Metal-filled resin formulations, 3D printing methods, and additively manufactured parts

Abstract

The present invention relates to a metal-filled resin formulation for the production of parts, in particular for 3D printing methods, based on layer-by-layer photopolymerization, which contains a photopolymerizable matrix component, a dense metal filler with a specific minimum volume fraction, and a photopolymerization initiator. By selective layer-by-layer curing of the metal-filled resin formulation, the parts are additively produced using light irradiation. The present invention particularly relates to the high-precision production of radiation-absorbing parts based on lithographic additive methods such as SLA, where wall thicknesses of up to less than 100 μm are possible, despite good radiation hardness and good surface quality, based on the special selection of the formulations used.

Description

[Technical Field]

[0001] The present invention relates to metal-filled resin formulations, particularly for 3D printing methods, as well as 3D printing methods in which such metal-filled resin formulations are used to manufacture parts. The present invention also relates to parts manufactured using such 3D printing methods. The present invention is particularly directed to the additive manufacturing of three-dimensionally formed parts for absorbing electromagnetic radiation, such as X-ray radiation. [Background technology]

[0002] In several technical applications, radiation-absorbing materials and components made from them are increasingly used in a wide variety of, sometimes complex, shapes. Lead, previously the standard material used for such applications, has been gradually replaced by other metals and polymer / metal composites. In the case of polymer / metal composites, today, a metal filler with a high density or high atomic number (e.g., tungsten) is often embedded in a thermoplastic matrix (e.g., polyamide). This material is typically processed into industrial components using conventional polymer molding processes, such as injection molding or extrusion (see, for example, U.S. Patent Nos. 5,929,949; 5,929,949; 5,929,949; and 5,929,949).

[0003] Although a higher proportion of metal fillers can achieve higher densities and therefore better part performance in terms of radiation absorption, in some cases, mechanical strength must be reduced, which can make such materials difficult to process. Basically, with the above-mentioned conventional approaches, complex geometric shapes can only be realized at high cost and effort, even if they are possible. However, with the increasing miniaturization and development of application fields, the demand for the production of highly complex shapes with thin walls and high precision is increasing, and conventional molding methods are increasingly reaching their limits.

[0004] In generative or additive manufacturing methods, commonly referred to as 3D printing processes (German: 3D-Druckverfahren), one or more starting materials are sequentially deposited and cured in multiple layers based on a digitized geometric model of the object. For example, in stereolithography (SL or SLA), a part is built up layer by layer from a light-curable resin formulation (German: lichthaerbare Harzformulierung), such as acrylic, epoxy, or vinylester resin. For this purpose, the respective resin formulation is prepared in a bath in liquid form (typically with a viscosity in the range of <2 Pa·s) and hardened into a material (e.g., a synthetic resin or composite) in selected areas of the surface by polymerization using laser irradiation, known as photopolymerization. After each step, the thin material layer thus formed is submerged a few millimeters into the liquid and then returned to its original position, one layer thick below the previous one. The liquid resin mixture on top of the material is then evenly distributed by a wiper or squeegee, after which the laser is again moved over the liquid surface, resulting in the creation of a three-dimensional part in stages.

[0005] 3D printing offers enormous design freedom and makes it possible to produce at a reasonable cost objects that could not be produced using conventional methods, or that would only be possible at considerable cost. For these reasons, 3D printing methods are now very widespread in industrial design, medical technology, the automotive industry, the aerospace industry, and general industrial product development, where resource-efficient process chains are used for the demand-based small-scale and large-scale production of individualized parts, and in some cases also for the flexible, on-demand production of necessary spare parts.

[0006] For example, Non-Patent Document 1 describes the use of additive beam melting processes to manufacture thin collimator structures made of tungsten.

[0007] Certain additive manufacturing techniques, such as SLA, LCD (liquid crystal display) processes, digital light processing (DLP) or other light-emitting processes using active light masks, or combinations thereof, are characterized by an astonishingly high precision and therefore offer particularly promising solutions for the production of ultra-fine feature components.

[0008] For example, U.S. Patent No. 5,929,633 describes a two-step process for producing a tungsten collimator, in which, after the SLA step, a layer of radiation-absorbing metal is deposited on the polymeric layer by cathodic sputtering. This metal layer is then lifted off the SLA layer and retained as a layer portion of the collimator. This procedure is repeated as needed to produce the final collimator from tungsten as a layer process. However, directly producing a collimator from a radiation-absorbing material using SLA would be a substantially simplified and more economical process solution.

