Method and device for producing marbled molded parts and method for producing the device

Abstract

The present invention relates to a method for producing marbled molded parts, wherein: a first molding compound (1) and at least one further molding compound (3) are injected into an injection mold (9) from an injection unit (5) of a screw injection molding machine (7); the injection unit (5) comprises a hollow barrel (11), a screw (13) having a screw tip (15) and a nozzle (17), the screw (13) being arranged in the hollow barrel (11) so that the screw can rotate and can move in the direction of the longitudinal axis (19) of the hollow barrel (11) between a front position (21) and a rear position (23); the distance (25) between the screw tip (15) and the nozzle (17) is smaller in the front position (21) than in the rear position (23); the first molding compound (1) comprises a first polymer compound and a first colorant, and the at least one further molding compound (3) comprises at least one further polymer compound and optionally at least one further colorant. The invention also relates to a device for producing marbled moldings, and a method for producing the device.

Description

Technical Field

[0001] The present invention relates to a method for producing marbled molded parts, wherein a first molding compound and at least one further molding compound are injected into an injection mold from an injection unit of a screw injection molding machine, wherein the injection unit comprises a hollow barrel, a screw with a screw tip, and a nozzle, the screw being rotatable and arranged in the hollow barrel so as to be movable in the direction of the longitudinal axis of the hollow barrel between a front position and a rear position, the distance between the screw tip and the nozzle being smaller in the front position than in the rear position, wherein the first molding compound comprises a first polymer compound and a first colorant, and the at least one further molding compound comprises a further polymer compound and optionally at least one further colorant.

[0002] The invention also relates to a device for producing marbled mouldings, comprising an injection unit comprising a hollow barrel with an interior, a screw and a nozzle with a nozzle head and a nozzle body, wherein the screw (also referred to as a conveying screw) is rotatable and arranged in the hollow barrel so as to be movable in the direction of the longitudinal axis of the hollow barrel between a front position and a rear position, and a method for producing the device. Background Art

[0003] Marbled moldings typically have at least one marbled (i.e., patterned) visible surface, displaying surface effects such as color shades, color streaks, lines, and structures. In marbled moldings, at least a portion of the colorant present is not evenly distributed. The formation of the marbling effect depends on the proportions of the different colors and the base color of the molding. Marbled moldings generally do not look exactly the same. If they display a recurring, recognizable pattern in the color structure, they can also be referred to as repeatable marbled moldings. Specifically, the base color, shades, and main pattern are repeated in repeatable marbled moldings, although variations in color intensity may occur.

[0004] The production of molded parts, in particular polymer molded parts made from powders, granules, or molding compounds (which can each be in the form of a mixture), is typically carried out using screw injection molding machines. To produce colored polymer articles, colored polymer granules are usually used, or neutral-colored granules are mixed with colored polymer granules with a high pigment concentration before or during liquefaction of the polymer in the extruder. The mixing elements used in the injection molding unit typically produce a mixture comprising an uncolored base material and colored granules with a high concentration of colorant mixed with maximum homogeneity, resulting in a component with a streak-free surface.

[0005] Screw injection molding machines generally achieve uniform plasticization, where the injected molding compound has a uniform temperature. In the production of marbled molded parts, this homogenization is undesirable because, despite the uniform temperature, the injected molding compound is not completely mixed, so that remnants of different color components can still be seen in the finished part.

[0006] In particular for producing repeatable marble patterns, requiring uniform repetition of color variations and color distribution, the machines used generally supply at least two marbling components separately (eg in two separate injection units) to the injection mold.

[0007] Devices for producing marbled mouldings, in particular nozzles, are also known which make it possible to combine moulding compounds from two separate injection units into one injection mould.

[0008] The production of reproducible marbled molded parts in a two-component injection molding machine is complicated because two injection units are required and must be operated, each having a screw, a barrel, a feeding device and corresponding hydraulics for moving the screw.

[0009] Furthermore, inserts for the hollow barrel of a screw injection molding machine having a modified screw are generally known, which enable the production of marbled moldings in a one-component injection molding machine, but do not ensure the reproducibility of the marble pattern.

[0010] AT 406 753B describes the use of a displacement body, known as a torpedo, upstream of the nozzle. This displacement body has different surface configurations for producing a marbling effect. Using a short screw with a torpedo creates a non-homogeneous melt, thus producing the marbling effect.

[0011] DE 27 14 509 A1 relates to a device for producing marbled mouldings made of polymer material, which uses a single-zone short screw followed by a displacement body in a heatable zone of the barrel.

[0012] US 4,176,152 describes an injection molding machine having a barrel and a reciprocating screw. A heat transfer and laminating body is positioned between the screw and the barrel outlet. In particular, the body has a rib structure on its outer periphery.

[0013] DE 42 04 015 A1 discloses an injection nozzle for thermoplastic compounds, comprising a nozzle head and a base part. The nozzle head is movable in the axial direction so as to open and close a second hole leading to the axial hole and for supplying a second thermoplastic molding compound.

[0014] DE 10 2004 053 575 A1 likewise relates to a nozzle for an injection molding machine in which two resins of different compositions and colors are processed. A first channel in the nozzle communicates with a first injection unit, and a second channel in the nozzle communicates with a second injection unit.

[0015] JP 2003 200456 and JP 2005 262759 also describe nozzles for injecting two different resins from two separate plasticizing units.

[0016] TW 411314B relates to a method for producing plastic products with color gradients using a conical nozzle.

[0017] DE 43 32 242 A1 discloses a method and a device for producing marbled polymer objects by injection molding, wherein color pigments are supplied via an introduction port at the beginning of the screw blades.

[0018] DE 100 13 617 A1 relates to a method for producing a plastic article having at least one marbled visible surface. For this purpose, solid particles which can be aligned by the action of a magnetic field are added to a thermoplastic compound before or during liquefaction.

[0019] EP 1 556 198 B1 describes a mixing element which can replace a non-return valve at the screw tip of an injection molding machine. Summary of the Invention

[0020] The object of the present invention is to provide a method for producing marbled molded parts, wherein the marble pattern produced is reproducible. Furthermore, a device for producing marbled molded parts is proposed, with which the design of the marble pattern can be varied in a targeted manner, while achieving a high degree of expressiveness and reproducibility of the marble pattern, and the same screw injection molding machine can be used to produce different patterns without requiring modifications.

[0021] The object of the present invention is to provide a method for producing a marbled molded part, wherein a first molding compound and at least one further molding compound are injected into an injection mold from an injection unit of a screw injection molding machine, wherein the injection unit comprises a hollow barrel, a screw having a screw tip, and a nozzle, the screw being rotatable and arranged in the hollow barrel so as to be movable in the direction of the longitudinal axis of the hollow barrel between a front position and a rear position, the distance between the screw tip and the nozzle being smaller in the front position than in the rear position, the first molding compound comprising a first polymer compound and a first colorant, and the at least one further molding compound comprising another polymer compound and optionally at least one further colorant, comprising the following steps:

[0022] a) optionally feeding a first amount of a first molding compound onto the screw when the screw is in the rear position,

[0023] b) optionally advancing the screw from the rear position into the front position,

[0024] c) feeding a second amount of at least one additional molding compound onto the screw,

[0025] d) plasticizing the first molding compound and the at least one further molding compound in the hollow barrel, rotating the screw and conveying at least a portion of the first molding compound and at least a portion of the at least one further molding compound into the free space in the hollow barrel between the nozzle and the screw tip, and moving the screw from the front position to the rear position,

[0026] e) optionally feeding a new first amount of a first molding compound onto the screw when the screw is in said rear position,

[0027] f) injecting the first molding compound and at least one further molding compound from the free space in the hollow barrel into the cavity of the injection mold, the screw advancing from the rear position to the front position,

[0028] g) cooling the first molding compound and the at least one further molding compound in the injection mold to form a marbled molding, and

[0029] h) removing the marbled molded part from the injection mold,

[0030] wherein steps c) to h) are repeated, step e) is performed before step f), and step a) is optionally performed before step b), and wherein feeding a new first amount of the first molding compound in step e) and optionally feeding a first amount of the first molding compound in step a) are performed temporally or spatially separated from feeding a second amount of the at least one further molding compound in step c).

