WO2003078135A1 - Multi-screw extruder comprising at least one elongated, separate discharge screw - Google Patents

Abstract

The invention relates to a multi-screw extruder for processing/treating an elastomer, in particular a thermoplastic elastomer, such as e.g. natural rubber, synthetic rubber or rubber blends. Said multi-screw extruder comprises a plurality of parallel processing screws, arranged in a housing, with processing elements, at least in subsections, that transport the material. Said processing elements of adjacent processing screws are arranged so that they intermesh and the inner walls of the processing chamber on both sides of the processing screws have cylindrical recesses running parallel to said processing screws and to each other, in which the processing screws are mounted on both sides. The processing chamber of the multi-screw extruder, at least in the vicinity of its exit-side end, consists of at least one cylindrical processing sub-chamber, in which a respective transport screw, equipped with transport elements at least in one axial subsection, is rotatably mounted.

Description

 MULTI-SHAFT EXTRUDER WITH AT LEAST ONE EXTENDED, SEPARATE DISCHARGE SCREW

The invention relates to a multi-shaft extruder for processing an elastomer, in particular a thermoplastic elastomer, such as e.g. Natural rubber, synthetic rubber or rubber mixtures, the multi-shaft extruder having a multiplicity of processing shafts arranged in a housing and parallel to one another with processing elements which convey at least in axial partial areas. These machining elements of adjacent machining shafts are arranged in an interlocking manner, and the inner walls of the process space on both sides of the machining shafts have parallel cylindrical recesses in which the machining shafts are mounted on both sides. In this way, a first sub-process space and a second sub-process space on the one side and the other side of the barrier formed by the mutually parallel machining shafts in the housing are determined.

Such multi-shaft extruders, especially ring extruders, are particularly well suited for compounding tasks based on distributive and dispersive mixing, since in the process space both the thorough mixing and the shear of the processed material take place. This advantage of the multi-shaft extruder is paid for by the disadvantage that it has a relatively weak pumping or conveying effect. When processing / processing an elastomer, in particular a thermoplastic elastomer, such as natural rubber, synthetic rubber or rubber mixtures, there is therefore an increasing compression of the product towards the outlet-side end region. This is associated with an increase in mechanical resistance. In these densified areas, the product is subjected to particularly high mechanical and thermal stresses during its processing, which can lead to mechanical and / or thermal damage to the elastomer molecules of the product. The object of the invention is therefore to prevent this compression and potential damage to the elastomer in the multi-screw extruder mentioned at the outset.

This object is achieved in the multi-shaft extruder mentioned at the outset in that the process space of the multi-shaft extruder consists, at least in its outlet-side end region, of at least one cylindrical partial process space, in each of which a conveyor shaft is rotatably mounted, which has conveyor elements at least over an axial sub-region. In this way, a pumping action is imparted to the outlet-side end region, which counteracts the compression mentioned and the associated impairments of the product.

The at least one cylindrical sub-process space with the conveyor shaft mounted therein is expediently arranged collinearly along the axial extension of at least one machining shaft of the plurality of mutually parallel machining shafts arranged in the housing. This collinear arrangement is structurally relatively easy to implement.

It is particularly advantageous if a cylindrical partial process space with the conveyor shaft mounted therein is arranged collinearly along the axial extension of every second machining shaft of the plurality of mutually parallel machining shafts arranged in the housing. This is particularly simple in terms of production technology. The housing of the multi-shaft extruder according to the invention can then be formed by overlapping parallel bores to a certain depth, which form the process space in which the machining shafts with the intermeshing machining elements are rotatably supported. The length of this process space along the axial product conveying direction then corresponds to the depth of the overlapping bores. In order to form the cylindrical sub-process space for the pumping shaft that supports the pumping action, every second one of the overlapping parallel bores is simply made with a greater depth than the other of the overlapping parallel bores. The difference in the drilling depths corresponds to the length of the cylindrical partial process rooms with pump effect. The product conveyed through the processing space through the processing shafts thus travels along the machining shafts extended by the conveyor shafts either directly into the pumping cylindrical partial process spaces or at the end of the non-extended machining shafts it is introduced obliquely into the adjacent cylindrical partial process spaces. In order to facilitate this oblique introduction of the product during operation and thus to keep the resistance low and to avoid dead areas, the transition area between the end of the small depth holes to the wall area of the larger depth holes forming the cylindrical partial process spaces is preferred than contrary to the product Convex surface pointing in the direction of conveyance, in particular as a cone or truncated cone, so that the product is deflected by the convex surface, in particular the lateral surface of the cone or truncated cone.

