3D printing with flame retardants

Abstract

A 3D printing kit may include a polymeric build material and a fusing agent. The polymeric build material may include polymer particles having a D50 particle size of about 2 µm to about 150 µm. The fusing agent may include an aqueous liquid carrier containing water and an organic cosolvent, a radiation absorber that generates heat from absorbed electromagnetic radiation, and about 5 wt % to about 20 wt % of a flame retardant containing dicyandiamide.

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 often used for rapid product prototyping, mold generation, master pattern generation, and low-volume manufacturing. Some 3D printing techniques can be considered additive methods because they involve applying successive layers of material. This can be distinguished from other mechanical processes that typically rely on removing material to create the final part. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1A and Figure 1B Schematic diagrams collectively showing an exemplary three-dimensional printing set according to the present disclosure;

[0005] Figure 2 is a flowchart illustrating an exemplary method of printing a three-dimensional object according to the present disclosure; and

[0006] Figure 3 is a schematic diagram of an exemplary three-dimensional printing system according to the present disclosure.

[0007] Details

[0008] Three-dimensional printing can be an additive process that involves applying successive layers of polymeric building materials on which a fusing agent is printed to bind the successive layers of polymeric building materials together. More specifically, a fusing agent containing a radiation absorber can be selectively applied to a layer of polymeric building material on a support bed, such as a building platform supporting the polymeric building material, to pattern selected areas of the layer of polymeric building material. The layer of polymeric building material can be exposed to electromagnetic radiation, and due to the presence of the radiation absorber on the printed portion, the light energy absorbed in those portions of the layer on which the fusing agent is printed can be converted into thermal energy to melt or coalesce the portion, while other portions of the polymeric building material do not reach a temperature suitable for melting or coalescing. This can then be repeated on a layer-by-layer basis until a three-dimensional object is formed.

[0009] Accordingly, a three-dimensional printing kit (or "kit") may include a polymer building material and a fusing agent. The polymer building material may include polymer particles having a D50 particle size of about 2 μm to about 150 μm. The fusing agent may include an aqueous liquid carrier containing water and an organic cosolvent, a radiation absorber that generates heat from absorbed electromagnetic radiation, and about 5% by weight to about 20% by weight of a flame retardant containing dicyandiamide. In one example, the flame retardant may further include dicyandiamide, monocyanamide, melamine, guanidine melamine, polyguanidine melamine, guanidine carbonate, guanidine urea, or a combination thereof. In another example, the flame retardant may be present in the fusing agent at about 8% by weight to about 16% by weight. In another example, the radiation absorber may include carbon black, a metal dithiolene complex, a near-infrared absorbing dye, a near-infrared absorbing pigment, a metal nanoparticle, a conjugated polymer, or a combination thereof. In a further example, the radiation absorber may be present in the flux at about 0.1 wt % to about 10 wt %. In one example, the aqueous liquid carrier may further include about 0.01 wt % to about 2 wt % of a surfactant. In another example, the polymeric building material may include polyamide, polyethylene, polyethylene terephthalate (PET), polystyrene, polyacrylate, polyacetal, polypropylene, polycarbonate, polyester, acrylonitrile butadiene styrene, thermoplastic polyurethane, engineering plastics, polyetheretherketone (PEEK), polymer blends thereof, amorphous polymers thereof, core-shell polymers thereof, and copolymers thereof. In another example, the kit may further include a detailing agent. The detailing agent may include a detailing compound to reduce the temperature of the polymeric building material to which the detailing agent is applied.

[0010] In another example of the present disclosure, a method of printing a three-dimensional object (or "method") may include iteratively applying individual polymer building material layers of a polymer building material containing polymer particles having a D50 particle size of about 2 µm to about 150 µm, and iteratively and selectively distributing a fusing agent to each polymer building material layer based on a 3D object model. The fusing agent may include an aqueous liquid carrier containing water and an organic cosolvent, a radiation absorber that generates heat from absorbed electromagnetic radiation, and about 5% by weight to about 20% by weight of a flame retardant containing dicyandiamide. The method may further include iteratively exposing each polymer building material layer in which the fusing agent is distributed to electromagnetic radiation to selectively fuse the polymer particles of the polymer building material in contact with the radiation absorber and form a fused three-dimensional object. In a more specific example, the flame retardant may further include dicyandiamide, monocyanamide, melamine, guanidine melamine, polyguanidine melamine, guanidine carbonate, guanidine urea, or a combination thereof. In another example, the radiation absorber may include carbon black. In one example, the flame retardant may be applied to each polymeric build material layer at a flame retardant / polymeric build material weight ratio of about 1:20 to about 1: 100. In another example, the method may further include iteratively and selectively dispensing a thinning agent laterally to each polymeric build material layer at a boundary between a first region of each polymeric build material layer in contact with the fusing agent and a second region of each polymeric build material layer not in contact with the fusing agent.

[0011] In another example, a three-dimensional printing system (or "system") may include a polymeric building material including polymer particles having a D50 particle size of about 2 µm to about 150 µm, and a fluid applicator fluidly connected or fluidly connectable to a fusing agent. The fluid applicator may be directable to iteratively apply the fusing agent to a layer of the polymeric building material. The fusing agent may include an aqueous liquid carrier containing water and an organic co-solvent, a radiation absorber that generates heat from absorbed electromagnetic radiation, and about 5% to about 20% by weight of a flame retardant containing dicyandiamide. In one example, the system may further include an electromagnetic radiation source positioned to provide electromagnetic radiation to the polymeric building material layer having the fusing agent applied thereto.

