JP3383823B2 - Battery separator, method of manufacturing the same, and battery using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a battery separator suitable for an alkaline storage battery such as a nickel-cadmium battery, a nickel-zinc battery and a nickel-hydrogen battery, a method for producing the same, and a battery using the same. .

[0002]

2. Description of the Related Art Generally, as a battery separator, a non-woven fabric made of nylon or polypropylene fiber by a dry process (hereinafter referred to as a dry non-woven fabric), a non-woven fabric manufactured by a wet paper making process (hereinafter referred to as a wet non-woven fabric), etc. Although used, non-woven fabrics made of nylon fibers are inferior in alkali resistance, and therefore non-woven fabrics made of polyolefin fibers such as polypropylene are preferably used.

However, since a nonwoven fabric made of polyolefin fibers is hydrophobic and is inferior in wettability when used as a battery separator, various methods of hydrophilizing a nonwoven fabric made of polyolefin fibers have been proposed.
Examples of the hydrophilic treatment method include sulfonation treatment, fluorination treatment, corona discharge treatment, and vinyl monomer graft polymerization treatment. Particularly, in improving the self-discharge property of the secondary battery, the sulfonation treatment is useful. Yes, various methods have been proposed. For example, JP-A-7-278
Japanese Patent No. 963 proposes a battery separator in which a syndiotactic styrene-based polymerization component having a glass transition temperature lowered by 5 ° C. or more is used as an easily sulfonated fiber and is immersed in a concentrated sulfuric acid solution to be sulfonated. In addition, JP-A-8-
Japanese Patent No. 273654 discloses a battery separator excellent in strength, which is obtained by entanglement of polyolefin-based ultrafine fibers, partially having a fused portion, and hydrophilically treated to give a nonwoven fabric.

[0004]

However, the above battery separator has the following problems. For example, in Japanese Patent Application Laid-Open No. 7-278963, syndiotactic polystyrene fibers generally have poor spinnability, and it is difficult to make them finer. Even if they can be made finer, their productivity is improved. Inferior and costly. Also,
In Japanese Unexamined Patent Publication No. 8-273654, not only the ultrafine fibers themselves are sulfonated but also one kind of ultrafine fibers are fused, so that the denseness originally obtained is impaired and the breathability and liquid retention are poor. .

In order to solve the above-mentioned conventional problems, the present invention provides a battery separator having excellent strength and liquid retention and capable of contributing to improvement of battery capacity without shortening battery life. It was done for the purpose.

[0006]

In order to achieve the above object, the first battery separator of the present invention has a syndiotactic poly (1,2-butadiene) structure as its molecular structure and its unsaturated bond. Is a porous sheet containing a resin component having an ion exchange group introduced into at least a part thereof. In the separator, the resin component is preferably synthetic fiber (A). Further, in the separator, the porous sheet is preferably a non-woven fabric containing the synthetic fiber (A) and the heat-adhesive fiber (B).

Further, in the above separator, the main functional group of the ion exchange group is preferably a sulfone group. In the separator, the synthetic fiber (A) is a sheath-core type composite fiber, and the sheath component is syndiotactic porous fiber.
Poly (1,2-butadiene) resin, and its unsaturated bond
An ion exchange group is introduced into at least a part of
The exchange group is preferably a sulfone group.

In the separator, the content of the syndiotactic poly (1,2-butadiene ) resin component constituting the synthetic fiber (A) is preferably 5% by weight or more. Further, in the separator, it is preferable that the heat-adhesive fiber (B) is a sheath-core type composite fiber and the sheath has a melting point which is lower than the melting point of the core by 10 ° C. or more. Further, in the separator, the fibers constituting the non-woven fabric are composed of synthetic fibers (A) and thermal adhesive fibers (B), the content of the synthetic fibers (A) is 10 to 90% by weight, and the thermal adhesive property is The content of the fiber (B) is preferably in the range of 90 to 10% by weight.

