DE975936C - Method and device for producing threads from polyvinyl alcohol - Google Patents

Description

Method and device for producing threads from polyvinyl alcohol The invention relates to a method and a device for spinning threads made of polyvinyl alcohol by the wet draw spinning process. The spinning solution is in Upward direction into a coarse flowing precipitating liquid, higher specific Weight spun. A very specific flow profile is maintained, so that the spinning solution or the spun threads in the area of the first io to 5o cm above the spinneret not subjected to any stretching stress, then through stepless change of flow velocities steplessly stretched and then in End portion of the spinning channel are solidified. For this purpose, the spinning channel points above The spinneret has a cylindrical chamber 10 to 50 cm long, to which a spinning funnel is attached known design with a conical front part and cylindrical end part.

The coordination of the process and device to the special chemical, colloid chemical and physical conditions in polyvinyl alcohol spinning leads to a simple. and reliable production of polyvinyl alcohol threads excellent quality. There are already numerous procedures and Devices for wet draw spinning known. For example, it is suggested been used in the spinning of copper oxide ammonia cellulose solutions the spinning solution and to lead the precipitating liquid in the same direction through a funnel-shaped channel and to stretch the coagulating threads by the action of the flowing precipitating liquid. The conical funnel inlet begins directly at the spinneret, which Stretching begins immediately after the spinning solution emerges from the nozzle. the Spinning takes place from top to bottom.

In another device for spinning viscous liquids such as copper oxide ammonia cellulose, the precipitating liquid is in two different forms Areas of the spinning channel fed. In the area of the second precipitation liquid feed the flow speed increases by leaps and bounds, there is no smooth transition possible. This device also spins from top to bottom.

In a modified device for spinning viscose solutions behind the spinneret is a chamber into which the spinning water is introduced. In The spinning water is then discharged again in a subsequent intermediate chamber This is followed by another chamber through which the precipitating liquid circulates. The device is comparatively complicated, here too the spinning is from top to bottom.

According to another embodiment for the wet spinning of copper silk falls water in the area of the spinneret and in an area below it additionally introduced a hardening liquid. Here too, the spinning takes place up down.

In yet another spinning funnel for the production of rayon threads the spinneret is surrounded by a cylindrical precipitation liquid inflow chamber; The conical funnel part begins immediately in front of the nozzle opening, which then turns into a cylindrical piece passes over. At the end of the thread channel behind the cylindrical one The precipitating liquid becomes piece through another conical constriction of the funnel throttled. Again, in the opposite direction as in the invention, namely spun top down.

Finally, reference should be made to a method in which from above spun down and the precipitation liquid in the stretching area in countercurrent to the Thread run is guided.

It has also been proposed to reverse the direction of spinning and spin from the bottom up. So it is known that one is involved in the spinning of polyvinyl chloride solutions in certain solvents use the same nozzles and Spinning funnel as in the case of copper oxide ammonia or. Use viscose draw spinning process and here. can also spin from bottom to top .. Notes on compliance of a particular flow profile roughly in accordance with the method of the invention are not given, however. In another device for spinning cellulose solutions from bottom to top the spinning tube is provided with a device that serves to to impart a rotary movement to the liquid about the longitudinal axis of the spinning tube and thereby twisting the single threads together. The spinning channel does not have a funnel-shaped one Part on in which the liquid by its acceleration causes a stretching of the coagulating Could cause threads.

Finally, it has been proposed to use a solution containing acrylic acid spinning from bottom to top through a funnel that is immediately behind the Spinneret begins. The train therefore sets in immediately after the spinning solution emerges from the nozzle. The spinning solution is also transformed into a precipitating liquid of deeper depth specific gravity expressed as the spinning solution.

It has been known for many years for the manufacture of threads from polyvinyl alcohol, the processes used in the manufacture of rayon, d. H. Wet draw spinning process of the type described above, preferably in Come into consideration. The basic possibility of polyvinyl alcohol according to the rules the manufacture of artificial silk, and the rich selection on offer Procedural forms has evidently given rise to the prejudice that one is for polyvinyl alcohol specific improvement is unnecessary and no longer possible. Through the invention this prejudice is dispelled. According to the method and device of Invention, threads can be produced which, in terms of tensile strength and elongation properties, The number of broken threads and the like are superior to the threads known up to now and open up a broader application of textile technology.

