JPH0555975B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a separator for a storage battery, and more particularly to a separator for a storage battery mainly made of glass fiber. [Prior Art] Various types of storage battery separators containing glass fibers have already been proposed and put into practical use, and these can be broadly classified into the following three types. That is, there are those that are mainly made of short glass fibers, those that are a mixture and molding of short glass fibers and synthetic fibers, and those that have powder held in short glass fibers. Among these, as a separator made of a sand mixture of glass fiber and powder, for example,
There is a separator described in No. 206046, and although this separator has good liquid absorption properties, there are problems in that the powder easily peels off and falls off from the separator and also has low tensile strength. On the other hand, separators made by mixing short glass fibers and synthetic fibers include JP-A-49-38126, JP-A-54-22531, JP-A-56-99968, JP-A-53
-136632 and Japanese Patent Publication No. 58-663, these have high mechanical strength (tensile strength, rigidity, etc.) and have the advantage of being easy to assemble the storage battery, but they do not have liquid absorption, It has the disadvantages of poor liquid retention and short lifespan due to the presence of organic matter in the system. On the other hand, as separators mainly made of glass fiber, there are those that use a binder such as an organic liquid adhesive and those that do not use such a binder. [Problems to be solved by the invention] Among separators mainly made of glass fiber, those that do not use a binder can freely expand in volume due to their liquid absorption ability, and have excellent liquid retention and absorption properties for electrolyte. This separator is the best in terms of battery characteristics, but because it is shaped simply by the force of water vitrification and entanglement of the glass fiber surface, its strength and hardness are low, making it difficult to assemble batteries using machines. It has the disadvantage that it is difficult to withstand sufficiently, and work efficiency is poor. On the other hand, when organic fibers or thermoplastic binders are used, their adhesive effects improve strength and hardness, but they are less hydrophilic than glass, so the liquid retention and absorption properties of the separator are reduced. Deteriorate. Moreover, a liquid-soluble binder has the problem that it dissolves into the electrolytic solution, causing a decrease in battery performance, and is not preferable from the viewpoint of oxidation resistance. [Means for Solving the Problems] The present invention solves the problems of the prior art described above, and provides a separator for storage batteries that has good strength and hardness, as well as excellent liquid retention and liquid absorption properties. The gist of the present invention is a separator for a storage battery, which is mainly made of glass fibers and is characterized in that the glass fibers are bonded together with a water glass adhesive. The present invention will be explained in more detail below. The glass fibers constituting the storage battery separator of the present invention are mainly composed of small glass fibers with an average diameter of 2 μm or less, 0 to 35% by weight of large glass fibers with an average diameter of 10 to 30 μm, and 0 to 35% by weight of large glass fibers with an average diameter of more than 2 μm and less than 10 μm. It is preferable that it contains 0 to 30% by weight of medium and small diameter glass fibers. Medium-thin and large-diameter glass fibers are cheaper than small-diameter ones, and especially large-diameter glass fibers have the advantage that the tensile strength of the separator can be improved by using them together. The preferred average diameter of small diameter glass fibers is 0.5~
It is 1.0 μm, more preferably 0.6 to 0.9 μm. If the diameter exceeds 1.0 μm, the pore size of the separator becomes large, and conversely, if the diameter is smaller than 0.5 μm, the manufacturing cost becomes high. The preferred content of this small diameter glass fiber is 60% by weight or more of the glass fiber weight, especially 65% by weight or more of the glass fiber weight.
Particularly preferably % by weight or more. This is because if the content is less than 60% by weight, liquid absorption and liquid retention properties tend to be insufficient. Further, the average length of this small diameter glass fiber is preferably 7 to 50 mm, more preferably 10 to 40 mm.
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. Such small-diameter glass fibers can be manufactured by the FA method (flame method), centrifugation method, or other short glass fiber manufacturing methods. In addition, in the present invention, the average diameter of the glass fibers is
Photographs were taken of three locations on the sample using an electron microscope.
