JP2000191823A - Wholly aromatic polyamide porous membrane and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide wholly aromatic polyamide porous membranes good in substance permeability and, simultaneously, good in heat resistance, mechanical strength, and external appearance, and suitable for heat-resistant separation filtering membranes, battery separators and the like, and a method for producing the same. SOLUTION: Wholly aromatic polyamide porous membranes having a MacMillan's number of 1-100 and a tensile modulus at 100 deg.C of not smaller than 100 kg/mm2 are produced by treating a fine particle dispersion membrane formed from a fine particle dispersion overall aromatic polyamide solution comprising an overall aromatic polyamide, inert fine particles, and a solvent which dissolves the wholly aromatic polyamide but does not dissolve the fine particles in a bath liquid which does not dissolve the wholly aromatic polyamide but dissolves the fine particles to dissolve and remove the fine particles from the membrane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-strength, high-heat-resistant porous membrane made of wholly aromatic polyamide and a method for producing the same. More specifically, a wholly aromatic polyamide porous material excellent in mechanical strength and heat resistance suitable for a filter for separation filtration, a support film for a low-strength film or structure, an electric double layer capacitor, a battery separator, and the like. The present invention relates to a membrane (porous film) and a method for industrially producing the porous membrane.

[0002]

2. Description of the Related Art In recent years, high-molecular polymer porous membranes have been used for filters for separation and filtration, support membranes for low-strength films and structures, electric double layer capacitors, battery separators, and the like.

[0003] As such a polymer porous membrane, for example, polyolefin porous membranes represented by polyethylene and polypropylene as described in JP-A-3-64334, JP-B-54-34790, JP-A-58-179243, JP-A-58-2109
No. 34, for example, a polyester porous membrane. However, such a polyolefin or polyester porous membrane is difficult to use in applications requiring heat resistance and mechanical strength. For example, in recent years, polyethylene porous membranes have been used for lithium ion secondary batteries, but safety is very important in lithium ion secondary batteries because flammable organic solvents are used for electrolytes. Nevertheless, there is a problem that the polyethylene porous membrane is easily melted particularly at the time of abnormal temperature rise due to an external short circuit or the like, and the electrode is further short-circuited inside the battery. Also,
In filtration of a high-temperature solution or the like, even if the temperature is lower than the temperature at which the porous membrane is melted, the mechanical strength of the porous membrane rapidly decreases, and the porous membrane is easily broken.

Japanese Patent Application Laid-Open Nos. Hei 6-263904 and Hei 6-263906 propose porous membranes of aliphatic polyamides and semi-aromatic polyamides.
Since they do not always have sufficient mechanical strength and heat resistance, their applications are limited.

On the other hand, wholly aromatic polyamides generally have high mechanical strength and excellent heat resistance. Already, taking advantage of such properties of wholly aromatic polyamide, wholly aromatic polyamide fibers have been used for fiber applications requiring mechanical strength and heat resistance. Further, for the same purpose, a wholly aromatic polyamide film is disclosed in "Journal of the Fiber Society", Vol. 48, N
o. 1 (1992) pp. 43-48.

In Japanese Patent Application Laid-Open Nos. 5-290822, 5-335005 and 7-37571, nonwoven fabrics using wholly aromatic polyamide fibers are proposed from the viewpoint of heat resistance. However, with such a nonwoven fabric, it is difficult to make the thickness less than about 100 μm in order to maintain the mechanical strength, and it is not possible to respond to a higher market demand.

[0007] It is possible to simply press-press a non-woven fabric of wholly aromatic polyamide fibers to reduce the film thickness while maintaining the mechanical strength. However, in this case, the porosity of the non-woven fabric is reduced. In addition, the transmittance of liquid and the like is reduced. Further, the surface of the nonwoven fabric is not uniform as compared with a so-called porous film, and there may be a case where there is a great difference in the permeability of gas, liquid, or the like depending on the location.

For this reason, a porous film of wholly aromatic polyamide has been studied. Since a wholly aromatic polyamide has a melting temperature higher than a thermal decomposition temperature and is difficult to form a film using a melt extrusion film forming technique, it is general that a film is generally formed by a solution casting method. Therefore, the following production method has been proposed for a wholly aromatic polyamide porous membrane having a small thickness.

Japanese Patent Publication No. Sho 59-14494 discloses a technique in which a wholly aromatic polyamide solution is cast on a substrate, cooled and solidified at a temperature of 0 ° C. or less, and then a solvent is extracted at a temperature near the same. Has been introduced. However, in this case, the pore shape of the film formed differs depending on the cooling temperature, or even if the cooling temperature is sufficiently controlled, the pore shape varies due to the fluctuation of the solution film thickness when the solution is cast. In the actual manufacturing process, it is difficult to form a porous film having a uniform pore shape.

Also, Japanese Patent Publication No. 59-36939, Japanese Patent Application Laid-Open No. 53-144974, Japanese Patent Publication No. 61-5192,
No. 8, JP-A-59-59213,
In JP-A-12171, JP-A-2-222430, JP-A-10-6453, etc., a wholly aromatic polyamide solution is cast and then immersed in a coagulation bath to form a wholly aromatic polyamide porous membrane. A so-called wet coagulation film forming method is described. 48, no. 2 (1992), pp. 49-67, the shape of the pores differs in the film thickness direction, the coating layer is formed on the surface of the porous film, or the shape of the pores varies due to the change in solidification conditions. Therefore, it is difficult to form a wholly aromatic polyamide porous film having a uniform pore shape by a simple wet coagulation film forming method.

[0011]

SUMMARY OF THE INVENTION The present invention provides high heat resistance,
It is an object of the present invention to provide a wholly aromatic polyamide porous membrane having high strength and a uniform pore shape and a method for producing the same. This provides a wholly aromatic polyamide porous membrane that can be suitably used as a heat-resistant separation filtration membrane, a battery separator, or the like, which requires a particularly thin porous membrane having excellent mechanical strength and heat resistance. .

[0012]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object, and as a result, a solution comprising a wholly aromatic polyamide and a solvent for dissolving the wholly aromatic polyamide has been prepared. Is used to form a porous film by dissolving and removing the fine particles in the film after dissolving and removing the fine particles in the film using a mixed solution in which the insoluble fine particles are dispersed, and then forming the film by a solution casting drying method, a wet film forming method or a combination thereof. The present inventors have found that a wholly aromatic polyamide porous membrane having high heat resistance, high strength and a uniform pore shape can be produced by the method, and the present invention has been completed.

