weight polyethylene component, and it is more preferable to use an ultrahigh molecular weight polyethylene having excellent strength. The ultra-high molecular weight means that the average molecular weight is 1,000,000 to 5,000,000.

The linear density of the high-strength fiber is set to a linear density of 40 to 650 μg / m so as not to lower the retention of the electrolyte.
It is preferred that The fiber length of the high-strength fiber is 1 to
It is good if it is 110 mm, but if the fiber web is formed by a wet method, a high-strength fiber having a length of 1 to 25 mm is used, and if it is formed by a dry method, 25 to 110 mm
Use long high-strength fibers. In the case where the fiber web is formed by a wet method, the thickness is more preferably 5 to 20 mm so that the fiber web can be easily entangled and a uniform and strong fabric web can be formed.

It is preferable that the high-strength fiber contains 15 mass% or more so as to have an excellent short prevention property.
On the other hand, from the relationship with the blending amount of other fibers, 60 mass%
It is preferred that: A more preferable blending amount is 15 to
50 mass%, and the most preferable compounding amount is 25 to 4
0 mass%.

The separator of the present invention also contains fused fibers so that the tensile strength and the softness are improved and the yield is further improved. The fused fibers are divided fiber A and divided fiber B
The split fiber A constituent resin component, the split fiber B constituent resin component, and the high-strength fiber so as not to decrease the liquid retention property of the ultrafine fibers (A ₁ , A ₂ , B ₁ ) generated from the resin and the strength of the high-strength fiber. A resin component having a melting point lower than the melting point of the constituent resin component (hereinafter, also referred to as a “low melting point component”) at least on the fiber surface. This low-melting point component is more than 10% of any of the constituent resin components of the split fibers A and B and the high-strength fiber constituent resin component.
It preferably has a melting point lower by at least 15 ° C, preferably by at least 15 ° C.

[0026] The fusible fiber also as excellent alkali resistance, preferably made of the same resin component one or more polyolefin ultrafine fiber A ₁ which can be generated from the split fibers A described above. In addition, as a resin component constituting the split fiber B,
Since it is preferable to include polyethylene and polypropylene, it is preferable to use high-density polyethylene as the polyethylene constituting the split fiber B and use low-density polyethylene as the low-melting-point component of the fusion fiber.

The fusion fiber may be composed of a single component or may be composed of two or more resin components. The latter improves the tensile strength of the separator. Therefore, it can be suitably used. This 2
When it is composed of more than two kinds of resin components, they may be arranged in any manner, and for example, a core-sheath type, an eccentric type, and a side-by-side type can be used.

The linear density of the fused fiber is set to a linear density of 100 to 450 μg / m so as not to lower the retention of the electrolyte.
It is preferred that Further, the fiber length of the fused fiber is 1 to 1
It is good if it is 10 mm, but if the fiber web is formed by a wet method, a fused fiber having a length of 1 to 25 mm is used,
When formed by a dry method, a fused fiber having a length of 25 to 110 mm is used. In the case of forming a fiber web by a wet method, in order to more easily entangle, and to form a fiber web having a uniform and strong base fabric,
More preferably, it is 5 to 20 mm.

It is preferable that such a fusion fiber contains 15 mass% or more so that the tensile strength and the softness are improved. On the other hand, from the relationship with the amount of other fibers, 50 m
It is preferably at most ass%. The more preferable amount is 15 to 40 mass%, and the most preferable amount is 20 to 35 mass%.

The separator of the present invention is produced from the split fiber A, the split fiber B, the high-strength fiber, and the fusion fiber as described above. If necessary, the separator may contain fibers other than these fibers. You can go out. As excellent also alkali resistance The other fibers, is preferably the same polyolefin resin component and the resin component constituting the microfine fibers A ₁ which can be generated from the split fibers A fiber comprising one or more.

