JP2011233482A - Thinned material for nonaqueous electric/electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for a nonaqueous electric/electronic component, excellent in a shutdown function that is an important characteristic on a safety of a nonaqueous electric/electronic component, in particular, a secondary battery, shape stability at high temperature, and electrolyte/ion permeability while an electrolyte is held.SOLUTION: The separator for a nonaqueous electric/electronic component is obtained by heat treating a thinned material in a dry state at a temperature of a melting point of a thermoplastic polymer or higher. The thinned material exists in a state where the thermoplastic polymer that has a melting point of 200°C or lower, a layer comprising particles that does not have a melting point at 300°C or lower, and a layer of a polymeric organic substance that substantially does not have a melting point at 300°C or lower are in contact.

Description

  The present invention relates to a separator that separates a positive electrode material and a negative electrode material and allows an electrolyte or ions in an electrolytic solution to pass through in a non-aqueous electric / electronic component, for example, a non-aqueous secondary battery. In particular, a non-aqueous system made of a thin leaf material composed of a sheet made of a plurality of materials having different thermal characteristics, useful as a separator for a non-aqueous secondary battery using ions of alkali metals such as lithium and sodium as current carriers. The present invention relates to a separator for electrical and electronic parts.

Secondary batteries, capacitors, fuel cells, and solar cells are used as power sources for portable electronic devices and the like, and are partially put into practical use as power sources for electric vehicles and hybrid vehicles. In particular, expectations are high for compact, lightweight, high-performance secondary batteries and capacitors that have high energy density and can withstand long-term storage, and are widely applied. In particular, expectations are high for secondary batteries and capacitors that use non-aqueous electrolytes with high withstand voltage and high energy density. A typical lithium secondary battery mainly includes a positive electrode using a composite oxide of Li ions and a transition metal as a positive electrode active material, a negative electrode using a carbon-based material capable of inserting and extracting Li ions as a negative electrode active material, A separator interposed between the positive and negative electrodes, and an electrolytic solution composed of an electrolyte such as LiPF ₆ or LiBF ₄ and an organic solvent. Further, the power generation element is housed in a battery container and sealed by a positive electrode terminal, a negative electrode terminal, and a gasket connected to the positive electrode and the negative electrode, respectively. A current collector using a predetermined metal is pressure-molded in a strip shape for each of the positive electrode and the negative electrode.

In this case, as a general characteristic required for the separator,
(1) In addition to the function of isolating the electrode material, it has a function of shutting down the battery circuit (shutdown characteristics) when a large current flows due to a short circuit of each part,
(2) It has the above-mentioned shutdown characteristics and at the same time has heat resistance that does not melt even when the temperature rises due to a large Joule heat due to an instantaneous large current,
(3) Electrolyte / ion permeability is good in the state of holding the electrolyte,
(4) having electrical insulation;
(5) It is chemically stable to the electrolyte and at the same time is electrochemically stable (long life characteristics).
(6) It has mechanical strength, the film thickness can be reduced, and the like.
In particular, the long-life characteristic is very important in terms of stable running when the battery is used as a power source for an electric vehicle and a hybrid vehicle because it relates to the life of the battery and reduces the number of battery replacements.

Conventionally, a porous sheet formed using a polyolefin-based polymer such as polyethylene or polypropylene has been widely used as the separator. This porous sheet is obtained by 1) a method of kneading a solvent having a plastic effect and a polymer, forming a film, and then extracting and washing the solvent (generally called a wet method), or 2) by extruding a molten polymer. It is manufactured by a method (generally referred to as a dry method) in which after forming into a sheet, it is subjected to stretching treatment to form cracks and form fine holes. The separator manufactured in this way is used in a battery by stacking one or more layers or winding it in a roll.
By using polyethylene with a melting temperature of 130 ° C. and polypropylene with a melting temperature of 170 ° C. as the material of the separator, heat generated when an excessive current flows in the battery due to an external short circuit as described above, or external The separator is thermally shrunk / melted due to the temperature rise due to the factor, and the micropores are closed accordingly, so that the battery circuit is cut off. From the viewpoint that it is safer to close the micropores at a lower temperature, the separator material is mainly polyethylene.

