Injection molding compounds and methods for their manufacture, as well as their use and application

Abstract

Method for manufacturing an injection molding compounder (1) with an extruder (20) and an injection unit (40), comprising the following steps: a) Providing an injection unit (40) with an injection screw (44) arranged in an injection housing (41) and a filling opening (33) for plastic granules, b) Providing an extruder (20) with at least one extruder screw (24) arranged in an extruder housing (21), a feed opening (22) for feeding one or more plastic materials, and an outlet (28), c) Inserting an insert (10) into the filling opening (33) for plastic granules of the injection unit (40), wherein the insert (10) has a central channel (13) and an outer wall (12) surrounding the central channel in an annular manner, and wherein a heating element and / or an insulating element (14), in particular a heating element (14), is provided in the outer wall (12) of the insert (10), d) Connection of the outlet (28) of the extruder (20) via a melt line (30) to the insert (10) in the filling opening (33) for plastic granules of the injection unit 40), wherein the insert (10) is releasably attached in the filling opening (33) and is connected on the side facing away from the filling opening to the outlet (28) of an extruder via a melt line (30), so that it is possible to connect and disconnect the insert (10) or the melt line (30) attached to it.

Description

[0001] The invention relates to a method for manufacturing an injection molding compounder, a corresponding injection molding compounder with an insert in the filling opening of the injection unit, such an insert and its use.

[0002] US2002 / 0079607A1 relates to a molding material consisting of resin-coated reinforcing fiber strands in a molten resin mass, prepared at a molding station for controlled feeding to a molding machine. Continuous fibers from supply spools are entrained and coated with pressurized molten resin flowing through a coating device. The movement of the fibers and resin through the coating nozzle can be controlled to produce any desired quantity of molding material precisely and predictably; that is, the coating device can be operated discontinuously to deliver any predetermined quantity of molding material to a receiving device. The receiving device can be the feed screw for an injection molding machine or simply a plate that can be moved to and from a compression molding machine.The fiber strands can be cut into predetermined lengths by a cutting device located downstream of the aforementioned coating device.

[0003] WO2013 / 121049A1 describes an injection molding compounder comprising: an extruder with at least one extruder screw arranged in an extruder housing, an injection unit with an injection screw arranged in an injection housing, wherein the injection unit has an effective length defined from the injection nozzle of the injection unit to the furthest end of the threads of the injection screw, characterized in that a melt inlet is provided on the injection housing, which is connected to an outlet of the extruder, wherein the melt inlet is located further than one-third of the effective length (h) from the injection nozzle. According to the description and figures of WO2013 / 121049A1, a melt inlet is advantageously provided independently of the feed opening for plastic granules of the injection unit. As a less preferred option, the introduction of the melt from the extruder into the granule hopper of the injection unit is briefly mentioned.

[0004] It has now been surprisingly found that introducing the melt into the granulate hopper of the injection unit in this way leads to significant problems in the processing and quality of the plastic materials and the workpieces produced from them.

[0005] When the granules are introduced into the injection unit's hopper in this manner, the melt from the extruder outlet cools down too quickly against the hopper wall. This not only leads to deposits on the hopper but also results in inhomogeneous plastic material being fed into the injection unit. This material inhomogeneity often persists during further processing within the injection unit. Furthermore, the hopper and other components at the injection unit's feed opening must be cleaned regularly, as otherwise operational reliability will be impaired.

[0006] The present invention therefore aims to overcome the disadvantages of the prior art, in particular the aforementioned problems in introducing the melt into the granule hopper of the injection unit.

[0007] This problem is solved by the aspects of the invention as described herein. In particular, it is solved by the features of the independent claims. Preferred and particularly advantageous embodiments are described in the dependent claims.

[0008] Thus, a first aspect of the invention relates to a method for manufacturing an injection molding compounder (1) with an extruder (20) and an injection unit (40), comprising the following steps: a) Providing an injection unit (40) with an injection screw (44) arranged in an injection housing (41) and a filling opening (33) for plastic granules, b) Providing an extruder (20) with at least one extruder screw (24) arranged in an extruder housing (21), a feed opening (22) for feeding one or more plastic materials, and an outlet (28), c) Inserting an insert (10) into the filling opening (33) for plastic granules of the injection unit (40), wherein the insert (10) has a central channel (13) and an outer wall (12) surrounding the central channel in an annular manner, and wherein a heating element and / or an insulating element (14), in particular a heating element (14), is provided in the outer wall (12) of the insert (10), d) Connection of the outlet (28) of the extruder (20) via a melt line (30) to the insert (10) in the filling opening (33) for plastic granules of the injection unit 40), wherein the insert (10) is releasably attached in the filling opening (33) and is connected on the side facing away from the filling opening to the outlet (28) of an extruder via a melt line (30), so that it is possible to connect and disconnect the insert (10) or the melt line (30) attached to it.

[0009] A second aspect of the invention relates to an injection molding compounder (1) having the following features: a) an extruder (20) with at least one extruder screw (24) arranged in an extruder housing (21), a feed opening (22) for supplying one or more plastic materials, and an extruder outlet (28), b) an injection unit (40) comprising an injection screw (44) arranged in an injection housing (41) and a filling opening (33), wherein an insert (10) is inserted into the filling opening (33) of the injection unit, the insert having a central channel (13) and an outer wall (12) surrounding the central channel in an annular manner, wherein a heating element and / or an insulating element (14) is provided in the outer wall (12) of the insert (10), and wherein the extruder outlet (28) is connected to the insert (10) in the filling opening (33) of the injection unit (40) via a melt line (30), wherein the insert (10) is detachably attached in the filling opening (33) and is connected on the side facing away from the filling opening via a melt line (30) to the outlet of an extruder (28), so that the insert (10) or the melt line (30) attached to it can be connected and disconnected.

