DE102020103912A1 - Transport device for conveying plastic particles and method for comminuting plastic particles - Google Patents

Abstract

The present invention relates to a transport device (1) for transporting plastic particles (2) along a transport path (3) which extends from an inlet area (4) to an outlet area (6) opening into a further processing device (5), wherein the transport device (1) is designed to compact the plastic particles (2) during transport along the transport path (3) to a predetermined degree of compaction. The invention also relates to a method for compacting and / or comminuting plastic particles (2, 2 '). The transport device comprises a housing (7) extending along the transport path (3) with a housing interior (8), the housing (7) in the inlet area (4) having inlet means (9) for receiving the plastic particles (2) and in the outlet area (6) ) Outlet means (10) for discharging the compacted plastic particles (2 '), a screw (11) which is rotatably received in the housing (7) and drivable via a drive and which is formed from a screw body (12) which extends along the The transport path (3) extends from a first screw body end (21) to a second screw body end (22) and has a web (13) extending helically along the screw body (12), the screw body (12) in the direction of the second screw body end (22) has an increasing diameter (D), a helical transport channel (14) running between the web (13), the transport channel (14) extending in the direction of the second screw body rper end (22) has decreasing cross-sectional area (Q), and one in the region of the second screw body end (22) in alignment with the screw body (12) arranged screw tip (15) which tapers conically in the direction of the transport path (3) To effectively bring the plastic particles to a desired further processing temperature during transport in the direction of the further processing device and to convert them into a form that is advantageous for further processing, the housing (7) has at least one coolant and / or heating medium inlet (16) via which a cooling system - or heating means, in particular liquid nitrogen or air, can be introduced into the transport channel (14), in particular in countercurrent to a conveying direction of the plastic particles (2, 2 ').

Description

The present invention relates to a transport device for transporting plastic particles along a transport path. The transport device is designed to compact the plastic particles during transport along the transport path to a predetermined degree of compaction. The present invention also relates to a method for compacting and / or comminuting plastic particles.

Crushed plastics, especially powdered plastics, are required for different uses. Such materials can be used, for example, as starting materials for additive manufacturing processes (e.g. 3D printing processes), powder coating processes or the like. Depending on the area of application, the required particle size or particle size distribution (also grain size distribution) can vary. In order to produce such a powder, it is known to comminute a polymeric starting material initially present in lumps, for example a thermoplastic polymer, in a comminution step (carried out in a comminution device such as a grinding device) to a powder. The powder is then sieved in a sieving process in such a way that the desired particle size distribution is obtained. Such a sieved powder can be packaged and delivered to customers. The above-mentioned lumpy polymeric starting material (which is subjected to the comminution) can be present, for example, in the form of granules, that is to say in the form of granular raw material plastic particles. Plastic granulate comprises granular particles of a uniform size, but without having a uniform geometric shape or flat surfaces. Polymer granules are usually produced by means of continuous screw kneading and extrusion processes, in which a solid polymer starting material is transferred into the melt by adding thermal energy and / or mechanical shear forces and the resulting polymer strand is cut into polymer granules via a cutting process.

From the DE 20 2016 106 243 U1 a device for the production of powdery plastics is known. A hot plastic melt is fed to a nozzle device from which the melt emerges and separates into small droplets which fall down vertically. These are cooled and collected using cryogas. This is followed by sieving and packing.

It is also known to first dissolve a plastic in a solvent and to obtain particles therefrom, for example to atomize or spray the resulting solution and to keep the resulting droplets isolated until the solvent has essentially evaporated. With this process it is not necessary to heat the plastic to higher temperatures, so that chemical changes are not to be feared. However, the solvent can act chemically on the plastic and adversely affect its properties.

Devices and methods for comminuting (in particular grinding) plastics at cryogenic temperature are known in industrial use. the WO 2007/008480 A1 describes a method for grinding at cryogenic temperature and for producing a plastic powder. the EP 2 957 598 A1 discloses a process for the production of polyamides which are converted into powder by means of cryogenic milling. A sieving process then takes place.

A cryogenic temperature is generally understood to mean a temperature below minus 150 ° C. For the present invention, on the other hand, temperatures above minus 150 ° C. are also suitable, as long as a sufficient cooling effect can be achieved.

When plastics (especially plastic granulate) are comminuted, a powdery end product is generally not obtained immediately, as required and desired by the market. The customer specifies a desired grain size distribution of the powdery material, as required, for example, for a specific 3D printer. In order to obtain the desired particle size distribution, the pulverulent plastics (as obtained by the comminution) are sieved at least once, and several sieving processes can be carried out sequentially without any problems. The grain size distribution is also dependent on the type of comminution process and sieving. According to the terminology used in the present description of the invention, a “particle size distribution” is also to be understood synonymously as a “particle size distribution”.

As already mentioned, most plastics can only be comminuted to a desired fineness or grain size distribution when they are cooled. It is known from the prior art to dose plastic granulate together with coarse powder (undesired particle size or particle size distribution) returned by a comminution device into a cooling screw and to cool it by means of a coolant. Subsequently, the plastic particle mixture is fed to a further processing unit, in particular a comminution unit, comminuted in the latter and then sieved. Classic cooling screws exist in many variants, for example trough and pipe variants however, it has the disadvantage that the corresponding trough or pipe cannot be completely filled with material. When using liquid nitrogen as a coolant, it evaporates when it hits the plastic particles. In particular, the plastic particles of the powdery (recycled) plastic component cause the liquid nitrogen to evaporate particularly quickly due to their high specific surface area. _{The N 2} gas layer that forms in the process makes the cold transition between the particles more difficult and increases the necessary dwell time of the plastic particles until the temperature required for comminution is reached.

Classic cooling screws also often have disadvantages with regard to a lack of gas tightness, which is why (uncooled) powder material is often introduced into the comminution device in an undesirable manner. As a result of such a suction effect in the direction of the comminution device, the dwell time of finer powder material in the cooling screw can be significantly shorter than the dwell time of the granular plastic particles. The resulting temperature differences have a negative effect on homogeneous size reduction.

