JP2022147097A - Meta-type wholly aromatic copolyamide laminated film, and multilayer porous film on which the laminated film is laminated - Google Patents

Abstract

To provide a laminated film composed of a meta-type wholly aromatic copolyamide which is excellent in stability of a coating liquid and reduces thermal shrinkage as much as possible, and a multilayer porous film in which the laminated film is laminated on a polyolefin porous film.SOLUTION: A laminated film is composed of a meta-type wholly aromatic copolyamide and has a content of inorganic particles to the total mass of the resin of 150-1,900 parts, wherein a laminated film containing 2-(4-aminophenyl)-5(6) aminobenzimidazole (DAPBI) in a component constituting the meta-type wholly aromatic copolyamide is laminated on a polyolefin porous film.SELECTED DRAWING: None

Description

The present invention relates to a meta-type wholly aromatic copolyamide laminated film and a laminated porous film obtained by laminating the laminated film. The present invention relates to a meta-type wholly aromatic copolyamide laminated film containing aminophenyl)-5(6)aminobenzimidazole (DAPBI) and a laminated porous film obtained by laminating the laminated film on a polyolefin porous film.

Polyolefin porous membranes such as polyethylene and polypropylene are used as separators for lithium-ion batteries. When some abnormality occurs in the battery, the temperature inside the battery may rise. At that time, the pores of the polyolefin porous membrane are clogged as the temperature rises, shutting down the battery (shutdown function).

When the temperature further rises and exceeds the melting point of polyolefin, the porous membrane contracts and the battery short-circuits. After that, the electrolytic solution and the positive electrode are accompanied by decomposition reactions, which may cause a thermal runaway reaction and ignite.
In order to impart heat resistance to such a polyolefin porous film, the heat resistance has been enhanced by a technique of coating polyvinylidene fluoride, water-based acrylic resin, etc. together with inorganic particles such as alumina.

However, the heat resistance required for batteries, such as charging in a shorter time, is increasing year by year. Aramid resins have therefore been used in place of these resins.
For example, para-aramid resins represented by polyparaphenylene terephthalamide have heat resistance and high mechanical stability, but in order to coat the aramid resin, it must be dissolved in a solvent. In this case, polyparaphenylene terephthalamide has a strong intermolecular interaction, so that crystals tend to precipitate, and the stability of the coating solution is poor, resulting in low productivity (Patent Document 1).

On the other hand, meta-aramid resins, typified by polymetaphenylene isophthalamide, have much better stability in coating liquids than para-aramid resins, but are inferior in heat resistance and moreover, wet coating methods can be used to coat liquids. When applying and fixing on the polyolefin porous membrane, if too much pressure is applied, the coating liquid will enter the pores on the surface of the polyolefin porous membrane and cause clogging. There is a risk that the ion permeability will decrease at the interface of On the other hand, if the coating pressure is too low to prevent this, the coating liquid will not be sufficiently fixed on the polyolefin porous membrane, and the porous layer may be partially peeled off. Such a separator is difficult to handle, and the contact between the separator and the electrode may deteriorate.In addition, the heat resistance of the separator is reduced at the point where the porous layer is peeled off, resulting in a high shrinkage rate of the entire separator. As a result, the safety of the battery is also affected (Patent Documents 2 and 3).

JP 2007-299612 A Japanese Patent Application Laid-Open No. 2008-300362 JP 2009-21265 A

An object of the present invention is to solve the problems in the prior art, and to provide a laminated film made of a meta-type wholly aromatic copolyamide having excellent stability of the coating liquid and having a reduced thermal shrinkage rate as much as possible, and a laminate film thereof. An object of the present invention is to provide a laminated porous membrane in which a laminated membrane is laminated on a polyolefin porous membrane.

As a result of intensive studies to solve the above problems, the present inventors added 2-(4-aminophenyl)-5(6)aminobenzimidazole (DAPBI) to a meta-type wholly aromatic polyamide as a third component. ) into the molecular chain can solve the above problems, and have completed the present invention.

