JP3012801B2 - Battery separator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates <br/> battery separators. More specifically, nickel-cadmium batteries,
Nickel - zinc batteries, nickel - are those related to the preferred battery separators for alkaline storage batteries such as hydrogen batteries.

[0002]

2. Description of the Related Art Conventionally, as battery separators, nonwoven fabrics manufactured by a dry method made of nylon or polypropylene fibers (hereinafter referred to as dry nonwoven fabrics), nonwoven fabrics manufactured by a wet papermaking method (hereinafter referred to as wet nonwoven fabrics), A synthetic resin porous film or the like is used.

[0003]

The main properties required for a battery separator include liquid absorption, liquid retention, winding properties, short-circuit prevention, chemical resistance, and the like. In general, a wet-type nonwoven fabric is dense and has excellent uniformity, so that a separator having high anti-short property can be obtained by using this. However, the wet nonwoven fabric has a short fiber length of the constituent fibers, and it cannot be denied that it is inferior to the dry nonwoven fabric in terms of the strength of the nonwoven fabric. In particular, a wet nonwoven fabric has a problem that it tends to be torn during winding because of its low tear strength.

On the other hand, a dry nonwoven fabric is larger than a wet nonwoven fabric having a similar basis weight in both tensile strength and tear strength, and when this is used for a battery separator, it can be obtained with excellent winding properties. However, dry nonwovens are inferior to wet nonwovens in terms of uniformity. In other words, the dry nonwoven fabric has poor so-called "texture" and a large difference in fiber density.
When this is used as a separator, there is a problem that the positive electrode and the negative electrode are likely to be short-circuited in a rough portion, and this is more noticeable as the dry basis weight of the dry nonwoven fabric is smaller.

As described above, both the wet-type nonwoven fabric and the dry-type nonwoven fabric have advantages and disadvantages as battery separators, and there has been a strong demand for a separator having both advantages.

The present invention has been made in view of the above circumstances, and has been developed from a nonwoven fabric which has excellent liquid retention and liquid absorption properties, is dense and has excellent uniformity, and has improved tensile strength and tear strength. an object of the present invention is to provide a composed of battery separators.

[0007]

In order to achieve the above object, the battery separator of the present invention comprises an upper layer, a middle layer and a lower layer.
Layers, and the upper and lower layers are wet nonwoven fabrics,
A three-layer laminated nonwoven fabric in which the middle layer is a dry nonwoven fabric,
The wet and dry nonwovens are both polyolefin heavy
Combined (component A) and ethylene vinyl alcohol copolymer
(B component) and the splittable conjugate fiber is split and has a fineness
20% by weight or more of ultra-fine fibers of 0.08 to 0.7 denier
And a heat-adhesive fiber, each fiber layer of the heat-adhesive fiber
It is characterized by being bonded and integrated by thermal bonding . According to this configuration, the strength of the entire nonwoven fabric is ensured by the dry nonwoven fabric layer, and the uniformity of the entire nonwoven fabric is ensured by the wet nonwoven fabric occupying the surface.

[0008] In the invention of the battery separator, the laminated nonwoven fabric is composed of an upper layer, a middle layer, and a lower layer,
Upper and lower layers are wet-laid nonwoven fabric layer, the intermediate layer is a dry nonwoven fabric layer, it is further improved short circuit prevention properties for both sides of the nonwoven fabric is covered with a dense and uniform layer, and minimize the thickness of the entire nonwoven fabric be able to.

[0009] In the configuration, a range having a basis weight of 8~40g / m ² of upper and lower wet-laid nonwoven fabric layer, it is preferred basis weight of the dry nonwoven fabric layers of the middle layer is in the range of 20 to 80 g / m ² .

Further, in the invention of the battery separator, the wet nonwoven fabric layer is composed of short-circuit fibers having a length of 5 to 15 mm, and contains at least 20% by weight of ultrafine fibers having a fineness of 0.8 to 0.7 denier. Is preferred. By including the ultrafine fibers in the wet nonwoven fabric layer, a denser and more uniform nonwoven fabric can be obtained.

