METHOD FOR PRODUCE AN ADDITIVELY MANUFACTURED AND TREATED ITEM

Description

[0001] The present invention relates to a method for producing an object by additive manufacturing. The present invention further relates to an object produced by such a method.

[0002] Additive manufacturing processes are those methods used to build objects layer by layer. They therefore differ significantly from other methods of manufacturing objects, such as milling or drilling. In the latter methods, an object is processed by removing material to achieve its final geometry. Thus, an additive process is a building process, whereas conventional processes can be described as subtractive processes.

[0003] Based on materials such as polymers, which are predominantly used in powder-based additive manufacturing processes today, objects are created whose mechanical properties can differ fundamentally from the characteristics of materials known from other plastics processing methods, such as injection molding. During processing by additive manufacturing methods, the thermoplastic materials used lose their specific characteristics.

[0004] Polyamide 12 (PA12) is currently the most widely used material for powder-based additive manufacturing processes, such as laser sintering. PA12 is characterized by high strength and toughness when processed by injection molding or extrusion. For example, a standard PA12 exhibits an elongation at break of more than 200% after injection molding. In contrast, PA12 objects manufactured using laser sintering show elongations at break of around 15%. The component is brittle and can therefore no longer be considered a typical PA12 component. The same applies to polypropylene (PP), which is offered as a powder for laser sintering. This material also becomes brittle and thus loses the tough-elastic properties typical of PP; the reasons for this lie in the morphology of the polymers.

[0005] During the melting process using lasers or IR, and especially during cooling, an irregular internal structure develops in so-called semi-crystalline polymers (e.g., PA12 and PP). The internal structure (morphology) of semi-crystalline polymers is sometimes characterized by a high degree of order. A certain proportion of the polymer chains form tightly packed, crystalline structures upon cooling. During melting and cooling, these crystallites grow irregularly at the boundaries of the incompletely melted particles, at the former grain boundaries of the powder particles, and at additives contained in the powder. The irregularity of the resulting morphology promotes crack formation under mechanical stress. The residual porosity, which is unavoidable in powder-based additive manufacturing processes, further promotes crack growth.

[0006] The resulting components exhibit brittle properties. For an explanation of these effects, see European Polymer Journal 48 (2012), pages 1611-1621. Elastic polymers based on block copolymers, also used in laser sintering, exhibit an atypical property profile when processed into objects as powders using additive manufacturing processes. Thermoplastic elastomers (TPEs) are currently used in laser sintering. Objects manufactured from currently available TPEs exhibit high residual porosity after solidification, and the original strength of the TPE material is not measurable in the finished object. In practice, these porous components are therefore subsequently infiltrated with liquid, curing polymers to achieve the required property profile.Despite the aforementioned additional measures, the strength and elongation remain at a low level. The additional processing costs, in addition to the still inadequate mechanical properties, result in poor economic viability for these materials.

[0007] In laser sintering processes using polymer particles, these are typically processed in a closed volume or chamber so that the particles can be processed in a heated atmosphere. This reduces the temperature difference that must be overcome for the particles to sinter under laser influence. Generally speaking, the thermal properties of the polymer influence the possible processing temperatures in laser sintering processes. Therefore, various solutions for such polymers and their processing methods have been proposed in the prior art.

[0008] US 2005 / 0080191 A1 relates to a powder system for use in solid free-form manufacturing processes, comprising at least one polymer with reactive and fusible properties, wherein the at least one polymer is selected to react with a liquid binder and is fusible at a temperature above the melting point or glass transition temperature of the at least one polymer. The at least one polymer may comprise at least one reactive polymer and at least one fusible polymer, and the at least one fusible polymer may have a melting point or glass transition temperature in the range of approximately 50 °C to approximately 250 °C.

[0009] US 2018 / 229405 A1 discloses a method for manufacturing a 3D object that facilitates the removal of support material from the object. The method involves moving the object to a position opposite a microwave source and activating the microwave source to change the phase of the support material from solid to liquid. A controller monitors either the elapsed time or the object's temperature to determine when to stop activating the microwave source. The microwave irradiation does not damage the object because the support material has a dielectric loss factor greater than that of the object.

[0010] US 2016 / 074911 A1 describes a washing device for 3D-printed articles for removing support material from the article, comprising a washing unit and a soaking unit, wherein the soaking unit includes a chamber for holding an article to be soaked, a pump for circulating a soaking liquid through the chamber, and a heater with thermostatic control for heating the soaking liquid to a predetermined temperature for circulation through the chamber; and wherein the washing unit includes a housing that defines a washing chamber with at least one liquid ejection nozzle for spraying an article contained therein with a washing liquid.

[0011] In the current state of the art, there is still a need for additive manufacturing processes in which the resulting components have homogeneous material properties.

[0012] It is therefore the object of the present invention to overcome, at least in part, the disadvantages known from the prior art. In particular, it is the object of the present invention to provide a means by which, in particular, high stability of the manufactured components, especially also parallel to a layer direction, and / or homogeneous component properties can be achieved.

[0013] The problem is solved according to the invention by a method having the features of claim 1. Preferred embodiments of the invention are described in the dependent claims, in the description or the figures, wherein further features described or shown in the dependent claims or in the description or the figures can individually or in any combination constitute an object of the invention unless the context clearly indicates otherwise.

[0014] The present invention relates to a method for producing a treated object comprising the steps of: a) Producing the object using additive manufacturing, wherein The object is produced by repeatedly arranging at least one first material on a substrate in a spatially selective manner, layer by layer, corresponding to a cross-section of the object. The process is further defined as follows: b) at least partial contact of the additively manufactured item, which is still on the substrate or has already been detached from the substrate, with a powder bed of a second material heated to ≥ T for a time ≥ 1 min, preferably for a time of ≥ 1 min to ≤ 2 h, in order to obtain the treated item, where - T stands for a temperature of ≥ 25 °C, preferably ≥ 50 °C, more preferably ≥ 75 °C, particularly preferably ≥ 150 °C.

[0015] The contact of the obtained item with the powder bed according to process step b) is carried out for a period of time ranging from ≥ 1 minute to ≤ 174 hours. Preferably, the contact of the obtained item with the powder bed according to process step b) can be carried out for a period of time ranging from ≥ 10 minutes to ≤ 48 hours, more preferably from ≥ 15 minutes to ≤ 24 hours, and more preferably from ≥ 20 minutes to ≤ 8 hours.

[0016] Furthermore, a method for producing a treated article is disclosed, comprising the steps: a) Producing the object using additive manufacturing, wherein The object is produced by repeatedly arranging at least one first material on a substrate in a spatially selective manner, layer by layer, corresponding to a cross-section of the object. The process is further defined as follows: b) at least partial contact of the additively manufactured object, which is still on the substrate or has already been detached from the substrate, with a liquid made of a second material heated to ≥ T for a time ≥ 1 min, preferably for a time of ≥ 1 min to ≤ 2 h, in order to obtain the treated object, wherein - T stands for a temperature of ≥ 25 °C, preferably ≥ 50 °C, more preferably ≥ 75 °C, particularly preferably ≥ 150 °C.

[0017] The contact of the received object with the liquid according to process step b) is carried out for a period of time ranging from ≥ 1 minute to ≤ 174 hours.

[0018] For example, during the treatment durations described above, particularly for a treatment duration of ≥ 1 minute to ≤ 72 hours, the treatment of the object in process step b) may also involve a change in the temperature T of the powder bed or the liquid, preferably during process step b), and the temperature curve may optionally include temperatures from -190°C to +2000°C. This can enable a particularly adaptive treatment, allowing for responses to, or consideration of, changing properties of the object during the treatment.

[0019] Such a process allows for the particularly advantageous production of an object by means of additive manufacturing, whereby

[0020] The manufactured object exhibits high stability and homogeneous properties. The present invention thus relates to a method for manufacturing an object by additive manufacturing. The object to be manufactured is not fundamentally limited. In particular, additive manufacturing effectively allows for the production of a wide variety of objects for diverse applications, enabling unlimited geometries. Accordingly, the object to be manufactured is not subject to any limitation; rather, the method described here can, in principle, be used to form any object that can be produced by an additive process. However, the method described here is particularly preferred for objects that require high stability or homogeneous mechanical properties.

[0021] Regarding additive manufacturing, this is also not limited. In principle, this procedure can be used for any additive manufacturing process.

[0022] Additive manufacturing processes are those methods used to build objects layer by layer. They therefore differ significantly from other methods of manufacturing objects, such as milling or drilling. In the latter methods, an object is processed by removing material to achieve its final geometry.

[0023] Additive manufacturing processes utilize various materials and process techniques to build objects layer by layer. In fused deposition modeling (FDM), for example, a thermoplastic filament is melted and deposited layer by layer onto a movable build platform using a nozzle. As it solidifies, a solid object is formed. The nozzle and build platform are controlled based on a CAD drawing of the object. If the geometry of the object is complex, for example, with geometric undercuts, support materials must also be printed and then removed after the object is finished.

[0024] In addition, there are additive manufacturing processes that use thermoplastic powders to build objects layer by layer. Here, thin layers of powder are applied via a recoater and then selectively melted using an energy source. The surrounding powder supports the component geometry. This makes it more economical to manufacture complex geometries than with the previously described FDM process. Furthermore, various objects can be tightly packed within the so-called powder bed and manufactured accordingly. Due to these advantages, powder-based additive manufacturing processes are considered among the most economical additive manufacturing methods on the market. They are therefore predominantly used by industrial users. Examples of powder-based additive manufacturing processes include selective laser sintering (SLS) and high-speed sintering (HSS).They differ in the method used to introduce energy for selective melting into the plastic. In laser sintering, energy is introduced via a directed laser beam. In the so-called High Speed ​​Sintering (HSS) process, as described, for example, in EP 1648686, energy is introduced via infrared (IR) emitters in combination with an IR absorber selectively printed into the powder bed. Selective Heat Sintering (SHS) utilizes the printing unit of a conventional thermal printer to selectively melt thermoplastic powders.

