Manufacture of a metal mold for replicating an assembly having a predetermined three-dimensional shape

Abstract

The invention relates to a manufacturing method for replicating a metal mold for a component having a predetermined three-dimensional shape, the manufacturing method comprising: (a) manufacturing a glass-like mold having a predetermined three-dimensional shape by using a moldable nanocomposite comprising an organic binder and glass particles dispersed therein; and (b) replicating the glass-like mold obtained in step (a) by melting a metal inside the glass-like mold or by melting a metal outside the glass-like mold and pouring it onto or into the glass-like mold, followed by cooling, or by pressing the glass-like mold into a ductile metal substrate, thereby obtaining a metal mold for replicating a component having an inverted predetermined three-dimensional shape. Furthermore, the invention relates to a replication method for a component having a predetermined three-dimensional shape, the metal mold obtained by the manufacturing method being used for replicating the component, wherein the glass particles of the moldable nanocomposite comprise glass particles of a first type having a diameter in the range of 5 nm to 500 nm.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a metal mold for replicating components having a predetermined three-dimensional shape. Furthermore, this invention relates to a method for replicating components having a predetermined three-dimensional shape. Background Technology

[0002] Polymer components, that is, components made of polymer materials, can be manufactured on an industrial scale using replication processes. Compared to subtractive or additive manufacturing processes, replication processes, such as injection molding, allow for the rapid and scalable manufacture of polymer components because they do not require any shape-defining steps during manufacturing. That is, in these replication processes, thermoplastics or resins are injected into a molding tool and then cured, where the molding tool has already defined the final three-dimensional shape of the polymer component. Unlike thermoplastics, resins can develop cross-linked structures upon curing.

[0003] As described above, to obtain a polymer component, the thermoplastic or resin in a moldable state when injected into a molding tool needs to be hardened. In the case of thermoplastics, hardening occurs upon cooling, transforming the softened thermoplastic into a polymer component with a final three-dimensional shape. In the case of resins, hardening occurs upon curing or polymerization induced by external stimuli such as heat or radiation, transforming the liquid component of the resin into a polymer component with a final three-dimensional shape. Since the final three-dimensional shape of the polymer component is predetermined by the shape of the molding tool, it is often referred to as the predetermined three-dimensional shape. Of course, the shape of the molding tool is inverse of the final three-dimensional shape of the polymer component. In other words, the molding tool has an inverted predetermined three-dimensional shape.

[0004] For example, replication processes such as injection molding allow for the shaping of very complex structures, which are limited only by the surface properties of the forming tool. In this context, metal molds have proven particularly well-suited as forming tools because of their sufficient durability, allowing them to be used to manufacture thousands of polymer components over a long period of time using the same forming tool.

[0005] The cost of each forming tool ranges from over €10,000 to several million euros. The manufacture of metal molds is a cost-related step in replicating the production of polymer components. Currently, most metal molds used in industry are obtained through subtractive manufacturing, particularly CNC machining techniques such as milling, drilling, or grinding. Additive manufacturing is gaining popularity in rapid mold making (often referred to as rapid prototyping). However, given the unsatisfactory surface properties, such as high roughness and the presence of defects, which are often caused by additive manufacturing of metals, rapid prototyping has not yet been widely adopted on an industrial scale.

[0006] Against this backdrop, C. Richter et al., Progress in Biomedical Optics and Imaging (2017, Vol. 10061) described a method for manufacturing forming tools for polymer replication, which includes: generating microstructures in a photoresist by photolithography; casting the microstructures into a high-temperature silicone resin used as a primary mold for creating the metal forming tool; and melting a eutectic alloy of Sn, Ag and Cu directly inside the silicone under light pressure in an oven to obtain the metal forming tool after cooling to room temperature.

[0007] In addition, PL Schilardi et al., Journal of the Argentine Chemical Society (2003, Vol. 91, pp. 143-152) described microtransfermolding using metal stamps.

[0008] In addition, F. Kotz et al., Progress in Biomedical Optics and Imaging (2019, Vol. 10875) described high-throughput thermal replication of transparent fused silica glass. Summary of the Invention

[0009] In view of the above, the object of the present invention is to overcome the aforementioned disadvantages associated with the manufacture of metal molds known in the art. In particular, the technical problem behind the present invention is to provide a method for manufacturing a metal mold that allows for the cost-effective provision of metal molds in order to be scalable to industrial scale, while also allowing for the provision of metal molds with sufficient surface properties such as low roughness and no defects.

[0010] The aforementioned technical problems behind this invention have been solved by providing embodiments having the features of the appended claims.

[0011] In particular, in one aspect, the present invention provides a method for manufacturing a metal mold for replicating an assembly having a predetermined three-dimensional shape, the manufacturing method according to the invention comprising:

[0012] (a) A glass mold is manufactured by using a moldable nanocomposite material containing an organic binder and glass particles dispersed therein, the glass mold having a predetermined three-dimensional shape and being obtained as follows:

[0013] (i) Before, during and / or after the organic binder hardens, the moldable nanocomposite material is shaped into a predetermined three-dimensional shape to obtain a primary structure;

[0014] (ii) By removing the organic binder, the primary structure obtained in step (i) is debonded, thereby obtaining a secondary structure having cavities formed therein;

[0015] (iii) Optionally, the cavity of the secondary structure obtained in step (ii) is filled with at least one glass-forming precursor; and

[0016] (iv) Sintering the secondary structure obtained in step (ii), optionally filled with at least one glass-forming precursor in step (iii), to obtain a glass mold; and

[0017] (b) A metal mold for replicating the component is obtained by replicating the glass mold obtained in step (a) by melting metal inside the glass mold, or by melting metal outside the glass mold and pouring it onto or into the glass mold, followed by cooling, or by pressing the glass mold into a malleable metal substrate. The metal mold has an inverted, predetermined three-dimensional shape.

