JP6256038B2 - Aromatic polyamide porous membrane and separator for secondary battery - Google Patents

Description

  The present invention relates to an aromatic polyamide porous membrane and a separator for a secondary battery using the same.

  A porous membrane made of an aromatic polyamide has been studied as a heat-resistant separator used in a secondary battery or the like, and is disclosed in, for example, Patent Documents 1 to 4.

  However, a porous film generally used for a separator is often white or yellowish white because light is scattered by a large number of pores present therein, and is not transparent. For this reason, there is a limit to a method for inspecting a defect or a foreign substance existing in the porous film in the process of manufacturing the porous film or the battery. Further, when the positive and negative electrodes and the separator are laminated at the time of manufacturing the battery, it is difficult to recognize the position of each member with an optical detector or the like, and there is a concern that the initial failure due to winding deviation may cause the yield to deteriorate.

  Patent Documents 1 to 3 disclose aromatic polyamide porous membranes containing a large number of flexible components such as meta-orientation and ether bonds, but these have a pore structure due to a decrease in bonding force between molecular chains due to the flexible components. It is easy to coarsen and does not have transparency. On the other hand, Patent Document 4 discloses an aromatic polyamide porous membrane containing a large number of para-orientations, which are rigid components, but has a large non-uniformity in pore diameter and does not form a dense pore structure as a whole, so that it is sufficiently transparent. Sex has not been obtained.

JP 2012-82399 A JP 2012-207221 A JP 2005-209989 A JP-A-9-208736

  As described above, it is difficult to impart transparency to the aromatic polyamide porous membrane having gas permeability enough to be used for a battery separator.

  An object of this invention is to provide the aromatic polyamide porous membrane which has transparency, and the separator for secondary batteries using the same, without impairing air permeability in view of the said situation.

  In order to achieve the above object, the present invention has the following configuration.

(1) An aromatic polyamide porous film having a film thickness of 10 to 30 μm, a light transmittance of 20 to 80% at a wavelength of 750 nm , and a Gurley permeability of 1 to 300 sec / 100 ml .

  (2) The aromatic polyamide porous film according to (1), wherein the light transmittance at a wavelength of 550 nm is 20 to 80%.

( 3 ) A separator for a secondary battery using the aromatic polyamide porous membrane according to (1) or (2) .

  Since the aromatic polyamide porous membrane of the present invention has good air permeability even though it has transparency, it can be suitably used for a secondary battery separator such as a lithium ion secondary battery. When the aromatic polyamide porous membrane of the present invention is used as a battery separator, since the separator has transparency, defect inspection at the time of manufacture and position detection of members when stacking battery members are facilitated, and initial defective products. Can be reduced.

  As the aromatic polyamide used in the present invention, those obtained by block copolymerization of a flexible aromatic polyamide portion and a rigid aromatic polyamide portion are suitable.

The flexible aromatic polyamide portion in the present invention is a compound in which at least ^one of Ar ¹ and Ar ² in Chemical Formula (1) has a flexible structure represented by any one of group a in Chemical Formula (2). Say. Further, the rigid aromatic polyamide portion means that in Ar (1), Ar ¹ and Ar ² both have a rigid structure represented by b in Chemical Formula (2).

  Chemical formula (1):

  Chemical formula (2):

Here, X and Y are any group of —O—, —CH ₂ —, —CO—, —S—, —SO ₂ —, and —C (CH ₃ ) ₂ —.

  The aromatic polyamide constituting the aromatic polyamide porous membrane of the present invention is a rigid aromatic polyamide having a strong cohesive force in which molecular chains of a flexible aromatic polyamide portion having a high pore-forming ability are present in the molecular chain at regular intervals. It is physically crosslinked by the part. For this reason, the holes formed by the film forming method described later have a fine and uniform structure. Thereby, since scattering of the light in a porous film is suppressed and the light transmittance increases, high transparency can be obtained.

  The proportion of the flexible aromatic polyamide portion in the aromatic polyamide used in the present invention is preferably 50 to 90 mol%, and preferably 60 to 80 mol based on the total number of moles of the flexible aromatic polyamide portion and the rigid aromatic polyamide portion. % Is more preferable. When the proportion of the flexible aromatic polyamide portion is less than 50 mol%, the rigidity of the polymer is high and the pore forming ability is lowered, so that the Gurley air permeability may not fall within the scope of the present invention. On the other hand, if the proportion of the flexible aromatic polyamide portion exceeds 90 mol%, the pore structure becomes coarse and the light transmittance may not fall within the scope of the present invention.

