Extrusion tool for extruding a layer of plastic

Abstract

Extrusion tool (10, 12, 14, 16) for extruding a plastic layer or co-extruding a multi-layer co-extrusion composite, in particular blow head, with the following features: a. the extrusion tool (10, 12, 14, 16) has at least one inlet (70, 72) for the entry of a melt into the extrusion tool (10, 12, 14, 16), and b. the extrusion tool (10, 12, 14, 16) has an outlet (40) for the exit of the plastic layer or the multilayer coextrusion composite from the extrusion tool (10, 12, 14, 16), and c. The extrusion tool (10, 12, 14, 16) has several extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) arranged between the at least one inlet (70, 72) and the outlet (40), which are in fluid communication with the at least one inlet (70, 72), and d. the extrusion tool (10, 12, 14, 16) has a central axis (2) which is arranged in the extrusion direction of the melt, characterized in that e. the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) each have a sealing section (122, 222, 322, 522, 722, 922), wherein the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) are arranged in the sealing section (122, 222, 322, 522, 722, 922) at a first distance around a cylinder extending along the central axis (2), wherein the first distance is constant or substantially constant and f. the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) each have a distribution section (126, 226, 326, 526, 726, 926), wherein the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) are arranged in the distribution section (126, 226, 326, 526, 726, 926) at a second distance from the central axis (2), wherein the second distance increases and / or decreases compared to the first distance, wherein g. the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) each transition after their sealing section (122, 222, 322, 522, 722, 922) in the extrusion direction into their respective distribution section (126, 226, 326, 526, 726, 926).

Description

[0001] The invention relates to an extrusion tool for extruding a plastic layer or co-extruding a multi-layer co-extrusion composite, as well as a system for producing a multi-layer co-extrusion composite. State of the art

[0002] Various technical solutions are known in the field of plastic extrusion, particularly regarding the design of spiral distributors in die heads. These spiral distributors can be arranged axially or horizontally. Furthermore, conical spiral distributors exist, as well as hybrid designs that start horizontally and then bend conically.

[0003] In axially arranged helical distributors, the molten plastic is distributed via spiral coils that run around a cylinder, with the channel depth decreasing in the extrusion direction. This causes the melt to continuously exit the grooves into an annular gap located on the cylinder's outer surface. The coils can be positioned either inside or outside this annular gap.

[0004] Horizontal spiral distributors shape the melt using helical coils located in a plane that is generally perpendicular to the extrusion direction. After forming an annular flow, the melt is deflected in the extrusion direction. Here, too, the coils can be arranged above or below the distribution plane when viewed in the extrusion direction.

[0005] Conical spiral distributors are characterized by the fact that the spirals are arranged on a conical surface whose diameter increases either from the inside out or from the outside in. In the horizontally conical form, the spirals begin in a plane perpendicular to the extrusion direction and transition into a conical surface in the area of ​​the spirals.

[0006] In coextrusion blow heads, the helical distributors of the individual layers are combined in different ways. In axial helical distributor blow heads, several concentric helical distributors with different diameters are arranged. The melt is generally fed into the annular gap from both the inside and the outside. In horizontal helical distributor blow heads, several horizontal helical distributors are arranged one above the other, with the melt of the individual layers usually being fed into the coextrusion annular gap from the outside in. There are also blow heads in which horizontal or conical, or horizontal-conical, helical distributors are arranged on the outside and, additionally, axial or horizontal-conical helical distributors are arranged on the inside.

[0007] Axial coil distributors have the disadvantage that multiple distributors must be arranged on different diameters. This means that only a limited number of axial distributors can be accommodated in a given radial installation space. Furthermore, both the flow paths and the wetted surface area of ​​the outer coil distributors increase, which impairs efficiency.

[0008] Horizontal spiral manifolds require a relatively large amount of radial installation space and generate high buoyancy forces, which must be sealed with complex screw connections. Purely conical spiral manifolds have the disadvantage that sealing the beginning of the spirals on the conical surface is difficult and expensive to manufacture. While sealing the beginning of the spirals is simpler with horizontal-conical spiral manifolds because they lie in a single plane, these manifolds also require a large amount of radial installation space and generate significant buoyancy forces. Object of the invention

[0009] Therefore, there is a need to develop an extrusion tool that overcomes the aforementioned disadvantages and enables a more efficient and space-saving distribution of the plastic melt.

[0010] According to the invention, an extrusion tool for extruding a plastic layer or for co-extruding a multi-layer co-extruded composite is proposed, in particular a blow head, which, in accordance with a generic extrusion tool, has the following features: The extrusion tool has at least one inlet for the entry of a melt into the extrusion tool and an outlet for the exit of the plastic layer or the multi-layer co-extruded composite from the extrusion tool. Several extrusion channels are arranged between the at least one inlet and the outlet, which are in fluid communication with the at least one inlet. In addition, the extrusion tool has a central axis, which is arranged in the extrusion direction of the melt.

[0011] It is proposed that each extrusion channel has a sealing section, wherein the extrusion channels are arranged in the sealing section at a first distance around a cylinder extending along the central axis, the first distance being constant or substantially constant. It is further proposed that each extrusion channel has a distribution section, wherein the extrusion channels are arranged in the distribution section at a second distance from the central axis, the second distance being larger and / or smaller than the first. According to the invention, each extrusion channel transitions into its respective distribution section after its sealing section in the extrusion direction.

