WO1998039152A1 - Extrusion device - Google Patents

Abstract

The invention relates to an extrusion device, specially for producing a foamed polymer, comprising at least one endless screw (2) for conveying at least one polymer which is fed by a feeding device (3), a feeding device (4) for providing a foaming agent once the polymer has melted, a mixing device (5) for mixing the polymer melt and the foaming agent, a throttle (6) for reducing pressure in the supplied polymer/foaming agent mixture, and an extrusion tool (7). In order to simplify overall design of the inventive device and to reduce its production cost, while guaranteeing increased flexibility with regard to various process requirements and/or assembly and reconstruction requirements, the endless screw (2) and the feeding device (3) are arranged in an extruder and the feeding device (4), mixing device (5), throttle (6) and extrusion tool (7) are configured as individual units (10) which can be connected to the extruder outfeed.

Description

 Ex rusion direction

The invention relates to an extrusion device, in particular for producing a foamed polymer, with at least one extruder screw for transporting at least one polymer added by a feed device, a feed device for a blowing agent after the polymer has melted, a mixing device for mixing polymer melt and blowing agent, and a throttle for production a pressure drop in the polymer / blowing agent mixture supplied and an extrusion tool.

Such an extrusion device is known from DE 19 521 520. In the known device, all of the above-mentioned units of the extrusion device are combined in one extruder and arranged one behind the other in the transport direction.

At least one polymer is fed to the extruder screw through the feed device and then melted. A blowing agent, such as CO ₂ , N ₂ or the like, is fed to the polymer melt via the feed device and then the polymer melt and blowing agent are mixed with one another in the mixing device in order to produce a mixture or solution which is as single-phase as possible.

DE 19 521 520 describes in particular how, by controlling a throttle at the outlet end of the mixing device, a sudden pressure drop in the polymer / blowing agent mixture is achieved independently of a set flow rate. This special control of the throttle decouples the pressure drop and flow rate from one another, which in particular enables the nucleation rate to be kept constant. Due to the constant pressure drop rate and nucleation rate, nucleation takes place homogeneously over the entire cross section of the throttle discharge opening. This gives the foamed polymer a higher and more uniform lower cell density, the foamed polymer having a microcellular or submicrocellular structure of good quality and without restriction in the shape. Regarding the mode of operation of the throttle and its control, reference is expressly made to DE 19 521 520, the advantages of the throttle and its control also apply to the present application.

A disadvantage of DE 19 521 520 is that the extrusion device as a whole is structurally relatively complex and expensive, since the extrusion device or the extruder as a whole can only be used to produce foamed polymer with a microcellular or submicrocellular structure. Furthermore, due to the entire structure of the extrusion device, an individual adaptation or adjustment to different process conditions and an expandability or convertibility of the extrusion device is not possible at all or only to a small extent.

The object of the application is therefore based on the object of improving the extrusion device mentioned at the outset in such a way that the device as a whole is structurally simpler and less expensive, with increased adaptability to different process conditions and / or construction and conversion requirements being possible at the same time.

This object is achieved in the extrusion device according to the invention in that the extruder screw and feed device are combined in one extruder and the feed device, mixing device, throttle and extrusion tool are designed as individual modules which can be connected to the feed end of the extruder.

This means that any existing extruder for thermoplastic or thermoelastic plastics, such as a screw extruder with or without a grooved feed zone, a twin screw extruder or a screw press, can be used. to be converted by additional attachment of all or at least some of the individual modules for the production of foamed polymer with a microcellular or submicrocellular structure. This simplifies the construction of the extruder itself and reduces the costs, since the existing modules can be converted in a simple manner by the individual modules. Furthermore, the extrusion device can be easily adapted to different process conditions by appropriate arrangement of more or fewer individual modules and can be converted quickly and easily by exchanging or additionally arranging individual modules. The actual extrusion screw and feed device for at least one polymer-containing extruder is used in this context only for melting the polymer in a manner known per se.