  In the aromatic polyamide porous membrane of the present invention, the light transmittance at a wavelength of 750 nm is preferably 20 to 80%, more preferably 20 to 70%, and further preferably 30 to 60%. The light transmittance in the porous membrane is high when the pore structure is uniform and fine due to the pore structure inside the membrane, and is low when the pore structure is uneven or coarse. If the light transmittance at a wavelength of 750 nm is less than 20%, it may be difficult to perform defect inspection during battery manufacture and position detection during member lamination. In addition, since the pore structure inside the film is non-uniform or coarse, when used as a secondary battery separator, dendritic metal growth or cycle deterioration may occur. Further, as a more preferable condition, the light transmittance at a wavelength of 550 nm is 20 to 80%, and more preferably 30 to 70%. The shorter the wavelength of the light beam, the higher the accuracy of defect inspection and position detection at the time of manufacture. On the other hand, since scattering by the internal holes is likely to occur, it is preferable to have a more uniform and fine hole structure. As a method for controlling the pore structure in order to make the light transmittance within the above range, a porous membrane can be prepared by using the aromatic polyamide obtained by the block copolymerization described above and a film-forming stock solution formulation and a film-forming method described later. It is preferable to manufacture.

  The thickness of the aromatic polyamide porous membrane of the present invention is preferably 10 to 30 μm, more preferably 15 to 30 μm. If the thickness is less than 10 μm, the strength is low, the film breaks during processing, the voltage resistance is low, and the electrodes may be short-circuited when used as a secondary battery separator. If the thickness exceeds 30 μm, the light transmittance may not fall within the scope of the present invention. In addition, when used as a separator for a secondary battery, the output may decrease due to an increase in separator resistance, or the thickness of the active material layer that can be incorporated in the battery may be reduced, resulting in a decrease in capacity per volume. The thickness of the aromatic polyamide porous membrane of the present invention varies depending on the concentration of the stock solution, the viscosity of the stock solution, the additives in the stock solution, the casting thickness, the porosity, the wet bath temperature, the heat treatment temperature, and the stretching conditions. It can be controlled according to the conditions. Specifically, in the membrane-forming stock solution, the higher the membrane-forming stock solution concentration and the membrane-forming stock solution viscosity, and the more additives in the membrane-forming stock solution, the thicker the resulting porous membrane tends to be. Further, in the film forming process, the thickness of the porous film obtained tends to increase as the casting thickness increases, the wet bath temperature increases, the heat treatment temperature decreases, and the draw ratio decreases.

  The aromatic polyamide porous membrane of the present invention preferably has a Gurley air permeability of 1 to 300 sec / 100 ml, more preferably 5 to 200 sec / 100 ml. If the Gurley air permeability is less than 1 sec / 100 ml, the strength of the porous film may be reduced, causing breakage during processing, or short-circuiting between electrodes when used as a secondary battery separator. When the Gurley air permeability exceeds 300 sec / 100 ml, the battery output may be reduced when used as a separator. In order to keep the Gurley air permeability within the above range while having a fine pore structure, the aromatic polyamide obtained by the block copolymerization described above is used to form a porous film by the following film-forming solution formulation and film-forming method. It is preferable to produce a membrane.

  Next, the manufacturing method of the aromatic polyamide porous membrane of this invention is demonstrated. First, in the case of polymerizing aromatic polyamide using, for example, diamine and acid dichloride as raw materials, aprotic organic polar solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethylformamide, dimethylsulfoxide, etc. It can synthesize | combine by superposition | polymerization in the inside, interfacial polymerization using an aqueous medium, etc. Polymerization in an aprotic organic polar solvent is preferable because the molecular weight of the polymer can be easily controlled.

