JP2009218238A - Separator for electrochemical element and method of manufacturing the same, and aluminum electrolytic capacitor or electric double layer capacitor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator which has low possibility of short-circuiting even when containing fully aromatic fiber or used as a separator for a winding type electrochemical element, and to provide a method of manufacturing the same. <P>SOLUTION: The separator for electrochemical element is made of non-woven fabric having a three-layer structure containing fully aromatic fiber, and any surface layer of the non-woven fabric contains ≥90% of mass ratio occupied by the fully aromatic fiber. The separator is manufactured by forming the non-woven fabric through a heat treatment after forming a laminate web having a third web different from first and second slurries laminated between first and second webs containing ≥90% by mass of fully aromatic fiber for all materials. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a separator for an electrochemical element, a method for producing the same, and an aluminum electrolytic capacitor or an electric double layer capacitor using the same. In particular, the present invention relates to a separator that can be suitably used for a wound type electrochemical device, a method for producing the separator, and a wound type aluminum electrolytic capacitor or a wound type electric double layer capacitor using the separator.

  Electric double layer capacitors have a relatively large capacity, and have a long service life and quick charge / discharge. Therefore, in addition to conventional applications such as power supply smoothing and noise absorption, personal computer memory backup power supplies and secondary power supplies In recent years, it has been used as a secondary battery for electric vehicles.

  This electric double layer capacitor has a structure in which a pair of electrodes are immersed in an organic electrolyte. When a voltage is applied to the electric double layer capacitor, ions having the opposite sign to the electrode are distributed in the vicinity of the electrode to form an ion layer, while charges having the opposite sign to the ion are accumulated inside the electrode. Next, when a load is connected between the electrodes, the charges in the electrodes are discharged, and at the same time, ions distributed in the vicinity of the electrodes are separated from the vicinity of the electrodes and return to the neutralized state.

  In such an electric double layer capacitor, if a pair of electrodes come into contact with each other, it becomes difficult to form an ion layer in the vicinity of the electrodes. Therefore, a separator is usually disposed between the pair of electrodes. .

As this separator, electrolytic paper having a two-layer structure made of cellulose pulp is known. However, this electrolytic paper may not provide sufficient short-circuit prevention. In this case, if two or more sheets of this electrolytic paper are used, the above problems can be reduced. However, since there is a problem that the internal resistance is increased, the applicant of the present application stated that “two or more fiber layers are used. A laminated fiber sheet having, as the fiber layer, a porous fiber layer in which the number of through-holes having a major axis of 0.3 mm or more per 100 cm ² is 200 or more, and a through-hole having a major axis of 0.3 mm or more, A separator for an electric double layer capacitor characterized in that it includes a small pore fiber layer having a number per 100 cm ^{2 of} less than 200 ”(Patent Document 1).

  In addition, “a separator for an electrochemical element, characterized in that it comprises a wet nonwoven fabric having 10% or more of wholly aromatic polyester fibers on the surface and 10% or more of wholly aromatic polyamide fibers on the opposite surface.” (Patent Document 2), “Separator for electrochemical elements, characterized in that the heat-resistant fibrillated fibers are unevenly distributed and the content of the fibers is one surface> the opposite surface” (Patent Document 3), “ A separator for an electrochemical element in which heat-resistant fibrillated fibers are unevenly distributed and the content of the fibers is one surface> the opposite surface, and the Gurley air permeability is 0.5 s / 100 ml to 50.0 s / 100 ml Electrochemical element separator characterized by being "(Patent Document 4)," Electrochemical element separator comprising a porous sheet having two layers, wherein the first layer has a fibrillation heat resistance. For electrochemical elements, the fiber content is greater than that of the second layer, and cellulose is contained in any one of the layers, and the cellulose content is 7.5 to 67% by mass relative to the entire porous sheet. A separator for an electrochemical element that can also be used for an electric double layer capacitor has been proposed, such as “Separator” (Patent Document 5).

JP 2002-313680 A (Claim 1) JP 2003-59766 A (Claim 1) JP 2004-335281 A (Claim 1) Japanese Patent Laying-Open No. 2005-63684 (Claim 1) JP 2007-67155 A (Claim 1)

  The electric double layer capacitor separators of Patent Documents 1 to 5 as described above are less likely to cause a short circuit, can reduce internal resistance, heat resistance, electrolyte retention, electrode resistance, self-discharge characteristics, characteristic retention, And / or have a long lifetime. However, when an electric double layer capacitor is manufactured using such an electric double layer capacitor separator, the electrode surface is damaged, and as a result of the active material falling off, a short circuit may occur. Such a phenomenon may occur when the separator for an electric double layer capacitor as described above contains a wholly aromatic fiber such as a wholly aromatic polyamide fiber, or when the separator for an electric double layer capacitor is used as a wound type electric double layer capacitor. It was remarkable when used.

  In addition to the electric double layer capacitor as described above, the occurrence of defective products due to a short circuit is the same when used as an electrolytic capacitor such as an aluminum electrolytic capacitor or a separator of an electrochemical element such as a lithium ion secondary battery. It was a phenomenon that occurred.

  The present invention has been made in order to solve the above-described problems, and even if it includes a wholly aromatic fiber or is used as a separator for a wound-type electrochemical element, it is possible to generate a short circuit. It is an object of the present invention to provide a separator having low properties, a manufacturing method thereof, and an aluminum electrolytic capacitor or an electric double layer capacitor using the same.

  The invention according to claim 1 of the present invention is “a separator for an electrochemical element made of a nonwoven fabric having a three-layer structure containing wholly aromatic fibers, and the mass occupied by the wholly aromatic fibers in any surface layer of the nonwoven fabric. A separator for electrochemical devices, wherein the ratio is 90% or more of the mass of each surface layer. "

  The invention according to claim 2 of the present invention is “the separator for an electrochemical element according to claim 1, characterized by including a thermoplastic resin that bonds the wholly aromatic fibers to the intermediate layer of the nonwoven fabric”.

  The invention according to claim 3 of the present invention is “the separator for an electrochemical element according to claim 2, wherein the amount of the thermoplastic resin in the intermediate layer of the nonwoven fabric is 20 to 50% of the mass of the intermediate layer. Is.

  The invention according to claim 4 of the present invention is as follows: “(1) First slurry containing 90% by mass or more of all aromatic fibers, (2) First slurry containing 90% by mass or more of all aromatic fibers” A slurry preparation step of preparing a second slurry that is the same as or different from (3), and a third slurry that is different from the first slurry and the second slurry, a first web derived from the first slurry by rolling up each of the slurries, After forming the second web derived from the second slurry and the third web derived from the third slurry, respectively, the third web is laminated so that the third web is positioned between the first web and the second web. A separator for an electrochemical element, comprising: a laminated web forming step for forming a laminated web having a layer structure; and a non-woven fabric forming step in which the laminated web is made into a nonwoven fabric by heat treatment. It is a production method. ".

  The invention according to claim 5 of the present invention is that “the thermoplastic resin fiber is included in the third slurry in the slurry preparation step and the thermoplastic resin is formed by the heat treatment in the nonwoven fabric forming step so that the wholly aromatic is formed by the thermoplastic resin. The manufacturing method of the separator for electrochemical elements according to claim 4, wherein fibers are bonded.

