Pigment Dispersion 76-13 ethyl phthalocyanine 25 in the absence of any milling of grinding aid. 26 These large planar molecules appear the dispersions when used in printing inks, paints, and coatings, without any additional conditioning of the milled product. Pigment derivatives are by no means limited to phthalocyanines. Quinacridone pigments have been surface treated with sulfonated quinacridone derivatives 27 either as the sulfonic acid form or as the metal sulfonate salt, with a wide range of metals possible. As in the preceding cases, the planar sulfonated quinacridone molecules appear to lie flat on the quinacridone pigment surface and thus improve con- Pigment derivatives of azo red, 28 oranges, and yellows 29 have also been used for surface treating the corresponding pigments. With azo yellows, treatments can be carried out in situ with fatty amines to groups of the pigment and the —NH 2 groups of primary amines, to form —C**=N— Schiff bases. 29−32 Derivatives of monoarylide and diarylide yellow pigments can also be prepared by reacting the pigment with a primary diamine and a glycidyl ether 33 to produce a Schiff base. The structure of one of these FIGURE 76.10 Tr ansmission electron photomicrograph and particle size distribution of a surface-treated diarylide yellow AAOT, Pigment Yellow 14. 24 16 8 0 No. of Particles 0.05 0.10 0.15 0.20 Particle Diameter (µm) Diam aver = 0.073 µm DK4036_book.fm Page 13 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC to lie flat on the copper phthalocyanine surface, as shown in Figure 76.14, and they impart stability to siderably the dispersion properties of the pigment, especially when used in coating applications. Figure produce easily dispersible products through a Schiff base reaction between the —C**=O (carbonyl) 76.15 represents the arrangement of sulfonated quinacridone derivative on the pigment surface. 76-14 Coatings Technology Handbook, Third Edition FIGURE 76.11 Optical photomicrograph of liquid ink prepared with untreated diarylide yellow AAOT. Shows FIGURE 76.12 Optical photomicrograph of liquid prepared with surface-treated diarylide yellow AAOT. Does not DK4036_book.fm Page 14 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC flocculation of pigment particles. Same pigment as that of Figure 76.9. show flocculation of pigment particles. Same pigment as that of Figure 76.10. Pigment Dispersion 76-17 molecules. The remaining parts of the resin molecules (long chains) extend away from the surface, creating a considerable amount of steric hindrance around each pigment particle, thus resulting in steric stabilization of the dispersion. Alumina-coated titanium dioxide, iron oxide red, and other inorganic pigments and fillers can be surface treated with alkanolamines (aminoalkanols), having the general formulas where R 1 , R 2 , and R 3 are alkyl groups containing from 1 to 22 carbon atoms in the chain. 35 The dispers- ibility of these pigments is increased considerably when used in paint formulations containing air drying resin vehicles. The stability of the dispersion is similarly improved because of the steric stabilization imparted to the pigment particles by the R 1 , R 2 , and R 3 long chain alkyl groups. Organic isocyanate adducts 36 are used as effective dispersing agents for several classes of inorganic pigments, including zinc oxide, iron oxides, Prussian Blue, cadmium sulfide, ultramarine, vermilion, and chrome pigments (zinc, barium, and calcium chromates). These agents improve the dispersion charac- teristics and the flocculation resistance of the above-listed pigments when incorporated into conventional alkyd paint vehicles with organic solvents, where these systems also contain a substantial amount of titanium dioxide. 