Clean production and dyeing of fluorescent yellow dyes based on naphthalic anhydride in supercritical carbon dioxide

Supercritical carbon dioxide (scCO₂) was selected as the medium for the synthesis and dyeing of four naphthalimide dyes (Y-1, Y-2, Y-3, and Y-4). They were synthesized through the reaction of 4-bromo-1,8-naphthalene dianhydride with various amines. These dyes demonstrated good photophysical properties and thermal stability, aligning with the prerequisites for scCO₂ dyeing. Consequently, the scCO₂ dyeing of polyester fabrics using these four dyes was investigated, and the optimal dyeing conditions were established in the range of 1820 MPa, 120130℃, and 8090 min. Surface analysis confirmed the uniform distribution of the dyes on the fabrics, with no significant damage to the fabric structure under the dyeing conditions. Additionally, the dyed fabrics exhibited good color fastness to soap washing and friction with level 4 or above. Overall, the clean preparation and dyeing of naphthalimide dyes hold promise for reducing environmental pollution.