Ian Holme introduces some of the added-value auxiliaries in the market for use in the essential process of fabric pretreatment
Fabric pretreatment can present major challenges to dyers and finishers because if the pretreatment is non-uniform, it is almost impossible later to attain the highest standards of performance. The chemical engineering of pretreatment auxiliaries to perform highly specific functions in desizing, scouring and bleaching processes continues to reach new heights.
Chemical manufacturers also have to bear in mind various environmental issues as well as maximising process efficiency, especially in respect of right-first-time fabric pretreatment. Particular importance is attached to the effective removal of impurities and to the attainment of uniform, high levels of whiteness and fabric absorbency.
Absorbency is a key factor in cold pad batch dyeing and continuous dyeing, as well as in fabric printing.
Bleaching of viscose fabric has been conducted with care, particularly with regard to the pH, which must be carefully controlled and not too alkaline to avoid fabric damage.
Based in Turkey, Eksoy Textile Chemicals & Dyes introduced a novel peroxide activator, Viscocolor, which is suitable for application in hydrogen peroxide bleaching. Viscocolor is a low pH peroxide activator with a strong sequestering effect. Using soda ash at low temperatures (e.g. 60°C-70°C) viscose knitted fabrics can be bleached at pH 9.5 to a full white, which is enhanced using Optic CO from Eksoy Textile Chemicals & Dyes, a fluorescent brightener suitable for high whites on viscose fabric.
The removal of silicone oil-containing lubricants from polyamide, and especially polyamide/elastane blends can be problematic.
Zschimmer & Schwarz from Germany produced a new highly effective and hydrocarbon-free detergent, Tissocyl RC9, for this purpose, which provides spontaneous emulsification of silicone oils at low temperatures. Tissocyl RC9 can be dosed and pumped, and is biodegradable. It is a versatile product that ensures good emulsification of ester oils and mineral oils.
Modern cotton fabric pretreatment methods are designed to save energy and water by integrating treatments e.g. combined desize/ scour/ wash off, combined scour/ bleach/ wash off or full integration (singe/ desize/ scour/ bleach/ wash off).
Cold-pad-batch bleaching can save energy but extends the processing time because of the long dwell time (16-24 hours) required. This must be followed by a thorough hot wash (95°C or higher) to remove fibre impurities e.g. cotton waxes. Auxiliary manufacturers are optimising their product ranges in order to provide maximum performance within selected integrated treatments as well as providing products optimised for use in jet, winch, beam, hank and package processing.
Optimising auxiliaries for specific pretreatments
Optimisation of auxiliaries for use on specific fabric pretreatment ranges is now a major area of interest for both auxiliary and machine makers.
The Bozzetto Group from Italy recommends the addition of Idrosolvan RO7 when cotton /elastane knitted fabric is bleached on the Goller continuous pad-steam range. Idrosolvan RO7 is a pure nonionic detergent that is free of alkyl phenol ethoxylates and silicone free.
For cotton knitted fabrics on the Goller system, Bozzetto Group recommend Celidon CBA (a peroxide stabiliser designed for high temperature bleaching) together with Sequion M500. The latter is a versatile product combining the functions of a sequestering, dispersing and antiscaling agent. An anionic /nonionic detergent such as Biomegapal VS New is also used on cotton knitted fabrics. Biomegapal VS New is APEO-free, silicone-free and is a low foaming anionic /nonionic product that is stable in alkali up to 5° Baumé.
Bozzetto Group headquartered in Italy recommend Biomegapal VS New or DS-100 (an anionic / nonionic detergent and wetting agent stable up to 12° Baumé) for use in the Erbatech Scout BP cold pad batch pretreatment process. For such treatments Megalase HT-S is used for hot/ cold desizing of starch sizes.
Megalase HT-S is an effective α-amylase enzyme for starch desizing. For hydrogen peroxide bleaching Celidon ME (peroxide stabiliser) is used with Sequion MC200, a phosphonate-based sequestering / dispersing / antiscaling agent). For combined desizing and bleaching an oxidising auxiliary for starch-based sizes, such as Megalase KO LIQ is used in addition.
DNG Clay is a clay-based ecologic combined bleaching agent supplied by Denge Kimya, Çorlu Tekirdag, Turkey. This auxiliary is an amphoteric grey liquid with a neutral pH based upon a natural fine-grained, laminar aluminium silicate. It can be readily dispersed in water and has been designed for use in peroxide bleaching in overflow and jet machines. DNG Clay is used to provide wetting, cleaning and peroxide stabilisation in cotton fabric bleaching.
Ecological properties become crucial attributes
Tannex Noveco is a new multi-purpose product for all discontinuous bleaching applications from Tanatex Chemicals of The Netherlands. This low foaming product is based on natural minerals, is readily soluble in water, and can be dosed automatically.
New Tannex Noveco auxiliary meets international ecological standards |
Tannex Noveco is designed for use in full-white bleaching and in bleaching prior to dyeing. It can also be used for the scouring of elastane and stripping of fluorocarbons. This versatile multi-functional auxiliary is GOTS (Global Organic Textile Standard) certified and its components meet with the Restricted Substances Lists of most international brands and retailers.
The Smart Prep system from Huntsman Textile Effects is designed for the discontinuous pretreatment of cellulosic fibres and their blends. The system is designed to save money, water, energy and time and prepare fabric ready for dyeing. Their Smart Bleach treatment utilises Clarite 3X together with Invadine DA or a combination product Clarite Com. Neutralising, after clearing and peroxide elimination is completed in Huntsman’s Smart Rinse treatment that uses Invatex AC and Invazyme CAT.
Huntsman Textile Effects produced a full white with its Smart White process. This is a single bath peroxide bleach process using Clarite WIN, which provides optimal peroxide stabilisation combined with rapid, uniform wetting action. To obtain the full white, Huntsman Textile Effects recommends Uvitex BHT, which is a high affinity fluorescent brightening agent. Neutralisation/ afterclearing is then completed after bleaching using Invatex AC.
The company recently introduced its innovative PremaxX continuous and semi-continuous pretreatment concept for cost-effective pretreatment with maximum dependability. Clarite One is an efficient, ecological, and economical all-in-one product for peroxide bleaching of cellulosic fibres and blends. It is a combination product that simplifies bleaching recipes because this one auxiliary combines the functions of complexing, dispersing, washing, rewetting, degreasing, emulsifying and peroxide regulation. This multifunctional auxiliary can be used with silicate-containing and silicate-free recipes, providing excellent white effects together with exceptionally high protection of fibres against chemical damage.
Clarite One is APEO-free and AOX-free and contains no antifoam. It meets most sustainable textile standards such as GOTS and meets German waste water order / appendix 38. Suitable for exhaust and continuous pad-steam processes, it is predominantly designed for cold-pad-batch peroxide bleaching.
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