JP2001283818A - Separator for alkaline battery and alkaline battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for a battery which has an excellent ammonia capture property, and a high capacity retainability with little self-discharge, and a long life, through use of this separator. SOLUTION: This separator for the battery with robustness, excellent in self-discharge and ammonia capture property, and highly transmissive of oxygen gas reinforced with one or more layers of a sheet-type substance made of fibers with vinyl alcohol resin as a main component laminated with a sheet-like substance made of fiber with polyolefinic resin containing sulfonate group as a main component is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline battery separator and an alkaline battery using the battery separator. Such an alkaline battery, particularly an alkaline secondary battery, is used for batteries of, for example, electric vehicles and electric tools.

[0002]

2. Description of the Related Art A battery is roughly divided into a positive electrode, a negative electrode, an electrolyte, a separator, and a container. The positive electrode and the negative electrode are separated by the separator, and are housed in the container while being immersed in the electrolyte solution.

[0003] Alkaline secondary batteries, particularly nickel-metal hydride batteries, have high capacities and are being applied to electric vehicles and power tools, but their disadvantage is that they have a large self-discharge amount. It is also reported that the amount of self-discharge greatly varies depending on the type of separator.

For example, functional materials (pages 32 to 42, vo
l. 19, no. 8, August 1999) discloses a separator using a fiber whose surface layer is an ethylene-vinyl alcohol copolymer (conventional example 1), in which an OH group of polyvinyl alcohol holds an electrolytic solution. Is shown. However, when the above-mentioned separator is used, there is a problem that the capacity retention ratio is low and the self-discharge amount is large, and it has been shown that the separator has no function of suppressing self-discharge at all. In addition, it has been pointed out that while the sulfonated separator is permanently hydrophilic, the polyvinyl alcohol-based separator has a problem in durability. In other words, the polyvinyl alcohol-based fiber has a problem in terms of long-term durability.

[0005] Further, in the above publication, in order to obtain a high capacity retention, a separator obtained by grafting a vinyl monomer having a carboxylic acid such as acrylic acid (Conventional Example 2) requires a nonwoven fabric as a base material. , 5 to 15% by weight, a very large amount of grafting is required, and it is shown that the gas permeability indicating gas permeability is reduced. Although separators are strongly required to be thinner to improve battery capacity,
In order to obtain sufficient electrolyte retention when the thickness is reduced, it is required to mix ultrafine fibers. However,
In Conventional Example 2, there is a problem that it is difficult to cope with the problem of air permeability.

Further, in the above publication, a sulfonated separator (conventional example 3) is capable of maximizing the capacity retention, and a product treated with fuming sulfuric acid has been put to practical use. Fiber diameter is 10 μm
It is described that the product of m is only practically used. Also, there is no established theory on the self-discharge suppression mechanism.
It is described that it has not been clarified. Further, it has been shown that the sulfonation-treated separator has a drawback that the liquid absorbing speed of the electrolytic solution is low and the ability to hold the electrolytic solution is low.

Some studies have been made on the sulfonated separator before the above literature, but none of the properties required for the separator satisfying the overall properties has been obtained. For example, a 28th Battery Symposium Proceedings (Page 113, 1987) proposes a separator in which polypropylene is sulfonated (conventional example 4). When such a nonwoven fabric separator made of sulfonated polypropylene is used, Although it is described to show a higher capacity retention rate than conventional nylon separators, the purpose is to not elute nitrogen-based impurities from the separator,
No measures have been taken to improve the capacity retention rate.

Japanese Patent Application Laid-Open No. Hei 10-326607 discloses a measure for increasing the degree of sulfonation in order to improve the liquid absorption rate and the liquid retaining property of the electrolytic solution. It is shown that the sulfur concentration can be used as an index of the degree of sulfonation, and examples thereof include a separator having a sulfur concentration of 7 mg / g.
This is thought to be the result of increasing the surface area by making it extremely small, such as denier. (Conventional example 5)
That is, by increasing the surface area, it is considered that the total amount of sulfonic acid groups introduced was increased while avoiding the intensive introduction of sulfonic acid groups. It is the same as the method, but rather, the strength is reduced due to ultrafineness, and there is a larger problem in strength.

Further, as disclosed in the same publication, the single fiber fineness is 0.01 to 0.1 denier (0.011 to 0.1 denier).
In order to obtain a 1 dtex) polypropylene fiber separator, as a production method, a raw material comprising a mixed fiber of a sea-island type composite fiber having a sea component as a polyamide resin and an island component as polypropylene and an olefin-based binder fiber, This is sulfonated to dissolve and remove the polyamide resin to obtain a polypropylene fiber of 0.01 to 0.1 denier (0.011 to 0.11 dtex). With such a manufacturing method, it is difficult to completely remove the polyamide resin only to the central portion of the sea-island type composite fiber by the sulfonation treatment alone, and there is a problem that the remaining polyamide may cause self-discharge of the battery. Was.

