3D printing

Abstract

A 3D printing kit may include a binder fluid and a particulate build material. The particulate build material may include metal particles in an amount of about 95% to about 99.995% by weight and carbon black particles in an amount of about 0.005% to about 2% by weight, where the weight percentages are based on the total weight of the particulate build material.

Description

[0001] background

[0002] Three-dimensional (3D) printing can be an additive printing method used to manufacture three-dimensional solid parts from digital models. 3D printing is commonly used for rapid product prototyping, mold generation, master mold generation, and low-volume manufacturing. Some 3D printing technologies are considered additive because they involve applying successive layers of material. This is different from other mechanical machining methods that typically rely on removing material to produce the final part. Some 3D printing methods use chemical binders or adhesives to bond the build materials together. Other 3D printing methods involve partial sintering, melting, etc. of the build materials. For some materials, partial melting can be achieved using heat-assisted extrusion, and for other materials, curing or sintering can be achieved using, for example, ultraviolet or infrared light. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 Illustrate an exemplary particulate build material and three-dimensional printing kit according to the present disclosure;

[0005] Figure 2 illustrating an exemplary three-dimensional printing kit in an exemplary use according to the present disclosure;

[0006] Figure 3 is a flow chart illustrating an exemplary three-dimensional printing method in an exemplary use according to the present disclosure;

[0007] Figure 4 is a bar graph of Hausner Ratio vs. particle bed material in exemplary uses according to the present disclosure; and

[0008] Figure 5 is a graph of Hausner Ratio vs. weight percent carbon black pigment in exemplary uses according to the present disclosure.

[0009] Details

[0010] Three-dimensional (3D) printing can be an additive process that involves applying successive layers of particulate building materials onto which a chemical binder or adhesive is printed to bind the successive layers of particulate building materials together. In some methods, the application of a binder can be used to form a green body object, from which a sintered three-dimensional physical object can then be formed. More specifically, a binder fluid can be selectively applied to a layer of a metallic particulate building material on a build platform to pattern selected areas of the layer, and then another layer of particulate building material is applied thereon. The binder fluid can be applied to another layer of particulate building material, and these processes can be repeated to form a green part (also referred to as a 3D green body or object), which can then be thermally sintered to form a sintered 3D object.

[0011] According to examples of the present disclosure, small metal particles can provide several benefits for three-dimensional printing, including the production of rigid metal parts with high object resolution. In addition, small particle size can also positively affect the sintering of 3D green body objects in some cases, such as sintering rate. For example, as the particle size decreases, the sintering rate or the time that the particles are kept at the sintering temperature can also be reduced. Therefore, although smaller particle size can provide these and possibly other advantages, small metal particles often exhibit interparticle cohesion so that the particles agglomerate. As the interparticle cohesion becomes stronger, the flowability of the metal particle building material can be adversely affected. For example, as the particle size decreases, the interparticle cohesion can be improved. Therefore, if small metal particles are used for particulate building materials, for example, in order to benefit from the use of smaller particle size particles, agglomeration is often a problem to be solved. "Sintering" typically occurs below the temperature and / or time range originally used for completely melting the particles.

[0012] It has been discovered that control additives can, in many cases, enable the utilization of fine-grained build material powders while mitigating or preventing particle agglomeration because they can reduce interparticle cohesive forces (van der Waals, electrostatic attraction, etc.) between metal particles. However, typical flow control additives, such as semi-metals and / or metal oxides, such as silica and / or alumina, are not soluble or miscible with certain types of metal particulate build materials when heated to sintering temperatures and, therefore, can form inclusions in the sintered 3D object, which can reduce overall mechanical strength, increase brittleness, and reduce the structural properties of the sintered 3D object. According to the present disclosure and in the embodiments herein, carbon black particles can alternatively be used as a flow control additive for the metal particles of the particulate build material without the concurrent reduction in mechanical strength, increased brittleness, and / or reduced structural properties that can be caused by some other types of flow control additives. This may be because the carbon black particles can, in some cases, be incorporated into the sintered 3D object during the forming process by forming metal carbides with the metal particles, and / or, in other cases, can be removed or partially removed during the sintering process by reacting to form gases that, for example, escape from the boundaries of the 3D object during the forming process.

[0013] Accordingly, in one example, a three-dimensional printing kit may include a binder fluid and a particulate building material. The particulate building material may include metal particles in an amount of approximately 95% by weight to approximately 99.995% by weight and carbon black particles in an amount of approximately 0.005% by weight to approximately 2% by weight based on the total weight of the particulate building material. In one example, the particulate building material may not contain oxide or semi-metallic oxide flow control additives. In one example, the metal particles may include copper, cobalt, nickel, tungsten carbide, gold, silver, ferrous alloy, stainless steel, steel, high carbon steel, tool steel, alloys thereof, or mixtures thereof. In another example, the metal particles may be stainless steel. In a further example, the metal particles may have a D50 particle size distribution value of approximately 2 μm to approximately 40 μm. In another example, the carbon black particles have a D50 particle size distribution value of approximately 10 nm to approximately 200 nm. In yet another example, the surface area of ​​the carbon black particles may be approximately 50 m 2 / g to about 600m 2 In one example, the binder fluid may include water and the latex particles in an amount of about 5 wt % to about 30 wt %.

