Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02265059 1999-03-08AgW2434Process for producingpolytetramethylene adipamide fibers'A'**Description:The invention relates to a process for producing fibers madefrom polytetramethylene adipamide using the meltâspinning proc-ess, with the process steps of melting the starting polymer inan extruder, feeding the polymer, possibly containing addiâtives, to a meltâspinning apparatus, pressing this molten poly-mer through spinnerets to form filaments, cooling the spunfilaments by subjecting them to forced air, applying a finishto the filaments, removing the filaments with a suitable draw-ing-off apparatus, drawing the spun filaments, and relaxing thedrawn filaments.The manufacture of polytetramethylene adipamide fibers isknown. Fibers spun from this polymer, normally referred to asnylon 4,6, are used primarily for industrial textiles. One ofthe major advantages of polytetramethylene adipamide fibers istheir increased thermal resistance compared to other aliphaticpolyamides such as nylon 6,6 (polyhexamethylene adipamide) ornylon 6 (polycaproamide).One process for producing fibers from this polymer is describedin JP-A 59 â 088 910. The fibers are spun in a conventionalmanner using the meltâspinning process at a melt temperature of300-340°C. To produce the melt, the use of a twin-screw ex-truder is recommended when using polymer powder as a startingCA 02265059 1999-03-08material. A non-aqueous finish is applied to the freshly spunfilaments, and drawing is performed continuously in a oneâstagespinning/drawing process.Another description of a spinning process is contained in JP-A05 - 132 820. In this case, a granulate is converted to a meltat a temperature of 290â320°C. Spinning is performed in thistemperature range. The freshly spun material is drawn continu-ously after applying a non-aqueous finish.A spinning process for polyamide fibers in general, in whichpolytetramethylene adipamide can also be used as the startingpolymer, is described in US 4 859 389. In this case as well,the use of a non-aqueous finish is proposed.A spinning temperature of 300°C +/- 3°C and granulate as astarting material is recommended by Schmack et al. (ChemicalFibers International 45 (1995), pp. 475-477. This document con-tains no information concerning the finish.The previously described processes have two serious disadvan-tages, namely the expensive steps required to melt the polymer,such as via a twinâscrew extruder, and the use of a non-aqueousfinish. The latter is quite unfavorable chiefly for ecologicalreasons.In polymer production, polytetramethylene adipamide is neces-sarily produced in the form of powder. On normal extruders suchas are commonly used for fiber production, this powder cannotbe melted in such a way that results in a homogeneous melt forproblemâfree melt spinning. For this reason, as JP-A 59 â 088910 teaches, the process must be conducted with a twin-screwextruder when polymer powder is to be melted. This type of ex-truder is often not available in fiber manufacturing plants, sothat costly investment is required in order to process polytet-ramethylene adipamide into fibers.CA 02265059 1999-03-08Another possibility consists of re-melting the polymer powderand forming a granulate, which can then be melted on conven-tional extruders prior to spinning into fibers. This process isnot only costly, but there is also the danger of oxidative orthermal damage to the polymer due to the double melting proc-ess.Another significant disadvantage arises from the necessity men-tioned in the prior art of using non-aqueous finishes, becauseaccording to the statements made in these descriptions the in-fluence of aqueous finishes can result in formation of so-called spherulites on the fiber surface, which have a negativeimpact on the drawing properties of the spun material. Suchnon-aqueous solutions contain the actual finish in mineral oil,for example.In addition to the higher costs compared to aqueous finishingsystems, the disadvantage of the non-aqueous finish can be seenprimarily in the reduced ability to remove the finish by wash-ing and in increased waste water pollution.For this reason, the object arose to provide a process thatdoes not exhibit the disadvantages mentioned herein and thatthus meets the prerequisite for a more cost-effective produc-tion of polytetramethylene adipamide fibers.Surprisingly, it has been discovered that production of thesefibers is especially advantageous if pellets pressed from thepowder resulting from polymer production are used as the start-ing material for melting.These pellets preferably have a cylinder-like shape. The lengthof the pellets is normally between 0.1 and 8 mm, preferably be-tween 1 and 6 mm. The diameter of the pellets is between 0.1CA 02265059 1999-03-08and 5 mm, preferably between 1.5 and 4 mm, with a range of 2.5to 3.5 mm being especially