VTT Technical Research Centre of Finland and Aalto University are taking Finnish fibre technologies towards industrial scale manufacturing in their joint TeKiDe project. The project transforms wood fibres and discarded cotton textiles, such as used sheets and towels, into viscose-type fibre to be used as raw material for textile products.
The project develops particularly the carbamate, BioCelSol and Ioncell-F technologies that are more environmentally friendly and safer than the production method of viscose, based on the use of carbon disulfide. The project is funded by the Helsinki-Uusimaa Regional Council's Structural Fund for Mainland Finland programme, the City of Espoo, VTT and Aalto University.
The test runs will be performed at VTT's Bioruukki piloting centre in Espoo, where a piloting environment based on wet spinning technique has been built during spring.
A single piloting process includes several steps: collection of waste textiles; removal of mechanical parts, such as buttons and zippers; grinding of textiles; chemical pretreatment; cellulose modification (such as carbamation), dissolution in sodium zincate; filtering of the solution; air removal; spinning; post-processing of the fibre (such as bleaching) and drying.
The TeKiDe project began last autumn and will be completed by the end of 2018.
In its own part of the project, the Aalto University prepares for the scale-up of the Ioncell-F process. The Ioncell-F technology, based on direct dissolution of cellulose, has been developed in collaboration between Aalto University and the University of Helsinki. The process uses dry-jet wet spinning technique, which gives excellent tenacity to fibres. The most important part of the project is to develop a recovery system that would enable closed water and chemical loops in the process. The project will select equipment suited for the process and examine in which respects equipment used for other technologies developed during the project could be used for the piloting of the Ioncell-F process as well. The scale-up and piloting will not be implemented as part of this project.
Carbamate and BioCelSol technologies
In the first trial, approximately 150 kg of cellulose carbamate fibre will be produced from recycled cotton using carbamate technology owned by VTT. Dissolution of cellulose is enhanced by forming carbamate groups in cellulose chains with the help of urea. The cellulose carbamate thus formed dissolves in cold sodium zincate solution, which is regenerated into carbamate fibre by precipitating the solution in acid.
Another potential technology to be demonstrated is BioCelSol, which is jointly owned by VTT and the Tampere University of Technology. In BioCelSol technology, the dissolution of cellulose is enhanced by means of mechanical and enzymatic treatments before dissolution in sodium zincate. The trials using BioCelSol technology have not been confirmed yet.