According to the method of the invention, spinning with a rectified flow of spinning solution or spun thread and precipitating liquid, which has a higher specific weight than the spinning solution, is spun from bottom to top in a spinning tube with a funnel-shaped inlet, with the spinning solution and precipitating liquid according to the invention in a range of 1o Flow up to 50 cm behind the spinneret free of eddies and at approximately the same and constant speed and only then the threads are stretched in the usual way by changing the flow speeds in the funnel-shaped part of the spinning tube and solidified in the cylindrical end part of this tube. The coagulated threads can be drawn off from the cylindrical end part of the spinning channel at a speed which is greater than the speed of the precipitating liquid flowing upwards.

The improvement in thread properties that can be achieved by the invention should be based on a particularly favorable coordination of the spinning process with the coagulation properties based on polyvinyl alcohol. It has been found that in the spinning of polyvinyl alcohol solutions the conditions are significantly different from those in the case of spinning from z. B. viscose or other fiber formers. No chemical occurs during spinning Conversion a, the coagulation takes place comparatively slowly, the aggregation ability the coagulated portion is very strong, and the plasticity of the polyvinyl alcohol aggregates is limited. The thread guide according to the invention appears to these relationships To be satisfied in an optimal way: In the 10 to 5o cm long starting area without any Tensile or stretching load can cause a sufficiently strong thread cover to be free from interference without too much aggregation occurring. If now with passage slowly and steplessly exerted an increasing pull through the funnel-shaped part the thread is already in a state that can withstand this tensile load, on the other hand, the state of aggregation also allows a favorable orientation to. When passing through the cylindrical upper part of the funnel, coagulation, Aggregation and orientation have already progressed to such an extent that faster Roll withdrawal no longer causes damage, but strength-increasing Structural improvement. Such or similar conditions are not included in any of the above cited procedures and not given in any of these devices.

In the method of the invention is in the upward direction from bottom to spun up. For this purpose, the spinning channel can be arranged perpendicularly or at a slight incline In any case, the spinning process is supported by the buoyancy of the specifically lighter ones Spinning solution or the specifically lighter threads in the specifically heavier precipitating liquid significantly supported. The specific gravity of polyvinyl alcohol solutions (approx 1q. ° io polyvinyl alcohol) averages 1.03 to 1.04 at 25 ° C, that of the precipitating liquid (about 4009 Na2S04 per liter) about 1.31. The lift is therefore noticeably greater than z. B. in the spinning of viscose (i, lo to 1.12 or 1.29 to 1.35). About that in addition, the spinning from bottom to top closes any in a manner known per se Difficulties due to air entry into the spinning channel, tearing off of a hanging column of precipitating liquid etc. and enables many units to be set up on a small footprint.

In the method of the invention, the spinning solution and the precipitating liquid flow in the first stage, ie on the first 10 to 50 cm long section above the spinneret, both at approximately the same and constant speed v and V (cf. FIGS. -). In the second stage, ie in the conical part of the funnel, the speed of the precipitating liquid increases gradually from v to v1, whereby the speed of the threads half-coagulated at this point in time also increases from h to h1 and a tension is exerted on the threads. In the third stage, ie in the cylindrical upper part of the funnel, the final tension is generated by an external take-off at a somewhat higher speed h3 than the flow speed h2 of the precipitating liquid, with an essentially constant speed difference V3 - v2. In this way, the spinning runs very smoothly with the lowest possible frictional resistance. Both single threads and bundles of threads can be spun.

The ratio of the conveying speed during spinning to the immersion length is caused by factors such as average polymerization of the polyvinyl alcohol, composition and temperature of the precipitating liquid, thread denier, number of nozzle holes and their diameter, etc. For example, under the following conditions: Average degree of polymerization of polyvinyl alcohol. . . . . . . . . . i 60o concentration of the spinning solution. . . . . . . . . . . . . . . 13.80 / 0 Composition of the precipitating liquid ........ 39og per liter of aqueous solution of Na2S O4 Temperature of the precipitating liquid. ........... q.5 ° C nozzle holes ............ iooo diameter of each hole 0.08 mm thread denier. . . . . . . . . . . . 1.5 to 2.0 the ratio of the spinning speed to the immersion length is as follows: Spinning speed m / min. 70 I 50 I 30 Most suitable immersion length, mm ........ I 150o 1000 700 When wet spinning the polyvinyl alcohol threads, the immersion length must be 80 to 150 mm at 50 m / min. Spinning speed, since the coagulation takes place very slowly; with a long immersion length, the flow resistance on the semi-coagulated filaments is often excessively great and the filament bundle is broken. Furthermore, it is difficult to maintain a suitable take-off speed which corresponds to the coagulation state of the threads in order to spin out a thread with good molecular orientation and good physical properties.

