Method and device for polymer precipitation

Abstract

The precipitant is provided in the precipitant receiver (9), the polymer solution in the receiver container (6). By means of the precipitant pump (7), the precipitant is supplied under pressure to the nozzle assembly (4), and the open jet (1) is generated. The polymer solution impinges in the form of a continuous, un-atomised polymer solution jet (2) on the flat side of the open jet (1). At the location (3) of the impingement of the polymer solution jet (2), the mean differential speed between the precipitant flow and the polymer solution is greater than or equal to one metre per second. Due to corresponding shear forces at the impingement location (3), a good distribution of the polymer solution on the surface of the open jet (1) and at the same time an immediate, thorough mixing of polymer solution and precipitant is achieved. In the open jet (1) the polymer contained in the supplied polymer solution is precipitated as solid polymer particles. In the collection container (11), the resultant mixture of precipitant, solvent and precipitated polymer is collected. In the centrifuge (13) or a filtering device, the polymer particles are separated from the liquid.

Description

[0001] METHOD AND DEVICE FOR POLYMER PRECIPITATION

[0002] The present invention relates to a method and an apparatus for polymer precipitation.

[0003] The basic physical prerequisite for precipitation in general is the mixing of two liquids or liquid mixtures, whereby a substance is dissolved or dispersed in one liquid (or mixture) but is not soluble or dispersible in the other liquid (or mixture), or at least soluble or dispersible to a significantly lesser extent. In the phase diagram of a three-component mixture, a corresponding miscibility gap occurs for the region of the three substances in which precipitation is possible. Precipitation can also be caused by a substance dissolved or dispersed in one of the liquids that causes a substance dissolved or dispersed in the other liquid to flocculate or agglomerate.

[0004] Polymer precipitation is a common process for separating polymers in a liquid medium. The primary goal is to convert polymers contained in a solvent or solvent mixture into the solid state, particularly in particulate form, and / or to separate polymers already in particulate form from a suspension. Polymer precipitation is also used as a purification process, for example, to separate previously added reagents (e.g., smaller molecules) or impurities, or to separate polymer fragments or smaller chains.

[0005] The precipitated polymer, ie converted into a solid of the desired consistency, is separated in a further step mechanically, for example by filtering and / or centrifuging, and / or thermally, ie by drying.

[0006] If the temperature, concentration, volume, and addition rate are appropriately selected during polymer precipitation, precipitation occurs upon addition of the liquid in which the polymer to be precipitated is dissolved to the fluid (antisolvent, referred to in this application as the precipitant) in which the polymer is insoluble or only soluble to a significantly lesser extent. The previously dissolved polymer precipitates in the form of solid particles. If the solvent of the polymer solution and the precipitant are not or not completely miscible, interaction at the interfaces can lead to the formation of the solid.

[0007] During the precipitation of polymers, impurities such as reactants, catalysts or short polymer chains, which are more soluble in the precipitant than in the solvent of the polymer solution, can also be removed.

[0008] The purity of the resulting solid can depend heavily on the selected process parameters. Differences in the concentration of the polymer solution can lead to nanoparticles, microparticles, or particles in the millimeter range. During polymer purification, undesirable particle size ranges can lead to serious disadvantages: Particles that are too small may remain in suspension and must be separated from it by further process steps, such as extraction. Furthermore, there is a risk of undesirable side reactions due to the large surface area. Furthermore, with separation by extraction, it is possible that components already separated during extraction may be re-extracted by precipitation. On the other hand, particles that are too large may still contain solution within and thus be contaminated with their solvent and the impurities it contains.

[0009] The person skilled in the art knows that some polymers are difficult or impossible to obtain in the desired purity by precipitation, either due to poor solubility, a tendency to swell or the tendency to rapidly agglomerate into solvent-contaminated lumps of low density during precipitation.

