Granulating device for producing pellets coated with at least one layer of polymer core of polymer and / or non-polymer material, related method and pellets

Abstract

A granulation device for granulating a polymer strand into pellets made of a polymer core coated with at least one layer of a polymer and / or non-polymer material wherein the granulation device comprises: at least one melt providing device; a die head having an inlet side and an outlet side, the inlet side being connected to a melt supply device, the die includes at least one inlet line for polymer forming a polymer core connected to a plurality of die channels of a first type, at least one inlet line for polymer and / or non-polymer material connected to a plurality of die channels of a second type, at least one inlet line for a heating medium and at least one outlet line; and at least one granulation blade, which is arranged on the outlet side of the die head and allows the wire material leaving the outlet of the die head to be cut into granules.

Description

Technical Field

[0001] The present invention relates to a granulating device for granulating a polymer strand into pellets made of a polymer core coated with at least one layer of a polymer and / or a non-polymer material. Background Art

[0002] Granulating a polymer strand into polymer pellets is a well-known process in the chemical and composite industries. In addition to non-expandable and unexpanded polymer pellets, expandable pellets (such as expandable polystyrene pellets) containing a compressed blowing agent dispersed in the polymer are often produced therefrom, or expanded pellets, i.e., pellets that have been expanded (or correspondingly, foamed) with a blowing agent, such as expanded polylactic acid pellets. Typically, the polymer, optionally mixed with a blowing agent, is fed into the channels of a die and extruded through the channels of the die, and is extruded out of the die through the die outlet. One or more rotating blades are disposed directly downstream of the die outlet of the die, which cut the strand continuously extruded through the die outlet into pellets, such as expanded pellets having a diameter of, for example, about 5 mm. While leaving the die outlet, the polymer melt strand is cooled in order to solidify the polymer melt into a solid polymer. This can be achieved, for example, by underwater granulation, where cold water flows downstream of the die outlet of the die such that the polymer melt is extruded through the die outlet as a polymer melt strand into a water bath, where the polymer strand cools and solidifies and is cut into pellets by the one or more rotating blades. Granulation can also be achieved by a water ring granulation or a hot die face granulation system. Often, not only a polymer melt made of a polymer optionally containing a blowing agent is extruded and extruded through the die as a polymer melt strand, but also each polymer melt strand containing a core made of a polymer optionally containing a blowing agent, where the core is coated with one or more additional polymer and / or non-polymer material layers.

[0003] The key component of the granulation device is the die head, which includes a die head body and a die head plate. The die head plate includes one or more outlets and is actually multiple outlets. In theory, the polymer melt in the die head should have a temperature only slightly higher than the melting point of the polymer in order to keep the energy cost of the granulation process as low as possible. In addition, in the case where the polymer melt contains a blowing agent, the temperature of the polymer melt at the die head outlet should be as close as possible to the melting point of the polymer so that the polymer melt solidifies as quickly as possible after leaving the die head outlet, so as to solidify before the mixture of the polymer and the blowing agent foams (in the case of producing expandable pellets), or so as to solidify at such a time before or simultaneously with cutting the strand into pellets (in the case of producing expanded pellets) so that uniform foaming of the mixture of the polymer and the blowing agent is achieved. In addition, the temperature across multiple die head outlets should be as uniform as possible in order to obtain pellets of the same or at least very similar sizes, which requires that each individual strand leaves its die head outlet at the same temperature and with a temperature distribution across the cross-section of the strand. However, it must be reliably avoided that the polymer melt has solidified in the die head outlet, because this will cause blockage of the die head outlet, which will stop or at least severely interfere with the granulation process and cause a change in the pellet size distribution. Since the outlet side of the die head is cooled, for example, in the case of underwater granulation, by cold water circulating around the outlet side of the die head, there is a temperature gradient in the die head. More specifically, the temperature gradually decreases in the end section of the die head in the direction towards the die head outlet. In addition, there is a temperature gradient in the channel through which the polymer melt is guided through the die head to the die head outlet, where the temperature decreases from the outer periphery of the channel through its cross-section into its interior. If the temperature of at least a part of the polymer melt strand is too low inside the outlet, then unwanted solidification may occur inside the die head outlet and thus blockage of the die head outlet may occur. Therefore, it would be desirable to regulate and maintain an accurate and uniform temperature distribution inside the die head and across the die head outlet side during the granulation process, so as to ensure reliably avoiding blockage of the die head outlet by solidified polymer, so as to thereby increase the energy efficiency of the granulation process and so as to ensure good and uniform foaming of the polymer melt in the case of producing expanded polymer pellets. If small-sized pellets are produced, then the targeted control of the temperature of the die head and the polymer melt becomes even more critical, because then small-sized die head outlets are to be used (which, due to their small size or correspondingly small diameter), are particularly prone to the above-mentioned problems, such as blockage due to solidification of the polymer inside the die head outlet.

[0004] To heat the die head, one or more oil channels are typically provided in the die head body through which heating oil flows. However, the die heads used in prior art pelletizing apparatuses do not allow for satisfactory precise temperature control of the die head, and particularly in the case of die heads of pelletizing apparatuses for producing pellets consisting of a polymer core coated with at least one layer of polymer and / or non-polymer material. This is because conventional die heads are manufactured using conventional manufacturing techniques such as milling, which are associated with significant manufacturing constraints. Thus, the shape of the oil channels is limited to simple paths and cannot be easily routed between or around the polymer channels to locally control the melt temperature. This is particularly applicable to pelletizing a polymer strand into pellets made of a polymer core coated with at least one layer of polymer and / or non-polymer material, which requires two different types of polymer channels in the die head. Summary of the Invention

[0005] In view of the above, the fundamental object of the present invention is to provide a pelletizing apparatus for pelletizing a polymer strand into pellets made of a polymer core coated with at least one layer of polymer and / or non-polymer material, which allows for regulating and maintaining a precise and uniform temperature distribution within and across the die head outlet side during the pelletizing process, and thus allows for precise temperature control of the die head, which allows for producing pellets of uniform size and including a polymer core coated with at least one layer of polymer and / or non-polymer material, and which particularly allows for producing expanded pellets of a polymer core coated with at least one layer of polymer and / or non-polymer material having a relatively small size of 1 - 5 mm.

[0006] According to the present invention, this object is achieved by providing a pelletizing apparatus for pelletizing a polymer strand into pellets made of a polymer core coated with at least one layer of polymer and / or non-polymer material, wherein the pelletizing apparatus comprises:

[0007] - at least one melt supply device (such as an extruder),

[0008] - a die head having an inlet side and an outlet side, wherein the inlet side is connected to the melt supply device, and wherein the die head comprises:

[0009] - at least one inlet line for the polymer for forming the polymer core, which is connected to a plurality of first type die head channels, wherein each first type die head channel comprises an end section terminating at the die head outlet side,

[0010] - At least one inlet line for polymer and / or non-polymer materials, which is connected to a plurality of die channels of a second type, wherein each die channel of the second type includes an end section that terminates at the die outlet side, and wherein the end sections of at least 50% of the die channels of the second type and preferably each end section surround the end section of a die channel of a first type, such that the end section of the die channel of the first type and the end section of the die channel of the second type form a combined die channel that terminates at the outlet side of the die as the die outlet.

[0011] - At least one inlet line and at least one outlet line for a heating medium, wherein the at least one inlet line and the at least one outlet line for the heating medium are connected to each other through one or more heating channels, and wherein preferably at least 50% of the combined die channels are at least partially surrounded by separate heating channels.

[0012] - At least one granulation blade, which is arranged on the outlet side of the die and allows the strand exiting the die outlet to be cut into pellets.

[0013] This solution is based on the surprising finding that by using a precise production process for the die of a granulation device, such as an additive manufacturing process, the heating medium channels can be formed such that heat is distributed much more uniformly to and across the polymer channels, i.e., distributed to and across the first type of die channels and distributed to and across the second type of die channels, i.e., by providing heating channels such that at least 50% of the combined die channels are at least partially surrounded by separate heating channels. In this regard, a separate heating channel means that each of at least 50% of the combined die channels is surrounded by its own (i.e., a separate heating channel), or in other words, each of at least 50% of the combined die channels is surrounded by a different heating channel or a different longitudinal section of the corresponding heating channel, where a heating channel means a void surrounded by one or more walls such that a heating medium can flow through the void of the heating channel. Thus, the first and second types of die channels can be heated separately, and the heating medium channels can be arranged closer to the first and second types of channels. This allows for the regulation and maintenance of precise temperature control of the die during the granulation process, which allows for the production of pellets with a polymer core coated with at least one layer of polymer and / or non-polymer material having a uniform size, and in particular allows for the production of expanded pellets with a polymer core coated with at least one layer of polymer and / or non-polymer material having a relatively small size of 1 to 5 mm or 2 to 5 mm. In particular, the clogging of individual die outlets by cured polymer is reliably avoided. Furthermore, the use of a precise production process (such as an additive manufacturing process) for the die of a granulation device allows for further advantageous measures for improving the temperature control of the die, which will be further described below, such as providing heat-insulating cavities close to the outlet side of the die, and integrating a wear-resistant protective layer on the outlet side of the die, which is in contact with the at least one granulation blade.