That is, a first aspect of the present invention is a solution casting and drying method from a fine particle dispersion solution comprising a wholly aromatic polyamide, inert fine particles, and a solvent which dissolves the wholly aromatic polyamide but does not dissolve the fine particles. And / or immersed in a bath solution that does not dissolve the wholly aromatic polyamide and can dissolve the fine particles, and dissolves and removes the fine particles from the film. And a method for producing a wholly aromatic polyamide porous membrane.

Further, the present invention includes the following inventions with respect to the first invention. (1) A method for producing a wholly aromatic polyamide porous membrane, wherein the wholly aromatic polyamide is a wholly aromatic polyamide consisting essentially of a repeating unit represented by the following formula (1).

[0015]

-NR ¹ -Ar ¹ -NR ² -CO-Ar ² -CO- (1) (where R ¹ and R ² are the same or different, and are a hydrogen atom, a halogen atom and a carbon number of 5 or less. And Ar ¹ and Ar ² are the same or different and may have an orthophenylene group, a metaphenylene group, a paraphenylene group, a 1,4-naphthylene group, , 5-naphthylene group, 2,6-naphthylene group,
2,5-pyridylene group and 2 represented by the following formula (2)
Selected from valency groups. )

[0016]

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(Here, X is selected from the group consisting of an ether group, a sulfide group, a methylene group, a carbonyl group and a sulfonyl group.) (2) The wholly aromatic polyamide is represented by the above formula (1). At least 7.5 mol% of the total amount of Ar ¹ and Ar ^{2 in} the repeating unit is a para-oriented wholly aromatic polyamide comprising a unit represented by the following formula (3): Manufacturing method.

[0018]

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(3) A method for producing a wholly aromatic polyamide porous membrane, wherein the solvent in which the wholly aromatic polyamide is dissolved is an amide-based solvent. (4) A method for producing a wholly aromatic polyamide porous membrane, wherein the proportion of the wholly aromatic polyamide in the solid content in the fine particle dispersion is 10 to 70% by volume. (5) A method for producing a wholly aromatic polyamide porous membrane, wherein the average particle diameter of the fine particles is in the range of 1/50 to 1/5 of the thickness of the formed fine particle dispersed film. (6) A method for producing a wholly aromatic polyamide porous membrane, wherein the fine particles are a metal or a metal compound. (7) The fine particle dispersion solution is further dissolved in a solvent for dissolving the wholly aromatic polyamide with each other and slightly dissolving the wholly aromatic polyamide, and is also dissolved in a solvent in which the wholly aromatic polyamide is not soluble. A method for producing a wholly aromatic polyamide porous membrane, comprising an organic substance. (8) The method for producing a wholly aromatic polyamide porous membrane, wherein the organic substance is a polyalkylene oxide, preferably polyethylene oxide, and has an average molecular weight of more than 1500 and less than 7500. (9) In the method for producing a wholly aromatic polyamide porous membrane, the fine particle-dispersed membrane is formed through at least two steps of a solution casting and drying step and a wet coagulation step. For producing a wholly aromatic polyamide porous membrane. (10) The method for producing a wholly aromatic polyamide porous membrane, wherein the drying temperature in the solution casting drying step is not less than (the boiling point of the solvent −60 ° C.). (11) The method for producing a wholly aromatic polyamide porous membrane, characterized in that the wholly aromatic polyamide porous membrane is stretched in at least one direction at least 1.2 times before or after the step of dissolving and removing the fine particles. . (12) A wholly aromatic polyamide porous membrane, wherein the bath solution for dissolving and removing the fine particles, preferably metal compound fine particles, is an aqueous alkaline solution having a concentration of 5 N or less or an aqueous acid solution having a concentration of 5 N or less. Manufacturing method.

[0020] A second aspect of the present invention is a method for manufacturing a semiconductor device by the above method.
If the number of Macmillans is greater than 1 and less than 100
And the tensile modulus at 100 ° C. is 100 kgf /
mm ^TwoNovel wholly aromatic poly, characterized by the above
It relates to an amide porous membrane. In this second invention,
The Macmillan number is greater than 1 and less than or equal to 40;
The tensile modulus at 0 ° C. is 100 kgf / mm^TwoAbove
Novel wholly aromatic polyamide porous membrane characterized by the following
Is also included.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION (Wholly aromatic polyamide) The wholly aromatic polyamide used in the present invention is, specifically, a polyamide mainly composed of a repeating unit represented by the following formula (1).

[0022]

Embedded image —NR ¹ —Ar ¹ —NR ² —CO—Ar ² —CO— (1) In the formula (1), R ¹ and R ² are the same or different, and are a hydrogen atom, a halogen atom, or a carbon number. Ar ¹ and Ar ² are an orthophenylene group, a metaphenylene group, a paraphenylene group, a 1,4-naphthylene group,
It is independently selected from a 5-naphthylene group, a 2,6-naphthylene group, a 2,5-pyridylene group or a divalent organic group represented by the following formula (2). In these groups, all or part of the hydrogen constituting the aromatic nucleus may be substituted with a halogen atom or a lower alkyl group.

[0023]

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In the formula (2), X represents an ether group, a sulfide group, a methylene group, a carbonyl group or a sulfonyl group.

Further, such a wholly aromatic polyamide is
It may be a combination of a plurality of repeating units, that is, a copolymerized unit.

Among the wholly aromatic polyamides as described above,
As the wholly aromatic polyamide that can be used in the present invention, a solvent to which a solution casting drying method described below can be applied, that is, a solvent that can be substantially volatilized and dried, and / or a wet film forming method can be applied, that is, solution extraction is possible. Any kind of a wholly aromatic polyamide soluble in a suitable solvent may be used, and the type thereof is not particularly limited.

Such wholly aromatic polyamides include ortho-oriented wholly aromatic polyamides, meta-oriented wholly aromatic polyamides, para-oriented wholly aromatic polyamides, and meta-para-oriented wholly aromatic polyamides. However, from the viewpoint of mechanical strength desired as a porous membrane, a wholly aromatic polyamide containing a para-oriented aromatic polyamide as a main component is more preferable among them.

Such para-oriented wholly aromatic polyamides also include fully para-oriented wholly aromatic polyamides typified by poly (paraphenylene terephthalamide). However, from the viewpoint of ease of solution preparation, solution stability, chemical resistance, and high mechanical strength, it is preferably at least 7 based on the total amount of Ar ¹ and Ar ² in the repeating unit of the above formula (1). A para-oriented wholly aromatic polyamide containing a group represented by the following formula (3) at a ratio of not less than 5.5 mol%, more preferably not less than 7.5 mol% and not more than 50 mol% is suitable.

[0029]

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Among them, Ar ¹ is a combination of a paraphenylene group and a group of the above formula (3) (the group of the above formula (3) is at least 15 mol% to 50 mol% based on the total amount of Ar ¹ and Ar ² ). %
And Ar ² is more preferably a paraphenylene group.

