JP4907055B2 - Battery separator and battery using the same - Google Patents

Description

  The present invention relates to a battery separator and a battery using the same.

  Conventionally, a separator has been used in a battery so that a positive electrode and a negative electrode are separated to prevent a short circuit, and an electrolysis reaction can be smoothly performed while holding an electrolytic solution. As one of the separators, one made of a non-woven fabric using a nylon-based fiber having excellent electrolyte retention is known. However, since this nylon fiber is easily decomposed by an electrolytic solution (particularly an alkaline electrolytic solution), it has a low reliability over a long period of time.

  As a separator for an alkaline battery using such a nylon-based fiber that improves the resistance to electrolytic solution, “a high melting point polyamide fiber with an elongation of 41 to 45% and a polyamide composite adhesive fiber with an elongation of 65% or less A linear fat having a melting point at least 10 ° C. lower than the melting point of the high-melting polyamide whose core is higher than 165 ° C. and whose core component constitutes the core component. An alkaline battery separator containing a group polyamide has been proposed (Patent Document 1). Although this separator can certainly exhibit excellent performance in terms of resistance to electrolyte, a battery using this separator is prone to migration of the active material and has a short battery life. In recent years, there has been a demand for higher capacity of batteries, and as one means for achieving this higher capacity, while increasing the amount of active material and reducing the volume occupied by the separator, it has been performed. When a strong external force is applied to the separator in order to reduce the volume occupied by the separator, the separator may be broken by an electrode (particularly, an edge of the electrode) to cause a short circuit.

JP-A-4-212267 (Claims etc.)

  The present invention has been made to solve the above-described problems, and has a battery separator that can produce a battery having a long battery life by being excellent in electrolytic solution resistance and less prone to migration of an active material, and a battery life The first object is to provide a long battery. It is a second object of the present invention to provide a battery separator and a high-capacity battery that can produce a high-capacity battery without being broken and short-circuited even if the external force is strong.

The invention according to claim 1 of the present invention includes “(1) a polyamide-based adhesive fiber having a polyamide-based resin as an adhesive component, and (2) a polyamide-based ultrafine fiber comprising a polyamide-based resin and having a fiber diameter of 5 μm or less. The separator for alkaline secondary batteries is characterized by comprising a fiber sheet, and the fiber sheet does not contain nylon 6 homopolymer. The separator for an alkaline secondary battery of the present invention (hereinafter sometimes simply referred to as “separator”) includes a polyamide-based ultrafine fiber, resulting in a smaller average fiber diameter and a smaller average flow pore diameter. , Migration of the active material can be suppressed. Moreover, since the present inventors have found that when the separator contains nylon 6 homopolymer, the separator is easily decomposed by the electrolytic solution, the fiber sheet constituting the separator of the present invention contains nylon 6 homopolymer. Not. Therefore, the separator of this invention is excellent in electrolyte solution resistance. For the above reasons, if the separator of the present invention is used, an alkaline secondary battery having a long life can be produced.

The invention according to claim 2 of the present invention states that “the adhesive component of the polyamide-based adhesive fiber is a nylon copolymer having one or more components selected from nylon 610, nylon 612, nylon 11, and nylon 12 as a copolymer component. The separator for an alkaline secondary battery according to claim 1, wherein the separator is made of a polymer. Nylon 610 constituting a part of the adhesive component of the polyamide fibrous, nylon 612, nylon 11, and nylon 12 is often a methylene group, excellent electrolyte resistance, since hardly degraded by the electrolyte, an alkaline secondary battery Can extend the lifespan.

The invention according to claim 3 of the present invention is characterized in that “the polyamide-based ultrafine fiber is produced by removing the sea component of the sea-island fiber containing the polyamide-based resin as an island component,” Alternatively, the separator for an alkaline secondary battery according to claim 2. The individual ultrafine fibers produced in this manner have almost no change in fiber diameter in the fiber axis direction, and the fiber diameters between the ultrafine fibers are almost the same, so that the separator has a uniform average flow pore diameter. Therefore, the migration of the active material can be effectively suppressed.

