JPH07312215A - Battery separator - Google Patents

Abstract

PURPOSE:To improve alkaliproofness, oxidation resistance, initial hydrophilic property, and durable hydrophilic property by sticking prescribed fluorocarbon surface active agent to nonwoven fabric composed of fiber containing sulfonated polysulfon, polyvinyl chloride, etc. CONSTITUTION:Mix polymer formed by mixing sulfonated polysulfon (SPSF), polyvinyl chloride (PVC), and methacrylic acid ester polymer is used as fiber constituting a separator. In this case, these mixing rate is set to SPSF 15-40wt.%, PVC 20-85wt.%, and methacrylic acid ester polymer 0-65wt.%. Fluorocarbon surface active agent superior in durable hydrophilic property is added to nonwoven fabric mainly composed of such mix polymer fiber by a prescribed quantity. Surface tension of flourocarbon surface active agent is set to 40dyne/cm.25 deg.C or less in 0.1% aqueous solution. This constitution can provide a separator superior in alkaliproofness, oxidation resistance, initial hydrophilic property, and durable hydrophilic property and improve it into high quality.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a battery separator excellent in alkali resistance, oxidation resistance, initial hydrophilicity and durable hydrophilicity.

[0002]

2. Description of the Related Art Conventionally, as a separator for an alkaline battery, a nonwoven fabric of polyamide fiber or polyolefin fiber having excellent alkali resistance has been widely used.

However, a battery separator using a polyamide nonwoven fabric has a drawback that it is oxidized and deteriorated by oxygen gas generated during charging, and a polyamide fiber type separator of a secondary battery has a high temperature (6
There is a problem that a deterioration phenomenon appears at an early stage due to poor oxidation resistance against a severe battery reaction in an electrolytic solution at 0 to 80 ° C.).

On the other hand, a battery separator using a polyolefin fiber has an advantage that it is excellent in oxidation resistance, but on the other hand, since it is inferior in hydrophilicity, it has a low electrolyte retaining property. Therefore, in the battery separator of polyolefin fiber, there are problems such as high electric resistance in liquid, poor permeability of gas generated during charging, and risk of bursting due to increase in internal pressure during charging in a sealed battery. there were.

In order to improve the oxidation resistance of the above-mentioned polyamide, it has been proposed to combine polyamide fiber and polyolefin fiber. However, this reduces the deterioration because the mixing ratio of fibers that undergo oxidative decomposition decreases as a whole. It is only possible to do, not a fundamental solution.

As a technique for improving the hydrophilicity of polyolefin, a method of treating a polyolefin fiber separator with fuming sulfuric acid or chlorosulfuric acid for sulfonation, a method of treating with hot concentrated sulfuric acid for sulfonation, and sulfur trioxide ( S
Many methods have been proposed, such as a method of treating with O ₃ ) in a gas for sulfonation, a method of graft-polymerizing acrylic acid or methacrylic acid by electron beam irradiation, but the sheet may be severely deteriorated in strength or its appearance may be very poor. It has not reached the stage of mass production because there are problems such as deterioration in quality and industrial instability.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above conventional problems and provide a battery separator excellent in alkali resistance, oxidation resistance, initial hydrophilicity and durable hydrophilicity. is there.

[0008]

The present invention adopts the following means in order to achieve the above object. That is, the present invention is
Sulfonated polysulfone 15-40% by weight, degree of polymerization 90
A non-woven fabric composed of fibers containing 20 to 85% by weight of polyvinyl chloride of 0 to 1800 and 0 to 65% by weight of a methacrylic acid ester-based polymer has a surface tension of 40 dyne / cm · 25 ° C. in an aqueous solution of 0.1%. It is a battery separator to which the following fluorosurfactant is attached in an amount of 0.1 to 2.0% by weight.

The fiber constituting the battery separator of the present invention is a mixed polymer of sulfonated polysulfone (hereinafter abbreviated as SPSF), polyvinyl chloride (hereinafter abbreviated as PVC), and methacrylic acid ester-based polymer. However, the mixing ratio of SPSF is 15 to 40% by weight,
PVC is 20 to 85% by weight, and methacrylic acid ester polymer is 0 to 65% by weight. If the mixing ratio of these is out of the range, the spinnability, dimensional stability and strength / elongation property of the fiber are adversely affected. Exert.