[0009] Furthermore, Patent Document 6 describes the use of a colloid of polymer macromolecules in a solvent as a matrix material, into which metal particles can be mixed. In a productive manufacturing process, a green part is first produced using this material, which is then dried under the influence of temperature.

[0010] US Patent No. 6,269,999 describes the additive manufacturing of radiation-absorbing and metal-containing radiological phantoms using lithographic processes, where nanometer-sized metal particles are used.

[0011] Patent document 8 describes a method for producing dental prostheses or restorations, and suitable photoinitiators for initiating the required photoreaction are described, for example, in Non-Patent Document 2. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] German Patent Application Publication No. 102004027158 [Patent Document 2] U.S. Patent Application Publication No. 2008 / 0023636 [Patent Document 3] German Patent Application Publication No. 102007028231 [Patent Document 4] International Patent Application Publication No. 2012 / 034879 [Patent Document 5] U.S. Patent Application Publication No. 2020 / 0077966 [Patent Document 6] International Patent Application Publication No. 2020 / 198404 [Patent Document 7] International Patent Application Publication No. 2020 / 141519 [Patent Document 8] International Patent Application Publication No. 2019 / 048963 [Patent Document 9] International Patent Application Publication No. 2018 / 032022 [Patent Document 10] U.S. Patent Application Publication No. 2020 / 0024394 [Non-patent literature]

[0013] [Non-Patent Document 1] ATSidambe et al. “Laser powder bed fusion of a pure tungsten ultra-fine single pinhole collimator for use in gamma ray detector characterization” International Journal of Refractory Metals and Hard Materials, Volume 84, 2019 [Non-patent document 2] W. Arthur Green “Industrial Photoinitiators: A Technical Guide” Taylor & Francis Group, 2010, ISBN: 978-1-2745-1 Summary of the Invention [Problem to be solved by the invention]

[0014] Against this background, the present invention is based on the problem of finding an accurate and practical solution for the production of radiation-absorbing components, which preferably allows even complex thin-walled structures to be produced cost-effectively. [Means for solving the problem]

[0015] According to the present invention, this problem is solved by a metal-filled resin formulation (hereinafter also referred to as "metal-filled resin formulation") having the features of claim 1, a 3D printing method having the features of claim 9, and an additively manufactured part having the features of claim 11.

[0016] That is, the following solutions are proposed: - a metal-filled resin formulation, preferably radiation-absorbent, for layer-by-layer photopolymerization for the production of parts, in particular for 3D printing methods, the resin formulation comprising a photopolymerizable matrix component, the photopolymerizable matrix component comprising at least one of the monomers, oligomers and prepolymers from the group consisting of monofunctional and / or polyfunctional radically and / or cationically polymerizable compounds, and a metal filler, the metal filler having a density of at least 8.5 g / cm 3 , preferably at least 10 g / cm 3 a photopolymerizable matrix component having a volume fraction of 5 to 80 vol%, preferably 5 to 70 vol%, and particularly preferably 5 to 60 vol%, based on the total of the photopolymerizable matrix component and the metal filler; a metal filler having a volume fraction of 20 to 95 vol%, preferably 30 to 95 vol%, and particularly preferably 40 to 95 vol%, based on the total of the photopolymerizable matrix component and the metal filler; a photopolymerization initiator adapted to the photopolymerizable matrix component and the light wavelength used for photopolymerization, the photopolymerization initiator having a content of 0.05 to 10 phr, preferably 0.1 to 5 phr, and particularly preferably 0.3 to 3 phr, based on the photopolymerizable matrix component; and a metal filler having a fine particle fraction of less than 10% having a particle size of less than 1 micrometer. - a 3D printing method based on layer-by-layer photopolymerization for the production of parts, in particular radiation-absorbent parts, using a metal-filled resin formulation according to the invention, which 3D printing method comprises providing the metal-filled resin formulation in a production bath, on a production bed and / or as a wet layer, and selectively hardening the metal-filled resin formulation layer-by-layer by polymerization in the production bath, on the production bed and / or in the wet layer using selective light irradiation to form the part. - Additively manufactured parts, in particular radiation-absorbent, produced using the 3D printing method according to the invention.

