JPH06163024A - Alkaline battery separator - Google Patents

Abstract

PURPOSE:To provide an alkaline battery separator being excellent in an electrolyte absorbing characteristic, a swelling degree and internal resistance by forming main body fiber of a fibrilation material of cellulose fiber deposited by dry and wet type spinning after cellulose is dissolved into solvent. CONSTITUTION:Cellulose fiber can be obtained by depositing and drawing cellulose by dry and wet type spinning to coagulate it in coagulating liquid after a spinning undiluted solution formed by dissolving the cellulose into amine oxide is discharged into gas from a base. Since this solvent spinning cellulose fiber has a high wet young's modulus and permanent set is hardly caused in the water, when it is beaten by a heater or the like, it is beaten effectively by stress, and a long fibril is created. An alkaline battery separator is formed by using a fibrilation material of this cellulose fiber as main body fiber. Since a battery is formed by arranging this separator 3 between a positive electrode 2 and a negative electrode 4, an electrolyte absorbing characteristic, a swelling degree and internal resistance can be improved.

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 using zinc as a negative electrode active material such as an alkaline manganese battery and a silver oxide battery, and further to an alkaline battery in which mercury is not added to a zinc negative electrode. The present invention relates to an alkaline battery separator which improves battery performance such as improvement of life and prevention of internal short circuit.

[0002]

2. Description of the Related Art Performances required for a separator for an alkaline battery include alkali resistance, electrolyte solution absorbing property, and separating property.

Alkali resistance means that the separator does not undergo alteration or elution with respect to alkali such as potassium hydroxide aqueous solution used as an electrolytic solution. If it is lacking, it may adversely affect the battery reaction or cause the separator to deteriorate. The deterioration causes an internal short circuit between both electrodes of the battery.

The electrolyte solution absorbing property means that the electrolyte solution contains a sufficient amount of the electrolyte solution necessary for the battery reaction. If the electrolyte solution is lacking in the electrolyte solution, the battery reaction is hindered and a large current characteristic of an alkaline battery cannot be taken out. Occurs.

The term "separability" means that it has fine pores, and if it is lacking, the needle-like crystals of conductive zinc oxide produced by the battery reaction will penetrate the separator and cause an internal short circuit.

Various studies have been conducted on the conventional separator for alkaline manganese battery in order to satisfy the above performance.

[0007] For example, as a material for improving the electrolyte absorbability, there is a wet non-woven fabric in which polyvinyl alcohol fiber and hydrophilic fiber are combined, as described in JP-B-53-11059. For example, as a material for improving the separability, there is a combination of polyvinyl alcohol fiber having 0.8 denier or less and cellulose fiber as described in JP-A-62-154559.

However, in recent years, it has been required to reduce the amount of mercury added to the negative electrode in order to suppress the self-discharge reaction of zinc for the purpose of environmental protection, and before 1985, it was 9.0% with respect to zinc. In 1987, the amount added was 1.5% by weight, and in 1992 it was decided to add no mercury.

As the addition ratio of mercury decreases, needle-like crystals of zinc oxide become finer, which tends to cause an internal short circuit in the battery. In addition, since the amount of zinc oxide dissolved in the electrolytic solution increases, the battery reaction is hindered, so that the battery life until reaching the final voltage tends to be shortened.

Therefore, various studies have been conducted on separators having higher separability and liquid electrolyte absorbing property until the current mercury addition rate becomes 1.5% by weight with respect to zinc.

For example, as described in JP-A-1-146249, there is one mainly composed of polyvinyl alcohol fiber having a denier of 0.5 or less. However, this is because by making the fibers used thin, extremely good separability is obtained, and even if the mercury addition rate is 1.5% by weight with respect to zinc, internal short circuit does not occur, but the density of the separator is However, the electrolyte absorbency is lowered due to the increase, and the amount of electrolyte is insufficient even when the swelling of the combined cellulosic fibers is taken into consideration. As a means for solving this, a separator prepared by mixing beaten alkali-resistant cellulose fibers and synthetic fibers, as described in JP-A No. 2-119049, has been studied. This is beaten cellulosic fiber to make it finer,
By densifying the separator, even if the mercury addition rate is 1.5% by weight with respect to zinc, the separator has excellent separability, and due to the swelling of the cellulosic fiber itself, it also has excellent electrolyte solution absorption. there were.

However, when the zinc negative electrode to which mercury is not added is used, as described above, the tendency of the acicular crystals of zinc oxide to become finer is more remarkable than when the mercury addition rate is 1.5% by weight. Because of the large size, even with the above separator, the separating property and the electrolyte absorbing property were insufficient.

As described above, in the alkaline battery using the mercury-free zinc negative electrode, an alkaline battery separator satisfying both the separation property and the electrolytic solution absorbing property has not been obtained until now.

[0014]

DISCLOSURE OF THE INVENTION The present invention provides an alkaline battery in which mercury is not added to a zinc negative electrode, which does not cause an internal short circuit, improves the battery life up to the final voltage, and does not lower the electric capacity. Therefore, it is an object of the present invention to provide an alkaline battery separator which is excellent in both the separability and the electrolytic solution absorbing property, has a low swelling degree, and can reduce the internal resistance of the battery.

