WO1992016977A1

WO1992016977A1 - Separator for closed type lead-acid battery

Info

Publication number: WO1992016977A1
Application number: PCT/JP1992/000306
Authority: WO
Inventors: Koji Horimoto; Motofumi Nakamura; Motoyuki Esaki; Yoshitaka Tanaka
Original assignee: Mitsui Petrochemical Industries, Ltd.; Gs Kasei Kogyo K.K.
Priority date: 1991-03-13
Filing date: 1992-03-13
Publication date: 1992-10-01

Abstract

A separator for a closed type lead-acid battery comprises a porous mat manufactured by a method wherein polyolefine synthetic pulp as its main component is mixed with a binder of a melting point lower than that of the synthetic pulp, the mixture is made into paper, and the paper is heat-treated at a temperature lower than the melting point of the synthetic pulp and higher than the melting point of the binder. The separator is cheap as no glass fiber is used, excellent in water retention and acid resistance, and has a low density. Closed type lead-acid batteries using this separator are excellent in capacity of discharging at a high rate at a low temperature.

Description

Satsuki Itoda

Technical background of sealed lead-acid battery separator

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator for a sealed lead-acid battery comprising a porous mat, and more particularly, to a porous pine obtained by dry-making a material mainly composed of a polyolefin synthetic pulp. The present invention relates to a separator for a sealed lead-acid battery, which is composed of a battery.

Conventional technology

Eve's sealed lead-acid battery, in which oxygen gas generated from the positive electrode is absorbed by the negative electrode while the battery is being charged, comes in two types: retainer type and gel type. In the retainer type, a mat-like separator with liquid retention properties is inserted between the positive and negative plates to maintain the electrolytic properties necessary for battery discharge and to separate the electrodes, thereby eliminating maintenance. In recent years, it has been used as a backup power supply for portable devices, computers in an emergency (power failure), or a power supply for automobiles, etc., taking advantage of its characteristics such as liquid leakage and position-free.

In general, a closed type lead-acid battery of the retainer type uses a mat made of ultra-fine glass fiber (hereinafter referred to as a glass separator) (see, for example, Japanese Patent Application Laid-Open No. 60-110118). No. 61, Japanese Patent Application Laid-Open No. 59-73842), and a separator composed of a polyolefin-based wet nonwoven fabric has also been proposed (Japanese Patent Application Laid-Open No. 62-268890). No. Refer to the gazette). However, in separators using extra-fine crow fibers, glass fibers are very expensive and are not considered to be industrially suitable materials.Moreover, in separators made of polyolefin-based wet nonwoven fabric, Must be bulky in order to have sufficient liquid retention, as a means of mixing glass fibers, etc., which is inevitably disadvantageous in terms of cost.

On the other hand, batteries that are used for many purposes are generally required to be lighter and have higher capacities. In particular, the rapid expansion of the market and the increase in There is a growing demand for even lighter batteries and higher capacities for applications such as equipment, backup power supplies, and automotive power supplies.

The gist of the invention

An object of the present invention is to provide a separator for a sealed type lead-acid battery which is reduced in cost, improves low-temperature high-rate discharge capacity, is excellent in battery discharge characteristics, and is lightweight.

The present invention has been proposed to achieve the above object, and uses a mat made of a material mainly composed of a polyolefin-based synthetic valve made porous by a special method as a separator. It is characterized by the following.

That is, according to the present invention, 100 to 50% by weight of a polyolefin-based synthetic pulp and 0 to 50% by weight of a binder having a melting point lower than that of the synthetic pulp are dry-processed. And a separator for a sealed lead-acid battery characterized by comprising a porous mat obtained by the above method.

Further, according to the present invention, polyolefin-based synthetic pulp

Closed hermetic lead storage, comprising porous mat obtained by dry-papermaking 98 to 50% by weight and a binder having a melting point lower than that of the synthetic pulp, 2 to 50% by weight. A battery separator will be provided.

