EP0168582A2 - Process and apparatus for conditioning synthetic fibre material - Google Patents

Abstract

The conditioning of synthetic fiber material to perfect products with low residual solvent contents using comparatively small amounts of steam is possible in a steam-tight conditioning device from several zones with a rotating sieve belt using superheated steam from 105 to 150 ° C and a residence time of the material in the device of over 3 minutes .

Description

The invention relates to a method and an apparatus for conditioning cables or nonwovens made of synthetic fibers with the aid of steam, in particular threads and fibers made of acrylonitrile polymers with at least 40% by weight of acrylonitrile units, optionally after previous crimping.

Devices for steaming continuously conveyed synthetic fiber material are preferably screen drum and screen belt dampers (for example in DE-OS 2 060 941 or GB-PS 1 208 792). Steam pipes, tunnels and U-shaped steaming boots, cf. eg international textile practice Dec. 1981, page 1410 or man-made fibers / textile industry Nov. 1981, page 821 or Feb. 1982, page 96. Combinations of crimping devices with a subsequent fixing chamber (for example US Pat. No. 2,865,080) are also described in a wide variety of shapes and designs, in particular for texturing and fixing processes. These steaming units are used for Drying and shrinking of fiber cables, as well as to stabilize crimp and spin dyeing of the fibers.

EP-OS 98 477 describes for the first time a continuously operating dry spinning process for acrylonitrile threads and fibers, in which the spinning cable of 100,000 dtex and more is prepared shortly before or immediately after leaving the spinning shafts, then stretched, crimped and then fixed without the cable comes into contact with an extraction liquid for the spinning solvent, such as water. The majority of the spinning solvent is already driven out in the spinning shafts in this process. The solvent content of the threads is usually less than 10% by weight, based on the fiber solids content, but more than 1% by weight when leaving the spinning shafts.

The known conditioning devices are not suitable for this method. Either the amount of steam required was too high or raw clay damage or matting of the fiber cables occurred.

The object of the present invention was to provide a suitable conditioning device for the continuous dry spinning process, it being possible to integrate an upstream crimping process. The conditioning device has to perform the tasks of stabilizing the crimp, reducing the shrinkage built up by the stretching process and removing the remaining portions of spinning solvent. The method and device should be suitable for the conditioning of cables and nonwovens.

The object is achieved in that in a vapor-tight conditioning device the synthetic fiber material is exposed to at least two stages of superheated steam from 105 to 150 ° C. on a circulating wire belt and has a dwell time of over 3 minutes in the conditioning device.

The invention therefore relates to a method for conditioning synthetic fiber material, in particular synthetic fiber cables or nonwovens, characterized in that the synthetic fiber material is exposed in a vapor-tight conditioning device on a circulating screen belt to at least two stages of superheated steam from 105 to 150 ° C. and a dwell time in the conditioning device of over 3 minutes.

The term “vapor-tight” is understood to mean that the uncontrolled vapor losses at the inputs and outputs of the synthetic fiber material together are less than 1%. If a crimping device is integrated in the conditioning device in an absolutely vapor-tight manner, the entry into the crimp is considered to be the input for the synthetic fiber material. Stuffer box and blow curls are preferred.

The superheated steam is expediently conducted in countercurrent to the fiber material and the fibers in the individual treatment stages with the aid of fans material fed multiple times. The superheated steam is preferably generated in the conditioning device into which saturated steam enters, which is overheated with the aid of heat exchangers.

The temperature of the superheated steam is preferably 120 to 140 ° C, the residence time is preferably 5 to 15 minutes. The process works efficiently with a covering density of up to 15 kg / m ² , preferably up to 10 kg / m ² . The document density can easily be calculated from the documentable surface of the sieve belt, the dwell time and the throughput (kg / h).

The process is particularly suitable for the conditioning of spun cables made of acrylic fibers with at least 40% by weight of acrylonitrile units, preferably at least 85% by weight of acrylonitrile units, which are obtained by a continuous dry spinning process in the course of which they are not mixed with an extraction liquid for the spinning solvent Have made contact.

