JPH11273653A - Nonwoven fabric for battery separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a self-discharge quantity, and to realize a thin type by setting an ion exchange quantity to a specific value in composite nonwoven fabric containing at least sulfonated polyolefine fiber. SOLUTION: A value of an ion exchange quantity is set to 0.04 to 0.30 meq/g. Sulfonated polystyrene fiber is used as a component of composite nonwoven fabric, and the average fiber diameter is desirably sat between 1 to 20 μm. When aliphatic polyolefine fiber is used as a mixing component, an average fiber diameter is desirably set between 0.5 to 15 μm, and ductility is desirably set not less than 40%. When polypropylene fiber is used as aliphatic polyolefine, the mixing ratio is desirably set to 25% to 85% of the whole nonwoven fabric weight, and a thickness of compounded nonwoven fabric is desirably set between 50 and 150 μm. The total weight of the compounded nonwoven fabric is desirably set between 15 to 100 g/m<2> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonwoven fabric particularly suitable for battery separator applications.

[0002]

2. Description of the Related Art Conventionally, nonwoven fabrics made of fibers such as polyolefins and polyamides have been used as battery separators because of their excellent shielding properties and strength characteristics.

[0003] However, the polyamide fiber has a problem that the cycle life is not good because the polyamide is decomposed and eluted in an alkaline solution, and the eluted component promotes self-discharge of the secondary battery. In addition, fibers made of polyolefin do not have such a problem of elution, but have poor wettability to an electrolytic solution due to the hydrophobic nature of the material, so that it is necessary to graft-polymerize a hydrophilic component or sulfonate, which is disadvantageous in cost. there were. In the sulfonation of polyolefin, there are many processing restrictions such as generally requiring the use of high-temperature concentrated sulfuric acid. On the other hand, graft polymerization has a problem that the hydrophilicity decreases over time. In particular, when ultrafine fibers are used to meet the demand for thinner separators in response to recent demands for battery downsizing, liquid retention and other properties are improved, but the strength of the nonwoven fabric is significantly reduced due to high-temperature concentrated sulfuric acid sulfonation treatment. This causes a problem that the process passability is reduced. On the other hand, nonwoven fabrics made of polystyrene fibers can be easily sulfonated and easily impart hydrophilicity.Therefore, it has been considered that the nonwoven fabrics are formed into a nonwoven fabric by various methods to form a battery separator. However, there has been a problem that the sheet is easily cut or a problem that the self-adhesiveness is not so good, so that the ultrafine fibers have been practically hardly used. The reason why the hydrophilicity of the separator is important is that gas does not remain in the separator when the battery is used for a long period of time and there is no wet part, and when oxygen gas generated during high-speed charging is transmitted through the separator and quickly escapes. This is presumed to be due to the necessity of re-permeation of the electrolyte into the battery, which is a very important factor for prolonging the life of the battery and quick charging. A melt-blowing method for producing ultrafine fibers of syndiotactic polystyrene is described in JP-A-4-257310.
Discloses a method for producing fibers of 0.1 to 50 μm. However, according to the method disclosed in the present invention, the strength of the obtained nonwoven fabric is low and cannot be incorporated as a battery separator. Japanese Patent Application Laid-Open No. 4-174964 discloses a fiber comprising a mixture of a sulfonated polystyrene and a polyolefin. there were. Further, the strength of the obtained nonwoven fabric was not sufficient. Japanese Patent Application Laid-Open No. 60-99057 discloses a method of blending fibers by the melt blow method.
There has been disclosed a method for producing an ultrafine fiber nonwoven fabric in which various kinds of thermoplastic resins are combined in a parallel type and spun by a melt blow method. Japanese Patent Application Laid-Open No. 7-82649 discloses an ultrafine mixed fiber product comprising a high melting point component and a low melting point component having a melting point difference of 10 ° C. or more, and a production method. These mixed-type nonwoven fabrics have low adhesive strength between fibers, and have been subjected to a fusion treatment by post-processing such as calendering to improve the dimensional stability of the nonwoven fabric, but the effect was not sufficient.

