DE2261996A1 - METHOD AND DEVICE FOR THE PRODUCTION OF FIBERS FROM POLYMER SOLUTIONS - Google Patents

Description

* "'^ 42 Oberhäuser, December 18, 1972

• ■ '■ ^riii Anw - file: 75,531

, outside 2281996

. 30 p _ATENT REGISTRATION

Dipl.Ing * Vladimir-Stoyj Doz.Dipl.Ing «Artur Stoy, Dipl.Ing. Josef Kucera $ Diplilng * Jaroslav Prokop and Diploma Renata Ürbanovä ^ all in Prague, ÖSSR

Applicant: Cesköslovenska akadetnie ved «^ Praha 1

Method and apparatus for producing fibers from

Polymer solutions

Czechoslovak priority from December 22nd, 1971 claimed (PV 8911-71)

The invention relates to a method for processing polymer solutions into fibers, threads, strings, artificial horse hair, Tubes etc. and the associated device. The new Process that combines the advantages of wet and dry spinning is that the polymer solution through a spinneret is squeezed out and withdrawn into the coagulation bath via a space in which a lower than

3Ö982S / 1Ö89

atmospheric pressure is maintained.

In further description, all products, the thickness of which is much smaller than the length, are called "threads" or "Fibers" referred to.

So far, the polymer solutions have usually been processed into threads or the like either on the "wet" or "dry" route. Dry spinning consists in that the polymer solution through a spinneret into a heated spinning shaft is spun, where the solvents are evaporated so that at the bottom a dry or almost dry bundle of threads is deducted. As the last remnants of solvents, especially those that are less volatile are difficult to evaporate, in some cases subsequent washing is carried out. The biggest The advantage of dry spinning is that the take-off speed is 2 to 4 times and the concentration of the solution 1.5 to 2 times higher than wet spinning, which increases performance and reduces solvent consumption will. However, it is not possible in this way solutions of polymers in high-boiling or even non-volatile To process solvents, especially if the polymer is already at the temperatures to be used decomposed. Another disadvantage lies in the loss of solvent and in the fact that the spinning shaft must be quite long to achieve a suitable spinning speed. On the other hand, they are low-boiling Solvents are also not very beneficial because they are difficult to recover. In addition, is also

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difficult to get good quality fiber because one very volatile solvent (e.g. methylene chloride) escapes too quickly or the thread can be oriented sooner,

! with fine cavities in the thread. I.

During wet spinning, the polymer solution is through a

Spinneret squeezed into a coagulation bath, where the Solvent is washed out by a suitable liquid (e.g. water or a solution of electrolytes). at In this process, the thread is not thermally stressed, and the coagulation path is also shorter and polymer solutions can also be processed in non-volatile solvents (e.g. polyacrylonitrile in an aqueous zinc chloride solution, proteins or cellulose xanthogenates in alkaline solutions), · the solvents can, however, be recovered from dilute solutions; the concentration of spinning solutions is proportional low and the achievable spinning speeds are far lower, so that the performance of a wet spinning device with a comparable size is several times lower than with the dry spinning process.

These advantages and disadvantages can be seen from a comparison of conditions in the two methods:

The spinning solution leaves the spinneret in the form of a thin stream and is exposed to the action of the environment. The solvent diffuses into the gaseous or liquid medium. With a quick. . Diffusion into the surrounding liquid occurs on the - ■ surface of the coagulating spinning solution: uino thin 'chew,' - \ which slows down further diffusion and the thread then acts, ·

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like an osmotic cell. As a result, often arise microscopic voids in the structure of the fiber, which make the mechanical properties of the fiber very unfavorable influence. For this reason, the coagulation in the bath must be as slow as possible, so that the reduction the solvent concentration in the surface layer by diffusion, the interior can be balanced. The rate of coagulation must therefore be deliberately limited, such as by low temperature of the spinning bath or so that the fiber bundle through a series of spinning baths with gradually decreasing concentration the solvent respectively. is passed with increasing concentration of the precipitant. Other reasons of the limited Spinning speeds are: Strong throwing off of the bath by the rapidly rotating godets and stronger hydrodynamic resistance, whereby the still liquid respectively. semi-liquid streams of spinning solution are stressed too much until it is torn. A further disadvantage resides in the viscoelastic nature of the spinning solution, which particularly at high withdrawal speeds. For all of these reasons, the thread gets the most in the Interrupted near the spinneret, where the spinning solution has not yet sufficiently coagulated. This liquid zone can however, it is not removed or shortened by increasing the rate of coagulation, and with consideration on the above-mentioned osmotic phenomena, which lead to the emergence of heterogeneous fibers with poor mechanical Properties lead.