[0012] An extrusion die for extruding a single layer of plastic or for co-extruding a multi-layer co-extrusion composite is a technical device used to press thermoplastic materials under pressure through a shaping opening to produce continuous products with a defined cross-sectional geometry. This die is an integral component of an extrusion line and significantly influences the quality and properties of the extruded product.

[0013] This includes, in particular, blow heads used in blown film extrusion. A blow head is an extrusion tool that forms the molten plastic into an often thin-walled, tubular preform, which is then expanded into a film by blowing in air. Blow heads can be designed for the production of both single-layer and multi-layer co-extruded films.

[0014] Single extrusion dies are used to extrude monolithic plastic sheets from a single material. They typically consist of an inlet for the melt, shaping channels, and an outlet that creates the desired shape. Coextrusion dies allow for the simultaneous extrusion of multiple plastic sheets, preferably from different materials. They have multiple inlets for the different melts and special manifold systems to combine the sheets in a controlled manner.

[0015] Blow heads are specialized extrusion tools used in blown film production. They form the melt into a tubular preform that is then inflated with air. Blow heads are available in various designs, for example, with axial or horizontal helical distributors to ensure uniform material distribution.

[0016] Tools with spiral distributors contain helical channels (helixes) that distribute the melt evenly around the circumference. Variants include axial, horizontal, conical, and horizontal-conical spiral distributors, which are used depending on the application and desired material distribution.

[0017] The inlet of the extrusion die serves as the connection between the extruder, which generates the molten plastic, and the extrusion die itself. The liquefied plastic mass is fed through this inlet into the interior of the die, where it is further processed and shaped. Various thermoplastic materials can be processed in this way, such as: - Polyethylene (PE) - Polypropylene (PP) - Polyvinyl chloride (PVC) - Polystyrene (PS) - Polyethylene terephthalate (PET) - Polycarbonate (PC) - Polyamide (PA) - Ethylene vinyl alcohol (EVOH)

[0018] The outlet preferably shapes the melt into the desired form and / or allows the extruded material to be removed from or discharged from the tool. The extrusion channels guide the melt from the inlet to the outlet and preferably ensure a uniform distribution of the material across the cross-section of the tool.

[0019] The central axis serves as a reference line for the design and alignment of the tool.

[0020] The sealing section is a part of the extrusion channel that prevents material exchange between adjacent extrusion channels, whether within the same layer or between different layers. In this section, the extrusion channels are arranged at a first spacing around a cylinder along the central axis, with the first spacing being constant or substantially constant. This arrangement ensures an effective seal between the extrusion channels, so that the melt in each extrusion channel is completely separated from the melt in adjacent extrusion channels.

[0021] In this context, the term "constant" means that the initial distance of the extrusion channels from the central axis remains constant along the entire length of the sealing section. "Substantially constant" means that minor deviations from this constant distance are permissible, provided they do not impair the function of the sealing section. This definition implies that the extrusion channels in the sealing section are arranged essentially parallel to the central axis. In other words, they follow a substantially cylindrical path. This arrangement ensures uniform melt flow and effectively prevents material transfer between adjacent extrusion channels. The parallel and cylindrical alignment of the extrusion channels in the sealing section ensures that the melt remains isolated in each extrusion channel until it is distributed in a controlled manner within the distribution section.

[0022] Typically, in the sealing area, the melt flows either in the extrusion channel in a spiral or helical direction, or in the already opening gap in the main extrusion direction. To prevent the melt from flowing in directions other than the main extrusion direction or backwards, the extrusion channels in this area are sealed against other channels. At the end of the sealing area, the melt flow is usually uniform across the entire circumference. In the distribution area, described in detail later, this distribution is further optimized and overlapped multiple times, so that at the end of the distribution area (end of the helical distributor), the melt is free of weld lines and flows into an annular gap already described in the prior art.

[0023] Weld lines along the extrusion direction typically arise from the merging of partial melt flows from different extrusion channels. These can create weak points in the blown film and impair the mechanical properties and homogeneity of the finished film.

[0024] Multiple overlaps in the distribution area refer to the targeted merging and overlapping of partial flows of the melt across several helical coils of the distribution area. This typically occurs in stages, ensuring that the partial flows are not only evenly distributed but also continuously mixed. This process, particularly in axial, horizontal, or conical helical distributors, ensures that the melt is homogenized and any discontinuities, such as weld lines, are eliminated.

[0025] The spiral helixes of the distribution structures typically allow for a controlled release of the melt into the annular gap due to their decreasing channel depth. In axial helical distributors, this occurs along the cylinder axis, while in horizontal and conical distributors, the flow behavior is further influenced by deflections and altered geometries. These steps ensure a constant and uniform melt flow in the annular gap and improve the quality of the produced plastic layers.

[0026] Controlled material handling is particularly important in the production of multilayer coextrusion composites to avoid unwanted material mixing and to ensure the quality of the final product.