[0010] The injection molding compound according to the invention is obtainable in particular by the method according to the first aspect of the invention, and by the method according to the invention for producing an injection molding compound as described herein.

[0011] A third aspect of the invention relates to the use of an insert (10) in a filling opening (33) for plastic granules of an injection molding unit for introducing a plastic melt, wherein the insert (10) has a central channel (13) and an outer wall (12) surrounding the central channel in an annular manner, wherein the insert (10) is heated, in particular via a heating element provided in the outer wall (12) of the insert (10) and / or an inlet cooling system with cooling channels (5) in the area of ​​the filling opening (33), wherein the insert (10) is releasably attached in the filling opening (33) and is connected on the side facing away from the filling opening (33) via a melt line (30) to the outlet (28) of an extruder (20), so that it is possible to connect and disconnect the insert (10) or the melt line (30) attached to it.

[0012] A fourth aspect of the invention relates to an insert (10) for a filling opening (33) for plastic granules of an injection molding unit, wherein the insert (10) is dimensioned so that it can be inserted into or connected to the filling opening (33) in a melt-tight manner, wherein the insert (10) has a central channel (13) and an outer wall (12) surrounding the central channel (13) in an annular manner, wherein a heating element and / or an insulating element (14) is provided in the outer wall (12) of the insert (10), wherein the insert (10) has a releasable connecting element, in particular a bayonet closure, ring clamp quick-release fastener or a quick coupling.

[0013] Thus, in contrast to WO 2013 / 121049A1, according to the present invention the granule hopper of the injection unit is removed and the melt is introduced after removal of the granule hopper of the injection unit.

[0014] An insert is placed into the filling opening for plastic granules of the injection unit, which has a central channel for guiding a plastic melt and an outer wall surrounding this central channel in a ring shape.

[0015] The insert is connected to or secured within the injection unit's plastic granule feed opening in such a way that this connection is melt-tight, meaning that no melt escapes when molten plastic is introduced from the extruder outlet via a melt line, even under pressure. Specifically, the melt line is also melt-tight, connecting one end to the insert in the injection unit's plastic granule feed opening and the other end to the extruder outlet.

[0016] The insert is detachably secured in the filling opening, allowing the insert and the attached melt line to be connected and disconnected. This enables different extruder and injection units to be repeatedly connected and disconnected, depending on the desired combination and intended production. Suitable detachable (pressure-tight or melt-tight) connecting elements are familiar to those skilled in the art and include, but are not limited to, screw connections, bayonet fittings, ring clamp quick-release couplings, or quick-release couplings.

[0017] According to the invention, the problems associated with introducing the melt into the granulate hopper of the injection unit are thus surprisingly avoided.

[0018] Within the scope of the present invention, it was further surprisingly found that not only the (unheated) surface of the granule hopper, but the entire unheated area of ​​the filling opening for plastic granules in an injection unit leads to problems when introducing plastic melt from the extruder outlet (via the melt line) into the filling opening.

[0019] In a conventional filling opening for plastic granules in an injection unit, elevated temperatures should be avoided, as this can lead to partial melting of the plastic granules in the area of ​​the granule hopper or filling opening, resulting in disruptive deposits on the hopper and in the filling opening. Therefore, prior art typically incorporates infeed cooling with cooling channels in the area of ​​the plastic granule filling opening. This allows the temperature to be kept low, particularly through the use of water as the cooling medium in the cooling channels.

[0020] Within the scope of the present invention, it has now been surprisingly discovered that such a feed-in cooling system in the area of ​​the filling opening for plastic granules can be used in the method according to the first aspect of the invention (and the corresponding injection molding compounder) to heat the area of ​​the filling opening, and in particular the insert in the filling opening, and thus avoid the risk of partial solidification of the plastic melt in this area and inhomogeneity of the plastic material. The existing cooling device with cooling channels is used for heating in an elegant manner.

[0021] In principle, water can be used as a temperature control medium for such heating if heated sufficiently, e.g., with a high-temperature water heater (for example, the Tempro Plus D200 Ecodrive from WITTMANN BATTENFELD Deutschland GmbH, Nuremberg, Germany). According to a preferred embodiment of the present invention, an oil-based temperature control medium, in particular a thermal oil, is used and circulated through the cooling channels. Suitable temperature control media and thermal oils are familiar to those skilled in the art in this field. Any temperature control media or thermal oils that can be used continuously for heating to the usual melting temperatures of a polymer melt, in particular a temperature range of 110°C to 330°C, can be used. Non-limiting examples of suitable thermal media or thermal oils are the DURATHERM thermal oils from Duratherm Extended Life Fluids, Lewiston, USA.

[0022] Within the scope of the present invention, it has been shown that the outer wall of the insert, which surrounds the central channel (for guiding the molten plastic), preferably also has at least one heating element and / or one insulating element. This helps to avoid the aforementioned problems of a temperature drop in the molten plastic from the melt line upon contact with the insert or the area of ​​the filling opening.

[0023] Suitable heating elements are familiar to the expert, such as heating tapes and heating cartridges (Ihne & Tesch GmbH, Lüdenscheid, DE), https: / / www.elektrowaermetechnik.de / produkte.html.