[0015]

DISCLOSURE OF THE INVENTION The above object of the present invention is to provide an alkaline battery in which a fibrillation product of a solvent-spun cellulose fiber obtained by dissolving cellulose in a solvent and directly precipitating the cellulose is at least a part of a main fiber. Is achieved by a separator.

As such a solvent-spun cellulose fiber, a fiber having a wet Young's modulus of 20 g / d or more and an orientation Δn of 42 × 10 ⁻³ or more is preferable, and a fiber obtained by dissolving cellulose in an amine oxide is used. Solvent-spun cellulose fibers obtained by dry-wet spinning a stock solution in water to precipitate cellulose are particularly preferable.

Further, as such a separator,
A fibrillation product of the solvent-spun cellulose fiber and a polyvinyl alcohol fiber having a denier of 1 denier or less are substantially used as main fibers, and a weight ratio of the fibrillation product to the polyvinyl alcohol fiber is 95: 5 to 25:75, and A polyvinyl alcohol-based binder is present, and the weight ratio of the binder to the main fiber is 3: 97-3.
A 0:70 alkaline battery separator is preferred.

[0018]

In the separator of the present invention, a fibril of solvent-spun cellulose fiber obtained by dissolving cellulose in a solvent to directly precipitate the cellulose is used as at least a part of the main fiber. A fibrillated product of cellulose fibers having a rate of 20 g / d or more and an orientation Δn of 42 × 10 ⁻³ or more is used. The advantages obtained by using a fibrillated product of cellulose fiber having such characteristics are as follows.

That is, since the wet Young's modulus is high, there is little settling in water, and beating produces extremely long fibrils. Therefore, the separator has extremely excellent separator performance. Moreover, since the formed fibrils also have a high Wetting Young's modulus, they do not sag in the alkaline solution even after being used as a separator, and are extremely excellent in the electrolyte solution retention. In addition, since the fibrils produced by beating have a high orientation due to the high orientation, the alkali resistance is high, and in this respect also, the electrolyte retention is excellent. In particular, in the present invention, when the beating degree is increased and the fibril is highly fibrillated, a thin and long fibrillated product is obtained, so that a separator having particularly excellent performance is obtained.

From the viewpoint of resource recycling, the solvent-spun cellulose fibers used in the present invention are solvent-spun using cellulose II alone or a mixture of cellulose II and cellulose I (wood pulp, cotton, etc.) as a raw material. Although some are also included, solvent-spun cellulose fibers in which only cellulose I is used as a raw material and cellulose II is directly deposited therefrom are most suitable.

The solvent-spun cellulosic fibers referred to in the present invention are so-called regenerated cellulosic fibers such as conventional viscose rayon and cuprammonium rayon, in which cellulose is chemically converted into a cellulose derivative and then converted back into cellulose. Differently, it means a fiber obtained by precipitating cellulose from a solution obtained by simply dissolving it in a solvent without chemically changing the cellulose.

Such solution-spun cellulose fibers are completely different in performance from conventional regenerated cellulose fibers such as viscose rayon, polynosic rayon, strong rayon, and cuprammonium rayon in which cellulose II is regenerated via viscose. It is a thing. This solution-spun cellulose fiber is a cellulose fiber in which the fiber internal fibrils have been extremely well developed to the innermost layer portion of the fiber, and it is known that the wet Young's modulus, the crystallinity, and the orientation are high (Tex.
tile Research Journal; No. 2; p61; 198
7). By subjecting such solvent-spun cellulose fibers to beating treatment using an appropriate method as described later, a desired fibrillated product can be obtained.

The solvent used in the production of the solvent-spun cellulose fiber used in the present invention may be any solvent as long as it dissolves cellulose without any chemical reaction, and specific examples thereof will be given. , An inorganic solvent such as a zinc chloride aqueous solution, an organic solvent such as an amine oxide represented by N-methylmorpholinoxide or a mixed solvent thereof with water,
Of these, amine oxide is preferable.

A preferred example of the cellulose fiber having the above-mentioned characteristics is produced by a method in which a spinning dope prepared by dissolving cellulose in an amine oxide is dry-wet spun in water to precipitate cellulose, and the resulting fiber is further stretched. Solvent-spun fibers are mentioned, and typical examples of such fibers are:
It is a solvent-spun cellulose fiber sold under the trade name of Tencel by Courtalls Ltd. of England or under the trade name of Solsion by Ranging GmbH of Austria.

The dry-wet spinning is a method in which the spinning solution is once discharged from a spinneret into a gas represented by air and then immediately introduced into a coagulating bath to coagulate the spinneret. A method is used in which a spinning stock solution placed in a gas of 5 to 200 mm and discharged from a spinneret is passed through the gas and then introduced into a coagulation bath to coagulate the stock solution.