[0027] After the sealing section, the extrusion channels transition into their respective distribution sections. This means that, in the direction of extrusion—that is, in the direction the melt flows through the extrusion die—the extrusion channels transition into their respective distribution sections after the sealing section. This implies that, after the sealing section, along the central axis and in the direction of melt flow, the extrusion channels change their function from sealing and initial coarse distribution to optimal melt distribution. The extrusion channels thus continue in the extrusion direction, guiding the melt from the sealing section into the distribution section, where their distance from the central axis changes.

[0028] The inward or outward bending of the extrusion channels supports a compact design of the extrusion tool.

[0029] In the distribution section, the extrusion channels change their distance from the central axis by increasing and / or decreasing the second distance relative to the first. This means that the extrusion channels can run either outwards or inwards to distribute the melt radially. Hybrid configurations are also possible, where the distance both increases and decreases to achieve optimal melt distribution.

[0030] The hybrid dies can feature extrusion channels where some channels increase their distance from the central axis, meaning they extend outwards, while others decrease their distance and extend inwards. In such a hybrid die, the main direction in the distribution section can, for example, be inwards first and then outwards, or vice versa. Alternatively, the extrusion channels can increase or decrease together in a first section and then reverse this change in a second section. This hybrid die has some spiral distributors opening inwards and others opening outwards within a single die head. This arrangement allows for a very compact design with moderate sealing forces.

[0031] This means that an extrusion channel could, for example, initially increase its spacing by extending outwards and then decrease it again by retracting inwards. Furthermore, sections with a constant spacing can also exist between the areas where the spacing increases or decreases. Additionally, these variations can occur both within a single plane and across different planes of the die head. Within a plane, the extrusion channels might, for example, initially narrow and then widen again, or vice versa. In this context, a "plane" refers to a vertical position along the extrusion direction within the die head. Multiple extrusion channels, potentially belonging to different layers, can be located on such a plane. For instance, one extrusion channel might widen outwards while another widens inwards.This allows, for example, flexible adjustment of the flow geometry to achieve specific flow characteristics. At different levels, one or more levels can taper while other levels widen simultaneously. This configuration allows, for example, precise control of the melt flow across multiple levels and contributes to further improving the homogeneity of the extruded plastic layer or co-extrusion composite. Between these sections, there can also be areas where the distance to the central axis remains constant. The described hybrid forms can also be used for particularly compact designs.

[0032] This specific arrangement and design of the extrusion channels ensures efficient distribution of the polymer melt. This contributes to the production of high-quality polymer sheets or multi-layer co-extruded composites with uniform material properties and minimal flow irregularities.

[0033] One embodiment of the extrusion tool according to the invention provides that one or more extrusion channels are each assigned to a layer of the coextruded composite. This means that specific extrusion channels are available for each layer of the multilayer composite, through which the corresponding polymer melt is guided. This arrangement enables precise control over the material properties of each individual layer and prevents unwanted mixing between the layers. By guiding the melts separately, each layer can be provided with different polymers or additives to achieve specific properties such as barrier properties, adhesion, or mechanical strength. This results in a higher-quality end product with improved functionalities and opens up diverse design possibilities in coextrusion technology.

[0034] Another embodiment of the extrusion tool according to the invention provides that the extrusion channels assigned to the different layers each have their own inlet. This allows the extrusion tool to be designed so that the different layers of the coextruded composite can be formed from different materials. Alternatively or additionally, extrusion channels assigned to several layers can each have a common inlet, so that the extrusion tool is designed to form several layers of the coextruded composite from the same material.

[0035] Another embodiment of the extrusion tool provides that the extrusion channels in the sealing section and / or the distribution section run spirally or essentially spirally around the cylinder along the central axis. The pitch of the helix can be variable to precisely control the melt flow and the distribution of the materials. Hybrid designs may exist in which the pitch of the helix varies in different sections. Furthermore, the extrusion channels may have a wave-like shape in certain areas to allow for even finer adjustment of the melt flow and to further minimize flow irregularities.

[0036] Another embodiment of the extrusion tool provides that the extrusion tool has several segments, which are designed as separate components. These segments can be designed such that each segment encompasses the extrusion channels of several layers of the coextruded composite. Alternatively, each segment can, for example, also encompass the extrusion channels of a single layer of the coextruded composite. In a preferred embodiment, the segments of the extrusion tool are stackable so that they can be easily assembled and disassembled.

[0037] In this embodiment, the cylinder around which the extrusion channels run in a spiral or essentially spiral pattern can also be segmented. This allows for flexible adaptation of the extrusion tool to various production requirements and facilitates cleaning, maintenance, and the replacement of individual segments. The segmented design also contributes to modular expandability, as additional segments can be added for further layers or channels to enable more complex co-extrusion composites.

[0038] Another embodiment of the extrusion die provides for a transition zone between the sealing section and the distribution section of each extrusion channel. This transition zone ensures a smooth transition between the constant arrangement of extrusion channels in the sealing section and the variable arrangement in the distribution section, guaranteeing a uniform and uninterrupted material flow. The transition length of this zone can range from 1:1000 to 1:2 of the total length of the extrusion channel, meaning that the length of the transition zone can vary depending on the specific die design. This transition length allows the melt to be transferred smoothly and without turbulence from a structured flow path in the sealing section to a uniform distribution in the distribution section.