The dry nonwoven fabric layer constituting the laminated nonwoven fabric is a hydroentangled nonwoven fabric made of staple fibers having a length of 25 to 125 mm, and contains at least 20% by weight of ultrafine fibers having a fineness of 0.08 to 0.7 denier. It is desirable. The nonwoven fabric in which the fibers are entangled by the water flow is excellent in liquid retention because fine voids are formed between the fibers, and by including extra fine fibers, many fine voids are formed. Therefore, the use of such a dry nonwoven fabric has a favorable effect on the liquid absorption and liquid retention properties of the entire nonwoven fabric.

Since the ultrafine fibers contained in the wet non-woven fabric layer and the dry non-woven fabric layer are formed by dividing the splittable conjugate fiber , a uniform non-woven fabric having a good surface condition can be obtained.

[0013] Then, the splittable conjugate fiber, polyolefin polymer (component (A)), Ru splittable conjugate fiber der consisting of ethylene-vinyl alcohol copolymer (B component). By using a splittable conjugate fiber comprising such a component, chemical resistance and hydrophilicity can be imparted to the nonwoven fabric.

Each of the nonwoven fabric layers constituting the battery separator of the present invention contains a heat-adhesive fiber, and the respective nonwoven fabric layers are bonded by heat-adhesion of the heat-adhesive fiber to be integrated.
You. When each layer is integrated with an external adhesive, there is a concern that the adhesive is eluted into the electrolytic solution, but if the interlayer bonding is performed using a heat-adhesive fiber, such inconvenience can be avoided. .

From the viewpoint of alkali resistance, the heat-adhesive fiber is preferably a core-sheath composite fiber having a polypropylene core and a high-density polyethylene sheath.

Next, in order to obtain the battery separator of the present invention,
Is a method for manufacturing a battery separator in which a plurality of non-woven fabric layers are laminated, wherein one or more dry non-woven fabric layers in which constituent fibers are entangled and integrated by injecting a high-pressure water flow in the thickness direction, and a wet non-woven fabric. And a wet-type nonwoven fabric layer is disposed on at least one surface, and the whole is integrated in the thickness direction. According to this manufacturing method, the battery separator of the present invention can be efficiently and rationally manufactured.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the contents of the present invention will be described in more detail.

The battery separator of the present invention is a laminated nonwoven fabric comprising a plurality of nonwoven fabric layers, wherein a dry nonwoven fabric layer is an intermediate layer.
And, and, upper and lower layer Ru wet-laid nonwoven fabric layer der. Here, the dry non-woven fabric layer, refers to those consisting of parallel web and a semi-random web of the staple fiber. These webs, or which is thermally bonded to a portion of the configuration fibers as thermal bonding fibers, by or entangling the constituent fibers to each other by the action of high pressure water stream, the constituent fibers are entangled with each other It becomes a non-woven fabric.

These nonwoven fabrics have higher tensile strength and tear strength than wet nonwoven fabrics, and serve to impart strength to the entire laminated nonwoven fabric. In addition, the wet nonwoven fabric layer is composed of a web formed by dispersing a fiber material in water or flowing a slurry over a net and dewatering,
The fibers are bonded together by an adhesive or entanglement between the fibers. The length and material of the fibers constituting the web are not particularly limited, but in the present invention, in order to obtain a nonwoven fabric having a uniform structure, the fiber length of the constituent fibers is desirably 20 mm or less. If such fibers are used, a nonwoven fabric having a uniform and dense structure in which constituent fibers are arranged in random directions can be obtained. Therefore, if it is arranged on the surface, the short-circuit prevention property can be improved.

[0020] Dry nonwoven fabrics and wet nonwoven fabrics differ greatly in the denseness and uniformity of the nonwoven fabric structure due to differences in the manufacturing process. Here, the average pore diameter and the maximum pore diameter measured according to the method described in ASTM F316 are used as a scale indicating the denseness and uniformity of the nonwoven fabric structure. It can be said that the smaller the average pore size of the nonwoven fabric, the denser the nonwoven fabric. Comparing the average pore diameters of a dry nonwoven fabric and a wet nonwoven fabric having substantially the same basis weight and the same fiber density, the dry nonwoven fabric is generally larger and the wet nonwoven fabric is smaller. In addition, it can be said that the smaller the difference between the maximum pore diameter and the average pore diameter, the more uniform the nonwoven fabric structure. Generally, dry nonwoven fabrics have a large ratio of maximum pore diameter / average pore diameter. This ratio tends to increase as the basis weight decreases, and a dry nonwoven fabric with a small basis weight shows a remarkable difference in density at a glance. On the other hand, the wet nonwoven fabric has a ratio of maximum pore diameter / average pore size smaller than that of the dry nonwoven fabric, and is excellent in uniformity. Even when the basis weight is reduced, the ratio of the maximum pore diameter / average pore diameter does not increase as in the dry nonwoven fabric.

