JPH10324758A - Para-aramid-based porous film and separator for battery or cell and lithium secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject inexpensive film, good in handleability and having a high tear strength while making the best of characteristics of a para- aramid such as high heat resistance by including a specific substrate and a specified para-aramid polymer therein. SOLUTION: This film is obtained by including (A) a porous substrate which is a woven fabric, a nonwoven fabric or a paper, composed of a fiber and/or a pulp and having <=40 g/m<2> weight per unit area, >=40% void ratio and <=70 μm thickness, (B) a para-aramid polymer which is a porous para-oriented aromatic polyamide, capable of coating the component A or filling the voids of the component A and having preferably 1.0-2.8 dL/g intrinsic viscosity and, as necessary, (C) a thermoplastic polymer, meltable at the time of heat-up and <=260 deg.C and capable of blocking the voids of the components A and/or B in an amount of >=10 wt.% based on the total amount of the components A and B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a para-oriented aromatic polyamide (hereinafter sometimes referred to as "para-aramid") porous film, a battery separator using the para-aramid porous film, and a lithium secondary battery. .

[0002]

2. Description of the Related Art A lithium primary battery or a lithium secondary battery using a non-aqueous electrolyte is greatly expected from the characteristics that a high voltage and a high energy density can be obtained. Since the battery temperature rises due to internal and external short circuits, various safety measures need to be taken. These batteries mainly have a structure in which a separator made of an electrically insulating porous film is interposed between a positive electrode and a negative electrode, and an electrolyte solution in which a lithium salt is dissolved is impregnated in the gaps of the film. In order to solve the problem, attempts have been made to add various devices to the separator.

[0003] In particular, as a safety measure to which a separator can contribute in a secondary battery, attention has been paid to shutdown and short-circuit characteristics. Here, when the battery temperature rises due to troubles such as overcharging or external or internal short circuit, a part of the separator melts, the void is closed, and the current is cut off is called a shutdown (also called a fuse). This temperature is called the shutdown temperature. When the temperature rises further, the separator melts, a large hole is formed, and a short circuit occurs again, a short circuit is called, and the temperature at that time is called a short temperature. It is required for a battery separator to have a low shutdown temperature and a high short temperature.

[0004] As such a battery separator material, the use of a wholly aromatic polyamide polymer excellent in heat resistance, chemical resistance and the like has been studied. For example, JP-B-59-36939 and JP-B-59-14494 describe a method for producing a porous film of an aromatic polyamide, and suggest that the porous film can be used as a battery separator. Further, Japanese Patent Application Laid-Open No. 5-33500
No. 5 describes that Nomex (registered trademark) paper (metaramid paper) manufactured by du Pont is used as a separator of a lithium secondary battery. Similarly, JP-A-7-78608 and JP-A-7-3775
No. 1 also proposes to use a nonwoven fabric or a paper-like sheet made of meta-aramid for a battery separator.

However, the above-mentioned aramid film, nonwoven fabric or paper-like sheet alone cannot provide a shutdown function, and the method described in JP-B-59-36939 or the like makes it possible to obtain a para-aramid porous film industrially. In the case of non-woven fabrics or paper-like sheets made of meta-aramid disclosed in JP-A-7-78608 and the like, which have a thickness of substantially 50 μm or less and have sufficient strength, they must be industrially manufactured. Is difficult, and a separator having excellent electrical properties cannot be obtained. Furthermore, current aramid films, nonwoven fabrics or paper-like sheets are expensive and are not used in large quantities as separators. Therefore, conventionally, a porous film having a small thickness has been used as a separator of a lithium secondary battery. For example, Celgar made by Hoechst Co., Ltd.
d (registered trademark) is suitably used as a separator of a lithium secondary battery. However, Celgard (registered trademark) made of polyethylene or polypropylene has poor heat resistance, and a porous film having good heat resistance and excellent mechanical properties has been desired.

On the other hand, in order to ensure the safety of a battery when a short circuit occurs inside and outside the battery, JP-A-3-291848 and JP-B-4-1692 disclose that a porous film of a thermoplastic resin is heated. It has been proposed to provide a battery separator with a shutdown function of interrupting current by providing a fusible closing material and covering the surface of the microporous membrane by heating and melting the closing material. Also,
JP-A-60-52 and JP-A-60-136161 disclose a method in which a polyethylene resin powder is adhered to a polypropylene non-woven fabric, the powder is heated and melted to close a hole in the non-woven fabric, and the battery is shut down in a battery separator. It has been proposed to have a function. Each of these uses a thermoplastic resin and has a low short-circuit temperature, and its use is limited in terms of safety.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a para-aramid-based porous film which is inexpensive, has good handling properties, and has high tear strength, while taking advantage of para-aramid's high heat resistance. It is another object of the present invention to provide a battery separator that has the safety of shutting down when overheated, does not melt even when heated, has a high short-circuit temperature, and is excellent in safety. Another object of the present invention is to provide a lithium secondary battery having a high short-circuit temperature and excellent safety by using the separator.

[0008]

The present invention comprises (1) a substrate comprising fibers and / or pulp, and a para-aramid polymer which covers the substrate and / or fills voids in the substrate. Further, the present invention relates to a para-aramid-based porous film in which the substrate and the para-aramid polymer are both porous. Further, the present invention provides (2) in the para-aramid-based porous film according to (1), 10% by weight or more of a thermoplastic polymer that melts at 260 ° C. or less based on the total amount of the base material and the para-aramid polymer. The present invention relates to a para-aramid-based porous film, wherein the thermoplastic polymer melts when the temperature rises and closes the gap between the substrate and / or the para-aramid polymer. The present invention also relates to (3) a battery separator using the para-aramid-based porous film described in (1) or (2). The present invention also relates to (4) a lithium secondary battery using the battery separator according to (3).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Para-aramid porous film of the present invention,
(1) A substrate comprising fibers and / or pulp, and a para-aramid polymer covering the substrate and / or filling voids in the substrate, wherein both the substrate and the para-aramid polymer are porous It is characterized by being.
Further, the para-aramid porous film of the present invention,
(2) In the para-aramid-based porous film according to the above (1), the thermoplastic polymer that melts at 260 ° C. or lower is 10% based on the total amount of the base and the para-aramid polymer.
% By weight, characterized in that the thermoplastic polymer melts when the temperature rises and closes the pores of the substrate and / or the para-aramid polymer. The para-aramid porous film of the present invention is suitably used as a battery separator.

[0010] The substrate in the present invention is made of fiber and / or pulp and is porous.
Non-woven fabric or paper may be used. Of these, use of paper is preferred in terms of cost and thinness. The material of the substrate may be an organic or inorganic material as long as it is electrically insulating, may be a synthetic or natural material, and may be organic fiber and / or inorganic fiber and / or organic fiber pulp and / or inorganic fiber pulp. No. Specifically, examples of the organic fibers include fibers made of a thermoplastic polymer and natural fibers such as manila hemp. As a fiber comprising the thermoplastic polymer, rayon, vinylon, polyester,
Fibers such as polyolefin are exemplified. Examples of the inorganic fibers include glass fibers. When the substrate according to the present invention is used for a battery separator, the weight per unit area of the substrate according to the present invention is preferably 40 g / m ² or less, more preferably 15 g / m ² or less. The porosity of the substrate is preferably 40% or more, more preferably 50% or more. Further, the thickness of the substrate,
It is preferably 70 μm or less, more preferably 25 μm or less.
μm or less.

