Device for granulating PVC, and corresponding method

Abstract

The invention relates to a device for granulating plastics, preferably PVC, comprising: an extruder (1) for melting plastic; a granulating head (2) for dividing the melt into a plurality of individual strands; a granulator (3) for cutting the individual strands into granules or pellets; and a feed shoe (4) to which an air stream is applied in order to convey the granules to the next processing step. The feed shoe (4) comprises a first section (I) having an inlet opening (9) for supplying the granules or pellets, or a mixture of conveying air and granules or pellets, and a second section (II) for supplying the air stream (10), wherein an inlet nozzle (11) in the form of a conical section is provided for the air stream (10), wherein the conical section tapers in the direction of the air stream (10) and adjoins the first section (I) of the feed shoe (4). The feed shoe (4) also comprises a third section (III) having an outlet opening (8), the cross-section of which widens in the conveying direction (14) of the granules or pellets. According to the invention, at least one recess (13) is provided in the transition region from the second section (II) to the first section (I). The invention also relates to a corresponding method.

Description

[0001] Device for PVC granulation and a corresponding method

[0002] Description:

[0003] The invention relates to a device for granulating plastic, preferably PVC, comprising an extruder for melting plastic, a granulating head for dividing the melt into a plurality of individual strands, a granulator for separating the individual strands into granules or grains, a feed shoe which is supplied with an airflow to feed the granules to the next process step, the feed shoe having a first section comprising an inlet opening for feeding the granules or grains or a mixture of conveying air with granules or grains, and a second section for supplying the airflow, wherein an inlet nozzle designed as a cone section is provided for the airflow, the cone section tapering in the direction of the airflow and adjoining the first section of the feed shoe, further comprising a third section having an outlet opening.which increases in cross-section in the conveying direction of the granules or grains, as well as a related method.

[0004] An arrangement for granulating, in particular, polymer material, comprising a feed or plasticizing unit and a granulation unit with a perforated plate and a cutter head that separates the molten polymer material, is known. In these devices, the separated material, in the form of granules or grains, is fed to a feed shoe and subsequently conveyed to the downstream process by means of an air stream.

[0005] The familiar dispensing shoes have a dead space in which material deposits typically accumulate. When these deposits clump together, they can be very difficult to remove. Temperature-sensitive materials can be exposed to excessively high temperatures for too long, which can lead to material damage. If, for example, color-sensitive materials are being processed, very thorough cleaning is required between batches.

[0006] The purpose of the invention is to further develop a feed shoe in which the known weaknesses are eliminated and which can still convey with a sufficiently large mass throughput during granulation.

[0007] The solution to the problem relating to the device is characterized in connection with the preamble of claim 1 in that at least one recess is provided in the transition area from the second section to the first section.

[0008] Registration_BCG161 DE docx BCG 161 DE Sep-24 This recess prevents a dead space in the transition area, as the airflow from the second section into the first section creates a kind of suction effect and thus carries granules or grains along with it.

[0009] According to the further development plan, the recess is provided in the bottom area of ​​the first section, or several recesses are provided in the transition area between the second and first sections. This ensures that the bottom area of ​​the first section is also subject to flow, thereby selectively conveying any granules or grains located there. This can be further enhanced by incorporating additional recesses in this transition area. These recesses can also be designed as slots or bores, depending on what is most suitable from a fluid dynamics perspective.

[0010] To optimize the flow characteristics, a further development phase envisages the inlet nozzle having a specially designed inlet and outlet contour for the airflow. This could include, for example, the length of the conical section and / or the inlet and outlet diameters of the inlet nozzle.

[0011] This advantageously ensures that the bottom area is designed in such a way that there is a largely smooth transition from the second section to the first section, with this transition being designed according to fluid dynamic principles.

[0012] Furthermore, this ensures that the first and second sections are designed in such a way as to create a vacuum, thus conveying any granules or grains located in the soil, as described above. This is particularly effective if the design creates a Venturi effect.

