| 摘要 |
<p>1484230 Recovering PVC SOC ITALIANA RESINE SIR SpA 29 July 1975 [10 Sept 1974] 31719/75 Heading C3P In a process for cleaning PVC deposits from polymerization vessels by solution in a solvent, the solvent and polymer are recovered by feeding the solution gradually into an evaporation zone containing an inert solid powder under conditions such that the powder form is maintained and for a period such that the ratio of polymer to inert solid does not exceed 5 : 1. In examples PVC deposits are dissolved in cyclohexanone or toluene/dimethyl formamide or vinyl chloride/vinyl acetate copolymer in tetrahydrofuran, concentrated if desired and evaporated in a mixing apparatus containing calcium carbonate, kaolin or diatomaceous earth, in the presence of a heat stabilizer.</p> |