The other fibers have a linear density of 100 to 450 μg / m so as not to deteriorate the retention of the electrolyte.
It is preferred that The fiber length of the other fibers is 1 to 1
It is good if it is 10 mm, but when the fiber web is formed by a wet method, another fiber having a length of 1 to 25 mm is used,
When formed by a dry method, another fiber having a length of 25 to 110 mm is used. In the case of forming a fiber web by a wet method, in order to more easily entangle, and to form a fiber web having a uniform and strong base fabric,
More preferably, it is 5 to 20 mm. In addition, it is preferable that the compounding quantity of another fiber is 35 mass% or less.

The separator of the present invention is obtained by forming a fiber web containing the above-mentioned split fibers A, split fibers B, high-strength fibers, and fused fibers by a dry method such as a card method or an air-lay method or a wet method. The dry method and the wet method can be formed by a conventionally known method. Further, when the fiber web formed by the dry method and the fiber web formed by the wet method are laminated, the tensile strength of the fibers constituting the fiber web formed by the dry method and the uniformity of the fiber web formed by the wet method are increased. This is a preferred embodiment because a separator having both of the above can be formed.

Next, a nonwoven fabric is formed by the splitting process of the split fibers A and B, the entanglement process of the fibers, and the fusion process of the fusion fibers. The splitting process, the entanglement process, and the fusion process of the split fibers A and B may be performed in any order, and may be performed any number of times. For example, the splitting process of the split fiber A, the splitting process of the split fiber B, the entanglement process, and the fusion process may be performed in this order, or the fusion process, the split process of the split fiber A and the split fiber B, and the entanglement process. They may be performed in this order, or may be performed in the order of fusion, splitting of split fibers A and B, entanglement, and fusion. In the present invention, the polyolefin ultrafine fiber B ₁
The split fiber B that can generate only the split fiber B is used, and the resin component constituting the split fiber B has high compatibility and is difficult to split, so after performing the fusion treatment to reduce the degree of freedom of the fiber, It is preferable to perform the splitting process and the entanglement process on the split fibers A and B. In addition, if the splitting process and the entanglement process of the split fiber A and the split fiber B are performed after the fusion process, the rigidity obtained by the fusion process is reduced. Therefore, it is necessary to perform the fusion process again. preferable. In addition, although the division | segmentation process of the division | segmentation fiber A and the division | segmentation fiber B may be performed simultaneously and may be performed separately, it is more preferable to perform simultaneously at the time of manufacture. The splitting process and the entanglement process of the split fiber A and the split fiber B may be performed separately, but the splitting process and the entanglement process of the split fiber A and the split fiber B are performed as in the case of processing by a fluid flow. It is preferable from the viewpoint of production to carry out simultaneously.

Examples of the dividing process applicable to the present invention include a fluid flow such as a water flow, a needle, a calender, and a flat press. Among these, the division by the fluid flow is preferable because the division and the entanglement of the fibers can be performed simultaneously.

Examples of the entanglement treatment applicable in the present invention include a treatment with a fluid flow (particularly a water flow) and a needle. This entanglement treatment by the fluid flow is preferable because the entire fiber web can be uniformly entangled.

The preferable conditions for division and entanglement by the fluid flow or the entanglement conditions include, for example, a nozzle diameter of 0.0
A pressure of 1 M from a nozzle plate in which nozzles are arranged in one or more rows at a pitch of 5 to 0.3 mm and a pitch of 0.2 to 3 mm
What is necessary is just to eject a fluid flow of Pa to 29 MPa to the fiber web. Such a fluid stream is ejected at least once onto one or both sides of the fiber web. If the non-opening portion of the net or the perforated plate on which the fiber web is placed is large when treated with a fluid flow, the resulting nonwoven fabric also has large holes, and a short circuit is likely to occur. It is preferable to use a support having a thickness of 0.25 mm or less.

The fusing treatment in the present invention may be performed under no pressure, under pressure, or may be performed after fusing under no pressure. From the viewpoint of adjustment, it is preferable to apply pressure simultaneously or after fusion.
Examples of the fusion device include a heat calender, a hot air penetration type heat treatment device, and a cylinder contact type heat treatment device. The heating temperature is preferably in the range from the softening temperature of the low melting point component of the fused fiber to the melting point when heating and pressurizing are performed simultaneously. Is preferably carried out within the range from the softening temperature of the low melting point component of the fused fiber to a temperature 20 ° C. or more higher than the melting point. The pressurizing conditions include a linear pressure of 5 to 30 N /
cm.