[0012] When a three-dimensional printing kit, a method of printing a three-dimensional object, and / or a three-dimensional printing system are discussed herein, such discussions may be considered applicable to each other, regardless of whether they are explicitly discussed in the context of that instance. Thus, for example, when a polymeric building material is discussed in relation to a three-dimensional printing kit, such disclosure is also related to and directly supported in the context of a method of printing a three-dimensional object, a three-dimensional printing system, and vice versa.

[0013] Unless otherwise specified, the terms used herein have their ordinary meanings in the technical field. In some cases, some terms are more specifically defined throughout the specification or included at the end of this specification, so these terms may have the meanings as described herein.

[0014] 3D Printing Kit

[0015] exist Figure 1A and Figure 1B A three-dimensional printing set is shown in the figure as an example. The three-dimensional printing set may include, for example, Figure 1A The polymer building material 110 shown in FIG. Figure 1B The polymeric building material may include polymer particles 112 having a D50 particle size of about 2 μm to about 150 μm. The fusing agent may include an aqueous liquid carrier 122 containing water and an organic cosolvent, a radiation absorber 124 that generates heat from absorbed electromagnetic radiation, and about 5 wt % to about 20 wt % of a flame retardant 126 containing dicyandiamide.

[0016] In some examples, the 3D printing kit may further include other fluids, such as colorants, thinning agents, and the like. The thinning agent may, for example, include a thinning compound, which may be a compound that can reduce the temperature of the polymeric building material when applied to the polymeric building material. In some examples, the thinning agent may be applied around the edge of the application area of ​​the fusing agent. This can prevent agglomeration around the edge caused by heat from the fusing agent application area. The thinning agent may also be applied in the same area where the fusing agent is applied to control the temperature and prevent excessive temperatures when the polymeric building material is fused.

[0017] The polymeric build material may be packaged or co-packaged with a fusing agent, coloring agent, detailing agent, etc. in a separate container, and / or may be combined with a fusing agent at the time of printing, such as loaded together into a three-dimensional printing system.

[0018] Method for printing three-dimensional objects

[0019] A flowchart of an exemplary three-dimensional (3D) printing method 200 is shown in Figure 2The method may include 210 iteratively applying respective polymer building material layers of a polymer building material comprising polymer particles having a D50 particle size of about 2 µm to about 150 µm, 220 iteratively and selectively dispensing a fusing agent onto the respective polymer building material layers based on the 3D object model, wherein the fusing agent may include an aqueous liquid carrier containing water and an organic co-solvent, a radiation absorber that generates heat from absorbed electromagnetic radiation, and about 5 wt % to about 20 wt % of a flame retardant containing dicyandiamide, and 230 iteratively exposing the respective polymer building material layers in which the fusing agent is dispensed to electromagnetic radiation to selectively fuse the polymer particles of the polymer building material in contact with the radiation absorber and form a fused three-dimensional object.

[0020] In printing in a layer-by-layer manner, the polymer building material may be spread, a fusing agent may be applied, the polymer building material layer may be exposed to energy, and then the build platform may be lowered a distance of 5 µm to 1 mm, which may correspond to the thickness of the printed layer of the three-dimensional object, so that another layer of the polymer building material may be added thereon to receive another application of the fusing agent, and so on. During the building process, the radiation absorber in the fusing agent may be used to convert energy into thermal energy and promote heat transfer to polymer particles of the polymer building material in contact with the fusing agent containing the radiation absorber. In one example, the fusing agent may increase the temperature of the polymer particles of the polymer building material to above the melting point or softening point of the polymer particles, thereby allowing the polymer building material (or its polymer particles) to fuse (e.g., sinter, bond, solidify, etc.) and form the layers of the three-dimensional object. The method may be repeated until all the layers of the polymer building material have been created and the three-dimensional object has been formed. In some examples, the method may further include heating the polymer building material before dispensing.

[0021] In one example, the method may further include iteratively and selectively dispensing a thinning agent laterally onto each polymeric building material layer at a boundary between a first region where each polymeric building material layer is in contact with the fusing agent and a second region where each polymeric building material layer is not in contact with the fusing agent. This may prevent agglomeration around the edges caused by heat from the region where the fusing agent is applied. The thinning agent may also be applied in the same region where the fusing agent is applied to control the temperature and prevent excessive temperatures when the polymeric building materials are fused.

