Polyester chemical recycling is a two-step process: depolymerisation and polymerisation. In the depolymerisation process, polymer chains are broken down into their fundamental units (monomers), which are isolated and used in a subsequent polymerisation stage, producing new polymers with properties similar to the virgin polymer. Thus textile waste can be recycled an infinite number of times without losing any of its properties.

>  It allows the recycling of all types of textile waste regardless of its state of degradation, i.e. post-industrial, pre-consumer or post-consumer origin.
>  It allows waste to be recycled independently of the pollutants present in the textile fibres (additives, dyes and coating).
> It allows waste to be recycled an infinite number of times without loss of properties (upcycling).
> It reduces the consumption of fossil-based raw materials, using textile waste as raw material to produce new textile products.
> To implement a chemical process with almost zero waste through the reuse of all chemical reagents involved in the process, thus reducing the consumption of fossil raw materials.

CHEMICAL RECYCLING OF POLYESTER TEXTILE FIBRES

Among the different polyester chemical recycling technologies, thermal depolymerisation and catalytic depolymerisation are of particular interest. The many advantages of catalytic depolymerisation over other technologies mean that this strategy is being studied in greater depth by the scientific community, with the first industrial plants opening in Japan, the United States and India.

Depending on the solvent used in the catalytic depolymerisation reaction, the process is called glycolysis, hydrolysis, methanolysis, aminolysis or ammonolysis. Among the available depolymerisation processes, glycolysis is the most well-studied and developed, due to its many advantages: (i) simplicity and flexibility, (ii) low investment and maintenance costs, (iii) milder reaction conditions, (iv) low solvent volatility. (v) The main products are bis(2-hydroxyethylene terephthalate), BHET, an intermediate product in polymerisation and (vi) the glycolysis process which can be easily applied to conventional PET production plants.

CHEMICAL RECYCLING OF COTTON TEXTILE FIBRES

Chemical cotton recycling is still in its infancy and needs further R&D before it can be implemented on a commercial scale. Specifically, chemical cotton recycling is a process of fibre dissolution and regeneration through spinning by means of a “dry jet wet spinning” process.

In this line, ionic liquids (IL) have proven to be efficient solvents for cellulose-based materials and can be used for the chemical reprocessing of cotton. Recent studies on the application of IL as a solvent for cellulosic fibres showed important benefits during the process, such as low vapour pressure, the excellent mechanical properties of the fibres obtained, and the fact that it can be performed in a single step. The process, known as Ioncell-F, creates chemically recycled natural fibres with mechanical properties far superior to commercial viscose and Lyocell fibres.

AITEX is currently developing several research projects, both at national and European level, focused on the chemical recycling of textile waste, mainly polyester and cotton. To this end, we are studying and validating a pilot process using new more active and sustainable catalysts, adsorbents with greater efficiency in the purification and elimination of pollutants, as well as the optimisation of the main process variables to develop a more sustainable, efficient and profitable chemical recycling technology on an industrial scale.

Learn about the R&D projects on textile chemical recycling