EP1276922B2 - Method for spinning a spinning solution and spinning head - Google Patents

Abstract

The present invention relates to a spinning head (8) for spinning a spinning dope, which is provided with a tubular, thin-walled spinning capillary (7) having a discharge opening (94). The spinning dope used is e.g. a mixture of cellulose, tertiary amine oxide and water. In order to reduce the fibrillation tendency of the fibres spun by means of the spinning head and in order to increase the non-looping property, the present invention is so conceived that the spinning capillary (7) is heated directly close to the discharge cross-section (94). By means of this simple measure, it is possible to reduce the fibrillation tendency and to increase the non-looping property.

Description

The invention relates to a method according to the preamble of claim 1 and spinning head according to the preamble of claim 8.

Here, at least one spinning capillary is to be understood as meaning the last section of the spinning head through which the spinning solution flows and which forms the spinning solution outlet opening. Through the spinning capillary of the spun yarn is formed.

A generic method is for example from the WO 99/47733 known. There, a spinning head is described, which has a Vorkapillare (referred to in the document as a capillary) and in the flow direction of the spinning solution to the Vorkapillare subsequent spinning capillary (referred to in the document as the mouth). The precapillaries and the spinning capillary are made of a two-piece metal block. The diameter of the pre-capillary is 1.2 to 2.5 times the diameter of the spinning capillary.

In the field of Vorkapillare are in the spinning head of the WO 99/47733 Provided openings that serve to receive a heater. By the heater, the metal block of the spinning head is heated in the field of Vorkapillare.

The spinning block of the WO 99/47733 is surrounded by a gas chamber in which a heated gas is contained, which flows from the spinning head essentially parallel to the spinning solution emerging from the spinning solution outlet opening and encloses the spinning solution at the exit.

The operating temperature of the spinning head in the region of the Vorkapillare and the spinning capillary is between 70 ° C and 140 ° C. The temperature of the outflowing gas is, preferably 70 ° C, so it is below the temperature of the spinning head.

The disadvantage of the spinner after WO 99/47733 is that can be realized by the construction of the spinning head described therein only small hole densities. An additional disadvantage is that an influence on the temperature is only possible in the region of the pre-capillary. Due to the high cellulose concentrations during the spinning of NMMO / water / cellulose solutions and the strong structural viscosity, an influence on the spinning temperature is required. In addition, attention must be paid to a good uniformity of the temperature control, which in the in the WO 99/47733 described spinneret or in the heating system is not the case.

Given the WO 99/47733 Thus, the object is to improve the generic spinning heads so that the spun fibers have a lower Fibrillierungsneigung and a high loop strength.

The fibrillation tendency is determined by a so-called "shaking test". The shaking test is in the journal "Chemiefaser textile industry" 43/95 (1993), p. 879 ff. And in WO 96/107779 described.

A generic spinner is from the JP61-194204A known. This spinneret is used for spinning polymers of high molecular weight and has a projecting spinneret, which is traversed in the longitudinal direction of electric current to generate heat.

The WO 98/26122 A1 is concerned with the production of a nonwoven fabric from a cellulose solution, wherein the extruded fiber is drawn by a gas flow at high speed.

In the US 3,437,725 For example, there is described a spinner for melt-spinning a linear polymer in which spinneret inserts extend through two plates separated by an isolation space.

The fibers are shaken in normal length in water in the presence of glass beads over a period of time. The degree of fibrillation of the fiber is determined by observation under the microscope: If a large amount of split-off fibrils is detected under the microscope, this gives a high and therefore poor fibrillation value.

This object is achieved according to the invention for the method mentioned by the features of claim 1.

Surprisingly, it has been found that by influencing the temperature profile of the solution during extrusion through the spinning capillaries, a largely fibrillation-free cellulose fiber having good fiber characteristics, such as e.g. good loop strengths can be produced.

For the spinning head mentioned above, this object is achieved by the features of claim 8.

By this simple measure cellulosic fibers can be produced with a lower fibrillation tendency and a higher loop strength than in the prior art.

In order to be able to control the wall temperature and thus the temperature of the spinning solution close to the wall quickly and specifically, the temperature of the spinning capillary wall should be quickly adjustable by the heating device and react quickly to changes in temperature. This is achieved in that the spinning capillary is designed as a spider capillary tube in the form of a substantially thin-walled tube and that the heating device acts directly on the wall region of the spinning capillary tube near the spinning solution outlet opening. Due to the thin-walled design of the spinning capillary, the wall temperature reacts quickly with a change in the temperature of the heating device, since hardly any inert material is present. The direct action of the heater on the thin-walled spinning capillary also ensures a quick response.

The spinning capillary tube is surrounded by a spinning chamber filled with heating fluid near the spinning solution outlet opening.

When spinning head the WO 99/47733 Although the Vorkapillar is heated, but not the spinning capillary, which extends to the Spinnlösungsaustrittsöffnung. The pre-capillary has a larger diameter than the capillary. Due to the jump in cross section from the pre-capillary to the capillary, the temperature distribution in the spinning solution built up in the pre-capillary is disturbed, so that over the short length of the capillary a temperature distribution favorable for spinning the spinning solution can no longer build up.

