Underwater granulation device and process

Abstract

The invention relates to an underwater granulating device for producing granules from flowable, curable plastic, comprising a perforated plate-nozzle arrangement which has a melt inlet for supplying liquid melt and melt outlets for delivering a plurality of melt strands into an adjacent cutting chamber, a cutting device for producing granule particles from the melt strands, and a cutting chamber arranged adjacent to the perforated plate-nozzle arrangement which can be filled with water or other liquid. - which has at least one (water) inlet for supplying water or other liquid into the cutting chamber - and has at least one (water) granule outlet for removing a mixture of water or other liquid and granules from the cutting chamber. According to the invention, the device can have a gas inlet connectable to a gas source for the indirect or direct introduction of gas into the cutting chamber, such that the introduced gas interacts with granules within the cutting chamber. Furthermore, the invention relates to an underwater granulation process.

Description

[0001] The invention relates to an underwater granulating device and an underwater granulating method for producing granules or pellets from a melt of plastic, in particular a polymer.

[0002] In particular, the invention relates to a granulating device for producing granules from flowable, curable plastic, comprising a perforated plate nozzle arrangement having a melt inlet for supplying liquid melt and melt outlets for discharging a plurality of melt strands into an adjacent cutting chamber, a cutting device for producing granulate particles from the melt strands, and a cutting chamber arranged adjacent to the perforated plate nozzle arrangement which can be filled with water or other liquid, said cutting chamber having at least one (water) inlet for supplying water or other liquid into the cutting chamber and at least one (water) granulate outlet for discharging a mixture of water or other liquid and granulate from the cutting chamber, as well as a method according to the preamble of claim 9.In general, water is the preferred liquid, but other liquids or liquid mixtures can also be used.

[0003] Granulation devices and methods are known, for example from EP 3 711 923 A1 or EP 3 915 747 A1, which originate from the applicant. In such underwater granulation devices, a plastic which flows when heated, also called a melt, is fed to a nozzle arrangement with a perforated plate having a plurality of fluid channels. The liquid melt flows through the perforated plate and is arranged adjacent to a cutting chamber filled with water. Melt strands flowing out of the holes in the perforated plate are separated into individual granulate particles or pellets of melt by a usually rotating knife in contact with the nozzle plate and are then discharged into the cutting chamber, which is also called the "water box". The individual particles come into contact with the water in the cutting chamber and thus form individual granules or pellets which solidify over time.Water is continuously fed into the cutting chamber. The pellets are cooled by contact with the water and solidify.

[0004] The pellets thus formed are transported out of the cutting chamber by the flow of water together with the pellets in a two-phase flow of water and pellets. To accelerate the removal of the mixture of water and pellets from the cutting chamber, according to WO2009 / 155196, air was introduced into a transport pipe downstream of the granulation device to accelerate the transport of the water with the produced pellets to a centrifugal dryer. After removal, the pellets are separated from the water and dried in a drying process using a drying device. The pellets thus produced can later be melted and used to manufacture plastic products, e.g., through injection molding processes and machines, or in production processes, e.g., as a liquid adhesive.

[0005] The pellet or granulate particles resulting from the discharge from the nozzle plate and cutting in the cutting chamber exhibit irregular shapes, ranging from more or less elongated, sometimes curved, to rounded or elliptical. Often, a near-spherical shape is desired, as this offers advantages in terms of crystallization, flowability, and packing density during transport.

[0006] The object of the present invention is to provide a granulating device and a granulating method for producing pellets or granules in an underwater granulating process in order to positively influence the shape of the pellets in the cutting chamber, in particular in such a way that the pellets produced approximate a spherical shape.

[0007] The invention solves the problem with a granulating device according to claim 1 and with a method according to claim 9.

