ABSTRACT
Vinylchloridemonomer(VCM)canbepolymerisedbyanyofthefollowing techniques:suspension,bulk(massorgasphase),emulsionand solution/diluent.ThelargesttonnageofPVCanditscopolymersismadeby thesuspensionpolymerisationroutewhichproducesacoarsepowderof 100-150J.lmmeansize(seeChapter1).AconsiderablequantityofPVCis madebytheemulsionprocess,whoseproductisalatexcontainingparticles below1-2J.lminsizewhichcanbeuseddirectlyor,asismoreusual,spray driedtoproduceafriablepowdersuitableforgeneralpurposeextrusionor formixingwithplasticiserstoformpastesusedinspreadingandcoating applications(seeChapter3).Anumberofattemptshavebeenmadeto producePVCbythewell-knownbulkpolymerisationroute,whichisused extensivelyforothermonomers,e.g.styreneandmethylmethacrylate,but theonlyprocesstoreachcommercialstatusisthatdevelopedbyPechiney StGobain(PSG}-nowRhone-PoulencIndustriesLtd,thisprocessbeing thesubjectofthischapter.AlargetonnageofPVCisnowmadebythis process,themajoritybyanumberofPVCmanufacturerswhoarelicensees ofthePSGprocess:seeTable2.1.Smallquantitiesofvinylacetate copolymersareproducedbysolutioncopolymerisationforcoating applicationsbutthisisaratherspecialisedfieldinvolvingonlyonemajor company,UnionCarbide,andisnotwithinthescopeofthisbook.Afew yearsagomuchinterestwascreatedbythedevelopmentofabulk'gas phase'polymerisationprocessbasedonaftuidisedbedreactorbutthe processhasnotyetreachedcommercialstatus.Thisprocessisconsideredin moredetaillaterinthischapter.
