Internal mixer for polymer processing, and method for operating said mixer

Abstract

A mixer (1) for mixing materials (13) in polymer processing has a mixing chamber (2) and more than two rotors (6a-6d) arranged in the mixing chamber (2). The rotors (6a-6d) can especially be designed to mesh with each other.

Description

[0001] Description

[0002] Internal mixer for polymer processing and method for operating this mixer

[0003] The present invention relates to a mixer for mixing mixtures in polymer processing. In particular, the mixture can be elastomers for the rubber processing industry. In addition to a polymer material, the mixture can also contain one or more additives. The mixer is designed in particular as an internal mixer with a mixing chamber into which the components of the mixture are poured, a subsequent mixing process takes place, and the mixed mixture is finally discharged through a discharge opening.

[0004] The fundamentals of rubber processing are described in the 1989 publication "Technology of Rubber Processing" by Andreas Limper, Peter Barth, and Franz Graj ewski. The publication EP 3 746 278 Bl discloses an internal mixer for mixed material with intermeshing rotors.

[0005] The object is to provide a mixer for polymer processing with improved properties. In particular, the mixer can have improved mixing performance.

[0006] According to a first aspect, a mixer for mixing mixtures in polymer processing is provided. The mixer has a mixing chamber in which more than two rotors are arranged for mixing the mixture.

[0007] The mixture comprises, for example, a main component and one or more additives. The main component can be a polymer material, in particular an elastomer, for the rubber processing industry. The additives can be one or more powdered additives and / or liquid components, such as an oil.

[0008] The mixer is, in particular, an internal mixer for carrying out a discontinuous mixing process. One or more components are introduced into the mixing chamber, the mixture is mixed by rotating the rotors and finally the mixture is discharged by opening a discharge opening. A further mixing process can then be carried out. The addition of one or more components, in particular a polymer, can be carried out via a stamp which presses the components into the mixing chamber. This is also referred to as a stamp kneader. Further additives can be introduced directly into the chamber, for example via nozzles.

[0009] It can also be a tandem mixer with a first mixing chamber and a second mixing chamber. At least one of the mixing chambers has more than two rotors.

[0010] The rotors can be designed to mesh with one another. In particular, the mixer is designed such that the direction of rotation of the meshing rotors differs. In this case, operation is only possible if the direction of rotation of the meshing rotors differs. For example, the rotation circles of the rotors overlap, so that a complete rotation of a rotor is only possible when the rotor that is in mesh with this rotor rotates. For example, all of the rotors are designed to mesh with one another, so that a complete rotation of a rotor is only possible when all of the other rotors are rotating. A rotor can mesh directly with another rotor or indirectly via one or more other rotors.

[0011] For example, each rotor is in direct mesh with exactly two other rotors. It is also possible for each rotor to be in direct mesh with more than two other rotors. The intermeshing design of a rotor with more than one rotor increases the total meshing area in the mixing chamber. For example, the material to be mixed can pass through more than one meshing area with each rotor rotation, so that the mixing result is improved and / or the mixing process is accelerated due to the particularly effective mixing in the meshing area. Overall, the size of the total meshing area is larger for the same chamber volume than in a mixing chamber in which only two rotors are arranged.

[0012] At least one of the rotors can be arranged below another rotor in the direction of gravity. This has the advantage that mixture components, such as powdered components, can accumulate on the lower rotor during filling, and stirring is reduced by the presence of the upper rotor.

[0013] Exactly four rotors can be arranged in the mixing chamber. For example, the rotors mesh with each other in a sequential manner. The rotors can be arranged at the corners of a square.