The fiber density of the dry nonwoven fabric layer is about 0.25
湿 0.37 g / cm ³ is preferable, and the fiber density of the wet nonwoven fabric layer is preferably about 0.36-0.54 g / cm ³ .

[0022] In general, the thickness of the battery separator is increased, the insertion amount of the positive electrode and the negative electrode is reduced, the positive electrode active material and to decrease the battery performance such as battery capacity decreases the amount of the negative electrode active material with it It is considered that the thickness of the separator is desirably as small as possible. Therefore, in the present invention, the laminated nonwoven fabric is composed of only the upper layer, the middle layer, and the lower layer, and the upper and lower layers are wet nonwoven layers.
Middle layer has been configured by the dry nonwoven fabric layers.

In this three-layer laminated nonwoven fabric, the upper and lower wet nonwoven fabric layers preferably have a basis weight of 8 to 40 g / m ² . It is difficult to produce a wet nonwoven fabric having a basis weight of less than 8 g / m ^{2 in} terms of process, and even if such a wet nonwoven fabric is laminated, it is difficult to obtain the effect of the present invention of improving short-circuit prevention. On the other hand, if it exceeds 40 g / m ² , the thickness of the entire laminated nonwoven fabric becomes undesirably large. It is desirable that the basis weight of the middle dry nonwoven fabric layer is 20 to 80 g / m ² . If it is less than 20 g / m ² , a good texture cannot be obtained, and sufficient strength cannot be imparted to the entire laminated nonwoven fabric. If it exceeds 80 g / m ² , the entire thickness is undesirably increased.

In the present invention, in order to further improve the uniformity of the nonwoven fabric, to use ultrafine fibers. However, if the fineness is too small, it becomes difficult to produce a uniform nonwoven fabric because the fibers are entangled when preparing the slurry,
It must also be noted that the air permeability is reduced. In the present invention, it is desirable that the wet nonwoven fabric contains at least 20% by weight of ultrafine fibers having a fineness of 0.08 to 0.7 denier.

In order to make the ultrafine fibers exist in the wet nonwoven fabric, the paper may be made by using the ultrafine fibers themselves. However, the fine fibers are easily entangled in the slurry, so that the uniformity of the nonwoven fabric may be reduced. Therefore, in the present invention, and paper using a splittable conjugate fiber comprising a plurality of components, which Ru to form ultrafine fibers by splitting each component. Since the splittable conjugate fibers are sequentially split when preparing the slurry, a uniform nonwoven fabric can be obtained with less entanglement in the slurry as compared with the case where ultrafine fibers are used from the beginning. However, in the case of using a splittable conjugate fiber (also referred to as a splittable conjugate fiber), the ratio of the ultrafine fibers actually formed in the nonwoven fabric is within the above-described range in consideration of the degree of splitting. Need to determine the usage.

In the present invention, the splittable conjugate fiber is a conjugate fiber having a polyolefin polymer as an A component and an ethylene-vinyl alcohol copolymer as a B component.
It is desirable to use a splittable conjugate fiber having a fiber cross section as shown in FIG. This splittable conjugate fiber is excellent in chemical resistance, and furthermore, ethylene-vinyl alcohol copolymer also has hydrophilicity, so that by using this, it is possible to impart chemical resistance and hydrophilicity to the separator. . As the polyolefin polymer, polypropylene and polyethylene can be preferably used.
The ethylene vinyl alcohol copolymer having an ethylene content of 20 to 50 mol% can be preferably used in consideration of the fiber production processability and hydrophilicity. Also, A,
The composite ratio (area ratio) of both components B is 30/70 to 70 / A / B in terms of easiness of the spinning step and affinity for the electrolytic solution.
It is desirable to set it to 30.

Further, it is desirable that the wet nonwoven fabric contains heat-adhesive fibers in addition to the ultrafine fibers. Simultaneously with the integral coupling between the nonwoven layers, partly brought joining structure fiber 維同 mechanic wet nonwoven fabric, it is to improve the strength of wet-laid nonwoven fabric.