Moreover, it is in the device of WO 99/47733 not possible to heat the capillary wall to a temperature which is greater than the core temperature of the spinning solution. Due to the large run length of the pre-capillary tube and the low flow rate of the spinning solution in the pre-capillary, the spinning solution in the pre-capillary heats up to the temperature of the pre-capillary wall. For two reasons, the wall temperature of the capillary at the WO 99/47733 lower than the temperature of the spinning solution:

On the one hand, the spinning head of the WO 99/47733 the gas from the gas chamber through the annular gap along the outer wall of the capillary. The temperature of this gas is below the temperature of the spinning solution. Thus, in the device of WO 99/47733 the area of the capillary near the exit opening is actually cooled below the core temperature of the spinning solution by the gas.

On the other hand, by the heater at the spinning head of the WO 99/47733 the wall of the capillary near the outlet only indirectly heated: The heater is located near the Vorkapillare and acts primarily only on the Vorkapillare. The downstream capillary is heated only indirectly by heating the capillary block. The wall temperature of the capillary near the outlet opening is thus at the spinning head of WO 99/47733 always smaller than the temperature of the pre-capillary.

In a particularly advantageous embodiment of the invention, the wall of the spinning capillary can be heated directly by a heater. In direct heating, the heater acts directly on the spinning capillary wall. This is in a conventional spinner such as the WO 99/47733 not the case. There, the wall of the spinning capillary is heated indirectly over the large mass of the spinning block. Direct heating of the spinning capillary wall, on the other hand, has the advantage that the temperature of the wall can be controlled more accurately and with a faster response, since there are no large inert masses which can react only slowly to changes in temperature.

For precise adjustment of the wall temperature of the spinning capillary and for exact process control, a temperature control device can be provided in a further advantageous embodiment, by wel-che the wall temperature of the spinning capillary is controlled to an adjustable value. Such a temperature control device makes it possible to automatically adapt the wall temperature to changes in the spinning process, for example to different spinning solutions or spinneret geometries.

The wall temperature of the spinning capillary can be regulated in one embodiment depending on the mass flow rate of the spinning solution through the spinning capillary. Due to the mass flow rate, the heat transfer from the capillary wall increases, so that the heating of the capillary wall must be adjusted accordingly. It is advantageous if fluctuations in the mass flow rate through the spinning capillary can be compensated for by regulating the wall temperature.

Also, in a further advantageous embodiment, the wall temperature of the spinning capillary depending on the spinning pressure in the spinning solution, preferably from the spinning pressure of the spinning solution in the capillary, are regulated. The flow rate and thus the heat transfer in the spinning solution also depends on the spinning pressure and thus the flow velocity in the spinning solution: With increasing spin pressure, the flow speed of the spinning solution through the spinning capillary increases. Again, it is advantageous if fluctuations in the spinning pressure are compensated by controlling the wall temperature of the spinning capillary.

The fibrillation tendency can be reduced in particular if, in a further advantageous embodiment, the heating of the spinning capillary wall during operation generates a predetermined temperature profile over the flow cross section of the spinning capillary. Due to the temperature-dependent viscosity of the spinning solution, the temperature profile of the spinning solution in the spinning capillary is specifically influenced by this temperature profile. In particular, by a strong heating of the capillary wall, it is possible to substantially reduce the viscosity of the spinning solution in the wall area. The heating leads to a reduced wall friction in the spinning solution and a fuller flow profile in the capillary: The distribution of the flow velocity over the flow cross-section no longer has the strongly curved profile of a pipe flow, but has a broad maximum that is almost constant up to the Wall of the spinning capillary extends down. Thus, the fibrillation tendency can be improved by influencing the flow profile over the wall temperature.

This effect of the wall temperature on the flow profile of the spinning solution in the spinning capillary can be further increased in an advantageous embodiment, although in the flow direction of the spinning solution heating the Spinnkapillarwand in operation a predetermined temperature profile of the Spinnkapillarwand can be adjusted. In this embodiment, the velocity profile In the spinning capillary is influenced by a targeted change in the temperature distribution in the flow direction. The formation of a pipe flow profile is reliably avoided and the flow profile can be optimized by adjusting the temperature distribution in the flow direction again.

For this purpose, several independently operating heating devices can be provided on the spinning capillary in the direction of flow.

A particularly uniform heating of the spinning capillary wall can be achieved if the wall of the spinning capillary outside of a heated Heating fluid is washed around. In contrast to an electric heater - as for example in the WO 99/47733 is described - arise in a fluid heating no abrupt changes in the spatial temperature distribution. In addition, local overheating can be avoided. The temperature of the heating fluid is at least 100 ° C, preferably around 150 ° C. The temperature of the heating fluid may advantageously also be between 50.degree. C., 80.degree. C. or 100.degree. C. and 150.degree. C. or 180.degree. Due to the high flow velocities in the end capillary of the spinning head, the wall temperature of the spinning capillary can even be greater than the decomposition temperature of the spinning solution. The residence time of the spinning solution in the spinning capillary is not sufficient to bring the spinning solution to decomposition temperature.

In a further embodiment, at least one temperature sensor may be provided for detecting the capillary wall temperature and / or the spinning solution temperature in the capillary wall region. By the temperature sensor, an electrical signal is output, which is representative of the Kapillerwandtemperatur. With the help of such a sensor, the temperature of the capillary wall can be determined at any time directly or indirectly. The signal can be fed to a control device, by means of which the wall temperature can be regulated. For this purpose, the temperature control device changes the temperature of the heating fluid accordingly.