In the separator, the fibers constituting the non-woven fabric are synthetic fibers (A) and heat-adhesive fibers (B).
And a fine fiber (C) having a fineness of 0.5 denier or less, and the fine fiber (C) is preferably a partially divided composite fiber. Further, in the separator, the ratio of the fibers constituting the nonwoven fabric is such that the content of the synthetic fiber (A) is 10 to 50% by weight and the content of the heat-adhesive fiber (B) is 10.
~ 50% by weight, 0 of partially divided ultrafine fibers (C)
It is preferably about 80% by weight.

Further, in the separator, it is preferable that the ultrafine fibers (C) contain a hydrophilic group containing —OH group as a main component. Further, in the separator, it is preferable that a sulfone group is introduced into at least a part of the unsaturated bonds of the syndiotactic poly (1,2-butadiene) structure at a temperature of 60 ° C. or lower.

The second battery separator of the present invention is a nonwoven fabric containing the heat-adhesive fibers (B), and has a syndiotactic poly (1,2-butadiene) structure as its molecular structure. It is characterized in that a porous sheet containing a resin component in which an ion exchange group is introduced into at least a part of a saturated bond is attached. In the first to second battery separators of the present invention, the porous sheet is preferably the nonwoven fabric. The first to the first aspects of the present invention
In the second battery separator, a porous film can be used as the porous sheet. in this case,
The resin component having the ion exchange group of the present invention introduced therein may occupy at least a part of the surface of the porous film. The film may be a single component of the above resin, or may be a porous multi-layer film laminated with a film of another polymer, for example, a synthetic resin film such as a polypropylene or polyethylene film.

Next, in the method for producing a battery separator of the present invention, the molecular structure is a syndiotactic poly (1,2-butadiene) structure, and an ion exchange group- introducable group is introduced into at least a part of the unsaturated bond. Of the fiber web containing the synthetic fiber (A) occupying at least a part of the fiber surface with the resin component containing entangled to form a non-woven fabric, and then the syndiotactic poly at a temperature of 60 ° C. or lower. It is characterized in that a sulfone group is introduced into at least a part of the unsaturated bond of the (1,2-butadiene) structure. In the method, the entanglement treatment between the constituent fibers of the fiber web,
High-pressure water injection treatment is preferred. Next, the battery of the present invention is characterized by incorporating any one of the battery separators described above.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The battery separator of the present invention comprises a resin component (hereinafter, referred to as 1,2-SBD) having a syndiotactic poly (1,2-butadiene) structure as a molecular structure, and its unsaturated bond Of a porous sheet containing a resin component having an ion exchange group introduced into at least a part thereof.

The 1,2-SBD used in the present invention has a melting point (Tms) of 75 to 150 ° C. and a crystallinity of 15 to 50.
%, 1,2 bond is 90% or more, melt index (M
According to JIS K 7210, a temperature of 190 ° C. and a weight of 2160 g) of 10 to 150 g / 10 minutes is preferably used.

The porous sheet containing 1,2-SBD is 1,2-SBD
Is a nonwoven fabric made of synthetic fiber (A) occupying at least a part of the fiber surface, a porous film, or a laminate containing one or more layers of these.

Examples of the ion exchange group introduced into at least a part of the unsaturated bond of 1,2-SBD include a sulfone group, a carboxyl group, an amino group and the like. Among them, the sulfone group causes self-discharge. This is preferable because an effect of suppressing the same can be obtained.

