EP0349889A2 - Spinning process and apparatus - Google Patents

Abstract

Spinning apparatus comprising a ring type spinneret and a quench stick arranged centrally underneath the spinneret plate at a distance therefrom, characterised in that between the spinneret plate and the upper edge of the quench stick there is arranged a ring slot diaphragm with a narrow ring slot through which the spun filaments can pass without interference. <IMAGE>

Description

The present invention relates to a method and an apparatus for producing synthetic fibers of particularly high uniformity and high dynamic efficiency, in which the freshly spun filaments are cooled by central blowing.

DE-C 1 278 684 and US-A-3 259 681 already disclose melt spinning processes in which the filaments are cooled by central blowing immediately after they emerge from the nozzle plate. In these known methods, the filaments are spun from a spinneret, the nozzle holes of which are arranged on one or more concentric circles, the diameter of the smallest nozzle hole circle being large enough to install a blowing candle below the center of the spinneret. This blow-on candle consists of a tubular hollow body made of a porous gas-permeable material which is closed on one side and to which the cooling air is supplied from the other side. During operation, a radially outward flow of cooling air is created, which penetrates the filament curtain, which is only a few "layers" thick (corresponding to the number of concentric nozzle hole circles) and envelops the blowing candle. This arrangement is intended to significantly increase the cooling effect and it was also expected that the cooling of the individual filament layers would be made more uniform. In practice, however, it turns out that the central blowing does not provide sufficiently uniform filaments and that there are often malfunctions due to filament breakage.

From US-A-4 414 169 a method is known for the production of heavy duty polyester multifilament yarns. In this process, the filaments are cooled by blowing directly under the spinneret and drawn off under relatively high tension. The filaments are then drawn in two stages. In this method, the blowing of the filaments directly under the spinneret can also take place by means of an outward gas flow which is fed centrally to the filament bundle. In this process, too, the uniformity of the filaments cooled by central blowing leaves much to be desired and filament breaks occur too frequently during production.

From DE-A-36 29 731, EP-A-40 482 and EP-A-50 483 melt spinning processes are known in which the filaments are also cooled immediately after exiting the nozzle plate by central blowing and in which immediately after the blowing, the filaments are also subjected to a central preparation. The preparation is applied through a central sliding body wetted with the preparation, over which the circular filament sheet slides, or through a centrally located, radially spraying spray nozzle.

These known methods and devices also have the disadvantage that the filaments obtained are not uniform enough for many applications and that malfunctions due to filament breakage occur too often.

A proposal to improve the uniformity of polyester filaments is known from US-A-3 858 386. There, polyester filaments are melt-spun, then passed through a heating zone below the surface of the nozzle and then cooled by central blowing. The The aim of this process is a polyester yarn with an improved uniformity of its physical properties, in particular the Uster values and the strength measured over the cross section of a filament strand. The heating zone through which the filaments pass immediately after exiting the spinning plate is 15 to 60 cm long and has a temperature of 260 to 460 ° C.

However, the polyester yarns obtained in this way have high values of thermal shrinkage, which for some areas of application such as difficulties for the manufacture of tire cords.

The present invention therefore relates to a spinning device which can be used to carry out a stable and reproducible process for producing very uniform, high-strength synthetic fibers which have low shrinkage and low elongation and thus high dynamic efficiency.

The spinning device according to the invention consists of an annular spinneret, a blowing candle arranged centrally at a distance below the spinning plate and an annular slot diaphragm arranged between the spinning plate and the upper edge of the blowing candle.

• Figur 1 zeigt schematisch eine Aufsicht auf die Spinnplatte (1) einer Ringspinndüse mit einer etwa quadratischen, die Spinnbohrungen (3) aufweisenden Ringfläche (2).
• Figur 2 zeigt schematisch eine Aufsicht auf die Spinnplatte (1) einer bevorzugten Ringspinndüse mit auf 3 konzentrischen Kreisen (2a) angeordneten Spinnbohrungen (3).
• Figur 3 zeigt schematisch eine Aufsicht auf eine Ringschlitzblende (4) mit dem von dem Innenteil (5) und dem Außenteil (6) gebildeten kreisförmigen Schlitz (7).
• Figur 4 zeigt schematisch einen senkrechten Schnitt durch eine erfindungsgemäße Spinnvorrichtung mit der Spinndüse (8), den Spinnbohrungen (3), den daraus extrudierten Filamenten (9), der Ringschlitzblende (4), deren Innenteil (5) mittels eines Distanzstückes (10) an der Anblaskerze (11) befestigt ist. Der Mantel (12) der Anblaskerze besteht aus einem porösen, gasdurchlässigen Material; die Kühlluftzufuhr erfolgt durch das Flachrohr (13).
• Figur 5 zeigt einen Querschnitt durch das Flachrohr (13).