When using a heating fluid can be provided in a further advantageous embodiment, at least one temperature sensor for detecting the temperature of the heating fluid through which the temperature of the heating fluid in the form of an electrical signal to the control device can be output. In this embodiment, the wall temperature of the spinning capillary can be determined and controlled via the detection of the helical fluid temperature.

For the spinning head, it may be particularly advantageous if the region of the spinning capillary wall heated by the heating device, whose temperature is higher than the core temperature of the spinning solution, extends substantially as far as the spinning solution outlet opening. The spinning solution outlet opening is a particularly critical point at which a high wall temperature has particularly positive effects on the Fibrillierungsneigung. In particular, it has been shown that when the outlet opening is heated, the jet expansion immediately after the exit of the spinning solution from the outlet opening, the so-called strand widening, can be suppressed. This leads to an improved surface structure of the spun fibers and thus to a further increased Schtingenfestigkeit or a reduced Fibrillierungsneigung.

In this case, in another advantageous embodiment, the region of the spinning capillary wall heated by the heating device, whose temperature is higher than the core temperature of the spinning solution, can extend essentially over the entire length of the spinning capillary. In this embodiment, a complete heating of the spinning capillary is possible, which leads due to the reduced viscosity of the spinning solution near the wall and due to the run length in the spinning capillary to complete formation of a full velocity profile over the cross section of the spinning capillary.

The wall thickness of the spinning capillary tube is advantageously less than 200 μm, preferably less than 150 μm.

In a further embodiment, the spinning solution outlet opening of the spinning capillary tube can be surrounded at least in sections by a gap opening, from which a transport fluid flows in operation in the direction of the spinning solution emerging from the spinning solution outlet opening during operation. The transport fluid surrounds the spinning solution jet emerging from the outlet opening of the spinning capillary and leads to a reduced speed jump on the lateral surface of the jet. This stabilizes the jet and calms the flow on the lateral surface. In this case, the speed of the transport fluid emerging during operation from the gap opening can essentially correspond to the speed of the spinning solution emerging from the spinning solution outlet opening.

It is particularly advantageous if the heating chamber is connected to the gap opening. Thus, the heating fluid can pass through the gap opening over the area of the spinning groove wall, which is located in the vicinity of the outlet cross-section. Thus, the spinning capillary wall can be heated up to the outlet cross-section.

When the heating fluid exits the gap opening at a corresponding speed, it can simultaneously serve as a transport fluid. Thereby it is unnecessary to provide a separate transport fluid for stabilizing the spinning solution jet.

To form a stable and full flow profile, the largest possible run length in the spinning capillary is necessary. Therefore, the ratio of the length of the spinning capillary to its diameter should be as large as possible. In an advantageous embodiment of the spinning capillary, the length of the spinning capillary can be at least 20 times to 150 times its diameter. In this case, the length flowing into this ratio may be the length through which the spinning solution flows and / or the diameter of the inner diameter of the spinning capillary.

The flow cross-section of the gap, through which the fluid exits parallel to the spinning solution, can be variable in a further advantageous embodiment by an adjustable housing, for example adjustable jaws. As a result, the speed of the fluid emerging from the gap can be changed depending on the spinning process and the spinning jet speed and thickness.

The spinning capillary can also be heated directly by being surrounded by an electric heating element.

The spinning capillary can be formed in a further advantageous embodiment as a precision steel tube. It can also have a circular outlet opening. The diameter of the outlet opening may be less than 500 microns, preferably less than 250 microns. For special applications, for example, the spinning of dope to lyocell fibers, the diameter may also be less than 100 microns to 75 microns.

The spinner head may be incorporated into a spin line having a surge tank containing a spin solution of tertiary amine oxide, a spin head forming a spin filament from the spin solution, and a spin solution line through which the spin solution is passed to a spin head. This Spirinanlage then performs the inventive method.

The invention also relates to the product produced by the method according to the invention by the spinning head or the spinning apparatus according to the invention, which is distinguished by the improved loop strength and the lower Fibrillierungsneigung and may be in the form of a filament, a staple fiber, a spunbonded fabric or a film.

The structure and mode of operation of the method according to the invention and of the spinning head according to the invention are explained below on the basis of exemplary embodiments.

Fig. 1

eine schematische Ansicht einer Spinnanlage;

Fig. 2

ein erstes Ausführungsbeispiel des erfindungsgemäßen Spinnkopfes im Querschnitt;

Fig. 3

ein zweites Ausführungsbeispiel des erfindungsgemäßen Spinnkopfes im Querschnitt;

Fig. 4

ein drittes Ausführungsbeispiel des erfindungsgemäßen Spinnkopfes im Querschnitt;

Fig. 5

ein viertes nicht beanspruchte Ausführungsbeispiel des Spinnkopfes im Querschnitt.

Show it:

Fig. 1

a schematic view of a spinning system;

Fig. 2

a first embodiment of the spinning head according to the invention in cross section;

Fig. 3

a second embodiment of the spinning head according to the invention in cross section;

Fig. 4

a third embodiment of the spinning head according to the invention in cross section;

Fig. 5

A fourth not claimed embodiment of the spinning head in cross section.

