Static mixing elements with a separator and deflecting surfaces and static mixers

Abstract

The invention relates to static mixing elements with a separator (2), preferably in a tube (1) with two blade-like deflecting surfaces (4, 5) adjoining same which, in the axial projection, completely cover a sector of the cross-section and delimit two axial sections (I, II) and two windows (8, 9) for the axial passage of the flow. The deflecting surfaces have raised edges (6,7). The fact that the deflection surfaces are simultaneously inclined towards the separator and raised from the cross-sectional plane and the axial projection of the deflecting surfaces covers a sector of over 56% of the cross-section makes it possible to significantly improve the mixing quality compared to known structures, in particular with a circular cross-section.

Description

[0001] Static mixing elements with a separating web and deflection surfaces and static mixers

[0002] Technical area

[0003] The invention relates to static mixing elements and static mixers in a flow channel, preferably in a circular tube with at least one separating web per mixing element, deflection surfaces, and windows for axial flow. Such static mixers are preferably used in laminar flow regimes with highly viscous media. Typical applications include disposable mixers for curing resins, adhesives, or static mixers for plastic melts in plastics processing with injection molding machines or by extrusion.

[0004] State of the art

[0005] To date, many static mixers are known and in use in which the flow is divided into partial streams by dividers or channels and deflected by deflection surfaces. A static mixer is formed by several such mixing elements arranged linearly one behind the other in a pipe or flow channel in the direction of flow. In many known static mixers, the flow is divided into two partial streams, twisted or rearranged, compressed and expanded again. The mixing process is similar to the process in a calender (calender model). According to an idealized concept, in laminar flow, layers are formed in each mixing element and the number of layers doubles from mixing element to mixing element. In practice, the actually achieved number of layers or their thickness after a large number of mixing elements often deviates from this ideal by orders of magnitude.The oldest static mixers using this mixing principle were the Multiflux (US 3051453) and the Wendeimischer (US 3286992). The Wendeimischer is still widely used today for so-called disposable mixers for reactive resins and adhesives, because it allows entire mixer rods made up of many such mixing elements in one piece and to be produced cost-effectively in large quantities using simple, two-part plastic injection molds. The mixing elements of the Wendeimischer take up only a small proportion of the mixer volume and therefore have a low pressure drop. The length of a mixing element is typically 1.5 pipe diameters D, and the required mixer length for homogenization is typically 30D (D = pipe diameter). In contrast, the mixing elements of the Multiflux mixer take up up to 30% of the mixer volume and therefore have a much greater pressure drop.However, the mixer length required for homogenization is much shorter than with the rotary mixer, typically 10D. Both mixers divide the flow into two channels or partial streams and then recombine them to divide them again. The rotary mixer has a circular cross-section of the flow channel, while the Multiflux mixer, in its original form, was preferably used with a square cross-section of the flow channel because this achieved a better mixing result. However, versions of this mixer with a circular cross-section of the flow channel are also known, which can also be manufactured with a two-part plastic mold.

[0006] Today, static mixers according to EP 0749776A1 or EP 0815929A1, for example, are available for use as disposable mixers. They use the same mixing principle as the Multiflux mixer, but with a simpler and improved shape. Here, too, entire mixer rods can be manufactured using simple, two-part plastic injection-molded tools. The length of a mixing element according to these inventions is only approximately 0.5 D, and the mixing elements occupy a volume of less than 10% of the volume allocated to the mixer. This results in low pressure loss and a very short homogenization length of approximately 8 D. A large number of similar, derived, or related mixer structures are known today, for example, according to US Pat. No. 3,239,197.

[0007] EP 1 149 626A1, WQ2017 / 027275A2, EP 1 125 626A1, EP 2 599 540, or EP 3 338 882A1.

[0008] The relative standard deviation s / x from a concentration measurement across the cross-section is often used as a measure of mixing quality for a mixture in a static mixer. Where s is the measured standard deviation and x is the measured mean concentration in a cross-section. This relative standard deviation is also referred to as the coefficient of variation (COV). The conductivity method [Chem. -Ing.- Tech. 52(1980) 4, pp. 285-291] is often used to measure concentration. Two viscous partial streams with different electrical conductivities are forced through the static mixer and mixed. To measure conductivity or concentration, a measuring probe is drawn across the outlet cross-section. A newer, experimental measurement method is the LIF (Laser Induced Fluorescence) method [The Canadian Journal of Chemical Engineering, Volume 76, June 1998].A fluorescent tracer induced by a laser beam is used to measure the concentration. With this measurement method, the flow is not influenced by a measuring probe. Numerical flow simulation (CFD) eliminates the need for experiments entirely. The COV depends on the measurement method and the sample size. In numerical flow simulation, the result can also be strongly influenced by the model used and numerical factors. A mixture with a COV of 1% is considered homogeneous. The corresponding mixer length is called the homogenization length.