The nonwoven fabric formed in this way is excellent in short-circuit prevention properties, rigidity and the like, and can be used to efficiently manufacture batteries. The separator of the present invention is formed by performing a hydrophilic treatment so as to be more excellent in the liquid holding property. Examples of the hydrophilic treatment include a sulfonation treatment, a fluorine gas treatment, a graft polymerization of a vinyl monomer, a surfactant treatment, a discharge treatment, and a treatment for imparting a hydrophilic resin.

The sulfonation treatment is not particularly limited, but includes, for example, treatment with fuming sulfuric acid, sulfuric acid, sulfur trioxide, chlorosulfuric acid, sulfuryl chloride or the like. Among these, sulfonation treatment with fuming sulfuric acid is preferred because it has high reactivity and can be relatively easily sulfonated.

The fluorine gas treatment is not particularly limited. For example, fluorine gas diluted with an inert gas (eg, nitrogen gas, argon gas, etc.), oxygen gas, carbon dioxide gas, and sulfur dioxide gas are used. For example, a treatment with a mixed gas with at least one kind of gas selected from the above. The method in which the sulfur gas is attached to the nonwoven fabric in advance and then brought into contact with the fluorine gas is a more efficient and permanent hydrophilization treatment method.

The graft polymerization of the vinyl monomer includes:
As the vinyl monomer, for example, acrylic acid, methacrylic acid, acrylate, methacrylate, vinylpyridine, vinylpyrrolidone, or styrene can be used. In addition, when styrene is graft-polymerized, it is preferable to sulfonate in order to impart affinity with the electrolytic solution. Among these, acrylic acid can be suitably used because it has excellent affinity with the electrolytic solution.

Examples of the method for polymerizing these vinyl monomers include a method in which a nonwoven fabric is immersed in a solution containing a vinyl monomer and a polymerization initiator and heated, a method in which a vinyl monomer is applied to a nonwoven fabric and then radiation is applied, and a method in which a nonwoven fabric is irradiated. A method of contacting with a vinyl monomer after irradiation with radiation,
There is a method of impregnating a nonwoven fabric with a vinyl monomer solution containing a sensitizer and then irradiating the nonwoven fabric with ultraviolet rays. If the surface of the nonwoven fabric is modified by ultraviolet irradiation, corona discharge, plasma discharge, etc. before contacting the vinyl monomer solution with the nonwoven fabric, the graft polymerization can be performed efficiently because the affinity with the vinyl monomer solution is high. .

The surfactant treatment includes, for example, an anionic surfactant (for example, an alkali metal salt, an alkyl sulfonate, or a sulfosuccinate salt of a higher fatty acid), or a nonionic surfactant (for example,
The nonwoven fabric can be immersed in a solution of polyoxyethylene alkyl ether or polyoxyethylene alkylphenol ether, or the solution can be applied, sprinkled, or coated on the nonwoven fabric.

Examples of the discharge treatment include corona discharge treatment, plasma treatment, glow discharge treatment, creeping discharge treatment, and electron beam treatment.

In the treatment for imparting a hydrophilic resin, for example, a hydrophilic resin such as carboxymethyl cellulose, polyvinyl alcohol, crosslinkable polyvinyl alcohol, or polyacrylic acid can be attached. After dissolving or dispersing these hydrophilic resins in a suitable solvent, the nonwoven fabric is immersed in this solvent, or this solvent is applied to the nonwoven fabric,
It can be dusted or coated and dried to adhere. The amount of the hydrophilic resin attached is preferably 0.3 to 1 mass% of the whole separator so as not to impair the air permeability.

