JP2002298821A - Battery separator and battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery separator which is hardly broken, pierced, teared or dropped off due to sufficient fusion of fused fibers, and has excellent formation. Providing used batteries. SOLUTION: The battery separator of the present invention has a temperature of 14 ° C.
A nonwoven fabric is provided in which a polypropylene fiber having a shrinkage of 8% or less at 0 ° C. is fused with a fusion fiber containing a propylene copolymer as a fusion component. The battery of the present invention uses the battery separator described above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a battery separator and a battery.

[0002]

2. Description of the Related Art Conventionally, a positive electrode and a negative electrode of an alkaline battery are separated so as to prevent a short circuit and to maintain an electrolytic solution so that an electromotive reaction can be carried out smoothly. A separator is used.

[0003] In recent years, as electronic devices have become smaller and lighter, the space occupied by batteries has become smaller.
Since batteries need to have at least the same performance as before,
There is a demand for higher capacity batteries. For that purpose, it is necessary to increase the amount of the active material of the electrode, so that the volume occupied by the separator is inevitably reduced.

As a method of reducing the volume occupied by the separator, there is a method of strongly winding the separator around the electrode plate. However, if the separator is strongly wound around the electrode plate, the separator may be broken by the tension at the time of winding around the electrode plate, or the burr of the electrode plate may penetrate the separator, or the separator may be torn by the edge of the electrode plate. There was a problem that the yield was poor.

[0005]

The inventors of the present invention have studied the problem of breakage, breakthrough or tearing of such separators. As a result, polypropylene fibers are generally used as separators having excellent electrolytic solution resistance. It is known that fusion is performed by a fusion fiber containing a resin as a fusion component. However, it has been found that such a separator has a low fusion force due to the fusion fiber. The fact that the fusion force of the fusion fiber is weak can be confirmed also from the polypropylene fiber falling off.
When the ultrafine fibers having a fiber diameter of 5 μm or less were included as the polypropylene fibers, the ultrafine fibers were liable to fall off, and it became clear that there was a problem in the fusion force of the fusion fibers.

Therefore, the present inventors have found that if a fusion fiber containing a propylene-based copolymer as a fusion component is used in order to improve the fusion force of the fusion fiber, the affinity with the polypropylene fiber is high. Thus, the polypropylene fibers were fused using a fusion fiber containing a propylene-based copolymer as a fusion component, based on the idea that the fusion force would be improved. The use of such a fusion fiber certainly improves the fusion force,
Breakage, breakthrough, tearing of the separator as described above,
Or the direction of the problem of falling off of the fiber was in the direction to be solved, but since this fused fiber was easily contracted by the heat at the time of fusing, the texture tended to deteriorate,
In the worst case, a short circuit was expected to occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and since the fused fibers are sufficiently fused, breakage, penetration, tearing or falling off of the fibers is less likely to occur. Moreover, it is an object of the present invention to provide a battery separator having excellent formation and a battery using the battery separator.

[0008]

According to the present invention, there is provided a method for controlling a temperature of 140.
A separator for batteries (hereinafter simply referred to as a "characteristic"), wherein a polypropylene-based fiber having a shrinkage factor of 8% or less at a temperature of not more than 8% is provided with a nonwoven fabric fused by a fusion fiber containing a propylene-based copolymer as a fusion component. A "separator").

In other words, the nonwoven fabric constituting the separator of the present invention is sufficiently fused with the fusible fibers containing the propylene copolymer as the fusible component. In addition, the separator is not broken, the burr penetrates through the separator, the separator is hardly torn by the edge, and the fibers are hardly dropped. Further, since the polypropylene fibers are hardly shrunk even by the heat acting when the fusion fibers are fused, the polypropylene fibers are excellent in formation with minimum deterioration of the formation of the separator.

Since the battery of the present invention uses the battery separator described above, short-circuiting hardly occurs and the battery can be manufactured with high yield.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The nonwoven fabric constituting the separator of the present invention, when fused fibers to be described later are fused, so that the shrinkage thereof is suppressed so as not to damage the formation of the nonwoven fabric, and an electrolyte-resistant solution is used. It contains polypropylene fibers having a shrinkage of 8% or less at a temperature of 140 ° C. (hereinafter, may be referred to as “low-shrink PP fibers”) so as to have excellent properties. The lower the shrinkage of the low-shrink PP fiber, the better the effect is. Therefore, the more preferable shrinkage of the low-shrink PP fiber is 7% or less. Note that this “heat shrinkage” is determined by JI
It refers to the value of dry heat shrinkage measured using an oven dryer at a temperature of 140 ° C. based on SL 1015.

The low-shrinkage PP fiber constituting the nonwoven fabric of the separator of the present invention is not particularly limited as long as it has the above-mentioned shrinkage rate. Low shrink PP so that the burr of the electrode plate does not penetrate the separator or the separator is torn by the edge of the electrode plate
The tensile strength of the fiber is preferably at least 8 cN / dtex, more preferably at least 8.9 cN / dtex, even more preferably at least 10 cN / dtex. Although the upper limit of the tensile strength is not particularly limited,
About 50 cN / dtex is appropriate. This “tensile strength” means a value measured according to JIS L 1015 (chemical fiber staple test method).

The low-shrinkage PP fiber is prevented from being broken by the tension when the separator is wound around the electrode plate, the burr of the electrode plate penetrating the separator, or the separator being torn by the edge of the electrode plate. In addition, the Young's modulus is preferably 800 kg / mm ² or more, and more preferably 850 kg / mm ² or more. The upper limit of the Young's modulus is not particularly limited. This "Young's modulus" is JISL 1015: 199
Refers to the value of apparent Young's modulus calculated from the initial tensile resistance measured by the method specified in Sections 9, 8.11. Note that the initial tensile resistance is a value measured by a constant-speed tension-type testing machine.