76.9 The Characterization and Assessment of Dispersion The extent to which a pigment is dispersed in the medium or the degree of dispersion is normally assessed in terms of color strength, gloss, brightness, and transparency, and it also has an effect on the rheological properties of the system. 37−39 Since all these properties are governed by the size and distribution of the pigment particles in the dispersion, one can, today, measure these properties using any of the latest particle size analyzers based on the light scattering principle of the dispersed particles. 12 With these instruments, a very dilute suspension is required, and it is necessary to know the refractive index and viscosity of the suspending medium. The average particle diameters and the particle size distributions obtained are those of individual particles, aggregates, agglomerates, and flocculates in the dispersion. The advantages of these instruments are that they are quite easy to operate, they give results rapidly, and they allow the dispersion process to be followed at different times and at different stages. the particle size results for a green-shade phthalocyanine blue, C.I. Pigment Blue 15:3, in an aqueous dispersion. The distribution is quite narrow, and the mean particle diameter is 0.117 µm. These results gation exists in the dispersion. Such particle size analyzers, based on light scattering, can be used very effectively to study particle size changes that occur during the dispersion of pigments in fluid systems. Furthermore, time studies may be carried out on the flocculation of pigments by determining particle size immediately after dispersion and then later, after the dispersions have been allowed to stand for certain periods. This gives a measure 76.10 Conclusion There is no question as to the desirability and effectiveness of a fully dispersed and stabilized pigmented system. Such a dispersion brings out the optimum color properties of the pigment in terms of color strength, gloss, transparency, and rheology. When a pigment is completely dispersed, it contains a larger RCHCHNH RCHCH R etc. OH OH NH 1222 3 2 −− − −−−,, ||| DK4036_book.fm Page 17 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC One such instrument is the Coulter model N4 Submicron Particle Analyzer. Figure 76.17 represents are very similar to those obtained from inspection of the transmission electron micrographs of Figure of the stability of the dispersion. 76.1 for the same phthalocyanine blue pigment in the dry powder form, showing that very little aggre- Pigment Dispersion 76-19 12. T. G. Vernardakis, Am. Ink Maker, 62(2), 24 (1984). 13. P. Sorensen, J. Paint Technol., 47, 31 (1975). 14. J. S. Hamptom and J. F. MacMillan, Am. Ink Maker, 63(1), 16 (1985). 15. B. G. Hays, Am. Ink Maker, 62(6), 28 (1984). 16. A Topham, Prog. Org. Coat., 5, 237 (1977). 17. K. Merkle and H. Schafer, in Pigment Handbook, Vol. III. T.C. Patton, Ed. New York: John Wiley, 1973, pp. 157−167. 18. A. E. Ambler and R. W. Tomlinson, U.S. Patent 3,296,001 (January 3, 1967), ICI. 19. T. C. Rees and R. J. Flores, U.S. Patent 4,032,357 (June 28, 1977), Sherwin-Williams. 20. T. G. Vernardakis, Dyes Pigments, 2, 175 (1981). 21. J. F. Stansfield and A. Topham, U.S. Patent 3,996,059 (December 7, 1976), ICI. 22. P. K. Davies, L. R. Rogers, J. F. Stansfield, and A. Topham, U.S. Patent 4,057,436 (November 8, 1977, ICI. 23. Anon., British Patent 1,544,839 (April 25, 1979), BASF. 24. W. H. McKellin, H. T. Lacey, and V. A. Giambalvo, U.S. Patent 2,855,403 (October 7, 1958), American Cyanamid. 25. V. A. Giambalvo and W. Berry, U.S. Patent 3,589,924 (June 29, 1971), American Cyanamid. 26. S. L. Johnson, G. McLaren, and G. H. Robertson, U.S. Patent 4,448,607 (May 15, 1984), Sun Chemical. 27. E. E. Jaffe and W. J. Marshall, U.S. Patent 3,386,843 (June 4, 1968), DuPont. 