[0031] In addition, a device for producing marbled molded parts is proposed, comprising exactly one injection unit, the injection unit comprising a hollow barrel having an interior, a screw, and a nozzle, wherein the screw is rotatable and arranged in the hollow barrel so as to be movable between a front position and a rear position in the direction of the longitudinal axis of the hollow barrel, the distance between the screw tip and the nozzle being smaller in the front position than in the rear position, and wherein the nozzle comprises a nozzle head and a nozzle body, the nozzle being detachably connected to the hollow barrel, the nozzle head having at least two channels, the at least two channels being connected to an outlet of the nozzle at a first end of each channel and to the interior of the hollow barrel at a second end of each channel, wherein the at least two channels pass through the nozzle head in a curved manner. The nozzle head can also be referred to as a nozzle cap. The outlet is arranged on the side of the nozzle facing the injection mold. A first molding compound and at least one additional molding compound are injected into the injection mold through the outlet.

[0032] Preferably, the method according to the invention is carried out using an apparatus according to the invention for producing marbled moldings. The apparatus is an injection molding machine, in particular a one-component injection molding machine.

[0033] The temporally or spatially separated feeding of the first molding compound and the at least one additional molding compound limits the homogenization of the first molding compound and the at least one additional molding compound during the plasticization process, resulting in a clear color boundary and a reproducible marble pattern in the produced molded part. The feeding of the first molding compound and the at least one additional molding compound can also be referred to as continuous or discrete. Thus, the first molding compound is distributed non-homogeneously in the at least one additional molding compound before being injected into the free space between the nozzle and the screw tip.

[0034] Depending on the geometry of the nozzle, a defined repeatable (ie reproducible) pattern is formed on at least one visible face of the produced marbled molding.

[0035] A reproducible marble pattern is understood to mean a pattern in which, when different molded parts are produced by the same method and the same apparatus, the human eye does not perceive the differences as noticeably different when compared to one another. The molded parts produced according to the present invention have a reliably reproducible and recognizable pattern. This is achieved, in particular, by means of a defined feed molding compound.

[0036] The marbled molded parts produced according to the present invention can be used for decorative purposes, particularly in the consumer goods industry. The marbled molded parts can be completely marbled or include at least one visible marbled surface. The marbled molded parts can be three-dimensional or flat. The marbled molded parts are preferably household items (such as plates, trays, cups, coasters, handles, or toilet seats), consumer goods (such as laptop cases or protective cases for phones or smartphones), toys (such as turntables or spinning tops), accessories for the fashion industry (such as buttons), or decorative elements for vehicle interiors (such as sun visors or covers).

[0037] The first molding compound and at least one further molding compound are fed to the barrel of the injection unit and, by the rotation of the screw of the injection molding machine, are conveyed forward in the conveying direction toward the nozzle. This at least partially (preferably completely) plasticizes the first molding compound and the at least one further molding compound. The at least one further molding compound and, optionally, the first molding compound accumulate in the free space between the nozzle and the screw tip and move the screw axially backwards into a rear position of the barrel. Preferably, the screw injection molding machine used in the method according to the invention comprises exactly one injection unit, more preferably exactly one barrel, further preferably exactly one screw. The device according to the invention preferably comprises exactly one barrel, further preferably exactly one screw.

[0038] Feeding, which can also be referred to as metering, involves the first molding compound or at least one additional molding compound being fed into the barrel and, in particular, into the screw, for example, via a hopper. The first molding compound and the at least one additional molding compound are supplied in portions separated in time and / or space from one another. "Portioned" means that the first molding compound and, preferably, the at least one additional molding compound are fed non-continuously into the barrel in discrete portions (i.e., in the form of the first or second amount).

[0039] Plasticization, also known as dosing, involves conveying the first molding compound and the at least one further molding compound via the screw in the direction of the nozzle and at least partially melting in the process. Preferably, at least a portion of the first molding compound and at least a portion of the at least one further molding compound are completely melted during the plasticization in step d).

[0040] Feeding the second amount of at least one further moulding compound in step c) is preferably performed after advancing the screw in step b).

[0041] More preferably, the feeding of the new first amount of the first molding compound in step e) and the optional feeding of the first amount of the first molding compound in step a) are completed before the start of the advancement in step b). Furthermore, the advancement in step b) is preferably completed before the start of the feeding of the second amount of at least one further molding compound in step c).

[0042] The first molding compound is preferably first contacted with the screw and then with the at least one further molding compound.

[0043] The first molding compound and / or the at least one further molding compound can be fed separately and directly into the barrel, in particular directly onto the screw via a metering system.

[0044] More preferably, feeding the second amount of at least one further moulding compound is started when the screw is in the front position.The screw is preferably in the front position when the screw has been moved maximally in the direction of the nozzle.

[0045] The at least one further moulding compound (in particular the second amount of the at least one further moulding compound) may be fed continuously. Preferably, the second amount of the at least one further moulding compound is fed continuously at least during the plasticising in step d).

[0046] In particular, when the feeding of the new first quantity of the first molding compound in step e) and optionally the first quantity of the first molding compound in step a) and the second quantity of at least one further molding compound in step c) are fed in a spatially separated manner, the second quantity of at least one further molding compound can be fed continuously during the feeding of the new first quantity of the first molding compound in step e) and optionally during the feeding of the first quantity of the first molding compound in step a).

[0047] When the feeding of the new first quantity of the first molding compound in step e) and optionally the first quantity of the first molding compound in step a) and the second quantity of at least one further molding compound in step c) are fed in a spatially separated manner, the new first quantity of the first molding compound or the first quantity of the first molding compound is preferably fed at a greater distance from the nozzle than the second quantity of the at least one further molding compound.

[0048] After plasticizing, the rotation of the screw is preferably stopped and the screw is moved forward in the conveying direction to a front position so that the plasticized first molding compound and the plasticized at least one further molding compound are pushed through the nozzle into the cavity of the injection mold (the cavity may also be referred to as the interior).

[0049] Feeding a new first amount of the first molding compound to the screw while the screw is in the rear position synchronizes the rhythm or timing of pattern formation with the injection operation, thereby ensuring repeatability of the pattern in continuously produced marbled molded parts. More preferably, the screw is stationary in the rear position while feeding the first amount of the first molding compound.

[0050] The volume of plasticized molding compound, which is present between the nozzle and the screw tip before injection into the free space and consists of at least one further molding compound and optionally the first molding compound, is also referred to as shot volume.

[0051] After the injection in step f), the hollow barrel is filled again. A second amount of at least one additional molding compound is fed, plasticization is again achieved, and the screw moves back to the rear position. Thereafter, a first amount of the first molding compound is fed and injection is again achieved.

[0052] When the first amount of the first molding compound is fed in step a), the plasticization of the at least one further molding compound and optionally the first molding compound has preferably already been completed at least once, more preferably at least twice, and in particular at least four times. Preferably, when the first amount of the first molding compound is fed in step a), the at least one further molding compound and optionally the first molding compound are present in the hollow barrel.

[0053] Preferably, the first molding compound and / or the at least one additional molding compound are fed into the rear portion of the barrel. The rear portion is understood to mean the end of the barrel distal to the nozzle of the screw injection molding machine, preferably no more than 50% of the total length of the barrel, more preferably no more than 20% of the total length of the barrel. The first molding compound and the at least one additional molding compound can be fed into the barrel at the same location, at different locations, or at a feed port. More specifically, the first molding compound and the at least one additional molding compound are fed into the barrel at multiple locations of the same feed port.

[0054] The first molding compound and the at least one further molding compound can be fed in the form of powder, granules or plastic blocks.The first molding compound and / or the at least one further molding compound can each be in the form of a homogeneous mixture and / or a heterogeneous mixture.

[0055] Preferably, the first molding compound and / or the at least one further molding compound are fed in the form of granules. Granules generally refer to free-flowing solid materials, for example cylindrical or lens-shaped, and preferably have a maximum length of 1 mm to 10 mm, more preferably a maximum length of 3 mm to 6 mm.

