NONWOVEN FABRIC FOR LEAD ACID BATTERIES USING GLASS FIBER AND HEAT-FUSIBLE BINDER FIBER

Abstract

[Problem] To provide a nonwoven fabric (pasting mat) that does not undergo bonding between the nonwoven fabrics (pasting mats) even under severe conditions (a pressure in winding and a high temperature and a high humidity in transportation, storage, and production).

[Means for Resolution] A pasting mat for lead acid batteries, containing a microglass fiber and a heat-fusible binder fiber, the pasting mat having a thickness under a pressure of 20 kPa of 0.1 mm or more and 0.5 mm or less, and having a bonding strength between the pasting mats after being left for 48 hours under a pressure of 5 to 10 kPa in an environment of a temperature of 70 to 90° C. and a humidity of 75% of less than 0.05 N.

Claims

1: A pasting mat for lead acid batteries, comprising a microglass fiber and a heat-fusible binder fiber, the pasting mat having a thickness under a pressure of 20 kPa of 0.1 mm or more and 0.5 mm or less, and having a bonding strength between the pasting mats after being left for 48 hours under a pressure of 5 to 10 kPa in an environment of a temperature of 70 to 90° C. and a humidity of 75% of less than 0.05 N.

2: The pasting mat for lead acid batteries according to claim 1, wherein the bonding strength between the pasting mats after being left for 48 hours under a pressure of 5 kPa in an environment of a temperature of 70° C. and a humidity 75% is less than 0.05 N.

3: The pasting mat for lead acid batteries according to claim 1, wherein the bonding strength between the pasting mats after being left for 48 hours under a pressure of 10 kPa in an environment of a temperature of 70° C. and a humidity of 75% is less than 0.05 N.

4: The pasting mat for lead acid batteries according to claim 1, wherein the bonding strength between the pasting mats after being left for 48 hours under a pressure of 10 kPa in an environment of a temperature of 90° C. and a humidity of 75% is less than 0.05 N.

5: The pasting mat for lead acid batteries according to claim 1, wherein the pasting mat has a tensile strength of 5 N/10 mm.sup.2 or more.

6: The pasting mat for lead acid batteries according to claim 1, wherein the heat-fusible binder fiber is an organic fiber having a core/sheath structure with a sheath of a crystalline heat-fusible polyolefin resin or a crystalline heat-fusible polyester resin.

7: The pasting mat for lead acid batteries according to claim 1, wherein the heat-fusible binder fiber has a fineness of 2.2 dtex or less.

8: The pasting mat for lead acid batteries according to claim 1, which is a wound body wound with a pressure of 5 kPa or more applied.

9: The pasting mat for lead acid batteries according to claim 1, wherein the heat-fusible binder fiber is contained in an amount of 3.0% by weight or more.

10: The pasting mat for lead acid batteries according to claim 1, wherein the microglass fiber has a number average fiber diameter of 4.5 μm or less.

11: The pasting mat for lead acid batteries according to claim 1, wherein the microglass fiber has a number average fiber diameter of 2 μm or less.

12: The pasting mat for lead acid batteries according to claim 1, wherein the microglass fiber and the heat-fusible binder fiber are contained in a total amount of 60% by weight or more.

13: A lead acid battery comprising the pasting mat for lead acid batteries according to claim 1.

Description

DESCRIPTION OF EMBODIMENTS

[0029] The nonwoven fabric (pasting mat) for lead acid batteries of the present invention is obtained by wet-papermaking mainly from a microglass fiber and a heat-fusible binder fiber, and in addition to the microglass fiber and the heat-fusible binder fiber, an inorganic powder, such as silica, or a non-heat-fusible organic fiber or resin, such as a cellulose, a carbon fiber, a polyacrylonitrile fiber, or a non-heat-fusible polyester fiber, which is excellent in acid resistance and oxidation resistance, may be contained.