[0017] The idea underlying the present invention is to incorporate high-density metal materials into a photocurable resin formulation and form this composite into virtually any complex part shape by a light-based, and therefore particularly precise, additive method. To this end, the present invention uses a metal-filled resin formulation that integrates a polymerizable matrix component with one or more metal fillers. In this case, a photoinitiator initiates a rapid photoreaction, thereby imparting sufficient green strength to the composite, in combination with the matrix component, to maintain the desired shape fidelity during the 3D printing process and post-processing. In this case, light irradiation can optionally be applied directly to the surface of the resin formulation or introduced into the resin formulation through a carrier medium transparent to light irradiation.

[0018] In addition to guaranteeing ultra-fine and complex geometries with wall or structure thicknesses in the 100 μm range and at the same time high resolutions of up to 10 μm and precision of 3D parts in the printing process with adequate surface quality, the cured composite material is particularly capable of absorbing radiation doses with energies in the keV range or even above at a specified wall thickness. This is achieved by the use of radiation-absorbing metals, which preferably have a density comparable to or greater than that of lead, reaching a filler content of at least 20% by volume in the composite. The resulting density of the photopolymerized composite is therefore likewise sufficiently high, for example 4.5 g / cm. 3 It can also be set to a value greater than 0.

[0019] As a result, the effectiveness and performance of the technical 3D parts produced in this way can be significantly improved, for example, by improving the directionality of light in radiation collimators. The ability to quickly and efficiently mass-produce and supply parts for new and existing applications is another major benefit of the 3D printing technology used. Light-based techniques are particularly advantageous here, as their precision allows parts to be manufactured with consistent surface quality compared to traditional manufacturing methods such as injection molding. This also provides the desired backward compatibility for cost-effective, on-demand production of spare parts in existing applications.

[0020] Existing material solutions, consisting of metal-filled composites with desired radiation-absorbing properties that can be produced by conventional methods, are based on a thermoplastic matrix. However, the additive processing methods that can be used are limited to extrusion-based 3D printing methods (e.g., fused filament fabrication) or powder-bed methods (e.g., laser powder bed fusion), which significantly fall short of the potential of light-based 3D printing technologies in terms of their achievable resolution or feature size (achievable part resolution of over 50 μm, minimum wall thickness of over 150 μm). These limitations become even more pronounced, especially when composite materials are used.

[0021] Another advantage of producing composite materials via SLA-based techniques is the efficient use of materials, since all of the unpolymerized formulation can be reused in the printing process.

[0022] The digital manufacturing aspect of light-based 3D printing methods, among other things, allows for tool-free production of target shapes. This reduces the production risk of new shapes many times over, since start-up costs for a new production campaign do not need to be procured upfront and there is no need to consider wait times for tooling. Without such production risk, shape and product iterations can be quickly and cost-effectively transferred to field testing, so product optimization can continuously move forward.

[0023] Advantageous embodiments and developments are evident from the dependent claims and the description with reference to the drawings.

[0024] According to one development, the photopolymerizable matrix component can comprise acrylates, in particular methacrylates, acrylamides, in particular methacrylamides, vinyl esters, vinyl ethers and / or cyclic ethers, and the like.

[0025] In principle, however, any photocurable matrix component or correspondingly behaving material is of interest here, which, under light irradiation, in particular in the presence of a suitable photoinitiator system, is structurally crosslinked and hardened by a photochemical process.

[0026] According to one development, the photopolymerizable matrix component can be adapted to cure under irradiation with light of wavelengths between 150 and 1000 nm, preferably between 200 and 550 nm.

[0027] The photopolymerizable matrix component can therefore be cured not only by near-infrared and visible light, but also by UV light, in particular. The photoinitiator(s) are adjusted accordingly. The achievable through-curing depth of the additional structure and thus the layer thickness can be, for example, in the range of 10 to 500 μm, preferably 40 to 300 μm, particularly preferably 70 to 250 μm.

[0028] According to one development, the metal filler may comprise tungsten, molybdenum and / or tantalum or another suitable metal.