[0056] The first molding compound preferably comprises a first particulate material comprising a first polymer compound and a first colorant. The first particulate material may also be referred to as a colored particulate material, which is preferably produced in an upstream step prior to the method of the present invention. The first molding compound may also be referred to as marble batch or fine material.

[0057] In particular, the at least one further molding compound may comprise, before being fed, a mixture comprising at least two further particulate materials, in particular a second particulate material and a third particulate material. The at least one further polymer compound may be present in the second particulate material, and the at least one further colorant may be present in the third particulate material.

[0058] Preferably, the marbled molding comprises a first molding compound and at least one further molding compound.

[0059] Preferably, the screw has a feed zone, a compression zone and a metering zone, which can also be referred to as an injection zone or homogenization zone.

[0060] The screw is preferably a single-blade screw. In particular, the screw has exactly one passage, in which the first molding compound and at least one further molding compound are conveyed. Further preferably, the screw has flat screw blades. The blade depth in the feed zone is preferably 0.05 to 0.15 times the outer diameter of the screw, and the blade depth in the metering zone is 0.025 to 0.075 times the outer diameter of the screw. The compression ratio refers to the ratio between the passage volume (Gang volume) of the feed zone of the screw and the passage volume of the metering zone of the screw, which is preferably at least 2, more preferably greater than 2. Preferably, the screw has a length in the range of 20 to 23 times the outer diameter of the screw. Low screw blades have the advantage that less material can be accommodated for the same diameter.

[0061] The screw of the device according to the invention may comprise a non-return valve, preferably said non-return valve being arranged between the nozzle and the screw blades.The screw tip may have blades, in particular 3 to 4 blades.

[0062] The injection unit preferably includes a heating device. The heating device may completely surround the hollow barrel, preferably partially surround the hollow barrel. The nozzle may also include a heating device. The heating device facilitates melting of the first molding compound and the at least one additional molding compound.

[0063] Preferably, cooling the first molding compound and the at least one further molding compound in the injection mold in step g) is performed simultaneously with plasticizing the first molding compound and the at least one further molding compound in the hollow barrel in step d), and optionally, cooling the first molding compound and the at least one further molding compound in the injection mold in step g) is performed at least partially simultaneously with feeding the second amount of the at least one further molding compound in step c).

[0064] Preferably, steps c) to h) are repeated more than once, more preferably more than three times, further preferably more than four times, and particularly preferably more than five times, thereby continuously producing a plurality of marbled moldings. Preferably, steps a) to f) are performed in the order specified.

[0065] Furthermore, the injection in step f) is preferably repeated at an injection frequency, and each injection or advance can be referred to as a shot. Furthermore, the feeding of the new first amount of the first molding compound in step e) is preferably repeated at a feeding frequency. The feeding frequency is preferably selected so that it deviates from the injection frequency by no more than 10%, further preferably by no more than 5%, particularly preferably by no more than 1%. Correspondingly, the feeding of the new first amount of the first molding compound in step e) is particularly preferably performed with the injection cycle in step f). In this case, the feeding of the new first amount of the first molding compound in step e) is preferably performed at a different time than the injection in step f). More preferably, the feeding frequency is equal to the injection frequency. In this case, the first amount of the first molding compound is always performed with the same time delay or time advance as the injection.

[0066] For marbled moldings, feeding a new first amount of the first molding compound in step e) and / or feeding a first amount of the first molding compound in step a) can be performed before or after feeding a second amount of at least one further molding compound in step c).

[0067] Like the first molding compound, the barrel can also be supplied with at least two further molding compounds, whereby multi-colored molded parts can be produced which additionally have a marble pattern. The at least one further molding compound can be divided into a plurality of parts, in which case the plurality of parts are preferably each fed continuously or stepwise.

[0068] The injection mold may include various types of gates. Preferably, the injection mold includes a gate selected from the group consisting of: a hot runner, a tapered gate, a strip gate, a manifold, and a tunnel gate. The injection mold preferably has a tapered gate.

[0069] After the injection in step f), the screw can apply holding pressure to the molded part in the injection mold. Preferably, the holding pressure is applied before the plasticization in step d). When applying the holding pressure to the molded part in the injection mold by the screw, the screw is preferably in the front position of the barrel or still moving in the conveying direction, thereby pushing more plasticized molding compound into the mold and thereby compensating for material shrinkage during cooling of the molded part.

[0070] Preferably, the second amount of at least one further molding compound in step c) is fed when applying a holding pressure on the injection mold. More preferably, the second amount of at least one further molding compound in step c) is fed when starting to apply a holding pressure.

[0071] Preferably, the ratio of the maximum internal free volume of the barrel that can be occupied by the first molding compound and the at least one additional molding compound to the internal volume of the cavity is not greater than 15, more preferably not greater than 10, further preferably not greater than 5, and in particular from 2 to 5. The maximum internal free volume of the barrel can also be referred to as the melt channel. The maximum internal free volume of the barrel preferably refers to the cylindrical internal volume of the barrel minus the volume occupied by the screw present in the barrel.

[0072] Preferably, the internal free volume below the feed opening and in particular above the screw is filled only with the first molding compound and / or at least one further molding compound or with granules of the first molding compound and / or granules of the at least one further molding compound in the range of 0% to 80% by volume, more preferably 10% to 50% by volume. This can also be referred to as underfeeding, in which the first molding compound and the at least one further molding compound are fed at a reduced mass flow rate compared to the maximum mass flow rate that can be conveyed by the screw.

[0073] Correspondingly, the barrel and the screw are designed such that, in particular before injection, there are preferably not more than 15 shots, more preferably not more than 10 shots, further preferably not more than 5 shots, in particular 2 to 5 shots in the injection unit.

[0074] The low internal free volume of the barrel results in a short residence time of the first molding compound and the at least one additional molding compound in the injection unit, which prevents homogeneous mixing of the first molding compound and the at least one additional molding compound, thereby promoting the production of the marble pattern. The residence time of the first molding compound and / or the at least one additional molding compound in the barrel is preferably in the range of 1 second to 15 minutes, more preferably in the range of 0.1 minutes to 4 minutes, and particularly preferably in the range of 0.5 minutes to 2 minutes.

[0075] Due to the method according to the invention, the first molding compound comes into contact with the at least one further molding compound in the barrel as late as possible, thereby minimizing the degree of mixing. Due to the reduced residence time caused by the correspondingly small internal free volume of the barrel, mixing of the first molding compound with the at least one further molding compound is also reduced.

[0076] Preferably, the ratio of the sum of the mass of the first amount of the first molding compound and the mass of the second amount of the at least one further molding compound to the mass of the marbled molding is 0.5 to 1.5, more preferably 0.8 to 1.2, further preferably 0.9 to 1, and in particular 1. This ratio is, for example, greater than 1 when at least one pouring nozzle is present in the production of the marbled molding, which also contains the first molding compound and the further molding compound but is removed from the marbled molding after production and is not part of the marbled molding. A ratio of less than 1 can be present, for example, when inserts, in particular metal inserts, are integrated into the molding or when a two-component molding is produced that may have different hardnesses, wherein first the first component is injected into the cavity and then the second component, the first component and / or the second component having a marbled appearance. Since the ratio is close to 1, the marbling (especially the individual elements of the marbling pattern, such as rings or vertices) are positioned at similar locations in successively produced marbled moldings, which means that the reproducibility of the marbling on different marbled moldings is optimized, especially because the specific mass ratio is matched to the size of the molding and the injection rhythm. This avoids overlapping of different patterns from different injection operations.

[0077] Accordingly, each shot is preferably added individually, with the first molding compound for one shot and at least one further molding compound for the same shot being supplied spatially and / or locally separately in step e) and optionally in step a) or step c). The first molding compound and the at least one further molding compound are preferably added in specific amounts, wherein the first amount and the second amount are each sufficient for exactly one shot.

[0078] Preferably, the mass ratio of the first amount to the second amount is less than 0.1, more preferably less than 0.01 and in particular less than 0.001. The first moulding compound is used to form a marble pattern in at least one further moulding compound constituting the base compound.