  Of course, in order to protect the battery circuit, it is possible to incorporate a safety device function such as PTC in the external circuit in addition to the separator. However, considering that secondary batteries for electric vehicles and hybrid vehicles, which are expected to develop greatly in the future, may damage the external safety device circuit due to the impact of a collision accident, Regarding safety, a separator having a shutdown function is considered indispensable from the viewpoint of foolproofing. Further, along with this shutdown characteristic, the shape retention force of the separator when the temperature rise continues after shutdown is an important factor. That is, when a polymer having a melting point within the temperature range of 120 to 170 ° C. such as polyethylene and polypropylene is used for the separator, if the temperature rise continues for some reason even after shutdown, the separator itself melts, resulting in current The problem that the blocking function disappears almost completely has been pointed out. If the separator shape is lost too quickly, a short circuit of the electrode is caused and a dangerous state is caused.

In order to solve the above problems, a high melting point material and a low melting point material are combined as a material for the separator of the secondary battery, and the low melting point material has a shutdown function and the high melting point material has a shape maintaining function at a high temperature. Several multi-component materials have been proposed.
For example, Patent Document 1 discloses a composite fiber nonwoven fabric having a core-sheath structure, and Patent Document 2 shows a microporous film formed of a plurality of types of materials having different melting points.
On the other hand, Patent Document 3 proposes a structure in which a microporous film made of a low melting point resin and a nonwoven fabric made of a polymer having a higher melting point are laminated.
However, the melting points of the high melting point compounds shown in these patent documents are 270 ° C. at the maximum, and Tg (glass transition temperature), which is a standard temperature at which the thermal motion of the polymer starts, is 100 ° C. or less. Therefore, when a sudden and local temperature rise occurs, it cannot be said that the separator shape and the short-circuit prevention function are completely maintained. In particular, in the case of a polymer constituting an ordinary separator, since the thermal conductivity is generally small, the possibility of local temperature rise and melting cannot be denied.
In addition, a separator in which a polyethylene porous film and a polypropylene porous film are laminated has been put into practical use, but in this case as well, the problem of being thermally unstable is not essentially solved.
In addition, it has been proposed to use thermally stable aramid (aromatic polyamide) as a separator component (see Patent Document 4, Patent Document 5, and Patent Document 6). Although these use aramid fiber / pulp excellent in heat resistance, there is no description about providing a shutdown function.

Patent Document 7 discloses a nonwoven fabric for battery separators containing at least fibrillated organic fibers. This nonwoven fabric may contain low melting point fibers such as polyethylene fibers and polypropylene fibers. However, when the low melting point component is in a fiber form, even if it is melted, the area that can be covered is not large, and it is difficult to say that the shutdown function described above is sufficient.
Patent Document 8 discloses a battery separator which is a sheet formed by mixing a thermoplastic polymer having a melting point of at least 200 ° C. and a paper material made of an organic compound having substantially no stable melting point. . The aramid used as an organic compound in Patent Document 8 has a very high equilibrium moisture content of at least 1.0%, and heat treatment at a temperature of at least 150 ° C. is necessary to remove the bound water present in the aramid. However, Patent Document 8 does not describe any removal of moisture. If the water is not removed or if the water is not removed sufficiently, the water extracted in the electrolyte reacts with the electrolyte after the electrolyte is injected, and gas is generated during long-term use. There is a possibility that the lifetime of the battery becomes shorter.