The invention according to claim 4 of the present invention is “a separator for an alkaline secondary battery according to any one of claims 1 to 3, further comprising a fiber sheet containing aramid fibers”. Since aramid fibers are excellent in strength and are not easily broken by external force, the fiber sheet as a separator is also difficult to break by external force. Therefore, a high-capacity alkaline secondary battery can be manufactured without causing a short circuit when manufacturing the battery.
The invention according to claim 5 of the present invention is “the alkali sheet according to any one of claims 1 to 4, further comprising a fiber sheet including a polyamide-based thick fiber having a fiber diameter exceeding 5 μm. Secondary battery separator ".
The invention according to claim 6 of the present invention is characterized in that it consists of a nonwoven fabric bonded only by fusing of the adhesive component of the polyamide-based adhesive fiber, according to any one of claims 1 to 5. "Separator for alkaline secondary battery".

The invention according to claim 7 of the present invention is “the separator for an alkaline secondary battery according to any one of claims 1 to 6, wherein the fiber sheet has an average fiber diameter of 10 μm or less”. is there. When the fiber sheet has an average fiber diameter of 10 μm or less and contains polyamide ultrafine fibers to some extent, migration of the active material can be effectively prevented.

The invention according to claim 8 of the present invention is “the separator for an alkaline secondary battery according to any one of claims 1 to 7, wherein the average flow pore diameter of the fiber sheet is 13 μm or less”. is there. When the average flow pore size of the fiber sheet is 13 μm or less and the polyamide ultrafine fibers are included to some extent, migration of the active material can be effectively prevented.

The invention according to claim 9 of the present invention is “an alkaline secondary battery comprising the battery separator according to any one of claims 1 to 8”. Therefore, it is an alkaline secondary battery with a long battery life. Particularly, the alkaline secondary battery using the separator of claim 4 is a high-capacity alkaline secondary battery.

  The separator of the present invention can produce a battery having a long battery life by being excellent in electrolytic solution resistance and being less prone to migration of an active material. Moreover, by including an aramid fiber, a high-capacity battery can be manufactured without being broken and short-circuited even if the external force is large.

  Since the battery of the present invention includes the separator, the battery has a long battery life. It can also be a high capacity battery.

  The separator (fiber sheet) of the present invention includes polyamide-based adhesive fibers and ultrafine fibers so that the electrolyte retainability is excellent. In the present invention, a polyamide-based adhesive fiber having a polyamide-based resin as an adhesive component (hereinafter simply referred to as “adhesive fiber”) so that it is highly compatible with the ultrafine fiber and has excellent adhesion to the ultrafine fiber. Is included). The adhesive component of the adhesive fiber is not limited to nylon 6 homopolymer so as to have excellent electrolytic solution resistance, and may be any polyamide-based resin having a melting point lower than that of the ultrafine fiber. Nylon copolymers having one or more components selected from nylon 612, nylon 11 and nylon 12 as copolymerization components are preferred because they have many methylene groups and are excellent in resistance to electrolytes. Among these, nylon 11 or nylon 12 having a high ratio of methylene groups to amide groups is preferably used as the copolymer component, and nylon 12 is particularly preferably used as the copolymer component. The ratio (molar ratio) of the copolymer component is not particularly limited as long as the melting point of the adhesive component is lower than that of the ultrafine fiber. The adhesive component may be a nylon 6 homopolymer, and even if nylon 6 is included as a copolymer component of the adhesive component, it is excellent in electrolytic solution resistance, and may be a nylon 6 copolymer.