The SPSF, which is a constituent component of the fiber constituting the battery separator of the present invention, has a sulfonic acid group introduced into polysulfone, and the ratio of the sulfonic acid group in the sulfonated polysulfone is 3 to 30% by weight, preferably. Is 6
It is about 20% by weight, and the polymerization degree of polysulfone is not particularly limited. Sulfonation of polysulfone is performed with a sulfonating agent such as chlorosulfonic acid and fuming sulfuric acid.
If the sulfonation is less than 3% by weight in terms of sulfonic acid group,
If the liquid retention is insufficiently improved and exceeds 30% by weight,
Sulfonation itself is difficult and also disadvantageous in terms of cost.

In the composition constituting the fiber constituting the battery separator of the present invention, composition components other than SPSF and PVC have excellent alkali resistance at high temperature, and are suitable for the solvent used for fiber shaping. It is selected from soluble polymers. Examples of such polymers include methacrylic acid ester-based polymers, that is, acrylic resins such as polymethylmethacrylate, polystyrene resins, ABS resins, styrene / acrylic acid ester copolymer resins, etc., and do not exceed 65% by weight in the composition. It can be contained in the range.

The fibers constituting the battery separator of the present invention have an alkali resistance at a high temperature of 2% by weight at a weight reduction ratio of the fibers after being immersed in an aqueous solution of 35% by weight potassium hydroxide in a boiling state at atmospheric pressure for 1 hour. It has the following alkali weight loss rates. This alkali weight loss rate shows a value equivalent to that of polypropylene fiber. Further, as the oxidation resistance at high temperature, the weight loss rate of the fiber after soaking in a mixed solution of 5 parts by weight of potassium hydroxide 35% by weight aqueous solution and 20 parts by weight of potassium permanganate 5% by weight aqueous solution under normal pressure boiling for 1 hour And has an oxidation weight loss rate of 2% by weight or less.

Further, the fiber constituting the battery separator of the present invention has a liquid retention of 35% by weight or more and forms a non-woven fabric by being composed of the above composition, particularly a composition containing sulfonated polysulfone. Improves the electrolyte retention when used as a battery separator.

The fiber constituting the battery separator of the present invention is not particularly limited in its shape, but the single fiber fineness of the fiber is 3 denier or less, preferably 2 denier or less. It is possible to obtain fine fibers from the composition of the present invention. By using fibers having such a fineness, it is possible to obtain a thinner battery separator, and it is possible to adapt to miniaturization of the battery. The cross-sectional shape of the fiber is not particularly limited and may be any of circular, Y-shaped, cross-shaped, triangular and other irregular shapes, and is appropriately selected in consideration of the liquid retaining property.

By selecting the above fiber composition, the fibers constituting the present invention have a boiling water shrinkage of 15% or less. If the boiling water shrinkage rate is excessively high, there is a problem that streak wrinkles occur due to shrinkage in the drying step during the formation of the nonwoven fabric, but if the fiber has a boiling water shrinkage rate of 15% or less, there is a process problem. Never be.

The fibers constituting the battery separator of the present invention can be obtained from a composition containing SPSF and PVC, preferably by a wet spinning method. As the solvent in the wet spinning, dimethylacetamide and dimethylformamide are preferably used, and dimethylsulfoxide and acetone can also be used. A composition containing sulfonated polysulfone and polyvinyl chloride is mixed and dissolved in such a solvent to prepare a spinning dope. The viscosity of the spinning dope is 100 at 50 ° C.
-2000 poise, preferably 150-1000 poise, and the solid content concentration of the stock solution is adjusted to fall within this viscosity range, but the solid content concentration of the spinning stock solution is 50% by weight or less in order to prevent gelation. It is preferable. In addition, a light resistance, heat resistance stabilizer and the like can be added to the spinning dope, if necessary.

