JPH06267525A - Separator for lead-acid battery - Google Patents

Abstract

PURPOSE:To improve the acid-proof property and to reduce the dirt in a battery by mixing mineral oils having specific weight mean molecular weights respectively to a minute porous formation sheet which consists of a polyolefin system resin and acid-proof inorganic powder, so as to include a specific wt.% of mineral oil. CONSTITUTION:As the manufacturing method, a mixture of a polyolefin system resin, an acid-proof inorganic powder, and, 30 to 70wt.% of a mineral oil with the weight mean molecular weight Mw 900 or more, and 70 to 30wt.% of a minaral oil with the weight mean molacular weight less than Mw 600, mixed as a placticizer and a peptizer, is made in a sheet form. And the mineral oil is extracted partially by a solvent, or extracted perfectly by a solvent so as to manufacture a minute porous formation sheet, and then the mineral oil is included 5 to 20wt.% by a coating or an impregnation so as to make a separator for lead storage battery. A battery integrating such a separator reduces the dirt in the battery by the synergetic effect of both mineral oils, and the acid- proof property is improved without increasing the electric resistance.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a polyolefin resin, an acid resistant inorganic powder, and a mineral oil that is easily eluted as a plasticizer and a pore-forming agent are mixed, molded into a sheet by an extruder, and then immersed in a solvent. Although a molded sheet for a microporous lead acid battery containing 5 to 30 wt.% Of mineral oil produced by eluting most of the mineral oil and leaving a part thereof is known, it has poor oxidation resistance. The weight average molecular weight of the mineral oil was Mw 700-800, and the molecular weight distribution was 150-3,900.

In order to improve the oxidation resistance of the above-mentioned lead-acid battery separator, it is conceivable to increase the content of the above-mentioned conventional mineral oil, but with the increase, the contamination in the battery increases, and , Inconvenience that the inconvenience that the electric resistance value increases increases.

Therefore, in order to improve the oxidation resistance of such a conventional separator, the applicant has reviewed the mineral oil from the viewpoint of the weight average molecular weight in Japanese Patent Application No. 3-350561 previously filed, and About 5 mineral oils with a molecular weight of 900 or more
We have proposed a lead-acid battery separator in which the microporous molded sheet contains ˜30 wt.%.

[0005]

However, the lead-acid battery separator according to the above-mentioned application has been improved in oxidation resistance, but when used in the separator battery, it has a problem of fouling in the battery. . Therefore, improvement of this point is desirable.

[0004]

SUMMARY OF THE INVENTION The present invention provides a lead-acid battery separator that satisfies both the above-mentioned needs and provides both excellent oxidation resistance and reduced fouling in the battery. A microporous molded sheet made of resin and acid-resistant inorganic powder, in a lead storage battery separator containing mineral oil, a mineral oil having a weight average molecular weight of Mw 900 or more of about 30 to 70 wt.% And a weight average molecular weight of less than Mw 600. Of mineral oil about 70
It is characterized by containing about 5 to 20 wt.% Of mineral oil formed by mixing about 30 to 30 wt.%.

[0006]

When the electrode plate assembly is assembled by a conventional method using the separator of the present invention and is assembled into a battery for use in a battery, the separator contains about 5% of the above specific mineral oil.
Since it contains ~ 20wt.%, The contamination in the battery is reduced,
At the same time, it provides improved oxidation resistance without increasing electrical resistance. It is considered that this is due to the synergistic effect of the above-mentioned oxidation resistance of the mineral oil on the high molecular weight side and the mineral oil on the low molecular weight side.

In this case, the mineral oil is prepared by mixing the above-mentioned high molecular weight mineral oil and low molecular weight mineral oil in a ratio of about 30 to 70 wt.% To about 70 to 30 wt.%. Is easy and
Moreover, the optimum effect of reducing the contamination of the battery and the effect of improving the oxidation resistance are surely brought about.

[0008]

EXAMPLES Next, examples of the present invention will be described. The method for producing the lead-acid battery separator of the present invention may be any conventionally known means, and the means for containing the mineral oil of the present invention comprises the polyolefin-based resin, the inorganic powder, and the mineral oil blended as a plasticizer and a pore-forming agent. After the mixture is formed into a sheet, a part of the mineral oil is extracted with a solvent to form a microporous formed sheet with about 5 to 20 w.
t.%, or after the mineral oil is almost completely extracted with the solvent to produce a microporous molded sheet, the mixture is coated with or impregnated with about 5% of the mixture.
Any means of about 20 wt.% May be used.