[0030] When a non-heat-fusible monofilament organic fiber is blended together with the heat-fusible binder fiber, the compression breaking strength (shearing force) of the nonwoven fabric (pasting mat) can be increased (see, for example, Japanese Patent No. 4261821), making it possible to obtain a further superior nonwoven fabric (pasting mat).

[0031] Besides, a combined effect by a combination with various non-heat-fusible materials can be expected.

[0032] As the microglass fiber for use in the nonwoven fabric (pasting mat) for lead acid batteries of the present invention, a C glass fiber is preferred since the nonwoven fabric is used in sulfuric acid as with a separator for lead acid batteries, but the microglass fiber is not limited to the C glass fiber as long as it is an acid-resistant glass fiber.

[0033] The fiber diameter of the microglass fiber is different depending on the combined heat-fusible binder fiber or other auxiliary materials, but from the viewpoint of inhibition of stratification which is a function of a pasting mat, the number average fiber diameter is preferably 4.5 μm or less. When the stratification inhibition is to be more improved, for example, because of use in a lead acid battery for ISS, the number average fiber diameter is preferably 2 μm or less.

[0034] Examples of synthetic resin components of the heat-fusible binder fiber used for the nonwoven fabric (pasting mat) for lead acid batteries of the present invention include synthetic resins, for example, polyolefin resins, such as a polyethylene resin and a polypropylene resin, a polystyrene resin, a polymethyl methacrylate resin, a polyacrylonitrile resin, a nylon resin, a polyester resin, and a polyfluoroethylene resin. Heat-melting components among the above resins are polyolefin resins, such as a polyethylene resin and a polypropylene resin, and a polyester resin which is heat fusible.

[0035] In the present invention, from the viewpoint of an improving effect on the tensile strength (sheet strength), a heat-fusible resin having a highly crystalline structure, for example, a polyolefin resin, such as a polyethylene resin or a polypropylene resin, or a low-melting-point crystalline polyester resin is preferably used, and a polyethylene resin is particularly preferred.

[0036] In the case of a non-crystalline heat-fusible resin, such as a modified polyethylene resin or a modified polyester resin, specifically, a polyethylene copolymer (CoPE) or a copolymerized polyethylene terephthalate (CoPET), the adhesiveness is too high, and thus, under a pressure in winding or under conditions of a high temperature and a high humidity in transportation, storage, and production, bonding between the surfaces of the superposed nonwoven fabrics (pasting mats) occurs, unfortunately causing top layer delamination of the nonwoven fabric (pasting mat) in peeling and other problems.

[0037] Regarding the fiber diameter of the heat-fusible binder fiber, since the number of heat-fusible binder fibers contained in the nonwoven fabric (pasting mat) decreases as the fiber diameter increases, a heat-fusible binder fiber having a fineness of 2.2 dtex or less is preferred from the viewpoint of tensile strength.

[0038] The heat-fusible binder fiber used for the nonwoven fabric (pasting mat) for lead acid batteries of the present invention is preferably one having a core/sheath structure because of its high improving effect on the tensile strength (sheet strength).

[0039] In this case, the core may be a generally used resin, such as a polyethylene resin, a polypropylene resin, or a polyester resin, but is preferably an acid resistant one having a melting point of 160° C. or higher.

[0040] The sheath is preferably a crystalline heat-fusible resin, for example, a polyolefin resin, such as polyethylene resin or a polypropylene resin, a low-melting-point crystalline polyester resin. In the case of a polyolefin resin or a modified polyester resin which is a non-crystalline heat-fusible resin, specifically, a polyethylene copolymer (CoPE) or a copolymerized polyethylene terephthalate (CoPET), the adhesiveness is too high, and thus bonding between the surfaces of the superposed nonwoven fabrics (pasting mats) occurs under a pressure in winding or under conditions of a high temperature and a high humidity in transportation, storage, and production, unfortunately causing top layer delamination of the nonwoven fabric (pasting mat) in peeling and other problems.

