Textiles: manufacturing – Thread finishing – Surface modification of running length
Reexamination Certificate
2000-05-26
2003-04-08
Vanatta, Amy B. (Department: 3765)
Textiles: manufacturing
Thread finishing
Surface modification of running length
C028S271000
Reexamination Certificate
active
06543105
ABSTRACT:
TECHNICAL SECTOR
The present invention relates to a device for intermingling, relaxing, and/or thermosetting of filament yarn in a melt spinning process, as well as associated processes.
During the melt spinning of filament yarns, a melt-spinnable polymer is melted and, in this state, is extruded through fine nozzle orifices of a spinneret plate. This results in a number of melt strands, which are solidified by cooling in an air stream, and are drawn out over a number of rollers with increasing surface speed to form fine filaments. These are then merged to form a unitary yarn, and are finally wound up as bobbins.
The drawing of the filaments is effected on the one hand, provided they are not yet solidified and the polymer has not yet fully crystallised out and is still somewhat capable of flowing, in the area of the cooling way upstream of the first godet roller. This is also referred to as spin drawing. On the other hand, the filaments, after solidifying, are mostly mechanically drawn, as a result of which an orientation effect of the macromolecules of the polymer is achieved, and the definitive expansion and strength values of the yarn are set.
The ratio between spin drawing and mechanical drawing is dependent on the spinning speed. The lower the spinning speed, the higher the degree of mechanical drawing required to obtain what is referred to as fully-drawn yarn. The draw ratio can in this situation be up to 1:4. At medium to low operating speeds (depending on the polymer used, for example, up to about 50 m/s), it may therefore be necessary for the filaments in the area of the drawing zone to be heated up to a temperature above the glass transition point of the second order, in order to facilitate drawing. At high spinning speeds (depending on the polymer used, for example, above about 85 m/s), the draw ratio is substantially smaller, and typically amounts to only about 1:1.3, as a result of which such additional heat treatment can be done away with.
After the extrusion, i.e. the spin drawing and/or drawing, there remain internal tensions in the filaments, which impair the form stability of the yarn, and may lead to the yarn being shortened as tension builds up on the bobbin, with the result that, as a minimum, it becomes impossible to continue winding without some intervention. The forces which arise in this situation may even lead to the destruction of the bobbin tubes. In order to avoid this disadvantageous effect, the yarn is in most cases, after drawing has been carried out, subjected to a repeat heat treatment, by means of which, among other things, it is already shortened before winding, an effect referred to as relaxation shrinkage.
Each filament yarn is also inclined to shorten still further, if subjected after manufacture to higher temperatures of, for example, 100° C. or more. This tendency towards longitudinal contraction is referred to, depending on the temperature treatment, as shrinkage at the boil (water 95° C.-100° C.) or hot-air shrinkage (hot air 160° C.-200° C.), in which situation downstream industry will only tolerate yarn of which the shrinkage values are within certain limits, e.g. shrinkage at the boil between 6% and 11%. This procedure, referred to as thermal shrinkage can also be reduced by heat treatment of the yarn after drawing, designated hereinafter as thermosetting. Compared with relaxation, however, in this case the attainment of a higher temperature and/or longer period of treatment is required. It has also been shown that, by increasing the spinning speed, the orientation of the macromolecules can be increased in such a way that the yarn will already feature conventional commercial thermal shrinkage values without additional thermosetting. In such a case, relaxation is sufficient to achieve adequate longitudinal stability of the yarn on the bobbin.
In order to improve the cohesion of the individual filaments in the yarn, and therefore improving what is referred to as the thread cohesion, the filaments are frequently also provided with a thread cohesion medium and/or entangled, with the intermingling being carried out as the final stage before winding, but in any event after drawing has been carried out. A distinction needs to be drawn between this and what is referred to as pre-intermingling before drawing. This treatment serves only to provide even distribution of the spin finish preparation on the thread, and a certain degree of cohesion of the filaments, in order in this way to suppress the separation and breakage of individual filaments during the subsequent drawing process. The larger part of the pre-intermingling process applied is nullified again by the drawing process.
PRIOR ART
Known in the prior art are processes and devices for intermingling, relaxation, and thermosetting, although these are not capable of use, or at least are not effective, in respect of all three types of processing, simultaneously or alternatively, and, in addition, are characterised in terms of apparatus by being either elaborate or expensive, and/or by high consumption of energy or treatment gas.
In the case of yarns produced at low to medium spinning speeds, the prior art allows for control of the thermal shrinkage values to be achieved by the fact that the threads are subjected, after drawing, to adjustable heat treatment by means of heated drawing godets.
As already mentioned, increasing the spinning speed allows for the orientation of the macromolecules in the thread to be increased in such a way that the yarn also features a commercially conventional thermal shrinkage after drawing, even without heat treatment. In this case, only relaxation of the yarn is required in order to avoid shrinkage of the yarn on the bobbin and damage to it. CH 623 611 describes such a process, whereby the yarn is guided through one or more steam jets after drawing by means of unheated godets, the steam emerging from apertures in a treatment chamber open to the side, arranged approximately at right angles to the yarn. The steam nozzles are fed with an overpressure of some 1.7 bar (g), but the steam relaxes to atmospheric pressure almost entirely on emergence from the nozzles, with the result that the yarn may be said to be processed at atmospheric pressure. Accordingly, the maximum steam processing temperatures for the yarn which can be achieved are only about 105° C. In addition to relaxation, during this process intermingling of the individual filaments of the yarn also takes place.
U.S. Pat. No. 5,750,215 and U.S. Pat. No. 5,558,826 describe in similar fashion a relaxation process and intermingling with steam, with mentioned also being made of thermosetting adjustment. In this case, too, according to the description, the yarn is treated under atmospheric pressure. Before winding, however, there is still a certain distance of 2-3 m for the yarn to run after the steam treatment, during which the yarn may undergo additional relaxation (due to “lagging”). It may therefore be doubted whether the steam treatment described is sufficiently effective on its own. In addition to this, a comparable first steam processing of the yarn to determine the drawing point is carried out as early as in the drawing zone between two pairs of godets, which may likewise lead to the impairment of the effect of the second steam treatment. The prognostications for the determination of the drawing point are, incidentally, in contradiction to DE 2204397, in which reference is made to the fact that, as from 3000 m/min, it is no longer possible to set a defined drawing point, and this accordingly need not, or cannot, be monitored any longer.
A further device is described in WO 98/23797, in which several threads are conducted through a steam chamber at atmospheric pressure before being wound up. In the chamber the steam does not impinge on the threads directly, and is released to the outside through lateral apertures. Only relaxation is achieved, and no provision is made for thermosetting or intermingling.
U.S. Pat No. 5,634,249, and EP 0 703 306 which corresponds to it, describes a intermingling effect
Kemp Ulrich
Ruppenthal Marcel
Inventa-Fisher AG
Morgan & Lewis & Bockius, LLP
Vanatta Amy B.
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