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In contrast, these disadvantages do not occur in dry spinning because the fiber is in the gaseous medium offers only negligible resistance; the oenotic phenomena do not occur and it is therefore, by evaporation of the solvent, a superficial skin with a high polymer concentration is possible right from the start to form, which gives the still liquid thread a relative strength. This skin that always is still plasticized with the solvent, is relatively smäss ig easily deformed and by the tension partially stretched on take-off. This will make the thread partially oriented and gains better mechanical properties. This causes so-called nozzle stretching the well-known "skin effect", whereby the thread is oriented higher on the surface than on the inside. to This unevenness has further disadvantages, in particular the stress on the polymer high temperature, large dimensions of the spinning shaft and the volatility and the possibility of recovery limited choice of solvents.

The method according to the invention combines the advantages of the two known methods, the disadvantages being largely reduced respectively. be eliminated. The invention lies in the fact that the spinning solution is squeezed out of the spinneret into a spinning shaft that is gas-tight at the top a lid containing the spinneret is closed and immersed with its open lower end in the spinning bath being in the spaces between the spinneret and the surface the spinning bath a lower gas pressure than in the

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surrounding atmosphere is maintained, so that the level the spinning liquid in the spinning shaft is higher than in the rest of the spinning bath.

The execution of the method and the characteristics of the The device used for this purpose is illustrated in the following examples with reference to the accompanying schematic drawings explained in more detail.

Example 1.

Spinning solution 1 (Fig. 1), e.g. a solution of polyacrylonitrile in conc. Nitric acid is pressed out through the spinneret 2 in the form of a thread 3. The room 6 between the spinning nozzle 2 and the spinning bath (coagulation bath) 5 is delimited by the spinning shaft 4. In this Space 6 is maintained with the help of the suction device 7, a negative pressure, whereby the level of the spinning bath on the desired constant height is raised. The thread 3 is passed in the space 6 through a stream of a gas: The Gas, e.g. carbon dioxide, is advantageously at an elevated temperature and is preferably in countercurrent to the thread guided so that it through the mouth 8 above the bath surface is fed and discharged through the pipe 9 under the spinneret. This turns the squeezed out stream the spinning solution evaporates part of the solvent under reduced pressure and at elevated temperature, so that the thread troin 3 enters the coagulation bath with a lower solvent content and increased viscosity. Through this becomes the amount of to be recovered from the spinning bath

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Solvent reduced, and also allows the Increased viscosity of the thread flow when entering the bath, use a higher take-off speed. 'That through Evaporation of some of the solvent from the surface The skin formed by the stream of filaments has a beneficial effect in this case, since it slows down the otherwise too rapid coagulation. The result is the same as if you focused one more Spinning solution with a higher viscosity would have used · At the same time, the temperature of the spinning bath be held higher without the risk of the thread becoming inhomogeneous and brittle due to excessively rapid coagulation. The desired increase in viscosity is therefore only achieved behind the spinneret, so that the hydrodynamic Resistance in the nozzle is not increased. Finally, the spinning solution is pressed out of the nozzle by the Negative pressure relieved. Of course, this arrangement also has the advantage of having wider nozzle openings with subsequent nozzle openings Tapering of the thread flow in the gas space 6 in the foreground. The thread bundle is over the godet 10 deducted.

The nozzle stretching under the spinneret can be used better here than with the known method, where an air-filled space is simply maintained between the spinneret and the spin bath because the rapid evaporation of part of the solvent gives the filament stream a certain mechanical strength. As a result, the filament stream is not so easily broken due to viscoelastic phenomena. Opposite to the usual dry spinning possesses the new process

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the advantage that the evaporation takes place at reduced pressure and consequently at a lower temperature, so that the sensitive spinning solution is not thermally stressed. In the present example with polyacrylonitrile In concentrated nitric acid, the usual dry spinning would be almost impossible, since this solution contains higher temperatures with discoloration. now.

