300 © Color. Technol., 118 (2002) Web ref: 20020605 Coloration Technology Society of Dyers and Colourists Printing of cationised cotton with reactive dyes Mehmet Kanik a and Peter J Hauser b a Department of Textile Engineering, College of Engineering & Architecture, University of Uludag, 16059 Bursa, Turkey Email: mkanik@uludag.edu.tr b College of Textiles, North Carolina State University, 2401 Research Drive, Raleigh, North Carolina 27695, USA Email: peter_hauser@ncsu.edu The printing properties of cationised cotton that had been pretreated with 2,3-epoxypropyltrimethyl- ammonium chloride were examined. Fixation (steaming) time, colour yields, colorimetric properties, fastness properties, staining of the white grounds and penetration behaviour were evaluated for a number of reactive dyes with cationised cotton fabrics. The cationisation of cotton was found to be very effective in reducing steaming times and washing off processes, and in increasing colour yield. Fastness and other properties of the printings are also discussed. Introduction Reactive dyes are one of the most commonly used dyes for cotton printing because of their high wet fastness, brilliant colours and variety of hue [1,2]. Approximately 25% of the total print production in the world is performed by reactive printing [3]. However, the fixation (colour) yield of reactive dyes on cotton after printing is relatively inefficient. In general, the reactive dyes used in printing often have a degree of fixation of only 60%, whereas in dyeing a degree of fixation of over 90% can be achieved [4]. In order to achieve the characteristic high level of wet fastness, it is necessary to remove the unfixed dye effectively. For this purpose, time-consuming, energy intensive and expensive washing off procedures are required. This washing off process has a major environmental impact owing to the large amount of dye removed and the large amounts of water required. Furthermore, unfixed reactive dyes in the wastewater may pose an environmental hazard. In recent years, there have been many efforts to reduce the environmental effect of reactive dyeing and printing [5– 13]. The achievement of high dye fixation with reactive dyes, ideally close to 100% as in pigment printing, would therefore be of great benefit. The chemical modification of cotton in order to improve its dyeability with anionic dyes such as reactive, direct, acid, sulphur and vat dyes has received considerable attention in recent years. All of the pretreatments introduced cationic groups in the form of quaternary, tertiary or secondary amino residues. In this way, anionic reactive dyes are attracted by the cationic charges on the fibre, and as a result a high degree of dye– fibre fixation, a reduced washing off procedure, reduced or no electrolyte use, and equivalent wet fastness pro- perties with the untreated cotton can be obtained [14–32]. Unlike dyeing, to date only a few research papers have been published on the printing of cationised cotton fabrics. Martini described a method for the production of pattern effects via cationisation and oxidation [33]. Another similar process was developed by Shin et al. for obtaining patterned dyeings [34]. Both of these methods can be used for mono colour (different tones) pattern effects. Tabba and Hauser showed that the wash fastness and crock fastness of pigment prints can be improved, and fixation time reduced, by the cationisation of cotton fabrics [35]. In this study a nonpolymeric cationic reactant, 2,3- epoxypropyltrimethylammonium chloride, was used. Application and optimisation parameters of this reactant to dyeing processes have been investigated in detail by Tabba and Hauser and others [25–31]. Other workers have used very similar chemistry to improve the dyeing of cotton with direct and reactive dyes [32]. This present work has focussed on studying reactive printing with cationically-modified cotton (cationic cotton). Experimental Materials A scoured and bleached, optical brightener-free woven (twill 3:1) 100% cotton fabric, with a weight of 235 g/m 2 and a density of 46 threads/cm in the warp and 20 threads/ cm in the weft directions was used throughout this study. As the cationic reagent, 3-chloro-2-hydroxypropyl- trimethylammonium chloride, which is commercially avail- able as a 69% solution in water (CR-2000, Dow Chemical), was used. The dyes used were CI Reactive Yellow 181, CI Reactive Red 218, CI Reactive Blue 72 (turquoise) and CI Reactive Blue 99 (navy blue). All dyes were in liquid form and were obtained from commercial sources. A synthetic thickener, Alcoprint RTA, and an oxidising agent, Rezerv E Salt Flake (sulphonic acid sodium salt), both supplied by Ciba, were used for the printing pastes. Three commercial washing agents, Rucotex KST 150 (naphthalene sulphonate, an anionic after-washing agent), Hydrocol SIX (alkylaryl sulphonate, an anionic reserving and fixing agent for polyamide fibres) and Rucocleaner MU (alkylamine