[0004]

The conventional nonwoven fabric containing polystyrene, which is easily sulfonated, has poor strength and elongation characteristics, so that the problem of breakage of the nonwoven fabric when passing through a manufacturing process, a processing process, or the like is likely to occur. . For example, when used for a battery separator, a high strength of at least about 5 kg / 5 cm is required from the viewpoint of permeability in a manufacturing process, and it is difficult to use polystyrene by itself. It has been considered to mix various fibers in order to improve the strength and elongation characteristics of the nonwoven fabric. However, fibers having a low elongation cause defects in the nonwoven fabric, so that the fibers are cut and the strength and elongation of the nonwoven fabric are reduced. Improvements in properties were very difficult. Also, the sulfonated polypropylene nonwoven fabric had insufficient hydrophilicity, and the self-discharge of the battery was not small. Furthermore, the ultrafine fiber nonwoven fabric corresponding to the demand for thinning has a low strength and elongation characteristic and is likely to cause a problem in processability.

[0005]

Means for Solving the Problems The present invention has been studied diligently to solve the above-mentioned problems, and has been developed for an alkaline (secondary) battery having good self-discharge and good process passability suitable for an alkaline battery separator. The following measures are taken to provide a nonwoven fabric particularly suitable as a separator.

That is, the present invention relates to a composite nonwoven fabric containing at least sulfonated polyolefin fibers, which has an ion exchange amount of 0.04 to 0.30 meq / g. is there. Preferably, the nonwoven fabric for a battery separator as described above, wherein the composite nonwoven fabric contains at least a sulfonated polystyrene fiber and an aliphatic polyolefin fiber. The nonwoven fabric for a battery separator as described above, wherein the sulfonated polystyrene fiber has an average fiber diameter of 1 μm to 20 μm, and the aliphatic polyolefin fiber has an average fiber diameter of 0.5 to 15 μm. The composite nonwoven fabric has a thickness of 50 to 150 μm and a basis weight of 15 to 1
The nonwoven fabric for a battery separator according to the above, wherein the nonwoven fabric has a weight of 00 g / m ² . The nonwoven fabric for a battery separator as described above, wherein the sulfonated polystyrene fiber is produced by a melt blow method. The nonwoven fabric for a battery separator as described above, wherein 25 to 85% of the total weight of the nonwoven fabric is composed of polypropylene fibers, and the total surface area of the polypropylene fibers is equal to or greater than the total surface area of the sulfonated polystyrene fibers. The nonwoven fabric for a battery separator according to the above, wherein the fiber arrangement frequency in one direction of the nonwoven fabric is 25 to 150% higher than the fiber arrangement frequency in the direction perpendicular to the direction. The nonwoven fabric for battery separator as described above, wherein the crimped polyolefin fiber is contained in an amount of 5 to 85% based on the total weight of the nonwoven fabric. Ultra high molecular weight polyethylene fiber having a strength of 10 to 50 g / d or more is 5 to 10% based on the total weight of other components.
The nonwoven fabric for battery separator according to the above, wherein the nonwoven fabric is contained at 0%.

Hereinafter, the present invention will be described in detail. Polyolefin fibers that can be suitably used in the composite nonwoven fabric of the present invention include, for example, aromatic polyolefin fibers such as polystyrene fibers and aliphatic polyolefins such as polyethylene fibers and polypropylene fibers,
The means for producing the fibers is generally melt spinning. As a method for producing ultrafine fibers suitable for the present invention, sea-island or split type composite spinning may be performed, followed by elution or splitting of sea components. However, the splittable fibers are not necessarily preferable because the fibers need to be split by applying a mechanical external force by a water flow or the like, and the number of steps increases.
In order to produce ultrafine fibers at low cost, it is considered particularly preferable to use the melt blow method. Polystyrene has the disadvantage that the fiber obtained due to the problem of crystallinity of the polymer tends to have low elongation, but has many suitable characteristics such as a high melting point and easy chemical modification. In particular, syndiotactic polystyrene is suitable as a functional material because of its excellent workability, heat resistance, chemical resistance and the like. Also,
As the aliphatic polyolefin, polyethylene and polypropylene are common but not particularly specified,
It is desirable that the composition has good alkali resistance.

