JP2006310274A - Separator for liquid lead acid battery and liquid lead acid battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator for a liquid type lead acid battery decreasing a reducing substance quantity generated in the lead acid battery by setting a content of a surface-active agent substantially to zero while ensuring specified mechanical strength and an electric resistance characteristic, and also to provide a liquid type lead-acid battery using the separator. <P>SOLUTION: This separator for a liquid type lead acid battery is a wet papermaking sheet which is formed of a material containing 13-23 mass% of synthetic pulp, 10-30 mass% of glass fibers having an average fiber diameter not greater than 3μm, 40-60 mass% of inorganic powder, 0-5 mass% of natural pulp and 10-25 mass% of a sheath-core synthetic fiber without substantially containing a resin emulsion binder, and bound by thermofusion of a low-melting-point component of the sheath-core synthetic fiber, and wherein a content of the surface-active agent is substantially zero and its density is not smaller than 0.26 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a separator for a liquid lead storage battery mainly composed of synthetic pulp and inorganic powder used mainly in combination with a glass mat, and a liquid lead storage battery using the separator.

  Conventionally, as a separator for a liquid type lead-acid battery, a separator of a type in which an acid-resistant microporous sheet and a glass mat are combined is known. The microporous sheet is generally a sheet having a fine pore structure that is wet-made mainly composed of synthetic pulp (generally polyethylene) and inorganic powder, and is called a pulp separator. Since the pulp separator does not have sufficient oxidation resistance, an auxiliary material called a glass mat is usually combined and used in combination.

The pulp separator is a mechanical member having a tensile strength of 1.4 MPa or more for the purpose of not damaging at the time of launching by stacking when assembling the separator into a battery and withstanding the friction with the electrode plate due to vibration during battery use. Strength is required. In the conventional pulp separator, this strength is ensured mainly by the following two actions.
(1) A synthetic pulp and a material mainly composed of inorganic powder are formed into a sheet by wet papermaking, dried at a temperature of about 110 ° C., and then heat treated at a temperature of about 180 ° C. (about 30 seconds). The pulp is melted to bind the contact points between the synthetic pulp and other materials.
(2) A resin emulsion binder (generally an acrylic emulsion resin) is added during wet papermaking (mixed paper) or added (impregnated) to wet paper after wet papermaking. Bonds contacts between all materials including synthetic pulp and inorganic powder.

  However, with regard to the action of (1), the synthetic pulp melted by the heat treatment (the synthetic pulp content in the pulp separator is usually about 50% by mass) is not limited to spread to the contact portion with other materials, Since the surface of hydrophilic materials such as inorganic powder is covered with a film, the surface state of the hydrophilic material changes from hydrophilic to hydrophobic, and the electrical resistance of the separator is significantly deteriorated (increased). End up.

  As for the action of (2), the resin particles of the resin emulsion binder adhere to the surface of the hydrophilic material such as inorganic powder, and the surface of the hydrophilic material is made into a film by heating during subsequent drying or heat treatment. Therefore, the surface state of the hydrophilic material changes from hydrophilic to hydrophobic, and the electrical resistance of the separator is significantly deteriorated (increased).

  For this reason, the conventional pulp separator is designed so as to suppress the deterioration (rise) of electrical resistance by adding a surfactant.

However, the conventional pulp separator produced by adding a surfactant can suppress deterioration (increase) in electrical resistance, but has the following adverse effects.
In other words, when the initial charge (chemical conversion) is performed in a liquid lead-acid battery using a pulp separator containing a surfactant, the inside of the battery is exposed to a high temperature and oxidizing atmosphere. The agent acts as a reducing substance to inhibit activation (oxidation-reduction reaction) of the positive electrode and the negative electrode during the initial charge, and there is a problem that it becomes difficult to obtain a specified battery capacity after the initial charge. .

  Therefore, in view of the above-mentioned conventional problems, the present invention provides a liquid lead-acid battery separator mainly composed of synthetic pulp and inorganic powder mainly used in combination with a glass mat. Liquid lead-acid battery separator that reduces the amount of reducing substances generated in the lead-acid battery by ensuring that the surfactant content is substantially zero while ensuring electrical resistance characteristics, and a liquid type using the separator It aims at providing lead acid battery.

