JP3060632B2 - Separators for liquid lead-acid batteries - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator for a liquid lead-acid battery, and more particularly to a separator for a liquid lead-acid battery which is easy to manufacture, has excellent oxidation resistance and good heat resistance.

[0002]

2. Description of the Related Art A liquid lead-acid battery, which is mainly used for automobiles, has a (+) electrode plate and a (-) electrode plate in which a protective mat made of glass fiber and a separator are separated. It is configured. Here, the function of the separator is as follows: (a) The (+) plate and the (-) plate come into contact in the battery,
Prevent short circuit.

(B) It absorbs an electrolytic solution and allows ions to pass therethrough.

[0004] Therefore, the separator is composed of a chemically resistant thin sheet having a myriad of microscopic pores on the order of microns.

In recent years, in addition to being thin and excellent in acid resistance and oxidation resistance, a separator of an automobile storage battery has been required to have further lower electric resistance.

Excellent heat resistance.

[0007] The material has excellent holding power for the active material and is inexpensive.

Has been required.

The separator having a low electric resistance here is
The low temperature starting performance and the low temperature and high rate discharge performance are due to the demand for batteries that are more excellent, and the heat resistance of the batteries requires high temperature use due to the narrowing of the engine room and the welding of electrode plates during battery assembly. This is due to being able to withstand temperature. Another reason is that it has recently been particularly required to have a function of more effectively preventing the active material from dropping off due to vibrations while the vehicle is running, and to be inexpensive.

Conventionally, as those having the above-mentioned characteristics, a glass fiber = 35 to 80% by weight synthetic fiber = 3 to 30% by weight inorganic powder = 3 to 30% by weight liquid binder = 10 to 15% by weight A separator has been proposed (JP-A-62-180954).

In addition, the following has been proposed as a storage battery separator. JP-A-63-284755: Glass fiber having an average fiber diameter of 0.3 to 3.5 μm = 23 to
48% by weight Silica powder having a specific surface area of 100 m ² / g or more = 57 to 77
% By weight Synthetic fiber = 0 to the total of glass fiber and silica powder
15% by weight A web layer having a density of 0.2 to 0.4 g / cm ³ and a glass fiber layer all adhered with an acrylic binder.

Japanese Patent Publication No. 64-5751: Inorganic powder having a specific surface area of 100 m ² / g or more = 20% by weight or more One or more of natural pulp, synthetic pulp, synthetic fiber and inorganic fiber Water content = 50% or more Dehydration press, dried, density 0.4-0.6g /
those with cm ^3.

Further, the following has been proposed by the present applicant. Japanese Patent Application No. 2-124747: Glass fiber having an average fiber diameter of 1 μm or less = 30 to 55% by weight Inorganic powder = 15 to 52% by weight, total 70 to 82% by weight, and organic component 18 to 30% by weight
Including.

[0014]

Hitherto, there has not been provided a separator for a liquid lead-acid battery which has excellent heat resistance and oxidation resistance, is easy to manufacture and is provided at low cost.

That is, the separator disclosed in JP-A-62-180954 has a large amount of synthetic fibers and lacks heat resistance. In the separator disclosed in JP-A-63-284755, since the amount of silica powder in the web layer is large, the paper strength of the sheet is weak and the production is not easy. Further, the separator disclosed in Japanese Patent Publication No. 64-5751 is composed of a mixture of inorganic powder and pulp or fiber. If the amount of inorganic powder is large, the sheet strength is low, and if the amount of pulp or fiber is large, heat resistance is poor. Furthermore, Japanese Patent Application No. 2-1
In the separator of No. 24471, the specific surface area (10 m ² / g or more) of the inorganic powder is small, the oxidation resistance is insufficient, and the heat resistance is slightly inferior.

As described above, a separator for a liquid lead-acid battery which satisfies all of heat resistance, oxidation resistance and ease of production has not been provided, and its development has been desired.