preferred.In using these pellets as a starting material, the conventionalsingle-screw extruders common in fiber production can be em-ployed, and the polymer selected for fiber production can bemelted without difficulty.The polytetramethylene adipamide used as the polymer for fiberproduction is understood to be not only a homopolymer with thiscomposition but also a copolymer with at least 85% polytet-ramethylene adipamide units. Caprolactam is primarily used asthe comonomer. Preferred fractions of caprolactam in the poly-mer are 3-10%. The use of the comonomer influences the thermalproperties of the polytetramethylene adipamide, i.e., an in-creased comonomer fraction results in a reduction of the melt-ing point.The polymer can contain additives such as stabilizing agents.These can be added during polymer production or measured intothe molten polymer via a master batch. Other possibilities areto introduce the additive into the molten polymer in the ex-truder or to sprinkle the additive onto the pellets prior tomelting.If a polymer with a caprolactam fraction in the aforementionedrange is used, the melt temperature can be about 300°C. Fiberproduction occurs in the manner conventionally used in themelt-spinning process, by feeding the melt to spinnerets andpressing the melt through the spinneret openings, thereby form-ing the fibers. Downstream from the spinneret is a coolingzone, conventional in melt spinning, in which forced air is di-rected onto the fibers.CA 02265059 1999-03-08An aqueous-based finish is applied to the freshly spun fila-ments. Products that are not water-soluble are present in thefinish batch in the form of an emulsion.It has been shown that the use of an aqueous finish also en-ables fully satisfactory operation in the subsequent drawingstage and that it is possible to dispense with using a non-aqueous, i.e., benzine-based, finish, in contrast to the teach-ings of the prior art.Fiber production can be continuous, using a spinning/drawingprocess, or discontinuous. In the first case, the freshly spunproduct is not wound up but rather fed directly following spin-ning to a drawing zone, where it is drawn.In the discontinuous process, the freshly spun product is woundup. The resulting spools are fed to a drawing machine. In pro-ducing filament yarns, drawing is performed using galette sys-tems that are operated at different speeds and temperatures.The difference in speeds provides the adjustment of the drawratio. Drawing can be performed in one or two stages. Afterdrawing is completed, the yarn can be fed through a so-calledrelaxation zone, whereby the galettes arranged at the exit fromthis zone are operated at a slower speed than the galettes onthe feed side. Another possibility is to transfer the relaxa-tion process to the wind-up zone, i.e., to operate the wind-upmachinery at a slower speed that the feed machinery.The described procedure results in a filament yarn that is es-pecially suitable for use in industrial textiles. However, thefilament yarns produced according to the invention are alsowell suited for non-industrial applications such as clothing.The described process is preferably conducted to producepolytetramethylene adipamide filament yarns. It can also be em-ployed for producing staple fibers, however. Moreover, spunbon-CA 02265059 1999-03-08ded nonwovens can be made from this polymer under the condi-tions described for the spinning stage.Embodiment exampleA polymer containing 94% polytetramethylene adipamide and 6%caprolactam was used in the form of pellets to produce a fila-ment yarn. The pellet length had a mean of 4.2 mm and a stan-dard deviation of 1.3 mm. The mean of the pellet diameter wasdetermined to be 2.7 mm. The standard deviation was 0.08 mm.The pellets were melted in an extruder having four separatelyheated zones. The following temperatures were set in the indievidual heating zones:Zone 1 315°CZone 2 310°CZone 3 305°CZone 4 290°CThe temperature in the melt duct was 302°C. The melt was fed toand pressed through a spinneret with 36 openings. The freshlyspun filaments were cooled by forced air at 150 m3/h. Subse-quently, the aqueous finish was applied via finishing galettes.The concentration of the finishing agent in the finishing batchwas about 15%. The filaments spun in this manner were wound upat a rate of 600 m/min.The spools were fed to a drawing machine that drew the yarn ata rate of 580 m/min. On the drawing machine, drawing was per-formed at a ratio of 1:3.91 over a soâcalled hot plate whosetemperature was set at 210°C. The temperature of the feedgalettes was 105°C and that of the removal galettes was 215°C.Subsequently, relaxation was performed at a ratio of 1:O.97.CA 02265059 1999-03-08The yarn produced in this manner exhibited the following prop-erties:Yarn titerNumber of filamentsTensile strengthElongation at break %Hot-air shrinkage (190°C)235 dtex3669.8 cN/tex15.9%3.3%
