JPH0381263B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in separators used in sealed lead-acid batteries. Recently, a pine-like separator mainly made of fine glass fibers with a fiber diameter of about 0.2 to 5.0 μm has been put into practical use as a separator for sealed lead-acid batteries that do not require maintenance. shows performance. However, since this type of fine glass fiber is expensive, lead-acid batteries using it also have the disadvantage of being expensive. In order to eliminate this drawback, we reduced the amount of expensive fine glass fibers and replaced them with cheap synthetic fibers or
A mixture of glass fibers having a fiber diameter of about 20 μm or a mixture of silicon oxide-based inorganic powder have been proposed. However, in the former case, if the amount of synthetic fiber or glass fiber with a large fiber diameter is increased in order to lower the price, the liquid absorption characteristics of the electrolyte will deteriorate. In the latter case, if the amount of inorganic powder mixed is increased to lower the price, the entanglement between the fine glass fibers becomes worse and the strength becomes so weak that it cannot withstand handling, so thermoplastic synthetic fibers are mixed. Even if an improved method of heat treatment is taken, the amount of fine glass fibers is actually 50% by weight.
However, the company was unable to reduce prices sufficiently. The present invention eliminates the above-mentioned drawbacks, and aims to provide a storage battery separator that has good properties such as liquid absorption properties, tensile strength, and maximum pore diameter, and is easy to handle and inexpensive. It is formed by mixing up to 10% by weight of fine glass fibers, 10-20% by weight of fibrillar synthetic fibers, 20-40% by weight of monofilamentous fibers, and 30-60% by weight of hydrophilic inorganic powder. , the average fiber diameter as fine glass fiber is
Use fibers of 0.6 μm or less, use fibrillar synthetic fibers with a freeness of 5 sec/g or more, use polyester or glass with a fiber diameter of 8 to 13 μm as monofilament fibers, and use diatomaceous earth or glass as inorganic powder. It is characterized by the use of perlite. The present invention will be explained in detail below. In general, when fibrillated synthetic fibers are used for separators, the strength of the separator can be improved because the branched fibers cause more entanglement between fibers than when monofilament fibers are used. is known. However, simply using fibrillar synthetic fibers does not make it possible to obtain the above-mentioned separator for a storage battery. The present inventors have discovered that a desired separator can be obtained by appropriately selecting the freeness and mixing amount of fibrillar synthetic fibers, and by using appropriate amounts of monofilament fibers and hydrophilic inorganic powder in combination. was confirmed from many experimental results. Table 1 shows conventional separators mainly made of fine glass fibers (samples O and P), as well as those with a smaller amount of fine glass fibers than conventional separators, fibrillar synthetic fibers, monofilament fibers, and hydrophilic separators. The separators of the present invention (Samples A to E), which were formed using various types and amounts of inorganic powder and had good properties, and the separators as comparative examples with insufficient properties (Samples F to N) are shown in terms of mixture composition, raw material price, and characteristics of the mixture. The raw material price is 100 for sample O.
is the raw material price required to obtain a separator with the same apparent thickness. The liquid absorption characteristics are shown by the time required to suck up 90 mm of dilute sulfuric acid by standing the separator vertically and sucking up 1.30 d of dilute sulfuric acid from below. In addition, three characteristics of the separator are listed: liquid absorption characteristics, tensile strength, and maximum pore diameter. In relation to battery life, it is desirable that the liquid absorption characteristics be 600sec/90mm or more and the maximum pore diameter be 30μm or less.
It is known that a tensile strength of 0.25 kg/15 mm or more is desirable in relation to the battery assembly process. In Table 1, Samples B, E, and I differ only in the freeness of the fibrillar synthetic fibers in the mixed composition. Sample B with freeness of 5sec/g and
