Thermolysis and analysis of TDI char by supercritical methanol using TGA, DSC, IR and SEM
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Thermolysis and analysis of TDI char by supercritical methanol using TGA, DSC, IR and SEM Gen‑ding Yu1,2 · Jing‑ling Li1,3 · Ling‑zhu Gong1,4 · You‑gen Chen5 · Liu‑fang Ni1,2 · Lei Peng1,2 · Zhu‑wu Jiang1,3 · Long‑bin Yang1,3 · Yih‑Shing Duh1,4 Received: 17 July 2019 / Accepted: 3 October 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract TDI’s synthetic plant generates about 5 mass % of tar by phosgenation process, which has been currently a bottleneck needed to be broken through for the worldwide TDI companies. At present, the reduction fraction of TDI tar is up to 48% relative to the mass of tar and renders the residue of solid crust known as TDI char. In this study, a suasive and effective reduction method has been found, the supercritical methanol is executed to depolymerize the TDI char, and in short, the char can be readily methanolyzed at supercritical state of methanol. With the outstanding depolymerization capability than various existing approaches, the destruction fraction can achieve 81 mass % at supercritical point. A best value as high as 95 mass % is first discovered at 270 °C, exceeding the efficiency at supercritical state. Characterizations of the intrinsic properties of raw char and char remnant after methanolysis have been implemented by TGA, DSC, FT-IR and SEM-EDS. For industrial applications, the diverse methodologies for recovering TDI or related components by alkaline hydrolysis, distillation, vacuum distillation and thermolysis are also discussed and compared with methanolysis in order to recognize the optimal abatement technique. Keywords Polymer char · Depolymerization · Methanolysis · Supercritical fluid · Polymer degradation Abbreviations ATR Attenuated total reflectance DNT Dinitrotoluene DSC Differential scanning calorimeter DTG Derivative thermogravimetric curve EDS Energy-dispersive X-ray spectroscopy * Jing‑ling Li [email protected] * Yih‑Shing Duh [email protected] 1
FTIR Fourier transform infrared spectrometry IPA Isophthalic acid MTD M-toluenediamine PCB Printed circuit board PET Poly(ethylene terephthalate) SCF Supercritical fluid SEM Scanning electron microscopy STA Simultaneous thermal analysis TDA Toluenediamine, o-toluenediamine TDI Toluene diisocyanate TGA Thermogravimetric analyzer
School of Ecological Environment and Urban Construction, Fujian University of Technology, Fuzhou, Fujian, China
Introduction
Indoor Environment Engineering Research Center of Fujian Province, Fujian University of Technology, Fuzhou, Fujian, China
Introduction to TDI and application
2
3
Center of Safe and Energy‑Saving Engineering Technology for Urban Water Supply and Drainage System, Fujian University of Technology, Fuzhou, Fujian, China
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Institute of Chemical Safety, Fujian University of Technology, Fuzhou, Fujian, China
5
School of Civil Engineering, Fujian University of Technology, Fuzhou, Fujian, China
Polyurethane made of toluene diisocyanate (TDI) is a promising polymer material with excellent physical and chemical properties. Recen
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