[0014] The outlet side of the die can be arranged opposite to the inlet side of the die.

[0015] According to the present invention, the die head includes a first type of die head channel and a second type of die head channel. The first type of die head channel is for a polymer forming the polymer core of the granulated material to pass through the die head and its die head outlet, and the second type of die head channel is for a polymer and / or non-polymer material forming a layer coating the polymer core to pass through the die head and its die head outlet. The terms "first type" and "second type" are only used in this context to distinguish between the two types of channels. Both the first type of die head channel and the second type of die head channel include an end section terminating at the outlet side of the die head plate. In other words, the end section of the first type of die head channel and the end section of the second type of die head channel are positions where the channels extend from inside the die head body until the most downstream end of the die head outlet. Each end section of the second type of die head channel surrounds the end section of the first type of die head channel such that the end section of the first type of die head channel and the end section of the second type of die head channel form a combined die head channel terminating at the outlet side of the die head as the die head outlet. In other words, when viewed in the cross-section of the die head, each combined die head channel is the sum of the end section of the first type of die head channel (central when viewed in the cross-section of the die head) and the end section of the second type of die head channel surrounding the end section of the first type of die head channel. During die head operation, the polymer forming the polymer core of the granulated material is extruded through the first type of die head channel, and the polymer and / or non-polymer material forming a layer coating the polymer core is extruded through the second type of die head channel. Due to the inertia of the polymer melt or the mixture of polymer melt and blowing agent forming the polymer core of the granulated material, due to the pressure with which it is extruded through the first type of die head channel, and due to the temperature at which it is extruded through the first type of die head channel being slightly higher than its melting point, the polymer melt or the mixture of polymer melt and blowing agent extruded through the first type of die head channel does not or at least does not significantly mix with the polymer and / or non-polymer material extruded through the second type of die head channel in the combined die head channel. Except for its end section, each first type of die head channel is surrounded by a die head wall (i.e., by the material of the die head) on its entire peripheral surface, while each second type of die head channel is surrounded by a die wall (i.e., by the material of the die head) on its entire peripheral surface, including its end section.

[0016] Preferably, at least the end section of the first type of die head channel and at least the end section of the second type of die head channel have a circular cross-section, wherein each end section of the second type of die head channel concentrically surrounds the end section of the first type of die head channel so as to form a combined die head channel terminating at the outlet side of the die head plate as the die head outlet.

[0017] According to the present invention, at least 50% of the end sections of the second type of die channels surround the end sections of the first type of die channels such that the end sections of the first type of die channels and the end sections of the second type of die channels form a combined die channel that terminates at the die plate at the outlet side which is the die outlet. Good results are particularly obtained when at least 70%, preferably at least 80%, more preferably at least 90%, still more preferably at least 95%, yet more preferably at least 99% of the end sections of the second type of die channels and most preferably each end section of the second type of die channels surround the end sections of the first type of die channels such that the end sections of the first type of die channels and the end sections of the second type of die channels form a combined die channel that terminates at the die plate at the outlet side which is the die outlet.

[0018] In a further development of the inventive concept, it is proposed that at least 50%, preferably at least 80%, more preferably at least 90%, still more preferably at least 95%, yet more preferably at least 99% of the combined die channels and most preferably all combined die channels taper in the axial direction towards the die outlet. The axial direction means the axial direction of the die, i.e., the direction from the die inlet side to the outlet side, i.e., the longitudinal direction. For example, any one of the combined die channels can taper gradually or in one or more steps from its upstream end to its downstream end (which is the die outlet). Alternatively, any combined die channel can have a first upstream section of the same size or corresponding diameter and a second downstream section that tapers from its upstream end to its downstream end (which is the die outlet). More specifically, in this variant, any combined die channel can have a first cylindrical upstream section and a second downstream section that tapers gradually or in one or more steps from its upstream end to its downstream end.

[0019] Alternatively, any modular die channel can have a first upstream section and a second section at its downstream end, the first section tapering gradually or in one or more steps from its upstream end to its downstream end, and the second section having the same dimensions or a corresponding diameter. More specifically, in this variant, any modular die channel can have a first section and a second cylindrical downstream section, the first section tapering gradually or in one or more steps from its upstream end to its downstream end. Still alternatively, any modular die channel can taper stepwise from its upstream end to its downstream end (which is the die outlet), i.e., it can have a first upstream section having the same dimensions or a corresponding diameter over its length, a second section downstream of it, and a third section downstream of it, the second section tapering gradually or in one or more steps from its upstream end to its downstream end, and the third section having the same dimensions or a corresponding diameter over its length. More specifically, in this variant, any modular die channel can have a first cylindrical upstream section, a second section tapering gradually or stepwise (i.e., in one or more steps) from its upstream end to its downstream end, and a third cylindrical section downstream of it.

[0020] Preferably, at least 50%, more preferably at least 80%, even more preferably at least 90%, still more preferably at least 95%, yet more preferably at least 99% of the die outlets, and most preferably all die outlets have a size or a corresponding diameter of 0.1 to 5 mm, preferably 0.2 to 3 mm, more preferably 0.5 to 1.5 mm, and most preferably 0.8 to 1.2 mm, such as approximately 1.0 mm. Thereby, relatively small pellets can be obtained, and in particular, expanded pellets having a small size or a corresponding diameter of 1 to 5 mm or 2 to 5 mm. In a preferred case, when viewed in cross-section, the die outlet has a circular form, and it is the diameter that is referred to, and when the die outlet has a non-circular form when viewed in cross-section, it is the size that is referred to, and in this regard, the size means the pipeline having the longest length fitted into the die outlet. In the case of a tapered modular die channel, the minimum size or the corresponding diameter of the tapered modular die channel is within the above range, while the maximum size or the corresponding diameter of the tapered modular die channel can be more than twice up to twenty times the minimum size or the corresponding diameter.

[0021] According to the present invention, at least 50% of the modular die channels are at least partially surrounded by individual heating channels. Preferably, at least 70%, more preferably at least 80%, even more preferably at least 90%, still more preferably at least 95%, yet more preferably at least 99% and most preferably all of the modular die channels are at least partially surrounded by individual heating channels. The modular die channels that are at least partially surrounded by individual heating channels mean that at least a part of the outer circumference of at least one section of the modular die channel is surrounded by an individual heating channel. In this regard, a section means any section of the modular die channel that extends from a point in the die in the direction of the downstream end of the modular die channel (i.e., in the direction of the die outlet), i.e., an axial section means a longitudinal section, respectively meaning a section that extends along the length of the modular die channel. Preferably, the section from which at least a part of the outer circumference is surrounded by an individual heating channel extends to cover 10% to 90%, preferably 15% to 60%, and most preferably 20% to 45% of the length of the modular die channel, where the length means the dimension in the flow direction of the modular die channel. For example, when viewed in the axial direction of the die, the modular die channel is at least partially surrounded by individual heating channels in the region that extends from a position 1 to 30 mm from the die plate outlet side into the die by 1 to 100 mm, and more preferably from a position 1 to 15 mm from the die plate outlet side into the die by 3 to 60 mm.

[0022] In addition, it is preferred that the individual heating channels surround at least 50%, more preferably at least 75%, still more preferably at least 90%, even more preferably at least 95% of the outer circumference of the aforementioned section of the modular die channel and most preferably all of the outer circumference is surrounded by individual heating channels. Similarly, it is preferred that the section of the modular die channel surrounded by the individual heating channels extends to cover preferably 10% to 90%, more preferably 15% to 60%, and most preferably 20% to 45% of the length of the modular die channel.

[0023] For example, good results are obtained when at least 50% of the outer circumference of a section extending over 10 to 90% of the length of the combined die head channel is surrounded by individual heating channels, or when at least 50% of the outer circumference of a section extending over 15 to 60% of the length of the combined die head channel is surrounded by individual heating channels, or when at least 50% of the outer circumference of a section extending over 20 to 45% of the length of the combined die head channel is surrounded by individual heating channels, or when at least 75% of the outer circumference of a section extending over 10 to 90% of the length of the combined die head channel is surrounded by individual heating channels, or when at least 75% of the outer circumference of a section extending over 15 to 60% of the length of the combined die head channel is surrounded by individual heating channels, or when at least 75% of the outer circumference of a section extending over 20 to 45% of the length of the combined die head channel is surrounded by individual heating channels, or when at least 90% of the outer circumference of a section extending over 10 to 90% of the length of the combined die head channel is surrounded by individual heating channels, or when at least 90% of the outer circumference of a section extending over 15 to 60% of the length of the combined die head channel is surrounded by individual heating channels, or when at least 90% of the outer circumference of a section extending over 20 to 45% of the length of the combined die head channel is surrounded by individual heating channels, or when at least 95% of the outer circumference of a section extending over 10 to 90% of the length of the combined die head channel is surrounded by individual heating channels, or when at least 95% of the outer circumference of a section extending over 15 to 60% of the length of the combined die head channel is surrounded by individual heating channels, or when at least 95% of the outer circumference of a section extending over 20 to 45% of the length of the combined die head channel is surrounded by individual heating channels, or when all of the outer circumference of a section extending over 10 to 90% of the length of the combined die head channel is surrounded by individual heating channels, or when all of the outer circumference of a section extending over 15 to 60% of the length of the combined die head channel is surrounded by heating channels, or when all of the outer circumference of a section extending over 20 to 45% of the length of the combined die head channel is surrounded by heating channels.

