JPH0457068B2 - - 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, JP-A 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. A separator for a storage battery consisting of a press-formed plate in which the intertwined synthetic fibers are thermally fused to each other and constituted as one body.'' JP 56-560110 discloses a separator made of glass fiber and perlite. is disclosed, and Utility Model Application Publication No. 49-122327 discloses that one or two of linter pulp, synthetic fibers, and glass fibers are mixed with silicic acid powder, or a product containing silicic acid powder as the main component and acid-resistant inorganic fine powder is added to make a synthetic resin. Disclosed are separators bonded together. Furthermore, JP-A-58-206046 discloses a separator made of glass fiber or synthetic fiber holding SiO ₂ particles. [Problems to be Solved by the Invention] However, in the above-mentioned separator, unless a special binder is used, the powder particles are likely to peel off or fall off when the separator is handled, which may cause trouble in battery assembly work. 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. For these reasons, it is desired to provide a separator for storage batteries that has a large liquid absorption height, can retain a large amount of electrolyte even in the upper part of the separator, and is free from the risk of deterioration in battery performance due to binder elution. [Means for Solving the Problems] In order to solve the above problems, the separator for storage batteries of the present invention comprises fibers mainly composed of alkali-containing silicate glass fibers and alkali-containing silicate glass powders. The pore size is made fine by intervening the powder particles in the gaps between the glass fibers, and the fibers and the powder particles are mutually bonded to each other mainly by water-glass-like substances produced during paper-making. Fibers mainly composed of alkali-containing silicate glass fibers with an average diameter of 1.0 to 5.0 μm and powders mainly composed of alkali-containing silicate glass powders having an average diameter of 20 μm or less are bonded together using a wet process. A separator for a storage battery in which the fibers are intertwined and the powder particles are interposed between the fibers, and the amount of the powder is 5 to 30% by weight of the weight of the separator. The gist is a separator for storage batteries with features. In order to solve the above problems, the present applicant has filed an application for a storage battery separator mainly composed of alkali-containing silicate glass fibers and alkali-containing silicate glass powder with an average diameter of 0.5 to 1.0 μm. . (Patent application No. 59-70682, hereinafter referred to as the "prior application")
The separator of this prior application has fine pores because it contains glass fibers of small diameter.
Excellent liquid holding power. However, since the separator of this prior application uses fine glass fibers,
Material costs tend to be high. That is, in the case of a separator made of glass fiber, by reducing the diameter of the glass fiber, the liquid retention property is significantly improved, but the cost also increases considerably as the diameter is reduced. The present invention provides a separator for a storage battery that makes use of the advantages of the invention of the prior application and at the same time can reduce the material cost. Figure 1 shows average diameters of 0.6μm, 0.7μm and
This figure shows the liquid absorption characteristics of separators manufactured using three types of 0.8 μm glass fibers. (In addition,
The manufacturing method and the following method for measuring liquid absorption properties are in accordance with the examples described below. ) As shown in Figure 1, the thicker the fiber diameter, the lower the liquid absorption height, especially at 40 cm.
There is a significant decrease in the height above. According to the present invention, powder particles are inserted into the gaps between relatively large-diameter glass fibers, thereby forming a separator with fine pores and improving liquid retention.
The liquid absorption height increases. In addition, such fibers and particles are mainly bonded to each other by a water glass adhesive layer formed on the surface of the alkali-containing silicate glass fibers and powder, and can be bonded to each other without using a special binder.
There is no peeling or falling off of the powder, making it easier to handle. 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 1.0 to 5.0 μm, more preferably 1.05 to 5.0 μm.
It is 4.5 μm. If the diameter exceeds 5.0 μm, the porosity of the separator becomes small, and conversely, if the diameter becomes smaller than 1.0 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 1.0 to 5.0 μm or less,
Alkali-containing silicate glass fibers having a diameter of 5 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 5 μm or more preferably has a length of 5 mm to 80 mm. Such alkali-containing silicate glass fibers having an average diameter of 1.0 to 5.0 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 diameters of each of the 20 fibers to the nearest 0.1 μm, and taking the average value. Note that a suitable range of the glass composition will be described later. 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 weight of the separator.
This is because if the amount of organic fibers mixed exceeds 7% by weight, depending on the material of the organic fibers, it may have an adverse effect on battery performance. When thermoplastic organic fibers are used, they preferably have 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, the powder will be explained. The powder used in the separator of the present invention is mainly composed of alkali-containing silicate powder, and it is also possible to use only alkali-containing silicate powder, or in a range of 50 parts by weight or less out of 100 parts by weight of powder. Silica powder (preferably silica powder having a specific surface area of 100 m ² /g or more) can be mixed and used. The average diameter of the glass powder used is 20 μm or less, preferably 6 μm or less. When the average diameter exceeds 20 μm, the spacing between the glass fibers becomes wider and the liquid absorbency decreases.
The bonding strength between the particles and the fibers decreases, making it easier for the particles to fall off from the separator. In the present invention, the average diameter of the glass powder is determined by photographing three locations of the sample using an electron microscope, measuring the diameter of each of 100 particles in units of 0.1 μm, and calculating the average value. In the separator of the present invention, the amount of powder mainly composed of alkali-containing silicate glass powder is 5 to 30% by weight of the separator weight. Particularly preferred is 8 to 25% by weight. If the amount of powder is less than 5% of the weight of the separator, the effect of improving the liquid absorbency will be poor, and if it exceeds 30%, the tensile strength of the separator will be insufficient. Such powders are less expensive than glass fibers and therefore contribute to lower manufacturing costs. Next, the compositions of glass fiber and glass powder will be explained. The glass fibers and glass powder 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 according to JISC-2202 in the state of glass fibers with an average fiber diameter of 1 to 5 μm. In addition, the composition of such glass fiber and powder is 60 to 60% by weight.
75% _SiO2 and 8-20% _R2O ( _Na2O , _K2O
mainly contains alkali metal oxides such as
(However, SiO ₂ + R ₂ O is 75 to 90%).Other examples include those containing one or more of CaO, MgO, B ₂ O ₃ , Al ₂ O ₃ , ZnOFe ₂ O ₃ , etc. It will be done.
An example of a preferable alkali-containing silicate glass is shown in Table 1 below.