The heat-adhesive fiber is not particularly limited as long as it is softened and melted by heat and has a function of bonding the fibers, and a single fiber made of polypropylene or polyethylene, or a core component / sheath component made of polypropylene is used. / High-density polyethylene, polypropylene / low-density polyethylene, polypropylene / ethylene-propylene random copolymer, and the like, and one or more core-sheath type composite fibers can be arbitrarily selected and used. Further, the content can be determined according to the substance of the heat-adhesive fiber so as to exert the above-described action. However, if the content is too large, the flexibility of the entire nonwoven fabric is impaired, and the liquid retaining property is undesirably reduced.

In the present invention, it is desirable to use a core-sheath type composite fiber having a core component made of polypropylene and a sheath component made of high-density polyethylene. Since this fiber is composed of a polyolefin-based component, it has excellent chemical resistance, and has good bonding properties with the above-mentioned splittable composite fiber made of polypropylene and an ethylene-vinyl alcohol copolymer. And when using this sheath-core type composite fiber,
It is desirable that the content be in the range of 10 to 80% by weight. If the amount is less than 10% by weight, the nonwoven fabric layers cannot be sufficiently bonded to each other, and if it exceeds 80% by weight, the flexibility is impaired.

Other fibers may be contained in the wet nonwoven fabric as long as the ultrafine fibers and the heat-adhesive fibers are contained in the above-mentioned range. As other fibers, for example,
Polypropylene fiber and polyethylene fiber with excellent chemical resistance
Any fiber can be used.

The fibers constituting the wet nonwoven fabric, such as the above-mentioned splittable conjugate fibers and heat-bondable fibers, preferably have a fiber length of 5 to 15 mm. If it is less than 5 mm, sufficient strength is not imparted to the nonwoven fabric, and if it is more than 15 mm, the dispersibility of the fibers in the slurry becomes poor, especially when the nonwoven fabric is produced by a wet papermaking method, so that a uniform nonwoven fabric cannot be obtained. .

Next, the dry nonwoven fabric will be described. As described above, in the dry non-woven fabric, using the the staple fiber non-woven fabric
To use . In the present invention, it is most preferable to use a hydro-entangled nonwoven fabric obtained by subjecting a staple fiber web having a fiber length of 25 to 125 mm to a high-pressure water treatment to entangle the fibers. This is because such a nonwoven fabric exhibits excellent tensile strength and tear strength because the fibers are strongly entangled by the action of the high-pressure water flow. In addition, compared to the case where the fibers are entangled or bonded by other methods, a nonwoven fabric having a structure in which a large number of fine voids are formed between the fibers can be obtained, from the viewpoint of improving water absorption and liquid retention. Its use is desirable. 10 to 10 as high pressure water flow
It is preferable to use a spray nozzle (spray gun) having a water pressure of about 0 kg / cm ² .

[0033] In addition, in this in the nonwoven fabric, that contains the ultra-fine fibers. This is because the inclusion of the ultrafine fibers forms a number of finer voids, so that the liquid retention and liquid absorption properties are further improved. However, if the fineness of the ultrafine fibers is too small, it is difficult to obtain a uniform nonwoven fabric in the process, which is not preferable. Accordingly, in the present invention, that it contains fineness from 0.08 to 0.7 denier microfibers 20 wt% or more on dry nonwoven fabric.

In order to make the ultrafine fibers exist in the dry nonwoven fabric, the web may be prepared using the ultrafine fibers. However, since the fine fibers have poor card permeability, a uniform nonwoven fabric having a good surface condition can be obtained. difficult. Therefore, also in the case of producing a dry nonwoven fabric, it is desirable to use a splittable conjugate fiber similarly to the wet nonwoven fabric. When the splittable conjugate fiber is used, ultrafine fibers are formed by being divided into the respective components by the action of the high-pressure water flow, and the ultrafine fibers are entangled with each other, so that a more dense and high-strength nonwoven fabric can be obtained.

The splittable conjugate fiber used for the dry nonwoven fabric, similar to those used in the wet-laid nonwoven fabric from the viewpoint of chemical resistance and hydrophilicity, using a splittable conjugate fiber comprising a polyolefin polymer and an ethylene-vinyl alcohol copolymer I do . Since the splittable conjugate fiber is as described in detail above, the description is omitted here.