[0039] Another embodiment of the extrusion tool provides that the angle between the main axis of extension of the extrusion channels in the respective sealing section and the main axis of extension of the extrusion channels in the respective distribution section lies between 0° and ±90°. This means that the extrusion channels can change direction along their course, with the angle being up to a full 90° rotation, but smaller angles of 85° or 80° are also possible.

[0040] The described embodiments preferably allow for a dense arrangement of numerous layers in a minimal space.

[0041] Preferably, this angle is between ±1° and ±85°, which allows for a moderate change in the direction of the extrusion channels without causing the flow to become too abrupt. Particularly preferably, the angle is between ±10° and ±80°, which results in gentler material handling while still allowing for adjustment of the extrusion channels in the distribution section.

[0042] In a particularly preferred embodiment, the angle between the main axis of extension of the extrusion channels in the sealing section and that in the distribution section is between ±30° and ±60°. This specific orientation ensures optimal melt distribution by providing a moderate but effective change in the flow direction, which can contribute to improved homogeneity and material distribution in the final product. This allows many layers to be arranged in a compact installation space while simultaneously requiring comparatively low sealing forces.

[0043] Sealing forces are the forces acting on sealing surfaces to ensure a reliable seal between components. They prevent the escape of fluids and / or gases through a sealing area and ensure that the sealing materials used are in optimal contact. The magnitude of the sealing forces depends on various factors, such as the material of the sealing surfaces, the contact pressure, the shape and geometry of the seal, and the requirements for the sealing effect (e.g., internal pressure conditions).

[0044] In technical systems with extrusion channels, moderate sealing forces support a stable and durable seal without excessive material wear or additional energy expenditure. This has the further advantage that fewer or smaller screws can be used, which significantly simplifies the design and enables a more compact construction. This allows for a reduction in the system's installation space and weight without compromising functionality or sealing performance.

[0045] Another embodiment of the extrusion tool provides that the extrusion channels are formed by grooves within components of the extrusion tool, with several components together forming, in particular, a segment. These grooves run along the surfaces of the components and, once the components are assembled, form the complete extrusion channels.

[0046] Each groove has a base and preferably two lateral flanks. The base is the lowest surface of the groove and connects the two lateral flanks. The flanks extend from the base to the outer surface of the sealing section or the respective surface of the component into which the groove is integrated. The flanks are preferably parallel to each other, thus promoting uniform flow guidance.

[0047] The transition area between the base and the flanks can be rounded or shaped in a similar way. This serves, for example, to avoid dead corners and areas of reduced flow, thereby optimizing material flow and minimizing deposits. This design helps to ensure the efficiency and uniform distribution of the melt flow within the extrusion channels.

[0048] The angle of the groove flanks can also be described relative to an imaginary centerline of the groove. This imaginary centerline preferably runs along the geometric center of the groove's cross-sectional geometry and extends from the base to the outer surface of the sealing section or the surface of the respective component into which the groove is formed. Particularly for grooves with non-parallel flanks or more complex geometries, such as a semicircle, an open V, or dynamic geometries, this method simplifies the precise description of the groove angle.

[0049] The imaginary centerline of the grooves in the extrusion channels preferably runs at least partially at an angle of more or less than 90° relative to the cylindrical surface in the sealing section, particularly at an angle in the range of ±15° to ±165° relative to the cylindrical surface, and especially preferably at an angle of inclination in the range of ±45° to ±135° relative to the cylindrical surface. The aforementioned angles can thus be specified with reference to the imaginary centerline of the groove. This reference enables a uniform and clear definition of the flank orientation, even with asymmetrical or varying cross-sections. This method of description increases the geometric adaptability of the grooves while simultaneously improving the precision and traceability during the manufacturing and design of the extrusion die.

[0050] In a preferred embodiment, the extrusion channels are formed by opposing grooves within several components of the extrusion tool. In this configuration, each component has a groove that together forms a closed channel. Alternatively, the extrusion channels can also be formed by grooves in a single component of the extrusion tool, in which case a groove in one extrusion channel does not have a corresponding groove in an opposing component.

[0051] Furthermore, the grooves can have different shapes in different sections to precisely control the melt flow. Hybrid designs are also possible, where in certain sections of the extrusion die the grooves are formed by opposing components, while in other sections the grooves are only present in a single component.

[0052] Another embodiment of the extrusion tool provides for adjusting the angle between the surface into which the groove is formed and the flank of the groove adjacent to this surface. In a first embodiment, the flanks of the grooves of the extrusion channels in the sealing section run perpendicular to the cylindrical surface. Alternatively or additionally, the flanks of the grooves of the extrusion channels in the sealing section can run at an angle to the cylindrical surface, at least partially. This angle of inclination, relative to the surface into which the groove is formed, can be in the range between 15° and ±165°, and preferably in the range between ±45° and ±135° relative to the cylindrical surface. This inclination allows the melt flow to be selectively influenced in order to achieve different flow properties or to improve accessibility for manufacturing.

[0053] In certain sections, the extrusion channels can also run in the opposite direction to the extrusion direction, allowing for the recirculation or distribution of the melt before it is directed in the final extrusion direction. This design of the extrusion channels enables control of the material distribution and contributes to the uniform formation of the plastic layers or the co-extruded composite.