  The adhesive fiber of the present invention is a fiber provided with the adhesive component as described above, but may be composed of only the adhesive component or may include a component other than the adhesive component. If a non-adhesive component having a higher melting point than the adhesive component is provided as a component other than the adhesive component, the adhesive fiber can maintain its fiber form even if the adhesive component is fused, and the separator (fiber sheet) It is a preferred adhesive fiber because it has excellent strength and is difficult to break by external force. In such an adhesive fiber having a suitable adhesive component and a non-adhesive component, the adhesive component and the non-adhesive component may be arranged in any way, but arranged so as to cover the non-adhesive component with the adhesive component ( That is, it is preferable to arrange in a core-sheath shape because it can be a separator having a wide adhesion area and excellent strength. In the case of such a core-sheath adhesive fiber, it is preferable that the core component (non-adhesive component) and the sheath component (adhesive component) are arranged concentrically so that they can be uniformly bonded to the polyamide-based ultrafine fiber or the like. However, it need not be concentric. Moreover, in the case of the core-sheath-like adhesive fiber, the mass ratio of the core component (non-adhesive component) and the sheath component (adhesive component) is not particularly limited. It is preferable that the core component (non-adhesive component): sheath component (adhesive component) = 20: 80 to 80:20 so that the fiber shape maintainability by the core component is excellent.

  The non-adhesive component has a higher melting point than that of the adhesive component (preferably higher by at least 10 ° C.), and may be composed of a resin component other than nylon 6 homopolymer. 66, nylon 12, nylon 46 and the like. Among these, nylon 66 which is excellent in terms of spinnability and cost is preferable. In the present invention, the “melting point” refers to a temperature that gives a maximum value of a melting endothermic curve obtained by heating from room temperature at a heating temperature of 10 ° C./min using a differential scanning calorimeter. When there are two or more maximum values, the highest temperature maximum value is taken as the melting point.

  The fiber diameter of the adhesive fiber of the present invention is not particularly limited, but the fiber diameter is small so that it can be a separator having a small average fiber diameter and a small average flow pore diameter in cooperation with the polyamide-based ultrafine fiber described later. Is preferably 18 μm or less, and more preferably 14 μm or less. In addition, although the minimum of a fiber diameter is not specifically limited, It is preferable that it is 8 micrometers or more from the point of productivity of a separator (fiber sheet). “Fiber diameter” in the present invention refers to the diameter when the cross-sectional shape is circular, and when the cross-sectional shape is non-circular, the diameter of the circle when converted to a circle having the same area is used. Say.

  Further, the fiber length of the adhesive fiber of the present invention is not particularly limited, but the shorter the fiber length, the higher the degree of freedom of the adhesive fiber, which can be a densely structured fiber sheet, which is more excellent in migration prevention properties. Therefore, it is preferably 10 mm or less, and more preferably 5 mm or less. On the other hand, the lower limit of the fiber length of the adhesive fiber is not particularly limited, but is preferably 1 mm or more.

  Since the content of such an adhesive fiber is determined depending on the balance with other fibers such as a polyamide-based ultrafine fiber as will be described later, it is not particularly limited. ) It is preferable that it is 30-70 mass% of the whole, and it is more preferable that it is 40-60 mass%.

  In addition to the adhesive fibers as described above, the separator of the present invention includes a polyamide ultrafine fiber (hereinafter sometimes simply referred to as “ultrafine fiber”) having a fiber diameter of 5 μm or less and made of a polyamide resin. As a result, the average fiber diameter and the average flow pore diameter of the separator are reduced, and migration of the active material can be effectively suppressed. The smaller the fiber diameter of this ultrafine fiber, the better the effect. Therefore, the fiber diameter of the ultrafine fiber is preferably 4 μm or less, more preferably 3 μm or less, and further preferably 2 μm or less. preferable. The lower limit of the fiber diameter of the ultrafine fiber is not particularly limited, but is suitably 0.01 μm or more.

  The polyamide resin constituting the ultrafine fiber is not particularly limited as long as it is made of a polyamide resin other than nylon 6 homopolymer so that the electrolyte solution resistance is excellent. For example, nylon 66, nylon 610, Nylon 612, Nylon 11, Nylon 12 and other aliphatic polyamides, or aromatic polyamide resins having an aromatic dicarboxylic acid as a copolymerization component can be mentioned. Among these, nylon 66, nylon 12, and aromatic polyamide resin are preferable, and nylon 12 and aromatic polyamide resin excellent in electrolytic solution resistance are particularly preferable.

