Dyeing Acceleration Of Small Molecular Organic Cations On Dyeing Silk Fibers With Reactive Dyes

The silk is known as the "Fiber Queen", and silk is the traditional high-end apparel fabrics. The traditional silk dyeing commonly uses acid dyes, acid mordant dyes, with mordant dyes, direct dyes, which the fastness to washing of dyed silk is lower. In recent years, reactive dyes are also increasingly used for silk dyeing. The reactive dye molecules can react chemically with the silk fibroin molecules to form a covalent bond, so the fastness to washing of dyed silk is very high, that are able to reach more than4generally. However, the fixation rate of the reactive dyes on silk is very low, and the dyeing process requires a lot of neutral salt promote dyeing. The chroma of dyeing wastewater and salt content is high, the pollution is serious, and the processing load is big.In recent years, in order to improve the fastness to washing of dyeing silk and reduce the pollution of dyeing wastewater, scholars have done a lot of research. For example, suspension staining method, that is, adding some additives to make the dyes aggregate to form a suspension during dyeing; using disperse dyes, dispersed reactive dyes and acid dyes dyeing silk in supercritical carbon dioxide conditions; dyed silk with sulfur dyes; Silk was modified by grafting cationic or chitosan; introduction of the hydrophobic chain or amino-polymerase chain with different forms in reactive dye molecules.This paper designs a high efficiency acceleration-dyeing principle of new kind of silk fabric with reactive dyes. The acceleration effect of a series of small molecular organic cations as an accelerant agent in dyeing silk fiber with reactive dyes was studied. The study includes the acceleration effect of the reactive dyes on dyeing silk using five kinds of small molecules organic cations. The color fastness of dyed silk acceleration-dyeing with small molecules organic cations was studied. We studied dye adsorption rate curve of reactive dyes on dyeing silk fiber using small molecules organic cations and sodium sulfate as additives respectively, and analysis the staining kinetics and thermodynamics by using the quasi-first and quasi-second order adsorption kinetics simulation equations to fit the experimental data. We analysis that concentration of small molecule cation and temperature influenced on the reactive dye solution absorption spectrum curve. We also analysis that concentration of accelerant influenced on the surface potential of the silk fabric. The results show that:(1) Small molecules organic cationic has a high efficient role in promoting reactive dyes on dyeing silk, which displayed the high dyeing rate and fixation rate. The greater hydrophobicity of small molecule cation was, the better accelerant role on reactive dyes would be. So the acceleration effect of cetyl trimethyl ammonium bromide was the best, which the dye uptake were closed to100%. When dodecyl trimethyl ammonium bromide used as an accelerant agent, the dyeing rate close to98%.When the carbon atom number of the longest hydrophobic hydrocarbon chain of small molecules cationic was greater than or equal to12, the cation hindered the fixing reaction between the reactive dye molecules and fiber macromolecules, which resulted in lower fixation rate (less than85%). When the number of carbon atoms was less than or equal to8, the cation did not hinder the reaction of the reactive dye fixing, but also promoted fixing reaction, which made the rate of fixation and dye uptake was about98%. Utilization ratio of reactive dyes was increased, and the chroma of dyeing wastewater was reduced.(2) When small molecules organic cation was at lower concentrations (2-6g/L) as an accelerant agent of reactive dyes on dyeing silk, it could be get a higher dyeing rate and fixation rate. Compared with the neutral salt accelerant-dyeing, concentration of accelerant agent decreased more than40times.(3) It were studied that color fastness of dyed silk with three accelerant agents-octyl trimethyl ammonium chloride, hexyl butyl dimethyl ammonium bromide and di-hexyl dimethyl ammonium bromide. The color fastness of dyed silk with small molecules organic cations were equal to or even higher than sodium sulfate accelerant agent, which all were more than four grade, part of the fastness to washing could even reach five.(4) When small molecules organic cation was used as an accelerant agent of silk fiber reactive dyeing, dye initial adsorption rate was higher than the sodium sulfate to promote dye. The higher the temperature was, the higher the initial dye adsorption rate would be. The dyeing equilibrium was achieved in30min, final equilibrium adsorption capacity varied with temperature. Sodium sulfate as an accelerant agent, the impact of temperature on dye adsorption rate was greater. The dye began balance after50min. The higher the temperature was, the greater the equilibrium adsorption capacity would be, but it still was lower than small molecules organic cation as an accelerant agent.(5) When reactive dyes dye silk fiber using small molecules organic cation as an accelerant agent, the adsorption process fit the quasi-second order kinetic adsorption simulation equations, and it was fairly consistent between the equilibrium adsorption capacity by fitting curve calculated and the experimental values.(6)The concentration of small molecular organic cation had an effect on the absorption spectrum curve of reactive dye solution. The higher concentration of small molecules organic cation was, the lower absorbance of the same dye concentration would be, and the maximum absorption wavelength moved3～5nm to longer wavelengths. The higher the temperature was, the higher the absorbance would be, the maximum absorption wavelength moved2～7nm to short wave. It was indicated that there was interaction between small molecular cations with reactive dyes. Maybe cations formed ion pair with reactive dye anions, which made the dye charge were neutralized partly and dye molecules aggregated, thus the water-soluble of anionic dyes was reduced. Therefore the substantivity of reactive dyes was be increased in favour of dyeing.(7) The higher concentration of sodium sulfate was, the smaller absolute value of the surface potential of the silk fabric would be. Sodium sulfate at a concentration of30g/L, the fabric surface potential reached balance basically, but still negative. When the concentration of small molecular cation in the dye liquor was still very low, the absolute value of the fabric surface potential declined sharp. This indicated that the small molecular cation could effectively compress the diffuse double layer. When concentration of small molecular cation was large slightly, fabrics potential became to positive eventually. This showed that the small molecular organic cation can neutralize effectively carboxyl of silk fibroin macromolecules and the negative charge of reactive dyes dyed on the fabric. And the remaining amino ion had positively charged, so it made the surface potential become to positive eventually. These was conducive to reactive dyeing silk in particular.