Further, according to the present invention, a sealed lead-acid battery having further excellent characteristics as described above is obtained by using the polyolefin synthetic pulp having a specific surface area of 1 m ² or more as measured by a BET adsorption method. Separate evenings will be provided.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view of an apparatus for measuring the maximum pore diameter of a separator in an embodiment of the present invention.

Details of the Invention

The polyolefin-based synthetic pulp is subjected to a hydrophilic treatment, particularly a hydrophilic treatment using an aqueous solution of a surfactant, so that a separator for a sealed lead-acid battery having more excellent respective physical properties can be obtained. By heat-treating the porous mat to such an extent that the bulkiness is not impaired, the strength of the mat can be increased, and 45% by weight of the synthetic pulp can be added. Suitable for sealed lead-acid batteries by blending various synthetic fibers, natural pulp, and acid-resistant inorganic powder in the following ranges A separator can be provided.

Since the separator obtained by the present invention is manufactured by dry paper-making in particular, there is a feature that a bulky material can be easily obtained without shrinkage due to surface tension of water during drying.

Raw material

In the present invention, as the synthetic pulp used as a main material, a polyolefin-based synthetic pulp is used, and in particular, a solution or a solution obtained by flash spinning emulsion is preferably used.

Polyolefin-based synthetic pulp is known per se, and those manufactured by various methods as described below can be used.

The details of the method for producing polyolefin-based synthetic pulp are described in detail in Ency-clopedia of Chemical Technology 3rd ed. Ol. 19 P420 to 425. Examples include a method of performing a beating treatment after performing a solution flash or an emulsion flash.

Among them, those produced by emulsion flash method using polyvinyl alcohol (PVA) as a hydrophilizing agent are preferably used. In this case, the PVA content is preferably 0.01 to 10% by weight.

In addition, these polyolefin synthetic pulp have a specific surface area of 1 m ² Zg or more as measured by the BET adsorption method. Preferably, it is

Examples of the polyolefin used include homopolymers of olefins such as polyethylene and polyethylene, copolymers of ethylene and propylene, copolymers of ethylene and 1-butene, and copolymers of ethylene and 1-methylpentene. Copolymers of ethylene and another α-olefin are preferred, and among them, crystalline polyolefin is preferably used in terms of mechanical strength.

The polyolefin-based synthetic pulp thus obtained has a fiber length of 0.1 to 10 and can be easily dry-processed thereafter. It has excellent discharge characteristics and is lightweight and inexpensive. '

Further, since the polyolefin-based synthetic pulp is itself hydrophobic, it is possible to use a hydrophilic-treated synthetic pulp in order to improve the water retention of the obtained separator.

In the present invention, as long as the object of the invention is not impaired, for example, in the range of 45% by weight or less, polyester, acrylic, polypropylene, polyethylene, polystyrene, methyl meth acrylate, acrylonitrile, Various synthetic fibers such as vinylidene chloride resin, natural fibers, glass fibers, silica fibers, alumina silicate fibers, inorganic fibers such as slag fibers, and acid-resistant inorganic powders such as silica powder and diatomaceous earth are required. Mix according to be able to.

Matte

In the present invention, it is an important requirement that, after mixing the above-described raw materials, dry papermaking and matting are performed. Dry papermaking is a method in which the above-mentioned synthetic pulp is made into a sheet in a dried state mainly using a card or the like.For example, a binder having a lower melting point than the polyolefin-based synthetic pulp is added to the above-mentioned synthetic pulp. The method called fiber bonding, in which the two are mixed and thermally fused at the melting temperature of the binder, is the shortest, simple and economical. As a specific method of the fiber bond method, a hot air penetration type method in which the above-mentioned raw material sprayed on a running mesh-shaped support is heated from above while vacuuming from below, and the formed web is A method in which a low-melting binder mixed with a hot roll is melted to fix a polyolefin-based synthetic pulp; a method in which the formed web is melt-bonded to the binder in a heat oven; an infrared heater; or A method of melting the binder using ultrasonic energy and bonding the webs may be used, but a hot air penetration method is preferably used in terms of heat treatment temperature and imparting bulkiness of the product.

