Spritzgießcompounder

Abstract

The invention relates to an injection molding compounder with an extruder having at least one extruder screw arranged in an extruder housing and a filling opening for feeding one or more plastic materials, an injection unit with an injection screw arranged in an injection housing and optionally a filling opening, wherein a melt inlet is provided on the injection housing which is connected to an outlet of the extruder via a melt line, wherein the melt line is designed to be movable. Furthermore, the operation of such an injection molding compounder is disclosed, as well as the use of a movably designed melt line for connecting an extruder to an injection unit in an injection molding compounder.

Description

[0001] The invention relates to an injection molding compounder, a method for operating the injection molding compounder and the use of a movable melt line for connecting an extruder to an injection unit in an injection molding compounder.

[0002] 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 end of the turns of the injection screw remote therefrom, 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 further than one third of the effective length (h) away from the injection nozzle.

[0003] While the injection molding compounder described therein offers advantages in the processing of plastics due to the combination of an extruder with an injection unit via a melt inlet, it has some disadvantages, as is generally the case with the state of the art.

[0004] In particular, the prior art describes a rigid, immovable connection of the extruder outlet with the injection unit or the melt inlet of the injection unit.

[0005] Within the scope of the present invention, it was found that the rigid, immobile connection between the extruder and the injection unit leads to a number of problems and disadvantages during their movement, in particular when the injection unit moves forwards and backwards relative to the tool. For example, the rigid coupling of the extruder unit to the injection unit leads to wear problems, in particular in the area of ​​the connection between the two units and the respective connection points at the extruder outlet and the melt inlet. It must be taken into account that both the extruder unit and the injection unit have a considerable weight and corresponding moments of inertia. In addition, the injection unit moves forwards and backwards quite abruptly. In addition, the extruder unit is usually at an angle to the injection unit, which increases the susceptibility of the connection to wear and damage during forward and backward movement.Retraction of the injection unit is increased. It was further discovered that due to the inevitable movement of the extruder unit during a movement of the injection unit, the extruder unit itself, and especially attached structures such as a dosing system for supplying the precise amounts of plastic, are exposed to considerable vibrations and can fluctuate, which can result in wear and inaccuracies in measurement or dosing.

[0006] It has surprisingly been found within the scope of the present invention that these and other disadvantages of the prior art can be reduced or avoided by the device according to the invention, the use according to the invention or the method according to the invention.

[0007] An object of the present invention is therefore to provide an injection molding compounder which reduces or avoids the described disadvantages of the prior art.

[0008] This object is achieved by the features of the independent claims. Preferred and particularly advantageous embodiments emerge from the subclaims.

[0009] Thus, a first aspect of the invention relates to an injection molding compounder, comprising: an extruder with at least one extruder screw arranged in an extruder housing and a filling opening for supplying one or more plastic materials, an injection unit with an injection screw arranged in an injection housing and optionally a filling opening, wherein a melt inlet is provided on the injection housing, which is connected to an outlet of the extruder via a melt line, wherein the melt line is designed to be movable.

[0010] It was found that the movable melt line can prevent the aforementioned problems of wear and tear, increased material and defect susceptibility, and significantly improve the flexibility of connecting the extruder and injection unit via the melt line.

[0011] The terms "movable melt line" and "movably configured melt line" are used synonymously. According to the invention, the extruder and the injection unit are movable relative to one another via the melt line, and are not rigidly (immovably) connected to one another. It was also surprisingly found that the movable melt line allows the movement of the extruder to be reduced or minimized when the injection unit is moved (in particular when the injection unit is moved forwards and backwards during the production cycle, or any other movements or displacements of the injection unit and / or the extruder during the production cycle or during repair, maintenance, cleaning, assembly, etc.). This reduces wear and material fatigue, and also minimizes or avoids fluctuations in the structures on the extruder.

[0012] According to a first advantageous embodiment, the movable melt line is formed in one or more sections or entirely from a flexible hose.

[0013] The flexible hose can be made from any suitable material, in particular plastic material, that can withstand the pressures and temperatures typical during extruder operation. Preferably, but not limited to, the flexible hose is made from a plastic material that melts at high temperatures, preferably polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), perfluoroalkoxy polymer (PFA), or polyimide (PI). In many cases, the flexible hose has a braid or sheath, in particular made of metal. Accordingly, it is preferred if the flexible hose is designed for an operating temperature of at least 140°C, preferably at least 200°C, in particular at least 220°C, and an operating pressure of at least 10 bar. The melt from the extruder conducted through the melt line has different temperatures depending on the plastic material being processed.Therefore, the properties of the flexible hose must be designed accordingly. Since some plastics, such as PBS or plastics containing recycled materials, are generally processed at lower temperatures, the use of flexible hose materials is recommended, even if they are not extremely heat-resistant.