Based on the foregoing, the present invention is based on the object of providing a transport device for transporting plastic particles along a transport path, with which plastic particles are effectively brought to a desired further processing temperature during transport in the direction of a further processing device, in particular cooled, and converted into a form that is advantageous for further processing can be.

To solve this problem, a transport device with the features of claim 1 is proposed.

Furthermore, the present invention is based on the object of providing a method for compacting and / or comminuting plastic particles, in which the plastic particles can be brought to a desired temperature before comminution, in particular cooled, and converted into a form that is advantageous for comminution.

To solve this problem, a method with the features of claim 15 is proposed.

It should be pointed out that the features listed individually in the claims can be combined with one another in any technically meaningful manner (also across category boundaries, for example between method and device) and show further embodiments of the invention. The description additionally characterizes and specifies the invention, in particular in connection with the figures.

It should also be pointed out that a conjunction “and / or” used here between two features and linking them must always be interpreted in such a way that only the first feature can be present in a first embodiment of the subject matter according to the invention, in a second embodiment only the second feature can be present and, in a third embodiment, both the first and the second feature can be present.

1. a. ein sich entlang des Transportwegs erstreckendes Gehäuse mit einem Gehäuseinnenraum, wobei das Gehäuse im Einlassbereich Einlassmittel zur Aufnahme der Kunststoffpartikel und im Auslassbereich Auslassmittel zum Auslass der kompaktierten Kunststoffpartikel aufweist;
2. b. eine drehbar in dem Gehäuse aufgenommene und über einen Antrieb antreibbare Schnecke, die gebildet ist aus
   • • einem Schneckenkörper, der sich entlang des Transportwegs von einem ersten Schneckenkörper-Ende bis zu einem zweiten Schneckenkörper-Ende erstreckt und einen sich wendelförmig entlang des Schneckenkörpers erstreckenden Steg aufweist, wobei der Schneckenkörper in Richtung des zweiten Schneckenkörper-Endes einen zunehmenden Durchmesser aufweist,
   • • einem zwischen dem Steg verlaufenden wendelförmigen Transportkanal, wobei der Transportkanal eine in Richtung des zweiten Schneckenkörper-Endes abnehmende Querschnittsfläche aufweist,
   • • und einer im Bereich des zweiten Schneckenkörper-Endes fluchtend zum Schneckenkörper angeordneten Schneckenspitze, die sich in Richtung des Transportwegs konisch verjüngt.

The present invention initially relates to a transport device for transporting plastic particles along a transport path that extends from an inlet area to an outlet region opening into a further processing device, the transport device being designed to move the plastic particles towards a predetermined degree of compaction when being transported along the transport path compact, comprehensive

1. a. a housing extending along the transport path with a housing interior, the housing having inlet means for receiving the plastic particles in the inlet area and outlet means for discharging the compacted plastic particles in the outlet area;
2. b. a screw rotatably received in the housing and drivable via a drive, which is formed from
   • A screw body which extends along the transport path from a first screw body end to a second screw body end and has a helically extending web along the screw body, the screw body having an increasing diameter in the direction of the second screw body end,
   • • a helical transport channel running between the web, the transport channel having a cross-sectional area that decreases in the direction of the second screw body end,
   • And a screw tip arranged in the area of the second screw body end in alignment with the screw body, which tapers conically in the direction of the transport path.

Furthermore, it is provided in a transport device according to the invention that the housing has at least one coolant and / or heating medium inlet has, via which a cooling or heating medium, in particular liquid nitrogen or air (for example warm air), can be introduced into the transport channel, in particular in countercurrent to a conveying direction of the plastic particles. As an alternative to the use of liquid nitrogen as the coolant, which is preferred according to the invention, cooling gases such as CO ₂ or water vapor can also be used as the coolant. As an alternative or in addition to a coolant inlet - as expressed by the “and / or” link - a heating medium inlet can be provided, via which a warming / heating medium, for example hot air, can be introduced into the transport channel in countercurrent. It is also possible to use one and the same inlet for introducing such a warming / heating medium. However, the variant is particularly preferably to provide at least one coolant inlet and to cool the plastic particles in countercurrent, which is why reference is made in the following to advantageous embodiments of this variant in particular.

As mentioned, the transport device, in addition to transporting (ie conveying) the plastic particles, is designed to compact the plastic particles fed to the transport device. “Compaction” means that the supplied plastic particles - in particular a mixture of plastic particles of different particle sizes, this can be, for example, a mixture of granular raw material plastic particles and plastic particles from plastic particles returned from the further processing device - are compressed into a compact product stream of plastic particles . This means that the volume of a bed or mass of plastic particles present at the inlet area of the transport channel decreases when it is conveyed through the transport device or the plastic particles are compressed or pressed. Correspondingly, the plastic particles fed to the transport device can be processed by compacting into a compressed strand or a compressed rod made of plastic particle mass - without the need to melt the plastic material.

As above under point a. mentioned, the transport device comprises a housing extending along the transport path with a housing interior, the housing having inlet means for receiving the plastic particles in the inlet area and outlet means for discharging the compacted plastic particles in the outlet area. The housing interior can preferably have a cylindrical geometry, that is to say provide a cylindrical housing interior with a constant diameter. Alternatively, however, it can also be provided that the housing interior has a changing diameter or a changing shape along the transport path, for example the housing interior can taper along the transport path in the manner of a conical geometry, i.e. have a decreasing diameter at least in sections. In order to ensure sufficient compaction of the plastic particles, the shape of the screw body must be adapted to the shape of the interior of the housing. In the case of a housing interior that tapers along the transport path, the screw body can, for example, have a constant diameter.