In the following reference is made to FIGS. 1 to 5.

• Figure 1 shows schematically a top view of the spinning plate (1) of an annular spinneret with an approximately square ring surface (2) having the spinning bores (3).
• FIG. 2 schematically shows a top view of the spinning plate (1) of a preferred ring spinning nozzle with spinning bores (3) arranged on 3 concentric circles (2a).
• FIG. 3 schematically shows a top view of an annular slot diaphragm (4) with the circular slot (7) formed by the inner part (5) and the outer part (6).
• Figure 4 shows schematically a vertical section through a spinning device according to the invention with the spinneret (8), the spinning bores (3), the filaments (9) extruded therefrom, the ring slot diaphragm (4), the inner part (5) of which by means of a spacer (10) the blow-on candle (11) is attached. The jacket (12) of the blow-on candle consists of a porous, gas-permeable material; the cooling air is supplied through the flat tube (13).
• Figure 5 shows a cross section through the flat tube (13).

A ring spinneret in the sense of the present invention is a spinneret whose spinning plate has a zone in the center which is free of bores. The zone in which there are holes thus has the shape of a frame surrounding the hole-free zone, i.e. a self-contained, not necessarily circular, ring surface.

FIG. 1 shows schematically the spinning plate of an annular spinneret with an approximately square annular surface (2) having the bores (3).

The area containing the bores can e.g. be square, rectangular, polygonal or oval and have a correspondingly smaller hole-free zone of square, rectangular, polygonal or oval shape in their center.

Appropriately, the width of the ring surface containing the bores, measured from the center in the radial direction, is approximately the same in all directions. Such a design ensures a particularly even cooling of all spun filaments guaranteed. The uniform cooling of all filaments is also favored if the ring surface has the highest possible central symmetry. A circular ring surface is therefore particularly preferred.

The spinning bores can be uniformly distributed within the ring surface in a manner known per se. It is particularly expedient to arrange the spinning bores on self-contained lines, and correspondingly on circular lines in the case of a circular ring surface.

A preferred ring spinneret is therefore one which has 1 to 10, preferably 1-4, nozzle hole circles. A spinneret with 2 or 3 hole circles is particularly preferred, in which the nozzle holes of the individual hole circles are arranged “on a gap”.

FIG. 2 schematically shows the bottom view of such a ring spinneret preferred for the construction of the spinning device according to the invention. The nozzle holes (3) are arranged on concentric circles (2a), the smallest of which has the diameter d _i , the largest of which has the diameter d _a .

For the sake of simplicity, the following explanations are based on the use of such a ring spinneret with a circular ring surface having the bores. The person skilled in the art can easily transfer all information to non-circular ring spinnerets.

The blow-on candle used in the method according to the invention has a structure known per se. It consists of a tubular hollow body made of gas-permeable material, for example sintered metal, which is closed on one side and to which the cooling air flow is supplied from the other side. The diameter of the blowing candle naturally depends on the diameter d _i des smallest nozzle hole circle together. As a rule, the diameter D of the blowing candle is
D = (0.5-1.0) d _i preferably (0.7-0.8) d _i
and has an amount of 45 to 180 mm. The length of the blow-on candle is usually 500 to 1500, preferably 800 to 1300 mm.

The distance between the spinning plate and the upper edge of the blowing candle is advantageously between 50 and 500 mm, preferably 100 to 200 mm.

The annular slit diaphragm arranged between the spinning plate and the upper edge of the blowing candle is a plate which has a slit which is closed in itself. The slot of the ring slot diaphragm does not necessarily have to be circular. Rather, its shape is similar to the shape of the annular surface of the annular spinneret provided with spinning bores.