  In addition, the polyamide-type resin which comprises an ultrafine fiber does not need to be 1 type, and may contain 2 or more types. The ultrafine fiber containing two or more types of polyamide resins having different melting points can improve the separator strength because at least the polyamide resin having the lowest melting point is fused. Hard to occur. Thus, in the ultrafine fiber containing two or more types of polyamide resins having different melting points, the polyamide resin having the lowest melting point may be exposed on the fiber surface so that the above-described effects can be exhibited. There is no particular limitation. In the case of an ultrafine fiber containing two or more types of polyamide resins having different melting points, the mass ratio between the polyamide resin (A) having the lowest melting point and the other polyamide resins (B) is not particularly limited. However, it is preferable that A: B = 20: 80 to 80:20.

  The fiber length of the ultrafine fiber of the present invention is not particularly limited, but the shorter the fiber length, the higher the degree of freedom of the ultrafine fiber, and it can be a densely structured fiber sheet, which is superior in migration prevention It is preferably 3 mm or less, and more preferably 2 mm or less. On the other hand, the lower limit of the fiber length is not particularly limited, but is preferably 0.1 mm or more. The cross-sectional shape of the ultrafine fiber is not particularly limited, and may be circular or non-circular.

  Since the content of such ultrafine fibers is determined depending on the balance with other fibers such as the adhesive fibers as described above, it is not particularly limited, but a separator (fiber sheet) so as to have excellent migration prevention properties. It is preferable that it is 3-30 mass% of the whole, and it is more preferable that it is 5-20 mass%. In the present invention, two or more types of ultrafine fibers having different fiber diameters, fiber lengths, and / or polyamide resin compositions may be included.

  Such ultrafine fibers are preferably produced by removing sea components of sea-island type fibers (especially sea-island type fibers produced by a composite spinning method) containing polyamide resin as island components. The individual ultrafine fibers produced in this manner have almost no change in fiber diameter in the fiber axis direction, and the fiber diameters between the ultrafine fibers are almost the same, so that the separator has a uniform average flow pore diameter. This is because the migration of the active material can be effectively suppressed. In addition, since it has passed through a drawing process by a drawing yarn machine or the like at the stage of the sea-island fiber before extraction, the ultrafine fiber produced by extraction is excellent in strength and is not easily broken by external force. On the other hand, the ultrafine fiber produced by the melt blow method is not used in the present invention because it has not undergone a drawing process different from the spinning process, has a low strength, and is easily broken by an external force.

  The separator (fiber sheet) of the present invention contains the above-mentioned adhesive fibers and ultrafine fibers, but preferably contains aramid fibers in addition to these fibers. This is because an aramid fiber is excellent in strength and is not easily broken by an external force, and a fiber sheet as a separator is also hardly broken by an external force. More specifically, para-aramid fibers made of copolyparaphenylene 3.4'oxydiphenylene terephthalamide or polyparaphenylene terephthalamide or meta-aramid fibers made of polymetaphenylene isophthalamide should be used. Can do. Among these, it is preferable to use an aramid fiber made of copolyparaphenylene, 3.4 'oxydiphenylene, and terephthalamide, which is excellent in resistance to electrolytic solution.

  The fiber diameter of the aramid fiber that can be used in the present invention is not particularly limited, but it can be a separator having a small average fiber diameter and a small average flow pore diameter in cooperation with the above-mentioned adhesive fiber and ultrafine fiber. The fiber diameter is preferably 13 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. In addition, although the minimum of a fiber diameter is not specifically limited, It is preferable that it is 6 micrometers or more from the point of raw material availability. In addition, the fiber length of the aramid fiber is not particularly limited, but the shorter the fiber length, the higher the degree of freedom of the aramid fiber, which can be a densely structured fiber sheet, and is superior in migration prevention, It is preferably 10 mm or less, and more preferably 6 mm or less. On the other hand, the lower limit of the fiber length is not particularly limited, but is preferably 1 mm or more. Moreover, the cross-sectional shape of the aramid fiber is not particularly limited, and may be circular or non-circular.