[0025] Direct powder bed systems are known as laser melting processes and are commercially available under various trade names such as Selective Laser Melting (SLM), Laser Cusing, and Direct Metal Laser Sintering (DMLS). The only exception to this process principle is electron beam melting (EBM), which uses an electron beam under full vacuum. Welding equipment for metallic powder beds is currently available in Europe from Concept Laser GmbH, EOS GmbH, ReaLizer GmbH, Renishaw, and SLM Solutions GmbH. These companies offer a variety of systems based on the similar principle of selective laser melting but use different names for their respective processes. 3D Systems, based in the USA, also offers systems based on selective laser melting.Choosing the right machine depends on the end user's requirements, with the type of laser unit, powder handling, and build-up chamber being some of the main features of the system to be considered.

[0026] Arcam AB, based in Sweden, manufactures powder bed welding systems that use an electron beam as the energy source for the melting process. A hybrid system combining powder bed welding with CNC milling is offered by the Japanese company Matsuura.

[0027] Another system that utilizes a powder bed is the Höganäs Digital Metal process. Developed by fcubic, this system employs a precision inkjet printer to deposit a special "ink" onto a 45-micrometer-thick layer of metal powder. Another 45-micrometer layer of powder is applied, and the printing process is repeated until the component is complete. The part is then unbound and sintered to achieve its final size and strength. One of the advantages of this system is that the build process occurs at room temperature (RT, equivalent to 20°C) without the partial melting that occurs with laser or electron beam technologies. Furthermore, no support structures are required during the build, as these are supported by the powder bed itself.

[0028] Although powder feed systems use the same starting material, the way in which the material is added layer by layer differs considerably. The powder flows through a nozzle, where it is melted by a jet directly onto the surface of the part being treated.

[0029] Powder-feed systems are known as laser cladding, directed energy deposition, and laser metal deposition. The process is highly precise and based on the automated deposition of a material layer with a thickness ranging from 0.1 mm to several centimeters. The metallurgical bond between the cladding material and the base material, and the absence of undercutting, are some of the key features of this process. It differs from other welding techniques in that only a small amount of heat is applied to penetrate the substrate.

[0030] One development of this technology is the Laser Engineered Net Shaping (LENS) powder delivery system used by Optomec. This method allows material to be added to an existing part, meaning it can be used to repair expensive metal components that may have been damaged, such as crushed turbine blades and injection mold inserts, and offers high flexibility in clamping the parts and the coating materials.

[0031] Companies offering systems based on the same principle include BeAM from France, Trumpf from Germany, and Sciaky from the USA. An interesting hybrid system approach is offered by DMG Mori. The combination of laser cladding with a 5-axis milling system opens up new application areas in many industries.

[0032] Markforged's ADAM (Atomic Diffusion Additive Manufacturing) process begins with the selection of various metal powders. Next, the powder is embedded layer by layer in a plastic binder. After printing, the part is sintered in a furnace, which burns off the binder and solidifies the powder into a final, full-density metal part.

[0033] In summary, exemplary additive manufacturing processes applicable within this procedure include those described above and are further examples of additive manufacturing processes listed below. Suitable processes include, for example, high-speed sintering, selective laser melting, selective laser sintering, selective heat sintering, binder jetting, electron beam melting, fused deposition modeling, fused filament fabrication, welding, friction stir welding, wax deposition modeling, contour crafting, metal powder deposition processes, cold gas spraying, electron beam melting, stereolithography, 3D screen printing, light-controlled electrophoretic deposition, FDM printing of thermoplastics highly filled with metal powder, nano metal powder inkjet printing, DLP (direct light processing), inkjetting, and continuous light interface processing (CLIP).

[0034] The process described here initially comprises, according to process step a), the production of an object by means of additive manufacturing, wherein the object is produced by repeatedly arranging, layer by layer and spatially selectively according to a cross-section of the object, in particular by applying and / or melting and / or polymerizing and / or bonding, at least one first material onto a substrate. This step is therefore a typical process for additive manufacturing.

[0035] In principle, any surface on which the object can be built can serve as a substrate. For example, but not limited to, the substrate can be a solid material. The material from which the object is to be formed is built up in several successive layers, corresponding to the cross-section of the object to be produced. The cross-section of the object is thus the cross-section of each layer, so that the object as a whole is built up according to the cross-sectional profile and therefore according to its geometry.

[0036] In additive manufacturing processes, or 3D printing processes that use the area-based method, a photopolymer solution is exposed to light, just as in stereolithography. However, the exposure is not point-by-point using a laser beam, but rather across an entire area. An exposure matrix is ​​projected onto the respective layer to harden the material in those areas.

[0037] In the DLP (Digital Light Processing) process, a dot pattern is projected onto the photopolymer surface from above, and the build platform sinks into the solution layer by layer. The advantage of this method is that the curing process can be varied by adjusting the intensity of the exposure. This allows, for example, easier removal of support structures if they are less cured.

[0038] In 3D printing known as LCM (Lithography-based Ceramic Manufacturing), the photopolymer bath is exposed from below, not from above. This process is specifically used to expose a mixture of solid components (ceramic) and a photopolymer solution. The resulting green body is then sintered after 3D printing, and the binder is burned out. An advantage of this 3D printing method is the ability to use different types of granules.

[0039] CLIP (Continuous Liquid Interface Production) technology enables the production of objects without visible layers. The photopolymerization of the liquid resin is controlled by precisely adjusting the amount of UV light (curing) and oxygen (preventing curing). The bottom of the resin tank is made of a light- and air-permeable material, similar to that used in contact lenses. This allows for the creation of a so-called "dead zone" in the bottom layer using oxygen, which facilitates the further construction of the object as it is continuously drawn upwards from the tank.

[0040] In stereolithography (SLA), a light-curing plastic, also known as a photopolymer, is cured in thin layers by a laser. The process takes place in a melt bath filled with the base monomers of the photosensitive plastic. After each layer, the workpiece is lowered a few millimeters into the bath and then moved back to a position one layer thickness below the previous layer.

[0041] Particularly when the initial material is a metal, an additive manufacturing process using inkjet technology can be employed. Binder jetting is one example.

[0042] Furthermore, any material that can be processed using an additive manufacturing process can be used as the first material. Thus, for example, any material that can be melted and solidified under suitable conditions can be used. Additionally, only one first material can be used, a mixture of materials can be used, or several first materials can be used. If several first materials are used, they can be arranged in different layers or in the same layers.

[0043] Basically, the first material can be in powder form on the substrate or applied to the substrate in already molten form.

[0044] In an advantageous embodiment of the process according to the invention, at least a portion of the first material comprises a meltable polymer. Preferably, the entire first material, or all particles used as the first material in the process, comprise a meltable polymer. It is further preferred that at least 90 wt.% of the particles have a particle diameter of ≤ 0.25 mm, preferably ≤ 0.2 mm, and particularly preferably ≤ 0.15 mm. The particles containing the meltable polymer can, for example, be homogeneously structured, such that no other meltable polymers are present in the particles.

[0045] Suitable powders of thermoplastic materials can be produced via various common processes such as milling processes, cryo-milling, precipitation processes, spray drying processes and others.

[0046] In addition to the meltable polymer, the particles can contain further additives such as fillers, stabilizers, and the like, as well as other polymers. The total additive content in the particles can be, for example, ≥ 0.1 wt.% to ≤ 60 wt.%, preferably ≥ 1 wt.% to ≤ 40 wt.%.

[0047] In another preferred embodiment, the meltable polymer is selected from: polyetheretherketone (PEEK), polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyethersulfones, polyimide, polyetherimide, polyesters, polyamides, polycarbonates, polyurethanes, polyvinyl chloride, polyoxymethylene, polyvinyl acetate, polyacrylates, polymethacrylates, TPE (thermoplastic elastomers), thermoplastics such as polyethylene, polypropylene, polylactide, ABS (acrylonitrile butadiene styrene copolymers), PETG (a glycol-modified polyethylene terephthalate), or also polystyrene, polyethylene, polypropylene and mixtures and / or alloys of the aforementioned polymers.

[0048] Preferably, the meltable polymer is a polyurethane, which is obtained at least partially from the reaction of aromatic and / or aliphatic polyisocyanates with suitable (poly)alcohols and / or (poly)amines or mixtures thereof. Preferably, the (poly)alcohols used are those from the group consisting of: linear polyester polyols, polyether polyols, polycarbonate polyols, polyacrylate polyols, or a combination of at least two thereof. In a preferred embodiment, these (poly)alcohols or (poly)amines have terminal alcohol and / or amine functionalities. In a further preferred embodiment, the (poly)alcohols and / or (poly)amines have a molecular weight of 52 to 10,000 g / mol. Preferably, these (poly)alcohols or (poly)amines as starting materials have a melting point in the range of 5 to 150 °C.Preferred polyisocyanates that can be used, at least partially, for the production of the meltable polyurethanes are TDI, MDI, HDI, PDI, H12MDI, IPDI, TODI, XDI, NDI, and decane diisocyanate. Particularly preferred polyisocyanates are HDI, PDI, H12MDI, MDI, and TDI.

[0049] It is also preferred that the meltable polymer is a polycarbonate based on bisphenol A and / or bisphenol TMC.

[0050] Alternatively, the first material can be a metal. In this configuration, potential applications include medical technology, the aerospace industry, the automotive sector, and jewelry manufacturing. Suitable metals for the first material include tool steels, maraging steels or martensitic-hardening steels, stainless steel, aluminum or aluminum alloys, cobalt-chromium alloys, nickel-based alloys such as superalloys, titanium and titanium alloys of commercial purity, copper and copper alloys, and precious metals such as gold, platinum, palladium, and silver. In the process according to the invention, an object is built up layer by layer. If the number of repetitions for application and irradiation is sufficiently small, the object being built up can also be described as two-dimensional. Such a two-dimensional object can also be characterized as a coating.For example, ≥ 2 to ≤ 20 repetitions of application and irradiation can be performed to build it up.