The housing as such is not limited to a cylindrical shape as long as the housing interior has the said cylindrical shape. For example, various functional elements (for example temperature control units or coolant inlets - this will be referred to in more detail later) can be arranged on the outer area of the housing, which lead to an outer housing shape deviating from an ideal cylindrical shape. Due to such a cylindrical geometry of the housing interior, it can be advantageous for the transport device to be arranged horizontally, in particular to enable the plastic particles to be transported against gravity (this would be the case, for example, with a vertical arrangement). The feeding of the plastic particles through the inlet means can for example be done by a feeding unit which conveys the plastic particles under application of pressure (e.g. pneumatically or hydraulically) into the transport device. Alternatively, the plastic particles can be fed in purely based on weight, e.g. in the form of a bed which is placed in a storage container (e.g. a funnel, silo or feed pipe) connected to the inlet means. An inlet means can initially be understood as an opening in the housing, for example a hole opening. The inlet means can also comprise several adjacent housing openings, for example in order to guide two different types of plastic particles (a “different type” can mean a chemical, physical or mechanical deviation, in the simplest case a different particle diameter) into the inlet area of the transport device. Furthermore, an inlet means can be understood to mean a housing opening provided with a blocking means (e.g. a shutter element or a blocking valve). Furthermore, an inlet means can also be understood to mean one or more filler nozzles arranged (molded or mounted) on the housing.

As above under point b. executed, the transport device further comprises a rotatably received in the housing and drivable via a drive screw. The snail can set it in a rotary motion or rotation via a suitable drive (for example an electric drive).

The screw is formed from a screw body which extends along the (preferably horizontal) transport path from a first screw body end to a second screw body end and has a helical web extending along the screw body, the screw body in the direction of the second screw body -End has an increasing diameter. The screw body is preferably arranged in the housing in such a way that its longitudinal axis extends beyond the inlet area, i.e. plastic particles fed into the transport device via the inlet means hit the screw body at least partially in a channel section of the transport channel formed by the screw body and the web . It is crucial that the plastic particles already reach the transport channel in an inlet area arranged in the area of the inlet means and can be conveyed further in the direction of the outlet area.

As already mentioned, the screw body has an increasing diameter in the direction of the second screw body end, as a result of which the transport channel becomes smaller - while the inner diameter of the housing interior along the transport path remains the same. Such a design has the effect that the plastic particles or a plastic particle mass conveyed through the transport channel due to the screw movement are pressed or compacted.

As mentioned, the transport channel extends helically along the screw body, the transport channel being spatially delimited by two adjacent web areas, a screw body base and a cylindrical inner wall of the housing. Due to the configuration of the screw body described above, in particular due to the increasing diameter of the screw body along the transport path, the transport channel has a decreasing volume in the same direction. The decrease in volume can also be described by a cross-sectional area of the transport channel that decreases in the direction of the second screw body end. The provision of the ridge on the screw body enables the plastic particles to be transported along the transport channel in cooperation with the rotational movement of the screw or the screw body carried out via the drive, while the compaction takes place through the narrowing of the transport channel.

In the area of the second end of the screw body, a screw tip is arranged in alignment with the screw body, which tip tapers conically in the direction of the transport path and is also a component of the screw. The screw tip can be designed in one piece with the screw body or attached to it by suitable fastening means. As will be mentioned later, according to an advantageous embodiment of the invention it can be provided that the transport channel terminates in the connection area with a disk-like mouthpiece, the mouthpiece having an opening which is designed to allow the compacted plastic particles, for example in the form of a compacted plastic strand through which the opening can pass in the direction of the further processing device. The aforementioned screw tip now causes the plastic particles or the particle mass to be uniformly compacted or pressed in the region of the mouthpiece or the opening provided there. It is advantageous in this context if the screw tip is adapted to the geometry and size of the opening of the mouthpiece, in particular to the effect that the screw tip ends in the center of the opening of the mouthpiece. The screw tip thus serves, among other things, to guide the plastic strand or a compacted plastic particle mass of a certain consistency in the direction of the mouthpiece. The mouthpiece can taper conically along the transport path, which can lead to a more even distribution of pressure (or distribution of the pressing forces) in the area of the screw tip.

The compacted plastic mass that can be generated with the present transport device facilitates the conduction of heat between the plastic particles due to increased solid heat conduction, because in the case of the cooling variant, the heat conduction, compared to the systems known from the prior art, is not caused by the evaporation of the coolant (e.g. liquid nitrogen) Gas layer inhibited, rather an effective heat conduction between the plastic particles is made possible.

The compaction also prevents particularly small particles from rushing through the transport channel without them being adequately cooled; in contrast, these particles are also adequately cooled in the transport device described here.

Overall, the design of the transport device proposed here, in particular the provision of the screw tip, the design of the transport channel and the mouthpiece, results in a more uniform supply of a Material flow of compacted plastic particles in the direction of a further processing device connected to the transport device, for example a comminution device, allows.

As already mentioned, the transport device is characterized in that the housing has at least one cooling or heating medium inlet via which a cooling or heating medium, in particular liquid nitrogen or air, can be introduced into the transport channel, in particular in countercurrent to a transport direction of the plastic particles . Reference is made below to the cooling variant: The supply of coolant through such a coolant inlet into the transport channel enables cryogenic cooling of the plastic particles or a compacted plastic particle mass. Cooling may be necessary in particular during comminution processes, for example when grinding plastics, because the majority of polymers can only be comminuted to a desired fineness when cooled. Such cryogenic cooling can also increase the economic efficiency of comminution processes. In contrast to systems known from the prior art, the local transport device enables more effective cooling with an improved throughput of plastic particles at the same time. If, for example, liquid nitrogen is used as the coolant and this is introduced into the transport channel, the liquid nitrogen evaporates when it hits the plastic particles located in the transport channel. In particular, plastic particles with a small diameter cause rapid evaporation due to their high specific surface area. The gas layer of nitrogen that forms and is distributed around the plastic particles makes it more difficult to conduct heat and thus to cool all of the plastic particles. With the countercurrent cooling principle on which the present invention is based, this disadvantage is counteracted and the cooling efficiency is improved. The latter applies in particular to the heat or cold transfer of small particles.

