JPS60225352A - Separator for storage battery - Google Patents

Abstract

PURPOSE:To increase the tensile strength and stiffness of a separator so as to improve the characteristic of holding electrolyte by mixing glass fibers of small and large diameters, acrylic and polyester fibers and a polyvinyl alcohol fiber in a wet method, and heating and drying it. CONSTITUTION:A contained alkaline silicate glass fiber with an average diameter of 0.5-1.0mu; 60-90wt%, a contained alkaline silicate glass fiber with the average diameter of 10-20mu; 8-35wt%, an acrylic fiber and a polyester fiber with 1.0-1.5d; 2-7wt% and a hot water soluble polyvinyl alcohol fiber with 0.5-1.0d are dispersed in water. These are mixed in a wet method and a separator for a storage battery is formed by heating it to given temperature. This separator has excellently physical properties such as tensile strength, bladder ratio, maximum small hole diameter and buckling strength and it is possible to provide the separator with cheap cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a separator for a storage battery, and more particularly to a separator for a storage battery made of glass fiber and synthetic fiber.

[Background of the Invention] As a separator for a storage battery containing glass m-fiber,
Various types have already been proposed and put into practical use, but they can be broadly classified into the following three types. Namely, 1) those mainly composed of short glass fibers, 2) those made by mixing and molding short glass fibers and synthetic fibers (e.g. Japanese Patent Application Laid-Open No. 49-38126), and 2) those in which short glass fibers hold powder ( For example, Japanese Patent Publication No. 58-20'
6'046).

Among these, the one mainly composed of short glass fibers has a short fiber length and is hydrophilic, so if it contains a large amount of short glass s#I with a small diameter, it will not work properly in a storage battery. Although it has excellent liquid retention and liquid absorption properties, which are the basic properties of the glass, the small diameter glass m# is expensive, so the separator formed from it is also expensive. Furthermore, a separator formed without using an organic binder has low tensile strength and low rigidity, making it difficult to assemble a storage battery. Furthermore, when molding is performed using an organic binder, there is a risk that the binder will dissolve into the electrolyte when it is incorporated into a storage battery and used, thereby degrading the performance of the storage battery.

A mixture of short glass fibers and synthetic fibers has a high mechanical strength (tensile strength, stiffness, etc.) and has the advantage of being easier to assemble a storage battery, but synthetic fibers are more hydrophilic than glass fibers. Due to its low properties, its electrolyte retention properties are poor.

(Although the mixed material of glass fibers and powder on the side has good liquid absorption properties, there are problems in that the powder easily peels off and falls off from the separator and has low tensile strength.

[Object of the Invention] An object of the present invention is to provide a separator for storage batteries that solves the problems of the above-mentioned prior art, has high tensile strength and rigidity, has excellent electrolyte retention properties, and is inexpensive. It is in.

[Structure of the Invention] The present invention comprises 60 to 90% by weight of alkali-containing silicate glass fibers with an average diameter of 0.5 to 1.0 μm, and an average diameter of 10 to 20 μm.
alkali-containing silicate glass fiber #I 8 to 35% by weight,
2 to 7% by weight of 1.0 to 1.5 denier acrylic fibers and/or polyester fibers, and 0.04 to 0.04 to 0.04 to 1.0 denier hot water-soluble polyvinyl alcohol fibers.
The above object is achieved by a separator for a storage battery which is wet-mixed with 0.6% by weight and then heated and dried.

That is, the storage battery separator of the present invention has the following excellent features a to d.

a. Contains thin glass fibers with an average diameter of 0.5 to 1.0 gm, and has excellent liquid retention and liquid absorption properties.

b. This thin glass fiber has an average diameter of 10 to 20 gm.
Since large-diameter glass fibers are mixed in, the large-diameter glass fibers become a skeleton and the small-diameter glass fibers are intertwined between the skeletons, improving tensile strength and porosity. become. Furthermore, since large-diameter glass fibers are significantly lower in cost than small-diameter glass fibers, the price of the separator is also lower.

