JP2022100369A - Separator for liquid lead-acid batteries - Google Patents

Abstract

Kind Code: A1 A separator for a liquid lead-acid battery comprising a microporous film produced using silica fine powder, which is synthetic amorphous silica produced by a precipitation method, as a main raw material, and used in a battery using the separator. Separator that can reduce the amount of alkali metal ions and halogen ions that are eluted from the separator into the electrolyte even when the deterioration progresses, making it less likely to hinder the improvement of charge acceptance and reduce the deterioration of battery life performance. to provide SOLUTION: Silica fine powder, which is synthetic amorphous silica produced by a sedimentation method in which amorphous silica is synthesized by precipitation by reacting an aqueous alkali silicate solution with a mineral acid, and then the purity is adjusted by filtering and washing with water. A liquid lead-acid battery separator comprising a microporous film containing 40% by weight or more, wherein the microporous film (10 cm × 10 cm × 2 sheets) is immersed in 126 g of sulfuric acid having a specific gravity of 1.26 at a temperature of 50 ° C. for 24 hours When left to stand, the concentration of alkali metals (Li, Na, K, Rb, Cs) (ICP emission spectroscopic analysis) is 5 mg/100 cm2/sheet or less (however, the base thickness of the microporous film is converted to 0.2 mm value), and the concentration of halogen content (F, Cl, Br, I) (ICP emission spectroscopic analysis) is 0.4 mg/100 cm2/sheet or less (however, the base thickness of the microporous film is converted to 0.2 mm). A separator for a liquid lead-acid battery, characterized by: [Selection figure] None

Description

The present invention is not a so-called closed-type lead-acid battery (also referred to as a control valve type lead-acid battery) in which the electrolytic solution is made non-fluidized to be maintenance-free, but a so-called liquid having a fluid electrolytic solution, which is a conventional method. The present invention relates to a separator for a liquid lead-acid battery used for a lead-acid battery (also referred to as a vent-type lead-acid battery or an open-type lead-acid battery).

Conventionally, as a separator for a liquid lead storage battery, a polyethylene separator, which is a polyolefin resin having a weight average molecular weight of 500,000 or more (usually an ultra-high molecular weight polyethylene) of 20 to 60% by weight and a specific surface area of 50 m ² / g or more. 40-80% by weight of inorganic powder (usually silica fine powder), 0-30% by weight of plasticizer (usually mineral oil) that also serves as a pore-opening agent, and 0-10% by weight of surfactant (solid content). There is a separator made of a microporous film containing 0 to 5% by weight of an agent (antioxidant, weather resistant agent, etc.).

The separator made of a microporous film is usually a raw material composition in which the polyolefin resin, the inorganic powder, the plasticizer (combined in a larger amount than the separator composition), the surfactant and the additive are mixed. The base thickness is about 0.1 to 0.3 mm, which is obtained by extruding into a sheet shape while heat-melting and kneading, rolling and molding to a predetermined thickness, and then extracting and removing all or part of the plasticizer. The sheet has an average pore diameter (mercury injection method) of about 0.01 to 0.5 μm and a porosity (mercury injection method) of about 50 to 90% by volume.

The role of the inorganic powder is to adsorb and support a plasticizer when the raw material composition is heated, melted and kneaded, and to create a microporous structure (dense and complicated pore structure and high porosity) of the microporous film. That, to withstand the sheet shrinkage that occurs when the plasticizer is removed in the process of manufacturing the microporous film and to maintain dimensional stability, and the drying step (moisture removal step) that is performed before use when the microporous film is installed in the battery. To withstand sheet shrinkage and maintain dimensional stability even during heat treatment such as, improve the electrolyte absorption property of the microporous film, improve the electrolyte wettability of the microporous film, and microporous For example, to improve the electrolyte retention of the film.

Therefore, usually, silica fine powder is used as the inorganic powder, and in particular, from the viewpoints of having a large specific surface area, a large amount of oil absorption, and a large number of hydrophilic groups (silanol groups), a dry method or a wet method is used. Among the manufacturing methods of the method, synthetic amorphous silica manufactured by the precipitation method of the wet method is used.

On the other hand, in the case of in-vehicle use of lead-acid batteries, the lead-acid batteries mounted on idling stop vehicles are required to have high charge acceptability because the amount of discharge is large. When trying to improve the charge acceptability of lead-acid batteries, it is known that the presence of a large amount of alkali metal (Li, Na, K, Rb, Cs) ions in the electrolytic solution hinders the improvement of charge acceptability. (Patent Document 1).

Further, in a lead-acid battery, if a large amount of halogen (F, Cl, Br, I) impurities are mixed, it may corrode the lead or lead alloy plate lattice or pole column and cause a decrease in battery life performance. It is also known (Patent Document 2).

The synthetic amorphous silica produced by the precipitation method is a method of precipitating and precipitating amorphous silica by reacting an aqueous solution of an alkaline silicate (sodium silicate) with a mineral acid (sulfuric acid) under neutral or alkaline conditions. The produced amorphous silica contains salts such as sodium sulfate as a by-product, and is subjected to a treatment (treatment to increase purity) to remove the salts by filtration and washing with water in a subsequent step. It has been.

International Publication No. 2014/128803 Japanese Unexamined Patent Publication No. 2005-251394

However, since the salt removal treatment in the process of producing the amorphous silica is not perfect, the produced amorphous silica usually contains a trace amount of sodium sulfate as a by-product. Therefore, the microporous film produced using such silica fine powder also contains a small amount of sodium sulfate, and when used as a separator for a lead storage battery, an electrolytic solution is used as the battery is used. If Na ions are eluted inside and the amount of elution is large, it may be a factor that hinders the improvement of charge acceptability.

