IE23508B1 - Fibres and filaments having improved crimp characteristics and method for their production - Google Patents

Abstract

<PICT:0805033/IV (a)/1> <PICT:0805033/IV (a)/2> <PICT:0805033/IV (a)/3> <PICT:0805033/IV (a)/4> <PICT:0805033/IV (a)/5> <PICT:0805033/IV (a)/6> <PICT:0805033/IV (a)/7> <PICT:0805033/IV (a)/8> Filamentary material having potential crimp properties is produced by feeding at least two different synthetic fibre-forming polymers, which are of such a nature that one of the polymers has both a higher shrinkage characteristic and better recovery properties than the other or others when they are in the physical form in which they exist in freshly spun filaments, separately to a shaping orifice adapted to receive the polymers in an eccentric fashion, extruding the polymers simultaneously through the orifice to produce a composite filamentary material which has along its length a cross-section made up of two or more distinct components consisting of the different polymers arranged eccentrically, drawing down the filamentary material so formed, and subsequently stretching it. The expression "better recovery properties" is defined as the extent to which a yarn, which is in a condition comparable to that in which it would be in a finished fabric, recovers its original length after being stretched at a constant rate of elongation, and is expressed as elongation recovered/total elongation X 100 for a stated total elongation. The yarn is allowed to recover at the same rate as that at which it was extended. One compound is regarded as having a higher shrinkage characteristic than another when it shrinks to a greater degree on being heated in an inert medium to about 50 DEG C. to 150 DEG C. In a modification of the process the polymer having the high shrinkage characteristics has not initially the better recovery properties and the filamentary material after being stretched is subjected to a length-stabilizing treatment whereby said polymer is converted into a physical form in which it has the better recovery properties. The filamentary products can be crimped by subjecting them to a shrinking treatment while they are under substantially no tension. The length stabilizing treatment may be a heat treatment under tension at a temperature high enough and for a time long enough to cause crystallization of the component having the higher shrinkage characteristics. The temperature is generally higher than the apparent minimum crystallization temperature of this component. The latter temperature is defined as the lowest temperature at which a marked rate of density change occurs within six hours. Alternatively, length stabilization may be effected by contacting the composite filament, under tension, with certain polar organic liquids which are latent solvents for the amorphous regions of the component to be length-stabilized. When the components are polyethylene and polyethylene terephthalate, the polar solvent used may be acetone, chloroform, methylene chloride, tetrachloroethane, phenol or m-cresol. The extrusion may be such that the components are localized and held together in a "side-by-side" structure in which each component forms part of the surface of the composite filament, as shown in Fig. 9 or, preferably, may be such that one component forms a core and the other a sheath in which the core is disposed eccentrically, as shown in Fig. 8. As shown in Fig. 2, molten polymer 13 from which the core of the composite filament will be formed is fed from the chamber 3 of filter pack 1 of a spinneret assembly through ducts 5 in the bottom of the chamber 3, grooves 6 and ducts 8 in the adapter 7 and tubes 31 (Figs. 2 and 5) into the extrusion ducts and orifices 9 contained in the bottom portion or spinneret face 10. Simultaneously molten polymer 14, from which the sheath of the composite filament will be formed, is fed from the chamber 2 in the filter pack 1 through ducts 5 in the bottom of this chamber, ducts 11, the adapter 7 and grooves 12 in the spinneret face 10 into the orifice 9. As the core polymer melt leaves tube 31, which is surrounded by the polymer melt 14 coming from chamber 2 and is eccentrically disposed in the orifice 9, bonding occurs between the two polymer melts, so that in the tapered section 30 of orifice 9, polymer melts 13 and 14 are extruded simultaneously, polymer 14 completely surrounding the core polymer 13 which is disposed as eccentrically as possible in the sheath polymer 14. The resulting filaments (Fig. 8) have substantially round, smooth surfaces and cores. Component 13 may have better recovery properties than component 14. If component 14 has a higher shrinkage than component 13, the crimped structure shown in Fig. 10 and termed "alpha-crimp" is obtained. If component 13 has both higher shrink characteristics and