[0008] In the granulating device according to the invention or, analogously, in the method, at least one gas inlet connectable to a gas source is provided for introducing gas directly or indirectly into the cutting chamber, such that the gas introduced directly or indirectly can interact with the granules within the cutting chamber. The gas introduced directly or indirectly into the cutting chamber according to the invention moves in the water in the cutting chamber and interacts with the pellets released by the perforated plate nozzle arrangement, which are initially still somewhat flowable and then cool and solidify and float in the water in the cutting chamber (water box). After introduction, the gas typically forms a plurality of gas bubbles which are subject to buoyancy within the water and thus begin to move, in addition to a flow of the water introduced into and flowing through the cutting chamber.The gas bubbles can come into contact with the pellets, they can influence the movement of the pellets in the water, can lead to mixing and additional movement of the pellets, and the like. Overall, this leads to the pellets in the cutting chamber taking on rounder and more uniform, homogeneous shapes during solidification than in the prior art. The size and homogeneity of the frequently desired round or elliptical shape of the resulting pellets can also be favorably influenced by the introduced gas. Overall, the three-phase gas-water-pellet flow or movement in the cutting chamber allows for better pellet quality to be achieved in the underwater pelletization process.According to the invention, improved properties of the pellets or granules produced can be achieved by the gas introduced into the cutting chamber. In particular, the gas introduced directly or indirectly into the cutting chamber ensures that the pellets produced are even more advantageously close to a compact shape, in particular a spherical shape, or ideally even have a spherical shape. The improved approximation of the pellets to a spherical shape according to the invention, for example in the case of PET plastic, further advantageously results in less energy being required later when liquefying the pellets, because the further crystallization behavior of the pellets is also improved.By approaching a spherical shape, the produced pellets or granules contain higher internal heat, resulting in greater crystallinity or a higher degree of crystallinity, which offers advantages for further processing of the pellets in plastics processing plants, particularly during melting. The introduced gas also allows for improved process operation outside of otherwise optimal operating modes, reducing wear between the blade and the die plate, as well as clogging of the nozzle openings in the die plate.

[0009] The gas is preferably air, but other gases or gas mixtures can also be used. The air is preferably provided from a compressed gas source. This provides a further factor influencing the solidification process of the plastic in the form of the introduced gas and the gas bubbles that typically form. The solidification can also be specifically influenced by the amount of gas introduced into the cutting chamber according to the invention, measured, for example, as a volume flow or mass flow, as a further variable in the process of solidification and formation of pellets of the most homogeneous, good quality possible. Furthermore, chemical reactions triggered by the introduced gas in the cutting chamber are possible, be it through the reaction of gas molecules with molecules of the plastic or the like.Alternatively, it is also possible according to the invention to introduce other gases or mixtures, such as noble gases, argon, nitrogen, or the like, directly or indirectly into the cutting chamber instead of air, preferably gases that do not react with the molecules contained in the pellets. Alternatively, liquids other than water can also be introduced directly or indirectly into the cutting chamber according to the invention, for example, mixtures of water and other liquids.

[0010] A particularly preferred embodiment of the granulating device according to the invention provides for a gas nozzle arrangement connectable to the gas inlet and having a plurality of nozzle openings for discharging the gas into the cutting chamber. The gas nozzle arrangement is arranged directly within the cutting chamber or within a (water) supply channel connected to the cutting chamber, such that a plurality of gas bubbles can be formed in the cutting chamber, which can be filled with water or another liquid. Such a gas nozzle arrangement can assist bubble formation, so that a plurality of, for example, small gas bubbles are generated, which then interact intensively with the pellet particles in the cutting chamber.

[0011] According to a further preferred embodiment, it is proposed that the gas nozzle arrangement be arranged upstream of the outlet of the cutting chamber, preferably directly in or on the cutting chamber or indirectly in or on a (water) supply channel, preferably within a (water) supply pipe. In this way, the gas can be introduced alternatively or cumulatively indirectly and / or directly into the cutting chamber. In this way, a plurality of gas bubbles can advantageously form, which then advantageously interact intensively with the cut pellets introduced into the cutting chamber. Due to the buoyancy of the gas, preferably the air, in the flowing water, the velocity components of the flowing water and the buoyant gas can add up, so that the gas bubbles reach the area of ​​the pellets suspended in the water at increased speed, which can influence the formation of the pellets.In this way, the homogeneity and quality of the resulting pellets can be further positively influenced. In particular, the invention achieves that the formed pellets come closer to a compact shape, in particular an optimal spherical shape, although a spherical shape is often only aspired to and a precise spherical shape is rarely achieved in practice. Tests have shown that the invention achieves an improved approximation to a spherical or compact shape compared to the prior art. The roundness of the pellets is increased according to the invention.

[0012] It is therefore expedient if the gas nozzle arrangement is arranged below the perforated plate nozzle arrangement.

