Patent GB-829748-A (GB)
Title: Production of polymeric polymethylene terephthalates
Inventor: HIGGINS THOMAS CHARLES
IPC: C08G63/78
Filed: 1957-01-17
Abstract: An apparatus for the continuous polycondensation of bis-hydroxyalkyl terephthalate comprises a number of closed heated chambers linked in series by heated ducts, a feed inlet for the first chamber for supplying bis-hydroxyalkyl terephthalate and a final outlet from the last chamber for discharging polycondensed material, the inlet orifice for each chamber being near the bottom of the chamber and the outlet orifice being higher than the inlet, the inlet and outlet orifices being offset in relation to each other, the final outlet being linked to a collection zone and means being provided for causing a pressure drop from the feed inlet to the final outlet.  The arrangement is such that liquid undergoing polymerization from a previous chamber passes substantially through the whole depth of liquid in each chamber, thereby causing agitation of the polymerizing mass.  Additional agitation may be effected by bleeding an inert gas through the chambers.  The product may be further polycondensed in the apparatus of Specification 823,100.  In Fig. 1, three jacketed autoclaves 1, 2 and 3 connected in series by pipes 5 and 6 are arranged side by side, the bis-hydroxyalkyl terephthalate being fed to the apparatus through pipe 4 and polymethylene terephthalate being withdrawn through pipe 7 at which vacuum is applied.  In Fig. 2, eight jacketed compartments are arranged one above the other, the bis-hydroxyalkyl <PICT:0829748/III/1> <PICT:0829748/III/2> terephthalate being fed to the apparatus through pipe 20 and polymethylene terephthalate being withdrawn through tube 28 at which vacuum is applied.ALSO:A polymethylene terephthalate is made by the continuous polycondensation of a bishydroxyalkyl terephthalate by passing the polymerizable liquid through a number of reaction zones in series, maintained under reduced pressure, and through which there is a pressure drop, characterized in that polymerizable liquid and the evolved vapours from a previous zone or zones pass through substantially the whole depth of liquid in each following zone, thereby causing agitation of the liquid, before passing to a successive zone or zones.  The bis-hydroxyalkyl terephthalate may be in the form of a low polymer and may be admixed with a bishydroxyalkyl isophthalate.  Additional agitation may be provided by bleeding in inert gas through the zones.  The bis-hydroxyalkyl terephthalate <PICT:0829748/IV (a)/1> <PICT:0829748/IV (a)/2> may be polycondensed to an intrinsic viscosity of 0.1-0.5 and the product continuously polycondensed further by the process of Specification 823,100.  A mixture of calcium acetate and antimony oxide may be used as catalyst.  Temperatures of from 240-290 DEG  C. may be used and may increase in successive compartments.  In Fig. 1, the reaction zones comprise three jacketed autoclaves 1, 2 and 3 arranged side-by-side and connected in series by tubes 5 and 6. The bis-hydroxyalkyl terephthalate is fed to the apparatus through pipe 4 and polymethylene terephthalate withdrawn through pipe 7 at which a vacuum is applied.  In Fig. 2, the reaction zones comprise eight jacketed compartments arranged one above the other and connected in series by tubes 21-27.  The bis-hydroxyalkyl terephthalate is fed to the apparatus through tube 20 and polymethylene terephthalate withdrawn through tube 28 at which a vacuum is applied.