[0013] It is highly advantageous if the inlet opening area is as large as possible, thus ensuring a smooth transition to the lower part of the first section. A rectangular shape is preferred, and the rectangle may have rounded corners, thereby avoiding any sharp edges. This results in the interior of the first section being largely free of edges or corners and consequently offering optimal airflow.

[0014] The solution to the problem with regard to the method, in conjunction with the preamble of claim 8, is characterized in that the feed shoe is designed such that an airflow is supplied via a second section, through which a negative pressure prevails in a first section, whereby the granules or grains that are supplied to the feed shoe via the inlet opening are additionally drawn in, besides the prevailing gravity.

[0015] BCG 161 DE Sep-24 and are fed to the next process step via the third section of the task shoe.

[0016] The airflow supplied via the second section conveys the granules or grains fed in the first section across the third section; due to the design of the feed shoe, a negative pressure is already generated at the inlet opening of the first section, which supports the feeding of the granules or grains.

[0017] Advantageously, the flow behavior from the second section through the first section to the third section is designed in such a way that a Venturi effect is created, which supports the carrying of the granules or grains even from areas that are not directly exposed to the airflow.

[0018] Due to the design of the feed shoe, even higher temperatures and stickier granules or grains can be conveyed, as the airflow directly surrounds the granules or grains and delivers them to the next process step. This largely prevents them from remaining in the feed shoe.

[0019] The drawings schematically show a device according to the invention:

[0020] Fig. 1 Schematic diagram of the system

[0021] Fig. 2 3D sketch of the application shoe

[0022] Fig. 3 Side view of the task shoe

[0023] Fig. 4 Section through the feed shoe

[0024] Fig. 5 Section through the feed shoe

[0025] Fig. 6 Rotated 3D view of the application shoe

[0026] Figure 1 shows a schematic diagram of the system. Plastic material to be granulated is fed into extruder 1, melted there, and transferred to a granulating head 2. In the granulator 3, the plastic mass, divided into several individual strands, is cut into granules or grains by a blade. The granules or grains then enter a feed shoe 4, from which they are fed to a granule cooler 5 and a collection container 7. The schematic path of the plastic is shown by the dotted line 6.

[0027] Figure 2 shows a 3D sketch of the feed shoe 4. The feed shoe 4 comprises a first section I into which the granules or grains are fed from the granule gate 3 to the feed shoe 4 via the inlet opening 9. The second section II of the feed shoe 4 comprises an inlet nozzle 11 through which an airflow 10 flows through the feed shoe 4. The airflow 10

[0028] BCG 161 DE Sep-24 already generates a negative pressure at the inlet nozzle 11, thus assisting the feeding of the granules or grains. Depending on the embodiment, a mixture of conveying air and the granules or grains can already be supplied to the feed shoe 4 at this point. The airflow 10 conveys the granules or grains via the third section III to the next process step. Both the second section II and the third section III are conical in shape. The second section II tapers in diameter in the conveying direction 14, while the third section III, which has an outlet opening 8, increases in diameter in the conveying direction 14. Figure 3 is a side view of the feed shoe 4. Next to the inlet opening 9, a recess 13 and the bottom area 12 of the first section I are visible. Furthermore, the sectional view AA is shown according to the illustration in Figure 4.

[0029] Figure 4 shows a section through the feed shoe 4 as shown in Figure 3. Granules or grains are fed into the first section I of the feed shoe 4 via the inlet opening 9. The interior 15 of the first section I of the feed shoe 4 is designed so that it is largely smooth from the inlet nozzle 11 to the bottom section 12, with as few corners or edges as possible. In particular, the bottom section 12 has no undercuts due to a recess 13, thus eliminating dead spaces. An airflow 10 is supplied through the inlet nozzle 11 to the second section II of the feed shoe 4, conveying the fed granules or grains via the third section III and the outlet opening 8 to the next process step. The conveying direction is indicated by position number 14. The marked section BB corresponds to the section shown in Figure 5.

