Textile Recycling Technologies, Colouring and Finishing Methods

3.2.2 Nylon Recovery and Recycling 
The closed-loop recovery of Nylon-6 has been widely used in the carpet industry, through 
combining mechanical and chemical (depolymerization) processes.
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Chemical or monomer 
recovery systems are applied to volatized caprolactam after spinning operations during Nylon-6 
fibre formation.
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The depolymerization of Nylon-6,6 is more complicated, since it is composed 
of two different monomers and often requires a larger volume of reagents, which may be 
potentially more damaging, and produce more waste product.
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Chemical recycling of Nylon-6,6 
is not performed commercially, and monomer recovery systems are not feasible given that the 
processing of the compound does not yield large volumes of residual monmers.
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 Nylon-6,6 is 
commonly recycled mechanically from pre-consumer fibres.
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3.2.2.1 Mechanical Recycling 
The process for the mechanical recycling of nylon may involve the following steps (outlined in 
Figure 11): 
-Cleaning process to remove impurities 
-Shredding and grinding 
-Melting into chips/pellets from which they can be used in new applications 
-For fibre production: the recycled chips are melted and respun into filaments
Figure 11: General route for mechanical recycling of nylon.
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Due to its lower melting temperature (compared to PET), nylon is highly susceptible to 
contamination by microbes, bacteria, and nonrecyclable impurities remaining in the material, and 
thereby requires a cleaning process prior to recycling.
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3.2.2.2 Chemical Recycling 
Chemical recycling of nylons (6 and 6,6) includes a depolymerization process followed by 
distillation to obtain and recover their monomeric constituents: caprolactam (for Nylon-6), and 
HMDA and adipic acid (for Nylon-6,6).
Various chemical processes have been demonstrated and developed, and are summarized in Figure 
12. Barriers to their widespread adoption have included high costs, challenging materials issues, 
multiple processing steps requiring high operational knowledge, which are thought to pose 
difficulties for technology transfer.
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Figure 12: Overview of different approaches for chemical recycling of nylon. 
Produced from 
[68].
Current chemical recycling operations for both Nylon-6 and Nylon-6,6 (to a lesser extent) include 
the ammonolysis method, created by DuPont (Figure 13), and patented processes for Nylon-6 
chemical recovery by TORAY - CYCLEAD™, Aquafil, and Hyosung.
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Figure 13: Overview of DuPont ammonolysis chemical recycling process for nylon. 
Reproduced from
 [69].
 
 

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