  Since the content of such aramid fibers is determined by the balance with other fibers such as the above-mentioned adhesive fibers and ultrafine fibers, it is not particularly limited, but the separator is not easily broken by an external force. (Fiber sheet) It is preferable that it is 5-30 mass% of the whole, and it is more preferable that it is 10-20 mass%.

  The separator of the present invention can contain polyamide thick fibers having a fiber diameter of more than 5 μm in addition to the fibers as described above. This polyamide-based thick fiber is also made of a polyamide-based resin other than nylon 6 homopolymer, like the adhesive fiber. For example, it may contain an aliphatic polyamide such as nylon 66, nylon 610, nylon 612, nylon 11 or nylon 12, or a polyamide thick fiber made of an aromatic polyamide resin having an aromatic dicarboxylic acid as a copolymerization component. it can.

  This polyamide thick fiber has a fiber diameter of more than 5 μm, and the upper limit thereof is preferably 15 μm or less so as not to impair the migration prevention property of the separator. Moreover, it is preferable that the fiber length of a polyamide-type thick fiber is 1-10 mm, and a cross-sectional shape may be circular or non-circular.

  The separator of the present invention can be composed of the polyamide-based fibers as described above. As a preferable polyamide-based fiber combination, adhesive fiber: extra fine fiber: aramid fiber: polyamide-based thick fiber = 30 to 70: 3 It is preferably 30: 5 to 30:10 to 50, and more preferably adhesive fiber: extra fine fiber: aramid fiber: polyamide thick fiber = 40 to 60: 5 to 20:10 to 20:20 to 40 .

  Although the fiber sheet which comprises the separator of this invention may have what kind of structure, it is preferable to have a nonwoven fabric structure which can be a fiber sheet with a smaller average flow hole diameter. Further, the fiber sheet of the present invention does not contain nylon 6 homopolymer so as to be excellent in electrolytic solution resistance. For example, when the adhesive fiber has a core-sheath shape and the nylon 6 homopolymer constitutes the core component, it does not correspond to the fiber sheet of the present invention because the nylon 6 homopolymer is included.

The fiber sheet as the separator of the present invention preferably has an average fiber diameter of 10 μm or less. By having such an average fiber diameter, migration of the active material can be effectively prevented, and thus a more preferable average fiber diameter is 8 μm or less. In addition, although the minimum of an average fiber diameter is not specifically limited, It is preferable that it is 1 micrometer or more. The average fiber diameter in the present invention refers to a value calculated by weighted average from the fiber diameter of each fiber and the abundance ratio of each fiber. For example, when a fiber having a fiber diameter of A (μm) is Xmass%, a fiber having a fiber diameter of B (μm) is Ymass%, and a fiber having a fiber diameter of C (μm) is Zmass%, The average fiber diameter (Av) of the separator made of these fibers can be calculated from the following equation.
Av = 1 / (X / 100A + Y / 100B + Z / 100C)

  The average flow pore size of the fiber sheet as the separator of the present invention is preferably 13 μm or less. This is because the migration of the active material can be effectively prevented by having such an average flow pore size, and the more preferable average flow pore size is 12 μm or less. The lower limit of the average flow pore size is not particularly limited, but is preferably 1 μm or more. The “average flow pore size” in the present invention refers to a value obtained by the bubble point method (ASTM-F316-86).

The basis weight and thickness of the fiber sheet which is the separator of the present invention are not particularly limited, but the basis weight is 20 to 150 g / m ^{2 so} that it is difficult to break by external force and the capacity of the battery can be increased. preferably, more preferably from 30 to 100 g / ^{m 2,} and even more preferably 40 and 80 g / ^{m 2.} Further, the thickness is preferably 0.05 to 0.3 mm, more preferably 0.08 to 0.2 mm, and still more preferably 0.1 to 0.15 mm.