Sample E with a freeness of 10 sec/g has all good properties, but sample I with a freeness of 2 sec/g has insufficient tensile strength. Therefore,
It is understood that the freeness of fibrillated synthetic fibers is required to be 5 sec/g or more. Furthermore, fibrillar synthetic fibers improve tensile strength, but when the amount mixed is 5% by weight as in Sample J, the tensile strength is insufficient. Therefore, as in Sample C, it is understood that the amount of fibrillar synthetic fibers mixed is required to be 10% by weight or more. Although polyethylene is used as the fibrillar synthetic fiber, acrylic fiber may also be used. Monofilamentous fibers are used in proportions of 20 to 40% by weight. As the monofilament fiber, glass or polyester having a fiber diameter of 8 to 13 μm is used. A comparison of Samples E and K shows that they differ only in the fiber diameter of the polyester used and the type of inorganic powder, and Sample K has insufficient liquid absorption properties. This is thought to be due to the difference in the fiber diameter of the polyester, and from this it is understood that it is preferable to use a polyester with a fiber diameter of 8 μm. Further, when fine glass fibers are not used (sample A), it is preferable to use a mixture of glass and polyester as the monofilament fibers. Diatomaceous earth or perlite is used as the hydrophilic inorganic powder. These are used in proportions of 30 to 60% by weight. Furthermore, from samples L, M, etc.
It is understood that in order to obtain desirable liquid absorption properties, the amount of inorganic powder mixed must be at least 30% by weight. Moreover, if the mixing amount exceeds 70% by weight, it becomes impossible to fix the inorganic powder between the fibers in the paper-making process, and the strength becomes extremely weak, which is not preferable. Therefore, up to 60% by weight is considered appropriate. Note that the amount of fine glass fibers is preferably reduced to 10% by weight or less in order to reduce the overall raw material cost. In addition, in the example in Table 1, the average fiber diameter is 0.6 μm.
Although the following is used, of course it may be less than this. If the average fiber diameter is 1.0 μm or less, good properties can be maintained, but if the average fiber diameter is 2.0 μm or more, the properties of the separator deteriorate, which is not preferable. Fine glass fiber of 10% by weight or less as above,
By mixing and forming 10 to 20% by weight of fibrillar synthetic fibers, 20 to 40% by weight of monofilamentous fibers, and 30 to 60% by weight of hydrophilic inorganic powder, the average fiber diameter is reduced as fine glass fibers. but
Use fibrillar synthetic fibers with a freeness of 5 sec/g or more, use polyester or glass with a fiber diameter of 8 to 13 μm as monofilament fibers, and use diatomaceous earth or glass as inorganic powder. By using perlite,
An inexpensive separator with good properties as a separator, including liquid absorption properties, tensile strength, and maximum pore diameter, can be obtained. As described above, the present invention prevents a decrease in liquid absorption properties due to an increase in the amount of synthetic fiber mixed by using a hydrophilic inorganic powder in combination, and
By using fibrillated synthetic fibers with a freeness of 5 sec/g or more, the amount of expensive fine glass fibers mixed is as low as 10% by weight or less while maintaining tensile strength, and heat treatment after sheet processing is not required. You can get a cheap separator that doesn't. The separator of the present invention can be manufactured at a much lower cost than conventional separators, and by using the separator of the present invention, it is cheaper and has better performance than conventional separators. It is possible to provide a storage battery that is substantially equivalent to the above, and its industrial value is great.

【table】

[Table] Shown by time.

Claims (1)

[Claims] 1 Formed by mixing 10% by weight or less of fine glass fibers, 10 to 20% by weight of fibrillar synthetic fibers, 20 to 40% by weight of monofilamentous fibers, and 30 to 60% by weight of hydrophilic inorganic powder, Fine glass fibers with an average fiber diameter of 0.6 μm or less are used, fibrillar synthetic fibers with a freeness of 5 sec/g or more are used, and monofilament fibers are polyester or glass with a fiber diameter of 8 to 13 μm. use,
A separator for a storage battery characterized by using diatomaceous earth or perlite as an inorganic powder.