Paste Compositions for Additive Manufacturing

Abstract

1. Additive manufacturing paste composition for producing three-dimensional shaped articles of a target material, the paste composition comprising: - 70 to 99.8 wt. % of particles of the target material, based on the weight of the composition, the particles being one or more compounds selected from the group of metals and metal alloys and mixtures thereof; - at least one binder component; - at least one additive component that is a lubricant; and - one or more solvents that are miscible with each other, wherein the total concentration of the at least one additive component and the at least one binder is 0.06 wt. % to 10.0 wt. % based on the weight of the paste composition, and wherein at least one of the additive component and the binder component or mixtures thereof is shear thinning.

Description

[Technical Field]

[0001] Technical Field The present invention relates to a paste composition for use in the additive manufacturing of three-dimensional objects of a material of interest, in particular a metal or metal alloy or mixtures thereof. The present invention also relates to a method for the additive manufacturing of three-dimensional objects using such a paste composition, and to three-dimensional objects obtainable by additive manufacturing of the paste composition. [Background technology]

[0002] Background technology Additive manufacturing, particularly robocasting, is a well-known technique in the art. Typically, starting with a CAD model of the desired object, robocasting involves forming a viscous paste into a continuous filament that is deposited layer by layer on a positioning stage or platform according to a predetermined pattern. This process ultimately results in an object with the desired shape.

[0003] Robocasting systems typically include a material deposition device with one or more nozzles and / or nozzle arrays. A paste composition containing the desired material is controllably dispensed or extruded through the one or more nozzles in the form of a continuous filament. The robocasting system further includes a positioning stage on which successive layers of the filament are deposited to print the three-dimensional object. The positioning stage may be a table that may be movable in the XY plane. The dispenser may be driven by conventional means in one or more of the X, Y, and Z directions, although several methods of moving the platform and deposition device relative to each other are possible.

[0004] During use, the paste composition is delivered from a reservoir to one or more nozzles and extruded in the form of filaments. The paste composition has shear-thinning properties, which restricts the flow of the deposited filaments but facilitates their dispensing from the nozzle. As a result, the paste composition retains its shape after being extruded from the nozzle. Nozzles with larger openings generally result in the formation of filaments with larger cross-sections, and in three-dimensional objects, layers may be visually distinct from one another, but the surface of the object typically exhibits a certain relief due to the filaments. On the other hand, nozzles with smaller nozzle openings generally result in the deposition of filaments with smaller cross-sections, which may enable the creation of objects with smoother surfaces. Depending on the size of the three-dimensional object being produced, nozzles with smaller nozzle openings may require longer processing times.

[0005] Three-dimensional shaped articles can typically be obtained by a process that involves depositing interconnected filaments in a predetermined arrangement in multiple stacked layers. Each layer contains multiple adjacent filaments or filament segments, and the distance between the continuous filaments or filament segments in one layer and the continuous filaments or filament segments in subsequent layers can be the same or different. The filaments in successive layers are connected to each other at least where the successive layers contact each other, thereby forming a shaped article. The filaments in successive layers may be positioned at an angle relative to each other.

[0006] After the desired number of filament layers are deposited according to the desired pattern, a very brittle and soft three-dimensional structure, the so-called "green body," is often obtained. Typically, a drying process follows the deposition or distribution step to evaporate the solvent from the green body. This step may be followed by a calcination step to burn off and / or decompose at least a portion of the organic components present in the paste composition. A sintering or firing step may also be provided to strengthen and / or compress the three-dimensional structure and / or fuse the particles of the desired material to obtain a three-dimensional molded article with desired mechanical properties.

[0007] The three-dimensional article may be a substantially dense solid object, which may be hollow, or may be formed into several parallel filaments in one layer, deposited at a distance from each other so that holes and channels are formed between the filaments, resulting in a porous structure containing voids or pores between the filaments. In successive layers, the filaments may be positioned at an angle relative to each other. The paste composition may be deposited on the printing platform or printing surface itself without the need for a support structure to support the deposited paste. If necessary, for example, in the case of overhanging parts, the use of a support structure may be envisioned. The paste composition generally includes the material from which the final object will be constructed (also referred to as the target material). The target material is typically incorporated into the paste composition in the form of particles. The paste composition usually also contains a binder component to bind the particles of the target material together, at least during filament deposition.

[0008] Ideally, a paste composition is used that allows for rapid dispensing, extrusion, or flow of material through the nozzle of the device, as well as reproducible deposition when the extruded material impacts the positioning stage. When a subsequent layer or layers are applied, adjacent layers can flow together to some extent to form a unitary structure, and it is often desirable for successive layers to be connected to one another to some extent. While some material flow may be desired, it should be limited to such an extent that it does not distort the desired shape of the printed structure or "green body."

[0009] As it moves through the nozzle during dispensing, the paste composition experiences high shear conditions. To facilitate the deposition of filaments in the intended shape, paste compositions are often used with pseudoplastic rheology so that they can flow smoothly through the nozzle during dispensing and solidify rapidly upon deposition when the shear stress is removed. If the paste is too fluid during deposition, there is a risk that the extruded filaments of the paste material will spread uncontrollably. On the other hand, if the paste composition is too viscous during deposition, the layers or filaments of the paste material may appear like rope strings with rounded tops, limiting the ability of successive layers to flow together, which is necessary to achieve a unitary structure. Therefore, under shear stress, a paste formulation ideally exhibits sufficient shear thinning to allow the paste to flow through a small-diameter nozzle without requiring extremely high driving pressures.

[0010] There is a need for paste compositions for use in additive manufacturing, particularly robocasting, that have a high solids content to enable the production of articles with high density and high mechanical strength. Additionally, there is a need for paste compositions that exhibit the desired rheological behavior in view of the additive manufacturing technique involved, i.e., the dispensing or deposition of the paste through a nozzle, and that allow for breakage rates to be kept to an absolute minimum.

[0011] It is therefore one object of the present invention to provide a paste composition containing particles of a target material for use in additive manufacturing of said target material into three-dimensional shaped articles having a desired shape, particularly for use in robocasting. Another object of the present invention is to maximize the solids content of the paste composition without adversely affecting the quality of the printed object. Summary of the Invention [Problem to be solved by the invention]

[0012] Summary of the Invention The present invention therefore seeks to provide a paste composition containing particles of a material of interest, particularly for use in additive manufacturing of said material of interest into three-dimensional shaped articles having a desired shape, particularly for use in robocasting, and further seeks to maximize the solids content of the paste composition. [Means for solving the problem]

[0013] This is achieved according to the present invention by an additive manufacturing paste composition for producing molded articles of the target material according to the first claim.

[0014] Additionally, there is provided an additive manufacturing paste composition for producing three-dimensional shaped articles of a material of interest, said paste composition comprising: - 70 to 99.8% by weight of particles of a target material, based on the weight of the composition, wherein the target material is one or more compounds selected from the group consisting of metals and metal alloys and mixtures thereof; at least one binder component, at least one additive component which is a lubricant; one or more solvents that are miscible with each other, wherein the combined concentration of the at least one additive component and the at least one binder is from 0.06 wt. % to 10.0 wt. % based on the weight of the composition, and at least one of the additive component and the binder component or a mixture thereof is shear thinning.

