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( Shogo Kumagai ),( Harendra Kumar ),( Tomohito Kameda ),( Yuko Saito ),( Toshiaki Yoshioka ) 한국폐기물자원순환학회 2022 ISSE 초록집 Vol.2022 No.-
The wire harness assembly, used to conduct electricity to vehicle components and electrical and electronic appliances, is abundantly present in waste electrical and electronic equipment (WEEE) and end-of-life vehicles (ELVs). Wire harnesses usually consist of copper (Cu) strands coated with thin polyvinyl chloride (PVC) cables. Current technologies for recycling this waste are either ineffective or have significant limitations because they are currently only available for thick and uniform cables. Therefore, this work developed combined PVC swelling by organic solvent and ball or rod milling approaches for the recovery of high purity Cu and PVC from thin and ununiform cables in waste wire harnesses. We developed both lab-scale and bench-scale milling reactors to thoroughly investigate the milling efficiency and the separation mechanism, and the subsequent scaling up for the developed process. The PVC swelling behavior and the plasticizer removal from the PVC coatings by the selected organic solvents were thoroughly evaluated by employing Hansen Solubility Parameters (HSPs) and the effectiveness of the swelling ratio on the separation of PVC coatings and Cu wires were investigated by using lab-scale reactor. n-Butyl acetate and acetone were selected as the best solvents for PVC swelling and plasticizer removal. This work achieved complete recovery of PVC coatings, Cu wires, and plasticizers from the waste WH cables by the bench-scale reactors. Thus, this work established both the academic and technical bases of the developed approaches combining PVC swelling and milling processes.
Steam Pyrolysis of Poly(4,4’-Oxydiphenylene-Pyromellitimide) using Ni-Based Catalyst
( Shogo Kumagai ),( Tomoyuki Hosaka ),( Guido Grause ),( Tomohito Kameda ),( Toshiaki Yoshioka ) 한국폐기물자원순환학회(구 한국폐기물학회) 2015 한국폐기물자원순환학회 3RINCs초록집 Vol.2015 No.-
Poly(4,4’-Oxydiphenylene-Pyromellitimide) (PI) is often used in flexible printed circuit boards. However, the excellent thermal stability of PI makes it difficult to recycle. In this work, steam pyrolysis of PI, known under the trade name “Kapton®”, was carried out in order to recover synthetic gas. Pyrolysis of PI at 900 ºC produced a significant amount of char, and less of gases such as H<sub>2</sub>, CO, and CO<sub>2</sub>. Furthermore, 37 mL/g sample of hydrogen cyanide (HCN) was also produced, among other toxic compounds. However, a significant amount of char was converted into H<sub>2</sub> and CO in the presence of steam, producing 2082 mL/g sample of H<sub>2</sub> and CO rich gases with 15 wt% of char. Additionally, Ni-based catalysts such as Ni-Mg, Ni-Al, and Ni-Mg-Al oxides were synthesized to decompose HCN, resulting in minimum volume of 0.6 mL/g sample in the presence of Ni-Mg-Al.
( Shogo Kumagai ),( Ryosuke Yabuki ),( Tomohito Kameda ),( Yuko Saito ),( Toshiaki Yoshioka ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-
Development of effective recycling technique for polyurethane (PU), which is one of the most common polymers used in electrical and electronic equipment and automobile, is an inevitable task. However, it is extremely difficult since there are wide variety of PU materials with different combinations and ratios of monomers. This work focused on pyrolysis technique, which cleaves several chemical bonds in polymers and produces gas, liquid, and solid by heat. One well-known major hurdle in the pyrolysis of PUs is the emission of toxic hydrogen cyanide (HCN) and the efficient removal of HCN must be achieved for the recovery of useful chemicals from PU wastes through the pyrolytic approach. In this work, product gas from thermal degradation of PU materials such as cushion (flexible PU foam) and insulator (rigid PU form) at 500 °C were converted into H<sub>2</sub>-rich syngas and the toxic HCN in it was simultaneously removed by Ni/Mg/Al catalyst at 800 °C under 50 vol% steam/He flow. The resultant total gas production was maximum 1623 mL/g (H<sub>2</sub>: 946 mL/g), which was ~30 times bigger than that obtained from simple pyrolysis of PUs. Meanwhile, there was a drastic reduction of HCN concentration in the product gas from a maximum at 2.8 to minimum 0.2 vol%.
Influences of hard- and soft- segment ratios on pyrolysis behavior of polyurethane elastomers
( Yuya Nishiyama ),( Shogo Kumagai ),( Tomohito Kameda ),( Yuko Saito ),( Atsushi Watanabe ),( Suguru Motokucho ),( Hisayuki Nakatani ),( Toshiaki Yoshioka ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 한국폐기물자원순환학회 심포지움 Vol.2019 No.1
Introduction Polyurethane elastomers (PUEs) are typical block copolymers which are composed of alternative hard segment (HS) and soft segment (SS), with the physical and chemical properties of them can be varied by changing HS and SS ratios. Pyrolysis is a promising method for polymeric wastes recycling because it can convert various polymers into chemical feedstock only by heat1). In this study, seven kinds of PUEs with different HS and SS ratios were synthesized (Fig. 1), then influences of hard- and soft-segment ratios on pyrolysis behavior were investigated. Methods, Results and discussion 1. Identification of pyrolysis products: Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was employed to characterize the pyrolysis products under elevated temperature shown in Fig. 2. All the PUEs produced MDI, MAI and MDA (Fig. 3) from HS through pyrolysis, which were formed by pyrolytic urethane bond cleavage via 4-membered and 6-membered transition states shown in Scheme1. 2. In-situ monitoring of ticpyrolysis products: In-situ monitoring of pyrolysis products, called evolved gas analysis-MS (EGA-MS), was performed under the same pyrolysis conditions as the previous section. EGA chromatogram and representative products are shown in Fig. 4. Pyrolysis of various PUEs with different HS and SS clearly showed presence of three pyrolysis zones. In the zone 1, HS decomposition products such as CO<sub>2</sub>, butanediol (BD) and MDI are generated from five PUEs having HS. This suggested that formation of isocyanate end shown in Scheme1-I was dominant at this temperature. In the zone 2, SS-derived products and CO<sub>2</sub> were mainly formed from the five PUEs with low HS ratios. MDI was not produced in this zone, while MAI and MDA were produced. These results revealed that the high temperature promoted formation of the amine end shown in Scheme1-Ⅱ. In addition, a part of the SS-derived product could be generated by decomposition of MDI between HS and SS. In the zone 3, SS-derived products were produced from all PUEs, and the SS decomposition was continued. Thus, the temperature-dependent pyrolysis behavior was proposed (Scheme2) based on the findings in this work. Conclusion Temperature-dependent pyrolysis behavior of PUEs with different hard- and soft-segment ratios was investigated through pyrolysis tests employing Py-GC/MS and EGA-MS techniques. The findings in this work will be helpful to control product selectivity and feedstock recovery through pyrolytic approach.