What is talc? | EUROTALC

Talc is used as an anti-sticking agent, an anti-caking agent, a lubricant, a carrier, a thickener, a strengthening filler, a smooth filler, and an adsorbent. Jumptonavigation Youarehere> Home> Whatistalc? Whatistalc? GeologyandOccurrencePhysico-chemicalPropertiesFunctionsand ApplicationsRegistrynumbers Theterm“talc”hasfourcomplementarymeanings: Talcisamineral:itishydratedmagnesiumsilicate.Talcisarockknownassteatiteorsoapstone,whichiscomposedofvaryingproportionsofthemineraltalc,oftencombinedwithothermineralssuchaschloriteandcarbonate.Talcisanindustrialrawmaterialinpowderform,whichisusedinawiderangeofapplications.Talcisacosmeticpowder.Thisisitsmostwidelyknownapplication—butoneofthesmallestintermsofconsumption. GEOLOGYANDOCCURRENCE https://www.youtube.com/watch?v=Bl2yRXDTjps Talcdepositsalwaysresultfromthetransformationofexistingrocksunderhydrothermalactivity.Throughthisprocess,thecomponents(MgO,SiO2,H2O)requiredforformingtheparentrockintotalcarebroughtbyhydrothermalwater.Thesizeandthegeometryofthefinaldepositdependuponthesizeandnatureoftheparentrock,andtheintensityandscaleofthephenomenon.Thegeologicalcontextrequiredforsuchatransformationtooccurisknownasalowtomediumtemperatureandpressuremetamorphism.Tectonicmovementsalwaysplayamajorrole:earthmovementsallowthehydrothermalfluidtopenetratethemother-rock,generatingpermeabilitythatmakesreactionsinsidetherockmasspossible.Thesurroundingpressure,eitheratthetimeofthetransformationoratalaterstage,determinesthemineral’sdegreeofplatyness,otherwiseknownaslamellarity(lowpressure/lowlamellarity,highpressure/highlamellarity). Thetypeofmineralisationdependsessentiallyonthenatureoftheparentrock.Talcdepositsareclassifiedaccordingtotheparentrockfromwhichtheyderive.Therearefourtypesoftalcdeposits: Derivingfrommagnesiumcarbonates.Morethanhalfofworldproductioncomesfromthiskindofdeposit,foundinancientmetamorphosedcarbonatesequences.Thistalcisgenerallypureandwhite.Derivingfromserpentines.Thistypeofdepositprovidesabout20%oftheworld’stalc.Here,thecrudeoreisalwaysgreybutcanbeup-graded—generallyusingflotationtechniques—toimprovemineralogyandwhiteness.Derivingfromalumino-silicaterocks.About10%ofworldproductioncomesfromthesedeposits.Theyaresometimesfoundincombinationwithmagnesiumcarbonate deposits.Thecrudeoreisgenerallygreyduetothepresenceofchlorite(anotherphyllosilicate),butnoup-gradingisgenerallynecessaryaschlorite,liketalc, isafunctionalmineralconferringbenefitstoanumberofindustrialapplications.Derivingfrommagnesiumsedimentarydeposits.Talcisformedbydirecttransformationofmagnesiumclays.Nodepositsbelongingtothiscategoryarecurrentlybeingmined.Thiswidediversityoforiginandtypesnaturallygivesrisetoawidevarietyoforesandproductgrades,whichdifferaccordingtotheirmineralogicalcomposition,colourandcrystallinestructure(micro-crystallineorlamellar). Back PHYSICO-CHEMICALPROPERTIES Talcisanaturalmineral(Mg3Si4 O10(OH)2 –molecularweight379.26).Asshownintheoppositefigure,itselementarysheetiscomposedofalayerofmagnesium-oxygen/hydroxyloctahedra,sandwichedbetweentwolayersoftetrahedralsilica.Themainsurfaces,knownasbasalsurfaces,oftheelementarysheetcontainneitherhydroxylgroupsnoractiveions,makingtalcbothhydrophobicandinert.  