When they are conditioned, a stable crimp, a residual solvent content of less than 1% by weight and a cook-shrink-free acrylic fiber with steam consumption which is less than 1 kg per kg of fiber material produced are produced in the device according to the invention.

Another object of the invention is a conditioning device in which the method according to the invention can be carried out. The conditioning device is shown in FIGS. 1 to 3.

• Fig. 1 shows a longitudinal section through the device
• Fig. 2 shows a cross section through the device at the level of the damping zone B.
• Fig. 3 shows a cross section through the device at the level of the damping zone C.

The device according to the invention consists of a sieve belt damper, which is closed in a vapor-tight manner and is divided into several zones A to D, the individual zones being separated from one another, zones B and C may occur several times, and zone A an inlet device and a suction device for solvent-laden steam , Zone B has a fan, a heat exchanger and a suction for solution-laden steam, Zone C has a fan, a heat exchanger and a steam supply and Zone D has a suction for solvent-laden steam.

Optionally, there is a zone E in which the synthetic fiber material is cooled before it is passed on for further use, storage, packaging or cutting.

In Fig. 1 a stuffer box crimp (1) is integrated in the conditioning device (2). The crimped fiber cable (5) is paneled onto a conveyor belt (6), for example a perforated or sieve belt, via the closed channel (3) and a traversing device (4). After passing through the entrance zone (A), in which there is no forced circulation of the steam, this happens folded fiber cables through the sealing flap (7) into the steam zones (B) and (C). Both zones are separated from each other by baffles and equipped with circulation fans (8). At the same time, live steam is introduced at (10) into the steaming zone (C) via a heat exchanger (11) so that the steam temperature is at least 105 ° C. The process steam flows through the folded fiber cable and is then sucked off by means of fans (8), reheated via the heat exchanger (10) and sent again through the fiber cable. A partial flow of the steam from the steam zone (C) reaches the steam zone (B) in the opposite direction to the direction of the fiber cable. Here the steam is again passed through fans (8) via heat exchangers (12), led through the fiber cable and a partial stream loaded with residual spinning solvent is removed via the suction (13). Belt seals in the form of sliding sealing flaps (7) at the level of the folded fiber cable and sealing strips (14) of the surrounding sieve belt (6) largely prevent steam from escaping. The amounts of steam that nevertheless escape through the sealing flaps (7) and sealing strips (14) are in the inlet zone (A) and the outlet zone (D) via suction devices (13), which are provided with adjustable throttle valves, not shown in the figure, led away. The folded fiber cable is then sent through a cooling zone (E). Air from room temperature is blown through the cooling zone by means of a fan (15). The fiber cable is then fed to a cutting device and further processed into staple fibers or paneled in cardboard boxes as an endless belt.

2 and 3 show, on the basis of cross sections through the steaming zones B and C, the path of the process steam through the conditioning device. The live steam, which enters the steaming zone (C) via the entry point (10), flows through the heat exchanger (11) and experiences overheating. The steam then flows through the paneled fiber cable (5) and is fed back to the heat exchanger for renewed circulation via an intake duct (16) by means of fans (8) via a pressure duct (17). A partial stream of the steam passes from the steaming zone (C) into the circulated amount of steam in the steaming zone (B), where the steam is circulated as in the steaming zone (C), reheated via the heat exchanger (12) and removed as a partial stream via the suction (13).

In a further embodiment of the invention, a crimping process can be combined with the conditioning.

The direct coupling of the crimping and conditioning device has proven to be extremely advantageous for continuous fiber production. In a particularly preferred case, a stuffer box (1) is connected directly to the conditioning device via a closed channel (3) according to FIG. 1. In addition to a stuffer box, the use of a blow nozzle crimp, which is analogously coupled to the conditioning device, especially at high production speeds, has proven to be very cheap.

example 1

The 30% by weight spinning solution of an acrylonitrile copolymer composed of 93.6% acrylonitrile, 5.7% methyl acrylate and 0.7% sodium methallylsulfonate with a K value of 81 (Fikentscher, Cellulosechemie 13, (1932), page 58) in dimethylformamide was obtained from Dry spun 1264-hole nozzles with a 0.2 mm nozzle hole diameter at a take-off speed of 60 m / min on a 20-shaft spinning system. The dwell time of the spun threads in the spinning shafts was 4 seconds. The shaft temperature was 210 ° C and the air temperature was 380 ° C. The throughput of air was 40 m ³ / h for each shaft, which was blown in at the head of the shaft in the longitudinal directions to the threads.

