HK1201992B - Separator for alkaline battery and alkaline battery - Google Patents

Description

Separator for alkaline battery and alkaline battery

Technical Field

The present invention relates to a separator for an alkaline battery used in an alkaline battery such as an alkaline manganese battery, a silver oxide battery, or a zinc-air battery, and an alkaline battery using the same.

Background

Conventionally, as the characteristics of a separator for separating a positive electrode active material and a negative electrode active material in an alkaline battery, it has been required to have durability that does not interfere with ion conduction and that can hold an electrolyte solution in an amount sufficient for an electricity generation reaction for a long time: preventing an internal short circuit caused by contact of a positive electrode active material and a negative electrode active material; preventing internal short circuit caused by dendrite such as conductive zinc oxide; and does not shrink or change quality with respect to a potassium hydroxide electrolyte or a positive electrode active material such as manganese dioxide, nickel oxyhydroxide, silver oxide, or the like.

As a separator for an alkaline battery having such characteristics, a mixed paper of synthetic fibers and cellulose fibers is used, which is mainly composed of vinylon fibers or nylon fibers of alkali-resistant synthetic fibers, and which contains regenerated cellulose fibers such as mercerized pulp or rayon fibers, polynosic fibers, or organic solvent-based cellulose fibers having excellent alkali resistance, and further contains, as a binder, soluble polyvinyl alcohol fibers soluble in water at 60 to 90 ℃.

In the production of the separator, fibrillatable cellulose fibers such as mercerized pulp, high-strength fibers, and organic solvent-based cellulose fibers may be subjected to beating treatment as necessary, and used as fibrillated fibers. By blending fibrillated cellulose fibers, the diaphragm can be provided with denseness, and occurrence of internal short-circuiting due to dendrites can be prevented.

Among these cellulose fibers, mercerized pulp can be produced by a simple process in which the pulp is immersed in a high-concentration alkaline aqueous solution and then the alkaline solution is removed. In the production of mercerized pulp, there is no need for complicated steps such as a step of dissolving cellulose pulp, a step of spinning from a dissolving solution to regenerated cellulose fibers, and a step of recovering a solvent, which are required for the production of regenerated cellulose fibers such as rayon and organic solvent-based cellulose fibers. Therefore, mercerized pulp is low in price.

Separators for alkaline batteries are widely used, which are obtained by mixing alkali-resistant synthetic fibers such as vinylon fibers with soluble polyvinyl alcohol fibers as a binder in mercerized pulp and papermaking the mixture (see, for example, patent documents 1 and 2). Alternatively, a separator for alkaline batteries is widely used, which is obtained by blending regenerated cellulose fibers with these mercerized pulp, synthetic fibers, and soluble polyvinyl alcohol fibers and then papermaking the blend (see, for example, patent document 3).

Patent document 1 provides a separator for an alkaline dry battery, which is obtained by papermaking of mercerized kraft pulp alone or a mixture of mercerized kraft pulp in an amount of 50 mass% or more and at least one selected from the group consisting of synthetic fibers, synthetic resin pulp, and alkali-resistant resin added thereto, and papermaking of the mixture.

Patent document 2 proposes a separator for an alkaline battery, which is obtained by binding alkali-resistant cellulose fibers such as mercerized pulp and high-tenacity fibers, which can be beaten, with synthetic fibers by using a binder such as polyvinyl alcohol fibers, in association with a demand for mercury-free alkaline batteries. The alkaline battery separator contains alkali-resistant cellulose fibers in a range of 10 to 50% by mass, and the beating degree of the alkali-resistant cellulose fibers is set in a range of 500 to 0ml in terms of CSF value.

Patent document 3 discloses a separator for alkaline batteries, which is characterized by comprising alkali-resistant synthetic fibers, a fibrillated product of organic solvent-based cellulose fibers having a beating degree of 10 to 550ml in CSF, and mercerized pulp having a beating degree of 450ml or more in CSF, in a mass ratio of 30 to 60%: 5% -20%: 35 to 50 percent.

As the organic solvent-based cellulose fibers used for the separator described in patent document 3, for example, regenerated cellulose fibers such as Lyocell (registered trademark) and Tencel (registered trademark) are known. The organic solvent-based cellulose fiber is defined by the tencel name in the fiber wording defined in JIS standard and ISO standard, and hereinafter, the organic solvent-based cellulose fiber is referred to as a tencel fiber.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. Sho 54-87824

Patent document 2: japanese laid-open patent publication No. 2-119049

Patent document 3: japanese patent laid-open publication No. 2006-236808

Disclosure of Invention

Problems to be solved by the invention

The mercerized pulp used for the separator for an alkaline battery has a high content of alpha-cellulose and a small amount of components soluble in an alkaline electrolyte. And, it is a cellulose fiber which has a small dimensional shrinkage in an alkaline electrolyte and is suitable for a separator for an alkaline battery. Further, since a dense separator having excellent shielding properties for bipolar active materials can be obtained at low cost by blending mercerized pulp fibrillated by beating the separator, it is widely used as a separator for an alkaline battery.

However, the use of a separator containing mercerized pulp has a problem that corrosion of zinc alloy powder as a negative electrode active material of an alkaline battery increases. Therefore, an increase in the amount of gas generated in the alkaline battery and a decrease in the characteristics after storage become problems.

In order to solve the above problems, the present invention provides a separator for an alkaline battery, which generates a small amount of gas and can suppress a decrease in the characteristics of the alkaline battery after storage, and an alkaline battery including the separator.

Means for solving the problems

The separator for an alkaline battery of the present invention is interposed between a positive electrode and a negative electrode of the alkaline battery to separate active materials of the two electrodes, and is characterized in that the separator contains 20 to 90 mass% of cellulose fibers, the remainder being composed of alkali-resistant synthetic fibers, and the cellulose fibers containing dissolving pulp.

The alkaline battery of the present invention is characterized by comprising the above-described separator for an alkaline battery as a separator for separating a positive electrode active material from a negative electrode active material.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a separator for an alkaline battery and an alkaline battery, which can suppress a decrease in characteristics after storage, can be provided.

Drawings

Fig. 1 is a central longitudinal sectional view of an alkaline battery using the separator for an alkaline battery of the present invention.

Detailed Description

Before describing the embodiments of the present invention, the outline of the present invention will be described.

The invention provides an alkaline battery, wherein the separator for the alkaline battery reduces the corrosion of zinc alloy powder and has excellent storage characteristics.

Among cellulose fibers used for a conventional separator for an alkaline battery, mercerized pulp refers to pulp obtained by subjecting chemical pulp for paper making, which is mainly obtained by sulfate method digestion, to an immersion treatment (mercerization treatment) in a high-concentration sodium hydroxide aqueous solution of 18 mass% or more.

By mercerizing, alkali-soluble components such as low-molecular-weight cellulose and hemicellulose are removed from chemical pulp for papermaking, and high-purity pulp having an α -cellulose content of 97% or more is obtained. In addition, the crystal structure of cellulose I of chemical pulp is entirely changed to the crystal structure of cellulose II by mercerization treatment. Therefore, pulp having reduced dimensional shrinkage in the alkaline electrolyte and excellent alkali resistance suitable for the separator for alkaline batteries can be obtained.

Mercerized pulp can be produced by a simple process in which chemical pulp for papermaking is immersed in a high-concentration alkaline aqueous solution and then the alkaline solution is removed as described above. Therefore, mercerized pulp is substantially free from the cleavage of cellulose molecular chains during the production thereof, and is composed of cellulose having a higher polymerization degree than regenerated cellulose fibers. Therefore, the regenerated cellulose fibers are difficult to dissolve in an alkaline electrolyte and have excellent alkali resistance as compared with regenerated cellulose fibers.

However, in recent years, it has been reported that when a separator containing mercerized pulp is used, corrosion of zinc alloy powder as a negative electrode active material of an alkaline battery occurs. Corrosion of zinc alloy powder refers to the following phenomena: the zinc alloy powder and the electrolyte react independently of the battery electrogenesis reaction to produce hydrogen gas and zinc oxide or zinc hydroxide as reaction products.

If the amount of gas generated by corrosion of the zinc alloy powder increases rapidly, the pressure inside the battery increases, and the possibility of electrolyte leakage increases. Even if liquid leakage does not occur, zinc oxide or zinc hydroxide precipitates by corrosion around the zinc alloy powder of the negative electrode when the battery is stored for a long period of time, and the electron conduction between the zinc alloy powders is reduced. Therefore, the internal resistance of the battery increases. In addition, the negative electrode active material is also consumed. Therefore, in an alkaline battery using a separator mixed with mercerized pulp, the battery capacity is reduced by long-term storage.

In a conventional alkaline battery, a negative electrode in which mercury is added to zinc powder to thereby mercury-alloy the surface of zinc is used. If mercury alloying is performed, the hydrogen overpotential of the zinc powder becomes sufficiently high, and corrosion is hard to occur. Therefore, even when a separator containing mercerized pulp is used, corrosion of the negative electrode active material is less likely to occur, and the amount of hydrogen generated and the battery performance are not substantially affected.

However, mercury-free is required from the viewpoint of prevention of environmental pollution later, and mercury-alloyed zinc negative electrodes have disappeared in other alkaline batteries except for some residue in button-type alkaline batteries. At present, zinc alloy powder having improved corrosion resistance, which is obtained by adding a metal such as aluminum, bismuth, or indium to zinc instead of mercury, has been used as a negative electrode active material for alkaline batteries.

