Abstract:

Objective In the process of dyeing with reactive dyes, there are problems such as easy hydrolysis of reactive groups, low fixation and dye utilization rates, and high consumption of inorganic salts. Dyeing accelerants provide an effective way to solve these problems, as they can act as bridging groups to achieve covalent bonding between hydrolyzed dyes and fibers. A double active group dyeing accelerant with quaternary ammonium cationic and epoxy groups was designed and synthesized in this article. The epoxy group in its molecular structure can undergo bonding reactions with fibers, and the quaternary ammonium salt cationic groups can form ionic bonds with hydrolyzed dyes and unfixed dyes.

Method Trimethylallyl ammonium chloride (TMAAC) and allyl glycidyl ether (AGE) were used as reaction monomers to synthesize a double active group dyeing accelerant with epoxy and quaternary ammonium salt structure through free radical polymerization reaction. The synthesis process was optimized, and the molecular structure and thermal properties of the synthesized products were characterized. Dyeing accelerant was applied to cotton fabric dyeing, using Reactive Red 3BFN, Reactive Yellow HER, and Reactive Blue RGN as the dyes. The fixation rate, apparent color yield, and color fastness were tested.

Results The conversion rate of polymerization reaction increased with the increase of monomer AGE and TMAAC mass ratio. Initiator can accelerate the generation process of free radicals, but a large amount of free radicals were triggered when the dosage of initiator is too high, leading to collisions and quenching between free radicals, which would reduce the efficiency of the polymerization reaction. The conversion rate of polymerization reaction showed an increase with the increase of reaction temperature and reaction time, but excessive polymerization temperature would lead to chain cracking and side reactions. The research result analysis revealed 80 ℃ and 6 h as the optimal reaction temperature and reaction time. Infrared spectroscopy testing showed that the allyl double bonds in TMAAC and AGE disappeared. Thermogravimetric analysis tests showed that the dyeing accelerant has good thermal stability. The starting temperature for thermal decomposition was 165.80 ℃. The maximum weight loss rate temperature was 407.33 ℃. The apparent viscosity of the dyeing promoter decreases with increasing shear rate, which is consistent with the characteristics of pseudoplastic fluids. In the frequency range of 0.1-202 rad/s, the storage modulus G' is lerger than loss modulus G", the loss coefficient tanδ is lerger than 1, the elastic effect was dominant. When the angular frequency is greater than 202 rad/s, G'<G", tanδ>1, the viscous effect was dominant.

Conclusion To solve the problems of low fixation rate and high consumption of inorganic salt in reactive dyeing, a dyeing accelerant with double active group was synthesized through free radical polymerization reaction. The optimized process condition for synthesizing dyeing accelerant was that the dosage ratio of monomer AGE and TMAAC was 1∶3, initial concentration of total monomers was 30% of the total mass of the system, initiator dosage was 0.5% of the monomer mass, reaction temperature was 80 ℃, and reaction time was 6 h. Infrared spectroscopy testing showed that the synthesized product exhibited characteristic absorption peaks of epoxy groups and quaternary ammonium salts. Thermogravimetric analysis testing showed that the dyeing accelerant had good thermal stability below 300 ℃. By using dyeing accelerant during the dyeing process, the average fixation rate had been increased by 22.6%, and the consumption of inorganic salts can be reduced by 66%. Dyeing accelerant can play a bridging role between dye molecules and fiber molecules, significantly improving dye utilization and reducing inorganic salt onsumption. It has good application prospects in the field of printing and dyeing processing.

Key words: dyeing accelerant, free radical polymerization reaction, reactive dye, fixation rate, inorganic salt, dye uptake, dyeing assistant