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/ JL v 4 N PIGMENT HANDBOOK Volume I PROPERTIES AND ECONOMICS Second Edition Edited by PETER A. LEWIS New York A Wiley-lnterscience Publication JOHN WILEY & SONS Chichester Brisbane Toronto Singapore Magnesium Silicate l-B-d-5 ALLAN M. HARVEY Director of Environmental Affairs R. T. Vanderbilt Company, Inc. Norwalk, Connecticut TALC Pigment White 26 Colour Index Number 77718 French Chalk Hydrous Magnesium Silicate Pyrophyllite (Aluminum Analog of Talc) Soapstone Steatite Chemical Formula, Theoretical Mg6(Sig02o)(OH)4 3Mg 4Si02 H20 Chemical Composition, Theoretical (wt %) Mg 19.2 Si 29.6 H 0.5 0 50-7 100.0 MgO SiO HO 31.7 63.5 4.8 100.0 The term talc has two meanings. Mineralogically, it means the pure mineral talc cor responding to the chemical formula for hy drous magnesium silicate. Commercially, it means the talc products of commerce, both those of industrial grades and those of phar maceutical or cosmetic grades. Industrial grades of talc vary widely in talc mineral content from below 50% up to ranges ap proaching pure talc mineral assay. These grades may contain one or more minerals associated with pure mineral talc such as dolomite, calcite, magnesite, mica, chlo rite, quartz, amphiboles, and/or serpentine minerals. Ordinary usage restricts the term soap stone to impure, massive talc rock, while the high-purity, massive talc is called steatite. Pyrophyllite is similar to talc in many of its characteristics and has the for mula AI4[Si8Oi0](OH)4 . 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. The important desirable properties include soft ness and smoothness, color, luster, high slip tendency, moisture content, oil and grease absorption, chemical inertness, fu sion point, heat and electrical conductivity, dielectric strength, and others. The mineral composition of industrial grade talcs varies considerably, depending on the geographical location of the ore body. Montana talc production is mostly pure talc or steatite. Texas talcs are high in carbonate content and are generally dark in color. Vermont talcs contain considerable carbonate. New York talcs contain a high amount 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- 219 220 Allan VI. Harvey scribed as brightness, which is a measure of lite production, which is 7% of the total talc reflectance in terms of percent compared plus pyrophyllite, came mostly from North with the reflectance of pure magnesium ox Carolina. ide as the standard 100%. The chemical Other talc-producing states include Cali composition of talc found in nature is quite fornia, Georgia, and North Carolina. To variable. It is an extremely soft mineral and gether with the four principal states, the is rated No. 1 on the Mohs scale of hard 1984 total of pyrophyllite and talc mined in ness (diamond = 10). It varies in color from the United States was 1,230,000 short tons, snow-white to green to greenish gray and which is about 15% of total world produc various shades of gray. Talc usually forms tion. The talc and pyrophyllite sold in the as a secondary mineral after alteration of United States in 1984 was valued at $20.8 high magnesium and silicon-bearing rocks million. A total of 230,000 short tons of talc such as those that contain serpentines, were exported by the United States in 1984. pyroxenes, or high silica dolomites. Imports of talc into the United States Talc deposits can be classified into four have increased measurably in the past 5 major categories: steatite, soft platy talc, years because of increased crude from Aus tremolitic talc, and mixed talc ores. The tralia and ground material from Canada. crystal habit of the talc mineral in these The total of talc imports into the United ores can be foliated (leafy), granular, lamel States for consumption in 1984 was 50,000 lar (platelike), fibrous, or massive, with short tons. Import sources for the years each form contributing to the particular 1980-1983 were Canada, 34%; Italy, 30%; properties of various industrial grades. Australia, 13%; France, 8%; and others, Typical properties of an average represen 15%. tative talc pigment are listed below. U.S. Consumption of ground talc during 1984 was in the following areas: ceramics, 35%; paints, 18%; roofing, 11%; paper, 9%; TYPICAL PROPERTIES plastics, 6%; cosmetics, 5%; and rubber, 3%. Consumption of pyrophyllite was Talc mainly in refractories, 26%; ceramics, 24%; Appearance White lustrous powder insecticides, 19%; and roofing, 10%. Density (g/cm3) 2.7- 2.85 (lb/gal) 22.5-23.7 Bulking value (gal/ lb) 0.044-0.042 HISTORICAL BACKGROUND Brightness (GE) Index of refraction Melting point (F) ro pH value Oil absorption (lb/ 75-95 1.54-1.59 --2600 -1400 8.8- 9.5 Soapstone for utensils and ornaments was mined by prehistoric Indians on Santa Cat alina Island, California. In the mid-1800s, soapstone from deposits along