Such a wholly aromatic polyamide has a film-forming ability, and its polymerization degree is preferably high in order to sufficiently develop the mechanical strength of the wholly aromatic polyamide porous membrane. Specifically, using concentrated sulfuric acid as a solvent, the logarithmic viscosity measured at 30 ° C. at a concentration of 0.5 g / 100 ml is preferably 1.0 or more, and more preferably 1.7 to
3.0 is more preferred.

(Solvent) Here, various organic solvents can be used as a solvent capable of dissolving the wholly aromatic polyamide to prepare a stable solution and substantially volatilizing and drying, but from the viewpoint of solubility. Preferred examples of the solvent include amide solvents. Such amide solvents include, for example, tetramethylurea, hexamethylphosphoramide, N, N-dimethylacetamide, N-methylpyrrolidone-2, N-methylpiperidone-2, N, N-
Dimethylethylene urea, N, N, N ', N'-tetramethylalonamide, N-methylcaprolactam, N-
Acetylpyrrolidine, N, N-diethylacetamide,
N-ethylpyrrolidone-2, N, N-dimethylpropionamide, N, N-dimethylisobutylamide, N-
Examples include methylformamide, N, N-dimethylpropylene urea, and mixtures thereof. Particularly preferred solvents include N-methylpyrrolidone-2, hexamethylphosphoramide, N, N-dimethylacetamide and mixtures thereof. These solvents may contain a dissolution promoter such as calcium chloride.

Various solvents and organic solvents can be used as a solvent which can be subjected to solution extraction in the coagulation bath.
Specific examples include concentrated sulfuric anhydride and the amide solvents described above. However, the use of concentrated sulfuric anhydride in the process is highly dangerous, and it is more preferable to use the amide-based solvent described above.

The concentration of the wholly aromatic polyamide in the solution of the wholly aromatic polyamide dissolved in such a solvent depends on the degree of polymerization of the wholly aromatic polyamide, the solubility, the viscosity of the solution and the film forming means. From the viewpoint of manufacturing,
A range of 50% by weight, especially 3-20% by weight is preferred.

The amount of the wholly aromatic polyamide is defined as the solid content in the above-mentioned fine particle dispersion solution, that is, the total amount of the total aromatic polyamide out of the residual components obtained by removing the solvent components in the fine particle dispersion solution such as the wholly aromatic polyamide and the fine particles. Group polyamide 10 to 7
It is preferable that the volume is 0% by volume. When the amount of the wholly aromatic polyamide is less than 10% by volume, the porosity of the porous film becomes large, but it is difficult to produce the porous film having the strength intended for the present invention. On the other hand, if it exceeds 70% by volume, the fine particles are likely to be isolated in the formed fine particle dispersed film. Such isolated fine particles are difficult to dissolve and remove, and even if dissolved, isolated pores do not contribute to the material permeability as a porous film. A more preferred ratio of wholly aromatic polyamide is 20.
６０60% by volume.

(Inert Fine Particles) On the other hand, the inert fine particles used in the present invention are inert fine particles which do not adversely affect the wholly aromatic polyamide and are insoluble or hardly soluble in the solvent in which the wholly aromatic polyamide is dissolved. And it is soluble in another solvent different from that. The average particle diameter is preferably in the range of 1/50 to 1/5 of the thickness of the formed fine particle dispersed film. Here, the formed fine particle-dispersed film is a film at the time of forming a film from a wholly aromatic polyamide solution containing the fine particles by a solution casting drying method and / or a wet film forming method.
The thickness of the film is selected depending on the application. When used as a support material for structural materials, the film thickness is not particularly limited,
When used as a membrane for passing substances such as gas and liquid, or when it is necessary to efficiently dissolve and remove fine particles dispersed in production, the film thickness is 1 mm or less, preferably 0.5 mm or less. Further, the lower limit of the film thickness is not particularly limited, but is preferably 1 μm or more from the viewpoint of handleability after film formation.

The average particle diameter of the fine particles to be used is selected according to such a film thickness. If the average particle diameter is smaller than 1/50 of the film thickness, the dissolution liquid hardly penetrates when the fine particles are dissolved and removed, and even after the dissolution treatment. Fine particles easily remain, and even if vacancies are formed, they do not effectively act as vacancies in the film,
Material permeability may be relatively reduced. If the thickness is larger than 1/5 of the film thickness, the mechanical strength of the porous film tends to be extremely reduced.

On the other hand, the addition amount of such fine particles is determined by the amount of the wholly aromatic polyamide in the dispersion solution as described above, and the solid content in the fine particle dispersion solution, that is, the whole aromatic polyamide alone and the fine particles are For example, it is preferable that the proportion of the wholly aromatic polyamide be 10 to 70% by volume of the residual component amount when the solvent component in the fine particle dispersion solution is removed. The addition amount of such fine particles is defined by the amount of the wholly aromatic polyamide in the fine particle dispersion solution, and the solid content in the fine particle dispersion solution, that is, the wholly aromatic polyamide alone and the fine particles, the fine particle dispersion solution. It is preferable that the proportion of the wholly aromatic polyamide be 10 to 70% by volume of the residual component amount when the solvent component is removed.
When the total aromatic polyamide is less than 10% by volume,
Although the porosity increases as a porous film, it is difficult to produce a porous film having the strength intended for the present invention. On the other hand, if it exceeds 70% by volume, the fine particles are likely to be isolated in the formed fine particle dispersed film. Such isolated fine particles are difficult to dissolve and remove, and even if dissolved, isolated pores do not contribute to the material permeability as a porous film. A more preferable ratio of the wholly aromatic polyamide is 20 to 60% by volume. A suitable addition amount of the fine particles based on the wholly aromatic polyamide is 60 to 400% by volume based on the wholly aromatic polyamide.

As described above, the inert fine particles need to be those which can be dissolved and removed by bath solution treatment as described above. Specifically, an alkaline aqueous solution having a concentration of 5 N or less,
It is preferable to dissolve in an aqueous acid solution or water having a concentration of 5 N or less.

The material of the inert fine particles is selected from a wide range of organic materials and inorganic materials satisfying the above conditions. However, from the viewpoint of ease of forming fine particles, inorganic materials, and further, from the viewpoints of solubility and economy. It is preferable to select from a metal material and a metal compound material.

