JPH0430143B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in separators for lead-acid batteries, and in particular provides a separator suitable for envelopes used in MF (maintenance-free) batteries. In recent years, automotive batteries have rapidly become smaller, lighter, and more MF-based, and lattice alloys have changed from the conventional Pb-Sb system to lower
It has become more and more Sb-free (Pb-Ca type). Compared to conventional Pb-Sb alloys, Pb-Ca alloys have lower electrical resistance, better corrosion resistance, and less self-discharge in batteries, so they are suitable for MF batteries, but during use, The disadvantage is that the positive electrode lattice is significantly elongated. To compensate for these shortcomings, MF batteries generally have a design structure in which the positive or negative electrode plate is enveloped with a separator to prevent shortening due to grid elongation. Separators for MF batteries are capable of enveloping and do not break even if the electrode plates are deformed during use, as well as being thin with low resistance, having excellent oxidation resistance, and containing little eluted impurities. Therefore, using conventional products as is will cause many problems in terms of battery performance. Further, examples of separators having the above-mentioned characteristics include extrusion-molded microporous ultra-high molecular weight polyolefins and sintered PVC (polyvinyl chloride). However, the former is expensive, and the latter cannot necessarily be said to have sufficient characteristics. The present invention achieves the above-mentioned properties by impregnating a paper product containing lipophilic polymer fibers such as polyethylene, polypropylene, polystyrene, polyacrylonitrile, polyacrylic acid ester type or polyester type with oil mainly composed of alkanes and cycloalkanes. The purpose of the present invention is to provide an inexpensive separator that satisfies the characteristics of an envelope separator. The present invention will be explained below with reference to Examples. [Example 1] 45 wt% polyethylene (SWP) fiber, 10 wt% polyacrylonitrile fiber, 6 μm C glass fiber
Water-soluble oil emulsion (10% aqueous oil solution) in a paper structure consisting of 7wt% and 38wt% silica fine powder.
Impregnated with equal amount of
Separator A impregnated with oil was obtained. In addition,
The oil emulsion used here is a water-soluble oil made by mixing a petroleum-based anion activator with refined mineral oil whose main components are alkanes and cycloalkanes, and is prepared by diluting it with water as specified in JISK2241. did. SWP is the trade name for polyethylene synthetic pulp. [Example 2] Separator B was obtained in the same manner as in Example 1, except that it was impregnated with a 20% aqueous oil solution and dried at 135°C. [Example 3] Separator C was applied in the same manner as in Example 2 to a paper product consisting of 40 wt% polyethylene (SWP) fibers, 15 wt% polyester fibers with a thickness of 6 d, and 45 wt% diatomaceous earth.
I got it. [Example 4] 80wt% polypropylene fiber, fine silica powder
Separator D was obtained in the same manner as in Example 1 using a paper product containing 20 wt%. Table 1 shows the characteristics of the separator produced in the above example and the NS40Z・MF battery (positive electrode plate is enveloped)
The performance is shown below. For comparison, the paper article described in Example 1 (before being impregnated with oil in Example 1) was prepared as Separator E as a conventional example.

[Table] As is clear from the results in Table 1, the life performance of the battery using the oil-impregnated separator of the present invention was superior to that of the conventional product not impregnated with oil. Separator B impregnated with 20% oil had considerably higher electrical resistance, but was the best in terms of life performance. After the end of the life test, the remaining amount of oil in each separator was analyzed using a Soxhlet extractor, and it was found to be over 80% for each separator. The optimal amount of oil to be impregnated into the separator of the present invention varies depending on the type, shape, and amount of the lipophilic polymer fibers used in the separator, but usually it is 1/10 or more of the amount of the lipophilic polymer fibers, and 1/10 or more of the amount of the lipophilic polymer fibers. /
2 or less. If it is less than 1/10, almost no oil impregnation effect will be seen, and if it is more than 1/2, the electrical resistance will become extremely high or the oil will be liberated during use in the battery, which is not preferable. The oil used in the present invention is mainly composed of alkanes represented by the general formula C _o H _2o+2 and cycloalkanes represented by the general formula C _o H _2o , and may be either paraffinic or naphthenic. But that's fine. In the example, oil was emulsified using an emulsifier and impregnated into a separator, but in this case, the surfactant remains in the separator after water is evaporated by drying, so treatment with an impregnating agent is not necessary. Not necessary. In addition to the method described in the examples, there are also methods for impregnating the separator with oil, such as directly impregnating the separator with oil.
Alternatively, the oil may be dissolved in an organic solvent such as methanol and impregnated. It is thought that the oil impregnated into the separator selectively adsorbs to the lipophilic polymer fibers and prevents the polymer from deteriorating due to electrochemical oxidation. Moreover, this oil does not turn into harmful impurities during use in batteries. As described above, the separator of the present invention has significantly improved the characteristics of conventional separators that can be obtained in large quantities and at low cost by paper-making methods, and satisfies the characteristics as a separator for envelopes.In particular, it has excellent oxidation resistance, It is not necessarily limited to use in envelopes, but can also be used in batteries using general Pb-Sb grids, and has great industrial value.

Claims (1)

[Claims] 1 A paper product containing polyethylene, polypropylene, polystyrene, polyacrylonitrile, polyacrylic acid ester or polyester lipophilic polymer fibers, and an alkane represented by the general formula C _o H _2o+2 and an alkane represented by the general formula C _o H _2o A separator for lead-acid batteries for enveloping a positive electrode lattice made of a Pb-Ca alloy, characterized in that it is impregnated with an oil containing the shown cycloalkane as a main component.