[0014] In principle, however, the materials processed are not limited within the scope of the present invention, and all materials and material combinations familiar to the person skilled in the art can be used. Materials used include, in particular, thermoplastic polymers or thermosetting polymers and mixtures thereof. Depending on requirements, organic or inorganic or fibrous fillers or ceramics may be used. It has been found that the injection molding compounder with a movable melt line according to the present invention not only achieves uniform and homogeneous mixing of the components, but also reduces the disadvantageous reduction in the chain length of the polymers and the breakage of fibrous fillers.

[0015] As explained above, according to one embodiment the movable melt line cannot be formed entirely from a flexible hose, but only in one or more sections. For example, in areas where the melt line has to be deflected, or where mobility or flexibility is advantageous due to a relative movement of the extruder to the injection unit, it can be advantageous to use a flexible hose material, while in the other sections of the melt line a rigid pipe material, in particular a metal pipe, is used. The rotatable or pivotable elements with the corresponding connection pieces can also be made of metal, while the part of the melt line in between is made of a hose material. Furthermore, depending on the spatial conditions and adjustment options of the extruder orThe use of one or more flexible hose elements (together with one or more rigid pipe sections and / or one or more rotatable or pivoting elements) may be advantageous for the injection unit. Multiple bends can also simply be formed in the melt line if spatially necessary or advantageous.

[0016] In principle, the melt line can also have more than two pivot points. Likewise, the melt line can have one or more diversions or bends, depending on the spatial arrangement of the extruder relative to the injection unit and their desired mobility (relative to each other). For example, this can be advantageous if the extruder is located below or above the injection unit.

[0017] According to a further advantageous embodiment, the movable melt line has a first pivot point near or at the end towards the melt inlet and a second pivot point near or at the end towards the extruder outlet.

[0018] A pivot point is understood here as a point that can be pivoted or rotated in at least one plane, in particular in one plane. Rotatable or pivotable elements that provide such a pivot point are familiar to those skilled in the art and include, in particular, conventional swivel joints, rotary heads, or rotary screw connections for pipes. Pipe swivel joints, in particular, are used as rotatable pipe connectors and can be installed in the movable melt line. They are an advantageous connecting element given the existing operating conditions and high pressures. The ability to rotate or pivot can be provided, for example, by a conventional ball bearing. Depending on the desired mobility and spatial conditions (in particular the position of the extruder relative to the injection unit), several of the above-mentioned rotatable or pivotable elements can also be combined. The connecting parts of the rotatable element can be, for example,Welded connection parts such as weld ends, pipe bends, or flanges are also possible. Screw connections or other conventional connection parts for melt-tight (pressure-resistant) connections on both sides of the rotating or pivoting elements are also possible.

[0019] According to a preferred embodiment, the melt line can be rotated or pivoted, in particular in the horizontal direction, by means of the first and the second pivot point during a relative movement of the extruder with respect to the injection unit.

[0020] According to a preferred embodiment, the melt line runs horizontally between the two pivot points. By arranging the two pivot points in the same (horizontal) plane, relative movements between the extruder and the injection unit can be compensated or absorbed particularly advantageously.

[0021] It is further preferred that the melt line is diverted at an angle of 0 to 90° at one or both pivot points, in particular at an angle of 90° in one plane. This allows the course of the melt line to be adapted particularly favorably to the spatial arrangement between the extruder and the injection unit. In addition, the relative movements between the extruder and the injection unit can be compensated or absorbed particularly advantageously by the rotation or pivoting at the pivot point. It is also possible for one or more diversions of the melt line to take place not at the pivot points, but at other parts of the melt line, depending on the spatial conditions and adjustment options for the extruder and the injection unit.

[0022] According to an advantageous embodiment, the melt line is diverted at the first pivot point into the axis of the melt inlet, and / or the melt line is diverted at the second pivot point into the axis of the extruder outlet.

[0023] In many cases, it is preferable for the movable melt line, and preferably also the pivot points, to be equipped with heating elements and / or insulating elements. This allows the melt in the melt line to be easily maintained at the desired temperature or brought to this temperature. Conventional heating elements (such as heating cartridges or heating bands) and / or insulating elements, which can be attached, for example, along the outside of the melt line, are familiar to those skilled in the art and are commercially available.

[0024] As a rule, the injection unit of the injection molding compounder is mounted on movable supports, particularly on rails, so that it can move forwards or backwards relative to the mold.