Thesizeofanindividualtalcplateleti.e.afewthousandelementarysheets,canvaryfromapproximately1microntoover100micronsdependingontheconditionsofformationofthedeposit.Itisthisindividualplateletsizethatdeterminesatalc’slamellarity.Ahighlylamellartalcwillhavelargeindividualplateletswhereasamicrocrystallinetalcwillhavesmallplatelets. Theelementarysheetsarestackedontopofoneanother,likeflakypastry,andbecausethebindingforces(knownasVandeWaal’sforces)linkingoneelementarysheettoitsneighboursareveryweak,theplateletsslideapartattheslightesttouch,givingtalcitscharacteristicsoftness.  Talcisodourless.Itisinsolubleinwaterandinweakacidsandalkalis.Althoughtalchasamarkedaffinityforcertainorganicchemicals,itgenerallyhasverylittlechemicalreactivity.Itisneitherexplosivenorflammable.Above900°C,talcprogressivelylosesitshydroxylgroupsandabove1050°C,itre-crystallisesintodifferentformsofenstatite(anhydrousmagnesiumsilicate).Talc’smeltingpointisat1500°C.  Talcsdifferaccordingtotheirmineralogicalcomposition,i.e.thetypeandproportionof associatedmineralspresent.Themostcommonmineralfoundwithtalcischlorite,whichisstructurallyandchemicallyverysimilar.Dolomiteandmagnesitearealsooftenpresent.Aswehaveseenabove,talcsalsodifferintheirdegreeoflamellarity.  Peoplealwaysthinkoftalcaswhitebutitcanalsobegrey,green,blue,pinkandevenblack.  Basically,talcismanytalcs.   Organophilicproperties  Talcshowsanaffinityforcertainorganicchemicals.Itisthereforeorganophilic.Inthecaseoftalc’saffinityforpolypropylene,alikelyexplanationisthatthepositionoftheoxygenatomsonthesurfaceofthetalcplateletcorrespondstothecarbonbondsonthesurfaceofthepolypropylenecrystal.  Talc’sorganophilicpropertiesareusedtogreatbenefitinanumberofapplications,forinstance,ithelpspolypropylenetocrystallise.Inpapermaking,thetalcparticlesattracttheundesirableresindroplets,i.e.organicchemicals,inthepulpontotheirsurface.Thisisknownaspitchcontrol.Inbodypowderapplications,perfume,alsoorganic,isadsorbedontothetalcsurfaceandretained. Back FUNCTIONSANDAPPLICATIONS Thefivemainpropertiesoftalcthatmakeitauniquesubstanceforindustrialanddomesticapplicationsare: Lamellarity(composedofplateletsthatslideoffeachother)Softness(unctuousandnonabrasive)ChemicalinertnessAffinityfororganicchemicalsWhiteness Talcisusedasananti-stickingagent,ananti-cakingagent,alubricant,acarrier,athickener,astrengtheningfiller,asmoothfiller,andanadsorbent. Anti-stickingagent Inmanyindustrialprocesses,talcisusedtopreventtwomaterialsfromstickingtogether.Talcpowderingofmouldsiswidelyusedforexampleintyremanufacturingorfoundryapplications.Certainfoodstuffsorconveyorbeltsarealsopowderedwithtalc,toexcellenteffect.Similarly,chipboardsarepowderedtostopthemfromstickingtogetherinstorage. Anti-cakingagent Talcisextensivelyusedinanimalfeed.Itwrapseachfeedparticle,settingupanaturalbarrierthatstopsmoistureescapingfromorenteringthetreatedfeed.Talcalsoimprovesthefluidityofthematerial,whichhelpstokeepequipmentclean(minimisingbacteriaproliferation),lowersenergyconsumption,reducesproductionstoppages,andmakestheoperator’sjobsafer. Lubricant Talcisusedasalubricantinpharmaceuticalsforexample.Aswellasnotreactingwithactiveingredients,itfacilitatestheingestionofsoliddrugs(pills,powders,etc).Talcalsohelpsmouldanddemouldpills.Itiswidelyusedasalubricantinthetransportofdrymaterials. Carrier