[0079] Preferably, the ratio of a first concentration of the first colorant in the first molding compound to another concentration of the at least one further colorant in the at least one further molding compound is greater than 20, more preferably greater than 50, and in particular greater than 100. Accordingly, preferably, the first colorant in the first molding compound has a higher concentration than the at least one further colorant optionally present in the at least one further molding compound. The at least one further molding compound may have been colored by the at least one further colorant before the at least one further molding compound is brought into contact with the first molding compound.

[0080] Preferably, the first molding compound comprises 10% to 60% by weight of the first colorant, more preferably 20% to 40% by weight of the first colorant, based on the first molding compound. The at least one additional molding compound preferably comprises 0.1% to 6% by weight of the at least one further colorant, more preferably 0.2% to 4% by weight of the at least one further colorant, based on the at least one additional molding compound.

[0081] By means of the concentration ratios mentioned, good recognizability and definition of the marble pattern is ensured, which contributes to the reproducibility of the pattern.

[0082] The second amount may comprise one or more further moulding compounds. The first polymer compound and / or the at least one further polymer compound are preferably thermoplastic moulding compounds. More preferably, the first polymer compound and / or the at least one further polymer compound comprise a polymer selected from the group consisting of: polypropylene (PP), polyethylene (PE), polyoxymethylene (POM), polyethylene terephthalate (PET), polybutylenterephthalat (PBT), polyamide (PA), polycarbonate (PC), polyarylethersulfonen (PSU, PESU, PPSU), thermoplastic polyurethane (TPU), polybutylene terephthalate ( The first molding compound may be a filler or reinforced molding compound. More particularly, the at least one further molding compound and optionally the first molding compound may include at least one filler such as talc, glass beads or fibers such as glass fibers or carbon fibers.

[0083] More preferably, the polymer present in the first polymer compound is also present in at least one additional polymer compound. Further preferably, the first polymer compound and / or the at least one additional polymer compound comprise PBT; more preferably, the first polymer compound and the at least one additional polymer compound comprise PBT.

[0084] During the method, the first colorant and / or the at least one additional colorant may be soluble or insoluble in the first molding compound and / or the at least one additional molding compound. The first colorant and / or the at least one additional colorant are preferably color pigments. The first colorant is preferably a black colorant. The first colorant preferably comprises carbon black or a diaminophenazine compound (such as aniline black). More preferably, the first colorant comprises carbon black or at least one diaminophenazine compound (such as aniline black). The at least one additional colorant is preferably a blue colorant, a green colorant, a yellow colorant, a red colorant, a beige colorant, an orange colorant, a white colorant, a gray colorant, a brown colorant or a gold colorant.

[0085] The viscosity of the first molding compound and / or the at least one further molding compound (each in plasticized form) is preferably in the range of 50 Pa·s to 1000 Pa·s. The injection rate of the plasticized molding compound from the nozzle into the mold is preferably greater than 25 cm 3 / s, more preferably from 50cm 3 / s to 100cm 3 / s, especially from 60cm 3 / s to 80cm 3 / s, for example 70cm 3 The dynamic pressure generally refers to the pressure of the free space in the barrel, and is preferably 1 bar to 100 bar, more preferably 10 bar to 70 bar, further preferably 20 bar to 50 bar.

[0086] The nozzle temperature is preferably 150° C. to 450° C., more preferably 180° C. to 400° C. The temperature of the first molding compound and the at least one further molding compound at the screw tip is preferably between 150° C. and 450° C., more preferably 180° C. to 400° C. The injection pressure is preferably 400 bar to 1000 bar.

[0087] The nozzle head preferably has 2 to 8, more preferably 3 to 8, more preferably 3 to 6, for example 3, 4 or 6, channels, which may also be referred to as holes, passages or apertures. Preferably, the centers of the radial cross-sections of the channels are equidistant from one another. The shape, number and arrangement of the channels influence the geometry of the resulting marble pattern. Preferably, at least two channels are connected to the first end of each channel via a through hole in the nozzle body, the through hole in the nozzle body being connected to the interior of the hollow barrel. Here, "connected" should be understood as fluidly connected, which may also be referred to as flow.

[0088] Preferably, the channels are separated from one another between their first end and their second end. More preferably, at least two channels each open separately via their first end to the front end face of the nozzle head and via their second end to the rear end face of the nozzle head. More specifically, at least two channels do not have any passages and / or holes leading to one another between their first end and their second end. Accordingly, preferably, no exchange of plasticized molding compound between the channels occurs in the nozzle head; instead, the plasticized molding compound comprising the first molding compound and at least one further molding compound is pushed separately through the separate channels. Accordingly, preferably, no additional mixing occurs in the channels. Thus, the two separate channels prevent homogeneous mixing of the first molding compound with the further molding compound, which facilitates reproducibility.

[0089] At least in the method according to the invention, the at least two channels can extend straight and / or along a curved path through the nozzle head, or can each form a spiral, in particular at least partially form a spiral. In the device according to the invention for producing marbled molded parts, the at least two channels extend through the nozzle head in a curved manner. Preferably, in the method according to the invention, the at least two channels extend through the nozzle head in a curved manner. Further preferably, the at least two channels extend through the nozzle head in an at least partially curved manner, i.e., only partially or completely.

[0090] When at least two channels extend straight through the nozzle tip, these channels can also be referred to as straight bores. The channels are preferably parallel to the longitudinal axis of the nozzle tip, preferably parallel to the longitudinal axis of the barrel. It is also possible for the at least two straight channels to extend obliquely relative to the longitudinal axis of the nozzle tip. This inclination imparts a slight distortion to the plasticized molding compound.

[0091] Furthermore, the channels can also have different cross-sectional geometries and / or different cross-sectional dimensions.

[0092] In a preferred embodiment, at least two channels each form a spiral at least in part. Within the scope of the present invention, a spiral should be understood as a three-dimensional spiral, which can also be referred to as a helix. The spirals formed by the at least two channels, respectively, impose distortion on the plasticized molding compound, which is reflected in the marble pattern of the molding compound produced. More specifically, at least two channels each have a central axis, wherein the central axis of the corresponding channel in the form of a spiral is arranged around the longitudinal axis of the nozzle head. Further preferably, the central axes of the at least two channels at each position are arranged at the same distance from each other, and further preferably, are arranged at the same distance from the longitudinal axis of the nozzle head. In addition, the distance between the central axes of the at least two channels can also vary and can increase or decrease in the conveying direction. In each case, the central axis extends through the center of the cross-sectional area of the corresponding channel. The spiral can be rotated to the right or to the left in the conveying direction.

[0093] The spirals formed by each of the at least two channels preferably have the same geometry, such as slope and number of turns, and are offset from each other by a radial angle relative to the longitudinal hot runner axis. The slope (especially the slope angle, for example, with a constant slope and a constant diameter) is defined as follows:

[0094]

[0095] Wherein, α is the slope angle, S is the distance of one complete turn in the longitudinal axis direction of the nozzle tip, which may be referred to as the pitch height, and D is the diameter of the helical portion.

[0096] The helical portion preferably has a slope of less than 70° at at least one location.

[0097] The spiral portion (formed in each case by one of the at least two channels) can have a constant slope. The constant slope is preferably in the range of 5° to less than 60°, further preferably in the range of 10° to 40°, and particularly preferably in the range of 15° to 30°. For example, the constant slope is 20°.

[0098] Preferably, the spiral portion has a different slope at each of the at least two different positions. Preferably, the at least two different positions on the spiral portion have different distances from the outlet leading to the nozzle. Preferably, a first slope of the spiral portion at a first position differs from a second slope of the spiral portion at a second position by at least 20°; preferably, the difference between the first slope and the second slope (especially the maximum difference) is greater than 30° and less than 90°, for example 60°.

[0099] Preferably, the slope of the spiral decreases in the direction of the nozzle outlet. For example, the slope of the spiral can change from a first position (e.g., at the second end face, relatively close to the hollow barrel) of greater than 70° to a second position (closer to the nozzle outlet) of less than 30°, such as in the conveying direction of the plasticized molding compound. The change (especially a continuous change) from a high slope to a gentle slope in the conveying direction of the plasticized molding compound can achieve good flow entry while simultaneously imparting a significant distortion at the outlet of at least two channels.

