Influence Of Neutral Salts, Alkalis And Soluble Polymers On Aggregation Of Reactive Dyes

During continuous dyeing, low ratio dyeing, ink jet printing and conventionalexhaustion dyeing, some reactive dyes often aggregate because of the high concentrationsof dyes, neutral salts and alkalis. The aggregation of reactive dyes has negative influenceon their sorption and diffusion and dyeing levelness, and increases the quantity of loosecolor on fiber surface and the difficulty of soaping-off, thus decreases the fastness to washand rubbing. As for Ink Jet Printing, dye aggregates jam the nozzles. The research on theaggregation of reactive dyes is of importance, for the improvement on thecommercialization, and the quality of dyed and printed products. In this paper the influenceof neutral salts, alkalis and water soluble polymers on the aggregation of reactive dye wasinvestigated by UV-Visible spectrophotometry. The application of water-solublepolyacrylic acid and acrylic/maleic copolymers to reactive dyeing and soaping-off was alsoperformed with the aim at selecting appropriate water-soluble polymers as dyeingauxiliaries and washing agents(1) Aggregation of reactive dyes in neutral salt solutionThe aggregation of reactive dyes in neutral salt solution was increased as theconcentration of the neutral salt solution were increased. The sulfatoethylsulfone dyes withsmall molecules had low aggregation degree, The sulfatoethylsulfone dye containingcopper phthalocyanine chromophore exhibited high aggregation degree and two peaks invisible absorption spectrum, which corresponded to the monomer and dimmer absorption, respectively. The aggregation degree of the reactive dyes with H-acid structure varied fromtheir chromophores and reactive groups, and among these dyes, C.I. Reactive Red 120 hadvery high aggregation degree and multiform aggregates in concentrated sodium sulfatesolution.(2) Aggregation of reactive dyes in neutral salt and alkalis solutionUnder the room temperature, when sodium carbonate added to the sulfatoethylsulfonedye solution with neutral, parts of dyes hydrolyzed and eliminated, the hydroxyls in thedyes were ionized, the sodium ion also some effects on the aggregation of the dyes, but generally speaking, the aggregation of this kind of dyes changed little. As for C.I reactiveRed 120, its wavelength moved toward shortwave when the alkalis were added into the dyesolution. The maximal absorbance decreased markedly, the aggregation degree of the dyeincrease.Compared the reactive dyes in neutral salts solution through heating treatment, thesulfatoethylsulfone was eliminated immediately, the sulfatoethylsulfone dyes changed intoethylsulfone dyes hydrolyzed. So the aggregation of the sulfatoethylsulfone dyes wasdecided buy a great deal of elements. The aggregation degree of C.I. Reactive Orange 16with small molecules had a bit change after heating, the aggregation degree of C.I Blue 19with small molecules decreased after heating, while the C.I Reactive Blue 21 aggregationgreatly, the aggregation degree changed a bit during the heating process. As for C.IReactive Red 120, the hydrolyzed dyes were increased as the heating time went on. It wasmarkedly that dyes aggregation with hydrolyzed dyes.When the neutral salts were added to the reactive dyes Solution with alkalis in mediumtemperature, the aggregation degree of the reactive dyes were increased, but its sensibilityto neutral salts were determined by the dyes. The neutral salts had little effects in the C.IReactive Orange 16 and C.I Reactive Blue 19 with small molecules. As for C.I ReactiveRed 120, the aggregation degree had four while C.I Reactive Blue 21 is sensibility toneutral salts in alkali condition, the aggregation degree was high when the dye solutionwith alkalis were heated in 60℃.(3) Effect of water-soluble polymers on the aggregation of reactive dyes.Each soluble polymer can released the reactive dyes from aggregating, the ability wasdifferent cause of the dyes and polymers. The polymer had les function on dyes with smallaggregation degree, and it had higher function as aggregation degree of the dyes was high,the capability of the polymer was increase as the polymer's concentration was grown. Ingenerally speaking, the ability of MA-AA was better.(4) The application of water-soluble polymers to dyeing and soaping of the dues.Water-soluble polyacrylic acid and acrylic/maleic copolymers had the effect on antireaetivedyes speckling. When they used as soaping agent they almost had no influence onexhaustion, fixation of reactive dyes and K/S value of dyeings.When PAAS was used as soaping agent, and there were not any other soaping agent,PAAS had function of anti speckle and washing the loose color on the fiber surface like other two agent which were sold in the market, but it had no effect on C.I Reactive Red120. HPMA, MAAA, AA-AMPS had non effect of anti speckle. When Ca²⁺ were addedinto the C.I. Reactive Red 120 soaping solution, PAAS gave the best play to wash theloose color on the fiber surface. PAAS had the best effect on washing the loose color onthe fiber surface in C.I. Reactive Red 120 solution, it could acquired excellent effect in badwater quality. According to the fastness results, PAAS of the fastness to washing wascorresponded to other two agents which were sold in the market, and it was of benefit tofastness to rubbing.