JPH0410352A - Separator for storage battery - Google Patents

Abstract

PURPOSE:To reduce electric resistance and enhance heat resistance by impregnating a web layer forming material incorporating therein specific silica powder and acrylic resin in a first layer portion of a separator main body made of a glass fiber layer so as to form a web layer. CONSTITUTION:Glass fiber constituting a separator main body is bonded with an acrylic resin having a glass transition point of 30-80 deg.C, thus obtaining the separator main body, which comprises a first layer portion formed of mainly glass fiber having an average fiber diameter of 17-21mum and a second layer portion made of mostly glass fiber having an average fiber diameter of 11-16mum. A web layer forming material incorporating therein 70-90 parts by weight of silica powder having a specific surface area of 10m<2>/g or more and 30-10 parts by weight of an acrylic resin having a glass transition point of 10-30 deg.C, is impregnated in the first layer portion, thereby obtaining a web layer. Therefore, it is possible to obtain a separator having low electric resistance and excellent in heat resistance.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a separator for storage batteries, and is particularly suitable as a separator for lead-acid batteries used in automobiles, etc., and has low electrical resistance and excellent heat resistance, and retains active materials. The present invention relates to a separator for storage batteries that has a large force and can be manufactured at low cost.

[Prior Art] The basic characteristics required for lead-acid batteries for automobiles include the following (1) to (2), and in recent years, the requirements for these characteristics have become even more severe.

■ Electrical resistance is as low as possible. This is an essential condition for making storage batteries thinner.

■ It has sufficient rigidity and has excellent battery productivity.

■ Resistant to carbonization and oxidation in electrolytes, and its properties are stable over long periods of time.

■ It has micropores all over the surface, and the pores are formed in a labyrinth shape, making it difficult to cause lead penetration short circuits and being thin.

■ Materials are inexpensive and can be produced stably by hand in large quantities.

■ Prevent harmful substances from eluting into the battery.

Early lead-acid batteries used wooden separators, but the electrolyte was dilute sulfuric acid, which caused the separators to carbonize early. Next to wooden separators, microporous rubber separators and separators made from valves are commonly used, and these separators have been in use for more than 30 years. The microporous rubber type had the best oxidation resistance within the battery. The oxidation resistance of the valve separator was not as good as the microporous rubber type, and the physical strength was also somewhat insufficient, but since the cost was low, we made the substrate slightly thicker to make the separator more durable. It was used. Furthermore, there is a type of separator with a glass mat attached to these, which has contributed to improving the lifespan and durability of batteries.

In recent years, in the field of storage batteries, efforts have been made to make separators thinner. The thin separator has the following characteristics (1) to (2).

■ Low electrical resistance allows for the design of high-performance batteries.

■ Made using relatively easily available, low-cost materials.

■ The material is chemical fiber and inorganic powder, and it is finished into a thin plate shape of about 0.25 mm using a papermaking method. Alternatively, after applying a solution of a polymer compound to a thin sheet of chemical fiber, the solvent is evaporated to form micropores, or after a mixture of a polymer compound and an additive is made into a sheet, the additive is extracted to form micropores. I'm letting you do it.

Recently, with the advent of separators that can draw the highest cold cranking current, such as glass separators developed in the United States, ultra-low resistance separators have been developed in Japan and are currently used in some automotive lead-acid batteries. ing.

By the way, among separators for storage batteries, especially separators for storage batteries for automobiles, in addition to being thin and having excellent acid resistance, oxidation resistance, and stacking property (rigidity), they also have: (1) lower electrical resistance;

■ Excellent heat resistance.

■ Excellent retention of active materials.

■ It should be provided at a low price.

is required.

Here, the separator with low electrical resistance (■) is due to the demand for batteries with even better low-temperature, high-rate discharge performance, and the heat resistance (■) is required because batteries are used at high temperatures due to the narrowing of engine rooms. (2) is a demand for a device that has a function to more effectively prevent the active material from falling off due to vibrations while the car is running, and is inexpensive.

