JPH056760A - Manufacture of separator for storage battery - Google Patents

Abstract

PURPOSE:To improve a wetting property with sulfonating solution, expedite olefinating work, and manufacture a storage battery separator improved in the liquid absorbing property of electrolyte. CONSTITUTION:A porous sheet made of polyolefin resin is subjected to corona discharge treatment, and then the resulting sheet is dipped into sulfonating solution and sulfonated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a storage battery separator.

[0002]

2. Description of the Related Art Conventionally, a separator made of a polyolefin resin has been used as a storage battery separator. However, in order to improve the affinity with an electrolytic solution, a porous sheet made of a polyolefin resin is immediately used for sulfonation of fuming sulfuric acid or the like. A separator in which the surface of the polyolefin resin is sulfonated by directly substituting a part of hydrogen atoms of the polyolefin resin with a sulfone group is known.

[0003]

However, even if the porous sheet made of the polyolefin resin is directly immersed in the sulfonation liquid to perform the sulfonation treatment as in the above-mentioned conventional method,
Since the wettability of the porous sheet with respect to the sulfonation liquid is poor, sulfonation is not performed sufficiently, unevenness occurs in the sulfonation treatment, and the result that the electrolyte absorbability of the sulfonated separator is poor is recognized. It was Therefore, before immersing the porous sheet in a sulfonation solution, the porous sheet was immersed in a surfactant to impart wettability to the surface thereof, and then immersed in the sulfonation solution. As a result, the surfactant adhering to the surface hinders the sulfonation, and further, the sulfonation liquid is contaminated with the surfactant, which makes it impossible to use as the sulfonation liquid. Therefore, before the sulfonation treatment of the porous sheet with the sulfonation liquid, the wettability is improved without using a surfactant, and the sulfonation treatment is performed by immersing the porous sheet in the subsequent sulfonation liquid. In this case, a method for producing a storage battery separator which can sufficiently perform sulfonation treatment with the sulfonation liquid and has improved liquid absorption is desired.

[0004]

[Means for Solving the Problems] A method for manufacturing a separator for a storage battery according to the present invention, which has solved the above-mentioned problems, is such that a porous sheet made of a polyolefin resin is subjected to corona discharge treatment and then immersed in a sulfonation liquid. And sulfonation treatment is performed.

[0005]

When the porous sheet made of the polyolefin resin is subjected to corona discharge treatment, its surface is oxidized by active oxygen generated by corona discharge and becomes an active surface having a reactive group such as a carboxyl group and a carbonyl group. Therefore,
Next, when this porous sheet having an active surface is immersed in a sulfonation solution for sulfonation treatment, the wettability with respect to the sulfonation solution is significantly improved. It is possible to easily and swiftly penetrate into the inside and to perform the sulfonation process quickly, and to obtain an excellent separator in which the entire surface of the porous sheet is sufficiently sulfonated to the inside, and thus obtained. Further, the separator of the present invention has a remarkably good affinity for the electrolytic solution for a storage battery, and exhibits an excellent large liquid absorbing property.

[0006]

EXAMPLES Next, examples of the present invention will be described in detail. The polyolefin resin porous sheet may be a woven fabric such as polypropylene or polyethylene, or a non-woven fabric. Porous sheets are preferred. According to the invention, the porous sheet is first of all subjected to a predetermined corona discharge treatment. Here, the corona discharge treatment means that the pair of electrodes are placed in air at room temperature and pressure, and a high voltage is applied between both electrodes to cause corona discharge and active oxygen such as ozone produces the porous sheet. To the surface for a predetermined time to oxidize the surface and
It means to generate a reactive group such as H group. This treatment is generally performed at a frequency of 10 KHz to 50 KHz and a voltage of 20 to 40 KV, and the treatment speed at this time is preferably 0.5 to 5 m / min in the case of a pair of electrodes. Thus, not only on both sides of the porous sheet, but also on the entire surface of the porous sheet including the fiber surface in the numerous pores, C = O
An active surface with reactive groups, such as groups, COOH groups, is obtained. Next, the porous sheet having an active surface thus obtained by the corona discharge treatment is immersed in a sulfonation liquid to be subjected to the sulfonation treatment. As the sulfonation liquid, any sulfonation liquid generally composed of fuming sulfuric acid, chloric sulfuric acid, sulfur trioxide, high-concentration hot sulfuric acid, etc. is selected and used. When the porous sheet is dipped in the sulfonation liquid, the surface of the porous sheet is the active surface as described above, so that the wettability with the sulfonation liquid is extremely good. It rapidly and sufficiently penetrates into a myriad of pores, and the entire surface of the porous sheet is in good contact with the sulfonation liquid. Therefore, a short time of immersion brings about a large amount of sufficient sulfonation over the entire surface. As a result, this sulfonation treatment operation can be carried out rapidly, resulting in an improvement in productivity and a separator having remarkably improved liquid absorbability with respect to the electrolytic solution. That is, in the sulfonation in this case, since a large amount of reactive groups are scattered over the entire surface of the porous sheet, the sulfonation group (—SO ₃
H) easily and rapidly reacts with the reactive group, and has a sulfone group on the entire surface thereof. Therefore, a separator having an improved affinity for the electrolytic solution can be obtained. Thus, the sulfonation-treated porous sheet is pulled up, washed with water,
Although it is dried, in order to avoid heat generation during washing with water, it is once immersed in an aqueous solution of sulfuric acid, then washed with water and dried. Thus, the production of the storage battery separator having an extremely good electrolyte absorbing property is completed.