The size of the voids in the battery separator using the para-aramid porous film of the present invention, or when the voids can be approximated to a sphere, the diameter of the sphere (hereinafter, sometimes referred to as the pore diameter) is 0.1. The range is preferably about 01 μm to 1 μm, and the average pore size or average pore diameter is preferably about 0.01 to 0.1 μm. When the average size or pore size of the voids is less than 0.01 μm,
If the effect of the present invention is insufficient and exceeds 1 μm, there is a possibility that a problem such as a short circuit is likely to occur when carbon powder or a small piece of the main component of the positive electrode or the negative electrode falls off. In a battery separator, particularly a lithium secondary battery separator, the porosity is high and the pore size is preferably small, so that the para-aramid porous film of the present invention is suitably used as a battery separator, particularly a lithium secondary battery separator. Used.

The thickness of the para-aramid porous film of the present invention is preferably 5 to 100 μm. When the thickness is less than 5 μm, the film has insufficient strength and is difficult to handle.
As a film, thicker is easier to handle,
Although there is no particular limitation in the nickel-cadmium battery, in the case of the lithium secondary battery, in order to minimize the internal resistance, it is desirable to use a separator as thin as possible without causing a short circuit. That is, in the lithium secondary battery separator,
The thickness is preferably 5 to 100 μm, more preferably 5 to 50 μm, and particularly preferably 5 to 30 μm.

In the present invention, the para-aramid is obtained by condensation polymerization of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid halide, and the amide bond has a para-position of an aromatic ring or an alignment position similar thereto. For example, 4,4′-biphenylene, 1,5-naphthalene,
It consists essentially of recurring units linked in opposite directions, such as 2,6-naphthalene or the like, coaxial or parallel.

Specifically, poly (paraphenylene terephthalamide), poly (parabenzamide, poly (4,
4'-benzanilide terephthalamide), poly (paraphenylene-4,4'-biphenylenedicarboxylic acid amide), poly (paraphenylene-2,6-naphthalenedicarboxylic acid amide), poly (2-chloro-paraphenylene terephthalamide) And para-aramid having a para-oriented or para-oriented structure such as paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer.

[0015] The para-aramid polymer in the present invention comprises:
It is preferably a porous, fibril-like polymer. The fibril-like polymer is microscopically non-woven, has layered and porous voids, and forms a so-called para-aramid porous resin. The para-aramid polymer in the present invention has an intrinsic viscosity of 1.0 dl.
/ G to 2.8 dl / g, preferably a para-oriented aromatic polyamide, more preferably 1.7 dl / g to intrinsic viscosity.
It is preferably 2.5 dl / g.

[0016] The para-aramid porous film of the present invention comprises a substrate comprising the above-mentioned fiber and / or pulp,
The para-aramid polymer is coated, or the space of the substrate is filled with the para-aramid polymer,
Alternatively, the base is coated with the para-aramid polymer, and the voids of the base are filled with the para-aramid polymer.

In the present invention, examples of the thermoplastic polymer include polyolefin resin, acrylic resin, styrene resin, polyester resin and nylon resin. In particular, polyethylene such as low-density polyethylene, high-density polyethylene, and linear polyethylene, or a low-molecular-weight wax component thereof, or a polyolefin resin such as polypropylene is preferably used. These can be used alone or in combination of two or more. The thermoplastic polymer used in the present invention is preferably a powder having an average particle diameter of preferably 10 μm or less, more preferably 6 μm or less, in view of dispersibility in a solvent and smoothness of a coated surface. The shape of the powder particles is not particularly limited, and may be spherical or random.

When used as a resin comprising a thermoplastic polymer in a battery separator which is a use of the present invention,
Any material that melts when the temperature is raised may be used. When used as a separator for a lithium secondary battery, preferably 100
It is preferable from the viewpoint of the shutdown function that the polymer melts at a temperature of from 260C to 260C.

In the para-aramid porous film (2) of the present invention, the thermoplastic polymer is dispersed in the whole or part of the film in the form of particles. When the battery separator of the present invention is used, when the temperature of the battery is locally or entirely increased, the thermoplastic polymer is melted, enters the micropores of the para-aramid porous film and seals the micropores, Make sure no current flows. Further, even when the temperature rises, it does not flow out because it enters not the surface but the micropores. Moreover, since the resin layer made of aramid does not melt,
Keep the film shape. In this way, the battery is shut down.

The above-mentioned para-aramid has a normal temperature of 200 ° C.
It is known that there is almost no deterioration in strength to the extent, and that the composition has excellent heat resistance. In addition, it is self-extinguishing and maintains its form without being melted by heat up to about 500 ° C., and is thermally decomposed at a higher temperature. Therefore, since the thermal decomposition temperature of aramid is higher than the thermal decomposition temperature of other members used in the battery, the short-circuit temperature of the battery is determined by the thermal decomposition temperature or the heat melting temperature of the other members.

Next, a method for producing the battery separator of the present invention will be described. The battery separator of the present invention can be produced, for example, from the following steps (a) to (f).

(A) In a polar amide-based solvent or a polar urea-based solvent in which 2 to 10% by weight of an alkali metal or alkaline earth metal chloride is dissolved, 1.00 mol of para-oriented aromatic diamine is para-oriented. After adding 0.94 to 0.99 mol of an aromatic dicarboxylic acid dihalide, the temperature was lowered to -20.
The concentration of the para-oriented aromatic polyamide produced by condensation polymerization at a temperature of from 50 to 500C is from 1 to 10%, and the intrinsic viscosity is from 1.0 to 2.
A para-oriented aromatic polyamide dope of 8 dl / g is prepared.

(B) A thermoplastic polymer is dispersed in the aramid dope, and the thermoplastic polymer dispersed dope is applied to a substrate and impregnated to form a thermoplastic polymer film. Alternatively, a dope may be applied to a base film, and then a substrate may be placed on the base film for impregnation. (C) The above-mentioned dope of aramid alone is formed on the above-mentioned thermoplastic polymer film. The above step (b),
(C) can be produced even if the order of dope is reversed, that is, a dope of aramid alone is applied to a substrate first, and a thermoplastic polymer is dispersed, and a dope is applied later. Further, it can be manufactured as three layers of (c), (b) and (c) or as three layers of (b), (c) and (b). Aramid polymer solution is formed into a film on a substrate, and further, an aramid polymer solution in which a thermoplastic polymer is dispersed, and aramid polymer solution is formed into a multi-layer film on a substrate to be manufactured. Can be.

(D) The film is kept preferably at a temperature of 20 ° C. or higher and at a constant humidity to precipitate para-aramid, and then immersed in a coagulating liquid. Alternatively, it is immersed in a coagulation liquid to simultaneously precipitate and coagulate para-aramid to obtain a wet porous film. Alternatively, a part or all of the solvent can be evaporated to obtain a semi-dried or dried porous film. At the time of drying, the film tends to shrink, and if the shrinkage is uniformly controlled and dried, a clean film without wrinkles can be obtained. The coagulation liquid may be an aqueous solution or an alcoholic solution, and is not particularly limited.However, it is industrially preferable to use an aqueous solution or an alcoholic solution comprising a solvent used for the aramid polymerization solution. This is preferable because the process is simplified. Specifically, it is an aqueous solution of a polar amide solvent or a polar urea solvent. These solvents include N, N-dimethylformamide, N, N-dimethylacetamide, N
-Methyl-2-pyrrolidone (hereinafter may be abbreviated as NMP), or tetramethylurea.
It is not limited to these.

(E) A solvent and a chloride of an alkali metal or an alkaline earth metal are washed and removed from the wet porous film on which para-aramid is deposited. Alternatively, the alkali metal or alkaline earth metal chloride is washed and removed from the dried porous film. For this removal method, a method of immersing the film in a solution to elute the solvent and chloride is adopted. As a solution for eluting the solvent or the chloride, water, an aqueous solution, or an alcohol-based solution is preferable because both the solvent and the chloride can be dissolved.

(F) The film from which the solvent and chloride have been removed is dried to produce the desired porous film. The drying temperature is preferably lower than the melting temperature of the polymer to be heated and melted. At the time of drying, a mirror-finished roll or the like is brought into contact with the film surface, and the surface is transferred and dried, whereby a smooth and clean film is obtained.