If the cross-sectional shape of the low-shrinkage PP fiber is non-circular, the burr of the electrode plate may penetrate the separator,
This is preferable because the separator is not easily torn by the edge of the electrode plate. This is because even if the burr or edge of the electrode plate abuts on this low-shrinkage PP fiber, the low-shrinkage PP fiber is not slippery, the misalignment of the fiber contact is suppressed, and the force from the burr or edge is dispersed and received. It is thought that it is possible. Since the non-circular cross-sectional shape of the low-shrinkage PP fiber is non-circular, the nonwoven fabric can have a dense structure, so that the separator can be thinner. Specific cross-sectional shapes include, for example, an oval shape, a polygonal shape (eg, a triangular shape, a square shape,
A pentagonal shape, a hexagonal shape, and the like, and an alphabetical shape (for example, an X shape, a Y shape, an I shape, a V shape, and the like). Among these, a polygonal shape such as a pentagonal shape or a hexagonal shape is preferable.

Further, it is preferable that the low-shrinkage PP fiber can be fibrillated because burrs of the electrode plate hardly penetrate the separator or the separator is hardly torn by the edge of the electrode plate. This is because the burrs and edges of the electrode plate
It is considered that the low-shrinkage PP fiber becomes fibrillated when it comes into contact with the P fiber and can receive the force from the burrs and edges, so that the cutting force by the edges and burrs does not easily act.

The low-shrinkage PP fiber may be partially or entirely fibrillated, or may not be fibrillated. If a part or the whole is fibrillated as in the former, even if the burr or edge of the electrode plate abuts on the low-shrink PP fiber, the low-shrink PP fiber is hard to slip and does not cause misalignment of the fiber contact. Further, it is considered that the fibers can be finely divided into fibrils and short-circuits due to burrs and edges can be prevented. In addition, due to the fact that some or all of the low-shrink PP fibers are fibrillated,
The effect of further improving the retention of the electrolyte is also achieved.

The term "fibrillable" means that the fibers can be branched into fine fibers by an external force, and the fibrillated state can be easily confirmed by an electron micrograph.

Such a low-shrink PP fiber is made of a non-woven fabric of 10 mass so that burrs on the electrode plate do not penetrate the separator or the separator is torn by the edge of the electrode plate.
%, More preferably 20% by mass or more. On the other hand, the content is preferably 90 mass% or less, more preferably 70 mass% or less, in view of the balance with a fusion fiber described below.
More preferably, it is 0 mass% or less.

Such a low-shrink PP fiber has, for example, an isotactic pentad fraction (IPF) of 95 to 10.
A pressurized water tank is placed at the introduction point of the object to be drawn and the drawn-out part of the drawn object of the melt-spun fiber of isotactic polypropylene having a ratio (Q value) of 0% and a weight average molecular weight / number average molecular weight of less than 4. A stretching apparatus using a stretching tank filled with high-temperature pressurized steam therein has a stretching tank temperature of 120.
It can be obtained by stretching at a temperature of at least 70 ° C. and a stretching magnification of at least 7 times. The low-shrinkage PP fiber obtained by such a method is highly oriented and crystallized in the fiber direction, and when the fiber side surface is observed in a crossed Nicols state under polarized light, the refractive index differs in the fiber direction, intermittent. It has a unique stripe pattern consisting of linear dark and light portions.

The nonwoven fabric constituting the separator of the present invention comprises:
When forming the electrode plate group, the low shrinkage P as described above is used so that the separator is broken, burrs penetrate the separator, or the separator is hardly torn by the edge.
In addition to the P fiber, a fusion fiber containing a propylene-based copolymer as a fusion component (hereinafter, referred to as a “PP-based fusion fiber”), which can be strongly fused with the above-described low-shrink PP fiber, The PP-based fused fibers are fused.

In the PP-based fused fiber used in the present invention, the fused component preferably has a melting point of 135 ° C. or more. When the fusion component has such a melting point, the non-woven fabric can be maintained even when the temperature inside the battery becomes high, and the electrical insulation can be exhibited. Since the melting point of the low-shrink PP fiber is about 170 ° C., the fusion of the PP-shrink fiber is performed so that the low-shrink PP fiber is not melted by heat generated when the low-shrink PP fiber is melted. The melting point of the component is 1
The temperature is preferably 60 ° C. or lower, more preferably 150 ° C. or lower.

The "melting point" in the present invention means a temperature at which a maximum value of a melting endothermic curve obtained by using a differential scanning calorimeter at a heating temperature of 10 ° C./min from room temperature is obtained. In addition,
When there are two or more maximum values, the maximum value at the highest temperature is determined as the melting point.

Examples of the propylene copolymer which is a fusion component of the PP fusion fiber include ethylene-butene-propylene copolymer, ethylene-butadiene-propylene copolymer, ethylene-propylene copolymer and the like. Can be mentioned. Among them, ethylene-butene-
The propylene copolymer is suitable because it can be excellent in heat resistance having a melting point of 135 ° C. or more and has excellent fusion force with the low-shrinkage PP fiber.

This PP-based fused fiber may be composed only of the fused component, or may contain a non-fused component having a higher melting point than the fused component in addition to the fused component. When the non-fused component is contained as in the latter case, the strength of the nonwoven fabric can be further improved. The cross-sectional shape of the latter PP-based fused fiber is preferably a core-sheath type, an eccentric type, or a sea-island type so that there are many fused components that can participate in fusion. In addition, the non-fused component is one point lower than the melting point of the fused component.
It is preferably made of a resin higher than 0 ° C., and more preferably made of a resin higher than 20 ° C. As this non-fusion component,
For example, polypropylene, polymethylpentene, methylpentene copolymer, 6 nylon, 66 nylon, polyester and the like can be mentioned.

Such a PP-based fused fiber is strongly fused with the low-shrinkage PP fiber, and when the electrode group is formed, the separator may be broken, burrs may penetrate the separator, or the separator may be torn by the edge. 10 mass of non-woven fabric so that the PP fiber
%, Preferably 30% by mass or more, and more preferably 50% by mass or more. On the other hand, 90 mass% of the non-woven fabric is
Or less, more preferably 80 mass% or less.