  Hereinafter, a polymerization method in an aprotic organic polar solvent will be described. In order to obtain a polymer having a high molecular weight, the water content of the solvent used for the polymerization is preferably 500 ppm or less (mass basis, the same shall apply hereinafter), more preferably 200 ppm. As the diamine and acid dichloride used, it is preferable to pay attention to moisture absorption and to use a high purity. In addition, the polymerization reaction of the aromatic polyamide is exothermic, but if the temperature of the polymerization system rises, side reaction may occur and the degree of polymerization may not be sufficiently increased. It is preferable to cool. The temperature of the solution during polymerization is more preferably 30 ° C. or lower. Furthermore, when acid dichloride and diamine are used as raw materials, hydrogen chloride is produced as a by-product in the polymerization reaction, but when neutralizing this, an inorganic neutralizing agent such as lithium carbonate, calcium carbonate, calcium hydroxide, Alternatively, an organic neutralizer such as ethylene oxide, propylene oxide, ammonia, triethylamine, triethanolamine, diethanolamine may be used.

  The aromatic polyamide of the present invention is preferably obtained by block copolymerization of a flexible aromatic polyamide portion and a rigid aromatic polyamide portion. At this time, after first polymerizing only the flexible aromatic polyamide part or the rigid aromatic polyamide part, block copolymerization may be carried out by adding another raw material monomer to the same reaction system and polymerizing, or After the aromatic polyamide portion and the rigid aromatic polyamide portion are polymerized in separate reaction systems, block copolymerization may be performed by mixing both together with a small amount of monomer.

The logarithmic viscosity (η _inh ) of the aromatic aromatic polyamide used in the present invention is preferably 1.5 to 3.5 dl / g, more preferably 2.0 to 3.0 dl / g. When the logarithmic viscosity is less than 1.5 dl / g, the bonding force between the polymer molecular chains is low, the pore structure of the resulting porous film is coarsened, and the light transmittance may not fall within the scope of the present invention. In addition, the strength of the porous membrane may be lowered. On the other hand, when the logarithmic viscosity exceeds 3.5 dl / g, it may be difficult to produce a porous membrane.

  Next, the film forming stock solution used when manufacturing the aromatic polyamide porous film of the present invention will be described. The polymer solution after polymerization may be used as a film-forming stock solution as it is as a film-forming stock solution, or the polymer is isolated and then dissolved again in the above organic solvent or an inorganic solvent such as sulfuric acid to form a film-forming stock solution. May be prepared. The content of the aromatic polyamide in 100% by mass of the film-forming stock solution is preferably 5 to 15% by mass. More preferably, it is 7-12 mass%. When the content of the aromatic polyamide is less than 5% by mass, the pore structure of the porous membrane is coarsened, and the light transmittance may not fall within the scope of the present invention. In addition, mechanical properties such as toughness and strength may be lowered. On the other hand, when the content of the aromatic polyamide in the raw film forming solution exceeds 15% by mass, the solution viscosity is high, the film forming property is lowered, or the pore forming ability is lowered, so that the Gurley air permeability is within the scope of the present invention. It may not be inside.

  A hydrophilic polymer may be mixed with the film-forming stock solution for the purpose of improving pore forming ability. By mixing the hydrophilic polymer, it is possible to control the aggregation of the aromatic polyamide molecules and induce the formation of pores in the process of forming the porous film from the film-forming stock solution.

  The hydrophilic polymer is a polymer that contains at least one substituent selected from the group consisting of a polar substituent, particularly a hydroxyl group, an acyl group, and an amino group, among polymers that are soluble in an aprotic organic polar solvent. It is preferable. Examples of such a polymer include polyvinylpyrrolidone, polyethylene glycol, polyethyleneimine, polyacrylamide, polyvinyl alcohol, polyallylamine, and polyacrylic acid.

  It is preferable to mix water in advance with the film-forming stock solution in order to cause the polymer precipitation in the subsequent production process of the porous film to proceed promptly and uniformly and make the pore structure within the scope of the present invention. The water to be mixed is preferably 2 to 20% by mass, more preferably 4 to 15% by mass with respect to 100% by mass of the film-forming stock solution. When the mixing amount of water is less than 2% by mass, it takes time for the polymer to precipitate, and excessive densification of the pore structure or non-uniformity of the pore structure in the thickness direction may proceed. On the other hand, when the mixing amount of water exceeds 20% by mass, precipitation of aromatic polyamide occurs in the film-forming stock solution before casting, resulting in uneven pore structure of the resulting porous film, pinholes, etc. The disadvantages may occur. Although it does not specifically limit as water to mix, It is preferable to use the water processed by the reverse osmosis, the water processed by the combination of a filter, activated carbon, an ion exchange membrane, etc., or distilled water.

