Chemical Characterization of Pigments
In this chapter, the correlation between chemical constitution and pigment performance is outlined in terms of empirical rules. These correlations essentially apply independently from the application medium for all industrial uses of pigments. While the properties of soluble dyes are determined almost exclusively by their chemical constitution, application characteristics of pigments which are by definition insoluble in the medium in which they are applied see Sec. 1.1 are largely controlled by...
Group I Naphthol AS Pigments Sec Pigment Red
P.R.2 provides a medium red shade, which is somewhat yellower than the Naphthol AS pigment P.R.112. Its main area of application is the printing inks field. In some systems, P.R.2 is even slightly stronger than P.R.112, although it does not quite achieve the same lightfastness. 1 1 SD letterpress proof prints equal step 5 on the Blue Scale, 1 25 SD prints reach step 4. The corresponding values for P.R.112 are 1 2 to 1 step higher. Most of the commercially available products have specific...
Filtration Drying Milling
Following manufacture and possibly further processing, the pigment is separated from the suspension and dried. Both processes can be carried out either continuously or by batch operation, depending on the tonnage of the product. Plate-and-frame filter presses are particularly suited to batch operations. Modern frames are made of polymers mainly polypropylene , which have replaced wood as a building material. Large amounts of products, on the other hand, are filtered routinely via...
General Ang
The a- and -types of Copper Phthalocyanine Blue reign supreme among commercially available phthalocyanine pigments. There is also an increasing amount of interest in the phase-stabilized form of the a-crystal modification. Both modifications are also supplied as flocculation resistant types. In view of the fact that phthalocyanine blue pigments are utilized in a host of applications, the requirements for their use vary considerably. A large number of special-purpose types are therefore supplied...
Azo Pigment Synthesis by Continuous Operation
A number of publications describe continuous techniques used to manufacture azo colorants, especially azo pigments selection see 6 . The widespread interest in continuous methods is readily explained by the expected advantages - product standardization through uniform reaction conditions, - increased productivity compared to batch processes, - improved methods of process and quality control. In contrast to azo dyes, whose coloristic properties are almost exlusively defined by their chemical...
Gloss
The gloss of a pigmented system is a function not only of the degree of pigment dispersion but also frequently of the particle size distribution Sec. 1.6.5 . This is a common phenomenon in very thin applications, such as in offset printing, which produces layers less than 1 m thick. Fig. 78 Electron micrographs of Pigment Red 3 samples of different particle sizes. Fig. 78 Electron micrographs of Pigment Red 3 samples of different particle sizes. The effect of the particle size on the gloss of a...
Chemistry Manufacture Keg
The synthetic route to perinone pigments, as to perylene pigments, starts from an anhydride, in this case from the monoanhydride of naphthalene tetracarboxylic acid. The perinone ring system is thus formed by condensation with aromatic o-di-amines. Reaction of o-phenylenediamine with the monoanhydride is typically achieved in glacial acetic acid at 120 C. A mixture of the cis and trans isomers evolves, which appear as mixed crystals The isomers are separated by taking advantage of the...
Diazotization Mechanism
Contrary to earlier assumptions, the aryl ammonium ion is not able to undergo diazotization since the crucial step in the diazotization mechanism is the electrophilic nitrosation of the free amino group in the free-base primary aromatic amine 12 Formation of the diazonium ion 14 proceeds via the diazo hydroxide 13 The diazotization reaction requires an excess of acid formation of the active ni-trosating agent XNO proceeds via the underlying equilibrium The reaction mechanism is reviewed in more...
H Jrs
P.Y.182, which has been available for some years, provides somewhat reddish shades of yellow and is tinctorially strong. It is sensitive to a variety of organic solvents, especially to ketones such as methylethylketone and cyclohexanone, as well as to aromatic solvents such as toluene or xylene. In this respect, the pigment equals step 2 on the 5-step scale Sec. 1.6.2.1 . P.Y.182 is targeted for the paint and the plastics industry. The paint industry utilizes P.Y.182 especially in various types...