28. J. Mitchell and A. Topham, U.S. Patent 3,446,641 (May 27, 1969), ICI. 29. J. Mitchell and A. Topham, British Patent 1,139,294 (January 8, 1969), ICI. 30. Anon., British Patent 1,080,115 (August 23, 1967), KVK. 31. F. Dawson, J. Mitchell, L. R. Rogers, W. Todd, and A. Topham, British Patent 1,096,362 (December 29, 1967), ICI. 32. G. H. Robertson, U.S. Patent 4,220,473 (September 2, 1980), Sun Chemical. 33. R. J. Schwartz and T. Sulzberg, U.S. Patent 4,468,255 (August 28, 1984), Sun Chemical. 34. M. J. B. Franklin, K. Goldsbrough, G. D. Parfitt, and J. Peacock, J. Paint Technol., 42, 740 (1970). 35. H. Linden, H. Rutzen, and B. Wegemund, U.S. Patent 4,167,421 (September 11, 1979), Henkel. 36. F. Hauxwell, J. F. Stansfield, and A. Topham, U.S. Patent 4,042,413 (August 16, 1977), ICI. 37. W. Carr, J. Oil Colour Chem. Assoc., 65, 373 (1982). 38. K. Tsutsui and S. Ikeda, Prog. Org Coat., 10, 235 (1982). 39. R. Polke, Am. Ink Maker, 61(6), 15 (1983). DK4036_book.fm Page 19 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC 77 -1 77 Colored Inorganic Pigments 77.1 The Colour Index System 77- 1 77.2 Pigment Selection 77- 2 77.3 Inorganic Blues 77- 2 77.4 Inorganic Browns 77- 3 Browns 77.5 Inorganic Greens 77- 5 77.6 Inorganic Oranges 77- 6 Orange 77.7 Mercury Cadmium Red 77.8 Inorganic Violets 77- 8 Violets 77.9 Inorganic Yellows 77- 9 This chapter describes the chemistry, manufacture, and properties associated with the major classes of colored inorganic pigments as used in the coatings industry. Thus, pigmentary inorganic whites such as titanium dioxide are not covered. 77.1 The Colour Index System The Colour Index System is a coding system developed under the joint sponsorship of the Society of Dyers and Colourists (SDC) in the United Kingdom and the Association of Textile Chemists and Colorists (AATCC) in the United States. The system is referred to as the “Colour Index.” In referring to pigments using the Colour Index System, we may describe, for example, Molybdate Orange as Pigment Red 104, Colour Index number 77605. The Colour Index names for pigments are abbreviated as follows: Peter A. Lewis Sun Chemical Corporation DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC Iron Blue • Cobalt Blue • Ultramarine Blue • Cobalt Chromate Natural Iron Oxides • Iron Oxide Browns • Mixed Metal Oxide Chrome Green • Chromium Oxide Green • Hydrated Cadmium Orange • Chrome Orange • Cadmium Mercury Chromium Oxide Green • Mixed Metal Oxide Greens Iron Oxide Reds • Molybdate Orange • Cadmium Red • Strontium Yellow • Primrose Chrome Yellow • Cadmium Zinc Ye llows • Mixed Metal Oxide Yellows • Bismuth Vanadate/ Inorganic Reds 77-6 Ultramarine Violet • Manganese Violet • Mixed Metal Oxide Molybdate Yellow Ye llow • Zinc Chromate • Cadmium Sulfide Yellow • Iron Oxide 78 -1 78 Organic Pigments 78.1 78.2 The Colour Index System 78- 1 78.3 Pigment Selection 78- 2 Organic Yellows 78.1 Introduction A definition of a pigment, as distinct from a dyestuff, has been prepared by the Dry Color Manufac- turers’ Association (DCMA) in response to a request from the Toxic Substances Interagency Testing Committee. This definition should clarify the term “pigment” and “dyestuff,” which are often errone- ously used interchangeably: Pigments are colored, black, white, or fluorescent particulate organic and inorganic solids which usually are insoluble in, and essentially physically and chemically unaffected by, the vehicle or substrate in which they are incorporated. They alter appearance by selective absorption and/or by scattering of light. Pigments are usually dispersed in vehicles or substrates for application, as for instance in inks, paints, plastics, or other polymeric materials. Pigments retain a crystal or particulate structure throughout the coloration process. As a result of the physical and chemical characteristics of pigments, pigments and dyes differ in their application; when a dye is applied, it penetrates the substrate in a soluble form after which it may or may not become insoluble. When a pigment is used to color or opacify a substrate, the finely divided, insoluble solid remains throughout the coloration process. 