JP3411089B2 - Nonwoven fabric, method for producing the same, and battery separator using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a nonwoven fabric, a method for producing the same,
And a battery separator using the same.

[0002]

2. Description of the Related Art Conventionally, a so-called hydroentangling method has been known as a method for producing a nonwoven fabric, in which a fiber web is entangled with a water stream to entangle the fibers. In the general hydroentangling method, since the nozzles for ejecting water are arranged and fixed in a direction perpendicular to the moving direction of the long fibrous web, the water flowing in the moving direction of the fibrous web (long direction) is However, there was a problem that the entanglement locus due to remained and deteriorated the quality of the obtained nonwoven fabric. For example, when a nonwoven fabric obtained by the hydroentanglement method is used as a battery separator, it has a entanglement locus due to the water flow, that is, a relatively large hole, so that a dendritic metal generated at the time of discharging and / or charging the battery There is a problem in that a short circuit due to the precipitation of so-called (so-called dendrite) or a short circuit due to the movement of the electrode active material is likely to occur and the service life is short.

Therefore, a method of jetting water while rotating and / or simply vibrating the nozzle so that an entanglement locus is not generated by the water entanglement method (Japanese Patent Publication No. 61-60186).
No. 1, Japanese Patent Publication No. 18181, Japanese Patent Laid-Open No. 3-14693, etc.) or a method in which a net or an opening plate is installed between a nozzle and a fiber web to scatter water (Japanese Patent Laid-Open No. 5-239753).
No.) etc. have been proposed. However, even if the hydroentanglement is performed by such a method, a entanglement locus to some extent remains, which is not a fundamental solution.

On the other hand, in order to improve the quality of the nonwoven fabric,
After laminating fibers or pulp-like materials that are thinner than the fibers that make up the fiber web on the base fiber web, they are entangled with a water stream to form thin fibers or pulp-like materials between the base fiber webs. Filling method (Japanese Patent Laid-Open No. 54-1207).
No. 83) is also proposed. However, even in this method, although the entanglement locus can be made inconspicuous, it is not a method of completely eliminating the entanglement locus.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and has no entanglement locus,
An object of the present invention is to provide a nonwoven fabric having a uniform surface condition, a method for producing the same, and a battery separator using the same.

[0006]

In the nonwoven fabric of the present invention, the fibrous substance is adhered to the entangled fiber web in which the sparse portion is mixed by flowing the dispersion liquid of the fibrous substance into at least the sparse portion. The average pore size is 12 μm or less.

In the method for producing a nonwoven fabric according to the present invention, a entanglement treatment is performed on a fibrous web to form an entangled fibrous web in which sparse parts are mixed, and then a fibrous material is formed on one surface of the entangled fibrous web. This is a method in which the dispersion is allowed to flow down and the fibrous material is attached to at least the sparse portion of the entangled fiber web.

The battery separator of the present invention is made of the above non-woven fabric, and the non-woven fabric has an air permeability (F) of 0 <F≤20 (cc / c).
m ² / sec) is suitable for a sealed battery, and the basis weight of the entangled fiber web is 20 to 80 g / m ² and the amount of fibrous material attached is 0.3 to 15 g / m ² . Therefore, a short circuit due to the movement of dendrites or electrode active materials is unlikely to occur.

Further, when the entangled fiber web is mainly composed of polyolefin fibers having a fineness of 0.6 denier or less, it is excellent in uniformity, and when hydrophilized, it is used as a separator for alkaline batteries. It is suitable.

Further, the thickness of the fibrous material is 0.1 to 150 μm.
And a fibrillar substance having a length of 1 to 5 mm is excellent in adhesiveness to the entangled fiber web, and a non-woven fabric having a uniform surface state is obtained, and the fibrous substance has a fibrillar branched structure. If it is, the adhesive force to the fiber web is strong.
Moreover, when the fibrous material is made of a polyolefin resin and more preferably subjected to a hydrophilic treatment, it is suitable as a separator for an alkaline battery.

[0011]

In the nonwoven fabric of the present invention, the fibrous material is attached to at least the sparse portion of the entangled fiber web in which the sparse portion is mixed.
The average pore size is 12 μm or less. Thus, the non-woven fabric of the present invention is a non-woven fabric having a uniform surface state with an average pore diameter of 12 μm or less, in which a fibrous substance is adhered to the sparse portion of the entangled fiber web to eliminate the entanglement locus. is there.

As described above, since the nonwoven fabric of the present invention has a uniform surface state with no entanglement locus, it is used as a separator for batteries, medical concealment base materials (gowns, leak-proof sheets, etc.), filters, and synthetic materials. It can be suitably used for various applications such as a leather substrate, an electrical insulating substrate, an FRP substrate, and a patch substrate. Hereinafter, the nonwoven fabric of the present invention will be described in more detail with a focus on the case where it is used for battery separators.

The type, fineness, fiber length, etc. of the fibers constituting the entangled fiber web of the present invention may be appropriately selected according to the use of the nonwoven fabric. For example, when used as a separator for an alkaline battery, 50% by weight of a polyolefin fiber having excellent alkali resistance and oxidation resistance is used.
Above, more preferably 70% by weight or more, most preferably 100% by weight.

Examples of the polyolefin fiber include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl alcohol copolymer,
Ethylene-butene-propylene copolymer, methyl pentene, and fibers consisting of a single resin component such as a polyolefin resin component such as polyethylene or polypropylene graft-polymerized with a hydrophilic group such as maleic acid, and these resin components Concentric circle or eccentric core-sheath type, side-by-side type composite fibers, or chrysanthemum flowers in which one component 1 is arranged between the other components 2 as shown in FIGS. 1 (a) to 1 (d). With a fiber-shaped cross section,
As shown in (e), a splittable or non-splittable conjugate fiber having a layered fiber cross section in which one component 1 and another component 2 are alternately laminated can be used.