[0041] In the nonwoven fabric (pasting mat) for lead acid batteries of the present invention, the amount of the heat-fusible binder fiber blended is preferably 3.0% by weight or more, more preferably 5.0% by weight or more, and particularly preferably 12% by weight or more.

[0042] With an amount thereof less than 3.0% by weight, the tensile strength (sheet strength) of the nonwoven fabric (pasting mat) is short.

[0043] The amount of the heat-fusible binder fiber blended is preferably 40% by weight or less, more preferably 30% by weight or less, and particularly preferably 25% by weight or less.

[0044] With an amount thereof more than 40%, the ability to hold the electrolyte decreases, and sulfuric acid released from a pole plate in charging cannot be held, causing stratification of the electrolyte.

[0045] In the nonwoven fabric (pasting mat) for lead acid batteries of the present invention, the total amount of the microglass fiber and the heat-fusible binder fiber blended is preferably 60% by weight or more, more preferably 65% by weight or more, and particularly preferably 70% by weight or more.

[0046] In the nonwoven fabric (pasting mat) for lead acid batteries of the present invention, the thickness of the nonwoven fabric (pasting mat) is preferably 0.1 to 0.5 mm, more preferably 0.1 to 0.25 mm, and particularly preferably 0.1 to 0.20 mm.

[0047] When the thickness of the nonwoven fabric (pasting mat) is small, a function to inhibit stratification deteriorates, and in the current ISS use environment, the thickness of the nonwoven fabric (pasting mat) is desired to be 0.1 mm or more.

[0048] On the other hand, in a general lead acid battery for automobiles, since the distance between the positive electrode and the negative electrode (pole gap) is about 1.5 mm or less, a too large thickness of the nonwoven fabric (pasting mat) makes it difficult to use a separator. Thus, the thickness is to be reduced to 0.5 mm or less. In addition, since the pole gap is 1.0 mm or less in recent lead acid batteries for automobiles, the thickness of the nonwoven fabric (pasting mat) is desirably 0.25 mm or less. Furthermore, since the pole gap is 0.6 mm or less in lead acid batteries for automobiles for ISS, the thickness of the nonwoven fabric (pasting mat) is desirably 0.20 mm or less.

[0049] In the nonwoven fabric (pasting mat) for lead acid batteries of the present invention, in order to use it in a general battery production process with no problem, the tensile strength (sheet strength) of the nonwoven fabric (pasting mat) is preferably 2.5 N/10 mm.sup.2 or more, and from the viewpoint of improving the productivity in the future, the tensile strength is desirably 5.0 N/10 mm.sup.2 or more, and further desirably 7.5 N/10 mm.sup.2 or more.

[0050] When the tensile strength is lower than 2.5 N/10 mm.sup.2, the battery assembly performance and the basic properties in charging/discharging reaction deteriorate, and the battery life decreases.

[0051] In the nonwoven fabric (pasting mat) for lead acid batteries of the present invention, from the viewpoint of preventing stratification of the electrolyte, the maximum pore size of the nonwoven fabric (pasting mat) is preferably less than 100 μm, and more preferably 40 μm or less.

[0052] In the nonwoven fabric (pasting mat) for lead acid batteries of the present invention, the coefficient of extension of the nonwoven fabric (pasting mat) is preferably in the range of 2.0% or more and less than 9.0%, and more preferably in the range of 2.5% or more and 7.5% or less.

[0053] In the charging/discharging reaction in use of a battery, absorption and release of the electrolyte are repeated, resulting in expansion and contraction of the nonwoven fabric (pasting mat).

[0054] In addition, the nonwoven fabric (pasting mat) for lead acid batteries is delivered mainly in a roll shape in delivery, and the nonwoven fabric (pasting mat) is pulled out from the roll and used in assembling a battery. Thus, when the coefficient of extension of the nonwoven fabric (pasting mat) for lead acid batteries as measured under a room temperature condition is 9.0% or more, the nonwoven fabric (pasting mat) for lead acid batteries is extended by a force in pulling out the nonwoven fabric (pasting mat) for lead acid batteries and the dimensions in the width direction and the thickness direction of the nonwoven fabric (pasting mat) vary.