[0024] Similarly, according to the present invention, at least 50% of the combined die channels are at least partially surrounded by separate heating channels. In this regard, being surrounded by separate heating channels means that, when viewed in the cross-section of the die, preferably, in the region where the combined die channel is surrounded by the heating channel, the distance between the outer circumference of the combined die channel and the outer circumference of the separate heating channel is 1 to 10 mm and preferably 3 to 6 mm. Further, in the region where the combined die channel is surrounded by the heating channel, the distance between the outer circumference of the combined die channel and the inner circumference of the separate heating channel is the distance between the outer circumference of the combined die channel and the outer circumference of the separate heating channel minus the size of the separate heating channel, such as its diameter in the case of a circular heating channel. Preferably, in the region where the combined die channel is surrounded by the heating channel, the distance between the outer circumference of the combined die channel and the inner circumference of the separate heating channel is 1 to 10 mm and more preferably 3 to 6 mm. Such a relatively small distance between the outer circumference of the combined die channel and the outer circumference of the separate heating channel can be obtained in particular by producing the die using an additive manufacturing process, such as i) a powder bed fusion process, ii) a material extrusion process for metals, including manufacturing a green part using a material extrusion process as step 1 and debinding and sintering the green part produced in step 1 as step 2, iii) a binder jetting process for metals, including manufacturing a green part using a binder jetting process with metal powder as step 1 and debinding and sintering the green part produced in step 1 as step 2, or iv) a wire- or powder-based laser metal deposition. From the above four processes, i) the powder bed fusion process and iv) the wire- or powder-based laser metal deposition are particularly preferred, and i) the powder bed fusion process is most preferred.

[0025] In order to achieve the at least partial surrounding of the aforementioned combined die channels by separate heating channels, in a further development of the idea of the present patent application, it is proposed that each of the one or more heating channels has a meandering form and preferably a serpentine form. Thereby, each of the one or more heating channels can be easily guided close to each combined die channel, and the sectional size of each combined die channel surrounded by the one or more heating channels can be easily adjusted by the form and size of the meandering or preferably serpentine shape. The one or more heating channels can be directly connected to an inlet line for the heating medium and an outlet line for the heating medium, each of the one or more heating channels having a meandering form and preferably a serpentine form. Alternatively, one or more other lines can be arranged between the one or more heating channels and the inlet line for the heating medium and / or the outlet line for the heating medium, each of the one or more heating channels having a meandering form and preferably a serpentine form.

[0026] In a further development of the inventive concept, at least 70%, preferably at least 80%, more preferably at least 90%, still more preferably at least 95%, yet more preferably at least 99% and most preferably all of the outer circumferences of at least one section of the combined die channels are surrounded by separate heating channels. Similarly, it is preferred that the section of the combined die channels surrounded by the separate heating channels extends over a length of the combined die channels of preferably 10 to 90%, preferably 15 to 60% and most preferably 20 to 45%. Good results are particularly obtained when all of the combined die channels are surrounded by separate heating channels around the entire outer circumference of a section extending over a length of the combined die channels of 10 to 90%, or when all of the combined die channels are surrounded by separate heating channels around the entire outer circumference of a section extending over a length of the combined die channels of 15 to 60%, or when all of the combined die channels are surrounded by separate heating channels around the entire outer circumference of a section extending over a length of the combined die channels of 20 to 45%.

[0027] Even if less preferred, it is possible that at least 80% or at least 90% or at least 95% or preferably at least 99% of the combined die channels are surrounded by separate heating channels around the entire outer circumference of a section extending over a length of the combined die channels of 10 to 90%, or that at least 80% or at least 90% or at least 95% or preferably at least 99% of the combined die channels are surrounded by separate heating channels around the entire outer circumference of a section extending over a length of the combined die channels of 15 to 60%, or that at least 80% or at least 90% or at least 95% or preferably at least 99% of the combined die channels are surrounded by separate heating channels around the entire outer circumference of a section extending over a length of the combined die channels of 20 to 45%.

[0028] According to a first particularly preferred embodiment of the present invention, all outer circumferences of at least one section of all modular die channels are surrounded by separate heating channels, wherein all the separate heating channels are connected to each other through connecting channels, such that the at least one inlet line for the heating medium is connected to the at least one outlet line for the heating medium via all or at least some of the separate heating channels and the connecting channels. Also preferably, the section of the modular die channel surrounded by the separate heating channels extends over preferably 10% to 90%, more preferably 15% to 60%, and most preferably 20% to 45% of the length of the modular die channel. In this embodiment, particularly good results are achieved when each outer circumference of a section of all modular die channels is completely surrounded by a separate heating channel, wherein all the separate heating channels are connected to adjacent separate heating channels through connecting channels, and wherein the at least one inlet line for the heating medium and the at least one outlet line for the heating medium are connected to different separate heating channels and / or different connecting channels. Thus, the inlet line for the heating medium, the outlet line for the heating medium, and the connecting channels serve as supply channels to supply the heating medium to the separate heating channels, while the separate heating channels have the function of regulating the target temperature distribution within the die and within the channels surrounded by the separate heating channels. The separate heating channels can have any suitable form. For example, the separate heating channels can have the form of a hollow body surrounding the outer circumference of a section of the modular die channel. For example, each separate heating channel can have the form of a hollow cylinder that concentrically surrounds the outer circumference of a section of the modular die channel, and the distance between the outer peripheral region of the section of the modular die channel and the outer peripheral region of the separate heating channel is preferably 1 to 10 mm, and preferably 3 to 6 mm.

[0029] According to a second particularly preferred embodiment of the present invention, the die head comprises an inlet line and an outlet line for the heating medium, both of which are connected to each other via a central heating channel, preferably an annular heating channel, from which a plurality of heating channels branch off, each heating channel at least partially and preferably completely surrounding at least one section of the combined die head channel. "Central" has no specific meaning in this context and is only used to distinguish the central heating channel from the individual heating channels. Thus, the central heating channel (preferably an annular heating channel) serves as a supply channel to supply the heating medium to the individual heating channels branching off therefrom (and preferably having a smaller diameter than the central heating channel (preferably an annular heating channel)), while the individual heating channels branching off from the central heating channel (preferably an annular heating channel) have the function of regulating the target temperature distribution within the die head and within the channel surrounded by the individual heating channels. The individual heating channels branching off from the central heating channel (preferably an annular heating channel) and surrounding the combined die head channel can have any suitable form. For example, the individual heating channels branching off from the central heating channel (preferably an annular heating channel) and surrounding the combined die head channel can include a section in the form of a hollow body surrounding the outer circumference of a section of the combined die head channel, which section is connected to another section connecting the hollow body section to the central heating channel (preferably an annular heating channel). For example, each individual heating channel branching off from the central heating channel (preferably an annular heating channel) and surrounding the combined die head channel can include a section in the form of a hollow cylinder concentrically surrounding the outer circumference of a section of the combined die head channel at a distance of 1 to 10 mm and preferably 3 to 6 mm from the outer circumference of the individual heating channel, where the hollow cylinder is connected to another section connecting the hollow cylinder to the central heating channel (preferably an annular heating channel). Each individual heating channel branching off from the central heating channel (preferably an annular (supply) heating channel) can extend individually from the end opposite to the end from which it branches off from the central heating channel (preferably an annular (supply) heating channel) to the outlet line for the heating medium and can be connected to the outlet line for the heating medium at its most downstream end. Alternatively, some or each individual heating channel branching off from the annular (supply) heating channel can extend from the end opposite to the end from which it branches off from the central heating channel (preferably an annular (supply) heating channel) to a collection channel, which in turn can be connected to the outlet line for the heating medium. As described in the following embodiments, the collection channel can also be an annular channel.

[0030] Particularly preferably, the die head includes at least one inlet line and at least one outlet line for the heating medium, both of which are connected to each other via a central heating channel (preferably an annular heating channel), wherein a plurality of individual heating channels branch off from the central heating channel (preferably an annular heating channel), and each individual heating channel branches off from the central heating channel (preferably an annular heating channel) and completely surrounds at least one section of the combined die head channel, and the section of the combined die head channel surrounded by the individual heating channels extends over preferably 10 to 90%, preferably 15 to 60%, and most preferably 20 to 45% of the length of the combined die head channel.

