JPH0555977B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a separator for storage batteries, and particularly to a separator for storage batteries that has extremely good tensile strength, liquid absorbency, and liquid retention. [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 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. In particular, when assembling a battery, a long separator is sometimes folded by moving it back and forth in a zigzag pattern, and electrodes are placed between them.However, with separators made only of Gaass fiber, there is a problem in that the tensile strength decreases significantly due to bending. . 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 above-mentioned conventional technology, has good strength and hardness, has little strength loss after bending, and has good liquid retention and liquid absorption properties. The present invention provides an excellent separator for storage batteries, which is characterized in that it is mainly made of glass fibers, contains thermoplastic organic fibers, and the fibers are bonded to each other with a water glass adhesive. This is a summary. The present invention will be explained in more detail below. The fibers constituting the separator of the present invention are glass fibers and thermoplastic organic fibers. Among these, the glass fibers that are the main body of the separator for storage batteries are mainly 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 over 2 μm. It is preferable that it contains 0 to 30% by weight of glass fibers having a medium diameter of less than 10 μm. Medium-thin and large-diameter glass fibers are cheaper than small-diameter ones,
Particularly, 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 preferred is % 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 is from 5.0 to the weight of glass fiber.
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. In the present invention, there is no particular restriction on the composition of the glass fibers that constitute the main component of the separator, but it is preferable to use alkali-containing silicate glass fibers. That is, when alkali-containing silicate glass fibers are used, water glass-like substances are generated on the surface of the glass fibers during the papermaking process of the manufacturing process, and together with the water-glass adhesive added later, this generated water-glass substance is The adhesiveness also allows the fibers to be better adhered to each other, and the adhesive strength is further improved. In the present invention, among alkali-containing silicate glass fibers, those having good acid resistance are preferably used since they are used in storage batteries. 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 mμ or less. In addition, the composition of such glass fiber is 60 to 75% by weight.
Mainly contains SiO ₂ and 8-20% R ₂ O (alkali metal oxides such as Na ₂ O and K ₂ O) (but
SiO ₂ + R ₂ O is 75-90%), other examples include CaO,
Examples include those containing one or more of MgO, B ₂ O ₃ , 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] Furthermore, as the thermoplastic organic fiber, polyolefin-based, acrylic-based, and other organic fibers can be used, but polyester fibers are most suitable in terms of acid resistance and oxidation resistance. The thermoplastic organic fiber preferably has an average diameter of 30 μm or less and an average length of 3 to 20 mm. In the present invention, the blending ratio of glass fibers and thermoplastic organic fibers is preferably such that the thermoplastic organic fibers account for 2 to 8% by weight of the glass fibers. If the blending ratio of thermoplastic organic fibers is too small, the effect of preventing a decrease in strength after bending will not be sufficiently obtained, and if it is too large, the liquid absorption rate will be reduced. Preferably, the separator for a storage battery of the present invention is obtained by intertwining small, medium, and large diameter alkali-containing silicate glass fibers and thermoplastic organic fibers having the composition as described above by wet papermaking, and It is bonded with a water glass adhesive added in the above. 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, first, a paper product made of thermoplastic organic fibers such as glass fibers is manufactured. That is, when using alkali-containing silicate glass fibers as glass fibers, the glass fibers and thermoplastic organic fibers are soaked in water for a certain period of time, e.g.
After that, the fibers are dispersed using a water jet dispersing machine or the like without cutting them as much as possible, and then wet-processed. In this case, the pH in the papermaking tank is preferably less than about 3, for example about 2.5. By performing wet papermaking in such an acidic region, an adhesive layer of water glass derived from glass fibers is formed on the surface of the fibers. Next, by heating this to a predetermined temperature, for example, 80 to 180°C, it becomes possible to bond the glass fibers to each other by the water glass on the surface. 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. Note that the thermoplastic organic fibers mixed as part of the fibers may also be used in the post-process heat treatment process (e.g. drying process).
It exerts a molding or adhesion effect in the process, increasing the strength of the separator. Normally, the paper product mainly made of glass fibers produced by wet paper forming in this way is dried along a drum dryer and made into a product, but in producing the separator of the present invention, the obtained paper product After drying the body or before drying, a water glass adhesive is applied to the paper body by a so-called external addition method in which the paper is passed through a bath of water glass adhesive, 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. Note that during papermaking, 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 varies depending on the storage battery used, but is generally 0.3 to 3 mm.