However, when a separator containing mercerized pulp is used in an alkaline battery using zinc alloy powder to which mercury is not added as a negative electrode active material, the above-described corrosion of the negative electrode is promoted, and there are problems such as an increase in the amount of hydrogen gas generated and a decrease in the performance after storage of the battery.

It is known that the corrosion resistance of the negative electrode active material is improved by using a zinc alloy powder in which the indium addition rate is increased. However, indium is also used in transparent conductive films of flat panel displays, and is therefore very expensive. Therefore, from the viewpoint of cost reduction of the zinc alloy powder, the amount of rare metal such as indium added tends to be reduced as much as possible. Also due to this tendency. In recent years, corrosion of zinc alloy powder by a separator mixed with mercerized pulp has become a particular problem.

In view of the above problems, the present inventors have studied the corrosion of zinc alloy powder and found that: in the case of mercerized pulp obtained by treating paper-making pulp with only a high-concentration NaOH aqueous solution of 18 mass% or more, corrosion of zinc alloy powder is large and gas generation amount is large; in contrast, the amount of gas generated decreases in the case of dissolving pulp.

As a result of the investigation, it was found that when dissolved pulp was mixed in the separator instead of the conventional mercerized pulp, corrosion of zinc alloy powder of the negative electrode of the alkaline battery was suppressed, and a separator with a small amount of gas generation was obtained.

According to the results of the studies by the present inventors, most of hemicellulose contained in chemical pulp for papermaking such as wood is removed by mercerization treatment, and pulp having a high α -cellulose content can be obtained. However, in the case of conventional mercerized pulp, hemicellulose that is hardly soluble in an alkaline aqueous solution remains in the pulp even if the α -cellulose content is 97% or more. Therefore, in the case of a separator containing conventional mercerized pulp, hemicellulose remaining in the mercerized pulp is gradually eluted into an alkaline electrolyte composed of a 30 to 40 mass% potassium hydroxide (KOH) aqueous solution. Moreover, hemicellulose eluted into the electrolyte causes corrosion of the zinc alloy powder, and therefore, the amount of gas generated is large, and the storage characteristics of the battery are degraded.

Hemicellulose is a generic term for polysaccharides other than cellulose contained in wood pulp and non-wood pulp. The main component of pulp is cellulose, which is a crystalline polysaccharide obtained by linear polymerization of only glucose. On the other hand, hemicellulose is a polysaccharide having a branched chain including monosaccharides such as xylose, mannose, arabinose, galactose, glucuronic acid and galacturonic acid. Hemicellulose is a polysaccharide having a lower molecular weight and is amorphous than cellulose. Polysaccharides such as xylan, arabinoxylan, mannan, glucomannan, and glucuronoxylan are known as typical hemicellulose.

That is, in order to solve the above problems, the present invention is directed to a separator interposed between a positive electrode and a negative electrode of an alkaline battery for separating active materials of the two electrodes, the separator including dissolved pulp. The separator contains 20 to 90 mass% of cellulose fibers, and the balance is alkali-resistant synthetic fibers. The cellulose fibers include dissolving pulp.

Also provided is a separator for alkaline batteries, which contains dissolved pulp and regenerated cellulose fibers. Also disclosed is a separator for alkaline batteries, which is obtained by using a lyocell fiber as a regenerated cellulose fiber. Also disclosed is an alkaline battery comprising a separator for alkaline batteries, which contains such cellulose fibers.

[ embodiment ]

Embodiments of the present invention will be described below.

(dissolving pulp)

The alkaline battery separator of the present embodiment contains dissolved pulp. The dissolving pulp is bleached high-purity chemical pulp.

The normal papermaking pulp has a low α -cellulose content and poor alkali resistance, and is not suitable for a separator for an alkaline battery. Further, mercerized pulp, which has been conventionally used for separators for alkaline batteries, has a high content of α -cellulose and is excellent in alkali resistance. However, since only the papermaking pulp is mercerized to obtain a pulp, hemicellulose that is hardly soluble in an alkaline solution remains, and the amount of gas generated by corrosion of the negative electrode is large. Therefore, cellulose fibers are not preferable as separators for alkaline batteries.

The separator of the present embodiment is preferably high-purity dissolving pulp having a small hemicellulose content and an α -cellulose content of 92% or more.

The dissolving pulp to be mixed in the separator for alkaline batteries of the present embodiment and Na added to the wood or non-wood chips₂S, NaOH, and the like, are different in the method and process for producing ordinary papermaking pulp by digesting the same. The dissolving pulp used for the separator of the present embodiment is prepared by subjecting wood or non-wood chips to a cooking treatment with high-temperature steam before the cooking, and hydrolyzing hemicellulose contained in the chips under acidic conditions. After the digestion treatment, digestion is performed to prepare a paper pulp. The pulp after the digestion is treated with an alkaline aqueous solution such as sodium hydroxide of about 2 to 10 mass% to extract and remove hemicellulose remaining in the pulp.

The method of digesting dissolving pulp may be a sulfite method, a sulfate method, or an alkali method. When the digestion method is a sulfite method, an acidic or neutral to alkaline sulfite digestion method can be used. In particular, the acidic sulfite digestion is preferably acidic in the digestion, and the digestion of the chips under acidic conditions before the digestion is not required. In addition, among these digestion methods, the sulfate method produces a dissolved pulp having a high α -cellulose content at a high purity (less hemicellulose). Therefore, dissolving pulps based on the sulphate process are particularly preferred.

The dissolving pulp is classified and standardized in JIS P2701, and among the sulfite-process pulp and the sulfate-process pulp specified in JIS P2701, the dissolving pulp of the present embodiment is preferable, and in particular, the dissolving pulp having a small amount of hemicellulose and a large amount of α -cellulose is preferable.

In the separator of the present embodiment, the alkaline battery in which the corrosion of the zinc alloy powder of the negative electrode can be sufficiently reduced can be realized by blending the dissolving pulp.

(Crystal Structure)

The crystal structure of the dissolving pulp mixed in the separator of the present embodiment preferably has a crystal structure of cellulose II. By having the crystal structure of cellulose II, the dimensional shrinkage of the separator can be reduced.

Commercially available dissolving pulp is basically pulp of the crystal structure of cellulose I. If a large amount of pulp containing the crystalline structure of cellulose I is contained, the separator undergoes a large size shrinkage in the alkaline electrolyte. Therefore, in the case where the content of the dissolving pulp in the separator is set to a high content of 70 mass% or more, it is preferable to use dissolving pulp having a crystal structure of cellulose II.

The dissolving pulp having the crystal structure of cellulose II is obtained by subjecting the dissolving pulp having the crystal structure of cellulose I to alkali treatment with an aqueous sodium hydroxide solution having a concentration of 10 to 18 mass%. By this treatment, a part or all of the crystal structure of cellulose I is converted into the crystal structure of cellulose II. This makes it possible to obtain dissolved pulp which is less likely to shrink in the alkaline electrolyte and less likely to generate gas due to corrosion of the negative electrode.

It should be noted that dissolving the pulp removes hemicellulose, and thus the amorphous fraction in the pulp is reduced. Therefore, the penetration of the alkaline electrolyte into the fibers of the dissolving pulp is suppressed. Thus, swelling of the fibers of the dissolving pulp is reduced.

As a result, even when the dissolving pulp is composed of a crystal structure of only cellulose I, the dimensional shrinkage in the electrolyte is significantly smaller than that of the general papermaking pulp. In addition, the size shrinkage of the dissolving pulp separator containing a mixture of the crystal structures of cellulose I and cellulose II can be reduced to the same extent as that of the separator using the conventional mercerized pulp.

Dissolved pulp having only the crystal structure of cellulose I tends to shrink greatly in an alkaline electrolyte. Therefore, by blending a synthetic fiber such as vinylon fiber having a small dimensional change in an alkaline electrolyte in an amount of 30 mass% or more based on the mass of the separator, the dimensional shrinkage of the separator in the electrolyte can be suppressed to 2.0% or less, which is not a problem in practical use. Therefore, even dissolving pulp having only the crystal structure of cellulose I can be sufficiently applied to the separator of the present embodiment.

(kind of Material)

As the dissolving pulp to be mixed in the separator of the present embodiment, dissolving pulp obtained from wood of coniferous trees or broadleaf trees, and dissolving pulp obtained from non-wood can be used.

As the coniferous tree, there can be used dissolving pulp obtained from Pinus radiata, Pinus humilis Bunge, Pinus south, spruce, Douglas fir, hemlock, etc. Further, as the broad-leaved trees, there can be used dissolving pulp obtained from beech, oak, Japanese ash, alder and the like.

The dissolving pulp obtained from conifers has an average fiber length of about 2mm, and is easy to pulp, and therefore, is suitable for high-pulp beating with a CSF value of 100ml or less. Therefore, the separator is particularly suitable for obtaining a separator having high gas tightness and excellent dendrite shielding properties.

On the other hand, dissolving pulp obtained from broadleaf trees has an average fiber length of about 0.7mm, and is not suitable for high beating with a CSF value of 100ml or less. However, the average fiber diameter was as small as about 15 μm, and a homogeneous separator was obtained even by mild beating.

As the non-wood dissolving pulp, there can be used dissolving pulp obtained from seed fibers such as cotton, linter, kapok, etc., vein fibers such as abaca, sisal, etc., bast fibers such as flax, jute, kenaf, hemp, etc., gramineous plants such as bamboo, thatch, bagasse, etc., and fruit fibers such as coconut, etc. Compared with wood pulp, non-wood pulp is pulp of fibers having a fiber diameter as small as about 10 μm and a fiber length as long as about 3 to 7 mm. Therefore, by using the non-wood dissolving pulp, a separator having a lower density, a lower electric resistance, and a higher density and a higher shielding property than those of the wood dissolving pulp can be obtained.