As the crosslinkable polyvinyl alcohol, for example, there is polyvinyl alcohol in which a part of hydroxyl groups is substituted by a photosensitive group. More specifically, a styrylpyridinium-based photosensitive group, styrylquinolinium And poly (vinyl alcohol) substituted with styrylbenzothiazolium. This crosslinkable polyvinyl alcohol can be crosslinked by light irradiation after being attached to the nonwoven fabric in the same manner as other hydrophilic resins. Polyvinyl alcohol in which a part of such hydroxyl groups is substituted with a photosensitive group has excellent alkali resistance and contains many hydroxyl groups capable of chelating with ions.
During discharging and / or charging, ions and chelates are formed before the dendritic metal is deposited on the electrode plate, and short-circuiting between the electrodes hardly occurs.

The thus obtained separator of the present invention has an areal density of 30 to 100 g / m ² , more preferably 4 to 100 g / m ² .
0 to 80 g / m ² . If the areal density is less than 30 g / m ² , the tensile strength may be insufficient, and 100 g / m 2
^If it exceeds ² , the thickness becomes too thick.

The tensile strength of the separator of the present invention in the vertical direction (length direction) is set to 80 N / 50 so as not to be broken by the tension at the stage of manufacturing the battery (electrode group).
mm or more, and more preferably 100 N / 50 mm or more. This tensile strength is 50mm width
Is fixed to a tensile strength tester (Tensilon UTM-III-100, manufactured by Orientec) (distance between chucks: 100 mm) and measured at a tensile speed of 300 mm / min.

The tear strength of the separator of the present invention in the vertical direction is 10 N / 50 mm or more in order to prevent the separator from being torn by the edge of the electrode plate when manufacturing a battery (electrode group configuration). Preferably 2
0 N / 50 mm or more, more preferably 25 N /
Most preferably, it is 50 mm or more. Incidentally, the tear strength is a value obtained by JIS L ^{1096 -1990} (general fabric test method, trapezoid method).

The stiffness in the vertical direction of the separator of the present invention is determined so that the shape of the separator is maintained when the battery (electrode group configuration) is manufactured so that the electrode plate and the separator do not have a winding deviation. Preferably at least 10 mg, 15 m
g or more is more preferable. Note that the rigidity is J
It refers to a value obtained by IS L 1096 (bending resilience, A method (Gurley method)).

As described above, the separator of the present invention is excellent not only in the retention of the electrolyte, but also in the short-circuit prevention, the tear strength, and the softness, so that the battery can be stably manufactured. is there.

The separator of the present invention may be, for example, a primary battery such as an alkaline manganese battery, a mercury battery, a silver oxide battery, an air battery, a nickel-cadmium battery, a silver-zinc battery,
Silver-cadmium battery, nickel-zinc battery, nickel-
It can be used for secondary batteries such as hydrogen batteries.

Examples of the separator of the present invention will be described below, but the present invention is not limited to these examples.

[0054]

【Example】

(Example 1) As the split fiber A, a polypropylene component as shown in FIG.
0.8 μg / m polypropylene microfine fiber A ₁ (melting point:
160 ° C.) and an ethylene-vinyl alcohol copolymer component (symbol 11 in the figure, linear density 20.8 μg)
/ M of ethylene - vinyl alcohol copolymer microfine fibers A ₂
20 m of fiber having an orange cross section, a linear density of 333 μg / m, and a fiber length of 6 mm.
as%, divided fiber B, as shown in FIG. 3, a polypropylene component (symbol 12 in the figure, circular, linear density 2.
2 μg / m polypropylene ultrafine fiber B _1-1 (melting point:
160 ° C), fan-shaped, linear density 8.9μg
/ M polypropylene extra fine fiber _B1-2 (melting point: 160
C)) and a high-density polyethylene component (symbol 11 in the figure, eight high-density polyethylene ultrafine fibers B ₂ having a linear density of 8.9 μg / m (melting point: 130 ° C.) can be generated). With orange cross-section, linear density 144 μg
/ M, fiber 20 mass% of fiber length 15 mm, single fiber strength 9 g / d, linear density 222 μg /
m, polypropylene fiber having a fiber length of 10 mm (melting point: 16
0 ° C) 35 mass%, and as a fusion fiber, a core component is made of polypropylene, and a sheath component is made of low-density polyethylene (melting point: 110 ° C), a linear density of 222 µg / m,
A fiber web was formed from a slurry obtained by mixing and dispersing 25 mass% of a core-sheath type fiber having a fiber length of 10 mm with a conventional wet papermaking method.