The form of the synthetic fiber (A) used in the battery separator of the present invention is not particularly limited as long as 1,2-SBD occupies at least a part of the fiber surface. For example, single fiber, sheath-core type composite fiber, eccentric sheath-core type composite fiber,
A parallel type conjugate fiber, a division type conjugate fiber, a fiber having an irregular cross section, or the like can be arbitrarily used. Among them, the sheath-core type composite fiber having 1,2-SBD as the sheath component can effectively utilize the effect because the sheath component 1,2-SBD covers the fiber surface. It is preferable because it can retain its strength. The thermoplastic resin used as the core component is not particularly limited, but its melting point (Tmc) is 1,2-SB.
A resin which is higher than the melting point (Tms) of D by 10 ° C. or more is preferable.
For example, one or more selected from polyamide-based resins such as nylon 6 and nylon 66, homopolymers or copolymers such as polyolefin-based resins such as polyethylene, polypropylene and polymethylpentene, and ternary copolymers may be used. can do. Of these, polyolefin resins are preferable in terms of workability.

The content of 1,2-SBD constituting the synthetic fiber (A) is preferably 5% by weight or more. If the content of 1,2-SBD is less than 5% by weight, the number of ion-exchange groups in the fiber will be small and the capacity preservation rate when incorporated in a battery will be poor.

The content of the synthetic fiber (A) in the nonwoven fabric is preferably 10 to 90% by weight from the viewpoint of improving the strength of the nonwoven fabric. More preferably, 10 to
It is 50% by weight. If the content is less than 5% by weight, the number of ion-exchange groups in the non-woven fabric is small and the effect cannot be obtained. If the content exceeds 80% by weight, the 1,2-SBD resin itself becomes ionic. This is because the strength of the non-woven fabric is lowered because it deteriorates after introducing the exchange group.

In the present invention, the thermoadhesive fiber (B) which melts at a temperature lower than Tmc in the nonwoven fabric is 10 to 90% by weight.
It is preferably contained. More preferably, 10 to
It is 50% by weight. This is because if the melting temperature of the heat-adhesive fiber (B) is Tmc or higher, the shape of the synthetic fiber (A) cannot be retained when heat-treated with the synthetic fiber (A). Further, if the content of the heat-adhesive fiber (B) is less than 10% by weight, sufficient nonwoven fabric strength cannot be obtained, and if it exceeds 90% by weight, the synthetic fiber (A) becomes small and its effect is sufficient. This is because it is not demonstrated. The heat-adhesive fiber (B) is not particularly limited as long as it has a melting point lower than Tmc, and examples thereof include polyester resins such as copolyester, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer. Polyolefin resins such as ethylene-methyl acrylate copolymer are used, but polyolefin resins are preferable from the viewpoint of alkali resistance.

The form of the heat-adhesive fiber (B) used in the present invention is not particularly limited, and a single fiber, a sheath-core type composite fiber, an eccentric sheath-core type composite fiber, a parallel type composite fiber, a split type composite fiber, Alternatively, fibers having a modified cross section can be optionally used, but in the case of improving the strength of the non-woven fabric, the melting point of the sheath as the heat-adhesive fibers (B) is 10 ° C. higher than the melting point of the core.
The sheath-core type composite fiber composed of the low resin is preferable. The above resin is preferable as the sheath component, and the core component,
For example, polyamide resins such as nylon 6 and nylon 66 and polyolefin resins such as polyethylene, polypropylene and polymethylpentene are used. Further, the fineness of the heat-adhesive fiber (B) is preferably 0.5 to 5 denier. When it is less than 0.5 denier, the dispersibility of the fibers in the slurry during wet papermaking is poor, and the fibers are entangled with each other, resulting in poor processability and quality. When it exceeds 5 denier, the size of voids becomes large. Excessively, it causes a short circuit when assembling the battery, which is not preferable.

The nonwoven fabric of the present invention may contain 0 to 80% by weight of ultrafine fibers (C) having a fineness of 0.5 denier or less. This is because when the fineness of the ultrafine fibers (C) exceeds 0.5 denier, the voids become too large and the liquid absorbency and liquid retention are poor. When the content rate in the nonwoven fabric exceeds 80% by weight,
The air permeability is lowered, and the gas permeability required for a sealed battery is poor, which is not preferable. The ultrafine fibers (C) having a fineness of 0.5 denier or less may have any shape, but preferably two or more types of ultrafine fibers obtained by dividing a splittable conjugate fiber composed of two or more resin components into each component. (C).
The splittable conjugate fiber composed of two or more kinds of resin components is as shown in, for example, (a), (b) and (c) of FIG. In FIGS. 1A to 1C, 1 is the first component and 2 is
Indicates the second component.