A spinning plant 1, by means of which the process according to the invention is carried out, is known in Fig. 1 shown schematically.

In a spinning solution storage tank or reactor 2 is a high-viscosity spinning solution 3 with a tertiary amine oxide, for example, a solution of cellulose, water and N-methylmorpholine-N-oxide (NM-MO) included.

The spinning solution is conveyed by a pump 4 from the spinning solution reservoir 2 through a spinning solution line 4 'and a pressure equalizing tank 5 to a manifold block 6. With the manifold block 6, a plurality of spinning capillaries 7 is connected. The distributor block 6 and the spinning capillary 7 are part of a spinning head 8.

The surge tank is used to compensate for any pressure and / or volume flow fluctuations in the spinning solution line 4 'and to ensure a uniform feed of the spinning head 8 with spinning solution.

High-viscosity spinning solution jets 9 emerge from the spinning head 8 at high speed. These spinning solution jets 9, after exiting the spinning head 8, flow through an air gap 10 or a non-precipitant. In this step, the spinning solution is accelerated and thereby stretched.

Thereafter, the dope rolls dip into a precipitation bath 11 or a bath of non-solvent or aqueous amine oxide solution. From the precipitation bath 11, the spinning solution is drawn off in the form of fiber by means of a removal device 12.

The following is based on the Fig. 2 the structure of a first embodiment of the spinner head 8 according to the invention described.

The spinner head 8 is fixed to a frame 50 and insulated by a layer 52 of heat-insulating material, so that no heat losses occur when the spinner is heated.

The spinner head 8 is constructed modularly from the distributor block 6, a substantially disk-shaped or plate-shaped pressure distribution plate 54, a substantially disk-shaped or plate-shaped spinneret body 56 having a distributor space 56a, at least one spinning capillary 7 and a holding device 60.

The pressure distribution plate 54 of the spinneret body 56 is supported by the retainer 60 at Distributor block 6 held in the direction of a center axis M of the spinning head. For this purpose, the holding device 60 forms a ring-shaped or slot-shaped recess in which the pressure distributor plate 54 and the nozzle holder 56 are accommodated. At the one end of the annular recess, a shoulder 60 a is formed, which engages in a corresponding recess 60 b of the spinneret body 56.

The spinneret body 56 rests with one of its end surfaces substantially on the entire surface of the pressure distribution plate 54. In the end face of the nozzle body 56, a sealing member 62 is attached, so that between the pressure distribution plate 54 and the spinneret body 56 no spinning solution can escape.

The pressure distribution plate 54 rests with its spinneret body 56 facing away from the end face substantially over the entire surface of the manifold block 6. Also in this area, a sealing element 62 is attached, so that even between the distributor block 6 and the pressure distribution plate no spinning solution can escape.

By a screw 64 engaging in the holding device 60, the holding device 60 is pulled in the direction of the distributor block 6. As a result, the shoulder 60a of the holding device 60 exerts a pressure on the corresponding recess 60b of the nozzle body 56. The nozzle body 56 transmits this pressure via the pressure distribution plate 54 back to the manifold block 6. In this way, the nozzle body 54 and the nozzle holder 56 are held firmly and tightly on the manifold block 6 and are at the same time for maintenance or replacement with other geometries by loosening the screw 64th easily replaceable.

The spinning capillary 7 is attached to the spinneret body 56. The spinning capillary is in the form of a tube with an annular cross-section and an inner diameter of less than 500 microns.

The inner diameter of the spinning capillary 7 is constant over the entire length of the spinning capillary.

Precision steel tubes from medical technology are used as tubes for the spinning capillary 7, the inner diameter of which is less than 500 μm and sometimes less than 250 μm. Especially for Lyocell fibers, internal diameters of less than 100 μm to less than 50 μm can also be provided.

The spinning capillary 7 is thin-walled and has a wall thickness of at most 200 microns. In the case of the spinning capillary, the length is at least 20 times, preferably at least 150 times, the inside diameter. Experiments have shown here that with increasing length-inner diameter ratio of the spinning capillary Fibrillierungsneigung the fibers decreases.

Usually, a plurality of spinning capillaries 7 are arranged next to each other or in a plurality of rows on the spinner head 8 offset from one another. Like this in Fig. 1 is shown, a plurality of spinning heads as previously described can be arranged in any arrangement to an economical production unit. Each nozzle body 56 includes a plurality of spinning capillaries 7 single or multi-row, stretched or arranged in a ring.

For uniform flow of the capillaries 7 of the distribution chamber 56a is designed as a V-groove in stretched or annular, as a single groove or multi-row V-groove. The pressure distribution plate 54 is located above the distributor space 56a designed as a V-groove.

The spinning capillary 7 is surrounded by an inner housing 66 and an outer housing 68.

The inner housing 66 forms with the outer surface 7a of the spinning capillary an outwardly closed heating chamber 70, which is flowed through by a heating fluid. The inner housing 66 forms a unit with the nozzle body 56. On the unit nozzle body 56 and inner housing 66 includes an outer housing 68 at. In this case, the spinning capillary 7 protrudes slightly beyond the inner housing 66 or the outer housing 68.