[0022] In another example, the three-dimensional object formed by the method can be flame retardant according to various flammability standards, such as safety and flammability standards for component plastic materials established by the Underwriters Laboratory (UL). Therefore, in some examples, the three-dimensional object formed can prevent or slow down the further development of the object ignition when ignited. For example, relative to a three-dimensional object formed by the same polymer construction material and a flux, but without a flame retardant, this flame retardant property can be an improvement. Exemplary flame retardancy standards can be related to the tendency of the three-dimensional object to extinguish or reduce the spread of flames once the material is ignited. In one example, the three-dimensional object can exhibit a flame retardant rating of UL 94 V-0 (IEC 60695-11-108). This rating means that on a vertical specimen with a thickness of about 2 mm (or more), the combustion stops within 10 seconds. The dripping of particles is allowed as long as they do not burn. A specimen with a thickness of less than 2 mm and not meeting the UL94 V-0 standard but passing the standard as a comparable 2 mm thick specimen can obtain a UL94 V-0 rating. In another example, the three-dimensional object can show a flame retardant rating of UL94 V-1 (IEC 60695-11-108). This rating means that on a vertical specimen, combustion stops within 30 seconds, and dripping of particles is allowed as long as they do not burn. In yet another example, the three-dimensional object can show a flame retardant rating of UL94 V-2 (IEC 60695-11-108). This rating means that on a vertical specimen, combustion stops within 30 seconds, and dripping of burning particles is allowed. In order to determine whether the three-dimensional object meets the standard, a standard size object can be prepared using the materials and methods used to generate the object, and its thickness can be about 0.8 mm to about 4 mm. In one example, the thickness can be about 4mm. In order to achieve the UL94 V-0 rating, the thickness of the object should be at least 2 mm and meet the above-mentioned UL94 V-0 peripheral standards. The flame height of the ignition source can be 20mm, and the flame can be applied twice, ten seconds each time. Once the first combustion is over, the second flame can be applied. After the flame is applied, the material may be indicated as failing the test, or may be rated as UL 94 V-2, UL 94 V-1, or UL 94 V-0 based on the above standards. In one example, the three-dimensional object may be a material rated, for example, as UL 94 V-2 or higher, or UL 94 V-1 or higher, or UL 94 V-0 or higher. Although in some examples, one of the US 94 standards may be met, in some examples, the three-dimensional object may be a material rated according to these UL 94 blue card standards. For example, including dicyandiamide in the flux may enhance flame retardancy, but the printed object may not meet one of these UL 94 standards even if flame retardancy has been enhanced.

[0023] 3D printing system

[0024] exist Figure 3 Schematically illustrates a three-dimensional printing system 300 according to the present disclosure. The three-dimensional printing system may include a polymer build material 110 and a fluid applicator 310. The polymer build material may include polymer particles having a D50 particle size of about 2 μm to about 150 μm. The fluid applicator is connected or connectable to a flux 120. The flux may include an aqueous liquid carrier containing water and an organic co-solvent, a radiation absorber that generates heat from absorbed electromagnetic radiation, and about 5 wt % to about 20 wt % of a flame retardant containing dicyandiamide.

[0025] In more detail, fluid applicator 310 can be a digital fluid ejector, such as a thermal or piezoelectric jet architecture. The fluid applicator can be a flux applicator in one example, which is fluidically connected or fluidically connectable to the flux 120 to iteratively apply the flux to the polymer building material 110 to form the individually patterned object layers 340. The fluid applicator can be any type of device capable of selectively dispensing or applying the flux. For example, the fluid applicator can be a fluid ejector or a digital fluid ejector, such as an inkjet printhead, such as a piezoelectric printhead, a thermal printhead, a continuous printhead, etc. The fluid applicator can also be a sprayer, a dropper, or other similar structure for applying the flux to the polymer building material. Therefore, in some examples, the application can be by spraying or ejecting the flux from a digital fluid jet applicator similar to an inkjet pen.

[0026] In one example, the fluid applicator may be Figure 3 315, but may be supported by any of a number of structures. In another example, the fluid applicator may include a motor (not shown) and may be operable to move back and forth, and the fluid applicator may also move back and forth to provide x-axis and y-axis motion over the polymeric build material when positioned over or adjacent to the polymeric build material on the powder bed of the build platform.

[0027] In one example, the three-dimensional printing system may further include a build platform 320 to support the polymer build material 110. The polymer build material may be introduced from a polymer build material supplier 360 onto the build platform or onto a portion of the polymer build material previously applied as a powder bed. Once present on the build platform or the powder bed, the applied polymer build material layer may be flattened by any of a number of techniques and / or devices suitable for establishing a thin layer of polymer build material. The build platform may be positioned so that a flux can be applied from a fluid applicator to the polymer build material layer. The build platform may be configured to drop in height so that subsequent layers of polymer build material may be applied by a supplier and / or a spreader. The polymer build material may be layered in the build platform at a thickness of about 5 μm to about 1 mm. In some examples, each layer may have a relatively uniform thickness. In one example, the thickness of the polymer build material layer may be about 10 μm to about 500 μm or about 30 μm to about 200 μm. In addition, heat can be applied to the build platform or from any other direction or time to bring the polymeric build material to a temperature close to its fusion temperature so that it is easier to raise the temperature enough to fuse the polymeric build material. For example, heat can be applied from the build platform, from above to the polymeric build material in the powder bed, or to the polymeric build material before spreading on the powder bed to preheat the polymeric build material to within about 10°C to about 70°C of the fusion temperature of the polymer particles so that less energy can be applied to bring the polymer particles to their fusion temperature.

