New York

PIGMENT HANDBOOK

PROPERTIES AND ECONOMICS

Second Edition

Edited by

PETER A. LEWIS

A Wiley-ln|ersclenee Publication

JOHN WIIAEY & SONS

Chichester " Brisbane " Toronto S̄ingapore

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MagnesiumSNcate I-B-d-5

ALLAN Mo HARVEY

Director of Environmental AffairsR. T. Vanderbiit Company’, Inc.Norwalk, Connecticut

TALC

Pigment While 26Colour Index Number 77718French ChalkHydrous Magnesium SilicatePyrophyllite (Aluminum Analog of Talc)SoapstoneSteatiteChemical Formula. Theoretical

MgdSisOz0)(OH)~3Mg . 4SiO2 -

Chemical Composition, Theoretical (wt %)

Mg 19.2 MgO 31.7Si 29.6 SiO 63.5H 0.5 HO 4.8O 50.7 100.0

I00.0

The term talc has two meanings. Mineral-ogically. ~t means the pure mineral talc cor-responding to the chemical formula for hy-drous magnesium silicate. Commercially, itmeans the talc products of commerce, boththose of industrial grades and those of phar-maceutical or cosmetic grades, Industrialgrades of talc vary widely in talc mineralcontent from below 50% up to ranges ap-proaching pure talc mineral assay. These

grades may contain one or more m~neralsassociated with pure mineral talc such asdolomite, calcite, magnesi~e, mica. chlo-rite. quartz, amphiboles, and!or serpentinem i neral s.

Ordinary usage restricts [he term soap-stone to impure, massive talc rock, whilethe high-purity, massive talc is calledsteatite. Pyrophylfite is similar to talc mmany of its characteristics and has the for-mula Al4[SisO~0](OH)a. French talc is a fine-grained talc used for marking cloth.

Grades of talc are most frequently identi-fied with the end use. such as in ceramics.paint, roofing, insecticides, and paper. Theimportant desirable properties include soft-hess and smoothness, color, luster, highslip tendency, moisture con[ent, oil andgrease absorption, chemical inermess, fu-sion point, heat. and electrical conductivity,dielectric strength, and others.

The mineral composition of industrial-grade talcs vanes considerably, dependingon the geographical location of the orebody. Montana talc production is mostlypure ~alc or steatite. Texas talcs are high incarbonate content and are general}y dark incolor. Vermont talcs contain considerablecarbonate. New York talcs contain a highamount of associated amphibole minerals,California talcs vary considerably in min-eral content depending on the mine loca-tion.

PROPERTIES

Both color and purity are important charac-teristics of talc. They can be partially de-

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220 A~tan ,M. Harvey

scribed as brightness, which Is a measure ofreflectance in terms of percent comparedwith the reflectance of pure magnesium ox-ide as the standard 100%. The chemicalcomposition of talc tbund in nature ts quitevariable. It is an extremely soft mineral andis rated No. I on the Mobs scale of hard-hess (diamond = 10). It varies in color fromsnow-white to green to greenish gray andvarious shades of gray. Talc usually formsas a secondary mineral after alteration ofhigh magnesium and silicon-bearing rockssuch as those that contain serpentines¯pyroxenes, or high silica dolomites.

Talc deposits can be classified into fourmajor categories: steatite, soft platy talc.tremolitic talc, and mixed talc ores. Thecrystal habit of the talc mineral in theseores can be foliated (leafy), granular, lamel-lar (platelike). fibrous, or massive, witheach form contributing to the particularproperties of various industrial grades,Typical properties of an average represen-tauve talc pigment are listed below.

TYPICAL PROPERTIES

AppearanceDensity (g/crn

(Ib/gal)Bulking value (gat/

Brightness (GE~Index of refractionMelting poin~

~ ~C)pH valueOil absorption rib/

100 lb~

Talc

White lustrous powder2.7-2,85

~2 5-2~i "~

0,044-0,04275-95

1.54-1.59--2600~ ~4008,8-9.5

23-52

ECONOMICS OF USE

There are approximately 30 producing talcmines located in I1 states in the UnitedStates. In order of volume the principalmining districts producing 82% of theyearly total in 1984, were Texas. Montana.New York. and Vermont, Total pyrophyl-

life production, which is 7% of the total talcplus pyrophyllite, came mostly from NorthCarolina.