[0010] Other established processes involve the precipitation of polymers in cold solvents, such as ether or hexane at -80°C. However, this can result in the condensation of large amounts of water, and the process is difficult to scale due to its high energy consumption. Spray drying is another method for obtaining solid, undissolved polymer. This process differs from the others in that it does not involve purification by removing unwanted substances dissolved in the solvent; instead, it relies solely on the removal of the solvent, thus even concentrating impurities. Material loss, and especially energy consumption, is generally quite high, and spray drying processes are only suitable for solvents with a correspondingly low boiling point or high vapor pressure.

[0011] On a laboratory scale, the precipitation of some polymers in a beaker using a stirrer bar, in which a suitable precipitant is placed and the polymer solution is gradually added, works reliably.

[0012] For larger-scale polymer separation, large reactors are disclosed, for example, in WO 2014 / 207106 A1. Continuous flow processes are also known.

[0013] US 2012 / 245239 A1 and EP 0462317 A2 describe high-pressure nozzle chambers, and WO 2008 / 035028 A1 discloses swirl chambers with counter-rotating rotors and spray drying.

[0014] In the patent specification US 3,953,401 a process is described in which atomized polymer solution is applied to a gently moving precipitant surface, ie either to the stirrer vortex of the precipitant placed in a stirred tank, the surface of an open precipitant channel or the precipitant film flowing over a container wall.

[0015] Large-scale applications can essentially be divided into two categories, each with its own advantages and disadvantages: completely enclosed systems such as continuous flow, high-pressure nozzle chambers, or swirl chambers, and large open reactors. In enclosed systems, there is generally no gas-liquid phase boundary in the reaction chamber, so that floating or flotation is not possible, unlike in open systems with an existing gas-liquid phase boundary. In enclosed systems, the polymer solution is always added in the precipitation medium, which can limit the permissible concentration range of the polymer solution depending on the polymer. Some polymers, for example, have a strong tendency to form large particles or threads that exhibit strong adhesive properties and then easily adhere to the reactor edge or the stirrer.To prevent adhesion or other adverse effects, for example, KR 20080051399 A uses multiple precipitants simultaneously, initially producing fine particles and then larger particles in a subsequent step. However, this results in a solvent mixture that cannot be recycled without further processing.

[0016] In open systems, the addition can also take place outside the liquid phase. In this case, obstacles such as the floating of the precipitated product (flotation) or the formation of a covering layer on the surface of the precipitant must be overcome. The latter is particularly problematic, since the formation of a covering layer greatly slows or even completely prevents further precipitation of the polymer.

[0017] Against this technical background, it is the object of the present invention to provide an alternative technique for separating a polymer from a polymer solution, which at least partially avoids or reduces known disadvantages of conventional methods.

[0018] According to one aspect of the invention, this object is achieved by a method according to claim 1. According to a further aspect of the invention, this object is achieved by a device according to claim 12. Advantageous embodiments of the invention can be implemented according to one of the dependent claims.

[0019] The present invention therefore provides, in particular, a process for polymer precipitation in which a polymer solution is added to a precipitant stream, the precipitant stream being introduced as a free jet at the point where the polymer solution is added to the precipitant stream, preferably as a free jet emerging into a gaseous medium, in particular air. According to the usual definition, a free jet in the context of the present invention is understood to mean the flow of a fluid from an opening into the free environment, i.e., in particular, without a wall boundary of the jet transverse to its flow direction (main propagation direction).

[0020] According to the invention, the polymer is precipitated into a jet of precipitant. Due to the differential velocity between the precipitant and the polymer solution, the jet distributes the added polymer solution at the point of its addition. This effect is amplified by the flow of surrounding fluid, particularly air, that the free jet generates in its vicinity due to fluid mechanics. Small droplets of the solution are located directly in the precipitant and rapidly exchange solvent and soluble impurities through diffusion, since the diffusion paths between the polymer solution and the precipitant are short. Solvent is completely removed from the polymer.