[0025] The extruder is also usually mounted on a movable bearing, particularly on rails, so that it can move forward or backward relative to the injection molding unit. This movement of the extruder relative to the injection unit therefore occurs at an angle, particularly at an angle of approximately 90°, relative to the forward and backward movement of the injection unit relative to the mold.

[0026] The extruder described above has a feed opening for one or more plastic materials. This feed opening is used as standard to feed one or more plastic materials, particularly in granulate or powder form, to the extruder screw. A hopper is conventionally inserted into the feed opening to enable or facilitate the filling with the plastic materials.

[0027] According to a preferred embodiment, a conventional dosing system is arranged above the filling opening (or the hopper inserted therein), in which the supplied plastic materials are dosed volumetrically or gravimetrically and fed to the filling opening (via the hopper). Such dosing systems are familiar to those skilled in the art.

[0028] In the prior art, the dosing systems are connected to the extruder in such a way that they follow every movement of the extruder. According to a preferred embodiment of the present invention, however, the dosing system is not (rigidly) connected to the extruder or coupled to it in such a way that no relative movement of the dosing system with respect to the extruder is possible. Rather, the dosing system is attached or anchored independently of the extruder, so that it does not (needs to) move with the extruder when it moves (e.g., on the rails, see above).

[0029] The dosing system can be either fixed to the floor or mounted on a frame on which the extruder is mounted movably (e.g. on rails). This allows the extruder to move relative to the injection unit during the production cycle without the dosing system moving (rigidly) with it. Within the scope of the present invention, it has been discovered that this prevents damage or increased wear to the dosing system. In particular, the risk of measurement or dosing inaccuracies during the dosing of the plastic materials to be fed due to (abrupt) movements of the extruder can also be avoided.

[0030] Preferably, the extruder's feed opening is provided with a hopper attachment that is sufficiently large to ensure the supply of one or more plastic materials from the dosing system throughout the entire production cycle. The production cycle includes a maximum approach of the extruder to the injection unit (while the latter is moved toward the mold to inject material) as well as a maximum distance of the extruder from the injection molding unit when the injection unit is retracted from the mold (and material can be injected).

[0031] 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. At least one melt line represents a movable melt line within the meaning of the invention. Preferably, all melt lines are movable melt lines within the meaning of the invention.

[0032] A second aspect of the present invention relates to the use of a movable melt line for connecting an extruder to an injection unit in an injection molding compounder. According to a preferred embodiment, the movable melt line is formed in one or more sections or entirely from a flexible hose, as described herein. Alternatively or additionally, the melt line has a first pivot point near or at the end toward the melt inlet, and a second pivot point near or at the end toward the extruder outlet, as described herein. The above explanations regarding the first aspect of the invention with regard to the movable melt line and its various embodiments apply accordingly to the second aspect of the invention.

[0033] A third aspect of the present invention relates to a method for operating an injection molding compounder according to the first aspect of the invention, as described herein. The extruder and the injection molding unit move relative to one another, in particular between a first production position in which the injection unit is moved toward the tool (in order to inject material into the mold) and a second injection-discharge position in which the injection unit is retracted relative to the tool. Thus, as is familiar to those skilled in the art, the injection molding compounder is used in a conventional manner for injection molding, with particular advantages being achieved and disadvantages being avoided by the movable melt line and the embodiments of the invention, as described herein.

[0034] The present invention also advantageously provides the possibility of a particularly flexible stand-alone arrangement, in which the extruder unit (preferably arranged on a frame for movement) can be easily and flexibly coupled to various injection units via the flexible melt line according to the present invention, depending on the desired production. According to a preferred embodiment, the movable melt line is provided with a detachable connection at one or both ends, so that the extruder and the injection unit can be repeatedly coupled or uncoupled via the movable melt line. Suitable detachable (pressure- or melt-tight) connecting elements are familiar to the person skilled in the art and include, without limitation, in particular screw connections, bayonet closures, quick-release ring clamps, or quick couplings.