In addition, 0.01 to 0.1 denier (0.0
When a microfiber of 11 to 0.11 dtex) is used for the separator, the gas permeability becomes too low, and oxygen gas generated in the positive electrode at the end of charging of the battery cannot be sufficiently transmitted to the negative electrode. There is a concern that electrolyte leakage may occur and further the battery may burst. In addition, since the fiber strength is extremely reduced due to the ultrafine structure, the fiber may be disconnected and short-circuit may occur.

[0011]

As described above, the sulfonated separator has a relatively high capacity retention rate and has the advantage that its characteristics do not change even when used at a high temperature. With ultrafine fibers having a fiber diameter, it was impossible to produce a separator having sufficient strength. That is, there was a problem that it was not possible to ensure both the retention of electrolyte solution and the strength by using ultrafine fibers. Further, there has been a problem that the liquid absorbing speed of the electrolytic solution is low, and the productivity in the battery manufacturing process is reduced.

Further, the capacity retention is not sufficient, and if the sulfonation is high, that is, if the content of sulfur is increased to further improve the capacity retention, collapse and peeling of the fiber surface portion have occurred. As a result of intensive studies by the present inventors, the reason is that polyolefin-based resin fibers (for example, polypropylene spun-pound fibers, polypropylene / polyethylene composite core-sheath fibers, etc.) commonly used in conventional separators have high intrinsic viscosity. It turned out that it was. Polyolefin resin fibers with high intrinsic viscosity are widely used from the viewpoint of ease of spinning, but such high intrinsic viscosity polyolefin resin fibers are excellent in acid resistance, so if you forcibly proceed with sulfonation, As described above, the strength of the fiber is reduced, and the sulfonated portion is disintegrated and peeled off. As a result, the amount of the sulfonic acid group is not so large.

Therefore, the present inventors have found that a polyolefin-based resin fiber having a specific intrinsic viscosity can be highly sulfonated without causing collapse of the fiber surface even when sulfonation is performed. Further, in the above separator, it has been found that the number of effective trap sites for ammonia as an impurity is greatly increased, and as a result, a separator having a significantly improved capacity retention rate can be obtained. -96546).

Further, in the present invention, in addition to the capacity retention rate by the improvement of the ammonia trapping performance, the separator strength is high, fiber breakage does not occur, the retention of the electrolyte is maintained, the gas permeability is high, and It has made it possible to provide excellent separators. Using this separator, (1) the amount of self-discharge is further reduced and the capacity retention rate is excellent, (2) there is no failure due to short-circuiting of the battery, and (3) the retention of the electrolytic solution is reduced even after repeated charging and discharging. (4) It is an object of the present invention to provide an alkaline battery which has a long service life without any increase in internal pressure and high safety.

[0015]

A battery separator according to the present invention comprises a sheet-like material [A] mainly composed of a fiber composed of a polyolefin resin having a sulfonic acid group, and a vinyl alcohol-based resin. Sheet [B] made of the following fibers are laminated in one or more layers.

One of the sheet materials [A] has a bulk density of 0.5 g / cm ³ or more, and another sheet material has a vinyl alcohol resin as a main component. Fiber with a bulk density of 0.5 g / cm
A battery separator, wherein the sheet-like nonwoven fabric [B] is less than ³ , and the sheet-like nonwoven fabric [A] and the sheet-like nonwoven fabric [B] are each laminated at least one layer.

The sheet-like material [A] needs a function of trapping a substance causing self-discharge existing inside the battery. As already shown in Japanese Patent Application No. 11-96546,
The largest factor of self-discharge is ammonia, and the sheet-like material [A] is required to have a high ammonia trapping ability. As a separator having high ammonia trapping performance, a separator grafted with a vinyl monomer can be used in the present invention, but in terms of overall performance including heat resistance, the use of a fiber obtained by sulfonating the following special polyolefin is optimal.

A fiber obtained by sulfonating a polyolefin resin fiber having an intrinsic viscosity of 0.2 to 1.0 dl / g, and the fiber after the sulfonation has a total sulfur content per 1 g. Those exceeding 10 mg and 50 mg or less are optimally usable.

When a polyolefin resin fiber having an intrinsic viscosity of 0.2 to 1.0 dl / g is sulfonated with a sulfonating agent (such as sulfuric acid), the mechanical strength of the polyolefin resin itself such as the collapse of the fiber surface is reduced. A large amount of sulfur atoms, that is, ammonia trap sites such as a sulfonic acid group can be introduced in a state where the reduction does not occur so much. In other words, the sulfur content can be increased without decreasing the single fiber fineness and increasing the fiber surface area.
, A polyolefin-based resin fiber having a high sulfur content can be obtained. Also, since the fiber strength does not decrease much, the risk of short-circuiting due to fiber cutting of the separator when the separator is incorporated in the battery is reduced.

