WO2005044532A2

WO2005044532A2 - Device and method for granulation of materials with thermoplastic properties and granulating die plate for arrangement in such a granulation device

Info

Publication number: WO2005044532A2
Application number: PCT/AT2004/000391
Authority: WO
Inventors: Johann Brandstätter
Original assignee: Starlinger & Co Gesellschaft M.B.H.
Priority date: 2003-11-05
Filing date: 2004-11-04
Publication date: 2005-05-19
Also published as: WO2005044532A3; AT505894B1; AT505894A1

Abstract

The invention relates to a granulation die (5, 15), for arrangement on a device (1), for the granulation of materials with thermoplastic properties, in particular, thermoplastic plastics, comprising several melt channels (3), embodied as through openings which are individually or collectively at least partly surrounded by temperature control elements (11, 21). The temperature control elements can be embodied as heating or cooling elements which permit the targeted congealing, or holding open of individual melt channels.

Description

Granulating device and granulating perforated plate

The invention relates to a device for granulating substances with thermoplastic behavior, in particular thermoplastic plastics, and to a granulating perforated plate for arrangement in the granulating device.

The invention further relates to a method for granulating substances with thermoplastic behavior, in particular thermoplastic plastics, comprising producing a melt of the substance with thermoplastic behavior, feeding the melt to a melt distributor for distributing the melt to a plurality of melt channels formed in a pelletizing die plate, and the like Cutting off pieces of the melt as they emerge from the melt channels of the pelletizing die, followed by cooling the cut off pieces of melt until solidification.

Granulation devices and processes for the production of granules from substances with thermoplastic behavior can in principle be divided into the following categories.

Low-viscosity substances, such as B. polyethylene (PE) or PVC, can be granulated by a so-called air granulation process, which is used in particular in an output range of up to 100 kg per hour. Individual strands of the molten material, which emerge from the melt channels of a perforated plate, are cut with knives running on the end face of this perforated plate. The resulting disks or balls are thrown away from the knife by the centrifugal force and thereby introduced into a continuous air stream in which they are cooled until their surface has solidified.

A water ring granulation process works similarly, in which the strands of the molten material are cut into granules in an air atmosphere when they exit the perforated plate in the hot state and the granules are thrown into a continuously circulating water stream by means of the centrifugal force exerted by the knives and cooled and therein then the solidified granules are separated again from the water flow on a sieve or a centrifuge.

In the case of underwater pelletizing, the perforated plate is in a continuous stream of water, so that the actual granulation process, ie the cutting of the melt strands emerging from the perforated plate into granules, takes place in the water. By the Water the granules are lifted from the knife and transported to a sieve or a centrifuge.

A disadvantage of all these pelletizing systems, however, is that the speed of the knife rotating on the end face of the perforated plate and thus the length of the pellet can only be changed within certain limits. The reasons for this are described below.

In the case of air granulation and water ring granulation, in which the actual cutting process takes place in an air atmosphere, the granules must be thrown off the knife by the centrifugal force. Since the centrifugal force on the individual granules increases quadratically with the speed of the knife, the highest possible knife speed is desirable during the granulating process. However, since, on the other hand, a predetermined shape of the granulate is to be achieved, the melt channels, in particular their number and the cross section of their outlet openings in the perforated plate, must be matched to the respective throughput of the granulation system. However, it is also desirable to keep the pressure build-up of the perforated plate to an upstream extruder, which generates the melt and feeds it to the perforated plate via a melt distributor, in order to minimize thermal damage to the plastic melt in the extruder, since the pressure increases the temperature of the melt also rises. Thus, the requirements for minimal thermal degradation with the lowest possible pressure build-up on the perforated plate to achieve the least possible thermal damage to the material to be granulated and the demand for the highest possible blade speed during granulation in order to prevent the granules from sticking to the knife and thus preventing chain formation , contradict each other.