Next, this fiber web was heat-treated at 125 ° C. to fuse only the low-density polyethylene component of the fused fibers. Next, this fused fiber web was placed on a net having a wire diameter of 0.15 mm, and the nozzle diameter was 0.13 m.
m, pressure from a nozzle plate with a pitch of 0.6 mm
A water stream of 7 MPa was jetted twice alternately on both sides alternately to split the split fibers A and B and to entangle the fibers. Thereafter, the entangled fiber web is heat-treated at 125 ° C., and only the low-density polyethylene component of the fusion fiber is fused again. Further, the fusion nonwoven fabric is calendered at a linear pressure of 9.8 N / cm. A fluorine gas treatment was performed using a mixed gas of oxygen, oxygen gas and sulfur dioxide gas to form a separator having an areal density of 50 g / m ² and a thickness of 0.12 mm.

(Example 2) The same split fiber A as in Example 1 was 35 mass%, and the same split fiber B as in Example 1 was 20 ma.
ss%, the same high-strength fiber as in Example 1 was 20 mass%,
A slurry in which the same fused fibers as in Example 1 were mixed and dispersed by 25 mass was formed into a fiber web by a conventional wet papermaking method. Then, heat treatment, division and entanglement treatment, heat treatment, calender treatment, and fluorine gas treatment are performed in exactly the same manner as in Example 1 to obtain an areal density of 50 g / m ² and a thickness of 0.12 m.
m of separators were formed.

(Embodiment 3) In exactly the same manner as in Embodiment 1,
The formation of the fiber web, heat treatment, division and entanglement treatment, heat treatment, calendar treatment, and fluorine gas treatment were performed to form a separator having an area density of 60 g / m ² and a thickness of 0.15 mm.

Example 4 The same split fiber A as in Example 1 was 40 mass%, and the same high strength fiber as in Example 1 was 35 mass%.
The wet fiber web having an areal density of 30 g / m ² was formed from a slurry in which s% and 25 mass% of the same fused fibers as in Example 1 were mixed and dispersed by a conventional wet papermaking method.

On the other hand, a split fiber B exactly the same as the split fiber B of Example 1 except that the fiber length was 25 mm was 40 ma.
Except that the ss% and the fiber length are 45 mm, the same high-strength fiber as the high-strength fiber of Example 1 except for 35 mass% and the fiber length of 38 mm is exactly the same as the fused fiber of the first embodiment. 25 mass% of the fibers were carded to form a unidirectional fiber web. On the unidirectional fiber web, a unidirectional fiber web similarly formed is crossed by a cross layer with respect to the length direction of the unidirectional fiber web to form a laminated fiber web having an area density of 20 g / m ^2. Was formed.

Next, after laminating the wet fiber web on the crossed fiber web side of the laminated fiber web, heat treatment, division and entanglement treatment, heat treatment, calender treatment, and fluorine gas treatment are performed in the same manner as in Example 1. , Area density 50g / m
^2. A separator having a thickness of 0.12 mm was formed.

Example 5 A laminated fiber web and a wet fiber were prepared in the same manner as in Example 4 except that a wet fiber web having an area density of 40 g / m ² formed in the same manner as in Example 4 was used. Lamination with a web, heat treatment, division and entanglement treatment, heat treatment, calender treatment, and fluorine gas treatment were performed to form a separator having an areal density of 60 g / m ² and a thickness of 0.15 mm.