The non-woven fabric constituting the separator of the present invention comprises:
In addition to the low shrinkage PP fiber and the PP-based fused fiber as described above, it is preferable to include an ultrafine fiber having a fiber diameter of 5 μm or less. By including such ultrafine fibers, a nonwoven fabric having a more uniform formation can be obtained, and thus a separator that is less likely to cause a short circuit can be obtained. Since the smaller the fiber diameter of the ultrafine fiber, the more uniform the texture, the fiber diameter of the ultrafine fiber is preferably 4 μm or less, more preferably 3 μm or less, and more preferably 2 μm or less. Is more preferred. On the other hand, the lower limit of the fiber diameter of the ultrafine fibers is suitably about 0.01 μm so as to have a certain strength.

The term "fiber diameter" in the present invention refers to the diameter of a circular cross-sectional shape when it is circular, and refers to the diameter of a circle having the same area when the cross-sectional shape is non-circular.

It is preferable that the ultrafine fibers have substantially the same fiber diameter so that a uniform pore size is formed by the ultrafine fibers and the formation is uniform. That is, the value (σ / d) obtained by dividing the standard deviation value (σ) of the fiber diameter distribution of the ultrafine fibers by the average value (d) of the fiber diameters of the ultrafine fibers is 0.2 or less (preferably 0.18 or less). It is preferred that When the fiber diameters of the ultrafine fibers are all the same, the standard deviation value (σ) is 0, and the lower limit of the value (σ / d) is 0.

This “average value (d) of fiber diameters of ultrafine fibers”
Means a value obtained by taking an electron micrograph of the nonwoven fabric, measuring the fiber diameters of 100 or more (n) ultrafine fibers in the electron micrograph, and averaging the measured fiber diameters (χ). The “standard deviation value (σ)” of the ultrafine fiber refers to a value obtained by calculating the measured fiber diameter (χ) from the following equation. Standard deviation = {(nΣχ ² − (Σχ) ² ) / n (n−1)}
^1/2 where n means the number of the measured ultrafine fibers, and χ means the fiber diameter of each ultrafine fiber. When two or more kinds of ultrafine fibers are present, it is preferable that the above relation is established for each of the ultrafine fibers.

It is preferable that the ultrafine fibers have substantially the same diameter in the fiber axis direction so that the formation of the nonwoven fabric is excellent.

The resin component constituting the ultrafine fiber of the present invention comprises:
For example, it can be composed of at least one kind of polyamide resin, polyolefin resin, etc., but has excellent electrolytic solution resistance, does not generate a nitrogen-containing compound which is considered to be a cause of self-discharge, and has the above-mentioned characteristics. It is preferable to be substantially composed of a polypropylene-based resin, which is excellent in the fusibility with such PP-based fused fibers. The term “substantially” means that the fiber surface is mainly made of polypropylene resin because it is mainly the fiber surface that affects the electrolytic solution resistance and the fusion property with the PP-based fusion fiber. Say. For example, an ultrafine fiber composed of a polyamide resin and a polypropylene resin and in which only the polypropylene resin occupies the fiber surface is substantially an ultrafine polypropylene fiber.

When the ultrafine fibers are substantially made of a polypropylene resin as described above, the ultrafine fibers can be firmly fused with the PP-based fusion fibers, so that the problem that the ultrafine fibers fall off hardly occurs.

[0033] The microfiber has a circular cross-sectional shape, so that the texture of the nonwoven fabric can be further improved.

The ultrafine fiber of the present invention can be obtained, for example, by removing at least one resin component from a conjugate fiber containing two or more resin components. That is, at least a resin component that can be easily decomposed and removed by a solvent and a resin fiber that is not easily decomposed and removed by the solvent can be obtained by decomposing and removing the resin component from the composite fiber. it can. For example, by immersing a composite fiber composed of a copolymerized polyester and a polypropylene in a 10 mass% sodium hydroxide aqueous solution at a temperature of about 80 ° C., the copolymerized polyester component is decomposed and removed to obtain an ultrafine fiber composed of a polypropylene. it can. As described above, the ultrafine fibers generated by removing at least one type of resin component from the conjugate fiber containing two or more types of resin components have a very low possibility that the ultrafine fibers are in a connected state.
The non-woven fabric containing the ultrafine fibers has a better texture.

As described above, the ultrafine fibers having substantially the same fiber diameter or the ultrafine fibers having substantially the same diameter in the fiber axis direction can be formed, for example, by restricting the sea component at the spinneret into the sea component. It can be obtained by removing the sea component of the sea-island type fiber obtained by a composite spinning method such as a method of extruding and compounding the components. In addition, the method of removing the sea component of the sea-island type fiber obtained by spinning after mixing the resin constituting the island component and the resin constituting the sea component, which is generally called a mixed spinning method, or a melt blow method However, it is difficult to obtain ultrafine fibers having substantially the same fiber diameter or ultrafine fibers having substantially the same diameter in the fiber axis direction.

Ultrafine fibers having a circular cross-sectional shape are, for example, those having a circular cross section as a base for extruding an island component into a sea component and extruding the island component when spinning a sea-island type fiber. Can be obtained by using

It is preferable that the ultrafine fibers are short fibers having a high degree of freedom so that the fine fibers are uniformly dispersed so that the formation of the nonwoven fabric is excellent. When the ultrafine fibers or the resin components that are the sources of the ultrafine fibers are pressed against each other when cutting, the formation of the nonwoven fabric deteriorates, so the resin components that are the sources of the ultrafine fibers or the ultrafine fibers when cutting are performed. It is preferable to use an ultrafine fiber or a conjugate fiber that can generate an ultrafine fiber, which is difficult to press against each other. Examples of such ultrafine fibers or composite fibers that can generate such ultrafine fibers that are difficult to press-bond include, for example, ultrafine fibers with high crystallinity or composite fibers containing a resin component with high crystallinity. More specifically, when the ultrafine fiber or the composite fiber contains polymethylpentene or contains polypropylene, the melting point of the polypropylene is preferably 166 ° C or more (preferably 168 ° C or more).