[0013] A further preferred embodiment of the invention is characterized in that the gas nozzle arrangement is arranged within a (water) supply pipe forming the (water) supply channel, which is preferably oriented substantially vertically and preferably arranged substantially below the perforated plate nozzle arrangement and, during operation, supplies the water-gas mixture to the cutting chamber. This allows for the strong and homogeneous formation of a large number of gas bubbles in the area of ​​the water supply, resulting in strong interaction between the gas bubbles suspended in the water flow and the solidifying pellets. By using a (water) supply pipe in which the gas nozzle arrangement is arranged, a very simple construction is realized, and gas connections directly in the area of ​​the cutting chamber are avoided.

[0014] According to an advantageous development of the invention, with a view to a favorable, intensive mixing of air bubbles and pellets, it is proposed that the melt outlets of the perforated plate nozzle arrangement are arranged such that granulate particles and water-gas mixture move towards each other at least partially within the cutting chamber essentially at an angle between 60 and 120, preferably approximately 90°.

[0015] Preferably, the granulating device is designed such that a water-granulate discharge channel for discharging the granulate-water-gas mixture is arranged at an upper section of the cutting chamber, which is preferably designed as a tube and is preferably arranged at least in sections substantially vertically in order to discharge the granulate-water-gas mixture during operation and to transport it further for separation of the pellets and drying.

[0016] Particularly strong bubble formation by introducing a high gas volume flow can be achieved by designing the gas nozzle arrangement as a ring nozzle.

[0017] The advantages described above are equally achieved by an underwater granulation method according to the invention for producing granules from flowable, curable plastic, preferably using the granulation device according to the invention, wherein the method according to the invention comprises the following steps: liquid plastic in the form of a melt is fed to a perforated plate nozzle arrangement with a perforated plate and is discharged from the perforated plate through a plurality of flow channels in the perforated plate in the form of a plurality of melt strands, the discharged melt strands are separated into separate granulate or pellet particles by means of a cutting device, the granulate particles are discharged into a cutting chamber filled with water or other liquid, water or other liquid is introduced into the cutting chamber through at least one (water) inlet,Water or other liquid and granules are removed from the cutting chamber through at least one outlet, wherein, according to the invention, gas or a gas mixture is introduced into the cutting chamber through a gas inlet such that the gas interacts with granule particles within the cutting chamber filled with water or other liquid. Regarding the technical effects and advantages, reference is made to the above descriptions of the device to avoid repetition.

[0018] Preferably, it is provided that gas is passed through the gas inlet to a gas nozzle arrangement connected thereto with a plurality of nozzle openings, the gas is released from the nozzle openings into the cutting chamber, a plurality of gas bubbles form within the cutting chamber or within a water supply channel connected to the cutting chamber and the gas bubbles in the cutting chamber interact with the granulate particles and thereby influence the shape of the granules or particles during solidification, which advantageously leads to greater compactness or roundness of the pellets.

[0019] It is further preferred if gas is introduced through the gas nozzle arrangement upstream of the cutting chamber outlet, preferably directly into or at the cutting chamber or indirectly into or at a (water) supply channel formed by a (water) supply pipe. Preferably, the gas nozzle arrangement is arranged below the perforated plate nozzle arrangement and / or gas is introduced by means of the gas nozzle arrangement into a (water) supply pipe forming the (water) supply channel, which is preferably oriented substantially vertically and preferably arranged substantially below the perforated plate nozzle arrangement and, during operation, supplies the water-gas mixture to the cutting chamber.

[0020] The invention is described below using exemplary embodiments with reference to the accompanying figures. They show: Fig. 1: a first embodiment of a granulating device and granulating method in a schematic representation; Fig. 2: a second embodiment of a granulating device in perspective view; Fig. 3: the granulating device from Fig. 2 in side view; Fig. 4: a part of the granulating device in an enlarged side view with gas bubbles shown; Fig. 5: the granulating device in front view; Fig. 6: a sectional view of the granulating device; Fig. 7: a section of the granulating device with gas nozzle arrangement; Fig. 8: a partial section according to Fig. 7; Fig. 9: a partial section of the granulating device with gas nozzle arrangement in an alternative embodiment; Fig. 10: a partial section according to Fig. 9; Fig. 11: a partial section of the granulating device with gas nozzle arrangement in a further embodiment; Fig. 12: a partial section according to Fig. 11; Fig. 13: granules produced according to the state of the art without fumigation according to a first test; Fig. 14: Granules produced according to the invention according to the method according to the invention with the device according to the invention according to the first experiment; Fig. 15: granules produced according to the state of the art without gassing according to a second test; Fig. 16: Granules produced according to the invention according to the method according to the invention with the device according to the invention according to the second experiment.

