# US 7,407,702 B2 · Polymetaphenylene isophthalamide-based polymer porous film, process for its production and battery separator

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- Number: US 7,407,702 B2
- Document ID: US7407702B2
- Status: Granted
- Kind: B2
- Application number: 10/776,184
- Filed: 2004-02-12
- Published: 2004-08-19
- Granted: 2008-08-05
- Earliest claimed: 1999-09-13
- Assignees: Teijin Limited
- Inventors: Takao Ohno; Jiro Sadanobu; Tsutomu Nakamura; Susumu Honda; Toyoaki Ishiwata
- Web page: https://patentgrep.com/patent/US7407702B2

## CPC

- B32B 27/08: of synthetic resin
- B01D 67/0011: {Casting solutions therefor}
- B01D 67/00165: {Composition of the coagulation baths}
- B01D 69/02: characterised by their properties
- B01D 69/141: {Heterogeneous membranes, e.g. containing dispersed material; Mixed matrix membranes}
- B01D 71/56: Polyamides, e.g. polyester-amides
- B32B 27/18: characterised by the use of special additives
- B32B 27/304: {comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF}
- B32B 27/34: comprising polyamides
- B32B 27/36: comprising polyesters
- B32B 38/0036: {Heat treatment (for heating or cooling of layers during lamination B32B37/06, B32B37/08)}
- C08J 5/18: Manufacture of films or sheets
- C08J 9/28: by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
- H01M 50/414: Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M 50/417: Polyolefins
- H01M 50/426: Fluorocarbon polymers
- H01M 50/446: Composite material consisting of a mixture of organic and inorganic materials
- H01M 50/491: Porosity
- B01D 2323/081: Heating
- B01D 2323/12: Specific ratios of components used
- B01D 2325/22: Thermal or heat-resistance properties
- B01D 2325/24: Mechanical properties, e.g. strength
- B32B 2305/026: Porous
- B32B 2307/306: Resistant to heat
- B32B 2307/724: Permeability to gases, adsorption
- B32B 2309/025: Temperature vs time profiles
- B32B 2377/00: Polyamides
- B32B 2457/10: Batteries
- C08J 2201/0542: from an organic solvent-based polymer composition
- C08J 2377/10: Polyamides derived from aromatically bound amino and carboxyl groups of amino carboxylic acids or of polyamines and polycarboxylic acids
- H01M 50/431: Inorganic material
- H01M 50/434: Ceramics
- Y02E 60/10: Energy storage using batteries
- Y10T 428/249978: Voids specified as micro
- Y10T 428/249979: Specified thickness of void-containing component [absolute or relative] or numerical cell dimension
- Y10T 428/24998: Composite has more than two layers
- Y10T 428/249981: Plural void-containing components
- Y10T 428/249986: Void-containing component contains also a solid fiber or solid particle
- Y10T 428/249991: Synthetic resin or natural rubbers
- Y10T 428/249992: Linear or thermoplastic
- Y10T 428/249993: Hydrocarbon polymer
- Y10T 428/31725: Of polyamide
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A polymetaphenylene isophthalamide-based polymer porous film having a satisfactory porous structure that exhibits excellent gas permeability and heat resistance. It is produced by a process which comprises casting a dope of the polymetaphenylene isophthalamide-based polymer and coagulating it in a coagulating bath. The porous film may also contain inorganic whiskers, and a composite porous film may be formed in combination with a separate thermoplastic polymer film.

## Claims

### Claim 1

A polymetaphenylene isophthalamide-based polymer porous film with a gas permeability of 0.2-1000 ml/sec, which retains at least 60% of its gas permeability after heat treatment at 350° C. for 10 minutes compared to before treatment, while also having a porous structure with a porosity of 60-80% and a cross-sectional pore laminar coefficient of 2.5 or greater, and having a specific Young's modulus of 200-800 (kgf/mm2)/(g/cm3) in at least one direction, and containing inorganic whiskers having a long axis dimension L of 10-100 μm.

### Claim 2 (depends on 1)

A porous film according to claim 1, which has a thickness of 1-10 μm and is self-supporting.