[0021] In conventional precipitation processes, however, the droplet size depends on the concentration and solvent and is therefore difficult to change.

[0022] This creates a process that is simple and cost-effective to implement, allows for thorough mixing of the precipitant and polymer solution, is easily scalable, and can be adapted to a wide range of boundary conditions using easily adjustable parameters, such as the volumetric flow rates of the precipitant and polymer solution as well as the velocity of the free jet. According to the invention, a very pure product is achieved by keeping the diffusion paths between the polymer solution and the precipitant short, as explained above.

[0023] The process according to the invention is useful not only for the purification of polymers after polymerization or for modifying the solid product properties. Due to the high velocity differences between the polymer solution and the precipitant, even swelling polymers, which are not usually obtainable by precipitation, can be converted into a solid form.

[0024] Furthermore, the process according to the invention offers a new way for the continuous production of submicron particles up to nanoparticles.

[0025] Another possible use of the process according to the invention is the separation of polymer blends due to the resulting shear forces, in particular when polymers with fillers or polymer mixtures are to be separated from one another.

[0026] Another application area of ​​the process according to the invention is the expansion of polystyrene. Due to the high air entrainment in the vicinity of the free jet, it is possible for the produced polymer particles to have particularly large surface areas and / or even contain cavities within.

[0027] In a manner that will be surprising to those skilled in the art, the process according to the invention can even precipitate polymers whose solvent is insoluble in the precipitant. As far as the precipitant is concerned, the skilled person is surprisingly not even restricted to the use of liquids; rather, the process according to the invention can also be advantageously implemented with gaseous precipitants such as steam or carbon dioxide, i.e., the aggregate state of the precipitant stream in the free jet can be gaseous, or the precipitant jet can be introduced as an aerosol jet. However, in many of the precipitation tasks for which the process according to the invention can be advantageously used, the aggregate state of the precipitant stream in the free jet will be liquid.

[0028] Preferably, the polymer solution is added to the precipitant stream without atomization—that is, not sprayed onto the free jet, but poured, dripped, or sprayed in the form of one or more liquid jets. This reduces the equipment required compared to atomization. Technical problems such as clogging or unevenly spraying atomizing nozzles are thus avoided from the outset. The shear forces acting on the surface of the free jet ensure sufficient distribution of the polymer solution, making atomization unnecessary in most cases.

[0029] The free jet is particularly preferably generated as a flat jet, advantageously e.g. by means of a flat jet nozzle or flat nozzle or an arrangement of two or more nozzles arranged in a row laterally. A flat jet is defined as a jet whose extent in the region of the addition of the polymer solution in a first spatial direction orthogonal to the main propagation direction of the free jet is at least twice, preferably at least four times as wide as in a second spatial direction which is orthogonal to both the first and the main propagation direction of the free jet. The surface area of ​​the free jet onto which the polymer solution can impinge is thus larger than that of a round jet for the same precipitant flow. The main propagation direction of the free jet is the spatial direction orthogonal to the area through which the volume flow of the precipitant is highest.

[0030] According to a particularly advantageous embodiment, the average differential velocity Av between the precipitant stream and the polymer solution upon impact with the precipitant stream is greater than or equal to one meter per second, preferably greater than or equal to three meters per second.The mean differential velocity Av upon impact is calculated as the difference between a first quotient, which is formed from the volume flow QF of the precipitant flow in the main propagation direction of the precipitant flow (in the numerator) and the area AF through which the precipitant flow flows perpendicular to the main propagation direction of the precipitant flow at the median impact point (in the denominator), and a second quotient, which is formed from the volume flow Qp of the polymer solution not yet impacted by the precipitant flow in the main propagation direction of the precipitant flow (in the numerator) and the area Ap through which the polymer solution flows perpendicular to the main propagation direction of the precipitant flow at the median impact point (in the denominator). Therefore, Av = QF / AF - Qp / Ap.