[0021] The Fig. 1 and the Fig. The two embodiments shown in Figures 2-12 each show an (underwater) granulating device 1 and a method for producing granules 3 or pellets 3 from flowable, curable plastic, for example a polymer, which can also be referred to as a pelletizing device 1. In the Fig. 1 and Fig. 4 schematically shows a plurality of particles of pellets or granules 3. In the two embodiments, the same reference numerals are used for the same or essentially the same parts and components.

[0022] At the Fig. 1 or Fig. The granulating device 1 shown in Figure 2 is provided with a perforated plate nozzle arrangement 6, which is known per se and typically comprises a perforated disk with a plurality of cylindrical passages. The perforated plate nozzle arrangement has a melt inlet 8 for supplying liquid melt and melt outlets for discharging a plurality of melt strands into an adjacent cutting chamber 2. The cutting chamber 2 is also referred to as a water box 2 because, during operation, it is filled with water, which flows through the cutting chamber 2. Instead of water, other liquids or liquid mixtures can also be used in the device 1.

[0023] One in Fig. 1 not, but in Fig. The cutting device 12 shown in Figures 2-6 and described in more detail with reference to these, with a drive and a knife rotatable by the drive, serves to produce individual particles of granulate 3 from the melt strands, which are discharged from the nozzle arrangement 6, preferably having a perforated disk, into the cutting chamber 2, which is arranged adjacent to the perforated plate nozzle arrangement 6 and can be filled with water or another liquid. The cutting chamber 2 has (at least) one water inlet 14, preferably arranged in the lower region, for the indirect supply of water, in this example, into the cutting chamber 2, and (at least) one water-granulate outlet 16, arranged in the upper region, for discharging a mixture of water, granulate, and gas from the cutting chamber.The water inlet 14 of the cutting chamber 2 is coupled to an adjoining water supply pipe 38, through which a water supply channel 36 is formed for supplying water into the cutting chamber 2. The outlet 16 in the upper region of the cutting chamber 2 is coupled to a water-granulate discharge pipe 18, through which granulate 3—together with water and gas—can be discharged upwards and fed to a separating device known per se to a person skilled in the art for separating the produced granulate 3 from the water, and preferably to a drying device known per se (not shown) for drying the produced granulate 3.

[0024] Fig. 1, and more precisely the initial example according to the Fig. 2-11 show the device 1 with at least one gas inlet 19 connectable to a gas source (not shown) for introducing gas into the cutting chamber 2, such that introduced gas can interact with granulate 3, particularly and preferably in the form of moving bubbles within the cutting chamber 2. In the exemplary embodiments, the gas inlet 19 is arranged within the water supply pipe 38 connected to the cutting chamber 2, so that introduced gas can be introduced indirectly through the supply pipe 38 and then directly through the inlet 14 into the cutting chamber 2, in the exemplary embodiment as a water-gas mixture flowing into the cutting chamber 2 through the water supply pipe 38 and the inlet 14.It is also according to the invention that gas can be introduced into the cutting chamber 2 through a gas inlet 19 located within the cutting chamber 2 or a gas inlet 19 formed in a wall of the cutting chamber 2 and is introduced during operation from a gas source. The introduced gas is preferably air and preferably forms a plurality of gas bubbles, which are introduced into the cutting chamber 2 indirectly by flowing through the feed pipe 38, as shown, or directly, as described, and interact with the particles of granulate 3.

[0025] Through a Fig. 1 and Fig. 4, water or other liquid can initially be supplied in a single-phase flow, indicated by the arrow 39, from a reservoir by means of a pump, preferably upwards through the vertical supply pipe 39. The gas inlet 19 is connected to a gas nozzle arrangement 20 with a plurality of nozzle openings 44 for discharging the gas into the cutting chamber 2. The gas nozzle arrangement 20 can be arranged in a manner not shown within the cutting chamber 2 or, as shown in the exemplary embodiments, within a (water) supply channel 36 connected to the cutting chamber 2 and formed by the supply pipe 38, wherein in both cases it is preferably achieved that a plurality of gas bubbles 24 are formed in the cutting chamber which can be filled with water.A gas stream, indicated by the arrow 41 here in the form of bubbles 24 forming, flows together with the supplied water (arrow 39) in a two-phase flow through the feed pipe 38 and through the inlet 19 into the cutting chamber 2 and can interact there with the produced granules 3. A stream of granules 3, illustrated by the arrow 43, then flows together with water and gas in a three-phase flow (of granule particles, water, air) further upwards out of the cutting chamber 2 through the outlet 16 and the preferably at least partially vertically arranged discharge pipe 18 for further processing, in particular separation of the granules 3 and drying.