Other talc-producing states include Cali-fornia. Georgia, and North Carolina. To-gether with the four principal states, the1984 total of pyrophyllite and talc mined inthe United States was 1,230,000 short tons.which is about 15% of total world produc-tion. The talc and pyrophyllite sold in theUnited States in 1984 was valued at $20,8million. A total of 230.000 short tons of talcwere exported by the United States in 1984.

Imports of talc into the United Stateshave increased measurably in the past 5years because of increased crude from Aus-tralia and ground material from CanadaThe total of talc imports into the UnitedStates for consumption ~n 1984 was 50.000short tons Import sources for the years1980-t983 were Canada, 34~- Italy, 30%:Australia. 13% France. 8%: and others,

U.S, Consumption of ground talc during1984 was in the following areas: ceramics¯35%; paints. 18%; roofing, 11%: paper,plastics, 6%: cosmetics̄ ~>v: and rubber3%, Consumption of pyrophyllite wasmainly in refractories, 26%. ceramics¯ 24%:insecticides. 19%: and roofing,

HISTORICAL BACKGROUND

Soapstone tbr utensils and ornaments wasmined by prehistoric Indians on Santa Cat-alina Island, California. In the mid-1800s.soapstone from deposits along the westernfoothills of the Sierra Nevada Mountainswas used by settlers for building and orna-mental stone.

Talc mining m the United States datesback to I878 when Colonel Henry Palmeropened the first commercial talc mine onthe Nelson Freeman farm near Talcville. asmall town in St. Lawrence County¯ NewYork, In 1893. this operation was sold tothe International Pulp Company, which be-came the International Talc Company in1940. In 1974. the International Talc Corn-

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party ceased operations and sold off someof its ore bodies and mills to the Gouver-neur Talc Company, a subsidiary of theR. To Vanderbilt Company, Inc.

Talc mining in Vermont began in 1902with the opening of a mine in the town ofJohnson. Eastern Magnesia Talc Companyopened its talc mine there in 1924, and inthe late 1950s, in conjunction with Johnsonand Johnson Company, introduced a frothflotation process into the operation to pro-vide the high-purity talc required for cos-metic use. Texas talc was first mined com-mercially in 1952. Development of thecarbonate-derived Montana talc took placein the 1950s,

The commercial uses for talc. soapstone,and pyrophyllite are extensive and grow-lng. World production in 1958 was about3 ~< 106 tons. of which the United Statesproduced about 47%, World production isnow over 8 × 10~ tonslyr. More recently,the use of talc as a filler for thermoplasticand thermosetting plastics has been addedto the traditional applications in the ce-ramic, paint, paper, and pharmaceutical in-dustries.

MAJOR USES

Paper

As a filler talc is effective as an inexpen-sive titanium dioxide extender and is out-standing as a pitch control additive, Talcalso assists in improvement of gloss, opac-ity, and brightness. Steatitic talcs are fa-vored over the tremolitic talcs as paperfillers because of the latter’s abrasive qual-ity. Research in Finland indicates that thedeficiencies of talc as a coating pigment canbe overcome and talc may wel! challengekaolin in this market segment

The particle size of talc fillers rangesfrom 5 ~m to less than 0.5 urn. with surfaceareas of 4- 16 m2/g. When used as an ex-tender or replacement for the white hidingpigment titanmm dioxide, talc has a distinctweight advantage (lair den.~ity 2.8 versus

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4.2 for manium dioxide), This featuregrows in importance as postal rates in-crease.

The unique property of preferentiallywetting oily materials in the presence ofwater makes talc extremely effective inpitch control, Pitch and other oleoresinouscomponents of paper pulps cause seriousproblems when they deposit on rolls, wire,and other parts of the paper machine, Talcreadily adsorbs the pitch particles render-ing them less sticky and preventing agglom-eration.