[0029] As a rule, here it is at least 8.5 g / cm 3 , preferably at least 10 g / cm 3 Of interest are any metals, any metallic materials and / or any combination of metallic materials, particularly preferably having a density comparable to or greater than that of lead.

[0030] According to one development, the corresponding resin formulation has a viscosity of at least 4.5 g / cm 3 , preferably at least 6 g / cm 3 , particularly preferably at least 8 g / cm 3 The density of the granular material may be 0.05 to 0.15.

[0031] According to the present invention, the metal filler comprises less than 10% fine particle fraction having a particle size of less than 1 micrometer.

[0032] The strong absorption of the metal fillers used, especially in the 150-1000 nm spectral range, can limit the achievable curable layer thickness. This limitation is highly dependent on the filler level and particle size, particle shape, and particle distribution. The higher the filler level and / or the smaller the particle size, the greater the barrier to light entering the formulation and enabling photopolymerization and subsequent structuring of the photopolymerizable matrix component. For this reason, it is advantageous to have a small particulate component.

[0033] According to one development, the metal filler may have a particle size distribution in which D10>2 μm and D90<100 μm.

[0034] In addition to the average particle size, the particle size distribution is also important. The particle size distribution of a sample can be measured, for example, by laser diffraction and can be characterized using several indices, Dxx. For example, D50 means that 50% of the particles are smaller than the specified value. Other important parameters include D10 as a measure of the smallest particles in the sample, and D90, and sometimes D95, D99, and / or D100, for larger particles. For example, the closer D10 and D90 are, the narrower the particle size distribution.

[0035] Here, the particle size of the smallest particles is considered to be substantially greater than 2 μm (index D10). The upper particle size limit D90 is limited by the desired wall thickness and the required surface roughness (for example, less than 100 μm).

[0036] According to one development, the metal filler may have a monomodal particle size distribution, but also a bimodal or multimodal particle size distribution.

[0037] Particle size distributions with multiple maxima in the density distribution are called multimodal, i.e., bimodal, trimodal, etc. Multimodal distributions are preferred to achieve high loading levels or to facilitate the processability of metal-filled resin formulations. Thus, the density distribution of the metal-filled particles in this case may have only a single maximum, or at best, two or more maxima.

[0038] According to one development, the metal filler may comprise rounded and / or round particles.

[0039] For example, rounded and / or round metal particles in the resin formulation according to the invention result in increased flowability or reduced wear behavior during processing, which has an advantageous effect on the processing of the resin formulation.

[0040] According to one development, the metal-filled resin formulation may further contain rheological additives, nanoparticle fillers with particle sizes of less than 1 micrometer, light absorbers, adhesion promoters, antifoaming agents, leveling additives and / or thermal initiators. In particular, each additive may be present in a content of 0.01 to 20 phr relative to the photopolymerizable matrix component.

[0041] For example, metal particles of a metal filler can be stabilized within a matrix component by adding a rheological additive, which forms a network of physical bonds that prevents the particles from sinking within the matrix component.

[0042] Alternatively or additionally, nanoparticles may be added to prevent settling.

[0043] The metal-filled resin formulations used preferably have suitable settling stability (e.g., greater than 4 weeks at room temperature and / or greater than 2 days at process temperature) to ensure storage stability of the resin product and isotropic filler distribution in the layers of the part produced during the 3D printing process.

[0044] When particles are at risk of light scattering during the 3D printing process, the addition of light-absorbing substances (e.g., UV absorbers, HALS) can prevent curing outside of the desired exposed areas.

[0045] Additionally, other substances or mixtures can be added to accelerate cure (e.g., UV-cure adhesion promoters, defoamers to reduce air void content, leveling additives for a stable resin layer on the production bed, etc.).

[0046] According to one development, the 3D printing method can include process types SLA (e.g. laser), LCD process (e.g. display), DLP (e.g. projector) active light mask and / or other suitable light-emitting processes with active light mask, where it is understood that a person skilled in the art can combine suitable processes.

[0047] Much more precise additive manufacturing processes are light-based techniques such as stereolithography (SLA) or digital light processing (DLP), which use so-called photopolymerizable resin formulations (mainly acrylate- or epoxy-based). Using these techniques, the resin formulations used can be locally and precisely cured layer by layer by light excitation, enabling the production of 3D parts with resolutions down to 10 μm (in the case of SLA) and part features down to less than 100 μm. Additionally, such 3D printing methods are advantageous over material extrusion or powder-bed methods due to their high material efficiency, reduced energy consumption, achievable part density, and excellent scalability.