That is, according to the present invention,
1. A laminated film made of a meta-type wholly aromatic copolyamide resin containing inorganic particles, wherein the content of the inorganic particles relative to the total mass of the resin is 150 to 1900 parts, and the meta-type wholly aromatic copolyamide is Composed of a repeating unit represented by the following formula (1), Ar ₁ in the following formula (1) is represented by the following formula (2) and the following formula (3), and Ar ₂ in the following formula (1) is represented by the following formula ( 2), wherein the molar ratio of the compound represented by the following formula (2) and the compound represented by the following formula (3) in Ar ₁ is 60/40 to 20/80.

as well as,
2. A laminated porous membrane obtained by laminating the laminated film according to 1 above on a polyolefin porous membrane, wherein the laminated porous membrane has a thermal shrinkage rate of 12.0% or less at 150 ° C. porous membrane,
is provided.

According to the present invention, a laminated film made of a meta-type wholly aromatic copolyamide having excellent coating liquid stability and reduced thermal shrinkage as much as possible, and the laminated film laminated on a polyolefin porous film. Since the laminated porous membrane can be obtained at low cost, it can be suitably used for applications such as separators used in lithium ion batteries.

FIG. 2 is a plan view schematically showing the measurement positions of the thickness of the polyolefin porous membrane and the laminated porous membrane in the present invention. FIG. 2 is a plan view showing the outline of the measurement position of the thermal shrinkage rate of the laminated porous membrane in the present invention.

The present invention will be described in detail below.

<Meta type wholly aromatic copolyamide>
The meta-type wholly aromatic copolyamide in the present invention is a polymer in which one or more divalent aromatic groups represented by the above chemical formula (1) are directly linked via amide bonds. In addition, the benzene ring shown in the chemical formula (2) is bonded to the aromatic group at the meta position, and these divalent aromatic groups include lower alkyl groups such as methyl group and ethyl group, methoxy group, A halogen group such as a chloro group, a cyano group, or the like may be included. Furthermore, 40 to 80 mol% of the aromatic group of Ar ₁ is a meta-type all-metal compound containing 2-(4-aminophenyl)-5(6)aminobenzimidazole (DAPBI) represented by the above chemical formula (3) as a third component. It is an aromatic copolyamide.

<Method for producing meta-type wholly aromatic copolyamide>
The meta-type wholly aromatic copolyamide in the present invention can be produced according to a conventionally known method. For example, it can be obtained by reacting an aromatic dicarboxylic acid dichloride (hereinafter also referred to as "acid chloride") component and an aromatic diamine component by low-temperature solution polymerization or interfacial polymerization in an amide-based polar solvent. The molecular weight of the meta-type wholly aromatic copolyamide used in the present invention is not particularly limited as long as it can form a film.

[Raw material for meta-type wholly aromatic copolyamide]
(Aromatic dicarboxylic acid dichloride component)
As the aromatic dicarboxylic acid chloride component used in the production of the meta-type wholly aromatic copolyamide, isophthaloyl chloride is used as one that satisfies the above chemical formula (1). Derivatives having a substituent such as a halogen or an alkoxy group having 1 to 3 carbon atoms on the aromatic ring, such as 3-chloroisophthaloyl chloride and 3-methoxyisophthaloyl chloride, may also be used. Let these be the first component.

(Aromatic diamine component)
As the aromatic diamine component used in the production of the meta-type wholly aromatic copolyamide, metaphenylenediamine, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylsulfone, which satisfy the above chemical formula (1) etc. is used. In addition, derivatives having a substituent such as a halogen or an alkoxy group having 1 to 3 carbon atoms on the aromatic ring, such as 2,4-toluylenediamine, 2,6-toluylenediamine, 2,4-diaminochlorobenzene, 2, 6-diaminochlorobenzene or the like may be used. Let these be the 2nd component.

