Polyesters polyamide mixtures, dyeing

Elastomeric polyurethane fibers [96, pp. 609-615], are contained in stretch articles and in knitted fashion materials. Light shades can be dyed tone-on-tone on polyamide-polyurethane mixtures with disperse dyes at 95-98°C and pH 6-7. However, the wetfastness of these dyeings on polyurethanes is lower than on polyamide. Because of the temperature sensitivity of polyurethane fibers, mixtures of elastomeric and polyester fibers must be dyed with small-molecular, rapidly diffusing disperse dyes in 30 min at 120 °C according to the HT process [148], Modified PES fibers that are dyeable at 100°C without a carrier are often used in mixtures with elastomeric fibers. In all dyeing processes for elastomeric fibers, dyeing equipment that permits low-strain guidance of the material and the lowest possible thermal stress are important. 

Disperse colouring materials are used principally for colouring cellulose acetate, polyamide and polyester fibres. Their chemical structure is similar to that of the fat-soluble dyes. They belong to the compound classes of nitrodiphenylamine derivatives and azo- and anthraquinone dyes without a sulphonate group. They are more or less easily soluble in organic solvents but insoluble or difficultly soluble in water. Mixtures of disperse dyes can be separated on alumina columns, using solvents such as ether, methylene dichloride, ethyl acetate and tetrahydrofuran [71]. PC-separations on cellulose paper are incomplete [14, 30, 31, 73, 85]. Separations are better on acetyl-paper [29, 30, 43] or pre-treated paper [19, 20, 25, 44, 73]. 

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