[0048] For example, so-called hot lithography can be used as a special form of SLA (see, for example, US Pat. No. 5,629,399), which aims to process highly filled formulations by targeted heating of the process zone in combination with a layer doctor technique, resulting in particularly good material resistance and a smoother surface. Hot lithography is therefore particularly suitable for processing filled material systems, such as the metal-filled resin formulation according to the invention, and therefore for producing technical 3D parts from composite materials with high precision and good surface quality.

[0049] According to one development, the component may be designed to absorb electromagnetic radiation with an energy of at least 1 keV, in particular at least 50 keV.

[0050] For example, the component may be configured to absorb electromagnetic radiation having an energy in the range of 50 keV to about 300 keV, and the wall thickness may therefore be selected depending on the radiation energy, for example in the range of 100±50 μm or more.

[0051] According to one development, the part may have a wall thickness of less than 150 μm.

[0052] The minimum wall thickness can therefore in particular be less than 100 μm.

[0053] According to one development, the part has a density of at least 4.5 g / cm 3 , preferably at least 6 g / cm 3 , particularly preferably at least 8 g / cm 3 is.

[0054] The resulting density of the photopolymerized composite material can therefore be in the range of lead or even higher.

[0055] According to one development, the organic components can be fired in a separate step from the green part by heat treatment (e.g. in a convection oven), and the resulting brown part is then subjected to a sintering process to form a metal, metal oxide or combination metal and metal oxide part.

[0056] According to one development, the fired part can furthermore be infiltrated with a metallic and / or non-metallic matrix, which allows the properties (eg radiation absorption, strength, etc.) to be adjusted.

[0057] The above-mentioned configurations and developments can be combined with one another in any way, provided this is reasonable. Further possible embodiments, developments and implementations of the invention also include combinations of the features of the invention described above in connection with the examples or in the following specification, but not explicitly described. In particular, those skilled in the art can add individual aspects as improvements or supplements to each basic form of the invention. [Brief explanation of the drawings]

[0058] The invention will be explained in more detail below with reference to an embodiment presented in the schematic diagram of the drawing.

[0059] [Figure 1] 1 shows a schematic diagram of a 3D printing apparatus for carrying out a 3D printing method according to one embodiment of the present invention; [Figure 2] 2 shows a detailed view of a part manufactured using the 3D printing apparatus of FIG. 1 based on a metal-filled resin formulation according to one embodiment of the present invention. [Figure 3] Figures 1 and 2 show a schematic flow chart of the 3D printing method used.

[0060] The accompanying drawings are intended to provide a further understanding of embodiments of the present invention. They illustrate embodiments and serve to clarify the principles and concepts of the present invention. Other embodiments and many of the described advantages will become apparent with reference to the drawings. Elements in the drawings are not necessarily shown to scale relative to each other.

[0061] In the figures, identical, functionally identical and identically acting elements, features and components are given the same reference numerals, respectively, unless otherwise specified. DETAILED DESCRIPTION OF THE INVENTION

[0062] 1 shows a schematic diagram of a 3D printing apparatus 100 for carrying out a 3D printing method M according to one embodiment of the present invention. A schematic flow chart of process M is shown in FIG.

[0063] The process M is used in the embodiment described below for the manufacture of a radiation-absorbing component 10. The component 10 is, for example, a scattered radiation collimator, which is used to suppress unwanted scattered radiation for a radiation detector in a transmission tomography apparatus, for example an X-ray computed tomography apparatus. During an examination, for example in X-ray computed tomography, such scattered radiation can occur due to interaction with the object. To prevent unwanted artifacts in the captured image, such scattered radiation is stopped by a corresponding collimator element, usually made of a suitably dense metallic or metal composite material, before it enters the detector.