(Comparative Example 1) 40 mass% of the same split fiber B as in Example 1 and 35 ma of the same high-strength fiber as in Example 1
A fiber web was formed from a slurry in which ss% and the same fused fiber as in Example 1 were mixed and dispersed by 25 mass by a conventional wet papermaking method. Subsequently, heat treatment, division and entanglement treatment, heat treatment, calender treatment, and fluorine gas treatment were performed in exactly the same manner as in Example 1 to form a separator having an areal density of 50 g / m ² and a thickness of 0.12 mm.

Comparative Example 2 45 mass% of the same split fiber A as in Example 1 and 30 ma of the same high-strength fiber as in Example 1
A fiber web was formed from a slurry in which ss% and the same fused fiber as in Example 1 were mixed and dispersed by 25 mass by a conventional wet papermaking method. Subsequently, heat treatment, division and entanglement treatment, heat treatment, calender treatment, and fluorine gas treatment were performed in exactly the same manner as in Example 1 to form a separator having an areal density of 50 g / m ² and a thickness of 0.12 mm.

(Comparative Example 3) The same split fiber B as in Example 1 was 40 mass%, and the same fused fiber as in Example 1 was 25 mass%.
s, and single fiber strength 4 g / d, linear density 222 μg / m,
Polypropylene fiber with a fiber length of 10 mm (melting point: 160
C) A fiber web was formed by mixing and dispersing 35 mass% of the slurry by a conventional wet papermaking method. Subsequently, heat treatment, division and entanglement treatment, heat treatment, calender treatment, and fluorine gas treatment were performed in exactly the same manner as in Example 1 to form a separator having an areal density of 50 g / m ² and a thickness of 0.12 mm.

(Various physical properties) Examples 1 to 5 and Comparative Examples 1 to
The tensile strength in the vertical direction (length direction), the tear strength in the vertical direction, and the bending resistance in the vertical direction of the separator No. 3 were as shown in Table 1.

[0066]

[Table 1]

(Penetration resistance index) Examples 1 to 5 and Comparative Example 1
, And a separator of thicknesses of about 2 mm, and a stainless steel jig attached to a handy compression tester (KES-G5, manufactured by Kato Tech) (thickness: (0.5 mm, tip angle: 60 °) was pierced vertically at a speed of 0.01 cm / s, and the force required to cut the top separator was measured. At this time, when the force required to cut the separator of Comparative Example 3 was set as a reference (100), the ratio of the force required to cut each separator was defined as the penetration resistance index (%) of the separator. The results were as shown in Table 1.

(Pressure Retention Ratio) The separators of Examples 1 to 5 and Comparative Examples 1 to 3 cut to a diameter of 30 mm were respectively
After reaching water equilibrium at a temperature of 20 ° C. and a relative humidity of 65%, the mass (M ₀ ) was measured. Next, the separator was immersed in a potassium hydroxide solution having a specific gravity of 1.3 (20 ° C.) for one hour so that the air in the separator was replaced with the potassium hydroxide solution, thereby keeping the potassium hydroxide solution. Next, this separator is sandwiched between three upper and lower filter papers (diameter 30 mm),
After applying a pressure of 5.7 MPa for 30 seconds using a pressure pump, the mass (M ₁ ) of the separator was measured. Then, the pressurized liquid holding ratio was determined by the following equation. In addition, this measurement was performed four times for one separator, and the average was defined as the liquid holding ratio under pressure. The results were as shown in Table 1. Note that the liquid retention rate under pressure (%) = [(M ₁ −M ₀ ) / M ₀ ] × 100.

(Cycle life test) As a current collector of an electrode, a paste nickel positive electrode (33 mm, 182 mm length) using a foamed nickel base material, and a paste hydrogen storage alloy negative electrode (mesh metal alloy, 33 mm, 247 mm)
Long) and created. Next, the separators of Examples 1 to 5 and Comparative Examples 1 to 3 cut to a width of 33 mm and a length of 410 mm were sandwiched between the positive electrode and the negative electrode, respectively, and spirally wound to form a SC-type electrode group. did. This electrode group was housed in an outer can, and 5N-potassium hydroxide and 1N-lithium hydroxide were injected as electrolytes into the outer can and sealed to form a cylindrical nickel-hydrogen battery.