Examples of such a metal material include aluminum, copper, iron, indium, magnesium, manganese, nickel, tin, zinc and the like. Examples of the metal compound material include metal oxides such as copper (I) oxide, copper (II) oxide, indium oxide, magnesium oxide, nickel oxide, tin (II) oxide, and zinc oxide. According to the study of the present inventors, it has been found that the use of metal oxides is particularly preferred, and zinc oxide is particularly preferred. Here, the reason why the above-mentioned metal oxide fine particles are particularly preferable is that the temperature range in which the polymer is handled, for example, 300
It is difficult to be deformed at the time of stretching at a temperature of ° C., and the dissolution characteristics are not largely changed by oxidation as in the case of metal fine particles.

(Vacancy generating accelerator) The porous fine film is formed by dispersing the inert fine particles in the solution containing the wholly aromatic polyamide and forming the film, and then dissolving and removing the inert fine particles from the film with a bath solution. Can be satisfactorily formed, but more preferably, as shown below, an organic substance for promoting vacancy generation (hereinafter, sometimes referred to as a vacancy generation accelerator) in the fine particle dispersion solution. Is preferably further added. That is, as the vacancy generation promoter, a) the aromatic polyamide is substantially insoluble in each other, b) the organic solvent for dissolving the aromatic polyamide, and c) the aromatic polyamide is dissolved. Use organic substances that dissolve in liquids that do not
A method in which this is contained in a wholly aromatic polyamide solution together with inert fine particles, a film is formed from this, and then the fine particles and organic substances are dissolved and removed is suitably adopted.

In other words, such a vacancy generation promoter dissolves in an organic solvent that dissolves the wholly aromatic polyamide, but phase-separates from the wholly aromatic polyamide with the removal of the solvent during film formation. From the viewpoint of workability, the organic substance serving as the vacancy generation promoter is preferably a solid substance at 30 ° C., that is, a substance that does not become sticky due to the organic substance after the film is formed. And, more preferably, those which are dissolved together in the fine particle dissolving treatment step are preferable. As such an organic substance, a polyalkylene oxide such as polyethylene oxide and polypropylene oxide is preferable.
Furthermore, polyethylene oxide can be mentioned from the viewpoint of higher water solubility. However, properties such as solubility and melting point of polyethylene oxide vary greatly depending on its average molecular weight.
Those between 00 are preferred. Average molecular weight of 1500
If it is lower than the above, a suitable porous membrane structure may not be obtained at the time of phase separation from the wholly aromatic polyamide, and a two-layer laminated structure of the wholly aromatic polyamide and polyethylene oxide may be obtained. If the average molecular weight is lower than 1500, the solvent of the wholly aromatic polyamide solution may be impregnated and sticky even after the film is formed. On the other hand, when the average molecular weight is larger than 7500, it becomes difficult to dissolve in the fine particle dispersion solution containing the wholly aromatic polyamide, and even if it is dissolved, the mixed solution becomes a paste and becomes difficult to be cast. Becomes difficult to dissolve during dissolution and removal.

As described above, the total amount of the inert fine particles and the organic substance is such that the total aromatic polyamide solid content in the solid content in the fine particle dispersion solution is 10 to 70% by volume. It is preferable that When the amount of the wholly aromatic polyamide is less than 10% by volume, the porosity of the porous film is increased, but it is difficult to produce the porous film having the strength intended in the present invention. Also, 70
When the content is equal to or more than the volume%, the fine particles are easily isolated in the formed fine particle dispersed film. Such isolated fine particles are difficult to dissolve and remove, and even if dissolved, isolated pores do not contribute to the material permeability as a porous film. Generally, the amount of the organic substance added as a vacancy generation promoter is preferably 50 to 300% by weight based on the weight of the wholly aromatic polyamide.

(Preparation of Fine Particle Dispersion and Film Formation) In the present invention, the wholly aromatic polyamide is dissolved, and the fine particle dispersed wholly aromatic polyamide contains inert fine particles and a porogen accelerating agent optionally added. A solution is prepared, and a film of fine particle-dispersed wholly aromatic polyamide is formed from the solution.

In preparing the solution, inert fine particles (and a vacancy generation accelerator) may be added to a solvent in advance, and the wholly aromatic polyamide may be dissolved therein. Inactive fine particles and the like may be added to the wholly aromatic polyamide solution obtained by solution solution polymerization dissolved in water.

The film can be formed only by the solution casting and drying step or the wet coagulation step. However, according to the study of the present inventors, at least after the solution casting and drying step is performed first, It is preferable to carry out the wet coagulation step in two steps. Here, the solution casting and drying step is to cast a fine particle-dispersed wholly aromatic polyamide solution onto a support made of a substrate such as glass, metal, plastic, or a belt so as to have a constant solution thickness, and remove the solvent by volatilization. This is a step of forming a residual solid content film on the substrate. Known techniques can be used for the solution casting / drying method itself, and it can be selected from coating techniques such as gravure coating, roll coating, and die coating depending on the solution thickness, viscosity, and the like.
In addition, solvent volatilization removal is specifically performed by heating drying, vacuum drying,
Known drying techniques such as vacuum heating drying can be applied. Also,
In the wet coagulation step, a fine particle-dispersed wholly aromatic polyamide solution is cast on a substrate of glass, metal, plastic, or the like so as to have a constant solution thickness, and a poor solvent for the wholly aromatic polyamide and dissolution of the wholly aromatic polyamide Immersing in a coagulation liquid bath having an affinity for the solvent used for extracting and removing the solvent component of the wholly aromatic polyamide solution to form a residual solid film on the substrate or in the coagulation solution It is. For the casting at this time, the above-mentioned known solution casting method can be adopted.

In a preferred film-forming method, the solvent is not completely evaporated and dried in the solution casting and drying process, but the process is switched to the wet coagulation process during the evaporation and the solvent is effectively removed. By combining the two solvent removal steps in this order,
(A) In addition to the effect of simply removing the solvent efficiently, the film can be easily peeled off from the support.
(B) of the finally produced wholly aromatic polyamide porous membrane,
The surface properties of the membrane surface (support surface) in contact with the support and the opposite surface (air surface) are very close, and both surfaces show good substance permeability. Further, (c) the wet coagulation method alone The exceptional effect that the problem that the structure of the porous membrane is greatly changed depending on the coagulation condition, which is observed, can be suppressed.

At this time, in order to further increase the material permeability of the porous membrane, in the solution casting drying step, the drying temperature is set to (the boiling point of a solvent that dissolves the wholly aromatic polyamide and does not dissolve the fine particles). 60 ° C.) or higher. The reason for raising the temperature in this way is not only the effect on the manufacturing process that the solvent volatilization rate is increased and the time for the drying process is shortened, but also the rapid volatilization of the solvent, and particularly the fine pores on the surface of the fine particle dispersed film. It also has the effect of being easy to do. Therefore, a porous membrane having good substance permeability can be produced.