More preferably, the intrinsic viscosity is 0.4 dl / g or more and 0.9 dl / g or less. The intrinsic viscosity is a value measured using a tetralin solvent as described later.

The sulfur content can be used as an index of the ammonia trapping ability, and the total sulfur content per gram of fiber is 10 m.
If it exceeds g, the ammonia trapping rate will be high. It has been known that the higher the sulfur content, the higher the ammonia trapping ability is. However, a separator having a total sulfur content exceeding 10 mg has not been realized until now, and this has now been realized. Also, conventionally, it was difficult to fabricate, and the relationship between the separator having a total sulfur amount of more than 10 mg and the ammonia trapping ability has not been studied. However, the separator having a total sulfur amount of more than 10 mg produced by the present inventors was used. As a result of the investigation, it was found that the ammonia trapping rate was dramatically improved in the separator.

On the other hand, even if the total sulfur amount exceeds 50 mg, the improvement of the ammonia trapping rate cannot be expected so much.
It is not preferable to set the total sulfur amount to more than 5 g because the strength of the steel is significantly reduced even by the method of the present invention.
0 mg or less. It is more preferably 30 mg or less, and further preferably 20 mg or less.

The content of the fiber is preferably 20% by weight or more based on the total weight of the separator, and more preferably 30% by weight or more, when used in a battery. The separator satisfactorily traps ammonia, resulting in reduced self-discharge and improved capacity retention.

The bulk density of the sheet material [A] is 0.5 g / c.
If it is at least m ³ , the liquid retention property is high and the chance of contact with ammonia present in the electrolyte solution or the like increases, and ammonia can be trapped efficiently. In addition, by increasing the bulk density, it is possible to satisfactorily separate the positive electrode and the negative electrode, that is, it is possible to satisfactorily block active substances from the positive electrode and the negative electrode,
Excellent short circuit prevention of battery. More preferably, the bulk density of the sheet material [A] is 0.6 g / cm ³ or more.

On the other hand, the permeability of oxygen gas generated at the end of charging of the battery is required as a characteristic of the separator. If the bulk density is too high, the gas permeability is inferior.
Accordingly, the bulk density of the sheet material [A] is 0.85 g / c.
It is preferably at most m ³ , which allows the separator to function well without causing a decrease in gas permeability.

In addition, in the present invention, the total sulfur content of the sheet-like material [A] is preferably 150 mg / m ² or more.

As described above, 150 mg / m^Two If more than
Sufficient sulfonic acid groups available for ammonia trap
And has excellent ammonia trap performance.
You. More preferably 160 mg / m^Two That is all. on the other hand
When there are too many sulfonic acid groups, that is, when the total sulfur content is large
Is 500 mg / m
^TwoThe following is preferred.

In the case of laminating the sheet material [A] having an extremely high ammonia trapping property, the sheet material [B] is not particularly required to have an ammonia trapping ability and is required to have high reinforcing performance. However, self-discharge-causing substances such as ammonia must not be eluted from the sheet-like material [B], and fibers having high strength represented by general-purpose polyamide resin but capable of eluting ammonia cannot be used. .

The fiber most suitable for the sheet-like material [B] is a fiber mainly composed of a vinyl alcohol resin. Although the fiber does not have a function of suppressing self-discharge as shown in Conventional Example 1, it has an affinity for an electrolytic solution without a special hydrophilization treatment and at the same time has a higher strength than a general polyolefin-based resin. I have. Therefore, there is no adverse effect such as a decrease in strength due to the sulfonation treatment and a decrease in air permeability due to grafting of the carboxylic acid-containing resin, and thus a sheet-like material [B] having high strength and affinity for an electrolyte can be obtained.

The vinyl alcohol resin used in the present invention includes, in addition to a resin obtained by homopolymerization of vinyl alcohol, a copolymer of vinyl alcohol represented by an ethylene-vinyl alcohol copolymer and another vinyl monomer. it can. If the vinyl alcohol monomer component is contained in an amount of 30% by weight or more based on the sheet-like material [B], it is possible to maintain sufficient affinity for the electrolyte solution, and preferably 40% by weight or more.

As described above, the sheet-like material [A] cannot be made so coarse from the viewpoint of ammonia trapping efficiency, but the sheet-like material [B] has a lower bulk density. When the bulk density of the sheet material [B] is less than 0.5 g / cm ³ as described above, the gas permeability is very good. In addition, ammonia present in the electrolyte solution or the like satisfactorily passes through the sheet material [B] and reaches the sheet material [A]. The bulk density of the sheet [B] is more preferably 0.45 g / cm ³ or less.

On the other hand, from the viewpoint of reinforcing the sheet-like nonwoven fabric [A], the bulk density of the sheet-like nonwoven fabric [B] is 0.15 g.
/ Cm ³ or more.

As described above, by increasing the density of the sheet-like nonwoven fabric [A] having a high total sulfur content and decreasing the density of the sheet-like nonwoven fabric [B] as the reinforcing layer, the efficiency of ammonia trapping is increased.