[0054] Another embodiment of the extrusion die provides that the respective distribution sections of the extrusion channels transition into an end section of the extrusion die. This end section serves to further convey the plastic layer or a layer of the multilayer coextruded composite in the extrusion direction. The end sections ensure a uniform distribution of the melt before it exits the extrusion die. The end section thus forms the final section of the die from which the finished product emerges in its intended shape, with the individual layers of the coextruded composite preferably already positioned precisely on top of each other at this stage and able to be extruded uniformly.

[0055] Another embodiment of the extrusion die provides that several end sections of the extrusion die are arranged in such a way that a first layer of the coextruded composite within the extrusion die can be joined with further layers of the coextruded composite in one of the end sections. This means that the melts from the individual extrusion channels intended for the different layers are brought together in their respective end sections to form the multilayer coextruded composite. The arrangement of the end sections allows the first layer of the composite to be seamlessly joined with the subsequent layers, resulting in a uniform, stable, and well-adhering multilayer structure. This ensures that the coextruded composite can be produced in a single extrusion step, with the layers being applied precisely and in a controlled manner.

[0056] Another embodiment of the extrusion tool provides that a pre-distributor is arranged between the at least one inlet and the at least one sealing section. Alternatively or additionally, at least a portion of a pre-distributor can be arranged on the cylinder. The pre-distributor is then generally located in the same sealing surface as the sealing section of the subsequent helical distributor, whereby the sealing surface of the helical distributor can also include a part of the pre-distributor.

[0057] The transition from the pre-distributor to the spiral distributor, which forms the actual extrusion channel, can be implemented in various ways. In a first embodiment, the pre-distributor can transition into the spiral distributor from below, with the end of the pre-distributor located in the same sealing area as the beginning of the spiral distributor. In another embodiment, the transition occurs laterally, for example, through bores that guide the melt from the pre-distributor into the spiral distributor. A further possibility is that the transition occurs laterally in a parting plane between horizontal plates.

[0058] With a lateral feed to the spiral distributor, the melt can be fed into the distributor from both the side where the grooves are located and the opposite side. This flexible design of the pre-distributor and the transitions allows for optimal adaptation to different flow conditions and materials, improving uniform layer formation and material distribution in the co-extrusion process.

[0059] Another aspect of the invention relates to a system for producing a multilayer coextruded composite. This system is equipped with at least one extruder unit for supplying molten material from thermoplastic materials. The extruder unit comprises an extrusion die according to the embodiments described above.

[0060] The at least one extruder melts the thermoplastic material and feeds it to the extrusion die, which guides and distributes the melt(s) to the corresponding extrusion channel(s). The extrusion die itself is preferably designed to extrude multiple layers of material in a single step. The extrusion unit preferably comprises several individual extruders.

[0061] By combining the extruder unit with the extrusion die as described, the system can seamlessly produce multilayer composites. This system ensures high precision and efficiency in the production of co-extruded products by precisely metering, separately guiding, and applying the melts of the thermoplastic materials in uniform layers.

[0062] One embodiment of the system for producing a multilayer coextruded composite provides that each layer or layer group of the coextruded composite is assigned a separate extruder unit. These extruder units are each designed to provide a material melt made of a thermoplastic material.

[0063] For each individual layer of the coextruded composite, a specific extruder unit is used, which feeds the respective material into the corresponding extrusion channels of the extrusion die. In the case of a layer group consisting of several layers of the same material, a common extruder unit can be used to supply the melt. This configuration allows for the targeted feeding of different thermoplastic materials to each layer or layer group, enabling optimal control over the material composition and layer thickness of the multilayer coextruded composite.

[0064] By assigning an extruder unit to each layer or layer group, the system achieves a high degree of flexibility and adaptability. This allows for the simultaneous processing of different materials, enabling the efficient production of multilayer products with various functions and properties, such as barrier properties or mechanical strength.

[0065] In one embodiment, the extrusion tool includes cooling fluid channels. These can be designed, for example, to hold an oil as the cooling fluid, in order to enable temperature control to temperatures of 200-300°C.

[0066] Further advantages and aspects of the invention will become apparent from the claims and from the following description of preferred embodiments of the invention, which are explained below with reference to the figures. Fig. Figure 1 shows an exemplary embodiment of an extrusion tool according to the invention as an overview. Fig. Figure 2 shows a sectional view of the extrusion tool of Fig. 1 Fig. Figure 3 shows a sectional view of a further embodiment of an extrusion tool according to the invention. Fig. Figure 4 shows a detailed view of the extrusion tool. Fig. 3 Fig. Figure 5 shows a further embodiment of an extrusion tool according to the invention. Fig. Figure 6 shows a detailed view of the extrusion tool from Fig. 5 Fig. Figure 7 shows a further embodiment of an extrusion tool according to the invention.

[0067] Fig. Figure 1 shows a first embodiment of an extrusion tool 10 designed for co-extruding a multi-layer co-extruded composite. In this example, the extrusion tool is designed as a blow head. The illustration in the figure shows the external view of the blow head, which comprises several segments 20, 22, 24.

[0068] At the lower end of the die head, two inlets 70 and 72 are visible, which serve to supply melt from an extruder (not shown). This melt is guided through several extrusion channels, of which only the first extrusion channel 100 is indicated here, in the extrusion die 10 and discharged at the upper end via an outlet 40 as an annular gap. The outlet 40 is designed to allow the extrusion of a two-layer co-extruded composite.