The range of the amount of the chloride of the alkali metal or alkaline earth metal in the para-aramid solution in the step (a) is determined with respect to the amount of the para-aramid (more precisely, the amide group in the para-aramid) as described later. . Generally,
If the alkali metal or alkaline earth metal chloride is less than 2% by weight, the solubility of para-aramid is insufficient, and
If it exceeds 0% by weight, the alkali metal or alkaline earth metal chloride will not be dissolved in the polar amide solvent or polar urea solvent. When the para-aramid concentration is less than 1% by weight, productivity is remarkably reduced, which is industrially disadvantageous. When the amount of para-aramid exceeds 10% by weight, para-aramid precipitates and it is difficult to obtain a stable para-aramid solution.

The para-aramid in the step (a) is expressed by an intrinsic viscosity (in the present invention, the intrinsic viscosity is defined later), and is preferably from 1.0 to 2.8 dl / g, more preferably from 1 to 2.8 dl / g. Refers to para-aramid exhibiting a value of 0.7 to 2.5 dl / g. If the intrinsic viscosity is less than 1.0 dl / g, sufficient film strength cannot be obtained. 2.8 dl intrinsic viscosity
/ G is difficult to become a stable para-aramid solution,
Para-aramid precipitates and it is difficult to form a film.

As the para-oriented aromatic diamine used in the condensation polymerization of para-aramid in step (a), paraphenylenediamine, 4,4'-diaminobiphenyl,
-Methyl-paraphenylenediamine, 2-chloro-paraphenylenediamine, 2,6-dichloro-paraphenylenediamine, 2,6-naphthalenediamine, 1,5-naphthalenediamine, 4,4'-diaminobenzanilide, 3, 4'-diaminodiphenyl ether and the like can be mentioned. The para-oriented aromatic diamine can be used for condensation polymerization by mixing one kind or two or more kinds.

As the para-oriented aromatic dicarboxylic acid dihalide used in the condensation polymerization of para-aramid in the step (a), terephthalic acid dichloride, biphenyl-4,
4'-dicarboxylic acid dichloride, 2-chloroterephthalic acid dichloride, 2,5-dichloroterephthalic acid dichloride, 2-methylterephthalic acid dichloride, 2,
Examples thereof include 6-naphthalenedicarboxylic acid dichloride and 1,5-naphthalenedicarboxylic acid dichloride. The para-oriented aromatic diamine can be used for condensation polymerization by mixing one kind or two or more kinds.

In step (a), the condensation polymerization of para-aramid is carried out in a polar amide solvent or a polar urea solvent. These solvents include, but are not limited to, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, or tetramethylurea.

In the step (a), an alkali metal or alkaline earth metal chloride is preferably used for the purpose of improving the solubility of para-aramid in a solvent. Specific examples include, but are not limited to, lithium chloride or calcium chloride.

The amount of the chloride to be added to the polymerization system is 0.5 to 6.0 per 1.0 mol of the amide group formed by the condensation polymerization.
The mole range is preferred, and the range of 1.0 to 4.0 moles is more preferred. If the amount of chloride is less than 0.5 mol, the solubility of the para-aramid to be formed becomes insufficient, and if it exceeds 6.0 mol, the amount of chloride substantially dissolved in the solvent is not preferable.

[0034]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Test / evaluation methods or criteria in Examples and Comparative Examples are as follows. (1) Intrinsic Viscosity In the present invention, the intrinsic viscosity is defined by the following measuring method. For a solution in which 0.5 g of the para-aramid polymer was dissolved in 100 ml of 96-98% sulfuric acid and for a 96-98% sulfuric acid, the flow time was measured at 30 ° C. using a capillary viscometer. Was used to determine the intrinsic viscosity. Intrinsic viscosity = ln (T / T ₀ ) / C
[Unit: dl / g] where T and T ₀ are the flow times of the para-aramid sulfate solution and sulfuric acid, respectively.
Is the concentration of para-aramid in the para-aramid sulfate solution (dl
/ G).

(2) Measurement of Film Thickness The thickness of the obtained film is JIS K7130-1.
992. (3) Porosity The film was cut into a square having a side length of 10 cm, and the weight (Wg) and thickness (Dcm) were measured. The weight of the material in the sample was divided by calculation, the weight (Wi) of each material was divided by the true specific gravity, and the porosity (vol%) was determined from the following equation, assuming the volume of each material. Porosity (%) = 100 − ｛(W1 / true specific gravity 1) + (W2 /
True specific gravity 2) + .. + (Wn / true specific gravity n)｝ / (100 ×
D)

(Equation 1)

The basis weight of the film is 10 cm
It was cut out into a square with a corner, and its weight was measured and determined by the following equation. Film weight (g / m ² ) = weight of sample (g)
/0.01

(4) Measurement of tear strength JIS K-7128-1 manufactured by Dumbbell Co., Ltd.
A test piece was punched out with a dumbbell cutter for the 991 C method (right angle tearing method), and JIS was used using an Instron universal tensile tester model 4301 manufactured by Instron Japan.
The tear strength was measured according to the K-7128-1991 C method (right angle tearing method). Both ends of the sample were gripped by a chuck of a universal tensile tester, pulled at a speed of 200 mm / min, and the load and displacement at that time were recorded by a recorder.
The tear strength was determined from the load at which the sample was torn. Thereafter, the tear propagation resistance was determined from the average value of the load until the sample was completely broken. The tear strength and the tear propagation resistance were determined by the following equations. Tear strength (kg / mm) = Maximum load when sample tearing started / Sample thickness Tear propagation resistance (kg / mm) = Average value of load from start of sample tearing until complete breakage / Sample thickness

(5) Measurement of the internal electric resistance of the flat battery (for the purpose of measuring the electric resistance of the separator, evaluating the shutdown operation and evaluating the heat resistance) A film was cut into a square having a side length of 25 mm, and L
Impregnate the electrolyte with a 1N propylene carbonate solution of iBF ₄ . This is 0.5mm thick, 18mm diameter 2
Between the electrodes of a platinum disc, 1K between the electrodes
The internal electric resistance of the flat battery was measured by applying a voltage of 1 volt at Hz, and the internal electric resistance at 25 ° C. was defined as the electric resistance of the separator. The flat battery was placed on a hot plate, and the temperature was raised from 25 ° C. to 260 ° C. at a rate of 10 ° C./min. The temperature at which the internal electric resistance increases in this process is defined as the shutdown operating temperature. Further, the temperature was lowered from 260 ° C. to 25 ° C. at a rate of 10 ° C./min. The internal electric resistance at 25 ° C. after the temperature decrease was taken as the internal electric resistance of the separator after heating, and the heat resistance of the separator was determined by comparing it with the internal electric resistance before heating.

(6) Evaluation as Battery Separator The positive electrode was made of lithium nickelate powder and carbonaceous conductive material powder.
And a mixture (polyvinylidene fluoride) in a weight ratio of 87: 10: 3 (N-methylpyrrolidone solvent) was added to 20 pastes.
It was applied to a μm aluminum foil, dried and pressed to produce a 85 μm thick sheet. For the negative electrode, a paste (N-methylpyrrolidone solvent) in which graphite powder and polyvinylidene fluoride were mixed at a weight ratio of 90:10 was applied to a 10-μm copper foil, dried and pressed to prepare a 100-μm-thick sheet. The electrolytic solution is prepared by dissolving lithium hexafluorophosphate in a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (1 mol / L concentration).
The used solution was used. As the separator, a porous film described in Examples of the present invention was used. The battery has a positive electrode area of 2.
A 34 cm square plate-type structure was prepared, and the above-prepared ones were stacked in the order of a negative electrode sheet, a separator and a positive electrode sheet in an argon atmosphere box, and then the separator was sufficiently impregnated with an electrolytic solution. Charge the prepared flat battery with a charging voltage of 4.
Eight cycles were repeated at 2 V and a discharge voltage of 2.75 V, and the discharge capacity at the eighth cycle (discharge current: 1.5 mA) was measured. The cycle deterioration was measured.