[0031] The median impact point is defined as the plane spanned orthogonally to the main propagation direction of the precipitant stream, upstream and downstream of which half of the supplied polymer solution stream impacts the precipitant stream. "Upstream" and "downstream" mean upstream and downstream, respectively, with respect to the precipitant stream.

[0032] As a simplified design criterion in an advantageous embodiment, the difference between the average speed of the precipitant stream as it exits a nozzle and the average speed of the polymer solution as it exits a polymer solution outlet opening can be selected to be greater than or equal to one meter per second, preferably greater than or equal to three meters per second, wherein the average speed of the precipitant stream as it exits the nozzle is the quotient of the volume flow of the precipitant stream exiting the nozzle and the area through which the stream flows through the nozzle opening AD, and the average speed of the polymer solution as it exits the polymer solution outlet opening is the quotient of the volume flow of the polymer solution exiting the polymer solution outlet opening and the area through which the stream flows through the polymer solution outlet opening.

[0033] According to an advantageous embodiment, the Reynolds number Re at the exit of the precipitant stream from a nozzle to form the free jet is at least 2300, wherein the Reynolds number Re is formed as the product of the quotient of the volume flow QF of the precipitant stream exiting the nozzle (in the numerator) and the flow area of ​​the nozzle opening AD (in the denominator) and the quotient of the smallest diameter do of the nozzle at its outlet (in the numerator) and the dynamic viscosity VF of the precipitant (in the denominator) according to Re = Qr / Ao-do / vF. In this way, turbulent jet formation can be achieved, which is particularly beneficial for the mixing of precipitant and polymer solution.

[0034] According to another advantageous embodiment, the polymer solution is added in a gas-filled chamber at a gas pressure below 0.2 MPa. This allows for a technically inexpensive implementation of the process at ambient pressure.

[0035] According to an advantageous embodiment, the precipitant and solvent in the polymer solution are selected such that the ratio of the maximum solubility of the polymer in the precipitant of the precipitant stream to the concentration of the polymer in a solvent contained in the polymer solution is at least a factor of 10, preferably at least a factor of 25, particularly preferably at least a factor of 100 smaller than the ratio between the volume flow of the solvent upon addition of the polymer solution and the volume flow of the precipitant stream. According to a particularly preferred embodiment, the main propagation direction of the free jet at its outlet from a nozzle is inclined downwards at an angle to the horizontal of at least 20 and at most 70 degrees, preferably at least 35 and at most 55 degrees.

[0036] The present invention further provides a device for polymer precipitation, which has a precipitant feed for feeding precipitant, a nozzle arrangement for generating a free jet of fed precipitant, and an addition device for adding polymer solution to the free jet.

[0037] According to an advantageous embodiment, the nozzle arrangement comprises a flat jet nozzle or flat nozzle. A flat nozzle is understood in particular to be a nozzle whose outlet opening, transverse to the outlet opening, is at least twice as wide as its height, preferably at least four times as wide as its height. In other words, the greatest lateral extent of an area spanned by the edge of the outlet opening of the nozzle is in particular at least twice as large, preferably at least four times as large, as the lateral extent of this area orthogonal to its greatest lateral extent. A flat nozzle is also understood to be a nozzle which has a notch or groove at its outlet which is open laterally to the main outlet direction on two opposite sides, e.g. in the form of a milled out section, wherein the notch or grooveThe groove, in its projection in the main exit direction, is at least twice as wide as its height, preferably at least four times as wide as its height. In other words, the largest lateral dimension of the notch or groove, in its projection in the main exit direction, is in particular at least twice as large, preferably at least four times as large, as the lateral dimension of the projection orthogonal to its largest lateral dimension.

[0038] According to a particularly preferred embodiment, the nozzle arrangement defines an exit direction for the free jet, which is inclined downwards at an angle of at least 20 and at most 70 degrees, preferably at least 35 and at most 55 degrees. Preferably, the device further comprises a collecting device for collecting the mixture formed by adding the polymer solution and a separating device, for example a centrifuge and / or filter device, for separating precipitated polymer from the collected mixture.