In addition, in the present invention, the average fiber diameter of the fibers constituting the sheet-like material [A] is 8 μm or less, and the average fiber diameter of the fibers constituting the sheet-like material [B] is 10 μm or more. Desirably.

The average fiber diameter of the fibers of the sheet material [A] is 8
If it is not more than μm (corresponding to 0.45 dtex in the case of polypropylene), the liquid retaining property of the electrolyte is good and the fiber surface area is sufficiently large, so that ammonia can be satisfactorily trapped on the fiber surface. When the ultra-fine fibers made of the general-purpose polyolefin resin are sulfonated, the strength is extremely reduced as compared with the case where the fiber diameter is large, and as a result, there is a concern that the fibers are cut and pinholes are generated.
There is a problem that a short circuit occurs inside the battery incorporating the separator, but when the polyolefin resin fiber having the intrinsic viscosity of 0.2 to 1.0 dl / g in the present invention is used, extreme strength is not obtained. Since there is no drop, there is little possibility that the fiber is torn and a pinhole is formed.

The average fiber diameter of the fibers of the sheet material [A] is 3 μm or more (0.064 d in the case of polypropylene).
tex), more preferably 4 μm or more (corresponding to 0.102 denier in the case of polypropylene). If it is 3 μm or more (more preferably 4 μm or more), it becomes easy to maintain the uniformity of the sheet-like material, and the probability of occurrence of pinholes decreases,
Therefore, the battery exhibits excellent characteristics for preventing short circuit. At the same time, fine inter-fiber gaps allowing gas permeation can be secured, so that the permeability of gas generated at the end of charging can be sufficiently maintained. Regarding gas permeability, JIS L
According to the permeability A method of 1096, it is preferably 7 cm ³ / cm ² / s or more as measured by a Frazier-type tester.

If the fibers are thin and the bulk density is high as described above, the contact efficiency with ammonia becomes extremely high, so that the self-discharge can be suppressed well when the battery is used, and This is the capacity retention rate.

When the average fiber diameter of the fibers of the sheet material [B] is 10 μm or more, a sufficient reinforcing effect is exhibited.
More preferably, it is 12 μm or more. On the other hand, if the fiber system is too thick, the nonwoven fabric becomes non-uniform, so that the thickness is more preferably 50 μm or less.

Further, the alkaline battery according to the present invention comprises:
The gist is that the battery separator [A] is disposed on the battery positive electrode side, and the sheet separator [B] is disposed on the battery negative electrode side. With the above arrangement, oxygen gas generated from the positive electrode at the end of charging can be more efficiently transmitted to the negative electrode side. When the arrangement is reversed, the gas permeability deteriorates, the internal pressure of the battery increases, and the risk of electrolyte leakage and battery rupture increases.

Conventionally, it has been pointed out that a nonwoven fabric containing a vinyl alcohol-based resin as a main component, when repeatedly charged and discharged, has a reduced hydrophilicity and a reduced ability to retain an electrolytic solution. However, the inventor's detailed study has confirmed that the above-mentioned performance degradation is highly affected by oxidative degradation that occurs particularly strongly near the positive electrode. Therefore, in the separator of the present invention, a sheet-like material mainly composed of a polyolefin-based resin fiber having a sulfonic acid group is disposed on the positive electrode side with high oxidation resistance, and the strength is high but the oxidation resistance is high. By arranging a “sheet-like material containing a vinyl alcohol-based resin as a main component” having a low density on the negative electrode side, it was found that the above-mentioned performance degradation could be avoided, and the present invention was reached.

As a result, when the separator of the present invention is incorporated in a battery in the above arrangement, the electrolyte can be stably maintained without deterioration of the separator even after repeated charge / discharge cycles for a long period of time. It became possible to obtain a battery.

The gist of the alkaline battery of the present invention is that the alkaline battery separator is used for separating a positive electrode from a negative electrode.

As described above, the alkaline battery separator of the present invention is (1) excellent in the ammonia trapping performance, so that the self-discharge amount is further reduced and the capacity retention rate is excellent, and (2) the strength is high and no failure due to short circuit of the battery occurs. (3) Long life without deterioration of electrolyte retention even after repeated long-term charge / discharge, (4) Excellent alkaline battery having excellent gas permeability, high safety, and simultaneously the above characteristics Can be provided.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The type of polyolefin resin used for the battery separator of the present invention is not particularly limited, and examples thereof include hydrocarbon-based resins such as polyethylene, polypropylene, polybutene, polystyrene, and ethylene-propylene copolymer. It is a fiber composed of resin. Especially in the sulfuric acid treatment described below, polypropylene
The treatment can be performed in a very wide temperature range from 90 to 150 ° C., and a high-temperature treatment of, for example, 120 ° C. or more is also possible.