If the pressure in the polymer melt supplied by the extruder is too low for further processing in the downstream individual modules, a first pressure increasing device can advantageously be arranged downstream at the exit end of the extruder in the direction of transport downstream as the first connected individual module. Such a pressure increasing device can be designed as an active device, for example as a pump. This increases or, if necessary, decreases the pressure prevailing in the polymer melt output by the extruder to a pressure required for further processing by the subsequent individual modules.

In order to be able to connect the individual modules to one another and also to the extruder in a simple manner, connecting flanges are arranged on these or can be arranged between them during assembly. A connection of the individual modules to one another and also to the discharge end of the extruder can be established in the usual way, for example by screwing or the like, via the connecting flanges. The connecting flanges can also be designed as separate components, in particular the connecting flange between the extruder and the Most can be designed as an adapter connection flange on this individual module to be fastened. This can be selected appropriately for each extruder and create a transition to the individual modules. Furthermore, connecting flanges can be combined as individual components and connecting flanges at the ends of extruders and / or individual modules.

In order to further increase the flexibility of the various devices formed by means of the individual modules, the individual module forming the mixing device can be composed of sub-modules, for example. As a result, depending on the polymer used or the polymer mixture used or other process conditions, the mixing device, for example, can be designed for more or less length with more or less different mixing elements or the like.

To control or regulate the pressure in the mixing device or subsequent to it, at least one second pressure increasing device, in particular a pump, can be arranged as a further individual module between the sub-modules of the mixing device and / or at the end of the mixing device downstream in the transport direction. This allows the pressure in the homogeneously mixed polymer melt to be optimally adapted for further processing.

In order to cause a blowing agent added to the polymer melt and, for example, homogeneously distributed in the polymer melt by the first mixing device, to form a single-phase melt / blowing agent solution, at least one diffuser designed as a single module can be arranged between the first mixing device or the second pressure increasing device and the throttle . This can be connected accordingly to the other individual modules by means of the connection flanges mentioned above. The individual module forming the diffuser can also be composed of various sub-modules, which are selected and assembled in a corresponding number depending on requirements.

For example, a second mixing device can additionally be arranged in the individual module forming the diffuser. A further homogenization of the melt / blowing agent mixture is thereby achieved.

In this context, it is sufficient if the second mixing device is arranged in at least one submodule of the diffuser. Of course, the second mixing device and the diffuser can also be formed by separate sub-modules, as a result of which the mixing and diffusion zone can be exactly separated from one another and individually adjusted.

Depending on requirements, at least one third pressure increasing device, in particular a pump, can be arranged as a further individual module between the sub-modules for the second mixing device and / or the diffuser.

For the production of foamed polymer with a microcellular or submicrocellular structure, it is particularly advantageous if the throttle has at least two rotatably driven, intermeshing gear wheels. For further explanations of such a throttle, constructed similarly to a gear pump, reference is once again expressly made to DE 19 521 520, which was mentioned at the beginning as a genus. The gears can be driven mechanically, electrically or in some other way.

In order to monitor the pressure at various points in the extrusion device as process parameters and, if necessary, to control or regulate it, pressure sensors can be assigned at least to the input and output sides of the pressure increasing devices and / or the throttle. A simple assignment of a pressure sensor is provided if one is arranged in a corresponding connection flange. This can be done, for example, in the separate connecting flanges mentioned at the beginning. However, a pressure sensor can also be arranged in a connection flange formed on the corresponding individual module. The latter is advantageous, for example, in the case of the pressure booster devices, since their inlet and outlet pressure are generally measured.

During the processing of the polymer melt by the extrusion device, additional heating of the polymer melt in one or more individual or sub-modules may be necessary. For this purpose, a heating device can be arranged in at least one individual and / or sub-module.

Due to the various possible pressure increases in the polymer melt or in the polymer / blowing agent mixture and its processing by means of a mixer or the like, the temperature of the mixture can assume unfavorably high values for further processing, so that in at least one individual and / or sub-module a cooling device can be arranged.

In order to be able to control the temperature in the molten polymer or in the polymer / blowing agent mixture and, if necessary, to control or regulate it by means of heating devices and / or cooling devices, at least one temperature sensor can be assigned to an individual and / or sub-module.