Dioxazine Pigments
The dioxazine molecule is derived from triphenodioxazine, a linear system of five anellated rings. Apart from Pigment Violet 37, the commercially most representative one is Pigment Violet 23, an extremely lightfast and weatherfast compound with good to excellent solvent and migration resistance. Applications include the pigmentation of coatings, plastics, printing inks, and for spin dyeing. Apart from producing violet shades, the pigment also lends itself to the shading of phthalo-cyanine blue...
H Boz
Colour Index Constitution Numbers 21107 P.Y.124 and 21107 1 P.Y.87 are misleading, since both pigments exhibit different chemical structures. sitive to light. In this respect, P.Y.12 types are satisfactory only in areas where fastness to light is of less concern. High gloss has its advantage for types that are to be used in the uppermost and very thin layer of a three or four color print. Common printing techniques Sec. 1.8.1.1 for letterpress and offset application produce roughly 1 m ink...
Aluminum Pigment Lakes
This class includes the aluminum salts of some carboxylic acids or sulfonic acids of polycyclic dyes. P.R.172 is the aluminum salt of tetraiodofluorescein 142 Fluorescein 147 is prepared by the same route as Pigment Red 90 see p. 575 . The compound is iodized with iodine and potassium iodate in an acidic medium. The iodic acid reoxidizes the resulting hydrogen iodide back to iodine 5 147 8 I2 4 HIO3 5 142 12 H2O Aluminum chloride is used to convert tetraiodofluorescein, also known as...
BONA Pigment Lakes
These pigments derive their name from 2-hydroxy-3-naphthoic acid, which is used as a general coupling component for the entire group. The compound is also known as beta-oxynaphthoic acid BONA . The history of BONA pigment lakes parallels that of f-naphthol pigment lakes. Literary evidence of the use of 2-hydroxy-3-naphthoic acid, which was first synthesized in 1887 by Schmitt and Burkard as a coupling component, dates from 1893 Kostanecki . However, it was not until 1902 that the compound began...
Group II Naphthol AS Pigments Sec Pigment Red
P.R.5 affords a bluish red shade, somewhat similar to that of P.R.8, although the former is much more lightfast. Its commercial significance and its primary use depend on the region In Europe it is primarily employed in printing inks, while the American and Japanese markets mainly utilize the pigment in the paint field. Compared to other members of its class, P.R.5 exhibits good fastness to solvents. In the printing inks field, P.R.5 is in direct competition with the much more bluish P.R.146,...
Test Methods
Manufacturers of organic pigments frequently use additives in an attempt to improve parameters such as the wetting time and wetting volume and thus to enhance the dispersibility of their products. The decision about each individual approach is usually made on the basis of empirical data concerning the application properties of the products. This is understandable in view of the fact that the dispersibil-ity of a pigment is known to depend on its medium and on the conditions under which it is...
H H Vei
maroon bluish red carmine carmine red P.Y.120 lends itself to all printing methods. Its lightfastness in letterpress and offset prints is also very good. Depending on the depth of shade, prints equal step 7 to step 6 on the Blue Scale. P.Y.120 thus scores approximately 1 step higher than the similarly colored P.Y.97. P.Y.120 is used primarily to color high grade gravure inks for posters, metal sheets, and packaging purposes. The pigment has gained particular recognition in gravure inks for...
The Red and Brown Series Pigment Red
P.R.171 affords a dull, very bluish red, referred to as maroon. The pigment generally provides good fastness properties. The commercially available types are highly transparent. P.R.171 is used in plastics and in paints. Its lightfastness in PVC equals step 7 to step 8 on the Blue Scale, depending on the exact composition of the tested system, the pigment concentration, and the TiO2 content. Incorporated in plasticized PVC, P.O.171 is migration resistant and heat stable up to 180 C. It is used...
Flush Pastes
Flushing is sometimes considered an alternative to the dispersion process, because it is the direct transfer of pigments in an aqueous phase, as they emerge from the synthesis, to a nonaqueous phase without previously drying and milling the colorant. The nonaqueous phase commonly consists of binders, such as alkyd resins, mineral oils, celluloseacetobutyrate, or other suitable water-insoluble vehicles. The idea is to displace the adsorbed water from the surface of the pigment particles and to...