The spinning dope is spun from the spinneret into a coagulation bath and shaped into fibers. The pore diameter of the spinneret is appropriately selected according to the target fineness, and the fineness can be adjusted depending on the condition after spinning, but in order to set the single fiber fineness to 3 denier or less, the pore diameter is about 60 μm or less. Is desirable.

As the coagulant for the coagulation bath, water, alcohol or the like is used. The ratio of the solvent to the coagulant in the coagulation bath and the temperature are
It can be appropriately selected in consideration of spinnability according to the composition in the spinning dope. The undrawn yarn from the coagulation bath is washed and drawn to impart mechanical performance, and is collected as dried or undried to obtain a nonwoven fabric material for a battery separator.

The conditions for washing, stretching and drying the unstretched yarn are not particularly limited and may be appropriately selected depending on the fiber composition, but for the purpose of reducing the boiling water shrinkage of the fiber, stretching is performed in boiling water after stretching. It is also possible to add a step of relaxing the yarn to 20% or less. The obtained fiber has voids in the fiber cross section, and further has numerous wrinkles along the fiber axis in the fiber side surface. The wrinkles on the side surfaces of the fibers communicate with the voids inside the fibers to give the fibers high liquid retention. Such a fiber structure is clearly exhibited by the fiber shaping by the wet spinning method, and the water retention rate of the fiber itself is as high as 45 to 61%.

Here, the water retention rate of the fiber is a value calculated by the following method. That is, after soaking in deionized water for 24 hours, centrifugal dehydration was performed at a load of 1000 G for 10 minutes, and the fiber weight (W
₁ ) is measured. The dry weight (W ₂ ) of this fiber is measured and calculated by the following formula. Water retention rate _{= [(W 1 -W 2)} / W 2] × 100 (%)

In the present invention, the fibers as described above are used as a nonwoven fabric for a battery separator. Examples of the method for producing a non-woven fabric include a method of forming a web with a card and making a non-woven fabric with a needle punch, a method of wet papermaking, and the like. Usually, 5 to 50% by weight of the binder is used to fix the fibers together. The binder used at this time is selected taking into consideration that there is no problem in alkali resistance and oxidation resistance and that it has electrical insulation. Examples of binders that satisfy such conditions include vinyl chloride-vinyl acetate copolymer fibers or resins, and polyolefin fibers or resins such as polyethylene and polypropylene.

The thickness of the non-woven fabric is set according to the purpose, but it is generally set to 0.05 to 0.3 mm. A thinner non-woven fabric has an advantage that it is easier to be wet with an electrolytic solution. However, if the non-woven fabric is too thin, a problem in strength appears and a short circuit easily occurs. Further, if the nonwoven fabric is thick and has a high density, it takes time for the electrolytic solution to completely permeate into the inside, which hinders smooth charge / discharge reaction.

The liquid retention rate of the battery separator of the present invention is 25.
It has a high performance of 0% or more. The higher the liquid retention rate is, the better, and it is possible to increase the capacity of the battery, reduce the size of the battery, and rapidly charge the battery. When the liquid retention rate is 200% or less, the smooth battery reaction does not occur and the discharge capacity decreases.

Further, the liquid absorbing speed of the battery separator of the present invention is a high speed of 20 seconds or less in terms of liquid drop disappearing speed.
If the liquid absorption rate is 60 seconds or more, the permeation and diffusion of the electrolytic solution is poor, and it takes time to inject the electrolytic solution during battery assembly.
The battery performance is deteriorated, for example, the permeation of oxygen gas generated during charging is deteriorated.