[0014] In another example, a particulate build material for 3D printing may include metal particles in an amount of about 95% to about 99.995% by weight and having a D50 particle size distribution value of about 2 μm to about 150 μm, and carbon black particles in an amount of about 0.005% to about 2% by weight and having a D50 particle size distribution value of about 10 nm to about 200 nm, wherein the weight percentages are based on the total weight of the particulate build material. In one example, the metal particles may include copper, cobalt, nickel, tungsten carbide, gold, silver, an iron-based alloy, stainless steel, steel, high carbon steel, tool steel, alloys thereof, or mixtures thereof, and the particulate build material may be free of oxide or semi-metal oxide flow control additives.

[0015] In another example, a 3D printing method may include iteratively applying individual build material layers of a particulate build material, the particulate build material comprising metal particles in an amount of approximately 95% to approximately 99.995% by weight and carbon black particles in an amount of approximately 0.005% to approximately 2% by weight, based on the total weight of the particulate build material; and selectively applying a binder fluid to the individual build material layers based on a 3D object model to define individually patterned layers that accumulate and bond together to form a 3D green body object. In one example, the method may further include heating the plurality of individually patterned layers during the molding process to expel water, thereby further solidifying the 3D green body object. In another example, the method may further include sintering the 3D green body object at an elevated temperature of approximately 500° C. to approximately 3,500° C. to fuse the metal particles together and form a sintered 3D object. In yet another example, sintering can be performed in an atmosphere including a gas reactive with carbon at the elevated temperature to convert carbon from the carbon black particles into gas, such that the carbon black particle content in the sintered 3D object is lower than the particle content in the 3D green body object. In a further example, sintering can be performed at the elevated temperature in an atmosphere inert to carbon.

[0016] It is noted that when discussing 3D printing kits, particulate build materials, and / or 3D printing methods herein, such discussions are considered applicable to each other, regardless of whether they are explicitly discussed in the context of that example. Thus, for example, when discussing metal particles in relation to 3D printing kits, such disclosure also relates to and directly supports particulate build materials and 3D printing methods in the context of such materials, and vice versa.

[0017] It is also to be understood that, unless otherwise specified, the terms used herein have their ordinary meanings in the relevant technical field. In some cases, some terms are more specifically defined throughout this specification or included at the end of this specification, so these terms may have the meanings as described herein.

[0018] Microparticle building materials and 3D printing kits

[0019] According to an example of the present disclosure, particulate building material 110 and 3D printing kit 100 are shown in FIG. Figure 1 The particulate build material may, for example, include metal particles 102 in an amount of about 95 wt % to about 99.995 wt % and carbon black particles 104 in an amount of about 0.005 wt % to about 2 wt %, based on the total weight of the particulate build material. Figure 1 The 3D printing kit in the embodiment of the present invention may include a particulate build material combined with a binder fluid 106. The binder fluid 106 is shown as droplets applied to the particulate build material, but may alternatively be packaged in a container with the particulate build material as part of the kit. In some more specific examples, the metal particles may have a D50 particle size distribution value of approximately 2 μm to approximately 40 μm, and / or the carbon black particles may have a D50 particle size distribution value of approximately 10 nm to approximately 200 nm. More specifically, in some cases, the particulate build material and / or the 3D printing kit may not contain semi-metallic or metal oxide flow control additives, such as fumed silica, alumina, etc., as these may, in some cases, adversely affect the structural properties of the sintered 3D object. For example, fumed silica and alumina may not be removed or properly bonded to the sintering material and may therefore be present but not firmly bonded to grain boundaries of the sintered 3D object. Consequently, the presence of silica and / or alumina within the sintered 3D object may reduce the mechanical strength of the sintered 3D object.

[0020] exist Figure 2 In the application, examples are shown Figure 1100 , wherein a particulate building material 110 is deposited from a particulate building material source 108 onto a building platform 102, where it can be flattened or smoothed, for example, by a mechanical roller or other flattening technique. In this example, a binder fluid 106 can include water and a binder, such as a latex particle binder or another polymer binder, which can be ejected from a fluid ejector 114 onto the particulate building material, for example, to selectively pattern the particulate building material. The selective printing location of the binder fluid can be a layer corresponding to a layer of a 3D printed object, for example, from a 3D object model or computer model. Heat (h), for example, from a heat source 112, can be used at various layers (or groups of layers, or after forming a 3D green body object) to remove solvent from the binder fluid, which can contribute to faster solidification of the various layers. In one example, heat can be applied from the top, e.g., before applying the next layer of particulate build material or after forming multiple layers, etc., and / or can be provided by the build platform from below the particulate build material and / or from a source of particulate build material (preheating the particulate build material before dispensing it onto the build platform or a previously applied 3D object layer). After printing each layer with the binder fluid, the build platform can be lowered a distance (x), which in one example can correspond to the thickness of the printed layer, so that another layer of particulate build material can be added thereon and printed with the binder fluid, etc. This method can be repeated on a layer-by-layer basis until a green body is formed that is sufficiently stable to be moved into a furnace 130 suitable for sintering, e.g., sintering, annealing, melting, etc. The green body, in this example, comprises a 3D object formed from a solidified green body object layer 124 comprising a particulate build material and a binder fluid that delivers latex particles thereto.

[0021] Metal particles

[0022] The particulate build material may comprise any type of metal particles that can be sintered together at a sintering temperature (above the temperature at which a green body is formed). Sintering may be performed by sintering, annealing, melting, etc., the metal particles within the particulate build material together. In one example, the particulate build material may comprise from about 95% to about 99.995% by weight of metal particles, based on the total weight of the particulate build material.