In the case of the temperature sensor, it can also be advantageous if it is arranged in a connecting flange, in one piece with a module or separately from this. In the case of connection flanges separate from the various modules and the arrangement of pressure sensors or temperature sensors in them, such connection flanges in principle form separate modules which can be arranged between the other individual and / or sub-modules of the extrusion device as required. In order to determine the corresponding pressure and temperature values and, if necessary, to be able to use them to control or regulate the extrusion device, a first regulating device can be connected to the pressure and temperature sensors for determining the respective values.

In order to be able to determine further process parameters of the extrusion device, the first control device can also be connectable to the pressure increase devices designed as gear pumps and / or the speed pickups assigned to the extruder and / or the throttle. As with the pressure and temperature values, the corresponding speed values can not only be determined, but can also be used by the control device to control or regulate the extrusion device.

In order to supply a sufficient amount of blowing agent to the molten polymer depending on the various process parameters, such as the type of blowing agent, for example, the first regulating device for metering the blowing agent with the blowing agent supply device can be used. For reasons of redundancy or for separate monitoring of the propellant supply device, a second regulating device can be connected to the propellant supply device in accordance with the first regulating device with speed sensors, temperature sensors and / or pressure sensors or at least for metering the propellant.

In order to be able to control or regulate the blowing agent supply, in particular as a function of the amount of polymer melt supplied by the extruder and / or also as a function of the transport speed of the polymer melt or the polymer / blowing agent mixture in the individual modules and sub-modules, the second control device can continue to be connectable to the speed pickups and / or the first control device. The location of the feeding of the propellant can be varied in the simplest manner in that an injection opening connected to the propellant supply device is formed in a connecting flange, this injection opening preferably being formed in a connecting flange at an upstream inlet end of the mixing device in the transport direction. However, the injection opening can also be formed in a sub-module forming the individual module of the mixing device or in a corresponding connecting flange of this sub-module.

Due to the composition of the first or second mixing device from sub-modules, these can have, for example, static or mechanically driven mixers or mixing elements. In addition, static and mechanically driven mixers can also be arranged in combination in a single or sub-module.

The modular structure of the extrusion device can continue in the extrusion tool in such a way that it has a forming die and / or a fine drawing die and / or a cooling device as a sub-module.

Furthermore, first and / or second control devices can also be designed as control modules, and in the case of the second control device it can in particular be part of the individual module forming the propellant supply device. Known cable connections or other connection devices - also wireless - can be used to connect the control devices to the corresponding sensors and sensors.

An advantageous exemplary embodiment of the invention is explained and described in more detail below with reference to the figure enclosed in the drawing. It shows:

Fig. 1 shows a basic structure of an extrusion device according to the invention.

In Fig. 1, an embodiment of the extrusion device according to the invention is shown in principle.

In the transport direction 11, behind a known extruder 8 with extruder screw 2 and feed device 3, a number of individual modules 10 are arranged one behind the other. Directly at a discharge end 9 of the extruder 8, a gear pump as a pressure increasing device 12 is arranged as a single module 10 via a connecting flange 13. This connects in the transport direction 11 as a further individual module 10 to a mixing device 5. A connecting flange 13 is also provided between the mixing device 5 and the first pressure increasing device 12.

Further connection flanges 13 between further individual modules 10 or sub-modules 14 forming an individual module are only shown in principle and can be designed both as connection flanges formed at the respective ends of the modules or as connection flanges 13 separately formed between the modules and arranged between them. These are attached to the corresponding modules for their connection by conventional measures, such as screwing or the like.

The first mixing device 5 is composed of three sub-modules 14. Mixing elements 32 are arranged in each of the sub-modules 14, which may comprise static, mechanically driven or a combination of static and mechanically driven mixing elements.