the western foothills of the Sierra Nevada Mountains 100 lb) 23-52 was used by settlers for building and orna mental stone. Talc mining in the United States dates ECONOMICS OF USE back to 1878 when Colonel Henry Palmer opened the first commercial talc mine on There are approximately 30 producing talc the Nelson Freeman farm near Talcville, a mines located in 11 states in the United small town in St. Lawrence County, New States. In order of volume, the principal York. In 1893, this operation was sold to mining districts, producing 82% of the the International Pulp Company, which be yearly total in 1984. were Texas. Montana, came the International Talc Company in New York, and Vermont. Total pyrophyl- 1940. In 1974, the International Talc Com I-B-d-5 Magnesium Silicate 221 pany ceased operations and sold off some 4.2 for titanium dioxide). This feature of its ore bodies and mills to the Gouver grows in importance as postal rates in neur Talc Company, a subsidiary of the crease. R. T. Vanderbilt Company, Inc. The unique property of preferentially Talc mining in Vermont began in 1902 wetting oily materials in the presence of with the opening of a mine in the town of water makes talc extremely effective in Johnson. Eastern Magnesia Talc Company pitch control. Pitch and other oleoresinous opened its talc mine there in 1924, and in components of paper pulps cause serious the late 1950s, in conjunction with Johnson problems when they deposit on rolls, wire, and Johnson Company, introduced a froth and other parts of the paper machine. Talc flotation process into the operation to pro readily adsorbs the pitch particles render vide the high-purity talc required for cos ing them less sticky and preventing agglom metic use. Texas talc was first mined com eration. mercially in 1952. Development of the Ultrafine particle size talc products can carbonate-derived Montana talc took place be used along with clay, calcium carbonate, in the 1950s. and titanium dioxide pigments to control The commercial uses for talc, soapstone, rheological properties, calendering, gloss, and pyrophyllite are extensive and grow ink holdout, opacity, and brightness. ing. World production in 1958 was about 3 x 106 tons, of which the United States produced about 47%. World production is now over 8 x I06 tons/yr. More recently, Paint the use of talc as a filler for thermoplastic Talc is used in many different types of coat and thermosetting plastics has been added ing. Initially, the primary application for to the traditional applications in the ce talc was in linseed oil house paints to im ramic, paint, paper, and pharmaceutical in part improved durability and resistance to dustries. film cracking. Its use in house paints has continued, but as finer and more diversified grades were developed, the application of MAJOR USES talc has grown in other solvent-thinned as well as water-thinned coatings. Some ex Paper amples are primers, undercoaters, traffic paints, industrial coatings, and interior and As a filler, talc is effective as an inexpen exterior trade sales paints. sive titanium dioxide extender and is out The maximum fineness of talc in a given standing as a pitch control additive. Talc paint is often determined by the use of a also assists in improvement of gloss, opac Hegman gauge, which consists of a preci ity, and brightness. Steatitic talcs are fa sion steel block into which a wedge-shaped vored over the tremolitic talcs as paper channel, 0.5-2 in. wide and up to 0.005 in. fillers because of the latter's abrasive qual deep, has been cut and marked with a linear ity. Research in Finland indicates that the scale. A drop of paint is placed at the deficiencies of talc as a coating pigment can deeper end of the channel and scraped to be overcome and talc may well challenge ward the shallow end. Fineness is indicated kaolin in this market segment. at the point on the scale at which talc parti The particle size of talc fillers ranges cles are seen to protrude above the paint from 5 /m to less than 0.5 pm, with surface surface. Hegman numbers and approximate areas of 4-16 m2/g. When used as an ex particle size, respectively, are 8 = 0 pm. tender or replacement for the white hiding 7 = 1 3 /im, 6 = 25 /xm, 5 = 40 pm. 4 = 50 pigment titanium dioxide, talc has a distinct urn, 3 = 65 pm, and 2 = 76 pm, 1 = 89 pm. weight advantage (talc density 2.8 versus and 0 = 100 pirn. 222 Allan iM. Harvey Although there are specific differences in Ceramics the mineralogy of talc from various geo graphical sources, the reasons for its use may be classified on a general basis. As with other extender pigments, talc has spe cific properties that make its use advanta geous for requirements of particular formu lations. Among its features are availability with high brightness, chemical inertness in coatings, good suspension properties, good suspension of other