Determination of colour sensitivity for the dyeing of disperse dyes

The present project has developed the theory of colour sensitivity of dye recipes such that it covers variations in dyeing process. A numerical model has been established for the purpose of predicting colour sensitivity of matching recipes. The aim is to provide a tool for dyeing practitioners in recipe selection to increase dyeing reproducibility and thus to improve the performance of ‘right-first-time’ production. The present development may also have significance in on-line process control.; This research work consists of three parts: (a) to propose a prediction model; (b) to verify the model; and (c) to apply the model for determining the limit of accuracy of dyeing process control.; A set of preliminary dyeing experiments on polyester was carried out using six commercial disperse dyes to investigate the quantitative effects of individual factors and to determine the involvement of each factor in the prediction of colour sensitivity of a matching recipe. The investigation concluded that the factors of dye concentration, temperature, time and liquor ratio should be involved in the prediction model for disperse dye-polyester system.; The relationship between the effect of an error simultaneously occurring in individual factors of temperature, time and liquor ratio and that of the error separately occurring in the individual factors on resultant dyeing was investigated. The investigation was carried out by calculating the dye uptake change and measuring the resultant colour change due to simultaneous error and separate errors respectively. It has been revealed that the effect of a simultaneous error could be approximately simulated by the sum of the effects of the errors separately occurring in the individual factors.; Based on computer colour matching technology, the method to predict the colour sensitivity of a matching recipe with respect to individual dyeing parameters was established by building up a set of calibration dyeing with various conditions for disperse dyes on polyester. These resultant data, the so-called ‘individual colour sensitivity’, were used to calculate the total colour sensitivity covering all the involved factors.; After the verification of the proposed model, the prediction method was then employed for several applications. One of them was to investigate the probability of dyeing of 30 matching recipes for 15 target colours passing a pre-set colour control tolerance of 1 ΔE with various errors occurring in dyeing process. The model was also applied to determine the limit of accuracy of different matching recipes for the process control.; The predicted colour sensitivity was correlated with activation energy, standard affinity and heat of dyeing respectively. It was revealed that the energy level of a dyestuff took a very important role in the colour sensitivity of a recipe with respect to temperature change, specially at higher concentrations.; Compatibility of the employed disperse dyes with various concentrations were determined by using laboratory dyeing method. These values were used to calculate the compatibility of matching recipes for the target colours. The comparison of colour sensitivity with the compatibility of recipes indicated that generally a compatible mixture could be helpful to improve the reproducibility in dyeing except for some dye mixtures with high concentration and energy level. (Abstract shortened by UMI.)...