[0009] The formation of layers in laminar flow can also be demonstrated very easily and precisely by forcing two highly viscous resin components, each mixed with a hardener and curing quickly and with different pigment colors, through a mixer. The cured mixer rod is then cut open after each mixing element. This permanently freezes the mixing process or the mixing state in a cross-section, free from influences by diffusion or other factors, and can be easily analyzed. The only disadvantage is that the mixer under investigation is lost or even "frozen." Today, mixer prototypes can be easily and inexpensively produced from plastic using 3D printing. This has made this old method of investigation very interesting again. A simple evaluation is the counting of the layers formed, or even simpler and more reliable, the measurement of the maximum layer thickness I in a cross-section.If one compares the measurements of the maximum layer thickness I, for example, with the conductivity method, it can be seen that the homogenization length (COV = 1%) is reached at a layer thickness of approx. 25 pm. Since this layer thickness is hardly measurable anymore, it is determined by exponential extrapolation. The mixing effect of the known static mixers in the laminar range is sometimes very good and, although not ideal, follows an exponential layer formation law. Many static mixers with a circular pipe cross-section have one problem in common that has not yet been solved. The layer thicknesses across the cross-section and beneath the layers can vary greatly, or the layers may not extend across the entire cross-section. In mixers similar to the Multiflux mixer or like EP 0749776A1 with a circular pipe cross-section, a significant deviation in the thickness of the layers in the edge regions compared to the layers in the inner region can be seen.This effect is less pronounced with a square cross-section of the flow channel. Therefore, disposable mixers with these or similar mixer geometries, such as those according to EP 0749776, are usually offered with square housings, even though a circular tube would be preferred. For many applications, a square housing is not an option, and other static mixers are preferred. One example of this is static-dynamic mixing systems in which a mixer helix is ​​additionally driven to rotate.

[0010] Fig. 1 shows the distribution of the layers and layer thicknesses which was determined from the cross-sectional images during tests with a static mixer according to EP 0749776 with a square cross-section. The images were traced from the photographic evaluation of the cross-sectional images. Image a) shows the condition at the inlet (mixture 1:1, black / white), image b) the condition at the outlet of the first element and image c) the condition at the outlet of the second element. It can be clearly seen that the number of layers formed corresponds very well to the expectations according to the calender model but also that the layer thicknesses are not uniform even with the square flow cross-section and the edge layers are significantly larger than expected. This deviation is maintained across all other mixing elements, although the thickness of the layers nevertheless decreases continuously and exponentially with increasing mixer length.The mixing quality, in the form of a decreasing maximum layer thickness I, is significantly lower than expected for an ideal mixing law. Fig. 7, trend line 2 shows the course of the measured maximum relative layer thickness l / l0 for this mixer as a function of the relative mixer length L / D. Trend line 3 shows the course of the relative layer thickness over the relative mixer length according to the same measurements for a spiral mixer with a circular flow cross-section. After just a few pipe diameters, the layer thickness is already an order of magnitude higher than in line 2. In the European patent application.

[0011] EP 3907461 A1 describes a possible solution for further improving layer formation in the mixer according to EP 0749776. This involves enlarging the deflection surfaces beyond the separating web on the inlet side in a suitable shape and direction, thereby reducing the window areas. This allows a somewhat more uniform distribution of layer thicknesses to be achieved. This solution was primarily developed for applications as a mixer heat exchanger, also to simultaneously improve heat transfer to the tubes. However, it has been shown that when this solution is used for one-way mixers or for other static mixing tasks without heat transfer, the pressure drop is increased more than desired. All of the static mixers mentioned above, with the exception of the spiral mixers, also exhibit unfavorable residence time behavior because zones with greatly differing axial flow velocities or even stagnant zones occur.Such zones cure prematurely when processing resins with a short pot life, resulting in the need for more frequent mixer replacement. Thus, no satisfactory solution has yet been found for the problem of uneven layer thickness distribution or thicker layers at the edge, especially in disposable mixers with a circular flow channel.

