Process for processing reused or recycled bulk material, particularly solids such as granules, powders, grains, films, scraps, etc., preferably for plastics processing machines and plastics processing systems therefor

Description

[0001] The invention relates to a method for processing bulk material, in particular solids such as granules, powders, grains, films, snippets, or the like, for plastics processing injection molding machines and a plastics processing plant as described in the preambles of claims 1 and 13.

[0002] Public opinion and political decisions are increasingly leading the plastics industry towards the reusability of plastic materials and increased use of recycled materials, i.e. towards a circular economy.

[0003] Buyers of plastic parts with high quality and safety standards, such as automotive companies that largely outsource the production of their plastic parts or injection-molded parts to contract manufacturers, find themselves in a difficult situation when they use recycled material, regrind or regranulate mixed with new products, particularly single-type or single-variety granules. This is because, on the one hand, they are unable to control the actual recycled material / regrind content in a finished plastic part, and, on the other hand, an uncontrolled high recycled material / regrind content can lead to long-term quality problems. If the recycled material / regrind content is too high, this can change the mechanical properties of the finished plastic part and lead to premature cracking or breakage. Precise control of the composition of the material used in the injection molding process, particularly for a finished injection-molded part or

[0004] Plastic part, by the buyer is almost impossible and is often based purely on trust.

[0005] To counteract this and avoid any future problems caused by regrind / recyclate exposure to plastic parts, automotive companies or other buyers of plastic parts typically require the use of 100% virgin material, usually even pure virgin material. However, an on-site audit of the production facility by the buyer can much more easily verify the exclusive use of this virgin material than the correct mixing ratio of virgin material to regrind / recyclate.

[0006] The increased awareness of environmental protection and the shift in public opinion from a throwaway economy (linear economy) to a circular economy reinforces the need to allow a certain proportion of regrind / recycled material even in long-lasting plastic products.

[0007] US 4013745 A discloses a process for extruding a plastic film with small thickness variations. In this process, reclaimed material (recycled material), formed from edge trim material and waste products, is shredded and mixed with virgin material before plasticizing and extrusion. The weight of both the reclaimed material and the virgin material is continuously measured and fed into a control system to maintain a constant fill level of the screw extruder to ensure a consistent film thickness.

[0008] Furthermore, US 2017 / 312971 A1 describes a process for producing polyester ribbons, in which the extruded polyester ribbon is trimmed and the trimmed edge strips are fed directly into the melt mixing device, so that exposure to moisture is relatively short and thus a drop in viscosity in the melt mixing device is minimized. Viscosity is measured and controlled such that the viscosity varies by no more than 10%, preferably by no more than 5%, relative to a target value.

[0009] US 2020 / 078999 A1 discloses a system for controlling an injection molding machine with a mold, wherein the mold forms a mold cavity and is controlled according to an injection cycle. The injection of a molten polymer into the mold cavity according to the injection cycle is carried out using a screw that moves from a first position to a second position. Using a sensor, at least one variable is measured during the subsequent material feed and plasticizing, wherein at least one operating parameter of the injection molding machine is adjusted based on the at least one measured variable during the metering movement of the cylindrical screw.

[0010] The object of the invention is therefore to provide a method for processing bulk material, in particular solids such as granules, powder, grains, films, shreds, or the like, preferably for plastics processing machines and a plastics processing plant, in which on the one hand the disadvantages mentioned are avoided and on the other hand to enable documentation or quality assurance for the mixing ratio of ground material / recyclate to new material.

[0011] This object is achieved by the invention. Further advantageous measures and embodiments are described in the subclaims.

[0012] The method according to the invention is characterized in that the at least one dosing device combines these at least two separate bulk materials in any desired sequence, wherein simultaneously or after dosing, the respective dosed bulk material weight is determined and the information on the bulk material weights and / or resulting information representing the material throughput of each individual or all of the supplied bulk materials is transmitted from the control of the dosing device to the plastics processing machine or to a higher-level control and in the plastics processing machine, a physical representation of the flow behavior in the form of a melt flow index or an equivalent to the melt flow index (key figure for the viscosity),of the supplied bulk material and / or the material throughput or consumption of the machine is determined and this information is linked in the plastics processing machine or in the higher-level control system, whereby the melt flow index (21) or an equivalent value to the melt flow index (21) is determined for each production cycle of injection-molded parts (3). The advantage here is that the automatic physical representation of the flow behavior of the mixed bulk material, in particular the melt flow index parameter or a viscosity index, creates a system that allows the purchaser of the produced plastic parts or injection-molded parts to have the mixing ratio of virgin material and regrind / recyclate documented, to be able to audit it, and to reliably identify any possible deviations. In a production audit, the basic parameters for the production of a part are typically defined: material or materials to be used process parameters of the machine and peripherals cycle time regrind proportion etc.