The third component is 2-(4-aminophenyl)-5(6)aminobenzimidazole (DAPBI), which satisfies the above chemical formula (3).
The third component is used by mixing with the second component. The molar ratio between the second component and the third component is preferably 60/40 to 20/80, more preferably 60/40 to 40/60. If the molar ratio of the second component is more than 60%, the viscosity of the coating liquid increases, which is not preferable. Moreover, if the molar ratio of the second component is less than 40%, the heat resistance of the laminated film is lowered, which is not preferable.

[Polymerization solvent]
Examples of solvents for polymerizing the meta-type wholly aromatic copolyamide include organic polar amides such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and N-methylcaprolactam. Solvents, water-soluble ether compounds such as tetrahydrofuran and dioxane, water-soluble alcohol compounds such as methanol, ethanol, and ethylene glycol, water-soluble ketone compounds such as acetone and methyl ethyl ketone, and water-soluble nitrile compounds such as acetonitrile and propionitrile. mentioned. These solvents can be used singly or as a mixed solvent of two or more. The solvent used is desirably dehydrated and preferably has a water content of less than 100 ppm.

In the production of the meta-type wholly aromatic copolyamide used in the present invention, N-methyl-2-pyrrolidone (NMP ) or N,N-dimethylacetamide (DMAc).

Moreover, it is preferable that the content of water in the solvent used in the present invention is 100 ppm or less. If it exceeds 100 ppm, the reaction rate of the monomer is lowered, and the intended degree of polymerization is not achieved, which is not preferable.

[Other polymerization conditions, etc.]
The concentration of the meta-type wholly aromatic copolyamide (hereinafter sometimes abbreviated as polymer) is preferably 4 to 30% by mass. If it is less than 4%, the viscosity is too low and the strength for solidification cannot be obtained, which is not preferable. On the other hand, if it exceeds 30% by mass, the polymer cannot be completely dissolved and precipitates, which is not preferable.

In order to improve the solubility of the meta-type wholly aromatic copolyamide polymer to be produced, an appropriate amount of a generally known inorganic salt may be added before, during, or at the end of the polymerization. Examples of such inorganic salts include chlorides of alkali metals such as lithium chloride, sodium chloride and calcium chloride, and chlorides of alkaline earth metals such as magnesium chloride and calcium chloride. Of these, lithium chloride and calcium chloride are preferred.

Terminals of the meta-type wholly aromatic copolyamide can also be capped. When the terminal is blocked with a terminal blocking agent, for example, phthaloyl chloride and its substituted products, aniline and its substituted products, etc. can be used as the terminal blocking agent.
Moreover, in order to capture acids such as hydrogen chloride that are produced, aliphatic or aromatic amines, quaternary ammonium salts, etc. can be used in combination.

After completion of the reaction, if necessary, a basic inorganic compound such as sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide, etc. may be added to carry out a neutralization reaction.
After the neutralization reaction, the precipitated salt is preferably removed through a filtration process.

Since the polymer solution obtained by the above method maintains a solution state at 0 to 80° C., it can be used as it is as a coating solution for a polyolefin porous membrane. It is also possible to form a solid by immersing the polymer solution obtained in the present invention in a poor solvent and solidifying it.

[Coagulation method]
The method for preparing the meta-type wholly aromatic copolyamide and the solvent-containing polymer solution (dope) is not particularly limited, and known methods can be employed.

Solvents used for preparing the polymer solution (dope) include, for example, N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF),
Dimethyl sulfoxide (DMSO), N-methylcaprolactam (NMC) and the like can be mentioned. Moreover, the solvent used may be a single solvent or a mixed solvent in which two or more solvents are mixed. Furthermore, the solvent used for the polymerization of the meta-type wholly aromatic copolyamide may be used as it is.