[0012] Description of the invention

[0013] The object of the present invention is to find a static or disposable mixer with low pressure loss that achieves a significantly more uniform distribution of layer thicknesses across the cross-section and thus a shorter homogenization length than known static (disposable) mixers, particularly with a circular tube as the mixer housing, with low pressure loss. This mixer can be easily manufactured with a two-part open / close (O / C) tool and as a complete mixer rod as a monolithic part. In addition, an improvement in the residence time distribution and a reduction in stagnant zones should be achieved.

[0014] The problem is solved by the features of patent claim 1. The further independent and dependent claims describe particularly advantageous embodiments or applications of the invention.

[0015] The term "blade-like deflection surfaces" includes both completely flat and curved deflection surfaces, for example concave and / or convex curved deflection surfaces.

[0016] Short description of the drawings

[0017] The invention is explained below with reference to drawings.

[0018] Fig. 1 Representation of the layer thicknesses after measurement with curing resins in a mixer according to EP 0749776 with a square cross-section. The image was traced from the photographic analysis. a) Mixer inlet, b) Outlet from mixing element 1, c) Outlet from mixing element 2

[0019] Fig. 2 Perspective view of a pipe 1 with a static mixing element according to the invention with a length H and two blade-like deflection surfaces 4, 5 with edges 6, 7 on the inlet side (section I) and a separating web 2 with a width D and a height h in an axial plane through the pipe axis 3 on the outlet side (section II). Cross-sectional planes E1 (mixing element inlet), E2 (intermediate plane at the transition from deflection surfaces to the separating web), and E3 (mixing element outlet). The arrows indicate the crossflow directions in the individual sections. The preferred axial flow direction is indicated by the large arrow in the pipe axis.

[0020] Fig. 3 Axial section (plane EB, Fig. 4) through the pipe axis and perpendicular to the separating web 2 of a mixing element according to the invention with inclined deflection surfaces and a flow area F that is larger than the value Dxh without inclination. The cross-sectional areas are not hatched for clarity. The directional arrows indicate the cross-flow directions in sections I and II, respectively.

[0021] Fig. 4 View from the inlet side of a mixing element type A according to the invention with a separating web 2 in an axial plane EA and deflecting surfaces 4 and 5 and windows 8 and 9 in a pipe 1. In this example, the edges 6, 7 on the inlet side form a common, straight web through the pipe axis which is at an angle ß to the separating web 2.

[0022] Fig. 5 View from the inlet side of a mixing element type B according to the invention, which is constructed as a mirror image of the element type A, with deflection surfaces 4' and 5' offset from the separating web 2 and 2', respectively, and windows 8' and 9'. The separating webs 2, 2' of successive mixing elements type A and type B are preferably parallel to each other in a common axial plane EA in the center of the pipe. The inlet edges of the rims are preferably chamfered.

[0023] Fig. 6 Representation of the distribution and thickness of the layers formed after tests with curing resins at the outlet of the second mixing element for a mixer according to the invention in a circular tube. This image was traced from the photographic evaluation. Fig. 7 Course of the measured maximum layer thickness I compared to the initial thickness Io as a function of the relative mixer length L / D for the mixer according to the invention (1) with a circular cross-section, a mixer according to EP 0749776 with a square cross-section (2), and a helical mixer (3) as exponential trend lines.

[0024] Fig. 8 Longitudinal section transverse to the separating web (plane EB) through a complete mixer rod made of mixing elements type A and type B with lateral connecting elements 10,11 in a flow channel 1.

[0025] Fig. 9 View from the inlet side of the mixer rod according to Fig. 8 with lateral connecting elements 10, 11 that adapt to the pipe cross-section and can be manufactured as a disposable mixer with a simple, two-part plastic injection-molded tool. The opening direction of the tool, which is divided in the plane EB, is indicated by the arrows C / O.

[0026] Fig. 10 Longitudinal section (plane EB) through a mixing element according to the invention with a ring 12 for reinforcement, which can be manufactured as a particularly strong, monolithic mixing element, e.g., as a precision casting or by 3D printing, and is inserted into a tube with a diameter of D. Individual mixing elements with a ring can also be manufactured from plastic or wax using a simple, two-part tool.