[Table] The separator for storage batteries of the present invention is prepared by adding fibers mainly composed of alkali-containing silicate glass fibers and powder mainly composed of alkali-containing silicate glass powder to water whose pH value is maintained at, for example, 2.5 to 3.5. a certain period of time, e.g. 5
Disperse the fibers using a water jet dispersion machine for ~20 minutes without cutting them as much as possible, then perform wet papermaking.
By forming an adhesive layer (perhaps a water glass layer) on the surfaces of the glass fibers and glass powder, and then heating this to a predetermined temperature, for example 80 to 180°C, the glass fibers and glass powder are bonded to each other by the water glass on their surfaces. It can be obtained by gluing it to. That is, since the glass fibers and glass powder 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 forms on the surface of the glass fibers. This water glass layer acts as an adhesive to bond the glass fibers and glass powder together. 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, so that the dialkyl sulfosuccinate adheres to the glass fibers in an amount of 0.005 to 10% by weight. The hydrophilicity of succinate 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. [Function] Fine powder mainly composed of alkali-containing silicate glass powder enters the voids between fibers mainly composed of alkali-containing silicate glass fibers, and the pore size distribution of the entire separator becomes small. This improves liquid absorption properties. In addition, such fibers and particles are mainly bonded to each other by a water-glass adhesive layer formed on the surface of the alkali-containing silicate glass fibers and powder, and the powder does not peel or fall off even without the use of a special binder, making it easy to handle. becomes easier. Furthermore, since glass fibers having a relatively large average diameter of 1.0 to 5.0 μm are used, the price of the glass fibers is also low, and the manufacturing cost of the separator can be reduced. [Example] Examples and comparative examples will be described below. Example 1 Using glass fiber whose composition is A in Table 1,
Average diameter 0.8μm, average length 10mm, by flame method.
And glass fibers with an average diameter of 1.5 μm and an average length of 10 mm were produced. In addition, a glass powder with an average diameter of 5 μm obtained by crushing glass cullet having a similar composition 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 glass powder constituting this separator were bonded to each other by water glass formed on the surface thereof. These separators had the thickness, basis weight, density, tensile strength, liquid retention, and maximum pore diameter as shown in Table 2. The method for measuring these characteristic values is as follows. (1) Thickness Measure the specimen while pressing it with a load of 20 kg・dm ² in the thickness direction. (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 ) is expressed as the value given by (3) Fabric weight This is the value obtained by dividing the sample weight by the sample area. (4) Tensile strength: Displays the external force (Kg) when pulling both ends of a sample with a width of 15 mm and causing it to break. (5) Immerse the liquid-retentive sample in water until it is saturated, then suspend the sample in the air for 5 minutes. After that, the weight of the sample is measured to calculate the amount of water contained in the sample, and this value is obtained by dividing this amount of water by the volume of the sample, and the unit is g-water/ ^cm3 -separator. becomes. (6) Immerse the maximum pore diameter test piece in the methanol solution for at least 30 minutes, set the sample on the sample holder, and pipette 5 to 10 c.c. of methanol from above. Flow air gently and read the air pressure when bubbles are generated from methanol to determine the maximum pore diameter using a calculation formula.