Pulp having a high α -cellulose content, such as mercerized pulp, is known to be suitable as the cellulose fiber that has been conventionally blended in the separator for alkaline batteries.

The reason why pulp having a high α -cellulose content is suitable is based on the following findings and presumptions: the higher the purity of the pulp, the less the dissolved components in the alkaline electrolyte, the less the dissolution in the electrolyte and the dimensional change in the electrolyte, and the more excellent the alkali resistance.

On the other hand, the influence of pulp or regenerated cellulose fibers in the separator on the corrosion of the zinc alloy powder of the alkaline battery has not been clarified so far.

(regenerated cellulose fiber)

As the cellulose fiber to be mixed in the separator of the present embodiment, a regenerated cellulose fiber may be mixed in addition to the dissolving pulp. By adding regenerated cellulose fibers as cellulose fibers, the density of the separator becomes lower, and the electrolyte retention amount of the separator increases. Therefore, the resistance of the separator is reduced, and the amount of retained liquid is increased, so that the heavy load discharge characteristics of the alkaline battery can be improved.

On the other hand, when only dissolving pulp is used as the cellulose fiber to be mixed in the separator, a thin separator having excellent shielding properties between the two electrodes can be produced. By thinning the separator, the amount of active material in the battery can be increased, and therefore the capacity of the battery can be increased.

As the regenerated cellulose fiber to be blended in the separator of the present embodiment, rayon fiber, modal fiber, polynosic fiber, cuprammonium fiber, tencel fiber, and the like can be used. The regenerated cellulose fiber used preferably has a fineness of 0.5dtex to 3.3dtex in fiber diameter and a fiber length of 2mm to 7mm, for example.

Among these regenerated cellulose fibers, the high tenacity fibers, the cuprammonium fibers, and the tencel fibers can be fibrillated by a beating process.

When the above described regenerated cellulose fibers capable of fibrillation are blended as the cellulose fibers, the dissolving pulp and the regenerated cellulose fibers are subjected to beating treatment in accordance with the degree of masking required for the separator, and are fibrillated. Further, if the separator is made of paper by blending synthetic fibers therein, the required shielding property of the separator can be provided. In order to adjust the physical properties of the separator, only one of the dissolving pulp and the regenerated cellulose fiber may be subjected to beating treatment and used for the separator.

In the case of beating the dissolving pulp and the regenerated cellulose fibers, the fibrils can be more sufficiently mixed when beating in a mixed state. It is particularly preferable to use a fully mixed raw material for papermaking because a homogeneous separator can be obtained. The dissolving pulp and the regenerated cellulose fiber may be individually pulped and then mixed.

The polymerization degree of cellulose in the regenerated cellulose fiber is as low as about 300 to 500. Therefore, the regenerated cellulose fibers are more easily dissolved in the alkaline electrolyte than the dissolved pulp of the present embodiment, and are inferior in alkali resistance.

(blending ratio)

The content of the cellulose fibers in the separator of the present embodiment is preferably in the range of 20 to 90 mass%. When the content of the cellulose fiber in the separator is less than 20% by mass, the retention rate of the electrolyte solution in the separator decreases, and the overall discharge performance of the battery, particularly the heavy-load discharge characteristic, decreases.

On the other hand, if the content of the cellulose fibers in the separator is large, the alkali-resistant synthetic fibers in the separator inevitably decrease. Therefore, the size of the separator in the electrolyte solution shrinks greatly, and the wet strength of the separator decreases. As a result, the separator is easily broken, and internal short-circuiting of the battery is easily caused. Therefore, the content of the cellulose fiber in the separator is preferably 90 mass% or less.

When dissolving pulp and regenerated cellulose fibers are used as the cellulose fibers of the separator, the total content of the dissolving pulp and the regenerated cellulose fibers may be 20 mass% or more. If the regenerated cellulose fiber is contained in an amount exceeding 60 mass%, the liquid retention rate of the separator becomes too high. Therefore, particularly in the case of a small alkaline manganese cell of the mono-3 or mono-4 type, the separator swells in the electrolyte, and the volume occupied by the separator in the cell becomes large. In this case, it is necessary to reduce the amount of active material in the battery, and it is therefore difficult to improve the battery performance.

(alkali-resistant synthetic fiber)

The alkali-resistant synthetic fiber blended in the separator is selected from materials that do not cause dissolution and shrinkage in the electrolyte. For example, in addition to polyvinyl alcohol fibers such as vinylon fibers and polyvinyl alcohol fibers, polyamide fibers such as nylon-6 fibers and nylon-6, 6 fibers, polypropylene fibers, polyethylene fibers, polypropylene (core)/polyethylene (sheath) composite fibers, and polyolefin fibers such as polyethylene synthetic pulp are preferable. The synthetic fiber preferably has a fineness of 0.1dtex to 3.3dtex, and a fiber length of 2mm to 7 mm.

Among these alkali-resistant synthetic fibers, vinylon fibers are particularly preferable. The vinylon fiber is a polyvinyl alcohol fiber obtained by acetalizing a spun polyvinyl alcohol fiber by reacting it with formaldehyde or the like. Vinylon fibers are substantially insoluble in an alkaline electrolyte and have little dimensional change in the electrolyte. Therefore, when the electrolyte is mixed in the separator, the dimensional shrinkage of the separator in the electrolyte can be reduced.

The polyvinyl alcohol fiber is a fiber obtained by spinning a polyvinyl alcohol resin solution. The polyvinyl alcohol fiber can be heated and stretched to increase the dissolution temperature in water from about 60 ℃ to over 100 ℃.

In the prior art, as a binder for binding cellulose fibers and synthetic fibers mixed in a separator, a readily soluble polyvinyl alcohol fiber having a water-soluble temperature of 60 to 90 ℃ has been used in a separator for an alkaline battery. The alkali-resistant synthetic fibers of the present embodiment also include the above-described easily soluble polyvinyl alcohol fibers used as a binder.

When the easily soluble polyvinyl alcohol fibers are used as the binder in the separator, the content of the easily soluble polyvinyl alcohol fibers in the separator is preferably in the range of 5 to 20 mass%.

Although the content of the easily soluble polyvinyl alcohol fibers is in the above-described range of 5 to 20% by mass, the wet strength of the separator is more preferably set in the range of 5 to 20N/15 mm. When the wet strength is less than 5N/15mm, the separator is easily broken, and the battery is easily internally short-circuited by impact during transportation or lowering of the alkaline battery. On the other hand, the separator having a wet strength of more than 20N/15mm has an excessively large binder effect, and thus swelling of the separator in the electrolyte is suppressed. Therefore, the heavy load discharge characteristics of the alkaline battery are likely to be reduced due to a decrease in the liquid retention rate of the separator or an increase in the resistance.

The separator of the present embodiment is made by a conventional papermaking method using the above-mentioned materials, such as an inclined short wire paper machine, a cylinder paper machine, or a fourdrinier paper machine. Further, a separator obtained by laminating paper layers having different fiber ratios, densities, and denseness may be produced using a combination paper machine obtained by combining the paper wire sections of these paper machines. Further, although the same paper stock is used, if a laminated separator is produced using a combination paper machine having a plurality of paper web portions, a separator having smaller pores than a single-layer separator and less likely to cause internal short-circuiting of the battery due to dendrites can be obtained.

The beating process of dissolving cellulose fibers such as pulp and lyocell fibers used in the separator of the present embodiment can be performed by using various beaters such as a disc refiner, a beater, and a high-speed disintegrator.

Examples

Next, specific examples of the separator for an alkaline battery of the present invention and an alkaline battery using the same will be described. The present invention is not limited to the contents of the examples.

[ test of amount of gas generated from dissolved pulp ]

First, before specific examples, the characteristics of dissolving pulp used for a separator for an alkaline battery will be described in comparison with mercerized pulp and papermaking pulp used in the past.

Table 1 shows the measurement results of the type of pulp material, the α -cellulose content, the crystal structure, the area shrinkage, and the amount of gas generated, for chemical pulps such as dissolving pulp and mercerizing pulp used in examples and comparative examples.

[ Table 1]

The measured values of the pulps shown in table 1 were measured by the following methods.

(1) Alpha-cellulose content

The content of alpha-cellulose was determined according to the method for determining "alpha, beta and gamma-cellulose in Pulp" specified in TAPPI (Technical Association of the Pulp and Paper Industry, American society for Pulp and Paper Industry) Standard method T203.

(2) Crystal structure

The pulp sheet was fixed to a sample holder of an X-ray diffraction apparatus, and the X-ray diffraction pattern was measured using an X-ray tube (X-ray tube) with a Cu target. The diffraction peak ascribed to cellulose I or cellulose II was confirmed from the measured X-ray diffraction pattern, and the crystal structure of the pulp was judged as cellulose I, cellulose II, or a mixture thereof (I + II).

(3) Area shrinkage rate

In the measurement of the area shrinkage of pulp, 10% by mass of easily soluble polyvinyl alcohol fiber was blended in a sample (dissolution temperature 70 ℃ C.), and the basis weight was 30g/m²The sheet was cut into a predetermined size (100mm × 100mm) and the area was measured, and then immersed in a 40% KOH aqueous solution at 70 ℃ for 8 hours, and the area of the immersed test piece was measured in a state of being wetted with the KOH aqueous solution, and the area shrinkage was determined by the following equation.

