Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2001-10-04
2002-07-16
Edwards, N (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S364000, C428S395000, C204S210000, C204S211000, C204S211000
Reexamination Certificate
active
06420025
ABSTRACT:
DESCRIPTION
The present invention relates to a process of producing a synthetic ultrafine endless yarn on the basis of polyester or polyamide in the range from 0.25 to 0.9 denier per POY filament by melt spinng at draw-off speeds between 2000 and 6000 m/min. To the polyester or polyamide a second immiscible amorphous polymer may be added in an amount of 0.05 to 5 wt %.
Several authors have dealt with the problems in the production of fine and ultrafine filaments:
In “Advanced Fiber Spinning Technology” (Woodhead Publishing Ltd., 1994, p. 191), Nakajima describes a process of spinning ultrafine fibers, the filaments being quenched directly upon spinning in addition to the normal cross-flow quenching by means of a radially directed cold stream of air.
Tekaat (publication on the “Internationale Chemiefasertagung” in Dornbirn 1992, p. 8) describes studies in the production of microfilament yarns. It was found out that in the case of high filament counts the blow air can only hardly penetrate through the thread bundle, and the filaments in the middle cool down much later than the filaments close to the edge.
According to Ziabicki (“Fundamentals of Fibre Formation”, J. Wiley & Sons), 1976, p. 196 ff. and p. 241), the cooling conditions directly below the nozzle package are decisive for the thread quality. In addition, the bundle of threads exerts a considerable resistance to the flow, which may lead to the fact that the blow air flows around the bundle instead of flowing through the same.
For producing microfibers, some patents propose an additional heating of the filaments with heating gas or with radiant heating:
U.S. Pat. No. 5,310,514 (Corovin) claims a process of producing microfilaments, wherein for protecting the freshly spun filaments a stream of hot air flows out of an annular slot in the nozzle package parallel to said filaments. The temperature of the hot air is about ±10 K of the melt temperature. The technical design is very complex and the constancy of the air stream necessary in this critical range is hard to ensure.
EP 0 455 897 A (Karl Fischer) describes a process of heating the individual filaments via a system of passages inside the nozzle plate, through which hot air is passed. This should improve the draft of the filaments. A compensation of the heat losses of the filaments close to the edge is not possible. In this case, the hot gas flows around each filament individually. This should promote the draft of the thread. The temperatures may lie in the range of the melt temperature or above.
GB patent 1,391,471 (Hoechst) describes a heater for technical yarns. With this heater, a yarn of low prestretch orientation can be produced with an increased throughput. The apparatus consists of two conical shells, the lower one of which is heated, and the upper polished shell of which reflects a large part of the thermal radiation onto the filaments. It is expressly pointed out that only little radiation should impinge on the nozzle plate. The temperature profile along the heating section is greatly parabolic with a maximum approximately at half the running length (about 120 K above the melt temperature).
U.S. Pat. No. 5,661,880 (Barmag) claims a radiant heating of the filaments discharged from the spinneret. There is described a process for stretch-spinning with a conical heating section. With preferably 450-700° C., the temperature on thee heating surface distinctly lie above the melt temperature. There is also claimed a heating of the nozzle plate by heating bands extending in or on the same. The contact time available for the heat transfer to the melt is thus reduced to a few seconds. No distinction is made between a heating of the inner and outer melt flows. A premature orientation of the melt in the nozzle capillaries should thus be prevented. In addition, deposits on the nozzle should be reduced and the throughput should be increased.
U.S. Pat. No. 5,182,068 (ICI) describes a process which should reduce necking at draw-off speeds above 5000 m/min. It is stated that a heated snap-back with a constant temperature profile (3000) over the running length only effects a shift of the neck point, whereas a snap-back with progressively decreasing temperature profile (300→200° C.) leads to a distinct defusing of the neck point. The thread speed before necking is increased, and the neck-draw ratio before/after necking is decreased. There are claimed speeds above 7000 m/min.
GB patent 903,427 (Inventa) describes a spinning tube with a length of at least 1 m, in whose upper portion there is a temperature of 10-80 K below the melt temperature. The temperature in the lower tube portion is less than 100° C. Heating may be effected either directly or via a heat transfer medium.
U.S. Pat. No. 5,250,245 (DuPont) describes a spin orientation process for producing fine polyester filaments with improved mechanical properties and uniform titers. This is achieved by choosing a suitable polymer viscosity and correspondingly adapted spinning conditions.
U.S. Pat. No. 4,436,688 (Zimmer) claims a process with draw-off speeds between 600 and 6000 m/min, wherein the spun filaments perform a snap-back. The length thereof depends on the draw-off speed and the filter surface load.
U.S. Pat. No. 5,866,050 (DuPont) discloses a heating of the spinning package such that the filaments emerge from the nozzle bores with almost the same temperature. The process does not consider the different cooling behavior of the middle and outer filaments in particular with very fine and highly capillary titers.
For the heat conduction of the filaments directly upon extrusion, different methods are proposed in the above-mentioned references. Some of these methods have the disadvantage that they impair the formation of a stagnation zone directly after the extrusion of the thread by supplying a heating gas. However, this stagnation zone is absolutely necessary for achieving a high evenness of the yarn.
Many of the above-mentioned processes employ the radial or unilateral supply of heat to the filaments, which leads to the fact that in particular the outer filaments are subject to a decrease in tension, which deteriorates the running smoothness and thus reduces the evenness of the yarn.
The difference in the cooling behavior between inner and outer filaments is decisive for the running stability. It should therefore be possible to adapt the temperature profile of the emerging filaments in dependence on the polymer throughput. To influence the temperature profile of the filaments that have emerged already such that this cooling behavior is prevented has so far not been taken into account by the prior art.
What is still problematic is the question how low breakage rates can be achieved in the POY. It is the object of the invention to achieve an evenness with ultrafine yarns (about 0.25-0.89 dpf) as it can be achieved with the current method principle in the commonly used production of high-count yarns (about 1.0-1.2 dpf).
The quenching systems most frequently used in practice are based on a unilateral quenching, in order to facilitate access. It should be possible to utilize this principle of the unilateral quenching.
In accordance with the invention, the solution of this object is effected by a process and a yarn as stated in the claims.
The solution of this object is achieved by the complex cooperation of several essential process steps. Subsequently, the individual process steps for the production of ultrafine microfibers will be described from the extrusion of the melt to the take-up of the POY yarn.
As raw material, there is used a polyester such as polyethylene terephthalate (PET), polypropylene or polybutylene terephthalate or polyamide such as PA 6 or PA 6.6 or copolymers thereof. There is preferably used PET with an intrinsic viscosity between 0.59 and 0.66 dl/g. A sufficient structural homogeneity and a sufficient thermal homogeneity of the melt before reaching the spinning package must be ensured.
To the base polymer, a second immiscible amorphous polymer may be added in an amount of 0.05 to 5 wt %. Th
Möller Andreas
Schuettrichkeit Heinz
Wagner Reinhard
Wandel Dietmar
Dubno Herbert
Edwards N
Zimmer Aktiengesellschaft
LandOfFree
Method for producing ultra-fine synthetic yarns does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for producing ultra-fine synthetic yarns, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for producing ultra-fine synthetic yarns will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2909578