Since the solvent-spun cellulose fiber used in the present invention has a high wet Young's modulus and has little settling in water, it is effectively beaten by the stress at the time of beating by a beater, refiner, etc., and an extremely long fibril is formed. To do. Since the crystallinity and orientation of the fiber are high, the fibril itself produced by beating has a high degree of crystallinity and orientation, and since it has a high alkali resistance, it has a high fiber shape retention in an electrolyte that is strongly alkaline. . This long and highly crystalline fibril has a remarkable effect on the separability described later. As described above, the solvent-spun cellulose fiber has a high wet Young's modulus, and the fibril is extremely well developed to the innermost layer part of the fiber, and the fiber is completely divided by beating to obtain only ultrafine fibers. Rather, the long outer fibrils are partially bonded to each other, and the bonding points retain the original fiber diameter, and further have a predetermined fibril diameter after beating. Such solvent-spun cellulose fibers are extremely effective as a separator for alkaline batteries in which mercury is not added, as described below.

The advantages of the separator of the present invention using the solvent-spun cellulose fibers described above are, firstly, that the electrolytic solution effective for the reaction is sufficiently retained in the separator until the final voltage is reached. In the case of a normal separator, most of the electrolytic solution is held in the voids between the fibers, so the electrolytic solution tends to move to the negative electrode side during use, and the electrolytic solution necessary for the reaction is exhausted. In contrast, when the beaten solvent-spun cellulose fiber of the present invention is used, the electrolytic solution is firmly held between the fibrils, whereas the negative electrode side of the electrolytic solution has a harmful effect of inhibiting large current discharge. Is less likely to occur, and a sufficient amount of electrolytic solution exists at the interface between both electrodes and the separator until the final voltage is reached, and the battery reaction proceeds smoothly.

There are some regenerated celluloses such as conventional viscose rayon, polynosic rayon, strong rayon and cuprammonium rayon which are fibrillated by beating. However, the wet Young's modulus of these regenerated celluloses is generally low, and even if it is high. Since it is about 18 g / d, it causes large fatigue in water and is extremely difficult to be fibrillated even when the external stress at the time of beating is strong. The fibril obtained by beating is a short fibril obtained by fibrillating the outermost layer of the fiber. Since it is a form in which the hair is densely packed on the fiber surface, even when the beating degree is the same as the solvent-spun cellulose fiber of the present invention, the electrolytic solution is firmly held between the fibrils, and the electrolytic solution goes to the negative electrode side. You can't make it hard to move.

Therefore, the wet Young's modulus of the solvent-spun cellulose fiber used in the present invention is 20 g / d or more, preferably 25 g / d or more. However, the wet Young's modulus is 150
Those of g / d or more are difficult to manufacture by the current industrial technology. Further, regarding the beating degree of the solvent-spun cellulose fiber used in the present invention, when the CSF is more than 700 ml, sufficient fibrils for holding the electrolytic solution are not formed, and when the beating degree is less than 25 ml, As the internal resistance increases, it is impossible to obtain a uniform texture. Therefore, 25 to 700 ml expressed in CSF
Is preferred, and more preferably 25-500 m
1, more preferably 50 to 200 ml.

A second advantage of the separator of the present invention using solvent-spun cellulose fibers is that it suppresses an increase in internal resistance of the battery. When beatenable cellulosic fibers such as hemp pulp, cotton linter pulp, and wood pulp are used, as described above, CSF 300 to 7
When beaten to a beating degree of 00 ml, it is possible to firmly hold the electrolyte solution between the fine pulps like the fibrils of the solvent-spun cellulose fiber having the same beating degree to prevent the electrolyte solution from moving to the negative electrode side. However, since these cellulosic fibers are merely fragmented by beating, the density of the separator increases and the internal resistance of the battery increases. On the other hand, when the beaten solvent-spun cellulose fiber of the present invention is used, the main skeleton of the fiber constitutes the separator, and because of the form having appropriate voids, the density of the separator does not increase, and the internal resistance of the battery is Does not rise.

When regenerated cellulose fibers such as conventional viscose rayon, polynosic rayon, strong rayon and copper ammonia rayon are beaten to be fibrillated, the main skeleton of the fiber is the same as the solvent-spun cellulose fiber. Since the separator has a proper void and therefore the internal resistance of the battery does not tend to increase, these fibrils lack alkali resistance, and therefore do not contribute to the separate property described later, and thus as a separator. Not suitable for use.

If the single-fiber denier of the solvent-spun cellulose fiber of the present invention before beating is less than 0.4 denier, the density of the separator increases and the internal resistance of the battery is increased. It is preferably not less than 1.0, more preferably not less than 1.0 denier.