Another important parameter during granulation is the type of melt to be granulated or which additives have been added to the melt. In general, it can be said that low-viscosity materials, such as PE or PVC, are easy to granulate at a low knife speed, while higher-viscosity materials, such as polypropylene (PP) or polyamide (PA), have to be granulated with a higher knife speed. During underwater pelletizing, the pellets are washed away from the knife by the continuous flow of water. This type of granulation is therefore largely independent of the knife speed. Nevertheless, the number and cross-section of the outlet bores must be precisely matched to the material to be processed or the throughput, since it, especially when the enthalpy values of the plastic melt are low, e.g. B. in polyethylene terephthalate (PET), with a too low throughput of the melt through the outlet bores to a "freezing" of individual holes, that is the partial or complete blockage of the holes by solidified melt due to cooling of the melt below its solidification point.

This freezing of the outlet bores can lead to deformed granules, uneven granules, a high proportion of dust in the granules until the granulating device comes to a complete standstill.

In order to improve this freezing behavior in the case of underwater pelletizing, it has already been proposed to prevent the individual holes from cooling and freezing by means of better thermal separation by means of an insulating layer. From WO 03/031132 AI, for example, a pelletizing plate is known in which the end face of the pelletizing plate facing the knives is constructed from a ceramic layer, which is a poor temperature conductor.

From EP 0 739 700 B1 an underwater pelletizing plate with a wear protection layer is known, in which a thin insulating layer is provided between the actual pelletizing plate and a wear protection layer, which forms a running surface for the knives, whereby conical melt channels are used to try to get as much as possible Bring the melt close to the face of the pelletizing plate and thus prevent the holes from freezing.

All of these approaches help to a certain extent, but the number of holes and the outlet cross-section in the pelletizer plates have to be matched to the material to be processed and the throughput within relatively narrow tolerances. This means that each time the material to be granulated is changed, granulating devices have to be converted by attaching a granulating perforated plate that is matched to the material to the granulating device.

When processing melts with very different viscosity values such as HDPE and PET on an extruder (compounding company), the high Pressure build-up of HDPE on a PET perforated plate for increased energy consumption and high thermal damage to the melt. A longer changeover process of the granulating device (changing the perforated plate or closing individual melt channels) is essential.

The present invention has set itself the task of improving the above-mentioned disadvantages of known granulating devices in that a wide variety of materials and throughputs can be processed in a granulating device without changing the granulating perforated plate. It is a further object of the invention to operate a pelletizing device by deliberately freezing individual outlet bores of a pelletizing plate in order to enable adaptation to different materials to be pelletized, but at the same time to counteract the unintentional freezing of individual melt channels, especially in the case of underwater pelletizing.

This object is achieved by providing a pelletizing plate with the characterizing features of claim 1, by providing a device for granulating substances with thermoplastic behavior according to the characterizing features of claim 19, and by the method for granulating substances with thermoplastic behavior set out in claim 25 , Advantageous embodiments of the invention result from the subclaims.

The pelletizing plate according to the invention for arrangement on a device for pelletizing substances with thermoplastic behavior has a plurality of melt channels designed as through-openings, the melt channels being at least partially surrounded individually or in groups by temperature control elements. By means of this embodiment according to the invention, the melt channels are tempered to very close to their outlet opening, in contrast to existing pelletizing systems. Depending on the mode of operation of the pelletizing plate, the melt channels can be kept individually or in groups in a targeted manner at a sufficiently high temperature to prevent the melt from cooling, and on the other hand, by cooling individual or groups of melt channels, specific "freezing" of individual outlet openings of the Perforated pelletizing plate can be achieved in order to achieve the pressure build-up in the pelletizing device and thus the adaptation to different materials.

In an advantageous embodiment of the granulating perforated plate according to the invention, the melt channels are surrounded by temperature control elements at least over 90 °, preferably at least over 180 °. Alternatively or in addition, it can be provided that that the temperature control elements extend over part of the axial length of the melt channels. The aforementioned measures achieve a uniform temperature control of the melt channels. If it is further provided that the temperature control elements extend close to the melt outlet end of the melt channels, then undesirable temperature influences of the atmosphere outside the pelletizing plate or a water flow flowing around the pelletizing plate can be prevented. In particular, this can prevent undesired freezing of the melt.