[Table] From Table 2, it is recognized that the separator of the present invention has superior liquid retention properties compared to Nos. 1 and 3, which did not use powder. The liquid retention property is lower than that of No. 2, which uses a combination of glass fiber with an average diameter of 0.8 μm and glass powder, but as mentioned above, it is lower than that of conventional example (No. 1,
It is more expensive than 3) and can be put to practical use. Also, compared to No. 2, it uses inexpensive glass fiber with a large diameter, so the material cost is low and it is extremely practical. Example 2 The liquid absorption properties of the separator No. 4 (example) and the separator No. 3 (conventional example) of Example 1 were measured as follows. Hold the sample vertically and immerse its lower part in a sulfuric acid solution with a specific gravity of 1.30 for 24 hours. Then, it is cut every 10 cm from the bottom, and the weight W of each 10 cm width portion (the sum of the weight of the separator cut piece and the weight of the sulfuric acid contained in the cut piece) is determined. The sulfuric acid content is calculated as a magnification by dividing this weight W by the weight (W) of a separator cut piece of the same size that has not been immersed in sulfuric acid (W/w). The results are shown in Figure 2. From Figure 2, No. 4 according to Example has excellent liquid absorption properties, especially in areas higher than 40 cm, which is much better than No. 5, which does not contain glass powder. That is clear. Example 3 Glass fibers having average diameters of 1.1 μm and 19 μm were produced using glass having the composition A in Table 1. This and the glass powder used in Example 1 were blended in the proportions shown in Table 3 to produce a separator in the same manner as in Example 1, and its liquid absorption properties were measured in the same manner as in Example 2. The results are shown in FIG.

[Table] From FIG. 3, it is clearly recognized that the glass powder blended with No. 7 has superior liquid absorption properties compared to No. 6. [Effects] 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. In addition, since glass fiber, which has a relatively large diameter and is inexpensive, is used, and glass powder and silica powder are considerably less expensive 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.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are graphs showing measurement results of liquid absorption characteristics of various separators.

Claims (1)

[Claims] 1 Fibers mainly composed of alkali-containing silicate glass fibers with an average diameter of 1.0 to 5.0 μm and powders mainly composed of alkali-containing silicate glass powders having an average diameter of 20 μm or less are wet-mixed, and the fibers are entangled. Also, a separator for a storage battery comprising the powder particles interposed between fibers, wherein the amount of the powder is 5 to 30% by weight of the weight of the separator.