GB533306A - Improvements relating to the melt spinning of fibre-forming synthetic linear polymers - Google Patents

Abstract

533,306. Artificial filaments &c. DU PONT DE NEMOURS & CO., E. I. Aug. 9, 1939, Nos. 23045 and 23046. Convention dates, Aug. 9, 1938 and June 30, 1939. [Class 2 (ii)] [Also in Groups V and XIII] Fibre-forming synthetic linear polymers are brought into a form suitable for feeding into a melt-spinning apparatus, by melting them, extruding into ribbon, sheet, or thin rod form, quenching with a cooling liquid and cutting into small pieces. Polymers which may be used include polyamides particularly those of the diamine-dibasic acid type or those obtained by polymerization of monoamino-monocarboxylic acids. Solid ethylene polymers may also be used. As shown in Fig. 2, an autoclave 1 is provided in which polymerization of the organic compound is effected. After the polymerization has been effected, the molten material is extruded as a ribbon through a slot at the lower end of the extension 2 of the autoclave. The ribbon falls on to a positively driven drum 4 which is preferably cooled internally, e.g. by a stream of water. Water is sprayed from nozzle 5 on to the ribbon which thus becomes solidified. The still hot ribbon is passed through trough 6 containing water where it is cooled, and it is then wound on reel 7. The ribbon is then cut into small flakes, squares, or other small pieces, e.g. by a punch press. It may be heated, e.g. by steaming, prior to cutting, in order to avoid irregular breakage or splitting. The flakes or cuttings are then dried, e.g. in a rotary tumbler. For the production of filaments, bristles, and like extruded products, the chips or flakes are fed as shown in Fig. 3 into hopper 8 and melted by the heated grid 9. The molten material is fed by pump 10 through filter pack 11 and out through the orifices of the spinneret 12. The filaments produced are wound on bobbin 14. As shown in Fig. 5, the ribbon of molten material extruded from the autoclave 1a is received on a drum 4a and sprayed with water or other non-solvent from nozzles 5a. The solidified ribbon is removed by roll 15 which stretches the ribbon and passes it to jet blowers 17. The dry but still hot ribbon is passed over roll 18 and down through feed rolls 19 into cutter 20. The chips or flakes fall into a mixer 21. They may then be supplied to a melt-spinning apparatus. The extrusion operation may be carried out in an inert atmosphere. If desired, the molten ribbon may be extruded directly into the quenching liquid, the casting drum being dispensed with, or the molten polymer may be extruded between rollers submerged in the quenching liquid. Casting drums with grooved surfaces may be used. Alcohols, hydrocarbons, or chlorinated hydrocarbons may be used instead of water. In an example, hexamethylene diammonium adipate is heated with acetic acid and water in an autoclave until the temperature reaches 219‹C. and the pressure 250 lb. per sq. inch. The pressure is kept constant by release of steam while the temperature rises to 270 ‹C. The pressure is then gradually released to atmospheric. Nitrogen pressure is then applied and the molten mass is extruded. The ribbon is cooled with water and cut into flakes. Specifications 461,236 and 471,950 are referred to. The Specification as open to inspection under Sect. 91 comprises also the use of a cooled gas or a cooled belt or pair of belts for chilling the extruded ribbon of molten polymer. This subject-matter does not appear in the Specification as accepted.