“Bangladesh is step ahead to replace exhaust dyeing with more sustainable, economical and better quality production CPB dyeing”

Bangladesh textile and apparel industry is seeing a remarkable change in terms of sustainability. A huge amount of water and energy are being consumed during dyeing processes. Profitability crisis and environmental issues are being a great concern for the industry now. Factories here in Bangladesh are struggling to remain competitive, maintaining global stringent compliance requirements, and keeping sustainability intact. However major point is to consider that changing towards sustainability does not make any adverse effect on the quality of the finished product.

Exhaust dyeing is a widely used process in Bangladesh where Cold Pad Batch (CPB) dyeing process was ignored through this long journey of Bangladesh textile industry for knitted fabric. B Ahmed Rahi, CEO of Trade Ray and Textile Technology Manager, ERBATECH GmbH has a 10 years holistic working experience with CPB dyeing as a pioneer. Recently he shared his successful journey of CPB dyeing with Textile Today and urged the manufacturers to use CPB towards a greener world. Let’s hear his story.

CPB dyeing process

CPB dyeing is higher quality dyeing method for woven and knitted cellulosic fibers. The process reduces the use of salt, water, energy, and dyestuff, chemical and thus significantly reduces the chemical concentration of effluent. It is needless to say that it facilitates the bacterial treatment effectively.

CPB dyeing attempts the utmost cost-effective and advantageous approach of dyeing cotton with reactive dyestuffs. The elimination of salt addition also supports the minimum energy and water consumptions; hence rendering it more eco-friendly and fixation of dye is also much higher.

Robintex Group and Northern Tosrifa are a most successful pioneer company in Bangladesh in using CPB dyeing. And since 2014 many more companies are using CPB dyeing. In the initial stage of CPB dyeing, it was very challenging, so the interested factories had to take consultation and a lot of training to run the project. However, the whole industry was in a learning process but now I think we are strong enough to start dyeing with CPB process. All the chemical and machine suppliers are also developed a lot in the meantime.

When I started my journey in late 2007 at Consumer Knitex Limited, I got amazed to see how much sustainable and the easier process can be the CPB dyeing process than exhaust dyeing. At that time a Sri-Lankan, representing for a world-famous brand visited our factory and decided to place his order after check out our settings. That was my start of the journey and through this journey; I found CPB dyeing is more economical and environment-friendly than exhaust dyeing. The method gives you the required fastness standards with ease and minimum costs, and less energy.

Features of CPB dyeing

In CPB dyeing, material and liquor ratio is 1:1 and no steam is required. It is not required of salt, hence less TDS in ETP. No anti-creasing agent is required and there is shiny fabric surface without crease marks. It is more lustrous fabric compared to conventional process. It is also suitable for delicate fabrics. Through this dyeing reactive dyes can be exhausted up the maximum. There is no need for enzymatic bio polishing.

Figure 2: Engr Badruddin Ahmed Rahi, CEO of Trade Ray and Textile Technology Manager, ERBATECH GmbH.
For occurring less frictionless fuzz is created on the fabric surface and less pressure of effluent in ETP as well. There is high reproducibility and needed minimum re-work and high flexibility in batch size (from color samples up to 1.000 kg batches).

In the dye bath, there are water, fabrics, and dyestuff. In exhaust dyeing, 60% to 75% dyes are fixed on fabric; residual 25%-40% dyes got hydrolyzed and could not react with fabric due to higher liquor ratio. In CPB dyeing liquor ratio is 1:1, so the dye pickup is up to almost 95% and so it saves up to 30% dyeing cost.

Benefits of CPB dyeing over exhaust dyeing

The CPB dyeing has a lot of benefits by which factories can save a lot of resources. It is more sustainable and environment-friendly and needs the relatively low cost of equipment. In CPB dyeing process it needs less surface area and low amount of effluent. Conventional exhaust dyeing system emits up to 1 kg salt per kg of fabric where no salt is required in CPB. It requires very less electricity and reduces labor cost. After all fabric quality is more improved here than exhaust method

Challenges of CPB dyeing 

There are some challenges in CPB dyeing process:

• Is to train people to change their mindset to the practice of semi-continuous processing.
  
• One extra step for drying is needed.
  
• The yarn needs to be free of seed particles and this is not regular in Bangladesh.
  
• Uniformity of quality of yarn and knitting process.

Frequently asked questions: 

How to deal with small batches?
– CPB can deal small batches even few meters.

How to do bio polishing?
– CPB process cannot do bio polishing or it is needed since no additional friction is added while processing. The finished fabric itself gets a lustrous effect.

How to match lab to bulk and batch to batch shade?
– CPB process has got a different concept of the lab to bulk and batch to batch shade consistency since these are mostly an exhaust dyeing issue.

How does it work without salt?
– Salt is an exhausting agent needed for exhaust processing, it does not have a participation in the dye-fiber covalent bonding. In CPB additional exhaustion agent is not needed since dye bath liquor ratio is 1:1, cold water and longtime dwelling.

New exhaust dyeing machines are also low liquor ratio then how CPB is still beneficiary?
– Latest low liquor ratio exhaust dyeing machines are only reducing water not proportionately the number and amount of chemicals. CPB is reducing water consumption along with a significant amount of chemicals and dyestuff.

I am certainly not arrogant to claim that by using the CPB dyeing we will be able to maintain sustainability in dyeing process hundred percent, all I want to show that is CPB dyeing is a small step in the right way keeping a better quality of production.

Thanks for the information : https://www.textiletoday.com.bd/