JPH0381266B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a separator for a storage battery, and particularly to a separator for a storage battery with improved electrolyte retention. [Prior Art] A mat-like sheet of glass fiber with an average diameter of 1 μm or less has been proposed as a separator with excellent electrolyte retention for sealed lead-acid batteries.
In particular, it has been put to practical use in small-capacity sealed lead-acid batteries that use plates with a height of approximately 120 mm or less. However, in large batteries where the electrode plate height is, for example, 180 mm or more, the upper part of the mat-shaped sheet holds a much smaller amount of electrolyte than the lower part, so there is a drawback that the desired performance cannot be obtained. This is because the diameter of the fibers is relatively large, so the height of liquid absorption due to capillary action is reduced. A combination of fibers and powder is known as a separator intended to improve the electrolyte retention property by increasing the liquid absorption of the separator. For example, Japanese Patent Application Laid-open No. 54-22531 states that ``paper is made by mixing fibrillated thermoplastic synthetic fibers with a mouth water content of 200 to 600 c.c., thermoplastic synthetic fibers, and acid-resistant inorganic fibers or powder. , and the intertwined synthetic fibers are thermally fused to each other to form a single press-formed plate.'' is disclosed in JP-A-56-560110. Japanese Utility Model Application Publication No. 49-122327 discloses a separator consisting of one or two of linter pulp, synthetic fibers, and glass fibers, and silicic acid powder, or a separator containing silicic acid powder as the main component and acid-resistant inorganic fine powder added thereto. A separator made of mixed paper and bonded with a synthetic resin is disclosed. Further, JP-A-58-206046 discloses a separator made of glass fiber or synthetic fiber holding SiO ₂ particles. However, unless a special binder is used in the above-mentioned separator, the powder particles are likely to peel off or fall off when the separator is handled, which may cause problems in battery assembly work and the like. Furthermore, the use of a binder increases the cost of raw materials, and in a storage battery incorporating the separator, the binder gradually dissolves during use, contaminating the electrolyte and potentially deteriorating the performance of the battery. [Object of the Invention] The object of the present invention is to solve the problems of the above-mentioned prior art, and to solve the problem of the above-mentioned conventional technology. The object of the present invention is to provide a separator for a storage battery that is [Structure of the Invention] In order to achieve this object, the separator for storage batteries of the present invention is produced by wet-mixing fibers mainly composed of alkali-containing silicate glass fibers and powders mainly composed of silica powder. Powder particles mainly composed of silica are interposed in the gaps to make the pore size finer, and the fibers or the fibers and the powder particles are bonded to each other mainly by water glass-like substances produced during papermaking. Fibers mainly composed of alkali-containing silicate glass fibers with an average diameter of 0.5 to 1.0 μm and an average area of 100 m ² /g
A separator for a storage battery, in which the above-mentioned powder mainly composed of silica powder is wet-mixed and heat-treated so that the fibers are entangled and the powder particles are interposed between the fibers, the separator comprising: A separator for a storage battery, characterized in that the amount of powder is 1 to 40% by weight of the weight of the separator. That is, according to the present invention, silica powder is inserted into the spaces between the glass fibers, thereby forming a separator with fine pores and improving the liquid holding power. In addition, these fibers and particles are bonded to each other mainly through a water glass-like adhesive layer formed on the surface of the alkali-containing silicate glass fibers, and the powder does not peel or fall off without using a special binder, making it easy to handle. becomes. The present invention will be explained in more detail below. First, fibers will be explained. The fibers constituting the separator of the present invention are mainly composed of alkali-containing silicate glass fibers. That is, it may contain only alkali-containing silicate glass fibers, or it may contain other fibers, such as thermoplastic organic fibers that are often mixed in glass fiber separators. The average diameter of the alkali-containing silicate glass fibers, which are the main fibers, is 0.5 to 1.0 μm, more preferably 0.6 to 1.0 μm.