[0055] In this case, the distance between pole plates and the size thereof set for preventing the short-circuiting on the side surface of the battery electrodes vary, causing an early battery short-circuiting.

[0056] When the nonwoven fabric (pasting mat) is pulled out from the roll and is used in assembling a battery, with a coefficient of extension less than 2.0%, cracking occurs in the nonwoven fabric (pasting mat), resulting in a defective product which cannot be delivered.

Examples

[0057] The present invention will be described more specifically below with reference to Examples, Reference Examples, and Comparative Examples, but the present invention is not to be limited to the following Examples without departing from the gist thereof.

[0058] Nonwoven fabrics (pasting mats) for lead acid batteries of Examples 1 to 14, Reference Examples 1 to 2, and Comparative Examples 1 to 12 were produced using the following materials.

[Compounding Materials]

(1) Microglass Fiber

[0059] CMLF-208, manufactured by Nippon Sheet Glass Co., Ltd., number average fiber diameter: 0.8 μm

(2) Non-Adhesive Monofilament Organic Fiber

[0060] EP133-5, manufactured by Kuraray Co., Ltd., polyethylene terephthalate, fineness: 1.45 dtex

(3) Heat-Fusible Binder Fiber

[0061] A: Melty 6080, manufactured by UNITIKA LTD., two-component core/sheath type (core: polyethylene terephthalate, sheath: polyethylene), fineness: 1.50 dtex
B: PZ08-5, manufactured by Daiwabo Holdings Co., Ltd., one-component all-fusion type (polypropylene), fineness: 0.80 dtex
C: Casven 8080, manufactured by UNITIKA LTD., two-component core/sheath type (core: polyethylene terephthalate, sheath: polyethylene terephthalate), fineness: 1.10 dtex
D: RCE 1.7, manufactured by UBE INDUSTRIES, LTD., two-component core/sheath type (core: polypropylene, sheath: low-melting-point polyethylene), fineness: 1.70 dtex
E: Melty 4000, manufactured by UNITIKA LTD., one-component all-fusion type (copolymerized polyethylene terephthalate), fineness: 2.20 dtex
F: Melty 4080, manufactured by UNITIKA LTD., two-component core/sheath type (core: polyethylene terephthalate, sheath: copolymerized polyethylene terephthalate), fineness: 1.22 dtex

[Production of Nonwoven Fabric (Pasting Mat)]

[0062] The nonwoven fabrics (pasting mats) for lead acid batteries of Examples 1 to 14, Reference Examples 1 to 2, and Comparative Examples 1 to 12 were produced by the following procedure according to the formulation shown in Tables 1 to 2.

[0063] About 7 to 10 g of materials were put in a container of an industrial mixer (MX-152SP, manufactured by Panasonic Corporation), about 1000 ml of an aqueous sulfuric acid solution of pH 3 was added thereto, and the mixture was subjected to disaggregation (rotation speed: about 9700 rpm) for 60 seconds. The sample in a slurry form was put in a square sheet machine for experiments. An aqueous sulfuric acid solution of pH 3 was further added thereto and the mixture was uniformly stirred so as to obtain a concentration of 0.25% by weight, followed by forming a sheet. The sheet was dried with heat using a compartment dryer at a temperature of 180° C. for 30 minutes to produce a separator. In drying the sheet, attention was paid so that water vapor did not remain in the dryer.

[Methods for Test and Evaluation]

[0064] For the Examples, Reference Examples, and Comparative Examples, evaluation was made under the following conditions. The results are collectively shown in Tables 1 to 2.

(1) Weight (g/m.sup.2)

[0065] The produced nonwoven fabric (pasting mat) was cut into a size of 100 mm×100 mm to make a test piece. The weight of ten such test pieces was measured with an electronic balance and the weight (g/m.sup.2) was calculated.