[0031] According to a third particularly preferred embodiment of the present invention, the die head includes an inlet line and an outlet line for the heating medium, both of which are connected to each other via two central heating channels (preferably annular heating channels), wherein, when viewed in the axial direction of the die head, the two central heating channels (preferably annular heating channels) are arranged at a distance from each other and are connected to each other via a plurality of individual heating channels, and each heating channel at least partially and preferably completely surrounds a section of the combined die head channel. More specifically, the first central heating channel (preferably an annular heating channel) connected to the inlet line for the heating medium serves as a supply channel, while the second central heating channel (preferably an annular heating channel) connected to the outlet line for the heating medium serves as a collection channel. For example, the individual heating channels that branch off from the central heating channel (preferably an annular heating channel) and surround the combined die head channel may include a section in the form of a hollow body that surrounds the outer circumference of a section of the combined die head channel, wherein this section is connected to a first additional section that connects the hollow body section to one of the two central heating channels (preferably an annular heating channel), and is connected to a second additional section that connects the hollow body section to the other of the two central heating channels (preferably an annular heating channel). For example, the hollow body is a hollow cylinder. The distance between the two central heating channels (preferably annular heating channels) may be 20 to 300 mm, and preferably 50 to 200 mm. Preferably, in addition to the optional aforementioned section in the form of a hollow body (such as a hollow cylinder), the individual heating channels have a circular cross-section and a diameter of 3 to 30 mm and more preferably 10 to 20 mm. Similarly, each individual heating channel that branches off from the central heating channel (preferably an annular heating channel) and surrounds the combined die head channel may include a section in the form of a hollow cylinder that concentrically surrounds the outer circumference of a section of the combined die head channel at a distance of 1 to 10 mm and preferably 3 to 6 mm from its outer circumference.

[0032] Particularly preferably, the die head includes at least one inlet line and at least one outlet line for the heating medium, both of which are connected to each other through two central heating channels (preferably annular heating channels), wherein, when viewed in the axial direction of the die head, the two central heating channels (preferably annular heating channels) are arranged at a certain distance from each other and are connected to each other through a plurality of individual heating channels, wherein each individual heating channel completely surrounds at least one section of the combined die head channel, and the section of the combined die head channel surrounded by the individual heating channels extends over preferably 10 to 90%, preferably 15 to 60%, and most preferably 20 to 45% of the length of the combined die head channel.

[0033] In yet another alternative embodiment for achieving at least partial surrounding of the combined die head channel as described above, the die head includes an inlet line for the heating medium, from which a plurality of (preferably non-annular) individual heating channels branch out, each heating channel at least partially and preferably completely surrounding at least one section of the combined die head channel. Similarly, the individual heating channels branching out from the inlet line have the function of regulating the target temperature distribution within the die head and within the channels surrounded by the heated channels. The individual heating channels branching out from the inlet line and surrounding the combined die head channel can have any suitable form. For example, the heating channels branching out from the inlet line for the heating medium and surrounding the combined die head channel can include a connecting section and a section in the form of a hollow body surrounding the outer circumference of a section of the combined die head channel, wherein each connecting section is arranged between the inlet line for the heating medium and the section in the form of a hollow body. Each section in the form of a hollow cylinder concentrically surrounds the outer circumference of a section of the combined die head channel, and the distance between the outer circumference of the combined die head channel section and the outer circumference of the hollow cylinder is preferably 1 to 10 mm, and more preferably 3 to 6 mm. Each individual heating channel section in the form of a hollow body in this embodiment is connected at its end opposite to the end connected to the connecting section to a collecting channel, which can have the form of an annular ring. The collecting channel is in turn connected to the outlet for the heating medium. Similarly, each hollow body preferably has the form of a hollow cylinder, which has a circular cross-section and a diameter of 3 to 30 mm and more preferably 10 to 20 mm. In addition, it is preferred that each hollow cylinder concentrically surrounds the outer circumference of a section of the combined die head channel, and the distance between the outer peripheral region of the hollow cylinder and the outer peripheral region of the combined die head channel is 1 to 10 mm and preferably 3 to 6 mm.

[0034] Any of the above heating channel arrangements can be obtained in particular by producing the die using an additive manufacturing process, such as i) a powder bed fusion process, ii) a material extrusion process for metals, including as step 1 the production of a green part using a material extrusion process, and as step 2 the debinding and sintering of the green part produced in step 1, iii) a binder jetting process for metals, including as step 1 the production of a green part using a binder jetting process with metal powder, and as step 2 the debinding and sintering of the green part produced in step 1, or iv) wire- or powder-based laser metal deposition. From the above four processes, i) the powder bed fusion process and iv) wire- or powder-based laser metal deposition are particularly preferred, and i) the powder bed fusion process is most preferred.

[0035] The melt supply device is preferably an extruder.

[0036] Regarding the number of inlet lines for the polymer for forming the polymer core that are connected to the plurality of first type die channels, the present invention is not particularly limited. For example, each first type die channel can be connected to its own inlet. Alternatively, the die can include one inlet line for the polymer for forming the polymer core, where the inlet line is connected to the plurality of first type die channels and preferably branches into the plurality of first type die channels. Still alternatively, some of the first type die channels can be connected to their own inlet lines, while others can be connected to one inlet line and preferably branch from one inlet line. In each of these embodiments, the inlet line can have a rectangular, square, circular, oval, or polygonal cross-section. However, preferably, the inlet line has a circular cross-section. The inlet line for the polymer for forming the polymer core is preferably connected to a (first) extruder (as the melt supply device).

[0037] However, good results are obtained when the die includes one inlet line for the polymer for forming the polymer core, where the inlet line extends a certain distance into the die (body) before branching into the first type die channels at a point located 20 to 200 mm and preferably 50 to 100 mm from the die outlet side.

[0038] Further preferably, the die outlet is arranged at least in an annular ring region on the die outlet side, while one or more inlet lines preferably enter the inlet side of the die in the central region of the die (seen in the cross-section of the die). Thus, if the die includes only one or a few inlets for the polymer to form the polymer core, which preferably enter the inlet side of the die in the central region of the die, the first type of die channels connected to or even branching out from the inlet lines need to include sections leading to the radially outer part of the die. Thus, particularly preferably, the die includes one inlet from which the first type of die channels branch out, each of the first type of die channels including a first section, a second section and an end section, the first section being connected to the inlet line and extending at an angle of 10° to 90° and preferably 30° to 60° or 70° to 90° relative to the axial direction of the die, the second section having a first end and a second end, the first end being connected to the first section at the end of the second section opposite to the end of the first section connected to the inlet, wherein the second section is curved such that its second end extends at least substantially parallel to the axial direction of the die, and the end section (which forms a combined die channel with the end section of the second type of die channel) is connected to the second end of the second section. In this regard, at least substantially parallel to the axial direction means that the second end of the second section of the first type of die channel extends at an angle of -20° to +20°, preferably -10° to +10°, more preferably -5° to +5° and most preferably 0° relative to the axial direction of the die.

[0039] The first type of die channels may have a rectangular, square, circular, oval or polygonal cross-section. However, preferably, the first type of die channels have a circular cross-section. Alternatively, it is possible that only one section of the first type of die channels has a circular cross-section, such as the second section in the foregoing embodiment.

[0040] The total number of the first type of die channels in the die depends on the throughput of the first type of die channels, wherein each of the first type of die channels preferably has a throughput of 0.5 to 4 kg / h and more preferably between 0.8 and 2.5 kg / h.

[0041] Regarding the number of inlet pipelines of the die for polymer and / or non-polymer materials, the present invention has no particular limitation either. For example, each second type of die channel can be connected to its own inlet. Alternatively, the die can include one inlet pipeline for polymer and / or non-polymer materials, wherein the inlet pipeline is connected to a plurality of second type of die channels and preferably branches into a plurality of second type of die channels. Still alternatively, some second type of die channels can be connected to their own inlet pipelines, while others can be connected to one inlet pipeline and preferably branch out from one inlet pipeline. In each of these embodiments, the inlet pipeline can have a rectangular, square, circular, oval or polygonal cross-section. However, preferably, the inlet pipeline has a circular cross-section. The inlet pipeline for polymer and / or non-polymer materials can be connected to a (second) extruder (as a melt supply device).

[0042] However, when the die includes one inlet pipeline for polymer and / or non-polymer materials, good results are obtained where the inlet pipeline for polymer and / or non-polymer materials extends a certain distance into the die (body) before branching into the second type of die channels at a point located 20 to 200 mm and preferably 50 to 100 mm from the die outlet side.

[0043] The inlet pipeline for polymer and / or non-polymer materials can enter the die via the inlet side of the die or via the side of the die. In this case, the die generally has a circular cross-section in the peripheral region of the die.

[0044] Especially for the preferred embodiment, where the die outlet is arranged at least in the annular ring region on the outlet side of the die plate and the die includes one inlet for polymer and / or non-polymer materials to enter the die via the inlet side of the die, preferably, each of the second type of die channels includes a first section, a second section and an end section. The first section is connected to the inlet pipeline and extends at an angle of 1° to 90° and preferably 1° to 20° with respect to the axial direction of the die. The second section has a first end and a second end. The first end is connected to the first section at the end of the second section opposite to the end of the first section connected to the inlet. Wherein the second section is curved such that its second end extends at least substantially parallel to the axial direction of the die. The end section (which forms a combined die channel with the end section of the first type of die channel) is connected to the second section. Also, in this regard, at least substantially parallel to the axial direction means that the second end of the second section of the second type of die channel extends at an angle of -20° to +20°, preferably -10° to +10°, more preferably -5° to +5° and most preferably 0° with respect to the axial direction of the die. At least the second section of the second type of die channel preferably has a cylindrical form.