The inventor of the present invention has proposed, as one ideal configuration of a nonwoven fabric suitably used as a battery separator, two types of fibers having different characteristics in order to satisfy various required characteristics such as strength balance and liquid retention. It has been confirmed that it is necessary to share the functions by using the above.
Here, the different characteristic means that there is a difference in composition such as a kind of a polymer, or a difference in form such as a cross-sectional shape or a fiber diameter of a fiber. The mixed state may be uniform or may have non-uniformity such as a density gradient. It is presumed that the same effect can be obtained by mixing different types of polymers to form fibers, but it is difficult to obtain thin fibers due to instability in the fiber manufacturing process and deterioration in operability, which is less preferable. Absent. Also, kneading a water-soluble component such as ethylene glycol into the polymer is not preferable because it is thought that elution to the battery electrolyte is likely to occur and self-discharge of the battery is induced.
When mixing in a polymer state such as kneading is indispensable for some reason, it is considered that the mixing amount is preferably at most 3% or less.

The ion exchange amount of the nonwoven fabric is 0.04 to 0.3
It needs to be between 0 meq / g. Within the range studied by the present inventors, the ion exchange amount was 0.04 meq /
When the ion exchange amount is larger than 0.30 meq / g, the self-discharge characteristics do not directly affect the self-discharge characteristics, but the constituent fibers such as polystyrene and aliphatic polyolefin are not preferable. Was excessively advanced, and the fibers were damaged, and the strength of the nonwoven fabric was extremely reduced.
It is preferable that the sulfonated nonwoven fabric has a small amount of impurities, and it is particularly preferable that the nonwoven fabric is thoroughly washed with pure water or a liquid having the same quality as the electrolytic solution. Further, when the ion exchange amount is large, hydrophilicity is increased, and there is an advantage that the separator is easily wetted with the electrolytic solution.

In the present invention, sulfonated polystyrene fibers are suitably used as one component of the composite nonwoven fabric, but the average fiber diameter is preferably between 1 and 20 μm. If the average fiber diameter of the polystyrene fiber is smaller than 0.5 μm, the strength of the nonwoven fabric becomes particularly weak, which is a problem. It is particularly preferred that the average fiber diameter of the polystyrene fibers is between 2 and 12 μm. When aliphatic polyolefin fibers are used as the mixed component, the average fiber diameter is preferably between 0.5 and 15 μm, particularly preferably between 1 and 6 μm. When the aliphatic polyolefin fiber is used in combination with polystyrene, it acts as a binder for the polystyrene fiber having low elongation in the composite nonwoven fabric, so that the elongation is 40%.
If it is smaller, the elongation at break of the nonwoven fabric after composite becomes small, which is problematic. Therefore, it is desirable that the elongation is 40% or more from the viewpoint of processability. In many cases, it is difficult to process at 10% or more. In addition, the composite nonwoven fabric of the present invention is preferably improved so that the strength of the nonwoven fabric is increased by strengthening the adhesion between fibers by means of heat fusion such as calendering. Since the degree decreases, it is necessary to properly balance the high elongation in consideration of the processability. However, if the elongation of the aliphatic polyolefin fiber is low, the condition range for calendering becomes extremely narrow, and the desired strong elongation balance cannot be obtained, or even if possible, the setting range of the conditions is extremely narrow and adjustment is difficult. became.

It is necessary that the fibers used in the present invention include at least fibers which have been sulfonated. It is presumed that the sulfonation improves the wettability of the liquid, and improves the liquid retention and rapid chargeability. As a method of sulfonation treatment, a method of performing heating concentrated sulfuric acid treatment in a liquid phase or a treatment by sulfurous acid gasification can be considered, but sulfonation is performed in a gas phase of a sulfurous acid gas atmosphere that does not reduce the strength of the nonwoven fabric less. Is preferred. It is preferable that the sulfonation treatment is performed at a temperature of 100 ° C. or less where the strength and elongation characteristics of the fiber are not significantly reduced. In addition, after sulfonation, since impurities are duplicated during the treatment, it is necessary to wash well with pure water or the like. Since polystyrene is more easily sulfonated than aliphatic polyolefin, one of the constituents of the present invention is polystyrene.
It is particularly preferable to use one.