In connection with a preferred ring spinning nozzle with an arrangement of the spinning bores within a circular ring surface (corresponding to FIG. 2), an annular slot diaphragm with a circular ring slot is naturally also used. The following information relating to such a preferred ring slot diaphragm can also be easily transferred to other embodiments with non-circular ring slots.
FIG. 3 schematically shows a top view of such a preferred ring slot diaphragm with a circular slot. The inner edge of the ring slot (7) is formed by the inner part (5) of the ring slot diaphragm, which consists of a circular plate with the diameter d _p . The outer part (6) of the ring slot diaphragm, which forms the outer edge of the ring slot, consists of a plate with a circular cutout, with the diameter d _r , wherein d _{r is} greater than d _p and the slot width s is accordingly (d _r -d _p ) / 2. The dimensions of the ring slit diaphragm naturally also depend on the arrangement of the spinneret holes, ie on the diameters d _i and d _{a of} the smallest and largest hole circle in the spinning plate. Advantageously, d _p = (0.5 to 1.0) · d _i , preferably (0.7 to 0.8) · d _i .

The following relationship expediently applies to the slot width s:
s = (1.0 to 4.5) · (d _a -d _i ), preferably (3.0 to 4.0) · (d _a -d _i ).

In practice _, the following dimensions are usually chosen for d _i and d _a :
d _i = 50 to 200 mm, preferably 50-180;
d _a = 55 to 205 mm.

The distance A _{b of} the ring slit diaphragm from the spinning plate is related to the distance A _{k of} the spinning plate from the upper edge of the blowing candle. The ring slot diaphragm is expediently spaced apart
A _b = (0.3 to 0.8) · A _k , preferably (0.4 to 0.7) · A _k
arranged below the spinning plate.

In general, the ring slit diaphragm should be dimensioned in such a way that the smallest possible ring slit (i.e. with the smallest possible s) is provided, which is just wide enough to allow all spun filaments to pass through without interference.

The inner part of the ring slot diaphragm is separated from the outer part by the slot. In principle, it is possible to connect the inner part and the outer part to one another by means of very narrow webs such that the inner part lies in the plane of the outer part. However, it is preferred to install the inner part and outer part separately in the spinning device. The The outer part of the ring slot diaphragm can be attached, for example, in the usual way by means of a flange at the desired distance below the spinneret, while the inner part is fastened by means of a spacer either in the center of the spinneret or on the blowing candle so that it lies in the plane of the outer part of the ring slot diaphragm . Any sufficiently temperature-resistant material, such as metal, ceramic or even high-temperature-resistant plastic, can be used as the material for the ring slot diaphragm. A ring slit diaphragm is preferred which is made of a heat-insulating material or which is coated with such a material. For example, a ring slit diaphragm can be made of metal and coated with a bonded mineral fiber fleece for thermal insulation.

In a structurally particularly advantageous embodiment of the spinning device according to the invention, the cooling air is supplied from the side in a manner known per se at the lower end of the blow candle. The air supply ducts expediently have the shape of a flat tube, ie they do not have a round, but an extremely elliptical or rectangular cross section with a long axis which is 5 to 10 times the short axis. These air supply ducts are installed with the long cross-sectional axis in the direction of the thread running direction. The advantage of this construction is that, despite the lateral air supply, no splitting of the filament bundle is necessary, as is described in US Pat. No. 3,858,386. The strong cooling of the filaments in the area of the blowing candle leads to trouble-free running of the filaments. The air supply ducts are preferably provided with a low-friction surface, for example with a matt chrome plating or a coating with fluoropolymers.

Those spinning devices according to the invention which have a combination of several preferred features are particularly preferred.

The spinning device according to the invention shows its particular advantages when spinning take-off speeds of over 2000 m / min. is worked.

The present invention therefore also relates to a spinning process for producing very uniform high-strength yarns with low shrinkage and low elongation, in which the spinning device described above is used and at spinning take-off speeds of more than 2000 m / min., Preferably at 2500 to 4000 m / min. is worked.

The filaments spun according to the invention can be further processed directly afterwards or in a separate process step in a manner known per se, in particular in a customary manner, optionally in one or more stages at elevated temperature.

Particularly advantageous results are obtained if polyesters are used whose i.V., measured in o-chlorophenol / phenol (50/50) at 25 ° C., is above 0.7 dl / g, in particular above 0.8 dl / g.

According to the method according to the invention, spun threads are obtained whose filaments within the thread bundle are more uniform than before. The heat is dissipated quickly and evenly, so that short lengths of the spinning shaft are also possible. An additional heating device to delay the cooling of the spun filaments is not necessary in the method according to the invention and is also not desirable. Such a device would destroy the high pre-orientation of the filaments desired here.

Another surprising advantage is that with a cylinder-symmetrical blowing from the inside to the outside in connection with the ring slot diaphragm already at 2600 m / min. Spinning take-off speed the same pre-orientation of the filaments is achieved, which can only be achieved with cross-blowing at a spinning take-off speed of 3000 m / min.

