Page 29 - Basic Principles of Textile Coloration

18 AN INTRODUCTION TO TEXTILES, DYES AND DYEING

DyStar, are all reactive dyes with vinyl sulphone reactive groups, used mainly for
dyeing cotton.

A reference to the colour of the dye usually follows the brand name. The name
may also include other descriptive references to particular characteristics of the
dye, such as particularly good fastness properties, ability to form metal complexes,
or its physical form. The commercial name usually ends with an alphanumeric
code. These codes range from quite simple to quite obscure. They may relate to
the particular hue of the dye, the relative amount of actual colorant in the
formulation, or the application properties.

For example, Indanthren Golden Yellow RK is a vat dye manufactured by BASF
(Badische Anilin und Soda Fabrik). ‘Indanthren’ is the brand name used for their
range of vat dyes. ‘Golden Yellow’ indicates the colour and the code ‘RK’ shows
that this dye is a reddish yellow and applied using a cold-dyeing method. The
letter ‘R’ stands for the German word rot = red (the dye is listed as CI Vat Orange
1) and the ‘K’ comes from the German kalt = cold. On the other hand, BASF
manufacture Procion Red H-E3B. ‘Procion’ is their brand name for reactive dyes
for cotton. All the Procion dyes with ‘H-E’ in the code are dyes with two identical
reactive groups. Reaction of the dye with the cotton occurs under hot (‘H’)
conditions. The ‘3B’ in the code shows that this is a bluish red (B = blue); bluer
than similar red dyes with a code B, but redder in hue than dyes with a 6B in the
code. In other cases, the alphanumeric code following the name of the dye may be
of little or no value to the dye user. An old paper on dyestuff nomenclature by C L
Bird [3] is still useful reading on this subject.

One major problem with the Colour Index classification is that dyes from
different suppliers, which have the same registered CI Generic Name and
Constitution Number, may have quite different dyeing properties. The Colour
Index information is simply an indication that dyes of the same Generic Name
contain the same base colorant. The different commercial products will usually
contain different amounts of the predominant dye, of other minor dye
components, and of auxiliary chemicals. They may, therefore, have different
dyeing properties. Some manufacturers erroneously use the Colour Index
nomenclature without official registration and their products may not be
equivalent, or even close, to those with registered names.

Figure 1.9 illustrates the approximate relative annual consumption of the major
types of fibres and dyes estimated for the year 2000. The inner pie chart gives the
data for fibres and the lengths of the outer arrows indicate the relative proportions
of the various kinds of dyes used. There is a close relationship between the relative