  The invention according to claim 6 of the present invention is as follows: “The heat treatment in the nonwoven fabric forming step irradiates the laminated web with infrared rays under no pressure to melt the thermoplastic resin fibers, and solidifies the molten thermoplastic resin under no pressure. The manufacturing method of the separator for electrochemical devices according to claim 5, characterized in that the treatment is performed.

  The invention according to claim 7 of the present invention is “a wound type electric double layer capacitor using the separator for an electrochemical element according to any one of claims 1 to 3”.

  The invention according to claim 8 of the present invention is “a wound aluminum electrolytic capacitor using the separator for electrochemical elements according to any one of claims 1 to 3”.

  In the invention according to claim 1 of the present invention, in any surface layer of the nonwoven fabric, the mass ratio of the total aromatic fibers is 90% or more of the mass of each surface layer, and the binding force between the total aromatic fibers is weak. Therefore, even when the electrochemical device is manufactured, even if it rubs against the electrode, the surface of the electrode is damaged and the total aromatic fiber is removed before the active material is removed. , Active material can be prevented from falling off. As a result, an electrochemical element having a low possibility of causing a short circuit can be manufactured.

  Since the invention concerning Claim 2 of this invention contains the thermoplastic resin which adhere | attaches a fully aromatic fiber in the intermediate | middle layer of a nonwoven fabric, it is a separator which has intensity | strength required in order to manufacture an electrochemical element.

  The invention according to claim 3 of the present invention is a separator having sufficient strength for manufacturing an electrochemical element because the amount of the thermoplastic resin in the intermediate layer of the nonwoven fabric is 20 to 50% of the mass of the intermediate layer. .

  The invention according to claim 4 of the present invention can manufacture the separator for an electrochemical element according to claim 1. That is, in any surface layer, a separator for an electrochemical element made of a nonwoven fabric having a three-layer structure including wholly aromatic fibers, in which the mass ratio occupied by wholly aromatic fibers is 90% or more of the mass of each surface layer is manufactured. can do.

  The invention according to claim 5 of the present invention can manufacture the separator for an electrochemical element according to claim 2. That is, a separator for an electrochemical element including a thermoplastic resin that adheres a wholly aromatic fiber to the intermediate layer can be manufactured.

  In the invention according to claim 6 of the present invention, the thermoplastic resin fibers constituting the third web can be irradiated with infrared rays and melted uniformly, so that the strength of the separator for electrochemical elements can be improved. it can. Moreover, since the molten thermoplastic resin is solidified under no pressure and it is difficult to form a film, it is possible to manufacture a separator that can manufacture an electrochemical element with low internal resistance without impairing ion permeability.

  The invention according to claim 7 of the present invention uses the separator according to any of the above, and even if the electric double layer capacitor is wound at the time of manufacture, it is possible to suppress the falling off of the active material, so that a short circuit hardly occurs. This is a wound type electric double layer capacitor.

  The invention according to claim 8 of the present invention uses the separator according to any one of the above, and can suppress polishing of the aluminum foil even when the aluminum electrolytic capacitor is wound at the time of manufacture. It is an electrolytic capacitor.

  The nonwoven fabric constituting the separator for electrochemical elements of the present invention (hereinafter simply referred to as “separator”) contains wholly aromatic fibers. As described above, the separator of the present invention includes wholly aromatic fibers, and these wholly aromatic fibers are generally excellent in heat resistance, and therefore can be used as separators for electrochemical devices for various purposes.

  This wholly aromatic fiber means one in which the main chain of the resin constituting the fiber is composed of repeating units of an aromatic ring. Examples of such wholly aromatic fibers include para-type wholly aromatic polyamide fibers such as copolyparaphenylene 3.4'oxydiphenylene terephthalamide, polyparaphenylene terephthalamide, and metametaphenylene isophthalamide. Examples include fully aromatic polyamide fibers, polybenzoxazole fibers, polyamideimide fibers, aromatic polyetheramide fibers, polybenzimidazole fibers, and liquid crystal polyester fibers. These wholly aromatic fibers have excellent heat resistance and at the same time have rigidity, and tend to damage the electrode by friction and cause a short circuit when in contact with the electrode. By setting it as a structure, the characteristic of a wholly aromatic fiber can be utilized, suppressing a short circuit. Among these wholly aromatic fibers, para- or meta-based wholly aromatic polyamide fibers are preferably included so as to be excellent in electrical insulation performance and heat resistance.

  The preferred wholly aromatic polyamide fiber preferably occupies 50% by mass or more, more preferably 70% by mass or more of the wholly aromatic fiber so as to be excellent in electrical insulation performance and heat resistance. 90 mass% or more is more preferable, and 100 mass% is most preferable.

  Such a fully aromatic fiber is preferably in a fibrillated state, in which a single fiber is split and branched by mechanical shearing force and the like, and innumerable fine fibers are generated. This is because such a fillable and fine fiber reduces the frictional force of the wholly aromatic fiber with the electrode and makes it difficult to damage the electrode. Therefore, it is preferable that 50% by mass or more of the total aromatic fiber is a fibrillated wholly aromatic fiber, 70% by mass or more is more preferably a fibrillated wholly aromatic fiber, and 90% by mass or more of the total fibrillated total fiber. More preferably, it is an aromatic fiber, and most preferably 100% by mass is a fibrillated wholly aromatic fiber. The separator of the present invention is composed of a nonwoven fabric having a three-layer structure as will be described later. However, in both surface layers in contact with the electrodes, the total fragrance in which 90 mass% or more of the total aromatic fibers are fibrillated so that the above-described action can be easily performed. Preferably, it is a group aromatic fiber, more preferably 100% by mass fibrillated wholly aromatic fiber.

  The freeness of such a suitable fibrillated wholly aromatic fiber is preferably 300 ml CSF or less, preferably 200 ml CSF or less, so as to be a non-woven fabric (separator) having a dense structure that hardly damages the electrode. More preferably, it is 115 mlCSF or less. In addition, although the minimum of the freeness is not particularly limited, it is preferably 50 mlCSF or more so as to be excellent in productivity. This “freeness” means a value measured by a JIS P8121 Canadian standard freeness tester.

  In the present invention, non-fibrillated wholly aromatic fibers can be included in addition to fibrillated wholly aromatic fibers. By including such non-fibrillated wholly aromatic fibers, it becomes easy to maintain the thickness of the nonwoven fabric (separator) under pressure. As a result, a short circuit may be effectively prevented. In addition, as mentioned above, it is preferable that the fully aromatic fiber on both surfaces is fibrillated so that the electrode is not easily damaged by the fully aromatic fiber, so that the non-fibrillated wholly aromatic fiber exists only in the intermediate layer. It is preferable.

  The fineness and fiber length of such non-fibrillated wholly aromatic fibers are not particularly limited, but if the fineness of non-fibrillated wholly aromatic fibers is large compared to the thickness of the nonwoven fabric, Even if it exists only, the fineness is preferably 1 dtex or less, more preferably 0.8 dtex or less, because the electrode may be damaged by being exposed to the surface of the nonwoven fabric during pressurization. The lower limit of the fineness is not particularly limited, but about 0.01 dtex is realistic. On the other hand, the fiber length is not particularly limited, but it is preferably 0.1 to 20 mm suitable for the wet method because the non-woven fabric is preferably manufactured by a wet method so as to be a non-woven fabric having a dense structure. Is preferred.