[0035] The general structure of the injection molding compounder is described in the aforementioned WO2013 / 121049A1, with the statements therein expressly incorporated into the present description by reference. Specifically: An injection molding compounder has an extruder with at least one extruder screw arranged in an extruder barrel, and an injection unit with an injection screw arranged in an injection barrel, wherein the injection unit has an effective length defined from the injection nozzle of the injection unit to the end of the turns of the injection screw remote therefrom. This effective length is preferably defined in the advanced position of the injection unit, i.e. immediately after the injection process. A melt inlet is provided on the injection barrel and is connected to an outlet of the extruder, wherein the melt inlet can be more than one-third of the effective length away from the injection nozzle. The direction of the effective length is preferably measured in the axial direction of the injection unit. Furthermore, the effective length is preferably then considered ordefined when the injection screw or the pusher screw is in its position furthest from the injection nozzle. Due to the described design, the melt produced by the extruder is guided at least along part of the injection screw and is further mixed and homogenized there and in the process. For this reason, the mixing and homogenization within the extruder can only be partial mixing or partial homogenization, which is not yet sufficient for the actual injection process. In combination with the further homogenization and mixing in the injection unit, the required material quality is achieved. In addition to the system-inherent advantage of an injection molding compounder that a compound is produced in a single production process and processed immediately afterwards, there is the advantage of gentle treatment of the plastic material.This is because the melt is processed in a distributed manner, resulting in a reduced overall mechanical load on the material. The chain length of the plastic molecules is thus not excessively reduced, and accordingly, the fiber length of added fibers is also not reduced (e.g., due to fiber breakage). Preferably, the extruder has exactly one extruder screw. Because the melt flows along at least part of the injection screw after leaving the extruder, the melt is further mixed there. Therefore, it may be sufficient to use a single-screw extruder, in which the material is processed more gently and, although less homogenized, this disadvantage is offset by the further mixing within the injection unit.

[0036] In particular, the melt inlet can be located more than half the effective length from the injection nozzle, and preferably more than two-thirds of the effective length from the injection nozzle. This defines the distance the melt is guided within the injection unit, and a longer melt path increases mixing and homogenization.

[0037] Furthermore, a control system may be configured to switch the (rotary) drive of the extruder screw on and off depending on the cycle phase of an injection process. Within the injection cycle, a period of activated extruder screw drive and a period of deactivated extruder screw drive are provided. Especially with a single-screw extruder, it is technically easy to start and stop the extruder and thus provide the required melt at any time.

[0038] Preferably, a control system is provided to switch the drive of the extruder screw 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 sense, the conveying volume flow of the extruder screw can be adapted to the volume of melt that can be absorbed by the injection unit during the return movement of the injection screw. This can be done as a simple control system in the sense that the extruder is switched on (or off) depending on the cycle times of the injection process. Alternatively or additionally, sensors such as pressure sensors can be provided on the injection unit. These sensors determine the material requirement of the injection unit and, by switching them on (or off) at a precise time, allow the extruder to provide the required amount of material for the injection unit.To ensure that the melt line between both components is filled evenly or completely with melt at all times, the injection unit is supplied with exactly the amount of melt provided by the extruder.

[0039] In particular, the control system can be configured to regulate the volume flow of melt delivered by the extruder to the injection unit depending on a deviation between a target filling level specified for the injection phase and a measured actual filling level of the injection unit. Target parameters for filling and filling speed are specified for the injection unit, which specify the axial position at which times the injection screw should be. The displacement of the injection screw during filling is directly determined by the extruder's delivery volume. If a deviation between the actual filling speed and the specified target values ​​occurs, the delivery volume of the extruder screw can be adjusted accordingly within a control loop.

[0040] In particular, the controller is configured to switch the rotary drive of the injection screw and the rotary drive of the extruder screw on and off, wherein a time lead or a delay, or in particular a simultaneity, is provided for switching on the rotary drive of the extruder screw relative to the switching on of the rotary drive of the injection screw or relative to the injection stroke of the injection screw. Preferably, a time lead or a delay, or a simultaneity, is provided for switching off the rotary drive of the extruder screw relative to the switching off of the drive of the injection screw. This also includes, in particular, the ability of the extruder screw to operate 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 tailored to a short cycle time, good mixing and low material stress.

[0041] Preferably, an input and / or a 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 with each other depending on different materials or material combinations of the melt within an injection cycle. Targeted setpoint inputs can be made using the input unit, and the storage module can contain a database with various advantageous operating conditions depending on different materials, thus making it easier for the user to use the injection molding compounder under the best possible operating conditions.

[0042] Furthermore, according to one embodiment, a valve is arranged in the melt line between the extruder outlet and the melt inlet of the injection unit. This is at least a two-way valve, which alternatively directs the melt into the injection unit or releases it to the environment. A three-way valve can also be used, which, according to one embodiment, additionally includes the closed valve state. If the valve is a pressure relief valve, excessive melt pressure generated by the extruder can be reduced for safety reasons. A controllable valve can prevent the produced melt from being delivered to the injection unit too early during the plasticizing phase of the plastic. The extruder and injection unit can also be easily, quickly, and safely decoupled.

[0043] In particular, the extruder outlet is connected to the melt inlet of the injection unit via a pressure-tight or melt-tight, movable melt line, as described herein, and the extruder is preferably configured to convey plastic melt through the extruder screw via the movable melt line to the injection unit. In particular, no further conveying elements, such as pistons, pumps, screws, the use of gravity, or the like, are provided here. With the aid of the conveying properties of the extruder, the produced melt is thus conveyed to the injection unit and fed there into a section of the screw where the pressure is preferably not yet very high.