  The separator of the present invention can be produced by forming a fiber sheet by a conventional method using at least the above-described adhesive fibers and ultrafine fibers. For example, when the fiber sheet is made of a suitable non-woven fabric, it can be produced as follows.

  First, an adhesive fiber and an ultrafine fiber which are nonwoven fabric constituent fibers are prepared. Preferably, an aramid fiber and / or a polyamide-based thick fiber is prepared in addition to the adhesive fiber and the ultrafine fiber.

  Next, the prepared polyamide fibers are appropriately blended, and a fiber web is formed by a dry method or a wet method. In the present invention, by using a short fiber length and having a dense structure, the migration-preventing property can be further improved. Therefore, it is easy to use a short fiber length, and the fibers are uniformly and densely dispersed. It is preferable to form the fiber web by a wet method that is easy to cause. As this suitable wet method, a conventionally known method can be adopted, for example, a horizontal long net method, an inclined wire type short net method, a circular net method, or a long net / circular net combination method can be adopted. it can. Two or more wet fiber webs may be combined. By making the sheets together in this way, it is possible to reduce the average flow pore size and improve the migration prevention property.

  Then, the fiber web can be bonded to obtain a nonwoven fabric, that is, a separator. In addition, as a joining method, it is preferable to join only by melt | fusion of the adhesive component of an adhesive fiber, without implementing an intertwining etc. This is because, when bonded in this manner, the fiber dispersion state of the fiber web is not impaired and the migration preventing property is excellent. The fiber web can be fused under pressure, can be carried out under no pressure, or can be carried out under pressure after heating.

  The separator produced in this way contains polyamide fibers and thus has excellent electrolyte retention. However, in order to further improve the electrolyte retention, various hydrophilization treatments can be performed. it can. Examples of these hydrophilic treatments include sulfonation treatment, fluorine gas treatment, vinyl monomer graft polymerization treatment, surfactant application treatment, discharge treatment, hydrophilic resin application treatment, and the like. Among these, discharge treatment (for example, corona discharge treatment, plasma treatment, glow discharge treatment, creeping discharge treatment, or electron beam treatment) is preferable because it is excellent in hydrophilic durability and hardly damages the polyamide fiber. is there. In particular, under atmospheric pressure in the air, a fiber sheet is placed between a pair of electrodes each carrying a dielectric so as to be in contact with both of these dielectrics, and an AC voltage is applied between these electrodes. In addition, the method of generating discharge in the fiber sheet internal gap can hydrophilize not only the outer side of the fiber sheet but also the fiber surface constituting the inner side of the fiber sheet, and has excellent electrolyte retention in the separator Therefore, it is preferable.

  A separator having an average fiber diameter of 10 μm or less can be manufactured by considering fiber blending (particularly the amount of ultrafine fibers), and a separator having an average flow pore diameter of 13 μm or less is as thin as a polyamide fiber. , Increasing the blending ratio of ultrafine fibers, making the fiber sheet into a nonwoven fabric structure, forming a fiber web by a wet method, combining the fiber webs formed by a wet method, It can manufacture by combining only by fusion | fusion, or combining these suitably.

  The battery of the present invention can be exactly the same as a conventional battery except that it includes the separator as described above. For example, a cylindrical nickel-cadmium battery has a structure in which an electrode plate group in which a nickel positive electrode and a cadmium negative electrode are spirally wound through the separator of the present invention as described above is inserted into a metal case. The case is sealed with an insulating gasket by a sealing plate provided with a safety valve. Note that the battery of the present invention does not need to be cylindrical, and may be rectangular or button-shaped. In the case of a square type, it has a laminated structure in which a separator is disposed between a positive electrode and a negative electrode. Moreover, a sealed type or an open type may be used.

