Dyebath cycle

Transfer of Disperse Dye on Polyester. A specimen of dyed polyester is placed in a standard dyebath with an equal weight of undyed polyester and the dyeing cycle completed. The rate of transfer from dyed to undyed fabric is compared to that obtained with a range of five standard dyes and the dye under test is given the same number as the dye it most closely resembles. 

For a ten-cycle dyebath reuse sequence, the average energy consumption was calculated, using plant data and Table XXIV, to be 2.85 x 103 BTU/lb. Ten cycles was conservatively assumed to be the maximum number of cycles that the model plant could adequately schedule. 

Savings and Cost/Benefit Analysis. The bench scale experiments were successful Tn overcoming major technical problems while demonstrating that dyebath/auxiliary bath reuse is indeed feasible with reactive dyes on cotton-containing fabrics. In addition, a shortened-cycle dyeing procedure coupled with reuse for cotton/polyester blends was shown to further increase energy, mass, and time savings (Table XXX). 

BORCODYE D-6-LF may be added undiluted into the dyebath at the start of the dyeing cycle and can be applied under atmos-heric or pressure conditions. It is low foaming and yields excellent results on piece goods, yarn, package dyeing and carpet. 

The effects of the addition of salt, concentration of dye and the dyebath temperature may also be considered in the design of the pH control algorithm. If the desired pH at any given cycle is not achieved, the next cycle s pH value should compensate for this shortcoming. A simple flowchart of this process is given in Fig. 7.26. 

In conclusion, pH control in the dyebath is influenced by a number of factors, some of which, including the salt content, have a relatively large impact on the measured value. Some of the parameters are rather complicated, and subtle changes may be exerted due to the presence of fibre. Providing relatively small changes in pH can be tolerated (up to 0.5 pH units), it is reeommended to consider approximations in various parts of a given control cycle, as this would result in a mueh simpler control algorithm. 

The change in the desired exhaustion rate in the model is governed by a change in temperature. In order to calculate the set temperature required for any given exhaustion, the dyeing period is divided into a series of control cycles . Within each cycle it is assumed that the rate of exhaustion has a first-order dependence on the current concentration of dye in the dyebath. 

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