(Stretching) The membrane subjected to the fine particle removal treatment develops porosity at this point. However, in order to further increase the permeability or the mechanical strength, it is better to further perform the stretching treatment. This is preferable in that the properties of the aromatic polyamide porous membrane are brought out. Examples of such a stretching treatment include uniaxial stretching, sequential biaxial stretching, simultaneous biaxial stretching, and rolling. The stretching may be performed before or after the fine particle removal processing described below.

As for the stretching ratio at that time, the effect of improving the mechanical strength by stretching is unlikely to be remarkable unless the film is stretched at least 1.2 times in one direction of the porous membrane. It is preferable that the magnification is as high as possible without breaking.

(Dissolution and Removal of Fine Particles) In the present invention, the fine particles are dissolved and removed from the fine particle dispersion film formed as described above and stretched as necessary to form a porous film. The dissolving solution for dissolving and removing the fine particles is not particularly limited as long as it has the above function, but industrially, an aqueous alkaline solution having a concentration of 5N or less or an aqueous acid solution having a concentration of 5N or less is used. Is preferably selected depending on the type of the fine particles. When a stronger alkali or acid solution is used for dissolution and removal, the decomposition and deterioration of the wholly aromatic polyamide become remarkable, and the mechanical strength of the resulting porous membrane may be extremely reduced. It is not preferable because dissolution of the wholly aromatic polyamide may occur. The alkali used here is preferably sodium hydroxide, potassium hydroxide or the like, and the acid is preferably an inorganic acid such as nitric acid, hydrochloric acid or sulfuric acid.

As a solvent for preparing such a dissolving solution, water is generally and preferably used, but is not limited thereto. In particular, in the case where the fine particles are an organic substance, the use of an organic solvent or water in which the fine particles are easily dissolved may be more effective in dissolving and removing than dissolving and removing with an aqueous solution of an acid or an alkali. At that time, an organic solvent in which the wholly aromatic polyamide is easily dissolved cannot be selected.

Dissolution and removal of the inert fine particles are carried out by immersing a wholly aromatic polyamide film (fine particle dispersed film) containing the fine particles in a bath of the above-mentioned solution. The immersion bath may be a bath in which the liquid flows or a bath in which the liquid does not flow. Also,
The fine particle dispersion film may be left standing or moved in the bath. The dissolution and removal conditions depend on the dissolution rate of the fine particles, the saturation solubility, the freezing point of the dissolution solution, the boiling point, and the like. However, it is preferable that the dissolution and removal be performed within 24 hours within a temperature range of 0 to 100 ° C. .

(Post-treatment) The porous membrane from which the fine particles have been extracted and removed is washed, if necessary, and then dried to form a porous membrane of the product.

(Porous Membrane) The porous membrane of the wholly aromatic polyamide produced in this manner usually has an ionic conductivity, that is, a Macmillan number which is greater than 1 and is 100 as one index indicating the ease of substance transfer. Heat tensile elastic modulus, which is one of the following values and is one index indicating heat resistance and mechanical strength, is 100 kgf / mm ² or more at 100 ° C. It is a large value of 40 or less, and the heating tensile elastic modulus is 10
It becomes 100 kgf / mm ² or more at 0 ° C. and shows excellent performance.

The Macmillan number indicates how many times the apparent specific resistance becomes relatively larger when the porous membrane is filled with the electrolytic solution than the specific resistance of the electrolytic solution used for the measurement. Is 1 or more. On the other hand, if the upper limit of 100 is a higher value, it cannot be said that the substance can be satisfactorily moved. Further, the heating tensile elasticity is a high elasticity even at a high temperature of 100 ° C., and is 100 kgf / mm as a value that can be judged to have mechanical strength in the manufacturing process and handling.
^Two or more are preferred.

[0058]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited by these Examples and Comparative Examples. In addition, various evaluations described in each Example and Comparative Example were performed in the following manner. 1) Logarithmic viscosity: The logarithmic viscosity of the polymerized wholly aromatic polyamide was measured at 30 ° C. at a concentration of 0.5 g / 100 ml using concentrated sulfuric acid as a solvent. 2) Stretching ratio: Stretching was carried out sequentially by biaxial stretching. And
The stretching ratio at this time was represented by pre-stretching ratio × post-stretching ratio. 3) Macmillan number: Macmillan number, which is a parameter representing ionic conductivity, was determined as follows. First, the specific resistance 1 of an organic electrolytic solution in which lithium tetrafluoroborate was dissolved at 1 mol / liter in an organic solvent in which propylene carbonate and ethylene carbonate were mixed in an equal weight ratio was determined. Next, the prepared porous membrane was immersed in this solution and sufficiently permeated, and then sandwiched between disc-shaped stainless steel electrodes having a radius of 1 cm.
The complex impedance was measured between kHz and 1 Hz, and the measured data curve on the high frequency side was extrapolated to the real axis to obtain the actually measured resistance value, and the Macmillan number was calculated using the following equation (a). Macmillan number = (measured resistance value × electrode area / porous film thickness) / specific resistance 1 ‥‥ (a) 4) Tensile modulus: The tensile test was carried out using an Instron type tensile tester with reference to JIS K7127. 100 ℃
Under an environment of 10 cm / min. The measurement sample was cut out in the direction of post-stretching so as to have a length of 5 cm and a width of 1 cm, and a tensile test was performed at intervals of 2 cm.
The measured value was indicated by a tensile modulus.

Example 1 In a flask under a nitrogen stream,
6.968 g of 3,4′-diaminodiphenyl ether and 3.764 g of paraphenylenediamine were dehydrated and purified from N
After dissolving in 300 g of -methylpyrrolidone-2 (boiling point: 202 ° C), the mixture was cooled in an ice water bath. After cooling, 14.136 g of terephthalic acid dichloride powder was quickly added to the solution, followed by vigorous stirring. Further, when the temperature of the solution exceeded 50 ° C. due to the heat of reaction, the temperature was raised to 85 ° C., and the mixture was stirred for 1 hour. Thereafter, 5.15 g of calcium hydroxide was added to neutralize the by-produced hydrochloric acid, and a yellow transparent high-viscosity solution was obtained. The concentration of the wholly aromatic polyamide in this solution was 6.0% by weight.

For the measurement of logarithmic viscosity and the like, a part of the solution was taken out, mixed with water, the precipitated polymer (wholly aromatic polyamide) was separated, washed with water and dried, and the logarithmic viscosity was measured. 3.2. The specific gravity of this wholly aromatic polyamide was 1.34.

