Device for processing plastics material

Abstract

The invention relates to a device (1) for plastics processing, comprising a housing (2) with a process chamber (5) formed therein, a first screw shaft (6), and a second screw shaft (7); wherein the device (1) has a conveying portion (11), an extrusion portion (14), and a mixer portion (17) arranged between the conveying portion (11) and the extrusion portion (14); wherein the first screw shaft (6) has a fifth screw flight (18) and the second screw shaft (7) has a sixth screw flight (19) in the mixer portion (17); wherein the first screw shaft (6) and the second screw shaft (7) do not mesh in the mixer portion (17).

Description

[0001] DEVICE FOR PROCESSING PLASTIC MATERIAL

[0002] The invention relates to a device for processing plastic material with a conveying section, an extrusion section and a mixer section for mixing the plastic material between the conveying section and the extrusion section.

[0003] A machine of the same type is known from EP 0 509 569 A2. This machine is used to produce thermoplastic polymers. The machine comprises a plurality of coaxial sections arranged one behind the other in the extrusion direction, formed integrally with one another, and forming a longitudinally extending chamber within them, in which a pair of cooperating coaxial screws is located. This machine further comprises a mixer section in a central region, wherein the screws in this region have an oval cross-section, are designed to mesh with one another and consequently interact to effect material mixing of the thermoplastic polymers.

[0004] A disadvantage of the embodiment known from the prior art is that the plastic material cannot be mixed gently in the mixer section, to the detriment of the material quality, and at the same time an avoidably high energy expenditure is required for the mixing in the mixer section.

[0005] The object of the present invention was to overcome the disadvantages of the prior art and to provide a device by means of which the efficiency of a generic machine is improved and plastic material can be mixed gently.

[0006] This object is achieved by a device and a method according to the claims.

[0007] The device according to the invention for processing plastic material, in particular for extruding granular plastic, comprises a housing with a longitudinal extension in an extrusion direction and with a process chamber formed therein, an integrally formed first screw shaft with a first longitudinal axis, and an integrally formed second screw shaft with a second longitudinal axis,

[0008] - wherein the first screw shaft and the second screw shaft are accommodated in the housing within the process chamber and the first longitudinal axis and the second longitudinal axis are aligned along the longitudinal extent, - wherein the device has a conveying section, wherein the first screw shaft has a first screw flight and the second screw shaft has a second screw flight meshing with the first screw flight in the conveying section,

[0009] - wherein the device has an extrusion section downstream of the conveying section in the extrusion direction, wherein the first screw shaft has a third screw flight and the second screw shaft has a fourth screw flight meshing with the third screw flight in the extrusion section, and

[0010] - wherein the device has a mixer section formed between the conveying section and the extrusion section, wherein the first screw shaft has a fifth screw flight and the second screw shaft has a sixth screw flight in the mixer section, characterized in that the first screw shaft and the second screw shaft are non-combing in the mixer section.

[0011] The term "intermeshing" means, for example, that the screw flights of the first screw shaft in the conveying section engage with the flights between the screw flights of the second screw shaft, whereby the screw flights do not necessarily touch each other, so that material can be processed between the intermeshing screw shafts and transported in the extrusion direction by the rotary motion initiated by driving the screw shafts with a drive device. A screw flight is also understood to be a helically running flight with a flight pitch and a flight height.

[0012] Furthermore, the term non-intermeshing refers to a pair of screw flights that are aligned with each other without collision or overlap, so that the respective screw flights do not interlock, but rather their respective envelopes touch each other or even have a distance from each other.

[0013] In particular, it can be provided that a first envelope surface of the first screw shaft in the mixer section has a minimum relative distance from a second envelope surface of the second screw shaft in the mixer section in the transverse direction to the extrusion direction, from a range comprising 0% to 10%, in particular 0% to 3%, relative to a first diameter of the first envelope surface. Specifically, the distance between the envelopes can only be the necessary tolerance to enable collision-free running of the screw shafts.