[0069] The extrusion tool 10 has a central axis 2 along which a cylindrical central cavity runs. The extrusion channel 100 spirals around a cylinder along the central axis 2. Furthermore, only one extrusion channel 100 is indicated in this illustration; it winds spirally around the central axis and serves to distribute the melt evenly.

[0070] The illustration also shows a section plane 4, which is in Fig. 2 is described in more detail and shows a detailed view of the interior.

[0071] Fig. 2 shows that in Fig. 1 Extrusion tool 10 shown in section plane 4. The central axis 2, the segments 20, 22 and 24, as well as the outlet 40, which is designed as an annular gap, are clearly visible.

[0072] Each extrusion channel contains a sealing section 122, 222, which separates the melt in this area between two superimposed turns. This sealing section 122, 222 runs perpendicular to a surface 3 of the cylindrical central cavity. Immediately following each sealing section 122, 222 in the extrusion direction is the distribution section 126, which tapers inwards relative to the respective sealing section 122, 222 and ensures a uniform distribution of the melt. Between each sealing section 122, 222 and the respective distribution section 126, 226 is a transition area 124, 224, which allows the melt to transfer from the respective sealing section 122, 222 to further distribution.

[0073] The angle relative to the central axis 2 between the respective main extension axis of the extrusion channels in the respective sealing section 122, 222 and the main extension axis of the extrusion channels in the respective distribution section 126, 226 is approximately -45°.

[0074] In this embodiment, the extrusion channels are formed by grooves within the segments 20, 24. The grooves are only formed on one side of each segment 20, 24, which simplifies the design.

[0075] Following each distributor section 126, 226, there is an end section 130, 230, which directs the layer until they can finally be placed on top of each other in the common outlet 40, or shortly before it, to create the desired co-extrusion composite.

[0076] Fig. Figure 3 shows an alternative embodiment of an extrusion tool 12, which is also designed as a blow head. The blow head is defined by an equivalent cutting plane 4 according to Fig. 1 cut so that the internal structure of the extrusion tool is visible.

[0077] In this embodiment, extrusion channel 100 forms a middle layer of the extruded coextruded composite. In a subsequent section in the extrusion direction, the melts from extrusion channels 200 and 300 are applied to this middle layer from both sides. In a further step, the same process is carried out with the melts from extrusion channels 400 and 500, followed by the melts from extrusion channels 600 and 700, and finally from extrusion channels 800 and 900. A total of nine layers are thus stacked on top of each other, which are discharged as a coextruded composite from outlet 40.

[0078] It can be seen that the angle, relative to the central axis 2, between the respective main extension axis of the extrusion channels 200, 300, 400, 500, 600, 700, 800 and 900 in the sealing section and the main extension axis of the channels in the distribution section is approximately -45°. A special feature of this embodiment is that this angle is the same for each of the layers, except for the middle layer of extrusion channel 100.

[0079] This figure is shown in detail again according to section plane 6 in Fig. 4. This figure is described again in detail according to section plane 6 in Fig. 4 described.

[0080] Fig. 4 shows a detailed view of the in Fig. Figure 3 shows the extrusion tool 12. Various segments 20, 22, 24, 26, 28, 30, which form the extrusion tool, are clearly visible. The extrusion channels, which guide the melts and form the individual layers of the coextruded composite, run within these segments.

[0081] Each of the extrusion channels contains a sealing section 122, 322, 522, 722, 922, which separates the material flow and prevents the different windings of the extrusion channels from mixing. Following each sealing section is a transition area 124, 324, 524, 724, 924, which allows a transition between the sealing section 122, 322, 522, 722, 922 and the subsequent distribution section 126, 326, 526, 726, 926.

[0082] Immediately following the transition areas, the aforementioned distribution section 126, 326, 526, 726, 926 begins, which guides the melt and ensures a uniform distribution across the entire layer. This is followed by an end section 930, marked here only for the uppermost layer of this figure, which directs the layer until it can finally be deposited onto the other layers at the common outlet 40, or shortly before it, to create the desired co-extruded composite.

[0083] Fig. Figure 5 shows an alternative embodiment of an extrusion tool 14, which is designed as a blow head. The blow head is shown in an equivalent section plane 4, similar to the preceding figures. In this embodiment, a middle layer for the coextrusion composite is again provided, with the sealing sections 122, 222, 322, 422, 522, 622, 722, 822 and 922 being marked in this figure.

[0084] In a section following the middle layer in the extrusion direction, melts from the next two extrusion channels are applied to this middle layer from both sides. This is followed in further stages by melts from the subsequent extrusion channels, then from the following extrusion channels, and finally from the last extrusion channels, resulting in a total of nine layers. The finished coextruded composite is then discharged via outlet 40.

[0085] A key difference in this embodiment is that the angles between the main axis of extension of the respective superimposed extrusion channels in the sealing section and the main axis of extension of the channels in the respective distribution section now exhibit different angles along the extrusion direction. This enables a particularly short overall height of the extrusion tool 14.

[0086] This figure is shown in detail again according to section plane 6 in Fig. 6 described.

[0087] Fig. Figure 6 shows a detailed view of the in Fig. 5. Extrusion tool 14. In this detailed view, various segments 20, 22, 24, 26, 28, 30 can be seen, which form the structure of the extrusion tool. Within these segments run the extrusion channels, which guide the melts and create the individual layers of the coextruded composite.