[0045] According to an alternative preferred embodiment of the present invention, the die head includes an inlet line for the polymer and / or non-polymer material to enter the die head at the side of the die head, wherein the inlet line is connected to an annular ring channel, and a plurality of second type die head channels branch out from the annular ring channel. Each of the second type die head channels may include a first section and an end section, which together with the end section of the first type die head channel form a combined die head channel, wherein the first section connects the end section of the second type die head channel to the annular ring channel, and the annular ring channel serves as a supply channel to supply the polymer and / or non-polymer material to the second type die head channels branching out therefrom (and preferably has a smaller diameter than the annular ring channel). The first section of the second type die head channel preferably has a cylindrical form.

[0046] According to yet another alternative preferred embodiment of the present invention, the die head includes an inlet line for the polymer and / or non-polymer material to enter the die head at the side of the die head, wherein the inlet line branches into two to four lines, preferably two lines, and the second type die head channels branch out from these lines. In addition, each of the second type die head channels of this embodiment may include a first section and an end section, which together with the end section of the first type die head channel form a combined die head channel, wherein the first section connects the end section of the second type die head channel to one of the lines branching out from the inlet line. The first section of the second type die head channel preferably has a cylindrical form.

[0047] According to the present invention, the granulating die head comprises: at least one inlet line for a polymer for forming a polymer core, which is connected to a plurality of first-type die head channels, wherein each first-type die head channel comprises an end section terminating at the outlet side of the die head plate; and at least one inlet line for a polymer and / or non-polymer material, which is connected to a plurality of second-type die head channels, wherein each second-type die head channel comprises an end section terminating at the outlet side of the die head plate, wherein the end sections of at least 50% of the second-type die head channels and preferably each end section surround the end section of the first-type die head channel, such that the end section of the first-type die head channel and the end section of the second-type die head channel form a combined die head channel terminating at the outlet side of the die head plate as the die head outlet. However, the die head may comprise one or more additional inlets for applying one or more additional polymers and / or non-polymer materials as additional layers onto the coating layer produced by extruding a polymer and / or non-polymer material through the second-type die head channels. In such an embodiment, the die head comprises at least one additional inlet line for a (second) polymer and / or non-polymer material connected to a plurality of third-type die head channels, wherein each third-type die head channel comprises an end section terminating at the outlet side of the die head plate, wherein the end sections of at least 50% of the third-type die head channels surround the end section of the first-type die head channel and the surrounded end sections of the second-type die head channels, such that the end section of the first-type die head channel, the end section of the second-type die head channel and the end section of the third-type die head channel form a combined die head channel terminating at the outlet side of the die head plate as the die head outlet. In this embodiment, it is preferred that the end sections of at least 70%, preferably at least 80%, more preferably at least 90%, still more preferably at least 95%, yet more preferably at least 99% of the third-type die head channels and most preferably each end section surround the end section of the first-type die head channel and the surrounded end sections of the second-type die head channels, such that the end section of the first-type die head channel, the end section of the second-type die head channel and the end section of the third-type die head channel form a combined die head channel terminating at the outlet side of the die head plate as the die head outlet.

[0048] According to another embodiment of the present invention, the die head includes at least one or more additional inlet lines for (third or higher numbered) polymeric and / or non-polymeric materials, which are connected to a plurality of fourth type die head channels and optionally another type of die head channels, wherein each fourth type die head channel and optionally another type of die head channel includes an end section terminating at the outlet side of the die head plate, and wherein at least 50% of the end sections of the fourth type die head channels and optionally another type of die head channels surround the end section of the first type die head channel, the surrounded end sections of the second type die head channels, and the surrounded end sections of the third type die head channels, such that the end section of the first type die head channel, the end sections of the second type die head channels, the end sections of the third type die head channels, the end sections of the fourth type die head channels, and optionally another type of die head channels form a combined die head channel that terminates at the outlet side of the die head plate which serves as the die head outlet. In this embodiment, it is preferred that at least 70%, preferably at least 80%, more preferably at least 90%, still more preferably at least 95%, yet more preferably at least 99%, and most preferably each end section of the end sections of the fourth type die head channels and optionally another type of die head channels surrounds the end section of the first type die head channel, the surrounded end sections of the second type die head channels, and the surrounded end sections of the third type die head channels, such that the end section of the first type die head channel, the end sections of the second type die head channels, the end sections of the third type die head channels, the end sections of the fourth type die head channels, and optionally another type of die head channels form a combined die head channel that terminates at the outlet side of the die head plate which serves as the die head outlet.

[0049] According to a further particularly preferred embodiment of the present invention, one or more heat insulating cavities are provided in the die head and particularly preferably close to but upstream of the die head outlet side.

[0050] For example, the heat insulating cavity can be one or more hollow bodies, particularly hollow bodies having the aforementioned geometry and dimensions, which are filled with air as the heat insulating material.

[0051] In cross-section, the die head preferably has a circular shape or an annular ring shape with an open central part of the annular ring. The diameter of the die head depends on the total throughput passing through the die head, the size of the particles produced, and the distance between individual die head channels at the outlet, wherein each first type die head channel preferably has a throughput of 0.5 to 4 kg / h and more preferably between 0.8 and 2.5 kg / h, and wherein the distance between individual die head channels at the outlet is preferably greater than 0.5 mm and more preferably greater than 1 mm.

[0052] The die head can be made of metal, preferably made of steel or nickel-based alloys such as Hastelloy.

[0053] In a further development of the inventive concept, it is proposed that the die head includes a wear protection layer on the outlet side of the die plate. The wear protection layer is considered to be part of the die head and is preferably a thin surface coating, a surfacing layer or a cemented carbide part connected to the die plate. The wear protection layer is more preferably made of cemented carbide, which consists of fine carbide particles bonded into a composite by a binder metal. The cemented carbide preferably contains tungsten carbide (WC), titanium carbide (TiC) or tantalum carbide (TaC) as aggregates and a metal binder serving as a matrix. The thickness of the wear protection layer can be from 1 to 5,000 μm, and more preferably from 10 to 2,000 μm. Such a wear protection layer is preferably provided on the outlet side of the die plate by spraying, surfacing or brazing the wear protection onto the die head, or even more preferably by an additive manufacturing process. The wear protection layer has the function of protecting the outlet side of the die plate from wear caused by contact with the rotating blade.

[0054] The granulation blades can be arranged in the granulation device in any known manner. For example, the granulation device can include a blade head that includes one or more radial arms, and at least one of the granulation blades is mounted on the radial arm. The blade head is preferably connected to a rotatable blade shaft for rotationally driving the blade head about the axis of rotation.

[0055] The granulation device can also include an underwater granulation unit that includes a water chamber for cooling the strand extruded through the outlet die. Alternative preferred granulation units are a water ring granulation device and a hot die surface granulation device with air cooling.

[0056] The relevant disadvantage of the die head of the granulation device of the prior art is that the corresponding die head is assembled from a plurality of, in fact, dozens of different components connected to each other. However, the production of such a die head is complex, laborious and expensive. In view of this, according to a further particularly preferred embodiment of the present invention, the die head of the granulation device according to the present invention is made of only one component, or is an assembly in which at most three different components are connected to each other. More preferably, the die head of the granulation device is made of only one component, or is an assembly consisting of only two different components. When such a die head is produced by an additive manufacturing process, the die head can be made of only one component, or is an assembly of at most three different components and preferably is made of only two different components connected to each other, wherein the additive manufacturing process is i) a powder bed fusion process, ii) a material extrusion process for metals, including manufacturing a green body component using a material extrusion process as step 1, and debinding and sintering of the green body component produced in step 1 as step 2, iii) a binder jetting process for metals, including manufacturing a green body component using a binder jetting process for metal powder as step 1, and debinding and sintering of the green body component produced in step 1 as step 2, or iv) a laser metal deposition based on wire or powder. From the above four processes, i) the powder bed fusion process and iv) the laser metal deposition based on wire or powder are particularly preferred, and i) the powder bed fusion process is the most preferred. Preferably, the powder bed fusion process can be a laser powder bed fusion process or an electron powder bed fusion process.

[0057] In another aspect, the present invention relates to a method for producing the aforementioned granulation device, wherein the die head is produced by an additive manufacturing process.

[0058] Regarding the type of the additive manufacturing process, the present invention is not particularly limited. However, good results are obtained when the additive manufacturing process is one of the following: i) a powder bed fusion process, ii) a material extrusion process for metals, including manufacturing a green body component using a material extrusion process as step 1, and debinding and sintering of the green body component produced in step 1 as step 2, iii) a binder jetting process for metals, including manufacturing a green body component using a binder jetting process for metal powder as step 1, and debinding and sintering of the green body component produced in step 1 as step 2, or iv) a laser metal deposition based on wire or powder.

[0059] The powder bed fusion process can be a laser powder bed fusion process or an electron powder bed fusion process.

[0060] For each of the above processes, the above-mentioned preferred wear protection layer can also be provided on the outlet side of the die head plate. Similarly, the wear protection layer is considered to be a part of the die head.

[0061] In another aspect, the present invention relates to a process for producing pellets comprising a polymer core coated with at least one polymer and / or non-polymer material, wherein the process is carried out using the granulating device described above. The process comprises the following steps: feeding a polymer forming the polymer core into at least one inlet line for the polymer forming the polymer core, feeding a polymer and / or non-polymer material into at least one inlet line for the polymer and / or non-polymer material, feeding a heating medium into the at least one inlet line and withdrawing the heating medium from at least one outlet line for the heating medium, and cutting the strand exiting the die outlet of the die plate into pellets using the at least one granulating blade.

