JPS6228543B2 - - Google Patents

Description

[Detailed description of the invention]

As a conventional separator for lead-acid batteries, a pulp separator is used, which is made by impregnating a paper body mainly made of natural pulp such as linter pulp with phenol resin and drying and hardening it. This is undesirable because it has low acid resistance, short oxidation resistance time, is hard and brittle due to the use of cured resin, and is prone to breakage during the manufacturing process and battery assembly.
In order to improve the oxidation resistance time, it has been proposed to make a separator by mixing this raw material with acid-resistant inorganic fibers or inorganic powder and synthetic fibers with a small amount of binder to give flexibility. However, due to the deterioration of adhesion due to the incorporation of inorganic fibers or inorganic powder, the acid resistance becomes weaker, resulting in a disadvantage that it cannot withstand long-term use. The applicant previously proposed a separator for storage batteries in Japanese Patent Application Laid-Open No. 47-31134, which is made by making a paper mixture of thermoplastic synthetic fibers and inorganic fibers or inorganic powder, and then heat-forming the paper. Although the oxidation resistance is significantly improved compared to the above, the acid resistance strength is inferior and the electrical resistance is increased. The present invention addresses these conventional drawbacks and provides a separator for lead-acid batteries that has improved acid resistance, oxidation resistance, and electrical resistance at the same time. A separator for a lead-acid battery is produced by making paper by uniformly mixing inorganic fibers or inorganic powder, heating the paper, heat-sealing the intertwined synthetic fibers, and press-forming to a predetermined thickness. Fibrillated acrylic fiber with water content of 200 to 600 c.c.
20% by weight, non-fibrillated thermoplastic synthetic fiber 40~
70% by weight, acid-resistant inorganic fiber or inorganic powder 15
These three components are suitably selected from a range of blending amounts of ~45% by weight so that the total blending amount of these three components is 100% by weight, mixed uniformly to make paper, and heated at about 130 to 160°C to form these fibrillated acrylics. It is characterized by being made by heat-sealing fibers and non-fibrillated synthetic fibers. Next, embodiments of the present invention will be described. The acrylic fiber is beaten and fibrillated using a Peter etc. Thus, the Canadian freeness level is 200~
600 c.c. fibrillated acrylic fiber, commonly used non-fibrillated thermoplastic synthetic fiber such as polyvinyl chloride, and acid-resistant inorganic fiber or inorganic powder such as glass fiber or powder or a mixture thereof are uniformly mixed. Mix and make paper in the usual manner. In this case, the amount of fibrillated acrylic fibers with a freeness of 200 to 600 c.c. ranges from 5 to 20% (by weight). If it is less than 4%, the amount of fibrillated fibers will be too small and a tightly entangled structure between the paper layer fibers cannot be obtained, and if it is more than 21%, the paper layer will be too clogged and the diffusion of the electrolyte will be impaired, making it unsuitable for use. It was found that this resulted in a significant increase in electrical resistance as described below. In addition, the amount of non-fibrillated synthetic fiber added is in the range of 40 to 70%; if it is less than 35%, the thermal fusion properties between the fibers will be poor and good flexibility as a separator will not be obtained; If this is the case, a relatively coarse separator structure will be obtained, resulting in poor retention of inorganic fibers or inorganic powder. Also in this case,
Glass fibers, asbestos fibers, silicic acid powder, diatomaceous earth, etc. are used as inorganic fibers and inorganic powders, and the amount added varies depending on the size, type, etc.
% range. If it is less than 12%, there will be almost no effect to prevent lead powder from entering from the battery electrode plate, and the oxidation resistance time will not be sufficient. On the other hand, if it is more than 50%, the good entanglement between the paper layer fibers and the heat-sealing effect will deteriorate, resulting in a decrease in strength. It was found that this is not preferable because it causes cracking and becomes brittle. The three ingredients mentioned above are appropriately selected from the range of addition amounts so that the total amount of these ingredients is 100% by weight, and the paper is made by uniformly mixing them. Fibrillated acrylic fibers and non-fibrillated synthetic fibers are heated in a heating furnace to heat and melt their surfaces without losing their fiber morphology. Its temperature ranges from about 130 to 160°C. If it is below 120°C, sufficient fusion between the fibers cannot be obtained, and if it is above 165°C, the fibers lose their shape and entanglement strength is lost, resulting in a decrease in the strength of the separator, which is undesirable. For comparison, when some or all of the fibrillated acrylic fibers or non-fibrillated thermoplastic synthetic fibers constituting this paper were replaced with linter pulp fibers or their fibrillated fibers, the overall result was a sufficient 1. A separator with physical fusion strength was not obtained, and acid resistance and oxidation resistance life were reduced. In addition, a separator was made by replacing the fibers in the above-mentioned paper by heat-sealing and adding a binder to bond the fibers together, but a separator with sufficient strength could not be obtained. Thus, the paper that has undergone the above heat fusing process is
Then, pressure was applied using a press plate, a press roller, etc. to obtain a thin molded separator. Separator thickness is 0.5mm
The front and back are normal, and the bulk specific gravity is 0.35 to 0.55
g/cm ³ , preferably 0.40 to 0.50 g/cm ³ , and is adjusted within this range by the above-mentioned pressurization. When the bulk specific gravity is in the range of 0.35 to 0.55 g/cm ³ , the oxidation resistance time is significantly extended and the electrolyte diffusivity is significantly improved. Next, more specific comparative test examples will be explained.
Fibrillated acrylic fibers with different degrees of freeness are made by beating acrylic fibers with a regular beater for 10 to 60 minutes, and for each fibrillated acrylic fiber with a constant freeness, 10% of this is mixed with 40% of polyethylene fiber.
%, PVC fiber 20%, glass fiber 10%,
and 20% silicic acid powder with a particle size of 1μ are mixed and made into paper using a normal papermaking method to form a paper layer with a thickness of 0.5mm, which is then heated and melted in a heating furnace at 140°C. Pressure-fused with a press roll to form an integral piece, and the thickness
Separators A to E of fibrillated acrylic fibers having a diameter of 0.4 mm and a bulk specific gravity of 0.45 g/cm ³ were obtained according to their freeness.
In addition, a similar fabrication was made using 10% non-fibrillated acrylic fiber instead of the 10% fibrillated acrylic fiber, and a separator F with the same thickness and bulk specific gravity and freeness was obtained.
10% fibrillated linter pulp of 400c.c. is used as a replacement, and the thickness is adjusted by pressure bonding it together with a binder.
Separators G with the same bulk specific gravity were obtained. Various tests were conducted on these various separators A to G, and the results shown in the table below were obtained. For comparison of these various properties, the phenolic resin-impregnated pulp separator mentioned at the beginning (hereinafter referred to as pulp separator), which is commonly used in practical use, is also shown. Furthermore, in order to clarify the effect of the fibrillated acrylic fiber of the present invention, instead of this, fibrillated polyolefin fibers (polypropylene and polyethylene fibers) were used with a freeness of 200 c.c. and 400 c.c., respectively.
cc and 600c.c., and each of them is 10%
Separators H, I, and J were prepared in the same manner as in the present invention except for mixing, and the same tests were conducted on them, with the results shown in the table below. As a result, the products of the present invention, namely separators B, C, containing fibrillated acrylic fibers with a freeness of 200 to 600 c.c.
D is significantly superior to pulp separators in all properties including acid resistance, oxidation resistance, and electrical resistance.
On the other hand, separators A and F that contain fibrillated acrylic fibers that greatly exceed this water content range and separators F and G that do not contain the same fibrillated acrylic fibers are inferior in acid resistance strength and oxidation resistance time, and the present invention Separators H, I, and J containing fibrillated polyolefin fibers having the same freeness as the fibrillated acrylic fibers of the present invention have the same freeness as the fibrillated acrylic fibers of the present invention in terms of acid resistance strength and oxidation resistance time. It was recognized that the performance was significantly inferior to that of separators B, C, and D containing separators.

