Part 1: Cationization of Cotton Terry Towel Fabrics by Exhaustion Method; Labscale and Commercial Scale Trials

The incompatibility of cotton fibres with numerous dyestuffs can be addressed through the utilisation of considerable quantities of electrolytes. Nevertheless, the extensive utilisation of electrolytes during reactive dyeing inevitably results in the formation of a significant volume of wastewater. To address this challenge, cotton is cationized with cationic agents, thereby enhancing its dyeability with anionic dyestuffs. This study was derived from the findings of a doctoral thesis conducted as a result of a collaborative project between Pamukkale University and Ozanteks Textile Company, a prominent towel and bathrobe manufacturer in Turkey. This research paper consists of two parts. The first part of this reseach paper consist of two sections. In the initial section of this paper, 100% cotton terry towel fabrics were subjected to cationization procedures during and after the bleaching process in a laboratory setting, utilising six distinct commercial cationization agents. Subsequently, the cationized cotton terry towel fabrics were subjected to dyeing processes, namely salt-free reactive dyeing, conventional reactive dyeing, and acid dyeing. The CIELAB values, rubbing and washing fastness, and colour strength (K/S) values of the cotton terry towel fabrics were compared. Subsequently, a decision analysis study (analytical hierarchical process, AHP) was conducted to identify the optimal cationization agent and processes for big commercial-scale applications. The criteria included color strength, colour fastness, and cationic agent cost. In light of the findings of the AHP studies, CA1 coded cationization agent (based on polyammonium compounds) was identified as the optimal cationic agent for utilisation in commercial dyeing, the specifics of which will be outlined in the subsequent paper. Moreover, the findings indicated that cationization should be carried out after bleaching. The second section of the paper presents the results of big commercial scale cationization, reactive and acid dyeings carried out using the selected cationization agent and processes. After commercial scale dyeings, colour strength (K/S) values, physical properties (tensile strength and water absorbency properties) and colour fastness properties (washing fastness, perspiration fastness, water fastness) of cotton terry towel fabrics were analyzed. Furthermore, a comprehensive investigation was conducted into the environmental impacts of cationization and dyeing processes on a commercial scale. This investigation encompassed the analysis of ammonium nitrogen (NH4+), chemical oxygen demand (COD) values, overall water usage, chemical consumption, and energy consumption in the context of these dyeing processes. The outcomes showed that, color strength values of salt-free dyeings were close to the conventional dyeings and it is a promising approach for cationization and salt-free dyeing. Additionally, AATC79, EN 14697 and ASTM 4772 test results showed that, salt-free dyeing process had really high absorbency values. Moreover, salt-free dyeing process saved 28% in total chemical consumption, 31% in total water consumption and 16% in total energy consumption when compared to conventional dyeing process. This work demonstrates a promising commercial scale cationization and dyeing process for cotton terry towel fabrics. The second part of the study examined the cationisation of cotton fabrics used for bed sheets - an important home textile product - using the pad-batch method, followed by dyeing.

Woven fabrics are generally dyed in open-width form (with the fabric spread out), which is why pad-batch dyeing processes are typically preferred for woven fabrics. In other words, rope dyeing is not commonly used for woven fabrics. Rope dyeing can cause crease marks and uneven dyeing on woven fabrics. Therefore, the first part of the article describes the cationisation and dyeing of towel fabrics using the rope dyeing method (exhaustion), while the second part describes the cationisation and dyeing of bed sheet fabrics using the open-width dyeing method (pad-batch). The CIELAB values, rubbing and washing fastness, and colour fastness (K/S) values of the cotton bed sheet fabrics were statistically compared.