Simple assembly of the pelletizing plate and excellent temperature distribution around the melt channels is achieved if the temperature control elements are arranged in the annular grooves surrounding the melt channels. The same advantageous effects are achieved by an alternative embodiment of the granulating perforated plate, in which the temperature control elements are arranged in the stepped bores defining the melt channels. An embodiment of the granulation perforated plate according to the invention in which the temperature control elements are designed as sleeve bodies provided with temperature control means is particularly easy to manufacture. The sleeve bodies can advantageously be made of ceramic or metal, preferably aluminum or nickel. From a manufacturing point of view and because of the excellent controllability of the temperature distribution, it is advantageous if the sleeve bodies partially define or continue the melt channels. In order to be able to choose the manufacturing tolerances closely, it proves to be advantageous if the materials of the sleeve body and the pelletizing plate are selected such that they have a similar thermal expansion coefficient.

It has been found to be particularly effective to use the entire body of the ceramic granulating plate, e.g. Sl-carbide or SI-nitride, on the one hand due to the low thermal conductivity of ceramic, and on the other hand due to the good wear properties of ceramic. As an alternative to this, the perforated pelletizing plate can also be made of steel, optionally with a coating of hard metal, which has advantages in manufacture due to the good machinability of steel.

In a preferred embodiment of the invention, the granulating perforated plate is made in one piece. This avoids problems with the tightness and fit of joining surfaces, such as exist in the case of a multi-piece design, and can thus permit greater manufacturing tolerances.

In a further embodiment of the granulating perforated plate according to the invention, it has a clamping flange for simple attachment to a melt distributor or the like. The temperature control elements of the granulating perforated plate according to the invention can, on the one hand, be designed as, preferably controllable, heating elements. With these heating elements, freezing of individual melt channels or their exit holes can be reliably prevented by keeping the melt flowing through at a temperature above its solidification point. Heating elements with heating means in the form of a resistance heater or in the form of lines for the flow of heat transfer medium have proven to be inexpensive and easy to regulate.

The temperature control elements of the granulating perforated plate according to the invention can, on the other hand, also be designed as cooling elements, which preferably have coolants in the form of lines for the flow of cooling medium. In this embodiment, it is possible to allow individual outlet openings to freeze in a targeted manner. In order to guarantee that only those holes with solidifying melt freeze where this is intended, the pelletizing plate itself can be heated.

For an exact control of the temperature in or on the melt channels of the granulating perforated plate, it is advantageous if temperature sensors are provided on or near the melt channels, or if temperature sensors are integrated in the temperature control elements. The temperature sensors are connected to a control device provided on the pelletizing device for individual or group control of temperature control elements of the pelletizing die, the control comprising switching on / off or maintaining a predetermined temperature of the temperature control elements or driving a predetermined temperature profile. The control device can advantageously be designed as a controller, the controlled variable of which is alternatively one or more of melt pressure, melt temperature, temperature of temperature control elements or temperature of the pelletizing plate.

The invention can be used particularly advantageously in underwater pelletizing.

In order to avoid thermal stresses due to different coefficients of thermal expansion between the pelletizing die and a melt distributor of the pelletizer, to which the pelletizer die is to be fastened, the pelletizing die is preferably fastened to the melt distributor by clamping means which absorb the thermal expansions. In order to achieve an optimal knife run over the end face of the pelletizing plate, the contact pressure of the knives against the pelletizing plate can be regulated in one embodiment of the pelletizing device according to the invention.

The process according to the invention for granulating substances with thermoplastic behavior, in particular thermoplastic plastics, comprises producing a melt of the substance with thermoplastic behavior, feeding the melt to a melt distributor for distributing the melt to a plurality of melt channels formed in a pelletizing die, and cutting off pieces the melt as it emerges from the melt channels of the pelletizing die, followed by cooling of the melted pieces to solidification, the melt channels in the pelletizing die being brought individually or in groups to respective temperatures which are above or below the solidification temperature of the melt flowing through. The selective tempering of the melt channels preferably takes place as a function of the melt material and / or the melt pressure.

In one embodiment of the method according to the invention, the temperature control of the melt channels comprises the switching on / off or temperature regulation of heating elements at least partially surrounding the respective melt channel.