Due to the countercurrent principle, the coolant gas (N ₂ ) can flow through the transport channel in a direction opposite to the conveying direction of the plastic particles. Correspondingly, a portion of the coolant gas can exit through the inlet area of the housing (for the plastic particles) and cause the plastic particles to be precooled (before the inlet) into the transport device or the transport channel. At the same time, the coolant gas (in particular N ₂ ) can render the plastic particles inert at the points mentioned. When flowing through the plastic particles (in an area upstream of the inlet to the housing, e.g. a silo or funnel), such an inert gas also ensures that no ambient moisture can come into contact with the plastic particles before they are fed into the transport channel, which is particularly important when processing hygroscopic polymers (e.g. polyamide, e.g. PA6, or thermoplastic urethane, TPU) is advantageous. The exiting coolant gas can also be diverted after exiting the inlet area of the plastic particles in the direction of a comminution device downstream of the transport device, in particular a grinding device, in order to be used for cooling the comminution process. The cooling gas can also be introduced into the sieve circuit of a sieve device arranged downstream of the comminution device, which is used to inert other device components (the comminution device or sieve device). This significantly increases the effectiveness of the coolant or cooling gas used. In addition to the discharge or diversion of the cooling gas through the inlet area (the plastic particles), one / or more outlet (s) provided specifically for discharging the cooling gas can additionally or alternatively be arranged in the housing.

As already described above, the cross-sectional area of the transport channel decreases along the transport path of the plastic particles (in the direction of the second housing end). Conversely, this means that the channel narrows in this direction. This primarily results from the increasing diameter of the screw body along the transport path while the inside diameter of the housing in which the screw body is received remains the same. The screw body thus has an increasing screw body pitch in one direction along the transport path. As a result, coolant (e.g. liquid nitrogen or nitrogen gas) introduced into the transport channel in countercurrent to the direction of transport of the plastic particles is pressed out over the length of the transport channel between the plastic particles. This in turn avoids liquefaction of the plastic particles and the nitrogen gas can be recycled after exiting the transport channel, used for cooling or as an inert gas.

According to a further advantageous embodiment of the invention, it can be provided in a transport device according to the invention that the at least one cooling and / or heating medium inlet is arranged in a housing section arranged adjacent to the outlet area. The coolant and / or heating medium inlet can be designed in the form of an injection nozzle and can be controlled via a corresponding inlet valve. The arrangement of the at least one coolant and / or heating medium inlet in the area of the second housing end enables a flow through the transport channel in countercurrent. The cooling and / or heating medium inlet can also comprise several inlets distributed over the circumference of the housing, which ensures a uniform flow of cooling or heating medium into the transport channel. As already expressed by the terminology used above for the arrangement of “at least one coolant and / or heating medium inlet”, several cooling and / or heating medium inlets can be distributed or arranged over the length of the transport channel (that is, along the transport path), around one to ensure particularly flexible coolant or heating medium metering or temperature setting at different points of the transport channel.

According to a further advantageous embodiment of the invention, it can be provided in a transport device according to the invention that the device has at least one temperature control unit, in particular heating unit, with which a temperature in the housing interior (and thus the plastic particles or the plastic compound) can be set is. Depending on the starting material, i.e. depending on the type, chemical and physical properties of the plastic particles to be transported and compacted, it may be necessary to go through a heating-cooling cycle before further processing (e.g. comminution). It may also be necessary to run through a plurality of heating-cooling cycles before the compacted plastic particles are fed into a further processing device (comminution device such as a mill). To this end, according to a further advantageous embodiment of the invention in a transport device according to the invention, a plurality of spaced apart temperature control units, in particular heating units, are arranged on the housing along the transport path, with which the temperature in the housing interior can be adjusted is. Also for reasons of the size of the transport channel varying (decreasing) over the transport route, it may be necessary to set the temperature in a targeted manner at several points of the transport channel. Furthermore, by such a configuration (if desired), temperature gradients can be set in a targeted manner over the length of the transport channel. The temperature control units can be designed in such a way that at a certain longitudinal position of the housing there is a symmetrical temperature input with respect to a cylindrical housing interior; for this purpose, the temperature control units can include temperature control elements distributed symmetrically around the inner circumference. The temperature control units can also surround the housing in a ring shape and extend along a predetermined longitudinal section.

According to a further advantageous embodiment of the invention, it can be provided in a transport device according to the invention that the housing has a plurality of coolant inlets distributed along the transport path, which are preferably each arranged between two adjacent temperature control units. This enables several of the aforementioned cooling-heating cycles to be applied to the plastic particles conveyed in the transport channel or the compacted plastic mass. For some types of plastic (for further processing following compaction, in particular comminution), it can be advantageous to go through a heating cycle prior to cooling. The reverse variant of an initially executed cooling process and a subsequent heating process is also possible.

According to a further advantageous embodiment of the invention, a temperature measuring unit arranged on the housing can be provided in a transport device according to the invention such that a temperature present in the transport channel and / or the plastic particles can be measured. The temperature measuring unit can in principle be arranged at any point on the housing or the transport channel. Furthermore, several such temperature measuring units can be provided at different points on the housing or the transport channel in order to check the temperature along the transport channel. Based on the measured temperature, the inlet of coolant into the transport channel or the heating of the transport channel or the plastic particles can be initiated. This can be carried out by a suitable control unit which is connected in terms of control technology to the temperature control unit (s) and / or the coolant supply unit (s).

According to a further advantageous embodiment of the invention, it can be provided in a transport device according to the invention that the device is designed and optimized for conveying and compacting a mixture of plastic particles of different particle sizes, the mixture of plastic particles preferably being a mixture of granular raw material plastic particles and plastic particles of plastic particles returned from the further processing device. In particular, the mixture of plastic particles can have particle sizes of 1 μm to 5 mm, that is to say cover a relatively large size range. When plastics are shredded, it is often not possible to produce the full amount of the shredded plastic particles in a desired particle size distribution. Accordingly, the comminuted particles must be sieved with a sieve device following the comminution. The crushed material sieved out, for example, with a particle size that is too large (but in powder form) can be used with the present Invention can be subjected to a new comminution process in a particularly simple manner, namely by being fed together with granular raw material plastic particles to the transport device proposed by the invention and compacted in this before a plastic strand produced therefrom is fed back to the comminuting device.

