Swedish researchers have succeeded in making new viscose from worn-out cotton sheets. The development is significant since till now viscose textiles were made of biomass from the forest, and there was no such thing as fully recycled viscose.
- The new technique developed at Lund University could soon be a commercial proposition that instead produces viscose from recycled textiles—and therefore saves on valuable forest resources.
- Late last year, the researchers published a study that shows the process. In the coming years there are plans for a pilot plant somewhere in Europe. The method has already been tested regarding the spinning of viscose threads, and the results were excellent.
THE RESEARCH: Edvin Bågenholm-Ruuth, doctoral student in chemical engineering at Lund University, and his colleagues found a way to loosen up and convert the complex cotton fibres into viscose fibres.
- The inexpensive process requires a simple salt—zinc chloride—which dissolves in water. Another advantage is that a smaller percentage of the toxic substance carbon disulphide is needed compared to standard processes. The result is good-quality viscose fibre, even though the process needs to be further optimised.
- The textiles are first placed in a zinc chloride solution and within one hour everything is transformed into a gooey mass.
- Water is added, leading to the precipitation of a fluffy white mass known as a “dissolving pulp,” which can be filtered off from the liquid. This pulp can then replace the corresponding wood pulp used in today’s viscose process.
- In the next stage, the pulp is treated with a number of chemicals, including carbon disulphide, to make it soluble in sodium hydroxide. The pulp is dissolved, spun and then cut into viscose fibres.
VISCOSE NOW: Viscose, sometimes referred to as artificial silk, is a common constituent of clothes such as blouses, skirts and dresses. The raw material is cellulose, in most cases wood.
- Old textiles around the world end up at the rubbish tip and are often burned. In Sweden, they are generally burned to produce district heating.
- There are already viscose variants that are to some extent produced using old cotton fibres. However, a satisfactory product often requires a high percentage of “virgin” fibre.
PRODUCTION: A company, ShareTex, has been formed to apply the technology and the hope is that this could happen on a commercial scale within five to seven years.