The outer housing 68 surrounds the inner housing 66 and forms with the outer surface of the inner housing 66, a further heating chamber 72, but in contrast to the heating chamber 70 is open to the outside. In this case, the heating chamber 72 forms a gap 74 which surrounds the end of the spinning capillary 7 arranged opposite to the spinning head. The heating chamber 72 is also flowed through by a heating fluid, which exits from the gap and flows substantially parallel to the center axis M.

In order to change the geometry of the gap 74, the outer housing 68 is held displaceably on the inner housing 66 in the direction of the center axis M.

In the embodiment of FIG. 2 For both chambers 70, 72, the same type of heating fluid can be used. This is a gas which is inert to the spinning solution and which can be heated to 150 ° C., for example via a heat exchanger (not shown here). Alternatively, a different heating fluid can be used for the chambers 70, 72. The heating chamber 70 forms the heating device for the spinning capillary 7.

The distributor block 6 and the holding device 60 are designed as substantially massive blocks with large mass and provided with heating channels 76, 78, 80 for hot water, hot air, heat transfer oil, steam or optionally heating rods. Due to their large mass and due to the thermal insulation, the operating temperatures of the distributor block 6 and the holding device 60 are subject to only slight fluctuations.

The function of the spinning block according to the invention is described below.

The spinning solution flows through the manifold block 6 via a feed line 82, which is connected via seals 83 to the spinning solution supply, into a settling chamber 84 with a screen disk or plate 86 with flow openings 88. The settling chamber 84 and the screen plate 86 are formed by the pressure distribution plate 54. In the direction of flow in front of the screen disk 86 is a filtration unit 90. The settling chamber 84, the screen disk 86 and the filtration unit 90 extend over all the spinning capillary 7 takes place.

As a result of the flow cross-section of the settling chamber 84, which is greatly enlarged in comparison with the feed line 82, the flow velocity of the spinning solution is reduced and the flow is made uniform. The spinning solution continues to flow through the filtration unit 88 and the openings 90 of the pressure distribution plate 54, whereby a further homogenization of the flow and pressure profile over the flow cross-section and a uniform feed of all capillaries 7 takes place.

From the settling chamber 84, the spinning solution in the spinning head 8 flows through the pressure distribution plate 54 into the distribution space 56a formed by the spinneret body 56. In the distribution space 56a, the flow cross-section gradually decreases in the flow direction. As a result, the spinning solution is accelerated and at the same time the flow cross section is gradually reduced to the flow cross section of the spinning capillary 7.

The spinning capillaries 7 adjoin the distributor chamber 56a in the direction of flow of the spinning solution and terminate in the direction of flow in the spinning solution outlet openings 94. Through the spinning solution outlet openings 94, the spinning solution emerges from the spinning head at high speed or at a high mass throughput. A typical mass flow rate per spin capillary is 0.03 to 0.5 g / min. Higher throughputs up to 1.5 g / min are possible at higher heating temperatures of the spinning capillaries. The pressure in the spinning solution can be up to 400 bar.

For the operation of the spinning head 8, it is important that the spinning solution is maintained at operating temperature during the flow through the spinning head. For this purpose, the heating channels 76, 78 and 80 already briefly mentioned above are provided in the distributor block 6 and in the holding device 60.

The manifold block heating channels 76 are located near the supply line 82 and maintain the dope in the supply line 82 at operating temperature. The heating channels 76 are flowed through by a heating fluid, such as hot water, heat transfer oil or steam.

The heating channel 78 is arranged so far down in the region of the holding device 60 that it heats the distribution space 56a already before the spinning mass enters the capillary 7. By the heating element 78 is also traversed by a heating fluid such as hot air, hot water, heat transfer oil, steam.

Optionally, a second Verteilerblockheizelement 80 may be provided which is externally attached to the spinning solution outlet opening 94 opposite portion of the spinner head 8. In the embodiment of Fig. 2 the distribution block heater 80 serves to heat the upstream portion of the supply line 82.

The heating channels 76, 78, 80 may be connected to a common heating circuit or form separate heating circuits. The heating circuits of the heating channels 76, 78, 80 may also be connected to the heating chamber.

The Fibrillierungsneigung is in the first embodiment, see. Fig. 2 , thereby reduced, that the spinning capillary 7 is heated in the region of the outlet opening 94 from the outside. This is achieved in that the heating fluid in the heating chamber 70 flows around the outer surface of the spinning capillary 7 and thus directly heats the spinning capillary 7. Due to the thin-walled design of the spinning capillary 7 and the large outer surface due to their length, a high heat transfer from the heating fluid via the spinning capillary wall to the spinning solution takes place. In order to achieve the best possible heating of the spinning capillary wall, the contact surface of the heating fluid with the outer wall of the spinning capillary should be as large as possible.

Since the spinning solution flows in the spinning capillary at a high speed, the temperature of the heating fluid can also be safely above the decomposition temperature of the spinning solution: Due to the high speed of the spinning solution along the heated wall, the dwell time of the spinning solution in the capillary is not sufficient for the spinning solution reached the wall temperature of the spinning solution.

Surprisingly, it has been found that even at wall temperatures of about 150 ° C. Fibers could be spun that have a very low Fibrillierungsneigung. The fibrillation tendency was even lower and the loop strength higher than at a wall temperature of 105 ° C.