[0088] Each of the extrusion channels has a sealing section 122, 322, 522, 722, 922, which separates the melt flow between the turns of the respective extrusion channels. Downstream of the sealing sections 122, 322, 522, 722, 922 is a transition area 124, 324, 524, 724, 924, which creates a transition between the sealing and the distribution of the melt.

[0089] The subsequent distribution sections 126, 326, 526, 726, and 926 vary in their angle to the main axis of extension of the extrusion channels, so that the melt distribution is adapted to the requirements of each layer. The angle between the sealing section and the distribution section differs for each layer. In this embodiment, the layer angles are approximately ±15° for the second layer (counting from the inside out) following the innermost layer, ±30° for the third layer, ±40° for the fourth layer, and ±50° for the fifth layer.

[0090] Fig. Figure 7 shows another alternative embodiment of an extrusion tool 16, which serves as a blow head for a three-layer coextrusion composite. This illustration shows a section of the blow head.

[0091] A special feature of this embodiment is that the grooves of the extrusion channels in the sealing section of the two upper layers from reference numeral groups 200 and 300 are not perpendicular to the cylindrical surface. Instead, the extrusion channels in the upper two layers are arranged at an angle to the central axis. In the middle layer, the angle of inclination is approximately minus 70 degrees, while in the upper layer it is plus 70 degrees. This arrangement of the channels enables optimized material flow and melt distribution in the upper two layers of the coextruded composite, as well as improved accessibility during manufacturing and any subsequent surface treatment.

[0092] Additionally, parts of the inlet channels 74, 76, and 78, which serve to supply the melt to the extrusion die, can be seen in this figure. The inlet channels 74, 76, and 78 are each formed as a half-groove between two segments 20, 21 and 21, 22 and 23, 24.

[0093] Another feature of this embodiment is the pre-distribution channels 80, which are arranged between a melt inlet in the blow head and the spiral distributor and direct the melt to the spiral distributor, typically by branching it out to several ports. The pre-distribution channels 80 are each arranged as a double groove between segments 21, 22 and 22, 23 and enable a uniform distribution of the melt in the blow head, so that the melt reaches the spiral distributor in an optimal manner. Reference symbol list 2 central axis 4, 6 section plane 10, 12, 14, 16 Extrusion tool 20, 21, 22, 23, 24, 26, 28, 30 segments 40 outlet 70, 72 Admission 74, 76, 78 Inlet channel 80 Cooling fluid channel 100, 200, 300, 400, 500, 600, 700, 800, 900 extrusion channel 122, 222, 322, 522, 722, 922 Sealing section 126, 226, 326, 526, 726, 926 Distribution section 124, 224, 324, 524, 724, 924 Transition area 130, 230 End section