The combination of thermoplastic resins used in the splittable conjugate fiber is polyolefin resin /
Polyamide-based resin, polypropylene / ethylene vinyl alcohol copolymer, polypropylene / polymethylpentene, polypropylene / polyethylene, polymethylpentene / polyethylene, polymethylpentene / ethylene vinyl alcohol copolymer, etc. are used, and three types of resins are used. In some cases, the resins may be composed of different components. In particular, the polyolefin-based splittable conjugate fiber is preferable in terms of alkali resistance, and among them, the polyolefin-based splittable conjugate fiber having one component of an ethylene vinyl alcohol copolymer containing a hydrophilic group having a —OH group as a main component is This is preferable because the hydrophilicity is improved and excellent cycle characteristics are obtained in the battery. The splittable conjugate fiber thus obtained is split by a high-pressure water jetting treatment or the like, which will be described later, to form an ultrafine fiber (C).

Furthermore, the battery separator of the present invention may be mixed with other fibers as long as the above content is satisfied,
For example, in order to secure voids formed between the fibers, the synthetic fiber (D) having a fineness of 5 denier or less may be contained at 40% by weight or less. In particular, the fineness is preferably larger than the fineness of the ultrafine fibers (C) obtained by the split expression of the splittable conjugate fibers, and is the same as or smaller than the fineness of the heat-adhesive fibers (B), 0.5 to 5 denier. Is preferred. The above-mentioned fibers are selected from those that do not substantially melt at the temperature at which the heat-adhesive fibers (B) melt, and commonly-used synthetic fibers such as polypropylene, polyester, nylon, etc. can be used. From the viewpoint, polyolefin fibers are preferable. When the amount of the above fibers exceeds 40% by weight, the adhesive area becomes too small and the strength of the nonwoven fabric becomes weak, which is not preferable. When the above fiber exceeds 5 denier,
It is not preferable because a dense void in the nonwoven fabric cannot be secured. In particular, a polypropylene fiber having a fineness of 0.5 to 2 denier, which is slightly rigid and has high strength, is most preferably applied in order to impart alkali resistance to the separator and to secure appropriate voids.

Next, a method for manufacturing the battery separator of the present invention will be described. The form of the fibrous web containing each of the above-mentioned fibers was obtained by a dry method obtained by a card method, an air lay method or the like, a wet web obtained by a wet method, or a direct method such as a melt blow method or a spun bond method. Fiber webs alone or at least one of these
A laminate including two or more layers is used. For example,
A fibrous web composed of 1,2-SBD may be used as the first layer, and a fibrous web containing no fibers composed of 1,2-SBD may be used as the second layer, which may be laminated, or at least one layer may be 1,2-SBD. A dry web / wet web combination may be used as long as it contains fibers consisting of Among them, the wet web is preferable in terms of the denseness and uniformity of the fibrous web.

Next, the synthetic fiber (A) itself may be melted in the fibrous web, or the heat-adhesive fiber (B) may be melted, which may be appropriately performed depending on the treatment method of the fibrous web. The method for treating the fibrous web may be any of thermal calendaring, hot air processing, high-pressure water jetting, and the like. For example, when the splittable conjugate fiber is contained, the fiber web is subjected to high-pressure water jetting and split. It is advisable to divide the type composite fibers to form the ultrafine fibers (C) and to entangle the fibers. The high-pressure water jet process has a pore size of 0.05 to 0.
It is advisable to inject a columnar water stream having a water pressure of 25 to 150 kg / cm ² onto the front and back surfaces of the nonwoven fabric one or more times from nozzles provided with 5 mm orifices at intervals of 0.5 to 1.5 mm. Also in the case of laminating the fibrous webs, for example, different fibrous webs may be bonded together during wet papermaking, during high-pressure water jetting, or during heat calendering or hot-air processing, or the fibrous webs may be treated using the above-mentioned treatment method. It is also possible to temporarily make a non-woven fabric, laminate two or more layers of the obtained non-woven fabric, and carry out the pasting by a publicly known pasting method, for example, thermal adhesion using a heat roll, binder adhesion or the like. Also 1,2-
It may be laminated with a porous film containing or not containing SBD.

