JPH03182047A - Battery separator - Google Patents

Abstract

PURPOSE:To reinforce a separator by combing a paper raw material slurry containing a specific quantity of colloidal silica to total weight of glass and glass fiber having a mean fiber diameter of a specific value or lower. CONSTITUTION:A paper raw material slurry, containing 1-10wt.% of colloidal silica to the total weight of glass and glass fiber having a mean fiber diameter of 2mum or below, is combed to be a separator. The large fiber diameter of glass fiber causes the maximum fire diameter of the separator to be large, and liquid retention force due to a capillary phenomenon to be lowered to obtain the insufficient layer-forming prevention effect. Moreover a smaller adding quantity of colloidal silica than the range causes sufficient effect to be unobtainable, and too much adding quantity causes too hardness allowing the detraction of a cushioning property. Consequently the separator is strengthened with constitution in the range.

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 excellent liquid absorption and retention properties, high strength, and excellent durability.

[Prior Art] Conventionally, it has been known that a paper sheet mainly made of glass fibers with an average fiber diameter of 2 μm or less exhibits good performance as a separator for a sealed lead-acid battery.

However, such paper sheets made of ultra-fine glass fibers have low strength, making them difficult to handle and having poor workability during battery assembly.

Therefore, there is a need for a technique for reinforcing a paper sheet made of ultra-fine glass fibers without causing a deterioration in the performance of the paper sheet, and the following methods have been proposed in the past.

■ Reinforcement method by blending organic synthetic fibers (
JP-A-60-225352, JP-A No. 62-246252, JP-A No. 62-252066).

■ Reinforcement method using water glass adhesive (Unexamined Japanese Patent Publication No. 6
2-281263, 62-252064).

■ A method of reinforcing using an acrylic binder (Japanese Patent Application Laid-Open No. 62-252065).

■ Method of reinforcing by thermal bonding
No. 252063, No. 63-80472).

■ A method of reinforcing by blending natural cellulose (Japanese Patent Application Laid-open Nos. 63-224144 and 64-52375).

■ A method of increasing the density of paper-made sheets to improve their strength.

[Problems to be solved by the invention] However, all of the above methods (■ to ■) have some drawbacks, and no solution has been obtained, and it is desired that an even better reinforcing method be developed. .

That is, in the method (2) using organic synthetic fibers, organic synthetic i
Since the a-fibers are hydrophobic, there is a drawback that the liquid absorption performance of the obtained separator is slightly reduced. The method (2) using a water glass adhesive has the disadvantage that the flexibility of the obtained separator decreases because the water glass adhesive becomes hard when it hardens. In the method (2) using an acrylic binder, since the acrylic binder is a liquid, a film is formed inside the separator, which has the disadvantage that the liquid absorption performance of the resulting separator is reduced. In the thermal bonding method (2), if the heating conditions are too high, the obtained separator will become a board, so it is difficult to set conditions to prevent this, and the range of manufacturing conditions is narrow. In addition, the method using natural cellulose (2) has the disadvantage that since natural cellulose is an organic substance, its acid resistance and heat resistance are lower than that of glass fiber, and as a result, the acid resistance and heat resistance of the resulting separator are also reduced. .

Furthermore, the method (2) of increasing the density has the disadvantage that the porosity of the obtained separator decreases, resulting in a decrease in liquid absorption performance.

The present invention solves the above-mentioned conventional problems and is capable of reinforcing a storage battery separator mainly made of ultra-fine glass fiber without reducing liquid absorption performance, heat resistance, acid resistance, flexibility, etc. The purpose is to provide separators.

[Means for Solving the Problems] The storage battery separator of the present invention has glass having an average fiber diameter of 2 μm or less, and 1 to 1% of the total weight of the glass fibers.
It is characterized by being made from a papermaking raw material slurry containing 10% by weight of colloidal silica.

That is, the present inventors have repeatedly studied a method for manufacturing a storage battery separator that has excellent liquid absorption performance, heat resistance, acid resistance, flexibility, etc., as well as high strength and excellent handling workability.
The following findings were obtained.

It has been known that silica powder is effective in improving the performance of separators for storage batteries (Japanese Patent Laid-Open No. 60-22195
No. 4, No. 61-269852, EP No. 253987)
. However, since silica powder lacks adhesive strength with glass I fibers, it is difficult to mix the silica powder, and it is technically difficult to manufacture a separator for M batteries made of glass fibers and silica powder. Therefore, the present inventors have repeatedly conducted research on methods of introducing silica, and have found that by using colloidal silica, a good adhesive effect is expressed, and that a mixed paper of glass fiber and silica (dried silica gel in the present invention) is used. The present invention was completed based on the discovery that a high-performance separator made of carbon fibers can be easily obtained.

The present invention will be explained in detail below.