Ultrafine particle size talc products canbe used along with clay, calcium carbonate.and titanium dioxide pigments to controltheological properties, calendering, gloss,ink holdout, opacity, and brightness,

Paint

’Talc is used in many different types of coat-ing. Initially, the primary application fortalc was in linseed oil house paints to im-part improved durability and resistance tofilm cracking, Its use in house paints hascontinued, but as finer and more diversifiedgrades were developed, the application oftalc has grown in other solvent-thinned aswell as water-thinned coatings. Some ex-amples are primers, undercoaters, trafficpaints, industrial coatings, and interior andexterior trade sales paims,

The maximum fineness of talc in a givenpaint is often determined by the use of aHegman gauge, which consists of a preci-sion steel block into which a wedge-shapedchannel, 0.5-2 in. wide and up to 0.005 m.deep, has been cut and marked with a linearscale. A drop of paint is placed a~ thedeeper end of the channel and scraped to-ward the shallow end. Fineness is indicatedat the point on the scale a~ which talc parti-cles are seen to protrude above the paintsurface. Hegman numbers and approximateparticle size, respectively, are 8 = 0 tam.7 = 13~m, 6= 25p, m, 5 =40~m. 4 = 50tam. 3 = 65/xm, and 2 = 76 ~m. I = 89.~m.and 0 = 100 ,~m.

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Although there are specific differences inthe mineralogy of talc from various geo-graphical sources, the reasons tot" ~ts usemay be classified oa a general basis. Asw~th o~her extender pigments, talc has spe-cific properties ~ha~ make ~s use advanta-geous t~r requirements of particular flsrmu~lations. Among its /~atures are availaNlitywith h~gh brightness, chemical inertness incoatings, good suspension properties, goodsuspension of other p~grnents, good brush-ability and flow, provision of him roughnessfrom coarse grades, good color stabilityon exterior exposure (does uo~ slain

brown-off ~, and ease of dispersion to itsultimate ~neness wi~hou~ requiring highshear, The ease of dispersion propertyames s~mple adjustment of gloss or viscos-ity of fitfished coatings by its use as aadd ingredient.

Just as talcs from various geographicalsources have many common effects onpaint properties, specific differences existwhich are a~tributable ~o minera/ogy andlated ~o particle shape Some talcs arehighly platy whereas others contain at~sorm-mt~l of particle shapes ranging fromptaly, to prismatic, blocky, and acicuiarPlaty talcs render a higher degree of waterresistance ~o paint films than do their as-sorted particle shape counterparts. In addi-tion. the high degree of impermeabilityleads to oetler enamel hold-ore properties.Platy lairs are less abrasive and impar~good sanding propemes to metal primers.Talcs containing assorted particle shapesprovide more blister-resistant films by at-.lowing ~ransmissma of vapors, Entrapmentof volatiles withi~ films is also ~ess ~ikely tooccur. Because of lhe~r abilhv to providehigher hardness ~oa the Mobs scale) andmore efficient pigment packing within thefilm. talcs containing assorted particleshapes aid abrasion resistance of paint

mee~ ~t~ many varied ~ippl~catitm~.~rades range m Hcgrmm finene ~ trom 0 to~ or 7 and in oil ab~orptam from ;t~ou[ 23 to55,

Indus,’.rial talcs vary widely in their minerabogy and morphology, as indicated previ-ously. Those difference.., give cerw.in talcsadvantages (physical and,’~_r pvro~hvsical~when considered for specific applications,For example, tremolitic talcs with theirblocky morphology are outstanding for usein ceramm wall tile, virtually eiiminalinglaminations, tmproving product den_,,ity,and permitting faster pressing. Ceramicbodies that can De fired safely at ra~id cy-cles are produced with high unitbrmreal expansion and low moisture expanstom[n electrical porcelain, hotelware, and san>taryware, these talcs can be used as aa au.x~iliary flux, resulting in a tighter and strongerbcxly, with a decrease of moisture expan-sion and increase in thermat expansion,These properties result in improved resis--mnce to crazing in glazed ceramicware. Ifcontrolled t\>r specific resistance or solublesalt content. ~remolitic talcs are of value inhigh-talc, low-temperature cas~ing bodies.Talc can be used as a low-flux repmcementfor magnesium oxide. Talc also can be .:sod~o replace clay in many ceramic bodies.promoting translucency and dtmtbititv of"the finished ware.