Adjacent to the connecting flange 13 between the first mixing device 5 and the first pressure increasing device 12 is the mixing device 5 at the input end 30 of the first submodule 14 an injection port 29 is formed therein. This is connected via a corresponding connection line to the feed device 4 as a further individual module 10. By means of the feed device 4, a blowing agent can be added to the polymer melt fed from the extruder 8 and the first pressure increasing device 12 to the first mixing device 5. The feed device 4 can also be arranged directly on the mixing device 5.

A heating device 23 is embodied in the middle sub-module 14 of the first mixing device 5 as an example. Such a heating device can also be present in other individual or sub-modules.

A second pressure-increasing device 16 designed as a gear pump is connected to the last sub-module 14 of the first mixing device 5 in the transport direction 11 at the downstream end 15. This is also designed as a single module 10 with corresponding connection flanges 13 only indicated in principle.

A diffuser 17 is arranged between the second pressure increasing device 16 and a throttle 6 as a further individual module. This forms an individual module 10 composed of four sub-modules 14. Again, the corresponding connecting flanges 13 between the sub-modules and between them and the second pressure increasing device or throttle 6 are only indicated in principle.

In the first submodule 14, which follows the second pressure increasing device 16 in the transport direction 11, the diffuser 17 is formed with an additional mixing device 18. Such an additional or second mixing device 18 can also be designed as a separate module unit, see the third submodule 14 in the transport direction of the diffuser 17. Analogously to the first mixing device 5, the mixing device has corresponding mixing elements 32, which in turn are used as static see, mechanically driven or can be formed by a combination of static and mechanically driven mixing elements.

In the second sub-module 14 in the transport direction 11, a cooling device 24 is also arranged, which continues in the third and fourth sub-modules. Instead of a cooling device, a heating device can also be arranged in one or more of the sub-modules 14 of the diffuser 17 if required.

A further, third pressure increasing device 19 can be arranged as a single module 10 between the first and second submodule 14 of the diffuser 17, as is only shown in principle in FIG. 1.

It should be noted that further pressure booster devices can be arranged between the various individual or sub-modules if required.

The throttle 6 connects to the diffuser 17 as a further individual module 10. The throttle 6 has two rotatably driven, meshing gears 20 and 21. Regarding the mode of operation and control of such a throttle 6 for forming foamed polymer with a microcellular or submicrocellular structure, reference is again made to DE 19 521 520. Their technical teaching regarding such a choke is used analogously in the present invention.

In the transport direction 11, the throttle 6 is connected as a further individual module 10 to the extrusion tool 7, which can be constructed from further sub-modules, not shown.

The extrusion device 1 according to the invention also has a number of pressure sensors 22, speed sensors 27 and at least one temperature sensor 27. The pressure sensors 22 are arranged, in particular, on the respective inlet and outlet sides of the pressure booster devices 12, 16 and the throttle 6 either directly in these or in the connecting flanges arranged between them and the respectively preceding or following modules. The various pressure sensors 22 are specified in more detail as p1 to p6. The arrows shown indicate the signal flow from the pressure sensors 22 to a first control device 36 as a control module 31.

The speed sensors 27 are specified in more detail by vl to v4. The speed sensor 27 (v4) is assigned to the extrusion screw 2 of the extruder 8 and measures its speed. The further speed sensors 27 (vl to v3) are used to measure the speed of the pressure booster devices 12, 16, which are each designed as gear pumps, or the throttle 6, which is constructed analogously to a gear pump 12 measured from the extruder 8 polymer melt. Further, analog temperature sensors can, depending on requirements, be assigned to various other individual or sub-modules 10, 14 following in the transport direction 11.

The further arrows running between the different speed sensors 27 (vl to v4) and the temperature sensor 25 (Tl) identify the respective signal flow. In particular, the speed of the extrusion screw 2 and the respective gear wheels of the pressure increasing device 12, 16 and the throttle 6 can be controlled or regulated according to a predetermined program by the first control device 26.

For the controlled or regulated metering of propellant by the propellant supply device 4, this is connected to a second control device 28, as is characterized by the signal case arranged between the two. The second control device 28 is part of the extrusion device 1 according to the invention as a further control module 31. As shown by further signal arrows running in the direction of the second control device 28, the second control device 28 also receives signals from the speed sensors 27 (vl to v3).

