Development of Luteolin–Trehalose Environmentally Friendly Auxiliary Agent and Its Application to the Optimization of Process Parameters for Dyeable Wool Fabrics

Auxiliary agents are essential in textile dyeing for improving dye evenness, adhesion, and overall performance, yet traditional agents with high phenolic content can cause oxidation and toxicity, posing environmental and health risks. To overcome these issues, eco-friendly, water-soluble polyphenol sugar auxiliary agents, named LP2T, LP4T, LP6T, LP10T, and LP20T, were synthesized by modifying poorly soluble luteolin using polyethylene glycol with molecular weights of 200–2000 as hydrophilic segments and trehalose as a stabilizing component. Compared with commercial agents SDS and Triton X-100, the luteolin–trehalose agent, particularly LP20T, demonstrated superior dyeing evenness and dye uptake. Using Taguchi design and Grey relational analysis (GRA), the study optimized key dyeing parameters including auxiliary type, temperature, dye concentration, auxiliary concentration, and dyeing time for wool fabric. Optimal conditions for single-quality performance were achieved with LP20T at 90 °C, 1.25% on weight of fabric, 1 g/L, and 60 min for evenness, and at 90 °C, 0.5% on weight of fabric, 0.25 g/L, and 30 min for dye uptake. Multi-quality optimization identified LP20T at 75 °C, 0.25% on weight of fabric, 0.50 g/L, and 40 min as the best overall condition, resulting in excellent evenness and high dye uptake compared to SDS and Triton X-100. This study demonstrates that the luteolin–trehalose auxiliary agent achieves high dyeing performance with reduced temperature, time, and chemical use, enhancing production efficiency while minimizing cost, pollution, and ecological impact, providing a sustainable solution for textile dyeing.