[0014] Alternatively, the rotors can also be designed to be tangential, so that the rotation circles do not overlap and thus a complete rotation of one rotor is possible without rotation of another rotor. In this case, it is possible for all rotors to be designed to be tangential, so that none of the rotors meshes with another rotor. It is also possible for some of the rotors to be tangential to one another and thus mesh neither directly nor indirectly, and for some other rotors to be designed to mesh with one another. For example, only pairs of rotors can be designed to mesh with one another and the pairs can be designed to be tangential to one another. The rotors can surround an inner region in which one or more components of the mixer are arranged. The inner region is an area that is not in the meshing area of ​​the rotors.

[0015] For example, a temperature sensor is located inside. This internal location allows temperature measurement without being influenced by the temperature of the mixing chamber's housing wall, allowing for more precise temperature determination.

[0016] Alternatively or additionally, a dispensing device for introducing at least one component of the mixture can be arranged in the interior. For example, this could be an injection nozzle for introducing a liquid additive, such as oil. By introducing the component in the interior, the mixing of the component into the mixture can be improved. Furthermore, the formation of a lubricating film on a wall of the mixing chamber can be reduced.

[0017] According to a further aspect, a method for operating the mixer described above is specified. In the method, the mixture is mixed by simultaneous operation of more than two rotors. One or more components of the mixture can be introduced into the mixing chamber by means of a plunger. In addition, one or more components can be introduced directly into an interior area surrounded by the rotors. This can be, for example, a liquid additive, such as oil.

[0018] The rotors can be designed to mesh with each other, whereby the direction of rotation of the meshing rotors differs.

[0019] The direction of rotation of the rotors can be such that the

[0020] Rotors that feed a main component of the mixture into a feeder, and after entering the mixing chamber, convey the mixture directly into the rotor's engagement zone. It is also possible to select an opposite direction of rotation.

[0021] In the process, a filler, in particular a powdered filler, can be introduced into the mixing chamber. The filler can then collect in a lower region of the mixing chamber due to gravity. In particular, the filler can collect in the region of one or more rotors which are arranged below one or more other rotors in the direction of gravity. Only then is a ram lowered into the feed system to introduce another component of the mix. In this way, ram-induced stirring of the filler can be reduced.

[0022] The present invention comprises several aspects , in particular devices and methods . The features , properties and

[0023] The same implementation forms should also apply to the other aspect.

[0024] Furthermore, the description of the objects specified here is not limited to the specific embodiments. Rather, the features of the individual embodiments can be combined with one another—where technically feasible.

[0025] In the following, the objects described here are explained in more detail using schematic examples.

[0026] It shows :

[0027] Figure 1 shows in cross section a mixer according to a

[0028] Embodiment, Figure 2 shows in cross section the mixing chamber of the mixer from Figure 1 in an enlarged view,

[0029] Figure 3 shows a further embodiment of a mixing chamber in cross section,

[0030] Figure 4 shows a mixer according to a further embodiment in cross section,

[0031] Figure 5 shows in cross section a representation of the accumulation of a component of the mixture in a mixing chamber,

[0032] Figure 6 shows a further embodiment of a mixing chamber in cross section,

[0033] Figure 7 shows a further embodiment of a mixing chamber in cross section,

[0034] Figure 8 shows a schematic view of the process steps of a mixing process.

[0035] Preferably, in the following figures, the same reference numerals refer to functionally or structurally corresponding parts of the various embodiments.

[0036] Figure 1 shows an embodiment of a mixer 1 having a mixing chamber 2. The mixing chamber 2 can be filled from above via a feeder 3 and emptied downwards via a discharge flap 4. The mixed material is, for example, one or more polymers, in particular a raw rubber mixture. The material is fed in using a ram 5, which conveys the mixed material into the mixing chamber 2.

[0037] The mixer 1 is, in particular, a so-called internal mixer designed to perform a discontinuous mixing process. The material to be mixed is introduced into the mixing chamber 2, a mixing process is performed, and after the mixing, the mixing chamber 2 is emptied.