According to a further advantageous embodiment of the invention, a housing opening opening into the transport channel can be provided as inlet means in a transport device according to the invention, the housing opening for receiving the plastic particles being connectable to a feed unit, in particular a feed hopper, the plastic particles, via the feed unit, in particular a mixture of the plastic particles can be fed into the transport channel. Such a feed hopper can additionally be connected to a feed unit, via which plastic particles, in particular plastic powder, returned from a further processing device into the feed hopper and together with other plastic particles, e.g. granular raw material plastic particles. The granular raw material plastic particles and the returned plastic particles can also be dosed directly into the transport channel via two separate housing openings. The supply via a feed funnel, in which the different plastic particles are initially placed and optionally mixed / loosened by an additional mixing or loosening device, is preferred, however, in order to produce a homogeneous compacted plastic mass.

According to a further advantageous embodiment of the invention, it can be provided in a transport device according to the invention that the housing has at least one further housing opening for metering additives, in particular liquids, solids or pasty substances, into the transport channel. Melted plastics can also be inserted into the transport channel via such a housing opening. It is also possible to add a release agent via such a housing opening, for example in order to reduce the stickiness and agglomeration of a plastic compound located within the transport device. In this context, it should be pointed out that a transport device according to the invention is readily suitable in combination with one in the international patent application (registration number PCT / EP2019 / 069103 ) of the same applicant as the present application described device for comminuting a thermoplastic polymer to be used. With a combination of the transport device described here and the comminution device described there, the release agent can also be introduced in the transport device. The disclosure content of the mentioned PCT / EP2019 / 069103 is hereby included in the subject of disclosure of the present application. Such a metering in of the additives mentioned can also be referred to as side loading. For this purpose, a housing opening provided for this purpose can be provided at one or also at several points on the housing. The respective housing openings can be equipped with associated metering units, for example nozzles. Manual metering via the housing openings can also be made possible. The housing openings can also be equipped with closable (liquid- and gas-tight) flaps. The metering in of additives may be necessary in order to provide a desired consistency, color, moisture content or other property of the compacted plastic particle mass.

According to a further advantageous embodiment of the invention, it can be provided in a transport device according to the invention that the housing closes gas-tight and / or pressure-tight in the outlet area. A gas-tight or pressure-tight connection is necessary in order to prevent plastic particles from rushing through into the further processing device and from uncontrolled escape of (gaseous) coolant. The gas or pressure tightness of the transport device in the outlet area can be provided, for example, by a compacted plastic strand (formed from compacted plastic particles or compacted plastic mass) which passes through an opening in a mouthpiece provided in the outlet area. Alternatively or additionally, a connection area can be arranged in the outlet area, via which the housing can be connected to the further processing device in a gas-tight and / or pressure-tight manner. The entire transport device, in particular the transport channel, is preferably designed to be gas-tight and / or pressure-tight.

According to a further advantageous embodiment of the invention, it can be provided in a transport device according to the invention that the transport channel terminates with a mouthpiece in the outlet area, the mouthpiece having an opening which is designed to allow the compacted plastic particles, for example in the form of a compacted plastic strand , can pass through the opening in the direction of the further processing device. With a mouthpiece provided with an opening as the end of the transport channel, the compacted plastic mass (formed from the plastic particles) can be of a special type - for subsequent processing, e.g. Comminution advantageous - shaping. Ultimately, the shape, shape and size of the opening in the mouthpiece is decisive for the shape and size of the compacted plastic strand emerging from the transport device. The opening of the mouthpiece can have different geometries, for example a continuously cylindrical geometry, a conically tapering geometry or a conically increasing geometry along the transport path in the direction of the further processing device. The mouthpiece can have different cross-sectional geometries in a direction transverse to the transport path, for example a circular, elliptical one.

According to a further advantageous embodiment of the invention, it can be provided in a transport device according to the invention that the opening has a cross-sectional area which corresponds to the cross-sectional area of the transport channel at the location where the screw body has the largest diameter. This special requirement avoids undesired pressing and thus a possible (likewise undesired) melting of the plastic after it has passed through the transport channel. Openings that are too small are therefore undesirable.

According to a further advantageous embodiment of the invention, it can be provided in a transport device according to the invention that the screw body is designed in such a way that a ratio formed from the largest diameter and the smallest diameter of the screw body assumes values of 1.1 to 3.0. This range of values indicates particularly advantageous dimensions of the diameter of the screw body.

1. a. den Füllgrad des Transportkanals, beispielweise mit Kunststoffpartikeln, Kühl- oder Heizmittel und/oder Zusatzstoffen;
2. b. eine Drehzahl der Schnecke;
3. c. die Art von zu dosierten Zusatzstoffen,
4. d. eine im Transportkanal vorliegende Temperaturverteilung, und/oder
5. e. einem Querschnittsverlauf des Transportkanals entlang des Transportwegs.

According to a further advantageous embodiment of the invention, it can be provided in a transport device according to the invention that the degree of compaction can be adjusted by

1. a. the degree of filling of the transport channel, for example with plastic particles, cooling or heating agents and / or additives;
2. b. a speed of rotation of the screw;
3. c. the type of additives to be dosed,
4. d. a temperature distribution present in the transport channel, and / or
5. e. a cross-sectional profile of the transport channel along the transport path.

