Bio-based cardanol formaldehyde sulfonate: synthesis, characterization and textile application as a dye leveling agent

Purpose The increasing demand for sustainable dyeing auxiliaries has led to the development of bio-based alternatives to petroleum-derived agents. This study aims to thoroughly evaluate these newly synthesized leveling and dispersing agents (DAs) by examining the dyeing of polyester fabrics with disperse dyes (C.I. Disperse Red 60 and C.I. Disperse Blue 56) at various DA types and concentrations. Design/methodology/approach In this work, the authors synthesized a series of bio-based cardanol formaldehyde sulfonate oligomers (CFSO) from renewable cashew nutshell liquid (CNSL). Using four different sulfonating agents – sodium bisulfite, sodium dithionite, sodium hydroxymethanesulfinate and sodium formaldehyde bisulfite – followed by formaldehyde condensation, the authors created a range of materials with diverse molecular structures. Extensive characterization through FTIR, 1H NMR, GPC, PXRD and thermal analysis confirmed their stable, low-molecular-weight nature, showing their resilience in high-temperature dyeing processes. Application trials with C.I. Disperse Blue 56 and C.I. Disperse Red 60 on polyester fabrics demonstrated significant improvements in dye exhaustion and color uniformity with the CFSO samples. Compared to traditional dispersing and leveling agents, these bio-based oligomers more effectively reduced uneven dyeing, indicating a more controlled and efficient dyeing process. Findings When tested with C.I. Disperse Red 60, all CFSO series consistently surpassed both Setamol® WS and sodium naphthalene formaldehyde sulfonate (SNF) in dispersing efficiency. For C.I. Disperse Blue 56, only CFSO-SB exhibited superior performance relative to the two commercial dispersants. Originality/value Derived from renewable CNSL, the CFSO series provides a high-performance, biodegradable alternative to petroleum-based auxiliaries in polyester dyeing. Even at low concentrations, these bio-based agents achieve leveling effects comparable to industry standards, effectively supporting the goals of green chemistry in textile processing.