[0015] The expression that one or more solvents are miscible with each other means that the one or more solvents mix together in all proportions used in the compositions of the present invention to form a homogeneous phase.

[0016] In a preferred embodiment, the balance to 100% by weight is made up of one or more solvents and conventional additional components present in the paste composition.

[0017] According to a preferred embodiment, the at least one additive component may be soluble in a solvent, in particular the additive component may be a solvent-soluble wax, fat or oil, or a mixture of two or more thereof, and at least one of the additive component and the binder component or mixture thereof is shear-thinning. According to another preferred embodiment, the at least one additive component may be a solvent-dispersible wax, solvent-dispersible fat or solvent-dispersible oil, or a mixture of two or more thereof, and at least one of the additive component and the binder component or mixture thereof is shear-thinning.

[0018] Achieving a high solids content is important because it enables the production of filaments and 3D-printed articles made from high-density materials and high mechanical strength, which may be desirable for certain applications. Achieving a high solids content also enables the production of filaments and 3D-printed articles with limited organic material content. Reducing the amount of organic material in the paste composition is important because organic material remaining after calcination and / or sintering can adversely affect the mechanical properties and mechanical strength of 3D-printed articles. Carbon-based impurities can cause brittleness in materials containing them after sintering, especially if the material is a metal or metal alloy. Therefore, carbon-based impurities can adversely affect mechanical properties, especially mechanical strength, and can cause the density of the final product to be lower than originally intended. Furthermore, carbon can become incorporated or accumulate in the target material, especially if the target material contains a metal and / or metal alloy, causing deterioration of mechanical properties. Some applications may require an article with the highest possible purity.

[0019] Reducing the amount of organic material in the paste composition can reduce the risk of filament shrinkage and shrinkage of the 3D printed article during drying and calcination, which can induce crack formation and lead to rejection of the 3D printed article.

[0020] The paste compositions of the present invention can be produced as homogeneous pastes that exhibit minimal risk of phase separation between the fluid phase (including at least the solvent) and the solid phase, even when the particle content of the target material is high. Preventing phase separation can be important during paste preparation and storage, but is most important during dispensing.

[0021] The inventors have observed that the risk of phase separation remains minimal with the paste compositions of the present invention during the extrusion process, where the paste composition is displaced under pressure from a reservoir toward and through a nozzle, formed into one or more filaments of the desired cross-section and length, and then expelled from the nozzle onto a printing table. This is surprising, since the pressure used for filament formation often approaches values ​​that cause phase separation. Typically, the nozzle has a cross-section that is substantially smaller than the cross-section of the paste delivery section. This advantageous effect is surprisingly observed with paste compositions of the present invention in which the target material is composed of metal particles and / or metal alloy particles, which would otherwise easily cause phase separation, especially when the content of such particles rises to 70.0 to 99.8 wt. by weight relative to the weight of the paste composition. As a result, paste compositions are provided that are not, at least as contemplated by the present invention, highly concentrated target materials, and thus not previously suitable for processing in 3D printing processes utilizing paste extrusion processes.

[0022] Preventing phase separation is important because it allows for the desired homogeneity in the composition to be achieved across the cross-section and length of the formed filament. Such filaments may have more uniform density, porosity, mechanical strength, and other mechanical properties across the length and cross-section of the filament. Molded articles produced by depositing multiple stacked layers of interconnected filaments of the paste composition of the present invention in a predetermined arrangement may have a substantially homogeneous composition in each stacked layer and throughout the article. Such molded articles may have more uniform density, porosity, mechanical strength, and other mechanical properties.

[0023] Preventing phase separation is further important in terms of preventing remnants of material from being left behind during displacement of the paste composition through the nozzle, which may cause clogging of the nozzle, formation of defects in the filament, and therefore rejection of the article formed therefrom.

[0024] While the force required to achieve paste extrusion from a nozzle may vary for different materials, it has been found that, when using the paste compositions of the present invention, once conditions are established for a particular paste composition, adjustments to these conditions may not be necessary during the extrusion process. In particular, once the pressure applied to the paste composition is established to produce a filament of a desired cross-section and / or length, adjustments may not be necessary during the extrusion process. Therefore, the pressure applied to the paste composition may be kept substantially constant throughout the extrusion process and may only need to be adjusted within a minimal range. Other conditions, such as the temperature of the paste composition, may also only need to be adjusted within a minimal range. This is advantageous because it minimizes the risk of variations in the filament produced during the extrusion step, such as variations in composition and / or density. These variations may result in different mechanical properties, such as different mechanical strengths, in the filament and, consequently, in 3D-printed articles incorporating such filaments. Maintaining consistent conditions during the extrusion of the paste composition is even more important because it reduces the risk of phase separation.

[0025] Thus, the present invention provides a paste composition that exhibits high cohesive strength even when subjected to pressure and shear forces.

[0026] The binder and target material contribute to controlling the viscosity of the paste composition of the present invention so that it can take the form of a viscous paste with the desired viscosity suitable for use in robocasting, as described above. The paste composition of the present invention is suitable for delivery from the container through any tubing involved, if necessary, to an extrusion device, and further to and through a nozzle, which typically has a cross-section smaller than that of the paste composition delivery section. Because at least one of the at least one binder component and at least one additive component is shear-thinning, the viscosity of the paste composition decreases to some extent when the paste composition is subjected to shear force. Due to the shear-thinning properties, the viscosity can be reduced to such an extent that extrusion through a nozzle can be achieved, and the paste composition can be formed into filaments of the desired cross-section and length. As a result of the shear-thinning properties, the pressure required to achieve extrusion can be reduced, thereby minimizing the risk of phase separation in the paste. It has been found that the viscosity at least partially recovers upon removal of the shear force. Viscosity recovery appears to be nearly instantaneous, although some variation may occur with different materials. As a result, some flow of the paste composition in the filament may occur after the filament is dispensed from the nozzle. This improves adhesion of the filaments in contact with each other in continuous filaments and / or continuous layers. According to further embodiments, some flow may be desirable, but the flow of the paste composition should be limited so as not to excessively deviate from the desired shape of the resulting filament and 3D article.

[0027] The present invention also relates to the use of a solvent-dispersible or solvent-soluble wax, fat, or oil, or a mixture of two or more thereof, in a paste composition for additive manufacturing, particularly robocasting, where the paste composition is displaced through a nozzle with a reduced diameter by subjecting the paste composition to pressure and is expelled from the nozzle in the form of a long, continuous filament. The present invention particularly relates to the use of a water-soluble or water-dispersible wax, fat, and / or oil in a paste composition of the present invention for additive manufacturing, particularly robocasting. Accordingly, as described below, the water-dispersible wax preferably comprises lanolin. A small amount of additive is sufficient to facilitate the displacement of the paste composition through the nozzle and nozzle opening and to counteract nozzle clogging.