[0039] The invention is explained in more detail below by way of example with reference to the accompanying schematic drawings. The drawings are not to scale; in particular, for reasons of clarity, the relationships of individual dimensions to one another may not correspond in some cases to the dimensional relationships in actual technical implementations. Preferred embodiments are described, to which, however, the invention is not limited.

[0040] In principle, each variant of the invention described or suggested within the scope of this application can be particularly advantageous, depending on the economic and technical conditions in the individual case. Unless otherwise stated, or to the extent technically feasible, individual features of the described embodiments are interchangeable or can be combined with one another or with features known per se from the prior art.

[0041] It shows

[0042] Fig. 1 is a process flow diagram for an embodiment of the present invention, Fig. 2 is a schematic perspective view of the geometric conditions at the point of addition of polymer solution to the precipitant jet according to an embodiment of the present invention,

[0043] Fig. 3a shows an example of a flat nozzle in plan view

[0044] Fig. 3b shows an example of a flat nozzle in a cross-sectional view in the section plane indicated in Fig. 3 A by the broken line AA'.

[0045] Corresponding elements are designated by the same reference numerals in the drawings. Fig. 1 shows a process flow diagram for an exemplary embodiment of the present invention. The precipitant, for example water, is provided in the precipitant reservoir 9, and the polymer solution, for example PLGA in acetone, is provided in the reservoir 6. By means of the precipitant pump 7, which can be a pump type customary in the art, for example a centrifugal pump, the precipitant is fed under pressure from the precipitant reservoir 9 to the nozzle arrangement 4, and the free jet 1 is generated. The medium surrounding the free jet, in which the precipitant is present in the liquid state, is air.

[0046] The free jet is a flat jet whose extent, as symbolized in Fig. 2, transverse to the main propagation direction of the free jet 1 and to the force of gravity g is greater by a factor of more than 2 than its extent in the direction of gravity g. In the region of the free jet 1 is the point 3 of addition of the polymer solution, which impinges on the flat side of the free jet 1 in the form of a continuous, unatomized polymer solution jet 2. The addition device 5 can advantageously be a nozzle from which the polymer solution jet 2 emerges under pressure, or simply a pipe opening from which the polymer solution jet 2 flows out following the force of gravity g.

[0047] The feed pump 8 feeds the polymer solution to the addition device 5. A pump type known per se from the prior art, for example, a peristaltic pump, can also be used as the feed pump 8.

[0048] At the point 3 where the polymer solution jet 2 hits the free jet 1, more precisely: at the median point of impact M, the mean differential velocity Av between the precipitant stream and the polymer solution is greater than or equal to one meter per second:

[0049] Av = QF / AF - Qp / Ap > 1 m-s 1

[0050] This includes

[0051] QF is the volume flow of the precipitant flow in the main propagation direction H,

[0052] AF is the area through which the precipitant flow flows perpendicular to the main propagation direction H of the free jet 1 at the median point of impact M, Qp is the volume flow of the polymer solution not yet impacted by the free jet 1 in the main propagation direction H of the free jet,

[0053] Ap the area Ap through which the polymer solution jet 2 flows perpendicular to the main propagation direction H of the free jet 1 at the median point of impact M

[0054] The median point of impact M is defined as a plane spanned orthogonally to the main propagation direction H of the free jet 1, in front of and behind which half of the polymer solution supplied per unit of time impacts the free jet 1, whereby the main propagation direction H of the free jet 1 is understood to be the spatial direction orthogonal to the area through which the volume flow of the precipitant is highest.