Further, such ultrafine fibers are preferably in a state where individual ultrafine fibers are dispersed. That is, it is preferable that the bundle of the ultrafine fibers does not substantially exist. This is because the presence of the bundle of ultrafine fibers tends to deteriorate the texture of the nonwoven fabric despite the presence of ultrafine fibers. Such a nonwoven fabric in which a bundle of ultrafine fibers is present, after forming a fibrous web containing a dividable fiber that can be divided by swelling the resin component by a solvent or a dividable fiber that can be divided by removing the resin component by a solvent, It is easy to form by dividing the splittable fibers, but if the fiber web is formed by using the separated ultrafine fibers separated and dispersed into individual ultrafine fibers, there is substantially no bundle of ultrafine fibers. A nonwoven fabric in which ultrafine fibers are dispersed can be obtained.

Such an ultrafine fiber preferably accounts for 10% by mass or more of the nonwoven fabric, and more preferably accounts for 15% by mass or more, so that the formation of the nonwoven fabric is excellent. On the other hand, the aforementioned low-shrink PP fiber and PP
It is preferably 80% by mass or less, more preferably 50% by mass or less, in view of the balance with the system fusion fiber.

The nonwoven fabric constituting the separator of the present invention comprises:
Furthermore, polyphenylene sulfide fiber and / or wholly aromatic
The heat resistance of the non-woven fabric is improved
And it is hard to deteriorate even when the battery gets hot.
This is a preferred embodiment. This polyphenylenesulf
90% by mole or more of the constituent units of the [-C₆H ₄
S-] means a fiber consisting of a polymer composed of
Aromatic polyamide fibers polymerize only monomers having aromatic rings
Refers to fibers made of a polymer having an amide bond.
These polyphenylene sulfide fibers and / or all
Aromatic polyamide fibers are not suitable for heat resistance.
It preferably occupies 10 mass% or more of the woven fabric,
More preferably, it occupies 30 mass% or more. What
The low-shrink PP fiber, PP-based fused fiber,
70 mass% or less due to combination with extra fine fibers
It is preferably lower than 50 mass%.
More preferred.

The fibers constituting the nonwoven fabric of the present invention, that is, low-shrinkage PP fibers, PP-based fused fibers, ultrafine fibers, polyphenylene sulfide fibers, or wholly aromatic polyamide fibers can be in an undrawn state. It is preferable that each fiber is in a drawn state so as to be excellent.

The fineness of the fibers constituting the nonwoven fabric of the present invention, that is, the low shrinkage PP fibers, PP-based fused fibers, polyphenylene sulfide fibers or wholly aromatic polyamide fibers is not particularly limited. 001-5d
tex, and preferably 0.01 to 3 dtex.

The fiber length of the fibers constituting the nonwoven fabric of the present invention, that is, low-shrinkage PP fiber, PP-based fused fiber, ultrafine fiber, polyphenylene sulfide fiber, or wholly aromatic polyamide fiber is not particularly limited. However, the shorter the fiber length, the higher the degree of freedom of the fibers, the more evenly the fibers are dispersed, and the better the formation. Therefore, the fiber length is preferably 0.1 to 25 mm (more preferably 0.1 to 20 mm), and preferably 1 to 25 mm.
It is preferably a fiber cut to に 25 mm (more preferably 0.1 to 20 mm). Therefore, it is preferable that the nonwoven fabric of the present invention is a wet nonwoven fabric which is composed of fibers having such a fiber length and which can be excellent in texture.

When the nonwoven fabric is made of a suitable wet nonwoven fabric, it is preferable to use the PP-based fused fiber of the present invention. That is, the fibers constituting the wet nonwoven fabric generally have no crimp and no entanglement between the fibers, and thus have no strength. Therefore, when the fibers are entangled with each other by applying a fluid flow such as a water flow so that the strength is improved, the formation of the wet nonwoven fabric is disturbed, and a through hole extending from the upper surface to the lower surface of the wet nonwoven fabric is easily generated. Therefore, a short circuit is likely to occur. Therefore, in order to improve the strength of the wet nonwoven fabric in a state where the fibers are not entangled with each other, it is necessary to increase the fusion force of the fusion fibers. However, even if a conventional fusion fiber containing a polyethylene resin as a fusion component is used, it is difficult to increase the fusion force with the low-shrink PP fiber, and the low-shrink PP fiber is likely to fall off. Met. In particular, when ultrafine fibers were included as the fibers constituting the wet nonwoven fabric, the fibers were easily dropped because of the thinness. However, the fused fibers of the present invention have a low shrink PP
Since it has excellent fusion force with fibers, it can be a wet non-woven fabric that is excellent in strength and hard to fall off low-shrink PP fibers, and even if it contains ultrafine fibers, it is hard to fall off ultrafine fibers. It is.

The fiber length refers to a length obtained by JIS L 1015 (chemical fiber staple test method) B method (corrected staple diagram method).

The fibers constituting the non-woven fabric constituting the separator of the present invention are preferably not fibrillated except for the low-shrinkage PP fibers. Without such fibrillation, the formation is more uniform. As this "fibrillated fiber", for example, a fiber obtained by beating a mechanically dividable splittable fiber with a beater or the like, pulp,
Fibers obtained by a flash spinning method can be exemplified.

The nonwoven fabric constituting the separator of the present invention comprises:
Preferably, the form is maintained substantially only by fusion of the fibers. When the shape is substantially maintained only by the fusion of the fibers as described above, the formation is excellent, a short circuit is unlikely to occur, and the electrolyte can be uniformly distributed. For example, if the fibers are fixed not only by fusion but also by entanglement, a through-hole connected from the front surface to the back surface of the nonwoven fabric is formed by an action for entanglement of the fibers (for example, a fluid flow such as a water flow). Is likely to cause a short circuit,
When the fibers are fixed substantially only by fusion, the arrangement of the fibers is not disturbed, and a short circuit is unlikely to occur.