The present invention has been made in view of the above-mentioned conventional circumstances, and has as its object to provide a separator for a liquid lead-acid battery which is easy to manufacture, provided at low cost, and has excellent oxidation resistance and heat resistance. And

[0018]

According to the present invention, there is provided a separator for a liquid lead-acid battery, comprising a glass fiber 5 having an average fiber diameter of 2 μm or less.
10 to 20% by weight of a polyester fiber having an average fiber diameter of 3.0 to 14 μm and an average fiber length of 3 to 15 mm, and a silica powder 45 to 5 having a specific surface area of 150 m ² / g or more.
5% by weight and 20 to 30% by weight of an acrylic resin binder having a glass transition point of 10 to 40 ° C, and a density of 0.2
０．４0.4 g / cm ³ .

Hereinafter, the present invention will be described in detail.

The glass fiber constituting the separator for a liquid lead-acid battery of the present invention has an average fiber diameter of 2 μm or less. A relatively small diameter glass fiber having an average fiber diameter of 2 μm or less is extremely effective for improving the liquid retaining property of a separator and improving papermaking. Further, such a small-diameter glass fiber is effective for reducing the density of the separator and reducing the pore diameter, thereby reducing the electrical resistance of the separator and improving the low-temperature start-up characteristics of the storage battery.

If the content of the glass fiber is less than 5% by weight, the dimensional stability is deteriorated. If the content is more than 15% by weight, the amount of the polyester fiber or acrylic resin binder is inevitably reduced and the strength is reduced.

Therefore, the mixing ratio of the glass fiber is 5 to 15
% By weight.

The polyester fiber constituting the separator for a liquid lead-acid battery of the present invention has an average fiber diameter of 3.0 to 14.
μm and an average fiber length of 3 to 15 mm. If the average fiber diameter of the polyester fiber is less than 3.0 μm, it becomes expensive, and if it exceeds 14 μm, the strength and the oxidation resistance decrease. When the average fiber length is less than 3 mm, the strength is reduced, and when the average fiber length exceeds 15 mm, good dispersion cannot be obtained.

If the blending ratio of such polyester fibers is less than 10% by weight, the sheet strength at the time of papermaking is insufficient and the production becomes difficult. If it exceeds 20% by weight, heat resistance will be insufficient. Therefore, the mixing ratio of the polyester fiber is set to 10 to 20% by weight.

Incidentally, polyester fibers are relatively excellent in heat resistance among synthetic fibers and are suitable for the present invention. As the polyester fiber, polyethylene terephthalate fiber is particularly preferable.

The silica powder used in the separator for a liquid lead-acid battery of the present invention has a specific surface area of 150 m ² / g or more. When the specific surface area is less than 150 m ² / g,
Oxidation resistance becomes insufficient.

If the mixing ratio of such a silica powder is less than 45% by weight, the oxidation resistance becomes insufficient, and if it exceeds 55% by weight, the sheet strength at the time of papermaking becomes insufficient and production becomes difficult. Therefore, the mixing ratio of the silica powder is 45 to 55% by weight.
And

The acrylic resin binder used in the separator for a liquid lead-acid battery of the present invention has a glass transition point ( _TG ) of 10 to 40 ° C. When T _G is less than 10 ° C., the binder is soft and the sheet is easily clogged. When T _G exceeds 40 ° C., the binder becomes hard, and the flexibility of the sheet deteriorates.

If the blending ratio of such an acrylic resin binder is less than 20% by weight, the effect of improving the oxidation resistance and the strength by the blending of the acrylic resin binder cannot be sufficiently obtained. If it exceeds 30% by weight, the sheet is too clogged and the electric resistance becomes high. Therefore, the mixing ratio of the acrylic resin binder is set to 20 to 30% by weight.

In the present invention, the acrylic resin binder has the effect of coating the surface of the polyester fiber to close the separator, improve the oxidation resistance, and increase the sheet strength after drying.

