美国微孔膜专利

METHODOFMAKINGATRILAYERBATTERYSEPARATORFIELDOFTHEINVENTIONTheinventionisdirectedtoamethodofmakingatrilayer,shutdownbatteryseparator.BACKGROUNDOFTHEINVENTIONTrilayer,shutdownbatteryseparatorsareknown.See:JapanesePatentApplicationNos.98395/1994and98394/1994bothfiledMay20,1994byUbeIndustries,Ltd.(theUbetrilayerseparator);U.S.patentapplicationSer.No.359,772filedDec.20,1994,nowabandoned,byHoechstCelaneseCorporation(theCELGARD~Separator);Japa-nesePatentApplicationNo.55550/1995filedMar.15,1995byNittoDenkoKogyoK.K.(theNittoDenkotrilayerseparator);andJapanesePatentApplicationNo.56320/1995filedMar.15,1995byKurehaChemicalIndustryCo.,Ltd.(theKurehatrilayerseparator).Trilayer,shutdownbatteryseparatorareporousfilmsandhavebecomeacommercialsuccess,withinthebatteryindustry,particularlywithinthesecondary(orrechargeable)lithiumbatteryindustry.Thesuccessisbelievedtobedue.inpart,totheseparator'spuncturestrengthandtheseparator'sabilitytoreducetheriskofinternalshortcircuitwithinthebattery.Theseparator'spuncturestrengthis,atleast,importantbecauseitenablestheseparatortowithstandtherigorsofbatterymanufacture.Theseparator'sabilitytoreducetheriskofinternalshortcircuitisbelievedtobeimportantbecauseinternalshortcircuitmayleadtounexpectedbatteryrupture.TheUbetrilayerseparatorisaporoustrilayerfilmhavingapolypropylene-polyethylene-polypropyleneconstruction.Ube'sprocessincludesthestepsof:extrudingapolypropylenenon-porousprecursor;extrudingapolyethylenenonporousprecursor;formingthepolypropylene-polyethylenepolypropylenenon-poroustrilayerprecursor;bondingthetrilayerprecursortogetheratatemperaturerangingfrom120-1400C.betweenniprollersandthentakinguptheprecursorforsubsequentprocessing;heat-treating(annealing)thebondedprecursoratatemperaturerangefrom110-1400C.;andstretchingthebonded,annealedprecursortoformtheporous,trilayerseparator.Thestretchingstepconsistedofthreediscretesteps:cold-stretching(temperaturerangingfrom-200t0500C.andadrawratioof5-200%);hot-stretching(temperaturerangingfrom70-1300C.andadrawratioof100-400u/o);andheattreating,alsobelievedtobereferredtoasannealingand/orrelax(temperaturerangingfrom75-1750C.andadraftratioof-10to-50%or0%).TheCELGARD~separatorisaporoustrilayerfilmhavingapolypropylene-polyethylene-polypropyleneconstruction.TheCELGARDseparatorprocessincludesthestepsof:formingaporouspolypropyleneprecursor;formingaporouspolyethyleneprecursor;formingaporoustrilayerprecursor;andbondingtheporoustrilayerprecursortoformthetrilayerbatteryseparator.TheNittoDenkoseparatorisaporoustrilayerfilmhavingpolypropylene-polyethylene-polypropyleneconstruction.TheNittoDenkoseparatorprocessincludesthestepsof:co-extrudingatrilayerprecursorhavingapolypropylene-polyethylene-polypropylenenon-porousconstruction;annealing(heat-treating)thetrilayerprecursor;andstretchingtheannealedtrilayerprecursortoformtheporoustrilayerbatteryseparator.TheKurehaseparatorisaporoustrilayerfilmhavingapolypropylene-polyethylene-polypropyleneconstruction.TheKurehaseparatorprocessincludesthestepsof:co-extrudingatrilayerprecursor,theprecursorcontainingaporeformingaid(e.g.,afineinorganicparticleorasolventextractablemateriaD;andformingtheporesintheprecursorbystretchingtheparticle-loadedprecursororbysolventextractionoftheextractable-ladenprecursor.Thereisaneedtocontinuetoimprovetheprocessformakingtrilayershutdownseparatorssothat:manufacturingthroughputcanbeincreasedwhileminimizingthecapitalinvestment;andmanufacturingcostcanbeminimizedbyminimizingmaterialhandlingcostsandincreasingproduc-tionquality.SUMMARYOFTHEINVENTIONAmethodofmakingaporous,trilayer,shutdownbatteryseparatorhasthefollowingsteps:extrudinganon-porouspolyethyleneprecursor;extrudinganon-porouspolypropyleneprecursor;forminganon-poroustrilayerprecursor,thetrilayerprecursorhavingthepolyethyleneprecursorsandwichedbetweentwopolypropyleneprecursors;simultaneouslybondingandannealingthetrilayerprecursortoformabondedandannealedtrilayerprecursor;stretchingthebondedandannealedtrilayerprecursor;andformingtherebytheporousbatteryseparator.Amethodofmakingatrilayer,shutdownbatteryseparatorhasthefollowingsteps:extrudinganon-porouspolyethyleneprecursor;extrudinganon-porouspolypropyleneprecursor;forminganon-poroustrilayerprecursor,thetrilayerprecursorhavingthepolyethyleneprecursorsandwichedbetweentwopolypropyleneprecursors;bondingthetrilayerprecursortoformabondedprecursor;annealingthebondedprecursor;andstretchingthebonded.annealedprecursortoformthebatteryseparator.Theannealingstepfurtherincludesannealingintwozones,eachzoneatadifferenttemperature.DESCRIPTIONOFTHEDRAWINGSForthepurpose.ofexplainingtheinvention,thereisshowninthedrawingsvariouspreferredaspectsoftheinvention;itbeingunderstood,however,thatthisinventionisnotlimitedtotheprecisearrangementsandinstrumentalitiesshown.FIG.1isaschematicillustrationoftrilayerprecursorformationset-up.FIG.2isaschematicillustrationofabonding∕annealingstring-upconfiguration.FIG.3isaschematicillustrationofanotherbonding/annealingstring-upconfiguration.DETAILEDDESCRIPTIONOFTHEINVENTIONAtrilayer,shutdownbat