Incidentally, fibers may be entangled with each other when producing a nonwoven fabric. For example, when a fiber web is formed by a wet method, fibers are more or less entangled. However, since this entanglement does not disturb the arrangement of the nonwoven fabric constituent fibers, it can be considered that the entanglement is not substantially entangled. As described above, "substantially only fusion of fibers" means a state in which the fibers are fixed only by fusion after forming the fiber web. The fusion of the fibers is usually formed by fusion of PP fusion fibers.

Although the areal density (weight per m ² ) of the nonwoven fabric of the present invention is not particularly limited, it is 5 to 100 g / m ^2.
m ² , more preferably 10 to 80 g / m ² .

Although the thickness of the nonwoven fabric of the present invention is not particularly limited, it is preferably from 0.02 mm to 0.3 mm, and more preferably from 0.02 mm to 0.2 mm.

The “thickness” in the present invention refers to JIS B
7502: refers to a thickness measured by an outer micrometer (0 to 25 mm) specified in 1994.

The nonwoven fabric constituting the separator of the present invention preferably has an "average formation index" as an index of formation of 0.15 or less so that the formation is excellent. When the formation is excellent as described above, a short circuit is unlikely to occur, and the electrolyte can be kept uniform. A more preferable average formation index is 0.12 or less.

This “average formation index” is calculated in Japanese Patent Application No. 11-15 / 1997.
The value obtained by the method described in No. 2139. That is, it means a value obtained as follows. (1) Light is emitted from a light source to an object to be measured (nonwoven fabric), and among the irradiated light, light reflected by a predetermined region of the object to be measured is received by a light receiving element to acquire luminance information. . (2) A predetermined area of the measured object has an image size of 3 mm square and 6 m
The image is equally divided into an m square, a 12 mm square, and a 24 mm square to obtain four divided patterns. (3) The luminance value of each of the equally divided sections for each of the obtained divided patterns is calculated based on the luminance information. (4) An average luminance (X) for each divided pattern is calculated based on the luminance value of each section. (5) Find the standard deviation (σ) for each divided pattern. (6) The coefficient of variation (CV) for each divided pattern is calculated by the following equation. Coefficient of variation (CV) = (σ / X) × 100 Here, σ indicates the standard deviation of each divided pattern, and X indicates the average luminance of each divided pattern. (7) A coordinate group obtained as a result of setting the logarithm of each image size as the X coordinate and the variation coefficient corresponding to the image size as the Y coordinate is regressed to a linear line by the least squares method, and its slope is calculated. Is defined as the formation index. (8) The formation index is measured three times, and the average value is defined as the average formation index.

[0054] The nonwoven fabric of the present invention, the average Needle penetration force unit surface density (g / ^{m 2)} is preferably at around 14gf or higher, and more preferably at least 15 gf,
More preferably, it is 16 gf or more. This value is 14g
If f or more, the fibers constituting the nonwoven fabric are further divided by the burr of the electrode plate and the like, so that short-circuit is less likely to occur when forming the electrode plate group. In addition, that this value is high also means that it is an excellent formation in which the fibers are uniformly dispersed.

The average needle-type penetration resistance refers to a value obtained as follows. That is, a cylindrical through hole (inner diameter:
One non-woven fabric is placed so as to cover the cylindrical through-hole of the support base having 11 mm), and a fixing material having a cylindrical through-hole (inner diameter: 11 mm) is further placed on the non-woven fabric through the cylindrical through-hole of the support base. It is placed so as to match the center of the hole, and the nonwoven fabric is fixed. Thereafter, a needle (curvature radius at the tip: 0.5 m) attached to a handy compression tester (KES-G5, manufactured by Kato Tech) is applied to the nonwoven fabric.
m, diameter: 1 mm, protrusion length from the jig: 2 cm)
The needle pierces the nonwoven fabric vertically at a speed of 0.01 cm / s, and the force required for the needle to penetrate the nonwoven fabric is measured, and this force is defined as the needle-type penetration resistance. This needle-type penetration resistance is measured at 30 places of the nonwoven fabric, and the average value is defined as the average needle-type penetration resistance. Next, the average needle-type penetration resistance per unit area density is calculated by dividing the average needle-type penetration resistance by the surface density (g / m ² ).

The separator of the present invention is provided with the above-mentioned nonwoven fabric, and can be composed of only the nonwoven fabric, or the nonwoven fabric has a perforated film, woven fabric, knitted fabric, net,
Threads and the like can be laminated. In order to increase the capacity of the battery, it is advantageous that the separator is thinner.

Since the non-woven fabric constituting the separator of the present invention is mainly composed of polypropylene fibers,
The affinity with the electrolyte is low, and the retention of the electrolyte may be poor. In such a case, an oxygen and / or sulfur-containing functional group (for example, a sulfonic acid group, a sulfonate group, a sulfofluoride group, a carboxyl group, a carbonyl group, etc.) is introduced into a separator (for example, a nonwoven fabric). Preferably, a hydrophilic monomer is graft-polymerized, a surfactant is provided, or a hydrophilic resin is provided.

The separator of the present invention may be, for example, a primary battery such as an alkaline manganese battery, a mercury battery, a silver oxide battery, or an air battery, a nickel-cadmium battery, a silver-zinc battery,
Silver-cadmium battery, nickel-zinc battery, nickel-
It can be suitably used as a separator of a secondary battery such as a hydrogen battery, and particularly preferably as a separator of a nickel-cadmium battery or a nickel-hydrogen battery.

The nonwoven fabric of the present invention can be manufactured, for example, as follows.

First, the above-mentioned low-shrinkage PP fiber and fused fiber, preferably ultrafine fiber, polyphenylene sulfide fiber, wholly aromatic polyamide fiber and the like are prepared.

Next, a fiber web is formed using the prepared fibers. The method for forming the fiber web is not particularly limited, but is preferably formed by a wet method in which the fibers are easily dispersed uniformly. Examples of the wet method include a horizontal long net system, an inclined wire short net system, a circular net system, a long net / circular net combination system, a short net / circular net combination system, and the like.