In the present invention, it is necessary that the non-woven fabric mainly composed of the fibers of the mixed polymer contains a predetermined amount of a fluorosurfactant having excellent durability and hydrophilicity. It improves the hydrophilicity of the electrolytic solution after cycling. The fluorine-based surfactant used here can be basically represented by the following chemical formula: perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl polyoxyethylene ethanol, perfluoroalkyl ammonium salt. , Fluorine-based alkyl esters and the like can be preferably used. C _n H _{2n + 1-m} F _m X (where n = number of carbon atoms, m = number of fluorine additions, x = hydrophilic group)

Fluorine-based surfactants are more stable than conventionally used hydrocarbon-based surfactants, do not undergo oxidative decomposition as easily as hydrocarbon-based surfactants, and have hydrophilicity in electrolyte solution after charge / discharge cycles. It can be exhibited without inferior to the initial hydrophilicity.
The stability against oxidative decomposition can be evaluated, for example, as follows. That is, 250 ml of a 5% aqueous solution of potassium permanganate containing a predetermined concentration of a surfactant and 30 ml of a 35% aqueous solution of potassium hydroxide are mixed to obtain 80
A solution of 0.2 cc left for a certain period of time at a temperature of 20 ± 2
Leave at equilibrium for 24 hours in the condition of ℃ and relative humidity of 65 ± 2%, drop it on a separator non-woven fabric that has not been treated with additives kept horizontally, until the liquid droplet is absorbed by the non-woven fabric and disappears. To measure the time. Table 1 shows the results of the above evaluations performed on the fluorine-based surfactant and the hydrocarbon-based surfactant. As is clear from this, it is clear that the fluorosurfactant maintains the initial performance even under the condition that it is easily oxidized and decomposed.

[0027]

[Table 1]

In the present invention, the surface tension of the fluorinated surfactant applied to the battery separator must be 40 dyne / cm · 25 ° C. or less in a 0.1% aqueous solution. If the surface tension is larger than this, the initial hydrophilicity will be poor, and the intended purpose cannot be achieved. The amount of adhesion to the non-woven fabric needs to be 0.1 to 2.0% by weight based on the untreated non-woven fabric. If the adhered amount is less than 0.1% by weight, there is no significant improvement effect on the durability and hydrophilicity. On the contrary, if the adhered amount exceeds 2.0% by weight, the amount dropped into the electrolytic solution increases. As a method of attaching the surfactant to the nonwoven fabric, a method of making the surfactant into an aqueous solution, immersing the nonwoven fabric in the aqueous solution, and then drying it is generally used.

Further, in the case where the liquid absorption rate and the liquid retention rate when the electrolytic solution is absorbed by the nonwoven fabric decrease due to the influence of the binder used for forming the fiber into the nonwoven fabric, the influence of the thickness and the density, etc. It can be improved by incorporating a surfactant having excellent alkali resistance and the ability to improve the liquid retention of the electrolytic solution.

The surfactant used for improving the liquid retention property is required to have alkali resistance, and when the surfactant is eluted in the electrolytic solution and partially decomposed, the surfactant is phosphorus and nitrogen. With, since phosphorus ions and nitrate ions are generated in the electrolytic solution to promote self-discharge and hinder battery performance, it is desirable that the surfactant does not contain phosphorus and nitrogen, formula _{R-O- (CH 2 CH 2} O) n CH 2 COOM ( wherein R is an alkyl group, M is sodium, potassium, or hydrogen) carboxylated polyoxyethylene alkyl ether carboxylic acid represented by, carboxylated poly Oxyethylene alkyl ether carboxylate and the like are preferably used.

The amount of the surface-active agent used for improving the liquid retention property to be attached to the nonwoven fabric is 0.1 to 0.1% with respect to the untreated nonwoven fabric.
It is preferably 2.0% by weight. If the adhered amount is less than 0.1% by weight, there is no remarkable effect on the liquid absorption rate, and conversely, if the adhered amount exceeds 2.0% by weight, the amount of the drop into the electrolytic solution increases.

As a method for attaching the surfactant for improving liquid retention to the nonwoven fabric, this surfactant is made into an aqueous solution,
A method of immersing a non-woven fabric in combination with a fluorosurfactant or alone and then drying is generally used.

[0033]

【Example】

The present invention will be described in more detail with reference to the following examples. The test methods used in the examples are as follows.

[Alkali weight loss rate] 35% potassium hydroxide
Weight reduction rate (%) after boiling the separator in an aqueous solution for 1 hour under normal pressure. The sample was weighed after standing for 24 hours at a temperature of 20 ± 2 ° C. and a relative humidity of 65 ± 2%.