In order to achieve the above object, the separator for a liquid lead-acid battery according to the present invention, as described in claim 1, has a synthetic pulp content of 13 to 23% by mass and glass fiber having an average fiber diameter of 3 μm or less, and 10 to 30% by mass. A material containing 40 to 60% by mass of inorganic powder, 0 to 5% by mass of natural pulp, and 10 to 25% by mass of a core-sheath type synthetic fiber and substantially free of a resin emulsion binder (however, in all materials, The total amount of the organic material having a binder function including the synthetic pulp and the core-sheath type synthetic fiber (the natural pulp is not included) is 25 to 47% by mass, including the glass fiber and the inorganic powder. The total amount of the inorganic material having oxidation resistance is 53 to 75% by mass) and is bound by heat melting of the low melting point component of the core-sheath type synthetic fiber, so that the content of the surfactant is substantially zero. And the density is 0. Characterized in that it is a 6 g / cm ³ or more wet papermaking sheet.
Moreover, the separator for liquid lead-acid batteries according to claim 2 is the separator for liquid lead-acid batteries according to claim 1, using an electrolytic cell composed of the wet papermaking sheet, the positive electrode plate, the negative electrode plate, and dilute sulfuric acid. The amount of reducing substance released and eluted after electrolysis at a direct current of 1.2 A and about 25 ° C. for 24 hours is 0.5 ml / 100 cm ² or less (N / 100 potassium permanganate solution per 100 cm ^{2 of the} wet papermaking sheet) It is a conversion value of consumption).
Moreover, the separator for liquid lead-acid batteries according to claim 3 is the separator for liquid lead-acid batteries according to claim 1 or 2, wherein the synthetic pulp and the sheath component of the core-sheath type synthetic fiber are of the same type. It is made of a material.
A separator for a liquid lead storage battery according to claim 4 is the separator for a liquid lead storage battery according to claim 3, wherein the material is polyethylene.
Moreover, the separator for liquid lead acid batteries of Claim 5 WHEREIN: The separator for liquid lead acid batteries in any one of Claims 1 thru | or 4 WHEREIN: That the average fiber diameter of the said glass fiber is 1.5 micrometers or less. Features.
A separator for a liquid lead storage battery according to claim 6 is formed by laminating and integrating a glass mat for a liquid lead storage battery with the separator for liquid lead storage battery according to any one of claims 1 to 5. And
Moreover, in order to achieve the said objective, the liquid lead acid battery of this invention used the separator for liquid lead acid batteries in any one of Claims 1 thru | or 6 as described in Claim 7. To do.

  Incidentally, in deriving the invention of claim 1, the present inventors, in the conventional pulp separator, the synthetic pulp that was generated as an adverse effect of the binding action due to the thermal melting of the synthetic pulp to obtain mechanical strength As a result of intensive investigations focusing on the mechanism of the phenomenon of covering the surface of a hydrophilic material in the form of a film (film formation phenomenon), the occurrence of the film formation phenomenon is related to the blending amount of synthetic pulp. It has been found that if the blending amount of the pulp is suppressed to 23% by mass or less, the film forming phenomenon can be prevented as much as possible.

According to the present invention, in a liquid lead-acid battery separator mainly composed of synthetic pulp and inorganic powder mainly used in a form combined with a glass mat, the synthetic pulp is 13 to 23% by mass and the average fiber diameter is 3 μm or less. Glass fiber 10 to 30% by mass, inorganic powder 40 to 60% by mass, natural pulp 0 to 5% by mass, and core-sheath type synthetic fiber 10 to 25% by mass and substantially containing a resin emulsion binder No material (however, the total amount of organic materials having a binder function including the synthetic pulp and the core-sheath type synthetic fiber (not including the natural pulp) is 25 to 47% by mass in all materials, The total amount of the inorganic material having oxidation resistance including glass fiber and the inorganic powder is 53 to 75% by mass), and is bound by thermal melting of the low melting point component of the core-sheath type synthetic fiber. interface The content of sexual agent substantially zero, the density is so as to constitute at 0.26 g / cm ³ or more wet papermaking sheet, while ensuring the mechanical strength and electrical resistance characteristics of the prescribed, surfactants It is possible to provide a liquid lead-acid battery separator capable of reducing the amount of reducing substances generated in the lead-acid battery by setting the content of the agent to substantially zero. It is possible to suppress deterioration of battery performance (particularly battery capacity after initial charge) due to the amount of substance.