The large length of the spinning capillary ensures that the wall-near layer of the spinning solution heats up. Since the viscosity decreases with increasing temperature in the conventional spinning solutions, the viscosity of the flow of the spinning solution is reduced by the spinning capillary 7 in the near-wall region. Over the large, over the entire range heated run length of the spinning capillary 7 can thus form a fuller velocity profile in the Kemströmung.

The formation of the velocity profile along the spinning capillary 7 is in FIG. 2 schematically explained with reference to four velocity profiles A, B, C and D. The velocity profile A forms shortly after the distributor space 56a and is characterized by a narrow maximum in the region of the core flow, in the vicinity of the center line M. Towards the walls of the spinning capillary 7, the velocity profile A drops steeply.

By heating the spinning capillary wall, the viscosity of the spinning solution in the wall area is reduced, the velocity profile becomes increasingly uniform and the maximum speed gets wider. This is shown schematically in the velocity profile B.

In the spinning solution exit port 94, the velocity distribution in the core flow is nearly constant and drops steeply toward the walls. This is shown by the velocity profile C. The steep drop in the wall area is possible due to the low viscosity and the strong heating of the spinning capillary wall up to the outlet opening 94.

The velocity profile D schematically shows a velocity profile after exit of the spinning solution from the outlet opening 94. The inert fluid from the chamber 72 and the spinning solution from the outlet opening 94 together form a wide jet.

According to the invention, therefore, the great length compared to the diameter of the capillary and the direct heating of the capillary act together and lead to an advantageous velocity profile. It is important that the temperature of the spinning capillary wall is above the temperature of the core of the spinning solution flow in the middle of the spinning capillary. The temperature in the core of the spinning solution flow through the capillary 7 corresponds approximately to the operating temperature of the distributor block 6 and the holding device 60 with the pressure distribution plate 54 and the nozzle body 56 set therein by the heating channels 76, 78, 80. The core flow remains during the flow through the spinning capillary unaffected and does not change its temperature.

Due to the small wall thickness of the capillary 7, moreover, the temperature of the spinning capillary wall 7 can be controlled precisely and with a fast response: Due to the low mass of the spinning capillary wall, the wall temperature reacts immediately to temperature changes in the heating chamber 70.

For targeted adjustment of the wall temperature and thus the targeted flow influencing of the flow through the capillary 7, a control device (not shown) may be provided. The control device is connected to sensors (not shown) which detect the temperature of the capillary wall and / or the heating fluid in the heating chamber 70, the flow rate of the spinning solution through the capillary and the operating pressure in the spinning solution. In this way, a control loop can be constructed by means of which the temperature of the wall is independently or externally adjustable to changing operating conditions. Thus, fluctuations of the operating parameters can be compensated without the spinning quality deteriorates.

As tests have shown, the fibrillation tendency can be decisively reduced if the wall of the spinning capillary 7 is also heated in the region of the outlet opening 94.

For this purpose, in the embodiment of the Fig. 2 the heating fluid from the heating chamber 72 passed through the gap 74 on the outer wall of the spinning capillary past 7 from the spinning head 8. In this way it is ensured that the spinning capillary is actually heated over its entire length and that over the length of the spinning capillary 7 forming fuller flow profile can not regress at the end of the run length due to a colder wall to this point.

The fluid flows out of the gap 74 at a high velocity that is at least equal to the outflow velocity of the dope from the exit port 94. The fluid thus also acts as a transport fluid, which entrains and stabilizes the spinning solution jet.

If the exit velocity of the fluid is greater than the speed of the spinning solution, a tensile stress acts on the edge of the spinning solution jet, stretching the high-viscosity jet.

Like the fluid in the heating chamber 70, the fluid in the heating chamber 72 may be part of a control circuit for the wall temperature of the spinning capillary 7. For this purpose, as described above, a plurality of sensors for detecting the operating parameters of the spinning system and sensors for detecting the temperature of the spinning capillary wall and the heating fluid can be provided. The signals of these sensors are supplied to a temperature control device, by means of which the temperature of the heating fluid in the heating chamber 70 is regulated.

By dividing into two Heizkammem 70,72 the temperatures of the two helical fluids of these chambers are adjustable. It has proved to be advantageous if the Spinnkapillarwand near the outlet opening 94 is maintained at a higher wall temperature than the central region of the spinning capillary. By this measure, the above-described strand expansion can be suppressed.

By dividing the chamber 70 into further independent heating chambers, the temperature profile along the spinning capillary, in particular in the case of a large capillary length, can be controlled even more precisely in the flow direction of the spinning solution in a further embodiment. Each of these chambers can be provided with its own sensors.

The following is with reference to Fig. 3 the structure of the second embodiment explained.

In this case, only the differences from the first embodiment will be discussed. The same components or similar components with the same function as in the first embodiment are in Fig. 3 provided with the same reference numerals.

The second embodiment according to Fig. 3 differs essentially by the structure of the heating chamber 70: The embodiment of Fig. 3 has only a single heating chamber 70 in the region of the spinning capillary, which reaches up to the outlet opening 94 of the individual spinning capillary 7 and forms the gap 74. Each spinning capillary 7 may have its own heating chamber 70, but it is also possible for a plurality of spinning capillaries 7 to be combined in a heating chamber 70. A second chamber 72 and a second housing 68 are not available.