[0062] As described above, the polymer forming the polymer core and / or the polymer and / or non-polymer material may each contain a blowing agent. The blowing agent may be a chemical blowing agent or a physical blowing agent. Suitable chemical blowing agents are selected from the group consisting of azodicarbonamide and acid / carbonate mixtures such as citric acid and sodium bicarbonate, and any combination of two or more of the above compounds, while suitable physical blowing agents are selected from the group consisting of: ethane, propane, butane, isobutane, pentane, isopentane, cyclopentane, carbon dioxide and nitrogen, and halogenated compounds and any combination of two or more of the above compounds.

[0063] The polymer forming the polymer core and / or the polymer material may be any thermoplastic polymer such as polyethylene, polypropylene, polystyrene, polyester, polylactic acid, polyamide, etc., and any copolymer of two or more of the above polymers.

[0064] The non-polymer material may include processing aids, oils, etc.

[0065] In particular, the following combinations of the polymer composition forming the polymer core and the polymer and / or non-polymer material may be used, each combination optionally including a blowing agent for forming a coating:

[0066] 1. A core of expanded and / or non-expanded polymer with a coating layer made of a material enabling the molding of particles that are otherwise difficult to mold. Thus, a specific example is a core made of expanded polypropylene with high mechanical properties and a polypropylene coating layer having a lower melting temperature to allow better molding.

[0067] 2. A core of expanded and / or non-expanded polymer with a coating layer made of the same polymer but containing a flame retardant additive. This has the advantage that the flame retardant is less exposed to high shear and high temperatures when introduced later in the process. Thus, a specific example is polystyrene as the core and flame-retardant polystyrene as the coating.

[0068] 3. A core of an expanded and / or non-expanded polymer having a coating layer made of a colored material. Thus, a specific example is an uncolored polyethylene as the core and a colored polyethylene as the coating.

[0069] 4. A core of an expanded and / or non-expanded polymer having a coating layer made of an additive that provides dipoles and is thus sensitive to microwave heating. Thus, a specific example is foamed polyethylene as the core and a coating containing an additive that provides dipoles.

[0070] 5. A core of an expanded and / or non-expanded polymer having a coating layer made of an antistatic agent and / or a conductive additive. Thus, a specific example is foamed polypropylene as the core and a polypropylene containing graphite as the coating.

[0071] 6. A core of an expanded and / or non-expanded polymer having a coating layer made of a material that enhances mechanical properties, such as a material with better mechanical properties or a reinforcing material containing similar fibers or the like. Thus, a specific example is foamed polypropylene as the core and a polypropylene containing nanocellulose as the coating.

[0072] 7. A core of an expanded and / or non-expanded polymer having a coating layer made of a water-soluble material, which is beneficial for subsequent recycling. Thus, a specific example is foamed polypropylene as the core and polyvinyl alcohol as the coating.

[0073] 8. A core of an expanded and / or non-expanded explosive polymer having a coating layer made of an encapsulating material.

[0074] 9. A core of an expanded and / or non-expanded polymer having a coating layer, wherein the core or the coating layer is made of a recycled polymer, such as a foamed polypropylene core and a recycled polypropylene outer layer.

[0075] 10. A core of an expanded and / or non-expanded polymer having a coating layer containing inflated beads or hollow beads.

[0076] 11. A core of an expanded and / or non-expanded polymer having a coating layer made of a processing aid (such as a lubricant, such as an oil).

[0077] In another aspect, the present invention relates to a granule comprising a polymer core coated with at least one layer of a polymer and / or non-polymer material, and the granule can be obtained by the above method.

[0078] In a further development of the idea of the present invention, it is proposed that the granule has a diameter of at most 10 mm, preferably 0.1 to 7 mm, more preferably 1 to 5 mm, and most preferably 1 to 3 mm. The corresponding volume of the granule preferably has a d of at most 10 mm, preferably 0.1 to 7 mm, more preferably 1 to 5 mm, and most preferably 1 to 3 mm.50 - Diameter.

[0079] Furthermore, it is preferred that any one of the core and / or the at least one layer of polymer and / or non - polymer material is a foam. The cell size of the foam can be less than 500 μm.

[0080] In addition, it is preferred that the coating layer of the polymer and / or non - polymer material covers at least 50%, more preferably at least 60%, even more preferably at least 80%, still more preferably at least 90%, yet more preferably at least 95% and most preferably the entire surface of the polymer core.

[0081] In a further development of the inventive concept, it is proposed that the thickness of one or more coating layers of the polymer and / or non - polymer material is preferably equal to or less than the radius of the polymer core of the granulate. Description of the Drawings

[0082] Specific embodiments according to the present invention will subsequently be described with reference to the accompanying drawings and by way of example.

[0083] Figure 1a is a schematic view of a granulating device for granulating a polymer strand into granulates, the granulates being made of a polymer core coated with at least one layer of polymer and / or non - polymer material.

[0084] Figure 1b is Figure 1a a schematic perspective view of the die of the granulating device shown.

[0085] Figure 1c is Figure 1a a schematic top view of the die of the granulating device shown.

[0086] Figure 1d is Figure 1a a schematic side view of the lower part of the die of the granulating device shown.

[0087] Figure 1e is with Figure 1a a schematic perspective view of the granulate produced by the granulating device shown.

[0088] Figure 1f is Figure 1e a schematic cross - sectional view of the granulate shown.

[0089] Figure 2a is a schematic perspective view of the die of a granulating device according to another embodiment of the present invention.

[0090] Figure 2b is Figure 2a a schematic top view of the die of the granulating device shown.

[0091] Figure 3aIs a schematic perspective view of a die head of a pelletizing device according to another embodiment of the present invention.

[0092] Figure 3b Is Figure 3a A schematic top view of the die head of the pelletizing device shown.

[0093] Figure 4a Is a schematic perspective view of a die head of a pelletizing device according to another embodiment of the present invention.

[0094] Figure 4b Is Figure 4a A detailed view of a section of the die head of the pelletizing device shown.

[0095] Figure 5a Is a schematic perspective view of a die head of a pelletizing device according to another embodiment of the present invention.

[0096] Figure 5b Is Figure 5a A detailed view of a section of the die head of the pelletizing device shown.

[0097] Figure 6a Is a schematic perspective view as seen from the top of the die head of a pelletizing device according to another embodiment of the present invention.

[0098] Figure 6b Is Figure 6a A schematic perspective cross-sectional view of the die head of the pelletizing device shown.

[0099] Figure 6c Is from Figure 6a And 6b A schematic perspective view as seen from the bottom of the die head of the pelletizing device shown. Detailed Description

[0100] The pelletizing device 10 for pelletizing a polymer strand into expanded pellets shown in FIG. 1 includes a first extruder 12, a second extruder 14, a die head 16 including a die head body 16a and a die head plate 16b, and an underwater pelletizing unit 18 including a water chamber 20 and a blade head 22, wherein the blade head 22 includes a plurality of blades 24, and the expanded pellets are made of a polymer core coated with at least one layer of polymer and / or non-polymer material. The first extruder 12 includes an inlet line 26 for the polymer forming the polymer core of the pellets, an inlet line 28 for the blowing agent, and an outlet line 30 leading to the die head body 16a. Similarly, the second extruder 14 includes an inlet line 32 for the polymer and / or non-polymer material and an outlet line 34 leading to the die head body 16a. The die head 16 has a cylindrical form and includes an outlet side 36 (including the die head outlet in the die head plate 16b ( Figure 1a(not shown in the figure), (here it is relative), the inlet side 38 and the peripheral region 40. The outlet pipeline 30 of the first extruder 12 enters the die body 16a on the inlet side 38 of the die body, while the outlet pipeline 34 of the second extruder 14 enters the die body 16a on the peripheral region 40 of the die body. Additionally, the die body 16a is connected with an inlet pipeline 42 for the heating medium and an outlet pipeline 44 for the heating medium on its peripheral region 40.