Patent Document 9 describes that a shutdown layer and a heat-resistant porous layer are provided and para-aramid is applied to a polyethylene porous film. The equilibrium moisture content of para-aramid is very high, at least 2.0%, and when removing water, a temperature of at least 150 ° C. is necessary to remove the bound water present in the aramid, but the polyethylene porous film Since the air permeability of 700 seconds / 100 cc is large, heat treatment at a temperature of 150 ° C. or higher closes the pores of the polyethylene porous film. In other words, moisture cannot be removed sufficiently. If the water is not removed sufficiently, the water extracted from the electrolyte will react with the electrolyte after the electrolyte is injected, and gas will be generated during long-term use. Problems can occur.
Patent Document 10 discloses a porous sheet formed from a thermoplastic polymer having a melting point of 200 ° C. or lower, which includes a thin leaf material made of an organic compound having substantially no stable melting point. Examples of organic compounds having no stable melting point include aramid. Since the equilibrium moisture content of aramid is very high, at least 2.0% or more, it may be exposed to the surface during the manufacturing process even though it is encapsulated. In this case, since the air permeability of the porous sheet is as large as 400 seconds / 100 cc, the same problem as in the case of Patent Document 8 may occur.
Patent Document 11 discloses a sheet in which a non-woven sheet layer made of an organic compound having substantially no stable melting point and a porous sheet layer formed from a thermoplastic polymer having a melting point of 200 ° C. or lower are laminated. As an organic compound having substantially no stable melting point, aramid and the like are mentioned. However, in this case as well, since the air permeability of the sheet is as large as 300 seconds / 100 cc, the same as in the case of Patent Document 8 above. Problems can occur.

JP 61-232560 A Japanese Patent Laid-Open No. 63-308866 JP-A-1-258358 Japanese Patent Laid-Open No. 5-33005 Japanese Patent Laid-Open No. 7-37571 JP-A-7-78608 JP-A-9-27311 Japanese Patent Laid-Open No. 11-40131 JP 2002-151044 A JP 2006-054127 A JP 2006-264029 A

There is no sheet-like material for separators for non-aqueous electrical and electronic parts, such as batteries and capacitors, especially secondary batteries, which have both shutdown function, high-temperature shape stability, long life characteristics, and high output. there were. In the future, development of a battery separator having such a safety device function, long life characteristics, and high output is awaited for the development of lithium secondary batteries in industrial applications.
The object of the present invention is to provide a shutdown function, shape stability at high temperatures, and electrolyte / ion permeability in a state of holding an electrolyte, which are important characteristics for the safety of non-aqueous electrical and electronic parts, particularly secondary batteries. By using an excellent separator as a separator between conductive members, a safe, long-life, high-power non-aqueous electrical / electronic component is provided.

In view of such a situation, the present inventors have a shutdown function and high-temperature shape stability, can further reduce the water content by heat treatment at a high temperature, and have low resistance in a state in which the electrolytic solution is retained. As a result of diligent studies to develop a separator material, a thin leaf material composed of a plurality of sheets made of a plurality of specific substances having different thermal characteristics has been developed and the present invention has been completed.
Thus, according to the present invention, a thermoplastic polymer having a melting point of 200 ° C. or less, a layer composed of particles having no melting point at 300 ° C. or less, and a layer of an organic polymer material having substantially no melting point at 300 ° C. or less are in contact. The present invention provides a separator for non-aqueous electrical and electronic parts obtained by heat-treating a thin leaf material existing in a dry state at a temperature not lower than the melting point of the thermoplastic polymer in a dry state.