Subsequent drawing of the filaments spun according to the invention gives filament yarns or fibers with good strength, with a low sum of elongation and shrinkage and with a high dynamic efficiency.

Embodiment

A spinning device according to the invention (FIG. 4) is used for the following exemplary embodiment. As features essential to the invention, this has an annular spinneret (8) which has two concentric circles with a total of 200 spinning bores (3) lying on a gap. The smaller circle of holes has a diameter d _i of 166 mm, the larger of 177 mm.

In the center below the nozzle there is an 800 mm long blow-on candle (11) with a diameter of 105 mm and a jacket (12) made of sintered metal, the upper edge of which is 100 mm away from the nozzle plate.

At a distance of 70 mm below the nozzle plate there is an annular slot cover (4) made of 2 mm thick VA sheet with a layer made of 5 mm thick rock wool fleece. The inner edge of the circular slot has a diameter of 120 mm, the slot width is 40 mm. The inner part (5) of the screen is attached to the blowing nozzle with a spacer (10) 30 mm long.

The cooling air is supplied from the side through an upright, flat tube (13) tapered at the upper edge, the cross section of which is illustrated in FIG. 5, with a height of 600 mm and a maximum width of 60 mm.

With this spinning device a polyethylene terephthalate from I.V. of 0.90 dl / g, measured in o-chlorophenol / phenol (50/50) at 25 ° C, with a nozzle temperature of 315 ° C and at a take-off speed of 2600 m / min. The spun filaments are combined, provided with a low protective twist and wound up.

The yarn obtained is then drawn at a drawing temperature of 265 ° C. in a ratio of 1: 3.11. The filament yarn obtained in this way can be processed further in the usual way, for example twisted, textured or, combined into cables, cut into staple fibers. The data of the filaments obtained are: Titer: 1440 dtex f 200 Tensile strength: 72 cN / tex Elongation at break: 8.7% Elongation at a load of 54 cN / tex: 6.2% Hot air shrinkage at 200 ° C: 6.4%

The filaments show an excellent uniformity of the textile data compared to conventionally produced yarns over the yarn cross section.

Claims (12)

1. Spinning device with an annular spinneret and a blowing candle arranged centrally at a distance below the spinning plate, characterized in that an annular slot diaphragm is arranged between the spinning plate and the upper edge of the blowing candle. 2. Spinning device according to claim 1, characterized in that the annular slot of the annular slot diaphragm is similar to the ring surface provided with bores of the annular spinneret. 3. Spinning device according to at least one of claims 1 and 2, characterized in that the ring surface provided with bores of the ring spinneret and the ring slot of the ring slot diaphragm are circular. 4. Spinning device according to at least one of claims 1 to 3, characterized in that the annular spinneret has 1 to 10 concentric nozzle hole circles (2a). 5. Spinning device according to claim 4, characterized in that the inner diameter d _{p of} the ring slot
d _p = (0.5 to 1.0) · d _i
where d _{i is} the diameter of the inner nozzle hole circle. 6. Spinning device according to at least one of claims 4 and 5, characterized in that the slot width s of the ring slot
s = (1.0 to 4.5) (d _a -d _i ),
where d _{i is} the diameter of the inner,
d _{a is} the diameter of the outer nozzle hole circle. 7. Spinning device according to at least one of claims 1 to 6, characterized in that the ring slot diaphragm at a distance
A _b = (0.3 to 0.8) · A _k
is arranged below the spinning plate, where A _{k is} the distance between the spinning plate and the upper edge of the blowing candle. 8. Spinning device according to at least one of claims 1 to 7, characterized in that the inner and outer part of the ring slot diaphragm are mounted separately lying in one plane. 9. Spinning device according to at least one of claims 1 to 8, characterized in that the ring slot diaphragm consists of a heat-insulating material or composite material or is covered thereby. 10. A process for the production of very uniform high-strength polyester yarns with low shrinkage and low elongation, characterized in that a thread-forming polyester is spun by means of a device according to claim 1 at a spinning take-off speed of more than 2000 m / min and the filaments obtained directly afterwards or in a separate one Step are processed in a conventional manner. 11. The method according to claim 10, characterized in that a polyester with an I.V. of> 0.7 dl / g is spun. 12 The method according to at least one of claims 10 and 11, characterized in that the spun filaments are drawn directly afterwards or in a separate step in a manner known per se.

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