Further, when the salt removal treatment in the manufacturing process of the amorphous silica is performed by washing with water, the water used for washing may be mixed with Cl, which is a halogen. That is, when tap water (containing residual chlorine) is used, or when groundwater containing salt (sodium chloride) is used. Therefore, the microporous film produced by using silica fine powder washed with water using such water also contains a small amount of Cl, and is used as a separator for a lead storage battery. Will elute Cl ions into the electrolytic solution as the battery is used, and if the amount of elution is large, it may promote corrosion of the electrode plate lattice and the electrode column, and may be a factor of deteriorating the battery life performance.

Therefore, in view of the above-mentioned conventional problems, the present invention provides a separator for a liquid lead-acid battery made of a microporous film manufactured by using silica fine powder which is a synthetic amorphous silica manufactured by a precipitation method as a main raw material. Therefore, even when the battery is used in a battery using this, the amount of alkali metal ions and the amount of halogen ions eluted from the separator into the electrolytic solution can be reduced, and the improvement of charge acceptability can be less likely to be hindered. It is an object of the present invention to provide a separator that can prevent a decrease in battery life performance.

In order to achieve the above object, the separator for a liquid lead storage battery of the present invention is a precipitation method in which an aqueous alkali silicate solution is reacted with a mineral acid to synthesize amorphous silica by precipitation precipitation, and then the purity is adjusted by filtration and washing with water. A separator for a liquid lead storage battery comprising a microporous film containing 40% by weight or more of silica fine powder, which is a synthetic amorphous silica produced in the above, wherein the microporous film (10 cm × 10 cm × 2 sheets) is heated. The concentration (ICP emission spectroscopic analysis) of the alkali metal content (Li, Na, K, Rb, Cs) when immersed in 126 g of sulfuric acid having a specific gravity of 1.26 at 50 ° C. for 24 hours and left to stand is 5 mg / 100 cm ² / sheet or less. (However, the base thickness of the microporous film is converted to 0.2 mm), and the concentration of halogen (F, Cl, Br, I) (ICP emission spectroscopic analysis) is 0.4 mg / 100 cm ² / sheet or less (however, value). However, it is characterized in that the base thickness of the microporous film is 0.2 mm conversion value).

Further, the filtration / washing is performed using ion-exchanged water or groundwater containing no salt (sodium chloride).

Further, the microporous film is characterized by being a microporous film mainly composed of the silica fine powder and a polyolefin-based resin.

The microporous film has a base thickness of 0.1 to 0.3 mm, an average pore diameter (mercury injection method) of 0.01 to 0.5 μm, and a porosity (mercury injection method) of 50 to 90 volumes. % Is a microporous film.

According to the present invention, there is a separator for a lead storage battery made of a microporous film manufactured by using silica fine powder which is a synthetic amorphous silica manufactured by a precipitation method as a main raw material, and a battery using the separator is used. Even when the battery is used more and more, the amount of alkali metal ions and halogen ions eluted from the separator into the electrolytic solution can be reduced, the improvement of charge acceptability can be less likely to be hindered, and the battery life performance can be less likely to be deteriorated. A separator can be provided.

In the separator for a liquid lead storage battery of the present invention, an aqueous alkali silicate solution is reacted with a mineral acid to synthesize amorphous silica by precipitation, and then the purity is adjusted by filtration and washing with water (amorphous by removing salts as by-products). A microporous film containing 40% by weight or more of silica fine powder (hereinafter, may be simply referred to as "the silica fine powder"), which is a synthetic amorphous silica produced by a precipitation method (to increase the purity of quality silica). Therefore, when the microporous film (10 cm × 10 cm × 2 sheets) was immersed in 126 g of sulfuric acid having a specific gravity of 1.26 at a temperature of 50 ° C. for 24 hours and left to stand, the alkali metal content (Li, Na, K, Rb, The concentration of Cs) (ICP emission spectroscopic analysis) is 5 mg / 100 cm ² / sheet or less (however, the base thickness of the microporous film is 0.2 mm equivalent), and the halogen content (F, Cl, Br, I). The condition is that the concentration (ICP emission spectroscopic analysis) is 0.4 mg / 100 cm ² / sheet or less (however, the base thickness of the microporous film is converted to 0.2 mm).

Alkali metal content (Li, Na, K, Rb, Cs) when the microporous film (10 cm × 10 cm × 2 sheets) was immersed in 126 g of sulfuric acid having a specific gravity of 1.26 at a temperature of 50 ° C. for 24 hours and left to stand. By setting the concentration (ICP emission spectroscopic analysis) to 5 mg / 100 cm ² / sheet or less, in the liquid lead storage battery using the separator for the liquid lead storage battery of the present invention, the alkali eluted from the separator into the electrolytic solution. Since the amount of metal ions can be suppressed, it is less likely to hinder the improvement of charge acceptability. Therefore, when the microporous film (10 cm × 10 cm × 2 sheets) was immersed in 126 g of sulfuric acid having a specific gravity of 1.26 at a temperature of 50 ° C. for 24 hours and left to stand, the concentration of alkali metal (ICP emission spectroscopic analysis) was 4 mg. / 100 cm ² / sheet or less is more preferable.

The concentration of halogen (F, Cl, Br, I) (ICP) when the microporous film (10 cm × 10 cm × 2 sheets) was immersed in 126 g of sulfuric acid having a specific gravity of 1.26 at a temperature of 50 ° C. for 24 hours and left to stand. Halogen ions eluted from the separator into the electrolytic solution in the liquid-type lead storage battery using the separator for the liquid-type lead storage battery of the present invention by setting the emission spectroscopic analysis) to 0.4 mg / 100 cm ² / sheet or less. Since the amount can be suppressed, it is less likely that the battery life performance is deteriorated by promoting the corrosion of the plate grid and the pole column. Therefore, when the microporous film (10 cm × 10 cm × 2 sheets) is immersed in 126 g of sulfuric acid having a specific gravity of 1.26 at a temperature of 50 ° C. for 24 hours and left to stand, the concentration of halogen (ICP emission spectroscopic analysis) is 0. 2 mg / 100 cm ² / sheet or less is more preferable, and 0.1 mg / 100 cm ² / sheet or less is further preferable.