  The battery of the present invention is, for example, a primary battery such as an alkaline manganese battery, a mercury battery, a silver oxide battery, or an air battery, or a nickel-cadmium battery, a silver-zinc battery, a silver-cadmium battery, a nickel-zinc battery, a nickel- It can be a secondary battery such as a hydrogen battery or a lead storage battery, preferably an alkaline secondary battery, particularly preferably a nickel-cadmium battery.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

  First, the following fibers were prepared.

(Core-sheath adhesive fiber A)
Nylon 66 is the core component (melting point: 255 ° C.), and nylon copolymer of nylon 6 and nylon 12 (molar ratio; (nylon 6): (nylon 12) = 35: 65) is the sheath component (melting point: 139 ° C. ) Core-sheath adhesive fiber A (fiber diameter: 14 μm, fiber length 5 mm, concentrically arranged, cross-sectional shape: circular, mass ratio; (core component): (sheath component) = 50: 50) .

(Core-sheath adhesive fiber B)
Nylon 6 is the core component (melting point: 221 ° C.), and nylon copolymer of nylon 6 and nylon 12 (molar ratio; (nylon 6): (nylon 12) = 35: 65) is the sheath component (melting point: 139 ° C. ) Core-sheath adhesive fiber B (fiber diameter: 17 μm, fiber length 5 mm, concentrically arranged, cross-sectional shape: circular, mass ratio; (core component): (sheath component) = 50: 50) .

(Extra fine fiber A)
Prepare sea island type fiber (fineness: 1.7 dtex, length: cut to 2 mm) obtained by the composite spinning method, in which 25 island components of nylon 66 are present in the sea component of polylactic acid. Then, this sea-island type fiber is immersed in a 10 mass% sodium hydroxide aqueous solution, and polylactic acid, which is a sea component, is extracted and removed by hydrolysis, then air-dried, and ultrafine fiber A made of nylon 66 (fiber diameter: 2 μm, The fiber length was 2 mm and the cross-sectional shape was circular.

(Extra fine fiber B)
Prepare sea island type fiber (fineness: 1.7 dtex, length: cut to 2 mm) obtained by the composite spinning method, in which 25 island components of nylon 12 are present in the sea component of polylactic acid. Then, this sea-island type fiber is immersed in a 10 mass% sodium hydroxide aqueous solution, and polylactic acid, which is a sea component, is extracted and removed by hydrolysis, and then air-dried to form ultrafine fibers B made of nylon 12 (fiber diameter: 2 μm, The fiber length was 2 mm and the cross-sectional shape was circular.

(Aramid fiber)
An aramid fiber (fiber diameter: 8 μm, fiber length: 6 mm, cross-sectional shape: circular) made of copolyparaphenylene, 3.4 ′ oxydiphenylene, terephthalamide was prepared.

(Polyamide thick fiber)
A polyamide-based thick fiber made of nylon 66 (fiber diameter: 9 μm, fiber length: 5 mm, cross-sectional shape: circular) was prepared.

(Examples 1 to 2 and Comparative Examples 1 to 3)
After forming a wet fiber web by the wet method (tilted wire type short net system) with the fiber composition shown in Table 1, the fiber web is supplied to a hot air through heat treatment machine set at a temperature of 155 ° C. and dried, and at the same time After the sheath component of the sheath-like adhesive fiber A or B was melted, it was continuously crimped by two press rolls (pressure: 5 N / mm) set at a temperature of 90 ° C. to produce a crimped wet nonwoven fabric. The thickness of this pressure-bonded wet nonwoven fabric was adjusted using a two-roll calender to produce a thickness-adjusted pressure-bonded wet nonwoven fabric.