The present inventors have developed a separator in which only small-diameter glass fibers with an average diameter of 0.91 Lm are wet-mixed, heated and dried, and a separator in which 70% by weight of glass fibers with an average diameter of 0.97 Lm and a large one with an average diameter of 19 meters are made. When we measured the physical properties of a separator made of 30% by weight of glass fibers wet-mixed, heated and dried, we found that a separator with a mixture of small-diameter glass fibers and large-diameter glass fibers was better than one with only small-diameter glass fibers. ,
It was observed that the tensile strength and porosity were high, and the maximum pore diameter was small.

Contains a small amount of synthetic fiber to the extent that it does not adversely affect the C1 liquid retention characteristics, and uses a synthetic fiber that has a large effect of increasing tensile strength and rigidity even in a small amount, and has high mechanical strength and liquid absorption. And there is no decrease in liquid retention.

That is, as mentioned above, it has been conventionally practiced to improve the mechanical strength of the separator by mixing synthetic fibers into the separator for storage batteries, and acrylic fibers and the like with strong acid resistance are widely used as the synthetic fibers.

However, synthetic fibers such as acrylic fibers have less wood-philicity than glass fibers, and if they are mixed in too much, they reduce the liquid retention properties of the separator, whereas if they are mixed in small amounts, they can improve mechanical strength. The effect becomes smaller. Therefore, the present inventors investigated synthetic fibers that can significantly improve the mechanical strength of separators by mixing a small amount with glass fibers, and found that they have a trace amount of hot water solubility compared to acrylic fibers and/or polyester fibers. It has been found that the combination of polyvinyl alcohol [I] is suitable.

d, the glass fiber is an alkali-containing silicate glass fiber,
Glass fibers can be bonded together without using a water-soluble organic resin binder. That is, the separator of the present invention is formed by wet papermaking, and during this papermaking, an adhesive layer, perhaps a water glass layer, is formed on the surface of the glass fiber due to the reaction between the alkali silicate in the glass fiber and the papermaking water, and this water Glass fibers are bonded to each other by the glass layer, and sufficient bonding strength is developed.

The configuration of 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 alkali-containing silicate glass fibers and organic fibers.

The alkali-containing silicate glass fibers include two types, small diameter ones and large diameter ones, and the average diameter of the small diameter glass m#I is 0.5 to 1.0 #Lm, more preferably 0.6 to 0
．． It is 9 m. If the diameter exceeds 1.0 pLm, the porosity of the separator becomes small, and conversely, if the diameter becomes smaller than 0.5 gm, the manufacturing cost becomes high.

The content of this small diameter glass m#I is 60% of the total am weight.
-90% by weight, particularly preferably 65-85% by weight. If the content is less than 60%, the liquid absorption and liquid retention properties will be insufficient, and if the content exceeds 90%, the cost of the separator will be high.

Moreover, the average length of this small-diameter glass jIita is preferably 7 to 50 mm, more preferably 10 to 40 m. When the average length is shorter than 1O+m, the strength of the separator decreases, and when it is longer than 50 m layer, it becomes difficult to uniformly disperse the separator in water during papermaking. Such alkali-containing silicate glass fibers with an average diameter of 0.5 to 1.0 pm are produced using the FA method (flame method).

It can be produced by centrifugation or other short glass fiber production methods. In addition, in the present invention, the average diameter of the glass fibers is determined by taking photographs of three locations on the sample using an electron microscope, and determining the average diameter of each glass fiber at 20 mm.
It is calculated by measuring the diameter of the m-cone of a book in units of 0 and 1 #Lm and taking the average value of these measurements.

As a large diameter glass am, the average diameter is 10 to 20 ILm,
Preferably 8 to 3 of the total fiber weight is 12 to 19 μm.
It contains 5% by weight, preferably 10-30%. average diameter is 1
0. When u and m are smaller, or when the content is less than 8%, the tensile strength improvement effect becomes small, and when the average diameter exceeds 2 olm or the content exceeds 35%, the separator The liquid absorption and liquid retention properties of the liquid are reduced. The length of this large diameter glass fiber is 5 to 80 layers, especially 6 to 4
011w1 is preferred.

A suitable range of the composition of the glass fiber will be explained next.