It is desirable that the heat-bondable fiber is also contained in the dry nonwoven fabric. This is because, at the same time as integrating the respective nonwoven fabric layers, the constituent fibers in the dry nonwoven fabric are joined together to further improve the strength of the nonwoven fabric. As in the case of the wet nonwoven fabric, the type and content of the heat-adhesive fiber are not particularly limited. However, for the same reason as in the case of the wet nonwoven fabric, the core / sheath core / sheath composite fiber having a core / sheath of 10 to 80 wt. %.

As long as the splittable conjugate fiber and the heat-adhesive fiber are contained in the nonwoven fabric at a ratio within the above-mentioned range, the dry nonwoven fabric may contain other fibers. Other fibers, for example, polypropylene fiber having excellent chemical resistance, can optionally be used polyethylene textiles.

Next, the integration of the wet nonwoven fabric and the dry nonwoven fabric will be described. The integration of the two nonwoven fabric layers is desirably performed by making the heat adhesive fibers exist in each nonwoven fabric layer and utilizing the thermal adhesiveness. The nonwoven fabric integrated by such means does not cause a problem such as elution of the adhesive which is likely to occur when an external adhesive is used, and does not have a possibility of adversely affecting the electrolytic solution. In addition, since the integration is achieved only by a heat treatment, a complicated operation such as application of an adhesive is not required, which is advantageous in a manufacturing process.

The method of laminating the two nonwoven fabrics and the method of heat treatment are not particularly limited. For example, after separately preparing and laminating a wet nonwoven fabric and a dry nonwoven fabric, a heat treatment is performed using a hot air penetration dryer or a hot roll, and the heat-bonding fibers contained in each nonwoven fabric layer are softened or melted. The nonwoven fabric layers may be bonded together to be integrated. In addition, the wet nonwoven layer in the wet state immediately after papermaking is laminated on the dry nonwoven layer, and this layer is heated on a Yankee dryer, and the drying of the wet nonwoven layer and the bonding between the respective nonwoven layers proceed simultaneously to be integrated. It can also be done. This method is particularly suitable when the wet nonwoven fabric layer contains fibers made of an ethylene vinyl alcohol copolymer. Ethylene vinyl alcohol copolymer has wet heat adhesion, and when it is heated in a wet state, it acts as a heat adhesive fiber,
This is because the strength of the nonwoven fabric can be further improved.

The laminated non-woven fabric thus obtained includes:
A process for improving the separator performance may be performed. For example, hydrophilicity can be further improved by applying a surfactant or performing a surface treatment such as a corona discharge treatment or a plasma treatment. Further, the nonwoven fabric can be further densified by performing a heat calendering treatment, and a thin nonwoven fabric can be obtained.

[0041]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples.

[0042]

Example 1 (Preparation of slurry for papermaking) A fineness of 1.5 denier, a fiber length of 10 mm, and a core / sheath component of polypropylene / high-density polyethylene (composite ratio: 50 /
50) The thermo-adhesive fiber which is the core-sheath type composite fiber of 30% by weight, the component A is polypropylene, and the component B is an ethylene vinyl alcohol copolymer (ethylene content 38 mol%), and is shown in FIG. A component / B
3 denier, fiber length 6 with volume ratio of 50/50
A slurry was prepared by mixing 50% by weight of a splittable conjugate fiber having a thickness of 0.5 mm and 20% by weight of a polypropylene fiber having a fineness of 0.7 denier and a fiber length of 10 mm so as to have a concentration of 0.5%.

(Production of Dry Nonwoven Fabric) The component A is polypropylene, the component B is an ethylene vinyl alcohol copolymer (ethylene content 38 mol%), and has a cross-sectional shape as shown in FIG. B / 50 volume ratio 50/50, 3 denier, fiber length 45m
Adhesion is 50% by weight of a split type composite fiber having a m of 1.5 m, a denier of 1.5 denier, a fiber length of 51 mm, and a core / sheath type composite fiber having a core component / sheath component of polypropylene / high density polyethylene (composite ratio 50/50) 30% by weight of synthetic fiber and 1.5 fineness
Denier, 20 polypropylene fibers with a fiber length of 45 mm
% By weight to obtain a parallel web having a basis weight of 30 g / m ² . Then, the web was subjected to high-pressure water flow treatment (water pressure 60 kg / cm ² ) to split the splittable conjugate fibers and simultaneously entangle the fibers. Next, a heat treatment was performed in a hot air penetration type dryer at 135 ° C. to dry the fibers, and at the same time, the fibers were bonded to each other by the heat-adhesive fibers to obtain a nonwoven fabric. The obtained nonwoven fabric contained about 47.5% by weight of ultrafine fibers having a fineness of about 0.2 denier formed by dividing the splittable conjugate fiber.