[0028] The present invention also relates to a method for producing a three-dimensional shaped article of a material of interest using additive manufacturing, the method comprising: forming a green structure by feeding interconnected filaments of an additive manufacturing viscous paste composition into a nozzle and dispensing from said nozzle onto a printing surface in a predetermined arrangement in a plurality of successively layered layers to form a green structure; and drying the green structure to obtain the three-dimensional shaped article, wherein the filaments of successive layers are connected to each other at least at points of contact between the filaments of successive layers, and said paste composition comprises: - 70 to 99.8% by weight of particles of a target material, based on the weight of the composition, wherein the target material is one or more compounds selected from the group consisting of metals and metal alloys and mixtures thereof; at least one binder component, at least one additive component which is a lubricant; one or more solvents that are miscible with each other, wherein the total concentration of the at least one additive component and the at least one binder is 0.06 wt % to 10.0 wt % based on the weight of the composition of particles of the material of interest, and at least one of the additive component and the binder component or mixture thereof is shear thinning.

[0029] When preparing the paste composition of the present invention, it may be preferable to mix the components. Mixing can be carried out at any temperature deemed suitable by those skilled in the art, but preferably the components are mixed at room temperature. The temperature maintained during mixing can be controlled to a desired level or can be allowed to develop to a specific temperature as a result of the mixing energy. Preferably, the temperature of the mixture during mixing is maintained below 75°C or at a maximum of 60°C or 50°C, preferably at a maximum of 40°C, more preferably at a maximum of 30°C and a minimum of 10°C, preferably at a minimum of 15°C, more preferably at a minimum of 20°C.

[0030] The dispensing of the paste composition of the present invention can be carried out at any temperature that a person skilled in the art deems appropriate. A person skilled in the art can select an appropriate dispensing temperature taking into account the properties of the paste composition, particularly the properties and amount of the particles of the target material, the properties and amount of the binder material, and the properties and amount of at least one additive component. When dispensing is carried out at a high temperature, for example, when it is desired to reduce the viscosity of the paste composition, a person skilled in the art may want to increase the temperature of the paste composition in the paste reservoir, in the nozzle, or in any part of the dispensing device located between the paste reservoir and the nozzle.

[0031] The present invention further relates to a molded article formed by additive manufacturing, particularly robocasting, of the paste composition described herein or using the method described herein. In particular, the present invention relates to a three-dimensional molded article. More specifically, the present invention relates to a three-dimensional molded article obtained by extrusion of the paste composition of the present invention, the molded article having interconnected filaments in a predetermined arrangement in a plurality of stacked layers, the filaments in successive layers being connected to each other. Thereby, the molded article can be a porous structure in which pores are formed by filaments positioned at a distance from each other in a plurality of stacked layers, which can be a substantially dense solid object or a hollow structure, or a combination of such structures.

[0032] The present invention also relates to a computer-implemented method for printing a porous structure, the computer-implemented method comprising at least the following steps: receiving a model of the porous body to be manufactured; - defining a printing path according to the desired characteristics of the porous body; - depositing a filament of a paste composition described herein according to a printing path; and operating the additive manufacturing system to perform the steps of:

[0033] The received model may be, for example, a 3D representation of the object to be printed. The method may further include, prior to depositing the layer of filament, determining a predetermined arrangement of the filament, which is at least one of an interfilament distance, a filament diameter, a material, an interfilament property, and an intrafilament property.

[0034] BRIEF DESCRIPTION OF THE DRAWINGS These and other features and advantages of embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a schematic diagram of the extrusion process. [Figure 2] 1 is a schematic diagram of an embodiment of a porous structure. [Figure 3] 1 is a schematic diagram of an embodiment of a porous structure. [Figure 4] FIG. 1 shows the force applied to the load cell of a filament deposition device as a function of time for the paste compositions described in the examples below. [Figure 5] FIG. 1 shows the force applied to the load cell of a filament deposition device as a function of time for the paste compositions described in the examples below. [Figure 6] FIG. 1 shows the force applied to the load cell of a filament deposition device as a function of time for the paste compositions described in the examples below. [Figure 7] 4-7 show the force applied to the load cell of a filament deposition device as a function of time for the paste compositions described in the Examples below. More specifically, Figures 4-7 show the force in Newtons versus time in minutes. DETAILED DESCRIPTION OF THE INVENTION

[0036] MODE FOR CARRYING OUT THE INVENTION A first aspect of the present invention is to provide an additive manufacturing paste composition for producing three-dimensional shaped articles of a target material.

[0037] A second aspect of the present invention is to provide the use of one or more of a solvent dispersible wax, a solvent dispersible fat or a solvent dispersible oil, or a mixture of two or more thereof, in a paste composition for additive manufacturing, in particular robocasting.

[0038] A third aspect of the present invention is to provide a method for producing three-dimensional shaped articles of a material of interest using additive manufacturing.

[0039] A fourth aspect of the present invention is to provide a three-dimensional shaped article obtained by extrusion from said paste composition using additive manufacturing, in particular using robocasting.

[0040] A fifth aspect of the present invention provides a computer-implemented method for printing a porous structure, the computer-implemented method being configured to operate an additive manufacturing system.

[0041] A specific application of the paste compositions described herein is as additive manufacturing paste compositions, particularly robocasting paste compositions, applicable to the production of strong, open, porous articles and dense articles with a dense structure. Such articles may be obtained by layer-by-layer deposition of continuous filaments, for example, by depositing interconnected filaments in a predetermined arrangement in multiple stacked layers, where the filaments of successive layers are connected to each other to form the article. This allows the filaments of successive layers to be positioned at an angle to each other. The article may have isotropic or anisotropic properties depending on the filament arrangement. Specific filament orientations or designs can be used to obtain the desired anisotropic properties of the article.

[0042] The paste composition can be extruded through a nozzle for three-dimensional filament deposition. The deposited filaments can form a layered network. Layers can be printed sequentially on top of each other, resulting in a structure formed by the lamination of successive layers. The filaments can be spaced apart to define channels between them. In this way, a porous structure with pores, i.e., holes or channels between the filaments, can be obtained. Two adjacent layers can be aligned and positioned on top of each other. However, it is also possible for the filaments in the upper layer to extend in a different direction than the fibers in the lower layer. Layer-by-layer deposition of filaments can involve extruding material through a deposition nozzle to form a filament while the deposition nozzle is moving relative to the print bed. The nozzle can move relative to the print bed, and / or vice versa. Thus, kinematic reversal is also contemplated. Different types of porous structures can be obtained. Such structures can represent meshes, lattices, filament networks, scaffolds, filament skeletons, etc. Many types of arrangements and structures are possible. The specific arrangement of the filaments can be selected based on the application.

[0043] It will be appreciated that extruded filaments may be known in the art as struts, fibers, rods, rasters, extrudates, and other terms.

[0044] The paste composition of the present invention is suitable for use in different types of direct extrusion additive manufacturing arrangements, in which a viscous paste composition is fed from a paste feed or supply or reservoir toward a nozzle and displaced through the nozzle under pressure. As a result, the paste composition is discharged from the nozzle in the form of a long continuous filament, strut, fiber, rod, extrudate, or the like of the paste composition, or in the form of a plurality of such filaments, struts, fibers, rods, extrudates, or the like of a specific length that exits the nozzle. Between the paste composition feed or supply and the nozzle, the arrangement may include several tubing and any other suitable components, such as an extrusion screw. The filament or filaments thus produced are positioned in a 3D arrangement to provide a 3D-shaped object or article.