Thechemicalinertnessoftalcisofobviousinterestforcarrierapplications.Excipientsin pharmaceuticalsandcosmetics (dryormoist)areaclassicexample.Apartfromitsinertness,talcalsohastheadvantageofnotgeneratingbacterialgrowthandofreleasingfragrancesprogressively.Carriersarealsocriticalinapplicationssuchas fertilisersandplantprotection.Addingtalctoactiveingredientsresultsinawell-managedrelease,allowingthepracticalandsafehandlingofverysmallandverylargequantitiesofactivesubstances. Thickener Talcisabletoinfluencetheviscosityofwater-andsolvent-basedformulations.In paints forexample,itincreasescoveringpower,improvesflowandpreventssettling.Italsoimprovestheadhesionandfinalmechanicalpropertiesofthecoating.Talcenablespaints,withthenecessarylowviscosities,tobeformulatedwithsignificantlylessorganicsolvents.Theuseoftalcintheformulationofarangeofliquidproducts(paint,cosmetics,glues,etc.)alsocontributestocontrollingsedimentationratesduringstorage. Strengthener Talcisusedtoreinforcevarioustypesof resins,principally polypropylene (PP).Althoughthetalcusedinsuchapplicationsisfinelyground,itneverthelessmaintainsitslamellarstructure.ThisgivesthePPthebesttrade-offbetweenrigidityandimpactstrength.Applicationsinclude domesticappliances,foodpackagingfilms and,aboveall, automotivecomponentssuchasbumpersanddashboards.Talcisalsousedasasemi-reinforcingfillerin rubber.Talc’spropertiesbringbenefitsto ceramics (household,construction,refractoryandtechnical).Itreducesfiringtimeandtemperature,improvesvitrificationandconsequentlytheresistanceoftheceramic.Italsoimprovesthermalshockresistance,particularlyimportantin catalyticexhausts. Smoothfiller Talc’ssmoothnessisappreciatedinproductsthatrequiresupplenessandsmoothness.Atypicalexampleis colouringpencils which,forasmoothandregulareffect,mustberobust,butatthesametimesofterthanthepaper.Intermsofvolume,talcisalsotheprincipalingredientin putties,particularlypolyesterputtieswhereitimprovesadhesionandsandability. Adsorbent Talc’sadsorptionproperties,i.e.adsorbingontothesurfaceonly,arekeyinanumberofapplications,particularlypitchcontrolin papermaking wheretalcisusedtoabsorborganicimpurities(pitch,unwantedanions)whicharesticky.Talcalsogreatlyimprovesprintingrunnability.Asafillerinpaper,itincreasessmoothnessandmachinability,reducesfriction,abrasionandporosity.In papercoating,ithelpstoimproveinktransfer,finishfeelandlegibilityofprinting.Talc’sadsorptionpropertiesarealsovaluableinthe treatmentofwastewater bytheactivatedsludgemethod.Providinganadequatesupportsurface,talcplateletsactually“ballast”thebacteriausedinsuchtreatments,therebyimprovingsedimentationandavoidingthereleaseofbacteriainthefinalcleaneffluent. Back REGISTRYNUMBERS Thefollowingtablegivesanon-exhaustivelistofthemainregistriesinwhichtalcandchloritearelisted.Dependingontheregistries,substancesmaybegivenaninventorynumberorsimplybelisted.TalcChloriteCAS14807-96-61318-59-8EINECS238-877-9215-285-9AICS(Austrailia)yesnoCEPA(DSL/NDSL)(Canada)yes(DSL)yes(DSL)ECLSerialNo(Korea)1-6869312-1666ENCS/MITI(Japan)nonoNEPA(China)––PICCS(Phillipines)yesyesTSCA(USA)yesyes Back