On the other hand, the porous film of the present invention comprises 1,2-SB
Easily obtained by melt extruding D, 1,2-SB
Other thermoplastic resins may be mixed as long as the content of D is at least 5% by weight. In addition, 1,2-SBD may be a single porous film, or may be laminated with two or more layers of one or more other film. Furthermore, 1,2-SBD
It may be bonded to a non-woven fabric containing or not containing.

Then, ion-exchange groups are introduced into the porous sheet containing 1,2-SBD. The ion exchange group is easily introduced by a known introduction method. For example, a method of introducing a vinyl monomer by ultraviolet irradiation, or a method of immersing a sulfonic group in dilute fuming sulfuric acid cooled to 10 ° C. or 80 to 98% by weight concentrated sulfuric acid for introduction may be mentioned.
In particular, 1,2-SBD can introduce an ion-exchange group under relatively weak conditions as compared with the conventional introduction method.
In 8 wt% concentrated sulfuric acid, sulfone groups can be introduced in a short time at a temperature of 60 ° C. or less, and highly sulfonation can be achieved without lowering the strength of the porous sheet. When a sulfone group is introduced into the porous sheet, the sulfonation rate is preferably at least 3 mol%. This is because if the sulfonation rate is less than 3 mol%, the self-discharge of the battery cannot be sufficiently suppressed. In order to promote sulfonation, the nonwoven fabric surface may be activated by ultraviolet rays or radiation and then subjected to sulfonation treatment. When concentrated sulfuric acid is used, it is dried in the post-treatment.

After that, a heat calendering treatment is performed to adjust the thickness to a predetermined value to obtain the battery separator of the present invention. In the battery separator thus obtained, the basis weight of the porous sheet is preferably 30 to 100 g / m ² . If it is less than 30 g / m ² , the strength of the sheet becomes low, so that a short circuit easily occurs between the positive electrode and the negative electrode.
This is because if it exceeds 0 g / m ² , the air permeability and the like will decrease.

The tensile strength of the obtained battery separator in at least one direction is preferably 5 kgf / 5 cm or more. More preferably, it is 10 kgf / 5 cm.
This is because when the tensile strength is less than 5 kgf / 5 cm, the rolling property when the battery is assembled is poor.

[0031]

