de - Beste verfügbare Techniken (BVT) - Umweltbundesamt

Chapter 1
Apart from one or two notable exceptions, all dye types used today were discovered in
the 1880s. The introduction of the synthetic fibres such as nylon, polyester and polyacrylonitrile
during the period 1930 – 1950, produced the next significant challenge. The discovery of
reactive dyes in 1954 and their commercial launch heralded a major breakthrough in the dyeing
of cotton. Intensive research into reactive dyes followed over the next two decades and is still
continuing today.
One important theme in research today is the replacement of tinctorially weak chromogens, such
as anthraquinone, with tinctorially stronger chromogens, such as (heterocyclic) azo dyes.
Considerable activity is also being dedicated to high tech applications, especially in the
electronics and non-impact printing industries.
1.3.1.2 Pigments
Pigments are defined as colouring agents that are practically insoluble in the application
medium, whereas dyes are colouring agents that are soluble in the application medium.
In colouring, the crystalline pigment is applied in the solid state, not in the dissolved form, to
the medium being coloured. Both the chemical and the physical properties of the pigments (e.g.
particulate size, particulate size distribution, special types of surface and specific surface area,
crystal modification, and crystal form) are important for their industrial application.
Many organic pigments and dyes have the same basic chemical structure. The insolubility
required in pigments can be obtained by excluding solubilising groups, by forming insoluble
salts (lake formation) of carboxylic or sulphonic acids, by metal complex formation in
compounds without solubilising groups, and particularly by incorporating groups that reduce
solubility (e.g. amide groups).
Figure 1.5 shows the largest areas of use of organic pigments.
Printing inks
50 %
Other
5 %
Figure 1.5: Main uses of organic pigments
Plastics
20 %
Paints and
coatings
25 %
The remaining organic pigments (“Other”) are used in textile printing and a number of smaller
sectors, including contactless printing processes, office articles and accessories (e.g. coloured
pencils, crayons, chalks), and the colouring of wood, cosmetics, and paper.
6 Dezember 2005 OFC_BREF