Patent GB-950429-A (GB)
Title: Composite filaments of linear polyamides and their production
IPC: D01D5/30
Filed: 1962-08-17
Abstract: Composite filaments consisting of two continuous adherent eccentrically arranged components of synthetic linear polyamides are made by co-spinning two molten polymer components, one component consisting essentially of a crystalline homopolyamide or isomorphic copolyamide and the other component consisting essentially of a non-isomorphic random copolyamide containing at least 20% by weight of each of the two polymer units therein, and exhibiting equaterial X-ray reflections similar to those of the first component, drawing the composite filaments under conditions such that only the homopolyamide or isomorphic copolyamide component becomes crystalline, heat-relaxing the drawn filaments, cooling the resulting crimped filaments, and then stretching them to remove the crimp. The drawn filaments may be relaxed by at least 20% by passing them under low tension either through a jet of heated air or through a steam atmosphere.  Composite filaments so made have a crimp retraction of at least 6%, preferably at least 12%, under a tension of 0.0012 gpd. when subjected to steam at 100 DEG C., a crimp helix diameter of 8-15 mils and a crimp helix spacing of 45-70 mils after the filaments have been crimped. Such filaments are especially useful in knitting hose, the leg yarns of which may have a crimp retraction of at least 12% and the welt and foot-yarns of which may have a crimp retraction of at least 6%, under the above conditions. The leg yarns may be monofoils in which the components are in side by side relationship, and the other yarns may comprise a plurality of composite filaments in which the filaments are in sheath-core relationship. Composite filaments may also be composed of filaments in side-by-side relationship. Preferably, the homopolyamide is polyhexamethylene adipamide, polyhexamethylene sebacamide or polycaproamide, and the copolamide is a copolymer of polyhexamethylene adipamide and either polyhexamethylene sebacamide or polyhexamethylene isophthalamide. A preferred copolyamide component contains 30-70% polyhexamethylene sebacamide, or from 20-40% polyhexamethylene isophthalamide. Other suitable crystallisable homopolyamides include polyheptanamide, polyundecanamide, polyoctamethylene oxamide, polytetramethylene suberamide, polyhexamethylene suberamide, polydecamethylene decanamide, polyxylylene azelamide and poly-2-methyl hexamethylene terephthalamide, and a suitable crystallisable isomorphic copolymer is that of polyhexamethylene adipamide and polyhexamethylene terephthalamide.  The two components are preferably present in approximately equal proportions by weight, or alternatively with a major amount of the copolyamide present.  In apparatus as shown, the two melts are pumped respectively to the annular cavity 12 and the inner cavity 14 of the spinneret assembly 10 and discharge through the passages 16, 18 to the holes 20 in spinneret plate 22.  The spun filaments are air quenched and wound into a package 24 in known manner.  The yarn 26 is subsequently withdrawn from the package, drawn to a ratio of 5.3 over a draw pin 28 heated to 105 DEG C. and passed from the draw roll 30 through a pair of meshing nylon gears 32, rotated by means of the air jet shown, into the crimping chamber 34 where the yarn is crimped into helical form by a jet of heated air, the air temperature at the chamber exit being 155 DEG C.  The yarn is then passed through an eyelet in a baffle plate 36 which deflects most of the hot exhaust air away from a cold air aspirator 38, cooled by passing it through aspirator 38 in which room temperature air is drawn over it, led through a lower guide 40 and then around three snubbing pins 42 where tension is applied to remove the crimp before the yarn passes around withdrawal roll 44 to package 46.  The yarn is permitted to retract by 22% of its as-drawn length between draw roll 30 and withdrawal roll 44.  In a modification, the pin 28 is only heated to 40 DEG C. and the yarn is passed upwardly from draw roll 30 through an inverted crimping chamber 34, being carried through the crimping chamber by the hot air stream, advanced over a pin located at about the same position as the gears 32, which are omitted, and the yarn is then passed downwardly to guide 40, baffle plate 36 and aspirator 38 being omitted.  From guide 40, the yarn advances as in Fig. 1.  Air temperature at the exit of chamber 34 is 195 DEG C. and the yarn is permitted to retract by 22% between draw-roll 30 and withdrawal roll 44.ALSO:Composite filaments consisting of two continuous adherent eccentrically arranged components of synthetic linear polyamides are made by co-spinning two molten polymer components, one component consisting essentially of a crystalline homopolyamide or isomorphic copolyamide and the other component consisting essentially of a the other component consisting essentially of a non-isomorphic random copolyamide containing at least 20% by weight of each of the two polymer units therein, and exhibiting equatorial X-ray reflections similar to those of the first component drawing the composite filaments under conditions such that only the homopolyamide or isomorphic copolyamide component becomes crystalline, heat-relaxing the drawn filaments, cooling the resulting crimped filaments, and then stretching them to remove the crimp.  