[0038] More than two rotors 6a, 6b, 6c, 6d are arranged in the mixing chamber 2. The rotors 6a-6d each have, for example, a rotor base and one or more rotor blades. The rotors 6a-6d are designed to mesh with one another. Thus, the rotational circles of the rotors 6a-6d overlap, so that none of the rotors 6a-6d can complete a complete revolution without at least one other of the rotors 6a-6d also rotating. In particular, intermeshing rotors 6a-6d cannot rotate at different speeds. The intermeshing of the rotors 6a-6d can be designed analogously to the intermeshing of gears. The engagement regions 17 of the rotors 6a-6d, i.e., the regions in which the rotational circles overlap, are indicated here by circles. In the embodiment shown here, a complete rotation of one of the rotors 6a-6d is only possible when all rotors 6a-6d are rotating.Each of the rotors 6a-6d is directly engaged with two other rotors 6a-6d.

[0039] The rotors 6a-6d are arranged at the corners of a square. Depending on the design of the rotors 6a-6d, a different arrangement is also possible. More than four rotors 6a-6d can also be arranged in the mixing chamber. In particular, in the case of intermeshing rotors, in which two rotors are in engagement with each other, the number of rotors should be an even number. The intermeshing design of the rotors 6a-6d can increase the dispersive and / or distributive mixing performance of the mixer 1. This is based on the fact that the mixing performance in the engagement area of ​​intermeshing rotors 6a-6d is particularly high. The more than two intermeshing rotors 6a-6d increase the number of times the material to be mixed passes through the engagement area per rotor revolution. In particular, the number can be doubled.In addition, with four rotors 6a-6d the volume of mix is ​​divided into four areas of intervention, whereby the probability of a pass is four times higher.

[0040] With such a mixer 1, the volumetric advantages of a large mixer can be achieved with the qualitative advantages of a small mixer. The qualitative advantages of a small mixer lie, among other things, in the smaller gap size between the rotors in the engagement area and between the rotors and the mixing chamber wall. With the concept according to the invention, the overall engagement area is increased. Thus, a high mixing quality can be achieved with a smaller number of rolls over, i.e. with fewer complete rotations of the rotors 6a-6d. In this way, the mixing time can be shortened and thus the throughput can be increased with the same quality of the mix, compared to mixers with only two rotors. Alternatively, a higher quality of the mix can be achieved with the same mixing time and the same throughput.

[0041] In addition, the temperature of the mixed material can be better controlled. For example, cooling channels through which a cooling liquid flows are formed in a wall 7 of the mixing chamber 2 and / or in the rotors 6a-6d. If more than two rotors are formed, the ratio of temperature control surface to mixing chamber volume is more favorable because more temperature-controllable surface is available. For example, the ratio of temperature control surface to mixing chamber volume, based on a mixing chamber volume of, for example, approx. 250 l, is approx. 21% higher in the embodiment shown here than in a mixer corresponding to the state of the art with only two rotors.

[0042] For the same mixing chamber volume, the distance between the rotor base and the wall 7 of the mixing chamber 2 is smaller than in a mixing chamber with only two intermeshing rotors. This means that the temperature of the mix can be changed more quickly. This is particularly important for mix materials such as rubber, which are poor heat conductors. This means that a lower temperature can be set during the mixing process. The higher viscosity and the resulting higher shear and tensile stresses mean that better mixing quality can be achieved. Alternatively, the mixer 1 can be operated at higher speeds so that an increase in throughput can be achieved at the same temperature.

[0043] This allows for improved mix temperature control and monitoring during mixing. In particular, compared to conventional mixers, mixing can be performed at a lower temperature, thus improving the mixing quality. Alternatively, mixing can be performed at a higher speed at the same temperature, thus increasing throughput.

[0044] A further advantage of having more than two intermeshing rotors 6a-6d is that oils and other liquid components can be incorporated into the mix more effectively. The forced displacement of the mix in the engagement area of ​​the rotors 6a-6d accelerates the incorporation of an oil into a rubber matrix. In the embodiment shown, there are four such engagement areas, so that good mixing quality can be achieved with fewer overruns of the rotors 6a-6d. For example, the mixing time can be shortened and the throughput increased while maintaining the same quality. Alternatively, the mixing quality can be improved compared to conventional mixers while maintaining the same mixing time and throughput.