[0051] A process for manufacturing an object from a precursor, which may also be part of the process described here and in particular of step a), comprises the following steps: I) Deposition of a radically cross-linked resin onto a support, which can also be referred to as a substrate, such that a layer of build-up material bonded to the support is obtained, corresponding to a first selected cross-section of the precursor; II) Deposition of a radically cross-linked resin onto a previously deposited layer of the build-up material, such that a further layer of the build-up material is obtained, corresponding to a further selected cross-section of the precursor and bonded to the previously deposited layer; III) Repeating step II) until the precursor is formed; wherein the deposition of a radically cross-linked resin, at least in step II), is carried out by exposure to light and / or irradiation of a selected area of ​​a radically cross-linkable resin, corresponding to the respective selected cross-section of the precursor.

[0052] In the process, after step III), step IV) is carried out: IV) Treating the precursor obtained after step III) under conditions sufficient to obtain post-crosslinking in the radically crosslinked resin by the action of further actinic radiation and / or thermally induced post-curing.

[0053] In this embodiment, the object is thus obtained in two manufacturing stages. The first manufacturing stage can be considered the build-up stage. This build-up stage can be realized using radiation-optical additive manufacturing processes such as inkjet printing, stereolithography, or DLP (digital light processing) and is the subject of steps I), II), and III). The second manufacturing stage can be considered the curing stage and is the subject of step IV). Here, the precursor or intermediate object obtained after the build-up stage is transformed into a mechanically more durable object without further altering its shape. The material from which the precursor is obtained in the additive manufacturing process is generally referred to as the "build-up material" within the scope of the present invention.

[0054] In step I) of the process, a radically cross-linked resin is deposited onto a substrate. This is usually the first step in inkjet, stereolithography, and DLP processes. In this way, a layer of build-up material bonded to the substrate is obtained, which corresponds to a first selected cross-section of the precursor.

[0055] As instructed in Step III), Step II) is repeated until the desired precursor is formed. In Step II), a radically cross-linked resin is deposited onto a previously applied layer of build-up material, resulting in another layer of build-up material corresponding to a further selected cross-section of the precursor and bonded to the previously applied layer. The previously applied layer of build-up material can be the first layer from Step I) or a layer from a previous iteration of Step II).

[0056] According to the invention, the deposition of a radically crosslinked resin is carried out, at least in step II) (preferably also in step I), by exposing and / or irradiating a selected area of ​​a radically crosslinkable resin, corresponding to the respective selected cross-section of the object. This can be achieved either by selective exposure (stereolithography, DLP) of the resin or by selective application of the resin followed by an exposure step which, due to the previous selective application of the resin, no longer needs to be selective (inkjet process).

[0057] In the context of the present invention, the terms "radically crosslinkable resin" and "radically crosslinked resin" are used. Here, the radically crosslinkable resin is transformed into the radically crosslinked resin by exposure to light and / or irradiation, which triggers radical crosslinking reactions. "Exposure" in this context refers to the application of light in the range between near-infrared and near-ultraviolet light (1400 nm to 315 nm wavelength). The other shorter wavelength ranges are covered by the term "irradiation," for example, far-ultraviolet light, X-rays, gamma rays, and electron beams.

[0058] The selection of the respective cross-section is best carried out using a CAD program with which a model of the object to be manufactured has been created. This operation is also called "slicing" and serves as the basis for controlling the exposure and / or irradiation of the radically crosslinkable resin.

[0059] The radically crosslinkable resin preferably has a viscosity (23 °C, DIN EN ISO 2884-1:2006-09) of ≥ 5 mPas to ≤ 100,000 mPas. Thus, it can be considered a liquid resin, at least for the purposes of additive manufacturing. Preferably, the viscosity is ≥ 50 mPas to ≤ 10,000 mPas, more preferably ≥ 500 mPas to ≤ 1,000 mPas.

[0060] In addition to the curable components, the radically crosslinkable resin preferably includes a non-curable component, such as stabilizers, fillers and the like.

[0061] The treatment in step IV) can in the simplest case be storage at room temperature RT (20 °C), or preferably at a temperature above room temperature RT.

[0062] It is preferred that step IV) is only carried out once the entire build-up material of the precursor has reached its gel point. The gel point is considered reached when, in a dynamic mechanical analysis (DMA) using a plate-on-plate oscillation viscometer according to ISO 6721-10:2015 at 20 °C, the graphs of the storage modulus G' and the loss modulus G" intersect. If necessary, the precursor is subjected to further exposure and / or irradiation to complete the radical crosslinking. The radically crosslinked resin can exhibit a storage modulus G' (DMA, plate-on-plate oscillation viscometer according to ISO 6721-10:2015 at 20 °C and a shear rate of 1 / s) of ≥ 10⁶ Pa.

[0063] The radically crosslinkable resin may further contain additives such as fillers, UV stabilizers, radical inhibitors, antioxidants, mold release agents, water scavengers, slip additives, defoamers, leveling agents, rheology additives, flame retardants, and / or pigments. These auxiliaries and additives, excluding fillers and flame retardants, are typically present in an amount of less than 10% by weight, preferably less than 5% by weight, and particularly preferably up to 3% by weight, based on the radically crosslinkable resin. Flame retardants are typically present in amounts of at most 70% by weight, preferably at most 50% by weight, and particularly preferably at most 30% by weight, calculated as the total amount of flame retardants used based on the total weight of the radically crosslinkable resin.

[0064] Suitable fillers include, for example, AlOH 3, CaCO 3, metal pigments such as TiO 2, and other known conventional fillers. These fillers are preferably used in amounts of no more than 70 wt.%, more preferably no more than 50 wt.%, and particularly preferably no more than 30 wt.%, calculated as the total amount of fillers used based on the total weight of the radically crosslinkable resin.

[0065] Suitable UV stabilizers may preferably be selected from the group consisting of piperidine derivatives, such as 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-1,2,2,6,6-pentamethylpiperidine, bis-(2,2,6,6-tetramethyl-4-piperidyl)-sebacate, bis(1,2,2,6,6-pentamethyl-1-4-piperidinyl)-sebacate, bis-(2,2,6,6-tetramethyl-4-piperidyl)-suberate, bis-(2,2,6,6-tetramethyl-4-piperidyl)-dodecanedioate; benzophenone derivatives such as 2,4-dihydroxy, 2-hydroxy-4-methoxy, 2-hydroxy-4-octoxy, 2-hydroxy-4-dodecyloxy or 2,2'-dihydroxy-4-dodecyloxy-benzophenone; Benztriazole derivatives, such as2-(2H-Benzotriazol-2-yl)-4,6-di-tert-pentylphenol, 2-(2H-Benzotriazol-2-yl)-6-dodecyl-4-methylphenol, 2-(2H-Benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-(5-Chlor-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2-(2H-Benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol, Isooctyl-3-(3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenylpropionat), 2-(2H-Benzotriazol-2-yl)-4,6-bis(1,1-dimethylethyl)phenol, 2-(2H-Benzotriazol-2-yl)-4,6-bis(1 -methyl-1 -phenylethyl)phenol, 2-(5-Chlor-2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylethyl)phenol; Oxalaniliden, wie z.B. 2-Ethyl-2'-ethoxy- oder 4-Methyl-4'-methoxyoxalanilid; Salicylsäureestern, wie z.B. Salicylsäurephenylester, Salicylsäure-4-tert-butylphenylester, Salicylsäure-4-tert-octylphenylester; Zimtsäureesterderivaten, wie z.B.α-Cyano-β-methyl-4-methoxycinnamic acid methyl ester, α-Cyano-β-methyl-4-methoxycinnamic acid butyl ester, α-Cyano-β-phenylcinnamic acid ethyl ester, α-Cyano-β-phenylcinnamic acid isooctyl ester; and malonic ester derivatives, such as 4-methoxybenzylidene malonic acid dimethyl ester, 4-methoxybenzylidene malonic acid diethyl ester, 4-butoxybenzylidene malonic acid dimethyl ester. These preferred light stabilizers can be used individually or in any combination with one another.

[0066] Particularly preferred UV stabilizers are those that completely absorb radiation with a wavelength < 400 nm. These include, for example, the aforementioned benzotriazole derivatives. Most preferred UV stabilizers are 2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol and / or 2-(5-chloro-2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylethyl)phenol.

[0067] Optionally, one or more of the UV stabilizers mentioned as examples are added to the radically crosslinkable resin, preferably in amounts of 0.001 to 3.0 wt.%, particularly preferably 0.005 to 2 wt.%, calculated as the total amount of UV stabilizers used based on the total weight of the radically crosslinkable resin.

[0068] Suitable antioxidants are preferably sterically hindered phenols, which can preferably be selected from the group consisting of 2,6-di-tert-butyl-4-methylphenol (ionol), pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, 2,2'-thio-bis(4-methyl-6-tert-butylphenol) and 2,2'-thiodiethyl bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. These can be used individually or in any combination with each other, as required. These antioxidants are preferably used in amounts of 0.01 to 3.0 wt.%, particularly preferably 0.02 to 2.0 wt.%, calculated as the total amount of antioxidants used based on the total weight of the radically crosslinkable resin.

[0069] Suitable radical inhibitors or retarders are those that specifically inhibit uncontrolled radical polymerization of the resin formulation outside the desired (irradiated) area. These are crucial for good edge sharpness and imaging accuracy in the precursor. Suitable radical inhibitors must be selected according to the desired radical yield from the irradiation / exposure step and the polymerization rate and reactivity / selectivity of the double bond carriers. Examples of suitable radical inhibitors include 2,2-(2,5-thiophendiyl)bis(5-tert-butylbenzoxazole), phenothiazine, hydroquinones, hydroquinone ethers, quinone alkyds and nitroxyl compounds, as well as mixtures thereof, benzoquinones, copper salts, catechols, cresols, nitrobenzene, and oxygen. These antioxidants are preferably used in amounts of 0.001 wt% to 3 wt%.