As a preferred example of the lead-acid battery separator of the present invention, one or more polyolefin resin 20 to 60 is used.
wt.% and specific surface area 100 to 400 m ² / g oxidation resistant inorganic powder
A microporous molded sheet composed of a mixture with 80 to 40 wt.% Contains about 5 to 20 wt.% Of the mineral oil.

The mineral oil which is a feature of the present invention is generally a mixture of a mineral oil having a weight average molecular weight of 900 or more and a mineral oil having a weight average molecular weight of less than 600, which is referred to as a lubricating oil or a process oil. These mineral oils are classified according to their chemical composition, paraffinic lubricating oil from paraffinic base oil rich in paraffinic hydrocarbons, naphthenic lubricating oil from naphthenic base oil, olefinic lubricating oil, aromatic lubricating oil. A lubricating oil or the like prepared by mixing a plurality of types of oils or various lubricating oils refined according to the degree of refinement and the viscosity is used as a base oil. Further, as the mineral oil, a lubricating oil to which additives such as a high boiling fraction, an antioxidant and a phosphoric acid type peroxide inhibitor are added can be used.

In the present invention, mineral oil was examined from its weight average molecular weight. The weight average molecular weight was measured by gel permeation chromatography (GPC) using polystyrene of known molecular weight as a standard sample to prepare a calibration curve. And analyzed by the relative method. The analysis of the mineral oil was performed using chloroform as a solvent, Shodex AC-802 as a column, and a sample concentration of 20 mg.
/ Ml, the detector was a differential refractometer (RI).

For each of the three types of mineral oil having a weight average molecular weight of Mw 530, Mw 790 and Mw 1100, a content of 5 wt.% Was added to a mixture of 40 wt.% Polyethylene resin having a high molecular weight of 1 million and 60 wt.% Silicic acid powder.
~ 20wt.% In different range, added and kneaded to produce lead acid battery separators with different mineral oil contents by the above conventional manufacturing method, and incorporate this into automobile battery to perform overcharge test. After that, the battery surface was tested for dirt and oxidation resistance. The results are shown in Table 1 below.

[0013]

[Table 1] In the present invention, regarding the stains in the battery, visually observing the battery after the test, the stain-free ones are ranked from rank 0, the conventional stains having a lot of stains are ranked, and the degree of stains is divided into 10 levels and put into practical use. The target was rank 3 or lower, which is not a problem.
As for the oxidation resistance of the separator, the strength before and after the test was compared, and the target was 70% or more, which is not a problem in practical use.

As is clear from Table 1, the weight average molecular weight
The mineral oil of Mw 530 has a mineral oil content of about 5 to 20 wt.%, And the fouling inside the battery is good at rank 3 or lower, but the oxidation resistance is poor at 70% or lower. Mineral oil with a weight average molecular weight of Mw 790 has a mineral oil content of 5
In wt.%, the contamination in the battery is good at rank 2, but the oxidation resistance is inferior at 62%. When the mineral oil content is 10 to 20 wt.%, The oxidation resistance is good at 70% or more, but the fouling inside the battery is inferior to rank 4. Mineral oil having a weight average molecular weight of Mw1100 has a mineral oil content of 5 to 20.
At wt.%, the stain inside the battery is inferior at rank 4 or higher, but the oxidation resistance is good at 73% or higher.

Furthermore, the inventors of the present invention have conducted many tests over a long period of time on the influence on the fouling in the battery and the oxidation resistance by mixing the mineral oils having such respective weight average molecular weights. , A mineral oil having a weight average molecular weight of 900 or more and a mineral oil having a weight average molecular weight of less than 600 is uniformly mixed with a microporous molded sheet composed of a mixture of a polyolefin resin and an inorganic powder in an amount of about 5 to 20 wt. It has been concluded that the inclusion of the lead content in the battery makes it possible to obtain a lead storage battery separator having a target value rank of 3 or less and an oxidation resistance target value of 70% or more.

Next, using the above mineral oil as a sample, various mixed oils were prepared, respective separators containing the mixed oils were prepared, and the results of testing the oil stain and the oxidation resistance are described in detail below. . 100 weight parts of a mixture of 40 wt.% Of polyethylene resin having a weight average molecular weight of 1,000,000 or more and 60 wt.% Of silicic acid powder having a specific surface area of 250 m ² / g. Mineral oil of Mw 530 and mineral oil of weight average molecular weight Mw 1100 were mixed in a ratio of 50:50, 140 parts by weight was added and mixed by a mixer, and the mixture was extruded by a twin-screw extruder, Thickness 0.25m
m, rib pitch 10 mm, rib height 1.0 mm, upper width 0.4 mm,
A large number of long ribbed molding sheets with 0.8 mm lower ribs arranged parallel to the length direction were prepared, and each molding sheet was dipped in at least one solvent layer containing trichlorethylene at room temperature. A part of the mixed oil contained in each molded sheet was extracted, and the mixed oil content as shown in each sample No. was pulled up while remaining so as to vary in the range of about 5 to 20 wt.%. Then, each oil-containing microporous molded sheet was dried with a drier to volatilize the solvent, and then cut into a predetermined size to manufacture each microporous lead acid battery separator.