[0023] In one example, the metal particles can be a single-phase metallic material composed of one element. In this example, sintering, such as sintering, annealing, etc., can be performed at a temperature lower than the melting point of the element of the single-phase metallic material. In other examples, the building material particles can be composed of two or more elements, which can be in the form of a single-phase metal alloy (e.g., various particles are alloys) or a multiphase metal alloy (e.g., different particles can include different metals). In these examples, sintering typically occurs within a certain temperature range. Regarding alloys, materials that form alloys of metals and non-metals (e.g., metal-metalloid alloys) can also be used.

[0024] In some examples, the metal particles may include particles of copper, cobalt, nickel, tungsten carbide, gold, silver, iron-based alloys, stainless steel, steel, high carbon steel, tool steel, alloys thereof, or mixtures thereof. Specific alloy examples may include CoCr MP1, CoCrSP2, maraging steel MS1, hastelloy C, hastelloy X, nickel alloy HX, inconel IN625, inconel IN718, stainless steel GP1, stainless steel 17-4PH, stainless steel 316L, and stainless steel 430L. In one example, the metal particles may be stainless steel.

[0025] In one example, the metal particles may have a D50 particle size of 2 μm to 40 μm. In some examples, the particles may have a D50 particle size distribution value of about 15 μm to about 25 μm, about 5 μm to about 20 μm, about 10 μm to about 40 μm, about 2 μm to about 30 μm, or about 2 μm to about 35 μm. Individual particle sizes may be outside these ranges, as "D50 particle size" is defined as the particle size at which half of the particles are larger than the D50 particle size and approximately half of the particles are smaller than the D50 particle size (based on the metal particle content of the particulate building material by weight).

[0026] As used herein, particle size can refer to the diameter value of a spherical particle, or in a non-spherical particle, can refer to the longest dimension of the particle. Particle size can be presented as a Gaussian distribution or a quasi-Gaussian distribution (or a normal distribution or a quasi-normal distribution). A quasi-Gaussian distribution is a distribution curve that may appear to be Gaussian in shape but slightly skewed in one or another direction (towards the smaller or larger end of the particle size distribution range). That is, an exemplary quasi-Gaussian distribution of metal particles can be typically characterized using "D10", "D50" and "D90" particle size distribution values, where D10 refers to the particle size at the 10th percentile, D50 refers to the particle size at the 50th percentile, and D90 refers to the particle size at the 90th percentile. For example, a D50 value of 25 μm means that 50% of the particles (by number) have a particle size greater than 25 μm and 50% of the particles have a particle size less than 25 μm. The particle size distribution values ​​do not necessarily relate to a Gaussian distribution curve, but in one embodiment of the present disclosure, the metal particles may have a Gaussian distribution or more generally a quasi-Gaussian distribution with an offset peak near D50. In practice, a true Gaussian distribution does not typically exist because there is some skewness, but a quasi-Gaussian distribution may still be considered "Gaussian" as used in practice. The shape of the particles of the particulate building material may be spherical, non-spherical, random, or a combination thereof.

[0027] carbon black particles

[0028] In some examples, the particulate build material may further include about 0.005% to about 2% by weight of carbon black particles, based on the total weight of the particulate build material. In some examples, the carbon black particles may be present at about 0.005% to about 1.5%, about 0.01% to about 1%, or about 0.05% to about 2%.

[0029] In one example, the carbon black particles may have a D50 particle size distribution value of about 10 nm to about 200 nm. In further examples, the carbon black particles may have a D50 particle size distribution value of about 10 nm to about 50 nm, about 15 nm to about 75 nm, about 50 nm to about 150 nm, or about 20 nm to about 120 nm.

[0030] The surface area of ​​the carbon black particles can vary. In some examples, the surface area of ​​the carbon black particles can be approximately 50 m 2 / g to about 600m 2 In other examples, the surface area of ​​the carbon black particles may be about 150 m 2 / g to about 550m 2 / g, about 200m 2 / g to about 400m 2 / g, about 75m 2 / g to about 250m 2 / g, or about 115m 2 / g to about 345m 2 The surface area of ​​the carbon black particles can be measured by the Brunauer-Emmett-Teller (BET) method based on the adsorption of N2 gas on the surface of the carbon black particles.

[0031] The carbon black particles may be commercially available carbon black. Exemplary commercially available carbon black particles may include and / or Available from Cabot Corporation (USA); available from Palmer Holland (USA) Color Black FW 200, Color Black FW 2, ColorBlack FW 2V, Color Black FW 1, Color Black FW 18, Color Black S 160, Color Black S 170, Special Black 6, Special Black 5, Special Black 4A and / or Special Black 4, all available from (Germany); available from Columbian Chemicals (USA) and / or and LHD9303Black from Sun Chemical (USA). In one example, the carbon black particles can be or a combination thereof, are available from (Germany). In one example, carbon black particles can act as a flow control additive to a particulate build material and can improve the flowability of the particulate build material.

[0032] Adhesive fluid

[0033] Binder fluid can comprise aqueous liquid vehicle and adhesive particles, such as latex particles, so that particulate construction materials are bonded together to form 3D green body objects in the construction process. Binder fluid can be applied to the particulate construction materials on a layer-by-layer basis. Heat (lower than metal sintering temperature) can be applied on a layer-by-layer basis, after forming multiple layers of green body or in some cases after forming green body completely. Binder fluid as herein described can further comprise liquid connection material composition, such as organic cosolvent, biocide, viscosity modifier, pH adjusting agent, sequestrant, preservative etc. Binder fluid can be used for bonding particulate construction materials together in three-dimensional printing process. In three-dimensional printing process, binder fluid can be applied to the particulate construction materials on a layer-by-layer basis and can move into the void space between the particles of particulate construction materials.