  The film-forming stock solution prepared as described above is made into a porous film by a so-called solution film-forming method. The solution casting method includes a dry method, a dry-wet method, a wet method, a deposition method, and the like, and any method may be used, but the deposition method is preferable because the pore structure can be easily controlled. When producing a porous membrane by the precipitation method, the polymer solution is formed by absorbing the water after forming the membrane by casting the membrane-forming stock solution onto a support such as a glass plate, drum or endless belt. Precipitate. At this time, the method of absorbing water may be any of the method of adhering mist-like water, the method of introducing into water, or the method of introducing into humidity-controlled air. A controllable method for introducing into the humidity-controlled air is preferably used. In the method for producing a porous film by absorbing moisture in a humidity-controlled atmosphere, it is preferable that the temperature of the atmosphere is 20 to 90 ° C. and the relative humidity is 55 to 95% RH.

  The aromatic polyamide porous membrane obtained by the above process is peeled off from the support or from the support and introduced into a wet bath to remove the solvent, hydrophilic polymer, inorganic salt, and the like. The bath composition is not particularly limited, but it is preferable to use water or an organic solvent / water mixed system from the viewpoint of ease of handling and economy.

  Next, the porous film that has been desolvated is subjected to heat treatment using a tenter or the like. It is preferable to perform heat processing at 230-300 degreeC. At this time, preliminary drying may be performed at 100 to 210 ° C. in advance for the purpose of removing moisture taken into the polymer. Moreover, you may extend | stretch or relax in the width direction when performing heat processing.

  Since the aromatic polyamide porous film of the present invention has a dense pore structure and excellent heat resistance in addition to transparency, it can be suitably used as a separator for a secondary battery. When the aromatic polyamide porous membrane of the present invention is used as a separator for a secondary battery, since the separator has transparency, defect inspection at the time of manufacture and position detection of the member when stacking battery members are facilitated. Defective products can be reduced. Accordingly, the secondary battery using the aromatic polyamide porous membrane of the present invention as a separator is not only a small electronic device but also an automobile such as an electric vehicle (EV), a hybrid vehicle (HEV), and a plug-in hybrid vehicle (PHEV). It can be suitably used as a power source for large industrial equipment such as industrial batteries and industrial cranes. Further, it can be suitably used as a stationary large power storage device for power leveling in a solar cell, a wind power generation device or the like or for a smart grid. Examples of the secondary battery of the present invention include a sodium ion secondary battery, a sodium molten salt battery, a magnesium secondary battery, a lithium sulfur battery, and a metal-air battery in addition to the lithium ion secondary battery.

[Methods for measuring physical properties and methods for evaluating effects]
The physical properties were measured in the examples according to the following method.

(1) Logarithmic viscosity (η _inh )
The polymer was dissolved at a concentration of 0.5 g / dl in N-methyl-2-pyrrolidone (NMP) containing 2.5% by mass of lithium bromide, and the flow time was 30 ° C. using an Ubbelohde viscometer. Was measured. The flow time of the blank solution in which the polymer was not dissolved was also measured in the same manner, and the logarithmic viscosity (η _inh ) was calculated using the following formula.

η _inh (dl / g) = [ln (t / t ₀ )] / 0.5
t: Flow time of polymer solution (sec)
t ₀ : Flowing time of blank solution (sec)
(2) Thickness The thickness of the porous membrane was measured using a constant pressure thickness measuring device FFA-1 (manufactured by Ozaki Seisakusho). The probe diameter is 5 mm and the measurement load is 1.25 N. Ten locations were measured at 20 mm intervals in the width direction of the porous membrane, and the average value was determined.

(3) Gurley air permeability The measurement was performed using a B-type Gurley densometer (manufactured by Yasuda Seiki Seisakusho) according to the method defined in JIS-P8117 (1998). The sample porous membrane is clamped to a circular hole with a diameter of 28.6 cm and an area of 645 mm ² , and the air inside the cylinder is passed from the test hole to the outside of the cylinder by the inner cylinder (inner cylinder mass 567 g), and 100 ml of air passes. By measuring the time to do, it was set as the Gurley air permeability. In addition, when the passage time exceeded 1,000 sec, the measurement was interrupted with no air permeability.

(4) Light transmittance The light transmittance at an incident angle of 0 ° was measured using a spectrophotometer U-4100 (manufactured by Hitachi, Ltd.) and a variable angle transmission measurement accessory. The slit width was set to 2 nm, the gain was set to 2, and measurement was performed in the wavelength range of 400 to 800 nm at a scanning speed of 600 nm / min, and light transmittances at 750 nm and 550 nm were obtained. It affixed on clear glass so that the back surface side (base material side) of a sample might turn into a glass side, and measured by making light inject from the glass surface side.