[Oxidation weight loss rate] 250 ml of 5% potassium permanganate aqueous solution and 30 m of 35% potassium hydroxide aqueous solution
After immersing the sample in a mixed solution of 1 and boiling for 1 hour,
The alkali content was thoroughly washed with water and dried to determine the weight loss rate (%) of the sample. The weight of the sample is the same as above.

[Water retention rate of fiber] The fiber was immersed in deionized water for 24 hours, then centrifuged and dehydrated at a load of 1000 G for 10 minutes, and the weight (W ₁ ) of the fiber was measured. Dry weight of this fiber (W ₂ )
Was measured and calculated by the following formula. Water retention rate _{= [(W 1 -W 2)} / W 2] × 100 (%)

[Tensile Strength] 5 × 2 from the longitudinal and lateral directions of the sample
Five 0 cm test pieces were collected and JISL109
According to 6 (Tensile test method for fabrics), gripping interval 10c
m and a tensile speed of 300 mm / min, one by one, and the tensile load when the test piece was cut is read and expressed as an average value.

[Durability and hydrophilicity] An untreated sample left standing for 24 hours at a temperature of 20 ± 2 ° C. and a relative humidity of 65 ± 2% was held in a state of being horizontally floated from the floor. 250 ml of 5% potassium permanganate aqueous solution containing 35% concentration of surfactant and 35 m of 35% potassium hydroxide aqueous solution
was mixed with 1 and left at 80 ° C. for a certain period of time.
The time until the liquid drop disappeared after 2 cc was dropped was expressed in seconds.

[Electrolytic solution absorption rate] 2.5 × 25 from the sample
cm test piece, temperature 20 ± 2 ℃, relative humidity 65 ±
The test piece is allowed to stand for 24 hours in a 2% state, and then the test piece is heated to a temperature of 20%.
Pin with a pin on a horizontal rod supported at a certain height on a water tank containing ± 2 ° C 35% aqueous potassium hydroxide solution, align the lower end of the test piece in a line and lower the horizontal rod, and the lower end of the test piece is 5m.
It was stood vertically so as to be immersed in the liquid by m, and the height at which the potassium hydroxide aqueous solution was raised by the capillary phenomenon was measured after 30 minutes.

[Separator absorption rate] What is the drop disappearance rate? A sample left standing for 24 hours at 20 ± 2 ° C and 65 ± 2% RH was kept horizontally floating from the floor. The time required for the droplets to disappear after 0.2 cc of 35% potassium hydroxide aqueous solution was dropped is expressed in seconds.

[Liquid retention rate of separator] 35% [Specific gravity 1.
30 (20 ° C.)] This is the ratio of the weight of the liquid retained after the sample was immersed in an aqueous solution of potassium hydroxide for 1 hour, taken out, and allowed to naturally drop droplets for 10 minutes to the weight of the sample.

(Sulfonation of polysulfone) Polysulfone 6 was used by using Udel P-1800 (manufactured by Teijin Amoco Engineering Plastics Co., Ltd.) as polysulfone.
To a mixture of 0 part by weight and 240 parts by weight of dimethylformamide, 15.4 parts by weight of chlorosulfonic acid was added in portions at 50 to 60 ° C. to react, and the temperature was raised stepwise to finally reach 80 to 60 ° C.
The polysulfone was sulfonated at 90 ° C. for 3 to 4 hours to obtain SPSF having a sulfonic acid group content of 15% by weight.
The amount of sulfonic acid group used in this example was 3% by weight, 6%
SPSFs of 9% by weight, 9% by weight and 20% by weight were obtained under the same conditions as above, only by increasing or decreasing the amount of chlorosulfonic acid. In the examples, polysulfone is the above-mentioned Udel P-18.
00 was used as is.