The third advantage is that extremely good separability can be obtained. As mentioned above, conventional viscose rayon, polynosic rayon, strong rayon, and regenerated cellulose fibers such as cuprammonium rayon may also be fibrillated by beating, but since they are regenerated cellulose, they have crystallinity and orientation. Sex is generally low,
Even if it is high, the crystallinity is about 50% and the orientation Δn is 40.
It is less than × 10 ^-3 . Therefore, since these regenerated cellulose fibers lack alkali resistance of the fibers, it becomes impossible to maintain the fiber shape such as elution into the electrolytic solution, and therefore ultrafine fibers cannot be used. In particular, the fibrils produced by beating are ultrafine, and are more easily eluted into the electrolyte,
It is not possible to obtain a separate property with this fibril. Further, since the crystallinity of the fiber inner layer portion of these regenerated cellulose fibers is lower than that of the fiber outer layer portion, the fiber inner layer portion lacking alkali resistance is exposed by fibrillation of the fiber outer layer portion, and the fiber component is changed as the beating progresses. It is likely to be eluted in the electrolytic solution, and is therefore unfavorable for use as a separator.

With respect to these regenerated cellulose fibers, the crystallinity is 50% or more, more preferably 55% or more, and the orientation is Δn = 42 × 10 ⁻³ or more, more preferably 44 × 1.
In the case of using the cellulose fiber of 0 ^-3 or more, that is, when the solvent-spun cellulose fiber of the present invention is used, the fully crystallized fibrils grow to the inner layer portion of the fiber, and thus the fibril after beating is extremely excellent in alkali resistance. Moreover, the inside of the fiber exposed by beating is also excellent in alkali resistance. Therefore, the long fibrils generated by beating are uniformly entangled in the voids formed by the main fiber skeleton to uniformly fill the voids, while suppressing an increase in the internal resistance of the battery while maintaining extremely good separability for a long time. To be done.

The fibril diameter of the solvent-spun cellulose fiber of the present invention after beating is preferably 5 μm or less, more preferably 3 μm or less, because if the fiber diameter exceeds 5 μm, effective separation property cannot be obtained. The single-fiber denier of the solvent-spun cellulose fiber of the present invention before beating is preferably 3.0 denier or less, more preferably 2.0 denier or less, because if it exceeds 3.0 denier, the separability is impaired. . The fibrils obtained by beating regenerated cellulose fibers such as conventional viscose rayon, polynosic rayon, strong rayon, and copper ammonia rayon are short fibrils obtained by fibrillating the outermost layer of the fiber as described above. Since the fibers are densely packed on the surface of the fiber, the voids formed by the main skeleton of the fiber cannot be evenly filled even in the state where the fiber morphology at the initial stage of battery incorporation is maintained. Is likely to occur and cannot be used as a separator.

Further, the features of the separator of the present invention are that the separator has a low expansion degree and can be filled with a large amount of the negative electrode active material. When a cellulosic fiber is usually used as the separator, the swelling of the fiber due to the electrolytic solution increases the degree of swelling as a separator, and when the battery is created, the filling amount of the negative electrode active material decreases, so This has the adverse effect of reducing the capacity. Even when beatenable cellulosic fibers, such as hemp pulp, cotton linter pulp, and wood pulp, are used, the fibers are merely subdivided by beating, and swelling as a separator is suppressed even if they are entangled. However, when the beaten solvent-spun cellulose fibers of the present invention are used, the fibrils swell as fibers because the fibrils are entangled with the fiber main skeleton constituting the separator to support the fiber main skeleton. As a separator, the degree of swelling tends to be suppressed to a low level. When beating regenerated cellulose fibers such as conventional viscose rayon, polynosic rayon, strong rayon, and cuprammonium rayon, it is entangled with the fiber main skeleton composed because the fibrils generated are extremely short as described above. Unable to support the main fiber skeleton,
The swelling degree of the separator becomes high, which is not preferable.

As the binder used in the present invention, a polyvinyl alcohol-based binder is used from the viewpoint of electrolytic solution resistance. The form may be fibrous, powdery or solution-like, but when a separator is produced by wet papermaking, it is preferably a fibrous binder.
When the polyvinyl alcohol-based binder is in the form of powder or solution, it is necessary for these to dissolve in order to express the paper strength of the separator, but at this time polyvinyl alcohol forms a film, and the fibers of the separator are separated. As a result, the electrolyte absorbability is lowered and the internal resistance of the battery is increased. On the other hand, when a fibrous binder is used, the same phenomenon as above occurs when it is used normally, that is, when it is completely dissolved, which is not preferable, but the moisture content before carry-in is decreased or the drying temperature is increased. When the point adhesion is performed only at the intersections of the binder fiber and the main fiber while the fiber form is left without completely dissolving the binder by means such as lowering it, the electrolyte absorbability is lowered, and the inside of the battery The strength of the separator can be increased without increasing the resistance. If the water temperature of the polyvinyl alcohol-based binder fiber suitable for this purpose is lower than 60 ° C, the binder will be completely dissolved even if the above-mentioned method of use is used, which is not preferable. Is preferably 60 to 98 ° C., because
The temperature is more preferably 70 to 90 ° C, and the drying temperature at the time of papermaking is a dryer temperature of 70 to 150 ° C, preferably 80 to 120 ° C.

The binder is added in such a manner that the weight ratio of the polyvinyl alcohol-based binder to all the main fibers is 3/9.
When it is less than 7, the necessary separator strength cannot be obtained, and when it is more than 30/70, the amount of the main fiber effective for battery performance is small.
/ 70 is preferable.