It is calculated by measuring the diameter of each 20 fibers in units of 0.1 μm and taking the average value. When medium-sized glass fibers are used, the preferred average diameter is 2.0 to 5.0 μm, especially 3.0 to 4.0 μm.
It is. In addition, the content and glass fiber amount are 5.0~
Preferably it is 30.0% by weight, especially 10.0-25.0% by weight. By blending glass fibers with medium and small diameters, the amount of small-diameter glass fibers can be reduced, which is advantageous in terms of cost. The length of this medium-thin diameter glass fiber is preferably 7 to 50 mm, particularly 10 to 40 mm. When using large-diameter glass fibers, the preferred average diameter is 10 to 20 μm, particularly 12 to 19 μm. Further, the content is preferably 8 to 35% by weight, particularly 10 to 30% by weight, based on the weight of the glass fibers.
If the average diameter is smaller than 10 μm or the content is less than 8% by weight, the tensile strength improvement effect becomes small, and if the average diameter exceeds 20 μm or the content exceeds 35% by weight, the separator Liquid absorption and liquid retention are reduced. The length of this large diameter glass fiber is preferably 5 to 80 mm, particularly 6 to 40 mm. A suitable range of the composition of the glass fiber will be explained next. The composition of the glass fibers constituting the separator of the present invention is not particularly limited, but it is preferable to use alkali-containing silicate glass fibers. That is, when alkali-containing silicate glass fibers are used, water glassy substances are generated on the surface of the glass fibers during the papermaking process of the manufacturing process, and the water glassy substances produced together with the water glassy adhesive added as described below. The adhesiveness also allows the fibers to be better adhered to each other and the adhesive strength to be further improved. In the present invention, among alkali-containing silicate glass fibers, those having good acid resistance are preferably used because they are used in storage batteries. This degree of acid resistance is based on JISC-2200 for glass fibers with an average fiber diameter of 1 mμ or less.
It is desirable that the weight loss when measured according to the method is 2% or less. In addition, the composition of such glass fibers is 60 to 75% SiO ₂ and 8 to 20% 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】

[Table] Preferably, the separator for a storage battery of the present invention has thin, medium-thin, and large-diameter alkali-containing silicate glass fibers having the above compositions intertwined with each other by wet paper-making and added during the manufacturing process. It is bonded with a glass-like adhesive. In the present invention, the water glass adhesive includes:
In addition to water glass, examples include inorganic adhesives containing water glass, specifically "Silpap700." The amount of water-glass adhesive added also varies depending on the composition, average diameter, average length, etc. of the glass fibers, but if it is too small, the effect of improving the strength of the separator by adhesion will be low, and if it is too large, the adhesion will be too strong. Generally, it is 1 to 10% by weight in terms of solid content based on the weight of the glass fiber, since this inhibits the swelling property during liquid absorption and worsens the liquid absorption.
It is preferable that In order to manufacture such a separator for a storage battery according to the present invention, a glass fiber paper product is first manufactured.
In this case, glass fibers cut in advance to a predetermined length may be blended in a desired ratio and mixed to form a paper. However, it is advantageous to use the following method, for example. That is, relatively long glass fibers of small diameter, medium diameter, and large diameter cut into predetermined lengths are prepared by the FA method (flame method), centrifugation method, and other short glass fiber manufacturing methods. These fibers of each diameter are blended in appropriate proportions and disintegrated and dispersed using a pulper. Alternatively, the glass fibers may be cut into shorter lengths by an appropriate cutting means while being fed to the paper machine net. Note that the cut glass fibers are made into paper on a net, but at that time, the pH and/or
Alternatively, it is preferable that the pH inside the papermaking tank is less than about 3, for example about 2.5. By disintegrating and/or wet papermaking in such an acidic region, an adhesive layer of water glass derived from glass fibers is formed on the surface of the glass fibers, and then this is heated to a predetermined temperature, e.g., 80 to 160°C.
