Study On The Aggregation Performance Of Reactive Dye Solution With High Concentration

As a common phenomenon, the aggregation of dyes has an effect on the diffusion of dye in the solution, the adsorption and the bonding between dyes and fabric which will affect the final effect of dyeing, In many commonly technologies such as dyeing with small bath-ratio, dyeing with cold pad-batch, liquid reactive dyes and so on, the condition of the reactive dye molecules in solution become more complex which is due to the high concentration of reactive solution. Therefore it is imperative to detailed study the state of dye molecules in solution. This paper take reactive orange13as the main object, in discussion the aggregation performance of reactive dye solution with high concentration by viscosity, conductivity, ultra micro spectrophotometry and the testing of the particles’diameter.Firstly, the correlation between the changes of conductivity of reactive dye solutions and its aggregation in different conditions was studied. The results showed:1) The change of dye solution’s conductivity was related to the structure of dye molecule. The reactive dye solution with more simple structure of dye molecule and water soluble groups had higher conductivity and smaller trendy to aggregate. The conductivity of reactive dye solution was directly proportional to the concentration and temperature. However, the critical intervals were respectively observed:the concentration was30-40m mol/L and the temperature was about50℃, in which the change rate of conductivity was different with others. And it was mainly due to the co-effect of the inhibition of ionization by aggregation of dyes in high concentration and the disaggregation of dyes by raising the temperature. 2) Additives such as sodium sulfate would exacerbate the aggregation of dyes because of the common-ion effect. But the conductivity of dye solution was increased when the concentration of sodium sulfate was less than3g/L which was beneficial to promote the dissolution of dye, and the reason should be attributed to the salt-effect of trace electrolyte; Additives such as anionic surfactant had significant effect on improving the stability of dye solution at50℃.Secondly, the viscosity and its change rules of reactive dye solution with high concentration in different situation were studied. The results indicated:1) In general, the viscosity of reactive orange13solutions were increased as the dye concentration increased. Rising temperature or pH value would reduce the viscosity of solutions and make the dyes disaggregate. However, abnormalities were existed under high concentration: the viscosity of reactive dye solution suddenly raised when its concentration was higher than70mmol/L; The viscosity of high concentration dye solutions (>80mmol/L) had a trendy of increasing firstly and then decreasing among50-70℃; The viscosity of dye solution with certain concentration was abrupt decreased between pH=5-6. All of these changes would be contributed to the state change of aggregation and disaggregation of dyes in high concentration solution.2) The addition of electrolytes would lead to the viscosity of reactive orange13solutions with high concentration present an approximate linearly increase which indicated the serious aggregation of dyes. But it could be alleviated by raising temperature. In addition, when anionic surfactant was added at an appropriate temperature, the viscosity of the solution was increase while the stability of the solution might be increased. However non-ionic surfactants made less influence on the viscosity and the aggregation of dye solution.Thirdly, the aggregation of reactive orange13solutions of high concentration was studied by the UV/Vis spectrophotometry combined with the test of particle size. The results showed:1) When it comes to the solutions with high concentration, a large bathochromic shift of its maximum absorptive wavelength (λmax) and the increase of particle size were induced. This phenomenon implied the formation of different dye molecules aggregates; With the rising of temperature or pH value, the λmax of dye solution (40mmol/L) had a hypsochromic shift and the particle size decreased that indicated they had contributions to the significantly disaggregation of dye aggregates. But the temperature didn’t cause complete disaggregation in respect that the λmax of solution only shifted to495nm.2) By contrast, when electrolytes containing different metallic ions were added, all the λmax of the reactive orange13solutions showed bathochromic shift. And along with the change of the particle size, it was reflected that a great aggregation of dye molecules would be occurred with the addition of electrolyte. The effect of different ion which had the same valence on the aggregation have a law of K+>Na+>Li+, while the effect of bivalent ions (Ca+, Mg+)on the aggregation is much greater than monovalent ion (Na+).3) Urea had a remarkable effect on the dissolution of the reactive dye in solution (40mmol/L) at50℃. The dissolve effect reached the maximum when the amount of urea was150-175g/L, then the λ max and size were invariability even continue adding urea. Compared to urea, TM-1was better for dissolution and depolymerization of dye solutions because less dosage of TM-1could obtain the same effect as urea (10%). However, the water-soluble substances such as sodium polyacrylate, polyvinylpyrrolidone and maleicacid/acrylic copolymer just played a limited role in the disaggregation of dye aggregates under certain conditions.