A Sustainable Pad Dyeing Technology to Realize Clean Coloration of Biobased PA56 in a Nonaqueous Medium System

PA56, a biobased polymer polymerized from pentodiamine and adipic acid derived via biological fermentation, exhibits excellent performance characteristics. It has been widely used in the garment industry. In this paper, we used a nonaqueous medium (decamethylcyclopentasiloxane) as a heat method instead of the traditional steam fixation method to improve dye utilization on the PA56 fabrics and shorten fixation time. First, PA56 fabrics were pretreated to improve their wettability and levelness property by the synergistic action of a penetrant and a refining agent. The influence of fixation conditions, such as pH value, temperature, time, and wet pickup rate, on the K/S value was investigated to establish the optimal process for PA56 fabrics in the pad-D5 fixation method. It was found that the fixation rate of PA56 fabrics can reach 99.7% for C.I. Reactive Blue 19 at the optimal dyeing conditions (wet pickup: 20%, pH value: 11.0, temperature: 70 °C, and fixation time: 1.5 min). Compared with traditional steam fixation, the K/S value of dyed PA56 fabrics increased obviously. Additionally, FTIR, TGA, DSC, and XPS analyses further indicated that the nonaqueous medium had no discernible influence on the physical and chemical properties of PA56 fabrics. A higher color depth, constant mechanical properties, and good fastness were obtained by this dyeing method. Meanwhile, this technology can reduce energy consumption and save 29.0% reactive dyes compared with the steam fixation method. It also eliminated the prebake step. Therefore, this technology meets the current demand of energy savings and emission reduction. It is expected to promote the sustainable development of PA56 fabrics.