78.2 The Colour Index System The Colour Index System is a coding system as developed under the joint sponsorship of the Society of Dyers and Colourists (SDC) in the United Kingdom and the Association of Textile Chemists and Colorists (AATCC) in the United States. The system is referred to as the “Colour Index.” (This system is registered as a trade name and the use of the “u” in “Colour” must be retained.) By giving a compound a “Colour Index Name” and a “Colour Index Number,” a colored compound can be readily placed into a classifi- cation according to its chemical constitution and color. This description is recognized by many govern- ment bodies as adequate information for inclusion in hazard data sheets or material safety data sheets to fully identify the pigment in question and to provide accurate reference when including a pigment in any inventory listing. Thus, for example, phthalocyanine blue has a Colour Index name Pigment Blue 15 and the Colour Index number 74160. Peter A. Lewis Sun Chemical Corporation DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC Introduction 78-1 Organic Blues • Organic Greens • Organic Oranges • Reds • Organic Pigments 78 -5 Pigment Green 7, the blue-shade green, is based on chlorinated copper phthalocyanine with a chlorine content that varies from between 13 to 15 atoms per molecule. Pigment Green 36, the yellower shade, is based on a structure that involves the progressive replacement of chlorine on the phthalocyanine structure with bromine. The composition of Pigment Green 36 varies with respect to the total halogen content, chlorine plus bromine, and in the ratio of bromine to chlorine. Figure 78.3 illustrates the proposed structures of the phthalocyanine greens. In practice, no single pigment consists of a specific-molecular species; rather, each pigment is a complex mixture of closely related isomeric compounds. These pigments are ideal, since their tinctorial and fastness properties allow their use in the most severe application situations. They possess outstanding fastness to solvents, heat, light, and outdoor exposure. They can be used in masstone shades and tints down to the very palest of depths. Phthalocyanine greens are manufactured by a three-step process: crude phthalocyanine blue is first manufactured, then halogenated to give a crude copper phthalocyanine green, and finally conditioned to give the pigmentary product. 78.3.2.2 Miscellaneous Greens may find some minor application in the coatings industry. FIGURE 78.3 Structure of copper phthalocyanine greens. C CC C C C Cu Br Br Br Br Br Br Cl Cl Cl Cl Cl Cl NN CC NN NN N N C CC C C C Cu Br Br Br Br Br Br Br Cl ClCl Br Br NN CC NN NN N N Pigment Green 36 (Bluest shade also known as 3y) C C C C C C Cu Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl ClCl Cl Cl N N CC NN NN N N Pigment Green 7 Pigment Green 36 (yellowest shade also known as 6y) DK4036_book.fm Page 5 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC Ta ble 78.2 gives a summary of the properties of some other commercially available organic greens that Organic Pigments 78 -7 FIGURE 78.4 Structure of azo-based oranges. NO 2 N N NNN C C CH N HO NO 2 O 2 N NN HO Cl SO 3 − NN HO Orthonitroaniline Orange PO 2 PO 5 PO 13 PO 16 PO 34 PO 38 PO 46 Dinitroaniline Orange N C COCH 3 CH 3 O Cl CH 3 Pyrazolone Orange 2 N NN NN C CH CH 3 H 3 C H 2 N O Cl 2 2 NH C O C O CNH O NNCH Dianisidine Orange Tolyl Orange Cl HO NHCOCH 3 Naphthol Orange H 5 C 2 Clarion Red Ba 2+ 2 DK4036_book.fm Page 7 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC 78 -8 Coatings Technology