JP5664022B2 - Aromatic polyamide porous membrane, porous film and battery separator - Google Patents

Description

  The present invention relates to an aromatic polyamide porous membrane, a porous film, and a battery separator using them, which can be suitably used for filters, separation membranes, battery separators, printed boards and the like.

  Conventionally, as an aromatic polyamide porous membrane, as described in Patent Documents 1 to 3, for example, it is disclosed that a nonwoven fabric or a paper-like sheet made of wholly aromatic polyamide fibers is used for a battery separator. However, a non-woven fabric or a paper-like sheet has a thin thickness of substantially 50 μm or less and has sufficient strength, and there is no local non-uniformity due to the presence or absence of fibers, etc., and fibers are not detached during processing. It is difficult to industrially manufacture what is not.

  Furthermore, Patent Document 4 discloses an aromatic polyamide porous film characterized in that after a metal oxide fine particle dispersed in a polymer solution is cast to obtain a film, the metal oxide fine particle is dissolved and removed. ing. However, this technique has not completely removed the metal oxide fine particles, and it is difficult to form a dense continuous pore structure.

  When used as a separator for a lithium ion secondary battery, in particular for mobile applications such as mobile phones and notebook computers, so-called shut-down property, in which permeability is lost at around 130 ° C., may be required as a safety measure. Since the porous film of aromatic polyamide has substantially no melting point, there is a problem that the shutdown function is not exhibited.

  For such a porous film having no shutdown property, various methods for combining with a low melting point resin have been proposed (see, for example, Patent Documents 5 to 15). Among these, a method of imparting shutdown property by applying particles having a low melting point to the film surface is particularly preferably used in order to keep the thickness of the film thin. In many cases, polyethylene particles are used as such particles. However, polyethylene and aromatic polyamides have different molecular structures and have a problem of low adhesion.

  Further, as the capacity and output of the lithium ion battery improve, the shutdown operation speed increases, but the battery may be easily deteriorated. The cause of deterioration can be various, but it may be deteriorated by a short circuit caused by the insulating properties of the separator.

JP-A-5-335005 JP-A-7-78608 Japanese Patent Laid-Open No. 7-37571 JP 2001-98106 A Japanese Patent Laid-Open No. 10-6453 JP 2000-100408 A JP 2000-223107 A JP 2006-164661 A JP 2006-164873 A JP 2006-289657 A JP 2007-149507 A JP 2007-275580 A JP 2007-299612 A JP 2007-324073 A JP 2008-41606 A

  The present invention solves the above-mentioned conventional problems, can be thinned, has excellent heat resistance, is stable in operation at high temperatures, and can be provided with shutdown properties. It aims at providing the separator for batteries using them.

In order to achieve the above object, the present invention has a three-dimensional network structure having continuous holes, has an opening density of at least one surface of 5 to 1,000 / 10 μm ² , and has a glossiness of 20 at 60 ° incidence. It is characterized by being -120% aromatic polyamide porous membrane.

  According to the present invention, as described below, the film can be thinned while having a desired porosity and Gurley value, excellent in heat resistance, stable in operation at high temperatures, and can be provided with a shutdown property. A porous porous polyamide membrane can be obtained, and can be suitably used for filters, separation membranes, battery separators, printed boards and the like.

It is a schematic sectional drawing which shows the three-dimensional network structure which concerns on one embodiment of this invention. It is the schematic which shows the structure which has a straight hole. It is the schematic which shows the structure which has the through-hole which the straight hole curved or branched. It is a schematic diagram showing a structure in which spherical or disk-like holes are connected by a very narrow path.

As the aromatic polyamide that can be used in the present invention, those having a repeating unit represented by the following chemical formula (1) and / or chemical formula (2) are preferable.
Chemical formula (1):

Chemical formula (2):

Here, examples of the groups Ar ₁ , Ar ₂ , and Ar ₃ include the following chemical formulas (3) to (7):
Chemical formulas (3) to (7):

The group of X and Y is
Group _{A: -O -, - CO -,} - CO 2 -, - SO 2 -,
Group B: —CH ₂ —, —S—, —C (CH ₃ ) ₂ —
Etc. can be selected.

  Furthermore, some of the hydrogen atoms on these aromatic rings are halogen groups such as fluorine, bromine and chlorine (especially chlorine), nitro groups, alkyl groups such as methyl, ethyl and propyl (especially methyl groups), methoxy and ethoxy, Those substituted with a substituent such as an alkoxy group such as propoxy are preferred because the moisture absorption rate is reduced and the dimensional change due to humidity change is reduced. In addition, hydrogen in the amide bond constituting the polymer may be substituted with another substituent.