The drawn filaments may be relaxed by at least 20% by passing them under low tension either through a jet of heated air or through a steam atmosphere.  Composite filaments so made have a crimp retraction of at least 6%, preferably at least 12%, under a tension of 0.0012 gpd. when subjected to steam at 100 DEG C a crimp helix diameter of 8-15 mils and a crimp helix spacing of 45-70 mils after the filaments have been crimped.  Such filaments are especially useful in knitting hose, the leg yarns of which may have a crimp retraction of at least 12% and the welt and foot-yarns of which may have a crimp retraction of at least 6%, under the above conditions.  The leg yarns may be monofils in which the components are in side by side relationship, and the other yarns may comprise a plurality of composite filaments in which the filaments are in sheath-core relationship.  Composite filaments may also be composed of filaments in side-by-side relationship.  Preferably, the homopolyamide is polyhexamethylene adipamide, polyhexamethylene sebacamide or polycaproamide, and the copolyamide is a copolymer of polyhexamethylene adipamide and either polyhexamethylene sebacamide or polyhexamethylene isophthalamide.  A preferred copolyamide component contains 30-70% polyhexamethylene sebacamide, or from 20-40% polyhexamethylene isophthalamide.  Other suitable crystallisable homopolyamides include polyheptaneamide, polyundecanamide, polyoctamethylene oxamide, polytetramethylene suberamide, polyhexamethylene suberamide, polydecamethylene decanamide, polyxylylene azelamide and poly-2-methyl hexamethylene terephthalamide, and a suitable crystallisable isomorphic copolymer is that of polyhexamethylene adipamide and polyhexamethylene terephthalamide.  The two components are preferably present in approximately equal proportions by weight, or alternatively with a major amount of the copolyamide present.  In apparatus as shown, the two melts are pumped respectively to the annular cavity 12 and the inner cavity 14 of the spinneret assembly 10 and discharge through the passages 16, 18 to the holes 20 in spinneret plate 22.  The spun filaments are air quenched and wound into a package 24 in known manner.  The yarn 26 is subsequently withdrawn from the package, drawn to a ratio of 5.3 over a draw pin 28 heated to 105 DEG C. and passed from the draw roll 30 through a pair of meshing nylon gears 32, rotated by means of the air jet shown, into the crimping chamber 34 where the yarn is crimped into helical form by a jet of heated air, the air temperature at the chamber exit being 155 DEG C.  The yarn is then passed through an eyelet in a baffle plate 36 which deflects most of the hot exhaust air away from a cold air aspirator 38, cooled by passing it through aspirator 38 in which room temperature air is drawn over it, led through a lower guide 40 and then around three snubbing pins 42 where tension is applied to remove the crimp before the yarn passes around withdrawal roll 44 to package 46.  The yarn is permitted to retract by 22% of its as-drawn length between draw roll 30 and withdrawal roll 44.  In a modification, the pin 28 is only heated to 40 DEG C. and the yarn is passed upwardly from draw roll 30 through an inverted crimping chamber 34, being carried through the crimping chamber by the hot air stream, advanced over a pin located at about the same position as the gears 32, which are omitted, and the yarn is then passed downwardly to guide 40, baffle plate 36 and aspirator 38 being omitted.  From guide 40, the yarn advances as in Fig. 1.  Air temperature at the exit of chamber 34 is 195 DEG C. and the yarn is permitted to retract by 22% between draw-roll 30 and withdrawal roll 44.  Women's hose are knitted using a 15 denier monofil, except in the welt, heel and toe where a 40 total denier 13 filament yarn is used, the course count being 45 to 70 courses per inch over the knee, calf and ankle sections of the hose.  The hose feet are knitted 1/2 size larger than the finished size desired.  The hose are wrapped loosely in cheese cloth, boiled off in hot water for 10 minutes and put on a hose board, and steamed for 10 minutes with 5 psi steam to induce shrinkage.  Thereafter the hose are dyed in known manner, placed while damp on the hose board and resteamed.  The finished hose resemble non-stretch hose in appearance, especially in clarity of stitch, but have the fit and comfort of stretch hose.  Support hose may be made using 30 denier yarn.  Sweaters, stretch tricot fabrics, men's hose and woven fabrics may also be made from the yarn.