Chemistry Reference
In-Depth Information
group to reducing medium of polymer melt the majority of azo-dyes fail. However, it should
be noted, that, in spite of the variety of synthesized dyes, their use for direct introduction into
the polymer is limited owing to inorganic salts impurities. At light stabilization of polymers it
is very important for dyes and additives being introduced to be more lightfast than the
polymer, otherwise at the material service the process of deterioration of its physico-chemical
characteristics in comparison with undyed one accelerates.
There are many works of patent character in which methods of obtaining PETP-fibres
stock dyed [275-279] are described. Pigments (black and TiO
2
) in the form of dispersions and
pastes and additives soluble in polymer melt [280] are used for dyeing and stabilization.
In the work [33] it is shown that coloured synthetic polymers obtained by chemical
modification directly during the process of their production by using aromatic compounds
with different functional groups possess not only high colour strength but also high thermal
stability.
Geller [281] used derivatives of oxyxanthane, containing six-member chelate cycle with
intramolecular hydrogen bond for dyeing. Allen with his research workers used derivatives of
amine antroquinone and oxyantroquinone as dyes. Krichevskiy [274] studied the effect of
dispersed azo- and antroquinone dyes on physico-chemical properties of polyesters. In the
work [282] direct turquoise lightfast and in the work [84] phthalocyan polyazodyes were used
for PETP stock dyeing. Obtained fibres possessed high resistance to the effect of heat and
light.
Increase of polyester fibre light stability is observed at presence of electron-acceptor
para-substituents in the derivatives of 4 amine benzene.
Allen and his research workers found out that substituent location influences stabilizer
efficiency. Cholles [283] indicated that substituent nature influences its efficiency.
Majority of dispersed dyes, used for PETP dyeing, are instable themselves [284, 286].
That is why it may be supposed that increase of dye concentration leads to accumulation of
being formed radicals in the thin surface layer of the sample without mixing, as a result of
which the rate of chain break rises and suppresses chain photooxidation of polymer. This
effect was called by the authors [175] effect of concentration inhibition, which was observed
in the case of polycaproamide light stabilization by action dyes.
Since there are data on stabilizing action of dyes at photo- and thermal destruction of
PETP then it becomes very interesting to introduce such dyes-stabilizers by the method of
stock dyeing, that is to introduce the dye into polymer at any stage of its production or fibre
forming.
Polymer stock dyeing through the stage of obtaining dye polymeric concentrate (DPC)
[168, 283] is in the centre of attention. Methods of dyeing at polymer synthesis and by the
way of introducing dyed composition into polymer melt are combined in this method. DPC
obtaining is carried out in the process of polymer synthesis in the presence of large amount of
the dye (up to 50% of polymer mass).
Both initial granulate and ground production wastes of polymer may be used according to
this method of dyeing. Dyeing may be fulfilled according to both periodic and continuous
schemes. Hence, more uniform distribution of the dye in polymer mass is achieved and this
gives the possibility of obtaining better monotone fibre dyeing during the whole technological
process.
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