[0045] In further embodiments, it is also possible for one or more rotors to be designed to be tangent to one another, so that one or more rotors can perform a complete rotation independently of one or more other rotors. For example, only the two upper rotors 6a, 6b and only the two lower rotors 6c, 6d can mesh with one another, so that the rotation circles of the upper rotors 6a, 6b do not overlap with the rotation circles of the lower rotors 6c, 6d and the upper rotors 6a, 6b can rotate independently of the lower rotors 6c, 6d. All rotors can also be designed to be tangent to one another.

[0046] In a further embodiment, it is also possible for one or more rotors to be directly engaged with more than two rotors.

[0047] The rotors 6a-6d can be operated during mixing with a direction of rotation as shown in Figures 1 and 2. The direction of rotation of the two upper rotors 6a, 6b, i.e., the rotors 6a, 6b closest to the feed 3, is such that the mixed material introduced from above is conveyed into an inner area 8 between the four rotors 6a-6d. In this way, a particularly good intake behavior of the mixer 1 can be achieved.

[0048] Figure 3 shows an embodiment in which the direction of rotation of the rotors 6a-6d is opposite to the direction of rotation shown in Figure 2.

[0049] In particular, the upper rotors 6a, 6b have a direction of rotation through which the mixed material is first conveyed outwards. Through the interaction of the upper rotors 6a, 6b with the lower rotor 6c, 6d located below them, the mixed material is then conveyed into the inner region 8. Due to the shown direction of rotation of the lower rotors 6c, 6d, the mixed material is conveyed through the engagement area of ​​these rotors 6c, 6d directly towards the discharge flap 4, so that the discharge behavior of the mixer 1 can be optimized.

[0050] It is also possible to change the direction of rotation during operation to achieve optimized intake behavior at the beginning of the mixing process and optimized discharge behavior at the end of the mixing process. For example, the direction of rotation shown in Figure 2 is first present, followed by the direction of rotation shown in Figure 3.

[0051] Figure 4 shows a further embodiment of a mixer 1. It is, in particular, a so-called tandem mixer.

[0052] The mixer 1 has a first mixing chamber 9 and a second mixing chamber 10. The first mixing chamber is an upper mixing chamber and the second mixing chamber is a lower mixing chamber. Otherwise the structure is analogous to the mixer shown in Figure 1. The mix is ​​conveyed by a piston 5 via the feed 3 into the upper mixing chamber 9 and there subjected to a first mixing process. The mix then passes through a first discharge flap 11 of the first mixing chamber 9 into the second mixing chamber 10 and there subjected to a second mixing process. The mix then falls downwards out of the mixer 1 when a second discharge flap 12 is opened.

[0053] In each of the two mixing chambers 9, 10, four intermeshing rotors are arranged, as described for the embodiments of Figures 1 to 3. It is also possible for only the upper mixing chamber 9 or only the lower mixing chamber 10 to have more than two rotors. It is also possible for one of the mixing chambers 9, 10 to have a larger number of rotors than the other of the mixing chambers 9, 10. Specific embodiments of the mixing chambers, as described for Figures 1 and 2, can also be combined with one another.

[0054] Figure 5 shows an embodiment of a mixing chamber 2 according to the previously described embodiments, wherein a component of the mixture 13 is depicted in the mixing chamber 2 in the form of a powdered filler 14.