In the aromatic polyamide used in the present invention, the above aromatic ring having para-orientation preferably accounts for 80 mol% or more of the total aromatic ring, more preferably 90 mol% or more. Is to occupy. Para-orientation here means a state in which the divalent bonds constituting the main chain on the aromatic nucleus are coaxial or parallel to each other. When this para orientation is less than 80 mol%, the rigidity and heat resistance of the porous membrane may be insufficient. Furthermore, when the aromatic polyamide contains 60 mol% or more of a repeating unit represented by the following chemical formula (8), it is preferable because stretchability and porous properties are particularly excellent.
Chemical formula (8):

  The aromatic polyamide porous membrane of the present invention (hereinafter sometimes simply referred to as a porous membrane) has a three-dimensional network structure having continuous pores. When the three-dimensional network structure forms continuous pores, the porosity can be increased while maintaining the rigidity and heat resistance of the porous membrane, and the electrolyte and air can be sent quickly to the entire obtained space. It is preferable because it is possible. The three-dimensional network structure referred to in the present invention refers to a structure in which a fibrous structure made of a polymer constituting a porous film is joined in three or more branches and has a three-dimensional network structure. (See FIG. 1). On the other hand, a structure having a straight hole (see FIG. 2) as a hole structure not belonging to the three-dimensional network structure (see FIG. 2), a structure having a through hole in which the straight hole is curved or branched (see FIG. 3), and a spherical or discoidal hole There are structures that are connected by narrow paths (see Fig. 4), but these hole structures have too few paths to connect from one opening on one side to the other side. When the thinnest part or the thinnest part existing in the path is blocked by deformation or foreign matter, the air permeability and ionic conductivity are significantly reduced.

The aromatic polyamide porous membrane of the present invention has an opening density of at least one surface of 5 to 1,000 / 10 μm ² , preferably 10 to 800/10 μm ² , and such an opening. The glossiness at 60 ° incidence on the surface having density is 20 to 120%, preferably 40 to 120%. If the opening density of the surface is less than 5/10 μm ² , the length of the path from one opening on one side to the other side becomes long and complicated, and air permeability and ion conduction The degree may decrease. Moreover, since there are few opening parts, when processing the surface, there exists a tendency for an opening part to be obstruct | occluded, and there exists a strong possibility that air permeability and ion conductivity may fluctuate in that case. On the other hand, when the opening density on the surface exceeds 1,000 pieces / 10 μm ² , the opening area tends to be small although the opening area is large. In this case, the liquid permeability may be remarkably lowered.

  The glossiness at 60 ° incidence is preferably 20 to 120%, since it is possible to suitably improve battery storage characteristics that are considered to be due to the effect of suppressing the generation of dendritic crystals and to impart shutdown properties by lamination of thermoplastic resins. If it is less than 20%, the surface is inhomogeneous, and when it is used by being overlapped or bonded to another object, it may be stabbed or caught, resulting in deterioration of battery characteristics. The upper limit of the glossiness is not particularly defined, but it is 120% because it is difficult for the porous film to exceed 120% in the measurement method.

  The aromatic polyamide used in the present invention preferably has a refractive index of 1.55 or more. By increasing the refractive index to 1.55 or more, it is possible to increase the glossiness of the surface when a porous film is formed, and it is possible to suppress a decrease in glossiness even if stretching is performed.

  The aromatic polyamide porous membrane of the present invention is a single-layer membrane (single membrane) in which an interior having a three-dimensional network structure and a surface having an opening and a predetermined glossiness are continuously formed. Is preferred. When a film with an opening is bonded to a porous film having a three-dimensional network structure, the opening of both the porous film and the film is blocked, air permeability is uneven, or the film is peeled off from the bonding part. May occur.

  The aromatic polyamide porous membrane of the present invention preferably has a Gurley permeability of 0.5 to 1,000 seconds / 100 ml. If the Gurley air permeability is less than 0.5 seconds / 100 ml, the strength will be significantly reduced. If the Gurley air permeability is greater than 1,000 seconds / 100 ml, the resistance to ventilation and liquid passage will be large, and it will be useful for filters and separators. It becomes difficult to use realistically.

  The thickness of the aromatic polyamide porous membrane of the present invention is preferably 0.1 to 50 μm, more preferably 1 to 25 μm. If it is less than 0.1 μm, the strength is insufficient and film breakage tends to occur during processing. When it exceeds 50 μm, when used as a battery separator, the capacity of the electrode and the electrolyte solution that can be incorporated in the battery is reduced accordingly, and as a result, the capacity of the battery is reduced.

  The aromatic polyamide porous membrane of the present invention preferably has a breaking elongation of 5% or more in both the length direction and the width direction. If the elongation at break is less than 5%, when there is local compression or deformation, the adjacent porous membrane may not follow and deform, but may tear and crack at the interface. The upper limit is not particularly defined, but generally about 100% is the limit for porous membranes.

  The aromatic polyamide porous membrane of the present invention preferably has a breaking strength in at least one direction of 20 MPa or more. More preferably, it is 50 MPa or more. When the breaking strength is less than 20 MPa, the workpiece may be easily broken due to variations in protrusions and tension during the process. The upper limit is not particularly defined, but generally about 1 GPa is the limit if it is a porous film.

  The aromatic polyamide porous membrane of the present invention preferably has a Young's modulus in at least one direction of 300 MPa or more. More preferably, it is 500 MPa or more. If the Young's modulus is less than 300 MPa, deformation may occur due to pressure fluctuations when gas or liquid is permeated. The upper limit is not particularly defined, but generally about 10 GPa is the limit if it is a porous film.