[0018] The glass particles in the moldable nanocomposite material include first-type glass particles with diameters ranging from 5 nm to 500 nm.

[0019] Advantageously, the manufacturing method according to the invention, characterized by the above-described process steps, allows for the cost-effective provision of metal molds in a scalable industrial-scale manner. This is because the glass mold obtained in step (a) is subsequently replicated into a metal mold in step (b). In other words, according to the invention, the manufacturing of the metal mold itself is a replication process, meaning that step (b) can be repeated several times as needed, thereby obtaining more than one metal mold using the same or different glass molds. As a result, the manufacturing method according to the invention does not suffer from the disadvantages particularly known in CNC machining techniques, such as low throughput.

[0020] Advantageously, the manufacturing method according to the invention, characterized by the above-described process steps, also allows for the provision of metal molds with sufficient surface properties such as low roughness and defect-free characteristics. This is because a moldable nanocomposite material containing an organic binder and glass particles dispersed therein is used to manufacture the glass mold. Since the glass particles of the moldable nanocomposite material are not molten, i.e., only the organic binder of the moldable nanocomposite material needs to be in a moldable state, the glass mold can be manufactured at a relatively low temperature in step (a). For example, when the glass mold is manufactured by means of a replication process using a template made of polymer material, the template does not degrade. In other words, according to the invention, the template is neither exposed to molten glass nor to molten metal. On the other hand, the glass mold obtained in step (a) is heat-resistant, and therefore it can come into contact with the molten metal in step (b). Since the metal mold is a direct replication of the glass mold, meaning that the metal mold has the shape of an inverted glass mold, the surface properties of the metal mold are essentially only affected by the surface properties of the glass mold. As a result, the manufacturing method according to the invention does not suffer from disadvantages particularly known due to rapid molding, such as low resolution and poor surface quality. Attached Figure Description

[0021] The attached figure shows :

[0022] Figure 1 This invention shows (a) a glass mold and (b) a metal mold obtained by pouring molten metal onto the glass mold.

[0023] Figure 2 The replicating component and the metal mold used for replicating the component are shown. The replicating component is made of poly(methyl methacrylate).

[0024] Figure 3 The manufacture of a metal mold obtained in the following work example is shown schematically.

[0025] Figure 4 Evaluations of the metal molds obtained in the following work examples are shown: (a) white light interferometry of the metal mold; and (b) microscopic images of the metal mold. Detailed Implementation

[0026] The manufacturing method according to the present invention and its specific process steps as described above are described in detail below.

[0027] In step (a) of the manufacturing method according to the invention, a glass mold is manufactured using a moldable nanocomposite material comprising an organic binder and glass particles dispersed therein. The glass mold obtained in step (a) has a predetermined three-dimensional shape. According to the invention, the nanocomposite material used to manufacture the glass mold is moldable, meaning that its organic binder is in a moldable state. With the organic binder in a moldable state, the moldable nanocomposite material can be shaped to manufacture a glass mold having a predetermined three-dimensional shape.

[0028] According to the present invention, a glass mold is obtained in step (a) through steps (i) to (iv) as defined above. Before discussing steps (i) to (iv) in more detail, the composition of a moldable nanocomposite material having an organic binder and glass particles dispersed therein as essential components is first described:

[0029] There are no further restrictions on the organic binder of moldable nanocomposites, as long as it is in a moldable state, that is, as long as it can be transformed into a moldable state, so that the moldable nanocomposites can be shaped to manufacture glass molds.

[0030] In one embodiment of the invention, the organic binder of the moldable nanocomposite is a thermoplastic that can harden upon cooling. Therefore, cooling transforms the softened thermoplastic into a solid, causing the organic binder to no longer be in a moldable state. As a result of the hardening of the thermoplastic used as the organic binder, the primary structure obtained in step (i) further described below retains its shape.

[0031] When the organic binder is a thermoplastic, it may be selected from polyesters based on aromatic or aliphatic dicarboxylic acids and diols and / or hydroxycarboxylic acids, polycarbonates based on aliphatic or aromatic diols, such as polyethylene, polypropylene, polybutene, polymethylpentene, polyisobutylene and other polyolefins, poly(ethylene-vinyl acetate), ethylene propylene rubber (EPR), poly(ethylene propylene diene), poly(vinyl butyral) (PVB), polyacrylates and polymethacrylates, cyclic olefin polymers, and polyamides such as polyoxymethylene and other polyacetals, polyethers such as polyethylene glycol (PEG), including bisphenol-based aromatic polyethers, or polyurethanes, or combinations thereof, but not limited thereto.