On the other hand, the wholly aromatic polyamide solution 100
50 parts by weight of N-methylpyrrolidone-2, 37.3 parts by weight of zinc oxide fine particles having an average particle diameter of 1 μm (manufactured by Kojundo Chemical Co., specific gravity 5.47) and 9 parts by weight of polyethylene oxide (average molecular weight 3000) The mixture was uniformly dispersed and mixed at 80 ° C. to obtain a zinc oxide fine particle dispersion. Then, the dispersion solution is cast on a glass plate at 80 ° C. so as to have a thickness of 0.4 mm, and is dried in a drying oven at 130 ° C. for 40 minutes. I got

Thereafter, the white film was successively biaxially stretched to 1.4 × 1.5 in an environment of 150 ° C. Next, the stretched white film was immersed in a 5% nitric acid aqueous solution for 1 hour to dissolve and remove zinc oxide fine particles and polyethylene oxide dispersed in the film. Then, pure water washing was performed to obtain a porous membrane.

The results of evaluating the properties of the wholly aromatic polyamide porous membrane thus produced are shown in the column of Example 1 in Table 1 below. This indicates that the porous membrane produced according to the present invention has good strength and ionic conductivity.

Example 2 To 100 parts by weight of the wholly aromatic polyamide solution obtained by the solution polymerization in Example 1, 50 parts by weight of N-methylpyrrolidone-2 and aluminum fine particles having an average particle diameter of 3 μm (manufactured by Kojundo Chemical Co., Ltd.) , Specific gravity 2.699) 18.4
Parts by weight and polyethylene oxide (average molecular weight 300
0) 9 parts by weight were uniformly dispersed and mixed at 80 ° C. to obtain a fine particle dispersed solution. Then, the dispersion solution is cast on a glass plate at 80 ° C. so as to have a thickness of 0.4 mm, and is dried in a drying oven at 130 ° C. for 40 minutes. I got

Subsequently, the gray film was successively biaxially stretched to 1.5 × 1.5 in an environment of 150 ° C. Next, this stretched gray film was placed in a 3.5% aqueous sodium hydroxide solution for 1 hour.
By immersing for 5 hours, the aluminum fine particles and polyethylene oxide dispersed in the film were dissolved and removed. Thereafter, the membrane was washed with pure water to obtain a porous membrane.

The results of evaluating the properties of the wholly aromatic polyamide porous membrane thus produced are shown in Example 2 in Table 1 below. This indicates that the porous membrane produced according to the present invention has good strength and ionic conductivity.

Example 3 To 100 parts by weight of the wholly aromatic polyamide solution obtained by the solution polymerization in Example 1, 50 parts by weight of N-methylpyrrolidone-2 and aluminum fine particles having an average particle diameter of 3 μm (manufactured by Kojundo Chemical Co., Ltd.) , Specific gravity 2.699) 18.4
Parts by weight and polyethylene oxide (average molecular weight 600
0) 6 parts by weight were uniformly dispersed and mixed at 80 ° C. to obtain a fine particle dispersed solution. Then, the mixed solution is cast on a glass plate at 80 ° C. so as to have a thickness of 0.4 mm, and dried in a drying oven at 130 ° C. for 40 minutes. I got

Subsequently, the gray film was successively biaxially stretched to 1.5 × 1.5 in an environment of 150 ° C. Next, this stretched gray film was placed in a 3.5% aqueous sodium hydroxide solution for 1.5 times.
This was immersed for a period of time to dissolve and remove the aluminum fine particles and polyethylene oxide dispersed in the film. Then, pure water washing was performed to obtain a porous membrane.

The results of evaluating the properties of the wholly aromatic polyamide porous membrane thus produced are shown in Example 3 in Table 1 below. This indicates that the porous membrane produced according to the present invention has good strength and ionic conductivity.

Example 4 100 parts by weight of the wholly aromatic polyamide solution obtained by the solution polymerization of Example 1 was 50 parts by weight of N-methylpyrrolidone-2 and aluminum fine particles having an average particle diameter of 3 μm (manufactured by Kojundo Chemical Co., Ltd.). Specific gravity 2.699) 12.3 parts by weight and polyethylene oxide (average molecular weight 154)
0) 12 parts by weight were uniformly dispersed and mixed at 80 ° C. to obtain a fine particle dispersed solution. Then, the mixture was cast on a glass plate at 80 ° C. so as to have a thickness of 0.4 mm.
A drying treatment was performed in a drying oven at 30 ° C. for 40 minutes, and after the drying treatment, a self-supporting gray film was obtained.

Subsequently, the gray film was successively biaxially stretched to 1.5 × 1.5 in an environment of 150 ° C. Next, this stretched gray film was placed in a 3.5% aqueous sodium hydroxide solution for 1.5 times.
This was immersed for a period of time to dissolve and remove the aluminum fine particles and polyethylene oxide dispersed in the film. Then, pure water washing was performed to obtain a porous membrane.

The results of evaluating the properties of the wholly aromatic polyamide porous membrane thus produced are shown in Example 4 in Table 1 below.
Column. Thus, the porous membrane produced according to the present invention is:
It turns out that it has good strength and ionic conductivity.

Example 5 100 parts by weight of the wholly aromatic polyamide solution obtained by the solution polymerization in Example 1 was mixed with 32.7 parts by weight of N-methylpyrrolidone-2 and a surfactant ("Homogenol" L-manufactured by Kao Corporation). 18) 0.7 parts by weight and average particle diameter 1 μ
m zinc oxide fine particles (manufactured by Kojundo Chemical, specific gravity 5.47) 2
1.9 parts by weight were uniformly dispersed and mixed at 70 ° C. under a nitrogen stream to obtain a zinc oxide fine particle dispersion. Thereafter, 0.16 parts by weight of a leveling agent (SH28PA manufactured by Shin-Etsu Chemical) was further mixed. Then, this dispersion solution was cast on a glass plate at 80 ° C. so as to have a thickness of 0.6 mm, dried in a drying oven at 130 ° C. for 8 minutes, and then immersed in water for 2 minutes. After the drying treatment, a self-supporting white film was obtained. And
This white film was successively biaxially stretched to 1.5 × 1.5 in an environment of 310 ° C. Next, the stretched white film was immersed in a 5% nitric acid aqueous solution for 30 minutes to dissolve and remove the dispersed zinc oxide fine particles. Then, pure water washing was performed to obtain a porous membrane.

The results of evaluation of the properties of the wholly aromatic polyamide porous membrane thus produced are shown in Example 5 in Table 1 below.
Column. This indicates that the porous membrane according to the present invention produced by the above method has particularly excellent strength and ionic conductivity during heating.