  The elongation at break, strength at break, and Young's modulus were measured at 25 ° C. and 65% relative humidity using Robot Tensilon RTA (Orientec) according to the method defined in JIS-K7127 (1999). did. The test piece has a width of 10 mm, a length of 100 mm, and a pulling speed of 300 mm / min.

  Next, although the manufacturing method of the aromatic polyamide porous membrane of this invention is demonstrated below as a representative example, it is not limited to this.

  First, aromatic polyamide, but when it is obtained from acid chloride and diamine, solution polymerization in aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), etc. Or by interfacial polymerization using an aqueous medium. At this time, in order to suppress the formation of low molecular weight substances, mixing of water and other substances that inhibit the reaction should be avoided, and it is preferable to take efficient stirring means. In addition, the equivalence of the raw materials is important, but can be appropriately adjusted when there is a possibility that the film forming property may be impaired. Further, calcium chloride, magnesium chloride, lithium chloride, lithium bromide, lithium nitrate or the like may be added as a dissolution aid.

  When aromatic diacid chloride and aromatic diamine are used as monomers, hydrogen chloride is produced as a by-product, but when neutralizing this, is it possible to use a group I of the periodic table such as calcium hydroxide, calcium carbonate or lithium carbonate? Inorganic neutralizing agents represented by salts consisting of Group II cations and hydroxide ions, carbonate ions and other anions, and organic neutralizations such as ethylene oxide, propylene oxide, ammonia, triethylamine, triethanolamine, and diethanolamine Agent is used. Further, for the purpose of improving the humidity characteristics of the porous membrane, benzoyl chloride, phthalic anhydride, acetic chloride, aniline, etc. may be added to the polymerized system to block the end of the polymer. The reaction between isocyanate and carboxylic acid is carried out in an aprotic organic polar solvent in the presence of a catalyst.

In order to obtain the aromatic polyamide porous membrane of the present invention, the intrinsic viscosity η _{inh of the} polymer (value measured at 30 ° C. as a 100 ml solution in 98 mass% sulfuric acid in 0.5 g of polymer) is 0.5 It is preferable that it is (dl / g) or more because the handling property when a porous film is formed is improved.

  These polymer solutions may be used as a film-forming stock solution as they are, or a film-forming stock solution may be prepared by isolating the polymer once and then re-dissolving it in an organic solvent or an inorganic solvent such as sulfuric acid. The polymer concentration in the film-forming stock solution is preferably about 2 to 30% by mass. The thickness is more preferably 5 to 25% by mass, and still more preferably 8 to 20% by mass because a thin and stable porous film having a stable porous property can be obtained efficiently. In addition, when water is absorbed, the polymer is rapidly deposited and the opening density of the surface can be controlled. Therefore, a hydrophilic polymer may be mixed. The hydrophilic polymer to be mixed is preferably 2 to 40% by mass. More preferably, it is 5-30 mass%, More preferably, it is 8-25 mass%. Although control is possible depending on the polymer concentration and film forming conditions described later, the opening density is low when the hydrophilic polymer to be mixed is small, and the opening density tends to be high when the amount is large. The hydrophilic polymer is preferably at least one hydrophilic polymer selected from the group consisting of polyvinylpyrrolidone, polyethylene glycol, polyethyleneimine, polyacrylamide, polyvinyl alcohol, polyallylamine, polyacrylic acid and polyvinyl sulfate.

  The film-forming stock solution prepared as described above is made into a porous film by a so-called solution film-forming method. Solution casting methods include dry and wet methods, wet methods, and deposition methods, and any method can be used. However, since the internal structure of the porous membrane can be easily controlled arbitrarily, the deposition method is more suitable. preferable.

  When producing a porous membrane by a precipitation method, the polymer is precipitated by absorbing the water after forming the membrane shape by casting the solution on a support such as a glass plate, drum, or endless belt. . 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 method of introducing into the conditioned air that can be controlled 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. When the temperature is lower than 20 ° C, the absolute humidity is low, so moisture absorption proceeds slowly, and the solubility of the polymer changes uniformly throughout the solution film, so that a glossy surface may not be formed, and the temperature exceeds 90 ° C. Depending on the solvent used in the polymer solution, it may dry out, forming a dense layer on the surface and forming a glossy surface, but the internal porous structure may not be formed. In addition, when the relative humidity is less than 55% RH, moisture absorption does not proceed and the solubility of the polymer does not decrease, so that a pore structure may not be formed. When the relative humidity exceeds 95% RH, the solubility of the surface polymer rapidly increases. It may be reduced to form a dense layer on the surface, and a porous structure may not be formed. Since the porous structure of the present invention is formed more quickly, it is more preferable that the temperature is 30 to 80 ° C. and the relative humidity is 60 to 95% RH, the temperature is 40 to 70 ° C., and the relative humidity is 65 to 65%. More preferably, it is 90% RH.

  Under high temperature and high humidity, a porous film with a small three-dimensional network structure with a large individual pore diameter and a high gloss surface can be obtained. Under low temperature and low humidity, the porosity is low. A porous film having a large three-dimensional network structure with a small pore diameter and having the same glossiness on both surfaces can be obtained.