[0013] Should there be a change in the mixing ratio of virgin material to regrind / recyclate during production or a resulting change in the melt flow index (MFI, MFR) or a flow behavior indicator, this can be demonstrated as follows: If the changed mixing ratio is adjusted accordingly via the dosing device, the changed dosing parameters are visible in the database or directly on the device or control system of the plastics processing machine. If there is an obvious discrepancy in material consumption between the machine and the dosing device, the reason may be an intermediate conveyor or another conveying point. This additional conveying point could be reached via a conveyor with two material inlets. Typically, such conveyors are used for adding regrind in a so-called inline recycling plant. This case, too, is very easily recognizable in the database or directly on the individual control systems.If the new material has already been mixed with regrind, but is only added as new material in the dosing device, the characteristic value for the flow behavior of the supplied bulk material or the melt flow index (MFI, MFR) determined by the plastics processing machine indicates a deviation from the target state.

[0014] This ensures that every change in the mixing ratio is recorded and stored, in particular in a database that the customer can access and evaluate at any time.

[0015] In production, the relevant process parameters are stored in an external data server, e.g., an MES system, or directly in the control system of the plastics processing machine or the dispensing device. Typically, the relevant and current process parameters and process specifications are saved in a database after the completion of the production cycle of the plastics processing machine. Depending on the level of networking of other production resources involved in the production of the plastic part, the parameters of the production resources are also transferred to the database and saved. The data from the dispensing device must, of course, also be stored in the database.

[0016] A dosing device can be a gravimetric dosing device, a volumetric dosing device, a conveyor with a material switch (i.e. with several individually switchable material inlets) with subsequent or continuous weighing of the respective material addition or the like.

[0017] Advantageous measures include equipping the dosing device with one or more load cells to determine the material weight, or with a counting device for determining bulk material units that mathematically equal the material weight. This ensures that the exact weight or quantity of the bulk material fed into the plastics processing machine is determined and stored for quality assurance purposes.

[0018] Advantageous measures include the plastics processing machine determining a physical parameter proportional to the flow behavior of the melt, such as a melt flow index, from the process parameters of the polymer melt being processed from the bulk material fed in after dosing. This parameter is then created for tracking purposes and can be quickly and easily verified by the users of the plastic parts, such as the automotive industry. At the same time, this flow behavior parameter, in particular the melt flow index, can be determined and stored for each plastic part produced, so that the mixing ratio, in particular the proportion of regrind / recyclate added, can be determined even after a longer period of time.

[0019] Also advantageous are measures where the mixing or weight ratio of the at least two bulk materials after the dosing process must correspond to a freely selectable or adjustable specification or a selected or transferred recipe. In batch dosing, the finished dosed batch is formed from at least one or more dosing processes per bulk material, or in continuous dosing, at least one bulk material is continuously drawn into the plastics processing machine and at least one bulk material is continuously added after adjustment. This ensures that any mixing ratio for the production of a plastic part can be specified and adjusted according to the customer's specifications.Once all parameters for manufacturing the plastic part have been set and production has begun, traceability can be easily achieved using the determined flow behavior, particularly the melt flow index. This provides the customer or client with a comprehensive quality assurance protocol in which the mixing ratio is not only specified for the first time, but also automatically determined and monitored, preferably via the plastics processing machine or a work cell control system.

[0020] However, measures where the higher-level control system can be an external work cell control system for the logical management and data communication of production resources, such as the plastics processing machine and the dosing device, with or without connection to a downstream MES or ERP system, or directly to an MES or ERP system, are also advantageous. This ensures that the production data or process data are not used for non-process-relevant tasks, such as calculations, storage, etc.

[0021] The parameters do not place a load on the plastics processing machine, especially the injection molding machine, but rather are performed via the external work cell control system. The work cell control system handles all tasks not directly related to the production of the plastic part. The work cell control system can query, record, and save all data from the other production resources. It should be noted that when using a work cell control system, the production resources required to create an injection-molded part are combined in a so-called work cell.

[0022] Also advantageous are measures in which at least the information determined by the plastics processing machine and by the at least one dosing device, such as individual bulk material weights, the mixing ratio of the materials, material consumption or corresponding differences, a key figure for the flow behavior of the fed bulk material or the melt flow index, is displayed, evaluated or documented, preferably in the control system of the plastics processing machine or in a system connected to the control system of the plastics processing machine and / or the dosing device, for example a higher-level control system. This makes it possible to display the parameters essential for quality assurance directly during the manufacturing process in order to enable quick and easy monitoring.It is possible to display the actual values with correspondingly color-coded target values or tolerance ranges, making it immediately clear whether the actual values are within the specifications. It is also possible to send or display a warning signal if the actual values deviate outside the tolerance or target values to quickly alert the operating personnel.

[0023] However, measures are also advantageous where at least the information determined by the plastics processing machine and at least one dosing device, such as individual bulk material weights, the mixing ratio of the materials, material consumption or corresponding differences, a key figure for the flow behavior of the supplied bulk material, or the melt flow index, must be within adjustable differences from reference templates in order to be able to determine correct bulk material supply during ongoing operation or in a test operation, for example, during an audit. This ensures simple and quick control.

[0024] However, measures that provide at least one, preferably two, reference templates are also advantageous. These templates reflect the approved regrind ratio, as well as no regrind ratio, i.e., the exclusive use of virgin material, since all intermediate stages are considered to be within the permitted mixing ratio. This ensures that the contracted employee can manufacture the product, especially the injection-molded parts, within this range, while all parts produced outside this range are considered scrap or recorded.

