| 摘要 |
<p>Thermoplastic linear polyesters such as polyethyleneterephthalate and polytetramethyleneterphthalate (sometimes called polybutyleneterephthalate) are prepared in the form of a pure, controlled particle size powder form either bulk material of virgin nature or, more importantly, form scrap containing a variety of contaminants, the process involves dissolving the polyester values in a polar solvent at an elevated temperature, under conditions chosen so that there is no degradation of the molecular weight of the original polyester, filtering the hot solution, cooling the filtrate to a temperature at which the polyester values being to crystallization begins in order to control the particle size, filtering off and washing the powdered polyester after precipitation is complete with the solvent used for initial solution of the polyester, treating the filtrate obtained therefrom after removal of the polyester values by known techniques for purposes of recovery of pure solvent and recovery of other values which may be present as contaminants in the original polyester by flushing with water, a lower alcohol, and/or an alkyl ketone, or by distillation.</p> |