[0024] According to another preferred embodiment, channels extending radially around the melt line are heated with a thermal oil.

[0025] According to a particularly preferred embodiment, at least one heating element is provided in the outer wall of the insert according to the invention.

[0026] Alternatively or in addition to the at least one heating element in the outer wall of the insert, at least one insulating element is provided in the outer wall of the insert. In particular, at least one insulating element is provided in addition to at least one heating element in the outer wall. Suitable insulating elements are familiar to those skilled in the art, such as glass, ceramic, and non-thermally conductive stainless steel.

[0027] According to the invention, the extruder outlet is connected to the insert (in the filling opening for plastic granules of the injection unit) via a melt line.

[0028] The insert particularly preferably has at least one temperature sensor and preferably at least one pressure sensor. It has been found that such a temperature sensor advantageously allows the temperature of the polymer melt to be monitored directly in the area of ​​the filling opening. Using conventional devices for heating or tempering the temperature control medium in the cooling channels and / or the at least one heating element in the outer wall of the insert, as described herein, the polymer melt can be brought to a sufficient temperature or maintained at that temperature in the area of ​​introduction into the injection unit.

[0029] The preferably integrated pressure sensor also enables monitoring and regulation of the pressure directly at the point where the plastic melt enters the injection unit, allowing the operation of the injection unit to be adjusted and optimized as needed. This makes it possible to reduce the load on the injection unit and ensure a high throughput of plastic material from the extruder to the injection unit.

[0030] According to a further preferred embodiment, the outer wall of the insert is at least partially hollow, with the heating element and / or insulating element described above being inserted into the cavity in the outer wall of the insert.

[0031] As described above, during operation of the injection molding compounder according to the invention, the temperature of the temperature control medium in the cooling channels is preferably adjusted so that it is at least equal to or higher than the melting temperature of the plastic material conveyed through the melt line. For this purpose, a circuit for the temperature control medium (in the cooling channels) is preferably provided, comprising a device for heating the temperature control medium, a sensor for detecting the temperature of the temperature control medium, and a corresponding control unit for setting the desired temperature. Such circuits and devices for regulating the temperature of a temperature control system are familiar to those skilled in the art, and there are no restrictions on their use within the scope of the present invention.

[0032] According to the invention, the plastic melt (from the extruder outlet, via the melt line) is not introduced into the granule hopper of the injection unit, but, after removal of the granule hopper, it is introduced directly into the filling opening (for plastic granules) of the injection unit.

[0033] Reference is made here to the preceding and following detailed description of the use in the filling opening with regard to the individual aspects of the invention.

[0034] The intake cooling with cooling channels in the area of ​​the filling opening (with the temperature control medium used according to the invention) and its use according to the invention for heating or temperature control of the insert to or above the melting temperature of the plastic material conveyed through the melt line has already been described.

[0035] Another aspect of the invention, as described above, relates to the use of an insert in a filling opening for plastic granules of an injection molding unit for introducing a plastic melt.

[0036] As previously described, the insert has a central channel and an outer wall surrounding the central channel in a ring shape. The insert is heatable, preferably via a heating element provided in the outer wall of the insert and / or a cooling system with cooling channels in the area of ​​the filling opening.

[0037] It is advantageous that the insert can be reattached to the filling opening in a detachable manner. On the side of the insert facing away from the filling opening, it is connected to a melt line, which is connected to the outlet of an extruder. This connection, as well as the connection between the insert and the filling opening described above, is particularly melt-tight and pressure-tight with respect to the usual temperatures and pressures encountered during the processing of plastic materials in an injection molding compound.

[0038] Preferably, a rotatable or swiveling connection is located on one side of the insert, to which the melt line is attached. This rotatable or swiveling connection advantageously allows the melt line to be attached to the injection unit in a highly variable or movable manner, thus enabling greater flexibility in the spatial arrangement of the extruder unit and the injection unit relative to each other, as well as greater variability in the connection and disconnection of different units, depending on the desired combination and production.

[0039] Another aspect of the present invention relates, as described above, to an insert for a filling opening for plastic granules of an injection unit. The insert is dimensioned, in particular, such that it can be inserted into or connected to the filling opening in a molten-tight manner. As already described, the insert preferably has a central channel for guiding the plastic melt and an outer wall surrounding the central channel in an annular fashion. Particularly advantageously, and therefore preferably, a heating element and / or an insulating element, as is known to those skilled in the art and described herein, is provided in the outer wall of the insert. As also already described, in addition to the at least one heating element and / or insulating element, the insert preferably also has a temperature sensor and / or a pressure sensor.This (these) sensor(s) is (are) preferably arranged in the outer wall at the end of the insert facing the filling opening.

[0040] As mentioned above, the general design of the injection molding compounder (but without the inventive method of connecting the injection unit to the extruder outlet) corresponds to that described in the aforementioned WO2013 / 121049A1, the details of which are expressly incorporated into the present description by reference. In detail: An injection molding compounder thus comprises an extruder with at least one extruder screw arranged in an extruder housing, and an injection unit with an injection screw arranged in an injection housing, wherein the injection unit has an effective length defined from the injection nozzle of the injection unit to the furthest end of the threads of the injection screw. This effective length is preferably defined in the advanced position of the injection unit, i.e., immediately after the injection process.