Hereinafter, for the sake of convenience, the phrase “pulp separator” and the phrase “liquid-type lead-acid battery separator” will be used in combination, but both are substantially the same separator.
The pulp separator of the present invention comprises 13 to 23% by mass of synthetic pulp, 10 to 30% by mass of glass fibers having an average fiber diameter of 3 μm or less, 40 to 60% by mass of inorganic powder, 0 to 5% by mass of natural pulp, A material containing 10 to 25% by mass of a core-sheath type synthetic fiber and substantially free of a resin emulsion binder (however, in all materials, an organic material having a binder function including the synthetic pulp and the core-sheath type synthetic fiber) The total amount (not including the natural pulp) is 25 to 47% by mass, and the total amount of the inorganic material having oxidation resistance including the glass fiber and the inorganic powder is 53 to 75% by mass). The wet papermaking with a surfactant content of substantially zero and a density of 0.26 g / cm ³ or more, which is bound by heat melting of the low melting point component (sheath component) of the core-sheath type synthetic fiber. Be a sheet As a condition.

  In addition, the pulp separator of the present invention has a deterioration in electrical resistance due to a decrease in hydrophilicity that has occurred as an adverse effect of the binding action of the synthetic pulp and resin emulsion binder to obtain mechanical strength in the conventional pulp separator ( The basic design concept is not to use a surfactant that was used to suppress the rise), so how to obtain mechanical strength without deteriorating (raising) electrical resistance It becomes a point.

  In the conventional pulp separator, in order to obtain the specified mechanical strength (tensile strength of 1.4 MPa or more), the binding action by heat melting of the synthetic pulp and the binding action by the resin emulsion binder were used. However, in the pulp separator of the present invention, the binding action by the thermal melting of the synthetic pulp, the binding action by the thermal melting of the low melting point component (sheath component) of the core-sheath type synthetic fiber, and the glass fiber having the fine diameter Utilizes the entanglement effect of.

  Regarding the binding action of the synthetic pulp due to heat melting, as described above, the synthetic pulp melted in the conventional pulp separator is coated with the hydrophilic material surface in the form of a film (film formation phenomenon). Although there was an adverse effect of making the surface state hydrophobic and deteriorating (increasing) the electrical resistance, based on the new knowledge described above, in the pulp separator of the present invention, by suppressing the blending amount of synthetic pulp to 23% by mass or less, Generation | occurrence | production of the said filming phenomenon accompanying the binding effect by the thermal melting of a synthetic pulp, ie, the deterioration (rise) of the electrical resistance accompanying the binding effect by the thermal melting of the said synthetic pulp, is suppressed as much as possible.

  As for the binding action of the core-sheath type synthetic fiber, as described above, the core-sheath type synthetic fiber is bonded by thermal melting of the low melting point component (sheath component). There is no occurrence of a phenomenon of covering the surface of the hydrophilic material with a binding action by the fiber in the form of a film, and there is no deterioration (increase) in electrical resistance due to the binding action by the core-sheath type synthetic fiber.

  As described above, in the pulp separator of the present invention, in order to obtain a prescribed mechanical strength, the binding action of the synthetic pulp by thermal melting and the binding of the low melting point component of the core-sheath type synthetic fiber by thermal melting. Adhesion action and the action of entanglement by the glass fiber of the fine diameter is utilized, but with respect to any action, as a result, there is no adverse effect of increasing the electrical resistance of the separator, the pulp separator of the present invention is The specified mechanical strength can be secured without deteriorating (increasing) the electrical resistance. That is, the pulp separator of the present invention can suppress the deterioration (rise) of electrical resistance without using any surfactant, and can secure a specified mechanical strength.