[0070] In addition to and especially after the process step a) described above, and thus after the assembly of the object or after the assembly of the geometry of the object, the process described here further provides that the process includes the following additional process step: b) at least partial contact of the additively manufactured object, which is still on the substrate or has already been detached from the substrate, with a liquid heated to ≥ T or a powder bed of a second material heated to ≥ T for a time ≥ 1 min in order to obtain the treated object, wherein T represents a temperature of ≥ 25 °C, preferably ≥ 50 °C, more preferably ≥ 75 °C, and particularly preferably ≥ 150 °C, wherein the temperature is preferably chosen such that, if applicable, for example in the case of a polymer as the first material, the glass transition temperature Tg of the first material is reached, and wherein in particular the second material is different from the first material.

[0071] In this process step, the previously formed object is further processed to obtain the desired object. In particular, this process step b) serves to improve the properties of the produced object, especially with regard to its stability and the homogeneity of its properties, as well as to maintain the desired geometric shape of the previously formed object.

[0072] This involves at least partial, and therefore only partial or even complete, contact between the additively manufactured object, whether still on the substrate or already detached from it. Thus, the object can be detached from the substrate and placed in the liquid or powder bed to enable contact. Furthermore, the substrate can be contained within a chamber into which powder can be placed to form the powder bed, or a liquid can be filled to contact the object with the liquid or powder bed. However, this step is not limited to the aforementioned examples.

[0073] The contacting is to take place under defined conditions. Specifically, the contacting is to occur at elevated pressure, i.e., at a pressure above atmospheric pressure of 1 bar. Alternatively, the contacting can also be carried out at a reduced pressure, i.e., at a pressure below atmospheric pressure of 1 bar. However, contacting at normal pressure, i.e., at 1 bar, is also fundamentally covered by the scope of the present invention.

[0074] Furthermore, it is specifically provided that the contacting is carried out using a powder bed or a liquid which is heated to a temperature T before or during the contacting of the object and the powder bed or liquid. This temperature T is in the range of ≥ 25°C, preferably ≥ 50°C, more preferably ≥ 75°C, and particularly preferably ≥ 150°C. For example, the temperature T to which the powder bed or liquid is heated can be in the range of ≥ 45°C, for example ≥ 60°C, more preferably ≥ 90°C, more preferably ≥ 120°C, more preferably ≥ 150°C, and more preferably ≥ 180°C.

[0075] Furthermore, in a selected embodiment, contact is provided with a transparent liquid that has sufficient UV-VIS transparency and UV-VIS stability to re-crosslink the preformed object preferably at temperatures above the build chamber temperature of the upstream build process, optionally regioselectively, by means of radiation.

[0076] Furthermore, it is provided that contact is maintained for a defined period. This period is preferably in the range of ≥ 1 minute, for example ≥ 5 minutes, more preferably ≥ 5 minutes, more preferably ≥ 10 minutes, more preferably ≥ 15 minutes, more preferably ≥ 20 minutes, but preferably < 72h, more preferably < 48h, and most preferably < 24h. Preferably, the contact is provided for a period in the range of 1 minute to 72h, or more preferably 10 minutes to 48h, or more preferably 20 minutes to 24h.

[0077] In a preferred embodiment, the additively manufactured item is contacted with the powder bed or liquid, wherein the liquid or powder bed has a temperature < 50°C and is subsequently heated together with the additively manufactured item to the desired final temperature.

[0078] In a further preferred embodiment, the additively manufactured item is cooled in a controlled manner to a temperature of < 50°C after the desired contact time with the heated liquid or powder bed before being removed and cleaned from the liquid or powder bed.

[0079] In this way, post-crosslinking, sintering, crystallization or melting processes can be specifically controlled to change the properties of the additively sintered component in a desired way.

[0080] In another preferred embodiment, the additively manufactured item is contacted with the already preheated powder bed or liquid, wherein the liquid or powder bed has a temperature > 50°C, optionally already the target temperature.

[0081] In a further preferred embodiment, the additively manufactured item is quenched to a temperature of < 50°C, preferably < 30°C, after the desired contact time with the heated liquid or powder bed within a time of < 10 min, preferably < 5 min. Preferably, the item is quenched for a time in the range of 1 second to 10 min after the desired contact time with the heated liquid or powder bed. The quenching is preferably carried out by immersion in a fluid with a temperature below 50°C, preferably at a temperature in the range of 10 to 50°C.

[0082] The fluid can be any fluid that a person skilled in the art would select for this purpose and that meets the requirements mentioned elsewhere. Preferably, the fluid is water, preferably at room temperature (20°C).

[0083] In this way, crystallization and melting processes, especially glass transition processes, can be controlled in a targeted manner to change the properties of the additively sintered component in a desired way.

[0084] Desired properties may include crystallite size, density, degree of crystallinity, hardness, strength, tensile elongation, abrasion resistance, transparency, and others.

[0085] Furthermore, the material of the powder bed or the liquid, and thus of the second material, is selectable and not fundamentally limited. Suitable powders are, in particular, those that do not decompose under the selected conditions and that also do not react with the first material(s). It may be preferable for the powder of the powder bed to be inert with respect to the first material(s).

[0086] The same applies to the liquid. It, too, is generally selectable, provided it is inert with respect to the first material(s) and thus with respect to the materials from which the object is constructed. Furthermore, when using liquids, it is important that the liquid is not a solvent for any of the first materials.

[0087] In a preferred embodiment, powders that reversibly liquefy upon heating in contact with the additively manufactured object, or liquids that solidify, can also be used. Examples include salts that melt at the desired sintering temperature or concentrated salt solutions that solidify at the desired temperature through evaporation of, for example, solvents, or precipitation in, for example, solvents, upon contact with the additively manufactured object. In this way, the object can be encased in a stable shell during the process, which can subsequently be preferably washed off with solvents such as water or alcohol.

[0088] In a further preferred embodiment, the additively manufactured article can be repeatedly immersed in a salt solution or other concentrated solutions of a low-molecular-weight material with a high melting point or glass transition point and subsequently dried until a stable crust forms. The crust preferably stabilizes the shape of the additively manufactured article for subsequent heat treatment and can be easily washed off with water or another solvent after this treatment. Preferably, the solvent or water does not swell the additively manufactured article during treatment, or only ≤ 10 vol.%, preferably ≤ 5 vol.%, and particularly preferably ≤ 3 vol.%.

[0089] In a preferred embodiment, the 3D-manufactured object to be tempered can be immersed in a salt solution, removed from it, the salt on the surface dried, optionally under the influence of heat, optionally the process repeated several times to create a stable salt crust in which the object is heated at the desired temperature and the salt crust is removed from the object mechanically or by suitable solvents such as water, alkalis, or acids after the heat treatment.

[0090] In another preferred embodiment, the additively manufactured object can be repeatedly immersed in a concentrated solution of a low-molecular-weight material with a high melting point or glass transition temperature and subsequently dried until a stable crust forms. The crust stabilizes the shape of the additively manufactured object for subsequent heat treatment and can be easily washed off with water or other solvents after this treatment.

[0091] A particular advantage of the described methods, where a crust is formed around the object, is that porous structures can be specifically stabilized or preserved through infiltration and stabilization of the pores in the product during subsequent temperature stress.

[0092] "No solvent" means, in particular, that the solubility of the component under consideration in the liquid at 20 °C is ≤ 10 g / L, preferably ≤ 1 g / L, more preferably ≤ 0.1 g / L, and particularly preferably ≤ 0.01 g / L. Particularly suitable liquids also do not cause any unwanted discoloration of the object and cause the object to swell only reversibly or preferably not at all.

[0093] With regard to liquids, particularly suitable examples are characterized in particular by the fact that they can be repeatedly heated up to the softening temperature of the first material, such as the thermoplastic, without showing any signs of degradation.

[0094] Preferably, the surface tension of the liquid as the second material is at least 10 mN / m lower or higher than the surface tension of the first material, such as the thermoplastic material of the component.

[0095] Preferably, low-volatility, non-polar liquids can be used that can be heated under pressure to the desired temperatures, but can then be easily removed from the treated object.

[0096] In principle, it is preferable that the first material or materials are different from the material of the powder bed and the liquid, or from the second material. The second material can be any material that a person skilled in the art would use for this purpose. Preferably, the second material has a higher melting point than the first material.

[0097] In a further preferred embodiment, the liquid used in process step b) is selected as the second material from the group consisting of silicone oils, paraffin oils, fluorinated hydrocarbons, polyethylene waxes, salt water, molten metals, molten salts, or ionic liquids and mixtures thereof. In the case of salt water, a saturated alkali or alkaline earth chloride solution such as, for example, LiCl, KCl, NaCl, and / or MgCl₂, CaCl₂, and mixtures thereof, is preferred. It has been shown that the aforementioned materials or liquids are particularly advantageous because they are stable even under the applied conditions, such as temperature and pressure, and are non-discoloring or do not discolor the object, are non-oxidizing or reducing, and exhibit only a low acidic or basic potential in water, and furthermore enable effective treatment of the object.

