Chemistry Reference
In-Depth Information
Coincidence of polymers synthesis or forming fibres from them with dyeing is
progressive method in technological and economic respects by which fibres in complete
marketable state may be produced directly at the chemical fibres factory.
It should be noted that in connection with strict measures on environmental protection
stock dyeing, as practically wasteless production, becomes the most important among other
methods. Besides, due to the shortage of service water there is no longer any necessity for
sewage treatment of textile-finishing production from different impurities (dye, surface-active
substances (SAS), salts and so on).
The most important fact is that dyes for stock dyeing in overwhelming majority provide
colours with high stability indexes to all physico-chemical effects which are often
unachievable during usual dyeing methods [273]. Dyes used for stock dyeing not only effect
negatively on the fibre strength, but, in some cases, they are able to protect it from
thermooxidative and photochemical destruction.
The process of obtaining and forming thermoplastics polymers is carried out at high
temperatures, achieving 300
0
C, which, in its turn, sets a strict limit on selection of dyes and
restricts the assortment of the latter, as the majority of used dyes for PETP fibres do not bear
long action of high temperature and agressive melt medium.
That is why for dyeing PETP-fibres in the process of obtaining or forming polymer there
may be used only those dyes which meet definite requirements, namely:
(1)
to be resistant to high temperatures (250-300
0
C) throughout the process of obtaining
from the melt, to be resistant to agressive melt medium, chemical action both on the
part of separate components, being a part of the melt, and products of their chemical
decay, and on the part of physical action during polymer processing;
(2)
to solve and combine with polymer quite well, and in the case of pigment - to
disperse well;
(3)
to give the fibre paint stable to physico-chemical action.
The dye, being introduced into reaction mass at the stage of polymer synthesis when the
additive undergoes monomers action, which, as a rule, are more reactive, than polymer, is
under much harder conditions. Dyeing composition may be introduced at any stage of
polymer synthesis in the form of powder, suspension and paste. Dyeing of granules is carried
out by mixing with pigments powder in dry or wet form, in addition some part of the dye
comes to waste waters which causes economic problems. This disadvantage may be
eliminated if the dye will be introduced directly into prepared polymer mass.
Dyes, used for thermoplastic polymers, may be divided into two groups:
(1)
soluble in spinning melt;
(2)
high-dispersed pigments, which must be uniformly distributed in polymer melt and
provide stable dispersions.
Both groups have their own advantages and disadvantages. In the first case great
demands are made to dyes solubility, in the second - to the degree of dye particles dispersion.
Lately, a great number of new dyes has been synthesized, among them - azo dyes, water
- soluble anthraquinone esters [274], derivatives of phthalocyanide [275], derivatives of
piperidines [124], dyes of perylene series [276] and others. Because of low resistance of azo-
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