[Coagulation bath]
In the production method of the present invention, the polymer is wet-coagulated as described above, and the composition of the coagulating liquid is preferably a poor solvent for the meta-type wholly aromatic copolyamide. The coagulation liquid does not necessarily have to have a single composition, and may be, for example, a mixed solution of NMP and water. From the viewpoint of solvent recovery efficiency, the coagulation bath composition (NMP/water) preferably has a high NMP concentration, and the NMP concentration is preferably in the range of 40% to 60%.

[Other processes]
After pulling up the polymer from the coagulating liquid, the filament formed by coagulating in the coagulating bath is washed with water to gradually remove the solvent. Therefore, the temperature of the washing bath is preferably 60° C. or less.

[Remelting]
Next, the obtained polymer is dissolved in a solvent as it is, or after being cut or pulverized, and then dissolved again. The solvent to be used is not particularly limited, but examples include N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO), N-methylcaprolactam (NMC) and the like. . Moreover, the solvent used may be a single solvent or a mixed solvent in which two or more solvents are mixed. Of these, N-methylpyrrolidone (NMP) is preferred.

For redissolution, a known mixer such as a uniaxial mixer, a ribbon mixer, or a planetary mixer can be used. It is preferable to select a planetary mixer considering that the yarn is used without being cut. For the dissolution, after the solvent is put into the mixer, the thread or the cut thread and the powdered polymer are dispersed in the solvent. Heat while dispersing. The temperature is preferably 60°C or higher. A temperature of 80° C. or higher is more preferable because the dissolution time can be shortened. After raising the temperature, it is also possible to mix metal halide salts such as lithium chloride, calcium chloride, and lithium bromide in order to further increase the solubility.

[Adjustment of coating liquid]
A coating solution is prepared using a polymer solution obtained by polymerization or a polymer solution coagulated and re-dissolved after polymerization. The solvent to be used is not particularly limited, but examples include N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO), N-methylcaprolactam (NMC) and the like. . Moreover, the solvent used may be a single solvent or a mixed solvent in which two or more solvents are mixed. Of these, N-methylpyrrolidone (NMP) is preferred.

Inorganic particles are mixed with this polymer solution to obtain a coating liquid. Inorganic particles include wet or dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, aluminum hydroxide, boehmite, magnesium hydroxide, magnesium carbonate, zinc carbonate, zinc oxide, antimony oxide, Cerium oxide, zirconium oxide, tin oxide, lanthanum oxide, magnesium oxide, barium carbonate, zinc carbonate, basic carbonate, barium sulfate, calcium sulfate, lead sulfate, zinc sulfide, mica, titanium mica, talc, clay, kaolin, fluorine lithium chloride and calcium fluoride.

The content of the inorganic particles is preferably 150-1900 parts per 100 parts of the polymer. If the content of the inorganic particles is less than 150 parts, collisions between the particles that resist the shrinkage stress when the polyolefin porous membrane shrinks are less likely to occur, which is undesirable. On the other hand, if the content of the inorganic particles exceeds 1,900 parts, the amount of the polymer relative to the inorganic particles is too small, so that the particles fall off without being supported, which is not preferred.

The polymer concentration of the coating liquid is preferably 4% by mass or more and 10% by mass or less. If the concentration of the polymer is less than 4% by mass, the amount of the polymer is so small that powder may fall off, which is not preferred. On the other hand, if the polymer concentration exceeds 10% by mass, the viscosity of the coating liquid becomes too high, making it difficult to apply the coating to an appropriate thickness, which is not preferred.

In the present invention, the above coating solution is applied to the polyolefin porous membrane and then wet-coagulated. Hydrophobic additives are added to the coating liquid in order to obtain the densest solidified form possible during wet solidification. Known fluorine-based, organic silicone-based and olefin-based additives can be used as the hydrophobic additive. Among these, a fluorine-based additive having a high water-repellent effect is preferable. The amount to be added is preferably 0.5 to 10% by mass with respect to the amount of solvent in the coating liquid. If the amount added exceeds 10% by mass, the coagulation rate will be significantly lowered and the productivity will be deteriorated, which is not preferable. On the other hand, if the amount added is less than 0.5% by mass, the water-repellent effect is small, and water penetrates into the coating layer, lowering the density of the coating layer, which is not preferable. A preferable addition amount is 1 to 9 mass percent, more preferably 2 to 8 mass percent.