Next, the fibers are fused and fixed by fusing the fused fibers constituting the fiber web.
A nonwoven fabric that can be used as a separator can be manufactured. When the fibers are fixed to each other only by fusion as described above, a nonwoven fabric can be manufactured in which the arrangement of the fibers is not disturbed, the formation is excellent, a short circuit does not easily occur, and the electrolyte solution can be uniformly distributed. The fusion of the fusion fibers may be performed under no pressure, or may be performed under pressure,
Alternatively, pressure may be applied (preferably immediately applied) after the fusion component of the fusion fiber is melted under no pressure.

When the separator made of the nonwoven fabric of the present invention is used for a high-capacity battery, it is preferable that the thickness of the nonwoven fabric (separator) be thin so that the capacity can be increased. When the thickness of the nonwoven fabric after the thickness is large, it is preferable to adjust the thickness by passing the nonwoven fabric between a pair of rolls.

The nonwoven fabric having an average formation index of 0.15 or less contains low-shrinkage PP fibers, uses ultrafine fibers as fibers, or fixes fibers only by fusion (an entanglement treatment is applied). No), or use non-fibrillated fibers as fibers other than low-shrink PP fibers,
The fiber can be manufactured by adjusting these conditions, such as using a short fiber having a fiber length of about 0.1 to 25 mm or forming a uniform fiber web by a wet method.

The non-woven fabric having an average needle penetration resistance of 14 gf or more per unit area density according to the present invention uses PP-based fused fibers as a fused fiber, or is added immediately after the PP-based fused fiber is melted. Such as pressing and fusing, using a low-shrink PP fiber having high tensile strength, dispersing the low-shrink PP fiber uniformly by a wet method, or using a wholly aromatic polyamide fiber. It can be manufactured by adjusting the conditions.

When the separator of the present invention is formed by laminating a perforated film, a woven fabric, a knitted fabric, a net, a yarn, or the like on the above-described nonwoven fabric, the PP constituting the fiber web is used.
Simultaneous with or after forming the nonwoven fabric by fusing the system-fused fibers, forming the PP-based fused fiber, perforated film, woven fabric, knit, net or yarn constituting the fiber web or nonwoven fabric Can be integrated by utilizing the fusibility of the resin component to be formed.

Since the nonwoven fabric constituting the separator of the present invention is preferably composed mainly of polypropylene fibers so as to have excellent alkali resistance, the retention of the electrolyte may be poor. In that case, it is preferable to perform a hydrophilic treatment in order to improve the retention of the electrolytic solution. Examples of the hydrophilic treatment include a sulfonation treatment, a fluorine gas treatment, a graft polymerization treatment of a vinyl monomer, a surfactant treatment, a discharge treatment, and a treatment for imparting a hydrophilic resin.

The sulfonation treatment is not particularly limited. For example, the above-mentioned nonwoven fabric, or the nonwoven fabric and the perforated material are placed in a solution containing fuming sulfuric acid, sulfuric acid, sulfur trioxide, chlorosulfuric acid, or sulfuryl chloride. A method of introducing a sulfonic acid group by immersing an integrated product (hereinafter, simply referred to as an “integrated product”) with a film, a woven fabric, a knitted fabric, a net, a thread, or the like, a sulfur monoxide gas, a sulfur dioxide gas, or a sulfur trioxide gas For example, a method in which a sulfonic acid group is introduced into a nonwoven fabric or an integrated product by causing an electric discharge to act in the presence of such a method.

The fluorine gas treatment is not particularly limited. For example, fluorine gas diluted with an inert gas (eg, nitrogen gas, argon gas, etc.), oxygen gas, carbon dioxide gas, and sulfur dioxide gas may be used. Hydrophilization can be achieved by exposing the nonwoven fabric or the integrated material to a mixed gas with at least one gas selected from the above. In addition, after previously adhering the sulfur dioxide gas to the nonwoven fabric or the integrated material, when contacted with fluorine gas,
Permanent hydrophilicity can be imparted more efficiently.

The graft polymerization of the vinyl monomer includes:
As the vinyl monomer, for example, acrylic acid, methacrylic acid, acrylate, methacrylate, vinylpyridine, vinylpyrrolidone, or styrene can be used. In addition, when styrene is graft-polymerized, it is preferable to sulfonate in order to impart affinity with the electrolytic solution. Among these, acrylic acid can be suitably used because of its excellent affinity with the electrolytic solution.

As a polymerization method of these vinyl monomers, for example, a method in which a nonwoven fabric or an integrated material is immersed in a solution containing a vinyl monomer and a polymerization initiator and heated, or a method in which radiation is applied after the vinyl monomer is applied to the nonwoven fabric or the integrated material. There are a method of irradiation, a method of irradiating the nonwoven fabric or the integrated body with a vinyl monomer and then bringing the same into contact with a vinyl monomer, and a method of impregnating the nonwoven fabric or the integrated body with a vinyl monomer solution containing a sensitizer and then irradiating ultraviolet rays. In addition, before contacting the vinyl monomer solution with the nonwoven fabric or the integrated material, if the surface of the nonwoven fabric or the integrated material is modified by ultraviolet irradiation, corona discharge, plasma discharge, etc., the affinity with the vinyl monomer solution is high. The graft polymerization can be performed efficiently.

The surfactant treatment includes, for example, an anionic surfactant (for example, an alkali metal salt, an alkyl sulfonate or a sulfosuccinate salt of a higher fatty acid) or a nonionic surfactant (for example,
The nonwoven fabric or the integrated product can be immersed in a solution of polyoxyethylene alkyl ether or polyoxyethylene alkylphenol ether, or the solution can be applied to the nonwoven fabric or the integrated product by application or spraying.

Examples of the discharge treatment include a corona discharge treatment, a plasma treatment, a glow discharge treatment, a creeping discharge treatment and an electron beam treatment. Among these discharge treatments, a nonwoven fabric or an integrated body is arranged between a pair of electrodes each carrying a dielectric under atmospheric pressure in the air so as to be in contact with both dielectrics, and between these two electrodes. Applying an AC voltage and generating a discharge in the voids inside the nonwoven fabric,
The surface of the fibers constituting the interior of the nonwoven can also be treated. Therefore, the retention of the electrolyte in the separator is excellent.

