Reactive dyes fixing

The kinetics of alkaline hydrolysis of a series of eleven vinylsulphone reactive dyes fixed on cellulose have been investigated at 50 °C and pH 11. Bimodal hydrolytic behaviour was observed under these conditions, the reaction rates being rapid at first but becoming slower as the concentration of fixed dye remaining gradually decreased. These results were attributed to differences in the degree of accessibility of the sites of reaction of the dyes within the fibre structure [87]. 

Schindler W, T auwald E and Kruger R, Are reactive dyes fixed with covalent bonds after one-bath dyeing and low-swell finishing of PES/cotton , Melliand Textilberichte, 1990, 71(5), 388-392, E176-E178. 

Basilen . [BASF BASF AG] Reactive dyes fix cellulosic fibers. 

These dyes are not very commercially important, and the dyeing mechanism has been described in detail elsewhere (15,25). The difficulty in applying fiber-reactive dyes to wool is the result of the same reactions already described. They are negatively charged and the wool is positively charged so ionic attraction exists. The fiber-reactive dyes are essentiaUy acid leveling or milling dyes and so this attraction can be controUed by pH. Once the dye is fixed no... 

These constraints cause different reactive groups to be developed for dyeing wool. They fall into two groups novel reactive groups with more than one type of group in each molecule in order to increase the amount of dye fixed and minimise the wash-off problem, eg, Lanasol Dyes by CIBA-GEIGY, and those based on ceUulosic reactive dyes, but where the dye is appHed to the wool in a nonreactive form. On boiling, this form slowly converts to the reactive form that fixes rapidly in situ eg, the Hostalan Dyes by Hoechst, introduced in 1971 were precursors of vinyl sulfone dyes. 

Biomass from an anaerobic digester Reactive dyes disperse dyes Fixed bed with recycle and fixed bed Continuous Anaerobic B Reticulated sintered glass n.a. 37 6.4-7.2... 

Acid dye affinity, 19 759 Acid dyes, 9 184-186, 189-190, 215-216, 226, 243 26 395-396 anthraquinone, 9 301, 327-329 azo, 9 389-394 Acid dyestuffs, 9 223 Acid extractants, 10 750 Acid fixing reactive dyes, 9 478-481 Acid foods, heat preservation of, 12 80 Acid functional polyesters, 10 402 Acid gas constituents, 12 376-378 Acid gases, 10 612-613... 

Modern reactive dyes, 9 470-492 acid fixing, 9 478-481 covalent dye fixation, 9 489-491 fiber pretreatment, 9 481-486 for wool fibers, 9 491-492 neutral fixing reactive dyes, 9 477 478 polyfunctional, 9 471-477 reactive fibers, 9 486-489 Modified alkyds, 2 148, 158-160 Modified brass, UNS designation,... 

Interest in acid-fixing reactive dyes has remained active because of their environmentally attractive features (section 1.7). The freedom from competing hydrolytic reactions potentially offers exceptionally high fixation, extreme stability of the dye-fibre bonds and complete suitability of the unfixed dyes for recycling. In contrast to conventional reactive dyes, sensitisation problems arising from reaction with skin proteins are not anticipated. Unlike the haloheterocyclic reactive dyes, there is no risk of release of AOX compounds to waste waters. Heavy metals are not involved in the application of acid-fixing reactive dyes, nor are the electrolytes or alkalis that normally contaminate effluents from conventional reactive dyeing. 

Fig. I. Amounts and forms of tiber-reactive dye on the fiber as a function of time for a low affinity dye. where X represents the reactive group. Point A represents the amount of dye exhausted in neutral conditions ft is the total amount of dye exhausted at theentlof the dyeing process, i.e., [dye-OH) + dyc-X i [dye-O-cetl] and C is ihe amount of dye fixed dye-0-cell. ...

Instead of a continuous procedure the dye can be fixed on the fiber after application by batching on a roll at a controlled temperature. For reactive dyes a cold batch process is widely used. 

The anchor components of reactive dyes determine both the fixing properties and the wetfastness of the dyed material. More than 300 electrophilic anchors for reactive dyes are described in the patent literature. Of this large number, fewer than ten are currently of practical importance for dyeing cellulose fibers (Figure 4.1). 

Currently, a wide range of reactive dyes of varying constitution is available which are suitable for many different applications [33], [6, p. 510-516], In most cases, dye is fixed to the substrate under alkaline conditions. However, dyes with phos-phonate groups are applied in an acid dyeing bath, and quaternary nicotinic acid derivatives require neutral conditions. These dyes are used mainly for dyeing PES-CEL blends. 

In a one-bath two-stage batch process, the bath contains all the dyes from the start. After the PES component is dyed at 130°C, the bath is cooled to ca. 80°C, and alkali is added to fix the reactive dyes to the CE L component. Careful selection of dyes is required because the reactive dyes must be stable at pH 4-5 and 130°C. 

The thermosol pad steam process is especially important. Disperse and reactive dyes are padded together, and alkali and salt are padded after the thermosol passage. If a steamer is not available, the reactive dye can be fixed continuously by means of alkali shock in a roller vat with a relatively high alkali concentration. 

Reactive dyes with methylolamide-like groups were used on cotton at one time [342]. Bonding to cellulose was similar to that in etherification treatments to produce wrinkle resistance. However, because of technical problems in their application, usage of these formaldehyde-based reactive dyes has essentially ceased. Fixatives are used, which act through methylol groups, to improve color fastness of direct and other dyes on cotton. Their mechanism includes bonding (etherification) between dye and cellulose as well as between dye molecules. 

A resinous substantive dye fixative, cationic in nature and considered to be in the durable categories. This material is used in the fixation of direct dyestuff and fiber reactives having a minimum effect on shade to give good dye fixation to wet bleeding and laundering. 

Cationic, resinous fixative. Most effective and economical. Improves wetfastness properties of direct and reactive dyes on cellulosics and blends. 

Extremely good fastness on the cellulosic component can be obtained with reactive dyes. The cold dyeing members are preferable because the conditions of alkalinity and temperature necessary to fix the high-tempera-ture reactive dyestufiFs would be harmful to the wool. When Procion dyes are applied cold the protein fibre is left practically unstained, unless it has been chlorinated previously, and must be brought up to shade with neutral dyeing acid dyes such as those on page 575. The Procion dyes which have been found suitable are ... 

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