Example 1
35 mol% of 4,4′-diaminodiphenyl ether (4,4′-DPE) was dissolved in N-methyl-2-pyrrolidone (NMP) dehydrated under a nitrogen stream with respect to the total number of moles of raw material monomers. To the solution, 35 mol% of 2-chloro-terephthalic acid chloride (CTPC) with respect to the total number of moles of raw material monomers was added and stirred for 1 hour to polymerize the flexible aromatic polyamide portion. Next, 15 mol% of 2-chloro-paraphenylenediamine (CPA) with respect to the total number of moles of raw material monomers was added to the polymerization solution and dissolved. Thereafter, 15 mol% of 2-chloro-terephthalic acid chloride is added to the total number of moles of the raw material monomers, and the mixture is stirred for 1 hour to synthesize a rigid aromatic polyamide portion. Polymerized. This solution was neutralized with lithium carbonate and diethanolamine to obtain an aromatic polyamide solution having a polymer concentration of 12% by mass. The logarithmic viscosity of the obtained aromatic polyamide was 2.3 dl / g.

  Next, polyvinyl pyrrolidone (PVP, viscosity characteristic value K90), water and NMP for dilution are added to the obtained aromatic polyamide solution so as to have the following composition, and the mixture is stirred at 60 ° C. for 2 hours. A film-forming stock solution was obtained. The content of each component in the film-forming stock solution is 9% by weight of aromatic polyamide, 5% by weight of PVP and 6% by weight of water with respect to 100% by weight of the film-forming stock solution, and the remaining 80% by weight is NMP and polymerization stock solution. Are neutralized salts (lithium chloride, diethanolamine hydrochloride).

  This film-forming stock solution was applied in a film form from a die onto a polyethylene terephthalate (PET) film having a thickness of 50 μm. This film-like material was introduced into a humidity-controlled air tank conditioned at a temperature of 40 ° C. and a relative humidity of 85% RH for 2 minutes to devitrify the entire film-like material. The devitrified film was peeled from the PET film and introduced into a water bath for 10 minutes to extract the solvent. After solvent extraction, heat treatment was performed in an oven at 230 ° C. for 1 minute to obtain an aromatic polyamide porous membrane. The evaluation results of the obtained porous membrane are shown in Table 1.

(Example 2)
An aromatic polyamide porous membrane was obtained in the same manner as in Example 1 except that the coating thickness from the die was changed. The evaluation results of the obtained porous membrane are shown in Table 1.

(Example 3)
4,4′-DPE was dissolved in NMP at 40 mol% with respect to the total number of moles of raw material monomers. 40 mol% of CTPC with respect to the total number of moles of raw material monomers was added to the solution and stirred for 1 hour to polymerize the flexible aromatic polyamide portion. Next, 10 mol% of CPA with respect to the total number of moles of raw material monomers was added to the polymerization solution and dissolved. Thereafter, 10 mol% of CTPC was added to the total number of moles of the raw material monomers, and the mixture was stirred for 1 hour to synthesize a rigid aromatic polyamide portion and block copolymerized. Thereafter, neutralization was performed in the same manner as in Example 1 to obtain an aromatic polyamide solution having a polymer concentration of 12% by mass. The logarithmic viscosity of the obtained aromatic polyamide was 2.2 dl / g.

  Using this polymerization solution, a film-forming stock solution and a porous film were produced in the same manner as in Example 1. The evaluation results of the obtained porous membrane are shown in Table 1.

Example 4
4,4′-DPE was dissolved in NMP at 30 mol% with respect to the total number of moles of raw material monomers. 30 mol% of CTPC with respect to the total number of moles of raw material monomers was added to the solution and stirred for 1 hour to polymerize the flexible aromatic polyamide portion. Next, 20 mol% of CPA with respect to the total number of moles of raw material monomers was added to the polymerization solution and dissolved. Thereafter, 20 mol% of CTPC was added to the total number of moles of raw material monomers, and the mixture was stirred for 1 hour to synthesize a rigid aromatic polyamide portion, which was then block copolymerized. Thereafter, neutralization was performed in the same manner as in Example 1 to obtain an aromatic polyamide solution having a polymer concentration of 12% by mass. The logarithmic viscosity of the obtained aromatic polyamide was 2.3 dl / g.