[0034] In one example, the adhesive fluid can include water and about 5 wt % to about 30 wt % of the amount of latex particles. In some examples, latex particles can exist with about 5 wt % to about 30 wt %, about 10 wt % to about 25 wt % or about 5 wt % to about 20 wt %. Latex particles can be polymers with different morphologies. In one example, latex particles can include two different copolymer compositions, which can be completely separated core-shell polymers, partially embedded mixtures or closely mixed as polymer solutions. In another example, latex particles can be each spherical particle, which contains the polymer composition of hydrophilic (hard) component and / or hydrophobic (soft) component that can be dispersed mutually. In one example, this mutual dispersion can be according to IPN (interpenetrating network). In another example, latex particles can be made up of the hydrophobic core surrounded by continuous or discontinuous hydrophilic shells. For example, particle morphology can be like raspberries, and wherein the hydrophobic core can be surrounded by several smaller hydrophilic particles attached to the core. In yet another example, the latex particles may include 2, 3, or 4 or more relatively large polymer particles that may be attached to each other or that may surround a smaller polymer core. In yet another example, the latex particles may have a single phase morphology, may be partially embedded, may be multilobed, or may include any combination of any morphologies disclosed herein.

[0035] In some instances, the latex particles can be heteropolymers or copolymers. As used herein, heteropolymers can include a hydrophobic component and a hydrophilic component. The heteropolymer can include from about 65% to about 99.9% (by weight of the heteropolymer) of the hydrophobic component and from about 0.1% to about 35% (by weight of the heteropolymer) of the hydrophilic component. In one example, the hydrophobic component can have a glass transition temperature lower than that of the hydrophilic component.

[0036] In some instances, the latex particles may be composed of polymerization or copolymerization of acrylic monomers, styrene monomers, or combinations thereof. Exemplary monomers may include C1-C20 linear or branched alkyl (meth)acrylates, alicyclic (meth)acrylates, alkyl acrylates, styrene, methyl styrene, polyol (meth)acrylates, hydroxyethyl (meth)acrylates, (meth)acrylic acid, or combinations thereof. In a specific class of examples, the latex particles may be styrene (meth)acrylate copolymers. The terms "(meth)acrylate" or "(meth)acrylic acid" and the like refer to monomers, copolymerized monomers, and the like, which may be acrylates or methacrylates (or a combination of the two), or acrylic acid or methacrylic acid (or a combination of the two). In some instances, the terms "(meth)acrylate" and "(meth)acrylic acid" are used interchangeably because acrylates and methacrylates are salts and esters of acrylic acid and methacrylic acid, respectively. In addition, referring to one compound rather than another may depend on pH. Furthermore, even if the monomers used to form the polymer are in the form of (meth)acrylic acid during preparation, pH modification during preparation or subsequently upon addition to a jettable fluid, such as an adhesive fluid, can also affect the properties of that moiety (acid form vs. salt or ester form). Thus, monomers or polymer moieties described as (meth)acrylic acid or (meth)acrylate should not be interpreted so strictly as to disregard relative pH levels, ester chemistry, and other general organic chemistry concepts. In yet another example, the latex particles can include a copolymer having copolymerized methyl methacrylate present at about 50% by weight or more or copolymerized styrene present at about 50% by weight or more. In more specific examples, both can be present, one or the other at about 50% by weight or more.

[0037] In other examples, the latex particles in the adhesive fluid include vinyl, vinyl chloride, vinylidene chloride, vinyl ester, acrylate, methacrylate, styrene, ethylene, maleate, fumarate, itaconate, α-methylstyrene, p-methylstyrene, methyl methacrylate, hexyl acrylate, hexyl methacrylate, butyl acrylate, butyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, octadecyl acrylate, octadecyl methacrylate, stearyl methacrylate, vinylbenzyl chloride, isobornyl acrylate, tetrahydrofurfuryl acrylate, methacrylic acid, methyl methacrylate ... The present invention also provides a polymerizable monomer comprising 2-phenoxyethyl acrylate, benzyl methacrylate, benzyl acrylate, ethoxylated nonylphenol methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, trimethylcyclohexyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, alkoxylated tetrahydrofurfuryl acrylate, isodecyl acrylate, isobornyl methacrylate, isobornyl acrylate, dimethyl maleate, dioctyl maleate, acetoacetoxyethyl methacrylate, diacetone acrylamide, N-vinylimidazole, N-vinylcarbazole, N-vinylcaprolactam, combinations thereof, derivatives thereof, or mixtures thereof. These monomers include low glass transition temperature (Tg) monomers that can be used to form the hydrophobic component of the heteropolymer.

