Method for Dyeing Aramid Fibers and Dyed Aramid Fibers

Abstract

Methods for dyeing aramid fibers, and the dyed arimid fibers produced by these methods, which comprises a dye providing step in which a vat dye or a sulfur dye is provided to aramid fibers, a solvent treatment step in which the aramid fibers are treated by a treating solution containing a polar solvent, and after the solvent treatment step, a heat treatment step in which the aramid fibers are subjected to a heat treatment, if necessary, and having one or more dyeing operations comprising the combination of the respective steps dyeing operations. The dyeing methods can be applied to either of the para-type aramid fibers, the para-type copolymerized aramid fibers and the meta-type aramid fibers, which can be dyed to a practical color depth required for developing new applications of the aramid fibers. Colorfastness of the dyed product, in particular, colorfastness to light, is improved.

Description

TECHNICAL FIELD[0001]The present invention relates to a method for dyeing aramid fiber, in particular, to a method for dyeing which can dye the aramid fibers with a practical color depth. The present invention also relates to aramid fibers dyed by the method.BACKGROUND ART[0002]A wholly aromatic polyamide fiber is also called as an aramid fiber, which has high strength and high modulus of elasticity, and excellent heat resistance, dimensional stability, chemical resistance, etc., and has been used for wide uses as industrial use fibers. The aramid fibers can be roughly classified into three kinds of para-type aramid fibers (polyparaphenylene terephthalamide fiber, etc.), para-type copolymerized aramid fibers (copolymerized fibers with polyparaphenylene terephthalamide and 3,4′-oxydiphenyleneterephthalamide), and, meta-type aramid fibers (polymetaphenylene isophthalamide fibers or copolymerized fibers containing the same as a main component, etc.) depending on the position of an amid...

AI Technical Summary

Benefits of technology

The present invention provides a method for dyeing aramid fibers with good colorfastness and a practical color depth. This method can be applied to either type of aramid fiber, and color unevenness or dimensional change is not markedly generated after dyeing. The method uses vat dyes or sulfur dyes with good colorfastness, especially colorfastness to light. The aramid fibers can be dyed with a very dark color, such as black and navy blue, that had been deemed difficult. The method uses a lightness value in the L*a*b* colorimetric system, with a smaller value being evaluated as a dark color. The aramid fibers can also be pre-dyeing or post-dyeing stepped using other dyes to improve dyeing quality and color depth. This method allows for the effective use of aramid fibers in various applications and advances their usefulness.

Problems solved by technology

These aramid fibers have rigid molecular structure and high crystallinity, and a practical color depth cannot be obtained by the same dyeing method as applied to the general fibers, and colorfastness of the obtained dyed product cannot be said to be practically sufficient.

Such dope-dyed fibers are limited in hue, so that there is the problem that they cannot sufficiently correspond to various hues required for developing new applications of various kinds of protective working clothes or aramid fibers.

Moreover, in the para-type aramid fibers or the para-type copolymerized aramid fibers, and also including the dope-dyed fibers, fibers having a practical color depth such as black and navy blue have not yet been industrially produced.

However, these dyeing methods using a dyeing carrier or a polar solvent at high temperatures are methods mainly for dyeing meta-type aramid fibers, and they are insufficient for dyeing para-type aramid fibers or para-type copolymerized aramid fibers.

Moreover, in the dyeing of the meta-type aramid fibers, when the dyeing method which uses these dyeing carriers or polar solvents at high temperature is employed, it involves the problems of causing color unevenness of the dyed product, and dimensional change or lowering in physical properties due to shrinkage, etc.