The microporous film is preferably a microporous film mainly composed of the silica fine powder and a polyolefin-based resin, and the microporous film has a base thickness of 0.1 to 0.3 mm and an average. A microporous film having a pore diameter (mercury injection method) of 0.01 to 0.5 μm and a porosity (mercury injection method) of 50 to 90% by volume is preferable. The base thickness is a term used to distinguish the microporous film from the total thickness including the rib-shaped protrusions when the microporous film has rib-shaped protrusions, and excludes the height of the rib-shaped protrusions (ribs). It refers to the film thickness (when no protrusions are provided).

As described above, the silica fine powder has a plasticizer adsorbed and carried when the raw material composition is heated, melted and kneaded, and the microporous structure of the microporous film (dense and complicated pore structure and high void ratio). To withstand sheet shrinkage that occurs when the plasticizer is removed during the manufacturing process of the microporous film, and to maintain dimensional stability. To withstand sheet shrinkage and maintain dimensional stability even during heat treatment such as step), to improve the electrolyte liquid absorbency of the microporous film, to improve the electrolyte wettability of the microporous film, fine The dry method has roles such as improving the electrolyte retention of the porous film, and therefore has a large specific surface area, a large amount of oil absorption, and a large number of hydrophilic groups (silanol groups). Alternatively, among the manufacturing methods of the wet method, it is necessary to use the synthetic amorphous silica produced by the precipitation method of the wet method, but the synthetic amorphous silica produced by the precipitation method of the wet method is subordinate to the synthetic amorphous silica. Although salts such as sodium sulfate are contained as organisms and the salts are removed by filtration and washing in a subsequent step, the removal of salts is not complete and tap water is used for washing. Since groundwater containing (containing residual chlorine) and salt (sodium chloride) can be used, it contains a small amount of Na and Cl, which can adversely affect the battery performance. Therefore, in the present invention, the silica fine powder is a synthetic amorphous silica produced by the precipitation method of the wet method, and has an alkali metal content (Li, Na, K, Rb, Cs) and a halogen content (F, Cl, The content of Br, I) is an alkali metal when the finally obtained microporous film (10 cm × 10 cm × 2 sheets) is immersed in 126 g of sulfuric acid having a specific gravity of 1.26 at a temperature of 50 ° C. for 24 hours and left to stand. Silica reduced to a level where the concentration of minutes (ICP emission spectroscopic analysis) is 5 mg / 100 cm ² / sheet or less and the concentration of halogen content (ICP emission spectroscopic analysis) is 0.4 mg / 100 cm ² / sheet or less. Use fine powder. Further, the washing treatment (treatment for removing salts of by-products) in the manufacturing process of the amorphous silica of the present invention is performed using ion-exchanged water or groundwater containing no salt (sodium chloride). Is preferable. In the present application, the groundwater containing no salt (sodium chloride) refers to groundwater having a salt (sodium chloride) concentration of 300 ppm or less.

The base thickness of the microporous film is preferably 0.1 to 0.3 mm, but if it exceeds 0.3 mm, the electrical resistance deteriorates, and if it is less than 0.1 mm, it has good short-circuit resistance. (The short circuit mentioned here is a permeation short circuit called dendrite short circuit, a local weak part of the base material, high pressure pressure from the convex part of the electrode plate, impact or piercing, oxidative wear due to the oxidizing force from the electrode plate, etc. Refers to both normal short circuits caused by perforations or cracks caused by) becomes difficult to maintain.

The void ratio (mercury press-fitting method) of the microporous film is preferably 50% by volume or more, but when it is 50% by volume or more, the internal resistance (electrical resistance) is low as a separator for a liquid lead-acid battery. It can be suppressed and contributes to higher performance of liquid lead-acid batteries. Therefore, the porosity (mercury press-fitting method) of the microporous film is more preferably 60 to 90% by volume, more preferably 70 to 90% by volume.

The method for obtaining the microporous film is preferably by melt-kneading a raw material composition mainly composed of a polyolefin resin, the silica fine powder and a plasticizer, and removing a part or all of the plasticizer after film formation. .. As a result, it is possible to obtain a film in which innumerable communication holes having a uniform, fine, and intricately intricate path are formed in the entire film. An example of a specific manufacturing method is shown below. First, a raw material obtained by adding various additives (surfactant, antioxidant, weathering agent, etc.) to a predetermined amount of polyolefin resin, the silica fine powder, and a plasticizer as needed is added to a Henshell mixer, a Ladyge mixer, or the like. Stir and mix with the mixer of the above to obtain a raw material mixture. Next, this mixture is put into a twin-screw extruder with a T-die attached to the tip, extruded into a sheet while being heated, melted and kneaded, and passed between a pair of forming rolls having a predetermined groove engraved on one roll. A film-like material obtained by integrally molding a rib having a predetermined shape on one side of a flat plate-shaped sheet is obtained. Next, the film-like material is immersed in a suitable solvent (for example, n-hexane) to extract and remove a predetermined amount of mineral oil and dried to obtain the desired microporous film. The raw material composition refers to a composition composed of all raw materials brought into the melt-kneading process, and means "all raw materials (compositions)" to the last, and specifically, a raw material mixture. It does not mean that it refers to melt-kneaded products.