[0038] In other examples, the composition of the latex particles may include an acidic monomer. In some examples, the acidic monomer content may be 0.1% to 15% by weight, 0.5% to 12% by weight, or 1% to 10% by weight of the latex particles, with the remainder of the latex particles being composed of non-acidic monomers. Exemplary acidic monomers may include acrylic acid, methacrylic acid, ethacrylic acid, dimethacrylic acid, maleic anhydride, maleic acid, vinyl sulfonate / ester, cyanoacrylic acid, vinyl acetic acid, allyl acetic acid, ethylidene acetic acid, propylidene acetic acid, crotonic acid, fumaric acid, itaconic acid, sorbic acid, angelic acid, cinnamic acid, styryl acrylic acid, citraconic acid, glutaconic acid, aconitic acid, phenyl acrylic acid, acryloyloxy propionic acid, aconitic acid, phenyl acrylic acid, acryloyloxy propionic acid, vinyl benzoic acid, In some embodiments, the present invention provides the hydrophilic monomers of the present invention.N-vinylsuccinamic acid, mesaconic acid, methacryloyl alanine, acryloyl hydroxyglycine, sulfoethyl methacrylic acid, sulfopropyl acrylic acid, styrenesulfonic acid, sulfoethyl acrylic acid, 2-methacryloyloxy first-1-sulfonic acid, 3-methacryloyloxy propane-1-sulfonic acid, 3-(vinyloxy) propane-1-sulfonic acid, ethylenesulfonic acid, vinylsulfuric acid, 4-vinylphenyl sulfuric acid, ethylenephosphonic acid, vinylphosphoric acid, vinylbenzoic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, their combination, their derivative or their mixture.These acidic monomers are hydrophilic monomers that Tg is higher than above-mentioned low Tg monomer, and can be used for forming the hydrophilic component of heteropolymer.Other examples of high Tg hydrophilic monomer can comprise acrylamide, methacrylamide, monohydroxylated monomer, monoethoxylated monomer, polyhydroxylated monomer or polyethoxylated monomer.

[0039] In one embodiment, the selected monomers can be polymerized with a copolymerizable dispersant to form a polymer, heteropolymer, or copolymer. The copolymerizable dispersant can be a polyoxyethylene compound, such as Compounds (Montello Inc.), such as polyoxyethylene alkylphenyl ether ammonium sulfate, polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene styrenated phenyl ether ammonium sulfate, or mixtures thereof. Any suitable polymerization method can be used. In some embodiments, aqueous dispersions of latex particles can be prepared by emulsion polymerization or copolymerization of any of the above monomers.

[0040] In one example, latex particles can be prepared by polymerizing a high Tg hydrophilic monomer to form a high Tg hydrophilic component and attaching the high Tg hydrophilic component to the surface of a low Tg hydrophobic component. In another example, latex particles can be prepared by polymerizing a low Tg hydrophobic monomer and a high Tg hydrophilic monomer in a ratio of low Tg hydrophobic monomer:high Tg hydrophilic monomer of 5:95 to 30:70. In this example, the low Tg hydrophobic monomer can be dissolved in the high Tg hydrophilic monomer. In yet another example, latex particles can be prepared by polymerizing a low Tg hydrophobic monomer and then adding a high Tg hydrophilic monomer. In this example, this polymerization process can result in a higher concentration of the high Tg hydrophilic monomer being polymerized at or near the surface of the low Tg hydrophobic component. In yet another example, latex particles can be prepared by copolymerizing a low Tg hydrophobic monomer and a high Tg hydrophilic monomer and then adding additional high Tg hydrophilic monomer. In this example, the copolymerization process can result in a higher concentration of the high Tg hydrophilic monomer copolymerized at or near the surface of the low Tg hydrophobic component.

[0041] Other suitable techniques, particularly for producing core-shell structures, may include grafting a hydrophilic shell onto the surface of a hydrophobic core, copolymerizing hydrophobic and hydrophilic monomers in a ratio that produces a more hydrophilic shell, adding hydrophilic monomer (or excess hydrophilic monomer) toward the end of the copolymerization process so that a higher concentration of hydrophilic monomer is copolymerized at or near the surface, or any other method may be used to produce a shell that is more hydrophilic than the core.

[0042] In one embodiment, the low Tg hydrophobic monomer can be selected from C4 to C8 alkyl acrylate monomers, C4 to C8 alkyl methacrylate monomers, styrene monomers, substituted methylstyrene monomers, vinyl monomers, vinyl ester monomers, and combinations thereof; and the high Tg hydrophilic monomer can be selected from acidic monomers, unsubstituted amide monomers, alcohol-containing acrylate monomers, alcohol-containing methacrylate monomers, C1 to C2 alkyl acrylate monomers, C1 to C2 alkyl methacrylate monomers, and combinations thereof. The resulting polymer latex particles can exhibit a core-shell structure, a hybrid or blended polymer structure, or some other morphology.

[0043] In some examples, the latex polymer can have a weight average molecular weight (Mw) of about 5,000 Mw to about 2,000,000 Mw. In still other examples, the weight average molecular weight can be about 100,000 Mw to about 1,000,000 Mw, about 100,000 Mw to about 500,000 Mw, about 150,000 Mw to about 300,000 Mw, or about 50,000 Mw to about 250,000 Mw. The weight average molecular weight (Mw) can be measured by gel permeation chromatography using polystyrene standards.

[0044] In some examples, the latex polymer particles may be latent and can be activated by heat (either applied iteratively or after the green body is formed). In these cases, the activation temperature may correspond to a minimum film forming temperature (MFFT) or glass transition temperature (Tg), which may be greater than ambient temperature. As referred to herein, "ambient temperature" may refer to room temperature (e.g., about 18°C ​​to about 22°C). In one example, the latex polymer particles may have an MFFT or Tg that is at least about 15°C higher than ambient temperature. In another example, the bulk material (e.g., the more hydrophobic portion) of the latex polymer particles may have an MFFT or Tg of about 25°C to about 200°C. In another example, the latex particles may have an MFFT or Tg of about 40°C to about 120°C. In yet another example, the latex polymer particles may have an MFFT or Tg of about 50°C to about 150°C. In yet another example, the latex polymer particles may have a Tg of about -20°C to about 130°C, or in another example, about 60°C to about 105°C. At temperatures above the MFFT or Tg of the latent latex polymer particles, the polymer particles can coalesce and can bind materials.