[0027] Fig. 11 View from the inlet side of a mixing element according to the invention with ring 12 according to Fig. 10

[0028] Fig. 12 Longitudinal section through a mixing element according to the invention with convexly curved deflection surfaces

[0029] Fig. 13 Longitudinal section through a mixing element according to the invention with concavely curved deflection surfaces Fig. 14 View from the inlet side of a mixing element according to the invention in which the edges of the deflection surfaces form a curved line

[0030] Fig. 15 View from the inlet side of a mixing element according to the invention with a square flow cross-section.

[0031] Examples of implementation

[0032] The static mixer according to the invention, preferably in a pipe 1, consists of mixing elements, each with a separating web 2 of height h in a plane through the pipe axis 3, parallel to the axial flow direction and extending across the entire cross-section. Attached to the separating web 2 are two blade-like deflection surfaces 4, 5 with edges 6, 7 which, in the axial projection, completely cover a sector of the cross-sectional area and two windows 8, 9 for the axial passage of the flow. It is particularly advantageous if the covered sector amounts to 56% - 67% of the radial cross-sectional area. If the edges 6, 7 on the inlet side form a straight web across the cross-section, this corresponds to an angle ß = 100 - 120°. With greater coverage, the pressure loss increases and a reversal occurs such that the layers near the separating web become larger than at the edge. The deflection surfaces separate two axial sections I and II.Section I is the area upstream from the deflection surfaces to the inlet plane E1. The inlet plane E1 is perpendicular to the pipe axis 3 and touches the upper edge of a mixing element. Section II is the area downstream from the deflection surfaces to the outlet plane E3. The outlet plane E3 is parallel to the inlet plane E1 and also perpendicular to the pipe axis 3 and touches the lower edge of a mixing element or the separating web 2. In section I, the flow is shifted transversely to the axial flow direction in opposite directions into the windows 8, 9, split and compressed and the partial flows reach opposite sides of the separating web 2 in section II. Here the flow is expanded again to its full cross-section. In the outlet plane E3, the partial flows are brought together again to be split again in the next mixing element. The edges 6, 7 keep the flow on the deflection surfaces 4 and 5.5 and prevent it from getting into the adjacent window on the same side of the separating web 2. The lateral edges of the deflection surfaces meet at the pipe axis and form a straight or curved surface which also runs across the entire cross-section and projects beyond the deflection surface against the direction of flow. The edges preferably run parallel to the direction of flow, at least at the inlet. However, they can also be inclined relative to this. The height of the edge above the deflection surface can vary across the diameter. Preferably, however, the edges are raised up to the inlet plane E1 of a mixing element and also form a straight or curved web surface on the inlet side, or the edges 6 and 7 together form a straight web which runs across the entire cross-section. The deflection surfaces 4, 5 lie in planes perpendicular to the pipe axis, but are raised from the cross-sectional plane E2 and against the direction of flow.The cross-sectional plane E2 runs perpendicular to the pipe axis, parallel to the planes E1 and E3 and through the upper edge of the separating web 2. As a result of the deflection surfaces being raised, the area F (Fig. 3) under the deflection surfaces in section II and perpendicular to the separating web 2 in section II is increased by 25 - 50%. If the deflection surfaces are flat and straight, this would correspond to an angle of inclination of a = 15 - 30° to the cross-sectional plane E2. The inclination on both sides of the separating web 2 should be opposite and towards the respective window. The area F, downstream of the deflection surfaces 4, 5 and extending to the outlet plane E3, forms the passage area in a mixing element for the cross flow along the separating web 2. It is perpendicular to the separating web 2 in the plane EB through the pipe axis. The arrows in Fig. 2 and 3 indicate the transverse flow directions in the individual sections.The preferred axial flow direction is from section I to section II (large arrow in Fig.2) or from level E1 to level E2.

[0033] In mixing tests with curing resins using such mixing elements in which only the deflection surfaces were inclined by an angle α but not enlarged (β = 90°), a surprising significant increase in layer thicknesses was observed at the edge compared to deflection surfaces in the cross-sectional plane. This applies to both square and circular cross-sections. If, on the other hand, with deflection surfaces in the cross-sectional plane (α = 0°), only the coverage by the deflection surfaces is increased or the angle β > 90° is selected, somewhat more uniform layer thicknesses result. However, this measure is significantly more effective if the deflection surfaces are raised above the cross-sectional plane at the same time. The distribution of layer thicknesses is most even with a clever combination of the two measures.