It is therefore desirable to give the precipitating liquid a flow rate in the same direction as that of the moving threads to give to the frictional resistance of the spun threads compared to the precipitating liquid and to reduce the required Pulling the spun threads in the most suitable coagulation state through utilization to obtain the flow rate of the precipitating liquid. For example is made under the following conditions: concentration of the spinning solution. . . . . . . . . . . . . . . . . . 13% aqueous. Solution of polyvinyl alcohol composition of the Precipitating liquid ............... saturated solution of Na? S04 temperature of the precipitating liquid ..................... 4150 C conveyor speed during spinning ................. 50 m / min.

the flow rate of the precipitation liquid has an effect on the properties of the thread as follows: Flow rate the precipitation liquid m / min. 0 I 8 I 16 I 24 Denier ........... 21270 2.67 2.76 2.64 Dry strength, g / d ............. 2.40 3.02 2.89 z, 40 Dry elongation, 0/0 26.6 243 21.6 42.7 Wet strength, g / d 1.76 2.6.1 2.40 1.00 Wet elongation,% .. 31.5 22, o 23.8 49.7 As can be seen, the mechanical properties of the spun threads can be improved compared with a conventional precipitating liquid if the threads are given a suitable pull by the flow rate of the precipitating liquid. However, the tension caused by the precipitating liquid must be closely related to the coagulation state of the spun filaments. An example of the position in which tension is applied to the spun threads by increasing the flow rate is given as follows: Position in which the flowing speed of the precipitation liquid a train is exercised. Distance tion (d) from the nozzle to the lower end of the spinning tube, cm 10 1 20 1 30 1 50 Denier ........... 3.71 3.99 3.99 3.92 Dry strength, g / d ............ 2.34 2.61 2.94 2.62 Dry elongation, 0/0 33.1 28.1 22.8 20.4 Wet strength, g / d 1.64 1.71. 2.47 2, o6 Wet elongation,%. . . 31.7-27.8 25.0 22.9 As can be seen from the above, the position in which the tension is exerted on the spun yarn by the flow rate must be precisely set in accordance with other spinning conditions. If the unkeagulated draw begins as soon as the spinning solution exits the coagulating bath, it causes the threads to break.

The invention is shown in the drawing, for example, and although FIG. 1 shows an elevation of the spinning machine, FIG. 2 shows a longitudinal section.

In the drawing, i denotes a vertical jacket pipe in which Inside a pipe -: 2 is attached longitudinally displaceable, through which the precipitating liquid and the freshly spun threads flow upwards. 3 denotes an overflow container, the upper end of the inner tube 2 passes through the bottom. 4 designated a cylindrical chamber, at the bottom of which the spinneret 5 is arranged, which is connected to the filter 6. The cylindrical chamber 4 has window openings provided, which Aurch cover 7 are closed. 8 denotes a pump, for example a gear pump. An annular tube 9 (Fig. 2) is arranged around the spinneret, that a number of small nozzles for the precipitation liquid from the line 1o with the Regulating valve i i possesses. The overflow container 3 is provided with a drain pipe 12, which diverts the excess of the precipitation liquid to a funnel 13, from where the precipitating liquid is returned to the collecting container 14. 15 denotes take-off rollers for forwarding the spun threads.

As shown in Fig. 2, the lower end 16 of the tube 2 is after flared on the outside; the length of the ironic part must correspond to the working conditions the spinning solution and the precipitating liquid be chosen appropriately. So is the distance adjustable between the lower end of the tube 2 and the annular tube 9, that the tube 2, based on the outer tube i or on the cylindrical chamber, is movable. The adjustable arrangement is not necessary if the best Distance for a given spinning solution, a precipitating liquid, and a final one The length and slope of the conical part have been determined. The space between pipes i and 2 serve as a heating or cooling jacket or as a heat insulating chamber, however, the jacket tube i can be omitted if the whole arrangement is through suitable means is thermally controlled.