As the main fibers constituting the separator of the present invention, as described above, from the viewpoints of separation property, electrolyte solution absorption property, decrease in internal resistance of battery, and low swelling degree,
Basically, beaten solvent-spun cellulose fibers are used, but a combination of this and other synthetic fibers is preferable for improving the texture. Generally, as the beating degree of the solvent-spun cellulose fibers progresses, the texture of the separator tends to deteriorate due to the aggregation of the cellulose fibers, but the aggregation can be prevented by mixing the synthetic fibers. As described above, it is necessary that the beating degree is in the range of 700 to 25 ml in order to retain the electrolytic solution, reduce the internal resistance, and improve the texture, but even when using CSF of 700 ml, the main fiber A synthetic fiber content of 5% by weight or more is preferred.

Examples of the synthetic fibers used in the present invention include polyvinyl alcohol fibers, polyamide fibers, polyolefin fibers and the like from the viewpoint of electrolytic solution resistance. Particularly preferred are polyvinyl alcohol fibers.

Further, other cellulosic fibers may be mixed and mixed within a range that does not significantly impair the above performance. However, the most preferable one is one in which only the beaten solvent-spun cellulose fibers and polyvinyl alcohol fibers are the main fibers.

The reason why the polyvinyl alcohol-based fiber is used as a part of the main fiber is that the polyvinyl alcohol-based fiber is extremely excellent in electrolytic solution resistance among various fibers and also excellent in electrolytic solution absorption. However, the main reason is not only this but also the effect of lowering the swelling degree of the separator. As described above, the polyvinyl alcohol-based binder is used as the binder in the separator of the present invention, but the polyvinyl alcohol-based fiber and the polyvinyl alcohol-based fiber have a high adhesive force because the hydrogen bonding force of both effectively works. Therefore, both the polyvinyl alcohol-based binder and the polyvinyl alcohol-based fiber form the skeleton of the separator and serve as a support for the other main fibers including the beaten solvent-spun cellulose fiber, and the swelling of the separator can be suppressed as a whole. When the polyvinyl alcohol fiber is not used, it is difficult to suppress swelling because the adhesive force between the other main fiber and the polyvinyl alcohol binder is weak. When solvent-spun cellulose fibers beaten as described above are used, although there is a tendency to suppress swelling by the entanglement force of the fibrils,
When combined with a polyvinyl alcohol fiber, a lower degree of swelling is obtained, which is extremely effective.

As a preferable denier of the polyvinyl alcohol fiber, as described above, in the case where mercury is not added to the zinc negative electrode, it is extremely higher than that in the case of adding 1.5% by weight. Since a high degree of separation is required, 1 denier or less, especially 0.5 denier or less,
More preferably, it is a polyvinyl alcohol fiber having a denier of 0.3 or less. However, simply thinning the fibers is not preferable because it leads to a decrease in electrolyte absorbability and an increase in internal resistance of the battery.

Here, the meaning of using fine denier fibers comes into play only in combination with the solvent-spun cellulose fibers beaten as described above. That is, since the beaten solvent-spun cellulose fibers satisfy the requirements of the electrolyte solution absorbency and the decrease of the internal resistance of the battery, even if the polyvinyl alcohol fiber is 1 denier or less, the decrease of the electrolyte solution absorbency and the battery Without increasing the internal resistance, and in combination with the effect of fibrils of beaten solvent-spun cellulose fibers, a higher degree of separation property can be obtained, and internal short circuit does not occur even when mercury is not added. In particular, in the thick denier that has been used conventionally, the effect is small because the number of lines is small at the same mixing ratio, but by thinning the effect is large with a small mixing ratio, and by doing so,
It is possible to increase the mixing ratio of beaten solvent-spun cellulose fibers as an electrolyte holding material. Therefore, the polyvinyl alcohol fiber used in the present invention is preferably 1 denier or less. However, from the current industrial technology,
Although it is difficult to directly obtain polyvinyl alcohol fibers having a denier of less than 01 denier, ultrafine fibers can be obtained by a method such as fibrillation.

The blending ratio of the beaten solvent-spun cellulose fibers used in the present invention with respect to all the main fibers is 95% by weight or more, and the degree of swelling is large. 95 to 25 because it tends to decrease and the internal resistance tends to increase.
Wt% is preferred, more preferably 90-30 wt%,
More preferably, it is 75 to 40% by weight.

In the method for producing the separator of the present invention, solvent-spun cellulose fibers are beaten to a predetermined CSF, and this is mixed with synthetic fibers of 1 denier or less and, if necessary, other cellulose-based or synthetic fibers, Further, a binder is added and dispersed in water to carry out ordinary wet papermaking.