[Coating]
The amount of coating on the polyolefin porous membrane is preferably about 20 to 40 g/m ² . Coating methods include a doctor knife method, a knife coater method, a gravure coater method, a screen printing method, a spray method, a roll coater method, a comma coater method and a Meyer bar method. In the present invention, a substrate coated with an aromatic polyamide polymer composition is immersed in a poor solvent coagulating liquid to wet-coagulate the polymer composition to form a porous layer. The method of coagulation includes a method of spraying a coagulating liquid, a method of immersing in a coagulating liquid, and the like.

The coagulating liquid may be any liquid that can coagulate the polymer composition, but in the present invention, water is preferable. Pure water from which is removed is preferred. This pure water preferably has an electrical conductivity of 1.0 μS/cm. From the viewpoint of solvent recovery, water containing 0 to 40% by mass of the solvent used in the polymer composition is preferred.

In the laminated porous membrane thus obtained, the difference in air permeability (Δair permeability) between the laminated membrane and the polyolefin porous membrane is preferably 25 to 120 sec/100 cc. If the air permeability difference (Δ air permeability) is less than 25 sec/100 cc, the structure of the laminated film becomes loose and low shrinkage cannot be achieved. There is On the other hand, when the difference in air permeability (Δ air permeability) is greater than 120 seconds/100 cc, a separator with low shrinkage and no powder fallout can be obtained, but the movement of lithium ions between the positive electrode and the negative electrode is inhibited. and may degrade battery performance.

Moreover, the heat shrinkage rate of the obtained laminated porous membrane at 150° C. must be 12.0% or less, preferably 10.0% or less. If the heat shrinkage ratio exceeds 12.0%, the dimensional change becomes too large, and the positive electrode and the negative electrode are short-circuited, making the separator unsuitable.

The present invention will be described in detail below with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to the following Examples and Comparative Examples. Further, each physical property in the examples was measured by the following methods.

EXAMPLES The present invention will now be described in more detail with reference to examples and comparative examples. However, these examples and comparative examples are intended to aid understanding of the present invention, and the scope of the present invention is not limited by these descriptions.

(1) Intrinsic Viscosity of Aramid Resin In the present invention, the intrinsic viscosity of the aramid resin is defined by the following measuring method. A solution of 0.5 g of an aramid polymer dissolved in 100 ml of 96 to 98% by mass sulfuric acid and 96 to 98% by mass sulfuric acid were each measured at 30 ° C. with a capillary viscometer for the flow time, and from the obtained flow time ratio The intrinsic viscosity was determined by the following formula.
Intrinsic viscosity = ln (T/T0)/C [unit: dl/g]
Here, T and T0 are the flow times of the aramid-sulfuric acid solution and sulfuric acid, respectively, and C is the aramid concentration (g/dl) in the aramid-sulfuric acid solution.

(2) Viscosity of Coating Liquid The viscosity of the coating liquid was measured using a Brookfield DV2T viscometer.

(3) Thickness of laminated film The polyolefin porous film and the laminated porous film that serve as the base material were punched out to a size of 10 cm × 10 cm, and the thickness of each was measured at nine points as shown in Fig. 1, and the average value was calculated. The thickness was calculated from the formula of The interval between measurement positions shown in FIG. 1 was 2.5 cm.
Thickness of laminated membrane = (Average thickness of laminated porous membrane) - (Average thickness of polyolefin porous membrane)

(4) Thermal shrinkage rate of laminated porous membrane The obtained laminated porous membrane was punched into a size of 10 cm × 10 cm, and as shown in FIG. A mark was put so that the length of 8 cm could be known in two directions. This sample piece was sandwiched between glass cloths, placed in a dryer set at a temperature of 150° C. for 60 minutes, and the heat shrinkage rate was measured from the dimensional change before and after heat drying of the marked 8 cm length. Note that the heat shrinkage rate was the average value in the MD direction and the TD direction.

