Patent GB-964407-A (GB)
Title: Drawn filament yarns of thermoplastic polymeric materials
IPC: D01F6/60
Filed: 1962-03-29
Abstract: 964,407. Dissimilar filament yarns. E. I. DU PONT DE NEMOURS & CO. March 29, 1962 [March 31, 1961], No. 12072/62. Heading B5B. [Also in Division D1] A yarn comprises drawn filaments of at least two kinds, each kind being of a different thermoplastic polymeric composition characterized in that all of the filaments have substantially equal viscoelastic properties at room temperature and each kind of filament has substantially different viscoelastic properties after exposure to elevated temperature. The different kinds of filaments may have substantially equal initial moduli and stress-decay, and maximum work loss temperatures within 30‹ C. of each other, and substantially different boil-off shrinkage, preferably a difference of at least 1%. The first kind of filament is desirably a homopolymer, e.g. a polyolefin, polyamide or polyester, and the second kind of filament may be a melt or copolymer, and contain 70-95% by weight of the same structural units as the first kind and 5-30% by weight of different structural units. The first kind of filament is preferably polyhexamethylene adipamide or polycaproamide, 5-30% of the structural units of the second kind of filament may be a poly(N-vinylamide), preferably a polyvinyl lactam e.g. N-vinylpropiolactam, N- vinyl-pyrrolidone, and N-vinyl valerolactam, or polyvinyl pyrrolidone or polyhexamethylene isophthalamide. Copolyamides based on polyhexamethylene adipamide, in which, during polymerization, part of the hexamethylene diamine is replaced with another amine e.g. m-xylylene diamine or part of the adipic acid is replaced with another acid e.g. sebacic acid, may be used. The filaments may be melt-spun, and are preferably of non-round cross-section preferably heart, cruciform, shield or multilobal shape, especially trilobal shape. Intermingling of the filaments may be effected by spinning the different filaments from different orifices of the same spinneret. In Fig. 3, plate 32 has a central cavity 33 and a ring-shaped cavity 34, adapted to receive two different melts which are distributed to annular channels 35, 36 in plate 31, which discharge through passages 37, 38 to alternate holes of the spinneret which are arranged in a circular pattern. Alternatively, separate filament bundles may be intermingled by passing them through an air jet to interlace them. Filaments interlaced in this way need not be twisted in processing. Filaments are then drawn. Yarn 1 consisting of filaments from at least two different polymers is withdrawn from a supply source 2 and stretched in passing over the snubbing pin 6 between feed roll 4 and draw roll 8. The substantially equal room temperature visco-elastic properties are imparted to the filaments by relaxing them by a percentage of their drawn length that is substantially equal to the hot relaxation percentage at which the instantaneous retractions of the different kinds of filaments are substantially the same. In Fig. 4, curves are plotted for nylon 66, a nylon 66/polyhexamethylene isophthalamide copolymer (66/6I) and a nylon 66/polyvinyl pyrrolidone copolymer (66/pvp.). Thus, the percentage relaxation for a yarn comprising nylon 66 filaments and 66/6I filaments would be determined by the point of intersection of the curves 66 and 66/6I. Preferably, the percentage relaxation is from 5-15%, especially 9.5-13.5%, and does not vary more than 1.5% from the point of coincidence of their relaxation-retraction curves. Filaments may be relaxed by passing them under tension through a zone of heated fluid or a heated atmosphere. In Fig. 1, yarn from draw roll 7 passes through heating means 9 to relaxing roll 11, the relative peripheral speeds of rolls 7 and 11 controlling the degree of relaxation. Heat applied is adjusted to give sufficient contraction of the yarn to ensure slight tension. Alternatively, in Fig. 2, a stepped draw roll 7<SP>1</SP> replaces roll 7 and the yarn is drawn around the larger diameter portion 17 of roll 7<SP>1</SP>, passes through steam tube 9<SP>1</SP>, over roll 20, and is relaxed around the smaller diameter portion 18 of roll 7<SP>1</SP>. Fabrics made from the yarns have a warm, dry, hard and enhanced bulk, compared to conventional nylon fabrics, and are free from processing difficulties associated with mixed shrinkage yarns.