### Claim 3 (depends on 1)

A process for the production of a polymetaphenylene isophthalamide-based polymer porous film according to claim 1, comprising casting a dope prepared by dissolving a polymetaphenylene isophthalamide-based polymer in an amide-based solvent, and coagulating it in a coagulating bath comprising an amide-based solvent containing a non-solvent for said polymer to produce a polymetaphenylene isophthalamide-based polymer porous film according to claim 1.

### Claim 4 (depends on 3)

A process according to claim 3, wherein the concentration of the amide-based solvent in the coagulating bath is 30-80 wt % and the temperature is 0-98° C.

### Claim 5 (depends on 3, 4)

A process according to claim 3 or 4, wherein the non-solvent for the polymetaphenylene isophthalamide-based polymer is water.

### Claim 6 (depends on 3)

A process according to claim 3, wherein the dope prepared by dissolving a polymetaphenylene isophthalamide-based polymer in an amide-based solvent contains no inorganic salts.

### Claim 7 (depends on 3)

A process according to claim 3, wherein after coagulation, the porous film is rinsed with water, dried and then stretched to a factor of 1.3-5 in the uniaxial direction or to a factor of 1.3-10 in the orthogonal biaxial directions on an area scale, at a temperature of 270-340° C.

### Claim 8 (depends on 3)

A process according to claim 3 wherein, after coagulation, the porous film is further stretched in a stretching bath comprising an amide-based solvent containing a non-solvent for the polymetaphenylene isophthalamide-based polymer.

### Claim 9 (depends on 8)

A process according to claim 8, wherein the concentration of the amide-based solvent in the stretching bath is 5-70 wt % and the temperature is 0-98° C.

### Claim 10 (depends on 3)

A process according to claim 3, wherein the coagulation is followed by immersion in a bath comprising an amide-based solvent containing a non-solvent for the polymetaphenylene isophthalamide-based polymer, with an amide-based solvent concentration of 50-80 wt % and a temperature of 50-98° C.

### Claim 11 (depends on 10)

A process according to claim 10, wherein the dimethylformamide-insoluble portion of the porous film after immersion is 10% or greater.

### Claim 12 (depends on 10, 11)

A process according to claim 10 or 11, wherein after the immersion the porous film is rinsed with water, dried and then heat treated at a temperature of 290-380° C.

### Claim 13 (depends on 10, 11)

A process according to claim 10 or 11, wherein after the immersion the porous film is rinsed with water, dried and then stretched to a factor of 1.3-5 in the uniaxial direction or to a factor of 1.3-10 in the orthogonal biaxial directions on an area scale, at a temperature of 270-380° C.

### Claim 14 (depends on 10, 11)

A process according to claim 10 or 11, wherein after the immersion the porous film is further stretched in a stretching bath comprising an amide-based solvent containing a non-solvent for the polymetaphenylene isophthalamide-based polymer.

### Claim 15 (depends on 14)

A process according to claim 14 wherein, after the stretching, the porous film is rinsed with water, dried and then heat treated at a temperature of 290-380° C.

### Claim 16 (depends on 14)

A process according to claim 14, wherein the concentration of the amide-based solvent in the stretching bath is 5-70 wt % and the temperature is 0-98° C.

### Claim 17 (depends on 3)

A process according to claim 3, wherein the dope used is one in which inorganic whiskers are dispersed and a polymetaphenylene isophthalamide-based polymer is dissolved in an amide-based solvent.

### Claim 18 (depends on 17)

A process according to claim 17, wherein the weight ratio of the polymetaphenylene isophthalamide-based polymer to the whiskers is 50:50 to 99:1.

### Claim 19 (depends on 17, 18)

A process according to claim 17 or 18, wherein the inorganic whiskers have a short axis dimension D of 0.01-10 μm and an L/D ratio of 1.5 or greater.

### Claim 20 (depends on 1)

A porous film comprising at least two layers including a polymetaphenylene isophthalamide-based polymer porous layer and a heat-melting thermoplastic polymer porous layer, wherein the polymetaphenylene isophthalamide-based polymer porous layer is a polymetaphenylene isophthalamide-based polymer porous film according to claim 1.

### Claim 21 (depends on 20)

A porous film according to claim 20, wherein the thermoplastic polymer is a polyolefin with a molecular weight of 400,000 or greater.