Area shrinkage (%) { (a1-a2)/a1} × 100

A1 area before immersion

A2 area after immersion

(4) Hydrogen gas generation amount

To a commercially available zinc alloy powder for a negative electrode of an alkaline manganese battery to which aluminum (Al), bismuth (Bi) and indium (In) were added, pulp and KOH electrolytic solution (dissolved zinc oxide) were added, and the mixture was left at 70 ℃ for 10 days to measure the amount of generated hydrogen gas (volume μ l of generated hydrogen gas with respect to 1g of zinc). In the measurement of each pulp, the ratio by mass of 1: 0.05: 1 weighing a certain amount of zinc alloy powder: pulp: KOH electrolyte was used to measure the amount of gas generated using an apparatus similar to that shown in FIG. 2 disclosed in Japanese patent application laid-open No. 2008-171767.

In table 1, pulps a to E are commercially available dissolving pulps obtained from wood.

Further, the pulp F and the pulp G were pulps obtained by subjecting the pulp a as dissolving pulp of conifer trees to alkali treatment with aqueous NaOH solutions of 12 mass% and 17.5 mass%. Similarly, the pulp H was obtained by alkali-treating the pulp E, which was a dissolving pulp of broadleaf trees, with an aqueous NaOH solution having a concentration of 17.5 mass%.

The pulp A, B, C was kraft-based dissolving pulp (DKP) of coniferous trees derived from southern pine, radiata pine, and slash pine, and the pulp D was acid sulfite-based dissolving pulp (DSP) of coniferous trees derived from radiata pine. Further, the pulp E is dissolving pulp (DKP) of broad-leaved trees obtained from eucalyptus.

Pulps I to L are dissolving pulps derived from non-wood materials. Pulp I is an alkaline process based dissolving pulp of cotton linters (DAP). Pulp J is an alkaline based dissolving pulp of sisal (DAP). The pulp K is an alkaline-based dissolving pulp (DAP) of kenaf. Further, the pulp L is a kraft-based dissolving pulp (DKP) of bamboo.

Pulp M is porosier pulp from Rayonier inc. usa, and is a pulp obtained by mercerizing softwood pulp of southern pine.

Further, the pulp N is mercerized pulp obtained by treating jute pulp for non-wood papermaking with a 20 mass% NaOH aqueous solution. The pulp O is needle-leaved tree pulp (NBKP) for paper making mainly from spruce.

As is clear from table 1, the pulp O as a papermaking pulp has an α -cellulose content as low as 88.1%, a gas generation amount as large as 300 μ l/g, and an area shrinkage rate as large, and therefore, is not suitable as a cellulose fiber for an alkaline battery separator.

Further, it is found that pulp M, which is commercially available as mercerized pulp, has an α -cellulose content of 97.5% and an area shrinkage of 3.0% and is therefore excellent in alkali resistance. However, the gas generation amount was as large as 190. mu.l/g.

Similarly, in the pulp N obtained by mercerizing jute pulp, the content of α -cellulose was as high as 97.0%, the area shrinkage was as small as 3.2%, but the gas generation amount was as large as 180 μ l/g. This is because the pulp M and the pulp N are formed from pulp obtained by a conventional method by digesting, which is paper making pulp. Namely, it is considered that: even if mercerization is performed, a large amount of hemicellulose contained in wood or non-wood remains in the pulp, and the amount of gas generated is large.

On the other hand, pulps a to E are wood dissolving pulps of coniferous trees and broad-leaved trees. Alpha-cellulose content ranged from 97.6% for pulp E to 92.2% for pulp D. The gas generation amount of these dissolved pulps was 118. mu.l/g for pulps A and E. And, the pulp D having an α -cellulose content of 92.2% was 145. mu.l/g. Thus, with a decrease in the α -cellulose content, hemicellulose contained in the dissolving pulp increases, and therefore the amount of gas generated increases.

The pulps F and G were pulps obtained by treating the pulp a as dissolving pulp of coniferous trees with aqueous NaOH solutions of 12 mass% and 17.5 mass%. In the area shrinkage, the pulp a was 12.3%, while the pulp F was reduced to 3.2% and the pulp G was reduced to 2.8%. The pulp H was obtained by treating pulp E, which was a dissolving pulp of broadleaf trees, with a 17.5 mass% NaOH aqueous solution. By this treatment, the area shrinkage was reduced from 13.0% of pulp E to 2.8% of pulp H. Therefore, it can be seen that: the dissolving pulp changes its crystal structure from cellulose I to cellulose II by treatment with an aqueous NaOH solution, whereby shrinkage in the alkaline electrolyte is reduced.

By subjecting the dissolving pulp to alkali treatment, the hemicellulose content of the dissolving pulp can be further reduced, and the gas generation amount can be further reduced. For example, in the case of the α -cellulose content, pulp a was 97.4%, while pulp F was increased to 98.1% and pulp G was increased to 98.5%. Similarly, the amount of gas generated was 118. mu.l/G for pulp A, 114. mu.l/G for pulp F and 112. mu.l/G for pulp G. Thus, the amount of gas generation in the pulp F and the pulp G obtained by subjecting the pulp a to the alkali treatment is reduced due to the reduction in the hemicellulose content.

The X-ray diffraction patterns of pulp A, pulp F and pulp G were measured.

The pulp a before treatment was the diffraction pattern of cellulose I.

The pulp F treated with the aqueous 12 mass% NaOH solution showed a diffraction pattern of a mixture of cellulose I and cellulose II. In addition, the pulp G substantially exhibits an X-ray diffraction pattern of the cellulose II.

From the above results, as shown in table 1, the area shrinkage rate was further reduced by subjecting the dissolving pulp having the crystal structure of cellulose I to alkali treatment with an aqueous NaOH solution or the like to change the crystal structure of cellulose II. In this way, when the dissolved pulp having the crystal structure of cellulose II is mixed in the separator, the amount of gas generation is reduced, and the dimensional shrinkage of the separator in the electrolyte can be reduced.

The paper pulp I-L is non-wood dissolving paper pulp. Pulp I is a dissolving pulp produced by digesting cotton linters with steam at about 150 c under acidic conditions and then subjecting the pulp to alkaline digestion. The alpha-cellulose content of pulp I was as high as 99.2%. The alpha-cellulose content of ordinary cotton linter pulp is around 98%, and thus pulp I is presumed to be substantially free of hemicellulose.

Further, the pulp J is a dissolving pulp produced from sisal hemp by the same method, and the pulp K is a dissolving pulp produced from kenaf hemp by the same method. The pulp L is a bamboo dissolving pulp produced by a sulfate process similar to the wood dissolving pulp using bamboo as a raw material.

Although not shown in table 1, the hydrogen gas generation amount was measured for arabinoxylan and glucomannan, which are hemicellulose substances, in addition to the above-mentioned chemical pulp. However, the amount of hydrogen gas generated by these hemicellulose substances is 50 times or more of that of the above-mentioned dissolving pulp, and the amount of gas generated is too large, so that it is difficult to measure. From this result, it is considered that the corrosion of the zinc alloy powder is increased by hemicellulose contained in the pulp.

[ test of physical Properties of separator and amount of gas generated ]

Next, as cellulose fibers to be blended in the alkaline battery separator, the pulps a to N described in table 1 were used to produce alkaline battery separators of examples and comparative examples shown below. The pulp O is a general pulp for papermaking, and is not suitable for a separator for an alkaline battery because the alkali resistance is significantly deteriorated and the gas generation amount is also extremely large. Therefore, a separator using the pulp O could not be produced.

(example 1)

Pulp G described in Table 1 (pulp obtained by alkali-treating dissolved pulp A obtained from a softwood tree, α -cellulose content: 98.5%) was subjected to 50 mass% beating treatment until the CSF value was 350ml, 40 mass% of vinylon fibers (fineness 0.6dtex. fiber length 3 mm: FFN fibers manufactured by Unitika Limited.) and 10 mass% of polyvinyl alcohol fibers (fineness 1.1dtex. fiber length 3 mm: SML fibers manufactured by Unitika Limited.) were mixed with the pulped pulp, and the mixed raw material was subjected to papermaking by an inclined short wire papermaking machine to obtain a pulp having a thickness of 96.5 μm and a basis weight of 33.4G/m²And a density of 0.346g/cm³The membrane of (1).

(example 2)

The procedure of example 1 was repeated except that the pulp G was changed to the pulp F (the content of α -cellulose was 98.1% in the pulp obtained by alkali-treating the dissolving pulp A), to obtain a pulp having a thickness of 95.3 μm and a basis weight of 32.9G/m²And a density of 0.345g/cm³The membrane of (1).

(example 3)

The procedure of example 1 was repeated except that the pulp G was changed to pulp B (needle-leaved tree dissolving pulp, α -cellulose content: 96.0%), to obtain a paper pulp having a thickness of 91.0 μm and a basis weight of 33.0G/m²Density of 0.363g/cm³The membrane of (1).

(example 4)

The preparation of a pulp having a cellulose content of 94.7% was carried out in the same manner as in example 1 except that the pulp G was changed to pulp C (needle-leaved tree dissolving pulp, α — cellulose content)Thickness of 90.1 μm and quantitative of 33.2g/m²Density of 0.368g/cm³The membrane of (1).

(example 5)

The procedure of example 1 was repeated except that the pulp G was changed to pulp D (needle-leaved tree dissolving pulp, α -cellulose content: 92.2%), to obtain a paper pulp having a thickness of 89.8 μm and a basis weight of 33.1G/m²And the density is 0.369g/cm³The membrane of (1).