It is preferable that The storage battery separator of the present invention thus obtained has a tensile strength of
400g/15mm width x 1mm thickness or more, buckling strength 30g/
It is preferable that the width is 10 mm or more and the thickness is 1 mm or more, and the liquid absorption rate is 80 mm/5 minutes or more. Further, it is preferable that the rate of decrease in tensile strength after one reciprocating bending is 30% or less. [Function] The separator for a storage battery of the present invention is mainly made of glass fiber, and is made by using a combination of thermoplastic organic fiber and a water glass adhesive, and the glass fiber is made from a thermoplastic organic fiber and a water glass adhesive. Because they are bonded together by water glass, their strength and hardness are significantly improved. Moreover, basic strength improvement can be obtained by using a water glass adhesive, and the purpose of using thermoplastic organic fibers is to improve the brittleness of the separator and reduce the strength loss after bending. The amount can be significantly reduced. Therefore, it is possible to significantly improve the strength of the separator by using an amount of thermoplastic organic fiber that does not impede the liquid absorption and liquid retention properties of the separator. [Example] Examples and comparative examples will be described below. Examples 1 and 2 Constituent fibers having the composition shown in Table 2 were poured into water, 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 is performed, and a water glass adhesive (manufactured by Central Glass Co., Ltd.,
Silpap 700 (trade name) 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, liquid retention under pressure, and bending strength. Comparative Example 1 A separator was produced in the same manner as in Example 1, except that the polyester fibers and water glass adhesive were not used, and its various properties were measured. The results are shown in Table 2. Comparative Example 2 Except that polyester fiber was not used,
A spallator was manufactured in the same manner as in Example 1, and its significant characteristics were measured. The results are shown in Table 2.

[Table] From Table 2, the following is clear. That is, the separator of the present invention, which is mainly composed of glass fibers and is bonded with thermoplastic organic fibers and added water glass, has liquid absorption properties that are as excellent as those of the separator made only of glass fibers (Comparative Example 1).
It has liquid retention properties and maintains high properties in other respects as well, and its tensile strength and buckling strength have been significantly improved. When compared with the separator (Comparative Example 2), the bending strength is significantly improved, and the combined use of the water glass adhesive of the present invention and the thermoplastic organic fiber provides a significantly superior effect. The fibers marked *1 to *3 in Table 2 are as follows. *1 Glass fiber A: Composition = C average diameter in Table 1 = 0.8 μm Average length = 10 mm *2 Glass fiber B: Composition = C average diameter in Table 1 = 4 μm Average length = 15 mm *3 Polyester fiber: Meltei (4080) (3
Denier, 10 mm) (manufactured by Unitika) The methods for measuring these 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 T is the thickness of the sample (weight W) where a load of 20 kg is applied to an area (S) of 10 cm x 10 cm, the formula:
It is expressed as a value given by W/(S×T)(g/cm ³ ). Loss on ignition (%) Heat the sample in air at 600℃ 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. Liquid retention under pressure (g/cc) 20Kg/dm Thickness under ² loads is 1mm and dimensions are 10cm
When a 10 cm x 10 cm sample is soaked with water and a 20 kg load is applied in the thickness direction, the water content (g) in the sample is determined, and this is expressed as the value divided by the sample volume (cc). Bending strength (g/15mm width) A sample with a width of 15mm is bent back and forth once, then put back together, and both ends are pulled, and the value of the external force when it is determined is divided by the thickness to obtain a width of 15mm and a thickness of 15mm. 1
Displayed in mm value (g). [Effects of the Invention] As detailed above, the storage battery separator of the present invention is mainly made of glass fibers, and the glass fibers are made of thermoplastic organic fibers that are heated and melted with a water glass-like adhesive that is added during the manufacturing process. Since it is glued and is mainly made of glass fiber, it has liquid absorption properties and
Good liquid retention, especially under pressure. Since the glass fibers are stably bonded by water glass, high strength and hardness can be obtained. Furthermore, due to the adhesive action of the thermoplastic organic fibers, the decrease in strength after bending is significantly improved. Moreover, since it is used in combination with a water glass adhesive, only a small amount of thermoplastic organic fibers is required, and the liquid absorbing and liquid retaining properties of the separator are not impaired. 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, which is mainly composed of glass fibers, contains thermoplastic organic fibers, and is characterized in that the fibers are bonded to each other with a water glass adhesive. 2. The separator for a storage battery according to claim 1, wherein the content of the thermoplastic organic fiber is 2 to 8% by weight based on the weight of the glass fiber. 3 Glass fibers are mainly 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 10 μm with an average diameter of more than 2 μm.
The separator for a storage battery according to claim 1 or 2, which contains less than 0 to 30% by weight of glass fiber. 4. The separator for a storage battery according to any one of claims 1 to 3, 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. 5. Any one of claims 1 to 4, wherein the thermoplastic organic fiber is a polyester fiber.
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 tensile strength of 400 g/15 mm width x 1 mm thickness or more. 7 Tensile strength reduction rate after one round trip of bending is 30
% or less, the storage battery separator according to any one of claims 1 to 6. 8. Any one of claims 1 to 7 whose buckling strength is 30 g/10 mm width x 1 mm thickness or more.
A separator for storage batteries as described in . 9. The storage battery separator according to any one of claims 1 to 8, which has a liquid absorption rate of 80 mm/5 minutes or more.