  Further, in the method for producing a porous film by absorbing moisture in a humidity-controlled atmosphere, the time from casting on a support to the completion of precipitation of the polymer is preferably 0.1 to 30 minutes. If it is less than 0.1 minutes, the porosity may change greatly in the thickness direction, and the porous film may curl or become weak and vulnerable to bending. Glossiness may decrease.

  The solution (polymer film) after the polymer deposition is introduced into a wet bath, and the solvent is removed. The bath composition is not particularly limited as long as the solubility of the polymer is low, but it is preferable to use water or an organic solvent / water mixed system in view of economy and ease of handling. Further, the wet bath may contain an inorganic salt. At this time, stretching may be performed simultaneously, and the stretching ratio is preferably 1.02 to 3 times. More preferably, it is 1.05 to 2 times.

  At this time, in order to reduce impurities in the porous film, the bath composition is preferably organic medium / water = 70/30 to 5/95 and a bath temperature of 40 ° C. or higher. Furthermore, in order to finally remove the solvent completely, it is effective to pass through a water bath. The water bath preferably has a temperature of 30 ° C. or higher because the residual solvent and the like can be efficiently removed. If it is less than 30 degreeC, a solvent and the added water-soluble polymer remain | survive, and the glossiness of a surface may be reduced by evaporating or decomposing | disassembling at the time of subsequent drying heat processing. Although the upper limit of the bath temperature is not particularly defined, it is efficient to suppress the temperature to 80 ° C. in view of the influence of bubble generation due to water evaporation or boiling. The introduction time is preferably 1 to 20 minutes.

  After the removal of the solvent, the porous membrane is dried and heat-treated in a tenter. The temperature at this time is preferably higher because the dimensional stability at high temperature is improved, but it is necessary to be lower than the thermal decomposition temperature of the polymer used. In an aromatic polyamide, thermal decomposition occurs at 350 to 400 ° C., and therefore it is preferable to perform heat treatment at a temperature lower than that. Preferably it is 150-320 degreeC. More preferably, it is 180-300 degreeC. At this time, stretching in the width direction and relaxation may be performed.

  The aromatic polyamide porous membrane of the present invention can be suitably used for filters, separation membranes, battery separators, printed boards and the like.

The aromatic polyamide porous membrane of the present invention described above has a surface having an opening density and a glossiness in the above-described ranges (opening density: 5 to 1,000 pieces / 10 μm ² , 60 ° glossiness: 20 to 120%). It is preferable to provide a thermoplastic resin layer to form a porous film. When it is provided on the surface where the opening density is less than 5/10 μm ² , the opening is likely to be sealed by the binder or particles contained in the thermoplastic resin layer and should be avoided. On the other hand, when the opening density is provided on the surface exceeding 1,000 pieces / 10 μm ² , since the diameter of the opening is small, when the thermoplastic resin layer is provided using a binder, the opening is sealed by the binder. there is a possibility.

  Further, when it is provided on the surface where the glossiness at 60 ° incidence is less than 20%, there are many protrusions and undulations on the surface, and it is difficult to form a thermoplastic resin layer uniformly, or the contact area between layers is remarkably large. Therefore, the adhesive strength may decrease.

  Further, the thermoplastic resin layer preferably has a melting point of 100 to 150 ° C. Thereby, the porous film can be provided with a shutdown property. When the melting point of the thermoplastic resin layer is less than 100 ° C., when used as a separator for a lithium ion secondary battery, the use environment is not problematic for other materials of the battery, and the film penetrates at a low temperature of about 100 ° C. The hole is shielded and shut down, resulting in malfunction. On the other hand, when the melting point exceeds 150 ° C., when a separator is used, a self-heating reaction may start in the battery before shutting down. When used as a separator, it is preferable that the shutdown functions at 130 to 150 ° C, so the melting point of the thermoplastic resin layer is preferably 120 to 150 ° C, more preferably 125 to 150 ° C. When the thermoplastic resin layer has a plurality of melting points, the highest temperature melting point may be within the above range.

  The thermoplastic resin layer formed on the aromatic polyamide porous film preferably contains particles having a melting point of 100 to 150 ° C. and a binder having a melting point of 100 to 150 ° C. When the thermoplastic resin layer is only particles, the particles may fall off and contaminate the production process. Conversely, when the thermoplastic resin layer is only a binder, the shutdown property can be exhibited, but the aromatic polyamide porous membrane In some cases, the binder penetrates into the pores, impairing permeability. In addition, when both particle | grains and a binder show multiple melting | fusing point, the highest temperature melting | fusing point should just be in the said range.

  The particles used for the thermoplastic resin layer are not particularly limited as long as the melting point is in the range of 100 to 150 ° C., but when used in a lithium ion battery which is a non-aqueous electrolyte secondary battery, moisture is brought into the system. Polyolefins can be preferably used, and in particular, particles made of high-density polyethylene, low-molecular-weight polyethylene, or the like can be preferably used.

  Especially as a binder used for a thermoplastic resin layer, if melting | fusing point exists in the range of 100-150 degreeC, and also hold | maintains the aromatic polyamide porous membrane surface and particle | grains, and particle | grains do not generate | occur | produce easily. Although it is not limited, when used for a lithium ion battery that is a non-aqueous electrolyte secondary battery, as in the case of particles, since it is extremely disliked to bring moisture into the system, the base material does not have many hydrophilic functional groups. It is preferable to use a propylene copolymer having excellent affinity with polypropylene.