References for Section Wlg
1 DRP 257 488 Meister Lucius amp Br ning 1909. 2 K. Hunger, E.F. Paulus and D. Weber, Farbe Lack 88 1982 453-458. 3 E.F. Paulus, W. Rieper and D. Wagner, Z. Kristallogr. 165 1983 137-149. 4 A. Whitaker, Z. Kristallogr. 166 1984 177-188. 5 DE-OS 2 616 981 BASF 1976. 7 DE-OS 3833226 Hoechst 1988. 8 NPIRI Raw Materials Data Handbook, Vol. 4, Pigments, 1983, 4-234 B.L. Kaul, JOCCA 1987, 349-354. 9 A. Whitaker, J. Soc. Dyers Col. 99 1983 121-123 ibid., Z. Kristallogr. 166 1984 177. 10 A. Whitaker,...
Diazotization
Diazotization is the reaction of a primary aromatic amine with a nitrosating agent, such as sodium nitrite or, to a lesser extent, with nitrosylsulfuric acid NOSO4H, nitrous gases, or organic nitrites in an aqueous acidic solution at a temperature between 0 and 5 C, converting the amine to its diazonium salt AfNHj 2 Hr hfaNO - gt ArN N Y9 2 H-,0 Wot The diazotization reaction was discovered in 1858 by Peter Griess. Following a suggestion by Kolbe, he treated picramic acid...
Hydroxyanthraquinone Pigments
The class of hydroxyanthraquinone pigments comprises two different groups of compounds metal complexes of hydroxyanthraquinones on the one hand and metal salts of hydroxyanthraquinone sulfonic acids on the other hand. Some of the products are metal chelates. The first group includes 1,2-dihydroxyanthraquinone, commonly known as alizarin, 1,4-dihydroxyanthraquinone quinizarin , and 1,2,4-trihydroxyan-thraquinone purpurin . Alizarin in particular has been known and appreciated for thousands of...
Flavanthrone
Flavanthrone has also been used for a long time as a vat dye. It gained recognition as a pigment when more and more lightfast and durable paints were required. The yellow pigment is registered in the Colour Index as Pigment Yellow 24, 70600. It has the structure 94 The synthetic route involves treating 1-chloro-2-aminoanthraquinone with phthalic anhydride PA , which initially affords 1-chloro-2-phthalimidoanthra-quinone 95. Subsequent Ullmann reaction with copper powder in refluxing...
Tinctorial Strength 1
Like other optical characteristics, the tinctorial strength of a pigment, i.e., its ability to add color to a substrate, is controlled by the conditions under which it is applied. Tinctorial strength may be defined either as an absolute value or relative to another pigment. Attempts to assess absolute values by visual methods at best afford semiquantitative results while the relative strength of one pigment compared to another is more easily assessed by a human observer. It is determined...
Commercially Available Bisacetoacetarylide Pigments and Their Properties
P.Y.16 covers the medium yellow range. Increasingly stringent industrial requirements in some areas slowly restrict the use of this originally versatile product. P.Y.16 shows good to very good resistance to a variety of organic solvents, including alcohols and esters however, it exhibits no fastness to some other solvents, such as xylene and other aromatic hydrocarbons. Recrystallization may be a problem if the pigment is to be processed in systems containing aromatic solvents, such as some...
Migration
The term migration refers to the occurrence of bleeding and blooming. Dissolved portions of pigment may migrate from their medium of application to the surface or into a similar material that their system is in contact with. A number of seemingly related phenomena that may arise during the processing or application of a pigmented system which shows similar results, such as plate-out or chalking, are caused by different effects and are mentioned elsewhere Sec. 1.6.4.1, 1.6.4.2 . The theoretical...