(2) Thickness (mm)

[0066] The produced nonwoven fabric (pasting mat) was cut into a size of 100 mm×100 mm to make a test piece. Ten such test pieces were stacked, and measurement was performed with the “thickness measuring tool” shown in FIG. 1 of the Storage Battery Association Standard, SBA S0406-2017 7.2.2.b) for AGM separator for lead acid battery.

(3) Apparent Density (g/cm.sup.3)

[0067] Measurement was performed according to the method described in the Storage Battery Association Standard, SBA S0406-2017 7.2.3 for AGM separator for lead acid battery, and the apparent density was calculated by the following calculation formula.

Apparent density (g/cm.sup.3)=[weight (g/m.sup.2)]/[thickness (mm)]/1000

(4) Tensile Strength (N/10 mm.sup.2)

[0068] Measurement was performed by the following procedure according to the method described in the Storage Battery Association Standard, SBA S0406-2017 7.2.7 for AGM separator for lead acid battery.

[0069] The produced nonwoven fabric (pasting mat) was cut into a size of 10 mm×70 mm to make a test piece. Measurement with a tensile tester (chuck distance: 50 mm, tension rate: 200 mm/minute) was repeated 10 times, and the average was calculated and taken as the tensile strength (N/10 mm.sup.2).

(5) Bonding Strength (N)

[0070] a. As testing conditions, three patterns: “left for 48 hours under conditions of a temperature of 70° C., a humidity of 75%, and a pressure of 5 kPa”, “left for 48 hours under conditions of a temperature of 70° C., a humidity of 75%, and a pressure of 10 kPa”, and “left for 48 hours under conditions of a temperature of 90° C., a humidity of 75%, and a pressure of 10 kPa” were employed.
b. The produced nonwoven fabric (pasting mat) was cut (5 kPa pressure: 100 mm×100 mm, 10 kPa pressure: 70 mm×70 mm) to make a sample (each set included two samples).
c. As a pretreatment, the samples (two samples for each set) were left for one hour in a thermostatic and humidifying chamber set to the same temperature and humidity conditions as the testing conditions.
d. The pretreated samples (two samples for each set) were interposed between two sheets of fine paper (cut into the same size as the samples), which were interposed between two acrylic boards (120 mm×120 mm×10 mm thickness), which were then placed in a thermostatic and humidifying chamber set to the same temperature and humidity conditions as the testing conditions. A prescribed weight (5 kPa pressure: 5 Kg, 10 kPa pressure: 10 Kg) was placed on the acrylic board.
e. After leaving for 48 hours, the samples were taken out of the thermostatic and humidifying chamber, and the bonding strength was measured.
f. The bonding strength was measured as follows according to the “Touch and Close Fastener 7.4.2 Peeling Strength” of JIS L3416:2000.

[0071] A test piece of 25 mm width remaining in the bonded state was taken from the treated samples, and the “bonding strength” of a 50-mm bonded part was measured with an autograph (manufactured by Shimadzu Corporation). The maximum value was taken and the average of the results of six measurements in total was calculated.

[0072] When the bonding state was not maintainable until the test piece was attached to a grip, the “bonding strength” was determined as “0.00”.

(6) Top Layer Delamination (“None”, “Scuffing”, “Delamination”)

[0073] The state of the top layer delamination was determined by peeling the bonded samples (two samples for each set) by hands and visually checking whether scuffing of either sample surface and top layer delamination occur.

[0074] When a piliform state as formed by rubbing was found on either nonwoven fabric (pasting mat) surface, the case was determined as “scuffing”.

[0075] When a peeled and detached part was found on either nonwoven fabric (pasting mat) surface, the case was determined as “delamination”.

[0076] When neither “scuffing” nor “delamination” was found, the case was determined as “none”.

[0077] Such evaluation results of Examples 1 to 14, Reference Examples 1 to 2, and Comparative Examples 1 to 12 were collectively shown in Tables 1 to 2.