[0025] Advantageous are measures in which additional data originating from both the plastics processing machine and the dosing device(s), preferably in the control system of the plastics processing machine or in a system connected to the control system of the plastics processing machine and / or the dosing device, for example a higher-level control system, are evaluated and / or documented, for example the current process parameters of the machine and / or process parameters of the dosing device(s), etc. This enables seamless tracking and quality assurance.

[0026] Advantageous measures include the possibility of connecting the dosing device(s) directly to the plastics processing machine, allowing data processing between the two production devices that goes beyond material consumption and / or a key figure for the flow behavior of the incoming bulk material or melt flow index. This creates a compact work cell.

[0027] However, measures where the plastics processing machine documents or analyzes the characteristics of the bulk melt, for example in the form of a key figure or melt flow index, during dosing or injection into the molding tool, or immediately executes a configurable action are also advantageous. This creates simple and fast traceability, as tracking can be carried out very easily by determining or calculating a specific parameter. If this parameter lies within a specified tolerance range, the manufactured plastic part can be used. However, if the deviation is too large or the limit values are exceeded, the manufactured plastic part is declared scrap.

[0028] Measures where the dosing device documents and analyzes the characteristics of the bulk material mixture, or immediately executes a configurable action, are advantageous. This ensures that excessive deviations are automatically and quickly addressed, minimizing waste production.

[0029] Furthermore, the object is achieved by a plastics processing plant for processing reused or recycled bulk material, in particular solids such as granules, powder, grains, films, snippets, or the like, in which the plastics processing injection molding machine and / or an external work cell control is designed to physically represent a flow behavior in the form of a melt flow index, the supplied bulk material and / or the material throughput or consumption of the machine and to carry out the method according to claims 1 to 12.

[0030] The advantage here is that the graphical representation of the parameter representing the mixing ratio allows for easy monitoring directly at the production site. This allows operators to intervene immediately in the event of excessive deviations and make appropriate adjustments or changes to bring the parameter back within the desired range.

[0031] The invention is explained in more detail with reference to an embodiment shown in the drawings, whereby the invention is not limited to the illustrations shown, in particular the structure and composition of the systems.

[0032] They show: Fig. 1 an overview of a plastics processing production cell with several production resources, in a simplified, schematic representation; Fig. 2 a diagrammatic representation of a work cell for dosing at least two bulk materials, in particular a new material and a regrind / recyclate, in a simplified, schematic representation; the dosing takes place next to the injection molding machine; Fig. 3 another embodiment of a work cell for conveying two bulk materials, in particular a new material and a regrind / recyclate, in a simplified, schematic representation; the dosing takes place directly on the injection molding machine Fig. 4 an embodiment of a work cell for conveying three bulk materials, in particular a new material and two recyclates, in a simplified, schematic representation; Fig.Fig. 5A simplified schematic representation of the effect of bulk material with different melt flow indices on the pressure curve during the injection process of the injection molding machine. Fig. 6A simplified schematic representation of the injection profiles over time for two materials of different viscosities.

[0033] By way of introduction, it should be noted that in the various embodiments, identical parts are provided with identical reference symbols or component designations, whereby the disclosures contained in the entire description can be applied mutatis mutandis to identical parts with identical reference symbols or component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., refers to the described figure and, if the position changes, is to be applied mutatis mutandis to the new position. Individual features or combinations of features from the illustrated and described embodiments can also represent independent inventive solutions in their own right.

[0034] In the Fig. 1 bis 6 1 shows a production cell or plastics processing plant 1, preferably for injection molding applications, in which the individual production means 2 or devices 2 are involved in producing one or more products / semi-finished products or injection-molded parts 3 or plastic part 3 in the plastics processing plant 1. In the exemplary embodiment shown, an injection molding machine 4 is used as the plastics processing machine 4, to which a robot 5 or automatic handling device is assigned for removing the produced injection-molded part 3, wherein the injection-molded part 3 is removed from an opening mold 7 by a removal device 6, in particular a gripper equipped with gripping tongs or suction nozzles, and is placed on a device, for example a conveyor belt 8. For the sake of completeness, it is mentioned that the solution according to the invention can also be applied to other plastics processing machines 4 orApplications such as extrusion, calendering, rotational molding, foaming, injection blow molding, etc.

[0035] In order to produce an injection-molded part 3 or plastic part 3, ground material 9 or bulk material 9, in particular plastic granules, is fed to the injection molding machine 4 via a granule conveyor 10 and possibly via a dosing device 11. A temperature control device 13a and / or cooling device 13b can be used to keep the injection mold, in particular the molding tool 7, at operating temperature by supplying a temperature control medium, or to heat or cool it accordingly, thus enabling optimal processing of the ground material 9 or bulk material 9, which must be plasticized for injection into the molding tool 7. In addition, the system has a monitoring device 15, in particular a camera system, to enable automatic quality control of the produced product 3.

[0036] To enable the individual devices to be configured or programmed, they feature corresponding control electronics and control logic, which are operated via connected displays 16 and / or a red control 17 or control 17. For the sake of completeness, it should also be mentioned that all devices are connected to corresponding lines, in particular power supply, network lines, fluid supply lines, material lines, etc., which have not been shown in the illustration for the sake of clarity.

