Silicone Rubber中英文.docx
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Silicone Rubber中英文.docx
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SiliconeRubber中英文
SiliconeRubber
1、BasicStructure基本结构
Technicallyknownas'polyorganosiloxanes',siliconesarepolymericcompoundsinwhichsiliconatomsjointogetherwithoxygenaschainsornetworks.Theremainingvalencesofsiliconlinkwithorganicgroups-mainlymethylgroups.
技术上我们称之为聚有机硅氧烷类,硅酮是硅原子与氧连接或网接而成的聚合物。
硅链上剩余的原子价上连接有机基团----主要是甲基。
Thediagramshowsatypicalsiliconemolecule.图片是一个典型的硅酮分子。
Itisessentiallyanorganicallymodifiedquartz,i.e.twooxygenatomsattachedtoeverysiliconatomhavebeenreplacedbymethylgroups.Thischangesthestructurefromthethree-dimensionalbackboneofquartztolinearpolymermolecules.SiliconesthereforearecomposedoftheelementsSi,O,CandH.Siliconemoleculesareusuallytangledupineachother.However,themethylgroupsarefreetorotateaboutthe-Si-O-Si-chain.
它其实就是一个有机的改良的石英,也就是说,每个硅原子上附加两个氧原子而且被甲基重组。
这是石英从线性聚合分子向三维主链的结构转化。
因此硅酮由元素硅,氧,碳,氢组成。
硅酮分子经常是相互之间缠绕。
但是,甲基基团是可以围绕硅氧链进行自由旋转的。
Inthiswaysiliconesunitethedurabilityofquartzandthemanyqualitiesofmodernplastics.
Othergroupscanbeattachedtothesilicon-oxygenbackboneinsteadofmethylgroups.Thelinearsiliconepolymerscanbecrosslinkedtoeachothertodifferentextents,i.e.covalentlyviagroupsofatoms.Thisexplainsthevariousdifferentpropertiesofthecorrespondingsilicones.
其他基团可以附加在硅氧主链上来替代甲基。
这些线性硅聚合物可以不同程度的相互进行交联,也就是说,借助原子基团的共价键。
这说明相应的硅酮会有不同的特性。
2、AShortHistoryofSilicones'Production
Siliconesareindustriallyproducedcompoundsderivedfromtheelementsilicon.Althoughsiliconisthesecondmostcommonelementintheearth'scrust,itshighaffinityforoxygenmeansthatitisonlyfoundincompoundswithoxygen,namelyassilicatesandsilicondioxidethatmakeupmineralsandsand.Elementalsiliconwasdiscoveredatarelativelylatestagebecauseoftheveryhighsilicon-oxygenbondenergies.
Theprincipalstepsinthedevelopmentofsiliconechemistrywere:
▪ThediscoveryofsiliconbyBerzeliusin1824fromthereductionofsilicontetrafluoridewithpotassium.
▪Kipping,generallyconsideredthefatherofsiliconechemistry,laidthefoundationoftheindustrywith,amongotherthings,thepreparationofvarioussilanesbymeansofGrignardreactionsandthehydrolysisofchlorosilanestoyield"largemolecules".
3、Silicon
»Theelementsilicon元素硅
DerivedfromtheLatinsilex,meaning'flint',siliconisthecommonestbuildingblockofourplanetafteroxygen.Itmakesup26%oftheplanet'scrustandhasalsobeenfoundinmeteoritesandlunarrocks.Itisalwaysfoundinchemicallyandthermicallystablemineralcombinationsbutneverinitspureform.Siliconisthekeytoallsiliconechemistryasitsatomicstructuredictatesthepropertiesofsilicones.
26%oftheEarth'scrustismadeofSilicon
»Chemistry
SiliconandoxygenhaveastrongchemicalaffinityandthereforesilicononlyoccursnaturallyintheparticularlystableformofSi-Ocompoundssuchascalcium,magnesiumandironsilicates,aswellasSiO2assandandquartz.Thetetravelantstructureiscommontoallcompoundsinwhichsiliconissurroundedbyoxygenatoms.
Todayelementalsiliconisobtainedthroughtheelectro-thermicreductionofSiO2withcarbonat1,400degreesCelsius.
Elementalsiliconisadarkgrey,metallicshiny,hard,andbrittleoctaedricmaterial.Ithasameltingpointof1,423°Candaboilingpointof2,630°C.Likecarbon,siliconhasacrystallinestructuresimilartothatofdiamonds.
AsarepresentativeofthefourthmaingroupofthePeriodicTablesilicon,likecarbon,displaysbothmetallicandnon-metallicqualities.Thereareneverthelesssomeimportantdifferencesbetweenthetwo.ThechemicalcompoundsofSiandCarepredominantlytetravalent,howeverbotharecapableofforminghigherorlowercoordinationnumbers.ThedifferencebetweenSiandCliesinthesignificantlylowerelectronegativityofSicomparedtoC(1.8asopposedto2.5)andinthelargeratomicdiameter(1.15Åasopposedto0.77Å).Siliconformsverystablesinglebondswiththeelectronegativeoxygenwhilecarbonmayalsoformdoublebonds.Doublebondsinsiliconchemistryaregenerallylimitedtoasmallnumberofunstablesilanecompounds.
Silanes
Silanesarethehomologuesofsaturatedcarbon-hydrogencompounds,thatis,ofalkanes.TheyallsharethegeneralformulaSinH2n+2.Unsubstitutedsilanes,madeofsiliconandhydrogenonly,areveryunstableandcanonlybeproducedintheabsenceofoxygen.Muchmoreimportantarethemethylsilanes,wheresomeorallhydrogenatomsinthesilanesareformallyreplacedbythemethylgroups.Ifthehydrogenatomsarepartiallyreplacedbychlorineatomsandotherhydrogenatomsbymethylgroups,theimportantclassofmethylchlorosilanesresults,oftenabbreviatedaschlorosilanes.Methylchlorosilanesformthebasisforallsiliconechemistry.