In an alternative embodiment of the method according to the invention, the temperature control of the melt channels comprises switching on / off or temperature control of cooling elements at least partially surrounding the respective melt channel, wherein in a further development of this embodiment the pelletizing plate is heated away from the melt channels.

The invention will now be explained in more detail using exemplary embodiments with reference to the drawings. The drawings show:

1 shows a section through a granulating device according to the invention;

Fig. 2 is an enlarged sectional view of a detail of an inventive

Pelletizing plate on the pelletizer of Fig. 1;

3 shows an enlarged sectional illustration of a detail of an alternative embodiment of a granulating perforated plate according to the invention; and

Fig. 4 is a circuit diagram of a control of temperature control elements in an inventive

Granulator. 1 shows a longitudinal section through a granulating device 1 according to the invention for granulating substances with thermoplastic behavior, in particular thermoplastic plastics. The granulating device 1 comprises a melt distributor 2 for distributing a supplied melt (arrow S) of a substance with thermoplastic behavior to a plurality of melt channels 3. For this purpose, the melt distributor has an inlet 2a for connection to an extruder (not shown), which produces the melt and by corresponding pressure build-up promotes to the melt distributor. A conical cavity 2b extends from the inlet 2a, into which said melt channels 3 open. The materials to be granulated with thermoplastic behavior are not restricted in any more detail; Examples include thermoplastic materials, such as PE, PET, PA, PVC, or mixtures thereof, it being possible for these plastics to also be provided with additives. The melts produced from the materials with thermoplastic behavior can have a wide variety of viscosities. The extruder can be configured, for example, as an extruder for processing plastic waste, as is well known to those skilled in the art. The melt distributor 2 is made of a metal, such as steel. The melt distributor 2 is connected on its end face to a pelletizing plate 5 by means of a clamping ring 4 and expansion screws 6, a peripheral section of the pelletizing plate 5 being designed as a clamping flange 5d. The melt channels 3 are formed in the pelletizing plate 5. The pelletizing plate 5 is further aligned with the melt distributor 2 in such a way that the open, front end of the conical cavity 2b coincides with the melt channels 3. A sealing ring 7 runs in a groove on the front side of the melt distributor 2 around the front end of the conical cavity 2b and seals the interface to the pelletizing plate 5. The contact pressure of the pelletizing plate 5 against the end face of the melt distributor 2 is set by the expansion screws 6, which also absorb any thermal expansion of the pelletizing plate 5. The pelletizing plate 5 is made in one piece from ceramic, for example SI carbide or SI nitride, or from steel, optionally with a coating of hard metal on its end face 5a. Knives 8, which are attached to a shaft 9 and are moved by rotation (arrow R) of the shaft 9 over the outlet holes 5c, are located on the end face 5a of the granulating perforated plate 5 facing away from the melt distributor 2, in order to remove pieces of melt strands emerging from the outlet holes 5c cut off, the length of which depends on the rotational speed of the shaft 9, the spacing of the pelletizing holes and the conveying speed of the melt strands. The knives 8 are biased against the end face 5 a so that they exert a predetermined, adjustable contact pressure (arrow p). A pelletizing housing 10 lies sealingly against the end face 5a of the pelletizing perforated plate 5 and surrounds the rotating knives 8. The melt pieces cut off by the knives 8 are caused by the knives 8 Centrifugal force hurled against the inside of the peripheral wall of the granulating housing 10. Inside the granulating housing 10 there is a coolant, for example an atmosphere of cooled air or a cooling water flow, in which the melted pieces quickly solidify and thereby form granules. If necessary, the walls of the granulation housing 10 can also be cooled in order to prevent granulate particles from adhering.

Referring now also to FIG. 2, which shows a section of the granulating perforated plate 5 in longitudinal section, one of the melt channels 3 formed in the granulating perforated plate 5 can be seen in this drawing, which opens at the end face 5 a of the granulating perforated plate 5 in the outlet opening 5 c , The melt channel 3 is formed by a through hole which tapers in conical steps towards the outlet opening 5c in order to bring as much hot melt material as possible close to the outlet opening 5c and thereby prevent the outlet opening 5c and parts of the melt channel nearby it from being unwanted freeze, ie the melt solidifies in it when the end face 5a of the granulation perforated plate 5 is exposed to the coolant for cooling the granulate particles and thus cools down in this area to a temperature below the solidification point of the melt. The result would be granulate particles of irregular shape and size, or a complete closure of the outlet opening with the associated reduction in the granulation performance up to the complete stoppage of the granulation device.