Example 6 In the same manner as in Example 5, 0.16 parts by weight of a leveling agent (SH28PA manufactured by Shin-Etsu Chemical) was mixed with the zinc oxide fine particle dispersion solution prepared in Example 5. Then, this zinc oxide fine particle dispersion was cast on a glass plate at 80 ° C. so as to have a thickness of 0.6 mm, dried in a drying furnace at 150 ° C. for 10 minutes, and then immersed in water for 2 minutes. After the drying treatment, a self-supporting white film was obtained. Thereafter, the white film was successively biaxially stretched to 1.5 × 1.5 in an environment of 310 ° C. Next, the stretched white film was immersed in a 5% nitric acid aqueous solution for 30 minutes to dissolve and remove the dispersed zinc oxide fine particles. Then, pure water washing was performed to obtain a porous membrane.

The results of evaluating the properties of the wholly aromatic polyamide porous membrane thus produced are shown in Example 6 in Table 1 below.
Column. This indicates that the porous membrane according to the present invention produced by the above method has particularly excellent strength and ionic conductivity during heating.

Example 7 The zinc oxide fine particle dispersion prepared in Example 6 was cast on a glass plate at 80 ° C. so as to have a thickness of 0.6 mm, and dried in a drying oven at 180 ° C. for 8 minutes. The treatment was followed by immersion in water for 2 minutes. After the drying treatment, a self-supporting white film was obtained.

The white film was successively biaxially stretched to 1.5 × 1.5 in an environment of 310 ° C. Next, the stretched white film was immersed in a 5% nitric acid aqueous solution for 30 minutes to dissolve and remove the dispersed zinc oxide fine particles. Thereafter, the membrane was washed with pure water to obtain a porous membrane.

The results of evaluating the properties of the wholly aromatic polyamide porous membrane produced in this manner are shown in Example 7 in Table 1 below.
Column. This indicates that the porous membrane according to the present invention produced by the above method has particularly excellent strength and ionic conductivity during heating.

Example 8 The zinc oxide fine particle dispersion prepared in Example 6 was cast on a glass plate at 80 ° C. so as to have a thickness of 0.6 mm, and dried in a drying oven at 130 ° C. for 30 minutes. Processing was performed. After the drying treatment, a self-supporting white film was obtained. Then, this white film is 1.5 × under an environment of 310 ° C.
The film was sequentially biaxially stretched to 1.5. Next, the stretched white film was immersed in a 5% nitric acid aqueous solution for 30 minutes to dissolve and remove the dispersed zinc oxide fine particles. Thereafter, the membrane was washed with pure water to obtain a porous membrane.

The results of evaluating the properties of the wholly aromatic polyamide porous membrane thus produced are shown in Example 8 in Table 1 below.
Column.

Example 9 To 100 parts by weight of the wholly aromatic polyamide solution obtained by the solution polymerization of Example 1, 49 parts by weight of N-methylpyrrolidone-2 and a surfactant (Homogenol L-18 manufactured by Kao) 1 part by weight, and zinc oxide fine particles having an average particle diameter of 1 μm (manufactured by Kojundo Chemical Co., specific gravity 5.4)
7) 32.8 parts by weight were uniformly dispersed and mixed at 70 ° C. under a nitrogen stream to obtain a zinc oxide fine particle dispersion. Thereafter, 0.16 parts by weight of a leveling agent (SH28PA manufactured by Shin-Etsu Chemical) was further mixed. Then, this dispersion solution was cast on a glass plate at 80 ° C. so as to have a thickness of 0.8 mm, dried in a drying oven at 130 ° C. for 12 minutes, and subsequently immersed in water for 2 minutes. After the drying treatment, a self-supporting white film was obtained.

Subsequently, the white film was successively biaxially stretched to 1.5 × 1.5 in an environment of 310 ° C. Next, the stretched white film was immersed in a 5% nitric acid aqueous solution for 30 minutes to dissolve and remove zinc oxide fine particles dispersed in the film. Thereafter, the membrane was washed with pure water to obtain a porous membrane.

The results of evaluating the properties of the wholly aromatic polyamide porous membrane thus produced are shown in Example 9 in Table 1 below.
Column. This indicates that the porous membrane of the present invention produced by the above-described method has excellent strength and also has extremely good ionic conductivity.

[0085]

【table 1】

Comparative Example 1 N-methylpyrrolidone-2 was further mixed with 100 parts by weight of the wholly aromatic polyamide solution obtained by the solution polymerization of Example 1 to obtain a film forming solution. Then, this solution was cast on a glass plate at 80 ° C. so as to have a thickness of 0.7 mm, and was immersed in pure water at 25 ° C. as it was. After 5 minutes, the film spontaneously separated from the glass plate. The membrane was washed with pure water and dried at a constant length to obtain a self-supporting pale yellow membrane. Then, the pale yellow film was sequentially biaxially stretched to 2 × 2 in an environment of 150 ° C.

The results of evaluating the properties of the wholly aromatic polyamide porous membrane thus produced are shown in the lower part of Table 1 above. This indicates that the porous membrane formed by the conventional wet coagulation method using water as a coagulation bath has extremely poor ionic conductivity.

Comparative Example 2 100 parts by weight of the wholly aromatic polyamide solution polymerized in Example 1 was added with N-methylpyrrolidone-
2 were mixed by 50 parts by weight to obtain a film forming solution. And 80
This solution was cast to a thickness of 0.9 mm on a glass plate at 25 ° C, and was immersed in 25 ° C n-octanol as it was. After 1 hour, the film spontaneously separated from the glass plate. After pulling up the membrane, washing with methanol, and drying with a fixed length,
A self-supporting white film was obtained. Then, apply this white film to 150
The biaxial stretching was performed successively to 1.4 × 2 in an environment of ° C.

The results of evaluating the properties of the wholly aromatic polyamide porous membrane thus produced are shown in the lower part of Table 1 above. This indicates that the porous membrane prepared by the above method also has poor ionic conductivity.

Comparative Example 3 100 parts by weight of the wholly aromatic polyamide solution polymerized in Example 1 was mixed with N-methylpyrrolidone-
2 and 9 parts by weight of polyethylene oxide (average molecular weight 3000) were uniformly dispersed and mixed at 80 ° C. to obtain a dispersion solution. Then, the polyethylene oxide dispersion solution is cast on a glass plate at 100 ° C. so as to have a thickness of 0.7 mm, and is dried in a drying furnace at 150 ° C. for 25 minutes to form a self-supporting pale yellow film. Obtained. Then, the pale yellow film was sequentially biaxially stretched to 2 × 2 in an environment of 150 ° C. Next, the stretched pale yellow film was immersed in pure water at 70 ° C. for 10 minutes, and further subjected to ultrasonic cleaning for 10 minutes.
Polyethylene oxide dispersed in the film was dissolved and removed. Then, pure water cleaning was performed.