Further, as described above, in order to provide the mechanical strength to the pulp separator of the present invention, the total amount of organic materials having a binder function including the synthetic pulp and the core-sheath type synthetic fiber is 25 in all materials. On the other hand, in order to ensure good hydrophilicity (electrolyte affinity) and oxidation resistance of the pulp separator of the present invention, the glass fiber and the inorganic powder are included in all materials. The total amount of the inorganic material having oxidation resistance needs to be 53 to 75% by mass. The organic material having the binder function does not include the natural pulp.
The total amount of organic materials having a binder function is 25 to 47% by mass in all materials, while the total amount of inorganic materials having oxidation resistance is 53 to 75% by mass. Therefore, the total amount of the organic material is 47 mass% at the maximum regardless of whether or not it has a binder function. Therefore, regarding the total amount of the organic material having a binder function in which the maximum value is 47% by mass in all materials, the organic material having no binder function (for example, the natural pulp) is included in all the materials. In this case, the amount obtained by subtracting the content is the actual upper limit value.

  As the synthetic pulp, pulp-like polyolefin fibers, pulp-like acrylic fibers, etc. can be used, but in terms of excellent acid resistance and binder properties, pulp-like polyolefin fibers are preferred, and in particular, pulp-like fibers having a low melting point and excellent adhesion. Polyethylene fibers are preferred. The synthetic pulp is necessary for imparting acid resistance to the pulp separator and as a binder for binding other materials. The compounding quantity of the said synthetic pulp is 13-23 mass% in all the materials which form the said pulp separator. This is because if it is less than 13% by mass, the mechanical strength of the separator is lowered, the surface smoothness and stacking property for stacking and the wear resistance (surface hardness) are lowered, and the acid resistance is lowered. This is because if it exceeds mass%, a film-forming phenomenon tends to occur as described above, and the electrical resistance of the separator increases, which is not preferable.

  Since the glass fiber forms a skeleton of the wet papermaking sheet and forms a network structure that determines pores, those having an average fiber diameter of 3.0 μm or less are used. In order to form a fine network structure and to increase the mechanical strength of the sheet, it is preferable to use glass fibers having an average fiber diameter of 1.5 μm or less. The compounding quantity of the said glass fiber is 10-30 mass% in all the materials which form the said pulp separator. This is because if the amount is less than 10% by mass, the mechanical strength of the separator is lowered, which is not preferable. If the amount exceeds 30% by mass, the blending amount of the inorganic powder is reduced and short circuit resistance (dendrite short resistance) is deteriorated. In addition, it is not preferable because the unit price of the product is increased particularly when a glass fiber of 1.5 μm or less is used.

The inorganic powder can be selected from acid-resistant inorganic fine powders such as silica, diatomaceous earth, talc, mica, and alumina. Silica is preferred because it has few impurities and is excellent in acid resistance. In the case of silica, it is preferable to use a silica having a specific surface area of 50 to 500 m ² / g and a secondary particle diameter of about 5 to 15 μm. The said inorganic powder is hold | maintained between the network structure which consists of glass fiber, a synthetic pulp, and a core-sheath type synthetic fiber, and there exists an effect which makes the pore diameter of a separator small and prevents a lead osmosis | permeation short circuit. In all the materials forming the pulp separator, the amount of the inorganic powder is 40 to 60% by mass. This is because if the amount is less than 40% by mass, the effect of preventing lead permeation short-circuiting is reduced and the short-circuit resistance is deteriorated, which is not preferable. If the amount exceeds 60% by mass, drainage resistance at the time of wet papermaking increases and the productivity increases. This is because it is not preferable.