When the fineness of the fibers constituting the entangled fiber web of the present invention is 0.6 denier or less, the surface area of the fibers is large, so that the affinity with the electrolytic solution is high and the retaining property of the electrolytic solution is excellent. So, fiber weight less than 0.6 denier is 50% by weight
It is preferably contained in the above amount, and most preferably 70% by weight or more. A fiber having such a fineness can be easily obtained by splitting the above-mentioned splittable conjugate fiber. In addition, this splittable conjugate fiber,
Since it can be divided at the same time as being entangled by the entanglement treatment, it is not only preferable in manufacturing, but the distance between the entanglement points of the fiber is short
Since the voids are also minute and dense, a capillary effect is generated, the electrolyte retaining property is excellent, and a short circuit due to the physical movement of the dendrite or the electrode active material can be physically prevented, so that it can be suitably used.

Even if the splittable conjugate fiber is contained, it is not necessary to split it completely or completely, and preferably 50% or more, more preferably 80% or more. The degree of splitting of the splittable conjugate fiber can be easily confirmed by a 20 × or more magnifying microscope.

The finer the fibers constituting the entangled fiber web are, the more easily the capillary effect is generated, and the holding power of the electrolytic solution is increased to prolong the service life. However, if the fibers are too thin, the voids formed are minute. Not only does it increase the electrical resistance, but also the strength is lost, so the fineness of the fiber is 0.
It is preferably from 01 to 0.6 denier, more preferably from 0.05 to 0.4 denier.

The splittable conjugate fiber containing a polyethylene resin component and a polypropylene resin component is excellent not only in electrolytic solution resistance, but also when subjected to a hydrophilic treatment such as sulfonation or fluorine treatment described later, Since the polyethylene resin component and the polypropylene resin component have different degrees of hydrophilicity, they have good gas permeability and are particularly suitable for use in a sealed secondary battery. That is, while the polyethylene resin component is relatively easily hydrophilized, the polypropylene resin component is hard to be hydrophilized,
Since the polyethylene resin component easily holds the electrolytic solution, the polypropylene resin component becomes in a state of poor electrolytic solution, and the generated gas can be quickly transmitted to the other electrode,
Even when it is used as a separator of a sealed secondary battery, the internal pressure does not rise, so there is no danger of bursting.

In order to improve the dimensional stability of the fibrous web, it is preferable to partially heat-bond the fibrous web. As this method, there is a method of fusing one fusible ultrafine fiber obtained from the splittable conjugate fiber constituting the fibrous web, or fusing a mixed low melting point polyolefin-based fusing fiber. In the case of fusing one of the ultrafine fibers constituting the former fiber web, so as not to destroy the micropore structure of the fiber web, for example, than the melting point of the resin component having the lowest melting point constituting the fiber web, 5-15 ° C
It is necessary to take measures such as significantly shortening the treatment time even if the treatment is carried out at a relatively low temperature or even at a temperature higher than the melting point of the resin component.

On the other hand, in the case of incorporating the latter low melting point polyolefin fusion bonding fiber and fusing, if the fineness of the polyolefin fusion bonding fiber is 1 denier or more, the surface condition of the obtained fiber web becomes rough, Moreover, since the retention of the electrolytic solution is likely to be lowered due to the fusion of the hydrophobic polyolefin-based fusion fiber, it is preferably 50% by weight or less in the fiber web,
More preferably, it is preferable to keep it to 30% by weight or less.
Examples of the low melting point polyolefin fusion-bonded fiber include, for example, low-density polyethylene, medium-density polyethylene, ethylene-vinyl alcohol copolymer, and other resin components, all-melt type fiber, or partially melt-type core-sheath type fiber. , Side-by-side type, eccentric type and the like can be used. The fused fibers are preferably fused at a temperature lower than the melting point of any resin component of other fibers constituting the fiber web so as not to impair the retention of the electrolytic solution by the other fibers. . On the other hand, the fineness of the fused polyolefin fiber is 1
If it is less than denier, the content in the fiber web is not limited, but it is necessary to appropriately set the fusion bonding conditions so as not to destroy the micropore structure of the fiber web.

Among these low melting point polyolefin fusion-bonded fibers, the partially melted composite fibers can be preferably used because the strength of the fusion-bonded fibers can be maintained by the non-melting resin component. Further, among the partially melted conjugate fibers, when the conjugate fiber containing the polypropylene resin component and the polyethylene resin component is hydrophilized, as in the case where the splittable conjugate fiber is hydrophilized, a closed secondary Even when gas is generated in the battery, the gas can be quickly transmitted to the other electrode, and the internal pressure does not rise, so there is no danger of bursting and it can be used favorably.

As described above, when the fibrous web contains fusible fibers, it may be fused by heat treatment or the like before the entanglement treatment, after the entanglement treatment, or after the adhesion treatment of the fibrous material described later. In this case, the dimensional stability can be improved.

The fineness and fiber length of the fibers as described above are not particularly limited, but fibers having a fineness of 1 to 10 denier and a fiber length of 3 to 60 mm can be suitably used.

Examples of the method for forming a fiber web from such fibers include a dry method such as a card method and an air lay method, a wet method, a spun bond method, a melt blow method, and the like. Since it is possible to form a uniform fibrous web with, it is a preferable method for forming a fibrous web.

When the fibrous web is formed by the card method, the fibers may be oriented in one direction, or may be oriented so as to intersect with each other by a cross layer, or these fibrous webs may be laminated. Among these, the fiber web containing fibers oriented so that the fibers intersect, the subsequent entanglement treatment, the fibers are easily entangled,
Since the strength is excellent and the difference in strength between the vertical direction and the horizontal direction is small, it is a suitable orientation direction of the fiber web.

