JPH08250096A - Battery separator and method for manufacturing the same - Google Patents

Abstract

(57) [Abstract] [Purpose] Synthetic resin base film 3 having hydrophilic groups
Cellulosic films 2 and 2 are laminated and integrated on both sides of
Provided is a battery separator that prevents the generation of wrinkles and air pockets by laminating and integrating a graft membrane 1 having ion permeability on at least one surface thereof. [Structure] Cellophane (thickness 21 μm) 2 and 2 in a state of containing water are brought into contact with PVA film (thickness 30 μm) 3 and dried to obtain a cellophane / PVA film / cellophane laminate, and then ion A battery separator is manufactured by pressure-bonding and laminating the permeable graft membrane 1.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an alkaline battery separator. More specifically, the present invention relates to a separator for alkaline batteries in which a graft film having ion permeability is laminated and integrated on the surface of a cellulose film.

[0002]

2. Description of the Related Art Conventionally, a cell separator in which cellophane, cellophane, and an ion-permeable graft membrane are laminated in this order is known. In addition, JP-A-6-3
According to Japanese Patent Publication No. 02312, a separator for an alkaline battery is proposed in which a film obtained by grafting a hydrophilic vinyl monomer such as acrylic acid or methacrylic acid on a polyolefin resin film is bonded to cellophane, and a liquid-retaining paper is bonded thereon. ing.

[0003]

However, the conventional product has a problem that it is difficult for cellophane to adhere to each other and wrinkles and air traps are easily formed. A separator having wrinkles or air pockets is not preferable because it causes an increase in internal electric resistance of the battery.

In order to solve the above-mentioned problems of the prior art, it is an object of the present invention to provide a battery separator free from wrinkles and air pockets and a method of manufacturing the same.

[0005]

In order to achieve the above-mentioned object, the battery separator of the present invention comprises a synthetic resin substrate film having a hydrophilic group, and a cellulose-based film laminated and integrated on both sides thereof, and at least one of them. And a graft membrane having ion permeability is laminated and integrated on the surface of the.

In the method for producing a battery separator of the present invention, the cellulosic film is made to contain water and brought into contact with both sides of a synthetic resin base material film having a hydrophilic group, followed by drying to laminate and integrate them. It has a configuration in which a graft membrane having ion permeability is pressure-bonded and laminated on at least one surface to integrate the layers.

In the above structure, the synthetic resin substrate film having a hydrophilic group is preferably polyvinyl alcohol. Further, in the above structure, the ion-permeable graft membrane is preferably a graft membrane obtained by graft-copolymerizing at least one vinyl monomer capable of imparting ion-permeability to a synthetic resin film.

In the above construction, it is preferable that the cellulosic film is cellophane.

[0009]

According to the battery separator of the present invention described above,
The cellulosic film is laminated and integrated on both sides of the synthetic resin substrate film having a hydrophilic group, and the graft membrane having ion permeability is laminated and integrated on at least one surface of the substrate film, so that wrinkles and air traps are formed. It is possible to realize a battery separator that does not have a battery. As a result, a battery separator having high production efficiency and high reliability can be realized.

Further, according to the method for manufacturing a battery separator of the present invention, water is added to a cellulosic film to bring both surfaces of a synthetic resin substrate film having a hydrophilic group into contact with each other, and the layers are integrated by laminating. Then, a graft membrane having ion permeability is pressure-bonded and laminated on at least one surface thereof to form a monolithic laminate, whereby a battery separator with high production efficiency and high reliability can be realized.

According to the preferable example in which the synthetic resin substrate film having a hydrophilic group is polyvinyl alcohol (PVA), both PVA and the cellulosic film have a hydrophilic group (—OH group). Therefore, it can be easily integrated with water, for example. Where P
The _{VA, [- CH 2 CH (} OH) -] is indicated by _n, for example, produced by hydrolyzing polyvinyl acetate with an acid or alkali.

In the above description, cellophane (cellophane) is a thin film of cellulose, which is a kind of regenerated cellulose and is also called a viscose film. Cellophane itself is well known to those skilled in the art.

[0013]

EXAMPLES The present invention will be described more specifically below with reference to examples. In order to solve the problems of the prior art, the inventors of the present invention have, as a result of various studies, found that a graft film obtained by graft-copolymerizing at least one vinyl monomer capable of imparting ion permeability to a plastic film, or a laminated film thereof, PVA
It has been found that wrinkles and air pockets can be eliminated by laminating a laminate composed of at least two cellophane laminated via a film, and the present invention has been completed.

The ion-permeable graft membrane used in the present invention is widely used by those skilled in the art, and at least one vinyl monomer capable of imparting ion permeability is graft-copolymerized to a plastic film. Any grafted film can be used. Typical examples are polyolefin films such as polypropylene and polyethylene,
Examples include those obtained by graft-polymerizing an ethylenically unsaturated carboxylic acid such as acrylic acid or methacrylic acid onto a plastic film such as polytetrafluoroethylene or polyamide. With respect to 100 parts by weight of the above ethylenically unsaturated carboxylic acid, 100 parts by weight or less of a hydroxyalkyl ester unit such as hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxymethyl methacrylate, and hydroxyethyl methacrylate are used. In addition, it may be graft-polymerized.