  Natural pulp is an effective material for maintaining strength during the production of wet papermaking sheets (especially when wet paper is dried). In all the materials forming the pulp separator, the blending amount of the natural pulp is 0 to 5% by mass. Depending on the paper machine which manufactures the wet papermaking sheet used as the pulp separator, the strength of the formed sheet may be maintained without blending natural pulp, and the blending amount of natural pulp may be 0% by mass. On the other hand, if the blending amount of the natural pulp exceeds 5% by mass in all the materials forming the pulp separator, the acid resistance of the pulp separator deteriorates, which is not preferable.

  As the core-sheath type synthetic fiber, the core is made of polypropylene and the sheath is made of polyethylene, the core is made of polyethylene terephthalate and the sheath is made of polyethylene, the core is made of polyethylene terephthalate and the sheath is made of copolymer polyester. You can choose from things. Considering the binder effect, the specific gravity is greater than water, and when dispersed in water, it is less likely to float in water, making it easier to disperse. Polyester (polyethylene, polypropylene, specific gravity about 0.9) is more polyester-based. It is preferable to select (specific gravity about 1.2). However, when considering acid resistance and oxidation resistance, a polyolefin type is preferable to a polyester type. Therefore, for the sheath component of the core-sheath type synthetic fiber, it is preferable to select a polyolefin type in consideration of acid resistance and oxidation resistance, and in particular, to select polyethylene having a low melting point in consideration of adhesiveness. On the other hand, regarding the core component of the core-sheath type synthetic fiber, it is preferable to select a polyester type in consideration of the binder effect (dispersibility). That is, as the core-sheath type synthetic fiber, a core-sheath type synthetic fiber having a core part made of polyethylene terephthalate and a sheath part made of polyethylene is used in consideration of acid resistance and oxidation resistance, a binder effect (dispersibility), and adhesiveness. Is preferred. The core-sheath type synthetic fiber is a material that forms the skeleton of the pulp separator, and the pulp separator has tensile strength and piercing strength (for example, the separator is damaged by a large convex portion on the surface of the electrode plate to open a hole. It has an effect of improving the mechanical strength such as an index of resistance to the like. The compounding quantity of the said core-sheath type synthetic fiber is 10-25 mass% in all the materials which form the said pulp separator. This is because if it is less than 10% by mass, the mechanical strength of the separator is lowered, the amount of synthetic pulp is increased, and the above-mentioned filming phenomenon is liable to occur and the electrical resistance is increased. This is because if it exceeds mass%, the blending amount of the synthetic pulp is decreased, and the mechanical strength and acid resistance of the separator are decreased, which is not preferable.

Moreover, it is preferable that the synthetic pulp and the sheath component of the core-sheath type synthetic fiber are made of the same material. As described above, both the synthetic pulp and the sheath component of the core-sheath type synthetic fiber have a role of giving a binder effect to the wet papermaking sheet by their own thermal melting. The binder effect is efficiently exhibited by the melting effect, and a high binder effect can be obtained even with a small addition amount of synthetic pulp and core-sheath type synthetic fiber, and the addition amount of organic material while giving the specified mechanical strength to the separator The amount of the inorganic material (glass fiber, inorganic powder) having good hydrophilicity and oxidation resistance can be increased to increase the hydrophilicity and oxidation resistance of the separator.
In particular, as the material of the sheath component of the synthetic pulp and the core-sheath type synthetic fiber when the same kind of material is used, the polyethylene recommended in the description of the synthetic pulp and the core-sheath type synthetic fiber is selected. It is preferable to do this.

The wet papermaking sheet used as the pulp separator of the present invention has a density of 0.26 g / cm ³ or more. When the density of the sheet is less than 0.26 g / cm ^3, the average pore diameter of the pulp separator increases, and when using the battery, the risk of lead penetration and dendrite shorting increases, and the separator performance decreases. It is not preferable. For the same reason, the density is more preferably 0.32 g / cm ³ or more.