Comparative example 1

The procedure of example 1 was repeated except that the pulp G was changed to pulp M (commercially available mercerized pulp of conifer, α -cellulose content: 97.5%), to obtain a paper having a thickness of 87.3 μ M and a basis weight of 32.9G/M²Density 0.377g/cm³The membrane of (1).

(example 6)

Pulp E (dissolving pulp of broad leaf trees, α -cellulose content of 97.6%) was beaten at 20 mass% until CSF was 500ml, 70 mass% of vinylon fibers (fineness 0.6dtex. fiber length 3 mm: FFN fibers manufactured by Unitika Limited.) and 10 mass% of polyvinyl alcohol fibers (fineness 1.1dtex. fiber length 3 mm: SML fibers manufactured by Unitika Limited.) were mixed with the beaten pulp, and the mixed raw materials were subjected to papermaking with a cylinder papermaking machine to obtain a pulp having a thickness of 100.7 μm and a basis weight of 33.1g/m²And a density of 0.329g/cm³The membrane of (1).

(example 7)

A thickness of 93.2 μm and a basis weight of 33.2g/m were obtained in the same manner as in example 6 except that the pulp E was 70 mass% and the vinylon fibers were 20 mass%²Density 0.356g/cm³The membrane of (1).

(example 8)

Pulp H (pulp obtained by alkali-treating dissolving pulp E, α -cellulose content: 98.3%) was subjected to 90 mass% beating treatment to a CSF value of 500ml, and vinylon fibers (fineness: 0.6dtex, fiber length: 3 mm: Unitika Limite) were mixed with the pulped pulpd. Produced FFN fiber) 5 mass% and polyvinyl alcohol fiber (fineness 1.1dtex. fiber length 3 mm: SML fiber manufactured by Unitika limited) 5 mass%. The mixed raw material was papermaking by means of a cylinder paper machine to obtain a paper having a thickness of 84.6 μm and a basis weight of 32.5g/m²Density 0.384g/cm³The membrane of (1).

Comparative example 2

A thickness of 111.4 μm and a basis weight of 33.4g/m were obtained in the same manner as in example 6 except that 15% by mass of the pulp E and 75% by mass of the vinylon fibers were used²Density of 0.300g/cm³The membrane of (1).

Comparative example 3

The pulp was beaten to a CSF value of 500ml by 97 mass% and mixed with 3 mass% of polyvinyl alcohol fibers (fineness: 1.1 dtex: fiber length 3 mm: SML fibers manufactured by Unitika Limited.). The mixed raw material was subjected to papermaking by a cylinder paper machine to obtain a sheet having a thickness of 82.5 μm and a basis weight of 32.8g/m²And the density is 0.398g/cm³The membrane of (1).

(example 9)

Pulp A (dissolved pulp obtained from a softwood tree, α -cellulose content 97.4%) 10 mass% and lyocell fiber (fineness 1.7dtex. fiber length 3 mm: Tencel fiber produced by Lenzing Fibers Limited.) 10 mass% were mixed, and then beaten until CSF value was 350ml, and vinylon fiber (fineness 0.6dtex. fiber length 3 mm: FFN fiber produced by Unitika Limited.) 70 mass% and polyvinyl alcohol fiber (fineness 1.1dtex. fiber length 3 mm: SML fiber produced by Unitika Limited.) 10 mass% were mixed with the beaten raw materials, and the mixed raw materials were subjected to papermaking with a cylinder papermaking machine to obtain a thickness of 105.4 μm and a basis weight of 33.6g/m²Density 0.319g/cm³The membrane of (1).

(example 10)

A thickness of 100.2 μm and a basis weight of 32.9g/m were obtained in the same manner as in example 9 except that 30% by mass of the pulp A, 20% by mass of the lyocell fibers and 40% by mass of the vinylon fibers were used²0.328g in density/cm³The membrane of (1).

(example 11)

A thickness of 99.8 μm and a basis weight of 33.0g/m were obtained in the same manner as in example 9 except that 30% by mass of the pulp A, 40% by mass of the lyocell fiber and 20% by mass of the vinylon fiber were used²Density of 0.331g/cm³The membrane of (1).

Comparative example 4

The procedure of example 10 was repeated except that the pulp A was changed to the pulp M, to obtain a paper having a thickness of 93.6 μ M and a basis weight of 33.2g/M²And a density of 0.355g/cm³The membrane of (1).

(example 12)

Pulp E30 mass%, rayon fiber (fineness 1.1dtex. fiber length 4mm)30 mass%, polyethylene/polypropylene composite fiber (fineness 2.2dtex. fiber length 5 mm: Daiwabo Polytec Co., manufactured by ltd NBF (H) fiber) 10 mass%, vinylon fiber (fineness 1.1dtex. fiber length 3 mm: FGN fiber manufactured by Unitika Limited. 20 mass%, and polyvinyl alcohol fiber (fineness 1.1dtex. fiber length 3 mm: SMM fiber manufactured by Unitika Limited.) 10 mass% were mixed. The mixed raw material was papermaking by means of an inclined short wire papermaking machine to obtain a thickness of 321.0 μm and a basis weight of 71.5g/m²And a density of 0.223g/cm³The membrane of (1).

The pulp E was used in an unbaked state, and its CSF value was 730 ml. The separator of example 12 is large in thickness and also large in basis weight, and therefore is suitable for use in large alkaline manganese batteries of the single 1 or single 2 type.

(example 13)

The pulp F was subjected to 75 mass% beating treatment to a CSF value of 0 ml. To this beating raw material, 5 mass% of polyethylene synthetic pulp (SWP EST-8 manufactured by Mitsui chemical Co., Ltd.) and 20 mass% of polyvinyl alcohol fibers (fineness 1.1dtex. fiber length 2 mm: AH fiber manufactured by Unitika Limited.) were mixed. The mixed raw material was subjected to papermaking by a fourdrinier papermaking machine to obtain a paper having a thickness of 55.2 μm,Quantitative determination of 32.2g/m²And a density of 0.583g/cm³The membrane of (1).

(example 14)

Tencel Fibers (fineness 1.7dtex. fiber length 3 mm: Tencel Fibers of Lenzing Fibers Limited.) were beaten to 30% by mass to a CSF value of 0 ml. The pulped material was mixed with unbaked pulp E30 mass%, vinylon fibers (fineness 0.6 dtex: fiber length 3 mm: FFN fibers manufactured by Unitika Limited.) 30 mass%, and polyvinyl alcohol fibers (fineness 1.1 dtex: fiber length 3 mm: SML fibers manufactured by Unitika Limited.) 10 mass%. The mixed raw material was subjected to papermaking using a cylinder-inclined short wire combination papermaking machine to obtain a sheet having a thickness of 85.4 μm and a basis weight of 31.2g/m, which was formed by stacking 2 layers²Density 0.365g/cm³The membrane of (1).

(example 15)

Pulp I (non-wood cotton linter dissolved pulp) was beaten at 40 mass% to a CSF value of 200ml, and 20 mass% rayon fiber (fineness 1.1dtex. fiber length 3mm), 30 mass% vinylon fiber (fineness 0.6dtex. fiber length 2 mm: FFN fiber manufactured by Unitika Limited.) and 10 mass% polyvinyl alcohol fiber (fineness 1.1dtex. fiber length 3 mm: SML fiber manufactured by Unitika Limited.) were mixed. The mixed raw material was papermaking by means of a cylinder paper machine to obtain a sheet having a thickness of 103.5 μm and a basis weight of 33.2g/m²And a density of 0.321g/cm³The membrane of (1).

(example 16)

Pulp J (non-wood sisal hemp dissolved pulp) was beaten at 40 mass% to a CSF value of 400ml, and polyvinyl alcohol fibers (fineness 0.6dtex. fiber length 2 mm: FFN fiber manufactured by Unitika Limited.) at 50 mass% and polyvinyl alcohol fibers (fineness 1.1dtex. fiber length 3 mm: SML fiber manufactured by Unitika Limited.) at 10 mass% were mixed. The mixed raw material was papermaking by means of a cylinder paper machine to obtain a sheet having a thickness of 102.6 μm and a basis weight of 33.5g/m²And a density of 0.327g/cm³The membrane of (1).

(example 17)

Pulp K (non-wood kenaf dissolving pulp) was beaten at 40 mass% to a CSF value of 300ml, and polyvinyl alcohol fibers (fineness 0.6dtex. fiber length 2 mm: FFN fiber manufactured by Unitika Limited.) at 50 mass% and polyvinyl alcohol fibers (fineness 1.1dtex. fiber length 3 mm: SML fiber manufactured by Unitika Limited.) at 10 mass% were mixed. The mixed raw material was subjected to papermaking by a cylinder paper machine to obtain a sheet having a thickness of 96.8 μm and a basis weight of 32.6g/m²Density 0.337g/cm³The membrane of (1).

(example 18)

Pulp L (non-wood bamboo dissolving pulp) was subjected to 30 mass% beating treatment to a CSF value of 180ml, and vinylon Fibers (fineness 0.6dtex. fiber length 2 mm: FFN Fibers manufactured by Unitika Limited.) 40 mass%, undashed lyocell Fibers (fineness 1.7dtex. fiber length 3 mm: TENCEL Fibers manufactured by Lenzing Fibers Limited.) 20 mass%, and polyvinyl alcohol Fibers (fineness 1.1dtex. fiber length 3 mm: SML Fibers manufactured by Unitika Limited.) 10 mass% were mixed. The mixed raw material was subjected to papermaking by a cylinder machine to obtain a sheet having a thickness of 110.0 μm and a basis weight of 32.8g/m²Density 0.298g/cm³The membrane of (1).