TABLE-US-00001 TABLE 1 Fiber diameter Example Example Example Example 1 Item (dtex) Unit 1 2 3 4 2 Non- C glass glass Fiber diameter — wt % 97 95 90 88 adhesive short fiber 0.8 μm 3 fiber Kuraray PET EP133-5 1.45 4 Heat-fusible UNITIKA PET/PE 6080 1.50 3 5 10 12 5 binder fiber Daiwabo PP PZ08-5 0.80 6 UNITIKA PET/PET Casven 8080 1.10 7 UBE PP/PE RCE 1.7 1.70 8 UNITIKA Co-PET 4000 2.20 9 UNITIKA PET/coPET 4080 1.22 10 Raw material disaggregation Concentration wt % 0.25 0.25 0.25 0.25 11 pH — 3 3 3 3 12 Time 88 C 60 60 60 60 13 Papermaking condition pH — 3 3 3 3 15 Temperature ° C. 180 180 180 180 16 Time min 30 30 30 30 17 Weight g/m2 33 33 33 32 18 Thickness 20 kpa mm 0.20 0.20 0.20 0.20 19 Apparent density g/cm3 0.17 0.17 0.17 0.16 20 Tensile strength N/10 mm2 2.9 5.1 7.1 7.7 21 Top layer delamination 70° C. × 75% × 48 hr Visual none none none none  5 kpa observation 22 Bonding strength N 0.00 0.00 0.00 0.00 23 Top layer delamination 70° C. × 75% × 48 hr Visual none none none none 10 kpa observation 24 Bonding strength N 0.00 0.00 0.00 0.00 25 Top layer delamination 90° C. × 75% × 48 hr Visual none none none none 10 kpa observation 26 Bonding strength N 0.00 0.00 0.00 0.00 Example Example Example Example Example Example Example Example Example Example 1 5 6 7 8 9 10 11 12 13 14 2 85 83 75 70 60 75 75 75 70 60 3 10 30 4 15 17 25 30 40 20 20 5 25 6 25 7 25 8 9 10 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 11 3 3 3 3 3 3 3 3 3 3 12 60 60 60 60 60 60 60 60 60 60 13 3 3 3 3 3 3 3 3 3 3 15 180 180 180 180 180 180 180 180 180 180 16 30 30 30 30 30 30 30 30 30 30 17 0.21 0.21 0.20 0.20 0.21 0.20 0.19 0.20 0.20 0.20 18 0.16 0.16 0.17 0.17 0.16 0.16 0.16 0.16 0.16 0.16 19 8.2 9.4 10.1 13.1 14.6 2.5 12.7 7.4 9.9 10.4 20 21 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 none none none none none scuffing none none none none 22 23 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 none none none none scuffing scuffing nene none none scuffing 24 25 0.00 0.00 0.00 0.00 0.02 0.04 0.00 0.00 0.00 0.03 26