[0037] A plastics processing plant 1 or production cell 1 for the production of injection-molded parts 3 or plastic parts 3 therefore consists not only of the production machine 4, but also of a wide variety of production resources 2, in particular peripheral devices, e.g. temperature control devices 13a, cooling devices 13b, hot runner systems, granulate dryers 12, tool dryers, dosing devices 11, robots 5, automation systems, etc. The production resources 2 generally use internal sensors, i.e. sensors directly integrated into the control system of the production resource 2, or external sensors, which in turn are connected to the control logic of the production resource 2 via direct wiring or a device interface. These sensors transmit analog or discrete states, which subsequently trigger actuators in the production resource 2 in order to effect the behavior necessary for the functionality of the production resource 2.

[0038] As already mentioned at the beginning, virgin material 18 is typically used as bulk material 3 to produce an injection-molded part 3 or plastic part 3 in order to easily ensure traceability. However, the trend in recent years has been increasingly toward a larger proportion of secondary raw materials 19, so-called recyclates 19, but this is primarily for a few types of plastic, such as PET, while the proportion for the majority of other types is growing more slowly.

[0039] The plastics processing industry is therefore encouraged to increase the proportion of recycled plastics for all types of plastic. However, the addition of recyclate 19 to virgin material 18 is particularly critical for technically and functionally high-quality plastics, since recyclate 19 does not necessarily have to have the same physical properties as the corresponding primary raw material 18, i.e., the virgin material 18. This can be related to the number of recycling processes already carried out, i.e., how often the plastic has been recycled, as well as to the consistency of the shape properties and the purity of the recyclate 19. An excessive proportion of recyclate 19 or the use of inferior recyclate 19 can impair the quality of the finished product 3 and cause visual and physical defects. Furthermore, the actual proportion of recyclate used in the finished plastic part 3 cannot be easily determined.Apart from visual defects, an incorrect composition of materials in plastic parts 3 can only be detected retrospectively, for example, in the case of premature breakage or cracking. In the worst case, these defects can have safety-relevant effects on the finished product 3, but in any case, they can result in a warranty claim or a loss of reputation for the manufacturer of the finished product 3. Many manufacturers therefore require their suppliers to use 100% virgin material 18 for the production of technically sophisticated plastic parts 3, as this is easily traceable and can be reliably verified during an audit. However, it is foreseeable that public opinion and political requirements will stipulate the mandatory use of a certain regrind proportion.

[0040] According to the invention, the admixture of at least a second material component or a second bulk material 9, in particular a ground material or recyclate 19, to the virgin material 18 is to be monitored, documented, and recorded. In particular, traceability and compliance with a specified mixing ratio between the virgin material 18 and the second bulk material 9, in particular the recyclate 9, should be possible.

[0041] Buyers of high-quality plastic parts 3 conduct regular audits to verify their suppliers' production conditions and compliance with the specifications for the production of their plastic parts 3. This includes, among other things, the use of the material suppliers prescribed for the respective plastic parts 3 or any mixtures for the production of plastic parts 3 with special characteristics, such as color, flame retardancy, UV resistance, regrind content, etc. Likewise, process parameters of the plastics processing machine 4, in particular the injection molding machine 4, and quality parameters, which must be set either manually or automatically and continuously or after a specified number of units or production time.

[0042] Furthermore, it should be noted that regrind 9 typically arises within the production plant as production waste (sprues or defective parts) (i.e., so-called inline recycling 19) or is purchased externally (post-consumer recycling 19). In any case, it can offer a cost advantage over virgin material 18 or its use is prescribed by official regulations in the spirit of the circular economy. For producers of plastic parts 3, it is often advantageous to use a high regrind proportion or at least inline recycling 19. For safety reasons, buyers of high-quality or critical plastic parts 3 currently prefer not to use recyclate 19, but the maximum approved and released recyclate proportion, i.e., the mixing ratio, must never be exceeded.

[0043] For the controlled addition of at least one further component, for example bulk material 9 in the form of a recyclate 19 to virgin material 18, a device 11 for dosing a single or multiple components is used, which in the plastics processing industry is typically known individually as a dosing device 11. These devices can be equipped with one or more weighing cells, in which case such devices then fall under the term gravimetric dosing devices 11. The material dosing of the individual components takes place either in batch 20 or in continuous operation. In batch operation 20, the prescribed components, i.e. the bulk materials 9, are dosed to the respective specified percentage (recipe), whereby each percentage is naturally converted to absolute or relative weights for the weighing of the individual dosing processes within a batch 20.After weighing, a batch 20 can be mixed and then made available to the plastics processing machine, in particular the injection molding machine 4. A batch 20 is typically used for multiple production cycles, i.e., more bulk material 9 or regrind or recyclate 9 is fed to the injection molding machine 4 than is required to produce a single injection-molded part 3, so that multiple injection-molded parts 3 are produced from one batch 20. In the meantime, the next batch 20 can already be prepared and conveyed to the injection molding machine 4 before it is used. Another type of dosing device 11 separates the bulk material(s) into defined material units (down to granulate size, so-called single-grain dosing devices 11) and then mixes them into a batch 20.In a dosing device 11 operating continuously, the weight losses in the individual material containers of the bulk materials 9 are determined and monitored, and a corresponding predetermined material mixture is generated from this. The material component to be added is fed into the continuous material flow.