As the treatment for imparting a hydrophilic resin, for example, a hydrophilic resin such as carboxymethyl cellulose, polyvinyl alcohol, crosslinkable polyvinyl alcohol, or polyacrylic acid can be attached. After dissolving or dispersing these hydrophilic resins in an appropriate solvent, the non-woven fabric or the integrated material can be immersed in the solvent, or the solvent can be applied or sprayed on the non-woven fabric or the integrated material, and dried and adhered. it can. The amount of the hydrophilic resin to be applied is 0.3 to 5 ma of the entire separator so as not to impair the air permeability.
It is preferably ss%.

As the crosslinkable polyvinyl alcohol, for example, there is polyvinyl alcohol in which a part of the hydroxyl group is substituted with a photosensitive group. More specifically, a styrylpyridinium-based photosensitive group, styrylquinolinium is used as the photosensitive group. And poly (vinyl alcohol) substituted with styrylbenzothiazolium. This crosslinkable polyvinyl alcohol can be crosslinked by light irradiation after being attached to a nonwoven fabric or an integrated material in the same manner as other hydrophilic resins. Such a polyvinyl alcohol in which a part of the hydroxyl group is substituted by a photosensitive group is excellent in alkali resistance and contains a large amount of a hydroxyl group capable of forming a chelate with an ion. It forms a chelate with the ions before the metal is deposited, and is less likely to cause a short circuit between the electrodes.

The battery of the present invention uses the separator as described above. The separator described above has a low shrink PP
Since the fibers are sufficiently fused by the PP-based fused fiber and have excellent texture, short-circuiting is less likely to occur, and the fiber can be manufactured with high yield.

The battery of the present invention can be exactly the same as a conventional battery except that the separator as described above is used.

For example, a cylindrical nickel-hydrogen battery has a structure in which a nickel positive electrode plate and a hydrogen-absorbing alloy negative electrode plate are spirally wound via the above-described separator and inserted into a metal case. Have. As the nickel positive electrode plate, for example, a sponge-like nickel porous material filled with an active material composed of a nickel hydroxide solid solution powder can be used.As the hydrogen storage alloy negative electrode plate, for example,
Nickel plated perforated steel sheet, foamed nickel, or nickel net, AB ₅ (rare earth) alloy, AB / A ₂ B
System (Ti / Zr based) alloy, or _AB 2 (Laves
A phase-filled alloy can be used. As the electrolyte, for example, a two-component system of potassium hydroxide / lithium hydroxide or a three-component system of potassium hydroxide / sodium hydroxide / lithium hydroxide can be used. Further, the case is sealed by a sealing plate provided with a safety valve via an insulating gasket. Further, a positive electrode current collector and an insulating plate are provided, and if necessary, a negative electrode current collector is provided.

The battery of the present invention does not need to have a cylindrical shape, but may be a prismatic type, a button type, or the like. In the case of a square type, the battery has a laminated structure in which a separator is arranged between a positive electrode plate and a negative electrode plate.

Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0081]

EXAMPLES Example 1 Low shrinkage PP fiber having a heat shrinkage of 7% at a temperature of 140 ° C. (tensile strength: 10.7 cN /
dtex, Young's modulus: 850 kg / mm ² , cross-sectional shape: almost pentagonal, melting point: 174 ° C, can be fibrillated,
Fiber diameter: 13.6 μm, fineness: 1.3 dtex, cut fiber length: 10 mm, stretched, intermittent with different refractive indices in the fiber direction when the fiber side surface is observed in crossed Nicols state under polarized light (Having a striped pattern consisting of a linear dark portion and a bright portion).

As the PP-based fused fiber, the core component (non-fused component) is made of polypropylene (melting point: 161 ° C.), and the sheath component (fused component) is an ethylene-butene-propylene copolymer (melting point: 137 ° C.) PP-sheath composite fusible fiber (fineness: 2.2 dtex, fiber diameter: 17.5)
μm, a cut fiber length: 5 mm, a mass ratio of the core component to the sheath component of 1: 1, non-fibrillated, stretched) was prepared.

Next, the low-shrinkage PP fiber 30 mass
% And 70 mass% of the PP-based core-in-sheath composite fused fiber were mixed and dispersed to form a fiber web by a wet method (horizontal net method).

Next, this fiber web was dried for 1 minute by a suction dryer set at a temperature of 140 ° C., and then subjected to a heat treatment in an oven set at a temperature of 140 ° C. for 30 seconds to dry the fiber web and the PP system. The core-sheath composite fused fiber was fused with a sheath component (ethylene-butene-propylene copolymer) to obtain a fused nonwoven fabric.

Next, the thickness of the fused nonwoven fabric was adjusted by passing the same between calender rolls (linear pressure: 9.8 N / cm) heated to 40 ° C. to adjust the thickness of the separator of the present invention (area density: 60 g / m ² , thickness: 0.15 mm, fibers are arranged substantially two-dimensionally).

Example 2 The same low-shrinkage PP fiber and PP-based core-sheath composite fused fiber as in Example 1 were prepared.

Further, in the sea component composed of poly-L-lactic acid, there are 25 island components composed of polypropylene.
A sea-island type fiber (fineness: 1.65 dtex, fiber length: 2 mm) cut after spinning by the composite spinning method was prepared.
Next, the sea-island type fiber was subjected to a temperature of 80 ° C.
% Sodium hydroxide aqueous solution for 30 minutes to obtain poly-L-
The lactic acid is extracted and removed, and the polypropylene ultrafine fiber (fiber diameter: 2 μm, ρ / d: 0.083, melting point: 172 ° C., fiber length: 2 mm, not fibrillated, stretched, substantially in the fiber axis direction (Cross-sectional shape: circular) having the same diameter.

Next, 30% by mass of low-shrink PP fiber,
A fiber web was formed from a slurry obtained by mixing and dispersing 50 mass% of the PP-based core-in-sheath type composite fusion fiber and 20 mass% of the polypropylene ultrafine fiber by a wet method (horizontal netting method).

