1997 Fiscal Year Final Research Report Summary
A Design of Recyclable Polymer-Preparation of Styrofoams with Dispersed Catalyst
| Project/Area Number |
08555256
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
資源開発工学
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| Research Institution | Faculty of Engineering, Shizuoka University |
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Principal Investigator |
UENO Akifumi Dept.of Eng., Shizuoka University Professor, 工学部, 教授 (30135420)
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| Co-Investigator(Kenkyū-buntansha) |
OKADA Mitsunori Furukawa Electric Co., Senior Researcher, 主任研究員
KUROYANAGI Takashi Japan Electric Cable Technology Senior Engineer, 技師(研究職)
AZUMA Naoto Coop.Research Center, Shizuoka Univ., Associate Prof., 地域共同研究センター, 助教授 (50192464)
MORIOKA Yoshio Dept.of Management, Hiroshima Pref.Univ., Professor, 経営学部, 教授 (70022241)
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| Project Period (FY) |
1996 – 1997
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| Keywords | waste plastics / Recycle / Chemicals recovery / degradation / polystirene / styrofoam / solid bases / barium oxidc |
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| Research Abstract |
Catalytic degradation of waste polystirene into stirene was studied using various kinds of solid acids and bases as catalysts at 623 K in flowing nitrogen. Partially because of the high yield of distilllates from polystirene and partially because of the high selectivity into stirene in the distilllates yielded, solid bases were emphasized to be effective for the chemical recycling of waste polystirene. This is ascribed to the difference in the degradation mechanisms of polystirene on solid bases and acids. On solid acids the degradation will start with the addition of proton to branched phenyl group of polystirene to produce pi-complex cation, which is converted into sigma-complex cation to be released as benzene. Cations remained on C-C bonds attack to the neighbor phenyl group to produce indan derivatives. Thus, many kinds of by-products are detected in the oils obtained by solid acids, although the main product is still stirene including both stirene monomer and dimer. While in the
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oils obtained by solid bases neither benzene nor indan derivatives ara detected, which is the case observed in the oils produced by a simple thermal degradation of polystirene. This suggests that the degradation on solid bases proceeds in a way similar to that in the simple thermal degradation, i.e., depolymerization starting with the formation of carboanions by the elimination of a hydrogen atom of polystirene adsorbed on base sites.
Among the solid bases barium oxide was the best for the chemical recycling of waste polystirene into stirene. More than 85 wt % of polystirene was converted into stirene monomer and dimer, when it was degraded at 623 K in the presence of barium oxide as a cataiyst. Then, we tried to disperse a small amount of bariumu oxide powder into polystirene pellets when they are molded into thin films using a heating twin-roller. The amount of barium oxide powder dispersed was I wt % of polystirene pellets employed. Thus we prepared polystirene films with dispersed barium oxide catalyst as a model of recyclable plastic. The films were crushed into small pieces sized adout 5 x 5 mm, and submitted to a thermal degradation test without addition of any other catalytic compounds. More than 85 wt % of the films was degraded into stirene monomer and dimer at 623 K.
The polystirene films with dispersed catalyst were expanded into styrofoams by means of absorption/desorption of nitrogen gas at room temperature with 30 atmandat 393 K,respectively, using an autoclave. Homogeneously expanded styrofoams were prepared by a rapid evolution of nitrogen absorbed in the films. In some commercial processing a small amount of calcium carbonate powder is dispersed in polystirene films as foaming additives to prepare homogeneously expanded styrofoams, so that the barium oxide powder can work as foaming additives for the production of styrofoams as well as the degradation catalyst. It was observed that the styrofoams with dispersed barium oxide catalyst were well converted into stirene monomer and dimer when they were simply degraded at 673 K without assistance of any other catalytic compounds. Less
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