Talcs are used in plastics prectominantly asreinforcing and extender agents, where thep[aly s~ruclure enhances certain physicatproperties. In tge case of potypropy}enetalc provides increased sti{)hess ;tsd creepresistance. Phtsucs using talc for fiihn~ andreinforcement inc[ude polyesterpolystyrene, HDPE nylon, epoxie>, alkyds,and PVC. Examples of uses for talc-filledplasdcs are PVC ~oor tile and polyesterbody patch, Major markets are the automo-tive, applia~cc, elec~ro,fic~, {!ooru~g, homet~rni~hings, and wire and cab~c

(.?o.,:metic talcs normally ha,,.c aassay of 905’3 ,,)r more, A good cosmetic

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bS-do5 Magnesium Silicate 223

should be reasonably light-colored, haveThe new generation of talc mills includesgood slip. be free of gritty or hard mineralparticles, and conform with certain fra-grance-retention standards. In addition~ forpurposes of health and safely, the bacteriacontent of cosmetic talcs is monitored care-fully to ensure as bacteria-free a product aspossible,

Miscellaneous Uses

The uses of talc are many and varied. Itfinds use as a dusting powder for ceramicsanitaryware and unvulcanized rubber, as afiller in asphalt roofing, pesticides, textiles.upholstery fabric, and rug backings, as wellas a number of applications where its lubri-cating properties are of value.

complex froth flotation, sedimentation, hy-drocycloning, centrifugal sizing, dry andwet magnetic separation, spray drying, andnew grinding techniques, Since white coloris a desirable feature in many applications,lhe grinding equipment should not discolorthe talc during the size reduction operation.For very fine particle size, vertica!-shiftpulverizing mills and jet-milling equipmentare used. The latter uses ~he fluid energyprinciple with either compressed a~r orsteam providing the energy PorceIain-linedflint-pebble mills are used for larger particlesize talcs,

PIGMENT GRADES

PIG MENT MAN UFACTURE

Most of ~he domestic talc mining produc-tion comes from open p~ts, but significantquantities are prodt,ced from undergroundmines located throughout the UnitedStates.

Talc milling has traditionally involveddry-processing operations. Since high-pu-rity talc products are not demanded bymuch of the industrial talc market, benefi-clarion is not usually carried out. However.the talc milling industry is gradually chang-ing from uncomplicated grinding plants tosophisticated processing operations that in-volve many beneficiation procedures.

Because industrial talcs vary widely in theirmineral composition, the particular proper-ties demanded by each end use can be real-ized by a carefu~ evaluation of each manu-facturer’s grades. In o~her words, thedifferent combinations of the various min-erals that can occur in industrial talcs (seeTable I) can result in widely different prop-ertms, with interchangeability betweenmanufacturers products not necessarilyguaranteed.

In addition, the shapes of the differentmineral particles in an industrial talc varywith the talc source, resulting in further di-versification° These particles can be pre-dominantly acicular. )laty, or granular witheach type conferring a desirable propertyon the finished talc product.

Table 1 Minerals Commonly Asso¢ialed wilh Talc

Serpenm~e Mg~ISi20,I(OHAnthophyllile" I M._e, Fe)vl Si~ ()zzJ~()HTrcmo~ite" Ca:( Mg. Fe),] Si~Dolomae (TaMg{CO~:Calc~e CaCO,Magnesile MgCO~M~ca K2 AlalSi~ Ale {):.Chlorite {Mg. AI. Fc~ :[~Si.Quartz" SiO-.