[0055] Before the actual mixing process, a polymer, in particular a rubber material, and the powdered filler 14 are added through the feeder 3 into the mixing chamber 2. For example, the filler 14 is added to the feeder 3 through chutes attached to the side. Once the dosing is complete, the plunger 5 lowers and presses the mixture components into the mixing chamber 2. During movement, the plunger 5 displaces air, essentially like an air pump. This can lead to powdered mixture components being stirred up, which are then often inadvertently sucked away by an aspiration system. The filter dust that is sucked away often has an undefined composition and is difficult to return without a loss of quality, so that disposal is the only option, which is subject to a charge.

[0056] In the embodiment shown, the powdered filler 14 can now fall gravimetrically into the lower half of the mixing chamber 2, in which the lower rotors 6c, 6d are arranged. The upper rotors 6a, 6b arranged above it shield the filler 14 from the air turbulence induced by the ram, so that less material is lost through aspiration. This allows the material quality to be increased through better control of the filler quantity and thus a more precise composition according to the recipe. In addition, a reduction in material costs and environmentally friendly operation are possible due to less material disposal. Furthermore, less cleaning work has to be carried out, so that the mixing cycles can be shortened. In particular, cleaning of the ram 5 during mixing can be omitted.

[0057] Figure 6 shows a further embodiment of a mixing chamber 2 for the mixer 1 as previously described. In addition to the features described in the preceding figures, a temperature sensor 15 for measuring the temperature of the mixed material is arranged in an inner region 8 surrounded by the rotors 6a-6d.

[0058] The inner region 8 is not touched by any of the rotors 6a, 6d, making this region well-suited for arranging additional components. For example, the inner region 8 is located at the center of the arrangement of the rotors 6a-6d.

[0059] Compared to an arrangement of the temperature sensor 15 in a region of the wall 7 of the mixing chamber 2, the temperature sensor 15 in the embodiment shown here is placed deeper in the mixing chamber 2. This enables more precise temperature measurement, and disruptive peripheral influences, such as temperature control of the mixing chamber 2, are less significant.

[0060] Figure 7 shows a further embodiment of a mixing chamber 2 for the mixer 1 as previously described. A dispensing device 16 for introducing one or more components of the mixture is provided in the interior region 8.

[0061] For example, the dispensing device 16 is an injector, in particular an injection valve, for liquid mixture components. These may be oil or other liquid components.

[0062] The discharge is therefore carried out far from the wall 7 of the

[0063] Mixing chamber 2, so that the formation of lubricating films on the inside of the wall 7 can be reduced. Typically, such components are injected through a lateral region of the wall 7 of the mixing chamber 2, so that lubricating films easily form there, leading to reduced power consumption of the mixer 1 and a longer mixing time. By discharging the material directly into the interior area 8, the mixing time can be shortened and the machine's throughput increased due to the lower tendency for lubricating film formation.

[0064] The dispensing device 16 can be present in addition to or alternatively to the temperature sensor 15 of Figure 6.

[0065] For example, the dispensing device 16 and the temperature sensor 15 are arranged side by side. For example, the dispensing device 16 and / or the temperature sensor 15 are arranged along an axis that runs parallel to the rotational axis of the rotors 6a-6d.

[0066] Figure 8 shows a method for mixing a mixture with a mixer 1 as previously described.

[0067] In the process, the mixing chamber 2 is filled with components of the mixture. In a first step A, a powdered material can be added to the mixing chamber 2. After a waiting period, during which the powdered material settles in the mixing chamber 2, as shown, for example, in Figure 5, a main component, such as a polymer, is added. The addition can take place in a step B via a plunger that presses the material into the mixing chamber 2.

[0068] In a further step C, a liquid

[0069] A mixture component, such as oil, is added to an internal area 8 between the rotors 6a-6d. For example, step C takes place before and / or during mixing of the mixture. It is possible for only one of steps A and C or both of these steps to be carried out.

[0070] After mixing, the mixed material is removed from the mixing chamber 2, for example by opening a discharge flap 4.