When the fibrous web used as the separator for the battery contains the low melting point polyolefin fusion bonding fiber, a fiber web layer of only the low melting point polyolefin fusion bonding fiber is formed and adhered to the layer. However, when it contains a low melting point polyolefin-based fused fiber, it is preferably mixed with another fiber.

By subjecting the above fiber web to entanglement treatment such as hydroentanglement or needle punching,
An entangled fiber web in which sparse parts are mixed is formed. Among these, the hydroentangling treatment is a more preferable entanglement treatment because the whole fibrous web can be tightly entangled. Hereinafter, description will be given based on the hydroentangling process.

When a nonwoven fabric is used for a battery separator, when the fiber web is entangled with a water stream, the fibers are oriented in the substantially thickness direction of the fiber web. Of course, the entangled fiber web has excellent resistance to the electrolytic solution even when the electrode plate is expanded as in a secondary battery, as well as being able to withstand pressure. Further, when the splittable conjugate fiber is included as the constituent fiber of the fiber web, the ultrafine fibers obtained by splitting are closely entangled, so that not only the strength is excellent, but also the entangled fiber web can be thinned. It is possible to fill the battery with a large amount of the electrode active material by the amount of the thinning, so that the battery can have a high capacity. Furthermore, since the oil agent attached to the fibers can be washed away by the hydroentangling treatment, not only the adverse effect of the oil agent on the battery performance can be eliminated, but also the hydrophilic treatment described below can be efficiently and stably performed, which is preferable.

As the water entanglement treatment, for example, the nozzle diameter is 0.05 to 0.3 mm, more preferably 0.10 to 0.1.
8 mm, pitch 0.2 to 3 mm, more preferably 0.4 to 1.
A nozzle plate having 2 mm arranged in a line or a nozzle plate having nozzles arranged in two or more lines in a lattice or staggered pattern is used, and the treatment is carried out with a water flow having a water pressure of 10 to 300 kg / cm ² . Such hydroentangling treatment need not be performed once, and may be performed twice or more. Also, the surface to be treated with the water flow does not have to be only one side of the fiber web, and both sides may be treated, and after first lightly treating with 10 to 30 kg / cm ² , 50 kg
It is preferable to treat at a rate of / cm ² or more.

In the hydroentangling treatment, if the support, such as a net or a perforated plate on which the fiber web is placed, has large holes, the entangled fiber web obtained will also have large holes. Therefore, the diameter of the wire or filament constituting the net is 0.08 to 0.3 mm, and more preferably 0.0 to 0.3 mm.
1 to 0.2 mm, fine mesh of 50 mesh or more, more preferably 70 to 120 mesh woven plain weave net, average area per hole is 0.01 to 0.08 mm ² ,
More preferably, it is 0.02 to 0.05 mm ² , and the porosity is 20 to
It is preferred to use a support having a porous structure of 40%, more preferably 25-35%.

The entangled fiber web obtained by such a hydroentangling method has, as schematically shown in FIG. 2 (a), a porous sparse portion 4 having few fibers or no fibers at all. It is a mixture. In the sparse portion, the hole-shaped sparse portion 4 has a hole diameter (the longest length that can be taken) of 0.5 mm or less, more preferably 0.2 mm or less. In the entangled fiber web, the area of 4 is preferably 10% or less, more preferably 5% or less. This is because if the hole diameter of the hole-shaped sparse portion 4 exceeds 0.5 mm or exceeds 10% in the entangled fiber web, the fibrous material, which will be described later, cannot easily completely adhere to the sparse portion. . The hole-shaped sparse portion 4 can be measured from the shadow formed by shining light from one surface of the entangled fiber web.

The basis weight of the entangled fiber web thus obtained is not particularly limited and may be appropriately selected depending on the intended use of the nonwoven fabric. For example, when used as a battery separator, it is preferably ²⁰ to 80 g / m ² . If it is less than 20 g / m ² , the absolute amount of fibers is small, so the electrolyte retention is poor, and if it exceeds 80 g / m ² , the thickness of the nonwoven fabric obtained becomes thicker, and the electrode active material that can be filled in the electrode is This is because the amount becomes smaller. In the case where entangled fiber web is mainly composed of the following fibers 1 denier is preferably from basis weight 30~70g / m ^2, more preferably from 40 to 60 g / m ^2. On the other hand, when the entangled fiber web is mainly composed of fibers having a denier of more than 1 denier, the basis weight is preferably 50 to 75 g / m ² .

Entangled fiber web 3 obtained as described above
Of the non-woven fabric 6 of the present invention by attaching the fibrous material 5 to at least the sparse part, and if necessary, to the part other than the sparse part.
(See FIG. 2B).

The fibrous material in the present invention has a thickness of 0.1 to 15 so that it can be attached to a sparse portion of the entangled fiber web.
It is preferably 0 μm. If the thickness is less than 0.1 μm, the adhesion of the fibrous material to the entangled fiber web is poor, resulting in 15
When it exceeds 0 μm, the smoothness of the obtained nonwoven fabric surface is deteriorated, so that it is more preferably from 1 to 50 μm. The thickness of the fibrous material 5 is a value converted into a circular cross-sectional shape in the case of a fibrous material having an irregular cross-sectional shape,
In the case of the fibrous material 5 ′ having a fibrillar branched structure, it means the thickness of the unbranched trunk portion (D in FIG. 3).