Comparative example 5

Pulp N (mercerized jute pulp) was subjected to beating treatment at 40 mass% to a CSF value of 300ml, and polyvinyl alcohol fibers (fineness 0.6dtex. fiber length 2 mm: FFN fiber manufactured by Unitika Limited.) at 50 mass% and polyvinyl alcohol fibers (fineness 1.1dtex. fiber length 3 mm: SML fiber manufactured by Unitika Limited.) at 10 mass% were mixed. The mixed raw material was subjected to papermaking by means of a cylinder paper machine to obtain a sheet having a thickness of 97.5 μm and a basis weight of 32.4g/m²And a density of 0.332g/cm³The membrane of (1).

Table 2 shows various measurement data of the separators of examples 1 to 18 and comparative examples 1 to 5.

The measured values of the separators of the above examples and comparative examples were measured by the following methods.

(1) The measurement was carried out according to the method of the Canadian Standard Freeness (CSF) JIS P8121.

(2) Thickness of

Two separators were stacked, the thickness was measured at regular intervals using a dial thickness gauge, 1/2 was obtained as the thickness of each sheet, and the average value of the measured values was used as the thickness of the separator.

(3) Quantification of

The area and mass of the separator were measured to determine the per (m) of the separator²) Mass (g) of (c).

(4) Wet strength

A test piece 15mm wide was cut out from the separator in the longitudinal direction, and after the test piece was immersed in a 40% KOH aqueous solution, the excess 40% KOH aqueous solution adhering to the test piece was blotted with filter paper or the like. The tensile strength of the test piece wetted with the 40% KOH aqueous solution was measured as the wet strength of the separator according to the method specified in JIS P8113.

(5) Liquid retention rate

The separator was cut into a square of 50mm × 50mm and the mass after drying was measured, followed by immersion in a 40% KOH aqueous solution for 10 minutes. The test piece was directly attached to a glass plate inclined at an angle of 45 degrees and fixed for 3 minutes, and an excess 40% KOH aqueous solution was removed by flowing down, and the mass of the test piece after liquid retention was measured in this state, and the liquid retention rate was calculated by the following equation.

Liquid retention rate (%) - (W2-W1)/W1X 100

W1-mass before impregnation

W2 mass after immersion

(6) Dimensional change rate and area shrinkage

The separator was cut into a square of 100mm × 100mm in the Machine Direction (MD) and the Cross Direction (CD), and after the lengths in the machine direction and the cross direction were correctly measured, the separator was immersed in a 40% KOH aqueous solution for 30 minutes. After the impregnation, the longitudinal and transverse lengths of the separator were accurately measured, and the dimensional change rates of the separator in the longitudinal and transverse directions were determined according to the following equation.

Size change rate (%) { (a1-a2)/a1} × 100

A 1-length before impregnation

A 2-length after impregnation

When the measured value of the dimensional change rate is positive, the shrinkage rate of the separator is indicated. The area shrinkage of the separator is the sum of the dimensional shrinkage in the longitudinal direction and the dimensional shrinkage in the transverse direction.

(7) Air tightness

An orifice having a 6mm diameter hole diameter was attached to a test piece mounting portion of a type B measuring instrument of JIS P8117 (method for testing air permeability of paper and paperboard), and an area (28.26 mm) of 6mm diameter of 100ml of air passing through a diaphragm was measured²) The time required for the fraction (sec/100 ml).

(8) Resistance (RC)

A separator was inserted between platinum electrodes (platinum black-plated circular plate-shaped electrodes having a diameter of 20 mm) which were immersed in a 40% KOH aqueous solution and arranged in parallel at an interval of about 2mm, and the resistance between the electrodes increased with the insertion was regarded as the resistance of the separator. The resistance between the electrodes was measured at a frequency of 1000Hz using an LCR meter. This measurement method is called resistance, but is a method of measuring the ionic resistance of a separator in an electrolytic solution (40% KOH aqueous solution).

(9) Hydrogen gas generation amount

A separator and a KOH electrolytic solution (dissolved zinc oxide) were added to a commercially available zinc alloy powder for an alkaline manganese battery negative electrode to which aluminum (Al), bismuth (Bi), and indium (In) were added, and the mixture was left at 70 ℃ for 10 days to measure the amount of generated hydrogen gas (volume μ l of hydrogen gas generated with respect to 1g of zinc). In the measurement of each pulp, the ratio by mass of 1: 0.05: 1 weighing a certain amount of zinc alloy powder: a diaphragm: KOH electrolyte was used to measure the amount of gas generated using an apparatus similar to that shown in FIG. 2 disclosed in Japanese patent application laid-open No. 2008-171767.

[ Table 2]

Next, the separators of the above examples and comparative examples were examined.

(alpha-cellulose content)

As shown in table 2, the cellulose fibers of the separators of examples 1 to 5 and comparative example 1 were made of softwood pulp, and the physical properties of the separators were compared with each other so that the content of the pulp was 50%.

The gas generation amount of the separator of example 1 using the pulp G having an α -cellulose content of 98.5% was 82 μ l/G. In contrast, the gas generation amount of the separator of example 3 using the pulp B having an α -cellulose content of 96.0% was 95 μ l/g. Further, the gas generation amount of the separator of example 5 using the pulp D having an α -cellulose content of 92.2% was 110 μ l/g.

From the results, it is understood that as the α -cellulose content of the dissolving pulp decreases, the hemicellulose content in the separator increases, and therefore the gas generation amount increases. Further, as the α -cellulose content of dissolving pulp decreases, the wet strength of the separator tends to increase and the liquid retention rate tends to decrease.

On the other hand, in comparative example 1 using pulp M, which is commercially available mercerized pulp, the amount of gas generated from the diaphragm was 140. mu.l/g. It is understood that the gas generation rate of the separator of comparative example 1 is greater although the α -cellulose content of the pulp M is as high as 97.5%. In this way, even if the content of α -cellulose is high, the separator using mercerized pulp other than dissolving pulp retains hemicellulose that cannot be removed in the mercerization treatment, and therefore the amount of gas generated increases.

(Crystal Structure)

Examples 3 to 5 are septa of dissolving pulp using conifers having a crystalline structure of cellulose I. The area shrinkage of these separators is 1.9% to 2.1%.

On the other hand, in the separator of example 1 using the pulp G having the crystal structure of cellulose II obtained by alkali-treating the pulp a with 17.5% NaOH, the area shrinkage rate was 0.5%. In example 2 using the pulp F having a crystal structure comprising cellulose I and cellulose II obtained by alkali-treating the pulp a with 12% NaOH, the area shrinkage of the separator was 0.7%.

From the results, it was found that by using a portion of the dissolving pulp having the crystal structure of cellulose II for the separator, the dimensional shrinkage of the separator in the electrolytic solution can be reduced.

(amount of dissolving pulp mixture)

Examples 6 to 8 and comparative examples 2 to 3 show physical property values of the separator using dissolving pulp of broad-leaved trees and changing the mixing ratio of the dissolving pulp.

Example 6 is a separator mixed with 20 mass% of pulp E, and example 7 is a separator mixed with 70 mass% of pulp E. In comparative example 2, 15 mass% of the same pulp E was mixed into the separator. In the separator of comparative example 2, the mixing ratio of pulp was as low as 15% by mass, and therefore the wet strength was as high as 21.3N/15mm and the liquid retention rate was as low as 360%. Thus, it can be seen that: since the content of the cellulose fiber is small, the vinylon fiber mainly constituting the separator is firmly bonded to the easily soluble polyvinyl alcohol fiber dissolved during the papermaking. In addition, the separator of comparative example 2 had an air-tightness as low as 1.0 second, and the barrier property of the separator was poor.

On the other hand, in example 6 in which the compounding ratio of the pulp E was 20 mass%, the wet strength of the separator was decreased to 17.6N/15mm, the liquid retention rate was increased to 420%, and the air density was increased to 3.0 seconds/100 ml. In example 7 in which the compounding ratio of the pulp E was 70 mass%, the wet strength was decreased to 10.5N/15mm, the liquid retention rate was increased to 450%, and the air density was increased to 7.2 sec/100 ml.

The area shrinkage of the separator in example 7 was 2.5%, and the area shrinkage of the separator was larger than those of the separators in comparative examples 2 and 6, which were 0.3% and 0.5% respectively. Thus, it can be seen that: the separator of example 7 in which 70 mass% of the pulp E having the crystal structure of cellulose I was compounded exhibited a large dimensional shrinkage in the electrolyte.

Example 8 is a separator of pulp H blended with 90 mass% of a crystal structure of substantially cellulose II. The area shrinkage of the separator of example 8 was 2.3%. Although the compounding ratio of the dissolving pulp of the separator of example 8 was increased to 90 mass% compared to the separator of example 7 in which the pulp E of the crystal structure of cellulose I was compounded by 70 mass%, the area shrinkage rate was lower than that of example 7.

From the results, it was found that the area shrinkage of the separator was reduced by the dissolving pulp containing the crystal structure of cellulose II. When only dissolving pulp having a crystalline structure of cellulose I is blended in the separator, the blending amount of the dissolving pulp is preferably 70 mass% or less. Also, in the case where more than 70 mass% of dissolving pulp is compounded, it is preferable to contain dissolving pulp having a crystal structure of cellulose II.

Comparative example 3 is a separator blended with 97 mass% of pulp H. The separator of comparative example 3 had a wet strength of 4.0N/15mm and an area shrinkage of 3.7%. This is lower in wet strength and higher in area shrinkage than in the examples. Therefore, when the separator of comparative example 3 is subjected to impact during transportation or during lowering, the separator is highly likely to be broken.

