Procédé et appareil de polycondensation continue pour la production des polyesters

摘要

1,070,287. Polycondensation apparatus. MONSANTO CO. June 5, 1964 [June 11, 1963], No. 23355/64. Heading B1X. A polymerization column for the continuous production of polycondensation polymers is horizontally partitioned into distinct zones A, B and C, namely a reaction zone, an evaporation zone, and a final zone, and has level control means 28 and 29 maintaining the liquid in zones A and B at a predetermined level. The column is run with different pressures in each zone but with the same temperature throughout. The reaction zone A has a plurality of suspended buckets 16, the output of one bucket becoming the input of the next lower bucket, controlled by standpipe overflows 14. The monomer product from zone A is introduced into zone B through a spray nozzle 20 to impinge against the inner surface of the column, for falling film and flash evaporation with vapours fed off through vent 22 after passing through demister 24. The prepolymer product then passes to zone C which is under a high vacuum and consists of a plurality of sub-zones defined by discs 33 and 34 interconnected by controls 32 and 52. In the upper part of zone C the discs 32 and controls 32 are equivalent to the reaction buckets in zone A, and packing 38 may be provided in cases of low viscosity between discs 33 and perforated discs 34 in the lower part of zone C. The liquid level between the perforated discs is controlled by varying the area of inter-sub-zone gas discharge. Normally gas flows through a cap portion (56, Fig. 3, not shown) which is gas but not liquid permeable or through slot (58, Fig. 4, not shown) of control 52. As the liquid rises the area for gas discharge decreases so increasing the pressure and causing liquid flow through the perforated disc. The polymer is withdrawn from zone C by a screw or gear pump 64. The vacuum source communicates through port 68. The apparatus is applicable to the production of polyethylene terephthalate by carrying out ester interchange between ethylene glycol and dimethyl terephthalate to form bis-2-hydroxyethyl terephthalate monomer (in zone A) which is polymerised under reduced pressure (in zone C). The buckets may be removed from the zone A and a spray nozzle installed to define a dual-zone evaporator, as in a nylon run.