  The particles constituting the thermoplastic resin layer of the present invention and the binder preferably have a mass composition ratio of 95: 5 to 60:40. When the mass composition ratio of the binder is less than 5, the adhesion between the aromatic polyamide porous membrane and the particles is poor, and the particles may easily fall off. On the other hand, if the mass composition ratio of the binder exceeds 40, the binder may enter the pores of the aromatic polyamide porous membrane, thereby impairing permeability. The mass composition ratio of the particles and the binder is more preferably 90:10 to 65:35, and particularly preferably 90:10 to 70:30.

  In order to use the porous film of the present invention for a battery separator or the like, the porous film preferably has air permeability, and the Gurley air permeability is in the range of 10 to 500 seconds / 100 ml. It is preferable from the viewpoint of reduction and further improvement of output density. If the Gurley air permeability is less than 10 seconds / 100 ml, metallic lithium deposited on the negative electrode in the lithium ion secondary battery may penetrate through the porous film and cause a short circuit. On the other hand, if the Gurley air permeability exceeds 500 seconds / 100 ml, the air resistance is poor, so the internal resistance of the battery is high, and a high output density may not be obtained.

  Since the porous film of the present invention preferably has shutdown properties when used as a separator of a lithium ion secondary battery, the Gurley air permeability after heat treatment at 130 ° C. for 30 seconds is 120 minutes / 100 ml or more. Preferably there is. Shut-down means that the air permeability is lost, and that the Gurley air permeability is 120 minutes or more indicates that the air permeability is substantially lost and the air permeability is infinite. Yes.

  In addition, the measurement of the Gurley air permeability measured the time which 100cc of air passes according to the method prescribed | regulated to JIS-P8117 (1998). The measurement was performed at three places at intervals of 5 cm or more in one direction, and at three places at intervals of 5 cm or more in the perpendicular direction, and a total value was obtained. Moreover, when the measurement could not be performed by the above method, measurement was performed at 10 points at intervals of 5 cm or more in one direction of the porous film, and an average value was obtained.

  The total thickness of the porous film of the present invention including the thermoplastic resin layer is preferably 1 to 100 μm. If the total thickness is less than 1 μm, a short circuit may easily occur in the battery due to insufficient strength of the film. On the other hand, when the thickness of the whole film exceeds 100 μm, the distance between the electrodes is long and the resistance becomes large. The thickness of the entire film is more preferably 2 to 25 μm.

  The porous film of the present invention preferably has a thermal shrinkage rate at 200 ° C. in at least one direction of 2% or less. If it exceeds 2%, a short circuit may occur due to the shrinkage of the separator when the battery is used at a high temperature or stored for a long time. The lower limit is 0%. Since heat resistance becomes higher and safety is improved, the heat shrinkage rate at 200 ° C. is more preferably 1.5% or less, still more preferably 1.0% or less.

  The measurement of the heat shrinkage rate can be performed as follows. The porous film is cut into a strip shape having a width of 1 cm and a length of 22 cm so that the long side is in the measurement direction. Mark 1 cm from both ends of the long side, heat-treat in a hot air oven at 200 ° C. for 30 minutes under substantially no tension, return to room temperature, measure the distance between the marks, Calculate with the following formula.

Thermal shrinkage rate (%) = ((interval before heat treatment−interval after heat treatment and cooling) / interval before heat treatment) × 100
The method of providing the thermoplastic resin layer on the aromatic polyamide porous film to obtain the porous film of the present invention is not particularly limited. For example, the aromatic polyamide porous film may be applied to the Mayer bar method or gravure coating. A method of forming a thermoplastic resin layer by applying a coating agent dispersed in a solvent to the surface by a method, a die coating method, or the like, and then drying it can be employed. Here, the particles and the binder are weighed and mixed so that the coating composition has a predetermined composition ratio. Further, the solvent can be freely selected as long as it does not attack the aromatic polyamide. It is preferable to use an aqueous liquid from the viewpoint of safety and prevention of scattering of the volatile solvent to the environment.

  The porous film of the present invention not only has excellent heat resistance and mechanical properties, but also has a shutdown property, and thus is particularly preferable as a separator for non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries. Can be used. Examples of the electricity storage device other than the lithium ion secondary battery include an electric double layer capacitor such as a lithium ion capacitor. Since such an electricity storage device can be repeatedly used by charging and discharging, it can be used as a power supply device for industrial devices, household equipment, electric vehicles, hybrid vehicles, and the like.

[Methods for measuring physical properties and methods for evaluating effects]
The measurement method of physical properties and the evaluation method of effects in the present invention were performed according to the following methods.

(1) Surface Opening Density Using a Field Emission Scanning Microscope (UHR-FE-SEM), observe 10 points (times) in a 5 × 2 μm range at any location on the aromatic polyamide porous membrane under the following conditions. did.