When polypropylene fibers are used as the aliphatic polyolefin, the mixed component ratio is preferably from 25% to 85%, particularly preferably from 50% to 70% of the total weight of the nonwoven fabric. If it is less than 25%, the reinforcing effect as a binder will be small. When the sulfonation ratio is higher than 85%, the fiber is greatly damaged at the time of sulfonation treatment, and the mechanical properties thereof are deteriorated.

The thickness of the composite nonwoven fabric is 50 to 150.
It is desirable to be between μm. If the thickness is less than 50 μm, the liquid retaining property of the electrolytic solution is reduced and the shielding property is reduced, which is not preferable. In addition, the strength of the nonwoven fabric is undesirably reduced. Conversely, if it is larger than 150 μm, the size of the battery is undesirably increased.

The total basis weight of the composite nonwoven fabric is 15 to 10
Desirably, it is between 0 g / m ² . 15g / weight
If it is smaller than m ^2, no effect of improving the strength by the composite was observed. This is presumed to be because it is difficult to uniformly disperse the olefin fibers and the olefin fibers are ubiquitous. On the other hand, if it is more than 100 g / m ^2, there is no need to improve by combining. 40 when used as a battery reparator
８０80 g / m ² was particularly preferred.

Further, the tensile strength of the composite nonwoven fabric is 1.5 to
The width is preferably 30 kg / 5 cm. 1.5kg
When the width is smaller than / 5 cm width g, there is a problem that the nonwoven fabric is easily cut in the calendering step for improving the strength or the laminating step with the reinforcing material. In particular, in battery separator applications, the width is preferably 5 kg / 5 cm or more, and more preferably 7 kg / 5, since it is used on a tape having a narrow width.
cm width or more, particularly preferably 10 kg / cm or more. In the nonwoven fabric of the present invention, it is also preferable to improve the strength of the nonwoven fabric by strengthening the adhesion between the fibers by means of heat fusion such as calendering.

The polystyrene fiber usable in the present invention is M
Desirably, the fiber is made of a polymer having an FR of 20 to 500 g / 10 min. This MFR range was a range in which an instability phenomenon did not occur when polystyrene was formed into fibers by melt spinning. Further, it is desirable that the MFR of the fiber composed of the aliphatic polyolefin is larger than the MFR of the organic fiber such as polystyrene, and is 20 to 1000 g / 10 min. It is considered that the fact that the MFR of the aliphatic polyolefin is large means that the fiber functioning as a binder has a high fluidity at the time of the heat bonding treatment and can increase the bonding area between adjacent fibers. Further, when fiberization is performed by the melt blow method, there is an effect that the fiber is easily made thinner.

Hereinafter, the role of the aliphatic polyolefin fiber in the composite nonwoven fabric containing polystyrene having a low elongation will be described. Aliphatic polyolefin fibers with relatively high elongation are entangled with low-elongation polystyrene fibers to increase the adhesion between fibers and to prevent deformation of low-elongation fibers by deforming themselves. do. Therefore, the fiber diameter of the aliphatic polyolefin fiber with high elongation is
It is preferably smaller than 75% of the fiber diameter of the low elongation polystyrene fiber. This is because the aliphatic polyolefin fiber with good adhesiveness and high elongation wraps around the low elongation polystyrene fiber, so that the aliphatic polyolefin fiber length is relatively long and the bending resistance of the fiber is smaller. It is presumed that it is necessary.

[0018] In the scope of the present inventors, when polypropylene fibers and polystyrene fibers are used as the constituent fibers, the mixing ratio of the polypropylene fibers or the fibers is adjusted so that the surface area of the polypropylene fibers in the nonwoven fabric is equal to or larger than the surface area of the polystyrene fibers. Adjusting the diameter was particularly preferred for improving the balance between the strength of the nonwoven fabric and the hydrophilicity.