[0045] The paste composition of the present invention is particularly suitable for use in additive manufacturing techniques that utilize the direct extrusion of a viscous paste into a 3D-shaped article with the desired filament configuration and structure. The paste composition of the present invention is suitable for use in, for example, screw extrusion or syringe extrusion. Combinations of these techniques are also possible. In a syringe extruder, the material can be placed in a syringe, and the printer can depress a plunger at a controlled rate to displace the paste composition through a nozzle, dispensing or extruding filaments in the desired shape, length, and 3D configuration. The syringe can be filled with the paste composition of the present invention. Different types of syringe extrusion systems are possible. Pneumatic pressure can be applied to the plunger. Alternatively, the plunger can be depressurized by mechanical displacement, achieved, for example, by an electric motor. Mechanical displacement can allow more direct control over the volumetric extrusion rate, whereas in pneumatic printers, the extrusion rate can depend more on the interplay between needle geometry, material viscosity, air pressure, and blockage by previously extruded filament. Other alternative designs are also possible. In a screw extruder, the material can be fed into a screw surrounded by a tight-fitting sleeve called a barrel. As the screw rotates, it can force material through a nozzle at the end of the barrel. The rate at which material extrudes from the nozzle can depend on the screw rotation speed. The screw extruder can accommodate material in paste form, but can also use granules, for example. The additive manufacturing software can control the extrusion rate based on the desired diameter of the extruded filament and the speed at which the nozzle is moving. A variety of systems can be used to implement the extrusion-based additive manufacturing method according to the present invention.

[0046] An additive manufacturing paste composition for 3D printing a material of interest according to an embodiment of the present invention comprises the following components: - 70.0 to 99.8% by weight of particles of a target material, the target material being one or more compounds selected from the group consisting of metals and metal alloys and mixtures thereof, based on the weight of the composition; at least one binder component, at least one additive component which is a lubricant; one or more solvents that are miscible with each other, wherein the sum of the concentrations of the at least one additive component and the at least one binder is from 0.06 wt. % to 10.0 wt. % based on the weight of the composition, and at least one of the additive component and the binder component or mixture thereof is shear thinning.

[0047] The paste composition may further contain a solvent and any further conventional additional components. The paste composition of the present invention exhibits several material and mechanical properties that make it particularly suitable for use in additive manufacturing, particularly robocasting, of three-dimensional shaped articles for the following reasons:

[0048] First, it has been found that the paste composition of the present invention can meet certain criteria regarding the rheology of the composition. Due to the presence of the binder and additive, the paste composition itself exhibits a desired cohesiveness and viscosity high enough to obtain a paste-like mass exhibiting the desired rheological properties, which can be displaced through a nozzle for the purpose of forming the paste into struts or any other desired form of filaments or fibers. The filaments are intended to be positioned on a printing surface in a 3D layered arrangement, with adjacent layers of filaments contacting each other and adhering to each other at least at their contact points, providing a so-called green shape that, when subjected to drying and sintering, produces the desired 3D article of the desired material. The presence of a limited amount of at least one of the binder or additive components appears to have a beneficial effect on the extrusion behavior of the paste when used in combination with a wide variety of target materials, particularly one or more metals, one or more metal alloys, or mixtures thereof. In particular, the presence of a limited amount of at least one of the binder or additive components provides pseudoplastic properties to the paste composition, allowing it to flow through and be ejected from a nozzle opening, such as the nozzle of an extrusion device typically used in robocasting, without the need for excessive force. The presence of a limited amount of at least one of the binder or additive components appears to be sufficient to facilitate transport of the paste composition through and ejection from the nozzle, minimizing the risk of adhesion to the walls that define the nozzle opening, causing paste clogging in the nozzle and resulting in defects in the filament extruded from the nozzle.

[0049] In addition, as described above, the paste compositions of the present invention may exhibit improved cohesive strength, which also means that the paste compositions may exhibit minimal risk of phase separation of the fluid and solid phases during production and storage of the paste compositions. This effect was observed even when the paste composition was subjected to typical pressures used in extrusion equipment to achieve displacement of the paste from a feed section toward and through a nozzle having a relatively small cross section compared to the dimensions of the feed section when converting the bulk paste into filaments by extrusion through a nozzle or multiple nozzles.

[0050] As a result of the shear thinning properties and improved cohesive strength, paste compositions having a higher solids content, i.e., a higher concentration in terms of weight percentage of the target material, can be produced and used to produce three-dimensional molded articles, compared to paste compositions known in the art that do not contain at least one of the binder and additive components. Thus, three-dimensional molded articles can be obtained with a higher content of the target material, higher density, and higher purity due to the reduced organic content resulting from the binder material, at least one additive, and at least one solvent. Furthermore, the need to increase the force or pressure applied to the paste in the load cell of the extrusion or deposition device to achieve a desired extrusion rate or speed may become unnecessary. Increasing the pressure is a typical measure taken during the extrusion of paste compositions when phase separation of the liquid from the paste occurs, and separation of the solvent from the remainder of the paste composition imposes the need to increase the pressure to achieve a paste with an increased solids content that can be transported through the extruder nozzle.

[0051] The paste compositions of the present invention may also exhibit minimal tendency to cause nozzle clogging or defects in the filament exiting the nozzle, for example, in the form of localized deformations or interruptions. It will be understood that the extent to which these effects are observed may depend on the specifics of the paste composition with respect to the concentration and nature of the paste components, the size distribution of the particles of the material of interest, etc.

[0052] Second, depending on the dimensions and geometrical arrangement of the filaments and to minimize the risk of deformation of the paste composition as it flows and exits the nozzle, the paste composition contains a sufficiently high concentration of particles of the target material, i.e., the material from which the molded article is essentially made, to enable the production of an article with the desired mechanical strength and integrity. Consequently, it is desirable for the paste composition to contain as little solvent, binder, additive, and other components as possible. Therefore, the concentration of the target material in the paste composition of the present invention is at least 70.0 wt %, preferably at least 75.0 wt %, and preferably at least 80.0 wt %, based on the total weight of the paste composition. With a particle concentration of the target material of at least 70.0 wt %, a three-dimensional molded article with a high solids content, high material density, high mechanical strength, high purity, and low organic content can be obtained after sintering. High purity can be important for certain applications and is beneficial to the mechanical strength and properties of the molded article. It will be understood that the concentration of the target material can vary within certain ranges, as various properties and densities of potential target materials must be taken into consideration. The concentration of the target material in the paste composition is generally up to 99.8 wt. %, preferably up to 99.5 wt. %, more preferably up to 99.0 wt. %, more preferably up to 95.0 wt. %, and most preferably up to 90.0 wt. % of the total weight of the paste composition, depending on the nature and density of the target material. Depending on the particle density and particle size of the target material, a high concentration of material particles in the paste can cause temporary or long-lasting clogging of the deposition device nozzle, leading to interruption of the deposited filament or local thickening of the deposited filament and subsequent rejection of the print. As a result, mass production using such pastes is characterized by a high failure rate.

[0053] To impart pseudoplastic properties to the paste composition of the present invention, the total concentration of the at least one additive component and the at least one binder is typically at most 10.0 wt.%, preferably at most 7.5 wt.%, or 7.0 wt.%, more preferably at most 6.0 wt.%, based on the total weight of the composition, depending on the nature and density of the target material. It is further understood that the total concentration of the at least one additive component and the at least one binder is typically at least 0.06 wt.%, preferably at least 0.1 wt.%, more preferably at least 0.4 wt.%, even more preferably at least 0.7 wt.%, more preferably at least 1.0 wt.%, and most preferably at least 1.5 wt.%, based on the total weight of the composition.