[0041] Furthermore, a control system may be installed to switch the (rotary) drive of the extruder screw on and off depending on the cycle phase of an injection process. Specifically, within the injection cycle, a period of time when the extruder drive is activated and a period when it is deactivated are provided. Particularly with a single-screw extruder, it is technically easy to start and stop the extruder and thus provide the required melt at any given time.

[0042] Preferably, a control system is provided to switch the extruder screw drive on and off depending on the cycle phase of an injection process and / or the fill level of the injection unit. This achieves a functional coupling between the injection screw and the extruder screw. In this way, the extruder screw's feed rate can be adapted to the volume of melt that the injection unit can take in during the injection screw's return stroke. This can be achieved with a simple control system, in that the extruder is switched on (or off) depending on cycle times of the injection process. Alternatively or additionally, sensors, such as pressure sensors, can be provided on the injection unit to determine the material requirement of the injection unit and, by switching the extruder on (or off) at a precise time, supply the required quantity of material to the injection unit.To ensure that the melt line between the two components is evenly or completely filled with melt at all times, the injection unit is supplied with exactly the amount of melt provided by the extruder.

[0043] In particular, the control system can be configured to regulate the melt flow rate from the extruder to the injection unit based on deviations between a predefined, injection-phase-dependent target fill level and the measured actual fill level of the injection unit. Target parameters are specified for the injection unit regarding filling and filling speed, indicating the axial position of the injection screw at specific times. The movement of the injection screw during filling is directly determined by the extruder's feed rate. If a deviation occurs between the actual filling speed and the predefined target values, the feed rate of the extruder screw can be adjusted accordingly within a closed-loop control system.

[0044] In particular, the control system is configured to switch the rotary drive of the injection screw and the rotary drive of the extruder screw on and off, wherein the switching on of the rotary drive of the extruder screw is preceded or delayed, or in particular, occurs simultaneously with the switching on of the rotary drive of the injection screw or with the injection stroke of the injection screw. Preferably, the switching off of the rotary drive of the extruder screw is preceded or delayed, or occurs simultaneously with the switching off of the drive of the injection screw. This also includes, in particular, the ability to operate the extruder screw synchronously with the rotary drive of the injection screw.Due to the coordination of the drives of the extruder and the injection unit, depending on the material or compound used, mixing and processing conditions can be achieved that are optimally suited to a short cycle time, good mixing and low material stress.

[0045] Preferably, an input and / or storage module is provided for entering and / or storing operating parameters for the drives of the injection screw and the extruder screw, so that the injection screw and the extruder screw can be operated with a time offset or synchronously within an injection cycle, depending on different materials or material combinations of the melt. The input unit allows for targeted setpoint inputs, and the storage module can contain a database of different advantageous operating conditions depending on different materials, thus making it easier for the user to operate the injection molding compounder under optimal conditions.

[0046] In one embodiment, a valve is arranged in the melt line between the extruder outlet and the injection unit's feed opening. This valve is at least a two-way valve, which can either direct the melt into the injection unit or discharge it to the environment. A three-way valve can also be used, which, according to one embodiment, additionally includes a closed position. If the valve is a pressure relief valve, excessively high melt pressure supplied by the extruder can be reduced for safety reasons. A controllable valve can prevent the generated melt from being discharged to the injection unit too early during the plasticizing phase. Furthermore, the extruder and injection unit can be easily, quickly, and safely decoupled.

[0047] In one embodiment, no buffer extending beyond the melt line is provided between the extruder outlet and the injection unit's feed opening, and in particular, no buffer with a variable volume is provided, so that the melt produced in the extruder is fed directly and immediately to the injection unit. This can also be expressed as follows: The duration of an injection cycle can be divided into any number of points in time or time intervals, whereby at each of these points in time, the volumetric flow rate of the pipe connection is constant at every point between the extruder outlet and the injection unit. In this sense, there is no buffer in which the melt produced by the extruder accumulates until the injection unit requests it. Rather, the extruder feeds directly into the injection unit.This reduces the dwell time of the melt in the pipe connection and achieves better production control. Alternatively, or preferably, this can also be expressed as follows: in a functioning injection molding compounder, the fill level of the pipe connection between the extruder outlet and the injection unit is uniformly filled with melt over several injection cycles, regardless of the cycle phase of the injection unit.

[0048] Thus, according to a preferred embodiment, only the melt line (possibly equipped with a valve) is provided between the extruder and the injection unit.

[0049] When using the injection molding compounder, the melt that is conveyed in the extruder along the longitudinal direction of the extruder is deflected in the direction of the longitudinal direction of the injection unit.

[0050] According to one embodiment, the length-to-diameter ratio of the extruder screw is at least approximately 20. According to another embodiment, the value is preferably between 18 and 40, and in particular between 20 and 30.

[0051] A preferred method for producing an injection-molded workpiece with an injection molding compounder according to the invention comprises the steps of feeding one or more injection molding materials to an extruder, producing a melt by melting and / or mixing the one or more injection molding materials in the extruder, feeding the melt via the melt line into the filling opening of an injection unit (via the insert according to the invention), and guiding the melt in the injection unit towards an injection nozzle connected to an injection mold.

[0052] Preferably, a phase is provided within a cycle of manufacturing the injection-molded part in which the extruder screw is not driven, and preferably, the injection screw is driven during the phase in which the extruder screw is not driven. This stops the further supply of melt to the extruder before and / or during the injection phase of the melt into the mold.