The microporous film has a total content of the polyolefin resin, the silica fine powder and the plasticizer of 90% by weight or more, a polyolefin resin content of 20 to 60% by weight, and a silica fine powder content of 40 to 80%. It is preferable that the content of the plasticizer is 0 to 30% by weight and the content of the surfactant is 0 to 8% by weight. When the content of the polyolefin resin is less than 20% by weight or the content of the silica fine powder is more than 80% by weight, the mechanical strength, oxidation resistance and sealing property of the microporous film by the polyolefin resin can be ensured. If the content is not sufficient and the content of the polyolefin resin exceeds 60% by weight or the content of the silica fine powder is less than 40% by weight, it is difficult to secure a large void ratio and a fine and complicated pore structure of the microporous film. As a result, the good electrical resistance characteristics of the microporous film separator cannot be maintained.

As the polyolefin-based resin, homopolymers or copolymers such as polyethylene, polypropylene, polybutene, and polymethylpentene, and mixtures thereof can be used. Above all, it is preferable to use polyethylene as a main component in terms of moldability and economy. Polyethylene has a lower melt molding temperature than polypropylene, has good productivity, and can reduce manufacturing costs. By setting the weight average molecular weight of the polyolefin resin to 500,000 or more, the mechanical strength of the film can be ensured even in a microporous film containing a large amount of silica fine powder. Therefore, it is more preferable that the polyolefin-based resin has a weight average molecular weight of 1 million or more, more preferably 1.5 million or more. Polyolefin-based resins have good mixability with silica fine powder, and are chemically stable and highly safe while maintaining strength while binding the skeleton of silica fine powder as an adhesive functional material in a microporous film. ..

As the silica fine powder, those having a fine particle size and a pore structure inside or on the surface can be used. Among the inorganic powders, silica has a wide selection range of various powder characteristics such as particle size and specific surface area, is relatively inexpensive and easily available, and has few impurities. When the specific surface area of the silica fine powder is 100 m ² / g or more, the pore structure of the microporous film is made finer (densified) and more complicated to improve short-circuit resistance, and the electrolyte solution of the microporous film is retained. It is preferable because the force is increased and the surface of the powder is provided with a large number of hydrophilic groups (-OH) to enhance the hydrophilicity of the microporous film. Therefore, it is more preferable that the specific surface area of the silica fine powder is 150 m ² / g or more. Further, the specific surface area of the silica fine powder is preferably 400 m ² / g or less. When the specific surface area of the silica fine powder exceeds 400 m ² / g, the surface activity of the particles is high and the cohesive force is strong, so that the silica fine powder is difficult to be uniformly dispersed in the microporous film, which is not preferable.

As the plasticizer, it is preferable to select a material that can be a plasticizer for the polyolefin resin, and various organic liquids that are compatible with the polyolefin resin and can be easily extracted with various solvents or the like can be used, and specifically. Can be used as a mineral oil such as an industrial lubricating oil made of saturated hydrocarbon (paraffin), a higher alcohol such as stearyl alcohol, an ester plasticizer such as dioctyl phthalate, and the like. Of these, mineral oil is preferable because it is easy to reuse. The plasticizer is preferably blended in an amount of 30 to 70% by weight in a raw material composition mainly composed of a polyolefin resin, silica fine powder, and a plasticizer.

As described above, the plasticizer is porous by melting and kneading a raw material composition mainly composed of a polyolefin resin, silica fine powder, and a plasticizer, forming a film-like material having a predetermined shape, and then removing the plasticizer. The content of the plasticizer in the separator made of a microporous film may be zero. However, the separator for a liquid lead-acid battery can contribute to the improvement of oxidation resistance by containing an appropriate amount of a plasticizer such as mineral oil. In such a case, the content of the plasticizer in the separator is preferably 5 to 30% by weight. However, if the content of the plasticizer is increased, the void ratio of the microporous film decreases and the electrical resistance of the separator made of the microporous film deteriorates. Therefore, from this viewpoint, the content of the plasticizer is 20. It is more preferably 0% by weight or less.

As the solvent used for extracting and removing the plasticizer, a saturated hydrocarbon-based organic solvent such as hexane, heptane, octane, nonane, and decane can be used.

In addition to the raw material composition or the microporous film, if necessary, a surfactant (hydrophilic agent), an antioxidant, an ultraviolet absorber, a weather resistant agent, a lubricant, an antibacterial agent, an antifungal agent, and a pigment , Dyes, colorants, antifogging agents, matting agents and the like may be added (blended) or contained within a range that does not impair the object and effect of the present invention.

The microporous film contains a large amount of the silica fine powder having a large specific surface area and high hydrophilicity, and has hydrophilicity by itself, and has a wettability with respect to a sulfuric acid electrolytic solution of a liquid lead storage battery which is an aqueous solution. It has the permeability (penetration property) of the sulfuric acid electrolytic solution, but when the sulfuric acid electrolytic solution is injected into the laminate in which the electrode plate and the separator are densely incorporated in the battery case, it is quickly contained in the voids of the separator. In order to absorb the electrolytic solution and quickly replace the voids of the separator with the electrolytic solution, the microporous film may contain 0.2 to 8% by weight of a surfactant (solid content). preferable.

As a method of incorporating the surfactant into the microporous film, a method of adding the surfactant to the raw material composition before film formation in a dispersed state in advance (internal addition method), or a method of forming the film and removing the plasticizer. There is a method (adhesion treatment) for post-treatment (adhesion treatment) of the porous film, but the manufacturing process can be simplified and the surfactant can be less likely to seep out from the microporous film of the present invention. , A method of adding in advance to the raw material composition (internal addition method) is preferable. The content (required amount) of the surfactant (solid content) is 0.2 to 8% by weight in the microporous film. Even if the content of the surfactant (solid content) is increased above this range, the effect of improving the hydrophilicity of the microporous film does not greatly increase, and conversely, the void ratio of the microporous film is lowered. As a separator for a liquid lead-acid battery, it causes an increase in internal resistance (electrical resistance), and as a separator for a liquid lead-acid battery, it causes an increase in self-discharge. Therefore, the content of the surfactant (solid content) is more preferably 0.2 to 5% by weight in the microporous film.