»Methylsilanes
Methylsilanesaretherawmaterialsformanufacturingsilicones.TheyareproducedbydirectreactionbetweensiliconandmethylchlorideintheMuellerRochowsynthesis.Theyareextremelymobile,colourless,liquidsthataresolubleinorganicsolventsand,insomecases,inanhydrousalcohol.Silaneshavelowmolecularweightsandarethushighlyvolatile.
IndustrialsiliconeproductionhasitscommercialbasisinthedirectsynthesisofmethylchlorosilanesfromsiliconandmethylchlorideviaaprocesscalledtheMueller-Rochowsynthesis.Thistechnique,developedindependentlyin1940/41byprofessorsRMuellerinGermanyandEGRochowintheUnitedStates,takesplaceinthepresenceofacoppercatalystatapproximately280°C.FinelygroundandwellmixedSiandCuarebroughttogetherinafluidbedreactorwithmethylchlorideingaseousform.Thisproducesasilanemixturefromwhicharederivedthemostimportantorganochlorosilanes.
Decisiveforthecommercialproductionprocessistogaindimethyldichlorosilane(CH3)2SiCl2,themostimportantorganochlorosilane.OptimalproductiondependsontheselectivityandactivityofthecoppercatalystaswellasonthehomogeneityoftheSi/CH3Clmixtureandaneventemperaturedistributioninthereactor(avoiding'hotspots').Contaminationofthecoppercatalyst,forexamplebylead,hasadrasticnegativeeffectwhileantimonyadditives,ontheotherhand,canpromotetheyield.
Modernfluidbedreactorshaveacapacityofapproximately40,000tonnesofrawsilanesperyearandmore.TodayEuropeanmanufacturersnolongerconsiderascommerciallyviableplantsproducinglessthan60,000tonnesperyear.
Duringtheprocess,thesolidelementsofthereactionmixture,suchas,forexample,unconvertedelementalsiliconandthecoppercatalyst,areseparatedfromthegases.Thesolidsarefedbackintothereactionprocessandthegases,aftercondensation,separatedintoliquidcrudemixtureandgaseousmethylchloride.Thelatteristhenalsofedback.
Duetothesometimesverysmalldifferencesbetweentheboilingpointsofsilanes(egmethyltrichlorosilaneat66°C,dimethyldichlorosilaneat70°C)distillationunitshavetofractionatetheminseveralstagestoobtaintheindividualsilanes.Thedistillationcolumnsthereforehavemanyplatesandthushighseparationefficiency.Evensmallamountsofcontaminants(e.g.CH3SiCl3in(CH3)2SiCl2),inthepartspermillion(ppm)range,interferewiththefurtherprocessingoftheorganochlorosilanestosilicones.
Organochlorosilanesareverysensitivetohydrolysis,thatis,theyreactreadilywithwaterandvigorouslygiveoffhydrochloricacid.Forsafetyreasonsincaseofleaks,distillationcolumnsareusuallynotcooledwithwaterbutwithair.
»SpecialSilaneSyntheses
Manufacturersuseothermethodstoproducechlorosilanestolaboratorystandardortomanufacturespecialsilanes,suchasthosecontainingphenylgroups.
ThefollowingsynthesesstillplayanimportantroleinadditiontotheMueller-Rochowdirectsynthesisofsilanes:
Additionreaction(hydrosilylation);Nucleophilicsubstitution;Grignardreaction.Thepurposeofallthesesynthesesistoincorporateorganicfunctionalgroups.
»TypicalReactionsoftheChlorosilanes
Thehallmarkofchlorosilanechemistryistheirpronouncedtendencytopolycondensation.Organochlorosilanesreactviolentlywithwaterreleasinghydrochloricacid.Careisneeded,sincetypicallynearly250lHClarereleasedperkgofdimethyldichlorosilane.Insiliconeproductionthehydrochloricacidformedisreturnedtotheprocessandreactedwithmethanoltoproducethefeedstockmaterialmethylchloride.
»Silanols
Thereactionofthemonomerorganochlorosilaneswithwater(hydrolosis)ormethanol(methanolysis)producessilanols,which,usingHClcatalysis,leaddirectlytofurtherreactedoligomersorpolymersiloxanes('sil'representssilicon'ox'standsforoxygenand'ane'describesthesaturatednatureofthebond).Thedescription'silicone'forthewholeclassofpolysiloxanesisanimitationoftheoxygen-carbonbondsofcarbonchemistrywhichareknownas'ketones'.Thelatterhowever,becauseoftheirparticularcharacteristics,formdoublebondsinsteadofsinglebonds.
Mono-,di-,tri-ortetrafunctionalsiloxaneunitswithSi-Obondsarisefrompolycondensationaccordingtothenumberofchlorineatomsofthebasicsilanemolecule.
Thediversehalogenatedsilanesserveasbuildingblocksforthesynthesisofthevariousproducttypesofsiliconessuchasfluidsorresins.
DimethyldichlorosilaneenablestheformationoflongSi-Ochains.Atfirstthehydrolysisormethanolysisofdimethyldichlorosilanegivesamixtureofshortchained,difunctionalandthereforelinearsiloxaneswithOHandgroupsaswellascyclicsiloxaneshavingnormallybetweenthreeandsixchainunits.Thelinearsiloxanesshowahelixstructurewit
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