[0098] Advantageously, the powder bed used in process step b) contains particles as a second material selected from the group consisting of silicon dioxide, such as sand or glass, polytetrafluoroethylene, aluminum oxide, metals, metal salts, sugars, organic salts, polyethylene wax, polyester, polyacrylic acid, polyethylene oxide, polyoxymethylene, polycarbonate, or a mixture comprising at least one of the aforementioned substances. Powders with a high thermal conductivity of ≥ 0.2 W / (m·K) are particularly preferred. The thermal conductivity can be determined as described in the publication TK04 Application Note, 2015, TeKa, Berlin, Germany, "Testing fragments and powder". Alternatively, powders that are solid at 23°C and readily and reversibly transform between a solid and a melt at the application temperature are preferred.Products exhibiting a low viscosity (< 10,000 mPas, preferably < 5,000 mPas, more preferably < 2,000 mPas, and most preferably < 1,000 mPas) in the melt at a temperature of 20°C above the softening temperature, and high brittleness as a powder (i.e., low deformability as a solid at 23°C), preferably an elongation at break of < 50%, more preferably < 30%, and more preferably < 20% in the tensile test according to DIN EN ISO 527-2:2012, are particularly advantageous. It has been shown that the aforementioned materials are especially beneficial because they are stable even under the applied conditions, such as temperature and pressure, and also allow for effective treatment of the object. Furthermore, the aforementioned materials can be removed from the object essentially without leaving any residue.

[0099] If the second material is used in the form of a powder bed, the powder particles of the second material preferably have a particle size in the range of 5 to 5000 µm, or more preferably in the range of 10 to 2000 µm, or more preferably in the range of 50 to 500 µm. The particle size is determined by laser diffraction using static laser diffraction analysis according to ISO 13320:2009-10.

[0100] It is particularly preferred if the second material or the powder bed contains a metal salt. In particular, a salt with a higher melting point than the first material can be selected for the second material. This allows the object to be treated even at high temperatures, advantageously reducing the risks to the user during handling and contact with such salts at higher temperatures, as they are easily and quickly removed from skin or clothing. Furthermore, it is preferable if the salt is water-soluble, as this allows for simple rinsing of the salt or the second material after treatment or after process step b).It may be particularly preferred that the metal salt is selected from the group consisting of sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl₂), calcium chloride (CaCl₂), potassium carbonate (K₂CO₃), lithium chloride (LiCl), magnesium oxide (MgO), magnesium sulfate (MgSO₄), calcium oxide (CaO), calcium carbonate (CaCO₃), and magnesium fluoride (MgF₂).

[0101] The use of such metal salts can result in an improved surface structure and enhanced durability. The improved surface structure manifests itself, for example, in reduced surface porosity. The improved properties include, for example, increased hardness, increased modulus, and increased tensile strength compared to the untreated object.

[0102] Furthermore, it can be advantageous for the aforementioned second materials—that is, the powders or liquids described above, or other substances suitable as second materials—that they are water-soluble. This is because water-soluble substances, in particular, can be easily dissolved on the object and thus removed from it.

[0103] Furthermore, it may be preferred that the second material is soluble in an acid, a base, or an organic solvent. In this embodiment as well, substances can be easily dissolved in the object and thus removed from it.

[0104] Furthermore, it can be provided that process step b) is carried out using critical carbon dioxide as the second material. Critical carbon dioxide, or supercritical CO₂, is produced when the pressure and temperature are above the critical point for carbon dioxide: Therefore, the carbon dioxide should be present, in particular, at a temperature above 304.13 K (30.980 °C) and at a pressure above 7.375 MPa (73.75 bar). The advantage of this configuration is that the carbon dioxide can effectively treat the object under supercritical conditions and, after treatment, can be removed from the object particularly easily and without residue as a gas under normal conditions.

[0105] In the process according to the invention, the object obtained by the additive manufacturing process is thus at least partially contacted by a heated liquid or a heated powder bed. The resulting object remains dimensionally stable due to the binder, and the at least one first material can be "sintered" or post-cured to form the treated object.

[0106] It has been shown that, in particular, contacting the object with the powder bed or with the liquid, as described elsewhere, can significantly improve the properties of the object and also the process itself.

[0107] The process described here offers several advantages over the state of the art or conventional selective laser sintering or high-speed sintering processes. For example, the build chamber temperature can be low in a process analogous to binder jetting. The subsequent, but spatially separable, sintering process significantly simplifies and reduces costs, as heated build chambers are not required.

[0108] The inventive method furthermore allows the processing of almost any thermoplastic powder, since the problems of the build chamber process in the SLS and HS processes do not arise. According to the inventors, the inventive method also enables, for the first time, the reliable processing of non-crystalline thermoplastics, preferably based on organic polymeric materials, into mechanically high-quality components, i.e., components with at least 50% of the strength of injection-molded components, with a build chamber temperature preferably < 5°C, particularly preferably < 20°C, and most preferably < 40°C of the softening temperature of the powder used.

[0109] In the inventive process, complex component geometries can still be realized, since the liquid / powder bed, analogous to the powder in the SLS and HS processes, counteracts gravity in a protective manner.

[0110] In particular, it has been shown that the object can achieve improved stability, even in a direction parallel to the plane of the layers created to build the object. Furthermore, a high degree of homogeneity in the mechanical properties can be achieved. This is also due to the fact that the inventive method can be carried out under pressure. The pressure is preferably achieved by mechanical compression of the powder or liquid phase. In a preferred embodiment, the pressure can also be obtained by applying an overpressure, for example, of a gas.

[0111] In a further preferred embodiment, the gas used is an inert gas that is neither oxidizing nor reducing at the preferred treatment temperature. Preferred inert gases are CO₂, N₂, argon, and neon.

[0112] The inventive method makes it possible to obtain materials with higher density, hardness and strength than through conventional sintering processes, since the binder prevents some of the porosity that arises in a normal sintering process.

[0113] After sintering, the temperature of the liquid or powder is preferably reduced to a value of < 50 °C below the softening temperature of the object being treated, and the treated object is obtained. Preferably, the treated object is washed.

[0114] After obtaining the object or after process step b), it can be removed from the powder bed or liquid and, if necessary, further detached from the substrate. The object can then be cleaned of any remaining powder bed or liquid residue.

[0115] When a powder bed is used, the object can be cleaned of powder residue using standard methods such as brushing or compressed air. If liquids are used, these can be washed off with additional solvents that are inert to the object, and / or the object can be dried.

[0116] Preferably, the process may include at least one further process step or a combination of further process steps, selected from: A) Detaching the additively manufactured item from the substrate before process step b); B) At least partially removing unreacted first material, in particular liquid material, powder, or support material, from the additively manufactured item before process step b); C) Post-curing the additively manufactured item produced in process step a) by means of actinic radiation; D) Cooling the heated liquid or powder bed to a temperature in the range of < 200°C, in particular in the range of ≤ 160°C, preferably in the range of ≤ 130°C, more preferably in the range of ≤ 50°C, and more preferably in the range of ≤ 30°C before removing the treated item after process step b);E) at least partial mechanical removal of the second material from the object during or after process step b), for example by filtering, blowing, suction, shaking, centrifuging or a combination of at least two of these;and F) Washing off the second material after process step b) after removing the article from the liquid or powder with a solvent, wherein the solvent is not a solvent or reactant for the first material at a temperature in a range of T ≤ 200°C, in particular in a range of ≤ 150°C, preferably in a range of ≤ 100°C, further preferably in a range of ≤ 60°C, further preferably in a range of ≤ 40°C, further preferably in a range of ≤ 20°C, for a period of preferably ≤ 30 min, in particular in a period of ≤ 25 min, more preferably in a period of ≤ 20 min, more preferably in a period of ≤ 15 min, more preferably in a period of ≤ 10 min, more preferably in a period of ≤ 5 min. Preferably, the time period is ≥ 1 second to ≤ 30 minutes, or preferably ≥ 10 seconds to ≤ 20 minutes.

[0117] During the washing process, the second material is preferably removed in the first washing step to more than 90%, or preferably to more than 95%, or preferably to more than 99%, based on the total surface area of ​​the object.

[0118] The steps A) to F) described above thus describe further advantageous steps, each of which can be carried out alone or in a combination that is generally selectable, if the object has been sufficiently treated with the powder bed or with the liquid according to process step b).

[0119] Process step A) allows the object to be treated with the powder bed or liquid in a particularly simple way and also allows particularly homogeneous properties to be obtained.

[0120] Process step B) makes it possible for the powder bed or liquid to act directly on the object without any interfering substances present on the object causing inhomogeneities.

[0121] Process step C) further allows the object to achieve particularly high stability while maintaining homogeneous properties.

[0122] Furthermore, process step D) allows for a process-technically advantageous removal of the object from the powder bed or the liquid.

[0123] Process step E) continues to make it possible to obtain the object in a high purity.

[0124] This process step can be performed on both residues of the powder bed and the liquid. The same principle applies accordingly to process step F).

[0125] After receiving the object, and in particular before process step b), its dimensional stability can be further enhanced by common post-processing methods such as coating or infusion with suitable coating or infusion agents, such as an aqueous polyurethane dispersion, followed by drying and curing at temperatures of 20 °C or more below the softening temperature – where the softening temperature is defined as the melting temperature of the untreated object – before it comes into contact with the inert liquid or inert powder material.

[0126] In a further preferred embodiment, during contact of the object with the liquid or powder bed according to process step b), the liquid or powder bed is at least temporarily pressurized. Preferably, the relative pressure, i.e., the overpressure, is in the range of ≥ 1 bar to ≤ 1000 bar, particularly ≥ 1.5 bar to ≤ 200 bar, more preferably ≥ 2 bar to ≤ 50 bar, most preferably ≥ 2.5 bar to ≤ 20 bar, and most preferably ≥ 4 bar to ≤ 10 bar. The pressure increase can be carried out in suitable autoclaves made of glass or metal by injecting a suitable gas or by mechanically reducing the autoclave volume. By applying overpressure to the liquid or powder bed, the temperature of the liquid or powder bed can be reduced compared to process variants without pressurization, for example by ≥ 5 °C or ≥ 10 °C.

