Patent GB-692069-A (GB)
Title: Process of heat-setting elastic oriented polyamide fibres, filaments, yarns, threads and like structures
IPC: D01F6/60
Filed: 1951-05-02
Abstract: Filaments, fibres, yarns, threads and like structures of a molecularly oriented copolyamide formed from (1) at least one unsubstituted aliphatic diamine containing a straight chain of at least five carbon atoms separating the amino groups; (2) at least one N-alkyl substituted aliphatic diamine and/or at least one N,N1-dialkyl substituted aliphatic diamine containing a straight chain as in (1); (3) optionally a N-aralkyl substituted aliphatic diamine or N,N1-diaralkyl aliphatic diamine containing a straight chain as in (1), and (4) at least one straight chain aliphatic dibasic carboxylic acid containing at least six carbon atoms in the chain, are heated at an annealing temperature of 60-80 DEG  C. at constant length for at least 3 seconds, and are thereafter subjected to a heat-setting treatment at 90-100 DEG  C. for a period of time which exceeds the annealing period.  Preferably, the copolyamide filaments or like structures are not allowed to cool between the annealing and heat-setting treatments.  Molecular orientation may be effected by hot or cold drawing or stretching treatment.  Optimum relative proportions of unsubstituted, mono-, and di-substituted diamines, when plotted on a graph, lie within an area having the limits 75-0-25 to 45-0-55 and 0-55-45 to 0-90-10, these numbers representing the mols. per cent successively of the di-, mono- and unsubstituted amines.  Diamines specified are hexamethylene diamine and the N-mono- and N,N1-di-isobutyl and lauryl derivatives thereof. N-alkyl substituted hexamethylene diamines may be used in admixture with unsubstituted decamethylene diamine.  N-benzyl diamines may be included in the constituents of the copolymer.  The dibasic acid may be sebacic, azelaic, pimelic, adipic or suberic acid or it may be bis-4-carboxybutyl sulphide.  There may be used an interpolyamide made from hexamethylene diamine and adipic acid, a mixture of N,N1-di-isobutyl hexamethylene diamine with N-isobutylhexamethylene diamine and sebacic acid, and caprolactam. The copolyamides may be prepared from a mixture of separately prepared diamine dibasic acid salts as described in Specification 474,999.  The copolyamides may be formed into filaments by melt-spinning at 200-285 DEG  C.  Annealing of the stretched oriented filaments may be carried out by immersion in a liquid at 60-80 DEG  C. or by exposure to a hot gas such as air, or nitrogen, having a high relative humidity, and in this case the temperature of the gas may be somewhat higher than the annealing temperature of the filaments.  Heat setting may also be effected by immersion in a hot liquid or by exposure to a hot gas.  Filaments may be treated in single strands or in package form.  In an example, an aqueous solution of a mixture of hexamethylenediammonium sebacate and the corresponding salts of the N-isobutyl and N,N1-di-isobutyl derivatives is first heated at atmospheric pressure until the temperature reaches 132 DEG  C.  It is then heated to 225 DEG  and then to 260 DEG  C. under a pressure of 250 lbs. per sq. inch.  The pressure is gradually released and vacuum is gradually applied until the p  desired degree of polymerization is reached.  The molten polymer is melt-spun and the filaments produced are cold-drawn.  Yarn containing the filaments is annealed in water at 60-80 DEG  C. and then heat-set by treatment with water at 90-100 DEG  C. Specifications 543,466 and 557,544 also are referred to.