[0045] The latex particles can have a particle size that can be ejected by thermal jetting or printing, piezoelectric jetting or printing, drop-on-demand jetting or printing, continuous jetting or printing, etc. In one example, the latex particles can have a particle size of about 10 nm to about 400 nm. In other examples, the latex particles can have a particle size of about 10 nm to about 300 nm, about 50 nm to about 250 nm, about 100 nm to about 300 nm, or about 25 nm to about 250 nm.

[0046] Among the various adhesive fluids described herein, these fluids can be aqueous fluids and can include liquid vehicle ingredients such as water, organic cosolvents, biocides, viscosity modifiers, pH adjusters, sequestrants, preservatives, latex polymers, etc. More details on useful liquid vehicles are provided below.

[0047] 3D printing method

[0048] A flowchart of an exemplary three-dimensional (3D) printing method 200 is shown in Figure 3The method may include iteratively applying 210 individual build material layers of a particulate build material comprising approximately 95% to approximately 99.995% by weight metal particles and approximately 0.005% to approximately 2% by weight carbon black particles, based on the total weight of the particulate build material; and selectively applying 212 a binder fluid to the individual build material layers based on the 3D object model to define individually patterned object layers that accumulate and bond together to form a 3D green body object. In some examples, the method may further include heating the plurality of individually patterned layers during the molding process to expel water, thereby further solidifying the 3D green body object. The particulate build material, metal particles, carbon black particles, and binder fluid may be as described above.

[0049] In more detail, iteratively applying individual layers of a particulate build material can include applying each layer of the build material at a thickness that can be, for example, about 50 μm to about 300 μm. A binder fluid can be selectively printed by a print head, which can be a piezoelectric print head, a thermal inkjet print head, or a continuous inkjet print head. In one example, the binder can be applied at a temperature ranging from ambient temperature (about 25° C.) to about 100° C. After printing each layer with the binder fluid and subsequently heating in some cases to expel water and further solidify the 3D green body object, the build platform can be lowered a distance (x), which can correspond to the thickness of the printed layer of the 3D green body object, so that another layer of particulate build material can be added thereto, printed with the binder fluid, solidified, and so on. This method can be repeated on a layer-by-layer basis until a complete 3D green body object is formed that is sufficiently stable to be moved to a furnace suitable for sintering, such as sintering, annealing, melting, and the like.

[0050] In some examples, heat may be applied to each layer (or group of layers) on which the binder fluid is printed to expel water from the binder fluid and further solidify the layers of the 3D green body object. For example, heat may be applied at a temperature of approximately 18°C ​​to approximately 300°C, or approximately 50°C to approximately 200°C. In one example, heat may be applied from the top and / or heat may be provided from below the particulate build material by the build platform. In some examples, the particulate build material may be heated before dispensing. Additionally, heating may be applied after the binder fluid is applied to each layer or after all printed binder fluid has been applied. The temperature at which the metal particles of the particulate build material are bonded together by the applied binder is higher than the temperature of the environment in which the patterning portion of the 3D printing process is performed, for example, patterning at approximately 18°C ​​to approximately 300°C and sintering at approximately 500°C to approximately 3,500°C. In some examples, the metal build material particles may have a melting point of approximately 500°C to approximately 3,500°C. In other examples, the metal build material particles may be an alloy having a range of melting points.

[0051] Thus, after forming the 3D green body object, the entire 3D green body object can be removed from the powder bed and moved to a furnace and heated to a temperature of about 500°C to about 3,500°C, or more typically about 500°C to about 1,500°C, to fuse the metal particles together and form a sintered 3D object. In some examples, this temperature can be about 600°C to about 1,200°C, about 800°C to about 1,200°C, or about 750°C to about 1,500°C. Sintering can occur at a temperature below the melting temperature of the metal particles. Depending on the metal particles, in one example, these temperature ranges can be used to melt the outer layer of the metal particles and allow the metal particles to sinter to each other while not melting the interior of the metal particles.

[0052] The final sintering temperature range can vary depending on the material, but in one example, the sintering temperature can be about 10°C below the melting temperature of the metal particles of the particulate build material to about 50°C below the melting temperature of the metal particles of the particulate build material. The sintering temperature can also depend on the particle size and the time the heating is performed, such as the time sufficient at the high temperature to physically merge or composite the particle surfaces together. For example, the sintering temperature for stainless steel can be about 1400°C, and one example of a sintering temperature for aluminum or aluminum alloys can be about 550°C to about 620°C. The sintering temperature can sinter and / or otherwise fuse the metal particles to form a sintered 3D object.

[0053] In some examples, carbon black particles can interact with metal particles at elevated temperatures and can form metal carbides during sintering. In these examples, the carbon black particles can be incorporated into the printed 3D object. In other examples, sintering can be performed in an atmosphere including a gas that reacts with carbon at the elevated temperature to convert the carbon black particles into a gas, such that the carbon black particle content in the sintered 3D object is lower than that in the 3D green body object.

[0054] In one example, the heating can be performed in a gaseous reactive atmosphere that can include a controlled amount of oxygen. In some examples, the oxygen can be present in the gaseous reactive atmosphere at a level of about 1e-8 atm. to about 1e-6 atm. The controlled oxidation of the carbon black can form carbon dioxide (CO2) and carbon monoxide (CO) as byproducts.