  Such fibrillated or non-fibrillated wholly aromatic fibers are preferably contained in a non-woven fabric (separator) in an amount of 40 mass% or more, and 50 mass% or more so as to be excellent in electrical insulation performance and heat resistance. More preferably, it is more preferably 60 mass% or more. On the other hand, since it is preferable to include a thermoplastic resin that adheres wholly aromatic fibers so that the form of the nonwoven fabric (separator) can be maintained, it is preferably 95 mass% or less. The wholly aromatic fibers may contain two or more kinds of wholly aromatic fibers that differ in terms of resin composition, presence / absence of fibrils, freeness, fineness, and / or fiber length. When two or more kinds of wholly aromatic fibers are included, the total mass is preferably within the above range.

  The nonwoven fabric that is the separator of the present invention preferably contains a thermoplastic resin for adhering the wholly aromatic fibers so that the shape of the nonwoven fabric can be maintained in addition to the aforementioned wholly aromatic fibers. The thermoplastic resin may be in a fiber form, or may be in a non-fiber state in which the thermoplastic resin does not continuously extend in a fibrous form and is aggregated among all aromatic fibers.

  This thermoplastic resin does not damage the fully aromatic fiber and can maintain the form of the nonwoven fabric (separator), so that the melting point is lower than the carbonization temperature of the fully aromatic fiber (preferably a melting point lower by 20 ° C. or more, more preferably 30). Preferably, it has a melting point that is lower than ° C. Moreover, it is preferable that it has melting | fusing point of 200 degreeC or more (preferably 210 degreeC or more, more preferably 220 degreeC or more) so that it may be excellent in heat resistance. Such a thermoplastic resin varies depending on the type of wholly aromatic fiber, and is not particularly limited. Examples of preferable thermoplastic resins having a melting point of 200 ° C. or higher include polyester resins, polyamide resins, and polyphenylene sulfide resins. , Polyvinyl chloride resin, polyurethane resin and the like. Among these, a polyester resin having a high melting point is preferable.

  “Melting point” in the present invention refers to a temperature obtained from a differential thermal analysis curve (DTA curve) obtained by differential thermal analysis specified in JIS K 7121, and “carbonization temperature” refers to heat specified in JIS K 7120. The temperature obtained by gravimetric measurement.

  Such a thermoplastic resin preferably accounts for 5 mass% or more of the nonwoven fabric (separator) so that the mechanical strength of the nonwoven fabric (separator) is excellent. On the other hand, it is preferable to occupy 60 mass% or less, more preferably 50 mass% or less, and even more preferably 40 mass% or less in relation to the total aromatic fiber. The thermoplastic resin may contain two or more types of thermoplastic resins that differ in terms of the resin composition. When two or more types of thermoplastic resins are included, the total mass is preferably within the above range.

  The nonwoven fabric constituting the separator of the present invention preferably contains wholly aromatic fibers and a thermoplastic resin, but has a three-layer structure. Thus, by having a three-layer structure, it is possible to have sufficient strength for manufacturing an electrochemical element without damaging the electrode. That is, in any surface layer of the nonwoven fabric, the mass ratio occupied by the total aromatic fibers is 90% or more of the mass of each surface layer, and the bonding force between the total aromatic fibers is weak, so that an electrochemical element is manufactured. In this case, even if the electrode is rubbed with the electrode, the frictional force can be relaxed by dropping off the fully aromatic fiber, so that damage to the electrode can be suppressed. As a result, an electrochemical element having a low possibility of causing a short circuit can be manufactured. In addition, when the ratio of the total aromatic fibers in both surface layers is increased in this way, it tends to be difficult to maintain the form of the nonwoven fabric (separator). Strength can be imparted and the nonwoven fabric can be maintained.

  Thus, in the present invention, in any surface layer of the nonwoven fabric, the mass ratio of the total aromatic fibers is 90% or more of the mass of each surface layer, but the total aromatic fibers in one surface layer The mass ratio and the mass ratio of all aromatic fibers in the other surface layer do not need to be the same, and may be different. Similarly, the wholly aromatic fibers of one surface layer and the wholly aromatic fibers of the other surface layer may differ in terms of resin composition, presence or absence of fibrils, drainage, fineness, and / or fiber length. good. In addition, as described above, it is preferable that any surface layer includes fibrillated wholly aromatic fibers, and 90% by mass or more of wholly aromatic fibers are fibrillated wholly aromatic fibers. Preferably, 100% by mass is a fibrillated wholly aromatic fiber. The surface layer can contain the thermoplastic resin as described above in addition to wholly aromatic fibers.

  The intermediate layer preferably contains a thermoplastic resin for adhering the wholly aromatic fibers as described above so that the form of the nonwoven fabric (separator) can be maintained with respect to both the surface layers. More specifically, the amount of the thermoplastic resin in the intermediate layer is preferably 20 to 50%, more preferably 20 to 40% of the mass of the intermediate layer. This is because if it is less than 20%, it tends to be difficult to maintain the form of the nonwoven fabric (separator), while if it exceeds 50%, the heat resistance may be impaired.

  Such an intermediate layer preferably contains the same wholly aromatic fiber as described above in addition to the thermoplastic resin so as not to impair the heat resistance of the nonwoven fabric (separator). Such fully aromatic fibers are preferably contained in an amount of 50 to 80%, more preferably 60 to 80% of the mass of the intermediate layer. The wholly aromatic fiber contained in the intermediate layer may differ from the wholly aromatic fiber contained in the surface layer in terms of resin composition, presence / absence of fibrils, freeness, fineness, and / or fiber length. In addition, as described above, as the wholly aromatic fiber constituting the intermediate layer, when the wholly aromatic fiber having no fillable is included, it becomes easy to maintain the thickness of the nonwoven fabric (separator) under pressure, and the short circuit is effectively performed. Sometimes it can be prevented.

  Although the nonwoven fabric (separator) of the present invention has a three-layer structure, the mass ratio is not particularly limited, but the nonwoven fabric form can be maintained by the intermediate layer, and the intermediate layer is difficult to be exposed. Since a certain thickness is necessary so that the electrode is not easily damaged, (mass of one surface): (mass of intermediate layer): (mass of other surface) = 10-20: 60-80: 10-20 It is preferable that (mass of one surface): (mass of intermediate layer): (mass of other surface) = 15-20: 60-70: 15-20.

  The “surface layer” in the present invention means a layer including the surface of the nonwoven fabric, and means a layer that peels without fluffing by adhering a cloth tape or the like and pulling the cloth tape. On the other hand, the “intermediate layer” means a layer existing between both surface layers, for example, a layer obtained by removing both surface layers with a cloth tape as described above. Thus, the nonwoven fabric (separator) of the present invention has two surface layers and one intermediate layer, and even if the intermediate layer can be peeled off without further fluffing, it is exposed on the surface of the nonwoven fabric. Therefore, the intermediate layer is regarded as one layer.

Although the fabric weight of the nonwoven fabric (separator) of this invention is not specifically limited, It is preferable that it is 10 g / m < ² > or more, and it is 14 g / m < ² > or more so that the intensity | strength of a nonwoven fabric (separator) is excellent. Is more preferable. On the other hand, it is preferably 30 g / m ² or less, more preferably 28 g / m ² or less so that the nonwoven fabric (separator) does not become unnecessarily thick. Further, the thickness is preferably 15 μm or more, more preferably 20 μm or more so that the strength of the nonwoven fabric (separator) is excellent. On the other hand, it is preferably 85 μm or less and more preferably 60 μm or less so that the internal resistance can be lowered. Furthermore, it is preferred apparent density is 0.30~0.70g / cm ^3, and more preferably 0.35~0.50g / cm ^3. The “weight per unit area” refers to the basis weight obtained based on the method specified in JIS P 8124 (paper and paperboard—basis weight measurement method), and the “thickness” is a measured value according to the method specified in JIS B 7502, that is, The value measured with an outer micrometer at 5N load is the apparent density, and the apparent density is the quotient obtained by dividing the basis weight (unit: g / cm ² ) by the thickness (cm).