[0127] It may be further preferred that, during contact of the object with the liquid or powder bed according to process step b), the liquid or powder bed is at least temporarily subjected to reduced pressure or a vacuum. Preferably, the relative pressure, i.e., the reduced pressure, is in the range of ≥ 0.01 bar to ≤ 1 bar, particularly ≥ 0.03 bar to ≤ 0.9 bar, more preferably ≥ 0.05 bar to ≤ 0.8 bar, and most preferably ≥ 0.08 bar to ≤ 0.7 bar. The vacuum can be created in suitable autoclaves made of glass or metal by removing the appropriate gas present in the autoclave or by mechanically increasing the autoclave volume. By applying negative pressure to the liquid or powder bed, the temperature of the liquid or powder bed can be reduced compared to process variants without pressurization, for example by ≥ 5 °C or ≥ 10 °C.

[0128] It may be further preferred that, during the contact of the article with the second material in the form of the liquid or the powder bed according to process step b), the powder bed or the liquid is at least temporarily flooded with an inert gas, or that an inert gas is at least temporarily introduced into the liquid. An inert gas may in particular be understood to be a gas that does not react with the material of the article or with the material of the powder bed or the liquid. In particular, the gas should be such that it has no oxidizing properties with respect to the material(s) of the article and the powder bed or the liquid. The inert gas may be particularly preferably selected from the group consisting of helium (He), argon (Ar), nitrogen (N₂), and carbon dioxide (CO₂).

[0129] It may further be preferred that the temperature T set in process step b), expressed in degrees Celsius, is on average ≤ 95% of the decomposition temperature of the first material, where the decomposition temperature is determined as a loss of 10 wt.% in a TGA measurement under nitrogen at a heating rate of 20°C / minute of the first material. This allows effective treatment of the object to be combined with a treatment that is gentle on the object.

[0130] It may be further preferred that the temperature T during process step b) is in a range of ≥ 40 °C to ≤ 2000 °C. It may be particularly preferred that the temperature T is in a range of ≥ 50 °C to ≤ 1500 °C, more preferably in a range of ≥ 60 °C to ≤ 1000 °C, more preferably in a range of ≥ 80 °C to ≤ 800 °C, more preferably in a range of ≥ 100 °C to ≤ 600 °C, and more preferably in a range of ≥ 140 °C to ≤ 300 °C.

[0131] Furthermore, it is preferred that the temperature T at process step b) is greater than a temperature 50°C below the Vicat softening temperature (VST = ). Vicat softening temperature ) of the first material, and that the temperature T is lower than a temperature that is 150°C above the Vicat softening temperature of the first material, wherein the Vicat softening temperature can be determined according to DIN EN ISO 306:2014-03. It is particularly preferred that the temperature T at process step b) is higher than a temperature that is 30°C below the Vicat softening temperature (VST = Vicat softening temperature ) of the first material, and that the temperature T is less than a temperature that is 120°C above the Vicat softening temperature of the first material, further preferably that the temperature T at process step b) is greater than a temperature that is 25°C below the Vicat softening temperature (VST = Vicat softening temperature) of the first material, and that the temperature T is less than a temperature that is 100°C above the Vicat softening temperature of the first material, further preferably that the temperature T at process step b) is greater than a temperature that is 20°C below the Vicat softening temperature (VST = Vicat softening temperature ) of the first material, and that the temperature T is lower than a temperature that is 90°C above the Vicat softening temperature of the first material, further preferably that the temperature T at process step b) is higher than a temperature that is 15°C below the Vicat softening temperature (VST = Vicat softening temperature ) of the first material, and that the temperature T is lower than a temperature 80°C above the Vicat softening temperature of the first material. This allows for effective treatment of the object combined with a gentle treatment.

[0132] In a further preferred embodiment, the temperature T in process step b) is further selected such that, when a fusible polymer is used as the first material, the elastic modulus, determined by DMA storage modulus as G' (DMA, plate / plate oscillation viscometer according to ISO 6721-10:2011-08 at a shear rate of 1 / s), of the fusible polymer at this temperature is ≥ 10⁵ Pa to ≤ 10⁸ Pa, preferably ≥ 5 × 10⁵ Pa to ≤ 5 × 10⁷ Pa, more preferably ≥ 1 × 10⁶ Pa to ≤ 1 × 10⁷ Pa. This allows for effective treatment of the object while minimizing the risk of deformation of the green body.

[0133] In a further preferred embodiment, the temperature T, expressed in degrees Celsius, is, when the first material contains a binder, ≤ 95%, preferably ≤ 90%, more preferably ≤ 85%, of the decomposition temperature of the binder after crosslinking, wherein the decomposition temperature is defined as the temperature at which a mass loss of ≥ 10% is detected in a thermogravimetric analysis at a heating rate of 20 °C / min in a nitrogen stream. This embodiment again enables effective and gentle treatment of the object.

[0134] In the following, or in Tables 1 and 2, particularly preferred but in no way limiting examples of combinations of first materials and materials for the powder bed or the liquid are mentioned according to the invention.

[0135] Examples of particularly suitable combinations of meltable polymers or thermoplastics for process step a) as the first material and liquids as the second material for process step b) in the process according to the invention are listed below in Table 1: Table 1: Material examples for first and second material Meltable polymer (first material) Liquid (second material) Thermoplastic polyurethane (TPU) Silicone oil, PE waxes, fluorocarbons Polycarbonate (PC) Silicone oil, PE waxes Polymethyl methacrylate (PMMA) Saltwater, silicone oil, PE waxes Polyamide (PA) Silicone oil, fluorocarbons Polypropylene (PP) silicone oil, salt water Polystyrene (PS) silicone oil, salt water Acrylonitrile butadiene styrene (ABS) Silicone oil, PE waxes, salt water Polyethylene (PE) silicone oil, salt water Polychloroprene Rubber (CR) silicone oil, salt water Styrene-butadiene block copolymers (SBS) silicone oil, salt water Polyvinyl chloride (PVC) silicone oil, salt water Polyvinyl acetate (PVA) Silicone oil, PE waxes

[0136] Examples of particularly suitable combinations of meltable polymers or thermoplastics for process step a) as the first material and for materials of a powder bed as the second material for process step b) in the process according to the invention are listed below in Table 2: Table 2: Material examples for first and second material Meltable polymer (first material) Powder bed (second material) Thermoplastic polyurethane (TPU) NaCl, MgSO4, MgCl2, CaCO3 Polycarbonate (PC) NaCl, MgSO4, MgCl2, CaCO3 Polymethyl methacrylate (PMMA) NaCl, MgSO 4 , MgCl 2 , CaCO 3 Polyamid (PA) NaCl, MgSO 4 , MgCl 2 , CaCO 3 Polypropylen (PE) NaCl, MgSO 4 , MgCl 2 , CaCO 3 , Stärke, Zucker Acrylnitrilbutadienstyrol (ABS) NaCl, MgSO 4 , MgCl 2 , CaCO 3 , Stärke, Zucker Polyethylen (PE) NaCl, MgSO 4 , MgCl 2 , CaCO 3 , Stärke, Zucker Polychloropren Rubber (CR) NaCl, MgSO 4 , MgCl 2 , CaCO 3 , Stärke, Zucker, Styrol-Butadien-Blockcopolymere (SBS) NaCl, MgSO 4 , MgCl 2 , CaCO 3 , Stärke, Zucker Polyvinylchlorid (PVC) NaCl, MgSO 4 , MgCl 2 , CaCO 3 , Stärke, Zucker Polyvinylacetat (PVA) NaCl, MgSO 4 , MgCl 2 , CaCO 3 , Stärke, Zucker Polyfluorethylen (PTFE) NaCl, MgSO 4 , MgCl 2 , Polyetheretherketon (PEEK) NaCl, MgSO 4 , MgCl 2 , Polyamid 6 NaCl, MgSO 4 , MgCl 2 , CaCO 3 Polyamid 66 NaCl, MgSO 4 , MgCl 2 , CaCO 3 Polyamdid 12 NaCl, MgSO 4 , MgCl 2 , CaCO 3 Polyamid 46 NaCl, MgSO 4 , MgCl 2 , CaCO 3 Polyamid 11 NaCl, MgSO 4 , MgCl 2 , CaCO 3 Copolyamid NaCl, MgSO 4 , MgCl 2 , CaCO 3 Copolyesteramid NaCl, MgSO 4 , MgCl 2 , CaCO 3 Copolyetheramide (PEBA) NaCl, MgSO4, MgCl2, CaCO3 Polyaryle tetraketone (PEAK) NaCl, MgSO4, MgCl2, CaCO3 Polyimides NaCl, MgSO4, MgCl2, CaCO3 Polyarylsulfone NaCl, MgSO4, MgCl2, CaCO3

[0137] The present disclosure further relates to a treated article obtainable by a method as described in detail above. Such an article may, in particular, have improved mechanical properties. The article produced according to the inventive method has a surface with a mean roughness Ra (DIN EN ISO 4287:2010-07) of ≤ 500 µm, preferably of ≤ 200 µm, or preferably of ≤ 100 µm, or preferably in a range of 10 to 500 µm, or preferably in a range of 50 to 100 µm.

[0138] Such an object is characterized in particular by its exceptionally high stability and, furthermore, by its particularly homogeneous mechanical properties.

[0139] Regarding mechanical properties, particular importance should be placed on density as a measure of high physical stability and tensile strength, which especially represents the stability of the object in the plane of the layer.

[0140] In this regard, it is particularly preferred that, in a tensile test based on DIN EN ISO 527-2:2012, the product exhibits a tensile strength greater than that of the untreated item, or in other words, that the layers of the treated item exhibit a tensile strength relative to each other after process step b) that is greater than that before process step b). It is particularly preferred that, in a tensile test based on DIN EN ISO 527-2:2012, the layers of the treated item exhibit a tensile strength greater than that of the untreated item by ≥ 10%, preferably by ≥ 20%, more preferably by ≥ 30%, more preferably by ≥ 50%, and more preferably by ≥ 100%, wherein the values ​​described above refer to the tensile strength of the untreated item or the item before process step b).