better recovery properties than component 14, the crimped structure shown in Fig. 11 and termed "beta-crimp" is obtained. The beta-crimp may be converted into the alpha-crimp in a length-stabilizing operation. A bundle of filaments which comprises composite filaments containing the components in various ratios may be spun through the type of spinneret shown in Figs. 6 and 7, in the upper portion 16 of which are two chambers 17, 18 from which the polymer melts are fed via ducts 19, circular recesses 22 and grooves 20 in the spinneret plate 21 into the spinneret extrusion ducts and orifices 24. The different polymer melts fed from chambers 17 and 18 meet but do not mingle in the duct 24 and are extruded simultaneously to form composite filaments whose two components are disposed in side-by-side relationship, as shown in Fig. 9. Poly mers which may be used for producing composite filaments by the modification of the process which includes the length stabilizing step are polyamides, such as poly(hexamethylene adipamide), poly(hexamethylene sebacamide), and poly(epsilon-caproamide), polysulphonamides formed by reacting organic sulphonic acid halides, e.g. dichlorides, with primary or secondary organic diamines, as described, for example, in U.S.A. Specification 2,667,468, polymers containing sulphonamide groups as well as carbonamide groups and formed by reacting organic monocarboxylic-sulphonic acid dihalides with diamines, polyesters such as polyethylene terephthalates, the corresponding copolymers containing small proportions of sebacic acid or adipic acid, and polyesters containing recurring units derived from glycols with more than two carbon atoms in the chain, polyurethanes, polyureas, and polyvinyl compounds. Polymers which may be used in the form of the process which does not require the length stabilization step are those described in Specification 785,214. In all the examples the composite filaments are produced by meltspinning, but they may also be produced by dry-spinning, wet-spinning, or a combination of dry- and melt-spinning, the core, for example, being melt-spun and the sheath being dry-spun. In the method involving length-stabilization, the crimp may be developed in the filaments by exposing them while free from tension to boiling or hot water, moist heat or steam, nitrogen, carbon dioxide, air or any other gaseous or liquid medium inert to the filament components. The crimping temperature should usually be higher than the second-order transition temperatures of the filament components. The temperature used is generally about 100 DEG C., but may be within the range 50 DEG to 150 DEG C., and the crimping time required may be only a few seconds. The polymer component with the higher shrinkage characteristic should preferably have, when in filamentary form, a minimum initial modulus of elasticity of at least 5 grams per denier, a shrinkage of at least 7 per cent in boiling water, a permanent set (when extended to 50 per cent of its elongation-at-break and the load released) below 10 per cent at 60 per cent RH and 70 DEG F. and an elongation-at-break higher than 15 per cent at 60 per cent RH and 70 DEG F. In an example, molten polyethylene terephthalate and molten poly(hexamethylene adipamide) are extruded simultaneously at 285 DEG C. through a multi-hole spinneret assembly of the type shown in Fig. 2 to form composite filaments in which the polyester is the core and the polyamide the sheath. The filaments are attenuated by drawing them from the spinneret at about 500 times the speed with which the polymers leave the spinneret holes, and after cooling are continuously drawn as a bundle over a draw pin heated to 85 DEG C. On its path to the draw roll the filament bundle is led over a hot plate heated to 140 DEG C., the total draw imposed on the yarn being 3.56. The filaments thus produced are substantially uncrimped and a tight helical beta-crimp is imparted to them by immersing them for a short time in boiling water while free from tension. In another example, polyethylene and polyethylene terephthalate are melt-spun simultaneously in a similar manner to form filaments having a core of polyethylene and a sheath of polyester. After spinning and winding, the quenched sheath-core filaments are passed through a water bath at 30 DEG C. to a roll maintained at 65 DEG C. and then to an unheated roll which stretches the yarn 2.6 times its original length. The yarn is then wound tightly on a bobbin, immersed in acetone at room temperature for one minute, skeined and crimped by hanging in boiling water, tension free, for one minute. Specifications 579,081, 580,764, 580,941, [all in Group IV], and U.S.A. Specifications 2,071,250, 2,071,253, 2,130,523, 2,130,948, 2,190,770, 2,287,099, 2,465,319, 2,578,899 and 2,604,689 also are referred to. [GB805033A]