The surfactant may be any material that can improve the hydrophilicity of the microporous film, and any nonionic surfactant, cationic surfactant, or anionic surfactant can be used. As the nonionic surfactant, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl allyl ethers, fatty acid monoglycerides, sorbitan fatty acid esters and the like can be used. As the cationic surfactant, aliphatic amine salts, quaternary ammonium salts, polyoxyethylene alkylamines, alkylamine oxides and the like can be used. As the anionic surfactant, alkyl sulphonate, alkylbenzene sulphonate, alkylnaphthalen sulphonate, alkyl sulfosuccinate, dodecylbenzene sulphonate and the like can be used. Above all, since it is possible to impart high hydrophilicity to the polyolefin resin by adding a small amount and it has relatively high heat resistance, a surfactant is added in advance to the raw material composition to form a microporous film. Alkylbenzene sulphonate, alkyl sulfosuccinate, and dodecylbenzene sulphonate are preferable because they can be manufactured (manufactured by heat melt molding).

Next, examples of the present invention will be described in detail together with comparative examples.
(Example 1)
As a polyolefin resin, 1000 parts by weight of an ultra-high molecular weight polyethylene resin powder (melting point of about 135 ° C.) with a weight average molecular weight of 1.5 million and a specific surface area of 200 m ² by the BET method, which is a synthetic amorphous silica produced by the precipitation method. / G of silica fine powder (however, the content of salts such as sodium sulfate produced as a by-product in the manufacturing process is reduced by increasing the flow rate of the washed water more than before, and the Cl content is higher than before. By using a small amount of washing water, the mixing of Cl content is reduced, and the finally obtained microporous film (10 cm x 10 cm x 2 sheets) is immersed in 126 g of sulfuric acid with a specific gravity of 1.26 at a temperature of 50 ° C. for 24 hours. The concentration of the alkali metal (Li, Na, K, Rb, Cs) (ICP emission spectroscopic analysis) was 5 mg / 100 cm ² / sheet or less, and the halogen content (F, Cl, Br, I) was left unattended. Concentration (ICP emission spectroscopic analysis) is 0.4 mg / 100 cm ² / sheet or less) 2590 parts by weight, paraffin mineral oil 5380 parts by weight as a plasticizer, and alkyl sulfosuccinate as a surfactant. 109 parts by weight of (solid content) is mixed with a Ladyge mixer, and this raw material composition is extruded into a sheet while being heated, melted and kneaded using a twin-screw extruder with a T-die attached to the tip, and put into one roll. A film in which a plate-shaped sheet is integrally molded with a plate-contacting main rib having a predetermined shape on one surface of a flat plate-shaped sheet by passing it between a pair of molding rolls in which a predetermined groove is carved for the plate-contacting main rib. I got a substance. Next, this film-like material was immersed in n-hexane, a predetermined amount of paraffin-based mineral oil was extracted and removed, and the film was dried to obtain 22.9% by weight of polyethylene resin, 59.3% by weight of silica fine powder, and paraffin. It is composed of 16.0% by weight of paraffin oil and 1.8% by weight of surfactant (solid content), has a base thickness of 0.20 mm, has a void ratio of 62% by volume by the mercury intrusion method, and is by the mercury intrusion method. A ribbed microporous film having an average pore diameter of 0.09 μm and a maximum pore diameter of 0.65 μm by a mercury intrusion method was obtained. This was used as a separator for a liquid lead-acid battery of Example 1.

(Example 2)
As a polyolefin resin, 1000 parts by weight of an ultra-high molecular weight polyethylene resin powder (melting point of about 135 ° C.) with a weight average molecular weight of 1.5 million and a specific surface area of 200 m ² by the BET method, which is a synthetic amorphous silica produced by the precipitation method. The content of / g of silica fine powder (however, the content of salts such as sodium sulfate produced as a by-product in the manufacturing process is further reduced by increasing the flow rate of the washed water as compared with Example 1 and further reduced, and more than before. By using water-washed water with a low Cl content, the mixing of Cl content is reduced, and the finally obtained microporous film (10 cm x 10 cm x 2 sheets) is placed in 126 g of sulfuric acid with a specific gravity of 1.26 at a temperature of 50 ° C. The concentration of the alkali metal content (Li, Na, K, Rb, Cs) (ICP emission spectroscopic analysis) was 4 mg / 100 cm ² / sheet or less and the halogen content (F, Cl, Br) when left to stand for 24 hours. , I) concentration (ICP emission spectroscopic analysis) is 0.4 mg / 100 cm ² / sheet or less) 2590 parts by weight, paraffin mineral oil 5380 parts by weight as a plasticizer, and alkyl as a surfactant. 109 parts by weight of sulfosuccinate (solid content) was mixed with a Ladyge mixer, and this raw material composition was extruded into a sheet while being heated, melted and kneaded using a twin-screw extruder with a T-die attached to the tip. A pair of forming rolls having a predetermined groove for the electrode plate contact main rib are passed through the roll, and the electrode plate contact main rib having a predetermined shape is integrally formed on one surface of the flat plate-shaped sheet. A processed film-like substance was obtained. Next, this film-like material was immersed in n-hexane, a predetermined amount of paraffin-based mineral oil was extracted and removed, and the film was dried to obtain 22.9% by weight of polyethylene resin, 59.3% by weight of silica fine powder, and paraffin. It is composed of 16.0% by weight of paraffin oil and 1.8% by weight of surfactant (solid content), has a base thickness of 0.20 mm, has a void ratio of 62% by volume by the mercury intrusion method, and is by the mercury intrusion method. A ribbed microporous film having an average pore diameter of 0.09 μm and a maximum pore diameter of 0.65 μm by a mercury intrusion method was obtained. This was used as a separator for a liquid lead-acid battery of Example 2.