Incidentally, the rate of evaporation can be better with the present method than with an open one Spinning shaft can be regulated, namely not only by the supply of heat, flow of the gaseous medium and gas pressure in room 6, but also by the vapor tension of the solvent. This also enables solutions spinning of polymers in very volatile solvents such as methylene chloride, which otherwise lead to dry spinning are less suitable. The evaporated solvent is recovered in a closed circuit, whereby the losses are reduced.

After all, the spinning shaft is significantly shorter than in dry spinning: However, it is very much important first vertical part of the thread path in the coagulation bath is significantly extended before the coagulating thread flow is bent on the first trigger roller.

The invention therefore uses dry spinning in the first phase of thread formation and wet spinning in the second out, that is, both methods in the areas where their advantages can be best exploited.

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2261991

The new process is particularly well suited else to known producing Bikomponentfäden _s that are curled permanently after stretching, stabilizing and drying. As is known, two different types of spinning solutions are introduced into each spinning opening. The relatively wide spinning orifices facilitate the construction and manufacture of such double nozzles, and the two spinning solutions have enough time to combine continuously before entering the coagulation bath, so that the bicomponent thread later has no tendency to elongate splitting.

^{The enthalpy 5} required to evaporate part of the solvent can be provided by heating the gas flowing into the room, by heating the wall of the spinning shaft or by heating the spinning nozzle itself. It is best to combine all of these possibilities. Heating the spinneret has the advantage that the viscosity of the spinning solution drops precisely in the spinning orifice, where it is particularly desirable with regard to the hydrodynamic resistance and the required spinning pressure. This also the use of more concentrated polymer solutions BEZW. of higher molecular weight polymers.

The amount of heat supplied and the temperature * must not be so high that the spinning solution decomposes or would cause the solvent to boil. The resulting bubbles could cause the stream of filaments under the nozzle to tear. For this

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Basically, what is most necessary is to supply the required amount of heat largely through thermal radiation from the heated shaft wall and through heating of the gas stream ^1.

After entering the spinning bath, most of the solvent ^{that is} still present is washed out, the stream of filaments turns into a gel, and the resulting, essentially still unstretched filament is passed over the take-off roller 10 for washing, stretching, stabilizing and drying The sequence of these operations can be partially changed. For example, the thread can first be drawn and then washed, or stabilization can only follow after drying, if necessary on the bobbin or in the form of staple fibers the colors or other post-treatment operations are already classified *

As mentioned above, the coagulation speed is allowed do not exceed the value at which the inhomogeneous thread begins to form. For this purpose were various measures taken so far, such as the Leading the bundle of threads through a series of baths with gradually BEZW. gradually decreasing concentration the polymer solvent, respectively. with increasing concentration of the precipitant. An advantage of the present The process is based on the fact that no special measures have to be taken, as it is a mild one Coagulation required condition automatically sets itself. In parts of the spinning bath in the spinning shaft where the threadstrcin comes into contact with the precipitant for the first time comes is namely the solvent concentrate

8 26/108 9 "

the highest since most of the solvent is present is washed out here and this part of the spinning bath cannot be diluted directly with the rest of the spinning bath will. The concentrations are balanced by diffusion and convection over the limited cross-section of the lower end of the spinning shaft, so that in the course of the spinning an equilibrium of Adjusts concentration in both parts of the spinning bath. In addition, too rapid coagulation is also caused by prevents the skin formed in the gas space of the spinning shaft on the surface of the yarn stream. All of these circumstances enable the spinning speed to be exceptional hold up high.

The geometric arrangement of the spinning bath in the L-shape is spatially favorable, as is the volume of the The spinning bath is relatively small.

The main advantages of the method can be as follows can be summarized:

^e ?

1. Small size / volume of the device;

2. High withdrawal speed;

3 Reduced amount of solvent in the spinning bath, thereby facilitating recovery;

4 «Lower temperature at which the solvent is vaporized in the first part of the device; . . .