[0028] After the fusing agent is selectively applied to the polymeric building material, the polymeric building material can be exposed to energy (e) from an electromagnetic radiation source 330. The electromagnetic radiation source can be positioned so that each layer of the polymeric building material is exposed to the radiation energy to selectively fuse the polymer particles of the polymeric building material in contact with the radiation absorber (forming a fused layer 350), thereby iteratively forming a three-dimensional object. The radiation source can be an infrared (IR) or near-IR light source, such as an infrared or near-IR curing lamp, an infrared or near-IR light emitting diode (LED), or a laser having a desired infrared or near-IR electromagnetic wavelength, and can emit electromagnetic radiation having a wavelength of about 400 nm to about 1 mm. In one example, the emitted electromagnetic radiation can have a wavelength of about 400 nm to about 2 µm. In some examples, the radiation source can be operably connected to a lamp / laser driver, an input / output temperature controller, and / or a temperature sensor.

[0029] Polymer building materials

[0030] The polymer building material can be used as a bulk material for a three-dimensionally printed object. As mentioned, the polymer building material can include about 80% to 100% by weight of polymer particles. In another example, the polymer building material can include about 85% to about 95% by weight, about 90% to 100% by weight, or 100% by weight of polymer particles.

[0031] In one example, the polymer building material may include polyamide, polyethylene, polyethylene terephthalate (PET), polystyrene, polyacrylate, polyacetal, polypropylene, polycarbonate, polyester, acrylonitrile butadiene styrene, thermoplastic polyurethane, engineering plastics, polyether ether ketone (PEEK), polymer blends thereof, amorphous polymers thereof, core-shell polymers thereof, and copolymers thereof. In another example, the polymer building material may include polyamide, polyethylene, polystyrene, polypropylene, polycarbonate, polymer blends thereof, amorphous polymers thereof, core-shell polymers thereof, and copolymers thereof. In another example, the polymer building material may include polyamide.

[0032] The polymer building material may comprise polymer particles of similar size or polymer particles of different sizes. The term "size" or "particle size" as used herein refers to the diameter of a substantially spherical particle, or the effective diameter of a non-spherical particle, such as the diameter of a sphere having the same mass and density (as determined by weight) as the non-spherical particle. Substantially spherical particles (e.g., spherical or nearly spherical) may have a sphericity of >0.84. Thus, any individual polymer particle having a sphericity of <0.84 may be considered non-spherical (irregularly shaped). For example, the polymer particles may have a D50 particle size of about 2 µm to about 150 µm, about 25 µm to about 125 µm, about 50 µm to about 150 µm, about 20 µm to about 80 µm. The D50 particle size is based on the equivalent spherical volume of the polymer particle. The D50 particle size may be measured by laser diffraction, microscopic imaging, or other suitable methods, but in some instances, the particle size (or particle size distribution) may be measured using the Malvern TM Mastersizer TM Measurement and / or Characterization. When the polymer particles are not spherical, for example having an aspect ratio of about 1:1, this tool considers the particle size based on the diameter of the equivalent spherical volume of the polymer particles.

[0033] The polymer construction material may further include flow additives, antioxidants, inorganic fillers or any combination thereof in some instances. Typically, the amount of any of these or other similar components may be about 5% by weight or less. Exemplary flow additives may include fumed silica and / or the like. Exemplary antioxidants may include hindered phenols, phosphites, thioethers, hindered amines and / or the like. Exemplary inorganic fillers may include particles such as alumina, silica, fibers, carbon nanotubes, cellulose and / or the like. Some additives may be present in a variety of additive categories, for example, fumed silica may be both a flow additive and a filler. In some instances, fillers or other types of additives may be embedded in polymer particles or compounded with polymer particles.

[0034] The polymer building material can be printed into a three-dimensional object with a resolution of about 10 μm to about 150 μm, about 20 μm to about 100 μm, or about 25 μm to about 80 μm. "Resolution" as used herein refers to the size of the smallest feature that can be formed on a three-dimensional object. Depending on the size of the polymer particles present in the polymer building material, the polymer building material can form a layer of about 10 μm to about 150 μm thick, so that the fused layer of the printed object can have approximately the same thickness or, for example, several to multiple times (e.g., 2 to 20 times) thicker than the D50 particle size of the polymer particles. This can provide a resolution in the z-axis direction (e.g., the building direction of the layer) of about 10 μm to about 150 μm. However, in some instances, the polymer building material can also have a sufficiently small particle size and a sufficiently consistent particle shape to provide an x-axis and y-axis resolution (e.g., an axis parallel to the support surface of the building platform) of about the size of the polymer particles, such as about 2 μm to about 150 μm.

[0035] Fusing agent

[0036] In more detail, regarding the fusing agent 120 available in the three-dimensional printing kit, the method for printing a three-dimensional object, or the three-dimensional printing system as described herein, the fusing agent may include an aqueous liquid carrier, a radiation absorber that generates heat by absorbed electromagnetic radiation, and a flame retardant containing dicyandiamide of about 5 wt % to about 20 wt %. The aqueous liquid carrier may include water and an organic co-solvent. In one example, the aqueous liquid carrier may include about 25 wt % to about 90 wt % or about 30 wt % to about 75 wt % of water, and about 5 wt % to about 60 wt % or about 10 wt % to about 50 wt % of an organic co-solvent. In one example, the aqueous liquid carrier may include an organic solvent / water ratio of about 2:1 to about 1:2, about 1:1 to about 1:2, about 1:1 to about 1:1.5, or about 1:1 to about 1:1.25.

