1) Sulfur Dyes
United States Patent 5,961,670, by Cote et al., October 5, 1999 has a summary on sulfur dyes of the type manufactured at the Damascus,
Virginia plant. This information is reproduced below:
Sulfur dyes represent a general class of dyes having a long history. They are generally prepared from aromatic intermediates or starting
materials which are reacted with sulfur or a sulfur compound in a process generally viewed as involving both coupling and thionation. In
earlier times, the dyes were made from relatively complex materials, including natural materials, whose chemical structure was often not
precisely known. In more modern times, chemicals of discrete and known structures are used as starting materials. However, in either
case, the structures of the resulting sulfur dyes are still seldom exactly known, and probably often involve variable and complex mixtures.
As a result, sulfur dyes are generally described in the Colour Index, the authoritative work on dyes generally, by their starting materials,
conditions of manufacture and a few fundamental properties such as color and solubility. Given this background, the successful
improvement and modification of sulfur dyes has been typically a matter of trial and error.
The aromatic intermediates (starting materials) used in making sulfur dyes can, for purposes of this invention, be described as relatively
common aromatic compounds, such as benzene, naphthalene, diphenyl, diphenylamine, azobenzene and the like which bear at least one
nitro, nitroso, amino, substituted amino, or hydroxy group. The Colour Index also has classified these intermediates to include:
1)Mononuclear Benzenoid Amino and Nitro Compounds; 2) Binuclear Benzenoid Amino and Nitro Compounds; 3) Substituted Phenols; 4)
Substituted Naphthalenes; 5) Polycyclic Compounds; 6) Indophenols; and 7) Acridine, Azine, Oxazone and Thiazone Compounds. One or
more such intermediates, which may be from the same or different intermediate classification, may be used in making a single dye
product and other chemical intermediates, not fitting the above definition, are occasionally used in combination with such intermediates.
In preparation of sulfur dyes, there may be used sulfur itself, but a sulfur compound which is a polysulfide is more typically used, e.g.
sodium polysulfide. Other sulfur compounds providing a source of sulfur may also be used, such as sodium sulfide.
Sulfur dyes may be made by processes which have been divided into well-recognized categories such as sulfur bake, polysulfide bake,
fluid polysulfide melt and solvent melt. In all these process categories the basic reaction of the intermediate(s) with the sulfur or sulfur
compound is carried out. The fluid polysulfide melt reaction, for example, involves forming a coupling mass by initial reaction of the
intermediate(s) and the sulfur of sulfur compound and heating the coupling mass under reflux or pressure in a closed vessel to effect
thionation. Such process is widely used in making many sulfur dyes, including the most commonly used sulfur dye known as C.I. Sulfur
Black 1 (C.I. No. 53185, the solubilized form upon reaction with sodium bisulfite being C.I. No. 53186). The processes may vary in a number
of respects as is well-known including work up after formation of the crude thionation product. Hence, presscakes may be formed from
the crude product after different treatments of the crude products and the presscakes handled differently depending on product forms
which can include powders, pastes, grains and liquids including aqueous solutions. Sulfur dyes commonly exist in two well-known forms;
one in which the dye exhibits its color (oxidized form) and one in which it is of lesser color or colorless (reduced or leuco form), the
reduced form being returned to the color form by oxidation and the reduced form being produced by chemical reduction of the color form.
Since the dyes can be sold and used in either form, further reaction in work up of the crude thionation product may be carried out to
obtain the desired product form. Final products are more usually the reduced form.
In general, compositions used as dyes, including sulfur dye compositions, must satisfy a number of criteria and do so to varying extents,
hence creating a continuing interest in new dyes, including new sulfur dyes. Among the criteria of interest are the effects of a dye upon
the substrate it is used to dye. Sulfur dyes, for example, are well-known to be inclined to weaken fabrics, an effect called "tendering".
While this effect varies depending upon the particular sulfur dye, it is particularly significant with a number of sulfur dyes of varying color
and chemical compositions. Whether or not tendering is experienced more with dyes of darker shades or with dyes prepared from
particular intermediates is unclear. However, it is caused to a high level by most black dyes, such as those prepared from
2,4-dinitrophenol and its equivalent intermediates, and is distinctly and disturbingly high in the case of the most widely used sulfur dye, i.e.
C.I. Sulfur Black 1, the use of which would be greater but for its tendering effect.
Synonyms: C.I. 58000; Mordant Red 11; 1,2-Dihydroxyanthraquinone:
Alizarin Red (sold in powder and paste forms) was produced in two coal-fired autoclaves at Damascus. Considerable skill was required
by the chemical operator to build a fire that would heat the autoclaves to the proper reaction temperature. The autoclaves were
scrapped during the plant demolition in 1986.
The classic synthesis of Alizarin involves the sulfonation of anthraquinone followed by reaction with sodium hydroxide at 200 C. (C.
Graebe, C. Liebermann, Chem. Ber., 1869, 2, 332)
3) Oil Dyes
Ceres Blue N (Solvent Blue 14) was 1,4-bis(pentylamino)-9,10-anthraquinone:
Ceres Blue ZV (Solvent Blue 59) was 1,4-bis(ethylamino)-9,10-anthraquinone:
These products were used for the coloration of gasoline and plastics.
Chemistry of Damascus Plant Dyes
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