[0044] According to one embodiment, no buffer extending beyond the melt line is provided between the extruder outlet and the melt inlet of the injection unit, 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 periods, whereby at each of these points in time the volume flow of the pipe connection is constant at each of its points 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 this melt. Rather, the extruder feeds directly into the injection unit.This reduces the melt's dwell time in the pipe connection and achieves better production control. This can also be expressed, preferably or alternatively, as follows: in a working 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 injection unit's cycle phase.

[0045] Thus, according to a preferred embodiment, only the movable melt line (optionally equipped with a valve) is provided between the extruder and the injection unit. The mobility and corresponding movement of the melt line reduces unwanted settling of material and advantageously prevents cracking of the material and the formation of contaminants.

[0046] When using the injection molding compounder, the melt that is conveyed in the extruder along the longitudinal direction of the extruder is redirected towards the longitudinal direction of the injection unit.

[0047] According to one embodiment, the ratio of length to diameter of the extruder screw is at least approximately 20. According to another embodiment, the value is preferably between 18 and 40, in particular between 20 and 30.

[0048] A method for producing an injection-molded workpiece using an injection molding compounder 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 movable melt line through an inlet opening of an injection unit into the injection unit, and guiding the melt in the injection unit towards an injection nozzle connected to an injection molding tool, wherein an injection screw of the injection unit has a winding length defined by the axial length of the turns of the injection screw and the inlet opening is arranged on the injection unit such that the melt is preferably guided along the turns of the injection screw over at least one third of the winding length.As an alternative to the winding length, the effective length defined above can also be considered here.

[0049] Preferably, within a cycle of producing the injection-molded workpiece, a phase is provided 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. Thus, the further supply of melt to the extruder is stopped before and / or during the injection phase of the melt into the tool.

[0050] A corresponding injection molding compounder can be manufactured by attaching a melt inlet to an injection unit, in particular a commercially available injection unit, and connecting it to an extruder, in particular a commercially available extruder, via a movable melt line as described herein. In particular, the injection molding compounder can continue to be used in a conventional manner without using the filling openings for the plastic granules present on the injection unit. The filling opening, like the granule hopper, can remain on the injection unit, allowing it to be operated conventionally as an alternative. This allows a plastics processing company to utilize existing components and only require minor adaptations.Even after the melt inlet has been attached, the injection unit can still be used as an injection unit independently of the extruder if the melt inlet is closed with, for example, an end cap.

[0051] Preferred embodiments of the present invention are described below by way of example with reference to figures. They show: Fig. 1 a schematic structure of an injection molding compounder with an extruder and an injection unit in a first position, Fig. 2 a schematic structure of an injection molding compounder with an extruder and an injection unit in a second position.

[0052] Fig. 1 is essentially similar to Fig. 1 of WO2013 / 121049, to which reference is expressly made. The attached Fig. 1 shows an injection molding compounder 1 in a first position, in which the injection unit 40 is connected to the tool 50, so that plastic material can be injected into the mold via the injection nozzle 49. The extruder unit 20 is connected to an injection molding unit 40 via the movable melt line 30, so that the plastic material liquefied in the extruder 20 is fed into the injection molding unit. The extruder has the task of producing the plastic melt and achieving a certain mixing of the various components. As will be explained in more detail below, the quality or uniformity of the mixing achieved in the extruder does not have to be as high as is required for the injection process, since the melt provided by the extruder is conveyed to the injection unit, where further supplementary mixing and increased homogeneity takes place. The extruder orThe extruder unit is also called a compounder and is used as such. One advantage of an injection molding compounder is that the plastic mixture required in the injection unit is produced in a simultaneous process in the extruder. The conventional production of compound granules is eliminated, thus saving the energy required for remelting the granules and avoiding the stress on the material caused by granulation and the associated damage to the material.

[0053] In the embodiment shown, the melt enters the injection unit 40 from the melt line 30 at the rear end. The melt inlet is therefore located at the end of the injection unit opposite the injection nozzle 49. According to other embodiments of the invention, a melt inlet can also be provided laterally, as in Fig. 1 of WO2013 / 121049A1 (reference numeral 48 therein), may be provided in the injection housing 41. According to the invention, the housing of the injection unit 40 thus has a melt inlet, which is connected to the extruder outlet 28, i.e., the melt outlet from the extruder, via the movable melt line 30. The melt inlet is a connection attached to the injection housing 41, for example, welded or screwed, to which the movable melt line 30 can be attached in a pressure-tight manner. In the embodiment shown, the movable melt line 30 has a straight pipe section 31. Furthermore, it has a first pivot point 33 at the end toward the melt inlet of the injection unit and a second pivot point 32 at the end toward the extruder outlet.