Embodiment 1 1. Polymerization of poly (paraphenyleneterephthalamide) Poly (paraphenyleneterephthalamide) (hereinafter abbreviated as PPTA) using a 3-liter separable flask having a stirring blade, a thermometer, a nitrogen inlet tube and a powder addition port. ) Was manufactured. Dry the flask thoroughly,
Methyl-2-pyrrolidone (hereinafter abbreviated as NMP) 220
After adding 0 g, 151.07 g of calcium chloride powder vacuum-dried at 200 ° C. for 2 hours was added, and the mixture was heated to 100 ° C. and completely dissolved. After returning to room temperature, 68.23 g of paraphenylenediamine was added and completely dissolved. While maintaining this solution at 20 ° C. ± 2 ° C., 124.97 g of terephthalic acid dichloride was added in 10 portions and added about every 5 minutes. However, one of the 10 divided terephthalic acid dichlorides was dissolved in NMP of the same weight as the terephthalic acid dichloride and the final addition was performed. After that, while stirring
The solution was aged for 1 hour while maintaining the solution at 20 ° C. ± 2 ° C. Fifteen
The mixture was filtered through a 00 mesh stainless steel wire mesh. The obtained polymerization liquid showed a liquid crystal phase having a PPTA concentration of 6% and exhibited optical anisotropy. A part of the PPTA polymerization solution was sampled, reprecipitated with water, taken out as an aramid polymer, and the obtained P
When the intrinsic viscosity of PTA was measured, it was 1.82 dl / g.

2. Preparation of PPTA dope for coating PPTA dope for coating Was weighed into a 500 ml separable flask having a stirring blade, a thermometer, a nitrogen inlet tube, and a liquid addition port, and stirred for 15 minutes. 250 g of NMP was added, and finally, an isotropic phase solution having a PPTA concentration of 1.0% by weight was prepared and stirred for 60 minutes. Thereafter, defoaming was performed under reduced pressure to obtain a coating dope. PPTA dope for coating 100 g of the PPTA dope of Example 1 having a stirring blade, a thermometer, a nitrogen inlet tube, and a liquid addition port.
Weighed into a 00 ml separable flask and 200 g of N
MP was added slowly. Finally, the PPTA concentration is 2.
A 0% by weight solution of the isotropic phase was prepared and stirred for 60 minutes.
Thereafter, defoaming was performed under reduced pressure to obtain a coating dope.

3. Preparation of porous film 0.05mm thick PE on 3mm thick aluminum plate
Place the EK film, and place the base material (polyester paper,
Product name 0132TH-8 fine denier type, weight 8
g / m ² , thickness 20 μm, porosity 71%; product of Japan Vilene Co., Ltd.). A 3 cm width of one side of the substrate was fixed to an aluminum flat plate with a heat-resistant tape. From the side fixed with the tape, the above coating dope was coated from above the base material with a bar coater manufactured by Tester Sangyo Co., Ltd. with a bar coating clearance of 0.
1 mm, coating speed 0.2 m / min. The other end of the substrate is 5
The coating was performed until the cm was left. Dope for coating,
After the above-mentioned dope for coating was applied, 5 cm of the base material was left in the same manner as described above with a coating clearance of the bar of 0.5 mm from the side fixed with the heat-resistant tape, and applied. This is 23
PPTA was deposited in an atmosphere of 50 ° C. and a humidity of 50% for 20 minutes. The opposite side of the previously fixed substrate was fixed to an aluminum flat plate with heat-resistant tape. Put this in a hot air oven at 80 ° C for 1
The solvent was evaporated for 2 hours. The base material was fixed,
The heat-resistant tape was removed, immersed in ion exchange water, and washed for 12 hours while flowing ion exchange water. The washed wet film is sandwiched between polyester fabrics from both sides, further sandwiched between aramid felts, placed on a 3 mm thick aluminum plate, and a 0.1 mm thick nylon film is placed on top of it and sealing around it Sealed with a material and dried at 80 ° C. for 6 hours while evacuating the inside.

4. Physical properties of porous film The above dried film has a thickness of 29 μm and a porosity of 51
%, And a basis weight of 18 g / m ² . Observation of the film with a scanning electron microscope revealed that one surface was made of a fibril-like or layer-like PPTA resin having a pore diameter of about
It was a porous layer having pores of 5 to 0.2 μm. On the other side, polyolefin particles (trade name: PEW40)
00; a product of Seishin Enterprise) was captured and fixed by the porous PPTA resin. Observation of the cross section revealed that a fibril-like PPTA resin of about 0.1 μm or less was filled between the polyester fibers of the base paper. The tear strength of this film is 6 kg / mm, and the tear propagation resistance is 3 kg.
/ Mm, the handleability was excellent.

5. Measurement of Internal Electric Resistance The internal electric resistance at 25 ° C. of the film before heating was 12Ω. As the temperature of the sample was increased, the internal electric resistance was gradually decreased, but the internal electric resistance was increased at some point, and was 21Ω at 260 ° C. This is 2
The internal electrical resistance after heating when the temperature is lowered to 5 ° C is 30
Ω. From the above results, this separator shuts off current when the temperature rises,
It has been found that it has heat resistance to maintain the function as a separator separating the inside of the electrode even at ℃.

6 Evaluation as Battery Separator The discharge capacity at the eighth cycle of the obtained film was 7 mA.
H (discharge current: 1.5 mA), and it operated normally without cycle deterioration. From the above results, it was found that the present separator has performance as a battery separator.

Embodiment 2 1. Preparation of PPTA dope for coating PPTA dope for coating Of 50 g of PPTA dope and 24 g of polyolefin particles (trade name: PEW4000; manufactured by Seishin Enterprise Co., Ltd.) were weighed into a 500 ml separable flask having a stirring blade, a thermometer, a nitrogen inlet tube and a liquid addition port, and stirred for 15 minutes. . 250 g of NMP was added, and finally, an isotropic phase solution having a PPTA concentration of 1.0% by weight was prepared and stirred for 60 minutes. Thereafter, defoaming was performed under reduced pressure to obtain a coating dope. PPTA dope for coating 100 g of the PPTA dope of Example 1 having a stirring blade, a thermometer, a nitrogen inlet tube, and a liquid addition port.
Weighed into a 00 ml separable flask and 200 g of N
MP was added slowly. Finally, the PPTA concentration is 2.
A 0% by weight solution of the isotropic phase was prepared and stirred for 60 minutes.
Thereafter, defoaming was performed under reduced pressure to obtain a coating dope.

2. Preparation of porous film 0.1mm thick PET on 3mm thick aluminum plate
A film was placed thereon, and a substrate (polyester paper, trade name H30008, basis weight 8 g / m ² , thickness 30 μm, porosity 81%; product of Nippon Vilene Co., Ltd.) was placed thereon. One end of the substrate and the PET film was fixed to an aluminum flat plate with a tape. From the side fixed with the tape, the coating dope was coated from above the substrate with a bar coater manufactured by Tester Sangyo Co., Ltd. using a bar coater of 0.1 mm and a coating speed of 0.2 m / min. Was applied. Dope for coating,
After the above coating dope was coated, the coating was performed in the same manner as described above with a coating clearance of a bar of 0.5 mm from the side fixed with the tape. This was placed in an atmosphere at 23 ° C. and a humidity of 50% for 20 minutes to precipitate PPTA. It is immersed in ion-exchanged water to coagulate, and while flowing ion-exchanged water, 12
Washed for hours. The washed wet film is sandwiched between polyester fabrics from both sides, further sandwiched between aramid felts, placed on a 3 mm thick aluminum plate, and a 0.1 mm thick nylon film is placed on top of it and sealing around it Seal with a material and evacuate the inside,
Dry at 0 ° C. for 6 hours.