### Claim 22 (depends on 20)

A porous film according to claim 20, wherein the thermoplastic polymer is a polyvinylidene fluoride-based polymer.

### Claim 23 (depends on 22)

A porous film according to claim 22, wherein the polyvinylidene fluoride-based polymer is a copolymer composed mainly of vinylidene fluoride and a perfluoro lower alkyl vinyl ether.

### Claim 24 (depends on 20, 21, 22, 23)

A porous film according to any one of claims 20 to 23 wherein, at elevated temperatures, the thermoplastic polymer layer melts and plugs the pore gaps, while the polymetaphenylene isophthalamide-based polymer layer retains its shape without melting.

### Claim 25 (depends on 1)

A process for the production of a porous film which comprises forming a porous layer of a polymetaphenylene isophthalamide-based polymer onto one or both sides of a porous film made of a heat-melting thermoplastic polymer, or forming a porous layer made of a heat-melting thermoplastic polymer onto one or both sides of a porous film of a polymetaphenylene isophthalamide-based polymer, wherein the polymetaphenylene isophthalamide-based polymer porous layer is a polymetaphenylene isophthalamide-based polymer porous film according to claim 1.

### Claim 26 (depends on 20, 21, 22, 23)

A battery separator comprising a porous film according to any one of claims 20 to 23.

### Claim 27 (depends on 26)

A lithium ion battery comprising a battery separator according to claim 26.

### Claim 28

A polymetaphenylene isophthalamide-based polymer porous film containing inorganic whiskers having a long axis dimension L of 10-100 μm and having a porosity of 10-80% and a specific Young's modulus of 200-5000 (kgf/mm2)/(g/cm3) in at least one direction and having a cross-sectional pore laminar coefficient of 2.5 or greater.

### Claim 29 (depends on 28)

A polymetaphenylene isophthalamide-based polymer porous film according to claim 28, wherein the weight ratio of the polymetaphenylene isophthalamide-based polymer to the whiskers is 50:50 to 99:1.

### Claim 30

A polymetaphenylene isophthalamide-based polymer porous film containing inorganic whiskers with a long axis dimension L of 10-100 μm, a short axis dimension D of 0.01-10 μm and an L/D ratio of 1.5 or greater, and having a porosity of 10-80% and a specific Young's modulus of 200-5000 (kgf/mm2)/(g/cm3) in at least one direction, and having a cross-sectional pore laminar coefficient of 2.5 or greater.

### Claim 31 (depends on 1, 2, 28, 29, 30)

A method of using a porous film according to any one of claims 1 and 2,28,29,30 comprising placing said porous film as a battery separator between a positive electrode and a negative electrode in a battery.

### Claim 32 (depends on 1)

A lithium ion battery comprising a battery separator situated between a positive electrode and a negative electrode, wherein said battery separator consists of a porous film according to any one of claims 1, and 2,28,29,30.

### Claim 33

A polymetaphenylene isophthalamide-based polymer porous film with a gas permeability of 0.2-1000 ml/sec, which retains at least 60% of its gas permeability after heat treatment at 360° C. for 10 minutes compared to before treatment, while also having a porous structure with a porosity of 60-80% and a cross-sectional pore laminar coefficient of 2.5 or greater and containing inorganic whiskers having a long axis dimension L of 10-100 μm, and which is obtained by a process comprising a step of casting a dope prepared by dissolving a polymetaphenylene isophthalamide-based polymer in an amide-based solvent and a step of coagulating the cast dope in a coagulating bath comprising an amide-based solvent containing a non-solvent for the polymer.

### Claim 34

A method of using a polymetaphenylene isophthalamide-based polymer porous film, comprising disposing a polymetaphenylene isophthalamide-based polymer porous film as a separator between an anode and a cathode of a battery, wherein the porous film has a gas permeability of 0.2-1000 ml/sec, retains at least 60% of its gas permeability after heat treatment at 360° C. for 10 minutes compared to before treatment, while also having a porous structure with a porosity of 60-80% and a cross-sectional pore laminar coefficient of 2.5 or greater and containing inorganic whiskers having a long axis dimension L of 10-100 μm, and having a specific Young's modulus of 200-5000 (kgf/mm2)/(g/cm3) in at least one direction.