The method of the sulfonation treatment is particularly limited.
Is not specified, for example, SO _ThreeGas, SO_TwoGas, etc.
Phase treatment with sulfuric acid solution and fuming sulfuric acid
Logical methods and the like.

In particular, according to the liquid phase treatment method using a sulfuric acid solution,
Sulfonation can be performed with high uniformity, and is most preferable. When sulfonic acid groups are introduced by immersion in concentrated sulfuric acid at 90 to 150 ° C., treatment at a high temperature of 120 to 150 ° C. can introduce sulfonic acid groups most efficiently,
That is, it is preferable because the total sulfur amount can be efficiently increased.

[0047] In the vapor phase treatment method according to the SO3 gas, using 0.5 to 30% by volume of SO ₃ gas, 15
Processing at 40 ° C. (for example, room temperature) is possible. Note that S
The optimum O ₃ gas concentration is 2 to 20% by volume.

Alternatively, the total sulfur content is more than 10 mg / g,
A sheet [A] (hereinafter sometimes referred to as an A layer) mainly containing fibers made of polyolefin-based resin of not more than mg / g, and a sheet made of fibers mainly composed of a vinyl alcohol-based resin. [B] (hereinafter sometimes referred to as layer B) is laminated to form a separator.

In the sheet of the layer A, the polyolefin resin fibers having a total sulfur content of more than 10 mg / g and not more than 50 mg / g obtained as described above are contained in an amount of 30% by mass or more, preferably 50% by mass or more. It is desirable to do. The A layer that satisfies the above is desirable because it can exhibit high ammonia trapping properties.

In the present invention, the method of joining the sheet-like materials [A] and [B] is not particularly limited as long as the method does not inhibit gas permeability and does not cause elution of impurities. A method in which the fibers of the sheet materials [A] and [B] are entangled and joined using a flow, or a method in which the fibers are heat-bonded by hot pressing can be used.

The bonding method most suitable for the present invention is a method of bonding using an adhesive at the interface between the sheet-like materials [A] and [B]. As the adhesive, any adhesive can be used as long as it has a lower melting point than the fibers constituting the [A] and [B] layers and does not deteriorate at the same time when immersed in the electrolytic solution. , Ethylene copolymer,
Resins containing at least one of acrylic acid copolymer, methacrylic acid copolymer and vinyl acetate copolymer can be used favorably.

The amount of the adhesive used is preferably in the range of 0.1 to 20% based on the weight of the separator. If the amount of the adhesive used is small, two layers may be peeled off when the battery is incorporated into the battery. If the adhesive is applied too much, the gap between the fibers is blocked, and the air permeability is undesirably reduced. It is desirable that the adhesive is applied to the interface between the two layers, and heated and pressed at a temperature at which the fibers constituting the separator do not melt to bond the adhesive.

The A layer and the B layer are not limited to the case where each layer is laminated one by one, but may be a laminate of two or more layers.

The layer A and the layer B are preferably laminated in such a manner that the polyolefin resin fibers of the layer A are uniformly distributed in the plane direction of the separator. This is because ammonia that has passed through the separator due to diffusion can be trapped without escape.

The sheet-like material composed mainly of a vinyl alcohol resin used for the layer B is prepared by a card method,
Fibers obtained by spunbonding or splitting a film are effectively used, and a sheet-like material produced simultaneously with fiberization by a melt blow method may be used. Also, a sheet-like material formed by wet papermaking has high uniformity and can be used effectively.

Further, by mixing a composite fiber of polyethylene and polypropylene (side pi side type, core-sheath type, etc.) and fusing and adhering the polyethylene component, a fiber mainly composed of a vinyl alcohol resin is strongly bonded. And maintain good strength. Further elongation is 2-10
% Of ultrahigh molecular weight polyethylene is effective because the strength is improved and the reinforcing effect is more excellent.

[0057]

<Example 1> As a raw material of the layer A, an intrinsic viscosity of 0.1 was used.
Using a 58 dl / g propylene resin, the extrusion temperature from the orifice is 220 ° C, and the single hole discharge rate is 0.5 g / mi.
n. The fiber is made into a non-woven fabric on a collection conveyor while fiberizing the above-mentioned propylene resin by melt drawing with a 0.6 kg / cm ² air flow at 250 ° C. (melt blow method). Then, this was added to 98% by weight concentrated sulfuric acid at 135 ° C. for 5 minutes.
Then, it was immersed for a minute to perform sulfonation treatment. As the B layer, a polyvinyl alcohol wet papermaking nonwoven fabric [V, manufactured by Hirose Paper Co., Ltd.]
N24] was used. Next, an aqueous dispersion of fine powder of polyethylene as an adhesive [Mitsui Chemicals, Chemipearl M200] was attached to the B layer and dried at 60 ° C., whereby 8.5% by weight of the polyethylene powder was added to the B layer. . In addition, 11
Layer A and layer B were integrated by hot pressing at 0 ° C. to form a separator. Then, using the above separator, the battery was assembled with the surface of layer A on the positive electrode side and the surface of layer B on the negative electrode side, to produce a sealed nickel-metal hydride secondary battery of SC (subsea) size.