<Example 1>
[Polymerization of meta-type wholly aromatic copolyamide]
200 g of N,N-dimethylacetamide (DMAc) with a moisture content of 100 ppm or less, 2.636 g of metaphenylenediamine, and 3.620 g of DAPBI are placed in a reaction vessel at room temperature, dissolved and mixed in a nitrogen atmosphere, and then isophthalate is added while stirring. 8.143 g of acid chloride was added. Subsequently, polymerization reaction was carried out at 85° C. for 60 minutes to obtain a transparent and viscous polymer solution. Then, 15.74 g of an NMP slurry solution of 22.5% calcium hydroxide was added and a neutralization reaction was carried out to terminate polymerization and obtain a meta-type wholly aromatic copolyamide solution.

[Creation of coating liquid]
The resulting polymer solution was adjusted with DMAc so as to have a polymer concentration of 6% by mass, and alumina was added to 900 parts per 100 parts of the polymer to prepare a coating liquid for lamination.
[Coating of coating liquid]
A polyolefin porous membrane having a thickness of 10 μm and an air permeability of 170 sec/100 cc was coated using a Meyer bar. After coating, it was immersed in water, solidified and dried to obtain a laminated porous membrane. The thickness of the obtained laminated porous membrane was 14 μm.

<Example 2>
[Polymerization of meta-type wholly aromatic copolyamide]
It was carried out in the same manner as in Example 1.
[Creation of coating liquid]
The obtained polymer solution was adjusted with DMAc so that the polymer concentration was 6% by mass, and alumina was added so as to be 1900 parts per 100 parts of the polymer to prepare a coating liquid for lamination.
[Coating of coating liquid]
It was carried out in the same manner as in Example 1.

<Example 3>
[Polymerization of meta-type wholly aromatic copolyamide]
It was carried out in the same manner as in Example 1.
[Creation of coating liquid]
The obtained polymer solution was adjusted with DMAc so that the polymer concentration was 6% by mass, and alumina was added so as to be 400 parts per 100 parts of the polymer to prepare a coating liquid for lamination.
[Coating of coating liquid]
It was carried out in the same manner as in Example 1.

<Example 4>
[Polymerization of meta-type wholly aromatic copolyamide]
200 g of N,N-dimethylacetamide (DMAc) having a moisture content of 100 ppm or less, 1.757 g of metaphenylenediamine, and 5.429 g of DAPBI were placed in a reaction vessel at room temperature, dissolved and mixed in a nitrogen atmosphere, and then isophthalate was added while stirring. 8.143 g of acid chloride was added. Subsequently, polymerization reaction was carried out at 85° C. for 60 minutes to obtain a transparent and viscous polymer solution. Subsequently, a neutralization reaction was carried out using a 22.5% NMP slurry solution of calcium hydroxide to terminate the polymerization and obtain a meta-type wholly aromatic polyamide solution.

[Creation of coating liquid]
The resulting polymer solution was adjusted with DMAc so as to have a polymer concentration of 6% by mass, and alumina was added to 900 parts per 100 parts of the polymer to prepare a coating liquid for lamination.
[Coating of coating liquid]
It was carried out in the same manner as in Example 1.

<Example 5>
[Polymerization of meta-type wholly aromatic copolyamide]
200 g of N,N-dimethylacetamide (DMAc) with a moisture content of 100 ppm or less, 0.879 g of metaphenylenediamine, and 7.239 g of DAPBI were placed in a reaction vessel at room temperature, dissolved and mixed in a nitrogen atmosphere, and then isophthalate was added while stirring. 8.143 g of acid chloride was added. Subsequently, polymerization reaction was carried out at 85° C. for 60 minutes to obtain a transparent and viscous polymer solution. Subsequently, a neutralization reaction was carried out using a 22.5% NMP slurry solution of calcium hydroxide to terminate the polymerization and obtain a meta-type wholly aromatic polyamide solution.