[0032] In another embodiment of the invention, the organic binder of the moldable nanocomposite material is a resin capable of curing upon initiation of curing or polymerization by an external stimulus. In this context, heat or radiation, particularly UV radiation, can be mentioned as the external stimulus. In some cases, even mixing as an external stimulus may be sufficient, for example in two-part resins, where the liquid components of the resin exhibit sufficient reactivity with each other. Furthermore, as needed, the external stimulus may include an initiator added to the organic binder to promote the curing or polymerization of the organic binder. Suitable initiators are known to those skilled in the art, such as acetophenones like 2,2-dimethoxy-2-phenylacetophenone (DMPAP), azo compounds like azobisisobutyronitrile (AIBN), benzophenone derivatives, fluorescein and its derivatives such as Bengal red, quinones such as camphorquinone, and phosphine derivatives such as diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, but are not limited thereto. Thus, curing or polymerization initiated by an external stimulus transforms the liquid component of the resin into a solid, causing the organic binder to no longer be in a moldable state. When exposed to external stimuli, depending on the resin used, the resin either cures, resulting in a cross-linked structure, or polymerizes, resulting in a non-cross-linked structure. In other words, the term "resin" as used herein includes not only thermosetting resins but also thermoplastic resins. That is, as a resin, this document may refer to any monomer and / or oligomer and / or polymer composition without limitation. As a result of the curing of the resin used as an organic binder, the primary structure obtained in step (i) retains its shape, as further described below.

[0033] When the organic binder is a resin, it may be selected from acrylate resins and methacrylate resins, unsaturated polyester resins, vinyl ester resins, epoxy resins, thiol-olefin resins, or polyurethane resins, but is not limited thereto. In particular, when the organic binder is a resin, 2-hydroxyethyl methacrylate (HEMA) or a mixture of 2-hydroxyethyl methacrylate and tetraethylene glycol diacrylate (TEGDA) may be mentioned as organic binders.

[0034] In addition to the organic binder, the moldable nanocomposite material also contains glass particles as an essential component. The glass particles are dispersed within the organic binder. Depending on the organic binder used, the dispersion of the glass particles can be achieved by any means known in the art. When a thermoplastic is used as the organic binder, the thermoplastic can be softened or dissolved in a suitable organic solvent or gas phase before adding the glass particles. When a resin is used as the organic binder, the glass particles can be added directly to the liquid component of the resin.

[0035] In a preferred embodiment of the invention, the glass particles of the moldable nanocomposite material are fused silica glass particles. Fused silica glass is characterized by being composed of high-purity amorphous silica. Hereinafter, fused silica glass is understood to be glass in which the silica mass fraction is at least 99% based on the total mass of the glass, and typical impurities include Al, Ca, Cu, Fe, Na, K, Li, and Mg, each present in amounts less than 15 ppm. That is, fused silica glass substantially does not contain any components typically added to other types of glass to lower their melting point. Thus, fused silica glass exhibits high thermal stability, enabling it to withstand the temperatures encountered when in contact with molten metal in step (b) further described below.

[0036] According to the present invention, the glass particles of the moldable nanocomposite material comprise glass particles with a diameter in the range of 5 nm to 500 nm, preferably in the range of 7 nm to 400 nm. These glass particles are also referred to as first-type glass particles. These are glass particles with a diameter in the nanometer range that make the moldable composite material containing an organic binder and glass particles dispersed therein a first-type moldable nanocomposite material.

[0037] In addition to glass particles with diameters ranging from 5 nm to 500 nm, preferably from 7 nm to 400 nm, the glass particles in the moldable nanocomposite material may also include glass particles with diameters ranging from 2 µm to 50 µm, preferably from 2 µm to 40 µm. These glass particles are also referred to herein as second-type glass particles. In the case where the glass particles comprise both first-type and second-type glass particles, i.e., a bimodal mixture of glass particles, the smaller-diameter glass particles can fill the gaps between the larger-diameter glass particles. Therefore, a denser packing of glass particles in the moldable nanocomposite material is achieved, which in turn leads to less shrinkage during sintering in step (iv) further described below. In principle, the glass particles may also comprise any other type of glass particles with diameters different from both the first-type and second-type glass particles. Such multimodal mixtures of glass particles are also within the scope of this invention.

[0038] In this document, the diameters of Type I, Type II, and any other types of glass particles should be understood as the average diameter measured according to ISO 9276-2. According to the invention, it is not necessary for the glass particles to be (perfectly) spherical. That is, the glass particles can also be spherically similar, i.e., they can be near-spherical. For example, for Type I glass particles with diameters in the range of 5 nm to 500 nm, preferably in the range of 7 nm to 400 nm, this means that these glass particles can substantially have no dimensions with a diameter less than 5 nm, preferably no dimensions with a diameter less than 7 nm, and substantially no dimensions with a diameter greater than 500 nm, preferably no dimensions with a diameter greater than 400 nm.

[0039] There are no limitations on the amount of glass particles in the moldable nanocomposite material, which is at least 5 parts by volume, preferably at least 30 parts by volume, and more preferably at least 50 parts by volume, based on 100 parts by volume of organic binder. The higher the amount of glass particles in the moldable nanocomposite material, as further described below, the denser the packing of glass particles in the glass mold obtained in step (b). Surprisingly, as discovered by the inventors, even when the amount of glass particles in the moldable nanocomposite material is quite high relative to the organic binder, for example, more than 55 parts by volume based on 100 parts by volume of organic binder, the moldable nanocomposite material can still be shaped to manufacture glass molds.

