Cold Pad Batch Dyeing Process, Save around 50% Water.

Cold Pad Batch Dyeing:

Pad Batch Dyeing is one of the widely used technique for semi-continuous dyeing process. It is mainly used in the dyeing of cellulosic fiber like cotton or viscose (knit and woven especially woven fabric) with reactive dyes. Pad batch dyeing is a textile dyeing process that offers some unique advantages in the form of versatility, simplicity, and flexibility and a substantial reduction in capital investment for equipment. It is primarily a cold method that is the reason why it is sometimes referred to as the cold pad batch dyeing.

A report provided by a Leading fabric supplier Wah Fung Group showing that its Cold Pad Batch dyeing technology achieves 13% carbon savings and over 50% water savings in fabric manufacturing compared with the conventional processes using exhaust dyeing.

Cold Pad Batch technology, although used in Europe, has not been widely adopted in other developing country because the capital cost is higher than conventional technology. But it is believed that improved environmental impact, resource efficiency savings and the higher quality of CPB-dyed fabric present a strong alternative than the conventional exhaust dyeing .

The Cold Pad Batch (CPB) method is relatively more environment friendly due to high dye fixation and non requirement of thermal energy.The CPB method for dyeing cotton involves ultrasonic energy resulting into a one third decrease in batching time.

•  Improved colour strength and % fixation of reactive dyes using ultrasonic energy in CPB method. 
• A significant decrease of four hours in batching time (from 12 hours to 8 hours) is achieved. 
• The reduced batching time provides one and half time more production in the given time. 
• A one third decrease in concentrations of caustic soda and sodium carbonate has also been achieved. 
• This would result into a reduced chemical cost as well as a subsequent environmental benefit.

Working Principle of Cold Pad Batch Dyeing Process: 

The technique or process used in pad-batch dyeing starts with saturating first the prepared fabric with pre-mixed dye liquor. Then it is passed through rollers. The rollers, or padders, effectively forces the dyestuff into the fabric. In the process, excess dye solution is also removed. After removal of excess dye stuff the fabric is subsequently “batched”. This batching is done by either storing it in rolls or in boxes. It takes a minimum of 4-12 hours. The batches are generally enclosed by plastic films. This prevents absorption of carbon dioxide and water evaporation. Finally as the reaction is complete the fabrics are washed. This is done by becks, beams, or any other washing devices.

Special Features of Pad Batch Dyeing Process

• Significant cost and waste reduction as compared to other conventional dyeing processes. 
• Total elimination of the need for salt and other specialty chemicals. For example there is no need for anti-migrants, leveling agents and fixatives that are necessary in conventional dye baths. 
• Optimum utilization of dyes that eliminates specialty chemicals, cuts down chemical costs and waste loads in the effluent. All this results in a formidable reduction in waste water treatment costs. 
• Excellent wash fastness properties. 
• Pad batch dyeing cuts energy and water consumption owing to low bath ratio (dye:water) required for the process. This is because unlike other dyeing processes it does not function at high temperatures. 
• A uniform dye quality is achieved with even color absorbency and colour fastness. 
• As compared to rope dyeing, Pad batch dyeing produces much lower defect levels. 
• In pad batch dyeing, qualities like high shade reliability and repeat-ability are common. This is because of high reactivity dyes with rapid fixation rate and stability. 
• Lastly Pad batch dyeing can also improve product quality. The fabric undergoing the cold pad batch dyeing process is able to retain an uniformly colored appearance. It shows added luster and gives a gentle feel. The fabric gives a brighter look in shades.