[0037] In more detail, the flux may contain a radiation absorber. The amount of the radiation absorber in the flux may vary depending on the type of radiation absorber. In some examples, the amount of the radiation absorber in the flux may be from about 0.1 wt % to about 10 wt %. In another example, the amount may be from about 0.5 wt % to about 7.5 wt %. In another example, the amount may be from about 1 wt % to about 10 wt %. In a specific example, the amount may be from about 0.5 wt % to about 5 wt %.

[0038] Exemplary radiation absorbers can include carbon black, metal dithiol ene complexes, near infrared absorbing dyes, near infrared absorbing pigments, metal nanoparticles, conjugated polymers, or combinations thereof. In one example, the radiation absorber can be carbon black. In some examples, the radiation absorber can be colored or colorless.

[0039] Examples of near infrared absorbing dyes may include ammonium dyes, tetraaryl diamine dyes, cyanine dyes, phthalocyanine dyes, dithiol ene dyes, and the like. Various near infrared absorbing pigments may also be used. Non-limiting examples may include phosphates having various counter ions such as copper, zinc, iron, magnesium, calcium, strontium, and the like and combinations thereof. Non-limiting specific examples of phosphates may include M2P2O7, M4P2O9, M5P2O 10 、M3(PO4)2、M(PO3)2、M2P4O 12 And combinations thereof, wherein M represents a counterion with an oxidation state of +2. For example, M2P2O7 may include compounds such as Cu2P2O7, Cu / MgP2O7, Cu / ZnP2O7 or any other suitable combination of counterions. The phosphates described herein are not limited to counterions with an oxidation state of +2. Other phosphate counterions may also be used to prepare other suitable near-infrared pigments. Additional near-infrared absorbing pigments may include silicates. Silicates may have counterions identical or similar to phosphates. A non-limiting example may include M2SiO4, M2Si2O6 and other silicates in which M is a counterion with an oxidation state of +2. For example, the silicate M2Si2O6 may include Mg2Si2O6, Mg / CaSi2O6, MgCuSi2O6, Cu2Si2O6, Cu / ZnSi2O6 or other suitable combinations of counterions. The silicates described herein are not limited to counterions with an oxidation state of +2. Other silicate counterions may also be used to prepare other suitable near-infrared pigments.

[0040] In more detail, the flame retardant can be present in the flux at about 5 wt % to about 20 wt %. In other examples, the flame retardant can be present at about 5 wt % to about 15 wt %, about 8 wt % to about 16 wt %, about 8 wt % to about 12 wt %, or about 10 wt % to about 20 wt %. The flame retardant can include dicyandiamide. Dicyandiamide has the chemical structure shown in Formula I below.

[0041] (I).

[0042] Without being limited by theory, the heteroatoms in dicyandiamide may contribute to its performance as a flame retardant. In some instances, the flame retardant may further comprise dicyandiamide, cyanamide, melamine, guanidine melamine, polyguanidine melamine, guanidine, guanidine carbonate, guanidine urea, or a combination thereof. In some instances, the flame retardant is soluble or partially soluble in an aqueous liquid carrier. Incorporating a flame retardant into the fusing agent may allow for voxel-based flame retardant application. This may allow for additional flame retardant to be applied to portions of a three-dimensional object formed therefrom that may be more easily ignited (e.g., thinner portions and overhanging portions).

[0043] In some examples, other liquids or dispersed additives may also be present in the aqueous liquid carrier. In some examples, the aqueous liquid carrier may further include a surfactant of about 0.01 wt % to about 2 wt % or about 0.01 wt % to about 0.5 wt %. Regarding other additives, in some examples, the fusing agent may further include a dispersant. The dispersant can help disperse the radiation absorber, the flame retardant, or a combination thereof. In some examples, the dispersant itself may also absorb radiation. Non-limiting examples of dispersants that can be included as radiation absorbers alone or with pigments may include polyoxyethylene glycol octylphenol ether, ethoxylated aliphatic alcohols, carboxylates, polyethylene glycol esters, sorbitan esters, carboxamides, polyoxyethylene fatty acid amides, poly(ethylene glycol) p-isooctylphenyl ether, sodium polyacrylate, and combinations thereof. As described more fully below, other additives may be present as part of the aqueous liquid carrier.

[0044] Refining agent

[0045] In some examples, the three-dimensional printing kit, the method of printing a three-dimensional object, and / or the three-dimensional printing system may further include a thinning agent and / or its application. The thinning agent may include a thinning compound capable of cooling the polymeric build material when applied. In some examples, the thinning agent may be printed around the edges of the portion of the polymeric build material that is printed by the fusing agent or can be printed by the fusing agent. The thinning agent can increase the selectivity between the fused and unfused portions of the polymeric build material by reducing the temperature of the polymeric build material around the edges of the portion to be fused. In other examples, the thinning agent may be printed in the fusing agent printing area to provide additional cooling when printing the three-dimensional object.

[0046] In some examples, the refiner can be a solvent that can evaporate at the temperature of the particulate building material carried on the powder bed or the building platform. As mentioned above, in some cases, the polymer building material in the powder bed can be preheated to a preheating temperature within about 10°C to about 70°C of the fusion temperature of the polymer building material. Therefore, the refiner can be a solvent that evaporates when in contact with the polymer building material at the preheating temperature, thereby cooling the printed part by evaporative cooling. In some examples, the refiner can include water, a co-solvent, or a combination thereof. In a further example, the refiner can be substantially free of radiation absorbers. That is, in some examples, the refiner can be substantially free of ingredients that absorb enough energy from the energy source to fuse the polymer building material. In some examples, the refiner can include a colorant, such as a dye or a pigment, but the amount is small enough that the colorant does not cause the polymer building material printed with the refiner to fuse when exposed to the energy source.