According to a further advantageous embodiment, a cylindrical sub-process space is arranged in the axial extension of each of the plurality of machining shafts, the radius of each cylindrical sub-process space and the conveyor shaft rotatably mounted in it being smaller than the radius of the cylindrical indentations of the process space inner walls that the cylindrical partial process spaces are separated from each other by housing material. This is also easy to manufacture. The housing of the multi-shaft extruder according to the invention can then also be formed by overlapping parallel bores to a certain depth with a certain drilling radius in order to form the process space in which the machining shafts with the intermeshing machining elements are rotatably mounted. The length of this process space along the axial product conveying direction then corresponds to the depth of the overlapping bores with the specific drilling radius. In order to form all the cylindrical partial process spaces for the pumping shaft that enables the pumping action to be carried out, each of the existing overlapping parallel bores, which have the specific depth and the specific drilling radius, are extended to a greater depth with a smaller drilling radius. The difference in drilling depths also corresponds to the length of the cylindrical partial process rooms with pumping action. The product conveyed through the processing shafts by the machining shafts thus always goes directly along the machining shafts extended by the conveying shafts into the pumping, cylindrical partial process chambers. To operate at the transitions from the resistance to the first determined drilling radii of the process space to the smaller drilling radii of the cylindrical partial process spaces and to avoid dead areas, here too the transition between the bore areas of large radii to the wall areas of the bore areas forming small cylindrical radii is preferably beveled, here in particular a truncated cone surface is also possible.

Instead of the above-mentioned collinear designs, the process space of the multi-shaft extruder in its outlet-side end area can also consist of a cylindrical partial process space with a conveyor shaft mounted therein, the partial process space and the conveyor shaft stored therein being assigned differently than collinearly to the plurality of mutually parallel processing shafts arranged in the housing are.

In a particularly preferred embodiment, the multiplicity of machining shafts are arranged in a ring-like, in particular circular, manner, the first sub-process space being an inner process space arranged radially inside the shaft ring and the second sub-process space being an outer process space arranged radially outside the shaft ring, and the first housing part a core arranged radially inside the process space and the second housing part is a jacket arranged radially outside the process space, which surrounds the process space. With this arrangement of the processing shafts there are as many gusset areas as there are shafts, which enables intensive and as uniform as possible processing of the product even with relatively short process space lengths or small UD ratios of the extruder.

The process space of such a ring extruder preferably consists in its outlet-side end area of a cylindrical partial process space with a conveying shaft mounted therein, the axis of the partial process space and the conveying shaft mounted therein running parallel to the plurality of mutually parallel machining shafts arranged in the housing. In this way, a common pump area is formed at the end of the process room. The axis of the sub-process space and the conveyor shaft mounted therein are preferably arranged centrally with respect to the shaft ring consisting of the machining shafts. This geometry enables the bearing and the drive of the common conveyor shaft of the cylindrical subpro zessraumes in or through the core of the ring extruder. Here too, there is a bevel, in particular a truncated cone, from the outer process area inner surface with its cylindrical indentations (outer "flower") to the cylindrical inner surface of the partial process room in order to keep the resistance low and to avoid dead areas.