5 Uniform coagulation of the polymer, approx the first phase is the difference in solvent concentrations in the filament stream and

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BATH ORIGINAL

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Kpagulat'ijOfiöCiag is low;

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?. Big Bgge igt niqht fnif. · Dgai S ^ injigad iß Berufjr-upg and therefore it is better protected vpr the Kprrpsipn:

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If so, Eplvmec in a solution aitelg-ePitsGü is. ¥ gpdampit in tree 6 in first Beihg das

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The maintenance of the Badniweau in de? Spinning

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i can advantageously RiC ^ §gp Ai? fe: ² 'YS-P ^ iipfeiJS &l; be: Pie bifataigrung des B ^ uraes 6 between the spinning bath and the spinneret, with the help of ^the p§ i | o | ires? öurci

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11, the valve closes 12. If the jRcuGk im falls

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Ravine 6 spdass, dag ffi ^ gai; qe, S spin_f] bad _; gs ggg ^ f ^ Hg the valve 13 opens automatically and the bath rises again to the mouth 11. At the back, the valve 13 is on

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Separator of the liquid '1§ ejinfrpschai tut, cjjüocn iiQden

ORiQtNAL INSPECTEO

through the three-way valve 16 with the containers 17a or 17b connected is. When "one of the containers is full, the tap 16 is switched over to the other container. In full Container is the vacuum, respectively by means of the 'valve 18a. 18b canceled and the liquid is BEZW through the valve 19a. 19b released back into the spinning bath. It is of course it is possible to use any other means for maintaining the level mentioned above however, is particularly simple and reliable.

Any gas such as air, nitrogen, carbon dioxide, argon or the like can be used as the gas medium flowing under the spinneret, depending on the type and sensitivity of the polymer. The purpose of the flow of the gas in the space 6 is to remove the solvent vapors as quickly as possible so that the equilibrium concentration of the solvent between the spinning solution and the gas is not reached. Only in cases where the evaporation of a part of the solvent used is expressly undesirable, such as when spinning the polyacrylonitrile solutions in an aqueous zinc chloride or calcium thiocyanate solution, where only the water could be evaporated, is the flow of the gas medium intentionally prevented or the gas supplied with the Steam the solvent component (e.g. water) so far '·, saturated that the excess evaporation from the-. Spinning solution is suppressed. Even in such cases. however, the method according to the invention is advantageous, d, a, ..

309 8 2% / Vo8ΊΤ ° ^{Λ; ΐ}

at least other volatile components such as the monomeric acrylonitrile can be removed from the spinning solution. The other advantages, especially the self- ■ active adjustment of the concentration gradient in the bath, and the space-saving arrangement is of course retained,

Example 3

Fig. 3 illustrates an example of the cycle of gas through the spinning device according to Fig. 1. The gas with the solvent vapors is sucked off through the mouth 9 by means of the circulation pump 20 and cooled in the cooler 21, some of the vapors condensing. The condensate is separated in the separator 22, which is advantageously also cooled, and the remaining gas is passed back into the space 6 via the heater 23. The condensed portion is alternately drained into the storage containers 17a, 17b via the three-way valve 16. After filling, the containers are alternately separated from the separator 22 by means of the valve 16; 18b and the recovered solvent is passed through outlet 19a or 19b for further processing. This circuit can be designed in different ways, the only condition is that the negative pressure in the upper part of the spinning shaft must be kept constant. It is not necessary to remove the solvent from the circulating gas only by condensation. The condensation can either entirely through sorption on activated carbon or the like

3 0 9 8 26/1 0 8

- 3-1 =

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replaces or, only in addition, the choice of U:

ar * t GQr Lpsungsmit ^ g ^. hgngt j ^ pn den Siggnscfegite, !! dps; yellow.n and wgn. den, 'QkonpjaigGhgn ga ||]: pr, e.n ab. .