[0034] The enlarged baffles reduce the narrowest cross-section in the windows in the axial projection. This would increase the pressure drop in the mixing elements if the baffles were located in the cross-sectional area E2, resulting in zones with very different flow velocities or even stagnant zones. The additional inclination or elevation of the baffles relative to the cross-sectional plane increases the flow cross-section for propagation toward the separating web in section II. This reduces the pressure drop and simultaneously improves the velocity distribution and residence time distribution. Both the baffles and their edges can have a curved, arched, or helical shape instead of a flat one (Figs. 12, 13, and 14). To further improve the residence time distribution, the transitions from the webs or edges to the baffles can have large curves.If the mixing elements are connected with connecting elements or with an outer ring, the deflection surfaces or the edges and webs at the transitions to these elements can also be wedge-shaped or reinforced with large curves in order to reduce dead zones and increase strength.

[0035] There is no upper limit for the height h of the separating web 2 or for the length H of a mixing element. The pressure loss decreases with increasing length h of the separating webs or H of the mixing elements. If, on the other hand, the length is shortened, the empty volume fraction decreases and the pressure loss increases, but the mixing quality (layer thickness) related to 1 mixing element remains approximately the same. Thus, the mixing quality per length increases. It has been shown that an optimal result of mixing quality and pressure loss is achieved in most cases when h=0.2 - 0.35 D and H=0.4 - 0.7 D are selected. The mixing elements normally have an empty volume fraction of > 90%. A static mixer is formed by a sequence of inventive mixing elements type A (Fig. 4) and type B (Fig. 5) arranged one behind the other in the direction of flow until the desired mixing state is achieved. The elements type A and type B are identical except for the mirror-image arrangement of the deflection surfaces, i.e.The windows 8 and 9 of type A and the windows 8' and 9' of type B are located on opposite sides of the separating web 2 or 2', respectively. The deflecting surfaces 4 and 4', or 5 and 5', are inclined opposite to the separating web 2 or 2', respectively. The separating webs 2 or 2' of consecutive mixing elements preferably lie in a common axial plane EA through the pipe center. This ensures that the windows and deflecting surfaces of consecutive mixing elements overlap each other. Mixing elements arranged one behind the other are preferably installed without gaps for a compact design. However, they can also be installed with gaps.

[0036] With the help of the described experiments with curing resins and the cross-sectional images, the beneficial effect of this invention idea was clearly demonstrated.

[0037] Fig. 6 shows the distribution of the layers formed and their thickness at the outlet of the second mixing element in an inventive design of the mixing elements for a circular pipe. This image was also traced from the photographic analysis of the sectional images. The distribution of the layer thicknesses across the cross-section is already significantly more uniform here than in Fig. 1c. The trend continues in the further mixing elements according to the exponential decrease in layer thicknesses. Fig. 7 shows the course of the measured maximum layer thickness I in comparison to the initial thickness l0 as a function of the relative mixer length L / D for the inventive mixer with a circular cross-section (1) and the mixer according to EP 0749776 with a square cross-section (2), as well as for a helical mixer (3), also with a circular cross-section, as exponential trend lines.A major advance is that with the mixer according to the invention, even in a circular pipe, the relative layer thickness l / lo of the known mixer according to EP 0749776 with a square cross-section is halved after only 6 pipe diameters. Due to the exponential decrease in layer thickness, the difference becomes increasingly greater the longer the mixing distance. The result is a significantly shorter homogenization length of only approximately 6D. Thanks to the possibility of using normal pipes as housings, the mixers are significantly cheaper to manufacture and easier to handle.

[0038] Because the deflection surfaces cover at least 56% of the cross-sectional area in the projection, the formation of mix-resistant strands that are only slightly deflected by the separating web 2 is avoided at the same time, because these are better intercepted by the deflection surfaces.

[0039] Description of manufacturing and implementation examples

[0040] Individual mixing elements as shown in Fig. 2 can, for example, be easily manufactured from two sheets cut out (laser, water jet) or punched. The sheets are bent to the required shape and the two halves are joined together using a conventional method such as welding, gluing, soldering, riveting, screwing, etc. Of course, the mixing elements can also be assembled from more than two individual parts. The mixing elements are then inserted into a pipe either individually or connected to complete mixer rods using connecting elements. The connecting elements also ensure that the mixing elements are correctly aligned one behind the other. The connecting elements also serve to absorb the axial forces caused by the pressure drop. Supports or retaining rings are used to axially position the mixer in the pipe, or the mixing elements are at least partially connected to the pipe, e.g. by welding.Individual mixing elements or entire mixer rods made of plastic or metal can also be manufactured using a 3D printing process.