[0054] As from Fig. 1 in conjunction with Fig. As can be seen in Figure 2, this results in an advantageous relative mobility of the extruder compared to the injection unit. Fig. 2, the injection molding compounder 1 with an extruder and an injection unit is in a second position, wherein the injection unit 40 is spaced from or retracted from the tool 50. In this position, plastic material can be injected, for example. The movable melt line with the first and second pivot points (33, 32) means that the extruder does not necessarily have to move rigidly with the injection unit, but this is compensated for by the rotation at the first or second pivot point of the melt line. In the concrete embodiment shown, therefore, only a slight displacement of the extruder relative to the injection unit takes place, which can be ensured, for example, by the extruder being displaceable on rails perpendicular to the longitudinal axis of the injection unit. Displaceability of the extruder in the direction of the forward or backward movement of the injection unit is not required.Vibrations, wear, and damage due to the movements of the injection unit, which occur with a non-inventive, immobile melt line, can also be reduced or avoided. The effective travel distance of the extruder when the injection unit moves forward or backward is also reduced due to the movable melt line with the two pivot points 32 and 33.

[0055] Corresponding advantages also arise in an embodiment according to the invention (not shown), in which the movable melt line 30 is at least partially formed from a movable hose. Due to the flexibility of the hose, the relative movements between the extruder and the injection unit can be very advantageously absorbed or compensated. The length of the movable melt line can be selected such that all desired or required relative positions of the extruder to the injection unit can be followed by the movable melt line, advantageously with only a slight movement or displacement of the extruder relative to the injection unit. When using a flexible hose of sufficient length, movement of the extruder when the injection unit moves can possibly even be completely avoided.Suitable hose materials, for example, made of a high-melting plastic material such as polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), perfluoroalkoxy polymer (PFA), or polyimide (PI), are commercially available and familiar to those skilled in the art. Examples include THOMAFLUID® high-tech PTFE high-pressure hoses (RCT Reichelt Chemietechnik GmbH + Co., Heidelberg), especially those with single or double stainless steel braiding.

[0056] The inner diameter of the movable melt line (e.g., the flexible hose) and preferably also of the melt inlet can be routinely optimized by a person skilled in the art and will generally be between 5 mm and 50 mm, in particular 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 speeds and the same thread 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.

[0057] The injection unit 40 has an injection nozzle 49 at the output end, which is connected to a mold half of the injection mold 50.

[0058] When using the injection molding compounder, one or more plastic materials are fed to the extruder 20, which has at least one extruder screw 24 in an extruder housing 21, via the feed opening 22, where they are melted and mixed by heating. In addition to the one feed opening 22 shown, additional feed openings (not shown) may be provided.

[0059] The plastic melt leaves the extruder at the extruder outlet 28 and is conveyed into the injection unit 40 via the movable melt line 30. A valve (not shown) can be installed in the movable melt line, in particular a valve that can be brought into a closed position in which the outflow of the melt from the extruder is prevented. Thus, at the beginning of the processing, the valve can initially be closed until the plastic material in the extruder is sufficiently heated and homogenized. Plastic with inadequate properties can be released into the environment when the valve is in the discharge position. The valve is preferably a controlled valve that can be brought into a desired position via a drive such as an electric, pneumatic, or hydraulic drive. In addition to safety aspects, the valve also serves to ensure quick and clean changeover from one material to the next.Material that may have been in the extruder 20 for too long when the compounder was started up and may have degenerated, or that may have been mixed during a material change, can be discharged to the outside via the open position of the valve.

[0060] The melt inlet into the injection unit 40 is provided in the region of the injection unit remote from the injection nozzle 49, so that the melt, which is introduced into the melt inlet of the injection unit 40 via the movable melt line 30, is guided along a considerable portion of the injection screw 44 on its way to the injection nozzle 49 and is further homogenized along this path. In particular, it is possible to define an effective length h from the outer end of the injection nozzle in the axial direction of the injection unit to the end of the turns of the injection screw 44 remote from the injection nozzle 49. The injection screw 44, which is a pusher screw, is axially displaceable within the injection housing, and the effective length h is defined in the retracted state, i.e., in the position remote from the injection nozzle 49. The position of the melt inlet is preferably in the range of 0.85 h + / - 0.15 h from the injection nozzle.The melt inlet can also be located farther from the injection nozzle than the far end of the screw flights. In this case, the melt is directed along the entire length of the flights of the injection screw 44, achieving the best possible mixing of the melt on the injection unit side.