[0044] The mechanical components of the dosing devices 11 are controlled by a computing unit (not shown) which can be installed directly in the dosing device 11, remote or external and / or integrated into a primary machine (production machine 4).

[0045] This computing unit determines the mixing ratio of the bulk materials 9 produced in batch 20 or continuous operation, in particular the virgin material 18, and the at least one additional component added, in particular the recyclate 19, in weight units, percentages, or other quantities, which are available individually for each bulk material component and can subsequently be combined. Depending on the configuration of the computing unit, these and other values can be transmitted to the plastics processing machine 4 and / or a higher-level computing unit (control system, work cell control, PC) with appropriate software for evaluation, logging, storage, display, control, etc., for example, an MES or ERP system.

[0046] The plastics processing machine 4 in turn determines the material throughput for the production of the respective plastic parts 3. In the case of an injection molding machine 4, this is, for example, the dosed bulk material 9, i.e. drawn into an injection cylinder by an injection screw and melted, which is then injected into a shaping tool 7 for the production of the finished parts or injection-molded parts 3.

[0047] Advanced process technologies of the plastics processing machine 4 make it possible to calculate fluctuations in the viscosity of the melt, the melt flow index (MFI, MFR) 21 or another parameter proportional to the viscosity, by analyzing the behavior of the bulk melt in relation to the process parameters and possible ambient conditions.

[0048] This melt flow index or the viscosity index 21 is determined for each production cycle of an injection-molded part 3, so that this value is available for each injection-molded part 3.

[0049] It should be noted that when determining the melt flow index 21 or the viscosity 21 index, corresponding fluctuations due to changing parameters or minor mixing differences within a batch 20 are possible, so that a tolerance range should preferably be defined to check whether an injection-molded part 3 is good or reject. These fluctuations can be due to various factors, including a variable proportion of regrind 9 or recyclate 19. Other factors include insufficiently dried primary material, which, however, can be detected and ruled out by continuously transmitting and monitoring the dew point of an upstream material dryer and the correct residence time of the primary material in the drying vessel. Apart from that, a change in the bulk material composition is the main reason for strongly fluctuating viscosity 21 of material 9 (18, 19).

[0050] For example, it is possible that in a setup / reference operation, the required composition (recipe) of the bulk material 9 is set after the dosing process, and in subsequent injection molding cycles, the calculated melt flow index or the viscosity index 21 is automatically determined. After the system has stabilized, reference values are saved. During ongoing operation, these parameters are checked for extensive agreement and permissible differences. The parameters material throughput of the dosing device, i.e., the dosing unit 11, and material throughput of the plastics processing machine 4 are also logged so that any admixture of bulk material 9 after the dosing process can be detected.

[0051] In many applications, the permissible admixture of recyclate 19 or secondary material 19 represents an upper limit. A significantly less critical situation is a fall below the amount of regrind / recyclate 19, or even a complete non-use of regrind / recyclate 19. In such cases, two different reference settings 22, 23 can be saved, which represent the lower 23 and upper limits 22 of the melt flow index 21 or the characteristic value for the viscosity 21. All values in between, with the corresponding feedback from the dosing device 12, are acceptable.

[0052] By determining the melt flow index 21 or the key figure for the viscosity 21 directly during the injection process of the injection molding machine 4, it is possible for the first time to generate a parameter which allows conclusions to be drawn about the addition of regrind / recyclate 19 to the new material for each injection-molded part 3 produced. For example, it is also possible that when the plastics processing plant 1 is put into operation, an injection-molded part 3 is first produced using only new material 18 and the reference setting 23 determined or calculated from this is saved as the lower reference curve 23. Then, a further cycle is started with the maximum addition of recyclate 19 and the resulting curve is saved as the reference setting 22, i.e. the upper limit. Once the two upper and lower reference settings 22, 23 have been determined, the prescribed production cycle can be carried out with correspondingly adjusted parameters, in particular the addition orthe mixing ratio between virgin material 18 and recyclate 19 or regrind 9.

[0053] For the first time, it is now possible to determine the melt flow index 21 or a viscosity index 21 during the production of an injection-molded part 3, and to immediately determine whether this injection-molded part 3 lies within the tolerance or has an unacceptably high proportion of regrind / recyclate 18, 19. It is also possible for a certain presetting of clusters for rejects, i.e., when the melt flow index or a viscosity index 21 of the injection-molded part 3 lies outside the two reference settings 22, 23, to send out a warning signal, SMS, email, or the like, preferably from the plastics processing machine 4, so that the operator or maintenance personnel can make a change to the material composition as quickly as possible.For the sake of completeness, it is mentioned that if a reject is identified based on the determined melt flow index or the viscosity index 21 of the injection-molded part 3 just produced, this is communicated to the removal unit, in particular to the robot 5, so that it deposits the injection-molded part 3 separately. Furthermore, it is mentioned that the determination of the reference settings 22, 23 or curves 22, 23 can preferably be determined during an audit, so that the client can precisely control which material, in particular virgin material 18 and admixture or material, in particular recyclate 19, is used.