[0064] For this and other radiation absorbing structures, polymer / metal composites are often formed today by conventional polymer molding techniques such as injection molding or extrusion, using metal fillers with high density and / or high atomic number, such as tungsten, in which case the density of the resulting composite is at least 4.5 g / cm. 3 , which corresponds to a tungsten loading of more than 18.5% by volume, although a higher loading would be ideal to achieve a density similar to or even higher than that of lead. It should be noted that while a higher density improves component performance in terms of radiation absorption, the composite's lower mechanical strength must be taken into account, which can lead to brittleness in the finished part. Furthermore, processing such composites is difficult with a higher percentage of metal loading, and complex shapes can no longer be realized. Therefore, the polymer matrix must be specifically optimized to ensure good processability and the required (thermo)mechanical properties.

[0065] Due to the ever-increasingly required miniaturization of applications or development efforts, there is also a great demand for the production of highly complex geometries (e.g., wall thicknesses of less than 100 μm and resolutions or accuracies down to 10 μm to increase the sensitivity of collimators), which are not achievable by conventional molding processes. Furthermore, with the above-mentioned mass production methods, on-demand production of degradable spare parts is either economically unfeasible or must be mitigated by sufficient storage capacities at the current state of the art.

[0066] Therefore, additive manufacturing techniques, namely 3D printing, are currently being proposed for the production of such precise radiation-absorbent shaped components. However, 3D printing methods realized to date, such as those that directly process metallic materials (e.g., laser powder bed fusion, see the aforementioned non-patent document 1) or those that use thermoplastic-based metal composites (e.g., fused filament fabrication, see patent document 10), similar to injection molding or extrusion methods, are severely limited in terms of the achievable part resolution (>50 μm) and the minimum achievable wall thickness (>150 μm). These limitations are even more pronounced when composite materials are used.

[0067] For this reason, innovative approaches are currently being pursued, in which metal-filled resin formulations are structured locally and precisely freeform by photoexcitation, layer by layer, with high precision, part features down to <100 μm or resolution down to 10 μm, using stereolithographic 3D printing methods such as SLA. In this case, the metal-filled resin formulation should have a density of at least 4.5 g / cm in order for the final part 10 to absorb radiation with an energy above 50 keV, for example. 3These 3D printing methods are selected to have a material density equal to or greater than 1000 Å. Access to complex geometries and low wall thicknesses allows for improved part performance in many applications (e.g., improved light directionality in collimators). Additionally, these 3D printing methods offer advantages over material extrusion or powder bed processing methods due to their high material efficiency, reduced energy consumption, achievable part densities, and high scalability.

[0068] Process M thus optionally includes, in M1, providing a metal-filled resin formulation 1 by providing a wet layer of metal-filled resin formulation 1 in a production bath and / or on production bed 6 and / or generally. Process M further includes, in M2, selectively curing the metal-filled resin formulation 1 layer by layer by photopolymerization in the production bath and / or on production bed 6 and / or in the provided wet layer using selective light irradiation to form a part. Light irradiation can be applied directly to the surface of the resin formulation as needed (FIG. 1) or can be introduced into the resin formulation through a support medium that is transparent to light irradiation.

[0069] A corresponding exemplary structure for the "top-down" method is shown in Figure 1. A metal-filled resin formulation 1 is present in a production bath 6. A control device 7, e.g., a computer, controls, on the one hand, a laser 8, which moves a laser beam 9 selectively over the surface of the resin formulation 1 in the production bath 6 via a deflection mirror 11. On the other hand, the control device 7 controls a lowering device 13 in the production bath 6 to gradually lower a work table 12, on which a part 10 is constructed by hardening of the resin formulation 1, layer by layer, caused by means of a laser beam.

[0070] Formulation 1, as used herein, comprises a mixture of a photostructurable matrix component (component A) and one or more metal fillers (component B). Formulation 1 is constructed as follows: - Photopolymerizable matrix component A: Monomers, oligomers, prepolymers or mixtures thereof, consisting of the group of monofunctional and / or polyfunctional radically and / or cationically polymerizable compounds, such as (meth)acrylates, (meth)acrylamides, vinyl esters, vinyl ethers, cyclic ethers, etc., in a volume fraction of 5 to 80% by volume, preferably 5 to 70% by volume, particularly preferably 5 to 60% by volume, based on the sum of components A and B. - Metal fillers (component B), especially radiation-absorbing, such as refractory metals: 8.5 g / cm 3 or more, preferably at least 10 g / cm 3 or more, and a volume fraction of 20 to 95 volume %, preferably 30 to 95 volume %, particularly preferably 40 to 95 volume %, based on the total of component A and component B, preferably tungsten, molybdenum or tantalum, preferably with a low fine particle fraction (less than 1 μm, less than 10%), D10>2 μm and D90<100 μm, preferably with a unimodal or bimodal distribution, and preferably with a rounded or round particle shape. Photopolymerization initiator: adjusted to the photopolymerizable component A and the wavelength of light used for curing, and has a content of 0.05 to 10 phr, preferably 0.1 to 5 phr, particularly preferably 0.3 to 3 phr, relative to component A.