[0040] In addition to the organic binder and the glass particles dispersed therein, the moldable nanocomposite material can contain more than one additional reagent as needed, which facilitates the manufacture of glass molds and their replication in metal molds. According to the invention, preferably, when the total mass of the moldable nanocomposite material is 100% by mass, the content of any additional reagent considered as a whole in the moldable nanocomposite material does not exceed 20% by mass, more preferably not more than 15% by mass, even more preferably not more than 10% by mass, and even more preferably not more than 5% by mass. That is, the moldable nanocomposite material according to the invention is substantially composed of an organic binder and glass particles dispersed therein, including any initiators added to the organic binder. Hereinafter, the term "substantially composed of" means that, when the total mass of the moldable nanocomposite material is 100% by mass, the content of the organic binder and glass particles dispersed therein, including any initiators added to the organic binder, preferably reaches at least 80% by mass, more preferably at least 85% by mass, even more preferably at least 90% by mass, and even more preferably at least 95% by mass.

[0041] For example, a dispersant may be added to promote the dispersion of glass particles in an organic binder. Alcohols, nonionic surfactants such as polyoxyethylene alkyl ethers or polyoxymethylene, and anionic surfactants such as fatty acids and their salts, or aliphatic carboxylic acids and their salts, such as stearic acid and its salts, or oleic acid and its salts, may be mentioned herein without limitation. Another example of a dispersant suitable for use in this invention is 2-[2-(2-methoxyethoxy)ethoxy]acetic acid. According to the invention, the presence of a dispersant is not essential. That is, the invention also includes embodiments in which the moldable nanocomposite material does not contain any dispersant.

[0042] To facilitate the debinding of the primary structure in step (ii) as further described below, the moldable nanocomposite preferably also includes a phase-forming agent dispersed in the organic binder. A phase-forming agent that is solid or viscous at room temperature (understood herein as 25°C) forms an internal phase in the organic binder. Examples of phase-forming agents include alcohols, ethers, and silicone oils, and combinations thereof, which have sufficiently high molecular weights and / or are appropriately functionalized to be solid or viscous at room temperature. Hereinafter, the term "viscous" should be understood to mean a viscosity of at least 1 mPa·s at room temperature as measured according to DIN 53019. As further described below, the phase-forming agent can be removed from the organic binder before or during the debinding of the primary structure in step (ii), for example by means of heat treatment that causes the phase-forming agent to evaporate or sublimate or decompose. Alternatively, the phase-forming agent can be removed by means of solvent or gas-phase extraction.

[0043] As a specific example, phenoxyethanol (POE) can be mentioned as a phase forming agent. POE has a viscosity of approximately 30 mPa·s at room temperature, making it a viscous substance. It can evaporate at atmospheric pressure and a temperature of 242°C. However, due to its high vapor pressure, a considerable amount has already been removed at lower temperatures. Furthermore, PEG and 2-[2-(2-methoxyethoxy)ethoxy]acetic acid, as mentioned above, can also be used as phase forming agents.

[0044] It is worth noting that once the primary structure is formed, the organic binder is in a solid state (not a liquid, gel, or paste state). As those skilled in the art will know, a solid is characterized by the inability to determine its viscosity. In this document, the moldable nanocomposite material does not contain any thickeners or any low-viscosity solvents such as water. According to specific embodiments of the invention, the moldable nanocomposite material is free of triglycerides, waxes and paraffins, as well as any plasticizers such as phthalates and any derivatives thereof.

[0045] To enhance the mechanical stability of the glass mold obtained in step (a), the moldable nanocomposite material may further include a powder of ceramic material or a precursor of ceramic material dispersed in an organic binder. In this context, the term "powder of ceramic material" means that the particles contained in the powder are made of ceramic material. In the case where the moldable nanocomposite material includes a powder of ceramic material, the particles contained in the powder, in addition to the glass particles outlined above, need to have a suitable diameter, i.e., a suitable size. Furthermore, the term "precursor of ceramic material" means that the ceramic material is formed from the precursor during sintering in step (iv), as further described below. In the case where the moldable nanocomposite material includes a precursor of ceramic material, the precursor may be at least one metal-containing compound selected from the group consisting of organometallic compounds, metal complexes, and metal salts, or a combination of two or more thereof. That is, the precursor of the ceramic material acts as a metal source for the ceramic material. The means outlined above for dispersing glass particles in an organic binder also apply here for dispersing the powder of ceramic material and / or the precursor of the ceramic material in the organic binder.

[0046] In step (i), the moldable nanocomposite material according to the invention, as described in detail above, is shaped into a predetermined three-dimensional shape before, during, and / or after the organic binder hardens. This yields a primary structure (also known as a green body). Depending on the organic binder used, hardening is either completed upon cooling or during curing or polymerization induced by an external stimulus. The shape of the primary structure obtained in step (i) already reflects the shape of the glass-like mold obtained in step (iv), as further described below.

[0047] The moldingable nanocomposite material can be shaped into a predetermined three-dimensional shape by any suitable means known in the art. In particular, the moldingable nanocomposite material can be shaped in step (i) by a subtractive manufacturing process, an additive manufacturing process, a replication process, or a combination thereof. Depending on the process applied, an organic binder having glass particles dispersed therein is hardened before, during, and / or after the shaping of the moldingable nanocomposite material.

