Basic dyes wash fastness

Cationic (Basic) Dyes. These water-soluble cationic dyes are applied to paper, polyacrylonitrile (e g. Dralon), modified nylons, and modified polyesters. Their original use was for silk, wool, and tannin-mordanted cotton when brightness of shade was more important than fastness to light and washing. Basic dyes are water-soluble and yield colored cations in solution. For this reason they are frequently referred to as cationic dyes. The principal chemical classes are diazahemi-cyanine, triarylmethane, cyanine, hemicyanine, thiazine, oxazine, and acridine. Some basic dyes show biological activity and are used in medicine as antiseptics. 

The basic dyes are of poor fastness to light and vary with regard to washing fastness from poor to moderate. Some examples on wool are tabulated. below to provide general conception of their fastnesses. 

The basic type of dye closely resembles that used for dyeing polyester fibers, but the selection of compounds is based on other criteria. Requirements regarding sublimation resistance are not as stringent, whereas fastness to ozone, exhaust gases, and washing are important. Substitution by amino, and especially by alkyl-amino, groups tends to decrease lightfastness of the dyes in polyester fibers. This is not the case for acetate and polyamide fibers. 

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