The length of the fibrous material is preferably 1-5 mm. If it is less than 1 mm, it tends to pass through the sparse part of the entangled fiber web and the adhesion is poor. If it exceeds 5 mm, the fibrous materials are entangled with each other and the dispersibility is poor, and the adhesion is not uniform. Since it is hard to adhere inside the entangled fiber web, it is more preferably 1 to 3 mm. The length of the fibrous material refers to the length that can be taken the longest in the fibrous material, and if the fibrous material is curved, the length when straightened. Say.

The fibrous material having such thickness and length is
Preferably 50% by weight or more, more preferably 70% by weight
Above, most preferably 100% by weight is used.

As such a fibrous material, for example, those having a fibrillar branched structure, divided or non-divided fibers, and the like can be used, and more specifically, cellulose-based, acrylic-based, aramid-based , Polyethylene-based, polypropylene-based synthetic pulp, wood pulp, plant pulp such as linter pulp, cotton pulp, hemp pulp, acrylic fiber or cellulose fiber obtained by solvent spinning method, etc. to be fibrillated. Those with a branched structure, ultrafine acrylic fibers or polyester fibers with a fiber diameter of 5 μm or less, or polypropylene / polyester,
1 (a), which is a combination of resin components such as polyester / polyamide, polypropylene / ethylene-vinyl acetate copolymer, polypropylene / polyethylene, polypropylene / ethylene-vinyl alcohol copolymer.
~ (E) a splittable conjugate fiber having a cross-sectional shape similar to,
Ultrafine fibers divided by a beater or refiner can be used. Among these, a fibrous material having a fibrillar branched structure is likely to adhere to a sparse portion of the entangled fiber web and has high concealing property, and thus can be suitably used.

When the non-woven fabric is used as a separator for alkaline batteries, polyethylene, polypropylene, aromatic polyamide synthetic pulp, wood pulp, plant pulp, or solvent spinning method is used as a fibrous material. The obtained cellulose fiber is beaten to have a fibril-like branched structure, nylon or aromatic polyamide fiber having a fiber diameter of 5 μm or less, or resin such as polypropylene / polyethylene or polypropylene / ethylene-vinyl alcohol copolymer. Figure 1 consisting of combinations
The ultrafine fibers obtained by splitting the splittable conjugate fiber having the same cross-sectional shape as (a) to (e) with a beater, a refiner, or the like are excellent in electrolytic solution resistance and thus can be preferably used. Among these, polyethylene-based, polypropylene-based synthetic pulp, and ultrafine fibers obtained by splitting the splittable conjugate fiber made of a combination of polyolefin-based resins are most excellent in electrolytic solution resistance, and thus can be used more preferably,
Polyethylene-based and polypropylene-based synthetic pulps are the most suitable fibrous materials because of their excellent adhesiveness and hiding power.

As a method of attaching such a fibrous material to the entangled fiber web, for example, one side of the entangled fiber web is
There is a method of flowing the dispersion of the fibrous material, a method of dropping the fibrous material from the upper surface while sucking from the lower surface of the entangled fiber web, but in the former method, the dispersion is of the entangled fiber web. Easy to flow through the sparse part,
The fibrous material surely adheres to the sparse part of the entangled fiber web,
This is a more suitable adhesion method because it is easy to obtain a nonwoven fabric having a uniform surface condition. Note that examples of the flow-down device for the dispersion liquid of the fibrous material include a flow coater and a wet former. Also in the method of flowing down the dispersion of the fibrous material, when suction is performed from the lower surface of the entangled fiber web (a suitable suction pressure is -500 mmAq or more),
The adhesive force of the fibrous material with the entangled fiber web can be further enhanced.

The amount of the fibrous material attached to the entangled fiber web depends on the state of the sparse portion of the entangled fiber web, but is 0.1 to 40% by weight based on the weight of the entangled fiber web. It is preferable to attach the fibrous substance of. When the amount is less than 0.1% by weight, the surface of the fibers is uneven and the entanglement locus remains, even if the fibrous substances are adhered. Weak adhesion to fiber web,
This is because it is easy to fall off, and more preferably 0.2 to 30.
%, Most preferably 0.5 to 20% by weight. The adhered amount of the fibrous material can be appropriately adjusted by adjusting the concentration of the dispersion of the fibrous material, the flow rate of the dispersion, the moving speed of the conveyor, and the like.

When the nonwoven fabric of the present invention is used as a battery separator, the entangled fiber web has a basis weight of 20 to 80 g / m ^2.
Since it is preferable that the amount of the fibrous substance is 0.02,
Although the ~32g / m ^2, when used as a separator, in order to more reliably prevent the movement of the dendrite or the electrode active material is preferably at 0.3 g / m ² or more, more preferably 0 and at .5g / m ² or more, too dense a nonwoven surface, too electric resistance becomes high, so as not to impair the air permeability is preferably at 15 g / m ² or less, more preferably 10 g / m ² or less.

The fibrous material of the present invention may be simply attached to the entangled fiber web, but it is an ultrafine fiber obtained by dividing a splittable conjugate fiber composed of a combination of polyethylene-based or polypropylene-based synthetic pulp or polyolefin-based resin. By heat-bonding the fibers, the adhesion with the entangled fiber web can be increased, and thus these fibrous materials can be preferably used.

When a non-woven fabric is used for a battery separator, it is preferable to use polyethylene fibers and / or polypropylene fibers as the fibers constituting the entangled fiber web, and thus the fibers constituting the entangled fiber web. As a fiber and / or a high-density polyethylene resin component
Alternatively, it is preferable to use polypropylene fibers and use a fibrous material composed of a low-density polyethylene resin component to fuse only the fibrous materials without lowering the liquid retention of the entangled fiber web.