(Example 3)
As a polyolefin resin, 1000 parts by weight of an ultra-high molecular weight polyethylene resin powder (melting point of about 135 ° C.) with a weight average molecular weight of 1.5 million and a specific surface area of 200 m ² by the BET method, which is a synthetic amorphous silica produced by the precipitation method. / G of silica fine powder (however, the content of salts such as sodium sulfate produced as a by-product in the manufacturing process is reduced by increasing the flow rate of the washed water more than before, and Cl is higher than that of Example 1. By using water washed with a small amount of water, the mixing of Cl content is further reduced, and the finally obtained microporous film (10 cm x 10 cm x 2 sheets) is placed in 126 g of sulfuric acid with a specific gravity of 1.26 at a temperature of 50 ° C. The concentration of the alkali metal (Li, Na, K, Rb, Cs) (ICP emission spectroscopic analysis) was 5 mg / 100 cm ² / sheet or less and the halogen content (F, Cl, Br) when left to stand for 24 hours. , I) concentration (ICP emission spectroscopic analysis) is 0.1 mg / 100 cm ² / sheet or less) 2590 parts by weight, paraffin mineral oil 5380 parts by weight as a plasticizer, and alkyl as a surfactant. 109 parts by weight of sulfosuccinate (solid content) was mixed with a Ladyge mixer, and this raw material composition was extruded into a sheet while being heated, melted and kneaded using a twin-screw extruder with a T-die attached to the tip. A pair of forming rolls having a predetermined groove for the electrode plate contact main rib are passed through the roll, and the electrode plate contact main rib having a predetermined shape is integrally formed on one surface of the flat plate-shaped sheet. A processed film-like substance was obtained. Next, this film-like material was immersed in n-hexane, a predetermined amount of paraffin-based mineral oil was extracted and removed, and the film was dried to obtain 22.9% by weight of polyethylene resin, 59.3% by weight of silica fine powder, and paraffin. It is composed of 16.0% by weight of paraffin oil and 1.8% by weight of surfactant (solid content), has a base thickness of 0.20 mm, has a void ratio of 62% by volume by the mercury intrusion method, and is by the mercury intrusion method. A ribbed microporous film having an average pore diameter of 0.09 μm and a maximum pore diameter of 0.65 μm by a mercury intrusion method was obtained. This was used as a separator for a liquid lead-acid battery of Example 3.

(Comparative Example 1)
As a polyolefin resin, 1000 parts by weight of an ultra-high molecular weight polyethylene resin powder (melting point of about 135 ° C.) with a weight average molecular weight of 1.5 million and a specific surface area of 200 m ² by the BET method, which is a synthetic amorphous silica produced by the precipitation method. / G of silica fine powder (however, the content of salts such as sodium sulfate produced as a by-product in the manufacturing process is the same as before, and when the Cl content is the same as the conventional washing-treated water, the mixing of Cl content is reduced. The concentration of alkali metal (ICP emission) when the finally obtained microporous film (10 cm × 10 cm × 2 sheets) was immersed in 126 g of sulfuric acid having a specific gravity of 1.26 at a temperature of 50 ° C. for 24 hours and left to stand. Spectral analysis) exceeds 5 mg / 100 cm ² / sheet, halogen concentration (ICP emission spectroscopic analysis) exceeds 0.4 mg / 100 cm ² / sheet) 2590 parts by weight, and paraffin-based mineral as a plasticizer 5380 parts by weight of oil and 109 parts by weight of alkyl sulfosuccinate (solid content) as a surfactant are mixed with a Ladyge mixer, and this raw material composition is used as a twin-screw extruder with a T-die attached to the tip. It is extruded into a sheet while being heat-melted and kneaded, passed between a pair of forming rolls in which a predetermined groove for a main rib for contacting a electrode plate is carved in one roll, and a predetermined shape is formed on one surface of the flat plate-shaped sheet. A film-like material obtained by integrally molding the main rib for contacting the electrode plate was obtained. Next, this film-like material was immersed in n-hexane, a predetermined amount of paraffin-based mineral oil was extracted and removed, and the film was dried to obtain 22.9% by weight of polyethylene resin, 59.3% by weight of silica fine powder, and paraffin. It is composed of 16.0% by weight of paraffin oil and 1.8% by weight of surfactant (solid content), has a base thickness of 0.20 mm, has a void ratio of 62% by volume by the mercury intrusion method, and is by the mercury intrusion method. A ribbed microporous film having an average pore diameter of 0.09 μm and a maximum pore diameter of 0.65 μm by a mercury intrusion method was obtained. This was used as a separator for a liquid lead-acid battery of Comparative Example 1.

