Study On The Reaction Differences Between Reactive Dyes And Different Nucleophilic Groups And Dyeing Controlling Technology For Multi-component Fabrics

Natural-fiber fabrics occupy an important position in the high-grade textiles, and the dyeing application of reactive dyes can effectively improve the color fastness of the natural-fiber fabrics. The natural-fiber fabrics of multi-components is regarded as the development trend for the high-grade textiles, however, reactive dyes remains the dyeing problems of poor reproducibility and controllability on single natural-fiber fabrics. So, there is no doubt that to achieve a controllable dyeing of reactive dyes on multi-components natural-fiber fabrics is quite a challenging job.In this paper, simulation reaction method and high performance liquid chromatography (HPLC) analysis technology were applied to deeply study on the reaction performances of five kinds of typical reactive dyes with four major nucleophilic groups in natural fibers, and the actual dyeing method was used to investigate the dyeing performances of reactive dyes with different active groups on cotton, wool, silk and their blend fabrics. Combined with the research results from simulation reaction method and actual dyeing method, we put forward the applicable reactive dyes for multi-component natural-fiber fabrics and regulation principle and method in dyeing process of reactive dyes in terms of reaction capacity, content and distribution of nucleophilic groups and the surface and physical structures of fibers.In the study of simulation reaction method, methanol, isopropyl amine, paracresol and ethanethiol were used as nucleophilic reagents to simulate the nucleophilic groups of alcohol hydroxyl, amino, phenolic hydroxyl and sulfydryl groups in natural fibers, respectively. HPLC was used to analyze and compare the reaction rate, reaction efficiency and optimal reaction conditions of different nucleophilic groups with MCT reactive dyes, VS reactive dyes, MCT/VS reactive dyes,2,4-difluoro-5-chloropyrimidine reactive dyes and bromarcylamide reactive dyes and the competition abilities of different nucleophilic reagents in mixed nucleophilic reagent system. The main results are as followings:(1) It was found by HPLC that phenolic hydroxyl and amine groups have different reaction performances with different types of reactive dyes, in which phenolic hydroxyl groups obviously have better reactivity with MCT reactive dyes than amino groups, however, the reactivity of amino groups with VS reactive dye is vastly superior to phenol hydroxyl groups. It is thought that the planar adaptability between benzene ring of phenol hydroxyl and s-triazine ring and the crowding-out effect of benzene ring to leaving groups make phenolic hydroxyl groups quickly close to s-triazine ring and finish the nucleophilic substitution reaction; A phenomenon of one amino group reacting with two vinyl sulfone groups confirmed by HPLC is regarded as a good interpretation for high reaction efficiencies of amino groups with VS reactive dyes. HPLC analysis further indicated that in the reaction with MCT/VS reactive dyes, phenolic hydroxyl groups react with MCT active groups in priority, while the amino groups react with VS active groups preferentially. In the pH rang of 8-9, both phenolic hydroxyl and amine groups can fully react with MCT/VS reactive dyes, which provides good theoretical guidances for MCT/VS reactive dyes dyeing on silk with phenolic hydroxyl and amine groups as the main nucleophilic groups; (2) HPLC analysis also proved that phenolic hydroxyl groups have higher reactivity with 2,4-difluoro-5-chloropyrimidine reactive dyes than amino groups, however, amino groups have better reactivity with a-bromarcylamide reactive dyes than phenol hydroxyl groups. Thus,2,4-difluoro-5-chloropyrimidine reactive dyes are preferable silk fiber rich in phenolic hydroxyl groups, while-bromarcylamide reactive dyes are more appropriate for wool fibers abundant in amino groups; (3) According to HPLC analysis, sulfydryl groups had high reaction rate and reaction efficiency with different reactive dyes in the wide range of pH values and temperatures, which account for the total fixation rate of reactive dyes on wool surface rich in sulfydryl groups; (4) It was confirmed by HPLC analysis that in weak alkali condition, alcohol hydroxyl groups have very low reaction rates with different types of reactive dyes. With the rise of pH value, although the reaction rates and reaction efficiencies of alcohol hydroxyl groups with reactive dyes increase, the hydrolysis rate of reactive dyes increases, which is thought as the primary reason for the low utilization rate of reactive dyes on cotton.In actual dyeing method, the exhaustions, fixations and total fixation efficiencies of above five kinds of typical reactive dyes on cotton, wool, silk, and their multi-component natural-fiber fabrics were studied. The results are as folio wings:(1) MCT/VS reactive dyes are most appropriate for silk fibers, and when the dyeing temperature is 70℃ and the pH values is in the range of 8-10, the Fixations of MCT/VS reactive dyes on silk are more than 90% with good reproducibility and high stability; And 2,4-difluoro-5-chloropyrimidine reactive dyes are secondary appropriate for silk fibers, however, VS reactive dyes and α-bromarcylamide reactive dyes have relatively poor dyeing performances on silk.; (2) For the dyeing performances of reactive dyes on wool, the adaptabilities of the involved five kinds of reactive dyes in ous study are in the following order:a-bromarcylamide reactive dyes> VS reactive dyes ≈ MCT/VS reactive dyes> 2,4-difluoro-5-chloropyrimidine reactive dyes> MCT reactive dyes; (3) With respect to cotton fibers, all sorts of reactive dyes have low total fixation efficiencies, while the MCT/VS reactive dyes have relatively higher fixation rates. It is found that the above results from the practical dyeing method are in accordance with the simulation reaction method. (4)In the dyeing process of bicomponent natural-fiber fabrics, MCT/VS reactive dyes are suitable for bicomponent fabrics of silk/wool, silk/cotton and cotton/wool. By selecting dyes and adjusting dyeing temperatures, pH values, dyeing times and the ways to add alkaline and salt, the distributions of reactive dyes on each component of fibers can be effectively controlled and regulated, and exhaustions, fixations and dyeing reproducibility can be improved, which is helpful to achieve tone-on-tone or two-tone color effects on multi-component fabrics of natural fibers.