(regenerated cellulose fiber)

Examples 9 to 11 are separators in which lyocell fibers as regenerated cellulose fibers were mixed with dissolving pulp and used as cellulose fibers. In the separator of example 9, 10 mass% of dissolving pulp and 10 mass% of lyocell fiber were blended, and the total content of cellulose fiber was 20 mass%. Example 10 dissolving pulp 30 mass% and tencel fiber 20 mass% were compounded, and the total contained 50 mass% of cellulose fiber.

In example 9 in which the mixing ratio of the cellulose fiber was 20 mass% in the same manner as in example 6, the liquid retention rate of the separator of example 6 was 420%, and the liquid retention rate of the separator of example 9 in which the lyocell fiber was mixed was improved to 440%.

In addition, in example 10 in which the blend ratio of the cellulose fibers was 50 mass%, the liquid retention rate of the separators of examples 1 to 5 was 410% to 430% as compared with examples 1 to 5, and the liquid retention rate of the separator of example 10 was increased by 500%. As described above, it was found that the liquid retention rate of the separator was increased by blending lyocell fibers as regenerated cellulose fibers in the separator.

The resistance of the separator of example 6 was 12.5m Ω, while the resistance of the separator of example 9 was reduced to 10.6m Ω. The electrical resistance of the separators of examples 1 to 5 was 13.4m Ω to 15.5m Ω, while the electrical resistance of the separator of example 10 was reduced to 11.8m Ω. From the results, it was found that the electrical resistance of the separator was reduced by blending the lyocell fibers.

In general, when the liquid retention rate of the separator increases and the resistance decreases, the amount of electrolyte that can be used for the discharge reaction increases, and the internal resistance of the battery decreases. Therefore, the use of the separator containing the tencel fiber can improve the discharge characteristics of the battery.

In addition, the separator of example 11 was compounded with 30 mass% of dissolving pulp and 40 mass% of tencel fiber, and the total content of cellulose fiber was 70 mass%.

If the separator is mixed with dissolving pulp and regenerated cellulose fiber as cellulose fiber, a separator having a high retention rate of the electrolyte can be obtained. However, if the electrolyte retention rate of the separator is increased, the separator inevitably swells in the electrolyte, and the thickness increases. In particular, if the regenerated cellulose fiber is contained in an amount exceeding 60 mass% of the separator, the liquid retention rate of the separator becomes too high, and therefore the volume occupied by the separator in the battery increases due to swelling. Therefore, in a small-sized battery of the mono-3 or mono-4 type, etc., it is necessary to reduce the amount of active material and to make it difficult to improve the battery performance. Therefore, the separator is preferably configured such that the dissolving pulp is 10 to 50 mass%, the regenerated cellulose fiber is 10 to 40 mass%, and the remainder is the alkali-resistant synthetic fiber, based on the mass of the separator.

Comparative example 4 a separator was formed using pulp M, which is a commercially available mercerized pulp used conventionally, in the same compounding amount as pulp a of dissolving pulp of the separator of example 10.

The gas generation amount of the separator of example 10 was 90. mu.l/g, while the gas generation amount of the separator of comparative example 4 was increased to 130. mu.l/g. From the results, it is understood that corrosion of the zinc alloy powder is increased by using commercially available mercerized pulp other than dissolving pulp for the separator.

(beating treatment)

The separator of example 12 was a separator using as cellulose fibers unbleached hardwood tree dissolving pulp and rayon fibers, and had a thickness of 321 μm and a basis weight of 71.5g/m². In addition, the liquid retention rate is as high as 780%.

As with the separator of example 12, the thick separator occupies a large volume in the battery, and is therefore unsuitable as a separator for a small alkaline battery of type 3 or 4 alone. The thick separator in example 12 is suitable for single 1 or single 2 type large alkaline manganese batteries. The gas tightness of the separator of example 12 was as low as 1.0 sec/100 ml, and the thickness of the separator was as thick as 321 μm, so that internal short-circuiting of the battery due to dendrite was difficult to occur.

In addition, the separator of example 13 contained highly beaten dissolving pulp with CSF of 0 ml. The density of the separator of example 13 was as high as 0.583g/cm³And the air density is as high as 2000 seconds/100 ml or more. Therefore, the separator has a particularly excellent dendrite-inhibiting effect and high shielding properties.

Example 14 is a separator formed by stacking 2 layers by papermaking a raw material containing highly pulped lyocell fibers having a CSF of 0ml and unbaked dissolving pulp with a cylinder-inclined short wire combination paper machine. The separator of example 14 had a low electric resistance of 12.5 m.OMEGA.by compounding unbleached dissolving pulp, although the air density was as high as 50.5 seconds/100 ml.

Further, by stacking, a separator more homogeneous than a single layer can be obtained.

(non-wood dissolving pulp)

Examples 15 to 18 are separators using non-wood dissolving pulp.

The separator of example 15 was prepared by compounding a cotton linter dissolving pulp having an α -cellulose content of 99.2% and rayon fibers as cellulose fibers, and contained 60 mass% in total of the cellulose fibers.

Further, the separator of example 16 was mixed with 40 mass% sisal hemp dissolving pulp as the cellulose fiber, and the separator of example 17 was mixed with 40 mass% kenaf hemp dissolving pulp as the cellulose fiber.

Example 18 is a separator in which 30 mass% of bamboo dissolving pulp and 20 mass% of undrawn lyocell fibers were mixed as cellulose fibers.

The separators of examples 9 to 11 used cellulose fibers obtained by mixing lyocell fibers with dissolving pulp and subjecting the mixture to beating treatment. In addition, the separator of example 18 was used without beating the tencel fibers.

The undrawn lyocell fibers have a characteristic of higher rigidity than the pulped lyocell fibers, and when mixed in a separator, the compression resistance in the thickness direction is improved. Therefore, when ungathered lyocell fibers are blended, the compression resistance of the separator in the thickness direction is improved, and even when the separator is pressed by a reaction product (increase in volume) of the active material at the end stage of discharge of the alkaline battery, the electrolyte contained in the separator is hardly lost, and the battery life is improved.

The separator of comparative example 5 was compounded with 40 mass% of a pulp obtained by mercerizing a jute pulp for paper making. The gas generation amount of the separator of comparative example 5 was as large as 138. mu.l/g, as in the separator of comparative example 1 in which mercerized pulp of conifer was blended. This is because hemicellulose that is hardly soluble in an alkaline solution remains in pulp even when chemical pulp for papermaking is mercerized. It is considered that the corrosion of the negative electrode active material is promoted by hemicellulose in the pulp, and the amount of gas generated increases.

[ test for characteristics of Battery ]

Next, 30 single 3-type cylindrical alkaline manganese batteries (LR-6) each having a structure shown in fig. 1 were produced by using the separators of the examples and comparative examples shown in table 2 to separate the positive electrode active material from the negative electrode active material.

An alkaline manganese battery 1 shown in fig. 1 has a cylindrical cathode can 2 with a bottom, and a cathode terminal 2a is formed at one end. A cylindrical positive electrode mixture 3 made of manganese dioxide and graphite is press-fitted into the positive electrode can 2. Inside the separator 4 wound in a cylindrical shape, a gelled negative electrode 5 is filled, in which zinc alloy powder not added with mercury is dispersed and mixed in a gelled electrolyte. Further, a negative electrode current collector 6 and a resin sealing member 7 for sealing the opening of the positive electrode can 2 are provided, and a negative electrode terminal plate 8 serving as a negative electrode terminal is welded to the head of the negative electrode current collector 6 at the resin sealing member 7. The positive electrode terminal side of the separator 4 wound in a cylindrical shape is sealed with a base paper 9, and the gelled negative electrode 5 is prevented from contacting the positive electrode can 2. The resin casing 10 is packaged in close contact with the outer surface of the positive electrode can 2 with the positive electrode terminal 2a and the negative electrode terminal plate 8 exposed.

The cylindrical alkaline manganese battery 1 is specifically manufactured by the following method.

First, each separator 4 is wound to produce a separator cylinder, the cylinder is brought into close contact with the cylindrical inner wall of the positive electrode, and then a base paper is inserted to seal the positive electrode terminal 2a side of the cylinder of the separator 4. After the electrolyte solution was injected, the gelled negative electrode 5 was injected to a predetermined position, and a resin sealing member 7 having a negative electrode current collector 6 attached thereto was inserted, and the end of the positive electrode can 2 was crimped and fixed to produce an alkaline manganese battery. The number of winding times of the separator 4 was 2. In the alkaline manganese battery manufactured this time, the separator is wound in a cylindrical shape in the longitudinal direction and inserted into the positive electrode, and therefore the separator is positioned in the transverse direction in a direction connecting the positive electrode terminal and the negative electrode terminal plate of the battery.

(transport test of Battery)

For the alkaline manganese battery manufactured by the above method, a transportation test was performed.

For the transport test, the alkaline manganese batteries were loaded on a truck in a case-packed state after being manufactured and transported in an area of about 1000 km. Further left for 1 week after transportation. Then, the open circuit voltage of the alkaline manganese battery was measured, and the alkaline manganese battery with a voltage reduced to 1.5V or less was regarded as a defective battery, and the separators of the examples and comparative examples of the defective battery were investigated and found.

The open circuit voltage of the alkaline manganese battery measured immediately after the production was 1.6V or more. The separator in which no defective cell was found in the transportation test was marked as o, and the separators in which 1 or more defective cells were found were marked as x, and are described in table 3.