[0047] Aqueous liquid carrier

[0048] The term "aqueous liquid carrier" as used herein may refer to a liquid in a flux, a refiner, and / or other fluid reagents that may be present, such as a colorant. The aqueous liquid carrier may contain water alone or in combination with various additional components. For example, with respect to a flux, the aqueous liquid carrier contains water and an organic cosolvent, but with respect to a refiner, the aqueous liquid carrier may be water, or may contain water and an organic cosolvent. Examples of components that may be included in addition to water may include organic cosolvents, surfactants, buffers, antimicrobial agents, antifouling agents, chelating agents, buffers, and the like. In one example, the aqueous liquid carrier may contain water and an organic cosolvent. In another example, the aqueous liquid carrier may contain water, an organic cosolvent, and a surfactant. In yet another example, the aqueous liquid carrier may contain water, an organic cosolvent, a surfactant, and a buffer (or a buffer and a chelating agent).

[0049] The liquid carrier may include, for example, water which may be deionized. In one example, water may be present in the flux, refiner or other fluid agent at a weight percentage that may vary from about 25 wt % to about 90 wt % or from about 30 wt % to about 75 wt %.

[0050] The liquid carrier may include one or more organic co-solvents. Some examples of co-solvents that can be added to the carrier include 1-(2-hydroxyethyl)-2-pyrrolidone, 2-pyrrolidone, 2-methyl-1,3-propanediol, 1,5-pentanediol, triethylene glycol, tetraethylene glycol, 1,6-hexanediol, tripropylene glycol methyl ether, ethoxylated glycerol-1 (LEG-1), or a combination thereof. In one example, the co-solvent may include 2-pyrrolidone. Whether a single co-solvent or a combination of co-solvents is used, the total amount of one or more co-solvents in the flux, refiner, or other fluid agent may be about 5 wt % to about 60 wt %, about 10 wt % to about 50 wt %, about 15 wt % to about 45 wt %, or about 30 wt % to about 50 wt %, based on the total weight percentage of the flux or the total weight percentage of the refiner.

[0051] The aqueous liquid carrier may also include a surfactant. The surfactant may include a nonionic surfactant, a cationic surfactant and / or an anionic surfactant. In one example, the fusing agent includes an anionic surfactant. In another example, the fusing agent includes a nonionic surfactant. In yet another example, the fusing agent includes a blend of an anionic surfactant and a nonionic surfactant. Exemplary nonionic surfactants that can be used include self-emulsifiable nonionic wetting agents based on acetylenic diol chemistry (e.g., SURFYNOL from Air Products and Chemicals, Inc., USA). ® SEF), fluorinated surfactants (e.g. CAPSTONE from DuPont, USA ® In other examples, the surfactant can be an ethoxylated low foam wetting agent (e.g., SURFYNOL from Air Products and Chemicals, Inc., USA). ® 440, SURFYNOL® 465 or SURFYNOL ® CT-111) or ethoxylated wetting agents and molecular defoamers (e.g. Surfynol ®420). Still other surfactants may include wetting agents and molecular defoamers (e.g., SURFYNOL from Air Products and Chemicals, Inc., USA). ® 104E), alkylphenyl ethoxylates, solvent-free surfactant blends (e.g., SURFYNOL® CT-211 from Air Products and Chemicals, Inc., USA), water-soluble surfactants (e.g., TERGITOL ® TMN-6, TERGITOL ® 15S7 and TERGITOL ® 15S9) or a combination thereof. In other examples, the surfactant may include a nonionic organic surfactant (e.g., TEGO® Wet 510 from Evonik Industries AG, Germany), a nonionic secondary alcohol ethoxylate (e.g., TERGITOL® 15-S-5, TERGITOL® 15-S-7, TERGITOL® 15-S-9, and TERGITOL® 15-S-30, all from The Dow Chemical Company, USA), or a combination thereof. Exemplary anionic surfactants may include alkyl diphenyl oxide disulfonates (e.g., DOWFAX ® 8390 and DOWFAX ® 2A1), oleyl polyoxyethylene (3) ether phosphate surfactant (e.g., CRODAFOS™ N3Acid from Croda, UK). Exemplary cationic surfactants that can be used include dodecyl trimethyl ammonium chloride, hexadecyl dimethyl ammonium chloride, or a combination thereof. In some examples, the surfactant (which may be a blend of multiple surfactants) can be present in the flux, refiner, or other fluid agent in an amount of about 0.01 wt % to about 2 wt %, about 0.05 wt % to about 1.5 wt %, or about 0.01 wt % to about 1 wt %.

[0052] In some instances, the liquid carrier may also include a chelating agent, an antimicrobial agent, a buffer, or a combination thereof. Although the amounts of these may vary, if present, these may be present in the fluxing agent, thinning agent, or other fluid agent in an amount of about 0.001% to about 20%, about 0.05% to about 10%, or about 0.1% to about 5% by weight.