If the fiber diameter of the glass fiber used in the present invention is excessively large, the maximum pore diameter of the separator will become large, and the liquid retention capacity due to capillarity will decrease, so there is a risk that the effect of preventing stratification of the electrolyte solution will not be sufficiently obtained. Therefore, the average fiber diameter is set to 2μ
m or less, preferably 0.9 μm or less. On the other hand, if the glass fiber diameter is too small, the cost of the separator increases, so it is preferably 0.4 μm or more, particularly 0.8 μm or more. That is, in the present invention, the average fiber diameter of the alkali-containing glass fibers used is 2 μm or less, preferably 0.4 to 0.9 μm, more preferably 0.6 to 0.9 μm.
It is desirable that the thickness be 0.9 μm.

On the other hand, colloidal silica is a product in which negatively f-charged amorphous silica particles are dispersed in water to form a colloid. The colloidal silica used in the present invention preferably has the following characteristics. .

Si IJ force (S i 02 ) content: 20-403 i% pH: 2-4 Particle size = 7-50 μm Viscosity (25°C): 25c, p Below specific gravity (20°C): 1.12-1. 28 In the wood invention, such colloidal silica is added to the papermaking raw material slurry so that the amount of colloidal silica added is 1 to 10% by weight based on the total weight of the papermaking material and the glass fibers. If the amount of colloidal silica added is less than the above range, sufficient effects of the present invention cannot be obtained,
On the other hand, if the amount is too high, it becomes too hard and the cushioning properties are impaired.

The separator for storage batteries of the present invention can be manufactured in the same manner as conventional separators for storage batteries, except for adding a predetermined amount of colloidal silica to the papermaking raw material slurry.
In order to obtain sufficient adhesion with the dry silica gel described later, the paper-made mat obtained on the paper-making net was dried at 140°C.
It is preferable to incubate at ~180°C for about 3 to 10 minutes.

[Function] Required characteristics of the reinforcing material for a storage battery separator mainly composed of glass fiber include the following conditions.

(2) In consideration of heat resistance and acid resistance, inorganic materials are preferable.

(2) In consideration of liquid absorbency, it is preferable to use a material that is highly hydrophilic and does not form a film.

(2) From the viewpoint of manufacturing operations, it is preferable to be stable against changes in temperature, pH, etc.

■ From the viewpoint of improving strength, it is desirable that the adhesive has a high adhesive strength and does not impair flexibility.

Colloidal silica is an excellent reinforcing material that satisfies all of the above required properties.

In other words, colloidal silica becomes a dry gel solid when dried and exhibits extremely high adhesive strength.Also, since the silica particles have a large surface area and have silanol groups on the surface, they are highly hydrophilic and have effective liquid absorption performance. can be improved. Moreover, it is stable to heat and pH.

Therefore, the separator for storage batteries of the present invention obtained by paper-making with the addition of colloidal silica has extremely excellent properties.

[Example] The present invention will be described in more detail by giving Examples and Comparative Examples below.

Examples 1 and 2, Comparative Examples 1 to 6 Storage battery separators were manufactured using the papermaking raw material formulations shown in Table 1, and their various properties were measured. The results are shown in Table 1.

The details of the raw materials used are as follows.

Glass fiber: Average fiber diameter 0.8 μm Natural cellulose: Cellulose obtained by beating coniferous bulbs in a beater for 24 hours (Canadian freeness 40cc (1.5% concentration by weight)) Acrylic synthetic fiber: Freeness 200 cc (3% by weight concentration) of fibrillated fiber colloidal silica: "Snowtex 0" manufactured by Shirataki Chemical Co., Ltd. In addition, the method for measuring the characteristic values in Examples and Comparative Examples is as follows.

■ Density (g/crn') 20 to area (S) of sample (weight W) 10cm x lOcm
When T is the thickness of the sample when a load of kg is applied, it is expressed as a value given by the formula: W/(SXT)(g/crn'').

■ Thickness (mm) Measure the sample while pressing it with a load of 20 kg/drr/ in the thickness direction. (JISC-2202) ■
Weighing (g/crn'') This is a value obtained by dividing the sample weight by the sample area.

■ Tensile strength (g/10mm width) Find the value (g) of external force when pulling both ends of a 10mm wide sample and it cuts it, divide by the thickness (mm),
mm, expressed as a value per 1 mm of thickness.

(2) Liquid absorption speed (seconds/100 mm) This is determined 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 time required for the liquid level to rise by 100 mm.

■ Heat resistance Place in an oven at 300°C for 30 minutes and measure the weight change rate before and after. Less than 5% is considered good.

From Table 1, it is clear that the separator for storage batteries of the present invention provides a separator for storage batteries that is excellent in heat resistance, liquid absorption, etc., and has high strength.

[Effects of the Invention] As detailed above, the storage battery separator of the present invention has excellent liquid absorption performance, heat resistance, acid resistance, and flexibility, as well as high strength and ease of handling. is provided.

Claims (1)

[Claims] (1) A separator for a storage battery made from a papermaking raw material slurry containing glass having an average fiber diameter of 2 μm or less and colloidal silica in an amount of 1 to 10% by weight based on the total weight of the glass fibers.