(Lamination of Wet Non-Woven Layer and Dry Non-Woven Layer) Using a two-layer paper machine as shown in FIG. 5, a web having a basis weight of 12.5 g / m ² was produced by each of the paper machines (7A) and (7B). Paper is made, and a dry nonwoven fabric (4) is sandwiched between the wet nonwoven fabrics (3A) and (3B) to form a three-layer laminated nonwoven fabric (6).
It was created. Subsequently, this was dried on a Yankee dryer (5) at 135 ° C., and the non-woven fabric layers were bonded and integrated by the heat-adhesive fibers and the ethylene vinyl alcohol copolymer in each non-woven fabric layer. Then, a surfactant was applied to this to obtain a nonwoven fabric (6) for a battery separator. The basis weight of the obtained nonwoven fabric is 55 g / m ² , and the wet nonwoven fabrics located in the upper and lower layers contain about 45% by weight of ultrafine fibers having a fineness of about 0.2 denier formed by dividing the splittable conjugate fiber. I was

[0045]

Example 2 The basis weight was exactly the same as in Example 1 for both the material and the production method, except that the proportion of the constituent fibers in the papermaking slurry was 50% by weight of the splittable conjugate fiber and 50% by weight of the heat-adhesive fiber. A laminated nonwoven fabric for a battery separator of 55 g / m ² was prepared. The wet nonwoven fabrics located in the upper and lower layers of the laminated nonwoven fabric contained about 45% by weight of ultrafine fibers having a fineness of about 0.2 denier formed by dividing the splittable conjugate fiber.

[0046]

Comparative Example 1 A paper was made using the slurry used in Example 1, dried with a Yankee dryer at 135 ° C., and the fibers were joined with a heat-adhesive fiber and an ethylene vinyl alcohol copolymer to obtain a basis weight of 55 g / g. create a wet nonwoven m ^2, and used as a comparative example. This wet nonwoven fabric contained about 45% by weight of ultrafine fibers having a fineness of about 0.2 denier formed by dividing the splittable conjugate fiber.

[0047]

Comparative Example 2 The same fibers as the dry nonwoven fabric used in Example 1 were mixed in the same ratio to prepare a parallel web having a basis weight of 55 g / m ² , and this was subjected to high-pressure water flow treatment and heat treatment in the same manner as in Example 1. To produce a nonwoven fabric, which was used as a comparative example. This nonwoven fabric contained about 47.5% by weight of ultrafine fibers having a fineness of about 0.2 denier formed by dividing the splittable conjugate fiber.

Table 1 shows the physical properties of the battery separators of Examples 1 and 2 and Comparative Examples 1 and 2.

[0049]

[Table 1] In addition, the evaluation of the physical property value in a table | surface was performed by the following method. (1) Tensile strength and elongation: Measured in accordance with JIS L 1096 tensile test method for woven fabric. (2) Tear strength: Measured according to the test method for tear strength of woven fabric according to JIS L 1096. (3) Liquid absorption speed: Three test pieces of 25 × 250 mm are sampled from the sample width direction and brought into a water equilibrium state. Next, the test piece is pinned to a horizontal bar supported at a predetermined height on a water tank containing a potassium hydroxide aqueous solution (hereinafter abbreviated as KOH solution) having a specific gravity of 1.30 and kept at 20 ° C. Align the lower end of the test piece with the line, lower the horizontal bar, and stand vertically so that the lower end of the test piece is immersed in the liquid by 5 mm.
The height at which the solution rose was measured after 30 minutes. (4) Liquid retention ratio: The weight (W) of the test piece in the water equilibrium state was 1
Measure to mg. Next, the test piece is immersed in a KOH solution having a specific gravity of 1.30, and after absorbing the KOH solution for one hour, withdrawn from the solution and left for 10 minutes, the weight (W ₁ ) of the test piece is measured and maintained. Liquid ratio (%) = ((W ₁ −W) /
The liquid retention was calculated from the formula of W) × 100. (5) [Winding property]: Indicated by ◎, △, Δ, × in order of the separator having good winding property. (6) Average pore diameter, maximum pore diameter: Measured according to the bubble point method described in ASTM F316. (7) Air permeability: JIS L using a Frazier type testing machine
It was measured according to 1096.