All of the aforementioned parameters offer scope for adapting a degree of compaction and can be adapted automatically (e.g. using a corresponding algorithm) or manually. The degree of filling can be adjusted by filling with plastic particles via the inlet means, charging with coolant via the coolant inlets and charging with additives via separate housing openings. All of the named inlets or housing openings can be lockable in a pressure-tight manner. The speed of the screw can be adjusted via the drive or an associated control unit. The type of additives to be dosed can be set by selecting the appropriate material. The temperature distribution can be adapted via the type and amount of coolant or heating medium to be metered and the selection of a suitable coolant and / or heating medium inlet (if several cooling and / or heating medium inlets are provided), as it were via the control of one or more temperature control Units). The cross-sectional course of the transport channel can be adjusted by the shape and size of the screw body and the shape and size of the housing interior. It is also conceivable to provide space-changing elements (e.g. extendable flaps, blades, flanges, etc.) on the screw body and / or an inner wall of the housing interior, with which the shape and size of the housing interior can be adjusted. Furthermore, the web arranged on the screw body can also be used to change the cross-sectional profile of the transport channel, because the web contributes with its dimensions, in particular its web width, to the shape and size of the transport channel.

A transport device according to the invention is also characterized overall by its compact design. Instead of providing separate heating and cooling screws, the mentioned functionalities (cooling, heating, ultimately a targeted temperature setting and temperature control) are combined in one device. The transport device can also be operated as a transport and heating screw without any problems, for example by dispensing with a supply of coolant. With the temperature control units and the coolant inlets, temperature control zones and cooling zones can be freely defined along the transport route. In that area of the screw body near the screw tip, pressure increasingly builds up during compaction, which is why this section can also be referred to as the pressure build-up zone.

It should be mentioned that the further processing device can be a shredding device, but also a pure filling device, which means that no further processing (e.g. shredding) takes place immediately after the compaction. In this case, the compacted plastic mass can be filled, stored or transported away for further processing.

In a further embodiment of the invention it can be provided to provide an arrangement of a plurality of the screws described above (for example parallel or in series) in a common housing or in separate housings. When the screws and thus also the screw body (including the web) are arranged in a common housing, they can be arranged and designed in such a way that they jointly form a transport channel (both with a parallel arrangement and with an arrangement in series). When arranged in separate housings, separate transport channels are formed. Arranging the screws one behind the other (in a row) can enable plastic particles to be compacted in different (for example increasing) degrees of compaction in the individual screw stages. A parallel arrangement can increase throughput.

1. a. Zuführen der Kunststoffpartikel, insbesondere einer Mischung von Kunststoffpartikeln unterschiedlicher Partikelgröße, in eine Transportvorrichtung;
2. b. unter Einsatz der Transportvorrichtung: Befördern der Kunststoffpartikel entlang eines Transportweges bis zu einer Weiterverarbeitungseinrichtung, wobei die Kunststoffpartikel beim Befördern auf einen vorbestimmten Kompaktierungsgrad kompaktiert werden;
3. c. unter Einsatz der Weiterverarbeitungseinrichtung: Zerkleinern, insbesondere Mahlen, der Kunststoffpartikel.

As mentioned at the beginning, the object on which the invention is based is also achieved by a method for compacting and / or comminuting plastic particles. The procedure consists of the following steps:

1. a. Feeding the plastic particles, in particular a mixture of plastic particles of different particle sizes, into a transport device;
2. b. using the transport device: transporting the plastic particles along a transport path to a further processing device, the plastic particles being compacted to a predetermined degree of compaction during transport;
3. c. using the further processing device: comminuting, in particular grinding, the plastic particles.

According to the proposed invention, when the plastic particles are conveyed and compacted, a cooling or heating medium, in particular liquid nitrogen or air, is introduced into the transport channel in countercurrent to a conveying direction of the plastic particles.

All of the above-described design options of a transport device according to the invention can also be used to design a method according to the invention, which is why reference is made to the preceding statements at this point.

Accordingly, it can be advantageous that a transport device designed according to one of claims 1 to 14 is used in a method proposed by the invention.

According to a particularly advantageous embodiment of a method according to the invention, it can be provided that the transport device is supplied with a mixture of granular raw material plastic particles and plastic particles of plastic particles returned from the further processing device. In addition to processing such plastic particles (e.g. with different particle sizes), soft and / or sticky plastics or plastic mixtures, for example thermoplastic polymers, can be processed or comminuted with the above-mentioned method without any problems.

The cooling and compacting of the plastic particles during transport in the direction of the further processing device (in particular the comminution device) enables an efficient and economical comminution process. In this case, the coolant required for compacting can be set precisely in a particularly simple and flexible manner. The pressure-tight design and connection of the transport device with the further processing device prevents undesired (non-compacted) plastic material from being whirled up from the transport device and reaching the further processing device in a comminution method carried out according to the invention.

According to a further embodiment of a method proposed by the invention, it can be provided that plastic particles returned exclusively from the further processing device are fed to the transport device. With such a configuration, no feed of raw material plastic particles is undertaken. It can be provided that plastic particles are continuously fed from the further processing device via the inlet area of the transport device (for compacting). At the same time, however, it can also be provided that returned plastic particles are initially placed in a buffer and fed to the transport device as required (that is, discontinuously). In this case, the buffer is advantageously connected to the inlet area and to a return line of the further processing device.

• 1 eine Darstellung eines Ausführungsbeispiels einer mit der Erfindung vorgeschlagenen Transportvorrichtung.

Further features and advantages of the invention emerge from the following description of a non-restrictive exemplary embodiment of the invention, which is explained in more detail below with reference to the drawing. This drawing shows schematically:

• 1 a representation of an embodiment of a proposed with the invention transport device.

In the 1 is an embodiment of a proposed with the invention transport device for conveying plastic particles 2 , 2 ' along a transport route 3 illustrated schematically. It can first be seen that the transport route 3 starting from an inlet area 4th up to one in a further processing facility 5 opening outlet area 6th extends. At the processing facility 5 it is - in the embodiment described here - a comminution device, in particular a grinding device. The further processing device 5 is not shown in detail here, since its configuration is not the core of the present invention. It can be seen, however, that plastic particles 2 from the further processing device 5 along a return line 26th to the inlet area 4th or to the feed unit 20th the transport device 1 be returned, for example in the event that the further processed or comminuted plastic particles 2 do not have the desired particle size or particle size distribution.