[0054] The target material contained in the paste composition of the present invention can be selected from a wide variety of metals or metal alloys known to those skilled in the art. The target material can be a metal in a metallic state or a mixture of two or more metals in a metallic state. According to an embodiment, the metal can be selected from the following: titanium, tantalum, tungsten, molybdenum, copper, aluminum, silver, platinum, iron, gold, tin, and combinations of two or more thereof.

[0055] The target material can be a metal alloy or a mixture of two or more alloys. An alloy is a combination of two or more metals or a metal combined with one or more other elements. Examples of metal alloys suitable for use in the present invention include aluminum alloys; stainless steel alloys, including austenitic, ferritic, and martensitic stainless steel alloys; cobalt alloys; copper alloys; nickel alloys; silver alloys; gold alloys; platinum alloys; ferroalloys, such as iron-chromium alloys, silver-copper alloys, titanium alloys, beryllium copper alloys, titanium-6 aluminum-4 vanadium, and zinc alloys.

[0056] The material of interest may also be a mixture of one or more metals and one or more metal alloys. Preferably, the target material has a particle morphology and shape, typically characterized by a specific particle size distribution and a specific surface area. The target material particles typically have an average particle size of at least 5 μm, preferably at least 10 μm, more preferably at least 15 μm, even more preferably at least 20 μm, and most preferably at least 25 μm, although smaller particles, e.g., having an average diameter of 1 or 2 μm, may also be present. It is further understood that the average particle size is generally at most 100 μm, preferably at most 90 μm, more preferably at most 80 μm, even more preferably at most 70 μm, more preferably at most 60 μm, even more preferably at most 50 μm, and most preferably at most 40 μm. According to a preferred embodiment, the target material particles have an average particle size in the range of 30 to 50 μm. However, it will be apparent to those skilled in the art that the average particle size and the preferred range of the average particle size may vary for different target materials and may be outside the ranges stated above. The particle size of the target material can be suitably selected by those skilled in the art depending on the cross section of the nozzle through which the paste composition is displaced and extruded, so that extrusion of a filament of the desired cross section can be achieved while minimizing the risk of nozzle clogging.

[0057] Those skilled in the art will therefore understand the general relationship between the average particle size of a material of interest and its weight percentage relative to the total weight of a paste composition. It will be appreciated that, to be printable in an acceptable manner, materials having a finer particle size are generally limited to a lower maximum weight percentage than compositions in which the material has a coarser particle size, the latter requiring less force on the load cell to comfortably push the paste through the nozzle and allowing for rheological properties to be manipulated. It will be further appreciated that one of the advantages of the present invention is that the inclusion of at least one additive component can shift such limitations on the maximum operable weight percentage to higher values.

[0058] According to an embodiment of the present invention, the at least one binder component can be an inorganic or organic compound, or a mixture of one or more inorganic compounds and one or more organic compounds. It will be understood that the nature of the binder, i.e., whether a binder with a more hydrophilic or more hydrophobic nature is used, can vary depending on the nature and composition of the paste composition. However, preferably, the at least one binder is an organic compound, more preferably an organic compound that can modify the rheology or flow properties of the paste composition under the influence of pressure. According to a preferred embodiment, the at least one binder component is selected from the following: plasticizers, hydrocolloids, cellulose derivatives such as methylcellulose and ethylcellulose, and / or combinations thereof; polymeric alcohols, in particular polyvinyl alcohol; polyalcohols, such as polyethylene glycol, polyvinylpyrrolidone; poloxamers, i.e., nonionic triblock copolymers capable of self-assembly and thermogelation and composed of a central hydrophobic chain of polyoxypropylene (poly(propylene oxide)) flanked by two hydrophilic chains of polyoxyethylene (poly(ethylene oxide)), commonly available under the names Syperonic (Croda), Pluronic (BASF), and Kolliphor (BASF); and combinations of two or more of the aforementioned binder materials. It will be clear to those skilled in the art that other materials exhibiting equivalent properties can be used as well.

[0059] Suitable plasticizers for use in the present invention are typically C8 to C 14and monomeric esters of alcohols and organic acids, which may be saturated or unsaturated and either mono- or polycarboxylic organic acids. Examples of organic acids suitable for use in the plasticizers of the present invention include trimellitic acid (e.g., octyl trimellitate - TMO), sebacic acid (e.g., dioctyl sebacate - DOS, diisodecyl sebacate - DIDS), azelaic acid (e.g., dioctyl azelate - DOZ), adipic acid (e.g., dioctyl adipate - DOA, diisodecyl adipate - DIDA, ditridecyl adipate (DTDA), phthalic acid (e.g., dibutyl phthalate - DBP, dioctyl phthalate - DOP, diundecyl phthalate - D), and the like. Examples of suitable plasticizers include esters of UP, ditridecyl phthalate-DTDP), citric acid, benzoic acid, glutaric acid, fumaric acid, maleic acid, oleic acid (e.g., butyl oleate), palmitic acid, and azelaic acid, as well as mixtures of two or more thereof. Phosphoric acid esters may also be used. Those skilled in the art will be able to select an appropriate plasticizer based on the temperature at which the composition will be processed and the volatility of the plasticizer. Preferred are those plasticizers with a high molecular weight, preferably at least 300, more preferably at least 350.

[0060] Examples of alcohols suitable for use in such monomeric plasticizers include linear or branched C8-C 14 In a preferred embodiment, a C9 fatty alcohol or diol is used containing at least 60% by weight, or at least 80% by weight, but up to 95% by weight, of straight-chain alcohol. The concentration of branched C9 alcohol can be up to 40% by weight, preferably 5-40% by weight. The alcohol can contain at least 15% by weight of branched nonyl alcohol, with a branch at the 2-carbon position.

[0061] The above-mentioned plasticizers may be used in combination with at least one polymeric plasticizer, however, it is preferred that the content of polymeric plasticizer is at least 10.0% by weight, based on the total amount of plasticizers present.

[0062] Suitable polymeric plasticizers include those obtained by condensing a dicarboxylic acid, tricarboxylic acid, or polycarboxylic acid, or a mixture of two or more of the aforementioned carboxylic acids, with a diol, or by condensing a mixture of various carboxylic diacids with one or more diols. Suitable dicarboxylic acids for preparing such polymeric plasticizers include phthalic acid, terephthalic acid, adipic acid, sebacic acid, succinic acid, citric acid, trimellitic acid, and the like. Other suitable polycarboxylic acids include aromatic tricarboxylic acids and their derivatives, particularly alicyclic carboxylic acids selected from the group consisting of 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, and their derivatives. Examples of suitable diols for use in such polymeric plasticizers include, for example, ethylene glycol, propylene glycol, butanediol, and hexanediol. Other suitable polymeric plasticizers for use with the present invention include, in particular, polyphthalates or polyadipates.