[0053] The liquid carrier may contain a chelating agent. One or more chelating agents may be used to minimize or eliminate the harmful effects of heavy metal impurities. Examples of suitable chelating agents may include disodium ethylenediaminetetraacetate (EDTA-Na), ethylenediaminetetraacetic acid (EDTA), and methylglycine diacetic acid (e.g., TRILON from BASF Corp., Germany). ® M). If included, the total amount of one or more chelating agents in the fusing agent, thinning agent or other fluid agent, whether a single chelating agent or a combination of chelating agents is used, may be from 0.01 wt % to about 2 wt % or from about 0.01 wt % to about 0.5 wt %.

[0054] The liquid carrier may also contain an antimicrobial agent. Antimicrobial agents may include biocides and fungicides. Exemplary antimicrobial agents may include NUOSEPT ® (Ashland Inc. (USA)), VANCIDE ® (RT VanderbiltCo., USA), ACTICIDE ® B20 and ACTICIDE ® M20 (Thor Chemicals, UK), PROXEL® GXL (Arch Chemicals, Inc.. USA), BARDAC® 2250, 2280, BARQUAT® 50-65B and CARBOQUAT® 250-T (Lonza Ltd. Corp., Switzerland), KORDEK® MLX (The Dow Chemical Co., USA) and combinations thereof. In one example, if included, the total amount of antimicrobial agent in the fusing agent, thinning agent or other fluid agent can be from about 0.01 wt % to about 1 wt %.

[0055] In some examples, the liquid carrier may further comprise one or more buffer solutions. In some examples, the one or more buffer solutions may withstand small pH changes (e.g., less than 1) when a small amount of a water-soluble acid or a water-soluble base is added to a composition comprising the one or more buffer solutions. The one or more buffer solutions may have a pH range of about 5 to about 9.5, or about 7 to about 9, or about 7.5 to about 8.5. In some examples, the one or more buffer solutions may comprise a polyhydroxy-functional amine. In other examples, the one or more buffer solutions may include potassium hydroxide, 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid, 2-amino-2-(hydroxymethyl)-1,3-propanediol (TRIZMA® sold by Sigma-Aldrich, USA), 3-morpholinopropanesulfonic acid, triethanolamine, 2-[bis-(2-hydroxyethyl)-amino]-2-hydroxymethylpropane-1,3-diol (bis trismethane), N-methyl-D-glucamine, N,N,N'N'-tetrakis-(2-hydroxyethyl)-ethylenediamine and N,N,N'N'-tetrakis-(2-hydroxypropyl)-ethylenediamine, β-alanine, betaine, or a mixture thereof. In other examples, the one or more buffer solutions may include 2-amino-2-(hydroxymethyl)-1,3-propanediol (TRIZMA® sold by Sigma-Aldrich, USA), β-alanine, betaine, or a mixture thereof. If included, the buffer solution may be added to the fusing agent, thinning agent or other fluid reagent in an amount of about 0.01 wt % to about 10 wt %, about 0.1 wt % to about 7.5 wt %, about 0.05 wt % to about 5 wt %.

[0056] definition

[0057] 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.

[0058] 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, such as 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, such as a range of about 1% to about 5% by weight includes 1% to 5% by weight as an expressly supported subrange.

[0059] As used herein, "kit" may be synonymous with and understood to include a plurality of components, wherein the different components may be separately contained prior to use (although in some cases packaged together in separate containers), but these components may be combined together during use, such as during the three-dimensional object construction method described herein. The container may be any type of vessel, box, or receptacle made of any material.

[0060] As used herein, "dispensing", when referring to a possible fusing agent, refers to any technique that can be used to place or arrange a fluid, such as a fusing agent, on or in a layer of a polymeric building material to form a green body object. For example, "applying" can refer to "spraying", "jetting", "dripping", "spraying", etc.

[0061] As used herein, "jetting" or "ejection" refers to a fluid reagent or other composition discharged by a jetting or ejection architecture, such as an inkjet architecture. The inkjet architecture may include a thermal or piezoelectric architecture. In addition, such an architecture may be configured to print different droplet sizes, such as up to about 20 picoliters (pL), up to about 30 pL, or up to about 50 pL, etc. Exemplary ranges may include about 2 pL to about 50 pL, or about 3 pL to about 12 pL.

[0062] As used herein, for convenience, multiple items, structural elements, compositional elements, and / or materials may be set forth in general lists. However, these lists should be interpreted as if each member of the list were provided as a separate and unique member. Therefore, unless otherwise indicated, any member of such a list should not be construed as a de facto equivalent of any other member of the same list based on appearance in the same group.

[0063] Concentration, size, amount and other numerical data may be presented in range format in this article.It is to be understood that such range format is used only for convenience and brevity, and should be flexibly interpreted as including the numerical value clearly listed as the limit of the range, and also including all single numerical values ​​or sub-ranges contained in the range, just as clearly listing each numerical value and sub-range.For example, the weight ratio range of about 1 wt % to about 20 wt % should be interpreted as including the clearly listed limit of 1 wt % and 20 wt %, and also including each weight, such as about 2 wt %, about 11 wt %, about 14 wt %, and sub-range, such as about 10 wt % to about 20 wt %, about 5 wt % to about 15 wt %, etc. Example

[0064] The following examples illustrate embodiments of the present disclosure. Many modifications and alternative compositions, methods and systems may be devised without departing from the present disclosure. The appended claims are intended to cover such modifications and arrangements.