In the present invention, it is particularly preferable that at least one component of the fibers constituting the composite nonwoven fabric is a fiber produced by a melt blow method and having an average fiber diameter of 0.5 μm to 12 μm. The reason is that if the fiber diameter of the fibers constituting the non-woven fabric used for the filter application is small, the filtration performance can be improved, so that the fiber diameter of 10 μm or less is very suitable for this application. Also in the battery separator, it is necessary to make the fibers extremely thin in order to improve the liquid retaining property and the cover property with a small thickness. Generally, the strength of a nonwoven fabric made of ultrafine fibers is low, and the effect of improving the strength and elongation of the nonwoven fabric according to the present invention is large. However, if the average fiber diameter is smaller than 0.5 μm, there is little room for improvement in strength, which is not preferable.

Since the composite nonwoven fabric of the present invention has a small fiber diameter, the strength of the nonwoven fabric tends to decrease. As a method of increasing the strength of the nonwoven fabric, the fiber arrangement frequency in one direction of the nonwoven fabric is 25 to 150% higher than the fiber arrangement frequency in the direction perpendicular to the direction.
Higher is desirable. It has been found that when the fiber arrangement amount is large, the strength and elongation characteristics in that direction are improved even in the composite nonwoven fabric. As a method of changing the fiber arrangement, a method such as using a parallel card machine, or using a force such as wind to drop the fibers from the non-vertical direction to the collecting surface when forming a nonwoven sheet into a sheet is considered. Can be Generally, it is considered that the fibers are arranged in the machine direction of the nonwoven fabric so that the process-passing property is good, but it is presumed that the fiber arrangement method can be changed depending on the application to which the fibers are applied. Fiber alignment in the direction where higher strength is desired is 25 times greater than in the orthogonal direction.
% Or more is desirable. If it is smaller than that, the properties of the nonwoven fabric are isotropic, and fibers with low elongation become defects, and the nonwoven fabric becomes inferior in high elongation properties. On the other hand, if the sequence is 15
If it is higher than 0%, when the tension is applied in this direction, the width of the sheet in the direction perpendicular to the direction becomes large, and the uniformity of the entire sheet is impaired, which is not preferable.

Further, as a means for improving the strength and elongation characteristics and piercing resistance of the composite nonwoven fabric of the present invention, a strength of 10 to 50 is used.
It is preferable that the ultra-high molecular weight polyethylene fiber having a weight average molecular weight of 1,000,000 or more of g / d is contained as a third component in an amount of 5 to 100% based on the total mass of the other composite nonwoven fabric. Polyethylene has a stable chemical structure and is not easily degraded in the fiberization and post-processing steps, and has good weather resistance. Therefore, there is no need to add various stabilizers, so that there is no problem of sediment in the battery separator electrolyte. Due to its excellent mechanical properties and chemical stability, ultra-high molecular weight polyethylene compensates for the decrease in strength of nonwoven fabric due to thinning and ultra-fine nonwoven fabric,
It is preferable to add the electrode because it is possible to prevent the protrusion of the electrode from piercing the separator to form a hole. If the amount of the fiber is less than 5% of the total weight of the nonwoven fabric, the effect of improving the strength characteristics and the like is not so large. On the other hand, if it exceeds 100%, the amount of the original functional fibers is so small that characteristics such as hydrophilicity cannot be obtained, and the elongation of the nonwoven fabric is undesirably small. As a method for mixing the ultrahigh molecular weight polyethylene fibers, in the case of spinning by a melt blow method, a blowing method called coform is preferable. When other nonwoven fabric manufacturing methods are applied, means such as mixing the raw materials before card processing or papermaking can be used. As the form of the polyethylene fiber, a short fiber having a length of 3 to 20 mm is preferable when the method for producing the nonwoven fabric is a wet method, and a short fiber having a length of 25 to 80 mm is preferable when the method is a dry method. It is also preferable to make these short fibers crunch in order to improve the elongation of the nonwoven fabric.

When polystyrene fibers are used as one component of the composite nonwoven fabric, the fact that crimped polyolefin short fibers are contained in an amount of 5 to 85% based on the total weight of the nonwoven fabric increases the strength of the nonwoven fabric. It is preferable in doing. When the polyolefin fibers are opened by a card, there is an effect that the fibers can be separated one by one due to the presence of crimps. The olefin fiber preferably has a crimp number of 0.5 to 6 d, a crimp number of 10 to 25 co / inch, and a crimp rate of 5 to 30%. When the mixing amount of the fibers is less than 5%, the effect of improving the strength is small. On the other hand, when the mixing amount is more than 85%, the uniformity of the nonwoven fabric is impaired, the unevenness becomes large, and the discharge capacity retention rate is lowered.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to embodiments. The physical properties shown in the examples were measured by the following methods.