The heating chamber 70 is in the execution after Fig. 3 a tube 100 in a circular or oval design, which surrounds the outer surfaces of the spinning capillaries and forms an annular space 102 between spinning capillary 7 and housing 66. The annular space 102 opens as an annular gap 74.

The heating fluid in the annular space 102 heats the entire outer wall of the spinning capillary 7 up to the outlet opening 94. The heating fluid is thus part of a heating device which acts directly on the spinning capillary wall and can be used for targeted control of the wall temperature.

The tube 100 is made of a. Precision steel tube manufactured.

The heating fluid flows out of the annular space 102 in parallel and coaxial with the spinning solution jet from the spinning solution outlet opening. As a result, a smooth guidance of the spinning solution jet can be achieved.

The following is with reference to the Fig. 4 explains the third embodiment of the spinning head according to the invention.

In this case, only the differences from the second embodiment will be discussed. For components of the third embodiment, which are the same as those of the second embodiment and / or have a same function, are in Fig. 4 the same reference numerals as in Fig. 1 used.

The embodiment of Fig. 4 differs from the second embodiment in that the gap formed by the housing 66 74 is not ring-but gap-shaped. The housing 66 may be formed in one piece, or have two perpendicular to the center line M slidable jaws 104a, 104b. By moving the jaws in the In Fig. 4 shown arrow direction, the width of the gap 74 can be adjusted.

The following is with reference to the Fig. 5 the fourth embodiment of the spinning head explained.

In this case, only the differences from the second embodiment will be discussed. For components of the fourth embodiment, which are the same as those of the second embodiment and / or have an identical function, are in Fig. 4 the same reference numerals as in Fig. 1 used.

In the spinning head according to the fourth embodiment, no heating chamber is provided. A heating of the spinning capillary no longer takes place via a heating fluid, but via an electric heating jacket 110, which is part of the heating device of the spinning head.

The heating jacket 110 may also be part of a control circuit for controlling the temperature of the spinning capillary wall, as described above.

In order to achieve precise control of the temperature profile along the length of the spinning capillary, the heating jacket can be subdivided into a plurality of independently operating heating jacket segments.

Claims (36)