  Using this polymerization solution, a film-forming stock solution and a porous film were produced in the same manner as in Example 1. The evaluation results of the obtained porous membrane are shown in Table 1.

(Example 5)
Using the aromatic polyamide solution obtained in the same manner as in Example 1, the content of each component in the film-forming stock solution was 11% by weight aromatic polyamide and 2% by weight PVP with respect to 100% by weight of the film-forming stock solution. An aromatic polyamide porous membrane was obtained in the same manner as in Example 1, except that water was 6% by mass, NMP and neutralized salt were 81% by mass, and the coating thickness from the die was changed. The evaluation results of the obtained porous membrane are shown in Table 1.

(Example 6)
25 mol% of 4,4′-DPE was dissolved in NMP based on the total number of moles of raw material monomers. 25 mol% of CTPC with respect to the total number of moles of raw material monomers was added to the solution and stirred for 1 hour to polymerize the flexible aromatic polyamide portion. Next, 25 mol% of CPA based on the total number of moles of raw material monomers was added to the polymerization solution and dissolved. Thereafter, 25 mol% of CTPC was added to the total number of moles of raw material monomers, and the mixture was stirred for 1 hour to synthesize a rigid aromatic polyamide portion and block copolymerized. Thereafter, neutralization was performed in the same manner as in Example 1 to obtain an aromatic polyamide solution having a polymer concentration of 12% by mass. The logarithmic viscosity of the obtained aromatic polyamide was 2.3 dl / g.

  Using this polymerization solution, a film-forming stock solution and a porous film were produced in the same manner as in Example 1. The evaluation results of the obtained porous membrane are shown in Table 1.

(Example 7)
4,4′-DPE was dissolved in NMP at 45 mol% with respect to the total number of moles of raw material monomers. 45 mol% CTPC with respect to the total number of moles of raw material monomers was added to the solution and stirred for 1 hour to polymerize the flexible aromatic polyamide portion. Next, 5 mol% of CPA with respect to the total number of moles of raw material monomers was added to the polymerization solution and dissolved. Thereafter, 5 mol% of CTPC was added to the total number of moles of the raw material monomers, and the mixture was stirred for 1 hour to synthesize a rigid aromatic polyamide portion, and block copolymerized. Thereafter, neutralization was performed in the same manner as in Example 1 to obtain an aromatic polyamide solution having a polymer concentration of 12% by mass. The logarithmic viscosity of the obtained aromatic polyamide was 2.3 dl / g.

  Using this polymerization solution, a film-forming stock solution and a porous film were produced in the same manner as in Example 1. The evaluation results of the obtained porous membrane are shown in Table 1.

(Example 8)
35 mol% of 4,4'-DPE was dissolved in NMP with respect to the total number of moles of raw material monomers. 34 mol% of CTPC with respect to the total number of moles of raw material monomers was added to the solution and stirred for 1 hour to polymerize the flexible aromatic polyamide. Next, in a reaction vessel different from the above flexible aromatic polyamide, 15 mol% of CPA was added to NMP and dissolved with respect to the total number of moles of raw material monomers. Thereafter, 14 mol% of CTPC was added to the total number of moles of the raw material monomers and stirred for 1 hour to polymerize the rigid aromatic polyamide. After mixing the flexible aromatic polyamide and rigid aromatic polyamide obtained in the same container in the same container, add 2 mol% CTPC with respect to the total number of moles of raw material monomers, and stir for 1 hour to block copolymerize did. This solution was neutralized with lithium carbonate and diethanolamine to obtain an aromatic polyamide solution having a polymer concentration of 12% by mass. The logarithmic viscosity of the obtained aromatic polyamide was 2.4 dl / g.

  Using this polymerization solution, a film-forming stock solution and a porous film were produced in the same manner as in Example 1. The evaluation results of the obtained porous membrane are shown in Table 1.