The mode of operation of the extrusion device 1 according to the invention is briefly described below.

The device 1 comprises in particular a number of individual modules 10 and control modules 31, which each extruder 8 known per se for thermoplastic or thermoelastic plastics, such as Screw extruders with or without a grooved entry zone, twin screw extruders, screw presses or the like are connected downstream in the transport direction 11.

The polymer melted by the extruder 8 and fed to it via the feed device 3 is fed to the first pressure increasing device 12 at a certain temperature T1 and a certain pressure P6. In this, the pressure P6 of the polymer melt is raised to the pressure P5. A corresponding blowing agent is then metered into the polymer melt by the blowing agent supply device 4. This can be any mixture of gaseous substances at room temperature as well as a chemical blowing agent.

After the blowing agent has been metered in, this and the polymer melt are mixed in the first mixing device 5 by the corresponding mixing elements 32 and an essentially multiphase polymer / blowing agent mixture is formed. During the passage through the first mixing device, the pressure in the polymer / blowing agent mixture changes from p5 to p4. The pressure in the mixture is increased from p4 to p3 by the second pressure increasing device 16. In the subsequent diffuser 17, the generally still multi-phase polymer / blowing agent mixture is given sufficient time under the relatively very high pressure p3 to p2 to form a single-phase polymer / blowing agent solution. A second mixing device 18 with corresponding mixing elements 32 can be arranged within the diffuser 17 in order to further homogenize the polymer / blowing agent mixture or solution.

In the transport direction 11 following the diffuser 17, the polymer / blowing agent solution is passed through the throttle 6 and by means of which the pressure is suddenly reduced from p2 to pl. As a result, cell nuclei are generated in the polymer / blowing agent solution, see also DE 19 521 520, and phase separation is initiated. The polymer / blowing agent solution is then fed to the extrusion die 7, in which the cell nuclei now expand to larger cells due to a further drop in pressure.

The first control device 26 regulates or controls the speeds vl to v4 of the throttle 6, the pressure increasing devices 13, 16 and the extruder screw 2 of the extruder 8. The speed is regulated or controlled as a function of the pressures p1 to p6 and the other speeds from left to v4. The aim of the regulation or control is to keep each of the pressures pl to p6 at an individually desired level.

The second regulating device 28 regulates or controls the metering of the propellant from the feed device 4 as a function of the speeds vl to v3.

If further pressure-increasing devices 19 are inserted in the first mixing device 5 or in the diffuser 17, their speeds or inlet and outlet pressures can likewise be supplied to one or both of the control devices 26, 28. Depending on the pressures p1 to p6 and the amount of blowing agent supplied, the cell size, cell density and the absolute density of the end product delivered by the extrusion tool 7 can be set almost arbitrarily, see also DE 19 521 520 in this connection, whereby according to the invention due to the modular structure and the module-like expansion, the process conditions and parameters in the various individual and / or sub-modules can essentially be individually adjusted, see for example pressure, temperature and flow rate.