[0026] The Fig. 1 and 4-6 illustrate the water-granulate discharge channel 17 for discharging the granulate-water-gas mixture at the upper section of the cutting chamber 2, which is designed as a discharge pipe and is preferably arranged at least in sections substantially vertically in order to discharge the granulate-water-gas mixture during operation.

[0027] As in particular the Fig. 2 and Fig. 3, the device 1 comprises a machine frame 32, which is preferably movable by means of rollers, on which the cutting device 12 with drive 34 and rotating blade, which is designed as an electric motor, and a gear connected between the drive 23 and the blade are arranged. In a manner known per se, the rotating blade is driven by means of a preferably horizontally arranged shaft 33 ( Fig. 4 and Fig. 6), which extends through the interior of the cutting chamber 2, wherein the cutting edges of the knife are in contact with the perforated disc and separate the flowing out still liquid melt into particles, which then form the granulate 3 and solidify in the water or other liquid in the cutting chamber 2. The shaft 33 for driving the knife is also in Fig. 6 shown.

[0028] As in the embodiment according to Fig. As shown in Figure 16, the cutting chamber 2 is mounted in a piping system, which in particular comprises the water supply pipe 38 and a water-granulate discharge pipe 18, each of which is coupled to further pipes. In the upper discharge pipe 18, a three-phase flow of water (or another liquid), the pellets 3, and gas, in particular air, forms. As shown in Figure 16, Fig. 1 and Fig. 4, these three components of the three-phase flow flow in the direction of arrows 39, 41, 43.

[0029] In a manner not shown, the water connection 40 is connected to further pipes to supply the water or other liquid from below through the connection 40 by means of a pump from a reservoir. At the top, in the Fig. 2-4 also shows the discharge pipe 18. This allows water or other liquid to be recycled.

[0030] As the Fig. 1-4 clearly illustrate, the gas nozzle arrangement 20 for introducing gas into the water or other liquid through the plurality of nozzle openings 44 is positioned downstream of the (water) connection 40 within the supply pipe 38. At the same time, the gas nozzle arrangement is arranged upstream of the outlet 6 of the cutting chamber 2, or in a manner not shown directly in or on the cutting chamber 2, or as shown in the exemplary embodiment, in or on a water supply channel 36, preferably within a water supply pipe 38. In the exemplary embodiment shown, it is preferably provided that the gas nozzle arrangement 20 is positioned on a section of the pipe 38 that is detachably attached to the further section of the pipe 38.In the preferred embodiment, the nozzle arrangement 20 is arranged within the water supply channel 36 connected to the cutting chamber 2, such that gas can flow in through the gas inlet 19 and then enter the cutting chamber 2 through the inlet 14. According to the invention, this type of gas introduction or direct introduction of gas into the cutting chamber 2 results in gas, preferably a plurality of gas bubbles, being formed in the water-filled cutting chamber 2. The gas nozzle arrangement 20 is arranged upstream of the water inlet 14 in the region of the water supply. As can also be seen from the figures, the gas nozzle arrangement 20 is arranged below the perforated plate nozzle arrangement 6.In this way, the gas bubbles 24 that form rise upwards and reach the area of ​​the melt particles discharged into the cutting chamber 2 by the nozzle arrangement 6, which form the granulate 3 and solidify in the water within the cutting chamber 2 in the further process.

[0031] Fig. 4 shows that the melt outlets of the perforated disk of the perforated plate nozzle arrangement are arranged such that the granulate particles and the water-gas mixture move towards each other at least partially within the cutting chamber 2 essentially at an angle between 60 and 120, preferably approximately 90°. The channels within the perforated disk are arranged essentially horizontally, and the melt flows from right to left into the cutting chamber 2, while the (water) gas mixture flows essentially vertically upwards through the inlet 14 into the melting chamber 2, see also the arrows 39 and 41 in Fig. 1. In this way, an interaction occurs during operation between the gas bubbles within the water and the particles of granulate 3. The mass or volume flow of the water, the gas and the mass flow of the melt can be adjusted and varied by appropriately adjusting the pumps, the gas supply and the water supply and can be optimized so that granulate 3 is produced in a good quality, especially in a compact form.