[0048] In subtractive manufacturing processes, an organic binder containing dispersed glass particles hardens before the moldingable nanocomposite material is shaped. In other words, after the organic binder hardens, the moldingable nanocomposite material is shaped into a predetermined three-dimensional shape. Suitable subtractive manufacturing processes include, but are not limited to, laser-based structuring techniques and CNC machining techniques such as milling, drilling, grinding, sawing, lathing, and polishing.

[0049] In additive manufacturing processes, an organic binder containing dispersed glass particles hardens during the shaping of the moldable nanocomposite. In other words, during the hardening of the organic binder, the moldable nanocomposite is shaped into a predetermined three-dimensional shape. Suitable additive manufacturing processes include, but are not limited to: selective laser sintering and selective laser melting, fused filament fabrication (also known as fused deposition modeling), stereolithography, two-photon polymerization, inkjet printing, and volumetric printing techniques.

[0050] In the case of replication processes, an organic binder containing dispersed glass particles hardens after shaping the moldable nanocomposite material. In other words, the moldable nanocomposite material is shaped into a predetermined three-dimensional shape before the organic binder hardens. Suitable replication processes include, but are not limited to, casting, injection molding, (injection) compression molding, extrusion, thermoforming, cold drawing or hot drawing, hot embossing, nanoimprinting, and blow molding.

[0051] In one embodiment of the invention, the moldable nanocomposite material is shaped in step (i) by casting the moldable nanocomposite material onto a template and then hardening it. The template has an inverted predetermined three-dimensional shape. That is, the shape of the template is inverted with the final three-dimensional shape of the component to be replicated. Thus, the template has the shape of a forming tool for replicating the component. Therefore, in this embodiment, the moldable nanocomposite material is shaped in step (i) by means of a replication process.

[0052] Regarding the material of the template, the present invention has no further limitations. Since the template is neither exposed to molten glass nor molten metal, as mentioned above, there are no particular limitations regarding the temperature resistance of the material, as long as the template can be replicated into a glass mold in step (i).

[0053] For example, but not limited to, the template is made of a polymeric material. The polymeric material can be derived from thermoplastics or resins. In this document, polymeric material should be understood to encompass not only carbon-based polymers. For example, polymeric material also encompasses silicon-based polymers, such as polysiloxanes, also known as silicones. Where necessary, to impart sufficient mechanical stability to the template, the polymeric material can be at least partially crosslinked. Partial crosslinking can be achieved by using a thermosetting resin, such as a suitable silicone resin having at least three or more reactive functional groups per molecule.

[0054] As needed, templates can be obtained in advance through subtractive manufacturing processes, additive manufacturing processes, replication processes, or combinations thereof. In this context, the methods outlined above for shaping moldable nanocomposites are equally applicable here.

[0055] For example, but not limited to, the template can be obtained in advance using photolithography. In photolithography, a photoresist is irradiated onto a substrate covered with a mask. The photoresist can be positive or negative. When previously irradiated, negative photoresist is insoluble in the developing solution; that is, the areas of the photoresist that have been irradiated by the mask remain on the substrate and form the template. When not previously irradiated, positive photoresist is insoluble in the developing solution; that is, the areas of the photoresist that have not been irradiated by the mask remain on the substrate and form the template. Suitable subtractive manufacturing processes include, but are not limited to, CNC machining, laser cutting, and waterjet cutting as described above. Suitable additive manufacturing processes include, but are not limited to, selective laser sintering and fused filament fabrication, two-photon polymerization, direct laser writing, lithography, and especially stereolithography as described above.

[0056] In the case of obtaining a template in advance using a replication process, the template is replicated from an existing component having a predetermined three-dimensional shape. In this document, the existing component can be identical to the component to be replicated. As with the case of using a template, the existing component can be made of a polymer material. Furthermore, as with the case of using a template, the existing component can be obtained in advance using a subtractive manufacturing process, an additive manufacturing process, a replication process, or a combination thereof. In this context, the considerations outlined above regarding templates also apply to the existing component. The existing component can be replicated into the template using a thermoplastic or resin. To do this, a liquid component of a softened thermoplastic or resin is cast onto the existing component. This is then cured to obtain a template made of a polymer material. As mentioned above, the polymer material, for example, covers not only carbon-based polymers but also silicon-based polymers.

[0057] As described above, to shape moldable nanocomposites into a predetermined three-dimensional shape, one or more subtractive manufacturing processes, additive manufacturing processes, and replication processes can be combined. For example, when a moldable nanocomposite is shaped by means of a replication process and the primary structure has a visible artifact produced by the replication process, a subtractive or additive manufacturing process can be applied as a post-processing to the primary structure. In particular, such post-processing can be readily applied when the primary structure is obtained by casting the moldable nanocomposite into a template. Suitable means for post-processing are known to those skilled in the art, including, but not limited to, CNC machining techniques as described above. The above considerations also apply to templates and existing components.

[0058] In step (ii), the primary structure obtained in step (i) is debonded by removing the organic binder. Thus, a secondary structure, also known as a brown body, is obtained. As a result of debonding, i.e., removing the organic binder, the secondary structure has cavities formed therein.