[0054] Ideally, the material throughput through the plastics processing machine 4 corresponds to the determined material throughput through the at least one dosing device 11 and injection-molded parts 3 are produced with a melt flow index or viscosity index 21 within the tolerance ranges, i.e. the reference settings 22, 23.

[0055] Any changes or manipulations in the audited manufacturing process can be easily detected with the inventive solution, since any change in the mixing ratio before, during, or after the dosing device 11 is directly detected by evaluating the melt flow index 21 or the viscosity index 21. This means that the dosing characteristics of the individual components, in particular the virgin material 18 and the recyclate 19, are also logged and stored as parameters during the initial audit. Should the dosing characteristics change during production, the deviation from the original parameters is detected and documented.

[0056] If, for example, the operator of the plastics processing machine 4, in addition to the material which was produced with the aid of the at least one dosing device 11, conveys at least one further material with the aid of a conveying device with a dosing switch (a valve for feeding the machine with more than one material) after the dosing device 11, but still before the material filler neck of the plastics processing machine 4, it is recognized that a higher percentage of other components, for example regrind 9, is introduced and the melt flow index or the viscosity index 21 would be outside the tolerance ranges 22, 23.In principle, it would also be possible to mix the primary material, i.e. the new material 18, with regrind, in particular recyclate 19, in order to then meet the specified mixing ratio of primary component and secondary components, but at the same time to add a higher proportion of secondary components / regrind, which is also detected via the melt flow index or the viscosity index 21.

[0057] The parameters available and determined for process monitoring are in principle available to the dosing device(s) 11, the plastics processing machine 4, or ultimately to a computing unit for recording, logging, analysis, display, etc. Ideally, the individual data are recorded and linked. If the plastics processing machine 4 is an injection molding machine 4, then the recording frequency is typically one production cycle, i.e. for each injection-molded part 3 or simultaneously produced injection-molded parts 3. After the production of the injection-molded part 3, the individual data of the injection molding machine 4, for example material throughput, temperatures, pressures, sensor values, process parameters, key figures for flow behavior or melt flow index (MFI, MFR) 21, etc., are saved and displayed on the machine if necessary.The mixing ratio in any physical form (percent, absolute, relative weight, etc.), process parameters for the dosing process, material throughput, etc. are stored by one or more dosing devices 11, so that a seamless tracking of all parameters is possible.

[0058] This data can now be compared for accuracy or compliance with the audited values immediately after the production cycle or in a subsequent analysis. Any deviation can be displayed at any time on the external processing unit, the control system of the injection molding machine 4, or the control system of the dosing device 11.

[0059] In particular, Fig. 2 a work cell for processing bulk material 9 as virgin material 18 and / or bulk material 9, in particular as recyclate 19, which is mixed together from at least two components, wherein the dosing device 11 is placed externally to the plastics processing machine 4. This dosing device 11 is a so-called gravimetric dosing device 11, with two material containers 24a, 24b in this illustration. One material container 24a is supplied with recyclate 19 via a mill 25 and the other material container 24b is supplied with virgin material 18 via a conveyor device 26. Alternatively, the supply can also come from an external source. The virgin material 18 and the recyclate 19 are dosed in the desired, i.e. predetermined, ratio and then typically mixed in the mixing container 27 located below the dosing container or material container 24a, 24b.In this illustration, the mixed material, in particular the batch 20, is conveyed to the plastics processing machine 4 by a conveyor 28, which is mounted above the material filling nozzle.

[0060] Fig 3 . shows another variant of a design of a work cell for processing bulk material 9 as virgin material 18 and / or bulk material 9, in particular recyclate 19, which is mixed together from at least two components, wherein the dosing device 11 is placed directly on the plastics processing machine 4. This dosing device 11 is again a so-called gravimetric dosing device 11, with two material containers 24a, 24b in this illustration. One material container 24b is supplied with bulk material 9, in particular recyclate 19, via a conveyor device 26 and the further material container 24a from a mill 25. Alternatively, the supply can also come from an external source. The virgin material 18 and the further bulk material 9, in particular recyclate 19, are dosed in the desired, i.e. predetermined, ratio and typically then mixed in a mixing container 27.In this illustration, the mixed material is made available directly to the material filler neck of the plastics processing machine 4.

[0061] Fig 4 . Shows a work cell for processing virgin material 18 and / or bulk material 9, in particular recyclate 19a, which is mixed together from at least two components, wherein the dosing device 11 is placed externally to the plastics processing machine 4. This dosing device 11 is a so-called gravimetric dosing device 11, with two material containers 24a, 24b in this illustration. The material containers 24a, 24b are supplied with recyclate 19a and virgin material 18 via a conveyor from an external source 29a, 29b. The virgin material 18 and the recyclate 19a are dosed in the desired, i.e. predetermined, ratio and typically then mixed in the mixing container 27 located below the dosing container. In this illustration, the mixed material is conveyed to the plastics processing machine 4 by a conveyor 28, which is mounted above the material filler neck.This conveyor 28 is equipped with a mixing switch which can convey another material component 9, also recyclate 19b.