Claims

Extrusion die (10, 12, 14, 16) for extruding a plastic layer or co-extruding a multi-layer co-extrusion composite, in particular a blow head, with the following features: a. the extrusion die (10, 12, 14, 16) has at least one inlet (70, 72) for the entry of a melt into the extrusion die (10, 12, 14, 16), and b. the extrusion die (10, 12, 14, 16) has an outlet (40) for the exit of the plastic layer or the multi-layer co-extrusion composite from the extrusion die (10, 12, 14, 16), and c. The extrusion tool (10, 12, 14, 16) has several extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) arranged between the at least one inlet (70, 72) and the outlet (40), which are in fluid communication with the at least one inlet (70, 72), andd.The extrusion tool (10, 12, 14, 16) has a central axis (2) which is arranged in the extrusion direction of the melt, characterized in that. the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) each have a sealing section (122, 222, 322, 522, 722, 922), wherein the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) are arranged in the sealing section (122, 222, 322, 522, 722, 922) at a first distance around a cylinder extending along the central axis (2), wherein the first distance is constant or substantially constant andf.The extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) each have a distribution section (126, 226, 326, 526, 726, 926), wherein the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) are arranged in the distribution section (126, 226, 326, 526, 726, 926) at a second distance from the central axis (2), wherein the second distance increases and / or decreases compared to the first distance, wherein g. the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) each transition after their sealing section (122, 222, 322, 522, 722, 922) in the extrusion direction into their respective distribution section (126, 226, 326, 526, 726, 926). Extrusion tool (10, 12, 14, 16) according to claim 1, with the following further feature: one or more extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) are each assigned to a layer of the coextrusion composite. Extrusion tool (10, 12, 14, 16) according to claim 2, with the following further features: a. Extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) assigned to different layers each have their own inlet (70, 72), so that the extrusion tool (10, 12, 14, 16) is designed to allow the different layers of the coextrusion composite to be formed from different materials, and / or b. The extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) assigned to several layers each have a common inlet (70, 72), so that the extrusion tool (10, 12, 14, 16) is designed to form several layers of the coextrusion composite from the same material. Extrusion tool (10, 12, 14, 16) according to one of the preceding claims, with the following further feature: the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) run in the sealing section (122, 222, 322, 522, 722, 922) and / or in the distribution section (126, 226, 326, 526, 726, 926) in a spiral or substantially spiral shape around a cylinder along the central axis (2). Extrusion tool (10, 12, 14, 16) according to one of the preceding claims, with the following further features: a. the extrusion tool (10, 12, 14, 16) has several segments (20, 21, 22, 23, 24, 26, 28, 30), in particular segments designed as separate components (20, 21, 22, 23, 24, 26, 28, 30), and b. each segment (20, 21, 22, 23, 24, 26, 28, 30) comprises the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) of several layers of the coextrusion composite, or c. Each segment (20, 21, 22, 23, 24, 26, 28, 30) comprises the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) of a layer of the coextrusion composite, preferably with the further feature: d. the segments (20, 21, 22, 23, 24, 26, 28, 30) of the extrusion tool (10, 12, 14, 16) are stackable. Extrusion tool (10, 12, 14, 16) according to one of the preceding claims, with the following further feature: the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) of different layers are arranged along the central axis (2). Extrusion tool (10, 12, 14, 16) according to one of the preceding claims, with the following further features: a. a transition area (124, 224, 322, 522, 722, 922) is arranged between the sealing section (122, 222, 322, 522, 722, 922) and the distribution section (126, 226, 326, 526, 726, 926) of an extrusion channel (100, 200, 300, 400, 500, 600, 700, 800, 900), and b. The transition area (124, 224, 324, 524, 724, 924) has a transition length of 1:1000 to 1:2 of the length of the extrusion channel (100, 200, 300, 400, 500, 600, 700, 800, 900). Extrusion tool (10, 12, 14, 16) according to one of the preceding claims, with the following further features: a. The angle between the main extension axis of the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) in the respective sealing section (122, 222, 322, 522, 722, 922) and the main extension axis of the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) in the respective distribution section (126, 226, 326, 526, 726, 926) is between 0° and ±90° (85, 80, 30-60),b. Preferably, the angle between the main extension axis of the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) in the respective sealing section (122, 222, 322, 522, 722, 922) and the main extension axis of the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) in the respective distribution section (126, 226, 326, 526, 726, 926) is between ±1° and ±85°.Particularly preferably, the angle between the main extension axis of the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) in the respective sealing section (122, 222, 322, 522, 722, 922) and the main extension axis of the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) in the respective distribution section (126, 226, 326, 526, 726, 926) is between ±10° and ±80°. In particular, preferably the angle between the main extension axis of the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) in the respective sealing section (122, 222, 322, 522, 722, 922) and the main extension axis of the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) in the respective distribution section (126, 226, 326, 526, 726, 926) is between ±30° and ±60°. Extrusion tool (10, 12, 14, 16) according to one of the preceding claims, with the following further features: a. the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) are formed by grooves within components of the extrusion tool (10, 12, 14, 16), and b. each groove has a base and two lateral flanks, and c. the base forms the lowest surface of the groove and connects the lateral flanks to each other, and d. the flanks extend from the base to the outer surface of the sealing section (122, 222, 322, 522, 722, 922), and e. Several components form, in particular, a segment (20, 21, 22, 23, 24, 26, 28, 30), preferably with at least one of the following additional features: f. the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) are formed by opposing grooves within several components of the extrusion tool (10, 12, 14, 16), or g.The extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) are formed by grooves in a component of the extrusion tool (10, 12, 14, 16), so that a groove of an extrusion channel (100, 200, 300, 400, 500, 600, 700, 800, 900) does not have a corresponding groove opposite it. Extrusion tool (10, 12, 14, 16) according to claim 9, with at least one of the following further features: a. the flanks of the grooves of the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) run perpendicular to the outer surface in the sealing section (122, 222, 322, 522, 722, 922) and / or b. The flanks of the grooves of the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) run in the sealing section (122, 222, 322, 522, 722, 922) at least sectionally relative to the outer surface at an angle of more or less than 90°, in particular with an angle in the range between ±15° and ±165° relative to the outer surface, and in particular preferably with an angle of inclination in the range between ±45° and ±135° relative to the outer surface. Extrusion tool (10, 12, 14, 16) according to one of the preceding claims, with the following further feature: the respective distribution sections (126, 226, 326, 526, 726, 926) of the extrusion channels (100, 200, 300, 400, 500, 600, 700, 800, 900) transition into an end section (130, 230) of the extrusion tool (10, 12, 14, 16), so that the plastic layer or a layer of the multilayer coextrusion composite can be conveyed from the end section (130, 230) in the extrusion direction. Extrusion tool (10, 12, 14, 16) according to claim 11, with the following further feature: several end sections (130, 230) of the extrusion tool (10, 12, 14, 16) are arranged to each other in such a way that a first layer of the coextrusion composite in the extrusion tool (10, 12, 14, 16) can be joined with further layers of the coextrusion composite. Extrusion tool (10, 12, 14, 16) according to one of the preceding claims, with the following further feature: a pre-distributor is arranged between the at least one inlet (70, 72) and the at least one sealing section (122, 222, 322, 522, 722, 922), and / or at least one area of ​​a pre-distributor is arranged on the cylinder. Apparatus for producing a multi-layer co-extrusion composite with at least one extruder device for providing material melts from thermoplastic materials, with an extrusion tool according to claims 1 to 13. The system according to claim 14, with the following further feature: each layer or layer group of the coextrusion composite is assigned an extruder device for providing a material melt of thermoplastic material.

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