Next, using these separator samples, the rib side was inserted between the anode plate and the cathode plate with the anode plate facing the anode plate, and JIS D 5301 automotive storage battery 36B20 type battery was prepared.
Created respectively. The following life test was performed on each of the batteries. That is, the battery was first subjected to 10.5 in water at 25 ° C.
Perform the initial charge for 18 hours at A, then in a 75 ° C water bath for 12 hours
In A, a high temperature overcurrent test with a feeling of 10 days was performed. After the high temperature overcharge test, the stain condition inside the battery was visually observed, and the stain was evaluated according to the above ranking. As the oxidation resistance of each separator sample, the strength of the separator after the high temperature overcharge test was compared with the normal strength of the separator before the test as 100. The measurement results are shown in Table 2 below.

[0018]

[Table 2]

As is clear from Table 2 above, the separators No. 2 to No. 5 containing the mineral oil in the range of about 5 to 20 wt.
It is found that the oil stain rank is 3 or less and the oxidation resistance is 70% or more, and if either of the above or both of the above values does not reach the respective target values, it deviates from this range.

Next, various mixed oils prepared by changing the compounding ratio of the mineral oil having the above-mentioned weight average molecular weight Mw 530 and the mineral oil having the weight average molecular weight Mw 1100 were used, each containing a fixed amount of about 11 wt.%. The separator was prepared, and the influence of the change in the compounding ratio on the stain inside the battery and the oxidation resistance was tested. The results are as shown in Table 3 below.

[0021]

[Table 3]

As is apparent from Table 3, the compounding ratio of the mineral oil having the weight average molecular weight Mw 530 to the mineral oil having the weight average molecular weight Mw 1100, which is each compounding raw material for preparing the mineral oil, is about
In the range of 30 to 70 to about 70 to 30, dirt in the battery is 3 or less,
It was found that the oxidation resistance was maintained at 70% or more.

Next, Table 4 shows the properties of the mineral oil prepared by mixing and mixing the above-mentioned mineral oil having the weight average molecular weight Mw 530 and the mineral oil having the weight average molecular weight Mw 1100 in a ratio of 50:50.

[0024]

[Table 4]

The lead acid battery for automobiles, which is constituted by using each of the above-described lead acid battery separators No. 2 to No. 5, No. 8 and No. 9 containing 10 wt.% Of this mineral oil, is as described above. It was an excellent lead-acid battery with little contamination in the battery, excellent oxidation resistance, and a small electric resistance value of 0.0015 Ω / 100 m ² / sheet or less.

As a result of many comparison tests, mineral oils to be mixed were found to have a weight average molecular weight of significantly lower than 700 and a weight average molecular weight of about 600 or less and a weight average molecular weight of 800 or more and a weight average molecular weight of about 900 or more. About 70-30w
It was found that the mineral oil formed by mixing at a ratio of t.% to about 30 to 70 wt.% brings about a reduction in the fouling in the battery and an improvement in the oxidation resistance as in the above.

[0027]

As described above, according to the present invention, in a lead storage battery separator containing a mineral oil in a microporous molded sheet of a polyolefin resin and an inorganic powder, a mineral oil having a weight average molecular weight of 900 or more is about 30 to 70 wt. % And weight average molecular weight 60
Since the mixed oil containing about 70 to 30 wt.% Mineral oil less than 0 was contained in about 5 to 20 wt.%, When this was used as a lead storage battery separator, the contamination in the battery was significantly reduced,
In addition, it is possible to provide a good quality lead acid battery with improved separator oxidation resistance.

Claims (1)

[Claims] A weight average molecular weight Mw 900 of a lead-acid battery separator comprising a microporous molded sheet made of a polyolefin resin and an acid resistant inorganic powder and containing mineral oil.
About 5 to 20 wt.% Of mineral oil is obtained by mixing about 30 to 70 wt.% Of the above mineral oil and about 70 to 30 wt.% Of mineral oil having a weight average molecular weight of less than Mw 600.
A lead-acid battery separator characterized by containing.