Ecofriendly one-bath waterless dyeing: Systhesis of novel pyrazolone benzothiazole disperse dyes suitable for cotton-containing fabircs in supercritical CO2

Traditional dyeing utilizes a substantial amount of water and necessitates the incorporation of significant quantities of dyes, auxiliaries, and salts, leading to the discharge of highly concentrated organic wastewater and severe water pollution issues. In this study, a novel pyrazolone benzothiazole disperse dye and its triazine disperse reactive dye were designed with the same yellow shade and synthesized. The results showed that the synthesized dyes could successfully realize one-step dyeing of cotton, polyester, and polyester-cotton in supercritical CO₂. At 100℃, 24 MPa, 60 min, and 2.5 % (o.w.f.) of dye concentration, the K/S value of polyester-cotton fabric was 8 by using the same amount of disperse dye and disperse reactive dye. When disperse reactive dye was used at 100℃, 24 MPa, 60 min, and the concentration of 1.5 % (o.w.f.), the K/S value of cotton fabrics can reach 7.3, and their ${\sigma }_{K/S}$ values were less than 0.03 and 0.006, respectively. Moreover, polyester reached the maximum K/S value of 15.96 at 120°C, 24 MPa, 60 min, and a dye concentration of 2.0 % (o.w.f.) with disperse dye. The ${\sigma }_{K/S}$ value was below 0.045. The fastness of washing and rubbing was above 4. This study provides novel disperse dye structures and dyeing methods for ecofriendly textiles dyeing in supercritical CO₂, especially for one-bath low temperature dyeing polyester-cotton fabrics.