Enzyme wash with stone and Acid Wash
Enzyme Wash – Production Department receives the Process Batch Card attached to it from the Batch Preparation Section. Different specifications (e.g. Garments weight and quality, wash type, shade, etc.) Mentioned in the Batch card.
- The steps for Enzyme wash with stone are as follows:
- Take water in bath at required level
- Load garment in the machine
- Add Detergent
- Circulate the garment and raise the temperature at 400C
- Continue circulating the garments for 5minutes
- Rinse and Drain
- Add Acetic acid wash to make the PH 4.5
- Add enzyme and stones
- Continue the circulation for 30 minutes and raise the temperature at 550C
- Rinse and Drain
- Add softener
- Continue circulating the garments for 5 minutes
- Drain and send the garments into the hydro extractor
- After hydro garments are send for dryer
Acid wash is mainly done after sulphur dyeing; this gives a unique look to the garments. The steps for acid wash are as follows:
- Load the machine with foam (cork sheet) or with stone
- Make a solution of potassium permanganate
- Spread the solution over foam or stone
- Load the dyed garment in the machine
- Continue circulate the garments for 30-60 minutes at constant temperature (room temperature)
- Un load the garments from the machine
- In an another machine take water bath at required level
- Load the garments in the machine
- Add sodium meta-bi-sulphite
- Circulate the machine until potassium permanganate is totally removed
- Rinse and drain
- Send the garments for dryer
Document flow for the pre-treatment process can be enumerated as below:
Based on the shade and other specification plans for the machines are prepared.
Print-out of the recipe is taken from the computer. The Recipe Card is used as an internal document to keep record of dyeing for a particular batch.
Availability of chemicals and dyestuff is checked and program is put in the Bacon Controller.
The recipe shit Card is used to keep track of the dyeing procedure continuity. Production Officer fills out different areas of the form.
The Operator fills out the Production Report and it is sent to the Planning department. This report contains information like the Quantity produced, Machine wise production, Amount of re-process, Machine utility percentage (%) and shift wise production.
Upon completion of Wash for a particular batch, if the wash is ‘OK’, then this garment is sent to the Finishing Department along with batch card.
Implementing enzymatic removal of residual hydrogen peroxide after bleaching
To achieve reproducible bleaching results, residual hydrogen peroxide content of 10-15% of the initial quantity should be still available after bleaching. The residual hydrogen content must be completely removed to prevent any change of shade with dyestuffs, which are sensitive to oxidation. Reducing agents and several rinsing steps are necessary in common peroxide removal techniques. High energy and water consumption and the use of sulphur containing reducing agents are the main disadvantages of the conventional technique.
Special enzymes (peroxides) catalyse the reduction of hydrogen peroxide to oxygen and water. No side reactions with the substrate or with dyestuff occur.
Peroxides are completely biodegradable. Rinsing steps after peroxide bleaching can be reduced (normally only one rinsing step with hot water is necessary). Peroxides have no negative influence on downstream dyeing processes. Therefore, after treatment with the enzymes in an exhaust process the liquor does not have to be drained prior to dyeing. Savings in energy and water consumption can be achieved. Wastewater pollution with reducing agents (used for conventional processes) is avoided.
Enzymatic peroxide removal is possible in a discontinuous, semi-continuous, and continuous way. The method is applicable both in new and existing installations.
No capital expenditure is necessary for implementation of the enzymatic process. Savings may result from reduced washing stages, i.e. water, energy, steam and time conservation. Savings in water and energy consumption can be in the range of 6-8% of production costs (exhaust technique) .
Suppliers for enzymatic peroxide removal agents are: Novozymes, Bayer, Ciba, etc
A typical process consequence is: peroxide bleaching – liquor change – one rinsing bath (hot water) – liquor change – enzymatic peroxide removal – dyeing without previous liquor change.