[0053] Preferred embodiments of the present invention are described below, without limitation, by way of example with reference to the figures. These show: Fig. 1 a schematic diagram of an injection molding compounder according to the invention with an extruder and an injection unit, Fig. 2 a schematic structure of an insert according to the invention in the filling opening of the injection unit.

[0054] Fig. Figure 1 shows an injection molding compounder 1 according to the invention with an extruder unit 20 and an injection unit 40.

[0055] The following reference symbols are used in the figures: 1 Injection Molding Compound 5 cooling channels 6 End of the channel facing the filling opening 13 7 Injection screw of the injection unit (symbolic) 10 deployment 11. Placing the stake (symbolically) 12 Outer wall of the insert Channel 13 14 insulating elements 18 side wall 20 extruder units 21 Extruder housings 22 Filling opening 24 extruder screws 28 Extruder / Extruder outlet 30 melt line 31 Pipe section 32 Connection point between extruder outlet 28 and pipe section 31 (symbolic) 33 Filling opening 40 Injection unit 41 cases 44 Injection screw 49 Injector nozzle 50 tools

[0056] Both units are connected via the melt line 30. This includes a pipe section 31 for conveying the polymer melt from the outlet of the extruder 28 (the melt-tight connection point between the extruder outlet 28 and the pipe section 31 is symbolically represented by circle 32) into the filling opening 33 (formerly for polymer granules; also symbolically represented by a circle) of the injection unit. The insert according to the invention in the filling opening is not shown separately in this figure, but in Fig. 2. explained in more detail:

[0057] Fig. Figure 2 shows the insert 10 with a central channel 13 and an outer wall 12 surrounding it in an annular manner. Heating elements and / or insulating elements 14 are provided in the outer wall. As described above, these are preferably arranged in cavities in the outer wall of the insert.

[0058] The insert is placed directly into the plastic granule filling opening of the injection unit, after the granule hopper has been removed as described above. This insertion is represented by reference numeral 11, and the insert is connected to the filling opening in a melt-tight and pressure-tight manner. The corresponding gap between the outer wall of the insert 12 and the side wall 18 of the filling opening (which extends through the housing 41 of the injection unit 40) is therefore shown in the figure for graphical purposes only; in practice, the two walls are directly connected to each other to ensure a melt-tight and pressure-tight seal.

[0059] The insert can be attached to the filling opening in any conventional way, in particular by screwing, clamping elements or the like.

[0060] Cooling channels 5 are provided in the area of ​​the filling opening (in the housing 41 of the injection unit 40 or the side wall 18), which, according to the invention, are used to enable heating of the filling opening or the insert located therein. For this purpose, a temperature control medium, in particular a thermal oil, is passed through the cooling channels 5 and heated, in particular, to a temperature that is at or above the melting temperature of the plastic melt passed through the inner channel 13.

[0061] Alternatively or additionally to this heating, the heating elements 14 already present in the insert are used. This allows the molten plastic, which is guided into the injection unit 40 via the central channel 13 or its end 6 facing the filling opening, to be kept at the desired temperature above the melting point, thus enabling particularly advantageous processing. The injection screw of the injection unit is symbolically represented by reference numeral 7 in the Fig. 2 shown.

[0062] At the lower end 6 of the outer wall of the insert (facing the filling opening or the injection screw) there is preferably at least one thermal sensor and particularly preferably at least one pressure sensor, which can be used to monitor the temperature and pressure of the plastic melt introduced into the injection unit and then, if necessary, to adjust them as desired.

[0063] As already explained, the application according to the invention not only enables the particularly advantageous introduction of a plastic melt from an extruder outlet into the filling opening for plastic granules of an injection unit, but also the advantageous temperature setting or regulation of the plastic melt in the area of ​​the filling opening in order to enable optimal further processing in the injection unit.

[0064] In principle, the materials processed within the scope of the present invention are not limited, and all materials and material combinations known to those skilled in the art can be used. In particular, thermoplastic polymers or thermosetting polymers and mixtures thereof are used as materials. Depending on the requirements, organic, inorganic, or fibrous fillers or ceramics may be used.

[0065] The extruder described above has a feed opening for one or more plastic materials. This feed opening is typically used to supply one or more plastic materials, especially in granular or powder form, to the extruder screw. A funnel is conventionally inserted into the feed opening to enable or facilitate the filling process with the plastic materials.

[0066] In a preferred embodiment, a conventional dosing system is arranged above the filling opening (or the funnel inserted therein), in which the supplied plastic materials are dosed volumetrically or gravimetrically and fed to the filling opening (via the funnel). Such dosing systems are familiar to those skilled in the art.

[0067] In principle, it is also possible within the scope of the present invention for the injection molding compounder to have more than one extruder. If two or more extruders are present, they can be connected to the injection unit via one (common) or several (separate) melt lines. According to the invention, at least one melt line connects the extruder outlet to the filling opening of the injection unit, as described herein.

[0068] Fig. 1 is essentially similar to the inventive method of connecting the extruder to the injection unit, except for the method of connection of the extruder to the injection unit. Fig. 1 of WO2013 / 121049, to which explicit reference is made. The attached Fig. Figure 1 shows an injection molding compounder 1 in a position where the injection unit 40 is connected to the mold 50, allowing plastic material to be injected into the mold via the injection nozzle 49. The extruder unit 20 is connected to an injection molding unit 40 via the melt line 30, so that the plastic material liquefied in the extruder 20 is fed into the injection molding unit. The extruder's function is to produce the plastic melt and achieve a certain degree of mixing of the different components. As will be explained in detail below, the quality or uniformity of the mixing achieved in the extruder does not need to be as high as required for the injection process, since the melt supplied by the extruder is conveyed to the injection unit where further supplementary mixing and increased homogeneity take place. The extruder, or rather,The extruder unit is also referred to as a compounder and is used accordingly. One advantage of an injection molding compounder is that the plastic mixture required in the injection unit is produced simultaneously within the extruder. The conventional production of compound granules is eliminated, thus saving the energy required for remelting the granules and preventing material stress and damage caused by granulation.