As a method of increasing the adhesive force of the fibrous material other than the above to the entangled fiber web, the pore diameter is 0.05 to 0.5 mm,
There is also a method in which a columnar flow having a water pressure of 50 kg / cm ² or less, more preferably 30 kg / cm ² or less is acted from a nozzle of 0.08 to 0.15 mm, but the fibrous material moves to improve the surface condition. You need to be careful not to damage it.

When the nonwoven fabric needs to have a soft texture, or when the fibrous material is fused and formed into a film, which reduces the air permeability, the fibrous material is fused. Without performing the above, the densification can be performed by pressurization at room temperature or at a temperature at which fusion does not occur, and the adhesive force of the fibrous material can be increased.

The nonwoven fabric obtained as described above has an average pore diameter of 12 μm or less, more preferably 10 μm or less, has no entanglement locus, and has a uniform surface condition. The average pore size is a value measured by a pore size distribution measuring device (manufactured by Coulter Electronics Co.).

When the nonwoven fabric of the present invention is used as a separator for a sealed secondary battery, the air permeability (F) is 0 <so that the gas generated in the battery can be quickly transmitted to the other electrode. It is preferable that F ≦ 20 (cc / cm ² / sec). More preferably, 0.5 ≦ F ≦ 10 (cc / cm ² / sec). This air permeability is based on the Frazier method (JIS standard).
L1096 (method A)).

The unit weight and thickness of the nonwoven fabric of the present invention may be appropriately changed depending on the use. The nonwoven fabric of the present invention,
Conventionally, to prevent sparse parts of the entangled fiber web from occurring,
It was not possible to solve even by means such as increasing the basis weight, and it was virtually impossible to manufacture the basis weight 30.
Even a entangled non-woven fabric with a low basis weight of about g / m ² was able to obtain a non-woven fabric with a uniform surface state by simply attaching a small amount of fibrous material, and can be applied to a wider range of applications. It is a thing.

For example, when it is used as a separator for a battery, as described above, the basis weight of the entangled fiber web is 20 to 20.
80 g / m ^2, preferably the amount of deposition of fibrous material is 0.3~15g / m ^2. Further, the thickness of the separator is preferably 0.2 mm or less, more preferably 0.15 mm or less so that many electrode active materials can be filled. On the other hand, if the separator is too thin, the retention of the electrolytic solution tends to deteriorate and the battery capacity cannot be increased. Therefore, the thickness is preferably 0.06 mm or more, more preferably 0.08 mm or more.

The entangled fiber web and / or fibrous material of the present invention contains polyolefin fibers, and when used as a battery separator, in order to further improve the retention of the electrolytic solution, It is preferable that the fibers, the fiber web, the entangled fiber web, or the non-woven fabric be subjected to a hydrophilic treatment. Examples of the hydrophilization treatment include, in addition to the surfactant treatment, sulfonation treatment, fluorine treatment, graft polymerization of vinyl monomers, and the like. These hydrophilization treatments can impart permanent hydrophilicity, so that they can be used for a long period of time. It is possible to obtain a separator excellent in the electrolyte retaining property.

The sulfonation treatment is not particularly limited, and for example, fuming sulfuric acid, sulfuric acid, chromic acid, nitric acid or the like may be used. Among them, the sulfonation treatment with fuming sulfuric acid has high reactivity and can be sulfonated relatively easily, and thus can be preferably used.

The fluorine gas treatment is also not particularly limited, and, for example, oxygen gas, carbon dioxide gas, sulfur dioxide gas, etc. may be added to fluorine gas diluted with an inert gas and the mixture gas may be used for treatment. . In addition,
A method of depositing sulfur dioxide gas in advance and then contacting it with fluorine gas is a more efficient and permanent hydrophilization treatment method.

As the graft polymerization of vinyl monomer,
As the vinyl monomer, for example, acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, vinylpyridine, vinylpyrrolidone, or styrene can be used. When styrene is graft-polymerized, it is preferably sulfonated in order to improve the affinity with the electrolytic solution. Among these, acrylic acid is most preferably used because it has excellent affinity with the electrolytic solution.

These vinyl monomers can be polymerized by, for example, immersing a nonwoven fabric in a solution containing the vinyl monomer and a polymerization initiator and heating it, coating the nonwoven fabric with the vinyl monomer, and then irradiating it with radiation. And the like, and a method of contacting with a vinyl monomer, a method of impregnating a nonwoven fabric or the like with a vinyl monomer solution containing a sensitizer, and then irradiating with ultraviolet rays. If the surface of the non-woven fabric is treated with UV irradiation, corona discharge, plasma discharge, etc. before contacting the non-woven fabric with the vinyl monomer solution, the affinity with the vinyl monomer solution will be increased and the grafting efficiency will be improved. It has the feature that it can be polymerized.

As described above, the method of graft-polymerizing a vinyl monomer is an excellent method of hydrophilizing, since it can be treated under mild conditions as compared with sulfonation and the like, so that deterioration of fibers is small.

Incidentally, such a hydrophilic treatment is a separate step,
Although only the fibrous material or only the entangled fiber web may be performed, the most efficient hydrophilicizing method is to perform hydrophilic treatment after forming the nonwoven fabric.

Since the fibrous material-adhered surface of the nonwoven fabric of the present invention is smooth and has fine pores formed, it is excellent in the retention of the electrolytic solution and the adhesion to the electrode plate, and further, the electric resistance can be reduced, The nonwoven fabric of the present invention is highly reliable as a battery separator.

The nonwoven fabric of the present invention can be suitably used as a separator for primary or secondary batteries, especially as a separator for alkaline secondary batteries. This battery may be an open type or a closed type, and the shape may be cylindrical, flat or prismatic. More specifically, alkaline manganese batteries, mercury batteries, silver oxide batteries, primary batteries such as air batteries, nickel-cadmium batteries, silver-zinc batteries, silver-cadmium batteries, nickel-
It can be suitably used as a separator for secondary batteries such as zinc batteries and nickel-hydrogen batteries.

