A similar phenomenon is observed in isoindolinone pigment where chlorination of these pigments results in a variety of shades from yellow and orange to red and brown in comparison to yellow coloured parent pigments. This results in a variation in the colour from red to magenta. Pigments PR122 and PR202 belong to same organic class with different nature of substituent at positions 2 and 9. Pigment PV 19 of quinacridone class exists in three polymorphic forms α, β and γ The beta form exists in violet colour whereas alpha and gamma forms are red in colour. This is attributed to the creation of a large variety of colours by different substitution patterns and polymorphism. One major feature of the organic pigments is that they offer a wide variety of colours in comparison to inorganic pigments which have a limited range of colours. Rather than dealing with detailed synthesis of these pigments, which has been discussed in earlier literature, this section deals with the structures of important organic pigments which make them suitable for automotive finishes. In line with the oxadiazines and thiadiazines being the most well known ring systems containing three heteroatoms, they are also the most well reviewed to date. All the six isomeric thiadiazines ( Table 5) are known with only the 1,5,2-isomer being poorly described. ![]() The 1,2,3- and 1,2,6-isomers have been reported, but there is no spectroscopic evidence to support either structure. Oxadiazines ( Table 4) of all six types are reported, four of the isomers having an extensive and well established chemistry. All six of the possible dithiazines ( Table 3) are described in the literature although the rarer 1,3,2- and 1,5,2-isomers are only known as the fully oxidized tetraoxides. Of the six possible dioxazines ( Table 2) only the 1,2,3-isomer is unknown. Thus, for example, 1,2,5-oxathiazines are only known as the 2,2-dioxides. A general feature of this and other sulfur-containing systems is that they are often only known with the sulfur atom in its higher oxidation states. Of these, six of the possible oxathiazines ( Table 1 ) have been reported. Two thirds of the 34 possible systems containing at least one nitrogen atom and oxygen and/or sulfur are known and well described. 51300 (42) and Sirius Light Violet FRL, or Remastral Violet FrL, C.I. Other examples are Sirius Light Blue FF2GL, or Remastral Blue FF2GL, C.I. 51320 (94) is prepared by condensation of chloranil and 3-amino-N-ethyl carbazole followed bysulphonation. Sirius Light Blue FFRL, or Remastral Blue FFRRL, C.I. Unsulphonated compounds are important pigments.ĭioxazine dyes are prepared by the reaction of benzoquinone derivatives, in particular tetrachloro benzoquinone (chloranil) with aromatic amines in presence of an acid binding agent, followed by oxidative cyclisations. ![]() Among these, the dioxazine dyes have the greatest industrial importance. The bisazine dyes include the fluoridine dyes ( X = N ), the dioxazine dyes ( X = O) and the dithiazine dyes. The groups D 1 and D 2 are not really required and are lacking in a large number of important dyes. The chromophore can be visualised as 1,4-didonor-2,5-diacceptor substituted benzene. These dyes have the general formula 39 where D 1 and D 2 represent the donor groups. Sekar, in Handbook of Textile and Industrial Dyeing, 2011 12.4 Bisazine dyes and copper phthalocyanine dyes
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