Next, in a state where the thickness-adjusted pressure-bonded wet nonwoven fabric is sandwiched between flat electrodes carrying silicone rubber (dielectric is in contact with the thickness-adjusted pressure-bonded wet nonwoven fabric), air (humidity: 60RH) %) In the presence of AC voltage (voltage: 24 kVp, output: 2.8 kW, output per unit area: 1.83 W / cm ² , frequency: 25 KHz, waveform: sine wave), Discharge was generated inside the thickness-adjusted pressure-bonded wet nonwoven fabric, and the thickness-adjusted pressure-bonded wet nonwoven fabric was hydrophilized to produce a separator. Various physical properties of these separators are as shown in Table 2.

(Measurement of battery life)
Nickel positive electrode (33 mm wide, 182 mm long) filled with a positive electrode active material mainly composed of nickel hydroxide on a nickel sintered substrate, and cadmium filled with a negative electrode active material mainly composed of cadmium hydroxide on a nickel sintered substrate A negative electrode (33 mm width, 247 mm length) was prepared. Next, each of the separators cut to a width of 33 mm and a length of 410 mm was sandwiched between the positive electrode and the negative electrode and wound in a spiral shape to create an SC-type electrode group. This electrode group is housed in an outer can, and 5N potassium hydroxide and 1N lithium hydroxide are injected into the outer can as an electrolyte, and sealed to create a cylindrical nickel-cadmium battery (battery capacity: 2000 mAh). did.

  After activating these cylindrical nickel-cadmium batteries, charging at 0.2C for 6 hours at room temperature and discharging to 0.2V at 0.2C to a final voltage of 0.8 V was repeated as one cycle, and 80% of the initial capacity The number of cycles until the capacity was reduced was determined. These results are shown in Table 2. In Table 2, the ratio was expressed as a ratio when the number of cycles in Comparative Example 3 was used as a reference (100). As is clear from this result, the battery using the separator of the present invention has a long battery life. This is because the nylon 6 homopolymer is not included, so that the electrolytic solution resistance is excellent, and because the ultrafine fiber is included, the average fiber diameter and the average flow pore size are small, and migration does not occur. I was able to predict it.

(Measurement of defective rate during battery manufacturing)
In the same manner as described above (measurement of battery life), when manufacturing a cylindrical nickel-cadmium battery, the defect rate was defined as the percentage at which the battery was short-circuited due to the burr of the electrode and could not be manufactured. These results are shown in Table 2. As is clear from this result, the battery using the separator of the present invention could be manufactured with a high yield. This could be expected to be due to the inclusion of aramid fibers.

Claims (9)

(1) a polyamide-based adhesive fiber having a polyamide-based resin as an adhesive component; and (2) a fiber sheet comprising a polyamide-based resin and including a polyamide-based ultrafine fiber having a fiber diameter of 5 μm or less. The separator for alkaline secondary batteries characterized by not containing a polymer. The adhesive component of the polyamide-based adhesive fiber is made of a nylon copolymer having at least one component selected from nylon 610, nylon 612, nylon 11, and nylon 12 as a copolymer component. The separator for alkaline secondary batteries according to 1. The separator for an alkaline secondary battery according to claim 1 or 2, wherein the polyamide ultrafine fiber is produced by removing a sea component of a sea-island fiber having a polyamide resin as an island component. . Furthermore, it consists of a fiber sheet containing an aramid fiber, The separator for alkaline secondary batteries in any one of Claims 1-3 characterized by the above-mentioned. The separator for an alkaline secondary battery according to any one of claims 1 to 4, further comprising a fiber sheet containing polyamide-based thick fibers having a fiber diameter exceeding 5 µm. The separator for an alkaline secondary battery according to any one of claims 1 to 5, wherein the separator is made of a nonwoven fabric bonded only by fusing of an adhesive component of a polyamide-based adhesive fiber. The separator for an alkaline secondary battery according to any one of claims 1 to 6, wherein an average fiber diameter of the fiber sheet is 10 µm or less. The separator for an alkaline secondary battery according to any one of claims 1 to 7, wherein an average flow pore size of the fiber sheet is 13 µm or less. Alkaline secondary battery characterized in that it comprises a separator for alkaline secondary battery according to any one of claims 1 to 8.