It is 0.9 μm. If the diameter exceeds 1.0 μm, the porosity of the separator becomes small, and conversely, if the diameter becomes smaller than 0.5 μm, the manufacturing cost increases. Moreover, the average length of this glass fiber is preferably 7
~50mm, more preferably 10-40mm. If the average length is shorter than 10 mm, the strength of the separator will be reduced, and if it is longer than 50 mm, it will be difficult to uniformly disperse it in water during papermaking. In addition to glass fibers with a diameter of 1 μm or less,
Alkali-containing silicate glass fibers of 1 μm or more, for example, 5 to 30 μm, can be contained in an amount up to 20% by weight of the separator weight. This glass fiber of 1μm or more is 5
Preferably, the length is from mm to 80 mm. Adding this large diameter glass fiber improves the tensile strength of the separator. Such alkali-containing silicate glass fibers having an average diameter of 0.5 to 1.0 μm can be produced by the FA method (flame method), centrifugation method, or other short glass fiber manufacturing methods. The average diameter of the glass fibers is calculated by taking photographs of three locations on the sample using an electron microscope, measuring the diameter of each of the 20 fibers in units of 0.1 μm, and taking the average value of these measurements. In addition, the suitable range of the composition of glass fiber will be explained next. The glass fibers constituting the separator of the present invention have an alkali-containing silicate glass composition, and can form water glass on the surface thereof. Moreover, since it is used for storage batteries, those with good acid resistance are preferably used. The degree of acid resistance is preferably such that the weight loss is 2% or less when measured in accordance with JISC-2202 using glass fibers with an average fiber size of 1 μm or less. In addition, the composition of such glass fibers is 60 to 75% SiO ₂ and 8 to 20% SiO 2 by weight.
R ₂ O (alkali metal oxides such as Na ₂ O, K ₂ O)
(However, SiO ₂ + R ₂ O is 75~
90%), and others such as CaO, MgO, _{B2O3 ,}
Examples include those containing one or more of Al ₂ O ₃ , ZnO, Fe ₂ O ₃ and the like. An example of a preferable alkali-containing silicate glass is shown in Table 1 below.

[Table] The separator of the present invention may contain thermoplastic organic fibers in addition to such alkali-containing silicate glass fibers, but in that case, the mixing ratio is preferably 7% by weight or less of the separator. . This means that when the mixing ratio of organic fiber exceeds 7% by weight,
This is because depending on the material of the organic fiber, it may have a negative effect on the performance of the storage battery. Note that when thermoplastic organic fibers are used, the tensile strength of the separator is improved. The thermoplastic organic fiber preferably has a length of 2 to 10 mm and an average diameter of 1 to 30 μm. Examples of thermoplastic organic fibers include acrylic fibers and polyester fibers. Next, silica powder will be explained. The powder used in the separator of the present invention is mainly composed of silica powder, and silica powder alone may be used, or alkali-containing silicate glass powder may be used in an amount less than 50 parts by weight out of 100 parts by weight of the powder. They can be used in combination. Since alkali-containing silicate glass powder is cheaper than silica powder, it can be used within a range that does not impair the properties of the separator. The silica powder used has a specific surface area of 100 m ² /g or more. Such silica powder is acid-resistant, bulky, and compatible with the battery electrolyte, so it is interposed between the glass fibers to increase the liquid absorption of the separator and improve the performance of the battery. The silica powder used is one manufactured by various known methods such as acid decomposition of sodium silicate and thermal decomposition of silicon halide. The specific surface area of silica powder is easily measured by a known method such as the BET method. In addition, when using an alkali-containing silicate glass powder, the average diameter is preferably 20 μm or less, particularly 6 μm or less. In the separator of the present invention, the amount of powder mainly composed of silica powder is 1 to 40% by weight of the separator weight. Particularly preferred is 5 to 30% by weight. If the amount of powder is less than 1% of the weight of the separator, the effect of improving the liquid absorbency will be poor, and if it exceeds 40%, the tensile strength of the separator will be insufficient. In the separator for storage batteries of the present invention, fibers mainly composed of alkali-containing silicate glass fibers and powders mainly composed of silica powder are soaked in water whose pH value is maintained at, for example, 2.5 to 3.5 for a certain period