When conveying the plastic particles 2 along the transport route 3 these are compacted or compressed in volume to a predetermined degree of compaction to form a strand of plastic mass 27 from the plastic particles 2 to create. The compacted plastic mass strand produced 27 becomes the further processing facility 5 , in particular the shredding device, fed, shredded there and, if necessary, sieved. Unless the crushed plastic particles 2 B do not correspond to a desired particle size or particle size distribution, these will enter the inlet area 4th of the transport device 1 associated housing 7th recycled, for example, together with granular raw material plastic particles 2a the transport device 1 to be fed and to go through a (possibly renewed) compaction. The raw material plastic particles 2a can be fed into the feed unit via a rotary valve 32 20th be introduced.

As shown, the transport device comprises 1 one along the transport route 3 extending housing 7th with a cylindrical housing interior 8th . The case 7th points in the inlet area 4th Inlet means 9 for receiving the plastic particles 2 , 2a , 2 B and in the outlet area 6th Outlet means 10 to the outlet of the compacted plastic particles 2 ' on. The inlet means 9 is in the example shown here by one in the transport channel 14th opening housing opening 19th formed, the housing opening 19th for receiving the plastic particles 2 , 2a , 2 B with a feed unit 20th , in particular a feed hopper, is connected. As shown, a feed unit connected to the feed hopper, in particular a transport pipe connected to the comminution device 28 , Plastic particles 2 B from the shredding device into the transport device 1 returned and subjected to compaction.

In the case 7th is a snail 11 rotatably recorded, the worm 11 via a drive 29 driven and set in rotation (as indicated by the arrow). The snail 11 is formed from a screw body 12th along the transport route 3 from a first screw body end 21 up to a second end of the screw body 22nd extends and one helically along the screw body 12th extending web 13th having, the screw body 12th in the direction of the second end of the screw body 22nd has an increasing diameter D.

The snail 11 further comprises one between the web 13th running helical transport channel 14th , the transport channel extending in the direction of the outlet area 6th having decreasing cross-sectional area. This results from the fact that the screw body 12th starting from a smallest diameter D1 (in the area of the first screw body end 21 ) in the direction of the second end of the screw body 22nd and a largest diameter D2 provided there has an increasing diameter D, while the inner diameter d of the housing interior 8th along the transport route 3 is constant. The transport channel narrows accordingly 14th towards the outlet area 6th . Nota bene that the bridge 13th in the radial direction (i.e. in the direction of an inner wall of the housing 30th ) to the inside wall of the housing 30th extends (illustrated by the dashed lines 31 ). The web diameter decreases along the transport path. From the 1 it can also be seen that in the area of the second screw body end 22nd in alignment with the worm body 12th a snail tip 15th is arranged, which is in the direction of the transport route 3 or the outlet area 6th conically tapered.

The case 7th has at least one coolant and / or heating medium inlet 16 on, via which a cooling or heating means, in the present case the introduction of a coolant such as liquid nitrogen (N ₂ ) is shown, into the transport channel 14th , especially in countercurrent to a direction of transport (along the transport route 3 ) the plastic particles 2 , 2a , 2 B , 2 ' , is initiated. The present is the coolant and / or heating medium inlet 16 in the area of the second end of the screw body 22nd arranged. Also on the housing 7th along the transport route 3 a plurality of temperature control units arranged at a distance from one another 17th arranged, which are in particular heating units. With these, the temperature inside the housing 8th can be set or preset Run through heating cycles. One is also provided on the housing 7th arranged temperature measuring unit 18th with which a measurement of one in the transport channel 14th and / or the plastic particles 2 , 2 ' present temperature is enabled. The coolant metering into the transport channel can be based on the measured temperature or temperature distribution 14th and / or heating of the transport channel 14th or the plastic particles 2 , 2 ' to adjust.

Next to the illustrated housing opening 19th to the inlet of the plastic particles 2 , 2a , 2 B has the housing 7th at least one further opening in the housing 23 for metering additives, in particular liquids, solids or pasty substances, into the transport channel 14th on, whereby a desired consistency or property of the plastic mass to be compacted can be set.

The case 7th is gas-tight with a connection area arranged at the second housing end with the further processing device 5 connected or merges into this. The transport channel 14th closes in the connection area with a mouthpiece 24 starting with the mouthpiece 24 an opening 25th which is designed to have the compacted plastic particles 2 ' , for example in the form of a compacted plastic mass strand 27 , through the opening 25th in the direction of the further processing device 5 can pass through. The opening 25th has a cross-sectional area which is the same as the cross-sectional area of the transport channel 14th corresponds to the place where the snail's body 12th has the largest diameter D2. The cross-sectional area of the opening 25th can be calculated, for example, according to the formula: cross-sectional area = π / 4 (d ² - D2 ² ), where d is the diameter of the interior of the housing 8th in one direction across the transport route 3 and D2 is the largest diameter of the screw body 12th is. The mouthpiece 24 can taper conically along the transport path (as shown). Such a design of the mouthpiece leads to a more uniform pressure distribution in the area of the screw tip 15th .

That via the coolant and / or heating medium inlet 16 in the transport channel 14th Introduced coolant or heating medium gas (eg the coolant N ₂ ) flows through the transport channel 14th in one direction opposite to the transport route 3 . Accordingly, it is possible for the coolant gas to reach the inlet area 4th the plastic particles 2 , 2a , 2 B advances. Via a diversion device 33 (eg a line) it is possible to divert the coolant or heating medium gas (N ₂ ) in the direction of a comminution device downstream of the transport device, in particular a grinding device, and to use it for cooling during the comminution process.