(Spinning) Polysulfone and SPSF in dimethylacetamide solutions (15 to 30% by weight) were prepared, and PVC and polymethylmethacrylate having a polymerization degree of 1100 were added to these dimethylacetamide solutions to prepare SPSF (or polysulfone) / The weight ratio of PVC / polymethylmethacrylate is 20/30/50,
Dimethylacetamide was added so that the solid content concentration became 35% by weight, and mixed and dissolved to prepare spinning stock solutions. The viscosity of these spinning solutions at 50 ° C. is about 17
It was 0 poise.

A stock solution for spinning was prepared with a pore size of 30 μm and a pore number of 5000.
Using the spinneret of 60 parts by weight of dimethylacetamide,
An undrawn yarn was obtained by spinning in a coagulation bath of 40 parts by weight of deionized water and a temperature of 40 ° C. The undrawn yarn was drawn 3 times in boiling water, washed in boiling water and simultaneously relaxed by 11% to obtain fibers a to e having different sulfone group contents. Table 2 shows the fineness, strength and elongation, boiling water shrinkage rate, alkali and oxidization weight loss rate, and liquid retention rate of the obtained fiber. While the water retention rate of fiber A is 31%, as the amount of sulfonic acid groups increases (b → c
→ d → e) The water retention rate was improved to 42-60%.

[0046]

[Table 2]

(Production of Nonwoven Fabric) 70% by Weight of Each Fiber Cut to a Length of 6 mm, Fineness of 2 Denier, Fiber Length of 5 mm
Polyolefin-based heat-sealing fiber (manufactured by Chisso Corporation, E
(PC type) 30 wt% is mixed, and a basis weight of 65 g / m ² and a thickness of 0.18 m are obtained by a wet papermaking method using a short-net paper machine.
The nonwoven fabrics A to E shown in Table 3 were obtained by making paper in m.

[0048]

[Table 3]

(Examples 1 to 4 and Comparative Example 1) Nonwoven fabric A
To E were immersed in a 0.3% aqueous solution of perfluoroalkyl carboxylate (Megafuck F-120 manufactured by Dainippon Ink and Chemicals, Inc.), squeezed to a liquid content of 150% with a pressing roll, and then 130 with a cylinder dryer. A sheet was formed by drying at ° C. The amount of perfluoroalkylcarboxylic acid salt deposited in the obtained sheet was 0.5% by weight based on the sheet. The alkali weight loss rate, the oxidation weight loss rate, and the centrifugal dehydration water retention rate were evaluated and are shown in Table 4.

Comparative Examples 2 and 3 Nonwoven fabrics A and D were treated in the same manner as in the above Examples except that a commercially available nonionic hydrocarbon surfactant was used instead of the perfluoroalkylcarboxylic acid salt. A sheet having 0.5% by weight of the nonionic hydrocarbon-based surfactant adhered was obtained. The alkali weight loss rate, the oxidative weight loss rate, and the centrifugal dehydration water retention rate were evaluated, and the results are shown in Table 4.

(Comparative Example 4) A commercial nylon fiber nonwoven fabric separator was evaluated for alkali weight loss rate, oxidative weight loss rate, and centrifugal dehydration water retention rate, and the results are shown in Table 4. The nylon fiber non-woven fabric separator was decomposed by the oxidative reduction treatment, and its original shape was not retained.

[0052]

[Table 4]

(Manufacture and Evaluation of Battery) Using the nonwoven fabrics obtained in Example 3 and Comparative Examples 1 and 4 as separators, three SC type sealed alkaline storage batteries each having an electric capacity of 1200 mAh were prepared, and the temperature was 60 ± 2 ° C. A charge / discharge cycle test was performed in the atmosphere. In the test, the battery was charged at a current of 10 hours for 15 hours, then discharged at a current of 1 hour until the final voltage became 1.0 V, and this operation was repeated. The charge / discharge cycle characteristics of these storage batteries are shown in FIG. The storage battery using a nylon nonwoven fabric separator, which is inferior in high temperature oxidation resistance, maintained a high discharge capacity for a long time, even compared to the storage battery using a nonwoven fabric A separator.