(Comparative Example 2)
As the silica fine powder, a silica fine powder having a specific surface area of 200 m ² / g by the BET method, which is a synthetic amorphous silica produced by the precipitation method (however, contains salts such as sodium sulfate produced as a by-product in the production process). The amount is the same as before, but by using washed water with less Cl content than before, the mixing of Cl content is reduced, and the temperature of the finally obtained microporous film (10 cm x 10 cm x 2 sheets) is increased. When immersed in 126 g of sulfuric acid with a specific gravity of 1.26 at 50 ° C. for 24 hours and left to stand, the concentration of alkali metal (ICP emission spectroscopic analysis) exceeds 5 mg / 100 cm ² / sheet, and the concentration of halogen (ICP emission spectroscopic analysis). 22.9% by weight of polyethylene resin, 59.3% by weight of silica fine powder, in the same manner as in Comparative Example 1 except that 0.4 mg / 100 cm ² / sheet or less was used. Consists of 16.0% by weight of paraffin-based mineral oil and 1.8% by weight of surfactant (solid content), the base thickness is 0.20 mm, the void ratio by the mercury intrusion method is 62% by volume, and the mercury intrusion method. A ribbed microporous film having an average pore diameter of 0.09 μm and a maximum pore diameter of 0.65 μm by the mercury intrusion method was obtained. This was used as a separator for a liquid lead-acid battery of Comparative Example 2.

(Comparative Example 3)
As the silica fine powder, silica fine powder having a specific surface area of 200 m ² / g by the BET method, which is a synthetic amorphous silica produced by the precipitation method (however, contains salts such as sodium sulfate produced as a by-product in the production process). The amount was reduced by increasing the flow rate of the water-washed water compared to the conventional method, but when the Cl content was the same as the conventional water-washed water, the cl content was not reduced and the finally obtained microporous property was used. When the film (10 cm × 10 cm × 2 sheets) was immersed in 126 g of sulfuric acid having a specific surface area of 1.26 at a temperature of 50 ° C. for 24 hours and left to stand, the concentration of alkali metal (ICP emission spectroscopic analysis) was 5 mg / 100 cm ² / sheet or less. , Polyethylene resin 22.9 weight in the same manner as in Comparative Example 1 except that the concentration of halogen (ICP emission spectroscopic analysis) was adjusted to exceed 0.4 mg / 100 cm ² / sheet). %, Silica fine powder 59.3% by weight, paraffin mineral oil 16.0% by weight, surfactant (solid content) 1.8% by weight, base thickness 0.20 mm, mercury press-fitting method A ribbed microporous film having a void ratio of 62% by volume, an average pore diameter of 0.09 μm by the mercury intrusion method, and a maximum pore diameter of 0.65 μm by the mercury intrusion method was obtained. This was used as a separator for a liquid lead-acid battery of Comparative Example 3.

Next, various characteristic evaluations were carried out for each of the separators of Examples 1 to 3 and Comparative Examples 1 to 3 obtained above by the following methods. The results are shown in Table 1. The MD (MD direction) is the manufacturing direction of the sheet to be manufactured, and the CD (CD direction) is the direction orthogonal to the MD direction.
<Base thickness>
Using a dial gauge (Peacock G-6 manufactured by Ozaki Seisakusho Co., Ltd.), arbitrary points and several points of the microporous film (where rib-like protrusions are not included) were measured.
<Tensile strength, elongation>
The microporous film is cut into a rectangular size of 10 mm × 70 mm in the MD and CD directions to obtain a test piece. Using a shopper type or similar tensile tester with a capacity of 294 N or less, set the grip interval (a) of the tester to about 50 mm, attach a test piece, and perform a tensile test at a tensile speed of 200 mm per minute. Read the tensile load (b) and distance (c) when cutting. The tensile strength is calculated by dividing the tensile load (b) by the cross-sectional area of the test piece. The elongation is calculated by dividing the distance (c) by the grip interval (a) of the testing machine.
<Porosity>
It was calculated by the following formula from the pore volume (mercury press-fitting method) and true density (immersion method) of the microporous film.
Porosity = Vp / ((1 / ρ) + Vp)
However, Vp: pore volume (cm ³ / g), ρ: true density (g / cm ³ )
<Average pore size>
The pore size distribution was calculated from the pressure and the volume of mercury at the time of mercury injection. The pore diameter at the time when mercury having a volume of 50% of the total pore volume was injected was defined as the average pore diameter (median diameter).
<Maximum hole diameter>
From the pore size distribution curve in the average pore size test, the pore size at which mercury injection was started was taken as the maximum pore size.
<Permeability>
A test piece obtained by cutting a microporous film into a square size of 70 mm × 70 mm is floated on the liquid surface of sulfuric acid having a specific gravity of 1.20 at a temperature of 20 ° C. The time until the part discolored was measured and used as the permeability (seconds).
<Electrical resistance>
The microporous film was cut into a square size of 70 mm × 70 mm to obtain a test piece, which was measured with a test device compliant with SBA S 0402.
<Oxidation resistant life>
A 50 mm x 50 mm square lead plate positive electrode and a negative electrode are laminated concentrically and in a square orientation with a microporous film separator cut into a 70 mm x 70 mm square. A rare group of electrodes consisting of a positive electrode (1 sheet), a separator (1 sheet), and a negative electrode (1 sheet) was subjected to a pressure of 19.6 kPa and incorporated into an electric bath, and then had a specific gravity of 1.300 (20 ° C.). 1000 ml of sulfuric acid electrolytic solution was injected, a DC constant current of 5.0 A was passed at a solution temperature of 50 ± 2 ° C., and the energization time was measured when the terminal voltage was 2.6 V or less or the voltage difference was 0.2 V or more. , The oxidation resistance time (h). In Table 1, the relative value when the value of Comparative Example 1 is 100 is displayed.
<Dendrite short characteristics>
A 70 mm x 70 mm square cut microporous film is sandwiched between two 50 mm x 50 mm square lead electrode plates (pure lead, 3 mm thick), and the microporous film and two lead electrode plates are sandwiched between them. Place the three squares horizontally in the battery case so that the centers of the three squares are aligned and the sides of the three squares are parallel to each other, and place a 5 kg weight (at the center of the square) on it. After that, a saturated lead sulfate aqueous solution is injected. After that, a current of 3.2 mA is applied to the lead electrode plate, and the change in voltage is continuously recorded. The voltage rises slightly after the start of energization and then gradually drops. The time is measured until the voltage drops to 70% of the maximum voltage at this time. In Table 1, the relative value when the value of Comparative Example 1 is 100 is displayed.
<ICP emission spectroscopic analysis>
Two pieces of microporous film cut into a square shape of 100 mm × 100 mm are placed in a beaker containing 126 g of sulfuric acid having a specific gravity of 1.26. This is placed in a constant temperature water tank maintained at 50 ° C. and allowed to stand for 24 hours. After standing for 24 hours, the microporous film is taken out from the sulfuric acid (extract). Sulfuric acid (extract) is diluted to 1/10, and the alkali metal content (Li, Na, K, Rb, Cs) and halogen content (F, Cl, Br, I) in the diluted solution are separated by ICP emission spectroscopy. Quantitative analysis is performed with an analyzer. The obtained value is converted from ppm to mg / 100 cm ² / sheet (weight per microporous film having an area of 100 cm ² ) (however, the base thickness per microporous film is 0. It is assumed that it is per 2 mm, and if the base thickness is different from this, the value is converted and corrected so that it is per 0.2 mm of the base thickness).
<Battery test (charge acceptability, battery life)>
The charge acceptability is based on JIS D 5301 (2006), and the charge current after the start of charging is measured when the battery is discharged at a 5-hour rate current for 2.5 hours. The battery life is a light load life test method based on JIS D 5301 (2006), and a charge / discharge cycle test is performed, and the number of cycles when the voltage at the 30th second becomes 7.2 V or less is measured. The charge acceptability and battery life in Table 1 are shown as relative values (relative results) when the value of Comparative Example 1 is 100.