[0141] It may be further preferred that the density of the treated item is greater than the density of the untreated item, or in other words, that the density after process step b) is greater than before process step b). It may be particularly preferred that the density of the treated item is greater than the density of the untreated item by an amount of ≥ 2%, preferably by an amount of ≥ 5%, more preferably by an amount of ≥ 8%, and more preferably by an amount of ≥ 10%, relative to the density of the untreated item or relative to the density of the item before process step b).

[0142] In particular, these mechanical properties can be improved by the method described here compared to conventional additively manufactured objects.

[0143] Regarding further advantages and technical features of the process, reference is made to the following description of the subject matter, and vice versa. Examples

[0144] The following are various experiments in which an object produced by an FDM or SLS process or DLP process as an additive manufacturing process according to process step a) and treated according to process step b) is examined for its properties before and after process step b). Testing procedure:

[0145] Shore A: In accordance with DIN ISO 7619-1:2012-02, the required specimen thickness was achieved by repeatedly stacking the resulting specimens. Tensile test: In accordance with DIN EN ISO 527-2:2012, the specimens were not stored for 24 hours under standard climate conditions prior to measurement. IR (ATR): Evaluation of the ratio of the maximum height of the isocyanate band in the wavenumber range of 2170 to 2380 to the maximum height of the CH stretching vibration in the wavenumber range of 2600 to 3200. Devices:

[0146] FDM printer: A Massportal Pharaoh XD 20 FDM / FFF 3D printer was used for the tests. This printer is characterized by a largely enclosed build chamber and a Bowden extruder. SLS printer: A Farsoon FS251P 3D printer was used for the tests. DLP printer: An Autodesk Ember 3D printer was used for the tests. Ingredients:

[0147] Silicone oil (silicone oil bath): Silotherm200 Infrasolv from LABC Labortechnik Zillger KG, colorless silicone oil (heat transfer oil) was obtained from a laboratory supply company and used as supplied. NaCl: Table salt with a grain size of 0.1 to 0.9 mm. Sand (filter sand): Quartz sand with a grain size of 0.4 to 0.8 mm. Resin A:

[0148] - 25 g of the reaction product of the 1,6-HDI trimer with hydroxyethyl acrylate and the following idealized structure: - 50 g of polyurethane acrylate Ebecryl 4101 (sourced from Allnex SA) - 25 g of butyl acrylate (sourced from Sigma Aldrich) - 3 g of photoinitiator Omnirad 1173 (referring to the IGM Resins ) (Alternatively, when using the Autodesk Ember 3D printer, 1.5g of the photoinitiator Omnirad BL 750 from IGM Resins and 0.13g of 2,5-Bis(5- tert -butyl-benzoxazol-2-yl)thiophene used as a radical scavenger instead of Omnirad 1137). - 0.5 g of a catalyst complex consisting of: 55.6 wt% Desmodur®N 3600 (Covestro Deutschland AG) and 44.4 wt.% Jeffcat ®< Z 110 (obtained from Huntsman Co). These components of Resin A were processed in a planetary gyratory mixer. Thinky ARE250 combined and mixed at room temperature for approximately 2 minutes at a speed of 2000 revolutions per minute.

[0149] Experiment 17: The radically curable resin A was applied three times to a glass plate using squeegees with different gap widths, thus simulating a 3D printing process similar to a DLP 3D printer. The glass plate was pre-treated with a 1% solution of soy lecithin in ethyl acetate and dried. The soy lecithin acted as a release agent to allow the cured films to be removed from the substrate later. The gap widths were 400 µm, 300 µm, and 200 µm. Each applied layer was cured in a UV curing system from the company [Company Name]. SuperficiThe films were cured using mercury and gallium radiation sources at a belt speed of 5 m / min. The lamp power and belt speed resulted in a radiation intensity of 1,300 mJ / cm², which acted upon the coated substrates. This created a three-layer structure with a total thickness of approximately 900 µm. The cured films were carefully peeled from the glass substrates to obtain test specimens for mechanical and IR spectroscopic characterization.

[0150] Unless otherwise stated, all infrared spectra were measured on a Bruker FT-IR spectrometer equipped with an ATR unit.

[0151] A Bruker FT-IR spectrometer (Tensor II) was used to measure the relative change in free NCO groups on films. The sample was contacted with the Platinum ATR unit. The contacted area of ​​the sample was 2 x 2 mm. During the measurement, the IR radiation penetrated the sample by 3–4 µm, depending on the wavenumber. An absorption spectrum was then generated from the sample. To compensate for uneven contact of the samples with varying hardness, baseline correction was performed on all spectra, and normalization was carried out in the wavenumber range 2600–3200 (CH2, CH3). The peak height of the "free" NCO group was determined in the wavenumber range 2170–2380, and the ratio of the NCO signal to the highest peak was determined in the range 2900–3200 (CH).

[0152] For the Shore A hardness measurement according to DIN ISO 7619-1:2012-02, individual layers of the film were joined together to form a test specimen at least 6 mm high and the hardness value was determined.

[0153] Experiment 18: The radically curable resin A was applied to a glass plate as described in Experiment 17, UV-cured, and peeled from the glass substrate. The free-standing film was then placed vertically into a salt bed so that it was completely surrounded by salt. It was subsequently cured for 1 hour at 185°C in an oven under normal atmospheric conditions. IR spectroscopy and hardness measurements were performed on this post-cured film as described in Experiment 17.

[0154] Experiment 19*: The radically curable resin A was applied to a glass plate as described in Experiment 17, UV-cured, and peeled from the glass substrate. The free-standing film was then placed vertically in the oven. It was subsequently cured for 1 hour at 185°C under normal atmospheric conditions. During the curing process, the film curved into a U-shape, which remained dimensionally stable after curing. IR spectroscopy and hardness testing were performed on this post-cured film as described in Experiment 17.

[0155] TPUs used according to the invention were produced using two common process methods: the prepolymer process and the one-shot / static mixer process.

[0156] In the prepolymer process, the polyol or polyol mixture is preheated to 180 to 210 °C, mixed with a portion of the isocyanate, and reacted at temperatures of 200 to 240 °C. The rotational speed of the twin-screw extruder used is approximately 270 to 290 rpm. This preliminary partial reaction yields a linear, slightly pre-elongated prepolymer, which reacts further with residual isocyanate and chain extender in the extruder. This process is described in detail in EP-A 747 409.

[0157] In the one-shot / static mixer process, all comonomers are homogenized within a short time (under 20 s) using a static mixer or other suitable mixing unit at high temperatures (above 250 °C) and then reacted and discharged via a twin-screw extruder at temperatures of 90 to 180 °C and a rotational speed of 260-280 rpm. This process is described by way of example in application DE 19924089. TPU A 1.75 mm Filament

[0158] The TPU (thermoplastic polyurethane) was produced from 1 mol of polyether polyol (DuPont) with a number-average molecular weight of 1000 g / mol based on polytetramethylene ether glycol, as well as 5.99 mol of 1,4-butanediol; 6.99 mol of technical-grade 4,4'-diphenylmethane diisocyanate (MDI) with >98 wt% 4,4'-MDI; 0.25 wt% Irganox® < 1010 (pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) from BASF SE) and 0.3 wt% Loxamide 3324 using the prepolymer process.

[0159] The filaments were extruded from the granules using standard methods, cooled in a water bath, dried in a warm air drying chamber, and wound onto a spool. Before being used in the 3D printer, the filaments were dried at 40°C for 48 hours.

[0160] TPU Powder Blend from Raw Materials TPU 1 / TPU 2: The powder blend was produced from TPU 1 and TPU 2 powders by weighing out the respective components. Both materials were mixed in a standard TM5 Thermomix at speed 10 for 2 x 5 seconds. raw material TPU 1

[0161] TPU (thermoplastic polyurethane) 1 was prepared from 1 mol polyesterdiol (Covestro) with a number-average molecular weight of approximately 900 g / mol based on approximately 56.7 wt% adipic acid and approximately 43.3 wt% 1,4-butanediol, as well as approximately 1.41 mol 1,4-butanediol, approximately 0.21 mol 1,6-hexanediol, approximately 1.62 mol technical-grade 4,4'-diphenylmethane diisocyanate (MDI) with >98 wt% 4,4'-MDI, 0.05 wt% Irganox®< 1010 (pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) from BASF SE), 1.1 wt% Licowax®< E (montanaic acid ester from Clariant), and 250 ppm Tin dioctoate, produced. raw material TPU 2

[0162] TPU (thermoplastic polyurethane) 2 was produced from 1 mol of polyesterdiol (Covestro) with a number-average molecular weight of approximately 900 g / mol based on approximately 56.7 wt% adipic acid and approximately 43.3 wt% 1,4-butanediol, as well as approximately 2.38 mol of 1,4-butanediol, approximately 0.22 mol of 1,6-hexanediol, approximately 2.6 mol of technical-grade 4,4'-diphenylmethane diisocyanate (MDI) with > 98 wt% 4,4'-MDI, 0.05 wt% Irganox® < 1010 (pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) from BASF SE), 1.1 wt% Licowax® < E (montanaic acid ester from Clariant), and 250 ppm Tin dioctoate, produced.

[0163] The TPU produced using raw materials TPU 1 and TPU 2 had 0.2 wt%, based on TPU, of hydrophobized pyrogenic silica added as a flow agent (Aerosil® < R972 from Evonik). The mixture was then mechanically processed into powder under cryogenic conditions (cryogenic comminution) in a pin mill and subsequently classified by a sieve machine. 90 wt% of the material had a particle diameter of less than 140 µm (measured by laser diffraction (HELOS particle size analysis)).

[0164] 1.75 mm filament PC1 based on Makrolon® XT5010, MVR (300 °C / 1.2 kg) 34 cm³ / 10 min: The filaments were extruded from the granules using a standard procedure, cooled with air and wound onto a winder.