[0014] The advantage here is that the plastic material can be mixed effectively and gently in the mixer section in a simple manner. The screw shafts can be synchronously coupled in motion, whereby they can be driven individually or jointly via a gearing by one or more drive devices. In particular, the fifth and sixth screw flights in the mixer section can be designed such that sections thereof have a non-constant pitch across the extrusion direction, thus further improving mixability.In any case, the inventive design of the device for processing plastics extends the residence time of the plastic material in the mixer section in a simple and effective manner and brings about a kneading effect, so that not only gentle mixing is achieved, but also outgassing of gaseous substances from the plastic material processed into modeling clay is promoted.

[0015] It can also be provided that the fifth screw flight and the sixth screw flight have different pitches from each other, whereby it can again be advantageous if the respective pitch is not constant over the length of the mixer section in the extrusion direction.

[0016] Furthermore, it can be expedient if the clear passage cross-section of the process chamber in the region of the mixer section is larger than the region of the conveying section. In particular, it is conceivable that the clear passage cross-section, viewed in the extrusion direction, is equal to or larger than the cross-sectional area of ​​the envelope of the first screw shaft in the mixer section. This ensures particularly gentle mixing of the plastic material, so that the material properties and thus the material quality are maintained, among other things by preventing plastic material from sticking in the area between the screw flights and the wall of the process chamber. Furthermore, by appropriately minimizing friction caused by bridging, the energy required to mix the plastic material can be reduced, thus improving the efficiency of the plastics processing device.Furthermore, the fifth screw flight can be provided with a flight direction opposite to the extrusion direction, so that, by means of the fifth screw flight, a feed direction of the plastic material can be effected counter to the extrusion direction upon rotation of the first screw shaft. Thus, in operative connection with the sixth screw flight, a circular flow of the plastic material can be adjusted in the mixer section, so that further improved mixing of the plastic material can be achieved while still maintaining the previously mentioned advantageous effects.

[0017] Furthermore, it can be provided that a mixer sub-section is formed in the mixer section, wherein the first screw shaft comprises a seventh screw flight and the second screw shaft comprises an eighth screw flight in the mixer sub-section, wherein the eighth screw flight has a flight direction counter to the extrusion direction, so that by means of the eighth screw flight, a feed direction of the plastic material counter to the extrusion direction can be effected upon rotation of the second screw shaft. This causes a further circular flow of the plastic material, so that further improved mixing is achieved. It is certainly conceivable that further such mixer sub-sections are provided in the mixer section, wherein a circular flow is formed with a flow direction alternating in the extrusion direction to the nearest mixer sub-section.

[0018] Another advantageous embodiment is one in which the process chamber is tapered in the extrusion direction, and the first longitudinal axis and the second longitudinal axis are positioned at an angle to each other within an angular range of 0.1° to 5°, in particular 0.5° to 3°. This facilitates the plasticization of the plastic material in a simple manner, while, in particular, different mixing zones are created in the mixer section, which has an advantageous effect on gentle mixing and the best possible homogenization of the mixed plastic material. Alternatively, the process chamber can also be designed so as not to taper in the extrusion direction.

[0019] According to a further development, it is possible for the housing in the mixer section to comprise a first opening, wherein the first opening is formed in the direction of the first screw shaft, so that a first insertion element can be inserted into the first opening in the direction of the process chamber and positioned in the first opening, so that the clear passage cross-section can be reduced by means of the first insertion element. In this way, in operative connection with the screw flight of the first screw shaft, the recirculation rate and thus the mixing of the plastic material can be easily increased or improved.

[0020] Furthermore, it can be expedient if the housing in the mixer section comprises a second opening, wherein the second opening is formed in the direction of an intermediate region between the first screw shaft and the second screw shaft, such that a second insertion element can be inserted into the second opening in the direction of the process chamber and positioned in the second opening, such that the clear passage cross-section can be reduced by means of the second insertion element. Particularly in the case of co-rotating screw shafts, this measure, in operative connection with both screw flights of the first and second screw shaft, can easily increase or improve the return conveyance proportion and thus the mixing of the plastic material. In this way, the conveying proportion of the plastic material in the extrusion direction through the mixer section can also be determined to a large extent.

[0021] Furthermore, it can be provided that the second insertion element, when positioned in the second opening, has a wedge-shaped cross-section facing the process chamber in a plane normal to the extrusion direction. In particular, it can be provided that the insertion element is wedge-shaped on its longitudinal side facing the screw shafts, wherein a contour of the wedge-shaped longitudinal side is formed at least in sections to be complementary in shape to the first envelope surface of the first screw shaft and to the second envelope surface of the second screw shaft in the mixer section. As a result, the return flow rate can be further increased or changed accordingly in sections in the region of the insertion element in order to further effectively increase mixing.