[0061] The injection molding compounder can have any commercially available injection unit or extruder unit as injection unit 40 or as extruder 20, which has been set up for the pressure- and melt-tight attachment of the movable melt line.

[0062] Since injection screws are often three-zone screws, they have an intake zone that accounts for approximately 50% of the screw length, followed by the compression and metering zones (each accounting for 25%). Due to the described location of the melt inlet, the melt is fed into the screw in the low-pressure area and is preferentially directed along the entire compression and metering zone.

[0063] The timing of an injection molding cycle can be determined according to Fig. 3 of WO2013 / 121049A1 and the corresponding description therein, to which reference is expressly made. In detail: In the upper area, the rotary drive R of both the extruder screw 24 (in dotted line) and the injection screw 44 (in dashed line) is shown. 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 be operated at the same rotational speed. The lower area of ​​the Fig. 3 of WO 02013 / 121049A1 shows the stroke of the injection screw, where the value “1” means that the injection screw 44 is in its front position, such as immediately after the injection process, and with 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.

[0064] At the beginning 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 time, the valve can be closed. As soon as a certain homogeneous melt quantity has been produced, the valve can be moved to the open position at time t1, allowing the melt to be discharged into the injection unit 40. At this time, the drive of the injection screw 44 is started, resulting in a time offset between the activation times ΔTa of both screws. The injection screw is in its forward position.

[0065] During the time period from t1 to t2, both the extruder and injection screws are driven and melt is generated. In the process, the injection screw 44 is moved into the retracted position, and the melt collects in front of the injection screw 44 for the next injection process. At time t2, a sufficient amount of melt has been generated for the injection movement taking place in the time range from t2 to t3. At time t2, the extruder screw 24 is stopped, and the lifting drive 143 of the injection unit 40 is activated. At time t3, the injection screw has advanced to its forward position, and the injection of the plastic into the injection mold has ended, so that the rotary drive of the injection screw 44 can be stopped. Thus, there is a time offset of ΔTb between the switching off of the two rotary drives.

[0066] It is not mandatory, as described above, that the rotary drive of the extruder screw be switched off at the same time as the lifting drive of the injection screw 44 is switched on. Alternatively, the extruder screw can be switched off only 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 melt continues to be pumped into the injection unit during the injection process of the plastic into the mold. This is possible because the melt inlet 48 is provided in the rear area of ​​the injection unit, i.e., away from the injection nozzle, and a lower pressure prevails there than in the front area.

[0067] At time t3, the injection process is completed, 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, and produce melt for the next cycle, thereby reducing the cycle time. In addition, a holding pressure is preferably applied via the stroke of the injection screw in the time period t3 to t4 to compensate for the shrinkage of the injected plastic.

[0068] The injection molding compounder according to the invention is particularly suitable for applications where different materials are to be mixed together. Since mixing takes place both in the extruder and in the injection unit, the residence time and mixing intensity in both units are reduced. Overall, thorough mixing reduces the thermal and mechanical stress on the materials.

[0069] Suitable materials include a mixture of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS), which is very sensitive to prolonged exposure to high temperatures. Polypropylene (PP) with, for example, 20% talc can also be used. Impact strength can be increased by adding glass fibers or other fibers. The shortened residence time of the melt in each of these units reduces the mechanical stress on the fibers and prevents fiber breakage, thus increasing the strength of the molded part. In reactive compounding, the addition of peroxide crosslinkers to polyethylene (PE) can produce a stable (lightweight) material. Various types of fibers can be used, such as glass fibers, carbon fibers, or natural fibers.In 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 better mixing within the extruder. Excessively long residence times can cause thermal and thermo-oxidative material damage.

[0070] Typically, less than 20% of the energy required for melting is introduced via the heat belts (not shown), but rather via the energy of the screw drive and the friction / shear in the melt. The two-stage process for producing the homogeneous melt provides a wide range of adjustable operating parameters to achieve thorough mixing with a short overall residence time. Also, with some plastics, such as polyamides or POM materials, there is a tendency for insufficient energy to be supplied in the compression zone of an injection screw, so that, with conventional processes, a wear-causing solid wedge can form in the injection screw.

[0071] With regard to a possible control of the injection molding compounder 1, reference is expressly made to the explanations in WO2013 / 121049A1, in particular to the Fig. 2. In principle, any conventional operation and control of the injection molding compounder familiar to the expert can be used.

[0072] When feeding material to the extruder, one type of material can be fed in, for example, from a hopper 22, or several dosing stations can be provided which are operated in a coordinated manner so that a mixture is created when filling into the extruder, or an additive, such as a dye or reinforcing fibers, is added to one or more plastic materials.