  The separator (nonwoven fabric) of the present invention includes, for example, (1) a first slurry containing 90% by mass or more of all aromatic fibers, and (2) a first slurry containing 90% by mass or more of all aromatic fibers. A slurry preparation step of preparing the same or different second slurry, and (3) a third slurry different from the first slurry and the second slurry, the first web derived from the first slurry, the first slurry, After forming the second web derived from the second slurry and the third web derived from the third slurry, the three webs are laminated so that the third web is positioned between the first web and the second web. It can be produced by a laminated web forming step for forming a laminated web having a structure and a non-woven fabric forming step in which the laminated web is made into a nonwoven fabric by heat treatment. According to this manufacturing method, in any surface layer, a separator made of a nonwoven fabric having a three-layer structure in which the mass ratio of the total aromatic fibers is 90% or more of the mass of each surface layer can be manufactured. A separator that can produce an electrochemical element that is less likely to be generated can be produced.

  More specifically, in the slurry preparation step, first, a first slurry, a second slurry, and a third slurry are prepared. Since the first slurry constitutes one surface layer of the separator (nonwoven fabric), it contains 90% by mass or more of the total aromatic fiber as described above. As described above, the wholly aromatic fibers constituting the surface layer are preferably wholly aromatic polyamide fibers, and preferably have fibrils. In addition, although 90 mass% or more of all materials consist of a fully aromatic fiber, the 1st slurry can contain the thermoplastic resin which can adhere a fully aromatic fiber other than a fully aromatic fiber. This thermoplastic resin may be in the form of powder or fiber, but if it is in fiber form, the fibers can be firmly bonded by being entangled with each other at the web forming stage and bonded in a state where there are many contacts. Moreover, since it is easy to handle, it is preferably in a fiber form.

  Since the second slurry also constitutes the other surface layer of the separator (nonwoven fabric), it contains 90 mass% or more of the total aromatic fibers as described above. Similar to the first slurry, the wholly aromatic fiber is preferably wholly aromatic polyamide fiber, and preferably has fibrils. This second slurry also comprises 90% by mass or more of all materials consisting of wholly aromatic fibers, but may contain a powder form and / or fiber form of a thermoplastic resin capable of bonding the wholly aromatic fibers in addition to the wholly aromatic fibers. it can. This thermoplastic resin is also preferably in fiber form. The second slurry may be the same as or different from the first slurry. Same as the first slurry is the total amount of aromatic fibers, resin composition, presence or absence of fibrils, freeness, fineness, and / or fiber length, the amount of materials other than total aromatic fibers, composition, physical properties, etc. , Means that they are blended so as to completely match, and different from the first slurry means that they are not the same.

  Since the third slurry constitutes an intermediate layer of a separator (nonwoven fabric), it differs from the first slurry and the second slurry. In particular, it is preferable to include a thermoplastic resin (particularly, a thermoplastic resin fiber) so that the form of the separator (nonwoven fabric) can be maintained. This thermoplastic resin preferably contains 20 to 50% of the total material. The thermoplastic resin preferably has a melting point lower than the carbonization temperature of the wholly aromatic fiber (preferably lower than 20 ° C, more preferably lower than 30 ° C) so that the fully aromatic fiber can be bonded. It preferably consists of a polyester resin. In addition, it is preferable that materials other than a thermoplastic resin are wholly aromatic fibers.

  The fineness of this suitable fiber-shaped thermoplastic resin (thermoplastic resin fiber) is not particularly limited, but is preferably 0.45 dtex or less. This is because the thermoplastic resin fibers can be uniformly dispersed. Moreover, when the fiber form of a thermoplastic resin fiber lose | disappears, it is because the space | gap formed by it can be disperse | distributed uniformly. The lower limit of the fineness of the thermoplastic resin fiber is not particularly limited, but is preferably about 0.01 dtex.

  Next, each slurry is rolled up to form a first web derived from the first slurry, a second web derived from the second slurry, and a third web derived from the third slurry, respectively. Lamination is performed such that the third web is positioned between the two webs to form a laminated web having a three-layer structure. It should be noted that each slurry can be rolled up by using a conventionally known net. For example, each slurry can be rolled up by a circular net, a short net, and a long net. In addition, since the orientation of the fiber formed by the circular net is different from the orientation of the fiber formed by the short or long net, it is preferable to form the web by combining the circular net and the short or long net. This is because by combining in this way, the hole diameter becomes smaller, the texture is improved, and the electrical insulation is improved. More specifically, the first slurry and the second slurry are rolled up by a circular mesh, and the third slurry is rolled up by a short mesh to form a laminated web, or the first slurry and the second slurry are rolled by a circular mesh. It is preferable that the third slurry is rolled up with a long mesh and a laminated web is formed.

  Next, the laminated web is heat treated to form a nonwoven fabric. This heat treatment is dried at a minimum so as to remove moisture contained in the laminated web. When the laminated web (particularly the third web) contains a thermoplastic resin (particularly thermoplastic resin fiber), the adhesiveness of the thermoplastic resin (particularly thermoplastic resin fiber) is expressed by heat treatment, It is preferable to increase the form stability of the nonwoven fabric by bonding all aromatic fibers. Such drying or bonding with a thermoplastic resin is, for example, a method of irradiating infrared rays, a method using an oven, a method of penetrating hot air, a method of irradiating ultrasonic waves, a method of irradiating a laser, or a method using a thermal calendar. It can be carried out by a method using a flat plate press apparatus.

  In particular, when the heat treatment is a treatment for irradiating the laminated web with infrared rays under no pressure to melt the thermoplastic resin fibers and solidifying the molten thermoplastic resin under no pressure, the separator can be uniformly melted. The strength of can be improved. Moreover, since it is difficult to form a film by solidifying the molten thermoplastic resin under no pressure, a separator capable of producing an electrochemical element having a low internal resistance without impairing ion permeability can be produced.

  More specifically, when infrared rays (in particular, far infrared rays having a wavelength of 5.6 to 1000 μm are preferable) are irradiated, the thermoplastic resin fibers constituting the third web located inside the laminated web can be heated uniformly. As a result, the thermoplastic resin fibers melt instantly. And this molten thermoplastic resin coagulates between fully aromatic fibers, such as a crossing point of fully aromatic fibers, and adheres fully aromatic fibers. This infrared irradiation is performed at a temperature that melts the thermoplastic resin fiber but does not carbonize the wholly aromatic fiber. That is, the irradiation is performed so that the temperature is equal to or higher than the melting point of the thermoplastic resin fiber and lower than the carbonization temperature of the wholly aromatic fiber. Such conditions are not particularly limited because they vary depending on the types of thermoplastic resin fibers and wholly aromatic fibers. The infrared irradiation conditions can be appropriately set by repeating the experiment. If pressure is applied to the thermoplastic resin in which the thermoplastic resin fibers are melted, the thermoplastic resin becomes a film, which fills the gaps and tends to impair ion permeability. Irradiate. Infrared rays generate heat by activating the molecular motion (vibration, amplitude) of the thermoplastic resin fiber, but melt and blow hot air so that the thermoplastic resin fiber melts more efficiently. Is preferred. The temperature of the hot air is not particularly limited because it varies depending on the resin composition of the thermoplastic resin fiber. For example, when the thermoplastic resin fiber is made of a suitable polyester fiber, it is preferably 260 ° C. or higher. When hot air is blown or circulated in this way, the molten thermoplastic resin is likely to aggregate at the intersection of all aromatic fibers due to the circulation of the hot air, and the strength of the separator is improved. Thus, “under no pressure” in the present invention means that no pressure is applied with a solid such as a roll, and in the case of a gas such as hot air, no pressure is considered.