3. Physical Properties of Porous Film The above dried film has a thickness of 35 μm and a porosity of 54
%, And a basis weight of 16 g / m ² . Observation of the film with a scanning electron microscope revealed that one surface was made of a fibril-like or layer-like PPTA resin having a pore diameter of about 0.1 μm or less.
It was a porous layer having pores of 0.5 to 0.2 μm. The other side is polyolefin particles (PEW4000)
Was captured and fixed by the porous PPTA resin. Observation of the cross section revealed that a fibril-like PPTA resin of about 0.1 μm or less was filled between the polyester fibers of the base paper. The tear strength of this film is 4 kg / mm,
The tear propagation resistance was 2 kg / mm, indicating excellent handling.

4. Measurement of Internal Electric Resistance The internal electric resistance at 25 ° C. of the film before heating was 11Ω. As you increase the temperature of the sample,
Although the internal electric resistance gradually decreased, the internal electric resistance increased from the middle and was 22Ω at 260 ° C. When the temperature was lowered to 25 ° C, the internal electrical resistance after heating was 3
It was 1Ω. Based on the above results, the present separator shuts off the current when the temperature rises.
It was found that it had heat resistance to maintain the function as a separator separating the inside of the electrode even at 0 ° C.

6. Evaluation as Battery Separator The discharge capacity at the eighth cycle of the obtained film was 7 mA.
H (discharge current: 1.5 mA), and it operated normally without cycle deterioration. From the above results, it was found that the present separator has performance as a battery separator.

Embodiment 3 1. Preparation of PPTA dope for coating 50 g of PPTA dope was stirred for 500 m having a stirring blade, a thermometer, a nitrogen inlet tube, and a liquid addition port.
1 g of separable flask was weighed, and 250 g of NMP was gradually added. Finally, a solution of a liquid crystal phase having a PPTA concentration of 1.0% by weight was prepared and defoamed under reduced pressure to obtain a coating dope.

2. Preparation of porous film 0.1mm thick PET on 3mm thick aluminum plate
A film was placed thereon, and a substrate (polyester paper, trade name H30008, basis weight 8 g / m ² , thickness 30 μm, porosity 81%; product of Nippon Vilene Co., Ltd.) was placed thereon. One end of the base material and the PET film was fixed to an aluminum plate with a tape. From the side fixed to the aluminum plate with tape, apply the above coating dope from above the base material with a bar coater manufactured by Tester Sangyo Co., Ltd.
m, coating speed 0.2 m / min. Was applied. This is 2
PPTA was deposited at 3 ° C. in an atmosphere of 50% humidity for 20 minutes. It was immersed in ion-exchanged water for coagulation, and washed for 12 hours while flowing ion-exchanged water. The washed wet film is sandwiched between polyester fabrics from both sides, further sandwiched between aramid felts, placed on a 3 mm thick aluminum plate, and a 0.1 mm thick nylon film is placed on top of it and sealing around it Sealed with a material and dried at 80 ° C. for 6 hours while evacuating the inside.

3. Physical Properties of Porous Film The above dried film has a thickness of 33 μm and a porosity of 77
% And a basis weight of 11 g / m ² . Observation of the film with a scanning electron microscope showed that both sides were about 0.1
The porous layer was made of a fibril-shaped or layer-shaped PPTA resin having a diameter of 0.05 μm or less and had pores having a pore diameter of 0.05 to 0.2 μm. When the cross section is observed, a fibril-like PPT of about 0.1 μm or less is formed between the polyester fibers of the base paper.
A resin was filled. The tear strength of this film is
4 kg / mm, tear propagation resistance was 2 kg / mm, and the handleability was excellent.

4. Measurement of Internal Electric Resistance The internal electric resistance at 25 ° C. of the film before heating was 16Ω. As you increase the temperature of the sample,
The internal electric resistance gradually decreased to 260 ° C. and was 4Ω. The internal electrical resistance after heating when the temperature was lowered to 25 ° C. was 16Ω. From the above results, it was found that the present separator had heat resistance to maintain the function as a separator separating the inside of the electrode even at 260 ° C.

5. Evaluation as Battery Separator The discharge capacity at the eighth cycle of the obtained film was 7 mA.
H (discharge current: 1.5 mA), and it operated normally without cycle deterioration. From the above results, it was found that the present separator has performance as a battery separator.

Embodiment 4 1. Preparation of PPTA dope for coating PPTA dope for coating 50 g of a PPTA dope of Example 5 having a stirring blade, a thermometer, a nitrogen inlet tube and a liquid addition port.
Weigh into a 00 ml separable flask and add 250 g of N
MP was added, and finally the PPTA concentration was 1.0% by weight.
And stirred for 60 minutes. afterwards,
It was defoamed under reduced pressure to obtain a coating dope. PPTA dope for coating 100 g of the PPTA dope of Example 1 having a stirring blade, a thermometer, a nitrogen inlet tube, and a liquid addition port.
Weighed into a 00 ml separable flask and 200 g of N
MP was added slowly. Finally, the PPTA concentration is 2.
A 0% by weight solution of the isotropic phase was prepared and stirred for 60 minutes.
Thereafter, defoaming was performed under reduced pressure to obtain a coating dope.

2. Preparation of porous film 0.1mm thick PET on 3mm thick aluminum plate
A film is placed, and a substrate (polyester cloth, trade name PET-07, basis weight 32 g / m ² , thickness 70 μm,
(Porosity: 67%: product of JALT Co., Ltd.). One end of the substrate and the PET film was fixed to an aluminum flat plate with a tape. From the side fixed with the tape, the coating dope was coated from above the substrate with a bar coater manufactured by Tester Sangyo Co., Ltd. using a bar coater of 0.1 mm and a coating speed of 0.2 m / min. Was applied. Dope for coating,
After the above coating dope was coated, the coating was performed in the same manner as described above with a coating clearance of a bar of 0.5 mm from the side fixed with the tape. This was placed in an atmosphere at 23 ° C. and a humidity of 50% for 20 minutes to precipitate PPTA. It is immersed in ion-exchanged water to coagulate, and while flowing ion-exchanged water, 12
Washed for hours. The washed wet film is sandwiched between polyester fabrics from both sides, further sandwiched between aramid felts, placed on a 3 mm thick aluminum plate, and a 0.1 mm thick nylon film is placed on top of it and sealing around it Seal with a material and evacuate the inside,
Dry at 0 ° C. for 6 hours.

3. Physical Properties of Porous Film The above dried film has a thickness of 73 μm and a porosity of 45
%, And the basis weight was 38 g / m ² . Observation of the film with a scanning electron microscope showed that both sides were about 0.1
The porous layer was made of a fibril-shaped or layer-shaped PPTA resin having a diameter of 0.05 μm or less, and had pores having a pore diameter of 0.05 to 0.2 μm. When the cross section is observed, a fibril-like PPT of about 0.1 μm or less is formed between the polyester fibers of the base cloth.
A resin was filled. The tear strength of this film is
10 kg / mm, tear propagation resistance was 2 kg / mm, and the handling was excellent.

4. Measurement of Internal Electric Resistance The internal electric resistance at 25 ° C. of the film before heating was 12Ω. As you increase the temperature of the sample,
The internal electric resistance gradually decreased to 260 ° C. and was 6Ω. When the temperature was lowered to 25 ° C., the internal electric resistance after heating was 12Ω. From the above results, it was found that the present separator had heat resistance to maintain the function as a separator separating the inside of the electrode even at 260 ° C.