[0073] Overall, the injection molding compounder, and in particular the extruder 20, the movable 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 can be provided.

[0074] According to one embodiment, the plastic components, additives, fillers, and / or fibers are added in the extruder, and preferably no additional 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 filling openings of the injection unit (not shown). The latter is particularly advantageous if the added materials are (temperature-)sensitive and potential damage in the extruder is to be avoided.

[0075] The extruder described in the above exemplary embodiment 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 greater mechanical stress on the material, which results in a reduced chain length of the monomers (or polymers) or the 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-screw (e.g., twin-screw) extruder.

[0076] 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.

[0077] The longitudinal alignment 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 in the transition to the longitudinal direction of the injection unit, and the material flow of the melt is swirled, achieving a material-friendly improvement in mixing. By further deflecting the melt flow (not shown), the mixing can be further increased. For example, the extruder can be aligned offset parallel to the injection unit, so that the melt line connected to the extruder outlet is first deflected in the direction of the melt inlet 48 and the melt flow is subsequently deflected a second time in the injection unit. A comparable result can be achieved if the extruder is arranged perpendicular to the injection unit and with a height offset from it. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] WO 2013 / 121049A1 [0002, 0035, 0053, 0063, 0071] WO 2013 / 121049

[0052] WO 02013 / 121049A1

[0063]

Claims

[1] Injection molding compounder, comprising: an extruder with at least one extruder screw arranged in an extruder housing and a filling opening for feeding one or more plastic materials, an injection unit with an injection screw arranged in an injection housing and optionally a filling opening, wherein a melt inlet is provided on the injection housing, which is connected to an outlet of the extruder via a melt line, wherein the melt line is designed to be movable. [2] Injection molding compounder according to claim 1, wherein the movable melt line is formed in one or more sections or entirely from a flexible hose. [3] Injection molding compounder according to claim 1, wherein the movable melt line has a first pivot point near or at the end towards the melt inlet, and a second pivot point near or at the end towards the extruder outlet. [4] Injection molding compounder according to claim 2, wherein the flexible hose is formed from a high-temperature melting plastic material, preferably polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), perfluoroalkoxy polymer (PFA) or polyimide (PI). [5] Injection molding compounder according to claim 4, wherein the flexible hose is provided with a braid or sheath, in particular made of metal. [6] Injection molding compounder according to claim 4 or 5, wherein the flexible hose is designed for an operating temperature of at least 140°C, preferably at least 200°C, in particular at least 220°C, and an operating pressure of at least 10 bar. [7] Injection molding compounder according to claim 3, wherein the melt line is rotatable or pivotable, in particular in the horizontal direction, by means of the first and the second pivot point during a relative movement of the extruder with respect to the injection unit. [8] Injection molding compounder according to claim 3 or 7, wherein the melt line runs horizontally between the two pivot points. [9] Injection molding compounder according to claim 3, 7 or 8, wherein at one or both pivot points the melt line is diverted at an angle of 0 to 90°, in particular 90°. [10] Injection molding compounder according to claim 9, wherein the diversion at the first pivot point occurs in the axis of the melt inlet, and / or the diversion at the second pivot point occurs in the axis of the extruder outlet. [11] Injection molding compounder according to one of the preceding claims, wherein the extruder and the injection unit are movable relative to each other via the melt line. [12] Injection molding compounder according to one of the preceding claims, wherein the injection unit is movably mounted on rails in order to be able to move forwards or backwards relative to the mold. [13] Injection molding compounder according to one of the preceding claims, wherein the extruder is movably mounted on rails in order to be able to move forwards or backwards relative to the injection unit. [14] Injection molding compounder according to one of the preceding claims, wherein a dosing system is arranged above the filling opening of the extruder, which is fastened or anchored independently of the extruder, so that the dosing system does not move when the extruder moves, in particular during the production cycle. [15] Injection molding compounder according to claim 14, wherein the filling opening is provided with a funnel attachment to ensure the feeding of one or more plastic materials from the dosing system into the filling opening, preferably both at a maximum approach and maximum distance of the extruder from the injection molding unit during the production cycle. [16] Use of a movable melt line for connecting an extruder to an injection unit in an injection molding compounder, wherein the movable melt line is preferably formed in one or more sections or completely from a flexible hose, and / or has a first pivot point near or at the end towards the melt inlet, and a second pivot point near or at the end towards the extruder outlet. [17] Method for operating an injection molding compounder according to one of claims 1 to 15, wherein the extruder and the injection molding unit move relative to each other, in particular between a first production position in which the injection unit is moved towards the tool, and a second injection position in which the injection unit is moved back relative to the tool.

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