1. A method of spinning a spinning dope comprising a mixture of cellulose, water and tertiary amine oxide, wherein the spinning dope is supplied to at least one spinning head, characterized in that the spinning dope in the spinning head (8) is conducted through at least one spinning capillary (7) in the form of a substantially thin-walled spinning capillary tube with a diameter constant across its length, said tube being provided with a spinning dope discharge opening (94) on its downstream end, through which said opening the spinning dope exits from the spinning head (8), wherein the wall close to the spinning dope discharge opening (94) is heated to a temperature which is higher than the core temperature of the spinning dope in the spinning capillary and is flown around at the outside at least sectionwise a heating fluid.
2. A method according to claim 1, characterized in that the wall of the spinning capillary is heated directly by a heating device (70, 72).
3. A method according to claim 1 or 2, characterized in that the wall temperature of the spinning capillary (7) is controlled to an adjustable value by means of a temperature controller.
4. A method according to one of the above-mentioned claims, characterized in that the wall temperature of the spinning capillary (7) is controlled in dependence upon the mass flow rate of the spinning dope through the spinning capillary (7).
5. A method according to one of the above-mentioned claims, characterized in that the wall temperature of the spinning capillary (7) is controlled in dependence upon the spinning pressure in the spinning dope, preferably in dependence upon the spinning pressure of the spinning dope in the spinning capillary (7).
6. A method according to one of the above-mentioned claims, characterized in that a predetermined temperature profile across the flow cross-section of the spinning capillary (7) is adjusted by heating the spinning-capillary wall when the spinning capillary is in operation.
7. A method according to one of the above-mentioned claims, characterized in that a predetermined temperature profile of the spinning-capillary wall is adjusted in the direction of flow of the spinning dope by heating the spinning-capillary wall when the spinning capillary is in operation.
8. A spinning head for spinning a spinning dope which consists of a mixture of cellulose, water and tertiary amine oxide and which flows through the spinning head, comprising at least one spinning capillary having a spinning-dope discharge opening at its downstream end, the spinning dope being discharged from the spinning head through said spinning-dope discharge opening, and further comprising a temperature-controlled heating device which acts on said spinning dope, wherein during operation of the spinning head the wall temperature of the spinning capillary generated by the heating device is higher in an area close to the spinning dope discharge opening than the core temperature of the spinning dope, characterized in that the spinning capillary (7) is formed as a spinning capillary tube in the form of a substantially thin-walled tube with an inner diameter that is constant across the length, and the spinning capillary tube is surrounded close to the spinning dope discharge opening (94) by a heating chamber (70, 72) containing a heating fluid.
9. A spinning head according to claim 8, characterized in that the area of the spinning-capillary wall which is heated by said heating device (70, 72) and the temperature of which is higher than the core temperature of the spinning dope extends essentially up to the spinning-dope discharge opening (94).
10. A spinning head according to claim 8 or 9, characterized in that the area of the spinning-capillary wall which is heated by said heating device (70, 72) and the temperature of which is higher than the core temperature of the spinning dope extends essentially over the whole length of the spinning capillary (7).
11. A spinning head according to one of the claims 8 to 10, characterized in that a control unit is provided, which acts on the heating device (70, 72) and by means of which the temperature of the directly heated wall area of the spinning-capillary tube (7) is adapted to be controlled, at least sectionwise.
12. A spinning head according claim 8, characterized in that the heating fluid of the heating device (70, 72) surrounds the spinning-capillary tube (7), at least sectionwise.
13. A spinning head according to one of the claims 8 to 12, characterized in that the spinning-dope discharge opening (94) of the spinning-capillary tube (7) is surrounded, at least sectionwise, by a gap opening (74), a transport fluid flowing out of said gap opening (74) essentially in the direction of the spinning dope discharged from the spinning-dope discharge opening (94) when the spinning head is in operation.
14. A spinning head according to claim 13, characterized in that the velocity of the transport fluid flowing out of said gap opening (74) when the spinning head is in operation corresponds substantially at least to the velocity of the spinning dope discharged from the spinning-dope discharge opening (94).
15. A spinning head according to one of the claims 13 to 15, characterized in that, the heating chamber (72) communicates with the gap opening (74).
16. A spinning head according to one of the claims 13 to 15, characterized in that the heating fluid serves as a transport fluid and is conducted from the heating chamber (72) through the gap opening (74).
17. A spinning head according to one of the claims 13 to 16, characterized in that an annular space (102) extends between said heating chamber (70) and said gap opening (74), said annular space (102) surrounding the capillary tube (7) from outside essentially along the whole length of said tube.
18. A spinning head according to claim 17, characterized in that the annular space (102) has a substantially oval cross-section.
19. A spinning head according to one of the claims 8 to 17, characterized in that the length of the spinning capillary (7) is 20 to 150 times as long as the diameter of said spinning capillary.
20. A spinning head according to claim 19, characterized in that said length is the length through which the spinning dope flows and/or that said diameter is the internal diameter of the spinning capillary (7).
21. A spinning head according to one of the claims 8 to 20, characterized in that the discharge cross-section (94) is circular.
22. A spinning head according to claim 21, characterized in that the discharge cross-section (94) has a diameter of less than 500 µm, preferably less than 250 µm.
23. A spinning head according to one of the claims 8 to 22, characterized in that the wall thickness of the spinning-capillary tube (7) is less than 200 µm, preferably less than 150 µm.
24. A spinning head according to one of the claims 8 to 23, characterized in that the temperature of the heating fluid in the heating chamber (70, 72) is at least 100°C, preferably approximately 150°C.
25. A spinning head according to one of the claims 8 to 23, characterized in that the temperature of the heating fluid in the heating chamber (70, 72) ranges from 50°C to 150°C.
26. A spinning head according to one of the claims 8 to 25, characterized in that the temperature of the heating fluid in the heating chamber (70, 72) ranges from 80°C to 150°C.
27. A spinning head according to one of the claims 8 to 25, characterized in that the temperature of the heating fluid in the heating chamber (70, 72) ranges from 100°C to 150°C.
28. A spinning head according to one of the claims 8 to 25, characterized in that the temperature of the heating fluid in the heating chamber (70, 72) ranges from 50°C to 180°C.
29. A spinning head according to one of the claims 8 to 28, characterized in that at least one temperature sensor is provided for detecting the temperature of the capillary wall and/or the temperature of the spinning dope in the area of said capillary wall, the capillary-wall temperature being adapted to be outputted to the control device in the form of an electric signal by means of said temperature sensor.
30. A spinning head according to claim 29, characterized in that the temperature sensor is implemented as an electric resistance element.
31. A spinning head according to one of the claims 8 to 30, characterized in that at least one temperature sensor is provided for detecting the temperature of the heating fluid, the temperature of the heating fluid being adapted to be outputted to the control device in the form of an electric signal by means of said temperature sensor.
32. A spinning head according to one of the claims 8 to 31, characterized in that the gap (74) is defined by a housing (100; 104a, 104b) which is movable transversely to the longitudinal axis of the spinning capillary, at least sectionwise, and that the flow cross-section of said gap (74) is variable.
33. A spinning system with a pressure equalizing container containing a spinning dope composed of cellulose, water and a tertiary amine oxide and of one or a plurality of stabilizing agents, said spinning system comprising a spinning head or a plurality of spinning heads by means of which the spinning dope can be spun so as to obtain formed bodies, and a spinning-dope conduit by means of which the spinning dope is conducted from said pressure equalizing container to said spinning head or said spinning heads, characterized in that the spinning head (8) is implemented according to one of the claims 8 to 32 and/or that the spinning system (1) is implemented for carrying out the method according to one of the claims 1 to 7.
34. A spinning system according to claim 33, characterized in that said spinning system includes an air gap (10) after said spinning head (8) or said spinning heads (8), the spinning dope flowing into and being drawn in said air gap (10) after having left the spinning-dope discharge opening (94).
35. A spinning system according to claim 33 or 34, characterized in that said spinning system (1) comprises a precipitation bath (11) downstream of said air gap (10), the spinning dope discharged from the spinning head (8) being immersed into said precipitation bath after having passed through the air gap (10) and after having been drawn so as to obtain a formed body.
36. A spinning system according to one of the claims 33 to 35, characterized in that a drawing-off device (12) is provided by means of which the spinning dope can be drawn off from the precipitation bath in the form of a precipitated thread or formed body.

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