Study On The Mechanism Of Cold Pad Batch Dyeing Of Silk Fabric With Heterobifunctional(MCT/VS) Reactive Dyes And Alkali

Cold pad batch dyeing process of silk fabric is one of the key technologies to attain the aim of reduction of water and energy. In prior researches, cold pad batch dyeing industrialization had been carried out through studying cold pad batch dyeing technique of silk fabric and alternating cold pad batch machine. Reactive dyes were easily to hydrolyze as they exist with alkali together during the cold pad batch dyeing,and many groups of silk fabric could react with reactive dyes,so the stability of the fixation was a problem to be solved;At the same time ,alkali system contained a lot of sodium silicate in cold pad batch dyeing process.Although it had good pH stabilization and high fixation, it had bad effects on the hand-feel of textiles and adhered to equipments.Therefore, hydrolysis performance and reaction performances with the nucleophlic group of silk fibroin of rective dyes in cold pad batch dyeing were studied in this paper,and it provided a theoretical guidance for cold pad batch dyeing of silk fabric with reactive dyes.What was more,a new fixation alkali which improved the quality of silk fabric was studied in cold pad batch dyeing of silk fabric.In this article, a kind of heterobifunctional reactive dyes C.I.reactive blue 222 which contained monochlorotriazine reactive group and sulfatoethylsulfonyl reactive group was selected.The hydrolysis performance of C.I.reactive blue 222 at the condition of differernt pH value of room temperature(20℃～40℃) was investigated by applying high-performance liquid chromatography(HPLC) and colorimetry analysis. The results indicated that: sulfatoethylsulfonyl reactive group was first converted into vinyl sulfone at alkaline condition of room temperature,then vinyl sulfone and monochlorotriazine reactive groups began to hydrolyze, but the hydrolysis was not equilibria, vinyl sulfone was preferable to monochlorotriazine reactive groups. Under higher temperature or alkali, the later began to hydrolyze, and finally more and more dyes changed into hydrolyzed dyes .The reaction performance of the main nucleophilic groups of silk fibroin with C.I. reactive blue 222 at the cold pad temperature under different pH value was studied by the simulated reaction. Isopropylamine, p-methyl-phenol and methanol were using for simulating the amino groups, phenol groups and hydroxyl groups of silk fibroin respectively.The results showed that the proper aminolysis reaction pH value of the C.I. reactive blue 222 was 10～12,then the phenolysis reaction was 10～11,and the alcoholysis reaction was about 11. The sequence of integrated response capability of C.I.reactive blue 222 with the nucleophlic group of silk fibroin was amine groups> phenol groups > alcoholic groups. The proper reaction pH value was 10～11 at 30℃according to the nucleophilic reaction and distributions of the main nucleophilic groups of silk fibroin, and it had been verified by the experiments of cold pad-batch dyeing of silk fabric.The reaction competences of the main nucleophilic groups of silk fibroin with different reactive dyes were different.The reactivity of isopropylamine reacted with different reactive dyes: heterobifnuctional reactive dye (C.I.reactive blue 222)> sulfatoethylsulfonyl reactive dye (C.I.reactive blue 19)> monochlorotriazine reactive dye (C.I.reactive red 24);the reactivity of p-methyl-phenol: monochlorotriazine reactive dye (C.I.reactive red 24) >heterobifnuctional reactive dye (C.I.reactive blue 222)> sulfatoethylsulfonyl reactive dye (C.I.reactive blue 19); the reactivity of methanol: monochlorotriazine reactive dye (C.I.reactive red 24) >heterobifnuctional reactive dye (C.I.reactive blue 222)> sulfatoethylsulfonyl reactive dye (C.I.reactive blue 19). Furthermore, the results of the experiments showed that monochlorotriazine reactive groups still reacted with nucleophilic groups of silk fibroin even if vinyl sulfone reactive groups were hydrolyzed in the heterobifnuctional reactive dye (C.I.reactive blue 222)In order to improve the application limitation of fixation alkali containing sodium silicate in cold pad batch dyeing of silk fabric, a new fixation system which did not contain sodium silicate was worked out according to the conditions of nucleophilic reaction. It had good pH stabilization, and the dyed fabric could get deep colour and good handle.