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224 Allan M. Harvey

PIGMENT SPECIFICATIONS ANDMANUFACTURERS

Three specifications e×~st for talc when it isto be used in coatings wherein the raw ma-terials must conform to certain qualities.These specifications are ASTM D 605-82,Military MIL-P-15173A. and Maritime 52-MA-523B, Table 2 lists manufacturergrades conforming to the different specifi-cations,

Table 2 Manufacturers’ Products (TradeNames) Meeting ASTM D 605-82, Maritime52.MA.523b, and Military MIL-P-15173ASpecifications for Magnesium Silicate(Talc) Pigments

Cyprus Vanderbilt

Mistron Frost Nytal 200Mistron Super

Frost Nytal 300Mistron Monomix Nytal 300HMistron RCS Nytal 400Mis[ron Ultramix I.T. XMistron 600 I.T. 3XMistron Mist I,T. 5XMistron 400 I.T. FTBeaverwhite 200 I.T. 325Beaverwhite 325Glacier" 200Glacier 325

Pfizer Whittaker.Clark & DanielsMicrotalc CP 10-40

Microtalc CP 14-35 Lo Micron 399Micro~alc CP 20-30 Lo Micron 26~0Microt~c MP 10-52 Talc 499Microtalc MP 12-50 Magnesium Silicate 971Microtalc MP 15-38 MicroTalc 1196Micro[alc MP 25-38 Micro 2611Microtalc MP 30-36 Pioneer 2620Yalcron CP 38-33 Visco XX 2794Talcron CP 14-31Talcron MP 40-27Yalcron MP 44-26Talcron MP 45-26

Note: Maritime 52-MA-523b and Military MIL-po15173A specifications each include two types of talcclassified on the basis of oil absorption. Grade~ listedin ~abJe conform to one of the lwo types. Consult man-ufacturer ~or further derail.,,.

Because of the common associatton ofindustrial talc with other minerals, asshown in Table I, talc specificauons allow abroad range in chemical and physical prop-erties, The associated minerals often impartproperties that render it more useful thanpure talc for many coating applications.

Cosmetic talc grades are defined by theCosmetic, Toiletry and Fragrance Associa-tions’s CTFA Specification. revised Octo-ber 7. 1976, The American IndustrialHygiene Association has issued (19821a Hygiene Guide Series specification tbrtalc.

HEALTH AND EN%’IRONMENTALASPECTS

The only federal government agencies regu-lating exposure to talc dust are the Occupa-tional Safety and Health Administration(OSHA) and the Mine Safety and HealthAdministration (MSHA). In OSHA’s Z-3Table of Minera! Dusts. under 29 CFRI9~0.1000, the 8 h, time-weighted averagelimit of exposure for talc is 20 x 106 parti-cles per cubic foot, The limit under MSHAis the same, The latest edition/1985-1986)of Threshold Limit Values reconamendedby the American Conference of Govern-mental Industria~ Hygienists lists two en-tries for talc: talc {containing no asbestosfibers)~2 mgim3: talc (containing asbestosfibers)--use asbestos TLV, However, veryfew industrial talcs contain asbestos, and inthose cases asbestos occurs only in traceamounts. Magnesium silicate (talc) is listedas GRAS (Generally Regarded as Safe)inindirect food applications according to thelimitations listed in Sections 182.90,175,300. and 177,1210 of Title 21. Code ofFederal Regulations,

BIBLIOGRAPHY

Industrial Minerals tznd R~.,(’k~. 4th ed.. AIMK. NewYo~R, 1975~

Mineral Commodity Summarie,~, Bureau of Mi~e~.U.S, Departmen! of ~he Interior, 1984.

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[,B-d~5 M~gnesittm Silicate

Mineral Facts and Problems, Bulletin 63 l, Bureau ofMines, U,S. Department of the interior, !980.

Minerals Yearbook, Vol. I, Metals and Minerals, Bu-reau of Mines, U~S. Department of the Interior.!983.

Raw Materiallndex; Pigment Section, National Painl

225

and Coatings Association, Washington, DC, Sept,1984.

Rock Forming Minerals, VoL J[ (W A. Deer, R. A.Howie, and J. Zussman, eds~), Longman GroupLtd~ London, 1962.

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