The thin leaf material according to the present invention includes a thermoplastic polymer excellent in a shutdown function by melting in a state impregnated with an electrolytic solution, and an organic polymer having no melting point at 300 ° C. or lower, which exhibits excellent characteristics in a high-temperature shape maintaining function. Since it is composed of a substance, particularly aramid, it has an excellent shutdown function and excellent shape retention at high temperatures. In addition, the thin leaf material according to the present invention can be expected to have a long life by removing moisture and being electrochemically stable by heat treatment in a dry state. In addition, the pores do not become small even after heat treatment in a dry state, and excellent electrolyte / ion permeability is exhibited in a state where the electrolytic solution is retained. Furthermore, the coating of a layer composed of a thermoplastic polymer having a melting point of 200 ° C. or lower and particles having no melting point at 300 ° C. or lower increases the tensile strength of the thin leaf material, enables further thinning, and improves the energy density. be able to. Further, since the liquid to be coated contains particles, even when a layer made of a thermoplastic polymer having a melting point of 200 ° C. or lower and a particle having no melting point at 300 ° C. or lower enters the pores of the aramid thin leaf material, Without being completely sealed, the electrolyte / ion permeability in the state where the electrolytic solution is retained is maintained, and the output density is improved.
Hereinafter, the separator for non-aqueous electrical and electronic parts of the present invention will be described in more detail.

[Melting point]
The melting point of the polymer in the present invention is measured by a thermal method such as DSC (Differential Scanning Calorimetry) or DTA (Differential Thermal Analysis). In general, polymers exhibit a wide range of melting behavior, reflecting non-single molecular weight components and differences in the degree of crystallization. In the present invention, the melting point is defined as the temperature corresponding to the endothermic peak by DSC analysis.

[Thermoplastic polymer having a melting point of 200 ° C. or lower]
The thermoplastic polymer having a melting point of 200 ° C. or lower used in the present invention is not particularly limited, but polyolefin is particularly preferable. Examples of the polyolefin include, but are not limited to, polyethylene, polypropylene, polybutene, polymethylpentene, and copolymers thereof. Of these, polyethylene, polypropylene, and copolymers thereof are preferred. These polymers are not limited to those having a linear structure, and may include structures such as a branched chain and a crosslinking site.
When such a thermoplastic polymer is heated to a temperature higher than the melting point in a dry state, it melts and fluidity is increased. Therefore, due to capillary action, the melting point is substantially reduced at 300 ° C. or less around the thin leaf material. It penetrates into gaps between organic polymer substances that do not exist. However, at that time, particles having no melting point move at 300 ° C. or lower at the same time, so that the voids can be efficiently filled while maintaining the voids. Further, since there is no void in the state immersed in the electrolytic solution, it melts and then expands into a film according to Newton's law. As a result, the separator of the present invention exhibits a shutdown function.

[Particles having no melting point at 300 ° C. or lower]
The particles having no melting point at 300 ° C. or lower used in the present invention are preferably spherical, cylindrical, or prismatic with an average primary particle diameter of 5 to 50 nm, particularly preferably 10 to 35 nm. It is not limited. The average primary particle diameter is generally measured by a dynamic light scattering method or the like. The material is not particularly limited as long as it does not impair the functions of the battery and the capacitor, and examples thereof include inorganic particles such as silicon dioxide, aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, and zirconia. These may be used alone or in combination of two or more.

[Organic polymer substance having substantially no melting point at 300 ° C. or lower]
Examples of the organic polymer substance having substantially no melting point used in the present invention include:
1) When the heating temperature is raised, the crosslinking reaction proceeds and the melting point substantially rises above the decomposition temperature of the organic polymer substance,
2) The melting point and decomposition temperature of the organic polymer substance are close to each other, and the organic polymer substance is thermally decomposed in parallel with the melting,
3) Those which do not have melting characteristics and therefore do not have a melting point can be used.
In the present invention, among these substances, organic polymer substances having substantially no melting point at 300 ° C. or lower are used. Examples of the organic polymer substance used in the present invention include aramid, polyimide, polyamideimide, polyacrylonitrile, polyarylate (fully aromatic polyester), cellulose, polyether ether ketone, polytetrafluoroethylene, and polyparaphenylene. Examples include, but are not limited to, benzobisoxazole. Of these, aramid is particularly preferred.
Examples of the shape of these organic polymer substances include fibers, fibrillated fibers, fibrids, microporous films, paper, non-woven fabrics, woven fabrics, etc., which are composed mainly of the above substances and are separators. As long as it has sufficient ion permeability, the shape is not particularly limited. Specific examples include aramid thin leaf materials described in JP2003-066455A, JP2005-307360A, and the like, but are not limited thereto.
The organic polymer material used in the present invention may contain water (such as bound water) at a high content of an equilibrium water content of generally at least 0.2%, usually at least 1.0%. The water content is removed by heat treatment according to the present invention, as will be described later.