Handbook, Third Edition latex-based paints and, with the exception of high bake enamels, in both architectural and industrial coatings. Pigment Orange 13 , Pyrazolone Orange, is synthesized by coupling tetrazotized 3,3-dichlorobenzidine onto 3-methyl-1-phenyl-pyrazol-5-one. The pigment is a bright, clean yellow-shade product that is tinctorially stronger than Pigment Orange 5. It may be recommended for interior coatings, particularly as a replacement for lead-based oranges. Pigment Orange 16 , Dianisidine Orange, is a diarylide orange that is prepared by coupling tetrazotized 3,3-dimethoxybenzidine onto acetoacetanilide. The pigment finds use in baking enamels, since its heatfastness is superior to that of other orange pigments with similar economics. Usage in interior coatings at full tone levels is also recommended. Pigment Orange 34 , To lyl Orange, is produced by coupling tetrazotized 3,3-dichlorobenzidine onto 3- methyl-1-(4-methyl-phenyl)-pyrazo-5-one. The pigment is a bright, reddish orange that offers moderate lightfastness and good alkali resistance, but poor solvent fastness. As such, the material is used in interior coatings applications, particularly where a lead-free formula is specified. Pigment Orange 38 , Naphthol Orange, is manufactured by coupling diazotized 3-amino-4-chloroben- zamide onto 4-acetamido-3-hydroxy-2-napthanilide. The pigment is a bright reddish orange that exhibits excellent alkali and acid fastness, moderate solvent fastness, and acceptable light- fastness when used at full tint. As such, the pigment finds use in baking enamels, latex, and masonry paints. Pigment Orange 46 , Clarion Red, is a metallized azo pigment manufactured by coupling diazotized 2- amino-5-chloro-4-ethylbenzene-sulfonic acid onto β -napthol and metallizing the product with barium to yield the pigment. The pigment has poor lightfastness, inferior alkali resistance, and inadequate solvent fastness, hence is not recommended for use in coatings. 78.3.3.2 Benzamidazolone-Derived Oranges The three benzimidazolone-derived oranges contain the azo chromophore and are all based on the 5- acetoacetylaminobenzimidazolone as the coupling component. Pigment Orange 36 is the product of coupling diazotized 4-chloro-2-nitroaniline to the benzimida- zolone. Pigment Orange 60 is the product of the coupling of 4-nitroaniline to the benzimidazolone. Because of the proprietary nature of this product, the structure of Pigment Orange 62 has not been fully declared (Figure 78.5 illustrates two typical structures): Pigment Orange 36 is a bright red-shade orange of very high tint strength. The opacified form of this pigment offers excellent fastness properties to both heat and solvents and a hue similar to the lead containing pigment, Molybdate Orange (PO 104). As such, Pigment Orange 36 finds major use in lead-free automotive and industrial high performance coatings. FIGURE 78.5 Structure of the benzimidazolone oranges. C C C C Cl N N H N H H N N NO 2 H 3 C PO 36 PO 60 O O O C C C C NO 2 N N H N H H N N H 3 C O O O Benzimidazolone Orange DK4036_book.fm Page 8 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC [...]... automotive coatings are required to show satisfactory durability to outdoor exposure in such states as Arizona and Florida for 2 and possibly 5 years before being approved for use in automotive finishes Similar requirements are placed on pigments chosen for use in automotive repair systems and marine coatings © 2006 by Taylor & Francis Group, LLC DK4036_book.fm Page 12 Monday, April 25, 2005 12: 18 PM 78 -12 Coatings. .. Redder shade; transparent; good exterior durability in full shade and tint; all exterior coatings and refinish applications Very green shade; good solvent fastness; excellent lightfastness; all exterior coatings and refinish applications DK4036_book.fm Page 22 