In a recent symposium at the CITVE Textile Institute of Portugal, on knitting, dyeing and finishing of knitted fabrics, Hermann Freericks, Thies GmbH & Co KG and Joao Sampaio, F.Sampaio Industrial Projects presented a key paper on the latest developments and benefits of ‘ first time right’ techniques in dyeing applications. A summary of the paper follows.
In the busy dyehouse, there are many process parameters which need to be constantly monitored if costly problems are to be avoided.
The integrated dyeing technology of Thies has been developed drawing on many years of experience to provide operators with complete control at every stage, from start to finish.
There can, for example, be a number of reasons for dyeing problems with a batch being caused during the pre-treatment stages, as a result of unsatisfactory oil removal, pre-bleaching, scouring, washing, rinsing, neutralisation or pre-fixation.
Of equal importance, of course, is the accuracy of the recipe in respect of both dyestuffs and chemicals. Weighing errors, incorrect dosing or mismatched heating gradients can all cause their problems.
After-treatment too, can lead to poor colour fastness, shade differences or inadequate fixation. Another vital requirement is achieving batch-to-batch reproducibility in order to ensure uniform quality results and ultimately, customer satisfaction.
Any of these issues can lead to the need to recolour an entire batch. And, if the problem is severe enough, to have to strip out the colour completely and start again – more than doubling the cost to the mill.
Thies has also analysed the reasons for off-shade dyeing results, and found that in around 40% of cases, insufficient pre-treatment of the textile raw material is the cause. Poor or fluctuating dyehouse waste quality and unsuitable methods, recipes or product selections are responsible in many other cases.
In order to avoid such problems, a constant liquor ratio must be ensured, along with accurate weighing of dyes and chemicals, their correct dissolving and the monitoring of all auxiliary concentrations and activity.
At the heart of today’s Thies dyeing ranges are the company’s MPS – Multi Product Supply – systems. Working in conjunction with all dyeing machines, including the iMaster H20 piece dyeing unit and the soft-TRD SIII long kier systems, they allow total automation of the entire dyehouse in order to achieve full reproducibility and reliability, while leading to time savings, streamlining production and cutting costs.
For liquid and solid chemicals and dyestuffs too, MPS guarantees the highest accuracy as a result of automatic optimisation with repeatable and constant additions, the ability to fully control the integrated mixing and storage tanks, and the flexibility to accommodate machines of varying sizes.
Further benefits result from the Thies CCR technology which combines the cooling and rinsing of the treated fabrics in a single step. This results in both significant water savings and shorter process times.
Thies industrial-scale tests have proved that the previous 41 minutes required to carry out the separate cooling and rinsing steps of an average material is reduced to 28 minutes as a result of the CCR function – for savings of 32%.
In addition to achieving right first time results, getting the liquor ratio as low as possible is one of the main keys to achieving further cost high materials efficiencies.
For 100% cotton, the Thies iMaster H20 achieves an ultra-low liquor ratio of approximately 1:3.5 with excellent running properties at up to 500 m/min.
In addition, the fabric speed, nozzle pressure and plaiter movement are automatically synchronized and shrinkage is strictly controlled.
The iMaster H20 is also capable of handling both light and heavy fabrics, as well as both full and part loads, as a result of its adjustable J-Box.
Thies soft-TRD III long kier systems meanwhile – capable of handling either 100kg, 150kg or 200kg per chamber and with between one and four chambers per machine – benefit from an enhanced design and unprecedented flexibility.
Uniformity in terms of the temperature distribution and the heat up of the fabric, liquor and kier itself, is complemented by a fully automatic dosing system and highly adjustable fabric speeds up to 600 m/min. The liquor ratio starts at 1:4,5 up to a maximum of 1:10 at operating temperatures of up to 140°C.
“In addition to being a supplier in respect of engineering and construction, Thies builds long-term partnerships with its dyehouse customers,” concluded Hermann Freericks adding. “We aim to provide single-source solutions and full service support worldwide, with the flexibility to implement the requirements of our customers and ensure they are getting the utmost in terms of repeatable performance and resource efficiency from our machines.”