EXAMPLES The contents of the present invention will be described below with reference to examples. In addition, what is simply displayed as% means% by weight. The sulfonation rate, tensile strength, liquid retention rate, and capacity retention rate were measured by the following methods. (1) Sulfonation rate: Expressed by the sulfonation rate of ethylene groups and calculated by the following formula. Sulfonation rate (mol%) =
{Weight increase rate (%) / 97} / {100/56} (2) Tensile strength: Width 5c according to JIS L 1096
Grasp a sample piece measuring 15 cm in length and 10 cm in length,
It was stretched at a tension rate of 30 cm / min using a constant-speed extension type tensile tester, and the load value at the time of cutting was taken as the tensile strength. (3) Liquid retention rate: Weight of test piece in water equilibrium state (W) is 1
Measure up to mg. Next, the test piece was immersed in a KOH aqueous solution having a specific gravity of 1.30, the KOH aqueous solution was absorbed for 1 hour, and then taken out from the solution. Then, the test piece was sandwiched between upper and lower two filter papers and weighted with 5 kg. Weight of the test piece (W
₁ ) is measured and the liquid retention rate (%) = ((W ₁ −W) / W) ×
The liquid retention rate was calculated from the formula of 100. (4) Cylindrical closed nickel-hydrogen battery: Positive electrode is nickel hydroxide, cobalt oxide, carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTF)
E), using an electrode prepared by coating a foamed nickel substrate with a paste of water, the negative electrode is a hydrogen storage alloy,
Cylindrical shape is obtained by using electrodes made by coating paste of carbonyl nickel, CMC, PTFE, and water on a foamed nickel substrate, sandwiching each separator between them and inserting into a battery case, and injecting electrolyte solution. A sealed nickel-hydrogen battery was produced. (5) Self-discharge test: Initial activation condition is 2 at a charging rate of 0.05C
0 hours, pause 0.5 hours, discharge 0.05C rate to final voltage 0.8V, then charge 0.1C rate for 12 hours, pause 0.5 hours, discharge 0.1C rate to final voltage 1.0V, after repeating 5 cycles After charging under the same conditions (0.1C rate) to the discharge capacity, 45 ℃
The ratio of the remaining capacity (0.1 C rate discharge, final voltage 1.0 V) when left standing for 14 days was defined as the capacity retention rate after self-discharge. Charging / discharging was performed at 25 degreeC. (6) Cycle life measurement: After initial activation, charging is 0.
The number of cycles was calculated when the utilization ratio to the theoretical capacity was 90% or less at a 1C rate for 10 hours, a rest time of 0.5 hours, and a discharge 0.1C rate (final voltage 1.0V). Charging / discharging was performed at 25 degreeC. (7) Defect rate: 100 for a cylindrical sealed nickel-hydrogen battery
The rate at which a short circuit occurred when assembled individually was defined as the failure rate. (8) Melt index (MI): According to JIS K 7210, the flow rate per 10 minutes is measured at a measurement temperature of 190 ° C. and a load of 2160 g.

[0032]

Examples 1 to 4 and Comparative Examples 1 and 2 [Preparation of fibers] The following fibers were prepared for carrying out the present invention. (1) Synthetic fiber (A): melting point 90 ° C., MI 45 g / 10 minutes
A sheath-core type composite fiber having a fineness of 2 denier and a fiber length of 10 mm, which comprises 1,2-SBD as a sheath component and polypropylene having a melting point of 163 ° C. as a core component. (2) Thermoadhesive fiber (B): A sheath-core type thermoadhesive conjugate fiber having a fineness of 2 denier and a fiber length of 10 mm, which has polyethylene having a melting point of 130 ° C. as a sheath component and polypropylene having a melting point of 163 ° C. as a core component. (3) Splittable conjugate fiber (C): polypropylene having a melting point of 163 ° C. as a first component and polymethylpentene having a melting point of 240 ° C. as a second component having a fineness of 2 denier having a cross-sectional shape shown in FIG. 1 (a). Split type composite fiber with a fiber length of 10 mm. (4) Synthetic fiber (D): polypropylene fiber having a melting point of 163 ° C., a fineness of 1 denier, and a fiber length of 10 mm. [Formation of Nonwoven Fabric] (Examples 1 to 3 and Comparative Examples 1 and 2) The above fibers were mixed in the proportions shown in Table 1 to obtain 0.5 in water.
A water slurry was prepared so as to have a concentration of 100% and wet-processed to prepare a wet non-woven fabric having a basis weight of 50 g / m ² . Next, by jetting a high-pressure columnar water stream having a water pressure of 100 kg / cm ² onto the front and back surfaces of the wet-laid nonwoven fabric, the splittable conjugate fiber (C) is split to form ultrafine fibers having a fineness of 0.25 to 0.3 denier. At the same time, the fibers were entangled and dried at 135 ° C. and heat-bonded at the same time. [Formation of Nonwoven Fabric] (Example 4) The above fibers (B), (C) and (D) were mixed in the proportions shown in Table 1 to prepare a slurry having a concentration of 0.5%.
Wet papermaking was carried out to prepare a wet non-woven fabric having a basis weight of 30 g / m ² . Next, by jetting a high-pressure columnar water stream having a water pressure of 100 kg / cm ² to the front and back surfaces of the wet-laid nonwoven fabric, the splittable conjugate fiber is split to form ultrafine fibers having a fineness of 0.25 to 0.3 denier and the fibers. The non-woven fabric (1) was produced by intertwining the spaces and drying and thermally adhering at 135 ° C. Separately, a slurry was prepared so that the fiber (A) had a concentration of 0.5% and was wet paper-made to prepare a wet non-woven fabric (2) having a basis weight of 20 g / m ² . The non-woven fabric (1) prepared above and the non-woven fabric (2)
Bonding was performed with a pair of hot rolls heated to 00 ° C. [Sulfonation treatment] The obtained non-woven fabric is kept at room temperature (about 20
), And treated with a concentrated sulfuric acid solution having a concentration of 93% by weight for the time shown in Table 1 to sulfonate. Then, the non-woven fabric was heat-calendered at 75 ° C. to obtain a battery separator. Example 1
~ 4, the conditions of Comparative Examples 1 and 2 and the physical properties of the battery separator are shown in Table 1.