Traditionally, separators for automotive storage batteries have been made using paper-made glass mats, which are made by applying adhesive to two strips of dry-processed glass mat and pasting them together on a paper-made sheet made of polyethylene fibers, inorganic powder, and binder. A separator made of paper mainly made of polyester fiber and inorganic powder and equipped with armor ribs on one side.

There was such a thing.

[Problems to be Solved by the Invention] However, as the characteristics required for separators for automobile storage batteries become more sophisticated, the separators of I and II described above are no longer able to fully satisfy the required characteristics. That is, the separator (2) is pasted with a glass mat obtained by the expensive dry-rolling method after papermaking, so the total cost of the separator is relatively high.

In addition, since polyethylene fibers are used, they have poor wettability with dilute sulfuric acid electrolyte and have poor degassing properties. On the other hand, the separator II has ribs on the surface that comes into contact with the electrodes, and has the drawbacks of lacking the ability to prevent the active material from falling off and having poor acid resistance.

[Means for Solving the Problems] A separator for a storage battery of the present invention has a separator body made of a glass fiber layer formed by bonding glass fibers with an acrylic resin having a glass transition point of 30 to 80°C, and the separator body has It has a first layer mainly made of glass fiber with an average fiber diameter of 17 to 21 μm, and a second layer mainly made of glass fiber with an average fiber diameter of 11 to 16 μm, and the first layer has a specific surface area. 70 to 90 parts by weight of silica powder with a particle size of 10 to 30°C and 30 to 1 part of an acrylic resin with a glass transition point of 10 to 30°C
The web layer is formed by impregnating a web layer forming material containing 0 parts by weight.

The present invention will be explained in detail below.

The glass fibers constituting the first layer of the storage battery separator of the present invention are mainly glass fibers having an average fiber diameter of 17 to 21 μm. When the average fiber diameter of the first layer portion is smaller than 17 μm, it is difficult for the web layer forming material to be impregnated to a uniform depth. If the average fiber diameter of the first layer portion exceeds 21 μm, the web layer forming material will escape to the lower layer, making it impossible to form a web layer on the surface portion.

In the second layer part, 1. In view of the slipperiness of the storage battery separator, it is necessary that the constituent glass fibers be mainly glass fibers having an average fiber diameter of 13 to 15 μm.

Note that the electrical resistance of the separator can also be reduced by setting the average fiber diameter of the first layer to 17 to 21 μm.

In the present invention, the average length of the glass fibers constituting the separator body is preferably about 6 to 30 mm.

In order to manufacture such a separator main body, the first layer portion and the second layer portion may be formed at the same time, or the main portion of one may be formed on top of the other main portion. Alternatively, the first layer portion and the second layer portion, which are separately produced, may be stacked on top of each other using a roll or the like.

In the present invention, the glass fiber has a glass transition point (Tg
) is bonded with acrylic resin at 30 to 80°C to form the separator body. Tg of acrylic resin used for adhesion is 30℃
If Tg is lower than 80° C., the resulting separator body will be too soft, whereas if Tg exceeds 80° C., the resulting separator body will be hard and brittle. Moreover, whether the separator body is soft or hard, it is not preferable because it becomes difficult to slip. In addition, when the separator and glass mat are combined and cut into small pieces and then placed on a stacker, the separator needs to have a certain degree of rigidity.
If the separator is too soft, sufficient rigidity cannot be obtained, which is not preferable. In the present invention, Tg is 30 to 80°C
By using this acrylic resin, it is possible to obtain a separator with good slippage and stackability.

Note that as the acrylic resin suitable for adhering the glass fibers of the separator body, an acrylic ester copolymer containing methyl methacrylate and acrylic acid as main components is desirable.