[0069] The molten metal enters the injection unit 40 from the melt line 30 via the filling opening of the injection unit.

[0070] According to the invention, the filling opening of the injection unit 40 is connected via the melt line 30 to the extruder outlet 28, i.e., the outlet of the melt from the extruder. In the illustrated embodiment, the melt line 30 has a straight pipe section 31.

[0071] The inner diameter of the melt line and preferably also of the inner channel in the insert according to the invention can be routinely optimized by those skilled in the art and will generally be between 5 mm and 50 mm, in particular between 10 mm and 30 mm, depending on the design of the injection molding compounder. The inner diameter is preferably dimensioned such that the injection unit can be filled via the extruder as desired. For example, if the compounder is designed with the same rotational speeds and the same pitch of both screws, this inner diameter can be identical to the melt cross-section within the injection unit. The melt cross-section is defined as the area of ​​the inner diameter of the injection housing 41 minus the cross-section of the injection screw 44.

[0072] The injection unit 40 has an injection nozzle 49 at its outlet end, which is connected to one half of the injection mold 50.

[0073] When using the injection molding compounder, one or more plastic materials are fed into the extruder 20, which has at least one extruder screw 24 in an extruder housing 21, via the feed opening 22 and melted and mixed within it by heating. In addition to the single feed opening 22 shown, further feed openings (not shown) may be provided.

[0074] The molten plastic exits the extruder at the extruder outlet 28 and is conveyed via the melt line 30 into the feed opening of the injection unit 40. A valve (not shown) can be installed in the melt line, in particular a valve that can be moved into a closed position in which the outflow of the melt from the extruder is prevented. Thus, at the beginning of the processing process, the valve can initially be closed until the plastic material in the extruder is sufficiently heated and homogenized. Plastic with insufficient properties can be discharged into the environment in the valve's open position. The valve is preferably a controlled valve that can be moved into a desired position by an actuator, such as an electric, pneumatic, or hydraulic actuator. In addition to safety aspects, the valve also facilitates a quick and clean changeover from one material to another.Material that may have been in extruder 20 for too long during the start-up of the compounder and may therefore have degenerated, or that has been mixed during a material change, can be discharged to the outside via the open position of the valve.

[0075] The injection molding compounder can have any commercially available injection unit or extruder unit as the injection unit 40 or as the extruder 20, which has been set up according to the invention for the pressure- and melt-tight attachment of the melt line.

[0076] The time sequence of an injection molding cycle can be described according to Fig. 3 of WO2013 / 121049A1 and the accompanying description therein, to which explicit reference is made. Specifically: In the upper section, the rotary drive R is shown for both the extruder screw 24 (in a dotted line) and the injection screw 44 (in a dashed line). The value "0" means that the corresponding drive is switched off, and "1" means that the drive is switched on, although this does not mean that the drives must operate at the same rotational speed. The lower section of the Fig. Figure 3 of WO2013 / 121049A1 shows the stroke of the injection screw, where the value “1” means that the injection screw 44 is in its forward position, as for example immediately after the injection process, and at the value “0” the injection screw is in the retracted position, in which a volume for the melt to be injected is created between the front end of the screw and the injection nozzle 49.

[0077] At the start of the injection cycle, the extruder screw 24 is started at time t0, and the melt is produced, mixed, and homogenized in the extruder. At this point, the valve may be closed. Once a certain amount of homogeneous melt has been produced, the valve can be opened at time t1, allowing the melt to be discharged into the injection unit 40. At this point, the drive of the injection screw 44 is started, resulting in a time offset ΔTa between the start-up times of the two screws. The injection screw is in its forward position at this time.

[0078] During the time interval from t1 to t2, both the extruder and injection screws are driven, generating melt. During this process, the injection screw 44 is moved into its retracted position, and the melt accumulates in front of it for the next injection operation. At time t2, a sufficient quantity of melt has been generated for the injection movement taking place between t2 and t3. At time t2, the extruder screw 24 is stopped, and the stroke drive 143 of the injection unit 40 is activated. At time t3, the injection screw has moved into its forward position, and the injection of the plastic into the injection mold is complete, allowing the rotary drive of the injection screw 44 to be stopped. Thus, there is a time offset of ΔTb between the switching off of the two rotary drives.

[0079] It is not mandatory that, as described above, the switching off of the rotary drive of the extruder screw takes place simultaneously with the switching on of the lifting drive of the injection screw 44, but alternatively the extruder screw can only be switched off at time t2', so that in the period t2 to t2' the lifting drive of the injection screw 44 and the rotary drive of the extruder screw are activated simultaneously and during the injection process of the plastic into the tool, melt continues to be conveyed into the injection unit.

