Dyeing with Substantive Dyes

Demonstration Experiment on Video

Dyeing with Substantive Dyes

Objectives: Direct Dyeing, Phthalocyanines, Light and Washing Fastness

Peter Keusch

German version

Materials and chemicals:
cotton yarn
Lurantin Light Turquoise Blue GL (BASF)
Glauber's salt (sodium sulfate)

Apparatus and glass wares:
hotplate
thermometer
glas stirring rod
metal forceps
crystallizing dish d = 12 cm
2 beakers 500 ml
2 snap-cap vials 10 mL

Experimental procedure:

0.3 g of Lurantin Light Turquoise Blue GL are dissolved in 100 mL of dist. water. The temperature of the water should be about 40 °C. 10 g of cotton yard are added to the dye solution. The temperature is slowly raised to boiling. Now 2 g of Glauber salt are added. The mixture is stirred. The yarn is treated about 20 minutes in the slight boiling bath.Then the fiber is washed with cold water to remove excess dye und died.

Result:

The dyeing process results in a homogeneous bright blue color of the treated cotton yarn.

Video clip (Download RealPlayer .rm file)

Discussion and background:

Lurantin Light Turquoise Blue GL belongs to a family of dyes called the phthalocyanines, which yield the color turquoise. The structure of phthalocyanines is similar to that of porphin ring that is a core skeleton in heme and chlorophyll. The four pyrrole groups in chlorophyll and heme are linked together by their a, a'carbons via methine (-CH=) bridges to form a tetra pyrrole ring (porphin ring). The four pyrrole rings in phthalocyanines (conjugated to benzene rings) are joined by aza nitrogens.

Substantive dyes such as for example Lurantin Light Turquoise Blue GL, are substances that are both water soluble and direct in dyeing. These "direct dyes" colour cellulose fibres (cotton yarn, linen, spun rayon) directly in a hot dye bath without a mordant and distinguish themselves by good to very good light fastness. The washing fastness is moderate. The direct dyes are attached to the fiber by dipole forces, the formation of hydrogen bridge bonds or van-der-Waals bonds. Summa summarum, the binding forces between fiber and dye are not very strong.

Glauber's salt is a leveling agent used to help achieve an even, intense dye color and a better dye fixation on the fiber.

References:
Demonstration Experiment on Video Dyeing with Vat Dyes
What kinds of chemical bonds attach dyes to fibers?

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