[0071] Reference sign

[0072] 1 mixer

[0073] 2 mixing chambers

[0074] 3 Feeding

[0075] 4 Drain flap

[0076] 5 stamps

[0077] 6a Rotor

[0078] 6b Rotor

[0079] 6c rotor

[0080] 6d rotor

[0081] 7 Wall

[0082] 8 Interior

[0083] 9 first mixing chamber

[0084] 10 second mixing chamber

[0085] 11 first emptying flap

[0086] 12 second emptying flap

[0087] 13 Mixture

[0088] 14 Filler

[0089] 15 temperature sensors

[0090] 16 Dispensing device

[0091] 17 Intervention area

Claims

Patent claims 1. Mixer (1) for mixing mixed material (13) in polymer processing, comprising a mixing chamber (2) and more than two rotors (6a-6d) arranged in the mixing chamber (2).

2. Mixer (1) according to claim 1, wherein the rotors (6a-6d) are designed to engage with one another.

3. Mixer (1) according to claim 2, wherein each rotor (6a-6d) is in direct engagement with two or more than two other of the rotors (6a-6d).

4. Mixer (1) according to one of claims 1 to 3, which is designed such that the direction of rotation of the intermeshing rotors (6a-6d) differs.

5. Mixer (1) according to claim 1, wherein the rotors (6a-6d) are tangential.

6. Mixer (1) according to one of the preceding claims, which has four or more than four rotors (6a-6d).

7. Mixer (1) according to one of the preceding claims, wherein at least one of the rotors (6a-6d) is arranged in the direction of gravity below another of the rotors (6a-6d).

8. Mixer (1) according to one of the preceding claims, comprising exactly four rotors (6a-6d) arranged at four corners of a rectangle.

9. Mixer (1) according to one of the preceding claims, in which the rotors (6a-6d) surround an inner region (8), wherein at least one temperature sensor (15) is arranged in the inner region (8).

10. Mixer (1) according to one of the preceding claims, in which the rotors (6a-6d) surround an inner region (8), wherein in the inner region (8) at least one dispensing device (16) is arranged for introducing at least one component of the mixed material (13).

11. Mixer (1) according to one of the preceding claims, comprising a plunger (5) for introducing one or more components of the mixture (13) into the mixing chamber (2) and a drain flap (4) for emptying the mixing chamber (2).

12. Mixer (1) according to one of the preceding claims, comprising a first mixing chamber (9) and a second mixing chamber (10), wherein at least in one of the mixing chambers (9, 10) more than two rotors (6a-6d) are arranged.

13. Method for operating a mixer (1) according to one of the preceding claims, in which the material to be mixed (13) is mixed in the mixing chamber by simultaneous operation of more than two rotors (6a-6d).

14. The method according to claim 13, wherein the rotors (6a-6d) are designed to mesh with one another, the direction of rotation of the meshing rotors (6a-6d) being different.

15. Method according to one of claims 13 or 14, in which at least one component of the mixture (13) is introduced into an inner region (8) which is surrounded by the rotors (6a-6d).

16. Method according to one of claims 13 to 15, wherein a direction of rotation of the rotors (6a-6d) which are closest to a feed (3) through which a main component of the mixed material (13) is introduced into the mixing chamber (2) is such that the mixed material (13) is conveyed into an engagement region of these rotors (6a-6d) after entering the mixing chamber (2).

17. Method according to one of claims 13 to 16, wherein a direction of rotation of the rotors (6a-6d) which are closest to a feed (3) through which a main component of the mixed material (13) is introduced into the mixing chamber (2) is such that the mixed material (13) is conveyed away from an engagement region of these rotors (6a-6d) after entering the mixing chamber (2).

18. Method according to one of claims 13 to 17, wherein before the mixing process at least one filler (14) is introduced into the mixing chamber (2) in such a way that the filler (14) can accumulate in a region of one or more of the rotors (6a-6d) which are arranged in the direction of gravity below one or more other of the rotors (6a-6d), and then a plunger (5) is lowered into a feeder (3).

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