Claims

claims 1. extrusion device (1), in particular for producing a foamed polymer, with at least one extruder screw (2) for transporting at least one polymer added by a feed device (3), a feed device (4) for feeding a blowing agent after melting of the polymer, one Mixing device (5) for mixing polymer melt and blowing agent, a throttle (6) for generating a pressure drop in the polymer / blowing agent mixture supplied and an extrusion tool (7), characterized in that the extruder screw (2) and feed device (3) in an extruder ( 8) are arranged and feed device (4), mixing device (5), throttle (6) and extrusion tool (7) are designed as individual modules (10) which can be connected to the outlet end (9) of the extruder (8). 2. Extrusion device according to claim 1, characterized in that a first pressure increasing device (12), in particular a pump, is arranged at the discharge end (9) of the extruder (8) as a single module which can be connected downstream in the transport direction to the extruder. 3. Extrusion device according to claim 1 or 2, characterized in that connecting flanges (13) for connecting the extruder (8) and a single module or for connecting the individual modules (10) to one another and / or between them are arranged. 4. Extrusion device according to at least one of the preceding claims, characterized in that the mixing device (5) from sub-modules (14) is composed. 5. Extrusion device according to at least one of the preceding claims, characterized in that between the sub-modules (14) of the mixing device (5) and / or on in Transport direction downstream end (15) of the mixing device at least a second pressure increasing device (16), in particular a pump, is arranged. 6. Extrusion device according to at least one of the preceding claims, characterized in that between the mixing device (5) or second pressure increasing device (16) and throttle (6) at least one diffuser (17) designed as a single module (10) is arranged. 7. Extrusion device according to at least one of the preceding claims, characterized in that the individual module (10) forming the diffuser (17) is composed of sub-modules (14). 8. Extrusion device according to at least one of the preceding claims, characterized in that a second mixing device (18) is formed in the diffuser (17). 9. Extrusion device according to at least one of the preceding claims, characterized in that the second mixing device (18) is arranged in at least one sub-module (14) of the diffuser (17). 10. Extrusion device according to at least one of the preceding claims, characterized in that the second mixing device (18) and diffuser (17) are formed by separate sub-modules (14). 11. Extrusion device according to at least one of the preceding claims, characterized in that at least a third pressure increasing device (19), in particular a pump, is arranged between the sub-modules (14) for the second mixing device (18) and / or the diffuser (16). 12. Extrusion device according to at least one of the preceding claims, characterized in that the throttle (6) has at least two rotatably driven, intermeshing gear wheels (20, 21). 13. Extrusion device according to at least one of the preceding claims, characterized in that pressure sensors (22) are assigned at least to the input and output sides of the pressure increasing devices (12, 16, 19) and / or the throttle (6). 14. Extrusion device according to at least one of the preceding claims, characterized in that each pressure sensor (12) is arranged in a corresponding connecting flange (13). 15. Extrusion device according to at least one of the preceding claims, characterized in that a heating device (23) is arranged in at least one individual and / or sub-module (10, 14). 16. Extrusion device according to at least one of the preceding claims, characterized in that a cooling device (24) is arranged in at least one individual and / or sub-module (10, 14). 17. Extrusion device according to at least one of the preceding claims, characterized in that at least one temperature sensor (15) is associated with an individual and / or sub-module (10, 14). 18. Extrusion device according to at least one of the preceding claims, characterized in that the temperature sensor (15) is arranged in a connecting flange (13). 19. Extrusion device according to at least one of the preceding claims, characterized in that a first control device (26) can be connected to the pressure and temperature sensors (22, 25) for determining the respective pressures and temperatures. 20. Extrusion device according to at least one of the preceding claims, characterized in that the first control device (26) associated with the pressure increasing device (12, 16, 19) designed as gear pumps and / or the extruder (8) and / or the throttle (6) Speed transducers (27) can be connected. 21. Extrusion device according to at least one of the preceding claims, characterized in that the first control device (26) for metering the blowing agent can be connected to the blowing agent supply device (4). 22. Extrusion device according to at least one of the preceding claims, characterized in that a second control device (28) for metering the blowing agent can be connected to the blowing agent supply device (4). 23. Extrusion device according to at least one of the preceding claims, characterized in that the second control device (28) can be connected to the speed pickups (27) and / or the first control device (26). 24. Extrusion device according to at least one of the preceding claims, characterized in that an injection opening (29) connected to the blowing agent supply device (4) in a connecting flange (13), preferably at an inlet end (15) upstream in the transport direction of the first mixing device (5) is trained. 25. Extrusion device according to at least one of the preceding claims, characterized in that the mixing device (5, 18) has static or mechanically driven mixers or a combination of these mixers. 26. Extrusion device according to at least one of the preceding claims, characterized in that the extrusion tool (7) has a molding die and / or a fine drawing die and / or a cooling device. 27. Extrusion device according to at least one of the preceding claims, characterized in that the first and / or second control device (26, 28) are designed as a control module (31).