of time, for example, 5 to 20 minutes. The fibers are dispersed without cutting as much as possible using a diversion type disperser, etc., and then wet-formed to form an adhesive layer, perhaps a water glass layer, on the surface of the glass fibers, and then heated at a predetermined temperature. For example, it can be obtained by heating glass fibers to 80 to 180° C. and thereby adhering them to each other with water glass on their surfaces. That is, since the glass fibers constituting the separator of the present invention have an alkali-containing silicate glass composition, the alkali components and silica components in the glass react with water for dispersion, and a water glass layer is formed on the surface of the glass fibers. , this water glass layer acts as an adhesive to adhere the glass fibers and silica powder. In addition, when thermoplastic organic fibers are used as part of the fibers, these organic fibers also exhibit a shaping or adhesion effect in the subsequent heat treatment step (for example, drying step), increasing the strength of the separator. The thickness of the separator itself of the present invention varies depending on the storage battery used, but is preferably 0.3 to 3 mm. Note that a dispersant may be used when dispersing the glass fibers in water. In addition, by spraying dialkyl sulfosuccinate onto a wet-processed fiber paper product, for example, a fiber paper product on a paper-making conveyor, the dialkyl sulfosuccinate can be applied to the glass fibers in an amount of 0.005 to 10% by weight. The hydrophilicity of fusuccinate can improve the liquid retention of the separator. Instead of spraying the dialkyl sulfosuccinate as described above, it may be mixed into the dispersion water in the papermaking tank. Note that storage batteries using the separator of the present invention may be left unused for a long time (for example, 6 months or more).
As a result of various experiments, it was found that the decrease in battery capacity during storage was extremely small. [Embodiments of the Invention] Examples will be described below. Examples 1, 2, 3 Using glass fiber whose composition is A in Table 1,
Average diameter 0.8μm, average length 10mm, by flame method.
Glass fibers with an average diameter of 19 μm and an average length of 25 mm were produced. In addition, a commercially available acrylic organic fiber (trade name: Cashmilon) was cut into a length of 7 mm and prepared. Furthermore, a commercially available silica powder having a specific surface area of 230 m ² /g (trade name: Carplex #80, manufactured by Shionogi & Co., Ltd.) was prepared. These fibers and powder were poured into water in the proportions shown in Table 2, stirred and dispersed using a water jet disperser, and sulfuric acid was added to bring the pH of the water to 2.7, which was maintained for about 10 minutes. Next, papermaking was performed and heated to 150°C to produce a pine-shaped storage battery separator. It was observed that each glass fiber and powder constituting this separator were bonded to each other by water glass formed on the surface of the glass fiber. These separators had the thickness, basis weight, density, tensile strength, and 24-hour liquid absorption height as shown in Tables 2 and 3. The method for measuring these characteristic values is as follows. (1) Thickness Measure with the sample pressed in the thickness direction with a load of 20 kg/dm ² . (JISC-2202) (2) Density When the thickness of the sample is T when a load (W) of 20 kg is applied to the area (S) of the sample 10 cm x 10 cm, the formula: W/(S x T) (g /cm ³ ). (3) Fabric weight This is the value obtained by dividing the sample weight by the sample area. (4) Tensile strength Displayed as the external force (Kg) when pulling both ends of a 15 mm wide sample and causing it to break. (5) 24-hour liquid absorption height The sample is held vertically and its lower part is immersed in a dilute sulfuric acid solution with a specific gravity of 1.30, and the height is expressed as the distance that the dilute sulfuric acid rises in 24 hours. (6) 24-hour liquid absorption distribution The sample subjected to the 24-hour liquid absorption height test is cut into sections of 10 cm in the height direction, and the weight of each cut piece is measured to determine the amount of liquid absorbed. Then, the amount of liquid absorbed is calculated as how many times the weight of the sample before liquid absorption. (Thus, for example, in Table 3 below,
The liquid absorption distribution value in the 30 to 40 cm portion of Example 2 is 6.92
