The paper describes the general techniques used and the results obtained in pilot plant and commercial dye‐house experiments carried out to demonstrate the potential of an inhouse spectrophotometer and minicomputer system in:
high‐accuracy recipe prediction to produce bulk dyehouse recipes without laboratory check dyeing
calculation of redye procedures to correct off‐shade bulk dyeing
control of dyehouse pass/fail matching by instrumental methods
preparation of recipe cards, druglines and cost information by computer methods.
A thermodynamic theory of dyeing is applied in practice to predict the necessary dyebath conditions to attain a target colour, and to predict the conditions for the redyeing of a thread lot where the target shade is not attained. 180 Vat recipes were predicted on a laboratory scale and 40 recipes on a bulk scale. All the dyeings were produced from tertiary mixtures of dyes and covered a wide gamut of colour space. The results indicate that general thermodynamic theories of dyeing can be used in a practical way to improve the performance of a dyeworks.
The general thermodynamic schemes for predicting the amount of dye on the fibre which have been used by other workers are outlined. A new approach is then developed for the complex system of vat dyes on cotton, and the affinities of 14 vat dyes are calculated. The theory is extended to mixtures, and the variables of temperature, amount of salt added, amount of dye added, and amount of reducing agent added required to give a known colour are predicted from the theory. Cotton thread was dyed under different predicted conditions and the resultant matched dyeings are good evidence of the validity of the theory. In addition, the effects of the main dyeing variables on the resultant colour are predicted from the theory.
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