Then, heat treatment and subsequent thickness adjustment were carried out in exactly the same manner as in Example 1 to obtain the separator (area density:
60 g / m ² , thickness: 0.15 mm, substantially free of bundles of ultrafine fibers, and fibers are arranged substantially two-dimensionally).

(Comparative Example 1) The same PP-based core-sheath composite fused fiber as in Example 1 was prepared.

A polypropylene fiber having a heat shrinkage of 9% at 140 ° C. (tensile strength: 8 cN / dtex,
Young's modulus: 400 kg / mm ² , cross-sectional shape: circular, melting point: 163 ° C., cannot be fibrillated, fineness: 2.2 dt
ex, fiber diameter: 17.7 μm, cut fiber length: 10
mm, stretched).

Next, the polypropylene fiber 30 ma
A fiber web was formed from a slurry in which ss% and 70 mass% of the PP core-sheath composite fused fiber were mixed and dispersed, by a wet method (horizontal long net method).

Next, heat treatment and subsequent thickness adjustment were carried out in exactly the same manner as in Example 1 to obtain a separator for comparison (area density:
60 g / m ² , thickness: 0.15 mm, fibers are arranged substantially two-dimensionally).

Comparative Example 2 The same low shrinkage PP fiber as in Example 1 was prepared.

Further, as the PE-based fused fiber, the core component (non-fused component) is made of polypropylene (melting point: 165 ° C.), and the sheath component (fused component) is made of high-density polyethylene (melting point:
131 ° C) PE-core composite sheath fused fiber (fineness:
2.2 dtex, fiber diameter: 17.5 μm, cut fiber length: 5 mm, mass ratio between core component and sheath component is 1: 1,
(Not fibrillated, stretched) was prepared.

Next, the low-shrinkage PP fiber 30 mass
% And PE-core composite sheath-fused fiber of 70 mass% are mixed and dispersed, and the slurry is wet-processed (horizontal net method).
Thus, a fiber web was formed.

Next, heat treatment and subsequent thickness adjustment were performed in exactly the same manner as in Example 1 to obtain a separator for comparison (area density:
60 g / m ² , thickness: 0.15 mm, fibers are arranged substantially two-dimensionally).

(Measurement of Average Formation Index) The average formation index of each separator (nonwoven fabric) was measured by the method described in the section of the embodiment of the invention. The results were as shown in Table 1. As is clear from Table 1, the separator (nonwoven fabric) of the present invention was excellent in formation having an average formation index of 0.15 or less by containing low shrinkage PP fibers having a small shrinkage.

[0099]

[Table 1] #: Average needle penetration resistance per unit area density

(Measurement of Average Needle Type Penetration Resistance per Unit Area Density) The average needle type penetration resistance per unit area density of each separator (nonwoven fabric) was determined by the method described in the section of the embodiment of the invention. It was measured. The results were as shown in Table 1. As is clear from Table 1, the separator (nonwoven fabric) of the present invention is more strongly fused by the PP-based core-fused composite fiber than when fused by the PE-based core-fused composite fiber. Therefore, it was found that the burr of the electrode plate was hard to penetrate. That is, it was found that short-circuiting was difficult when forming the electrode plate group.

(Measurement of Dropped Fiber) Each separator (non-woven fabric) was subjected to a pressing load of 650 gf in accordance with the C method (appearance retention type tester) specified in 4.3 of JIS L 1076. Contact area 26c
A friction test was performed under the conditions of m ² and 20 rotations.
After the friction test, from both the friction plate and the separator surface,
The fibers dropped from the separator (nonwoven fabric) were collected and their weight was measured. The weight was as shown in Table 1.
As is clear from Table 1, the amount of fibers dropped from the separator (nonwoven fabric) of the present invention is smaller than that of the separator (nonwoven fabric) fused by the PE-based sheath-fused composite fiber. It was confirmed that the fusion fibers were firmly fused.

[0102]

According to the battery separator of the present invention, when forming the electrode plate group, the separator is not broken, burrs penetrate the separator, the separator is hardly torn by the edge, and the fibers are hardly dropped. is there. Also,
The formation is also excellent.

Since the battery of the present invention uses the battery separator, short-circuiting hardly occurs, and the battery can be manufactured with high yield.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masahisa Tanaka 7-floor Kitatone, Sowa-cho, Sarushima-gun, Ibaraki Prefecture F-term in Japan Vilene Co., Ltd. BA03 BA05 BA09 BA21 BA23 BB02 CA20 CC12 EA10 5H021 BB11 CC02 EE02 EE04 EE07 EE15 EE23 HH00 HH03 HH05 HH06 5H028 AA05 HH00 HH03 HH05 HH08

Claims (10)

[Claims] 1. A non-woven fabric wherein a polypropylene fiber having a shrinkage of 8% or less at a temperature of 140 ° C. is fused by a fusion fiber containing a propylene copolymer as a fusion component. Battery separator. 2. The battery separator according to claim 1, wherein the propylene copolymer which is a fusion component of the fusion fiber comprises an ethylene-butene-propylene copolymer. 3. The battery separator according to claim 1, wherein the nonwoven fabric further includes ultrafine fibers having a fiber diameter of 5 μm or less. 4. The ultrafine fiber according to claim 3, wherein the ultrafine fiber is obtained by removing at least one resin component from a conjugate fiber containing two or more resin components. Battery separator. 5. The battery separator according to claim 1, wherein the nonwoven fabric further contains polyphenylene sulfide fibers and / or wholly aromatic polyamide fibers. 6. The battery separator according to claim 1, wherein the nonwoven fabric maintains its form substantially only by fusion of fibers. 7. The battery separator according to claim 1, wherein the nonwoven fabric is a wet nonwoven fabric. 8. The battery separator according to claim 1, wherein the non-woven fabric has an average formation index of 0.15 or less. 9. The battery according to claim 1, wherein the average needle-type penetration resistance of the nonwoven fabric is 14 gf or more per unit area density (g / m ² ). For separator. 10. A battery using the battery separator according to any one of claims 1 to 9.