[0071] The photopolymerizable component A is cured by targeted irradiation with light at wavelengths of 150 to 1000 nm, preferably 200 to 550 nm, using a tailored photoinitiator. Achievable through-cure depths, and therefore layer thicknesses, are in the range of 10 to 500 μm, preferably 40 to 300 μm, and particularly preferably 70 to 250 μm. The matrix component A, together with the photoinitiator, enables a fast photoreaction and provides the composite with sufficient green strength, thereby maintaining the desired shape fidelity during the 3D printing process and post-processing.

[0072] Optionally, additional components such as rheological additives, fillers with a particle size of less than 1 μm, absorbers, adhesion promoters, antifoaming agents, leveling additives, thermal initiators, etc. may be included in the formulation, each in a content of 0.01 to 20 phr relative to component A.

[0073] FIG. 2 shows a detailed view from FIG. 1 of the part 10 in manufacture.

[0074] In the lower region of the part 10, the metal-filled resin formulation 1 has already been transformed into a hardened material 5. Above this there is a thin layer of not yet hardened metal-filled resin formulation 1, i.e., of a photopolymerizable matrix component 2 with a metal filler material 3 dispersed therein, with a layer thickness 14 determined by the position of the depression device 13. By selective laser irradiation, this layer can be targeted and hardened in specific areas, and the part 10 can thus be expanded layer by layer upwards.

[0075] The presented resin formulation and photopolymer composites fabricated by SLA have the following material properties (4.5 g / cm for radiation absorption in the range of 50–300 keV). 3 or sufficient radiation resistance of the matrix), in combination with the described geometric freedom of the producible 3D parts (minimum wall thickness down to less than 100 μm), the achievable part resolution (down to 10 μm) and the resulting surface quality, offer decisive quality and performance improvements of the corresponding technical 3D parts (e.g. improved directionality of light in radiation collimators).

[0076] Resin formulations can be detected, for example, by particle determination (density, REM, particle size determination, RFA), matrix determination by Fourier transform IR spectroscopy, NMR spectroscopy, GPC, LC / GC-MS, UV / VIS spectroscopy and / or UV exposure testing.

[0077] The lithographically produced part 10 can be analyzed, for example, by microscopy of the SLA layer structure and by the particle size, particle shape, and / or particle distribution used. The particle distribution can be used to estimate, for example, the approximate filler content. Energy dispersive X-ray spectroscopy (EDS) can be used, for example, to analyze the filler used. Density measurements and ATR-IR spectroscopy can be used to determine, for example, the base matrix and filler content, including the information obtained by EDS. The associated radiation absorption can be measured relative to pure tungsten or lead, where a defined radiation intensity can be applied to the plaque and measured by radiation transmission. Finally, the absorption of scattered light radiation, as well as possible artifacts / radiation resulting from the material, are important and can be tested for each application.

[0078] In other words, the part 10 manufactured using this process M can be distinguished from conventionally manufactured structures both in terms of its material composition and in terms of its structuring (wall thickness, etc.) by appropriate measurement processes.

[0079] In the foregoing detailed description, various features are shown together in one or more examples to improve the consistency of the description. However, it is clear that the above description is merely illustrative and in no way limiting in nature. It covers all alternatives, modifications, and equivalents of the different features and exemplary embodiments. Many other examples will be immediately and directly apparent to those skilled in the art in light of the above description based on their technical knowledge.