[0033]

[Table 1]

As shown in Table 1, Examples 1 to 4 contain the synthetic fiber (A), so that they are highly sulfonated even under relatively weak sulfonation conditions, and the capacity preservation when incorporated in a battery is maintained. The rate was high and the tensile strength did not decrease. In Comparative Example 1, since the synthetic fiber (A) was not contained, the sulfonation treatment time was insufficient and the sulfonation could not be performed.
In Comparative Example 2, the sulfonation treatment time was lengthened to improve the sulfonation rate, but the tensile strength was significantly reduced.

[0035]

The battery separator of the present invention can be highly sulfonated even under relatively weak sulfonation conditions, and an excellent capacity storage rate can be obtained. Further, since deterioration of other fiber properties can be reduced, excellent tensile strength can be obtained. In addition, the tensile strength of the non-woven fabric is improved by using a heat-adhesive fiber as another fiber, and the liquid retention rate is improved by using an ultrafine fiber having a fineness of 0.5 denier or less.

The method for producing the battery separator of the present invention is as follows:
Synthetic fiber whose molecular structure is syndiotactic poly (1,2-butadiene) structure and whose resin component in which an ion exchange group is introduced into at least a part of its unsaturated bond occupies at least a part of the fiber surface Since the fiber web containing (A) is subjected to high-pressure water flow treatment to entangle the fibers, and then the non-woven fabric can be subjected to sulfonation under relatively weak conditions, a separator having high strength and low basis weight can be easily obtained. Not only that, but also in the safety of the manufacturing process. Since the battery of the present invention uses the above separator, a battery with less self-discharge can be obtained.

[Brief description of drawings]

FIG. 1 (a) is an enlarged sectional view of an example of a splittable conjugate fiber applicable to the present invention. (B) It is an enlarged cross-sectional view of an example of the splittable conjugate fiber applicable to the present invention. (C) It is an enlarged cross-sectional view of an example of the splittable conjugate fiber applicable to the present invention.

[Explanation of symbols]

1st component 2 Second component

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsunobu Kida 877 Komiya, Harima-cho, Kako-gun, Hyogo Dai Daiwabo Polytech Co., Ltd. Harima Research Institute (72) Hiroyuki Yamamoto Dai-877, Komiya, Kama-gun, Kako-gun Dai Wabowo Polytech Co., Ltd. Harima Research Institute (72) Inventor Shuji Hori 877 Komiya, Harima-cho, Kako-gun Hyogo Dai Daiwabo Polytech Co., Ltd. Harima Research Institute (72) Inventor Tetsuo Sakai 1-831 Midorigaoka, Ikeda-shi, Osaka Issue: Osaka Institute of Industrial Technology, Institute of Industrial Technology (56) Reference JP-A-4-187248 (JP, A) JP-A-4-198330 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) H01M 2/16 H01M 10/24

