Abstract:

Objective Aiming at many deficiencies in wool dyeing technology, such as the complex conventional dyeing process, high energy consumption, and harsh reaction conditions, a new type of mercerized wool reactive dyeing technology is developed. First, isatoic anhydride is adopted to perform aromatic primary amination modification on mercerized wool. Then, azo pigments are generated in situ on mercerized wool through diazotization and coupling reactions, achieving rapid reactive dyeing at room temperature. The in-situ synthesis and covalent fixation of dye molecules in the fiber matrix have been successfully realized.
Method In a DMF-water mixed system, isatoic anhydride was adopted to aminate mercerized wool, resulting in aromatic aminated wool. The modification rate of isatoic anhydride on mercerized wool was determined by the residual method. At room temperature, a mixed solution of hydrochloric acid (HCl) and sodium nitrite (NaNO₂) was adopted to diazotize the aromatic aminated wool. Further studies on the storage stability of diazotized wool under wet and dry conditions were conducted. Under room temperature and weak alkaline conditions, diazotized wool underwent coupling reactions with different coupling components, achieving coupling coloration and producing coupled colored woolen fabrics.
Results Mercerized wool was modified with aromatic primary amination, diazotization and coupled coloring modifications to achieve coloration. Diazotized wool reacted with different coupling components to produce different colors. Isatioc anhydride was completely hydrolyzed to o-aminobenzoic acid and the ultraviolet-visible absorption spectra of the hydrolyzed mixture was measured and the wavelength of its maximum absorbance was 309 nm. Using the standard working curve for hydrolysis of different concentrations of isatioc anhydride, the maximum consumption of isatoic anhydride modification on 1 g mercerized wool was found to be 0.022 5 g, and the reaction of diazotized wool with γ acid required 0.074 4 mmol γ acid. The K/S values of dry diazotized wool were basically unchanged after storage for different periods of time, indicating that the storage stability of dry diazotized wool was high. Fourier transform attenuated total reflection infrared spectroscopy characterization showed characteristic Infrared Spectroscopy peaks at different stages. Aromatic primary aminated wool showed an aryl ring adjacent disubstitution peak at 751 cm^-1 on the aryl ring, diazotized wool had a diazonium salt stretching vibration peak at 2 334 cm^-1, while the sulfonate characteristic peaks of coupled chromogenic wool were at 1 167 and 1 036 cm^-1. The color fastness to soap washing and color fastness to rubbing of the coupled colored fabrics were evaluated and the results showed that the color fastness to soap washing of the coupled colored fabrics reached level 4 and the color fastness to rubbing was level 3-4.
Conclusion The following conclusions can be drawn. 1) The acylation of isatioc anhydride can achieve a good aromatic amination modification on mercerized wool, with electron-rich groups such as amino, imino, hydroxyl, and mercapto as potential modification sites. The modification conditions of 40 ℃ and pH 8 are relatively mild, and under these conditions, the maximum modification reaction amount of isatoic anhydride on mercerized wool is 0.022 5 g. 2) Aromatic aminated wool can undergo a rapid diazotization reaction with nitrite at room temperature, and the resulting diazotized wool has excellent dry storage stability, with the K/S value remaining essentially stable within 10 d after coupled dyeing, which is favorable for long-term storage and application. 3) Diazotized wool can rapidly couple and color with coupling components of different structures under room temperature and weakly alkaline conditions, resulting in dyed mercerized wool with deep color and excellent color fastness performance. The depth value reaches 30, the color fastness to soap washing reaches level 4, and the color fastness to rubbing is above level 3. This is an energy-saving and efficient new reactive dyeing method for wool.

Key words: wool, isatoic anhydride, chemical modification of protein residue, diazo-coupling reaction, dyeing