Apparatus: Hitachi S-900H
Acceleration voltage: 5 kV
Sample preparation: Direct method Magnification: 10,000 times The obtained photograph was observed, the number of openings was counted, and the average value of 10 points (times) was taken as the number per 10 μm ² . In addition, when it is difficult to determine whether or not it is an opening, it may be determined by observing by an inclination method and the state of the shadow.

(2) Glossiness Measurement was performed according to a method (Gs (60 °)) defined in JIS-Z8741 (1997). A handy gloss meter manufactured by Suga Test Instruments Co., Ltd. was used as a measuring device.

(3) Thermoplastic resin layer (coat layer) and particles constituting thermoplastic resin layer, melting point of binder When thermoplastic resin layer contains particles and binder, particles and binder are individually measured by the following method, The highest melting point was taken as the melting point of the thermoplastic resin layer.

  An appropriate amount of the coating material in which the particles or binder are dispersed is collected, dried in a hot air oven at 70 ° C., and only the solid content is collected. A solid content of 5 mg was taken as a sample in an aluminum pan and measured using a differential scanning calorimeter (RDC220 manufactured by Seiko Denshi Kogyo). Regarding the melting peak observed when the temperature is increased from room temperature to 200 ° C. at a rate of 20 ° C./minute in a nitrogen atmosphere, the peak temperature on the highest temperature side is the melting point of the particle or binder, and among these, the melting temperature at the highest temperature is thermoplastic. The melting point of the resin layer was used.

  In addition, when the thermoplastic resin layer is not a mixture, or when a third component other than the particles and the binder is included, the coating is performed in the same manner as described above even after the particles and the binder are mixed at a predetermined composition ratio. The agent was dried and only the solid content was collected and measured with a differential scanning calorimeter, and the peak temperature on the highest temperature side was taken as the melting point of the thermoplastic resin layer. Note that the melting point of the thermoplastic resin layer can also be determined by taking a sample by scraping only the thermoplastic resin layer from the surface of the film having the thermoplastic resin layer and measuring under the same conditions.

(4) Coat layer adhesion Cellophane tape (Nichiban 18mm width) was applied to the coat layer surface, then the tape was peeled off vigorously. .

  ○: No change in both coating layer and porous film.

  Δ: Material destruction in the porous film.

  X: Interfacial peeling between the coat layer and the film.

(5) Gurley air permeability before heat treatment Measured according to the method defined in JIS-P8117 (1998).

First, the porous membrane of the sample is fastened to a circular hole having a diameter of 28.6 cm and an area of 645 mm ² , and the air in the cylinder is passed from the test hole to the outside of the cylinder by the inner cylinder (inner cylinder mass 567 g). The time required for 100 cc of air to pass through was measured and used as the Gurley permeability. As a measuring device, a B-type Garredenometer (manufactured by Yasuda Seiki Seisakusho) was used.

(6) Gurley air permeability after heat treatment The film was fixed to a stainless steel metal frame with an inner side of 100 mm square, and heat treatment was performed at 130 ° C. for 30 seconds in a hot air oven. After heat treatment, a film was collected from the metal frame and measured in the same manner as in (5) above to determine the Gurley air permeability after heat treatment.

(7) Shutdown operating temperature, internal electrical resistance ratio The film is cut into a square with a side length of 25 mm, and impregnated with an electrolytic solution of a 1N propylene carbonate solution of LiBF ₄ . This was sandwiched between two platinum disk electrodes with a thickness of 0.5 mm and a diameter of 18 mm, a voltage of 1 volt was applied between the electrodes at 1 KHz, and the internal electrical resistance of the flat battery was measured. Was used as the separator electrical resistance. The flat battery was placed on a hot plate and heated from 25 ° C. to 260 ° C. at 10 ° C./min. The temperature at which the internal electrical resistance increases during this process was taken as the shutdown operating temperature.

  The temperature was decreased from 260 ° C. to 25 ° C. at 10 ° C./min. The internal electrical resistance ratio after shutdown was determined by dividing the internal electrical resistance at 25 ° C. after the temperature drop by the internal electrical resistance before heating. In addition, when it became a value of 300 or more as a result of the calculation, it becomes a numerical value that is substantially meaningless, and is expressed as “∞”.

(8) Heat Shrinkage The porous film was cut into a strip shape having a width of 1 cm and a length of 22 cm so that the long side was in the measurement direction. Mark 1 cm from both ends of the long side, heat-treat in a hot air oven at 200 ° C. for 30 minutes with substantially no tension, return to room temperature, measure the distance between the marks, The following formula was used for calculation. The film was measured five times in the longitudinal direction (MD) and the width direction (TD), and the average value was obtained.

  Thermal shrinkage (%) = ((interval before heat treatment−interval after heat treatment and cooling) / interval before heat treatment) × 100.

(9) High-temperature storage test A lithium ion battery was prepared and evaluated as follows.

· Cathode material LiCoO ₂ (Seimi Chemical Co. C-012): 89.5 parts by mass of acetylene black (manufactured by Denki Kagaku Kogyo 75% pressed product): 4.5 parts by mass of polyvinylidene fluoride (manufactured by Kureha Chemical Industry): 6 parts by weight N-methyl-2-pyrrolidone: 40 parts by mass The above substances were mixed to prepare a slurry. The obtained slurry was applied onto an aluminum foil as a current collector, dried, and then punched.