As the beating method for the solvent-spun cellulose fiber used in the present invention, according to a commonly used beater, double disc cliff-iner, etc., the main skeleton of the fiber may be cut because the fiber is strongly rubbed by the metal. is there. In this case, even if the CSF is lowered, the apparent beating only proceeds, so that no effective fibril is actually generated. According to the studies by the present inventors, it is preferable to use a pulper with a crushed blade and a fiberizer (high-speed disintegrator) in which the tooth spacing is adjusted to the fiber length of the solvent-spun cellulose fiber for beating. The method using such a combination is such that, while avoiding contact between metals, by performing beating by internal turbulent flow and shearing action, the main skeleton of the fiber is not cut, and the long fiber due to separation from the surface in the axial direction of the fiber. It was revealed that this is an extremely effective beating method as compared with beating with a beater, a double disc cliff einer, etc.

[0048]

EXAMPLES The embodiments and effects of the present invention will be described in more detail by the following examples.

The fiber orientation Δn was determined by measuring the retardation of the fiber using a polarizing microscope and a Berek's conventor, and measuring the thickness of the fiber at the light-irradiated portion. Sought by.

[0050]

## EQU1 ## Δn = retardation / fiber thickness The beating degree CSF was measured according to the method described in JIS P8121.

According to an optical microscope observation, the solvent-spun cellulose fibers after beating were in a form in which the main fiber skeleton remained, and long fibrils were formed with the fiber skeleton as a binding site. Therefore, the fibril diameter after beating was The thickness of 10 fibrils was measured by observation with an optical microscope, and the average value was taken.

The wet Young's modulus was measured by a method according to JIS L-1073. Further, the crystallinity was obtained by taking an X-ray diffraction intensity curve, separating this into a crystal part and an amorphous part, determining the area of each, and then using the following formula.

[0053]

## EQU2 ## Crystallinity = 100 × (crystal part area) / (crystal part area + amorphous part area) Example 1 Wet Young's modulus is 26 g / d, orientation Δn = 45 × 1
0 ^-3 , crystallinity 58.5%, 1.5 denier, length 2 m
The solvent-spun cellulose fiber of m (Tencel manufactured by Courtols Co., Ltd.) was beaten with a pulper and a fiberizer to give CS.
F 150 ml of fibril compound was used. The fibril diameter of the fiber after beating was 0.5 μm, and cutting of the fiber main skeleton was hardly observed. This fiber is 59% by weight based on all the main fibers, and polyvinyl denaturation fiber of 0.3 denier and length 2 mm is 41% based on the total main fibers.
% By weight, and the main fiber composed of this mixture is further dissolved in water at a temperature of 75 ° C., 1.0 denier, and length of 3 mm
The polyvinyl alcohol fibrous binder of was added in an amount such that the weight ratio of all main fibers: binder was 85:15 to prepare a slurry.

This slurry was made into paper by a cylinder paper machine and dried at a dryer temperature of 110 ° C. to obtain a basis weight of 32.3 g /
A m ² -thick separator having a thickness of 0.107 mm was obtained. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Example 2 In the above Example 1, the composition ratio of the main fiber was changed to solvent-spun cellulose fiber: polyvinyl alcohol fiber = 80: 2.
In the same manner as in Example 1 except that the weight ratio was changed to 0 (weight ratio),
A separator having a basis weight of 34.2 g / m ² and a thickness of 0.108 mm was obtained. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Example 3 In Example 1, the beating degree (CSF value) of the solvent-spun cellulose fiber was 200 ml, and the fibril diameter was 0.8 μm (however, the cutting of the main fiber skeleton was hardly observed).
A separator was produced in the same manner as in Example 1 except that the fibrillated product was used. The obtained separator had a basis weight of 33.5 g / m ² and a thickness of 0.108 mm. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Example 4 In Example 1 above, the beating degree (CSF value) of the solvent-spun cellulose fiber was 50 ml and the fibril diameter was 0.1.
A separator was produced in the same manner as in Example 1 except that a fibrillated product having a size of 1 μm (a slight breakage of the main fiber skeleton was observed) was used. The resulting separator has a basis weight of 3
The thickness was 5.2 g / m ² and the thickness was 0.108 mm. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Example 5 Example 1 was repeated except that the polyvinyl alcohol fibrous binder in Example 1 was replaced with a polyvinyl alcohol fibrous binder having a dissolution temperature in water of 60 ° C., a thickness of 1.0 denier and a length of 3 mm. A separator was prepared in the same manner as in. The obtained separator has a basis weight of 35.4.
The thickness was g / m ² and the thickness was 0.107 mm. The polyvinyl alcohol-based fibrous binder was completely dissolved in this separator to form a film.

