The non-contact spray application also allows the defined application of high affinity optical brighteners, fixing agents, functional chemicals, special neutralization agents and oxidation chemicals. By optimizing the spraying parameters in the RotoDyer and RotoCoater spraying technology, significant water, chemical and energy savings were achieved in the finishing of textile fabrics as well as the warp yarn dyeing.
The inevitable existing limitations in sheet/slasher and rope dyeing technologies for warp yarn, smaller lot size, the tremendous cost pressure and increased global exigencies on sustainability and resource conservation have been motivating drivers of a technology leap forward for the Denim industry.
There is a high demand in upgrading the Denim warp yarn dyeing technology for ecological and economic reasons. The marketing story of sustainability is getting pushed to get reality with actions nowadays. This disruptive spray dyeing technology has been implemented in important Denim producing countries such as Turkey, India and Pakistan with great R&D support from DyStar Indigo team and an enthusiastic engagement of Artistic Fabric Garment Industries, Arvind and Orta Anadolu R&D team.
The standard Indigo warp yarn spray process uses a stable Hydrosulfite E type or an improved formate-based Hydrosulfite with the trade name HydroBlue®90 as the reducing agent. Selected special auxiliaries avoid the formation of vat skin, protect the reducing agent and the Indigo dye from the oxygen in the air, thus avoiding the oxidation of the Indigo dye that interferes with the application.
The newly developed PS2 Pad-Spray-Steam Process for yarn and fabric enables a salt-free continuous dyeing of Reactive dyes without limitation of colour depth. The diffusion behaviour of the dyes is comparable with Cold Pad Batch dyed material. Intermediate drying as normally used in classical pad-dry-chemical pad-steam process is eliminated. This will lead to significant energy savings and much lower investment costs as well.
REVOLUTION IN VAT AND REACTIVE DYEING ON WOVEN FABRIC
PS2 Pad-Spray-Steam Process has started successfully in February 2019 in Lahore/Pakistan at Nishat Mills with outstanding results.
In addition a new one-bath Pigment dyeing method using pigment preparations, combined with a auxiliaries package, is developed for Denim with great feedback in the Denim industry as well as at the retailers by promoting a sustainable “water-free dyeing” method for warp yarn.
A pre-reduced liquid Sulfur dye range with minimal sulfide content from Archroma in combination with advanced spray dyeing is successfully used for warp yarn with significant advantages in water saving. This modified Sulfur process fulfils all the ecological issues that effected Sulfur dyes and their application in the past.
PATENTED ROTODYER SPRAY APPLICATION
For functionalization minimum application (MA) on fabric, approximately 12% – 35% pick-up is very often applied on face side only. For warp yarn dyeing/finishing a pickup of 80 – 120% are even more can be easily realized.Spray dyeing is a disruptive technology and will replace long-established systems such as large slasher/rope dyeing machines with liquor volumes of 10,000 to 50,000 liters.
Due to low liquor volume (52 l) and reduced yarn content (6 m) in the RotoDyer this new spray dyeing conception results in the highest possible flexi- bility with small lot sizes and low liquor residues and yarn losses during recipe changes. A com- plex tank storage management with recycling tanks for Indigo dyeing becomes superfluous.
The non-contact spray application prevents dirt, fluff, grease, waxes, residual surfactants or alkali from being dragged into the spray solution. The RotoDyer spray technology supports “zero-discharge” concepts (e.g., Indigo filtration / recycling), is economical and sustainable (BAT candidate). The space requirement and the investment cost for warp dyeing equipment is drastically reduced.