In this case, the binder used for the polyolefin-based synthetic pulp, the polyolefin-based fiber, and the core have a melting point higher than the melting point of the synthetic pulp, and the sheath part has a melting point higher than the melting point of the synthetic pulp. Has a low melting point, so-called Composite fiber of sheath-core type, polyolefin resin powder, low melting point polyester powder, butyl chloride resin powder, evoxy resin powder, or emulsion thereof, natural or synthetic rubber latex, and acrylic emulsion At least one kind of pulp carried from the group is exemplified. Among them, it is preferable to use polyolefin synthetic pulp. This binder must have a melting point lower than the melting point of the polyolefin synthetic pulp as the main raw material, preferably 5 or lower. The mixing ratio of the polyolefin-based synthetic pulp and the binder is such that the polyolefin-based synthetic pulp is 100 to 50% by weight, preferably 98 to 50% by weight, the binder is 0 to 50% by weight, Preferably, it is 2 to 50% by weight. '

In addition to the above methods, for example, the air laid method described in Γ. For example, a method of randomly arranging binders having melting points in an air stream and bonding them by heat is exemplified.

The product obtained by dry papermaking can obtain a porous mat having high bulk (low density), that is, a high void ratio and excellent water retention, as compared with wet papermaking, which is an object of the present invention. It can be used very suitably as a separator for a sealed lead-acid battery.

Hydrophilic treatment In the present invention, the water retention of the mat can be further improved by subjecting the mat obtained as described above to a hydrophilization treatment. This hydrophilization treatment is performed, for example, by immersing the mat in an aqueous solution of a surfactant, or by spray-spraying the mat, followed by drying. As the surfactant to be used, an anionic surfactant is preferable. The degree of the hydrophilization treatment is preferably such that the amount of the surfactant attached is in the range of 0.05 to 5.0% by weight, more preferably 0.2 to 2.0% by weight.

Such a hydrophilization treatment is effective when synthetic pulp that has not been subjected to a hydrophilization treatment is used. The lead-acid battery separator made of the mat thus obtained has a low density of 0.05 to 0.30 gZee, is excellent in water retention, and is a sealed lead-acid battery using this. Is also excellent in low temperature and high rate discharge capacity.

In the separation of the present invention, the water retention and the maximum pore size are related to the following characteristics of the lead storage battery.

Water retention: In general, the capacity of a lead-acid battery is determined by the amount of active material on the plates and the amount of electrolyte. In the current sealed type lead-acid storage battery, the electrolyte is limited to that contained in the retainer mat and that contained in the electrode plates. Therefore, when the electrodes are the same, the battery capacity, especially under low temperature and high rate discharge, Since the capacity to be removed depends on the amount of the electrolyte contained in the retainer mat, the retainer mat preferably contains a larger amount of the electrolyte, that is, has better water retention.

Maximum pore diameter: The separator (or retainer mat in the case of a closed lead-acid battery of the retainer type) is inserted between the positive electrode and the single electrode, and serves to prevent contact short-circuit between the two electrodes. The separator should be as small as possible, since lead precipitated by repeated charge and discharge and lead powder released from the electrode plate will short-circuit both electrode plates through the pores of the separator and shorten the battery life. Is good. That is, since the life performance of the battery is affected by the size of the maximum pore diameter of the separator, the smaller the maximum pore diameter of the separator is, the better.