Example 6 The solvent-spun cellulose fiber obtained in Example 1 above had a wet Young's modulus of 24 g / d and an orientation Δn = 42 × 1.
0 ^-3 , crystallinity 53.5%, 4.0 denier, length 5 m
A fibril compound having a CSF value of 150 ml was obtained by beating in the same manner as in Example 1 using m solvent-spun cellulose fibers (fibril diameter: about 0.5 μm, cutting of the fiber main skeleton was observed in almost half of the fibers). ) Was used in the same manner as in Example 1 to prepare a separator. The obtained separator had a basis weight of 32.4 g / m ² and a thickness of 0.108 mm. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Example 7 In the above Example 1, the beating degree (CSF value) of the solvent-spun cellulose fiber was set to 20 ml and the fibril diameter was set to be 0.1.
A separator was produced in the same manner as in Example 1 except that a fibrillated product having a size of 05 μm (most of the main fiber skeleton was observed to be cut) was used. The obtained separator had a basis weight of 35.8 / m ² and a thickness of 0.107 mm. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Example 8 In Example 1, the beating degree (CSF value) of the solvent-spun cellulose fiber was set to 750 ml and the fibril diameter was set to 4.
A separator was produced in the same manner as in Example 1 except that a fibrillated product having a size of μm (disruption of the main skeleton of the fiber was not observed) was used. The obtained separator has a basis weight of 32.6 g.
/ M ² and the thickness was 0.107 mm. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Example 9 In the above Example 1, the composition ratio of the main fiber was changed to solvent-spun cellulose fiber: polyvinyl alcohol fiber = 40: 6.
In the same manner as in Example 1 except that the weight ratio was changed to 0 (weight ratio),
A separator having a basis weight of 33.2 g / m ² and a thickness of 0.107 mm was obtained. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Example 10 In the above Example 1, the composition ratio of the main fiber was changed to solvent-spun cellulose fiber: polyvinyl alcohol fiber = 97.3.
A separator having a basis weight of 34.9 g / m ² and a thickness of 0.106 mm was obtained in the same manner as in Example 1 except that the (weight ratio) was changed. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Example 11 In the above Example 1, the polyvinyl alcohol fiber used as a part of the main fiber was 0.5 denier and the length was 3 m.
m except that the polyvinyl alcohol fiber is replaced with the same as in Example 1 except that the basis weight is 33.9 g / m ² and the thickness is 0.1.
A 106 mm separator was made. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Example 12 In Example 1, the polyvinyl alcohol fiber used as a part of the main fiber was 1.0 denier and the length was 5 m.
m, except that the polyvinyl alcohol fiber is replaced with a polyvinyl alcohol fiber having a basis weight of 34.3 g / m ² and a thickness of 0.
A 106 mm separator was made. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Example 13 In Example 1, the polyvinyl alcohol fiber used as a part of the main fiber was 1.0 denier and the length was 5 m.
m in the same manner as in Example 1 except that the polypropylene fiber is replaced with polypropylene fiber having a basis weight of 32.9 g / m ² and a thickness of 0.106 m.
m separator was prepared. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Example 14 In the above Example 1, except that 37% by weight of the polyvinyl alcohol fiber used as a part of the main fiber was replaced with mercerized cotton linter pulp (orientation: 30 × 10 ⁻³ or less). As in Example 1, basis weight 35.
A separator having a thickness of 3 g / m ² and a thickness of 0.108 mm was produced. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Comparative Example 1 In Example 1, the fibrillated product of solvent-spun cellulose fiber was beaten with mercerized cotton linter pulp having an orientation of 30 × 10 ⁻³ or less by a pulper and a fiberizer to give a CSF value of 150 ml. Basis weight 3 in the same manner as in Example 1 above except that the fibril compound was replaced.
A separator having a thickness of 7.5 g / m ² and a thickness of 0.105 mm was produced. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Comparative Example 2 The fibrillated product of the solvent-spun cellulose fiber in the above Example 1 had a wet Young's modulus of 6 g / dr and an orientation Δn.
= 19 × 10 ⁻³ , crystallinity 32.1%, 1.5 denier (dr), length 2 mm viscose rayon was beaten to obtain a CSF value of 720 ml (this viscose rayon was beaten further). CSF value of 720 ml
A separator having a basis weight of 32.7 g / m ² and a thickness of 0.105 mm was produced in the same manner as in Example 1 except that the separator was replaced with the following. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Comparative Example 3 The fibrillated product of the solvent-spun cellulose fiber obtained in the above Example 1 had a wet Young's modulus of 18 g / dr and an orientation Δ.
Example 1 except that n = 39 × 10 ⁻³ , crystallinity 46.1%, 0.5 denier (dr), 2 mm long polynosic rayon was beaten and replaced with a fibril compound having a CSF value of 150 ml. Same as the basic weight of 35.9g /
A m ² separator having a thickness of 0.104 mm was prepared. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

Comparative Example 4 In the above Example 1, the whole main fiber was 0.3% without using the fibrillation product of the solvent-spun cellulose fiber.
Density: 23.8 mm, except that polyvinyl alcohol fibers were used, the same as in Example 1 except that the basis weight was 33.8 g /
A m ² -thick separator having a thickness of 0.107 mm was produced. In this separator, the polyvinyl alcohol fibrous binder was in a semi-dissolved state, and the fiber form remained.

With respect to the above 18 kinds of separators, the amount of electrolyte absorbed and the degree of swelling were measured by the following methods.

(1) Absorption of Electrolyte Solution The separator is sampled in a size of 5 cm × 5 cm, and the weight is measured. This is immersed in a 35 wt% potassium hydroxide aqueous solution at 25 ° C. for 30 minutes. Drain for 15 seconds and weigh. The amount of electrolyte absorbed is calculated by the following formula.