[0055] 3C (固) +2O 2(气) →CO 2(气) +2CO (气)

[0056] In some examples, oxygen can be present in the reducing atmosphere in an amount of about 25e-6 atm to about 5e-8 atm, or about 5e-7 atm to about 5e-8 atm, or about 25e-6 atm to about 25e-7 atm.

[0057] In still other examples, the heating can be performed in a gaseous reactive atmosphere that can include from about 0.5 wt % to less than 100 wt % hydrogen. The hydrogen can react with the carbon black pigment to form methane gas as shown below.

[0058] C (固) +2H 2(气) →CH 4(气)

[0059] As methane gas is generated, carbon black particles can be removed from the surface of the green body. In other examples, hydrogen can be present in the reducing atmosphere in an amount of about 2 wt % to about 100 wt %, about 2 wt % to about 20 wt %, about 25 wt % to about 50 wt %, or about 30 wt % to about 90 wt %.

[0060] 3D green body objects formed by the 3D printing methods herein can allow for the use of metal particles having a D50 particle size distribution value ranging from approximately 2 μm to approximately 40 μm. The carbon black particles can reduce inter-particle cohesion between the metal particles, thereby preventing or mitigating particle agglomeration of the metal particles and allowing for the spreading of a thin layer of particulate build material on a powder bed carrier substrate. Furthermore, the ability to utilize metal particles having a D50 particle size distribution value ranging from approximately 2 μm to approximately 40 μm can allow for faster sintering of the 3D green body object and achieve structural stability in the sintered 3D object.

[0061] definition

[0062] It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0063] As used herein, the term "about," when referring to a value or range, allows for a certain degree of variability in the value or range, for example, within 10% of the specified value or specified range limit, or within 5% in one aspect. The term "about," when modifying a numerical range, is also understood to include the range bounded by the exact numerical value indicated as a numerical subrange, for example, a range of about 1% to about 5% by weight includes 1% to 5% by weight as an expressly supported subrange.

[0064] As used herein, the terms "green part," "green body," and "layered green body" refer to any intermediate structure prior to sintering of any inter-particle material, including a green 3D object or object layer, a green 3D support structure or support structure layer, or an intermediate 3D breakaway interface or breakaway interface layer. As a green body, the particulate building materials may be (weakly) bound together by a binder fluid. Typically, the mechanical strength of the green body is such that the green body can be moved or removed from the build platform for placement in a sintering furnace. It is to be understood that any particulate building material that is not patterned with a binder fluid is not considered part of the green body, even if the particulate building material is immediately adjacent to or surrounds the green body. For example, unprinted particulate building material may be used to support a green body contained therein, but the particulate building material is not part of the green body unless the particulate building material is printed with a binder fluid or some other fluid used to generate a solidified part prior to sintering, such as sintering, annealing, melting, etc.

[0065] As used herein, the terms "3D part," "3D object," and the like refer to a target 3D object being constructed. A 3D object may be referred to as a "sintered" 3D object, meaning that the object has been sintered, e.g., sintered, annealed, melted, etc., or as a "green body" or "green" 3D object, meaning that the object has solidified but not yet sintered.

[0066] "Binder fluid" refers to a fluid comprising water and binder particles effective to bind layers of particulate build material when forming a green body. The binder fluid is typically applied to form a green body 3D object.

[0067] The term "fluid" does not mean that the composition is free of particulate solids, but rather may include solids dispersed therein, including carbon black pigment, latex particles, or other solids dispersed in the liquid vehicle of the fluid.

[0068] As used herein, "kit" can be synonymous with and understood to include multiple compositions, including one or more components, wherein the different compositions can be separately contained in one or more containers before and during use (e.g., building a 3D object), but the components can be combined together during the construction process. The container can be any type of vessel, box, or receptacle made of any material.

[0069] The terms "sintering" and "fusing" refer to the joining of adjacent particles of a particulate building material, for example, by sintering, annealing, melting, etc., and may include adjacent particles completely sintered into a common structure, such as melting together, or may include surface sintering, where the particles are not completely melted to the liquidus point but are able to bond the particles of the particulate building material to each other, such as forming bridges of material between particles at or near contact points.

[0070] As used herein, for convenience, multiple items, structural elements, component elements, and / or materials may be listed in general lists. However, these lists should be interpreted as if each member of the list were separately and uniquely identified. Therefore, unless otherwise indicated, no member of such a list should be construed as a de facto equivalent of any other member of the same list based on their appearance in the same group.

[0071] Concentrations, sizes, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used for convenience and brevity only and should be flexibly interpreted to include the values ​​explicitly listed as the limits of the range, as well as all individual values ​​or subranges contained within the range, just as if each value and subrange were explicitly listed. For example, a weight ratio range of about 1% to about 20% by weight should be interpreted to include the explicitly listed limits of 1% and 20% by weight, as well as individual weights such as about 2%, about 11%, about 14%, and subranges such as about 10% to about 20%, about 5% to about 15%, etc. Example

[0072] The following illustrates one embodiment of the present disclosure. However, it should be understood that the following illustrates the application of the principles of the present disclosure. Many modifications and alternative compositions, methods, and systems may be devised without departing from the spirit and scope of the present disclosure. The appended claims are intended to cover such modifications and arrangements.