In all of the configurations mentioned above, a shaping nozzle can be arranged at the end of the at least one cylindrical partial process space with the respective conveying shaft mounted therein.

The respective conveyor shaft of the cylindrical sub-process space is expediently driven by the same drive as the plurality of machining shafts. In the case of the collinear arrangements, in particular the respective delivery shaft of the cylindrical sub-process space is connected in a rotationally fixed manner to the respective processing shaft which is collinear with it and is driven by the same drive as the plurality of processing shafts.

Further features, advantages, tasks and possible uses of the invention result from the following description of preferred exemplary embodiments with reference to the drawing, in which:

1A schematically shows a central longitudinal section of a first exemplary embodiment of the housing of the multi-shaft extruder according to the invention;

Fig. 1B shows a cross section of the housing of Fig. 1A along the section plane I-I;

Fig. 1C shows a cross section of the housing of Fig. 1A along the section plane II-II;

2A schematically shows a central longitudinal section of a second exemplary embodiment of the housing of the multi-shaft extruder according to the invention; Fig. 2B shows a cross section of the housing of Fig. 2A along the section plane III-III;

Fig. 2C shows a cross section of the housing of Fig. 2A along the section plane IV-IV;

3A schematically shows a central longitudinal section of a third exemplary embodiment of the housing of the multi-shaft extruder according to the invention;

Fig. 3B shows a cross section of the housing of Fig. 3A along the section plane V-V; and

FIG. 3C shows a cross section of the housing of FIG. 3A along the sectional plane VI-VI.

1a schematically shows a central longitudinal section of a first embodiment of the housing of the multi-shaft extruder according to the invention. The housing 1 surrounds a process space 2 and two cylindrical partial process spaces 3, 4. The process space 2 of the multi-shaft extruder consists of several mutually parallel bores which partially overlap one another (see FIG. 2B). Machining shafts (not shown) are rotatably mounted in it. The machining shafts and the machining elements attached to them (screw elements, kneading elements, etc.) and the partially overlapping bores of the process space 2 are designed in such a way that the machining shafts with their machining elements are arranged to interlock. The process space 2 also has two cylindrical partial process spaces 3, 4, which are formed by the extension of the second or third bore of the five overlapping bores of the process space 2. In the entry area from the process space 2 into the cylindrical partial process space 3 or the cylindrical partial process space 4, a truncated cone-shaped bevel 3a or 4a is formed. These bevels 3a and 4a facilitate the transition from process room 2, in which an intensive mechanical processing of the product predominantly takes place, to sub-process rooms 3 and 4, thereby reducing the transport resistance of the extruder and avoiding dead areas in the process room. The second and third the five processing shafts (not shown) of the process space 2 extend from the process space 2 into the cylindrical sub-process space 3 or the cylindrical sub-process space 4. In their area projecting into the cylindrical sub-process spaces 3 and 4, the processing shafts have conveying areas (not shown), so that an excellent pumping effect is achieved in the operation of the multi-shaft extruder according to the invention in these cylindrical partial process rooms 3 and 4.

Fig. 1B shows schematically a cross section of the housing of Fig. 1A along the section plane l-l. The housing 1 surrounds the process space 2, which has mutually opposite indentations on its process space inner walls. The lower process chamber inner wall comprises five cylindrical indentations 2a, 2b, 2c, 2d and 2e, while the upper process chamber inner wall comprises five cylindrical indentations 2a ', 2b', 2c ', 2d', 2e '. A first sub-process space (bottom) and a second sub-process space (top) are formed by the mutually intermeshing machining shafts (not shown) which are rotatably supported between these cylindrical indentations of the process space inner walls. Between these two sub-process areas, the interlocking machining shafts (not shown) form a more or less permeable barrier depending on the nature of the machining elements.