[0032] How Fig. 1, the gas nozzle arrangement 20 can be supplied with gas by means of a preferably horizontally arranged pipe 29. The pipe 29 is connected to a compressed gas source in a manner not shown. It extends through an opening in the wall of the supply pipe 38. The openings 44 of the gas nozzle arrangement 20, which in the exemplary embodiment are arranged in the interior of the supply pipe or alternatively directly in the cutting chamber 2, serve to discharge the gas from the nozzle arrangement 20 into the water or other liquid and ultimately into the cutting chamber 2. See also Fig. 8-12. The openings 44 can be arranged optionally along a ring, a line, or any random pattern. Fig. 6 and Fig. 10 illustrate that the nozzle arrangement 20 is designed as a ring nozzle with a plurality of openings 44 which lie on a circle.

[0033] The Fig. The sectional view shown in Figure 6 shows the feed pipe 38 with the gas nozzle arrangement 20 arranged therein, designed as an annular nozzle with a plurality of openings 44. Gas, together with water, passes through the inlet 14 into the interior of the cutting chamber 2. Granules are also introduced into the cutting chamber in the form of particles with the aid of the nozzle arrangement 6 and the cutting device 12. There, the granules 3 come into contact with the water and the gas, in particular the gas bubbles 24. The mixture of granules 3, water, and gas flows out of the cutting chamber 2 through the outlet 16 and out through the pipe 18.

[0034] Fig. 7 and Fig. 8 illustrate the gas nozzle assembly 20 and the pipe 29 (pipeline 29) for supplying gas / air from a pressurized gas source to the nozzle assembly 20. Gas is introduced into the interior of the section of the supply pipe 38 through the pipe 29.

[0035] Fig. 9 and Fig. 10 show that the gas nozzle arrangement 20 can be designed as an annular nozzle with a plurality of openings 44, so that a plurality of gas bubbles are formed in the water stream.

[0036] The Fig. 11 and Fig. 12 show an alternative embodiment of a nozzle arrangement 20. Here, a plurality of bores with openings 44 are formed in the wall of a section of the (water) supply pipe 38, through which gas can be introduced into the interior of the supply pipe 38. For this purpose, the pipe 29 is provided with an annular space 46 ( Fig. 12), and from the annular space 46 the gas can flow through the openings 44 into the interior of the feed pipe 38.

[0037] The described figures equally illustrate the underwater granulation process according to the invention for producing granules 3 from flowable, curable plastic, which is preferably carried out using the granulation device 1. Liquid plastic in the form of a melt is fed to the perforated plate nozzle arrangement 6 with the perforated plate and discharged from the perforated plate through a plurality of flow channels in the perforated plate in the form of a plurality of melt strands. By means of the cutting device 12 with at least one rotating blade, a plurality of individual particles are generated on the perforated plate, which form the granules. The granule particles are discharged into the cutting chamber 2 (water box) filled with water or another liquid. Water or other liquid is introduced into the cutting chamber 2 through at least one (water) inlet 14.Gas is introduced into the cutting chamber 2 through a gas inlet 19, either directly or indirectly through a supply channel 36. The gas introduced into the cutting chamber 2 interacts with granulate particles within the cutting chamber 2, which is filled with water or other liquid. Water or other liquid, granulate 3, and gas are removed from the cutting chamber 2 through at least one outlet 17. Preferably, gas is fed through the gas inlet 19 to the gas nozzle arrangement 20 connected thereto, which has a plurality of nozzle openings 44. The gas from the nozzle openings 44 forms a plurality of gas bubbles 24 within the cutting chamber 2, or previously within the (water) supply channel 36 connected to the cutting chamber 2.According to the embodiment, it is preferred that gas is introduced by means of the gas nozzle arrangement 20 into the (water) supply channel 36, which is preferably aligned substantially vertically and preferably arranged substantially below the perforated plate nozzle arrangement 6 and supplies (water) gas mixture to the cutting chamber 2 during operation.