[0073] Example 1 -Carbon black as a flow additive

[0074] The effect of commercial carbon black powder on the flowability of stainless steel particles was evaluated. The test compositions included a control, which was 100% by weight 316L - 22 μm (80 wt%) stainless steel particles with a D50 particle size of approximately 10 μm and approximately 80 wt% of the particles passing through a 22 μm sieve (available from Sandvik AB, Sweden). Formulation A includes 99.9 wt% Stainless steel particles and 0.1 wt% fumed silica flow additive, Formulation BG includes 99.9 wt% Stainless steel particles and 0.1 wt% commercial carbon black powder. The flow control additives are shown in Table 1 along with the D50 particle size of each additive.

[0075] Table 1: Carbon black powder

[0076]

[0077] *AEROSILTM R812 is available from Cabot Corporation (USA)

[0078] Available from Palmer Holland (USA)

[0079] FW 1, FW 18, both available from (Germany)

[0080] By loading 35 ml of the composition / blend sample into a GRANUTOOLS TM The flowability of the composition / blend was evaluated using a GranuPack high resolution tap density analyzer from , Belgium. The tap density analyzer measures the Hausner ratio (H [n] ), which is an indicator of liquidity. [n] The value indicates good flowability.

[0081] like Figure 4 As shown in Figure 2, adding 0.1 wt% carbon black to the blend improved the The flowability of stainless steel particles. and The incorporation of provides a flowability improvement that is substantially similar to that achieved by incorporating the same amount of fumed silica flow additive.

[0082] Example 2 - Weight percentage of carbon black

[0083] To further determine the effective amount of carbon black as a flow additive, Several blends of 316L-22 μm stainless steel particles (available from Sandvik AB, Sweden) (having a D50 particle size distribution value of approximately 10 μm and approximately 80% by weight of the particles being able to pass through a 22 μm sieve) were mixed with varying amounts of (Germany) Carbon black was combined. Various blends contained 0.005 wt%, 0.01 wt%, 0.02 wt%, 0.05 wt% and 0.1 wt% carbon black, with the balance being stainless steel particles up to 100 wt%. The flowability of the blends was measured using the above method and a GranuPack high-resolution tap density analyzer.

[0084] like Figure 5 As shown in , even the incorporation of as little as 0.005 wt% carbon black improves flowability, for example, reduces the Hausner ratio (H) of stainless steel particles. [n]). The blend including 0.02 wt% carbon black achieved the greatest improvement in flowability.

Claims

1. A three-dimensional printing kit, comprising: Adhesive fluid; and A particulate building material comprising: 95% to 99.98% by weight of metal particles, and carbon black particles in an amount of 0.02% to 2% by weight, The weight percentages are based on the total weight of the particulate building material.

2. The three-dimensional printing kit of claim 1, wherein the particulate building material is free of oxide or semi-metal oxide flow control additives. 3 . The 3D printing kit according to claim 1 , wherein the metal particles comprise copper, cobalt, nickel, tungsten carbide, gold, silver, an iron-based alloy, steel, alloys thereof, or mixtures thereof. The 3D printing kit according to claim 3 , wherein the steel comprises stainless steel. The 3D printing kit of claim 3 , wherein the steel comprises high carbon steel. The 3D printing kit of claim 3 , wherein the steel comprises tool steel. The 3D printing kit according to claim 1 , wherein the metal particles are stainless steel.

8. The 3D printing kit according to claim 1, wherein the metal particles have a D50 particle size distribution value of 2 μm to 40 μm.

9. The 3D printing kit according to claim 1, wherein the carbon black particles have a D50 particle size distribution value of 10 nm to 200 nm.

10. The three-dimensional printing kit according to claim 1, wherein the surface area of ​​the carbon black particles is 50 m 2 / g to 600m 2 / g. 11 . The 3D printing kit of claim 1 , wherein the binder fluid comprises water and latex particles in an amount of 5 wt % to 30 wt %.

12. A particulate building material for three-dimensional printing, comprising: 95% to 99.98% by weight of metal particles having a D50 particle size distribution value of 2 μm to 40 μm, and carbon black particles in an amount of 0.02% to 2% by weight and having a D50 particle size distribution value of 10 nm to 200 nm, The weight percentages are based on the total weight of the particulate building material.

13. The particulate build material of claim 12, wherein the metal particles comprise copper, cobalt, nickel, tungsten carbide, gold, silver, an iron-based alloy, steel, alloys thereof, or mixtures thereof, and wherein the particulate build material is free of oxide or semi-metal oxide flow control additives.

14. The particulate build material of claim 13, wherein the steel comprises stainless steel.

15. The particulate build material of claim 13, wherein the steel comprises high carbon steel.

16. The particulate build material of claim 13, wherein the steel comprises tool steel.

17. A three-dimensional printing method, comprising: iteratively applying respective build material layers of a particulate build material comprising metal particles in an amount of 95% to 99.98% by weight, based on the total weight of the particulate build material, and carbon black particles in an amount of 0.02% to 2% by weight, based on the total weight of the particulate build material; Based on the 3D object model, a binder fluid is selectively applied to the individual build material layers to define individually patterned layers that accumulate and bond together to form the 3D green body object, wherein sintering is conducted in an atmosphere including a gas reactive with carbon at elevated temperature to convert carbon from the carbon black particles into gas, thereby resulting in a carbon black particle content in the sintered 3D object being lower than that in the 3D green body object.

18. The three-dimensional printing method of claim 17, further comprising heating the plurality of individually patterned layers during the molding process to displace water, thereby further solidifying the 3D green body object.

19. The three-dimensional printing method of claim 17, further comprising sintering the 3D green body object at an elevated temperature of 500°C to 3,500°C to fuse the metal particles together and form a sintered 3D object.

Images