As a method of coating the surface of the polyester fiber with the acrylic resin binder, an internal addition method in which the acrylic resin binder is simultaneously mixed with other materials. External addition type in which the sheet is dipped after the sheet is formed. Although there are two methods, the method is preferable because coating can be performed uniformly in the thickness direction.

The separator for a liquid lead-acid battery of the present invention can be easily produced by paper-making the above constituent materials according to a conventional method, but if the density is less than 0.2 g / cm ³ , the pore size becomes too large. Insufficient oxidation resistance. If the density is higher than 0.4 g / cm ³ , a large amount of material is required, and the cost is high. Therefore, the density of the separator for a liquid lead-acid battery of the present invention is set to 0.2 to 0.4 g / cm ³ .

[0033]

The constituent material of the separator for a liquid lead-acid battery of the present invention is composed of an inorganic material and an acrylic resin other than the polyester fiber, so that it has excellent heat resistance. In particular, polyester fibers are effective in improving sheet strength, but among synthetic fibers, they have excellent heat resistance, and thus do not impair the heat resistance of the separator.

Further, since the separator for a liquid lead-acid battery of the present invention contains a separator for a liquid lead-acid battery having a large specific surface area, the pore diameter of the sheet can be reduced and the oxidation resistance is excellent. Moreover, by coating the polyester fiber surface with an acrylic resin binder, the hole diameter of the sheet can be reduced, and the oxidation resistance is improved.
Further, the sheet strength is increased, and the production becomes easy.

In addition, the separator for a liquid lead-acid battery of the present invention has a density of 0.2 to 0.4 g / cm ³ , and therefore has excellent oxidation resistance and can be provided at low cost.

[0036]

EXAMPLES Examples and comparative examples will be described below. Examples 1 to 3 and Comparative Examples 1 to 5 Separators for a liquid lead-acid battery were manufactured using the materials shown in Table 1, and the measurement results of various characteristics are shown in Table 1. The materials used are as follows.

Small glass fiber: average fiber diameter 0.8 μm average fiber length 1.2 mm diatomaceous earth: specific surface area 20 m ² / g Silica powder: “Carplex # 80” (manufactured by Shionogi & Co., Ltd.) specific surface area 230 m ² / G Polyethylene synthetic pulp: "SWP E400" (manufactured by Mitsui Petrochemical Co., Ltd.) Polyester fiber: "Kuraray Ester 053" (manufactured by K.K.)
(Made by Kuraray) Average fiber diameter 7.0 μm Average fiber length 5.0 mm Acrylic resin binder: _TG 25.5 ° C. Production was performed as follows. That is, using the pulper, the material of the formulation shown in Table 1 with respect to the dispersion water,
The mixture was blended so that the total amount of the materials was 1% by weight, an appropriate amount of a fixing material was added, and the mixture was beaten for 20 minutes to produce a paper on a papermaking net. Then, it dried at 180 degreeC for 10 minutes, and obtained the separator.

Further, each measuring method and the like are as follows.

Basis weight (g / m ² ) A value obtained by dividing the sample weight by the sample area. (JIS P
8124) The thickness (mm) is measured in a state where the sample is pressed with a load of 20 kg / dm ^{2 in} the thickness direction. (JIS C 2202) Density (g / cm ³ ) Sample (weight W) 20 in area (S) of 10 cm × 10 cm
When the thickness of the sample when a load of kg is applied is T,
Formula: Expressed as a value given by W / (S × T) (g / cm ³ ).

A sample having a maximum pore diameter (μm) was cut into a size of 35 mm × 35 mm, and this was used as a test piece. After the test piece is immersed in a methanol solution for 30 minutes or more, the test piece is set in a sample holder, and 5 to 10 cc of methanol is poured from above with a pipette. Next, the three-way cock (for coarse adjustment) is fully opened and air is flowed. Then, gradually open the two-way cock (fine adjustment) (to the extent that the water in the U-shaped manometer moves gently) and reduce the air pressure when bubbles are generated from methanol on the sample holder to the differential pressure of the U-shaped meter. And the maximum pore diameter is determined by the following equation. Calculation formula Maximum pore diameter (μ) ≒ 30 r / Hg (mm) 30: Coefficient r: Methanol interfacial tension 23 Hg: Correction coefficient 760/10330 = 0.
0736 electric resistance (Ω · dm ² / sheet) According to JIS C2313.

