Dyeing of Silkworm Cocoon Using Acid Dye

Silkworm cocoons have been dyed using acid dyes (C. I. Acid Orange 7 and C. I. Acid Orange 63) while retaining their shape under various conditions, and the dyeing properties have been investigated for developing a new fiber technology. Whereas the corner of the cocoon shell was thin and could be dyed in shorter time, the center of the cocoon shell was thick and needed more time. The penetration depth of the dye molecule into the cocoon increased with time, but the penetration speed was not constant: the penetration rapidly increased within 5 minutes, but afterwards gradually increased. This result is due to the structural differences among the shell layer portions. In addition, when the dye bath was at a lower pH, the penetration speed was slightly slower. Moreover, the C. I. Acid Orange 63 molecule penetrated more slowly than the C. I. Acid Orange 7 molecule. These results are probably attributed to the difference in the adsorption state of the dye molecule on the fiber.