[0063] According to an embodiment of the present invention, the at least one binder component has a concentration of at least 0.01 wt.%, preferably at least 0.025 wt.%, more preferably at least 0.10 wt.% or 0.25 wt.%, most preferably at least 0.50 wt.% or at least 0.75 wt.%, or at least 1.0 wt.%, in weight percent dry matter, relative to the total weight of the paste composition. It is further understood that the at least one binder component is typically contained in the paste composition at a concentration of at most 7.5 wt.%, preferably at most 6.0 wt.%, more preferably at most 5.0 wt.%, most preferably at most 3.0 wt.%, in particular at most 2.5 wt.%, in weight percent dry matter, relative to the total weight of the paste composition.

[0064] According to an embodiment of the present invention, the at least one additive component is a wax, fat, or oil, or a mixture of two or more thereof, that can be dispersed in one or more solvents contained in the paste composition of the present invention. However, preferably, the at least one additive component is a water-dispersible wax, oil, or fat.

[0065] The term "wax" should be understood as defined by the Deutsche Gesellschaft fur Fettwissenschaft of DGF Standard Method MI 1. Because the chemical composition and origin of different waxes vary greatly, waxes are defined by their mechanical-physical properties. A substance is called wax if it can be kneaded at 20°C, is strong and hard to brittle and hard, has a coarse to fine crystalline structure, and is translucent to opaque in color but not glass-like; it melts above 40°C without decomposition; it is readily liquid (low viscosity) just above its melting point and is not stringy; it has a consistency and solubility that is strongly temperature-dependent; and it can be polished under light pressure. Waxes typically transition to a molten state between 40 and 130°C. In other words, the term "wax" as used herein refers to a substance that: (i) contains long-chain unsaturated alkyl chains (usually >C); 15 (ii) is kneadable and solid to brittle rigid at temperatures between 20°C and 25°C, and melts to a low-viscosity liquid at temperatures between 40°C and 45°C.

[0066] Waxes suitable for use in the present invention preferably have a melting point in the range of 40 to less than 80° C., preferably 45 to 65° C. Preferred waxes are those having a melting point of 1000° C. -1 Further preferred waxes have a viscosity of ≦10 mPa·s, preferably 5 to 10 mPa·s, and more preferably 3 to 4 mPa·s.

[0067] For the purposes of the present invention, the term "water-dispersible wax" refers to a wax that has a dispersibility in water of at least a certain minimum weight per liter of water at ambient temperature.

[0068] Waxes suitable for use in the present invention include vegetable and animal waxes, mineral waxes, petrochemical waxes, chemically modified waxes, and synthetic waxes. Examples of vegetable waxes suitable for use in the present invention include candelilla wax, carnauba wax, Japanese wax, esparto wax, cork wax, guar ma wax, rice germ oil wax, sugarcane wax, uricury wax, and montan wax. Examples of animal waxes suitable for use in the present invention include beeswax, shellac wax, spermaceti, lanolin (wool wax), and gluteal fat. Examples of mineral waxes suitable for use in the present invention include ceresin and ozokerite (earth wax). Examples of chemically modified waxes suitable for use in the present invention include montan ester wax, sazol wax, hydrogenated jojoba wax, or synthetic waxes such as paraffin, polyalkylene wax, and polyethylene glycol wax.

[0069] The most preferred additive component is animal wax, particularly lanolin, for its ability to aid in the extrusion of paste compositions with high metal and / or metal alloy contents with minimal phase separation and nozzle clogging, even at low temperatures, i.e., temperatures near room temperature, e.g., 15-50°C, preferably 20-40°C. This temperature may refer to the temperature maintained in the nozzle or the temperature of the paste composition. In exceptional circumstances where some clogging occurs, this can be easily remedied by slight heating of the nozzle. Lanolin is the name given to a derivative of wool fat, itself a yellow waxy substance secreted by the sebaceous glands of sheep. Essentially devoid of glycerides, lanolin is recognized as a wax rather than a fat. Like many other natural products, lanolin has a complex and variable composition. As used herein, lanolin refers to a complex mixture of compounds primarily composed of esters of higher fatty acids. More specifically, high purity grade lanolin is composed primarily of long chain waxy esters (about 97% by weight), with the remainder being lanolin alcohols, lanolin phosphoric acid, and lanolin hydrocarbons.

[0070] According to a preferred embodiment, at least one additive component is a fat dispersible in a solvent, particularly water, contained in the paste composition of the present invention. Within the scope of the present invention, a mixture of one or more substances is called fat if it contains or is at least one fatty acid triglyceride, exists in a solid state at a temperature of 25°C, and is substantially insoluble in water. In particular, the fat may be of animal or vegetable origin.

[0071] As an alternative to animal waxes, according to another preferred embodiment of the present invention, at least one additive component can be an oil. A compound is considered an oil if it exists in a liquid state at a temperature of 25°C, has a viscosity higher than that of water, and is immiscible with water (i.e., forms a separate phase when attempting to mix with water). The oil can be a fatty oil, i.e., a mixture of fatty acid triglycerides of animal or plant origin, a mineral oil, or a silicone oil, or a mixture of two or more of these.

[0072] As another alternative to animals, according to a further preferred embodiment, the at least one additive component may be a thixotropic polyamide composition, such as the compositions disclosed in WO2019133255.

[0073] The concentration of the additive may vary within certain limits, but it is preferred that the concentration of the at least one additive component is at least 0.05% by weight or at least 0.10% by weight, preferably at least 0.15% by weight, more preferably at least 0.20% by weight or at least 0.25% by weight, or most preferably at least 0.50% by weight, more preferably at least 0.75% by weight, based on the total weight of the composition. The maximum preferred concentration may vary, but preferably the maximum concentration of the at least one additive component is at most 7.5% by weight, preferably at most 6.0% by weight, more preferably at most 5.0% by weight, most preferably at most 3.0% by weight, and especially at most 2.5% by weight, based on the total weight of the paste composition, in percent dry matter.

[0074] According to an embodiment of the present invention, the paste composition may further contain one or more solvents. Typically, the solvent used in the paste composition of the present invention is water, preferably deionized water. Alternatively, the solvent may be one of the following: water, an organic solvent, an ionic liquid, or a mixture of two or more thereof, or a mixture of two or more thereof. The solvent used in the paste composition of the present invention is preferably one or more solvents selected from the group consisting of water, an alkanol, a ketone, or a mixture of two or more thereof, and more preferably one or more solvents selected from the group consisting of water, deionized water, ethanol, isopropyl alcohol, acetone, ethyl acetate, or a mixture of two or more thereof. Other solvents that may be considered for use in the present invention include 1,2-propanediol, 1,3-dioxolane, 1,4-dioxane, 1-methyl-2-pyrrolidinone, 2-(2-butoxyethoxy)ethyl acetate, acetonitrile, butoxyethyl acetate, dimethyl adipate, dimethyl carbonate, hexane, methyl ethyl ketone, methyl isobutyl ketone, n-pentane, xylene, etc. However, when the paste composition of the present invention contains an oil, fat, or wax, i.e., the oil, fat, or wax may represent the main constituent of the composition in terms of total mass, and may function, for example, as a solvent or carrier.