[Table] Furthermore, by setting the added amount of the fibrillated acrylic fiber of the present invention to 20% or less, it is possible to maintain an extremely small electrical resistance value of 0.001Ω/dm ² /sheet, as shown in the drawing. If the amount added is 25% or more, the value is 0.002Ω/dm ² /
It was found that the size becomes significantly larger and is not desirable. The electrical resistance test was conducted at 5A current according to JIS C-2313. As described above, according to the present invention, in a separator for a lead-acid battery, which is formed by uniformly mixing thermoplastic synthetic fibers and inorganic fibers or inorganic powder, making paper, and molding the same under heat and pressure, in particular, fibrillated acrylic fibers 5 ~
20% by weight non-fibrillated synthetic fibers 40-70% by weight
and 15 to 45% by weight of inorganic fibers or inorganic powder, these synthetic fibers can be thermally fused well to obtain a separator that is flexible, tough, and has good mechanical strength, as well as oxidation resistance. This has the effect of providing an excellent lead-acid battery separator having relatively high acid resistance and significantly low electrical resistance.

[Brief explanation of the drawing]

The drawing is a graph showing the relationship between the content of fibrillated acrylic fibers having a freeness of 200 to 600 c.c. in the separator and the electrical resistance value.

Claims (1)

[Claims] 1. Thermoplastic synthetic fibers and acid-resistant inorganic fibers or inorganic powder are uniformly mixed to make paper, the paper is heated to heat-fuse the intertwined synthetic fibers to each other, and pressure-molded to a predetermined thickness. A lead-acid battery separator consisting of 5 to 20% by weight of fibrillated acrylic fibers with a freeness of 200 to 600 c.c., 40 to 70% by weight of non-fibrillated thermoplastic synthetic fibers, acid-resistant inorganic fibers or inorganic powder. From the range of 15 to 45% by weight of each component, the total amount of these three components is 100% by weight, and the mixture is uniformly mixed to make paper at about 130 to 160℃.
A separator for a lead-acid battery, characterized in that the fibrillated acrylic fibers and the non-fibrillated synthetic fibers are thermally fused together by heating.