Bleaching and dyeing; fluid treatment and chemical modification – Overall dimensional modification or stabilization – e.g.,... – Modification of molecular structure of substrate by chemical...
Patent
1983-03-01
1984-12-11
Tungol, Maria Parrish
Bleaching and dyeing; fluid treatment and chemical modification
Overall dimensional modification or stabilization, e.g.,...
Modification of molecular structure of substrate by chemical...
8496, 8537, D06P 122, D06P 138, D06P 366, D06P 500
Patent
active
044876084
DESCRIPTION:
BRIEF SUMMARY
There are two main ways of dyeing self-supporting fibre assemblies such as fabric, yarn, tow or sliver, namely batch or continuous. Typical batch methods involve lowering the fibre assembly into a bath of the dye liquor, allowing it to remain in the bath for a predetermined period, sometimes with gentle agitation, and then removing it from the bath. Throughout this process the assembly may be carrying its own weight but will not otherwise be under tension.
In continuous methods the assembly is impregnated continuously with a dye liquor and, if necessary, is subsequently subjected to processes by which the dye is fixed. The continuous impregnation involves continuously drawing the assembly under tension through the or each impregnation stage. For instance the continuous assembly may be drawn through an impregnation bath, e.g. around a padding roll, and the act of drawing the assembly through the bath necessarily subjects the assembly to longitudinal tension. The continuous dyeing process may be carried out in a truly continuous fashion with any fixing or rinsing treatments being carried out continuously and successively on the fabric that is dyed with the dye, or it may be carried out in a semi-continuous process, with a batch of the assembly being continuously dyed, and this batch then being subjected to, for instance, a separate fixing operation.
Fibre assemblies formed of cotton and many other fibres can be dyed by either the described batch dyeing or continuous dyeing. Assemblies containing viscose are, however, more difficult to dye satisfactorily for a number of reasons. Viscose fibres tend to be weakened by the presence of aqueous liquors, especially if they are alkaline, and so in practice it is essential to minimise the tension applied during impregnation with the dye liquor. In practice this means that it is difficult or impossible satisfactorily to dye viscose fibres by continuous dyeing techniques without stretching the fibres.
Another problem that arises in continuous dyeing techniques, especially when the liquor is alkaline, is that the viscose fibres tend to absorb the dye very slowly and so inadequate dyeing occurs during normal padding or other continuous dyeing methods.
The normal way therefore of dyeing a self-supporting assembly of viscose fibres has been by batch dyeing. A typical method is known as winch dyeing and involves lowering a loop of fabric or tow on a winch into a bath of dye liquor, gently agitating the fabric or tow within the liquor, and then raising it out of the liquor and drying it. The dyes are normally substantive dyes and so their colour may not be as fast as desirable.
Vat and reactive dyes are known to have the potential advantage of being very fast, because of the fixing of the dye in or to the fibre, but have to be applied from an alkaline medium. This makes it difficult to obtain good colour intensity in viscose fibres. In practice therefore these dyes have tended not to be used with viscose fibres and, if they are to be used at all, reasonable results require prolonged batch dyeing and the use of large amounts of dye.
Many processes have been developed involving the chemical treatment of cotton fibres with, for instance, textile resins or cellulosic cross-linking agents and it is sometimes mentioned that viscose fibres can be subjected to similar treatments. In practice all such treatments are normally conducted on cotton fibres that have already been dyed.
There have also been a few proposals in the literature aimed specifically at the chemical treatment of viscose. One such proposal is in British patent specification No. 1,034,453 in which Example 2 describes impregnating viscose rayon fibre tow with a cross-linking agent, curing this, spinning and weaving the fibres, and then mercerising the fabric. The fabric is then "dyed in the normal fashion". As explained above, the normal fashion would have involved batch dyeing with a substantive dye.
In practice however there has been no successful chemical treatment of viscose fibres to give them good physical prope
REFERENCES:
patent: 2524113 (1950-10-01), La Piama
patent: 2739908 (1956-03-01), Marsh
patent: 3893804 (1975-07-01), Hepp et al.
patent: 3901014 (1975-08-01), Hiroi et al.
Kantner, Amer. Dyestuff Reporter 10/31/60.
Lintrend Limited
Rosen Lawrence
Tungol Maria Parrish
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