Claims (18)

(57) [Claims] 1. A battery comprising a porous sheet containing a resin component having a molecular structure of syndiotactic poly (1,2-butadiene) structure and an ion exchange group introduced into at least a part of its unsaturated bond. Separator. 2. The battery separator according to claim 1, wherein the resin component is synthetic fiber (A). 3. The battery separator according to claim 1, wherein the porous sheet is a non-woven fabric containing synthetic fibers (A) and heat-adhesive fibers (B). 4. The battery separator according to claim 1, wherein the main functional group of the ion exchange group is a sulfone group. 5. The synthetic fiber (A) is a sheath-core type composite fiber, and the sheath component is syndiotactic poly (1,2-butadiene).
En) resin, with at least part of its unsaturated bonds
Introduces ion-exchange groups, the battery separator according to claim 2 or 3 wherein the ion exchange group is a sulfonic group. 6. The battery separator according to claim 2, wherein the content of the syndiotactic poly (1,2-butadiene ) resin component constituting the synthetic fiber (A) is 5% by weight or more. 7. The battery separator according to claim 3, wherein the heat-adhesive fiber (B) is a sheath-core type composite fiber, and the sheath has a melting point of 10 ° C. or more lower than the melting point of the core. . 8. The fibers constituting the non-woven fabric are composed of synthetic fibers (A) and thermal adhesive fibers (B), and the content of the synthetic fibers (A) is 10 to 90% by weight, and the thermal adhesive fibers are The battery separator according to claim 3, wherein the content of (B) is in the range of 90 to 10% by weight. 9. The fibers constituting the non-woven fabric include synthetic fibers (A), heat-bonding fibers (B), and ultrafine fibers (C) having a fineness of 0.5 denier or less, and the ultrafine fibers (C) are partially contained. The battery separator according to claim 3, which is a composite fiber divided into. 10. The proportion of fibers constituting the non-woven fabric is such that the content of the synthetic fibers (A) is 10 to 50% by weight, the content of the heat-adhesive fibers (B) is 10 to 50% by weight, and the fibers are partially divided. The battery separator according to claim 3 or 9, wherein the ultrafine fibers (C) thus obtained are 0 to 80% by weight. 11. The battery separator according to claim 10, wherein the ultrafine fibers (C) contain a hydrophilic group containing —OH groups as a main component. 12. The battery separator according to claim 1, wherein a sulfone group is introduced into at least a part of the unsaturated bonds of the syndiotactic poly (1,2-butadiene) structure at a temperature of 60 ° C. or lower. 13. A nonwoven fabric containing a heat-adhesive fiber (B) has a syndiotactic poly (1,2-butadiene) structure as a molecular structure, and an ion exchange group is introduced into at least a part of its unsaturated bond. A separator for a battery, in which a porous sheet containing the resin component thus obtained is stuck. 14. The battery separator according to claim 12, wherein the porous sheet is the nonwoven fabric according to claim 3, 8, 9 or 10. 15. The battery separator according to claim 1, wherein the porous sheet is a film. 16. A syndiotactic poly whose molecular structure is syndiotactic.
Synthetic fiber (A) having a (1,2-butadiene) structure and occupying at least a part of the fiber surface with a resin component containing an ion-exchange group- introducable group in at least a part of its unsaturated bond
A non-woven fabric is formed by intertwining the constituent fibers of a fibrous web containing a sulfonic group to at least a part of the unsaturated bonds of the syndiotactic poly (1,2-butadiene) structure at a temperature of 60 ° C. or lower. A method for manufacturing a battery separator, which comprises introducing the battery separator. 17. The method for producing a battery separator according to claim 16, wherein the entanglement treatment between the constituent fibers of the fibrous web is a high-pressure water jet treatment. 18. A battery incorporating the battery separator according to claim 1.