| 摘要 |
<p>Batch direct esterification of terephthalic acid (I) with ethylene glycol (II) is carried out as follows. A slurry of (I) and (II) is prepd. at a controlled rate and with a (II):(I) molar ratio of 0.80-1.70 and the slurry is transferred to a storage vessel. It is then transferred from this to a feed vessel in an esterification zone, using a pump under the storage vessel, then to a prim. feed pipe using a prim. slurry feed pump below the feed vessel and finally to a number of batch esterification vessels using several sec. slurry feed pumps, each connecting the prim. feed pipe with one esterification vessel. Esterification is carried out in the presence of esterification prods. at a pressure of -0.5 to 1.0 kg/cm2G. The process gives prods. consisting mainly of bis(beta-hydroxyethyl) terephthalate (III) and/or its oligomers, which are useful for the prodn. of many polyesters of suitable quality for various applications. The stable slurry is transported over a long distance and is convenient to handle. Sepn. of the zone where finely-divided (I) is handled from the esterification zone prevents contamination of PET with (I) dust. No pressure vessels are needed, which facilitates periodic repair or cleaning of individual vessels. High conversions can be obtd. and copolymerisation and addn. reactions can be carried out easily in the esterification stage, making the process suitable for making small amts. of various prods.</p> |