Example 9
4,4′-DPE was dissolved in NMP at 30 mol% with respect to the total number of moles of raw material monomers. 30 mol% of isophthalic acid chloride (IPC) with respect to the total number of moles of raw material monomers was added to the solution and stirred for 1 hour to polymerize the flexible aromatic polyamide portion. Next, 20 mol% of CPA based on the total number of moles of raw material monomers was added to the polymerization solution and dissolved. Thereafter, 20 mol% of terephthalic acid chloride (TPC) is added to the total number of moles of raw material monomers, and the mixture is stirred for 1 hour to synthesize a rigid aromatic polyamide portion and block copolymerized with a flexible aromatic polyamide portion. Turned into. This solution was neutralized with lithium carbonate and diethanolamine to obtain an aromatic polyamide solution having a polymer concentration of 12% by mass. The logarithmic viscosity of the obtained aromatic polyamide was 2.3 dl / g.

  Using this polymerization solution, a film-forming stock solution and a porous film were produced in the same manner as in Example 1. The evaluation results of the obtained porous membrane are shown in Table 1.

(Example 10)
An aromatic polyamide porous membrane was obtained in the same manner as in Example 9 except that the coating thickness from the die was changed. The evaluation results of the obtained porous membrane are shown in Table 1.

(Example 11)
40 mol% of CPA was dissolved in NMP with respect to the total number of moles of raw material monomers. 40 mol% IPC with respect to the total number of moles of raw material monomers was added to the solution and stirred for 1 hour to polymerize the flexible aromatic polyamide portion. Next, 10 mol% of CPA based on the total number of moles of raw material monomers was added to the polymerization solution and dissolved. Thereafter, 10 mol% of CTPC was added to the total number of moles of the raw material monomers, and the mixture was stirred for 1 hour to synthesize a rigid aromatic polyamide portion, and block copolymerized with the flexible aromatic polyamide portion. This solution was neutralized with lithium carbonate and diethanolamine to obtain an aromatic polyamide solution having a polymer concentration of 12% by mass. The logarithmic viscosity of the obtained aromatic polyamide was 2.3 dl / g.

  Using this polymerization solution, a film-forming stock solution and a porous film were produced in the same manner as in Example 1. The evaluation results of the obtained porous membrane are shown in Table 1.

(Comparative Example 1)
In NMP, 4,4′-DPE was dissolved in 20 mol% with respect to the total number of moles of raw material monomers. 20 mol% of CTPC with respect to the total number of moles of raw material monomers was added to the solution and stirred for 1 hour to polymerize the flexible aromatic polyamide portion. Next, 30 mol% of CPA based on the total number of moles of raw material monomers was added to the polymerization solution and dissolved. Thereafter, 30 mol% of CTPC was added to the total number of moles of raw material monomers, and the mixture was stirred for 1 hour to synthesize a rigid aromatic polyamide portion, and block copolymerized. Thereafter, neutralization was performed in the same manner as in Example 1 to obtain an aromatic polyamide solution having a polymer concentration of 12% by mass. The logarithmic viscosity of the obtained aromatic polyamide was 2.1 dl / g.

  Using this polymerization solution, a film-forming stock solution was prepared and a film was produced in the same manner as in Example 1. However, the obtained film was not permeable and did not become a porous film.

(Comparative Example 2)
4,4′-DPE was dissolved in NMP at 47.5 mol% with respect to the total number of moles of raw material monomers. 47.5 mol% CTPC with respect to the total number of moles of raw material monomers was added to the solution and stirred for 1 hour to polymerize the flexible aromatic polyamide portion. Next, 2.5 mol% of CPA with respect to the total number of moles of raw material monomers was added to the polymerization solution and dissolved. Thereafter, 2.5 mol% of CTPC was added to the total number of moles of raw material monomers, and the mixture was stirred for 1 hour to synthesize a rigid aromatic polyamide portion and block copolymerized. Thereafter, neutralization was performed in the same manner as in Example 1 to obtain an aromatic polyamide solution having a polymer concentration of 12% by mass. The logarithmic viscosity of the obtained aromatic polyamide was 2.1 dl / g.

  Using this polymerization solution, the content of each component in the film-forming stock solution is 9% by weight of aromatic polyamide, 5% by weight of PVP, 8% by weight of water, NMP and neutralization with respect to 100% by weight of the film-forming stock solution. The salt was 78% by mass. Thereafter, a porous membrane was produced in the same manner as in Example 1. The evaluation results of the obtained porous membrane are shown in Table 1.