pigments, good brushability and flow, provision of film roughness from coarse grades, good color stability on exterior exposure (does not stain or "brown-off" ), and ease of dispersion to its ultimate fineness without requiring high shear. The ease of dispersion property en ables simple adjustment of gloss or viscos ity of finished coatings by its use as a post add ingredient. Just as talcs from various geographical sources have many common effects on paint properties, specific differences exist which are attributable to mineralogy and re lated to particle shape. Some talcs are highly platy whereas others contain an as sortment of particle shapes ranging from platy, to prismatic, blocky, and acicular. Platy talcs render a higher degree of water resistance to paint films than do their as Industrial talcs vary widely in their mineral ogy and morphology, as indicated previ ously. Those differences give certain talcs advantages (physical and/or pyrophysical) when considered for specific applications. For example, tremolitic talcs with their blocky morphology are outstanding for use in ceramic wall tile, virtually eliminating laminations, improving product density, and permitting faster pressing. Ceramic bodies that can be fired safely at rapid cy cles are produced with high uniform ther mal expansion and low moisture expansion. In electrical porcelain, hotelware, and sani taryware, these talcs can be used as an aux iliary flux, resulting in a tighter and stronger body, with a decrease of moisture expan sion and increase in thermal expansion. These properties result in improved resis tance to crazing in glazed ceramicware. If controlled for specific resistance or soluble salt content, tremolitic talcs are of value in high-talc, low-temperature casting bodies. Talc can be used as a low-flux replacement for magnesium oxide. Talc also can be used to replace clay in many ceramic bodies, promoting translucency and durability of the finished ware. sorted particle shape counterparts. In addi tion, the high degree of impermeability Plastics leads to better enamel hold-out properties. Platy talcs are less abrasive and impart good sanding properties to metal primers. Talcs containing assorted particle shapes provide more blister-resistant films by al lowing transmission of vapors. Entrapment of volatiles within films is also less likely to occur. Because of their ability to provide higher hardness (on the Mohs scale) and more efficient pigment packing within the film, talcs containing assorted particle shapes aid abrasion resistance of paint films. Several grades of talc are available to Talcs are used in plastics predominantly as reinforcing and extender agents, where the platy structure enhances certain physical properties. In the case of polypropylene, talc provides increased stiffness and creep resistance. Plastics using talc for filling and reinforcement include polyester phenolics. polystyrene, HDPE nylon, epoxies, alkyds. and PVC. Examples of uses for talc-filled plastics are PVC floor tile and polyester body patch. Major markets are the automo tive, appliance, electronics, flooring, home furnishings, and wire and cable industries. meet its many varied applications. The grades range in Hegman fineness from 0 to Cosmetics 6 or 7 and in oil absorption from about 23 to Cosmetic talcs normally have a talc mineral 55. assay of 90% or more. A good cosmetic tale l-B-d-5 Magnesium Silicate 223 should be reasonably light-colored, have good slip, be free of gritty or hard mineral particles, and conform with certain fra grance-retention standards. In addition, for purposes of health and safety, the bacteria content of cosmetic talcs is monitored care fully to ensure as bacteria-free a product as possible. Miscellaneous Uses The uses of talc are many and varied. It finds use as a dusting powder for ceramic sanitaryware and unvulcanized rubber, as a filler in asphalt roofing, pesticides, textiles, upholstery fabric, and rug backings, as well as a number of applications where its lubri cating properties are of value. The new generation of talc mills includes complex froth flotation, sedimentation, hydrocycloning, centrifugal sizing, dry and wet magnetic separation, spray drying, and new grinding techniques. Since white color is a desirable feature in many applications, the grinding equipment should not discolor the talc during the size reduction operation. For very fine particle size, vertical-shift pulverizing mills and jet-milling equipment are used. The latter uses the fluid energy principle with either compressed air or steam providing the energy. Porcelain-lined flint-pebble mills are used for larger particle size talcs. PIGMENT GRADES PIGMENT MANUFACTURE Most of the domestic talc mining produc tion comes from open pits, but significant quantities are produced from underground mines located throughout the United States. Talc