  In the material forming the pulp separator of the present invention, in addition to the above materials, a hydrophilic metal oxide sol such as silica sol is added internally (mixed, mixed) or externally added (inorganic binder). Impregnation, coating). In this case, in the obtained separator, the surface of the organic fiber (synthetic pulp, core-sheath type synthetic fiber, etc.) is coated with an inorganic substance, and the surface state of the organic fiber changes from hydrophobic to hydrophilic. In addition, the electrical resistance of the separator can be reduced. In addition, when the battery is used, there is an effect that the deterioration of the separator due to the sulfuric acid electrolyte is reduced and the amount of reducing organic substances that can be decomposed in the battery is reduced.

Next, examples of the present invention will be described in detail together with comparative examples.
Example 1
A core-sheath type synthetic fiber (average fineness) comprising 17% by mass of polyethylene synthetic pulp (Mitsui Chemicals SWP (registered trademark)), a core part made of polyethylene terephthalate (melting point 255 ° C.) and a sheath part made of polyethylene (melting point 135 ° C.) 1.2 dtex, average fiber length 5 mm) 18% by mass, 15% by mass of glass fiber having an average fiber diameter of 1 μm, and 50% by mass of silica fine powder having a specific surface area of 180 m ² / g, these are dispersed and mixed in water. Then, after adding an acrylamide-based adsorbent and adsorbing and supporting the silica fine powder on the surface of the other material, the sheet is formed with a normal paper machine, and passed through a press roll in a wet paper state. Adjustments were made. The sheet was dried at 110 ° C. and heat-treated at 180 ° C. for 30 seconds to obtain a liquid lead-acid battery separator having a thickness of 0.31 mm and a density of 0.28 g / cm ³ .

(Example 2)
For the purpose of improving the density, for a liquid lead-acid battery having a thickness of 0.30 mm and a density of 0.39 g / cm ^{3 in} the same manner as in Example 1 except that the sheet was formed with a higher basis weight. A separator was obtained.

(Example 3)
Synthetic pulp made of polyethylene (SWP (registered trademark) manufactured by Mitsui Chemicals), core-sheath type synthetic fiber (average fineness) consisting of polyethylene terephthalate (melting point 255 ° C) in the core and polyethylene (melting point 135 ° C) in the sheath Example 1 except that 13 mass% (1.2 dtex, average fiber length 5 mm), 14 mass% of glass fibers having an average fiber diameter of 1 μm, and 50 mass% of silica fine powder having a specific surface area of 180 m ² / g were used. Similarly, a separator for a liquid type lead storage battery having a thickness of 0.29 mm and a density of 0.40 g / cm ³ was obtained.

Example 4
A core-sheath type synthetic fiber (average fineness) comprising 17% by mass of polyethylene synthetic pulp (Mitsui Chemicals SWP (registered trademark)), a core part made of polyethylene terephthalate (melting point 255 ° C.) and a sheath part made of polyethylene (melting point 135 ° C.) Example 1 except that 13 mass% (1.2 dtex, average fiber length 5 mm), 20 mass% of glass fibers having an average fiber diameter of 1 μm, and 50 mass% of silica fine powder having a specific surface area of 180 m ² / g were used. A sheet was formed in the same manner, and this sheet was immersed in silica sol. After addition of 3% by mass of silica sol, the sheet was dried at 110 ° C. and heat-treated at 180 ° C. for 30 seconds. A separator for a liquid lead-acid battery having a density of 29 mm and a density of 0.35 g / cm ³ was obtained.

(Comparative Example 1)
Core-sheath type synthetic fiber (average fineness) consisting of 25% by mass of synthetic pulp made of polyethylene (SWP (registered trademark) manufactured by Mitsui Chemicals), polyethylene terephthalate (melting point 255 ° C) in the core and polyethylene (melting point 135 ° C) in the sheath Example 1 except that 13 mass% of 1.2 dtex, average fiber length of 5 mm), 13 mass% of glass fibers having an average fiber diameter of 1 μm, and 49 mass% of silica fine powder having a specific surface area of 180 m ² / g were used. Similarly, a separator for a liquid lead-acid battery having a thickness of 0.29 mm and a density of 0.38 g / cm ³ was obtained.

