| 摘要 |
<p>Disclosed is a method for reducing the portion of cyclical oligomeric ethers contained in polytetrahydrofuran (PTHF) or tetrahydrofuran (THF) copolymers, according to which the PTHF or the THF copolymers is/are extracted in one or several steps with a aliphatic, linear, branched, cycloaliphatic, or olefinic hydrocarbon containing 4 to 15 C atoms, mixtures of said hydrocarbons, or mixtures containing at least 50 percent by weight of said hydrocarbons at temperatures ranging from 30 to 200 °C, and the PTHF phase or THF copolymer phase is separated from the hydrocarbon phase. The extraction process takes place in a column comprising a central stirrer which extends across several superimposed stirring areas. The ratio between the circumferential speed cubed of the stirrer and the height of the stirrer is greater than 0.5 m2/s3.</p> |