[0062] If the additional mill 25 were added without permission, the resulting ratio of virgin material 18 to recyclate 19a and 19b would no longer be in the permitted and audited ratio and can be detected via the deviation of the key figure for the flow behavior of the supplied bulk material.

[0063] Furthermore, in Fig. 5 a schematic representation of the effect of bulk material with different melt flow index 21 on the pressure curve during the injection process of the injection molding machine is shown, in which the curve from a high-viscosity to a low-viscosity material is shown, whereby the switching time and the holding pressure level of the injection process change as a direct consequence and these factors are included in the calculation of the equivalent to a melt flow index

[0064] Fig. 6 shows the injection profile over time for two materials of different viscosity (32 for low viscosity and 31 for high viscosity). The highlighted area 33 represents the difference in injection work performed for materials of different viscosity.

[0065] To determine the viscosity 30, the sensor data from the drive and the injection unit of the plastics processing machine 4, in particular the injection molding machine 4, are determined, so that the viscosity 30 is calculated based on the feedback from the current controllers (not shown) of the drive(s) and the injection unit. Subsequently, the determined viscosity 30 for the currently produced injection-molded parts 3 is compared with the defined injection profiles 31, 32, which lie within the range 33 and thus the mixing of the bulk materials 9 is considered correct.

[0066] In general, it can be said that the production and consumption of plastics have increased rapidly worldwide since the beginning of mass production in the 1950s. A current and politically charged issue is the handling of plastic waste, especially with regard to ocean pollution and thus its prevention or reuse in the production process. In Austria, as is typical for other Central European countries, 98% of plastics are recycled or thermally recycled, while 2% are landfilled. Of particular interest is the coverage of plastics consumption with secondary raw materials, i.e., reused plastics. In Austria, the share of secondary raw materials in the study period of 2010 was 13%, while 87% was made from primary raw materials (sources: https: / / www.sciencedirect.com / science / article / pii / S0921344916302956?via%3Dihub and https: / / www.sciencedirect.com / science / article / pii / S0956053X17308802?via%3Dihub ).

[0067] A study on the production, processing, and recycling of plastics in Germany in 2015 conducted by Consultic Marketing & Industrieberatung GmbH in Alzenau indicates that 99 percent of plastic waste is recycled, of which 45% is recycled as a secondary raw material, 1% as a feedstock, and 53% as energy. Source: Consultic study: Study on the production, processing, and recycling of plastics in Germany in 2015, commissioned by BKV Beteiligungs- und Kunststoffverwertungsgesellschaft mbH, Frankfurt a.M., and PlasticsEurope, Brussels, IK-Industrievereinigung Kunststoffverpackungen (Industry Association for Plastics Packaging), VDMA German Mechanical and Plant Engineering Association, Frankfurt a.M., and bvse-Bundesverband Sekundärrohstoffe und Entsorgung (Federal Association for Secondary Raw Materials and Disposal), Bonn. It was prepared by Consultic Marketing & Industrieberatung GmbH in Alzenau, 2015.

[0068] In order to enable tracking of a mixing ratio, a method for processing reused or recycled bulk material 9, in particular solids such as granules, powders, grains, films, chips, or the like, preferably for plastics processing machines 4, was created, in which a device 11 for dosing at least two bulk materials 9 present in separate feed devices or containers 24a, 24b, of which at least one bulk material 9 is made of reused plastics, i.e. a so-called recyclate 19 or regranulate, supplies the plastics processing machine 4 with the dosed bulk material 9 after dosing, directly or via intermediate stations, wherein the at least one dosing device 11 brings these at least two separate bulk materials 9 together in any desired sequence,wherein, simultaneously or after dosing, the respective dosed bulk material weight is determined and the information on the bulk material weights and / or resulting information representing the material throughput of each individual or all of the bulk materials 9 fed in is transmitted from the control of the dosing device 11 to the plastics processing machine 4 or to a higher-level control system, and a physical representation of the flow behavior, for example a melt flow index 21, of the fed bulk material 9 and / or the material throughput or consumption of the machine is determined in the plastics processing machine 4 and this information is linked in the plastics processing machine 4 or in the higher-level control system.

[0069] For the sake of completeness, it should be noted that all devices or production resources 2 can be designed as so-called stand-alone devices and thus operate independently of others. The production resources 2 are connected directly or indirectly via cables or networks to enable data exchange between them.

Claims

1. Method for processing reused or recycled bulk material (9), in particular solids such as granulates, powders, grains, films, scraps or the like, for plastics-processing injection-moulding machines (4), wherein a device for dosing (11) at least two bulk materials (9) present in separate feed devices or containers (24), of which bulk materials (9) at least one bulk material (9) is made of reused plastics, i.e. a so-called recyclate, ground material (19) or regranulate, supplies the plastics-processing machine (4), after dosing, directly or via intermediate stations with the dosed bulk material (9), wherein the at least one device for dosing (11) combines these at least two separate bulk materials (9) in any desired sequence, wherein simultaneously with or after the dosing, the respective dosed bulk-material weight is determined, and the information on the bulk-material weights and / or information derived therefrom that represents the material throughput of each individual or of all supplied bulk materials (9) is transmitted from the controller of the device for dosing to the plastics-processing machine (4) or to a superordinate controller and in the plastics-processing machine (4) a physical representation of the flow behaviour in the form of a melt flow index (21) or a value equivalent to the melt flow index (21) of the supplied bulk material (9) and / or the material throughput or material consumption of the plastics-processing machine (4) is determined, and this information is linked in the plastics-processing machine (4) or in the superordinate controller, the melt flow index (21) or an equivalent value being determined for each production cycle of injection-moulded parts (3).