The melt channel 3 is surrounded by an annular groove 5b formed in the granulating perforated plate 5. In the annular groove 5b, a temperature control element is arranged, which is generally designated by the reference number 11. This temperature control element 11 surrounds the melt channel 3 around its entire circumference and a considerable part of its axial length. The annular groove 5b and the temperature control element 11 accommodated therein extend close to the outlet opening 5c in order to be able to ensure that a desired temperature in the melt channel 3 is maintained up to (almost) the outlet opening 5c.

The temperature control element 11 comprises a sleeve body 12 which holds the temperature control means 13. The end 12a of the sleeve body 12 facing away from the outlet opening 5c is conical in shape and defines a partial section of the melt channel 3 when the sleeve body 12 is inserted into the annular groove 5b. The sleeve body 12 is advantageously made of ceramic or metal, preferably aluminum or nickel. The materials of the sleeve body 12 and the pelletizing plate 5 should be selected so that they have a similarly large coefficient of thermal expansion in order to avoid material stresses due to different expansion. According to the invention, the temperature control elements can be designed both as cooling elements and as heating elements. For the purpose of explanation, however, it is assumed that the temperature control element 11 is a cooling element and the temperature control means 13 are coolants in the form of hose lines wound around the sleeve body 12 for the flow of a cooling medium. The mode of operation of the pelletizing device in this case is such that by cooling individual melt channels or groups of melt channels, these are cooled below a melting point of the melt flowing through and freeze the melt channels in a targeted manner in order to prevent further melt flow and thereby the operation of the pelletizing device to adapt to changed parameters with regard to the melt material and the pressure build-up in the melt lines of the granulating device. On the other hand, in order to ensure that the frozen melt channels “thaw” as quickly as possible if the parameters should change in such a way that it is necessary to restart these melt channels, the pelletizing plate 5 is itself heated (see heating element 14 in FIG. 1). It is also conceivable to design the temperature control elements so that both heating and cooling elements are available in order to optimize the thawing and freezing times of the melt channels.

In order to be able to control the temperature and the pressure build-up in the melt channels as precisely as possible, a temperature sensor 16 and a pressure sensor 17 are integrated in the annular projection 5d, which forms a section of the melt channel 3 and is surrounded by the annular groove 5b.

3 shows a detail of a further embodiment of a pelletizing plate 15 according to the invention in longitudinal section. Similar to the embodiment of the pelletizing plate from FIG. 2, a plurality of melt channels 3 in the pelletizing plate 15 also extend through the pelletizing plate 15 and open into an outlet opening 15c in an end face 15 of the pelletizing plate 15. In FIG To see pelletizing plate 15, which comprises a melt channel 3. The melt channels are expediently distributed in a circle in the pelletizing plate.

In contrast to the embodiment of FIG. 2, the granulating perforated plate 15 shown in FIG. 3 has a stepped bore 15b in which a temperature control element, generally designated 21, is received. This temperature control element 21 itself defines a considerable section of the melt channel 3. More specifically, the temperature control element 21 comprises a sleeve body 22, the inner wall of which defines the section of the melt channel 3. The sleeve body 22 holds temperature control means 23, which both Coolant can also be designed as a heating medium. For the purpose of explaining the invention, it is assumed in this illustrated embodiment that the temperature control element 21 is a heating element and the temperature control means 23 are heating means in the form of hose lines wound around the sleeve body 22 for flow through with a heat transfer medium or an electrical resistance wire wound around the sleeve body 22. The operation of the granulating device in this case is such that the heating elements are kept at a temperature by switching on / off or regulating the supplied energy in such a way that a desired temperature is reached in the melt channel, which is either above the solidification point of the melt flowing through, so that it is safe it is set that the melt channel, in particular its outlet opening 15c, does not freeze, or that the melt flowing below the solidification point lies in order to allow the melt channel to freeze in a targeted manner in order to adjust the granulating device to predetermined parameters, such as melt material or pressure build-up of the melt. In order to ensure that the melt channel freezes at least in the region of its outlet opening 15, the face of the pelletizing perforated plate 15 must be flowed with with coolant in such a way that the temperature in the pelletizing perforated plate is sufficiently low (at least in the region of the outlet opening 15c).