The amount of acrylic resin used for bonding such glass fibers is preferably 15 to 25% by weight based on the total weight of the glass fibers and acrylic resin constituting the separator body. If the acrylic resin content is less than 15% by weight, the adhesion will be insufficient, and if it exceeds 25% by weight, the electrical resistance will become high, which is not preferable in either case. Therefore, the density of the separator body obtained by bonding glass fibers with acrylic resin is preferably 0.13 to 0.25 g/crn', and the density of the separator body is less than 0.13 g/crn'. If it is, the life will be shortened, and if it exceeds 0.25 g/Cm', the electrical resistance will be high, which is not preferable.

In the present invention, the web layer forming material impregnated into the first layer of the separator body has a specific surface area of 10rr? /g
It is made by blending 70 to 90 parts by weight of the above silica powder and 30 to 10 parts by weight of an acrylic resin having a glass transition point of 10 to 30°C. That is, if the web layer forming material contains glass fiber or synthetic fiber, it is difficult to impregnate the separator body, so a material made of silica powder and acrylic resin is used.

If the specific surface area of the silica powder used is less than 10 rn'/g, the mesh becomes large and short circuits are likely to occur.

Therefore, the specific surface area of silica powder is 10rn"7g or more,
Preferably it is 1100d1 or more.

Furthermore, if the Tg of the acrylic resin exceeds 30° C., the liquid of the web layer forming material will not spread easily, and air bubbles will be formed, resulting in a decrease in the oxidation resistance of the resulting separator. If the Tg of the acrylic resin is less than 10° C., the liquid of the web layer forming material becomes too soft and flows down to the lower layer of the separator body, making it impossible to impregnate only the surface layer. Therefore, as the acrylic resin, one having a Tg of 10 to 30°C is used. As such an acrylic resin, an acrylic ester copolymer containing methyl methacrylate and acrylic acid as main components is desirable.

The web layer forming material becomes clogged when the proportion of silica powder is less than 70 parts by weight and the proportion of acrylic resin exceeds 30 parts by weight, and when the proportion of silica powder exceeds 90 parts by weight, the proportion of acrylic resin If the proportion is less than 10 parts by weight, the adhesion of the silica powder will be insufficient. Therefore, the web layer forming material includes 70 to 90 parts by weight of silica powder and 30 parts by weight of acrylic resin.
~10 parts by weight.

In the present invention, the total thickness of the separator body is 25
It is preferable to form a web layer by impregnating the above-mentioned web layer forming material into a surface layer portion in a range of 40% to 40% as a first layer portion. If the impregnated thickness of the web layer forming material, that is, the formation thickness of the web layer, is less than 25% of the total thickness of the separator body, a sufficient short-circuit prevention effect by the web layer will not be obtained;
If it exceeds 0%, the electrical resistance as a separator becomes too large.

In the present invention, the density of the web layer thus formed in the first layer portion is preferably 0.2 to 0.4 g/cm'. If the density of the web layer is less than 0.2 g/cm'', the oxidation resistance will decrease, and if it exceeds 0.4 g/cm'', the electrical resistance will increase, so either case is not preferred.

Although there is no particular restriction on the total thickness of the storage battery separator of the present invention, it is suitable for a thin separator of about 0.8 to 0.7 mm.

[Function] The separator for a storage battery of the present invention has a web layer, and the thickness of this web layer is sufficient if it is relatively thin, for example, 25 to 40% of the total thickness, so that the electrical resistance is small. Furthermore, since it is composed only of silica powder, glass fibers, and acrylic resin, it has excellent heat resistance.

Since the web layer is formed by applying a web layer forming material to the glass fiber layer, manufacturing is easy, production efficiency is high, and costs can be reduced.

Furthermore, since the web layer is integrated with the glass fiber layer, it has good wettability to electrolyte and gas release when used in a storage battery, and also prevents the glass 1a from peeling off and falling off.

Since the web layer is formed by impregnating the web layer forming material into the first layer of the glass 1a miscellaneous layer having a two-layer structure with different impregnation rates, it can be easily formed to have a uniform thickness. , a separator with high properties can be obtained.