The glass fibers constituting the separate material of the present invention have an alkali-containing silicate glass composition, and are capable of forming water glass on their surfaces. Furthermore, since it is used in storage batteries, those with good acid resistance are preferably used. The degree of acid resistance is determined by the weight loss of 2 when measured according to JISC-2202 using glass fibers with an average fiber diameter of 1#L or less.
% or less is desirable. In addition, the composition of such glass fiber is 60 to 75% SiO and 8% by weight.
Mainly contains ~20% R2O (alkali metal oxides such as Na2o, Ni2O, etc.), but SiO+
R20 is 75-90%), and in addition, for example, cao, M
Examples include those containing one or more of (7) such as go, B2O2, Al2O2, ZnO, Fe2O3. Examples of preferable alkali-containing silicate ring glasses are shown in Table 1 below.

Table 1 The separator of the present invention contains thermoplastic acrylic fibers and/or polyester as organic fibers in addition to such alkali-containing silicate glass fibers. 2-7
% by weight, preferably 3 to 6%,
If the mixing ratio of these m-fibers exceeds 7% by weight, depending on the material of the fibers, it may have an adverse effect on the performance of the storage battery, and if it falls below 2%, the strength improvement effect will be reduced.

Note that acrylic s#l and/or polyester fibers are 1.
0 to 1.5 denier is used, and its length is 2
~10tim is preferable.

The separator of the present invention further contains hot water-soluble polyvinyl alcohol Ih1s as the organic fiber.

As mentioned above, acrylic fiber, polyester fiber! is more hydrophobic than glass fiber, so if the amount of these fibers increases, the liquid retention and absorption properties of the separator will decrease, but by mixing a small amount of hot water-soluble polyvinyl alcohol fiber, the separator's tensile strength Strength and buckling strength are significantly improved. Therefore, only a small amount of acrylic fiber and/or polyester fiber is required, and the strength of the separator is increased, and a decrease in liquid retention and absorption properties can be prevented.

The amount of polyvinyl alcohol fiber mixed is 0.04 to 0.6% by weight of the separator weight, especially 0.05 to 0.
．． Preferably, it is 2% by weight.

Moreover, the length is preferably about 2 to low.

The separator for storage batteries of the present invention comprises small diameter and large diameter alkali-containing silicate glass fibers, acrylic fibers and/or polyester fibers, and hot water soluble polyvinyl alcohol tRr.
A is dispersed in water whose pH value is maintained at 2.5 to 3.5 for a certain period of time, for example 5 to 20 minutes, using a water jet dispersion machine, etc., without cutting the fibers as much as possible. Wet papermaking is performed to form an adhesive layer, perhaps a water glass layer, on the surface of the glass fiber, and then the paper is heated to a predetermined temperature, e.g.
It can be obtained by adhering glass fibers to each other by means of water glass on their surfaces by heating to 1.80°C. That is, since the glass fibers constituting the separator of the present invention have an alkali-containing silicate glass composition as described above, the alkali components and silica components in the glass react with water for dispersion, resulting in a water glass layer. This water glass layer is formed on the surface of the glass fiber and acts as an adhesive to bond the glass am.

Note that the acrylic fibers, polyester fibers, and polyvinyl alcohol fibers mixed as part of the fibers also exert a shaping or adhesion effect in the subsequent heat treatment step (for example, the drying step), thereby 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 31 m1B. Note that a dispersant may be used when dispersing the fibers in water. Further, a dialkyl sulfosuccinate is sprayed onto a wet-formed fiber paper product, for example, a fiber paper product on a paper-making conveyor, so that the glass fiber has a 0.
By attaching the dialkyl sulfosuccinate in an amount of 0.005 to 10% by weight, the liquid retention property of the separator can be improved due to the hydrophilicity of the dialkyl sulfosuccinate. Instead of spraying the dialkyl sulfosuccinate as described above, it may be mixed into the dispersion water in the papermaking tank.

Note that if paper is made by mixing powder such as silica powder or glass powder with short glass fibers, a separator with a small maximum pore diameter can be obtained. However, this separator has a high density and a low porosity.