(Comparative Example 3)
CPA and 4,4′-DPE were dissolved in NMP at 15 mol% and 35 mol% with respect to the total number of moles of raw material monomers, respectively. 50 mol% of CTPC was added to this solution based on the total number of moles of raw material monomers, and polymerization was carried out for 2 hours. Thereafter, neutralization was performed in the same manner as in Example 1 to obtain an aromatic polyamide solution having a concentration of 12% by mass. The logarithmic viscosity of the obtained aromatic polyamide was 2.1 dl / g.

  Using this polymerization solution, the content of each component in the film-forming stock solution is 9% by weight of aromatic polyamide, 5% by weight of PVP, 12% by weight of water, NMP and neutralization with respect to 100% by weight of the film-forming stock solution. The salt was 74% by mass. Thereafter, a porous membrane was produced in the same manner as in Example 1. The evaluation results of the obtained porous membrane are shown in Table 1.

(Comparative Example 4)
An aromatic polyamide solution was obtained in the same manner as in Comparative Example 3 except that CPA and 4,4′-DPE were both 25 mol% based on the total number of moles of raw material monomers. The logarithmic viscosity of the obtained aromatic polyamide was 2.4 dl / g.

  Using this polymerization solution, a film-forming stock solution and a porous film were produced in the same manner as in Comparative Example 3. The evaluation results of the obtained porous membrane are shown in Table 1.

(Comparative Example 5)
An aromatic polyamide solution was obtained in the same manner as in Comparative Example 3 except that CPA and 4,4′-DPE were respectively 35 mol% and 15 mol% with respect to the total number of moles of the raw material monomers. The logarithmic viscosity of the obtained aromatic polyamide was 2.1 dl / g.

  Using this polymerization solution, a film-forming stock solution and a porous film were produced in the same manner as in Comparative Example 3 except that the coating thickness from the die was changed. The evaluation results of the obtained porous membrane are shown in Table 1.

(Comparative Example 6)
An aromatic polyamide solution was obtained in the same manner as in Comparative Example 3 except that CPA and 4,4′-DPE were 42.5 mol% and 7.5 mol%, respectively, with respect to the total number of moles of raw material monomers. The logarithmic viscosity of the obtained aromatic polyamide was 2.5 dl / g.

  Using this polymerization solution, the content of each component in the film-forming stock solution is 10% by weight of aromatic polyamide, 4% by weight of PVP, 4% by weight of water, NMP and neutralization with respect to 100% by weight of the film-forming stock solution. The salt was 82% by mass. Thereafter, the membrane was produced in the same manner as in Example 1. However, the obtained membrane was not permeable and did not become a porous membrane.

(Comparative Example 7)
Using the aromatic polyamide solution obtained in the same manner as in Comparative Example 2, the content of each component in the film-forming stock solution was 10% by weight aromatic polyamide and 2% by weight PVP with respect to 100% by weight of the film-forming stock solution. An aromatic polyamide porous membrane was obtained in the same manner as in Example 1 except that water was 8% by mass, NMP and neutralized salt were 80% by mass, and the coating thickness from the die was changed. The evaluation results of the obtained porous membrane are shown in Table 1.

(Comparative Example 8)
Using the aromatic polyamide solution obtained in the same manner as in Comparative Example 3, the content of each component in the film-forming stock solution was 11% by weight aromatic polyamide and 2% by weight PVP with respect to 100% by weight of the film-forming stock solution. An aromatic polyamide porous membrane was obtained in the same manner as in Example 1 except that water was 8% by mass, NMP and neutralized salt were 79% by mass, and the coating thickness from the die was changed. The evaluation results of the obtained porous membrane are shown in Table 1.

(Comparative Example 9)
Using the aromatic polyamide solution obtained in the same manner as in Comparative Example 5, the content of each component in the film forming stock solution was 11% by weight aromatic polyamide and 4% by weight PVP with respect to 100% by weight of the film forming stock solution. An aromatic polyamide porous membrane was obtained in the same manner as in Example 1 except that water was 8% by mass, NMP and neutralized salt were 77% by mass, and the coating thickness from the die was changed. The evaluation results of the obtained porous membrane are shown in Table 1.

Claims (3)

An aromatic polyamide porous film having a thickness of 10 to 30 μm, a light transmittance of 750 nm at a wavelength of 20 to 80% , and a Gurley permeability of 1 to 300 sec / 100 ml . The aromatic polyamide porous film according to claim 1, wherein the light transmittance at a wavelength of 550 nm is 20 to 80%. The separator for secondary batteries using the aromatic polyamide porous membrane of Claim 1 or 2 .