[Example] The present invention will be explained in detail by giving examples below.

Example 1 Glass fibers with the average fiber diameter shown in Table 1 were used as the material for the first layer, and glass fibers with the average J@fiber diameter shown in Table 1 were used as the material for the 342nd layer. ℃ acrylic resin (adhesive amount is 20% by weight based on the total weight of the separator body)
), each with a density of 0.0 as the layer thickness shown in Table 1.
After forming a separator main body of 14 g/am', a web layer consisting of 80 parts by weight of silica powder having a specific surface area shown in Table 1 and 20 parts by weight of an acrylic resin having a Tg shown in Table 1 was formed on the first layer. Density 0.34g/c after applying the material
m' storage battery separator was manufactured. The coating conditions during manufacture were as shown in Table 1.

Various properties of the obtained separator for storage batteries were investigated by the following methods, and the results are shown in Table 1 along with the results of determination of quality as a separator for storage batteries.

Electric 7 resistance (Ω・drn”7 pieces) Measured according to JIS C2313.

Oxidation resistance (hrs/) A 7cm x 7cm sample was placed in dilute sulfuric acid with a specific gravity of 1.3 +, -
Set it inside the electrode plate and apply a load of 5 kg. A current of 2.5 A was applied at 45°C, and the terminal voltage was measured every 4 hours.
Measure the time until the voltage difference drops by 0.2v or more or becomes 2.6v or less.

Place in a heat resistant 300°C oven for 30 minutes and measure the weight change rate before and after. Less than 5% is considered good.

Workability (slip property) Prepare two samples of 10 cm x 10 cm. Fix one sheet and set a spring scale on the remaining one. Place the remaining one on top of the fixed one, and place a plastic plate and 20
Place a 0g weight on it and pull the spring scale at 100m/sec. 50g or less is considered good.

Web layer thickness knee Take an enlarged photo of the cut surface and mark T and t below.

tl and t2 were measured, and α was determined using the following formula.

T...Total thickness to...Average web layer thickness tl...Minimum web layer thickness t2...Maximum web layer thickness r Microsilica" (Showa Kagaku Kogyo Fin) Silica powder (
Surface = 120rrl”/ “Nip Seal” (Japanese Silkani Industry ■) From Table 1,
The separators with numbers 1 to 5 and 7 to 12, which are outside the scope of the present invention, are poor in any of the properties, whereas the separators with numbers 6 and 6 according to the embodiment of the present invention have good properties in all. It is clear that the acrylic resins used were all acrylic acid ester polymers manufactured by Toagosei, and the silica powder was as follows.

Silica powder (specific surface area = 20rr?/g [Effects of the invention]) As detailed above, the separator for storage batteries of the present invention has: (1) low electrical resistance;

■ Excellent heat resistance and oxidation resistance.

■ High retention power of the anode active material.

■Excellent squishing slipperiness.

■ It is possible to make it thinner.

■ Excellent electrolyte wettability and gas release.

Provided is a high-performance storage battery separator that has excellent features such as the following and can be manufactured easily, efficiently, and at low cost. According to the storage battery separator of the present invention,
Improved performance and lower costs of storage batteries will become a reality.

Agent: Patent attorney Tsuyoshi Shigeno

Claims (1)

[Claims] (1) It has a separator body made of a glass fiber layer formed by bonding glass fibers with an acrylic resin having a glass transition point of 30 to 80°C, and the separator body has an average fiber diameter of 17 to 21
The first layer has a first layer mainly made of glass fiber with an average fiber diameter of 11 to 16 μm, and the first layer has a specific surface area of 10 m^2/g. 70 to 90 parts by weight of the above silica powder and a glass transition point of 10 to 3
A separator for a storage battery, characterized in that a web layer is formed by impregnating a web layer forming material containing 30 to 10 parts by weight of an acrylic resin at 0°C.