[0055] Due to the high differential velocity and corresponding shear forces at the impact point 3, the impinging polymer solution jet 2 is effectively torn apart, resulting in a good distribution of the polymer solution on the surface of the free jet 1 and, at the same time, immediate and effective mixing of the polymer solution with the precipitant. Mixing can be further improved by making the jet flow as turbulent as possible. This can be achieved particularly when the Reynolds number at the outlet of the flat nozzle 4 is at least 2300:

[0056] Re = QF / AD^D / VF^ 2300

[0057] This includes

[0058] QF is the volume flow of the precipitant emerging from the flat nozzle 4,

[0059] AD is the flow area of ​​the nozzle opening, do is the smallest inner diameter of the flat nozzle 4 at its outlet and VF is the dynamic viscosity VF of the precipitant.

[0060] The protective tray 10 serves to collect any precipitant, polymer or solvent lost by splashing or dripping in the area of ​​the polymer solution addition.

[0061] In the free jet 1, the polymer contained in the supplied polymer solution is precipitated in the form of solid polymer particles by mixing the precipitant and solvent. The resulting mixture of precipitant, solvent, and precipitated polymer is collected in the collecting tank 11. The suspension pump 12, which can again be a pump of a type known per se from the prior art, conveys the mixture to the centrifuge 13 or a filter device for solid-liquid separation. Here, the polymer particles are separated from the liquid. In the dryer 14, any residual liquid can be thermally removed from the polymer particles, if necessary.

[0062] Precipitant purified from solvent in the separation apparatus 15 can be recycled, ie returned and reused in the precipitant receiver 9.

[0063] While Figure 1 schematically shows a flat nozzle or slotted nozzle with a substantially rectangular outlet, the outlet opening can also be rounded on the narrow sides, for example, by being produced by squeezing an originally cylindrical or oval tube. Figures 3a and 3b show a flat jet nozzle with a notch 16 orthogonal to the cylindrical nozzle bore 17. In its projection perpendicular to the main outlet direction, the maximum lateral extent of the groove DD is 3.2 times the lateral extent do orthogonal to it.

[0064] EXAMPLE 1 :

[0065] To produce nanoparticles, 50 mg of polylactide-co-glycolide (PLGA) is dissolved in 2 ml of dimethyl sulfoxide (DMSO) and precipitated in water. The precipitant, water, is introduced as a free jet, which exits a flat jet nozzle into ambient air at a flow rate of approximately 400 ml / min at an angle of approximately 45° (downward tilt) to the horizontal. The PLGA solution is applied to the precipitant stream in the direction of gravity from a vertically mounted cannula with a syringe pump at a flow rate of approximately 99 ml / h. A small amount of precipitant (approximately 0.5 l) is added to the collecting container for the precipitant stream to prevent it from drying out.

[0066] The resulting particles have a harmonic intensity-averaged particle diameter (Z-average) of 89.5 nm and a polydispersity index of 0.15, determined by dynamic light scattering. The zeta potential is -27 mV. After the PLGA solution is used up, the nanoparticles contained in the collected precipitant are concentrated and purified by tangential flow filtration with the addition of 5 ml of 3% polyvinyl alcohol solution.

Claims

PATENT CLAIMS 1. A process for polymer precipitation in which a polymer solution (2) is added to a precipitating agent stream (1), characterized in that the precipitating agent stream (1) is presented as a free jet at the location (3) of the addition of the polymer solution (2) to the precipitating agent stream (1).

2. Method according to claim 1, wherein the precipitating agent stream (1) is presented as a free jet exiting into a gaseous medium.

3. Method according to one of the preceding claims, wherein the state of matter of the precipitating agent stream in the free jet is liquid.

4. Method according to one of the preceding claims, wherein the polymer solution (2) is presented unatomized at the location (3) of its addition to the precipitating agent stream (1).