[0038] It is preferred to supply the gas, preferably compressed air, continuously according to the invention. Continuous supply of gas should be understood here as meaning that the volume flow or mass flow of the gas is constant, wherein the size can be varied, i.e. different volume or mass flows can be set. Alternatively, however, with the method according to the invention, using the device according to the invention, it is also possible to supply the gas with variable volume or mass flows. For example, it is also possible according to the invention to supply the gas intermittently, i.e. to switch the gas supply on in a certain phase and to interrupt the gas supply in another phase. Those skilled in the art will understand how to achieve a continuous or variable or discontinuous, intermittent supply of gas. For example, corresponding valves can be switched on or off.be switched off and / or the gas supply can be varied using appropriate throttle valves, or different volume or mass flows can be set. The person skilled in the art understands that gas, especially air, can be supplied from a gas source such as a compressed gas system. The gas supply can be controlled and adjusted by appropriately controlling the device.

[0039] Fig. 13 shows a schematic image of plastic granules 3 produced according to the prior art. Fig. 14 shows plastic granulate 3 produced under similar production conditions according to the production method according to the invention using a device 1 according to the invention. Fig. 13 and Fig. 14 show different results without fumigation according to the invention ( Fig. 13) and with fumigation according to the invention ( Fig. 14).

[0040] The following parameters were set for this test: the test setup corresponds to the example shown in Fig. 1.Mass flow, plastic melt: 150 kg / h; 60°C process water temperature

[0041] Granule shape very irregular ( Fig. 13): Fig. Figure 13 shows that particles produced according to the state of the art are elongated and in some cases far from a compact, ideal spherical shape. The ratio of a particle's smallest width to its largest length is far from 1. The value 1 is achieved in an ideal sphere.

[0042] With fumigation according to the invention: Mass flow, plastic melt: 150 kg / h 60°C process water temperature 10% gassing with compressed air; granulate shape significantly improved in the sense of more compact and round and larger, closer to a spherical shape ( Fig. 14). From the shape of the particles according to Fig. 14 (according to the invention) to Fig. 13 (prior art) shows that the gassing according to the invention results in particles that are significantly more spherical in shape and significantly more compact. The ratio of the smallest length to the largest length is closer to the value 1 for an ideal spherical shape.

[0043] Fig. 15 shows a schematic image of plastic granules 3 produced according to the prior art. Fig. 16 shows plastic granules produced under similar production conditions according to the production method according to the invention using a device 1 according to the invention.

[0044] Fig. 15 and Fig. 16 show different results without fumigation according to the invention ( Fig. 15) and with fumigation according to the invention ( Fig. 16). The following parameters were set for this experiment: the test setup corresponds to the example shown in Fig. 1.Mass flow, plastic melt: 200 kg / h 50°C process water temperature Granule shape very irregular ( Fig. 15)

[0045] With fumigation according to the invention: Mass flow, plastic melt: 200 kg / h 50°C process water temperature 50% gassing with compressed air Granule shape visually little changed ( Fig. 16), but it is evident that the shape of the granules is rounder and closer to a sphere.

[0046] Measurements show that by fumigation according to the invention ( Fig. 16) an improvement in the roundness of granules 3 is achieved. The roundness improves from 0.661 to 0.765, with 1.0 representing spherical. Roundness is determined by dividing the smallest length by the largest length of a particle.

[0047] The surface area of ​​the individual granules also decreases, which suggests a positive change towards a spherical shape according to the invention.

[0048] The comparison of the Fig. 13 and Fig. 15 (state of the art) with the Fig. 14 and Fig. 16 (Invention) show that the inventive gassing of the process water influences the shape of the granulate formation during the solidification process. The inventive interaction of gas bubbles in the process water in the region of the cutting chamber 2 during the solidification of the granulate particles leads to an improved quality of the granulate 3, in that the granulate is more compact and closer to a spherical shape than according to the prior art. List of reference symbols 1 underwater granulating device 2 cutting chamber (water box) 3 Granules or pellets (particles) 6 hole plate nozzle arrangement 7 hole plate 8 Melt inlet 10 melt outlets 12 Cutting device 14 (Water) inlet 16 (Water) granulate outlet 17 (Water) granulate discharge channel 18 (Water) granulate discharge pipe 19 Gas inlet 20 Gas nozzle arrangement 24 gas bubbles 29 pipe 31 gearboxes 32 machine frame 33 Wave 34 Drive (cutting device) 35 knives 36 (Water) supply channel 38 (Water) supply pipe 39 Arrow water stream 40 (water) connection 41 Arrow gas flow 43 Arrow granulate flow 44 nozzle openings 46 Annular space QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3 711 923 A1