[0059] Depending on the organic binder used, the primary structure obtained in step (i) can be debonded in step (ii) by means of heat treatment, chemical reaction, reduced pressure, solvent or gas phase extraction, or a combination thereof. For example, prior to heat treatment, the primary structure can first be immersed in a solvent for solvent extraction. In principle, any means that can remove the organic binder can be applied without adversely affecting the glass particles and the powder and / or precursors (if present) of the ceramic material forming the secondary structure. In this context, those skilled in the art routinely select appropriate conditions for the application of organic binder removal in step (ii).

[0060] For example, in the case of debonding achieved by heat treatment, depending on the size of the glass mold to be obtained, the temperature applied during debonding is typically in the range of 100°C to 600°C, for example, in the range of 150°C to 550°C; the heating rate is typically in the range of 0.1°C / min to 5°C / min, for example, in the range of 0.5°C / min to 1°C / min; and the holding time is typically in the range of 2 minutes to 12 hours. In cases where the size is relatively small, a few seconds are sufficient for debonding the primary structure in step (ii). Heat treatment can also be carried out in a stepwise manner. Based on the above considerations, by means of reduced pressure, i.e., pressure below atmospheric pressure, which makes the organic binder more volatile, debonding by heat treatment can be further promoted.

[0061] After the organic binder is removed, the glass particles and the powder and / or precursor of the ceramic material (if present) adhere together due to hydrogen bonding. This imparts mechanical stability to the secondary structure. Considering the size of the glass particles, with diameters in the nanometer range, the glass particles possess a high specific surface area, which allows sufficient interactions to maintain the mechanical stability of the secondary structure.

[0062] Before or during the removal of the organic binder in step (ii), the phase-forming agent (if present) may be removed from the primary structure, for example by evaporation or sublimation, or by decomposition. The removal of the phase-forming agent (if present) may also be accomplished by means of solvent or gas-phase extraction. In principle, the same means described above for the removal of the organic binder may be applied.

[0063] As a result of removing the phase-forming agent (if present), debonding of the primary structure in step (ii) is facilitated. This is because the internal phase formed by the phase-forming agent in the organic binder creates pores in the primary structure when it is removed. Through these pores, the residual organic binder can then be removed in a more controlled manner. Therefore, it is easier to prevent damage to the secondary structure, especially when it is a thick structure. The same applies when the organic binder is removed in several steps. For example, in the case where the organic binder is a combination of two or more binder components exhibiting different thermal decomposition behaviors, debonding can be carried out sequentially. In this case, after removing the first binder component, i.e., the binder component with the lowest decomposition temperature, the pores created in the primary structure after removing the first binder component facilitate the removal of further binder components.

[0064] In optional step (iii), the cavity of the secondary structure obtained in step (ii) may be filled with at least one glass-forming precursor. The at least one glass-forming precursor (also referred to as a filler) must have suitable dimensions so that it can be introduced into the cavity formed in the secondary structure. By filling the cavity of the secondary structure with at least one glass-forming precursor, the shrinkage of the secondary structure during sintering in step (iv), as further described below, can be reduced. Furthermore, by selecting a suitable glass-forming precursor, the hardness of the resulting glass mold can be increased, and / or its coefficient of thermal expansion can be altered, for example, its coefficient of thermal expansion can be minimized. There are no further limitations on the at least one glass-forming precursor herein, and it can be selected in an appropriate manner based on the intended purpose.

[0065] There are no limitations; for example, silicon-based glass-forming precursors such as tetraethyl orthosilicate (Si(OC2H5)4), also known as TEOS, can be used. In particular, glass-forming precursors that form glasses indistinguishable from the glass particles in the moldable nanocomposite material can be used herein. However, glass-forming precursors that form glasses distinguishable from the glass particles in the moldable nanocomposite material can also be used herein. For example, when the moldable nanocomposite material contains fused silica glass particles as glass particles, titanium-based glass-forming precursors such as tetraethyl orthosilicate (Ti(OC2H5)4) can also be used. Other metal alkoxides that can be used herein include titanium isopropoxide, titanium ethoxy, zirconium ethoxy, aluminum isopropoxide, vanadium isopropoxide, niobium ethoxy, tantalum ethoxy, and potassium tert-butoxide. More suitable glass-forming precursors are known to those skilled in the art. These may also be used herein.

[0066] When the glass particles in a moldable nanocomposite material are fused silica glass particles and the cavities of the secondary structure are filled with a silica-based glass forming precursor such as TEOS, glass molds made of high-purity fused silica glass with a density comparable to conventionally processed fused silica glass can be obtained. As a result, the glass molds obtained in step (a) are particularly resistant to high temperatures. Even if the secondary structure is not filled with a glass forming precursor in step (iii), the Vickers hardness of the glass molds obtained after sintering in step (iv) is comparable to that of conventionally processed fused silica glass.

[0067] In step (iii), the cavity of the secondary structure can be filled with at least one glass-forming precursor by immersing the secondary structure in a solution containing at least one glass-forming precursor, exposing the secondary structure to physical or chemical vapor deposition in an atmosphere containing or generating at least one glass-forming precursor, or a combination thereof. However, in principle, any other filling process can also be applied in this regard. For example, a sol-gel process can also be applied. Depending on at least one additive that optionally fills the cavity of the secondary structure in step (iii), the secondary structure can first be immersed in a solution containing one glass-forming precursor, and then exposed to physical or chemical vapor deposition containing or generating another glass-forming precursor. Depending on the situation, the cavity of the secondary structure can be filled with at least one glass-forming precursor even before the primary structure has completely debonded. In this case, it is a partially debonded primary structure filled with at least one glass-forming precursor.