・ Negative electrode material Mesocarbon microbeads (MCMB: Osaka Gas Chemical 25-28): 93 parts by mass Acetylene black: 2 parts by mass Polyvinylidene fluoride: 5 parts by mass N-methyl-2-pyrrolidone: 50 parts by mass To prepare a slurry. The obtained slurry was applied onto a copper foil as a current collector, dried, and then punched.

LiPF ₆ was dissolved in a solvent in which propylene carbonate and methyl carbonate were mixed at a mass ratio of 3: 7 so as to have a concentration of 1 mol / L, and this was used as an electrolytic solution. The film was sandwiched between the positive electrode and the negative electrode as a separator, and after punching, each terminal of the positive electrode and the negative electrode was taken out and inserted into an aluminum laminate type outer package. After sealing three sides of the outer package, drying was performed at 120 ° C. for 1 hour, an electrolyte was injected, and the fourth side was sealed under reduced pressure. In this way, 10 lithium-ion batteries were prepared for each film, and charging / discharging was repeated 3 times at 1C, then fully charged at 1C, and 100 hours without applying current to the atmosphere at 45 ° C. It was allowed to stand and evaluated according to the following criteria.

  A: All operated normally without short circuit.

  ○: There was one battery whose positive and negative electrodes were short-circuited.

  (Triangle | delta): There were 2-3 batteries which the positive and negative electrodes short-circuited.

  X: Four or more batteries with positive and negative electrodes short-circuited.

  Hereinafter, the present invention will be described more specifically based on examples, but it goes without saying that the present invention is not limited thereto.

Example 1
In dehydrated N-methyl-2-pyrrolidone (hereinafter referred to as NMP), 2-chloroparaphenylenediamine corresponding to 80 mol% with respect to the total amount of diamine, and 20 mol% with respect to the total amount of diamine4, 4'-Diaminodiphenyl ether was dissolved, and 2-chloroterephthalic acid chloride (hereinafter referred to as CTPC) corresponding to 98.5 mol% with respect to the total amount of the diamine was added thereto, and polymerized by stirring for 2 hours. A solution of a group polyamide was obtained. The solution temperature at the start of the polymerization was 4 ° C., CTPC was divided into 10 equal parts and added at 10 minute intervals to suppress the temperature rise during the polymerization to 28 ° C. This solution was put into a mixer together with water, and the polymer was precipitated while stirring, and then taken out.

  After this polymer was dissolved in N-methyl-2-pyrrolidone, polyvinyl pyrrolidone (hereinafter referred to as PVP) having a weight average molecular weight of 10,000 was added to obtain a uniform film forming stock solution. Each addition amount was prepared to be 10% by mass of polymer, 70% by mass of NMP, and 20% by mass of PVP.

  This film-forming stock solution was coated on a 100 μm polyethylene terephthalate film in a film shape with a thickness of about 120 μm with a die coater and treated for 2 minutes in humidity-conditioned air at a temperature of 30 ° C. and a relative humidity of 85% RH. Next, the devitrified porous layer was peeled off, and then introduced into a 60 ° C. water bath for 2 minutes to extract the solvent. Subsequently, drying was performed at 90 ° C. for 1 minute in the tenter. Finally, heat treatment was performed at 250 ° C. for 2 minutes while maintaining the width direction, and a porous film was obtained.

  Next, as a coating agent, 80 parts by mass of Chemipearl “W100” (melting point: 128 ° C.) manufactured by Mitsui Chemicals Co., Ltd., 20 parts by mass of Chemipearl “EP150H” (melting point: 115 ° C.), 80 parts by mass of ion-exchanged water, ethanol (Special grade) A suspension mixed with 20 parts by mass was prepared. The coating agent was coated on the surface in contact with the polyethylene terephthalate film with a Mayer bar, and then dried in a hot air oven at 70 ° C. for 1 minute to obtain a porous film having a total thickness of 25 μm and a coating layer thickness of 3 μm.

  The main production conditions are shown in Table 1, and the evaluation results are shown in Tables 2 and 3. All the characteristics were excellent.

(Examples 2-3)
A polymer solution obtained in the same manner as in Example 1 was cast, precipitated, stretched, dried, and heat treated under the conditions shown in Table 1 to obtain a porous film.

  Thereafter, a coat layer was formed in the same manner as in Example 1.

Example 4
After the polymer obtained in the same manner as in Example 1 was dissolved in N-methyl-2-pyrrolidone, PVP having a weight average molecular weight of 10,000 was added to obtain a uniform film forming stock solution. Each addition amount was prepared to be 10% by mass of polymer, 65% by mass of NMP, and 25% by mass of PVP. This polymer solution was cast, precipitated, stretched, dried, and heat treated under the conditions shown in Table 1 to obtain a porous film.

  Thereafter, a coat layer was formed in the same manner as in Example 1.