Fig. 1 C shows schematically a cross section of the housing of Fig. 1A along the section plane II-II. One can see the two cylindrical partial process spaces 3 and 4, which are completely surrounded by the housing 1. In the axial extension of the third machining shaft (not shown) supported by the cylindrical indentations 2c and 2c 'there is a housing area 1a which separates the two sub-process spaces 3 and 4 from one another.

2A schematically shows a central longitudinal section of a second exemplary embodiment of the housing of the multi-shaft extruder according to the invention. The left half of the extruder is identical to the left half of the extruder of Fig. 1A. Here, too, a housing 1 surrounds a process space 2 and five further cylindrical partial process spaces 5, 6, 7, 8 and 9. These five cylindrical partial process spaces 5, 6, 7, 8 and 9 are separated from one another by four separating housing areas 1a, 1b, 1c, 1d Cut. The transition from the process space 2 into the five cylindrical partial process spaces 5, 6, 7, 8 and 9 are each formed as a truncated cone-shaped bevel 5a, 6a, 7a, 8a and 9a.

FIG. 2B shows a cross section of the housing of FIG. 2A along the section plane III-III and is identical to FIG. 1 B.

Fig. 2C shows a cross section of the housing of Fig. 2A along the section plane IV-IV. One can see the five cylindrical partial process spaces 5, 6, 7, 8 and 9, which are completely surrounded by the housing 1, here also between neighboring ones cylindrical sub-process rooms each a separating of the housing area 1 a, 1a, 1c and 1d.

3A schematically shows a central longitudinal section of a third exemplary embodiment of the housing of the multi-shaft extruder according to the invention. The housing consists of a core 10 and a casing 11, between which an essentially circular process space 2 extends, which merges into a coreless partial process space 3 surrounded only by the casing 11. Similar to the process space 2 of the first and the second exemplary embodiment, the process space 2 of this third exemplary embodiment consists of several parallel bores, which partially overlap one another and are arranged on a circular line. In the present case, there are eight partially overlapping holes, which are arranged on a circular line. In this way, eight cylindrical indentations 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h are formed on the radially outer process space inner wall on the inside of the jacket 11, while on the radially inner process space inner wall on the outer surface corresponding cylindrical indentations 2a ', 2b', 2c ', 2d \ 2e', 2f, 2g ', 2h' are formed for the core 10 (see FIG. 3B). An axial bore 10a extends in the interior of the core 10 and is formed collinearly or coaxially with the cylindrical partial process space 3. A shaft (also not shown) extends through the bore 10a of the core 10 over the process space into the cylindrical partial process space 3.

FIG. 3B schematically shows a cross section of the housing from FIG. 3A along the section plane VV. The pro- gram extends between the core 10 and the jacket 11. Zessraum 2, wherein the entirety of the outer cylindrical indentations 2a to 2h and the entirety of the inner cylindrical indentations 2a 'to 2h' appear as an outer or inner "flower", between which the propagation waves (not shown) are rotatably mounted. The bore 10a can be seen in the interior of the core 10.

FIG. 3C schematically shows a cross section of the housing from FIG. 3A along the sectional plane VI-VI. One recognizes the cylindrical partial process space 3 surrounded by the housing 1.

In all three exemplary embodiments, a conveyor shaft equipped with conveying elements, at least in axial subregions, extends into the cylindrical subprocess spaces. In operation, these conveying waves help to make the pressure increase of the product mentioned at the beginning in the end region of the intermeshing machining waves less than in the prior art.