[0022] Furthermore, it can be provided that the insertion element, when positioned in the opening provided for it, has a wave-shaped contour along the extrusion direction on its long side facing the process chamber. This implements a further measure for improved mixing of the plastic material. In particular, it can also be provided that a sawtooth profile is formed instead of the wave-shaped contour, thereby increasing the conveying portion in the extrusion direction. In accordance with these embodiments, it can also be provided that the side surfaces of the insertion element(s) protruding into the process chamber have corresponding contours that promote mixing or conveying in a specific direction.Likewise, tapered contours can also be provided so that the transitions of the insertion elements projecting into the process chamber to the wall of the process chamber are designed to run continuously, thus avoiding dead areas for gripping the plastic material.

[0023] According to a particular embodiment, it is possible for the insertion element to be designed to completely close the opening, wherein the insertion element comprises a degassing device for removing gases from the process chamber and / or an additive supply device for supplying additives into the process chamber. Particularly in the area of ​​the mixer section, it can be advantageous if additives can be supplied so that they can be effectively mixed into the plastic material. It can also be particularly advantageous in this section if openings are provided for degassing the plastic material.

[0024] According to an advantageous development, the aperture can be provided with a longitudinal extension in the direction of extrusion, wherein the insertion element can be assembled from insert elements arranged in a row in the extrusion direction. This measure makes it easy to achieve a variable penetration depth of the insertion elements across the extrusion direction. This allows the mixing to be adjusted in specific areas according to the requirements for the degree of mixing and also in combination with specific material properties for different plastic materials, insofar as the device can also be used for different plastic materials.

[0025] In particular, it can be advantageous if the penetration depths of the first insertion element and / or the second insertion element, or individual insertion elements, can be adjusted or adjusted by means of a control and regulating device in the openings provided for this purpose. This allows the mixing of the plastic material to be easily adapted to changing operating parameters, such as changing the plastic material, adding additives, degassing, or, for example, starting up the device for continuous operation. For a better understanding of the invention, it is explained in more detail with reference to the following figures.

[0026] They show in a highly simplified, schematic representation:

[0027] Fig. 1 shows a longitudinal section through a possible embodiment of the device for plastics processing;

[0028] Fig. 2 shows a cross section through the design of the device for plastics processing in the area of ​​the mixer section.

[0029] By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or component designations. The disclosures contained throughout the description can be applied analogously to identical parts with identical reference symbols or component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., refers to the directly described and illustrated figure, and these positional information must be applied analogously to the new position in the event of a change in position.

[0030] Fig. 1 shows a longitudinal section through a possible embodiment of the device 1 for plastics processing in a highly simplified, schematic representation.

[0031] In Fig. 2, a highly simplified and schematic representation of a cross section through the possible embodiment of the device 1 for plastics processing is shown, wherein again the same reference numerals or component designations are used for the same parts as in the previous Fig. 1.

[0032] The device 1 can comprise a housing 2 with a longitudinal extension 3 in an extrusion direction 4 and with a process chamber 5 formed therein, an integrally formed first screw shaft 6 with a first longitudinal axis 8, and an integrally formed second screw shaft 7 with a second longitudinal axis 9, wherein the first screw shaft 6 and the second screw shaft 7 are received in the housing 2 within the process chamber 5 and the first longitudinal axis 8 and the second longitudinal axis 9 are aligned along the longitudinal extension 3. In particular, it can be provided that the process chamber 5 is tapered in the extrusion direction 4 and the first longitudinal axis 8 and the second longitudinal axis 9 are positioned to one another at an angle 10 from an angular range comprising 0.1° to 5°, in particular 0.5° to 3°.However, this does not necessarily have to be the case, since an alternative embodiment of the device 1 is also conceivable in which the first longitudinal axis 8 and the second longitudinal axis 9 are aligned parallel to one another.

[0033] The device 1 can further comprise a conveying section 11, wherein the first screw shaft 6 can comprise a first screw flight 12 and the second screw shaft 7 can comprise a second screw flight 13 meshing with the first screw flight 12 in the conveying section 11.