[Aramid]
In the present invention, an aramid means a wholly aromatic polyamide, which means a linear polymer compound in which 60% or more of the bonds connecting aromatic rings such as benzene rings or naphthalene rings are amide bonds. In the case of an aramid having a benzene ring, it is roughly classified into a meta-aramid and a para-aramid according to the substitution position of the amide bond. Examples of the meta-aramid include polymetaphenylene isophthalamide and a copolymer thereof, and examples of the para-type include polyparaphenylene terephthalamide and a copolymer thereof, poly (paraphenylene) -copoly (3,4 diphenylene). Ether) terephthalamide and the like, but are not limited thereto. The method for producing aramid is also not particularly limited, and generally includes a solution polymerization method by a condensation reaction of an aromatic diamine and an aromatic acid dichloride, a two-step interfacial polymerization method, and the like. It is manufactured. It should be noted that other components can be copolymerized with the aramid as long as the properties of the aramid are not impaired. The form of the aramid used in the present invention is not particularly limited, but forms such as an aramid fibrid, an aramid short fiber, a fibrillated aramid, and an aramid thin leaf material are preferable.

[Aramid thin leaf material]
The aramid thin leaf material used in the present invention is not particularly limited as long as it is in the form of a thin porous sheet produced using the above-mentioned aramid as a raw material. Thin leaf materials using short fibers are preferred.
Aramid short fibers are obtained by cutting fibers made from aramid. Examples of such fibers include Teijin Techno Products Co., Ltd. “Teijin Conex (registered trademark)” and “Technola (registered trademark)”. ”,“ Nomex (registered trademark) ”by DuPont,“ Kevlar (registered trademark) ”,“ Twaron (registered trademark) ”by Teijin Aramid, and the like. Is not to be done.

[Equilibrium moisture content]
In the present invention, the equilibrium moisture content is a value calculated according to JIS L-1015 for a sample exposed to an environment of a temperature of 20 ° C. and a relative humidity of 65% for 96 hours after the sample is completely dried.

[A thermoplastic polymer having a melting point of 200 ° C. or lower, a layer composed of particles having no melting point at 300 ° C. or lower, and a layer of an organic polymer material having substantially no melting point at 300 ° C. or lower exist in contact with each other. Thin leaf material]
In the present invention, a state in which a thermoplastic polymer having a melting point of 200 ° C. or less, a layer composed of particles having no melting point at 300 ° C. or less, and a layer of an organic polymer substance having substantially no melting point at 300 ° C. or less are in contact The thin leaf material present in the above is a thin porous sheet-like material composed of at least two layers, and the pore size is small even when heated at a temperature above the melting point of the thermoplastic polymer in a dry state. Moreover, what can hold | maintain the shape as a separator is used.
Here, in the “contact state”, a layer composed of a thermoplastic polymer having a melting point of 200 ° C. or less and particles having no melting point at 300 ° C. or less is coated on the organic polymer substance at least partially. State etc. are included.