LIST OF REFERENCE NUMBERS

casing

Process space cylindrical sub-process space cylindrical sub-process space a, 4a bevel a, 1 b, 1c, 1d separating housing area, 6, 7, 8, 9 cylindrical process space a, 6a, 7a, 8a, 9a bevel 0 core 0a hole in core 1 jacket a to 2h cylindrical indentations of the process room inner wall (outer flower) a 'to 2h' indentations of the process room inner wall (inner flower)

Claims

claims 1.Multi-shaft extruder for processing / processing a product, e.g. thermoplastic polymer or elastomer, in particular polyester or natural rubber, synthetic rubber, the multi-shaft extruder having a multiplicity of processing shafts arranged in a housing and parallel to one another with processing elements which convey at least in axial partial areas, the processing elements of adjacent processing shafts being arranged in an interlocking manner and the process space inner walls have on both sides of the machining shafts to the machining shafts and mutually parallel cylindrical recesses in which the machining shafts are mounted on both sides, as a result of which a first sub-process space and a second sub-process space on one side and on the other side determine the barrier formed in the housing by the mutually parallel machining shafts are characterized in that the process space (2, 3, 4; 2, 5, 6, 7, 8, 9; 2, 3) of the multi-shaft extruder at least in its outlet-side end region a us at least one cylindrical partial process space (3, 4; 5, 6, 7, 8, 9; 3), in which in each case a conveyor shaft is rotatably mounted, which has conveyor elements at least over an axial partial region. 2. Multi-shaft extruder according to claim 1, characterized in that the at least one cylindrical sub-process space (3, 4; 5, 6, 7, 8, 9) with the conveyor shaft stored therein collinearly along the axial extension of at least one machining shaft of the plurality in the housing (1) arranged, mutually parallel machining shafts. 3. Multi-shaft extruder according to claim 2, characterized in that in each case a cylindrical sub-process space (3, 4) with the conveyor shaft mounted therein collinearly along the axial extension of every second machining shaft A plurality of processing shafts arranged parallel to one another is arranged in the housing (1). 4. Multi-shaft extruder according to claim 2, characterized in that in the axial extension of each of the plurality of machining shafts a cylindrical part process space (5, 6, 7, 8, 9) is arranged, the radius of each cylindrical part process space and that in it rotatably mounted conveyor shaft is such an amount smaller than the radius of the cylindrical indentations of the process space inner walls that the cylindrical partial process spaces are separated from one another by housing material. 5. Multi-shaft extruder according to claim 1, characterized in that the process space of the multi-shaft extruder in its outlet-side end area consists of a cylindrical partial process space (3) with a conveyor shaft mounted therein, the partial process space (3) and the conveyor shaft mounted therein of the plurality in the housing (1) arranged, mutually parallel processing shafts are assigned. 6. Multi-shaft extruder according to one of claims 1 to 5, characterized in that the plurality of machining shafts are arranged in a ring-like manner, the first partial process chamber being an inner process chamber arranged radially inside the shaft ring and the second partial process chamber being an outer process chamber arranged radially outside the shaft ring and the first housing part is a core (10) arranged radially inside the process space and the second housing part is a jacket (11) arranged radially outside the process space, which surrounds the process space. 7. Multi-shaft extruder according to claim 6, characterized in that the process space of the multi-shaft extruder in its outlet-side end region consists of a cylindrical partial process space (3) with a conveyor shaft mounted therein, the axis of the partial process space and the conveyor shaft mounted therein parallel to that A large number of processing shafts arranged in the housing (1) run parallel to one another. 8. Multi-shaft extruder according to claim 7, characterized in that the axis of the sub-process space (3) and the conveyor shaft mounted therein is arranged centrally with respect to the shaft ring consisting of the machining shafts. 9. Multi-shaft extruder according to one of claims 1 to 8, characterized in that a shaping nozzle is arranged at the downstream end of the at least one cylindrical partial process chamber with the respective conveyor shaft mounted therein. 10. Multi-shaft extruder according to one of claims 1 to 9, characterized in that the respective conveyor shaft of the cylindrical sub-process space is driven by the same drive as the plurality of machining shafts. 11. Multi-shaft extruder according to claim 2 to 6, characterized in that the respective conveyor shaft of the cylindrical sub-process space (3, 4; 5, 6, 7, 8, 9) is rotatably connected to the respective processing shaft, which is collinear with it, and by the same drive how the multitude of machining shafts is driven.