[0034] The device 1 can also have an extrusion section 14 downstream of the conveying section 11 in the extrusion direction 4, wherein the first screw shaft 6 has a third screw flight 15 and the second screw shaft 7 has a fourth screw flight 16 in the extrusion section 14, meshing with the third screw flight 15.

[0035] The device 1 can also have a mixer section 17 formed between the conveying section 11 and the extrusion section 14, wherein the first screw shaft 6 has a fifth screw flight 18 and the second screw shaft 7 has a sixth screw flight 19 in the mixer section 17. It can be provided that the first screw shaft 6 and the second screw shaft 7 are not intermeshing in the mixer section 17, i.e. that a first envelope surface 20 of the first screw shaft 6 in the mixer section 17 has a minimum relative distance 22 from a range comprising 0% to 10%, in particular 0% to 3% relative to a first diameter 23 of the first envelope surface 20 to a second envelope surface 21 of the second screw shaft 7 in the mixer section 17 in the transverse direction to the extrusion direction 4. This ensures that the first screw shaft 6 and the second screw shaft 7 in the mixer section 17 are non-combing.

[0036] Furthermore, this and the design of the process chamber 5 in the mixer section 17 result in a clear passage cross-section 24 of the process chamber 5 in the region of the mixer section 17 being larger relative to the region of the conveyor section 11. This results in particularly gentle mixing of the plastic material, so that the material properties and thus subsequently the material quality are maintained, among other things by avoiding the plastic material from sticking in the area between the screw flights 18 and 19 and the wall 25 of the process chamber 5. Furthermore, by appropriately minimizing friction caused by bridging, the energy required to mix the plastic material can be reduced, thus improving the efficiency of the plastics processing device.

[0037] It can also be provided that the fifth screw flight 18 has a flight direction opposite to the extrusion direction 4, so that, by means of the fifth screw flight 18, a feed direction of the plastic material can be effected opposite to the extrusion direction 4 upon rotation of the first screw shaft 6. This can achieve a circular flow of the plastic material in operative connection with the sixth screw flight 19. This is particularly possible in the present embodiment if the screw shafts 6 and 7 rotate in the same direction.

[0038] Furthermore, it can also be provided that a mixer section 26 is formed in the mixer section 17, wherein the first screw shaft 6 comprises a seventh screw flight 27 and the second screw shaft 7 comprises an eighth screw flight 28 in the mixer section 26, wherein the eighth screw flight 28 has a flight direction counter to the extrusion direction 4, so that by means of the eighth screw flight 28, a feed direction of the plastic material counter to the extrusion direction 4 can be effected upon rotation of the second screw shaft 7. This ensures that the first screw shaft 6 within the mixer section 17, viewed in the extrusion direction 4, initially has a flight direction counter to the extrusion direction 4 and then, namely in the mixer section 26, has a flight direction in the direction of the extrusion direction 4.Likewise, the second screw shaft 7 within the mixer section 17, viewed in the extrusion direction 4, can initially have a flight direction in the direction of extrusion 4 and then, in the extrusion direction 4, namely in the mixer section 26, have a flight direction opposite to the extrusion direction 4. This creates circular flows, on the one hand, in the mixer section 26 and, on the other hand, in the remaining area of ​​the mixer section 17, which promote the mixing of the plastic material.

[0039] Furthermore, it can be provided that the housing 2 in the mixer section 17 comprises a first opening 29, wherein the first opening 29 is formed in the direction of the first screw shaft 6, so that a first insertion member 30 can be inserted into the first opening 29 in the direction of the process chamber 5 and can be positioned in the first opening 29, so that the clear passage cross-section 24 can be reduced by means of the first insertion member 30. Furthermore, it can also be provided that the housing 2 in the mixer section 17 comprises a second opening 31, wherein the second opening 31 is formed in the direction of an intermediate region 32 between the first screw shaft 6 and the second screw shaft 7, so that a second insertion member 33 can be inserted into the second opening 31 in the direction of the process chamber 5 and can be positioned in the second opening 31, so that the clear passage cross-section 24 can be reduced by means of the second insertion member 33.It can be advantageous if the second insertion element 33, when positioned in the second opening 31, has a wedge-shaped cross-section facing the process chamber 5 in a plane normal to the extrusion direction 4. Furthermore, it can also be advantageous for the respective insertion element 30 and / or 33, when positioned in the opening 29 or 31 provided for it, to have a wave-shaped contour on its long side facing the process chamber 5 along the extrusion direction 4. In the embodiment described here, both openings 29 and 31 are provided, so that both insertion elements 30 and 33 could each have a wave-shaped contour. However, embodiments of the device 1 are also conceivable in which only one of the two openings 29 and 31 is provided and thus only one of the otherwise possible two insertion elements 30 and 33 can be inserted.