(Comparative Example 1)
After the polymer obtained in the same manner as in Example 1 was dissolved in N-methyl-2-pyrrolidone, PVP having a weight average molecular weight of 10,000 was added to obtain a uniform film forming stock solution. Each addition amount was prepared to be 10% by mass of polymer, 75% by mass of NMP, and 15% by mass of PVP. This polymer solution was cast, precipitated, stretched, dried, and heat treated under the conditions shown in Table 1 to obtain a porous film.

  Thereafter, a coat layer was formed in the same manner as in Example 1.

(Comparative Example 2)
A polymer obtained in the same manner as in Example 1 was dissolved in N-methyl-2-pyrrolidone, and then a polyethylene glycol having a weight average molecular weight of 300 (hereinafter referred to as PEG) was added to make the polymer completely and completely compatible. A membrane stock solution was obtained. Each addition amount was prepared to be 10% by mass of polymer, 70% by mass of NMP, and 20% by mass of PEG. This polymer solution was cast, precipitated, stretched, dried, and heat treated under the conditions shown in Table 1 to obtain a porous film.

  Thereafter, a coat layer was formed in the same manner as in Example 1.

(Comparative Example 3)
The polymer solution obtained in the same manner as in Example 4 was cast, precipitated, stretched, dried, and heat treated under the conditions shown in Table 1 to obtain a porous membrane.

Thereafter, a coat layer was formed in the same manner as in Example 1.
In the shutdown operation temperature measurement, the internal electric resistance was maximized at 130 ° C., but thereafter it was lowered and shutdown was not obtained.

(Comparative Example 4)
To dehydrated N-methyl-2-pyrrolidone (hereinafter referred to as NMP), metaparaphenylenediamine corresponding to 80 mol% with respect to the total amount of diamine and 4,4 ′ corresponding to 20 mol% with respect to the total amount of diamine. -Diaminodiphenyl ether was dissolved, 2-chloro terephthalic acid chloride corresponding to 98.5 mol% with respect to the total amount of diamine was added thereto, and polymerized by stirring for 2 hours to obtain an aromatic polyamide solution. The solution temperature at the start of the polymerization was 4 ° C., CTPC was divided into 10 equal parts and added at 10 minute intervals to suppress the temperature rise during the polymerization to 28 ° C. This solution was put into a mixer together with water, and the polymer was precipitated while stirring, and then taken out.

  After this polymer was dissolved in N-methyl-2-pyrrolidone, polyvinylpyrrolidone (hereinafter referred to as PVP) having a weight average molecular weight of 60,000 was added to obtain a uniform film forming stock solution. Each addition amount was prepared to be 10% by mass of the polymer, 88% by mass of NMP, and 2% by mass of PVP.

  This film-forming stock solution was coated on a 100 μm polyethylene terephthalate film in a film shape with a thickness of about 120 μm with a die coater and treated for 2 minutes in humidity-conditioned air at a temperature of 30 ° C. and a relative humidity of 85% RH. Next, the devitrified porous layer was peeled off, and then introduced into a 60 ° C. water bath for 2 minutes to extract the solvent. Subsequently, drying was performed at 90 ° C. for 1 minute in the tenter. Finally, heat treatment was performed at 250 ° C. for 2 minutes while maintaining the width direction, and a porous film was obtained.

  Next, as a coating agent, 80 parts by mass of Chemipearl “W100” (melting point: 128 ° C.) manufactured by Mitsui Chemicals Co., Ltd., 20 parts by mass of Chemipearl “EP150H” (melting point: 115 ° C.), 80 parts by mass of ion-exchanged water, ethanol (Special grade) A suspension mixed with 20 parts by mass was prepared. The coating was coated on the surface not in contact with the polyethylene terephthalate film with a Mayer bar, and then dried in a hot air oven at 70 ° C. for 1 minute to obtain a porous film having a total thickness of 22 μm and a coating layer thickness of 3 μm.

  The main production conditions are shown in Table 1, and the evaluation results are shown in Tables 2 and 3.

  The present invention relates to an aromatic polyamide porous membrane that can be suitably used for filters, separation membranes, battery separators, printed circuit boards, and the like, but the application range is not limited thereto.

1: Resin composition 2: Continuous hole 3: Resin composition 4: Straight hole 5: Resin composition 6: Through hole in which straight hole is curved or branched 7: Resin composition 8: Spherical shape connected by a very thin path or Disk-shaped holes

Claims (7)

Aromatic polyamide porous membrane having a three-dimensional network structure having continuous pores, an opening density of at least one surface of 5 to 1,000 / 10 μm ² , and a glossiness of 20 to 120% at 60 ° incidence . The aromatic polyamide porous membrane according to claim 1, which is a single layer membrane. The aromatic polyamide porous membrane according to claim 1 or 2, wherein the Gurley air permeability is 0.5 to 1,000 seconds / 100 ml. The separator for batteries which uses the aromatic polyamide porous membrane in any one of Claims 1-3. The surface of the aromatic polyamide porous membrane according to any one of claims 1 to 3, having an opening density of 5 to 1,000 pieces / 10 μm ² and a glossiness of 20 to 120% at 60 ° incidence. A porous film provided with a thermoplastic resin layer. The porous film according to claim 5, wherein the Gurley air permeability is 10 to 500 seconds / 100 ml. A battery separator comprising the porous film according to claim 5.