  In order to solidify the molten thermoplastic resin and bond the wholly aromatic fibers, it may be left in a gas having a temperature of less than 200 ° C. (for example, at room temperature). You may spray or circulate the gas below ° C. Even if pressure is applied during the solidification of the thermoplastic resin, the thermoplastic resin becomes a film, fills the voids, and tends to impair ion permeability. Therefore, it is preferable to solidify under no pressure.

  Such heat treatment need not be performed once, and may be performed twice or more. For example, after the molten thermoplastic resin is solidified under no pressure, the heat treatment can be performed again to crystallize the thermoplastic resin, thereby improving the heat resistance. In particular, when thermoplastic resin fibers are melted by the action of infrared rays, they are melted instantaneously, and when this molten thermoplastic resin is quenched, it solidifies in an amorphous state, resulting in a decrease in heat resistance. However, heat treatment for crystallization can be performed to increase heat resistance. Moreover, after drying a laminated web with a dryer, infrared rays can be irradiated as described above, and the molten thermoplastic resin can be solidified and bonded without pressure.

  The heat treatment for crystallization is not particularly limited as long as it is a heat treatment for crystallizing the thermoplastic resin. For example, it can be performed by an oven method, a method of blowing hot air, or a method of circulating hot air. The heat treatment temperature is not particularly limited as long as it is a heat treatment that causes the thermoplastic resin to crystallize, and varies depending on the composition of the thermoplastic resin. For example, when the thermoplastic resin is made of a suitable polyester, the temperature is preferably 130 to 230 ° C. In the case of polyester, crystallization tends to be insufficient at a temperature lower than 130 ° C., and when it exceeds 230 ° C., it approaches the extrapolated dissolution start temperature (the temperature at which the resin starts to melt), and the shape of the polyester begins to change. More preferably, it is 150-220 degreeC. Further, the heat treatment for crystallization is preferably performed under no pressure so that the thermoplastic resin hardly forms a film. Note that “crystallize” means that a crystallization peak is not drawn on a DSC curve drawn by differential scanning calorimetry of the manufactured separator.

  In addition, such crystallization adopts a method using an oven, a method of blowing hot air, or a method of circulating hot air as a heat treatment for forming a nonwoven fabric, and is performed for a time sufficient for the thermoplastic resin to crystallize. Can also be implemented.

  After the heat treatment as described above, the thickness can be adjusted by performing a calendar process, but it is preferable not to perform the process in the present invention. This is because when the calender treatment is performed and the thickness is adjusted, the surface of the nonwoven fabric becomes smooth, the frictional force with the electrode becomes high, the electrode is damaged, and the electrochemical element tends to be short-circuited.

  The electrochemical device of the present invention uses the separator of the present invention as described above. Since the separator of the present invention can produce an electrochemical device without damaging the electrodes, the electrochemical device of the present invention is Short circuit is unlikely to occur. In particular, when a wound electrochemical device is manufactured, a gap is easily generated between the separator and the electrode, and the electrode is easily damaged by the separator. However, when the separator of the present invention is used, the electrode is hardly damaged. Therefore, it can be an electrochemical element in which a short circuit hardly occurs. The electrochemical element is not particularly limited as long as it is a component that uses the exchange of electrons between substances. For example, an electrolytic capacitor such as an electric double layer capacitor or an aluminum electrolytic capacitor, a lithium ion secondary battery, a solid polymer type aluminum Examples include electrolytic capacitors. Among these, even an electrolytic capacitor such as a wound electric double layer capacitor or a wound aluminum electrolytic capacitor, in which the electrode is particularly easily damaged, is less likely to cause a short circuit.

  Since the wound type electric double layer capacitor of the present invention uses the separator of the present invention, short-circuiting hardly occurs. The wound electric double layer capacitor of the present invention has the same structure as the conventional one except that the separator of the present invention is used. For example, conductive carbon particles are added to a polarizable electrode material containing at least activated carbon, a paste using alcohols, ketones, esters, and amides as a solvent is filled in a current collector, and supported from the supported positive electrode and negative electrode In the state in which an electrode group composed of a positive electrode, a separator, a negative electrode, and a separator is wound, an electrolyte solution (tetrafluoroborate salt, perchlorate salt, hexafluorophosphate salt, etc. And dissolved in a solvent such as lactones, ethers, and dimethyl sulfoxide).

  Since the wound aluminum electrolytic capacitor of the present invention uses the separator of the present invention, short-circuiting hardly occurs. The wound aluminum electrolytic capacitor of the present invention has the same structure as that of the prior art except that the separator of the present invention is used. For example, in a state where a capacitor element laminated in the order of an anode foil, a separator, a cathode foil obtained by etching an aluminum foil, and a separator is wound on the surface of the etched aluminum foil by a chemical conversion treatment, Electrolytic solutions (lactones, carbonates, nitriles, furans, sulfolanes, ethers, amides, etc., solvents such as malonic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, dimethylmaleic acid, amino acid And a structure in which an electrolyte such as benzoic acid is dissolved) and inserted into the case.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples. The “tensile strength in the longitudinal direction” refers to a tensile tester according to JIS P-8113 after taking a rectangular sample (longitudinal direction: 200 mm, width direction: 15 mm) from a nonwoven fabric (separator). It is the tensile strength measured using the Orientec company make and UCT-500) at a grip interval of 100 mm.

Example 1
A fibrillated para-type wholly aromatic polyamide fiber (registered trademark: Twaron 1094, manufactured by Teijin, carbonization temperature: 500 ° C. or higher, freeness (CSF): 150 ml) and polyethylene terephthalate, fineness of 0.11 dtex, fiber length A 3 mm polyester fiber (registered trademark: Tepyrus, manufactured by Teijin, melting point: 260 ° C, softening temperature: 253 ° C, glass transition temperature: 90 ° C) was prepared.

  Next, the para-type wholly aromatic polyamide fiber is fibrillated with a refiner and para-type wholly aromatic polyamide fiber (freeness (CSF): 90 ml) and polyester fiber are dispersed at a mass ratio of 90:10. First slurry and second slurry were prepared.

  Moreover, the para type | system | group fully aromatic polyamide fiber (freezing degree (CSF): 90 ml) which promoted the said fibrillation, and the said polyester fiber were disperse | distributed by the mass ratio of 80:20, and the 3rd slurry was prepared.

  Next, the first slurry for the forward flow circle and the third slurry for the inclined wire type short net of the paper machine equipped with the forward flow circle, the inclined wire type short network, the forward flow network, and the Yankee dryer, After supplying the second slurry to the forward flow network and forming the first web, the third web, and the second web, respectively, the third web is positioned between the first web and the second web. Laminated and formed a laminated web having a three-layer structure. Subsequently, the laminated web was dried by a Yankee dryer set at a temperature of 120 ° C. to form a laminated dry web having fiber orientations unidirectional, random, and unidirectional. . The mass ratio of the first web, the second web, and the third web was 1: 1: 1.