[0040] It can also be provided that the insertion member 30 or 33 is designed to completely close the opening 29 or 31, wherein the first insertion member 30 can have a degassing device 34 for removing gases from the process chamber 5.

[0041] Furthermore, it can also be provided that the opening 29 or 31 has a longitudinal extension 3 in the direction of the extrusion direction 4, wherein the insertion member 30 or 33 can be assembled from insertion elements 35 arranged in a row in the extrusion direction 4. Finally, it can also be useful with this measure if the first insertion member 30 and / or the second insertion member 33 or individual insertion elements can be set or adjusted in their penetration depths in the openings 29 or 31 provided for this purpose by means of a control and regulating device.

[0042] The embodiments show possible embodiments, whereby it should be noted at this point that the invention is not limited to the specifically illustrated embodiments thereof, but rather various combinations of the individual embodiments with each other are also possible and this possibility of variation lies within the skill of the person skilled in the art in this technical field due to the teaching of technical action by means of the objective invention.

[0043] The scope of protection is determined by the claims. However, the description and drawings must be used to interpret the claims. Individual features or combinations of features from the various embodiments shown and described may represent independent inventive solutions. The problem underlying these independent inventive solutions can be derived from the description.

[0044] All information on value ranges in this description is to be understood as including any and all sub-ranges thereof, e.g. the information 1 to 10 is to be understood as including all sub-ranges starting from the lower limit of 1 and the upper limit of 10, ie all sub-ranges begin with a lower limit of 1 or greater and end with an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

[0045] For the sake of clarity, it should finally be pointed out that, in order to better understand the structure, some elements have been shown out of scale and / or enlarged and / or reduced in size.

[0046] Reference symbols

[0047] Device 32 intermediate area

[0048] Housing 33 Second insert element

[0049] Longitudinal extension 34 Degassing device

[0050] Extrusion direction 35 insert elements

[0051] Trial Chamber

[0052] First worm shaft

[0053] Second worm shaft

[0054] First longitudinal axis

[0055] Second longitudinal axis

[0056] angle

[0057] Funding section

[0058] First snail bridge

[0059] Second snail bridge

[0060] Extrusion section

[0061] Third snail bridge

[0062] Fourth snail bridge

[0063] Mixer section

[0064] Fifth snail bridge

[0065] Sixth snail web

[0066] First enveloping surface

[0067] Second enveloping surface

[0068] Relative distance

[0069] First diameter

[0070] Clear passage cross-section

[0071] Wall of the process chamber

[0072] Mixer section

[0073] Seventh snail bridge

[0074] Eighth snail bridge

[0075] First breakthrough

[0076] First insertion organ

[0077] Second breakthrough

Claims

Patent claims 1. Device (1) for processing plastic material, in particular for extruding granular plastic, comprising a housing (2) with a longitudinal extension (3) in an extrusion direction (4) and with a process chamber (5) formed therein, an integrally formed first screw shaft (6) with a first longitudinal axis (8), and an integrally formed second screw shaft (7) with a second longitudinal axis (9), - wherein the first screw shaft (6) and the second screw shaft (7) are accommodated in the housing (2) within the process chamber (5) and the first longitudinal axis (8) and the second longitudinal axis (9) are aligned along the longitudinal extension (3), - wherein the device (1) has a conveying section (11), wherein the first screw shaft (6) has a first screw flight (12) and the second screw shaft (7) has a second screw flight (13) meshing with the first screw flight (12) in the conveying section (11), - wherein the device (1) has an extrusion section (14) downstream of the conveying section (11) in the extrusion direction (4), wherein the first screw shaft (6) has a third screw flight (15) and the second screw shaft (7) has a fourth screw flight (16) meshing with the third screw flight (15) in the extrusion section (14), and - wherein the device (1) has a mixer section (17) formed between the conveying section (11) and the extrusion section (14), wherein the first screw shaft (6) has a fifth screw flight (18) and the second screw shaft (7) has a sixth screw flight (19) in the mixer section (17), characterized in that the first screw shaft (6) and the second screw shaft (7) are non-combing in the mixer section (17).

