A fashionable process

A PILOT facility in Finland has successfully trialled an environmentally-friendly process to recycle worn and discarded cotton into new, high-quality fibre.

Developed at VTT Technical Research Centre in Finland, and subsequently spun into yarn at Tampere University of Technology, the recycled fabric was observed to possess characteristics rivalling commercial yarns.

This provides an alternative method to the commonly-used “viscose process”, which requires carbon disulfide for dissolution – a toxic and highly flammable material.

Ali Harlin, research professor at VTT, told The Chemical Engineer more about the process used to manufacture the “natural-feeling” fibre.

“Collected textiles are sorted according to cotton content,” he said. “Cotton content less than 90% starts to be an issue for economics, but not a technical limitation.”

Next, the fabric is shredded, with components like buttons removed. It is then bleached and subjected to carbamate dissolution, by adding urea and heating for three hours at 130°C.

“The carbamate is pulverised. This can now be stored in the dry for long periods of time, and is easy to transport,” he said. When required, this can then be dissolved in sodium hydroxide, and the solution filtered to remove impurities, before finally being spun like viscose fibres.

A startup called The Infinite Fiber Company has been established to advance the process design and license the technology. It is currently undertaking further research to achieve process reliability and develop a range of cellulose-based fibres at VTT’s Bioruukki pilot centre.