Bleaching of indigo‐dyed denim fabric by electrochemical formation of hypohalogenites <i>in situ</i>

Bechtold, Thomas; Maier, Peter; Schrott, Wolfgang

doi:10.1111/j.1478-4408.2005.tb00252.x

Cited by 14 publications

(16 citation statements)

References 2 publications

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“…The colours are described in CIELab-coordinates, L corresponding to the brightness (100 = white, 0 = black), a to the redgreen coordinate (positive sign = red, negative sign = green) and b to the yellow-blue coordinate (positive sign = yellow, negative sign = blue). Details for the bleach effect are given elsewhere [11,20].…”

Section: Technical Scale Processmentioning

confidence: 99%

“…Details describing bleach effects and comparison of bleach results are given elsewhere [11,20]. The comparison of the bleach effects indicated that, under similar process conditions e.g.…”

Section: Bleach Processmentioning

confidence: 99%

“…The comparison of the bleach effects indicated that, under similar process conditions e.g. concentration of oxidant, pH, temperature and duration a more intensive bleach effect is observed using electrochemically prepared bleach baths [11,20]. This finding may be explained as being due to partial disproportionation of the commercial NaOCl solution to less bleaching NaClO 3 and NaCl during storage; however, detailed studies are in progress.…”

Section: Bleach Processmentioning

confidence: 99%

“…Processes for electrochemical production of bleach chemicals have been studied for delignification of pulp and for textile bleach processes [6][7][8][9][10][11][12][13]. The electrochemical formation of hydrogen-peroxide on-site has been investigated [14,15].…”

Section: Introductionmentioning

confidence: 99%

“…The use of electrochemical methods to form organic oxidizing agents for denim bleach has been described [13]. Limited scientific information is available about the electrochemical in-situ formation of hypo-halogenites for bleach operations [9,10,16,17]. The in-house preparation of NaOCl also has been described, however the efficiency of the bleach process has been described as rather low [12].…”

Section: Introductionmentioning

confidence: 99%

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On-site formation of hypochlorite for indigo oxidation – Scale-up and full scale operation of an electrolyser for denim bleach processes

Bechtold

Turcanu

Campese³

et al. 2005

J Appl Electrochem

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On-site production of hypochlorite for denim bleach was investigated using undivided unipolar electrolysers. The current efficiency of the electrolysis process was studied at laboratory scale with up to 20 A cell current and at the technical scale using a 1200 A electrolyser. NaCl solutions in the concentration range 0.236-0.944 M NaCl (13.8-55.2 g l )1 ) were used. Anodic current densities up to 400 A m )2 were used. Hypochlorite solutions with active chlorine concentration c(Cl)=0.10-0.12 M were obtained with current efficiency of 58-70%. For denim bleach processes a concentration of active chlorine up to c(Cl)=0.12 M is required. This corresponds to approximately 30 ml l )1 of commercial hypochlorite solution. Electrical energy consumption calculated per kg of active chlorine formed ranges from 5.7 to 8.6 kWh kg )1 . By coupling the electrolyser to a commercial 30 kg capacity drum washing machine the electrochemically prepared oxidant was successfully used in bleach processes. The technique overcomes problems of insufficient reproducibility of bleach, chemical costs and released wasted water due to the use of commercial NaOCl solution.

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Section: Technical Scale Processmentioning

confidence: 99%

“…Details describing bleach effects and comparison of bleach results are given elsewhere [11,20]. The comparison of the bleach effects indicated that, under similar process conditions e.g.…”

Section: Bleach Processmentioning

confidence: 99%

Section: Bleach Processmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On-site formation of hypochlorite for indigo oxidation – Scale-up and full scale operation of an electrolyser for denim bleach processes

Bechtold

Turcanu

Campese³

et al. 2005

J Appl Electrochem

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Surface activation of dyed fabric for cellulase treatment

Schimper¹,

Ibănescu²,

Bechtold³

2011

Biotechnology Journal

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Surface activation of fabric made from cellulose fibres, such as viscose, lyocell, modal fibres and cotton, can be achieved by printing of a concentrated NaOH-containing paste. From the concentration of reducing sugars formed in solution, an increase in intensity of the cellulase hydrolysis by a factor of six to eight was observed, which was mainly concentrated at the activated parts of the fabric surface. This method of local activation is of particular interest for modification of materials that have been dyed with special processes to attain an uneven distribution of dyestuff within the yarn cross-section, e.g., indigo ring-dyed denim yarn for jeans production. Fabrics made from regenerated cellulose fibres were used as model substrate to express the effects of surface activation on indigo-dyed material. Wash-down experiments on indigo-dyed denim demonstrated significant colour removal from the activated surface at low overall weight loss of 4-5%. The method is of relevance for a more eco-friendly processing of jeans in the garment industry.

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