2. Device (1) according to claim 1, characterized in that a first enveloping surface (20) of the first screw shaft (6) in the mixer section (17) has a minimum relative distance (22) from a range comprising 0% to 10%, in particular 0% to 3% relative to a first diameter (23) of the first enveloping surface (20).

3. Device (1) according to one of the preceding claims, characterized in that a clear passage cross-section (24) of the process chamber (5) in the region of the mixer section (17) is enlarged relative to the region of the conveying section (11).

4. Device (1) according to one of the preceding claims, characterized in that the fifth screw flight (18) has a flight direction opposite to the extrusion direction (4), so that by means of the fifth screw flight (18) a feed direction of the plastic material opposite to the extrusion direction (4) can be effected upon rotational movement of the first screw shaft (6).

5. Device (1) according to one of the preceding claims, characterized in that a mixer section (26) is formed in the mixer section (17), wherein the first screw shaft (6) comprises a seventh screw flight (27) and the second screw shaft (7) comprises an eighth screw flight (28) in the mixer section (26), wherein the eighth screw flight (28) has a flight direction counter to the extrusion direction (4), so that by means of the eighth screw flight (28) a feed direction of the plastic material counter to the extrusion direction (4) can be effected upon rotation of the second screw shaft (7).

6. Device (1) according to one of the preceding claims, characterized in that the process chamber (5) is tapered in the extrusion direction (4) and the first longitudinal axis (8) and the second longitudinal axis (9) are positioned to one another at an angle (10) from an angular range comprising 0.1° to 5°, in particular 0.5° to 3°.

7. Device (1) according to one of the preceding claims, characterized in that the housing (2) in the mixer section (17) comprises a first opening (29), wherein the first opening (29) is formed in the direction of the first screw shaft (6), so that a first insertion member (30) can be inserted into the first opening (29) in the direction of the Process chamber (5) can be inserted and positioned in the first opening (29) so that the clear passage cross-section (24) can be reduced by means of the first insertion member (30).

8. Device (1) according to one of the preceding claims, characterized in that the housing (2) in the mixer section (17) comprises a second opening (31), wherein the second opening (31) is formed in the direction of an intermediate region (32) between the first screw shaft (6) and the second screw shaft (7), so that a second insertion element (33) can be inserted into the second opening (31) in the direction of the process chamber (5) and can be positioned in the second opening (31), so that the clear passage cross-section (24) can be reduced by means of the second insertion element (33).

9. Device (1) according to claim 8, characterized in that the second insertion member (33), when the second insertion member (33) is positioned in the second opening (31), has a wedge-shaped cross-section facing the process chamber (5) in a normal plane to the extrusion direction (4).

10. Device (1) according to one of claims 7 to 9, characterized in that the insertion member (30 or 33), when positioned in the opening (29 or 31) provided for it, has a wave-shaped contour on its longitudinal side facing the process chamber (5) along the extrusion direction (4).

11. Device (1) according to one of claims 7 to 10, characterized in that the insertion member (30 or 33) is designed to completely close the opening (29 or 31), wherein the insertion member (30 or 33) comprises a degassing device (34) for removing gases from the process chamber (5) and / or an additive supply device for supplying additives into the process chamber (5).

12. Device (1) according to one of claims 7 to 11, characterized in that the opening (29 or 31) has a longitudinal extension (3) in the direction of the extrusion direction (4), wherein the insertion member (30 or 33) can be assembled from insertion elements (35) arranged in a row in the extrusion direction (4).

13. Device (1) according to claim 12, characterized in that the first insertion member (30) and / or the second insertion member (33) or individual insertion elements can be set or adjusted by means of a control and regulating device in their penetration depths in the openings (29 or 31) provided for this purpose.

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