[0003] EP 3 915 747 A1

[0003] WO 2009 / 155196

[0004]

Claims

[1] Underwater granulating device for producing granules from flowable, curable plastic, with a perforated plate nozzle arrangement having a melt inlet for supplying liquid melt and melt outlets for discharging a plurality of melt strands into an adjacent cutting chamber, a cutting device for producing granulate particles from the melt strands, and a cutting chamber arranged adjacent to the perforated plate nozzle arrangement and fillable with water or other liquid, - which has at least one (water) inlet for supplying water or other liquid into the cutting chamber - and at least one (water) granulate outlet for discharging a mixture of water or other liquid and granulate from the cutting chamber, characterized byat least one gas inlet connectable to a gas source for directly or indirectly introducing gas into the cutting chamber such that introduced gas can interact with granules within the cutting chamber. [2] Granulating device according to claim 1, characterized by that a gas nozzle arrangement connectable to the gas inlet is provided with a plurality of nozzle openings for the indirect or direct discharge of the gas into the cutting chamber, wherein the gas nozzle arrangement is arranged directly within the cutting chamber or within a (water) supply channel connected to the cutting chamber, such that a plurality of gas bubbles can be formed in the cutting chamber fillable with water or other liquid. [3] Granulating device according to claim 2, characterized bythat the gas nozzle arrangement is arranged upstream of the outlet of the cutting chamber, preferably directly in or on the cutting chamber or indirectly in or on a (water) supply channel, preferably within a (water) supply pipe. [4] Granulating device according to claim 2 or 3, characterized by that the gas nozzle arrangement is arranged below the perforated plate nozzle arrangement. [5] Granulating device according to claim 2-4, characterized by that the gas nozzle arrangement is arranged within a water supply pipe forming the water supply channel, which water supply pipe is preferably aligned substantially vertically and preferably arranged substantially below the perforated plate nozzle arrangement and, during operation, supplies the water-gas mixture to the cutting chamber. [6] Granulating device according to at least one of the preceding claims, characterized bythat the melt outlets of the perforated plate nozzle arrangement are arranged such that granulate particles and water-gas mixture move at least partially within the cutting chamber towards each other substantially at an angle between 60 and 120, preferably approximately 90°. [7] Granulating device according to at least one of the preceding claims, characterized by that a water-granulate discharge channel for discharging the granulate (water) mixture is arranged at an upper section of the cutting chamber, which is preferably designed as a tube and is preferably arranged at least in sections substantially vertically in order to discharge the granulate-water-gas mixture during operation. [8] Granulating device according to at least one of the preceding claims, characterized by that the gas nozzle arrangement is designed as a ring nozzle. [9] Underwater granulation process for producing granules from flowable, curable plastic, preferably using the granulating device according to at least one of the preceding claims, in which - liquid plastic in the form of a melt is fed to a perforated plate nozzle arrangement with a perforated plate and is discharged from the perforated plate through a plurality of flow channels in the perforated plate in the form of a plurality of melt strands, - the released melt strands are separated into separate granulate particles by means of a cutting device, - the granulate particles are released into a cutting chamber filled with water or other liquid, - Water or other liquid is introduced into the cutting chamber through at least one (water) inlet and - Water or other liquid and granules are removed from the cutting chamber through at least one outlet, characterized bythat gas is introduced into the cutting chamber through a gas inlet in such a way that the gas interacts with granulate particles within the cutting chamber filled with water or other liquid. [10] Method according to claim 9, in which gas is passed through the gas inlet to a gas nozzle arrangement connected thereto with a plurality of nozzle openings, When the gas is released from the nozzle openings into the cutting chamber, a large number of gas bubbles will form within the cutting chamber or within a (water) supply channel connected to the cutting chamber. The gas bubbles in the cutting chamber will interact with the granulate particles and thereby influence the shape of the granules or particles during solidification. [11] Method according to at least one of the preceding claims, characterized bythat gas is introduced through the nozzle arrangement downstream of the (water) inlet in the area of the water supply, wherein preferably the gas nozzle arrangement is arranged below the perforated plate nozzle arrangement. [12] Method according to at least one of the preceding claims, characterized by that gas is introduced by means of the gas nozzle arrangement into a (water) supply pipe forming the (water) supply channel, which is preferably aligned substantially vertically and preferably arranged substantially below the perforated plate nozzle arrangement and, during operation, supplies the water-gas mixture to the cutting chamber.

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