(Examples 5 to 7 and Comparative Example 5) Nonwoven fabric D
Was immersed in an aqueous solution having a different concentration of perfluoroalkylcarboxylate, and pressed and dried in the same manner as in Examples 1 to 4 and Comparative Example 1, and a separator having different amounts of perfluoroalkylcarboxylate attached was used. Created various. Note that the adhered amounts are 0.08, 0.10, 0.70, and 2.0, respectively.
% By weight.

The liquid absorption rate and liquid retention rate of these separators,
Also, the electrolytic solution absorption rate was evaluated and is shown in Table 5. The amount of perfluoroalkylcarboxylate deposited was preferably in the range of 0.1 to 2.0% by weight.

(Example 8) A perfluoroalkyl carboxylic acid salt was replaced with a perfluoroalkyl sulfonic acid salt (Megafac F-110 manufactured by Dainippon Ink and Chemicals, Inc.) in the same manner as in Examples 5-7. Various types of separators having different amounts of the fluoroalkyl sulfonate attached were prepared. Note that the adhered amounts are 0.10, 0.70,
It was 2.0% by weight. When the liquid absorption rate, liquid retention rate, and electrolytic solution absorption rate of these separators were evaluated, it was confirmed that the same effects as in Examples 5 to 7 were obtained.

Example 9 Perfluoro was carried out in the same manner as in Examples 5 to 7, except that the perfluoroalkylcarboxylic acid salt was changed to potassium perfluoroalkylsulfonic acid (Florard FC-98 manufactured by Sumitomo 3M). Various separators having different amounts of attached alkyl sulfonate were prepared. Note that the adhered amounts are 0.10, 0.70,
It was 2.0% by weight. When the liquid absorption rate, liquid retention rate, and electrolytic solution absorption rate of these separators were evaluated, it was confirmed that the same effects as in Examples 5 to 7 were obtained.

[0058]

[Table 5]

(Examples 10 to 12) Nonwoven fabric D was dipped in a mixed aqueous solution having different concentrations of potassium perfluoroalkylcarboxylate and carboxylated polyoxyethylene lauryl ether sodium (AKYPO-RLM45NV manufactured by Nikko Chemicals Co., Ltd.). Then, pressing and drying were carried out in the same manner as in the above-mentioned Examples to prepare various separators having different amounts of adhesion. The liquid absorption rate, the liquid retention rate, and the electrolytic solution absorption rate of these separators were evaluated, and the results are shown in Table 5. Even better results were obtained when the amounts of perfluoroalkylcarboxylate and carboxylated polyoxyethylene lauryl ether sodium were 0.1 to 2.0% by weight and 0.1 to 2.0% by weight, respectively. Was obtained.

[0060]

[Table 6]

From the above Examples and Comparative Examples, in comparison with the excellent performance of the present invention, in the separator for a battery using a commercially available hydrocarbon surfactant, the durability and hydrophilicity are drastically lowered, It is also apparent that the hydrophilicity of the electrolytic solution after the charge / discharge cycle becomes poor. In addition, in order to obtain a separator having good liquid absorption rate, liquid retention rate, electrolyte solution absorption rate, and durable hydrophilicity, not only a fluorine-based surfactant excellent in durable hydrophilicity but also alkali resistance and electrolytic solution are used. It has also been found that it is preferable to use a surfactant which is excellent in the ability to improve the liquid retaining property.

[0062]

The battery separator of the present invention constructed as described above is a high quality battery separator excellent in all of alkali resistance, oxidation resistance, initial hydrophilicity and durable hydrophilicity. The target value is extremely high.

[Brief description of drawings]

FIG. 1 is a graph in which the discharge capacities of alkaline storage batteries using different separators are plotted against the number of charge / discharge cycles.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location D04H 1/42 Q J X D21H 13/20

Claims (1)

[Claims] 1. Polyvinyl chloride 20 to 8 having 15 to 40% by weight of sulfonated polysulfone and a polymerization degree of 900 to 1800.
A non-woven fabric composed of fibers containing 5% by weight and 0 to 65% by weight of a methacrylic acid ester-based polymer has a surface tension of 40 dyne / cm · 25 ° C. in a 0.1% aqueous solution.
0.1 to 2.0% by weight of the following fluorine-based surfactant
The attached battery separator.