[0041] Complete mixer rods as disposable mixers made from a multitude of individual elements of type A and type B are manufactured in one piece using a plastic injection molding process or, from metal, also using a precision casting process (Figs. 8 and 9). The mixer parts are connected to one another by external, axial elements 10, 11, such that the entire part can be manufactured with a simple, two-part open / close tool (O / C), and the external shape is adapted to the circular pipe cross-section (Figs. 8 and 9). This design is particularly advantageous as a disposable mixer compared to previously known disposable mixers with the impractical, square housing cross-section.

[0042] If particularly high strength mixing elements are required, for example, when used as mixers for plastic melts during extrusion or injection molding of plastic parts, the individual mixing elements are firmly connected to an outer ring 12 (Figs. 10 and 11) to absorb the compressive forces, or they are manufactured as precision castings (lost-wax casting) or from a single piece using 3D printing. Mirror-image elements of type A and type B are then installed one behind the other in the housing in the direction of flow to form the static mixer. Special cams and grooves or pins and holes are used to correctly position the mixing elements one behind the other.

Claims

Patent claims 1 . Static mixing elements in a flow channel, preferably in a pipe (1 ) with the diameter (D), - the mixing elements each with a separating web (2) with a height (h), preferably in a plane EA through the pipe axis (3) parallel to the axial flow direction and extending over the entire diameter - followed by two blade-like deflection surfaces (4, 5) in planes transverse to the pipe axis which, in the axial projection, completely cover a sector of the cross-section and delimit two axial sections - and two windows (8, 9) for the axial passage of the flow from a first axial section (I) on the inlet side to opposite sides of the separating web (2) into a second axial section (II) on the outlet side - wherein the deflection surfaces (4, 5) on the inlet side have raised edges (6, 7) as a lateral boundary to the windows, which meet in the pipe axis and project beyond the deflection surface against the flow direction, characterized in that - the deflection surfaces or their axial projection completely cover an area of ​​at least 56% of the pipe cross-section and the deflection surfaces are mutually inclined towards the central web and the cross-sectional plane and / or raised from the cross-sectional plane, - such that the area (F) downstream of the deflection surfaces (4,5) and up to the outlet plane (E3) in the axial plane (EB), perpendicular to the separating web (2) and through the pipe axis (3) is increased by at least 25% compared to the value without inclination and / or elevation.

2. Static mixing elements according to claim 1, characterized in that the edges (6,7) form a common, straight web on the inlet side in the first axial section (I) which encloses an angle ß > 100° and ß < 120° with the separating web (2).

3. Static mixing elements according to claim 1 or 2, characterized in that the deflection surfaces (4, 5) are flat surfaces which are inclined against the flow direction by an angle a > 15° to the cross-sectional plane and mutually towards the separating web (2).

4. Static mixing elements according to one of the preceding claims, characterized in that the height (h) of the separating web is 0.2 - 0.35D and the total height (H) of a mixing element is 0.4 - 0.7D.

5. Static mixer in a flow channel comprising at least two mixing elements arranged one behind the other in the flow direction according to one of the preceding claims, characterized in that successive mixing elements are mirror images of each other and windows and deflection surfaces of successive mixing elements cover each other.

6. Static mixer in a flow channel comprising at least two mixing elements arranged one behind the other in the flow direction according to one of claims 1 - 4, characterized in that successive mixing elements are mirror images and windows and deflection surfaces cover each other, wherein preferably the mixing elements are connected to one another by axial connecting elements which are adapted to a circular tube, to form a mixer rod in such a way that the entire static mixer can be produced by a simple open / close tool.

7. Static mixer, in particular with high strength, in a flow channel made of mixing elements arranged one behind the other in the flow direction according to one of claims 1 - 4, characterized in that the individual mixing elements are firmly connected to an outer ring for reinforcement or form a monolithic part.

8. Static mixing elements and static mixers according to one of the preceding claims, characterized in that the deflection surface is at least partially wedge-shaped and / or thickened by large radii in the transition area to the pipe wall, ring, separating webs, edges or connecting elements.

9. Application of static mixing elements or static mixers according to one of the preceding claims in a circular pipe serving as a flow channel in the processing of plastic melts.

10. Use of static mixing elements or static mixers according to one of the preceding claims as disposable mixers in a circular tube serving as a flow channel in the processing of curing resins. 11.Static-dynamic mixer according to claim 6, characterized in that the mixer rod is connected to a drive which can set the mixer rod in rotation.

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