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1、METHODOFMAKINGATRILAYERBATTERYSEPARATORFIELDOFTHEINVENTIONTheinventionisdirectedtoamethodofmakingatrilayer,shutdownbatteryseparator.BACKGROUNDOFTHEINVENTIONTrilayer,shutdownbatteryseparatorsareknown.See:JapanesePatentApplicationNos.98395/1994and98394/199
2、4bothfiledMay20,1994byUbeIndustries,Ltd.(theUbetrilayerseparator);U.S.patentapplicationSer.No.359,772filedDec.20,1994,nowabandoned,byHoechstCelaneseCorporation(theCELGARD~Separator);Japa-nesePatentApplicationNo.55550/1995filedMar.15,1995byNittoDenkoKogyo
3、K.K.(theNittoDenkotrilayerseparator);andJapanesePatentApplicationNo.56320/1995filedMar.15,1995byKurehaChemicalIndustryCo.,Ltd.(theKurehatrilayerseparator).Trilayer,shutdownbatteryseparatorareporousfilmsandhavebecomeacommercialsuccess,withinthebatteryindu
4、stry,particularlywithinthesecondary(orrechargeable)lithiumbatteryindustry.Thesuccessisbelievedtobedue.inpart,totheseparator'spuncturestrengthandtheseparator'sabilitytoreducetheriskofinternalshortcircuitwithinthebattery.Theseparator'spuncturestrengthis,at
5、least,importantbecauseitenablestheseparatortowithstandtherigorsofbatterymanufacture.Theseparator'sabilitytoreducetheriskofinternalshortcircuitisbelievedtobeimportantbecauseinternalshortcircuitmayleadtounexpectedbatteryrupture.TheUbetrilayerseparatorisapo
6、roustrilayerfilmhavingapolypropylene-polyethylene-polypropyleneconstruction.Ube'sprocessincludesthestepsof:extrudingapolypropylenenon-porousprecursor;extrudingapolyethylenenonporousprecursor;formingthepolypropylene-polyethylenepolypropylenenon-poroustril
7、ayerprecursor;bondingthetrilayerprecursortogetheratatemperaturerangingfrom120-1400C.betweenniprollersandthentakinguptheprecursorforsubsequentprocessing;heat-treating(annealing)thebondedprecursoratatemperaturerangefrom110-1400C.;andstretchingthebonded,ann
8、ealedprecursortoformtheporous,trilayerseparator.Thestretchingstepconsistedofthreediscretesteps:cold-stretching(temperaturerangingfrom-200t0500C.andadrawratioof5-200%);hot-stretching(temperaturerangingfrom70-1300C.andadrawr
