An Efficient Method To Depolymerize Polyamide Plastics:  A New Use of Ionic Liquids

Abstract

Treatment of polyamides in an ionic liquid at 300°C resulted in the efficient depolymerization of polyamides to give corresponding monomeric lactam in good yields. The recovered monomer was collected by direct distillation of the reaction mixture. PP13 TFSI furnished the best results for the depolymerization. The ionic liquid could be recycled five times in the present reaction.Development of an effective method for treating waste plastics is one of the important problems in recent environmental issues. Among several treatments developed thus far, the ideal one is undoubtedly chemical recycling, in which waste plastics are converted into corresponding monomers suitable for repolymerization reactions that reform recycled plastic. 1 To accomplish optimal recycling, an easy and efficient method to depolymerize polymers into corresponding monomers must be developed. Depolymerization methods developed thus far are usually performed under hightemperature conditions, and therefore, high-boiling-point solvents or high-pressure apparatus is necessary. For these purposes, supercritical water 2 or other solvent systems 3 frequently have been employed, and pyrolysis of polymers has been used in some cases. 4 These methods have sometimes taken advantage of depolymerization; however, due to the high temperature of the reaction, special care is required to prevent the possibility of fire. In addition, special apparatus that tolerates the high-pressure conditions is essential to perform the reaction. Recently, ionic liquids have been of interest in many fields of chemistry because of their unique properties such as solubility, nonvolatility, highreactivity, low-flammability, etc. 5 Nonvolatility and stability at high temperature make the ionic liquids suitable for this purpose. Moreover, the possibility of recycling is important for achieving a zero-emission recycling system. To the best of our knowledge, thus far, there have been no practical reports on such use of ionic liquids. 6 In this paper, we discuss

Multifaceted catalytic hydrogenation of amides via diverse activation of a sterically confined bipyridine–ruthenium framework

“…80% consistent (the structures of the two monomer units cannot be disclosed here due to a confidentiality agreement with Toray). This might pave a new avenue for recycling monomer derivatives, as an alternative to the depolymerization of polyamides (e.g., 6-nylon) that proceeded at 300 °C 50 .…”

Separation Performance and Stability of PVDF-co-HFP/Alkylphosphonium Dicyanamide Ionic Liquid Gel-Based Membrane in Pervaporative Separation of 1-Butanol

“…The gel showed significantly lower thermal stability than the pure copolymer or the RTIL. The polymer's thermal degradation was possibly accelerated in the presence of the RTIL, which promoted amorphous phases and catalyzed the scission of carbon-carbon covalent bonds in PVDF-co-HFP (29).…”

Chemical Recycling of End‐of‐Life Polyamide 6 via Ring Closing Depolymerization

“…Purification of the product was carried out by extraction or distillation to isolate the monomer 3 and to recover the ionic liquid. However, under these conditions the ionic liquid tends to decompose, which hampers the overall atom economy of this procedure …”

“…However, under these conditions the ionic liquid tends to decompose, which hampers the overall atom economy of this procedure. [40][41][42][43] Recently, we have demonstrated the application of acetic anhydride as depolymerization reagent in the depolymerization of poly(bisphenol A carbonate) in the presence of DMAP as catalyst. [44] As major product diacetylated bisphenol A was obtained.…”