This means that the part between 30 and 40 cm in height of the test sample contains sulfuric acid solution whose weight is 5.92 (value of 6.92 - 1) times the weight of the 10 cm width of the sample before liquid absorption. Indicates that A liquid absorption distribution value of 1.00 indicates that the liquid absorption amount is 0. ) Comparative Examples 1 and 2 Separators were manufactured in the same manner as in the examples except that only glass fibers were used in the proportions shown in Table 2 without using powder, and their properties were measured. The results are also shown in Tables 2 and 3. Comparative Examples 3 and 4 Separators were produced in the same manner as in Example 2, except that the diameters of the glass fibers were 0.4 μm (Comparative Example 3) and 1.1 μm (Comparative Example 4), and their properties were measured. The results are also shown in Tables 2 and 3. Comparative Example 5 A separator was produced in the same manner as in Example 2 except that the specific surface area of the silica powder was 50 m ² /g,
Its properties were measured. The results are also shown in Tables 2 and 3. Comparative Example 6 A separator was produced in the same manner as in Example 2 except that the amount of glass fiber was 50% by weight and the amount of silica powder was 50% by weight, and its properties were measured. The results are also shown in Tables 2 and 3. Example 4 The amount of silica powder was 20% by weight. Further, an alkali-containing silicate glass powder having plasticity of A in Table 1 (specific surface area: 230 m ² /g) was used at a ratio of 10% by weight. Otherwise, a separator was manufactured in the same manner as in Example 2, and its characteristics were measured. The results are also shown in Tables 2 and 3.

【table】

【table】

[Table] Tables 2 and 3 show that the separator of the present invention has a significantly superior 24-hour liquid absorption level compared to Comparative Examples 1 and 2 that do not use powder, and a large amount of electrolyte is absorbed even in the upper part of the separator. Permitted to be retained. Furthermore, the following items are recognized from Tables 2 and 3. From a comparison of Examples 1 and 2, it is recognized that when glass fibers with a large diameter (19 μm) are mixed in, the tensile strength is slightly improved. A comparison of Examples 2 and 3 shows that the tensile strength increases significantly when acrylic fibers are mixed into the paper. From the comparison between Example 2 and Comparative Example 3, it is recognized that when the glass fiber diameter is smaller than 0.5 μm, the liquid absorption properties are excellent. However, manufacturing costs increased by approximately 300%. From the comparison between Example 2 and Comparative Example 4, when the glass fiber diameter is larger than 1.0 μm, the density becomes considerably high and the porosity becomes low. In addition, it is observed that the liquid absorbency deteriorates. From the comparison between Example 2 and Comparative Example 5, when the specific surface area of the silica powder is smaller than 100 m ² /g,
It is observed that the liquid absorbency deteriorates. From the comparison between Example 2 and Comparative Example 6, it is recognized that when the amount of silica powder exceeds 40% by weight, the tensile strength decreases. From a comparison of Examples 2 and 4, it is recognized that the tensile strength of the separator increases when part of the silica powder is replaced with glass powder. Note that the manufacturing cost of the separator of Example 4 using glass powder was about 93% of that of Example 2, resulting in a 7% cost reduction. When similar tests were conducted on glass fibers having compositions B and C in Table 1, similar results were observed. [Effects of the Invention] As detailed above, the separator for a storage battery of the present invention has excellent liquid retention ability, and in particular has a large liquid absorption height, so that a large amount of electrolyte can be retained even in the upper part of the separator. Incidentally, since silica powder is considerably cheaper than glass fiber, the material cost of the separator of the present invention is also low. In addition, the particles and fibers are mainly bonded with a water glass-like substance, so that the particles do not peel or fall off, so there is no inconvenience in handling. Furthermore, there is no risk of electrolyte contamination due to binder elution from the separator, and deterioration of battery performance due to binder elution is prevented. Also,
A storage battery using the separator of the present invention has less decrease in battery capacity due to long-term storage.

Claims (1)

[Claims] 1 Fibers mainly composed of alkali-containing silicate glass fibers with an average diameter of 0.5 to 1.0 μm and a specific surface area of 100 m ² /
A separator for a storage battery, in which a powder mainly composed of silica powder of 1.5 g or more is wet-mixed and heat-treated, the fibers are entangled, and the powder particles are interposed between the fibers, A separator for a storage battery, characterized in that the amount of the powder is 1 to 40% by weight of the weight of the separator.