Solid material comminution or disintegration – Processes – With application of fluid or lubricant material
Patent
1994-02-16
1995-10-31
Davis, Robert B.
Solid material comminution or disintegration
Processes
With application of fluid or lubricant material
241 29, 264 37, 264344, B02C 2318
Patent
active
054622336
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for recovering recyclable expanded particles from expanded particle moldings comprising expanded particles coated with specific interfacial material. The expanded particles comprise polyolefin and the like. Recyclable expanded particles are recovered from moldings produced thereof by the steps comprising melting, softening or dissolving the interfacial material and separating into individual particles.
BACKGROUND ART
Expanded particles of synthetic resins such as polystyrene, polyethylene and polypropylene are molded in various forms and widely used as packing medium, cushioning medium and insulation. After being used, expanded particle moldings are generally crushed with a crusher and then burnt up or buried under the ground. When the resins are burnt up, environmentally harmful gases such as carbon monoxide and carbon dioxide are generated in a large amount, and resins including chloride and nitrogen generate various types of gases poisonous to living things. Also, it is necessary to secure land to bury crushed resins under the ground. For the purpose of recycling the crushed resins, expanded particle moldings produced from the same resin must be collected. It requires a great deal of labor to select resins.
Japanese Patent Application Laid-Open Nos. 83145/1988 and 119687/1977 disclose a process for recovering recyclable resin chips from expanded particle moldings. The process comprises crushing expanded particle moldings comprising, for example, polystyrene or polyethylene, heat-melting the crushed expanded particle moldings to remove gas generated from the particles present in the melted resin, extruding the melted resin in a filament form and cutting the extruded resin into proper sizes. The recovered resin chips, however, have the drawbacks in that moldings of good quality cannot be produced therefrom because the resin chips have lost, in the recovering process, their suitable properties for expansion due to deterioration during heating and mixing of foreign substances therewith.
Japanese Patent Application Laid-Open No. 278939/1991 and German Offenlegungsshrift No. 2,462,040 disclose a process for mechanically separating expanded particles from expanded particle moldings of polystyrene or polyethylene and the like in a crusher. According to this process, expanded particle moldings are directly crushed by mechanical force. As a result, the recovered expanded particles tend to be mechanically damaged. Moreover, in this process, individual expanded particles are not completely separated so that there remain blocks of the expanded particles.
An object of the present invention is to solve the above problems and to provide a process for recovering recyclable expanded particles from used expanded particle moldings comprising synthetic resin, without producing bad effects on the environment.
DISCLOSURE OF THE INVENTION
The present invention relates to a process for recovering expanded particles from expanded particle moldings comprising expanded particles of a synthetic resin coated with a thermoplastic resin (interfacial material) whose melting point is lower than that of the synthetic resin of expanded particles or whose solubility is different from that of the synthetic resin of expanded particles, which process comprises the steps of softening or melting the interfacial material by heating or dissolving it with a solvent, and separating into individual particles by applying a shearing force under circumstances such that the bond strength among the expanded particles is weakened.
The resin suitable for recyclable expanded particles recovered from expanded particle moldings include: the following range: .multidot.cm/cm.sup.2 .multidot.sec.multidot.cmHg and .multidot.cm/cm.sup.2 .multidot.sec.multidot.cmHg; or the following range: .multidot.sec.multidot.cmHg and .multidot.cm/cm.sup.2 .multidot.sec.multidot.cmHg
In the above equations, Pe.sub.(N.sbsb.2.sub.) and Pe.sub.(C.sbsb.3.sub.H.sbsb.8.sub.) represent transmission coefficients of nitrog
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patent: 4839392 (1989-06-01), Kromrey
patent: 5198471 (1993-03-01), Naamau et al.
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patent: 5286424 (1944-02-01), Su et al.
patent: 5290505 (1994-03-01), Huber et al.
Derwent Abstract of Soviet Union 654,641 printed Mar. 1979.
Isao Kiba
Masamichi Kaneko
Asahi Kasei Kogyo Kabushiki Kaisha
Davis Robert B.
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