[0080] The embodiments have been chosen and described to best illustrate the principles underlying the invention and its practical applicability, thereby enabling those skilled in the art to best modify and utilize the invention and its various embodiments for its intended use. In the claims and the specification, the terms "comprise" and "have" are used as linguistically neutral terms for the corresponding term "comprise." Furthermore, the use of the singular terms "ein," "einer," and "eine" is not intended to exclude, as a general rule, the plural features and plural components described with the term. [Explanation of symbols]

[0081] 1 Metal-filled resin formulation 2. Photopolymerizable matrix components 3 Metal fillers 4. Photopolymerized matrix components 5 Curing material 6 Manufacturing bath, manufacturing floor 7 Control Device 8 Laser 9 Laser light 10 parts 11 Deflector mirror 12 Workbench 13 Submersion device 14 layer thickness 100 3D printing equipment M Process M1, M2 process steps

Claims

1. A metal-filled resin formulation (1) for a photopolymerization-based 3D printing method (M) for the manufacture of a radiation-absorbing part (10), the resin formulation (1) comprising: a photopolymerizable matrix component (2) comprising at least one of a monomer, an oligomer and a prepolymer from the group consisting of monofunctional and / or polyfunctional radically and / or cationic polymerizable compounds; The composition comprises a metal filler (3), the metal filler (3) having a density of at least 8.5 g / cm3, the photopolymerizable matrix component (2) having a volume fraction of 5 to 80 volume % based on the total of the photopolymerizable matrix component (2) and the metal filler (3), and the metal filler (3) having a volume fraction of 20 to 95 volume % based on the total of the photopolymerizable matrix component (2) and the metal filler (3); a photopolymerization initiator, the photopolymerization initiator being adapted to the photopolymerizable matrix component (2) and the wavelength of light used for photopolymerization, the photopolymerization initiator having a content of 0.05 to 10 phr relative to the photopolymerizable matrix component (2); The metal filler comprises a fine particle distribution of less than 10% having a particle size of less than 1 micrometer. Metal-filled resin formulation.

2. The photopolymerizable matrix component (2) comprises at least one of acrylate, acrylamide, vinyl ester, vinyl ether, and cyclic ether.

10. The resin formulation of claim 1.

3. The photopolymerizable matrix component (2) is adapted to cure under irradiation with light having a wavelength of 150 to 1000 nm.

10. The resin formulation of claim 1.

4. The metal filler (3) comprises at least one of tungsten, molybdenum, and tantalum.

10. The resin formulation of claim 1.

5. The metal filler (3) has a particle size distribution of D10>2 μm and D90<100 μm.

10. The resin formulation of claim 1.

6. The metal filler (3) has a monomodal or bimodal particle size distribution.

10. The resin formulation of claim 1.

7. The metal filler (3) has rounded and / or round particles.

10. The resin formulation of claim 1.

8. The metal-filled resin formulation (1) further comprises at least one of a rheological additive, a nanoparticle filler having a particle size of less than 1 micrometer, a light absorber, an adhesion promoter, an antifoaming agent, a leveling additive, and a thermal initiator.

10. The resin formulation of claim 1.

9. The metal-filled resin formulation (1) is characterized in that it comprises at least one of the rheological additive, the nanoparticle filler having a particle size of less than 1 micrometer, the light absorber, the adhesion promoter, the defoamer, the leveling additive, and the thermal initiator, each in an amount of 0.01 to 20 phr relative to the photopolymerizable matrix component (2).

9. The resin formulation of claim 8.

10. 10. A photopolymerization-based 3D printing method (M) for the manufacture of radiation-absorbing parts (10) using the metal-filled resin formulation (1) according to any one of claims 1 to 9, comprising: Providing (M1) said metal-filled resin formulation (1) in a production bath, on a production bed (6) and / or as a wet layer; selectively curing (M2) the metal-filled resin formulation (1) layer by layer by polymerization in the production bath, on the production bed (6) and / or in the wet layer using selective light irradiation to form the part (10); 3D printing method comprising:

11. The 3D printing method (M) is characterized in that it includes at least one active light mask from the process types of stereolithography, liquid crystal display process and digital light processing; 3D printing method according to claim 10.

12. The method of claim 11, wherein the component (10) to be manufactured absorbs electromagnetic radiation having an energy of at least 1 keV. 3D printing method according to claim 10.

13. The part (10) to be manufactured has a wall thickness of less than 150 μm. 3D printing method according to claim 10.

14. The part (10) to be manufactured has a density of at least 4.5 g / cm3. 3D printing method according to claim 10.

Images