A. Average fiber diameter (μm) A scanning micrograph of the fiber was taken at a magnification of 1000 times, and the width of the side of 1000 fibers arbitrarily extracted from the photograph was measured and determined by arithmetic mean. The method of distinguishing different fibers can also be confirmed by examining the fine fibers having different dyeing properties after dyeing, and when there is a difference in melting point, heating the nonwoven fabric by a hot stage or the like and observing the molten state of the fibers.

B. Weight (g / m ² ) Five sheets are cut out in a fixed area and weighed with a precision balance. The measured values were arithmetically averaged and converted to about 1 m ² to obtain the basis weight.

C. Thickness (μm) The thickness at the center of each sheet under a load of 20 g / cm ² was 5
The points were measured and the arithmetic average was taken as the thickness of the nonwoven fabric.

D. Nonwoven fabric strength The nonwoven fabric was cut into a rectangle having a width of 5 m and a length of 20 cm, set in a tensile tester, measured at a test length of 10 cm and a tensile speed of 20 cm / min, and the maximum stress at break was obtained.

E. Fiber arrangement distribution The fiber arrangement was evaluated by a method called code tracking. Specifically, after taking a scanning electron micrograph of the nonwoven fabric and thinning it to one pixel by image processing, a random point called a seed is designated, and the arrangement direction of the thin line near the point is computer-processed. Was measured by For details of the principle and measurement method, see Textile Research Journal, 66, (12).
745-753 (1996). The image analysis program is scheduled to be released from Toyobo Co., Ltd. in 1998. ± 15 of fiber arrangement angle in representative direction
The frequency in the degree direction was defined as the fiber arrangement frequency in the representative direction. In the embodiment, the arrangement state is described using the ratio of the frequency in the machine direction (M direction) and the frequency in the cross direction (C direction) which is a direction perpendicular to the machine direction.

F. After cutting out a sample with an ion exchange amount of about 30 cm ² and measuring the weight,
It was determined by performing a neutralization titration with 0.1 N potassium hydroxide. The values per unit weight are shown based on the weight at the time of drying.

Re. Nickel metal hydride battery capacity retention rate A nickel metal hydride battery having a 2,500 mAh capacity was prepared. After the battery was fully charged, the battery was allowed to stand at 40 ° C. for 7 days, and the discharge capacity was 100%. Indicated.

Examples 1-4 PP with MFR of 200-500 g / 10 min and MFR160
g / 10 min and 300 g / 10 min of syndiotechtech polystyrene were alternately transferred from adjacent orifices to 29 g / min.
Single hole discharge rate 0.25 to 0.75 g / min at 5 ° C
Extrusion was changed within a range of 30 at 0.8 kg / cm ²
The melt-blown nonwoven fabric having an average fiber diameter of polypropylene of 2 to 5 μm, an average fiber diameter of polystyrene of 5 to 6 μm, and a basis weight of about 50 g / m ² was obtained by drawing and thinning with an air flow of 0 ° C. . The thickness of the obtained nonwoven fabric was adjusted by calendering. Table 1 summarizes the properties of the nonwoven fabric. Regardless of the expectation that the larger the fiber diameter of the polypropylene fiber was, the higher the nonwoven fabric strength was, it was recognized that the smaller the fiber diameter of the polypropylene fiber was compared to the fiber diameter of the polystyrene fiber, the higher the nonwoven fabric strength was. Further, when the nonwoven fabric was formed so that the fibers were more arranged in the machine direction (M direction), the strength of the nonwoven fabric in that direction was greatly improved. The obtained nonwoven fabric was subjected to a sulfonation treatment in a sulfurous gas atmosphere to evaluate battery performance.