(Comparative Example 2)
Core-sheath type synthetic fiber (average fineness) consisting of 30% by mass of synthetic pulp made of polyethylene (SWP (registered trademark) made by Mitsui Chemicals), polyethylene terephthalate (melting point 255 ° C) in the core and polyethylene (melting point 135 ° C) in the sheath Example 1 except that 11 mass% (1.2 dtex, average fiber length 5 mm), 13 mass% of glass fibers having an average fiber diameter of 1 μm, and 46 mass% of silica fine powder having a specific surface area of 180 m ² / g were used. Similarly, a separator for a liquid lead-acid battery having a thickness of 0.30 mm and a density of 0.36 g / cm ³ was obtained.

(Comparative Example 3)
A core-sheath type synthetic fiber (average fineness 1.7 dtex, average fiber length 5 mm) composed of polyethylene terephthalate (melting point 255 ° C.) in the core and copolymer polyester (melting point 110 ° C.) in the sheath, and an average fiber diameter of 1 μm In the same manner as in Example 1, except that 10% by mass of glass fiber and 50% by mass of silica fine powder having a specific surface area of 180 m ² / g were used, the thickness was 0.31 mm and the density was 0.40 g / cm ³ . A liquid lead-acid battery separator was obtained.

(Comparative Example 4)
A core-sheath type synthetic fiber (average fineness 1.7 dtex, average fiber length 5 mm) consisting of polyethylene terephthalate (melting point 255 ° C.) in the core and copolymer polyester (melting point 110 ° C.) in the sheath, and an average fiber diameter of 1 μm In the same manner as in Example 1 except that 15% by mass of glass fiber and 35% by mass of silica fine powder having a specific surface area of 180 m ² / g were used, the thickness was 0.29 mm and the density was 0.23 g / cm ³ . A liquid lead-acid battery separator was obtained.

(Comparative Example 5)
49% by mass of synthetic pulp made of polyethylene (SWP (registered trademark) manufactured by Mitsui Chemicals), 15% by mass of polyester fiber, 7% by mass of glass fiber having an average fiber diameter of 1 μm, and fine silica powder 29 having a specific surface area of 180 m ² / g A sheet was formed in the same manner as in Example 1 except that% by mass was used. The sheet was dipped in a mixture of both so that an acrylic resin emulsion 3 external mass% and a surfactant 1 external mass% were added to the sheet, and then the sheet was dried at 110 ° C. and 180 ° C. Heat treatment was performed for 30 seconds to obtain a separator for a liquid type lead storage battery having a thickness of 0.28 mm and a density of 0.43 g / cm ³ .

(Comparative Example 6)
A sheet was formed in the same manner as in Example 1. The sheet was immersed in a mixed solution so that 5% by mass of acrylic resin emulsion 5 and 1% by mass of surfactant 1 were added to the sheet, and then the sheet was dried at 100 ° C. and 150 ° C. Heat treatment was performed to obtain a liquid lead-acid battery separator having a thickness of 0.30 mm and a density of 0.33 g / cm ³ .

(Comparative Example 7)
A sheet was formed in the same manner as in Example 1. After the sheet was immersed in the acrylic resin emulsion so that 5% by mass of the acrylic resin emulsion 5 was added to the sheet, the sheet was dried at 100 ° C. and heat-treated at 150 ° C. to obtain a thickness of 0.30 mm. A separator for a liquid lead-acid battery having a density of 0.36 g / cm ³ was obtained.

  Next, separator characteristics were measured for each of the liquid lead-acid battery separators of Examples 1 to 4 and Comparative Examples 1 to 7 thus obtained. The result is shown in FIG.

