Waste disposal and opt. reuse of styrene] foam - by degassing using low mol. wt. alkane(s) and/or alcohol(s) to cause redn. in vol. followed by re-expanding

摘要

Solid polystyrene foam (I) is treated with a degassing agent (II), liq. low mol. wt. alkanes (IIa) and/or alcohols (IIb) with a simultaneous redn. in vol. by degassing. (II) is then at least partially sepd. from the polystyrene which may be opt. reused. Pref. (IIa) is a 5-7C alkane, pref. pentane and (IIb) is a 2-5C monoalcohol, pref. ethanol. (II), pref. in small amts., is a solvent for (II) and is pref. a volatile solvent. Degassing of (I) is at room temp. to 40 deg. C and the sepn. of (II) may opt. occur at normal pressure. (I) is at least partially comminuted, pref. by milling to approximately the size of the initial foam beads. Moisture arising from water washing of (I), prior to treatment may be sepd. from the water immiscible (II). Polystyrene is reused by thermal processing, opt. in an admixture with fresh polystyren to form moulded foam articles. Foaming is by addn. of a low mol. wt. alkane, pref. pentane. Residual alkane content of the polystyrene following the defoaming step (less than 10 wt.%, pref. 4-8 wt.%) may be used for refoaming. Refoaming is after defoaming with ethanol at its b.pt. or with liq. alkanes at 15-25 deg. C without addn. of a solvent for polystyrene. Solvents for polystyrene are added at less than 10 vol%, pref. 3-5 vol% (w.r.t. alkane). (I) with a relatively large particle size is initially degassed and at least partially sepd. from (II) followed by further comminution to the primary bend size whereupon it is subjected to the effect of the appropriate liq. alkane as a propellant. Deactivated polystyrene that is propellant free or contains low amt.s of propellant is refoamed to its original capacity by the influence of the appropriate liq. alkanes as propellant. USE/ADVANTAGE - For the disposal and opt. reuse of solid polystyrene foam (I), partic. of moulded waste foam. Process is energy efficient and operates below 100 deg. C.