Comparative Examples 1-2 Syndiotechtech Polysty with MFR of 160 g / 10 min
At a temperature of 295 ° C., a single hole discharge rate of 0.5 g / min
Extruded after changing in the range of 0.8kg / cm ^TwoAt 30
It is made to draw and thin by an air flow of 0 ° C and the average fiber diameter becomes the average fiber diameter.
Is 50 g / m of 6 μm^TwoMelt blown non-woven fabric
Was. The thickness of the obtained nonwoven fabric is adjusted by calendering
did. Table 1 shows the properties of the obtained nonwoven fabric. Real
Since the amount of ion exchange is smaller than in Examples 1 to 4,
Poor ownership was a problem.

Examples 5 to 6 When spinning under the same conditions as in Example 1, 38 mm long short fiber ultra-high molecular weight polyethylene (Dyneema fiber manufactured by Toyobo Co., Ltd.) (UHMWPE in the table) was weighed against other materials. 6 in total
Blowing for 7% to 11% was performed. The blowing method is to send a short fiber non-woven fabric, which has been card-spread in advance, to an anti-hair machine, to loosen the fibers, and then to feed the melt blow traction gas by a secondary air flow. The fibers were uniformly dispersed in the nonwoven. The thickness of the obtained nonwoven fabric was adjusted by calendering. The properties of the obtained nonwoven fabric are shown in Table 1. The strength of the non-woven fabric was greatly improved by mixing short fiber ultra high molecular weight polyethylene. The higher the mixing amount, the better the strength.

Example 7 When spun under the same conditions as in Example 1, a fiber having a length of 51 mm and having a number of crimps of 15 cores / inch and a crimp rate of 15% was made of polyethylene and a core of polypropylene. About 11% of the total weight of the material was blown. The blowing method is
The short-fiber non-woven fabric that has been card-spread in advance is sent to the anti-hair machine, the fibers are loosened, and then sent into the melt-blowing traction gas by the secondary air flow. Was dispersed uniformly. The thickness of the obtained nonwoven fabric was adjusted by calendering. The nonwoven fabric properties are shown in Table 1. The strength of the nonwoven fabric was greatly improved by mixing the core-sheath composite fibers.

[0035]

[Table 1]

[0036]

According to the present invention, it is possible to provide a non-woven fabric for a separator for an alkaline secondary battery having excellent strength and elongation characteristics and low self-discharge. Further, since the nonwoven fabric of the present invention has an ion exchange group, it can be usefully applied as a chemical filter in a gas phase and a liquid phase.

Claims (9)

[Claims] 1. A non-woven fabric for a battery separator, comprising a composite non-woven fabric containing at least sulfonated polyolefin fibers, wherein the ion exchange amount is 0.04 to 0.30 meq / g. 2. The nonwoven fabric for a battery separator according to claim 1, wherein the composite nonwoven fabric contains at least a sulfonated polystyrene fiber and an aliphatic polyolefin fiber. 3. The sulfonated polystyrene fiber has an average fiber diameter of 1 μm to 20 μm, and the aliphatic polyolefin fiber has an average fiber diameter of 0.5 μm to 15 μm. The nonwoven fabric for a battery separator according to item 1. 4. The composite nonwoven fabric has a thickness of 50 to 150 μm.
In battery separator for non-woven fabric according to claim 1, wherein the basis weight is 15 to 100 / m ^2. 5. The nonwoven fabric for a battery separator according to claim 1, wherein the sulfonated polystyrene fiber is produced by a melt blow method. 6. A nonwoven fabric comprising 25 to 85% of the total weight of polypropylene fibers, wherein the total surface area of the polypropylene fibers is equal to or greater than the total surface area of the sulfonated polystyrene fibers. 5. The nonwoven fabric for a battery separator according to any one of 5. 7. The nonwoven fabric for a battery separator according to claim 1, wherein a fiber arrangement frequency in one direction of the nonwoven fabric is 25 to 150% higher than a fiber arrangement frequency in a direction perpendicular to the direction. . 8. The nonwoven fabric for a battery separator according to claim 1, wherein the crimped polyolefin short fiber is contained in an amount of 5 to 85% based on the total weight of the nonwoven fabric. . 9. An ultrahigh-molecular-weight polyethylene fiber having a strength of 10 to 50 g / d or more is 5 to 50% of the total weight of other components.
9. The composition according to claim 1, wherein the content is 100%.
The nonwoven fabric for a battery separator according to any one of the above.