milling has traditionally involved dry-processing operations. Since high-pu rity talc products are not demanded by much of the industrial talc market, beneficiation is not usually carried out. However, the talc milling industry is gradually chang ing from uncomplicated grinding plants to sophisticated processing operations that in volve many beneficiation procedures. Because industrial talcs vary widely in their mineral composition, the particular proper ties demanded by each end use can be real ized by a careful evaluation of each manu facturer's grades. In other words, the different combinations of the various min erals that can occur in industrial talcs (see Table I) can result in widely different prop erties, with interchangeability between manufacturers' products not necessarily guaranteed. In addition, the shapes of the different mineral particles in an industrial talc vary with the talc source, resulting in further di versification. These particles can be pre dominantly acicular. platy, or granular with each type conferring a desirable property on the finished talc product. Table 1 Minerals Commonly Associated with Talc Tale Serpentine Anthophyllite" Trcmolite" Dolomite Calcite Magnesite Mica Chlorite Quartz" MgJSisO:oJ(OH )a M g ,lS i;0 ?i(0H)4 (Mg. Fe)7|SiK0 ::|(0H ): Ca:(Mg.FeK|SK O-llOHF CaMgtCO,); CaCO, MgCO, K; AIjISift Al; 0;,,|(0H . F)4 (Mg. Al. Fc)i;|(Si. Al) 0 7ii|(()H) SiO; 224 Allan M. Harvey PIGMENT SPECIFICATIONS AND MANUFACTURERS Three specifications exist for talc when it is to be used in coatings wherein the raw ma terials must conform to certain qualities. These specifications are ASTM D 605-82, Military MIL-P-15I73A, and Maritime 52MA-523B. Table 2 lists manufacturer grades conforming to the different specifi cations. Table 2 Manufacturers' Products (Trade Names) Meeting ASTM D 605-82, Maritime 52-MA-523b, and Military MIL-P-15173A Specifications for Magnesium Silicate (Talc) Pigments Because of the common association of industrial talc with other minerals, as shown in Table I, talc specifications allow a broad range in chemical and physical prop erties. The associated minerals often impart properties that render it more useful than pure talc for many coating applications. Cosmetic talc grades are defined by the Cosmetic, Toiletry and Fragrance Associa tions's CTFA Specification, revised Octo ber 7, 1976. The American Industrial Hygiene Association has issued (1982) a Hygiene Guide Series specification for talc. HEALTH AND ENVIRONMENTAL ASPECTS Cyprus Mistron Frost Mistron Super Frost Mistron Monomix Mistron RCS Mistron Ultramix Mistron 600 Mistron Mist Mistron 400 Beaverwhite 200 Beaverwhile 325 Glacier 200 Glacier 325 Vanderbilt Nytal 200 Nytal 300 Nytal 300H Nytal 400 I.T. X I.T. 3X I.T. 5X I.T. FT I.T. 325 Pfizer Microtalc CP 10-40 Microtalc CP 14-35 Microtalc CP 20-30 Microtalc MP 10-52 Microtalc MP 12-50 Microtalc MP 15-38 Microtalc MP 25-38 Microtalc MP 30-36 Talcron CP 38-33 Talcron CP 14-31 Talcron MP 40-27 Talcron MP 44-26 Talcron MP 45-26 Whittaker, Clark & Daniels Lo Micron 399 Lo Micron 2610 Talc 499 Magnesium Silicate 971 MicroTalc 1196 Micro 2611 Pioneer 2620 Visco XX 2794 Noie: Maritime 52-MA-523b and Military MIL-PI5I73A specifications each include two types of talc classified on the basis of oil absorption. Grades listed in table conform to one of the two types. Consult man ufacturer for further details. 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 Health Administration (MSHA). In OSHA's Z-3 Table of Mineral Dusts, under 29 CFR 1910.1000, the 8 h, time-weighted average limit of exposure for talc is 20 x 106 parti cles per cubic foot. The limit under MSHA is the same. The latest edition (1985-1986) of Threshold Limit Values recommended by the American Conference of Govern mental Industrial Hygienists lists two en tries for talc: talc (containing no asbestos fibers)--2 mg/m3; talc (containing asbestos fibers)--use asbestos TLV. However, very few industrial talcs contain asbestos, and in those cases asbestos occurs only in trace amounts. Magnesium silicate (talc) is listed as GRAS (Generally Regarded as Safe) in indirect food applications according to the limitations listed in Sections 182.90. 175.300, and 177.1210 of Title 21, Code of Federal Regulations. BIBLIOGRAPHY Industrial Minerals and Rocks. 4th ed . AIME. New York. 1975. Mineral Commodity Summaries. Bureau of Mines. U.S. Department of the Interior. 1984 I-B-d-5 Magnesium Silicate 225 Mineral Facts and Problems, Bulletin 631, Bureau of Mines, U.S. Department of the Interior, 1980. Minerals Yearbook, Voi. I, Metals and Minerals, Bu reau of Mines, U.S. Department of the Interior, 1983. Paw Material Index, Pigment Section, National Paint and Coatings Association, Washington, DC, Sept. 1984. Rock Forming Minerals, Vol. I (W. A. Deer, R. A. Howie, and J. Zussman, eds.), Longman Group Ltd., London, 1962.