The pelletizing plate 5 or 15 according to the invention is characterized by high durability and a long service life, since it offers the possibility of reprocessing by grinding or lapping the end face 5a or 15a. Due to its one-piece construction, generous manufacturing tolerances are also possible, which in turn offers the possibility of manufacturing the perforated pelletizing plate from ceramic material, the ceramic material being able to be processed in the unfired state and thus inexpensively. The pelletizing plate according to the invention can be used particularly advantageously in underwater pelletizing or water ring pelletizing.

4 shows a block diagram of a plant for granulating thermoplastic waste or the like, which comprises an extruder 20, which produces plastic melt from the plastic waste fed to it and feeds it to a granulating device 1, which has a melt distributor 2 and a perforated pelletizing plate 5 according to the invention or 15, as already described in detail above. The pelletizing plate 5 or 15 comprises a plurality of melt channels 3, each of which is surrounded by a temperature control element 11 or 21. The granulating device 1 further comprises a microprocessor control 25, which has a controller 19 and a setpoint generator 18. The controlled variable of the controller 19 is the melt pressure prevailing in the melt distributor 2, which is measured by a pressure sensor 24 and fed to the controller. The output signal of the controller 19 controls switches 26, which can be designed, for example, as semiconductor relays (a switch is shown in the drawing). With the switches 26, the temperature control elements 11 or 21 are switched on / off individually or in groups such that a certain number of parts of the total number of melt channels 3 freeze and a further number of parts of the melt channels 3 remain open. This allows the target melt pressure in the melt distributor to be regulated. In addition to the melt pressure, the melt temperature, the temperature of temperature control elements or the temperature of the pelletizing die plate or combinations of these measured variables can also be used as control variables for the controller 19. Furthermore, the selective tempering of the melt channels can also take place as a function of the melt material. In particular, the same pelletizing plate can be used for different materials with different viscosities. Instead of a switch 26, the controller 19 can also control a power amplifier or a pump in order to regulate the electrical current or cooling medium / heat transfer medium current supplied to the temperature control elements.

Claims

claims:

1. Granulation perforated plate (5, 15) for arrangement on a device (1) for granulating substances with thermoplastic behavior, in particular thermoplastic plastics, with a plurality of melt channels (3) designed as through openings, characterized in that the melt channels (3) individually or in groups are at least partially surrounded by temperature control elements (11, 21).

2. pelletizing plate according to claim 1, characterized in that the melt channels (3) at least over 90 °, preferably at least over 180 °, their periphery of temperature control elements (11, 21) are surrounded.

3. pelletizing plate according to claim 1 or 2, characterized in that the temperature control elements (11, 21) extend close to the outlet openings (5c, 15c) of the melt channels.

4. pelletizing plate according to one of the preceding claims, characterized in that the temperature control elements (11, 21) extend over part of the axial length of the melt channels (3).

5. pelletizing plate according to any one of the preceding claims, characterized in that the temperature control elements (11) in the melt channels (3) surrounding annular grooves (5b) are arranged.

6. pelletizing plate according to one of claims 1 to 4, characterized in that the temperature control elements (21) in the melt channels (3) defining step bores (15b) are arranged.

7. pelletizing plate according to claim 5 or 6, characterized in that the temperature control elements (11, 21) are designed as temperature control means (13, 23) provided sleeve body (12, 22).

8. pelletizing plate according to claim 7, characterized in that the sleeve body (12, 22) made of ceramic or metal, preferably aluminum or nickel, are formed.

9. pelletizing plate according to claim 7 or 8, characterized in that the sleeve body (12, 22) partially define or continue the melt channels (3).