By heating to , it is possible to bond the glass fibers to each other by means of the water glass on their surfaces. That is, if the glass fibers constituting the separator have an alkali-containing silicate glass composition,
The alkali component and silica component in the glass fiber,
A water glass layer is formed on the glass fiber surface by reacting with water for dispersion in an acidic region of about PH2.5, and this water glass layer acts as an adhesive to firmly adhere the glass fibers to each other. Normally, the glass fiber paper product wet-formed in this way is dried along a drum dryer to produce a product, but in producing the separator of the present invention, the obtained paper product is dried. After or before drying, a water glass adhesive is applied to the paper product by a so-called external addition method in which the paper is passed through a water glass adhesive bath, and then heated and dried. By heating and drying, the glass fibers are firmly bonded by the attached water glass. Note that the method of adding the water glass adhesive is not limited to the external addition method described above, and other methods may also be used. However, when using the external addition method, a large amount of water glass is attached to the surface of the paper product, and it is heated and dried. By doing so, it is possible to obtain a separator whose surface portion is strongly bonded by the added water glass and whose strength is improved. In this way, the mechanical strength and hardness of separators with stronger adhesion on the surface are significantly higher due to the strength and hardness of the surface, and because the adhesion inside is weaker than on the surface, the separator has a tendency to swell when liquid is absorbed. It has excellent liquid retention and liquid absorption properties, which is extremely advantageous. When a large amount of water glass is attached to the surface area in this way, the amount of water glass attached to the surface area from the surface of the paper product to about 1/4 of its total thickness is equivalent to the amount of glass fiber in that area in terms of solid content. It is preferable that the amount is 5% by weight or more. In addition, in papermaking of glass fibers, a dispersant may be used to disperse the 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 net, 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. The thickness of the separator itself of the present invention is
It varies depending on the storage battery used, but in general,
It is preferably 0.3 to 3 mm. The storage battery separator of the present invention thus obtained has a tensile strength of 400 g/15 mm width x 1 mm.
Thickness or more, buckling strength is 30g/10mm width x 1mm thickness or more,
It is preferable that the liquid absorption speed is 80 mm/5 minutes or more. [Function] The separator for a storage battery of the present invention consists essentially only of a glass component mainly composed of glass fibers, and does not contain organic fibers or binders, so it has extremely excellent liquid absorption and liquid retention properties. In addition, organic fibers and other organic adhesives that are commonly used to improve the strength of separators can weaken the acid resistance of separators.
As in the present invention, a separator made of a glass component has extremely excellent acid resistance. Therefore, in the present invention, since the glass fibers constituting the separator are bonded to each other by water glass derived from a water glass adhesive, the strength and hardness thereof are significantly improved. [Example] Examples and comparative examples will be described below. Example 1 75% by weight of glass fibers with an average diameter of 0.8 μm and an average length of 10 mm having the composition C in Table 1 and 25 weight % of glass fibers with an average diameter of 4 μm and an average length of 15 mm having the composition of C in Table 1 % in water, stir and disperse with a water jet disperser, and add sulfuric acid to dissolve the water.
The pH was set to 2.7 and held for about 10 minutes. Next, papermaking is performed, and a water glass adhesive (manufactured by Central Glass Co., Ltd., trade name:
Silpap 700) was adhered to the glass fiber in an amount of 5% by weight in terms of solid content, and then heated and dried at 150°C to produce a mat-like separator for storage batteries. Table 2 shows the results of measurements of the separator's loss on ignition, liquid absorption rate, tensile strength, buckling strength, maximum pore diameter, and liquid retention under pressure. Comparative Example 1 Except that no water glass adhesive was used.
A separator was manufactured in the same manner as in Example 1, and its various properties were measured.