According to the present invention, since synthetic pulp mainly composed of polyolefin is used as a material, it has excellent water retention and a small maximum hole diameter as compared with synthetic fiber using synthetic fibers. This is because synthetic fibers made by melt-spinning and the like have a columnar structure, whereas polyolefin-based synthetic pulp is highly branched and has many coatings on its surface. It is considered that performance is exhibited. Further, according to the present invention, by dry-synthesizing the synthetic pulp, it is possible to provide a low-density and low-cost separator with excellent acid resistance. The sealed lead-acid battery used is characterized by excellent low-temperature high-rate discharge capacity. mmrn

The following were used as raw materials

A. High density polyethylene synthetic pulp

Average fiber length 丄 .0mm

Average fiber diameter 10

Melting point 1 35. C

1.5% of PVA adhesion

Specific surface area 8.2 m ² / g

B Linear low density polyethylene synthetic pulp

(Low melting point polyethylene synthetic pulp)

Average fiber length 丄, 0mm

Average fiber diameter 30 μm

Melting point 1 25 ° C

PVA adhesion 1.2%

Specific surface area 2.7 m ² / g

C-interpulp (cellulosic pulp)

After each of the raw materials A, B, and C is crushed by a hammer mill type crusher,

A-75% by weight, B-15% by weight, and C = 10% by weight were mixed and dry-processed by an air laid method to obtain a 2.0 mm thick mat.

This mat, by penetrating 1 3 hot air 2 ^e C 6 0 seconds Heat treatment was performed.

Next, hydrophilization treatment is performed with an anionic surfactant (aqueous solution of sodium dialkyl sulfosuccinate).

0.8% by weight of the mat was obtained.

Table 1 shows the physical properties of the obtained mat.

Example 2

As a raw material,

D. Using silica powder (Nibseal VN3 manufactured by Nippon Silica Co., Ltd.)

A = 68% by weight, B = 14% by weight, = 9% by weight,

D = 9% by weight,

A mat was obtained in the same manner as in Example 1 except that the above conditions were satisfied. Table 1 shows the separator characteristics of the obtained mat.

Example 3

Use ratio of each raw material,

A = 85% by weight, B = 15% by weight,

A mat was obtained in the same manner as in Example 1 except that Table 1 shows the physical properties of the obtained mat.

Comparative Example 1

With the same raw materials and proportions as in Example 1, wet papermaking was performed to obtain a 2.0 mm thick mat. The pine Bok, having conducted a heat treatment by through 1 2 0 seconds hot air 1 3 2 ^e C. Next, a hydrophilic treatment was performed with an anionic surfactant (aqueous sodium dialkyl sulfosuccinate) to obtain a mat having a surfactant adhesion of 0.8% by weight. Table 1 shows the physical properties of the obtained mat.

Comparative Example 2

For comparison of battery characteristics, we assembled a battery using a glass separator, which is the most common type for sealed lead-acid batteries, and measured the 5-hour rate discharge capacity and the low-temperature high-rate discharge capacity. Shown in

Comparative Example 3

A mat was prepared in the same manner as in Example 1, except that the following material was used as the material A.

A. Acryl fiber

Average fiber length 5.0mm

Average fiber diameter 13 μππι

Softening point 2 0 0 ^e C

Comparative Example 4

The performance of the melt blown spun fiber mat (melt blown nonwoven fabric) of polypropylene was compared as a comparison.

Average fiber diameter 2 fi rn

Comparative Example 5

A mat was prepared in the same manner as in Example 1, except that the following material was used as the material of A.

A. High density polyethylene synthetic pulp

Average fiber length 1.5mm

Average fiber diameter 80 μππι

Melting point 1 35. C

PVA adhesion 0.3% Specific surface area 0.7 m ² / g

Table 1

Item Implementation example Comparative example

1 2 3 1 Thickness 2.0 2.0 2.0 2.0 i mm)

Weight 240 260 240 500

(g / m

Density 0.12 0.13 0.12 0.25

(g / cc)

Space ratio 88 88 88 75

(%)

Electrical resistance 0.00040 0.00040 0.00400 (Q dm ² / sheet)

Water retention 1000 1050 950 300

(% By weight) o Maximum pore size 30 30 30 20 (I m)

o

Table 1-2

Item Comparison example

2 3 4 5 Thickness 2.0 2.0 2.0 2.0

(mm)

Basis weight 300 300 300 280

(g / m ² )

Density 0.15 0.15 0.15 0.14

(g / cc)

Space ratio 94 88 84 86

(%)

Electric resistance 0.00040 0.00040 0.000080

(Q dm ² / sheet)

Water retention 850 750 850 700

(% By weight)

Maximum pore size 20 80 50 80 (Mm) Separator characteristics were measured in accordance with JIS C 2313.