Next, each cylindrical nickel-metal hydride battery was subjected to a charge / discharge cycle consisting of 0.2 C, 150% charge, 1 C discharge, and 1.0 V discharge at the end voltage, and the discharge capacity was reduced to 50% of the initial capacity. At this point, it was determined that the charge / discharge cycle life had expired, and the charge / discharge cycle life was measured. The results are shown in Table 1. The results are shown as a ratio when the number of cycles in Example 1 is set as a reference (100).

(Battery Internal Pressure Test) A cylindrical nickel-hydrogen battery formed in the same manner as that used in the (cycle life test) was discharged at 0.5 C and 20 ° C., and the internal pressure of the battery at 150% of the capacity was measured. It was measured. The results are shown in Table 1. The results are shown as a ratio when the internal pressure of Comparative Example 1 is set as a reference (100).

[0072]

As described above, the separator for an alkaline battery of the present invention comprises:
Divided by physical action, polyolefin ultrafine fiber A
₁ and an ethylene - vinyl alcohol copolymer microfine fibers _{A 2} and 5～40Mass% occurrence can split fibers A and is divided by a physical action, 20 the polyolefin ultra-fine fibers _{B 1} only capable of generating split fibers B 55 mass%, single fiber strength 5 g / d or more of high-strength fiber of 20 to 45
s%, the split fiber A constituent resin component, and the split fiber B
Splitting the split fibers A and B with a fiber web containing at least 20 to 35 mass% of a fused resin having a constituent resin component and a resin component having a melting point lower than the melting point of the high-strength fiber constituent resin component on the fiber surface. Processing, fiber entanglement processing,
And a non-woven fabric formed by a fusion treatment of the fusion fibers, which is subjected to a hydrophilic treatment.

As described above, since the separator of the present invention is mainly composed of polyolefin-based ultrafine fibers (A ₁ , A ₂ , B ₁ ), it has excellent alkali resistance. The separator of the present invention is an ethylene - contains ultrafine fibers, such as vinyl alcohol copolymer microfine fibers A _2, and since has been hydrophilized, near the surface of the separator can hold an electrolyte solution mainly by hydrophilic treatment, the separator internal ethylene - because it can hold the electrolyte solution by a hydrophilic vinyl alcohol copolymer microfine fibers a _2, is excellent in retention of electrolyte. As described above, since the electrolyte retainability is excellent even in the interior of the separator, the separator has excellent oxygen absorption during overcharge and excellent internal pressure characteristics. Furthermore, since the burr of the electrode plate can be prevented from penetrating the separator by containing the high-strength fiber, the battery can be manufactured with a high yield by using the separator of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a split fiber A and a split fiber B of the present invention.

FIG. 2 is a schematic sectional view of another split fiber A and split fiber B of the present invention.

FIG. 3 is a schematic cross-sectional view of another split fiber A and split fiber B of the present invention.

FIG. 4 is a schematic cross-sectional view of another split fiber A and split fiber B of the present invention.

FIG. 5 is a schematic sectional view of another split fiber A and split fiber B of the present invention.

[Explanation of symbols]

 1 split fiber 11 one component 12 other component

Claims (1)

[Claims] 1. A divided by physical action, polyolefin microfine fibers A ₁ and ethylene - 5 to 40 mA vinyl alcohol copolymer microfine fibers A ₂ and capable of generating a split fibers A
ss%, is divided by a physical action, the split fibers B capable of generating only polyolefin microfine fibers _{B 1} 20～55M
ass%, high-strength fiber having a single fiber strength of 5 g / d or more
0 to 45 mass%, and at least a resin component having a melting point lower than the melting points of the split fiber A constituent resin component, the split fiber B constituent resin component, and the high-strength fiber constituent resin component on the fiber surface. 20-35mass fiber
a fiber web containing s%, a splitting process of the split fibers A and B,
A separator for an alkaline battery, wherein a nonwoven fabric formed by entanglement treatment of fibers and fusion treatment of the fusion fibers is subjected to hydrophilic treatment.