[0100] Preferably, the helix has a number of turns, which can also be referred to as turns, and the number of turns is further preferably in the range of greater than 0.25 to 5. Correspondingly, the helix preferably covers a rotation angle of greater than 90° to 180°. Further preferably, the number of turns is in the range of greater than 0.25 to 3, in particular in the range of greater than 0.50 to 3, for example in the range of 0.51 to 2.

[0101] When at least two (preferably at least three, more preferably exactly three) channels are in the form of a spiral, in a further embodiment, the first end of each channel is preferably radially offset relative to the second end of the channel by an angle of 45° to 180°, more preferably by an angle of 90° to 180°, particularly preferably by an angle of 110° to 130°, for example 120°. Channels in the form of a spiral can also be referred to as twisted holes.

[0102] When the at least two channels each at least partially form a helix, the at least two channels can each be designed, for example, as a screw blade or a twisted bore, which can also be referred to as a curved bore.

[0103] If the at least two channels are designed as screw blades, the portion of the nozzle head that separates the at least two channels from one another can form a plurality of blades. More preferably, the number of blades is equal to the number of the at least two channels, in which case the at least two channels are separated from one another in cross section by a bridge.

[0104] The design of the at least two channels (preferably at least three, more preferably exactly three) can also be described as a multi-blade (preferably three-blade) bridge (rotating radially along the central longitudinal axis of the nozzle) being arranged in a cylindrical bore, in particular a cylindrical flow channel bore. It is further preferred that the at least two channels are delimited by two coaxially arranged cylinders, each of which is part of the corresponding outer surface. More preferably, the at least two channels are delimited by the same two coaxially arranged cylinders.

[0105] The at least two channels may have different cross-sectional geometries and / or different cross-sectional dimensions. The at least two channels preferably have the same cross-sectional geometry and the same cross-sectional dimensions.

[0106] Preferably, the channels each have a circular, elliptical, ring segment-shaped or polygonal (such as a hexagon or triangle) cross section in a radial cross section of the nozzle head, preferably a triangular cross section. The triangular cross section may have at least one curved side line. The triangular cross section with at least one curved side line (preferably, when at least two channels are implemented, preferably when at least three channels are implemented, more preferably when exactly three channels are implemented) each takes the form of a spiral blade. The ring segment preferably covers an angle in the range of 100° to 180°. Specifically, when the number of at least two channels is at least four, the angle of the ring segment may be less than 100°. If the channel has a triangular cross section and the intermediate wall between at least two channels is designed as a spiral blade, this can also be described as providing the hot runner with a cylindrical central melt channel hole, in which a main shaft corresponding to a blade is arranged, which separates the at least two channels from each other. If the at least two channels are each designed as a twisted hole, then the at least two channels each preferably have a circular, elliptical or polygonal (such as a hexagon) cross section.

[0107] The cross-sectional area of the nozzle head portion (arranged with at least two channels) preferably has an opening ratio The porosity is the ratio of the area available for flow to the total area and ranges from 40% to 80%, more preferably from 50% to 75%. The porosity is preferably calculated based on the cross-sectional area (particularly the circular cross-sectional area), with the radius corresponding to the maximum distance of the walls of the at least two channels from the longitudinal axis of the nozzle head. For example, in the case of two channels, the porosity can be 68%, with each channel forming a spiral with a slope varying from 90° to 30°, while in the case of three channels, the porosity can be 51%, with each channel forming a spiral with a slope varying from 90° to 30°. Preferably, the flow areas of the first and second end faces leading into or out of the at least two channels are substantially the same size. Accordingly, the inlet and outlet areas of the at least two channels preferably differ from each other by less than 30%, more preferably by less than 10%, and particularly preferably by less than 5%, based on the inlet area. This applies to both the individual channels of the at least two channels and the sum of the inlet and outlet areas of the at least two channels.

[0108] The nozzle head can be in single-piece or multi-piece form. More specifically, "single-piece" means that the single-piece component is produced from a continuous material, in particular without any connections (e.g. welds and / or welding seams). For example, the walls of at least two channels (in particular when they are designed as blades) can be molded onto the hollow cylindrical basic shape of the insert or onto a centrally positioned solid cylindrical part of the insert. Continuous material is understood to mean a material with a homogeneous composition over the entire single-piece component. The single-piece component in particular does not consist of multiple layers or multiple components and / or does not have a coating made of other materials.

[0109] The nozzle head preferably includes an insert, preferably a cylindrical body, with at least two channels preferably arranged in the insert. Thus, nozzle heads with inserts having channels arranged in different patterns can be used, allowing for a high degree of flexibility in designing marble patterns within the machine. Different inserts can be interchanged within the nozzle head as needed. The insert is preferably designed to precisely fit within the preferably central cylindrical bore in the nozzle head. The use of inserts allows for the rapid, sequential production of different marble patterns within the same screw injection machine.

[0110] The insert is further preferably a single-piece component. Specifically, the outer surfaces (preferably all outer surfaces) of at least two channels are preferably completely closed and bounded by the single-piece insert. In a cross-section of the at least two channels, the first and second end surfaces are unaffected by the material of the insert, allowing plasticized molding compound to pass through the first and second end surfaces.

[0111] Furthermore, a method for producing the device according to the present invention is proposed, in which at least the nozzle head or at least the insert is manufactured using an additive method, in particular by 3D printing. Using an additive method to produce at least two channels enables the production of more complex channels, in particular curved spiral channels, such as those formed as helical blades. Furthermore, similar to cast components, this production method produces a surface roughness that positively influences the marble pattern. Preferably, the layers produced using the additive method have a layer height of 0.08 mm to 0.2 mm, for example, a layer height of 0.1 mm.

[0112] Furthermore, additively producing the device according to the invention, or at least the nozzle head, or at least the insert, allows for the production of undercuts, thereby achieving a larger flow area for at least two channels. In the context of the present invention, undercuts are understood to mean an increase in the diameter of the insert melt channel in the conveying direction. More specifically, the centrally arranged insert melt channel (arranged on the second end face) can have an increasing diameter in the conveying direction.

[0113] The additive method can also produce channels, wherein at least two channels have an undercut and in particular each channel has a turn greater than 0.5. Undercuts of at least two channels are to be understood to mean that the cross sections of the channels do not overlap at the first and second end faces on the axial projection.

[0114] Laser welding methods or melt layering methods such as fused deposition modeling (FDM) or fused filament fabrication (FFF) can be used as additive methods. To produce the nozzle or nozzle components (in particular at least the nozzle head or at least the insert), a metal injection molding feedstock (MIM feedstock) (e.g. ) as material. The MIM feedstock includes different types of steel, such as stainless steel or tool steel, so that the produced single-piece components (particularly inserts) can be specifically matched to the end use.

[0115] Preferably, the nozzle, nozzle tip, and / or at least the insert are produced from a metal-containing powder. More preferably, the nozzle, nozzle tip, and / or at least the insert are produced from a composition comprising: 30% to 70% by weight, more preferably 40% to 60% by weight, of at least one inorganic powder; and 30% to 70% by weight, more preferably 40% to 60% by weight, of at least one binder. The particle size of the at least one inorganic powder is preferably from 0.5 μm to 50 μm, more preferably from 0.1 μm to 30 μm. Furthermore, the at least one inorganic powder preferably comprises a precursor compound of a metal, a metal alloy, a ceramic material, or a mixture thereof. More preferably, the at least one inorganic powder preferably comprises a precursor compound of a metal, a metal alloy, a ceramic material, or a mixture thereof. The at least one binder preferably comprises a polymer composition (particularly POM). More preferably, the at least one binder comprises POM. The composition can be used in granular or filamentary form.

[0116] The nozzle can be designed as a needle valve nozzle or an open nozzle. An open nozzle comprises a nozzle head and a nozzle body, which have a single straight central bore. The nozzle body of a needle valve nozzle comprises a receiving device for a needle, which is preferably connected to the nozzle body via two bridges.

[0117] In addition to the insert, the nozzle head can also have one, two or more disks, which serve to position and / or fix the insert in the nozzle head. Particularly preferably, the insert is arranged between two disks. The disk preferably has a central hole.