Examples using the nonwoven fabric of the present invention as a separator will be described below, but the present invention is not limited to these examples.

[0060]

【Example】

(Example 1) As a fiber, as shown in FIG. 1 (c), polypropylene component (symbol 2 in the figure, circular polypropylene component: 0.04 denier, petal-shaped polypropylene component: 0.12 denier) and high It consists of a density polyethylene component (melting point: 130 ° C., symbol in the figure 1, 0.12 denier) and has a chrysanthemum-like cross-sectional shape, a denier of 2 denier, a splittable conjugate fiber with a fiber length of 5 mm. Nonylphenyl polyalkylene oxide ether 0.7
After adhering 10% by weight, the splittable composite fiber (10
(0% by weight) to 0.8% by dispersing with a pulper, and then using an inclined wet paper machine with a width of 1 m, paper making concentration 0.02%, speed 10 m / min paper making,
A fiber web was obtained.

This fiber web was wire-coated with a diameter of 0.132 m.
Placed on a 100-mesh plain woven wire for 10 m
Nozzle diameter 0.15 mm, pitch 0.1 mm
The nozzle plates are arranged in a row at 7 mm, and are sequentially treated with a water flow having a water pressure of 15 kg / cm ² and 30 kg / cm ² (A-side), and then inverted, and the same nozzle plate is used in order.
It was treated with a water flow having a water pressure of 50 kg / cm ² and 90 kg / cm ² (side B). Next, using a nozzle plate arranged in a line with a nozzle diameter of 0.15 mm and a pitch of 0.6 mm, the water pressure is 100 kg in sequence.
/ cm ² , 120kg / cm ² water flow (B side), then reverse and water pressure 60kg / cm ^{2 with} the same nozzle plate
Treated with the water flow of (A side), the splittable conjugate fiber is split by 90% or more, and the maximum pore diameter of the pore-shaped sparse portion 4 is 0.15 mm,
An entangled fiber web having a pore-like sparse portion 4 in the entangled fiber web of 3.6% and a basis weight of 55 g / m ² was obtained.

Next, low density polyethylene resin (melting point: 1
(10 ° C.), a maximum thickness of 3.5 μm and a length of 2.9 mm or less to synthetic pulp (manufactured by Daicel Chemical Industries, Ltd., trade name: Serish KY420S) was preliminarily treated with nonylphenyl polyalkylene oxide ether. After applying 7% by weight, 0.0005 of polyacrylamide was used as a sticky agent.
This synthetic pulp was dispersed with a pulper in 100% dissolved white water to obtain a synthetic pulp (100% by weight) dispersion having a concentration of 0.01%.

Then, the entangled fiber web was placed on a 100-mesh plain woven wire (conveyor) moving at 10 m / min, and the synthetic pulp was dispersed on the upper surface (B side) of the entangled fiber web by a flow coater. The liquid is allowed to flow down at a flow rate of 80 liters / minute, and at the same time, it is sucked at -1,050 mmAq by a suction box (opening slit 10 mm) installed below the plain weave wire, and it is 0 After adhering 0.8 g / m ² of synthetic pulp, it was dried by passing through an air through dryer at a temperature of 115 ° C., and only the synthetic pulp was lightly fused to obtain a nonwoven fabric.

Next, the non-woven fabric was passed through a treatment tank of fuming sulfuric acid at a SO ₃ concentration of 25% and a temperature of 30 ° C. at a speed of 2.5 m / min, washed with water, dried at a temperature of 70 ° C., and sulfonated. Processed. After that, densification is performed by passing between a steel roll and a cotton roll at 80 ° C (line pressure 50 kg / cm),
Basis weight 55.8 g / m ² , thickness 0.12 mm, average pore diameter 11 μm,
A separator having an air permeability of 4.5 (cc / cm ² / sec) was obtained.

(Example 2) A synthetic pulp concentration of 0.015
%, The flow rate of the synthetic pulp by the flow coater was 147 liters / minute, and suction was performed with a suction box-1,400 mmAq, in exactly the same manner as in Example 1, and at least the entangled fiber web. adhering synthetic pulp 2.2 g / m ² to sparse portion, basis weight 57.2 g / m ^2,
Thickness 0.12 mm, average pore size 10 μm, air permeability 3.6 (cc / cm
² / sec) separator was obtained.

(Example 3) The moving speed of the conveyor is 6 m /
Minutes, and suction box-1,450mmAq, except that suction 3.9g / m ² synthetic pulp of at least sparse parts of the entangled fiber web, exactly as in Example 2. A separator having a basis weight of 58.9 g / m ² , a thickness of 0.13 mm, an average pore diameter of 8 μm, and an air permeability of 2.0 (cc / cm ² / sec) was obtained.

(Example 4) A synthetic pulp concentration of 0.05%
In the same manner as in Example 3, except that suction box-1,500 mmAq was used for suction, 12.0 g / m ² of synthetic pulp was attached to at least the sparse portion of the entangled fiber web, and the basis weight was measured. A separator having a thickness of 67.0 g / m ² , a thickness of 0.14 mm, an average pore diameter of 6 μm and an air permeability of 1.1 (cc / cm ² / sec) was obtained.

Example 5 A synthetic pulp concentration of 0.07%
And it is except the, in the same manner as in Example 4, was attached to at least sparse portions of the entangled fiber web of synthetic pulp of 16.9 g / m ^2, a basis weight 71.9 g / m ^2, a thickness of 0. A separator having a diameter of 14 mm, an average pore diameter of 5 μm and an air permeability of 0 (cc / cm ² / sec) was obtained.