5. Evaluation as Battery Separator The discharge capacity at the eighth cycle of the obtained film was 6 mA.
H (discharge current: 1.5 mA), and it operated normally without cycle deterioration. From the above results, it was found that the present separator has performance as a battery separator.

Embodiment 5 1. Preparation of PPTA dope for coating PPTA dope for coating Of 25 g of PPTA dope and 4.5 g of polyolefin particles (trade name: PEW4000; manufactured by Seishin Enterprise Co., Ltd.) are weighed into a 500 ml separable flask having a stirring blade, a thermometer, a nitrogen inlet tube and a liquid addition port, for 15 minutes. Stirred. 275 g of NMP was added, and finally, a solution of an isotropic phase having a PPTA concentration of 0.5% by weight was prepared and stirred for 60 minutes. Thereafter, defoaming was performed under reduced pressure to obtain a coating dope.

[0062] 2. Preparation of porous film 0.1mm thick PET on 3mm thick aluminum plate
A film is placed, and a substrate (glass fiber cloth, product name: KS-1061 surface silane treated product, basis weight 21 g /
m ² , thickness 30 μm, porosity 73%: Kanebo Corporation product)
Was placed. One end of the substrate and the PET film was fixed to an aluminum flat plate with a tape. From the side fixed with tape,
The above coating dope was coated from above the substrate with a bar coater manufactured by Tester Sangyo Co., Ltd. to obtain a coating clearance of 0.
35 mm, coating speed 0.2 m / min. Was applied. This is placed in an atmosphere of 23 ° C. and 50% humidity for 20 minutes,
TA was deposited. Immerse in ion exchange water to solidify,
Washing was performed for 12 hours while flowing ion-exchanged water. The washed wet film is sandwiched between polyester fabrics from both sides, further sandwiched between aramid felts, placed on a 3 mm thick aluminum plate, and a 0.1 mm thick nylon film is placed on top of it and sealing around it Sealed with a material and dried at 80 ° C. for 6 hours while evacuating the inside.

3. Physical Properties of Porous Film The obtained film had a thickness of 62 μm, a porosity of 58%,
The basis weight was 26 g / m ² . When the film was observed with a scanning electron microscope, both sides of the front and back were about 0.1μ.
m or less of fibril-like or layered PPTA resin,
It was a porous layer having pores having a pore size of 0.05 to 0.2 μm. When the cross section was observed, a fibril-like PPTA resin of about 0.1 μm or less was filled between the glass fibers of the base material. The tear strength is 5 kg / mm and the tear propagation resistance is 3 kg / mm, which is excellent in handling.

4. Measurement of Internal Electric Resistance The internal electric resistance of the obtained film at 25 ° C. before heating was 12Ω. As the temperature of the sample was increased, the internal electric resistance gradually decreased, and the internal electric resistance increased halfway to 25Ω at 260 ° C. This is 25
The internal electrical resistance after heating when the temperature is lowered to ℃ is 50Ω
Met. From the above results, this separator shuts off the current when the temperature rises, the shutdown function and 260 ° C
However, it was found that it had heat resistance to maintain the function as a separator separating the inside of the electrode.

5. Evaluation as Battery Separator The discharge capacity at the eighth cycle of the obtained film was 6 mA.
H (discharge current: 1.5 mA), and it operated normally without cycle deterioration. From the above results, it was found that the present separator has performance as a battery separator.

Embodiment 6 1. Preparation of PPTA dope for coating PPTA dope for coating Was weighed into a 500 ml separable flask having a stirring blade, a thermometer, a nitrogen inlet tube and a liquid addition port, and stirred for 15 minutes. . 250 g of NMP was added, and finally, an isotropic phase solution having a PPTA concentration of 1.0% by weight was prepared and stirred for 60 minutes. Thereafter, defoaming was performed under reduced pressure to obtain a coating dope.

2. Preparation of porous film 0.1mm thick PET on 3mm thick aluminum plate
A film is placed, and a base material (vinylon paper, trade name Papillon BFH No. 1, basis weight 13 g / m ² , thickness 5) is placed on the film.
3 μm, porosity 82%: Kuraray Co., Ltd.).
One end of the substrate and the PET film was fixed to an aluminum flat plate with a tape. From the side fixed with the tape, the above coating dope was coated from above the substrate with a bar coater manufactured by Tester Sangyo Co., Ltd. using a bar coating clearance of 0.3 mm and a coating speed of 0.2 m / min. Was applied. This was placed in an atmosphere at 23 ° C. and a humidity of 50% for 20 minutes to precipitate PPTA. It was immersed in ion-exchanged water for coagulation, and washed for 12 hours while flowing ion-exchanged water. The washed wet film is sandwiched between polyester fabrics from both sides, further sandwiched between aramid felts, placed on a 3 mm thick aluminum plate, and a 0.1 mm thick nylon film is placed on top of it and sealing around it Sealed with a material and dried at 80 ° C. for 6 hours while evacuating the inside.

3. Physical Properties of Porous Film The obtained film has a thickness of 74 μm, a porosity of 75%,
The basis weight was 22 g / m ² . The film was observed with a scanning electron microscope.
The porous layer was made of the following fibril-shaped and layered PPTA resin and had pores having a pore size of 0.05 to 0.2 μm. When the cross section was observed, a fibril-like PPTA resin of about 0.1 μm or less was filled between the vinylon fibers of the base material. The tear strength is 7 kg / mm, the tear propagation resistance is 3 kg / mm, and the handleability is excellent.

4. Measurement of Internal Electric Resistance The internal electric resistance of the obtained film at 25 ° C. before heating was 14Ω. As the temperature of the sample was increased, the internal electric resistance gradually decreased, and the internal electric resistance increased halfway to 25Ω at 260 ° C. This is 25
The internal electrical resistance after heating when the temperature is lowered to ℃ is 50Ω
Met. From the above results, this separator shuts off the current when the temperature rises, the shutdown function and 260 ° C
However, it was found that it had heat resistance to maintain the function as a separator separating the inside of the electrode.

5. Evaluation as Battery Separator The discharge capacity at the eighth cycle of the obtained film was 6 mA.
H (discharge current: 1.5 mA), and it operated normally without cycle deterioration. From the above results, it was found that the present separator has performance as a battery separator.

Embodiment 7 1. Preparation of PPTA dope for coating PPTA dope for coating Of 50 g of PPTA dope and 24 g of polyolefin particles (trade name: PEW4000; manufactured by Seishin Enterprise Co., Ltd.) were weighed into a 500 ml separable flask having a stirring blade, a thermometer, a nitrogen inlet tube and a liquid addition port, and stirred for 15 minutes. . 250 g of NMP was added, and finally, an isotropic phase solution having a PPTA concentration of 1.0% by weight was prepared and stirred for 60 minutes. Thereafter, defoaming was performed under reduced pressure to obtain a coating dope. PPTA dope for coating 100 g of the PPTA dope of Example 1 having a stirring blade, a thermometer, a nitrogen inlet tube, and a liquid addition port.
Weighed into a 00 ml separable flask and 200 g of N
MP was added slowly. Finally, the PPTA concentration is 2.
A 0% by weight solution of the isotropic phase was prepared and stirred for 60 minutes.
Thereafter, defoaming was performed under reduced pressure to obtain a coating dope.