[0030] Figure 5 largely corresponds to the view shown in Figure 2, but with a section through the first section I of the feed shoe 4. This clarifies the smooth contour of the inner area 15. The inlet opening 9, the bottom area 12, and the recess 13 are shown analogously to the other figures.

[0031] Figure 6 shows a 3D view of the feed shoe 4 in a rotated view. This illustrates that in the transition area from the second section II to the first section I, a recess 13 is present in the base area 12 of the first section I. This transition area may also have further recesses 13 (not shown here). These can be designed as slots or bores.

[0032] The invention proposes a feed shoe in which dead spaces are avoided and sufficiently large masses can be conveyed during granulation.

[0033] BCG 161 DE Sep-24 Reference List:

[0034] 1 extruder

[0035] 2 granulating heads

[0036] 3 Granulator

[0037] 4 task shoe

[0038] 5 granule coolers

[0039] 6 Schematic diagram of the plastic

[0040] 7 collection containers

[0041] 8 Outlet opening

[0042] 9 Entrance opening

[0043] 10 Airflow

[0044] 11 Inlet nozzle

[0045] 12 Floor area of ​​I

[0046] 13 recess

[0047] 14 F conveying direction

[0048] 15 Interior of I

[0049] I first section of 4

[0050] II second section of 4

[0051] III third section of 4

[0052] BCG 161 DE Sep-24

Claims

6 Patent claims:

1. Device for granulating plastic, preferably PVC, comprising an extruder (1) for melting plastic, a granulating head (2) for dividing the melt into a plurality of individual strands, a granulator (3) for separating the individual strands into granules or grains, a feed shoe (4) supplied with an airflow to feed the granules to the next process step, the feed shoe (4) having a first section (I) comprising an inlet opening (9) for feeding the granules or grains or a mixture of conveying air with granules or grains, and a second section (II) for supplying the airflow (10), wherein an inlet nozzle (11) designed as a conical section is provided for the airflow (10), the conical section tapering in the direction of the airflow (10) and adjoining the first section (I) of the feed shoe (4),Furthermore, the feed shoe (4) comprises a third section (III) which has an outlet opening (8) that increases in cross-section in the conveying direction (14) of the granules or grains, characterized in that at least one recess (13) is provided in the transition area from the second section (II) to the first section (I).

2. Device according to claim 1, characterized in that the recess (13) is provided in the bottom area (12) of the first section (I) or that several recesses are provided in the transition area from the second section (II) to the first section (I).

3. Device according to claim 1 or 2, characterized in that the recess (13) is designed as a slot or bore.

4. Device according to at least one of the preceding claims, characterized in that the inlet nozzle (11) for the airflow (10) has a specially adapted inlet and outlet contour.

5. Device according to at least one of the preceding claims, characterized in that the bottom area (12) is designed such that there is a largely smooth transition from the second section (II) to the first section (I), wherein this transition is designed according to fluid dynamic principles.

6. Device according to at least one of the preceding claims, characterized in that the first section (I) and the second section (II) are designed such that a vacuum with Venturi effect is created.

7. Device according to at least one of the preceding claims, characterized in that the first section (I) in the area of ​​the inlet opening (9) is rectangular. BCG 161 DE Sep-24 8. Method for granulating plastic, preferably PVC, in which plastic is melted in an extruder (1), divided into a plurality of individual strands in a granulating head (2) and fed to a granulator (3) for separation, whereby granules or grains are produced which are fed to a feed shoe (4), characterized in that the feed shoe (4) is designed such that an airflow (10) is supplied via a second section (II), through which a negative pressure prevails in a first section (I), whereby the granules or grains which are fed to the feed shoe (4) via the inlet opening (9) are additionally drawn in besides the prevailing gravity and are fed to the next process step via the third section (III) of the feed shoe (4).

9. A method according to claim 8, characterized in that the flow behavior from the second section (II) through the first section (I) to the third section (III) corresponds to the Venturi effect.

10. A method according to claim 8 or 9, characterized in that, due to the design of the feed shoe (4) according to claim 1, even higher-temperature and sticky granules or grains are conveyed. BCG 161 DE Sep-24

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