10. Pelletizing plate according to one of the preceding claims, characterized in that it is made of ceramic, e.g. SI carbide or SI nitride, or in steel, optionally with a coating of hard metal.

11. pelletizing plate according to one of the preceding claims, characterized in that it is made in one piece.

12. pelletizing plate according to claim 10 or 11 in connection with claim 8, characterized in that the materials of the sleeve body (12, 22) and the pelletizing plate (5, 15) are selected so that they have a similar coefficient of thermal expansion.

13. Pelletizing plate according to one of the preceding claims, characterized in that it has a clamping flange (5d) for attachment to a melt distributor (2) or the like.

14. pelletizing plate according to one of the preceding claims, characterized in that the temperature control elements (21) are designed as, preferably controllable, heating elements.

15. pelletizing plate according to claim 14, characterized in that the heating elements (21) have heating means (23) in the form of a resistance heater or in the form of lines for the flow of heat transfer medium.

16. Pelletizing perforated plate according to one of claims 1 to 13, characterized in that the temperature control elements (11) are designed as cooling elements, which preferably have coolant (13) in the form of lines for the flow of cooling medium.

17. pelletizing plate according to claim 16, characterized in that it is heatable (at 14).

18. Pelletizing plate according to one of the preceding claims, characterized in that temperature sensors (16) are provided on or near the melt channels (3), or that temperature sensors are integrated in the temperature control elements.

19. Device (1) for granulating substances with thermoplastic behavior, in particular thermoplastic plastics, comprising a melt distributor (2) for distributing a supplied melt (S) of the substance with thermoplastic behavior to a plurality of melt channels (3), one on the melt distributor (2 ) arranged pelletizing perforated plate (5, 15) with a plurality of melt channels (3) designed as through openings for flow through with the melt supplied to the melt distributor, and knives (8) movable to cut through the orifices (5b, 15b) of the melt channels (3) of the granulating perforated plate small pieces of the melt strand, characterized in that the pelletizing plate (5, 15) is designed according to one of claims 1 to 18.

20. pelletizing device according to claim 19, characterized by a control device (25) for individual or group control of temperature control elements (11, 21) of the granulation perforated plate (5, 15), the control comprising switching on / off or maintaining a predetermined temperature of the temperature control elements ,

21. Granulating device according to claim 20, characterized in that the control device (25) comprises a controller (19), the controlled variable of which is one or a combination of melt pressure, melt temperature, temperature of temperature control elements or temperature of the granulation perforated plate.

22. Granulating device according to one of claims 19 to 21, characterized in that coolants are provided for cooling the cut-off melt pieces until solidification, the coolants preferably comprising a water flow (W) flowing towards the granulation plate (5) or flowing around it.

23. Granulating device according to one of claims 19 to 22, characterized in that the perforated granulating plate (5) is fastened to the melt distributor (2) by clamping means (4).

24. Granulating device according to one of claims 19 to 23, characterized in that the contact pressure (p) of the knives (8) against the granulating perforated plate (5) can be regulated.

25. A method for granulating substances with thermoplastic behavior, in particular thermoplastic plastics, comprising producing a melt (S) of the substance with thermoplastic behavior, feeding the melt to a melt distributor (2) for distributing the melt to several in a pelletizing plate (5 , 15) trained Melt channels (3), and the cutting off of pieces of the melt as they emerge from the melt channels of the pelletizing die, followed by cooling of the cut pieces of melt until solidification, characterized by the individual or group tempering of the melt channels (3) in the pelletizing die (5, 15 ) in order to bring them selectively to respective temperatures which are above or below the solidification temperature of the melt flowing through.

26. The granulation method according to claim 25, characterized in that the selective tempering of the melt channels takes place as a function of the melt material and / or the melt pressure.

27. Pelletizing method according to claim 25 or 26, characterized in that the tempering of the melt channels comprises switching on / off or temperature control of at least partially surrounding the respective melt channel (3) heating elements (22).

28. Granulation method according to claim 25 or 26, characterized in that the tempering of the melt channels comprises switching on / off or temperature control of at least partially cooling elements (12) surrounding the respective melt channel (3).

29. Granulation process according to claim 28, characterized by heating the perforated granulation plate.