Monday, April 25, 2005 12: 18 PM 78-22 Coatings Technology Handbook, Third Edition Cl O P.Y 60 N C N N CH C6H5 N C CH6 CH3 Cl Cl N C C Cl C C Cl O... all-around fastness properties It is recommended for lead-free coatings formulations for the production of high quality finishes and bright red shades CF3 CF3 Cl Cl N N N N OH Cl NH NH O FIGURE 78.15 Structure of Pigment Red 242 © 2006 by Taylor & Francis Group, LLC HO Cl O DK4036_book.fm Page 18 Monday, April 25, 2005 12: 18 PM 78-18 Coatings Technology Handbook, Third Edition NO2 PY 1 Hansa G H3C COCH3 OCH2... J D McGee and B D Bammel, Presented at the Eighth Annual ESD Advance Coatings Technology Conference, Detroit, MI, September 28–29, 1998 27 I Hazan, Presented at the Eighth Annual ESD Advance Coatings Technology Conference, Detroit, MI, September 28–29, 1998 © 2006 by Taylor & Francis Group, LLC DK4036_C080.fm Page 1 Thursday, May 12, 2005 9:53 AM 80 Driers Milton Nowak Troy Chemical References ... The thioindigo reds include Pigment Reds 36, 87, 88, 181, and 198 These pigments are noted for their © 2006 by Taylor & Francis Group, LLC DK4036_book.fm Page 16 Monday, April 25, 2005 12: 18 PM 78-16 Coatings Technology Handbook, Third Edition OH CO NH R NH CO HO A N N N N A A R Cl Cl Red M.Wt 828.5 Cl Cl Cl Red M.Wt 863 Cl Cl CH3 Cl Red M.Wt 803 FIGURE 78.14 Structures of the disazo condensation reds... (PY 34); excellent light and solvent fastness; industrial and automotive coatings Very green shade; good heat and lightfastness; industrial coatings Excellent fastness properties; specialty coatings and baking enamels; poor acid resistance Green shade; excellent overall fastness properties in full shade; industrial and specialty coatings Very green shade; excellent fastness properties; industrial and...DK4036_book.fm Page 10 Monday, April 25, 2005 12: 18 PM 78-10 Coatings Technology Handbook, Third Edition HO N N Lithol Rubine Add Cl PR 57 CH3 SO3− HO Cl N N SO3− Positions HO CH3 PR 52 Cl Bon Red CH3 C2H5 Methylene (—CH2—) Addition SO3− N N PR 200 Cl COO− N N HO... masstone levels; industrial finishes DK4036_book.fm Page 1 Monday, April 25, 2005 12: 18 PM 79 Amino Resins 79.1 Introduction 79-1 History 79.2 Amino Resin Synthesis and Background .79-2 Urea-Formaldehyde Resins • Melamine-Formaldehyde Resins 79.3 Coatings .79-3 Film Formation — Cross-Linking • Catalysts • Automotive Coatings — Clear Coats George D Vaughn* Surface Specialties Melamines 79.4... 25, 2005 12: 18 PM 78-21 Organic Pigments O O NH H3COC C COCH3 NH N N CH C NH P.Y 120 O H3COC O O NH COOH C COCH3 P.Y 151 NH N N CH C NH O O NH CF3 C COCH3 P.Y 154 NH N N CH C NH O O NH Cl C COCH3 P.Y 156 NH N N CH C NH O Cl O NH C COCH3 NH N N CH C NH P.Y 175 O FIGURE 78.20 Benzimidazolone yellow structures TABLE 78.7 Summary of Benzimidazole Yellow Properties Colour Index Name Common Name PY 120 Yellow... FIGURE 78.9 Routes to quinacridone © 2006 by Taylor & Francis Group, LLC trans linear quinacridone DK4036_book.fm Page 13 Monday, April 25, 2005 12: 18 PM 78-13 Organic Pigments TABLE 78.5 Types of Quinacridone Colour Index Name Hue Comments PO 48 PO 49 PR 122 PR 192 PR 202 PR 206 PR 207 PR 209 PV 19 Gold Deep Gold Magenta-yellow Red-yellow Magenta-blue Maroon Scarlet Yellow-shade red Violet-blue Red-yellow . marine coatings. FIGURE 78.7 BON maroon. N HO COO − Ca 2+ N SO 3 − DK4036_book.fm Page 11 Monday, April 25, 2005 12: 18 PM © 2006 by Taylor & Francis Group, LLC 78 -12 Coatings Technology. the pigment particles in the dispersion, one can, today, measure these properties using any of the latest particle size analyzers based on the light scattering principle of the dispersed particles. 12 . Red Ba 2+ 2 DK4036_book.fm Page 7 Monday, April 25, 2005 12: 18 PM © 2006 by Taylor & Francis Group, LLC 78 -8 Coatings Technology Handbook, Third Edition latex-based paints and, with