As a separator for storage batteries, it has the advantages of a small maximum pore diameter, high porosity, and excellent liquid retention and absorption properties, and the material price is low, and the separator price is also low. This is important for industrial production. Large diameter (e.g. average diameter 19pm)
) and glass powder are combined into a separator having the basic structure of the separator of the present invention, an inexpensive separator for storage batteries with excellent performance can be obtained.

[Embodiments of the invention] Examples will be described below.

The composition is A in Table 1, and the composition is 75 parts by weight of thin glass fibers with an average diameter of 0.8 pm and an average length of 10 mm.
A in the table, average diameter 19pm, average length 25mmc
7) Acrylic lag with 9920 parts by weight of glass and 1.2 denier thickness (manufactured by Kanebo Co., Ltd., trade name: Kanekalon S)
) cut to a length of 3 mm and 4.9 parts by weight of polyvinyl alcohol fiber #1 (manufactured by Spray Co., Ltd., trade name: VPB)
105) was cut to a length of 3 mm, and 1 part by weight of 001 was 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. Then, the paper was formed and heated to 150° C. to produce a mat-like storage battery separate material. 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.

Table 2 shows the results of measuring the tensile strength, porosity, maximum pore diameter, and buckling strength of the separator according to this example.

For comparison, the same characteristics were measured using the same fiber materials as in the examples but with different formulations as shown in Table 2.

Table 2 The method for measuring these characteristic values is as follows.

(1) Thickness: 1 inch) The sample is weighed 20 kg/
Measurement is performed under pressure with a load of drn'.

(JISC-2202) (2) Density (g/ctn') Sample 10cmX10cm
When T is the thickness of the sample when a load (W) of 20 kg is applied to the area (S) of

(3) Fabric weight (g/cm') This is a value obtained by dividing the sample weight by the sample area.

(4) Tensile strength (g) Indicate the external force (g) when pulling both ends of a sample with a width of lO and cutting it.

(5) Porosity (%) The density of the separator is expressed as ((ab)/a)X100 (%), where a is the density of the glass constituting the glass fibers.

(6) Maximum pore diameter (P) After fully immersing the mat-like sample in methanol, it was placed in a holder with an opening of 15 m5 in diameter, and air was gradually allowed to flow through the opening. Air bubbles were initially generated from the sample. The differential pressure ΔP of the air flow before and after passing through the sample is detected and calculated using the following formula.

Maximum pore diameter (pLn) = /ΔP (k constant) (7) Buckling strength (g) Between a pair of parallel plates, a radial O layer,
A sample with a length of 50 layers is sandwiched in the width direction, the clamping pressure of the parallel plates is gradually increased, and the load (g) when buckled is calculated.

From Table 2, it is recognized that the storage battery separators according to Examples have extremely high tensile strength and buckling strength, large porosity, and small maximum pore diameter. In particular, when comparing Example and Comparative Example 3, in which the only substantial difference was the presence or absence of polyvinyl alcohol fibers, it was found that the tensile strength and buckling strength were significantly improved by mixing the polyvinyl alcohol fibers. It will be done.

When similar tests were conducted on glass fibers B and C in Table 1, similar results were obtained.

[Effects of the Invention] As detailed above, the storage battery separator of the present invention has high tensile strength and rigidity, and thus facilitates the assembly work of the storage battery. In addition, it has a large porosity and can retain a large amount of electrolyte, and has a small maximum pore diameter and excellent liquid absorption. Furthermore, since large-diameter glass fibers are cheaper than small-diameter ones, they are inexpensive.

Agent: Patent attorney Tsuyoshi Shigeno

Claims (1)

[Claims] (1) The following fibers, i.e. average diameter 0.5-1. OPM alkali-containing silicate glass fiber 60-90% by weight, average diameter 10-20 g, m alkali-containing silicate glass fiber 8-35% by weight, 1.0-1
．． 2 to 7% by weight of 5 denier acrylic fibers and/or polyester fibers and 0.5 to 1.0 denier hot water-soluble polyvinyl alcohol fibers MO, 04 to 0.6% by weight are wet-mixed and heated. A storage battery separator characterized by being dried.