The following was found from the results of FIG.
(1) The separators of Examples 1 to 4 of the present invention have a low electrical resistance and a high tensile strength, and since they do not use a surfactant, the amount of reducing substances is small and has excellent characteristics. It was confirmed that this was a separator for a lead-acid battery.
(2) In Comparative Examples 1 and 2, since a large amount of synthetic pulp causing the film-forming phenomenon as described above was used, the hydrophilicity of the separator was inferior and the electrical resistance was deteriorated.
(3) In Comparative Examples 3 to 4, since a large amount of synthetic pulp or resin emulsion binder that causes the filming phenomenon as described above is not used, the same as in Examples 1 to 4 of the present invention. Thus, a separator that satisfies the specified electrical resistance characteristics and satisfies the target of the amount of reducing substance without using a penetrant (surfactant) has been obtained. However, since synthetic pulp is not used, the surface smoothness and wear resistance (surface hardness) for stacking properties are lowered, and the stacking properties are not good. Addition of adsorbent (flocculating agent) because the amount of inorganic powder is large compared to the amount of glass fiber and synthetic pulp that are effective for supporting inorganic powder. However, it is difficult to hold (support) the inorganic powder on other separator constituent materials, that is, the yield during wet papermaking of the inorganic powder is poor, so a large amount of inorganic powder must be used. Therefore, the manufacturing cost has increased. In addition, a large amount of core-sheath type synthetic fiber, which is an expensive material, is used, resulting in an increase in product cost. In addition, since the amount of core-sheath type synthetic fiber, which is a thick fiber, is very large, and the amount of glass fiber, which is a fine fiber, is small, the sheet skeleton obtained with such a material structure has a fine structure. As a result, the maximum pore size and the average pore size were increased because a fine network structure was not formed and the inorganic powder was hardly retained in the network structure.
(4) In the separators of Comparative Examples 5 to 7, the hydrophilicity of the separator is inferior because a large amount of synthetic pulp or resin emulsion binder that causes the filming phenomenon as described above is used. Since a surfactant for improving hydrophilicity was used, the amount of reducing substance increased. Moreover, in the case of the comparative example 7, since surfactant was not used, electrical resistance worsened.
(5) From the above results, the separators for liquid lead-acid batteries of Examples 1 to 4 of the present invention have mechanical strength of tensile strength of 1.4 MPa or more, low electrical resistance, and are activated in the battery. It was confirmed that the separator has excellent characteristics by suppressing the amount of reducing substances that have an adverse effect such as inhibiting the above.

Table showing separator characteristics for each of the liquid lead-acid battery separators of Examples 1 to 4 and Comparative Examples 1 to 7

Claims (7)

Synthetic pulp 13-23 mass%, glass fiber 10-30 mass% with an average fiber diameter of 3 μm or less, inorganic powder 40-60 mass%, natural pulp 0-5 mass%, and core-sheath type synthetic fiber 10 25% by mass and a material that does not substantially contain a resin emulsion binder (however, in all materials, an organic material having a binder function including the synthetic pulp and the core-sheath type synthetic fiber (the natural pulp is included) The total amount of inorganic materials having oxidation resistance including the glass fiber and the inorganic powder is 53 to 75% by mass). A liquid lead-acid battery characterized in that it is a wet papermaking sheet having a surfactant content of substantially zero and a density of 0.26 g / cm ³ or more, which is bound by thermal melting of low-melting-point components of fibers. Separator. Using an electrolysis cell comprising the wet papermaking sheet, the positive electrode plate, the negative electrode plate and dilute sulfuric acid, the amount of the reducing substance released and eluted after electrolysis at a direct current of 1.2 A and about 25 ° C. for 24 hours is 0.5 ml / The separator for a liquid lead-acid battery according to claim 1, wherein the separator is 100 cm ² or less (converted value of N / 100 potassium permanganate solution consumption per 100 cm ^{2 of the} wet papermaking sheet).   The separator for a liquid lead-acid battery according to claim 1 or 2, wherein the synthetic pulp and the sheath component of the core-sheath type synthetic fiber are made of the same material.   The liquid lead-acid battery separator according to claim 3, wherein the material is polyethylene.   The separator for a liquid lead-acid battery according to any one of claims 1 to 4, wherein an average fiber diameter of the glass fibers is 1.5 µm or less.   A separator for a liquid lead storage battery according to any one of claims 1 to 5, wherein a glass mat for a liquid lead storage battery is laminated and integrated.   A liquid lead-acid battery using the liquid lead-acid battery separator according to any one of claims 1 to 6.

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