Oxidation resistance time (hr / sheet ) A sample (a 0.3 mm thick separator and a 0.6 mm thick glass fiber (average fiber diameter: 19 μm) mat) were bonded to a test apparatus as shown in FIG. Stuff, size 70 × 7
0mm) 1 and set the load (lead block (70 × 70
mm) 5 kg) 2 and then placed in an acid-resistant container (about 132 ×
Approximately 1000 ml of dilute sulfuric acid (specific gravity: 1.300 / 20 ° C.) is injected as an electrolytic solution 4 into the (185 × 102 mm) 3 (the liquid surface 4a is maintained during the test). Next, while maintaining the electrolyte temperature at 45 ± 2 ° C. and applying a constant current (DC) of 2.5 A, the terminal voltage is measured at regular intervals. In FIG. 1, 5 and 6 are glass plates (70 ×
70 × 5mm), 7 and 8 are contact plates (insulating plates) (50 × 50
× 3 mm), 9 is an anode plate (pure lead plate) (50 × 50 × 3 m
m), 10 is a cathode plate (pure lead plate) (50 × 50 × 3 m
m) and 11 are acid-resistant resin stands.

The oxidation resistance time (hr) is such that the terminal voltage is 2.6.
The time is indicated by the time when the voltage drops below V or when the voltage drop rate becomes 0.2 V / hour or more.

Heat resistance (sec) was measured by the method shown in FIG. That is, a glass mat 13 is placed on an iron plate 12 at 420 ± 5 ° C. (actually measured by a thermocouple).
The sample 1 is placed, and at the same time, the stopwatch is operated. The stopwatch is stopped when discoloration, deformation, scorching, burning, etc. are observed, and the time is evaluated. The size of the sample 1 is 40 mm × 40 mm, and the hole diameter of the hole 13A of the glass mat 13 is 30 mm. Second
In the figure, 14 is a heater.

[0044]

[Table 1]

From Table 1, it is clear that the separator for a liquid lead-acid battery of the example has a long oxidation resistance, excellent heat resistance, high strength, and excellent workability in production.

[0046]

As described in detail above, the separator for a liquid lead-acid battery of the present invention has remarkably high heat resistance and oxidation resistance, and is easily manufactured and provided at low cost.

Therefore, according to the present invention, there is provided a high-performance liquid lead-acid battery separator suitable as an automotive liquid lead-acid battery separator and the like.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an apparatus used for measuring an oxidation resistance time in Examples and Comparative Examples.

FIG. 2 is a cross-sectional view showing an apparatus used for measuring heat resistance in Examples and Comparative Examples.

[Explanation of symbols]

 Reference Signs List 1 Sample 2 Load 3 Container 4 Electrolyte 9 Anode plate 10 Cathode plate 12 Iron plate 13 Glass mat 14 Heater

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-180954 (JP, A) JP-A-62-281263 (JP, A) JP-A-63-284755 (JP, A) JP-A-4- 19959 (JP, A) JP-A-4-229950 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 2/14-2/18

Claims (1)

(57) [Claims] 1. A glass fiber 5 having an average fiber diameter of 2 μm or less.
10 to 20% by weight of a polyester fiber having an average fiber diameter of 3.0 to 14 μm and an average fiber length of 3 to 15 mm, and a silica powder 45 to 5 having a specific surface area of 150 m ² / g or more.
5% by weight and 20 to 30% by weight of an acrylic resin binder having a glass transition point of 10 to 40 ° C, and a density of 0.2
A liquid lead storage battery separator having a capacity of up to 0.4 g / cm ³ .