[0074]

## EQU00003 ## Absorption of electrolyte (g / g) = (weight after immersion−weight before immersion) / weight before immersion (2) Swelling degree The separator was sampled in a size of 5 cm × 5 cm, and 18
The thickness is measured with a thickness meter under a load of 0 g / cm ² . This is immersed in a 35 wt% potassium hydroxide aqueous solution at 25 ° C. for 30 minutes. The liquid is drained for 15 seconds, the thickness is measured by the same method, and the degree of swelling is calculated by the following formula.

[0075]

Swelling degree (%) = (thickness after immersion−thickness before immersion) /
Thickness before immersion × 100 Next, an AA alkaline manganese battery using a mercury-free zinc negative electrode was prepared using these separators.

FIG. 1 shows an AA using the separator of the present invention.
The half cross-sectional view of a form alkaline dry battery is shown.

In FIG. 1, reference numeral 1 denotes a positive electrode can which also serves as a positive electrode terminal. A cylindrical positive electrode mixture 2 made of manganese dioxide and graphite is press-fitted into the positive electrode can 1. Reference numeral 3 denotes a bottomed cylindrical separator according to the present invention, in which a zinc negative electrode 4 in which a mercury-free zinc alloy powder is dispersed and mixed in a gel electrolyte is filled. 5 is a negative electrode current collector, 6
Is a resin sealing body that closes the opening of the positive electrode can 1. In this resin sealing body 6, a bottom plate 7 also serving as a negative electrode terminal is welded to the head of the negative electrode current collector 5 and arranged together with a metal washer 8. ing. The positive electrode can 1 is sealed by caulking the opening inside.

The battery prepared as described above was used in US ANSI.
Based on the standard, continuous discharge at 10Ω and 1 at 10Ω
After discharging for 1 hour per day, the time until the final voltage of 0.9V was reached was measured.

The results of the amount of absorbed electrolyte, the degree of swelling, and the discharge time are shown in Tables 1-5. In the table, ◎ is extremely good, ○ is good, △
Slightly bad, x means extremely bad.

[0080]

[Table 1]

[0081]

[Table 2]

[0082]

[Table 3]

[0083]

[Table 4]

[0084]

[Table 5]

From Tables 1 to 5, the products of the present invention are
It has excellent electrolyte absorption and low swelling, and thus has excellent battery performance with no shortage, and also has excellent electrolyte absorption, low swelling, and low internal resistance for large current discharge. It is clear that it is excellent.

[Brief description of drawings]

FIG. 1 shows a half sectional view of an AA alkaline battery using a separator of the present invention.

[Explanation of symbols]

 1 Positive electrode can 2 Positive electrode mixture 3 Separator 4 Negative electrode 5 Negative electrode current collector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoyasu Sone 1-2-1, Kaigandori, Okayama-shi Kuraray Co., Ltd. (72) Inventor Shingo Nakanishi 1-1239, Umeda, Kita-ku, Osaka Kuraray (72) Inventor Junichi Asaoka 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor, Yuji Motoya, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial

Claims (11)

[Claims] 1. A separator for an alkaline battery, characterized in that a fibrillated product of a cellulose fiber obtained by dissolving cellulose in a solvent to directly precipitate the cellulose is at least a part of the main fiber. 2. A cellulose fiber having a wet Young's modulus of 20.
The alkaline battery separator according to claim 1, wherein the orientation Δn is 42 × 10 ⁻³ or more at g / d or more. 3. The separator for an alkaline battery according to claim 1, wherein the cellulose fiber is a solvent-spun cellulose fiber obtained by dry-wet spinning a stock solution prepared by dissolving cellulose in an amine oxide to precipitate cellulose. 4. The alkaline battery separator according to claim 1, wherein the crystallinity of the cellulose fiber is 50% or more. 5. The alkaline battery separator according to claim 1, wherein the fibrillation product has a beating degree (CSF value) of 700 to 25 ml. 6. The alkaline battery separator according to claim 1, wherein the monofilament denier of the cellulose fiber before fibrillation is 0.4 to 3.0 denier. 7. The alkaline battery separator according to claim 1, wherein 5% by weight or more of the main fiber is a synthetic fiber having a denier of 1 or less. 8. The alkaline battery separator according to claim 7, wherein the synthetic fiber is a polyvinyl alcohol fiber. 9. A fibrillated product of a cellulose fiber having a wet Young's modulus of 20 g / d or more and an orientation Δn of 42 × 10 ⁻³ or more and a polyvinyl alcohol fiber having a denier of 1 or less are substantially used as main fibers. The weight ratio of the fibril compound to the polyvinyl alcohol fiber is 95: 5 to 25:
75, and further, a polyvinyl alcohol-based binder is present, and the weight ratio of the binder to the main fiber is 3:97 to 30:70. 10. The alkaline battery separator according to claim 9, wherein a fibrous binder is used as the binder. 11. An alkaline battery using the separator according to claim 1.