[0068] In step (iv), the secondary structure obtained in step (ii) is sintered (optionally filled with at least one glass-forming precursor in step (iii)). Thus, a glass mold is obtained.

[0069] Suitable sintering conditions are known to those skilled in the art and are routinely selected as needed. There are no limitations; depending on the size of the glass mold to be obtained, the temperature applied during sintering is typically in the range of 700°C to 1600°C, the heating rate is typically in the range of 1°C / min to 10°C / min, for example, 5°C / min, and the holding time is typically in the range of 0.5 hours to 8 hours, for example, 4 hours. In the case where the moldable nanocomposite material comprises a precursor of ceramic material dispersed in an organic binder, and / or where the cavity of the secondary structure is filled with a glass-forming precursor in step (iii), the secondary structure can be pre-sintered at an intermediate temperature to convert the ceramic material precursor into ceramic material, and / or to convert the glass-forming precursor into glass. For example, pre-sintering can be carried out at a temperature in the range of 400°C to 700°C.

[0070] When the glass particles dispersed in the moldable nanocomposite are fused silica glass particles, considering the low coefficient of thermal expansion and high thermal shock resistance of fused silica glass, both a relatively high heating rate and a relatively high cooling rate can be selected.

[0071] According to the invention, sintering does not require the application of pressure. Instead, the sintering in step (iv) can be suitably carried out at a pressure below atmospheric pressure, for example at a pressure of up to 0.1 mbar, preferably up to 0.01 mbar, and particularly preferably up to 0.001 mbar. Since sintering can be carried out at atmospheric pressure or even lower, no special requirements need to be followed regarding the sintering furnace in this invention.

[0072] After sintering, the resulting glass mold can be cooled to room temperature and then copied into a metal mold in step (b) as further described below.

[0073] In step (b) of the manufacturing method according to the invention, the glass mold obtained in step (a) by performing steps (i) to (iv) is replicated by melting metal inside the glass mold, or by melting metal outside the glass mold and pouring it onto or into the glass mold, followed by cooling, or by pressing the glass mold into a malleable metal substrate. Thus, a metal mold for replicating the component is obtained. The metal mold has a predetermined three-dimensional shape of the inverted component to be replicated. Figure 1 The diagram shows a metal mold obtained by pouring molten metal onto a glass mold according to the invention.

[0074] Regarding the metals, the present invention has no further limitations. For example, the metal may be selected from the group consisting of nickel, aluminum, copper, zinc and tin, or may be an alloy of these or other metals, such as brass, bronze or a multi-component alloy of AlMg7Si3Mn.

[0075] Depending on the shape of the glass mold corresponding to the shape of the component to be replicated, the metal can be melted inside or outside the glass mold and poured onto or into it. After completion, the metal solidifies by cooling. Alternatively, depending on the circumstances, the glass mold can be pressed into a metal substrate. To do this, the metal substrate needs to be malleable at room temperature or high temperature. Metals suitable for pressing include, but are not limited to, aluminum and copper. The metal mold can be used as is and requires no post-processing. However, for example, to remove features present in the mold, or to add features not present in the mold used to manufacture the glass mold, the metal mold can be post-processed, for example, by means of subtractive or additive manufacturing processes.

[0076] On the other hand, the present invention provides a method for replicating a component having a predetermined three-dimensional shape. In the replication method according to the present invention, a metal mold obtained by the manufacturing method according to the present invention as described above is used to replicate the component. Figure 2 The image shows the component being copied, along with the metal mold used to copy it.

[0077] According to the present invention, components can be replicated using the metal mold obtained according to the present invention through any replication process known in the art. For example, components can be replicated by means of injection molding, blow molding, hot stamping, thermoforming, or injection compression molding, but are not limited thereto.

[0078] Regarding the material of the component to be replicated, the present invention has no further limitations. In a preferred embodiment of the invention, the replicated component is made of a polymer material. The polymer material can be derived from thermoplastics or resins in the same manner as outlined in the template above.

[0079] The present invention, utilizing the above-described manufacturing method, allows for the cost-effective provision of metal molds for industrial-scale production, while simultaneously providing metal molds with sufficient surface properties such as low roughness and defect-free characteristics. In contrast to manufacturing methods known in the art, the predetermined three-dimensional shape of the component to be replicated is transferred into the metal mold without requiring any shape-defining steps as needed in subtractive or additive manufacturing. Surprisingly, the transfer of the predetermined three-dimensional shape can be accomplished based on a glass-like mold with the predetermined three-dimensional shape obtained during manufacturing. Once the glass-like mold is obtained, the step of replicating the glass-like mold into the metal mold can be repeated several times, using the same or different glass-like molds, as needed.

[0080] Furthermore, the present invention utilizing the above-described replication method allows for the provision of replicable components applicable to various technical fields. In particular, the metal mold transferred into the replicated component has sufficient surface properties, making it especially suitable for optical applications where high precision is essential, such as as a lens.