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dec 'Spiniidtige. Qgzw. im B.eck ^ lj dUEsh ^ elishen dig Spinning nozzle into which, Spinnscnaeht opens

Dag iEfindungsggmäsgp fe.cfahp.gn gigngt si ph f-μΐί sAll lyasen dip, usual from readings Me, csppnnen vißi? .Den, b ^ sondgcs ßuc splche. the solvents are volatile at all times Sq z. ^. koenin Lp "@ unge.n v.qxi EQljigkEy.lnitEi in konzgntEiertgii Salpeter ^ äuc ^, im Birnethylfocmamid, Birnethylsul ^ ox ^ d, cyclic ^ .thylgnk ^ jjtip.iiat sQjwig in dinwassEiertgii Salpeter v .sche.n series such as Einkchlocid, Kalzium-rode.x; iiati * iumi? hpdanid pdec won mixtures of these salts with other easily soluble salts ? e wpn ¥ in ^ lchlQßid in ^ yklQh ^ x subsequently chloEiectgs Bpl ^ in ^ lchlpEid in AcetP.nrAlkpholrGemischen,. Zel'luloaetciazetat im Methv seazetobutttEat im Acetpn, ZgllulQsediaz ^ tai

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dene manner forms wesdgn without j | .gn'Eghispia der to exceed. Bie. Spinning shaft e.g. can also kcgisfprmiggn also in angular pder glip.tigGh.gn

1 § 8 SI § I \ 81.1 ORIGINAL

Own cross-section. It can be provided with one or more heated zones ¹ as well as with cooled zones. For example, it is possible to give the gas space a different permeability than the spinning bath. The temperature of the spinning bath in the lower part of the spinning shaft can be different from the temperature of the rest of the bath, and so on. It can be advantageous to cool the bath in the lower parts of the spinning shaft in order to reduce the evaporation of the solvent therefrom and thereby promote the removal of the same solvent from the filament stream. At the same time, the conditions for visible coagulation are improved and the equalization of the concentrations between the two parts of the spinning bath is promoted by convection. The higher temperature of the spinning bath behind the spinning shaft is advantageous for more rapid washing out of the remaining solvent from the spinning thread, since the coagulation speed can be increased in this zone without endangering the quality of the thread.

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BAOORIOtNAL

Claims (1)

Claims Process for the production of νοη fibers and threads from polymer solutions ,, characterized in that, the. .. polymer solution through a spinneret into a spinning shaft. nerausgapressi, whose upper toilet, sealed at the top, is filled with a Qa ^ at a pressure lower than ethospherical, and-whose lower part, which extends below the surface of the spinning bath, is filled with the spinning bath, so that the fiber bundle is in the first Phase. dry and wet in the second phase. is spun. ,. . ^v 2. The method according to claim 1, characterized in that the diluted, preferably preheated gas through the The upper part of the spinning shaft is allowed to flow, the solvent being recovered from the discharged gas will. · ' 3. The method according to claim 1 or 2, characterized in that that the level of the spinning bath in the shaft is kept at a constant height so that the 'mouth of the pipe for evacuating the gas space at the desired level, preferably arranged adjustable is, wherein between this orifice and the source of the negative pressure, a valve is switched on, which is in the Direction of the gas flow only lets the gas through, not but the liquid. 3 0 98 2 6 / ΊΌ W Btö (MQMfiL I to 3, characterized in that that the gas-filled space below the spinning nozzle one more temperature than the spinning bath in car Spinning chute. 5. Verfahr, according to claim 1 to 4, 'characterized «, that the spinning bath in the spinning shaft is kept at a different temperature than the rest of the spinning bath. 6. Device for performing the method according to Claim 1 to 5, consisting of a vertical spinning shaft, the upper end of which through a spinneret holding gas-tight lid is closed and its lower end below the surface of the spinning bath is located, with means for reducing the gas pressure in the upper part of the spinning shaft, with inlets and outlets for gas and with a device for maintaining the level of the spinning bath in the spinning shaft on one arbitrary but constant height. 7. The device according to claim 6, characterized in that the device for maintaining constant levels consists of a tube whose mouth is set to the desired level of the spinning bath and that with the The source of the negative pressure is connected via a one-way valve, the float of which is heavier than the diverted gas, however, it is lighter than the spinning bath in the spinning shaft. 8. Apparatus according to claim 6 - 7 _t characterized in that the spinning shaft into two or more zones is shared with different temperature · 30M2I / 10 ·! BATH ORIGINAL Blank page