Patent GB-1256661-A (GB)
IPC: D01F6/62
Filed: 1970-02-24
Abstract: 1,256,661. Polypivalolactone filaments. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. 24 Feb., 1970 [26 Feb., 1969], No. 8810/70. Heading B5B. Filaments are manufactured from a polymer comprising at least 75% polypivalolactone, any balance being a monomer copolymerizable therewith or another polymer compatible therewith by extruding the molten polymer through a spinneret, cooling the shaped filaments by means of a liquid in a cooling zone and subsequently collecting them on a collecting device, the process being characterized by the use, during cooling in the liquid of a mechanical frictioning means over which the filaments are passed and by means of which the tension in the filaments is increased to a value of at least 0À1 gram per denier, preferably between 0À6 and 1À0 g.p.d. The polymer is preferably a polypivalolactone homopolymer.  The polymer has preferably an intrinsic viscosity between 0À75 and 1À75 dl/g. as measured in benzyl alcohol at 150‹ C. and is preferably extruded through orifices between 0À05 and 5 mm., in particular between 0À2 and 1À0 mm. in diameter. The temperature of extrusion may be between 240‹ and 310‹ C., preferably however between 260‹ and 290‹ C., and the filaments are advantageously led into a tube or chamber at a temperature between 175‹ and 310‹ C., in particular between 250‹ and 300‹ C., wherein the extension that follows the extrusion of a molten filament may occur to the extent that the thickness of the filaments is reduced to between ¢ and 1/40th the diameter of the spinning orifices. The cooling zone that follows should be no more than 1À5 metres, in particular less than 0À5 metres, away from the spinneret or, if used, the heating zone. If desired, the cooling zone may be insulated from the heated zone or spinneret. The cooling liquid is preferably water, but any liquid inert to the filaments may be used. The temperature is usually below 35‹ C. and preferably between 10‹ and 25‹ C.  The coolant may be applied to the filaments in several ways; for example by passing the latter through a bath as in Fig. I, or by spraying the coolant in an atomized form on to the filaments, or by guiding the filaments down the inside walls of a tube down which a liquid film is flowing. In this last case a vertical jet of coolant can be directed along the tube on to a horizontal surface so that the liquid is sent perpendicularly to the walls of the tube, so pressing the filaments into the liquid film on the walls. The mechanical frictioning means used may be a fork with two prongs, as illustrated in Fig. II, so arranged that the filament passes around both prongs, being deflected by the first prong through an angle of 60-150 degrees and then deflected around the second back to the direction in which they were previously travelling. Both prongs may be round or the first prong may have a sharp edge as in Fig. III (not shown), in order to give the filaments a high crimpability, and the second a round edge. The prongs should be thinner than 10 mm., preferably between 2 and 5 mm. Instead of a fork a draw-pin or series of draw-pins may be used, as illustrated in Fig. V (not shown), or a braked roller pair. The mechanical frictioning means should be located between 1 and 50 cm. from the start of the cooling zone and preferably between 4 and 25 cm. The filaments are drawn at a ratio of at least 1 : 1À05 and preferably at a ratio between 1 : 1À2 and 1 : 2.5 as a result of said frictioning. The filaments, irrespective of whether or not they are twisted together or assembled into a yarn may be heat-treated at 130-210‹ C., preferably between 160‹ and 190‹ C. If a yarn of filaments is allowed to shrink by at least 20%, a crimped yarn may be obtained, particularly if asymmetric tension was developed in the filaments. If, during heat treatment, shrinkage is prevented, the yarn may be drawn to yarn of very high tenacity. The filaments obtained are characterized by a positive birefringence, or orientation angle preferably between 8 and 12 degrees and in any case no more than 15 degrees and a density d #20 <SP>20</SP>   of no more than 1À158.