Example 6 A low density polyethylene resin (melting point: 110 ° C.) having a maximum thickness of 110 μm and a length of 3.
Except for using 100% of 0 mm or less synthetic pulp (trade name: SWP UL410, manufactured by Mitsui Petrochemical Industry Co., Ltd.), and setting the synthetic pulp concentration to 0.018%, exactly the same as in Example 2, A basis weight of 57.5 with 2.5 g / m ² of synthetic pulp attached to at least the sparse part of the entangled fiber web.
g / m ² , thickness 0.13 mm, average pore size 10 μm, air permeability 3.7
A (cc / cm ² / sec) separator was obtained.

(Embodiment 7) The moving speed of the conveyor is 6 m /
Minutes, and suction box-1,450mmAq except that suction was performed in exactly the same manner as in Example 6, 4.0g / m ² of synthetic pulp adhered to at least the sparse portion of the entangled fiber web, A separator having a basis weight of 59.0 g / m ² , a thickness of 0.14 mm, an average pore diameter of 10 μm, and an air permeability of 2.4 (cc / cm ² / sec) was obtained.

(Example 8) After 0.2% by weight of nonylphenyl polyalkylene oxide ether was adhered to a splittable conjugate fiber (fineness 2 denier, fiber length 3 mm) made of the same resin component as in Example 2. An ultrafine fiber having a concentration of 0.01% was obtained in the same manner as in Example 2 except that an ultrafine fiber (fibrous material) in which 90% or more of the splittable conjugate fiber was split was used by passing through a disc refiner twice. A fiber (100% by weight) dispersion was obtained. The thickness of the ultrafine fibers made of this polypropylene component is 2.
The diameter was 5 μm, the one having a petal-shaped cross section was 4.3 μm, and the ultrafine fiber composed of the high-density polyethylene component was 4.2 μm.

This ultrafine fiber dispersion was applied to the same entangled fiber web as in Example 2 in exactly the same manner as in Example 2 to obtain an ultrafine fiber of 2.3 g / m ^{2 in} at least a sparse portion of the entangled fiber web. A separator having a fiber weight of 57.3 g / m ² , a thickness of 0.12 mm, an average pore diameter of 10 μm, and an air permeability of 4.4 (cc / cm ² / sec) was obtained.

(Example 9) As a fiber, as shown in FIG. 1 (c), polypropylene component (symbol 2 in the figure, circular polypropylene component: 0.04 denier, petal-shaped polypropylene component: 0.12 denier) ) And an ethylene-vinyl alcohol copolymer component (100 to 11 under wet heat conditions).
A splittable composite fiber (manufactured by Daiwa Spinning Co., Ltd.) having a chrysanthemum-shaped cross-sectional shape of 2 denier and a fiber length of 6 mm, which has a melting point of 0 ° C. and a symbol of 0.12 in the figure).
2 ") was used in the same manner as in Example 1 to split the splittable conjugate fiber by 90% or more, the maximum hole diameter of the hole-like sparse portion 4 was 0.12 mm, and the hole-like shape in the entangled fiber web. An entangled fiber web having a sparse portion 4 of 3.0% and a basis weight of 55 g / m ² was obtained.

On the other hand, a concentration of 0.01% was obtained in the same manner as in Example 8 except that the same splittable conjugate fiber (fineness 2 denier, fiber length 3 mm) as the entangled fiber web was used. An ultrafine fiber (100% by weight) dispersion was obtained.
The splittable conjugate fiber is split by 95% or more,
The thickness of the ultrafine fibers made of polypropylene component is 2.5 μm for those having a circular cross section and 4.3 μm for those having petal-like cross sections, and the ultrafine fibers made of ethylene-vinyl alcohol copolymer component is 4.4 μm. Met.

Thereafter, in the same manner as in Example 8, after applying 2.2 g / m ² of ultrafine fibers to at least the sparse part of the entangled fiber web, the web was dried with a Yankee dryer at 105 ° C. and ethylene- A nonwoven fabric was obtained by fusing only the vinyl alcohol copolymer component. Then, after sulfonation in the same manner as in Example 1, densification treatment was performed to give a basis weight of 57.2 g.
/ m ² , thickness 0.12 mm, average pore size 10 μm, air permeability 2.0
A (cc / cm ² / sec) separator was obtained.

(Comparative Example 1) The same as in Example 1 except that the synthetic pulp was not adhered to the sparse part of the entangled fiber web, the basis weight was 55 g / m ² , the thickness was 0.12 mm, and the average pore diameter was 1
A separator having a thickness of 3 μm and an air permeability of 5.3 (cc / cm ² / sec) was obtained.

Comparative Example 2 A unit weight of 61 g / m ² was obtained in the same manner as in Example 1 except that the paper was made at a speed of 9.0 m / min.
To obtain a entangled fiber web. Then, the sulfonation and densification treatments were carried out in the same manner as in Example 1, and the basis weight was 61 g / m ² and the thickness was 0.1.
14 mm, average pore diameter 13 μm, air permeability 3.8 (cc / cm ² / sec)
To obtain a separator.

(Comparative Example 3) As fibers, 90% by weight of the splittable conjugate fiber as in Example 1 and 10% by weight of the same fibrous material (synthetic pulp) as in Example 1 were used, and as a surfactant, nonyl was used. After adhering 0.7% by weight of phenylpolyalkylene oxide ether, papermaking and hydroentangling were carried out in the same manner as in Example 1 to split the splittable conjugate fiber by 90% or more, and to form the sparse porous portion 4. Maximum hole diameter 0.14 mm, hole-like sparse part 4 in entangled fiber web 3.4%, basis weight 58 g / m ²
To obtain a entangled fiber web. Then, the entangled fiber web was subjected to sulfonation and densification treatment in the same manner as in Example 1,
A separator having a basis weight of 58 g / m ² , a thickness of 0.11 mm, an average pore diameter of 14 μm, and an air permeability of 2.9 (cc / cm ² / sec) was obtained.