Next, specific examples of the present invention will be described together with comparative examples. Example 1 After forming a 0.2 mm-thick web composed of polyethylene synthetic pulp and polypropylene fibers by a conventional wet papermaking method, this web was heated using a heat treatment device to cause interfiber bonding to form a porous sheet. Manufactured. Next, this porous sheet is subjected to a frequency of 30 KH by a corona discharge treatment machine.
Corona discharge treatment was performed at z, voltage of 30 KV, and treatment speed of 3 m / min. Next, the corona discharge-treated porous sheet was immersed in 30% fuming sulfuric acid at 18 ° C for 5 minutes for sulfonation treatment, and then a sulfuric acid aqueous solution having a specific gravity of 1.4 to avoid heat generation during washing with water. After immersing in water for 5 minutes, it was washed with water and dried to obtain the separator of the present invention. Example 2 A porous sheet having a thickness of 0.2 by a spun bond method.
A separator of the present invention was obtained by the same process as in Example except that a polypropylene non-woven fabric of mm was used. Comparative Example 1 A 0.2 mm-thick porous sheet composed of polyethylene synthetic pulp and polypropylene fiber produced by the same production method as in Example 1 was impregnated in an aqueous nonionic surfactant solution in advance, and then this was applied. A sulfonation treatment was performed by immersing in 30% fuming sulfuric acid at 18 ° C. for 5 minutes. Next, the specific gravity is 1.4
After being immersed in the sulfuric acid aqueous solution for 5 minutes, washed with water and dried to obtain a separator. Comparative Example 2 A separator was obtained in the same manner as in Comparative Example 1 except that a polypropylene non-woven fabric having a thickness of 0.2 mm manufactured by the same manufacturing method as in Example 2 was used.

Comparative Example 1 and the fuming sulfuric acid absorption rate of each of the porous sheets subjected to the corona discharge treatment produced in the process of producing the separator of the present invention in each of Examples 1 and 2 above.
The fuming sulfuric acid absorption rates of the respective porous sheets which were not subjected to the corona discharge treatment of No. 2 and No. 2 were compared. In the test method, the lower end 5 mm of each sample was vertically dipped in fuming sulfuric acid having a concentration of 30%, and the rising height of fuming sulfuric acid after 5 minutes was measured. The test results are shown in Table 1 below.

[0009]

[Table 1]

As is clear from Table 1, regardless of the form of the porous sheet, those treated with corona discharge have better liquid absorption of the sulfonation liquid than those not treated, and the sulfonation treatment is performed. It turns out that work can be done quickly.

Next, with respect to each of the separators manufactured in Examples 1 and 2 and Comparative Examples 1 and 2, the liquid absorbing speed of the electrolytic solution was tested. The test method is as follows:
mm was vertically dipped in a caustic potash aqueous solution having a specific gravity of 1.30 (20 ° C.), and the rising height of the alkaline aqueous solution after 5 minutes was measured. The test results are shown in Table 2 below.

[0012]

[Table 2]

As is clear from Table 2, regardless of the form of the porous sheet, those subjected to corona discharge treatment have a significantly large amount of sulfonation on the surface as compared with those not treated. , The affinity with the electrolyte is significantly improved,
It can be seen that a storage battery separator having an excellent liquid absorbing property can be obtained. The separator of the present invention thus obtained is Ni /
It can be applied as a storage battery separator such as an alkaline storage battery such as a Cd storage battery or a Ni / MH storage battery.

[0014]

As described above, according to the present invention, the porous sheet made of polyolefin resin is subjected to corona discharge treatment in advance and then immersed in the sulfonation liquid, so that the sulfonation treatment can be performed quickly. Therefore, the productivity of the separator can be improved, and the separator for a storage battery having significantly increased electrolyte absorbing property can be manufactured.

Claims (2)

[Claims] 1. A method for producing a separator for a storage battery, characterized in that a porous sheet made of a polyolefin resin is subjected to corona discharge treatment, then immersed in a sulfonation liquid, and then subjected to sulfonation treatment. . 2. The method for manufacturing a storage battery separator according to claim 1, wherein the porous sheet is a dry nonwoven fabric or a papermaking sheet.