2. Preparation of porous film 0.1mm thick PET on 3mm thick aluminum plate
A film is placed, and a base material (manila paper, basis weight 14) is placed thereon.
g / m ² , thickness 25 μm, porosity 57%: manufactured by Tokushu Paper Co., Ltd.). One end of the substrate and the PET film was fixed to an aluminum flat plate with a tape. From the side fixed with the tape, the coating dope was coated from above the substrate with a bar coater manufactured by Tester Sangyo Co., Ltd. using a bar coater of 0.1 mm and a coating speed of 0.2 m / min. Was applied. The coating dope was coated in the same manner as described above, with the coating clearance of the bar being 0.5 mm from the side where the coating dope was coated and from the side fixed with the tape. This is placed in an atmosphere of 23 ° C. and 50% humidity for 20 minutes, and the PPT
A was precipitated. It was immersed in ion-exchanged water for coagulation, and washed for 12 hours while flowing ion-exchanged water. The washed wet film is sandwiched between polyester fabrics from both sides, further sandwiched between aramid felts, placed on a 3 mm thick aluminum plate, and a 0.1 mm thick nylon film is placed on top of it and sealing around it Seal with material,
It dried at 80 degreeC for 6 hours, evacuating the inside.

3. Physical Properties of Porous Film The obtained film has a thickness of 40 μm, a porosity of 46%,
The basis weight was 26 g / m ² . The film was observed with a scanning electron microscope.
The porous layer was made of the following fibril-shaped and layered PPTA resin and had pores having a pore size of 0.05 to 0.2 μm. Observation of the cross section shows that about 0.2 mm between the manila fibers of the substrate.
A fibril-like PPTA resin of 1 μm or less was filled. The tear strength is 12 kg / mm, the tear propagation resistance is 9 kg / mm, and the handleability is excellent.

4. Measurement of Internal Electric Resistance The internal electric resistance of the obtained film at 25 ° C. before heating was 14Ω. As the temperature of the sample was increased, the internal electric resistance gradually decreased, and the internal electric resistance increased halfway to 25Ω at 260 ° C. This is 25
The internal electrical resistance after heating when the temperature is lowered to ℃ is 28Ω
Met. From the above results, this separator shuts off the current when the temperature rises, the shutdown function and 260 ° C
However, it was found that it had heat resistance to maintain the function as a separator separating the inside of the electrode. 5. Evaluation as Battery Separator The discharge capacity at the eighth cycle of the obtained film was 5 mA.
H (discharge current: 1.5 mA), and it operated normally without cycle deterioration. From the above results, it was found that the present separator has performance as a battery separator.

Embodiment 8 1. Preparation of PPTA dope for coating PPTA dope for coating Was weighed into a 500 ml separable flask having a stirring blade, a thermometer, a nitrogen inlet tube and a liquid addition port, and stirred for 15 minutes. . 250 g of NMP was added, and finally, an isotropic phase solution having a PPTA concentration of 1.0% by weight was prepared and stirred for 60 minutes. Thereafter, defoaming was performed under reduced pressure to obtain a coating dope.

2. Preparation of porous film 0.1mm thick PET on 3mm thick aluminum plate
A film was placed thereon, and a substrate (polyester paper, trade name H30008, basis weight 8 g / m ² , thickness 30 μm, porosity 81%; product of Nippon Vilene Co., Ltd.) was placed thereon. One end of the substrate and the PET film was fixed to an aluminum flat plate with a tape. From the side fixed with the tape, the above coating dope was coated from above the substrate with a bar coater manufactured by Tester Sangyo Co., Ltd. using a bar coating clearance of 0.3 mm and a coating speed of 0.2 m / min. Was applied. This is at 23 ° C and 5% humidity.
PPTA was precipitated by placing in a 0% atmosphere for 20 minutes.
It was immersed in ion-exchanged water for coagulation, and washed for 12 hours while flowing ion-exchanged water. After washing the wet film,
Sandwiched between polyester cloth from both sides, further sandwiched with aramid felt, placed on a 3 mm thick aluminum flat plate, put a 0.1 mm thick nylon film from above,
The periphery was sealed with a sealing material and dried at 80 ° C. for 6 hours while evacuating the inside.

3. Physical Properties of Porous Film The above dried film has a thickness of 42 μm and a porosity of 75
% And a basis weight of 12 g / m ² . Observation of the film with a scanning electron microscope revealed that one surface was made of a fibril-like or layer-like PPTA resin having a pore diameter of about 0.1 μm or less.
It was a porous layer having pores of 0.5 to 0.2 μm. The other side is polyolefin particles (trade name PEW40)
00; a product of Seishin Enterprise) was captured and fixed by the porous PPTA resin. Observation of the cross section revealed that a fibril-like PPTA resin of about 0.1 μm or less was filled between the polyester fibers of the base paper. The tear strength of this film is 4 kg / mm, and the tear propagation resistance is 2 kg
/ Mm, the handleability was excellent.

4. Measurement of Internal Electric Resistance The internal electric resistance at 25 ° C. of the film before heating was 11Ω. As the temperature of the sample was increased, the internal electric resistance was gradually decreased, and the internal electric resistance was increased halfway and was 20Ω at 260 ° C. The internal electrical resistance after heating when the temperature was lowered to 25 ° C. was 22Ω. From the above results, it was found that the present separator has a shutdown function to shut off current when the temperature rises, and a heat resistance to maintain the function as a separator separating the inside of the electrode even at 260 ° C.

6. Evaluation as Battery Separator The discharge capacity at the eighth cycle of the obtained film was 7 mA.
H (discharge current: 1.5 mA), and normal operation without cycle deterioration. From the above results, it was found that the present separator has performance as a battery separator.

Embodiment 9 1. Preparation of PPTA dope for coating PPTA dope for coating Was weighed into a 500 ml separable flask having a stirring blade, a thermometer, a nitrogen inlet tube and a liquid addition port, and stirred for 15 minutes. . 250 g of NMP was added, and finally, an isotropic phase solution having a PPTA concentration of 1.0% by weight was prepared and stirred for 60 minutes. Thereafter, defoaming was performed under reduced pressure to obtain a coating dope. PPTA dope for coating 100 g of the PPTA dope of Example 1 having a stirring blade, a thermometer, a nitrogen inlet tube, and a liquid addition port.
Weighed into a 00 ml separable flask and 200 g of N
MP was added slowly. Finally, the PPTA concentration is 2.
A 0% by weight solution of the isotropic phase was prepared and stirred for 60 minutes.
Thereafter, defoaming was performed under reduced pressure to obtain a coating dope.

2. Preparation of porous film 0.1mm thick PET on 3mm thick aluminum plate
A film was placed thereon, and a substrate (polyester paper, trade name H30008, basis weight 8 g / m ² , thickness 30 μm, porosity 81%; product of Nippon Vilene Co., Ltd.) was placed thereon. One side of the substrate and the end of the PET film were fixed to an aluminum plate with tape. From the side fixed with the tape, the coating dope was coated from above the substrate with a bar coater manufactured by Tester Sangyo Co., Ltd. using a bar coater of 0.1 mm and a coating speed of 0.2 m / min. Was applied. Dope for coating,
After the above coating dope was coated, the coating was performed in the same manner as described above with a coating clearance of a bar of 0.5 mm from the side fixed with the tape. This was placed in an atmosphere at 23 ° C. and a humidity of 50% for 20 minutes to precipitate PPTA. It is immersed in ion-exchanged water to coagulate, and while flowing ion-exchanged water, 12
Washed for hours. The washed wet film is sandwiched between polyester fabrics from both sides, further sandwiched between aramid felts, placed on a 3 mm thick aluminum plate, and a 0.1 mm thick nylon film is placed on top of it and sealing around it Seal with a material and evacuate the inside,
Dry at 0 ° C. for 6 hours.

3. Physical Properties of Porous Film The above dried film has a thickness of 37 μm and a porosity of 72
%, And a basis weight of 13 g / m ² . Observation of the film with a scanning electron microscope revealed that one surface was made of a fibril-like or layer-like PPTA resin having a pore diameter of about 0.1 μm or less.
It was a porous layer having pores of 0.5 to 0.2 μm. The other side is polyolefin particles (PEW4000)
Was captured and fixed by the porous PPTA resin. Observation of the cross section revealed that a fibril-like PPTA resin of about 0.1 μm or less was filled between the polyester fibers of the base paper. The tear strength of this film is 4 kg / mm,
The tear propagation resistance was 3 kg / mm, indicating excellent handling.