[0075] The compositions of the present invention may contain additional conventional components of viscous pastes. One type of conventional component, for example, includes one or more dispersants. Useful dispersants include, but are not limited to, Durban, Targon, and Triton. Preferably, they are applied in an amount of 0.01% to 5.0% by weight, preferably 0.1 to 3.0% by weight, and more preferably 0.5% to 3.0% by weight. Other conventional components that may be included in the paste compositions of the present invention include castor oil and its derivatives, organoclay, polyamide and its derivatives, fumed silica, carboxylic acid derivatives, preferably fatty acid derivatives (e.g., CH 19 COOH (capric acid), C 11 H 23 COOH (lauric acid), C 13 H27 COOH (myristic acid), C 15 H 31 COOH (palmitic acid), C 17 H 35 COOH (stearic acid), C 18 H 34 O2 (oleic acid), C 18 H 32 Examples of suitable thixotropic agents include, but are not limited to, thixotropic agents such as thixotropic agents (e.g., thixotropic agents containing thixotropic agents), thixotropic agents containing ...

[0076] The paste compositions described above are particularly suitable for use in robocasting, a technique in which a viscous paste is fed into a nozzle having a desired cross-section, displaced through the nozzle, and expelled from the nozzle to be deposited on a printing surface as a paste in the form of filaments, fibers, struts, beads, etc. Robocasting may also be referred to as 3D printing, 3DFD, 3D fiber deposition, filament deposition, microextrusion, etc., or a combination of two or more of these. In particular, the above-mentioned paste composition is suitable for us in a system for manufacturing three-dimensional structures, the system including: an extrusion unit including a nozzle having a nozzle outlet and a paste container in fluid communication with the nozzle outlet, the extrusion unit configured to deposit a filament of the paste composition through the nozzle outlet in a predetermined interconnected arrangement in a plurality of stacked layers to form a three-dimensional structure; a measurement unit including at least one sensor in the nozzle for monitoring a pressure value applied to a building material in a material container of the nozzle for discharging the building material through the nozzle outlet during discharging of the filament by the extrusion unit; and a processing unit configured to process the monitored pressure value to identify irregular increases and / or decreases in the pressure value relative to a plateau level of the pressure value reached during discharging, the processing unit also being configured to control the extrusion unit to adjust extrusion parameters to compensate for the irregular increases and / or decreases in the pressure value, where momentary spikes in the pressure value occur during the irregular increases and momentary decreases in the pressure value occur during the irregular decreases.Examples of deposition parameters that may be adjusted during the printing process to compensate for irregular rises or falls in pressure values ​​include, but are not limited to, adjusting, i.e., increasing or decreasing, the pressure applied to the printing material in the printing material reservoir, or in the nozzle, or at any point in the printing material feed line before the printing material exits the nozzle, adjusting the viscosity of the printing material, for example, by heating or cooling the printing material, by adjusting the amount of solvent contained in the printing material, by supplying a release agent to the reservoir, nozzle, or at any point in the printing material feed line before the printing material exits the nozzle, adjusting the printing material flow rate, subjecting the printing material to vibration, adjusting the nozzle opening, etc. To early compensate for irregular rises or falls in pressure values, the measurement unit may include a load sensor positionable in the nozzle reservoir, between the nozzle reservoir and the nozzle, or at the nozzle.

[0077] The present invention will now be explained in more detail in the detailed description of the drawings that follow. Figure 1 is a schematic diagram of a printing path in an extrusion process for producing a three-dimensional porous structure. The printing path shows how the filaments of the porous structure are deposited in multiple layers. The method involves depositing interconnected filaments 7, 9 in a predetermined arrangement in multiple stacked layers. The filaments 7, 9 of successive layers 11 are connected to each other to obtain a porous structure with interconnected pores. Furthermore, the filaments of successive layers may be inclined relative to each other.

[0078] In the extrusion process, the nozzle 1 is scanned along the print bed or positioning stage 3 which deposits the filament according to the illustrated print path 5. It will be appreciated that it is also envisioned that the print bed 3 moves instead of the nozzle 1 (kinematic reversal). Combinations are also possible. In alternative embodiments, both the nozzle 1 and the print bed 3 can move during at least a portion of the deposition process.

[0079] Figure 1a shows the print path 5 for the first layer on the print bed 3. Figure 1b shows the print path 5 for two layers. Figure 1c shows the print path 5 for the fourth layer, which is not yet completed.

[0080] By varying the deposition pattern, the local mechanical properties of the porous structure can be locally altered. In the example shown, the printed porous structure has a non-uniform interfilament distance (spacing).

[0081] 2 shows a cross-sectional side view of a schematic diagram of an embodiment of a porous structure 10, 10a in which multiple layers 11 of deposited filaments 2 are stacked together. The filaments 2 have a filament diameter D and an interfilament distance A (not shown). The interfilament distance may be constant or may vary in filament placement.

[0082] FIG. 3 shows a schematic diagram of an embodiment of a porous structure 10 having different filament arrangements. While the present invention has been described above with reference to particular embodiments, this is for the purpose of illustrating the invention and not for the purpose of limiting the invention, the scope of which is defined by the appended claims. Those skilled in the art will readily appreciate that different combinations of features than those described herein are possible without departing from the scope of the invention as claimed.

[0083] The present invention is further illustrated in the following examples. Examples 1 to 3 Ti powder (AP&C), consisting mainly of spherical particles of Ti-6Al-4V grade V with an average particle size of 0-20 μm, was mixed with methylcellulose in water (Across) and lanolin (Adeps Lanae, Fagron) in the amounts shown in Table 1 below. A homogeneous paste showing no phase separation was obtained.

[0084] [Table 1]

[0085] The pastes were 3D printed using a fiber deposition device to provide continuous filaments each having:

[0086] 1) Average diameter 400 μm at an extrusion rate of 250 μl / min 2) Average diameter 800 μm at an extrusion rate of 700 μl / min 4a and 4b show the applied force (N) on the Y-axis as a function of time (min) on the X-axis for Example 1 using 400 μm and 800 μm cross-section nozzles, respectively, thereby understanding that a consistent and moderate force is beneficial for smooth and successful deposition of paste filaments on the underlying layer.

[0087] From Figures 4a and 4b, it can be observed that a continuous increase in pressure applied to the paste composition is required to achieve extrusion.

[0088] 5 shows the applied force (N) on the Y-axis as a function of time (min) on the X-axis for Example 2 using a 400 μm cross-section nozzle. From these figures, it can be observed that when pressure is applied, extrusion of continuous filaments can be achieved by subjecting the paste composition to a substantially constant pressure.

[0089] Figures 6a and 6b show the applied force (N) on the Y-axis as a function of time (min) on the X-axis for Example 3 using 400 μm and 800 μm cross-section nozzles, respectively. From these figures, it can be observed that when pressure is applied, extrusion of continuous filaments can be achieved by subjecting the paste composition to a substantially constant pressure.

[0090] All paste compositions allowed the extrusion of filaments without any visible defects. The water content of the paste of Example 3 before and after extrusion was similar. In the case of Example 2, the water content of the paste composition after extrusion was reduced. It can be concluded that a minimum amount of additives is required to minimize phase separation.

[0091] Comparative example A. Example 1 was repeated, except that no lanolin was incorporated into the paste composition (see Table 1). A homogeneous paste was obtained that showed no phase separation.

[0092] Figures 7a and 7b show the applied force (N) on the Y-axis as a function of time (min) on the X-axis using 400 μm and 800 μm cross-section nozzles, respectively. From these figures, it can be observed that the force required to achieve continuous filament extrusion increases exponentially as a function of time. As soon as the paste composition was subjected to the force of the extruder plunger, water was continuously expelled from the paste, and the solids content of the paste increased over time, initiating phase separation.