[0081] Example

[0082] The invention is further illustrated by the following examples, but is not limited thereto.

[0083] First, microfluidic channels, which are the components to be replicated, are obtained using photolithography. To replicate the microfluidic channels into a template, a two-component polydimethylsiloxane-based resin is cast into the microfluidic channels, followed by curing, i.e., curing induced by mixing as an external stimulus, resulting in a cross-linked structure.

[0084] Subsequently, a moldable nanocomposite material containing an organic binder and dispersed glass particles was used to replicate the template. A commercially available product (“Glassomer L50”, a room-temperature liquid fused silica nanocomposite material that can be cured by UV irradiation) was used as the moldable nanocomposite material. To replicate the template into a glass mold, the moldable nanocomposite material was cast onto the template and then cured, i.e., cured by UV irradiation. After debinding and sintering by means of heat treatment, a glass mold made of high-purity fused silica glass was obtained. The moldable nanocomposite material used in this paper allows for easy replication of the template into temperature-stable glass molds.

[0085] Next, nickel is melted at 920°C and poured onto a glass mold to replicate the glass mold into a metal mold. After cooling to room temperature, a high-quality metal mold is obtained, which can be used as a component to be replicated, such as for replicating microfluidic channels.

[0086] Figure 3 The manufacture of the metal mold obtained in this paper is illustrated in a schematic manner.

[0087] Figure 4 Showing (a) white light interferometry and (b) microscope images, from Figure 4 As can be seen from the evaluation, the metal mold obtained in this paper has the shape of a microfluidic channel that is replicated with high fidelity.

Claims

1. A method for manufacturing a metal mold, the metal mold being used to replicate a component having a predetermined three-dimensional shape, the manufacturing method comprising: (a) A glass mold is manufactured by using a moldable nanocomposite material comprising an organic binder and glass particles dispersed therein, the glass mold having a predetermined three-dimensional shape, and is obtained as follows: (i) Before, during and / or after the organic binder hardens, the moldable nanocomposite material is shaped into the predetermined three-dimensional shape to obtain a primary structure; (ii) Debonding of the primary structure obtained in step (i) by removing the organic binder. This results in a secondary structure having a cavity formed therein; (iii) Optionally fill the cavity of the secondary structure obtained in step (ii) with at least one glass-forming precursor; and (iv) Sintering the secondary structure obtained in step (ii), optionally filled with at least one glass-forming precursor in step (iii), to obtain the glass mold; and (b) A metal mold for replicating the component is obtained by replicating the glass mold obtained in step (a) by melting metal inside or outside the glass mold and pouring it onto or into the glass mold, followed by cooling, or by pressing the glass mold into a malleable metal substrate. The metal mold has an inverted predetermined three-dimensional shape. The glass particles of the moldable nanocomposite material comprise glass particles of a first type with diameters ranging from 5 nm to 500 nm.

2. The manufacturing method according to claim 1, wherein the organic binder of the moldable nanocomposite material is a thermoplastic that can harden upon cooling.

3. The manufacturing method according to claim 1, wherein the organic binder of the moldable nanocomposite material is a resin that can harden upon curing or polymerization induced by external stimuli.

4. The manufacturing method according to any one of claims 1 to 3, wherein the glass particles of the moldable nanocomposite material are fused silica glass particles.

5. The manufacturing method according to any one of claims 1 to 3, wherein the diameter of the glass particles of the first type is in the range of 7 nm to 400 nm.

6. The manufacturing method according to any one of claims 1 to 3, wherein the glass particles of the moldable nanocomposite material, in addition to the glass particles of the first type, also comprise glass particles of the second type with a diameter in the range of 2 μm to 50 μm.

7. The manufacturing method according to any one of claims 1 to 3, wherein the moldable nanocomposite material further comprises a phase forming agent dispersed in the organic binder, the phase forming agent being solid or viscous at room temperature and forming an internal phase in the organic binder, the phase forming agent being selected from alcohols, ethers, silicone oils, and combinations thereof.

8. The manufacturing method according to any one of claims 1 to 3, wherein the moldable nanocomposite material is shaped in step (i) by a subtractive manufacturing process, an additive manufacturing process, a replication process, or a combination thereof.

9. The manufacturing method according to any one of claims 1 to 3, wherein the moldable nanocomposite material is shaped in step (i) by casting the moldable nanocomposite material into a template and then hardening it, the template having an inverted predetermined three-dimensional shape.

10. The manufacturing method according to claim 9, wherein the template is made of a polymer material.

11. The manufacturing method according to claim 9, wherein the template is obtained in advance by means of a subtractive manufacturing process, an additive manufacturing process, a replication process, or a combination thereof.

12. The manufacturing method according to any one of claims 1 to 3, 10 and 11, wherein the primary structure obtained in step (i) is debonded in step (ii) by means of heat treatment, chemical reaction, reduced pressure, solvent or gas phase extraction, or a combination thereof.

13. A method for replicating a component having a predetermined three-dimensional shape, wherein a metal mold is used to replicate the component, the metal mold being obtained by the manufacturing method of any one of claims 1 to 12.

14. The replication method of claim 13, wherein the component is replicated by means of injection molding, blow molding, hot stamping, thermoforming or injection compression molding.

15. The replication method according to claim 13 or 14, wherein the replicated component is made of a polymer material.

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