The ion-permeable graft membrane can be obtained by the above method. In some cases, the graft chain of the graft membrane, that is, the ethylenically unsaturated carboxylic acid can be obtained by neutralizing with an aqueous solution of potassium hydroxide or an aqueous solution of sodium hydroxide and then dipping or contacting with water.

The electric resistance of the PVA film is preferably 100 mΩ · in ² or less in order to prevent the internal resistance of the battery from rising. It is particularly preferably 20 mΩ · in ² or less. The thickness is usually preferably 50 μm or less, and particularly preferably 20 μm or less. Further, there is no problem even if one side or both sides of the PVA film is subjected to blocking prevention treatment such as embossing treatment.

The battery separator may be one in which a microporous membrane is laminated on the ion-permeable graft membrane side, or a hydrophilic substance layer may be formed on the ion-permeable graft membrane side. Further, even if a nonwoven fabric is laminated on the cellophane side, there is no problem. As a typical example of the combination, the configurations shown in FIGS. 1 and 2 can be cited as an example. FIG. 1 is a sectional view showing the structure of a battery separator according to an embodiment of the present invention. In FIG. 1, the PVA film 3
The cellophane 2 is laminated and integrated on both surfaces, and the ion-permeable graft membrane 1 is laminated and integrated on one surface thereof. Next, FIG. 2 is a sectional view showing the structure of a battery separator according to another embodiment of the present invention. In FIG. 2, cellophane 2 is laminated and integrated on both surfaces of PVA film 3, and ion-permeable graft membranes 1a and 1b are laminated and integrated on one surface thereof.

The battery separator of the present invention can be manufactured by the following method. For example, by contacting a cellophane with a PVA film in a water-containing state and then drying it to obtain a laminate of cellophane and a PVA film, by contacting the cellophane in a water-containing state with the PVA film side,
A cellophane / PVA film / cellophane laminate is obtained. Then, it can be manufactured by pressure-bonding the laminate and the ion-permeable graph film.

Next, an example of the present invention will be described to explain more specifically. (Example 1) PVA film manufactured by Kuraray Co., Ltd .: # 30 in a state where cellophane (thickness 21 μm) was made to contain water.
00 (thickness 30 μm) and then dried to obtain a laminated product of cellophane and PVA film, and then cellophane containing water is brought into contact with the PVA film side to laminate cellophane / PVA film / cellophane. I got the goods. Then, the laminated product and the ion-permeable graft film were pressure-laminated to produce a battery separator. As the graft film, a long polyethylene film having a thickness of 25 μm is irradiated with an electron beam of 20 Mrad,
A 40 wt% aqueous solution of methacrylic acid (liquid temperature 40 ° C)
For 5 hours, graft copolymerize polyethylene with methacrylic acid (graft ratio 35%) and pull up, and then dip this graft membrane in 10% by weight potassium hydroxide aqueous solution for 1 hour to convert the methacrylic acid moiety to potassium salt. did.

As a result, in the obtained separator, the films were in close contact with each other, and there were no air pockets or wrinkles. (Comparative Example 1) PVA: Gohsenol (GM-14) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. was dissolved in a mixed liquid of water and alcohol to obtain a solution having a concentration of 5% by weight. This PVA solution was applied to cellophane (thickness 21 μm) and pressure-bonded with another cellophane (thickness 21 μm) to obtain a cellophane laminate. Then, the laminated product and the ion-permeable graft membrane were pressure-laminated to produce a battery separator. This separator had many air pockets and wrinkles.

[0021]

As described above, according to the battery separator of the present invention, the cellulosic film is laminated and integrated on both sides of the synthetic resin substrate film having a hydrophilic group,
Since the graft membrane having ion permeability is laminated and integrated on at least one of the surfaces, wrinkles and air pockets can be prevented from occurring.

Further, according to the method for producing a battery separator of the present invention, water is added to a cellulosic film so that both surfaces of a synthetic resin substrate film having a hydrophilic group are brought into contact with each other and dried to laminate and integrate them, Then, a graft membrane having ion permeability is pressure-bonded and laminated on at least one surface thereof to form a monolithic laminate, whereby a battery separator with high production efficiency and high reliability can be realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a battery separator according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of a battery separator according to another embodiment of the present invention.

[Explanation of symbols]

 1,1a, 1b Ion-permeable graft membrane 2 Cellophane 3 PVA film

Claims (5)

[Claims] 1. A battery in which a cellulosic film is laminated and integrated on both sides of a synthetic resin substrate film having a hydrophilic group, and an ion-permeable graft membrane is laminated and integrated on at least one surface thereof. Separator. 2. A graft having an ion-permeable property on at least one surface of a synthetic resin substrate film having a hydrophilic group, which is made by contacting both sides of a cellulose resin film with water and bringing it into contact with both sides and drying. A method for manufacturing a battery separator in which membranes are laminated by pressing and laminating. 3. The battery separator and the method for producing the same according to claim 1, wherein the synthetic resin substrate film having a hydrophilic group is polyvinyl alcohol. 4. The graft membrane having ion permeability is a graft membrane obtained by graft-copolymerizing at least one vinyl monomer capable of imparting ion permeability to a synthetic resin film. Battery separator and manufacturing method thereof. 5. The battery separator according to claim 1, wherein the cellulosic film is cellophane, and the method for producing the same.