Carbonyl pigments: General principles

This chapter describes the general features of the chemical class of pigments designated as carbonyl pigments. These pigments are characterized by the presence of carbonyl groups linked to one another via an extended conjugated system, often forming polycyclic aromatic structures. Carbonyl pigments have experienced distinct phases in their histories. Certain carbonyl colorants, notably anthraquinonoids, were discovered in the early twentieth century and subsequently used as vat dyes for textiles, but their potential as high-performance pigments was not realized until the mid-twentieth century when demand began to emerge for pigments of the quality that they could provide. After conversion to a suitable physical form, several vat dyes were then introduced as vat pigments. Several other carbonyl pigment types did not originate as vat dyes but were developed specifically for pigment use. Carbonyl pigments provide a wider diversity of structural arrangements. The broad carbonyl chemical class may be categorized into several sub-types, each with its own characteristic structural features. These categories, which are discussed in separate chapters, include anthraquinonoids, quinacridones, diketopyrrolopyrroles, perylenes, perinones, indigoids, isoindolines, isoindolinones, and quinophthalones. These products generally owe their high levels of technical performance to their large molecular size and high molecular planarity, which lead to highly compact crystal structures and, in many cases, to the ability of the carbonyl group to participate in strong intra- and intermolecular hydrogen bonding.

Support vector machine classification model for color fastness to ironing of vat dyes

Investigations of quantitative relationships between structure and color fastness of dyes are crucial in seeking novel dyes. For the first time, this work reported a classification model based on a quantitative structure–property relationship to predict color fastness to ironing of vat dyes. By performing binary classification analysis based on a support vector machine (SVM) and genetic algorithm, 56 vat dyes in the training set together with seven molecular descriptors were used to develop the classification model, which was validated with 59 vat dyes in the test set. The optimal SVM model ( C = 208.465 and γ = 5.9692) possesses overall accuracy of 91.1% for the training set and 83.1% for the test set, which is more accurate than those from the binary logistic regression model (87.5% and 81.4%, respectively). Furthermore, the mechanism of molecular descriptors correlated with color fastness to ironing of vat dyes is discussed.

Eco-Friendly Vat Dyeing of Cotton Using Alkaline Iron (II) Salt as Reducing Agent

Sodium hydrosulphite is used commercially as the reducing agent for vat dyes in the dyeing of cotton. Large amounts of sodium sulphate, sulphur oxyanion and toxic sulphite are produced during the dyeing due to the dissociation of sodium hydrosulphite leading to severe air and water pollution. This research focuses on the use of alkaline iron (II) salt as the reducing agent for vat dyeing on cotton fabrics through a complete replace¬ment of hydrosulphite. The 34 Box-Behnken design was used to achieve optimum parameters and statistically analyse the performance of the new reducing system. The results showed that the alkaline iron (II) salt system was relatively effective in developing a comparable dyebath reduction potential, surface colour strength of cotton and colourfastness, if compared to the hydrosulphite-based reducing system. The dyebath stability in the presence and absence of the dye also showed superior results compared to that of the hydrosulphite system. Hence, it can be said that a complete substitution of sodium hydrosulphite with alkaline iron (II) salt is possible.

Antibacterial Finishing of Vat Dyed Cotton Fabrics with a Reactive N-Halamine

To obtain antibacterial properties for colored cotton fabrics, vat dyes were chosen to dye cotton because they can avoid serious discoloration during chlorination. In this study, we synthesized a reactive N-halamine precursor, 4-(4-(2,2,6,6-tetramethyl-4-piperidinol)-6-chloro-1,3,5-triazinylamino)-benzenesulfonate (BTMPT), and coated it on colored cotton fabrics that were dyed with three different vat dyes. The optimum pH for chlorination of the treated cotton fabrics was investigated. Chlorination at pH 11 achieved a small color difference and greater than 0.2% of active chlorine loading. When challenged, the chlorinated fabrics inactivated all inoculated Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) within 5 min. The treated cotton fabric had greater breaking strength than those treated with the traditional process, as well as good washing stability.

Cotton Dyeing with Vat Dyes using Alkaline Pectinase and Iron (II) Salt

Use of sodium hydrosulfite in the dyeing of cotton with vat dyes is criticized for generation of sulfur compounds leading to air and water pollution. In this study, attempts were made to dye cotton with alkaline pectinase along with iron (II) salt as an alternative formulation. A 43 Box-Behnken design was used for statistical analysis of performance for this new reducing system and to obtain optimum parameters for cotton dyeing. The results showed that alkaline pectinase along with iron (II) salt was quite effective in developing comparable dyebath potential, dye receptivity on cotton with comparable dye strength, and colorfastness, as compared to the hydrosulfite-based reducing system. Dyebath stability in presence and absence of dye also showed superior results compared to that of the hydrosulfite system.