[0165] In step 1, tensile bars in the shape according to ISO 527-2:2012 were produced from TPU A and PC1 S2 filaments using the FDM printing process (conditions see Table 3).

[0166] Furthermore, in step 1, S2 tensile bars according to ISO 527-2:2012 were produced from the powder mixtures of raw material TPU 1 and raw material TPU 2 using the SLS printing process (conditions see Table 3).

[0167] Furthermore, in step 1, S2 tension bars in the shape according to ISO 527-2:2012 were manufactured using the DLP printing process (conditions see Table 3).

[0168] In step 2, the obtained tensile bars were subjected to thermal post-curing. Comparative tests are marked with an asterisk (*); the post-curing conditions vary, see Table 4. Post-curing was carried out in a forced-air drying oven at the specified temperature. The specimens to be tested were placed lying down in a 250 ml aluminum tray containing the medium, completely submerged, and the drying oven was heated from room temperature (RT) to the target temperature within 30 minutes. After reaching the target temperature, the specimen was cured at the target temperature for the required time. Subsequently, the aluminum tray was removed from the drying oven while still hot and cooled to room temperature (RT) on a laboratory bench. The samples were removed after reaching RT, but no later than 30 minutes, dried, and cleaned of the medium, e.g., by rinsing with water.

[0169] Following thermal post-curing, the resulting tensile bars were further examined for mechanical and chemical composition; see Table 5. Results of the comparative tests are again marked with an asterisk (*). Table 3. Material and process conditions Material / SLS TPU blend TPU 1 / TPU 2 (50 / 50) TPU blend TPU 1 / TPU 2 (70 / 30) Installation room temperature [°C] 80 80 Laser power [W] 48 48 Layer thickness [mm] 0,12 0,12 Number of exposures per layer (fill scan count) 2 2 Overlap of laser tracks (slicer fill scan spacing) [mm] 0,15 0,15 Roller speed [mm / s] 180 180 Material / FDM TPU A PC1 Extruder temperature [°C] 245 285 Building board temperature [°C] 60 100 Extrusion speed [mm / s] 40 40 Layer height [mm] 0,2 0,2 Nozzle size [mm] 0,4 0,4 Material / DLP Resin A Installation room temperature [°C] 23 Layer height [mm] 0,05 Exposure / Layer [s] 1,7

[0170] The FDM process used printing without outer layers (top solid layer / bottom solid layer). Two outer perimeters and a 45° infill were used. All samples were printed in the Z direction, i.e., perpendicular to the build platform.

[0171] The properties of the items produced after process step 1 are described in more detail in the following Table 5 as comparative tests. Table 4. Post-sintering conditions Experiment (First Material) Temperature [°C] Time [min] Cooling time to room temperature [min] Medium (second material) TPU A 1* 23 - - - 2 180 60 30 Salt 3 190 60 30 Salt 4 200 60 30 Salt 5 210 60 30 Salt PC1 6* 23 -- -- -- 7 190 60 30 Salt 8 180 60 30 Salt TPU blend TPU 1 / TPU 2 (50 / 50) 9* 23 -- -- -- 10 200 60 30 silicone oil 11 200 60 30 Salt 12 200 60 30 sand TPU blend TPU 1 / TPU 2 (70 / 50) 13* 23 -- -- -- 14 200 60 30 silicone oil 15 200 60 30 Salt 16 200 60 30 sand Resin A 17* 23 -- -- -- 18 185 60 30 Salt * indicates comparative trial Table 5. Properties after treatment Attempt Shore A hardness Tensile strength [N / mm²] Maximum elongation at break [%] ISO / CH band ratio in IR TPU A 1* 2,8 1,4 2 8,8 8,6 3 8,6 12,7 4 9 9,1 5 11 6,2 PC1 6* 25 3 7 41 3,6 8 37 2,7 TPU blend TPU 1 / TPU 2 (50 / 50) 9* 3,75 133,0 10 6,03 209,7 11 16,0 400,5 12 8,57 385,0 TPU blend TPU 1 / TPU 2 (70 / 30) 13* 3,48 118,0 14 5,56 168,9 15 17,2 386,6 16 11,2 441,2 Resin A 17* 70 1:1 18 90 1:10 19* 90 1:10 * indicates comparative trial

[0172] A comparison of the results of the inventive method shows a significant improvement in the mechanical properties after temperature storage according to the invention compared to unheated samples. Furthermore, heat storage in media with a higher density than air has resulted in significantly improved dimensional stability of the test specimens, as they are less effectively exposed to gravity. This is particularly evident when complex components with unsupported geometries, as clearly seen in the comparative example in test 19, are thermally post-cured. The unsupported geometries were deformed by gravity during the curing process and cure in this deformed shape.

Claims

1. A process for producing a treated article, comprising the steps of: a) producing an article by additive manufacturing, wherein the article is produced by a repeated layerwise arranging, which is spatially selective according to a cross section of the article, of at least one first material on a substrate, characterized in that the process comprises the further process step of: b) at least partially contacting the article produced by additive manufacturing which is still present on the substrate or already detached from the substrate with a powder bed of a second material heated to ≥ T for a time ≥ 1 min to obtain the treated article, wherein - T is a temperature of ≥ 25°C, preferably of ≥ 50°C, more preferably of ≥ 75°C, particularly preferably of ≥ 150°C, wherein the contacting of the obtained article with the powder bed according to process step b) is performed for a period which is in a range from ≥ 1 minute to ≤ 174 hours.

2. The process as claimed in claim 1, characterized in that the process comprises at least one further process step or a combination of further process steps selected from: A) detaching the article produced by additive manufacturing from the substrate before process step b); B) at least partially removing unreacted first material from the additively manufactured article before process step b); C) post-curing the article produced by additive manufacturing in process step a) using actinic radiation; D) cooling the heated liquid or the heated powder bed to a temperature in a range of < 200°C before removal of the treated article after process step b); E) at least partially mechanically removing the second material from the article during or after process step b); and F) washing off the second material after process step b) after removal of the article from the liquid or the powder with a solvent, wherein the solvent is not a solvent or reactant for the first material at a temperature in a range of T ≤ 200°C for a period ≤ 30 min.

3. The process as claimed in either of claims 1 and 2, characterized in that the additive process is selected from the group consisting of high-speed sintering, selective laser melting, selective laser sintering, selective heat sintering, binder jetting, electron beam melting, fused deposition modeling, fused filament fabrication, build up welding, friction stir welding, wax deposition modeling, contour crafting, metal powder application methods, cold gas spraying, electron beam melting, stereolithography, 3D screen printing methods, light-controlled electrophoretic deposition, printing of thermoplastics highly filled with metal powder by the FDM process, nano metal powder in an inkjet method, DLP (direct light processing), inkjetting, continuous light interface processing (CLIP).

4. The process as claimed in any of claims 1 to 3, characterized in that the meltable polymer is selected from polyether ether ketone (PEEK), polyaryl ether ketone (PAEK), polyether ketone ketone (PEKK), polyethersulfones, polyimide, polyetherimide, polyesters, polyamides, polycarbonates, polyurethanes, polyvinyl chloride, polyoxymethylene, polyvinyl acetate, polyacrylates, polymethacrylates, TPE (thermoplastic elastomers), thermoplastics such as polyethylene, polypropylene, polylactide, ABS (acrylonitrile-butadiene-styrene copolymers), PETG (a glycol-modified polyethylene terephthalate) or else polystyrene, polyethylene, polypropylene and blends and / or alloys of the recited polymers.

5. The process as claimed in any of claims 1 to 4, characterized in that during contacting of the article with the powder bed according to process step b) the powder bed is at least for a time subjected to superatmospheric pressure, especially to a pressure in a range from ≥ 1 bar to ≤ 1000 bar.

6. The process as claimed in any of claims 1 to 4, characterized in that during contacting of the article with the powder bed according to process step b) the powder bed is at least for a time subjected to subatmospheric pressure at a pressure in a range from ≥ 0.01 bar to ≤ 1 bar.

7. The process as claimed in any of claims 1 to 6, characterized in that during the contacting of the article with the powder bed according to process step b) the second material in the form of the powder bed is at least for a time blanketed with an inert gas.

8. The process as claimed in any of claims 1 to 7, characterized in that the second material is water-soluble.

9. The process as claimed in any of claims 1 to 8, characterized in that the second material is soluble in an acid, a base or an organic solvent.

10. The process as claimed in any of claims 1 to 9, characterized in that the second material is selected from at least one of the group consisting of silicon dioxide, polytetrafluoroethylene, aluminum oxide, metals, metal salts, sugars, organic salts, polyethylene wax, polyester, polyacrylic acid, polyethylene oxide, polyoxymethylene polycarbonate and a mixture comprising at least one of the aforementioned substances for forming a powder bed.

11. The process as claimed in any of claims 1 to 9, characterized in that the second material is selected from metal salts for forming a powder bed.

12. The process as claimed in any of claims 1 to 11, characterized in that the temperature T established in process step b), expressed in degrees Celsius, is on average ≤ 95% of the decomposition temperature of the first material.

13. The process as claimed in any of claims 1 to 12, characterized in that the temperature T established in process step b) is in a range from ≥ 40°C to ≤ 2000°C.

14. The process as claimed in any of claims 1 to 13, characterized in that the temperature T established in process step b) is higher than a temperature that is 50°C below the Vicat softening temperature of the first material and wherein the temperature T established in process step b) is lower than a temperature that is 150°C above the Vicat softening temperature of the first material, wherein the Vicat softening temperature is determinable according to DIN EN ISO 306:2014-03.

15. The process as claimed in any of claims 1 to 14, characterized in that the temperature T of the powder bed preferably changes over the course of process step b) and the temperature curve optionally comprises temperatures of -190°C to +2000°C, especially wherein the contacting of the obtained article with the powder bed according to process step b) is performed for a period of ≥ 1 minute to ≤ 72 hours.