[0101] As Figures 1b to 1dAs shown in more detail in the figure, the inlet line 31 of the die body 16a for the polymer to form the polymer core, which is connected to the outlet line 30 of the first extruder, branches into a plurality of first type die channels 46, 46'. More specifically, each of the first type die channels 46, 46' branched from the inlet line 31 includes an upper first section 48, a second section 50, and an end section 52. The upper first section 48 is connected to the inlet line 31 and extends at an angle of approximately 45° with respect to the axial direction of the die 16. The second section 50 is connected to the first section 48 at a first end and is bent such that its opposite second end extends substantially parallel to the axial direction of the die 16. The end section 52 is connected to the second end of the second section 50. In addition, the inlet line 35 for the polymer and / or non-polymer material of the die 16 is connected to the outlet line 34 of the second extruder and enters the die body 16a at the peripheral region 40 of the die body. This inlet line 35 is connected to an annular ring channel 54, and a plurality of second type die channels 56, 56' branch from this annular ring channel 54. Each of the second type die channels 56, 56' includes a first section 58 and an end section 60. The end sections 60 of the second type die channels 56, 56' surround the end sections 52 of the first type die channels 46, 46', such that the end sections 52 of the first type die channels 46, 46' and the end sections 60 of the second type die channels 56, 56' form a combined die channel 62, which terminates at the outlet side of the die as the die outlet. Each combined die channel 62 tapers stepwise from its upstream end to its downstream end (i.e., the die outlet). In other words, each combined die channel 62 includes a first upstream section having the same diameter throughout its length, a second section having a diameter that gradually decreases from its upstream end to its downstream end downstream thereof, and a third section having the same diameter throughout its length downstream thereof. Additionally, the inlet line 42 for the heating medium and the outlet line 44 for the heating medium are connected to each other through two serpentine heating channels 64, 64', such that each combined die channel 62 is surrounded by different longitudinal segments of the heating channels 64, 64', i.e., such that each combined die channel 62 is surrounded by a separate heating channel. More specifically, the two serpentine heating channels 64, 64' are formed such that they partially surround all the combined die channels 62. More specifically, the serpentine heating channels 64, 64' wind around the combined die channels 62, where approximately 60% of the outer circumference of each combined die channel 62 is close to the heating channels 64, 64', i.e., preferably at a distance of 1 to 10 mm and more preferably 3 to 6 mm between the outer peripheral region of each combined die channel 62 and the outer peripheral region of one of the heating channels 64, 64'. A section extending over approximately 50% of the length of each combined die channel 62 is surrounded by the heating channels 64, 64'.Finally, the heat-insulating cavity 65 or, respectively, the heat-insulating layer 65 is arranged at a distance of approximately 1 to 20 mm upstream of the outlet side 36 of the die plate 16b, wherein the heat-insulating layer 65 has the form and dimensions of the outlet side 36 of the die plate 16b, except that a slit 67 including holes for forming the combined end channels 62 of the die outlet is provided in the heat-insulating layer 65.

[0102] During operation of the granulating device 10, a first polymer is supplied via the inlet line 26 to the heated first extruder 12, and an optional blowing agent is supplied via the inlet line 28 to the heated first extruder 12 in order to generate a mixture of polymer melt therein, with the optional blowing agent being uniformly distributed in the mixture. Furthermore, a second polymer is supplied via the inlet line 32 to the second extruder 14 in order to generate a melt of the second polymer therein. The mixture of polymer melt in which the optional blowing agent is uniformly distributed is supplied via the inlet line 31 to the die 16 and is then guided through the first type of die channels 46, 46'. The melt of the second polymer is supplied via the inlet line 35 to the die 16 and is then guided through the second type of die channels 56, 56'. The mixture flows through the first type of die channels 46, 46' into the combined die channel 62, and the melt of the second polymer flows through the second type of die channels 56, 56' into the combined die channel 62. Due to the inertia of the mixture of polymer melt in which the optional blowing agent is uniformly distributed, due to the pressure by which the mixture is extruded through the first type of die channels 46, 46', and due to the temperature of the mixture being extruded through the first type of die channels 46, 46' being slightly higher than its melting point, the mixture extruded through the first type of die channels 46, 46' does not or at least does not significantly mix with the melt of the second polymer extruded through the second type of die channels 56, 56' in the combined die channel 62. Thus, a strand (with the optional blowing agent uniformly distributed therein) of a molten polymer core coated with a layer of molten second polymer exits each die outlet and enters the water bath 20, where the strand is cooled and solidified. However, in the case where there is a blowing agent in the core, before the solidification is completed, the blowing agent causes the core of the strand to expand or, respectively, foam, and the strand is cut into expanded pellets 66 by the blade 24, as Figure 1e and 1f shown in the schematic perspective view and the schematic cross-sectional view, each pellet having a core 68 of expanded first polymer and a coating layer 70 of second polymer.

[0103] Figure 2a and 2b The die 16 shown in Figures 1b to 1c is similar to the die shown inFigure 2a and 2b In the embodiment shown, each of the plurality of second die channels 56, 56' branching from the annular channel 54 includes an upper first section 58 connected to the annular channel 54 and extending at an angle of approximately 30° relative to the axial direction of the die 16, a second section 72 having a first end connected to the first section 58 and curved such that its opposite second end extends substantially parallel to the axial direction of the die 16, and an end section 60 connected to the second end of the second section 72.

[0104] Figure 3a and 3b The die 16 shown does not include an annular channel 54. Instead, the inlet line 35 for the polymer and / or non-polymeric material branches into two inlet sub-lines 74, 74', from which the second die channels 56, 56' branch. Additionally, each of the second die channels 56, 56' of this embodiment may include a first section 58 and an end section 60, which together with the end sections 52 of the first die channels 46, 46' form a combined die channel 62, where the first section 58 connects the end section 60 of the second die channels 56, 56' to one of the inlet sub-lines 74, 74' branching from the inlet line 35. The first section 58 of the second die channels 56, 56' preferably has a cylindrical form.

[0105] Figure 4a and 4b The die 16 shown is similar to Figure 2a and 2bThe die head shown. However, it is different in that the die head 16 does not include two serpentine heating channels 64, 64'. Instead, the inlet line 42 for the heating medium and the outlet line 44 for the heating medium are connected to each other through two central annular heating channels 76, 76'. Looking along the axial direction of the die head 16, the two central annular heating channels 76, 76' are arranged at a certain distance from each other and are connected to each other through a plurality of (connected) individual heating channels 78, 78'. The heating channels 78, 78' connect the two central annular heating channels 76, 76', and they further completely surround a section of the combined die head channel 62. More specifically, the (connected) individual heating channels 78, 78' include a section 80, which has the form of a hollow cylinder and surrounds the outer circumference of a section of the combined die head channel 62. The section 80 having the form of a hollow cylinder is connected to a first additional section 82 of the heating channel 78, which connects the hollow body section 80 to one of the two central annular heating channels 76, and is also connected to a second additional section 84 of the individual heating channel 78, which connects the hollow body section 80 to the other of the two central annular heating channels 76'.

[0106] Figure 5a and 5b The die head 16 shown in Figure 4a and 4b is different from the die head shown therein in that the die head 16 does not include two central annular channels 76, 76', but includes only one central annular channel 76 for the heating medium. The central annular channel 76 for the heating medium is not a supply channel but a collection channel. More specifically, a plurality of individual non-annular heating channels 84 branch off from the inlet line 42 for the heating medium. Each individual non-annular heating channel 84 includes connecting sections 78, 78' and another section 80 in the form of a hollow cylinder that surrounds the outer circumference of a section of the combined die head channel 62, where each connecting section 78, 78' is arranged between the inlet line 42 for the heating medium and the section 80 in the form of a hollow cylinder. Each additional section 80 in the form of a hollow cylinder concentrically surrounds the outer circumference of a section of the combined die head channel 62, preferably at a distance of 1 to 10 mm and more preferably 3 to 6 mm. Each additional (heating channel) section in the form of a hollow body 80 of this embodiment is connected to the collection channel 76 at the end opposite to the end where it is connected to the connecting sections 78, 78'. The collection channel 76 is in turn connected to the outlet 44 for the heating medium.

[0107] Figures 6a to 6cThe die head 16 shown in [Figure] is different from the die heads shown in other figures in that the outer circumference of each section of one zone of all the combined die head channels 62 is completely surrounded by separate heating channels 76, 76', where all the separate heating channels 76, 76' are connected to each other by connecting channels 78, 78', such that the inlet line 42 for the heating medium is connected to the outlet line 44 for the heating medium via all the separate heating channels 76, 76' and the connecting channels 78, 78'.

[0108] List of Reference Numerals

[0109] 10 Granulation device

[0110] 12 First extruder

[0111] 14 Second extruder

[0112] 16 Die head

[0113] 16a Die head body

[0114] 16b Die head plate

[0115] 18 (Underwater) granulation unit

[0116] 20 Water chamber

[0117] 22 Blade head

[0118] 24 Blade

[0119] 26 Inlet line for the polymer for forming the polymer core into the first extruder

[0120] 28 Inlet line for the blowing agent into the first extruder

[0121] 30 Outlet line of the first extruder

[0122] 31 Inlet line for the polymer for forming the polymer core into the die head

[0123] 32 Inlet line for the polymer and / or non-polymer material into the second extruder

[0124] 34 Outlet line of the second extruder

[0125] 35 Inlet line for the polymer and / or non-polymer material into the die head

[0126] 36 Outlet side of the die head

[0127] 38 Inlet side of the die head

[0128] 40 Peripheral area of the core

[0129] 42 Inlet pipeline for heating medium

[0130] 44 Outlet pipeline for heating medium

[0131] 46, 46’ Die channel of the first type

[0132] 48 First section of the die channel of the first type

[0133] 60 Second section of the die channel of the first type

[0134] 52 End section of the die channel of the first type

[0135] 54 Annular ring channel

[0136] 56, 56’ Die channel of the second type

[0137] 58 First section of the die channel of the second type

[0138] 60 End section of the die channel of the second type

[0139] 62 Combined die channel

[0140] 64, 64’ Serpentine heating channel

[0141] 65 Heat insulation cavity / heat insulation layer

[0142] 66 Granules of expanded first polymer core coated with second polymer

[0143] 67 Slit in the heat insulation layer

[0144] 68 Core of the expanded first polymer

[0145] 70 Coating layer of the second polymer

[0146] 72 Second section of the die channel of the second type

[0147] 74, 74’ Inlet sub-pipeline

[0148] 76, 76’ Central annular heating channel / collection channel

[0149] 78, 78’ Connected heating channel / connection section of the heating channel