The spinning material with a total titre of 267,000 dtex, which still had a residual solvent content of 9.3% by weight, based on the solids content, was wetted in this way immediately before leaving the spinning shafts with an aqueous, oil-containing, antistatic preparation at 80 to 90 ° C. that the oil content of the threads was 0.25% by weight, the antistatic content was 0.06% by weight and the moisture was 1.2% by weight, based on the solids content. The preparation was dosed via gear pumps. The warm cable was then sent over a pair of rollers heated inductively to 150 ° C, with a contact time of approx. 2 seconds being achieved by looping several times over a feed roller. The cable took a tape temperature of 112 ° C, measured the radiation thermometer KT 15 (manufacturer: Heimann GmbH, Wiesbaden, Germany). The cable was stretched by 450%, with a stretch septet with coolable rollers serving as the second clamping point. The strip temperature after the stretching process was 61 ° C. Immediately afterwards, the cable was mechanically crimped in a stuffer box (1), which was connected to the conditioning device (2) by a closed channel (3), and paneled onto a continuous endless sieve belt (6) via a traversing device (4). The crimping speed was 270 m / min. After passing through the entrance zone (A), the folded, crimped fiber cable entered the damping zones (B) and (C), each 1 m long and 0.4 m wide. Both steam zones were separated from each other by baffles and equipped with circulation fans (8). At the same time, live steam, the quantity of which was regulated by a valve, came into the steaming zone (C) in counterflow to the fiber cable direction via the steam entry point (10). The amount of steam fed in was 48 kg / h with a calculated fiber cable throughput of 96.1 kg / h, so that a specific steam consumption of 0.5 kg steam per kg fiber cable was established. The incoming live steam and the circulated steam, which was heated to 135 ° C via heat exchangers (11) and (12), flowed through the folded, crimped fiber cable and a partial flow that came into the steaming zone (B) was then 8) suctioned off via an intake (16) and pressure channel (17), reheated via heat exchangers and again via the fiber cable cleverly. A partial stream, which was loaded with the remaining spinning solvent dimethylfomamide, was removed at the steam exit point (13) of the steaming zone (B) and fed to a distillation column. Belt seals in the form of abrasive sealing flaps (7) at the level of the folded fiber cable and sealing strips (14) at the level of the circulating sieve belt largely prevented unnecessary steam leakage. Smaller amounts of steam which reached the inlet zone (A) and the outlet zone (B) were also removed from the circuit there and fed to the distillation column. The residence time of the folded fiber cable in the steaming zones (B + C) of the conditioning device was 5.0 minutes. From this, a specific document density of approx. 10 kg / m2 was calculated. After leaving the conditioning device to stabilize the crimp, the fiber cable was sent over a 1.5 m long cooling zone (E). Air from room temperature is blown through the cooling zone by means of a fan (15). Then the fully shrunk fiber cable is cut into staple fibers with a cutting length of 60 mm, blown and fed to a packing press. The acrylic fibers produced in this way in a continuous process are shrink-free and have a single fiber final titer of 3.3 dtex. The fiber strength is 2.9 cN / dtex and the elongation is 39%. The residual solvent content in the staple fiber is 0.62% by weight. Yarns made from the fibers on a high-performance card at 120 m / min with a yarn count of 278 dtex have a yarn strength of 15.3 RKM, an elongation of 18.9% and a yarn boiling shrinkage of 2.4%.

The following table shows 267,000 dtex for spinning cables with the same total titer. which had different residual solvent contents of dimethylformamide and passed through the conditioning device under different steaming conditions, tape presentation and running mode in the secondary spinning mill were assessed. The different residual solvent contents in the fiber cable were achieved by varying the spinning air temperature and spinning air quantities under otherwise the same test conditions as in Example 1. The damper temperature, the amount of steam passed through per kg of fiber cable and the dwell time in the conditioning device were varied.

