METHOD FOR PRODUCING LAMINATED POROUS FILM, AND LAMINATED POROUS FILM

• US 20140234538A1
• Filed: 09/18/2012
• Published: 08/21/2014
• Est. Priority Date: 09/22/2011
• Status: Active Grant

• Current Assignee: Mitsubishi Chemical Corporation (Mitsubishi Chemical Group Corp.)
• Original Assignee: Mitsubishi Plastics Incorporated (Mitsubishi Chemical Group Corp.)
• Inventors: Yamada, Hiroto, Nemoto, Tomoyuki
• Granted Patent: US 9,343,719 B2
• Time in Patent Office: Days
• US Class Current: 427/126.4
• CPC Class Codes: B29C 48/00 Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor extrusion blow-moulding B29C49/04
• CPC Class Codes: B32B 2250/24 All layers being polymeric
• CPC Class Codes: B32B 2255/10 on synthetic resin layer or on natural or synthetic rubber layer
• CPC Class Codes: B32B 2255/26 Polymeric coating
• CPC Class Codes: B32B 2307/518 bi-axially
• CPC Class Codes: B32B 2307/704 Crystalline
• CPC Class Codes: B32B 2307/724 Permeability to gases, adsorption
• CPC Class Codes: B32B 2457/10 Batteries
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/32 comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: C08K 2003/2227 of aluminium
• CPC Class Codes: C09D 1/00 Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances
• CPC Class Codes: C09D 5/02 Emulsion paints including aerosols
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/4235 Safety or regulating additives or arrangements in electrodes, separators or electrolyte H01M10/4242 takes precedence
• CPC Class Codes: H01M 2220/30 Batteries in portable systems, e.g. mobile phone, laptop
• CPC Class Codes: H01M 50/403 Manufacturing processes of separators, membranes or diaphragms
• CPC Class Codes: H01M 50/417 Polyolefins
• CPC Class Codes: H01M 50/431 Inorganic material
• CPC Class Codes: H01M 50/449 having a layered structure
• CPC Class Codes: H01M 50/489 : Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
• CPC Class Codes: Y02E 60/10 : Energy storage using batteries

Abstract

The present invention produces a laminated porous film which improves the stability of an aqueous dispersion of a metal oxide without lowering battery characteristics, while having high binding properties and excellent heat resistance. This laminated porous film exhibits excellent characteristics when used as a separator for batteries. This laminated porous film is produced by forming a porous coating layer on at least one outer surface of a resin porous film, which is formed of a single layer or a laminate of a plurality of layers, by applying a coating liquid that contains a metal oxide, a resin binder and a volatile acid thereto and drying the applied coating liquid. The coating liquid is prepared so that the difference between the pH (pH₁) of the coating liquid and the pH (pH₂) of the coating layer is not less than 2.

Claims

1. A method of producing a laminated porous film comprising a porous coating layer formed on a porous resin film consisting of a single layer or a laminate of a plurality of layers by applying a coating solution containing a metal oxide, a resin binder, and a volatile acid to at least one outer surface of said porous resin film and drying said coating solution,

wherein a pH (pH₁) of said coating solution is so adjusted that a difference between said pH (pH₁) of said coating solution and a pH (pH₂) of said coating layer is not less than 2.

2. The method of producing a laminated porous film according to claim 1, wherein at least one layer of said porous resin film is a porous polyolefin resin film.

3. The method of producing a laminated porous film according to claim 1, wherein said pH₁ of said coating solution is set to pH1 to pH5.

4. The method of producing a laminated porous film according to claim 1, wherein said pH₂ of said coating layer is set to pH5 to pH8.

5. The method of producing a laminated porous film according to claim 1, wherein a boiling point of said volatile acid or a decomposition temperature thereof is −

100°

C. to 150°

C.

6. The method of producing a laminated porous film according to claim 1, wherein said volatile acid includes at least one acid selected from the group consisting of carbonic acid, formic acid, acetic acid, propionic acid, acrylic acid, nitric acid, nitrous acid, a halogen oxoacid, hydrosulfuric acid, sulfurous acid, and hydrohalogenic acid.

7. The method of producing a laminated porous film according to claim 1, wherein said volatile acid is contained in said coating solution at 0.001 to 1 mass % based on 100 mass % of said coating solution.

8. The method of producing a laminated porous film according to claim 1, wherein said metal oxide is alumina.

9. The method of producing a laminated porous film according to claim 1, wherein an average particle diameter of said metal oxide is 0.1 μ

m to 3.0 μ

m.

10. The method of producing a laminated porous film according to claim 1, wherein said resin binder comprises at least one member selected from the group consisting of polyether, polyamide, polyimide, polyamide imide, polyaramid, polyoxyethylene, polyvinyl alcohol, cyanoethyl polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylonitrile, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polymethyl methacrylate, polyacrylamide, polyvinyl acetate, ethylene vinyl acetate copolymer, poly(4-methyl-1-pentene), cyanoethyl cellulose, a polyacrylic acid derivative, a polymethacrylic acid derivative, and a maleic acid-modified polyolefin.

11. The method of producing a laminated porous film according to claim 1, wherein components contained in said coating solution are dispersed with a dispersion medium containing water as a main component thereof.

12. The method of producing a laminated porous film according to claim 1, wherein a pH of said coating solution is adjusted by selection of said volatile acid and a mixing ratio thereof.

13. The method of producing a laminated porous film according to claim 2, wherein said porous polyolefin resin film has a β

crystal activity.

14-19. -19. (canceled)