[0118] To carry out the method according to the invention for producing a reproducibly marbled moulding, any type of nozzle can be used. Depending on the configuration of the nozzle, different marble patterns can be produced on the moulding.

[0119] For example, using a needle valve nozzle can even produce a highly pronounced marble pattern. The exact form of the marble pattern is influenced by the geometry of the needle valve nozzle holder and, as well as the configuration of the screw tip. Due to the different internal screw geometry, the weld seams produced in the plasticized molding compound are also different, which is crucial in determining the marble pattern.

[0120] Nozzle tips with at least two channels can be used in combination with open nozzles.Nozzle tips with a central hole can be used in combination with needle valve nozzles.

[0121] More specifically, the outer diameter of the nozzle is smaller than the outer diameter of the hollow barrel. The nozzle head is detachably connected to the hollow barrel, in particular by a screw connection. Furthermore, at least at one point, the inner free cross-sectional area of the nozzle is smaller than the inner free cross-sectional area of the hollow barrel. Depending on the product to be produced, the hollow barrel has different inner diameters. For example, the inner diameter ranges from 10 mm to 150 mm or from 25 mm to 50 mm, such as 25 mm or 30 mm. The outlet has a channel, for example, with a diameter of 1.5 to 10 mm, or 3 to 6 mm, such as 5 mm.

[0122] When using an open nozzle without at least two channels, a circular, uniform distribution of color is visible. The optical effect produced by using only an open nozzle can be described as concentric circles. If at least two (e.g., three, four, or six) channels are used, the circular structure is disrupted, and a slight turbulence of the first molding compound in at least one additional molding compound is visible. The number of streaks that are visible corresponds to the number of channels that create the flow lines.

[0123] By designing at least two channels as spirals with a circular or oval radial cross section, the turbulent flow of the first molding compound in the at least one further molding compound is intensified. If the at least two channels are each designed as screw blades, the wave pattern in the form of stripes is formed into a marble pattern with very good reproducibility.

[0124] If the hollow barrel is supplied not only with the first molding compound but also with at least two further molding compounds, each further molding compound may comprise a further polymer compound and optionally at least one further colorant. The further molding compound may be added to the barrel together with the at least one further molding compound, or the further molding compound may be added to the barrel before or after the at least one further molding compound, optionally directly before or after the at least one further molding compound. The at least two further molding compounds may also be fed in sequentially. BRIEF DESCRIPTION OF THE DRAWINGS

[0125] Working embodiments of the present invention are shown in the accompanying drawings and will be described in more detail in the following description. The present invention is not limited to the working embodiments described herein and the aspects emphasized therein. On the contrary, many possible modifications are within the capabilities of those skilled in the art within the scope of the claims. The accompanying drawings show:

[0126] Figure 1 shows a first schematic diagram of a screw injection molding machine,

[0127] Figure 2shows a second schematic diagram of a screw injection molding machine,

[0128] Figure 3 shows the details of the screw injection molding machine,

[0129] Figure 4 shows the nozzle head,

[0130] Figure 5 Showing the details of the nozzle head,

[0131] Figure 6 A radial cross section showing details of the nozzle tip,

[0132] Figure 7 Another radial cross-section showing a detail of the nozzle head,

[0133] Figure 8 Another embodiment of the nozzle head is shown,

[0134] Figure 9 A radial cross section showing a detail of another embodiment of a nozzle head,

[0135] Figure 10 shows details of another embodiment of the nozzle head,

[0136] Figure 11 A radial cross section showing a detail of another embodiment of a nozzle head,

[0137] Figures 12 to 21 a top view or a perspective view showing different embodiments of at least two channels,

[0138] Figures 22 to 27 A top view, a perspective view or a longitudinal section respectively showing two further embodiments of at least two channels, and

[0139] Figure 28 An insert with undercuts is shown. DETAILED DESCRIPTION

[0140] Figure 1 A schematic diagram of a screw injection molding machine 7 is shown, which includes an injection unit 5. The injection unit 5 includes a hollow barrel 11, a screw 13 with a screw tip 15, and a nozzle 17 having a nozzle head 37 and a nozzle body 39. The screw 13 is rotatable and is arranged in the direction of the longitudinal axis 19 of the barrel 11. The screw 13 is in a rear position 23 in the hollow barrel 11, with a distance 25 between the nozzle 17 and the screw tip 15, so that a free space 27 is present in the hollow barrel 11 between the nozzle and the screw tip 15.

[0141] The nozzle 17 has a nozzle head 37, a nozzle body 39 and an outlet 40 and is adjacent to an injection mold 9 having a cavity 29 with an interior volume 33. Furthermore, the injection mold 9 has an inlet port 8 into the injection mold 9 and an inlet port 6 into the cavity 29.

[0142] The screw 13 has a metering zone 47, a compression zone 49, and a feed zone 51. The hollow barrel 11 has a longitudinal axis 19. The screw 13 can be used to convey the molding compound in a conveying direction 52 into the free space 27. The free space 27 is a portion of the interior 35 of the hollow barrel 11, which is bounded by the hollow barrel 11 and the screw 13.

[0143] Figure 2 A second schematic diagram shows a screw-type injection molding machine 7 having an injection mold 9, which essentially corresponds to Figure 1 However, according to Figure 2 The screw 13 is in the front position 21 in the hollow barrel 11. Figure 1 In comparison, the distance 25 has been reduced due to the advancement of the screw 13 .

[0144] Figure 3 Detail of the injection molding machine 7 is shown. A portion of the feed zone 51 of the screw 13 present in the hollow barrel 11 is shown. The barrel 11 has a longitudinal axis 19 along which the screw 13 is movable. Figure 3 , the screw 13 is in the rear position 23. A portion of the screw 13 is located below the feed opening 53. In the embodiment shown, the first molding compound and the further molding compound 3 are fed to the screw 13 through the feed opening 53. The feed opening 53 has a first area for feeding the first molding compound 1 and a second area 57 for feeding the further molding compound 3. By means of a cover 59, a second distance 61 is provided between the first area 55 and the second area 57, by means of which the first molding compound 1 and the further molding compound 3 are fed in spatially separated.

[0145] Figure 4 The nozzle head 37 of the nozzle 17 is shown with an outlet 40. An insert 42 having three channels 41 is arranged in the nozzle head 37. Each channel 41 is designed as a spiral blade. Each channel 41 has a first end 43 and a second end 45. The first end 43 of each channel 41 communicates with the outlet 40, and the second end 45 of each channel 41 communicates with the interior 35 of the hollow barrel 11, which is detachably connected to the nozzle 17. Figure 4 The hollow barrel 11 is not shown; it adjoins the nozzle 17 on its side facing away from the outlet 40 .

[0146] Figure 5Shown according to Figure 4 A half-section view of an insert 42 arranged in a nozzle head 37 is shown.

[0147] Figure 6 Shown according to Figure 4 and Figure 5 Detail of the nozzle head 37 in radial cross section. The insert 42 has three channels 41 , of which the first ends 43 are visible, each channel having a triangular cross section 63 .

[0148] Figure 7 Shown according to Figure 5 4 shows a radial cross-section of an insert 42. The triangular cross-section 63 of the channel 41 is visible as a solid line in a first viewing plane. The channel 41 with the triangular cross-section 63 is also visible as a dashed line in another plane, below the first viewing plane, so that the path of the channel 41 in the insert 42 can be seen. Bridges 65 separate the channels 41 from one another.

[0149] Figure 8 A further embodiment of a nozzle head 37 is shown. An insert 42 having four straight bores as channels 41 is arranged in the nozzle head 37 .

[0150] Figure 9 Shown according to Figure 8 The radial cross section of the insert 42 is shown in FIG.

[0151] Figure 10 Another embodiment of the nozzle head 37 is shown. The detail shows another insert 42 that can be arranged in the nozzle head 37. The insert 42 has three channels 41. The three channels 41 have a circular cross section 63, and each channel has a helical curvature. The first end 43 of each channel 41 is radially offset by 120° relative to the second end 45 of the channel 41. The first end 43 of each channel 41 communicates with the outlet 40 of the nozzle 17 (in which the insert 42 is arranged), and the second end 45 of each channel 41 communicates with the interior 35 of the hollow barrel 11, which is detachably connected to the nozzle 17 and is in a Figure 10 Not shown in the figure.