As can be seen from the table, superheated steam at temperatures up to 140 ° C is much better than saturated steam under otherwise identical conditions for removing residual solvent from the fiber cable. The lower the residual solvent content in the fiber cable in front of the conditioning device, the lower the residual solvent content in the fiber cable after passing through the conditioning device under otherwise identical conditions. Furthermore, it can be seen from the table that, in the case of fiber cables with solvent contents of around 10% by weight, generally steam quantities of less than 1 kg per kg of fiber cable are completely sufficient to significantly reduce the residual solvent content with residence times of about 5 minutes, below 1% by weight on fiber cables. All fibers were again shrink-free. With higher solvent contents in the fiber cable, the amount of steam and the dwell can be increased accordingly time in the conditioning device is also kept at low residual solvent. As the tests also show, good processing in the secondary spinning mill can only be guaranteed if there are no undissolved cut bandages as a result of rigidity in the fiber cable. This rigidity, which is understood to mean the partial caking or bonding of several crimped individual capillaries to form a compressed crimp package, is always avoided if the residual solvent content in the fiber cable is below 2% by weight.

Example 2

After stretching, part of the fiber cable according to Example 1 is fed to a blow nozzle instead of a stuffer box, which is also connected to the conditioning device by a closed channel (2). 1, the blow curl, which is operated with superheated steam at 140.degree. C., is constructed in front of the conditioning device in such a way that the blowing nozzle outlet opening and the subsequent channel lead into the conditioning device without kinking. All other conditions correspond to the details of Example 1. The acrylic fibers produced in this way in a continuous process have a single fiber final titer of 3.3 dtex. The fiber strength is 2.8 cN / dtex and the elongation is 33%. The residual solvent content in the staple fiber is 0.58% by weight. The fibers were again shrink-free. Yarns made from the fibers on a high-performance card at 140 m / min with a yarn count of 283 dtex have a yarn strength of 16.1 RKm, an elongation of 18.4% and a yarn boiling shrinkage of 2.4%.

Example 3

A part of the fiber cable from Example 1 was crimped in a stuffer box with a rotor blade into staple fibers for 60 mm staple length and applied to the conditioning device via a feed roller. The other conditions correspond again to the information from example 1. At the end of the cooling teeth (E) the fiber fleece is blown via a funnel-shaped suction device using a fan and fed to a packing press. Single fiber final titer 3.3 dtex; Fiber strength 2.5 cN / dtex; Elongation 34%. The residual solvent content in the staple fiber is 0.43% by weight. Again, no fiber shrinkage was found. Yarn values: yarn tenacity 15.8 Rkm with a yarn count of 290 dtex; Elongation 18.1%; Yarn shrinkage 2.7%; Carding speed 120 m / min.

Claims (4)

1. A method for conditioning synthetic fiber material, in particular synthetic fiber cables or nonwovens, characterized in that the synthetic fiber material is exposed in a steam-tight conditioning device on a circulating wire belt at least two-stage superheated steam from 105 to 150 ° C and in the conditioning device a dwell time of over 3 minutes Has. 2. The method according to claim 1, characterized in that the temperature of the superheated steam 120 to 140 ° C, the residence time 5 to 15 minutes and the coverage of the sieve belt to 15 kg / m ² . 3. Device for conditioning synthetic fiber material, consisting of a wire belt damper, which is closed in a vapor-tight manner and is divided into several zones A to D, the individual zones being separated from one another, zones B and C may occur several times, and zone A being an inlet device and a suction for solvent-laden steam, zone B has a fan, a heat exchanger and a suction for solution-laden steam, zone C has a fan, a heat exchanger and a steam supply and zone D has a suction for solvent-laden steam. 4. The device according to claim 3, characterized in that a crimping device is integrated in a vapor-tight manner in the conditioning device and a cooling zone E connects to the conditioning device.

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