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Sustainable reactive dyeing that saves resources

Many industrial sectors all over the world show a clear trend to sustainability and a conscientious handling of resources. The textile industry is not exempted from this trend. Furthermore, the worldwide consumption of cotton is increasing, which can lead to tensions in the area of water availability, land for agriculture and the use of agrochemicals.

Consequently, circular economy approaches, and an improved recycling of used textiles gain in importance. However, the reactive dyeing of cellulosic fibres like cotton and its blends is still being effected with water-based processes. In this field, too, a tendency towards cold pad batch processes or exhaust processes with short liquor ratios and lower temperatures of the dyeing and rinsing baths can be observed. The dye properties themselves are decisive for a successful use of reactive dyes in such processes: They must have a sufficiently high fixation speed, a very good ease of removal of hydrolysates and an excellent solubility. Moreover, reactive dyes are expected to reach high overall fastness levels, especially a good stability towards multiple washing and also light fastnesses, which allows a generally longer use of colored textiles, and to lead to reproducible, levelled dyeing results without causing problems. Last but not least due to a good color build-up they must also be efficiently applicable for dark shades.

Sustainable and economical dyeing

Compared with a conventional reactive dyeing at 60 °C, the dyeing process with BEZAKTIV GO is generally shorter, which also increases the productivity for the textile finisher. Savings in the required salt quantity can be simultaneously achieved. The unnecessary salt and the resulting lower electrolyte concentration in the dyebath not only allow for significant cost savings in the recipe but also for an improved washing off process of unfixed shares after the dyeing. The dyeing of medium to dark shades where in classic procedures quite a big share of unfixed dye must be washed off reveals the benefits of the “GO” process in particular. With the combination of a very high fixation degree and an excellent ease of removal of hydrolysates, the BEZAKTIV GO range allows for a very efficient rinsing and soaping process between 40 and 60°C. An additional positive effect is achieved by adding only low concentrations of the CHT auxiliary COTOBLANC SEL in the second soaping bath. As a result, excellent wet fastness levels can be achieved on the textile using a washing process with a low water and energy consumption.

Figure 1: Comparison of the rinsing baths in the reactive dyeing process (top: commodities / bottom: process at 60 °C using BEZAKTIV GO and COTOBLANC SEL).

Even for dyeings in the cold pad batch process the rather high fixation speed allows for shorter dwelling times. The good wash-off properties lead to savings in continuous washing processes, specially with dark shades or black.

BEZAKITV GO process-60
Figure 2: The GO Process stands out for lower temperatures and shorter process times.

p-Chloroaniline-free dyeing with BEZAKTIV ZERO GO

ZERO refers to the content of undesired arylamines (as e.g. p-chloroaniline) which are not detectable in these dyes.

Dyeing recipes for a dark red-brown adjusted with BEZAKTIV ZERO GO
Figure 3: Dyeing recipes for a dark red-brown adjusted with BEZAKTIV ZERO GO instead of bifunctional standard dyes.

Both dyeing results are free from reductively detachable arylamines and have good multiple washing fastnesses and a comparable fastness level. The variant with BEZAKTIV ZERO  GO, however, requires significantly lower dye and salt amounts and additionally helps save energy and water.

The BEZAKTIV ZERO GO dyes can, of course, also be applied in the “GO” process which saves both energy and water. These dyes have good fastness levels (like e.g. the multiple washing fastness according to ISO 105-C09) and can no longer reductively detach p-chloroaniline from the dyes textiles at detectable limits. The dyeing example shows that the BEZAKTIV ZERO GO dyes also lead to very deep colors and that they are especially well suited for dark shades. The problem with reductively cleavable p-chloroaniline of dyed cellulose mainly occurs with very dark shades and above all with black, for which most worldwide manufacturers use a black based on the Reactive Black 5. The BEZAKTIV ZERO Black GO does not contain any Reactive Black 5 and has therefore a very good multiple washing fastness according to ISO 105-C09 compared with a conventional reactive black. All additional elements of the ZERO GO range have also good multiple washing fastnesses, they allow for dyeing more brilliant shades and they can also be excellently used for shading the BEZAKTIV ZERO Black GO or BEZAKTIV ZERO Navy GO. The fastness improvement in multiple washing is mainly an enhanced stability towards oxidative influences and it is gaining in importance as it leads to an improved durability of the textiles, which is a contribution to sustainability in textile manufacture. Moreover, the elements of the BEZAKTIV ZERO GO dyes have high fixation degrees, can also be applied in continuous processes and fulfil highest ecological demands.  Among others, the BEZAKTIV ZERO GO and some of the BEZAKTIV GO dyes have received a C2C Material Health CertificateTM.

GO for Digitalization

Textile finishers can easily see the actual savings that are facilitated by the BEZAKTIV GO and ZERO GO dyes: The CHT Textile Dyes App offered by CHT Switzerland is a simple and smart calculation tool. The comparison with the above shown recipes clearly shows that the dye application amount and the necessary electrolyte concentration are much lower when using BEZAKTIV GO dyes than when using conventional, bifunctional reactive dyes. Besides the calculation programme the CHT Textile Dyes App additionally offers useful bits of information on the BEZAKTIV GO and ZERO GO products, ranging from color samples, all of the relevant fastness types and detailed product profiles up to useful recommendations for use.

BEZAKTIV GO comparison-savings
Figure 4: Comparison of the main cost factors when using conventional reactive dyes and BEZAKTIV GO.

Since the CHT Group is focused on sustainable chemical products and process solutions, the BEZAKTIV GO products also meet highest standards: All of the currently sold elements are bluesign®-approved and suited to meet the requirements made by GOTS and Standard 100 by OEKO-TEX.

If anyone has any feedback or input regarding the published news, please contact: info@textiletoday.com.bd

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