From the results in Table 1, the following was found.
(1) The separator of Example 1 of the present invention has an alkali metal concentration (ICP emission spectroscopic analysis) of 5 mg / 100 cm ² / sheet or less, which improves charge acceptability and a halogen concentration. By setting (ICP emission spectroscopic analysis) to 0.4 mg / 100 cm ² / sheet or less, corrosion of the electrode plate lattice and the electrode column was prevented, and the battery life was improved.
(2) The separator of Example 2 of the present invention has a charge acceptability by further setting the concentration of alkali metal (ICP emission spectroscopic analysis) to 4 mg / 100 cm ² / sheet or less with respect to the separator of Example 1. Has improved further.
(3) The separator of Example 3 of the present invention has a battery life of 0.1 mg / 100 cm ² / sheet or less in terms of halogen content (ICP emission spectroscopic analysis) with respect to the separator of Example 1. Has improved further.
(4) Therefore, it is considered that if the separators of Examples 1 to 3 of the present invention are applied to a lead storage battery for an automobile, it contributes to the improvement of charge acceptability and battery life required for an idling stop vehicle.
(5) Since the separator of Comparative Example 1 has an alkali metal concentration (ICP emission spectroscopic analysis) of more than 5 mg / 100 cm ² / sheet, the charge acceptability is not improved to 100%, and halogen. Since the concentration of the minute (ICP emission spectroscopic analysis) exceeded 0.4 mg / 100 cm ² / sheet, corrosion of the electrode plate lattice and the electrode column was promoted, and the battery life was not improved to 100%.
(6) The separator of Comparative Example 2 has a halogen concentration (ICP emission spectroscopic analysis) of 0.4 mg / 100 cm ² / sheet or less, which prevents corrosion of the electrode plate lattice and the electrode column and shortens the battery life. Although it improved, the concentration of the alkali metal (ICP emission spectroscopic analysis) was 5 mg / 100 cm ² / sheet or more, so that the charge acceptability was not improved to 100%.
(7) The separator of Comparative Example 3 has an alkali metal concentration (ICP emission spectroscopic analysis) of 5 mg / 100 cm ² / sheet or less, which improves charge acceptance, but has a halogen concentration (ICP emission spectroscopy). Since the spectroscopic analysis) was over 0.4 mg / 100 cm ² / sheet, corrosion of the electrode plate lattice and the electrode column was promoted, and the battery life was not improved to 100%.

Claims (4)

40% by weight of silica fine powder, which is a synthetic amorphous silica produced by a precipitation method in which the purity of amorphous silica synthesized by precipitation precipitation by reacting an aqueous alkali silicate solution and mineral acid is adjusted by filtration and washing with water. A separator for a liquid lead storage battery comprising a microporous film containing the above, wherein the microporous film (10 cm × 10 cm × 2 sheets) is immersed in 126 g of sulfuric acid having a specific gravity of 1.26 at a temperature of 50 ° C. for 24 hours and left to stand. At that time, the concentration of the alkali metal content (Li, Na, K, Rb, Cs) (ICP emission spectroscopic analysis) was 5 mg / 100 cm ² / sheet or less (however, the base thickness of the microporous film was converted to 0.2 mm). And, the concentration of halogen (F, Cl, Br, I) (ICP emission spectroscopic analysis) is 0.4 mg / 100 cm ² / sheet or less (however, the base thickness of the microporous film is 0.2 mm equivalent). Separator for liquid lead storage battery characterized by being present. The separator for a liquid lead-acid battery according to claim 1, wherein the filtration / washing is performed using ion-exchanged water or groundwater containing no salt (sodium chloride). The separator for a liquid lead-acid battery according to claim 1 or 2, wherein the microporous film is a microporous film mainly composed of the silica fine powder and a polyolefin-based resin. The microporous film has a base thickness of 0.1 to 0.3 mm, an average pore diameter (mercury injection method) of 0.01 to 0.5 μm, and a porosity (mercury injection method) of 50 to 90% by volume. The separator for a liquid lead storage battery according to claim 3, wherein the film is a microporous film.