[Creation of coating liquid]
It was carried out in the same manner as in Example 1.
[Coating of coating liquid]
It was carried out in the same manner as in Example 1.

<Comparative Example 1>
[Polymerization of meta-type wholly aromatic copolyamide]
200 g of N,N-dimethylacetamide (DMAc) having a moisture content of 100 ppm or less, 4.394 g of metaphenylenediamine, and 8.143 g of isophthalic chloride were added, and polymerized at 85°C for 60 minutes to obtain a transparent and viscous mixture. A polymer solution was obtained. Subsequently, a neutralization reaction was carried out using a 22.5% NMP slurry solution of calcium hydroxide to terminate the polymerization and obtain a meta-type wholly aromatic polyamide solution.

[Creation of coating liquid]
DMAc and water were evaporated from the resulting polymer solution so that the polymer concentration was 6% by mass, and 900 parts of alumina was added to 100 parts of the polymer to prepare a coating solution for lamination.
[Coating of coating liquid]
It was carried out in the same manner as in Example 1.

<Comparative Example 2>
[Polymerization of meta-type wholly aromatic copolyamide]
Add 200 g of N,N-dimethylacetamide (DMAc) with a moisture content of 100 ppm or less, 3.515 g of metaphenylenediamine, 1.810 g of DAPBI, and 8.143 g of isophthaloyl chloride, and polymerize at 85° C. for 60 minutes. A clear, viscous polymer solution was obtained. Subsequently, a neutralization reaction was carried out using a 22.5% NMP slurry solution of calcium hydroxide to terminate the polymerization and obtain a meta-type wholly aromatic polyamide solution.

[Creation of coating liquid]
DMAc and water were evaporated from the obtained polymer solution so that the polymer concentration was 6% by mass, and alumina was added to 900 parts per 100 parts of the polymer to prepare a coating solution for lamination.
[Coating of coating liquid]
It was carried out in the same manner as in Example 1.

<Comparative Example 3>
[Polymerization of para-type wholly aromatic polyamide]
200 g of N-methyl-2-pyrrolidone (NMP) with a moisture content of 100 ppm or less, 16.0 g of calcium chloride, and 4.394 g of paraphenylenediamine are placed in a reaction vessel at room temperature, dissolved and mixed in a nitrogen atmosphere, and then stirred. While adding 8.143 g of terephthaloyl chloride. Subsequently, polymerization was carried out at 85° C. for 60 minutes. A polymer precipitated during the polymerization, and a dissolved dope could not be obtained.
Table 1 shows the properties of the laminated porous membranes obtained in the above examples and comparative examples.

According to the present invention, a laminated film made of a meta-type wholly aromatic copolyamide having excellent coating liquid stability and reduced thermal shrinkage as much as possible, and the laminated film laminated on a polyolefin porous film. Since a laminated porous membrane can be obtained, its industrial value is extremely large.

Claims (2)

A laminated film made of a meta-type wholly aromatic copolyamide resin containing inorganic particles, wherein the content of the inorganic particles relative to the total mass of the resin is 150 to 1900 parts, and the meta-type wholly aromatic copolyamide is Composed of a repeating unit represented by the following formula (1), Ar ₁ in the following formula (1) is represented by the following formula (2) and the following formula (3), and Ar ₂ in the following formula (1) is represented by the following formula ( 2), wherein the molar ratio of the compound represented by the following formula (2) and the following formula (3) in Ar ₁ is 60/40 to 20/80. .

A laminated porous membrane obtained by laminating the laminated film according to claim 1 on a polyolefin porous membrane, wherein the thermal shrinkage of the laminated porous membrane at 150° C. is 12.0% or less. Laminated porous membrane.

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