List of reference symbols

1

Transport device

2

Plastic particles

2 '

compacted plastic particles

2a

Raw material plastic particles

2 B

crushed plastic particles

3

Transport route

4th

Inlet area

5

Further processing device

6th

Outlet area

7th

casing

8th

Housing interior

9

Inlet means

10

Outlet means

11

slug

12th

Snail body

13th

web

14th

Transport channel

15th

Snail tip

16

Cooling and / or heating medium inlet

17th

Temperature control unit

18th

Temperature measuring unit

19th

Housing opening (inlet means)

20th

Feed unit

21

first end of the screw body

22nd

second end of the screw body

23

Housing opening (further side loading)

24

Mouthpiece

25th

opening

26th

Return line

27

Plastic mass strand

28

Transport tube

29

drive

30th

Housing inner wall

31

line

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 202016106243 U1 [0003]
• WO 2007008480 A1 [0005]
• EP 2957598 A1 [0005]
• EP 2019/069103 [0038]

Claims (18)

Transport device (1) for transporting plastic particles (2) along a transport path (3) which extends from an inlet area (4) to an outlet area (6) opening into a further processing device (5), the transport device (1) is designed to compact the plastic particles (2) during conveyance along the transport path (3) to a predetermined degree of compaction, comprising a. a housing (7) extending along the transport path (3) with a housing interior (8), the housing (7) in the inlet region (4) having inlet means (9) for receiving the plastic particles (2) and in the outlet region (6) outlet means ( 10) to the outlet of the compacted plastic particles (2 '); b. a screw (11) which is rotatably received in the housing (7) and drivable via a drive and which is formed from • a screw body (12) which extends along the transport path (3) from a first screw body end (21) to a second screw body end (22) and a web (13) extending helically along the screw body (12) the screw body (12) having an increasing diameter (D) in the direction of the second screw body end (22), • a helical transport channel (14) running between the web (13), the transport channel (14) having a cross-sectional area (Q) which decreases in the direction of the second screw body end (22), • and one in the area of the second screw body end (22) in alignment with the screw body (12) arranged screw tip (15) which tapers conically in the direction of the transport path (3), the housing (7) at least one cooling and / or Has heating medium inlet (16) via which a cooling or heating medium, in particular liquid nitrogen or air, can be introduced into the transport channel (14), in particular in countercurrent to a conveying direction of the plastic particles (2, 2 '). Transport device (1) after Claim 1 , characterized in that the at least one cooling and / or heating medium inlet (16) is arranged in a housing section arranged adjacent to the outlet region (6). Transport device (1) after Claim 1 , characterized in that the device has at least one temperature control unit (17), in particular heating unit, with which a temperature in the housing interior (8) can be set. Transport device (1) after Claim 3 , characterized in that a plurality of spaced apart temperature control units (17), in particular heating units, are arranged on the housing (7) along the transport path (3), with which the temperature in the housing interior (8) can be adjusted. Transport device (1) according to one of the preceding claims, characterized in that the housing (7) has a plurality of cooling and / or heating medium inlets (16) distributed along the transport path (3), each of which is preferably between two adjacent temperature control units (17) are arranged. Transport device (1) according to one of the preceding claims, characterized by a temperature measuring unit (18) arranged on the housing (7) in such a way that a measurement of a temperature present in the transport channel (14) and / or the plastic particles (2, 2 ') is possible is. Transport device (1) according to one of the preceding claims, characterized in that the device is designed and optimized for conveying and compacting a mixture of plastic particles (2) of different particle sizes, the mixture of plastic particles (2) preferably being a mixture of granular raw material plastic particles and plastic particles are from plastic particles (2) returned from the further processing device (5). Transport device (1) according to one of the preceding claims, characterized by a housing opening opening into the transport channel (14) as inlet means, the housing opening (19) being connectable to a feed unit (20), in particular a feed hopper, for receiving the plastic particles (2) wherein the plastic particles (2), in particular a mixture of the plastic particles (2), can be fed into the transport channel (14) via the feed unit (20). Transport device (1) according to one of the preceding claims, characterized in that the housing (7) has at least one further housing opening (23) for metering additives, in particular liquids, solids or pasty substances, into the transport channel (14). Transport device (1) according to one of the preceding claims, characterized in that the housing (7) closes gas-tight and / or pressure-tight in the outlet area. Transport device (1) according to one of the preceding claims, characterized in that the transport channel (14) terminates in the outlet area (6) with a mouthpiece (24), wherein the The mouthpiece (24) has an opening (25) which is designed so that the compacted plastic particles (2 '), for example in the form of a compacted plastic strand, can pass through the opening (25) in the direction of the further processing device (5). Transport device (1) after Claim 11 , characterized in that the opening (25) has a cross-sectional area which corresponds to the cross-sectional area (Q) of the transport channel (14) at that location at which the screw body (12) has the largest diameter (D2). Transport device (1) after Claim 12 , characterized in that the screw body (12) is designed in such a way that a ratio formed from the largest diameter (D2) and the smallest diameter (D1) of the screw body (12) assumes values of 1.1 to 3.0. Transport device (1) according to one of the preceding claims, characterized in that the degree of compaction can be set by a. the degree of filling of the transport channel (14), for example with plastic particles (2), cooling or heating means and / or additives; b. a speed of rotation of the screw (11); c. the type of additives to be dosed, d. a temperature distribution present in the transport channel (14), and / or e. a cross-sectional profile of the transport channel (14) along the transport path (3). A method for compacting and / or comminuting plastic particles (2, 2 '), comprising the following steps a. Feeding the plastic particles (2), in particular a mixture of plastic particles (2) of different particle sizes, into a transport device (1); b. using the transport device (1): transporting the plastic particles (2) along a transport path (3) to a further processing device (5), the plastic particles (2) being compacted to a predetermined degree of compaction during transport; c. using the further processing device (5): crushing plastic particles (2, 2 '); during the conveying and compacting of the plastic particles (2) a cooling or heating medium, in particular liquid nitrogen or air, is introduced into the transport channel (14) in countercurrent to a conveying direction of the plastic particles (2, 2 '). Procedure according to Claim 15 , characterized in that one according to one of the Claims 1 until 14th trained transport device (1) is used. Procedure according to Claim 15 or 16 , characterized in that the plastic particles and plastic particles are supplied from plastic particles returned from the further processing device (5). Procedure according to Claim 15 or 16 , characterized in that the transport device (1) is fed exclusively from the further processing device (5) returned plastic particles.

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