[0152] Figure 11 Shown according to Figure 10 Radial cross section of the insert 42. The circular cross sections 63 of the three channels 41 are visible.

[0153] Figures 12 to 21 Five additional embodiments of the insert 42 are shown, each shown in top view or perspective view. Figures 12 to 21In the embodiment, the channels 41 each form a spiral 75 , while the central axis 67 of each channel 41 is arranged in the form of a spiral 75 and has a specific number of turns 50 .

[0154] according to Figure 12 and Figure 13 , the insert 42 has three channels 41 separated from one another by a solid cylinder 79. The slope of the spiral 75 decreases in the conveying direction 52 (i.e., from the second end 45 to the first end 43 of each channel 41). The first position 44 has a greater slope than the second position 48. The slope changes from approximately 90° to a relatively gentle slope of approximately 30°. This results in a favorable entry in terms of flow and a significant distortion, which is applied to the plasticized molding compound at the outlet (i.e., at the first end 43 of each channel 41). There is a constant free cross-section 63 and thus a constant open area. The spirals 75 each have a half turn 50, so that the bridge 65 between two channels 41 is rotated 180° compared to the first end 43 and the second end 45.

[0155] according to Figure 14 and Figure 15 The insert 42 corresponds to the Figure 12 and Figure 13 The insert 42, except according to Figure 14 and Figure 15 The insert 42 presents only two channels 41 .

[0156] according to Figure 16 and Figure 17 The insert 42 corresponds substantially to Figure 14 and Figure 15 The insert 42, except according to Figure 16 and Figure 17 The helical portion 75 of the insert 42 has a constant slope, and each helical portion 75 has about one-third of a complete turn 50, so that the bridge portion 65 is rotated about 120° toward the second end 45 compared to the first end 43. The slope is about 60°.

[0157] according to Figure 18 and Figure 19 The insert 42 corresponds substantially to Figure 16 and Figure 17 The insert 42, except according to Figure 18 and Figure 19 The helical portion 75 of the insert 42 has 1.5 turns 50 , so that there is a slope of approximately 20°.

[0158] according to Figure 20 and Figure 21 The insert 42 is similar to the Figure 12 and Figure 13There are three channels 41, each in the form of a spiral portion 75, the three channels 41 having a greater slope in the first position 44 than in the second position 48. Figure 20 and 21 The channels 41 of the insert 42 each partially form a spiral portion 75, and the first end 43 of the channel 41 opens into the first end face 83. Another portion of the channel 41 extends straight, opening from the second end 41 into the second end face 81. In addition, the channel 41 has a hexagonal cross section 63.

[0159] Figure 22 、 Figure 23 and Figure 24 The insert 42 shown in top view, perspective view and longitudinal section in FIG. 1 corresponds substantially to Figure 25 、 Figure 26 and Figure 27 The insert 42 shown in FIG. Figure 22 、 Figure 23 and Figure 24 The channel 41 of the insert 42 in the embodiment has a constant elliptical cross section 63. Due to the elliptical shape of the constant cross section 63, a higher open porosity is achieved in the cross section 63 compared to a partially circular cross section 63.

[0160] Figure 25 、 Figure 26 and Figure 27 The insert 42 shown in FIG corresponds to Figure 22 、 Figure 23 and Figure 24 Insert 42, except Figure 25 、 Figure 26 and Figure 27 The channel 41 of the insert 42 shown in FIG has a variable cross-section 63. The channel 41 has a circular cross-section 63 at the second end 45 and also along the straight portion of the channel 41. In the spiral portion 75, as the slope of the central axis 67 of the channel 41 increases relative to the longitudinal axis 19, the cross-section 63 changes from a circular shape to an oblate oval shape.

[0161] Figure 28 Insert 42 is shown with an undercut 91. Insert 42 includes three channels 41, each forming a spiral portion 75 with a variable slope. In insert 42, insert melt channel 85 terminates at second end face 81 of channel 41 in conveying direction 52. Insert melt channel 85 has undercut 91, so that first diameter 87 of insert melt channel 85 is smaller than second diameter 89 of insert melt channel 85 at second end face 81. Consequently, diameters 87, 89 of insert melt channel 85 increase in conveying direction 52.

[0162] Example

[0163] Example 1 Shell Production

[0164] To produce jelly shells on a hydraulic injection molding machine with a clamping force of 1000 kN, the hydraulic injection molding machine includes a barrel with an inner diameter of 30 mm. A first amount of a first molding compound is provided for each shell (i.e., for each shot). The first molding compound consists of black particles, includes carbon black as a black colorant, and has a concentration of 25% by weight in PBT. The mass of the first amount is 0.03 g.

[0165] In addition, a second amount of another molding compound is provided for each shell. The second amount is 55.32 g. Each second amount of the other molding compound includes 55 g of uncolored PBT granular material and 0.32 g of a colored PBT granular material containing a concentrated form of another colorant. The other molding compound is in the form of a granular mixture, with the uncolored PBT granules and the colored PBT granules premixed in the other molding compound.

[0166] Ten shells were produced in succession, and thus this process was repeated several times.

[0167] A first amount of the first molding compound is fed to the screw in the rear position, the empty blades of the screw being visible at the feed port. The screw is then moved to the front position towards the nozzle for injection.

[0168] Next, a second amount of the other molding compound is added to the screw. When the screw is in the forward position within the hollow barrel, the second amount of the other molding compound begins to be added. The screw rotates, plasticizing the first and second molding compounds until the screw retracts to the rearward position. Once plasticization is complete, the screw stops rotating.

[0169] Then, a first amount of the first molding compound is fed to the screw again. The plasticized molding compound is then injected into the injection mold, for which the screw is moved back (i.e., advanced) to the front position. After the injection, a second amount of another molding compound is added again and plasticization is performed again.

[0170] The correspondingly produced shells show a similar marble pattern, ie a repeatable marble pattern.

[0171] To produce 10 shells using the same process flow, the injection molding machine was configured differently, and the marble pattern was reproducible for each configuration. In each case, either a needle valve nozzle or an open nozzle was used. The nozzle tip included a single central hole, three straight holes, four straight holes, six straight holes, three channels each embodied as a spiral blade, or three channels each helically curved.

[0172] Example 2 Production of measuring cup

[0173] The multi-colored marbled measuring cups were produced in an electric injection molding machine with a clamping force of 1000 kN, a barrel with an inner diameter of 40 mm and an open nozzle. The process flow essentially corresponds to that of Example 1.

[0174] A first amount of the first molding compound (ie, for each shot) is provided to each measuring cup. The first molding compound also consists of black particles, and the mass of the first amount is 0.07 g.

[0175] In addition, a second amount of three additional molding compounds is provided for each measuring cup. The second amount is divided into three parts. The first part of the second amount contains a second molding compound composed of 68g of PBT granular material and 0.67g of concentrated blue PBT granular material. The second part of the second amount contains a third molding compound composed of 68g of PBT granular material and 0.67g of concentrated green PBT granular material. The third part of the second amount contains a fourth molding compound composed of 68g of PBT granular material and 0.67g of concentrated yellow PBT granular material. In summary, the molding compound provided corresponds to the mass of the measuring cup.

[0176] A first amount of the first molding compound is fed to the screw in the rear position, the empty blades of the screw being visible at the feed port. The screw is then moved to the front position towards the nozzle for injection of the molding compound already present on the screw.

[0177] After injection and before the start of plasticization, add the first part of the second amount. After the first third of the total plasticization duration, add the second part of the second amount. Continue plasticization and after the second third of the total plasticization duration, add the third part of the second amount.

[0178] After adding the third portion of the second amount, once the screw is no longer rotating and is in the rear position, the first amount of the first molding compound is added again.