TABLE-US-00002 TABLE 2 Fiber Reference Reference Comparative Comparative diameter Example Example Example Example 1 Item (dtex) Unit 1 2 1 2 2 Non- C glass glass Fiber diameter — wt % 100 75 95 93 adhesive short fiber 0.8 μm 3 fiber Kuraray PET EP133-5 1.45 25 4 Heat-fusible UNITIKA PET/PE 6080 1.50 5 binder fiber Daiwabo PP PZ08-5 0.80 6 UNITIKA PET/PET Casven 8080 1.10 7 UBE PP/PE RCE 1.7 1.70 8 UNITIKA Co-PET 4000 2.20 9 UNITIKA PET/coPET 4080 1.22 5 7 10 Raw material disaggregation Concentration wt % 0.25 0.25 0.25 0.25 11 pH — 3 3 3 3 12 Time 88 C 60 60 60 60 13 Papermaking condition pH — 3 3 3 3 15 Drying conditions Temperature ° C. 180 180 180 190 16 Time min 30 30 30 30 17 Weight g/m2 32 33 33 34 18 Thickness 20 kpa mm 0.20 0.19 0.20 0.20 19 Apparent density g/cm3 0.16 0.17 0.17 0.17 20 Tensile strength N/10 mm2 2.0 1.5 6.3 6.6 21 Top layer delamination 70° C. × 75% × 48 hr Visual none none delamination delamination  5 kpa observation 22 Bonding strength N 0.00 0.00 0.08 0.07 23 Top layer delamination 70° C. × 75% × 48 hr Visual none none delamination delamination 10 kpa observation 24 Bonding strength N 0.00 0.00 0.10 0.14 25 Top layer delamination 90° C. × 75% × 48 hr Visual none none delamination delamination 10 kpa observation 26 Bonding strength N 0.00 0.00 0.13 0.25 Comparative Comparative Comparative Comparative Comparative Comparative Comparative Comparative Comparative Comparative Example Example Example Example Example Example Example Example Example Example 1 3 4 5 6 7 8 9 10 11 12 2 90 68 85 75 70 60 95 75 70 50 3 10 30 4 5 6 7 8 5 25 9 10 12 15 25 30 40 20 20 10 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 11 3 3 3 3 3 3 3 3 3 3 12 60 60 60 60 60 60 60 60 60 60 13 3 3 3 3 3 3 3 3 3 3 15 190 180 180 180 180 180 180 180 180 180 16 30 30 30 30 30 30 30 30 30 30 17 34 33 32 33 33 33 33 31 31 33 18 0.19 0.20 0.21 0.20 0.19 0.19 0.20 0.10 0.20 0.21 19 0.17 0.16 0.16 0.17 0.17 0.17 0.17 0.17 0.16 0.16 20 7.4 6.1 6.7 13.2 15.9 22.3 4.9 10.2 10.8 11.2 21 delamination delamination delamination delamination delamination delamination delamination delamination delamination delamination 22 0.13 0.14 0.18 0.21 0.37 0.54 0.05 0.18 0.19 0.18 23 delamination delamination delamination delamination delamination delamination delamination delamination delamination delamination 24 0.21 0.23 0.25 0.61 0.73 0.98 0.07 0.32 0.49 0.47 25 delamination delamination delamination delamination delamination delamination delamination delamination delamination delamination 26 0.25 0.30 0.33 0.30 0.35 1.27 0.11 0.42 0.64 0.60

[0078] As can be seen in the test results of Examples 1 to 14, Reference Examples 1 to 2, and Comparative Examples 1 to 12 shown in Tables 1 to 2, by checking the state after leaving samples for 48 hours in a thermostatic and humidifying chamber under a pressure of 5 kPa or 10 kPa in an environment of a temperature of 70° C. or 90° C. and a humidity of 75% as bonding conditions between nonwoven fabrics (pasting mats) for the purpose of preventing delamination due to bonding between nonwoven fabrics (pasting mats), the type of the heat-fusible binder fiber that did not undergo delamination in the top layer in peeling even under the above bonding conditions and that gave a bonding strength of less than 0.05 N was able to be specified.

[0079] The top layer of a nonwoven fabric (pasting mat) that showed a bonding strength of less than 0.05 N did not undergo “delamination”. This is considered because the strength of the bonding is smaller than the strength of the nonwoven fabric (pasting mat) itself so that “delamination” does not occur.

[0080] In addition, regarding the case where “scuffing” occurred, the scuffing is considered to have little influence on the battery performance, but a problem may occur in a production process. Thus, no scuffing is more preferred.

[0081] From the test results of Examples 1 to 14, Reference Examples 1 to 2, and Comparative Examples 1 to 12 shown in Tables 1 to 2, it was able to be found that the nonwoven fabric (pasting mat) for lead acid batteries of the present invention does not undergo top layer delamination, which may be caused by bonding between the front and back surfaces of nonwoven fabrics (pasting mats), even under a pressure by winding and/or under temperature and humidity conditions in transportation, storage, and battery production, and that the present invention can provide a nonwoven fabric (pasting mat) that does not cause a defective quality and a production loss.