Synthesis, Properties And Theoretical Study Of Dye-polyether Derivatives As Hyper-dispersants

China now is the largest disperse dyes producing and exporting country in the world. The extensive use of dispersants in the dye commercialization results in a serious problem of water pollution due to the remaining dispersants in the dyeing effluent. The main purpose of this research is to reduce the dosage of dispersants by increasing their efficiency, and ultimately reduce the environment pollution from polyester dyeing. Focuses on this purpose, a class of new hyper-dispersants (dye-polyether derivatives) was designed and synthesized. The dispersing efficiency of dye-polyether derivatives on the parent dye dispersion was studied, the application performance of the dispersions was investigated, and the hydrolysis behavior and mechanism of hydrolysable dye-polyether derivatives were explored. Bridged on the scaling laws, the colloid theoretical modeling method was used to study the mechanism of dye-polyether derivatives in the dispersion system, and the computer simulation method was applied to analyze the adsorption behavior of the dye-polyether derivatives as well. The emphasis was to study the influence of the molecular structure on the dispersing efficiency. The main contents and results were listed as follow:(1) Based on the dye-polyether derivatives structure as target hyper-dispersant, a series of polyether derivatives of C. I. Disperse Yellow 64 was prepared by the substitution reaction between the poly(oxyalkylene) ethers and the dye, and a series of derivatives of C. I. Disperse Red 60, a series of derivatives of C. I. Disperse Blue 73 were prepared by the reaction between the poly(oxyalkylene)-isocyanates and C. I. Disperse Red 60, C. I. Disperse Blue 73, respectively. These products were characterized by FT-IR,1H NMR, SEC and amine titration, which indicated that the structures of obtained dye-polyether derivatives were correspondence with the designed structure. (2) The dispersion efficiency of the dye-polyether derivatives on the parent dye dispersion was investigated and the results indicated that the introduction of anchor group, the dye molecule, into the polyether was beneficial to enhance the affinity to the dye particle and increase the dispersion efficiency. It was also showed that their dispersion efficiency was greatly affected by the hydrophobicity of corresponding polyether, and increased with the increasing hydrophobicity within the experimental range. Totally speaking, the efficiency of the dye-polyether derivatives on the parent dye dispersion was high and they could stable the parent dye dispersion even at the dye to dye-polyether derivative weight ratio of 10:1. Temperature and pH had effect to a certain extent on the dispersion stability. The dispersion was applied for polyester dyeing and the results indicated that the dye uptake increased with the decreasing amount of dye-polyether derivative containing in the dye-bath, and was higher than that of conventional commercial dye. The leveling properties of the dyed fabrics was as good as that dyed with commercial dye while their levelness and fastness to soaping and rubbing were at least as good as the fabrics dyed with commercial dye at the same dyeing concentration. However, the COD values and the absorbance of the dyeing effluent were far lower than that of commercial dye because the less amount of dispersant was used and thus less amount of solubilized dye was left in the dye-bath after dyeing.(3) The results of hydrolysis behavior research showed that the urea-linked dye-polyether derivative could be hydrolyzed under certain conditions, and the hydrolysis rate increased with the increasing temperature, pH and hydrophilicity of polyether. The hydrolysis of dye-polyether derivative could be catalyzed following the addition-elimination mechanism under acid or alkali condition to reproduce dye, polyether and CO2, respectively. When [OH-] concentration hold constant, the hydrolysis of the dye-polyether derivative is the pseudo-first-order reaction and the reaction-rate constant increased with the increasing hydrophilicity of polyether. Most of the dye-polyether derivative was hydrolyzed under the condition of 130℃and 60 min when the pH was higher than 9, and the hydrolysis rate was quite low at the temperature of 85℃, which matched the prerequisite of designed hyper-dispersant in this research that the proposed dye-polyether derivatives shall be stable enough during storage and most of them should have been hydrolyzed at the end of dyeing.(4) The adsorption behavior of dye-polyether derivatives on the surface of parent dye particles was studied and the results showed that the whole adsorption process could be simulated by Langmuir-1 adsorption model, that is, a progressive increase of the amount of the adsorbed dye-polyether derivatives until an adsorption plateau corresponding to the saturation of the surface of the parent dye particles was reached. Under saturated adsorption, the chain distance and the adsorption energy of the dye-polyether derivatives were relevant to the hydrophobicity and the molecular weight of corresponding polyether. Based on the relevant information from the adsorption results, scaling laws was used to deduce the situation of adsorption layer. The results indicated that all the polyoxyethylene chains point toward the water in an extended brush configuration, the thickness of adsorption layer increased with the increasing molecular weight, and the chain density related to the molecular weight and the asymmetry of the corresponding polyether. In the dye dispersion system, the dye-polyether derivatives were nearly reached saturated adsorption. The surface coverage of the dye particle related with the hydrophobicity of the dye-polyether molecular, and decreased with the decreasing particle size and the reducing dosage of dye-polyether derivatives. Most of the dye-polyether derivatives were remained in the solution after equilibrium adsorption. Based on the informtion about adsorption layer, a further study of the dispersion system was carried out on the basis of polymer steric stabilization theory by using colloid theoretical modeling methods. The results had shown that the most important factor affecting the dispersion stability was the adsorption thickness. The dye-polyether derivatives could provide strong steric hindrance for particle collisions under saturated adsorption. At the dye to dye-polyether derivative weight ratio of 10:1, where the adsorption was close to saturation, the dispersion was theoretical stable. However, this conclusion excluded the factors of dynamic balances.(5) Computer simulation was also used to study the adsorption mechanism of dye-polyether derivatives in the dispersion system. The crystal morphology of C. I. Disperse Red 60 was predicted, and the growth rate of crystal faces related to the atoms and groups and their arrangements placed on the faces. By suing molecular dynamics method the adsorption behaviors of polyethers and dye-polyether derivatives model molecular on the four main crystal faces of C. I. Disperse Red 60 were simulated under vacuum environment. It was showed that the binding energy was relevant to both the crystal faces and the polymer structure. The polar groups on the faces and the small angle between aromatic rings and faces were beneficial to the formation of intermolecular hydrogen bonds andπ-πstacking, and thus increased the binding energy. The binding of dye-polyether derivatives to the crystal faces was stronger than that of polyethers due to the formation ofπ-πstacking between the dye aromatic rings of dye-polyether derivatives and the faces. The binding energy also increased with the increasing molecular weight of polyethers and dye-polyether derivatives. The adsorption behaviors of polyethers and dye-polyether derivatives on{0 0 2} surfaces of C. I. Disperse Red 60 were simulated under the situation of water solution. It was indicated that the dye-polyether derivatives system was more stable than the polyether system under the adsorption equilibrium, the dye section and the polyoxypropylene chain adsorbed on to the surface while the polyoxyethylene chain structural relaxed in the solution. The mesoscale simulation of polyethers and dye-polyether derivatives solution and dispersion systems had been carried out by Dissipative Particle Dynamics. The results showed that the solution exhibited various mesoscopic morphologies with the changing concentration relating to the molecular structure; the more hydrophobicity of the molecular, the more prone to phase separation and the easier formation of single scattered micelles. Self-aggregation of polyethers and dye-polyether derivatives in solution and adsorption onto the particle surface coexist; owing to the hydrophobicity of dye-polyether derivatives was higher than that of polyethers, their self-aggregation tendency was stronger and the adsorption amount was greater as well. The simulation results were consistent to some extent with that of experiment, which will give some helpful informations for the molecular design of hyper dispersants with the further improvement in the experiment and modeling method.