<Example 2> In the same manner as in Example 1, the raw material of the layer A (polypropylene resin having an intrinsic viscosity of 0.38 dl / g) was formed into a nonwoven fabric while being fiberized (melt blow method), and then 98 mass at 130 ° C. % Sulfuric acid for 10 minutes to perform a sulfonation treatment. Wet paper nonwoven fabric made of polyvinyl alcohol [VN2 manufactured by Hirose Paper Co., Ltd.]
4], and the layer A and the layer B were integrated into a separator in the same manner as in Example 1. Then, using the above separator, the battery was assembled with the surface of layer A on the positive electrode side and the surface of layer B on the negative electrode side, to produce a sealed nickel-metal hydride secondary battery of SC (subsea) size.

<Example 3> In the same manner as in Example 1, the raw material of the layer A (polypropylene resin having an intrinsic viscosity of 0.78 dl / g) was formed into a nonwoven fabric while being fiberized (melt blow method), and then 98 mass at 130 ° C. % Sulfuric acid for 10 minutes to perform a sulfonation treatment. A cut fiber of polyvinyl alcohol (0.5 dtex, 50 m
m) was used to obtain a nonwoven fabric by a card method. Then, an aqueous dispersion of fine powder mainly composed of vinyl acetate-ethylene as an adhesive [Mitsui Chemicals, Chemipearl V200] is attached to the B layer, and dried at 60 ° C., whereby the adhesive powder is applied to the B layer by 7 times. 0.5% by weight. Furthermore, layer A and layer B were integrated by hot pressing at 110 ° C. to form a separator. Then, using the above separator, the battery was assembled with the surface of layer A on the positive electrode side and the surface of layer B on the negative electrode side, to produce a sealed nickel-metal hydride secondary battery of SC (subsea) size.

<Example 4> In the same manner as in Example 1, the raw material of layer A (polypropylene resin having an intrinsic viscosity of 0.50 dl / g) was formed into a nonwoven fabric while being fiberized (melt blow method), and then 98 mass at 130 ° C. % Sulfuric acid for 10 minutes to perform a sulfonation treatment. Wet paper nonwoven fabric made of polyvinyl alcohol [VN2 manufactured by Hirose Paper Co., Ltd.]
4] was used. Then, an aqueous dispersion of fine powder mainly composed of an ethylene / α-olefin copolymer serving as an adhesive [Mitsui Chemicals, Chemipearl A100] is attached to the B layer, and dried at 60 ° C. to apply the adhesive powder to the B layer. 7.0% by weight. Furthermore, layer A and layer B were integrated by hot pressing at 110 ° C. to form a separator. Then, using the above separator, the battery was assembled with the surface of layer A on the positive electrode side and the surface of layer B on the negative electrode side, to produce a sealed nickel-metal hydride secondary battery of SC (subsea) size.

<Comparative Example 1> A layer was prepared in the same manner as in Example 1 above, using a polypropylene resin having an intrinsic viscosity of 1.22 dl / g as a raw material of the A layer.
It was immersed in 10% by mass of concentrated sulfuric acid for 10 minutes to perform a sulfonation treatment. Using a polyvinyl alcohol wet paper nonwoven fabric [VN24 manufactured by Hirose Paper Co., Ltd.] as the B layer, the A layer and the B layer were integrated into a separator in the same manner as in Example 1. Then, using the above separator, the battery was assembled with the surface of layer A on the positive electrode side and the surface of layer B on the negative electrode side, to produce a sealed nickel-metal hydride secondary battery of SC (subsea) size.

Comparative Example 2 A polypropylene resin having an intrinsic viscosity of 0.58 dl / g was used, the extrusion temperature from the orifice was 220 ° C., and the single hole discharge rate was 0.5 g / min. And 2
The polypropylene resin is formed into a non-woven fabric on a collection conveyor while the polypropylene resin is formed into fibers by melt-blowing at 50 ° C. with an air flow of 0.6 kg / cm ² (melt blow method). Only the single layer of the non-woven fabric was immersed in 98% by mass of concentrated sulfuric acid at 135 ° C. for 5 minutes to perform a sulfonation treatment to obtain a separator. The total sulfur of the separator is 15.9 mg / g. Then, a nickel-hydrogen secondary battery is manufactured using the separator.

Comparative Example 3 A nickel-hydrogen secondary battery was manufactured using polyvinyl alcohol wet papermaking nonwoven fabric “VN48 manufactured by Hirose Paper Co., Ltd.” as a separator.

The physical properties of the separators of Examples 1 to 4 and Comparative Examples 1 to 3 and the capacity retention of each of the nickel-metal hydride secondary batteries were measured. Tables 1 to 3 show these results.

