ICIS Innovation Awards: Textile dyes drive water conservation

Huntsman Textile Effects’ AVITERA SE range of dyes is a step change in the industry and addresses both environmental and economic sustainability

The textile industry is the backbone of many developing economies and has grown significantly in Asia over the last 20-30 years. But the industry is a heavy user of water and energy. The high water consumption is a particular problem because the world’s largest textile-producing nations are also those countries that are facing acute water scarcity.

The industry also produces wastewater contaminated with salt that is difficult to treat and it takes a long time for contaminated 
waterways to recover naturally.

There has been a complete disregard for environmental standards in the Asian textile industry, says Paul Hulme, global president, Huntsman Textile Effects. “I describe it as abuse in the industry and the relevant authorities could have done a better job of managing the environmental compliance issues,” he says. “What’s accumulated over the years is an environmental disaster with untreated effluent in the rivers, and untreated waste being buried.”

But the industry is changing. “Over the past two years the Chinese government is really beginning to enforce environmental legislation and standards,” says Hulme. Similar actions are also being taken in India, while non-government organisations (NGOs) such as Greenpeace have been exposing practices at textile mills and linking those mills to the retailers they supply. This has put pressure on retailers and brand owners to take more responsibility for their supply chains.

Roadmap
In response, in 2011, a group of major apparel and footwear brands and retailers made a shared commitment and published a joint roadmap to help lead the industry towards zero discharge of hazardous chemicals by 2020.

At the same time there is pressure to keep costs down. “From a commercial point of view, they’re looking for lower costs and higher productivity to make sure they remain competitive,” says Hulme.

The industry needs more sustainable products and processes, both from an environmental and a cost perspective. This has led to strong demand for shorter, more robust dyeing procedures, and reduced water and energy consumption.

“This is an industry that is going through some radical change, what was required was strong leadership. I think we’ve brought that strong leadership and we feel that we’ve got a responsibility to continue to do that,” says Hulme.

The timing is right for AVITERA SE, he says. “These are the first new reactive dye molecules that have been invented for almost 20 years.” Reactive dyes account for 65% of the global market for dyes. They were developed by Huntsman in the 1950s.

Reactive dyes were the first dyes produced that were able to react chemically with the fibre under alkaline conditions. This enables the dye to become part of the fibre, rather than remaining as an independent chemical entity within the fibre. The covalent bond that forms between cellulose and the reactive dye is much more resistant to everyday use of the textile than the physicochemical bond between direct dyes and cellulose.

Dyeing process
The reactive dyeing process has three stages. Firstly the water-soluble dye is adsorbed on to the cellulose surface and then it diffuses into the fibre matrix. This phase is reversible and any change in the composition of the bath, such as pH or temperature, can have an effect on the behaviour of the dye. The second stage fixes the dye. If the conditions are favourable – high temperature and/or high pH – the dye reacts with active sites in the cellulose, resulting in a strong covalent bond. In the third stage all the unfixed, adsorbed dye molecules are washed off to get highly colour-fast fabric.

Using current processes fabrics can be dyed and washed off at various temperatures and with different quantities of water. Hot dyeing systems need water at 80°C to make the bond between the dye and the fabric permanent and use boiling water and several rinsing baths to removed the unfixed dye. Warm dyeing systems operate at 60°C but still use a lot of water and high temperatures in the washing off stage. Current best available technology improves on the warm dyeing system by using less water in washing off.

Huntsman’s AVITERA SE range consists of tailor-made poly-reactive dyes that allow a very high rate of exhaustion of the dye from the bath to the fabric and then a high rate of fixing the dye to the fabric. Most reactive dye molecules have one or two reactive groups that bond with the fibre and approximately 60-80% of a conventional dye fixes to the fabric. AVITERA SE has three reactive groups enabling 90% of the dye to fix to the fabric. The gives a higher yield.

But the main cost saving is achieved through the reduction in the amount of water and energy needed to wash off the unfixed dye. As there is less unfixed dye to wash off, less water is needed and the process is shorter.

Using standard dyeing equipment with conventional reactive systems it takes an average of 100 litres of water to dye and finish 1kg of knitted cotton (excluding pre-treatment and finishing). AVITERA SE reduces this to 15-20 litres/kg.

Less salt is needed to enhance absorption and the washing process can therefore be done at lower temperatures of about 50°C because the unfixed dye is not bound to the fabric fibres in a high-salt solution. As a result of using a lower temperature both energy consumption and CO2 emissions are reduced.

“This molecule gives all the benefits to the customer of productivity and energy savings, as well as avoiding any harmful molecules that might end up in the water,” says Sarada Namhata, global vice president, research and technology, Huntsman Textile Effects.

Huntsman is encouraging its customers to think about the full processing costs. The unit price of an AVITERA SE dye will often be more expensive than the dye the customer has traditionally used, explains Hulme. But it will save them money when the processing costs are considered.

A textile mill using AVITERA SE, instead of current best-available technologies, can reduce water consumption, energy consumption and CO2 emissions by up to 50% each across the full process from pre-treatment through to finishing. Salt consumption can also be reduced by 20% and cycle time by 25%.

When compared to conventional dye house technologies, which the majority of textile mills in the developing nations use, the savings are greater, says Hulme. “The savings also allow them to increase capacity by 50% for zero capital,” he adds.

“We’re very proud of our business ethics and compliance. I think that really differentiates us in many cases to others in the market,” says Hulme. “We are increasingly seeing customers tell us that if their supplier tells them Huntsman is their partner then that ticks the box.”

Huntsman Textile Effects creates, manufactures and markets a broad range of chemical and dye products. Hulme explains that the company is one of the few chemical producers that also supplies dyes to its customers, but is not just a dye producer like many of its competitors.

The company has over 10,000 customers in 90 countries, employs 4,200 people and operates seven primary manufacturing facilities located in six countries (China, Germany, India, Indonesia, Mexico and Thailand).

Half of the 30-35 new products and innovations Huntsman brings to the market each year are related to the environment and sustainability. “We have a great [research and development] pipeline, continuously bringing out sustainable products and solutions to meet industry needs,” says Namhata. “This is very much aligned to Huntsman Corporation’s overall focus on sustainability as a company,” he continues.

Hulme explains that the company supports innovation using a business model with three pillars – sustainability and bringing solutions to customers; a continued focus on innovation; and collaboration with trade partners, governments and key customers. “Innovation is our over-arching theme and collaboration is key,” agrees Namhata.

AVITERA SE launched in 2011 and since then Huntsman has being going through the registration process in various countries and focusing on building up the colour shades and products to have a complete package for the customer.

Customers in western Europe, North America, Central America, South America and India are have started using AVITERA SE. For example, the textile mills that Lacoste and Marks and Spencer buy fabric from are using AVITERA SE.

Registration has also recently been completed in China. “It’s a very important market. It’s a country where the textile industry needs this type of innovation, but it’s taken three years to complete the approval and registration process. We always knew we’d have a three year lead time, particularly in key markets,” says Hulme.

The company is working directly with brands and retailers to coordinate with the mills and communicate with consumers. This improves cooperation throughout the textile value chain, resulting in greater environmental awareness and more sustainable textile processing. It is also working with the mills to adapt their production processes to ensure they achieve the possible savings using the AVITERA SE dyes.

“We’re excited about this and customers who have either taken it or are aware that it’s coming are also excited about it. They recognise that they need AVITERA SE, not just for the environment but to reduce processing costs and make sure they remain competitive. So I think the market is really going to embrace this,” says Hulme.