The mode of operation is as follows: The precipitating liquid flows out of the line 1o evenly without eddies and: slowly into the chamber 4 through the nozzles in the annular tube 9 and then flows at a certain speed after it has collected in the conical front part 16 into the pipe 2 upwards, whereupon the precipitating liquid flows over the * upper edge of the pipe through the drain pipe 12 and the funnel 13 into the collecting container 14 for repeated use. The spinning solution jets in the cylindrical chamber 4 move upwards due to the buoyancy of the surrounding precipitant liquid, the jets slowly beginning to coagulate to form threads. As the precipitating liquid flows into the conical front part, its speed gradually increases, and the liquid flows through the conical part with acceleration. This change in the speed of the precipitating liquid causes the semi-coagulated polyvinyl alcohol threads to stretch. The coagulation is almost complete when the filaments enter the cylindrical end part 2. Then the tension from the roller 15 caused by the difference in the speeds of the roller and the upwardly flowing spun threads exerts a certain stretching action on the uncoagulated part of the polyvinyl alcohol threads, whereby the coagulation is fully completed.

The take-off roller 15 promotes the spun strand and forwards it to the next trial. The speed of the roller is according to the conveyor speed, which determines the spinning speed, changeable.

If you mean the pull on the rope in a broad sense, this is it Ratio of the outflow speed of the spinning solution from the nozzle to the initial speed the role.

The higher the temperature of the precipitating liquid, the faster the coagulation takes place. But when the temperature of the precipitating liquid is increased, the threads become soft and difficult to stretch. Accordingly, in order to increase the speed, the temperature of the precipitating liquid cannot be increased beyond a certain limit. The permissible temperature of the precipitating liquid is 30 to 60 ° C. The space between pipes i and 2 can be used as a cooling room to prevent overheating, and also as a heat-insulating room or as a heating room to prevent undercooling at the beginning or to maintain it a desired temperature can be used.

Depending on the density and quality of the spinning solution, its separation can occur from the spinneret 5 can be difficult at times. In such a case you interrupt the supply of the precipitating liquid by closing the regulating valve i i in the stage in which the precipitating liquid is about 6omm above the spinneret, the window opens or the lid 7, and the spinning solution is discharged. The lid 7 closed and the regulating valve i i opened again to supply the precipitating liquid. The spinning solution, which floats on the precipitating liquid and with it upwards flows, exits at the end of the tube 2 and is then coagulated by the rollers 15, deducted. The windows make it easier to supervise and adjust the threads.

Claims (6)

PATENT CLAIMS: i. Process for the production of threads from polyvinyl alcohol using a wet draw spinning process, in which with a rectified flow of spinning solution or spun thread and precipitating liquid, which has a higher specific weight than the spinning solution, from bottom to top in a spinning tube with a funnel-shaped inlet is spun, characterized in that the spinning solution and the precipitating liquid flow eddy-free and at approximately the same and constant speed in a range from io to 50 cm behind the spinneret and then the threads are stretched and in the usual way by changing the flow speeds in the funnel-shaped part of the spinning tube solidified in the cylindrical end part of this tube. 2. Procedure according to claim i, characterized in that the coagulated threads from the cylindrical End part of the spinning channel can be drawn off at a speed which is greater than the speed of the precipitating liquid flowing upwards. 3. Apparatus for carrying out the method according to claim i or 2, characterized in that the subsection of the spinning channel above the spinneret (5) arranged in the center of the bottom is in the form of a 1o to 50 cm long cylindrical chamber (4) to which a Spinning funnel of known design with a conical front part (i6) and an upwardly leading tube (2) of constant diameter, over the upper end of which a take-off roller (i5) is arranged. 4. Apparatus according to claim 3, characterized in that the spinning funnel (conical front part 16 and tube 2) for regulating the length of the cylindrical chamber section (d) with respect to the spinneret (5) and the fixed chamber floor are arranged adjustable in height and one fixed to the upper edge of the chamber (4) connected jacket tube (i) closed off from the chamber and that the space between the funnel (2 and 1 6) and jacket tube (i) is designed to be heat-adjustable in a known manner for setting the desired temperature conditions. 5. Apparatus according to claim 3 or characterized in that the spinning funnel at the top opens into an overflow container (3) from which the Precipitation liquid returns to the outlet openings on the chamber floor in a known manner is fed. 6. Device according to claims 3 to 5, characterized in that the chamber (4) has window openings which can be closed by a cover (7). Considered publications: German Patent Nos. 172 264, 220 05 i, 509: 294, 538317, 644786, 716633, 802263; Swiss patent specification no. 160 i77; French Patent Nos. 585 587, 876 o32; "Melliand Textile Reports", 1935, p. 196, ills. I and 2.