The results of evaluating the properties of the wholly aromatic polyamide porous membrane thus produced are shown in the lower part of Table 1 above.
Shown in This indicates that the porous membrane formed by this method also has extremely poor ionic conductivity.

[Comparative Example 4] 100 parts by weight of the wholly aromatic polyamide solution polymerized in Example 1 was added to N-methylpyrrolidone-
2 and 9 parts by weight of polyethylene oxide (average molecular weight: 1000) were uniformly dispersed and mixed at 80 ° C. to obtain a polyethylene oxide dispersion. And 100 ° C
This dispersion solution was cast on a glass plate having a thickness of 0.7 mm and dried in a drying oven at 130 ° C. for 40 minutes. After the drying treatment, a self-supporting pale yellow film was obtained. Then, the pale yellow film was sequentially biaxially stretched to 2 × 2 in an environment of 150 ° C. Next, this stretched yellow film is placed in pure water at 70 ° C. for 1 hour.
It was immersed for 0 minutes, and further subjected to ultrasonic cleaning treatment to dissolve and remove the polyethylene oxide dispersed in the film.
Then, pure water cleaning was performed.

The results of evaluating the characteristics of the wholly aromatic polyamide porous membrane thus produced are shown in the lower part of Table 1 above. This shows that this porous membrane also has extremely poor ionic conductivity.

Comparative Example 5 100 parts by weight of the wholly aromatic polyamide solution polymerized in Example 1 was added with N-methylpyrrolidone-
2 and 9 parts by weight of polyethylene oxide (average molecular weight 7500) were uniformly dispersed and mixed at 80 ° C. to obtain a fine particle dispersion solution. Then, the mixture was cast on a glass plate at 100 ° C. so as to have a thickness of 0.7 mm.
Was dried in a drying furnace for 40 minutes. After the drying process,
Countless large holes having a diameter of about 0.1 to 1 mm were formed in the film, and a uniform film could not be produced.

[0095]

As described above, according to the present invention, it is possible to provide a wholly aromatic polyamide porous membrane having good substance permeability and excellent heat resistance, mechanical strength and appearance. Thereby, it can be suitably used for a heat-resistant separation filtration membrane, a battery separator, and the like, which require a particularly thin wholly aromatic polyamide porous membrane.

Claims (15)

[Claims] 1. A fine particle-dispersed membrane formed from a wholly aromatic polyamide, inert fine particles, and a fine particle-dispersed wholly aromatic polyamide solution comprising a solvent that dissolves the wholly aromatic polyamide and does not dissolve the fine particles. A method for producing a wholly aromatic polyamide porous membrane, which comprises treating in a bath solution that does not dissolve the wholly aromatic polyamide and can dissolve the fine particles, and dissolves and removes the fine particles from the film. 2. The wholly aromatic polyamide porous material according to claim 1, wherein the wholly aromatic polyamide is a wholly aromatic polyamide substantially consisting of a repeating unit represented by the following formula (1). Manufacturing method of membrane. Embedded image -NR ¹ -Ar ¹ -NR ² -CO-Ar ² -CO- (1) (where R ¹ and R ² are the same or different, and represent a hydrogen atom, a halogen atom and a carbon number of 5 or less. Selected from the group consisting of alkyl groups, Ar ¹ and Ar ² are the same or different, and may have an orthophenylene group, a metaphenylene group, a paraphenylene group, a 1,4-naphthylene group, 5-naphthylene group, 2,6-naphthylene group,
It is selected from a 2,5-pyridylene group and a divalent group represented by the following formula (2). ) (Here, X is selected from the group consisting of an ether group, a sulfide group, a methylene group, a carbonyl group, and a sulfonyl group.) 3. The above wholly aromatic polyamide has at least 7.5 mol% of the total amount of Ar ¹ and Ar ^{2 in} the repeating unit represented by the above formula (1) from the unit represented by the following formula (3). The method for producing a wholly aromatic polyamide porous membrane according to claim 2, characterized in that it is a para-oriented wholly aromatic polyamide. Embedded image 4. The method for producing a wholly aromatic polyamide porous membrane according to claim 1, wherein the solvent in which the wholly aromatic polyamide is dissolved is an amide-based solvent. 5. The method according to claim 1, wherein the proportion of the wholly aromatic polyamide in the solid content in the fine particle dispersion solution is 10 to 70% by volume. A method for producing a wholly aromatic polyamide porous membrane. 6. The method according to claim 1, wherein the average particle diameter of the fine particles is in the range of 1/50 to 1/5 of the thickness of the formed fine particle dispersed film. A method for producing a wholly aromatic polyamide porous membrane according to the above. 7. The method for producing a wholly aromatic polyamide porous membrane according to claim 1, wherein the fine particles are a metal or a metal compound. 8. The fine particle dispersion solution further dissolves in a solvent for dissolving the wholly aromatic polyamide and not dissolving with the wholly aromatic polyamide, and in a solvent where the wholly aromatic polyamide does not dissolve. The method for producing a wholly aromatic polyamide porous membrane according to any one of claims 1 to 7, wherein a soluble organic substance is dissolved. 9. The method for producing a wholly aromatic polyamide porous membrane according to claim 8, wherein the organic substance is a polyalkylene oxide. 10. The fine particle-dispersed film is formed through at least two steps of a solution casting drying step and a wet coagulation step.
The method for producing a wholly aromatic polyamide porous membrane according to any one of the above. 11. The method for producing a wholly aromatic polyamide porous membrane according to claim 10, wherein the drying temperature in the solution casting drying step is not less than (the boiling point of the solvent −60 ° C.). 12. A bath solution for dissolving and removing the fine particles, wherein 5
The method for producing a wholly aromatic polyamide porous membrane according to any one of claims 1 to 11, wherein the aqueous solution is an aqueous alkali solution having a concentration of not more than a specified amount or an aqueous acid solution having a concentration of not more than 5 specified. 13. The whole aromatic polyamide porous membrane is stretched 1.2 times or more in at least one direction before or after the step of dissolving and removing the fine particles. 13. The method for producing a wholly aromatic polyamide porous membrane according to any one of 12. 14. A wholly aromatic polyamide porous membrane produced by the production method according to any one of claims 1 to 13, wherein the number of Macmillans is greater than 1 and 100 or less, and the tensile strength at 100 ° C. is further increased. The elastic modulus is 100kgf /
a wholly aromatic polyamide porous membrane having a thickness of at least ² mm2. 15. The wholly aromatic polyamide porous membrane according to claim 14, wherein the Macmillan number is more than 1 and 40 or less.