[0065] Example 1 – Preparation of flux

[0066] Two flux formulations were prepared by mixing the components in Tables 1 and 2 below. Table 1 is an example flux prepared according to the present disclosure and Table 2 represents a "control" flux containing no flame retardant compound.

[0067] Table 1: Fuses containing flame retardants

[0068] Components Amount (weight %) Deionized water 43.94 2-Pyrrolidone (organic cosolvent) 40 Carbon black (radiation absorber) 5 Dicyandiamide (flame retardant) 10 Surfactant Blends 0.93 Buffer 0.10 Chelating agents 0.04

[0069] Table 2: Comparative flame retardants

[0070] Components Amount (weight %) Deionized water 66.4 2-Pyrrolidone (organic cosolvent) 19 Triethylene glycol 8 Carbon black (radiation absorber) 5 Surfactant Blends 1.2 Chelating agents 0.04 Biocides 0.32

[0071] Example 2 – Preparation of three-dimensional objects

[0072] Four dog-bone (or barbell) shaped three-dimensional printed objects were prepared using polymer build materials with nylon-12 (PA-12) particles. The fusing agents used with these polymer build materials were fusing agents prepared according to Table 1 (with flame retardant) and fusing agents prepared according to Table 2 (control without flame retardant), using common printing conditions set, such as a fusing speed of 22 inches per second per pass and a fusing agent of about 64 to about 70 continuous tones (contone). The powder bed was set to a temperature of 165°C. The dog-bone shaped object was formed to have an elongated middle section and two ends located on both sides. The three-dimensional printed object was printed using a multi-jet fusion (MJF) printer with a fusing agent from Table 1 or Table 2, and the fusing agent was iteratively sprayed layer by layer on the polymer build material PA-12 polymer particles. The same electromagnetic energy source was used to selectively form dog-bone shaped objects including multiple fused layers.

[0073] Example 3 – Flammability

[0074] Various dog bone shaped samples prepared according to Example 2 were evaluated for flammability in duplicate (two with the example fusing agent of Table 1, and two with the control fusing agent of Example 2). Testing was performed according to a procedure similar to that of the UL 94 Blue Card standard, except in terms of the object size parameters, to see if the flame retardant properties were enhanced. The samples were subjected to a 20 mm high flame for 10 seconds, the samples were removed from the flame, and the time at which extinguishing occurred was recorded. Once extinguished, the parts were immediately subjected to a 20 mm high flame for another 10 seconds, then the samples were removed from the flame, and then the second time at which extinguishing occurred was recorded. The results are shown in Table 3 below.

[0075] Table 3 - Flammability Test Results

[0076]

[0077] As can be seen above, samples A and B did not survive the second flame event as these samples were completely engulfed. Samples C and D printed with the fuse containing the flame retardant extinguished in less than 30 seconds.

Claims

1. A method for printing a three-dimensional object, comprising: iteratively applying individual layers of a polymeric building material comprising polymeric particles having a D50 particle size of 2 µm to 150 µm; iteratively and selectively dispensing a fusing agent onto each polymeric build material layer based on the 3D object model, wherein the fusing agent comprises an aqueous liquid carrier comprising water and an organic cosolvent, a radiation absorber that generates heat from absorbed electromagnetic radiation, and 5 wt % to 20 wt % of a flame retardant comprising dicyandiamide, and the flame retardant is applied on a voxel basis; and iteratively exposing individual layers of polymeric building material having a fusing agent dispensed therein to electromagnetic radiation to selectively fuse polymer particles of the polymeric building material in contact with the radiation absorber and form a fused three-dimensional object, wherein the radiation absorber comprises carbon black, metal dithiol-ene complexes, near infrared absorbing dyes, near infrared absorbing pigments, metal nanoparticles, conjugated polymers or combinations thereof, and The polymer building materials include polyamide, polyethylene, polyethylene terephthalate (PET), polystyrene, polyacrylate, polyacetal, polypropylene, polycarbonate, polyester, acrylonitrile butadiene styrene, thermoplastic polyurethane, engineering plastics, polyether ether ketone (PEEK), their polymer blends, their amorphous polymers, their core-shell polymers and their copolymers.

2. The method according to claim 1, wherein the flame retardant further comprises dicyanamide, monocyanamide, melamine, guanylmelamine, polyguanylmelamine, guanidine, guanidine carbonate, guanylurea or a combination thereof.

3. The method of claim 1, wherein the flame retardant is applied to each polymeric building material layer in a flame retardant / polymeric building material weight ratio of 1:20 to 1:

100.

4. The method of claim 1 further comprising iteratively and selectively dispensing a thinning agent laterally onto each polymeric building material layer at a boundary between a first region of each polymeric building material layer in contact with the fusing agent and a second region of each polymeric building material layer not in contact with the fusing agent.

5. The method of claim 1, wherein the flame retardant is present in the flux at 8 to 16 weight percent.

6. The method of claim 1, wherein the radiation absorber is present in the flux at 0.1 wt% to 10 wt%.

7. The method of claim 1, wherein the aqueous liquid carrier further comprises 0.01 wt% to 2 wt% of a surfactant.

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