[Thin leaf material in which aramid thin leaf material is coated with thermoplastic polymer and particles]
From the viewpoint of having sufficient strength and workability as a separator, a thin leaf material obtained by coating the aramid thin leaf material with the thermoplastic polymer and particles is preferably used in the present invention.
As a coating method, for example, the thermoplastic polymer is mixed with the particles in a melted state, homogenized and applied, and then the surface is made uniform by passing through an arbitrary gap such as between a pair of rolls. Method, after dispersing the fine particles of the thermoplastic polymer in a liquid, further dispersing the particles and applying the dispersion to one side, or impregnating the dispersion with an aramid thin leaf material, Examples include a method in which the surface is made uniform by passing an arbitrary gap such as between rolls and the amount of the dispersion attached is adjusted, and the liquid is removed by drying. At that time, after coating on one side, it may be further coated on the opposite side, the amount of adhesion may be adjusted, and the liquid may be removed by drying, or after repeating the above coating, impregnation and homogenization multiple times in any order The liquid may be removed by drying. The liquid may be removed by drying after repeating the above application, impregnation, homogenization, and drying a plurality of times in an arbitrary order.
Among them, the method of applying the dispersion of the thermoplastic polymer fine particles and the dispersion in which the particles are dispersed in water on one side, passing between a pair of rolls and drying is preferably used because it is environmentally friendly.
The particle size of the thermoplastic polymer fine particles measured by the dynamic light scattering method is preferably 300 nm or less, particularly preferably 200 nm or less. If the particle size is larger than 300 nm, it is difficult to uniformly disperse in the liquid and it is difficult to perform uniform coating. It becomes.
The total amount of the thermoplastic polymer to be applied and the particles is preferably in the range of 2 to 100%, particularly 10 to 50% by weight with respect to the aramid thin leaf material. The ratio of the thermoplastic polymer to the particles is preferably in the range of (thermoplastic polymer) / (particles) = 0.5 to 50% by weight. If the amount of the thermoplastic polymer with respect to the aramid thin leaf material is less than 1%, the thermal shutdown function is not sufficiently exhibited in the electrolytic solution, and if the total amount exceeds 100%, the thermoplastic resin is used during the coating. Cracks may occur between the polymer and the particle layer. Further, if the weight ratio of the thermoplastic polymer to the particles exceeds 50%, there is a possibility that the electrolyte / ion permeability in the electrolyte solution holding state of the thin leaf material may be hindered.

[Air permeability]
The thin leaf material before heat treatment of the present invention preferably has a Gurley air permeability of less than 100 seconds. When the air permeability of the thin leaf material before heat treatment is 100 seconds or more, the pores of the thin leaf material are small, and the thermoplastic polymer is film-like when heated at a temperature equal to or higher than the melting point of the thermoplastic polymer in a dry state. It may block the hole in the thin leaf material and hinder ion permeability.

[Heat treatment at a temperature above the melting point of the thermoplastic polymer in the dry state of the thin leaf material]
By heat-treating (drying) the thin leaf material at a temperature equal to or higher than the melting point of the thermoplastic polymer in a dry state, the moisture of the organic polymer substance containing moisture at a high equilibrium moisture content and the moisture contained in the particles are reduced. Can be removed. The temperature of the heat treatment is preferably the melting point of the thermoplastic polymer + 150 ° C. or less. The heat treatment can be performed only in the state of the thin leaf material, or can be performed after being combined with another member such as an electrode sheet. However, after the heat treatment is performed, the organic polymer material should not absorb water again. If possible, it is preferable to maintain the dry state and inject the electrolyte quickly.
The heat treatment is performed using, for example, a vacuum dryer in an atmosphere having a degree of vacuum of 20 mmHg or less, preferably 10 mmHg or less, or while introducing an inert gas such as nitrogen or argon into a heat drying oven. The heat treatment can be performed at a temperature equal to or higher than the melting point of the plastic polymer.
The thus obtained thin leaf material after the heat treatment generally has a moisture content of 100 ppm or less, particularly 20 ppm or less.
As a result, when the thin leaf material after heat treatment is used as a separator between conductive members, moisture is not extracted into the electrolytic solution, deterioration of the electrolytic solution is suppressed, and the life of electric and electronic parts is expected to be extended. For example, the lifetime of the nonaqueous electrolyte battery can be significantly increased.
Thus, the thin leaf material after the heat treatment according to the present invention can be advantageously used as a separator for non-aqueous electrical and electronic parts.