(Battery charge / discharge test) Examples 1 to 4 and 6 to 9
And using the separators of Comparative Examples 1 to 3, a battery capacity of 4
A sealed nickel cadmium secondary battery of 00 mA · Hr was created. This battery was charged at a room temperature of 20 ° C. with a current of 0.1 C for 11 hours and then discharged with a current of 0.8 C for 1 hour as one cycle, and the number of cycles until a voltage drop was measured. The results are shown in Table 1.
The separator of Example 5 has an air permeability of 0 (cc / cm ² / se
In c), the battery could be ruptured, so it was not tested, but it has an average pore diameter of 5 μm and has a uniform surface state, so it can be sufficiently used for other purposes.

[0080]

[Table 1]

[0081]

INDUSTRIAL APPLICABILITY The nonwoven fabric of the present invention has a structure in which at least the sparse portion of the entangled fiber web in which the sparse portion is mixed has the content of the fibrous material.
The non-woven fabric has a uniform surface state with no entanglement locus because it has a fibrous substance adhered by flowing down the sprinkling liquid and has an average pore diameter of 12 μm or less.

Since the method for producing the nonwoven fabric of the present invention is a method in which the dispersion liquid of the fibrous material is made to flow down to one side of the entangled fiber web, the fiber can be more reliably at least sparsely formed on the entangled fiber web. It is a method that can attach a substance.

The battery separator of the present invention is made of the above non-woven fabric, and the non-woven fabric has an air permeability (F) of 0 <F ≦ 20 (cc / c
m ² / sec) is suitable for a sealed battery, and the basis weight of the entangled fiber web is 20 to 80 g / m ² and the amount of fibrous material attached is 0.3 to 15 g / m ² . With this, short circuit due to the movement of dendrites and electrode active materials is unlikely to occur, and the air permeability is excellent.

Further, when the entangled fiber web is mainly composed of polyolefin fibers having a fineness of 0.6 denier or less, it is excellent in uniformity, and when hydrophilized, it is used as a separator for alkaline batteries. It is suitable.

Further, the thickness of the fibrous material is 0.1 to 150 μm.
When the length is 1 to 5 mm, the entangled fibrous web easily adheres to the sparse portion and is excellent in uniformity, and when the fibrous material has a fibril-like branched structure, Strong adhesion to the web. Moreover, when the fibrous material is made of a polyolefin resin and more preferably subjected to a hydrophilic treatment, it is suitable as a separator for an alkaline battery.

[Brief description of drawings]

FIG. 1 (a) is a schematic sectional view of a splittable conjugate fiber of the present invention (b) is a schematic sectional view of another splittable conjugate fiber of the present invention (c) is another splittable conjugate fiber of the present invention (D) A schematic cross-sectional view of another splittable conjugate fiber of the present invention (e) A schematic cross-sectional view of another splittable conjugate fiber of the present invention

FIG. 2 (a) is a schematic front view of the entangled fiber web of the present invention. FIG. 2 (b) is a schematic front view of the nonwoven fabric of the present invention.

FIG. 3 is a schematic front view of a fibrous material having a fibrillar branched structure of the present invention.

[Explanation of symbols]

1 one component 2 Other ingredients 3 Entangled fiber web 4 hole-like sparse part 5 fibrous material Fibrous material having 5'fibrillar branched structure 6 non-woven fabric D thickness

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI D04H 3/03 D04H 3/03 B D21F 13/02 D21F 13/02 (56) Reference JP-A-5339861 (JP, A ) JP 5-74440 (JP, A) JP 5-314961 (JP, A) JP 5-182654 (JP, A) JP 5-174806 (JP, A) JP 4- 167355 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 2/16 D04H 1/48 D04H 1/54 D04H 1/72 D04H 3/03 D21F 13/02

Claims (11)

(57) [Claims] 1. A entangled fiber web in which sparse parts are mixed,
Disperse the dispersion of fibrous material into at least the sparse part .
As a result , a non-woven fabric having a fibrous substance attached thereto and having an average pore diameter of 12 μm or less. 2. A entanglement treatment is applied to a fibrous web to form an entangled fibrous web in which sparse parts are mixed, and a dispersion of a fibrous material is allowed to flow down to one side of the entangled fibrous web. A method for producing a nonwoven fabric, characterized in that the fibrous material is attached to at least a sparse portion of the entangled fiber web. 3. A battery separator comprising the non-woven fabric according to claim 1. 4. The air permeability (F) of the nonwoven fabric is 0 <F ≦ 20.
(Cc / cm ² / sec) 4. The battery separator according to claim 3, which is characterized by being (cc / cm ² / sec). 5. The basis weight of the entangled fiber web is 20 to 80 g / m ^2.
And the amount of the fibrous material attached is 0.3 to 15 g / m ² , and the battery separator according to claim 3 or 4. 6. The battery separator according to claim 3, wherein the entangled fiber web is mainly composed of a polyolefin fiber having a fineness of 0.6 denier or less. 7. The battery separator according to claim 6, wherein the entangled fiber web is hydrophilized. 8. A fibrous material having a thickness of 0.1 to 150 μm and a length of 1 to 5 mm.
The battery separator according to claim 7. 9. The battery separator according to claim 3, wherein the fibrous material has a fibrillar branched structure. 10. The battery separator according to claim 3, wherein the fibrous material is made of a polyolefin resin. 11. The battery separator according to claim 10, wherein the fibrous material is hydrophilized.