4. Measurement of Internal Electric Resistance The internal electric resistance at 25 ° C. of the film before heating was 11Ω. As you increase the temperature of the sample,
The internal electric resistance gradually decreased to 260 ° C. and was 6Ω at 260 ° C. When the temperature was lowered to 25 ° C., the internal electrical resistance after heating was 11Ω. From the above results, it was found that the present separator does not have a shutdown function of interrupting the current when the temperature rises. This is presumably because the amount of the polyolefin added was small, so that when the polyolefin melted at the temperature, it was not possible to block the PPTA fibrils. However, even at 260 ° C., it was found to have heat resistance to maintain the function as a separator separating the inside of the electrode.

Embodiment 10 1. Preparation of PPTA dope for coating 50 g of PPTA dope was stirred for 500 m having a stirring blade, a thermometer, a nitrogen inlet tube, and a liquid addition port.
1 g of separable flask was weighed, and 250 g of NMP was gradually added. Finally, a solution of a liquid crystal phase having a PPTA concentration of 1.0% by weight was prepared and defoamed under reduced pressure to obtain a coating dope.

2. Preparation of porous film 0.1mm thick PET on 3mm thick aluminum plate
A film was placed thereon, and a substrate (polyester paper, trade name H30008, basis weight 8 g / m ² , thickness 30 μm, porosity 81%; product of Nippon Vilene Co., Ltd.) was placed thereon. One end of the base material and the PET film was fixed to an aluminum plate with a tape. From the side fixed to the aluminum plate with tape, apply the above coating dope from above the base material using a bar coater manufactured by Tester Sangyo Co., Ltd.
m, coating speed 0.2 m / min. Was applied. This is 2
PPTA was deposited at 3 ° C. in an atmosphere of 50% humidity for 20 minutes. It was immersed in ion-exchanged water for coagulation, and washed for 12 hours while flowing ion-exchanged water. The washed wet film is sandwiched between polyester fabrics from both sides, further sandwiched between aramid felts, placed on a 3 mm thick aluminum plate, and a 0.1 mm thick nylon film is placed on top of it and sealing around it Sealed with a material and dried at 80 ° C. for 6 hours while evacuating the inside.

3. Physical Properties of Porous Film The above dried film has a thickness of 31 μm and a porosity of 78
% And a basis weight of 9 g / m ² . When the film was observed with a scanning electron microscope, both sides of the front and back were about 0.1μ.
m or less of fibril-like or layered PPTA resin,
It was a porous layer having pores having a pore size of 0.05 to 0.2 μm. Observation of the cross section revealed that a fibril-like PPTA resin of about 0.1 μm or less was filled between the polyester fibers of the base paper. The tear strength of this film is 4kg
/ Mm, the tear propagation resistance was 2 kg / mm, and the handleability was excellent.

5. Measurement of Internal Electric Resistance The internal electric resistance at 25 ° C. of the film before heating was 14Ω. As the temperature of the sample was increased, the internal electric resistance gradually decreased to 250 ° C. and reached 5Ω. 2
At around 60 ° C., the internal electric resistance sharply dropped to 0.5Ω. When the temperature was lowered to 25 ° C., the internal electric resistance after heating was 0.5Ω. This is PP with excellent heat resistance
This is probably because the amount of the TA resin was small, and the polyester resin having a melting point of 255 ° C., which was the material of the PET paper used as the base material, flowed out at around 260 ° C., and the space between the electrodes became narrow. From the above results, it was found that the present separator did not have heat resistance of 250 ° C. or higher.

Comparative Example 1 1. Preparation of PPTA dope for coating 100 g of a PPTA polymerization solution having a stirring blade, a thermometer, a nitrogen inlet tube and a liquid addition port.
Weighed into a 00 ml separable flask and 200 g of N
MP was added slowly. Finally, the PPTA concentration is 2.
A 0% by weight solution of the isotropic phase was prepared and stirred for 60 minutes.
Thereafter, defoaming was performed under reduced pressure to obtain a coating dope.

2. Preparation of porous film 0.1mm thick PET on 3mm thick aluminum plate
The film was placed and one end of the PET film was fixed to an aluminum plate with tape. From the side fixed to the aluminum plate with the tape, the coating dope was coated with a bar coating clearance of 0.7 m using a bar coater manufactured by Tester Sangyo Co., Ltd.
m, coating speed 0.2 m / min. Was applied. This is 2
PPTA was deposited at 3 ° C. in an atmosphere of 50% humidity for 20 minutes. It was immersed in ion-exchanged water for coagulation, and washed for 12 hours while flowing ion-exchanged water. The washed wet film is sandwiched between polyester cloths from both sides, further sandwiched between aramid felts, placed on a 3 mm thick aluminum plate, and a 0.1 mm thick nylon film is placed on top of it and sealing around it Sealed with a material and dried at 80 ° C. for 6 hours while evacuating the inside.

3. Physical Properties of Porous Film The above dried film has a thickness of 25 μm and a porosity of 65
%, And the basis weight was 21 g / m ² . The film was observed with a scanning electron microscope.
The porous layer was made of a fibril-shaped or layer-shaped PPTA resin having a diameter of 0.05 μm or less, and had pores having a pore diameter of 0.05 to 0.2 μm. The tear initiation resistance is 1.4 kg / mm, and the tear strength propagation resistance is so small that the load cannot be read.
Poor handling.

[0091]

As described above, the para-aramid porous film of the present invention is inexpensive, has good handling properties, and has high tear strength, while taking advantage of the high heat resistance of para-aramid. Further, the battery separator of the present invention has the safety of shutting down when overheated, does not melt even when heated, and has a high short-circuit temperature, so that it is more excellent in safety. Furthermore, the lithium secondary battery of the present invention has a high short-circuit temperature and is more excellent in safety by using the separator.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01M 2/16 H01M 2/16 PL 10/40 10/40 Z

Claims (10)

[Claims] 1. A substrate comprising fibers and / or pulp, and a para-aramid polymer covering the substrate and / or filling the voids of the substrate, wherein the substrate and the para-aramid polymer are both A para-aramid porous film characterized by being porous. 2. The para-aramid porous film according to claim 1, wherein the thermoplastic polymer which melts at 260 ° C. or lower is 10% by weight or more based on the total amount of the base material and the para-aramid polymer. A para-aramid-based porous film, wherein the polymer melts when the temperature rises and closes the gap between the substrate and / or the para-aramid polymer. 3. The para-aramid polymer has an intrinsic viscosity of 1.0.
The para-aramid porous film according to claim 1 or 2, wherein the para-aramid-based porous film is a para-oriented aromatic polyamide having a molecular weight of ~ 2.8 dl / g. 4. The method according to claim 1, wherein the substrate has a weight per unit area of 40.
g / m ² or less, and the porosity is 40% or more,
The para-aramid porous film according to any one of claims 1 to 3, wherein the thickness is 70 µm or less. 5. The para-aramid porous film according to claim 1, wherein the substrate is woven fabric, non-woven fabric or paper. 6. The material of a substrate comprising fibers and / or pulp is an organic fiber and / or an inorganic fiber, and / or a pulp of an organic fiber and / or a pulp of an inorganic fiber. 6. The para-aramid porous film according to any one of items 1 to 5. 7. The para-aramid porous film according to claim 6, wherein the organic fibers are made of a thermoplastic polymer. 8. The para-aramid porous film according to claim 6, wherein the inorganic fibers are glass fibers. 9. A battery separator using the para-aramid porous film according to any one of claims 1 to 8. 10. A lithium secondary battery using the battery separator according to claim 9.