Silicone Rubber中英文.docx

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