  Next, a far-infrared ceramic heater (manufactured by Ryoka) set at a temperature of 490 ° C. and a far-infrared ceramic heater of a far-infrared irradiating device provided with 12 units each on the upper and lower sides at a speed of 10 m / min. Then, the polyester fiber was melted by passing through the laminated dry web for 12 seconds, and the melted polyester resin was agglomerated on the surface of the para-type wholly aromatic polyamide fiber and at the intersection. All the far infrared ceramic heaters were passed 110 mm apart. Also, hot air having a temperature of 260 ° C. was blown onto the moving laminated dry web.

Next, after air-cooling at room temperature under no pressure, it was allowed to pass through a dryer heated to a temperature of 220 ° C. for 3 seconds to promote crystallization of the polyester resin. The basis weight was 21 g / m ² , the thickness was 58 μm, and the apparent density was 0.36 g. A non-woven fabric (separator) of / cm ³ was produced. In this non-woven fabric (separator), fibrillated para-aromatic polyamide fibers account for 90% of the mass of each surface layer in any surface layer, and the intermediate layer is fibrillated para-based total aromatic polyamide fiber. It was composed of 80 mass% aromatic polyamide fiber and 20 mass% polyester resin. The polyester resin was present in a state of covering the para-type wholly aromatic polyamide fiber. Moreover, the tensile strength in the longitudinal direction of the nonwoven fabric (separator) was 10.1 N / 15 mm width.

(Example 2)
The nonwoven fabric (separator) produced in Example 1 was pressed (linear pressure: 300 N / cm) with a room temperature calendar, and the pressed nonwoven fabric (separator) having a basis weight of 21 g / m ² , a thickness of 35 μm, and an apparent density of 0.45 g / cm ^3. ) Was manufactured. The tensile strength in the longitudinal direction of this pressed nonwoven fabric (separator) was 11.5 N / 15 mm width.

(Example 3)
A first slurry and a second slurry, in which only para-type wholly aromatic polyamide fibers (freeness (CSF): 90 ml) in which para-type wholly aromatic polyamide fibers are fibrillated by a refiner, are dispersed (100%) are dispersed. A nonwoven fabric (separator) having a basis weight of 21 g / m ² , a thickness of 58 μm, and an apparent density of 0.36 g / cm ³ was produced in the same manner as in Example 1 except that it was prepared and used. In this nonwoven fabric (separator), in any surface layer, it is composed only of fibrillated para-type wholly aromatic polyamide fibers, and the intermediate layer is fibrillated para-type wholly aromatic polyamide fibers of 80 mass%. It was comprised from 20 mass% of polyester resins. The polyester resin was present in a state of covering the para-type wholly aromatic polyamide fiber. Moreover, the tensile strength in the longitudinal direction of the nonwoven fabric (separator) was 9.5 N / 15 mm width.

Example 4
The nonwoven fabric (separator) produced in Example 3 was pressed with a calendar at room temperature (linear pressure: 300 N / cm), pressed nonwoven fabric (separator) having a basis weight of 21 g / m ² , a thickness of 35 μm, and an apparent density of 0.45 g / cm ^3. ) Was manufactured. The tensile strength in the longitudinal direction of this pressed nonwoven fabric (separator) was 10.0 N / 15 mm width.

(Example 5)
A para-type wholly aromatic polyamide fiber (freeness (CSF): 90 ml) in which para-type wholly aromatic polyamide fiber has been promoted for fibrillation by a refiner and polyester fiber are dispersed at a mass ratio of 50:50. A nonwoven fabric (separator) having a basis weight of 21 g / m ² , a thickness of 56 μm, and an apparent density of 0.38 g / cm ³ was produced in the same manner as in Example 1 except that the slurry was prepared and used. In this non-woven fabric (separator), fibrillated para-aromatic polyamide fibers account for 90% of the mass of each surface layer in any surface layer, and the intermediate layer is fibrillated para-based total aromatic polyamide fiber. It was composed of 50 mass% aromatic polyamide fiber and 50 mass% polyester resin. The polyester resin was present in a state of covering the para-type wholly aromatic polyamide fiber. Moreover, the tensile strength in the longitudinal direction of the nonwoven fabric (separator) was 18.0 N / 15 mm width.

(Example 6)
The nonwoven fabric (separator) produced in Example 5 was pressed with a calendar at room temperature (linear pressure: 300 N / cm), pressed nonwoven fabric (separator) having a basis weight of 21 g / m ² , a thickness of 35 μm, and an apparent density of 0.45 g / cm ^3. ) Was manufactured. The tensile strength in the longitudinal direction of this pressed nonwoven fabric (separator) was 19.0 N / 15 mm width.

(Example 7)
A fibrillated para-type wholly aromatic polyamide fiber (registered trademark: Twaron 1094, manufactured by Teijin, carbonization temperature: 500 ° C. or higher, freeness (CSF): 150 ml), polyethylene terephthalate, fineness 0.11 dtex, fiber length 3 mm Polyester fiber (registered trademark: Tepyrus, manufactured by Teijin, melting point: 260 ° C, softening temperature: 253 ° C, glass transition temperature: 90 ° C), and non-fibrillated para-type wholly aromatic polyamide fiber (registered trademark: Technora, Teijin) Manufactured, carbonization temperature: 500 ° C. or higher, fineness: 0.8 dtex, fiber length: 3 mm).

  Next, the para-type wholly aromatic polyamide fiber is fibrillated with a refiner and para-type wholly aromatic polyamide fiber (freeness (CSF): 90 ml) and polyester fiber are dispersed at a mass ratio of 90:10. First slurry and second slurry were prepared.

  In addition, the para-type wholly aromatic polyamide fiber (freeness (CSF): 90 ml) that promotes the fibrillation, the para-type wholly aromatic polyamide fiber that is not fibrillated, and the polyester fiber are 70:10:20. A third slurry was prepared by dispersing at a mass ratio of

Next, in the same manner as in Example 1, formation of a laminated web having a three-layer structure, formation of a laminated dry web, heat treatment with a far-infrared ceramic heater and hot air, and heat treatment with a dryer were performed, and the basis weight was 21 g / m ² , thickness A nonwoven fabric (separator) having a thickness of 60 μm and an apparent density of 0.35 g / cm ³ was produced. In this non-woven fabric (separator), fibrillated para-aromatic polyamide fibers account for 90% of the mass of each surface layer in any surface layer, and the intermediate layer is fibrillated para-based total aromatic polyamide fiber. It was composed of 70 mass% aromatic polyamide fiber, 10 mass% para-type wholly aromatic polyamide fiber that was not fibrillated, and 20 mass% polyester resin. The polyester resin was present in a state of covering the para-type wholly aromatic polyamide fiber. Moreover, the tensile strength in the longitudinal direction of the nonwoven fabric (separator) was 12.0 N / 15 mm width.

(Example 8)
The nonwoven fabric (separator) produced in Example 7 was pressed with a calendar at room temperature (linear pressure: 300 N / cm), pressed nonwoven fabric (separator) having a basis weight of 21 g / m ² , a thickness of 35 μm, and an apparent density of 0.45 g / cm ^3. ) Was manufactured. The tensile strength in the longitudinal direction of this pressed nonwoven fabric (separator) was 12.7 N / 15 mm width.