Water retention measurement method

The weight percentage of the water contained in the separation evening relative to the weight of the separation evening when the sample is immersed in water and fully hydrated, and left (suspended) for 1 minute in a vertical state in the air.

Maximum pore size measurement method

The test piece 2 5 0 was immersed in a methanol solution, the apparatus shown Hosoananai in Figure 1 was replaced with methanol, gradually applying pressure gradually, from the surface of the test piece bubbles (N ₂ gas) Read the differential pressure at the time of appearance, and determine the maximum pore diameter of the sample from the surface tension of methanol (σ ½ 23). The calculation formula is

4σ 0.004σ Maximum pore size (cm)-g {i (H ₂ -Hi)-p ₂ d} H 2-H i 0.092

σ = methanol surface tension dyn / cm g = gravitational acceleration cm / sec ²

Η ₂ -Ηι = Head difference in manometer cm P i = Density of liquid in manometer g / cm ³ P ₂ = Density of methanol g / cm ³ d = Depth of methanol cm Separation of each Example and Comparative Example The same 2 V as in Comparative Example 2, using the same manufacturing plate electrode as in Comparative Example 2 Table 6 shows the results of measuring a 5-hour rate discharge capacity and a low-temperature high-rate discharge capacity by assembling a retainer-type sealed lead-acid battery with a nominal capacity of 6 Ah.

Table 2 — 1

The 5-hour rate discharge capacity was measured as the time from the start of discharge until the terminal voltage of the battery reached 1.70 V, and the time was defined as the discharge capacity.

The low-temperature high-rate discharge capacity was measured by measuring the time from the start of discharge until the terminal voltage of the battery reached 1.00 V, and that time was defined as the discharge capacity. The voltage at the 5th second is the terminal voltage of the battery 5 seconds after the start of discharging when measuring the low-temperature high-rate discharge capacity.

Claims

7 Claims

1. 100 to 50% by weight of polyolefin synthetic pulp, and 0 to 50% by weight of a binder having a lower melting point than the synthetic pulp, were obtained from a porous mat obtained by dry-paper-making. A separator for a sealed lead-acid battery, comprising:

2. The separator for a sealed lead-acid battery according to claim 1, wherein the blending ratio of the polyolefin-based synthetic pulp and the binder is 98 to 50% by weight and 2 to 50% by weight.

3. The sealed lead storage battery separator according to claim 1, wherein the melting point or the curing temperature of the binder is at least 5 lower than the melting point of the polyolefin-based synthetic pulp.

4. The separator for a sealed lead-acid battery according to claim 1, wherein a hydrophilically-treated synthetic valve is used as the morpholine-based synthetic valve.

5. The sealed lead-acid battery separator according to claim 1, wherein the porous mat has been subjected to a hydrophilic treatment using a surfactant aqueous solution.

6. The separator for a sealed lead-acid battery according to claim 1, wherein the porous mat is subjected to a heat treatment to such an extent that bulkiness is not impaired, thereby increasing the strength of the mat.

2. The separator for a sealed lead-acid battery according to claim 1, wherein a synthetic fiber, natural pulp, inorganic fiber, or acid-resistant inorganic powder is blended in a range of 7.4% by weight or less. Ta.

8. The sealed lead storage battery separator according to claim 1, wherein the polyolefin-based synthetic pulp has a specific surface area of 1 m ² _g or more as measured by a BET adsorption method.