[Table] From Table 2, the following is clear. That is, the separator made of glass fibers of the present invention and bonded with water glass to which fibers are added has excellent liquid absorption and liquid retention properties equivalent to those of conventional separators made of glass fibers. In addition to maintaining high properties in other properties as well, the tensile strength and buckling strength have been significantly improved, and the water glass fiber adhesion of the present invention has a significantly superior effect. be done. The methods for measuring various characteristic values in Examples and Comparative Examples are as follows. Thickness (mm) Measure the sample while pressing it with a load of 20 kg/dm ² in the thickness direction. (JISC-2202) Fabric weight (g/cm ³ ) This is the value obtained by dividing the sample weight by the sample area. Density (g/cm ³ ) When the thickness of the sample is T when a load of 20 kg is applied to the area (S) of sample (weight W) 10 cm x 10 cm,
It is expressed as a value given by the formula: W/(S×T) (g/cm ³ ). Loss on ignition (%) Heat the sample in air to 600°C until it reaches a constant weight, and calculate the loss by dividing the weight by the original weight of the sample. Liquid absorption rate (mm/5 minutes) Determine by holding the sample vertically, immersing its lower part in a dilute sulfuric acid solution with a specific gravity of 1.3, and measuring the rise in the liquid level over time after 5 minutes. Tensile strength (g/15mm width) Pull both ends of a 15mm wide sample and divide the external force when it breaks by the thickness and display the value (g) for a width of 15mm and a thickness of 1mm. Buckling strength (g/10mm width) Prepare a sample with a width of 50mm and a length of 100mm, hold the upper 50mm of the length with a holder, hold it so that the lower 50mm protrudes, and place the lower tip of the sample on the scale. The sample is pressed against the scale by making contact and gently lowering the holder, and the load (g) when buckled is determined. Then, it is converted into a value per 10 mm width and 1 mm thickness and displayed. Maximum pore diameter (μm) Immerse the sample piece in a methanol solution for at least 30 minutes, set the sample in the sample holder of a commercially available maximum pore diameter measuring device, and pipette 10 to 5 cc of methanol from the top. Let the air flow quietly,
Read the air pressure when bubbles are generated from methanol, and use a calculation formula to determine the maximum pore diameter. Liquid retention under pressure (g/cc) 20Kg/dm Thickness under ² loads is 1mm and dimensions are 10cm
When a 10cm x 10cm sample is soaked with water and a 20Kg load is applied in the thickness direction, the water content (g) in the sample is determined and expressed as the value divided by the sample volume (cc). [Effects of the Invention] As detailed above, the storage battery separator of the present invention is mainly composed of glass fibers, and the glass fibers are bonded together using a water glass adhesive added during the manufacturing process. , Since it is mainly made of glass fiber, it has liquid absorption properties,
Good liquid retention, especially under pressure. It also has excellent oxidation resistance. Since the glass fibers are stably bonded by water glass, high strength and hardness can be obtained. It has excellent effects such as Therefore, according to the separator of the present invention, a high-performance storage battery can be manufactured with excellent workability, and its industrial utility is extremely high.

Claims (1)

[Scope of Claims] 1. A separator for a storage battery, characterized in that the separator is mainly composed of glass fibers and the glass fibers are bonded to each other with a water glass adhesive. 2 Mainly made of glass fibers with an average diameter of 2 μm or less,
0 to 35% by weight of glass fibers with an average diameter of 10 to 30 μm and 0 glass fibers with an average diameter of more than 2 μm and less than 10 μm
The separator for a storage battery according to claim 1, comprising 30% by weight. 3. The separator for a storage battery according to claim 1 or 2, wherein the amount of the water glass adhesive is 1 to 10% by weight in terms of solid content based on the weight of the glass fibers. 4. The storage battery separator according to any one of claims 1 to 3, which has a tensile strength of 400 g/15 mm width x 1 mm thickness or more. 5. Any one of claims 1 to 4 whose buckling strength is 30 g/10 mm width x 1 mm thickness or more.
A separator for storage batteries as described in . 6. The storage battery separator according to any one of claims 1 to 5, which has a liquid absorption rate of 80 mm/5 minutes or more.