[0080] At time t3, the injection process is complete, and the rotary drives of the injection screw 44 and the extruder screw are switched off during the curing and cooling time of the melt in the injection mold. At time t4, the molded plastic workpiece is removed from the mold. At time t4, the next injection molding cycle can begin, so that time t4 is identical to t0 of the next cycle. Alternatively, the extruder screw 24 can be reactivated during the cooling time, i.e., the period from t3 to t4, to produce melt for the next cycle and thus reduce the cycle duration. Additionally, preferably during the period t3 to t4, a holding pressure is applied via the stroke of the injection screw to compensate for the shrinkage of the injected plastic.

[0081] The injection molding compounder according to the invention is particularly suitable for applications where different materials need to be mixed together. Since the mixing takes place both in the extruder and in the injection unit, the respective residence and mixing times and their extent are reduced in both of these units, and overall, with good mixing, the thermal and mechanical stress on the materials is reduced.

[0082] A suitable material, though not limited to specific options, is a mixture of polycarbonate (PC) and acrylonitrile budadiene styrene (ABS), which is very sensitive to prolonged exposure to high temperatures. Polypropylene (PP) with, for example, 20% talc can also be used. The impact strength can be increased by adding glass fibers or other fibers. In reactive compounding, a stable (lightweight) material can be produced by adding peroxide crosslinkers to polyethylene (PE). Various types of fibers are suitable, such as glass fibers, carbon fibers, or natural fibers. With conventional stand-alone injection molding machines, the typical average residence time of the plastic is 2 to 6 minutes, and the combined total residence time in the injection molding compounder can be reduced due to improved mixing within the extruder.Excessively long dwell times can cause thermal and thermo-oxidative material damage.

[0083] Less than 20% of the energy required for melting is typically supplied via the heating elements (not shown), but rather primarily through the energy of the screw drive and friction / shear within the melt. The two-stage process of producing the homogeneous melt allows for a wide range of adjustable operating parameters to achieve thorough mixing with a short overall residence time. Furthermore, some plastics, such as polyamides or POM materials, tend to receive insufficient energy in the compression zone of an injection screw, which can lead to the formation of a wear-inducing solids wedge within the screw during conventional processes.

[0084] Regarding a possible control of the injection molding compounder 1, reference is expressly made to the statements in WO2013 / 121049A1, in particular to the information therein. Fig. 2. Reference is made to this. In principle, any conventional operating method and control of the injection molding compounder, familiar to the expert, can be used.

[0085] When feeding material to the extruder, one type of material can be conveyed, for example, from a hopper 22, or several dosing stations can be provided that are operated in a coordinated manner so that a mixture is created when filling the extruder, or an additive, such as a dye or reinforcing fibers, can be added to one or more plastic materials.

[0086] Overall, the injection molding compounder, and in particular the extruder 20, the melt line 30 and the transition to the injection unit 40, is a system closed to the outside environment, although openings such as for degassing may be provided.

[0087] In one embodiment, the plastic components, additives, fillers, and / or fibers are fed into the extruder, and preferably no further material is added to the melt in the injection unit. In alternative embodiments, additional materials, such as glass fibers, natural fibers, peroxide crosslinkers, polylactic acid (PLA), or other plastic materials, can also be added via one or more feed ports of the injection unit (not shown). The latter is particularly advantageous if the added materials are temperature-sensitive and potential damage to the extruder is to be avoided.

[0088] The extruder described in the exemplary embodiment above is a single-screw extruder. It is known to those skilled in the art that, in general, a better mixing result can be achieved with a twin- or multi-screw extruder than with a single-screw extruder. However, the multi-screw extruder also causes a higher mechanical stress on the material, which results in a reduced chain length of the monomers (or polymers) or fibers and can thus lead to reduced component strength. Since the mixing result achieved by the (single-screw) extruder is further enhanced by the downstream passage of the melt through the injection unit, a higher component quality can be achieved with the (single-screw) extruder than with a multi- (e.g., twin-)screw extruder.

[0089] On the other hand, in alternative embodiments a multi-screw extruder can also be used and the mixing result achieved there can be further increased in the downstream injection unit.

[0090] The longitudinal orientation of the extruder is according to Fig.1 at a 90° angle to the injection unit. Thus, the melt is deflected by 90° at the inlet valve during the transition into the longitudinal direction of the injection unit, creating turbulence in the melt flow and resulting in a material-friendly improvement in mixing. Further mixing can be increased by a further (not shown) deflection of the melt flow. For example, the extruder can be aligned parallel to and offset from the injection unit, so that the melt line connected to the extruder outlet is first deflected towards the melt inlet 48, and the melt flow is then deflected a second time within the injection unit. A comparable result can be achieved if the extruder is arranged perpendicular to the injection unit and offset from it vertically.

[0091] In addition, the invention further relates to the following aspects: i) Method for manufacturing an injection molding compounder comprising an extruder and an injection unit, comprising the following steps: a) Providing an injection unit with an injection screw arranged in an injection housing and a filling opening for plastic granules with a granule hopper, b) Providing an extruder with at least one extruder screw arranged in an extruder housing, a feed opening for supplying one or more plastic materials, and an outlet, c) Removal of the granule hopper and connection of the extruder outlet via a melt line to the plastic granule filling opening of the injection unit. ii) Injection molding compounders obtainable by the above method i). iii) Use of a heated insert in the feed opening of an injection unit for introducing a plastic melt from an extruder unit via a melt line. The insert is connected to the feed opening of the injection unit on one side and to the melt line on the other.

[0092] The individual features of the aforementioned aspects of the invention (i) to (iii) have already been described, and express reference is made to them.