[0065]

[Table 1]

[0066]

[Table 2]

[0067]

[Table 3]

As can be seen from Tables 1 to 3 above, Examples 1 to 3 were used.
It is considered that the separator of No. 4 has a high total sulfur content in the A layer, and therefore has a high total sulfur content as a whole of the separator, and therefore, it is considered that the ammonia trapping rate is high, and as a result, the capacity retention of the battery is high. Further, the reinforcing effect of the layer B is sufficient, and the short-circuit probability sufficiently satisfies the value of 10% or less which is required for practical use.

On the other hand, the separator of Comparative Example 1 had a low ammonia trapping rate and a relatively low capacity retention rate of the battery. In the separator of Comparative Example 2,
Although the ammonia trap rate showed a high value, the drop in strength was large, the probability of short-circuit was extremely high, and at the same time, gas permeability was poor because all layers were made of only microfibers, which caused the battery to expand. The battery was deformed. In Comparative Example 3, since there was no ammonia trapping property, the capacity retention of the battery was low, and at the same time, there was a problem that the cycle life was short.

After the cycle life measurement of Comparative Example 3, the battery was disassembled and the separator was taken out, and it was visually confirmed that the portion in contact with the positive electrode was greatly deteriorated.

The methods for measuring the intrinsic viscosity, the total sulfur content, the bulk density, the ammonia trapping rate, the capacity retention rate, the cycle life, and the battery short-circuit rate will be described below.

Intrinsic viscosity (IV) Using tetralin as a solvent, a sample was dissolved in the tetralin, and the solution was filtered with a glass filter.
The measurement is performed at a temperature of 135 ± 0.1 ° C. using a hde viscometer. Incidentally, 0.2% by mass of BHT (2,4-di-t-butyl-p-cresol) is added to the tetralin used in advance to prevent oxidative deterioration when the sample is dissolved. The concentration of the sample solution is 1 g / 1000 cc
And A value of 0.35 is used as the Huggins constant (k '). The measuring method is described in “Experimental Chemistry Course 8 Polymer Chemistry (above), Chapter 5, Viscosity, Chemical Society of Japan, May 15, 1963
Day ".

The total sulfur content is carried out by a flask combustion method in accordance with the method described in "Basic Analytical Chemistry, Vol. 11, Japan Society for Analytical Chemistry (Kyoritsu Shuppan), pp. 34-43, September 1965". .

-Bulk density Carefully separate the A layer and the B layer, thoroughly wash the adhered impurities, perform hot air drying at 60 ° C for 2 hours, and further vacuum dry at 60 ° C for 20 hours. Then, the basis weight is measured on the basis of the weight after the weight becomes constant. Regarding the thickness of each of the layers A and B, the cross section of the separator is observed by SEM and the thickness of each layer is measured in an integrated state without separation. Then, the high density (g / cm ³ ) is calculated by the following equation (1). High density = weight per 1 cm ² (g / cm ² ) / layer thickness (cm) ... (1)

When it is difficult to separate the layers A and B, the adhered impurities are washed in the same manner as above while the layers A and B are integrated, and then dried with hot air at 60 ° C. for 2 hours at 60 ° C. Vacuum drying is performed for 20 hours, and the weight after reaching a constant weight is used. Then, 30 points of the cross section of the separator are measured at random, and image analysis is performed on a portion where the A layer and the B layer are independently present at the measurement point to obtain the volume occupied by the fiber. The bulk density is calculated based on the specific gravity.

Ammonia trap rate An 8N potassium hydroxide solution (1000 c) was placed in an eggplant-shaped flask.
c and a separator having a dry weight of 1.0 g were charged, and air was removed from the separator by vacuum degassing, and the separator was completely immersed in the potassium hydroxide solution. After degassing in vacuum, 0.1 cc of a 1N aqueous ammonia solution is added, and the ammonia concentration is adjusted to 3 × 104 mol. Then, the container is completely sealed, left at 45 ° C. for 72 hours, and the amount of remaining ammonia is measured. From this value, the amount of ammonia trapped in the separator is calculated based on the calibration curve.
The ammonia trap rate indicates the amount of trapped ammonia as a percentage (%) with respect to the initial abundance. The measurement of the ammonia concentration is performed by an absorption spectrophotometric method according to JIS K0102.42.2.

When measuring a separator having already trapped ammonia, as a pretreatment, the separator is first washed with pure water, and then the weight of the separator is 200 times the weight of the separator.
It is immersed in N-hydrochloric acid for 10 hours or more, washed again with water, and then dried under vacuum at 60 ° C. and 2 Pa for 20 hours for regeneration. Then, measure the amount of ammonia as described above,
Find the ammonia trap rate.

Capacitance Retention First, a paste-type nickel hydroxide positive electrode, a paste-type hydrogen storage alloy negative electrode, and a separator were wound around a spiral strip, and SC
A sealed battery of a size is produced. Note that an aqueous solution of potassium hydroxide to which lithium hydroxide is added is used as an electrolyte for this battery.