[Dry state]
In the present invention, the dry state is a state in which substantially no moisture exists in the ambient atmosphere, more specifically, a state in which the volume fraction of water in the gas is less than 2% and a negative pressure state, for example, The vacuum state is 20 mmHg or less, preferably 10 mmHg or less.

[Electrical and electronic parts]
The electric and electronic parts using the thin leaf material after heat treatment of the present invention as a separator between conductive members are an efficient shutdown function at 200 ° C. or lower due to the thermoplastic polymer, and a high temperature shape stabilization function based on aramid Have both. Therefore, the thin leaf material after the heat treatment of the present invention can be suitably used as a separator for a non-aqueous electrochemical battery, particularly a lithium secondary battery, which is composed of an anode, a cathode, an electrolyte and a separator, for example. . Such a battery can be used not only as a battery for electric devices such as conventional mobile phones and personal computers, but also as an energy storage / generation device for large devices such as electric vehicles.
Hereinafter, the present invention will be described more specifically with reference to examples.

[Measuring method]
(1) Measurement of basis weight and thickness of sheet The measurement was performed according to JIS C2111.
(2) Gurley Air Permeability Using a Gurley air permeability measuring instrument specified in JIS P8117, a sheet sample (area 642 mm ² ) held by a clamping plate having a circular hole with an outer diameter of 28.6 mm is 100 cc (0 .1 dm ³ ) air passage time (seconds) was measured.
(3) Porosity Hole volume / thin leaf material volume x 100 (%)
However, pore volume = hydrous weight−absolute dry weight. The hydrous weight is the weight after the thin leaf material is immersed in water for 10 minutes.
The absolutely dry weight is the weight after the thin leaf material is dried for 24 hours in a vacuum state with a vacuum degree of 15 mmHg or less.
(4) Measurement of tensile strength A Tensilon tensile tester was carried out at a width of 15 mm, a chuck interval of 50 mm, and a tensile speed of 50 mm / min.
(5) Measurement of moisture content of thin leaf material After heat treatment in a dry state, the moisture content was determined from the following equation by measuring the weight in a dry room having a dew point of -60 ° C.
(Weight of sample after heat treatment-absolute dry weight of sample) / weight of sample after heat treatment × 1000000 (ppm)
(6) Measurement of electrical conductivity The separator was cut into a circle with a diameter of 20 mm, sandwiched between two SUS electrodes, and calculated from the AC impedance at 60 kHz. At this time, the measurement temperature was 25 ° C. For the measurement, 1M lithium borofluoride ethylene carbonate / propylene carbonate (1/1 weight ratio) was used as an electrolytic solution.

[Raw material preparation]
As aramid short fiber, denier meta-aramid fiber (Teijin Techno Products Co., Ltd., Teijin Conex (registered trademark)) with a short fiber fineness of 0.8 is cut into a length of 5 mm, and fibrillated aramid is Twaron pulp. (Teijin Aramid Co., Ltd., Twaron (registered trademark)) was prepared to have a specific surface area of 14 m 2 / g and a freeness of 85 ml and used as a raw material for papermaking. Aramid short fibers do not exhibit a substantially stable melting point, and fibrillated aramid does not exhibit a melting point.

(Manufacture of aramid thin leaf material)
The prepared aramid short fibers and the fibrillated aramid were dispersed in water to prepare a slurry. This slurry was mixed so that the aramid short fibers and the fibrillated aramid had a blending ratio shown in Table 1, and processed with a tappy hand-making machine (cross-sectional area of 325 cm ² ) to produce a sheet. . Next, this was hot-pressed at a temperature of 330 ° C. and a linear pressure of 300 kg / cm with a metal calender roll to obtain an aramid thin leaf material. The equilibrium moisture content was 3.8%.
The main characteristic values of the aramid thin leaf material thus obtained are shown in Table 1.

