| 摘要 |
989,449. Removal of volatile constituents from plastic melts; evaporators. FARBENFABRIKEN BAYER A.G. Dec. 17, 1962 [Dec. 22, 1961], No. 45768/62. Heading BIB. An evaporator for removing volatile constituents from plastic melts comprises a vertical cylindrical chamber 8, in which rotates a worm 9 so that the edge of its thread is in wiping contact with the inside wall of the chamber, the lower section of the chamber having an annular horizontal slot 11 which communicates with an annular chamber 13 connected via outlet 14 to a vacuum pump (not shown). The evaporator is heated by radiant heating means 25 and heating jacket 24. The plastic melt to be treated enters chamber 8 via line 1, gear pump 2, pipe 4 and worm 5, and flows down the hot inside surface of the chamber and the thread of worm 9. The volatile constituents are vaporized and the vapours pass into chamber 13 via slot 11, and are withdrawn via outlet 14. The edges of slot 11 are sharp, and a lip 12 is provided on the lower edge to prevent the plastic melt entering chamber 13. Any foaming of the plastic melt will occur in the upper section of chamber 8, and will have subsided by the time the plastic melt passes slot 11. The plastic melt leaves chamber 8 via worm 16, and passes into discharge outlet 17. Some of the plastic melt flows back to the worm 16 via passage 18 and capillary tube 20, and the pressure of this recirculated material is measured by pressure sensitive device 19 connected to pressure gauge 26, which controls gear pump 2 via pipe 21 and variable drive means 3. The plastic melt is removed from outlet 17 by gear pump 22. One example is given of the removal of monomeric caprolactam from a melt of polycaprolactam. Also described is a modification of the evaporator wherein the central worm, at the annular slot, meshes with a worm wheel in such a way that the plastic melt is scraped from the worm. |