[0150] 80 First additional section of a separate heating channel in the form of a hollow cylinder

[0151] 82 Second additional section of a separate heating channel in the form of a hollow cylinder

[0152] 84 Non-annular heating channel

Claims

1. A granulating device for granulating a polymer strand into granules, the granules being made of a polymer core coated with at least one layer of a polymer and / or non-polymer material, wherein, The granulation device includes: - at least one melt supply device, - a die head having an inlet side and an outlet side, wherein the inlet side is connected to the melt supply device, and wherein the die head includes: - at least one inlet line for a polymer for forming a polymer core, which is connected to a plurality of first - type die channels, wherein each first - type die channel includes an end section terminating at the outlet side of the die head, - at least one inlet line for a polymer and / or a non - polymer material, which is connected to a plurality of second - type die channels, wherein each second - type die channel includes an end section terminating at the outlet side of the die plate, and wherein at least 50% of the end sections of the second - type die channels surround the end sections of the first - type die channels such that the end sections of the first - type die channels and the end sections of the second - type die channels form a combined die channel that terminates at the outlet side of the die head as the die outlet, - at least one inlet line and at least one outlet line for a heating medium, wherein the at least one inlet line and the at least one outlet line for the heating medium are connected to each other through one or more heating channels, and wherein at least 50% of the combined die channels are at least partially surrounded by individual heating channels, and - at least one granulation blade, which is arranged on the outlet side of the die head and allows the strand exiting the die outlet to be cut into pellets.

2. The granulating device according to claim 1, wherein, At least the end sections of the first - type die channels and at least the end sections of the second - type die channels have a circular cross - section, and wherein each end section of the second - type die channel concentrically surrounds the end section of the first - type die channel so as to form a combined die channel that terminates at the outlet side of the die head as the die outlet.

3. The granulating device according to claim 1 or 2, wherein i) at least 70%, preferably at least 80%, more preferably at least 90%, still more preferably at least 95%, yet more preferably at least 99% of the end sections of the second type of die channels and most preferably each end section of the second type of die channels surrounds the end section of the first type of die channels, such that the end section of the first type of die channels and the end section of the second type of die channels form a combined die channel, which terminates at the outlet side of the die plate as the die outlet, and wherein, ii) At least 70%, preferably at least 80%, more preferably at least 90%, still more preferably at least 95%, still more preferably at least 99% of the combined die channels and most preferably all of the combined die channels are at least partially surrounded by individual heating channels.

4. The granulation device according to any one of the preceding claims, wherein, In a cross - section of the die head, in the region where the combined die channel is surrounded by an individual heating channel, the distance between the outer circumference of the combined die channel and the outer circumference of the individual heating channel is 1 to 10 mm, and preferably 3 to 6 mm.

5. The granulation device according to any one of the preceding claims, wherein, At least 50%, preferably at least 75%, more preferably at least 90%, still more preferably at least 95% and most preferably all of the outer circumference of at least one section of the combined die channel is surrounded by an individual heating channel, and the section of the combined die channel surrounded by the individual heating channel extends to cover preferably 10% to 90%, preferably 15% to 60%, and most preferably 20% to 45% of the length of the combined die channel.

6. The granulation device according to any one of the preceding claims, wherein, At least 70%, preferably at least 80%, more preferably at least 90%, still more preferably at least 95%, yet more preferably at least 99% of the outer circumferences of all sections of the modular die channels and most preferably all of the outer circumferences of all sections of the modular die channels are surrounded by separate heating channels, wherein the sections of the modular die channels surrounded by the separate heating channels extend over a length of the modular die channels of preferably 10% to 90%, preferably 15% to 60% and most preferably 20% to 45%.

7. The granulation device according to any one of the preceding claims, wherein, The outer circumferences of all sections of all modular die channels are surrounded by separate heating channels, wherein all of the separate heating channels are connected to one another via connecting channels such that the at least one inlet line for the heating medium is connected to the at least one outlet line for the heating medium via all or at least some of the separate heating channels and the connecting channels, wherein the sections of the modular die channels surrounded by the separate heating channels extend over a length of the modular die channels of preferably 10% to 90%, preferably 15% to 60% and most preferably 20% to 45%.

8. The granulating device according to any one of claims 1 to 6, wherein, The die includes at least one inlet line and at least one outlet line for the heating medium, both of which are connected to one another via a central heating channel, preferably an annular heating channel, wherein a plurality of separate heating channels branch off from the central heating channel, preferably the annular heating channel, and each of the separate heating channels at least partially and preferably completely surrounds at least one section of the modular die channels.

9. The granulation device according to claims 1 to 6 and 8, wherein, The die includes at least one inlet line and at least one outlet line for the heating medium, both of which are connected to one another via a central heating channel, preferably an annular heating channel, wherein a plurality of separate heating channels branch off from the central heating channel, preferably the annular heating channel, and each of the separate heating channels branching off from the central heating channel completely surrounds at least one section of the modular die channels, wherein the sections of the modular die channels surrounded by the separate heating channels extend over a length of the modular die channels of preferably 10% to 90%, preferably 15% to 60% and most preferably 20% to 45%.

10. The granulation device according to any one of claims 1 to 6, wherein, The die includes at least one inlet line and at least one outlet line for the heating medium, both of which are connected to one another via two central heating channels, preferably annular heating channels, wherein, when viewed in the axial direction of the die, the two central heating channels, preferably the annular heating channels, are arranged at a distance from one another and are connected to one another via a plurality of separate heating channels, and each of the separate heating channels at least partially and preferably completely surrounds a section of the modular die channels.

11. The granulation device according to claims 1 to 6 and 10, wherein, The die head includes at least one inlet line and at least one outlet line for a heating medium, both the inlet line and the outlet line being connected to each other through two central heating channels, preferably annular heating channels, wherein, when viewed in the axial direction of the die head, the two central heating channels, preferably annular heating channels, are arranged at a distance from each other and are connected to each other through a plurality of individual heating channels, wherein each individual heating channel completely surrounds at least a section of the combined die head channel, and wherein the section of the combined die head channel surrounded by the individual heating channels extends over preferably 10 to 90%, preferably 15 to 60%, and most preferably 20 to 45% of the length of the combined die head channel.

12. The granulation device according to any one of the preceding claims, wherein, Each of the first type of die head channels includes a first section, a second section, and an end section. The first section is connected to the inlet line and extends at an angle of 10° to 90°, and preferably 30° to 60° or 70° to 90° with respect to the axial direction of the die head. The second section has a first end and a second end. The first end is connected to the first section at such an end of the second section that is opposite to the end of the first section connected to the inlet. wherein the second section is curved such that its second end extends at least substantially parallel to the axial direction of the die head, and the end section is connected to the second end of the second section.

13. The granulation device according to any one of the preceding claims, wherein, Each of the second type of die head channels includes a first section, a second section, and an end section. The first section is connected to the inlet line and extends at an angle of 1° to 90°, and preferably 1° to 20° with respect to the axial direction of the die head. The second section has a first end and a second end. The first end is connected to the first section at such an end of the second section that is opposite to the end of the first section connected to the inlet. wherein the second section is curved such that its second end extends at least substantially parallel to the axial direction of the die head, and the end section is connected to the second section.

14. The granulation device according to any one of the preceding claims, wherein, The die head includes an inlet line for a polymer and / or non-polymer material, the inlet line being connected to an annular ring channel, from which a plurality of second type of die head channels branch off.

15. The granulating device according to any one of the preceding claims, wherein, The die head is made of one piece or is an assembly of at most 3 different pieces connected to each other, wherein the die head is produced by an additive manufacturing process, and wherein the additive manufacturing process is: i) a powder bed fusion process, ii) a material extrusion process for metals, including manufacturing a green part using a material extrusion process as step 1, and debinding and sintering the green part produced in step 1 as step 2, iii) a binder jetting process for metals, including manufacturing a green part using a binder jetting process with metal powder as step 1, and debinding and sintering the green part produced in step 1 as step 2, or iv) laser metal deposition based on wire or powder.

16. A process for producing pellets, said pellets comprising a polymer core coated with at least one layer of a polymer and / or non-polymer material, wherein, The process is carried out using the granulating device according to any one of claims 1 to 14 and comprises the steps of: feeding a polymer forming a polymer core into at least one inlet line for the polymer forming the polymer core, feeding a polymer and / or non-polymer material into at least one inlet line for the polymer and / or non-polymer material, feeding a heating medium into the at least one inlet line, and withdrawing the heating medium from the at least one outlet line for the heating medium, and cutting the strand exiting the die outlet of the die plate into pellets with the at least one granulating blade.

17. A pellet comprising a polymer core coated with at least one layer of polymer and / or non-polymer material, obtainable by the process according to claim 16.

18. The pellet according to claim 17, wherein, The pellet has a diameter of at most 10 mm, preferably from 0.1 to 7 mm, more preferably from 1 to 5 mm, and most preferably from 1 to 3 mm, and / or wherein the core of the pellet and / or any one of the at least one layer of polymer and / or non-polymer material is a foam having a cell size of less than 500 μm.

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