Claims

[1] Method for producing an injection molding compounder (1) with an extruder (20) and an injection unit (40), comprising the following steps: a) Providing an injection unit (40) with an injection screw (44) arranged in an injection housing (41) and a filling opening (33) for plastic granules, b) Providing an extruder (20) with at least one extruder screw (24) arranged in an extruder housing (21), a feed opening (22) for feeding one or more plastic materials, and an outlet (28), c) Inserting an insert (10) into the filling opening (33) for plastic granules of the injection unit (40), wherein the insert (10) has a central channel (13) and an outer wall (12) surrounding the central channel in an annular manner, and wherein a heating element and / or an insulating element (14), in particular a heating element (14), is provided in the outer wall (12) of the insert (10), d) Connection of the outlet (28) of the extruder (20) via a melt line (30) to the insert (10) in the filling opening (33) for plastic granules of the injection unit 40), wherein the insert (10) is releasably attached in the filling opening (33) and is connected on the side facing away from the filling opening to the outlet (28) of an extruder via a melt line (30), so that it is possible to connect and disconnect the insert (10) or the melt line (30) attached to it. [2] Method according to claim 1, wherein step c) is carried out after removal of a funnel attachment that may be inserted in the filling opening (33). [3] Method according to claim 1 or 2, wherein the insert (10) has at least one temperature sensor and preferably at least one pressure sensor. [4] Method according to one of claims 1 to 3, wherein the filling opening (33) of the provided injection unit (40) according to claim 1 a) has a draw-in cooling system with cooling channels (5), and after connection according to claim 1 d) the draw-in cooling system is used during operation of the injection molding compounder (1) to heat or temper the insert (10) to the melting temperature of the plastic material conveyed through the melt line (30) or above. [5] Method according to one of claims 1 to 4, wherein a temperature control medium, in particular a thermal oil, is passed through the cooling channels (5). [6] Injection molding compounder (1), in particular obtainable by a method according to any one of claims 1 to 5, comprising the following features: a) an extruder (20) with at least one extruder screw (24) arranged in an extruder housing (21), a feed opening (22) for supplying one or more plastic materials, and an extruder outlet (28), b) an injection unit (40) comprising an injection screw (44) arranged in an injection housing (41) and a filling opening (33), wherein an insert (10) is inserted into the filling opening (33) of the injection unit, the insert having a central channel (13) and an outer wall (12) surrounding the central channel in an annular manner, wherein a heating element and / or an insulating element (14) is provided in the outer wall (12) of the insert (10), and wherein the extruder outlet (28) is connected to the insert (10) in the filling opening (33) of the injection unit (40) via a melt line (30), wherein the insert (10) is detachably attached in the filling opening (33) and is connected on the side facing away from the filling opening via a melt line (30) to the outlet of an extruder (28), so that the insert (10) or the melt line (30) attached to it can be connected and disconnected. [7] Injection molding compounder (1) according to claim 6, wherein cooling channels (5) are provided in the area of ​​the filling opening (33) of the injection unit (40), through which a temperature control medium, in particular thermal oil, flows. [8] Injection molding compounder (1) according to claim 6 or 7, wherein the insert (10) has at least one temperature sensor and preferably at least one pressure sensor. [9] Injection molding compounder (1) according to one of claims 6 to 8, wherein the outer wall (12) of the insert (10) has a cavity into which the heating element and / or the insulating element (14) is inserted. [10] Injection molding compounder (1) according to one of claims 6 to 9, wherein the temperature of the temperature control medium during operation of the injection molding compounder (1) is at or above the melting temperature of the plastic material conveyed through the melt line (30), and wherein preferably a circuit for the temperature control medium, a device for heating the temperature control medium, and a sensor for detecting the temperature of the temperature control medium are provided. [11] Use of an insert (10) in a filling opening (33) for plastic granules of an injection molding unit for introducing a plastic melt, wherein the insert (10) has a central channel (13) and an outer wall (12) surrounding the central channel in a ring shape, wherein the insert (10) is heated, in particular via a heating element provided in the outer wall (12) of the insert (10) and / or an inlet cooling system with cooling channels (5) in the area of ​​the filling opening (33), wherein the insert (10) is releasably attached in the filling opening (33) and is connected on the side facing away from the filling opening (33) via a melt line (30) to the outlet (28) of an extruder (20), so that it is possible to connect and disconnect the insert (10) or the melt line (30) attached to it. [12] Use according to claim 11, wherein the insert (10) is releasably attached to the filling opening (33) via a bayonet fitting, ring clamp quick-release fastener or a quick-release coupling. [13] Insert (10) for a filling opening (33) for plastic granules of an injection molding unit, wherein the insert (10) is dimensioned so that it can be inserted into or connected to the filling opening (33) in a melt-tight manner, wherein the insert (10) has a central channel (13) and an outer wall (12) surrounding the central channel (13) in an annular manner, wherein a heating element and / or an insulating element (14) is provided in the outer wall (12) of the insert (10), wherein the insert (10) has a releasable connecting element, in particular a bayonet closure, ring clamp quick-release fastener or a quick coupling. [14] Insert (10) according to claim 13, comprising a heating element, a temperature sensor and preferably a pressure sensor, wherein preferably the temperature sensor and / or the pressure sensor are arranged at the end facing the filling opening (33). [15] Insert (10) according to claim 13 or 14, wherein a rotatable or pivotable connection is provided at the end of the insert (10) facing away from the filling opening (33).

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