2. Method according to claim 1, characterised in that the device for dosing (11) is equipped with one or more load cells for determining the material weight or with a counting device for determining bulk-material units that arithmetically correspond to the material weight.

3. Method according to claims 1 and 2, characterised in that the plastics-processing machine (4) determines after dosing, from the process parameters of the polymer melt to be processed of the supplied bulk material (9), a physical quantity that is proportional to the melt's flow behaviour, for example a melt flow index (21).

4. Method according to any of the preceding claims, characterised in that the mixing ratio or weight ratio of the at least two bulk materials after the dosing process must correspond to a freely selectable or adjustable specification or to a selected or transmitted recipe, wherein, in batch dosing, the completed dosed batch (20) is formed from at least one or several dosing operations per bulk material (9), or, in continuous dosing, at least one bulk material (9) is continuously drawn in by the plastics-processing machine (4) and at least one bulk material (9) is continuously added after adjustment.

5. Method according to any of the preceding claims, characterised in that the superordinate controller can be an external work-cell controller for the logical management and data communication of production resources (2), for example the plastics-processing machine (4) and the device for dosing (11), with or without connection to a downstream MES or ERP system, or directly an MES or ERP system.

6. Method according to any of the preceding claims, characterised in that the information determined by the plastics-processing machine (4) and by the at least one device for dosing (11), such as individual bulk-material weights, the mixing ratio of the materials, material consumptions or corresponding differences, an indicator of the flow behaviour of the supplied bulk material, or the melt flow index (21), is displayed, evaluated or documented, preferably in the controller of the plastics-processing machine (4) or in a system connected to the controller of the plastics-processing machine (4) and / or the device for dosing (11), such as a superordinate controller.

7. Method according to any of the preceding claims, characterised in that the information determined by the plastics-processing machine (4) and by the at least one device for dosing (11), such as individual bulk-material weights, the mixing ratio of the materials, material consumptions or corresponding differences, an indicator of the flow behaviour of the supplied bulk material (9) or the melt flow index (21) must lie within adjustable deviations from reference templates in order to confirm correct bulk-material supply during ongoing operation or in a test operation, for example an audit.

8. Method according to any of the preceding claims, characterised in that at least one, preferably two reference templates or reference settings (22, 23) are provided that map, on the one hand, the approved addition of ground material and, on the other hand, no addition of ground material namely the exclusive use of virgin material (18) since all intermediate stages are regarded as a permitted mixing ratio.

9. Method according to any of the preceding claims, characterised in that additional data originating both from the plastics-processing machine (4) and from the one or more devices for dosing (11) are evaluated and / or documented, preferably in the controller of the plastics-processing machine (4) or in a system connected to the controller of the plastics-processing machine (4) and / or the device for dosing (11), such as a superordinate controller e.g. the current process parameters of the machine (4) and / or process parameters of the one or more devices for dosing (11).

10. Method according to any of the preceding claims, characterised in that the device or devices for dosing (11) can also be directly connected to the plastics-processing machine (4) and data processing extending beyond the material consumption and / or an indicator of the flow behaviour of the supplied bulk material (9) or melt flow index (21) can take place between the two production resources (2).

11. Method according to any of the preceding claims, characterised in that the plastics-processing machine (4) documents or analyses the characteristics of the bulk-material melt, e.g. in the form of an indicator or a melt flow index (21), during dosing and / or during the injection process into the shaping mould or immediately performs an adjustable action.

12. Method according to any of the preceding claims, characterised in that the device for dosing, in particular the dosing device (11), documents or analyses the characteristics of the mixture of the bulk-material components or immediately performs an adjustable action.

13. Plastics-processing installation (1) for processing reused or recycled bulk material (9), in particular solids such as granulates, powders, grains, films, scraps or the like, comprising at least one plastics-processing injection-moulding machine (4), a device for dosing (11), in particular a dosing device (11), of at least two bulk materials (9) or ground material (9) present in separate feed devices or containers (24), wherein at least one bulk material (9) is formed from reused plastics, i.e. a so-called recyclate (19) or regranulate, and further production resources (2) required for operating the plastics-processing machine (4) such as temperature-control units (13), flow regulators (14) and the like, which are connected directly or indirectly to the plastics-processing machine (4), in particular the injection-moulding machine (4), characterised in that the plastics-processing machine (4) and / or an external work-cell controller is configured to determine a physical representation of a flow behaviour in the form of a melt flow index (21) or an equivalent to a melt flow index (21) of the supplied bulk material (9) and / or the material throughput or consumption of the machine and to carry out the method according to claims 1 to 12.