(Comparative Examples 1 and 2: Production of aramid thin leaf material coated with thermoplastic polymer)
As a thermoplastic polymer aqueous dispersion, Sumitomo Seika Co., Ltd.'s "Zyxen (registered trademark) AC" (solids melting point 80-95 ° C., particle size 200 nm or less) adjusted to 20% solid content concentration The aramid thin leaf material was impregnated and applied by the dip nip method and dried at 60 ° C. for 4 hours.
Table 2 shows the main characteristic values of the thin leaf material thus obtained and heat treatment in a dry state, that is, when the heat treatment is performed in an atmosphere having a degree of vacuum of 3 mmHg using a vacuum dryer.

(Examples 1 and 2 and Comparative Example 3: Production of Aramid Thin Leaf Material Coated with Thermoplastic Polymer and Particles)
As an aqueous dispersion of a thermoplastic polymer, the solid content concentration of “Zyxen (registered trademark) AC” (solid melting point 80 to 95 ° C., particle size 200 nm or less) manufactured by Sumitomo Seika Co., Ltd. was adjusted to 20%. The mixture is mixed with silicon dioxide particles (AEROSIL (registered trademark) 50) having an average primary particle diameter of 30 nm manufactured by Nippon Aerosil Co., Ltd., and after stirring, applied to the aramid thin leaf material by the doctor blade method. And dried at 60 ° C. for 4 hours.
Table 2 shows the main characteristic values of the thin leaf material thus obtained and heat treatment in a dry state, that is, when the heat treatment is performed in an atmosphere having a degree of vacuum of 3 mmHg using a vacuum dryer.

  Further, the thin leaf materials of Examples 1 and 2 and Comparative Examples 1, 2, and 3 were heat-treated at 300 ° C. for 45 minutes, but no deformation or shrinkage of the thin leaf material itself was observed.

Claims (9)

  A thermoplastic polymer having a melting point of 200 ° C. or lower, a layer composed of particles having no melting point at 300 ° C. or lower, and a layer of an organic polymer substance having substantially no melting point at 300 ° C. or lower exist in contact with each other. A separator for non-aqueous electrical and electronic parts obtained by heat-treating a thin leaf material at a temperature not lower than the melting point of the thermoplastic polymer in a dry state.   The separator for non-aqueous electrical and electronic parts according to claim 1, wherein the moisture content of the thin leaf material after the thin leaf material is heat-treated at a temperature equal to or higher than the melting point of the thermoplastic polymer is 100 ppm or less.   The separator for non-aqueous electrical and electronic parts according to claim 1 or 2, wherein the organic polymer substance has an equilibrium moisture content of at least 0.2%.   The separator for non-aqueous electrical and electronic parts according to any one of claims 1 to 3, wherein the air permeability of the thin leaf material is less than 100 seconds before the thin leaf material is heat-treated at a temperature equal to or higher than the melting point of the thermoplastic polymer.   The separator for nonaqueous electrical and electronic parts according to any one of claims 1 to 4, wherein the organic polymer substance is aramid.   The separator for nonaqueous electrical and electronic parts according to claim 5, wherein the aramid is in the form of an aramid thin leaf material.   The non-aqueous electrical system according to claim 6, wherein the thin leaf material is formed by coating the aramid thin leaf material with a layer composed of the thermoplastic polymer having a melting point of 200 ° C or lower and particles having no melting point at 300 ° C or lower. Separator for electronic parts.   The separator for non-aqueous electrical and electronic parts according to any one of claims 1 to 7, wherein the thermoplastic polymer is a polyolefin.   A non-aqueous electrochemical cell comprising an anode, a cathode, an electrolytic solution, and a separator, wherein the separator for a non-aqueous electrical / electronic component according to claim 1 is used as the separator. Non-aqueous electrochemical battery characterized.