Never say dye

A polymerisation process developed by a Leeds University spinout could lead to polyester garments never fading in the wash and food packaging that absorbs UV rays, keeping contents fresh.

The Leeds University team, led by colouration technology lecturer Richard Blackburn, is commercialising the process through DyeCat.

The team’s patented technique introduces colourant into the polymerisation process so that polymers are pre-coloured and do not require dyeing.

This could also be used for introducing UV absorbers into the polymerisation process so that biodegradable polymers, such as polyactic acid (PLA) used in packaging, will have UV-absorbing capabilities. This UV barrier would then protect foodstuffs from UV degradation. Normally, coloured polyester garments are made by melting a polymer and passing it through a spinneret, which creates fine filaments that can be twisted together into a fibre. The fibre is then further processed and dyed.

Blackburn said that the traditional dyeing process involves harmful chemicals and gallons of water that must later be treated. ‘It also consumes a significant amount of energy and it creates pollution,’ he added. The Leeds researchers developed a polymerisation technique that uses an aluminium catalyst surrounded by a dye complex. The colour develops as the chemicals covalently bond to one another and the polymer grows.

The technique is more environmentally friendly because it does not use harmful wet chemical dyes and it is more economical because it cuts down a significant amount of processing.

The other advantage of the technique, according to Blackburn, is that it produces polymers with much brighter colours that do not wash out.

‘It is because the colour is distributed more homogenously through the fibre,’ he said. ‘It is also perfectly washfast because these dyes are covalently linked into the polymer chain.’

Blackburn added that the use of aluminium for the catalyst is also significant. Aluminium, he said, is a much safer choice than catalyst metals such as antimony, which is used in the production of polyester, and tin, which is used in the production of PLAs. Both are deemed toxic.

Other concerns focus on leaching. Many consumer groups worry about the chemical contents of plastics used to bottle drinks or wrap food and the possibility of those chemicals leaching out with time and deformation.

Blackburn said that the UV absorbers used in PLA packaging produced with his team’s process have no chance of escaping.

‘There is no potential for the UV absorber to leach out into the contact food because it is built into the polymer chain,’ he said.

The DyeCat team is so confident about the safety of its process that it is now targeting the medical market for biopolymer applications in medicine and surgery.

The key now will be to find the right partners to help the team take the products to market.

‘We could work with a small-scale manufacturer who wants to do some garments, even if it’s just a line of socks,’ said Blackburn.

‘However, in the long term, our technology might actually have some significant application in the medical field. That’s where I think it could have the biggest impact,’ he added.

Siobhan Wagner