References for Section Ejt
1 H. Zollinger, Chemie der Azofarbstoffe, Birkh user, Basel, 1958. 2 H. Zollinger, Color Chemistry, 2nd ed., VCH Verlagsgesellschaft, Weinheim. 1991 H. Zollinger, Diazo Chemistry I, VCH Verlagsgesellschaft, Weinheim, 1998. 3 A.C. Rochat and E. Stocker, XII. Congr. FATIPEC, Garmisch, 1974, Congress book, p. 371. 4 e.g. DE-OS 1 644 119 Ciba-Geigy 1966 DE-OS 1 644 127 Ciba-Geigy 1966. 5 A. Topham, J. Appl. Chem. 1968, Vol. 18, 233-235. 6 H. Nakaten, Chimia 15 1961 156-163 D. Patterson, Ber....
Chemistry Synthesis Starting Materials Azomethine TypeTetrachloroisoindolinone
Commercially used tetrachloroisoindolinone pigments have the general chemical structure 39 1 The synthetic route generally involves condensing two equivalents of 4,5,6,7-tetrachloroisoindoline-1-one derivatives with one equivalent of an aromatic diamine in an organic solvent. Suitable tetrachloroisoindoline-1-one derivatives are substituted in 3-position, which is occupied either by two monovalent groups A or one divalent group B . A may represent a chloro atom or a CH3O group, while B usually...
Crystallinity
Little is known as yet about the crystallinity of organic pigments and its determination. Most pigments, such as the members of the azo series, emerge from the manufacturing process as fine powders of poor crystallinity. Drying of the crude presscake immediately after synthesis without further finishing usually results in considerable agglomeration of the fine particles, which may later resist even the most determined dispersion efforts. Considering the crystal imperfections that are typically...
Chemistry Manufacture Mbs
E. Jacobson in 1882 fused phthalic anhydride with quinoline bases obtained from coal tar, which also contained quinaldine 136 . He thus received quinophthalone 137 . Quinophthalone derivatives bearing sulfonic or carboxylic acid functions represent suitable anionic dyes. Derivatives carrying basic side chains containing quarternary nitrogen, on the other hand, provide cationic dyes. The compounds are used especially as disperse dyes 1 . 137, the parent structure to all pigments which are...
Properties and Application 1
Quinophthalone pigments are marketed in very limited number. The pigments provide yellow to red shades and are used primarily to color paints and plastics. P.Y.138 type quinophthalone pigments afford exceedingly lightfast and weather-fast greenish yellow shades with good heat stability. Their main fields of application are in paints and in plastics. Most commercial P.Y.138 types have low specific surface areas of approximately 25 m2 g and consequently provide good hiding power, a feature which...
Bisacetoacetarylide Pigments
The fact that only a few of these pigments enjoy commercial importance eliminates the need to treat each individual species separately. Bisacetoacetarylide pigments are considered disazo pigments that are obtained from bifunctional coupling components. The latter are obtained by bisacetoace-tylation of aromatic diamines, especially of 4,4'-diaminodiphenyl or 1,4-di-aminophenyl derivatives with 2 equivalents of diketene or acetoacetic ester Only common aromatic amines are used as diazonium...
PlateOut
The term refers to the deposition of pigment on the surface of the processing equipment or on the system itself. In contrast to similar phenomena caused by blooming, plate-out does not reappear once the pigment film is rubbed off. Plate-out is commonly observed on the calendering and rolling equipment that is used to process pigmented PVC. It is caused by an incompatibility between components such as lubricants, stabilizers especially those of a barium cadmium basis , plasticizers, or other...
Solvent and Migration Fastness 1
The solubility of any crystalline material decreases as the particle size increases the correlation is quantitatively described by the Ostwald equation 24 in which c solubility of crystals with radius r, ce solubility of very large crystals, a surface tension, V molecular volume of the crystal, R gas constant, and T Kelvin temperature. Fig. 80 Influence of the gloss of air-dried alkyd resin systems containing Pigment Red 3 of different particle sizes with the drying time. Pigment content of the...
BleedingOverspraying Fastness
A pigment is said to bleed if some portion of it migrates from the application medium in which it is partly dissolved to a similar colorless or differently colored medium with which it is in contact. This phenomenon is of particular concern to the plastics and coatings industry. It is therefore not surprising that the phenomenon of bleeding has given rise to a variety of industrial standards, including generally accepted terminology 44, 45 , standardized tests to determine the tendency of a...