Example 9
A first slurry and a second slurry, in which only para-type wholly aromatic polyamide fibers (freeness (CSF): 90 ml) in which para-type wholly aromatic polyamide fibers are fibrillated by a refiner, are dispersed (100%) are dispersed. A nonwoven fabric (separator) having a basis weight of 21 g / m ² , a thickness of 58 μm, and an apparent density of 0.36 g / cm ³ was produced in the same manner as in Example 7 except that it was prepared and used. In this nonwoven fabric (separator), in any surface layer, it is composed only of fibrillated para wholly aromatic polyamide fibers, and the intermediate layer is fibrillated para wholly aromatic polyamide fibers of 70 mass%, It was composed of 10 mass% of a para-type wholly aromatic polyamide fiber that was not fibrillated and 20 mass% of a polyester resin. The polyester resin was present in a state of covering the para-type wholly aromatic polyamide fiber. Moreover, the tensile strength in the longitudinal direction of the nonwoven fabric (separator) was 11.3 N / 15 mm width.

(Example 10)
The nonwoven fabric (separator) produced in Example 9 was pressed with a calendar at room temperature (linear pressure: 300 N / cm), and pressed nonwoven fabric (separator) having a basis weight of 21 g / m ² , a thickness of 35 μm, and an apparent density of 0.45 g / cm ^3. ) Was manufactured. The tensile strength in the longitudinal direction of this pressed nonwoven fabric (separator) was 11.7 N / 15 mm width.

(Example 11)
Para-type wholly aromatic polyamide fiber whose fibrillation was promoted by a refiner using para-type wholly aromatic polyamide fiber (freezing degree (CSF): 90 ml), para-type wholly aromatic polyamide fiber that has not been fibrillated, and polyester fiber 50 g / m ² , thickness 58 μm, apparent density 0.36 g by the same procedure as in Example 7 except that the third slurry was prepared and used by dispersing at a mass ratio of 50:30:20. A non-woven fabric (separator) of / cm ³ was produced. In this non-woven fabric (separator), fibrillated para-aromatic polyamide fibers account for 90% of the mass of each surface layer in any surface layer, and the intermediate layer is fibrillated para-based total aromatic polyamide fiber. It was composed of 50 mass% aromatic polyamide fiber, 30 mass% para-type wholly aromatic polyamide fiber that was not fibrillated, and 20 mass% polyester resin. The polyester resin was present in a state of covering the para-type wholly aromatic polyamide fiber. Moreover, the tensile strength in the longitudinal direction of the nonwoven fabric (separator) was 8.7 N / 15 mm width.

Example 12
The nonwoven fabric (separator) produced in Example 11 was pressed with a calendar at room temperature (linear pressure: 300 N / cm), pressed nonwoven fabric (separator) having a basis weight of 21 g / m ² , a thickness of 35 μm, and an apparent density of 0.45 g / cm ^3. ) Was manufactured. The tensile strength in the longitudinal direction of this pressed nonwoven fabric (separator) was 9.0 N / 15 mm width.

(Example 13)
Para-type wholly aromatic polyamide fiber whose fibrillation was promoted by a refiner using para-type wholly aromatic polyamide fiber (freezing degree (CSF): 90 ml), para-type wholly aromatic polyamide fiber that has not been fibrillated, and polyester fiber According to the same procedure as in Example 7, except that the third slurry was prepared by dispersing at a mass ratio of 20:30:50 and used, and the basis weight was 21 g / m ² , the thickness was 58 μm, and the apparent density was 0.36 g. A non-woven fabric (separator) of / cm ³ was produced. In this non-woven fabric (separator), fibrillated para-aromatic polyamide fibers account for 90% of the mass of each surface layer in any surface layer, and the intermediate layer is fibrillated para-based total aromatic polyamide fiber. It was composed of 20% by mass of aromatic polyamide fiber, 30% by mass of non-fibrillated para-type wholly aromatic polyamide fiber, and 50% by mass of polyester resin. The polyester resin was present in a state of covering the para-type wholly aromatic polyamide fiber. Moreover, the tensile strength in the longitudinal direction of the nonwoven fabric (separator) was 17.5 N / 15 mm width.

(Example 14)
The nonwoven fabric (separator) produced in Example 13 was pressed with a calendar at room temperature (linear pressure: 300 N / cm), pressed nonwoven fabric (separator) having a basis weight of 21 g / m ² , a thickness of 35 μm, and an apparent density of 0.45 g / cm ^3. ) Was manufactured. The tensile strength in the longitudinal direction of this pressed nonwoven fabric (separator) was 18.1 N / 15 mm width.

(Comparative Example 1)
A para-type wholly aromatic polyamide fiber in which para-type wholly aromatic polyamide fiber has been fibrillated by a refiner is dispersed in a mass ratio of 80:20 and polyester fiber (dispersion degree (CSF): 90 ml). Except for preparing and using 1 slurry, 2nd slurry, and 3rd slurry, according to the procedure similar to Example 1, it is 21g / m < ² > of thickness, 56 micrometers in thickness, and an apparent density of 0.38 g / cm < ³ >. A nonwoven fabric (separator) was produced. In this nonwoven fabric (separator), both the surface layer and the intermediate layer were composed of fibrillated para-type wholly aromatic polyamide fibers 80 mass% and polyester resin 20 mass%. The polyester resin was present in a state of covering the para-type wholly aromatic polyamide fiber. Moreover, the tensile strength in the longitudinal direction of the nonwoven fabric (separator) was 9.4 N / 15 mm width.

(Comparative Example 2)
A para-type wholly aromatic polyamide fiber in which para-type wholly aromatic polyamide fiber has been fibrillated by a refiner is dispersed in a mass ratio of 85:15 and polyester fiber (dispersion degree (CSF): 90 ml). Except for preparing and using 1 slurry, 2nd slurry, and 3rd slurry, according to the procedure similar to Example 1, it is 21g / m < ² > of thickness, 56 micrometers in thickness, and an apparent density of 0.38 g / cm < ³ >. A nonwoven fabric (separator) was produced. In this nonwoven fabric (separator), both the surface layer and the intermediate layer were composed of 85 mass% of fibrillated para-type wholly aromatic polyamide fibers and 15 mass% of the polyester resin. The polyester resin was present in a state of covering the para-type wholly aromatic polyamide fiber. Moreover, the tensile strength in the longitudinal direction of the nonwoven fabric (separator) was 8.1 N / 15 mm width.

(Comparative Example 3)
A fibrillated para-type wholly aromatic polyamide fiber (registered trademark: Twaron 1094, manufactured by Teijin, carbonization temperature: 500 ° C. or higher, freeness (CSF): 150 ml), polyethylene terephthalate, fineness 0.11 dtex, fiber length 3 mm Polyester fiber (registered trademark: Tepyrus, manufactured by Teijin, melting point: 260 ° C, softening temperature: 253 ° C, glass transition temperature: 90 ° C), and core-sheath type composite polyester fiber (registered trademark: Melty, manufactured by Unitika, of core part) Melting point: 255 ° C., melting point of sheath part: 110 ° C., fineness 1.1 dtex, fiber length: 3 mm).

  Next, para-type wholly aromatic polyamide fibers in which fibrillation of the para-type wholly aromatic polyamide fibers was promoted by a refiner (freeness (CSF): 90 ml), polyester fibers, and core-sheath type composite polyester fibers were 50:20. : Dispersed at a mass ratio of 30 to prepare a first slurry, a second slurry, and a third slurry.