[0050]

As described above, according to the battery separator of the present invention, an upper layer, a middle layer, and a lower layer are provided, and
The upper and lower layers are wet nonwoven fabrics, and the middle layer is dry nonwoven fabrics
A three-layer laminated nonwoven fabric, wherein the wet nonwoven fabric and
Both dry nonwoven fabrics are polyolefin polymer (component A)
With ethylene vinyl alcohol copolymer (component B)
Split conjugate fiber is divided into fineness of 0.08 to 0.7
20% by weight or more of Neal's microfiber and heat-adhesive fiber
The respective fiber layers are joined together by the heat bonding of the heat bonding fibers.
By being embodied, it is excellent in liquid retention and liquid absorption,
It is possible to provide a battery separator made of a nonwoven fabric that is dense and has excellent uniformity and has improved tensile strength and tear strength.

As described above, the battery separator of the present invention
It has the advantages of both dry nonwoven fabric and wet nonwoven fabric, and is excellent in liquid absorption, liquid retention, ticket circulation, short prevention, and chemical resistance. Therefore, when this is incorporated into a battery, the battery performance can be greatly improved.

The laminated nonwoven fabric can be manufactured relatively easily by joining the respective nonwoven fabric layers with a heat-adhesive fiber, and is extremely advantageous in terms of manufacturing cost .

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view of an example of a splittable conjugate fiber that can be used in the present invention.

FIG. 2 is an enlarged cross-sectional view of an example of a splittable conjugate fiber that can be used in the present invention.

FIG. 3 is an enlarged cross-sectional view of an example of a splittable conjugate fiber that can be used in the present invention.

FIG. 4 is an enlarged cross-sectional view of an example of a splittable conjugate fiber that can be used in the present invention.

FIG. 5 is an explanatory view showing an example of manufacturing a battery separator of the present invention using a two-layer papermaking machine.

[Explanation of symbols]

 1 A component 2 B component 3 Wet nonwoven fabric 4 Dry nonwoven fabric 5 Yankee dryer 6 Laminated nonwoven fabric

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hirose Naoriku Hirose Paper Co., Ltd. 529 Heioka-cho, Tosa-shi, Kochi (56) References JP-A-5-182654 (JP, A) JP-A-7 -29561 (JP, A) JP-A-7-142047 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 2/16

Claims (5)

(57) [Claims] An upper layer, a middle layer and a lower layer, and
The layer and lower layer are wet nonwoven fabrics, and the middle layer is dry nonwoven fabric.
A three-layer laminated nonwoven fabric, wherein the wet nonwoven fabric is
Both the nonwoven fabrics are polyolefin polymer (component A) and
Consisting of a Tylene vinyl alcohol copolymer (component B)
The splittable conjugate fiber is split and has a fineness of 0.08 to 0.7 denier.
At least 20% by weight of ultrafine fibers
The respective fiber layers are joined together by the heat bonding of the heat bonding fibers.
A battery separator characterized by being integrated . Basis weight of 2. A top and bottom layer of wet-laid nonwoven fabric layer is in a range of 8~40g / m ^2, of the dry nonwoven fabric layers of the middle layer basis weight according to claim 1 in the range of 20 to 80 g / m ² Battery separator. 3. A wet-laid nonwoven fabric layer, the battery separator according to claim 1 or 2 comprising consists of short fibers of length 5 to 15 mm. 4. The dry nonwoven fabric layer has a length of 25 to 125 mm.
The battery separator according to any one of claims 1 to 3 , which is a hydroentangled nonwoven fabric made of the staple fiber of Claim 1. 5. The heat-adhesive fiber is a core-sheath type conjugate fiber having polypropylene as a core component and high-density polyethylene as a sheath component, and the conjugate fiber is contained in each nonwoven fabric layer in an amount of 10% by weight or more. 2. The battery separator according to 1 .