5. Method according to one of the preceding claims, wherein the free jet is generated as a flat jet.

6. A method according to any one of the preceding claims, wherein the mean differential velocity Av between the precipitating agent stream (1) and the polymer solution (2) upon impact with the precipitating agent stream (1) is greater than or equal to one meter per second, preferably greater than or equal to three meters per second, wherein the mean differential velocity Av upon impact is calculated as the difference between the volumetric flow rate QF of the precipitating agent stream (1) in the main propagation direction (H) of the precipitating agent stream (1) and the area AF through which the precipitating agent stream (1) flows perpendicular to the main propagation direction (H) of the precipitating agent stream (1) at the median point of impact. (M) formed quotient and the quotient formed from the volume flow rate Qp of the polymer solution (2) not yet having hit the precipitating agent flow (1) in the main direction of propagation (H) of the precipitating agent flow and the area Ap through which the polymer solution flows perpendicular to the main direction of propagation (H) of the precipitating agent flow (1) at the median point of impact (M) according to Av = QF / AF - Qp / Ap, where the median point of impact (M) is defined as a plane spanned orthogonally to the main direction of propagation (H) of the precipitating agent flow (1), in front of and behind which half of the polymer solution (2) supplied per unit time hits the precipitating agent flow (1), and where the main direction of propagation (H) denotes the spatial direction orthogonal to the area through which the volume flow rate of the precipitating agent is highest.

7. A method according to any of the preceding claims, wherein the difference between the mean velocity of the precipitating agent stream (1) as it exits a nozzle (4) and the mean velocity of the polymer solution (2) as it exits a polymer solution outlet opening is greater than or equal to one meter per second, preferably greater than or equal to three meters per second, wherein the mean velocity of the precipitating agent stream (1) as it exits the nozzle (4) is the quotient of the volume flow rate QF of the precipitating agent stream (1) exiting the nozzle (4) and the flow area through the nozzle opening AD, and the mean velocity of the polymer solution (2) as it exits the polymer solution outlet opening is the quotient of the volume flow rate of the polymer solution (2) exiting the polymer solution outlet opening and the flow area through the polymer solution outlet opening.

8. A method according to any one of the preceding claims, wherein the Reynolds number Re at the exit of the precipitating agent stream (1) from a nozzle (4) to form the free jet is at least 2300, wherein the Reynolds number Re is formed as the product of the quotient of the volumetric flow rate QF of the precipitating agent exiting the nozzle (4). precipitant flow rate (1) and the flow area of ​​the nozzle opening AD and the quotient of the smallest diameter do of the nozzle (4) at its exit and the dynamic viscosity VF of the precipitant according to Re = Qr / Ao-do / vF.

9. Method according to one of the preceding claims, wherein the location (3) of the addition of the polymer solution is in a gas-filled space at a gas pressure below 0.2 MPa.

10. Method according to any of the preceding claims, wherein the ratio of the maximum solubility of the polymer in the precipitating agent of the precipitating agent stream to the concentration of the polymer in a solvent contained in the polymer solution (2) is at least 10 times smaller than the ratio between the volume flow rate of the solvent during the addition of the polymer solution (2) and the volume flow rate (1) of the precipitating agent stream.

11. Method according to one of the preceding claims, wherein the main propagation direction of the free jet (1) is inclined downwards at its exit from a nozzle (4) at an angle to the horizontal of at least 20 and at most 70 degrees, preferably at least 35 and at most 55 degrees.

12. Device for polymer precipitation comprising a precipitant feed for supplying precipitant, a nozzle arrangement for generating a free jet from supplied precipitant, and an addition device (5) for adding polymer solution to the free jet.

13. Device according to claim 12, wherein the nozzle arrangement comprises a flat jet nozzle (4).

14. Device according to claim 12 or claim 13, further comprising a collecting device for collecting the mixture formed by adding the polymer solution, and a separating device for separating precipitated polymer from the collected Mixture.

15. Device according to one of claims 12 to 14, wherein the nozzle arrangement defines an exit direction for the free jet which is inclined downwards at an angle to the horizontal of at least 20 and at most 70 degrees, preferably at least 35 and at most 55 degrees.

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