POLYETHYLENE TEREPHTHALATE WASTE RECYCLING TECHNOLOGY TO PRODUCE TEREPHTHALIC ACID AMIDE

Abstract

The purpose of this study is to conduct and study the process of chemical recycling of solid household waste of polyethylene terephthalate (PET) with a mixture of amino alcohols (monoethanolamine and triethanolamine) under relatively mild conditions and without the use of catalysts. It was revealed that during the reaction of PET with a mixture of amino alcohols of a low molecular weight white product is formed, containing in its structure an aromatic core, two amide and two hydroxyl groups - N, N'-bis (2-hydroxyethyl) terephthalamide. The most effective purification and isolation of the target low molecular weight compound from the reaction mixtures is achieved by recrystallization from water. The structure of the obtained compound was studied using IR Fourier spectrometry, gas chromatography-mass spectrometry and differential scanning calorimetry, as well as some physicochemical properties of the obtained compound (solubility, melting point). A technological scheme for obtaining this low molecular weight substance in relatively large volumes by a periodic method with the regeneration of the initial amino alcohols for their reuse is proposed. The process is carried out in a heated batch reactor, which receives crushed PET waste, as well as a mixture of amino alcohols. The reaction mass is maintained at a temperature of 160 °C and periodic stirring for 3-4 h. After completion of the reaction and cooling the mixture is fed into the apparatus-crystallizer for further selection of the target product by crystallization from water. In addition, on the basis of the available experimental data and theoretical assumptions, the possibility in principle of using the obtained low-molecular compound as a monomer in the polycondensation reaction to obtain polyamidoesters is considered, similar to the principles of obtaining polyethylene terephthalate from diglycolterephthalate. It was shown that the depolymerization product enters into a polycondensation reaction with the formation of an oligomeric product - a viscous, resinous mass having a color from yellow to caramel.