[0179] Reference List

[0180] 1. First Molding Compound

[0181] 3 At least one additional molding compound

[0182] 5 Injection unit

[0183] 6 Entrance

[0184] 7 Screw injection molding machine

[0185] 8 Entrance

[0186] 9 Injection mold

[0187] 10 runners

[0188] 11 Hollow barrel

[0189] 13 screw

[0190] 15 Screw tip

[0191] 17 Nozzle

[0192] 19 longitudinal axis

[0193] 21 front position

[0194] 23 rear position

[0195] 25 Distance

[0196] 27 Free Space

[0197] 29 cavities

[0198] 31 Internal free volume

[0199] 33 Internal volume

[0200] 35 Internal

[0201] 37 nozzle tip

[0202] 38 through holes

[0203] 39 Nozzle body

[0204] 40 Exit

[0205] 41 channels

[0206] 42 Inserts

[0207] 43 first end

[0208] 44 First Position

[0209] 45 Second end

[0210] 47 Metering Area

[0211] 48 Second position

[0212] 49 Compression Zone

[0213] 50 laps

[0214] 51 Feeding Area

[0215] 52 Conveying direction

[0216] 53 Feeding port

[0217] 55 First Area

[0218] 57 Second Area

[0219] 59 Cover

[0220] 61 Second Distance

[0221] 63 cross section

[0222] 65 Bridge

[0223] 67 Central Axis

[0224] 75 spiral part

[0225] 79 solid cylinder

[0226] 81 Second end face

[0227] 83 First end surface

[0228] 85 Insert melt channel

[0229] 87 First Diameter

[0230] 89 Second diameter

[0231] 91 undercut

Claims

1. A method for producing a marbled molded part, wherein a first molding compound (1) and at least one further molding compound (3) are injected from an injection unit (5) of a screw injection molding machine (7) into an injection mold (9), in, The injection unit (5) comprises a hollow barrel (11), a screw (13) with a screw tip (15), and a nozzle (17), wherein the screw (13) is rotatable and movable in the direction of the longitudinal axis (19) of the hollow barrel (11) between a front position (21) and a rear position (23), the distance (25) between the screw tip (15) and the nozzle (17) being smaller in the front position (21) than in the rear position (23), wherein the first molding compound (1) comprises a first polymer compound and a first colorant, and the at least one additional molding compound (3) comprises another polymer compound, The method comprises the following steps: a) feeding a first amount of the first molding compound (1) onto the screw (13) when the screw (13) is in the rear position (23), b) advancing the screw (13) from the rear position (23) to the front position (21), c) feeding a second amount of the at least one further molding compound (3) onto the screw (13), d) plasticizing the first molding compound (1) and the at least one further molding compound (3) in the hollow barrel (11) of the screw (13), rotating the screw (13) and conveying at least a portion of the first molding compound (1) and at least a portion of the at least one further molding compound (3) into a free space (27) in the hollow barrel (11) between the nozzle (17) and the screw tip (15), and moving the screw (13) from the front position (21) to the rear position (23), e) feeding a new first amount of said first molding compound (1) onto said screw (13) when said screw (13) is in said rear position (23), f) injecting the first molding compound (1) and the at least one further molding compound (3) from the free space (27) of the hollow barrel (11) into the cavity (29) of the injection mold (9), the screw (13) advancing from the rear position (23) into the front position (21), g) cooling the first molding compound (1) and the at least one further molding compound (3) in the injection mold (9) to form a marbled molding, h) removing the marbled molding from the injection mold (9), wherein steps c) to h) are repeated, step e) is performed before step f), and step a) is performed before step b), and wherein feeding the new first amount of the first molding compound in step e) and feeding the first amount of the first molding compound in step a) are performed temporally or spatially separated from feeding the second amount of the at least one further molding compound in step c), and wherein feeding the second amount of the at least one further molding compound (3) in step c) is performed after the advancing in step b); wherein the nozzle (17) comprises a nozzle head (37) and a nozzle body (39), the nozzle (17) is detachably connected to the hollow barrel (11), and the nozzle head (37) has at least two channels (41), the at least two channels (41) being connected to an outlet (40) of the nozzle (17) at a first end (43) of each channel (41) and being connected to an interior (35) of the hollow barrel (11) at a second end (45) of each channel (41), wherein the at least two channels (41) pass through the nozzle head (37) in a curved manner, wherein the channels (41) are separated from each other at their first ends (43), the channels (41) are separated from each other at their second ends (45), and the channels (41) are separated from each other between their first ends (43) and their second ends (45).

2. The method according to claim 1, characterized in that The ratio of the maximum internal free volume (31) of the hollow barrel (11) that can be occupied by the first molding compound (1) and the at least one additional molding compound (3) to the internal volume (33) of the cavity (29) is not greater than 10.

3. The method according to claim 1 or 2, characterized in that The ratio of the sum of the mass of the first amount of the first molding compound (1) and the mass of the second amount of the at least one further molding compound (3) to the mass of the marbled molding is 0.5 to 1.

5.

4. The method according to claim 1 or 2, characterized in that The mass ratio of the first amount to the second amount is less than 0.

1.

5. The method according to claim 1 or 2, characterized in that The mass ratio of the first amount to the second amount is less than 0.

001.

6. The method according to claim 1 or 2, characterized in that The at least one further molding compound comprises at least one further colorant, the ratio of a first concentration of the first colorant in the first molding compound (1) to another concentration of the at least one further colorant in the at least one further molding compound (3) being greater than 20.

7. The method according to claim 1 or 2, characterized in that The at least one further molding compound comprises at least one further colorant, the ratio of a first concentration of the first colorant in the first molding compound (1) to another concentration of the at least one further colorant in the at least one further molding compound (3) being greater than 50.

8. The method according to claim 1 or 2, characterized in that The first polymer compound and / or the at least one additional polymer compound include polymers selected from the group consisting of polypropylene (PP), polyethylene (PE), polyoxymethylene (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyamide (PA), polycarbonate (PC), polyarylethersulfone, thermoplastic polyurethane (TPU), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polylactide (PLA), polybutylene sebacate terephthalate (PBSeT), polyethylene naphthalate (PEN), polymethyl methacrylate (PMMA), and styrene-containing polymers.

9. The method according to claim 8, characterized in that The styrene-containing polymer is acrylonitrile-butadiene-styrene copolymer (ABS).

10. The method according to claim 1 or 2, characterized in that The first molding compound ( 1 ) and / or the at least one further molding compound ( 3 ) are each fed in in the form of granules.

11. The method according to claim 8, characterized in that The styrene-containing polymer is polystyrene (PS).

12. A device for producing marbled mouldings, comprising exactly one injection unit (5), said injection unit comprising a hollow barrel (11) with an interior (35), a screw (13) with a screw tip (15) and a nozzle (17), said device comprising exactly one hollow barrel (11), in, The screw (13) is rotatable and is arranged in the hollow barrel (11) so as to be movable in the direction of the longitudinal axis (19) of the hollow barrel (11) between a front position (21) and a rear position (23), the distance (25) between the screw tip (15) and the nozzle (17) being smaller in the front position (21) than in the rear position (23), and wherein the nozzle (17) comprises a nozzle head (37) and a nozzle body (39), the nozzle (17) is detachably connected to the hollow barrel (11), and the nozzle head (37) has at least two channels (41), the at least two channels (41) being connected to an outlet (40) of the nozzle (17) at a first end (43) of each channel (41) and being connected to an interior (35) of the hollow barrel (11) at a second end (45) of each channel (41), wherein the at least two channels (41) pass through the nozzle head (37) in a curved manner, wherein the channels (41) are separated from each other at their first ends (43), the channels (41) are separated from each other at their second ends (45), and the channels (41) are separated from each other between their first ends (43) and their second ends (45).

13. The device according to claim 12, characterized in that The nozzle head (37) has 3 to 8 channels (41).

14. The device according to any one of claims 12 to 13, characterized in that The channels (41) each have a circular, elliptical or triangular cross section (63) in a radial cross section of the nozzle head (37).

15. The device according to any one of claims 12 to 13, characterized in that The nozzle head (37) comprises an insert (42), and the channel (41) is arranged in the insert (42).

16. A method for producing a device according to any one of claims 12 to 15, characterized in that The nozzle head (37) or at least the insert (42) is produced by an additive method.

17. The method of claim 16, wherein the additive process is 3D printing.

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