GB1221123A - Improvements in production of shaped articles, such as filaments, from polyamides by melt spinning - Google Patents

Abstract

1,221,123. Melt spinning polyamides. FIBER INDUSTRIES Inc. 8 March, 1968 [9 March, 1967 (3)], No. 11297/68. Heading B5B. An apparatus for the production of filaments, films &c. by melt extrusion of polyamides and in which vapour evolved from the heated polymer is carried away by a stream of inert gas comprises a feed hopper 10 for chips of the raw polymer, a heater tube 11 and a polymer melter 12. The flow of chips from hopper 10 is controlled by valve 13 situated in the throat 14 leading to the heater tube 11. The heater tube 11 has four heating zones 15 to 18 heated by electrical strip heaters 19 to 22 respectively, a heat insulating jacket 23 surrounding the assembly. Current supply to the strip heaters is through conventional controllers 24 to 27 and the temperature at five points along the tube 11 is measured by thermocouples 28 to 32. Instead of electrical strip heaters the tube 11 may be heated by circulation of a heating fluid through a jacket surrounding the tube. Polymer chips coming from tube 11 pass through conduit 33, connected to tube 11 by expansion joint 34, into the polymer melter 12. The melter has screw feed 36 rotated by motor 37 for feeding the polymer chips on to a melting grid 38 heated, like the melt chamber 39 containing it, by a heat transfer liquid to a temperature which, in the case of polyhexamethylene adipamide, may be between 280‹ and 305‹ C. The molten polymer passes through the melting grid 38 and the spout 40 and forms a pool 41 of molten polymer under a blanket of inert gas introduced through inlet 42, the pool being kept stirred by agitator 43. The molten polymer is fed by a spinning pump to a spinneret in the usual manner. In using the apparatus polyamide chips having a relative viscosity of less than 50, for instance, down to 45, and containing, for example, 0-5 to 1À5% water, are fed into feed hopper 10 and thence to tube heater 11. The chips, heated during their passage through the tube, lose water which is removed by a stream of inert gas which is passed into chip melter 12 through inlet 44 and an annular manifold which contains a number of outlets for the gas and is located between screw 36 and grid 38. The gas escapes into the atmosphere carrying with it water vapour through hopper 10. The gas supplied can be at room temperature or may be heated, e.g. to 170‹ C. or somewhat higher. Upon melting, further polymerization proceeds very rapidly with the liberation of water, and the relative viscosity of the polymer rises to a value which depends on the proportion of water removed during drying and which may be 55 to 65. Values of relative viscosity are determined at 25‹ C. in aqueous formic acid containing 90% by weight of formic acid. The relative viscosity is the ratio of the absolute viscosity of a polymer solution in this solvent containing 8À4% by weight of the polymer to the absolute viscosity of the solvent.