(discharge characteristics of Battery)

The results of the low-temperature light-load discharge test, the heavy-load discharge test, and the measurement of the discharge capacity after storage were performed on 10 alkaline manganese batteries of each example and comparative example in which no defective battery was found in the transportation test, and are shown in table 3.

The separator of example 12 was too thick for the single 3-type alkaline manganese battery (LR-6), and the amount of the negative electrode gel had to be reduced, and the discharge performance of the batteries could not be compared, and therefore, the separator was only used in the transportation test and excluded from the discharge test.

The discharge test was carried out by the following method.

(1) Low temperature light load discharge test

The alkaline manganese cell was connected to a resistance of 300 Ω at 0 ℃ and continuously discharged until the end voltage became 1.0V, and the number of short-lived cells having a discharge time of a predetermined time or less was examined. The number of batteries to be tested was 10 each. This low-temperature light-load discharge test is a test condition under which a short circuit of the battery due to conductive zinc oxide is likely to occur.

(2) Heavy load discharge test

The alkaline manganese cell was discharged at room temperature at a constant current of 1000mA, and the discharge time (minutes) until the end voltage was 1.0V was measured. The number of batteries to be tested was 10, and the average value of the 10 batteries was determined.

(3) Discharge capacity after preservation

After storing the alkaline manganese cell at 60 ℃ for 2 months, the cell was discharged at room temperature at a constant current of 350mA until the end voltage became 0.9V, and the discharge capacity (mAh) was measured. The number of batteries to be tested was 10, and the average value of the 10 batteries was determined.

[ Table 3]

(transportation test)

From the results of the transportation test shown in table 3, only the battery of comparative example 3 was confirmed to have a reduced voltage, but the batteries of other examples and comparative examples maintained a voltage of 1.5V or more, and no defective battery was confirmed at all.

As a result of the investigation by decomposing the defective battery of comparative example 3 in which the voltage was reduced, a crack was observed at the end of the separator fixed with the resin sealing member, and the negative electrode gel filled in the separator was overflowed on the positive electrode side, and a short-circuited portion was observed. This is considered to be because the separator of comparative example 3 has a cellulose fiber content as high as 97% and a small amount of synthetic fibers, and therefore has a wet strength as low as 4.0N/15mm, and also has a dimensional shrinkage as large as 2.2% in the transverse direction of the separator, and the separator inside the battery is broken by an impact applied to the battery during transportation.

On the other hand, the separator of example 8 had a cellulose fiber content of 90% and a wet strength of 6.5N/15 mm. The separator of example 13 had a cellulose fiber content of 75% and a wet strength of 5.5N/15 mm. No defects were observed in the batteries using the separators of examples 8 and 13. From the results, it is considered that if the wet strength of the separator is 5N/15mm or more, the internal short circuit can be prevented even if an impact is applied to the battery during transportation or the like.

(Low temperature light load discharge test)

Next, discharge tests were performed on the batteries except for comparative example 3 and example 12. As a result of the discharge test, the battery of comparative example 2 exhibited a short-lived battery. In contrast, the batteries of the other examples and comparative examples did not exhibit a short-life battery.

The battery of comparative example 2 used a separator having a gas tightness as low as 1.0 second/100 ml. Therefore, the barrier property of the separator is poor, and it is considered that short-circuiting due to dendrite of zinc oxide occurs in the low-temperature light-load discharge test.

On the other hand, a short-life battery did not appear in the battery of example 6. That is, in the battery of example 6 using the separator whose gas density was 3.0 seconds/100 ml, a short-life battery did not appear, and from the result, it was found that if the gas density of the separator was 3.0 seconds/100 ml or more, short-life due to dendrite could be prevented.

In the alkaline battery of the present embodiment, the number of windings of the separator was 2, and the alkaline battery was tested, and when the number of windings of the separator was further increased, the gap between the positive electrode and the negative electrode was increased, and even a separator whose gas tightness was less than 3.0 seconds/100 ml was less likely to have a short life. Therefore, the air-tightness of the separator of the present embodiment is not limited to 3.0 seconds/100 ml or more.

(heavy load discharge test)

Next, as is clear from the results of the heavy load discharge test, the battery of comparative example 2 using the separator having a cellulose fiber content as small as 15% and a wet strength as high as 21.3N/15mm exhibited the shortest discharge time of 25 minutes. In the battery of comparative example 2, since the cellulose fiber content of the separator was as low as 15%, vinylon fibers, which are the main component of the separator, were strongly bonded by the soluble polyvinyl alcohol fibers, and the amount of the electrolyte solution retained was small, and it was considered that the discharge time of the battery was short. The blending ratio of the easily soluble polyvinyl alcohol fibers in the separator of comparative example 2 was 10 mass%. When the compounding ratio of the easily soluble polyvinyl alcohol fibers exceeds 20% by mass, the wet strength of the separator is further increased. In addition, the pores of the separator are clogged with an excessive amount of easily soluble polyvinyl alcohol dissolved during papermaking. Therefore, the liquid retention rate of the separator further decreases, and the resistance of the separator significantly increases. The heavy load discharge characteristics of a battery using such a separator are further deteriorated.

In addition, when the results of the heavy load discharge test were compared between the batteries of examples 10 and 18 and the batteries of examples 1 to 5, in which the mixture ratio of the cellulose fibers was also 50 mass%, the discharge time of the batteries of examples 10 and 18 was 35 to 36 minutes, while the discharge time of the batteries of examples 1 to 5 was 31 to 32 minutes. The batteries of examples 10 and 18 were compounded with lyocell fibers in the separator. From the results, it was found that by using a separator blended with regenerated cellulose fibers such as lyocell fibers, the liquid retention rate of the separator was increased, and the heavy load discharge performance of the battery was improved.

(discharge capacity after preservation)

The discharge capacity of the batteries thus produced was 830mAh to 900mAh in the batteries of examples 1 to 11 and examples 13 to 18, measured after storage at 60 ℃ for 2 months. In contrast, the batteries of comparative examples 1, 4 and 5, which used a separator containing conventional mercerized pulp, had discharge capacities of 710mAh, 740mAh and 720 mAh. From the results, it was found that the capacity of the battery of the comparative example using the separator containing the conventional mercerized pulp was decreased.

The separators used in the batteries of comparative examples 1, 4, and 5 contain mercerized pulp having a large hemicellulose content. Therefore, it is considered that the corrosion of the zinc alloy powder of the negative electrode is promoted by the hemicellulose eluted into the electrolyte during the storage of the battery, and the discharge capacity of the battery is decreased.

Although not described in the examples, a separator having almost the same thickness and a fixed amount was prepared by trial using a conifer dissolving pulp having an α -cellulose content of 91.0% in the same raw material ratio as in examples 1 to 5, a single 3-cell having the same specification was prepared, and the discharge capacity was measured. The discharge capacity of the separator using the dissolving pulp having an α -cellulose content of 91.0% was 790 mAh. On the other hand, the battery of example 5 in which the α -cellulose content of the dissolving pulp contained in the separator was 92.2% had a discharge capacity of 840 mAh. Therefore, the α -cellulose content of the dissolving pulp used in the separator is preferably 92% or more.

In the above-described embodiments and examples, the battery tests of the separator were performed using the cylindrical alkaline manganese battery, but the separator of the present invention is not limited to the cylindrical alkaline manganese battery, and may be used for alkaline batteries such as a silver oxide battery as a button battery.

A separator of a silver oxide battery, which is a button-type battery, has resistance to the oxidizing power of silver oxide, which is a positive electrode active material, prevents silver ions from moving to a negative electrode, and needs to retain an electrolyte solution sufficient for an electric power generation reaction. Therefore, in a silver oxide battery, a separator is generally used which is a combination of a polyethylene film of graft polymerization having excellent oxidation resistance, a cellophane film having excellent silver ion migration inhibition, and a liquid retaining film having excellent liquid retaining properties of an electrolytic solution.

When the separator of the present invention is used in a silver oxide battery, it is particularly preferably used as a liquid retaining agent in contact with the negative electrode in the separator.

In recent years, button cells such as silver oxide cells have been freed from mercury in the negative electrode, and button cells in which generation of gas is suppressed and in which troubles such as swelling of the battery case do not occur can be easily produced by using the separator of the present invention.

Reference character translation

1 alkaline manganese cell, 2 positive electrode can, 2a positive electrode terminal, 3 positive electrode mixture, 4 diaphragm, 5 gel negative electrode, 6 negative electrode current collector, 7 resin sealing body, 8 negative electrode terminal board, 9 base paper, 10 resin sheathing material.

Claims (5)

1. A separator for an alkaline battery, which is interposed between a positive electrode and a negative electrode of the alkaline battery and separates active materials of the two electrodes, wherein the separator contains 20 to 90 mass% of cellulose fibers, the balance of which is alkali-resistant synthetic fibers, and the cellulose fibers contain dissolving pulp selected from sulfite pulp and sulfate pulp dissolving pulp specified in JIS P2701.

2. The separator for an alkaline battery according to claim 1, wherein the cellulose fibers comprise the dissolving pulp and regenerated cellulose fibers.

3. The separator for an alkaline battery according to claim 2, wherein the regenerated cellulose fiber is an organic solvent-based cellulose fiber.

4. The separator for an alkaline battery according to any one of claims 1 to 3, wherein the dissolved pulp has an α -cellulose content of 92% or more.

5. An alkaline battery comprising a positive electrode active material and a negative electrode active material separated from each other by a separator, wherein the separator according to any one of claims 1 to 4 is used as the separator.