[0093] Examples 4-5. Paste compositions were prepared using particles of the following desired materials: stainless steel and copper, as shown in Table 2. The paste compositions were prepared by mixing the desired materials with water or 1-propanol as a solvent, binder material, and additives, as shown in Table 2. A homogeneous paste showing no phase separation was obtained each time.

[0094] The stainless steel was obtained from Carpenter and was type Micro Melt 316L size-22 heat number 45704. The copper metal particles were obtained from Sigma Aldrich and had an average particle size of 14-25 μm.

[0095] Methylcellulose, 4000 cp obtained from Across was used as the binder material in Example 4. Hydroxypropyl cellulose obtained from Sigma Aldrich with a MW of 1,000,000 was used as the binder material in Example 5.

[0096] In both Examples 4 and 5, lanolin (Adeps Lanae, Fagron) was used as an additive component.

[0097] [Table 2]

[0098] The paste was extruded and subjected to a fiber deposition process to obtain continuous filaments with an average diameter of 400 μm at an extrusion rate of 250 μl / min. No phase separation was observed. The applied force to achieve extrusion could be kept constant.

Claims

1. 1. An additive manufacturing paste composition for producing a three-dimensional shaped article of a material of interest, said additive manufacturing paste composition comprising: - 70-99.8 wt.-% of particles of a material of interest, based on the weight of said additive manufacturing paste composition, said material of interest being one or more compounds selected from the group of metals and metal alloys and mixtures thereof; at least one binder component, at least one additive component which is a lubricant, said at least one additive component being a water-dispersible wax, a water-dispersible oil or a water-dispersible fat, or a mixture of two or more thereof; one or more solvents that are miscible with each other, at least one of said solvents comprising water; wherein a sum of a concentration of said at least one additive component and said at least one binder is from 0.06 wt.-% to 10.0 wt.-%, based on the weight of said additive manufacturing paste composition, and at least one of said additive component and said binder component or mixture thereof is shear thinning.

2. 2. The additive manufacturing paste composition of claim 1, wherein the at least one additive component is selected from the group consisting of vegetable and animal waxes, mineral waxes, petrochemical waxes, chemically modified waxes, and synthetic waxes; in particular vegetable waxes selected from the group of candelilla wax, carnauba wax, Japanese wax, esparto wax, cork wax, guarma wax, rice germ oil wax, sugar cane wax, ulic acid wax, montan wax; animal waxes selected from the group of beeswax, shellac wax, spermaceti, lanolin (wool wax), buttock fat; mineral waxes selected from the group of ceresin, ozokerite (earth wax); chemically modified waxes selected from the group of montan ester waxes, sazol wax, hydrogenated jojoba wax; or synthetic waxes selected from the group of paraffins, polyalkylene waxes, polyethylene glycol waxes.

3. 3. The additive manufacturing paste composition according to claim 1 or 2, wherein the remainder to 100 wt.% is constituted by said one or more solvents and conventional additional components of said additive manufacturing paste compositions.

4. 4. The additive manufacturing paste composition according to any one of claims 1 to 3, wherein the sum of the concentrations of said at least one additive component and said at least one binder is up to 7.5 wt-%, relative to the total weight of the additive manufacturing paste composition.

5. 5. The additive manufacturing paste composition of any one of claims 1 to 4, wherein said at least one additive component has a concentration of at least 0.05 wt-%, relative to the total weight of said additive manufacturing paste composition.

6. 6. The additive manufacturing paste composition according to any one of claims 1 to 5, wherein said at least one additive component has a concentration, in weight percent dry matter, of at most 7.5 wt.-%, relative to the total weight of said additive manufacturing paste composition.

7. 7. The additive manufacturing paste composition of any one of claims 1 to 6, wherein the particles of target material have a concentration of at least 75.0 wt.-%, relative to the total weight of the additive manufacturing paste composition.

8. 8. The additive manufacturing paste composition of any one of claims 1 to 7, wherein said at least one binder component is selected from the group consisting of plasticizers, hydrocolloids, cellulose derivatives or combinations thereof, polymeric alcohols, in particular polyvinyl alcohol, glycols, in particular polyethylene glycol or polypropylene glycol, methylcellulose, ethylcellulose, polyvinylpyrrolidone, and combinations thereof.

9. 9. The additive manufacturing paste composition of any one of claims 1 to 8, wherein said at least one binder component is a hydrophilic binder.

10. 10. The additive manufacturing paste composition of any one of claims 1 to 9, wherein said at least one binder component has a concentration, in weight percent dry matter, relative to the total weight of said additive manufacturing paste composition, that is at least 0.01 wt.-%.

11. 11. The additive manufacturing paste composition according to any one of claims 1 to 10, wherein said at least one binder component has a maximum concentration, in weight percent dry matter, of at most 7.5 wt-% relative to the total weight of said additive manufacturing paste composition.

12. 12. The additive manufacturing paste composition of any one of claims 1 to 11, wherein the concentration of the material of interest in the additive manufacturing paste composition is up to 99.5 wt.-%.

13. 13. The additive manufacturing paste composition of any one of the preceding claims, wherein the one or more solvents are selected from the group consisting of one or more solvents selected from the group of water, organic solvents, ionic liquids, or mixtures of two or more thereof.

14. 14. Use of one or more of a solvent dispersible wax, a solvent dispersible fat or a solvent dispersible oil, or a mixture of two or more thereof, in an additive manufacturing paste composition according to any one of claims 1 to 13 for additive manufacturing, in particular robocasting.

15. 1. A method for producing a three-dimensional shaped article of a material of interest using additive manufacturing, comprising: feeding interconnected filaments of an additive manufacturing viscous paste composition to a nozzle and dispensing from the nozzle onto a printing surface in a predetermined arrangement in a plurality of successively deposited layers to form a green structure; and drying the green structure to obtain the three-dimensional shaped article, wherein the filaments of the successively deposited layers are connected to each other at least at points of contact between the filaments of the successively deposited layers, and the additive manufacturing viscous paste composition is - 70-99.8 wt.-% of particles of said material of interest, based on the weight of said additive manufacturing viscous paste composition, said material of interest being one or more compounds selected from the group of metals and metal alloys and mixtures thereof; at least one binder component, at least one additive component which is a lubricant, said at least one additive component being a water-dispersible wax, a water-dispersible oil or a water-dispersible fat, or a mixture of the two; one or more solvents that are miscible with each other, at least one of said solvents comprising water; wherein the sum of the concentration of the at least one additive component and the at least one binder is 0.06 wt. % to 10.0 wt. %, based on the weight of the additive manufacturing viscous paste composition; The method, wherein at least one of the additive component and the binder component or a mixture thereof is shear thinning.

16. 1. A computer-implemented method for printing a porous structure, the computer-implemented method comprising at least: - receiving a model of the porous body to be manufactured, - defining a printing path according to the desired characteristics of said porous body; - depositing a filament of the additive manufacturing paste composition according to any one of claims 1 to 13 according to said printing path; 4. A computer-implemented method configured to operate an additive manufacturing system to perform the steps of:

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