As an initial activation process for preparation, the substrate is kept at 45 ° C. for 6 hours. Thereafter, the battery is charged at 0.2 C for 6 hours in an air atmosphere at 20 ° C., discharged at 0.2 C (discharge end voltage: 1.0 V), and this charge / discharge operation is repeated seven times.

Next, the battery was charged at 0.2 C for 6 hours, and after resting for 1 hour, the discharge capacity at 0.2 C discharge (final voltage: 1.0 V) was measured to obtain a measured value C0. Then, the battery was charged at 0.2 C for 6 hours, stored in an air atmosphere at 45 ° C. for 168 hours, then allowed to cool at 20 ° C. for 6 hours, and the discharge capacity at 0.2 C discharge (final voltage: 1.0 V) was measured. To be a measured value C1.
Then charge at 0.2 C for 6 hours, pause for 1 hour,
Measure the discharge capacity at 2C discharge (1.0 V final voltage),
The measured value is C2. The above-mentioned 0.2C discharge is to discharge a fully charged battery in 5 hours, and at this time, the discharge current value is set to an appropriate value.

The capacity retention is calculated by the following equation (2) based on the above measured values. Capacity retention (%) = C1 × 2 / (C0 + C2) × 100 (2)

The relationship between the self-discharge amount (%) and the capacity retention (%) is expressed by the following equation (3). Capacity retention = 100−self-discharge amount (3)

Cycle Life Using the battery after the above capacity retention ratio measurement, charge and discharge were repeated at 0.2 C, and the point in time when the discharge capacity reached 60% of the initial capacity was defined as the life. The number of charge / discharge cycles was defined as cycle life [times].

Battery Short-Circuit Rate By the time the measurement of the capacity retention rate was completed, the number of batteries that could not be measured due to short-circuiting inside the battery was counted and expressed as a percentage (%) of the prepared battery.

As described above, the battery separator and the alkaline battery according to the present invention have been specifically described with reference to the examples. However, the present invention is not necessarily limited to the above examples. It is also possible to carry out the present invention with appropriate modifications within a compatible range, and all of them are included in the technical scope of the present invention.

[0086]

The battery separator according to the present invention is excellent in ammonia trapping performance, and has high strength and little possibility of fiber cutting. Therefore, there is little possibility of short-circuit accident when the battery is used, and the reliability is high. It is high, has excellent oxygen gas permeability, and has a long life. Further, the battery using the separator has less self-discharge, and has excellent capacity retention,
The separator has excellent strength and does not increase the internal pressure of the battery. Therefore, it has a high capacity retention rate and excellent safety, and at the same time has a long life.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masahiro Yamashita 2-1-1 Katata, Otsu-shi, Shiga F-term in Toyobo Co., Ltd. Research Laboratory 5H021 AA06 BB09 CC02 CC04 EE04 EE05 EE18 EE21 HH03 HH05 HH07 5H028 AA05 BB10 EE01 EE06 HH00 HH01 HH03 HH05

Claims (8)

[Claims] 1. A sheet-like material [A] made of a fiber mainly composed of a polyolefin resin having a sulfonic acid group and a sheet-like material [B] made of a fiber mainly composed of a vinyl alcohol-based resin. A separator for an alkaline battery, wherein the separator comprises at least two layers. 2. In a battery separator in which a plurality of sheet-like materials are laminated, one of the sheet-like materials [A] has a bulk density of 0.5 g / cm ³ or more, The separator for an alkaline battery according to claim 1, wherein the sheet-like material is a sheet-like nonwoven fabric [B] having a bulk density of less than 0.5 g / cm ³ . 3. An average fiber diameter of fibers constituting said sheet-like material [A] is 8 μm or less, and an average fiber diameter of fibers constituting said sheet-like material [B] is 10 μm or more. 3. The separator for an alkaline battery according to 2. 4. The sheet-like material [A] has an intrinsic viscosity of 0.1.
2 to 1.0 dl / g polyolefin-based resin fiber obtained by sulfonation, and having a total amount of sulfur per 1 g of the obtained fiber of more than 10 mg and 50 mg or less in sheet form 2. The object according to claim 1, wherein
The separator for an alkaline battery according to any one of claims 1 to 3. 5. A polyolefin resin fiber having a total sulfur content of more than 10 mg / g and not more than 50 mg / g is contained in the sheet-like material [A], and is contained in an amount of 20% by mass or more based on the whole battery separator. The alkaline battery separator according to claim 1, wherein: 6. The sheet-like material [A] has a total sulfur content of 15
The separator for alkaline batteries according to claim 1, wherein the amount is 0 mg / m ² or more. 7. The alkaline battery according to claim 1, wherein said sheet-like material [A] is arranged on a battery positive electrode side, and said sheet-like material [B] is arranged on a battery negative electrode side. Separator. 8. An alkaline battery, wherein the battery separator according to claim 1 is used for separating a positive electrode from a negative electrode.