  Next, the first slurry for the forward flow circle and the third slurry for the inclined wire type short net of the paper machine equipped with the forward flow circle, the inclined wire type short network, the forward flow network, and the Yankee dryer, After supplying the second slurry to the forward flow network and forming the first web, the third web, and the second web, respectively, the third web is positioned between the first web and the second web. Laminated and formed a laminated web having a three-layer structure. Subsequently, the laminated web was dried by a Yankee dryer set at a temperature of 120 ° C. to form a laminated dry web having fiber orientations unidirectional, random, and unidirectional. . The mass ratio of the first web, the second web, and the third web was 1: 1: 1.

Subsequently, both surfaces of this laminated dry web were placed in a cylinder dryer (diameter: 1.2 m) heated to a temperature of 200 ° C., with a tempo of 20 m / min. To produce a nonwoven fabric (separator) having a basis weight of 20 g / m ² , a thickness of 55 μm, and an apparent density of 0.36 g / cm ³ . In this nonwoven fabric (separator), the fibrillated para-type wholly aromatic polyamide fiber accounts for 50% of the mass of each surface layer in any surface layer, and the sheath component of the core-sheath type composite polyester fiber It was in the state of being adhered by fusing. The core-sheath type composite polyester fiber maintained a fiber state and was in a filmed state. Moreover, the tensile strength in the longitudinal direction of the nonwoven fabric (separator) was 8.4 N / 15 mm width.

(Comparative Example 4)
In the same manner as in Example 1, a first slurry and a second slurry were prepared.

  Next, in a paper machine equipped with a forward flow network, a forward flow network, and a Yankee dryer, a first slurry is supplied to the forward flow network and a second slurry is supplied to the forward flow network, respectively. After forming the second web, the first web and the second web are laminated to form a laminated web having a two-layer structure, and then the laminated web is dried by a Yankee dryer set at a temperature of 120 ° C. A laminated dry web having a unidirectional and unidirectional fiber orientation was formed.

  And like Example 1, it tried to implement the heat processing by a far-infrared ceramic heater and a hot air, but it fractured | ruptured at the time of conveyance, and the nonwoven fabric (separator) could not be manufactured.

(Production of electric double layer capacitor)
First, an aluminum thin plate was prepared as a capacitor collecting electrode. In addition, an electrode prepared by mixing and rolling granular activated carbon, carbon black, and polytetrafluoroethylene (prepared by a rolling method) was prepared. Furthermore, the separator of Examples 1-14 and Comparative Examples 1-3 was prepared as a separator.

  Next, a separator, a negative electrode collector electrode, a negative electrode, a separator, a positive electrode, and a positive electrode collector were stacked in this order to form an electrode group, and then this electrode group was processed into a wound shape with a load of 500 g. Thereafter, the wound electrode group was dried at a temperature of 200 ° C. for 50 hours.

  In the glow box, the wound electrode group is impregnated with an electrolytic solution (a solution of tetraethylammonium tetrafluoroborate in propylene carbonate) under reduced pressure, and then the wound electrode group is inserted into an aluminum case with a sleeve. And sealed to produce a capacitor. 100 capacitors were manufactured for each separator.

(Production of aluminum electrolytic capacitors)
An aluminum foil having a thickness of 40 μm and an etching hole diameter of 1 to 5 μm was used as an electrode, and an anode connector was spot welded on one side of the electrode, and then immersed in a boric acid aqueous solution maintained at a temperature of 90 ° C. The aluminum foil surface was oxidized for a minute to form an aluminum oxide dielectric layer, which was used as the anode. Further, a cathode connector was spot welded to one side of the same aluminum foil electrode to form a cathode.

  Next, on the dielectric layer of the anode, a separator, a cathode, and a separator were laminated in this order to form an electrode group, and wound up to form a wound electrode group.

  Then, the wound electrode group is inserted into the cell, and after injecting an electrolytic solution (tetraethylammonium phthalate 24.1% by mass, γ-butyrolactone 70% by mass, ethylene glycol 5.9% by mass), the cell is sealed. An aluminum electrolytic capacitor was manufactured. 100 aluminum electrolytic capacitors were manufactured for each separator.

(Evaluation of electric double layer capacitor)
A direct current of 2.5 V was applied to each electric double layer capacitor for 72 hours, and then charged to 2.5 V, and the leakage current immediately after charging was measured. At this time, a leakage current of 10 mA or more was observed, or the defective rate of a shorted capacitor was calculated. The results are shown in Table 1.

(Evaluation of aluminum electrolytic capacitors)
After aging each aluminum electrolytic capacitor, a constant current of 10 mA was applied. In this voltage-time rising curve at the time of aging or at the time of constant current application, the defective rate of the shorted capacitor was calculated. The results are shown in Table 1.

  As is clear from Table 1, in any surface layer, the mass ratio of the total aromatic fiber is 90% or more of the mass of each surface layer, so that an electric double layer capacitor can be produced without causing a short circuit, It was found that electrochemical devices such as aluminum electrolytic capacitors can be manufactured.

  Further, from comparison between Examples 7 and 8, Examples 9 and 10, Examples 11 and 12, and Examples 13 and 14, it is understood that the case where the calendar process is not performed is more excellent in short circuit prevention. It was.

  Furthermore, from comparison between Examples 1 to 6 and Examples 7 to 14, it was found that when the wholly aromatic fibers consist only of fibrillated fibers, the short circuit prevention property is more excellent.

Claims (8)

A separator for an electrochemical device composed of a nonwoven fabric having a three-layer structure containing wholly aromatic fibers, and in any surface layer of the nonwoven fabric, the mass ratio of the wholly aromatic fibers is 90% or more of the mass of each surface layer A separator for an electrochemical element, characterized in that The separator for an electrochemical element according to claim 1, further comprising a thermoplastic resin for bonding the wholly aromatic fibers to the intermediate layer of the nonwoven fabric. The separator for an electrochemical element according to claim 2, wherein the amount of the thermoplastic resin in the intermediate layer of the nonwoven fabric is 20 to 50% of the mass of the intermediate layer. (1) A first slurry containing 90% by mass or more of all materials, (2) A second slurry containing the same or more than 90% by mass of all materials, and (3) A slurry preparation step of preparing a third slurry different from the first slurry and the second slurry;
Each slurry is rolled up to form a first web derived from the first slurry, a second web derived from the second slurry, and a third web derived from the third slurry, and then the first web and the second web. A laminated web forming step of forming a laminated web having a three-layer structure by laminating so that the third web is positioned between the web and a nonwoven fabric forming step of using the laminated web as a nonwoven fabric by heat treatment;
The manufacturing method of the separator for electrochemical elements characterized by including these. The thermoplastic resin fibers are included in the third slurry in the slurry preparation step, and the wholly aromatic fibers are bonded by a thermoplastic resin constituting the thermoplastic resin fibers by heat treatment in the nonwoven fabric forming step. 5. A method for producing an electrochemical element separator according to 4. The heat treatment in the nonwoven fabric forming step is a treatment for irradiating the laminated web with infrared rays under no pressure to melt the thermoplastic resin fibers and solidifying the molten thermoplastic resin under no pressure. 5. A method for producing a separator for an electrochemical element according to 5. The winding type electric double layer capacitor using the separator for electrochemical elements according to any one of claims 1 to 3. The winding type aluminum electrolytic capacitor using the separator for electrochemical elements in any one of Claims 1-3.